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Патент USA US3080013

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March 5, 1963
c. H. DENKER
3,080,003
CONTROL FOR HYDRAULIC SYSTEM
Filed May 3, 1960
4 Sheets-Sheet 1
March 5, 1963
- c. H. DENKER
3,080,003
CONTROL FOR HYDRAULIC SYSTEM
4 Sheets-Sheet 2
Filed May 3, 1960
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March 5, 1963
cfi-l. DENKER
3,080,003
CONTROL FOR HYDRAULIC SYSTEM
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. Man}! 5, 1963
c. H. DENKER
3,080,003
CONTROL FOR HYDRAULIC SYSTEM
Filed May 3, 1960
4 Sheets-Sheet 4
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Patented Mar. 5, 19%3
2
3,089,903
CQNTRGL BOB HYDRAEHJIC SYSTEM
Heretofore it was thought desirable to allow free ?ow
of ?uid through the check valve controlling ?uid ?ow
.
Chester H. Banker, fapiilion, Nebrn, assignor to sun
Chalmers Manufacturing Company, Milwaukee, Wis.
Filed May 3, 196%, der. No. 26,574
4 Qlaims. (Ci. 1'72—9)
This invention relates to hydraulic systems for tractors
and is more particularly concerned with the control mech
anism for such systems.
Heretofore, implements have been lifted by hydraulic
actuators under the selective control of an operator upon
movement of a control valve to apply pressure to the
hydraulic actuator. Also heretofore a load sensitive hy
draulic control mechanism has been employed wherein
the hydraulic actuator employed to lift a towed implement
is subjected to increased iiuid pressure upon increase in
implement draft load. Previous systems have employed
from the lift ram when the tractor hydraulic system was
adjusted for automatic weight transfer operations. How
ever, it was found that upon traversing short lengths of
low draft, such as when traversing a few feet of loose
sandy soil in an otherwise packed type soil, the control
valve would permit rapid draining of ?uid from the ram
through the check valve permitting the implement to lower
excessively and then when the tool encountered a packed
section of earth the ram would lift the tool excessively.
This caused what is known in the art as a hunting action
which resulted in an undesirable undulating of the bottom
depth of penetration of the soil by the tool. The bottom
of a plowed furrow, for instance, would have a wavy or
washboard contour.
It has been found that this undulating or hunting of the
tool can be satisfactorily minimized by placing the check
valve controlling flow from the lift mm in a flow restrict
sure ?uid is diverted to sump upon the pressure in the 20 ing position. Accurate positioning of the lowering valve
was found to be desirable to effectively combat the hunt
actuator reaching a predetermined value. Once the un
ing tendency of the previous automatic weight transfer
loading valve opens, ?uid at a lower pressure will main
system. It was found that the restricted lowering rate for
tain the unloading valve open so that ?uid ?ows to sump
(lowering the implement to the ground was a satisfactory
at a lower pressure than was required to open the un
restriction to ?uid ?ow from the lift ram during auto
loading valve.
an unloading valve whereby the major portion of the pres
Heretofore a spring ‘loaded dashpot has been employed
matic weight transfer operation of the tractor and im
at one end of the control valve. Such a motion retarding
plement.
device prevents rapid movement of the control valve.
Heretofore a positive hand control linkage has been uti
Also by use of the restricted ?ow position of the lower
ring valve during weight transfer the pressure in the lift
lized to move the main control valve to an implement
ram will not suddenly diminish when a slippery spot is
raising position against the biasing action of the dashpot.
encountered. When a slippery spot is traversed weight
transfer from the implement to the tractor driving wheels
is desired. The slippery condition however causes loss of
traction and thereby loss of drawbar pull. Upon reduc
If the operator moved the control valve too rapidly to a
full lift position, the pressure surges would sometimes be
so great the ‘unloading valve would open. Once opened
the unloading valve would remain open until a rather low
closing pressure was reached.
Also the operator often desires to quickly place the lift
and lower hand control in an implement raising position
so as to free his hand so employed for steering or other
functions. If he must keep his hand on the hand control
lever and slowly move the control lever to an implement
tion of drawbar pull the weight transfer linkage permits
the control valve to move to an implement lowering posi
tion thereby reducing pressure in the lift ram. However,
with a restricted lowering position of the lowering valve,
ram pressure is slowly reduced and usually sufficient lift
ing force is exerted on the implement to transfer enough
weight to the rear wheels of the tractor to enable the trac
raising position, it can be appreciated that the operator
is inconvenienced in not having the hand ‘available during
such time for other operations. Often the operator is
tor to successfully pull the implement through short dis
to reduce speed and turn the steering wheel at approxi~
tractor which avoids the hereinbefore described di?icul
ties.
tances of poor traction.
