Patent US3886741A successfully refreshed from Google Patents.
US3886741A
Expired / Lapsed
US
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Hydrostatic transmission anti-stall system
Assignee: Alfa Laval AB
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Filing: 1974-03-13
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Granted: 1975-06-03
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Expires: 1994-03-13
Abstract
Abstract An improved control system for a hydrostatic transmission includes an anti-stall system for preventing overloading of an engine which drives the hydrostatic transmission. This anti-stall system is provided with a rate control assembly which is effective to negate oscillating or overcorrecting tendencies of the anti-stall system during rapid changes in the loading of an engine which drives the transmission. The anti-stall system includes first and second valve assemblies which are interconnected by a conduit. The first valve assembly is operable to vary the fluid pressure in this conduit to effect operation of the second valve assembly and a variation in the output speed of the hydrostatic transmission. A rate control assembly is connected with the conduit between the first and second valve assemblies and is effective to induce a flow of fluid to retard operation of the first valve assembly in response to a rapid change in the fluid pressure in the conduit. The rate control assembly is rendered ineffective during steady state and slowly changing load conditions by a rate control orifice which allows low rates of fluid flow from the rate control assembly to pass through the first valve assembly without retarding its operation. A pair of rate control limit check valves are advantageously connected in parallel with the rate control orifice to enable the anti-stall valve assembly to quickly respond to relatively large changes in load.
Inventors
- 👤 Harold R Ward
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 12:57
CPC Classifications
F; F16; F16H; F16H61/00; F16H61/38; F16H61/40; F16H61/46; F16H61/478; B; B62; B62D; B62D11/00; B62D11/02; B62D11/06; B62D11/10; B62D11/14; B62D11/18; B62D11/183; F16H61/468
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
95 words
An apparatus for controlling the operation of a hydrostatic transmission driven by a prime mover and having a variable displacement hydrostatic unit, said apparatus comprising motor means for varying the displacement of the hydrostatic unit and the output speed of the hydrostatic transmission, anti-stall means for effecting operation of said motor means to vary the displacement of the hydrostatic transmission upon the occurrence of an impending overloading of the prime mover, and rate control means for retarding operation of said anti-stall means in response to a rapid increase in the loading of the prime mover.
Claim 2
Independent Claim
95 words
An apparatus for controlling the operation of a hydrostatic transmission driven by a prime mover and having a variable displacement hydrostatic unit, said apparatus comprising motor means for varying the displacement of the hydrostatic unit and the output speed of the hydrostatic transmission, anti-stall means for effecting operation of said motor means to vary the displacement of the hydrostatic transmission upon the occurrence of an impending overloading of the prime mover, and rate control means for retarding operation of said anti-stall means in response to a rapid increase in the loading of the prime mover.
Claim 3
Independent Claim
95 words
An apparatus for controlling the operation of a hydrostatic transmission driven by a prime mover and having a variable displacement hydrostatic unit, said apparatus comprising motor means for varying the displacement of the hydrostatic unit and the output speed of the hydrostatic transmission, anti-stall means for effecting operation of said motor means to vary the displacement of the hydrostatic transmission upon the occurrence of an impending overloading of the prime mover, and rate control means for retarding operation of said anti-stall means in response to a rapid increase in the loading of the prime mover.
Claim 4
Independent Claim
95 words
An apparatus for controlling the operation of a hydrostatic transmission driven by a prime mover and having a variable displacement hydrostatic unit, said apparatus comprising motor means for varying the displacement of the hydrostatic unit and the output speed of the hydrostatic transmission, anti-stall means for effecting operation of said motor means to vary the displacement of the hydrostatic transmission upon the occurrence of an impending overloading of the prime mover, and rate control means for retarding operation of said anti-stall means in response to a rapid increase in the loading of the prime mover.
Claim 5
Dependent Claim
33 words
An apparatus as set forth in claim 1 wherein said rate control means further includes orifice means for limiting the rate of flud flow between said anti-stall means and said rate control means.
Claim 6
Dependent Claim
79 words
An apparatus as set forth in claim 2 wherein said rate control means includes conduit means for conducting fluid from an upstream side of said orifice means to a downstream side of said orifice means and valve means operable from a closed condition blocking fluid flow through said conduit means to an open condition enabling fluid to flow through said conduit means in response to a predetermined pressure differential between the upstream and downstream sides of said orifice means.
