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Патент USA US2403913

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July‘ 15, 1945»
Original Filed Jan. 14, 1956
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Patented July 16', 1946
Arthur L. Ellis, Deep River, Conni, assignor to
Vickers Incorporated, Detroit, Mich., a corpora
tion of Michigan
Original application January 14, 1936, Serial No.
59,072. Divided and this application October 4,
1941, Serial No. 413,588
6 Claims.
This invention relates to p'ower transmissions,
particularly to control devices for power trans
missions of the variable speed type for transmit
ting power from a driving'member to a driven
member at any speed ratio therebetween. ‘With
power transmissions in which a positive and non
yielding drive is provided, such, for example, as
the well-known hydraulic type of transmission,
(Cl. 103-—38)
?uid circuit embodying one form of the present
Figures 2 and 3 are views corresponding to
Figure 1 showing the parts in different positions.
Figure 4 is a fragmentary cross section on line
4-4 of Figure 5 showing the control valves with
their operating mechanisms partly in elevation
Figure 5 is a cross section on line 5—5 of Fig
the application of an excessive resisting load on
ure 4.
the driven-member transmits an overload to the 10
cross section on line 6—6 of Fig
prime mover which operates the driving member
ure 4.
unless some provision is made for preventing this.
Figure 7 is a fragmentary perspective View of a
Should such an excessive load be imposed on the
portion of the valve control mechanism.
driven member while the ratio of power trans
Figure 8 is a top view partly in section of the
mission is such that the driven member moves at 15
power transmission mechanism and a portion of
a high speed relative to the driving member, the
the control system.
mechanical advantage of the driving member in
Figure 9 is a fragmentary sectional view on line
overcoming this load is small, so that the prime
9-9 of Figure 8.
mover becomes easily overloaded under these con
Figure 10 is a fragmentary sectional view on
20 line I 0-! 0 of Figure 8.
Sincegthe variable speed power transmission in
itself provides a means for increasing the me
chanical advantage of the driving member over
the driven member, it is an object of the present
invention to provide control means operative to
change the ratio of power transmission upon the
occurrence of an excessive load on the driven
member in such a way that the power transmis
sion itself will act to prevent transmission of the
overload to the driving member.
A further object is to provide in a power trans
mission of the character described a control
means responsive to the application of a predeter
mined amount of torque to the driving member
Referring now to Figure 8, there is illustrated
a power transmission of the well known “Water
bury” type comprising a variable displacement
pump or “A-end” I0 and a ?xed displacement
hydraulic motor or “B-end” l2. Transmissions
of this character are fully described in the
patents to Williams 1,044,838 and to Janney
1,020,285, so that it is unnecessary to describe the
construction of the transmission itself in detail.
30 For the purpose of this speci?cation it may be
stated that the “A-end” [0 comprises a drive shaft
l4, rotation of which causes ?uid to be pumped
to the “B-end” l2. The displacement of the pump
and consequently the quantity of ?uid pumped
for increasing the mechanical advantage of that 35 per
revolution of shaft I4 are regulated by a tilt
member over the driven member.
[6 which is shown in the neutral position.
A further object is to provide a novel control
Movement of the tilting box in a clockwise direc
system of the character described including a ' tion
away from the neutral position produces for
?uid motor having a differential piston and a pair
ward rotation of the “Bi-end” and its driven
of control valves therefor, one of which is op 40 member I 8, (arrow A) while movement of the
erable to determine the operativeness or non
tilting box counterclockwise away from the
operativeness of the piston and the other of which
neutral position causes rotation of the driven
is operable to determine its direction of move—
member E8 in the opposite direction. While the
position of the tilting box l6 may be controlled
Further objects and advantages of the present 45 in any suitable manner, in the form of the in
invention will be apparent from the following de~
vention illustrated, a control mechanism of the
scription, reference being had to the accompany~
type shown in the patent to Janney 1,220,424 is
ing drawings wherein a preferred form of the
vutilized and includes a non-rotative rod 20
mounted for sliding movement in bearings 22 and
present invention is clearly shown.
