GB2103141A

GB2103141A - Recycling waste plastics material

Info

Publication number: GB2103141A
Application number: GB08216204A
Authority: GB
Inventors: Stephen George Prince; Jack Warburton
Original assignee: Cristal Pigment UK Ltd; Lambert Howarth and Sons Ltd
Current assignee: Lambert Howarth and Sons Ltd; Tronox Pigment UK Ltd
Priority date: 1981-06-09
Filing date: 1982-06-03
Publication date: 1983-02-16
Also published as: GB2103141B

Abstract

An injection moulding machine includes a hopper 11 having at least two inlets 12, 13. The inlet 13 comprises two tubes 14, 15 hingeably connected by a joint 16 operable by a pneumatic cylinder 18. In use, tube 15 is held at an angle with respect to tube 14 (phantom lines) and waste plastics material, e.g. PVC or thermoplastic rubber, is placed into scoop 17. At intervals cylinder 18 is actuated to swing tube 15 into line with tube 14 so that the waste material falls through the hopper 11 and into a lower housing for melting and subsequent injection. A third inlet 21 may be provided for other plastics waste material. Approximately 6% waste material, supplied through inlet 13, may be mixed with unused plastics material fed through inlet 12. <IMAGE>

Description

SPECIFICATION Recycling waste plastics materials This invention relates to the recycling of waste plastics material such as Polyvinyl Chloride (PVC) or thermo-plastic rubber in injection moulding machines particularly, but not exclusively, for footwear.

Composite injection moulding machines for footwear vary in type being either stationary single pair machines or rotary machines dealing with, for example, three to six pairs of a particular type of footwear.

A machine has been proposed in which a rotary table is provided with a plurality of moulding stations each provided with a moulding head. A shoe upper on a last is mounted on the table at a first station and then moves to a second station where a split mould is closed around the base of the last leaving a space around the last into which plastics material such as polyvinyl chloride (PVC) or thermoplastic rubber (TR) is introduced to form a sole. The machine is progressively rotated to bring a successive moulding heads to the mould filling position until the first head reaches the penultimate station. The molten PVC orTR cools and sets during rotation of the table and the two halves of the mould open at the penultimate station so that the shoe on the last may be removed and replaced by a further upper on a iast and the cycle repeated.

The last with the upper and newly moulded sole thereon may then be transferred to an oven for heat curing the PVC or TR to set the shoe to the size of the last.

At the end of injection each station's mould on the aforementioned footwear machine, or appropriate receptacles on other machines, excess plastics material, such as PVC or TR, solidifies and would normally be discarded.

An object of the present invention is to provide an injection moulding machine which permits recycling of such waste plastics materials.

With this object in view, the present invention provides an injection moulding machine comprising a housing in which plastics material may be melted by the application of heat, an injection nozzle which serves to inject molten plastics material from the housing into appropriate receptacles, and a hopper which serves to feed solid plastics material into the housing, said hopper having a first inlet for unused plastics material and a second inlet for previously used plastics material, characterised in that the second inlet is in the form of a two part passageway comprising a first part which extends from the hopper at an inclination and a second part, remote from the hopper, which has a collecting receptacle at its free end and is hingeably connected to the first part so as to be swingable from a collecting position at an angle to the first part to a hopper loading position substantially in line with the first part.

The first part of the passageway is preferably connected to the second part of the passageway by a hinge joint which is operable by a pneumatic cylinder.

The two parts of the passageway are conveniently in the form of tubes.

In a prefered embodiment of the invention, the hopper has a third inlet for used plastics material formed from granules, said inlet comprising an outer tube attached to the hopper and an inner tube which is moveable in the relation to the outer tube so as to project into the hopper to a greater or lesser extent and thereby control the rate of flow of said material through said inlet.

The invention will be described further, by way of example, with reference to the accompanying drawing, in which: Fig. 1 is a diagrammatic perspective view of one embodiment of the injection moulding machine according to the invention; Fig. 2 is a diagrammatic plan view illustrating two injection moulding machines according to the invention located adjacent a multi-station foot wear moulding machine; Fig. 3 is a side elevation of the inlets to the hopper in a preferred embodiment of the injection moulding machine of the invention; and Fig. 4 is a fragmentary view of the collecting receptacle in the direction of the arrow 4 in Fig. 3.

As shown in Fig. 1, one embodiment of an injection moulding machine of the invention comprises a housing 10, in which plastics material may be melted by application of heat from internal heating elements, and two funnel-shaped hoppers 11 fitted to one side of the housing 10 so as to feed solid plastics material into said housing 10.

One or more injection nozzles (not shown) extend from the housing 10 and are operative to inject molten material from the housing 10 into appropriate receptacles, usually moulds.

Fig. 2 indicates that in another embodiment of the invention, the machine has only one hopper 11.

