Cam actuated interlock for pivot arm

Claim 1

A control system for an extensIble and retractable locking pin releasably securing a pivotable support member for a tool positioning mechanism of an earthworking vehicle in any one of a plurality of angularly spaced positions relative to a frame member of the vehicle, said control system comprising: a source of pressurized hydraulic fluid, a control valve connected to said source and having a neutral and a pair of operating positions, means reciprocably mounting said locking pin on one of said members, a double-acting hydraulic jack having extensible and contractable components connected to said one member and locking pin, respectively, and operable to move the latter between its extended and retracted positions, a plurality of openings in the other of said members, selectively, registrable with said pin upon pivotal movement of said support member to said angularly spaced positions, a pair of conduits interconnecting said control valve and jack, a plurality of cam means on said frame member spaced circumferentially in relation to the pivot axis of said pivotable support member at angular spacing corresponding to the angular spacing of said openings relative to said pivot axis, and a blocking valve hydraulically connected in flow controlling relation to at least one of said conduits including a flow control element operatively associated with said cam means and shiftable between open and closed positions, said flow control element shifting to its open position in response to predetermined cooperation with any one of said cam means thereby permitting extension of said jack to extend said pin into one of said openings aligned therewith, said flow control element being in its closed position when not cooperatively engaged by said cam means, thereby preventing extension of said locking pin.