GB2268436A

GB2268436A - Method and core for manufacturing electrofusion elbow socket connectors

Info

Publication number: GB2268436A
Application number: GB9212463A
Authority: GB
Inventors: Laurence Moger
Original assignee: Wavin BV
Current assignee: Wavin BV
Priority date: 1992-06-12
Filing date: 1992-06-12
Publication date: 1994-01-12
Anticipated expiration: 2012-06-12
Also published as: GB2268436B; GB9212463D0

Abstract

A method for manufacturing an electrofusion elbow socket connector utilises a core comprising two parts 2, 3 which are releasably connectable together in a substantially straight configuration to facilitate winding of an electrically conductive wire over the core parts for incorporation in the connector and in an elbow configuration for positioning in a mould for moulding the connector. <IMAGE>

Description

Method and core for manufacturing electrofusion elbow socket connectors This invention relates to the manufacture of electrofusion elbow socket connectors.

For injection moulding an elbow socket connector it is necessary to use a core comprising two parts which are extractable from respective ends of the connector after moulding. In the case of an electrofusion elbow socket connector the elbow is moulded in a thermoplastics material and a winding of electrically conductive wire is required at or adjacent the interior surface of each socket end of the elbow together with electrical connection means.

It will be understood that passing an electrical current through the winding generates heat to cause the adjacent material of the socket and a thermoplastics pipe end or spigot inserted therein to fuse. It is desirable to have the windings at the two socket ends electrically interconnected since then only two electrical connections, one at each end of the elbow, are required and the two fusion connections can be made simultaneously. In straight-through electrofusion socket connectors this is achieved by winding an electrically conductive wire continuously over the core used in the injection moulding process.

In the case of an elbow socket connector a similar procedure is unsuitable due to difficulties in winding onto a core having an elbow configuration.

In order to overcome this difficulty it is known to wind separate electrically conductive wires on each of the two core parts for the elbow connector in separate operations before they are assembled together in an elbow configuration and to electrically interconnect the separate windings after the two core parts have been so assembled together.

An object of the invention is to provide an alternative way of overcoming the difficulty in winding a wire onto a core in an elbow configuration which avoids the need to carry out the step of electrically interconnecting separate windings on the two core parts.

The invention includes a method of manufacturing an electrofusion elbow socket connector using a mould and a core wherein the core comprises two parts extractable from respective ends of the connector after moulding, comprising releasably connecting said two parts together in a substantially straight configuration, winding an electrically conductive wire over the core parts, releasing the releasable connection between the two parts and releasably connecting the two parts in an elbow configuration, positioning said core parts in the mould in said elbow configuration to define a mould cavity, injecting thermoplastics material into said mould cavity to mould an elbow connector having a winding of conductive wire disposed at or adjacent the interior surface thereof, and extracting said two core parts from the moulded connector from respective ends of the moulded connector.

Advantageously, the wire may be fixed to the two remote end portions of the core parts before the configuration of said core parts is changed from said substantially straight configuration to said elbow configuration.

Preferably, the wire is provided with a thermoplastics insulating coating and said fixing to said core part remote end portions is achieved by locally heating the coating. This local heating may be such as to fuse adjacent turns of the wound insulated winding together.

In a preferred embodiment of the invention, the core parts are rotated relative to each other during the change from said substantially straight configuration to said elbow configuration to produce slack turns in the wire wound over the adjacent end portions of the core parts, and the slack turns are tightened before the core parts are positioned in the mould.

Preferably, the wire is wound more densely over the two remote end portions of the core parts than the adjacent end portions when said core parts are in said substantially straight configuration.

The invention also includes a core for use with a mould for moulding an electrofusion elbow socket connector, said core comprising two parts extractable from respective ends of the connector after moulding, said parts being releasably connectable together in a first, elbow configuration for positioning in said mould and in a second, substantially straight configuration for facilitating winding of an electrically conductive wire over the core parts for incorporation in the connector.

The core parts may be provided with male and female connecting means for releasably connecting said core parts together in said first and second configurations. In this case, preferably one of said core parts is provided with male connecting means and the other of said core parts is provided with first female connecting means for receiving said male connecting means when said core parts are in said first configuration and second female connecting means for receiving said male connecting means when said core parts are in said second configuration.

At least one of said core parts may be provided with recessing at an end which is adjacent the other core part when said core parts are releasably connected together for positioning wire wound on said parts when said core parts are put in their second configuration. In a preferred embodiment both core parts are provided with said recessing and the recessing of the parts are aligned when the parts are in said second configuration.

Each of said core parts may be provided with a radially outwardly extending abutment, such as an annular rib, at the end thereof which is remote from the other part when the parts are connected for preventing wire wound on said parts slipping of said end.

