AU2013201229A1 - A sprung walking beam suspension - Google Patents

Abstract

-9 A pedestal assembly for use in a suspension assembly for suspending a tandem wheel axle assembly from a vehicle chassis. The pedestal assembly includes a longitudinally 5 extending body including a lower portion with means of connection to a walking beam connecting two longitudinally spaced wheel axles of said tandem axle assembly, and a forwardly projecting portion and a rearwardly extending portion. It further includes a hanger configured to be rigidly connected to an underside of said chassis, the hanger including a front portion with a means of hingedly suspending the forwardly projecting 0 portion of the pedestal body, and a rear portion which is springedly associated with the rearwardly extending portion of the pedestal body

Description

- 1 A SPRUNG WALKING BEAM SUSPENSION TECHNICAL FIELD The present invention relates to a sprung walking beam suspension for vehicles such as heavy 5 duty trucks or trailers and, in particular, to a walking beam suspension which overcomes deficiencies associated with known suspensions of this type including driver discomfort, adverse effects on vehicle durability, complex and expensive components, and low commonality of parts with existing vehicles. The invention further relates to a pedestal assembly forming part of the suspension assembly. 0 BACKGROUND Walking beams are used on many makes and models of vehicle to connect the axles. The beams are connected to the axles from below at their beam-ends. A suspension is mounted to the centre of the beams and serves to connect the beams and axle assembly to the vehicle frame. This type 5 of suspension is known as a walking beam suspension. Front and rear torque rods are generally provided to control movement of the axle assembly during brake and acceleration. An example of a walking beam suspension of the prior art is shown in Figure 1. In particular, there is shown a top perspective and an underside perspective view of a rear suspension 0 assembly 1 for a heavy duty truck (not shown). Also shown is a tandem axle assembly 2 with axles connected by longitudinally extending parallel walking beams 3, a transverse cross tube 4 connecting the walking beams 3, and front and rear torque rod assemblies 5 and 6 respectively. The suspension assembly 1 includes two suspension pedestals 7 configured to be connected at their bottom ends to each of the walking beams via conventional saddle caps 8, and welded to 5 the chassis (not shown in Figure 1) of a vehicle along their top planar surfaces 9. This configuration allows the axles to move relative to each other when the vehicle is driving along an uneven surface. Deficiencies associated with such prior art walking beam suspensions have been recognised by 30 the present Applicant. While these suspensions allow the axles to move relative to each other, they do not adequately absorb shock from the road, particularly on rough roads and/or at high speeds. This has been known to result in driver discomfort, and shock and wear to the vehicle and suspension. The skilled addressee would realise that repair and/or replacement of vehicle chassis' and suspension parts, particularly for heavy duty trucks and trailers, is labour intensive 35 and expensive. One solution which has been proposed is to use a suspension pedestal or support member which is pivotally attached to a hanger bracket suspended from the chassis, with air spring means or air bags located between the chassis and support member for absorbing shock. The problem with 40 existing solutions of this type is that they are often complex and bulky systems, particularly with the use of air bags which are prohibitively large, their load rating is poor, and the components - 2 used to control lateral movement of the suspension (typically transverse rods, often referred to as Panhard rods) are also bulky and require additional componentry to be added to the chassis. Parts of known suspensions also tend to lack commonality with existing designs and so are not easily retrofitted to existing vehicle chassis'. 5 It is therefore an object of the present invention to overcome the aforementioned problems, or at least provide the public with a useful alternative. SUMMARY OF THE INVENTION 0 Therefore, in one form of the invention there is proposed a pedestal assembly for use in a suspension assembly for suspending a tandem wheel axle assembly from a vehicle chassis, said pedestal assembly including: a longitudinally extending body including a lower portion with means of connection to a walking beam connecting two longitudinally spaced wheel axles of said tandem axle assembly, and a 5 forwardly projecting portion and a rearwardly extending portion; and a hanger configured to be rigidly connected to an underside of said chassis, said hanger including a front portion with a means of hingedly suspending the forwardly projecting portion of the pedestal body, and a rear portion which is springedly associated with the rearwardly extending portion of the pedestal body. 0 In preference said means of hingedly suspending the forwardly projecting portion of the pedestal body is in the form of a locating lug pair between which said forwardly projecting portion is adapted to be received, each component including coaxial apertures for receiving a hinge pin. 5 Preferably said rear portion of the pedestal body includes an upper surface adapted to support at least one elastomeric spring, and said rear hanger portion includes an inverted housing of stepped up dimension to that of the spring such that the spring is received in said housing and thereby supports the rear portion of the hanger. 