GB2211458A

GB2211458A - Moulding hollow articles

Info

Publication number: GB2211458A
Application number: GB8725226A
Authority: GB
Inventors: Sidney Harold Payne; Philip Barrowclough; Raymond Nelson Bushnell
Original assignee: ITW Ltd
Current assignee: ITW Ltd
Priority date: 1987-10-28
Filing date: 1987-10-28
Publication date: 1989-07-05
Anticipated expiration: 2007-10-28
Also published as: GB8725226D0; GB2211458B

Abstract

A method of producing a moulding 10 comprises injecting a non-plastics forming fluid under pressure into a stream of a plastics material entering a mould space, the fluid forming a central hollow core 20 within the plastics material, and the mould space being shaped to form frangible portions 24 such that the plastics material can be broken after its removal from the mould space so that the central core 20 of the moulding 10 is connected to atmosphere through more than one opening 28 thereby allowing a fluid, such as water, to flow through the moulding 10 from an entry opening 22 to the exit openings 28 for use in cleaning a windscreen when the moulding 10 is formed as part of a windscreen wiper harness. <IMAGE>

Description

MOULDINGS The present invention relates generally to mouldings and more particularly to mouldings capable of allowing a working fluid to flow therethrough.

It is known to inject a non-plastics forming fluid under pressure into a stream of plastics material entering a mould space. The fluid, which should be inert relative to the plastics material and could be a gas such as nitrogen, exerts pressure on the surrounding plastics material to pressurise the plastics material outwardly to fill the mould space, and then maintain that pressure until the plastics material is self-supporting. A disclosure of such a procedure appears in GB-2,139,548A to which the reader is instructed to refer.

It will be appreciated that the fluid is injected at a pressure and in an amount such that a central hollow core is formed by the fluid, within the plastics material, the central hollow core adopting an elongate configuration of narrow cross section, if the plastics material is itself being moulded into an elongate configuration of narrow cross section.

The fluid can be injected through a fluid injection passageway to a selected position within the mould space. The fluid injection passageway can be in the form of a tube whose outlet end is located between, preferably substantially mid-way between, the opposed internal mould surfaces of the mould space. Alternatively, the fluid can be injected into the plastics material through a fluid injection passageway located upstream of the mould space. In either case, as soon as the stream of plastics material has passed and immersed the outlet end of the fluid injection passageway, the fluid can be injected under pressure through the fluid injection passageway into the stream of plastics material. The fluid within the plastics material can occupy a central hollow core in the form of a channel.

After predetermined amounts of the fluid and the plastics material have been injected, they can be allowed to cool until the plastics material is self-supporting. An undesirably high pressure level of the fluid in the central hollow core can be relieved, by allowing the fluid to exit through the fluid injection passageway to atmosphere. Alternatively, the fluid exiting through the fluid injection passageway, which could now more properly be called a fluid ejection passageway, could be collected for re-use. Finally, the moulding is removed from the mould space thereby causing the central hollow core in the moulding to be connected to atmosphere.

Advantages of the above-noted procedure are that it can save weight and plastics material, can give a better surface finish and can lead to better filling, especially of narrow and extended mould spaces which are difficult to fill.

The present invention lies in the realisation that the above-noted procedure could be modified to give a moulding capable of allowing a- working fluid to flow therethrough.

A method of producing a moulding, in accordance with the present invention, comprises injecting a non-plastics forming fluid under pressure into a stream of a plastics material entering a mould space, the fluid forming a central hollow core within the plastics material, and the mould space being shaped such that the plastics material can be broken, after its removal from the mould space, to connect the central hollow core of the moulding to atmosphere through more than one opening.

The breaking operation is preferably capable of being performed manually.

The breaking operation could be performed at a single location but is preferably performed at a plurality of locations to give â complementary plurality of openings additional to that resulting from the injection of the forming fluid.