This application is a division of application 60 24 and having a sliding and pivoting connection
at 26 with a stud 28 on the tilting box I 6. A screw
Serial No. 59,072, ?led January 14, 1936, for Power
shaft 30 is connected to the shaft 20 by a swivel
32 and at its opposite end carries a splined head
In the drawings:
34 which is slidable but not rotatable relative to
Figure 1 is a diagrammatic illustration of ‘a
a slotted sleeve 36 (see Figure 9). The sleeve 36
a small area against which fluid pressure may
is journalled on bearings 38 and 40 and has a
projecting shaft 42 upon which is mounted a
hand wheel 44 by which the screw shaft 30 may
be exerted through a port I34 to counteract the
be rotated. The screw shaft 30 is threaded into
a rotatable nut 46 rigidly secured in the hub 48
of a gear 55 which in turn is journalled in the
bearing 52 by which the nut and gear are held
vided leading to the bore I28 and is so positioned
that a predetermined amount of movement of
force of the spring I22 and to move the valve
I25 to the right in Figure 6. A port I36 is pro
the valve I25 to the right opens a connection be
tween the port I34 and the port I35. The valve
against axial movement. The pitch of the
I25 is also provided with a reduced portion I38
threads of shaft 36 is sufficiently great as to make
is adapted to connect a port I40 with a
the thread reversible. That is, the shaft 30_may 10 port I42 in the position illustrated and to close
be threaded into or out of nut 4'6 by pushing or
01f the port I42 when valve I26 moves to the
pulling on the shaft 29, the shaft 30 turning in
right sufficiently to open port I35. A closure
swivel 32 and in nut 45. Gear 50 meshes with a
I43 protects the spring I22 and seals the end of
pinion 54 rigidly secured to the “B-end” driven
shaft I8. The lefthand end of the rod 20 carries 15
bore I28.
Referring now to Figure 5, the directional con
trol valve 98 includes a valve member I44 slidable
in a bore M8 formed in the valve block 98 and
operated directly with fluid under pressure.
having an end closure I48 at its outer end. The
The “A-end” driving shaft I4 carries a double
valve member I44 is operated, from the arm 92
clutch 69 having a movable member 52 splined 20 by means of the cam bar 94 having a cam [por
to the shaft I4 and slidable to engage either a
tion I55 which cooperates with a pin I52 formed
clutch member 64 rigidly secured to a shaft 65
on a lever arm I54. The arm I54 is pivoted at
or a clutch member 68 rotatably mounted on the
I56 to a bracket I58 formed in the housing 18
shaft I4. The shaft 6t may be that of any suit
and carries an adjustable stop screw I60 for de
able prime mover, for example, an electric mo
termining the lefthand position of the valve I44.
tor, .not shown, and is used for normally driving
The arm I54 also carries a pin I52 which pro
the power transmission. The clutch member 63
jects through a slot I54 in the bar 94 for the
carries a sprocket "It which is driven by a chain
purpose of preventing the cam bar 94 from lift
‘I2 from a manual drive: clutch unit ‘I4 by which
ing away from the pin I52 and also for positively
the"“A"-end” may be driven by hand from a hand
moving the arm I54 to the left when the cam
crank ‘it upon failure of power at the shaftGIi.
bar 94 reaches the lefthand limit of its travel.
" Means for moving the tilting box toward neu
The cam bar 94 is connected to the arm 92 by
tral position upon occurrence of an overload is
means of a pin I66 carried by the cam bar 94
provided and includes a housing 18 mounted on
and a slot It!) formed in the arm 92. A spring
top of the “A-end” directly over the upper trun
Ilfl abuts against a pin I12 on the arm 92 and
nion upon which the tilting box It is mounted.
a pin IE4 on the cam bar 94 and tends to keep pin
Referring now to Figure 4 the housing '58 carries
IE5 in the lefthand end. of slot I68.
a removable bearing 30 within which a stub shaft
The mechanism is so arranged and adjusted
a differential piston 55 operating in a cylinder 58
by which the rod 29 and tilting box It may be
v82 is mounted. The lower end of the ‘shaft 82
that in the ,position illustrated which corresponds
is adapted to be coupled directly to the tilting 4:0 to neutral position of the tilting box I6 the valve
box by means of a keyway 84. Shaft 82 has rig
I44 is maintained in its lefthand position by
idly secured thereto an arm 86 carrying a cam
the spring I'I? acting through the pin I14, cam
88 for the purpose of controlling a constant
bar 54, the righthand end of the slot I64, the
horsepower control valve generally designated at
pin I52, and the lever I54. Movement of the
96. Shaft 82 also carries an arm 92 having a 45 arm 92 away from ‘the position illustrated in a
lost motion connection with a cam bar 54 for the
clockwise direction in Figure 5 does not move
purpose of operating a directional control valve
the cam bar 94 but merely increases the tension
‘generally designated at 96. The valves 90 and
in the spring I'IO; the slot I63 permitting clock~
‘95' are formed within a valve block 98 secured
wise overtravel of the arm 92. Should the arm
to one side of the housing ‘I8. The valve block
92 move counterclockwise away from the position
t8 also includes a constant torque valve I55 (Fig
illustrated, the lefthand end of slot I88 abuts pin
ure 5) which is operated from the clutch unit 14
I55 moving cam bar 94 to the right. Cam I58
shown in Figure 8.
