Abstract:
The present invention provides a method and apparatus for separating rubber components and metal components of tread portions of road vehicle tyres. Each tread portion comprises a tread side and a back side, and the method comprising the steps: forming a chain of tread portions by connecting a plurality of tread portions in a longitudinal direction, said tread portions being connected such that the tread side of each tread portion faces in the same direction, such that the chain of tread portions comprises a tread side and a back side; causing the tread side of at least a part of the chain of tread portions to contact a curved surface; and directing at least one high-pressure jet against the back side of the part of the chain of tread portions contacting the curved surface, to cause separation of the rubber components from the metal components. In a preferred arrangement the at least one high-pressure jet is at least one ultra high-pressure water jet. An apparatus is provided to perform the method.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method and apparatus for the separation of the rubber components and metal components of tread portions of road vehicle tyres. 
       Background 
       [0002]    Road vehicle tyres contain large amounts of rubber material. Metal components, that give rigidity to the tyre, are typically embedded within the rubber material. In particular, tyres may have a metal wire mesh embedded within the tread portions. The tyres also include a fibrous material embedded within the rubber material. 
         [0003]    A large number of used vehicle tyres are removed each year, and it is desirable to recycle as many as possible. The recycling of tyres involves the separation of the rubber components and fibrous material from the metal components. This is conventionally achieved using a variety of batch processes, typically shredding and grinding.  FIG. 1  shows a known ultra high-pressure water arrangement for large tyres (e.g. aircraft or large earth mover tyres). A tyre  10  is placed on a horizontal surface  20 , and is subjected to an ultra high-pressure water jet from a head  30 . The water jet breaks down the rubber components and fibrous material into pieces, which are readily separated from the metal components. The rubber components, fibrous material, and metal components can then be separately processed. 
         [0004]    Generally, in the manufacture of tyres, different grades of rubber are used for different parts of the tyre. For example, the highest quality rubber is typically used in the tread portion, as it is required to grip the road surface. 
         [0005]    So as to maintain a distinction between the different rubber grades, it is desirable to separate them. The arrangement of  FIG. 1  does not allow for such separation. However, it is possible to separate the treads from the sidewalls of the tyre. 
         [0006]    It is desirable to provide a recycling method and apparatus that is able to efficiently and effectively recycle a large number of tyres. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention has been made with the aim of improving existing arrangements. 
         [0008]    According to a first aspect of the present invention, a method is provided for separating rubber components and metal components of tread portions of vehicle tyres, each tread portion comprising a tread side and a back side, the method comprising the steps: forming a chain of tread portions by connecting a plurality of tread portions in a longitudinal direction, said tread portions being connected such that the tread side of each tread portion faces in the same direction, such that the chain of tread portions comprises a tread side and a back side; causing the tread side of at least a part of the chain of tread portions to contact a curved surface; and directing at least one high-pressure jet against the back side of the part of the chain of tread portions contacting the curved surface, to cause separation of the rubber components from the metal components. 
         [0009]    In a preferred arrangement the at least one high-pressure jet is at least one ultra high-pressure water jet. 
         [0010]    Since the tread side of the chain of tread portions is in contact with the curved surface, the chain of tread portions is held firmly while the ultra high-pressure water jet is directed at the back side. This means the rubber components are broken-up into rubber crumb and separated from the metal components in an efficient and controllable manner. Furthermore, as the tread portions contact the curved surface tread side down, the tread portions are inverted against their natural curvature around the curved surface. The inverting of the tread portions against their natural curvature ensures that substantially the entire surface of the tread side of the tread portion is fully in contact with the curved surface. When the entire surface area of the tread side is in contact with the curved surface, little energy is lost from the ultra high-pressure water jets, and the break-up and separation of the rubber components is carried out efficiently. 
