A road train typically consists of a prime mover truck towing one or more semi-trailers and/or draw bar trailers. Each trailer is supported on at least one pair of laterally adjacent wheel assemblies. In the case of a semi-trailer having rear wheel assemblies, part of the load of the trailer is carried by the prime mover.

A draw bar trailer however includes both front and rear wheel assemblies and can therefore support their own load.

The wheel assemblies for such trailers are generally relatively simple in design. In modern trailer designs, the wheel assemblies are typically located by a trailing arm suspension in conjunction with a Panhard rod. Air springs are typically used to provide part or all of the support for the trailer load. Additional roll stiffness is usually provided by the trailing arms (which provide little on-centre roll stiffness) or separate anti-roll bars.

While such a wheel assembly arrangement is adequate for most on-road conditions, it would nevertheless be preferable that the trailer wheel assemblies also provide additional linear roll support for the road train to minimise the roll motion of the trailers. Furthermore, it would be preferable that the trailer wheel assemblies have relatively free cross-axle articulation (also called"warp") motion to enable the trailers to more safely traverse uneven road surfaces.

The Applicant has developed a number of different hydraulic suspension systems that provide for roll support while at the same time allowing free cross- axle articulation of the wheel assemblies of the vehicle. These suspension systems are for example described in U. S. Patent Nos. 5447332,5480188, 5562305,5915701 and 6010139. The use of such hydraulic systems can however be inconvenient or impractical on trailer wheel assemblies. It may firstly be necessary to provide hydraulic connecting assemblies to enable the hydraulic supply lines of the trailer and the prime mover to be connected. Such connections are where leakage of hydraulic fluid is most likely to occur. This problem is compounded where the road train has more than one trailer. Also, the

exposed portions of the hydraulic lines are vulnerable to being cut or split resulting in the potential breakdown of operation of the hydraulic suspension system. Repair of such hydraulic coupling can require specialised equipment, which is not ideal given that the requirements for a truck are usually easy, quick servicing anywhere with little down time.

It would therefore be advantageous to be able to provide a self-contained suspension arrangement which can also be relatively rugged and not as susceptible to damage as a hydraulic suspension system while at the same time providing roll support with free cross axle articulation.

A fully mechanical system that performs this function would be preferable because such a system would avoid many of the abovenoted problems. InFrench Patent 1155319 (Contant), there is described a mechanical suspension system which provides roll control while allowing for a degree of cross axle articulation.

The described system is however very complex incorporating many linkages and joints. Such a suspension system could not be readily located under the body of current vehicle models. in particular, a large number of mounting points are required on the vehicle chassis and a large package volume is required high up in the vehicle to allow clearance for the linkages to sweep through their motions during the suspension operation. Furthermore, the high number of linkages, pivotal supports and joints can result in excessive play within the system.

It is therefore an object of the present invention to provide a mechanical suspension arrangement which avoids or minimises the problems associated with the prior art.

With this in mind, the present invention provides a mechanical suspension arrangement for a vehicle having a body and at least a first and second pair of laterally adjacent wheel assemblies, the suspension arrangement including mechanical connection means respectively interconnecting a said wheel assembly from each said first to second pairs thereof along a side of the vehicle, each mechanical connection means including a link member extending at least substantially parallel to a said side of the vehicle and interconnecting a pair of the wheel assemblies on said vehicle side, roll support means respectively interconnecting each said mechanical connection means, wherein the suspension

arrangement provides roll support for the vehicle whilst simultaneously facilitating free cross-axle articulation motion of the interconnected wheel assemblies.

The term"vehicle"is defined to cover both vehicles incorporating built in drive arrangements such as automobiles and prime movers as well as trailers towed by other vehicles.

The roll support means may include a roll stabilizer bar rotatably supported on the vehicle body and respectively interconnected at opposing ends thereof to a said link member.

Each wheel assembly may include a wheel rotatably supported on a wheel axle. Each link member may be in the form of a beam, with each end of the beam being interconnected to a said wheel assembly. Therefore, any movement of one or both of the connected wheel assemblies results in movement of the beam.

