GB2529145A

GB2529145A - Mobile material processing unit

Info

Publication number: GB2529145A
Application number: GB1412581.9A
Authority: GB
Inventors: Paul Douglas; Terance Bratton
Original assignee: Louise Douglas
Current assignee: Louise Douglas
Priority date: 2014-07-15
Filing date: 2014-07-15
Publication date: 2016-02-17
Also published as: GB201412581D0

Abstract

A mobile materials processing apparatus 1, with various common materials processing subsystems, on a chassis 4, has at least two sets of tracks 12,13, separated along the longitudinal axis of the mobile materials processing apparatus 1. One of more of the sets of tracks 12,13 may be moveable away from the other along the axis of the mobile materials processing apparatus 1. One or more of the sets of tracks 12,13 may be pivoted outwards from the axis of the mobile materials processing apparatus 1. These features being all aimed at improving the stability of the materials processing apparatus, particularly when various conveyors extend from it, in an operational position. Also disclosed is a corresponding method of configuring the mobile materials processing apparatus 1.

Description

1 Mobile Material Processing Unit 3 The present invention relates to the field of material processing and in particular a mobile 4 material processing unit as commonly employed in the mining and construction industries.

6 Background to the Invention

8 Material processing units are machines designed for crushing, pre-screening and or 9 screening and or conveying solid materials. In particular, they are often employed to reduce large rocks into smaller rocks, gravel, or rock dust. They are employed primarily to 11 reduce the size, or change the form, of waste materials so they can be more easily 12 disposed of or recycled, or to reduce the size of a solid mix of raw materials (as in rock 13 ore), so that pieces of different composition can be differentiated.

Mobile material processing units employed for the above purpose are known in the art. In 16 general they comprise a processing module mounted on a mobile chassis. A feeder unit is 17 generally employed to convey raw material to the processing module. A hopper is typically 18 mounted upon the feeder unit so as to assist with loading the raw materials into the feeder 19 unit.

1 The processing module typically comprises a primary conveyor mounted on the chassis 2 and arranged to run substantially parallel to a longitudinal axis of the chassis. The primary 3 conveyor runs between the feeder unit and a screen box which provides a means for 4 screening the material into different size ranges. Each material size is then generally discharged from the unit via a respective discharge conveyor. Such material processing 6 units are generally referred to in the art as screening units.

8 The processing module may however further comprise a crushing tool mounted on the 9 chassis so as to locate between the feeder unit and the primary conveyor. The function of the crushing tool is to crush the material supplied to the feeder unit before the above Ii described screening process takes place. Such material processing units are generally 12 referred to in the art as crushing units.

14 The above described screening and crushing units generally also comprise a prime mover is mounted on the chassis. Moving means support the chassis and are arranged to be 16 power-operated by the prime mover in order to provide a means for the screening and 17 crushing units to move over the ground. Generally the prime mover comprises an engine 18 arranged to power a pair of endless tracks.

It is desirable for the above described screening and crushing units to be easily 21 manoeuvrable in order to assist normal operation and or transport between separate static 22 operating locations. Although a relatively expensive component part of such units, the 23 employment of a pair of endless tracks has been found to be a particularly suitable means 24 for propelling and steering such units.

26 However, with increasing operational demands being placed upon such screening and 27 crushing units there has been a general increase in the overall size and weight of these 28 devices. This has led to increased stability problems, both during normal operation and 29 when being moved between locations where they are to be deployed.

31 In order to address these issues it is known for screening and crushing units to comprise 32 foldable or telescopic discharge conveyors or ones that are rotatable, relative to the 33 chassis, that allow them to move between a retracted transport configuration and an 34 extended operational configuration.

1 It is also known to provide screening and crushing units with a hopper is pivotally mounted 2 about a horizontal axis so as to be rotatable relative to the chassis, see German patent 3 publication number DE 3,904,501. This arrangement allows the hopper to be rotated 4 between a raised operational position and a lowered transport position where it does not project, or only insignificantly projects above the crushing tool.

