Patent ID: 7806419

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 centering shaft axis, a rotational position of said centering shaft defining a neutral position corresponding to said selected center position; a hollow centering cylinder and stationary housing means for cooperating with said cylinder so that a cavity within said cylinder forms at least part of a centering chamber, said centering cylinder being arranged to reciprocate between a rest position and an active position for compressing resilient means in said centering chamber for exerting a resilient force against said cylinder; and, 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 engaging means for engaging an outer surface of an end wall of 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 engaging means for engaging said outer surface of said centering cylinder end wall so that rotation of said centering shaft away from said neutral position toward the other side causes compressive movement of said centering cylinder; wherein the exertion of said resilient force against said centering cylinder causes said centering cylinder and said first and second engaging means to resist rotation of said centering shaft away from its neutral position, and thereby 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.