Improvements in and relating to vehicle chassis

Abstract

A vehicle chassis 10 includes one or more longitudinal beams 12, one or more transverse beams 16 and an axle assembly 14. Transverse beams 16 and axle assembly 14 are rigidly affixed to longitudinal b

Description

This invention relates to improvements in and relating to vehicle chassis, and in particular, vehicle chassis for static caravans. Most static caravans have the same basic structure, namely a steel "ladder" chassis, which is supported above the ground by wheel / axle assemblies, which are in-turn affixed to the underside of the chassis. A floor plate is then affixed to the top of the chassis which serves to reduce racking of the chassis by triangulation and then the superstructure is built on top of the floor plate. This basic type of caravan construction is ubiquitous and has proven to be sufficiently durable for occasional road transportation, and also for long-term use on-site. In recent years, there has been a move towards improving material usage efficiency and reducing the carbon footprint of production lines. Steel is an inherently "expensive" material in terms of its actual cost, as well as its environmental impact during production, forming, assembly and disposal. The entire lifecycle of a steel chassis, from ore to recycling, involves substantial expenditure of energy and materials, as well as significant carbon emissions. In-line with most forms of vehicle manufacture, there is a drive towards greener, cleaner and more efficient manufacturing processes, as well as greener loverail ifecycles for manufactured vehicles. Aspects of the invention are set forth in the appended independent claim or claims. Preferred and / or optional features of the invention are set forth in the appended dependent claims. The invention thus subsists in a vehicle chassis, in particular, but without limitation, to a vehicle chassis for a static caravan, which is principally manufactured from wood, rather than from steel. This is contraindicated by the accepted practice in the field by virtue of the perceived lack of strength and longevity of wood compared with steel. However, when one considers that most caravans have a lifespan of around 10-20 years, manufacturing them to last indefinitely is wasteful. Therefore, whilst wood may not be immediately perceived as a viable material from which to make a vehicle chassis, throughout the anticipated lifespan of the chassis, its strength and durability is more than adequate. Moreover, wooden materials can be treated with preservatives and other coatings so as to ameliorate any of the perceived downsides of using wood over steel. The longitudinal beam or beams is / are manufactured from a wood composite material, such as from extruded or pultruded lengths made up of a mixture of wood chips, wood / paper fibres, and / or sawdust in a thermoplastic polymer matrix. This is an excellent way to use up waste wood and plastics, and results in a strong, lightweight, durable and weatherproof base material from which the chassis can be built. Another advantage of using wood composite materials is that they can be thermally or ultrasonically welded to one another, in place of, or in addition to, adhesives or mechanical fixings. Further, by using an extrusion or pultrusion process, the at least partially wooden I-beams can be formed as unitary extrusions or pultrusions of the wood composite material. In certain embodiments, the longitudinal beam comprises a straight, continuous upper beam, a central lower beam portion that is substantially parallel to the upper beam, and distal lower beam portions either side of the central lower beam portion, which are inclined relative to the central lower beam portion so as to form a substantially trapezoidal shaped longitudinal beam when viewed side on. The trapezoidal shape reduces the weight of the chassis towards its ends, away from the axle assembly, where the shear forces and bending moments and lesser. It also creates ground clearance away from the axle assembly, which is useful during transportation and / or siting on an uneven site. The or each transverse beam may also be at least partially manufactured from wood. In a preferred embodiment, the chassis has a plurality of longitudinal beams, which are preferably substantially parallel; and / or a plurality of transverse beams arranged substantially perpendicular to the longitudinal beam or beams. This creates a strong, rigid, "ladder" type structure, which will be familiar to those with knowledge of the industry. A wooden sheet (formed as continuous sheet, or from sheet sections) is preferably affixed to, and atop, the plurality of transverse beams. By gluing and / or screwing the sheet to the transverse beams, the overall strength and stiffness of the chassis can be markedly improved, as well as providing a convenient flat surface on which to build the superstructure of the vehicle. In a preferred embodiment of the invention, the longitudinal and transverse beams are interconnected using brackets, which suitably comprise opposing bracket portions located on opposing sides of the longitudinal and transverse beams to be connected, the opposing bracket portions. The vehicle chassis may additionally comprise any one or more of: a towbar assembly; a corner steady; a dolly wheel; road lighting; and a braking system. An embodiment of a chassis shall now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a chassis in accordance with the