GB2189737A

GB2189737A - Heat weldable pipe fittings

Info

Publication number: GB2189737A
Application number: GB08609933A
Authority: GB
Inventors: Gordon Harrison
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1986-04-23
Filing date: 1986-04-23
Publication date: 1987-11-04
Also published as: EP0243062B1; EP0243062A3; JPS62267118A; ATE91458T1; GB8609933D0; DE3786480D1; US4848718A; JPH0818353B2; HK99394A; EP0243062A2; ES2043653T3; CA1271908A; DE3786480T2

Abstract

Apparatus and method for producing heat weldable, thermoplastics, tubular pipe fittings for use with heat weldable piping or tubing. A core is shown in a moulding machine ready for moulding. The core has two parts 11 and 12, each having an outer core member 13, 13A and an inner axially retractable member 14, 14A. The inner members 14 and 14A are held together by a bolt 15 threaded into a bore 16. Pivoted at 18 and 19 in the outer members 13, 13A are two pivoted retractable segmental fingers 20 and 21 carrying radial projections 22, 23 respectively, to facilitate winding a heater wire and/or to receive a terminal post 24, 25 during a moulding operation. Each segmental finger 20, 21 also has a small projection 26 and the two projections 26 are arranged to guide and support the wire during winding of the wire and to hold the wire in position during a subsequent moulding operation. The outer portions of the core also have a very shallow continuous spiral or other form of track or groove to receive wire 30 which is wound onto the core before moulding commences.

Description

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SPECIFICATION

Heat weldable pipe fittings

5 This invention relates to apparatus and to a method for producing heat weldable, thermoplastics, tubular pipefittingsfor use with heat weldable piping or tubing.

Heat weldable thermoplastics tubularfittings are 10 known in which there is, on the inner surface of the fitting, or embedded in the fitting, a coil of wire which enables thefitting to be heated electrically so asto meltthe plastics and fuse the fitting to thermoplastics pipes ortubes.

15 An object of the invention is to provide an improved method and apparatusfor producing such pipe fittings.

In accordance with the present invention there is an apparatusfor moulding heat weldable 20 thermoplasticstubularfittingsthe apparatus comprising a core having at least one pivoted segment collapsible inwardly of the core, the or each segment carrying radial projections adapted to facilitate winding heater wire and to hold the heater 25 wire in position during subsequent moulding. The radial projections may also receive and support terminal posts during a moulding operation.

The core may be in two parts each part carrying one of said pivoted segments, the parts being axially 30 separable.

Preferably each part of the core comprises an outer member on which the segment is pivoted and an inner axially slidable member. The axially slidable members may be interconnected by a bolt which 35 draws the two parts of the core together, the bolt being rotatableso asto release the two parts.

The movement of the segments inwardly may be effected by axial movement of the inner core parts, afterthey have been released.

40 For instance, each inner core part may have a shoulder adapted to engage a corresponding shoulder on one of the pivoted segments so asto cause it to pivot and withdraw the radial projection inwardly into the body of the core.

45 Stops may be provided to limitthe axially outward movement of the inner core portions.

The outer periphery of the core may be provided with a shallow trackor groove onto which the electrical wire may be woynd. By arranging forthe 50 trackto be very shallow in depth - say 0.1 mm or approximately 20% of heater wire diameter, it has been found possible to withdraw the two core portions after moulding has been effected without the need to have a totally collapsible core or 55 mandrel.

From another aspect, the invention relates to a method of producing a thermoplastics welding pipe fitting comprising:

winding a heater wire on the outer surface of a 60 moulding core, the moulding core having oneor more inwardly retractable segments carrying radially projecting posts;

placing a metallic electrically conductive terminal overeach post to provide for attachment of the wire; 65 moulding thefitting by placing the core in a moulding machine and injecting plastics material so asto mouldthefitting and terminal post surrounds in situ;

inwardly retracting the segment(s) to remove the 70 radially projecting postsfromthe terminals; and axially removing the core from the moulded fitting.

By use of the invention it is possible to mould the fitting as a single integral moulding and in a 75 one-stage moulding process.

In the accompanying drawings:-

Figure 1 is an elevation, partly in section, of a moulding apparatus embodying the present invention;

80 Figure 2 shows the central portion of the same apparatus after moulding of a pipe fitting and with parts shown in different positions;

Figure3 is a section taken on line III shown in Figure 1; and 85 Figure 4\s a diagrammatic illustration of apparatus used to separate core parts to release the moulded pipe fitting.

In Figure 1 a core is shown in position in a moulding machine ready for moulding to 90 commence. The core is divided intotwo parts 11 and 12which meetatthejunction 10.

Each of the two parts has an outer core member 13, 13Aand an inner axially retractable core member 14, 14A. Theinnercore members 14and 14Aareheld 95 together by a bolt 15 threaded into a bore 16. The bolt may be rotated by a head member 17.

Pivoted at 18 and 19 in the outer core members 13, 13A are two segmental fingers 20 and 21 (see Figures 1,2 and 3). Each segmental finger 20,21 carries a 100 radial projection 22,23 respectively, adapted to facilitate winding a heater wire and/orto receive a terminal post 24,25 during a moulding operation.

Each segmental finger 20,21 also has a small projection 26 and the two projections 26 are 105 arranged to guide and support the wire during winding of the wire and to hold the wire in position during a subsequent moulding operation.

The outer portions of the core also have a very shallow continuous spiral orotherform of trackor 110 groove to receive wire 30 which is wound onto the core before moulding commences.

Each inner core portion 14,14A has a shoulder 27 and the shoulders are adapted, when the inner core members are retracted axially, to abut 115 corresponding shoulders 28 on the collapsible segmental fingers 20 and 21.

