Patent Description:
Many vehicles and work machines, such as articulated trucks, excavators, dozers, loaders and the like, may have a centre of mass which is relatively high above the ground. This may be as a result of loading during operation, for example where a dump body holds a large mass of material. Work machines are often equipped with work tools which can be raised for safety when not in use and when the vehicle is travelling, which also affects the centre of mass of the vehicle. Such work machines are also typically operated on rough and uneven terrain. As a result, there is a risk that the work machine may tip over as it travels over uneven terrain.

This risk is increased for articulated vehicles, in that these typically comprise a tractor (in which the power unit is usually mounted) and a trailer (which may have a container for holding a mass of material or goods for transportation) connected to one another via an oscillating hitch joint. The oscillating hitch joint enables the tractor and trailer to roll and yaw relative to one another. When operated on uneven terrain, one of the tractor and trailer s may become positioned at an unsafe roll and/or yaw angle and may cause the entire machine to turn over. Alternatively, if the articulated vehicle has an open container, such as a bucket or body mounted on the trailer, any materials or goods held in the open container may fall out when one of the tractor and trailer is positioned above certain roll and/or yaw angle thresholds.

The chassis system of such articulated vehicles may be designed to help reduce the likelihood of this from occurring as well as improving the vehicle ride dynamics. The chassis system of an articulated vehicle typically comprises a tandem axle, which provides a greater weight capacity than a single axle. A tandem axle comprises two axles one or both of the central and rear axles may be driven axles. The chassis system of tandem drive axles utilise special suspension arrangements which permits flexibility between the axles, but which are able to withstand hard operating conditions. One such type of suspension is an equalizing beam suspension, which may be of the leaf spring or rubber load cushion type. Equalizing beams link the suspensions of the adjacent axles and use the lever principle to distribute the load across the axles to reduce the effect of uneven terrain. Equalizing beam systems may also help to lower the centre of gravity of the axle load to provide better stability. Equalizing suspension systems may also include a torque rod to restrict lateral movement of the axles and to keep them centred, to further provide greater stability and roll stiffness.

In an articulated vehicle, the chassis frame has to provide the required geometry for the suspension and body layout, whilst also withstanding the loading from these systems. The oscillating hitch joint significantly reduces frame torsion compared to other vehicles. However, the chassis frame does still experience significant beam torsion, due to the effect of the axle loads being applied via the equalizing beams. A primary chassis cross member may therefore be provided, which has the function of stiffening the chassis to resist this loading, in addition to mounting and locating the rear suspension components in the required positions.

<CIT> describes the preamble of claim <NUM> and a suspension system for a load carrying machine. The suspension system includes a longitudinal frame, first and second axial assemblies, first and second suspension members, first and second balance beams and first and second pairs of flexible members which reduce shear and improve the service life.

The disclosure provides a spindle cross member for a chassis system for a vehicle comprising:.

The disclosure further provides a chassis system comprising a chassis frame and a suspension frame, said chassis frame comprising at least two longitudinal members and a plurality of cross members, at least one of said cross members being the spindle cross member as claimed in any one of the preceding claims and said suspension frame having a suspension frame head, wherein the suspension frame head is attached to the spindle cross member and is at least partially enveloped by the middle section wall.

The disclosure also provides a vehicle comprising a tractor and a trailer connected to the tractor by an articulated joint, said trailer having at least one axle, wherein the at least one axle is attached to the aforementioned chassis system.

The present disclosure is generally directed towards a chassis system having a spindle cross member as the primary cross member, which is suitable for a vehicle and in particular for an articulated vehicle. Although the following description only describes an articulated vehicle <NUM>, the chassis system may be used in any vehicle.

<FIG> illustrates an exemplary articulated vehicle <NUM> in which the chassis system of the present disclosure may be used. The articulated vehicle <NUM> may comprise a tractor <NUM> and a trailer <NUM>. The tractor <NUM> may be a tractor unit and may comprise a cab <NUM> and a power unit (not shown). The power unit may be of any suitable type, such as an internal combustion engine, a micro-turbine or an electric motor. A front axle (not shown) may be provided to support the tractor <NUM> having one or more ground engaging means <NUM>, such as wheels, mounted at either end of the front axle. The tractor <NUM> may comprise more than one axle and more than two ground engaging means <NUM> attached to each axle.

