US3855792A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydrostatic transmission drive system
Assignee: Eaton Corp
•
Filing: 1973-11-16
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Granted: 1974-12-24
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Expires: 1993-11-16
Abstract
Abstract An improved drive system includes a pair of hydrostatic transmissions which are driven by a common engine or prime mover and are drivingly connected with different tracks of a vehicle. The input or output speed ratios of the hydrostatic transmissions are simultaneously varied by operating a single speed control valve to port control fluid pressure to pressure responsive secondary or control motors in pump and motor actuators of the hydrostatic transmissions. A separate steering control valve is associated with each of the hydrostatic transmissions. The pump actuators each include a primary or swashplate motor which is operable to vary the effective displacement of a pump unit of the associated hydrostatic transmission. To effect operation of a swashplate motor, the associated secondary motor is operated to actuate a pilot valve from a null position and port fluid under pressure to the swashplate motor. When the swashplate motor has been operated to an extent corresponding to the extent of operation of the associated secondary motor, a floating link feedback assembly returns the pilot valve to its null position to interrupt operation of the swashplate motor. Shuttle type selector valves port control fluid pressure to the secondary motor actuators. The motor actuators are generally similar in construction to the pump actuators and each includes a secondary motor which operates a pilot valve to port fluid under pressure to a swashplate motor. Pressure regulator assemblies for the hydrostatic loops of the two hydrostatic transmissions contain pressure relief valves. The pressure relief valves have a valve member which is acted upon tending to move it in an opening direction by the fluid pressure in the hydrostatic loop of the associated transmission and is acted upon by a spring and a control pressure tending to urge the valve member in a closing direction. A master relief or pilot valve is opened when the pressure in one of the hydrostatic loops exceeds a predetermined pressure. Opening of the pilot stage relief valve reduces the force urging the relief valve member closd so that it can open and maintain the pressure at a predetermined level in the associated hydrostatic loop. Operation of a parking brake for the vehicle disengages the master relief valve and limits the pressure at which the pilot relief valve opens.
Inventors
- 👤 E Bojas
- 👤 H Ward
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 11:14
CPC Classifications
F; F16; F16H; F16H61/00; F16H61/38; F16H61/40; F16H61/42; F16H61/433; B; B62; B62D; B62D11/00; B62D11/02; B62D11/06; B62D11/10; B62D11/14; B62D11/18; B62D11/183; F16H61/423
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
297 words
An apparatus comprising a first hydrostatic transmission including a first pump unit, a first motor unit, first conduit means for conducting fluid from said pump unit to said motor unit during operation of said first hydrostatic transmission in a forward direction, second conduit means for conducting fluid from said motor unit to said pump unit during operation of said first hydrostatic transmission in the reverse direction, third conduit means for conducting fluid from said first conduit means during operation of said first hydrostatic transmission in the forward direction and for conducting fluid from said second conduit means during operation of said first hydrostatic transmission in the reverse direction, first relief valve means operable between a closed condition blocking fluid flow through said third conduit means and an open condition enabling fluid to flow through said third conduit means, a second hydrostatic transmission including a second pump unit, a second motor unit, fourth conduit means for conducting fluid from said second pump unit to said second motor unit during operation of said second hydrostatic transmission in a forward direction, fifth conduit means for conducting fluid from said second motor unit to said second pump unit during operation of said second hydrostatic transmission in the reverse direction, sixth conduit means for conducting fluid from said fourth conduit means during operation of said second hydrostatic transmission in the forward direction and for conducting fluid from said fifth conduit means during operation of said second hydrostatic transmission in the reverse direction, second relief valve means operable between a closed condition blocking fluid flow through said sixth conduit means and an open position enabling fluid to flow through said sixth conduit means and a common relief valve pilot control for controlling the opening of both said first and second relief valve means.
