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Патент USA US3026648

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March 27, 1962
3,026,638
P. F. H‘AYNER ET AL
AUTOMATIC BLADE SLOPE CONTROL SYSTEM
6 Sheets-Sheet 1
Filed Jan. 28, ' 1960
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Howard W. Boothroyd
INVENTORS
March 27, 1962
P. F. HAYNER ET AL
3,026,638
AUTOMATIC BLADE SLOPE CONTROL SYSTEM
Filed Jan. 28, 1960
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Paul E Hoyner
Thomas W. Thompson
Clifford Rwolker
Melvin G. Pfeifer
Herbert W. Compmon,Jn
Howard W. Boothroyd
INVENTORS
March 27, 1962
P. F. HAYNER ET AL
3,026,638
AUTOMATIC BLADE SLOPE CONTROL SYSTEM
Filed Jan. 28, 1960
6 Sheets-Sheet 3
Poul E Hoyner
Thomas W. Thompson
'
Clifford R. Wolker
Melvin G. Pfeifer
Herbert W. Compmon, Jr.
Howard W. Boofhroyd
INVENTORS
March 27, 1962
P. F. HAYNER ET AL
3,026,638
AUTOMATIC BLADE SLOPE CONTROL SYSTEM
Filed Jan. 28, 1960’
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Paul F. Huyner
Thomas W. Thompson
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Clifford R.Wolker
Melvin G. Pfeifer
Herbert W. Cumpman, Jr.
Howard W. Boo'rhroyd
INVENTORS
March 27, 1962
3,026,638
P. F. HAYNER ET AL
AUTOMATIC BLADE SLOPE CONTROL SYSTEM
6 Sheets-Sheet 5
Filed Jan. 28, 1960
Paul F. Hoyner
Thomas VV. Thompson
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Clifford R. Walker
Melvin G. Pféifer
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March 27, 1962
3,026,638
P. F. HAYNER ET AL
AUTOMATIC BLADE SLOPE CONTROL SYSTEM
6 Sheets-Sheet 6
Filed Jan. 28, 1960
BRIDGE INPUT
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Paul F. Huyner
Thomas W. Thompson
Clifford R. Walker
Melvin G. Pfeifer
Herber’r W. Cumpmun, Jr.
Howard W Boothroyd
INVENTORS
United ‘States Patent 0 "
3,026,638
Patented Mar. 27, 1962
2
1
for indication of the actual blade cutting angle as con
3,026,638
,
trasted with relatively complex gyroscopic means dis
closed in U.S. Patent 2,904,911. In addition, the prior
'
AUTGMATIC BLADE SLQPE CONTROL SYSTEM
Paul‘F. Hayner and Thomas W. Thompson, Nashua, N.H.,
Clifford R. Walker, Dracut, Mass, Melvin G. Pfeifer, '
art blade control systems are not continually operable
over the full range of blade orientation. Another ad
vantage of the present invention, therefore, is a linkage
of Delaware
to a feedback transducer allowing the system continu
Middlehury, Conn., Herbert W. Campman, Jr., and
Howard W. Boothroyd, Amherst, N.H., assignors to
Sanders Associates, Inc., Nashua, N.H., a corporation
coupling the aforementioned blade angle indicating means
Filed Jan. 28, 1960, Ser. No. 5,269
‘
18 Claims.
ously to operate irrespective of grader blade orientation.
(Cl. 37——156)
This invention relates generally to earth moving equip
10
ment for moving earth in a predetermined manner along
‘ It is an object of the present invention to provide an
improved automatic blade slope control system for a
road grading machine.
It is a further object of the present invention to pro
vide an improved automatic blade slope control system
tion is directed to an automatic angular control for main
taining a road grader blade at a preset slope during op 15 for a road grading machine having hydraulically actuated
grader blades.
eration. While the invention is subject to a wide range
An additional object of the present invention is to pro~
of applications, it is especially suited for use in road
vide a dynamically stable automatic blade slope control
grading apparatus for precise levelling and grading of
system for a road grading machine.
earth at a predetermined angle and will be particularly
the surface of the earth. More particularly, the inven
described in that connection. The expression “axis of 20
motion of the vehicle” as used herein is intended to de?ne
a line extending in the direction of vehicle motion.
With the advent of modern super highways and high
speed travel, the accuracy required for ?nished road
grades has been increased to eliminate ripples and‘bumps. 25
A further object of the present invention is to provide
an automatic blade slope control system operable irre-'
spective of grader blade orientation.
A further object of the present invention is to provide
an‘ improved mechanical resolving device.
7
In accordance with the present invention, there is pro
In many locales, the accuracy of the required slope is
vided an automatic blade slope control system in a ve
one-eighth of an inch in ten feet, or in terms of road
graders, one-eighth of an inch error between the ends of
hicle for road grading. The vehicle includes a vehicle
frame and a cutting blade assembly coupled to the frame.
A cutting blade is coupled to the assembly. The blade
,
.
In manually operated machines, the operator controls 30 is rotatable about an axis normal to its cutting edge.
the grader blade.
Means are provided for rotating the cutting blade about
a normal axis de?ning member. Means for rotating the
cutting blade and normal axis member are provided.‘
Hydraulic means are included for controlling the orien
adjusting the blade angle as the grader moves over un 35 tation of the cutting blade.
each side of the blade with manual valves that direct
hydraulic ?uid to actuators adjusting the height of each
side of the blade. The operator is expected to maintain
the desired angle or level of the blade by continually
even ground.
The problem of the‘blade control is fur
ther complicated by a requirement to keep the blade at
a depth equal to surveyors’ stakes set into the road bed
to show the ?nished grade level. A grader operator
A reference sensor means having an inertial mass is
provided for de?ning a vertical reference axis. > Refer
ence transducer means are coupled to the reference sens
sor means for producing a reference electrical signal
must be thoroughly experienced and have excellent re 40 representative of a desired predetermined blade slope
angle. There is also provided resolving means coupling
?exes to manually control the ?nished grade to the re
the cutting blade and a feedback transducer means. The
quired accuracy. To simplify the operator’s job and give
resolving means includes driving means coupled to the
a more accurate ?nished grade there are shown in the
blade. The driving means have a member rotatable
automatic control system must sense true vertical and 45 about an axis parallel to the normal axis member. There
is also provided, a first pivot support means a?ixed to
control the blade to maintain a predetermined level or
the driving means for providing a pivot support axis per
grade even over rough terrain. The system must func
prior art several automatic blade control systems.- Any
pendicular to the normal-axis member. Intermediate
tion accurately irrespective of grader orientation with
pivot means are provided,,pivotally coupled to the pivot
respect to a reference axis, the orientation of the grader
blade with respect to the grader, and irrespective of 50 support means for relative pivotal motion about the pivot ‘
support axis. The intermediate pivot means are pro
grader dynamics and vibrations.
vided with second pivot support means a?ixed thereto
There are described in the prior art various electro
for providing a second pivot support axis perpendicular‘
mechanical blade control systems. A blade slope con-_
to the ?rst pivot support axis. There are also provided
trol system utilizing electro-mechanical elements is dis
55 actuating means having a member coupled to the feed
closed in U.S. Patent ‘No. 2,904,911 issued to D. D. Co
back transducer means. The actuator means are pivot
lee on September 22, 1959. In the aforementioned sys
ally coupled to the support means for relative pivotal
tem, electric motors which are necessarily large in size
motion about the second support axis. The actuating
are used. In order to achieve greater system compact
means is rotated only in accordance vwith the rotation
ness the present system utilizes a small electro-hydraulic
valve for controlling blade position. The aforementioned 60 of the normal axis member in a plane perpendicular to
the axis of motion of the vehicle.
.
patent also shows the reference sensing means mechani
cally coupled to the grader blade thus making the refer
7 Feedback transducer means having a rotatable member
coupled to the actuating means are also provided. In
ence sensing means subject to dynamic vibrations and
oscillations of the grader blade. In the present inven 65 operation, the feedback transducer means produce an
electrical signal representative of the projected angle of
tion, the reference sensing means are located on or near
the normal axis de?ning member relative to the vehicle
the (3.6. of the rigid grader frame and not mechani
frame in a plane perpendicular to the axis of motion of
cally coupled to the blade. Therefore, in contrast to the
the vehicle. Comparator means, are provided, coupled
aforementioned patent, the reference sensing means of
to the reference and feedback transducer means for pro
this invention is relatively una?ected by the grader blade
dynamics. In addition, a novel feature of the present 70 viding an error signal in accordance, with the algebraic
invention is an inexpensive, simple, mechanical means
sum of the reference and feedback signals. Additionally
3,026,638
3
4
provided, are 'electro-hydraulic valve means coupled to
nectiug the blade 12 is a schematic mechanical resolver
the hydraulic means and responsive to the error signal
for continuously controlling the orientation of the cut
shown as line 16, which resolver 16 is in turn connected
to a pickoff device which is located in the plane Y'
ting blade at the desired predetermined blade slope angle.
For a better understanding of the present ‘invention,
together with other and further objects thereof, ‘refer
enc'eis made ‘to the following description taken in ‘con~
nection with the accompanying drawings and itss'cope
will be pointed out in the appended claims.
and is comprised of a pickoif resistant element 56‘ and
an associated contact arm 55.
It will be seen that as
the blade 12 is moved to different positions the pro
jected blade angle and its slope assume different posi
tions in the plane'Y. It is this projected line, for exam-l
ple A--B, which ‘is the true projected blade slope angle
In the drawings‘, FIG. 1 is an outline drawing, partially 10 and it is this line A-B which the earth sought tobe
schematic of a road grading machine embodying the
graded experiences, when the table is in the position
automatic cutting blade slope. control. system of .the
shown at 12. When the blade is in this position, 1t is
present invention;
imperative that there be obtained a signal which repre
FIG. 2 is a vector diagram illustrating cutting blade
sents this projected blade angle. The mechanical red
orientation in terms of a normalto the cutting blade 15' solver shown schematically as line 16 will be described,
edge;
more fully hereinafter, functions in such a manner that
.FIG. 3 is a schematic block diagram illustrating the
any movement of the blade 12 will cause the wiper arm
blade control system of this invention;
'
FIGQ4 is a side elevation .view, partially in section
illustrating the reference sensing device used in the con 20
trolsystem
of FIG.
