WO1995011087A1

WO1995011087A1 - Improvements relating to reclaiming tread rubber from vehicle tyres

Info

Publication number: WO1995011087A1
Application number: PCT/AU1994/000640
Authority: WO
Inventors: George Veres
Original assignee: Cmht Technology (Australia) Pty. Ltd.
Priority date: 1993-10-20
Filing date: 1994-10-20
Publication date: 1995-04-27
Also published as: TW249764B; CN1112480A

Abstract

A method of removing rubber from the tread portion of a tyre when that tread portion is in a strip form separated from the tyre sidewalls, said method comprising the steps of sequentially passing the tread portion strip through respective treatment zones and removing rubber from the opposite sides of the breaker strip of the tyre at the respective treatment zones. As the tread portion passes through the first treatment zone, rubber is removed down to the breaker strip of the tread portion and thereafter passing the tread portion through the second treatment zone to remove the rubber from the other side down to the breaker strip. Preferably the high quality tread rubber is removed in the first treatment zone and the carcass rubber in the second treatment zone.

Description

IMPROVEMENTS RELATING TO RECLAIMING TREAD RUBBER

FROM VEHICLE TYRES.

This invention relates to the processing of a vehicle tyre to separately reclaim the rubber from the tread portion of the tyre. A vehicle tyre is constructed in the form of a carcass made up of sheets or strips of reinforcing material impregnated and covered with a rubber compound, the carcass being secured to reinforcement rings forming the respective beads of the tyre, and forming sidewalls that support the tread of the tyre. The tread, made of a higher quality rubber compound, encircles the carcass and incorporates a metal filamentary reinforcement band commonly referred to as a 'breaker strip'. In view of the composition of the tread rubber of the tyre, it has a higher re-sale value and accordingly it is most desirable to carry out the reclaiming of the materials of the tyre in a manner to enable separation of the higher quality tread rubber from the remainder of the carcass of the tyre and in particular, from the rubber of that portion of the carcass that underlies the tread rubber and breaker strip.

It is also desirable to be able to effectively and independently remove the rubber and fibre reinforcement of the portion of the carcass forming the inner wall of the tread portion of the tyre below the breaker strip, although the market value thereof is substantially less than that of the tread rubber.

Throughout this specification, the term "tread portion" means the tyre tread, the breaker strip and the portion of the carcass integral with the breaker strip and immediately therebelow.

It is therefore the principle object of the present invention to provide a method and apparatus for the independent reclaiming of the tread rubber and carcass rubber respectively of the tread portion of a vehicle tyre in an effective and economic manner.

With this object in view, there is provided a method of removing rubber from the tread portion of a tyre when that tread portion is in a strip form separated from the tyre sidewalls, said method comprising the steps of sequentially passing the tread portion strip through respective treatment zones, inverting the strip between said treatment zones, and independently removing rubber from the opposite sides of the breaker strip of the tyre at the respective treatment zones.

More specifically, the method includes the steps of passing the tread portion through a first treatment zone wherein rubber is removed down to the breaker strip on one side thereof, and thereafter inverting the remainder of the tread portion and passing it through the second treatment zone to remove the rubber from the other side down to the breaker strip. Preferably the high quality tread rubber is removed in the first treatment zone and the carcass rubber is removed in the second treatment zone. Conveniently, as the tread portion of the tyre leaves the first treatment zone, it is caused to travel in a helical path so as to be rotated about the direction of its length through 180° to present the opposite side of the tread portion to be operated on in the second treatment zone.

Alternatively, the tread portion is moved along a path supported on one side while the opposed side is subject to treatment to remove rubber from the opposite side, and is then moved along a second path supported on said opposite side while rubber is removed from said one side.