In use, before being placed in a two-part mould 33, 33A (one half 33 only being shown in Figures 1 and 2) the core is assembled with the two halves of thecore 120 held together by the bolt 15 screwed into the bore 16. In this position it will be seen that the segmental fingers 20 and 21 form part of the outer surface of the core and the radial projections 22 and 23 and the small projections 26 extend radially beyondthe 125 surface of the core.

Wire is then wound on the outer surface of the core in the shallow trough or groove and the ends of the wire are wound round the post 2£, are guided by the posts 26 and then wound round the post 23. 130 Terminals 24 and 25 are attached to the ends of the

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wire and placed over the posts 22 and 23.

The core assembly is then placed in the mould half 33 and the metal terminals 24 and 25 are enclosed by shroud formers 22A, 23A as the mould is closed. 5 Thermoplastic material such as polythene is then injection moulded via passage 34to form the fitting 29 with the wire 30 embedded in its inner surface and the terminals 24and 25 moulded into thefitting.

The mould may now be opened up and the 10 moulded fitting removed on the mould core.

It is now necessary to remove the core from the fitting. This is done by unscrewing the bolt 15thus allowing the two parts ofthecoreto separate. Before separating the two parts the head member 17 and 15 the corresponding head member 17A are pulled axially and outwardly to the chain line position of Figure 1 so that the shoulders 27 on the inner portions 14and 14Aofthecore contact theshoulders 28 on the segmental fingers 20 and 21 causing the 20 segmental portions to pivot. The finger 20 pivots clockwise and drops into the space within the core thus removing the radial projection 22 and projection 26 from the moulded pipe fitting.

Similarly thefinger 21 pivots anticlockwise thus 25 releasing the projections 23 and 26 from the core.

Stops 31 and 32 are provided to limit the axial movement of the inner core portions relatively to the outer core portions and when thefull extent of the axial movement of the inner core portions has taken 30 place their outer ends will abut the heads of the stops and the whole core will separate so that the two parts of the core assembly will be removed axially from within the moulded pipe fitting.

Axial movement of the two core parts may be 35 effected by the apparatus shown in Figure 4. The core parts are shown diagrammatically at 11,12 in the mould 33,33A and are separated by attaching claws 35,36 carried on hydraulic rams 37 and 38 to head members 17,17A and simultaneously 40 retracting the two parts of the core axially until the core parts are clear of the moulded fitting.

Because the wire 30 is wound in a very shallow trough 31 it has been found possible to remove the core portions withoutthe need to have a totally 45 collapsible core or mandrel, the wire being retained in the moulded fitting and simply sliding overthe shallow trough.

The purpose of the projections 26 is to guide the wire and allowfor change in pitch of the winding. 50 Winding is in the same direction across both sides of the core.

Claims

55 1. An apparatusfor moulding heat weldable thermoplasticstubularfittings, the apparatus comprising a core having at least one pivoted segment collapsible inwardly of the core, the or each segment carrying radial projections adapted to 60 facilitate winding heater wire and to hold the heater wire in position during subsequent moulding.
2. An apparatus according to claim 1 and in which the radial projections are adapted to receive and support terminal posts during a moulding 65 operation.
3. An apparatus according to claim 1 or claim 2 and in which the core is in two parts each part carrying one of said pivoted segments, the parts being axially separable.
4. An apparatus according to claim 3 and in which each part of the core comprises an outer member on which the segment is pivoted and an inner axially slidable member.
5. An apparatus according to claim 4 and in which the axially slidable members are interconnected by a bolt which draws the two parts of the core together, the bolt being rotatable so asto release the two parts.
6. An apparatus according to claim 3 or claim 4or claim 5 and in which movement of the segments inwardly is effected by axial movement of the inner core parts, afterthey have been released.
7. Apparatus according to claim 6 and in which each inner core part has a shoulder adapted to engage a corresponding shoulder on one of the pivoted segments so asto cause it to pivot and withdraw the radial projection inwardly into the body of the core.
8. Apparatus according to any of claims 3 to 7 and in which stops are provided to limit the axially outward movement of the inner core portions.
9. Apparatus according to any preceding claim and in which the outer periphery of the core is provided with a shallow track or groove onto which the electrical wire may be wound.
10. Apparatus according to claim 9 and in which the track is of such shallow depth that the two core portions may be withdrawn after moulding has been effected withoutthe need to have a totally collapsible core or mandrel.
11. A method of producing a thermoplastics welding pipefitting comprising:

winding a heaterwire on the outer surface of a moulding core, the moulding core having one or more inwardly retractable segments carrying radially projecting posts;

placing a metallic electrically conductive terminal overeach postto provide for attachment of thewire;

moulding thefitting by placing the core in a moulding machine and injecting plastics material so asto mouldthefitting and terminal post surrounds in situ;

inwardly retracting the segment(s) to remove the radially projecting posts from the terminals; and axially removing the core from the moulded fitting.
12. Aheatweldabletubularfitting produced bya machine according to any ofclaimsl to 10and/orby the method of claim 11.
13. An apparatus for moulding heatweldable thermoplastics tubular fittings substantially as hereinbefore particularly described and as illustrated in the accompanying drawings.

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14. Amethodofmouldingheatweldable thermoplastics tubularfittings substantially as hereinbefore particularly described and as illustrated in the accompanying drawings.

Printed for Her Majesty's Stationery Office by Croydon Printing Company (UK) Ltd, 9/87, D8991685.

Published by The Patent Office, 25 Southampton Buildings, London, WC2A1 AY,from which copies may be obtained.