3;
'
'
‘ '
'
‘
-
‘ ‘
When the blade, for example, is in a new pos1t1on
121 we see that there is produced a new projected blade
FIG; 5 is an isometric view illustrating a resolver and
angle which is represented by the line A—-C, which line
:FIG. 6 is a schematic block diagram of the electrical
is on the plane Y. It is important, therefore, that the
change in blade slope be detected and of greatest im~
25 portance is that the change in the projected blade slope
linkage coupled to the cutting blade;
'
55 to move a directly proportional amount as the pro
jected blade angle.
system;
FIG. 7 is a schematic diagram illustrating the com
angle be detected. This change in projected blade slope
is represented by the angle and it will, be ‘noted that
parator circuit used in the control system of FIG.~3;
FIGS. 8 and 8a are detailed schematic electricalcir
cuit‘drawings of the system in FIG. 6; and
:FIG. 9 is a series of voltage wave form graphs‘ illus
trating'the operation of the electrical circuit of FIG. 8.
.Sincethe road grader and its operation are well known
30
operatiou'of this mechanical feedback transducer com
prised of the wiper 55 of the'resistant element 56 will
in the art, its structureand operation will be described
only insofar asis necessary to describe the present'inven
tion. The road grader includes a vehicle frame and
a cutting blade assembly coupled to the frame. The
cutting blade assembly includes a drawbar universally
be described more fully hereinafter.
A unique feature of this invention is directed to a‘
mechanical means of indicating the true projected angle
of the blade cutting edge irrespectiveof blade location
or blade position.
gimbaled to the forward end of the vehicle frame _to
which there is connected a cutting blade. ‘The cutting
hladehas a circular gear attached thereto for rotation
the contact arm 55 has'now moved to a‘second position
551 though exactly the same angle that the projected
blade slope angle traveled through in the plane Y. e The
7
'
The problem is further complicated by the fact ‘that
4.0
ofthe blade about an axis, in a substantially vertical
grader itself may travel along a slope that may vary,
and therefore the frame itself has a varying orientation
with respect to the V. and .H axes.
plane normal to its.cutting edge. In addition, the cut
ting blade assembly ismovable relative to the frame so
that the aforementioned normal'axis rotates relative to
,
-In order. to solve the problem of obtaining the true
blade cutting angle, a mechanical resolver is coupled
to the cutting blade and rotates an actuating member in
a plane perpendicularv to the axis of motion of the ve 45 accordance ‘with the slope of the blade relative to the
hicle. ‘Thus, the cutting blade may be used on either
grader frame. The actuating member is coupled to a
' I normal road gradingor for banking theside ofa road.
rotatable member of a feedback transducer which pro->
Hydraulic means are provided for controlling the orien
tation of the cutting blade. The control system operates
vides an electrical signal representative of the actual.
blade slope angle relative to the frame. By comparing‘
this signal with a reference signal representative of the
desired cutting angle relative to the grader frame auto
to maintain the blade at a preset
‘
slope angle and eleva-v
tion irrespective of vehicle frame orientation or of blade
orientation. ,An electrical signal which is related to the
actual blade cutting angle is comparedto an electrical
signal which isrelated to the desired blade cutting angle.
The control system operates to hydraulically reposition
the blade to the desired angle thus making the, algebraic
difference between the aforementioned electrical signals
matic blade controlis possible irrespective of grader
frame orientation withrespect to the true vertical or
55
horizontal.
Detailed Description
Referring now ‘in detail to the drawingwith particular >
zero.
reference to FIG. 1 there is here illustrated a road grader
1n which an automatic blade, slope control system lem
One of the major problems in a blade slope control
system is that of obtaining the true blade cutting angle. .60 bodying the present invention has been. incorporated.
The road grader being well known in the artis notshown
Referringv to FIGURE 2, the problem will be discussed
in detail. It generally consists of a frame It} to‘ which
in terms of an actual projected blade angle. FIGURE 2
there is coupled a‘ cutting blade assembly includingria
discloses an axis F which is in the direction of travel
universally gimbaled drawbar 11 supporting a cutting
of the roadgrader frame. Intersecting the axis Fisa
vertical axis V in the direction of the earth. ' The axis F 65 blade 12. Attached to the cutting blade. is a circular
gear 13 coupled through a pinion to a motor (not shown)
and V form a vertical plane X. A horizontal or trans
for rotating the blade relative to.the ,drawbar about an
verse .axis‘ H is shown intersecting the vertical ‘axis V.
axis in a substantially .vertical plane that is normal toits;
It is therefore seen that the axis V and H form a plane
cutting edge. Thus, there is provided a normal axis vdeY, which plane intersects the plane 'X. It is this plane
?ning member in the form of circular gear .13. HyYthat schematically represents a cross section of the
draulic actuator means 14.are provided for orientating;
earth tobegraded by the controlled blade system to
be described" hereafter.
'
[There is also shown a schematic representation of a
cuttingblade 12 shown in two different positions. Con
the bladerelative tov the graderframe 10.
In. the schematic. block diagram shown in‘ FIG. 3, elece
trical transmission is shown by _.a single line, mechanical
transmission _.by_. a adashv line, v___and hydraulic. transmission '
3,026,638
6 1
ment to the input shaft 26. Potentiometer resistance
element 25 is secured to shaft 26 for rotation therewith,
thus providing reference transducer means. The poten
tiometer may, for example, be of the type manufactured
by a double line. Referring now to FIGS. 1 and 3,
there is provided a reference transducer 15 which is
mounted on the grader frame 10 and receives as inputs,
true indication of the vertical of the earth from a refer
ence sensor 20, and the desired blade slope angle with
by The Markite Corp. of New York, N.Y., designated
as their model type 2094. The shaft 26 is manually
rotatable in a pair of ball bearings 22 mounted in a
bearing support 28 which is secured to the housing 19.
An inertial mass 23‘ is suspended from a shaft 29 by
bolts 30 and brackets 31 for pivotal movement with the
shaft 29 about its axis for defining a vertical reference
respect to true vertical by a manual setting. The output
of the reference transducer 15 is an electrical signal repre
sentative of the desired slope angle relative to the grader
frame. A mechanical resolver 16 disposed between the
blade 12 and feedback transducer 17 rotates in accord~
ance with the actual projected blade cutting angle rela
axis and thus providing reference sensor means. An
tive to the frame, and is one of the unique features of
inertial mass whose weight is approximately 7.8 pounds
this invention. A feedback transducer 17 mounted on
and whose center of gravity is approximately 4.5 inches
the grader frame 10 converts the mechanical input of the
resolver into an electrical signal. This electrical sig 15 from the axis of rotation has been found to be suitable
for this application. The axis of rotation of the pendu
nal is transmitted to a comparator 18 and, compared
lum is substantially co-incidental with the longitudinal
with the electrical output signal from the reference trans
axis about which the grader frame roll-s. Brackets 31
ducer 15. The comparator 18 has an output electrical
are longitudinally resilient for allowing the pendulum
signal representative of the error between the desired
cutting angle and the projected cutting angle of the blade.
20
This error signal is transmitted to an electro-hydraulic
servo valve 19 Whose output flow goes to a hydraulic
actuator 14. The actuator moves one end of the blade
13 in the direction to cancel the aforementioned error
to displace longitudinally when subjected to longitudinal
shock loads. There is further provided, rubber pads 32
along the faces of the pendulum for absorption of shock
loads in the event that the inertial mass 23 strikes the
housing 21. The shaft 29 is supported in bearings 33
which in turn are supported by hearing support 28.
signal. Thus, the system allows continuous angular con 25 A?ixed
to one end of the shaft are two diametrically
trol irrespective of blade position relative of the frame,
spaced
damping
vanes 34 for rotation with the pendu
inclination of the frame relative to true vertical, and
lum. Two diametrically spaced stationary damping vanes
irrespective of whether the grader is performing ordi-'
35 are secured to hearing support 28 for damping the
nary slope grading or banking.
pendulum as it rotates. The casing is evacuated and
Another serious problem encountered is maintaining
?lled with damping ?uid through the holes 36 and 37
a stable control system free of oscillation and capable of
for damping the pendulum. The input shaft is sealed
achieving desired accuracy and dynamic response. The
against oil leakage by the end seal 38.
grader characteristics themselves magnify the problem.
The potentiometer contact arm 24 is affixed to one end
Basically, the grader is a mass supported on elastic mem
of the pendulum shaft 29 for rotation therewith. Con
bers. As the blade is positioned to maintain a desired 35 tact arm 24 is in sliding contact with resistance element
cutting angle it causes a reaction on the frame. The
25. Electric pick-off elements not shown are provided.
motion of the frame due to the reaction tends to cause the
for electrical connection with contact arm 24 and re-'
blade to be further repositioned. When a high gain level
sistance element 25.
