GB2481257A

GB2481257A - Method and apparatus for reducing crawler track into reusable parts and material

Info

Publication number: GB2481257A
Application number: GB1010319.0A
Authority: GB
Inventors: Donald Charles Blair
Original assignee: AQUABLAST Ltd
Current assignee: AQUABLAST Ltd
Priority date: 2010-06-19
Filing date: 2010-06-19
Publication date: 2011-12-21
Also published as: GB201010319D0; WO2011158002A1; EP2582504A1

Abstract

The method of the invention involves the stepwise reduction of a rubberised crawler vehicle track (T), of the type having metal track elements (E) within a rubberised or elastomeric material matrix, into useable constituent parts. The reduction of the track is achieved by feeding a track section towards a material removal station 30 where a series of ultra high-pressure water jets are used to remove substantially all of the matrix material and to clean the remaining metal track elements and any supporting or reinforcing material. The track elements are recycled directly into new crawler tracks or collected as high-grade scrap. The matrix material is collected and graded. Disintegration of the matrix material creates a slurry. Apparatus 10 typically comprises a support base 15 over which parallel rails 21, 22 support a section of the track (T) as it is fed towards the station 30. Drive sprockets 25 engage the track (T). A rotary dryer (65 see fig 4) dries the rubber crumbs.

Description

METHOD OF AND APPARATUS FOR REDUCING A VEHICLE TRACK

INTO COMPONENTS FOR RE-USE AND RECYCLING

Field of the Invention

The present invention relates to a method of and apparatus for reducing a vehicle track into components for re-use and recycling. The invention is directed particularly to a method of and apparatus for obtaining commercially valuable materials from used crawler tracks of the type used by vehicles requiring levels of traction unavailable to vehicles using tyres. Although metal "caterpillar" or "tank" tracks are well-appreciated, there is a significant market for rubberised crawler tracks, such as those having embedded metal track components, together with reinforcing wire components, within moulded rubber, to form a rubber track.

The invention is also directed to crawler tracks that have been expended past their primary or secondary use and must be disposed of in an economically efficient and substantially environmentally friendly manner.

The method and apparatus as described hereinbelow are directed primarily with reference to the recovery of materials from rubberised vehicle tracks, such as rubber crumb, embedded metal track components, high-tensile steel, metal mesh material and any ancillary materials used in the construction thereof It will be appreciated by the skilled addressee that the invention may be applied to any elongate composite article having reinforcing material constrained within a rubber or elastomeric matrix.

Background to the Invention

There are well-established problems associated with the disposal of used vehicle tracks most significant being the space they occupy in landfill sites (and ancillary problems which have lead to a ban on using landfill sites as a disposal option in many jurisdictions) and the unsightly and often illegal stockpiles of tracks often accumulated by companies which used excavators and similar machines utilising rubberiseci metal tracks.

Due to the known difficulties in recycling such tracks, there have been derogations in the regulations covering their disposal, however, the problems associated with their disposal remain.

One of the significant factors concerning recycling of tracks is the high concentration of metal present which advantageously is reusable without being reprocessed. In some cases up 80% by weight of the vehicle track comprises steel. Within the last twenty years, and more particularly within the last decade, there has been a considerable upsurge in interest from commercial undertakings and impetus from government bodies to seek environmentally friendly solutions to problems such as the "tyre mountain" and those presented by accumulations of vehicle tracks.

In the past, suggested solutions have included techniques used to recycle tyres, including shredding prior to placement in landfill sites, using the tyres as a fuel element in power generation (and the resulting ash in cementatious products) and using the tyres as coastal erosion barriers, either for onshore placement or offshore as artificial reefs. It will be appreciated that none of these options are suitable for vehicle tracks, particularly shredding due to the high metal content of the tracks.

There are a number of other techniques applied to the recovery of components of or energy from vehicle tyres. Free burning of tyres is known to release toxic gases and thick smoke in addition to tarry oil. At significantly higher temperatures, tyre rubber can be an excellent fuel source, however, there remain problems with some released gases and the reinforcement within the tyre. There have been suggested pyrolytic techniques to overcome this particular scenario but most prior art solutions tend towards the separation of wire reinforcement and rubber material.

There are many examples of physical separation method and some suggest the use of nitrogen baths to render the rubber more brittle to extract the wire reinforcement within.

Many of the above solutions used for tyres have now been discredited as environmentally unsafe, too expensive to implement or are simply inappropriate to the recycling of vehicle tracks.

