US3785754A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Manual override system for a variable volume pump
Assignee: Caterpillar Inc
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Filing: 1972-04-27
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Granted: 1974-01-15
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Expires: 1992-04-27
Abstract
Abstract A hydraulic control system in which an engine driven variable displacement fluid pump provides a source of fluid pressure for powering work implements, and having automatically operable control means responsive to engine speed to control displacement of the variable displacement pump to correspond to engine horsepower, is provided with a manually operable control means to override the automatic control system for selectively controlling the displacement of the variable displacement pump.
Inventors
- 👤 D Miller
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 12:11
CPC Classifications
F; F04; F04B; F04B49/00; F04B49/002; F04B49/007
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
108 words
A hydraulic control system, said system comprising: a prime mover; a variable displacement pump driven by said prime mover; servo control means for changing the displacement of said variable displacement pump; a fixed displacement pump driven by said prime mover; automatically operable control means including an underspeed valve operative in response to the output of said fixed displacement pump to activate said servo control means to adjust the displacement of said pump to the output of said prime mover; and, manually operable control means including a pressure reducing valve for selectively overriding said automatically operable control means and thereby selectively reducing the displacement of said variable displacement pump.
Claim 2
Dependent Claim
108 words
A hydraulic control system, said system comprising: a prime mover; a variable displacement pump driven by said prime mover; servo control means for changing the displacement of said variable displacement pump; a fixed displacement pump driven by said prime mover; automatically operable control means including an underspeed valve operative in response to the output of said fixed displacement pump to activate said servo control means to adjust the displacement of said pump to the output of said prime mover; and, manually operable control means including a pressure reducing valve for selectively overriding said automatically operable control means and thereby selectively reducing the displacement of said variable displacement pump.
Claim 3
Dependent Claim
55 words
The control system of claim 1 wherein said pressure reducing valve disposed in conduit means down stream of said underspeed valve from said fixed displacement pump and is operative to simultaneously bypass said underspeed valve and provide a pilot signal to said servo control means for adjusting the volumetric displacment of said variable displacement pump.
Claim 4
Dependent Claim
29 words
The control system of claim 1 comprising a plurality of one-way check valves operative to prevent feed-back between said automatically operable control means and said manually operable control means.
Claim 5
Dependent Claim
39 words
The invention of claim 3 wherein said manually operable control means comprises a pilot operated pressure reducing valve operative to provide a pilot signal to said servo control means for adjusting the volumetric displacement of said variable displacement pump.
Claim 6
Dependent Claim
99 words
A hydraulic power system, said system comprising: a prime mover; a variable displacement pump driven by said prime mover; a fixed displacement pump driven by said prime mover; automatic hydrualic control means including an underspeed valve operative in responsive to the output of said fixed displacement pump to adjust the displacement of said pump as a function of the rpm of said prime mover as determined by said fixed displacement pump; and, manual control means including a pressure reducing valve operative to bypass said underspeed valve to override said automatic control means to reduce the displacement of said pump.
Claim 7
Dependent Claim
99 words
A hydraulic power system, said system comprising: a prime mover; a variable displacement pump driven by said prime mover; a fixed displacement pump driven by said prime mover; automatic hydrualic control means including an underspeed valve operative in responsive to the output of said fixed displacement pump to adjust the displacement of said pump as a function of the rpm of said prime mover as determined by said fixed displacement pump; and, manual control means including a pressure reducing valve operative to bypass said underspeed valve to override said automatic control means to reduce the displacement of said pump.
Claim 8
Dependent Claim
56 words
The invention of claim 5 wherein said control means comprises a fixed displacement pump driven from said prime mover; said underspeed valve is responsive to the output of said fixed displacement pump to generate a signal; and, a servo control means operative in response to said signal to adjust the output of said variable displacement pump.
Claim 9
Dependent Claim
13 words
The invention of claim 8 wherein said valve is a pressure reducing valve.
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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) | 1977-01-14 | 1977-07-16 | 1978-01-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-14 | 1981-07-16 | 1982-01-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-14 | 1985-07-16 | 1986-01-15 | $7700.00 | Window Closed / Lapsed |