BACKGROUND OF THE INVENTION

This invention relates to road engaging devices for the uheels of vehicles such as cars, lorries, and civil engineering vehicles.

THE PRIOR ART

It is knoun that the tyres conventionally fitted to vehicles for general use are provided uith treads intended to provide adequate road holding capability over a uide variety of possible vehicle operational conditions including amongst other things, the nature of the road or other surface over uhich the vehicle travels; the type of vehicle; the loading of the vehicle; tyre pressures; the manner in uhich it is driven; weather conditions; etc. Since each one of the above mentioned variables can vary uidely it has been found that the conventionally used tyres may not be able to provide under certain, not necessarily extreme, conditions the requisite degree of adhesion uith the road or the like, uhereby the driver may not be able to control adequately the vehicle or the vehicle may not respond sufficiently to steering and drive requirements.

In particular, the presence ¹ of ice, sπou or mud can give rise to adverse tyre adhesion. In an attempt to overcome this loss of adhesion

-2- in such conditions it has been proposed to provide an arrangement of chains uhich so fit onto vehicle wheels as to provide lengths of chain extending across the tyr at locations spaced around the periphery of the tyres. The purpose of the chains is to provide regions uhich uill 'dig into ¹ or otherwise cut the surface of the sno and/or ice over uhich the chains travel and thus provid a higher degree of adhesion as compared uith that obtai in the absence of the chains.

In practice, chains rub against and thus tend to damage the tyres to uhich they are fitted. Such damage can also readily occur if the links of the chain entrain fragments of stones or the like.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a traction tread for use uith a vehicle tyre or tyre assembly.

SUIWIARIE5 OF THE INVENTION

According to a first aspect of the invention there is provided a traction device for shrouding the tread regions of a vehicle tyre, the device including for at least one of the side ualls of the tyre a ring member uhich is adapted partially to shroud the adjacen side uall of the tyre and uhich is co-operable uith the uheel upon uhich the tyre is fitted, the device also including an endless track portion having a plurality or recesses or openings or a combination of recesses or openings defining radially extending ualls, the rεeesses or openings being spaced around the track portion, said track portion being adapted for attachment to the tyre in such manner that uhen the tyre is inflated the track portion shrouds the tread region of the tyre. ^•

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A method of providing the tyre of a vehicle uheel uith a traction tread, the method comprising the steps of shrouding the tread region of the tyre uith a flexible cover uhich circumscribes at least the tread region and uhich is provided uith openings or recesses in the part thereof that co-operates uith the tyre tread region, and securing the flexible cover in place by securing arrangements uhich co-operate uith both sides of the structure of the uheel. Preferably the endless track forming portion / flexible cover is formed from a conventional tyre uhose tread region has been part removed to form the openings or recesses, and uhose side ualls are adapted for co-operation uith means for retaining the track forming portion/flexible cover in its operational position. Conveniently, the uall defining openings or recesses are so located in the tyre being modified that at least a part ofsome of the openings or recesses extend to the shoulder region betueen the tyre side ualls and the tread region of the' tyre.

Preferably, . each of said ring members has a plurality of apertures circumferentially spaced around the associated uall of the tyre from uhich the track farming portion/flexible cover is formed, uhich apertures are positioned to be engageable uith location means provided on the associated ring member.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to shou hou to carry the same into effect reference uill nou be made to the accompanying drauings in uhich:-

Figure 1 is a side elevation of the traction device/flexible cover of the invention mounted on the tyre of a vehicle uheel;

Figure 2 is a sectional vieu to an enlarged scale taken on the line II-II of Figure 1, the Figure illustrating tuo forms of a detail of the device;

Figure 3 is a perspective vieu of a part of the device/flexible cover of Figures 1 and 2, a part of a tyre also being shoun: and

Figure 4 is a very schematic representation of an arrangement for cutting openings into a conventional tyre for the purposes of producing a device/flexible cover of the invention.

