Deflation control valve

Abstract

A deflation control valve that automatically varies the rate of air flow through said control valve to provide a constant but adjustable rate of change of pressure during the deflation or exhaust of gas held in a closed pressurisable vessel to which said valve is connectable comprising a valve body having a passage communicatable with said pressurisable vessel, said valve body defining a valve chamber communicating with said passage in which a flexible diaphragm is provided partially or substantially closing said valve chamber, said diaphragm being in sealing abutment with a seat in said valve housing around the periphery of said diaphragm, and forming on the opposing side a part of an exhaust chamber, said diaphragm, in use, being, on the valve chamber side subject to the gas pressure in said pressurisable vessel and, on the opposing side, subject to the gas pressure in the exhaust chamber, which may be atmospheric pressure, and said diaphragm having an aperture or port extending therethrough, and said diaphragm on one side being in communication with said valve chamber and, on the opposite side, being in communication with said exhaust chamber or atmosphere and being closeable or partially closeable by a displaceable closure disc, plate or platen which is releasably held in the closing position against said diaphragm and covering said port by an operable, controllable or adjustable release means, which by adjusting said release means to open and closed positions or intermediate positions, controls the rate at which gas flows through the valve, gas passing from the valve chamber through the port in the diaphragm and between the face of the closure disc and diaphragm to exhaust or atmosphere to allow the pressure of the pressure chamber to drop in a controlled manner.

1 . A deflation control valve that automatically varies the rate of air flow through said control valve to provide a constant but adjustable rate of change of pressure during the deflation or exhaust of gas held in a closed pressurisable vessel to which said valve is connectable comprising a valve body having a passage communicatable with said pressurisable vessel, said valve body defining a valve chamber communicating with said passage in which a flexible diaphragm is provided partially or substantially closing said valve chamber, said diaphragm being in sealing abutment with a seat in said valve housing around the periphery of said diaphragm, and forming on the opposing side a part of an exhaust chamber, said diaphragm, in use, being, on the valve chamber side subject to the gas pressure in said pressurisable vessel and, on the opposing side, subject to the gas pressure in the exhaust chamber, which may be atmospheric pressure, and said diaphragm having an aperture or port extending therethrough, and said diaphragm on one side being in communication with said valve chamber and, on the opposite side, being in communication with said exhaust chamber or atmosphere and being closeable or partially closeable by a displaceable closure disc, plate or platen which is releasably held in the closing position against said diaphragm and covering said port by an operable, controllable or adjustable release means, which by adjusting said release means to open and closed positions or intermediate positions, controls the rate at which gas flows through the valve, gas passing from the valve chamber through the port in the diaphragm and between the face of the closure disc and diaphragm to exhaust or atmosphere to allow the pressure of the pressure chamber to drop in a controlled manner. 
   
   
       2 . A valve as claimed in  claim 1 , where the resistance to the passage of gas from the higher pressure in said valve chamber to the lower pressure in said exhaust chamber is determined by the surface area of said diaphragm in contact with said closure disc, the local contact pressure between said diaphragm and said closure disc and the material, geometry and surface finish of said diaphragm and said closure disc. 
   
   
       3 . A valve as claimed in  claims 1  and  2 , such that, on releasing the release means slightly, the closure disc moves away from the diaphragm, the pressure difference between the higher pressure in the valve chamber and the lower pressure in the exhaust chamber urges said flexible diaphragm towards said closure disc, creating a curvature in said diaphragm such that the surface area of said diaphragm in contact with said closure disc and the local contact pressure between said diaphragm and said closure disc controls the rate at which gas can seep from the higher pressure area in the valve chamber through the port in the diaphragm to the lower pressure area in the exhaust chamber in a manner that is dependent on the position of the closure disc in relation to the diaphragm, the pressure difference between the higher and lower pressure areas and the nature of the materials, surface finishes and form of the diaphragm and closure disc, such that the valve automatically maintains a constant rate of pressure change in the pressurisable vessel as the pressure difference between the valve chamber and the exhaust chamber changes due to loss of gas from the pressurisable vessel. 
   
   
       4 . A valve as claimed in  claim 1 ,  2  and  3 , in which a manually operable release means is a reversibly rotatable and axially displaceable control knob bearable on the platen. 
   