invention; Figure 2 is a perspective view of a longitudinal beam of the chassis shown in Figure 1; Figure 3 is a perspective underside view of the chassis; Figure 4 is a perspective view of a central portion of the longitudinal beam shown in Figure 2; Figure 5 is a perspective view showing the mounting of an axle assembly to the chassis; Figure 6 is a plan view of the chassis; Figure 7 is a side view of the chassis. Referring to Figure 1 of the drawings, a chassis 10 comprises a pair of longitudinal beams 12, which are spaced-apart and which are substantially parallel to one another for the entire length of the chassis 10. A pair of axle assemblies 14 are fixed to the chassis 10 and shall be described in great detail below. A set of transverse beams 16 are also provided at spaced-apart locations, which are perpendicular to the longitudinal beams 12. This creates a "ladder" arrangement, which would be familiar to those in the art. At each end of the chassis 10, a towing assembly 18 is provided, which comprises a square-section tube for receiving a tow bar 20, which is shown in Figures 6 and 7 of the drawings. The tow bar 20 slides into the tube 18 and is held in place by a locking pin or bolt. The tow bar 20 can be removed and positioned at either end of the chassis 10, which is convenient to enable the chassis 10 to be towed from either end. The longitudinal beam 12 is formed as a central portion 120, which has substantially parallel upper 122 and lower 124 beam portions affixed to it. In the illustrated example, the wooden spacer 126 is formed as three pieces of OSB, with a small lightening hole between the edges of the pieces 126. A pair of slotted apertures 130 are provided through which the axles 14 of the axle assembly pass. By having slotted apertures 130, the positions of the axle assemblies 14 can be adjusted to achieve the correct balance of the chassis when placed on the floor and supported by its wheels. Running along the underside of the central portion 120 is a steel angle beam 140, to which the axle assemblies 14 are fixed mechanically. On either side of the central portion 120 of the longitudinal beam 12, there are a pair of tapered portions 150, in which the wooden spacer 128 interposed between the upper 122 and lower 124 beam portions is tapered. As can be seen from Figure 7 of the drawings in particular, this creates ground clearance at either end of the chassis 10. It also serves to lighten the chassis 10 where the bending modes and sheer forces are lesser. Referring to Figure 4 of the drawings, the central beam portion 120 is shown, which is manufactured, as previously described, from the upper wooden beam portion 122 and the lower wooden beam portion 124, each of which has a dado 132 formed in it. This provides a slot into which the side edges of the wooden spacer 126 can be fitted and glued so as to form an I-beam structure. As can also be seen in Figure 4 of the drawings, the wooden spacers 126 have through holes 134 for receiving brackets 160 as shown, in particular, in Figures 1 and 3 of the drawings. The brackets 160 serve to mechanically connect the spacers 126, 128 of the central 120 and outer 150 portions of the longitudinal beam 12, but also to provide a mechanical connection to structural transverse beams 161, which are also formed as wooden I-beams in the manner previously described. The purpose of the structural beams 161 is to maintain the longitudinal beams 12 in a parallel and spaced-apart configuration and to resist twisting of the longitudinal beams 12 about their long axis. The transverse beams 16 are fitted on top of the upper beam portion 122 of the longitudinal beams 12 and are held in place also by brackets. As can be seen from Figures 1 and 3 in particular, the transverse beams 16 are also formed as wooden I-beams with respective upper 160 and lower 162 beam portions each having a dado and an OSB spacer 164 therebetween. As can be seen from Figures 3 and 6, an OSB floor panel 170 is glued and / or screwed on top of the transverse beam 16 so as to prevent wrecking of the chassis and also to provide a floor surface upon which a subsequent superstructure can be built. Referring now to Figures 1 and 3 of the drawings, the brackets 160 are formed from plastics mouldings, which have an outer part, with spigots that fit into the aforementioned through holes 134. On the opposite side of the respective beam 12, 160, there is provided an opposing bracket portion, which has formations for receiving the spigots. A bolt or screw is used that passes through the through holes 134 and which clamps the opposing bracket portions together. This creates a rigid interconnection between the respective beams. Also fitted to the chassis are corner steadies 180, wheels 182 and other components that are necessary for roadworthiness, use on-site, transportation and so on. It will be appreciated from the foregoing description that the particular shape and / or configuration of the chassis 10 can be varied to suit the particular requirements and the use case for it. In other words, the aforedescribed chassis is merely illustrative of one embodiment of the invention. For example, the relative proportions of the various components could be altered, to make a shorter, longer, wider or narrower chassis 10 as required by the situation. One or several axle assemblies 14 could be used depending on the loading and the number of longitudinal beams 12 and transverse beams 16 could be altered as well as needs dictate.