Claim 2
Independent Claim
297 words
An apparatus comprising a first hydrostatic transmission including a first pump unit, a first motor unit, first conduit means for conducting fluid from said pump unit to said motor unit during operation of said first hydrostatic transmission in a forward direction, second conduit means for conducting fluid from said motor unit to said pump unit during operation of said first hydrostatic transmission in the reverse direction, third conduit means for conducting fluid from said first conduit means during operation of said first hydrostatic transmission in the forward direction and for conducting fluid from said second conduit means during operation of said first hydrostatic transmission in the reverse direction, first relief valve means operable between a closed condition blocking fluid flow through said third conduit means and an open condition enabling fluid to flow through said third conduit means, a second hydrostatic transmission including a second pump unit, a second motor unit, fourth conduit means for conducting fluid from said second pump unit to said second motor unit during operation of said second hydrostatic transmission in a forward direction, fifth conduit means for conducting fluid from said second motor unit to said second pump unit during operation of said second hydrostatic transmission in the reverse direction, sixth conduit means for conducting fluid from said fourth conduit means during operation of said second hydrostatic transmission in the forward direction and for conducting fluid from said fifth conduit means during operation of said second hydrostatic transmission in the reverse direction, second relief valve means operable between a closed condition blocking fluid flow through said sixth conduit means and an open position enabling fluid to flow through said sixth conduit means and a common relief valve pilot control for controlling the opening of both said first and second relief valve means.
Claim 3
Dependent Claim
43 words
An apparatus as set forth in claim 1 wherein said relief valve control means is operable to reduce the force applied to said one of said relief valve means while maintaining a substantially constant force on the other of said relief valve means.
Claim 4
Dependent Claim
197 words
An apparatus as defined in claim 1 further including first means for applying to said first relief valve means a force which urges said first relief valve means toward the closed condition and which force varies as a function of variations in the fluid pressure in said first conduit means during operation of said first hydrostatic transmission in the forward direction and which varies as a function of the fluid pressure in said second conduit means during operation of said first hydrostatic transmission in the reverse direction, and second means for applying to said second relief valve means a force which urges said second relief valve means toward the closed condition and which force varies as a function of variations in the fluid pressure in said fourth conduit means during operation of said first hydrostatic transmission in the forward direction and varies as a function of the fluid pressure in said fifth conduit means during operation of said second hydrostatic transmission in the reverse direction, and relief valve control means for limiting the force applied to at least one of said first and second relief valve means so that the force does not exceed a predetermined magnitude.
Claim 5
Dependent Claim
77 words
An apparatus as set forth in claim 1 further including brake means operable between a released condition and an engaged condition in which said brake means retards movement of the vehicle associated with said first and second hydrostatic transmissions, said relief valve control means including means for reducing said predetermined force from a relatively high force to a relatively low force in response to operation of said brake means from the released condition to the engaged condition.
Claim 6
Dependent Claim
252 words
An apparatus as set forth in claim 1 wherein said third conduit means includes a first shuttle valve means for directing fluid from said first conduit means to said first relief valve means during operation of said first hydrostatic transmission in the forward direction and for directing fluid from said second conduit means to said first relief valve means during operation of said first hydrostatic transmission in the reverse direction, said first hydrostatic transmission further including second shuttle valve means for directing fluid from said first relief valve means to said second conduit means during operation of said first hydrostatic transmission in the forward direction and for directing fluid from said first relief valve means to said first conduit means during operation of said first hydrostatic transmission in the reverse direction, said sixth conduit means including third shuttle valve means for directing fluid from said fourth conduit means to said second relief valve means during operation of said second hydrostatic transmission in the forward direction and for directing fluid from said fifth conduit means to said second relief valve means during operation of said second hydrostatic transmission in the reverse direction, said second hydrostatic transmission further including fourth shuttle valve means for directing fluid from said second relief valve means to said fifth conduit means during operation of said second hydrostatic transmission in the forward direction and for directing fluid from said second relief valve means to said fourth conduit means during operation of said second hydrostatic transmission in the reverse direction.
Claim 7
Dependent Claim
88 words
An apparatus as set forth in claim 5 wherein said first hydrostatic transmission further includes a first charge pressure relief valve means for enabling fluid to flow from said second shuttle valve means to drain during operation of said first hydrostatic transmission in either the forward or reverse direction, said second hydrostatic transmission further including second charge pressure relief valve means for enabling fluid to flow from said fourth shuttle valve means to drain during operation of said second hydrostatic transmission in eitHer the forward or reverse directions.
