referring to fig1 and 2 , there is shown a check valve vent assembly 10 which includes a valve body 11 , a diaphragm 12 , and a retainer 13 . the valve body 11 , as illustrated in fig1 may be a relatively small area of a wall of a housing to be vented , with oppositely facing surfaces 16 and 17 representing the interior and exterior , respectively , of such housing . the body 11 is stop drilled or otherwise formed with a central vent passage 18 , a cylindrical inner bore 19 , and successive concentric , cylindrical counterbores 20 and 21 . the intersection of a radial surface 23 at the base of the first counterbore 20 and the inner bore 19 forms an edge or annular valve seat 24 . as shown , the radial width of the surface 23 extending under the diaphragm 12 is relatively small compared to the diameter of the diaphragm , so that the diaphragm is axially supported by the body 11 solely at its outer periphery . the inner bore 19 has sufficient depth to receive a central area of the diaphragm 12 deflected inwardly by the retainer 13 . similarly , the first counterbore 20 is of sufficient depth to at least receive the thickness of the diaphragm 12 and a central portion 27 of the retainer 13 . the second or outer counterbore 21 , in turn , has a depth sufficient to fully receive the thickness of the outer peripheral portion of the retainer 13 and , as shown , has a depth at least equal to twice the thickness of the retainer to assure that all areas of the retainer are within or below the plane of the outer surface 17 of the body 11 . as illustrated , the vent passage 18 is substantially smaller in diameter than the intermediate bore 19 . the diaphragm 12 is a normally flat , imperforate , circular body of resilient material , preferably an elastomeric material having a preferable hardness of approximately 50 durometer ( shore a ). the illustrated diaphragm is blanked from elastomeric sheet stock in a thickness , for example , of 1 / 32inch , or is molded to size . the diaphragm 12 is dimensioned diametrally with respect to the associated bore 20 to provide a fit loose enough for ease of assembly but close enough to permit the bore to substantially center the diaphragm over the seat 24 . in the illustrated arrangement , for example , a nominal clearance of between 0 . 010 - 0 . 012 inch for a diaphragm diameter of 0 . 346 inch and a seat diameter of 0 . 275 inch is used . the retainer 13 is an integral body having a spiderlike configuration . the illustrated retainer 13 is formed by blanking from 0 . 010 inch steel sheet stock , and has a final rockwell hardness of appproximately 49 rc to be relatively rigid after assembly . the retainer 13 includes a plurality of circumferentially spaced legs 29 interconnected by a circular web 30 . the center section 27 of the retainer 13 protrudes from the plane of the web 30 and lies generally within an axial cone which intersects the inner circumferential boundary of the web . a pair of apertures 32 are punched or otherwise formed on opposite sides of the center section 27 . outer edges 34 of the legs 29 are described by a common circle which , in a free state , is slightly larger than the associated bore 21 to provide an interference fit therein . the legs 29 , in their free state , may be planar with the web 30 , or may be in a slightly dished condition away from the center section 27 as a result of the blanking process . the protrusion of the center section 27 is sufficient , when the legs 29 rest on a radial surface 35 at the base of the associated counterbore 21 , to engage and deflect a center portion of the diaphragm 12 inwardly so that the outer peripheral area of the diaphragm is resiliently held in sealing contact with the seat 24 . assembly of the diaphragm 12 and retainer 13 is accomplished by first positioning the diaphragm within its receiving bore 20 and subsequently forcing the retainer 13 into its bore 21 into abutting engagement with the surface 35 . due to the interference fit of the legs 29 with the bore 21 , the legs are preferably elastically deflected or folded slightly rearwardly into a relatively shallow or relatively flat conical configuration . this rearward deflection produces a wedging or self - locking action , wherein the outer edges 34 of the legs 29 tend to tightly engage the surface of the bore 21 . the wedging action provided by the leg structure allows the retainer 13 to be manually or mechanically inserted with a relatively light installation force in comparison to the axial resistance or retaining capacity of the retainer against forces tending to expel it . by proper dimensioning of the length of the legs 29 relative to the bore 21 and / or by application of relatively high forces , as desired , the legs can be set in a relatively flat or planar configuration in the bore . the assembly 10 is particularly useful in venting a chamber or enclosure of excess fluid pressure or volume . fluid pressure existing at the inner body surface 16 and communicated to the intermediate bore or chamber 19 by the vent passage or hole 18 is operative to lift the peripheral portion of the diaphragm 12 outwardly away from the seat 24 to relieve such pressure . movement of the radially outward portion of the diaphragm 12 is permitted by the axial spacing of the leg and web portions 29 , 30 from the apex of the center section 27 of the retainer 13 . fluid passes through the spaces between the legs 29 and the apertures 32 . by contrast , entrance of contaminating fluids or solids into the chamber 19 is checked by the seating action of the diaphragm 12 on the seat 24 . the shallow configuration of the assembly 10 permits it to be incorporated into an existing wall of a housing so that it shares such a wall as its own body , thereby avoiding the requirement for a separate supporting body , which would otherwise require its separate fabrication and assembly to the housing . one application of the assembly 10 is the venting to atmosphere of a chamber in a hydraulic control valve to prevent the occurrence of a hydraulic lock therein . in this case , the housing , as represented by the body 11 , is formed of brass , aluminum , or other readily machined or formed material , which is characteristically softer than the material forming the retainer 13 so that the legs 29 tend to bite into the housing surface at the bore 21 to thereby improve its resistance to removal from its installed position . referring to fig3 and 4 , there is shown an alternative embodiment of the retainer 13 , wherein a retainer 37 is provided with a slightly different configuration . the retainer 37 is an integral body , again blanked from steel sheet stock and having a plurality of circumferentially spaced legs 38 . outer edges 39 of the legs are defined by a diameter which , again , is dimensioned to interfere with the associated body bore 21 . an imperforate center section 41 of the retainer 37 is formed in the shape of a cone and projects from the plane defined by the legs 38 and an intermediate area 42 . this alternative retainer 37 is installed and functions in substantially the same manner as that set out above in connection with the retainer 13 , except that vented fluid escapes between the legs 38 exclusively , since there are no apertures in the body of the retainer . while the invention has been described in connection with specific embodiments thereof , it is to be clearly understood that this is done only by way of example , and not as a limitation to the scope of the invention as set forth in the objects thereof and in the appended claims .