Examples of material processing plant with which the invention is concerned include a crusher or shredder, a screening device, and a combined crusher and screening device.

Screening plants are well known and typically comprise a plant frame and one or more discharge conveyors for discharging different fractions of screened material to different stock piles. Screening plants typically also comprise a propulsion means such as crawler tracks which make the plant readily manoeuvrable in a quarry but transport along a road usually requires the plant to be transported by a low loader. Although many screening plants can be folded into transport positions of reduced height or length, putting the plant on a low loader means that the screening plant is raised to a position high above ground level. The overall height of the low loader/ screening plant combination can therefore be a problem when passing under bridges or along roads with overhanging trees.

Accordingly, in one aspect, the present invention provides a material processing plant adapted to be suspended between first and second separate wheeled units during transport, the first unit having a respective first coupling; the second unit having a respective second coupling; the plant comprising a plant frame; a front coupling and a rear coupling provided at the front and rear of the plant frame respectively; the front and rear couplings being arranged such that when the front coupling is connected to the first coupling and when the rear coupling is connected to the second coupling, the plant is suspended between the first and second units; and, a lifting or lowering means connected to one or both of said units, or to the plant frame, and operable to lift the plant for connecting the first coupling to the front coupling and the second coupling to the rear coupling.

The plant of the invention has the advantage that it can be connected to the two separate wheeled units to produce a transport device which is not as high as a material processing plant/low loader combination.

The plant can further comprise a locomotion means. The locomotion means can comprise crawler tracks. This has the advantage that the plant can be moved independently of the wheeled units.

Preferably, the lifting means comprises a front jack and a rear jack for lifting the front and rear of the plant frame respectively.

The front and rear jacks can be adapted to lift the front and rear of the plant frame independently. This has the advantage that the front of the plant can be lifted and connected to the first unit before the rear end of the plant is lifted.

In a preferred arrangement, the first wheeled unit is a tractor unit and the second wheeled unit is a bogie unit.

Preferably, at least one of the front and rear couplings is connected by a pivot to the plant frame and is pivotable between an extended position for connection with the corresponding tractor or bogie coupling and a retracted position. This has the advantage that when the plant is not connected to the tractor unit and bogie unit the front and rear couplings can be pivoted to the retracted position so reducing the length of the screening plant so improving its manoeuvrability.

The plant may be a crusher or shredder, a screening device or a combination of a crusher/shredder and a screening device, and may further include a discharge conveyor.

In a further aspect of the invention there is provided a transport device comprising a tractor unit comprising a tractor coupling; a bogie unit comprising a bogie coupling; and, a material processing unit comprising a plant frame; a front coupling and a rear coupling provided at the front and rear of the plant frame respectively; the front and rear couplings being arranged such that when the front coupling is connected to the tractor coupling and when the rear coupling is connected to the bogie coupling, the plant is suspended between the tractor unit and the bogie unit; and, a lifting means connected to the plant frame adapted to lift the plant for connecting the tractor coupling to the front coupling and the bogie coupling to the rear coupling.

The transport device of the present invention has the advantage that it is of a reduced height compared to e. g. a screening plant and low loader.

In a further aspect of the invention there is provided a method of assembly of a transport device, the transport device comprising a tractor unit comprising a tractor coupling; a bogie unit comprising a bogie coupling; and, a material processing unit comprising a plant frame; a front coupling and a rear coupling provided at the front and rear of the plant frame respectively; the front and rear couplings being arranged such that when the front coupling is connected to the tractor coupling and when the rear coupling is connected to the bogie e coupling, the plant is suspended between the tractor unit and the bogie unit; and, a lifting means connected to the plant frame adapted to lift the plant for connecting the tractor coupling to the front coupling and the bogie coupling to the rear coupling, comprising the steps of extending the lifting means to lift the plant frame from the ground; interengaging the tractor coupling with the front coupling and the bogie coupling and the rear coupling; and, retracting the lifting means so suspending the plant between the tractor unit and bogie unit.

Preferably, the front end of the plant frame is lifted and the front coupling connected to the tractor coupling before the rear end of the frame is lifted and the rear coupling connected to the bogie coupling. This has the advantage that as only one end of the plant is raised from the ground at a time the screening plant is always stable.

The present invention will now be described by way of example but not in any limitative sense with reference to the figures in which: Figure 1 shows a transport device comprising a material processing plant, a tractor unit and a bogie unit; Figure 2 shows a bogie unit acccrding to the invention in end view.

Figure 3 shows a bogie unit according to invention in side view.

Shown in figure 1 is a transport device 1 comprising a crushing plant 2, and first and second separate wheeled units, preferably comprising a tractor unit 3 and a bogie unit 4.

It should be understood that a crusher (or shredder) is one example only of a material processing plant with which the invention is concerned and other types of plant may be used e. g. a screening plant, or a combination of a screening and crushing/shredding plant.

The tractor unit 3 comprises a chassis 5 supported by wheels 6,7,8. The chassis 5 supports a drive unit 9 for supplying power to the wheels 6,7,8. Located over the rear wheels 7,8 and supported by the chassis 5 is a tractor coupling 10 comprising an aperture (not shown) for engagement with a fifth wheel type coupling provided on the plant 2.

The bogie unit 4 comprises a bogie chassis 11 connected to a plurality of bogie wheels 12,13,14. Supported by the chassis 11 is a bogie coupling 15 for coupling the screening plant 2 to the bogie unit 4. The bogie unit 4 is described in more detail with reference to figure 2.

