GB2368374A

GB2368374A - Pipe fitting and tool

Info

Publication number: GB2368374A
Application number: GB0026335A
Authority: GB
Inventors: Simon James Mounteney; Stephen Currid; Raymond William Doughty
Original assignee: Hepworth Building Products Ltd
Current assignee: Hepworth Building Products Ltd
Priority date: 2000-10-27
Filing date: 2000-10-27
Publication date: 2002-05-01
Anticipated expiration: 2020-10-27
Also published as: GB0026335D0; WO2002035135A1; AU2001295805A1; GB2368374B

Abstract

A pipe fitting system comprises a fitting (2, Fig.1) for coupling to a pipe (1, Fig.1) and a tool 16 for releasing the pipe from engagement with a gripping means 6 of the fitting. The gripping means comprises at least two axially extending and generally circumferentially facing opposed bearing surfaces 30 and the tool comprises a member 32 for insertion between the bearing surfaces in such a manner as to urge them apart by acting on them in a generally circumferential direction when the tool is moved towards the gripping means in a direction generally parallel to the longitudinal axis of the pipe.

Description

PIPE FITTING AND TOOL The present invention relates to a pipe fitting and a demounting tool for removing the fitting or a component of the fitting from engagement with a pipe.

Particularly, but not exclusively, the invention relates to a push-fit pipe fitting and tool for use in a plumbing application.

Throughout this specification, the expressions"axial","radial", "circumferential"and their derivatives are used extensively. For the avoidance of doubt, these expressions are to be taken with reference to the fitting or pipe overall and not with reference to any particular component. Therefore, where the terms are used in describing a component, they should be interpreted with reference to the component in situ within the fitting or upon the pipe, as appropriate.

Push-fit pipe fittings and demounting tools are generally well known. Figure 1 of the accompanying drawings shows a partial sectional view through such a known fitting and a pipe, together forming a joint.

As can be seen in Figure 1, the end of the pipe 1 is inserted into a socket defined by a body 7 and threaded cap 3 of the fitting 2 until an end stop 4 is reached. Located within the socket is a grab wedge 6, which takes the form of a contracting ring, through which the pipe 1 is inserted as it is pushed into the fitting 2. The body 7 is moulded from polybutylene or PVDL. The grab wedge 6 is formed from polysulphone.

The grab wedge 6 is a collet and therefore comprises a number of axially extending resilient fingers 9, provided with respective radially inwardly directed teeth 8 and separated by intermediate slots 11. The fingers 9 are integrally formed with a common annular base, which provides structure to the wedge 6. The fingers 9 each comprise a wedge mouth surface 14 which is generally radially inwardly directed and located towards the outer axial end of the respective finger 9, when the wedge 6 is located within the body 7 of the fitting 2 for use. The wedge mouth surfaces 14 together present a generally radially inwardly directed frustoconical bearing surface for the reception of the pipe I within the fitting 2. The wedge mouth surfaces 14 have the common objective of centering the pipe 1 during its insertion into the fitting 2, thereby ensuring good coaxial alignment upon the union of the two components.

An elastomeric 0-ring seal 5 made from EPDM is also situated inside the body 7 of the fitting 2 at a position that is axially inside, relative to the grab wedge 6. The 0ring 5 is of such a configuration that it can be compressed, in the radial direction, between a radially inner surface of the socket wall and a radially outer surface of the pipe wall, so as to form a seal between the two.

If a destructive axial force Fr is applied to the pipe 1 and tends to urge it out of the fitting 2, a radially outer camming surface 10 provided on the back of each finger of the grab wedge 6 co-operates with a complementary camming surface 12 situated in the mouth of the socket. As the force Fr is applied to the pipe 1, the grab wedge 6 moves with the pipe, due to the action of the teeth 8. As a result of this movement and the consequent interaction of the camming surfaces 10, 12, a radial closing force is applied to the grab wedge 6. This closing force serves to embed the teeth 8 more firmly into the pipe 1 and thus grip the pipe ever more securely. Eventually, the two camming surfaces wedge together, and, in combination with the teeth 8, prevent any further axial displacement of the pipe relative to the fitting.

