GB2192578A

GB2192578A - Pipe couplings

Info

Publication number: GB2192578A
Application number: GB08617665A
Authority: GB
Inventors: Terry George Nicholas
Original assignee: Wavin BV
Current assignee: Wavin BV
Priority date: 1986-07-18
Filing date: 1986-07-18
Publication date: 1988-01-20
Anticipated expiration: 2006-07-18
Also published as: GB2192578B; GB8617665D0

Abstract

A pipe coupling is made by injection moulding a socket (2) in a mould having a first core (6) defining an axially extending internal surface (8) of the socket, axially withdrawing the first core over the surface (8) to the illustrated position whereat an axially inner edge (10) defines an axially outer edge of a seal cavity formed between the internal surface (8) of the socket and a second core (7) of the mould. The material for the seal is then injected into this cavity through passage means (11 and 12), which are defined at least in part by the first core, to form the seal (4) in situ on the internal surface of the socket. <IMAGE>

Description

SPECIFICATION Pipe couplings This invention relates to pipe couplings comprising a socket having an internal seal for sealing contact with a pipe length received in the socket, and more particularly to a method of making such a pipe coupling.

Conventionally, the socket and seal of such pipe couplings are formed separately and then assembled together with some form of retention member for retaining the seal in the cou pling against displacement for example during fitting of a pipe length therein. Our British Patent Specification 1418645 shows an example of such arrangements.

An object of the present invention is to provide a method by which the seal can be formed integrally with the socket, thus avoiding the need to assemble the two together and the need to provide an additional retention member as aforesaid.

The present invention provides a method of making a pipe coupling comprising a socket having an internal seal for sealing contact with a pipe length received in the socket, the method including injection moulding the socket in a mould having first core means defining an axially extending internal surface of an end portion of the socket, axially withdrawing said first core means over said internal surface to a position whereat an axially inner edge of said first core means defines an axially outer edge of a cavity formed between said internal surface of the socket and a second core means of said mould, and injecting material for said seal into said cavity through passage means in said mould defined at least in part by said first core means to form said seal in situ on said internal surface of the socket.

The invention also includes a pipe coupling made by a method as defined in the last preceding paragraph.

Preferably, in the method the material for the seal is injected through passage means in said mould which exit to said cavity between said first core means and said internal surface of the socket.

Advantageously, the first core means may define at least one undercut axially extending groove in said internal surface of the socket.

Further, the second core means may define at least one recess in said cavity opposite said internal surface of the socket such that the seal formed in said cavity has as least one sealing projection.

In order that the invention may be well understood, an embodiment thereof, which is given by way of example only, will now be described, with reference to the accompanying drawing, in which: Figure 1 is an end view of a pipe coupling; and Figures 2 and 3 are semi-axial cross-sections of a mould for making the pipe coupling, illustrating successive steps in a method of making the coupling.

The pipe coupling 1 shown comprises a thermoplastics tubular socket 2 having a mouth 3 for receiving an end portion of a pipe length (not shown) and having an internal seal 4 for sealing contact with such an end portion received therein. The pipe coupling may form part of a variety of pipe fittings for example through couplings, pipe bends, or T or Y connectors or be formed integral with components to which pipes have to be connected.

The pipe fitting provided with the coupling 1 is injection moulded from plastics material and the portion of the mould concerned with the moulding of the coupling is shown in consecutive stages of the moulding operation in Figs.

2 and 3. Referring first to Fig. 2, the mould is shown in a condition for the moulding of the socket 2 of the coupling with the mould cavity in this condition filled with thermoplastics material, such as P.V.C., which has been injected thereinto to form the socket 2 along with the remaining part of the gutter fitting integral therewith and formed from the same thermoplastics material. In this condition the mould cavity is defined by an outer mould part 5 and first and second cores 6 and 7.

The first core 6 fits within an external recess of the second core 7 and defines an axially extending internal surface 8 of an end portion of the socket, as well as a stepped shoulder 9 axially inward of the surface 8.

