IMPROVEMENTS RELATING TO RECLAIMING TREAD RUBBER FROM VEHICLE TYRES

Abstract: A method of removing rubber from the breaker strip of the tread portion of a tyre, the method comprising the step of treating the tread rubber with UHP fluid jets with the jets inclined to the plane of the breaker strip of the portion of the tread being treated, so that the treat rubber is subjected to a cutting action in a direction inclined to said plane of the breaker strip. The portion of the tread rubber being treated by the UHP fluid jets is simultaneously subjected to treatment by UHP fluid jets inclined to each other and which intersect at or near the level of the breaker strip.

Description: IMPROVEMENTS RELATING TO RECLAIMING TREAD RUBBER FROM VEHICLE TYRES. This invention relates to the processing of a vehicle tyre to reclaim rubber therefrom particularly the rubber from the tread portion of the tyre. A vehicle tyre is constructed in the form of a carcass made up of a layer of reinforcing material impregnated with a rubber compound, the carcass being secured to a rubber impregnated metal reinforced rings forming the respective opposite beads of the tyre, and supporting the tread portion of the tyre. The tread portion, made of a higher quality rubber compound, encircles the central portion of the carcass, and incorporates a metal filamentary reinforcement band, commonly referred to as a 'breaker strip'. In view of the composition of the rubber of the tyre tread portion it has a higher re-sale value if free of foreign materials and other rubbers incorporated in the tyre. Accordingly it is desirable to carry out the reclaiming process in a manner to enable separate collection of the higher quality tread rubber from the rubber of the remainder of the carcass of the tyre, and in particular, from the portion of the carcass that underlies the tread rubber, and the breaker strip. A new and effective method and apparatus for separately removing the high quality tread rubber from the breaker strip and other components of the tyre is disclosed in published Australian Patent Application No. 19725/92 wherein ultra high pressure (UHP) water (or other fluid) jets issuing from an array of nozzles are used to paniculate the rubber of a tyre carcass. In this prior proposal the UHP jets are directed in a direction at right angles to the surface of the portion of rubber being removed. It has been found that this relative arrangement of the UHP jets to the surface of the portion of rubber being treated results in short lengths of the rubber remaining attached to the tyre reinforcement. In the removal of tread rubber this residual rubber is in the form of short individual fibres of rubber upstanding from the tyre breaker strip and attached thereto at one end. These residual tread rubber fibres represent a loss in the quantity of recovered high value tread rubber, and also necessitates the performing of a further treatment the breaker strip if the metal wires thereof are to be totally free of rubber and suitable to be recycled. It is therefore the object of the present invention to provide a method and apparatus for releasing the tread rubber from the breaker strip of a vehicle tyre whereby substantially all of the tread rubber is removed from the breaker strip in a single operation. With this object in view, there is provided a method of removing rubber from the breaker strip of the tread portion of a tyre the method comprising the step of treating the tread rubber with UHP fluid jets with at least some of the jets directed in a direction inclined to the plane of the breaker strip of the portion of the tread being treated, to thereby subject the tread rubber to a cutting action in a direction inclined to said plane of the breaker strip. The inclination of the respective UHP fluid jets are arranged so that the jets issuing from adjacent nozzles intersect at or near the interface of the breaker strip and the tread rubber. Conveniently, the portion of the tread rubber being treated by the UHP fluid jets is simultaneously subjected to treatment by UHP fluid jets inclined to each other, in one example, the simultaneous treatment is effected by first jets substantially normal to the plane of the breaker strip and second jets inclined to the plane of the breaker strip. The inclination of the respective UHP fluid jets are arranged so the inclined jet intersect the normal jets at or near the interface of the breaker strip and the tread rubber. In an alternative arrangement the UHP fluid jets are arranged in pairs each oppositely inclined. Conveniently, the tread portion of the tyre is subjected to treatment by a plurality of UHP fluid jet arranged in a bank which moves in a circular path. Preferably each bank moves in a circular path so that the paths of adjacent UHP fluid jets move in overlapping circular paths. The banks of jets and the circular paths thereof are arranged so together a band of tread rubber extending across the width of the tyre tread is processed simultaneously. The jets are conveniently each inclined to the plane of the breaker strip at an angle of 65° or more, preferably in the range of 70° to 80°. It is to be understood that if the angle of inclination is too low or flat in relation to the surface being cut, the jet is deflected or dispersed rather than penetrating the surface it contacts. Thus, the jets do not cut to the full depth of the tread rubber. In one configuration, two rows of jets are provided, the jets in the respective rows being oppositely inclined at equal angles to the breaker strip surface to form a bank of jets, the included angle therebetween being in the range up to 45° and preferably between 20° and 40°. Conveniently, there is provided more than one bank of nozzles each having a number of jet nozzles mounted therein, and each bank