Due to the perceived value of rubber crumb material as a staple commercial product and it's increasingly wide range of uses, there is a financially convincing argument that graded rubber crumb ought to be recovered from various sources, including vehicle tracks. More convincingly is the potential recovery of high-quality, high-grade metal elements constituting approximately 80% by weight of the vehicle track.

Although scrap rubber from tyres has been prohibited under the European Waste Directive from entering landfill sites, rubber vehicle tracks are exempted items as no suitable technology was available at the time of its drafting to separate metal and rubber in an environmentally responsible and economically viable manner.

One of the mechanical rending techniques known from the prior art literature is that disclosed in UK Patent Application Publication No. 2 447 450 which describes a method of recycling rubber tracks by presenting a track on a support having an opening corresponding to the shape of a metal drive element embedded within a rubber matrix and punching the drive element from the rubber matrix.

This action is repeated until all the drive elements are removed from the track matrix which is then shredded to recover rubber crumb and other components.

One of a number of disadvantages of the method described is that it assumes that drive elements within the track are discrete components or can be separated from an adjacent element by use of a press tool. In many instances, track drive elements are physically coupled together to provide the structural integrity normally associated with metal tracks and may have wire reinforcement bonded to the track elements.

In any event, the metal recovered during the above process is often still heavily contaminated with rubber and requires further cleaning before the metal could be used for recycling. If the drive elements are recovered for re-use in vehicle tracks, all previous rubber material must be removed. If the metal is to go to scrap, the value of the scrap is often diminished if "contaminants" are present and a clean result is preferred to maximise value.

Furthermore, the remaining rubberised track matrix must be further processed separately by shredding and any reinforcement components recovered, usually by magnetic separation. Conventional shredding machines are known to have their own technical disadvantages that need not be elaborated on here.

It is a primary object of the present invention to provide a method of reducing a rubberised vehicle track into its primary components which obviates the disadvantages associated with the prior art and seeks to maximise the extraction of commercially viable materials therefrom in an economically efficient and substantially environmentally friendly manner.

It is a particular object of the present invention to obviate the disadvantages associated with mechanical rending techniques.

An additional object of the invention is to provide apparatus to implement the method of the invention and to extract commercially viable materials from waste or expended rubberised vehicle tracks and similar elongate composite articles having a high percentage of reusable components.

Summary of the Invention

Accordingly, the present invention provides a method of reducing a vehicle track, of the type having metal track elements within a rubberised or elastomeric material matrix, into useable constituent parts, the method comprising: feeding a track section towards a material removal station progressively using drive means adapted to engage the track section; arid exposing the matrix material of the track to at least one high-pressure water jet to remove the matrix material from the track elements, whereby the track elements and any supporting or reinforcing material is substantially cleaned of all matrix material which can subsequently be collected and graded.

The drive means may be selected from a drive sprocket adapted to engage the interstitial spaces of the drive track section and a drive wheel or any other means 1 0 available to a person skilled in the art to move the track section through the material removal station.

In the above arrangement, the track elements are cleaned sufficiently to be recycled for the production of vehicle tracks or as high-grade scrap.

The method produces a rubber crumb slurry which may also include a fabric component.

The rubber crumb slurry is pumped to a separation tank where effluent water and the fabric component, where present, is extracted. The wet crumb is then fed to a press where further water is extracted before being conveyed to a dryer unit.

Advantageously, the method further includes screening dry crumb to size.

Where the track elements are embedded as discrete components in the rubberised or elastomeric material matrix, the method further comprises separating exposed track elements as they are released from the matrix.

Where the track elements are linked together, either by reinforcing components such as wire or by linking elements thereof, the exposed track elements are fed progressively towards a collection station using a drive wheel or drive sprocket adapted to engage the track elements of the track section.

The present invention further provides an apparatus for reducing a vehicle track, of the type having metal track elements within a rubberised or elastomeric material matrix, into useable constituent parts, the apparatus comprising conveyor means adapted to support a section of vehicle track and feed it towards a material removal station which includes at least one high pressure water jet so configured as to remove the matrix material from the track elements, whereby the track elements and any supporting or reinforcing material is substantially cleaned of all matrix material which can subsequently be collected arid graded.

The conveyor means advantageously comprises a drive means selected from a 1 0 drive sprocket adapted to engage the interstitial spaces of the drive track section and a drive wheel or any other means available to a person skilled in the art to move the track section through the material removal station.

Conveniently, where the drive means comprises a sprocket, it is at least similar to the drive sprockets of a vehicle on which such vehicle tracks are used.

1 5 In a first construction, where the track elements are embedded as discrete components in the rubberised or elastomeric material matrix, the apparatus includes means for separating and collecting exposed track elements as they are released from the matrix.

