AU2014240333B2

AU2014240333B2 - A Tandem Axle Suspension Assembly

Info

Publication number: AU2014240333B2
Application number: AU2014240333A
Authority: AU
Inventors: Neil Newnham
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-10-07
Filing date: 2014-10-07
Publication date: 2019-08-01
Anticipated expiration: 2034-10-07
Also published as: AU2014240333A1

Abstract

(Figure 1) The present invention relates to a suspension assembly for a tandem axle vehicle, a tandem axle vehicle including the suspension assembly, and a method of fitting a tandem axle arrangement to a vehicle. The suspension assembly includes: a trailing arm pivotally mountable to a vehicle frame and pivotable between raised and lowered positions; a biasing member for biasing the trailing arm into the lowered position; and a walking beam pivotally mountable to the trailing arm and having a wheel support mount located at or near each opposed end to, in use, distribute a load substantially equally between wheels mounted to each said wheel support mount. 152 o,,115 100 154o Figure 1

Description

A TANDEM AXLE SUSPENSION ASSEMBLY

TECHNICAL FIELD [0001] The present invention relates to a suspension assembly for a tandem axle vehicle, a tandem axle vehicle including the suspension assembly, and a method of fitting a tandem axle arrangement to a vehicle.

BACKGROUND [0002] Trailers, caravans and other like vehicles configured to be towed by domestic vehicles typically include a main vehicle frame to which is mounted a pair of wheels by way of an axle. The axle is in turn mounted to the vehicle frame via a suspension system, usually in the form of a leaf spring.

[0003] In some cases, when a greater load capacity is required, such as, e.g., with larger trailers, caravans and like vehicles, a tandem axle arrangement may be used, whereby two wheeled axles are located close together (i.e., one axle following or behind the other axle) to bear the increased load. Typically, the tandem axles are again in turn mounted to the main vehicle frame via leaf spring suspension systems, usually four leaf springs, two on each longitudinal side of the frame.

[0004] Whilst leaf spring suspension systems may be adequate for on road use, they have proven to be unsuitable for off-road use or use on rough road surfaces, particularly for vehicles with a tandem axle arrangement.

[0005] For example, due to the nature of their construction, namely the proximity of the axles, irregularities in a road or off-road surface may cause vertical movement of one of the tandem axles resulting in an unequal sharing of a vehicle load across the tandem axles. This in turn may result in increased transmission of shocks, jars and the like to the vehicle structure and impose greater stresses and strains on the axle system itself.

[0006] Whilst mechanical linkage systems, such as walking beams or rocker arms, are known for linking a front and rear axle of a tandem axle arrangement together to facilitate in load sharing between the axles, such systems have also proven to be unsuitable for off-road use or use on rough road surfaces.

2014240333 31 May 2019

SUMMARY OF INVENTION [0007] Embodiments of the present invention provide a suspension assembly for a tandem axle vehicle, a tandem axle vehicle including the suspension assembly and a method of fitting a tandem axle arrangement to a vehicle, which may minimize or overcome at least one of the problems mentioned above, or which may provide the public with a useful or commercial choice.

[0008] According to a first aspect of the present invention, there is provided a tandem axle suspension assembly for mounting along a longitudinal side of a vehicle, said assembly including:

a trailing arm having a first end pivotally mountable to a vehicle frame and a second end pivotable between raised and lowered positions relative to the vehicle frame;

a biasing member extending between the vehicle frame and the trailing arm to bias the second end of the trailing arm into the lowered position; and a walking beam pivotally mountable to the trailing arm and having a wheel support mount located at or near each opposed end of the walking beam to, in use, distribute a load substantially equally between wheels mounted to each said wheel support mount, wherein said suspension assembly is configured to enable load sharing between said wheels along the longitudinal side independent of a like said assembly mounted on an opposite longitudinal side of the vehicle.

[0009] According to a second aspect of the present invention, there is provided a vehicle having a tandem axle arrangement, said vehicle including:

a vehicle frame; and a respective suspension assembly attached to each longitudinal side of the vehicle frame, each suspension assembly including:

a trailing arm having a first end pivotally mountable to the vehicle frame and a second end pivotable between raised and lowered positions relative to the vehicle frame;

a biasing member extending between the vehicle frame and the trailing arm to bias the second end of the trailing arm into the lowered position; and a walking beam pivotally mountable to the trailing arm and having a wheel support mount located at or near each opposed end of the walking beam to, in use, distribute a load substantially equally between wheels mounted to each said wheel support mount,

2a

2014240333 31 May 2019 wherein the suspension assembly is configured to enable load sharing between said wheels along the longitudinal side to which it is attached independent from another like said suspension assembly attached to an opposite longitudinal side of the vehicle frame.