         [0011]    Preferably, the curved surface is a curved surface of a drive wheel, and the method further includes the step of rotating the drive wheel so as to pull the chain of tread portions around the curved surface towards the at least one high-pressure jet. The weight of the later tread portions in the chain urge earlier sections against the curved surface of the drive wheel. This action ensures that as large a section of the chain as possible is pressed against the curved surface. As each of the tread portions is pulled around the part of the curved surface, the remaining tread portions in the chain are drawn towards the drive wheel, so that tread portions are continuously drawn around the curved surface towards the high-pressure jet. 
         [0012]    Preferably, the curved surface has a high coefficient of friction similar to that of a road surface. This arrangement takes advantage of the inherent high-friction capabilities of the treads, and ensures that the tread side of the tread portions securely grips, by friction, the curved surface. Thus, it can be ensured that the chain is pulled towards the water jet by the rotation of the drive wheel. 
         [0013]    Preferably, an urging means is used for urging the back side of the chain of tread portions towards the curved surface. The urging means may include one or more rollers that contact the back side of the chain of tread portions. The urging means ensure that the tread side of the tread portions is held in contact with the curved surface. 
         [0014]    The at least one high-pressure jet is preferably directed in a substantially horizontal direction against the back side of the chain of tread portions. This helps ensure the rubber crumb falls in a direction away from the drive wheel, and so avoids the rubber crumb interfering with the operation of the drive wheel. 
         [0015]    Preferably, the metal components of the chain of tread portions are transported away from the curved surface after the rubber components have been separated. The metal components remain joined together after the rubber component has been removed. Therefore, the metal components can be continuously captured and moved away from the drive wheel. 
         [0016]    It is preferable for the chain of tread portions to be formed such that there is a degree of freedom of movement in the lateral and vertical directions between adjacent tread portions in the chain. This may be achieved by using a single connection to connect respective tread portions. Such a single connection may be a single clip or single staple. Using a single connection allows for certain movement of the tread portions as they are processed. This is particularly effective when the severed ends of the tread portions are not cut square. 
         [0017]    Preferably, the tread portions are tread portions of car tyres or light commercial vehicle tyres. 
         [0018]    According to a second aspect of the present invention, there is provided a method of connecting a plurality of tread portions of vehicle tyres together for use in a method of separating rubber components and metal components, each tread portion comprising a tread side and a back side, the method comprising the steps: forming a chain of tread portions by connecting a plurality of tread portions in a longitudinal direction, said tread portions being connected such that the tread side of each tread portion faces in the same direction, such that the chain of tread portions comprises a tread side and a back side, and wherein the chain of tread portions is formed such that there is a degree of freedom of movement between adjacent tread portions in the chain. 
         [0019]    According to a third aspect of the present invention, there is provided a separation and processing apparatus for separating rubber components and metal components of tread portions of road vehicle tyres, wherein each tread portion comprises a tread side and a back side, and a chain of tread portions is formed by connecting a plurality of tread portions in a longitudinal direction, said tread portions being connected such that the tread side of each tread portion faces in the same direction, such that the chain of tread portions comprises a tread side and a back side, the apparatus comprising: a curved surface adapted to contact the tread side of at least a part of the chain of tread portions; and at least one high-pressure nozzle arranged to direct at least one a high-pressure jet towards the back side of the part of the chain of tread portions contacting the curved surface, to separate the rubber components from the metal components. 
         [0020]    Preferably, the apparatus further includes a conveyor for transporting the metal components, after separation of the rubber components, away from the curved surface of the drive wheel. The conveyor may include means adapted to engage with the metal components. The conveyor ensures that the metal components of the tread portions are continuously captured and removed away from the curved surface. 
         [0021]    Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a view of a conventional apparatus for separating the rubber components of a vehicle tyre from the metal components. 
           [0023]      FIG. 2   a  is a side view of a typical road vehicle tyre. 
           [0024]      FIG. 2   b  is view of a tread portion after separation from the tyre sidewalls. 
           [0025]      FIG. 2   c  is a cross-sectional view through the tread portion. 
           [0026]      FIG. 3  is a view of a plurality of tread portions connected together in the longitudinal direction to form a chain of tread portions. 
