WO2010082842A1

WO2010082842A1 - Improved trailer having adjustable elevation

Info

Publication number: WO2010082842A1
Application number: PCT/NZ2009/000288
Authority: WO
Inventors: William Mark Tarahina Groves
Original assignee: BILL GROVES INTELLECTUAL PROPERTY Ltd
Current assignee: BILL GROVES INTELLECTUAL PROPERTY Ltd
Priority date: 2008-12-15
Filing date: 2009-12-15
Publication date: 2010-07-22
Anticipated expiration: 2011-06-15

Abstract

The present invention provides a trailer comprising a chassis, a pivoting four-bar linkage drawbar assembly including a coupling for engagement with a towing vehicle, one or more pairs of wheel mounting members pivotally mounted on opposing sides of the chassis, and operating means associated with the drawbar assembly and the wheel mounting members. The operating means is adapted to selectively pivot the drawbar assembly and/or wheel mounting members, whereby the chassis may be lowered, raised, and/or tilted with respect to the ground. As the chassis is lowered or raised, the position and orientation of the coupling remains substantially constant. This positioning of the tow hitch is gained through the pivoting tow hitch mounting combined with towbar parallelogram of the drawbar assembly which allows the trailer deck to be towed safely whilst raised or lowered.

Description

IMPROVED TRAILER HAVING ADJUSTABLE ELEVATION

FIELD OF INVENTION

This invention relates to the field of vehicle trailers. In particular, the invention relates to a trailer having a deck which can be raised, lowered, and/or tilted.

BACKGROUND

Trailers are commonly used to transport goods over long distances. The term "trailer" is used in this specification to mean any size or shape of container or vehicle intended to be towed by another, powered vehicle.

The clearance required between the ground and the underside of the trailer chassis means the deck of a typical trailer is significantly elevated, making it difficult to load and unload the trailer with large and/or heavy items. Often, this may require the use of a ramp or ramps from ground level to the trailer deck.

Alternatively, or additionally, it is common for many trailers to have a pivot point about which the deck may be rotated to some degree, tilting the deck downwards towards the rear end to facilitate easier loading and unloading, while the trailer chassis remains level and attached to the vehicle for stability. This solution is not ideal however, as the inclined deck of the trailer may not be suitable for loading and/or unloading certain items, or multiple items.

An improved solution to this problem would be to provide a mechanism whereby the deck of the trailer 'may be lowered relative to the wheels and parallel with the ground. Ideally, the mechanism should allow the underside of the chassis to be lowered to the extent that it rests on the ground, such that the trailer deck is substantially even with the ground. This would provide a very stable platform for loading, and items may be simply pushed or wheeled onto the deck with a hand trolley, wheelbarrow, dolly, or similar.

The main difficulty in designing such a mechanism is that the drawbar should ideally remain attached to the tow-bar of the towing vehicle for stability while being lowered and elevated, and the wheels, axles, and suspension assemblies etc. of the trailer must be retracted above the underside of the chassis, while maintaining sufficient structural strength for the trailer to bear heavy loads. United States Patent No. 6,592,1-39 to Shanahan, for example, discloses an elevatable trailer' having a telescopic frame or chassis, whereby retraction and extension of the frame causes wheel-mounting member to pivot such that wheels are raised and lowered, respectively, with respect to the frame. The drawbar is fixed relative to at least a portion of the frame, and is therefore lowered and raised with the frame. To maintain the trailer parallel with the ground, a modified tow-bar is required on the towing vehicle as shown in detail in Figure 12 of Shanahan. Due to the design, the modified tow-bar offers little stability to support the trailer as it is lowered. Parallel lowering of the trailer is not possible when coupled with an unmodified tow-bar.

Australian Patent Application No. 2005200640 entitled Trailer' discloses a trailer having a drawbar pivotally attached to a support frame or chassis, and hydraulic cylinders acting between the draw bar assembly and each wheel support member. Retraction of the hydraulic cylinders causes both the wheel support members and the drawbar to pivot, lowering the chassis towards the ground.

The trailer disclosed by the applicant's International Publication No. WO2007/000152 has a drawbar which is coupled with the chassis of the trailer by a parallelogram linkage, enabling the chassis to be lowered to the ground through an arcuate range of motion relative to the drawbar, whilst both the drawbar and chassis remain substantially parallel with the ground. However, this trailer is relatively expensive to manufacture, and is unable to tilt due to the linkage between the draw bar and the wheel-mount members.

