Patent ID: 7219908

Claim:
An apparatus for positioning at least one steerable member connected to a steering shaft for movement to either side of a selected center position in response to rotational reciprocation of the steering shaft to either side of a centering position, said apparatus comprising resistance means for providing a holding force resisting steering forces tending to move said steerable member to either side of said center position, said resistance means comprising: a centering shaft and means for connecting said centering shaft to the steering shaft for rotational reciprocation around a shaft axis, a rotational position of said centering shaft defining a neutral position corresponding to said selected center position; a movable centering cylinder cooperating with a stationary centering piston to define a centering chamber, said centering cylinder being arranged to reciprocate between a rest position and an active position for compressing a fluid within said centering chamber; actuating means for causing compressive movement of said centering cylinder away from said rest position in response to rotational movement of said centering shaft around said shaft axis to either side of said neutral position, said actuating means comprising first push means arranged to engage said centering cylinder so that rotation of said centering shaft away from said neutral position toward one side causes compressive movement of said centering cylinder, and second push means arranged to engage said centering cylinder so that rotation of said centering shaft away from said neutral position toward the other side causes compressive movement of said centering cylinder; and, centering fluid means for providing a pressurized fluid in said centering chamber so that fluid pressure against said centering cylinder provides said holding force by opposing movement of said steerable member toward either side of said selected center position and provides a return force continuously biasing said steerable member toward said selected center position during movement of said steerable member to either side of said selected center position, the rest position of centering cylinder corresponding to the neutral position of said centering shaft, and said fluid pressure causing said centering cylinder and said first and second push means to resist rotation of said centering shaft away from its neutral position; wherein said first push means comprises a first push arm and said second push means comprises a second push arm, and wherein each of said push arms have a proximate end rigidly connected to said centering shaft.