SYSTEME HYDROSTATIQUE DE COMMANDE POUR CHARGEUR ARTICULE

HYDROSTATIC CONTROL SYSTEM FOR ARTICULATE LOADER

Abrégé anglais

HYDROSTATIC CONTROL SYSTEM FOR ARTICULATE LOADER
ABSTRACT OF THE DISCLOSURE
The hydrostatic control system for an articulate loader provides an
improved method for controlling the output of a hydrostatic drive unit
for a front end loader, with cooperative connecting means disposed
between a pair of axially aligned drive pumps to provide selective
output of one or both pumps as dictated by operation of the control
mechanism.
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Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. An improved hydrostatic control system for controlling
the output of a hydrostatic drive unit for a vehicle, the
drive unit comprising:
a pair of output pumps axially aligned, each of
the output pumps having an infinitely variable position
swash plate operatively connected thereto to control the
output of the respective pumps;
a drive motor;
cooperative means between the drive motor and
the output pumps to couple the output pumps to the drive motor;
operative means to control the output of the drive
motor; and
the improvement comprising a lost motion connecting
means provided between the swash plates of the aligned
drive pumps to operatively couple the respective outputs
of the drive pumps, such lost motion connecting means
including selective operative means to selectively control
the output of one or both pumps.
2. An improved hydrostatic control system for controlling
the output of a hydrostatic drive unit for a vehicle as
claimed in claim 1 wherein the lost motion connection
between the swash plates of the axially aligned output
pumps includes a connecting member pivotally mounted on both
pumps, the forward connecting member including an elongated
slot which permits movement of one swash plate of the
vehicle independently of the second swash plate of the vehicle.
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3. An improved hydrostatic control system for controlling
the output of a hydrostatic drive unit for a vehicle as
claimed in claim 1 or 2 wherein a dampener is disposed between
the rear swash plate and an anchor adjacent the front swash
plate of the vehicle, the dampener fully extended when the
swash plates are aligned in the neutral position and a
compression spring disposed between the rod end and the
cylinder end of the dampener to maintain the rear swash
plate in the neutral position when the dampener is fully
extended.
4. An improved hydrostatic control system for controlling
the output of a hydrostatic drive unit for a vehicle as
claimed in claim 1 wherein the operative means to control
the output of the drive motor includes a pedal linkage
arrangement cooperatively connected between a foot pedal of
the vehicle and a servo control valve controlling the
output of a cylinder which is operatively coupled to the
forward swash plate of the pair of axially aligned drive
pumps whereby activation of -the servo control valve through
the foot pedal activates the cylinder to urge the front
swash plate forward, the lost motion connection permitting
the second motor to engage when the front swash plate has
been sufficiently extended in a forward or reverse direction.
5. An improved method for controlling the output of
a hydrostatic drive unit for a front end loader, wherein
the drive unit comprises:
a pair of output pumps axially aligned, each of the
output pumps having an infinitely variable position swash
plate operatively connected thereto to control the output of
the respective pumps;
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Claim 5 continued...
a drive motor;
cooperative means between the drive motor and the
output pumps to couple the output pumps to the drive motor;
operative means including a pedal member to control
the output of the drive motor; and
the improved method comprises providing a lost
motion connecting means between the swash plates of the
aligned drive pumps to operatively couple the respective
ouptuts of the drive pumps, such lost motion connecting
means including selective operative means to selectively
control the ouptut of one or both pumps.
6. An improved method for controlling the output of
a hydrostatic drive unit for a front end loader as claimed
in claim 5 wherein providing the lost motion connection
between the swash plates of the axially aligned output
pumps includes providing a connecting member pivotally
mounted on both pumps, the forward connecting member
including an elongated slot which permits movement of one
swash plate of the vehicle independently of the second swash
plate of the vehicle.
7. An improved method for controlling the output of
a hydrostatic drive unit for a front end loader as claimed
in claims 5 or 6 wherein providing the cooperative connecting
means includes providing a dampener disposed between the
rear swash plate and an anchor adjacent the front swash
plate of the vehicle, the dampener fully extended when the
swash plates are aligned in the neutral position and a
compression spring disposed between the rod end and the
cylinder end of the dampener to maintain the rear swash
plate in the neutral position when the dampener is fully extended.

