As the number of motor vehicles increases, used vehicle tires are stockpiled in increasingly greater amount all over the world, causing an ever increasing pressure on the environment, since their elimination or recycling by using known technologies is expensive and of low efficiency.

Basically similar problems arise about used rubber belts of conveyors and other multi-component elastic waste materials.

BACKGROUND ART One possible way to eliminate scrap rubber products, in particular vehicle tires, is using them for landfill, but this method has limited applicability and controversial results. Another way of eliminating scrap rubber products is to burn them. This method has, however, energetically low efficiency and causes environmental pollution. Moreover, burning non-combustible components of rubber products generate materials that may damage operational safety of the burning equipment.

An alternative method of processing and recycling used rubber products comprises grinding rubber material into granulate or in special cases, into extra fine-grained rubber powder that may be utilized in paint industry, rubber industry and road construction depending on the grain size and the degree of purity of the resulted material. In order to grind or mill off the rubber material, mechanical cutting tools have been normally used which are exposed to extraordinary operating conditions due to changing characteristics of the rubber when heating.

Although the cutting tool can be cooled, its cooling is very expensive and its wearing because of to the extreme heat is still significant. Deep-freezing the rubber material may ease grinding process, but high costs of this solution make it uneconomical. Yet another disadvantage of mechanical grinding is that it is not possible to remove all of the rubber material from the remaining part of the rubber product, such as metal reinforcing inserts, i. e. cords, of the tires.

New possibilities for processing rubber products and obtaining rubber granulate were created with the application of high pressure and ultra high pressure (i. e. above 1500-2000 bar) water jet technology, which was first applied basically for cleaning metallic surfaces as well as for clean surface cutting of various workpieces. This technology became applicable soon in the field of rubber processing. For example, US Patent No. 5,115,983 describes a method of subjecting used tires, either in whole or shred, to high pressure (cca. 400-700 bar) water jet, whereby rubber material of the tires is crumbled from the steel cord reinforcing the tires in the form of fine-grained granulate containing relatively small particles. This results in that the steel cord remains metallic clean. In order to increase the efficiency of grinding, abrasive material is added to the high pressure water jet, which, on the other hand, results in strong wearing effect in the whole equipment and in particular in the water jetting nozzles. Moreover, abrasive additives contaminate the rubber granulate thus obtained, therefore its application is limited to special cases. The main disadvantage of the above-mentioned method is that crumbling of all the rubber material from the steel cord is performed in one process, without separation rubber materials of different quality. In addition, this method does not allow to control the particle size of the crumbled rubber granulate.

Another similar method and an apparatus for performing that method is disclosed in DE 196 48 551 A1, which mainly relates to production of rubber granulate from used tires and rubber belt of conveyors. According to this method, after initially applied mechanical treatment, the laid rubber products are subjected to high pressure (800-2000 bar) water jets of adjustable nozzles arranged in a nozzle head, wherein water jets are directed, from a distance of 10-60 mm, to the surface of the rubber products in such a way that the water jets and the product surface define an acute angle of 25-45 degrees and thus the water jets form a special cutting cone. The object of this method is to provide effective separation of different materials in order to obtain metallic clean cord material. The separated rubber granulate so obtained also contains fabric cord residues deriving from the tires, therefore it can be mainly used to soak up oil-products and other chemicals.

It is obvious that this method does not deal with selective separation of rubber materials, therefore rubber granulate produced by this method cannot be utilized in the paint industry and the rubber industry. Moreover, size of the particles of the rubber granulate cannot be controlled by this method either.

There are other well-known methods of processing rubber of waste tires, wherein rubber material of the tread is recovered separately from other rubber materials of less value, such as side-wall material of the tires. Such a method is described, for example, in US Patent No. 5 482 215. According to this method, tires are collected and classified, and after their preliminary washing, said tires are subjected to cutting by high pressure water jet separating the tread from the two ring shaped side-wall portions of the tires. From the mantle portion, i. e. the removed tread, of each tires a strip is formed containing the reinforcement insert, i. e. the steel cords. In the next step, rubber material of the tread is mechanically removed in small portions from the steel cords. Side-walls of the tires are usually not processed because of the relatively high processing costs with respect to the amount and quality of the rubber material that could be recovered from them. The only feasible way to process side-walls of the tires is to grinding them into rubber granulate, without any selection, by using high pressure water jet, but even this procedure cannot offer total and cost-effective recycling of scrap tires.

