WO2010048674A1

WO2010048674A1 - A device for picking up and transporting a load

Info

Publication number: WO2010048674A1
Application number: PCT/AU2009/001419
Authority: WO
Inventors: Peter Robert Adamson; Lyal Douglas Allen; Andrew John Donald Strang
Original assignee: Strang International Pty Ltd
Priority date: 2008-10-30
Filing date: 2009-10-29
Publication date: 2010-05-06
Also published as: AP2011005702A0; NZ592672A; AU2009310633A1; ZA201103053B; AP3095A; AU2009310633B2

Abstract

A trailer (10) for picking up and transporting a load (200) includes a pair of chassis sides (12, 14) each chassis side including wheels (110) supporting the trailer, and a protrusion (150) for engaging with a load to be picked up and transported. The trailer also includes a cruciform link mechanism (36, 38) for expanding and contracting the trailer by moving the chassis sides (12, 14) towards and away from each other. This enables the device to be positioned on either side of a load (200) in an expanded state and subsequently contracted to engage with the load. The cruciform link mechanism (36, 38) is located above the load in use and comprises two link members (36, 38) of substantially equal length which are pivoted to each other at their respective centres (58) where they cross and which link the chassis sides together.

Description

"A device for picking up and transporting a load" Cross Reference to Related Applications

This application claims priority from Australian provisional patent application No 2008905616 filed 30 October 2008 entitled "A device for picking up and transporting a load" the entire contents of which are hereby incorporated by reference.

Field of the Invention

This invention relates to a device for picking up and transporting a load particularly, but not exclusively for carrying unitised or modularised loads.

Background of the Invention

Straddles are used to move loads in ports 'prior to loading them onto ocean going vessels, barges or the like. A typical straddle includes an inverted U shaped frame and a means for lifting and suspending a load such as a shipping container or unitised or modularised load from the frame. One type of modularised load which are commonly moved by straddles is aluminium ingots. For transport from a smelter to an end user, the aluminium ingots are set together in bundles, each of which weighs approximately one tonne. These bundles are held together by straps. Typically, a number of such stacked bundles are then consolidated together making up a shipping pack, often known as a "Superpack". The Superpack may be made up of any number of two high bundles consolidated together and may weigh 24 or up to 32 tonnes. These Superpacks are typically transferred from the smelter to a port by road on a flat bed truck. Once the trucks reach port they are unloaded and stored prior to transfer to dockside for transfer to an ocean going vessel or barge by a crane having an appropriate spreader attachment. The Superpacks are moved from the truck to a storage area by a straddle. Subsequently the straddle transfers the Superpack to dockside for loading onto an ocean going vessel.

The process including the use of straddles in particular has a number of disadvantages. First, the overall process of moving the ingots from the smelter to an ocean going vessel is relatively inefficient as it involves a number of separate operations of loading and unloading, and transport and storage by different carriers. Removing one or more steps from the process would increase efficiency.

Secondly, straddles are not very compact. When they are used to transport and move loads to storage, those loads have to be stored sufficiently far apart to allow the straddle to move between loads to pick up and transport the load to dockside. Thus the storage ratio of load area to floor space is poor using straddles.

Straddles also have a high capital cost and are expensive to maintain and run. The present invention seeks to address and attempts to alleviate at least some of the disadvantages of the prior art discussed above.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

Summary of the Invention

In a first broad aspect, there is provided a device for picking up and transporting a load including a pair of chassis sides, each chassis side including wheels supporting the device, and a protrusion for engaging with a load to be picked up and transported, the device further including a link mechanism for expanding and contracting the device by moving the chassis sides towards and away from each other to enable the device to be positioned on either side of a load in an expanded state and subsequently contracted to engage with the load wherein the link mechanism is located above the load in use and is a cruciform linkage comprising two link members of substantially equal length which are pivoted to each other at their respective centres where they cross and which link the chassis sides together.

Because the chassis sides themselves move inwards and outwards to pick up the load, the device can be more compact than say a traditional straddle in which there is a frame having a fixed width supporting a clamping and lifting apparatus inside the frame. This compactness provides a number of advantages. In preferred embodiments this enables the device to pick up and transport a load as wide as about 1500mm within an overall width of 2500mm when the device is closed. This enables the device to be within the legal width for vehicles for use on public roads in most jurisdictions. This has benefits in terms or reducing handling operations as it is possible for a load such as an ingot Superpack to be loaded onto the trailer and delivered to port and placed directly in a storage area. A similar trailer can subsequently transport the pack to dockside. Further, use of the invention may allow loads to be stored closer together providing a better storage ratio.