Ideally, the means comprises a gravity-fed chute.

Optionally or additionally, a magnetic conveyance means is adapted to extract or carry the track elements from the material removal station.

In a second construction, where the track elements are linked together, either by reinforcing components such as wire or by linking elements thereof, the exposed track elements are fed progressively towards a collection station using a drive wheel or drive sprocket adapted to engage the track elements of the track section.

Advantageously, the material removal station includes a platform on which there is provided a series of high-pressure water jet nozzles arranged to remove the matrix material from the track section.

Conveniently, the series of nozzles is of sufficient width to expose the width of the track section to jets of high-pressure water.

Optionally or additionally, the platform is moveable to scan across the width of the track section. Preferably, sets of rotating nozzles are used to provide enhanced removal of matrix material and cleaning of track elements and reinforcing material, where present.

Conveniently, the apparatus includes means for collecting and conveying a slurry of rubber crumb to a crumb processing station.

The apparatus further comprises means for separating rubber and any fabric 1 0 component that may be present from effluent water generated during the reduction of vehicle tracks, the apparatus comprising: a separation tank to extract a majority of effluent water from a rubber crumb slurry presented thereto; a press where further water is extracted from wet crumb from the separation tank; a damp crumb accumulator from which there is conveyed a batch of damp crumb for feeding to a dryer unit.

Advantageously, the apparatus further includes screening means for separating dry crumb according to size.

Brief Description of the Drawings

The invention will now be described more particularly with reference to the accompanying drawings which show, by way of example only, one embodiment of apparatus for reducing vehicle tracks into components for re-use and recycling in accordance with the invention. In the drawings: Figure 1 is a plan view of an apparatus for reducing a vehicle track into its component parts and includes a track section conveyor, a material removal station, a collection tank and a track element conveyor; Figure 2 is a side elevation of the apparatus of Figure 1; Figure 3 is a detailed cross-sectional elevation of the material removal station; and Figure 4 is a schematic perspective view of plant required for the dewatering, drying and grading of rubber crumb.

Detailed Description of the Drawings

Referring to the drawings and initially to Figures 1 and 2, one construction of apparatus 10 for reducing vehicle tracks of the type comprising track elements embedded within a rubberised or elastomeric matrix into its component or constituent parts is shown.

It is known from the prior art that most mechanical methods of extracting metal track components do not yield satisfactory results with respect to the recycling efficiency (cost of recycling versus the quality or value of recovered components or cost of alternative disposal). One of the primary disadvantages of the prior art is that the matrix material is not cleanly removed and the track components require further cleaning. Where there are large quantities of matrix material remaining, the value of scrap metal recovered is often lessened. Furthermore, the direct use of metal elements from within the track is not normally feasible unless it is well cleaned.

The apparatus 10 comprises a support base 15 over which a pair of parallel rails 21,22 are disposed for supporting a section of vehicle track T as it is fed towards a material removal station 30 and for supporting exposed track elements E as they are subsequently withdrawn from the material removal station 30 following removal of the matrix material. Spaced along the length of and positioned between the parallel rails 21,22 are a number of sprockets 25 adapted to engage the vehicle track T. This is done in substantially the identical manner in which power from a tractor unit is transferred from a driven sprocket to a crawler track.

In a preferred construction, each of the sprockets 25 is driven and ideally controlled via a central control processing unit (not shown).

The material removal station 30 comprises an enclosure 32 within which there is provided a platform 34 carrying a plurality of ultra high pressure water jet nozzles 36. In the illustrated construction, the nozzles 36 are disposed in a side-by-side transverse orientation and are adapted to move across the width of the track section T. It has been found that static arrangements of nozzles do not provide the same material removal efficiency or cleaning effect as a "scanning" arrangement.

Where the nozzles are adapted to scan and rotate, enhanced material removal and cleaning results.

The removal station 30 comprises the main enclosure 32 to which there is fixed an inlet cowl 37 and, on the other side of the platform 34, an outlet cowl 39, each of which cover a section of the parallel tracks 21,22, and are adapted to minimise the escape of vapour, rubber dust and debris from the material removal station 30.

Each water jet nozzle 36 creates an ultra high-pressure jet of water (that is at a pressure in excess of 40,000 psi) to remove matrix material from the track elements held within a track section. The matrix material, most commonly rubber, is blasted into relative small particles and together with the water forms a slurry of material for further processing.

