GB2565810A

GB2565810A - A vehicle trailer

Info

Publication number: GB2565810A
Application number: GB1713564.1A
Authority: GB
Inventors: Graham Ecob Christopher
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-08-23
Filing date: 2017-08-23
Publication date: 2019-02-27
Also published as: GB201713564D0

Abstract

A trailer (102) adapted to be towed by a vehicle (101), the trailer comprising a rigid frame (201) comprising at least one elongate central frame member (202) extending along an axis (X) extending lengthwise centrally or near-centrally widthwise of the trailer. The rigid frame further comprises a pair of outrigger portions (203-206) rigidly connected to either of the at least one central frame member and each extending outwardly therefrom in opposing directions; a pair of suspension arms (206-209) hingedly connected to either of the at least one elongate central frame member, and each extending outwardly therefrom, in opposing directions; a pair of wheel hub assemblies (210- 213) associated with said pair of suspension arms, the wheel hub assemblies of said pair being mounted to said suspension arms, each of said wheel hub assemblies being suitable for carrying a ground engaging wheel; and a pair of compressible suspension units (214-217), each pair of suspension units arranged to contact one of the suspension arms and one of the outrigger portions and extend therebetween.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a trailer adapted to be towed by a vehicle, and more particularly to an agricultural trailer adapted to be towed by an agricultural vehicle.

2. Description of the Related Art

Vehicle trailers typically comprise a flat ‘bed’ having an upper surface suitable for carrying a load, a rigid chassis, and at least one sprung axle or equivalent arrangement carrying ground engaging w heels.

Commonly the chassis is of a 'ladder¹ type construction, referred to as a ‘ladder’ chassis, comprising a pair of outermost rails rigidly joined by multiple cross members. The chassis will often be provided with a ‘beam’ type axle, in which a rigid, typically tubular, axle is arranged transversely of the chassis with a ground engaging wheel rotatably mounted at either end. As an alternative, the chassis may be equipped with a pair, or more, of independent axle stubs each fitted with a rotatable ground-engaging wheel.

In the majority of applications it is desirable that the axle is sprung relative to the chassis. Thus, the axle must be movably mounted to the trailer chassis. In the case of a ‘beam’ type axle, commonly the axle may be connected to the chassis by way only of a pair of compressible suspension members, such a leaf springs, in which arrangement the suspension member serves the joint purpose of providing suspension and mechanically coupling the axle to the trailer. An alternative configuration, more commonly used in the case of a pair of independent axle stubs, the axle pair may be mounted to one of a pair of suspension arms hingedly connected to the outer rails of the chassis, each arm provided with a suspension member controlling the movement of the suspension arm relative to the chassis. The former arrangement may be preferred for its relative simplicity and potential increase in load carrying ability, whilst the latter arrangement may allow for improved suspension characteristics.

In the case of the second above noted axle arrangement, i.e the instance in which the axle pair are mechanically coupled to the chassis by way of hingedly connected suspension arms, the suspension arms are commonly configured as ‘trailing’ arms.'ln the ‘trailing’ arm. configuration each suspension arm is hingedly connected to a respective outer chassis rail about a hinge axis extending transversely of the chassis,. and the arm is arranged to ‘trail’ downwardly and rearwardly from the hinge point, with the axle rigidly coupled adjacent the distal end of the suspension arm. A suspension unit is usually provided extending between the ’trailing’ suspension arm and the respective chassis rail. A variety of different suspension units are commonly used for such an application. The suspension units may generally be categorised as ‘passive’, such as a helical coil spring or a leaf spring, or may be ‘active’, such as an ‘air-bag’ cushion or hydraulic strut.

One advantage of the ‘trailing arm’ type suspension arrangement is its suitability for attachment to a ‘ladder¹ type chassis, as the suspension arm generally extends directly downwardly and rearwardly of the outer chassis rail, rather than outwardly of the chassis, thereby minimising the width added to the chassis by the axle. Furthermore, because the suspension arm extends rearwardly, and not outwardly, of the chassis outer rail, a suspension unit may be conveniently arranged to extend between the distal end of the suspension arm and the outer chassis rail. Moreover, the ‘trailing arm’ suspension arrangement, when supporting the load of the trailer, exerts a torque on the outer chassis rails that is orthogonal to their length, which allows a lighter/weaker construction of the outer rails and cross/member than might be permissible if the outer rails were subjected to a torque applied parallel to their length.

As will be appreciated, in many applications the primary demands of a trailer are simplicity of construction, and maximisation of the dimension of the load bed and load mass capability, which factors may often be prioritised over, for example, handling characteristics and driving performance. Given these primary requirements, it is understood that the above noted advantages are among the reasons for the ‘trailing arm' type suspension arrangement being a particularly common vehicle trailer suspension configuration.

