GB2054077A - Tube coupling - Google Patents

Abstract

A coupling for connecting together two tubes 13, 14 comprises a ring 11 and either a length of coiled plate or card or a length of longitudinally slit plastics tubing 12 which is diametrically contracted and held by the ring 11 so that a portion 26 overlaps and is thrust against the ring by a portion 27. In use the end parts 20 of the tubing 12 are inserted into the two tubes 13, 14 so that the portion 26 engages the interior of the tubes 13, 14. The tubes 13, 14 may be parts of a shower rail, tent pole, towel rail or like elongate member. <IMAGE>

Description

SPECIFICATION Improvements in or relating to couplings for tubes This invention concerns couplings for tubes and like elongate hollow members.

It is known to use a moulded, cast or machined doubie ended plug having a median flange as a coupling to join together the ends of two tubes, so that the tubes engage around the end parts of the plug and abut opposite shoulders of the flange.

Such plugs have inherent disadvantages, in that expensive dies or moulds are required, or expensive machining is required to make the plugs; if the plugs are solid or rigid the internal diameter of the tubes must be made with precision; if the plugs are resilient to accept pipes of slightly varying bore a relatively weak or sloppy joint may result; unless the plugs are a press or tight push fit in the pipes, some form of fastening, such as screws or adhesive, is required to secure the pipes to the coupling; and most are heavy or fragile, and suffer from the effects of vibration and/or corrosion.

What is needed is a relatively inexpensive to make, light, vibration and corrosion resistant, easy to assemble and reasonably strong coupling, which is effective for connecting pipes, whose bores vary slightly from a nominal bore, for forming joints in elongate assemblies such as shower head support bores or tent poles where compression strength and some longitudinal stiffness are required.

According to the present invention there is provided a coupling comprising a piece of stiff plastics or elastomeric material held in the form of an axially elongate coil by an annular ring of smaller axial length, wherein said coil has an external longitudinally extending marginal portion which overlaps a further portion of the piece of material, which further portion urges said marginal portion against the ring.

Said external marginal portion is preferably tapered in thickness, and may terminate at a longitudinal scraping edge at the periphery of the coil.

Axially opposite end portions of the coil are preferably tapered to facilitate the insertion thereof into pipes.

The piece of material may be formed by slitting along a length of stiff tubing having a bore larger than said nominal bore, and then contracting said slit tubing in a press; or by coiling a stiff card or plate of said material.

The invention includes an elongate assembly, such as a shower head support bar, a tent pole, a towel rail, or other support, comprising a first tube and a second tube of a common nominal bore connected together by said connector of the invention, wherein the coil projects into said tubes so as to frictionally engage therein, and wherein said marginal portion is urged against said tubes by said further portion.

The ring is preferably an offcut from the same tubing used to make the tubes so that the assembly has a substantially constant external diameter.

The invention will be described further, by way of example, with reference to the accompanying drawings, wherein: - Figure 1 shows a longitudinal cross section through a coupling of the invention; Figure 2 shows a transverse cross section through the coupling; Figure 3 shows a longitudinal cross section through part of a shower head support pipe assembly incorporating the coupling; and Figure 4 is a transverse cross section through a piece of pipe showing a line marking the position of a slit made when forming a coil of the coupling.

Referring to Figures 1 to 3, the coupling comprises a ring 11 and a coil 12, and is used to connect two pipes having end portions 1 3 and 14 (Figure 3).

The ring 11 and pipes are made from the same seam welded externally polished thin wall (0.5 mm) stainless steel piping of 18 mm diameter.

The coil 12 is made from a short length of semi-rigid thick walled (2 mm) pressure piping of a hard and stiff plastics material. As shown in Figure 4, the axially opposite end portions 20 of the length of piping are chamfered externally, and the length is slit longitudinally along a line 21 which is disposed at an acute angle to a radius 22 of the piping at a point whereat said line 21 and radius 22 intersect the external surface 23 of the piping. Said acute angle is preferably within the range of 30O to 600, and in this example is about 450, whereby to form cut surfaces 24 and 25 (Figure 2) having a width about 40 to 100% greater than said wall thickness.