Also positioned on the support base 15 and aligned with the material removal station 30 is a collection tank 40 for receiving a slurry of the rubberised matrix removed from the track section T by the action of the water jets. The slurry is then pumped to a crumb processing plant 60 which will be described in more detail with respect to Figure 4.

A pair of linked sprockets 42,43 are disposed below and to either side of the nozzle platform so as to ensure the track section is kept moving progressively through the material removal station. In the illustrated construction, the sprockets are driven by a common drive motor 44, however, separate electronically controlled motors are also considered.

In use, a section of vehicle track T, which has been de-coupled or otherwise opened to have a leading edge, is fed Onto the parallel rails 21,22 of the apparatus to be engaged by the first driven sprocket 25. The teeth of the sprocket engage corresponding receivers formed in the inner part of a vehicle track in exactly the same maimer as they would when mounted on a tracked vehicle such as a crawler.

As the section of track enters the material removal station, the platform 34 carrying the nozzles 36 starts a scarming programme which carries the nozzles laterally across the width of the track so that the ultra high-pressure jets of water are directed to the material matrix covering the track elements. The jets essentially disintegrate the matrix and create a slurry of water and matrix particulate. Most commonly, the material matrix is rubber.

The track is progressively fed into the material removal station at a predetermined speed to ensure maximum removal of matrix material from the vehicle track leaving only track elements and any supporting or reinforcing material resistant to 1 5 the action of the water jets. The supporting or reinforcing material most commonly comprises steel wire linking the track elements or a metal mat onto which the elements are bonded. Secondary reinforcing material includes fabric or plastics fibres, within the matrix material, however, this is removed with the matrix material for subsequent collection.

The remaining track elements and any supporting or reinforcing material is conveyed out of the material removal station along the parallel rails 21,22 at a speed consistent with the predetermined input feed speed.

In the most prevalent case, where the track elements are linked together, one of the sprockets 42 within the removal station 30 pushes the track section towards a collection conveyance sprocket 43 which, like the other sprockets has teeth which engage receivers within the track elements or within the interstitial spaces of the track section. The track elements are fed towards the end of the parallel rails 21, 22 for collection or further conveying.

Where the track elements are not linked or bound together by support wire, the individual track elements either accumulate on the parallel rails and are pushed towards a collection point or are directed towards a collection area at or near the material removal station. In such an arrangement, a chute having an optionally magnetic deflector component would address issues regarding potential contamination of the collected metal elements by the slurry formed by the apparatus and method of the invention.

Referring now to Figure 4, as referred to hereinabove there is provided a processing plant 60 for dewatering, drying and grading rubber crumb. The plant comprises a separation tank 61 into which a slurry of effluent water and rubber crumb is fed. Using a weir and trap system (although other systems are equally good) excess water is extracted and drained off, ideally for filtering and treating for re-use.

The wet crumb is pumped or otherwise conveyed to a filter belt press 62 where further water is extracted and the now merely damp crumb is accumulated in a storage vessel 64 to be fed batchwise into a rotary dryer 65 via a feed-screw 66.

Hot air is circulated through the rotary dryer 65 via hot air inlet 67 and outlet 68 paths. Ideally, hot air is taken from the ultra high-pressure compressor, used to provide the pressurised water to the nozzles at the material removal station, so as to utilise this source more effectively. Drying crumb is agitated within the dryer by helical blades 69 disposed therein. To unload the dryer, it is rotated in the opposite direction to that used to load and dry crumb. The dried crumb is fed to a vibrating screen sorter 70 to grade the crumb and to feed the graded crumb into storage containers 72.

Although reference has been made to drive sprockets throughout the description, it will be appreciated that drive wheels or any other suitable means available to the skilled addressee can be used as an alternative to move the track section through the material removal station.

It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the appended claims.

