WO1994021953A1

WO1994021953A1 - Tube coupling

Info

Publication number: WO1994021953A1
Application number: PCT/GB1994/000610
Authority: WO
Inventors: David Frederick Hawkins; David Ward
Original assignee: Willowside Limited
Priority date: 1993-03-25
Filing date: 1994-03-24
Publication date: 1994-09-29
Also published as: AU6287194A; GB9306150D0

Abstract

A tube coupling capable of simplified manufacture comprises a body (1a) having a bore and O-ring seal (5) to surround an inserted tube (3) and further having an end portion (6) surrounding a collet (7) with resilient legs (8) provided with tube-engaging surface portions (9) and body-engaging heels (13), in which the body (1a) is an integral moulding with its end portion (6) being formed as a cage comprising a crown (10) joined to the remainder of the body (1a) by pillars (bars) (11) which are separated by spaces (12), and in which the collet (7) is so shaped that its resilient legs (8) can be pressed into the cage portion (6) but that on radially outward relaxation of the legs (8), the heels (13) project into the inter-pillar spaces (12) of the cage portion (6).

Description

Tube coupling

This invention relates to a tube coupling, in particular for tubes employed for conveying liquids such as beverages. Couplings for such tubing are generally push-in fittings, typically comprising a hollow body to receive the tube end, which body is shaped to form a seat for an O-ring seal surrounding or abutting an inserted tube, thereby creating a seal between the body and tube. A collet is commonly disposed in an end portion of the body and in turn surrounds the tube. One type of collet has axially extending, circumferentially spaced, resilient legs at its inner end which legs are provided with tube-engaging surface portions and are so shaped that, in co-operation with the body end portion, they provide camming surfaces which act, on attempted withdrawal of the collet from the body, to tend to drive the tube-engaging surface portions of the collet legs radially inwardly and thereby resist further withdrawal of the collet and/or a said tube from the body of the coupling. With such a tube coupling, an end of a tube may be pushed into the coupling from the outer end of the collet until it is sealed to the body of the coupling by the O-ring seal. Any outward pull on the tube tending to remove the tube from the coupling body tends, by engagement of the tube-engaging portions of the collet legs, to pull the collet outwardly, and thus causes the legs, by operation of the camming surfaces, to be forced radially inwardly to grip the tube more tightly, with the result that removal of the tube from the coupling is resisted. On the other hand, if the collet is held in, the tube may easily be slid out of the coupling. Such tube couplings are usually made as injection mouldings of a synthetic resin material, the various parts of the coupling being made of the same or different materials, The design of coupling body is chosen according to its intended duty. For example for coupling a tube to another tube or tubes (an "end-to-end" connector) it is formed of two or more coupling body portions facing each other. For connecting a tube to an intermediate joining member, such as a threaded stem of a component such as a tap or valve (a "straight-through adapter"), it typically includes at one end a bore to receive a tube end and at the other end a thread to engage the component. The physical requirements of the material of the coupling body which are dictated by its use do however present certain problems during its manufacture.

The body design is also chosen with regard to the shape of internal components such as the internal collet. A legged collet is generally preferred since it offers advantages over alternatives such as a split collet in being less prone to distortion when in place in the coupling. One version of tube coupling employing a collet with legs is disclosed in British Patent Specification No 1 520 742 to John D. Guest, which describes and claims a "tube coupling having a collet comprising a cylindrical portion with a cylindrical bore and with resilient arms extending axially from one end of said cylindrical portion and arranged to co¬ operate with a cam surface, which cam surface is constituted by a member surrounding the collet and having an internal surface tapering to a smaller diameter in one axial direction and engaging the arms so that the arms are forced radially inwardly by axial movement of the collet in said one direction, wherein the collet has its arms spaced apart in the circumferential direction such that, in the absence of any tube within the collet, the arms can move radially inwardly to permit of the collet being withdrawn from said member by axial movement in said one direction, said collet having a head at its outer end".

In the manufacture of tube couplings such as defined in GB 1 520 742 the physical requirement for a tapering camming surface within the coupling body (which must have sufficient taper to provide the camming action required in use) means that a core portion of a mould used for forming that tapering surface cannot easily be withdrawn from the end of the body at which that taper is formed. Similarly the physical shaping of the coupling which is dictated by its function is almost inevitably such that the mould core cannot be withdrawn in the opposite direction. Thus such coupling bodies are manufactured in more than one piece. A main portion of the coupling body is manufactured and inserts are turned or moulded and secured into that main body portion to form the required taper for each tube to be inserted into the coupling. The inserts are usually secured into place by physical interference, as with a press fit, or by a plastics welding technique.