In some circumstances or applications, it may be necessary or desirable to raise the chassis or deck of a trailer above the traveling or towage position in order to facilitate loading and/or unloadinq of the trailer.

An example of trailer which may be elevated above a traveling position is disclosed by United Kingdom Patent No. 1 ,466,113, in which the rear end of the trailer is raised as the drawbar is displaced angularly relative to the frame.

The trailers of the prior art either cannot easily be raised substantially above the normal elevated towing position, or do not allow the trailer to be towed in either an elevated or partially- lowered position. In particular, it is generally desirable, if not necessary, for at least the trailer hitch of the drawbar to be substantially parallel with the ground during towing, since the towbar or hitch receiver on the towing vehicle is not generally designed for pulling a trailer at an angle with respect to the ground and orientation of the towing vehicle. Thus, for various reasons including limited' movement, complexity, high manufacturing costs, and limited load capacity, among others, the lowering and/or raising trailers according to the prior art are not entirely satisfactory. Accordingly, there is a need for an improved trailer which , enables the deck or chassis thereof to be lowered, raised, and/or tilted with respect to an ordinary traveling position to facilitate loading and/or unloading of the trailer.

OBJECT OF THE INVENTION

It is an object of the invention to provide a trailer which overcomes or ameliorates at least one disadvantage of the prior art, or at least to provide the public with a useful choice.

SUMMARY OF THE INVENTION

According to one aspect the invention may broadly be said to consist in a trailer comprising: a chassis; a drawbar assembly comprising a four-bar linkage and a coupling for attaching the trailer, in use, to a towing vehicle; one or more pairs of wheel mounting members provided pivotally on opposing sides of the chassis; and operating means associated with said drawbar assembly and wheel mounting members and adapted to selectively pivot said drawbar assembly and/or wheel mounting members, whereby the chassis may be lowered, raised, and/or tilted with respect to the ground.

Preferably the four-bar linkage comprises a doubie-rocker mechanism, whereby at least a portion of the drawbar assembly is pivotable with respect to the chassis while the coupling remains substantially parallel therewith.

Preferably the operating means comprises a hydraulic system comprising a bi-directional hydraulic cylinder coupled with the drawbar assembly, and at least one hydraulic cylinder coupled with the wheel mounting members.

Alternatively, the operating means may consist of any other suitable bi-directional force- amplification mechanism, such as a mechanical lever and ratchet system, worm drive, winch, or the like, coupled with each of the drawbar and wheel mounting members.

Preferably a hydraulic cylinder is coupled with each wheel mounting member, wherein the hydraulic cylinders are adapted to operate in pairs corresponding with the pairs of wheel mounting members such that the wheel mounting members in each pair are operated substantially identically.

Preferably each pair of hydraulic cylinders coupled with the wheel mounting members may be operated independently of any other pair and/or the hydraulic cylinder coupled with the draw-bar mechanism, whereby the trailer may be tilted to various degrees.

Preferably a wheel is rotatably mounted at or substantially adjacent a distal end of each whee mounting member by way of a stub axle.

Preferably the wheel-mount assemblies each include a trailing-arm suspension assembly.

Alternatively, the hydraulic system further comprises a hydraulic accumulator.

Alternatively, each wheel-mount assembly may include a torsion rod suspension system.

Preferably the trailer includes a locking means to secure the trailer in at least a normal traveling position.

According to a further aspect, the invention may broadly be said to consist in a hydraulic system for provision as the operating means of a trailer according to any one of the preceding statements.

According to a further aspect, the invention can broadly be said to consist in a kitset of parts for upgrading an existing trailer having a chassis, including: a drawbar assembly for attachment at a proximal end to the chassis, the drawbar assembly comprising a four-bar linkage and a coupling at a distal end for attaching the trailer, in use, to the tow-bar of a vehicle; at least one pair of wheel-mount assemblies for pivotal mounting on opposing sides of the trailer chassis, upon which wheels may be mounted with a stub axle; and operating means to be provided between the drawbar assembly and trailer chassis, anc between the wheel-mount assemblies and the chassis.

