GB1595692A - Socket end pipes - Google Patents

Description

(54) SOCKET END PIPES (71) We, THE HEPWORTH IRON COMPANY LIMITED, of Haitlehead, Stocksbridge, Sheffield, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- 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-bre, asbestos cent, or concree, such as are used h severs, 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 joiined, on site.

According to the invention, a plastics sleeve is injeChon moulded onto and projects from the end of a pipe (n general a pipe of other than plastics material, for example, day, asbestos, concrete or pitch-fibre), thereby form- ing a coupling socket.

The plastics sleeve is injection moulded directly onto the pipe end, with the surface of the latter forming part af the wall of the injection moulding cavity. A two-step injection moulting technique, for example, as described in our British Patent Specifications Nas. 1,477,074 and 134936/76 (Serial No.

1,572,099), 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.

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/ar an adhesive or chemical bend.

The sealing ring or rings can be of anv suitable deformable sealing material. The ring can be an internal projection integral with the sleeve itself and sufficiently thin to provide the necessary Hexibiity. Preferably, however, it is a ring of different iriaterial softer than the sleeve. It oan be plastioally deform- able, but is preferably resilient so as to mam- tan 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 af 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 pilpe and with a plastics sleeve or socket moulded thereon.

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 matriàl, 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 diarneter as the pipe 25 (or if desired a pipe af different diameter, the dimensions of the socket being selected accordingly). In the illustrated ex ample, the coupling socket has an optional end flange or rib 27 to hold a snap-on retain- ing ring for retaining a sealing ning at the end of the socket. The socket is mechanically keyed to the pipe by being moulded into a aircun,fential groove 28 in the external surface of the pipe. A primer or adhesive may Ibe 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 injection 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 plipe 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 surf aces abutting against a frustoconical surface of the ring 33 to provide mechanical support for the cuff; the other oblique surface of the cuff lies against a frusto-conqical surface of the cavity block 29 during moulding. Means may be 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 3 and away from this position. Alter- natively, the assembly 32 can be stationary, the pipe being inserted and nemoved by other means.

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 coonponents 37 to 40 are made of metal. A fruste-conical rubber seal 42 overlies the frusto-conical surface of the member 40 and is held in position by a lip 43 trapped in a circuinferential 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 oore 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 plastics 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.

It has been found that the plastics sleeve is so firmly retained in this way, that the appli cation 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, ar isolated recesses in the pipe surface rather than a con- tinuous peripheral groove.

The coupling socket thus formed on the pipe can be provided with one or more in ternal resilient sealing rings for exampLe as shown in broken lines at 45 in Figure 4.

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 tech niques analogous to that described above with reference to Figure 2, or in the abovementioned earlier patent applications. More specifically, the core assembly 31 can inolllde a periplieral 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 3 so that the moulding cavity 44 is partly defined by the exposed external surface of the sealing ring candied by the core assembly, the plastics material being injected into the moulding cavity so as to make contact sbul- taneously with the sealing ring and the pipe end. The sealing ring can be af therwnopllastic or thermosetting elastomer.

After moulding the cavity block is oplened 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 our British Patent Appl!ication No. 13936/76 (Serial No.

1,572,099). However, in the case of pipes of relatively small diameter, for example 4 inches (100 mm) the plastics socket and sealing ring aran, 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 patent application 13936/76 (Serial No. 1,572,099) with a grove 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 crosszsection 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).

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 manorial 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 nibs, of rectangular oross-section with a thickness in the circunaferential direction of 0.55 to 0.70 inch (14 to 18 mm).

WHAT WE CLAIM 1S:- 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.

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

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 of a pnsner.

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

7. The combination claimed in any preced ing claim in which the sleeve has a plurality of longitudinal internal integral ribs.

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

9. The aombinaleion claimed in any preced- ing claim wherein the said sealing ring con- sists of elastomeric material bonded directly to the plastics sleeve.

10. The combination claimed in claim 8 or 9 having 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 triangular cross sec tion 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.

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 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, and injection moulding plastics material in the moulding oavity bounded by the cavity block, the core, and the said end region of the pipe length thereby forming a plastics sleeve penmanently secured to and projecting from the pipe end to constitute a coupling socket.

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 mechanlical keying for the plastics sleeve.

15. A method as claimed in claim 13, in which the external surface of the pipe length in the said end region has a aircumferential 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 surface of the said end region before the injection moulding is carried out.

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 mat- erial is moulded, one said material being moulded onto the previously moulded other said material.

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 ning and the said end region of the pipe length in a second injection moulding step.

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 socket, substantially as herein described with reference to Figure 1 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (20)

**WARNING** start of CLMS field may overlap end of DESC **. A preferred crosszsection 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). 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 manorial 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 nibs, of rectangular oross-section with a thickness in the circunaferential direction of 0.55 to 0.70 inch (14 to 18 mm). WHAT WE CLAIM 1S:-

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.

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

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 of a pnsner.

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

7. The combination claimed in any preced ing claim in which the sleeve has a plurality of longitudinal internal integral ribs.

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

9. The aombinaleion claimed in any preced- ing claim wherein the said sealing ring con- sists of elastomeric material bonded directly to the plastics sleeve.

10. The combination claimed in claim 8 or 9 having 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 triangular cross sec tion 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.

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 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, and injection moulding plastics material in the moulding oavity bounded by the cavity block, the core, and the said end region of the pipe length thereby forming a plastics sleeve penmanently secured to and projecting from the pipe end to constitute a coupling socket.

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 mechanlical keying for the plastics sleeve.

15. A method as claimed in claim 13, in which the external surface of the pipe length in the said end region has a aircumferential 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 surface of the said end region before the injection moulding is carried out.

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 mat- erial is moulded, one said material being moulded onto the previously moulded other said material.

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 ning and the said end region of the pipe length in a second injection moulding step.

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 socket, substantially as herein described with reference to Figure 1 of the accompanying drawings.