[0010] As indicated above, the tandem axle suspension assembly of the present invention is for use with a vehicle requiring a tandem axle arrangement. The suspension assembly is [Text continues on page 3]

2014240333 07 Oct 2014 trailing or semi-trailing suspension assembly for use with a vehicle configured to be towed by a prime mover. Preferably, the suspension assembly is for use with a vehicle such as, for example, a trailer or caravan. That is, both axles of the tandem axle arrangement of the vehicle will be dead or unpowered axles. A person skilled in the art will appreciate, however, that the tandem axle suspension assembly of the present invention may ultimately be used with a powered vehicle, such as, for example, a front-wheel-drive vehicle having a rear non-powered tandem axle arrangement.

[0011] The vehicle frame (i.e., chassis) may be of any conventional size, shape and construction and may typically serve as a platform upon which the remainder of the vehicle is built. Typically, the vehicle frame may be formed from metal and may include a pair of longitudinally extending side frame members joined together by a plurality of transversely extending cross frame members. The frame members may be of tubular construction or of solid construction, typically tubular with a substantially square-shaped cross-section. Typically, the various frame members of the vehicle frame are permanently joined together using conventional welding techniques.

[0012] The trailing arm may be of any suitable size, shape and construction to support the walking beam and, in use, pivot between the raised and lowered positions in response to road or off-road induced forces. Typically, the trailing arm may include a beam longitudinally extending between the first and second ends. The beam may be of any suitable size, shape and construction and formed from any suitable material or materials. The beam may be of tubular or solid construction and preferably made of steel. The trailing arm may be of unitary construction or may be formed from two or more trailing arm pieces, preferably of unitary construction.

[0013] Advantageously, the use of a trailing arm in conjunction with a walking beam enables load sharing on independent sides of the vehicle thus providing a smoother ride, particularly over off-road or rough road surfaces.

[0014] The trailing arm may extend rearwardly (i.e., towards the rear of the vehicle) from the first end to the second end and include a walking beam mount for mounting the walking beam and a biasing member support for supporting the biasing member. The trailing arm may be of any suitable length. Preferably, both the walking beam mount and the biasing member support may be positioned or located between the first end and the second end of the trailing

2014240333 07 Oct 2014 arm.

[0015] The first end of the trailing arm may be pivotally mountable to the vehicle frame by any suitable means that allows the trailing arm to pivot about the first end and the second end to be pivotable between the raised and lowered positions. Likewise, the first end of the trailing arm may be mountable to any suitable part of the vehicle frame. For example, the first end of the trailing arm may be directly or indirectly pivotally mountable to the vehicle frame, preferably indirectly via a trailing arm mount to a suitable location along one of the longitudinally extending side frame members of the vehicle frame. Preferably, the first end of the trailing arm may have a bearing located at or near the first end of the trailing arm. The bearing may or may not include a polymer bushing.

[0016] The trailing arm mount may be of any suitable size, shape and construction, and may be connectable to a longitudinally extending side frame member in any suitable way. Preferably, the trailing arm mount may include a bracket connectable to one or more walls of the longitudinally extending side frame member and a pivot pin for pinning the bearing at the first end of the trailing arm to the bracket. More preferably, the trailing arm mount may include a substantially L-shaped frame-mounting bracket connectable to both an outer and lower wall of the longitudinally extending side frame member and a pair of mounting plates associated with the bracket to which the bearing of the trailing arm is pinned.

[0017] In instances where greater clearance is required between the longitudinally extending side frame members of the vehicle frame, e.g., when the trailer is a cable drum trailer, the trailer arm mount may be connectable to the one or more walls of the longitudinally extending side frame member in such a way that it does not extend laterally passed an inside edge of the longitudinally extending side frame member.

[0018] Any suitable type of biasing member may be used for biasing the second end of the trailing arm into the lowered position. Likewise, the biasing member may extend between the trailing arm and the vehicle frame in any suitable way and at any suitable location along the trailing arm. For example, the location of the biasing member along the trailing arm relative to the first end may control characteristics of the suspension assembly and/or the relative height of the vehicle frame with respect to the trailing arms for a particular load. For instance, a biasing member located at a position mid-way along the trailing arm relative to the first end may provide a higher ride height in which the trailing arm is positioned at a greater angle relative to

2014240333 07 Oct 2014 the vehicle frame as opposed to the biasing member being located at a position at or near the second end of the trailing arm, which would provide a lower ride height. Preferably, however, the biasing member extends between the trailing arm and the vehicle frame at a location at or near the second end of the trailing arm.

