US3917014A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydrostatic driving and steering transmission
Assignee: Eaton Corp
•
Filing: 1972-04-28
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Granted: 1975-11-04
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Expires: 1992-04-28
Abstract
Abstract A pair of improved valves are utilized in a drive system as steering control valves to regulate the operation of 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 displacement and input to output speed ratios of the hydrostatic transmissions are simultaneously varied by operating a single speed control valve to port control fluid to pressure responsive actuator assemblies which are operable to vary the effective displacement of the hydrostatic transmissions. Upon operation of one of the steering control valves, the actuator assembly of an associated hydrostatic transmission is activated to vary the output speed of the associated hydrostatic transmission and the speed at which one of the tracks of the vehicle is driven. Flow control assemblies are associated with the steering control valves to enable one of the steering valves to be actuated to vary the input to output speed ratio of the associated hydrostatic transmission while maintaining the input to output speed ratio of the other hydrostatic transmission constant. Each of the flow control assemblies includes an orifice for restricting fluid flow to the associated actuator assembly and a check valve which enables fluid to flow in an unrestricted manner from the associated actuator assembly. In one specific preferred embodiment, each of the steering control valves has more than 75% of its effective operating range between an initial condition in which the hydrostatic transmissions are operated at the same speed and a dead track condition in which the associated one of the hydrostatic transmissions is ineffective to drive a track of the vehicle.
Inventors
- 👤 Harold R Ward
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 10:06
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; F16K; F16K11/00; F16K11/02; F16K11/06; F16K11/065; F16K11/07; F16K11/0708
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
448 words
An apparatus comprising a plurality of hydrostatic transmissions having pump and motor units, first actuator means for varying the effective displacement of at least one unit of one of the hydrostatic transmissions in response to a variation in fluid pressure conducted to said first actuator means, second actuator means for varying the effective displacement of at least one unit of another one of the hydrostatic transmissions in response to a variation in fluid pressure conducted to said second actuator means, first, valve means for varying the fluid pressure conducted to said first actuator means to enable the displacement of the one hydrostatic transmission to be varied while maintaining the displacement of the other hydrostatic transmission constant, second valve means for varying the fluid pressure conducted to said second actuator means to enable the displacement of the other hydrostatic transmission to be varied while maintaining the displacement of the one hydrostatic transmission constant, first conduit means connnected in flUid communication with said first and second valve means and a source of fluid pressure for conducted fluid pressure to said first and second valve means from the source of fluid pressure, second conduit means connected in fluid communication with said first valve means and said first actuator means for conducting fluid to and from said first actuator means, third conduit means connected in fluid communication with said second valve means and said second actuator means for conducting fluid to and from said second actuator means, said first valve means including first flow control means for restricting fluid flow from said first conduit means through said first valve means to said second conduit means to maintain the fluid pressure conducted to said second valve means by said first conduit means substantially constant upon operation of said first valve means to thereby enable the displacement of the one hydrostatic transmission to be varied while maintaining the displacement of the other hydrostatic transmission constant, said first flow control means further including means for enabling fluid to flow in an unrestricted manner from said first actuator means through said second conduit means, said second valve means including second flow control means for restricting fluid flow from said first conduit means through said second valve means to said third conduit means and said second actuator means to maintain the fluid pressure in said first conduit means substantially constant upon operation of said second valve means to thereby enable the displacement of the other hydrostatic transmission to be varied while maintaining the displacement of the one hydrostatic transmission constant, said second flow control means further including means for enabling fluid to flow in an unrestricted manner from said second actuator means through said third conduit means.