The tractor <NUM> may be connected to the trailer <NUM> via a coupling <NUM>, which may be an articulation joint. The coupling <NUM> may allow the tractor <NUM> and trailer <NUM> to be orientated at a different yaw and/or roll angle to each other frame. The yaw angle of the tractor <NUM> may be different to the yaw angle of the trailer <NUM> about an articulation axis <NUM>. The articulated vehicle <NUM> may be steered by adjusting the yaw angle of the tractor <NUM> and trailer <NUM> about the articulation axis <NUM> utilising actuators (not shown), for example hydraulic cylinders, attached to each of the tractor <NUM> and trailer <NUM> on either side of the coupling <NUM>.

The trailer <NUM> may comprise a chassis system <NUM> and a body <NUM> adapted to carry a load, such as a dump or ejector body. The chassis system <NUM> may comprise a chassis frame <NUM> and the body <NUM> may be attached to the chassis frame <NUM> at a pivot point (not shown). A tipping system may be provided to rotate the body <NUM> about the pivot point. The tipping system may comprise at least one hydraulic actuator <NUM> connected to the body <NUM> and the chassis frame <NUM>. The body <NUM> may comprise an ejector mechanism, having an actuator which may move a plate within the body <NUM> to eject any material contained therein.

<FIG> and <FIG> shows the chassis system <NUM> of the trailer <NUM>. The chassis system <NUM> may comprise a tandem axle having two axles, namely a central axle <NUM> and a rear axle <NUM>. The chassis system <NUM> may, however, have more than two axles, although for the purposes of this embodiment only two axles will be referred to. The ground engaging means <NUM> (shown in <FIG>) may be mounted by suitable mounting means <NUM> located at each end of the central axle <NUM> and rear axles <NUM> of the trailer <NUM>. The ground engaging means <NUM> may provide support between the terrain <NUM> over which the articulated vehicle <NUM> travels and the tractor <NUM> and trailer <NUM>. The ground engaging means <NUM> may be of any suitable type, for example wheels or tracks, and may be operably connected via the central axle <NUM> and rear axles <NUM> to, and thus receive power from, the power unit.

Power may be transferred from the power unit, which may be located in the tractor <NUM>, to one or both of the central axle <NUM> and rear axles <NUM> by a drive shaft (not shown) via the coupling <NUM>, depending on whether one or both of the central axle <NUM> and rear axles <NUM> are driven axles. An end of the drive shaft may be operably connected to receive power from the coupling <NUM>. Transmission devices (not shown), such as differentials or universal joints, may transfer torque from the drive shaft to the central axle <NUM> and rear axles <NUM>.

The central axle <NUM> and rear axles <NUM> may be attached to the chassis frame <NUM> by the chassis system <NUM>. The chassis frame <NUM> has two longitudinal chassis members <NUM>, which may be parallel, and at least two cross members <NUM> are attached between the two longitudinal chassis members <NUM>. The chassis frame <NUM> has a spindle cross member <NUM>, which may act as the primary cross member to stiffen the chassis frame <NUM>, and which is attached between the two longitudinal chassis members <NUM>. A central suspension frame <NUM> may extend between a cross member <NUM> located at a front of the chassis frame <NUM> and the central axle <NUM>. A rear suspension frame <NUM> may extend between the spindle cross member <NUM> and the rear axle <NUM>. The central suspension frame <NUM> and rear suspension frame <NUM> may be configured as A-frames, comprising a suspension frame head <NUM>, a first arm <NUM> and a second arm <NUM>. Each first arm <NUM> and second arm <NUM> may have a first arm end <NUM> and a second arm end <NUM>. The first arm ends <NUM> of each first arm <NUM> and second arm <NUM> may be joined together at the suspension frame head <NUM> with the first arm <NUM> and second arm <NUM> extending outwardly from the suspension frame head <NUM> at an angle. The suspension frame heads <NUM> are pivotally attached to the respective cross member <NUM> and spindle cross member <NUM>. The suspension frame head <NUM> of the central suspension frame <NUM> may be attached to the cross member <NUM> by means of a pivot bearing <NUM> attached to the cross member <NUM>. The pivot bearing <NUM> may extend through a lug <NUM> attached to or formed in the suspension frame head <NUM>. The attachment of the rear suspension frame <NUM> to the spindle cross member <NUM> will be described below.

The second arm end <NUM> of the first arm <NUM> may be attached to the respective central axle <NUM> or rear axle <NUM> on one side of the chassis frame <NUM> and the second arm end <NUM> of the second arm <NUM> is attached the same central axle <NUM> or rear axle <NUM> on the other side of the chassis frame <NUM>.