Preferably, said one side is supported on a substantially flat surface and the said opposite side is supported on an arcuate or curved surface. Preferably in each treatment zone the tread portion of the tyre is subjected to ultra high pressure (UHP) fluid jet treatment which breaks down the rubber and any fibre reinforcement therein, into particles. The size of the particles being determined both by the nature of the UHP fluid jet equipment and the speed of traverse of the tread portion of the tyre through the respective treatment zone. Preferably the rate of feed of the tread portion into one or each of the treatment zones is marginally lower than the rate of withdrawal from the same treatment zone so that the area of the tread portion being subjected to the fluid jet treatment is maintained in a taut state which contributes to the effective operation of the UHP equipment. There is also provided by the present invention apparatus for removing rubber from the tread portion of a tyre when the tread portion is in a strip form separated from the sidewalls of the tyre, said apparatus comprising first and second treatment means, means to transfer the tread portion from said first to said second treatment means and adapted to invert the tread portion during said transfer whereby the opposite sides of the tread portion are presented for treatment at the respective treatment means. Conveniently, each treatment means includes a ultra high pressure fluid jet means for operating on the tread portion to break down and particulate the rubber on that side of the breaker strip presented to the UHP jets. Conveniently, the transfer means is arranged to move the tread portion along a part helical path, between the first and second treatment means, so that it is turned through 180° during the passage from one treatment means to the other.

Preferably, the tread portion transfer means is arranged so that as the tread portion strip passes the first treatment means, it is supported on one side, and as it passes the second treatment means, it is supported on the opposite side. The above described method and apparatus for removing rubber from the tread portion of a tyre enables the high value tread rubber to be removed from the tread portion of the tyre in an operation separated from the removal of the carcass rubber from the opposite side of the tread portion of the tyre thereby enabling a higher overall monetary return to be achieved from the process of recycling rubber from vehicle tyres.

The invention will be more readily understood from the following description of one practical arrangement of the apparatus as illustrated in the accompanying drawings.

In the drawings, Figure 1 is a side view of the tyre tread portion processor.

Figure 2 is a sectional view through one of the UHP treatment units.

Figure 3 is an enlarged detailed view of the treatment zone of the processor shown in Figures 1 and 2. Figure 4 is a view of a modified form of the second treatment zone that may be incorporated in the processor shown in Figure 2.

Figure 5 is a diagrammatic representation of a cross section of a typical vehicle tyre.

Referring first to Figure 5 the vehicle tyre 26 has a tread portion 21 sidewalls 27 and beads 28. Conventionally the bead 28 includes a rigid ring made of a number of coils of steel wire. The tread portion 21 comprises a breaker strip 22 normally composed of a metal fibre with a relatively thick outer layer of high quality tread rubber 29. The sidewalls 27 and the inner part 27a of the tread portion being formed of a lower quality rubber with a fabric reinforcement therein. This is the construction of a typical vehicle tyre that can be processed by the method of the present invention. Referring now to Figure 1 of the drawings, the processor for recovering the rubber from the tread portion of a vehicle tyre consists of two UHP treatment units 1 and 2 with an inverting conveyor 3 extending therebetween to transfer the tyre tread portion between the respective treatment units. Each of the treatment units are of the same construction and one of said units will now be described with reference to Figure 2.

As seen in Figure 2, in the treatment unit there is provided an input conveyor unit 5 and an output conveyor unit 6 located respectively on opposite sides of a treatment zone 7.

The input conveyor 5 comprises two endless belt 8 and 9 having respective substantially parallel linear flight sections 10 and 12 defining a linear passage therebetween along which the tread portion of the tyre is conveyed gripped between the flight sections 10 and 12. The flight sections 10 and 12 are spaced apart a distance selected so that the tread portion of the tyre, delivered there into by the intake roller 13, is effectively gripped between, and held flat by, the linear sections 10 and 12 for conveyance to the treatment zone 7.

The output conveyor 6 is of the same basic construction as described with respect to the inlet conveyor 5 with the parallel linear flights 10a and 12a of the conveyor 6 more closely spaced than the flights 10 and 12, in view of the reduction in the thickness of the tread portion of the tyre arising from the removal of portion of the rubber therefrom in the treatment zone 7. The conveyors 5 and 6 are driven from a single motor (not shown) and the drive to the respective conveyors is arranged to provide the linear speed of the flights 10a and 12a to be slightly greater than the linear speed of the flights 10 and 12, preferably of the order of 1% speed differential. This speed differential ensures that the tread portion is maintained in a taut state when passing through the treatment zone 7 to assist in the breakup and separation of the tread rubber into the required particle form.