In order that the invention may be well understood, an embodiment thereof, which is given by way of example only, will now be described, reference being made to the accompanying drawings, in which: Figure 1 is a side view of a core comprising two core parts releasably connected together in an elbow configuration for moulding; Figure 2 is a side view of the same two core parts releasable connected together in a substantially straight configuration for winding; Figures 3 and 4 are respectively side and front views of one of the core parts; Figures 5 and 6 are respectively side and front views of the other one of the core parts; and Figure 7 schematically illustrates a winding operation on the two core parts connected together in the substantially straight configuration.

Referring first to Figure 1, there is shown a core 1 for use with a mould (not shown) for moulding an electrofusion elbow socket connector. The core 1 comprises two parts 2 and 3 which are extractable from respective ends of the connector after moulding. The core parts are releasably connectable together in the elbow configuration illustrated in Figure 1 with adjacent end portions 9, 10 abutting at a split line 4 of the core 1. The end portions 5, 6 of the core part 2, 3 remote from the split line are diametrically enlarged with respect to the end portions 9, 10 to form the interior surfaces of two socket ends of the elbow connector.

Figure 2 shows the same core parts 2 and 3 releasably connected together in a substantially straight configuration. In this configuration, the electrically conductive wire to be incorporated in the connector to enable an electrofusion connection to be made between the socket ends of the connector and pipe ends or spigots inserted therein may be wound over the core parts more easily than if the core parts were in the elbow configuration shown in Figure 1.

Referring now to Figure 3-6 the means for releasably connecting the core parts together in the elbow configuration of Figure 1 and the straight configuration of Figure 2 in the embodiment of the invention are illustrated. As will be seen, in the embodiment the core parts 2, 3 are provided with male and female connecting means for releasably connecting the core parts together in the above-mentioned two configurations. More specifically, the core part 3 (Figures 3 and 4) is provided with male connecting means and the core part 2 is provided with first female connecting means for receiving the male connecting means when the core parts are in the elbow configuration and second female connecting means for receiving the male connecting means when the core parts are in the substantially straight configuration.

The male connecting means comprise two spaced apart steel dowels extending from the core part and the female connecting means comprise two sets of two spaced holes 11 for receiving the dowels 12 in the respective configurations.

The end portions 5, 6 are provided with a respective radially outwardly extending abutment 7, 8 at the ends thereof remote from the portions 9, 10 for preventing the wire from slipping off these ends after it has been wound around the core. As illustrated in Figure 2 these abutments 7, 8 may simply comprise projections. However, as will be seen in Figures 3-6 alternatively these abutments may comprise annular ribs.

At least one of the core parts is provided with recessing at an end which is adjacent the other core part when the core parts are releasably connected together for positioning wire wound on the parts when the core parts are in the elbow configuration. As shown in Figures 1 to 6, in the embodiment, both core parts 2, 3 are provided with respective recessing 13, 14 and the recessing of the parts are aligned when the parts are in the elbow configuration of Figure 1.

Referring now to Figure 7, a winding machines schematically illustrated at 20 is used for winding the electrically conductive wire over the core parts 2, 3 when the core parts are in the substantially straight configuration of Figure 2. The core parts in this configuration is placed in the machine 20 between a drive head 15 and a rotatable centre 16. Because the longitudinal axis of the two core parts 2, 3 will usually not be co-axial, these two axes are each positioned slightly out of line with the winding machine axis in order to cause minimal wobbling during rotation of the core during the winding step. It has been established that such slight wobbling presents no problems.Wire from a supply bobbin (not shown) is fed over a drive pulley 18 which is axially moveable parallel to the axis of the machine via a lead screw 19 and secured to a drive bar pin 17 which is fixed to and rotatable with the drive head. As the core is rotated in the machine, the pulley 18 is moved along the length of the core such that the wire is wound onto the core. Once the core has been fully wound, the wire is fixed to the two remote end portions of the core before the configuration of the core part is changed from the substantially straight configuration to the elbow configuration. Advantageously the wire is provided with a thermoplastics insulating coating and the fixing of the wire to the core part is achieved by locally heating the coating, for instance by using a soldering iron to fuse the coating to the core in a few locations spaced around the circumference of the core.This local heating may be such as to fuse adjacent turns of the wound insulated winding together.

Advantageously the wire is wound more densely over the two remote end portions 5, 6 of the core parts than the adjacent end portions 9, 10. This is because the end portions 5, 6 will later form the sockets of the elbow connector and heat is only required in the region of the sockets not the central body which corresponds to the end portions 9, 10.