moving in a circular path. Each nozzle bank do not rotate on a fixed axis but moves along a circular path while maintaining a substantially fixed orientation with respect to the tyre tread portion. The nozzles in each bank are arranged in two oppositely inclined rows so that the path described by adjacent nozzles, as the nozzle bank traverses the circular path, overlap. Preferably the paths of adjacent nozzles in the same row overlap one with the other and the paths of adjacent nozzles in opposite rows also overlap. There is also provided by the present invention apparatus for removing rubber from the breaker strip of the tread portion of a tyre comprising, an array of nozzles arranged to each receive UHP fluid to issue therefrom as UHP fluid jets, at least some of said nozzles being arranged so the UHP fluid jet issued therefrom is inclined to the plane of the breaker strip from which the rubber is to be removed. Preferably the nozzles are arranged in one or more banks each having two parallel rows of nozzles with the nozzles in one row inclined to the nozzles in the adjacent row. The inclination of the nozzles in the respective rows of each bank being conveniently such that in use the fluid jets intersect or cross substantially at the face of the breaker strip from which the tread rubber is to be removed. Preferably the included angle between the fluid jets in adjacent rows is up to 45° and more particularly between 20° and 40°. The invention will be more fully understood from the following description of one practical arrangement of a multi-nozzle block as illustrated in the accompanying drawings, and of the operation thereof. In the drawings, Figure 1 is a diagrammatic cross-sectional view of a typical vehicle tyre. Figure 2 is a side elevational view of the nozzle block. Figure 3 is a view from below of the nozzle block; shown in Figure 2. Figure 4 is a sectional view along the lines 3-3 in Figure 2; Figure 5 is an illustration of one arrangement overlapping nozzle paths; Figure 6 is an illustration fo multi-nozzle block layout. Figure 7 is a suitable drive mechanism to move a pair of nozzle blocks in respective circular paths. Referring first to Figure 1 , the conventional vehicle tyre 26 shown therein has a tread portion 21 opposite sidewalls 27 each having a bead 28. Conventionally each 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 metal fibres with relatively thick outer layer of high quality tread rubber 29 bonded thereto. The sidewalls 27 and the inner wall part 27a underlying the tread portion are formed of a lower quality rubber usually 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 2, the nozzle block 10 is made of steel or a material of comparable strength having regard to the fluid pressure at which the cutting process is to be performed. Extending upwardly from the lower face 18 of the nozzle block 10 are a series of fourteen nozzle cavities 11 arranged in two side by side rows. Each of seven nozzle cavities 11 in each row as seen in Figure 3 are collectively ad identified respectively as rows A and B. The centre lines only of the respective nozzle cavities are shown in Figure 2 for the sake of clarity. The cavities 11 in row A each communicate with distribution duct 14 by respective nozzle passages 13, and the cavities 11 in row B communicate with the distribution duct 15 by respective nozzle passages 16. Each of the distribution ducts 14 and 15 individually communicate with the chamber 17 by respective transverse ducts, such as at 19 extending between duct 15 and chamber 17. In use the chamber 17 is coupled to a source of high pressure liquid, such as water. The nozzle cavities 11 and the nozzle passages 13 and 16 are equally and oppositely inclined with respect to the lower face 18 of the nozzle block 10. The included angle between the respective passages 13 and 16 being of the order of 30°, and being symmetrical with respect to the central vertical plane through the nozzle block 10. The nozzle cavities 11 and their associated nozzle passages, resultantly having the axis thereof inclined at 75° to the plane of the lower face 18 of the nozzle block 10. Nozzles (not shown) of known construction are removably fitted into each of the nozzle cavities 11 , such as by threaded engagement. The bore size of the nozzle is selected to provide the desired diameter and velocity of the liquid jet issuing from the nozzle, having regard to the pressure at the nozzle of the fluid supplied from the chamber 17. The included angle between the jets issuing from the nozzles in the respective rows, and the distance between the rows of nozzles, are selected so that the plane of the respective rows of jets intersect at E as shown in Figure 4, a distance from the lower face 18 of the nozzle block 10 determined by the angle of inclination and the lateral spacing of the nozzle cavities. In use the nozzle block is located so that the intersection of the jets as indicated at E is substantially at or about the level of the upper surface of the metal reinforcement of the breaker strip in the tread portion 21 of the tyre being processed. This results in the tread rubber of the tyre being removed completely down to the level of the metal reinforcement, constituting the breaker strip. This relative relation of the nozzle block and the fluid jets to the breaker strip ensures that the tread rubber is removed right down to the surface of the breaker strip 22, thereby providing maximum recovery of the high value tread rubber, and a high level of cleaning of the tread rubber from the breaker strip prior to subsequent processing of the steel filaments forming the breaker strip. Th effectiveness of the removal of the tread rubber from the bis enhanced if the nozzle block 11 is subjected to a movement so that breaker strip the nozzle