The beam may be rigid, or may be flexible, for example taking the form of a box section which may be designed to deflect under high roll loads, or in some cases, it could even be a longitudinal leaf spring. The beam may be connected at one end thereof by a hinge to the wheel assembly. In particular, the hinge may be located on the wheel axle thereof. The hinge connection allows rotational motion of the beam about a pivot axis within a single plane. The other end of the beam may be connected by a drop link to the other wheel assembly. The drop link may be supported on the wheel axle. The drop link may be pivotally connected at opposing ends thereof to the beam and wheel assembly respectively. This drop link connection allows for displacement of the end of the beam away from or towards the wheel assembly. Therefore, any lateral movement of the beam towards or away from the side of the vehicle is limited by the hinge connection, with any lateral forces applied to the beam being resolved in the hinge connection. The drop link connection however allows for relative movement of the interconnected wheel assemblies.

At least a substantial portion of the roll stabiliser bar may extend laterally between the link members. The roll stabiliser bar may be interconnected to an intermediate section of the link member between the ends thereof. Lever arms may be provided at opposing ends of the roll stabiliser bar, each lever arm being respectively interconnected with a said link member. The lever arms thereof may be connected by a drop link to the link member. The use of the drop link

connection facilitates the mounting of the suspension arrangement under a vehicle body, with the roll stabiliser bar being located adjacent the vehicle body while the link members are located at a lower level adjacent the wheel assemblies. The drop links may also allow for relative displacement between the roll stabiliser bar and the link members During operation of the suspension arrangement, when there is roll motion of the vehicle, the wheels on one side of the vehicle are urged upwardly. This results in an upward movement of the link member which acts to apply a rotational force onto the roll stabiliser bar. This force results in rotation of the roll stabiliser bar which acts to apply an upward force on the link member on the opposing side of the vehicle. This action of the suspension arrangement acts to reduce the roll motion of the vehicle. When the vehicle travels on an uneven surface resulting in cross-axle articulation motion of the wheel assemblies, the intermediate connection of the roll stabiliser bar to the link member results in the link member moving in a"see-saw"fashion about that intermediate connection with little to no force being applied to the roll stabiliser bar. This ensures that there is little to no resistance to such motion by the suspension arrangement.

This suspension arrangement provides a fully mechanical interconnection between the wheel assemblies that does not require any external hydraulic fluid source. Furthermore, the suspension arrangement can function independently from the suspension arrangement of any other wheel assemblies of the vehicle.

The suspension arrangement may therefore be applicable for interconnecting at least two laterally adjacent pairs of wheel assemblies of a semi-trailer or a draw bar trailer. The suspension arrangement can be readily retrofitted onto existing vehicles to improve roll performance. The existing vehicle supports are retained to support the vehicle load.

It will be convenient to further describe the present invention with respect to the accompanying drawings, which illustrate a preferred embodiment of the suspension arrangement according to the present invention. Other embodiments of the invention are possible, and consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.

In the drawings:

Figure 1 is a perspective view of the mechanical suspension arrangement according to the present invention; Figure 2 is a perspective view of the mechanical suspension arrangement of Figure 1 in association with wheel assemblies of a vehicle.

The mechanical suspension arrangement 1 according to the present invention is adapted to interconnect two pairs of laterally adjacent wheel assemblies 2 of a vehicle. The vehicle can be a semi-trailer or drop bar trailer of a road train. It is also envisaged that the present invention could also be used on other vehicles such as motor cars.

The mechanical suspension arrangement 1 includes a pair of beams 3. Each beam 3 respectively extends between two wheel assemblies 2 on a side of the vehicle. Each wheel assembly 2 includes a wheel 7 rotatably supported on a wheel axle 9. In the case of trailers, the wheel axle 9 may be a solid axle supporting two laterally adjacent wheels 7. One end of the beam 3 is supported by a hinge connection 11 located on one wheel axle 9. The hinge connection 11 includes a hinge bracket 13 secured to the wheel assembly 2, for example, on the wheel axle 9. The beam 3 includes a pair of laterally extending pins 15 which cooperate with apertures 14 provided in the hinge bracket 13 to provide the hinge connection 11. A drop link connection 17 is located on the opposing side of the beam 3. This drop link connection 17 includes a drop link 19 pivotally supported on a drop link bracket 21 at one end thereof. The drop link 19 has an upper eye 20 for accommodating a pivot axle 22 pivotally supported by the drop link bracket 17. This drop link bracket 21 is supported on the opposing wheel assembly 2, for example, on the wheel axle 9. The other end of the drop link 19 is supported on a further pivotal connection 23 located at the opposing end of the beam 3. This drop link 19 therefore includes a lower eye a 24 pivotally supported on a pivot axle 26 of the pivotal connection 23.