Claim 8
Dependent Claim
196 words
An apparatus as set forth in claim 1 wherein said first relief valve means includes a first valve member movable between a closed position blocking fluid flow through said third conduit means and an open position enabling fluid to flow through said third conduit means, said first means including means for exposing a surface of said first valve member to the fluid pressure in said first conduit means during operation of said first hydrostatic transmission in the forward direction and for exposing said surface of said first valve member to the fluid pressure in said second conduit means during operation of said first hydrostatic transmission in the reverse direction, said second relief valve means including a second valve member movable between a closed position blocking fluid flow through said sixth conduit means, said second means including means for exposing a surface of said second valve member to the fluid pressure in said fourth conduit means during operation of said second hydrostatic transmission in the forward direction and for exposing said surface of said second valve member to the fluid pressure in said fifth conduit means during operation of said second hydrostatic transmission in the reverse direction.
Claim 9
Dependent Claim
89 words
An apparatus as set forth in claim 7 wherein said relief valve control means includes means for exposing said surface of said first valve member to a source of relatively low fluid pressure when the fluid pressure to which said surface of said first valve member is exposed exceeds the predetermined force and for exposing said surface of said second valve member to a source of relatively low fluid pressure when the fluid pressure to which said surface of said second valve member is exposed exceeds the predetermined force.
Claim 10
Independent Claim
287 words
An apparatus comprising a reversible hydrostatic transmission having a variable displacement pump unit with a movable swashplate, said apparatus comprising pump actuator means for varying the displacement of the pump unit during both forward and reverse operation of the hydrostatic transmission by moving the swashplate, said pump actuator means including reversible primary motor means for moving the swashplate of the pump unit in either one of two directions from an initial position, a pilot valve operable between a null position and any one of a plurality of positions enabling fluid to flow from a source of fluid to said primary motor means to effect operation of said primary motor means and movement of the swashplate of the pump unit in either one of the two directions, reversible secondary motor means for operating said pilot valve between the null and actuated positions, said secondary motor means being operable to varying extents in either one of two directions from an initial position in response to variations in control fluid pressure conducted to said secondary motor means, floating link feedback means interconnected between said pilot valve, said swashplate and said secondary motor means for operating said pilot valve from any one of the plurality of actuated positions to the null position in response to movement of the swashplate of the pump unit by said primary motor means to an extent which is a function of the extent of operation of said secondary motor means, pressure controller means for varying the control fluid pressure conducted to said secondary motor means as a function of the extent of operation of said pressure controller means from an initial condition to control the extent to which the swashplate of the pump unit is moved.
Claim 11
Independent Claim
287 words
An apparatus comprising a reversible hydrostatic transmission having a variable displacement pump unit with a movable swashplate, said apparatus comprising pump actuator means for varying the displacement of the pump unit during both forward and reverse operation of the hydrostatic transmission by moving the swashplate, said pump actuator means including reversible primary motor means for moving the swashplate of the pump unit in either one of two directions from an initial position, a pilot valve operable between a null position and any one of a plurality of positions enabling fluid to flow from a source of fluid to said primary motor means to effect operation of said primary motor means and movement of the swashplate of the pump unit in either one of the two directions, reversible secondary motor means for operating said pilot valve between the null and actuated positions, said secondary motor means being operable to varying extents in either one of two directions from an initial position in response to variations in control fluid pressure conducted to said secondary motor means, floating link feedback means interconnected between said pilot valve, said swashplate and said secondary motor means for operating said pilot valve from any one of the plurality of actuated positions to the null position in response to movement of the swashplate of the pump unit by said primary motor means to an extent which is a function of the extent of operation of said secondary motor means, pressure controller means for varying the control fluid pressure conducted to said secondary motor means as a function of the extent of operation of said pressure controller means from an initial condition to control the extent to which the swashplate of the pump unit is moved.
Claim 12
Dependent Claim
49 words
An apparatus as defined in claim 9 wherein said pilot valve comprises a valve spool movable in opposite directions from its null position and a charge pump for directing control fluid to said pressure controller means and to said pilot valve for directing fluid to said primary motor means.