According to a further aspect the invention consists in a trailer substantially as herein described with reference to any one of the embodiments illustrated in Figures 1 to 14 of the accompanying drawings. According to. a further aspect the invention consists in a kitset of parts substantially as herein described with reference to any one of the embodiments illustrated in Figures 1 to 14 of.-the accompanying drawings.

Further- aspects of the, invention, which should be considered in all its novel aspects,, will become apparent from the following description, given by way of example, and with reference to the accompanying drawings.

BRIEF DESCRIPTION OF FIGURES

The invention will now be described by way of example only with reference to the figures in which:

Figure 1 is a side view of a trailer according to a first embodiment of the invention in a traveling position; Figure 2 is an isometric view of the trailer of Figure 1 ;

Figure 3 is a detail view of an example four-bar linkage of the draw-bar assembly shown in

Figures 1 and 2;

Figure 4 is a detail view of a four-bar linkage of Figure 3 depicted when the trailer chassis is lowered towards the ground; Figure 5 is a side view of the first embodiment of the invention in a fully lowered position;

Figure 6 is an isometric view of the trailer depicted in Figure 5;

Figure 7 is a side view of the first embodiment of the invention in a tilted position;

Figure 8 is an isometric view of the trailer depicted in Figure 7;

Figure 9 is a side view of the first embodiment of the invention in a raised position; Figure 10 is an isometric view of the trailer depicted in Figure 9;

Figure 11 shows side views of a second embodiment of the invention in the (a) raised, (b) lowered, and (c) tilted positions;

Figure 12 shows a preferred four-bar linkage mechanism of the draw-bar assembly;

Figure 13 shows the linkage of Figure 12 when the trailer is in a lowered position; Figure 14 shows a torsion rod suspension assembly which may be used in various embodiments of the invention; and

Figure 15 is a diagram of an example hydraulic system for use with a trailer according to the present invention. DETAILED DESCRIPTION

The invention is described below by way of example. Throughout the description, like reference numerals will be used to refer to like features in different embodiments. Where reference is made to the trailer being lowered or raised, such reference is made with respect to the chassis of the trailer, whereupon the chassis is lowered or raised, respectively, in relation to the wheels, the ground, and a coupling which would commonly be attached to a towing vehicle.

Referring first to Figures 1 and 2, a wheeled transport vehicle according to a first embodiment of the invention is shown. In this embodiment, the invention consists in a two-wheeled vehicle to be towed by a powered vehicle for transporting goods. The trailer is shown in the traveling position, in which the wheels are lowered with respect to the chassis to provide sufficient ground clearance for a road-going vehicle. Although "wheels" are shown in each of the embodiments it is to be appreciated that other ground engaging means such as tracks could alternatively be used and this term is to have this wider meaning whenever used in this specification.

A trailer chassis 1 is connected with a draw-bar assembly 2 which includes a coupling 3 for coupling the trailer with the towing vehicle. The coupling 3 may comprise, for example, an assembly for coupling the trailer with a tow-bar ball, a "fifth wheel", or any other such coupling mechanism. A pair of wheel mounting members 4 are pivotally mounted on either side of the chassis, preferably in a bell-crank configuration, enabling the wheels to be pivoted in an arc upwards and/or downwards with respect to the chassis 1. Accordingly, wheels are mounted to the wheel mounting members 4 typically at or adjacent a distal end with a stub axle rotatable about an axis offset from the wheel mounting member pivot point 6

The wheel-mount assembly preferably also includes an independent or semi-independent suspension mechanism such as a trailing arm or torsion rod or beam suspension assembly.

Alternatively, according to certain embodiments, the suspension mechanism may comprise an accumulator provided in a hydraulic system including one or more hydraulic cylinders performing the function of operating means to pivot the wheel mounting members 4 as described in further detail below.

An accumulator is essentially an energy storage device which acts to hold the hydraulic fluid of the hydraulic system under pressure by applying a compressive force. Conversely, pivoting of the wheel mount members 6 due to bumps in the road during towing causes a compressive force to be applied and absorbed by the accumulator, thereby helping to at least partially isolate the,chassis 1 from bumps and vibrations in the road.