[0019] The biasing member may be a spring such as, for example, an air spring (i.e., an air bag), a coil spring or a leaf spring. The biasing member may be a hydraulic or pneumatic cylinder. The biasing member may include one or more of the aforementioned examples. Preferably, the biasing member may include a coil spring or an air spring.

[0020] If the biasing member is an air spring, the height of the air spring may be controllable by a ride height valve to thereby control the relative height of the vehicle frame with respect to the trailing arm for a particular load (i.e., ride height).

[0021] As indicated above, the trailing arm may include a biasing member support for supporting the biasing member that may be positioned or located between the first and second ends of the trailing arm, preferably at or near the second end. The biasing member support may be of any suitable size, shape and construction. For example, the biasing member support may include a plate connectable to an upper surface of a portion of the trailing arm at or near the second end, the plate being connectable to a lower end of the biasing member. The trailing arm at or near the second end may define a shelf portion, preferably a recessed shelf portion, to which the plate may be seated or connected to in turn connect to the lower end of the biasing member. Preferably, at least one portion of the plate may extend laterally of the trailing arm for supporting the lower end of the biasing member.

[0022] An upper end of the biasing member may be connectable to the vehicle frame, preferably an adjacent longitudinal side frame member, in any suitable way. For example, the upper end of the biasing member may directly or indirectly connect to an adjacently positioned longitudinal side frame member, preferably indirectly via a biasing member mount connectable to one or more walls of the adjacent longitudinal side frame member.

[0023] The biasing member mount may be of any suitable size, shape and construction, and may be connectable to a longitudinally extending side frame member in any suitable way. For example, the biasing member mount may include a bracket connectable to one or more walls of the longitudinally extending side frame member and a plate connectable to the upper end of the biasing member. Preferably, the biasing member mount may include a substantially L-shaped

2014240333 07 Oct 2014 bracket connectable to both an outer and lower wall of the longitudinally extending side frame member and a plate extending from the substantially L-shaped bracket for connecting to the upper end of the biasing member.

[0024] As with the trailing arm mount, in instances where greater clearance is required between the longitudinally extending side frame members of the vehicle frame, the biasing member mount may be connectable to the one or more walls of the longitudinally extending side frame member in such a way that it does not extend laterally passed an inside edge of the longitudinally extending side frame member.

[0025] The assembly may further include a damper for damping oscillations of the trailing arm relative to the vehicle frame. Any suitable type of damper may be used and may extend between the trailing arm and the vehicle frame at any suitable location. For example, the damper may be a telescopic damper and/or a spring, such as a coil spring. Fikewise, the damper may be part of the biasing member or may be a separate component, preferably separate. Preferably, the damper may be a telescopic damper and may extend between a location at or near the second end of the trailing arm and a location at or near the biasing member mount connected to the longitudinally extending side frame member.

[0026] An upper end of the damper may be mountable to the biasing member mount and a lower end may be pivotally mountable to the trailing arm. The upper and lower ends may be mountable by any suitable means.

[0027] The upper end of the damper may be mountable to a connection point associated with the biasing member mount, for example. Preferably, the connection point may include a plate extending laterally from a portion of the biasing member mount connected to an outer wall of the longitudinally extending side frame member. It is to be appreciated, however, that the upper end may be mountable to the longitudinally extending side frame member of the vehicle frame independent of the biasing member mount. The upper end of the damper may be pivotally mountable or not, preferably not.

[0028] The lower end of the damper may be pivotally mountable to the trailing arm by any suitable means. The lower end may be hingedly connected to the tailing arm, for example. Preferably, however, the lower end is pivotally mountable by way of a bearing at or near the second end of the trailing arm to which the lower end is pinned with a pivot pin. The bearing may or may not include a polymer bushing.

2014240333 07 Oct 2014 [0029] The assembly may further include at least one bump-stop mountable to either the vehicle frame or to the trailing arm to at least partially protect the vehicle frame and the suspension assembly from “bottoming” or “bottoming-out” caused when an excessive road or off-road induced force causes the second end of the trailing arm to run out of upward travel without the biasing member fully absorbing the energy or momentum of the upward travel of the second end of the trailing arm.

[0030] The at least one bump-stop may be of any suitable size, shape and construction. The at least one bump-stop may be part of the biasing member or may be a separate component. Similarly, the at least one bump-stop may be of unitary construction or may include two or more bump-stop pieces. The bump-stop may be sized, shaped and configured to withstand an excessive amount of force, typically in the order of about 500kg, about 600kg, about 700kg, about 800kg, about 900kg, about 1,000kg, about 1,100kg, about 1,200kg, about 1,300kg, about 1,400kg or about 1,500kg, preferably at least about 1,000kg.