By having fewer components as the chassis sides also perform the lifting, the device can also be less expensive to manufacture and maintain compared to a straddle. Two additional single link members may be provided, one of which extends from each chassis side and which are pivoted together where they meet, whose length is half the length of the link members of the cruciform link.

With such geometry, the sides of the chassis remain parallel when they open and close.

The device is most preferably a trailer for attachment to a prime mover or tractor, but could also incorporate its own drive means. The device is typically loaded from its rear, distal from the prime mover/drive means.

The rearmost end of each link of the cruciform link is typically pivoted near one end, such as the rear of the device for rotation about a vertical axis. The foremost end may slide in a slotted plate located near the opposite end of the device. Typically, each link will define a pin and the pin will slide in a slot defined in a plate attached to the top of the side wall of the device. The slot preferably extends parallel to the chassis side.

In a preferred embodiment, the device incorporates a hydraulic braking system for locking the link closed. The braking system may include brake plates disposed either side of the slotted plate which may be forced against the plate by hydraulic pressure. The hydraulic fluid may pass through a bore in the pin.

In a particularly preferred embodiment the main wheels of the device are mounted on the lower end of respective suspension cylinders attached to the sides of the device such that the weight of the trailer and its load creates a proportionate hydraulic pressure in a chamber in the suspension cylinders which is transmitted to the braking system for locking the link closed.

Thus the heavier the weight carried, the greater the braking force preventing accidental opening of the link and dropping of the load.

The use of a hydraulic suspension system for the wheels provides an improved ride and may improve durability of the device as well as allowing the chassis sides to be raised and lowered during loading of the device.

The main wheels are typically single wheels to keep the overall width of the trailer as narrow as possible and allow for the widest possible load within the desired 2500mm overall width of the device.

In a preferred embodiment two transverse wheels are mounted to the rear of each chassis side at the base of the chassis structure. These may allow the chassis sides to move laterally when the main wheels are raised and the chassis sides lowered to the ground.

The engaging means may comprise inwardly directed protrusions extending along the base of each chassis side. The additional single link members are typically connected to a chassis link and mounting assembly for connecting the trailer to a prime mover and may include hydraulic cylinders to allow the trailer to be adjusted out of alignment with the prime mover, where necessary for picking up a load, and realigned at completion of loading.

The chassis link and mounting assembly may include a hydraulic cylinder for raising and lowering the front of the trailer chassis during loading and unloading.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Brief Description of the Drawings

A specific embodiment of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:-

Figure 1 is a top plan view of a trailer embodying the present invention carrying a load of ingots;

Figure 2 is a side view of the trailer of Figure 1;

Figure 3 is an end view of the trailer of Figure 1, with an end component removed on the left hand side to show part of a cylinder rod;

Figure 4 is a perspective view of the trailer of Figure 1;

Figure 5 is a schematic diagram illustrating a hydraulic locking mechanism;

Figure 6 is a schematic diagram of the trailer from above showing the trailer with a load of ingots located between the sides of the chassis ready to be loaded;

Figure 7 is a schematic diagram of the trailer from above showing the trailer in a closed mode with a load of ingots carried between the sides of the chassis;

Figure 8 is a schematic diagram of a hydraulic circuit of the trailer; and

Figure 9 is a similar view to Figure 2 but which includes a cutaway view of a normally hidden, cylinder.

Detailed Description of a Preferred Embodiment

Referring to the drawings, Figures 1 to 5 show a device for picking up and transporting a load in the form of a trailer 10 whose front end may be turntable mounted to a truck or tractor prime mover (not shown). Typically the trailer or truck would have reversible seat and controls for use in manoeuvring the trailer.

The trailer includes two chassis sides, a right hand chassis side 12 and a left hand chassis side 14. Each chassis side includes an upper beam assembly, being right hand and left hand beam assemblies 16 and 18 respectively. The front end of the right beam assembly is pivoted about a vertical axis to one (proximal) end of a right scissor link in the form of a right hand link beam 20. The beam has a length of 1750mm. Likewise front end of the left beam assembly is pivoted about a vertical axis to one (proximal) end of a left scissor link in the form of a left hand link beam 22 which is also 1750mm long. The distal ends of the two links 20, 22 are pivotally linked about a vertical axis at 24.