Referring now to Figures 6 and '7, cam 88 is
thus moves the pin I52 downwardly causing a
clockwise movement of the arm I54 and moving
valve I44 to the'right. The construction is such
‘formed with a high portion IE2 at its amid-part
corresponding to neutral position of the tilting
box It and curved portions I04 and I65 sloping
away from the high part I02 symmetrically on
that the complete travel of valve I44 takes place
either side thereof. A roller cam follower I08 is
pivoted on a lever’ Hi), the latter being pivoted
at‘ H2 in a bracket H4 formed on the valve
block 98. ‘The outer end of the lever H0 carries
a link lit pivotally connected to a tension rod
vI I8 having an adjustable spring plate I22 at its a
outer end abutting a spring I22. The spring plate "
I20 is moved to the right in Figure 6 whenever
the arm 85 moves away from the neutral position
illustrated, thus "decreasing the compression of
the spring I22. The lefthand end of spring I22
abuts againstia spool I24 which in turn abuts
against a valve member I25 slidably mounted
within albore I28 formed in the valve block 98.
The lefthand end of the valve member I26 is
reduced in diameter at I30 to fit a reduced por
‘ats I32 or the bore-12s..‘ There is thus provided ‘' ‘
in a very small angle of movement of the arm
92 as compared with its total movement.
The bore I48 of the valve I44 has a port H6
at its lefthand end and a port I18 to the right
thereof. Valve I44 is formed with a reduced
portion I88 adapted to connect the ports I15 and
I18 when the valve is moved to the right. A bore
I82 is formed centrally of the member I44 and
connects by means of a cross bore I84 the right
hand end of the bore I46 with the interior of
the housing ‘I3. In the position illustrated in
Figure 5, the port I13 is in communication with
the righthand'end of the bore I46 by means of a
reduced portion I36 formed on the valve member
I44 and is, therefore, in communication with the
interior of the housing ‘I8 when the valve is in
the position shown. This communication is out
off. by the valve I44 beingmoved to the right.
I The constant torque valve I00 includes a valve
member I08 slidably mounted within, a bore I90.
The bore: I90 is formed with a port I92 com
municating with the port I16 through a conduit
I941 and a port I96 communicating with the port
I42of valve 90 through a conduit I998. The valve
I88 is formed similarly to the valve I44 except
that it is operated by means of a stem 200 pro
mechanism desired, and is arranged to move the
piston 56 and‘ tilting box I6 to the right when
in the position illustrated, and to move the same
to the left when the valve 2| 4 is moved to the
limit in the left-hand direction. An intermedi
ate position is provided in which the piston 56
is hydraulically locked against movement. The
valve 2| 6 is operated in response to the constant
A bracket 204 carries a 1O horsepower valve 90 and the constant torque valve
I00 to move the piston 56 and the tilting box
lever 206 having pivotal connection at 208 with
I6 toward neutral position irrespective of the
the stem 200 and at 2I0'with an operating rod
position ‘of valve
jecting outwardly from the valve block 98 through
a packing gland 202.
2I4 or, when the hand wheel 44
2I2. Inv the position illustrated in Figure 5 the
is being used for normal control, with su?icient
valve I88 closes oif communication between ports
to overcome the greatest manual effort
I92 and I96 and connects port I96 to the interior 15 force
which can be applied to wheel 44.
of housing 1.8. When the valve is moved to the
Fluid under pressure for operating the piston
right, the ports I92 and I96 are connected to
56 under the joint control of the valves 90, 96,
gether' and port I96 is cut oif from communica
I00, 2M, and 2I6 is provided with two alternate
tion with the housing 18.
