AU709261B2

AU709261B2 - Plastic recycling improvement

Info

Publication number: AU709261B2
Application number: AU12564/97A
Authority: AU
Inventors: Grant Andrew Wride
Original assignee: BUSHMAN POLYPRODUCTS Pty Ltd; Collex Pty Ltd
Current assignee: BUSHMAN POLYPRODUCTS Pty Ltd; Collex Pty Ltd
Priority date: 1996-02-07
Filing date: 1997-02-07
Publication date: 1999-08-26
Anticipated expiration: 2017-02-07
Also published as: AU1256497A

Description

This invention relates to plastic recycling and in particular to improvements in relation to taking product from a stirring chamber into moulds.

It is conventional now for plastics materials which are to be recycled to be introduced into a chamber in which there is some form of stirring by which the plastics themselves are heated to a temperature which will result in a melting of the plastics and merging and mixing of the plastics.

Plastics materials once heated and merged are taken off from the chamber by an auger or screw which forces the plastics materials through connecting conduits into a mould for subsequent cooling, and subsequent separation of 10 the cooled product from the mould.

The problem to which this invention is directed is the difficulty that with current apparatus and technology as it is known at this time, it is very difficult indeed to change over from one mould to another without problems.

The problem is that with current techniques, during changeover from one 1 5 mould to another, the screwdrive or auger drive can be damaged or a drive to the auger is damaged and it is not apparent as to why this is occurring.

The problem appears to be uniquely directed to recycled plastics materials which are being drawn from a primary or main mixing or stirring chamber for use in a mould.

2 0 If the auger or screw is stopped so as to not spill plastics material during any mould changeover, then there is a very high probability that upon attempting to restart, any reasonable sized shaft driving the screw will simply shear.

This may be to do with the characteristics of recycled plastics in which there is implicitly a significant porosity and therefore potential for a high degree of expansion or contraction or it might be that because there will be a variety of different plastics in most recycled mixers, adhesion to the walls of any supply conduit or screw thread may occur. Once the movement is allowed to stop and therefore the plastic adhere, breaking pressures for that initial adhesion fracture is such that it has been considered either very difficult or highly 3 0 expensive to find equipment sufficient to overcome this problem.

The problem is such that it is not known by the applicant that anyone in the world is currently able to solve the problem.

According to this invention, we have found a solution which is that instead of trying to reconnect a mould to an outlet conduit while the plastics materials are being caused to flow therethrough, we have proposed that there be used a change over valve so that at any one time, one mould is connected to at least one outlet and the changeover valve is such that it will provide for substantially constant flow of material therethrough even while the valve is in a changeover mode to connect to at least a second outlet.

1 0 It will be immediately seen by those familiar with this art as to how this solves the problem.

:Such a changeover valve can either have two or more outlets but in any case, a mould can be connected to a first outlet so that extruding plastics will be introduced into the first mould and during this period, a second loaded mould 1 5 can be removed from a second outlet and a further mould replaced at the second outlet of the changeover valve.

As the mould comes to a fill position, the changeover valve can then be operated and this will be arranged so that as it closes off the outlet to the first mould, it will open at the same rate the outlet to the second mould.

2 0 As such, the outflow from the main chamber of a recycling chamber will not be interrupted, and in practise the screw or auger driving the recycled plastics will be able to maintain a constant speed of rotation. Accordingly there is no need to stop the screw or auger until all of the batch of product has been distributed into its various moulds.

Accordingly the invention in one form can be said to reside in a plastics recycling apparatus including an outlet path for extruding plastics including a changeover valve such that it will provide for substantially constant flow of material therethrough even while the valve is in a changeover mode to connect to at least from a first outlet to a second outlet.

3 0 In preference the changeover valve is such that at any one time, one mould is connected to at least one outlet of the changeover valve.

In preference the changeover valve has at least two outlets such that a mould can be connected to a first outlet so that extruding plastics will be introduced into the first mould and during this period, a second loaded mould can be removed from a second outlet and a further mould replaced at the second outlet of the changeover valve.

In preference there is provided in the changeover valve, a spool which includes a top circular part and a bottom circular part and a screw threaded spigot and between the circular parts is a diversion part which is of a size and shape such that in one position a first outlet is fully closed, and a second outlet 1 0 is fully open and accessible through from the inlet.