'
is required in the closed loop of the servo system, the os
Referring now to FIG. 5, there is shown a novel fea
40
cillation of the frame in response to blade motion induces
ture of the present invention in the resolving means 16
a sustained oscillation of both the blade and frame, mak
coupling the cutting blade 12 to the rotatable feedback
ing the entire system unstable. Heavy damping of the
transducer 17 through feedback linkage 39‘.
reference inertial mass tends to reduce this problem, but
As shown in FIG. 5, a bracket 40 is attached to the
on the other hand, this heavy damping decreases the ac
drawbar 11 for movement therewith. A pin 41 having an
curacy of the system so that under dynamic conditions 45 axis parallel to the normal axis is a?ixed to the bracket 40.
the time for the reference inertial mass to return to a
The term parallel is also intended to include the normal
reference position is increased with the amount of damp
axis depending upon the desired location of the elements
ing. The amount of damping required also increases
in the grader. A driving member 42, for example a
with the difference between the natural frequency of the
sprocket, is mounted on pin 41 for. rotation about the
reference inertial mass and that of the grader. In the
pin axis. Driving member 42 is coupled to the cutting
present invention, a pendulum is utilized for vertical ref
blade by chain drive 43 thus there is shown a driving
erence indication. The system is stabilized with a mini
means. A ?rst pivot support including a hollow cylin
mum of pendulum damping by choosing a pendulum
drical bearing 44 having a centerline perpendicular to
whose natural frequency is substantially close to that of
the normal axis is af?xed to driving member 42 for move
the grader. Furthermore, in order to avoid excitation of ’ ment therewith. Thus there is shown a ?rst pivot sup~
the pendulum by any other oscillations of the grader the
pendulum is‘ located near the transverse axis about which
the grader rolls under operating excitations.
Referring now to FIGS. 1 and 4, a housing 21 at
tached to the grader frame 10 by means of bolts 22 con
tains the reference sensor 20 and transducer 15. Ref
erence sensor means 20 has an inertial mass 23 for de
?ning a vertical reference axis and is coupled to reference
transducer elements 24 and 25 to provide an electrical
signal representative of a desired predetermined blade
slope angle.
While there are many types of reference transducers
that may be used in this type of application such as
transformers, potentiometers, etc., the reference trans
ducer will be described in terms of a potentiometer.
The housing 21 is attached to the grader frame by
means of bolts 22. An input shaft 26 can be manually
rotated in accordance with a desired predetermined blade
slope angle. Any conventional means, such as a gear
port means. A pivot pin 45 is disposed within cylindri
cal bearing 44 with ends protruding therefrom for re
ceiving apertures of an intermediate pivot member in
cluding a yoke 46. Yoke 46 is pivotally movable relative
60
to pin 45. Thus we see there is provided intermediate
support means. A second pivot support including a hol
low cylindrical bearing 47‘having a centerline perpen
dicular to the ?rst pivot support is a?ixed to yoke 46
for movement therewith and, therefore, provides a sec
65 ond pivot support means. A pin 48 is disposed within
bearing 47 with ends protruding therefrom.
An actuating member is shown in FIG. 5. A disc 49
having tabs 50 extending perpendicularly therefrom, is
attached to yoke 46 by means of pin 48. The disc 49
70 is aligned so that a normal to the surface of the disc
passing through its center is parallel to the axis of
motion of the grader, and is rotatable in a plane perpen
dicular to the axis of motion of the vehicle. Three space
drive may be utilized to couple manual rotative move 75 links 51 are connected to disc 49 by means of ball joints
3,026,638
52 on the“ ends thereof. At opposite ends of space links
51 there is a disc 53 identical to disc 49. The space links
are connected to disc 53 by ball joints 52 not shown.
. Disc 53 is rotatable in a plane parallel to disc 49 in
response to the rotation of disc 49. A shaft 52 is keyed
to disc 53 for rotation therewith.
A contact arm 55 of
feedback transducer '17 is a?ixed to the shaft 59 for
rotation therewith. Resistance element 56 is stationary
in the respect that it does not rotate with respect to the
8
of this electrical‘ bridge is an" error signal which 'is fed
to the ampli?er 60. The ampli?ed error signal is con-v
verted and transmitted to an electro-hydraulic servo
valve 19 whose output ?'owtis proportional to the error
signal and which operates a hydraulic actuator for re
positioning the blade in direction and magnitude to bal
ance the electrical bridge circuit (thus cancelling the error
signal). Thus, the resulting cutting angle of the blade
relative to the vertical is equal to the operator’s selected
transducer housing. Thus we see that there are provided 10 angle relative to the vertical as measured by the inertial
actuating means and‘ feedback transducer means.
Although the feedback transducer 17 has been de
mass.
‘
The operation of the resolver, space linkage and feed;
back potentiometer will be, explained with reference to
scribed herein as a potentiometer other transducers may
equally be well suited. The feedback transducer 17 is
FIG. 1 and FIG. 5. As the blade rotates about a normal
. pivotally mounted by brackets 57 to the grader frame 10, 15 to its cutting edge, a chain drive rotates a sprocket 42.
and is mounted so that it may move axially and verti
The direction and magnitude of rotation of sprocket 42
cally with respect to the grader frame axis of motion.
is equal to the rotation of the blade in the plane formed
Referring now to FIG. 6, the electrical components of
by its cutting edge as it rotates.
the automatic control system consists of a direct current
For ‘purposes of explanation, we fill ?rst describe the
power supply 58, usually the 12 volt direct current
operation of the resolver if the blade were aligned so’
system available 'on' most road‘ graders, which is fed
that a normal to its cutting edge would be parallel to a
to an inverter 59, an AC ampli?er 60 and a DC.
transverse plane through the grader frame. As the'blade
ampli?er 61. From the inverter the‘ AC. signal is
12 is rotated by gear 13 sprocket 42 rotates‘, rotating yoke
transmitted to ‘an electrical bridge circuit between the
46 through pin 45. Yoke ,46 pivots about pin 48, and
‘feedback transducer, 17 and reference transducer 15 25 disc 49 does not rotate. Disc 49 is constrained by the
which provide a‘ comparator means. The output of
feedback linkage 39 ‘so that its plane of rotation is al
this electrical bridge circuit is transmitted to an alter
ways parallel to a planetransverse to the axis of mo
nating current ampli?er 60, is demodulated in the
demodulator 62 and transmittedto a direct current am
tion of the grader. Therefore, pin 48 would be aligned
so that its rotation in the tabs 50 would impart no rota
pli?er‘ 61 whose output signal is transmitted to an electro 30 tion to disc 49. It should be noted that, as the blade ro~
li'y'draulic servo‘ valve 19.
tates in this position, there is no change in the desired
‘FIG. 7 is a schematic of the electrical bridge circuit
projected‘cutting angle.
,
between the reference transducers and feedback trans
As the normal axis of the blade is rotated in‘ a plane
ducer'17. The resistance element 25 of the reference
transverse to the axis of motion of the grader, the bracket
transducer 15 ‘is connected in‘ parallel with the resistance 35 40 which is a?ixed to drawbar 1‘1 wouldbe similarly
element 56‘ of feedback transducer 17 between points 63
tilted. Sprocket 42 and bearing 44 would be tilted in a
and ground‘. An alternating current voltage is‘ supplied
like manner. Pin 45 in bearing 44 would tilt yoke 46
from the inverter 59 (shown in FIG. 6) between points
and rotate disc 49 throughrpins 48. Disc 53 would be
63 and ground in the circuit. Any error existing between
rotated by feedback links 51 in the same magnitude and
the‘ desired cutting‘ angle- ‘and actual cutting angle will
appear“ a voltage unbalance in the bridge‘circuit be
tween the reference transducer contact arm 24 and feed
back transducer contact arm55. This voltage unbalance
or error signal is picked off and fed to ampli?er?tl for
transmission to servo-valve 1,9. The servo valve operates
to correct the blade angle thereby balancing the voltage
and cancellingithe error signal.
Operation
V Referring now to FIG. 4, the operator selects a de
sired cutting angle'by rotating shaft 26 which in turn ro
fates resistance element 25. The ‘inertial mass 23 al
ways indicates true vertical and positions the contact arm
24 ofthe reference potentiometer 15 in a vertical di
rection.I_,A's_ the‘ grader frame‘ 10 rotates with respect to
true'vertic'al, the relative positions of resistance element
25 and; contact
24 changes. The reference poten
tiometer 15 has an output voltage proportional-to the op
erator’s' selected angle relative to true vertical less the
angle of'vthe frame‘relative to true vertical. Expressed
another way, the‘ output voltage is proportional to the
desired angle relative to the frame 10. This output volt
age is a command signal to the‘ angular positioning mech
anism.
’
40 direction.
The shaft 54 would rotate contact arm 55‘
relative to resistor element 56 of the feedback transducer
17.
Assume now that the normal axis of the blade was
rotated in the direction of motion and the blade'then ro-,
tated about its normal axis. Once again bracket 40 and
sprocket 42 would be tiltedyin the same manner as the
blade. When the brackets are in this position, the axis
of rotation of pin 48 and pin 41 would not be parallel.
As sprocket 42 rotates, it rotates bearing 44 which ro
tates ‘pin 45, yoke 46, bearing 47, and pin 48. Since pin
48 is constrained to rotate in the same plane as disc 49, a
cranking action takes place between pins 48 and tabs 56, '
thus rotating disc 49. The net combination of all rota
tions of disc 49 is proportional to the actual projected
blade cuttingangle relative to the grader frame.
9
s As the draw bar 11 to which the blade is attached
changes position relative to the frame, discs- 49 and 53
change their relative positions but are maintained parallel
to each other in a plane transverse to the direction of
grader travel. This is accomplished by use of gimbaled
feedback links 51 connecting .discs 49 and "59, andby
pivotal movement of feedback transducer 16 in the plane
of grader travel.
The operation of the electrical system will be described
V The cutting angle of the blade 12 relative to the frame 65 as utilizing a 12 volt battery direct current source, which
10 is derived by a mechanical resolver 16 whose opera
is common in road graders. However, the system can be,
tion will be described hereinafter. , The resolver 16 and
modi?ed to accommodate any commonly utilized electrical
‘linkage 39 rotate the‘ contact arm 55 of the feedback po
source.
tentiom'eter 17 in proportion to the projected cutting an
The positive terminal of the battery is connected to
gle of th‘e'blade [relative to thev frame. In the electrical 70 ground and the negative terminal is connected to conduc
bridge circuit shown schematically in FIG. 7, the output
tor 64 in FIG. 8. Negative 12 volts ‘is applied to the
voltage of the feedback potentiometer 17 (projected cut
center tap 65 of transformer 66. This negative voltage
ting angle relative to the‘ frame) is compared to the out
is applied to the collector leads 67 and 68 of transistors
putvoltage of. the reference potentiometer 1-5 (desired
69 and 70. For purposes of explaining the circuit opera~
cuttingiangle relative'to theiframe). The output voltage 75 tion, assume that transistor 70 is full “on” and ready to
3,026,638
10
. switch “off”.
