GB2174035A

GB2174035A - Moulding flowable plastics material

Info

Publication number: GB2174035A
Application number: GB08608409A
Authority: GB
Inventors: Michael Fraser
Original assignee: NYLACAST SYSTEMS Ltd
Current assignee: NYLACAST SYSTEMS Ltd
Priority date: 1985-04-18
Filing date: 1986-04-07
Publication date: 1986-10-29
Also published as: GB8509926D0; GB2174035B; GB8608409D0

Abstract

A method of moulding flowable plastics materials comprises the steps of providing a plurality of linked, mobile containers 4,6 which are adapted to hold said materials or components thereof and a further one 8 of which is adapted to house pump means, pumping the plastics materials through flexible conduits 10,12 to a moulding device 22, said moulding device including a mould cavity 20, maintaining a material inlet valve of said cavity in a closed position, evacuating the cavity through line 24 to provide conditions of partial vacuum therein, opening the cavity inlet valve to permit entry of the materials to the cavity and allowing solidification of a moulded product to take place. Alternative mould arrangements are shown in Figures 2 to 4 (not shown). <IMAGE>

Description

SPECIFICATION Moulding flowable plastics material The invention is concerned with improvements in or relating to moulding flowable plastics material.

Care must be taken in the moulding or casting of plastics materials, in filling the cavity of the moulding tool, to ensure that air or other gas is not entrained with the flowable material so that on setting the moulded product contains voids or similar imperfections which would mar the appearance, quality and/or durability of the product.

The invention provides a method of moulding flowable plastics materials comprising the steps of providing a plurality of linked mobile containers, at least one of which is adapted to hold said materials or components thereof and a further one of which is adapted to house pump means, pumping the plastics materials through flexible conduits leading from appropriate ones of said containers to a moulding device spaced therefrom, said moulding device including a mould cavity, maintaining a material inlet valve of said cavity in a closed position, evacuating the cavity to provide conditions of partial vacuum therein, opening the cavity inlet valve to permit entry of the materials to the cavity and allowing solidification of a moulded product to take place.

As required, the flowable plastics material may be a single component capable of being moulded into the desired shape or may comprise constituents of the required plastics mix for the production of the end product. An example of the latter may be a material falling within the category of reaction injection moulding (RIM) materials which include polyurethane and nylon.

The invention further provides apparatus for carrying out the method of the third paragraph of this specification, comprising at least one container for said materials or components thereof, pump means housed within another of said containers, means releasably to link said containers together, means to facilitate transportation of the containers across a floor area, and flexible conduit means adapted to convey said materials or components thereof to a moulding means, said moulding means being provided with means partially to evacuate a mould cavity thereof.

There will now be described with reference to the drawings an example of an apparatus and of the method according to the invention. It will be understood that the description is given by way of example only and not by way of limitation.

In the drawings: Figure 1 illustrates diagrammatically an arrangement of apparatus in which the method according to the invention may be carried out; and Figures 2 - 4 show alternative examples of moulding means of the details of suitable apparatus for use with the example of Figure 4.

The apparatus comprises a supply device particularly but not exclusively suitable for use in the moulding of nylon products, where two liquid components are to be mixed during the moulding operation.

Thus in the present example, the device 2 comprises a three/ part housing, a first part 4 enclosing a tank containing a caprolactam which contains a suitable activator, a second part 6 enclosing a tank containing a caprolactam to which has been added a suitable catalyst, a third part 8 containing a pump device for supplying the captrolactam melts through pipes 10 and 12 and also such heater devices as may be necessary to provide for example a circulation of heated oil to prevent premature solification. A flexible cable sheath 14 is supported by a pivotable bracket 16 mounted at an upper region of the device 2. It will be understood that the three parts 4, 6, 8, may readily be disassembled for ease of maintainance and replenishment.The provision of wheels or castors 18 enables the device to be moved from one mould member to another in a factory rather than relying on a conveyor or other arrangement for transferring the mould members themselves. The apparatus is arranged to supply two plastics materials for mixing in a mould cavity 20 of a two-part mould member 22. A vacuum line 24, with a control valve 26, is provided in an inlet 28. The example excludes a mixer head 30 adapted to supply two streams of plastics material from supply lines 10, 12. The mixer head causes the two streams to irnpinge so as to cause the turbulence necessary for proper mixing thus to ensure a uniform voidfreg product.