However, in many applications ‘trailing arm’ type suspension arrangements may not provide optimum trailer handling characteristics. A particular disadvantage of a trailing arm type suspension arrangement is when a trailer is required to carry a load having a relatively high centre of mass, and more particularly where a trailer is required to carry a load over an uneven ground surface and/or at speed. Agricultural trailers in particular, such as those adapted to be towed by an agricultural tractor unit, will often be required to carry such a ‘top-heavy’ load over an uneven surface. In these environments a trailer having a ‘trailing arm’ type suspension configuration can be prone to excessive sidewards lean, or even sidewards tipping, of the trailer.

Accordingly, it is desirable to provide a trailer having an alternative suspension arrangement, such that the trailer may be less prone to ‘lean’ or ‘tipping’ when carrying a ‘top-heavy’ load, and/or when carrying a load over uneven ground.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a trailer adapted to be towed by a vehicle, the trailer comprising: a rigid frame comprising at least one elongate central frame member extending lengthwise of the trailer along an axis extending lengthwise centrally or near-centrally widthwise of the trailer, the rigid frame further comprising a pair of outrigger portions rigidly connected at respective inner ends to either of said at least one central frame member and each extending outwardly therefrom, widthwise of the trailer, in opposing directions towards respective outer ends; a pair of suspension arms hingedly connected at respective inner ends thereof to either of said at least one elongate central frame member, and each extending outwardly therefrom, widthwise of the trailer, in opposing directions towards respective outer ends; a pair of wheel hub assemblies associated with said pair of suspension arms, the wheel hub assemblies of said⁵ pair being mounted to respective outer ends of said suspension arms, each of said wheel hub assemblies being suitable for carrying a ground engaging wheel; and a pair of compressible suspension units, each of said pair of suspension units arranged to contact one of said suspension arms and one of said outrigger portions and extend therebetween.

A benefit of this ‘wishbone’ type suspension arrangement, in which the suspension arms extend outwardly widthwise of the trailer, is that the trailer will tend to be more stable in use, and particularly when used to carry a ‘top-heavy’ load over an uneven ground surface, as compared to trailers of the prior art incorporating conventional ‘trailing arm’ type suspension arrangements.

Moreover, as the suspension arm pair are connected to a central or near central frame member, the suspension arm may be relatively longer for any given trailer width than would be possible in the event that the suspension arms were connected to the chassis of the trailer at a position other than centrally or near centrally. This increased length of the suspension arms, and their connection to the chassis centrally or near centrally widthwise of the trailer, allows for improved suspension characteristics.

Preferably, said rigid frame comprises one elongate central frame member extending approximately centrally widthwise of the trailer, and wherein said pair of outrigger portions being rigidly connected at respective inner ends to said elongate central frame member and each extending outwardly therefrom, and wherein said pair of suspension arms are hingedly connected at respective inner ends thereof to said elongate central frame member, and each extending outwardly therefrom, widthwise of the trailer, in opposing directions towards respective outer ends.

A benefit of this arrangement, and in particular the central frame member common to said pair of outrigger portions and said pair of suspension arms, is a relatively simpler construction.

Preferably, each said wheel hub is rigidly mounted to a respective suspension arm.

A benefit of this arrangement is simplicity of construction. A further benefit of this arrangement is that the height-wise space occupied by the suspension arm throughout its travel is lesser than would be required in the event the wheel hub were mounted to the suspension arm non-rigidly, in which instance a further heightwise spaced suspension arm or control arm would be required to maintain the alignment of the wheel hub.

Preferably, said trailer further comprises a pair of ground engaging wheels mounted to respective wheel hubs.

Preferably, each said ground engaging w heel is fitted with a pneumatic tyre.

Preferably, each of said suspension arms is hingedly connected to said at least one elongate central frame member about a hinge axis extending lengthwise of said trailer.

Preferably, each of said pair of compressible suspension units comprises a shock absorbing or dissipating device.

Preferably, each of said pair of compressible suspension units is arranged to extend between one of said suspension arms and one of said outrigger portions adapted to connect a suspension arm to a respective outrigger portion in a way such that movement of said suspension arm about said hinged connection causes said compressible suspension unit to be compressed between a respective said suspension arm and outrigger portion.

Preferably, each of said suspension units is arranged to contact a respective suspension arm at a position proximal its outer end, and to contact a respective outrigger portion at a position proximal its outer end. This arrangement may allow for improved suspension characteristics.

Preferably, said at least one elongate central frame member defines a generally planar upper surface and a generally planar under surface.

Preferably, said pair of suspension arms are hingedly connected at respective inner ends thereof to said under surface of said central frame member.

Preferably, said elongate central frame member comprises bracket portions extending downwardly from said under surface, and wherein said pair of suspension arms are hingedly connected at respective inner ends thereof to said bracket portions.

Preferably, said outrigger portions define a generally planar portion having a generally planar upper surface arranged to extend substantially in the plane of said upper surface of said central frame member, and further defining a lower surface.

