US3660975A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydrostatic transmission systems
Assignee: ZF International UK Ltd
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Filing: 1970-09-17
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Granted: 1972-05-09
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Expires: 1990-09-17
Abstract
Abstract An hydrostatic transmission in which there is provided an automatic pump displacement control, a manual override device for overriding the displacement control to keep the pump displacement at a low level, and a device sensitive to pump inlet pressure to render the override device inoperative when the pump inlet pressure exceeds a predetermined value.
Inventors
- 👤 Anthony Eugene Joseph Martin
- 👤 Bernard James Baker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 03:52
CPC Classifications
F; F16; F16H; F16H61/00; F16H61/38; F16H61/40; F16H61/46; F16H61/462; F01; F01B; F01B9/00; F01B9/04; F01B9/047
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
114 words
A hydrostatic transmission system comprising an engine driven variable displacement hydraulic pump, a hydraulic motor drivingly coupled to road wheels of a vehicle and hydraulically connected to the pump, an automatic control for the pump arranged to regulate the pump displacement to give a pump delivery pressure of the pump determined by at least one parameter of the transmission, a manually actuable override, mechanism arranged to override the automatic control so as to impose a limit on the pump displacement during forward drive conditions, and means sensitive to the inlet pressure of the pump to render said override means inoperative when the inlet pressure of the pump exceeds a predetermined value in overrunning conditions.
Claim 2
Dependent Claim
114 words
A hydrostatic transmission system comprising an engine driven variable displacement hydraulic pump, a hydraulic motor drivingly coupled to road wheels of a vehicle and hydraulically connected to the pump, an automatic control for the pump arranged to regulate the pump displacement to give a pump delivery pressure of the pump determined by at least one parameter of the transmission, a manually actuable override, mechanism arranged to override the automatic control so as to impose a limit on the pump displacement during forward drive conditions, and means sensitive to the inlet pressure of the pump to render said override means inoperative when the inlet pressure of the pump exceeds a predetermined value in overrunning conditions.
Claim 3
Dependent Claim
62 words
The systEm as claimed in claim 1 the automatic control including an hydraulic displacement varying unit and a servo-valve therefor, said override mechanism comprising a member movably mounted on part of said unit and means for displacing said member between an operative position in which it actuates said valve on movement of said part beyond a predetermined position and an inoperative position.
Claim 4
Dependent Claim
66 words
The system as claimed in claim 2 in which said unit is a piston and cylinder unit having a piston rod constituting said part, said valve being movable by a link extending parallel with said piston rod and said member being an arm pivotally mounted on said rod and co-acting with a spring loaded sleeve on the link when the arm is in its operative position.
Claim 5
Dependent Claim
32 words
The system as claimed in claim 2 in which said means for displacing said member is a piston and cylinder unit and a valve controlling the supply of fluid to said unit.
Claim 6
Dependent Claim
35 words
The system as claimed in claim 4 in which said valve is electrically actuable, with said means sensitive to the inlet pressure of the pump being a pressure switch connected in series with said valve.
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) | 1975-05-09 | 1975-11-08 | 1976-05-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-05-09 | 1979-11-08 | 1980-05-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-05-09 | 1983-11-08 | 1984-05-09 | $7700.00 | Window Closed / Lapsed |