8. An improved method for controlling the output of
a hydrostatic drive unit for a front end loader as claimed
in claim 5 wherein the operative means to control the output
of the drive motor includes a pedal linkage arrangement
cooperatively connected between a foot pedal of the vehicle
and a servo control valve controlling the output of a
cylinder which is operatively coupled to the forward swash
plate of the pair of axially aligned drive pumps whereby
activation of the servo control valve through the foot
pedal activates the cylinder to urge the front swash plate
forward, the lost motion connection permitting the second
motor to engage when the front swash plate has been
sufficiently extended in a forward or reverse direction.
9. An improved hydrostatic control system for controlling
the output of a hydrostatic drive unit for a vehicle, the
drive unit comprising:
a pair of hydrostatic output pumps axially aligned,
each of the hydrostatic ouptut pumps having an infinitely
variable position swash plate mounted thereon;
a drive motor;
cooperative means between the drive motor and the
ouptut pumps to couple the output pumps to the drive motor;
operative means to control the output of the
drive motor; and
the improvement comprising a lost motion connecting
means cooperatively connected between the swash plates of
the aligned hydrostatic drive pumps, the lost motion connecting
means including a lost motion connecting member pivotally
mounted at each end to respective front and rear swash
plates of the front and rear drive pumps, the lost motion
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Claim 9 continued...
connecting member having an elongated slot in which the
connection between the front swash plate and the lost motion
connecting member is disposed, said operative means including
a servo control valve controlling the horizontal forward and
reverse output of a cylinder rigidly coupled to the frame
whereby selective control of the servo control valve controls
the output of the cylinder operatively connected to the
front swash plate of the pair of axially aligned drive
pumps, and activation of the servo control valve causes the
cylinder to rotate the front swash plate until it engages
the forward edge portion of the slot provided on the lost
motion connecting member whereupon further rotation of the
front swash plate forces rotation of the rear swash plate
to selectively couple the output of both drive pumps to the
drive motor.
10. An improved hydrostatic control system for controlling
the output of a hydrostatic drive unit for a vehicle as
claimed in claim 11 wherein the cooperative connecting means
between the aligned drive pumps includes a dampener having
a rod end and a cylinder and mounted between the rear swash
plate and an anchor mounted to the frame adjacent the front
swash plate, the dampener being fully extended when the
front and rear swash plates are disposed in a neutral
position, the dampener being compressed when the rear swash
plate is moved forwardly, and a compression spring mounted
on the dampener between the rod end and the cylinder end
of the dampener to return the rear swash plate to a neutral
position when the operative means controlling the output
of the drive motor is released.
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11. An improved hydrostatic control system for controlling
the output of a hydrostatic drive unit for a vehicle as
claimed in claim 10 wherein the operative means to control
the output of the drive motor includes a cooperative pedal
linkage disposed between the servo control valve and an
operator foot pedal for controlling the output of the drive
motor.
12. An improved method for controlling the output of
a hydrostatic drive unit for a vehicle, the drive unit
comprising:
a pair of hydrostatic output pumps axially aligned,
each of the hydrostatic output pumps having an infinitely
variable position swash plate mounted thereon;
a drive motor;
cooperative means between the drive motor and the
output pumps to couple the output pumps to the drive motor;
operative means to control the output of the
drive motor; and
the improvement comprising providing a lost motion
connecting means cooperatively connected between the swash
plates of the aligned hydrostatic drive pumps, the lost
motion connecting means including a lost motion connecting
member pivotally mounted at each end to respective front
and rear swash plates of the front and rear drive pumps,
providing the lost motion connecting means with an
elongated slot wherein which the connection between the
front swash plate and the lost motion connecting member is
disposed, said operative means including a servo control
valve controlling the horizontal forward and reverse output
of a cylinder rigidly coupled to the frame, whereby selective
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claim 12 continued..
control of the servo control valve controls the output of
the cylinder operatively connected to the front swash plate
of the pair of axially aligned drive pumps and activation
of the servo control valve causes the cylinder to rotate
the front swash plate until it engages the forward edge
portion of the slot provided on the lost motion connecting
member whereupon further rotation of the front swash plate
forces rotation of the rear swash plate to selectively
couple the output of both drive pumps to the drive motor.
13. An improved method for controlling the output of
a hydrostatic drive unit for a vehicle as claimed in claim
12 wherein the cooperative connecting means between the
aligned drive pumps is provided with a dampener having
a rod end and a cylinder end mounted between the rear
swash plate and an anchor mounted to the frame adjacent
the front swash plate, the dampener being fully extended
when the front and rear swash plates are disposed in a
neutral position, the dampener being compressed when the
rear swash plate is moved forwardly, and providing a
compression spring mounted on the dampener between the
rod end and the cylinder end of the damepener to return the
rear swash plate to a neutral position when the operative
means controlling the output of the drive motor is released.
14. An improved method for controlling the output of
a hydrostatic drive unit for a vehicle as claimed in claim
13 wherein the operative means to control the output of
the drive motor includes a cooperative pedal linkage disposed
between the servo control valve and an operator foot pedal
for controlling the output of the drive motor.
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15. A hydrostatic drive comprising:
a hydraulic motor,
two variable displacement pumps driven jointly
by a common prime mover,
conduit means connecting the outlets of both
said pumps to the inlet of said motor without intervening
valves, and
operating means for varying the displacement of
one of said pumps for operating said motor in one operating
range, and
for varying the displacement of both said pumps
simultaneously for operating said motor in another operating
range.
16. A hydrostatic drive as in claim 15 wherein said
one operating range is a lower speed range and said other
operating range is a higher speed range.
17. A hydrostatic drive as in claim 15 wherein said
operating means includes a foot pedal, and wherein said
foot pedal moves farther in operating said operating
means through said one operating range than it does in
operating said operating means through said other operating
range.
18. A hydrostatic drive as in claim 15 wherein said
operating means includes a third operating range in which
said motor operates in the reverse direction from said
other two operating ranges.
19. A hydrostatic drive as in claim 18 wherein said
operating means includes a neutral position between said
first operating range and said third operating range.
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20. A hydrostatic drive as in claim 19 wherein said
operating means includes means for selectively changing the
displacement of said one pump from either said one or said
other operating range back to neutral.
21. A hydrostatic drive as in claim 20 wherein said
other pump is returned to neutral from said other operating
range by a spring which continuously urges said other
pump toward neutral.
22. A hydrostatic drive as in claim 18 wherein reverse
drive is achieved by changing the displacement of said one
pump in the opposite sense to said first operating range.
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Description