Preferably, each said suspension unit is arranged to contact said lower surface .of a respective outrigger portion.

Preferably, each said suspension unit compresses an axially elongated unit compressible axially.

Preferably, each said suspension unit is mechanically coupled at a first end to a respective outrigger portion and mechanically coupled at a second end to a respective suspension arm.

Preferably, each said suspension unit is mechanically coupled at a first end to said lower surface of a respective outrigger portion and mechanically coupled at a second end to a respective suspension arm.

Preferably, each said suspension unit comprises a resiliently compressible spring unit.

Preferably, each said compressible spring unit comprises a resiliently compressible coiled suspension spring.

Preferably, each said suspension unit further comprises a shock absorbing unit.

Preferably, each said shock absorbing unit is a mechanical linear actuator damper comprising a cylinder and piston assembly.

Preferably, said at least one elongate central frame member is provided at a first end with a tow hitch fixture suitable for mechanically coupling the trailer to a tow hitch fixture of a towing vehicle.

Preferably, said trailer is an agricultural trailer adapted to be towed by an agricultural vehicle.

Preferably; said trailer is an agricultural tractor trailer adapted to be towed by an agricultural tractor.

Preferably said trailer is adapted to be towed by a motorised vehicle.

According to a second aspect of the present invention there is provided an agricultural vehicle comprising a tow hitch fixture and comprising a trailer as claimed in any of the above statements mechanically coupled to said tow hitch fixture.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only with reference to the accompanying drawings, which are purely schematic and not to scale, of which:

Figure 1 illustrates an environment in which a vehicle and a vehicle trailer according to an embodiment of the present invention may be used;

Figures 2a, 2b, 2c & 2d, show the vehicle trailer previously identified in Figure 1 in isolation in top plan, bottom plan, side elevation, and rear elevation views respectively. In Figure 2e the trailer is shown in top plan view with the wheels removed;

Figures 3a, 3b, 3c, 3d & 3e, show the first axle assembly of the trailer 102 in a series of close-up views. In Figure 3a the first axle assembly is shown in a top plan view, in a bottom plan view in Figure 3b, in a side elevation view in Figure 3c, in a front elevation view in Figure 3d, and in a rear elevatio n view in Figure 3e.

Figure 4 shows the axle assembly and outrigger portion of the trailer in a side elevation partial cross-sectional view.

Figures 5a, 5b, 5c, 5d & 5e show a suspension arm of the trailer in isolation in top plan, bottom plan, front elevation, side elevation, and end elevation views respectively.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Figure 1

A Vehicle 101 and vehicle trailer 102 according to one embodiment of the present invention are shown schematically in a side elevation view in Figure 1.

In the specific embodiment described herein the vehicle 101 is an agricultural tractor, and the trailer 102 is an agricultural trailer adapted to be towed by the tractor 101. As will be appreciated, agricultural trailers such as trailer 102 may often be required to carry relatively heavy loads of bulk materials, typically over rough ground. Agricultural trailers of the type typically then have a relatively sturdier construction than a trailer intended solely for on-road use, and are usually equipped with ground engaging wheels fitted with high profile pneumatic tyres defining deep tread grooves, and with long-travel suspension. In the specific embodiment, said trailer 102 is constructed so as to be capable of carrying a load in the range of one to twenty tonnes and, as will be described, comprises a sturdy construction, ‘offroad’ tyres, and relatively long suspension travel.

As illustrated, in the embodiment said trailer 102 comprises a longitudinally elongated chassis 103, having at a first lengthwise end a tow hitch fixture 104 suitable for mechanically coupling the trailer 102 to the towing vehicle 101, and at a second end a bumper bar 105, which bumper bar 105 may, in embodiments, carry a further tow hitch fixture or a power take-off spur for example. A pair of wheeled ‘axle assemblies’ 106, 107 are provided proximal the second end of the trailer 102, attached by way of a suspension arm arrangement (as will be described further with reference to later figures). As will be described, an upper surface 108 of said chassis 103 defines a load bed on which a load may be carried.

Figures 2a, 2b, 2c, 2d & 2e

The trailer 102 previously identified with reference to Figure 1 is shown detached from the vehicle 101, in Figures 2a, 2b, 2c & 2d in top plan, bottom plan, side elevation, and rear elevation views respectively. In Figure 2e the trailer is shown in a top plan view with the wheels removed.

Referring to the Figures, in the embodiment said trailer 102 comprises principally of a chassis equipped with a pair of wheel carrying ‘axle assemblies'. It will be appreciated that the term ‘axle’ may typically be used to describe a unitary shaft carrying a pair of wheels. As will be described however, the wheels of trailer 102 are each freely rotatably mounted on a shaft that is entirely independent of the shaft of any other wheel. Thus, the term ‘axle’ as used in this specification is intended to define simply a pair of wheels and associated axle/suspension components that are aligned along a common transverse axis of the trailer as if mounted to a common ‘axle’.