           [0027]      FIG. 4  is a side elevation of a tread portion separation apparatus according to an embodiment. 
           [0028]      FIG. 5  is a cross-sectional view of the drive wheel, the curved surface and part of the chain of tread portions in contact with the curved surface according to an embodiment. 
           [0029]      FIG. 6  is a flow diagram showing a method of separating the rubber components and metal components of tread portions. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0030]      FIG. 2   a  shows a typical road vehicle tyre  10 , such as a car tyre or light commercial vehicle tyre. The tyre  10  includes a tread portion  110  and two sidewall portions  50 . The tread portion  110  may be separated from the sidewalls  50  by cutting. With reference to  FIG. 2   a , a pair of cuts may be made along the dotted lines A. Once the tread portion  110  has been separated from the sidewalls  50 , the tread portion  110  may be cut transversely across the width of the tread portion  110  (indicated by the dotted line B). Any means of cutting and separating the tread portion from the sidewalls may be used, such as a blade/saw, a laser, or one or more high-pressure water jets. Furthermore, the order of the cuts is not critical. For example, the tread portion  110  may first be cut along dotted line B. 
         [0031]      FIG. 2   b  shows the separated tread portion  110 . The tread portion  110  includes a tread side  200  and a back side  220 .  FIG. 2   c  shows a cross-section through the tread portion  110  (along line C in  FIG. 2   b ). Embedded within the tread portion  110  is a metal component  230  and a fibrous material (not shown). The metal component  230  typically comprises a metal mesh. The fibrous material makes up a small proportion (typically less than 8%) of the tread portion  110 . 
         [0032]    To commence the present separation method, a plurality of tread portions  110  are connected together in the longitudinal direction to form a chain of tread portions  300 .  FIG. 3  shows a plurality of linked tread portions. The plurality of tread portions are connected such that the tread side  200  of each tread portion  110  in the chain  300  faces the same direction. The chain of tread portions may then be considered as having a tread side and a back side.  FIG. 3  shows the back side of the chain  300 . The tread portions  110  may be connected to one another by stapling, stitching, gluing, or any appropriate means sufficient to make a secure attachment. Successive tread portions are preferably joined so that their respective metal components are connected. In preferred arrangements, a single connection is made, with it being particularly preferred that a single clip, staple, or other mechanical connection is used. 
         [0033]      FIG. 4  shows a side elevation of a separation apparatus. The apparatus includes a first conveyor  100  and a drive wheel  120 . The chain of tread portions  300  is placed on the first conveyor  100  with the tread side  200  facing down (e.g. with the back side facing up). The chain  300  is moved along the first conveyor  100  towards the drive wheel  120 . The first conveyor  100  terminates at the drive wheel  120 . The chain of tread portions  300  transfers from the first conveyor  100  to the drive wheel  120 . Preferably the first conveyor  100  has an “S”-shape or reversed curve. This shape assists in straightening the chain of tread portions  300  as it approaches the drive wheel  120 , and ensures the chain  300  more easily moves along the first conveyor. 
         [0034]    The first conveyor  100  may comprise any conveyor that is suitable for transferring the chain of tread portions to the drive wheel  120 . For example, the first conveyor  100  may be a belt conveyor including two or more pulleys about which a continuous belt rotates (not shown). Alternatively, a chute, or channel, may be used (not shown). However, in a preferred embodiment the first conveyor  100  includes a plurality of rollers  105  placed transversely with respect to the direction of the chain of tread portions  300 , and which rotate and provide a low friction means of transporting the chain  300  towards the drive wheel  120 . The expanded view A-A shows two sets of a plurality of rollers  105  are provided, such that a plurality of adjacent pairs of rollers  105 , spaced apart in a vertical direction, are located along the conveyor  100 . The rollers  105  provide a bi-directional guide-way for the chain  300 , allowing the chain  300  to travel freely between the two sets of rollers  105 . A distance (not shown) between each adjacent pair of rollers  105  is pre-set so as not to bind on the chain  300  as it passes between the adjacent rollers  105 . Although, in the preferred arrangement the distance between each pair of adjacent rollers  105  is pre-set and non-adjustable, a means of adjustment may be provided to cope with different thicknesses of tread portions. The rollers  105  may be formed of a metal, such as steel, or any other suitable material. In the preferred arrangement, the rollers  105  are non-powered, but powered rollers may be provided to propel the chain  300  towards the drive wheel  120 . 
