Field of the Invention

The present invention relates to an improved vehicle suspension system which is applicable with particular advantage to off road vehicles, especially trucks, for use on rough/rocky ground, for example, construction sites.

The invention relates to such vehicles which have at least two pairs of rear wheels to carry the weight of the vehicle. Clearly, it is desirable for the wheels to be allowed freedom of movement in as many directions as possible in order to accommodate the rocky ground over which the vehicle is to be driven. It is known to mount the forward and rearward axle of the rear bogie upon a rocker arm to give freedom of movement allowing pitching of the vehicle (ie. movement about a transverse horizontal axis) but even this does not give full freedom of movement between the four wheels. It is also known to mount each axle upon the rocker arm via a spring mounting such that the distance of the axle from the rocker arm may also vary.

In this specification, the term "longitudinal" will be taken to mean substantially in the direction of travel of the vehicle, "horizontal" will mean substantially parallel to the plane of travel of the vehicle and "transverse" will be taken to mean substantially perpendicular to the direction of travel.

Summary of the Invention

According to the invention, there is provided a vehicle having an improved suspension system, the vehicle including at least two rear wheel pairs.

comprising a left and right forward rear wheel mounted upon a forward rear axle and a left and right rearward wheel mounted upon a rearward rear axle; a left and right rocker arm each comprising an elongate member mounted to pivot about a horizontal transverse axis lying between the forward and rearward wheels, the left rocker arm being coupled to the left end of the forward and rear axles and the right rocker arm being coupled to the right end of the forward and rear axles, the coupling between each axle and its respective rocker arm being arranged such that each axle may move with respect to the rocker arm about a longitudinal axis of the rocker arm such that each of the four wheels an move independently of each other.

Thus, the wheels can "rock" and "pitch" relative to the rest of the vehicle ie. rotate about a longitudinal and a transverse axis. Such movement is independent of movement of any other wheel. This allows the vehicle to travel readily over extremely rough terrain.

Preferably, the relative movement is achieved by the rocker arm including a bore of circular cross-section with its axis transverse and horizontal with an arcuate inner surface and mounted within the bore a substantially spherical member, the spherical member being coupled to an axle fastening bracket via a pin, the axle fastening bracket being mounted upon the axle.

This allows the spherical member to rotate about an axis which is longitudinal and horizontal and which allows the axle to rotate with respect to the rocker arm. Because it is spherical, there is also freedom of movement in other directions although this is limited by the construction of the axle fastening bracket and the rocker arm. These serve to act as stops to limit the degree of movement.

Preferably, the spherical member is not exactly spherical but includes flats which bear against the axle fastening bracket. These flats can be used to aid insertion of the sphere for removal if it becomes worn.

The spherical member is preferably solid and may be metallic or a suitable polymer. Kevlar has been found to be an appropriate material for the member.

Preferably, the forward and rearward axles are coupled together via tie rods which act as load absorbing equalising beams. However, these also need to be mounted to accommodate the movement of the axles. Preferably, a tie rod extends from a central member mounted above the differential housing in the region of the typical mounting of the rocker beams to each axis which each end of the tie rod is mounted via a spherical coupling similar to that used to couple the axles to the rocker beam.

Brief Description of the Drawings

A vehicle arranged in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which :-

Figure 1 is a perspective schematic view of the vehicle;

Figure 2 is a horizontal section through the suspension of the vehicle with an enlarged detail of the spherical joint:

Figure 3 is a section along line A-A of Figure 2: and

Figure 4 is a section through line B-B of Figure 2.

Description of the Preferred Embodiment

Vehicle 1 comprises a discharge truck for use on a construction site. It includes an improved suspension system for rear wheels 3,5,7, and 9. The left and right forward wheels 3,5 are mounted respectively upon a forward axle 10 having left end 11 and right end 13. The left rear wheel 7 is mounted upon left end 15 of rear axle 14 and the right rear wheel 9 is mounted to its right end 17. A left and right rocker arm 19.21 each comprises an elongate member mounted to the truck via a bracket 23 pivotable about a horizontal transverse axis 25 lying between the forward and rearward wheels. The left rocker arm 19 is coupled to the left end 11 of the forward axle and left end 15 of rear axle via couplings 27, 29. The right rocker arm 21 is coupled to the right end of front axle 13 and right end of rear axle 17 via couplings 31,33 respectively. The couplings are arranged such that each axle can rotate with respect to the rocker arms about a longitudinal axis so that the four wheels can move independently of each other.

The coupling can be seen in more detail if the enlarged section of figure 2 and figure 3 is referred to where only one coupling 29 is illustrated. The rocker arm 19 includes a bore 35 of circular cross-section and an arcuate inner surface 37. Mounted within the bore is a substantially spherical member 39 coupled to axle fastening bracket 41 via pin 43. The spherical member 39 can rotate about the longitudinal axis of the rocker arm 19 but also in the direction parallel to the plane of the paper as shown in figure 3. Such movement is limited only by the structure of the axle bracket 41 bearing against rocker arm 19. However, the movements that the wheel can achieve is sufficient for the

wheel to be able to accommodate rocky terrain. As can be seen in figure 3, the spherical member 39 is not exactly spherical but includes flats 45 which are useful for removing and inserting the member.

Differential gear 47 couple the right and left sides of the axles 10 and 14 to allow differential movement between the wheels. However, in order to strengthen the structure and transmit load between the wheels, tie rods 49, 51 are mounted to position above the differential gears 47 in a central position over the differential gears 47 and coupling the rear axle to central member 53 and the forward axle to the central member 53 via brackets 55. 57 and spherical joints 59,61,63.65 of a similar construction to those uses to couple the axle fastening brackets to rocker arms.

The rear suspension bogie is suspended from the main vehicle chassis by a downwardly depending main load bearing bracket, movable connected to the rocker arm. The rocker arm is pivoted centrally about the downwardly depending bracket. At each end of the rocker arm are the large spherical plastic bush members inside the axle fastening bracket, which allow the axle to move in an up and down direction so that the forward and rearward rear wheels on the same side of the vehicle can be at different distances from the vehicle body, and can also rotate through an arc so that the left hand and right hand rearward rear wheels can also be at different distances from the body. This allows all four rear wheels of the bogie to move independently of each other.

Large spherical plastic bushes are located also at the end of the tyre rods which connect to the two axles above the differential housings, allowing the axles to move up and down freely and also through an arc, thus enabling the

wheels on opposite sides of the truck to be at different distances from the vehicle body as compared with each other.

Specific embodiments to the present invention may provide a torque reactive suspension system incorporating geometric lateral load absorbing equalising rocker arms and torque rods.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details φ the foregoing embodiment(s). The invention extends to any novel one. or any novel combination, of the features disclosed in this specification (including any accompanying claims,

abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.