GB2085992A - Improvements in or relating to releasable tube couplings - Google Patents

Abstract

A releasable tube coupling comprises a body (1) having an externally screw-threaded terminal portion (2) to which an internally tapered sleeve (9) is coaxially secured by means of an internally screw- threaded coupling member which may be integral with the sleeve (9) or, preferably, is in the form of a separately formed coupling nut (5). The sleeve (9) houses a sealing ring (15) and a pipe-gripping collet (18). If a tube (23) coupled to the device is accidentally pulled, for example, the arms of the collet (18) co-act with the tapered internal surface (25) of the sleeve (9) and exert an increased gripping force on the tube (23) thus preventing withdrawal thereof. However, if it is desired to withdraw the tube (23) from the coupling the collet (18) is pushed towards the body and the tube (23) is pulled out. <IMAGE>

Description

SPECIFICATION Improvements in or relating to releasable tube couplings This invention relates to releasable tube couplings of the kind including a body communicating with an open-ended chamber which contains the resilient arms of a collet for gripping the outer cylindrical surface of a tube inserted into the chamber. Such couplings also include a sealing ring for co-action with the outer surface of the inserted tube. A portion of the chamber wall converges towards that open end of the chamber through which the tube is inserted and engages the arms of the collet so that their grip on the tube will increase when an attempt is made to withdraw the tube from the chamber without first releasing the collet. There are many prior disclosures relating to aspects of such couplings and, by way of example, reference may be made to British patent specifications nos.

1 270 648 and 1 576131 and to pages 42 and 43 of the October 1971 edition of "Product Engineering".

The hitherto proposed couplings of this type have almost invariably utilised a body specifically designed for the purpose, as will be evident from the prior disclosures.

In one aspect, the present invention provides a releasable tube coupling comprising, in part, an externally threaded coupling body that may have been designed specifically for use in another form of tube coupling, for example a compression fitting. In another aspect, the present invention provides a kit of parts for association with such a body to form a releasable tube coupling.

Accordingly, in one aspect, the present invention provides a releasable tube coupling device comprising a hollow coupling body having at least one externally screw-threaded terminal portion having a bore there-through, a sleeve defining a chamber and being co-axiatly secured to said terminal portion by means of a substantially annular, internally screw-threaded coupling member that engages the external surface of one end portion of the sleeve and the external screw threads of said terminal portion, at least a portion of the chamber wall converging towards the end of the sleeve remote from the body, a collet having a plurality of generally axially extending resilient arms for gripping the outer surface of a tube to be coupled, the resilient arms of the collet being positioned within the chamber for engagement with the converging portion of the chamber wall whereby movement of the collet towards said end will cause the resilient arms to contract, and a sealing ring located within the coupling for co-action with the external surface of said tube and with an internal surface of the coupling.

The internally screw-threaded coupling member may be integral with the sleeve.

However, in preferred embodiments, the end of the sleeve adjacent to the externally threaded portion of the body (which end is hereinafter referred to as the inner end of the sleeve) is provided with a radially outwardly directed annular flange and a separately formed, substantially annular, internally screw-threaded coupling member fits over the sleeve and has a radially inwardly directed annular flange which abuts the flange on the sleeve and clamps the flange on the sleeve between an annular end face of the said terminal portion of the body and the flange on the coupling member. Preferably, a resilient sealing washer is disposed between the annular end face of the said terminal portion and the flange on the sleeve, but this is not essential as a metal to metal seal, for example, may suffice.

The sleeve is preferably made of a metal, such as brass, and may be made by, for example, diecasting, machining bar stock or swaging an originally tubular member as described in our British patent specification No. 1576131.

The internally threaded, substantially annular coupling member is preferably externally formed with a series of flats, for example six symmetrically arranged flats, to enable it to be tightened onto the externally threaded terminal portion of the body using a spanner. Alternatively, for example, the coupling member may have a knurled, externally cylindrical surface to enable it to be readily tightened by hand or using a wrench.

The collet preferably has a portion protruding from the end of the sleeve remote from the body (which end is hereinafter referred to as the outer end), and that portion is preferably provided with a radially outwardly extending flange to facilitate manual manipulation of the collet when releasing a tube from the coupling. The resilient arms of the collet are preferably sufficiently spaced from each other to permit the collet to be withdrawn from the outer end of the sleeve. The collet may be made of a metal and/or of a plastics material.

The sealing ring is preferably an O-ring made, for example, of a rubber. However a ring of alternative cross-section may be used and, whilst the ring is preferably resilient, it may in certain cases be substantially undeformable. Preferably the sealing ring is located within an internally cylindrical portion of the sleeve and has an external annular surface sealingly engaging said internally cylindrical portion of the sleeve.

The coupling body will usually have two or more like externally threaded terminal portions for coupling together two or more tubes and may, for example, have the configuration of a straight or bent coupling body (for coupling two tubes together) or of a T (for coupling three tubes together). Further, the coupling body may be of a type suitable, in conjunction with a nut and olive associated with the or each terminal portion, for coupling tubes by means of a compression fit. In other words, the body may be suitable for use in a compression fitting or in a releasable coupling of the invention and further any one coupling body may be such as to be coupled to at least one tube by means of a compression fit and to at least one other tube by a releasable coupling.