The chassis 103 of trailer 102 comprises a rigid frame, indicated generally at 201, the frame 201 being comprised principally of a single elongate central frame member 202, and a plurality of outrigger portions 203 to 206. As will be described, the chassis further comprises suspension arms 206 to 209, wheel hub assemblies 210 to 213, and suspension assemblies 214 to 217.

As illustrated, said elongate central frame member 202 is arranged to extend lengthwise substantially the full length of the trailer along an axis X extending lengthwise of the trailer approximately centrally width-wise of the trailer. Thus, said central frame member 202 acts generally as a central ‘spine’ to the trailer, to which the various ‘axle assembly’ components are mounted, and which provides the longitudinal and torsional rigidity to the trailer 102.

Referring to the Figures, in the embodiment, said elongate central frame member 202 defines a generally planar upper surface 218 and a generally planar lower surface 219. As previously described, a tow hitch fixture 104 is securely fitted to a first end of said central frame member 202 to facilitate mechanical coupling of said trailer to a towing vehicle.

Said rigid frame 201 further comprises first and second pairs of outrigger portions 203, 204 & 205, 206 rigidly connected at respective inner ends to said elongate frame member 202 and each extending outwardly therefrom, widthwise of the trailer, in opposing directions towards respective outer ends. As will be described, the purpose of said outrigger portion pairs is to support an upper end of a suspension assembly connected to a wheel carrying suspension arm. Thus, in the embodiment, said first outrigger portion pair 203, 204 extend in opposing directions along a common axis extending transversely of the trailer and aligned with the axis of said first axle assembly 106, and said second outrigger portion pair 205, 206 extend in opposing directions along a common axis extending transversely of the trailer and aligned with the axis of said second axle assembly 107.

Said trailer 102 further comprises two, substantially like, pairs of suspension arms, 206, 207 & 208, 209. Each of said suspension arms is hingedly connected at a respective inner end to said elongate central frame member 202 by way of a hinge pin, which hinge pins define a hinge axis extending lengthwise of said trailer about which the suspension arm may pivot. Each suspension arm extends outwardly from its inner end attached to said central frame member, width-wise of the trailer, generally along an axis common to the other suspension arm of that pair and in an opposing direction to the other suspension arm of the pair, towards an outer end.

As previously described, each of said suspension arm pairs 206, 207 and 208, 209, are arranged such that the suspension arms in a pair extend outwardly from the central frame member 202 in opposing directions along a common axis. Moreover, as illustrated, each suspension arm pair is aligned with an outrigger portion pair, 203, 204 & 205, 206, such that an outrigger portion extends above and along the same axis as a suspension arm defining an outrigger portion/suspension arm pair. Thus, as illustrated, said outrigger portion 203 is aligned directly above and extending along the same axis as suspension arm 206, outrigger portion 204 is aligned directly above and extending along the same axis as suspension arm 207, outrigger portion 205 is aligned directly above and extending along the same axis as suspension arm 208, and outrigger portion 206 is aligned directly above and extending along the same axis as suspension arm 209.

Chassis 102 further comprises a plurality of compressible suspension assemblies 214 to 217, each assembly arranged to extend between and connect a suspension arm and its respective outrigger portion. As will be understood, each suspension assembly extends between a suspension arm and its respective outrigger portion, to operatively connect the suspension arm to the respective outrigger portion in a way such that movement of the suspension arm about its hinged connection to said central frame member 202 causes said compressible suspension assembly to be compressed between the suspension arm and the outrigger portion, to thereby allow the movement of each suspension arm about its hinge axis to be controlled by the suspension assembly.

Figures 3a, 3b, 3c, 3d &3e

The ‘axle assembly’ 106 of said trailer 102 is shown in a series of close-up views in the Figures. In Figure 3a the axle assembly 106 is shown in a top plan view, in a bottom plan view in Figure 3b, in a side elevation view in Figure 3c, in a front elevation view in Figure 3d, and in a rear elevation view in Figure 3e.

As previously described, in the specific embodiment of the invention, described in detail herein, trailer 102 comprises first and second ‘axle assemblies’ 106 and 107. As previously noted, in the embodiment the term ‘axle assembly’ is used herein to denote a pair of wheels and associated axle/suspension components that are aligned along a common transverse axis of the trailer as if mounted to a common ‘axle’. In this respect, it will be appreciated that references herein to a ‘first axle assembly 106’ or similar are references to suspension arm pair 206, 207, suspension assembly pair 214, 215, wheel hub assembly pair 210, 211, and wheel pair 224, which components extend generally along a common first transverse axis. Similarly, references to a ‘second axle assembly 107’ or similar are references to suspension arm pair 208, 209, suspension assembly pair 216, 217, wheel hub assembly pair 212, 213, and wheel pair 224, which components extend generally along a common second transverse axis.

