US3915068A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydrostatic transmission
Assignee: Deere and Co
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Filing: 1974-08-30
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Granted: 1975-10-28
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Expires: 1994-08-30
Abstract
Abstract A hydrostatic drive system for a land vehicle includes a fluid pump, a fluid reservoir, a pair of fluid motors connected to drive wheels of the vehicle, a supply line connected between the pump and motors, a return line connected between the reservoir and motors, and a retarder valve movable between open and closed positions and biased toward the closed position interposed in the return line. The retarder valve includes a servo chamber responsive to fluid pressure therein to move the retarder valve to its open position. First and second fluid passage means establish communication between the servo chamber and the supply and return lines, respectively. An additional valve movable between open and closed positions and biased toward the open position is interposed in the second fluid passage means and is responsive to a predetermined pressure in the supply line to move to its closed position. The retarder valve provides a braking effect if the motors are driven mechanically and begin to function as pumps, for example, when the vehicle is going down an incline at a speed greater than the capacity of the drive system, and the second fluid passage means and the valve therein prevents the retarder valve from completely closing and locking the wheels as long as the system is in operation.
Inventors
- 👤 Max Paul Gassman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 20:06
CPC Classifications
F; F16; F16H; F16H61/00; F16H61/38; F16H61/40; F16H61/4157; F15; F15B; F15B11/00; F15B11/02; F15B11/04; F15B11/044; F15B11/0445; F16D; F16D57/00; F16D57/06; F15B2211/00; F15B2211/30; F15B2211/305; F15B2211/30525; F15B2211/3053; F15B2211/3055; F15B2211/50; F15B2211/505; F15B2211/50509; F15B2211/50518; F15B2211/50545; F15B2211/515; F15B2211/5156; F15B2211/555; F15B2211/60; F15B2211/61; F15B2211/613; F15B2211/70; F15B2211/705; F15B2211/7058; F15B2211/71; F15B2211/7114; F15B2211/7128
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
177 words
A hydrostatic drive system for a vehicle comprising: a source of fluid pressure; a fluid reservoir; fluid motor means drivingly coupled to drive wheel means of the vehicle and having inlet and outlet ports; supply line means interconnecting the source and motor inlet port; return line means interconnecting the reservoir and motor outlet port; retarder valve means movable between open and closed positions and biased toward the closed position interposed in the return line means; pressure responsive means associated with the retarder valve means to move the same toward its open position in response to fluid pressure; first passage means establishing communication between the supply line means and pressure responsive means; second passage means establishing communication between the return line means and the pressure responsive means; and valve means movable between open and closed positions and biased toward the open position interposed in the second passage means; and means associated with the last mentioned valve means responsive to a predetermined pressure in the supply line means to hold the last mentioned valve means in its closed position.
Claim 2
Dependent Claim
177 words
A hydrostatic drive system for a vehicle comprising: a source of fluid pressure; a fluid reservoir; fluid motor means drivingly coupled to drive wheel means of the vehicle and having inlet and outlet ports; supply line means interconnecting the source and motor inlet port; return line means interconnecting the reservoir and motor outlet port; retarder valve means movable between open and closed positions and biased toward the closed position interposed in the return line means; pressure responsive means associated with the retarder valve means to move the same toward its open position in response to fluid pressure; first passage means establishing communication between the supply line means and pressure responsive means; second passage means establishing communication between the return line means and the pressure responsive means; and valve means movable between open and closed positions and biased toward the open position interposed in the second passage means; and means associated with the last mentioned valve means responsive to a predetermined pressure in the supply line means to hold the last mentioned valve means in its closed position.
Claim 3
Dependent Claim
178 words
A hydrostatic drive system for a vehicle comprising: a source of fluid pressure; a fluid reservoir; fluid motor means drivingly coupled to drive wheel means of the vehicle and having inlet and outlet ports; supply line means interconnecting the source and motor inlet port; return line means interconnecting the reservoir and motor outlet port; retarder valve means movable between open and closed positions interposed in the return line means; means biasing the retarder valve means toward the closed position; servo means associated with the retarder valve means responsive to fluid pressure to bias the retarder valve means toward its open position in opposition to the biasing means; first pilot passage means interconnecting the supply line means and the servo means; second pilot passage means interconnecting the return line means and the servo means; valve means movable between open and closed positions and biased toward its open position interposed in the second pilot passage means; and means responsive to fluid pressure in the servo means biasing the valve means in the second pilot passage means to the closed position.