The use of an accumulator is preferred for trailers according to the invention which are adapted for towing in a raised or lowered position, being more stable in use than alternative suspension systems such as the torsion rod or trailing arm suspension due to the potential variation in the angle of the wheel mounting members 4 during towing. The accumulator is preferably of the gas type, although a hydraulic- or spring-type accumulator may alternatively be used.

The draw-bar assembly 2, or a portion thereof, is shown in detail as a preferred embodiment in two positions in Figures 12 and 13, and an alternative embodiment also illustrated in two different positions in Figures 3 and 4. The draw-bar assembly consists of a four-bar linkage comprising first and second link arms 7 and 8, and the shorter pivoting mounting plate or coupling member 9. The four-bar linkage is a double-rocker configuration, preferably in the form of a parallelogram linkage such that the orientation of the coupling member 9 does not change significantly during the motion of the linkage between, for example, the traveling position of Figure 3 and the lower position of Figure 4.

Referring to the preferred embodiment of the draw-bar assembly 2, the first and second link arms 7 and 8 of the four-bar linkage are each adapted to pivot angularly at or adjacent their proximal ends about displaced axes substantially orthogonal with respect to the longitudinal axis of the trailer chassis. The distal ends of the first and second link arms 7 and 8 are each pivotally coupled with the coupling member 9.

The link arms 7 and 8 are preferably substantially elongate to provide a wide range of height adjustments. A substantial portion of the draw-bar assembly 2 may thus be angled downwards or upwards from the towing vehicle and the chassis 1 when in lowered or raised positions, respectively, but the orientation of the pivoting coupling member 9 remains substantially constant regardless of the position of the draw-bar assembly.

According to the preferred embodiment as depicted in the drawings, the first link arm 7 is preferably a draw bar intended in use to bear the majority of the stress and strain in the four-bar linkage of the draw-bar assembly 2 between the trailer and the towing vehicle, and is designed accordingly. It therefore preferably comprises a strong elongate bar pivotally coupled to the chassis 1 and the coupling member 9 and provided centrally along a longitudinal axis at the front of the trailer. The second link arm 8 is preferably a connecting rod also provided along the central longitudinal 'axis of the trailer; immediately beneath the draw bar.

To effect angular displacement or pivoting of the four-bar linkage, either or both of the first and second link arms 7 and 8 are coupled with an operating means, which in the^' preferred embodiment comprises a hydraulic cylinder 10. Various configurations of the hydraulic cylinder 10 and link arms are possible, with a preferred configuration being illustrated in Figure 12, and an alternative configuration illustrated in Figures 3 and 4.

Referring to Figures 3 and 4, the proximal end of the first link arm 7 extends beyond the first- pivot point and is coupled with the hydraulic cylinder 10 provided between the link arm 7 and the chassis or a fixed portion of the draw-bar assembly. Many other variations may be made to this mechanism without departing from the scope of the invention. For example, the draw-bar assembly 2 may be provided with a plurality of each of the first and/or second link arms for increased strength, and those link arms may be provided substantially adjacent with the central longitudinal axis of the trailer chassis 1 or spaced apart and/or angled inwards towards the coupling member 9 at the distal end. However, according to the invention, the coupling 3 should remain substantially horizontal with the ground at a substantially constant height during operation of the trailer through a full range of motion, such that it may remain coupled with the towing vehicle.

The draw-bar assembly 2 is attached to the front end of the trailer chassis 1 at the proximal end, and the coupling member 9 at the distal end. The draw-bar assembly 2 may include a fixed portion in the form of an A-frame as shown in Figures 6 and 8 to lengthen the tongue or drawbar, increasing the distance between the chassis and a towing vehicle to allow the vehicle to maneuver while maintaining the load-bearing strength of the assembly 2. The tow-bar receiving coupling is mounted to the coupling member 3, whereby the chassis 1 may be lowered, raised or tilted with respect to the tow-bar receiving coupling 3 which remains substantially horizontal. The tow-bar ball receiving coupling or hitch 9 is preferably mounted to a top face of the coupling member 3, but may alternatively be mounted to any other face or integrated with the coupling member 3.

To secure the trailer in the traveling position, the drawbar assembly 2 and wheel mounting assemblies 4 preferably include a locking means. The locking means may be provided in the form of a manual or solenoid-operated locking pin to secure the wheel-mount and drawbar assemblies to the chassis in travel mode to prevent inadvertent use or failure of the locking means. Alternatively ;- the locking means mayxomprise a ratchet mechanism or any other such- locking means known in the field.