Moreover, as will be observed in the Figures, in the embodiment the construction of said first axle assembly 106 is substantially identical to the construction of said second axle assembly 107. For brevity then only the construction of said first axle assembly 106 (i.e. suspension arm pair 206, 207, suspension assembly pair 214, 215, wheel hub assembly pair 210, 211, and wheel pair 224) will be described in detail herein with reference to Figures 3a to 3e. It should be understood however that, given the construction of said second axle 107 is substantially identical to that of said first axle 106, the description herein of the construction and configuration of the first axle assembly 106 is equally instructive of the construction and operation of the second axle assembly 107.

Referring in particular to Figure 3b, it can be seen that in the specific embodiment said elongate central frame member 202 further comprises a plurality of bracket portions 301. Said bracket portions 301 are formed of rigid planar metal sheet sections rigidly joined to said central frame member 202 by welding, and arranged to extend downwardly of the lower surface 219 of the central frame member 202.

In the specific embodiment said suspension arms 206 and 207 are hingedly joined to said bracket portions 301 by way of hinge pins 302. Hinge pins 302 extend through apertures formed in the bracket portions 301, and through round tubular sections provided at the inner ends of the suspension arms 206, 207, and extend longitudinally of the trailer 102, along hinge axes 303, 304 respectively. Hinge axes 303, 304, extend lengthwise of the trailer 102, generally parallel and .adjacent to the central axis X. As will be understood, said suspension arms 206, 207 may hingedly rotate about said hinge axes 303, 304 respectively.

As previously described, each of said suspension arms 206 to 209 is provided with a suspension assembly 214 to 217 extending between the arm and its associated outrigger portion 203 to 206 respectively. As will be understood, the suspension assembly controls the movement of each suspension arm relative to a respective outrigger portion by mechanically coupling the suspension arm, which suspension arm is hingedly connected to the elongate central frame member 202, to the outrigger portion, which outrigger portion is rigidly connected to the elongate central frame member 202.

In the specific embodiment each suspension assembly 214 to 217 comprises two suspension units, a first unit being a shock absorber unit in the form of a piston/cylinder mechanical damper, and a second unit being a helical coiled spring unit. In the specific embodiment, as will be described, the shock absorber unit and spring unit of each suspension assembly are mutually separate components, being adapted for connection to a suspension arm and its respective outrigger portion at mutually different locations. Of course, in alternative embodiments the spring unit and shock absorber unit could be combined into a unitary component fixed to an outrigger portion and a sus pension arm at common fixing points.

Thus, referring in particular to Figures 3d and 3e, a first suspension assembly 214, comprising a coiled spring unit 305 and a shock absorber unit 306, is provided extending between said suspension arm 206 and said outrigger portion 203.

Said coiled spring unit 305 is arranged to contact at a first end said outrigger portion 203 at a position offset from the axis X of said central frame member 202, more particularly generally proximal the outer end of the outrigger portion 203, and to contact at a second end the suspension arm 206 at a position offset from the axis X of said central frame member 202, more particularly generally proximal the outer end of the suspension arm 206. Moreover, in the specific embodiment, said coiled spring 305 is mechanically coupled at a first end to said outrigger portion 203, and mechanically coupled at a second end to said suspension arm 206. The mechanical coupling between the ends of spring unit 305 and the outrigger portion 203 and suspension arm 206 advantageously maintains the desired alignment of the spring unit relative to the outrigger portion and suspension arm in use.

In the embodiment, said shock absorbing unit 306 takes the form of a conventional mechanical linear damper, comprising a piston that reciprocates within an oil filled cylinder. A first end of said damper 306 is mechanically connected to a fixing point 307 on said outrigger portion 203 proximal its inner end, and a second end of the damper 306 is mechanically connected to a fixing spigot 308 on the suspension arm 206.

Thus, as will be appreciated, said coil spring unit 305 and said shock absorber unit 306 are arranged to be compressed between said suspension arm 206 and said outrigger portion 203 on upwardly hinged movement of said suspension arm 206 about said hinge pin 302 relative to said outrigger portion 203. In this respect, as will be understood, the principle purpose of said coiled suspension spring unit 305 is to movably bias the suspension arm 206 downwardly of the outrigger portion 203, so as to support the mass of the trailer and load above the ground surface. Further, as will be apparent, the primary function of each said damper unit 306 is to control the hinged movement of the respective suspension arm relative to said rigid frame 201 by damping the movement of the suspension arm.

As illustrated, a substantially identical suspension assembly is provided to each suspension arm and outrigger portion pair. Thus, a further coiled spring unit 309 and shock absorber unit 310 pair are provided mechanically connected to and extending between said outrigger portion 204 and said suspension arm 207. Similarly, the outrigger portion 205 and suspension arm 208, and outrigger portion 206 and suspension arm 209 of said second axle 107 are provided with coil spring and damper units extending therebetween. It will thus be appreciated that each suspension arm 206 to 209 may move about its hinge axis independently of the movement of any other of said suspension arms.