The coupling body may be formed internally with an annular shoulder to serve as a tube stop.

Alternatively, a separately formed tube stop member may be located in the bore of the terminal portion and may be retained therein by co-action with the inner end of the sleeve.

In accordance with another aspect of the present invention there is provided a kit of parts comprising a sleeve, a substantially annular, internally threaded coupling member, a collet and a sealing ring, said parts being adapted to be assembled with a coupling body into a releasable tube coupling as defined above. Where appropriate, the kit of parts may additionally comprise a tube stop member.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings of which: Figure 1 is an axial section through one releasable tube coupling of the invention, only a part of the coupling body being shown, and Figure 2 is an axial section through another releasable tube coupling of the invention, again only a part of the coupling body being shown.

Referring to Figure 1, a coupling body 1 (only part of which is shown) made, for example, of brass has an integral terminal portion 2 having a fluid flow bore 3 therethrough. The body 1 is of a type made specially for compression fittings and may have two or more like terminal portions 2: for example, the body 1 may be a straight, elbow or T-coupling body. The body 1 may, however, have only one said terminal portion 2 for coupling a single tube, the body 1 being provided with means for connecting it into a device, for example a valve, with which the tube is to communicate.

The external surface of the terminal portion 2 is provided with a screw thread 4 for engaging an internally screw-threaded coupling member in the form of a nut 5 having external flats 6, 7 (of which there may be, for example, six symmetrically arranged around the periphery of the nut) engageable by a spanner. The nut 5 is provided with an integral, radially inwardly extending annular flange 8 (as in the case of conventional compression fitting nuts).

A sleeve 9 defining a chamber 10 is provided at its inner (left-hand) end with an integral, radially outwardly extending annular flange 1 1 which, when the nut 5 is screwed to tightness onto the terminal portion 2 of body 1, is securely clamped between the flange 8 of nut 5 and the outer, annular end face 12 of the portion 2. A sealing washer 13 is sandwiched between the end face 12 and the flange 1 1, although in some circumstances direct contact between the face 12 and the flange 11 will provide an acceptable fluidtight seal. Immediately adjacent to the flange 11, the sleeve 9 is provided with a short cylindrical portion 14, the internal surface of which coacts with the periphery of a rubber O-ring 1 5.The cylindrical portion 14 merges with an integral frusto-conical portion 16 which itself merges with a cylindrical portion 17 which terminates at the outer (left hand) end of the sleeve 9. The sleeve 9 may be made from metal by, for example, machining from bar stock (in which case the external surface of the sleeve 9 may be cylindrical) or, like the sleeve 9 shown, by swaging an originally cylindrical preform. Alternatively, for example, the sleeve 9 may be moulded from a plastics material. Although the sleeve 9 is shown to be clamped to the terminal portion 2 of body 1 the sleeve 9 could, for example, alternatively be engaged by the nut 5 by a threaded engagement.

A collet 18 is of a well-known type comprising a cylindrical body 19 provided with an integral flange 20 at one end and a series of radiallyseparate, axially extending, integral resilient arms 21 at the opposite end. The flange 20 is positioned outside the sleeve 9, as is shown, whilst the arms 21 are positioned within the chamber 10. Each arm 21 is provided adjacent to its free end with a tooth 22 for gripping the outer surface of a tube 23 and a head 24 for engagement with the tapered internal surface 25 of portion 1 6 of the sleeve 9 whereby movement of the collet 1 8 towards the outer end of the sleeve 9 will cause the free ends of the arms 21 to contract.In this manner, the grip exerted on the tube 23 by the teeth 22 will increase as the pressure within the coupling increases or if an attempt is made to pull the tube 23 from the chamber 10 without first pressing the flange 20 axially towards the outer end of the sleeve 9. The cylindrical body 1 9 of the collet 18 is located for axial sliding by the internal surface of the cylindrical portion 17 of the sleeve 9. The resilient arms 21 of the collet 1 8 are preferably sufficiently spaced from each other to permit the collet to be withdrawn from the sleeve 9 in the absence of the tube 23.

Upon insertion of the tube 23 into the coupling, the external surface of the tube 23 is engaged by the internal surface of the O-ring 15. The tube 23 is located radially by bore 26 in the terminal portion 2 and the extent of insertion of the tube 23 into the coupling is limited by an annular shoulder 27 formed integrally within the terminal portion 2 of body 1.

As already indicated, the body 1 is suitable, in conjunction with a nut and olive, for coupling, by means of a compression fit, a tube having an external diameter equal to that of the tube 23 shown in Figure 1. In Figure 2 there is shown a coupling using the same body 1 as shown in Figure 1 but adapted to couple a tube of smaller external diameter. Those parts of the coupling shown in Figure 2 that are similar or identical to corresponding parts of the coupling of Figure 1 bear the same reference numerals applied to Figure 1.

