GB2533917A

GB2533917A - Trailer

Info

Publication number: GB2533917A
Application number: GB1422565.0A
Authority: GB
Inventors: John Cartwright Alan
Original assignee: Tiger Trailers Ltd
Current assignee: Tiger Trailers Ltd
Priority date: 2014-12-18
Filing date: 2014-12-18
Publication date: 2016-07-13
Anticipated expiration: 2034-12-18
Also published as: GB2533917B

Abstract

A double deck trailer comprises a base 2 and a movable upper deck 8. The upper deck 8 is lifted by a plurality of lifting mechanisms 6, 7 such as hydraulic or pneumatic cylinders 15, 18 each comprising a plurality of actuators. Each actuator comprises a rod 14, 20 extendible from a barrel 16. The barrels are arranged side by side and the rods extend in opposite directions to push the upper deck 8 upwards. The lifting mechanism can be compact because the hydraulic cylinders 15, 18 are placed side-by-side. The total extension of the lifting mechanism is at least equal to the retracted length and can be 1.5 times that retracted length. A slide mechanism can be provided where the lift mechanism is coupled to the upper deck to allow the deck to be moved for unbalanced loads. The lifting mechanism can be provided in the trailer legs and used to lift the trailer roof.

Description

Trailer

Technical Field of the Invention

The present invention relates to a trailer (including a semi-trailer) and in particular to a so-called lifting double deck trailer.

Background to the Invention

It has been said that most conventional trailers have 35-40% usable space and that 50% of loads are limited by volume rather than weight. Accordingly double-deck trailers, which have two decks one directly above the other so as to use the full height of a trailer, have become popular There are several types of double deck trailers, including fixed deck trailers (in which the decks are both fixed in position), ratchet deck trailers, (in which the upper deck can he moved to different heights by a fork-lift truck and held in position), and lifting deck trailers, (in which the upper deck may be moved from a low, loading position, just above the lower deck, to a higher, loaded position, by hydraulic cylinders).

These lifting deck double deck trailers have, unsurprisingly, become popular.

However, they do still suffer certain disadvantages. For example, if uneven loads are put on the upper deck, they are liable to go out of balance and bend, damaging the connection between the deck and the supports that carry them. This can cause the supports to jam up and cause damage to the trailer.

The hydraulic mechanism for lifting the upper deck typically consists of a hydraulic cylinder in each of four legs disposed around the trailer, such that when the piston rods are retracted, the deck is at the base of the trailer and when the piston rods are extended can be lifted to about half the height of the trailer. The height it can be lifted to is limited by the height of the cylinder and a cylinder which takes up the full height of the trailer when extended takes up (just over) half the height of the trailer when the piston rod is retracted into the cylinder. Thus, a deck carried at the base of the trailer in the retracted position can only reach (just under) half of the height of the trailer when the piston rod is extended from the cylinder.

In order to improve the relative height that the deck can be lifted to, alternative lifting means have been proposed, in which a large hydraulic cylinder is situated underneath the trailer and rather than directly lifting the deck, the cylinder drives a system of pulleys and wires which gear the travel of the piston rod, such that the deck is lifted by wires, which can be geared to provide a much greater travel. This system too, however, suffers from a number of disadvantages; since a single cylinder is required to lift the deck, rather than four cylinders, and gearing is provided, so that for a given movement of the cylinder, the deck must move more than twice the distance, very powerful cylinders are required. Also, much of the system of wires and pulleys is beneath the trailer and subject to damage by the weather, e.g. water and road salt causing corrosion, and by objects in the road. The system is also complex. Nonetheless, in view of the benefits of being able to lift the deck more than half way up the trailer, these systems are popular.

The present invention seeks to obviate or ameliorate the disadvantages associated with the prior art and/or to provide additional advantages.

Summary of the Invention

According to a first aspect of the invention, there is provided a double deck trailer comprising a base and a movable upper deck; the trailer comprising a plurality of lifting mechanisms for raising and lowering the moveable upper deck and the plurality of lifting mechanisms each comprising a plurality of actuators, each actuator comprising a rod extendible from a barrel; wherein the barrels are arranged side by side and the rods extend in opposite directions.

