Solenoid gas valve

Abstract

A solenoid valve has a main body defining a gas inlet passage, a gas outlet passage, and a cavity; a core tube forming a closure for said the cavity so as to prevent an escape of gas; a cylindrical main piston slidably movable in said the cavity of said the main body, said the main piston forming a front chamber and a back chamber in said the main body, said the main piston having a gas conduit for passing the gas from said the gas inlet passage to said the front chamber and an axial hole for passing the gas from said the back chamber into said the gas outlet passage with a bleed orifice at one end of said the axial hole; said the main piston being spring biased to a closed position; a spring biased pilot piston; and an electrical coil means associated with said the core tube to provide a magnetic field for movements of said the pilot piston and said the main piston, so that when said the coil means is deenergized said the pilot piston closes said the outlet passage and causes a pressure equalization allowing said the return spring to push said the main piston to close the valve, while when said the coil means is energized said the pilot valve opens said the outlet passage and lowers a pressure which causes pushing of said the main piston to open the valve.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims: 
     
       1. 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. 
 
     
     
       2. A solenoid gas valve as defined in  claim 1  wherein the main body has a central axis, the inlet extends perpendicular to the central axis and the outlet extends along the central axis. 
     
     
       3. A solenoid gas valve as defined in  claim 1  wherein the annular flange and stop are ferromagnetic and the tube is non-ferromagnetic. 
     
     
       4. A solenoid gas valve as defined in  claim 1  wherein the spacer has circumferential openings to communicate between the inlet and the front chamber. 
     
     
       5. A solenoid gas valve as defined in  claim 1  wherein the guide bushing is ferromagnetic. 
     
     
       6. A solenoid gas valve as defined in  claim 1  wherein the surface of the end of the main piston is spherical and smooth and the cylindrical body of the main piston is spherical and smooth. 
     
     
       7. A solenoid gas valve as defined in  claim 1  wherein said return spring is a compression spring. 
     
     
       8. A solenoid gas valve as defined in  claim 1  wherein said pilot piston spring is a compression spring. 
     
     
       9. A valve comprising:
 a valve body having an inlet (16) and a downstream passageway (24) and a cavity communicating with each of the inlet and downstream passageway (24), the cavity including a front chamber (25) and a back chamber (15);   a solenoid coil (1);   a main piston (19) mounted for reciprocating movement in the valve body, the main piston having:   a passageway (27) terminating in an orifice (35);   being exposed to the front chamber (25) and the back chamber (15); and   a guide portion (26);   a pilot piston (9) constructed from ferromagnetic material and mounted for reciprocating movement in the guide portion (26);   a return spring (11) biasing the main piston (19) to a position which blocks flow between the inlet (16) and the downstream passageway (24);   a pilot piston spring (8) biasing the pilot piston (9) towards a position which blocks the orifice (35);   wherein the valve is adapted such that   when the coil (1) is energized, the pilot piston (9) is urged by the coil (1) away from the position which blocks the orifice, to allow gas from the back chamber (15) to bleed out of the valve through the orifice (35) and passageway (27);   when the main piston (19) is in the position which blocks flow between the inlet (16) and the downstream passageway (24) and the coil (1) is not energized, the front chamber (25) and back chamber (15) are in fluid communication with the inlet (16);   when gases in the back chamber (15) are bled from the valve via the orifice (35) and passageway (27), force resulting from the pressure difference between the front chamber (25) and back chamber (15) becomes greater than the force of the return spring (11), which results in the movement of the main piston (19) away from the position which blows flow between the inlet (16) and the downstream passageway (24), thereby allowing flow through the valve;   when the coil (1) is not energized, the pilot piston (9) seals against the orifice (35), allowing the pressure between the front chamber (25) and back chamber (15) to equalize, whereupon the main piston (19) is forced by the return spring (11) to the position which blocks flow through the valve.    
     
     
       10. A valve according to claim 9, wherein the guide portion (26) is ferromagnetic and, when the coil (1) is energized, is biased by the coil (1) away from the position which blows flow between the inlet (16) and the downstream passageway (24), thereby to avoid shut-off of the main piston in the event of an abrupt change in pressure.