US3774973A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Valves for controlling fault indicators in vehicular hydraulic braking systems
Assignee: Fiat SpA
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Filing: 1972-04-10
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Granted: 1973-11-27
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Expires: 1992-04-10
Abstract
Abstract This invention relates to a valve for connection in hydraulic brake systems of the kind having front and rear brake circuits with a pressure reducer incorporated in the rear brake circuit. The valve has at least one member which is moved by the pressure in the rear brake circuit when there is a fault in the front brake circuit to establish direct communication with the rear brake circuit, by-passing the pressure reducer to maintain braking efficiency, while at the same time establishing an electrical circuit for a fault indicator such as a warning lamp.
Inventors
- 👤 P Baldwin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 16:57
CPC Classifications
B; B60; B60T; B60T17/00; B60T17/18; B60T17/22; B60T17/226; B60T11/00; B60T11/10; B60T11/24; B60T11/28; B60T11/34
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
268 words
In a vehicular hydraulic braking system of the kind having a master cylinder, separate front and rear brake circuits, a pressure reducer incorporated in the rear brake circuit, and at least one damage indicator for indicating inadequate braking pressure in said circuits, the improvement comprising a valve controlling said damage indicator and connected to the front and rear brake circuits, said valve including: a body provided with first and second bores adapted to be connected to the front and rear brake circuits respectively, a first piston and a second piston each mounted for fluid-tight sliding movement in a respective cylindrical cavity in the body communicating with the first and second bores respectively, the pistons being subjected, when the valve is installed, to the hydraulic pressures in the respective bores, at least one insulated pin fixed in the body and connected in the circuit of said damage indicator, resilient means maintaining each piston spaced from the respective insulated pin, said resilient means exerting on the respective pistons forces substantially matching the thrusts thereon in use of the valve due to the hydraulic pressure in the first and second bores respectively, and means defining a passage in the valve body adapted to be connected directly to the rear brake circuit, said passage communicating witH the cavity which houses the first piston, said first piston normally isolating said passage from the two bores and connecting said second bore to said passage upon movement of said first piston, against the action of said resilient means, towards said insulated pin in the event of loss of braking pressure in the front brake circuit.
Claim 2
Dependent Claim
268 words
In a vehicular hydraulic braking system of the kind having a master cylinder, separate front and rear brake circuits, a pressure reducer incorporated in the rear brake circuit, and at least one damage indicator for indicating inadequate braking pressure in said circuits, the improvement comprising a valve controlling said damage indicator and connected to the front and rear brake circuits, said valve including: a body provided with first and second bores adapted to be connected to the front and rear brake circuits respectively, a first piston and a second piston each mounted for fluid-tight sliding movement in a respective cylindrical cavity in the body communicating with the first and second bores respectively, the pistons being subjected, when the valve is installed, to the hydraulic pressures in the respective bores, at least one insulated pin fixed in the body and connected in the circuit of said damage indicator, resilient means maintaining each piston spaced from the respective insulated pin, said resilient means exerting on the respective pistons forces substantially matching the thrusts thereon in use of the valve due to the hydraulic pressure in the first and second bores respectively, and means defining a passage in the valve body adapted to be connected directly to the rear brake circuit, said passage communicating witH the cavity which houses the first piston, said first piston normally isolating said passage from the two bores and connecting said second bore to said passage upon movement of said first piston, against the action of said resilient means, towards said insulated pin in the event of loss of braking pressure in the front brake circuit.
Claim 3
Dependent Claim
54 words
Valve as claimed in claim 1, wherein said first and second bores in the valve body are parallel through-bores and are each provided at their ends with threaded sockets adapted to receive the ends of pipes connected respectively to the master cylinder, the front brake circuit and the pressure reducer of the brake system.
Claim 4
Dependent Claim
85 words
Valve as claimed in claim 2, wherein the first cavity housing the first piston intersects the first bore and has an end wall at one end provided with an aperture communicating with the second bore, a plug closing the other end of said first cavity, and wherein the second cavity housing the second piston intersects the second bore and has an end wall at one end provided with an aperture communicating with the first bore, a plug closing the other end of said second cavity.