It is an object of this invention to provide an improved
at the end of the ?eld and must operate the hand throttle 45 lift-lower linkage for a hydraulic control system for a
matcly the same time as he operates the lift and lower
control lever. Further, it has been found that the dash
pot offers an undesira le feeling of resistance to the oper
ator with the heretofore employed positive lift and lower
hand control linkage.
Another problem heretofore existing in relation to the
lift and lower hand control was that of providing suitable
indexing for a restricted lowering of the implement.
Manufacturing tolerances made it difficult to coordinate
a predetermined position of the valve for lowering the
implement with a predetermined position of the hand
control lever. Further, it was di?icult to provide an accu
rate setting of the separate lowering valve for the different
weights of implements that might be mounted on the trac
It is a further object of this invention to provide a re
silient connection in the control linkage whereby the hand
control member may be quickly placed in its lift position
without suddenly overcoming the resistance offered by
the dashpot on the control valve.
it is a further object of this invention to provide an
improved hand control linkage for the lift and lower func
tion of the hydraulic system wherein the main control is
assured of a gradual opening from its implement lowering
position to a full implement lifting position so as to avoid
sudden surges of oil which would result in unloading the
system and in dropping the implement rather than rais
ing it.
tor. It can be ap reciated that a different weight of im
It is a further object of this invention to provide a re
and light implement or different rates of lowering for
"implements of the same weight. For instance, it is usually
t is a further object of this invention to permit the
operator to quickly place the lift and lower lever in an
silient member in the hand control lift and lower linkage
plement would produce di?erent rates of lowering when
which will prevent distortion or breakage of the linkage
the check valve for lowering the implement is placed in a
due to the operator using rute force to move the hand
predetermined position of fluid restriction. Accordingly,
vvit has been desired to provide adjusting means for allow 65 control lever quickly against the biasing action of the
dashpot employed on the main control valve.
ing, for instance, the same rate of lowering for a heavy
desirable to lower a cultivator quickly into the ground,
implement lift position without causing the unloading
whereas a planter should be lowered slowly so as to
valve to open.
avoid clogging of the seed channeling spout.
It is a further object of this invention to provide an
3,080,003
4..
adjustable linkage whereby the operator may adjust the
sage 58 but instead it is forced to pass through the check‘
lowering valve to a desired rate of implement lowering
to correspond to a predetermined position of the manu
valve 59 and conduit 61 to the ram 21. Upon further
movement of the spool 54 to the left a land 62 will block
allyoperated lift and'lowerlever.
the port 63 in the bore 56 thereby causing the pump 18
to supply fluid through its‘check valve 64 to the pressure
~' 7
~
It'isa' further object of this invention to provide a- con»
trol link-age for the lowering valve of the hereinbefore ‘de
scribed system wherein a restricted rate of 'loweringcan'
manifold 66.
As draft load'b'ecomes even greater, the
valve spool 54 is moved further to the left, causing'the
bee?ected during weight transfer operatiouthereby pre
land'68 to close port 69 in the valve bore 56 and-this
causes pump'17 to supply ‘oil through its check valve 71
weight transfer during short intervals of 'poor'tra'ctlon. 10 to the pressure manifold 66‘. Upon'further increases in
It-is a further, object'of'this invention to provide a'liftv
draft thevalvespool 54 moves even further to the left
and land 72.blocks port 73in thevalve bore 56' thereby‘
andelower linkagelfor a tractor hydraulic control‘ system
venting. undulating depth of’ said‘ working.‘ and. loss'of
ofthe automaticweight transfer type whichlias a; resilient
causing the ?uid‘pumped'b'y pump 16 to be supplied
connection which is‘selectively, adjustable to effect aldel
sired rate» of implement lowering.