It is desirable to be able to remove the pipe from the fitting, particularly if an error occurs during installation. In a number of prior art systems, this problem is addressed by the use of a tool having a wedge-shaped bearing surface, such as shown in Figure 2.

The illustrated tool 16 comprises a tool wedge 18, which has a generally frusto conical, radially outwardly directed tool wedge camming surface 20 for operation against the wedge mouth surfaces 14. In practice, the cap 3 of the fitting 2 is unscrewed from the body 7 of the fitting as a first stage of the demounting process. The body 7 can then be slid from the end of the pipe I (to the right in Figure 1), along with the seal 5.

This leaves the cap 3 and grab wedge 6 in position upon the pipe 1. The cap 3 is then slid in the opposite axial direction, along the length of the pipe (to the left in Figure I).

This step allows access to the grab wedge mouth surfaces 14. To address these surfaces, the tool 16 is fitted around the pipe 1, as shown in Figure 2, and slid towards the grab wedge 6 so that the tool wedge camming surface 20 is introduced to the wedge mouth surfaces 14. As the tool 16 is moved further in the axial direction, the tool wedge camming surface 20 bears against the wedge mouth surfaces 14 and urges the fingers 19 radially outwardly, due to the mutual camming action of the two surfaces 14 and 20.

Once a suitable radial displacement of the fingers 9 has taken place, the teeth 8 release their grip on the pipe 1 and the grab wedge 6 begins to move axially in common with the tool 16 and eventually slides off the end of the pipe 1.

Numerous variations upon this removal method are known in the art. These include systems in which it is not necessary to remove a cap or a corresponding part of the fitting body and, instead, the tool acts upon the grab wedge through the mouth of the fitting. In some cases, radial slots or the like are provided in the mouth of the fitting, to provide better access to the grab wedge, and the tool is correspondingly configured.

These known systems suffer from a number of disadvantages. One disadvantage is that, by not acting around the full circumference of the pipe, the conventional tools cause unbalanced dilation of the grab wedge during removal, thereby encouraging the teeth to leave score lines on the pipe. Even small score lines can lead to leaks, if the pipe is reused, and hence must be avoided. A further disadvantage is that the known systems require an annular gap to be provided at the mouth of the grab wedge, so as to provide access to the wedge mouth surfaces. This places a constraint upon the possible thickness of the fingertips, which is significant where the teeth are defined by metal inserts moulded into a plastics grab wedge. In such a case, there is a risk of the teeth shearing the tips of the fingers under axial loading and this risk tends to be inversely proportional to the thickness of the fingertips. Another disadvantage of the structure of the tips of the fingers is that, by providing the wedge mouth surfaces, the tips of the fingers can only have a restricted surface area, which makes it difficult to remove the wedge from its mould by pushing on this surface during the manufacturing process. A yet further disadvantage of the known fitting is that the annular gap limits the amount of support that the grab wedge can provide to the pipe following insertion. The gap can also facilitate the ingress of fluid or debris into the fitting.

The present invention sets out to overcome the above-described disadvantages.

According to a first aspect of the invention there is provided a pipe fitting system comprising a fitting for coupling to a pipe and a tool for releasing the pipe from engagement with at least part of the fitting; wherein the fitting comprises a socket for receiving the pipe; a seal adapted to be located within the socket for sealing between the pipe and the fitting; and gripping means adapted to be located within the socket for retaining the pipe within the socket; wherein the gripping means can at least partially surround the pipe when the pipe is located within the socket and comprises at least two axially extending and generally circumferentially facing opposed bearing surfaces; and the tool comprises a tool body, upon which is provided a member for insertion between the said bearing surfaces and for urging the said bearing surfaces apart by acting upon them in a generally circumferential direction when the tool is moved towards the said gripping means in a direction generally parallel to the axis of the pipe.

Such an arrangement enables the gripping means to be decoupled from a pipe by a purely circumferential interaction between the tool and the gripping means, thus avoiding the need for the wedge mouth surfaces such as found in the acknowledged prior art. This enables the mouth of the grab wedge to fit much more closely with the radially outer surface of the pipe, providing significantly enhanced support for the pipe and providing an initial resistance barrier to the ingress of fluid and/or contamination.

