Improvements in or relating to tube coupling collets

Abstract: The disclosure relates to a tube coupling collet for holding a tube in a tapered bore in a coupling body. The collet (10) comprises a plastics moulding having an annular head (11) with a plurality of resilient arms (12) extending axially from the head. A metal skeleton is embodied in the plastics moulding comprising an annular element (16) moulded in the annular head of the collet and integral legs (17) extending axially from the annular element within the resilient arms of the collet.

Description: This invention relates to tube coupling collets for holding tubes in tapered bores in a coupling body. Reference should be made to European Patent publications No.0 597 711 and 0 663 557 (published 19.07.95) for examples of such tube couplings. Such tube couplings are formed in both metals and plastics. In the case where plastics materials are used, there is a risk that chemical attack or fire could partially or completely destroy the plastics material and in that event, the tube will almost certainly be released from the coupling with the consequential risk of loss of fluid or gas. This invention provides a tube coupling collet for holding a tube in a tapered bore in a coupling body, the collet comprising a plastics moulding having an annular head with a plurality of resilient arms extending axially from the head and a metal skeleton embodied in the plastics moulding comprising an annular element moulded into the annular head and integral legs extending axially from the annular element within the resilient arms of the collet. Preferably, the ends of the collet arms remote from the annular head are formed with integral inturned teeth to engage with a tube in the collet and the ends of the metal skeleton legs within the ends of the plastic arms are inturned extending to the inner edges of the teeth to bite into the surface of the tube. Each collet arm may be connected to the annular collet head by spaced hinge elements and the legs of the metal skeleton may be likewise connected to the annular portion of the skeleton by spaced metal bridging elements embodied in the hinge elements of the plastics arms. The following is a description of a specific embodiment of the invention, reference being made to the accompanying drawings in which:- Figure 1 is a perspective view of a tube coupling collet embodying a metal skeleton in accordance with the invention; Figure 2 is an end view of the collet, as shown in Figure 1; Figure 3 is a section on the line 3-3 on Figure 2; Figure 4 is a sectional view of a collet in accordance with the invention embodied in a tube coupling body and holding a tube in place, and Figure 5 is a similar view to Figure 4 showing the collet after the collet has been subjected to attack by chemicals or excess heat. Referring firstly to Figures 1 to 3 of the drawings, there is shown a collet indicated generally at 10 for holding a tube in a tapered bore in a coupling body. The collet is formed as a plastics moulding and comprises an annular head 11 having three spaced arcuate section arms 12 projecting from the head. The arms are formed integrally with the head and are connected thereto by narrow hinge elements 13 at the edges of the arm. As best seen in Figure 3, the end of each arm remote from the annular head 11 is formed with an integral inturned tooth 14 which tapers to an edge 15 to engage the surface of a tube to be held in the collet. The plastics collet is moulded with a metal, for example steel, skeleton embodied in the collet, comprising an annulus 16 moulded in the plastics head 11 and resilient legs 17 extending through the collet arms. The legs 17 are connected to the annular portion of the skeleton by resilient bridging portions 18 which extend through the hinge portions 13 of the arms 12. At the free ends of the collet arms, the ends of the skeleton legs are turned inwardly through the inwardly projecting teeth 14 to the inner edges of the teeth 15 to reinforce the edges of the teeth which bite into the surface of the tube extending to the collet. Figure 4 of the drawings shows a collet of the form described and illustrated above embodied in a tube coupling as described and illustrated in European Patent publication No.0 597 711. Should the collet be subject to fire or chemical attack, the plastics material of the collet may be destroyed but the metal skeleton may survive and will continue to hold the tube in the coupling body, as illustrated in Figure 5. Also the metal skeleton will indicate whether the pipe was correctly assembled into the collet and fitting prior to the damage.

Claims: A tube coupling collet for holding a tube in a tapered bore in a coupling body, the collet comprising a plastics moulding having an annular head with a plurality of resilient arms extending axially from the head and a metal skeleton embodied in the plastics moulding comprising an annular element moulded in the annular head of the collet and integral legs extending axially from the annular element within the resilient arms of the collet. A tube coupling collet as claimed in claim 1, wherein the ends of the collet arms remote from the annular head are formed with integral inturned teeth to engage with a tube in the collet and the ends of the metal skeleton legs within the ends of the plastic arms are inturned extending to the inner edges of the teeth to bite into the surface of the tube. A tube coupling collet as claimed in claim 1 or claim 2, wherein each collet arm is connected to the annular collet head by spaced integral hinge elements and the legs of the metal skeleton are likewise connected to the annular portion of the skeleton by spaced metal bridging elements embodied in the hinge elements of the plastics arms.

Inventors: GUEST JOHN DEREK, GUEST, JOHN DEREK
Applicants: GUEST JOHN D, GUEST, JOHN DEREK
Application year: 1995
Main classification: F16L37
IPC codes: F16L37