Patent Description:
It is known from the state of the art to produce a tread surface of a solid tire which contacts the floor over which the tire is moving, comprising curable or cured non-marking material to avoid the presence of unwanted tire marks on the floor surface. Tires made of rubber containing carbon black, usually leave black markings when moving over the floor. Such markings are especially undesired in situations where for example high demands on hygiene are imposed, for example areas where food is being processed. It is also known from the state of the art that the marking of the floor can be avoided by replacing part of the traditional mixtures for the tread surface which contain carbon black with, for example, silica based mixtures to obtain a more non-marking material.

A tire having a tread surface made of such a non-marking mixture however presents the disadvantage that the electrical conductivity of the non-marking tread surface is low. Whereas with a tire having a tread surface comprising a carbon black mixture, electrical charges built up to the vehicle could be sufficiently conducted towards the ground, tires of which the tread surface is made of a non-marking mixture can only conduct the electrical charge towards the ground at a higher potential difference between the ground and the vehicle. As a consequence, tires having a tread surface made of a non-marking mixture often show spark discharges, which can be dangerous and are often unwanted, especially in environments containing explosive or inflammable materials.

More in particular <CIT> discloses an attempt to solve this problem and discloses a method for making a tire for a vehicle wheel comprising electrically conducting means, the tire comprising a tread surface delimited by two opposing tire sidewalls. A first step of the method consists of making a preliminary tire, the uncured tire, comprising a first layer comprising an outer circumferential surface and an inner circumferential surface interconnected by opposing first layer sidewalls. These first layer sidewalls delimit together the first layer which extends in circumferential direction of the tire. The first layer is made of a first material containing a reinforcing filling material. This first material comprises less than <NUM> pphr (parts per hundred) carbon black, at least <NUM> pphr of reinforcing filling material and has an electrical resistance above <NUM><NUM> Ωcm (Ohm centimetre), due to which it is called a non-conducting material of a non-conducting part of the tire. A second step consists of removing a part of the first layer, using for example a drilling or cutting tool, to create a path which extends at least from an inner circumferential surface of the first layer through the first layer towards an outer circumferential surface of the first layer. The path is subsequently filled under atmospheric pressure with a conducting material, the path-filling material, having an electrical resistance which is smaller than <NUM><NUM> Ωcm. Finally, the preliminary tire added with the conducting material becomes a final tire so that the respective first layer sidewalls become part of the respective tire sidewalls and so that a total ground contacting surface of at least <NUM><NUM> (squared millimetre) is created.

The prior art provides a way of creating a conducting path of conducting material through the non-conducting part of the tire, being for example the first layer. <CIT> provides a method that comprises the making of a path through for example the first layer, up to the inner circumferential surface of the first layer that is in contact with the rim of the wheel. The path is created by removing a part of the non-conducting material for example of the first layer, using a tool such as a knife or drilling tool. However, there is no way of telling with certitude whether the path has entered the conducting part of the tire, without having to take away an excessive amount of material which causes for example material waste and degenerative mechanical properties. Making the conducting path too short to reach the inner circumferential surface of the first layer is detrimental to the functioning of the tire as an anti-static tire because no charge would be able to flow easily through the path. A further concern with the existing methods lies in the fact that there is no disclosed way to ascertain that the path after curing is for example defect free such as for example filled entirely with conducting material, without for example interruption of the pathway by for example non-conducting material or air bubbles hindering the flow of charge through the path.

It is furthermore known in the prior art, such as from patent publication <CIT>, to provide an anti-static solid tire having a marking and non-conducting tread layer, second layer and third layer of the same material, and having an electrically conductive coating applied along the side walls of the tread layer, the second layer and the third layer.

It is furthermore known in the prior art, such as from patent publication <CIT>, to provide a non-marking anti-static solid tire having a non-marking and non-conducting tread layer, a marking and conducting second and third layer of the same material applied below the tread layer, and a non-marking and non-conducting layer covering the sidewalls of the tread layer, the second layer and the third layer. The non-marking and non-conducting tread layer is occasionally pierced by the underlying marking and conducting second layer such as to provide the anti-static properties of the solid tire.

It is furthermore known in the prior art, such as from patent publication <CIT>, to provide a marking anti-static solid tire having a marking and conducting tread layer, a non-marking and non-conducting second and third layer of the same material applied below the tread layer, and a marking and conducting layer covering the sidewalls of the tread layer, the second layer and the third layer.

There is thus need for a method for producing tires with a non-marking thread surface which are more easily provided with conducting material.

It is an object of the present invention to provide a tire obtained by such method.

The present invention relates to a tire for a vehicle wheel comprising electrically conducting means, the tire comprising a tread surface delimited by two opposing tire sidewalls, comprising a first cylindrical layer of a first material, comprising an outer circumferential surface and an inner circumferential surface, the inner and outer circumferential surface being interconnected by opposing first layer sidewalls and together delimiting the first layer. The tire also comprises a conducting material having an electrical resistance which is smaller than the electrical resistance of the first layer applied from the inner circumferential surface of the first layer towards the outer circumferential surface of the first layer so that the respective first layer sidewalls are part of the respective tire sidewalls and that the conducting material can be electrically connected to the electrically conducting means of the wheel, the conducting material extending from the inner circumferential surface of the first layer to the outer circumferential surface of the first layer.

