Patent Description:
A variety of anti-skid devices are available for mounting on vehicle tyres to enhance friction under extreme snow and ice conditions. Snow chains have been the standard for many years, though effective, they suffer from several disadvantages. Some of the disadvantages with such chains is that they are heavy, cumbersome, noisy in contact with bare pavement or with the inside of the fenders and require jacking-up the car to mount on wheels. A motorist faced with all these difficulties tends to leave the chains mounted even in ice and snow-free roads and this results in an accelerated rate of wear of the chains. In addition, these kinds of devices take up valuable space when not in use. To overcome the limitations of traditional snow chains, other types of anti-skid devices have been invented, these are devices composed of a plurality of arms radiating from a central housing, each arm is linked to a hook-like anti-slip component which extends transversally over the tread of the tyre. <CIT>, and <CIT>, Robeson, teaches an emergency traction device which may be easily and securely fitted on vehicles having tires of different diameters and widths. A first winch sizes and secures the traction device for the proper tire diameter and a second winch sizes and secures the traction device for the proper tire width.

<CIT>, offers a flat circular plate with continuous spiral threads rotatable mounted in central casing having five periphery openings in which rack members are slidably mounted, and where at outer ends has a shaft portion with traction hooks for engaging with outer part of tyre. The Hook connection limits radially outward movement, but it permits inward movement. This document discloses the features of the preamble of claim <NUM>.

<CIT>, Jeakal, disclose a snow chain device with an operating plate arranged in the outer centre of a tire and composed of a plurality of entrance passages arranged around the peripheral part, and a plurality of friction members, where a plurality of entrance members are connected with the other ends of the friction members and disposed to go into the entrance passages of the operating plate and a holding/releasing unit for holding and releasing the entrance member fitted into the operating plate by the forcible-inserting unit.

<CIT> discloses an anti-skid attachment for a vehicle wheel having a central ring placed on the wheel hub. The central ring is connected to lugs by radial arms.

The lugs are intended to cut the ice or provide more bite on the snow and are shaped in such a way as to encircle the tyre sides. Each lug is provided with a prismatic end to the said central ring and connected with guide means provided with a recess to house and guide the end of any of the lugs. A spring controls the axial movements of each lug, caused by the deformation of the tyre.

<CIT> discloses an anti-skid device with <NUM> arms, where cables are used for moving the arms for mounting and dismounting.

<CIT> discloses an anti-skid device with <NUM> arms, where tension springs are used for retaining the arms.

<CIT> discloses an anti-skid device with <NUM> arms, where a linkage system is used for moving the arms. The linkage system is quite complicated and consists of many parts.

Further examples of such devices are described in the following patents: (<NUM>) <CIT>, (<NUM>) <CIT>, (<NUM>) <CIT>, (<NUM>) <CIT>. Although these anti-skid devices fulfil their intended purposes, they suffer from several shortcomings, they are complex, cumbersome, made of many parts, expensive to manufacture, difficult to place upon the wheel, heavy, and take up space when not in use. In general, they lack simplicity. It is therefore an object of the present invention to overcome many of the disadvantages of the prior art and to present to the market an anti-skid device that is simple, effective and efficient, compact, lightweight and cheap to manufacture.

The primary object of this invention is to provide an anti-skid device which is easy to mount and dismount from the wheel without the need of skills, physical strength or a separate tool.

Another object of the invention is to provide an anti-skid device which is simple, compact and made of few parts.

Another object of this invention is to provide an anti-skid device which can be mounted from the front face of the wheel and can be adapted to different wheel sizes.

Another object of this invention is to provide an anti-skid device which remains fastened even if the wheel changes diameter due to the flattening of the tyre at the wheel-ground contact.

The springs or spring elements <NUM>, <NUM>, <NUM>, <NUM> used in the anti-skid device <NUM> may be composed of different materials including metals or polymers. Referring to the drawings in detail, <FIG> show an anti-skid device <NUM> according to the invention. As shown the device <NUM> according to the invention consists of three arms <NUM>.