7 A further alternative solution known in the art is the incorporation of a hopper unit that 8 comprises foldable sides. Although this again helps to reduce the height of the screening 9 and crushing units such hoppers designs are found to be significantly weaker than those of a single piece design, and so can exhibit reduced operational lifetimes. Ii

12 Support legs are also known to be employed as a means to maintain the overall stability of 13 screening and crushing units when the screening or crushing units is in a static operating 14 location. Is

16 It is therefore an object of an embodiment of the present invention to provide a screening 17 and or crushing units that obviates, or at least mitigates the foregoing disadvantages of the 18 screening and or crushing units known in the art.

Summary of the Invention

22 According to a first aspect of the present invention there is provided a crushing unit or 23 screening unit comprising 24 a chassis surmounted on a first and a second moving means, the first and second moving means both comprising one or more endless tracks, and 26 one or more discharge conveyors mounted on the chassis and movable between a 27 transport configuration and an operational configuration, 28 wherein the second moving means is separated from the first moving means along a 29 longitudinal axis of the chassis.

31 The employment of the second moving means provides the crushing unit and screening 32 unit with increased levels of stability when compared with those systems known in the art.

34 The crushing unit or screening unit may further comprise a primary conveyor mounted on the chassis.

2 The primary conveyor may be arranged substantially parallel to the longitudinal axis of the a chassis.

Most preferably the first moving means is moveable relative to the chassis to provide a first 6 means for varying the linear separation between the first and second moving means along 7 the longitudinal axis.

9 The one or more endless tracks of the first moving means may be moved independently of each other. Ii

12 The above crushing unit and screening unit have the advantage that they are movable 13 between a transport configuration where the linear separation of the first and second 14 moving means along the longitudinal axis is minimised and a first operational configuration where the linear separation of the first and second moving means along the longitudinal 16 axis is increased, thus increasing the stability of the units.

18 Preferably the first moving means is connected to the chassis by a first releasable 19 mounting mechanism.

21 The first moving means may be connected to the chassis within a first end chassis section.

23 Most preferably the second moving means is moveable relative to the chassis to provide a 24 second means for varying the relative separation between the first and second moving means along the longitudinal axis.

27 The one or more endless tracks of the second moving means may be moved 28 independently of each other.

Preferably the second moving means is connected to the chassis by a second releasable 31 mounting mechanism.

33 The second moving means may be connected to the chassis within a second end chassis 34 section.

1 Most preferably the crushing unit or screening unit is in a transport configuration when the 2 one or more endless tracks of the first and second moving means are arranged 3 substantially parallel to the longitudinal axis.

Most preferably the crushing unit or screening unit further comprise one or more rotation 6 control means that provide a means for varying the rotation position of an associated 7 endless track relative to the longitudinal axis so as to define an operational configuration 8 for the unit.

Optionally the crushing unit or screening unit further comprises a lateral position control ii means (e.g. a telescopic arm) that connects an endless track to an associated releasable 12 mounting mechanism. The function of the lateral position control means is to provide a 13 means to independently adjust the position of an endless track in a direction substantially 14 perpendicular to the longitudinal axis. Is

16 Optionally one of the one or more discharge conveyors is located between first and a 17 second moving means and arranged to be non-parallel to the longitudinal axis of the 18 chassis.

Most preferably the second moving means comprises a pair of endless tracks.

22 The first moving means may also comprise a pair of endless tracks.

24 In this embodiment the crushing unit or screening unit exhibits increased manoeuvrability when compared with those systems known in the art. This is a result of the fact that the 26 moving means offers increased skid steer torque over those systems known in the ad.

27 Having a second set of endless tracks also acts to increase the overall stability of the units 28 during transport and operation.

Preferably, the crushing unit or screening unit further comprises a feeder unit connected to 31 the chassis wherein the feeder unit provide a means for directing material towards the 32 primary conveyor.

34 Optionally, the crushing unit or screening unit further comprises a hopper connected to the feeder unit wherein the hopper provide a means for directing material into the feeder unit.