         [0035]    The drive wheel  120  includes an outer curved surface  125 , and rotates about an axle  128 . The curved surface  125  of drive wheel  120  is at least as wide as the width of the tread portions  110 . The curved surface  125  may be a smooth curved surface or may comprise a high-order regular polygon. It is preferable that the curved surface  125  comprises a material having a high coefficient of friction, and particularly a coefficient of friction similar to that of a road surface. This arrangement takes advantage of the inherent high-friction capabilities of the tread side  200  of the tread portions  110 , and ensures that the tread side  200  securely grips, by friction, the curved surface  125 . 
         [0036]    A plurality of rollers  130  are positioned around the circumference of the drive wheel  120  with respect to the first conveyor  100 . The rollers  130  are spaced away from the drive wheel  120  so as to allow the tread portions  110  to pass between them and the curved surface  125 . The rollers  130  are arranged to press the tread portions  110  against the curved surface  125 .  FIG. 4  shows three rollers, but any suitable number may be used. The rollers  130  may be formed of metal, such as steel, plastics, or any other suitable material, and preferably run on low friction bearings and/or axles. The rollers  130  may include a means (not shown) for urging the rollers  130  against the back side  220  of the tread portions  110 . The urging means may comprise a helical or coil spring, a torsion spring, or any suitable elastic material, or an adjustable means, such as a linear actuator (mechanical, hydraulic, pneumatic or electric). 
         [0037]    The chain of tread portions  300  is drawn around the drive wheel  120  due to the rotation thereof. The rollers  130  ensure that the tread side  200  of the tread portions  110  are held in contact with the curved surface  125 . As the drive wheel  120  rotates, the friction between the curved surface  125  and the tread side  200  causes the tread portions to be pulled around the curved surface  125 . The position of the first conveyor  100  with respect to the drive wheel  120  causes the weight of the later tread portions in the chain  300  to urge earlier sections against the curved surface  125  of the drive wheel  120 . This action ensures that as large a section of the chain  300  as possible is pressed against the curved surface  125 . As each of the tread portions  110  is pulled around the part of the curved surface  125 , the remaining tread portions  110  in the chain are drawn along the first conveyor means  100  towards the drive wheel  120 , so that tread portions  110  are continuously drawn from the first conveyor  100  around the curved surface  125 . 
         [0038]    Tread portions are manufactured in a ring shape. A tread portion  110 , even after separation from the sidewalls  50  and severed transversely across the width direction, retains a curvature in the longitudinal direction due to its inherent mechanical properties. The cross-section of the tread portion  110  (shown in  FIG. 2   c ) also tends to curve in the transverse direction. These curvatures are due to the elastic properties of the combined rubber and metal components and remain when the plurality of tread portions  110  are connected to form the chain  300 . The inherent elasticity of the tread portions  110  means that they are under tension, as they seek to revert back to their original shape. Pulling the chain  300  over the curved surface  125  forces each tread portion  110  to be inverted against its original shape. The inverting of the tread portions means that the resultant inverted tread portion  110  relaxes into an energy neutral state. The bending in the longitudinal direction also forces the natural curvature in the transverse direction (see  FIG. 2   c ) to straighten. This has the effect of flattening the chain  300  against the curved surface  125  of the drive wheel  120 . This is shown in  FIG. 5 . 