By arranging a pair of actuators side by side, but such that the rods extend in opposite directions, rather than in parallel, the distance of travel can be increased substantially. This is because each rod can extend by approximately the same distance as the total length of the actuator and thus, with the actuators side-by-side, the total extended length is approximately the length of one barrel, plus two rods, i.e. approximately three times the length of the barrel rather than approximately two times the length of the barrel.

The total extension of the lifting mechanisms may be at least equal to the total refracted length. The total extension may be at least 1.5 times the total retracted length.

Accordingly, the range is much greater than that obtained by conventional direct driven lift mechanisms with only one hydraulic cylinder in each support and both less complex and simpler to maintain than the existing alternative involving wires and pulleys.

The actuators may be hydraulic cylinders. Alternative actuators, e.g. pneumatic actuators could be used. The rods and barrels will normally be cylindrical.

The rod of at least one of the actuators in each lifting mechanism may be provided with a conduit therethrough. A further conduit may be provided between the two barrels. Hydraulic oil may be supplied to both barrels via the conduit through at the least one rod Each lifting mechanism may comprise a guide and a slide, the slide being slidable in relation to the guide and coupled to one of the rods such that actuation of either actuator moves the slide.

One rod may be coupled to the base and the other rod may be coupled to the slide.

The slide may be coupled to the moveable upper deck.

The upper deck may be slidably connected to at least two of the plurality of lifting mechanisms, so as to move relative to the lifting mechanisms when an unbalanced load is placed on the upper deck.

The upper deck may be slidably connected to at least two of the lifting 10 mechanisms via the slide.

The upper deck may be slidably connected to at least two of the lifting mechanisms such that it may slide back and forth relative to the lifting mechanisms when an unbalanced load is placed on the upper deck.

The lifting mechanisms may lift the moveable upper deck between a first loading position for loading the moveable upper deck and a raised travel position.

The lifting mechanism may lift the moveable upper deck to a second loading position, higher than the travel position, for loading beneath the upper deck.

The lifting mechanism may lift the roof of the trailer when lifting the moveable upper deck to the second loading position.

The lifting mechanisms may be provided in legs. The legs may be extendible.

According to a second aspect of the invention there is provided a double deck trailer comprising a base and a moveable upper deck, the movable upper deck connected to the base by a plurality of lifting mechanisms; wherein the upper deck is slidably connected to at least two of the lifting mechanisms, so as to move relative to the lifting mechanisms when an unbalanced load is placed on the upper deck.

Allowing the deck to slide relative to two of the lifting mechanisms to which it is attached, when an unbalanced load is placed on the upper deck allows the deck to go "out of balance" when an unbalanced load is placed on the upper deck.

This provision for sliding movement of the deck relative to the lifting mechanisms prevents unbalanced loads from breaking deforming the deck/legs/lifting mechanisms in the region of their connection.

The moveable upper deck may be slidably connected to at least two of the lifting mechanisms so as to slide back and forth relative to the lifting mechanisms -i.e. in the direction of travel of the trailer.

The lifting mechanisms may be provided in a plurality of legs.

The plurality of legs may comprise a pair of rear legs situated towards the rear of 15 the trailer and the deck may be slidably connected to lifting mechanisms in the pair of rear legs.

The upper deck may be slidably connected to the at least two lifting mechanisms by means of fasteners extending through slots.

The upper deck may be slidably connected to the at least two lifting mechanisms 20 via one or more bracket.

The lifting mechanisms may comprise a slide comprising the one or more bracket.

The one or more bracket may comprise slots. The upper deck may comprise slots. The at least two lifting mechanisms may comprise slots.

The fasteners may extend through holes in the at least two lifting mechanisms or the upper deck, or a bracket associated with the at least two lifting mechanisms or the 5 upper deck and slots in the other of the at least two lifting mechanisms or the upper deck, or a bracket associated with the at least two lifting mechanisms or the upper deck.

The moveable upper deck may be fixedly connected to at least two of the plurality of lifting mechanisms such that alignment of the moveable upper deck relative to the lifting mechanisms to which it is fixedly connected remains substantially fixed when an unbalanced load is placed on the upper deck, but alignment of the deck relative to the lifting mechanisms to which it is slidably attached changes.

Providing a fixed connection, in which the alignment of the deck relative to at least two of the lifting mechanisms is substantially fixed, as well as the sliding connection means that when an unbalanced load is placed on the deck, the deck can slide relative to the lifting mechanisms to which it is slidably connected, to rebalance itself, but will not readily change alignment during travel, because of the substantially fixed alignment between the deck and the lifting mechanisms to which it is fixedly attached.

