HEAT WELDABLE PIPE FITTINGS

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: This invention relates to apparatus and to a method for producing heat weldable, thermoplastics, tubular pipe fittings for use with heat weldable piping or tubing. Heat weldable thermoplastics tubular fittings are known in which there is, on the inner surface of the fitting, or embedded in the fitting, a coil of wire which enables the fitting to be heated electrically so as to melt the plastics and fuse the fitting to thermoplastics pipes or tubes. An object of the invention is to provide an improved method and apparatus for producing such pipe fittings. In accordance with the present invention there is an apparatus suitable for use in moulding heat weldable thermoplastics tubular fittings in a moulding machine, said apparatus comprising a core in cooperation with an outer mould, the 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 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 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 draws the two parts of the core together, the bolt being rotatable so as to release the two parts. The movement of the segments inwardly may be effected by axial movement of the inner core parts, after they have been released. For instance, each inner core part may have a shoulder adapted to engage a corresponding shoulder on one of the pivoted segments so as to cause it to pivot and withdraw the radial projection inwardly into the body of the core. Stops may be provided to limit the axially outward movement of the inner core portions. The outer periphery of the core may be provided with a shallow track or groove onto which the electrical wire may be wound. By arranging for the track to be very shallow in depth - say 0.1mm 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 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 moulding core, the moulding core having one or more inwardly retractable segments carrying radially projecting posts; placing a metallic electrically conductive terminal over each post to provide for attachment of the wire; moulding the fitting by placing the core in a moulding machine and injecting plastics material so as to mould the fitting 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. By use of the invention it is possible to mould the fitting as a single integral moulding and in a one-stage moulding process. In the accompanying drawings:- Figure 1 is an elevation, partly in section, of a moulding apparatus embodying the present invention; Figure 2 shows the central portion of the same apparatus after moulding of a pipe fitting and with parts shown in different positions; Figure 3 is a section taken on line III shown in Figure 1; and Figure 4 is 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 commence. The core is divided into two parts 11 and 12 which meet at the junction 10. Each of the two parts has an outer core member 13, 13A and an inner axially retractable core member 14, 14A. The inner core members 14 and 14A are held 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 radial projection 22, 23 respectively, adapted 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 would 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 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 the core 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 beyond the 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 22, are guided by the posts 26 and then wound round the post 23. Terminals 24 and 25 are attached to the ends of the 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. Thermoplastic material such as polythene is then injection moulded via passage 34 to form the fitting 29 with the wire 30 embedded in its inner surface and the terminals 24 and 25 moulded into the fitting. The mould may now be opened up and the 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 15 thus allowing the two parts of the core to separate. Before separating the two parts the head member 17 and 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 14 and 14A of the core contact the shoulders 28 on the segmental fingers 20 and 21 causing the 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 the finger 21 pivots anticlockwise thus 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 the full extent of the axial movement of the inner core portions has taken 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 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 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 it has been found possible to remove the core portions without the need to have a totally collapsible core or mandrel, the wire being retained in the moulded fitting and simply sliding over the shallow trough. The purpose of the projections 26 is to guide the wire and allow for change in pitch of the winding. Winding is in the same direction across both sides of the core.

Claims: An apparatus suitable for use in moulding heat weldable thermoplastics tubular fittings in a moulding machine, said apparatus comprising a core (11, 12) in cooperation with an outer mould (33, 33A), characterised by the core having at least one pivoted segment (20,21) collapsible inwardly of the core (11,12) the or each segment (20,21) carrying a radial projection (22,23) adapted to facilitate winding heater wire (30) and to hold the heater wire (30) in position during subsequent moulding. An apparatus according to claim 1 and characterised by the radial projections (22,23) being adapted to receive and support terminal posts (24,25) during moulding operation. An apparatus according to claim 1 or claim 2 characterised in that the core (11,12) is in two parts each part carrying one of said pivoted segments (20,21), the parts (11,12) being axially separable. An apparatus according to claim 3 and characterised in that each part (11,12) of the core comprises an outer member (13,13A) on which the segment (20,21) is pivoted and an inner axially slidable member (14,14A). An apparatus according to claim 4 and characterised in that the axially slidable members (14,14A) are interconnected by a bolt (15) which draws the two parts (11,12) of the core together, the bolt (15) being rotatable so as to release the two parts. An apparatus according to claim 3 or claim 4 or claim 5 characterised in that movement of the segments (20,21) inwardly is effected by axial movement of the inner core parts (14,14A), after they have been released. Apparatus according to claim 6 characterised in that each inner core part (14,14A) has a shoulder (27) adapted to engage a corresponding shoulder (28) on one of the pivoted segments so as to cause it to pivot and withdraw the radial projection inwardly into the body of the core. Apparatus according to any of claims 3 to 7 characterised in that stops (31,32) are provided to limit the axially outward movement of the inner core portions. Apparatus according to any preceding claim and characterised in that the outer periphery of the core is provided with a shallow track or groove onto which the electrical wire (30) may be wound. Apparatus according to claim 9 characterised in that the track is of such shallow depth that the two core portions may be withdrawn after moulding has been effected without the need to have a totally collapsible core or mandrel. A method of producing a thermoplastics welding pipe fitting characterised by winding a heater wire (30) on the outer surface of a moulding core (11, 12), the moulding core having one or more inwardly retractable segments (20, 21) carrying radially projecting posts (22, 23); placing a metallic electrically conductive terminal (24, 25) over each post (22, 23) to provide for attachment of the wire; moulding the fitting by placing the core in a moulding machine and injecting plastics material so as to mould the fitting and terminal post surrounds in situ; inwardly retracting the segment(s) (20, 21) to remove the radially projecting posts from the terminals; and axially removing the core from the moulded fitting.

Inventors: HARRISON, GORDON
Applicants: UPONOR BV
Application year: 1987
Main classification: B29C67
IPC codes: B29C33, B29C45, B29D23, B29L31