         [0039]    A nozzle head  140  is positioned further around the circumference of the drive wheel  120 , with respect to the first conveyor  100 . The nozzle head  140  directs at least one high-pressure jet against the back side  220  of the chain of tread portions  110 . Preferably, at least one ultra high pressure water jet is used, but the arrangement is not limited to the use of water, any suitable fluid may be used. An example is shown in  FIG. 4 , whereby the nozzle head  140  is positioned clockwise from the end of the first conveyor  100 . Thus, the chain of tread portions  300  is drawn around the drive wheel  120  prior to being presented to the nozzle head  140 . Preferably, the nozzle head  140  comprises a plurality of ultra high-pressure nozzles, and particularly ultra high-pressure water nozzles. Typically, the plurality of ultra high-pressure water jets each rotate at approximately 3000 rpm and operate at a pressure of approximately 2750 bar. Preferably, pure water is used for the ultra high-pressure water jet(s), because, as opposed to using water with abrasives, it reduces wear in the water nozzles and simplifies the filtering of the water and resultant broken rubber components. 
         [0040]    The action of the one or more ultra high-pressure water jets against the tread portions  110 , breaks-up the rubber component into pieces. These pieces are typically referred to as rubber crumb. The rubber crumb, once broken and separated from the metal component  230 , falls under gravity into a first hopper  160 , where it may be collected at a convenient time. The action of the one or more ultra high-pressure water jets also breaks the fibrous material, embedded within the rubber component, into pieces. The pieces of fibrous material, once separated from the metal component  230 , fall under gravity into the first hopper  160  together with the rubber crumb. The water from the ultra high-pressure water jet will also fall into the first hopper  160 , and is easily filtered from the rubber crumb and the fibrous material so that it can be recycled and used again in the ultra high pressure water jets. The rubber crumb and the fibrous material may be separated from each other, for example, by floatation. Preferably, the one or more ultra high-pressure water jets are powered and positioned to produce rubber crumb having average diameters of 150 μm or less. 
         [0041]    The present separation apparatus, together with the inherent characteristics of the tread portions, ensure that the chain  300  is held firmly against the curved surface  125  while the ultra high-pressure water jet is directed at the back side. Accordingly, the rubber components may be broken-up into rubber crumb and separated from the metal components in an efficient and controllable manner. To achieve consistent and efficient processing, it is important for the entire surface of a tread side  200  of the tread portion  110  to be in contact with the curved surface  125 . This ensures that the energy of the water jets is used for the break-up of the rubber component into rubber crumb. If the tread is not in contact with the curved surface it will be liable to move and/or vibrate, and part of the energy of the water jet(s) hence dissipate. This not only leads to inefficiency, but it also reduces the consistency of the size of the rubber crumb. Because in the present apparatus the tread portions  110  are inverted against their natural curvature as they are pulled around the drive wheel  120 , it is ensured that substantially the entire surface of the tread side  200  is fully in contact with the curved surface  125  of the drive wheel  120 . When the entire surface area of the tread side  200  is in contact with the curved surface, little energy is lost from the ultra high-pressure water jets, and the break-up and separation of the rubber components is carried out efficiently. 
         [0042]    Therefore the advantage of placing the plurality of tread portions  110  tread side  200  down is twofold. Firstly, the natural high-friction properties of the tread side  200  is used to grip the high-friction surface of the curved surface  125  of the drive wheel  120 , in order that the chain of tread portions  110  may be continuously pulled around part of the curved surface  125  towards the water nozzle head  140 . Secondly, the tread portions  110  are bent against their natural state around the curved surface  125  such that it can be ensured that substantially the entire surface of the tread side  200  is in contact with the curved surface  125  when being subjected to the one or more ultra high-pressure water jets. 
