AU698121B2

AU698121B2 - Trailer suspension systems

Info

Publication number: AU698121B2
Application number: AU76060/94A
Authority: AU
Inventors: Edward Arthur Lord
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-09-02
Filing date: 1994-09-01
Publication date: 1998-10-22
Anticipated expiration: 2014-09-01
Also published as: AU7606094A

Description

1 PCT/AU 94-/ 005 1 1 RECEIVED 1 8 MAY 1995

TITLE

Trailer Suspension Systems FIELD OF THE INVENTION This invention relates to trailer suspension systems and in particular relates to suspensions for use in off road trailers.

DISCUSSION OF PRIOR ART Trailers that are towed by domestic vehicles conventionally comprise a frame that supports a pair of wheels carried by an axle which is in turn supported I against the frame via a suspension usually in the form of a leaf spring. In some cases, larger trailers have tandem axles whereby the axles are spaced apart so that there are {I a pair of longitudinally spaced wheels on each side of the I 15 trailer. Whilst the suspension of such trailers may be adequate for on road use, these trailers have proved very unsuitable for off road usage. With the improvement in off road four wheel drive vehicles, there is a growing cdmand for trailers that provide performance that matches that of I 20 the off road vehicle.

It is the problems with conventional trailers when used in an off road environment that has brought about the present invention.

SUMMARY OF INVENTION According to one aspect of the present invention there is provided a tandem wheel trailer for off road use comprising: a trailer main frame, a pair of suspension wheei sets attached spaced Kc^c\TO^, AMENDED SHEET

IPEA/AU

2 apart to each side of the trailer main frame, each suspension wheel set comprising a suspension subset pivotally secured to the main frame of the trailer, each subset comprising a triangular member defining three corners, the first corner supporting an outwardly projecting stub axle which supports a wheel and tyre for axial rotation, a second corner being pivotally secured to the main frame, and the third corner being attached to one end of compliant means, the other end of the compliant means being secured to the third corner of the triangular member of the adjacent subset so that the compliant means is in the same vertical plane as the plane containing the wheels, whereby the suspension wheel sets do not reduce the S"effective ground clearance of the trailer and each wheel is 15 independently pivotable about the main frame but pivotal i movement of adjacent wheels is controlled by the compliant means interconnecting adjacent subsets.

Preferably, each compliant means comprises a coil spring.

20 It is understood that the invention relates to a 'cc c trailer with the suspension system described above, a Cf t' suspension system for attachment to an existing trailer and a kit of components that can be used to adapt an existing trailer to incorporate a suspension system for off road and 25 on road use.

DESCRIPTION OF DRAWINGS An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the frame of a trailer illtstrating the suspension assembly of the subject invention, Figure 2 is a schematic side elevation showing the association of a pair of suspension subsets of the suspension assembly, H:\Susan\Keep\peci\76060 94 1ST.doc 14/09/98 '3N o WO 95/06570 PCT/AU94/00511 -3 Figure 3 is a schematic view similar to Figure 2 but showing the suspension assembly with one wheel lifted higher than the other wheel, Figure 4 is an end elevational view showing one wheel of the trailer and the mounting of the associated subset to the trailer frame, Fi=,ires 5A and 5B are plan and side elevational views of the trailer frame, Figures 6A, 6B and 6C are respectivelj side and end elevational views of a sub-frame member that forms part of the suspension subset.