According to the present invention, the conducting material is applied along at least one of the opposing tire sidewalls. The conducting material is applied on the outer surface of at least one of the opposing tire sidewalls. The operator controlling the tire for example for a regular for example annual control, can now more easily inspect, for example visually, the integrity of the applied conducting material, with respect to for example the presence of cracks on the interface between the conducting material and the first layer material, for example the non-conducting material.

According to embodiments of the present invention, the conducting material is applied along at least one of the opposing first layer sidewalls of the tire. The conducting material is applied on the outer surface of at least one of the opposing first layer sidewalls.

According to embodiments of the present invention, the conducting material is partly enveloped by the first material, when applied along at least one of the tire sidewalls. The material of the first layer, and the conducting material are bound together to form one structural entity.

According to embodiments of the present invention, the conducting material is at least partly covered with a covering material. This covering material for example shelters the conducting material from the exterior environment of the tire.

According to embodiments of the present invention, the conducting material and the adjacent material of the first layer, for example non-conducting material, are at least partly covered with the covering material.

According to embodiments of the present invention, the covering material is applied to the outer surface of at least the conducting material, along the tire sidewall.

According to embodiments of the present invention, the material of the covering material is the same as the conducting material.

According to embodiments of the present invention, the covering material is applied to the outer surface of at least the conducting material, along the outer circumferential surface of the first layer.

According to embodiments of the present invention, the material of the covering material is the same as the material of the first layer. This embodiment provides a tire where the marking material for example the material of the conducting material, is completely shielded from the ground.

According to embodiments of the present invention, the thickness of the covering material is reduced in order to allow a flow of charge between the conducting material and the ground. Even when the covering material applied to the outer circumferential surface of the first layer is the material of the first layer, for example the non-conducting material, for example in order to shield the marking material from the ground, the tire can still be used as an anti-static tire thanks to the reduced thickness of the covering material.

According to embodiments of the present invention, the covering material comprises a hole for example in the centre of the covering surface, in order to allow the conducting material to protrude to the surface and to allow a flow of charge between the conducting material and the ground.

According to embodiments of the present invention, the shape of the covering material is at least semi-oval, rectangular or a simple polygon.

According to embodiments of the present invention, the conducting material is at least partly enveloped by the first material. In some embodiments of the invention the conducting material is entirely enveloped by the first material. The material of the first layer, and the conducting material are bound together to form one structural entity.

According to embodiments of the present invention, the conducting material fills at least one path which extends at least from the inner circumferential surface of the first layer through the first layer towards the outer circumferential surface of the first layer. These conducting paths provide a way for the charge to flow through the material of the first layer, which can be a non-conducting part of the tire.

According to embodiments of the present invention, the paths extend linearly from the inner circumferential surface towards the outer circumferential surface.

According to embodiments of the present invention, the paths extend radially from the inner circumferential surface towards the outer circumferential surface. In this embodiment the distance of the path from the inner circumferential surface towards the outer circumferential surface is minimised, requiring the least amount of conducting material and minimising the resistive path for the charge to flow.

According to embodiments of the present invention, the paths are cylindrical, having different possible cross-sectional shapes such as at least semi-circular, triangular, at least-semi oval, rectangular or a simple polygon. The choice of shape can be adapted by the person skilled in the art depending on the desired configuration.

According to embodiments of the present invention, at least two paths are present along the tire's circumference. The amount of paths can be adapted for example to the discharging needs of the tire.

According to embodiments of the present invention, the paths are evenly distributed along the circumference of the tire, in order to promote for example homogeneity of discharging and mechanical properties of the tire.

According to embodiments of the present invention, the paths on at least one of the sides of axial symmetry of the tire are evenly distributed along the circumference of the tire. The paths are on one axial side or on the two axial sides of the tire, wherein the axial symmetry plane divides the tire in two axial sides.

According to embodiments of the present invention, the paths of one of the sides of axial symmetry of the tire oppose the paths of the other side of axial symmetry of the tire.

According to embodiments of the present invention, the paths of one of the sides of axial symmetry of the tire and the paths of the other side of axial symmetry of the tire are interdigitated. The different embodiments can be adapted to for example the required discharging frequency or other discharging properties.

According to a preferred embodiment, the conducting materials have a total ground contacting surface area of at least <NUM><NUM>, in order to provide a sufficient ground contacting area to reduce the resistance to the flow of charge through the conducting material.

According to embodiments of the present invention, the material of the first layer comprises less than <NUM> pphr carbon black. Reducing the amount of carbon black for example reduces the risk of leaving marks on the ground, creating a non-marking tire.

According to embodiments of the present invention, the material of the first layer comprises less than <NUM> pphr carbon black.