[0031] If of unitary construction, the at least one bump-stop may be in the form of a body of rubber or like material locatable on one of the vehicle frame and the trailing arm and configured to interact with the other of the vehicle frame and the trailing arm when the biasing member fails to absorb the energy of the upward travel of the trailing arm in response to excessive road or off-road induced forces.

[0032] If formed of two or more bump-stop pieces, the at least one bump-stop may include a first bump-stop piece locatable on one of the vehicle frame and the trailing arm and configured to interact with a second bump-stop piece locatable on the other of the vehicle frame and the trailing arm when the biasing member fails to absorb the energy of the upward travel of the trailing arm in response to excessive road or off-road induced forces. The first and second bump-stop pieces may each be in the form of a body of rubber or like material. Alternatively, the second bump-stop piece may be in the form of a spacing member extending outwardly from the other of the vehicle frame and the trailing arm towards the first bump-stop piece. The spacing member may be formed from any suitable material, preferably metal.

[0033] Preferably, the second bump-stop piece may be located on or near the biasing member mount and may be positioned to align with the first bump-stop piece located at or near the second end of the trailing arm when the second end of the trailing arm and the vehicle frame are brought together. More preferably, the first bump-stop piece may be connected to the

2014240333 07 Oct 2014 biasing member support and the second bump-stop piece may be connected to the biasing member mount.

[0034] The walking beam may be of any suitable size, shape and construction to, in use, distribute a load substantially equally between wheels mountable to each said wheel support mount located at each opposed end of the walking beam. Typically, as with the trailing arm, the walking beam may be an elongate structure having a beam extending longitudinally between the opposed ends. The walking beam may be of unitary construction or may be formed from two or more walking beam pieces, preferably of unitary construction.

[0035] It is to be appreciated that the walking beam may be of any suitable length to support a wheel at or near each end. Accordingly, it follows that the length of the walking beam may be longer or shorter depending on the size of the wheels mounted at or near each end. For example, a longer walking beam may be used with wheels having a large diameter (i.e., rim size). Conversely, a shorter walking beam may be used with wheels having a small or smaller diameter.

[0036] The walking beam may be pivotally mountable to the trailing arm in any suitable way that allows the vehicle load to be distributed substantially equally between mounted wheels. For example, the walking beam may be directly or indirectly mounted to the trailing arm, preferably directly. Likewise, the walking beam may be mounted to the trailing arm at any suitable location along the walking beam. For example, the location at which the mounting beam is mounted to the trailing arm may control characteristics of the suspension assembly, particularly the smoothness of the ride. For instance, the walking beam may be mounted to the trailing arm at a location toward a forward end of the walking beam relative to the longitudinal axis of the vehicle frame to provide a smoother ride over road surfaces or non-road surfaces having many corrugations.

[0037] A pivot pin may pivotally pin the walking beam to the walking beam mount positioned or located between the first and second ends of the trailing arm, preferably mid-way between the first and second ends of the trailing arm. More preferably, the pivot pin may pivotally pin a central portion of the walking beam, which coincides with a central transverse pivot axis of the walking beam, to the walking beam mount.

[0038] In a preferred embodiment, both the walking beam mount and the central portion of the walking beam may each include a bearing through which the pivot pin extends to pivotally

2014240333 07 Oct 2014 mount the walking beam to the trailing arm. Preferably, the bearings may include a polymer bushing.

[0039] As indicated above, a wheel support mount may be locatable at or near each opposed end of the walking beam for supporting a wheel. Any suitable type of wheel support mount may be used. Each wheel support mount may be sized and shaped for supporting a single wheel or dual wheels, for example. Preferably, each wheel support mount may extend from or near an end of the walking beam to entirely support a wheel.

[0040] The trailing arm and walking beam may be formed from any suitable material or materials of sufficient strength to, in use, withstand vertical bending forces, as well as forces caused by cornering, vehicle roll and travel over uneven surfaces. Typically, both the trailing arm and walking beam may be formed from steel.

[0041] According to a third aspect of the present invention, there is provided a method of fitting a tandem axle arrangement to a vehicle, said method including:

mounting the tandem axle suspension assembly as defined in the first aspect of the present invention to the vehicle.

[0042] The method may include one or more features or characteristics of the trailing arm and walking beam of the suspension assembly as hereinbefore described.

[0043] The method may be used for fitting a tandem axle arrangement to a new vehicle or for retro-fitting a tandem axle arrangement of an existing vehicle.

