Pressure fitting for plastic tubing

Claim 1

A pressure fitting for connecting one end of a length of resilient plastic tubing to a fluid enclosure, said fitting comprising a fitting body having an axial bore designed for communication with the enclosure and an enlarged counterbore which merges with the bore by way of an annular radial wall having an annular sealing recess at its inner portion, an elastomeric sealing ring seated in said recess, a tubing section of relatively soft yieldable resilient plastic material and of uniform outside diameter projecting through said counterbore and into said bore and fitting snugly within the latter, a tubular metal stiffener projecting through said counterbore and into the bore and fitting snugly within said tubing section, said counterbore, in combination with the adjacent portion of the tubing section, defining an annular socket within the fitting body, a socket-closing nut having a bore closely surrounding the tubing section and provided with a cylindrical section having threads received in said counterbore, the forward end face of the nut being spaced rearwardly from said radial wall and defining an annulus which surrounds the tube section a metal thrust ring surrounding the tubing section and having a flat radial front-end face and an annular recess in its rear side, said recess having a frustoconical inner wall and a radial bottom wall, a split pressure ring having a frustoconical outer wall, deSigned for camming engagement with said frustoconical inner wall and having a small radial front-end face designed for face-to-face contact with the radial bottom wall of the recess and a large radial rear end face designed for face-to-face engagement with the nut and a generally cylindrical inner surface designed for broad clamping area with the tubing section, the inside diameter of the pressure ring in its free state being greater than the overall diameter of the tubing section, said rear end face of the pressure ring being engageable with the nut so that upon tightening of the latter within the counterbore the pressure ring will be forced forwardly within the frustoconical recess, to effect camming engagement between the frustoconical outer wall thereof and the frustoconical inner wall of the recess and will thus become shrunk inwardly against the tubing section to clamp the latter to the stiffener and lock the tubing section against tensional pullout force, while at the same time the radial front end face of the pressure ring will seat against the bottom wall of the thrust ring and force the latter forwardly against the elastomeric sealing ring to deform the latter and cause the same to be forced in sealing relationship against the tubing section and fitting body.