According to embodiments of the present invention, the electric resistivity of the material of the first layer is above <NUM><NUM> Ωcm. The use of carbon black as a reinforcing material for elastomers is well known in the art. However, since carbon black leaves undesired black marks on the floor, its concentration is to be limited. It is another well-known fact that reducing the amount of carbon black as a reinforcing filling material in the first layer also tends to increase the electric resistivity of the first layer. The electric resistivity of the non-conducting material, for example the first layer material, should be measured according to ISO <NUM>.

According to embodiments of the present invention, the material of the first layer comprises between <NUM> pphr and <NUM> pphr reinforcing material.

According to embodiments of the present invention, the material of the first layer comprises <NUM> pphr reinforcing material.

According to embodiments of the present invention, the reinforcing filling material comprises a non-marking reinforcing filling material.

According to embodiments of the present invention, the reinforcing filling material comprises silica. Substituting an amount of carbon black as a reinforcing filling material with silica has several advantageous effects, for example reducing the rolling resistance of the tire.

According to embodiments of the present invention, the non-marking reinforcing filling material comprises a white non-marking reinforcing filling material.

According to embodiments of the present invention, the applied conducting material has an elastic modulus comparable to the elastic modulus of the material of the first layer, for example non-conducting material, for example the first layer material, for example in order to optimise load carrying properties.

According to embodiments of the present invention, the applied conducting material has an electric resistivity less than that of the material of the first layer, for example non-conducting material, for example the first layer material. In preference, the electric resistivity of the conducting material is less than <NUM><NUM> Ωcm, measured according to the ISO <NUM> standard.

According to the present invention, a further cylindrical layer, the second cylindrical layer, of a second material is provided which extends in circumferential direction of the tire and which comprises a second outer circumferential surface, wherein along the second outer circumferential surface the first layer of the first material is provided in such a way that the first inner circumferential surface of the first layer runs along the second outer circumferential surface, the material of the second layer having a smaller electrical resistance than the material of the first layer and wherein the conducting material extends at least up to the second layer. Although the presence of the first layer only will be sufficient for some applications, the tire may comprise more than one layer. Thereby the material used for building the first and second layer may be the same or different. The second material serves a typical function of the tire's design, as known by the person skilled in the art and any material adapted thereto can be used. The material of the second layer can for example comprise relatively soft rubber with good dynamic and resilient properties. The material of the second layer can for example comprise carbon black, since it does not contact the ground and can therefore leave no marks on the floor. The use of carbon black moreover combines good conducting properties with good dynamic and resilient properties. The conductivity of the material of the second layer is however not critical for the invention. When the second material of the second layer is not sufficiently conducting for discharging unwanted electric charges to the ground or when an increased discharge of such charges is desired, the conducting material is extended through the second layer so that the conducting material contacts the electrically conducting means, such as for example the rim.

According to embodiments of the present invention, the second layer may for example comprise a metal plate which is then mounted to the rim and thus to the electrically conducting means of the vehicle. Such a tire is a press-on tire and for example comprises at least one layer of rubber bonded to the metal plate.

According to the present invention, the second layer comprises a second inner circumferential surface on a side of the second layer opposite the second outer circumferential surface, wherein a third cylindrical layer of a third material is applied beneath the second layer in circumferential direction of the tire, the third layer comprising a third outer circumferential surface running along the second inner circumferential surface and wherein the third layer is in electrical connection with the second layer and the electrically conducting means of the wheel. The material of the third layer preferably comprises a hard rubber to ensure a firm mounting to the wheel, more preferably the rim. In case no third layer is present, the material of the third layer could be used for the second layer.

According to the present invention, the paths extends from the third layer, along the first and the second layer up to the outer surface of the first outer circumferential surface so that the conducting material of the path is electrically connected to the third layer. Although the path can fully extend through the third layer to contact the electrically conducting means, it is sufficient for the path to extend up to the third outer circumferential surface if the material of the third layer is sufficiently electrically conducting to conduct unwanted electric charges from the electrically conducting means towards the ground and is in electrical connection with the electrically conducting means of the wheel. Since the material of the third layer does not contact the ground, carbon black may be used as a reinforcing filling material, preferably providing the third layer with a sufficient electrical conductivity to permit conducting unwanted electrical charges to the ground along material of the second layer if it is sufficiently conducting and/or the conducting material of the path.

According to embodiments of the present invention, the third layer may for example comprise a metal plate which is then mounted to the rim and thus to the electrically conducting means of the vehicle. Such a tire is a press-on tire and for example comprises at least one layer of rubber bonded to the metal plate.

According to the present invention, the first layer is provided for contacting the ground. It is through this contact that the electric charge will be discharged.

According to the present invention, the conducting means is electrically interconnected with the ground.

According to embodiments of the present invention, a tread pattern is applied on the outer surface of the first layer. The tread pattern influences the behaviour of the tire, for example with respect to water evacuation or noise production.

According to the present invention, a method is provided for producing a tire wherein the tire is a solid tire.

According to embodiments of the present invention, a vehicle wheel is provided which comprises a tire according to the present invention and conducting means, for example a rim, the conducting material of the tire being electrically connected to the electrically conducting means of the wheel.

