Fluid pressure actuated electrical switch with electromagnetic biasing means for establishing different pressure levels for actuation and deactuation

Claim 1

A fluid pressure actuated electrical switch operated from a first electrical condition to a second electrical condition at a first predetermined fluid pressure attained by a source of variable fluid pressure to be sensed by the switch and operated from its second electrical condition back to its said first electrical condition at a second and lower predetermined fluid pressure, said switch comprising the combination of a first housing member of electrical insulating material, a second housing member of electrically conductive material, a flexible impervious diaphragm member peripherally secured between said housing members and defining a fluid pressurizable chamber with said second housing member, a centrally located bore formed in and extending through said second housing member to communicate at one end with said chamber therein and at its other end with said source of fluid pressure, an electrical solenoid oriented in the direction of and fixedly mounted within said bore of said second housing member, said solenoid including a central core having a passage extending therethrough in the direction of said bore to admit fluid to said pressurizable chamber and a coil of insulated wire wound about said core and electrically connected at one end to said second housing member and at its other end to said core, movable electrical contact means mounted centrally of and extending through said diaphragm member and cooperating with one end of said solenoid core constituting a fixed electrical contact of said switch, said movable electrical contact means covering the passage in said solenoid core when said switch is in its first electrical condition, electrical terminal means located externally of and extending into said first housing member, and a compression coil spring extending between and in electrical contact with said movable electrical contact means and said electrical terminal means, said spring opposing displacement of said diaphragm member by said source of fluid pressure and urging said movable contact means into engagement with said solenoid core and completing an electrical circuit path for said solenoid coil from said electrical terminal means, said spring, said movable contact means, said solenoid core and said second housing membeR.