Referring now to Figure 2, the flange 11 is provided with a short, axially extending annular projection 28 which serves to space the flange 11 axially from the sealing washer 13. The annular space 29 thus created accommodates an annular flange 30 of a "top-hat" tube stop member 31.

The tube stop member 31, which may for example be formed as a pressing, by machining, by diecasting or as a plastics moulding, comprises a central cylindrical portion 32 having the flange 30 at its right-hand end and an inwardly directed flange 33 at its opposite end. The internal surface of the central portion 32 locates the inserted portion of the tube 23 radially whilst the flange 33 limits insertion of the tube 23 into the coupling.

The flange 30 additionally serves to locate the O-ring 15 axially.

Rather than being retained in the coupling by a clamping arrangement, the tube stop member 31 may for example be secured to the sleeve 9 by any suitable means, such as by an adhesive or by welding in cases where both the sleeve 9 and the stop member 31 are made of appropriate materials.

The mode of operation of tube couplings of the kind to which this invention relates is well-known to those skilled in the art. Briefly, however, the tube 23, which may be rigid but which will normally be flexible and may be made of a metal or plastics material, is coupled to the coupling simply by inserting it until its end abuts the tube stop (shoulder 27 of Figure 1 or flange 33 of Figure 2) during which insertion the resilient arms 21 of the collet 18 are-forced outwards by contact of the tube 23 with the teeth 22. If fluid pressure in the tube 23 increases, or if the tube 23 is accidentally pulled, the grip exerted on the tube 23 by the teeth 22 will increase, as described earlier, thus preventing blow-out or accidental removal of the tube 23. However, the tube 23 may quickly be decoupled by pressing the flange 20 of the collet 1 8 axially towards the outer end of the sleeve 9 (whereby outwards axial movement of the collet 18, and hence contraction of the arms 22 is prevented) and simultaneously withdrawing the tube 23.

As already mentioned, a coupling of the invention may comprise, in part, a coupling body of a type intended for use in, say, a compression fitting and such a body may be adapted to a releasable coupling by combining it with a suitable kit of parts comprising a sleeve, an internally threaded coupling member, a collet and a sealing ring. However, it is not essential that the body be usable in couplings other than of the releasable kind, i.e. the body may be designed exclusively for use in releasable couplings.

Claims (13)

1. A releasable tube coupling device comprising a hollow coupling body having at least one externally screw-threaded terminal portion having a bore therethrough, a sleeve defining a chamber and being co-axially secured to said terminal portion by means of a substantially annular, internally screw-threaded coupling member that engages the external surface of one end portion of the sleeve and the external screw threads of said terminal portion, at least a portion of the chamber wall converging towards the end of the sleeve remote from the body, a collet having a plurality of generally axially extending resilient arms for gripping the outer surface of a tube to be coupled, the resilient arms of the collet being positioned within the chamber for engagement with the converging portion of the chamber wall whereby movement of the collet towards said end will cause the resilient arms to contract, and a sealing ring located within the coupling for co-action with the external surface of said tube and with an internal surface of the coupling.

2. A tube coupling device according to Claim 1 wherein said internally screw-threaded coupling member is integral with the sleeve.

3. A tube coupling device according to Claim 1 wherein said internally screw-threaded coupling member has been formed separately from the sleeve.

4. A tube coupling device according to Claim 3 wherein the end of the sleeve nearer to the coupling body has a radially outwardly directed flange and the coupling member fits over the sleeve and has a radially inwardly directed flange which abuts the flange on the sleeve and clamps the latter against an annular end face of the terminal portion of the body.

5. A tube coupling device according to Claim 4 wherein there is an annular sealing washer between the flange of the sleeve and said annular end face of the terminal portion of the body.

6. A tube coupling device according to any one of Claims 1 to 5 wherein the sealing ring is located within an internally cylindrical portion of the sleeve and has an external annular surface sealingly engaging said cylindrical portion of the sleeve.

7. A tube coupling device according to any one of Claims 1 to 6 wherein the coupling body is formed internally with an integral annular shoulder for serving as a tube stop.

8. A tube coupling device according to any one of Claims 1 to 6 having a separately-formed tube stop member located within the bore of said terminal portion of the body.

9. A tube coupling device according to Claim 8 wherein said tube stop device includes a radially outwardly directed flange secured between the terminal portion of the body and a portion of the sleeve.

10. A tube coupling device according to any one of Claims 1 to 9 adapted to couple together two or more tubes.

11. A tube coupling device according to any one of Claims 1 to 10 wherein the coupling body is of a type suitable, in conjunction with one or more nuts and olives, for coupling a tube or tubes by means of a compression fit.

12. A kit of parts comprising a sleeve, a substantially annular, internally threaded coupling member integral with, or formed separately from, said sleeve, a collet, a sealing ring and optionally a tube stop member, said parts being adapted to be assembled with a coupling body to form a releasable tube coupling device according to any one of Claims 1 toll.

13. A tube coupling device substantially as hereinbefore described with reference to, and as illustrated in, Figure 1 or Figure 2 of the accompanying drawings.