2 According to a second aspect of the present invention there is provided a method of 3 configuring a crushing unit or screening unit comprising one or more discharge conveyors 4 mounted on a chassis and movable between a transport configuration and an operational configuration, the method comprising surmounting the chassis on a first and second 6 moving means, each moving means comprising one or more endless tracks, wherein the 7 second moving means is separated from the first moving means along a longitudinal axis 8 of the chassis.

The method of configuring the crushing unit or screening unit may further comprise moving Ii the first moving means relative to the chassis to vary the linear separation between the 12 first and second moving means along the longitudinal axis. The one or more endless 13 tracks of the first moving means may be moved independently of each other.

Is Most preferably the method of configuring the crushing unit or screening unit further 16 comprises moving the second moving means relative to the chassis to vary the linear 17 separation between the first and second moving means along the longitudinal axis. The 18 one or more endless tracks of the second moving means may be moved independently of 19 each other.

21 The method of configuring the crushing unit or screening unit may further comprise 22 arranging for the one or more endless tracks of the second moving means to be 23 substantially parallel to the one or more endless tracks of the first moving means to define 24 a transport configuration for the unit.

26 Optionally the method of configuring the crushing unit or screening unit further comprises 27 arranging the rotational position of one or more of the endless tracks of the first or second 28 moving means relative to the longitudinal axis to define an operational configuration for the 29 unit.

31 Embodiments of the second aspect of the invention may comprise features to implement 32 the preferred or optional features of the first aspect of the invention or vice versa.

34 According to a third aspect of the present invention there is provided a crushing unit or screening unit comprising 1 a chassis surmounted on a first and a second moving means, the first and second moving 2 means both comprising one or more endless tracks, and 3 one or more discharge conveyors mounted on the chassis and movable between a 4 transport configuration and an operational configuration wherein the second moving means is separated from the first moving means along a 6 longitudinal axis of the chassis and the one or more endless tracks of the second moving 7 means are substantially parallel to the one or more endless tracks of the first moving 8 means when the crushing unit or screening unit is in a transport configuration.

The crushing unit or screening unit may further comprise a primary conveyor mounted on Ii the chassis.

13 The primary conveyor may be arranged substantially parallel to a longitudinal axis of the 14 chassis. Is

16 Embodiments of the third aspect of the invention may comprise features to implement the 17 preferred or optional features of the first aspect of the invention or vice versa.

19 Brief Description of the Drawings

21 There will now be described, by way of example only, various embodiments of the 22 invention with reference to the drawings, of which: 24 Figure 1 presents an isomeric view of a crushing unit in accordance with an embodiment of the present invention, shown in a transport configuration; 27 Figure 2 presents an isomeric view of an adjustable track system for the crushing unit of 28 Figure 1, shown in a transport configuration; Figure 3 presents an isomeric view of the crushing unit of Figure 1, shown in a first 31 operational configuration; 33 Figure 4 presents an isomeric view of the adjustable track system of Figure 2, shown in a 34 first operational configuration; 1 Figure 5 presents an isomeric view of the adjustable track system of Figure 2 in a second 2 operational configuration; 4 Figure 6 presents an isomeric view of the adjustable track system of Figure 2 in a third operational configuration; 7 Figure 7 presents an isomeric view of adjustable track system of Figure 2 in a fourth 8 operational configuration; Figure 8 presents an isomeric view of the adjustable track system of Figure 2 in a fifth Ii operational configuration; 13 Figure 9 presents an isomeric view of the adjustable track system of Figure 2 in a sixth 14 operational configuration; Is 16 Figure 10 presents (a) an isomeric view and (b) a top view of a crushing unit in accordance 17 with an alternative embodiment of the present invention, shown in an operational 18 configuration; Figure 11 presents an isomeric view of a screening unit in accordance with an 21 embodiment of the present invention, shown in a transport configuration; and 23 Figure 12 presents an isomeric view of the crushing unit of Figure 11, shown in a first 24 operational configuration.