Claim 2
Independent Claim
448 words
An apparatus comprising a plurality of hydrostatic transmissions having pump and motor units, first actuator means for varying the effective displacement of at least one unit of one of the hydrostatic transmissions in response to a variation in fluid pressure conducted to said first actuator means, second actuator means for varying the effective displacement of at least one unit of another one of the hydrostatic transmissions in response to a variation in fluid pressure conducted to said second actuator means, first, valve means for varying the fluid pressure conducted to said first actuator means to enable the displacement of the one hydrostatic transmission to be varied while maintaining the displacement of the other hydrostatic transmission constant, second valve means for varying the fluid pressure conducted to said second actuator means to enable the displacement of the other hydrostatic transmission to be varied while maintaining the displacement of the one hydrostatic transmission constant, first conduit means connnected in flUid communication with said first and second valve means and a source of fluid pressure for conducted fluid pressure to said first and second valve means from the source of fluid pressure, second conduit means connected in fluid communication with said first valve means and said first actuator means for conducting fluid to and from said first actuator means, third conduit means connected in fluid communication with said second valve means and said second actuator means for conducting fluid to and from said second actuator means, said first valve means including first flow control means for restricting fluid flow from said first conduit means through said first valve means to said second conduit means to maintain the fluid pressure conducted to said second valve means by said first conduit means substantially constant upon operation of said first valve means to thereby enable the displacement of the one hydrostatic transmission to be varied while maintaining the displacement of the other hydrostatic transmission constant, said first flow control means further including means for enabling fluid to flow in an unrestricted manner from said first actuator means through said second conduit means, said second valve means including second flow control means for restricting fluid flow from said first conduit means through said second valve means to said third conduit means and said second actuator means to maintain the fluid pressure in said first conduit means substantially constant upon operation of said second valve means to thereby enable the displacement of the other hydrostatic transmission to be varied while maintaining the displacement of the one hydrostatic transmission constant, said second flow control means further including means for enabling fluid to flow in an unrestricted manner from said second actuator means through said third conduit means.
Claim 3
Dependent Claim
67 words
An apparatus as set forth in claim 1 wherein said first and second flow control means include second and third orifice means for restricting fluid flow through said first and second conduit means toward the associated one of said actuator means and first and second bypass valve means for bypassing fluid from the associated one of said actuator means around the associated one of said orifice means.
Claim 4
Dependent Claim
69 words
An apparatus as set forth in claim 1 wherein said first and second flow control means each include a valve member biased toward a closed position under the influence of control fluid pressure conducted to the associated one of said actuator means, said valve member being movable from the closed position to an open position under the influence of fluid flow from the associated one of said actuator means.
Claim 5
Dependent Claim
41 words
An apparatus as set forth in claim 3 wherein said valve member includes means for defining an orifice through which control fluid can flow to the associated one of said actuator means when said valve member is in the closed position.
Claim 6
Dependent Claim
61 words
An apparatus as set forth in claim 1 wherein said first and second flow control means include first check valve means for at least partially blocking fluid flow through said second conduit means to said first actuator means and second check valve means for at least partially blocking fluid flow through said third conduit means to the said second actuator means.
Claim 7
Dependent Claim
72 words
An apparatus as set forth in claim 1 further including pressure controller means connected in fluid communication with said first conduit means and operable to any one of a plurality of settings to simultaneously vary control fluid pressure conducted through said second conduit means to said first actuator means and through said third conduit means to said second actuator means in accordance with variations in the setting of said pressure controller means.
Claim 8
Dependent Claim
295 words
An apparatus as set forth in claim 1 wherein said second conduit means includes a first passage means for conducting fluid pressure from said first valve means to said first actuator means during operation of said one hydrostatic transmission in a fOrward direction and for conducting relatively low fluid pressure from said first valve means to said actuator means during operation of said one hydrostatic transmission in a reverse direction opposite from said forward direction and second passage means for conducting fluid pressure from said first valve means to said first actuator means during operation of said one hydrostatic transmission in the reverse direction and for conducting relatively low fluid pressure from said first valve means to said first actuator means during operation of said one hydrostatic transmission in the forward direction, said first flow control means including first orifice means for restricting the flow of control fluid from said first valve means through said first passage means to said first actuator means, a first bypass passage connected in fluid communication with opposite sides of said first orifice means, and first check valve means for blocking fluid flow toward said first actuator means through said first bypass passage and for enabling fluid to flow from said first actuator means through said first bypass passage, said second flow control means including second orifice means for restricting the flow of fluid from said first valve means through said second passage means to said first actuator means, a second bypass passage connected in fluid communication with opposite sides of said second orifice means, and second check valve means for blocking fluid flow toward said first actuator means through said second bypass passage and for enabling fluid to flow from said first actuator means through said second bypass passage.