The present invention relates to a tire <NUM> for a wheel <NUM> for a vehicle comprising electrical conducting means <NUM>, as shown in <FIG>. The wheel <NUM> is suitable for use with any vehicle known to the person skilled in the art, such as for example fork lift trucks, especially when the tire is a solid tire.

A method for making the tire <NUM> for a vehicle wheel <NUM>, comprising electrically conducting means <NUM>, the tire <NUM> comprising a tread surface <NUM> delimited by two opposing tire sidewalls <NUM> comprises the consecutive steps of:.

The first material for example comprises less than <NUM> pphr carbon black and at least <NUM> pphr reinforcing filling material. A length of conducting material <NUM> is added along for example the first layer sidewall <NUM> of the tire sidewall <NUM>, for example by cutting away a piece of first layer material, which extends from at least a first inner circumferential surface <NUM> of the first layer through the first layer <NUM> up to a first outer circumferential surface <NUM> of the first layer <NUM>, and by adding the material along the cut first layer sidewall. In the final tire <NUM> the added conducting material <NUM> will be at least partly enveloped by the material of the first layer, for example non-conducting material, forming one structural entity. This way the conducting material <NUM> has a ground contacting surface <NUM>, which is electrically connectable to the electrically conducting means <NUM> of the wheel <NUM>.

The use of carbon black as a reinforcing filling material for elastomers is well known in the art. However, since carbon black leaves undesired black marks on the floor, sometimes its concentration is for example limited to below <NUM> pphr and a non-marking reinforcing filling material is used beside the carbon black. As non-marking reinforcing filling material white reinforcing filling materials are used, preferably silica. The use of non-marking reinforcing filling materials and the reduced concentration of conducting carbon black in the tire <NUM> however may increase the electrical resistance. The electrical resistance of the material of the first layer <NUM> as described above is for example larger than <NUM><NUM> Ωcm. The first material for example comprises less than <NUM> pphr of carbon black, more preferably less than <NUM> pphr carbon black. However, not only non-marking tires have relatively large electrical resistances. It is well know from the state of the art that in order to improve the balance between rolling resistance versus wet traction, tread compositions are made with lower carbon black loadings. Such compositions may cause the tire <NUM> to have a higher electrical resistance Which may interfere with charge dissipation and result in static charge accumulation. Although the exact composition of the material of the first layer <NUM> is not critical for the invention, the composition of the material of the first layer <NUM> preferably is chosen in function of the mechanical properties to be achieved since the first layer <NUM> will contact the ground.

In order to provide a connexion between the conducting means <NUM> and the ground, conducting material <NUM> is added along for example the first layer sidewall <NUM>. A length of uncured conducting material <NUM> is added along for example the first layer sidewall <NUM> of the tire sidewall <NUM>, for example by cutting away a piece of first layer material, and by applying the material along the cut first layer sidewall. Removing part of the material of the first layer can be done in any way known to the person skilled in the art. The material can for example be cut away, molten away, burned away, pushed away, etc. The material of the first layer of the preliminary tire, for example non-conducting material, can be an uncured material at the time the material is being removed as well as a cured material. The added conducting material <NUM> can also be an uncured material or a cured material or an incurable material. Alternatively, the length of conducting material <NUM> could be applied along for example the first layer sidewall <NUM> of the tire sidewall <NUM>, without cutting away a piece of first layer material. In this optic the conducting material <NUM> will enter the material of the preliminary tire, for example the material of the first layer which can be non-conductive, only during the curing process and has the added advantage of wasting less material with respect to the process where part of the material of the first layer, for example non-conducting material, is removed. In both alternatives the conducting material <NUM> in the finished tire <NUM> will have formed conducting paths <NUM>. In the alternatives where uncured curable material is used, the material has to be cured in order to obtain the finished tire. When curing must be executed, the paths <NUM>, created before curing for example by cutting away a piece of material from the first layer <NUM>, for example non-conducting material, or created during curing for example where the conducting material <NUM> is added along the uncut preliminary tire, will have be present after curing. In the final tire the lengths of conducting material <NUM> applied to the tire <NUM> are the paths <NUM> of the tire <NUM>.

The length of conducting material <NUM> preferably extends in radial direction of the tire <NUM>, more preferably linearly from the first inner circumferential surface <NUM> towards the first outer circumferential surface <NUM>. In one exemplary embodiment, a part of the first layer <NUM> is removed in the form of a straight, preferably radially extending path <NUM>, which extends from the first inner circumferential surface <NUM> up to the first outer circumferential surface <NUM>. A radially extending linear length of conducting material <NUM> appears to provide optimum discharge of undesired electrical charges. According to several embodiments of the invention, the cross-sectional shape of the conducting material <NUM> can be such as circular, triangular, oval, rectangular or a simple polygon. The choice of shape can be adapted by the person skilled in the art depending on the desired configuration. <FIG> provide drawings of different possible cross-sectional shapes for the length of conducting material. <FIG>, <FIG> disclose respectively cross-sectional shapes circular, oval, triangular and rectangular. In the embodiments of <FIG>, <FIG>, <FIG>, <FIG> and <FIG>, the shape of conducting material is rectangular, whereas the embodiment in <FIG> comprises a semi-circular shape.

