GB2360073A - A tube coupling with ultrasonically welded plastics member - Google Patents

Abstract

A tube coupling device comprises a hollow body member 1 moulded from a plastics material, and an axially sliding sleeve member 19 held in place by an annular plastics member 14, where the plastics member has been ultrasonically welded to the hollow body member. Preferably a grab ring 17 is housed within the hollow body member, and the axially sliding sleeve is a release sleeve for disconnecting the grab ring from the pipe. The hollow body member may be a swivel elbow, and the device may be connected to a pneumatic valve or a cylinder.

Description

2360073 1 Tube Coupling Devices This invention relates to releasable

push-in tube coupling devices of the type comprising a hollow body member having at least one terminal portion for receiving a tube, annular sealing means housed within the terminal portion for sealingly engaging the external surface of the tube, annular tube-gripping means housed within the terminal portion and comprising a plurality of teeth that extend generally towards the axis of said terminal portion and th at grip the external surface of the tube normally preventing withdrawal thereof, and release means axially movable between a first, inoperative, position and a second position in which it resiliently deforms said teeth generally radially outwardly in order to permit removal of the tube from the body member. Hereinafter, such a tube coupling device, which is already generally knovrn, is referred to as a "tube coupling device of the type described" and the present invention is concerned with various improvements thereto.

According to a first aspect of the present invention, the hollow body member of a tube coupling device of the type described comprises a plastics moulding and the release means comprises a sleeve that is held captive, as an axially sliding fl t, by an annular plastics member ultrasonically welded to said terminal portion. Preferably, the annular plastics member is in the form of an annular plug snugly received in, and ultrasonically welded to, the terminal portion. Further, the plug preferably serves to retain the annular tube-gripping means in place in the terminal portion. Coupling devices constructed in accordance with this aspect of the invention have the advantage that it is not necessary to use,, for example, a screw threaded cap to retain the release sleeve etc in place.

2 According to a second aspect of the present invention, the annular tubegripping means (which hereinafter is, as is usual in the art, referred to as a "grab ring") of a tube coupling device of the type described comprises a plurality of radially inner, substantially planar, teeth directed generally towards an axis passing through the centre of the grab ring, said teeth being spaced from one another and arranged in a circular symmetrical array about said axis, adjacent teeth being joined together at their roots by respective, radially outer, substantially planar elongate sections, the teeth and the elongate sections being integral with one another and inclined to one and the same side of a common plane passing through the roots of said teeth perpendicularly to said axis. We have found that such an arrangement improves the pull-out force and the number of tube insertion/tube removal cycles before grab ring failure compared with conventional grab ring designs. Preferably, the grab ring is made of stainless steel.

According to a third aspect of the present invention, in a tube coupling device of the type described, the hollow body member comprises a plastics moulding and includes a further terminal portion which is sealingly retained, as a snap fit, in a sleeve so as to be rotatable relative to the sleeve, the sleeve being adapted to be sealingly engaged, in use, with a fluid flow port of an apparatus such as, for example, a valve or a cyImider whereby the tube coupling device can swivel relative to the apparatus. The sleeve may, for example, be in the form of a nut having an external screw thread for engagement, in use, with a threaded fluid flow port of the apparatus. Swivel couplings constructed in accordance with this aspect of the invention are, compared to 3 conventional swivel couplings, simple to manufacture and tend not to suffer from the problem of seizing-up.

The aspects referred to above will now be described, by way of example only, with reference to the accompanying drawings which relate to a swivel elbow coupling device incorporating all three aspects. However, it is to be understood that a specific tube coupling device may embody, either alone or in combination, one or more of those aspects. In the drawings:

Figure 1 is a side elevation, in cross-section and to a scale of 4: 1 of a swivel elbow coupling device adapted to have a 4min O.D. flexible plastics tube coupled to it; Figure 2 is an end view, to a scale of 10: 1, of a grab ring suitable for use in the coupling device shown in Figure 1 but for coupling a 6min O.D. flexible tube; and Figure 3 is a side view of part of the grab ring shown in Figure 2.

Referring first to Fig 1, the coupling device includes an elbowshaped body 1 moulded as one piece in an engineering plastics material such as, for example, an acetal. The body 1 has two terminal portions 2 and 3 adapted, respectively, for releasably receiving a tube (not shown) and for swivel connection to a device such as a pneumatic valve or cylinder.

