# US 4,398,616 A · Steering system including independently operated rear wheel steering means for a vehicle

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- Number: US 4,398,616 A
- Document ID: US4398616A
- Status: Granted
- Kind: A
- Application number: 06/276,106
- Filed: 1981-06-22
- Granted: 1983-08-16
- Earliest claimed: 1981-06-22
- Assignees: Dresser Industries, Inc.
- Inventors: Donald G. Braden; David C. Riehl
- Web page: https://patentgrep.com/patent/US4398616A

## CPC

- B62D 7/1509: {with different steering modes, e.g. crab-steering, or steering specially adapted for reversing of the vehicle}
- B62D: MOTOR VEHICLES; TRAILERS (steering, or guiding on a desired track, of agricultural machines or implements A01B69/00; wheels, castors, axles, increasing wheel adhesion B60B; vehicle tyres, tyre inflation or tyre changing B60C; connections between vehicles of a train or the like B60D; vehicles for use on rail and road, amphibious or convertible vehicles B60F; suspension arrangements B60G; heating, cooling, ventilating or other air treating devices B60H; windows, windscreens, non-fixed roofs, doors or similar devices, protective coverings for vehicles not in use B60J; propulsion plant arrangements, auxiliary drives, transmissions, controls, instrumentation or dashboards B60K; electric equipment or propulsion of electrically-propelled vehicles B60L; power supply for electrically-propelled vehicles B60M; passenger accommodation not otherwise provided for B60N; adaptations for load transportation or to carry special loads or objects B60P; arrangement of signalling or lighting devices, the mounting or supporting thereof or circuits therefor, for vehicles in general B60Q; vehicles, vehicle fittings or vehicle parts not otherwise provided for B60R; servicing, cleaning, repairing, supporting, lifting, or manoeuvring, not otherwise provided for, B60S; brake arrangements, brake control systems or parts thereof B60T; air-cushion vehicles B60V; motor-cycles, accessories therefor B62J, B62K; testing of vehicles G01M)

## Abstract

A steering system for a construction vehicle operable to control the position of a pair of front wheels and a pair of rear wheels relative to the frame of the vehicle includes a hydraulic fluid circuit for distributing hydraulic fluid. A hydraulic cylinder is connected to each of the wheels for turning same in a desired manner. A steering wheel is interposed in the hydraulic fluid circuit for selectively directing hydraulic fluid to the cylinders for steering said wheels in a desired direction. A mode selector valve is interposed in the fluid flow circuit between the steering wheel and the cylinders for selectively selecting either four-wheel steer, crab steer, or front-wheel steer mode of steering for said vehicle. A control momentarily overrides the mode selector valve to isolate the rear hydraulic cylinders from the front hydraulic cylinders for permitting independent movement of the rear wheels of the vehicle.

## Claims

### Claim 1

A system for steering a construction vehicle having a pair of front wheels and a pair of rear wheels comprising:
a hydraulic fluid circuit for distributing hydraulic fluid;
hydraulic cylinder means connected to each wheel for steering the connected wheel;
steering means interposed in the hydraulic fluid circuit for selectively directing hydraulic fluid to said cylinder means for steering said wheels in a desired direction;
mode selector means interposed in the fluid flow circuit between said steering means and said cylinder means for selectively selecting either four-wheel steer, crab steer, or front-wheel steer mode of steering for said vehicle; and
override means for isolating said rear hydraulic cylinder means from said front cylinder means including flow control means for independently supplying fluid to said rear cylinder means for independently steering the rear wheels of the vehicle, said flow control means including rear steer valve means for selectively selecting rear steer mode of operation; and a dual pilot check valve interposed in the hydraulic fluid flow circuit between said mode selector means and said rear hydraulic cylinder means and operable when said rear steer valve means is positioned for selecting rear steer mode of operation to isolate said rear steer cylinder means from said mode selector means and said steering means.

### Claim 2

A system for steering a construction vehicle having a pair of front wheels and a pair of rear wheels comprising:
a hydraulic fluid circuit;
pump means disposed in said circuit for distributing hydraulic fluid through said circuit;
a pair of parallel conduits connected to the outlet of said pump means;
normally closed rear steer valve means disposed in a selected one of said pair of parallel conduits operable to control flow of fluid through said selected one conduit;
hydraulic cylinder means connected to each wheel for steering the connected wheel;
steering means interposed in the other of said pair of parallel conduits for selectively directing hydraulic fluid to said cylinder means for steering said wheels in a desired direction;
mode selector means interposed in the other of said pair of parallel conduits between said steering means and said cylinder means for selectively selecting either four-wheel steer, crab steer, or front-wheel steer mode of steering for said vehicle;
said selected one conduit being connected to said cylinder means for said rear wheels for delivering hydraulic fluid to said rear wheels cylinder means through said rear steer valve means when said valve means is opened; and
segregating means interposed in the fluid circuit between said rear wheels cylinder means and said mode slector means for preventing flow from said mode selector means to said rear wheel cylinder means when the rear steer valve means is opened.