These’and‘other'objects andiadvanta'ge's! of this iiiven'a
tion will become rapparentito technicians in the art‘ when‘
the following description islreadlini conjun‘cuon‘with the
, through. check valve 74 to the pressure manifold'??i Pres
sure ?uid inthe manifold 66 ?ows through the" check
drawings in which:
66, anunloadirlg valve mountedo-n' the ti'actor‘will'ldi
Thi-‘siunloadingv valve:
811 is connected ‘through a‘ passage 82' to‘ the‘ pressure:
manifold -66l Wheii the pressure in" chamber ‘8311f ‘the
unloading'valve' ‘81 I eiiceeds'a predetermined value, check"
valve 84" is moved oh its vseat compressing springs?
which biases'spool 87 against ithelball check valve‘i'84.‘:
Upon the ball ‘84' moving off itssea't; a‘lar'ger area of.
spool-87 is' exposed to the'high' pressure and is quickly'
moved-to the right against an abutment 89. In this po-T
valve’Fé. to passage 77' thence through‘ check valve 59"
tothe ram‘ supply conduit 61'.
If excessive pressure‘ develop in the pressure manifold“
FIG. 1 is a side view of a farm tractoria'ndmouiited' 20 vert the pressure ?uid to? sump.‘
plow-v in which this" invention is incorporated‘;
FIG. Z‘iSPa'Ver'ticalsectionI takehlongitudinallyof the"
tractor; '
FIG: 3 is a sectiont‘akeri alongthei lines III->111 of‘
FIG. 2; 1
FIG. 4' is'a section- t'ak'en'“ along"the"lines'IV’-"—IV of;
1:16.723’;~
_
_
V
w
‘
FIG. 57is a view t'ak'en'along the lines‘ V-—V in FIG. 3;
FIG; 6 is a section view taken along‘the lines‘VI-VI"
sition ?uid flows from the-chamber 83 through the port‘
30 91,;passa'ge' 92in the spool v87 thence‘ throughian annu
in FIG. 5;
FIG. 7 is a view taken along ‘the section line VIIL-VIIi
lar groove 93 to exhaust passage 94,‘ which is open to‘
sump; Passage 96 is also open to sump.
FIG. 8 is a‘se'ction vie'w'take n'along the'lines VIII'—
The lowering control valve in the form of check valve;
VIII of FIG‘. 7; and
‘
,
59‘is employed to control the?ow of ?uid from the ram‘
FIG. 9" is a‘ section’ taken" alongjth'e‘ lines IX--I_X of’ 35 21 to sump,‘ The check valve 59 includes a ball‘seat
FIG. 2 with the'unloadin'gvalve' shown schematically;
ing member 97. having a cylindrical bore 98 and a frusto
Referrin'git'o FIGS.‘ 1, land 3 a farm tractor'll has a‘
conical seating surface 99 atone endof the bore 98. A
hydraulic system 12'includin‘gi control valve means 11?;v
ball 101 has a loose ?t in bore 98' permitting; ?uidlto ?ow'f
for-controlling‘ men-ow of ‘?uid supplied‘ by pumps 16',
with restriction between the, ball 101 and the bore98l
17,‘ 18‘; 19 to the'hy'draulic actuator, in‘ the‘ form of a 40 When the ball, is, near its seat' 99‘ the coaction of‘ the
ram 21 pivotally connected‘ to the interior of the rear
spherical surface of the ball 1011 and (the seat 99'willbe
transmission housing '22; and‘for‘controlling ‘?ow of ?uid
from/the ram 21 to‘the' sump‘ 23,1which is th‘e'lower' part
to e?‘ect a second area of restriction to.-the ?ow of’?uid"
to'crahk arms‘28'which'are'secured'for rotation withia'
independently of the weight transfer linkage lever 49.?‘
from‘ the ram to‘ sump; Aplunger 162 is movableby a;
of the torqu‘e't'ube 242 r
p
p
_
lever 103. secured‘ for rotation with a rod 104‘. The
45
A plow 26 is’ con'nectedthroughfa pair’of lift links 27
other end of lever 103i is engag'eable with the spool: 54*
rock shaft 29 to which an arm 31 is‘ secured‘ on they
interior ofv the rear casing 32. The arm 31 is pivotally.