Claim 13
Dependent Claim
38 words
An apparatus as defined in claim 9 wherein said pilot valve when in its null position directs fluid leakage flow to said reversible primary motor meaNs which is constructed to enable leakage to flow therethrough without actuation thereof.
Claim 14
Dependent Claim
282 words
Apparatus for controlling the operation of a plurality of hydrostatic transmissions each having a variable displacement motor and a variable displacement pump with the displacement thereof being variable by movement of a swashplate thereof, said apparatus comprising respective fluid motor means associated with the pump swashplates and the motor swashplates to effect movement thereof, respective pilot valves for directing fluid to said fluid motor means to effect energization thereof, controllers for effecting actuation of said pilot valves including secondary fluid motors associated with said pilot valves, with each pilot valve being associated with a respective secondary fluid motor, said secondary fluid motors connected with the pilot valves for controlling movement of said pump swashplates being spring biased to a position in which said swashplates are in a neutral position and said pilot valves are in a null position, said secondary fluid motors connected with the pilot valves for controlling movement of said motor swashplates being spring biased to a position in which said motor swashplates are in maximum displacement position, the spring bias on said secondary fluid motors for controlling motor swashplate movement being greater than the spring bias on said secondary fluid motors for controlling pump displacement so that the pump displacement is increased before motor displacement is decreased, feedback means between each of said swashplates and said pilot valves so that said pilot valves are returned to their null position when said swashplates are moved to their desired position, and pressure controller means for controlling the fluid pressure conducted to all of said secondary motor means to control the extent to which the swashplates of the pump and motor units are moved under the control of said secondary motor means.
Claim 15
Dependent Claim
282 words
Apparatus for controlling the operation of a plurality of hydrostatic transmissions each having a variable displacement motor and a variable displacement pump with the displacement thereof being variable by movement of a swashplate thereof, said apparatus comprising respective fluid motor means associated with the pump swashplates and the motor swashplates to effect movement thereof, respective pilot valves for directing fluid to said fluid motor means to effect energization thereof, controllers for effecting actuation of said pilot valves including secondary fluid motors associated with said pilot valves, with each pilot valve being associated with a respective secondary fluid motor, said secondary fluid motors connected with the pilot valves for controlling movement of said pump swashplates being spring biased to a position in which said swashplates are in a neutral position and said pilot valves are in a null position, said secondary fluid motors connected with the pilot valves for controlling movement of said motor swashplates being spring biased to a position in which said motor swashplates are in maximum displacement position, the spring bias on said secondary fluid motors for controlling motor swashplate movement being greater than the spring bias on said secondary fluid motors for controlling pump displacement so that the pump displacement is increased before motor displacement is decreased, feedback means between each of said swashplates and said pilot valves so that said pilot valves are returned to their null position when said swashplates are moved to their desired position, and pressure controller means for controlling the fluid pressure conducted to all of said secondary motor means to control the extent to which the swashplates of the pump and motor units are moved under the control of said secondary motor means.
Claim 16
Dependent Claim
31 words
Apparatus as defined in claim 12 wherein each of said feedback means comprises a floating link feedback including a link pivotally connected to its associated secondary motor, pilot valve, and swashplate.
Claim 17
Dependent Claim
48 words
Apparatus as defined in claim 12 wherein each of said fluid motor means for moving said pump and motor swashplates comprises a pair of single-acting spring-biased fluid motors, with said pilot valves when in null position leaking fluid to said fluid motors and said fluid motors likewise leaking.
Claim 18
Dependent Claim
71 words
Apparatus as defined in claim 12 further including first steering valve means for varying the control fluid pressure conducted through said first conduit means to said pump and motor actuator means associated with one transmission, and second steering valve means associated with said pump and motor actuator means associated with another transmission, said first and second steering valve means having means for varying the control pressure in said fluid motor means.