Also pivoted about the same vertical axis is a chassis link and mounting assembly generally shown at 25 for connecting the trailer 10 to a prime mover. There are two hydraulic cylinders 26 and 27 each of which extends from the assembly to the ends of a respective scissor link 20, 22 adjacent where the link is pivoted to one of the chassis beams.

The assembly 25 includes a curved link 28 which is mounted for vertical rotation about axis 24 at its upper end. A further link 30 extends between the lower end of link 28, to which it is mounted about a vertical pivot axis and a turntable plate 32 for engagement with the prime mover. A hydraulic cylinder assembly 34 extends between the link 28 and link 30 adjacent the turntable plate 32. As will be described in more detail below in relation to operation of the trailer, the cylinder and chassis link and mounting assembly may be used to vary the height of the front of the trailer chassis during loading.

The chassis sides 12 and 14 are linked by a cruciform linkage best seen in Figures I₅ 6 and 7. The linkage includes a first link member in the form of a simple beam or strut 36 and a second link member in the form of a compound strut 38. Both struts are 3500mm long. One end of the simple strut 36 is pivoted to the left hand chassis side 14 adjacent the rear end of the trailer about a vertical axis 40. The other end of the simple strut defines a depending pin 42 which locates in a slot 44 defined in a plate 46 attached to the top of the right hand beam assembly 16 towards the front of the trailer. The compound strut is made of two relatively shorter beams 48, 50. A gap 52 is defined between the opposed ends of the beams which are linked by upper and lower plates 54, 56 (best seen in Figure 4) The simple strut passes through the gap 52 and is fixed to the plates by a pin defining a vertical pivot axis 58 half way along its length. In a mirror arrangement to that of the simple strut, one end of the compound strut 36 is pivoted to the right hand chassis side 12 adjacent the rear end of the trailer about a vertical axis 60. The other end of the simple strut defines a depending pin 62 which locates in a slot 64 defined in a plate 66 attached to the top of the left hand beam assembly 18 towards the front of the trailer. Hydraulic cylinders 68 and 70 are provided for pushing and pulling the end of each strut along its respective slot. Both sides of each cylinder 68, 70 are connected to a single hydraulic valve 71 (see Figure 8) so that both cylinders are lengthened or shortened simultaneously.

Although a detailed description of the operation of the trailer is included below, a short explanation of the geometry of the cruciform linkage will now be provided, with reference to Figures 6 and 7 in particular.

As discussed above, the link members 36 and 38 are pinned together, halfway along their overall length at pivot 58. From Figure 6 it can be seen that the half length dimension of each strut of the cruciform linkage is 1750mm long measured from the respective mounting on the chassis side to the pivot 58. The left and right scissor links are each 1750mm long. The longitudinal axes of the left hand side scissor link and compound strut 38 are parallel to each other as are the longitudinal axes of the lefthand side scissor link 22 and the simple strut 36. The vertical pivots of the struts 36 and 38 and the scissor links 20 and 22 are located on the central longitudinal axis of the trailer 10. As set out above, the ends of the cruciform links 36 and 38 adjacent the rear of the trailer are pinned to the chassis. The opposite ends are able to slide in the slotted plates of the chassis sides beams. This geometry, expands the straddle trailer width such that the sides 12 and 14 remain parallel to each other, as illustrated in Figures 6 and 7, where Figure 6 shows the trailer fully expanded.

A hydraulic braking system is provided for locking the link mechanism and preventing opening of the link mechanism. This system is shown schematically in Figure 5. The system will be described with reference to the brake on the right hand side of the chassis only, the brake on the left hand side being identical to that on the right.

