Patent US4870889A successfully refreshed from Google Patents.
US4870889A
Expired / Lapsed
US
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Hydraulic device for fuel pumping apparatus
Assignee: ZF International UK Ltd
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Filing: 1988-04-04
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Granted: 1989-10-03
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Expires: 2008-04-04
Abstract
Abstract A hydraulic device includes a piston slidable within a cylinder. Fluid under pressure is admitted to one end of the cylinder through an inlet which contains a restrictor. The piston is formed with an orifice and is biased by a first spring towards the one end of the cylinder. A thrust rod is engageable by the piston to transmit the movement of the piston to an external mechanism. When the piston is moved by rising fluid pressure the orifice is closed by the end of the thrust rod so that a higher value of fluid pressure is required to effect the initial movement of the piston than is required to allow the return movement of the piston.
Inventors
- 👤 Robin C. Wall
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 11:49
CPC Classifications
F; F15; F15B; F15B15/00; F15B15/08; F15B15/14; F15B15/1423; F15B15/1447; Y; Y10; Y10T; Y10T137/00; Y10T137/7722; Y10T137/7781; Y10T137/7784; Y10T137/7787; Y10T137/7791; Y10T137/7834
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
167 words
A hydraulic device comprising an actuating piston slidable in a cylinder under the action of fluid under pressure supplied to one end of the cylinder, spring means for opposing the movement of the piston by the fluid under pressure, a thrust rod for coupling the piston to a mechanism to be operated by the piston, an abutment plate mounted on the thrust rod, said spring means including a first spring acting between the abutment plate and the piston and a second spring acting between the abutment plate and an end closure at the other end of the cylinder, and means for limiting the movement of the thrust rod under the action of the second spring, characterized in that the piston defines an orifice through which fluid can flow from said one end of the cylinder, said thrust rod after a predetermined movement of the piston being engaged by said piston to close said orifice and acting to increase the pressure difference between the ends of the piston.
Claim 2
Dependent Claim
167 words
A hydraulic device comprising an actuating piston slidable in a cylinder under the action of fluid under pressure supplied to one end of the cylinder, spring means for opposing the movement of the piston by the fluid under pressure, a thrust rod for coupling the piston to a mechanism to be operated by the piston, an abutment plate mounted on the thrust rod, said spring means including a first spring acting between the abutment plate and the piston and a second spring acting between the abutment plate and an end closure at the other end of the cylinder, and means for limiting the movement of the thrust rod under the action of the second spring, characterized in that the piston defines an orifice through which fluid can flow from said one end of the cylinder, said thrust rod after a predetermined movement of the piston being engaged by said piston to close said orifice and acting to increase the pressure difference between the ends of the piston.
Claim 3
Dependent Claim
31 words
A hydraulic device according to claim 1 wherein said means for limiting the movement of the thrust rod under the action of the second spring is carried by the thrust rod.
Claim 4
Dependent Claim
21 words
A hydraulic device according to claim 2 characterized in that said thrust rod is guided for movement in said end closure.
Claim 5
Dependent Claim
37 words
A hydraulic device according to claim 2 including an inlet through which fluid can enter said one end of the cylinder characterized by a restrictor in said inlet, said restrictor and said orifice forming a fluid potentiometer.
Claim 6
Dependent Claim
50 words
A hydraulic device according to claim 4 characterized by an adjustable stop which limits the movement of the piston under the action of the first spring, said stop being adjustable to determine in conjunction with the adjacent end of the thrust rod, the degree of restriction offered by said orifice.
Claim 7
Dependent Claim
44 words
A hydraulic device according to claim 5 characterized in that said stop mounts a shield operable when engaged by the piston, to shield part of the end surface of the piston which is exposed to the pressure in said one end of the cylinder.
Claim 8
Dependent Claim
32 words
A hydraulic device according to claim 2 including a fluid inlet to said one end of the cylinder characterised by a restrictor in an outlet from the other end of the cylinder.
References Cited (Backward Citations)
GB423356A
Cited
FR882740A
Cited
FR998960A
Cited
US2875732A
Cited
FR1158728A
Cited
US3450005A
Cited
US3974853A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-10-02 | 1993-04-03 | 1993-10-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-10-02 | 1997-04-03 | 1997-10-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-10-02 | 2001-04-03 | 2001-10-03 | $7700.00 | Window Closed / Lapsed |