Prior proposals for eliminating the internal taper from a coupling body have involved complex internal recesses or ridges within the body and have presented disadvantages in manufacturing such that the designs have not achieved commercial application.

Among the manufacturing problems presented by prior proposals is the requirement for an additional moulding die and associated moulding equipment and/or for turning equipment. There is a requirement for welding and/or mechanical press apparatus, and for technicians trained to operate such apparatus. There is also a requirement for apparatus for testing that satisfactory welds or press fits have been formed. These requirements can add significantly to the cost of manufacture of such a tube coupling, and they demand a skilled and closely monitored labour force. It is a principal object of this invention to provide a tube coupling of construction in which these disadvantages are at least alleviated.

According to this invention, there is provided a tube coupling comprising a body having a bore for receiving an end of an appropriately sized tube, which body is shaped to form a seat for an O-ring seal surrounding the tube when the latter is inserted into the said body, to form a seal between such a tube and the body, such body having an end portion surrounding a collet which in turn surrounds such a tube, the collet having at its outer end a circumferentially continuous cylindrical portion with a cylindrical bore and having at its inner end a plurality of axially extending, circumferentially spaced, resilient legs which are provided with tube-engaging surface portions and are so shaped that, in co-operation with the body end portion, they provide camming surfaces which act, on attempted withdrawal of the collet from the body, to tend to drive the tube-engaging surface portions of the collet legs radially inwardly thereby to resist further withdrawal of the collet and/or a said tube from the body , characterised in that such body is an integral moulding with its end portion being formed as a cage comprising a crown which is joined to the remainder of the body by pillars which are separated by spaces, and said collet is so shaped that, in the absence of a tube, it can be pressed into the cage portion with radially inward deformation of its legs so that on radially outward relaxation of the legs, heels thereof project into the inter-pillar spaces of the cage portion to co-operate with the crown to provide said camming surfaces. Such a tube coupling has a number of advantages over those which have hitherto been commercially available. The camming action required to be provided for the legs of the collet to resist withdrawal of a tube does not require an internal taper within the coupling body. The inter-pillar spaces can readily be formed by separately withdrawable portions of a moulding die. Thus the requirement for the provision of camming surfaces does not, of itself, require a multi-part coupling body construction. Indeed, by adopting the present invention, most standard tube couplings of the kind referred to may be manufactured with their bodies as a single integral moulding. Thus manufacture is simplified, and manufacturing costs are reduced once the required moulding die has been made. The pillars of the body end portion serve as the bars of the cage and the spaces between the bars provide openings into which the heels of the collet legs can project. Engagement of the heels into the spaces not only provides the camming action in an axial direction to retain the collet and tube in the body but also by the presence of the bars prevents twisting of the collet about its axis. The cage configuration thus provides for an extremely secure disposition of the collet and tube within the body while simplifying the manufacture of the body. A further advantage of couplings according to the invention is that they avoid problems arising from a side load applied to the tube. Such a side load would otherwise tend to misalign the tube end or distort its cross-sectional shape within the body so as to break or open the seal and thereby open a leak path from the coupling.

The number of spaces around the circumference of the cage is necessarily the same as the number of pillars. The circumferential length of each space is preferably the same and is preferably similar to the circumferential length of the pillars. It is further preferred that the spaces and pillars are arranged symmetrically around the cage circumference.

The number of collet legs is similarly preferred to be the same as the number of spaces and pillars, so that each space receives the heel of one of the legs. A co-operating symmetrical configuration of cage and collet ensures a high contacting length of collet and body portion around the cage circumference, which assists in providing a strong coupling. Other advantages of symmetrical configurations of cage and collet are ease of manufacture and the absence of a need to match a specific leg to a specific space, thereby avoiding the need for a single alignment of collet in the cage and further avoiding the need for co-operating guide slots and guide projections on the cage and collet. The number of pillars and spaces should be at least three and is preferably four or six.

If preferred, a sleeve may be provided for surrounding at least the pillars of such body cage portion to mask the inter-pillar spaces. This has the advantage of militating against the ingress of dirt into such spaces, but at the cost of requiring an additional part. Such a sleeve may be made from any suitable material. It may for example be cut from a tube of an elastomer, or of a heat shrinkable material to promote ease of fitting. Such a sleeve may be of the same colour as the coupling body or of a contrasting colour or colours, and such colouring may be used to provide a colour coding of the size of the coupling, or of fields of use for which the coupling has been specifically designed, such as for example in beverage dispensing or pneumatic circuitry or data communications conduits. Alternatively, the colouring of the sleeve and body may form a colouring scheme associated with a particular manufacturer or factor, or the sleeve or body may carry some marking such as a corporate name or logo.