[0044] The method may include an initial step of aligning respective suspension assemblies along the longitudinal sides of the vehicle prior to mounting a respective suspension assembly to each longitudinal side of the vehicle.

[0045] The mounting may include fastening a trailing arm mount and biasing member mount to each longitudinal side of the vehicle. The trailing arm mount and biasing member mount may be fastened by any suitable means. Typically, the mounts may be welded to the respective longitudinal sides of the vehicle.

[0046] A first end of each trailing arm may then be pivotally mounted to each longitudinal side of the vehicle via the respective trailing arm mounts. A bearing located at or near the first end of each trailing arm may be pivotally pinned by a pivot pin to a pair of mounting plates ίο

2014240333 07 Oct 2014 associated with the substantially L-shaped frame-mounting bracket of each trailing arm mount.

[0047] Biasing members may then each be connected at a lower end to the second end of each trailing arm and at an upper end to an adjacently positioned biasing member mount. The lower end of the biasing member may be connected to the biasing member support located at or near the second end of the trailing arm.

[0048] Dampers may also then each be connected at a lower end at or near the second end of each trailing arm and at an upper end to a location at or near an adjacently positioned biasing member mount. The upper end of each damper may be mounted to a connection point associated with the adjacently positioned biasing member mount and the lower end may be pivotally mounted to each trailing arm. Preferably, the lower end of each damper may be pivotally mounted by way of a bearing at or near the second end of the trailing arm to which the lower end is pinned with a pivot pin.

[0049] The walking beam may then be pivotally mounted to the trailing arm to, in use, distribute the vehicle’s load substantially equally to wheels respectively mounted to opposed ends of the walking beam. A central portion of the walking beam may be pinned to the walking beam mount positioned or located between the first and second ends of the trailing arm. Preferably, both the walking beam mount and the central portion of the walking beam may include bearings through which the pivot pin may extend to pivotally mount the walking beam to the trailing arm.

[0050] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

[0051] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF DRAWINGS [0052] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

2014240333 07 Oct 2014 [0053] Figure 1 is a perspective view of a tandem axle suspension assembly according to an embodiment of the present invention;

[0054] Figure 2 is a side view of the tandem axle suspension assembly shown in Figure 1;

[0055] Figure 3 is a top view of the tandem axle suspension assembly shown in Figures 1 and 2;

[0056] Figure 4A is a side view of the tandem axle suspension assembly according to another embodiment in which the suspension assembly is shown at a minimum ride height;

[0057] Figure 4B is a side view of the tandem axle suspension assembly as shown in Figure 4A in which the suspension assembly is shown at an operational ride height;

[0058] Figure 4C is a side view of the tandem axle suspension assembly as shown in Figures 4A and 4B save that the suspension assembly is shown at a maximum ride height; and [0059] Figure 5 is a top view of a tandem axle suspension assembly according to another embodiment of the present invention.

DETAILED DESCRIPTION [0060] Figures 1 to 3 show a tandem axle suspension assembly (100) according to an embodiment of the present invention. The tandem axle suspension assembly (100) is for a vehicle configured to be towed such as, for example, a trailer or caravan. The assembly (100) includes a trailing arm (110) having a first end (112) pivotally mounted to a frame (10) of the vehicle and a second end (114) pivotable between raised and lowered positions relative to the frame (10). An air spring (120; i.e., a biasing member) extends between the frame (10) and the trailing arm (110) to bias the second end (114) of the trailing arm (110) into the lowered position relative to the frame (10) while a shock absorber (130; i.e., a damper) extends between the frame (10) and the trailing arm (110) to dampen oscillations of the air spring (120). A walking beam (140) is pivotally mounted to the trailing arm (110) and has a stub axle (142; i.e., a wheel support mount) located at or near each end of the walking beam (140) to, in use, distribute a load substantially equally between wheels (not shown) mounted to each said stub axle (142).

[0061] Referring to Figure 1, the trailing arm (110) is of a tubular construction having a

2014240333 07 Oct 2014 substantially rectangular cross-sectional shape. The trailing arm (110) is formed of fabricated steel plate of about 5mm in thickness with a length of about 1430mm, a width of about 75mm and a height of about 125mm.

[0062] In use, the trailing arm (110) extends rearwardly (i.e., towards the rear of the vehicle) from the first end (112) to the second end (114) and includes a load-distributing beam (115) extending between the first and second ends (112, 114) of the trailing arm (110). The trailing arm (110) further includes an air spring support (116; i.e., a biasing member support) for supporting the air spring (120) at or near the second end (114) of the trailing arm (110); and a walking beam mount (118) at a position about mid-way along a length of the trailing arm (110).