Claim 7
Independent Claim
213 words
An apparatus for controlling the operation of a hydrostatic transmission driven by a prime mover and having a variable displacement hydrostatic unit, said apparatus comprising fluid motor means for varying the displacement of the hydrostatic unit and the output speed of the hydrostatic transmission in response to a change in fluid pressure conducted to said fluid motor means, control means for directing fluid under pressure to said fluid motor means, anti-stall means operable from a first condition to a second condition to effect a change in the pressure of the fluid conducted to said motor means and operation of said motor means to reduce the output speed of the hydrostatic transmission in response to the occurrence of an impending overloading of the prime mover, said anti-stall means being operable from the second condition to the first condition to effect a change in the pressure of the fluid conducted to said motor means and operation of said motor means to increase the output speed of the hydrostatic transmission in response to a relieving of the impending overloading of the prime mover, and rate control means for providing an output to retard operation of said anti-stall means between the first and second conditions in response to rapid changes in the loading of the prime mover.
Claim 8
Independent Claim
213 words
An apparatus for controlling the operation of a hydrostatic transmission driven by a prime mover and having a variable displacement hydrostatic unit, said apparatus comprising fluid motor means for varying the displacement of the hydrostatic unit and the output speed of the hydrostatic transmission in response to a change in fluid pressure conducted to said fluid motor means, control means for directing fluid under pressure to said fluid motor means, anti-stall means operable from a first condition to a second condition to effect a change in the pressure of the fluid conducted to said motor means and operation of said motor means to reduce the output speed of the hydrostatic transmission in response to the occurrence of an impending overloading of the prime mover, said anti-stall means being operable from the second condition to the first condition to effect a change in the pressure of the fluid conducted to said motor means and operation of said motor means to increase the output speed of the hydrostatic transmission in response to a relieving of the impending overloading of the prime mover, and rate control means for providing an output to retard operation of said anti-stall means between the first and second conditions in response to rapid changes in the loading of the prime mover.
Claim 9
Independent Claim
196 words
An apparatus for controlling the operation of a hydrostatic transmission driven by a prime mover and having a variable displacement hydrostatic unit, said apparatus comprising motor means for varying the displacement of the hydrostatic unit and the output speed of the hydrostatic transmission, anti-stall means for effecting operation of said motor means to vary the displacement of the hydrostatic transmission upon the occurrence of an impending overloading of the prime mover, and rate control means for retarding operation of said anti-stall means in response to a rapid variation in the loading of the prime mover, said anti-stall means including a first valve assembly, a second valve assembly, conduit means for conducting fluid pressure from said first valve assembly to said second valve assembly, said first valve assembly including a first valve member and means for actuating said first valve member upon the occurrence of an impending overloading of the prime mover to vary the fluid pressure conducted by said conduit means to said second valve assembly, said second valve assembly including a second valve member and means for actuating said second valve member in response to a variation in the fluid pressure in said conduit means.
Claim 10
Independent Claim
196 words
An apparatus for controlling the operation of a hydrostatic transmission driven by a prime mover and having a variable displacement hydrostatic unit, said apparatus comprising motor means for varying the displacement of the hydrostatic unit and the output speed of the hydrostatic transmission, anti-stall means for effecting operation of said motor means to vary the displacement of the hydrostatic transmission upon the occurrence of an impending overloading of the prime mover, and rate control means for retarding operation of said anti-stall means in response to a rapid variation in the loading of the prime mover, said anti-stall means including a first valve assembly, a second valve assembly, conduit means for conducting fluid pressure from said first valve assembly to said second valve assembly, said first valve assembly including a first valve member and means for actuating said first valve member upon the occurrence of an impending overloading of the prime mover to vary the fluid pressure conducted by said conduit means to said second valve assembly, said second valve assembly including a second valve member and means for actuating said second valve member in response to a variation in the fluid pressure in said conduit means.
Claim 11
Dependent Claim
142 words
An apparatus as set forth in claim 5 wherein said means for actuating said first valve member includes a cylinder, a piston disposed within said cylinder and cooperating therewith to define a first chamber connected in fluid communication with said conduit means and a second chamber connected in fluid communication with said means for actuating said first valve member, said piston being movable under the influence of fluid pressures in said first chamber to decrease the size of said second chamber and induce a flow of fluid from said rate control means to said means for actuating said first valve member, said piston being movable under the influence of pressure in said second chamber to increase the size of said second chamber and induce a flow of fluid to said rate control means from said means for actuating said first valve member.
Claim 12
Dependent Claim
119 words
An apparatus as set forth in claim 4 wherein said anti-stall means includes means for providing a first and second fluid pressures, means for varying the magnitude of said first fluid pressure relative to said second fluid pressure as a function of variations in the operating speed of the prime mover, and means for effecting operation of said anti-stall means between the first and second conditions in response to variations in the difference between said first and second fluid pressures, said rate control means including means for providing a fluid pressure signal opposing variations in said first fluid pressure relative to said second fluid pressure in response to fluctuations in the difference between said first and second fluid pressures.