~ 7
HYUROSTATIC CONTROL SYSTEM FOR ~RTICULATE LOADER
_
BACKGROUND nF T~IE INVENTION
In a hydrost~tic drive system, it is desirable to have precise
control of the engine output in bo-th the -forward and reverse directions.
However, it is also desirable that the pedal contro'lling the output of
the hydrostatic drive pumps be limited to a relatively small amount oF
travel. Preferably, it would be advantageous to reduce the amount oF
pedal travel at higher speeds while providing a greater amount of pedal
travel at lower speeds so that the operator could have more precise
control over the output of the hydrostatic system particularly at low
speeds. It is an object of the present invention to provide a simple
control mechanism associated with the output o~ the hydros~atic drive
' moto~ to achieve precise pedal control for the operator.
Most conventional drive systems For hydrostatic front end 'loaders
use a single hydrostatic pump and a single hydrostatic motor. This does
not allow them to split the system and use half the oil for the low
speed range and all of the oil ~or the higher speed range. Further, in
a conventional system typically such operations as filling the loader
bucket or digging use all of the oil available -~rom the pump and i-t is
very di~ficult to control the amount o~ engine horsepower used. A
conventional system is constantly putting a drain on torque at high
speeds and there~ore operates very inef~iciently. Also ~n a conven-
tional systenl, pedal travel is directly proport~onal to output.
Further, in a conventional system, at higher speeds the deceler-
ation is so ~ast that only by ori~icing the pump down to reduce pedal
travel could a relatively slow rate of deceleration be produced.
However, i~ the pump ori~ice is reduced, when you are accelerating you
are accelerating very slowly and when you are decelerating you are
decelerating very slowly. Consequentlyi the cycle time ~or the machine
is considerably increased and should a ~ront end loader be driven into a
pile o~ dirt too hard at high speeds, the engine has a tendency to stall

