Joystick controllers for remotely controlled valves are in wide use. It is the current practice to utilize magnetic detents to retain a joystick in its stroked position when the joystick is moved from a neutral position to an operative position. Typically, the controllers are pilot valves each having two to four work ports with a joystick normally in a neutral position. When the joystick is in the neutral position, the work ports are open to the exhaust port. The joystick is moveable to numerous stroked positions to open or detent one or more of the work ports. Exemplary of such devices is the hydraulic valve detent mechanism of U.S. Pat. No. 4,342,335.
In the hydraulic valve detent mechanism of U.S. Pat. No. 4,342,335, plungers which operate valve members have outer ends which must remain in contact with an operating cam on the joystick at all times. This causes wear between the outer ends of the plungers and the cam which operates the plungers. By having the plungers in continuous engagement with the cam, considerable clearance is needed for operation of the cam. Consequently, the cam must be relatively large. The larger the cam, the more the cam moves away from the pivot point, necessitating more clearance to ensure operation. Since in U.S. Pat. No. 4,342,335 it is necessary to utilize the force exerted by one plunger to keep the other plunger stroked, the force exerted by the unstroked plunger on the operating cam is about two to four times the force exerted by an individual plunger when the cam is in the neutral position. This excess force creates additional friction and the additional friction results in an increase in the force necessary to move the joystick. On occasion, the frictional forces may be so high that the joystick is prevented from returning to its neutral position from its stroked position.
USPTO Backgrounds
USPTO Backgrounds