DESCRIPTION OF PREFERRED EMBODIMENT The accompanying drawings illustrate a tandem wheel trailer that is specifically designed for use off road. The trailer comprises a main frame 10 fabricated from structural sections that are welded or bolted together to form a skeletal outline of the kind shown in Figures I and 5B. As shown in Figure 1, the trailer carries a pair of wheels 11 and 12 spaced apart on each side at approximately the middle of the load bearing span of the trailer. The wheels are supported for axial rotation about a suspension assembly 30 mounted on each side of the trailer. The wheels and the suspension assembly are supported by a transversely extending reinforced cross-beam 20 that is centrally positioned across the load bearing I portion of the trailer as shown in Figures 5A and J ;The suspension assembly 30 on each side of the trailer is identical and thus a single side is described hereunder. As shown in Figures 1 and 2, the suspension assembly 30 comprises a pair of suspension subsets 31 and 32, each of which is pivotally secured to the frame 10 of the trailer and each of which supports for axial rotation a tyre and wheel assembly 11 and 12. The suspension subsets 31 and 32 are interconnected by a coil spring 33. Each suspension subset comprises a triangular sub-frame 35 of square section metal tube welded together to provide sides L t~ _e eFL_ lil. I~CII~ II e a-i SWO 95/06570 PCT/AU94/00511 36, 37 and 38. The triangle has three corners, the first corner comprises the mounting point 40 at which the subframe 35 is attached to the frame 10 of the trailer, the second corner 41 carries a stub axle 45 on which the tyre and wheel assembly 11 or 12 is mounted and the third corner 42 includes a projecting shaft 46 on which one end of the coil spring 33 is pivotally secured.

The mechanism by which the sub-frame 35 is pivotally secured to the main frame 10 of the trailer is shown in greater detail in Figure 4. A pair of spaced gusset plates 50 and 51 are welded transversely to the 1 reinforced cross-beam 20 and the gusset plates have two pairs of axially aligned apertures 52 and 53 through which solid steel shafts 54 and 55 are located in a parallel spaced apart array. The shafts 54 and 55 are welded to both the underside of the beam 20 and to the gusset plates and 51 as shown in Figure 4. Each solid steel shaft 54 v( or 55 projects outwardly of the side of the trailer and is arranged to support in a sliding manner thereon a steel cylindrical sleeve 60 that rotates about spaced nylon bearings 61 and 62. The sleeve 60 is in turn welded to the sides 36 and 38 of the sub-frame 35. A circlip 63 or other end fastener ensures that the outer sleeve 60 does not slide axially off the solid steel shaft 54. This arrangement ensures a very robust means of securing the sub-frames 35 to the main frame 10 of the trailer whilst allowing the sub-frames 35 to pivot about the axis of the projecting shafts 54 and 55. The stepped shaft 46 extends through both the sides 36 and 37 of the sub-frame 35 to project outwardly to locate a sleeve 70 which is attached to the coil spring 33. The end sleeve is held on by a circlip, not shown. The sleeve 70 forms part of a cylindrical end piece 72 which has its axis extending mutually perpendicular to the end sleeve 70. The end piece 72 extends into the first few coils of the coil spring 33 I to locate hat end of the coil spring. A similar arrangement is used to mount the other end of the coil r3j.

WO 95/06570 PCT/AU94/00511 spring 33 to the adjacent corner of the other sub-frame Figures 6A, 6B 6C show the sub-frame 35 in further detail. Figure 6B shows the side 36 with the projecting stepped shaft 46 for location of the coil spring 33.

Figure 6C shows the other side 37 with the stepped stub axle 45 which is designed to support a drum brake assembly, and a hub which rotates about roller bearings (not shown).

The tyre and wheel assembly is bolted to the hub in the conventional mannei. Since the mounting of the tyre and wheel assembly on a stub axle is well known to those skilled in this art, this aspect of the assembly is not described in detail herein.

When the laden trailer is used on a horizontal surface the suspension subsets and tyre and wheel assemblies assume the position as shown in Figure 2. The fact that each wheel is rotating about an axis that is laterally displaced from the mounting point of the subframe allows the wheel to move vertically as the trailer rides over bumps with the sub-frame pivoting about the main frame. Since the sub-frames are interconnected through the coil spring, the coil spring acts as a suspension means to absorb the upward forces that would otherwise be placed on the trailer as it rides over bumps. The suspension has a capacity to handle quite severe bumps as can be seen with reference to Figure 3 where one wheel 11 has been lifted a considerable distance off the ground whilst the sub-frame associated with that wheel pivots upwardly. It should be noted that the other wheel 12 always remains on the ground which means that the danger of lift off is substantially reduced, and load sharing retained.