At the outer end of each arm <NUM> is an attachment point <NUM> to which anti-slip elements <NUM> are removably fastened by sleeve <NUM>. The relationship between mount <NUM> and sleeve <NUM> allows the anti-slip elements <NUM> freedom to move in a single linear axis such that they may slide inwards (towards the centre of the wheel), but may not slide outwards beyond a fixed limit. A great advantage with this construction is that it allows the device to be fitted to a range of wheel diameters by adjusting the lengths of the arms <NUM>. At their inner ends the arms <NUM> are held slidably by a hub <NUM> comprising a housing <NUM>, backplate <NUM> and guides <NUM>, <NUM>. Handle <NUM> is part of the operating means used to operate the inwards or outwards movement of the arms <NUM> to facilitate device <NUM> being mounted onto a wheel. This will be described in more detail with reference to <FIG> and <FIG>. <FIG> shows the device <NUM> with arms <NUM> fully extended prior to being mounted on the wheel while <FIG> shows the device <NUM> fastened to the wheel. The handle <NUM> may be foldable/retractable and/or detachable from the device <NUM> when not in use.

In <FIG> there is shown the anti-slip element <NUM>. Each element <NUM> has a sleeve <NUM> that is connected to the outer end of the arm <NUM>. Each anti-slip element <NUM> is composed of two identical and symmetrical parts with a gap between allowing in this way a greater coverage of the tyre with an anti-slip surface. Sleeve <NUM> slidably receives the attachment point <NUM> of the arm <NUM>. In this preferred embodiment, attachment point <NUM> is wider than the majority of arm <NUM> and equipped with a flange <NUM> at its extremity. As can be seen in <FIG>, sleeve <NUM> assembles to arm <NUM> below attachment point <NUM>, before sliding outwards until it is stopped by flange <NUM>. Thus sleeve <NUM> and anti-slip element <NUM> are free to slide inwards but may not slide outwards due to the limiting effect of flange <NUM>. It is also possible to create sleeve <NUM> with a partially closed end, such that it is this partially closed end that limits the outward movement of sleeve <NUM> in relation to arm <NUM>. In this case flange <NUM> would not be required. This limited sliding interaction between anti-slip element <NUM> and arm <NUM> is important, in that it ensures that the upwards radial force created as the car drives over anti-slip element <NUM> is not transferred to arm <NUM> and thus to housing <NUM>. Thus the anti-slip element <NUM> is free to follow the depression of the tyre created as the car drives over anti-slip element <NUM> and will return outwards to the limit of its travel once the weight of the car is removed from anti-slip element <NUM> and the tyre retakes its original form once more.

Each anti-slip element <NUM> is equipped with multiple raised grip details <NUM> irregularly spaced, both, in the inner and the outer surfaces to increase friction with the ground, and to prevent any circumferential movement of the anti-slip components along the tyre tread. In this preferred embodiment, grip details <NUM> take the form of protuberances, but may also take the form of holes or local areas formed from a high friction material. Circumferential movement prevention is further enforced by the curved shape <NUM> of the left and right parts of the anti-slip element <NUM>. An additional benefit of the curved shape <NUM> is observed under braking conditions, where curved shape <NUM> will mechanically engage with the deformable rubber of the tyre, thus not relying solely upon the friction created by grip details <NUM>. This is important in that it reduces the forces exerted upon arms <NUM> and housing <NUM> during braking. Undesired outwards movement of the anti-slip element <NUM> relative to the tyre is prevented by shoulder <NUM>, cupping the inside wall of the tyre and preventing the device <NUM> from loosening from the tyre. This is particularly relevant in the case where a wheel spinning at higher speed while turning the car to the left or right may exert a combination of centrifugal and axial outwards forces on the device <NUM>, requiring an extremely secure fastening of device <NUM> to the tyre. In alternate embodiments, shoulder <NUM> may be replaced by one or more hook details, or a hinged flange detail able to be locked in a downwards position thus preventing outwards movement of anti-slip element <NUM>. Anti-slip element <NUM> could also be formed in other ways, for example as by a thick wire element shaped to perform the same task without deviating from the spirit of the invention.