In addition, much more flexibility is available to allow optimisation of the configuration of the mouth-end of the gripping means so as to provide ease of manufacture, and greater resistance to failure.

In a preferred embodiment, the gripping means comprises four or more said bearing surfaces, the said bearing surfaces being arranged in pairs with the respective bearing surfaces of each pair being in mutual circumferential opposition, and the tool comprises a plurality of the said members, the circumferential locations of the said members corresponding to the circumferential locations of the said pairs of bearing surfaces. Preferably, the said gripping means is defined by a collet comprising a plurality of axially extending fingers, each of the said fingers comprising at least one flank surface, the said flank surfaces defining the said bearing surfaces. In a particularly preferred embodiment, the mouth of the socket comprises an internal first camming surface that is generally frustoconical and increases in diameter from an axially outer position to an axially inner position, and relatively axially outer tips of the fingers of the gripping means each comprise a respective second camming surface on a radially outer portion thereof, such that axial movement of the gripping means in an axially outward direction within the socket causes the second camming surfaces to cam against the first camming surface, causing contraction of the gripping means and enhancing its grip on the pipe, whilst the said action of the tool members upon the bearing surfaces reverses the said contraction, thereby allowing axial movement of the gripping means in a direction opposite to that which caused the contraction.

This particular embodiment provides a further advantage over the prior art in that, despite the presence of the second camming surfaces, the tips of the fingers may be made relatively thick, since no internal tapering of the thickness is required in order to form the wedge mouth surfaces of the acknowledged prior art. This provides increased tip strength, resisting failure under axial loading, particularly where the gripping means comprises metal inserts moulded into the fingers to define the teeth.

The or each member may take the form of an axially-extending, radially projecting rib, which may comprise an arcuate axial end surface and/or have a circumferential thickness which tapers positively from an axial tip region thereof to an axially intermediate region thereof.

In one particularly preferred embodiment, mutually opposed ones of the said bearing surfaces may be inclined at an angle of substantially 110 with respect to each other in the circumferential direction.

According to a second aspect of the invention there is provided a pipe fitting for coupling to a pipe; the said fitting comprising a socket for receiving the pipe; a seal adapted to be located within the socket for sealing between the pipe and the fitting; and gripping means adapted to be located within the socket for retaining the pipe within the socket ; wherein the gripping means comprises a collet adapted to surround the pipe when the pipe is located within the socket, which collet comprises at least two axially extending and generally circumferentially facing opposed bearing surfaces adapted to be urged apart to cause release of the gripping means from the pipe upon the axial insertion of a removal tool therebetween; the regions of the collet defining and immediately inside of its pipe-receiving mouth having sides substantially parallel to the axis of the collet.

Preferably, the collet comprises a plurality of axially extending fingers, each of the said fingers comprising at least one flank surface; the said flank surfaces defining the said bearing surfaces. In a particularly preferred embodiment, the mouth of the socket comprises an internal first camming surface that is generally frustoconical and increases in diameter from an axially outer position to an axially inner position, and the fingers of the gripping means each comprise a respective second camming surface on a radially outer portion thereof, such that axial movement of the gripping means in an axially outward direction within the socket causes the second camming surfaces to cam against the first camming surface, causing contraction of the gripping means and enhancing its grip on the pipe.

In a particularly preferred embodiment, mutually opposed ones of the said bearing surfaces are inclined at an angle of substantially 110 with respect to each other in the circumferential direction.

According to a third aspect of the invention, there is provided a removal tool for use in removing at least a gripping means of a pipe fitting from engagement with a pipe ; the said tool comprising a tool body upon which is provided a member for insertion between circumferentially facing, opposed bearing surfaces of the gripping means for urging them apart by acting upon them in a generally circumferential direction when the tool is moved towards the said gripping means in a direction generally parallel to the longitudinal axis of the pipe.