26 In the description which follows, like parts are marked throughout the specification and 27 drawings with the same reference numerals. The drawings are not necessarily to scale 28 and the proportions of certain parts have been exaggerated to better illustrate details and 29 features of embodiments of the invention.

31 Detailed Descrirjtion of Preferred Embodiments 33 A first embodiment of a crushing unit 1 in accordance with an embodiment of the present 34 invention will now be described with reference to Figures 1 and 3. In particular, Figure 1 1 presents an isomeric view of the crushing unit 1 in a transport configuration while Figure 3 2 presents the same view of the crushing unit 1, this time in a first operational configuration.

4 The crushing unit 1 can be seen to comprise a feeder unit 2 and a processing module 3 mounted on a chassis 4. A hopper 5 is mounted on the feeder unit 2 so as to assist with 6 the loading of raw materials into the feeder unit 2.

8 In the presently described embodiment, the processing module 3 comprises a crushing 9 tool Sand a primary conveyor 7 that runs substantially parallel to a longitudinal axis 8 of the chassis 4 and which is arranged to convey material output from the crushing tool 6 to Ii one or more screen boxes 9. The screen boxes 9 therefore provide a means for screening 12 the crushed material into different size ranges. Each material size is then generally 13 discharged from the crushing unit 1 via discharge conveyors.

is In the presently described embodiment two discharge conveyors 10 and 11 are present.

16 The first discharge conveyor 10 is located below the feeder unit 2 and runs substantially 17 parallel to the longitudinal axis 8. The second discharge conveyor 11 is located below the 18 primary conveyor 7 and runs substantially perpendicular to the longitudinal axis 8.

The discharge conveyors 10 and 11 may be foldable, telescopic, or rotatable relative to the 21 chassis 4 so as to move them from the operational configuration, as shown in Figures 1 22 and 3, to a transport configuration.

24 The chassis 4 may be an integrated component of the primary conveyor 7 or the crushing tool S or a separate component connected to the primary conveyor 7 and the crushing tool 26 6.

28 A prime mover e.g. an engine (not shown) is also mounted on the chassis 4.

The chassis 4 is surmounted on a first 12 and a second 13 moving means, the second 31 moving means 13 being displaced along the longitudinal axis 8 relative to the position of 32 first moving means 12. The first 12 and second 13 moving means are arranged to be 33 power-operated by the prime mover in order to provide a means for moving the crushing 34 unit 1 over the ground. In the presently described embodiment the first 12 and second 13 moving means each comprise a pair of endless tracks. It is preferable for the tracks of the 1 first pair of endless tracks 12 to be arranged to be collinear to the tracks of the second set 2 of endless tracks 13 when in the transport configuration of Figure 1.

4 The crushing unit 1 is moved from the transport configuration to the first operational configuration of Figure 3 by moving the discharge conveyors 10 and 11 to their operational 6 position. Reversing these steps moves the crushing unit 1 back to the transport 7 configuration.

9 The employment of the second moving means 13 provides the crushing unit 1 with increased levels of manoeuvrability when compared with those systems known in the art.

Ii This is a result of the fact that the second pair of endless tracks offers increased skid steer 12 torque for the unit over those systems known in the art. Having a second moving means 13 also acts to increase the overall stability of the crushing unit 1, particularly when in the first 14 operational configuration of Figure 3. It is noted that employing the second set of endless IS tracks 13 for a crushing unit 1 is contrary to the normal practice in the art due to the 16 relative expense of such a component.

18 The separation of the first 12 and second 13 moving means may also be increased when 19 moving from the transport configuration of Figure ito the first operational configuration of Figure 3. This is achieved through the employment of an adjustable track system 14 21 which will now be described with reference to Figures 2 and 4. In particular, Figure 2 22 presents an isomeric view of the adjustable track system 14 in a transport configuration 23 while Figure 4 presents the same view of the adjustable track system 14, this time in a first 24 operational configuration.