Claims

1. A vehicle chassis comprising:a longitudinal beam;a transverse beam; andan axle assembly,the transverse beam and axle assembly being rigidly affixed to the longitudinal beam, whereinthe longitudinal beam comprises an at least partially wooden I-beam comprising a unitary extrusion or pultrusion of wood composite material.

2. The vehicle chassis of claim 1, wherein the wood composite material comprises an extruded or pultruded mixture of wood chips, fibres or sawdust in a thermoplastic polymer matrix.

3. The vehicle chassis of any preceding claim, wherein the longitudinal beam comprises a straight, continuous upper beam, a central lower beam portion that is substantially parallel to the upper beam, and distal lower beam portions either side of the central lower beam portion, which are inclined relative to the central lower beam portion so as to form a substantially trapezoidal shaped longitudinal beam when viewed side on.

4. The vehicle chassis of any preceding claim, comprising a plurality of longitudinal beams.

5. The vehicle chassis of claim 4, wherein the longitudinal beams are substantially parallel.

6. The vehicle chassis of any preceding claim, wherein the transverse beam is at least partiallymanufactured from wood.

7. The vehicle chassis of any preceding claim, comprising a plurality of transverse beams arranged substantially perpendicular to the longitudinal beam or beams.

8. The vehicle chassis of any preceding claim, further comprising a wooden sheet affixed to, and atop, the plurality of transverse beams.

9. The vehicle chassis of any preceding claim, wherein the longitudinal and transverse beams are interconnected using brackets.

10. The vehicle chassis of claim 9, wherein the brackets comprise opposing bracket portions located on opposing sides of the longitudinal and transverse beams to be connected, the opposing bracket portions.

11. The vehicle chassis of any preceding claim, further comprising any one or more of: a towbar assembly; a corner steady; a dolly wheel; road lighting; and a braking system.30 08 23AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS8CLAIMS1. A vehicle chassis comprising:a longitudinal beam;a transverse beam; andan axle assembly,the transverse beam and axle assembly being rigidly affixed to the longitudinal beam, whereinthe longitudinal beam comprises an I-beam formed as a unitary extrusion or pultrusion of wood composite material.

2. The vehicle chassis of claim 1, wherein the wood composite material comprises an extruded or pultruded mixture of wood chips, fibres or sawdust in a thermoplastic polymer matrix.

3. The vehicle chassis of any preceding claim, wherein the longitudinal beam comprises a straight, continuous upper beam, a central lower beam portion that is substantially parallel to the upper beam, and distal lower beam portions either side of the central lower beam portion, which are inclined relative to the central lower beam portion so as to form a substantially trapezoidal shaped longitudinal beam when viewed side on.

4. The vehicle chassis of any preceding claim, comprising a plurality of longitudinal beams.

5. The vehicle chassis of claim 4, wherein the longitudinal beams are substantially parallel.

6. The vehicle chassis of any preceding claim, wherein the transverse beam is at least partiallymanufactured from wood.

7. The vehicle chassis of any preceding claim, comprising a plurality of transverse beams arranged substantially perpendicular to the longitudinal beam or beams.

8. The vehicle chassis of any preceding claim, further comprising a wooden sheet affixed to, and atop, the plurality of transverse beams.

9. The vehicle chassis of any preceding claim, wherein the longitudinal and transverse beams are interconnected using brackets.

10. The vehicle chassis of claim 9, wherein the brackets comprise opposing bracket portions located on opposing sides of the longitudinal and transverse beams to be connected, the opposing bracket portions.

11. The vehicle chassis of any preceding claim, further comprising any one or more of: a towbar assembly; a corner steady; a dolly wheel; road lighting; and a braking system.30 08 23

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