Preferably, a plurality of the said members are arranged upon the tool body at predetermined circumferential intervals. In a preferred embodiment, the said tool body is defined by a pair of hinged jaws adapted to encircle the pipe at least partly with at least one said member projecting generally radially inwardly from each said jaw. The jaws may be hinged together at respective first adjacent ends thereof by a single hinge element and may be opened apart around the said hinge element to permit the pipe to enter between the said jaws via a gap between second, opposite ends of the jaws. The jaws may each define a respective flange which may be gripped to effect axial movement of the tool along the length of the pipe. Alternatively, the jaws may be resiliently connected together at respective first adjacent ends thereof by a first hinge element and resiliently connected together at respective second adjacent ends thereof by a second hinge element, the said arrangement being such as to cause the jaws to move away from each other upon opening up one or both of the hinge elements. In such a case, each hinge element may be provided with a grip, the said grips being mutually opposed such that squeezing the two grips together causes simultaneous opening-up of the two hinge elements, thereby urging the two jaws apart.

Preferably, the or each member takes the form of an axially extending, radially projecting rib. The or each rib may comprise an arcuate axial end surface, and have a circumferential thickness which tapers positively from an axial tip region thereof to an axially intermediate region thereof.

Preferably, the tool is formed integrally from a plastics material. In a particularly preferred embodiment, the plastics material is polypropylene.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a partial cross-sectional view of a known coupling fitted to the end of a pipe ; Figure 2 is a partial cross-sectional view of the grab wedge from the coupling of Figure 1 in the process of being removed from the pipe of Figure 1 by a demounting tool; Figure 3 is a plan view of a grab wedge forming part of a fitting in accordance with the invention; Figure 4 is a cross-sectional view of the grab wedge of Figure 3 being acted upon by a removal tool in accordance with the invention; Figure 5 is a perspective view of a removal tool in accordance with the invention; Figure 6 is a front view of the tool of Figure 5 located about a pipe which is gripped by a grab wedge in accordance with the invention; Figure 7 is a perspective view showing the operation of the tool of Figures 5 and 6 upon the grab wedge of Figure 6; Figure 8 is a perspective view of an alternative tool in accordance with the invention; and Figure 9 is a further perspective view of the tool of Figure 8.

In the illustrated embodiments of the present invention, only the grab wedge and tool differ from the above described prior art example and the remaining features will therefore not be described again in detail.

The described grab wedge according to the invention can be seen most clearly in Figures 3 and 4. It is moulded from polysulphone and has the same basic construction as the above described grab wedge 6; that is to say it comprises an annular base 13 integrally formed with six axially extending fingers 9. Each of the fingers 9 comprises a respective tooth 8 which is generally radially inwardly directed. The wedge 6 is formed from plastics material and the teeth 8 are formed from stainless steel and moulded into the wedge 6 in a conventional fashion. The fingers 9 between them define intermediate, axially extending slots 11. Each slot I I has its circumferential perimeter defined by a pair of opposed flanks 30 situated on respective adjacent fingers 9. The surfaces of the flanks are aligned with radii of the ring. Due to the circumferential separation between them, the flanks of any given slot are therefore inclined at an angle of 110 with respect to each other.

In Figure 4, the grab wedge 6 is shown in use with a wedge-interactive part of a tool 16 in accordance with the invention. Figure 4 is largely schematic and the features of the tool shown in this figure can therefore be taken as representing those of either of the specific tool embodiments described below.

As can be seen in the figure, the tool 16 comprises a generally arcuate body portion 31 with a radially inner surface of a diameter that is greater than that of the radially outer surface of the grab wedge 6, so as to enable the tool 16 to surround the wedge 6. The radially inner surface of the tool body 31 is provided with a series of six radially inwardly projecting, axially extending ribs 32. The ribs 32 are situated at a circumferential interval that corresponds with that of the slots 11. The circumferential width of each of the ribs 32 tapers positively from a minimum at its axial ends, to a maximum in its axial centre. Each rib 32 is symmetrical on either axial side of its axial mid-point. As will be clear from Figure 4, each rib also has an arcuate nose 34. This overall shape has the effect of defining a wedge with a circumferential thickness that increases from the axial end to the axial centre of the rib 32.

The tool 16 acts upon the grab wedge 6 in a circumferential manner. To this end, to release the grab wedge 6 from a pipe, the tool 16 is presented to the grab wedge, so that the noses 34 of the ribs 32 are introduced into the axial ends of the slots 11, as shown in Figure 4. The tool 16 is then urged towards the grab wedge 6 in the axial direction, causing the ribs 32 to move in the direction A in Figure 4. Other than at the nose portion 34, the ribs 32 have a circumferential thickness that is greater than the width of the slots 11, so that further axial movement of the tool 16 towards the grab wedge 6 drives the ribs 32 further into the slots 11 and the gradually increasing thickness of the ribs urges the fingers 9 apart, as illustrated by the arrows B in Figure 4.