Claim 5
Dependent Claim
30 words
Valve as claimed in claim 3, wherein the axes of said cylindrical cavities are parallel to one another and perpendicular to and coplanar with the axes of said two bores.
Claim 6
Dependent Claim
18 words
Valve as claimed in claim 3, wherein said cylindrical cavities and their respective plugs are of equal size.
Claim 7
Dependent Claim
33 words
Valve as claimed in claim 3 wherein two respective insulated pins are provided, extending axially through said plugs and projecting from surfaces of the latter which face said pistons in the respective cavities.
Claim 8
Dependent Claim
35 words
Valve as claimed in claim 1, wherein the resilient means which maintain the pistons spaced from said at least one insulated pin comprise helical springs acting on the pistons and located in the respective cavities.
Claim 9
Dependent Claim
70 words
Valve as claimed in claim 3, wherein each of the pistons has a head mounted in the part of the respective cavity disposed between the respective bore intersecting the cavity and the respective end wall of the cavity, and a stem which extends axially in the respective cavity and which in the normal position of the piston is spaced a short distance from the adjacent end of said insulated pin.
Claim 10
Dependent Claim
35 words
Valve as claimed in claim 8 wherein each piston head carries a disc-like sealing washer of elastic material in its end facing towards a respective apertured end wall of the respective cavity housing the piston.
Claim 11
Dependent Claim
30 words
Valve as claimed in claim 9, wherein the sealing washers are located in respective recessed seats in the respective piston heads, said seats having frusto-conical side walls with enlarged bases.
Claim 12
Dependent Claim
32 words
Valve as claimed in claim 10, wherein each piston head is formed, adjacent its frusto-conical recessed seat, with a frusto-conical external surface tapering towards the said recessed end of the piston head.
Claim 13
Dependent Claim
68 words
Valve as claimed in claim 8, wherein the difference between the length of each piston head and the length of the respective cavity in which the piston slides comprised between said apertured end wall of the cavity and said bore which it intersects, is greater than the axial separation between the adjacent ends of the piston stem and said insulated pin in the normal position of the piston.
Claim 14
Dependent Claim
71 words
Valve as claimed in claim 12, wherein each said piston head carries at least one annular sealing ring of elastic material making sealing contact with the cylindrical wall of the respective cavity and wherein said head has at least one circumferential annular channel in which said sealing ring is located, said channel being spaced from the respective end of the piston head which faces said end wall of the respective cavity.
Claim 15
Dependent Claim
98 words
Valve as claimed in claim 13, wherein the cavity in which the first piston slides communicates with the passage formed in the body and adapted to be connected directly to the rear brake actuators through an opening in part of the wall of the said cavity situated between the respective apertured end wall of the cavity and the zone in which said at least one annular sealing ring is carried by said piston head, when the latter is in a position in which the sealing washer carried thereby closes the aperture in said end wall of said cavity.
Claim 16
Dependent Claim
220 words
Valve as claimed in claim 1, wherein: the two bores are interconnected through the cavities of the pistons, the said bores and the cavities being coaxial so as to form a single through-bore; the pistons have at least one stem integral with at least one of the pistons, said pistons being spaced apart by said stem by equal distances from said insulated pin fixed to the valve body, said pin projecting laterally into said bore; apertured plugs close the opposite ends of said bore, the apertures of said plugs being adapted to be connected to the master cylinder; respective springs are interposed between the plugs and the pistons to maintain the latter spaced from the plugs and equidistant from the insulated pin, and respective first and second chambers are formed between said plugs and said pistons and are adapted to be connected to the front brakes and to the pressure reducer respectively, said passage in the body adapted to be connected directly to the rear brakes communicating with said bore at a position which is isolated from the second chamber when the pistons are equidistant from said insulated pin and which is put into communication with said chamber when the pistons move in the direction of the first chamber in the event of pressure loss in the front brake circuit.
Claim 17
Dependent Claim
38 words
Valve as claimed in claim 15, including two circumferential channels in said second piston, respective sealing rings in said channels, and an annular groove in the circumference of the second piston, said passage communicating with said annular 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) | 1976-11-26 | 1977-05-28 | 1977-11-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-26 | 1981-05-28 | 1981-11-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-26 | 1985-05-28 | 1985-11-27 | $7700.00 | Window Closed / Lapsed |