Claim 9
Dependent Claim
52 words
An apparatus as set forth in claim 7 further including pressure controller means connected in fluid communication with said first and second passage means and operable to any one of a plurality of settings to vary the control fluid pressure conducted through one of said passage means to said first actuator means.
Claim 10
Dependent Claim
108 words
An apparatus as set forth in claim 1 wherein said apparatus furher includes first output means associated with said first hydrostatic transmission for driving a first track of a vehicle and second output means associated with said second hydrostatic transmission for driving a second track of the vehicle, said first and second valve means each including a movable valve actuator member and means for varying the fluid pressure conducted to the associated one of said actuator means as a nonlinear function of movement of the associated actuator member and for varying the turning radius of the vehicle as a linear function of movement of the associated actuator member.
Claim 11
Independent Claim
855 words
An apparatus comprising first and second reversible hydrostatic transmissions having a variable displacement pump units, first actuator means for varying the input to output speed ratio of said first hydrostatic transmission during forward and reverse operation of said first hydrostatic transmission, second actuator means for varying the input to output speed ratio of said second hydrostatic transmission during forward and reverse operation of said second hydrostatic transmission, master control valve means for effecting operation of said first and second actutator means to simultaneously vary the input to output speed ratios of said first and second hydrostatic transmissions during forward and reverse operation of said first and second hydrostatic transmissions, first steering valve means for effecting operation of said first actuator means to vary the input to output speed ratio of said first hydrostatic transmission during forward and reverse operation of said first hydrostatic transmission, second steering valve means for effecting operation of said second actuator means to vary the input to output speed ratio of said second hydrostatic transmission during forward and reverse operation of said second hydrostatic transmission, first conduit means for conducting control fluid pressure from said master control valve means to said first steering control valve means and from said first steering control valve means to said first actuator means during forward operation of said first hydrostatic transmission and for connecting said first actuator means in fluid communication with low pressure fluid during reverse operation of said first hydrostatic transmission, second conduit means for conducting control fluid pressure from said master control valve means to said first steering control valve means and from said first steering control valve means to said first actuator means during reverse operation of said first hydrostatic transmission and for connecting said first actuator means in fluid communication with low pressure fluid during forward operation of said first hydrostatic transmisson, third conduit means connected in fluid communication with said first conduit means for conducting control fluid pressure from said master control valve means to said second steering control valve means and from said second steering control valve means to said second actuator means during forward operation of said second hydrostatic transmission and for connecting said second actuator means in fluid communication with low pressure fluid during reverse operation of said second hydrostatic transmission, fourth fluid conduit means connected in fluid communication with said second fluid conduit means for conducting control fluid pressure from said master control valve means to said second steering control valve means and from said second steering control valve means to said second actuator means during reverse operation of said second hydrostatic transmission and for connecting said second actuator means in fluid communication with low pressure fluid during forward operation of said second hydrostatic transmission, said first steering control valve means being actuatable to port control fluid pressure from said first conduit means to said second conduit means during forward operation of said first hydrostatic transmission and to port control fluid pressure from said second conduit means to said first conduit means during reverse operation of said first hydrostatic transmission to thereby effect operation of said first actuator means to vary the input to output speed ratio of said first hydrostatic transmission, said second steering control valve means being actuatable to port control fluid pressure from said third conduit means to said fourth conduit means during forward operation of said second hydrostatic transmission and to port control fluid pressure from said fourth conduit means to said third conduit means during reverse operation of said second hydrostatic transmission to thereby effect operation of said second actuator means to vary the input speed ratio of said second hydrostatic transmission, first orifice means for restricting the flow of control fluid from said first conduit means to said second conduit means upon actuation of said first steering control valve means during operation of said first hydrostatic transmission in the forward direction to prevent excessive fluid flow from said third conduit means to said first conduit means and operation of said second actuator means, second orifice means for restricting the flow of control fluid from said second conduit means to said first conduit means upon actuation of said first control valve means during operation of said first hydrostatic transmission in the reverse direction to prevent excessive fluid flow from said fourth conduit means to said second conduit means and operation of said second actuator means, third orifice means for restricting the flow of control fluid from said third conduit means to said fourth conduit means upon actuation of said second steering control valve means during operation of said second hydrostatic transmission in the forward direction to prevent excessive fluid flow from said first conduit means to said third conduit means and operation of said first actuator means, and fourth orifice means for restricting the flow of control fluid from said fourth conduit means to said third conduit Means upon actuation of said second steering control valve means during operation of said second hydrostatic transmission in the reverse direction to prevent excessive fluid flow from said second conduit means to said fourth conduit means and operation of said first actuator means.
