Patent ID: 7575089

Claim:
An apparatus for use in turning steerable vehicle wheels upon manual rotation of a steering wheel, said apparatus comprising: a front steering gear connected with steerable front wheels of the vehicle, said front steering gear being operable to turn the steerable front wheels of the vehicle upon manual rotation of the steering wheel; a rear steering gear connected with steerable rear wheels of the vehicle; a torque sensor connected with the steering wheel; and a controller which is connected with said torque sensor and rear steering gear, said controller being operable to effect operation of said rear steering gear in response to an output from said torque sensor upon manual application of at least a predetermined force to the steering wheel, said torque sensor having an output which corresponds to a force which is less than the predetermined force throughout turning of the steerable front wheels through their range of turning movement during normal operation of said front steering gear, said torque sensor having an output which corresponds to a force which is at least as great as the predetermined force which occurs when turning of the steerable front wheels in a direction that cannot be performed, said controller being operable to effect operation of said rear steering gear in response to the output from said torque sensor corresponding to at least the force which occurs when turning of the steerable front wheels in the direction that cannot be performed.