Advantageously, a seat is provided for such sleeve so that the outer surface of said body is substantially smooth and continuous.

In preferred embodiments of the invention, an internal seat is provided within the bore of the coupling body for limiting insertion of such a tube. This facilitates a rapid and reliable tube connection. The user will simply push the tube into the connector as far as is allowed by the seat. Thus for example in the case of a simple connector for joining two tubes, the user will then be assured that the ends of the two tubes are in the correct positions in relation to the connector and not displaced to one end or the other which could lead to an inadequate seal or failure of the connection. The internal diameter of the seat is preferably chosen to be equal to the internal diameter of the tube that is intended to be inserted, thereby providing a smooth internal flow path for liquid passing through the coupling.

It is further preferred that the internal bore of the coupling body between the insertion-limiting seat and the region where the collet is received is of an internal diameter intermediate between that of the bore where it receives the collet and of the bore through the seat. The diameter of the intermediate region of the bore is chosen according to the external diameter of the tube to be inserted into the body so as to hold the end of the tube firmly in a lateral direction.

The internal bore of the body which receives the collet passes through the crown and cage and further into the body to the point where it reaches a region of reduced internal diameter. The axial length of the bore through the crown and cage and to the said point is preferably sufficient to accommodate the full inserted length of the collet and an O-ring which both surrounds an inserted tube and abuts the inner end of the collet. Throughout the said axial length the bore preferably has no internal projections (i.e. no ridges or projections, for example as might be provided to secure an O-ring). The absence of such projections again simplifies manufacture and avoids the presence of recesses which could create dirt-traps within the coupling. Preferably, the collet is formed as a one-piece moulding, since this also simplifies manufacture. In one preferred embodiment of the invention, the tube- engaging surface portions of the legs of the collet are formed at toes thereof by stainless steel pieces insert- moulded into the collet. This promotes reliability and security of the fitting.

The collet legs also preferably include extended sole portions projecting beyond the heels and toes in an axial direction. ^"With the collet in position in the coupling, the outer edges of the extended soles bear upon the internal surface of bore beyond the cage portion to provide additional stability in the positioning of the collet within the coupling.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure la is an axial cross section through a tube coupling with a threaded connection (a "straight-through adapter"). Figure lb is a view of the tube coupling of Figure la. Figure lc is an axial cross section through an end-to-end tube coupling.

Figure 2 is an elevation of the inner end of a collet, and Figure 3 is a cross-section on the line I-I of Figure lc. In all of Figures la, lb and lc, the tube coupling comprises a body 1 (la for Figures la and lb; lc for Figure lc) having a bore 2 for receiving an end of a tube 3. In the embodiment illustrated in Figures la and lb, the coupling is a push-in connector to attach the end of a tube 3 to a threaded article. In the embodiment illustrated in Figure lc, the coupling is a double-ended coupling for connecting one tube 3 to another (not shown). It will be appreciated that the coupling could alternatively k>-e a branched connector for coupling one or more tubes to other tubes or other components.

In both of the illustrated embodiments the body 1 is shaped to form a seat 4 for an O-ring seal 5 to surround the tube 3 and to form a seal between that tube 3 and the body 1 of the coupling. The body 1 has an end portion 6 surrounding a collet 7 which in turn surrounds the tube 3. The collet 7 comprises at its outer end a circumferentially continuous cylindrical portion 21 with a cylindrical bore 22 and extending from the portion 21 has four circumferentially spaced, resilient legs 8. The legs 8 are provided with inwardly extending tube-engaging surface portions (toes) 9, outwardly extending heels 13 and projecting soles 19. The end of the collet 7 remote from the legs 8 has a circumferential rim 20 to limit the extent to which the collet 7 can be inserted into the coupling body 1. The coupling body 1 is an integral moulding with its end portion 6 being formed as a cage comprising a crown 10 which is joined to the remainder of the body by pillars (bars) 11 which are separated by spaces 12, and the collet 7 is so shaped that, in the absence of a tube, it can be pressed into the cage portion 6 with radially inward deformation of its legs 8 due to engagement of the heels 13 with the bore of the crown 10.