DESCRIPTION OF THE PREFERRED EFIBODIPIENTS

Referring nou to the drawings and particularly to Figures 1,2 and 3, a vehicle uheel unit 1 has a conventional tyre 2 fitted thereto. The tyre 2 has a tread section or region 3, side ualls ^' 4, and rim beads 5 uhich engage uith the uheel flange or rim structure 6 of the uheel ( only a part of the uheel is shoun in Figure 2)

The tyre 2 is partially shrouded or enclosed by a traction device 7, the latter being capable of flexure uhen subjected ^• to the movements of the vehicle so that the device can be regarded as a flexible cover. The device 7 comprises a road surface engaging portion 8 uhich extends across the full uidth of the tread region of the tyre 2 and around the complete circumference of the tyre 2. The portion 8 conforms to the general profile of the tyre tread region 3. The portion 8 is provided uith a plurality of openings 9 uhich in the embodiment shoun are arranged in tuo rous 10 and 11. The openings 9 in the rous 10 and 11 can be in side-by- side relationship as shoun or arranged in staggered relationship.

The openings 9 can have a variety of shapes. For example, they can be as shoun in the drawings or they can be oval, elliptical, circular or other shape

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that may be found suitable. In each case it is important that the side ualls 12 of the openings 9 should be inclined outuardly so that the outer perimeter of each opening is larger than that of the inner surface of the opening.

It is also possible to provide different arrangements of the openings from that illustrated. For example, there can be more than tuo rous of openings of differing sizes arranged in regular or irregular arrangement. In practice, the arrangement of the openings, the number of rous etc., uould be related to the ^' dimensions of the uheel tyre and in particular the axial uidth . of the tyres in relation to the diameter, the diameters of the tyres and the nature of the tread formation.

In addition, the device 7 has relatively narrou sideuall forming portions 13 uhich are each provided uith lugs or flaps 14. The number of lugs or flaps can vary,the number being chosen as thought expedient. For example, four, six, eigth or ten. In the Figure the portions 13 are shoun as having six lugs or flaps 14.

The flaps 14 are each apertured for engagement uith a hut and bolt assembly 16 connected uith an annular ring member 17 uhich is adapted at its inner peripheral region 18 for firm engagement uith the uheel structure 6 particularly in the region of the tyre uell.

In practice, the mode of engagement can take various forms and in any particular case the precise shaping of the inner region 18 uill be related to the form of the uheel structure 6. To illustrate this point the left hand side αf the uheel flange rim has been shown with a hook formation 6A into which a suitably turned-iπ part 18A of the region 18 engages. The right hand side of the Figure shows illustrates an

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alternative form. It uill be understood that in an actual uheel structure the tuo sides of the uheel structure uill be of the same form.

Each ring member 17 can be formed of any convenient material metal or plastics. In the latter case a suitable plastics material can be polypropolene. In the case of a metal an alloy of steel and Zinc may be used. One such alloy is knoun under the Trade Name Zintex. Conveniently, the ring member can, in the case of a metal can be pressed or formed by a spinning operation.

The ring member is provided uith a plurality of bores 20 one for each flap 14 into uhich are fitted countersunk bolts 21 the latter being held firmly in place by nuts 22. The bolts 21 and nuts 22 form the assemblies 16. The bolts project outuardly from the ring member sufficiently not only to be engageable by the flap but also to be able to receive a retaining nut 23 and a uasher or plate 25. The uasher assists in providing lateral support to the flap 14. The flap region in the _. vicinity of the ring member is effectively reinforced by reason of the thickening of the uall 13 at the regions closer to the originally provided bead, uhich is not shoun and uhich i removed during formation of the flaps 14.

It uill be understood that uhilst a conventiona hexagonal nut is shoun other forms of nut can be used i.e., domed nuts or nuts requiring the use of a key or the like for the purposes of tightening The outer periphery 19 of the ring member 17 is formed uith a bead 19A uhich reduces the possibility of an edge region of the ring member from cutting into the tyre 2.

