GB2294423A

GB2294423A - Vehicle tyre stripping apparatus

Info

Publication number: GB2294423A
Application number: GB9421670A
Authority: GB
Inventors: Raymond Joseph Bates; Edward Learmouth
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-10-27
Filing date: 1994-10-27
Publication date: 1996-05-01
Anticipated expiration: 2014-10-27
Also published as: GB9421670D0; GB2294423B

Abstract

Apparatus for stripping useable rubber from vehicle tyres comprises a table 4 has means (6 Fig. 1) for mounting a tyre 2 thereon, and a cutter assembly (28) which are rotatable relative to each other. The cutter assembly has a cutter block 32 which is movable relative to the tyre by control means. Different arrangements of cutter blade knives are possible (Figs 4 - 6). The apparatus may be adapted to detect electrical contact between a cutting blade (40, 44, 46 Figs 4 - 6) of the cutter assembly and the wire skeleton of a tyre 2, and withdraw the blade from the tyre to a predetermined extent upon detection of such contact. <IMAGE>

Description

VEHICLE TYRES This invention relates to vehicle tyres, and more particularly to apparatus for stripping usable rubber therefrom. It has especial, but not exclusive, application in connection with radial ply tyres in which rubber is moulded round a metallic skeleton.

Vehicle tyres are usually discarded in toto after the tread surface has been fully worn. However, even after a tyre tread has been re-cut, the carcass as a whole contains usable rubber, particularly in the side walls. The present invention is directed at apparatus for stripping rubber from the tyre carcass.

According to the invention, such apparatus comprises a table with means for mounting a tyre thereon; a cutter assembly having a block for supporting at least one stripping blade; and means for controlling the position of the block, and thereby a blade thereon, relative to the table during rotation of the table relative to the cutter assembly. Normally, the table will be rotated while the block is moved relative thereto across a side wall or the tread surface of a tyre mounted thereon. However, the apparatus can be operated equally effectively in some situations if the table is held stationary and the cutter assembly is moved relative thereto to strip rubber from a mounted tyre. Where rubber is being stripped from the tread face of a tyre carcass, there is no essential requirement for translational movement of the tyre relative to the blade block once the stripping is commenced.In those circumstances particularly, it is envisaged that the tyre may be held stationary and the entire relative movement accomplished by movement of the block bearing the stripping blades.

As mentioned above, apparatus according to the invention may be adapted to strip rubber from the tread surface or side wall of a tyre carcass. The stripped rubber is preferably in the form of lengths with cross-sections of the order of 100mm2. Rubber stripped in this form has a number of uses, and the relatively small cross-sectional dimensions enables lengths to be cut with relatively little power being required to drive the blade or blades through the rubber. The rubber may be cut in rings; spirals (from the side walls), or coils (from the tread face).

If cutting spirals or coils, single strips of rubber of considerable length may be removed. For example, a 15m strip can be cut from the side wall of an industrial vehicle tyre.

The dimensions of a rubber strip cut from a tyre in accordance with the invention is of course determined primarily by the depth of rubber available in the tyre carcass. According to the invention, means may be provided for setting or controlling the depth at which the stripping blade is located in the carcass, and this can typically be accomplished using a device which moves over the surface of the carcass in which the stripping blade is cutting. However, in order to remove the maximum quantity of rubber from the tyre carcass, particularly a carcass based on a wire skeleton, we have developed a sensing system which ensures that the stripping blades cut as close as is reasonably possible to the wire skeleton. The system comprises an electric circuit including a blade on the block and the wire skeleton of a tyre carcass.The circuit is closed by contact between the wire skeleton and the blade, which closure generates a control signal.

The generation of a control signal activates a mechanism which withdraws the block and blade from the skeleton. Such withdrawal opens the circuit, and the control signal ceases. The withdrawal mechanism will typically operate in steps of a predetermined extent, such that upon generation of the control signal the blade is withdrawn say, lmm. Using a system of this kind, it will be appreciated that the cutter assembly can move over the surface of a tyre side wall, closely following the contours thereof, and stripping substantially all available rubber from the carcass above or outside of the metal or wire skeleton.A tyre carcass that has been stripped to this extent over the side walls and the tread face, is much better suited for the reclamation of the skeleton metal than tyres carrying greater quantities of rubber which have of course to be burned off or otherwise removed before the metal can be reclaimed.

