International Safety Instruments, Inc.

Racal Health & Safety Limited

Peter J Jackson

There is described a demand valve for a breathing apparatus with a 'first breath' mechanism, wherein a demand valve is held closed by resiliently latching an operating diaphragm of the valve in a position wherein the valve is closed. The diaphragm is resiliently biased towards opening the valve, and the resilient latch is arranged to exert sufficient force so as not to be overcome by the resilient bias alone, but so as to be overcome by the combination of the resilient bias and a predetermined pressure difference across the diaphragm caused by sub-ambient pressure within the facepiece of the breathing apparatus.

Demand valves for breathing apparatus

There is described a demand valve for a breathing apparatus wherein a pilot jet of the demand valve is controlled by a pivoting lever resiliently held against a planar face in which the pilot jet is formed. The pilot jet is preferably formed in a land surface surrounded by a recessed area of the planar face, and opening of the pilot jet is effected by movement of a control projection mounted on the pivoting lever. The area of the control projection is preferably greater than the area of the land surface. A bypass arrangement for a demand valve is also disclosed

Demand valve for breathing apparatus

A breathing apparatus comprises a supply of breathable gas and a facepiece by which breathable gas is supplied to a wearer, the facepiece including a supply valve for delivering gas to the interior of the facepiece, and an exhaust opening closeable by an exhaust valve for allowing the egress of exhaled gas from the facepiece. The exhaust valve comprises a movable valve member which, in a first position, closes the exhaust opening in the facepiece, in a second position is displaced toward the interior of the facepiece relative to the first position while still in sealing engagement with the exhaust opening to open the supply of breathable gas, and in a third position is displaced outwardly of the facepiece relative to the first position to open the exhaust opening to allow the egress of exhaled gas. The valve member is biased towards the second position by a single significant biasing means. A sealing element is preferably interposed between the valve member and the exhaust opening.

Breathing apparatus and facepiece therefor

A positive pressure demand valve for breathing apparatus incorporates a tubular 'balanced piston' valve member for regulating the flow of breathing gas from an inlet to an outlet. A coaxial tension spring acts to bias the valve member open and a lever coupled to a pressure-responsive diaphragm acts to push the valve member closed when a predetermined pressure is attained within the outlet. A combined pressure-relief and bypass valve member enables the operation of the main valve member to be bypassed by porting gas through the center of the main valve seat. A 'first breath' mechanism is provided comprising a hooked link which can be pressed in by a button to maintain the main valve member closed and can be released by contact by the diaphragm when a negative pressure is applied to the outlet. The outlet is in the form of a bayonet connector which is locked into a corresponding inlet fitting on the user's mask by means of the same button.

Growing community of inventors

Findon, United Kingdom

Peter J Jackson