Patent ID: 7334770
Filing Date: 2008-02-26
Classification: F02M,F16K

Abstract:
1. A valve for controlling the flow of gas from a source of gas to a demand, said valve comprising: a housing defining an axis, a primary piston chamber through which the axis extends and a gas inlet, the gas inlet being coupled in use to said source; a disk arranged in sealed relation with said housing and defining a vent extending from said primary piston chamber, the vent extending, in use, to said demand; a column projecting axially from said disk into said primary piston chamber and having an interior passage having one end, in use, in communication with said demand and another end terminating in a bleed orifice, the column having a bleed hole seat surrounding the bleed orifice; a tubular sleeve having at one end a closure preventing the escape of gas, the other end being sealingly coupled to the housing such that the interior of the sleeve is in fluid communication with the primary piston chamber; a pilot piston received and movable within the sleeve, the pilot piston having a sufficiently loose fit within the sleeve to allow gas from one end of the pilot piston to reach the other end thereof; a pilot biasing element urging the pilot piston against the bleed hole seat to seal the bleed orifice; a coil for selectively creating a magnetic field to urge the pilot piston away from the bleed hole seat; a seal piston operatively mounted to said column for axial movement within the primary piston chamber between a closed position and an open position, said seal piston having an interior and further having an outer surface, the outer surface sealing against an inner surface of the housing defining part of the primary piston chamber when the seal piston is at the closed position; a primary biasing element urging the seal piston towards the closed position; a primary piston received in sealing relation within the interior of the seal piston and slideable in sealing relation along said column for axial movement within the seal piston between a closed position and an open position; and a spring disposed between the primary piston and the seal piston for urging the primary piston towards the closed position wherein: when the primary piston and the seal piston are each at their respective closed positions, they isolate the gas inlet from the primary piston chamber; when the seal piston and primary piston are away from their closed positions, the gas inlet is in communication with the primary piston chamber and the vent communicates with the primary piston chamber; a bowl channel hole provides for gas communication between the primary piston chamber and a portion of the interior of the seal piston captured by the primary piston; a channel hole provides for gas communication between the primary piston chamber and the inlet when the seal piston is not at the closed position; when the coil is not generating a magnetic field and the source is coupled to the inlet, the gas pressure at the inlet causes the seal piston to initially move away from the closed position, leaving the primary piston at the closed position to seal the vent, said movement of the seal piston away from the closed position allowing gas from the inlet to enter the primary piston chamber until the gas pressure has equilibrated whereupon the primary biasing element returns the seal piston to its closed position; after the gas pressure has equilibrated and the seal has returned to its closed position, subsequent generation of a magnetic field by the coil caused the pilot piston to unseat from the bleed hole seat, whereupon the instantaneous pressure differentials in the valve cause the primary piston and the seal position to move towards their respective open positions, the gas pressures in the valve thereafter equilibrating such that pressure differentials in the valve overcome the primary biasing element and the spring and the valve remains open to permit communication between the inlet and the demand via the vent; and when the valve is open and the coil ceases generating a magnetic field, the pilot piston seals against the bleed hole seat, whereupon pressure differentials across the valve, in combination with the spring and primary biasing element cause the seal piston and primary piston to revert to their closed positions and restrain flow through the valve.