Whilst the coil spring is used in a preferred embodiment to absorb the forces caused by vertical movement of the wheels, it is understood that the invention contemplates the use of other shock absorbing means such as pneumatic or hydraulic dampers, solid rubber blocks or other known spring mechanisms. It is further understood that additional damping may be provided by connecting pneumatic or hydraulic shock absorbers between one of the vertically extending sides of each sub-frame and the adjacent part of the main frame of the trailer.

Although the preferred embodiment has the suspension subsets mounted on laterally projecting shafts 54, 55 it is understood that each subset could include an inwardly projecting shaft which would locate in a cylindrical sleeve attached to the frame :f the trailer.

The suspension system and in particular the trailer described above has a number of advantages over existing trailer assemblies. The trailer has tandem wheels on each side mounted on stub axles. This means that there is no axle (or axles) extending across the trailer which reduces the ground clearance. The suspension that connects the wheels on each side of a trailer acts independently and each wheel is able to ride vertically relative to the adjacent wheel. There is no use of leaf springs that have a tendency of binding to act as a solid unit. The provision of a tandem trailer allows load sharing between the wheels and improves the mobility of the trailer especially vhen used off road. The suspension system allows for greater suspension travel and articulation without affecting the tray height of the trailer. When fully ladened, the suspension provides complete load sharing. When compared to conventional technology, the trailer of the subject invention with its load sharing suspension provides greater wheel travel, a softer suspension, reduced suspension friction, no roll steer and improved ground clearance. A tandem trailer when fitted with a suspension described above has improved stability over conventional load sharing tandem trailers. This is due to the softer suspension and the ability of this suspension to absorb impact loads over rough terrain.

W

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Claims

1. A tandem wheel trailer for off road use comprising: a trailer main frame, a pair of suspension wheel sets attached spaced apart to each side of the trailer main frame, each suspension wheel set comprising a suspension subset pivotally secured to the main frame of -he trailer, each subset comprising a triangular member defining three corners, the first corner supporting an outwardly projecting stub axle which supports a wheel and tyre for S" axial rotation, a second corner being pivotally secured to the main frame, and the third corner being attached to one end of compliant means, the other end of the compliant means being secured to the third corner of the triangular member of the adjacent subset so that the compliant means Sis in the same vertical plane as the plane containing the e wheels, whereby the suspension wheel sets do not reduce the 'et 20 effective ground clearance of the trailer and each wheel is independently pivotable about the main frame but pivotal t, movement of adjacent wheels is controlled by the compliant means interconnecting adjacent subsets. 25

2. The trailer according to claim 1 wherein each compliant means comprises a coil spring.

3. The trailer according to either claim 1 or claim 2 wherein the second corner of each triangular member is secured to the main frame by location of a shaft in a cylindrical sleeve, the shaft and cylindrical sleeve being carried by either the second corner of the member or the main frame of the trailer. 1 35 4. The trailer according to any one of the preceding claims wherein the trailer main frame comprises elongate side beams interconnected by spaced apart cross-beams, the j I H!\Suaan\Keep\Bpecl\76060 94 1ST.doc 14/09/98 I km 4 i;i r ;i: 8 suspension wheel sets being pivotally secured to the elongate side beams via support members secured to the elongate side beams to be in close proximity, the pivotal axes of the subsets being below the longitudinal plane of the side beams. The trailer according to claim 4 wherein the support members for the suspension subsets are interconnected by a transversely extending beam that is below the level of the cross-beams.

4 I *tir r. C I *14 t 44 44 Dated this 14th day of September 1998. EDWARD ARTHUR LORD By His Patent Attorneys GRIFFITH HACK Fellows Institute of Patent Attorneys of Australia :yi H1\SUoan\Keep\spOci\76060 94 1ST.doc 14/09/98 L i -4