Overload protection apparatus for hydraulic multi-function equipment

Claim 1

Overload protection apparatus for interrelated hydraulic multi-function equipment comprising: (a) a plurality of bi-directional motors each having a pair of fluid power lines including a forward and a reverse line connected thereto and an associated control valve interposed within each pair of said lines for selectively controlling the direction of the operation of said motors; (b) one of said motors being interconnected with each of the others in such a way that an increase in the load of one of said others will create a corresponding increase in the load of said one motor; (c) a source of fluid power connected to each of said valves to supply hydraulic fluid to said motors through said lines; (d) each of said motors having a fluid supply reservoir to which it is connected to receive the return of fluid therefrom; (e) an overload protection device including a manifold connected to the forward power lines of said other motors; (f) said manifold having a passage therein connected to a reservoir and to each of said forward power lines of said other motors; (g) a dumping valve interposed within said passage and normally closing off the same but being shiftable between containing and dumping positions to simultaneously bring each of said forward power lines into communication with its associated reservoir; and, (h) a sensor valve connected to said one motor and being operationally sensitive to an overload fluid pressure of predetermined magnitude therewithin; (i) said sensor valve being controllably connected to said dumping valve and causing the same to shift to dumping position when said sensor valve is operated by such an overload fluid pressure within said one motor; (j) said dumping valve being a pressure actuated spool valve positioned in said manifold and having pressure chambers at each end of the spool, one of said pressure chambers being exposed to the manifold directly and the other of said chambers being exposed to the manifold through a restriction, said latter pressure chamber including a bias spring bearing against the spool, and said spool having a recess therein which upon displacement of the spool aligns with a port to connect the passage in the manifold with the reservoir.