GB2100819A - Pipe joint for plastics pipes - Google Patents

Abstract

A pipe joint for coupling plastics pipes comprises a coupling sleeve 1, having a socket 13 arranged to receive a plastics pipe 4, a support sleeve 6 in the socket received internally of the pipe end, an annular retaining member 8 on the outer surface of the pipe end having a conical outer surface portion, and a retaining nut 11 engageable with an external thread 10 on the coupling sleeve and having a conical internal surface portion 12 engageable with the conical outer surface portion of the retaining member in order to apply (1) radial inward load on the retaining member to hold the pipe between the retaining member and the support sleeve, and (2) axial load in a direction inwardly of the socket to resist withdrawal of the pipe end. At least part of the outer surface of the support sleeve is wave-shaped and the retaining member is complementarily shaped. <IMAGE>

Description

SPECIFICATION Pipe joint for plastics pipes This invention relates to a pipe joint for use in coupling a plastics pipe thereto and comprising a coupling sleeve having a socket arranged to receive one end of a plastics pipe, an internal support sleeve arranged in the socket to be received internally of the pipe end when the latter is received by the socket, an annular retaining member arranged to fit on the outer surface of the pipe end, and a retaining nut engageable with an external thread on the coupling sleeve and also engaging with the annular retaining member so that the latter clamps the pipe end in the socket on the internal support sleeve.

Pipe joints of the above type are known, for example by the type of screwed pipe joints made by the firm E.P.B. Prandelli, or from German Utility Model 1949499, in which a plastics pipe is retained axially by means of saw-tooth like recesses arranged in the support sleeve. Pointed notches are thereby produced in the pipe end which, in the event of increase in tension in the pipe following a temperature change, can result in tearing-out of material from the pipe end, or other damage.

There is also the disadvantage with the known screwed pipe joints that, when the retaining nut is tightened, the annular retaining member is also able to turn at the same time, so that a twisting action can be applied to the pipe end, thereby providing additional torsional loading to the pipe.

The present invention has been developed primarily, though not exclusively, with a view to improving the construction of the known pipe joints, so as to obtain a pipe joint which can remain sealed even in the event of changes in temperature, and which also provides reliable retention in position of the pipe end for its required lite, without any tearing damage being created in the pipe end. In addition, during assembly of the pipe joint, no twisting action should be applied to the pipe end.

According to the invention there is provided a pipe joint for use in coupling a plastics pipe thereto and comprising a coupling sleeve having a socket arranged to receive one end of a plastics pipe, an internal support sleeve arranged in the socket to be received internally of the pipe end when the latter is received by the socket, an annular retaining member arranged to fit on the outer surface of the pipe end and having a conical outer surface portion, and a retaining nut engageable with an external thread on the coupling sleeve and having a conical internal surface portion which is engageable with the conical outer surface portion of the retaining member in order (1) to apply radial inward load on the retaining member so as to hold the pipe end between the retaining member and the internal support sleeve, and (2) to apply an axial load to the retaining member in a direction inwardly of the socket thereby to resist axial withdrawal of the pipe end from the socket, in which: at least part of the outer surface of the internal support sleeve is wave-shaped, as seen in longitudinal section, and at least part of the inner surface of the retaining member is complementarily wave-shaped; and the retaining member is moveable axially into the socket by the retaining nut into a position of locked engagement with the socket which opposes relative rotation between the retaining member and the socket.

The wave-shaped design of the internal support sleeve, and of the annular retaining member, shapes the end of the plastics pipe without formation of any harmful notches, i.e. localised high stress regions, and also retains the pipe end in position against axial withdrawal. The locked engagement which can be achieved between the retaining member and the socket opposes relative rotation between the retaining member and the socket, so as to ensure that no torsional affect is applied to the pipe end when the retaining nut is tightened on the thread on the coupling sleeve.

One embodiment of pipe joint according to the invention will now be described in detail, by way of example only, with the reference to the accompanying drawing in which:~ Figure 1 is a longitudinal sectional view of a pipe joint according to the invention, with a plastics pipe end received therein; Figure 2 is a sectional view taken on the line Il-Il in Figure 1; and Figure 3 is an enlarged detailed view of the cross section shown in Figure 2.

Referring now to the drawings, there is shown a pipe joint for use in coupling a plastics pipe thereto and comprising a coupling sleeve in the form of a connecting nipple 1 which can be connected, by means of an internal thread 2, to a pipe fitting, armature, or pipe end with an outer thread. The connecting nipple 1 has a socket arranged to receive one end of a plastics pipe 4, the socket being formed by a recess 3 which provides a centering means for the pipe 4, and also forms an annular shoulder 5 which serves as an abutment stop for the end of the pipe 4.

An internal support sleeve 6 is arranged in the socket to be received internally of the pipe end 4 when the latter is received by the socket. The support sleeve 6 is centered at one end in a recess 7 of the socket in the connecting nipple 1, and preferably the sleeve 6 is rigidly connected to the connecting nipple 1 ,for example by soldering, or the use of adhesives. Advantageously, the connecting nipple 1 and the support sleeve 6 are manufactured in one piece.