Due to the fact that the ribs 32 are circumferentially wider than the slots, the net effect is that the tips of the fingers 9 are urged radially outwardly, so as to provide the overall dilation necessary to accommodate the ribs 32 between the fingers 9. Eventually, after a sufficient degree of radially outward movement has been experienced, the teeth 8 are removed from engagement with the pipe and the grab wedge 6 can then be slid off the end of the pipe.

The removal process is illustrated further in Figure 7 with regard to a specific embodiment of the tool.

Hence it will be appreciated that the present invention achieves the necessary dilation to remove a grab wedge 6 from a pipe not by the direct radial camming action of the known system, but rather a circumferential action in which the finger flanks 30 cam over the sides surfaces 36 of the ribs 32. By making use of a circumferential camming action, rather than a radial camming action, it is not necessary to provide the wedge mouth surfaces 14 required by the known coupling system described above. This has the advantage of enabling maximisation of the volume of plastics material situated between the metal teeth inserts 8 and the tips of the fingers 9. By maximising the volume of this material, the risk of the fingertips being sheared off by the metal inserts 8 is substantially reduced, leading to significant operational benefits. In addition, as can be seen from Figure 4, the fingertips can be provided with a relatively broad and generally flat fingertip surface 15, which can be used to remove the grab wedge 6 from the mould during manufacture. This results in a substantial simplification of the moulding process, faster manufacturing times and hence cost and efficiency benefits.

As will also be appreciated from Figure 4, the fit of the grab wedge mouth around the pipe is somewhat closer due to the absence of the grab wedge mouth surfaces 14 found in the prior art. This feature enhances stability of the coupling and resists contamination.

Figures 5,6 and 7 show a preferred embodiment of a tool 16 for use in the invention. This embodiment comprises a pair of arcuate jaws 38,40, which together define the tool body 31. Ribs 32 are provided in a fashion corresponding to the configuration of Figure 4, although in this case, they are not circumferentially tapered, but have a largely constant circumferential thickness. The jaws 38,40 are connected together by a pair of intermediate, opposed hinge elements 42 and 44. Each of the hinge elements 42,44 being provided with an outwardly-facing finger grip 46,48. The finger grips 46,48 are provided with a series of friction-enhancing ribs 50.

The whole tool 16 is formed from polypropylene and Figure 5 shows it in the asmoulded condition. Due to the nature of the material from which it is formed, the hinge elements 42,44 have an inherent resilience. As a consequence of this resilience and its integral hooped construction of the tool as a whole, applying pressure simultaneously to the two finger grips 46,48 has the effect of urging the jaws 40, 38 apart, to the extent that a pipe and a grab wedge can be accommodated between the jaws. This can be seen most clearly in Figure 6. To remove a grab wedge 6 from a pipe, the user grips the finger grips 46,48 between thumb and forefinger and squeezes them together, thereafter threading the tool 16 over the end of the pipe and beyond the grab wedge 6. Once this has been achieved, the squeezing action on the finger grips 46, 48'can be released and the resilience of the tool 16 causes it to clamp onto the pipe, as shown in Figure 7. The tool 16 is further provided with orientation marks 51, which correspond to the circumferential positions of the ribs 32. Once the tool 16 has been located on the pipe,

one of the orientation marks 50 is aligned with one of the slots 11 in the grab wedge 6.

The tool 16 is then pulled towards the end of the pipe using the hinge elements 42, 44 and finger grips 46,48 for leverage and the ribs 32 enter into the mouths of the slots 11.

Further axial displacement of the tool 16 towards the end of the pipe causes the tool 16 to act upon the grab wedge 6 in the manner described above in relation to Figure 4. The grab wedge 6 can then be slid from the end of the pipe.

Once the grab wedge 6 has been removed from the pipe, it is retained within the tool 16, as shown in Figure 7. The grab wedge 6 can easily be removed from the tool 16 manually.

