GB2080467A

GB2080467A - Releasable tube couplings

Info

Publication number: GB2080467A
Application number: GB8121966A
Authority: GB
Original assignee: IMI ENOTS Ltd
Current assignee: IMI ENOTS Ltd
Priority date: 1980-07-21
Filing date: 1981-07-16
Publication date: 1982-02-03
Also published as: GB2080467B; NL8103425A; DE8121384U1; FR2489473A1; IT8122997A0; IT1138095B; ES8205048A1; ES504108A0; FR2489473B3; AU7256081A

Abstract

A unitary cartridge, for insertion into a body (18), for example a valve or manifold body or the body of a fitting for coupling two or more tubes, to form a releasable tube coupling device, comprises a collar (10) having an external surface for retention in the body (18), a tube gripping collet (19) retained in the collar (10) and a sealing ring (28) also retained in the collar (10). The collar (10) is preferably retained in the body (18) by means of an interference buttress (15) and, optionally, a sealant adhesive (34), by a sealant adhesive alone or by screw-threaded engagement. <IMAGE>

Description

SPECIFICATION Improvements in or relating to a releasable tube coupling and its manufacture This invention relates to improvements in or relating to a releasable tube coupling and its manufacture and more specifically to a cartridge for insertion into a body to form such a coupling, to a releasable tube coupling comprising a body containing such a cartridge, to a method of assembling the cartridge with the body, and to a releasable tube coupling produced by the method.

Releasable tube couplings formed by the insertion of a cartridge into a body are wellknown. UK Patent 1 270 648 teaches a releasable tube coupling comprising a body, a collar, a clamping member in the form of a collet and a tube seal in the form of an O-ring. The body is essentially provided with four co-axial bores of which the smallest serves as a flow passage for communication with the interior of the tube, the second smallest serves as a tube stop for locating the end of the tube radially and limiting its insertion into the body, the second largest provides a seating for the O-ring and the largest receives the collar as an interference push-fit.

This construction has been achieved by using a cartridge sub-assembly to facilitate mass production of the couplings and to enable customers to incorporate this type of releasable tube coupling in any individual body that can be provided with the requisite four co-axial bores. The cartridge sub-assembly includes a moulded plastics plug having an enlarged head bearing against the outer end of the collar, and an integral stem extending axially through the collar, the collet and the O-ring. The collet is constructed so that it has to be inserted into the inner end of the collar and the O-ring resilient grips the end of the stem to hold the sub-assembly together. In use, the stem end of the sub-assembly is inserted into the preformed bores in the body, and an axial load is applied to the enlarged head of the plug to force the collar into the largest bore.After this has been completed, the plug is pulled axially out of the outer end of the collar and is discarded. Although this cartridge sub-assembly has many advantages over previous proposals, and has indeed met with substantial commercial success, its use necessitates the prior formation of four accurately dimensioned co-axial bores and the provision of a "throw-away" support plug. Furthermore, the resultant coupling cannot be serviced as both the O-ring and the collet are trapped in the body by the collar which in turn cannot be withdrawn without the substantial risk of damaging both the collet and the body.Thus, although the cartridge sub-assembly enables this type of releasable tube coupling to be readily incorporated in a very wide range of bodies, there is the inevitable risk that any damage suffered by the cheapest component, that is the O-ring, will probably result in the scrapping of body which may incorporate several other similar tube couplings and is usually the most expensive component.

An object of the present invention is to provide a releasable tube coupling which mitigates at least some of these disadvantages.

According to one aspect of the invention a cartridge, for insertion into a body to form a releasable tube coupling, comprises a collar defining a chamber and having an external surface for retention within an aperture in the body, a collet having a substantially annular support portion supporting a plurality of generally axially extending, spaced, resilient arms each having means for gripping the outer cylindrical surface of an inserted tube, and a sealing ring for coaction with the outer surface of said tube, the resilient arms of the collet being positioned within the chamber for engagement with a portion of the chamber wall which converges towards one end of the collar whereby movement of the collet towards said one end of the collar will cause the ends of the resilient arms to contract, and the sealing ring being carried by the other end of the collar and having an annular sealing surface coacting with a complementary surface of the collar.