The outer surface of the support sleeve 6 is of a wave-shaped design, as seen in longitudinal section, so that it is composed of alternate arcuate bulges and recesses. An annular retaining member or collet 8 is arranged to fit on the outer surface of the pipe end, and has a conical outer surface portion to be engaged by a retaining nut 11, and has at least part of its inner surface formed with a wave-shape which is complementary to the wave shape of the support sleeve 6. The retaining member 8 is generally annular, and has at least one radially extending slot 9.

The retaining nut 11 is engageable with an external thread 10 on the connecting nipple 1, and has a conical internal surface portion 12 which engages with the conical outer surface portion of the retaining member 8 in order to apply radial inward load on the retaining member so as to hold the pipe end between the retaining member 8 and the internal support sleeve 6. In addition, the retaining nut 11 applies, via the engaging conical surfaces, an axial load to the retaining member 8 in a direction inwardly of the socket, whereby the pipe joint, when assembled, resists axial withdrawal of the pipe end from the socket.

The plastics pipe 4 is either pre-formed, at its end, with a wave shape corresponding to the external wave shape on the support sleeve 6 and the internal wave shape on the annular retaining member 8, or is resiliently deformable so as to adopt this wave shape upon assembly of the pipe joint. The wave shaping provided on the end of the plastics pipe 4 serves to retain the pipe against axial displacement, either further inwardly of the socket, or in a withdrawal direction. An annular seal 14, preferably in the form of a circular rubber seal or O-ring, is arranged in a recess 13 in the socket of the connecting nipple 1, and this seal undergoes compression as the annular retaining member 8 enters the socket, so as to provide a sealed connection of the pipe in the pipe joint.

As indicated above, the annular retaining member 8 is moved axially into the socket by the retaining nut 11, and the arrangement is such that the retaining member can move into a position of locked engagement with the socket which opposes relative rotation between the retaining member 8 and the socket. This locked engagement is provided by pointed peaks and notches arranged on the interengaging surfaces of the retaining member and the socket. Thus, the recess 13 is provided, at its open end of the outer periphery, with pointed peaks 16 and notches 17 distributed throughout its periphery.When the retaining member 8 is pushed axially into the socket, a cylindrical projecting portion 18 of the member 8 is moved into locking engagement with the peaks 1 6 and notches 1 7, thereby forming notches 19 in the retaining member 8 which forms a positive twist-locking coupling 15 with the peaks 16 and notches 17 of the connecting nipple 1.

As the retaining nut 1 1 is tightened on the thread 10, the retaining member 8 can only be moved axially and cannot be twisted, so that no torsional effect can be applied to the pipe 4, when the latter is receiving radial loading between the internal surface of member 8 and the external surface of support sleeve 6. Additional torsional loading of the pipe 4 is thereby avoided.

The annular retaining member is made of a material having a low co-efficient of friction with the retaining nut 11, and preferably is made of a plastics material having a low friction coefficient.

Polyacetal material has been shown to be particularly suitable material. The retaining nut 11 and the connecting nipple 1 are preferably made of metal, although these parts can also be made of a plastics material, such as polyvinyl chloride, for example. The support sleeve 6 is either made of the same material as the connecting nipple 1 (when they are formed in one piece), or if the nipple 1 is a separate part made of metal, the sleeve 6 is preferably made of brass or stainless steel.

Claims (9)

1. A pipe joint for use in coupling a plastics pipe thereto and comprising a coupling sleeve having a socket arranged to receive one end of a plastics pipe, an internal support sleeve arranged in the socket to be received internally of the pipe end when the latter is received by the socket, an annular retaining member arranged to fit on the outer surface of the pipe end and having a conical outer surface portion, and a retaining nut engageable with an external thread on the coupling sleeve and having a conical internal surface portion which is engageable with the conical outer surface portion of the retaining member in order (1) to apply radial inward load on the retaining member so as to hold the pipe end between the retaining member and the internal support sleeve, and (2) to apply an axial load to the retaining member in a direction inwardly of the socket thereby to resist axial withdrawal of the pipe end from the socket, in which: at least part of the outer surface of the internal support sleeve is wave-shaped, as seen in longitudinal section, and at least part of the inner surface of the retaining member is complementarily wave-shaped; and the retaining member is moveable axially into the socket by the retaining member into a position of locked engagement with the socket which opposes relative rotation between the retaining member and the socket.

2. A pipe joint according to claim 1, in which the locked engagement between the retaining member and the socket is provided by pointed peaks and notches arranged on the interengaging surfaces of the retaining member and the socket.

3. A pipe joint according to claim 2, in which the peaks and notches are arranged on the interengaging surface of the socket.

4. A pipe joint according to any one of the preceding claims, in which an annular seal is arranged in the socket so as to be compressed by the retaining member as the latter moves axially into the socket.

5. A pipe joint according to any one of the preceding claims, in which the retaining member is made of plastics material and comprises a generally annular member having at least one radially extending slot.

6. A pipe joint according to claim 5, in which the retaining member is made of polyacetal.

7. A pipe joint according to any one of the preceding claims, in which the internal support sleeve is formed in one piece with the coupling sleeve.

8. A pipe joint according to any one of claims 1 to 6, in which the internal support sleeve is arranged centrally in an annular recess formed in the socket.

9. A pipe joint according to claim 1 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawing.