CONDUIT COUPLINGS

Abstract: A conduit coupling shown as a channel conduit 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 6 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 6, to form the seal 4 in situ on the internal surface 8 of the socket.

Description: This invention relates to conduit couplings comprising a socket having an internal seal for sealing contact with a conduit length received in the socket, and more particularly to a method of making such a conduit coupling. Conventionally, the socket and seal of such conduit couplings are formed separately and then assembled together with some form of retention member for retaining the seal in the coupling against dis­ placement for example during fitting of a conduit length therein. Our British Patent Specifications 2037840 and 1418645 show examples of such arrangements, in channel conduit couplings and pipe conduit couplings respectively. 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. GB-A-2035192 discloses 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 disclosed method includes injecting moulding the socket in a mould having a first core which defines 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 the axially inner edge of said first core means defines an edge of a cavity formed between said internal surface of the socket and a second core means of the mould, and injecting material into said cavity through passage means defined by a first passage in an outer mould portion and a second passage in the moulded socket, which passages are blocked by a third core during moulding of the socket. The present invention provides a method of making a conduit coupling comprising a socket having an internal seal for sealing contact with a conduit 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, which passage means is 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 conduit coupling made by a method as defined in the last preceding paragraph. The invention is applicable both to conduit couplings comprising channel conduit couplings where the socket thereof defines a channel for receiving a channel conduit length, for example a gutter length, and to conduit couplings comprising pipe couplings where the socket thereof is tubular for receiving a pipe length. 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 at least one sealing projection. In order that the invention may be well understood, two embodiments thereof, which are given by way of example only, will now be described, with reference to the accompanying drawings, in which: Figure 1 is an end view of a channel conduit coupling; Figures 2 to 4 are axial cross-sections of a mould for making the coupling, illustrating successive steps in a method of making the coupling; Figure 5 is an end view of a pipe coupling; and Figures 6 and 7 are semi-axial cross-sections of a mould for making the pipe coupling, illustrating successive steps in a method of making the coupling. Referring first to Figures 1 to 4, the channel conduit coupling 1 shown comprises a gutter coupling having a thermoplastics socket 2 defining a channel 3 for receiving an end portion of a rainwater gutter length (not shown) and having an internal seal 4 for sealing contact with such an end portion received therein. The gutter coupling may form part of a variety of gutter fittings, for example gutter support brackets, unions and downpipe connectors. The gutter 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 Figures 2 to 4. Referring first to Figure 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 Figure 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 Figure 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 Figure 3. Injection of the seal material into the cavity therefor is via a 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 Figure 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. To 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 dovetail 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 corres­ ponding 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 Figure 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 Figure 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 mould is opened by retracting the cores 6 and 7 from the mould part 5 as indicated by the arrow 16 in Figure 4. The moulded fitting is carried by the cores during this retraction and is subsequently ejected from the cores by conventional ejector pins (not shown). It is to be understood that the illustrated gutter 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. Referring now to Figures 5 to 7, the pipe coupling 21 shown comprises a thermoplastics tubular socket 22 having a mouth 23 for receiving an end portion of a pipe length (not shown) and having an internal seal 24 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 21 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 Figures 6 and 7. Referring first to Figure 6, the mould is shown in a condition for the moulding of the sockets 22 of the coupling with the mould cavity in this condition filled with thermo­ plastics material, such as P.V.C. which has been injected thereinto to form the socket 22 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 25 and first and second cores 26 and 27. The first core 26 fits within an external recess of the second core 27 and defines an axially extending internal surface 28 of an end portion of the socket, as well as a stepped shoulder 29 axially inward of the surface 28. After the socket has been injection moulded, the first core 26 is axially withdrawn from the mould over the internal surface 28 of the socket 22 to a position as shown in Figure 7 whereat an axially inner edge 30 of the first core 26 which defines the stepped shoulder 29 of the socket in the condition of the mould shown in Figure 6 defines an axially outer edge of a cavity for the seal 24 formed between the internal surface 28 of the socket and the second core 27. A thermoplastics material for the seal is injected into this cavity and the seal 24 is thereby formed in situ on the internal surface 28 of the socket as illustrated in Figure 7. Injection of the seal material into the cavity therefor is via passage means provided in the mould and including at least one passage 31 in the outer mould part 25 (as shown in dotted line in Figure 7) and a further passage 32 defined by a groove along the edge 30 of the first core 26 adjacent the internal surface 28 of the socket. Thus, the passage means exit the seal cavity between the first core 26 and the internal surface 28 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. To 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 six undercut axially extending grooves 33 in the internal surface 28 of the socket which grooves are filled with the seal material. As shown, the grooves are dovetail in configuration and are formed by corresponding projections (not shown) on the surface of the first core 26 which defines the internal surface 28 of the socket 22. Additionally, in the illustrated embodiment the seal 24 is provided with sealing projections 34 which extend along the length of the seal for providing three separate axially spaced seals with a gutter length received in the socket 22. The projections are semi­ circular in cross-section and are formed by corres­ ponding recesses 35 provided in the second core 27 opposite the internal surface 28 of the socket. As will be appreciated from the drawings, when the mould is in the Figure 6 condition for moulding the socket, the recesses 35 of the second core 27 are blanked off by the first core 26 and when the first core 26 is withdrawn to its Figure 7 position the recesses 35 define part of the cavity for the seal. After formation of the seal 24 on the internal surface 28 of the socket, the cores 26 and 27 are axially withdrawn from the mould leftwards as viewed in Figure 3, the sealing member 24 being deformed by the core 27 as it is withdrawn thereover, and the mould 25 is removed from the pipe coupling, for example by axial movement rightwardly as viewed in Figure 7 or where the mould 25 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 34, or to be provided with some other sealing surface configuration defined by the second core 27. 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 28 of the socket filled with seal material.

Claims: 1. A method of making a conduit coupling (1; 21) comprising a socket (2; 22) having an internal seal (4; 24) for sealing contact with a conduit length received in the socket, the method including injection moulding the socket in a mould having first core means (6; 26) defining an axially extending internal surface (8; 28) of an end portion of the socket, axially withdrawing said first core means over said internal surface (8; 28) to a position whereat an axially inner edge (10; 30) 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 (7; 27) of said mould, and injecting material for said seal into said cavity through passage means (11, 12; 31, 32) in said mould, which passage means is defined at least in part by said first core means (6; 26) to form said seal (4; 24) in situ on said internal surface (8; 28) of the socket. 2. A method of making a pipe coupling (21) comprising a socket (22) having an internal seal (24) 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 (26) defining an axially extending internal surface (28) of an end portion of the socket, axially withdrawing said first core means over said internal surface (28) to a position whereat an axially inner edge (30) 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 (27) of said mould, and injecting material for said seal into said cavity through passage means (31, 32) in said mould, which passage means is defined at least in part by said first core means (26), to form said seal (24) in situ on said internal surface (28) of the socket. 3. A method of making a channel conduit coupling (1) comprising a socket (2) having an internal seal (4) for sealing contact with a channel conduit length received in the socket, the method including injection moulding the socket in a mould having first core means (6) defining an axially extending internal surface (8) of an end portion of the socket, axially withdrawing said first core means over said internal surface (8) to a position whereat an axially inner edge (10) of said first core means defines an axially outer edge of a cavity formed between said internal surface (8) of the socket and a second core means (7) of said mould, and injecting material for said seal into said cavity through passage means (11, 12) in said mould which passage means is defined at least in part by said first core means (6) to form said seal (4) in situ on said internal surface (8) of the socket. 4. A method as claimed in claim 1, 2 or 3, wherein the material for said seal (4; 24) is injected through passage means in said mould which exit to said cavity between said first core means (6; 26) and said internal surface (8; 28) of the socket. 5. A method as claimed in any one of the preceding claims, wherein said first core means (6; 28) defines at least one undercut axially extending groove (13; 33) in said internal surface (8; 28) of the socket. 6. A method as claimed in any one of the preceding claims, wherein said second core means (7; 27) defines at least one recess (15; 35) in said cavity opposite said internal surface (8; 28) of the socket such that the seal (4; 24) formed in said cavity has at least one sealing projection (14; 34). 7. A conduit coupling made by a method as claimed in claim 1, comprising a gutter coupling (1), the socket (2) thereof defining a channel for receiving a gutter length. 8. A conduit coupling made by a method as claimed in claim 1, comprising a pipe coupling (21), the socket (22) thereof being tubular for receiving a pipe length.

Inventors: NICHOLAS, TERRY GEORGE
Applicants: WAVIN B.V.
Application year: 1987
Main classification: B29C45
IPC codes: F16L47, B29C45