In a preferred embodiment the sealing ring is located wholly within the chamber and is retained within the collar by an abutment. In one preferred embodiment, the abutment comprises a constriction formed integrally with the collar at said other end thereof. The chamber is preferably machined from the said other end of the collar, and the constriction is formed by a subsequent inward deformation of the collar. The said other end of the collar preferably has a reduced thickness portion which is then pressed inwards to form an annular lip defining the constriction.

However, the constriction may result directly from a machining operation.

In an alternative preferred embodiment, the abutment is constituted by part of a tube stop device carried by the said other end of the collar.

In this embodiment, the tube stop device has a portion, for example an annular flange, located in the chamber a surface of the flange providing said abutment. This portion is preferably retained within the collar by a constriction, for example as described above, at said other end of the collar.

The tube stop device may have a tubular portion for locating the end of the tube radially and an inwardly directed flange remote from the tube seal for engaging the end of the tube to limit its insertion into the body.

The sealing ring is preferably an O-ring or may include a portion which projects axially from said other end of the chamber for forming a face seal with a complementary surface of the body and/or a portion which projects radially outwards from said other end of the chamber for forming an annular seal with a complementary surface of the body.

The collar may be provided with an external flange at its said one end to limit insertion of the collar into the body or at its said other end so that the collar can be inserted into the aperture from within the body.

The external surface of the collar preferably includes at least one portion which will provide an interference fit with the aperture in the body. The external surface of the collar may include an annular portion of slightly greater diameter to provide the interference fit.

In order to form a fluid-tight seal, or to enhance sealing, between the collar and the body, a sealing.

ring, for example an O-ring, may be provided in a circumferential groove formed in the external surface of the collar and/or a layer of sealant may be provided between the collar and the body. The sealant, if used, may additionally serve to retain, or help retain, the collar in the body. Alternatively the external surface of the collar may be provided with a screw thread for engagement with a complementary screw thread in the body.

The collet preferably has a portion extending from the said- one end of the collar, and the resilient arms of the collet are sufficiently spaced from each other to permit the collet to be withdrawn from said one end of the collar. The collet preferably has a flange positioned outside the collar and capable of abutting the said one end of the collar without damaging the sealing ring.

According to another aspect of the invention a releasable tube coupling comprises such a cartridge having its collar retained within an aperture in the coupling body. The releasable tube coupling may also comprise an adhesive and/or sealant between the external surface of the collar and the body.

According to a further aspect of the invention a method of assembling such a cartridge into an aperture of a body, to form a releasable tube coupling, comprises aligning the collar with the aperture, and applying an axial force to the collar to press the collar into the aperture. The method may also include applying an adhesive and/or sealant to the external surface of the collar and/or to the wall(s) of the body defining the aperture before assembly of the collar into the body.

The invention is now described, by way of example only, with reference to the accompanying drawings, in which~ Figure 1 is an axial section through one form of cartridge retained in an aperture in a body to make a releasable tube coupling; Figure 2 is a half axial section of a further form of cartridge retained in an aperture in a body to make a releasable tube coupling; Figure 3 is an axial section through yet a further form of cartridge retained in an aperture in a thinwailed body; and Figure 4 is an axial section of a cartridge similar to that shown in Figure 3 but which is screwthreadedly retained in a body.

With reference to Figure 1, a cartridge comprises a collar 10 which defines a chamber 11 and has an external surface comprising a long cylindrical portion 12, a pair of grooves 13 and 14, an interference buttress 15 and a short cylindrical portion 16. The cylindrical portions 12 and 16 are of generally the same diameter but the interference buttress 1 5 is of slightly greater diameter to provide an interference fit in an aperture 17 of the body 18. The interference buttress 15 therefore constitutes an annular portion of the external surface of the collar 10.