Figures 8 and 9 show views of an alternative removal tool 16 in accordance with the invention. In this embodiment, the jaws 38,40 have arcuate inner surfaces and ribs 32 substantially the same as those of the tool 16 of Figures 5 to 7. However, in this case the jaws are only joined together by a single hinge 52 and each of them extends radially into a flange 53, in a somewhat triangular fashion, away from the ribs 32. The generally triangular configuration of the flanges 53 leads to an overall generally diamond-shaped configuration for the tool 16, with each of the sides of the diamond being provided with ribbed finger grips 54.

The tool 16 is again moulded from polypropylene, to provide suitable resilience for the hinge 52. Figure 9 shows that the tool 16 is effectively hollowed-out, so as to reduce the amount of material required for its moulding. The hollowed out regions are provided with strengthening ribs 56.

In use, the tool 16 is merely opened out about the hinge 52 and located about the pipe, with the ribs 32 addressing the slots 11 in the manner described above. The tool is then employed in substantially the same manner, using the flanges 53 for leverage.

Although the present invention has been described above with reference to pushfit pipe couplings, its circumferential demounting technique can be employed in a wide variety of other situations. These can include various other types of couplings, for example, all of which fall within the scope of the invention. Even within the scope of push-fit fittings a large variety of variations and modifications are possible. For example, with appropriate adaptation of the fitting body, the invention could be applied in a unitary fitting in which there is no removable cap.

It should be understood that the overall configuration of the fitting is not important, as long as the general socket characteristics are present. For example, the invention can be employed in a range of typical fittings which might include a straight coupler, an elbow and a tee amongst many others. The various components can also be formed from a range of materials other than those described.

Many further modifications and variations will suggest themselves to those versed in the art upon reference to the foregoing illustrative embodiments, which are given by way of example only and which are not intended to limit the scope of the invention, that being determined by the appended claims.

