CA1112261A - Coupling pipes - Google Patents
Coupling pipesInfo
- Publication number
- CA1112261A CA1112261A CA363,020A CA363020A CA1112261A CA 1112261 A CA1112261 A CA 1112261A CA 363020 A CA363020 A CA 363020A CA 1112261 A CA1112261 A CA 1112261A
- Authority
- CA
- Canada
- Prior art keywords
- pipe length
- pipe
- sleeve
- sealing ring
- moulded
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
ABSTRACT
A clay or similar pipe has at one end a plastics coupling socket moulded directly onto the pipe end, with an elastomeric sealing ring in the socket. A technique for integrally moulding the sealing ring and socket member onto the pipe end is disclosed.
A clay or similar pipe has at one end a plastics coupling socket moulded directly onto the pipe end, with an elastomeric sealing ring in the socket. A technique for integrally moulding the sealing ring and socket member onto the pipe end is disclosed.
Description
This invention relates to pipes with socket ends for coupling together pipes. The in~ention 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 generala~pipe of other than plas-tics 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
two step injection moulding technique, for example 3 as described in our British Patent Specification 20 No. 1477074 and German Published Speci~ications DOS 26 033g3 and 27 15525, can be used to form a plastics coupling sleeve directly bonded to the pipe and provided wi-th one or more sealing rings.
The sealing ring provided in the plastics slee~e can be injection moulded onto the sleeve prevlously moulded onto the pipe end, or the sleeve can be injection moulded onto the previously moulded ring and the pipe end.
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The plastics sleeve can be secured to the pipe end by a mechanical key (for example, by means o~ a groove or grooves in the external pipe surface) and/or an adhesive or chemical ~ond.
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. Prefera~ly, 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 illustr~tes 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 end with a plastics sleeve or socket moulded thereon.
.
Figures 1 and 2 show the end portion o~ a plain-ended pipe 25, made of clay, pitch-~ibre, 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 10 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 9 the coupling socket has an optional end flange or rib 27 to hold a snap-on retaining ring for retai~ing a sealing ring at the end o~ the socket.
The socket is mechanically keyed to the pipe by being moulded into a circumferential groove 28 in the .
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ext~rnal surface of -the pipe. A prirner or adhes~ve may be applied to the external surface of ~he end region of the pipe before the m~ulding operation, -to improve the bonding of the moulded plastics material to the plpe.
The moulding is carried out in *aection rnoulding apparatus comprising a split cavity block 29 with at least one injection moulding noz~le ~0 for ~he plas~ics material, a retractable core assembly 31, and a locating and sealing assembly ~2 for the pipe 25. The assembly ~2 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 ~5.
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 plpe 25 to grip and f orm 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 mech~nical suppor-t for the cuff; the other oblique surface of the cuff lies against a frusto conical surface o the cavity block 29 during moulding. Means may be provided for moving the assembly ~2 axially so that by gripping ~he pipe with the cuff and then moving the assembly 32, the pipe can be moved to the moulding position sho~ in F~gure 1 and away from this position. Alternati~ely, the assembly 32 can be stationary, the pipe bein~ inserted and rernoved by other means.
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The core assembly ~1 includes a b~cking pla-~,e 37, a core ~leeve 38, a guide block 39 ~n the latter, an~ a cone member 40 slidable in the member 39 and loaded a~ay from the latter by one or rnore compress~on ~pr~ngs 41.
The components ~7 to 40 are made of metal. A frusto-conical rubber seal 42 overlies the frusto-conical surface o t~e member 40 and is held in position by a lip 43 trapped in a circumferential groove def~ned be~leen the ~lembers 38 and 39. The rubber seal 42 abuts agalnst and forms an end seal with the end of the pipe as shown in Figure 1.
With the pipe 2~ and core assem~ly 31 ln abutment, and the cavity block 29 closed9 they and the cuff ~4 define a moulding cavity 44 in communication with the nozzle or nozzles ~0~
15 . Polyethylene, polypropylene, or other sultable plast~cs material is now injected into the moulding cavity 44. This material enters the groove 28 to form a mechanica7 key with the pipe 25, and in addition may form a surface tension bond with the pipe surface, or an adhesi~e bond lf an adhesive has been applied to the p~pe before moulding. Depending on the roughness o~ the pipe surface, the plastics material may also penetrate into the surface region of the pipe.
