IE46200B1 - Improvements in socket end pipes - Google Patents

Description

This invention relates to pipes with socket ends· for coupling together pipes. The invention is applicable to the coupling of pipes made of glazed or unglazed clay, pitch-fibre, asbestos cement, or concrete, .such as are used in sewers, drains, or cable conduit.

A considerable inconvenience of the known coupling sleeves for clay and similar pipes is that the coupling . sleeves are separate articles which have to be fitted to the two pipes to be joined, on site.

According to the invention, a plastics sleeve is injection moulded onto and projects from the end of a pipe(in general a pipe of other than plastics material, for example, clay, asbestos, concrete or pitch-fibre), thereby forming a coupling socket.

The plastics sleeve is injection moulded directly onto the pipe end, with the surface of the latter forming part of the wall of the injection moulding cavity. A twostep injection moulding technique, for example, as described in Patent Specification No. 42251 and 44666 , can be used to form a plastics coupling sleeve directly bonded to the pipe and optionally provided with one or more sealing rings.

If a sealing ring is provided in the plastics sleeve, the ring can be injection moulded onto the sleeve previously moulded onto the pipe end, or the sleeve can be injection moulded onto the previously moulded ring and the pipe end. - 2 4 6 20ο The plastics sleeve can be secured to the pipe end by a mechanical key (for example, by means of a groove or grooves in the external pipe surface) and/or an adhesive or chemical bond.

The sealing ring or rings can be of any suitable deformable sealing material. The ring can be an internal projection integral with the sleeve itself and sufficiently thin to provide the necessary flexibility. Preferably, however, it is a ring of different material softer than the sleeve. It can be plastically deformable, but is preferably resilient so as to maintain sealing pressure throughout the life of the joint formed with the aid of the coupling sleeve. Suitable materials include natural and synthetic rubber and other elastomers, in particular thermosetting and thermoplastic rubbers, and resilient plastics materials.

Suitable materials for the sleeve include polypropylene and polyethylene.

Embodiments of the invention are shown by way of example only in the accompanying drawings, in which: Figure 1 illustrates the manufacture of a pipe coupling sleeve or socket by moulding plastics material onto a pipe end; and Figure 2 is a longitudinal section of a pipe and with a plastics sleeve or socket moulded thereon. - 3 46200 Figures 1 and 2 show the end portion of a plain-ended pipe 25, made of clay, pitch-fibre, asbestos cement, or concrete. A plastics sleeve 26, shown in Figure 2, made of any suitable slightly resilient plastics material, e.g. polyethylene or polypropylene, typically 0.04 to 0,06 inches (1 to 1.5 mm) thick, is injection moulded onto the end region of the pipe, to form a coupling socket for receiving a plain pipe end of the same diameter as the pipe 25 (or if desired a pipe of different diameter, the dimensions of the socket being selected accordingly). In the illustrated example, the coupling socket has an optional end flange or rib 27 to hold a snap-on retaining ring for retaining a sealing ring at the end of the socket.

The socket is mechanically keyed to the pipe by being moulded into a circumferential groove 28 in the - 4 46200 external surface of the pipe. A primer or adhesive may be applied to the external surface of the end region of the pipe before the moulding operation, to improve the bonding of the moulded plastics material to the pipe.

The moulding is carried out in ejection moulding apparatus comprising a split cavity block 29 with at least one injection moulding nozzle 30 for the plastics material, a retractable core assembly 31, and a locating and sealing assembly 32 for the pipe 25- The assembly 32 includes a metal ring 33, made in several parts for ease of manufacture, and a flexible cuff 34 mounted in annular slots in the ring 33 by means of peripheral lips. 35.