The trailer includes operatrng means for pivoting the draw-bar assembly and each of the wheel mounting assemblies 4 with respect to the chassis 1. According to the preferred embodiment, the operating means consists of a hydraulic system comprising a plurality of hydraulic cylinders

10 connected to a reservoir and pump by a network of hoses. The hydraulic system preferably also comprises a plurality of valves, and a control means adapted to control the valves and therefore operation of the hydraulic cylinders 10 so as to selectively control the lowering, raising, and/or tilting of the trailer.

A hydraulic cylinder 10 is preferably coupled between each wheel mount assembly 4 and the chassis 1 , and between the four-bar linkage and the chassis 1. The hydraulic pump is preferably powered electrically, or alternatively a combustion engine or hand-operated lever, for example, may be used to pump the pressurized fluid of the hydraulic cylinders. In the case of an electric pump, power is preferably sourced from the towing vehicle, but may alternatively be powered by a battery or generator provided on the trailer.

Alternatively, the operating means may comprise a pneumatic pump and pneumatic cylinders, worm-drive mechanisms coupled with electric motors, winches, or any other suitable means for imparting a force causing the draw-bar assembly 2 and wheel mounting members 4 to selectively pivot with respect to the chassis 1. In certain embodiments, the operating means may alternatively be indirectly coupled with a wheel mount assembly 5 through a linking member, which may comprise a torsion rod 140 in a trailer having torsion beam suspension, for example, as illustrated in Figure 14.

Other alternative mechanisms or arrangements will be apparent to those skilled in this area and may be utilized without departing from the scope of the invention.

The operating means is therefore adapted to lower the trailer chassis from the traveling position depicted in Figures 1 and 2, to the lowered position of Figures 5 and 6 by pivoting the wheel mounting members 4 upwardly with respect to the chassis so as to decrease the ground clearance of the chassis 1 until it reaches the desired height or rests upon the ground. In the illustrated embodiments, this involves retracting the piston rod of each hydraulic cylinder 10 associated with the wheel mounting members 4. In response, the bell-crank configuration of the wheel-mounting members causes the" wheels 5,-to pivot upwardly in an arc about the wheel mount member pivot points.

Simultaneously with pivoting the wheel mounting members 4, the distal end of the four-bar linkage, including the tow-bar receiving coupling 3, is preferably pivoted upwardly with respect to the chassis 1 , by independently actuating a further hydraulic cylinder 10 associated with the four-bar linkage as shown in detail in Figures 3, 4 and 12 by way of example. In both cases, the piston rod of the hydraulic cylinder 10 is retracted to cause the distal end of the linkage to pivot upwardly in an arc relative to the chassis 1.

The affect of pivoting the wheel mounting members 4 and draw-bar assembly 2 upwardly relative to the chassis 1 is to decrease the clearance between the ground and the underside of the chassis 1 while the trailer coupling 3 remains substantially horizontal at a substantially constant height. As a result, the trailer may remain coupled to a standard tow-bar of a towing vehicle as it is lowered, providing support to ensure the stability of the trailer.

According to the preferred embodiment of the invention, the chassis may be lowered until the wheels 5 are raised above the underside of the chassis 1 such that the chassis 1 comes to rest on the ground in the fully lowered position, facilitating easy loading and/or unloading of goods on and/or off the deck of the trailer. The trailer deck may therefore have a section which is tapered downwardly towards the rear end of the chassis, so that a wheeled vehicle such as an automobile, all-terrain vehicle (ATV), mobility scooter, motorcycle, hand trolley, wheelbarrow, dolly, or similar can easily be pushed or driven onto the deck of the trailer. Alternatively, or additionally, the trailer may be adapted for transporting animals, such as a horse float, for example, allowing a horse to embark and/or disembark with greater ease and safety. Other applications of the trailer will be apparent to those skilled in the art, and the foregoing applications are provided as examples only.

Actuation of the operating means to impart a force in the opposing direction has the reverse effect as that of lowering the trailer. Extension of the piston rods in each of the hydraulic cylinders 10 causes the chassis to be raised relative to the wheels 5 and tow-bar receiving coupling 3, whereby the trailer may be returned to a neutral or traveling position having a relatively normal ground clearance for transporting the load.