[0063] The first end (112) of the trailing arm (110) includes a bearing for pivotally mounting the trailing arm (110) to a trailing arm mount (150) connected to the frame (10). The trailing arm mount (150) includes a substantially L-shaped frame-mounting bracket (152) for connecting to both an outer and lower wall of a longitudinally extending side frame member of the frame (10) and a pair of mounting plates (154) associated with the plate (152) to which the bearing of the trailing arm (110) is pinned with a pivotal pin (156).

[0064] The air spring (120) for biasing the second end (114) of the trailing arm (110) into the lowered position relative to the frame (10) extends between the trailing arm (110) and the frame (10) at position at or near the second end (114) of the trailing arm (110). A lower end of the air spring (120) is connected to the air spring support (116) and an upper end of the air spring (120) is connected to an air spring mount (160; i.e., a biasing member mount) connected to the frame (10). As with the trailing arm mount (150), the air spring mount (160) includes a substantially L-shaped bracket (162) for connecting to both an outer and lower wall of a longitudinally extending side frame member of the frame (10) and a plate (164) extending from the substantially L-shaped bracket (162) for connecting to the upper end of the air spring (120).

[0065] Best shown in Figure 2, the air spring support (116) located at or near the second end (114) of the trailing arm (110) defines a recessed shelf portion to which a plate (117) connectable to a lower end of the air spring (not shown in Figure 2) is seated. At least a portion of the plate (117) extends laterally of the trailing arm (110) for supporting the lower end of the air spring (120).

[0066] The shock absorber (130) for damping the oscillations of the air spring (120)

2014240333 07 Oct 2014 extends between the trailing arm (110) and the frame (10) also at a position at or near the second end (114) of the trailing arm (110). An upper end of the shock absorber (130) is connected to a connection point in the form of a substantially horizontal plate (166) extending outwardly from a substantially vertical portion of the substantially L-shaped bracket (162) of the air spring mount (160). A lower end of the shock absorber (130) is pivotally mounted to the trailing arm (110) by way of a bearing at or near the second end (114) of the trailing arm (110) to which the lower end of the shock absorber (130) is pinned with pivot pin (119).

[0067] The walking beam (140), like the trailing arm (110), is of a tubular construction having a substantially rectangular cross-sectional shape. The walking beam (140) is formed of fabricated steel plate of about 5mm in thickness with a length of about 900mm, a width of about 50mm and a height of about 100mm.

[0068] The walking beam (140) is pivotally mountable to the trailing arm (110) to facilitate in the substantially equal distribution of a vehicle load between wheels respectively mounted to the stub axles (142) located at or near each end of the walking beam (140).

[0069] A central portion (144) of the walking beam (140), which coincides with a central transverse pivot axis of the walking beam (140), is pivotally mounted to the walking beam mount (118) positioned or located mid-way between the first and second ends (112, 114) of the trailing arm (110). The central portion (144) of the walking beam (140) and the walking beam mount (118) each include a bearing through which pivot pin (146) extends to pivotally mount the walking beam (140) to the trailing arm (110).

[0070] Referring to Figure 3, the stub axles (142) of the walking beam (140) are located at or near each opposed end of the walking beam (140) and are sized and shaped for supporting a single wheel (not shown). Each stub axle (142) is generally mounted to a respective stub axle mount (not shown) defined at or near an end of the walking beam (140) and secured in place by fasteners (not shown).

[0071] Figures 4A to 4C show another embodiment of the tandem axle arrangement (100) of the present invention in which wheels (400) are shown mounted to the respective stub axles (not shown).

[0072] In this embodiment, the air spring support (116), located at or near the second end (114) of the trailing arm (110), does not include a recessed shelf portion but only a plate (117)

2014240333 07 Oct 2014 connectable to an upper surface of the trailing arm (110) and to the lower end of the air spring (120).

[0073] Additionally, in this embodiment, the assembly (100) includes a bump-stop arrangement (410; i.e., two or more bump-stop pieces) for at least partially protecting the frame (10) and the assembly (100) from “bottoming” or “bottoming out” caused when an excessive road or off-road induced force causes the trailing arm (110) to run out of upward travel without the air spring (120) fully absorbing the energy of the upward travel of the trailing arm (110).

[0074] The bump-stop arrangement (410) includes a body of rubber (412) located at or near the second end (114) of the trailing arm (110) configured to interact with a spacing member (414) extending outwardly from the air spring mount (160) when the air spring (120) fails to absorb the energy of the upward travel of the trailing arm (110) in response to excessive road or off-road induced forces.