With reference to Figure 5 the slotted plate 46 includes two identical slotted plates 46a and 46b, one above the other. As referred to above, the pin 42 at the end of the link 36 is located and movable along slot 44 by means of hydraulic cylinder/ram 68. In theory, locking the hydraulic cylinder should lock the cruciform linkage in position and prevent the linkage opening. However, as the trailer is intended to carry loads of in excess of 20 tonnes, an additional robust braking system to lock the linkage is desirable. As shown in Figure 5, the braking system 80 is carried on the pin 42 and includes a top cap 82, a first brake disc 84 located above the plate 46a, a second brake disc 86 located below the plate 46a, a third brake disc 88 located above the lower plate 46b separated from the second disc by a gap 90, and a fourth brake disc 92 located below the lower plate 46b. A lower end cap 94 encloses the lower part of the brake disc 92, and a cylindrical housing 96 partly encloses the second and third brake discs and the gap between them. O-ring seals are provided adjacent the open ends of the caps and cylinder. As well as the gap 90 between the second 86 and third brake discs 88, a gap 98 exists between the first end cap 82 and the first brake disc 84, and a further gap 100 exists between the lower end cap 94 and the fourth brake disc 92.

The pin 42 defines a central longitudinal bore 102. The pin defines a series of channels 104, 106, 108 extending from the central bore to each of the gaps 98, 90 and 100, respectively. The bore is connected to the trailer's hydraulic circuit to be described in more detail below. It will be appreciated that hydraulic fluid passing from the bore 102 into the gaps will force the brake discs against the upper and lower surfaces of the upper and lower plates 46a and 46b, thus preventing opening (or closing of) the link mechanism when the brake is on. The brake also alleviates potential wear problems in the slots 44 by reducing movement and wobble.

It should be noted that while the braking mechanism as described uses four brake discs acting on two plates on each chassis side, it would be possible to have a single plate sandwiched between just two brake discs on each chassis side.

As shown in Figures 1 to 4 and 9, the trailer has three main wheel assemblies 110 on each side (although a larger trailer for carrying heavier loads might have four wheels on each side). Each wheel assembly includes a large single tyre 112 of a size and type commonly used on trailers. The width of the tyre is such that the tyre fits beneath the chassis beam, adjacent the load. The hubs of each wheel assemblies is mounted to the base of an inverted L-shaped wheel support leg 114, best seen in Figures 3 and 4. Each support leg 114 is mounted to a steering and suspension cylinder rod 116 which is part of a suspension cylinder assembly 118. The right hand side of Figure 9 is cut-away to show the suspension cylinder assembly 118. In the other views, the cylinder is largely hidden behind a removable cover 120 which is removable to allow access to the cylinder for repair or replacement. The other cylinders 118 are similarly covered.

Each of the three suspension cylinders 118 on their upper side 118a have their load connected to a single hydraulic accumulator 120 charged with nitrogen gas (refer to the hydraulic circuit diagram - Figure 8). The suspension system shares the load equally to each tyre, on each side. The three cylinders 118, are also connected to a hydraulic valve. The upper Suspension Cylinder cavity 118a, is the pressure cavity, which supports the load to each wheel and tyre.

The lower suspension cylinder cavities 118b of all three cylinders on both sides are also interconnected and connected to a single hydraulic valve 124. When the trailer is carrying a load, or is travelling empty, the lower cylinder cavities 118b are open through the valve, to the hydraulic reservoir 126.

The wheels of the trailer can be steered for allowing the trailer and prime mover to make tighter turns and improve manoeuvrability which is important in a dockside environment where space can be limited. As is best seen in Figure 1, rods emerge from the top of the suspension cylinders. The middle wheel on each side has a tie rod 130, which has spherical bearings at each end. The rear end of the tie rod 130 is connected to a pin at the top of the rear suspension cylinder 118 (best seen in Figure 9) and is concentric with that cylinder. The forward end of the rod 130 is connected to a plate 132 mounted on top of the middle cylinder which acts as an alignment arm. The tie rod 130 may be adjustable, for the purpose of aligning the middle wheels. The middle wheels remain permanently aligned parallel to the chassis sides in operation.

A steering ram 134 (a, b) has spherical bearings each end. The foremost end of this steering ram, connects to a pin at the top of, and concentric with, the middle suspension cylinder rod. The rearmost end of the steering ram 134 connects to the a rear steering arm 136 which is mounted to the top of the rear suspension cylinder rod. Thus, the steering ram is eccentrically mounted to the top of the rear suspension cylinder rod by means of the steering arm 136.

A steering idler arm 138 is mounted on a pin which is concentric with the middle suspension cylinder rod. The steering idler arm can swivel about the pin independently of the alignment arm 132. On the underside of the end of the arm 138, distal from the concentric pin, there is a depending pin to which one end of a tie rod 140 is mounted. The other end of the tie rod is mounted to the end of the rear steering arm 136 distal from the rear suspension cylinder rod.

