WO1989000112A1

WO1989000112A1 - Improvements relating to wheel attachments

Info

Publication number: WO1989000112A1
Application number: PCT/GB1988/000531
Authority: WO
Inventors: Thomas Bartlett Snell
Original assignee: WESSEX (UK) PLC
Current assignee: WESSEX (UK) PLC
Priority date: 1987-07-06
Filing date: 1988-07-06
Publication date: 1989-01-12
Anticipated expiration: 1990-01-06
Also published as: EP0365581A1; AU1966788A; GB8715797D0

Abstract

A wheel attachment, for giving increased support and traction, is an inflatable bag (9) of toroidal form. It is fitted co-axially to the wheel (1) and held there, when inflated, by a restraint (13, 29) bearing against the outer end and coupled to the wheel hub (3) by a tension member (11, 26) extending through, or forming part of, the central passage of the toroid. The tension member may be flexible or rigid, and it is attached to an anchorage (5) which may be permanently fitted to the wheel hub (3) using the existing studs. The inner end of the bag (9) may have an annular element (14) to locate against the wheel rim, but outside that there will be engagement between the bag and the side wall of the tyre (2). The bag may have a tread, or a treaded sleeve (30) may be supported by the bag being inflated within it.

Description

"Improvements Relating to Wheel Attachments"

This invention relates to wheel attachments and is concerned with adding support and traction for vehicles travelling on soft or muddy ground, or even for giving buoyancy.

There have been many proposals for adding a second wheel beside a primary one, but most of these have required the primary wheel to be specially adapted to receive them. A solution to that problem has been proposed in GB-B-2028239 and in WO87/04668 , where an anchorage member is fixed to the wheel hub using the existing studs, and the wheel attachment is in turn secured to this anchorage member by a central tension member pulling it in against the wheel rim. However, that was primarily for a rigid, or virtually rigid, drum-like attachment.

Rigid attachments have two main drawbacks. First, when they are not in use, they are bulky and awkward to store, and take up useful space in the vehicle. Generally, they cannot be left attached to the wheels for normal road use.

Secondly, they can be damaged if they meet a hard object, whereas a softer attachment would simply flex and ride over it.

Thirdly, they are not very efficient on some surfaces. To generate traction on boggy ground, for example, the preferred configuration of a- rigid attachment is that of a large cog, with axially parallel ribs. However, this is not good on soft sand, where it tends simply to churn through the surface layer and throw sand about. For that type of terrain, it would be preferable to have something that followed, to a certain extent at least, the principles of a tracked vehicle.

An inflatable attachment was proposed in US-4305621 but that proved impractical. Again, it was suggested that use could be made of existing wheel studs, and bracing the attachment against the rim of the wheel, but it meant, undoing all the wheel nuts to fit it and remove it, and that had to be done through a sealable opening in the bag. Altogether, it was awkward and impractical.

It is the aim of this invention to provide a more viable inflatable wheel attachment.

According to the present invention, there is provided a vehicle wheel attachment for increased support and traction comprising an inflatable bag, to be positioned co-axially with the wheel, characterised in that the bag is generally toroidal and a restraint is provided for connection to the wheel and to extend co- axially through the toroid to connect to the axial end remote from the wheel thereby to hold the bag, when inflated, firmly against the side of the wheel as an extension thereof.

Strictly speaking, a torus or toroid is a ring- shaped body of circular or elliptical cross section. However the words "toroid" and "toroidal" are used in this Specification, for convenience, in a wider sense to indicate a body of revolution generated by a closed curve rotated about a non-intersecting axis.

This shape means that there is access to the wheel hub through the bag without having to unseal it, thus making attachment much easier and the bag more reliable. The restraint may take various forms; it can be a rigid member, a flexible member, a¹ telescopic tube assembly, or it can be provided over the major part of its length by the inner wall of the toroid.

Preferably there is a substantially rigid load spreading member for engaging the bag at the axial end remote from the wheel and to which the restraint connects. It will normally be of disc-like form, and it may be progressively more flexible towards its outer periphery.

There-, may also be means for positively locating the bag against the wheel rim, and this may take the form of an annular element bonded to the bag for engagement with the wheel rim throughout its circumference. Also, there may be at least one further annular element for fitting to the first one to adapt the locating means to wheel rims of different sizes.