Claim 19
Dependent Claim
187 words
An apparatus as set forth in claim 12 further including first and second fluid conduits for conducting control fluid to and from the secondary fluid motors for controlling said pump pilot valves, a third fluid conduit for conducting control fluid under pressure to the associated one of said secondary fluid motors, said pressure controller means being operable to a first one of said plurality of settings to port control fluid pressure to said first fluid conduits and to port said second fluid conduits to drain, said pressure controller means being operable to a second one of said plurality of settings to port control fluid pressure to said second fluid conduits and to port said first fluid conduits to drain, said apparatus further including first and second valve means for connecting said first fluid conduits in fluid communication with the associated one of said third fluid conduits when said pressure controller means is operated to said first setting and for connecting said second fluid conduits in fluid communication with the associated one of said third fluid conduits when Said pressure controller means is operated to said second setting.
Claim 20
Independent Claim
298 words
An apparatus comprising a first hydrostatic transmission including a first pump unit, a first motor unit, first conduit means for conducting fluid from said pump unit to said motor unit during operation of said first hydrostatic transmission, second conduit means for conducting fluid from said motor unit to said pump unit during operation of said first hydrostatic transmission, first relief valve means operable between a closed condition blocking fluid flow and an open condition enabling fluid to flow from said first conduit means to reduce the fluid pressure in said first conduit means, a second hydrostatic transmission including a second pump unit, a second motor unit, third conduit means for conducting fluid from said second pump unit to said second motor unit during operation of said second hydrostatic transmission, fourth conduit means for conducting fluid from said second motor unit to said second pump unit during operation of said second hydrostatic transmission, second relief valve means operable between a closed condition blocking fluid flow and an open condition enabling fluid to flow from said third conduit means to reduce the fluid pressure in said third conduit means, means for applying to said first and second relief valve means fluid pressure forces which urge said first and second relief valve means toward their closed conditions during operation of said first and second hydrostatic transmissions, brake means operable from a released condition to an activated condition to retard movement of a vehicle with which said first and second hydrostatic transmissions are associated, said brake means including a brake unit which is separate from said pump and motor units, and control means for reducing the fluid pressure forces applied to said first and second relief valve means upon operation of said brake means from said released condition to said activated condition.
Claim 21
Independent Claim
298 words
An apparatus comprising a first hydrostatic transmission including a first pump unit, a first motor unit, first conduit means for conducting fluid from said pump unit to said motor unit during operation of said first hydrostatic transmission, second conduit means for conducting fluid from said motor unit to said pump unit during operation of said first hydrostatic transmission, first relief valve means operable between a closed condition blocking fluid flow and an open condition enabling fluid to flow from said first conduit means to reduce the fluid pressure in said first conduit means, a second hydrostatic transmission including a second pump unit, a second motor unit, third conduit means for conducting fluid from said second pump unit to said second motor unit during operation of said second hydrostatic transmission, fourth conduit means for conducting fluid from said second motor unit to said second pump unit during operation of said second hydrostatic transmission, second relief valve means operable between a closed condition blocking fluid flow and an open condition enabling fluid to flow from said third conduit means to reduce the fluid pressure in said third conduit means, means for applying to said first and second relief valve means fluid pressure forces which urge said first and second relief valve means toward their closed conditions during operation of said first and second hydrostatic transmissions, brake means operable from a released condition to an activated condition to retard movement of a vehicle with which said first and second hydrostatic transmissions are associated, said brake means including a brake unit which is separate from said pump and motor units, and control means for reducing the fluid pressure forces applied to said first and second relief valve means upon operation of said brake means from said released condition to said activated condition.
Claim 22
Dependent Claim
180 words
An apparatus as set forth in claim 17 further including fifth conduit means for conducting fluid from said first conduit means to said second conduit means, said first relief valve means including a first valve member movable between a closed position blocking fluid flow through said fifth conduit means and an open position enabling fluid to flow through said fifth conduit means, sixth conduit means for conducting fluid from said third conduit means to said fourth conduit means, said second relief valve means including a second valve member movable between a closed position blocking fluid flow through said sixth conduit means and an open position enabling fluid to flow through said sixth conduit means, said means for applying a fluid pressure force to said first and second relief valve means including means for exposing surfaces of said first and second valve members to a first fluid pressure, and said control means including means for exposing said surfaces of said first and second valve members to a source of a second fluid pressure which is less than said first fluid pressure.