It is to be appreciated that the particular arrangement of the draw-bar assembly 2, wheel mounting members 4, and hydraulic cylinders 10 illustrated in the accompanying drawings are given, by way of example only,_and that_^variations or modifications may be made ;thereto .without departing from the scope of the invention.. For example, the hydraulic cylinders 10 may be arranged in such a way that the piston rods must be extended to lower the trailer, and retracted to return the trailer to the traveling position. However, the configuration illustrated has- several advantages. Firstly, in some embodiments of the invention, the weight of the trailer may be sufficient to cause the retraction of the piston rods necessary to lower the trailer if the oil is depressurized and diverted back to a reservoir. Accordingly, simpler and less expensive single- acting hydraulic cylinders may potentially be used, although double-acting cylinders are generally preferred. Secondly, the force produced by any hydraulic cylinder is always greater when extending the piston rod as compared to retracting the extension rod, because of the reduced effective piston area due to the piston rod. That greater force is best applied in raising the chassis 1 of the trailer to counteract the effect of gravity upon the trailer and any load borne thereby.

Figures 7 and 8 show the trailer in a tilted position which is enabled by the independent or selective control of the hydraulic cylinders 10 associated with the draw-bar assembly 2 and each pair of wheel-mounting members 4. By at least partially lowering the tow-bar receiving coupling 3 relative to the chassis 1 , and/or partially raising the wheels 5 relative to the chassis as described herein above, the chassis 1 is caused to pivot about a substantially central axis transverse with the longitudinal axis of the trailer, causing the rear end of the chassis 1 to be lowered to the ground. This tilted position of the trailer enables self-propelled vehicles to be driven onto the trailer deck for transportation, and/or assists with unloading, allowing wheeled vehicles in particular to roll off the back of the trailer. Independent control of the operating means enables the angle of tilt and/or height of the front end of the trailer to be controlled.

In some circumstances, it may be preferable for the trailer to be raised above its traveling position to assist with loading and/or unloading. Trailers according to the present invention may be adapted to enable this as shown in Figures 9 and 10, in which the trailer chassis is raised above the level of the wheels 5 by extending the piston rods of the hydraulic cylinders 10 beyond that required in the normah traveling position. This causes the wheel-mounting members 4 and draw-bar assembly 2 to pivot downwardly, increasing the ground clearance beneath the underside of the chassis 1. Trailers according to the present invention therefore have particular application in loading, transporting, and unloading/installing suspended loads such as aircraft engines typically suspended from the underside of the wing of an aircraft, for example. The height to which-the chassis 1 may be raised Is determined primarily by the length of the bell-crank wheel-mounting members 4,- which is limited by the torque which the, hydraulic cylinder 10 may apply thereto, and the length of the piston rod of those hydraulic cylinders. The design of the trailer may therefore be adapted to meet the requirements of its intended use. Accordingly, the trailer may be adapted only to be raised above the normal traveling or towing position, lowered below the traveling position, tilted with respect to the ground, or any combination thereof without departing from the scope of the invention.

Preferably the trailer chassis 1 may also be secured in a raised position by way of a ratchet mechanism and/or locking pin as described herein above with respect to the traveling position. The raised position may be the maximum height of the elevated trailer chassis 1, and/or any intermediate position between the maximum height and the normal traveling position. Similarly, the locking means may also be adapted to secure the trailer in the lowered or tilted positions, and any intermediate position which may be required, in use.

Referring now to Figures 11(a) to (c), a second embodiment of a trailer according to the present invention is shown. This embodiment includes two pairs of wheel mounting members 4 and wheels 5 (of which only one from each pair can be seen in the drawings). The wheel mounting member 4 and wheel 5 of each pair is provided directly opposite on either side of the chassis 1. The weight of the trailer and any load borne thereby is preferably distributed substantially evenly between the wheel assemblies, allowing the trailer to bear heavier loads. Accordingly, further wheels may be added to the trailer without departing from the scope of the invention.

Figure 11 (a) shows the trailer in the raised position. Also illustrated is an additional hydraulic cylinder 10 provided on the chassis 1 which may be extended to assist in lifting the trailer chassis 1 to the raised position, and/or to provide additional stability. The support cylinder is preferably retractable above the underside of the chassis 1 such that the trailer may be lowered and/or tilted as shown in Figures 11 (b) and (c), respectively.