Where a tyre carcass has a metal skeleton, the skeleton is substantially continuous, and is accessible electrically via the beading at the inner boundary of each tyre wall. This beading provides a convenient location at which to make electrical contact with the skeleton. The tyre must of course be mounted on the table, and a convenient means for such mounting comprises radial jacks which anchor against the two tyre beads. One or more terminals can be mounted on the arms of the jacks which penetrate the inner layer of cover rubber to make contact with a respective bead. The electrical connection to the block of the cutter assembly is of course quite straightforward as the block and the blade mounted thereon will normally comprise a conductive metal in any event.

In the normal use of apparatus according theinvention, the table will be rotated as the cutter assembly is moved over the respective side wall or tread face of the tyre mounted thereon.

Typically, the table rotates as a speed of around one revolution per second, but faster or slower speeds and can be appropriate, and of course it may be desirable to accelerate the rotational speed as the cutter assembly moves radially inwards to ensure that the actual stripping rate remains substantially the same.

The speed of rotation, and thus the stripping speed, will in any event, normally be selected with reference to the action of the cutter assembly. For example, if strips of relatively small cross-section are being cut then a higher stripping speed may be possible. Faster stripping speeds are also possible if the operative blade or blades on the block are heated. It should also be noted that the faster the rate of stripping, the less power is required to move the block of the cutter assembly transversely to the plane of cutting.

Another factor determining the stripping speed is of course the number of blades in operation simultaneously. For example, if two orthogonal blades mounted on the block are to function simultaneously to strip a continuous length of rubber from a tyre carcass in the form of a spiral or coil, then the stripping speed will normally be less than would be used if a plurality of blades oriented substantially parallel are mounted in the block to cut rings in the tread face of the tyre carcass.

Rubber strips created using apparatus according to the invention have many uses, a number of which require particular crosssectional shapes. To some extent, a desired cross-sectional shape can be created directly as the stripping progresses, by suitable selection of blades and blade shapes. However, it is sometimes easier, particularly where more complex cross-sections are required, for a strip to be removed from a tyre carcass with a simple square or rectangular cross-section, and passed directly to a secondary cutter or groover which can effect a final shaping step. A typical situation in which such a secondary device can be useful is in the manufacture of inner seals for double-glazing units. A variety of different cross-sections are used for such seals, depending on the design of the unit and particularly the outer frame, and rubber stripped from tyres according to the present invention can be particularly useful in such applications.

The invention will now be described by way of example, and with reference to the accompanying schematic drawings wherein: Figure 1 is a prime view showing a tyre mounted on a rotatable turntable; Figure 2 is a side view of the turntable in Figure 1 showing the disposition of the cutter assembly; Figure 3 is a sectional view taken on line III III of Figure 2; Figures 4, 5 and 6 show alternative block with stripping blades mounted thereon in different configurations.

As shown in Figures 1 and 2 a tyre 2 is mounted on a turntable 4, and secured thereon by means of a four-way jack 6. Each foot 8 of the jack 6 is mounted on a rail 10 for substantially radial movement, enabling the jack 6 to be used to mount tyres of different internal diameters on the turntable 4. Each foot 8 has two sections 12 which actually engage the beads 14 of the tyre 2. Each section 12 also has a radial projection 16 which passes between the beads 14 to the interior of the tyre, and provides angles in which the two beads sit. The sections 12 also support at least one terminal which, when the sections 12 press against the bead 14, pierce the rubber of the tyre carcass 2, and make electrical contact with the wire bead and therefore with the wire skeleton around which the tyre is moulded.