As illustrated, a wheel hub assembly 210, 211, is rotatably mounted at an outer end of each suspension arm 206, 207, to which wheel hub a ground engaging wheel 224 fitted with a pneumatic tyre is mounted. In the embodiment, each wheel hub assembly 210, 211 comprises generally of an outer drum part 311, defining a plurality of threaded studs 312, and an inner roller bearing assembly (roller bearing assembly not visible in the Figures). The roller bearing assembly of each wheel hub assembly permits, the outer drum part 311 of each said wheel hub assembly to rotate freely relative to the respective suspension arm. As is conventional, a wheel 224 may then be mounted to the outer drum part 311 by way of passing threaded studs 312 through corresponding apertures defining in the wheel centre. As will be described further with particular reference to Figures 5a to 5e, each wheel hub assembly 210, 211 is rigidly mounted to a respective suspension arm 20, 207, such that the outer drum part 311 of each said wheel hub assembly may rotate freely relative to the suspension arm, but such that the outer drum part 311 may not pivot relative to the suspension arm.

As described, in the specific embodiment, said trailer 102 is configured as an agricultural trailer, and is thus intended for carrying of relatively heavy loads, Thus, in the embodiment, the components of said frame are formed of relatively thicksection metal. In the embodiment, said central frame member 202 is formed of a square tubular steel having a wall thickness of approx. 10 millimetre, whist each of said outrigger portions 203, 206 is formed of shaped 10mm thick sheet steel welded to the exterior of the central frame member at their inner ends. Equally, said suspension arms 206 to 209 are, in the embodiment, formed of square tubular steel section of 10 mm wall thickness. It will of course be appreciated however that the construction of the trailer 102, and in particular the choice of materials from which the chassis 103 is constructed, will depend on the intended application of the trailer. As an example, in an alternative embodiment, for example a trailer intended for carrying relatively lighter loads, the chassis may be formed of relatively thinner sections of aluminium metal, or even plastic or composite materials. Indeed, in an alternative embodiment, the invention embodies a commercial road-going trailer, which trailer may typically be used for carriage of goods by road. In such an alternative embodiment numerous, relatively minor, modifications and alterations may be effected to the trailer 102 in order to optimise the trailer for the on-road environment.

Moreover, it will of course be appreciated that numerous different modifications to the particular form of the various components of the chassis 103 may be effected to optimise the trailer in dependence on its intended application and functionality. In particular, the specific embodiment of the invention described in detail herein employs suspension assemblies, extending between each suspension arm and outrigger portion pair, each assembly comprising a coiled suspension spring unit and a piston/cylinder mechanical shock absorber unit. It will of course be appreciate however that numerous difference suspension set-ups will adequately perform the task of controlling the movement of the suspension arms 206 to 209 of the chassis. For example, in a particular alternative embodiment, the suspension assembly provided to each suspension arm and outrigger portion pair may consist only of a coiled suspension spring unit, like spring units 305, 309. In further alternative examples, either of the coiled spring units 305, 309 and/or the shock absorber units 306, 310 may be replaced with, for example, leaf spring units, air-bag units, hydraulic ram units, or friction disc dampers. In this respect it will be appreciated that the primary purpose of the suspension assembly of each suspension arm and outrigger portion pair is to advantageously control the movement of the suspension arm relative to the respective outrigger portion and the central frame member 202 of the chassis, and that numerous different suspension mechanisms may be deployed to achieve the required degree and function of suspension control.

Furthermore, as illustrated, in the particular embodiment said trailer 102 is a ‘twin-axle’ type trailer, comprising two ‘axle assemblies’ each carrying ground engaging wheels. Thus, in the embodiment, and as described, trailer 102 comprises two (substantially like) ‘axle assemblies’ 106 and 107. It will of course be appreciated however that in an alternative embodiment, and particularly in the instance that the trailer were intended for carrying of relatively lighter loads, the trailer could be equipped with only a single ‘axle assembly’. Indeed, further alternative embodiments of the invention may be equipped with three or more ‘axle assemblies’.

Figure 4

The axle 106 and outrigger portion 203 of trailer 102 is shown in a side elevation partial cross-sectional view in Figure 4. In the F igure the wheel hub assembly 210, the upper section of the outrigger portion 203, and the triangulated section 502 of the suspension arm 206 are omitted from view, and depicted by broken lines, so as to avoid obscuring other components.

As previously described, the construction of axle assemblies 106 and 107 is substantially identical. Moreover, the connection between each said suspension arm 206 to 209 and each said outrigger portion 203 to 206 is substantially identical, save for minor changes in dependence on the side of the trailer in which the suspension arm/outrigger portion extends. Thus, whilst Figure 4 illustrates the configuration only of said suspension arm 206 and outrigger portion 203, it should be understood that the configuration of said suspension, arm 207 and outrigger portion 204, said suspension arm 208 and said outrigger portion 205, and said suspension arm 209 and said outrigger portion 206, are substantially identical to that of suspension arm

206 and outrigger portion 203.