The plant 2 comprises a plant frame 15 having a rectangular base 16, a forward support portion 17 and a rear support portion 18. The rectangular base 16 supports a motor <BR> <BR> <BR> unit 19 and a locomotion means 20. The locomotion means 20 comprises a pair of crawler tracks 21, one located on each side of the rectangular base 16. The crawler tracks 21 are used to manoeuvre the plant 2. The plant 2 further comprises a hopper 22 connected to the upper edge 23 of the forward support <BR> <BR> <BR> portion 17. The hopper 22 includes an entrance port 24 located on its upper surface and an exit port 25 located on its lower surface. A number of evenly spaced bars (not shown) extend across the entrance port 24. A discharge chute 26 extends from a first end 27 below the hopper to a second end 28 rearward of the rear support portion 18. The discharge chute 26 includes a conveyor belt 29 for transporting material received by the first end 27 to the second end 28 and then discharging this received material at a point proximate to the plant frame 15.

In use material to be crushed is deposited on the entrance port 24 of the hopper 22 by quarry machinery. The bars across the entrance port 24 only allow quarry material smaller than the separation between the bars to fall through the hopper 22 onto the first end 27 of the discharge chute 26. The bars across the entrance port 24 prevent quarry material larger than the spacing between the bars from passing through the hopper 22. The bars divert this material to the side of the plant frame 15.

Provided on the underside of the rear support portion 18 of the plant frame 15 is a rear coupling 30 comprising a fifth wheel connector (not shown) adapted for interengagement with the bogie coupling 15.

Connected by a pivot 31 to the forward support portion of the plant frame 15 is an L shaped pivot arm 32. The pivot arm 32 comprises substantially orthogonal first and second arms 33, 34. The end of the second arm 34 rernote from the first arm 33 is connected to the pivot 31. Connected to the first arm 33 at a point remote from the second arm 34 is a front coupling 35 comprising a fifth wheel type coupling 36 suitable for engagement with the tractor coupling 18. The pivot arm 32 is shown in an extended position with the first arm 33 in the horizontal plane extending away from the screening plant 2. The pivot arm 32 can be pivoted from the extended position clockwise through approximately 90 degrees to the retracted position. In this position the second arm 34 lies in a vertical plane and abuts against the forward support portion 17 of the plant frame 15. The pivot arm 32 can be maintained in this position by a locking mechanism (not shown). The pivot arm 32 is typically maintained in the retracted position when not connected to the tractor unit 3 as this reduces the length of the plant 2 so increasing its manoeu-vrability.

Extending from the plant frame 15 is a lifting means 37 comprising four hydraulic pistons 38,39, one located proximate <BR> <BR> <BR> to each of the four corners of the rectangular base 16 of the plant frame 15. The hydraulic pistons 38,39 are shown in a retracted position off the ground.

Figures 2 and 3 show the bogie unit 4 in detail.

Extending upwardly from the bogie chassis 11 are two side walls 40,41 for guiding the rear support portion 18 of the plant frame 15 into correct alignment with the bogie unit 4.

Extending between the side walls s 40,41 is a guiding ramp 42 which extends upwardly away from the chassis as one moves from the front to the rear of the bogie chassis 11. Located within the guiding ramp 42 is the bogie coupling 15 which comprises an aperture 43 adapted to receive the rear coupling 30.

In order to assemble the transport device 1 shown in figure 1 the front pair of hydraulic pistons 38 is extended, raising a front portion of the crawler tracks 21 off the ground. The pivot arm 32 is then pivoted to the extended position so rotating the fifth wheel coupling 36 of the front coupling 35 into the horizontal plane. The front pistons 38 are then adjusted further if necessary until the front coupling 35 is at substantially the same height as the tractor coupling 10. The tractor unit 3 is then reversed towards the front coupling 35 and the tractor coupling 10 and front coupling 35 are interengaged.

Next, the rear pair of hydraulic pistons 39 are extended lifting the crawler tracks 21 off the ground. The rear pistons 39 are extended until the rear coupling 30 is at the same height as the bogie coupling 15. The bogie unit 4 is then moved towards the rear coupling 30 and the rear coupling 30 and bogie coupling 15 are interengaged.

Finally, all four pistons are retracted so suspending the plant 2 between the tractor unit 3 and the bogie unit 4.

In order to disassemble the transport device 1 into <BR> <BR> <BR> tractor unit 3, bogie unit 4 and plant 2 all four pistons 38, 39 are extended until they touch the ground and support the weight of the plant 2. The tractor unit 3 and bogie unit 4 are then disengaged from the plant 2 and removed from the plant 2. The <BR> <BR> <BR> pistons 38,39 are then slowly retracted lowering the plant 2 until the crawler tracks 21 reach the ground and support the screening plant 2. The pistons 38,39 can then be fully retracted to a position where they are remote from the ground.

The crawler tracks 21 can then be used to move the plant 2.

Other methods of assembling the transport device 1 are possible. For example the rear pistons 39 could be extended and the rear coupling 30 engaged with the bogie coupling 15 before the forward pistons 38 are extended. Alternatively, both forward and rear pistons 38,39 could be extended raising the plant 2 from the ground before either of the tractor unit 3 or bogie unit 4 are engaged with the plant 2.

As an alternative to providing lifting means on the plant frame, it will be possible to provide lifting/lowering means on one or both of the wheeled units, e. g. airbags, and operable to load and unload the plant relative to the wheeled units.