RECLAIMING RUBBER FROM THE SIDEWALL OF A VEHICLE TYRE

Abstract: A method of reclaiming rubber from the sidewall (20) of a vehicle tyre wherein successive sectors (26) of the sidewall are supported in sequence so the internal surface of the sector is substantially flat and presenting the external surface of said supported sector to a plurality of cutters (27). Each cutter is arranged to operate over substantially the full radial extent of the sector to reduce the thickness of the external rubber of the sidewall to substantially the level of the sidewall reinforcement. This operation is repeated along the full extent of peripheral side wall.

Description: RECLAIMING RUBBER FROM THE SIDEWALL OF A VEHICLE TYRE This invention relates to a method and apparatus of reclaiming rubber from vehicle tyres so that the rubber can be recycled in various forms and for any purposes. The increasing vehicle population of the world presents an increasing environmental problem in relation to the disposal of used vehicle tyres. Currently there are large stockpiles of used tyres throughout the world as there has not as yet been developed a method of recovering the constituent of the tyres which is both environmentally acceptable and commercially economic. Burying of tyres in landfill has been used as a method of disposal, however, in view of the size, construction and flexibility of tyres, this result in the respective tyre beads being pressed together forming cavities in the landfill that are difficult to fill with soil or sand, and effectively compact during the landfill operation. Further, it has been found that in these situations the soil tends to settle more than the tyres and the latter may subsequently resurface. Further the alternative practice of burning of tyres as a fuel also presents an environmental problem in the nature of the resulting products of combustion and is relatively inefficient due to low thermal output. Also there is the problem of tyres incorporating non combustible components such as steel reinforcing wires or mesh, which present a further difficulty in the operation of combustion equipment. There have been a number of proposals for stripping the rubber material from the metal or fabric reinforcement, however, most prior proposals have not proven to be economically viable. In order to maximise the financial return from the reclaiming of materials from vehicle tyres, it is desirable to be able to separate substantially all of the rubber content of the tyre from the metal or fabric reinforcement therein, and to further separate the rubbers of different chemical and/or physical characteristics. There are known methods of separately reclaiming the tread rubber from the other less valuable rubber such as is in the tyre sidewalls. These methods consist of separating the tread portion of the tyre from the respective sidewalls to provide an elongated tread strip incorporating a tread reinforcement belt, and then removing the tread rubber in a particle form from the tread reinforcement belt. The sidewall of the tyre is frequently not further processed as it is considered too costly relative to the quantity and quality of the rubber therein. The reduction of the sidewalls to particle form may be effected mechanically such as by rotary knives or by high pressure liquid jets, commonly referred to as ultra high pressure liquid cutting. However, this results in breaking down of the fiber reinforcement in the sidewall and then requires a further operation to separate the rubber from the reinforcement particles and hence incurs added costs. However the quality and quantity of the rubber in the sidewalls of truck and other heavy duty vehicles is much greater than in conventional passenger vehicles. If the outer rubber and the inner butyl rubber can be individually removed and collected, recycling thereof can be commercially viable. It is the object of the present invention to provide a method and apparatus for the processing of vehicle tyres to recover rubber from a tyre sidewall in a commercially economic manner. With this object in view, there is provided a method of reclaiming rubber from the sidewall of a vehicle tyre comprising supporting in sequence successive sectors of the sidewall so the internal surface of the sector is substantially flat, presenting the external surface of said supported sector to a plurality of cutters each arranged to operate over substantially the radial extent of the supported sector, and operates the cutters to reduce the thickness of the external rubber of the sector to substantially the level of the sidewall reinforcement. Conveniently, successive sectors of the sidewall after treatment of the external surfaces are supported so the treated external surface thereof is substantially flat, and the internal surface is presented to a further plurality of cutters similarly arranged to reduce the thickness of the internal rubber of the sidewall to substantially the level of the sidewall reinforcement. Preferably, the supporting of the sectors of the sidewall to provide the substantially flat external surface is effected after the external surface of that sector has been processed to reduce the thickness of the external rubber. As is known, the composition of the rubbers on the internal surface of the sidewall is a butyl rubber, having different characteristics and composition, and often has delaminating effects than the more conventional rubber on the external surface of the sidewall. Accordingly, it is significant that the rubber on the internal and external faces of the tyre sidewall is removed in separate operations and can be independently collected. As the internal surface of the sidewall, in the pre-treatment, is of a substantially smooth nature compared with the irregular nature of the external surface, it is more convenient to