Patent ID: 6422582
Filing Date: 2002-07-23
Classification: B62D,B63H

Abstract:
An apparatus for holding at a center position at least one steerable member mounted on a frame means for movement to either side of the center position, said apparatus comprising linkage means of variable length extending between said steerable member and said frame means, the length of said linkage means defining said center position and said linkage means comprising resistance means for providing a resistance force resisting steering forces tending to move said steerable member to either side of the center position, and center holding means for transmitting said steering forces to said resistance means, said holding means comprising:a holding piston; holding cylinder means for providing first and second holding chambers one on each side of said holding piston; fluid transfer means for providing a flow of fluid to and from each of said holding chambers; valve means remotely operable between a closed position for preventing said fluid flow from each of said holding chambers so that said holding piston is held in a locked position, and an open position for allowing said holding piston to move away from said locked position in said holding cylinder, said holding piston movement causing said fluid flow to one of said holding chambers and said fluid flow from the other of said holding chambers and permitting said steerable member to move to either side of said center position by changing the length of said linkage means in response to said steering forces; and, control means responsive to said resistance force for remotely operating said valve means so as to prevent said holding piston movement away from said locked position until said resistance force reaches a predetermined amount, said control means comprising: a first sensor means for providing a first signal in response to a predetermined amount of said resistance force, a second sensor means for providing a second signal in response to said holding piston being in said locked position, and switch means for actuating said valve means to said open position in response to said first signal and keeping said valve means open during said piston movement, and for actuating said valve means to said closed position in response to said second signal upon return of said holding piston to said locked position.