With most pla~ics material, in particular those mentioned above, the piastics sleeve formed by the injection moulding will shrink after moulding, thereby providing a very firm mechanical bond between the pla~tics sleeve and the pipe 25.
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It has been found that the plastics sLeeve is so ri rmly retained 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 above with reference to Figure 2 of co-pending application No. 296,238 filed February 3, 1978 from which this application is a divisional application 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 l 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 thermoplastic or thermosetting elastomer.
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After moulding the cavity block is opened and the moulded plastics socke-t 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 ~rom the groove, as described in our German Patent Specification DOS 27 15525.
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 wideni~g of the groove in which the sealing ring is moulded, that is to say the core can be constructed more simply than in the abo~e mentioned patent specification, 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 flexibillty a~ well as being resiliently deformable.
A preferred cross-section is basically an isosceles triangle, with the radially innermost apex radiused and the ad~oining sides slightly concave. Typically the sealing ring has a radial height of 0.1 - 0.15 inch (2.5 - 3.8 mm)-`: .
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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 generala~pipe of other than plas-tics 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
two step injection moulding technique, for example 3 as described in our British Patent Specification 20 No. 1477074 and German Published Speci~ications DOS 26 033g3 and 27 15525, can be used to form a plastics coupling sleeve directly bonded to the pipe and provided wi-th one or more sealing rings.
The sealing ring provided in the plastics slee~e can be injection moulded onto the sleeve prevlously moulded onto the pipe end, or the sleeve can be injection moulded onto the previously moulded ring and the pipe end.
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The plastics sleeve can be secured to the pipe end by a mechanical key (for example, by means o~ a groove or grooves in the external pipe surface) and/or an adhesive or chemical ~ond.
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. Prefera~ly, 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 illustr~tes 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 end with a plastics sleeve or socket moulded thereon.
.
Figures 1 and 2 show the end portion o~ a plain-ended pipe 25, made of clay, pitch-~ibre, 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 10 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 9 the coupling socket has an optional end flange or rib 27 to hold a snap-on retaining ring for retai~ing a sealing ring at the end o~ the socket.
The socket is mechanically keyed to the pipe by being moulded into a circumferential groove 28 in the .
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L
ext~rnal surface of -the pipe. A prirner or adhes~ve may be applied to the external surface of ~he end region of the pipe before the m~ulding operation, -to improve the bonding of the moulded plastics material to the plpe.
The moulding is carried out in *aection rnoulding apparatus comprising a split cavity block 29 with at least one injection moulding noz~le ~0 for ~he plas~ics material, a retractable core assembly 31, and a locating and sealing assembly ~2 for the pipe 25. The assembly ~2 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 ~5.
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 plpe 25 to grip and f orm 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 mech~nical suppor-t for the cuff; the other oblique surface of the cuff lies against a frusto conical surface o the cavity block 29 during moulding. Means may be provided for moving the assembly ~2 axially so that by gripping ~he pipe with the cuff and then moving the assembly 32, the pipe can be moved to the moulding position sho~ in F~gure 1 and away from this position. Alternati~ely, the assembly 32 can be stationary, the pipe bein~ inserted and rernoved by other means.
i.
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The core assembly ~1 includes a b~cking pla-~,e 37, a core ~leeve 38, a guide block 39 ~n the latter, an~ a cone member 40 slidable in the member 39 and loaded a~ay from the latter by one or rnore compress~on ~pr~ngs 41.
The components ~7 to 40 are made of metal. A frusto-conical rubber seal 42 overlies the frusto-conical surface o t~e member 40 and is held in position by a lip 43 trapped in a circumferential groove def~ned be~leen the ~lembers 38 and 39. The rubber seal 42 abuts agalnst and forms an end seal with the end of the pipe as shown in Figure 1.
With the pipe 2~ and core assem~ly 31 ln abutment, and the cavity block 29 closed9 they and the cuff ~4 define a moulding cavity 44 in communication with the nozzle or nozzles ~0~
15 . Polyethylene, polypropylene, or other sultable plast~cs material is now injected into the moulding cavity 44. This material enters the groove 28 to form a mechanica7 key with the pipe 25, and in addition may form a surface tension bond with the pipe surface, or an adhesi~e bond lf an adhesive has been applied to the p~pe before moulding. Depending on the roughness o~ the pipe surface, the plastics material may also penetrate into the surface region of the pipe.
