US4909342A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Four wheel steering system
Assignee: Eaton Corp
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Filing: 1988-09-02
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Granted: 1990-03-20
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Expires: 2008-09-02
Abstract
Abstract A closed hydraulic system (22 or 200) is provided for transmitting steering movement to a rear wheel steering assembly (16) in response to steering movement of a front wheel steering assembly (14). The front wheel steering assembly is controlled by a steering wheel (18) and a power steering assembly (20). The closed hydraulic system (22) includes a pump assembly (50) and an actuator assembly (52) connected together by conduits to define closed fluid flow branches (104,106) for moving a piston (90) in the actuator assembly in response to movement of a piston (72) in the pump assembly. In one embodiment (22) movement of the actuator piston is transmitted to the rear wheel steering assembly via a cam assembly which effects same direction rear wheel steering for rather small front wheel steering angles and which effects opposite direction rear wheel steering for greater front wheel steering angles. In another embodiment (200), the actuator piston (214) is connected directly to the rear wheel steering assembly. Both embodiments include a make-up valve (66) connected to an accumulator functioning as a reservoir to replace system fluid lost by leakage. The system embodiment (200) is provided with a valve for reversing fluid flow from the pump to the actuator to enable the actuator to provide same and opposite direction rear wheel steering relative to the front wheels.
Inventors
- 👤 David A. Janson
- 👤 Erlen B. Walton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 21:20
CPC Classifications
B; B62; B62D; B62D7/00; B62D7/06; B62D7/14; B62D7/15; B62D7/1554; B62D7/1563
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
285 words
A steering apparatus for a wheeled vehicle having front and rear dirigible wheel assemblies, the apparatus comprising: first means for transmitting left and right steering movement to a front wheel steering assembly in response to a steering wheel being turned left and right from a neutral position to effect left and right steering angles of the front wheels, second means for transmitting steering movement to a rear wheel steering assembly in response to steering movement of the front wheel steering assembly; the second means characterized by: a closed hydraulic system including first and second closed fluid flow branches comprising a fluid displacement assembly operative to effect fluid flow in both branches in response to steering movement of the front wheel steering assembly; a hydraulic actuator assembly operative to effect steering movement of the rear wheel steering assembly in response to said fluid flow, the fluid in the branches alternately increasing from a low pressure to an operational pressure in response to alternate steering movement of the front wheel steering assembly; a source of fluid under pressure less than the operational pressure in the closed branches; and a control assembly including a valve assembly having a first port connected to the fluid source, second and third ports respectively connected to the first and second branches, a valving member movable to a first position in response to the neutral position of the steering wheel and movable to at least a second position in response to a non-neutral position of the steering wheel, the valving member first position communicating the first port with the second and third ports and the second position blocking at least the communication to the port connected to the branch increasing to operational pressure.
Claim 2
Dependent Claim
285 words
A steering apparatus for a wheeled vehicle having front and rear dirigible wheel assemblies, the apparatus comprising: first means for transmitting left and right steering movement to a front wheel steering assembly in response to a steering wheel being turned left and right from a neutral position to effect left and right steering angles of the front wheels, second means for transmitting steering movement to a rear wheel steering assembly in response to steering movement of the front wheel steering assembly; the second means characterized by: a closed hydraulic system including first and second closed fluid flow branches comprising a fluid displacement assembly operative to effect fluid flow in both branches in response to steering movement of the front wheel steering assembly; a hydraulic actuator assembly operative to effect steering movement of the rear wheel steering assembly in response to said fluid flow, the fluid in the branches alternately increasing from a low pressure to an operational pressure in response to alternate steering movement of the front wheel steering assembly; a source of fluid under pressure less than the operational pressure in the closed branches; and a control assembly including a valve assembly having a first port connected to the fluid source, second and third ports respectively connected to the first and second branches, a valving member movable to a first position in response to the neutral position of the steering wheel and movable to at least a second position in response to a non-neutral position of the steering wheel, the valving member first position communicating the first port with the second and third ports and the second position blocking at least the communication to the port connected to the branch increasing to operational pressure.