DISCLOSURE OF THE INVENTION It is an object of the present invention therefore to provide a method of selective recovering components from multi-component elastic waste material, in particular from used vehicle tires, for the purpose of recycling, wherein said components are removed by high pressure water jet cutting that allows producing rubber powder of arbitrary size of particles.

Another object of the present invention is to provide an apparatus for performing the method according to the invention.

These and other objects of the invention are reached by a method of selectively recovering components from multi-component elastic waste material, in particular from used vehicle tires, for the purpose of recycling, wherein after cleaning and cutting up the multi-component elastic waste material to be processed, elastic portions are removed from the components of greater strength in the form of elastic material powder, in particular rubber powder, by applying high pressure water jet cutting, said elastic material powder being separately fed to the location of further processing, where the elastic material powder collected in wet state at cutting is subjected to dehydration and drying before packaging. The elastic material powder is removed from a workpiece by cutting, using high pressure water jets moving along a positive spatial path; said cutting is effected, in the form of simultaneous cutting and tearing procedure in subsequent steps, at the free end of the workpiece, while said free end is not supported; and during said cutting said elastic portions are selectively removed from said workpiece with respect to their quality and, finally, sorted and collected separately.

If the elastic waste material is available in the form of used tires, the previously collected and classified tires are preferably cleaned mechanically and/or by washing; said cleaning followed by cutting up the tires, by using high pressure water jets, into three parts, namely a strip-like mantle member and two ring- shaped side-wall members ; then the inner and outer rubber layer of the tire is removed, said layers enclosing a central binding layer embedding reinforcement cord; and finally the binding layer is also removed from the cords, and all the rubber materials produced as rubber powder are preferably collected separately with respect to their sort.

According to a preferred modification of the method of the present invention, water jets moving along a positive spatial path are oscillated perpendicularly to the direction of advancement of the workpiece, wherein oscillating is preferably defined by continuously controlling the amplitude and frequency thereof. The water jets are preferably a positive to perform planetary motion.

According to a further preferred modification of the method of the present invention, removing the elastic material powder, in particular the rubber powder, is carried out by applying high pressure water jets with a pressure of 1400-2000 bar, wherein the high pressure water jets are cooled either before injection or inside a cutting head which comprises a plurality of nozzles, each nozzle injecting a water jet. Cutting the various layers of the elastic material by using water jets is carried out on more than one side of said material at the same time.

With respect to energy-saving and environment protection it is advantageous, that the elastic material powder, in particular the rubber powder, removed by cutting with water jets and collected in wet state is fed into a filter unit, where the elastic material powder is separated from the water heated during the cutting process; said water is cleaned and fed into the evaporator of a heat exchanger, preferably into the evaporator of a heat pump, where it is cooled down to a temperature of 15-25 °C ; the cooled water is fed back to the water jet cutting process; the pulpy elastic material powder is dehydrated by applying centrifuge and subsequently dried in a drying unit by applying drying air-stream circulated by a ventilator ; said drying air is fed into a vapour condenser and subsequently into a closed chamber containing the condensation unit of the heat pump; said drying air is heated to at least 50 °C, then fed from the closed chamber back to the drying unit; said elastic material powder is finally fed from the drying unit to a sorter unit, in which rubber particles are classified, with respect to their size, and separately collected in dischargable containers.

The above-mentioned objects of the invention are also reached by an apparatus for producing elastic material powder, in particular rubber powder, from used tires cut into preferably three pieces by using high pressure water jets; said apparatus being preferably adapted to performing any method described before; wherein the apparatus comprises nozzles injecting high pressure water jets with a pressure of 1400-2000 bar, devices with driving unit for transporting workpieces and a container to collect the produced rubber powder together with the process water; said container is arranged under the transporting devices and optionally provided with a pump having rotary chamber. The plurality of nozzles injecting high pressure water jets are arranged above the transporting device and aligned at least in one row in a cutting head which extends perpendicularly to the feed direction of the workpiece; and said cutting head is adjustably mounted onto an actuating unit performing oscillating and/or planetary motion.

BRIEF DESCRIPTION OF DRAWINGS The invention will now be described in more detail in respect of the preferred embodiments thereof as illustrated in the accompanying drawings: Fig. 1 is the schematic front view of an embodiment of the apparatus according to the invention, which is designed to process strip shaped elastic workpiece into rubber powder; Fig. 2 is the perspective view of the water jet cutting head of the apparatus of Fig.

