Abstract:
A first stage pressure regulator for a two-stage underwater breathing apparatus, comprises a second movable wall ( 16, 18 ) for separating a balance chamber ( 10 ) from an ambient exposed chamber ( 17 ) . The second movable wall is formed by a disk-shaped piston ( 16 ) which is slideably and non sealingly guided along the peripheral walls that delimit the balance chamber ( 10 ), and by an elastically deformable diaphragm ( 18 ), which overlies the side of the piston ( 16 ) facing forward the ambient exposed chamber ( 17 ) . The elastically deformable diaphragm ( 18 ) forms with said piston ( 16 ) a diaphragm type pressure relief valve ( 20, 318 ).

Description:
FIELD OF INVENTION 
     The invention relates to a first stage pressure regulator for a two-stage underwater breathing apparatus, which first stage regulator is connected to a source of high pressure breathable gas, and comprises: 
     an inlet connected to the source of high-pressure gas and an outlet for gas having a lower pressure than the incoming gas; 
     a high pressure gas chamber communicating with said inlet and a low pressure gas chamber connected with said outlet; 
     the low pressure gas chamber communicating with the high pressure gas chamber through a regulating valve; 
     a balance chamber interposed between the low pressure gas chamber and a chamber communicating with the ambient or directly the ambient; 
     said low pressure gas chamber being sealingly separated from the balance chamber by a first movable wall; 
     said balance chamber being sealingly separated from the ambient exposed chamber by a second movable wall; 
     said first and said second movable walls being mechanically and rigidly interconnected by stem which is designed to transfer the force exerted on said movable walls; 
     said first movable wall being further connected by force transfer means to the closing element of the valve interposed between the high pressure gas chamber and the low pressure gas chamber; 
     a check valve being provided, for relieving the overpressure in the compensation chamber, between said compensation chamber and said ambient exposed chamber. 
     BACKGROUND OF THE INVENTION 
     First stage pressure regulators of the above type are known in the art. The overpressure that may build up in the balance chamber is relieved thanks to the tubular shape of the force transfer stem between the first and the second movable walls which sealingly separate the balance chamber from the low pressure gas chamber and the ambient exposed chamber respectively. A hole in the tubular wall puts in communication the inside of the tubular stem with the balance chamber, whereas a pressure relief valve is provided at the end for connection to the second movable wall which separates the balance chamber from the ambient exposed chamber, which valve is a one-way valve or a check valve whose shut-off direction corresponds to a flow direction from the ambient exposed chamber to the balance chamber. 
     A valve of this type is known, for example, from U.S. Pat. No. 5,097,860. 
     The provision of a balance chamber having means for transferring force to the regulating valve element between the high pressure gas chamber and the low pressure gas chamber, which force transfer means are two movable walls rigidly interconnected by the intermediate stem and a force transfer extension connected to the regulating valve element allows to adapt the pressure regulating valve calibration to ambient pressure conditions. 
     The first and the second movable walls generally consist of combinations of pistons cooperating with elastically deformable diaphragms, and elastic means are generally further provided for adjusting a certain preload on said movable walls, and operating in the same direction as the force exerted by ambient pressure. 
     The above construction of prior art pressure regulators has a number of drawbacks. The pressure relief valve is generally fixed to the tubular stem and requires the diaphragm to be also perforated in the area of the tubular stem. Furthermore, the pressure relief valve is very small and thence relatively expensive and makes assembly more difficult, besides being itself a construction part. 
     The tubular stem requires a transverse hole to be formed therein for communication of the inside tubular space with the balance chamber. 
     SUMMARY OF THE INVENTION 
     The invention has the object of improving a first stage pressure regulator as described hereinbefore, in which: 
     The movable wall for separating the balance chamber from the ambient exposed chamber is formed by a disk-shaped piston which is slideably and non sealingly guided along the peripheral walls of the balance chamber and by an elastically deformable diaphragm, which overlies the side of the piston facing toward the ambient exposed chamber and forms with said piston a diaphragm relief valve. 
     In a first variant embodiment, the diaphragm is sealingly and stably clamped at its peripheral edge, and has a relief hole in its central area, which is engaged on a coincident cylindrical or frustoconical extension of the piston projecting out of the side thereof facing toward the ambient exposed chamber. 
     The free end of the cylindrical or frustoconical extension possibly ends with a widened head having a diameter greater than that of the coincident through hole of the elastic diaphragm. 