30 Preferably the rear portion of the pedestal body is also restricted from lateral movement using a restriction means. Advantageously said restriction means is in the form of an end cap configured to receive the end of said pedestal rear portion and thereby prevent lateral movement thereof. 35 In preference said end cap and said rear portion include hardened steel wear plates at points of contact therebetween. Preferably said elastomeric spring is a disc-shaped rubber spring. 40 - 3 The present invention thus provides a pedestal assembly for use in a vehicle suspension which is hinged and sprung instead of rigidly welded to a vehicle chassis, thus improving shock absorption, driver comfort and vehicle durability. Also provided is a suspension which is less complex than prior art suspensions of this type, and which can achieve a much higher load rating 5 compared against similar size sprung suspensions utilising air bags for example. Furthermore, the suspension includes a lateral movement restrictor suspended from the hanger which means no additional componentry is required to be added to the chassis to restrict such movement. In a further form of the invention there is proposed a suspension for a vehicle chassis including 0 two laterally spaced, longitudinally extending beams, wherein each beam includes a pedestal assembly suspended therefrom, each pedestal assembly being configured as defined above. In preference said spaced apart pedestal assemblies are connected by a pedestal cross member. 5 In a still further form of the invention there is proposed a vehicle chassis including at least one suspension assembly as defined above. In a yet further form of the invention there is proposed a vehicle including at least one suspension assembly as defined above. 0 BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several implementations of the invention and, together with the description, serve to explain the advantages and principles of the invention. In the drawings: 5 Figure 1 illustrates a top and underside perspective view of a prior art walking beam suspension depicts a prior art leaf spring suspension system for a multi-axle trailer; 30 Figure 2 illustrates an exploded, top perspective view of a sprung walking beam suspension in accordance with the present invention; Figure 3 illustrates an assembled side view of the sprung walking beam suspension of Figure 2; 35 Figure 4 illustrates an assembled end view of the sprung walking beam suspension of Figure 2; and Figure 5 illustrates an underside perspective view of the sprung walking beam suspension 40 of the present invention when attached to a vehicle chassis. DETAILED DESCRIPTION The following detailed description of the invention refers to the accompanying drawings. Although the description includes exemplary embodiments, other embodiments are possible, and changes may be made to the embodiments described without departing from the spirit and scope of the invention. 5 The present invention relates to a sprung walking beam suspension 10 as depicted in Figures 2 to 4. As shown in Figure 5, the sprung walking beam suspension 10 is adapted to be connected to the underside of a longitudinal vehicle chassis 11 such that it suspends therefrom. Parts of the suspension assembly which are considered to be known in the art are not described in detail 0 herein. The suspension 10 of the present invention includes spaced apart and longitudinally extending pedestal assemblies 12 which are each shaped in a similar V-shaped configuration to that of the prior art. The present invention further relates to a pedestal assembly 12 forming part of the 5 suspension assembly 10, as well as a chassis and vehicle incorporating the suspension assembly 10. The pedestal assemblies 12 are connected at their lower ends to respective walking beams 14, which are interconnected by a transversely extending walking beam cross tube 16. The pedestals 0 themselves are connected by a pedestal cross member 17. Not shown in Figures 2-5 is a tandem axle assembly, which as per the assembly shown in Figure 1 is associated with front and rear ends of the walking beams such that there is a front and rear transverse wheel axle associated with each suspension. The walking beams 14 and the mounting 5 brackets (not shown) used to connect the walking beams to the axle housings are all conventional and so are not described in more detail. It is to be understood that while a tandem axle suspension is embodied herein, the present invention is not intended to be limited to use in associated with tandem wheel axle assemblies. 30 The pedestal assemblies 12 differ from prior art assemblies known to the Applicant in that they each include an upwardly and forwardly projecting portion 18 configured to be pivotable about a pedestal hinge pin 20, and a rearwardly extending portion 22 including a flat upper surface 24 for accommodating a rubber spring 25 there above, as shown most clearly in Figure 2. 35 Each assembly 12 further includes a pedestal hanger 26 configured to be mounted above the pedestal body, including a flat upper surface 28 of similar dimension to the upper surface 9 of pedestal assembly 7 of the prior art, a pair of vertical locating lugs 30 suspended from a front portion of the hanger and between which the front portion 18 of the pedestal is sandwiched and through which the pedestal hinge pin 20 passes, and an inverted spring housing 32 suspended 40 from a rear portion of the hanger and adapted to vertically receive the rubber spring 25. The flat upper surface 28 of each hanger is configured to be rigidly mounted to an under surface of spaced apart beams 33 forming part of a vehicle chassis 11 as shown in Figure 5.