The plurality of lifting mechanisms may comprise a pair of front lifting mechanisms situated towards the front of the trailer and the deck may be fixedly connected to the pair of front lifting mechanisms.

The deck may be fixedly connected to at least two of the plurality of lifting mechanisms by fasteners extending through holes.

The fasteners may be loosely fastened, such that the deck may pivot relative to the lifting mechanisms to which it is fixedly connected, but cannot slide relative thereto.

The fasteners which fixedly connect the deck to at least two lifting mechanisms may be provided with spring washers. The fasteners which slidably connect the deck to at least two lifting mechanisms may also be provided with spring washers. Each fastener may be connected via a plurality of spring washers, e.g. at least 8 conical washers mounted in series.

Each lifting mechanism may be connected to the deck by at least three fasteners. Detailed Description of the Invention In order that the invention may be more clearly understood an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 shows a side view of the trailer according to the invention with a moveable upper deck in a lowered position; Figure 2 shows a side view of the trailer of figure 1 with the moveable upper deck in an upper, loading position; Figure 3 shows a side view of the trailer of figures 1 and 2 with the moveable upper deck in a travel position; Figure 4 shows schematically one leg of the trailer of figures 1-3 viewed from the inside looking out, with the moveable upper deck in an upper loading position; Figure 5 shows schematically one leg of the trailer of figures 1-3 viewed from the inside looking out, with the moveable upper deck in a lower loading position; Figure 6A shows a side view of the hydraulic cylinders of the one of the lifting mechanisms of the trailer of figures 1-3; Figure 6B shows a lateral cross section through one of the hydraulic cylinders of figure 6A along the line A-A; Figure 6C shows a lateral cross section through one of the hydraulic cylinders of figure 6A along the line B-B; Figure 7 shows a longitudinal cross section through one leg of the trailer of figures 1-3 looking upward; Figure 8 shows a longitudinal cross section through another leg of the trailer of figures 1-3 looking upward; Figure 9 shows a cross sectional side view through the bracket connecting front leg to the front of the deck of the trailer of figures 1-3; and Figure 10 shows a cross sectional side view through the bracket connecting the rear leg to the rear of the deck of the trailer of figures 1-3.

With reference to the drawings, a trailer 1, in this case a semitrailer, comprises a chassis including a base 2 forming a lower deck upon which goods may be placed.

Wheels 3 are rotatably mounted beneath the base 2 and a roof 4 is mounted above and parallel to the base 2 on four telescopic comer posts 5 located at each of the front and back right and left hand comers. A front panel extends between the two front corner posts, doors are hingedly attached between the rear corner posts and curtains may be provided along the sides. The roof is also carried by four extendible legs; a pair of front extendible legs 6, one on each side of the trailer and mounted in the front half of the trailer and a pair of rear extendible legs 7 one on each side of the trailer and mounted in the rear half of the trailer. A movable upper deck 8 is also carried by the extendible legs 6,7.

As shown in figure 1, the moveable upper deck 8 may be moved to a first loading position for loading the moveable upper deck 8. In this position the moveable upper deck 8 sits on top of the base 2, so that items can be easily loaded onto the moveable upper deck 8. Then, as shown in figure 2, the moveable upper deck 8 may be raised to a second loading position, in which the roof 4 is also raised by the extendible legs 6, 7 so that e.g. a fork lift truck can be driven under the moveable upper deck 8, to load items onto the base 2. Once the loading operation is complete, the roof 4 and the moveable upper deck 8 may be moved lowered to a travel position shown in figure 3.

To achieve the lifting and lowering motion, each of the legs in each pair of legs 6, 7 is provided with a lifting mechanism 11 which carries the moveable deck 8. The lifting mechanism 11 of one leg 6is shown in figure 4 in the second loading position, with the roof 4 at its highest level, but it will be understood that the lifting mechanisms of the other leg in the pair of front extendible legs 6 is the same, as are the rear legs 7.