[0075] The body of rubber (412) is connected to the air spring support (117) adjacent the air spring (120) and is sized, shaped and configured to withstand an excessive amount of force in the order of about 1,000kg. The spacing member (414) is connected to the air spring mount (160) and positioned to align with the body of rubber (412) when the second end (114) of the trailing arm (110) and the frame (10) are brought together.

[0076] The use of the air spring (120) advantageously enables the height of the air spring (120) to be controlled by way of a height control valve (not shown) and thereby the relative height of the frame (10) with respect to the trailing arm (110) for particular vehicle load (i.e., ride height) to be controlled.

[0077] Figure 4A, for example, shows the frame (10) at a minimum height or lowered position in which the tandem axle suspension assembly (100) is at a minimum ride height. At this height, the spacing member (414) is resting on the body of rubber (412) and the angle of the trailing arm (110) relative to the frame (10) is at a minimum. The air spring (120) and shock absorber (130) are in a substantially uncompressed and compressed state, respectively.

[0078] Conversely, Figure 4B shows the frame (10) at a standard or operational height or neutral position in which the tandem axle suspension assembly (100) is in an operational position. The angle of the trailing arm (110) relative to the frame (10) is greater than that shown in Figure 4A and the air spring (120) and the shock absorber (130) are in a substantially

2014240333 07 Oct 2014 compressed and expanded state, respectively.

[0079] Figure 4C shows the frame (10) at a maximum height or raised position in which the tandem axle suspension assembly (100) is at a maximum ride height. At this height, the angle of the trailing arm (110) relative to the frame (10) is at a maximum. The air spring (120) and the shock absorber (130) are in greater compressed and expanded state, respectively, than as shown in Figure 4B.

[0080] Figure 5 shows another embodiment of the tandem axle arrangement (100) of the present invention in which the trailing arm mount (150) and the air spring mount (160) are positioned substantially flush with an inside edge of the frame (10). In this embodiment (as opposed to the embodiment shown in Figure 3), greater clearance is provided between the longitudinal sides of the frame (10), which is advantageous when the trailer is, e.g., a cable drum trailer.

[0081] A method of fitting a tandem axle arrangement to a vehicle is now briefly described. The method includes mounting a tandem axle suspension assembly (100) to each longitudinal side of the vehicle.

[0082] Prior to said mounting, the tandem axle suspension assemblies (100) are positionally aligned along the longitudinal sides of the vehicle.

[0083] Once aligned, a trailing arm mount (150) and an air spring mount (160) is fastened by welding to each longitudinal side of the vehicle.

[0084] The first end (112) of each trailing arm (110) can then be pivotally mounted to the trailing arm mount (150) on each longitudinal side of the vehicle. The first end (112) of the trailing arm includes a bearing, which is pinned with pivot pin (156) to a pair of mounting plates (154) associated with the L-shaped frame-mounting bracket (152) of each trailing arm mount (150).

[0085] Air springs (120) can then be fitted by connecting a lower end of each air spring (120) to an air spring support (116) at the second end (114) of each trailing arm (110) and an upper end to an adjacent air spring mount (160).

[0086] Similarly, shock absorbers (130) can be fitted by connecting an upper end of each shock absorber (130) to an adjacent air spring mount (160) and connecting a lower end of each

2014240333 07 Oct 2014 shock absorber (130) to a bearing located at or near the second end (114) of each trailing arm (110) by pivotally pinning the lower end to the bearing with pivot pin (119).

[0087] Walking beams (140) can then be pivotally mounted to each trailing arm (110) by pivotally pinning a central portion (144) of each walking beam (140) to the walking beam mount (118) positioned mid-way between the first and second ends (112, 114) of each trailing arm (110). The central portion (144) of each walking beam (140) and each walking beam mount (118) each include a bearing through which pivot pin (146) extends to pivotally mount the walking beam (140) to the trailing arm (110).

[0088] Wheels can then be fitted to the respective stub axles (142) located at or near the ends of each walking beam (140).

[0089] The height of the air springs (120) can then be adjusted and all connections tightened to required tensions.

[0090] Advantages of the present invention as exemplified include:

• the walking beam provides for substantially equal sharing of a vehicle load between wheels mounted to the walking beam thereby enabling better contact with a road or non-road surface;

• the trailing arm provides an independent suspension system in which wheels on either side of a vehicle can move vertically independent of the other side thereby facilitating in the vehicle maintaining traction where a solid-axle vehicle might lose contact;

• better traction and/or contact with a road or non-road surface in turn maximises tyre performance by allowing tyre tread to contact a road or non-road surface over a greater surface area wear more evenly; and • overall, the combination of a the walking beam with the trailing arm provides for a robust suspension assembly ideally suited for off-road use or use on rough road surfaces.