Claim 12
Independent Claim
855 words
An apparatus comprising first and second reversible hydrostatic transmissions having a variable displacement pump units, first actuator means for varying the input to output speed ratio of said first hydrostatic transmission during forward and reverse operation of said first hydrostatic transmission, second actuator means for varying the input to output speed ratio of said second hydrostatic transmission during forward and reverse operation of said second hydrostatic transmission, master control valve means for effecting operation of said first and second actutator means to simultaneously vary the input to output speed ratios of said first and second hydrostatic transmissions during forward and reverse operation of said first and second hydrostatic transmissions, first steering valve means for effecting operation of said first actuator means to vary the input to output speed ratio of said first hydrostatic transmission during forward and reverse operation of said first hydrostatic transmission, second steering valve means for effecting operation of said second actuator means to vary the input to output speed ratio of said second hydrostatic transmission during forward and reverse operation of said second hydrostatic transmission, first conduit means for conducting control fluid pressure from said master control valve means to said first steering control valve means and from said first steering control valve means to said first actuator means during forward operation of said first hydrostatic transmission and for connecting said first actuator means in fluid communication with low pressure fluid during reverse operation of said first hydrostatic transmission, second conduit means for conducting control fluid pressure from said master control valve means to said first steering control valve means and from said first steering control valve means to said first actuator means during reverse operation of said first hydrostatic transmission and for connecting said first actuator means in fluid communication with low pressure fluid during forward operation of said first hydrostatic transmisson, third conduit means connected in fluid communication with said first conduit means for conducting control fluid pressure from said master control valve means to said second steering control valve means and from said second steering control valve means to said second actuator means during forward operation of said second hydrostatic transmission and for connecting said second actuator means in fluid communication with low pressure fluid during reverse operation of said second hydrostatic transmission, fourth fluid conduit means connected in fluid communication with said second fluid conduit means for conducting control fluid pressure from said master control valve means to said second steering control valve means and from said second steering control valve means to said second actuator means during reverse operation of said second hydrostatic transmission and for connecting said second actuator means in fluid communication with low pressure fluid during forward operation of said second hydrostatic transmission, said first steering control valve means being actuatable to port control fluid pressure from said first conduit means to said second conduit means during forward operation of said first hydrostatic transmission and to port control fluid pressure from said second conduit means to said first conduit means during reverse operation of said first hydrostatic transmission to thereby effect operation of said first actuator means to vary the input to output speed ratio of said first hydrostatic transmission, said second steering control valve means being actuatable to port control fluid pressure from said third conduit means to said fourth conduit means during forward operation of said second hydrostatic transmission and to port control fluid pressure from said fourth conduit means to said third conduit means during reverse operation of said second hydrostatic transmission to thereby effect operation of said second actuator means to vary the input speed ratio of said second hydrostatic transmission, first orifice means for restricting the flow of control fluid from said first conduit means to said second conduit means upon actuation of said first steering control valve means during operation of said first hydrostatic transmission in the forward direction to prevent excessive fluid flow from said third conduit means to said first conduit means and operation of said second actuator means, second orifice means for restricting the flow of control fluid from said second conduit means to said first conduit means upon actuation of said first control valve means during operation of said first hydrostatic transmission in the reverse direction to prevent excessive fluid flow from said fourth conduit means to said second conduit means and operation of said second actuator means, third orifice means for restricting the flow of control fluid from said third conduit means to said fourth conduit means upon actuation of said second steering control valve means during operation of said second hydrostatic transmission in the forward direction to prevent excessive fluid flow from said first conduit means to said third conduit means and operation of said first actuator means, and fourth orifice means for restricting the flow of control fluid from said fourth conduit means to said third conduit Means upon actuation of said second steering control valve means during operation of said second hydrostatic transmission in the reverse direction to prevent excessive fluid flow from said second conduit means to said fourth conduit means and operation of said first actuator means.