     Advantageously, in this embodiment the elastic diaphragm has a bellows-shaped peripheral edge which is directly radially inwards from an annular peripheral lip or flange, which is designed to sealingly clamp said diaphragm. 
     According to an alternative embodiment, the peripheral edge of the piston which forms the movable separating wall between the balance chamber and the ambient exposed chamber is sealingly guided by the inner wall of the balance chamber, whereas said piston has at least one eccentric hole and supports a diaphragm valve on the side facing toward the ambient exposed chamber, at its central area and is free at its periphery. 
     In both embodiments, the diaphragm is preferably made of silicone or other highly elastic materials. 
     Further improvements will form the subject of the dependent claims. 
     The characteristics of the invention will appear more clearly from the following description of a few embodiments, which are shown without limitation in the annexed drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an axial cross sectional view of a first embodiment of the first stage pressure regulator according to this invention. 
         FIG. 2 , like  FIG. 1 , shows a variant embodiment of the first stage pressure regulator according to  FIG. 1 . 
         FIG. 3  shows, like the previous Figures, a second embodiment of the first stage pressure regulator according to this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A first embodiment of the first stage pressure regulator of the present invention is shown in  FIG. 1 . Such first stage comprises a substantially cylindrical body having a first high pressure gas chamber  1  which communicates with a gas source (not shown in detail) such as a bottle or the like, through an inlet  101 . A low pressure gas chamber  2 , with gas having a lower pressure than the incoming gas, has at least one, two or more outlets  102  for said low pressure gas. In the figure the outlets are in the form of threaded holes in which threaded fittings  103  of hoses or the like are sealingly tightened. A regulating valve is provided between the high pressure gas chamber  1  and the low pressure gas chamber  2 . This valve is composed of a stationary valve seat  4  and an element  5  which is mounted in such a manner as to be able to move towards and away from said valve seat. The valve element is mounted in such a manner as to slide along the axis of the passage  104  of the valve seat and has a surface exposed to the action of the high pressure gas which acts thereon in the opening direction, such sliding motion being opposed by preloadable elastic means  6 , which stably act in the closing direction of the valve element against said valve seat  4 . Pressure reduction occurs, as is known, thanks to the fact that the calibration of the elastic means and the ratio between the pressures in the two chambers causes the element to only open to such an extent and for such a time as to allow a small volume of high pressure air to pass in the low pressure gas chamber, and to expand in the low pressure gas chamber  2 . 
     The regulating valve element  5  extends through the passage  104  of the valve seat  4  by an actuating stem  7  in the low pressure gas chamber  2  and ends with a piston, preferably having a circular shape  8 . This piston  8  adheres by the surface opposite the control stem  7  against a first elastic diaphragm  9 , thereby forming a movable wall for separating the low pressure gas chamber  2  from a balance chamber  10 . The elastic diaphragm  9  is sealingly clamped along its outer peripheral edge. In the embodiment as shown, this occurs thanks to a threaded tubular member  11  which sealingly engages in an internally threaded bell joint  12  which peripherally delimits an annular shoulder  13  for clamping the peripheral edge of the diaphragm  9 , which is thus clamped between said shoulder  13  and the end edge of the tubular member  11 . The latter forms the peripheral shell wall of the balance chamber  10 . A second bell-shaped piston  14  adheres against the diaphragm side opposite the low pressure gas chamber  2 , and is rigidly connected by a central force transfer stem  15  to another piston  16 , which forms the other movable wall of the balance chamber  10 , that separates said balance chamber from an ambient exposed chamber  17 . In this embodiment, the piston  16  is unsealingly guided by the inner surface of the tubular member  11  which forms the inner shell wall of the balance chamber  10 , whereas the seal with the ambient exposed chamber is ensured by an elastic diaphragm  18 . The elastic diaphragm  18  is sealingly clamped along its inner peripheral edge, like the diaphragm  9 , between the externally threaded end side of the tubular member  11  and an internally threaded clamping ring  19 . Particularly the peripheral edge of the diaphragm  18  has an axial flange  118  which is engaged in an annular axial groove, formed in the thickness of the end edge of the tubular member  11 . The axial flange  118  is connected to the rest of the diaphragm  18  by an annular bellows-shaped part. The annular part for connection between the axial flange  118  and the annular bellows-shaped part  218  overlays the end edge of the tubular member  11  and is clamped between the latter and an annular radial shoulder  119  of the ring nut  19 . An axial frustoconical extension  20  extends from the central area of the side of the piston  16  facing toward the diaphragm  18 , thence toward the ambient exposed chamber  17 , which extension engages with a central through hole  318  of the elastic diaphragm  18 . The diameter of this hole substantially corresponds to the average diameter of the axial frustoconical extension  20  which acts as an a valve element, in combination with the natural elastic deformability of the diaphragm  18  and the hole  318 . The ambient exposed chamber  17  is closed from the ambient by a cap  21 , which has a plurality of apertures for communication with the ambient and overlays the ring nut  19 , while being locked in position, for example, by snap engagement means, in an engagement groove. Particularly, these means may consist of an end flange which is formed as a small radial neck at the free edge of the cap  21 , which is in snap engaging relationship with a groove formed between the end edge of the ring nut  19  for clamping the diaphragm  18  and a radial annular ridge of the tubular member  11  which is provided at an axial distance from said end edge of the ring nut  19 . 