The current in conductor 68 is now constant
and the rate of change of flux in the transformer 66 is
zero. At this time the voltage in conductor 68 is only
slightly negative‘ relative to ground and the voltage in
conductor 67 is highly negative relative to ground. When
the rate of change in flux is zero, the magnetic ?eld
.
posite one another or i.e. set at the same potential point
on the potentiometers. In the unbalanced case, current
?OWs through resistors 88 and 89 and the transformer
primary 91, which is a square wave signal whose magni
tude, depends upon the difference in voltage between the
variable arms of the transducers 15 and 17. This voltage
also has a phase angle reference of 0° or 180° in respect
to the voltage present on winding 86 of the transformer
66. The phase at 91 will be 0° or 180° depending upon
tends to make point 73 become more negative with re
which way the current ?ows through the transformer 90.
10
- spect to ground. As point 73 becomes negative, the volt
The direction of current ?ow is determined by which arm
age applied to the base of transistor 69 becomes negative.
on the transducers is more positive with respect to the
This is accomplished by the feedback network of resistors
voltage across the winding 86 on the transformer 66.
74 and 75 and capacitor 76. The capacitor 76 allows
The resistors 88 and 89 provide overload current pro
a steep switching wave front to be applied quickly to the
tection to the variable contact arms 24 and 55. In the
base of transistor 69. The negative voltage at the base
extreme unbalanced case it would be possible to draw a
of 69 turns the transistor 69 “on” even harder causing
signi?cant current from the sensor arms through the trans
more current to ?ow between points 71 and 72 causing
former primary 91. The’resistors prevent the current
a rate of change in flux in the transformer 66. This flux
from exceeding the ratings of the transducer arms.
change induces more voltage between 71 and 73 causing
From the secondary of the transformer 90, the voltage
point 73 to become more negative thus increasing the 20
is fed into the base connection of transistor 92. Trans
feedback through resistors 74 and 75. It is possible to in
former 90 provides an impedance match between the
duce a voltage between 71 and 73 greater than the 12 volts
transducer bridge and the transistor ampli?er as well as
supplied to the circuit. Diodes 77 and ‘78 are clamped
around the transformer 66 starts to collapse inducing a
voltage between points 71 and 73 of transformer 66 which
‘to the supply voltage by resistor 79 and capacitor 80,
which allows fast surges. These diodes clamp the volt
providing a means of going from a double ended circuit
(the bridge) ‘to a single ended circuit (the transistor).
Resistors 93 and 94 provide direct current bias to the
ages at 72 or 73 whenever the induced voltage 72-—71
or 71-73 tries to rise above the 12 volt supply voltage.
base of transistor 92.
the rate of change of ?ux between 71 and 72 goes to zero
alternating current signals. Without capacitor 96, the
Resistor 95 is also a transistor
biasing resistor and with resistors 93 and 94 provides
The current flow between points 71 and 72 increases
with the feedback to the base of transistor 69 through 30 direct current to transistor 92, and further provide tem
perature stability to its operation. Capacitor 96 is used
resistors 74- and 75 as long as the transformer 66 does
to minimize the degenerative effects of resistors 95 upon
not become saturated. When the transformer 66 saturates
gain at transistor 92 would be low. Resistor 97 acts as
causing the magnetic ?eld in 66 to collapse and induce
the
collector load resistor for transistor 92 and provides
a voltage in the opposite direction. At this time, point 35
direct current to the collector. The ampli?ed signal from
72 which was slightly negative as current ?owed, begins
transistor 92 is obtained at the junction of resistor 97 and
to become highly negative causing a positive feedback to
the
collector of transistor 92 with respect to ground. Ca
be applied to the base of transistor ‘70, through resistors
pacitor 98 couples the alternating current signal to the
81 and 82 and capacitor 83. This positive feedback turns
base of transistor 99 while preventing the previous col
transistor '70 “on” causing point 73 to reduce from highly
lector’s direct current voltage from biasing the base of
negative voltage to slightly negative voltage.
transistor 99. Resistors 100, 101, and 102 are direct
This positive going feedback voltage is applied to the
current biasing resistors and also supply a degree of tem
base of transistor 69 as before, tending to turnj69 “off”.
perature stability to transistors 99. The output voltage
'As 69 goes “off”, ‘72 begins becoming highly negative
of transistor 99 is supplied to the primary of transformer
and the rate of change of ?ux due to current flow between
45 103. Transformer 103 allows an impedance match from
71 and '73 causes the voltage to try to exceed -—l2 volts.
the transistor ampli?er 99 to the output stages. The
Diode 77 clamps the voltage to —12 volts as before. Point
transformer also allows the designer to proceed from
73 is becoming less negative as 70 goes “on” and 69 goes
a single ended circuit to a double ended “push-pull” out
‘Log?!’
If the voltage of 72 and 73 is observed with respect to 50 put circuit. Capacitor 1104 is used to maintain the square
shape of the signal supplied by the ampli?er. The output
ground, it will be seen to ?ip back and forth between
voltage of the input ampli?er is supplied to a half wave
—12. volts and almost 0 volts. The opposing collector
diode bridge 105 to be demodulated to a direct current
68 or 67 will ?ip from 0 to —l2 volts. The wave shape
voltage to drive the output stages. Reference voltage for
is square and the frequency of oscillation is dependent
demodulator is supplied by winding 86 of transformer
‘upon the saturation characteristics of the transformer 66, 55 the
66 through resistors 106 and 107, which limit the refer
the number of turns of the primary 72-—73, and the supply
ence current through the bridge 105. The direct current
voltage of ~12 volts.
output of the diode is either negative, positive or zero in
The square wave frequency output of the magnetically
saturating “flip—flop” is 400 cycles.
respect to ground as shown by the phase relationships
The degree to which the voltage is positive
or negative depends entirely upon the amplitude of the
signal supplied by transformer 103 to the bridge. FIG. 9
shows the output of the bridge with respect to ground
Capacitor 84 is added to the primary of the transformer 60 in FIG. 9.
66 to maintain the squareness of the waveform and min
imize the leakage inductance effects of the transformer.
Square wave voltage outputs are obtained from the
and the effect of capacitor 108 on the output.
transformer 66 by means of windings 85 and 86. Capaci
Capacitor 108 is essentially a ?lter capacitor to smooth
tor 87 keeps the output voltage of winding 85 as square (i5
the direct current pulsations as shown in FIG. 9b, and
as possible. Winding 85 supplies the signal voltage nec~
to apply a smooth bias current to transistors 109 and 110.
essary for the ampli?er, to the transducer elements 56 and
Resistors 111, 112, 113 and 114 are direct current bias
25. The amount of signal obtained from the transducers»
resistors for transistors 109 and 110. These transistors
15 and 17 depends upon the ‘position of the variable con
are biased “Class A” so that equal and opposite currents
70
tact arms 55 and 24 of the transducers. The transducers
are drawn through each half of an electrohydraulic servo
15 and 17 along with resistors 88 and 89 form a bridge
valve force motor.
network of which the primary of the transformer 90 is
When there is zero signal at the diode bridge 105 the
the load. FIG. 8a shows the bridge circuit when it is in
transistor 109 and 110 are operating quiescently and
the unbalanced state. At balance the two variable arms
24 and 55 in the transducers 15 and 17 are directly op 75 drawing equal and opposite currents through the force
3,026,638
1l"
motor 115. This causes no over all magnetic ?eld to be
generated’ by the force motor and therefore no force is
exerted on the output servov valve which is part of the
force motor 115. When a signal is applied-as in FIG. 9a,
transistor 109 is caused to conduct more heavily and
transistor 110 conducts less heavily thereby creating on
overall magnetic ?eld to be generated in the force motor
v115 of valve 19 (not shown). This ?eld causes the
servo valve to move in such a direction as to cause the
feedback transducer contact arm 55 to move in a direc
tion to balance the bridge of FIG. 8a, and cause no signal
to appear at the output of diode bridge 105. When an
error signal such as that shown in FIG. 9b is received
12
normal axis member and a ?rst pivot support. means
a?ixed thereto for providing. a pivot support axis perpen
dicular to said normal axis member, intermediate pivot
means pivotally coupled to said pivot support means for
relative pivotal ‘motion about said pivot support axis
and having second pivot support'means a?ixed thereto
for providing a second pivot support axis perpendicular
to said ?rst pivotv support axis, and an actuating means
having a member coupled to said feedback transducer
means, said actuator means being pivotally coupled to
said support means for relative pivotal motion ‘about said '
second support ‘axis whereby said actuating means is
rotated'only'in accordance With the rotation of said nor
transistor 110 conducts heavily while transistor 109 is
mal axis member in a plane perpendicular to the axis
caused to conduct less. This net change in current causes 15 of motion of said vehicle; feedback transducer means
the force motor L15 to move the servo valve in a direction
having a rotatable member coupled. to said actuating’
so that contact arm 55 balances the bridge network
means for producing a feedback electrical signal repre
shown in FIG. 8a. When the bridge is balanced no sig
sentative of the projected angle of said normal axis de—
nal appears at the output of diode bridge 105, as shown
?ning member relative to said frame in a plane perpen
in’ FIG. 90. Thus, by means of the input bridge, the 20 dicular to the axis of motion of said vehicle; comparator '
ampli?er, and the servo valve a closed loop system is
means coupled to said reference and feedback» transducer
attained whereby any error‘ caused by motion of the
means for, producing an‘error signal in accordance With ‘
road grader is immediately translated into a corrective
the algebraic sum of said reference and feedback signals;
force on the road grader blade. A servo valve of the
and electro-hydraulic valve means coupled to said by
type manufactured by Sanders Associates, Inc. of Nashua,
draulic means and responsive to said error signal for'
New Hampshire, and designated as theirlvlodel SA-24
continuously controlling the orientation of said. cutting
has been found to‘ be suitable in this application. The
blade at said desired predetermined blade slope angle.