The total ground contacting surface <NUM> of the lengths of conducting material <NUM> for example has a surface area of at least <NUM><NUM>. The presence of a large ground contacting surface area increases the possibility of discharging unwanted electrical charges from the vehicle towards the ground. To limit the risk that marks are left on the floor by the conducting materials <NUM>, the total ground contacting surface <NUM> has a surface area preferably smaller than <NUM><NUM>.

The addition of the conducting material <NUM> preferably takes place under atmospheric pressure. The conducting material <NUM> can for example be manually inserted into the path <NUM> after having removed a piece of material of the first layer, for example non-conducting material. The manual application is however not critical for the invention and the conducting material <NUM> can for example also be mechanically inserted. The conducting material <NUM> can be any material deemed appropriate by the person skilled in the art but preferably is chosen in function of the composition of the material of the first layer <NUM> and the desired mechanical characteristics. It has been found by the inventor that a conducting material with an elastic modulus comparable to that of the material of the first layer, for example non-conducting material, is preferable. Preferably, the conducting material <NUM> comprises carbon black since carbon black renders the conducting material <NUM> sufficiently conducting to discharge unwanted electric charges to the ground and offers the conducting material good mechanical properties. The conducting material <NUM> preferably is provided in the form of a solid body, more preferably a plastic deformable solid body. The composition of the conducting material is however not critical for the invention and can for example be in the form of a paste. The dimensions of the solid body are preferably adapted to the dimensions of the path <NUM> that must be obtained.

On the outer circumferential layer <NUM> of the first layer <NUM> preferably a tread pattern <NUM> is provided to the tire <NUM> comprising ribs delimited by grooves. The ground contacting surface <NUM> of the conducting material <NUM> preferably is provided on a rib of the tread pattern so that the ground contacting surface <NUM> can more easily contact the ground.

The resulting tire <NUM> is then mounted to a rim <NUM> to form the wheel <NUM> in such a way that the conducting material <NUM> contacts the electrical conducting means <NUM> of the wheel <NUM>, for example the wheel rim <NUM>. Any method known to the person skilled in the art can be used to mount the first layer <NUM> to the rim <NUM> of the wheel such as for example clamping the first layer <NUM> between different parts of the rim <NUM>. The electrical conducting means <NUM> comprise any electrically conducting means which can be mounted to a vehicle, such as a rim <NUM> of a wheel parts of the engine, the frame, etc. The conducting material <NUM> preferably is electrically connected to the electrical conducting means <NUM> after mounting the tire <NUM> to the wheel <NUM> of the vehicle. More preferably, the conducting material <NUM> is electrically connected to the rim <NUM> of the wheel after mounting the tire <NUM> to the rim <NUM>. The conducting material <NUM> can contact the rim <NUM> directly or can be electrically connected to the rim <NUM> by intermediate parts such as for example different layers of the tire <NUM> conducting the unwanted electrical charges to the ground.

Although the presence of the first layer <NUM> only will be sufficient for some applications, the tire <NUM> may comprise more than one layer. Thereby the material used for building the first and second layer may be the same or different. The tire <NUM> of the present invention in that case is produced by providing a second cylindrical layer <NUM> which extends in circumferential direction of the tire <NUM>, and thereafter providing on top of this second layer <NUM> the first layer <NUM> forming the tread surface <NUM>. The second layer <NUM> comprises a second outer circumferential surface <NUM>, the inner circumferential surface <NUM> of the first layer <NUM> runs along the second outer circumferential surface <NUM> and the conducting material <NUM> extends at least up to the second outer surface <NUM>. The second layer <NUM> can comprise any second material known to the person skilled in the art.

The length of conducting material <NUM> may fully extend through the first layer <NUM> and the second layer <NUM> and may directly contact the electrically conducting means <NUM>. However it may be sufficient for the conducting material <NUM> to extend up to the second outer circumferential surface <NUM>, if the material of the second layer <NUM> has an electrical resistance which allows unwanted electric charges to be conducted from the electrically conducting means <NUM> towards the conducting material <NUM> along the material of the second layer <NUM>. In such an embodiment, the electrical resistance of the material of the second layer <NUM> preferably is smaller than the electrical resistance of the material of the first layer <NUM>.

The material of the second layer preferably comprises relatively soft rubber with good dynamic and resilient properties. The material of the second layer <NUM> can for example comprise carbon black since it does not contact the ground and can therefore leave no marks on the floor. The use of carbon black moreover combines good conducting properties with good dynamic and resilient properties.

The conductivity of the material of the second layer <NUM> is however not critical for the invention. When the second material of the second layer <NUM> is not sufficiently conducting for discharging unwanted electric charges to the ground or when an increased discharge of such charges is desired, the conducting material <NUM> is extended through the second layer <NUM> and preferably extends up to a second inner circumferential surface <NUM> with the conducting material <NUM> preferably extending up to the second inner circumferential surface <NUM> so that the conducting material contacts the electrically conducting means <NUM>, such as for example the rim <NUM>, when the tire <NUM> is mounted to the rim <NUM>.