     A stationary abutment  23  for an elastic member  24 , for instance a helical spring, is placed in an intermediate position in the balance chamber  10 , in an axially adjustable manner, and is interposed between said stationary abutment and the bell-shaped piston  14 . This elastic member generates an adjustable preload on the assembly formed by the bell-shaped piston  14 , the force transfer stem  15  and the piston  16  subjected to the action of ambient pressure toward the low pressure gas chamber  2 , therefore in the opening direction of the regulating valve element  5 . 
     Advantageously, the stationary abutment  23  for the elastic member  24  consists of a cup-shaped annular member having an external thread for engagement with an internally threaded portion of the tubular member  11 , which allows to adjust the compression of the elastic member  24  by simply tightening or loosening the abutment  23 . 
     The operation of this first stage pressure regulator is easily understandable from the above description. The action of high pressure gas in combination with that of the elastic means associated to the valve element  5  is combined with the variable force exerted by ambient pressure, which is in turn assisted by the action of the elastic means  24 . Ambient pressure is exerted on the piston  16  and transferred by the stem  15  to the bell-shaped piston and, thanks to the elastic diaphragm  9 , to the piston  8  and to the element  5 . 
     The diaphragm  18  which separates the balance chamber  10  from the ambient exposed chamber  17  and cooperates with the piston  16  and the frustoconical extension  20  thereof is an overpressure relief valve, which is designed to relieve the overpressure that may build up and actually builds up in the balance chamber  10 . Such overpressure is obviously undesired, as it alters pressure balancing settings. The operation is schematically shown in  FIG. 1 . Assuming normal pressure conditions in the balance chamber  10 , the diaphragm is pushed, either naturally or under the action of ambient pressure, at its central portion against the piston  16 , therefore the central hole  318  slides along the frustoconical extension  20  in the increasing diameter direction, whereby a sealing condition is generated (see diaphragm outlined in dashed lines). When the balance chamber  10  is in overpressure conditions, the elastic diaphragm  18  bows in a direction opposite to that of the balance chamber  10  (see diaphragm outlined in full lines) and the hole  318  moves toward the apex of the frustoconical extension  20 , i.e. in the decreasing diameter direction, whereby the seal between said extension  20  and said hole  318  is released, which allows gas to escape from the balance chamber  10  to the ambient exposed chamber  17 . 
     Advantageously, as shown in  FIG. 1 , at the center of the diaphragm between the hole  318  and the annular bellows  218 , the diaphragm may have a non flat, concave shape, e.g. in its natural rest condition, which defines, in combination with the bellows, a well-determined and repeatable rest position of the diaphragm, corresponding to the sealing position against the piston  16  and the extension  20 . 