The cuff is hollow and the ring 33 contains one or more passages (not shown) through which an air or liquid under pressure can be introduced into the internal space 36 of the cuff thereby to expand.the cuff into contact with the pipe 25 to grip and form a peripheral seal around the latter. The cross section of the cuff is a trapezium, with one of the oblique surfaces abutting against a frusto-conical surface of the ring 33 to provide mechanical support for the cuff; the other oblique surface of the cuff lies against a frusto-conical surface of the cavity block 29 during moulding. Means may he provided for moving the assembly 32 axially so that by gripping the pipe with the cuff and then moving the assembly 32, the pipe can be moved to the moulding position shown in Figure 1 and away from this position. Alternatively, the assembly 32 can I be stationary, the pipe being inserted and removed by other means. - 5 46900 The core assembly 31 includes a backing plate 37, a core sleeve 38, a guide block 39 in the latter, and a cone member 40 slidable in the member 39 and loaded away from the latter by one or more compression springs 41.

The components 37 to 40 are made of metal. A frustoconical rubber seal 42 overlies the frusto-conical surface of the member 40 and is held in position by a lip 43 trapped in a circumferential groove defined between the members 38 and 39. The rubber seal 42 abuts against and forms an end seal with the end of the pipe as shown in Figure 3· With the pipe 25 and core assembly 31 in abutment, and the cavity block 29 closed, they and the cuff 34 define a moulding cavity 44 in communication with the nozzle or nozzles 30· Polyethylene, polypropylene, or other suitable plastics material is now injected into the moulding cavity 44. This material enters the groove 28 to form a mechanical key with the pipe 25, and in addition may form a surface tension bond with the pipe surface, or an adhesive bond if an adhesive has been applied to the pipe before moulding. Depending on the roughness of the pipe surface, the plastics material may also penetrate into the surface region of the pipe.

With most plffifcics material, in particular those mentioned above, the plastics sleeve formed by the injection moulding will shrink after moulding, thereby providing a very firm mechanical bond between the plastics sleeve and the pipe 25. - 6 4G2U9 It has been found that the plastics sleeve Is so firmlyretained in this way, that the application of a primer or adhesive to improve the bonding of the plastics material to the pipe is in many cases unnecessary.

If desired, two or more grooves 28 may be provided.

Other mechanical keying means can be used, for example a shallow flange or shoulder on the pipe end, or isolated recesses in the pipe surface rather than a continuous peripheral groove.

The coupling socket thus formed on the pipe can be . provided with one or more internal resilient sealing rings for example as shown in broken lines at 45 in Figure 2. Such sealing rings can be fitted into the socket after moulding, being secured for example by a retaining ring snapped over the flange 27 and/or by an adhesive. However, a sealing ring or rings can be bonded directly to the moulded plastics sleeve using techniques analogous to that described in Patent Patent is a divisional No. 46199 of which this / , or in the above-mentioned earlier patent applications. More specifically, the core assembly 31 can Include a peripheral moulding groove In which the sealing ring Is injection moulded, preferably In a first moulding step following which the core assembly carrying the moulded sealing ring is moved to the position shown in Figure 1 so that the moulding cavity 44 is partly defined by the exposed external surface of the sealing ring carried by the core assembly, the plastics material being injected into the moulding cavity so as to make contact simultaneously with the sealing ring and the pipe end. The sealing ring can be of thermoplatic or thermosetting elastomer. - 7 46200 After moulding the cavity block is opened and the moulded plastics socket together with the sealing ring is stripped from the core, for example by the core passing through a stripping ring. In this connection, the core may have two axially separable parts which meet at the groove 14 and can be separated to facilitate separation of the sealing ring from the groove, as described in Patent Specification No. .44666 However, in the case of pipes of relatively small diameter, for example 4 inches (100· mm) the plastics socket and sealing ring can, with dimensions such as those given by way of example, be sufficiently flexible to be stripped from the core without widening of the groove in which the sealing ring is moulded, that is to say the core can be constructed more simply than in the above mentioned Specification No. 44666 » with a groove of invariable dimensions in a one-piece core.

Preferably, the cross-section of the sealing ring is such that the ring has a certain amount of flexibility as well as being resiliently deformable.