In preference the size and shape and orientation within the housing of the i changeover valve is such that when the changeover valve is in a changeover mode from a first position to an alternate position so that second outlet is fully blocked and the first outlet is open, the position of a closure edge is such that it 1 5 will match with the position of a second closure edge so that as the spool is rotated the outlet will just start to be opened as the second outlet starts to be .closed.

In preference the invention is also directed to a method of moulding from a recycling apparatus which comprises the steps of directing molten plastics 2 0 material from the apparatus into a changeover valve to then be directed into a mould wherein the changeover valve is operated to change the flow of plastics **°material from a first outlet connected to a first mould to a second outlet connected to a second mould such that flow of plastics therethrough is maintained at substantially constant flow rate The invention will be better understood when described with reference to a preferred embodiment with the assistance of drawings in which: FIG 1 is a plan view of a changeover valve according to the embodiment with however a central spool shown only in cross section to assist in an understanding of how the arrangement works and showing the position of the 3 0 spool midway between a changeover from one outlet to the other, FIG 2 is the same view as in FIG 1 except that the spool is located so as to be fully diverting the plastics into one outlet as compared to the other, FIG 3 is a full perspective view of the spool which will be inserted into the valve body as shown in FIGS 1 and 2, FIG 4 is a side elevation of the valve spool as shown in FIG 3, FIG 5 is a cross sectional view along the lines 5-5 in FIG 1, and FIG 6 is a cross sectional view along the lines 6-6 in FIG 2.

Now referring to the embodiment in detail and with the assistance of the drawings the recycling unit includes a stirrer in a main chamber which is driven to the extent that plastics materials are caused to be heated to a stage where they melt and merge and thus can be treated as a fluid with relatively high viscosity.

An example of the type of a plastic recycler is described in an application for patent by R H WRIDE PTY LTD having a PCT International Publication No. WO 95/34418 and being published on the 21st December 1995.

This is typical but only illustrative of the type of recycler in question.

15 Output from the recycler is taken through a conduit by a screw or auger to effect transfer of the material and cause this at pressure to be driven into moulds.

The moulds will normally be of a type in which the material will be driven at one end into the mould and the other end will normally be open or visually accessible so that there can be a visual assessment as to when the mould is full.

Conventionally, a first mould is simply removed and a second brought into line as quickly as possible so that any overflowing plastic has to be dealt with in the best way possible. If mistakes are made or the screw is switched off for any period of time or there is a blockage of the line, then the damage to the auger or its drive can occur resulting in considerable time and cost during which useful production is no longer available.

It is at this stage the present invention comes into its own so that there is provided in an outlet from the screw or auger, a changeover valve which is now shown according to our embodiment. The valve has a housing 1 with an inlet 2 and two outlets 3 and 4.

The outlets are adapted in a conventional way to be connected in fluid communication so as to connect to the moulds as desired. Accordingly, the end fittings can be quite different and really can be modified as needed depending upon the type of mould etc.

There is provided in the changeover valve a spool 6 which includes a top circular part 7 and a bottom circular part 8 and a screw threaded spigot 9.

1 0 Between the circular parts 7 and 8, is a diversion part 10 which is of a size and shape such that in one position as shown in FIG 2, it will ensure that the outlet 3 is fully closed, and the outlet 4 is fully open and accessible through from the inlet 2.

S° The size and shape and orientation within the housing however is such that 15 when the valve is in a changeover mode from the position as shown in FIG 2 to an alternate position so that outlet 4 is fully blocked and outlet 3 is open, the position of the closure edge 11 is such that it will match with the position of .*closure edge 12 so that as the spool is rotated by an appropriate angle by a tool adapted to engage square cap 13, the outlet 3 will just start to be opened 2 0 as the outlet 4 starts to be closed.

S. As the spool proceeds through its rotation, the position as shown in FIG 1 is reached in which the outlet 3 is half open and outlet 4 is half closed or in other words the openings are of identical shape. Further rotation of the spool continues with the closure and opening rates in proportion so that there will be a constant flow rate from the auger.

In practice, there can be some tolerance in the close accuracy of this changeover so that it does not need to be exactly in proportion in terms of opening and closing apertures but by providing a changeover valve and having this allow for substantially continuous flow has provided a contribution 3 0 to the former difficulty that has been experienced.

While the constructional details of the valve as shown provide that the spool 6 as shown fits in a convenient way into the cylindrical stepped apertures of the valve body 1, and there is at the bottom a threaded section to which the spool 6 fits, clearly other alternative constructions can be made while achieving the required functions as generally described.