The output conveyor 6 delivers the partly treated tread portion 21 to the invertor conveyor 3 which is arranged in a helical form so that the tread portion of the tyre exiting from the treatment unit 1 is inverted prior to delivery to the treatment unit 2. The invertor conveyor 3 is in the form of a substantially rigid strip twisted to the required helical configuration with a plurality of rollers 15 extending transversely of the conveyor, and at spaced intervals therealong, the rollers being driven in unison to effect the transporting of the tread portion from treatment unit 1 to treatment unit 2.

Internally, treatment unit 2 is substantially identical to treatment unit 1 having the same arrangement of respective input and output endless conveyors and a treatment zone as previously described. Each of the treatment units 1 and 2 incorporates a respective UHP fluid supply unit 19 and 20 mounted on the frame of the treatment unit to supply the high pressure fluid onto the treatment zones 7 to breakdown into particle form the rubber of the tread portion on that side of the breaker strip 22 exposed to the jets of the UHP cutter unit 24. As seen in Figure 3 in the treatment zone 7 there is provided a UHP cutter units 24 which is preferably of the construction disclosed in detail in Australian Patent Application No. PM 7506 and that disclosure is incorporated herein by reference. As described in said prior patent application each UHP cutter unit includes two heads 17 carrying a plurality of jets, the head preferably being driven in an oscillatory or rotary movement when in operation, which assists in the breaking up of the rubber.

While the tread portion is being treated by the UHP cutter unit, it is supported on the fixed surface 24 and the particles of rubber generated by the cutter head 17 are carried away by the fluid through the passage 18 for subsequent separation from the fluid and drying prior to storage. As the treatment unit 1 removes the tread rubber and the treatment unit 2 the carcass rubber, the differing quality rubbers are separately removed and collected, leaving only the metal fibre breaker strip 22 to be discharged from treatment unit 2, which can be subsequently melted down or otherwise recycled.

An alternative construction of the tyre tread treatment apparatus is shown in Figure 4, this construction having the advantage of reduced complexity and hence reduced cost, and improved reliability together with floor space saving. For convenience and clarity only, the output conveyor 6 is shown in Figure 4 and in a somewhat simplified form for the sake of clarity. However, it is to be understood that the single treatment unit is of the same construction and function as that shown in Figures 1 and 2.

Basically, the alternative construction shown in part in Figure 4 comprises a single treatment unit of the same general construction as the first treatment unit 1 shown in Figure 2 with the invertor conveyor 3 and the second treatment unit 2 being replaced by the magnetic drum treatment unit 30. The drum 31 is mounted above the exit end of the output conveyor

6 of the first treatment unit 1 so that the plane of rotation of the drum is vertically above the lower flight of the output conveyor 6 and the drum is spaced therefrom a distance substantially equal to the thickness of the tyre tread portion issuing from the output conveyor 6. The tread portion at that location comprising the metal breaker strip 22 and the underside or carcass portion of the tread portion.

The peripheral surface 32 of the drum 31 is of steel or other suitable magnetic material and mounted within the drum is a stationary permanent magnet 35 which extends along a total arc of approximately 220°.

The magnet is positioned so that it extends at least from a location to the left of the vertical centre line of the drum 31 , at the lower side thereof adjacent the output conveyor 6, and preferably at least to the vertical axis at the top of the drum 31 or therebeyond to an extent of to about 15°.

Preferably, the magnetic strength of the magnet 35 is substantially uniform at least over the portion below the horizontal centre line of the drum 31. Also, at least over approximately the uppermost 45° of arc, the magnetic strength is preferably progressively decreased. This variation in the distribution of the strength of the magnet is for the purpose of having the high strength zone immediately above the delivery portion of the output conveyor 6 so that the metal mesh of the breaker band is attracted to, and held firmly in contact with the drum 31 as it rotates past the end of the output conveyor 6. As a result, as the drum rotates the remainder of the tread portion is transferred to be magnetically supported by the drum and released from the conveyor. The reduction in the strength of the magnet 35 over the upper portion of the periphery of the drum 31 is to reduce the magnetic force holding the breaker strip to the drum periphery so as to permit and assist in the separation of the metal breaker strip from the surface of the drum. The metal breaker strip 22 is discharged from the peripheral surface of the drum 35 into the chute 34 for subsequent use of melting down to raw material.