A preferred cross-section is basically an isosceles triangle, with the radially innermost apex radiused and the adjoining sides slightly concave. Typically the sealing ring has a radial height of 0.1 - 0.15 inch (2.5 - 3.8 mm). - 8 46ao The socket may have integrally moulded internal ribs 46 extending in the longitudinal direction of the sleeve and ending short of the sealing ring 3. These ribs help to centralise the inserted pipe end and in particular limit the extent to which the sealing ring can be compressed by the inserted pipe end e.g. if one pipe moves laterally. The ribs also facilitate moulding by distributing the plastics material in the mould. By way of example, in a socket with a diameter in the region of 4 to 4.5 inches (100 to 114 mm), there may be 48 ribs, of rectangular cross-section with a thickness in the circumferential direction of 0.55 to 0.70 inch (14 to 18 mm)

Claims (20)

CLAIMS:

1. In combination, a pipe length and a sleeve of plastics material injection moulded onto and projecting from the end of the pipe length to form a coupling socket. 5

2. The combination claimed in claim 1 in which the sleeve is mechanically keyed to the end of the pipe length.

3. The combination claimed in claim 2 in which the sleeve is mechanically keyed in a groove in the external surface of the pipe length. 10

4. The combination claimed in claim 1, 2 or 3 in which the sleeve is bonded to the external surface of the pipe length.

5. The combination claimed in claim 4 in which the sleeve is bonded to the said surface by an adhesive or a 15 primer.

6. The combination claimed in any preceding claim in which the sleeve consists of slightly resilient polyethylene or polypropylene.

7. The combination claimed in any preceding claim in 20 which the sleeve has a plurality of longitudinal internal I integral ribs.

8. The combination claimed in any of claims 1 to 6 further including an internal peripheral sealing ring of deformable material secured in the plastics sleeve at or adjacent to the end of the sleeve that projects from the 5 pipe length.

9. The combination claimed in any preceding claim wherein the said sealing ring consists of elastomeric material bonded directly to the plastics sleeve.

10. The combination claimed in claim 8 or 9 having 10 an injection-moulded sealing ring, the sleeve having been formed by injection moulding onto the sealing ring and the pipe length.

11. The combination claimed in any of claims 8 to 10 in which the internal sealing ring has a substantially 15 triangular cross section with concave faces.

12. A pipe length having a plastics coupling sleeve or socket secured on an end thereof, substantially as herein described with reference to Figure 2 of the accompanying drawings'. 20

13. A method of providing a pipe length with a coupling socket, in which an end region of the pipe length is disposed in an injection moulding cavity block and is engaged by external peripheral sealing means spaced from the pipe - 11 46200 end and by end sealing means sealing the pipe end, the cavity block having an internal surface radially spaced from the said end region and from a core coaxial with the pipe length and sealed thereto by the end sealing means, 5 and, injection-moulding plastics material in the moulding cavity bounded by the cavity block, the core, and the said end region of the pipe length thereby forming a plastics sleeve permanently secured to and projecting from the pipe end to constitute a coupling socket. 10

14. A method as claimed in claim 13, in which the external surface of the pipe length has in the said end region a shape providing mechanical keying for the plastics sleeve.

15. A method as claimed in claim 13, in which the 15 external surface of the pipe length in the said end region has a circumferential groove providing mechanical keying for the plastics sleeve.

16. A method as claimed in claim 13, 14 or 15 in which an adhesive or primer is applied to the external 20 surface of the said end region before the injection moulding is carried out. - 12 46200

17. A method as claimed in any of claims 13 to 16 in which in a separate injection moulding step a sealing ring of resilient material is moulded, one said material being moulded onto the previously moulded other said material. 5

18. A method as claimed in claim 17 in which the sealing ring is moulded on said core in a first injection moulding step, and the plastics material is moulded onto the sealing ring and the said end region of the pipe length in a second injection moulding step. 10

19. A method as claimed in any of claims 13 to 16 in which the plastics material is moulded onto a resilient sealing ring disposed on the core as well as onto the pipe end region.

20. A method of providing a pipe length with a coupling 15 socket, substantially as herein described with reference to Figure 1 of the accompanying drawings.