The terminal portion 2 defines a stepped bore 4 having, at its axially innennost end, an annular tube abutment surface 5 which serves to limit insertion of the tube into the body 1. A further annular abutment surface 6 in the bore 4 seats a sealing 0-ring 7 made of a suitable resilient material. The outer periphery of the 0-ring 7 sealingly engages the cylindrical surface of a section 8 of the bore 4. Intermediate the 4 surfaces 5 and 6, the bore 4 has a short cylindrical section 9 that serves to locate the tube radially.

The bore 4 has yet a flirther annular abutment surface 10 which seats a spacer ring 11. Intermediate the abutment surface 10 and the outermost end of the terminal portion 2, the bore 4 is formed with a pair of cylindrical sections 12, 12'which merge at an annular shoulder 13.

The bore sections 12 and 12' locate an annular plug 14 which is moulded in the same plastics hiaterial as the body 1 and which is ultrasonically welded to the latter. As can be seen, the axially innermost part of the plug 4 tapers down to an annular lip which abuts the spacer ring 11 so as to retain the latter firmly in place against the abutment surface 10.

The spacer ring 11, which may also be moulded in a plastics material, defines an annular surface 15 which faces a tapered section 16 of the plug 14. There is a small clearance between the annular surface 15 and the tapered section 16 which receives the periphery of a stainless steel grab ring 17, the nature of which will be described in more detail below.

The plug 14 defines a bore 18 in which a tubular release sleeve 19 moulded in a plastics material is retained. The release sleeve 19 comprises a cylindrical portion 20 having an integral, enlarged inner end 21 and an outer. integral flange 22. The release sleeve 19 is axially slidable in the bore 18 between an innermost limit (dictated by abutment of the flange 22 with the plug 14) at which its enlarged inner end 21 resiliently and radially deforms the teeth of the grab ring 17 away from the axis of the bore 4, and an outermost limit (as shown in the drawing and dictated by abutment of the enlarged inner end 21 of the sleeve 19 and a shoulder formed internally of the plug 14 adjacent to the bore 18) at which its enlarged inner end 21 is free of the teeth of the grab ring 17 which can then engage the external surface of an inserted tube. The release sleeve 19 is assembled into the plug 14 as a snap-fit.

Figs 2 and 3 of the drawings illustrate the grab ring 17 on an enlarged scale. The grab ring co mprises a plurality (specifically eight) equi-spaced peripheral sections 23, adjacent ones of which are joined together by radially extending leg portions 24 and inner tooth sections 25 each having a radially innermost tube-gripping edge 26. The peripheral sections 23 are deformed, along the dashed lines, out of the general plane of the ring 17 at an acute angle A, whereas opposed tooth sections 25 are deformed, also along the dashed lines, out of that plane at an included angle B thereto. The grab ring 17 is a one-piece pressing of, for example, stainless steel which may initially be pressed out in flat form from sheet stainless steel and then deformed as aforesaid by a punching operation. More specifically, with reference to the grab ring illustrated, we prefer to use stainless steel grade 30 LS21 (17%C, 7%Ni) to BS 1449 Part 2 having a thickness of 0.2nun, with angle A being about 20' and angle B about 9T.

Reverting to Fig 1 of the drawings, the terminal portion 3 of the body 1 is formed integrally with an external, annular rib 27 having a leading tapered surface 28 and a rear shoulder 29. The terminal portion 3 is held captive in a sleeve 30 which is preferably made of a metal such as brass. More particularly, the sleeve 30 is formed with an axial bore 31 formed intermediate its ends with an annular, inwardly projecting flange 31 which affords a bearing surface for a cylindrical section of the 6 terminal portion 3. The base of the flange 31 defines a shoulder 32. The terminal portion 3 is assembled with the sleeve 30 by inserting the former into the bore 31 until the rib 27 has (with a degree of resilient, radial deformation) passed through the flange 31 formed on the sleeve 30. The rib 27 then resiles back to its original position and so the terminal portion 3 cannot be withdrawn by virtue of cooperation between the shoulders 29 and 32. In other words, the terminal portion 3 is a snap fit in the sleeve 30. However, by virtue of a small clearance between the external surface of the terminal portion 3 and the bearing surface afforded by the flange 3 1, the terminal portion 3, and therefore the body 1 as a whole, can rotate (or "swivel") relative to the sleeve 30. The upper end of the sleeve 30 is configured to provide flirther bearing surfaces 33 and 34 which cooperate with correspondingly formed bearing surfaces on the terminal portion 3. Adjacent to its upper end, the bore 31 in sleeve 30 houses a resilient 0-ring 35 which forms a fluid tight seal with the external surface of the terminal portion 3. The sleeve 30, at its lower end, is formed with an external thread 3 6 and retains a resilient 0-ring 3 7 whereby the sleeve 30 may be sealingly coupled to the threaded port of, for example, a pneumatic cylinder.