<FIG> shows an exploded 3D view of the device <NUM>. At its inner end the device has a backplate <NUM> that rests against a wheel hub when in use. On the front side of the backplate <NUM> are U-shaped guides <NUM> that receive the arms <NUM> and allow them to slide in a guided manner (i.e. linearly) when extended or retracted. Optional guides <NUM> are also shown and may be included for adding strength. Further outwards are shown the arms <NUM>. Their design and function will be described in more detail with <FIG>. Further there is a ring <NUM> that interacts with a locking detail in the rear of cover <NUM>, used to lock the rotation of handle <NUM> and cover <NUM> and thus set the extension of arms <NUM>. In this embodiment, handle <NUM> is hingeably connected to cover <NUM> such that they rotate together. The housing <NUM> is fastened to the backplate <NUM> with screws mounted through multiple holes <NUM>. The arms will thus be held in place while still being allowed to move linearly in the guides <NUM> (<NUM>). The ring <NUM> is equipped with multiple slots <NUM> intended to engage with one or more locking teeth on the rear side of cover <NUM> (not visible in the exploded view). The teeth might be formed like a shark's fin and may be hinged and sprung such that they engage with the slots. Cover <NUM> pivots freely around the central axis of gear <NUM>. Cover <NUM> is attached to spring <NUM> which is in turn attached to gear <NUM>. The spring element <NUM> allows the user to introduce tension to the system. When the user rotates handle <NUM>, cover <NUM> rotates around the central axis of gear <NUM>, tightening spring <NUM> and in turn rotating gear <NUM>. Rotation of gear <NUM> clockwise causes arms <NUM> to retract inwards, tightening anti-slip elements <NUM> around the tyre. When anti-slip elements <NUM> are sitting tightly around the tyre, due to the spring <NUM>, the user can turn handle cover <NUM> slightly further, for example <NUM> degrees rotation, before locking the rotation of handle cover <NUM>. Thus, the anti-slip elements <NUM> are pretensioned inwards due to the compressed nature of spring <NUM>. This is advantageous in the case where the tyre is temporarily deformed inwards, for example if the car drives over a stone. Here the tyre will depress inwards, and due to the pre-tensioning of arm <NUM> and anti-slip element <NUM> by spring <NUM>, anti-slip element <NUM> will follow the movement of the tyre inwards, thus following the depression and maintaining a consistent fit with the tyre. This consistent fit prevents shoulder <NUM> of anti-slip element <NUM> that rests on the inside of the wheel from losing its grip, thus ensuring device <NUM> remains fastened securely on the wheel. It is a further advantage of the preferred embodiment that the use of three arms allows the device to be more easily attached to a wheel than say five arms. This is due to the fact that by attaching to the wheel with a single anti-slip element <NUM> positioned at the top of the tyre, the two lower arms <NUM> and anti-slip elements have clearance both to the metal body of the car surrounding the wheel, and to the wheel itself. A device equipped with <NUM> or <NUM> arms is more difficult to assemble to the wheel due to having to pass through the gap between wheel and car body while in extended position.

Equipping the device <NUM> with three arms <NUM> has the additional advantage in that in the event that the slidable connection between arm <NUM> and anti-slip element <NUM> becomes locked, for example a stone or grit lodges in the mechanism, that the resulting upwards displacement of the device <NUM> will not loosen an anti-slip plate positioned diametrically opposite the anti-slip plate being driven over.

<FIG> illustrates the point where the weight of the car compresses the tyre and shows anti-slip element <NUM> and sleeve <NUM> translated upwards relative to arm <NUM>, thus ensuring that force is not transferred to arm <NUM>. <FIG> illustrates the tyre having rotated further, and having resumed its former shape, with anti-slip element <NUM> returning to its original position.

As mentioned earlier, handle <NUM> is hingeably connected to cover <NUM>, such that it has a retracted position resting in a recess, and a folded outwards or usage position as shown in <FIG>. Handle <NUM> is arranged such that when the user pushes outward on handle <NUM> (whilst in its usage position), the teeth disengage, allowing cover <NUM> to rotate relative to part <NUM> and the rest of the device. When the user has tightened/loosened the system as desired, they release pressure on the handle <NUM>, and the sprung teeth will engage with the slots <NUM>. Folding handle <NUM> in gives an extra degree of security, locking the teeth in place. An alternate locking mechanism could be a handle with a pin engaging a series of holes or slots in a plate as shown in <FIG>.

In <FIG> the arms are shown in more detail. Each arm <NUM> has an elongated hole <NUM>. A series of rack teeth <NUM> are cut along one long side of the hole <NUM>. The pinion <NUM> is driven by the rotation of handle <NUM>, in this case connected by spring <NUM>. In this preferred embodiment there is one pinion <NUM> long enough to engage the rack teeth <NUM> in all the arms <NUM>. The turning of the handle <NUM> will cause the assembly to rotate and the pinion <NUM> will then engage with the teeth to extend or retract the arms <NUM>. Optionally there may be three pinions <NUM>, one for the rack teeth in each arm.