1 when separating the tread from a tire; Fig. 3 is the schematic front view of another embodiment of the apparatus according to the invention, designed to process basically the ring shaped side- walls of the used tires into rubber powder; and Fig. 4 is the perspective view of the cutting head of the apparatus of Fig. 3 when separating the side-walls from outside of a tire.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS It should be understood that the invention is not limited by the specific embodiments that will be described, and as it is apparent to those skilled in the art, the elastic waste material to be processed is not limited to used tires, and it may be any type of elastic waste material, like used rubber belt of a conveyor.

According to the method of the present invention, collected waste tires, as well as rejected tires, are in the first step classified by their manufacturer, type and size because of the different material composition of the tires produced by different manufacturer thus ensuring that the various kinds of rubber powder selectively produced later on will be suitable for respective types of tires. The classification, on the other hand, allows continuous processing of tires with the possibly lowest number of size adjustments. After classification said tires are mechanically cleaned by using wired brush disks and subsequently washed by using high pressure (70 bar) water jet to free them from any contamination. In the next step, the clean tires are cut up into three pieces by using ultra high pressure (2000-3000 bar) water jet, as it is well-known for those skilled in the art, wherein one piece is a strip-like mantle member A whereas the other two pieces are ring shaped side-wall members B. These smaller pieces can be stored and transported in a more economical way than whole tires. Tires can be cut up into several pieces, for example, by the apparatus described in US Patent No. 5 482 215.

Depending on their shape, pieces of the tires are then passed to the apparatus shown in Fig. 1 or Fig. 3 for subsequent selective recovery of the tire portions of different quality.

The strip-like mantle member A is passed to the rubber powder producing equipment shown in Fig. 1. This equipment comprises a plurality of nozzles generating high pressure (1400-2000 bar) water jets 13, said nozzles aligned at least in one row in a cutting head 1, which extends perpendicularly to the feed direction of the workpiece. Feeding of the workpiece is effected by driven feeding devices which may include a feed roller system 4 driven by an electric driving unit 2 and a continuously controlled secondary driving unit 3, said feed roller system 4 feeding the strip-like mantle member A of the tires cut up into three pieces (or in another case, the rubber belt of a conveyor) straight forward, in a linear way. The feed roller system 4 is associated with a support roller system 5, of which rollers are pushed, via the force of a spring, to the upper surface of the mantle member A. Under the feeding devices a collecting container 7 is situated, said container 7 comprising a pump 6 having a rotary chamber and designed to collect the removed rubber powder together with the process water fed into the cutting head 1 at high pressure. From the container 7, the mixture of process water and rubber powder is passed to a dehydration system by using said pump 6. The process water is preferably cooled down to at least 20 °C by a heat exchanger arranged before the water inlet, or a cooling system built in the cutting head 1. The dehydration system comprises a filter unit used to separate the rubber powder and the process water heated during the cutting/milling process. The clean process water is passed into the evaporator of a heat exchanger or a heat pump, where it is cooled down to a temperature of 15-25 °C. After cooling, the process water is fed back to the water jet cutting/milling process. At the same time, the pulpy rubber powder is subjected to dehydration using a centrifugal device following the filter unit, and the rubber powder thus obtained is fed into a drying unit applying heated air. Said heated air is fed, via a ventilator, from the drying unit to a vapour condenser and, subsequently to a closed chamber containing the condensation unit of the heat pump. After condensation, the air is heated to at least 50 °C and then fed from the closed chamber to the drying unit. The rubber powder is finally fed from the drying unit to sorter unit, in which rubber particles are classified and separately collected in dischargable containers.

The cutting head 1 is mounted onto an actuating unit performing a positive spatial oscillating and planetary motion, said actuating unit comprising a planetary plate 11 connected to an oscillating/planetary moving driving unit 10 driven by an electric driving unit 8 and an continuously controlled main driving unit 9. The planetary plate 11 is connected to a head-holder plate 12 onto which the water jet cutting head 1 is adjustably mounted.

During the continuous advancement, i. e. the secondary motion, of the workpiece, such as the mantle member A, the cutting head 1 performs a positive oscillating and planetary motion, which is the primary motion. Due to this combined motion, the set of high pressure water jets 13 of the cutting head 1 arranged at the free end of the workpiece tears rubber portions via a combined effect of cutting and tearing, from the surface of the free end of the workpiece, wherein said rubber portions constitute the rubber powder. In the case of cutting elastic material by high pressure water jets, when the processed surface of the workpiece is free and the produced chip is not supported, the cutting water jets operates, at least at the beginning of such a forming procedure, as a cutting device with regular profile.

