US 3145721 A
Description (OCR text may contain errors)
1964 A. E, MILLER 3,145,721
DEMAND VALVE Filed Dec. 8, 1961 INVENTOR 072% EZM-fier BY m w? W ATTORNEY United States Patent 3,145,721 DEMAND VALVE Arthur E. Miller, Buffalo, N.Y., assignor to Scott Aviation Corporation, Lancaster, N .Y. Filed Dec. 8, 1961, Ser. No. 158,037 2 Claims. (Cl. 137-64) This invention relates, in a breathing apparatus, to a demand valve which, in combination with a pressure regulating casing supplied with a breathing fluid under high pressure and a diaphragm whose outer surface is exposed to the ambient atmosphere, is adapted to provide breathing fluid at low pressure whenever the person using the breathing apparatus inhales and thereby actuates said diaphragm which latter, in turn, opens said demand valve.
The primary object of the invention is to provide a demand valve which is of relatively small diameter and yet which impedes the flow of breathing fluid to a minimum extent, whenever it is opened.
Other collateral objects of the invention and practical solutions thereof are described in detail in this specification and are illustrated in the accompanying drawing, in which FIG. 1 is a coaxial, longitudinal section through a pressure regulating casing 5 provided with a demand valve 14 and various accessories of the latter.
FIG. 2 is a fragmentary, enlarged section thereof taken transversely of the axis of the stem 15 of the demand valve 14, taken on line 22, FIG. 1.
For efliciency, this invention will be described exactly as it is here illustrated, but it is to be definitely understood that the patentable novelty of the invention is only to be determined by the originality of the concepts disclosed and by the scope of the appended claims.
The pressure regulating casing 5 is provided with screw threads 6 to enable the breathing fluid in its breathing compartment 7 to be discharged at relatively low pressure through its outlet 8 and into the breathing mask (not shown), or into the breathing mouthpiece (not shown), that is being worn by the user of the breathing apparatus. High pressure breathing fluid is supplied to said casing 5 by a breathing fluid supply duct 10 Whose pipe fitting 11 is screwed onto the outer end of a tubular boss 12 that is secured to one side of said casing 5, and thereby, in effect, constitutes a component part of said casing.
Said casing 5, concentrically with respect to the axis of its tubular boss 12, is provided with an annular valve seat 13 against whose face the demand valve 14 is adapted to make contact. This demand valve 14 is provided with the usual valve stem 15 and the enlarged, spherical head 16 and is very lightly held on its seat by the usual, conical, compression spring 17.
Adapted to tilt said valve stem 15 to the dotted line position of FIG. 1 is the usual rubber diaphragm 18 provided with the usual, metal, pressure plate 20 and also the thickened peripheral bead 21 which is clamped between the peripheral flanges 22 and 23 of the casing 5 and of its sheet metal cover 24, respectively, by an annular clamping ring 25. Said cover 24 is perforated at 26 so that the exterior face of said diaphragm 18 is exposed to the ambient atmosphere, while its inner face is in communication with the breathing compartment 7.
The extreme upward movement of the diaphram 18 is adjustably limited by a sheet metal, annular, cup 27 which is riveted to the lower end of an adjusting screw 28 that is manually adjusted, rotatably, by a sheet metal, cupshaped, adjusting head 30. Said adjusting screw 28 is frictionally held in place in its adjusted position by a stiff, helical, compression spring 31.
Connected integrally with the casing 5 (i.e., with its tubular boss 12) and located within the bore of the valve 3,145,721 Patented Aug. 25, 1964 seat 13 is a web 32 which is centrally pierced to receive the stem 15 of the demand valve 14 and to thereby center said demand valve on its annular valve seat 13. Web 32 has substantially diametrically opposed slender end portions 32' joining the central portion of the web to the annular seat, as shown in FIG. 2. The outer flat face of said web 32 is illustrated as being co-planar with the engaging face of the valve seat 13, but said valve seat, if desired, may be of the usual protruding ring-shape. Said valve seat is provided with a pair of kidney-shaped passageways 33 and 34 which are symmetrically disposed on opposite sides of a vertical plane that is coplanar with the axis of the demand valve 14 and its stem 15. It is in this same vertical plane that the axes of said demand valve and its stem swing vertically as the demand valve is being opened and closed. Passageways 33 and 34 extend from one web end portion 32' to the other, the cross sectional areas of the passageways being several times the cross sectional area of the web end portions, as shown in F1 2.
The advantages of this just-described arrangement are as follows: The demand valve 14, when it opens, is caused to tilt about its uppermost point of contact with its valve seat 13, and it is obvious that at this point there will be no flow of breathing fluid in any case, so this uppermost part of the web 32 offers no more obstruction to the flow of breathing fluid than would be if it were entirely absent. Whether the demand valve 14 has only just been cracked open, or is wide open, does not affect the fact that the interference to fluid flow is the same for small fluid flows as it is for large fluid flows. Hence, the volume of fluid flow is in substantially direct proportion to the degree of valve opening, and this is highly desirable. In addition to the foregoing, it will be noticed that there is a large, flat-faced area at the uppermost part of the valve seat 13 due to the fact that said valve seat is coplanar with the outer face of the web 32. Hence the inner face of the demand valve 14 is less apt to become mutilated after it has been subjected to prolonged use.
1. In a breathing apparatus having a compartment, a flexible diaphragm moved by variations in pressure in said compartment, and a valve seat having a bore communicating with said compartment, a demand valve comprising a valve head engageable with said seat, a valve centering web in said bore having an aperture coaxial with said seat, a valve stem extending from said head through said aperture for being moved by said diaphragm in a plane containing the axis of said stem to tilt said head and thereby open said valve, said web having substantially diametrically opposed slender end portions intersected by said plane, and a pair of arcuate passageways providing fluid flow through said seat when said valve is open, said passageways being symmetrically disposed on opposite sides of said plane and each extending from one of said web end portions to the other thereof, the cross-sectional area of said passageways being several times the cross sectional area of said web end portions, whereby said web end portions provide minimum restriction to fluid flow through said seat.
2. The combination of claim 1, wherein the surface of said web facing said head is coplanar with said valve seat.
References Cited in the file of this patent UNITED STATES PATENTS 2,445,359 Meidenbauer July 20, 1948 2,452,670 Meidenbauer Nov. 2, 1948 2,790,454 Benzel Apr. 30, 1957 2,843,119 Glasser July 15, 1958