Claims

CLAIMS: 1. A method of reducing a vehicle track, of the type having metal track elements within a rubberised or elastomeric material matrix, into useable constituent parts, the method comprising: feeding a track section towards a material removal station progressively using drive means adapted to engage the track section; and exposing the matrix material of the track to at least one high-pressure waterjet to remove the matrix material from the track elements, whereby the track elements and any supporting or reinforcing material is substantially cleaned of all matrix material which can subsequently be collected and graded.
2. A method of reducing a vehicle track as claimed in Claim 1, in which the drive means is selected from a drive sprocket adapted to engage the interstitial spaces of the drive track section and a drive wheel or any other like means operably to move the track section through the material removal station.
3. A method of reducing a vehicle track as claimed in Claim I or Claim 2, in which the method produces a rubber crumb slurry which may also include a fabric component.
4. A method of reducing a vehicle track as claimed in Claim 3, in which the rubber crumb slurry is pumped to a separation tank where effluent water and the fabric component, where present, is extracted.
5. A method of reducing a vehicle track as claimed in Claim 4, in which the wet crumb is fed to a press where further water is extracted before being conveyed to a dryer unit.
6. A method of reducing a vehicle track as claimed in Claim 4 or Claim 5, in which the method further includes screening dry crumb to size.
7. A method of reducing a vehicle track as claimed in any one of the preceding claims, in which, where the track elements are embedded as discrete components in the rubberised or elastomeric material matrix, the method further comprises separating exposed track elements as they are released from the matrix.
8. A method of reducing a vehicle track as claimed in any one of Claims 1 to 6, in which, where the track elements are linked together, either by reinforcing components such as wire or by linking elements thereof, the exposed track elements are fed progressively towards a collection station using a drive wheel or drive sprocket adapted to engage the track elements of the track section.
9. An apparatus for reducing a vehicle track, of the type having metal track elements within a rubberised or elastomeric material matrix, into useable constituent parts, the apparatus comprising conveyor means adapted to support a section of vehicle track and feed it towards a material removal station which includes at least one high-pressure water jet so configured as to remove the matrix material from the track elements, whereby the track elements and any supporting or reinforcing material is substantially cleaned of all matrix material which can subsequently be collected and graded.
10. An apparatus for reducing a vehicle track as claimed in Claim 9, in which the conveyor means comprises a drive means selected from a drive sprocket adapted to engage the interstitial spaces of the drive track section and a drive wheel or any other like means operably to move the track section through the material removal station.
11. An apparatus for reducing a vehicle track as claimed in Claim 10, in which where the drive means comprises a sprocket, it is at least similar to the drive sprockets of a vehicle on which such vehicle tracks are used.
12. An apparatus for reducing a vehicle track as claimed in any one of Claims 9 to 11, in which, where the track elements are embedded as discrete components in the rubberised or elastomeric material matrix, the apparatus includes means for separating and collecting exposed track elements as they are released from the matrix.
13. An apparatus for reducing a vehicle track as claimed in Claim 12, in which the means for separating and collecting exposed track elements comprises a gravity-fed chute.
14. An apparatus for reducing a vehicle track as claimed in Claim 12 or Claim 13, in which, a magnetic conveyance means is adapted to extract or carry the track elements from the material removal station.
15. An apparatus for reducing a vehicle track as claimed in Claim 14, in which, where the track elements are linked together, either by reinforcing components such as wire or by linking elements thereof, the exposed track elements are fed progressively towards a collection station using a drive wheel or drive sprocket adapted to engage the track elements of the track section.
16. An apparatus for reducing a vehicle track as claimed in Claim 15, in which the sprocket is at least similar to the drive sprockets of a vehicle using the vehicle tracks.
17. An apparatus for reducing a vehicle track as claimed in any one of Claims 9 to 1 6, in which the material removal station includes a platform on which there is provided a series of high-pressure water jet nozzles arranged to remove the matrix material from the track section,
18. An apparatus for reducing a vehicle track as claimed Claim 16, in which the series of nozzles is of sufficient width to expose the width of the track section to jets of high-pressure water.
19. An apparatus for reducing a vehicle track as claimed in Claim 16, in which the platform is moveable to scan across the width of the track section.
20. An apparatus for reducing a vehicle track as claimed in any one of Claims 1 7 to 19, in which sets of rotating nozzles are used to provide enhanced removal of matrix material and cleaning of track elements and reinforcing material, where present.
21. An apparatus for reducing a vehicle track as claimed in any one of Claims 9 to 20, in which, the apparatus includes means for collecting and conveying a slurry of rubber crumb to a crumb processing station.
22. An apparatus for reducing a vehicle track as claimed in any one of Claims 9 to 21, in which the apparatus further comprises means for separating rubber and any fabric component that may be present from effluent water generated during the reduction of vehicle tracks, the apparatus comprising: a separation tank to extract a majority of effluent water from a rubber 1 0 crumb slurry presented thereto; a press where further water is extracted from wet crumb from the separation tank; a damp crumb accumulator from which there is conveyed a batch of damp crumb for feeding to a dryer unit.
23. An apparatus for reducing a vehicle track as claimed in Claim 22, in which, the apparatus further includes screening means for separating dry crumb according to size.
24. A method of reducing a vehicle track substantially as herein described with reference to the accompanying drawings.
25. An apparatus for reducing a vehicle track substantially as herein described with reference to and as shown in the accompanying drawings.