After cutting, the chip not supported is torn from the workpiece by the kinetic energy of the water jets which create a tearing-shearing effect. This procedure is then repeated periodically. As a result, elementary rubber portions, i. e. rubber powder particles, with cut and torn surfaces are generated, of which specific surface is multiple of the surface of the conventional, mechanically ground rubber granulate or rubber powder. The basic novelty and the main advantage of the present invention is just this new kind of cutting technology, which additionally allows to control the particle size, morphology of the rubber powder and thickness of the layer being removed from the original material by proper adjustment of the nozzle size, the pressure of water jets and parameters of both the primary and the secondary motion of the cutting head 1 and the processed material. In fact, these features also allow an economical selective separation of various portions of the tires, said portions having different qualities. This separation process can be seen in Fig. 2 and 4.

Fig. 2 shows how successive layers of the strip-like mantle member A of a tire is removed. As it can be clearly seen in Fig. 2, the layer of the tread 14, which is the most valuable component of a tire, has been previously removed from the upper surface of the mantle member A by using the high pressure water jets 13 of the cutting head 1. The underneath surface of the mantle member A is covered by a butyl layer 15, which is, in fact, an inside sealing layer of rubber. Between the layer of the tread 14 and the butyl layer 15, there is a binding layer 17 embedding the reinforcement cords 16. When selectively removing the mantle member A, the layer of tread 14 is first removed until the surface of the binding layer 17 has been reached. In the next step, the butyl layer 15 is removed until the opposite surface of the binding layer 15 has been reached. After removing the layer of tread 14 and the butyl layer 15, the binding layer 17 embedding cords 16 is finally ground in order to obtain rubber powder in such a way that the reinforcement cords 16, which contain no rubber, remain undamaged.

Fig. 3 schematically shows the processing of ring shaped side-wall members B of a tire in an equipment based on the same principle as the equipment of Fig. 1. In this equipment, the workpiece, i. e. the side-wall members B are placed on radially aligned, cone-shaped supporting rollers 18 arranged in a circle. The supporting rollers 18 are rotated at constant rate, together with the workpiece, via a central rotating mechanism 19, which is driven by a primary driving unit 20, through an continuously controlled secondary driving unit 21. Other parts of this equipment and its operation is the same as that of the equipment shown in Fig. 1. With respect to Fig. 3, the same reference numbers are used for the respective components as in Fig. 1. The rubber powder produced by the equipment of Fig. 3 is collected, together with the process water, in the container 7 from which the mixture of water and rubber is fed into the dehydration system comprising the pump 6.

Processing of the ring-shaped side-wall members B of the tires is shown in Fig. 4.

In this process, an elastic lateral layer 22 is first removed from the outer surface of the tires by the cutting head 1, then by turning over the ring-shaped side-wall members B, the inside sealing butyl layer 15 is removed. When removing the lateral layer 22 and the butyl layer 15, the cutting head 1 producing the high pressure water jets 13 performs a positive oscillating and planetary motion, while the workpiece, i. e. the side-wall member B, rotates at variable rate around its own axis of rotation. By choosing proper values for the technological parameters, thickness of the removed rubber layer and particle size of the rubber powder may be readily controlled or fixed. Afterwards, the same equipment may be used to separate the binding layer 17 from the embedded cords 16 in a grinding process.

Dehydration of the rubber powder of the selectively removed rubber materials is preferably done by using a two-phase spiral centrifuge adapted to process said rubber powder, wherein the separated process water having a temperature of 60 °C is fed back, through a heat exchanger and a water treatment system, to the container feeding the pump, whereas the technological heat is used for hot-air drying the rubber powder leaving the centrifuge, said rubber powder containing about 8 % water.

After applying the centrifuge, the rubber powder containing about 8 % water is transported into a container via a hot-air stream which is preferably preheated by the heat released when cooling the process water and, if necessary, additionally heated further.

After the above operation, the rubber powder, which contains about 0.5-1 % water, is classified into a plurality of fractions with respect to the particle size by applying a free-oscillating one-column planar sieve.

Package of the rubber powder is defined by the type of the transportation required, said package including, for example, sack, container or tank vehicle.

The entirely rubber-free steel cords obtained by recycling the waste tires is preferably packaged in bales according to the requirements of the metallurgical end-user.

As described before, the method and the apparatus according to the present invention offers a full-scale and cost-effective alternative to process elastic waste materials, in particular used tires, without mechanically grinding thereof. Moreover, the method and the apparatus according to the present invention provides sorted production of high quality rubber powder with desired particle size and content.

Due to these and other features, the invention provides a versatile and efficient way of recycling.