US3848693A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dual hydraulic power steering system with hydrostatic control
Assignee: RH Sheppard Co Inc
•
Filing: 1973-11-01
•
Granted: 1974-11-19
•
Expires: 1993-11-01
Abstract
Abstract The power steering for wheels is provided by two separate and independent steering combinations of first and second power operating units, corresponding first and second power supply means and control means, and the improvement of a hydraulic coupling means for the steering input derived from the steering shaft of the vehicle. The coupling means includes overdrive means effective to operate the second control means in slight anticipation of said first control means so that the second operating unit leads the first in driving the interconnecting steering linkage. Coordinating means is provided to limit the effectiveness of the coupling means in response to a predetermined pressure. The coupling means comprises a hydraulic circuit that includes a hydrostatic pump and motor, said motor serving to operate the control means for the second unit. The limiting of the pressure fluid to the motor in the circuit is accomplished preferably at 5 ft.-lbs. of torque applied to the steering shaft by oppositely directed check valves connected between the transfer lines in the circuit. The pump is approximately 10 percent larger in volume to provide the overdrive of the control means of the second unit. Interruption of power to one of the units allows continued operation in a safe manner with partial force power steering.
Inventors
- 👤 R Sheppard
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 19:24
CPC Classifications
B; B62; B62D; B62D5/00; B62D5/06; B62D5/30
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
212 words
In a dual hydraulic power steering system for coordinated turning wheels of a vehicle comprising first and second power operating units, steering linkage means provided between said wheels and said power operating units to interconnect the same, corresponding first and second power supply means interconnected to the corresponding operating units, first and second control means to direct the flow of fluid as required to steer the vehicle, means for coupling said control means, steering shaft means to operate said first control means and said coupling means, each combination of operating unit, control means and supply means being independent for directly turning separate wheels and each combination providing less than the total maximum design force required to allow the operator of the vehicle to comfortably turn said wheels, the improvement comprising in said coupling means, overdrive means effective to operate said second control means so as to lead said first control means in operation of said operating units, and coordinating means to limit the effectiveness of said coupling means in response to a predetermined torque applied to said steering shaft means, whereby both of said combinations may normally operate in said system but with leading by said second combination, and, upon failure of one combination, partial force power steering may still be effective.
Claim 2
Dependent Claim
212 words
In a dual hydraulic power steering system for coordinated turning wheels of a vehicle comprising first and second power operating units, steering linkage means provided between said wheels and said power operating units to interconnect the same, corresponding first and second power supply means interconnected to the corresponding operating units, first and second control means to direct the flow of fluid as required to steer the vehicle, means for coupling said control means, steering shaft means to operate said first control means and said coupling means, each combination of operating unit, control means and supply means being independent for directly turning separate wheels and each combination providing less than the total maximum design force required to allow the operator of the vehicle to comfortably turn said wheels, the improvement comprising in said coupling means, overdrive means effective to operate said second control means so as to lead said first control means in operation of said operating units, and coordinating means to limit the effectiveness of said coupling means in response to a predetermined torque applied to said steering shaft means, whereby both of said combinations may normally operate in said system but with leading by said second combination, and, upon failure of one combination, partial force power steering may still be effective.
Claim 3
Dependent Claim
100 words
The power steering system of claim 1 wherein said coupling means comprises a hydrostatic pump driven by said steering shaft means, said steering shaft also being directly coupled to said first control means, hydrostatic motor means coupled to said second control means to operate the same, two hydraulic transfer lInes extending between said motor and said pump and two way check valve means between said transfer lines to form said coordinating means, whereby upon reaching a predetermined pressure in the pressure line of said coupling means, the corresponding check valve opens to limit the force of said second operating unit.
Claim 4
Dependent Claim
54 words
The power steering system of claim 2 wherein said two way check valve means comprises a pair of oppositely directed check valves connected between the transfer lines, said check valves being biased by individual springs so as to be designed to open upon reaching a predetermined hydraulic pressure to thereafter bypass said hydrostatic motor.
Claim 5
Dependent Claim
31 words
The power steering system of claim 3 wherein said check valves are operative to open to bypass said motor upon application of approximately 5 ft.-lbs. of torque to said steering shaft.
Claim 6
Dependent Claim
33 words
The power steering system of claim 2 wherein said hydrostatic pump is approximately 10 percent larger in volume than said hydrostatic motor so as to provide the overdrive means and the leading characteristic.
Claim 7
Dependent Claim
52 words
The power steering system of claim 1 wherein said first power operating unit comprises a power steering gear with direct manual drive connection from said steering shaft means to said steering linkage means, whereby upon failure of said first combination manual steering is available to supplement power steering through said second combination.
References Cited (Backward Citations)
US3602326A
Cited
US3730288A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-11-18 | 1978-05-20 | 1978-11-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-18 | 1982-05-20 | 1982-11-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-18 | 1986-05-20 | 1986-11-19 | $7700.00 | Window Closed / Lapsed |