Claim 4
Dependent Claim
178 words
A hydrostatic drive system for a vehicle comprising: a source of fluid pressure; a fluid reservoir; fluid motor means drivingly coupled to drive wheel means of the vehicle and having inlet and outlet ports; supply line means interconnecting the source and motor inlet port; return line means interconnecting the reservoir and motor outlet port; retarder valve means movable between open and closed positions interposed in the return line means; means biasing the retarder valve means toward the closed position; servo means associated with the retarder valve means responsive to fluid pressure to bias the retarder valve means toward its open position in opposition to the biasing means; first pilot passage means interconnecting the supply line means and the servo means; second pilot passage means interconnecting the return line means and the servo means; valve means movable between open and closed positions and biased toward its open position interposed in the second pilot passage means; and means responsive to fluid pressure in the servo means biasing the valve means in the second pilot passage means to the closed position.
Claim 5
Dependent Claim
30 words
A hydrostatic drive system as set forth in claim 2 wherein the retarder valve and the valve means interposed in the second pilot passage means are interconnected for simultaneous movement.
Claim 6
Dependent Claim
307 words
A hydrostatic drive system for a vehicle comprising: a source of fluid pressure; a fluid reservoir; fluid motor means drivingly coupled to drive wheel means of the vehicle and having inlet and outlet ports; supply line means interconnecting the source and motor inlet port; return line means interconnecting the reservoir and motor outlet port; retarder valve means interposed in the return line means including a valve body having a bore therein closed at both ends, a pair of ports connected to the return line and intersecting the bore at spaced locations; a spool slidably mounted in the bore and having lands at its opposide ends defining therebetween an annular grooved area of sufficient length to span the pair of ports and provide free communication therebetween; spring means acting between one closed end of the bore and one end of the spool biasing the spool toward a fluid blocking position in which the land on the one end of the spool blocks one of the pair of ports; the second closed end of the bore and the second end of the spool forming a servo chamber having a movable member therein responsive to fluid pressure therein to move the spool against the bias of the spring toward a fluid passing position in which the grooved area spans the pair of ports; first pilot passage means interconnecting the supply line means and the servo chamber; second pilot passage means interconnecting the servo chamber and return line means between the retarder valve means and motor means; and valve means interposed in the second pilot passage means; the last mentioned valve means being interconnected with the retarder valve means for movement therewith between a closed position when the retarder valve means is in its fluid passing position and an open position when the retarder valve means approaches its fluid blocking position.
Claim 7
Dependent Claim
307 words
A hydrostatic drive system for a vehicle comprising: a source of fluid pressure; a fluid reservoir; fluid motor means drivingly coupled to drive wheel means of the vehicle and having inlet and outlet ports; supply line means interconnecting the source and motor inlet port; return line means interconnecting the reservoir and motor outlet port; retarder valve means interposed in the return line means including a valve body having a bore therein closed at both ends, a pair of ports connected to the return line and intersecting the bore at spaced locations; a spool slidably mounted in the bore and having lands at its opposide ends defining therebetween an annular grooved area of sufficient length to span the pair of ports and provide free communication therebetween; spring means acting between one closed end of the bore and one end of the spool biasing the spool toward a fluid blocking position in which the land on the one end of the spool blocks one of the pair of ports; the second closed end of the bore and the second end of the spool forming a servo chamber having a movable member therein responsive to fluid pressure therein to move the spool against the bias of the spring toward a fluid passing position in which the grooved area spans the pair of ports; first pilot passage means interconnecting the supply line means and the servo chamber; second pilot passage means interconnecting the servo chamber and return line means between the retarder valve means and motor means; and valve means interposed in the second pilot passage means; the last mentioned valve means being interconnected with the retarder valve means for movement therewith between a closed position when the retarder valve means is in its fluid passing position and an open position when the retarder valve means approaches its fluid blocking position.
Claim 8
Dependent Claim
100 words
A hydrostatic drive system as set forth in claim 4 wherein the supply line means includes a pair of aligned ports in the valve body intersecting the bore in the area of the land on the one end of the spool, the spool is provided with a transverse bore in the land on the one end thereof in an area to be in communication with said pair of aligned ports throughout the range of movement of the spool, and the spool is provided with an additional bore extending between and establishing communication between the transverse bore and the servo chamber.
Claim 9
Dependent Claim
123 words
A hydrostatic drive system as set forth in claim 5 wherein the land on the second end of the spool is provided with an annular groove, and the second pilot passage means includes a second transverse bore extending from the annular groove to the additional bore and passage means establishing communication between the upstream one of the pair of ports connected to the return line means and the bore in the valve body in the area of the land on the second end of the spool to communicate with the annular groove as the spool approaches its fluid blocking position and to be blocked by the land on the second end of the spool when the spool is in its fluid passing position.
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) | 1978-10-27 | 1979-04-28 | 1979-10-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-27 | 1983-04-28 | 1983-10-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-27 | 1987-04-28 | 1987-10-28 | $7700.00 | Window Closed / Lapsed |