A front steering arm 142 is mounted on the rod of the front suspension cylinder. A tie rod 144 extends between the distal end of that arm and the steering idler arm 138.

In this manner, the front wheel steering is slave connected to the rear wheel steering on each side.

An electronic control system is provided by a programmed microprocessor (not shown). The control system measures the steering angle at the frailer to turntable, and steers the frailer wheel groups to allow tighter turns around columns and obstacles in buildings. For a left hand turn, the left hand side steering ram 134a is shortened, by the control system, and the right hand side steering ram 134b, is lengthened. In this manner the trailer wheel axles are coincident about an instantaneous centre on the left hand side of the frailer. The minimum inside turn radius for this steering system, to the instantaneous centre, is approximately 6 metres. This means that the frailer tyres tend to follow the truck/tractor tyre marks on the road, rather than run inside of the truck/tractor tyre marks on turns, as happens without trailer steering. For a right hand turn, the ram 134b is shortened and ram 134a is lengthened.

Referring to Figure 3 it can be seen that an inwardly directed protrusion in the form of an angle iron bar 150 is defined towards the base of each chassis side 12, 14. Each bar 150 extends along substantially the entire length of each chassis. As is best seen in Figure 3, when the wheels of the trailer are at a height for driving the trailer, the bars are at approximately the same height as the hubs of the main wheels. Also shown in Figure 3, are two smaller wheels 152 (rear transverse loading wheels). As is best seen in Figure 2, the lowermost part of the transverse wheels 150 are about 28mm below the base of the angle iron bars 150.

Figure 8 is a schematic diagram of the hydraulic circuit of the trailer. While much of the diagram is self-explanatory, it is to be noted that the hydraulic pressure caused by the weight of the trailer and any load it carries is transmitted to the two brakes 80 which lock the cruciform link mechanism. This positive feedback means that the heavier the load carried, the greater the braking force which locks the cruciform linkage.

Use of the invention will now be described with particular reference to Figures 6 and 7. It is to be noted that in the lower diagram the trailer has a width of 3000mm. However, when closed and loaded as illustrated in Figure 6, the trailer has a width of 2500mm which is a legal width for use on public roads in most countries. The invention will be described in terms of loading a "Superpack" or ingot pack of Aluminium ingots, although it will be appreciated by the skilled person that other loads may be carried by the trailer.

As discussed above, the prime mover driving the trailer typically includes a seat and controls that swivel the operator through 180°, allowing full and comfortable viewing of the Trailer during operation, when reversing. To load an ingot pack, the cruciform link is expanded by lengthening the hydraulic cylinders 68, 70 such that the trailer is 3 metres wide in the open mode, as illustrated in Figure 6. The six wheels 110 support the empty trailer weight. The truck and trailer 10 are substantially aligned with the ingot pack 200, and the trailer is reversed to enclose the ingot pack 200 within the trailer chassis, approximately centrally to each side 12, 14 of the trailer chassis. If necessary the two Scissor Link Cylinders, 26, 27 can be operated to trim this side to side alignment.

Next, the hydraulic valve 124, to the lower cavity of the suspension cylinders 118 is supplied with oil under pressure from the reservoir 126. Both valves 122 are activated to release oil in the cylinder cavities 118a, to the oil reservoir 126. The trailer chassis is lowered until the rear transverse wheels 152 take the weight of the trailer chassis 10. In this state the six wheels 112 are raised above road level as the cylinder rods 116 are drawn into the cylinders 118.

Next the hydraulic valve 160 to the turntable link cylinder 34 is operated to lower the front of the trailer chassis, until the chassis angle bars 150 are parallel to the road, to enable pick up of the ingot pack 200. This is done by putting the valves to the scissor link cylinders 26, 27 into a float mode, allowing the cylinders to shift as the ingot pack is clamped from each side.

The actual clamping of the ingot pack 200 from each side, is effected by shortening both cruciform rams 68, 70. The chassis sides move towards each other, until the cylinders are fully shortened. As the chassis sides move, the rear transverse loading wheel 152 on each chassis side rolls on the road surface, with the six trailer wheels 110 above the road surface. At this time, there is no hydraulic pressure to the link brakes 80 and the pins 102 slide easily in the slotted chassis plates 46a, b.