After the socket has been injection moulded, the first core 6 is axially withdrawn from the mould over the internal surface 8 of the socket 2 to a position as shown in Fig. 3 whereat an axially inner edge 10 of the first core 6 which defines the stepped shoulder 9 of the socket in the condition of the mould shown in Fig. 2 defines an axially outer edge of a cavity for the seal 2 formed between the internal surface 8 of the socket and the second core 7. A thermoplastics material for the seal is injected into this cavity and the seal 2 is thereby formed in situ on the internal surface 8 of the socket as illustrated in Fig. 3.

Injection of the seal material into the cavity therefor is via passage means provided in the mould and including at least one passage 11 in the outer mould part 5 (as shown in dotted line in Fig. 3) and a further passage 12 defined by a groove along the edge 10 of the first core 6 adjacent the internal surface 8 of the socket. Thus, the passage means exit to the seal cavity between the first core 6 and the internal surface 8 of the socket. The seal material is such that it chemically bonds with the thermoplastics material of the socket so that in the finished coupling the seal is securely fixed to the socket.The assist the fixing of the seal to the socket a mechanical interconnection between these two parts may also be provided and such an interconnection is provided in the embodiment in the form of three undercut axially extending grooves 13 in the internal surface 8 of the socket which grooves are filled with the seal material. As shown, the grooves are dove-tail in configuration and are formed by corresponding projections (not shown) on the surface of the first core 6 which defines the internal surface 8 of the socket 2.

Additionally, in the illustrated embodiment the seal 4 is provided with sealing projections 14 which extend along the length of the seal for providing three separate axially spaced seals with a gutter length received in the socket 2. The projections are semi-circular in cross-section and are formed by corresponding recesses 15 provided in the second core 7 opposite the internal surface 8 of the socket. As will be appreciated from the drawings, when the mould is in the Fig. 2 condition for moulding the socket, the recesses 15 of the second core 7 are blanked off by the first core 6 and when the first core 6 is withdrawn to its Fig. 3 position the recesses 15 define part of the cavity for the seal.

After formation of the seal 4 on the internal surface 8 of the socket, the cores 6 and 7 are axially withdrawn from the mould leftwards as viewed in Fig. 3, the sealing member 4 being deformed by the core 7 as it is withdrawn thereover, and the mould 5 is removed from the pipe coupling, for example by axial movement rightwardly as viewed in Fig. 3 or where the mould 5 is divided into one or more axial sections by moving those sections radially outwardly.

It is to be understood that the illustrated pipe coupling could be modified to have any desired number of sealing projections 14, or to be provided with some other sealing surface configuration defined by the second core 7.

Further, it is to be understood that when the chemical bond between the seal and socket materials is sufficient to ensure that the seal will be retained in position in use, the mechanical interconnection of the illustrated embodiment may be omitted. If the mechanical interconnection is provided it may, of course, comprise any desired number of undercut grooves in the internal surface 8 of the socket filled with seal material.

Claims

1. A method of making a pipe coupling comprising a socket having an internal seal for sealing contact with a pipe length received in the socket, the method including injection moulding the socket in a mould having first core means defining an axially extending internal surface of an end portion of the socket, axially withdrawing said first core means over said internal surface to a position whereat an axially inner edge of said first core means defines an axially outer edge of a cavity formed between said internal surface of the socket and a second core means of said mould, and injecting material for said seal into said cavity through passage means in said mould defined at least in part by said first core means to form said seal in situ on said internal surface of the socket.

2. A method as claimd in claim 1, wherein the material for said seal is injected through passage means in said mould which exit to said cavity between said first core means and said internal surface of the socket.

3. A method as claimed in claim 1 or 2, wherein said first core means defines at least one undercut axially extending groove in said internal surface of the socket.

4. A method as claimed in claim 1, 2 or 3, wherein said second core means defines at least one recess in said cavity opposite said internal surface of the socket such that the seal formed in said cavity has at least one sealing projection.

5. A method of making a pipe coupling substantially as herein described with reference to the accompanying drawing.

6. A pipe coupling made by a method as claimed in any one of the preceding claims.