cavities 11 and the nozzles assembled thereto, each move simultaneously in a circular path as shown diagrammatically in Figure 5. As seen in Figure 3 the nozzle cavities in row B are offset with respect to the nozzle cavities in row A by a distance equal to one half of the pitch between adjacent nozzles in the row. Further as seen in Figure 5 the circular path of the nozzle assembles is greater than the space between two adjacent nozzle in the same row W so that those paths of two adjacent nozzles in the same row overlap. Further it is seen that the path of the nozzle assembles in row B overlap the paths of the two adjacent nozzle assemblies in row A. As a result of this movement a strip of the width "C" is treated by the single nozzle head. Normally two or three nozzle heads are arranged to span the full width of the tyre tread portion, as shown diagrammatically in Figure 6, so that the full width of the tread portion of the tyre can be striped of tread rubber in a single pass. As shown, the tyre tread portion 25 is fed in the direction of the arrow D and the tread rubber 26 is progressively removed down to the upper surface of the metal breaker strip across the width of the tread. In one example, the nozzles in each of the rows A and B are spaced at a pitch of 9 mm and the circular movement of the nozzle block is 12 mm diameter so that there is an overlap of 2 mm in the paths of adjacent nozzles. Further, the nozzles in rows A and B are spaced in the direction of the row by 1/ 2 said pitch, and spaced laterally 9 mm. Thus, the path of movement of the nozzle in the direction across the rows A and B also overlay by 2 mm also. Typically the feed rate of the tread portion of the tyre past the nozzle bank is in the order of 350 to 1000 mm per minute. A simplified illustration of a drive mechanism suitable to effect the above referred to circular movement of two adjacent nozzle assemblies, as shown in Figure 6, will now be described with reference to Figure 7. Two nozzle assemblies 10 as previously described are rigidly mounted on the opposite sides of the carrier column 30, at the lower end thereof. The base plate 31 is rigidly mounted in a fixed position on the base or frame of the machine through which the tyre tread portion is fed for the removal of the tread rubber. Mounted on the base plate 31 is a gear box 32, and an electric motor 33 is mounted on the gear box 32. Within the gear box 32 are two spaced shafts 34 (shown in broken outline) which are derived to rotate in unison by the electric motor 33. Each shaft 34 has upper and lower eccentric portions which engage circular apertures in the respective drive rods 35 whereby rotation of the shafts 34 will impart a circular orbital movement to each of the rods 35, to move the rods in unison. The carrier bar 36 is fixedly secured at the respective ends thereof to the rods 35 so as to also describe a circular orbital motion with the rods 35. The circular orbital motion may be of the order of 400-500 cycles per minute. Mounted on the carrier bar 36 is a bracket 37 to which the carrier column 30 is attached so as to impart the circular orbital motion thereto. The bolts 38 attaching the bracket 37 to the carrier bar 36 permit adjustment of vertical position of the bracket and hence of the nozzle assemblies 10. This enalbes the nozzle assemblies to be correctly positioned relative to the size of tyre being processed so that the UHP jets intersect at the surface of the breaker strip.

Claims: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A method of removing rubber from a breaker strip of a tread portion of a vehicle tyre, the method comprising the step of treating the tread rubber with a plurality of UHP fluid jets with at least some of the jets directed in a direction inclined to the plane of the breaker strip of the portion of the tread being treated, to thereby subject the tread rubber to a cutting action in a direction inclined to said plane of the breaker strip. 2. A method as claimed in claim 1 wherein the inclination of two adjacent UHP fluid jets is arranged so that the jets are disposed in respective planes that intersect at or near an interface between the breaker strip and the tread rubber. 3. A method as claimed in claim 1 wherein the portion of the tread rubber being treated by the UHP fluid jets is simultaneously subjected to treatment by a plurality of UHP fluid jets each inclined to the interface between the breaker strip and the tread rubber. 4. A method as claimed in claim 3 wherein the portion of the tread rubber being treated by the UHP fluid jets is simultaneously subjected to treatment by first jets substantially normal to the plane of the breaker strip and second jets inclined to the plane of the breaker strip. 5. A method as claimed in any of the preceding claims wherein a plurality of UHP fluid jet are arranged in a bank and said bank of jets is moved in a circular path substantailly in the plane parallel to the breaker strip. 6. A method as claimed in claim 5 wherein the circular path is arranged so that the paths of adjacent UHP fluid jets move in overlapping circular paths. 7. A method as claimed in claim 6 where the banks of jets and the circular paths of movement thereof are arranged so a band of tread rubber extending in a direction across the width of the tread portion is processed simultaneously. 8. A method as claimed in any one of the preceding claims where the angle at which the jets are inclined to the plane of the breaker strip is between 65° and 80°. 9. A method as claimed in claim 8 wherein the angle is between 70° to 80°.

Inventors: VERES GEORGE, VERES, GEORGE
Applicants: CMHT TECHNOLOGY AUSTRALIA, VERES GEORGE, CMHT TECHNOLOGY (AUSTRALIA) PTY. LTD., VERES, GEORGE
Application year: 1995
Main classification: B29B17
IPC codes: B26D1, B29B17