[0091] In the present specification and claims (if any), the word “comprising” and its derivatives including “comprises ” and “comprise ” include each of the stated integers but does not exclude the inclusion of one or more further integers.

2014240333 07 Oct 2014 [0092] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0093] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims

1. A tandem axle suspension assembly for mounting along a longitudinal side of a vehicle, said assembly including:

2. The tandem axle suspension assembly of claim 1, wherein the first end of the trailing arm is pivotally mountable to the vehicle frame via a trailing arm mount connected to the vehicle frame.

3. The tandem axle suspension assembly of claim 2, wherein the trailing arm includes a bearing at or near the first end which is pinned to the trailing arm mount to pivotally mount the trailing arm to the vehicle frame.

4. The tandem axle suspension assembly of any one of claims 1 to 3, wherein the walking beam is pivotally mountable to a walking beam mount positioned or located between the first and second ends of the trailing arm.

5. The tandem axle suspension assembly of claim 4, wherein a central portion of the walking beam is pivotally mountable to the walking beam mount.

6. The tandem axle suspension assembly of claim 5, wherein the central portion of the walking beam coincides with a central transverse pivot axis of the walking beam.

7. The tandem axle suspension assembly of claim 5 or claim 6, wherein the walking beam mount and the central portion of the walking beam each include a bearing through which a pivot pin extends to pivotally mount the walking beam to the trailing arm.

2014240333 31 May 2019

8. The tandem axle suspension assembly of any one of claims 1 to 7, wherein the biasing member is connected at a lower end to a location at or near the second end of the trailing arm and at an upper end to the vehicle frame via a biasing member mount connected to the vehicle frame.

9. The tandem axle suspension assembly of any one of claims 1 to 8, wherein the trailing arm includes a biasing member support at or near the second end of the trailing arm to which the biasing member is connected.

10. The tandem axle suspension assembly of any one of claims 1 to 9, wherein the biasing member is any one of an air spring, a leaf spring and a coil spring.

11. The tandem axle suspension assembly of any one of claims 1 to 10, further including a damper extending between the vehicle frame and the trailing arm to dampen oscillations of the trailing arm relative to the vehicle frame.

12. The tandem axle suspension assembly of claim 11, wherein a lower end of the damper is pivotally mountable to the trailing arm at or near the second end of the trailing arm and an upper end of the damper is connectable to the vehicle frame via the biasing member mount.

13. The tandem axle suspension assembly of claim 12, wherein the lower end of the damper is pinned to a bearing located at or near the second end of the trailing arm to pivotally mount the damper to the trailing arm.

14. The tandem axle suspension assembly of any one of claims 1 to 13, wherein the vehicle is a vehicle configured to be towed or pulled by a powered vehicle.

15. The tandem axle suspension assembly of any one of claims 1 to 14, wherein the vehicle is a trailer or a caravan.

16. The tandem axle suspension assembly of any one of claims 1 to 15, further including a bump-stop to at least partially protect the vehicle and the suspension assembly when an excessive road or off-road induced force causes the second end of the trailing arm to run out of upward travel without the biasing member fully absorbing the upward travel of the second end of the trailing arm.

17. A vehicle having a tandem axle arrangement, said vehicle including: a vehicle frame; and

2014240333 31 May 2019 a respective suspension assembly attached to each longitudinal side of the vehicle frame, each suspension assembly including:

a trailing arm having a first end pivotally mountable to the vehicle frame and a second end pivotable between raised and lowered positions relative to the vehicle frame; a biasing member extending between the vehicle frame and the trailing arm to bias the second end of the trailing arm into the lowered position; and a walking beam pivotally mountable to the trailing arm and having a wheel support mount located at or near each opposed end of the walking beam to, in use, distribute a load substantially equally between wheels mounted to each said wheel support mount, wherein the suspension assembly is configured to enable load sharing between said wheels along the longitudinal side to which it is attached independent from another like said suspension assembly attached to an opposite longitudinal side of the vehicle frame.

18. The vehicle of claim 17, wherein the vehicle is a vehicle configured to be towed or pulled by a powered vehicle.

19. A method of fitting a tandem axle arrangement to a vehicle, said method including: mounting the tandem axle suspension assembly as defined in any one of claims 1 to 16 to the vehicle.

20. The method of claim 19, wherein the tandem axle suspension assembly is retro-fitted to the vehicle.