A collet 19 is of a well-known type comprising a cylindrical body 20 provided with an integral flange 21 at one end and a series of radiallyseparated, axially-extending, integral resilient arms 22 at the opposite end. The flange 21 extends from the right-hand end of the collar 10, as shown, whilst the arms 22 are positioned virithin the chamber 11. Each arm 22 Is provided adjacent its free end with a tooth 23 for coacting with the outer surface of a tube 24, and a head 25 for engagement with a portion 26-whereby movement of the collet 19 towards the right-hand end of the collar 10 will cause the free ends of the arms 22 to contract.In this manner, the grip exerted on the tube 24 by the teeth 23 will increase as the pressure within the coupling increases or if an attempt is made to pull the tube 24 from the chamber 11 without first pressing the head 25 of the collet 19 against the collar 10. The cylindrical body 20 of the collet 1 9 is located for axial sliding by a cylindrical portion 27 of the chamber wall.

A sealing ring, in the form of an O-ring 28, is provided for coaction with the outer surface of the tube 24 and is carried by the left-hand end of the collar 10, being located within a cylindrical portion 29 of the chamber wall such that the outer annular surface of the O-ring 28 sealingly coacts with the complementary surface provided by the cylindrical portion 29. The O-ring 28 is therefore located within the chamber 11 and is retained by a constriction in the form of an annular lip 30 whicy Is formed by crimping or pressing or otherwise inwardly deforming a cylindrical preform to this shape.

The collar 10 can be produced particularly efficiently as a series of high speed operations on brass bar stock using, for example, a computer controlled lathe, although it could be manufactured in other ways. In production the bores 29, 26 and 27 are formed by a first operation in the end of the stock, a second operation forms the external profile of the collar including the cylindrical preform, a third operation crimps or presses the cylindrical preform to provide the lip 30, and a final operation parts the completed collar from the stock. Alternatively, the lip 30 could be formed by undercut machining or the O-ring 28 could be located in an annular groove also formed by undercut machining.

Apart from being material efficient, the cartridge comprises a completely self-sufficient sub-assembly with the O-ring and collet retained in their operative positions without any need for throw-away components or special assembly tools. Furthermore, as the O-ring is positioned Inside the collar, the machining of the body 18 to accept the cartridge is simplified as only the single aperture 17, which is conveniently a plain cylindrical bore, has to be provided for accommodating both the collar.

will also be noted that the number of cartridge components is limited to the three essentially required and that the body 18 only has three bores, that is the bore 17, a bore 31 to locate the end of the tube 24 and to form an end stop 32, and the flow passage 33 for alignment with the bore of the tube. This construction of cartridge also serves to minimise the depth of the seating bores 17 and 31 in the body 18 thereby avoiding undue machining and consequent weakening of the body which may very well contain other fluid flow passages that must not be interrupted.

The cartridge is assembled into the body simply by aligning the collar 10 with the aperture 17 and then applying an axial force on the collet flange 21 to press the collar into position. If desired, the lefthand end of the collar may be provided with a short conical lead-in surface to assist with the initial alignment.

With previously known cartridge subassemblies the collet has always been inserted from the O-ring end of the collar and therefore has no flange 21 unless this has been formed subsequent to its insertion. However, the collet design illustrated is of a type developed for use with non cartridge assemblies, such as that shown in the October 1971 edition of "Product Engineering" on pages 42 and 43. With this collet design the resilient arms of the collet are sufficiently spaced from each other to permit the collet to be withdrawn from, and inserted via, the right-hand end of the collar by applying an appropriate axial force to the collet flange 21.By applying this cotlet design to a cartridge subassembly there is the added advantage that, after the collar has been permanently secured within the body 18, both the collet 19 and the O-ring 28 may be withdrawn for inspection and replacement thereby providing for the first time a cartridge fitting which can be serviced after use.