Claim 13
Dependent Claim
84 words
An apparatus as set forth in claim 10 further including a plurality of bypass passages each of which is connected in fluid communication with opposite sides of an associated one of said orifice means, a plurality of check valve means each of which is associated with one of the bypass passages for blocking fluid flow through the associated bypass passage toward one of aid actuator means and for enabling fluid to flow away from one of said actuator means throught the associated bypass passage.
Claim 14
Dependent Claim
105 words
An apparatus as set forth in claim 11 further including first means associated with said first hydrostatic transmission for driving a first track of a vehicle, second means associated with said second hydrostatic transmission for driving a second track of a vehicle, said first and second steering control valve means each including a movable valve actuator member and means for varying the control fluid pressure conducted to the associated one of said actuator means as a nonlinear function of movement of the associated actuator member and for varying the turning radius of the vehicle as a linear function of movement of the associated actuator member.
Claim 15
Dependent Claim
113 words
An apparatus as set forth in claim 10 wherein said master control valve means includes means for connecting said first and third conduit means in fluid communication with a source of control fluid under pressure and said second and fourth conduit means in fluid communication with a source of low pressure fluid upon operation of said master control valve means in a first direction and for connecting said second and fourth conduit means in fluid communication with a source of control fluid under pressure and said first and third conduit means in fluid communication with a source of low pressure fluid upon operation of said master control valve means in a second direction.
Claim 16
Dependent Claim
75 words
An apparatus as set forth in claim 13 wherein said master control valve means is operable to any one of a plurality of settings to simultaneously vary the control fluid pressure conducted through said first and third conduit means during forward operation of said first and second hydrostatic transmissions and to simultaneously vary the control fluid pressure conducted through said second and fourth conduit means during reverse operation of said first and second hydrostatic transmissions.
Claim 17
Independent Claim
594 words
An apparatus comprising a plurality of hydrostatic transmissions having pump and motor units, first actuator means for varying the effective displacement of at least one unit of one of the hydrostatic transmissions in response to a variation in fluid pressure conducted to said first actuator means, second actuator means for varying the effective displacement of at least one unit of another one of the hydrostatic transmissions in response to a variation in fluid pressure conducted to said second actuator means, first valve means for varying the fluid pressure conducted to said first actuator means to enable the displacement of the one hydrostatic transmission to be varied, second valve means for varying the fluid pressure conducted to said second actuator means to enable the displacement of the other hydrostatic transmission to be varied, first conduit means connected in fluid communication with said first and second valve means and a sourse of fluid pressure for conducting fluid pressure to said first and second valve means from the source of control fluid pressure, second conduit means connected in fluid communication with said first valve means and said first actuator means for conducting to and from said first actuator means, third conduit means connected in fluid communication with said second valve means and said second actuator means for conducting fluid to and from saiD second actuator means, said first valve means being operable from a first condition connecting said first and second fluid conduit means in fluid communication to a second conditon to effect a flow of fluid from said first conduit means to said second conduit means and operation of said first actuator means to vary the displacement of said first hydrostatic transmission, said second valve means being operable from a first condition connecting said first conduit means in fluid communication with said third conduit means to a second condition to effect a flow of fluid from said first conduit means to said third conduit means and operation of said second actuator means to vary the displacement of said second hydrostatic transmission, said first valve means including first flow control means for restricting fluid flow from said first conduit means through said first valve means to said second conduit means upon operation of said first valve means from its first condition to its second condition with said second valve means in its first condition to maintain the fluid pressure conducted to said second valve means by said first conduit means