Breathing apparatus

Abstract

A face mask ( 10 ) mechanically coupled to a lung demand valve (LDV) ( 12 ). The face mask ( 10 ) comprises a main mask and an inner mask ( 15 ) which fits over the wearer's mouth and nose. The interior of the inner mask ( 15 ) is in fluidic communication with the interior of the main mask ( 10 ) by means of non-return valves ( 16 ). The interior of the main mask is in fluidic communication with an inlet port ( 18 ) which is mechanically and fluidically coupled to a supply port ( 20 ) of an LDV. The LDV ( 12 ) includes a diaphragm and a cover ( 44 ) which comprises three parts ( 44 a, 44 b ) and ( 44 c ). Exhaled air is used to flush the space around the diaphragm. Thus, any toxic or undesirable gas in the vicinity of the diaphragm is pushed out to atmosphere by the exhaled air flowing past and around the diaphragm.

1 . A lung demand valve device for use with breathing apparatus, for delivering breathable gas from a pressurised supply to a user wearing a face mask, for inhalation, the device comprising 
 a body in which is housed a valve member, for controlling the rate of delivery of the breathable gas,    a movable diaphragm having a first face exposed to pressure within the body and a second face exposed to pressure outside the body, the diaphragm being responsive to the differential in pressure between its first and second faces to control the valve member,    and a duct arranged to direct exhaled air towards said second face of said diaphragm.    
   
   
       2 . A device according to  claim 1  wherein the device is detachably mountable on a mask of a breathing apparatus.  
   
   
       3 . A device according to  claim 1  wherein the device is permanently attached to a mask of a breathing apparatus.  
   
   
       4 . A device according to  claim 1  wherein the device is integral with a mask of a breathing apparatus.  
   
   
       5 . A device according to  claim 1  wherein the duct portion is arranged to abut an exhalation port of a mask.  
   
   
       6 . A device according to  claim 1  wherein the duct is arranged to direct exhaled air to a region surrounding the second face of the diaphragm, so as to flush ambient gases from said region.  
   
   
       7 . A device according to  claim 1  wherein the device comprises a cover member arranged to extend around the device for preventing the ingress of dirt into the housing, and wherein the duct comprises a portion of said cover.  
   
   
       8 . A device according to  claim 7  wherein said cover comprises a plurality of portions which portions are detachably fixed together.  
   
   
       9 . A device according to  claim 1  wherein the device comprises locating means arranged to co-operate with a mask to inhibit rotation of the device relative to a mask.  
   
   
       10 . Self-contained breathing apparatus including a lung demand valve device according to  claim 1 .  
   
   
       11 . A lung demand valve suitable for use in a self contained breathing apparatus, in which fluid for breathing is conveyed to a user on inhalation, the lung demand valve comprising: 
 a first fluid path,    a second fluid path,    a flexible diaphragm, separating the first and second fluid paths, and wherein the second fluid path is open to the atmosphere.    
   
   
       12 . A cover suitable for use on a lung demand valve for a self contained breathing apparatus, in which fluid for breathing is conveyed to a user on inhalation, in which the lung demand valve comprises: 
 a first fluid path, and    a diaphragm, enclosing at least a part of the first fluid path,    wherein the cover provides the lung demand valve with a second fluid path, so that the first and second fluid paths are separated by the diaphragm, and the second fluid path is open to the atmosphere, and wherein exhaled fluid is directed along the second fluid path to the diaphragm.    
   
   
       13 . A self-contained breathing apparatus in which fluid for breathing is conveyed to a user on inhalation, the apparatus comprising: 
 a face mask, connected to a lung demand valve, and worn by the user,    a high pressure cylinder containing the fluid for breathing,    a hose for conveying fluid from the cylinder to the lung demand valve, wherein the lung demand valve comprises:    a first fluid path for conveying fluid for inhalation to the face mask,    a second fluid path for conveying exhaled fluid from the face mask to the atmosphere, and    a flexible diaphragm, separating the first and second fluid paths, wherein exhaled air is directed to the diaphragm.