Whilst the engagement of the bore 1 7 by the buttress 15 provides more than adequate mechanical retention (tests have indicated that this will withstand separation forces in excess of five times the rated working pressure), it is preferred to have an adhesive sealant between the collar 10 and the body 18 to ensure that there is no leakage. Such adhesive sealant also serves further to increase the mechanical retention of the collar 10 in the body 18. It will be noted from Figure 1 that a layer 34 of such adhesive sealant is illustrated in the gap between the longer cylindrical portion 12 and the bore 17.This may either be applied to the collar 10, or into the bore 1 7, immediately prior to assembly, or may be applied during manufacture of the cartridge as an adherent layer capable subsequently of slight radial deformation to seal effectively against the wall of the bore 17.

The use of an adhesive sealant between the collar 10 and the body 18 additionally extends the usefulness of the various cartridges illustrated which can be applied to bodies made from a very wide range of materials including plastics materials, ceramics, glass and other brittle materials. With such materials, little or no interference fit would be used between the collar 10 and the body 18, and greater reliance would be placed on the sealant adhesive to withstand the blow-out force. In this connection there is also scope for making the collar 10 from a material compatible with that of the body and using some other process for securing them together such as adhesives, welding, ultrasonic welding or high frequency welding.

If desired, the interference buttress 15 may be omitted and the collar 10 be held in place by some other mechanical device, for instance by providing the collar 10 with an external screwthread for engagement with a complementary internal thread in the body 18 as shown in Figure 4.

Alternatively, an adhesive may be used both to retain the collar 10 in the aperture 17 and to provide a seal between the collar 10 and the body 18.

The general construction of Figure 1 can also be modified by, for example, using different designs of collet 19 and/or by using different types of sealing ring, for instance a sealing ring having a lip seal for coacting with the outer surface of the tube 24.

Instead of using the head 21 of the collet 19 as a tool for inserting the collar 10 into the body 18, a separate tool may be used having either an annular working face surrounding the head 21 and engaging the outer portion of the right-hand end face of the collar 10, or having a working face which can be interposed between the head 21 and the right-hand end face of the collar 10. When the head 21 of the collet 19 is to be used as the insertion tool, it will be essential to ensure that the head 21 can abut the right-hand end face of the collar 10 without the free ends of the collet arms 22 damaging the sealing ring 28. Alternatively, the coupling may be formed by first withdrawing the collet 19 from the collar 10, pressing the collar 10 into the body 18 using a suitable tool and then replacing the collet 19.

The same reference numerals have been used to indicate the same or equivalent components or parts in the other Figures, and these components or parts have the same function unless specifically stated to the contrary.

The construction illustrated in Figure 2 is very similar to that described with reference to Figure 1 and differs only in so far as the external surface of the collar 10 is concerned. The buttress 15 is shown embedded in the wall of the aperture 17 and with the cylindrical surfaces 12 and 16 also directly engaging the wall of the aperture 1 7. A fluid-tight seal between the surfaces 12 and 16 and the wall of the aperture 17 is ensured by a sealing ring 35 located, under radial compression, in an annular groove 36 formed in the collar 10.

Alternatively, provided the engaged surfaces have an appropriate finish and are manufactured to adequate tolerances, an adequate seal between the collar 10 and the body 18 may be achieved without the use of any additional sealing means such as the adhesive sealant 34 shown in Figure 1 or the O-ring 35 shown in Figure 2.

