US3812942A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydraulic system
Assignee: Robert Bosch GmbH
•
Filing: 1972-06-12
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Granted: 1974-05-28
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Expires: 1992-06-12
Abstract
Abstract A hydraulic system for operating a friction clutch has a cylinder, in an internal passage of which a first piston is displaceable between a rest position and a working position against the action of a biasing element associated with the friction clutch, which action tends to move the first piston to its rest position. A second piston is also displaceable in the passage in the same sense as the first piston between a starting position and an operated position and defines with the first piston at all times a chamber. Pressure fluid is accommodated in this chamber at all times and the chamber communicates with a non-pressurized space via suitable passage means when the second piston is in its starting position.
Inventors
- 👤 H Espenschied
- 👤 H Weyer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 16:12
CPC Classifications
F; F16; F16D; F16D25/00; F16D25/08; F16D25/12; F16D25/126; Y; Y10; Y10T; Y10T74/00; Y10T74/21; Y10T74/2142; Y10T74/2144; Y10T74/2147
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
277 words
In a hydraulic system for operating a clutch, particularly a friction clutch, a combination comprising a reservoir for hydraulic fluid; cylinder means having an internal passage; a first piston displaceable in said passage between a working position in which said clutch is disengaged and a plurality of rest positions in any one of which said clutch is engaged; linkage means linking said first piston with said clutch and urging said first piston towards one of said rest positions; a second piston displaceable in said passage in the same sense as said first piston between an operative position which said second piston occupies when said clutch is disengaged and a predetermined starting position which said second piston approaches in response to movement of said first piston from said working position towards said rest positions and which said second piston occupies when said clutch is engaged, said first and second pistons together defining a chamber forming part of said passage, and said second piston cooperating with said cylinder means to establish communication between said reservoir and said chamber only when said second piston is in said starting position so that said chamber is completely filled with hydraulic fluid in said starting position of said second piston; biasing means interposed between said first and second pistons to bear against said second piston and to return said second piston to said starting position in response to movement of said first piston from said working positions to any of said rest positions; and pump means for pumping hydraulic fluid from said reservoir to said passage so as to effect movement of said second piston from said starting position towards said operative position.
Claim 2
Dependent Claim
277 words
In a hydraulic system for operating a clutch, particularly a friction clutch, a combination comprising a reservoir for hydraulic fluid; cylinder means having an internal passage; a first piston displaceable in said passage between a working position in which said clutch is disengaged and a plurality of rest positions in any one of which said clutch is engaged; linkage means linking said first piston with said clutch and urging said first piston towards one of said rest positions; a second piston displaceable in said passage in the same sense as said first piston between an operative position which said second piston occupies when said clutch is disengaged and a predetermined starting position which said second piston approaches in response to movement of said first piston from said working position towards said rest positions and which said second piston occupies when said clutch is engaged, said first and second pistons together defining a chamber forming part of said passage, and said second piston cooperating with said cylinder means to establish communication between said reservoir and said chamber only when said second piston is in said starting position so that said chamber is completely filled with hydraulic fluid in said starting position of said second piston; biasing means interposed between said first and second pistons to bear against said second piston and to return said second piston to said starting position in response to movement of said first piston from said working positions to any of said rest positions; and pump means for pumping hydraulic fluid from said reservoir to said passage so as to effect movement of said second piston from said starting position towards said operative position.
Claim 3
Dependent Claim
53 words
In a hydraulic system as defined in claim 10; and further comprising control valve means interposed between said passage and said pump means, said valve means having a first position in which said pump means communicates with said passage, and a second position for preventing communication between said pump means and said passage.
Claim 4
Dependent Claim
15 words
In a hydraulic system as defined in claim 1, said biasing means being spring means.
Claim 5
Dependent Claim
26 words
In a hydraulic system as definEd in claim 1; further comprising abutment means in said chamber for limiting the displacement of said pistons in said passage.
Claim 6
Dependent Claim
53 words
In a hydraulic system as defined in claim 1; further comprising electrical contact means, and a projection on said second piston adapted to engage and operate said contact means when said second piston is in either of said positions thereof for providing a signal indicative of the position assumed by said second piston.
Claim 7
Dependent Claim
60 words
In a hydraulic system as defined in claim 1, said passage being stepped and having an internal shoulder and said second piston having an outer periphery provided with axially extending grooves, said grooves and said shoulder cooperating with one another so as to establish communication between said reservoir and said chamber when said second piston is in said starting position.
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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) | 1977-05-27 | 1977-11-26 | 1978-05-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-27 | 1981-11-26 | 1982-05-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-27 | 1985-11-26 | 1986-05-28 | $7700.00 | Window Closed / Lapsed |