US3865211A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Steering system with hydraulic power assistance
Assignee: ZF Friedrichshafen AG
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Filing: 1973-03-30
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Granted: 1975-02-11
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Expires: 1993-03-30
Abstract
Abstract Power operated steering system for vehicle wheels including two fluid circuits for each hydrostatic motor one of which is normally operative when its lines are pressurized. An indicator alerts the driver in response to loss of pressure in either fluid circuit because of hose line rupture or pump malfunction. The fluid circuit in which a break occurs, is automatically isolated from the system to prevent any loss of fluid from the system.
Inventors
- 👤 Karl-Heinz Liebert
- 👤 Werner Tischer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 20:38
CPC Classifications
B; B62; B62D; B62D5/00; B62D5/06; B62D5/30; B62D5/32; F; F15; F15B; F15B17/00
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
168 words
In a hydrostatic power assist steering system for an engine driven vehicle having dirigible wheels, a source of fluid under pressure 1 and 11, fluid motor means 8 and 9 connected to said wheels for applying steering force thereto, at least two fluid circuits 16-17 and 18-19 connected to said fluid motor means independently of each other, a control valve 3 connected to said source of fluid under pressure, manually operable steering control means 2 and 4 connected to the control valve for selectively supplying pressurized fluid from the source to the fluid motor means through one of the fluid circuits 16-17, pressure operated valves means 5 and 6 connected between said control valve and the circuits for normally conducting the pressurized fluid through said one of the fluid circuits, and valve actuating means 27 and 28 connected to the pressure operated valve means for connecting the control valve to the other of the fluid circuits 18-19 in response to depressurization of said one of the fluid circuits.
Claim 2
Dependent Claim
168 words
In a hydrostatic power assist steering system for an engine driven vehicle having dirigible wheels, a source of fluid under pressure 1 and 11, fluid motor means 8 and 9 connected to said wheels for applying steering force thereto, at least two fluid circuits 16-17 and 18-19 connected to said fluid motor means independently of each other, a control valve 3 connected to said source of fluid under pressure, manually operable steering control means 2 and 4 connected to the control valve for selectively supplying pressurized fluid from the source to the fluid motor means through one of the fluid circuits 16-17, pressure operated valves means 5 and 6 connected between said control valve and the circuits for normally conducting the pressurized fluid through said one of the fluid circuits, and valve actuating means 27 and 28 connected to the pressure operated valve means for connecting the control valve to the other of the fluid circuits 18-19 in response to depressurization of said one of the fluid circuits.
Claim 3
Dependent Claim
26 words
The combination of claim 1 including pressure sensing means 29-33 connected to said fluid circuits for indicating said depressurization of said one of the fluid circuits.
Claim 4
Dependent Claim
35 words
The combination of claim 2 wherein said source of fluid under pressure comprises a reservoir 11 containing a body of said fluid and a servo pump 1 interconnected between the reservoir and the control valve.
Claim 5
Dependent Claim
33 words
The combination of claim 3 wherein said manually operable steering control means comprises a control pump 2 connected to the control valve and a steering wheel 4 drivingly connected to the control pump.
Claim 6
Dependent Claim
34 words
The combination of claim 4 wherein said fluid motor means comprises a pair of servo motors 8 and 9 having opposed pressure chambers 21, 22, 23, 24 to which the fluid circuits are connected.
Claim 7
Dependent Claim
30 words
The combination of claim 5 wherein each of said fluid circuits includes a pair of pressure lines 16 and 17 or 18 and 19 respectively connected to said servo motors.
Claim 8
Dependent Claim
31 words
The combination of claim 6 wherein said pressure operated valve means comprises a pair of pilot valves displaceable between operative positions alternately connecting the control valve to the two fluid circuits.
Claim 9
Dependent Claim
37 words
The combination of claim 7, including precontrol means 50 and 51 connecting the pilot valves and the fluid circuits to the servo pump for pressurizing both of the fluid circuits during starting operation of the vehicle engine.
Claim 10
Dependent Claim
38 words
The combination of claim 3 including auxiliary valve means 7 connected between the servo pump and the reservoir for alternately conducting pressurized fluid to the control valve of connecting said one of the fluid circuits to the reservoir.
Claim 11
Dependent Claim
31 words
The combination of claim 1 wherein said pressure operated valve means comprises a pair of pilot valves displaceable between operative positions alternately connecting the control valve to the two fLuid circuits.
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) | 1978-02-10 | 1978-08-12 | 1979-02-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-10 | 1982-08-12 | 1983-02-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-10 | 1986-08-12 | 1987-02-11 | $7700.00 | Window Closed / Lapsed |