blade is controlled by the servo valve and its position
2. An automatic blade slope control system for use
is set'by the reference potentiometer 15. Any error due
in a vehicle for road ‘grading including a vehicle frame,
to grader motion is always corrected for by feedback 30 a cutting blade assembly coupled to said frame, a cutting
transducer 17 being moved in such a direction by the
blade coupled to said assembly and rotatable about an
servo valve action on the blade as to cause the system
axis normal to its cutting edge, means for rotating said
to remain in balance. Thus, the blade is continuously
cutting blade about a normal axis de?ning member, said
maintained at the desired predetermined slope angle.
cutting blade and said normal axis member being'rotat
An additional square wave signal from winding 85
able relative to a plane perpendicular to the axis of
of transformer 66 is transmitted to the bases of transistors
motion
of said‘ vehicle, means for rotating said cutting
‘169 and 110 through resistors 116 and 117. This square
blade and normal axis member, and hydraulic means for
wave .signal is of a predetermined amplitude set by the
controlling orientation of'said cutting blade, comprising:
resistance values ,of 116 and 117. This signal is termed
reference sensor means having an inertial mass pivotal
“dither.” “Dither” is used to cause the force motor’115 40 about an axis for de?ning a vertical reference axis; ref
to vibrate the servo valve slightly at a 400 cycle per sec
ond rate. Vibrating the servo valve serves the purpose
of overcoming the static friction of the servo valve when
it is at a null position. Thus, when an error signal is
erence transducer means, coupled to said reference sensor
means for producing a reference electrical signal repre
sentative of a desired predetermined blade slope angle;
resolving‘ means coupling said cutting blade and a ‘feed
received the valve will respond immediately to the signal. 45 back transducer means, said resolving means including
There will be no delay in its response to static friction.
driving means coupled to said blade and having a member
While it has hereinbefore described what .is, at present
rotatable aboutyan axis parallel to said normal axis mem
‘ considered, a preferred embodiment of the present in
ber and a ?rst pivot support means a?ixed thereto for pro
vention, vit will be apparent to those skilled in the art
viding a pivot support axis perpendicular to said normal
.that many and various changes and modi?cations may 50 axis member, intermediate pivot means pivotally coupled
‘be made therein without departingfrom the spirit of the
to said pivot support means for relative pivotal motion
invention, and it will be understood that all and any
about said pivot support axis and having second pivot
such changes and modi?cations which fall fairly within
the scope of this invention ‘as de?ned in the appended
claims are to be considered as a part of the invention.
~What isclaimed is:
1. An automatic ‘blade slope control system for use
in .a vehicle for road grading including a vehicle frame,
a cutting blade assembly coupled to said frame a cutting
support means a?ixed thereto for providing a second
pivot ‘support axis perpendicular to said first pivot support
axis, and anactuating means having a member coupled
to said feedback transducer means, said actuator means
being pivotally coupled to said support means for relative
pivotal motion about said second support axis whereby
said actuating means is rotated only. in accordance with
blade coupledto said assembly and rotatable about an 60 the rotation of said normal axis member in a plane per
‘axisnorinal to its cutting edge, means for rotating said
pendicular to the axis of motion of said vehicle; feedback
cutting blade about a normal axis de?ning member, said
transducer means having a rotatable member coupled to
:cutting blade and said normal axis member being rotat
said actuating means for producing a feedback electrical
able relative to a plane perpendicularto the axis of motion
signal representative of the projected angle of said normal
ofsaid vehicle, means for rotating said cutting blade and 65 axis de?ning member relative to said ‘frame in a plane
normal axis member, and hydraulic means for controlling
perpendicular to the axis of motion of said vehicle‘ com
orientationiof said cutting blade, comprising: reference
,parator means coupled to said reference and feedback
:
sensor means having an inertial mass for de?ning a ver
tical reference axis; reference transducer means coupled
transducer means for producing an error signal in accord
'ance with the algebraic sum of said reference and feed
to said reference sensor means for producing a reference 70 back signals; and electro-hydraulic valve means coupled
to said hydraulic means and responsive to said error sig
electrical signal representative of a desired predetermined
blade slope angle; resolving means coupling said cutting
blade anda feedback transducer means, said resolving
means including driving means coupled to said blade and
having a member rotatable about an axis parallel to said
nal for continuously controlling the orientation of said
cutting blade at said desired predetermined blade slope
angle.
a
3. Ari-automatic blade slope control system for use
3,026,638’
13
in a vehicle for road grading including a vehicle frame,
a cutting blade assembly coupled to said frame, a cutting
blade coupled to said assembly and rotatable about an
axis normal to its cutting edge, means for rotating said
cutting blade about a normal axis de?ning member, said
cutting blade and said normal axis member being rotata
ble relative to a plane perpendicular to the axis of mo
tion of said vehicle, means for rotating said cutting blade
and normal axis member, and hydraulic means for con
trolling orientation of said cutting blade, comprising:
14
perpendicular to said ?rst pivot support axis, and an
actuating means having a member coupled to said feed
back transducer means, said actuator means being piv
otally coupled to said support means for relative pivotal
motion about said second support axis whereby said
actuating means is rotated only in accordance with the
rotation of said normal axis member in a plane per
pendicular to the axis of motion of said vehicle; feed
back potentiometer means having a rotatable member
10 coupled to said actuating means for producing a feedback
reference sensor means having an inertial mass for de?n
electrical signal representative of the projected angle of
said normal axis de?ning member relative to said frame
ing a vertical reference axis; reference transducer means,
in a plane perpendicular to the axis of motion of said
having an element coupled to said reference sensor means,
velocity;
comparator means coupled to said reference
and a second element position adjustable relative to said
vehicle frame and movable therewith in normal opera 15 transducer and feedback potentiometer means for pro
ducing an error signal in accordance with the algebraic
tion for producing a reference electrical signal propor
sum of said reference and feedback signals; and electro
tional to the relative positions of said reference sensor
hydraulic valve means coupled to said hydraulic means
and transducer means and representative of a desired pre
and responsive to said error signal for continuously con
determined blade slope angle; resolvingpmeans coupling
said cutting blade and a feedback transducer means, said 20 trolling the orientation of said cutting blade at said de
sired predetermined blade slope angle.
resolving means including driving means coupled to said
5. An automatic blade slope control system for use
blade and having a member rotatable about an axis paral- ,
in a vehicle for road grading including a vehicle frame, a
lel to said normal axis member and a ?rst pivot support
cutting blade assembly coupled to said frame, a cutting
means af?xed thereto for providing a pivot support axis
perpendicular to said normal axis member intermediate 25 blade coupled to said assembly and rotatable about an
axis normal to its cutting edge, means for rotating said
pivot means pivotally coupled to said pivot support means
cutting
blade about a normal axis de?ning member, said
for relative pivotal motion about said pivot support axis
cutting blade and said normal axis member being rotata
and having second pivot support means af?xed thereto for
ble relative to a plane perpendicular to the axis of motion
providing a second pivot support axis perpendicular to
said ?rst pivot support axis, and an actuating means hav 30 of said vehicle, means for rotating said cutting blade and
normal axis member, and hydraulic means for control
ing a member coupled to said feedback transducer means,
ling orientation of said cutting blade, comprising: refer
said actuator means being pivotally coupled to said sup
ence sensor means having an inertial mass for de?ning
port means for relative pivotal motion about said second
a vertical reference axis; reference transducer means
support axis whereby said actuating means is rotated only
in accordance with the rotation of said normal axis mem 35 coupled to said reference sensor means for producing a
reference electrical signal representative of a desired pre
her in a plane perpendicular to the axis of motion of said
determined blade slope angle; resolving means coupling
vehicle; feedback transducer means having a rotatable
said cutting blade and a feedback transducer means, said
member coupled to said actuating means for producing
resolving means including driving means coupled to said
a feedback electrical signal representative of the project
ed angle of said normal axis de?ning member relative to 40 blade and having a member rotatable about an axis paral
lel to said normal axis member and a ?rst pivot support
said frame in a plane perpendicular to the axis of motion
means a?ixed thereto for providing a pivot support axis
‘ of said vehicle; comparator means coupled to said refer
perpendicular to said normal axis member, intermediate
pivot means pivotally coupled to said pivot support means
reference and feedback signals; and electro-hydraulic 45 for relative pivotal motion about said pivot support axis
and having second pivot support means af?xed thereto
valve means coupled to said hydraulic means and respon
for providing a second pivot support axis perpendicular
sive to said error signal for continuously controlling the
to said ?rst pivot support axis, and an actuating means
orientation of said cutting blade at said desired predeter
ence and feedback transducer means for producing an
error signal in accordance with the algebraic sum of said
having a member coupled to said feedback transducer
means, said actuator means being pivotally coupled to
said support means for relative pivotal motion about said
second support axis whereby said actuating means is
cutting blade assembly coupled to said frame, a cutting
rotated only in accordance with the rotation of said nor
blade coupled to said assembly and rotatable about an
mal axis member in a plane perpendicular to the axis of
axis normal to its cutting edge, means for rotating said
of said vehicle; feedback transducer means having
cutting blade about a normal axis de?ning member, said 55 motion
a rotatable member coupled to said actuating means for
cutting blade and said normal axis member being rotata
producing a feedback electrical signal representative of
ble relative to a plane perpendicular to the axis of mo
the projected angle of said normal axis de?ning member
tion of said vehicle, means for rotating said cutting blade
relative to said frame in a plane perpendicular to the axis
and normal axis member, and hydraulic means for con
of motion of said vehicle; said reference and feedback
trolling orientation of said cutting blade, comprising: ref
transducers having their elements connected in an elec
erence sensor means having an intertial mass for de?n
mined blade slope angle,
4. An automatic blade slope control system for use
in a vehicle for road grading including a vehicle frame, a
ing a vertical reference axis; reference transducer means
trical bridge circuit for producing a voltage unbalance
error signal in accordance with the algebraic sum of said
reference and feedback signals; and electro-hydraulic
reference electrical signal representative of a desired
predetermined blade slope angle; resolving means ‘cou 65 valve means coupled to said hydraulic means and respon
sive to said error signal for continuously controlling the
pling said cutting blade and a feedback transducer means,
‘orientation of said cutting blade at said desired prede
said resolving means including driving means coupled
coupled to said reference sensor means for producing a
to said blade and having a member rotatable about an
termined blade slope angle.
port axis perpendicular to said normal axis member, in
termediate pivot means pivotally coupled to said pivot
cutting blade assembly coupled to said frame, a cutting
6. An automatic blade slope control system for use
axis parallel to said normal axis member and a ?rst pivot
support means affixed thereto for providing a pivot sup 70 in a vehicle for road grading including a vehicle frame,
, support means for relative pivotal motion about said pivot
blade coupled to said assembly and rotatable about an
axis normal to its cutting edge, means for rotating said
‘cutting blade about a normal axis de?ning member, said
support axis and having second pivot support means af
?xed thereto for providing a second pivot support axis 75 cutting blade and said normal axis member being rotata
1.