because the dPceleration of the hydrostatic drive system is so slow that
you cannot back off the hydrostatic drive pumps fast enough.
The present invention employs a pair o, axially aligned hydrostatic
drive pumps plumbed together with a single hydrostatic output motor. A
precise control mechanism coupling the infinitely variable swash plates
oF the hydrostatic output pumps ~ith the operator speed control pedal
provides a precise control over pump output such that only half of the
pump output oil is used for the low speed range and all of the pump
output flow is used for the higher speed range. Essentially the control
mechanism enables the operator to use only one pump ~or the low speed
t~/~J~m ~
range and provides the operator with twice the pedal stroke For ix~ e
volume oF oil. BeFore the second pump is stroked, the operator is
utilizing the precise amount oF horsepower required, enabling him to
have very good control over digging and dumping. The second pump is
utilized only when the operator depresses the foot pedal further to
achieve higher speeds. The amount oF pedal travel at these higher
speeds is less than the amount oF pedal travel at lower speeds.
In the present system the control mechanism between the output
pumps provides that when the vehicle travels -in reverse only a single
pump is stroked so that there is limited travel speed in reverse.
However2 the control system could be easily modiFled to provide a -two
speed operation oFF a single pedal in both the Forward and reverse
directions.
A ~urther advantage oF the present system is that the con-trol
mechanism inherently provides an automatic two speed operation con-
trolled simply by the amount oF pedal travel exerted by the operator.
The operator can switch from a low speed operation to a high speed
operation by increasing the amount of pedal travel. There is no shift-
ing or Flipping of levers or other external operations associated with
the two speed output of the drive motor.

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Finally, the mechanism provides that when the openator takes his
foot off the pedal at high speeds the hydrostatic output motor does not
decelerate quickly. The second pump has a substantial dampening effect
on deceleration of the vehicle to provide smooth stops. Control between
the Front and rear pumps enabling the rear pump to "float" provides a
cushion that cannot be obtained with a single pump arrangemen-t. Deceler-
ation can be very gradual at high speeds and relatively swift at lower
speeds. The control mechanism between the hydrostatic output pumps not
only provides a dampening effect for smooth deceleration but also limits
the acceleration rate which ~ives the operator very smooth control oF
his vehicle.
Accordingly, the present invention provides an improved method for
controlling the output of a hydrostatic drive unit for a vehicle or
front end loader, the drive unit comprising a pair of output pumps
axially aligned9 a drive motor, cooperative means between the drive
motor and the output pumps to couple the output pumps to the drive
motor~ operative means to control the output of the drive motor, the
improvement compr~sing cooperative connecting means between the aligned
drive pumps to operatively couple the drive pumps, such connecting means
including selective operative means to selectively contrnl the output oF
one or both pumps.
The control and operation of -the present invention and the advantages
inherent therein will become more apparent through an examination oF the
accQmpanying drawing and through the more detailed description set Forth
below.
FIGURE 1 is a side elevational view of the drive system of an
articulate loader wherein the control mechanism oF the present invention
is clearly shown.
Drive system 10 o-F a hydrostatic -Front end loader (not shown)
includes hydrostatic drive pumps 12 and 14 operably coupled to a drive
motor 16 to produce an en~ine output.