Claims

CLAIMS: 1. A pipe fitting system comprising a fitting for coupling to a pipe and a tool for releasing the pipe from engagement with at least part of the fitting; wherein the fitting comprises a socket for receiving the pipe; a seal adapted to be located within the socket for sealing between the pipe and the fitting; and gripping means adapted to be located within the socket for retaining the pipe within the socket; wherein the gripping means can at least partially surround the pipe when the pipe is located within the socket and comprises at least two axially extending and generally circumferentially facing, opposed bearing surfaces; and the tool comprises a tool body, upon which is provided a member for insertion between the said bearing surfaces and for urging the said bearing surfaces apart by acting upon them in a generally circumferential direction when the tool is moved towards the said gripping means in a direction generally parallel to the axis of the pipe.
2. A pipe fitting system according to Claim 1 ; wherein the gripping means comprises four or more said bearing surfaces, the said bearing surfaces being arranged in pairs with the respective bearing surfaces of each pair being in mutual circumferential opposition, and the tool comprises a plurality of the said members, the circumferential locations of the said members corresponding to the circumferential locations of the said pairs of bearing surfaces.
3. A pipe fitting system according to Claim 1 or 2, wherein the said gripping means is defined by a collet comprising a plurality of axially extending fingers, each of the said fingers comprising at least one flank surface, the said flank surfaces defining the said bearing surfaces.
4. A pipe fitting system according to Claim 3, wherein the mouth of the socket comprises an internal first camming surface that is generally frustoconical and increases in diameter from an axially outer position to an axially inner position; and relatively axially outer tips of the fingers of the gripping means each comprise a respective second camming surface on a radially outer portion thereof, such that axial movement of the gripping means in an axially outward direction within the socket causes the second camming surfaces to cam against the first camming surface, causing contraction of the gripping means and enhancing its grip on the pipe, whilst the said action of the tool members upon the bearing surfaces reverses the said contraction, thereby allowing axial movement in a direction opposite to that which caused the contraction.
5. A pipe fitting system according to any preceding claim, wherein the or each member takes the form of an axially extending, radially projecting rib.
6. A pipe fitting system according to Claim 5, wherein the or each rib comprises an arcuate axial end surface.
7. A pipe fitting system according to Claim 5 or 6, wherein the or each rib has a circumferential thickness which tapers positively from an axial tip region thereof to an axially intermediate region thereof.
8. A pipe fitting system according to any preceding claim, wherein mutually opposed ones of the said bearing surfaces are inclined at an angle of substantially 11 with respect to each other in the circumferential direction.
9. A pipe fitting for coupling to a pipe; the said fitting comprising a socket for receiving the pipe, a seal adapted to be located within the socket for sealing between the pipe and the fitting, and gripping means adapted to be located within the socket for retaining the pipe within the socket; wherein the gripping means comprises a collet adapted to surround the pipe when the pipe is located within the socket, which collet comprises at least two axially extending and generally circumferentially facing opposed bearing surfaces adapted to be urged apart to cause release of the gripping means from the pipe upon the axial insertion of a removal tool therebetween; the regions of the collet defining and immediately inside of its pipe-receiving mouth having sides substantially parallel to the axis of the collet.
10. A pipe fitting according to Claim 9, wherein the collet comprises a plurality of axially extending fingers, each of the said fingers comprising at least one flank surface, and the said flank surfaces defining the said bearing surfaces.
11. A pipe fitting according to Claim 10, wherein the mouth of the socket comprises an internal first camming surface that is generally frustoconical and increases in diameter from an axially outer position to an axially inner position, and the fingers of the gripping means each comprise a respective second camming surface on a radially outer portion thereof ; such that axial movement of the gripping means in an axially outward direction within the socket causes the second camming surfaces to cam against the first camming surface, causing contraction of the gripping means and enhancing its grip on the pipe.
12. A pipe fitting according to any one of Claims 9 to 11, wherein mutually opposed ones of the said bearing surfaces are inclined at an angle of substantially I 10 with respect to each other in the circumferential direction.
13. A removal tool for use in removing at least a gripping means of a pipe fitting from engagement with a pipe ; the said tool comprising a tool body upon which is provided a member for insertion between circumferentially facing, opposed bearing surfaces of the gripping means for urging them apart by acting upon them in a generally circumferential direction when the tool is moved towards the said gripping means in a direction generally parallel to the longitudinal axis of the pipe.
14. A removal tool according to Claim 13, comprising a plurality of said members arranged upon the tool body at predetermined circumferential intervals.
15. A removal tool according to Claim 14, wherein the said tool body is defined by a pair of hinged jaws adapted to at least partly encircle the pipe with at least one said member projecting generally radially inwardly from each said jaw.
16. A removal tool according to Claim 15, wherein the jaws are hinged together at respective first adjacent ends thereof by a single hinge element and may be opened apart around the said hinge element to permit the pipe to enter between the said jaws via a gap between second, opposite ends of the jaws.
17. A removal tool according to Claim 16, wherein'the jaws each define a respective flange which may be gripped to effect axial movement of the tool along a length of the pipe.
18. A removal tool according to Claim 15, wherein the jaws are resiliently connected together at respective first adjacent ends thereof by a first hinge element and resiliently connected together at respective second adjacent ends thereof by a second hinge element, the said arrangement being such as to cause the jaws to move away from each other upon opening up one or both of the hinge elements.
19. A removal tool according to Claim 18, wherein each hinge element is provided with a grip, the said grips being mutually opposed such that squeezing the two grips together causes simultaneous opening-up of the two hinge elements, thereby urging the two jaws apart.
20. A removal tool according to any one of Claims 13 to 19, wherein the or each member takes the form of an axially extending, radially projecting rib.
21. A removal tool according to Claim 20, wherein the or each rib comprises an arcuate axial end surface.
22. A removal tool according to Claim 20 or 21, wherein the or each rib has a circumferential thickness which tapers positively from an axial tip region thereof to an axially intermediate region thereof.
23. A removal tool according to any one of Claims 13 to 22, wherein the tool is formed integrally from a plastics material.
24. A removal tool according to Claim 23, wherein the plastics material is polypropylene.
25. A pipe fitting system substantially as hereinbefore described with reference to Figures 3 to 7; or Figures 3,4, 8 and 9 of the accompanying drawings.
26. A pipe fitting substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.
27. A removal tool substantially as hereinbefore described with reference to Figures 5 to 7; or Figures 8 and 9 of the accompanying drawings.