26 The adjustable track system 14 can be seen to comprise the chassis 4 which itself 27 comprises two elongated supports 1 5a and 1 5b connected by four support struts 1 Ba, 1 6b, 28 1 6c and 1 6d. The elongated supports 1 5a and 1 5b can be seen to lie substantially parallel 29 to the longitudinal axis 8.

31 The support struts 16a, 16b, 16c and 16d can be seen to split the chassis 4 into three 32 distinct longitudinally separated sections, namely: a first end chassis sections 17, located 33 between the first and second support struts 1 Ba and 1 Sb; a central chassis sections 18, 34 located between the second and third support struts lSb and lSc; and a second end chassis sections 19 located between the third and fourth support struts 1 Bc and 1 Sd.

2 The first moving means 12 is connected to the first end chassis section 17 by a first a releasable mounting mechanism 20. In a similar manner, the second moving means 13 is 4 connected to the second end chassis section 19 by a second releasable mounting mechanism 21 7 The releasable mounting mechanisms 20 and 21 may comprise hydraulically driven 8 clamps. In the absence of a hydraulic pressure, the clamp is biased towards a closed 9 position such that the position of the corresponding moving means 12 or 13 is fixed relative to the chassis 4. However, when a hydraulic fluid is provided to the releasable ii mounting mechanisms 20 and 21 these disengage from the chassis 4 and thus allow the 12 corresponding moving means 12 or 13 to move, in a direction substantially parallel to the 13 longitudinal axis 8, relative to the chassis 4. In this way the adjustable track system 14 14 can be moved between a transport configuration as presented in Figure 2 and a first operational configuration as presented in Figure 4.

17 It will be appreciated by the skilled reader that in an alternative embodiment the individual 18 tracks within a pair of tracks may be released and moved independently of the other i.e. 19 individual tracks within the first moving means 12 and or the second moving means 13 may be moved along the longitudinal axis B independently of each other.

22 It will be further appreciated by the skilled reader that the releasable mounting 23 mechanisms 20 and 21 may comprise alternative mechanical means to the above 24 described hydraulically driven clamps.

26 The adjustable track system 14 may comprise one or more hydraulic jacks that provide a 27 means for increasing or decreasing the separation of the first moving means 12 and or the 28 second moving means 13 relative to the chassis 4. In this way angle of the chassis 4 29 relative to the ground may be adjusted so as to provide a means for the crushing unit 1 to compensate for uneven ground.

32 When the crushing unit 1 is to be deployed at a particular location the adjustable track 33 system 14 may be moved from the transport configuration of Figure 2 to the first 34 operational configuration, as presented in Figure 4. In this configuration the overall footprint of the endless tracks endless tracks 12 or 13 is increased and hence there is a 1 corresponding further increase in the overall stability of the crushing unit 1. As a result 2 there is a reduced restriction on the design of the various components of the crushing unit 3 1 upon the chassis 4 and a reduction in the need to deploy support legs. As described 4 above, the hydraulic jacks may be employed to adjust the angle of the chassis 4relative to the ground.

7 The adjustable track system 14 may further comprise a rotation control means 22 that 8 connects an endless track of the first 12 or second 13 moving means to an associated 9 releasable mounting mechanism 20 or 21. The function of the rotation control means 22 is to provide a means to independently adjust the rotational position of an endless track ii relative to the longitudinal axis S. In the presently described embodiments of Figures 5 to 12 9 the rotation control means 22 comprise a hydraulic actuator, activation of which causes 13 rotational movement of the endless track to occur. It will however be appreciated by the 14 skilled reader that the rotation control means 22 may comprise an alternative mechanical is component to provide this independent rotational functionality to each of the endless 16 tracks.

18 In a yet further alternative embodiment the adjustable track system may further comprise a 19 lateral position control means (e.g. a telescopic arm) that connects an endless track to an associated releasable mounting mechanism. The function of the lateral position control 21 means is to provide a means to independently adjust the position of an endless track in a 22 direction substantially perpendicular to the longitudinal axis.

24 Figures 5 to 9 present isomeric views of the adjustable track system 14 in second to sixth operational configurations, respectively.