3,026,638
ble relative to a plane perpendicular’ to the axis of mo
tion of said vehicle, means for rotating said cutting blade
and normal’ axis member, and hydraulic means for con
trolling orientation of said cutting blade, comprising: ref
crence sensor means having an inertial mass for de?ning
a vertical reference axis; reference transducer means cou—
pled to said reference sensor means for producing a ref
erence electrical signal representative of a desired prede
termined blade ‘slope angle; resolving means coupling
1y coupled to said support means for reltaive pivotal mo
tion about said second support axis whereby said actuat
ing means‘is rotated only in accordance with the rotation
of said normal axis member in a plane perpendicular to
the axis of motion of said vehicle;'feedback transducer
means having a rotatable member coupled to said actuat
ing means for producing a feedback electrical signal rep
resentative of the projected angleof said normal axis
de?ning member relative to said frame in a plane per
said cutting blade and a feedback transducer means, said 10 pendicular to the axis of motion of said vehicle; com
resolving means including driving means coupled to said
parator means coupled to said reference and feedback
blade and having a member rotatable about an axis paral
transducer means for producing an error signal in ac
lel to said normal axis member and a ?rst pivot support
cordance with the algebraic sum of said reference and
means a?ixed thereto for providing a pivot support axis
feedback signals; and electro-hydraulic valve means for
perpendicular to said normal axis member, intermediate 15 varying the flow of ?uid to said hydraulic means in re
pivot means pivotally coupled’ to said pivot support means
sponse to said error signal for continuously controlling
for relative pivotal motion about said pivot support axis
the orientation of said cutting blade at said desired pre
and having second pivot support means a?lxed thereto
determined blade slope angle.
for providing a second pivot support axis perpendicular
8. An automatic blade slope control system for use
to said ?rst pivot support axis, and an actuating means 20 in a vehicle for road grading including a vehicle frame,
' having a member coupled to said feedback transducer
a cutting blade assembly coupled to said frame, a cut
means, said actuator means being pivotally coupled to
ting blade coupled to said assembly and rotatable about
said support means for relative pivotal motion about
an axis normal to its cutting edge, means for rotating
said second support axis whereby said actuating means
said cutting blade about a normal axis de?ning mem
-is.rota'ted only in accordance with the rotation of said 25 ber, sai'd cutting blade and said normal axis member be
normal axis member in a plane perpendicular to the axis
ing rotatable relative to a plane perpendicular to the axis
ofmotion of said vehicle; said actuating means having
of motion of said vehicle, means for rotating said cutting
a ?rst rotatable member coupled to said intermediate
blade and normal axis member, and hydraulic means for
pivot means, a second rotatable member coupled to said
controlling orientation of said cutting blade, comprising:
feedback transducer means and linkage means coupling 30 reference sensor means having an inertial mass for de?n
said first and second rotatable members for constraining
ing a vertical reference axis; reference electrical signal
said members for rotation about an axis parallel to the
representative of“ a desired predetermined blade slope‘
direction of travel of said vehicle; ‘feedback transducer
' means having a rotatable member coupled to said actuat
angle; resolving means coupling said cutting‘ blade and
feedback transducer means, said resolving means includ
ing means second rotatable member for producing. a feed 35 ing a pin af?xed to said cutting blade assembly havingv an
back electrical signal representative of the projected angle
of said normal axis de?ning member relative‘ to said
frame in a plane perpendicular to the axis of motion of
said vehicle; comparator means coupled to said reference
axis parallel to said normal axis de?ning member, driv
ing means coupled to said blade and having a member
rotatable about said pin axis, and a ?rst pivot support
means a?‘ix'ed thereto for providing a pivot support axis
and feedback transducer means for producing an error 40 perpendicular to said normal axis member, intermediate
signal in accordance with the algebraic sum of said refer
enceyand feedback signals; and electro-hydraulic valve
means coupled to said hydraulic means and responsive
to ‘ said error signal for continuously controlling the
orientation of said cutting blade at said desired predeter
mined blade slope angle.
7. An automatic blade slope control system for use
in a vehicle for road grading including a vehicle frame,
a cutting blade assembly coupled to said frame, a cutting
blade coupled to said assembly and rotatable about an
axis normal to its cutting edge, means for rotating said
cutting blade about a normal axis de?ning member, said
cutting blade and said normal axis member being rotata
ble relative to ‘a plane perpendicular to the axis of mo
tion of said vehicle, means for rotating said cutting blade '
andnormal axis member, and hydraulic means for con
trolling orientation of said cutting blade, comprising:
reference sensor means having an inertial mass for de?n
ing a vertical reference axis; reference transducer means
coupled to said reference sensor means for producing a
‘reference electrical signal representative of a desired
pivot means pivotally coupled to said pivot support means
for relative pivotal‘ motion about said pivot support axis
and‘having second pivot support means a?ixed thereto
for providing a second pivot support axis perpendicular
to said ?rst pivot support axis, and an actuating means
having a member coupled to said feedback transducer
means, said actuator means being pivotally coupled to said
support means for relative pivotal motion about saidv
second support axis whereby said actuating means is
rotated only in accordance with the rotation of said nor
mal axis member in a plane perpendicular to the axis
‘of motion of said vehicle; feedback transducer means
having a ‘rotatable member coupled to said actuating
means for producing a feedback electrical signal repre
sentative of the projected angle of said normal axis de?n
ing member relative to said frame in a plane perpendicu
lar to the axis of motion of said vehicle; comparator.
means coupled to said reference and feedback transducer
the‘ algebraic sum of said reference and feedback sig
nals; and electro-hydraulic valve means coupled to said
predetermined blade slope angle; resolving means cou
pling said cutting blade and a feedback transducer means,
said resolving means including driving means coupled
hydraulic means and responsive to said error signal for
to said blade and having a member rotatable about an
axis parallel to‘said normal axis member and a ?rst pivot
support means af?xed thereto for providing a pivot sup
9. An automatic blade slope control system for use in
a vehicle for road grading including a vehicle frame, a
port axis perpendicular to said normal axis member, in
termediate pivot means pivotally coupled to said pivot
.57
means for producing an error signal in accordance with
continuously controlling the orientation of said cutting
blade at said desired predetermined blade slope angle.
cutting blade assembly coupled to said frame, a cutting
blade coupled to said assembly and rotatable about an
axis normal to its cutting edge, means for rotating said
support means for relative pivotal motion about said 70 cutting blade about a normal axis de?ning member, said
‘ ‘pivot support axis and having second pivot support means
cutting blade and said normal axis member being rotat
affixed thereto for providing a second pivot support axis
able relative to a plane perpendicular to the axis of mo
perpendicular to said ?rst pivot support axis, and an
tion o‘f‘said vehicle, means for rotating said cutting blade
' actuating means having a member coupled to said feed
and normal axis member, and hydraulic‘ means for con
back'transducer means, said actuator means being pivotal
trolling orientation of said cutting blade, comprising:.
w
3,026,638
17'
reference sensor‘means having an inertial mass pivotal
about an axis‘ for‘ defining a vertical reference axis; refer
ence transducer means having an element coupled to said
reference sensor means, and a second element position
adjustable relative to said vehicle frame and movable
therewith in normal operation for producing a reference
electrical signal proportional to the relative positions of
said reference sensor and transducer means and represen
rotated only in accordance with the rotation of said nor
mal axis member in a plane perpendicular to the axis
of motion of said vehicle; feedback potentiometer means
having a rotatable member coupled to said actuating
means for producing a feedback electrical signal repre
sentative of the projected angle of said normal axis de?n
ing member relative to said frame in a plane perpendic
ular to the axis of motion of said vehicle; comparator
tative of a desired predetermined blade slope angle; re
solving means coupling said cutting blade and a feed
back transducer means, said resolving means including
means coupled to said reference transducer and feedback
potentiometer means producing an error signal in accord
ance with the algebraic sum of said reference and feed
driving means coupled to said blade and having a mem
ber rotatable about an axis parallel to said normal axis
member and a ?rst pivot support means af?xed thereto
to said hydraulic means and responsive to said error
back signals; and electro-hydraulic valve means coupled
signal for continuously controlling the orientation of said
for providing a pivot support axis and perpendicular to 15 cutting blade at said desired predetermined blade slope
angle.