Claim 23
Independent Claim
436 words
An apparatus comprising a first hydrostatic transmission including a first pump unit, a first motor unit, first conduit means for conducting fluid from said pump unit to said motor unit during operation of said first hydrostatic transmission, second conduit means for conducting fluid from said motor unit to said pump unit during operation of said first hydrostatic transmission, first valve means operable between a closed condition blocking fluid flow and an open condition enabling fluid to flow from said first conduit means to reduce the fluid pressure in said first fluid conduit means, means for exposing at least a portion of said first valve means to a fluid pressure force urging said first valve means toward the closed condition, second hydrostatic transmission including a second pump unit, a second motor unit, third conduit means for conducting fluid from said second pump unit to said second motor unit during operation of said secOnd hydrostatic transmission, fourth conduit means for conducting fluid from said second motor unit to said second pump unit during operation of said second hydrostatic transmission, second valve means operable between a closed condition blocking fluid flow and an open condition enabling fluid to flow from said third conduit means to reduce the fluid pressure in said third conduit means, means for exposing a portion of said second valve means to a fluid pressure force urging said second valve means toward the closed condition, brake means operable from a released condition to an activated condition to retard movement of a vehicle with which said hydrostatic transmissions are associated, said brake means including biasing means for effecting operation of said brake means from the released condition to the engaged condition and pressure chamber means for receiving fluid under pressure to hold said brake means in the released condition against the influence of said biasing means, third valve means operable from a first condition to a second condition to effect a reduction in the fluid pressure in said pressure chamber means and operation of said brake means from said released condition to said activated condition under the influence of said biasing means and to simultaneously therewith effect operation of said first and second valve means from their closed conditions to their open conditions by effecting a reduction in the fluid pressure forces to which said portions of said first and second valve means are exposed, and selectively actuatable control means for effecting operation of said third valve means from said first condition to said second condition to effect operation of said brake means and a reduction in the fluid pressures in said first and third conduit means.
Claim 24
Independent Claim
436 words
An apparatus comprising a first hydrostatic transmission including a first pump unit, a first motor unit, first conduit means for conducting fluid from said pump unit to said motor unit during operation of said first hydrostatic transmission, second conduit means for conducting fluid from said motor unit to said pump unit during operation of said first hydrostatic transmission, first valve means operable between a closed condition blocking fluid flow and an open condition enabling fluid to flow from said first conduit means to reduce the fluid pressure in said first fluid conduit means, means for exposing at least a portion of said first valve means to a fluid pressure force urging said first valve means toward the closed condition, second hydrostatic transmission including a second pump unit, a second motor unit, third conduit means for conducting fluid from said second pump unit to said second motor unit during operation of said secOnd hydrostatic transmission, fourth conduit means for conducting fluid from said second motor unit to said second pump unit during operation of said second hydrostatic transmission, second valve means operable between a closed condition blocking fluid flow and an open condition enabling fluid to flow from said third conduit means to reduce the fluid pressure in said third conduit means, means for exposing a portion of said second valve means to a fluid pressure force urging said second valve means toward the closed condition, brake means operable from a released condition to an activated condition to retard movement of a vehicle with which said hydrostatic transmissions are associated, said brake means including biasing means for effecting operation of said brake means from the released condition to the engaged condition and pressure chamber means for receiving fluid under pressure to hold said brake means in the released condition against the influence of said biasing means, third valve means operable from a first condition to a second condition to effect a reduction in the fluid pressure in said pressure chamber means and operation of said brake means from said released condition to said activated condition under the influence of said biasing means and to simultaneously therewith effect operation of said first and second valve means from their closed conditions to their open conditions by effecting a reduction in the fluid pressure forces to which said portions of said first and second valve means are exposed, and selectively actuatable control means for effecting operation of said third valve means from said first condition to said second condition to effect operation of said brake means and a reduction in the fluid pressures in said first and third conduit means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-23 | 1978-06-24 | 1978-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-23 | 1982-06-24 | 1982-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-23 | 1986-06-24 | 1986-12-24 | $7700.00 | Window Closed / Lapsed |