The position of the ball 101 as shown in FIG. 9Frnay
be considered the position‘ of. minimum restriction of‘
con‘nected‘to the r'od'rend'of the ram‘ 21; The draft bar
iiuid?ow from the ram to sump, thus giving a slow im
33’ of‘the’plow'is pivotally’connecte‘d’ to a draw bar 34 50 plement descent. As the ball is permitted to move. to
which isppivotally connected ‘at its upper end to the hous
the right by movement of lever 103, the restriction‘ to
ing 22; The lower end of drawbar" 34 is pivotally con
fluid‘ flow fromv the ram 21_to- sump increases. When
nected to the'automatic weight transfer linkage‘36. The
the‘ ball 101 reaches a position nearly seating on its‘ seat
weight transfer linkage‘36 adjusts the position of a' con
99 the restriction to ?ow will be very great‘ and a very,
. trol valve which‘ controls the pressure in ram 21. A link 55 slow rate of implement descent is available. Although‘
37 is connected to lever arm 38which is 'nonrotatably con
a tapered bore, in. place‘ of cylindrical bore 98,‘ would
nected to‘a shaft 39 which is in turn pivotally supported
give satisfactory results; it has been found that a cylin
onia' bottom cover 40. An arm 41' is nonrotatably se
drical bore such as illustrated together with. the restricl
cured‘ to the shaft'39' within‘ the cover 40. A lever 42
tion'a?orded by coactio-n of the ball. and theseat99'pro
is pivotally‘supported on a shaft 43 mounted on the cover 60 vide a satisfactory range of restriction for various rates"
40' and has a camming face in abutmentvwith a camming
of descent of implements.
face‘of‘arm 41; A rod 44‘ is biased‘. by spring 46 and has
Referring to FIGS. 1, 2, 3, ‘4, 7 and 8, thecontrol
linkage for the hydraulic system will be described. ‘Ard
jacent the steering wheel 1% a quadrant 107 is welded
to the steering column 1&8. This‘ quadrant107' pivotall'y
an inverted U-portion'within which a roller on the upper
end of lever 42 ?ts. A lever 49 is pivotally connected
at one end to rod de'by a pin‘51 and‘is pivotally connected
at its central portionv to‘ an adjusting'member 52 by a
pivot pin 53 so that upon counterclockwise movement
.
carries a pair of rods 109 and 111. Spring biased hand
control levers 112 and 113 are secured ‘to the rods‘ 109
about the pivot pin 53,‘ as” viewed from‘ the‘ top, the other
end of lever 49 will move the control-valve spool'54.
and 111, respectively. Control rod 111 is rotatably sup
plunger pump 19Twill'not return to the sump through pas
cotter pin extending [through a rod: 111. This spring
ported by a ?ange 142 secured to a brace mounted on
Referring now to'FIGS. 2, 3" and 9, when the valve 70 torque tube 24. As shown in'FIGS. 7 and 8, the levers
spool 54 is moved to the left, as viewed in FIG. 9, by the
‘are pivotally connected ‘by pins 114 and 116 to the rods
lever 49 uponincreases in'edi'af't load, a sequence of events
11}? and 111, respectively. As shown in‘ FIG. 8,, lever
occurs. First the port 55 in the bore 56 is closed by a
113 has a spring 117‘ with-one end connected to a hook’
land 57 on the spool '54. _ Thus fluid pumped by small
formed on. the lever and its other end connected‘ to a
8,080,003
to
force of the operator if he attempted to move the lever
5
117 bimes the lever 113 upwardly so [that it will be in
faster than permitted by the control valve dashpot 146.
When the automatic weight transfer linkage is em
abutment with the quadrant if the pin 113 carried by
the lever 113 is in one of the windows 119 or 121.
When the lever 113 is moved to its lift position, the pin
118 engages window 121 in the quadrant 107 and the
control valve is moved to an implement raising position.
The control lever 112 operates the adiustlng member
52 through the rod 1%9 which is universally connected
to a rod 122 to which the adjusting member is nonro
ployed the pressure of the ?uid in the ram 21 will increase
and decrease in correspondence to draft load and it has
been found desirable to place the lift and lower lever 113
in the other direction of pivotal rotation. The connec
tion includes a positive force transmitting member in the
lowering the ball 101 may occupy a position similar to
that shown in PEG. 9 where the only restriction to return
the fluid from the ram would be that imposed by the
in a restricted lowered position during weight transfer
operation. The restricted lower position of the lift and
lower lever ll?) is shown in FIG. 7 and in that position
the pin 118 is abutting one edge of the window 119.
tatably connected.