In Figure 11(c), the trailer is shown in a tilted position. This drawing illustrates the preferred independent control of the operating means associated with the draw-bar assembly 2 and each pair of wheel mounting members 4. Compared with the raised and lowered positions in which the draw-bar assembly 2 and wheel mount members 4 are all pivoted down or up, respectively, relative to the chassis as illustrated in Figures 11 (a) and (b), in the tilted position the draw-bar assembly is pivoted downwards to raise the front end of the chassis, and/or both pairs of wheel mounting members are pivoted upwardly to varying degrees. However, to allow the chassis 1 to tilt downwards towards the rear, the rearmost pair of wheel mounting members 4 are- pivoted upwards to a greater degree than the front pair. Accordingly, the angle of tilt may_.be controlled by controlling the hydraulic cylinders 10. According to a second aspect, therefore, the invention may be said to consist in a hydraulic system adapted to operate a trailer as described herein.

- 5

From Figures 11 (a) and (b), it can be seen that the tow coupling 3 remains substantially horizontal and parallel with the chassis when the trailer is lowered and/or raised, and at a substantially constant height. This ensures that the trailer may remain securely coupled to the towing vehicle while allowing a wide range of vertical motion of the chassis 1.

10

A trailer according to the present invention may be adapted for transportation or towing in a raised or partially-lowered position, as opposed to just the "normal" travelling position referred to above. In this case, the parallel tow coupling 3 has a significant advantage in that the tow coupling 3 is always substantially parallel with ground and thus minimizes the angle between

15 the tow coupling 3 and the corresponding coupling provided on the towing vehicle, regardless of the height of the chassis 1 and/or coupling on the towing vehicle. Thus, the trailer may prevent accidental decoupling and/or excessive stresses on the trailer and towing vehicle which may otherwise arise due to an angled coupling between the trailer and towing vehicle. The trailer may therefore also be safely towed in a raised position, for example, as shown in Figure 11(a),

20 while complying with manufacturers specifications for the coupling and/or the towing vehicle.

The variable height of the trailer means that it may also be adapted for use with a wide range of vehicles, between which the height of the towbar or hitch receivers might vary significantly. In some embodiments, the operating means may therefore be designed to allow adjustment to the 25 height of the drawbar and tow coupling 3 independent of the wheel mounting members and chassis height adjustment.

While the invention is primarily directed towards a trailer intended for coupling with a towing vehicle, it may alternatively be coupled to any substantially stationary support object besides a 30 towing vehicle, and may alternatively include an appropriate coupling to couple the invention with the object to provide support in use.

Although the adjacent wheel-mounting members 4 on each side of the chassis are illustrated as being reversed in Figures 11 (a) - (c), they may alternatively be substantially identical such that

35 they pivot in the same direction. Similarly, although each pair of members 4 is preferably operated independently, this need not necessarily be the case. For example, according to a less¹ preferred embodiment of the invention, mechanical linkages may be provided between wheel mounting members 4 on each and/or opposing sides of the chassis 1. Such a. linkage may be provided to ensure synchronised- movement of all pairs of wheel mounting members, to reduce the number of hydraulic cylinders or other operating means required to operate each member 4, or to share the load therebetween. However, in such a case the trailer will be unable to tilt with more than one pair of wheels contacting the ground.

Referring now to Figure 15, a diagram of a hydraulic system suitable for use with a four-wheeled trailer according to the present invention is shown. The hydraulic system in this embodiment comprises a plurality of hydraulic cylinders 10 connected to a reservoir, pump 150, and a pair of accumulators 151 by a network of hoses. The hydraulic system preferably also comprises a plurality of valves 152, and a control means adapted to control the valves and therefore operation of the hydraulic cylinders 10 so as to selectively control the lowering, raising, and/or tilting of the trailer. One or more hydraulic accumulators 10 are preferably provided substantially adjacent or at least near the hydraulic cylinders 10 coupled with the wheel mounting members to absorb the compressive force of the pivoting wheel mount members due to their deflection in response to bumps in the road or changing loads on the chassis 1.

