IE46199B1

IE46199B1 - Coupling pipes

Info

Publication number: IE46199B1
Application number: IE252/78A
Authority: IE
Original assignee: Hepworth Iron Co Ltd
Priority date: 1977-02-04
Filing date: 1978-02-06
Publication date: 1983-03-23
Also published as: JPH0150797B2; IE780252L; DE2804645A1; JPS629088A; FR2379747B1; AU515539B2; JPS53101116A; JPS6131351B2; AU3300378A; DE2804645C2; IT1107058B; IT7867229A0; GB1595225A; CA1101905A; ZA78440B; BE863650A; FR2379747A1

Abstract

A plastics pipe coupling sleeve has at one end an integral internal rib for engaging an external sealing ring or a pipe, and at the other end an internal resilient sealing ring for engaging a second pipe. The coupling is made by injection moulding the sealing ring then injection moulding the plastics sleeve in contact with the sealing ring. Also disclosed is a technique for moulding a plastics coupling socket directly onto an end of a pipe.

Description

This invention relates to arrangements for coupling together· pipes. The invention is applicable to the coupling of pipes made of plastics, glazed or unglazed clay, pitchfibre, asbestos cement, or concrete, such as are used in sewers, drains, or cable conduit.

British Patent Specification No.1,080,305 describes clay piping of the type push-fitted together comprising plain-end pipe-lengths of round cross-section with an endless peripheral strip of resilient material secured close to each end of each pipe length and sleeves of slightly resilient synthetic plastic material, each sleeve having integral internal peripheral ribs adapted to make sealing engagement with the peripheral strips of two adjacent pipe lengths.

The coupling sleeve in Specification No.1,080,305 is generally symmetrical. This is not always convenient, for example, if pipes of different types and/or materials are to be coupled, e.g. pipes which are completely plain at one end to permit cutting and jointing.

According to one aspect of the present invention, there is provided a plain-ended pipe length having adjacent to one end an external peripheral groove containing a peripheral strip of sealing material, and a sleeve of plastics material having a first end region provided with an integral internal peripheral rib at or adjacent to the end which rib makes sealing engagement with the sealing material, and a second - 2 46189 end region extending beyond the end of the pipe length and provided with an internal peripheral deformable sealing ring at or adjacent to the other end of the sleeve, to make sealing engagement with a second pipe length inserted into the projecting region of the sleeve.

The sleeve may be provided with a plurality of the said ribs and/or a plurality of sealing rings.

The rib or ribs are preferably of rectangular cross section.

The sealing ring or rings oan be of any suitable deformable sealing nlaterial. 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.

Preferably, the sealing ring or rings and the plastics sleeve are formed by a two-step integral injection moulding process, for example, as described in Patent Specification No. 42251. - 3 46199 ' The pipe coupling sleeve may be permanently secured to an end of a pipe, for example by any suitable adhesive.

Embodiments of the invention are shown by way of example only in the accompanying drawings, in which: Figure 1 is a longitudinal section of a pipe end and coupling sleeve embodying the invention, and an end of a further pipe to be coupled; and Figure 2 illustrates the manufacture of a coupling sleeve as shown in Fig. 1.

Fig. 1 shows in longitudinal section a coupling sleeve 1 of stepped profile, 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. Adjacent to the narrower end 7 is an integral internal peripheral rib 2, and adjacent to the wider end 8 is an internal sealing ring 3 of rubber or other resilient material secured to the plastics sleeve.

The narrower end is designed to receive an end of a pipe 6, for example of clayware, provided with an external peripheral sealing ring 4 of, for example, synthetic or natural rubber, rubberised bituminous mastic, or resilient plastics material, generally as described in British Patent Specification No. 1,080,305. This ring is received in a peripheral groove in the pipe surface.

The rib 2 is of rectangular cross-section and - 4 4619 typically has a radial height of about 0.050 to 0.070 inch (1.3 to 1.8 mm). It serves for locating as well as for sealing the pipe end by engaging the external sealing ring of the latter. It is to be understood that specific dimensions are given herein by way of example only and the invention is not limited to articles of such dimensions The other end of the coupling sleeve can receive a plain-ended pipe end 5 of any material, the sealing ring 3 making sealing engagement with the external peripheral surface of the inserted pipe end. This ring is secured to the plastics sleeve by a bond and/or mechanical keying, preferably by injection moulding the ring onto the freshly injection moulded plastics sleeve, or vice versa, for example, as described in the above15 mentioned patent* applications.