10 By providing an adjustable link 123 it is possible to
The lift and lower lever 113 constitutes a part of a
select the desired position oi the check valve ltl‘l to
manually operable control linkage for selectively mov
correspond with a setting of the control lever 113 in its
ing the control valve from its implement lowering to its
restricted lowered position as shown in FIG. 7. Thus
implement raising position through pivotal swinging
the provision of an adjustable link in the lift and lower
movement of the lever 103 connected to rod 104. Re
control linkage markedly improves the weight transfer
ferring to FIGS. 2, 3, 4, 5 and 6, rod 194 and rod 111
system hereinbefore described.
have a connection providing positive movement in one
Also it is desired to provide means for lowering the
direction of pivotal rotation and a resilient connection
implements at different rates. For one rate of restricted
form of a link 123 pivoted at one end to an arm 1Z4
nonroatably secured to? rod 104. The other end of the
link 123 passes through a pivot member 126 carried by
a pair of arms 127.
cured to rod 111.
The arms 127 are nonrotatably se
.
spacing of the ball 191 and the bore $8‘, however, if
slower lowering is desired, such as in the case of lowering
a corn planter into the ground, the nut is turned by a
screw driver to change the length of link 23 so as to
position the ball 1.91 more closely to the seat 199' when
A nut 128 is secured to the threaded end of link 123
to vary the effective length thereof. The nut 123 has
the lever pin 118 is in the upper part of window ‘1.13,
an internally threaded part (129 which carries a nylon
thereby presenting two areas or‘ restriction to fluid ilow
locking washer 131. The rod 123 has a loose ?t with
from the return conduit 63 to the passage '77. The
a bore 132 in pin 126. A coil spring 133, which con 30 double restriction offered by the ball 1%1 ?tting in here
stitutes a resilient member, has an end abutting against
93 and the spherical surface of the ball 1%}. adjacent
a washer 134 which is held in place by a cotter pin 13%.
seat 99 e?ects a slow lowering rate.
The other end of coil spring 133, which surrounds the
When the operator has lowered an earth working
rod 123, abuts a recessed llat surface 137 of pin 125. A
tool by holding the lift and lower lever in its lowering
hole 138 is provided in side panel 139 and this hole is
position, he need merely release the lever and it will
in horizontal alignment with the nut 128 as shown in
automatically move upwardly until pin 113 engages the
FIG. 1. The hole 138 is so positioned as to permit a
upper edge ‘of the window 119 in bracket 197. The
screw driver to be inserted through the hole into the slot
pressure exerted by the ?uid on the ram side of the ball
14-1 in the head of the nut 128 to turn it to adjust the ef
101 during moments of decreasing draft load will urge
40
fective length of link 123.
the ball toward its seat 99 thereby urging the pin 118
the
The operation of the manual control linkage for
against the upper edge of window 119.
lifting and lowering of the implement will now be de
It is to be understood that although only one embodi
scribed. When the operator approaches the end or” the
ment of the invention has been shown and described in
?eld in a plowing or other soil working operation, he
detail, it is not intended to limit the patent granted
desires to place the lift lever in a raising position prior
hereon otherwise than is necessitated by the scope of the
to turning the tractor at the end of the furrow. it is
appended claims.
desirable to place the lift lever quickly to the full lift
What is claimed is:
position and heretofore this has caused high pressure
1. In a hydraulic control system for a tractor of the
to develop due to the sudden engaging of the pumps 1d,
type including a source of hydraulic pressure ?uid and a
17 and 18 to supply ?uid to the ram 21. Heretofore,
hydraulic actuator for r ising and lowering an implement
the pressure surge is often great enough to exceed the
connected in draft relation to said tractor, the combina—
predetermined pressure necessary to open the unloading
t-ion comprising: a control valve on said tractor for
valve thereby dumping the fluid to sump. Thus, instead
controlling the flow of ?uid to and from said actuator
of lifting the implement the operator would ?nd that
having an implement raising position and an implement
the pressure has ‘dropped in the ram su?lcien-tly that ther
lowering position, a dashpot yieldingly resisting move
would be no lifting action at all. Then the operator
ment of said control valve toward its implement raising
would have to move the lift and lower lever 113 to
position, a manually operable control linkage On said
implement lowering position to reduce the pressure in
tractor for selectively moving said valve from its imple
the pressure manifold 66 su?iciently to cause the un
ment lowering position to its implement raising position
loading valve 81 to close.