Claim 3
Dependent Claim
77 words
The steering apparatus of claim 1, wherein the valving member is movable to the second position in response to turning the steering wheel in one direction from the neutral position and to a third position in response to turning the steering wheel in the other direction from the neutral position, the valving member second and third positions respectively operative to block the one of the second and third ports connected to the branch increasing to operational pressure.
Claim 4
Dependent Claim
37 words
The steering apparatus of claim 2, wherein the valve assembly includes means mechanically connecting the valving member to a portion of the front wheel steering apparatus which moves in opposite directions in response to opposite steering directions.
Claim 5
Dependent Claim
111 words
The steering apparatus of claim 1, wherein the fluid displacement assembly and the hydraulic actuator assembly each including a reciprocal piston disposed in a bore of a housing with one end of each bore connected together by a first conduit means and the other end of each bore connected together by a second conduit means, whereby reciprocal movement of the displacement assembly piston effects a proportional reciprocal movement of the actuator assembly piston; and cam means disposed between the actuator piston and the rear wheel steering assembly for controlling the rear wheel steering angle according to the profile of the cam means and according to the distance the actuator piston moves.
Claim 6
Dependent Claim
75 words
The steering assembly of claim 4, wherein the profile of said cam assembly moves the valving member in a direction effecting steering movement of the rear wheel steering assembly in the same direction of the steering direction of the front wheel steering assembly for front wheel steering angles below a predetermined amount and in opposite directions as the steering direction of the front wheel assembly for front wheel steering angles greater than the predetermined amount.
Claim 7
Dependent Claim
169 words
The steering apparatus of claim 1, wherein the fluid displacement assembly and the hydraulic actuator assembly each including a reciprocal piston disposed in a bore of a housing defining a first and second variable fluid volume at each end of the piston, the assemblies including means for mechanically connecting the displacement and actuator pistons respectively to the front and rear wheel steering assemblies; the first and second fluid flow branches respectively including one volume of each assembly; and the control assembly including a rear wheel steering direction valve interposed in the branches between the assemblies, and having a valving member movable to a same direction position interconnecting the first and second displacement assembly volumes respectively with the first and second actuator assembly volumes for effecting same direction steering of the front and rear wheels and movable to an opposite direction position interconnecting the first and second displacement assembly volumes respectively with the second and first actuator assembly volumes for effecting opposite direction steering of the front and rear wheels.
Claim 8
Dependent Claim
57 words
The steering apparatus of claim 6, wherein the control assembly includes: actuation means operative to move the valving member of the direction valve to the same direction position for front wheel steering angles less than a first predetermined amount and then to the opposite direction position for front wheel steering angles greater than a second predetermined amount.
Claim 9
Dependent Claim
16 words
The steering assembly of claim 7, wherein the first and second predetermined amounts are the same.
Claim 10
Dependent Claim
50 words
The steering apparatus of claim 7, wherein the actuation means is operative to move the valving member of the direction valve to a third position interconnecting the displacement assembly volumes and hydraulically locking the actuator assembly volumes in response to front wheel steering angles between the first and second positions.
Claim 11
Dependent Claim
58 words
The steering apparatus of claim 6, wherein the control assembly includes: actuation means operative to move the valving member of the direction valve to the same direction position in response to vehicle speed being less than a first predetermined amount and to the opposite direction position in response to vehicle speed being greater than a second predetermined amount.
Claim 12
Dependent Claim
16 words
The steering assembly of claim 10, wherein the first and second predetermined amounts are the same.
Claim 13
Dependent Claim
49 words
The steering apparatus of claim 10, wherein the actuation means is operative to move the valving member of the direction valve to a third position interconnecting the displacement assembly volumes and hydraulically locking the actuator assembly volumes in response to vehicle speed being between the first and second amounts.
References Cited (Backward Citations)
US4776419A
Cited
US4776418A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-03-19 | 1993-09-18 | 1994-03-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-03-19 | 1997-09-18 | 1998-03-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-03-19 | 2001-09-18 | 2002-03-20 | $7700.00 | Window Closed / Lapsed |