The construction illustrated in Figure 3 is similar to that of Figure 2 but additionally includes a tube stop device 37 which can be formed as a pressing, by machining, by die-casting, or as a moulding, and is also carried by the collar 10. The tube stop device 37 comprises a central cylindrical portion 38 having an outwardly directed flange 39 at its right-hand end and an inwardly directed flange 40 at its opposite end. The outwardly directed flange 39 Is located within the chamber 11 and is retained by the annular lip 30, or by any other convenient constriction at the end of the collar 10. It will also be noted that the collar 10 includes a small shoulder 41, the flange 39 being held axially in place between the shoulder 41 and the lip 30.With this construction the sealing ring 28 is effectively retained in the chamber 11 by the flange 39, and the lip 30 can consequently be smaller or may be formed from a tubular preform of greater diameter.

The inner surface of the central cylindrical portion 38 locates the end of the tube 24 radially whilst the flange 40 limits its insertion into the body 18. Thus the cartridge itself defines the tube stop rather than part of the body 1 8. The tube stop device 37 may be secured to the collar 10 in any other convenient manner such as by using an adhesive, friction welding, ultrasonic or high frequency welding (in the case where both the collar and the tube stop are formed of appropriate materials), or by otherwise deforming the collar 10.

Cartridges of this construction are useful for most types of body in that they only require two bores, that is the bore 17 and the flow passage 33, and only the bore 17 needs to be formed accurately. Thus the machining of the body to accept such a cartridge is minimised with consequent cost saving and the cartridge can be used in applications where there is difficulty in providing a tube stop in the body. More particularly, this form of cartridge enables, for the first time, a releasable tube coupling to be fitted to a relatively thin-walled body such as a tube wall, or the wall of a large vessel as illustrated in Figure 3. With such applications the collar 10 can be provided with an external flange at its righthand to limit its insertion into the body.In cases where the collar 10 can be inserted from within the body, for instance in the case of the wall of a large vessel, the collar 10 can be provided with an external flange at the opposite end whereby the blow-out forces are transmitted directly from the collar to the body. With this latter arrangement the relative thickness of the body wall can be considerably reduced from that shown in Figure 3 as the external flange obviates the need for the interference fit between the collar and the body.

These constrictions may be further modified by the inclusion of a sealant adhesive between the collar and the body, as taught with reference to Figure 1, or of a seal or sealant adhesive between the external flange and the body when this flange is positioned within the body.

The cartridge shown in Figure 4 is similar to that shown in Figure 3, but instead of it being retained in the body 18 by means of an interference fit, it is screw-threadedly engaged therein. Thus, the body 18 is provided with an internal screw-thread 42 which engages an external screw-thread 43 on the collar 10. The outer end of the collar 10 is provided with a flange 44, the periphery of which is formed with two or more flats 45 whereby the collar 10 may readily be screwed to tightness into the body 18 using a spanner. The body 18 shown in Figure 4 is typical of a body conventionally used in compression fittings for connecting two or more tubes, e.g.

straight, bend orT-fittings and the assembly of one or more cartridges of the invention with such a body provides a simple and relatively inexpensive method of adapting such fittings to couple one or more tubes in releasable fashion. In analogy, other conventional screwed fittings, for example British Standard Pipe fittings or National Pipe Thread fitting, may be so adapted. By appropriately sizing the respective wall thickness of the collar 10 and of the collet 1 9, conventional fitting bodies may be adapted to releasably couple one or more tubes of any outside diameter up to a predetermined maximum diameter.

The mode of operation of the tube couplings of the type to which this invention relates is well known to those skilled in the art. Briefly, however, the tube 24, which may be rigid but which will usually be flexible and made of a plastics material, is coupled to the coupling simply by inserting it thereinto until its inserted end abuts the tube stop, during which insertion the resilient arms 22 are forced outwards by contact of the tube 24 with the teeth 23. If fluid pressure in the tube 24 increases or if the tube is pulled, the grip exerted on the tube 24 by the teeth 23 will increase, as described earlier, thus preventing blow-out or accidental removal of the tube 24. However, the tube 24 may quickly be decoupled by pressing the collet flange 21 axially inwards (whereby axial movement of the collet 1 9, and hence contraction of the arms 22, is prevented) and simultaneously withdrawing the tube 24.