   
       5 . A valve as claimed in  1 ,  2  and  3 , in which a manually operable release means is a non-axially displaceable rotary knob with cam and lever means for reversibly urging the platen into a closing position, the cam so formed that there appears to the user to be a linearly (or any other) proportional relationship between the angular position of the knob and the rate of change of pressure difference between the valve chamber and the exhaust chamber. 
   
   
       6 . A valve as claimed in  claim 5 , in which the displacement means associated with the knob and is such that the movement is amplified and thus greater movement of the knob enables a smaller movement of the disc or platen. 
   
   
       7 . A valve as claimed in any of  claims 1  to  6 , in which the closure disc and/or diaphragm has an air escape passage or means which varies in cross-section as the deformation of the diaphragm due to the pressure difference across it and the position (lifting and lowering) of the closure disc varies. 
   
   
       8 . A valve as claimed in  claim 7 , wherein alternate air escape control means is provided on or in the diaphragm to compensate for falling pressure in the pressurisable vessel. 
   
   
       9 . A valve as claimed in  claim 7  or  8 , in which the air escape means is an escape passage in the form of a recess to compensate, in use, for falling pressure in the pressure chamber and enable the rate of change of pressure in the valve chamber to be controlled. 
   
   
       10 . A valve as claimed in  claim 7 , wherein alternate air escape control means is provided on or in the closure disc to compensate for falling pressure in the pressurisable vessel. 
   
   
       11 . A valve as claimed in  claim 8 , in which the alternate air escape means is a small groove or channel or other airflow control enhancing feature on or in the surface of said diaphragm facing said closure disc. 
   
   
       12 . A valve as claimed in  claim 10 , in which the alternate air escape means is a small groove or channel, or a projection (such as a ridge or bump) or other airflow control enhancing feature on or in the surface of said closure disc facing said diaphragm. 
   
   
       13 . A valve as claimed in  claim 11 , in which the groove is elongate and diametrical and central and positioned over or through the port perforating the diaphragm and of a varying/differing cross-sectional area, largest in the centre of either the closure disc or the diaphragm and reducing to zero nearer to the edge of the closure disc or diaphragm, such that amount of surface area of the diaphragm in contact with the closure disc determines the minimum cross-sectional area of the groove through which gas escaping from the higher pressure chamber to the exhaust chamber has to flow. 
   
   
       14 . A valve as claimed in any of  claims 1  to  13 , in which the airflow control enhancing features are provided additionally or alternatively including the surface finish of the closure disc and/or the diaphragm and/or the shape of both parts and/or the softness and/or thickness of the diaphragm. 
   
   
       15 . A valve as claimed in any of  claims 1  to  14 , in which, in use, when the valve is closed, the diaphragm port is sealed or substantially closed by the closure disc or platen, which is held down by means extending from the release means. 
   
   
       16 . A valve is claimed in  claim 15 , in which the release means is an axially displaceable rotary knob secured with a fine screw thread to the valve body or a non-axially displaceable rotary knob having a cam which acts on lever means to achieve the same effect. 
   
   
       17 . A valve as claimed in any of  claims 1  to  16 , in which click or pawl and ratchet means are associated with the release means and regulate the movement of the control knob and provide audible and/or physical feedback to the clinician. 
   
   
       18 . A deflation control valve substantially as herein described with reference to the accompanying drawings. 
   
   
       19 . A deflation control valve as claimed in any of  claims 1  to  18  in combination with a sphygmomanometer. 
   
   
       20 . A deflation control valve in the form of a face valve for a sphygmomanometer comprising a valve body having a first outlet passage connectable to be communicatable with a pressurisable tube connected to a cuff of a sphygmomanometer, and an inlet passage connectable to a rubber bulb pump or like inflation means, said valve body defining a valve chamber in which a flexible diaphragm is provided partially or substantially closing the chamber and said diaphragm having a deflation, air-flow passage which on one side of the diaphragm is in communication with said inlet and outlet passage and, on the opposite side of the diaphragm, is in communication with an exhaust outlet or atmosphere and is closeable or partially closeable during inflation by a displaceable closure disc, plate or platen which is releasably held in the closing position against said passage by a manually operable, controllable or adjustable release means.