The bag may have internal flexible but substantially inextensible restraints to stabilise it when inflated. There nay be sufficient of these to lessen the need for the load spreading member, and even to eliminate that altogether.

Preferably there will also be means for holding the bag against the wheel in a compacted state when deflated, and the load spreading member may be adapted to be secured to the wheel to trap the bag between itself and the wheel. Thus, the bag can be left permanently attached, and inflated and deflated when required.

The bag may be formed with a tread on its external surface, but this may not be appropriate for all uses. Therefore, there may be provided one or more flexible sleeves, each with different treads, and the selected one can be frictionally held surrounding the bag when the latter is inflated within it.

The connection of the restraint to the wheel is conveniently through a fitting secured to the wheel hub using nuts, studs or bolts by which the wheel itself is attached to the vehicle.

For a better understanding of the invention some embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view, partly in ghost, of a vehicle wheel with an extra support attachment,

Figure 2 is a diagrammatic axial section of a wheel with such an attachment being stowed,

Figure 3 is a diagrammatic axial section of part of an alternative attachment,

Figure 4 is a diagrammatic axial section of part of another alternative attachment, and

Figure 5 is a diagrammatic axial section of yet another alternative attachment.

In Figure 1, a vehicle wheel 1 has a pneumatic tyre 2 and is mounted on screw threaded studs through its hub 3, which is secured by nuts 4 tightened onto those studs in conventional fashion. But some of those studs serve as the means by which an anchorage 5 is fixed to the hub, for example as described in GB-B-2028239 and in WO87/04668 , In this example, the anchorage is essentially a disc 6 with apertures around its periphery which register with alternate wheel studs, and with a central eye 7 on the side remote from the wheel. tϊut and bolt assemblies 8 fitted through those apertures secure onto the wheel studs. However, while that anchorage may be preferred, it will be clear, from subsequent description, that almost anything that will provide a central point to which to attach one end of a tension member will suffice. The extra support attachment itself is a toroidal inflatable bag 9. It is generally cylindrical but it has a narrow co-axial passage 10 which aligns witlT the wheel axis and through which extends a tension member 11 linked to the eye 7. Although shown as a rod, rigidity is not essential and it may take various different forms, as explained further below. At the outer end, remote from the wheel, this member 11 links to another eye 12 at the centre of a dished plate 13, convex towards the wheel. The radius of the plate is such that it spans the mouth of the passage 10 and substantially beyond that over the outer end of the bag to spread the load of the tension member 11, but its periphery is still well within the outer circumference of the bag when that is fully inflated. It may be bonded to the bag and effectively be part of it, or it may be an independent element. Preferably, it will be constructed so that towards its periphery it becomes increasingly flexible. This may be done by choice of materials and/or "feathering" it in thickness, and the purpose is to graduate the transition between flexible bag and rigid centre of the plate 13. The latter may be perforated to ensure that there is atmospheric pressure within the passage 10, but normally the wheel 1 has perforations which perform this function.

At the inner end, the bag is bonded co-axially to an

S /SCS annular plate 14 whose outer diameter is such that it fits snugly against the rim of the wheel around its whole circumference to be located thereby, and v/hich may be contoured for clearance over parts of the wheel radially within the rim. Its inner diameter, which may define the mouth of the inner end of the passage 10, is greater than the diameter of the anchorage disc 6. Indeed it may be very much greater, making the plate 14 virtually a ring. Also, since it may be desired to fit this extra support to wheels of different sizes, there may be a base ring of the minimum diameter required, to which may be fitted, simply by pressing for example, one or more larger rings which will locate against larger wheel rims. The mutual friction between the wheel rim and the plate or ring 14 , especially when the bag is inflated and pressing in on the member 14, is sufficient to keep the bag from rotating with respect to the wheel. However, since the bag will be of rubberised fabric or plasics material likely to have a very high co-efficient of friction with rubber, it may be possible to dispense with this locating plate or ring 14 and rely on the engagement of the inner end of the bag and the side wall of the tyre 2 to prevent mutual rotation.

The anchorage 5 may be left virtually permanently in place on the wheel 1, and when the extra support is required the bag 9 is offered up to the wheel and the tension member 11 is threaded through the passage 10. If the plate 13 is separate from the bag the latter is folded in towards the wheel while the final attachment is made between the member 11 and the eye 12, but if the plate is part of the bag, the final attachment is made between the member 11 and the eye 7 with the bag folded towards the plate 13. Inflation can then commence, with the plate 14 guided to locate against the wheel rim as necessary. As pressure increases, the bag assumes its toroidal shape and the member 11 comes under tension.