initially support the sectors of the tyre on the internal side of the tyre sidewall. The removal of the rubber on the external side, while the sector is supported on the flat internal side, produces a smooth external surface, to then be supported, while the rubber is removed from the internal side of the sidewall. Conveniently, the cutters used to remove both the internal and external rubber are of a construction that performs a cut along the total radial length of the supported sectors of the sidewall. The cutter can be in the form of an endless band supported on spaced rollers to form a cutter band of a length substantially equal to the radial extent of the tyre sidewall. not including the bead area. A series of such cutter bands may be provided in a side by side relation each set to perform a cut of substantially equal depth, and together a cut of a total depth to remove the sidewall rubber down to the level of the sidewall reinforcement. In a preferred form of apparatus for carrying out the above method, the tyre sidewall is supported to be rotatable about its axis and two support stations are provided spaced circumferentially along the rotational path of the support sidewall. Each support station is arranged to support the section of the sidewall as it passes therethrough. One support station contacts the inner face of the sidewall to support a section of the sidewall with the inner surface thereof substantially flat. At least one cutter is provided to operatively engage the outer surface of the supported section of the sidewall. Each cutter preferably extends substantially the whole of the radial width of the sidewall. The other support station, being upstream in the direction of rotation from said one support station, is arranged to contact the outer surface of the sidewall to support the section thereof while applying a cutter to the inner surface of the supported section of the sidewall. Conveniently, each of the supports comprise two pairs of rollers arranged in a spaced relation along the periphery of the sidewall, with the sidewall passing between the rollers of each pair. A plurality of cutters are arranged to operate on each of the section of the sidewall while supported, each cutter operating concurrently to progressively reduce the thickness of the rubber covering from each side of the tyre sidewall. The invention will be more readily understood from the following description of a practical application of the method of the invention and of the apparatus suitable for the performance thereof. In the drawings, Figure 1 is a diagrammatic representation of the stages of recovering the rubber from the tyre sidewall: Figure 2 is a diagrammatic plan view of an apparatus for use in carrying out the recovery of the rubber from the sidewall; Figure 3 is an enlarged more detailed illustration of the apparatus for supporting the sidewall and reducing the rubber content to a particle form. Referring now to Figure 1 of the drawings, there is shown in the tower drawing, a cross-sectional view of the sidewall of a typical truck of like high load capacity' vehicle tyre, which has been separated from the tread portion of the tyre. As shown, the sidewall portion of the tyre is made up of the outer sidewall rubber layer 10, the inner sidewall rubber layer 1 1 which is usually a butyl rubber, and the sidewall reinforcement strip 12 which is usually a woven mesh of metal fibres but may also be of a non-metalic fibre material. The bead portion of the tyre sidewall as represented at 14 includes the wire bead assembly 15 which is a concentrated assembly of metal fibres forming a substantially inelastic core to the bead area of the tyre. The reinforcing strip 12 extends partially about the bead wire assembly 15 as does additional bead area reinforcement fibre 16 and the encasing rubber cover 17. In the first stage of the recovery of the rubber from the sidewall. the external rubber casing 10 is removed from the fabric core 11. and the bead portion 14. This is the major portion of the rubber recovered from the sidewall, although its commercial value per unit weight is less than that of the inner lining butyl rubber 1 1. In the second stage, the relatively thin layer of butyl rubber 1 1 on the internal face of the sidewall is removed. This rubber is also removed for a significant portion of the bead area of the tyre as can be seen in the diagram of stage 2. In stage 3, the remaining rubber which is impregnated in the reinforcing strip 12 is removed so as to only leave the non-rubber woven material which forms the core. The separation of the final stage of rubber from the core may be carried out by use of ultra high pressure water jets which can be arranged to effectively remove the rubber material without breaking up the core material which is normally in the form of a woven metal mesh. The final stage 4 processes the bead area 15 of the tyre so as to remove all of the remaining rubber therefrom and leaving only the metal core of the tyre bead. This final stage may not always be performed, however, when processing large truck tyres or particularly heavy vehicles such as earth or rock transporting vehicle tyres, there is a substantial quantity of rubber remaining in the bead area 15 after the completion of stage 3 thus for economic reasons, stage 4 will be performed particularly as it releases the wire cords in a substantially clean state which are of significant value for metal recycling when so separated from the rubber. Referring now to Figure 2, there is illustrated diagrammatically, the layout of the equipment for carrying out stages 1 and 2 as described above with reference to Figure 1. The platform 20 of circular form is supported to rotate on its axis 21 and is of a size suitable to support the sidewalk portion of tyros within a specified range of tyre sizes. Subject