The mechanical suspension arrangement 1 further includes a roll stabiliser bar 5 which is pivotally supported on the body of the vehicle. At each end of the roll stabiliser bar 5 is provided a lever arm 25. A further drop link connection 27 is provided between the lever arm 25 and the adjacent beam 3. Each further drop link connection 27 includes a central drop link 29 which is pivotally connected to the free end of the lever arm 25 by a pivot connection 31. The central drop link

29 includes an upper eye 30 pivotally supported on a pivot axle 32 of the pivot connection 31. A support bracket 33 is located at an intermediate position along the beam 3. The other end of the further drop link 29 is pivotally connected to the intermediate support bracket 33 by means of a further pivot connection 35. The central drop link 29 includes a lower eye 34 pivotally connected on a pivot axle 36 of the further pivot connection 35.

During operation of the suspension arrangement 1, when the vehicle is undergoing roll, the wheel assemblies 2 on one side of the vehicle will be urged upwardly. This upward movement is transferred to the beam 3 interconnected to those wheel assemblies 2. This movement is also transferred through the further drop link connection 27 to the roll stabiliser bar 5 resulting in pivotal movement along its elongate axis. This rotational movement rotates the opposing lever arm 25 which through the associated further drop link connection 27 acts to lift the opposing beam 3 and therefore, the opposing wheel assemblies 2. The mechanical suspension arrangement 1 therefore acts to minimise roll of the vehicle under roll conditions in the manner described above.

It should be noted that the hinge connection 11 on one end of the beam 3 acts to limit the movement of the beam 3 to a single plane lateral to the pivotal axis of the hinge connection 11. Therefore, any sideward forces on the beam 3 are resolved into the hinge connection 11. The connection of the beam 3 by a drop link connection 17 at the opposing end thereof allows for some relative movement between the interconnected wheel assemblies 2 connected to that beam 3. Additionally, the drop link connection 27 between the beam 3 and the roll stabiliser bar lever arm 25 allows for some relative movement between the beam 3 and the roll stabiliser bar 5.

When the wheel assemblies 2 are undergoing cross-axle articulation motion, where one diagonally opposite pair of wheel assemblies 2 are moving in an opposing direction to the other diagonally opposite pair of wheel assemblies 2, then the beam 3 moves in a"see-saw"motion about the pivot axle 36 on the intermediate bracket 33 such that little to no motion is transferred through the drop link connection 27 to the roll stabiliser bar 5. The mechanical suspension arrangement 1 therefore allows for relatively free cross-axle articulation motion of the wheel assemblies 2.

In a two wheel bump situation where either the first or second laterally adjacent pair of wheel assemblies 2 are both travelling simultaneously over a bump, then the upward motion of each further drop link connection 27 simply results in rotation of the roll stabiliser bar 5 without any torsional force being applied by that roll stabiliser bar 5.

When there is a single wheel bump situation, the resultant motion transferred through the further drop link connection 27 to the roll stabiliser bar 5 is generally substantially absorbed by the twisting of that roll stabiliser bar with little effect on the other wheel assemblies 2.

It should be noted that the mechanical suspension arrangement 1 according to the present invention can be retrofitted on existing vehicles. The suspension arrangement 1 can therefore be used in conjunction with the existing vehicle supports. For example, in the case of a semi trailer using air springs, the suspension arrangement 1 will provide the roll support whereas the air springs will provide the support for the trailer load.

The above description is provided for the purposes of exemplification only, and it will be understood by a person skilled in the art that modifications and variations may be made without departing from the invention scope as defined in the appended claims.