The way in which a tube may be coupled to and, when desired, decoupled from the device described above will be apparent to those skilled in the art, but briefly it is as follows. With the release sleeve 19 in the position shown in the drawing (although if possible scratching of the outside of the tube needs to be avoided, the sleeve 19 may be depressed so as to deform the grab ring teeth 25,26 outwards), a tube of appropriate diameter is coupled to the device simply by inserting it through the sleeve 19 until the end of the tube abuts the surface 5. During this 7 operation, the leading end of the tube causes the grab ring 17 to deform in two modes. First, the peripheral sections 23 cantilever in a forwards direction, thereby causing the tooth sections 25 to splay slightly outwards. Secondly, the tooth sections 25 themselves are deformed outwardly relative to the peripheral sections 23. This arrangement, it has been found, improves the pull-out force and the number of tube insertion/tube removal cycles before grab ring failure compared with conventional, initially substantially planar, grab ring designs in which more stress is placed on the teeth both during tube insertion and tube 10 removal thus leading, in particular, to premature tooth breakage.

Once the leading edge of the tube has passed through the grab ring 17, it passes through the ring 11 and then through the O-ring 7 which becomes radially compressed and forms a fluid tight seal between the bore section 8 and the outer surface of the tube. The edges 26 of the tooth sections 25 engage the outer surface of the tube and if an attempt is made to withdraw the tube without first pushing the release sleeve 19 inwards, or if fluid pressure in the tube increases, the tooth sections 25, in cantilever fashion, increase their gripping force on the tube (and, in the case of a relatively soft plastics or soft metal tube, actually bite into the tube) thereby preventing withdrawal. However, if it is desired to withdraw the tube, the operator merely pushes the release sleeve 19 more or less fully inwards by applying finger pressure to the flange 22 whereby the edges 26 become clear, or substantially clear, of the tube, and then withdraws the tube. Upon releasing the sleeve 19, the grab ring 17 returns to its original position and the coupling device is again ready to receive a tube.

8 It will be appreciated that a coupling device of the invention may be of any configuration. Commonly used examples in addition to the one described above are straight and elbow connectors for connecting two tubes together and T-connectors for connecting three tubes together in which cases there would be, respectively, two and three tube receiving terminal portions.

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Claims (7)

1. CLAIMS: 1. A tube coupling device of the type described wherein the

   hollow, body member comprises a plastics moulding and the release means comprises a sleeve that is held captive, as an axially sliding fit, by an annular plastics member ultrasonically welded to said terminal portion of the hollow body.
2. 2. A tube coupling device according to claim 1 wherein the annular plastics member comprises an annular plug snugly received in, and ultrasonically welded to, the terminal portion.
3. 3. A tube coupling device according to claim 1 or claim 2 wherein the annular plastics member also serves to retain the grab ring in place in the terminal portion.
4. 4. A tube coupling device of the type described wherein the grab ring comprises a plurality of radially inner, substantially planar, teeth directed generally towards an axis passing through the centre of the grab ring, said teeth being spaced from one another and arranged in a circular symmetrical array about said axis, adjacent teeth being joined together at their roots by respective, radially outer, substantially planar elongate sections, the teeth and the elongate sections being integral with one another and inclined to one and the same side of a common plane passing through the roots of said teeth perpendicularly to said axis.
5. 5. A tube coupling device of the type described wherein the hollow body member comprises a plastics moulding and includes a farther terminal portion which is sealingly retained, as a snap fit, in a sleeve so as to be rotatable relative to the sleeve, the sleeve being adapted to be sealingly engaged, in use, with a fluid flow port of an apparatus whereby the tube coupling device can swivel relative to the apparatus.
6. 6. A tube coupling device according to claim 5 wherein the sleeve is in the form of a nut having an external screw thread for engagement, in use, with a threaded fluid flow part of the apparatus.
7. 7. A tube coupling device substantially as hereinbefore described 5 with reference to, and as illustrated in, the accompanying drawings.