Thus, as illustrated, in the embodiment said outrigger portions 203 defines a *

generally planar upper surface 401 arranged to extend substantially in the plane' of said upper surface 218 of said central frame member 202, and said outrigger portion 203 further defines a generally planar lower surface 402. As shown in the Figure, in the embodiment, coil spring unit 305 is arranged such that a first end is in contact with, and mechanically coupled to, the lower surface 402 of the outrigger portion 203, and such that a second end of the coil spring 305 is in contact with, and mechanically coupled to, the upper surface of the suspension arm 206.

In an alternative embodiment, the upper surface of said suspension arm 206 may be provided with a pivot platform, comprising upper and lower generally planar plates coupled together by way of an articulated spacer extending generally orthogonally from the centres of the plates and vertically spacing the plates. The lowermost plate may be affixed to the upper surface of said suspension arm 206, and the lower end of said coil spring 305 may be mechanically connected to the uppermost plate. Connecting the coil spring 305 to the suspension arm 206 using

X the described pivot platform allows the alignment of the coil spring to be maintained as approximately vertical throughout the extent of hinged movement of the suspension arm 206.

Figures 5a, 5b, 5c, 5d & 5e

The suspension arm 206 is shown in isolation in Figures 5a, 5b, 5c, 5d & 5e, in top plan, bottom plan, front elevation, side elevation, and end elevation views respectively.

As shown in the figures, and as previously described, said suspension arms 206 to 209 are substantially mutually identical, save for minor differences in the positioning of certain components of the arm in dependence on the side of the trailer to which the arm is to be attached. Thus, only suspension arm 206 will be described in detail with reference to Figures 5a, 5b, 5c, 5d & 5e, on the understanding that the construction of suspension arms 207 to 209 is substantially identical to that of suspension arm 206.

As illustrated, suspension arm 206 comprises a pair of rigid square tubular steel sections 501, 502, joined to form a partially triangulated arm. Each of said tube sections 501, 502 comprises at a first end an open tubular member 503, configured to receive a hinge pin 302 to thereby couple the suspension arm 206 to the bracket portions 301 of the chassis central frame member 202. As shown, said tube section 501 is provided with a projecting spigot 308 extending forwardly of the suspension arm, said spigot 308 being used for attachment of said second end of said shock absorber unit 306 to said suspension arm 206.

Referring to the Figures, it will be noted that the outer end of said suspension arm 206 defines a tubular section 505 integrally formed with said tube section 501. Said tubular section 505 defines an outer circumferential surface against which said roller bearings of said wheel hub assembly 210 may bear. Thus, in the specific embodiment, said wheel hub assembly 210 may be directly rotatably mounted to the tubular section 505 of said suspension arm 206, such that the wheel hub assembly 210 is rigidly coupled to the suspension arm 206 and is not permitted to tilt or pivot relative to the suspension arm. Rather, the rigid coupling between the wheel hub assembly and the suspension arm permits the wheel hub assembly only to rotate relative to the suspension arm through a plane extending generally orthogonal to the length of the suspension arm 206, that is a plane extending generally parallel to the length of the trailer 102.

The rigid mounting of the wheel hub assembly 210 relative to the suspension arm 206 ensures that the alignment of the wheel hub assembly 210, and so the wheel 224, is maintained only by the suspension arm connecting the wheel hub assembly 210 to the rigid frame 201. Thus, given that the alignment of the wheel hub assembly is maintained solely by the suspension arm 206, the requirement for alignment ‘control’ rods, or a second suspension arm in the manner of double wishbone suspension, is obviated.

I

This configuration advantageously reduces the complexity of the trailer chassis 103. Furthermore, this configuration enables the use of only the single suspension arm joining the wheel hub assembly to the rigid frame. In the alternative, if the wheel hub assembly 210 were pivotally mounted to the suspension arm 206, a ‘control arm’ or a further suspension arm, connecting to the wheel hub assembly at a vertically spaced position from the suspension arm 206, would need to be joined 5 to the rigid frame 201 at a vertically spaced position to that of suspension arm 206.

This configuration would thus require either raising of the height of the load bed of the trailer, or a reduction in the ground clearance of the trailer chassis.

Claims

Claims What we claim is:

1. A trailer adapted to be towed by a vehicle, the trailer comprising:

a rigid frame comprising at least one elongate central frame member extending lengthwise of the trailer along an axis extending lengthwise centrally or near-centrally widthwise of the trailer, the rigid frame further comprising a pair of outrigger portions rigidly connected at respective inner ends to either of said at least one central frame member and each extending outwardly therefrom, widthwise of the trailer, in opposing directions towards respective outer ends;

a pair of suspension arms hingedly connected at respective inner ends thereof to either of said at least one elongate central frame member, and each extending outwardly therefrom, width wise of the trailer, in opposing directions towards respective outer ends;

a pair of wheel hub assemblies associated with said pair of suspension arms, the wheel hub assemblies of said pair being mounted to respective outer ends of said suspension arms, each of said wheel hub assemblies being suitable for carrying a ground engaging w heel; and a pair of compressible suspension units, each of said pair of suspension units arranged to contact one of said suspension arms and one of said outrigger portions and extend therebetween.