The leg 6 is formed as a pair of metal struts 9 having a U-shaped cross section, each about 3.2 metres in length and 85mm across and welded to a backplate 10 which is also about 3.2 metres long and is about 35cm wide to define a long open cavity between the two struts 9. The cavity has a rectangular section with the short ends of the rectangle being defined by the sides of the two struts 9, one long side being defined by the panel of the backplate 10 extending between the struts 9 and the other side being open. Thus it has dimensions of about 3500mm x 18inm x 8.5mm. The lifting mechanism 11 is mounted in this cavity. The bottom end of the two struts 9 are attached to the base 2 of the trailer 1 via bolt holes 12 and the clevis 13 of the rod 14 of a first actuator, in this case a hydraulic cylinder 15 is attached at the bottom of the leg 6 so as to extend upward into the cavity. The rod 14 of the fast hydraulic cylinder 15is offset within the cavity, closer to one strut 9 than the other.

The barrel 16 of the first hydraulic cylinder 15, from which the rod 14 extends is also offset towards one of the struts 9 (the right hand side strut in figure 4). The barrel 16 of the first hydraulic cylinder 15 is clamped side-by-side next to the barrel 17 of another actuator, a second hydraulic cylinder 18, by means of two brackets 19. The second hydraulic cylinder 18 is also offset in the cavity, (this time to the left hand side in figure 4). Whereas the rod 14 of the first hydraulic cylinder 15 extends downward out of its barrel 16, the second hydraulic cylinder 18 is provided with a rod 20 which extends in the opposite direction, upwards out of the barrel 17. The rod 20 is connected at its top to a slide 21. The slide 21 is a substantially U-shaped body having a main planar portion having a height of about 1 metre and a width of about 45 cm, from which sliding anns extend by about 100cm around the sides of the two struts 9 and attached thereto by means of guide grooves 55 so as to slide up and down the leg 6.

With reference to figure 5, the bottom of the slide 21 is connected via a bracket to the moveable upper deck 8, in such a fashion that when the rods 14,20 are retracted into their respective barrels 16, 17, the moveable upper deck 8 sits atop the lower deck fotuied by the upper surface of the base 2. The clevis 13 at the base of the rod 14 of the first hydraulic cylinder 15 is in fact mounted to the base 2 below the bottom of the leg 6 and about 40em beneath the upper surface of the base 2. Thus it can be established that the total length from the bottom of the first rod 14 to the top of the second rod 20, when both hydraulic cylinders are retracted is about 1.4 metres. Each hydraulic cylinder 15, 18 has a working length of about 1.2 metres, so it can be seen that when the either rod is extended, the deck 8, which is carried by the slide 21 may be lifted and that it may be lifted by a total of about 2.4 metres. At the top of its extension, of course, because of the height of the leg 6, the top end of the slide 21 actually extends about 20cm beyond the top of the leg 6. This additional height of the extendible legs 6, 7can be used to lift the roof 4 by 20cm. The roof 4 may be telescopically attached via rods (not shown) extending into the channels formed in each of the U-shaped struts 9, in order to maintain alignment in the lifting operation.

A safety mechanism 36 is also shown in figure 5, which comprises a hydraulically operated wedge which extends out laterally from the legs 6, 7 when the deck 8 is raised, in order to catch the deck in the event of failure of part of the connection leading to the deck 8 falling.

Greater detail of the lifting mechanism can be seen in figures 6A-6C. With reference to figures 6A to 6C, it can be seen that the clevis 13 of the first rod 14 of the first hydraulic cylinder 15 is provided with an aperture 22 for receiving a clevis pin and a connector 23 for connection to an oil supply. A vent 24 is also provided for bleeding the oil supply. The first rod 14 is hollow, with a bore 24 extending through it, in which a pipe 25 carries hydraulic oil from the supply connector 23, through the piston 27 to an outlet 26 at the opposite end of the rod 14, such that oil can flow into a cavity 28 in the cylinder head 29 of the hydraulic cylinder 15. Flow of oil into this cavity 28 urges the piston 27, and hence the rod 14, downwards out of the bottom of the barrel 16. Therefore, with the rod attached to the base 2 of the trailer 1, oil supply causes the slide 21 to rise, lifting the moveable upper deck 8. However, oil may also pass out of the cavity 28 via an aperture 30 in the cylinder head 29. This aperture leads to a pipe 31 which extend from the cylinder head 29 at the top of the first hydraulic cylinder 15 down to the cylinder head 32 of the second hydraulic cylinder 18, which sits alongside the first hydraulic cylinder 15. A bore through the cylinder head 32 leads from the pipe 31 to an aperture 33 in a cavity 34 in the second cylinder head 32. hi the refracted position shown, a piston 35 rests atop the open end of the cavity 34 in the cylinder head 32 and thus introduction of hydraulic oil into the cavity 34 forces the piston 35, which carries the second rod 20, upwards as oil flows from the cavity 34 into the second barrel 17. The top of the second rod 20 is provided with a bore therethrough, for connection to the slide 21, so upward motion of the second rod 20 lifts the slide 21 upwards, hence lifting the moveable upper deck 8.