The clutch unit 14 illustrated in Figure 8 in 20 sources: The ?rst is the power circuit of the hy-'
draulic transmission itself, the valve plate there
cludes a main shaft 286 carried in bearings 288
of being indicated at 222. Conduits 224 and 226
and rigidly secured to the crank 16. Shaft 286
connect with each of the two valve ports 228 and
carries a hub 290 rigidly secured thereto which
230, respectively, and lead to a shuttle valve 232
drives a set of planetary pinions 292 cooperating
for the purpose of connecting a conduit 234 with
with a ?xed ring gear 294 and a sun pinion 296.
whichever of the conduits 224 and 226 has a
The sun pinion 296 is rigidly secured to a ?ywheel
pressure at a given instant. The other
298 journalled on the shaft 286 by means of
source comprises an auxiliary pump 236, of any
bearings 300. The hub 299 also carries a driv
suitable construction, having an intake 238 lead;
ing part 302 of a spring-loaded friction clutch
ing from the expansion tank, not shown, and
304. The driven part of the clutch 364 comprises
having a relief valve, not shown, which are cus
a hub member 306 freely rotatable on shaft 286.v
tomarily provided with hydraulic systems of this
The hub member 306 has splined thereto a cam
character. Pump 236 may be driven, forexam
member 308 (see Figure 10) which is spring
ple, by an electric motor 240. Pump 236 has an
pressed to the right by springs 3H0. The cam
outlet conduit 242 communicating with a shuttle
member 308 has a projection 3I2 engaging with
‘ valve 244 for the purpose of selectively delivering
a cam surface 3 I4 formed in the hub of a sprocket
to a conduit 246 ?uid from either conduit‘ 234'
3I6 which is'mounted on the hub member 306 so
or conduit 242 depending upon which has a high
as to be rotatable relative thereto. Cam mem
er pressure at a given instant.
ber 308 has 1a slot 3 I8 formed therein for engage
ment with a fork 320 which is pivotedly mounted 40
on a shaft 322.
Shaft 322 has a lever 324 con
the port I34. of the constant horsepower valve 90
while the conduit 242 has a branch 250 leading
to the port 252 of the valve 2I4. Conduit 246
communicates by means of a branch 254 with
the conduit I94 connecting ports I16 and I92 of
geared to the flywheel 298 in a manner to cause 45
valves 96 and I00, respectively, and has a second
the ?ywheel to revolve at a greater rate of speed
branch 256 leading to a port 258 of the valve
than the crank 16. The clutch 304 connecting
2I6. Valve 2I6 is formed with a, port 260 com
the shaft 286 to the rotatable hub 306 is arranged
municating by means of a conduit 262 with the
to ‘slip when a predetermined amount of torque
small end of the cylinder 58 and, in the position
is applied thereto. The force of the springs 3I0~
of the valve 2l6 illustrated, the ports 258 and
is so proportioned relative to the torque trans
260 are connected. When the valve 2I6 is moved
mitted by the clutch 304 that the projection
to the right by a spring 264, the port 260 is out
3H 2 may move substantially half the length of the
01f from‘communication with the port 258 and
cam surface 3 I 4 before springs 3 I 0 are compressed
in communication with a port 266 com
sufficiently to require a torque greater than the 55 municating
with the conduit 250.
maximum transmitted by clutch 304 for ‘further
The port I18 of valve 96 communicates by
travel of the member 3I2 along the cam surface
means of a conduit 268 with a port 210 of the
3I4. Thus, whenever the load applied to the
2I6. In the position illustrated in Figure 1
sprocket 3I6 is su?iciently great to cause clutch
304 to slip, the sprocket 3I6 must have moved 60 the Valve H6 is arranged to connect the port 210
with a port 212 leading by means of a conduit
relative to hub 306 an amount sufficient to move
214 to the large end of the cylinder 58. When
the cam member 308 to the left a predetermined
the valve 2I6 is moved to the right, as in Figure
amount. This movement of the member 308 is
3, port 212 is cut off from communication with
transmitted through the slot 3I8, fork 320, shaft
port 210 and connected with a port 216 leading
322, lever 324, linkage 326, to the operating rod
to a port 218 of the valve 2I4. Port 218 is con
2 I 2 for the constant torque valve I00.
nected with the port 252 by the valve 2| 4' in the
Referring now to Figure 1, the‘ hydraulic cir
position illustrated in Figure 1. When valve 2I4
cuit for the control mechanism of the present
is moved to its mid-position, the port 218 is cut
invention includes the mechanism above de
scribed, and in addition, a pilot control valve 2I4 70 off from communication with any port in the
valve 2I4. When moved to the limit of its travel
and a hydraulically operated valve 2I6 both of
to the left, valve 2I4 connects port 218 with a
which are formed in a second valve block‘ 2I8
port 260 leading to the expansion tank, now
formed in the body of the cylinder 58 (see Figure
shown. Conduits 28I and 283 connect the op
8'). The pilot control valve 2I4 may be operated
posite ends ofthe valve 2 I4 to the expansion tank
by a'hand lever 220 or by any suitable automatic - 75 tic-eliminate trappingeffects. The ports‘ I36 and
nected by means of a linkage 326 to the operat-‘
ing rod 2| 2 for the constant torque valve I00.