     The construction of the first stage pressure regulator as described above has further advantages. The construction of the balance chamber by using substantially a tubular member  11  with a ring nut  19  for clamping the peripheral edge of the diaphragm  16 , as well as the engagement of said tubular member in a threaded bell shaped seat of the rest of the regulator body in which the low pressure gas chamber  2  and the high pressure gas chamber  1  are formed, allows easy assembly and dismantling and fast replacement of diaphragms and the other parts, such as the pistons  16  and  14 . Furthermore, this construction affords an easier adjustment of the position of the stationary abutment  23  for the elastic member  24 . It is further worth noting that there is no mechanical continuity between the piston  14  and the control stem  7  which connects the piston  16  to the valve element, and that the bell-shaped piston  14  acts as a presser on a separate piston  8 , whereto said control stem  7  is attached. Therefore, dynamic functionality is obtained and maintained thanks to the provision of two separate construction parts. This allows to safely sealingly separate the balance chamber from the low pressure gas chamber by means of the elastic diaphragm  9  which is continuous, with no apertures therein, and is stably clamped at its periphery. This is of great importance, because any water ingress in the low pressure gas chamber would be highly undesired, said low pressure gas chamber  2  being the chamber wherefrom breathable air is taken. As is apparent, the construction of the first stage pressure regulator as shown in  FIG. 1  provides an advantageous improvement with respect to the use of a single piston in lieu of two separate pistons  14  and  8 , which single piston would be rigidly or integrally attached to the piston  16  and the element actuating stem  7 . In this case, seal could only be provided by peripheral gaskets of said single piston, cooperating between the latter and the inner shell wall of the balance chamber and being highly exposed to wear due to their sliding motion along said walls. 
     The variant of  FIG. 2  essentially shows a first stage pressure regulator having exactly the same construction as that described above with reference to  FIG. 1 . In  FIG. 2  like parts or parts having like functions of those of  FIG. 1  bear like numbers. 
     The substantial difference is that the free end of the frustoconical extension  20  of the piston  16  cooperating with the diaphragm  18  has a widened head  120  whose diameter is greater than the diameter of the hole  318  of the diaphragm  18  which is engaged on said extension. Such widened head has the function of preventing the diaphragm  18  from accidentally slipping off the frustoconical extension  20  in case of an abrupt overpressure relief. Here, if no widened head  120  were provided, an excessive deformation of the diaphragm might cause the diaphragm  18  to slip off the frustoconical extension  20  and, more seriously, to be radially offset with respect to said frustoconical extension  20 , whereby the diaphragm  18  might get caught at the end of said frustoconical extension when it is moved back to the rest and sealing position, and might not prevent water ingress from the ambient to the balance chamber  10 . 
       FIG. 3  shows yet another embodiment of the first stage pressure regulator according to this invention. Here again, the construction of said first stage is substantially identical to that of the previous figures, with the exception of the construction of the piston  16  and the diaphragm  18 . In fact, in this variant embodiment, the seal between the ambient exposed chamber  17  and the balance chamber  10  is provided directly by the piston  16 , which is sealingly guided along the inner wall of the balance chamber  10 , i.e. the tubular member  11 , thanks to annular peripheral sealing gaskets, e.g. an O-ring  116  received in a peripheral groove that is formed in the thickness of said piston  16 . The piston further has at least one through hole  216  in an eccentric position or two or more holes or a ring of through holes, which are sealingly closed by the diaphragm  16  on the side facing toward the ambient exposed chamber  17 . This diaphragm is a diaphragm element of a conventional diaphragm valve and is completely free at its periphery, whereas it is fixed to the piston  16  at its center. Fixation may occur in any manner whatever, e.g. by using a central axial pin for snap engagement in a snap hole  316  placed in coincidence with the piston  16 . Particularly, the central pin  418  and the snap hole are coaxial, whereas the through holes  216  are at radial distances therefrom which are smaller than the radius of the diaphragm  16 . 
     Particularly, the central pin  418  may have at least two opposite wedge-shaped teeth  518  or a ring of such wedge-shaped teeth or a radial annular conical projection, which is in elastic snap engagement with an inner annular shoulder or a ring of inner radial teeth or with corresponding inner radial teeth of the snap hole  316  in the piston  16 . The section of the teeth or the annular conical projection has a front with a smaller slope on the side facing toward the free end of the pin, to form a lead-in surface and a substantially radial and perpendicular front on the opposite side, to provide firm anchorage behind the shoulder or the inner radial teeth of the hole  316 . 
     This arrangement has the advantage of further simplifying construction and especially of facilitating the replacement of the diaphragm  16 , which is most exposed to the ambient, thence to deterioration. 
     It is worth noting that the cap  21  which delimits the ambient exposed chamber  17  from the outside, therefore the chamber  17  itself are not necessarily required, said cap only providing mechanical protection to the diaphragm  16  against any accidental damage. 
     Therefore, this invention shall be intended to also cover the sub-combination in which the ambient exposed chamber  17  is not provided, and is formed by the ambient itself.