As discussed above, the moveable upper deck 8 is connected to the slides 21 of each extendible leg 6, 7 via a bracket at the bottom of the slides 21. The brackets attaching the deck 8 to the front legs 6 are different from those attaching to the rear legs 7. As can be seen from figure 7, the bracket 37 attaching the slide 21 of the front legs 6 to the deck 8 comprises a laterally extending shelf 38, which is formed of hollow rectangular section tubular material. Three large holes 39 are drilled in the underside of the shelf 38 and three coaxial smaller holes 40 are drilled in the upper surface. The body of a bolt fits through both holes 39, 40, whilst a nut or bolt-head only fits through the larger hole 39.

The bracket 41 attaching the slide 21 of the rear legs 7 to the deck 8, shown in figure 8 also comprises a laterally extending shelf which is formed of hollow, rectangular section, tubular material. Three large holes 42 are also drilled in the underside of the shelf of the bracket 41, through which nuts or the head of bolts can fit, but rather than co-axial holes, three slots 43 are provided in the upper surface of the shelf, extending from front to back, relative to the direction of travel of the trailer. Accordingly, bolts inserted into the rear bracket 41 may slide back and forth in the slots.

Referring to figures 9 and 10, corresponding hollow rectangular section tubes 44, 52 are welded into the deck 8 so as to sit above the brackets 38, 41 of the front and rear slides 21. The tube 44 which connects the front half of the deck 8 to the front leg 6 is provided with three similar sets of holes, which in use are coaxial with the holes 39, 40 in the bracket 37. This time, small holes 45 are drilled though the underside of the tube 44 to allow the body 46 of a bolt to pass through them, and larger holes 47 are drilled in the top side of the tube to allow the head 48 of a bolt to pass through them.

The deck 8 is fixedly mounted to the front leg 6 with bolts 49 inserted through each hole 47 in the tube 44 extending through the small holes 40 through the bracket 38 and the small holes 40 through the bracket 38 to screw into a nut 50. Along the body 46 of each bolt 49 between the head 48 and the small holes 45 in the deck 8, four conical washers 51 are mounted in series. A similar set of four conical washers 51 are mounted in series along the body 46 of each nut 50 between the small holes 40 in the bracket 38 and the nut 50 and the nut 50 is tightened against the spring washers 51 to allow a degree of pivoting of orientation of the deck 8 relative to the bracket 38 and hence the front leg 6, whilst maintaining the fixed position relative to the front leg 6.

The tube 52 which connects the rear half of the deck 8 to the rear leg 7 is also provided with thee sets of holes which in use are coaxial with the holes 42 in the bracket 41. Once again small holes 53 are drilled through the underside of the tube 52 to allow the body 46 of a bolt to pass through them, and larger holes 54 are drilled in the top side of the tube to allow the head 48 of a bolt to pass through them.

The deck 8 is slidably mounted to the rear leg 7 with bolts 49 inserted through each hole 54 in the tube 52 extending through the small holes 53 through the bracket 38, then through the slot 43 in the bracket 41 to screw into a nut 50. Once again, along the body 46 of each bolt 49 between the head 48 and the small holes 53 in the deck 8, four conical washers 51 are mounted in series. A similar set of four conical washers 51 are mounted in series along the body 46 of each nut 50 between the slots 43 in the bracket 41 and the nut 50 and the nut 50 is tightened against the spring washers 51 to allow a degree of pivoting of orientation of the deck 8 relative to the bracket 41 and hence the leg 7, whilst also allowing a sliding motion of the rear of the deck 8, back and forth relative to the rear legs 7, should the load on the deck be unbalanced.