It will be seen that the crank 16 is directly
connected to the shaft 66 would be overloaded,
the constant‘ horsepower valve 98 operates to
move ‘the tilting box I6 toward neutral position.
I48 of valve 90 are connected together by means
of a conduit 282 leading to an operating cylinder
284 at the righthand end of valve 2I6 for over
coming the force of the spring 264 and moving
the valve 2I6 into the position illustrated in
It is a characteristic of hydraulic transmissions
of. the type described that the ?uid pressure in the
Figures 1 and 2.
In operation, the transmission being suitably
in direct proportion to the torque load imposed
working circuit of the transmission itself varies
upon the “B-end” shaft I8. When the shaft I8
is turning in one direction, one of the valve ports,
assembled with the shaft 86 connected to a prime
mover, preferably one of constant speed, and the
shaft I8 being connected to a load which it is 10 for example 238, becomes the pressure port and
desired to drive at variable speeds, the clutch 65
is shifted to engage the clutch member 64. If it
is desired to operate the “B-end” shaft [8 and
the load to a predetermined position, that is, by
“follow-up” control, the hand wheel 44 is turned
causing the screw shaft 30 to move axially inthe
nut 46 moving the tilting box out of neutral
position. Fluid is thus pumped from the “A-end”
to the “B-end” and the latter operating as a ?uid
motor turns the shaft I8 and the load. This
movement of shaft I8 turns the nut 46 through
the gears 58 and 54 in a direction tending to
move the screw shaft 36 back into the position
corresponding to neutral position of the tilting
box in the manner more fully described in the
the pressure existing in this port is transmitted
to the conduit 226 and the shuttle valve 232. On
rotation in the opposite direction the port 228
becomes the pressure port and the pressure
therein is transmitted to conduit 224 and shuttle
valve 232 which moves to the position opposite
to that illustrated in Figure 1. Any abnormal
pressure rise that occurs in either valve port 228
,or 230 is thus transmitted through conduits 234
20 and 248 to port I34 of the constant horsepower
valve 98. When this pressure exceeds the value
determined by the compression of the spring I22,
the valve member I28 moves to the right open
ing port I36 and permitting the ?uid to pass
25 through conduit 282~to the power cylinder 284
of the valve 2I6. The opening of port I36 to
Janney Patent 1,220,424. So long as handwheel
pressure fluid from port I34 initiates a sequence
44 is turned the “B-encl” shaft I8 will continue
of operations immediately causing a ratio of
to turn at a corresponding speed and direction.
transmission to be established which will be safe
Alternatively the transmission may be operated
under normal control of the pilot valve 2I4 in 30 for the particular overload imposed on the “B
end” shaft I8. That is, the mechanical advan
stead of under the control of handwheel 44, if it
tage of the “A-end” shaft I4 over the “B-end”
is desired to drive the load continuously at a
shaft I8 is increased to the point where the prime
given rate of speed for considerable intervals.
mover is not overloaded. The operation for this
Thus, during normal operation, when there is no
is as follows:
tendency to overload the prime mover, which is
Assuming that the tilting box is standing in
illustrated in Figure 3, the valve 2I6 lies in its
a position for forward drive, the piston 58 will
righthand position, in which the small end of the
be standing to the right of the mid-point'of its
cylinder 58 is constantly supplied with ?uid under
as illustrated in Figure 1. The directional
pressure through the conduit 262, ports 268 and
control valve 96 will also be in the position i1
266, conduits 258 and 242, and pump 236. The
lustrated in Figure 1 in which ?uid flow is cut
large end of the cylinder 58 under these condi
off between the ports I16 and I18 and the port
tions is subject to control by the valve 2I4
I18 is connected to the interior of the housing
through the conduit 214, and ports 212 and 216.