The actual working pressure will depend on the size of the attachment and the use to which it is to be put, but generally it will not be so much as that in the tyre 2. The aim is to achieve a large "footprint" which does entail the bag 9 flattening out to some extent where the load is imposed and acting like a linked track.

There may be a tendency, as inflation progresses, for the outer periphery or tread of the bag 9 to straighten out and become too cylindrical when a domed configuration is desired. Although the wall of the passage 10 may act as a tie shorter than the axial span of the tread, and therefore encourge the latter to bulge, it may be necessary to provide more constraints. These are illustrated as internal ties- 15 between the ends of the bag, and preferably they will be of virtually inextensible flexible line such as "Kevlar" .

SL/SCS There may also be diagonal braces 16 of similar material for stability. Alternatively, or in addition, there could be internal webs for this purpose, but perforated or fitted so that air can reach all compartments formed by them. It may also prove possible, with sufficient internal restraints and using the Figure 5 attachment described below, to dispense with the load spreading plate 13.

It would be a convenience in some circumstances not to have to remove the bag entirely when it is not required, but to collapse it against the wheel and retain it there. A flexible member 11, of wire, cord or chain, for example, would be used, or possibly a telescopic tube assembly. On release of air pressure it would be necessary to nip the central portion of the bag inwards, as shown in Figure 2, to ensure that it was not proud of the tyre 2, and this can be done by one or more straps 17.

It is then necessary to sandwich the bundled bag between the plate 13 and the side of the wheel, which entails holding the plate 13 close up to the anchorage 5.

One way of achieving this is shown in Figure 2, where the tension member 11 is -a wire or "Kevlar" cord passing through a hole in the centre of the plate 13 (which no longer has the eye 12) to terminate in a knob 18 larger than the hole. The outward thrust of the plate 13 is applied to this knob when the bag is inflated. But when out of use, and with the plate 13 pushed in towards the wheel 1, as in Figure 2, the freed length of the member 11 can be pulled taut and secured onto cleats 19 to hold the assembly stowed.

Another, neater arrangement is shown in Figure 3 where the member 11 is an assembly of telescopic tubes 20, the outer one being secured to the anchorage disc 6 around a central screw-threaded socket 21 and the innermost one to the plate 13, around a central hole 22. When telescoped as shown, and with the bag folded as in Figure 2, a bolt 23 can be introduced through the hole 22 and tightened into the socket 21, thus making the assembly secure.

It may be possible to provide an automatic catch between the plate 13 and the anchorage 5 so that the plate is held as it is pushed up against the disc 6. However, there could be a problem with the collapsed wall of the passage 10 or the member 11 interfering, although that could be alleviated by making the plate 13 skeletal, at least around the centre, so that obstructive portions of bag 9 or member 11 could be seen and prised clear. This is shown in Figure 4 where the plate 13 has fingers 24 to engage in spring catches 25 on the outer face of the anchorage disc 6. In a further arrangement, shown in Figure 5, instead of having a separate element 11, the bag itself is used to provide much of the tension member. The wall of the passage 10 is extended at the inner end as a short cylindrical tube 26 separate from the main body of the bag which curves outwards at the inner mouth of the passage 10 as before. This tube is bonded or otherwise fixed to a disc 27 which is secured to the anchorage disc 6 by one or more bolts 28 accessible through the passage 10. At the outer end the passage wall, which may be re-inforced as compared with the rest of the bag, transfers the tension generated by inflation to a cover 29 which acts as a load spreading member in the same way as the plate 13. However, it is rather larger, and at its periphery it curves back towards the wheel. The bond between the bag and this cover terminates within this periphery, which is slightly larger than the wheel rim if a locating ring 14 is provided, but which may match that of the rim if not.

When the bag is deflated, it can be folded within the cover 29, without the use of straps, as the cover is pressed up against the wheel. The periphery of the cover may engage the side wall of the tyre 2, or the wheel"^"rim,^" and this completely conceals the bag, apart from what can be seen of the wall of the passage 10 through the centre of the cover.