The opening resulting from the injection of the forming fluid may be utilised as an entry opening and the or each of the openings resulting from breaking the plastics material may be utilised as one or more exit openings. In use, a working fluid such as water would be intended to flow through the moulding from the entry opening to the or each of the exit openings, although in particular circumstances a reverse flow may be contemplated. The opening resulting from the injection of the forming fluid may be that formed by a fluid injection passageway located upstream of the mould space.

It may well be important for the working fluid to exit through each exit opening at a generally predetermined rate. This can be achieved by shaping the mould space to cause the formation of a constriction between adjacent portions of the central hollow core and by breaking the plastics material at the constriction after removal of the moulding from the mould space. The constriction in the central hollow core can result from a corresponding constriction in the mould space.

The present invention, which also extends to apparatus for performing the inventive method and to mouldings produced by performing the inventive method, will find many applications, of which a typical application is as a windscreen wiper harness, an embodiment of which will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a fragmentary longitudinal section through a moulding forming at least part of a windscreen wiper harness embodying the present invention; Figure 2 is a plan view of Figure 1; Figures 3 to 6 are enlarged sectional views taken respectively along the lines 3 - 3, 4 - 4, 5 - 5 and 6 - 6 of Figure 1; and Figure 7 is a view from the left hand end of Figure 1.

The accompanying drawings show a moulding 10 formed by injection moulding a plastics material such as polyester with a non-plastics forming fluid such as nitrogen following the principles disclosed in GB2,139,548A.

The moulding 10 forms half of a windscreen wiper harness when an identical moulding 10 is aligned therewith, such that connecting portions 12 thereof are adjacent to one another for connection together and to a wiper arm by an adaptor, whereas the moulding 10 forms an entire windscreen wiper harness when the connecting portion 12 is connected directly to a wiper arm by an adaptor.

As is conventional in a windscreen wiper harness, a main yoke 14 leads from the connecting portion 12 to a subsidiary yoke 16 on which are formed three sets of claws 18 which are to be secured to a wiper blade.

What is not conventional is that, as a result of the method of forming the moulding 10, a central hollow core 20 extends through the connecting portion 12, the main yoke 14 and the subsidiary yoke 16 up to, but not into, the claws 18.

The central hollow core 20 would be capable of use as a passageway for a working fluid, such as water, if one or more exit openings could be provided in addition to entry opening 22 provided as a result of the method of forming the moulding 10. To this end, one or more, preferably two, frangible portions 24 have been provided. A. constriction in the mould space, in which the moulding 10 was produced, resulted not only in an external annular groove 26 at the junction of the frangible portion 24 with the subsidiary yoke 16, but also in an internal constriction 28 between adjacent portions of the central hollow core 20 in the frangible portion 24 and the subsidiary yoke 16. The dimensions of the frangible portion 24 are chosen so that the dimensions of the constriction 28 are reliably controlled.

Manually breaking off the frangible portions 24, after removal of the moulding 10 from the mould space in which it was produced, enables the constrictions 28 to be utilised as exit openings.

Claims

C L A I M S

1. A method of producing a moulding comprising injecting a non-plastics forming fluid under pressure into a stream of a plastics material entering a mould space, the fluid forming a central core within the plastics material, and the mould space being shaped such that the plastics material can be broken, then breaking the plastics material so that, after its removal from the mould space, the central core of the moulding is connected to atmosphere through more than one opening.

2. A method according to claim 1, in which the plastics material is broken at one or more locations where one or more corresponding constrictions had been formed between adjacent portions of the central core.

3. A method according to claim 1 or claim 2, in which the plastics material is broken at a plurality of locations to give a complementary plurality of openings additional to an opening resulting from the injection of the forming fluid.

4. A method according to any preceding claim, in which the moulding is in the form of a windscreen wiper harness.

5. A method according to claim 4, in which the windscreen wiper harness includes a plurality of sets of claws which are spaced apart from one another along the length of the windscreen wiper harness and are separated from one another by one or more respective exit openings for a cleaning fluid, the or each of the exit openings having been formed by breaking off one or more respective frangible portions of the plastics material.

6. A method of producing a moulding substantially as hereinbefore described with reference to the accompanying drawings.

7. A moulding as produced by a method according to any one of the preceding claims.