Patent US3879946A successfully refreshed from Google Patents.
US3879946A
Expired / Lapsed
US
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Brake failure indicator
Assignee: Girling Ltd
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Filing: 1973-11-28
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Granted: 1975-04-29
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Expires: 1993-11-28
Abstract
Abstract A brake failure indicator comprises a piston having opposite ends exposed to the pressure in two hydraulic braking circuits, a ball located in a groove around the piston, a switch operated by radial movement of the ball caused by limited axial movement of the piston, and a self-energising indicating circuit operated by the switch.
Inventors
- 👤 Glyn Phillip Reginald Farr
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 06:52
CPC Classifications
B; B60; B60T; B60T17/00; B60T17/18; B60T17/22; B60T17/226; B60T13/00; B60T13/10; B60T13/12; B60T13/14; B60T13/142; G; G01; G01L; G01L19/00; G01L19/08; G01L19/12
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
131 words
Means for detecting a difference in pressure between two hydraulic circuits, said detecting means comprising a piston movable in a cylinder, each end of said piston being exposed to fluid in a chamber defined in said cylinder, and said piston being provided with a substantially circumferentially extending groove in the outer surface thereof, connecting means to connect each chamber to one of said hydraulic circuits, indicating means, an actuating member for said indicating means and having a portion located in said groove, the cross-sectional profile of said groove being such that axial movement of said piston causes said actuating member to be displaced to actuate said indicating means, and limiting means for limiting axial movement of said piston to prevent said portion of said actuating member being disengaged from said groove.
Claim 2
Dependent Claim
131 words
Means for detecting a difference in pressure between two hydraulic circuits, said detecting means comprising a piston movable in a cylinder, each end of said piston being exposed to fluid in a chamber defined in said cylinder, and said piston being provided with a substantially circumferentially extending groove in the outer surface thereof, connecting means to connect each chamber to one of said hydraulic circuits, indicating means, an actuating member for said indicating means and having a portion located in said groove, the cross-sectional profile of said groove being such that axial movement of said piston causes said actuating member to be displaced to actuate said indicating means, and limiting means for limiting axial movement of said piston to prevent said portion of said actuating member being disengaged from said groove.
Claim 3
Dependent Claim
53 words
Detecting means as in claim 1 wherein the actuating member is a ball received in said groove in said piston, and the sides of said groove are inclined in opposite directions for displacing said ball to actuate said indicating means, said ball being spring-loaded towards said piston and serving to centre said piston.
Claim 4
Dependent Claim
29 words
Detecting means as in claim 1 wherein said limiting means comprises stops arranged in said cylinder at each end of said piston to limit axial movement of said piston.
Claim 5
Dependent Claim
29 words
Detecting means as in claim 1 wherein said indicating means comprises an electrical switch which is operated by said actuating member, and a self-energising indicating circuit including said swtich.
Claim 6
Dependent Claim
20 words
Detecting means as in claim 4 wherein said indicating circuit includes a manual reset switch for de-energising said indicating circuit.
Claim 7
Dependent Claim
72 words
Detecting means as in claim 1, wherein said limiting means comprises opposite end walls defining opposite ends of a bore in said cylinder in which said piston works, and said end walls are adapted to be engaged by adjacent ends of said piston, the axial spacing between said end walls and the length of said piston being so chosen that said portion of said actuator member cannot become disengaged from said groove.
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) | 1978-04-28 | 1978-10-28 | 1979-04-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-28 | 1982-10-28 | 1983-04-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-28 | 1986-10-28 | 1987-04-29 | $7700.00 | Window Closed / Lapsed |