On full insertion of the collet 7 into the coupling body 1, the heels 13 on the collet legs 8 are able to project into the inter-pillar spaces 12 of the cage portion 6 on radially outward relaxation of the legs 8. The soles 19 project beyond the spaces 12 and, with the tube 3 in place, can bear against the internal bore of the body to give added stability to the position of the collet 7. The heels 13 are provided with surfaces 14 which slope inwardly away from the ends of the legs 8, and these sloping surfaces 14 co-operate with the crown 10 of the cage at the ends 15 of the inter-pillar spaces 12 to provide camming surfaces which act, on attempted withdrawal of the collet 7 from the coupling body 1, to tend to drive the tube-engaging toes 9 of the collet legs 8 radially inwardly, thereby to resist further withdrawal of the collet 7 and/or a tube 3 from the coupling body 1.

In the embodiment shown in Figures la and lb the end of the coupling opposite to the end for receiving the tube 3 carries an external thread 24 on the body portion la for connection to a threaded component such as a tap or valve. The bore 25 at this end of the body la has an internal diameter equal to the internal diameter of the tube 3. In the embodiment shown in Figure lc the cage portion 6 of the coupling body lc is provided with a pair of circumferential ribs 16 at each end of the inter-pillar spaces 12, so as to provide a seat for a sleeve (not shown) so that the outer surface of the body lc is substantially smooth and continuous when such a sleeve is in place to mask the inter-pillar spaces 12.

A seat 17 is provided within the bore of the coupling body 1 for limiting insertion of a tube such as the tube 3. The coupling body 1, its cage portion 6 and seat 17, the collet 7, O-ring 5 and any inserted tube 3 are thus disposed along a common axis (designated A-A in Figure 1). The collet 7 can readily be formed as a one-piece moulding. For additional grip on an inserted tube, the tube-engaging toes 9 may however, as illustrated, include metal pieces 18, for example of stainless steel, insert-moulded into the collet 7.

Claims

1. A tube coupling comprising a body 1 having a bore for receiving an end of an appropriately sized tube 3, which body 1 is shaped to form a seat for an O-ring seal 5 to surround the tube 3 when the latter is inserted into said body 1, to form a seal between such a tube 3 and the body 1, such body 1 having an end portion 6 surrounding a collet 7 which in turn surrounds such a tube 3, the collet 7 having at its outer end a circumferentially continuous cylindrical portion with a cylindrical bore and having at its inner end a plurality of axially extending, circumferentially spaced, resilient legs 8 which are provided with tube-engaging surface portions 9 and are so shaped that, in co-operation with the body end portion 6, they provide camming surfaces which act, on attempted withdrawal of the collet 7 from the body 1, to tend to drive the tube-engaging surface portions

9 of the collet legs 8 radially inwardly thereby to resist further withdrawal of the collet 7 and/or a said tube 3 from the body 1, characterised in that such body 1 is an integral moulding with its end portion 6 being formed as a cage comprising a crown 10 which is joined to the remainder of the body 1 by pillars 11 which are separated by spaces 12, and said collet 7 is so shaped that, in the absence of a tube 3, it can be pressed into the cage portion 6 with radially inward deformation of its legs 8 so that on radially outward relaxation of the legs 8, heels 13 thereof project into the inter-pillar spaces 12 of the cage portion 6 to co-operate with the crown 10 to provide said camming surfaces.

2. A tube coupling according to claim 1, in which the body pillars 11 and spaces 12 all have a similar circumferential length to each other.

3. A tube coupling according to claim 2, in which the number of collet legs 8 is the same as the number of pillars 11 and spaces 12,

4. A tube coupling according to claim 3, in which the circumferential length of each collet heel 13 is substantially the same as the that of the cage spaces 12.

5. A tube coupling according to any preceding claim, in which the number of pillars 11, spaces 13, and heels 13 is at least three.

6. A tube coupling according to any preceding claim, wherein a sleeve is provided for surrounding at least the pillars 11 of such body cage portion 6 to mask the inter- pillar spaces 12.

7. A tube coupling according to claim 6, wherein a seat is provided for such sleeve so that the outer surface of the coupling body 1 is substantially smooth and continuous.

8. A tube coupling according to any preceding claim, wherein a seat 17 is provided within the bore of the coupling body 1 for limiting insertion of such a tube 3.

9. A tube coupling according to any preceding claim, wherein said collet 7 is formed as a one-piece moulding.

10. A tube coupling according to any preceding claim, wherein the tube-engaging surface portions 9 of the collet legs 8 include metal-insert pieces moulded therein.