In <FIG> there is shown such an alternative embodiment for keeping the anti-slip element <NUM> in contact with the tyre. In this embodiment, arm <NUM> is formed as a hollow tube, wherein the rack <NUM> is a slideable element positioned inside arm <NUM>. In <FIG> the outer surface of arm <NUM> is removed such that the inner mechanism is visible. Now spring <NUM> is arranged to bias the arm to its retracted position. When the arms are extended the spring <NUM> will exert a force that seeks to retract the arms <NUM> and thus hold the anti-slip element <NUM> in a tight position against the tyre. Such an embodiment can be advantageous in that springs are internalised and do not increase the thickness of device <NUM>. One or several springs <NUM> may be used if greater spring force is required than that provided by a single spring <NUM>. A further variant of device <NUM> which utilizes the internal spring mechanism described here may be envisaged wherein anti-slip elements <NUM> are permanently affixed to arms <NUM> with no sliding relationship between them at attachment point <NUM>. Instead, in this embodiment, the inwards compression resulting from the wheel driving over the anti-slip element <NUM> would be allowed for by the relative movement of rack <NUM> to arm <NUM>. This has the advantage of simplifying the attachment of anti-slip components <NUM> to arms <NUM>, but the disadvantages of a greater space requirement when stored and that the arms <NUM> will slide relative to each other within housing <NUM>, which may result in more wear to these components.

<FIG> shows an embodiment of handle <NUM> and locking ring <NUM> alone for ease of understanding. As in the first embodiment described, ring <NUM> is penetrated with a plurality of holes <NUM>. A pin <NUM> is used to lock the rotation of handle <NUM> relative to ring <NUM>, whereby pin <NUM> connects removably with the nearest hole <NUM> to the desired locking position.

As a further alternative embodiment of the operating means, which is not according to the invention, it may be envisaged that the arms <NUM> slide linearly as described earlier, but are self-tightening with for example a one direction ratchet mechanism. In such an embodiment a handle <NUM> would not be necessary, and instead a release mnchanism would be activated tn allow the arms <NUM> tn move outwards for removal from the wheel.

When not in use the device is stored in the boot of the car. When it is needed the device will be placed beside the wheel and the handle first turned anti clockwise to extend the arms <NUM> outwards such that the device can be mounted onto the wheel. When in place around the tyre the handle <NUM> will be turned in the clockwise direction to retract the arms <NUM> until the anti-slip elements <NUM> fit tightly around the rim of the wheel. The same procedure is used to mount a second device on the other driving wheel. While it is not foreseen that it should be necessary to use the device on all four wheels of a <NUM> wheel drive car, it may at times be necessary since some <NUM>-wheel drive cars will adjust the power to the driving axle that has the least resistance.

Claim 1:
An anti-skid device (<NUM>) for enhancing traction on slippery roads comprising:
- <NUM> arms (<NUM>) protruding radially from a hub (<NUM>), which will be placed on the outside of a wheel and which terminate in anti-slip elements (<NUM>) intended to be arranged on the tread surface of the tyre,
- operating means connected to said hub (<NUM>) so as to allow the extension or contraction of said arms (<NUM>),
- said anti-slip elements (<NUM>) equipped with a shoulder (<NUM>) arranged to grip behind said wheel,
- said operating means equipped with locking means preventing extension of the arms (<NUM>) when being engaged, said arms (<NUM>) are equipped with a compressive joint (<NUM>) allowing the inwards displacement of anti-slip elements (<NUM>) to follow a displacement of the tyre without in turn displacing the hub (<NUM>)
characterized in that a handle (<NUM>) of the operating means is rotatably connected to the hub (<NUM>) and is connected to the arms (<NUM>) by gears (<NUM>) such that rotational reciprocating movement of the handle (<NUM>) is translated into linear movement of the arms (<NUM>), each arm (<NUM>) having an elongated hole (<NUM>) and a series of rack teeth (<NUM>) being cut along one long side of the hole (<NUM>), where the gears comprises a pinion (<NUM>) that is adapted to be driven by the rotation of the handle (<NUM>), such that turning of the handle (<NUM>) will cause the pinion (<NUM>) to rotate and engage with the teeth (<NUM>) to extend or retract the arms (<NUM>).