The turntable 4 is mounted on castors 20, and constrained by an axle pin 22 to allow only a rotational movement of the turntable 4 about the axle pin 22. A wheel 24 coupled to a variable drive mechanism 26 engages the peripheral surface of the turntable 4 to impart rotation thereto. The drive mechanism is a typically variable speed electric motor enabling the turntable 4 to be rotated at a speed appropriate to the stripping process being practised.

The cutter assembly generally indicated at 28 is mounted on a framework 30 adapted to be moved in a substantially radial direction relative to the tyre 2 mounted on the table 4. This movement may be motorised, in synchronism with the rotation of the turntable 4 such that the cutter assembly strips rubber from the tyre side wall in the form of a spiral with the lateral dimension of the cut length rubber being substantially constant.

The block 32 of the cutter assembly 28 is also adapted for vertical movement relative to the frame 30, and such relative movement is imparted by a stepping motor 34 mounted on one of a plurality (two are shown) of arms 36 extending from the framework 30. The block 32 is constrained to vertical movement by means of guide rods 38 extending through appropriate holes in arms 36.

A spring mechanism (not shown) continually biases the block 32 downwards as shown and into the upper side wall of the tyre 2, and will override the stepping motor 34 except when the motor is actuated.

Figures 4, 5 and 6 show various configurations of the blade or blades which can be assembled on the block 32. That shown in Figure 4 includes two blades 40 arranged orthogonally to strip away from the tyre carcass a strip of rubber with dimensions essentially defined by the configuration of the block 32 enclosed by the blades 40. When rubber is stripped from a tyre using blades arranged in this configuration, the horizontal movement of the framework 30 can be accomplished manually, as radially inward movement relative to the tyre 2 is of course constrained by the rubber of the tyre confined between the blades 40. The blades 40 are mounted on the block 32 by means of screws 42.

Figure 5 shows the mounting of a single vertical blade 44, which can be used to make circular or spiral cuts in the side wall of a tyre carcass 2, or to cut a strip or strips from the tread face of the tyre after a length or lengths have been similarly defined in that tread face, as described below. After the knife 44 has been used to define lengths of removable rubber in the upper side wall of a tyre carcass, the blade may switched to a horizontal orientation, and the block again used to strip the length or lengths of rubber from the tyre carcass 2.

Figure 6 shows an arrangement in which six knives 46 are mounted in parallel on the block 32. This configuration of blades is particularly used to define lengths of rubber in the tread face of the tyre carcass 2. Once these blades have circumscribed the tyre carcase once, to define the removable strips, the block 32 can be withdrawn and replaced by another block of the kind shown in Figure 5 with the blade 44 in the illustrated configuration to strip the lengths of rubber from the tread face.

It will be appreciated that the contour of the upper side wall of the tyre carcass 2 is not flat, and in order to extract the maximum amount of rubber from the carcass the block 32 of the cutter assembly 28 must be adapted to follow those contours with some accuracy. Any suitable mechanism can be used to achieve this, including a roller or some other body which set the depth at which the knives will cut. A variety of sensors of this general type can be suitable, but according to the present invention we have developed an electric system which provides and particularly accurate means by which the maximum amount of rubber can be stripped from a tyre moulded around a metallic skeleton.

Essentially, the system creates an electrical circuit including a blade on the block; the wire skeleton of the tyre carcass; and control circuitry for the stepping motor 34. In normal operation with the circuit open, the block 32 will be continuously biased such that the blade or blades cut deeper into the tyre side wall.

However, as soon as the blade makes contact with the wire skeleton of the tyre carcass, the circuit is closed and this activates the motor 34 to raise the block 32 against the force of the continuous bias discussed above. A motor 34 will normally operate only to shift the blade a small distance to once again break the circuit, whereafter the blade and block will resume their downward movement under the resilient biasing mechanism.

As a consequence the blade will once again shortly meet the wire skeleton of the tyre carcass, and the same sequence of events will be followed. The importance of the terminal 18 (Figure 3) in making electrical contact with the bead wire of the tyre will thus be appreciated.

The above embodiment of the invention is described with reference to the use of electrical motors to drive the turntable to and effect movement of the cutting block 32, and the framework 30.