Similarly a third layer <NUM> can be applied beneath the second layer <NUM> in circumferential direction of the tire <NUM>, the third layer <NUM> comprising a third material and a third outer circumferential surface <NUM> running along the second inner circumferential surface <NUM>.

Although the conducting material <NUM> can fully extend through the third layer <NUM> to contact the electrically conducting means <NUM>, it is sufficient for the conducting material <NUM> to extend up to the third outer circumferential surface <NUM> if the material of the third layer <NUM> is sufficiently electrically conducting to conduct unwanted electric charges from the electrically conducting means <NUM> towards the ground and is in electrical connection with the electrically conducting means <NUM> of the wheel <NUM>. The material of the third layer <NUM> preferably comprises a hard rubber to ensure a firm mounting to the wheel <NUM>, more preferably the rim <NUM>. Since the material of the third layer <NUM> does not contact the ground, carbon black may be used as a reinforcing filling material, preferably providing the third layer <NUM> with a sufficient electrical conductivity to permit conducting unwanted electrical charges to the ground along material of the second layer <NUM> and/or the conducting material <NUM>.

The material used to produce the first, second and third layer may be the same or different. Additional layers can still be added beneath the third layer, this is however not critical for the invention and the shape of the additional layer can be determined by the person skilled in the art.

Although the conducting material <NUM> may extend through all the layers provided beneath the first layer <NUM> for conducting the unwanted electrical charges from the electrically conducting means <NUM> up to the ground, the conducting material <NUM> preferably only extends through the first layer <NUM> when the material of the underlying layers are sufficiently conducting to discharge the unwanted charges towards the ground. Limiting the length of the conducting material <NUM> improves the homogeneity of the layered structure of the tire <NUM>, thus improving homogeneous wearing of the tire <NUM> and improving the homogeneity of the mechanical properties of the tire <NUM>. Decreasing the length of the conducting material <NUM> also decreases the amount of material that needs to be removed from the layers in certain embodiments, decreasing the time needed to make a tire <NUM> and decreasing loss of material caused by the removal.

<FIG> provide drawings of preferred embodiments of the tire according to different views. Parts a, b and c provide drawings in the radial plane of the tire <NUM>, whereas part d of <FIG> shows a circumferential cross-section of the first <NUM> and second layer <NUM> of the tire <NUM>.

<FIG> provide drawings of different possible cross-sectional shapes for the path <NUM>. <FIG>, <FIG> disclose respectively cross-sectional shapes circular, oval, triangular and rectangular.

<FIG> shows a first embodiment of the invention in a radial view wherein the conducting material <NUM> has a semi-circular cross-sectional shape and is applied on both sides of axial symmetry of the tire <NUM> in an interdigited configuration.

<FIG> shows a second embodiment of the invention in a radial view wherein the conducting material <NUM> has an semi-circular cross-sectional shape and is applied on both sides of axial symmetry of the tire <NUM> in an opposed configuration.

<FIG> shows a third embodiment of the invention in a radial view wherein the conducting material <NUM> has a semi-circular cross-sectional shape and is applied on one side of axial symmetry of the tire <NUM>.

<FIG> shows the embodiment of <FIG> in a circumferential view comprising first <NUM> and second layers <NUM>.

<FIG> shows a fourth embodiment of the invention in a radial view wherein the conducting material <NUM> has a semi-oval cross-sectional shape and is applied on both sides of the tire <NUM> in an interdigited configuration.

<FIG> shows a fifth embodiment of the invention in a radial view wherein the conducting material <NUM> has a semi-oval cross-sectional shape and is applied on both sides of axial symmetry the tire <NUM> in an opposed configuration.

<FIG> shows a sixth embodiment of the invention in a radial view wherein the conducting material <NUM> has a semi- oval cross-sectional shape and is applied on one side of axial symmetry of the tire <NUM>.

<FIG> shows the embodiment of <FIG> in a circumferential view comprising first and second layers.

<FIG> shows a seventh embodiment of the invention in a radial view wherein the conducting material <NUM> has a triangular cross-sectional shape and is applied on both sides of axial symmetry of the tire <NUM> in an interdigited configuration.

<FIG> shows a eighth embodiment of the invention in a radial view wherein the conducting material <NUM> has a triangular cross-sectional shape and is applied on both sides of axial symmetry of the tire <NUM> in an opposed configuration.

<FIG> shows a ninth embodiment of the invention in a radial view wherein the conducting material <NUM> has a triangular cross-sectional shape and is applied on one side of axial symmetry of the tire <NUM>.

<FIG> shows a tenth embodiment of the invention in a radial view wherein the conducting material <NUM> has a rectangular cross-sectional shape and is applied on both sides of axial symmetry of the tire <NUM> in an interdigited configuration.

<FIG> shows an eleventh embodiment of the invention in a radial view wherein the conducting material <NUM> has a rectangular cross-sectional shape and is applied on both sides of axial symmetry of the tire <NUM> in an opposed configuration.

<FIG> shows a twelfth embodiment of the invention in a radial view wherein the conducting material <NUM> has a rectangular cross-sectional shape and is applied on one side of axial symmetry of the tire <NUM>.