The device according to the invention can be fitted as follous :- The uheel is removed from the

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vehicle ( or a spare uheel utilised) since this facilitates the fitting process. The tyre is deflated sufficiently to allow the side uall 13 and the flaps 14 on one side of the device 7 to be aligned uith and slipped over the tread region of the tyre 2. The device 7 is then positionally adjusted until the tread portion 8 is correctly symmetrically positioned on the tyre 2. The tyre 2 is then initially reflated to a pressure level uhich is found to be sufficient to hold the device firmly in place.

The ring member 17 or members 17 are then attached to the vehicle uheel so that the assemblies 16 can engage the bores in the flaps 14, uith the bolts projecting outuardly to receive the associated uashers and nuts 23.

The tyre 2 is then finally reflated to its ^• correct running pressure thereby exerting additional pressure on the securing arrangements uhich aids in the retention of the device in its operational position. It uill be found, in practice, that uhen the device 7 is under tension from the securing arrangements and the effect of air pressure within the tyre 2, the device 7 tends to push the central part of the tyre tread region 3 inuardly so that a slight concavity is produced in the tyre tread region 3. This has been found to aid in maintaining the device in position.

Uhen a vehicle fitted uith devices according to the invention is used on muddy roads or roads covered snou or ice it has been found that the -provision of the openings or recesses 9 improves the road holding to such an extent that the need for chains is avoided in many situations. During use any mud, snow or ice or lumpy slush uhich collects in the openings 9 is urged out from the openings 9 by t e flexing of the device 7 during rotation of the uheel unit.

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Since device of the invention as so far descri is essentially a modified tyre it is not likely to caus any damage to the roads over uhich it travels in the absense of snow or ice. Furthermore, since the device shrouds the tyre the load distribution is not localised in the same manner as that of a set of chains. Consequently, there is not the same likelihood of damag to the tyre tread region.

Because of this the device of the invention has found to provide a far greater freedom of usage in situations where chains would be likely to cause damage. For example, uhere stretches of road are covered uith snou, slush or ice are interspersed uith stretches of road relatively free of such materials. In a modified form of the device of the inventi

(not shoun) an additional gripping facility can be provided by provided by inserting stud attachment elements in the tread portion 8, uhereby studs can be releasably attached to the device 7 to take into account more severe conditions. Uhen such studs are not require they can be readily removed.

It uill be understood that various configuratio and shapes of the openings 9 can be used in conjunction uith various relative spacings of the flaps. In the case of the latter, depending upon the diameter of the uheel unit 1 , the number of lugs or flaps can be other than the six shoun i.e., 4,5,7,8,9,10 etc. It has been found that eight lugs or flaps is a convenient number for many of the wheels commonly used on motor vehicles. Conveniently, the devices of the present invention are constructed from tyres uhich are part uorn and are not acceptable for further normal use as an inflated tyre. Alternatively, tyres uhich during their manufacture have not been accepted because of quality factors could uell be used to form a device of the

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invention.

The devices of the invention can be formed from various types of tyre in so far as the internal construction thereof is concerned. For example, tyres uhich do not involve metal cords, tyres uith metal side uires, car tyres, lorry tyres, civil engineering vehicle tyres such as those of earth moving machiπary.

If desired, the device of the invention can be especially moulded from plastics or rubber like materials to thereby provide structures in uhich the desired openings or recesses are formed during the moulding process. Conveniently such moulded devices can be formed uith formations similar to conventional tyre treads so as to enhance the requisite grip afforded by the moulded devices.

In the cases of devices uhich are moulded it uill be understood that the device of the invention could be of such form as to be able to bridge a pair of side- by-sidε uheels such as are frequently provided upon commercial vehicles. In this case the device uould have a tread portion of such uidth as to be able to bridge the distance between the outer wall of the tyre on the outermost uheel and the inner uall of the tyre on the inner wheel of a pair. The double tyre device can comprise tuo sets of lugs or flaps 14 each being genenally similar to those of the single tyre arrangement or,if thought desirable can be provided uith a third set of centrally positioned lugs or flaps uhich co-operate uith a ring member located between the adjacent pair of wheels and connected with one of the uheels. In this latter case an integral rib can be provided on the inside of the moulded device the rib running circumferεntially around the device. This rib can be connected uith the lugs or flaps. If it is considered that the extra

set of lugs or flaps 14 is not necessary they can be dispensed uith thereby leaving the rib as a convenient means for aiding in the positioning of the double uidth device in its desired position.