However, other drive mechanisms could be used, and particularly if it is intended to isolate any electric circuit which directly controls the vertical position of the blades, then pneumatic or fluid drive mechanisms might be used.

It will be appreciated that the stripping of rubber from a tyre carcass will be significantly facilitated if the cutting blade and therefore adjacent rubber is heated and thereby softened while it is cut. The blade can be heated by any suitable means, including of course a simple heater coupled to the block itself.

However, where the electrical positioning mechanism for the block is employed, the electrical circuit itself can be used to impart some heat to the tyre carcass as a whole. This is though, a rather expensive option in terms of energy consumption, and more straightforward heating systems are generally preferred.

The embodiment of the invention described above can be used to strip rubber from a wide variety of tyres, but it will be appreciated that the electrical positioning mechanism for the stripping blade block can only be used when the tyre carcass has a metal skeleton, as in radial tyres. When the apparatus is used on cross ply tyres, useful strips are formed, but because of the wider spread of fabric reinforcement within the carcass, it is not normally possible to create strips of rubber having the same quality or purity.

Claims

1. Apparatus for stripping rubber from vehicle tyres, comprising a table with means for mounting a tyre thereon; a cutter assembly having a block for supporting at least one stripping blade; and means for controlling the position of the block relative to the table during rotation of the table relative to the cutter assembly.

2. Apparatus according to Claim 1 wherein the table is rotatable.

3. Apparatus according to Claim 1 or Claim 2 wherein the controlling means is operable to advance the block in a direction substantially perpendicular to the plane of this table to strip rubber from the tread face of a tyre.

4. Apparatus according to any preceding claim wherein the controlling means is also operable to advance the block transversely over the plane of the table to strip rubber from a side wall of a tyre.

5. Apparatus according to any preceding claim wherein the controlling means includes a mechanism for locating the block relative to the carcass of a tyre mounted thereon.

6. Apparatus according to Claim 5 wherein the mechanism includes a sensor for contacting the tyre surface.

7. Apparatus according to Claim 5 including means for making an electrical circuit including a blade on the block and the wire skeleton of a tyre carcass, which circuit is closed by contact therebetween and generates a control signal upon such closure, and wherein the mechanism is operable in response to such control signal to withdraw the block from the skeleton and thereby open the circuit.

8. Apparatus according to Claim 7 wherein the mechanism is operable to withdraw the block in steps of predetermined extent in response to a said control signal.

9. Apparatus according to Claim 7 or Claim 8 wherein the mounting means includes at least one terminal for establishing electrical contact with the wire skeleton.

10. Apparatus according to Claim 9 wherein the mounting means comprises a multi-point jack for engaging the two beads of a tyre, said at least one terminal being mounted on at least one jacking point to penetrate the rubber and contact wire within a tyre bead.

11. Apparatus according to any of Claims 6 to 10 wherein the controlling means continuously biases the block towards the respective section of a tyre being stripped.

12. Apparatus according to any preceding claim wherein the controlling means comprises at least one electrical motor.

13. Apparatus according to Claim 8 and Claim 12 wherein the locating mechanism comprises a stepping motor.

14. Apparatus according to any of Claims 1 to 11 wherein the controlling means comprises pneumatic means.

15. Apparatus according to any preceding claim including means for rotating the table about an axis substantially coincident with that of a tyre mounted thereon.

16. Apparatus according to Claim 15 wherein the rotating means comprises a variable speed motor.

17. Apparatus according to any preceding claim wherein the block is adapted to support a plurality of stripping blades for simultaneous operation.

18. Apparatus according to Claim 17 wherein the block is adapted to carry a plurality of blades in substantially parallel alignment.

19. Apparatus according to Claim 17 wherein the block is adapted to carry a pair of blades in a substantially orthogonal arrangement.

20. Apparatus according to any preceding claim including an auxiliary shaping unit for receiving stripped rubber behind the cutter assembly, and shaping the cross-section thereof.

21. Apparatus according to any preceding claim including means for heating one or more blades on the block of the cutting assembly.