<FIG> shows a thirteenth embodiment of the invention in a radial view wherein the conducting material <NUM> has a covering material <NUM>, other than the conducting material <NUM>, added to at least the conducting material along the tire sidewall <NUM>, applied to both of the tire sidewalls <NUM> in an interdigited configuration. In the final tire, the material of the covering material <NUM>, for example non-conducting material, is merged with the first layer material <NUM> if the same material is used.

<FIG> shows a fourteenth embodiment of the invention in a radial view wherein the conducting material <NUM> has a covering material <NUM>, other than the conducting material <NUM>, added to at least the conducting material <NUM> along the tire sidewall <NUM>, added to both of the tire sidewalls <NUM> in an opposed configuration. In the final tire, the material of the covering material <NUM>, for example non-conducting material, is merged with the first layer material <NUM> if the same material is used.

<FIG> shows a fifteenth embodiment of the invention in a radial view wherein the conducting material <NUM> has a covering material <NUM>, other than the conducting material <NUM>, added to at least the conducting material <NUM> along the tire sidewall <NUM>, added to one of the tire sidewalls <NUM>. In the final tire, the material of the covering material <NUM>, for example non-conducting material, is merged with the first layer material <NUM> if the same material is used.

<FIG> shows a sixteenth embodiment of the invention in a radial view wherein the conducting material <NUM> has a covering material <NUM>, other than the conducting material <NUM>, added to the conducting material <NUM> along the tire sidewall <NUM>, applied to both of the tire sidewalls <NUM> in an interdigited configuration. In the final tire, the material of the covering material <NUM>, for example non-conducting material, is merged with the first layer material <NUM> if the same material is used.

<FIG> shows a seventeenth embodiment of the invention in a radial view wherein the conducting material <NUM> has a covering material <NUM>, other than the conducting material <NUM>, added to the conducting material <NUM> along the tire sidewall <NUM>, applied to both of the tire sidewalls <NUM> in an opposed configuration. In the final tire, the covering material <NUM>, for example non-conducting material, is merged with the first layer material <NUM> if the same material is used.

<FIG> shows an eighteenth embodiment of the invention in a radial view wherein the conducting material <NUM> has a covering material <NUM>, other than the conducting material <NUM>, added to the conducting material <NUM> along the tire sidewall <NUM>, applied to one of the tire sidewalls <NUM>. In the final tire, the covering material <NUM>, for example the non-conducting material, is merged with the first layer material <NUM> if the same material is used.

<FIG> shows a nineteenth embodiment of the invention in a radial view wherein the conducting material <NUM> has a covering material <NUM>, made out of the conducting material <NUM>, applied to at least the conducting material <NUM> along the tire sidewall <NUM>, applied to both of the tire sidewalls <NUM> in an interdigited configuration. In the final tire, the conducting material of the covering material <NUM> is merged with the conducting material <NUM> if the same material is used.

<FIG> shows a twentieth embodiment of the invention in a radial view wherein the conducting material has a covering material <NUM>, made out of the conducting material <NUM>, applied to at least the conducting material <NUM> along the tire sidewall <NUM>, applied to both of the tire sidewalls <NUM> in an opposed configuration. In the final tire, the conducting material of the covering material <NUM> is merged with the conducting material <NUM> if the same material is used.

<FIG> shows a twenty first embodiment of the invention in a radial view wherein the conducting material <NUM> has a covering material <NUM>, made out of the conducting material <NUM>, applied to at least the conducting material <NUM> along the tire sidewall <NUM>, applied to one of the tire sidewalls <NUM>. In the final tire, the conducting material of the covering material <NUM> is merged with the conducting material <NUM> if the same material is used.

<FIG> shows a twentieth second embodiment of the invention in a radial view wherein the conducting material <NUM> has a covering material <NUM>, made out of the conducting material <NUM>, applied to at least the conducting material <NUM> along the tire sidewall <NUM> and to at least the conducting material <NUM> along the outer circumferential surface <NUM> of the first layer <NUM>, applied to both of the tire sidewalls <NUM> in an interdigited configuration. The shape of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is rectangular. In the final tire, the conducting material of the covering material <NUM> is merged with the conducting material <NUM> if the same material is used.

<FIG> shows a twenty third embodiment of the invention in a radial view wherein the conducting material <NUM> has a covering material <NUM>, made out of the conducting material <NUM>, applied to at least the conducting material <NUM> along the tire sidewall <NUM> and to at least the conducting material <NUM> along the outer circumferential surface <NUM> of the first layer <NUM>, applied to both of the tire sidewalls <NUM> in an opposed configuration. The shape of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is rectangular. In the final tire, the conducting material of the covering material <NUM> is merged with the conducting material <NUM> if the same material is used.

<FIG> shows a twenty fourth embodiment of the invention in a radial view wherein the conducting material <NUM> has a covering material <NUM>, made out of the conducting material <NUM>, applied to at least the conducting material <NUM> along the tire sidewall <NUM> and to at least the conducting material <NUM> along the outer circumferential surface <NUM> of the first layer <NUM>, applied to one of the tire sidewalls <NUM>. The shape of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is rectangular. In the final tire, the conducting material of the covering material <NUM> is merged with the conducting material <NUM> if the same material is used.