27 In particular, in Figure 5 the endless tracks of the first moving means 12 have both been 28 rotated to approximately 45° relative to the longitudinal axis 8 while the endless tracks of 29 the second moving means 13 remain substantially parallel to the longitudinal axis S. 31 In Figure 6 the endless tracks of the first moving means 12 have both again been rotated 32 to approximately 45° relative to the longitudinal axis 8 while the endless tracks of the 33 second moving means 13 have both been rotated to approximately -45° relative to the 34 longitudinal axis S. 1 In Figure 7 the endless tracks of the first moving means 12 have both again been rotated 2 to approximately 45° relative to the longitudinal axis 8 while the endless tracks of the 3 second moving means 13 have also both been rotated to approximately 45° relative to the 4 longitudinal axis 8.

6 In Figure 8 the endless tracks of the first moving means 12 have been rotated to 7 approximately 900 and 90°, respectively, so that both now lie substantially perpendicular 8 to the longitudinal axis 8. In this configuration the endless tracks of the second moving 9 means 13 remain substantially parallel to the longitudinal axis 8.

Ii Finally, in Figure 9 the endless tracks of the first moving means 12 and the second moving 12 means 13 and have been rotated to approximately -90° and 90°, respectively, so that they 13 all lie substantially perpendicular to the longitudinal axis 8.

Is It will be appreciated by the skilled reader that the choice of operational configurations is 16 not limited to those presented in Figures 5 to 9. The choice of operation configuration 17 adopted will be dependent upon the use to which the crushing unit 1 is to be deployed and 18 the terrain upon which it is deployed. The adjustable track system 14 thus provides a 19 means for increased linear and radial movement for the crushing unit 1 to assist slewing motion during operation.

22 Although the above described embodiments have all been described in relation to the first 23 12 and second moving means 13 comprising a pair of endless tracks it will be appreciated 24 that one or both of these moving means may alternatively comprise one or more endless tracks.

27 Figure 10 presents (a) an isomeric view and (b) a top view of a further alternative 28 embodiment of the crushing unit ib, shown in a first operational configuration. This 29 embodiment differs from those described above in that it a third discharge conveyor 23 is present. Like the first 10 and second 11 discharge conveyors, the third discharge 31 conveyor 23 may be foldable, telescopic or rotatable, relative to the chassis 4.

33 As can be seen from Figure 10 the third discharge conveyor 23 is located centrally within 34 the crushing unit 1 and in particular between the first 12 and second moving means 13.

1 This arrangement is advantages for the stability of the crushing unit lb and the 2 compactness of the crushing unit lb when in its transport configuration.

4 In addition, it will be appreciated that in an alternative embodiment one of the moving means may not be connected to the chassis by a releasable mounting mechanism. In 6 such an embodiment the relative longitudinal positions of the first 12 and second moving 7 means 13 is controlled by the release and movement of a single moving means.

9 A first embodiment of a screening unit 24 in accordance with an embodiment of the present invention will now be described with reference to Figures 11 and 12. In particular, Ii Figure 11 presents an isomeric view of the screening unit 24 in a transport configuration 12 while Figure 12 presents the same view of the screening unit 24, this time in a first 13 operational configuration.

is The screening unit 24 can be seen to comprise many features in common with the above 16 described crushing units 1 and lb and thus like reference numerals are employed to 17 denote like components. In particular the screening unit 24 can be seen to comprise a 18 feeder unit 2 and a processing module 3 mounted on a chassis 4b. A hopper 5 is mounted 19 on the feeder unit 2 so as to assist with the loading of raw materials into the feeder unit 2.

21 In the presently described embodiment, the processing module 3 comprises a primary 22 conveyor 7 that runs substantially parallel to a longitudinal axis 8 of the chassis 4b and 23 which is arranged to convey material output from the feeder unit 2 to one or more screen 24 boxes 9. The screen boxes 9 therefore provide a means for screening the material into different size ranges. Each material size is then generally discharged from the crushing 26 unit 1 via discharge conveyors.