Although the invention has been described with respect to a trailer or transport vehicle, it will be appreciated by those skilled in the art that the invention may also be provided by way of a kitset of parts for upgrading an existing trailer. The kitset would typically include a drawbar assembly 2, at least one pair of wheel-mount members 4, and operating means for lowering and raising the chassis of the trailer.

From the foregoing, it will be seen that an elevatable trailer is provided which offers the capability of being lowered, raised, and/or tilted to facilitate loading and unloading, and returned a travel mode for transporting heavy loads. The trailer may be coupled to any standard or non- standard tow-bar of a towing vehicle and due to the drawbar assembly may remain coupled to the towing vehicle during use.

Although the invention has been described by way of example, it should be appreciated that variations and modifications may be made without departing from the scope of the invention. Furthermore, where known equivalents exist to specific features, such equivalents are incorporated as if specifically referred in this specification.

The words "include", "comprise" and variations such as "including", "comprises" or "comprising" when used in the specification are intended to be interpreted herein' in an inclusive sense rather than an exclusive sense, i.e. as meaning "including but not limited to".

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field in any country.

Claims

CLAIMS/

1 A trailer comprising' a chassis; a drawbar assembly comprising a four-bar linkage and a coupling for attaching the trailer, in use, to a towing vehicle; one or more pairs of wheel mounting memDers proviαeα pivoially on opposing sides of the chassis; and operating means associated with said drawbar assembly and wheel mounting members and adapted to selectively pivot said drawbar assembly and/or wheel mounting members, whereby the chassis may be lowered, raised, and/or tilted with respect to the ground.

2. The trailer of claim 1 wherein the four-bar linkage comprises an elongate double- rocker mechanism, whereby at least a portion of the drawbar assembly is pivotable with respect to the chassis while the coupling remains substantially parallel therewith.

3. The trailer of claim 1 or claim 2 wherein the operating means comprises a hydraulic system comprising a bi-directional hydraulic cylinder coupled with the drawbar assembly, and at least one hydraulic cylinder coupled with the wheel mounting members.

4. The trailer of claim 3 wherein a hydraulic cylinder is coupled with each wheel mounting member, wherein the hydraulic cylinders are adapted to operate in pairs corresponding with the pairs of wheel mounting members such that the wheel mounting members in each pair are operated substantially identically.

5. The trailer of claim 3 or claim 4 wherein the hydraulic cylinders coupled with the wheel mounting members may be operated independently of any other pair and/or the hydraulic cylinder coupled with the draw-bar mechanism, whereby the trailer may be tilted to various degrees.

6. The trailer of any one of claims 1 to 5 wherein each of the wheel mounting members are provided in a bell crank configuration and a wheel is rotatably mounted at or substantially adjacent a distal end of each wheel mounting member by way of a stub axle.

7. The trailer of any one of claims 1 to 6 wherein the wheel-mount assemblies each include a trailing-arm suspension assembly.

8. The trailer of any one of claims 1 to 7 wherein the hydraulic system further comprises an accumulator.

9 The trailer of any one of claims 1 to 8 wherein each wheel-mount assembly includes a torsion rod suspension system.

10. The trailer of any one of claims 1 to 9 wherein the trailer includes a locking means to secure the trailer in at least a normal traveling position.

11. A hydraulic system for provision as the operating means of a trailer according to any one of claims 1 to 10.

12. A kitset of parts for upgrading an existing trailer having a chassis, including: a drawbar assembly for attachment at a proximal end to the chassis, the drawbar assembly comprising a four-bar linkage and a coupling at a distal end for attaching the trailer, in use, to the tow-bar of a vehicle; at least one pair of wheel-mount assemblies for pivotal mounting on opposing sides of the trailer chassis, upon which wheels may be mounted with a stub axle; and operating means to be provided between the drawbar assembly and trailer chassis, and between the wheel-mount assemblies and the chassis to selectively pivot said drawbar assembly and/or wheel mounting members, whereby the chassis may be lowered, raised, and/or tilted with respect to the ground.

13. According to a further aspect the invention consists in a trailer substantially as herein described with reference to any one of the embodiments illustrated in Figures 1 to 14 of the accompanying drawings.

14. According to a further aspect the invention consists in a kitset of parts substantially as herein described with reference to any one of the embodiments illustrated in Figures 1 to 14 of the accompanying drawings.