Claims

1. A cartridge, for insertion into a body to form a releasable tube coupling, comprising a collar defining a chamber and having an external surface for retention within an aperture in the body, a collet having a substantially annular support - portion supporting a plurality of generally axially extending, spaced, resilient arms each having means for gripping the outer cyllndrical surface of an inserted tube, and a sealing ring for coaction with the outer surface of said tube, the resilient arms of the collet being positioned within the chamber for engagement with a portion of the chamber wall which converges towards one end of the collar whereby movement of the collet towards said one end of the collarsvill cause the ends of the resilient arms to contract, and the sealing ring being carried by the other. end:of the collar and having an annular sealing surface coacting with a complementary surface of the collar.

2. A cartridge, according to Claim 1, in which the sealing ring is located wholly within the chamber and is retained within the collar directly or indirectly by å constriction at said other end of the collar.

3. A cartridge, according to Claim 2, wherein the constriction is formed integrally with the rest of the collar.

4. A cartridge, according to Claim 3, in which the chamber has been machined from the said other end of the collar, and the constriction is formed by a subsequent inward deformation of the collar.

5. A cartridge, according to Claim 4, in which the said other end of the collar has a reduced thickness portion which has been pressed inwards to form an annular lip defining the constriction.

6. A cartridge, according to any one of Claims 2 to 5, wherein the sealing ring directly abuts a surface of said constriction facing the chamber defined by the collar.

7. A cartridge, according to any preceding claim, in which a tube stop device is also carried by the said other end of the collar.

8. A cartridge, according to Claim 7 when appendant to any one of Claims 2 to 5, in which the tube stop device has a portion that is retained within the collar, intermediate the constriction and the sealing ring, by the constriction.

9. A cartridge, according to Claim 7 or Claim 8, in which the tube stop device has a tubular portion for locating the tube radially and an inwardly directed flange remote from the sealing ring for engaging the end of the tube to limit the extent of insertion of the tube.

10. A cartridge, according to any preceding claim, in which the collar is provided with an external flange at its said one end to limit insertion of the collar into the body.

11. A cartridge, according to any preceding claim, wherein the sealing ring is an O-ring.

12. A cartridge, according to any preceding claim, in which the external surface of the collar includes at least one portion which will provide an interference fit with the wall(s) defining the aperture in the body.

13. A cartridge, according to Claim 12, in which the external surface of the collar has projecting therefrom an annular portion to provide the interference fit.

14. A cartridge, according to any preceding claim, wherein the collar has an annular recess in its external surface and, seated in the recess, a sealing ring the outer periphery of which stands proud of said external surface.

15. A cartridge, according to any one of Claims 1 to 11, in which the external surface of the collar is provided with a screw thread for engagement with a complementary screw thread in the body.

16. A cartridge, for insertion into a body to form a releasable tube coupling, substantially as described herein with reference to, and as illustrated in, any one of Figures 1 to 4 of the accompanying drawings.

17. A releasable tube coupling comprising a body and, retained in an aperture in the body, a cartridge according to any preceding claim.

18. A releasable tube coupling, according to Claim 1 7, in which an adhesive and/or sealant has been applied to the external surface of the collar before its assembly into the body.

19. A method of assembling a cartridge, according to Claim 12 or any Claim appendant thereto, into an aperture of a body to form a releasable tube coupling, comprising aligning the collar with the aperture, and applying an axial force to the collar so as to press the collar into the aperture.

20. A method, according to Claim 19, including applying an adhesive and/or sealant to the external surface of the collar and/or to the wall(s) defining the aperture before its assembly into the body.

21. A releasable tube coupling manufactured by the method of Claim 19 or Claim 20.

22. A body, including a cartridge, substantially as described herein with reference to, and as illustrated in any one of Figures 1 to 4 of the accompanying drawings.