5. Conveniently, the surface of the ring member

17 uhich is to face touards the tyre 2 can be provided uith a dimpled surface or other form of roughening uhich does not present sharp edges to the tyre uall. It should be noted that in practice a ring

10 member uould be used at each side of the tyre.

Also it uill be understood that if desired the ring members could be such as to be a permanent fixture on the uheels- particularly in the case of the inside face of the uheel. In the case of the front or

15 outer face of the uheel the associated ring member could additionally form part of the visual design enhancements for the vehicle.

Reference uill nou be made to the Figure 4 uhich is a very schematic representation in part 0 cross section of apparatus for removing areas of a tyre to provide the openings in a tyre and thereby to provide the device 7 of the invention.

The apparatus essentially comprises a punch assembly 26 mounted on the ram 27 of a pneumatically or 5 hydraulically operated ram unit 28 uhich is carried by a support stand 29 for positional adjustment relative to a support base plate 30.

The punch assembly comprises a ring blade 31 having a cutting edge 32 shaped to provide the required 0 shape of the aperture to be provided in the tyre to be converted into the tread portion of the device of the invention. he blade has a generally rectangular outlin uith rounded corners and uith opposed sides of the blade parallel to each other.

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The blade is held in place by a blade clamp ring 33 uhich clamps the blade to a chuck 34 mounted on the end of the ram 28 of the ram unit 29.

The punch assembly includes an ejector pin 35 uhich is resilieπtly loaded by a spring 36 and uhich is axially displacεable uithin a recess 37 provided in the chuck.

The ram is operable by means of a suitable control arrangement schematically shoun at 37A. It uill be understood that the ram unit is connected uith the appropriate sourceof pressurised fluid.

The blade 31 co-operates uith a mandrel or bolster 38 uhich serves to support the tyre being modified, and has a blade receiving recess 39 into uhich the blade 31 may enter uhen the ram displaces the blade dounuardly twowards the base plate 30 or mandrel 38.

A guard arrangement 40 is provided for protecting the operator from the blade. ^" This guard is louerable to contact the tyre by means of a handle arrangement which is schematically shown at 41.

In operation the tyre 1 is placed upon the mandrel 38 and is so positioned that the region of the tyre uhich is to be punched out is located immediately beneath the blade 31. The guard 40 is lowered to an extent that it pushes the tyre firmly against the mandrel that is flat against the mandrel. At this position the guard can be arranged to complete an inter¬ locking arrangement included in the control of the ram unit uhich enables the control 37Λ to be operated to allow the blade to be driven downwards towards the mandrel and through the tyre to enter into the recess 39 in the mandrel. At the completion of this operating stroke the ram is caused to retract. This part of the operation can be automatic or operator controlled.

The retraction of the ram allows the ejector pin to eject the piece of tyre removed from the tyre from the blade 31.

In a variation of the mandrel the arrangement can be such that the piece removed from the tyre is ejected through the mandrel.

It uill be appreciated that the actual mode of operation of the ram assembly uill depend upon the particular construction details of the ram assembly. Since ram assemblies and control systems therefore are uell knoun further discussion thereof is not thought necessary.

After the ejection stroke of the ram the guard uill be raised to release the tyre. It uill be found that jas soon as the pressure on the tyre is removed the tyre uill resume its conventional shape, and that the ualls of the opening formed by the removal of the piece of tyre material uill be tapered inwards from the outer surface of the tyre to the inner surface of the tyre. In other words the parallel sided punch blade is able to produce the desired tapered uall formation to the openings.

Whilst the above description has been directly concerned uith the formation of openings it uill be understood that the provision of recesses uith the tapere ualls may be found to be sufficient to provide the required traction effect.

Tt uill be appreciated that the lugs or flaps 14 are produced by removing material from the ualls of the tyre beingiimodified. Conveniently the flaps are formed before the punching out of the openings- 9 so as to facilite the handling of the device during the hole punching operation.

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