Device for detecting and indicating a difference in hydraulic pressure

Claim 1

A control device for detecting and signalling a difference in two fluid pressures, comprising; a body having a longitudinal bore therein, said body having first and second inlets communicating with opposite ends of said bore for supplying pressurized fluid from fluid pressure system means to said opposite ends of said bore; a slide bar slidably disposed in said bore for longitudinal movement between said inlets, said slide bar having a switch actuating portion thereon; a pair of pistons slidably disposed in said bore and associated with the opposite ends of said slide bar and disposed between said inlets and said slide bar so that the pressurized fluid supplied through said inlets is effective to urge said pistons inwardly of said bore, said pistons each having an abutment surface normally disposed in abutting contact with the adjacent end of said slide bar; a member associated with each piston for movement therewith inwardly of said bore, said member being adapted to abut against a stop in said body in the outer position of said member, said piston being movable relative to said member in a direction outwardly of said bore when said member is abutting against said stop; a pair of springs disposed in said bore, the springs abutting at corresponding ends against a stationary part of said body and the opposite ends of said springs abutting against said members for resiliently urging said members toward said stops and opposing movement of said pistons inwardly of said bore; said stops being spaced apart a distance such that when said members are abutting against said stops and said pistons are abutting against the ends of said slide bar, said slide bar is in a neutral position, each piston being movable outwardly of its associated member by a corresponding movement of said slide bar out of its neutral position caused by a difference in the pressures of the fluids supplied through the inlets; electric switch means having an actuator associated with said switch actuating portion of said slide bar for movement between a first condition when said slide bar is in said neutral position and a second condition when said slide bar is shifted out of said neutral position; and a warning circuit connected to said switch means for actuation thereby.