18 which is maintained at atmospheric pressure
Thus with the valve 2I4 in the position shown
the port 218 is blocked and piston 56 is held 45 by a connection to the expansion tank, not shown.
The valve 2I6 having ‘moved to the left, as il
stationary. With the valve 2I4 moved to the
by the ?uid pressure admitted to the
right, port 218 is connected with conduit 252 for
power cylinder 284 by valve 98, connects the
admission of ?uid under pressure from the aux
large end of control cylinder 58 to the tank
iliary pump 236 to the large end of the cylinder
58 causing piston 56 to move to the right and 50 through the conduit 214, port 212, port 218, con
duit 268, port I18, and bore I82. The small
thus moving the tilting box in a clockwise direc
end of the cylinder 58 is supplied with fluid
tion in Figure 8, and increasing the speed of
the “B-end” in a forward direction.
When the
under pressure either from the main power cir
cuit of the transmission or from the auxiliary
valve 2I4 is moved fully to the left, the port 218
is connected to port 288, thus exhausting ?uid 55 pump 236‘depending upon the position of the
shuttle valve 244. The cricuit for this ?uid is
from the large end of the cylinder 58 causing the
from the shuttle valve 244 through conduit 256,
piston 56 to move to the left under the constant
port 258; valve 2 I6, port 268, and conduit 262
pressure supplied to the small end of the cylinder
to cylinder ‘58. The piston 56 thus moves to
58. l The speed of the “B-end” in a forward direc
tion will therefore be reduced, or if the tilting 60 the left until the ratio of transmission is such
that the prime mover 66 may handle the overload box has been moved to the left past neutral
position the speed in the opposite direction will
be increased. During operation under normal
control of valve 2I4 the handwheel 44 is free to
turn with the “B-end” shaft I8. That is, with
the pump “on stroke” in any given position, the
member 26 and tilting box I6 will remain sta
‘ tionary while the gear 54 will rotate the gear 50
and nut 46 and carry along with them in their
rotation the screw shaft 30, the head 34, the
sleeve 36, and the handwheel 44, as a unit, with
out imparting longitudinal movement to the
member 20.
Should an excessive resisting load be imposed
upon the shaft I8 such that the prime mover
without danger.
The compression of the spring I22 is varied
by the cam 88 in accordance with the position
of the tilting box I6 and the shape of the cam
is such that the horsepower required at the
shaft 66 when valve '98 opens is constant for all
ratios of transmission. Since the horsepower
transmitted by the hydraulic transmission is
proportional to the product of the ?uid pressure
existing in the transmission and the speed of
the “B-end” shaft, the cam 88 may be so shaped
that the compression of the spring I22 will be
maintained at the proper value for any speed
ratio of transmission. Thus when the "B-end"
shaftIB is revolving slowly, the pressure which
may be built up without exceeding the limiting
horsepower is high. Since the position of the
takes control away from handwheel 44 whenever
safe loads are exceeded. This comes about from
the fact that the effort exerted by piston 56
tilting box I6 is determinative of the speed of
when valve 00 opens is greater than any effort
the shaft-I8, it will be seen that vwhen the tilt
which can be manually applied to handwheel
ing box I6 is near the neutral position the cam
44. Accordingly, when valve ‘96 opens, piston 56
88 holds the tension rod II8 to the left, as shown
toward neutral position as just described,
in Figure 6, applying a relatively high force to
bringing with it the shaft 30. In order to move,
the valve member I26. A relatively high pres
sure is therefore required to move the valve 10 the shaft 30 must at least slow down relative
to the “B-end” and may even stop or reverse.
member I26 to the right under these conditions.
In any event the rotation of shaft 30 must ‘be
Conversely when the “B-end” shaft I8 is re
algebraically less than the rotation of the
volving at a high speed, much lower pressure
“B-end” shaft I8 and nut 46 in order to cause a
in the system will produce an overload on the
prime mover so that with the tilting box in a 15 difference in speeds which is made up by the
translatory movement of shaft 30.
high speed position, as shown in Figure 1, the
The control mechanism thus far described also
cam 88 applies a smaller force to the valve
operates to limit the horsepower which may be
member I26 permitting it to open on a much
lower pressure. Thus, the full horsepower of
the prime mover may be utilized at low “B-end”
speeds without danger of overloading the prime
mover at high “B-end” speed.
transmitted back through the transmission from
the “B-end” shaft I8 to the “A-end” shaft 66.