2. A trailer as claimed in claim 1, wherein said rigid frame comprises one elongate central frame member extending approximately centrally widthwise of the trailer, and wherein said pair of outrigger portions being rigidly connected at respective inner ends to said elongate central frame member and each extending outwardly therefrom, and wherein said pair of suspension arms are hingedly connected at respective inner ends thereof to said elongate central frame member, and each extending outwardly therefrom, widthwise of the trailer, in opposing directions towards respective outer ends.

3. A trailer as claimed in claim 1 or claim 2, wherein each said wheel hub is rigidly mounted to a respective suspension arm.

4. A trailer as claimed in any of claims 1 to 3, further comprising a pair of ground engaging wheels mounted to respective wheel hubs.

5. A trailer as claimed in claim 4, wherein each said ground engaging wheel is fitted with a pneumatic tyre.

6. A trailer as claimed in any of claims 1 to 5, wherein each of said suspension arms is hingedly connected to said at least one elongate central frame member about a hinge axis extending lengthwise of said trailer.

7. A trailer as claimed in any of claims 1 to 6, wherein each of said pair of compressible suspension units comprises a shock absorbing or dissipating device.

8. A trailer as claimed in any of claims 1 to 7, wherein each of said pair of compressible .suspension units is arranged to extend between one of said suspension arms and one of said outrigger portions adapted to connect a suspension arm to a respective outrigger portion in a way such that movement of said suspension arm about said hinged connection causes said compressible suspension unit to be compressed between a respective said suspension arm and outrigger portion.

9. A trailer as claimed in any of claims 1 to 8, wherein each of said suspension units is arranged to contact a respective suspension arm at a position proximal its outer end, and to contact a respective outrigger portion at a position proximal its outer end.

10. A trailer as claimed in any of claims 1 to 9, wherein said at least one elongate central frame member defines a generally planar upper surface and a generally planar under surface.

11. A trailer as claimed in any of claims 1 to 10, wherein said pair of suspension arms are hingedly connected at respective inner ends thereof to said under surface of said central frame member.

12. A trailer as claimed in any of claims 1 to 11, wherein said elongate central frame member comprises bracket portions extending downwardly from said

J under surface, and wherein said pair of suspension arms are hingedly connected at respective inner ends thereof to said bracket portions.

13. A trailer as claimed in any of claims 1 to 12, wherein said outrigger portions define a generally planar portion having a generally planar upper surface arranged to extend substantially in the plane of said upper surface of said central frame member, and further defining a lower surface.

14. A trailer as claimed in any of claims 1 to 13, wherein each said suspension unit is arranged to contact said lower surface of a respective outrigger portion.

15. A trailer as claimed in any of claims 1 to 14, wherein each said suspension unit compresses an axially elongated unit compressible axially.

16. A trailer as claimed in any of claims 1 to 15, wherein each said suspension unit is mechanically coupled at a first end to a respective outrigger portion and mechanically coupled at a second end to a respective suspension arm.

17. A trailer as claimed in any of claims 1 to 16, wherein each said suspension unit is mechanically coupled at a first end to said lower surface of a respective outrigger portion and mechanically coupled at a second end to a respective suspension arm.

18. A trailer as claimed in any of claims 1 to 17, wherein each said suspension unit comprises a resiliently compressible spring unit.

19. A trailer as claimed in claim 18, wherein each said compressible spring unit comprises a resiliently compressible coiled suspension spring.

20. A trailer as claimed in any of claims 1 to 19, further comprising a shock absorbing unit arranged to contact one of said suspension arms and one of said outrigger portions and extend therebetween.

21. A trailer as claimed in claim 20, wherein each said shock absorbing unit is a mechanical linear actuator damper comprising a cylinder and piston assembly.

22. A trailer as claimed in any of claims 1 to 21, wherein said elongate central frame member is provided at a first end with a tow hitch fixture suitable for mechanically coupling the trailer to a tow hitch fixture of a towing vehicle.

23. A trailer as claimed in any of claims 1 to 22, wherein said trailer is an agricultural trailer adapted to be towed by an agricultural vehicle.

24. A trailer as claimed in any of claims 1 to 23, wherein said trailer is an agricultural tractor trailer adapted to be towed by an agricultural tractor.

25. An agricultural vehicle comprising a tow hitch fixture and comprising a trailer as claimed in any of claims 1 to 24 mechanically coupled to said tow hitch fixture.