Once the chassis sides 12, 14 are fully closed with the angle iron bars 150 below the respective outer edges of the ingot pack 200, hydraulic pressure in each side of the lower cavity 118b of the suspension cylinders 118 is released to the oil reservoir through hydraulic valve 124. The six wheels 112 return to the road surface.

Next, both hydraulic valves 122 to the upper cavity 118a of each trailer sides suspension cylinders 118 , is opened to supply oil into those three cavities on each side. The trailer chassis 10 lifts until the top faces of the angle iron bars 150 contacts the lower surface of the outer longitudinal edges of the ingot pack 200, on each side of the pack. At this stage the rear transverse wheels 152 will be above the road due to the shape of the ingot pack as shown in Figure 3. As oil is added to the suspension cylinder cavities 118a, the pressure in the cylinders 118 rises as oil fills the suspension cylinder hydraulic accumulator 120 on each side, until the pressure in the suspension cylinders is sufficient to lift the ingot pack 200 up from the road surface.

The lifting of the ingot pack 200 continues until the ingot pack is at the working height of about 350 mm above the road. The hydraulic pressure in the upper cavity 118a of suspension cylinders, on each side, clamps the brake 80 and the trailer is locked from opening. Finally, the length of each Scissor Link Cylinders, 20, 22, is equalized electronically. The ingot pack 200 is now loaded onto the trailer and is ready to be transported.

Unloading the ingot pack is essentially the reverse of the loading process. Although the present invention has been described with reference to a carrying a "Superpack" of aluminium ingots, it will be appreciated that the invention may be used for other applications such a transporting pallets containers and other loads.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A device for picking up and transporting a load including a pair of chassis sides, each chassis side including wheels supporting the device, and a protrusion for engaging with a load to be picked up and transported, the device further including a link mechanism for expanding and contracting the device by moving the chassis sides towards and away from each other to enable the device to be positioned on either side of a load in an expanded state and subsequently contracted to engage with the load wherein the link mechanism is located above the load in use and is a cruciform linkage comprising two link members of substantially equal length which are pivoted to each other at their respective centres where they cross and which link the chassis sides together.

2. A device for picking up and transporting a load as claimed in claim 1 wherein the device is adapted to pick up and transport a load as wide as about 1500mm within an overall width of 2500mm when the device is closed.

3. A device for picking up and transporting a load as claimed in claim 1 or claim 2 wherein two additional link members are provided, one link member extending from each chassis side, which are pivoted together where they meet, whose length is half the length of the link members of the cruciform link.

4. A device as claimed in any one of claims 1 to 3 wherein the device is a trailer for attachment to a prime mover or tractor.

5. A device as claimed in any one of claims 1 to 4 wherein a rearmost end of each link of the cruciform link is pivoted near one end of the device for rotation about a vertical axis and wherein a foremost end of each link may define a pin which slides in a slotted plate located near the opposite end of the device, which slot extends parallel to the chassis sides.

6. A device as claimed in claim 5 wherein the device incorporates a hydraulic braking system for locking the link closed including brake plates disposed either side of the slotted plate arranged to be forced against the slotted plate by hydraulic pressure.

7. A device as claimed in claim 6 wherein hydraulic fluid is arranged to pass through a bore in each pin of the link.

8. A device as claimed in claim 6 or 7 wherein wheels of the device are mounted on the lower end of respective suspension cylinders attached to the chassis sides such that the weight of the trailer and its load creates a proportionate hydraulic pressure in a chamber in the suspension cylinders which is transmitted to the hydraulic braking system for locking the link closed.

9. A device as claimed in claim 8 wherein the wheels are single wheels to keep the overall width of the trailer as narrow as possible and allow for the widest possible load within the overall width of the device.

10. A device as claimed in any one of claims 8 or 9 wherein two transverse wheels are mounted to the rear of each chassis side at the base of the chassis structure for allowing the chassis sides to move laterally when the main wheels are raised and the chassis sides lowered to the ground.

11. A device as claimed in any one of claims 3 to 10 wherein the additional single link members are connected to a chassis link and mounting assembly for connecting the trailer to a prime mover and including hydraulic cylinders to allow the trailer to be adjusted out of alignment with the prime mover, where necessary for picking up a load, and realigned at completion of loading.

12. A device as claimed in claim 11 wherein the chassis link and mounting assembly includes a hydraulic cylinder for raising and lowering the front of the trailer chassis during loading and unloading.