In terms of the specific construction of the changeover valve, the spool 6 can rise or fall a little while the top circular part 7 and the bottom circular part 8 will rise or fall a little through the changeover mode.

What is not shown but which is implicit in the arrangement is that the valve and of course any other parts have appropriate additional heating so as to assist in maintaining the recycled plastics material fluid.

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THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A plastics recycling apparatus including an outlet path for extruding plastics including a changeover valve such that it will provide for substantially constant flow of material therethrough even while the valve is in a changeover mode to connect to at least from a first outlet to a second outlet.

2. A plastics recycling apparatus as in claim 1 further characterised that the changeover valve is such that at any one time, one mould is connected to at least one outlet of the changeover valve.

3. A plastics recycling apparatus as in either of claim 1 further 10 characterised that the changeover valve has at least two outlets such that a mould can be connected to a first outlet so that extruding plastics will be *introduced into the first mould and during this period, a second loaded mould can be removed from a second outlet and a further mould replaced at the second outlet of the changeover valve.

*o 4. A plastics recycling apparatus as in either of claim 1 or 2 further characterised that in the recycling unit includes a stirrer in a main chamber which is driven to the extent that plastics materials are caused to be heated to a stage where they melt and merge and thus can be treated as a fluid with relatively high viscosity.

5. A plastics recycling apparatus as in any one of the preceding claims further characterised such that output from the recycler is taken through a conduit by a screw or auger to effect transfer of the material and cause this at pressure to be driven through the changeover valve into moulds.

6. A plastics recycling apparatus as in any one of the preceding claims further characterised in that there is provided in the changeover valve, a spool which includes a top circular part and a bottom circular part and a screw threaded spigot and between the circular parts is a diversion part which is of a size and shape such that in one position a first outlet is fully closed, and a second outlet is fully open and accessible through from the inlet.

Claims

7. A plastics recycling apparatus as in any one of the preceding claims further characterised in that the size and shape and orientation within the housing of the changeover valve is such that when the changeover valve is in a changeover mode from the position to an alternate position so that second outlet is fully blocked and the first outlet is open, the position of a closure edge is such that it will match with the position of a second closure edge so that as the spool is rotated the outlet will just start to be opened as the second outlet starts to be closed.
8. A plastics recycling apparatus as in any one of the preceding claims 1 0 further characterised such that as the spool proceeds through its rotation, the Saposition is reached in which the first outlet is half open and second outlet is half closed.
9. A plastics recycling apparatus as in any one of the preceding claims further characterised in that the outlets are of identical shape so that as rotation of the spool continues closure and opening rates of the respective outlets will be in proportion so that there can be maintained a constant flow rate of plastics therethrough during the changeover.
10. A plastics recycling apparatus as in any one of the preceding claims further characterised in that the changeover valve and of course any other 20 parts have appropriate additional heating so as to assist in maintaining the *-•recycled plastics material fluid.
11. A changeover valve for a plastics recycling apparatus characterised by including in the changeover valve, a spool which includes a top circular part and a bottom circular part and a screw threaded spigot and between the circular parts a diversion part which is of a size and shape such that in one position a first outlet is fully closed, and a second outlet is fully open and accessible through from the inlet and there is a proportionate opening of one outlet to the extent of closure of the other outlet through a range of changeover positions of the valve.
12. A plastics recycling apparatus outlet changeover valve substantially as described in the specification with reference to and as illustrated by figures of the accompanying drawings.
13. A method of moulding from a recycling apparatus which comprises the steps of directing molten plastics material from the apparatus into a changeover valve to then be directed into a mould wherein the changeover valve is operated to change the flow of plastics material from a first outlet connected to a first mould to a second outlet connected to a second mould such that flow of plastics therethrough is maintained at substantially constant flow rate
14. A plastics recycling apparatus substantially as described in the specification with reference to and as illustrated by the accompanying drawings. A method of moulding from a plastics recycling apparatus substantially as described in the specification with reference to and as illustrated by of the accompanying drawings. Dated this 7th day of Feburary 1997 GRANT ANDREW WRIDE By his Patent Attorneys, COLLISON CO. S. I ABSTRACT A plastics recycling apparatus including an outlet path for extruding plastics including a changeover valve such that it will provide for substantially constant flow of material therethrough even while the valve is in a changeover mode to connect to at least from a first outlet to a second outlet such that at any one time, one mould is connected to at least one outlet of the changeover valve. A changeover valve and a method of extruding to achieve these features are also described. 9:00 see**: :00000 $600 0 0 go**