- 5 The dimensions of the housing 32 and the rubber spring 25 are such that when the hanger is assembled, in the configuration shown in Figure 3 for example, the housing 32 does not contact with the upper surface 24 even when significant weight is placed on the upper hanger surface 28. 5 To this end, the skilled addressee would realise that the rubber spring 25 acts as a cushion and shock absorber. The spring rate can be adjusted by varying the height dimension of the housing 32, and maximum jounce can be adjusted by the restrictor bolt 34 extending through the centre of the spring, shown in Figure 2. 0 Each pedestal assembly further includes a lateral movement restrictor or end cap 36 suspended from the far rear end of each hanger 26 for housing the ends of the rearwardly extending portions 22 of each pedestal. The purpose of the restrictor 36 as the name suggests is to restrict lateral movement of each pedestal during use. In preference, the parts that contact between the lateral restrictor 36 and pedestal 26 are lined with hardened steel wear plates 38. In a preferred 5 embodiment, these wear plates will be constantly greased by the vehicle's auto greasing system (not shown). Each pedestal assembly 12 is thus hinged and sprung, that is, hinged at their front portions 18 to an underside of the vehicle chassis and sprung at their rear portions 22 by use of a rubber spring 0 25. The pedestal cross member 17 ensures that each of the assemblies move in unison. As mentioned in the preamble of the invention, prior art suspension systems involve rigidly welding each pedestal assembly to the vehicle chassis directly. On rough roads and/or at high speeds, such a rigid connection provides for poor shock absorption and low vehicle durability. It has been found that use of the hinged and sprung suspension of the present invention results in 5 improved shock absorption, which translates to improved driver comfort and improved vehicle durability. The use of rubber springs allows for the suspension to be installed to smaller size vehicle chassis', something which was previously not possible using air springs and the like which are 30 prohibitively large and more complex components. The rubber springs have a much higher load rating-to-size ratio than air bags and the like, so a much higher load rating can be achieved by the present invention without necessarily increasing its complexity. The lateral movement restrictor is also more space efficient and less complex than prior art means of controlling lateral movement, and importantly does not require any additional parts being added to the chassis. 35 This, combined with the fact that existing associated components can be used with the suspension, means the suspension can be easily retrofitted to existing vehicles in for example a fleet of vehicles by what is effectively just a replacement of each pedestal assembly. The invention uses the same walking beams and torque rods, and so also the same mounting brackets on the axle housings, as the prior art suspension shown in Figure 1. The skilled addressee would 40 understand the labour and cost benefits associated with this feature of the invention. Any additional component or aspect of the suspension 10 which the skilled addressee would - 6 understand as being known in the art has not been described in detail, including for example the inclusion of front and rear torque rods (not shown), and the means by which each pedestal connects with each walking beam. A description of those components has not been included for the purpose of brevity, but use of these components is considered to be within the scope of the 5 present invention. Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures 0 may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.

Claims (11)

1. A pedestal assembly for use in a suspension assembly for suspending a tandem wheel axle assembly from a vehicle chassis, said pedestal assembly including: 5 a longitudinally extending body including a lower portion with means of connection to a walking beam connecting two longitudinally spaced wheel axles of said tandem axle assembly, and a forwardly projecting portion and a rearwardly extending portion; and a hanger configured to be rigidly connected to an underside of said chassis, said hanger including a front portion with a means of hingedly suspending the forwardly projecting 0 portion of the pedestal body, and a rear portion which is springedly associated with the rearwardly extending portion of the pedestal body.

2. A pedestal assembly as in claim 1 wherein the means of hingedly suspending the forwardly projecting portion of the pedestal body is in the form of a locating lug pair between which said forwardly projecting portion is adapted to be received, each 5 component including coaxial apertures for receiving a hinge pin.

3. A pedestal assembly as in claim 1 wherein the rear portion of the pedestal body includes an upper surface adapted to support at least one elastomeric spring, and said rear hanger portion includes an inverted housing of stepped up dimension to that of the spring such that the spring is received in said housing and thereby supports the rear portion of the 0 hanger.

4. A pedestal assembly as in claim 1 wherein the rear portion of the pedestal body is also restricted from lateral movement using a restriction means.

5. A pedestal assembly as in claim 4 wherein the restriction means is in the form of an end cap configured to receive the end of said pedestal rear portion and thereby prevent lateral 25 movement thereof.

6. A pedestal assembly as in claim 1 as in claim 5 wherein the end cap and said rear portion include hardened steel wear plates at points of contact therebetween.

7. A pedestal assembly as in claim 3 wherein the elastomeric spring is a disc-shaped rubber spring.

- 8 8. A suspension for a vehicle chassis including two laterally spaced, longitudinally extending beams, wherein each beam includes a pedestal assembly suspended therefrom, each pedestal assembly being configured as in the claims above.

9. A suspension as in claim 8 wherein the spaced apart pedestal assemblies are connected 5 by a pedestal cross member.

10. A vehicle chassis including at least one suspension assembly as defined above.

11. A vehicle including at least one suspension assembly as defined above.