said normal axis member, intermediate pivot means piv
11. An automatic blade slope control system for use
otally coupled to said pivot support means for relative
in a vehicle for road grading including a vehicle frame, a
pivotal motion about said pivot support axis and having
cutting blade assembly coupled to said frame, a cutting
second pivot support means a?ixed thereto for providing
blade coupled to said assembly and rotatable about an
a second pivot support axis perpendicular to said ?rst
axis normal to its cutting edge, means for rotating said
pivot support axis, and an actuating means having a
cutting blade about a normal axis de?ning member, said
member coupled to said feedback transducer means, said
cutting blade and said normal axis member being rotat
actuator means being pivotally coupled to said support
able relative to a plane perpendicular to the axis of mo
means for relative pivotal motion about said second sup
port axis whereby said actuating means is rotated only in 25 tion of said vehicle, means for rotating said cutting blade
and normal axis member, and hydraulic means for con
accordance with the rotation of said normal axis member
trolling orientation of said cutting blade, comprising:
in a plane perpendicular to the axis of motion of said
reference sensor means having an inertial mass for de?n
vehicle; feedback transducer means having a rotatable
ing a vertical reference axis; reference transducer means,
member coupled to said actuating means for producing a
feedback‘ electrical signal representative of the projected 30 having an element coupled to said reference sensor
means, and a second element position adjustable relative
angle of said’ normal axis de?ning member relative to
to said vehicle frame and movable therewith in normal
said frame in a plane perpendicular to the axis of motion
operation for producing a reference electrical signal pro
of said vehicle; comparator means coupled to said refer
portional to the relative positions of said reference sensor
ence and feedback transducer means for producing an
error signal in accordance with the algebraic sum of said 35 and transducer means and representative of a desired
predetermined blade slope angle; resolving means cou
reference and feedback signals; and electro-hydraulic
pling said cutting blade and a feedback transducer means,
said resolving means including driving means coupled to
said blade and having a member rotatable about an axis
orientation of said cutting blade at said desired predeter
40 parallel to said normal axis member and a first pivot sup
mined blade slope angle.
port means af?xed thereto for providing a pivot support
‘ 10. An automatic blade slope control system for use
axis perpendicular to said normal axis member, inter
in a vehicle for road grading including a vehicle frame,
mediate pivot means pivotally coupled to said pivot sup
a cutting blade assembly coupled to said frame, a cutting
port means for relative pivotal motion about said pivot
blade coupled to saidv assembly and rotatable about an
axis normal to its cutting edge, means for rotating said 45 support axis and having second pivot support means
af?xed thereto for providing a second pivot support axis
cutting blade about a normal axis de?ning member, said
perpendicular to said ?rst pivot support axis, and an ac
‘cutting blade and said normalraxis member being rotat
mating means having a member coupled to said feedback
‘able relative to a plane perpendicular to the axis of mo
transducer means, said actuator means being pivotally
tion of said vehicle, means for rotating said cutting blade
and normal axis member, and hydraulic means for con 50 coupled to said support means for relative pivotal motion
valve means coupled to said hydraulic means and respon
sive to said error signal for continuously controlling the
trolling orientation of ‘said cutting blade, comprising:
about said second support axis Wherebysaid actuating
reference sensor means having an inertial mass for de?n
ing a vertical reference axis; reference transducer means,
having an element coupled to said reference sensor means,
axis of motion of said vehicle; feedback potentiometer
means is rotated only in accordance with the rotation of
said normal axis member in a plane perpendicular to the
and a second element position adjustable relative to said 55 means having a rotatable member coupled to said actuat
ing means for producing a feedback electrical signal rep
vehicle frame and movable therewith in normal operation
resentative of the projected angle of said normal axis
for producing a reference electrical signal proportional to
de?ning member relative to said frame in a plane per
the relative positions of said reference sensor and trans
pendicular to the axis of motion of said vehicle; said
ducer means and representative of a desired predeter
mined blade slope angle; resolving means coupling said 60 reference transducer and feedback potentiometer having
their elements connected in an electrical bridge circuit
for producing a voltage unbalance error signal in accord
ance with the algebraic sum of said reference and feed
cutting blade and a feedback transducer means, said re
solving means including driving means coupled to said
blade and having a member rotatable about an axis par
allel to said normal axis member and a ?rst pivot support
back signals; and electro-hydraulic valve means coupled
means a?ixed thereto for providing a pivot support axis 65 to said hydraulic means and responsive to said error signal
perpendicular to said normal axis member, intermediate
pivot means pivotally coupled to said pivot support means
for relative pivotal motion about said pivot support axis
and having second pivot support means af?xed thereto
for providing a second pivot support axis perpendicular 70
to said ?rst pivot support axis, and an actuating means
having a member coupled to said feedback transducer
means, said actuator means being pivotally coupled to
said support means for relative pivotal motion about said
second support axis whereby said actuating means is
for continuously controlling the orientation of said cutting
blade at said desired predetermined blade slope angle.
12. An automatic blade slope control system for use
in a vehicle for road grading including a vehicle frame,
a cutting blade assembly coupled to said frame, a cutting
blade coupled to said assembly and rotatable about an axis
normal to its cutting edge, means ‘for rotating said cutting
blade about a normal axis de?ning member, said cutting
blade and said normal axis member being rotatable rela
75 tive to a plane perpendicular to the axis of motion of
19
3,026,638
said vehicle, means for rotating said cutting blade and
normal axis member, and hydraulic means for controlling
, orientation of said cutting blade, comprising: reference
sensor means having an inertial mass for de?ning a ver
tical reference axis; reference transducer means, having
20
‘’
about ‘said pivot support axis and having second pivot
support means a?ixed thereto for providing a second pivot
support axis perpendicular to said ?rst pivot support axis,
and an actuating means having a member coupled to said
feedback means, said actuator means being pivotally
an element coupled to said reference sensor means, and
coupled to said support means for relative pivotal mo
a second element position adjustable relative to said ve
tion about said second support axis whereby said actuat
hicle frame and movable therewith in normal operation
ing means is rotated only in accordance with the rota
for producing a reference electrical signal proportional
tion' of said normal axis member in a plane perpendicular
to the relative positions of said reference sensor and trans 10 to the axis of motion of said vehicle; said actuating means
ducer means and representative of a desired predeter
having a ?rst rotatable member coupled to said inter
mined blade slope angle; resolving means coupling said
mediate pivot means, a second rotatable member coupled
cutting blade and a feedback transducer means, said re
to said feedback transducer means and linkage means
solving means including driving means coupled to said
coupling said ?rst and second rotatable members for
blade and having a member rotatable about an axis paral 15 constraining said members for rotation about an axis
lel to said normal axis member and a ?rst pivot support
means a?ixed thereto for providing a pivot support axis
perpendicular to said normal axis member, intermediate
parallel to the direction of travel of said vehicle; feed“
pivot means pivotally coupled to said pivot support means
ducing a feedbackclectrical signal representative of the
back transducer means having a rotatable member coupled
to said actuating ‘means second rotatable member for pro;
' for relative pivotal motion about said pivot support axis 20 projected angle of said normal axis de?ning member
and having second pivot support means affixed thereto
relative to said frame in a plane perpendicular to the
for providing a second pivot support axis perpendicular to
axis of motion of said vehicle; comparator means coupled
said ?rst pivot support axis and an actuating means having
to said reference and feedback transducer means'for
a member coupled to said feedback transducer means,
producing an error signal in accordance with the algebraic
said ‘actuator means being pivotally coupled to said sup 25 sum of said reference and feedback signals; and eleetroe
port means for relative pivotal motion about said second
hydraulic valve means coupled to said hydraulie‘means‘
support axis whereby said actuating means is rotated only 7 and responsive to said error signal for continuously corn"-~
in accordance with the rotation of said normal axis mem
trolling the orientation of said cutting blade at said dea
ber in a plane perpendicular to the axis of motion of
sired predetermined blade slope angle.
said vehicle; said actuating means having a ?rst rotatable 30
14. An automatic blade slope control system for use in
member coupled to said intermediate pivot means, a
a vehicle for road grading including va vehicle frame, a
second rotatable member coupled‘ to said feedback trans
ducer means and linkage means coupling said ?rst and
second rotatable members constraining said members for
rotation about an axis parallel to the direction oftravel
of said vehicle; feedback potentiometer means having a
cutting blade assembly coupled to said frame, a. cutting
blade coupled to said assembly and rotatable about an
axis normal to_its cutting edge, means for rotating said
cutting blade about a normal axis de?ning member, said
cutting blade and said normal axis member being rdt'titable
rotatable member coupled to said actuating means sec
relative to a plane perpendicular to the axis of motion at
ond rotatable member for producing a feedback electrical
said vehicle, means for rotating‘ said cutting blade and
signal representative of the projected angle of said nor
normal
axis member, and hydraulic means for controlling
mal axis de?ning member relative to said frame in a plane 40 orientation of said cutting blade, comprising: reference
perpendicular to the axis of motion of said vehicle; said
sensor means having an inertial mass for de?ning a ver-'
reference transducer and feedback potentiometer having
'tical
reference axis; reference transducer means coupled
their elements connected in an electrical bridge circuit
to said reference sensor means for producing‘ a reference
for producing a voltage unbalance error signal in ac
electrical signal representative of a desired predetermined
cordance with the algebraic sum of said reference and
blade
slope angle; ‘resolving means coupling said cutting
45
feedback signals; and electro-hydraulic valve means cou
blade
and a feedback transducer means, said vresolving
pled to said hydraulic means and responsive to said error
means including a pin a?ixedto said‘cutting blade as
signal for continuously controlling the orientation of said
cutting blade at said desired predetermined blade slope
angle.