Claim 13
Dependent Claim
214 words
An apparatus as set forth in claim 7 wherein said means for effecting operation of said anti-stall means between said first and second conditions includes first and second expansible chambers, means for conducting said first fluid pressure to said first expansible chamber, means for conducting said second fluid pressure to said second expansible chamber, said first and second expansible chambers being interconnected in such a manner that expansion of said first expansible chamber under the influence of said first fluid pressure contracts said second expansible chamber and expansion of said second expansible chamber under this influence of said second fluid pressure contracts said first expansible chamber, valve means connected with said first and second expansible chambers for effecting changes in the fluid pressure conducted to said motor means in response to expansion and contraction of said first and second expansible chambers, said rate control means including means for providing a fluid pressure signal tending to increase the fluid pressure in said second expansible chamber in response to an increase in said first fluid pressure relative to said second fluid pressure and for providing a fluid pressure signal tending to decrease the fluid pressure in said second expansible chamber in response to a decrease in said first fluid pressure relative to said second fluid pressure.
Claim 14
Dependent Claim
49 words
An apparatus as set forth in claim 4 wherein said rate control means includes means for discharging fluid to said anti-stall means during an impending overloading of the prime mover and for accepting fluid from said anti-stall means during a relieving of an impending overloading of the prime mover.
Claim 15
Dependent Claim
167 words
An apparatus as set forth in claim 4 wherein said anti-stall means includes valve mean operable between first and second positions to effect a change in the fluid pressure conducted to said motor means, expandable chamber mEans for effecting operation of said valve means between said first and second positions upon expansion and contraction of said expandable chamber means, and conduit means for conducting fluid to and from said expandable chamber means to effect expansion and contraction of said expandable chamber means and operation of said valve means between the first and second positions, said rate control means including means for discharging fluid to said expandable chamber means during a flow of fluid from said expandable chamber means through said conduit means and for accepting fluid from said expandable chamber means during a flow of fluid to said expandable chamber means from said conduit to thereby retard expansion and contraction of said expandable chamber means and operation of said valve means between said first and second positions.
Claim 16
Dependent Claim
29 words
An apparatus as set forth in claim 10 further including orifice means for retarding the flow of fluid to and from said expandable chamber means through said conduit means.
Claim 17
Dependent Claim
165 words
An apparatus as set forth in claim 4 further including pump means for supplying fluid at a first pressure which varies as a function of variations in the operating speed of the prime mover, said anti-stall means including orifice means connected in fluid communcation with said pump means for reducing the pressure of fluid from said pump to a second pressure which differs from said first pressure by an amount which varies as a function of variations in the operating speed of the prime mover, valve means for effecting a change in the pressure of the fluid conducted to said motor means, and actuator means for operating said valve means to effect a change in the pressure conducted to said motor means in response to a variation in the difference between said first and second pressures, said rate control means including means for retarding rapid changes in the difference between said first and second pressures during rapid changes in the loading of the prime mover.
Claim 18
Dependent Claim
49 words
An apparatus as set forth in claim 4, wherein said rate control means includes means for rendering said rate control means ineffective to retard operation of said anti-stall means when the magnitude of the change in the loading of the prime mover is in excess of a predetermined magnitude.
Claim 19
Independent Claim
120 words
An apparatus for controlling the operation of a hydrostatic transmission driven by a prime mover and having a variable displacement hydrostatic unit, said apparatus comprising motor means for varying the displacement of the hydrostatic unit and the output speed of the hydrostatic transmission, anti-stall means for effecting operation of said motor means to vary the displacement of the hydrostatic transmission upon the occurrence of an impending overloading of the prime mover, and rate control means for retarding operation of said anti-stall means in response to a rapid variation in the loading of the prime mover, said rate control means including means for receiving fluid from and discharging fluid to said anti-stall means to thereby retard operation of said anti-stall means.
Claim 20
Independent Claim
120 words
An apparatus for controlling the operation of a hydrostatic transmission driven by a prime mover and having a variable displacement hydrostatic unit, said apparatus comprising motor means for varying the displacement of the hydrostatic unit and the output speed of the hydrostatic transmission, anti-stall means for effecting operation of said motor means to vary the displacement of the hydrostatic transmission upon the occurrence of an impending overloading of the prime mover, and rate control means for retarding operation of said anti-stall means in response to a rapid variation in the loading of the prime mover, said rate control means including means for receiving fluid from and discharging fluid to said anti-stall means to thereby retard operation of said anti-stall 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) | 1978-06-02 | 1978-12-02 | 1979-06-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-02 | 1982-12-02 | 1983-06-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-02 | 1986-12-02 | 1987-06-03 | $7700.00 | Window Closed / Lapsed |