SL/SCS It is possible that, with wheel rim engagement by the cover, if the contour of the rim is suitable a press fit might be sufficient to hold the cover in place. However, with the disc 27 accessible, it will probably be preferred to have a more secure hold on the cover. This may be similar to that of Figure 3, for example, with a bolt, washered if necessary, screwing into the disc 27 , there not then being a central bolt 28.

This form of cover may be used instead of the plate 13 in previous examples, and it will be understood that the shapes shown are only two examples of many possibilities. For example the plate 13 may be flat or convex in the opposite direction.

The ground engaging surface of the bag will generally have some form of patterned tread. However, one type of tread may not be appropriate for all uses of the bag. Rather than have complete sets of bags with different treads, which would be a rather expensive solution to the problem, it will be preferred to have a basic bag adapted to receive outer sleeves, these having the treads. Such a sleeve, indicated at 30 in Figure 5, can be fitted loosely before full inflation of the bag, but when that is complete the bag will have expanded tightly up against the inside of the sleeve, which will be held fast by friction and the double curved interface, the sleeve preferably being domed similarly to the basic bag.

The air inlet (by which also the bag can be exhausted) will generally be at the outer end of the bag, clear of the plate 13, and inflation may be by any convenient or conventional means. Gas other than air could of course be used, for example in an emergency where a high pressure bottle is available. Also, where a catch arrangement such as that of Figure 4 is used, the wheel could be arranged to carry a small pressure bottle connected by a remotely controlled valve to the bag. The driver could then inflate the bag from his cab. If straps were used to hold the bag in, they would be weak enough to be snapped by this inflation, or their fasteners would be arranged to release.

Where the extra weight is not an adverse factor, but where extra solidity is required, it would be possible to fill the bags with liquid. They could indeed be used for storage: for example on a desert trip where such an ■ attachment would be of great help on soft sand, water could be carried by the bags.

As well as providing added support and traction on soft ground, it is possible that such bags could provide flotation means for carrying a wheeled vehicle across water.

Claims

CLAIMS 1^*. ^~ A vehicle wheel attachment for increased support and traction comprising an inflatable bag (9) to be positioned co-axially with the wheel (1), characterised in that the bag (9) is generally toroidal and a restraint (11,26) is provided for connection to the wheel (1) and to extend co-axially through the toroid to connect to the axial end remote from the wheel thereby to hold the bag (9), when inflated, firmly against the side of the wheel as an extension thereof.

2 . An attachment as claimed in Claim 1, characterised in that the restraint (11) is a rigid member.

3. An attachment as claimed in Claim 1, characterised in that the restraint (11) is a flexible member.

4. An attachment as claimed in Claim 1, characterised in that the restraint (11) is a telescopic assembly (20).

5. An attachment as claimed in Claim 1, characterised in that the restraint is provided over the major part of its length by the inner wall (10) of the toroid.

6. An attachment as claimed in any preceding claim, characterised in that a substantially rigid load spreading member (13, 29) is provided for engaging the bag (9) at the axial end remote from the wheel and to which the restraint (11) connects.

7. An attachment as claimed in Claim 6 characterised in that the load spreading member (13, 29) is of disc¬ like form, being progressively more flexible towards its outer periphery.

8. An attachment as claimed in any preceding claim, characterised by means (14) for positively locating the bag (9) against the wheel rim.

9. An attachment as claimed in Claim 8, characterised in that the locating means (14) is an annular element bonded to the bag (9) for engagement with the wheel rim throughout its circumference.

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10. An attachment as claimed in Claim 9, characterised in that there is at least one further annular element for fitting to the first one (14) to adapt the locating means to wheel rims of different sizes.

11. An attachment as claimed in any preceding claim, characterised in that the bag has internal flexible but substantially inextensible restraints (15, 16) to stabilise the bag when inflated.

12. An attachment as claimed in any preceding claim, characterised in that means (19; 21, 23; 24, 25) are provided for holding the bag (9) against the wheel (1) in a compacted state when deflated.

13^". An attachment as claimed in Claim 12, characterised in that^* the load spreading member (13, 29) is adapted to be secured to the wheel (1) to trap the bag therebetween.

14. An attachment as claimed in any preceding claim, characterised by a flexible sleeve (30) which is frictionally held surrounding the bag (9) when the latter is inflated within it.

15. An attachment as claimed in any preceding claim, characterised in that the connection of the restraint (11) to the wheel (1) is through a fitting (5) secured to the wheel hub using nuts, studs or bolts by which the wheel itself is attached to the vehicle.