As shown in <FIG> and <FIG>, a first equalizer beam <NUM> may be connected to, and extend between, the central axle <NUM> and rear axles <NUM> on one side of the chassis frame <NUM>. A second equalizer beam <NUM> may be attached to, and extend, between the central axle <NUM> and rear axles <NUM> on the other side of the chassis frame <NUM>. The first equalizer beam <NUM> and second equalizer beam <NUM> may be attached to the central axle <NUM> and rear axles <NUM> via resilient suspension mounts <NUM>. The suspension mounts <NUM> may comprise a pad of elastomeric material, such as rubber, sandwiched between two mounting plates.

As shown in <FIG>, the spindle cross member <NUM> comprises a main member <NUM> and a spindle end <NUM> located at either end of the main member <NUM>. The main member <NUM> may be steel and formed by a casting process. The spindle ends <NUM> may be forged, for example from boron steel which is then direct (thru) hardened. Spindle caps may be located on the spindle ends <NUM>. Manufacturing the main member <NUM> and spindle ends <NUM> using different materials and different manufacturing processes may allow the optimum construction in terms of balancing component strength in the areas subjected to the highest stresses against manufacturing costs. However the spindle cross member <NUM> may be manufactured as a single component.

A middle section of the main member <NUM> has a middle section wall <NUM> which is at least partially curved and which defines a central cavity <NUM> and has an opening <NUM>. The central cavity <NUM> may generally have a cup-like form. This may, for example, be C-shaped, U-shaped, hemispherical, or in the form of dome or an elongate parabolic dome. The thickness of the middle section wall <NUM> may taper from a central point towards the edges (which define the opening <NUM>) in a transverse direction of the spindle cross member <NUM>. As shown in <FIG>, the thickness t<NUM> at the central point of the middle section wall <NUM> is more than the thickness t<NUM> at the edges of the middle section wall <NUM>. Two bosses <NUM> may extend from the middle section wall <NUM> at a roof <NUM> of the dome into the central cavity <NUM> and the bosses <NUM> may be located one on either side of the dome vertex <NUM> and spaced apart in a longitudinal direction. The bosses <NUM> may define bores <NUM> which extend through the wall of the main member <NUM>.

On either side of the middle section of the main member <NUM> and located along a longitudinal axis of the spindle cross member <NUM> are tubular end sections <NUM>. The tubular end sections <NUM>, which may be formed by extensions of the middle section wall <NUM>, extend outwardly along the longitudinal axis of the spindle cross member <NUM>. The tubular ends sections <NUM> may be separated from the central cavity <NUM> by a section of the middle section wall. The tubular end sections <NUM> may define hollow end cavities <NUM> which may be at least partially cylindrical and may be located so that the tubular end sections <NUM> open outwardly in a longitudinal direction. The thickness t<NUM>, t<NUM> of the walls of the tubular end sections <NUM> may be less than the thickness t<NUM> of the middle section wall <NUM> (see <FIG>). Additionally the thickness of the walls of the tubular end sections <NUM> may taper as they extend away from the middle section of the main member <NUM>. As shown in <FIG> the thickness t<NUM> is less than the thickness t<NUM>.

The spindle ends <NUM> may comprise a first cylindrical end section <NUM>, a middle conical section <NUM> and a second cylindrical end section <NUM>, which has a larger diameter than the first cylindrical end section <NUM>. A flange <NUM> may extend from the second cylindrical end section <NUM>, which flange <NUM> may be sized to be inserted partially into an end cavity <NUM> of the tubular end sections <NUM> and secured therein, for example by welding. The longitudinal axis <NUM> of the spindle cross member <NUM> may extend through the centre of the spindle ends <NUM>.

The spindle cross member <NUM> may be affixed to the chassis frame <NUM> with the spindle ends <NUM> extending through apertures <NUM> in the longitudinal chassis members <NUM>. The spindle cross member <NUM> is secured in position, for example by welding the second cylindrical end section <NUM> of the spindle ends <NUM> to the respective longitudinal chassis member <NUM> on the outside of chassis frame <NUM> and by welding the main member <NUM> to the respective longitudinal chassis member <NUM> on the inside of chassis frame <NUM>.