In other words, should the load tend to drive
the prime mover,v the horsepower which may be
transmitted backward through the transmission
When the tilting box is in position for rota
is limited to the same value that may be trans
tion of the “B-end” shaft I8 in the reverse direc
tion, the parts take up the position illustrated 25 mitted therethrough in the normal direction.
Operation under these conditions is identical
in Figure 2 wherein the piston 56 lies to the left
of the mid-point of its travel and upon the oc
currence of an overload it is necessary to move
to that previously described, the only difference
being that if the port 230, for example, be the
pressure port when power is transmitted normally
the piston to the ‘right rather than to the left
as previously described. The directional con_ 30 through the transmission for a given direction of
rotation of the shaft I8, then the port 228 be
Ltrol valve 96 moves to the right during the ?rst
comes the pressure port when the load tends to
small increment of travel of the tilting box away
feed power back to the prime mover. Since the
from neutral position in a counterclockwise
occurrence of an abnormal pressure rise in either
direction in Figure 1 and Figure 8, and there
port causes movement of the tilting box I 6 toward
upon connects the port ‘210 of the valve 2I6
neutral position, it will be seen that an excessive
with the shuttle valve 244 through the conduits
amount of power feed-back will reduce the me
268, I94 and 254. Fluid under pressure is thus
advantage of the “B-end” shaft I8 upon
admitted from either the main power circuit or
from the auxiliary pump 236 to the large end
of the cylinder 58 from port 212 through con
duit 214. Thus, whenever the “B-end” shaft is
the “A-end” shaft, thus slowing down the “B
end” shaft and reducing the horsepower trans~
mitted back to the “A-end” shaft.
When the transmission is operated manually
by the crank ‘I6, as when a failure of the prime
rotating reversely and an overload occurs, the
movement of valves 90 and H6 to the right and
mover occurs, the horsepower which may be
left, respectively, admits ?uid under pressure to
both ends of the cylinder 58. Since the area of 45 transmitted through the transmission is limited
by the constant torque valve I00. Rotation of the
the piston 56 exposed to the lefthand end of the
crank 16 drives the shaft 286 which drives the fly
cylinder 58 is greater than the area exposed
wheel 298 at a higher rate of speed through the
in the righthand end, the resultant force tends
planetary gearing 292, 294, 298 for steadying the
to move the piston to the right toward neutral
position until the mechanical advantage of the 50 speed of operation of the shaft 288, and also drives
the sprocket 3I6 through the clutch 304 and
“A-end” shaft over the "B-end” shaft is in
through the spring-loaded cam mechanism 3I2,
creased sufficiently so that the prime mover may
3| 4. Upon the occurrence of an overload suf?~
handle the overload imposed.
cient to require an excessive torque upon the
During operation with normal control exer
cised through valve 2I4, the operation of valve 55 crank ‘I6, the sprocket 3 I 6 slips relative to the hub
306 causing the projection 3I2 to travel along the
90 causes this normal control to be temporarily
cam surface 3I4 compressing the springs 3I0. As
interrupted since valve 2| 6, in the position shown
soon as the projection 3I2 has traveled along the
in Figure 1, cuts off communication between
cam surface 3M a predetermined distance, the
conduit 216 and port 272. The cylinder 58 is
torque required for further travel exceeds the
thus out off from any control in?uence by valve
torque which the clutch 304 is capable of trans
2I4 until the valve 90 closes permitting valve
mission and thereafter the clutch 304 slips until
2I6 to move to the right into the position shown
the torque required falls off to a safe value.
in Figure 3. When normal control is exercised
The movement of the cam member 308 to ‘the
through valve 2I4, the handwheel 44 is free to
turn with the “B-end” shaft I8; the shaft 30 65 left caused by the cam 3 I4 actuates the fork 320 to
and nut 46 turning together as a single unit
pull the operating rod 2 I 2 to the left in Figures 1
at each particular setting of the control piston
and 8, thus moving the valve member I88 to the
56. When piston 56 moves, of course, the hand
right and connecting port I06 to port I92 instead
wheel 44 speeds up or slows down relative to
of to the tank. Fluid under pressure is thus ad
the “B-end” shaft I8 so long as piston 56 con 70 mitted from the shuttle valve 244 through the
tinues to push or pull the threaded shaft 30 into
ports I522 and I95, conduit I68, ports I42 and I40
or out of the nut 46. During operation with
and the conduit 282 to the power cylinder 284,
normal control exercised through handwheel 44
moving valve 2H3 to the lefthand position illus
instead of through valve 2I4, that is, during
trated in Figure l. The piston 56 is thus caused
operation with follow-up control, the valve 90 75 to move toward neutral position in the manner
pump comprising in combination, means for
- previously described in connection with the con
stant horsepower valve 90.