substantially constant upon operation of said first valve means to thereby enable the displacement of the one hydrostatic transmission to be varied while maintaining the displacement of the other hydrostatic transmission constant, said first flow control means further including means for enabling fluid to flow in an unrestricted manner from said first actuator means through said second conduit means, said second valve means including second slow control means for restricting fluid flow from said first conduit means through said second valve means to said third conduit means upon operation of said second valve means from its first condition to its second condition with said first valve means in its first condition to maintain the control fluid pressure conducted to said first valve means by said first conduit means substantially constant upon operation of said second valve means to thereby enable the displacement of the other hydrostatic transmission to be varied while maintaining the displacement of the one hydrostatic transmission constant, said second flow control means further including means for enabling fluid to flow in an unrestricted manner from said second actuator means through said third actuator means.
Claim 18
Independent Claim
594 words
An apparatus comprising a plurality of hydrostatic transmissions having pump and motor units, first actuator means for varying the effective displacement of at least one unit of one of the hydrostatic transmissions in response to a variation in fluid pressure conducted to said first actuator means, second actuator means for varying the effective displacement of at least one unit of another one of the hydrostatic transmissions in response to a variation in fluid pressure conducted to said second actuator means, first valve means for varying the fluid pressure conducted to said first actuator means to enable the displacement of the one hydrostatic transmission to be varied, second valve means for varying the fluid pressure conducted to said second actuator means to enable the displacement of the other hydrostatic transmission to be varied, first conduit means connected in fluid communication with said first and second valve means and a sourse of fluid pressure for conducting fluid pressure to said first and second valve means from the source of control fluid pressure, second conduit means connected in fluid communication with said first valve means and said first actuator means for conducting to and from said first actuator means, third conduit means connected in fluid communication with said second valve means and said second actuator means for conducting fluid to and from saiD second actuator means, said first valve means being operable from a first condition connecting said first and second fluid conduit means in fluid communication to a second conditon to effect a flow of fluid from said first conduit means to said second conduit means and operation of said first actuator means to vary the displacement of said first hydrostatic transmission, said second valve means being operable from a first condition connecting said first conduit means in fluid communication with said third conduit means to a second condition to effect a flow of fluid from said first conduit means to said third conduit means and operation of said second actuator means to vary the displacement of said second hydrostatic transmission, said first valve means including first flow control means for restricting fluid flow from said first conduit means through said first valve means to said second conduit means upon operation of said first valve means from its first condition to its second condition with said second valve means in its first condition to maintain the fluid pressure conducted to said second valve means by said first conduit means substantially constant upon operation of said first valve means to thereby enable the displacement of the one hydrostatic transmission to be varied while maintaining the displacement of the other hydrostatic transmission constant, said first flow control means further including means for enabling fluid to flow in an unrestricted manner from said first actuator means through said second conduit means, said second valve means including second slow control means for restricting fluid flow from said first conduit means through said second valve means to said third conduit means upon operation of said second valve means from its first condition to its second condition with said first valve means in its first condition to maintain the control fluid pressure conducted to said first valve means by said first conduit means substantially constant upon operation of said second valve means to thereby enable the displacement of the other hydrostatic transmission to be varied while maintaining the displacement of the one hydrostatic transmission constant, said second flow control means further including means for enabling fluid to flow in an unrestricted manner from said second actuator means through said third actuator means.
