Hydraulic pressure differential switch with snap over leaf contact

Claim 1

A control device for detecting and signalling a difference in two fluid pressures, which comprises: a body having a longitudinal bore therein and having a switch chamber extending transversely from said bore at a location between the ends of said bore, said body also having a neck portion extending between said switch chamber and said bore and providing communication therebetween; first and second inlets connected to opposite ends of said bore for supplying pressurized fluid from two independent fluid pressure systems to said opposite ends of said bore; an equilibrating piston slidably disposed in said bore and having a reduced portion which is positioned in confronting relation to said neck portion in the neutral position of said piston when the fluid pressure forces acting on opposite ends of said piston are substantially equal, said piston being slidable longitudinally in one or the other direction out of said neutral position in response to a difference in the fluid pressures acting on opposite ends of said piston; a bowed leaf spring mounted in said switch chamber adjacent said neck portion, said leaf spring having a plurality of radially extending legs received in an annular groove in the wall of said switch chamber, the central portion of said leaf spring being movable between a first position in which it is curved toward the neck portion in the neutral position of said equilibrating piston and a second position in which it is curved away from said neck portion; a ball slidably disposed in said neck portion and projecting into said reduced portion of said piston in the neutral position thereof, said ball being disposed to contact the central portion of the leaf spring so that longitudinal movement to said piston out of said neutral position will move said ball outwardly of said bore and said ball will move said leaf spring from said first position to said second position; a switch terminal disposed in said switch chamber and disposed to contact said leaf spring in said second position thereof; a warning circuit having a signalling device connected in circuit with an electric power source and said switch terminal, whereby a difference in the fluid pressure acting on opposite ends of said equilibrating piston will cause said signalling device to be actuated and the same will remain actuated until the spring is returned to said first position.