Once the unloading valve 81 60
was closed the operator then moved the lift lever 113
to the raised position. The use of a resilient member in
the form of coil spring 133 eliminates this undesirable
unloading occurring upon sudden movement of the lift
and lower lever to the lift position. The spring 153
interposed between rod parts 111 and 122 of the manual
control permits the lever 193 to slowly move the spool
54 to the left, as shown in FIG. 9, against the biasing
action of the dashpot 146 at the left end of the valve
spool 54. The dashpot 146 is biased against the spool
54 by a coil spring 149. The fluid level in the reservoir
is above the small opening 148. Also by having the
spring 133 in the lift lower linkage, damage to the lift
and lower control linkage is avoided. Heretofo-re, the
lift and lower linkage could be distorted by the brute
including ?rst and second rotatable parts, said second
part having a portion engageable with said control valve,
and a motion transmitting connection between said parts
including positive and yieldable force transmitting mem
bers providing positive engagement between said parts
upon rotation of said ?rst part in a d' ection permitting
said valve to move toward its implement lowering posi
tion and providing a yieldable connection between said
parts when said ?rst part is rotated in the opposite di~
rection urging said valve to move against said dashpot
toward its implement raising position.
2. The structure set forth in claim 1 in which said
means includes arms formed on said parts, said positive
force transmitting member is a link pivotally connected
at one of its ends to one vof said arms, and slidably con
nected at its other end to the other arm with means for '
8‘
implement raising andrlowering positions, a das‘npot for
urging said ?rst valve-toward its lowering position,‘ a‘
limiting'slidingwmovement of said‘link in onedirection
and :saidtyieldableforce transmitting member is a spring
interposed between said'parts biasing said link in said
one direction.
second valvefor controlling ?uid flow from said actuator
interposed, between said ?rst .valve and said actuatonrsaid
a
valvetbeing shiftable to increase or decrease said rate of}
3. In: a hydraulic system for attractor and draft/con
flow from said actuator, automatic weight transferlinlrage
‘betweenlsaid?rst ‘valve and said implementffor varying
nested implement: ahydraulic actuator for raising and
lowering said implement; a ?rst valve shiftable between
implement raisingvand loweringpositionga second’ valve
fluid pressure in-said'actuator in response to‘ variations'in
for controlling ?uid ?ow from said actuator interposed
betweensaid ?rst valve and said actuator, said valveIbeing
shiftablettoa position a?iording a slow implement lower
ing rate; automatic weight transfer linkage'between-said
?rstvalve andsaid' implementfor varying ?uid pressure’
in: said actuator vin response to variationsin implement
implement draft, :a control linkage for operating said
draft; a controlilinkage-for openatingsaidvalves'includ;
ing : a. hand operated member shiftable; between ‘ ai lowerv
valves including a hand operated: member shiftablej‘bea
tween a lower andlift position, said linkage including '1
a?rst and-second par-t having'an', adjustable connection" v
'therebetween, said second‘ part having portions thereof v
engageable with, saidvalves, said'sec'ond valve beingen-v ' i
‘ gageable by saidfsecond'part when-said hand operated‘
member is shifted to said 'lowenpositiont
-
and raise position connected to a‘ ?rst part-thereofaa
second partthavingportions:tbereofengageable with said
?rst-and second'valves; and adjustable‘connectingmeans; ‘
connecting saidl?rst and second parts, ‘said connecting; 20.
means adjustingthe e?ective-sp-acing betweentsaid' parts
t'o-limit the engagement of. said: second part with’ said
second- valve wherebyv the flow ratef'rom said'second; valve
is altered to provide’ a 1 desired implement lowering rate.
4.> In-aihydraulic systemforatractor and draft:con-. 25
nected'implement, a hydraulic actuator for" raising and
lowering said implement, a ?rst valvetshiftable between
References Cited'iin the tile of this‘patent'
UNITED STATES PATENTS
1,020,076-
Bowser ______________ __ Mar. 12, 1912
2,118,181
Ferguson _____ _'_____'__._._ Mayl24, 1938;
2,611,306
2,714,346
Strehlowetd _________ __ Sept. 23'; 1952»
Valin- ____________ __;____ Aug: 2,1955
FOREIGN PATENTS’
805,061
Great Britain _V_I___..___V_”__ Nov. 26;, 1958
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