to the range of tyre sizes to be processed platforms of different sizes may be required. As illustrated, there are two processing stations 21 and 22 arranged in a diametrically opposite relationship to the centre of rotation of the platform. At each station, there are provided two roller assemblies 25, each comprising two rollers 23 and 24, defining therebetween a rubber separation area 26, each including a cutter unit 27. As shown in Figure 2, the lower processing station 21 is arranged to remove the outer rubber from the sidewall assembly and the upper processing station is to remove the butyl rubber from the inner side of the tyre sidewall. The rollers of each operating station as seen in Figure 3 are of a tapered roller form, the degree of taper being related to the change in diameter from the inner to the outer end of each roller, and is selected so that the peripheral speed on the roller surface is substantially uniform along the length thereof. The pairs of rollers 23-24 are arranged relative to the plane of the rotating table 20 so as to deflect the sidewall along the major part of its radial extent, relative to the bead portion so that what is the inner side of the sidewall is substantially straight as seen in Figure 3 and as compared with the shape as shown in Figure 1. To assist in achieving this effect as seen in Figure 3. the peripheral surface of the lower roller 24 is a smooth continuous surface, whilst the upper roller 23 is made up of a number of sections of differing diameters so that they will contact the outer side of the sidewall at a number of locations along the radial extent of the sidewall. This aspect of the upper roller being clearly depicted in Figure 3 of the drawings. As can be appreciated form a viewing of Figures 2 and 3. as the support table rotates, and the sidewall of the tyre is passed between the two space pairs of support rollers, the sector of the sidewall between the two roller assemblies will be substantially supported with the underface of the sidewall substantially flat, and hence the cutter assembly 27 located therebetween can remove the outer layer of rubber from the sidewall down to the level of the sidewall reinforcement. The cutter may comprise a plurality of cutter elements set at different heights so that the outer rubber of the sidewall is progressively reduced in height as it passes beneath the cutter. Hence the particle size of the rubber removed from the outer side of the sidewall is maintained substantially uniform and of the required size which is determined by the degree of difference in height of the respective cutters. Preferably, the cutter is made up of an endless cutter band 30 such as 30 shown in Figure 3 having closely spaced teeth projecting from the periphery thereof. This cutting band may be of a construction similar to that employed in the commonly known chainsaw, although it is intended that the cutter band will be of a specific design for the purpose of cutting rubber at the desired level of particle size. As the sidewall leaves the opposite end of the support assembly, the outer surface of the sidewall will have had rubber removed therefrom in a particle form down to the level as indicated in stage 1 of Figure 1. The sidewall will then continue to rotate with the table 10 to reach the second cutter station at the diagonally opposite location. There it will again pass through to circumferentially spaced pairs of rollers and will now be subjected to a plurality of cutters located on the underside of the sidewall to thereby remove from the butyl rubber in the operation as represented at stage 3 in Figure 1. As the opposite faces of the sidewall are both substantially flat and hence the sidewall is of a substantially constant thickness, the rollers of each pair can now be of a substantially plain cylindrical form and are not required to have a stepped roller as previously referred to in respect of the first processing station. Again, an assembly of cutters of the same general form as previously described are provided between the respective roller assemblies on the underside of the portion of the sidewall supported between the rollers to remove the butyl rubber. In order to accommodate the depressed contour shape at 36 to effectively support the sidewall while being processed. The roller 23 is contoured to provide effective support of the sidewall while the external surface is being operated on by the cutter 30. It will be noted the support roller 24 on the under or inner wall of the sidewall is of a plain conical shape as also shown in Figure 3. The upper cutter assembly 30 in the form of an endless band 38 having a plurality of spaced cutter teeth 39 along the length thereof. As can be seen in Figure 2 each cutter assembly has a series of endless cutter bands, there being three side by side cutter bands 27 shown in Figure 2. Each of the cutter bands 39 are at a different level so that as the sidewall is fed past the cutter they are cut at progressively lower levels of the outer sidewall rubber. This results in the rubber particals produced being of a smaller size than if a single cutter was used to cut to the full depth of the rubber on the sidewall. As is seen in Figure 2 each of the cutter assemblies 21 and 27 have three cutter bands identified as A, B and C respectively however the number of cutter bands is selected relative to the fineness required of the rubber particles produced. Normally more cutters would be used to remove the external rubber than to remove the inner butyl rubber which is in a relatively thin layer on the inner face of the sidewall The process and mechanisum as described herein enable the rubber in the sidewall of large tyres to be effectively reclaimed for further use in an effective manner and at an acceptable cost to render economic recycling of this rubber.