In use, hydraulic oil is initially drained from all of the hydraulic cylinders15, 18, such that the moveable upper deck 8 sits atop the base 2 as shown in figure 1, in a first loading position for loading the moveable upper deck 8. Items are then loaded onto the moveable upper deck 8, although ideally the items will be balanced, they may be out of balance, i.e. unevenly weighted towards the front and/or one side of the moveable upper deck 8. Then, hydraulic oil is supplied through the connector 23 of each lifting mechanism in each of the four legs. This extends the rods 14, 20 from their respective barrels 16, 17 raising the slides 21 and lifting the deck 8 to the second loading position as shown in figure 2. Towards the top of the travel of the slides 21, they extend beyond the top of the remaining portion of the legs 6, 7, thus extending the legs upward to lift the roof If the upper deck is badly loaded, uneven forces act on the upper deck, and the deck will slide relative to the rear legs 7, whilst its position remains fixed relative to the front legs (albeit pivoting slightly on the conical washers). This allowance of movement prevents damage from the forces.

At this point e.g. a fork lift truck is driven under the moveable upper deck 8, to load items onto the base 2. Once the loading operation is complete, hydraulic oil is carefully allowed to drain from the hydraulic cylinders 15, 18 and the weight of the deck 8 forces one or both rods 14,20 into their respective barrels 15, 18. Once the roof 4 and the moveable upper deck 8 have been lowered to a travel position shown in figure 3, the draining of hydraulic oil is ceased and the moveable upper deck is held in position. The trailer (1) is then coupled to a truck (not shown), if it is not already coupled to a truck, and can be driven. During driving further forces may act on the moveable upper deck moving it relative to the legs 6, 7, but the fixed nature of the connection with the front legs 6 will prevent any undue rolling, whilst the ability of the rear legs to slide back and forth relative to the deck 8 will allow a certain degree of movement rather than damage to occur as a result of the forces.

The above embodiment is described by way of example only. Many variations 20 are possible without departing from the scope of the invention.

Claims

CLAIMS1, A double deck trailer comprising a base and a movable upper deck; the trailer comprising a plurality of lifting mechanisms for raising and lowering the moveable upper deck and the plurality of lifting mechanisms each comprising a plurality of actuators, each actuator comprising a rod extendible from a barrel, wherein the barrels are arranged side by side and the rods extend in opposite directions.
2. A double deck trailer according to claim I wherein the total extension of the lifting mechanisms is at least equal to the total retracted length.
3. A double deck trailer according to either of the preceding claims wherein the total extension of the lifting mechanisms is at least 1.5 times the total retracted length.
CD 4, A double deck trailer according to any of the preceding claims wherein the actuators are hydraulic cylinders.
5. A double deck trailer according to any of claims 1-3 wherein the actuators are pneumatic actuators.
6. A double deck trailer according to any of the preceding claims wherein the rods and barrels are cylindrical.
7. A double deck trailer according to any of the preceding claims wherein the rod of at least one of the actuators in each lifting mechanism is provided with a conduit therethrough.
8. A double deck trailer according to claim 7 wherein a further conduit is provided between the two barrels.
9. A double deck trailer according to claim 7 or 8 wherein hydraulic oil is supplied to both barrels via the conduit through at the least one rod.
10, A double deck trailer according to any of the preceding claims wherein each lifting mechanism comprises a guide and a slide, the slide being slidable in relation to the guide and coupled to one of the rods such that actuation of either actuator moves the slide.
11. A double deck trailer according to claim 10 wherein one rod is coupled to the base and the other rod is coupled to the slide.
12. A double deck trailer according to claim 10 or 11 wherein the slide is coupled to the moveable upper deck.
13. A double deck trailer according to any of the preceding claims wherein the upper CD deck is slidably connected to at least two of the plurality of lifting mechanisms, so as to move relative to the lifting mechanisms when an unbalanced load is placed on the upper deck.
14. A double deck trailer according to claim 13, when dependent on any of claims 10-12 wherein the upper deck is slidably connected to at least two of the lifting mechanisms via the slides.
15. A double deck trailer according to claim 13 or claim 14 wherein the upper deck is slidably connected to at least two of the lifting mechanisms such that it may slide back and forth relative to the lifting mechanisms when an unbalanced load is placed on the upper deck.
16. A double deck trailer according to any of the preceding claims wherein the lifting mechanisms are operable to lift the moveable upper deck between a first loading position for loading the moveable upper deck and a raised travel position.
17. A double deck trailer according to claim 16 wherein the lifting mechanisms are operable to lift the moveable upper deck to a second loading position, higher than the travel position, for loading beneath the upper deck.
18. A double deck trailer according to claim 17 wherein the lifting mechanisms are operable to lift the roof of the trailer when lifting the moveable upper deck to the second loading position.
19. A double deck trailer according to any of the preceding claims wherein the lifting mechanisms are provided in legs.