Preferably, as in the example illustrated, 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 3 has a radial height of 0.1 - 0.15 inch (2.5 - 3.8 mm). - 5 46199 The larger diameter portion of the sleeve has Integrally moulded internal ribs 9 extending in the longitudinal direction of the sleeve from the step 10 and ending short of the sealing ring 5. These ribs help to centralise the and inserted pipe end 5/in particular limit the extent to which the ring 3 can be compressed by the inserted pipe end e.g. if one pipe moves laterally. The ribs also facilitate moulding as explained below. By way of example, in a coupling with a diameter in the region of 4 to 4.5 inches (100 to 114 mm), there may be 48 ribs, of rectangular crosssection with a thickness in the circumferential direction of 0.55 to 0.70 inch (14 to 18 mm).

It will be seen that with a coupling sleeve of the kind described, it is no longer necessary that both of the pipe ends to be coupled should be provided with a sealing ring.

The coupling sleeve may be provided with an internal centring ring or centring projections (not shown).

It is not essential that the plastics sleeve should have a stepped profile; It can be a simple cylindrical 20 sleeve, or stepped in either direction to suit the diameters of the pipe ends to be coupled.

The sealing ring and plastics sleeve can be manufactured separately and fastened together for example by means of any suitable adhesive and/or a retaining ring. Preferably, however, the coupling sleeve is manufactured by a two-stage injection moulding process, in which one of the components is injection moulded first, and the other is then injection moulded directly onto the first-moulded component. - 6 46199 Figure 2 schematically illustrates means for manufacturing the coupling sleeve by first moulding the sealing ring 3 and then moulding the plastics sleeve onto the ring.

Figure 2 is in axial section, the apparatus being rotationally symmetrical about the axis 11.

Figure 2 shows a generally cylindrical core 12 of an injection moulding machine, the latter being provided with means for moving the core in the axial direction. The core has a circumferential groove 14 with a cross-section corresponding to the sealing ring 3. Between this groove and the end of the core, the external surface of the latter is stepped and provided with longitudinal slots 15 corresponding to the ribs 9 to be moulded on the plastics sleeve as shown in Figure 1.

Initially, the core is In the position shown at the left of Figure 2, in which the groove 14 is within a first split cavity block 16 provided with one or more injection moulding nozzles 17. The core and the cavity block 16 have conventional locking means 18 such that when the cavity block 16 is closed about the core, the injection nozzle Is or nozzles are aligned with the groove 14.

Rubber or other elastomeric material is then injected into the groove 14.

The cavity block 16 is then opened and the core Is moved axially to the position shown at 12a in Figure 2 in which its end face abuts the end of a second core 19 and both cores are within a second split cavity block 20.

The core 19 has a central axial injection nozzle 21 which »7 46199 communicates with a multiplicity of radial passages 22 formed by radial slots in the end face of the core 19 (and/or the core 12). These passages communicate with a generally tubular moulding cavity 23 which is defined by the internal surface of the cavity block 20 (which Is stepped to correspond to the external profile of the plastics sleeve), the external surface of the core 12 and the exposed external surface of the moulded sealing ring 3 which has been carried by the core into the second cavity block, and the external surface of the end region of the second core 19; this last includes peripheral rebates defining the portions of the moulding cavity corresponding to the rib 2 and the adjoining end part of the plastics sleeve. A peripheral groove 24 for moulding the rib 2 is thereby defined at the interface of the cores, and the radial passages 22 communicate with this groove. Alternatively, the groove 24 can be defined partly or wholly by a rebated portion of the end of the core 12.

Plastics material Is now injected through the nozzle and radial passages 22 into the cavity 23 where it contacts the exposed surface of the sealing ring and becomes bonded to the latter as described in the above mentioned patent applications. The slots 15 facilitate the flow of the plastics material to the regions of the moulding cavity remote from the passages 22. - 8 46199 The cavity block 20 is then opened and the core 12 is retracted, after which the moulded plastics sleeve together with the sealing ring is stripped from the core, for example by the core passing through a stripping ring mounted between the block 20 and the block 16. In this connection, the core 12 may have two axially sepa-able 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 Application No. 13936/76 (USSN 784314, DOS 2715525). However, the coupling sleeve shown in Figure 1 is particularly suitable for pipes of relatively small diameter, for example 4 inches (100 m^and the plastics sleeve and sealing ring can, with dimensions such as those given by way of example above, be sufficiently flexible to be stripped from the core without widening of the groove 14, that Is to say the core can be constructed more simply than in the above mentioned earlier patent application, with a groove of invariable dimensions in a one-piece core. Stripping is also facilitated by the fact that the rib 2 is moulded at the interface of the cores.