28 In the presently described embodiment two discharge conveyors 11 and 23 are present.

29 The discharge conveyor 11 is located below the feeder unit 2 and runs substantially parallel to the longitudinal axis 8. The other discharge conveyor 23 is located centrally 31 within the screening unit 24. This arrangement is advantages for the stability of the 32 screening unit 24 and the compactness of the screening unit 24 when in its transport 33 configuration.

1 The discharge conveyors 11 and 23 may be foldable, telescopic, or rotatable relative to the 2 chassis 4b so as to move them from the operational configuration, as shown in Figures 12, 3 to a transport configuration of Figure 11.

The chassis 4b may be an integrated component of the primary conveyor 7 or a separate 6 component connected to the primary conveyor 7.

8 A prime mover e.g. an engine (not shown) is also mounted on the chassis 4.

The chassis 4b is again surmounted on the first 12 and a second 13 moving means, the Ii second moving means 13 being displaced along the longitudinal axis S relative to the 12 position of first moving means 12. The first 12 and second 13 moving means are arranged 13 to be power-operated by the prime mover in order to provide a means for moving the 14 screening unit 24 over the ground. In the presently described embodiment the first 12 and IS second 13 moving means each comprise a pair of endless tracks. It is preferable for the 16 tracks of the first pair of endless tracks 12 to be arranged to be collinear to the tracks of 17 the second set of endless tracks 13 when in the transport configuration of Figure 11.

19 The screening unit 24 is moved from the transport configuration to the first operational configuration of Figure 12 by moving the discharge conveyors 11 and 23 to their 21 operational position. Reversing these steps moves the screening unit 24 back to the 22 transport configuration.

24 The screening unit 24 preferably comprises the adjustable track system 14 as described in detail above.

27 The crushing units 1 and lb and the screening unit 24 described above provides a number 28 of advantages when compared to those known in the art. In the first instance when in the 29 transport configuration these units are highly manoeuvrable since they are afforded increased skid steer torque and are more stable over those systems known in the art. The 31 presence of the second set of endless tracks 13 also provides these units with increased 32 stability. The employment of a second moving means comprising a set of endless track is 33 contrary to the normal practice in the art due to the relative expense of such a component.

1 The ability to move and reconfigure the first and second sets of endless tracks to the one 2 or more described operational configurations also provides the crushing units 1 and lb 3 and the screening unit 24 with further increased stability without the need to employ 4 support legs or to carefully design the weight distribution of the other components of these units. It also provides increased linear and radial movement for these units to assist 6 slowing motion during operation.

8 A crushing unit and screening is described that comprises two pairs of endless tracks 9 connected to a chassis at separate locations along a longitudinal axis. Employing two sets of endless tracks provides the units with increased stability and manoeuvrability. The two Ii pairs of endless tracks may form part of an adjustable track system where one or more of 12 these components is moveable relative to the chassis. This arrangement provides a 13 means for varying the linear separation between the pairs of endless tracks along the 14 longitudinal axis. The track system is therefore movable between a transport configuration Is where the linear separation of the first and second moving means along the longitudinal 16 axis is minimised and a first operational configuration where the linear separation of the 17 first and second moving means along the longitudinal axis is increased to further increase 18 the stability provided by the adjustable track system.

Throughout the specification, unless the context demands otherwise, the terms "comprise" 21 or "include", or variations such as "comprises" or "comprising", "includes" or "including" will 22 be understood to imply the inclusion of a stated integer or group of integers, but not the 23 exclusion of any other integer or group of integers.

Furthermore, reference to any prior art in the description should not be taken as an 26 indication that the prior art forms part of the common general knowledge.

28 The foregoing description of the invention has been presented for purposes of illustration 29 and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best 31 explain the principles of the invention and its practical application to thereby enable others 32 skilled in the art to best utilise the invention in various embodiments and with various 33 modifications as are suited to the particular use contemplated. Therefore, further 34 modifications or improvements may be incorporated without departing from the scope of the invention as defined by the appended claims.