Positive acting check valve of polyvinylchloride to open in response to predetermined line pressure

Claim 1

A normally closed spring-biased valve comprising: A. a valve housing of rigid polyvinylchloride which includes a body with an axial through passageway defined by a first downstream bore of a first diameter and a second upstream bore of a second diameter, said bores being opposed and aligned and in fluid communication with one another, said first bore being of a larger diameter than said second bore forming a valve seat shoulder in said body at the juncture of said bores; B. an axially movable valve member of rigid polyvinylchloride in the body comprising: a. a hollow cylindrical portion in said second bore with an open upstream end and a uniform cross section sized for axial movement in said second bore, and b. a closed headed downstream portion of a cross sectional area less than that of the first bore and greater than that of the second bore and effective to mechanically limit axial upstream movement of said cylindrical portion in said second bore, c. said cylindrical portion having a plurality of radial openings arranged in a circumferential path which is axially spaced from said headed end a first axial distance to permit fluid flow from the interior of the hollow cylindrical portion downstream into the first bore when the openings are in the first bore; C. stop means having an axially facing through passageway in said first bore, said stop means being axially from said valve seat shoulder a second axial distance which is greater than said first distance to mechanically limit downstream axial movement of the valve member, so that the radial openings are in fluid communication with the first bore when the valve member is in engagement with said stop means; D. an O-ring circumposed about said cylindrical portion and in abutting relation with said headed portion, said O-ring being sized to seal against fluid flow between said first bore and said second bore when said O-ring is captivated between said headed portion and said valve seat shoulder; E. compression spring means including means captivating said spring means between said stop means and said headed portion, said spring means being effective to normally urge said O-ring into sealing engagement with said headed portion and said valve seat shoulder and effective to yieldingly permit said valve member to move axially downstream in response to a predetermined upstream fluid pressure in said second bore to permit fluid flow through the hollow cylindrical portion, said radial openings, said axial through openings and said first bore; F. said second bore being sized to receive the ends of a standard companionate size diameter pipe to be connected in axial alignment with the valve; G. first means in the second bore to limit axial insertion of the pipe end; H. said cylindrical portion being of an axial length substantially greater than said second axial distance and the axial length of said second bore, between said means limiting axial insertion and said valve seat shoulder, being at least equal to the axial length of said cylindrical portion; I. guide means constraining said valve member to axial movement of translation only and comprising said cylindrical portion being of uniform cross section between said seat and upstream valve member end and sized for sliding engagement in said second bore and having an axial length such that, at all times, a substantial axial length of said cylindrical portion is in said second bore; J. said stop means comprising an end member of rigid polyvinylchloride secured in said first bore and said end member including an axially downstream facing socket in axial alignment with said axially facing through passageway, said socket being sized to receive the end of a standard companionately sized diameter pipe to be connected in axial alignment with the valve; and K. second means in said socket to limit axial insertion of an end of a standard size pipe to be connected to the valve.