Patent ID: 8066255

Claim:
A solenoid gas valve construction comprising: a main body defining an inlet, an outlet and a cavity communicating with both the inlet and outlet; a tubular core comprising an inwardly directed annular flange and disposed in the cavity, a tube surrounding the core, a stop occluding the end of the tube, an o-ring mounted about the core and sealing the core to the main body; a threaded nut, a spacer, a seal and a sleeve defining, in combination with the core, a main piston chamber; a guide bushing having communication conduit holes locating circumferentially thereon, the guide bushing being in abutment at one end with the stop such that a pilot piston chamber is defined by the guide bushing, the core and the stop; a main piston comprising an end, a recess portion, and a cylindrical body, the main piston being connected to the other end of said guide bushing and, together with said guide bushing, being slidably movable in said main piston chamber; said main piston segregating said main piston chamber to a front chamber and a back chamber, said main piston further having an axial passage including a drain orifice extending therethrough providing for communication between the pilot piston chamber and the outlet, the main piston further having a cavity located at an outer circumferential portion of the main piston to communicate with the front chamber and a passage connecting said cavity to said back chamber; a pilot piston slidably movable in said pilot piston chamber; an insert, having an axial through hole and disposed in said cavity, places into said cylindrical cavity of said main piston; the diameter of the axial through hole being smaller than that of said drain, the through-hole and passage defining a gas passage from said front chamber, to said back chamber; a return spring received within said back chamber between said main piston and said inwardly-directed annular flange of said core, to urge said main piston in a direction away from said core, so that said spherical end of said main piston presses against said valve seat to close the communication between the inlet and outlet; and a pilot piston spring biasing to urge said pilot piston in a direction away from said stop of said core, so that the pilot piston presses against said drain orifice of said passage to achieve a gas-tight seal.