CD
20. A double deck trailer according to claim 19 wherein the legs are extendible.
21. A double deck trailer comprising a base and a moveable upper deck, the movable upper deck connected to the base by a plurality of lifting mechanisms; wherein the upper deck is slidably connected to at least two of the lifting mechanisms, so as to move relative to the lifting mechanisms when an unbalanced load is placed on the upper deck.
22. A double deck trailer according to claim 21 wherein the moveable upper deck is slidably connected to at least two of the lifting mechanisms so as to slide back and forth relative to the lifting mechanisms.
23. A double deck trailer according to claim 22 wherein the lifting mechanisms are provided in a plurality of legs.
24. A double deck trailer according to claim 23 wherein the plurality of legs comprise a pair of rear legs situated towards the rear of the trailer and wherein the deck is slidably connected to lifting mechanisms in the pair of rear legs.
25. A double deck trailer according to any of claims 21 to 24 wherein the upper deck is slidably connected to the at least two lifting mechanisms by means of fasteners extending through slots.
26. A double deck trailer according to any of claims 21 to 25 wherein the upper deck is slidably connected to the at least two lifting mechanisms via one or more bracket.
27. A double deck trailer according to any of claims 21 to 26 wherein the lifting mechanisms comprise a slide comprising the one or more bracket.

CD
28. A double deck trailer according to claim 26 or 27 wherein the one or more bracket comprises slots.
29. A double deck trailer according to any of claims 21 to 28 wherein the upper deck comprises slots.
30. A double deck trailer according to any of claims 21 to 29 wherein the at least two lifting mechanisms comprise slots.
31. A double deck trailer according to any of claims 25 to 30 wherein fasteners extend through holes in the at least two lifting mechanisms or the upper deck, or a bracket associated with the at least two lifting mechanisms or the upper deck and slots in the other of the at least two lifting mechanisms or the upper deck, or a bracket associated with the at least two lifting mechanisms or the upper deck.
32. A double deck trailer according to any of claims 21 to 31 wherein the moveable upper deck is fixedly connected to at least two of the plurality of lifting mechanisms such that alignment of the moveableupper deck relativeto the lifting mechanisms to which it is fixedly connected remains substantially fixed when an unbalanced load is placed on the upper deck, but alignment of the deck relative to the lifting mechanisms to which it is slidably attached changes.
33. A double deck trailer according to claim 32 wherein the plurality of lifting mechanisms comprise a pair of front lifting mechanisms situated towards the front of the trailer and wherein the moveable upper deck is fixedly connected to the pair of front lifting mechanisms.
34. A double deck trailer according to claim 31 or 32 wherein the moveable upper O deck is fixedly connected to at least two of the plurality of lifting mechanisms by fasteners extending through holes.
35. A double deck trailer according to claim 34 wherein the fasteners are loosely fastened.
36. A double deck trailer according to claim 34 or 35 wherein the fasteners which fixedly connect the deck to at least two lifting mechanisms are provided with spring washers.
37. A double deck trailer according to any of claims 25 to 36 wherein fasteners which slidably connect the deck to at least two lifting mechanisms are provided with swing washers.
38. A double deck trailer according to claim 36 or 37 wherein each fastener is connected via a plurality of spring washers.
39. A double deck trailer according to claim 38 wherein the plurality of spring washers are conical washers.
40. A double deck trailer according to claim 38 or 39 wherein the plurality of washers are mounted in series
41. A double deck trailer according to any of claims 36 to 40 wherein the plurality of washers is at least 8 washers.
42. A double deck trailer according to any of the preceding claims wherein each lifting mechanism is connected to the moveable upper deck by at least three fasteners.
43. A double deck trailer substantially as described herein with reference to the accompanying drawings.