Located approximately in line with the horizontal axis of the drum 31 is a single UHP fluid jet head 36 carrying a plurality of jets nozzles which can preferably be of the same general construction as previously referred to with reference to Australian Patent Application No. PM 7506. These jets directs of high pressure liquid against the carcass material on the underside of the breaker strip 22 to thereby remove in a fine particle form this rubber material from the metal fibre of the breaker strip of the tyre tread portion. This released rubber material together with the used high pressure liquid are collected under gravity in the hopper 37 and are subsequently processed in a suitable separator to collect the rubber particles and to pass the water for subsequent recycling in the high pressure jet system.

The cost saving achieved with the construction shown in Figure 4 is substantial in that the second treatment unit 2 is completely replaced by the relatively simple drum and magnet structure.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method of removing rubber from a tread portion of a vehicle tyre when the tread portion is in a strip form separated from the tyre sidewalls, the method comprising the steps of sequentially passing the tread portion strip through respective treatment zones, and independently removing rubber from the opposing sides of the breaker strip of the tyre at the respective treatment zones, and independently collecting the rubber removed at each treatment zone.

2. A method of removing rubber from a tread portion of a vehicle tyre when the tread portion is in a strip form separated from the tyre sidewalls, said method comprising passing the tread portion through a first treatment zone wherein rubber is removed down to the breaker strip on one side of the tread portion, thereafter changing the orientation of the remainder of the tread portion and passing the tread portion through a second treatment zone wherein the rubber from the other side of the breaker strip is removed down to the breaker strip, and independently collecting the rubber removed at each treatment zone.

3. A method as claimed in claim 1 or 2 wherein the tread portion strip is inverted between leaving the first treatment zone and entering the second treatment zone.

4. A method as claimed in claim 1 or 2 wherein the tread portion strip is moved along a substantially linear path as it passes through the first treatment zone and along a curved path as it moves through the second treatment zone.

5. A method as claimed in any one of the preceding claims wherein the tread portion is subject to treatment by ultra high pressure liquid cutting jets in at least the first treatment zone to cut the tread rubber into particles and release the tread rubber from the breaker strip.

6. A method as claimed in claim 5 wherein the tread portion is subject to said treatment by ultra high pressure cutting jets in both the first and second treatment zones.

7. A method as claimed in claim 4 wherein second treatment zone includes a cylindrical surface, and the tread portion issuing from the first treatment zone is attached externally to said cylindrical surface and carried thereby through the second treatment zone.

8. A method as claimed in claim 7 wherein the tread portion is magnetically attached to said cylindrical surface.

9. Apparatus for removing rubber from the tread portion of a tyre when the tread portion is in a strip form separated from the sidewalls of the tyre, said apparatus comprising first and second treatment means, means to transfer the tread portion from said first to said second treatment means and adapted to change the orientation of the tread portion during said transfer whereby the opposite sides of the tread portion are presented for treatment at the respective treatment means.

10. Apparatus as claimed in claim 8 wherein each treatment means includes an ultra high pressure fluid jet means for operating on the tread portion to break down and particulate the rubber on that side of the breaker strip presented for treatment such as UHP jets.

11. Apparatus as claimed in claim 8 wherein the tread portion strip passes the first treatment means, it is supported on one side, and as it passes the second treatment means, it is supported on the opposite side.

12. Apparatus as claimed in claim 10 wherein the second treatment means includes a rotatable cylindrical surface and means to attach the tread portion to said cylindrical surface after leaving the first treatment means.

13. Apparatus as claimed in claim 11 wherein magnetic means are provided and arranged to attach said tread portion to the cylindrical surface by magnetic attraction.

14. Apparatus as claimed in any one of claims 9 to 13 wherein at least one of the treatment means includes ultra high pressure jet means arranged to issue streams of liquid to effect in operation removal of the tread rubber from the breaker strip.