         [0043]    A second conveyor  150  is located after (e.g. in a clockwise direction around the drive wheel  120  in the arrangement shown in  FIG. 4 ) the nozzle head  140 . Once the rubber has been removed, the metal components  230  remain intact. The second conveyor  150  is used to transport the metal components  230  of the tread portions  110  away from the drive wheel  120 . As the metal components  230  are sequentially connected, they may be removed in a single chain. A second hopper  170  may be provided to receive the metal components. The second conveyor  150  may comprise any suitable means for transferring the metal components  230  away from the drive wheel  120 , but preferably comprises two pulleys  152  about which a continuous belt rotates  156 . The belt  154  includes protrusions  156  operable to engage the metal components  230  to assist transporting them away from the curved surface  125 . In the example shown, the metal components  230  are carried away from the drive wheel  120 , along the direction of rotation of the belt  154  towards the second hopper  170 . At the end of the second conveyor  150 , the metal components  230  fall into the second hopper  170  under gravity. 
         [0044]    A restrictor  158  may be located above the belt  154 . The restrictor  158  is spaced apart from the belt  154  a distance to ensure that the metal components  230  remain engaged with the protrusions  156  and the belt  154 . 
         [0045]    The use of the above described apparatus in conjunction with a chain of inter-linked tread portions permits efficient harvesting of the rubber and metal materials from vehicle tyre treads. This leads to further advantages in recycling these materials. Preferably, the vehicle tyres are car tyres or light commercial vehicle tyres, such that the chain is formed of inter-linked tread portions of car tyres or light commercial vehicle tyres. 
         [0046]    The tread portions  110  are connected in series such that there is a degree of freedom of movement in the lateral and vertical directions between adjacent portions in the chain  300 . Preferred embodiments to achieve this aim include using a single clip or staple to connect consecutive tread portions. A metal staple  115  is envisaged as the preferred connection means, as it may be readily pressed though the tread portion. Allowing a freedom of movement between the tread portions aids the chain to pass through the separation apparatus. It is also more effective to join the pieces in the event that the tread portions are not cut square. 
         [0047]    The staple  115  is used to connect the metal components of successive tread portions within the chain  300 . This ensures that the metal components remain connected after the rubber component has been removed. The task of re-gathering the metal components thus becomes more straightforward. Once the rubber component and the fibrous material has been removed, the use of a single staple  115  allows for a degree of flexibility in the join between the metal components  230  as they move through the remaining part of the apparatus. Since the metal components  230  remain joined together after the rubber component has been removed, as one is pulled away from the drive wheel  120  by the second conveyor  150 , the remaining metal components  230  are pulled towards, and engage with, the second conveyor  150 . Therefore, the metal components  230  can be continuously captured and moved away from the drive wheel  120 . 
         [0048]    Preferably, the nozzle head  140  is arranged to direct the one or more high-pressure jets against the back side  220  of the tread portions  110  in an approximately horizontal direction. Accordingly, the rubber crumb will fall in a direction away from the drive wheel  120 . This is advantageous, since if the rubber crumb is allowed to come into contact with the drive wheel  120  it may interfere with the operation of the apparatus. 
         [0049]      FIG. 6  summarises the method used for separating the rubber components and metal components of tread portions of vehicle tyres. In step S 600  a chain of tread portions  300  is formed by connecting a plurality of tread portions  110  in a longitudinal direction. In step S 601  the tread side of at least a part of the chain of tread portions is caused to contact a curved surface  125 . In step S 602  a high-pressure jet, typically an ultra high pressure water jet, is directed against the back side  220  of the chain of tread portions to separate the rubber components from the metal components. The curved surface is a curved surface of a drive wheel, and in step S 603  the drive wheel  120  is rotated so as to pull the chain of tread portions around the curved surface  125  towards the at least one high-pressure jet. In step S 604  the separated and broken rubber components and fibrous material fall away under gravity into a first collection hopper  160 . In step S 605  the metal components  230  of the tread portions  110 , after the rubber components have been separated, are removed from the curved surface  125  of the drive wheel  120 . 
         [0050]    Although the present invention has been described in terms of preferred embodiments, it will be appreciated that various modifications and alterations might be made by those skilled in the art without departing from the scope of the invention. The invention should therefore be measured in terms of the claims which follow.