sembly having an axis parallel to said normal axis de=
' ?ning member, driving means coupled to said blade and
50 having a member rotatable about said pin axis and a
13. An automatic blade slope control system for use
?rst pivot support means af?xed thereto fer '"roviding a
in a vehicle for road grading including a vehicle frame,
pivot support axis perpendicular to said norma axis meme
a cutting'blade assembly coupled to said frame, a cutting
ber, intermediate pivot means pivotally coupled to said
blade coupled to said assembly and rotatable about an
pivot support means for relative pivotal motion about
axis normal to its cutting’ edge, means for rotating said 55 said pivot support axis and having second pivot support
cutting blade about a normal axis de?ning member, said
means a?ixed thereto for providing a second pivot sup‘-‘
cutting blade and said normal axis member being ro
tatable relative to a plane perpendicular to the axis of
port axis perpendicular to said ?rst pivot support axis,
and an actuating means having a member coupled to said
motion of said vehicle, means for rotating said cutting
‘feedback transducer means, said actuator means being
blade and normal axis member, and hydraulic means 60 pivotally coupled to said support means for relative pivotal
for controlling orientation of said cutting blade, com
motion about said second support axis whereby said ac‘;
prising: reference sensor means having an inertial mass
tuating means is rotated only in accordance with the
for de?ning a vertical axis; reference transducer means
rotation of said normal axis member in a plane perpen
coupled to said reference sensor means ‘for producing a
dicular to the axis of motion of said vehicle; said actuating
reference electrical signal representative of a desired pre 65 means having a ?rst rotatable member coupled to said
determined blade slope angle; resolving means coupling
intermediate pivot means, a second rotatable member
said cutting blade and a feedbackgtransducer means, said
coupled to said feedback transducer means and linkage
resolving means including a pin af?xed to said cutting
means coupling said ?rst and second rotatable members
blade assembly having an axis parallel to said normal axis
for constraining said members for rotation about an axis
de?ning member, driving means coupled to said blade 70 parallel to the direction of travel of said vehicle; feed
and having a member rotatable about said pin axis and a
back potentiometer means having a rotatable member
?rst pivot support means a?ixed thereto for providing a
coupled to said actuating means second rotatable meme
pivot support axis perpendicular to said normal axis
her for producing a feedback electrical signal representa-'
member, intermediate pivot means pivotally coupled to
tive of the projected angle of said normal axis de?ning
said pivot support means for relative pivotal motion 75 member relative to said ‘frame in a plane perpendicular‘
3,026,638
21
22
solving means coupling said cutting blade and a feedback
to the axis of motion of said vehicle; comparator means
coupled to said reference and feedback transducer means
for producing an error signal in accordance with the al
gebraic sum of said reference and feedback signals; and
electro-hydraulic valve means coupled to said hydraulic
means and responsive to said error signal for continuously
transducer means, said resolving means including a pin af
?xed to said cutting blade assembly having an axis parallel
to said normal axis de?ning member, driving means
coupled to said blade and having a member rotatable about
said pin axis and a ?rst pivot support means affixed thereto
for providing a pivot support axis perpendicular to said
controlling the orientation of said cutting blade at said
normal axis member, intermediate pivot means pivotally
desired predetermined blade slope angle.
coupled to said pivot support means for relative pivotal
15. An automatic blade slope control system for use
in a vehicle for road grading including a vehicle frame, 10 motion about said pivot support axis and having second
pivot support means affixed thereto for providing a sec
a cutting blade assembly coupled to said frame, a cut
ond pivot support axis perpendicular to said ?rst pivot
ting blade coupled to said assembly and rotatable about
support axis, and an actuating means having a member
coupled to said feedback transducer means, said actuator
an axis normal to its cutting edge, means for rotating
said cutting blade about a normal axis de?ning member,
means being pivotally coupled to said support means for
said cutting blade and said normal axis member being
rotatable relative to a plane perpendicular to the axis of
motion of said vehicle, means for rotating said cutting
relative pivotal motion about said second support axis
whereby said actuating means is rotated only in accord
ance with the rotation of said normal axis member in a
blade and normal axis member, and hydraulic means for
plane perpendicular to the axis of motion of said vehicle;
controlling orientation of said cutting blade, comprising:
reference sensor means having an inertial mass for de?n 20 said actuating means having a ?rst rotatable member
coupled to said intermediate pivot means, a second rotata
ble member coupled to said feedback transducer means and
linkage means coupling said ?rst and second rotatable
reference electrical signal representative of a desired pre
members for constraining said members for rotation about
determined blade slope angle; resolving means coupling
said cutting blade and a transducer means, said resolving 25 an axis parallel to the direction of travel of said vehicle;
feedback potentiometer means having a rotatable mem
means including driving means coupled to said blade and
ber coupled to said actuating means second rotatable
having a member rotatable about an axis parallel to said
member for producing a feedback electrical signal rep
normal axis member and a ?rst pivot support means
resentative of the projected angle of said normal axis
affixed thereto for providing a pivot support axis perpen
dicular to said normal axis member, intermediate pivot 30 de?ning member relative to said frame in a plane per
pendicular to the axis of motion of said vehicle; said
means pivotally coupled to said pivot support means for
ing a vertical reference axis; reference transducer means
coupled to said reference sensor means for producing a
reference transducer and feedback potentiometer hav
relative pivotal motion about said pivot support axis and
ing their elements connected in an electrical bridge circuit
having second pivot support means a?ixed thereto for
for producing a voltage unbalance error signal in accord
providing a second pivot support axis perpendicular to
said ?rst pivot support axis, and an actuating means hav 35 ance with the algebraic sum of said reference and feed
back signals; and electro-hydraulic valve means for vary
ing a member coupled to said feedback transducer means,
ing the flow of ?uid to said hydraulic means‘ in response
said actuator means being pivotally coupled to said sup
to said error signal for continuously controlling the orien
port means for relative pivotal motion about said second
support axis whereby said actuating means is rotated only ' tation of said cutting blade at said desired predetermined
blade slope angle.
in accordance with the rotation of said normal axis mem—
her in a plane perpendicular to the axis of motion of
said vehicle; feedback transducer means having a rotat
able member coupled to said actuating means for pro
17. An automatic blade slope control system for use
in a vehicle for road grading; including a vehicle frame,
a cutting blade assembly coupled to said frame, a cutting
blade coupled to said assembly, a vertical reference sensor
ducing a feedback electrical signal, representative of the
projected angle of said normal axis de?ning member rela 45 ?xedly mounted with respect to the frame, a reference
transducer operatively connected to said vertical sensor
tive to said frame in a plane perpendicular to the axis of
and producing a signal representative of the desired
motion of said vehicle; said reference and feedback trans
slope angle relative to said frame, resolving means, feed
ducers having their elements connected in an electrical
back transducer means, said resolving means intercon
bridge circuit for producing a voltage unbalance error
signal in accordance with the algebraic sum of said refer 50 necting said blade and said feedback transducer means to
drive said feedback transducer means through an angle
ence and feedback signals; and electro-hydraulic valve
directly linearly proportional to an actual projected blade
means for varying the ?ow of ?uid to said hydraulic
‘angle relative to said frame in all positions of said tool,
means in response to said error signal for continuously
controlling the orientation of said cutting blade at said
desired predetermined blade slope angle.
55
16. An automatic blade slope control system for use
in a vehicle for road grading including a vehicle frame, a
said feedback transducer producing a signal indicative of
said projected blade cutting angle relative to said frame,
a comparator, said comparator simultaneously receiving
said reference transducer signal and said feedback trans
ducer signal and having an output error signal repre-.
sentative of the algebraic sum of the signals received, an
cutting blade assembly coupled to said frame, a cutting
blade coupled to said assembly and rotatable about an
axis normal to its cutting edge, means for rotating said 60 electro-hydraulic valve, said electro-hydraulic valve being
controlled by said comparator output signal, a hydraulic
cutting blade about a normal ‘axis de?ning member, said
actuator connected to said electro-hydraulic valve and
cutting blade and said normal axis member being rotat
operated thereby in response to said comparator output
able relative to a plane perpendicular to the axis of motion
error signal, said hydraulic actuator being drivingly con
of said vehicle, means for rotating said cutting blade
and normal axis member, and hydraulic means for con 65 nected to one end of the said blade whereby there is
established continuous linear angular control of said blade
trolling orientation of said cutting blade, comprising:
irrespective of its position relative to the frame.
reference sensor means having an inertial mass pivotal
18. An automatic tool slope control system, including:
about an axis for de?ning a vertical reference axis; refer
ence transducer means, having an element coupled to
said reference sensor means, and a second element posi 70
tion adjustable relative to said vehicle frame and mov
a vertical frame,
able therewith ‘in normal operation for producing a refer
ence electrical signal proportional to the relative positions
a vertical reference sensor ?xedly mounted with respe t
of said reference sensor and transducer means and repre
sentative of a desired predetermined blade slope angle; re 75
a tool assembly coupled to said frame,
a tool coupled to said assembly,
to the frame,
‘a reference transducer operatively connected to said
vertical sensor and producing a signal representa
3,026,638
7
23
24
'
tive of the desired slope angle; relative to: said frame,
resolving means,
said resolving means interconnecting-said tool and said
thereby invresponse to said comparator output signal,
said actuator being drivingly connected to one end of
said tool whereby there is established continuous
feedback transducer means to drive said feedback
linear angular control of said tool irrespective of its
position relative to the frame.
transducer means through an angle directly linearly.
proportional to an actual projected tool. angle rela
tive to said frame in all positions of said tool,
said feedback transducer producing a signal indicative
of said projected tool angle relative to said frame,
References Cited in the ?le of this patent
UNITED. STATES PATENTS
2,766,731
2,902,979
2,904,911
2,905,878
2,929,362
2,931,965
Brandes ______________ __ ‘Oct. 16,
Gurries et a1. __________ __ Sept. 8,
Colee _______________ __ Sept. 22,
Olson _______________ __ Sept. 22,
Hayner __________ ____..__ Mar. 22,
Bell __________________ __ Apr. 5,
said valve being controlled by said comparator output
2,941,319
Beemer _____ __"__, _____ __ June 21, 1960‘
an, actuator connected to said valve and operated
537,077
vItaly ________________ __ Dec. 15, 1955
a comparator,
said comparator simultaneously receiving said reference
transducer signal and said feedback transducer sig
10
nal and having an output error signal representative
of the algebraic sum of the signals received,
a valve,
1,5
signal,
1956
1959
1959
1959
1960
1960
FOREIGN PATENTS
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