Claim 19
Dependent Claim
83 words
An apparatus as set forth in claim 15 further including pressure controller means connected in fluid communication with said first conduit means and operable to any one of a plurality of settings to simultaneously vary fluid pressure conducted through said second conduit means to said first actuator means and through said third conduit means to said second actuator means in accordance with variations in the settings of said pressure controller means when said first and second valve means are in their first conditions.
Claim 20
Independent Claim
391 words
An apparatus comprising a plurality of hydrostatic transmissions having pump and motor units, first actuator means for varying the effective displacement of at least one unit of one of the hydrostatic transmissions in response to a variation in control fluid pressure, second actuator means for varying the effective displacement of at least one unit of another one of the hydrostatic transmissions in response to a variation in control fluid pressure, first conduit means for conducting control fluid to and from said first actuator means, second conduit means connected in fluid communication with said first conduit means for conducting control fluid to and from said second actuator means, first valve means for varying the control fluid, pressure conducted to said first actuator means while maintaining the control fluid pressure conducted to said second actuator means substantially constant to enable the displacement of the one hydrostatic transmission to be varied while maintaining the displacement of the other hydrostatic transmission constant, said first valve means including first flow control means for reStricting fluid flow to said first actuator means through said first conduit means and for enabling fluid to flow in an unrestricted manner from said first actuator means through said first conduit means, second valve means for varying the control fluid pressure conducted to said second actuator means while maintaining the control fluid pressure conducted to said first actuator means substantially constant to enable the displacement of the other hydrostatic transmission to be varied while maintaining the displacement of the one hydrostatic transmission constant, said second valve means including second flow control means for restricting fluid flow to said second actuator means through said second conduit means and for enabling fluid to flow in an unrestricted manner from said second actuator means through said second conduit means, first output means associated with said first hydrostatic transmission for driving a first track of a vehicle and second output means associated with said second hydrostatic transmission for driving a second track of the vehicle, said first and second valve means each including a movable valve actuator member and means for varying the control fluid pressure conducted to the associated one of said actuator means as a nonlinear function of movement of the associated actuator member and for varying the turning radius of the vehicle as a linear function of movement of the associated actuator member.
Claim 21
Independent Claim
391 words
An apparatus comprising a plurality of hydrostatic transmissions having pump and motor units, first actuator means for varying the effective displacement of at least one unit of one of the hydrostatic transmissions in response to a variation in control fluid pressure, second actuator means for varying the effective displacement of at least one unit of another one of the hydrostatic transmissions in response to a variation in control fluid pressure, first conduit means for conducting control fluid to and from said first actuator means, second conduit means connected in fluid communication with said first conduit means for conducting control fluid to and from said second actuator means, first valve means for varying the control fluid, pressure conducted to said first actuator means while maintaining the control fluid pressure conducted to said second actuator means substantially constant to enable the displacement of the one hydrostatic transmission to be varied while maintaining the displacement of the other hydrostatic transmission constant, said first valve means including first flow control means for reStricting fluid flow to said first actuator means through said first conduit means and for enabling fluid to flow in an unrestricted manner from said first actuator means through said first conduit means, second valve means for varying the control fluid pressure conducted to said second actuator means while maintaining the control fluid pressure conducted to said first actuator means substantially constant to enable the displacement of the other hydrostatic transmission to be varied while maintaining the displacement of the one hydrostatic transmission constant, said second valve means including second flow control means for restricting fluid flow to said second actuator means through said second conduit means and for enabling fluid to flow in an unrestricted manner from said second actuator means through said second conduit means, first output means associated with said first hydrostatic transmission for driving a first track of a vehicle and second output means associated with said second hydrostatic transmission for driving a second track of the vehicle, said first and second valve means each including a movable valve actuator member and means for varying the control fluid pressure conducted to the associated one of said actuator means as a nonlinear function of movement of the associated actuator member and for varying the turning radius of the vehicle as a linear function of movement of the associated actuator member.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-11-03 | 1979-05-05 | 1979-11-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-03 | 1983-05-05 | 1983-11-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-03 | 1987-05-05 | 1987-11-04 | $7700.00 | Window Closed / Lapsed |