The cavity blocks 16 and 20 are shown as separate Components. Alternatively, a single cavity block may contain two axially spaced regions, the core 12 being disposed in a first such region for moulding of the sealing ring, and being thereafter moved, with the sealing ring, into the second region in which the second moulding cavity 23 is defined.

The particular construction of the cores and cavity block or blocks will depend on the materials to be moulded. The plastics sleeve will in general be a thermoplastic material, in particular polyethylene or polypropylene, but the rubber sealing ring may be either thermoplastic or thermosetting. To provide desired temperatures in the moulding cavities, the cavity blocks and/or cores may be provided with thermal insulation and/or heating means and/or cooling means in the regions of the moulding cavities.

A coupling sleeve as shown in Figure 1 can be permanently secured to the pipe end, for example by means of an adhesive.

Claims

CLAIMS:

1. A plain-ended pipe length having adjacent to one end an external peripheral groove containing a peripheral strip of sealing material, and a sleeve of plastics 5 material having a first end region provided with an integral internal peripheral rib at or adjacent +o the end which rib makes sealing engagement with the sealing material, and a second end region extending beyond the end of the pipe length and provided with an internal 10 peripheral deformable sealing ring at or adjacent to the other end of the sleeve, to make sealing'engagement with a second pipe length inserted into the projecting region of the sleeve.

2. A pipe length as claimed in claim 1 wherein the 15 said internal sealing ring consists of elastomeric material bonded directly to the plastics sleeve.

3. A pipe length as claimed in claim 2 having an injection-moulded, internal sealing ring and said plastics sleeve being injection-moulded onto the sealing 20 ring. A. A pipe length as claimed in claim 1, 2 or 3 in which the sleeve consists of slightly resilient polyethylene or polypropylene. - 11 46189

4. 5. A pipe length as claimed in claim 1, 2, 3 or 4, the rib being of rectangular cross section.

5. 6. A pipe length as claimed in any preceding claim in which the internal sealing ring has a substantially 5 triangular cross section with concave faces.

6. 7. A pipe length as claimed in any preceding claim in which the sleeve has a stepped internal profile defining a first end portion of smaller internal diameter and a second end portion of larger internal diameter. 10

7. 8. A pipe length as claimed in claim 7 in which the sleeve has a plurality of longitudinal internal integral ribs in the portion of greater internal diameter.

8. 9. A pipe length having a plastics coupling socket, substantially as herein described with reference to 15 Figure 1 of the accompanying drawings. - 12 46199

9. 10. A method of making a pipe length having a coupling socket, comprising providing a sleeve of plastics material which has an integral internal peripheral rib at or adjacent to one end, and has an internal peripheral deformable sealing 5 ring at or adjacent to its other end, and fitting the said one end of the sleeve onto an end of the pipe length having an external peripheral strip of sealing material, with the said internal rib making sealing engagement with the said sealing material and with the said other end projecting from the end of the pipe length for receiving an inserted second pipe length, the sealing ring being disposed to make sealing engagement with said second pipe length.

10. 11. A method as claimed in claim 10 which comprises 15 injection moulding an elastomeric material in an annular moulding cavity defined by a cavity block and a circumferential groove in a core, thereby forming the sealing ring, then effecting relative axial movement of the core and cavity block thereby disposing the core, 20 with the moulded ring still in the said groove, in a second cavity block or a second region of the first mentioned cavity block defining with the core and with the exposed surface of the sealing ring a second moulding cavity of tubular form, injection-moulding plastics. 25 material in the second cavity thereby forming the said sleeve bonded to the sealing ring, and stripping the moulded sleeve and sealing ring from the core. - 13

11. 12. A method as claimed in claim 11 in which the said groove is of invariable dimensions.

12. 13. A method as claimed in claim 11 or 12 in which the second moulding cavity is partly defined by a second 5 core, a circumferential groove for moulding the said rib being provided at the interface of· the said cores.

13.

14. ‘ A method of making a pipe having a coupling socket - substantially as herein described with reference to Figure 2 of the accompanying drawings.*