Each hopper 11 has three inlets, as indicated in Fig. 3. A first inlet 12 is in the form of a short vertical, flanged tube iocated centrally at the base of the hopper 11. A second inlet 13 is a two-part passageway comprising, two tubes 14, 1 5 which are hingeably connected to each other by a joint 1 6. The first tube 14 extends upwardly, at an angle of about 600 to the horizontal, from the side of the inlet 12. However, the lower end of the tube 14 extends a short distance into the inlet 12, as shown in Fig. 3. The second tube 1 5 has a collecting receptacle in the form of a scoop 17 at its free end. The hinge joint 1 6 is operable by a pneumatic cylinder 1 8 attached between flanges 19, 20 on the tubes 14 and 15 respectively so as to permit the tube 1 5 to swing from a position substantially perpendicular to the tube 14 when the cylinder 18 is withdrawn to a position in line with the tube 14 when the cylinder 18 is fully extended.

A third inlet comprises a short tube 21 extending at an angle of about 600 to the horizontal from the opposite side of the inlet 12 to the inlet 1 3. An inner tube 22 extends through the tube 21 and may be moved in~relation to this outer tube 21 by an operator pushing or pulling the end of the inner tube 22 which projects out of the end of the outer tube 21.

When the above described injection moulding machine is used, for example in conjunction with a footwear moulding machine as shown in Fig. 2 and described earlier in this specification, the tube 1 5 is held perpendicular to the tube 14 so that the scoop 17 lies adjacent moulding stations 9 to 10 around the edge of a rotary table 25. After the shoes on the last have been removed from the moulds, an operator collects waste pieces of solid PVC, which usually remain in the footwear moulds around the heel region and drops these pieces into the scoop 1 7. Such waste material may comprise up to 15% of the originally injected material. At intervals, e.g. after each mould cycle of the table 25, the penumatic cylinder 1 8 is automatically activated to raise the tube 1 5 into line with the tube 14 so that the aforesaid waste material falls through the tubes 15 and 14 and through the hopper 11 into the housing 10. Measured amounts of unused PVC, usually in the form of granules, are periodically released into the housing 1 0 through the inlet 12. As the lower end of the tube 14 extends into the inlet 12, the waste PVC mixes with the unused PVC granules as they are fed into the melting chamber.

The PVC entering the melting chamber within the housing 10 may contain up to about 6% waste PVC.

Certain forms of waste PVC such as complete footwear soles which are rejected as not coming up to required quality standards are obviously too large to be fed into the machine by way of the scoop 17. Accordingly, such waste is granulated and fed into the third inlet, i.e. tube 21 and 22.

The flow of this granular waste material is regulated depending on how far the tube 22 projects from the tube 21 into the central, unused PVC inlet 12. The further the tube 22 projects into the tube 12, the slower is the rate of flow through the third inlet 21/22.

When this type of injection moulding machine is used in conjunction with a large rotary machine, such as that shown in Fig. 2, two machines may be used each for a different colour of PVC.

Moreover, the machine operators may need to alter their position around the table 25 so that they are no longer within easy reach of an appropriate scoop 17 in which to deposit the waste material. Accordingly, transfer means 23 in the form of a tube, box section or channel having a continuously moving belt therein many be used to convey waste PVC to the appropriate scoop 17.

It should be appreciated that the foregoing is illustrative and not limitative of the scope of the invention and variations may be made thereto. For example, the size, shape and dimensions of the parts of the machine may vary.

It must also be pointed out that, while use of the machine of the invention has been described in relation to polyvinyl chloride, it is equally applicable to the recycling of thermoplastic rubber (TR) or other similar plastics materials.

Claims

1. An injection moulding machine comprising a housing in which plastics material may be melted by the application of heat, an injection nozzle which serves to inject molten plastics material from the housing into appropriate receptacles, and a hopper which serves to feed solid plastics material into the housing, said hopper having a first inlet for unused plastics material and a second inlet for previously used plastics material, characterised in that the second inlet is in the form of a two-part passageway comprising a first part which extends from the hopper at an inclination and a second part, receptacle at its free end and is hingeably connected to the first part so as to be swingable from a collecting position at an angle to the first part to a hopper loading position substantially in line with the first part

2. A machine as claimed in claim 1, characterised in that the first part of the passageway is connected to the second part of the passageway by a hinge joint which is operable by a pneumatic cylinder.

3. A machine as claimed in claims 1 or 2, characterised in that the two parts of the passageways comprise tubes.

4. A machine as claimed in claims 1, 2 or 3 characterised in that the hopper has a third inlet for used plastics material which has been formed into granules.

5. A machine as claimed in claim 4 characterised in that the third inlet comprises an outer tube attached at one end to the hopper and an inner tube which is moveable in relation to the outer tube so as to project into the hopper to a greater or lesser extent thereby controlling the rate of flow of plastics material through said inlet.

6. An injection moulding machine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

7. A method of recycling waste plastics material in an injection moulding machine as defined in any preceding claim, said method comprising the steps of placing waste plastics material in the collecting receptacle on the second part of the second inlet to the hopper when the second part is at an angle to the first part, and actuating the second part to swing into line with the first part so that the waste material falls down the resultant inclined passageway into the hopper whence it is fed into the housing, together with unused plastics material from the first inlet, for melting and subsequent injection.