Engine output speed control mechanism 18 comprises a foot pedal 20
coupled throuyh a control linkage 22 to a servo control valve 24 which
controls the output oF a cylinder 26 coupled to the respective infinitely
variable position swash plates 28 and 30 of pumps 12 and 14 respectively.
The control mechanism associated with the pump output lnc1udes the
lost motion connection 32 between rear and front swash plates 28 and 30
of hydrostatic output pumps 12 and 14 respectively. The lost mo~ion
connection 32 includes a link 34 pinned at respective rear and front
swash pla~es 28 and 30 as at pivotable pin connections 36 and 38. The
pin 38 which pins the member 34 to the front swash plate 30 oF the front
pump 14 passes through and is carried in an elongated slot 40 in the
member 34.
A dampener 42 is pinned between rear swash plate 28 and a Forward
anchor 45 rigidly mounted on the fralTIe adjacent the rear of the Front
swash plate 30 as at pivotable pin connections 44 and 46 respectively.
The dampener 42 is fully extended between the pin connections 44 and 46
when the swash plate 28 is in the neutral position. A cylinder end 48 of
the dampener 42 is mounted adjacent the rear swash plate 28 at the pin
connection 44 and a rod end 50 of the dampener 42 is pinned at
connection 46 on the anchor 45. A compression spring 52 is mounted
between the cylinder end 48 and the rod end 50 of the dampener 42. The
dampener 42 is ln a fully extended conditlon when the swash plate 28 is
in the neutral posl~lon. Compression spr~n~ 52 provides a constant
force on dampener 42 to maintain the dampener 42 in the extended posltlon
when no Force is applied to the swash plate 28 through member 34.
Cyllnder 26 is pinned on the swash plate 30 at cylinder end 26a at pin
connection 54 and rod end 26b of the cylinder 26 is pinned on the vehicle
frame at point 56.
When the foot pedal 20 is engaged downwardly to urge the vehicle in
a ~orward dlrectlon the pedal linkage 22 pivots bell crank 58 counter-
clockwise to urge link 60 outwardly and activate the servo cnntrol

valve 2~ to urge the cylinder end 26a oF the cylinder 2~ forward toward
the pin connection 56 at the rod end 26b oF the cylinder 26. When the
cylinder end 26a of the cylinder 26 is urged forward the ~ront swash
plate 30 of the forward pump 14 is also pulled forward to provide the
drive motor 16 with the output o~ the pump 14 to operate the vehicle
solely ~rom the output of th~ pump 14.
Should the operator increase the downward travel o~ the -foot
pedal 14 and respectively increase the outward travel of the link 60 to
further increase the travel of the cylinder 26, such increased travel
would further rotate the front swash plate 30 until the pin connection
38 abutted the end of the slot 40 in the lost motion connection member
34. When the end of the slot ~0 is reached~ increased movement of the
Front swash plate 30 will initiate movement of the rear swash plate 28
of the rear pump 12 to provide output from both of the drive pumps 12
and 14 to the motor 15.
Should the operator then remove his foot from the pedal 20 the
centering mechanism 62 would return the foot pedal 20 to a neutral
position and also return the servo control valve 24 and the cylinder 2
to a neutral position. The dam~ener 42 has been deslgned to provide
controlled acceleration and deceleration rates. The sprin~ 52 will
assure that the rear swash plate 28 will always return to a centered or
neutral position during deceleration~
As is readily apparent from a viewing o~ the drawing, it is clear
that the slot 40 in the lost motion connection member 34 is considerably
longer behind the pin connection 38 than it is to the front of the pin
connection 3S. Therefore, when the vehicle is operating in the reverse
mode and the front swash plate 30 is extended rearwardly, the rear swash
plate 28 remains in the neutral position because the vehicle is operating
with only the output of the front pump 14 when it operates in the
reverse direction.

Of course, with a modification of the lost motion connection member
34 and of the mounting arrangement for the dampener 42, it would be
s;mple enough to provide a two speed function in both directions.
However, in the present embodiment it was desirable to provide limited
speed in reverse to prevent the operator from traveling too fast in
reverse. The fact that the inventor chose to display and describe the
preferred embodiment should not limit the scope of protection available.
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