After the winding step, the wire is cut from the drive bar pin 17 at one end of the core and the pulley 18 at the other end and the core is removed from the winding machine. The wire will not unravel and will not slide from the core ends due to the local fixing of the wire to the core and additionally the provision of the abutments 7, 8.

Next, the core parts are axially separated - this is possible because the turns of the wire over at least the portions 9, lo are not fixed to the core and rotated relative to each other to enable them to be re-connected together in the elbow configuration of Figure 1. This relative rotation produces slack turns in the wire over the portions 9, 10, and these slack turns are tightened over the core and thereafter fixed in position by fusing to adjacent turns of the more densely wound portion of the winding and/or the core by heating, for example by using a soldering iron as mentioned previously. The piece of wire bridging the two core parts is pressed into the recessing 13, 14 to prevent its movement during the subsequent injection moulding stage.

Next the core 1 in the elbow configuration with the wire wound thereon is positioned in the mould to define the mould cavity and thermoplastic material is injected into the mould cavity to mould an elbow connector having the winding of conductive wire disposed at or adjacent the interior surface thereof.

The mould is opened and the two core parts 2, 3 are extracted from the moulded connector from respected ends thereof. The core parts 2, 3 are then reassembled in the substantially straight configuration shown in Figure 1 for a further production cycle.

The thermoplastics material which is injected into the mould may for example be a polyethylene, polypropylene or PVDF. The thermoplastics insulating coating provided on the wire may also be one of the above-mentioned thermoplastics materials but it is not necessary for the injected material to be the same as the coating material

Claims

CLAIMS: 1. A method of manufacturing an electrofusion elbow socket connector using a mould and a core wherein the core comprises two parts extractable from respective ends of the connector after moulding, comprising releasably connecting said two parts together in a substantially straight configuration, winding an electrically conductive wire over the core parts, releasing the releasable connection between the two parts and releasably connecting the two parts in an elbow configuration, positioning said core parts in the mould in said elbow configuration to define a mould cavity, injecting thermoplastics material into said mould cavity to mould an elbow connector having a winding of conductive wire disposed at or adjacent the interior surface thereof and extracting said two core parts from the moulded connector from respective ends of the moulded connector.
2. A method as claimed in claim 1, wherein the wire is fixed to the two remote end portions of the core parts before the configuration of said core parts is changed from said substantially straight configuration to said elbow configuration.
3. A method as claimed in claim 2, wherein said conductive wire is provided with a thermoplastics insulating coating and said fixing to said core part remote end portions is achieved by locally heating the coating.
4. A method as claimed in claim 3, wherein said local heating is such as to fuse adjacent turns of the wound insulated winding together.
5. A method as claimed in claim 2, 3 or 4, wherein the core parts are rotated relative to each other during the change from said substantially straight configuration to said elbow configuration to produce slack turns in the wire wound over the adjacent end portions of the core parts, and the slack turns are tightened before the core parts are positioned in the mould.
6. A method as claimed in any one of claims 1 to 5, wherein the wire is wound more densely over the two remote end portions of the core parts than the adjacent end portions when said core parts are in said substantially straight configuration.
7. A core for use with a mould for moulding an electrofusion elbow socket connector, said core comprising two parts extractable from respective ends of the connector after moulding, said parts being releasably connectable together in a first, elbow configuration for positioning in said mould and in a second, substantially straight configuration for facilitating winding of an electrically conductive wire over the core parts for incorporation in the connector.
8. A core as claimed in claim 7, wherein said core parts are provided with male and female connecting means for releasably connecting said core parts together in said first and second configurations.
9. A core as claimed in claim 8, wherein one of said core parts is provided with male connecting means and the other of said core parts is provided with first female connecting means for receiving said male connecting means when said core parts are in said first configuration and second female connecting means for receiving said male connecting means when said core parts are in said second configuration.
10. A core as claimed in any one of claims 7 to 9 wherein at least one of said core parts is provided with recessing at an end which is adjacent the other core part when said core parts are releasably connected together for positioning wire wound on said parts when said core parts are put in their second configuration.
11. A core as claimed in claim 10, wherein both core parts are provided with said recessing and the recessing of the parts are aligned when the parts are in said second configuration.
12. A core as claimed in any one of claims 7 to 11, wherein each of said core parts is provided with a radially outwardly extending abutment at the end thereof which is remote from the other part when the parts are connected for preventing wire wound on said parts slipping of said end.
13. A core as claimed in claim 12, wherein said abutment comprises an annular rib.
14. A core for use with a mould for moulding an electrofusion elbow connector substantially as hereinbefore described with reference to the accompanying drawings.
15. A method of manufacturing an electrofusion elbow connector substantially as hereinbefore described with reference to the accompanying drawings.