With most pla~ics material, in particular those mentioned above, the piastics sleeve formed by the injection moulding will shrink after moulding, thereby providing a very firm mechanical bond between the pla~tics sleeve and the pipe 25.
.:
. .
- , .J2~ L
It has been found that the plastics sLeeve is so ri rmly retained 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 above with reference to Figure 2 of co-pending application No. 296,238 filed February 3, 1978 from which this application is a divisional application 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 l 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 thermoplastic or thermosetting elastomer.
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After moulding the cavity block is opened and the moulded plastics socke-t 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 ~rom the groove, as described in our German Patent Specification DOS 27 15525.
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 wideni~g of the groove in which the sealing ring is moulded, that is to say the core can be constructed more simply than in the abo~e mentioned patent specification, 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 flexibillty a~ well as being resiliently deformable.
A preferred cross-section is basically an isosceles triangle, with the radially innermost apex radiused and the ad~oining sides slightly concave. Typically the sealing ring has a radial height of 0.1 - 0.15 inch (2.5 - 3.8 mm)-`: .
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The socket may have integrally moulded internalribs 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 - 10 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 0055 to 0.70 inch (14 to I8 mm).
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The socket may have integrally moulded internalribs 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 - 10 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 0055 to 0.70 inch (14 to I8 mm).
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Claims (13)
1. A pipe length having at an end thereof a socket adapted to receive a pipe spigot and to form a push-fit spigot-and-socket pipe joint, and wherein the said end of the said pipe length is substantially plain, and the socket consists of an open-ended unitary sleeve of injection-moulded plastics material having a first end region disposed about and mould-bonded to said substantially plain end of said pipe length, and a second end region projecting from said end for receiving an inserted end of a second pipe length, and wherein an internal peripheral sealing ring of resiliently deformable material is secured to said second end region for making sealing engagement with a said inserted end of a second pipe length.
2. The pipe length claimed in claim 1 in which the sleeve is mechanically keyed to the end of the pipe length.
3. The pipe length claimed in claim 2 in which the sleeve is mechanically keyed in a groove in the external surface of the pipe length.
4. The pipe length claimed in claim 1, in which the sleeve is bonded to the external surface of the pipe length.
5, The pipe length claimed in claim 4, in which the sleeve is bonded to the said surface by at least one of an adhesive and a primer.
6. The pipe length claimed in claim 1, 2 or 4 having an injection-moulded sealing ring, the sleeve having been formed by injection moulding onto the sealing ring and the pipe length.
7. 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 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.
8. A method as claimed in claim 7, in which the external surface of the pipe length has in the said end region a shape providing mechanical keying for the plastics sleeve.
9. A method as claimed in claim 8, in which the external surface of the pipe length in the said end region has a circumferential groove providing said mechanical keying for the plastics sleeve.
10. A method as claimed in claim 7, 8 or 9 in which a bonding medium is applied to the external surface of the said end region before the injection moulding is carried out.
11. A method as claimed in claim 7, 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.
12. A method as claimed in claim 11 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.
13. A method as claimed in claim 7, 8 or 9 in which the plastics material is moulded onto a resilient sealing ring disposed on the core as well as onto the pipe end region.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA363,020A CA1112261A (en) | 1977-02-04 | 1980-10-22 | Coupling pipes |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB4727/77A GB1595225A (en) | 1977-02-04 | 1977-02-04 | Coupling pipes |
| GB4727/77 | 1977-02-04 | ||
| CA296,238A CA1101905A (en) | 1977-02-04 | 1978-02-03 | Coupling pipes |
| CA363,020A CA1112261A (en) | 1977-02-04 | 1980-10-22 | Coupling pipes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1112261A true CA1112261A (en) | 1981-11-10 |
Family
ID=27165488
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA363,020A Expired CA1112261A (en) | 1977-02-04 | 1980-10-22 | Coupling pipes |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1112261A (en) |
-
1980
- 1980-10-22 CA CA363,020A patent/CA1112261A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |