US3865514A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Power transmission
Assignee: Vickers Inc
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Filing: 1973-07-25
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Granted: 1975-02-11
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Expires: 1993-07-25
Abstract
Abstract In a pressure compensated variable displacement pump for hydraulic power transmission systems, a start-up valve is provided for temporarily reducing the pump displacement to near zero to avoid imposing excessive torque upon the cranking motor of an internal combustion engine or upon a low starting torque electric prime mover driving the pump. The valve is applicable to pressure compensators of the type having a pilot circuit carrying a continuous bleed flow governed by a pressure responsive pilot relief valve. The start-up valve automatically bypasses the pilot relief valve when the system is at rest and for a predetermined interval during start-up of the prime mover.
Inventors
- 👤 Kurt R Lonnemo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 05:12
CPC Classifications
F; F04; F04B; F04B49/00; F04B49/02; F04B49/22
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
144 words
In a control system for a pressure compensated variable displacement hydraulic pump of the type having a spring biased, displacement reducing, servo motor operated by a three-way pilot valve connected to the pump outlet and to exhaust and having a control circuit including a restrictor and a relief valve in series between the pump outlet and the exhaust to carry a continuous bleed flow with the pilot valve responsive to the pressure drop through the restrictor, that improvement which includes a two-way start-up valve in parallel with the relief valve and biased to open position when not subjected to inlet pressure, the position of the start-up valve controlling the pressure on the downstream side of the restrictor, which in turn positions the three-way pilot valve and hydraulic damping means for restricting the rate of closing of the starT-up valve when subjected to inlet pressure.
Claim 2
Dependent Claim
144 words
In a control system for a pressure compensated variable displacement hydraulic pump of the type having a spring biased, displacement reducing, servo motor operated by a three-way pilot valve connected to the pump outlet and to exhaust and having a control circuit including a restrictor and a relief valve in series between the pump outlet and the exhaust to carry a continuous bleed flow with the pilot valve responsive to the pressure drop through the restrictor, that improvement which includes a two-way start-up valve in parallel with the relief valve and biased to open position when not subjected to inlet pressure, the position of the start-up valve controlling the pressure on the downstream side of the restrictor, which in turn positions the three-way pilot valve and hydraulic damping means for restricting the rate of closing of the starT-up valve when subjected to inlet pressure.
Claim 3
Dependent Claim
21 words
A control system as defined in claim 1 wherein the start-up valve has a restricted passage between its inlet and outlet.
Claim 4
Dependent Claim
24 words
A control system as defined in claim 1 wherein the hydraulic damping means comprises a displacement chamber having a restricted connection with the exhaust.
Claim 5
Dependent Claim
37 words
A control system as defined in claim 1 wherein the start-up valve has a restricted passage between its inlet and outlet and the hydraulic damping means comprises a displacement chamber having a restricted connection with the exhaust.
Claim 6
Dependent Claim
18 words
A control system as defined in claim 4 wherein the restricted passage is larger than the restricted connection.
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) | 1978-02-10 | 1978-08-12 | 1979-02-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-10 | 1982-08-12 | 1983-02-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-10 | 1986-08-12 | 1987-02-11 | $7700.00 | Window Closed / Lapsed |