Claims: CLAIMS 1. A method of reclaiming rubber from the sidewall of a vehicle tyre comprising supporting in sequence successive sectors of the sidewall so the internal surface of the sector is substantially flat, presenting the external surface of said supported sector to a plurality of cutters each arranged to operate over substantially the radial extent of the supported sector, and operates the cutters to reduce the thickness of the external rubber of the sector to substantially the level of the sidewall reinforcement. 2. A method as claimed in Claim 1 wherein subsequently successive sectors of the sidewall after treatment of the external surfaces are supported so the treated external surface thereof is substantially flat, and the internal surface is presented to a further plurality of cutters similarly arranged to reduce the thickness of the internal rubber of the sidewall to substantially the level of the sidewall reinforcement. 3. A method as claimed in Claim 1 wherein the supporting of the sectors of the sidewall to provide the substantially flat external surface is effected after the external surface of that sector has been processed to reduce the thickness of the external rubber. 4. A method as claimed in any one of Claims 1 to 3 wherein the sidewall is separated from the tread portion of the tyre prior to presenting the sidewall to the cutters. 5. A method as claimed in Claim 4 wherein the separated sidewall is rotated on the axis thereof and the external and internal surfaces are sequencially presented to the cutters. 6. A method as claimed in Claim 4 wherein one or more cutters are presented to the external surface of the sidewall and at the same time one or more cutters are presented to the internal surface of the sidewall. 7. A method as claimed in Claim 6 wherein at least one cutter is presented to the external surface of the sidewall and at least one cutter is presented to the internal surface of the sidewall at peripherally spaced locations about the axis of the sidewall. 8. A method as claimed in Claim 7 wherein at each spaced location means are provided to engage the sidewall on the side thereof opposite the cutter and arranged to restrict deflection of the sidewall while it is subjected to the action of the cutter. 9. A method as claimed in Claim 7 wherein at the location of each cutter the sidewall is supported on the side opposite the cutter to restrict deflection of the sidewall while it is subjected to the action of the cutter. 10. A method as claimed in Claim 9 wherein a section of the sidewall is supported at two peripheral spaced locations between respective complementary' rollers arranged to support the portion of the sidewall extending there between in a taut condition, and subjecting the taut part of the sidewall to a cutting action to remove sidewall rubber down to a preset level. 11. A method as claimed in Claim 10 wherein the sidewall rubber removed is that on the outer face of the sidewall. 12. Apparatus for reclaiming rubber from the sidewall of a reinforced vehicle tyre comprising means to support a sector of the sidewall in a substantially flat state as the sidewall rotates on its axis, and means to subjecting one side of said sector to a cutting action while in said substantially flat state to remove the sidewall rubber to substantially the depth of the sidewall reinforcement. 13. Apparatus as claimed in Claim 12 wherein means are provided to support a sector of the sidewall on said one side after said removal of the rubber therefrom, and means are provided to subject the other side of said sector of the sidewall to a cutting action while in said flat state to remove the sidewall rubber therefrom to substantially the depth of the sidewall reinforcement. 14. Apparatur as claimed m Claim 12 or 13 wherein each means to support the sector comprises two roller assemblies one defining the entry to the support sector and the other the exit from the support sector, the roller assemblies being arranged to maintain the portion of the side wall therebetween taut. 15. Apparatus as claimed in Claim 14 wherein each roller assembly comprises two superimposed rollers supported in a radial relation to the axes of the sidewall. 16. Apparatus as claimed in Claim 15 wherein cutter means are located between the two roller assemblies operatively arranged to remove rubber from one side of the tyre wall as it passes from one roller assembly to the other. 17. Apparatus as claimed in Claim 16 wherem the cutter means is adapted to progressively reduce the thickness of the rubber as it passes from one roller assembly to the other

Inventors: VERES GEORGE, VERES, GEORGE
Applicants: BENGOLD HOLDINGS PTY LTD, VERES GEORGE, BENGOLD HOLDINGS PTY. LTD., VERES, GEORGE
Application year: 1998
Main classification: B29B17
IPC codes: B26D1, B29B17