The slit piece of piping is then contracted in a press to allow the ring 11 to be pushed on; the contraction is performed so that the cut surface 25, which makes an obtuse angle with the external surface 23, is pushed inwards inside an external longitudinal marginal portion 26 on which the cut surface 24 is provided, to form the coil 12; and the contraction is such that the coil 12 comprises one and an eighth to one and a half turns, and in this example is about one and a quarter to one and a third turns.

Upon being released from the press, the coil within the ring tends to expand, so as to exert a considerable internal pressure on the ring 11; and the portion 26 is supported and urged radially outwards by a further portion 27 so that the chamfered edges 1 5 of the ring dig into or engage slightly in a scraping edge 28 formed by said surfaces 23 and 24. In this embodiment, the engagement between the ring and the coil is sufficient to hold the ring against an axial thrust of over 20 kilogrammes. Furthermore, as shown in Figure 1, the end portions 20 expand.

In use, the coupling is disposed co-axially between the end portions 1 3 and 14 so that the latter engage the chamfers, and then axial pressure and relative reciprocal rotary motions are applied to the pipes (i.e. the pipes are grasped, pushed towards each other and turned backwards and forwards), to cause the coupling to enter said portions 13 and 14. Only gentle forces are required, because when the portion 13 is rotated in a direction, relative tithe portion 14 towards said scraping edge 28, the edge 28 engages the portion 13 to hold the coupling whilst the other portion 14 is left free to move in the trailing direction of said edge 28, and vice versa when the portion 13 is rotated in the opposite direction, enabling the portions 13 and 14 to be pushed relatively easily along the coupling until they abut the ring.

It will be readily appreciated that the coupling is easy and inexpensive to make, can be fitted to pipes in a very simple and rapid manner, requires no fixings or adhesives, is easily releasable, can be used to connect internally unpolished, dirty and slightly rough or seamed pipes, even if the pipes are of frictionally different bores, will not crack or become slack in the pipes if subjected to vibration, is corrosion resistant, is strong in compression, and can be made to give a stiff joint having some pull apart resistance.

The invention is not confined to the precise details of the foregoing example. For instance the overall length of the coupling can be increased to give increased joint stiffness, and the wall thickness of the coil can be increased to increase the internal pressure on the ring and pipes. The shape of the end portions 20 can be varied, as can the form of the marginal portion 26. The latter is preferably tapered, but may have any form of taper and need not terminate at a scraping edge.

The coil may be rolled from a flat shaped blank, and may be of any suitable material.

Claims (7)

1. A coupling comprising a piece of plastics or elastomeric material held in the form of an axially elongate coil by an annular ring of smaller axial length, wherein said coil has an external longitudinally extending marginal portion which overlaps a further portion of the piece of material, which further portion urges said marginal portion against the inside of the ring.

2. A coupling as claimed in claim 1, wherein the external marginal portion is tapered in thickness, and terminates at a longitudinal scraping edge at the periphery of the coil.

3. A coupling as claimed in claim 1 or 2, wherein axially opposite end portions of the coil are tapered to facilitate the insertion thereof into pipes.

4. A coupling as claimed in claim 1, 2 or 3, wherein the piece of material is a longitudinally slit length of semi-rigid tubing having a bore larger than said nominal bore, which slit tubing is contracted within the ring.

5. A coupling substantially as hereinbefore described with reference to the accompanying drawings.

6. An elongate assembly comprising a first tube and a second tube of a common nominal bore connected together by a connector as claimed in any preceding claim, wherein the coil projects into said tubes so as to frictionally engage therein, and wherein said marginal portion is urged against said tubes by said further portion.

7. An assembly as claimed in claim 6, wherein the ring is an offcut from the same tubing as the tubes, so that the assembly has a substantially constant external diameter.