The first equalizer beam <NUM> and second equalizer beam <NUM> may be connected, one at each end, to the spindle cross member <NUM>. The first equalizer beam <NUM> and second equalizer beam <NUM> may have apertures <NUM>, located in which are bushings <NUM>. The first cylindrical end sections <NUM> of the spindle ends <NUM> may extend through the bushings <NUM> and may be secured therein by means of a fixing <NUM> attached to the ends of the first cylindrical end sections <NUM>. The bushings <NUM> may be conical in shape and may be made of an elastomeric material, such as rubber and may allow the first equalizer beam <NUM> and second equalizer beam <NUM> to rotate relative to the spindle cross member <NUM> and the chassis frame <NUM>.

The rear suspension frame <NUM> is pivotally attached to the spindle cross member <NUM>, which may be by means of a straddle bearing <NUM>, which may be a spherical plain bearing, the inner ring of which may comprise a pin. The straddle bearing <NUM> may be pressed into a lug <NUM> formed in the suspension frame head <NUM> of the rear suspension frame <NUM>. The straddle bearing <NUM> may be attached to the bosses <NUM> inside the central cavity <NUM> of the spindle cross member <NUM> by means of fixings <NUM>, such as bolts. The fixings <NUM> may extend through the bores <NUM> in the bosses <NUM>. The length of the bosses <NUM> and the depth of the central cavity <NUM> may be selected such that, when the rear suspension frame <NUM> is attached to the spindle cross member <NUM>, the axis of the straddle bearing <NUM>, and therefore the lug <NUM>, is coaxial with the longitudinal axis <NUM> of the spindle cross member <NUM>. In addition, the spindle cross member <NUM> envelops the lug <NUM>.

The spindle cross member <NUM> may be the primary structural cross member of the chassis frame <NUM> which may be subjected to significant forces, which it needs to be able to withstand so as to reduce stress in the chassis frame <NUM>. The main loading experienced by the spindle cross member <NUM> may be from the axle loads transmitted to the spindle ends <NUM> via the first equalizer beam <NUM> and second equalizer beam <NUM>. These forces may induce a bending moment across the spindle cross member <NUM> and torsion into the longitudinal chassis members <NUM> of the chassis frame <NUM>. The spindle cross member <NUM> may also experience loading from the rear axle <NUM> via the rear suspension frame <NUM>. The geometry of the main member <NUM> may not only provide a stiff load bearing structure which resists the induced bending moment to minimise damage during use, but may also minimise the risk of defects during casting. The "envelope" provided by the cup-like middle section wall <NUM> defining the central cavity <NUM> surrounds the suspension frame head <NUM> and may resist the bending moment across the spindle cross member <NUM>, induced by the axle loads on the spindle ends <NUM>. This may be achieved by maximising the section/ stiffness within the geometric constraints imposed by the rear suspension frame <NUM>; the stiffness provided by the tubular end sections <NUM> is maintained despite the constraints of the rear suspension frame <NUM>, through the blending of the geometry into the curved middle section wall <NUM>. The effect of the section change from the tubular end sections <NUM> to the middle section wall <NUM> in the midsection of the main member <NUM>, combined with the local longitudinal and transverse wall tapering, t<NUM> to t<NUM> and t<NUM> to t<NUM>, may result in a general increase in wall thickness towards the centre of the main member <NUM>. This may help to avoid shrinkage defects during the casting process as it may allow directional solidification towards the centre of the main member <NUM> where a riser is formed in the casting. The riser may be machined away as a part of the finishing process and the resulting flat machined surface may be used to receive the heads of the fixings <NUM> which may secure the straddle bearing <NUM> to the bosses <NUM> inside the central cavity <NUM> of the spindle cross member <NUM>.

Claim 1:
A spindle cross member (<NUM>) for a chassis system (<NUM>) for a vehicle (<NUM>) comprising:
a main member (<NUM>), having a middle section and end sections (<NUM>);
characterised in that said end sections (<NUM>) are tubular and that said middle section having an at least partially curved middle section wall (<NUM>) which defines a cavity (<NUM>) with an opening for receiving a head (<NUM>) of a suspension frame (<NUM>) of the chassis system (<NUM>), and said tubular end sections (<NUM>) being located at each end of the middle section located along a longitudinal axis (<NUM>) of the spindle cross member (<NUM>); and
in that means (<NUM>) are provided for pivotally attaching the head (<NUM>) of the suspension frame (<NUM>) to the middle section wall (<NUM>) within the cavity (<NUM>).