The plastics material supply lines 10, 12 are contained within the flexible cable sheath 14, together with other pipes as necessary to provide, if required, return pipes where recirculation of the plastics material is required and heating pipes where premature solidification of the plastics material is to be avoided. The cable sheath 14 thus carries the required pipes to the mixer head 30 from the mobile supply device, 2.

Alternative arrangements of moulding means are shown in Figure 2 - 4. The arrangement shown in Figure 2 comprises a mould member 32 comprising two portions 34, 36 partable to release a moulded product from a cavity 38 of the member.

A vacuum line 40 is provided, in an elongated inlet portion 42 of the mould member, and is used to create conditions of partial vacuum according to the method of the invention. A valve 44 controls the line 40. A further valve 46 controls an inlet 48 for the liquid plastics material 50.

Figure 3 shows a similar arrangement to that shown in Figure 2, like portions bearing like reference numerals. In the example of Figure 3, however, the vacuum line 10 is connected to an inlet 52 of the member 2 and the plastics material is supplied through an inlet 54 direct into the mould cavity 8.

In these two examples, the cavity 38 is partially evacuated while the valve 46 remains closed.

When the vacuum line 19 is closed by the valve 44, valve 46 is opened and the plastics material is allowed to flow into the cavity 38 under the influence of gravity and the suction effect of the conditions of partial vacuum.

Figure 4 shows a mould member 56 comprising two portions 58, 60 and having a first inlet 62 to which is connected to a vacuum line 64 controlled by a valve 66. The inlet 62 is provided in the upper mould portion 60, and at an opposed position in the lower portion 58 is an inlet conduit 68 controlled by a valve 70. A mouth portion of the inlet 68 is submerged in a heated reservoir 72 supplied with plastics material.

While the valve 70 is closed, the cavity 74 of the mould member 56 is partially evacuated and when valve 66 is closed, opening valve 70 has the effect of applying a suction effect at the inlet 68.

Various modifications may be made within the scope of the invention as defined in the following

Claims

claims. CLAIMS

1. A method of moulding flowable plastics materials comprising the steps of providing a plurality of linked, mobile containers, at least one of which is adapted to hold said materials or components thereof and a further one of which is adapted to house pump means, pumping the plastics materials through flexible conduits leading from appropriate ones of said containers to a moulding device spaced therefrom, said moulding device including a mould cavity, maintaining a material inlet valve of said cavity in a closed position, evacuating the cavity to provide conditions of partial vacuum therein, opening the cavity inlet valve to permit entry of the materials to the cavity and allowing soldification of a moulded product to take place.

2. A method as claimed in claim 1 wherein the materials are conveyed through said conduits to a mixing device prior to entry into the cavity.

3. A method as claimed in either one of claims 1 and 2, wherein heating means are also provided within said container adapted to house the pump means, a heat transfer medium being provided to transfer heat to said materials in the flexible conduits.

4. Apparatus for carrying out the method as claimed in claim 1, comprising at least one container for said materials or components thereof, pump means housed within another of said containers, means releasably to link said containers together, means to facilitate transportation of the containers across a floor area, and flexible conduit means adapted to convey said materials or components thereof to a moulding means, said moulding means being provided with means partially to evacuate a mould cavity thereof.

5. Apparatus as claimed in claim 4, wherein a mixing device is provided in association with the moulding means.

6. Apparatus as claimed in either one of claims 4 and 5, wherein the conduit means for said mate rials leads to a valve-controlled inlet to the moulding means.

7. Apparatus as claimed in either one of claims 4 and 5, wherein the conduit means for said materials leads to a holding reservoir containing an inlet conduit to the moulding means.

8. A method of moulding flowable plastics material substantially as hereinbefore described with reference to the drawings.

9. Apparatus for moulding flowable plastics material constructed and arranged substantially as hereinbefore described with reference and as shown in the drawings.