Thus, assuming that the crank 16 is operated
at a substantially constant speed, the occurrence
of an excessive load at the “A-end” shaft l4 tends ?»
to increase the mechanical advantage of the “A
end” shaft l4 over the “B-end” shaft 18 until the
ratio of power transmission is such that the over
load may be safely handled at the crank 16. Since
the power delivered to the crank 16 is ordinarily‘ 10
varying the pump displacement, means operat
ing on the displacement varying means for re‘;
ulati'ng the pump displacement in response to
pump discharge pressure variations, and means
for varying the response of the regulating means
to cause it to respond at different pressures in
accordance with changes in pump displacement,
said last-named means including a cam movable
with the displacement varying means and hav
ing a follower operatively associated with the
less than that of the prime mover, the constant
horsepower valve 90 will not operate for limiting
regulating means.
3. In a variable displacement pump the com
bination of a member movable to vary the pump
loads which are excessive when the transmission
is driven from the crank 16. In other Words, it is
desirable that the settings of the opertaing mech 15 displacement, control means for normally de
termining the position of said member, means
anism for the constant horsepower valve 90 and
responsive to the discharge pressure of the pump
the operating mechanism for the torque limiting
for moving said member, and means controlled
valve I01! be such that the valve I00 comes into
by the position of said member for varying the
operation at a much lower load on the shaft I8
than does the constant horsepower valve ~90. The 20 pressure response of the ?rst-mentioned means
in a manner to maintain the power required by
operation of the constant torque valve is subject
the pump below a predetermined maximum.
to the directional control valve 96 in the same
4. In a variable displacement pump the com
bination of a member movable to vary the pump
manner as is the constant horsepower valve 99.
Thus, whenever the tilting box lies on the coun
displacement, control means for normally deter
terclockwise side of neutral position in Figure 8,;
valve 96 will lie to the right in Figure 1 and con
nect the large end of cylinder 58 to pressure ?uid
whenever valve 216 is moved to the left by pres“
mining the position of said member, means re
sponsive to the discharge pressure of the pump
for moving said member, and means, including
a cam, controlled by the position of said member
‘for varying the pressure response of the ?rst
mentioned means in a manner to maintain the
sure ?uid from valve I00. This circuit is through
conduit 254, port I16, valve 96, port I18, conduit
268, port 210, valve 216, port 212 and conduit 214.
power required by the pump below a predeter
mined maximum.
The greater area of the large end of cylinder 58
is thus predominant over the area at the small
end and piston 56 is thereby moved to the right
5. In a variable displacement pump the com
bination of a member movable to vary the pump
toward neutral position.
It will thus be seen that the present invention
displacement, control means for normally deter
mining the position of said member, means, in
cluding a valve, responsive to the discharge pres‘
provides a control device for a variable speed
transmission whereby the transmission itself will
sure of the pump and a fluid motor controlled by
automatically prevent the overloading of its
prime mover regardless of the resisting load ap 40 ‘said valve for moving said member, and means
controlled ‘by the position of said member for
plied to the driven member of the transmission.
While the form of, embodiment of the invention
as herein disclosed constitutes a preferred form,
it is to be understood that other forms might be
adopted, all coming within the scope of the claims
which follow.
What is claimed is as follows:
1. A control device for a variable displacement
pump comprising in combination, means for
varying the pump displacement, means for reg
ulating the pump displacement in response to
pump discharge pressure variations, and means
operated concurrently with the displacement
varying the pressure response of the ?rst-men
tioned means in amanner to maintain the power
required by the pump below a predetermined
6. In a variable displacement pump the com
bination of a member movable to vary the pump
displacement, control means for normally deter
mining the position of said member, means, in
cluding a valve, responsive to the discharge pres
sure of the pump and a fluid motor controlled by
said valve for moving said member, and means,
including a cam, controlled by the position of said
member for varying the pressure response of the
varying means for varying the response of the
displacement regulating means to cause it to re 555 ?rst-mentioned means in a manner to maintain _
the power required by the pump below a prede
spond at different pressures in accordance with
termined maximum.
changes in pump displacement.
2. A control device for a variable displacement
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