Plastic tube fitting and joint

A joint between an injection molded plastic fitting and a plastic tube comprising:

• a molded resiliently yieldable plastic body sleeve on the fitting and having a threaded exterior and a longitudinal bore snugly receiving the end of the tube;
• molded plastic tube-clamping means including a resiliently yieldable threaded nut on the threaded exterior of the sleeve for longitudinal movement along the sleeve, and also including a ferrule integrally of and in one piece with the nut, the ferrule embracing the tube and driven longitudinally along the tube and sleeve by the nut, the ferrule having a conical outer peripheral surface with a gradual wedging taper converging toward the sleeve;
• the end of the tube having a peripheral groove in the exterior thereof and located within the sleeve;
• the body sleeve having a flared ferrule-receiving inner periphery between the bore and the end of the sleeve and adjacent the groove of the tube, the flared periphery having a conical ferrule-wedging surface adjacent the end of the sleeve and tapering along its length at a narrow angle relative to the body sleeve axis and tapering in the same direction as the conical surface of the ferrule, said flared periphery freely receiving the tapered ferrule substantially to the full length of said ferrule-wedging surface and thereafter snugly mating with the ferrule, and the flared periphery also having a conical ferrule-deforming surface adjacent the bore with a steep angled taper obliquely oriented with repsect to the ferrule-wedging surface of the flared periphery at a significant angle, the steep angled taper of the ferrule-deforming surface directing the ferrule inwardly of the bore and into the peripheral groove of the tube which is also deformed by the ferrule.

A joint between a fitting and a tube, and both formed of perfluoroalkoxy, comprising:

• a molded plastic body sleeve on the fitting and having a threaded exterior and a longitudinal bore snugly receiving the end of the tube, the inner periphery of the sleeve having a tube-sealing shoulder surface against which the end of the tube bears in sealed relation;
• a molded plastic clamping nut having a ferrule formed in one piece and integrally thereof, the nut having a threaded interior on the threaded sleeve, and the ferrule being spaced inwardly and concentrically with the threaded interior, the nut and ferrule defining a longitudinal bore coaxial and aligned with the bore of the sleeve and snugly fitting on the tube, the ferrule having a conical outer peripheral surface with a gradual wedging taper converging toward the sleeve and spaced inwardly of the sleeve embracing threaded interior of the nut, the ferrule also having a blunt end adjoining the outer peripheral surface and the tube-embracing inner bore,
• the end of the tube having a peripheral groove in the exterior thereof and located within and adjacent the end of the sleeve, the groove having side walls in sharp angled relation with respect to the exterior surface of the tube, and
• the body sleeve having a flared ferrule-receiving inner periphery between the bore and the end of the sleeve and adjacent the groove of the tube, the flared inner periphery having a conical ferrule-wedging surface adjacent the end of the sleeve and having the same direction of gradual wedging taper as the conical peripheral surface of the ferrule, the similarly tapering conical surfaces of the sleeve and ferrule having coordinated dimensions to be freely joined together substantially to the full length of said ferrule-wedging surface of the flared periphery and thereafter mated together in a snug fit as the ferrule is inserted into the flared periphery of the sleeve, the flared periphery also having a conical ferrule-deforming surface adjacent the bore and with a steep angled taper obliquely oriented with respect to the ferrule-wedging surface of the flared periphery at a significant angle and converging in the same general direction as said ferrule-wedging surface, the ferrule-deforming conical surface initially being spaced from the blunt end of the ferrule as the ferrule engages the sleeve, and the steep angled taper of the ferrule-deforming surface directing the ferrule inwardly of the sleeve bore and into the peripheral groove of the tube which is also deformed by the ferrule, the nut embracing the sleeve to prevent outward expansion of the sleeve during inward deformation of the ferrule as the nut is threaded along the sleeve to produce a seal between the ferrule and the sleeve and to urge the tube firmly against the fluid sealing seat of the sleeve.