<FIG> shows a twenty fifth embodiment of the invention in a radial view wherein the conducting material <NUM> has a first covering material <NUM>, made out of the conducting material <NUM>, applied to at least the conducting material <NUM> along the outer circumferential surface <NUM> of the first layer <NUM>, and a second covering material <NUM>, other than the conducting material <NUM>, added according to the method to the conducting material <NUM> along the tire sidewall <NUM>, applied to both sides of the axial symmetry of the tire <NUM> in an interdigited configuration. In the final tire <NUM>, the material of the covering material <NUM>, for example non-conducting material, is merged with the first layer material <NUM> if the same material is used. In the final tire, the conducting material of the covering material <NUM> is merged with the conducting material <NUM> if the same material is used. The shape of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is rectangular.

<FIG> shows a twenty sixth embodiment of the invention in a radial view wherein the conducting material <NUM> has a first covering material <NUM>, made out of the conducting material <NUM>, applied to at least the conducting material <NUM> along the outer circumferential surface <NUM> of the first layer <NUM>, and a second covering material <NUM>, other than the conducting material <NUM>, added according to the method to the conducting material <NUM> along the tire sidewall <NUM>, applied to both sides of the axial symmetry of the tire <NUM> in an opposed configuration. In the final tire <NUM>, the material, for example non - conductive, of the covering material <NUM> is merged with the first layer material <NUM> if the same material is used. In the final tire, the conducting material of the covering material <NUM> is merged with the conducting material <NUM> if the same material is used. The shape of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is rectangular.

<FIG> shows a twenty seventh embodiment of the invention in a radial view wherein the conducting material <NUM> has a first covering material <NUM>, made out of the conducting material <NUM>, applied to at least the conducting material <NUM> along the outer circumferential surface <NUM> of the first layer <NUM>, and a second covering material <NUM>, other than the conducting material <NUM>, added according to the method to the conducting material <NUM> along the tire sidewall <NUM>, applied to one side of the axial symmetry of the tire <NUM>. In the final tire <NUM>, the covering material <NUM>, for example non-conducting material, is merged with the first layer material <NUM> if the same material is used. In the final tire, the conducting material of the covering material <NUM> is merged with the conducting material <NUM> if the same material is used. The shape of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is rectangular.

<FIG> shows a twenty eighth embodiment of the invention in a radial view wherein the conducting material <NUM> has a first covering material <NUM>, other than the conducting material <NUM>, applied to at least the conducting material <NUM> along the outer circumferential surface <NUM> of the first layer <NUM>, and a second covering material <NUM>, other than the conducting material <NUM>, added according to the method to the conducting material <NUM> along the tire sidewall <NUM>, applied to both sides of axial symmetry of the tire <NUM> in an interdigited configuration. In this embodiment the thickness of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is reduced in order to allow the flow of charge between the conducting material <NUM> and the ground. In the final tire, the covering material <NUM>, for example non-conductive, is merged with the first layer material <NUM> if the same material is used. The shape of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is rectangular.

<FIG> shows a twenty ninth embodiment of the invention in a radial view wherein the conducting material <NUM> has a first covering material <NUM>, other than the conducting material <NUM>, applied to at least the conducting material <NUM> along the outer circumferential surface <NUM> of the first layer <NUM>, and a second covering material <NUM>, other than the conducting material <NUM>, added according to the method to the conducting material <NUM> along the tire sidewall <NUM>, applied to both sides of axial symmetry of the tire <NUM> in an opposed configuration. In this embodiment the thickness of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is reduced in order to allow the flow of charge between the conducting material <NUM> and the ground. In the final tire <NUM>, the material of the covering material <NUM>, which can be non-conductive, is merged with the first layer material <NUM> if the same material is used. The shape of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is rectangular.

<FIG> shows a thirtieth embodiment of the invention in a radial view wherein the conducting material <NUM> has a first covering material <NUM>, other than the conducting material <NUM>, applied to at least the conducting material <NUM> along the outer circumferential surface <NUM> of the first layer <NUM>, and a second covering material <NUM>, other than the conducting material <NUM>, added according to the method to the conducting material <NUM> along the tire sidewall <NUM>, applied to one sides of axial symmetry of the tire <NUM>. In this embodiment the thickness of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is reduced in order to allow the flow of charge between the conducting material <NUM> and the ground. In the final tire <NUM>, the for example non-conducting material of the covering material <NUM> is merged with the first layer material <NUM> if the same material is used. The shape of the covering material <NUM> applied on the outer circumferential surface <NUM> of the first layer <NUM> is rectangular.

<FIG> shows a thirty first embodiment of the invention in a radial view wherein the covering material <NUM> applied along outer circumferential surface <NUM> of the first layer <NUM> of the embodiment in <FIG> is provided with a round covering material <NUM>.

<FIG> shows a thirty second embodiment of the invention in a radial view wherein the covering material <NUM> applied along outer circumferential surface <NUM> of the first layer <NUM> of the embodiment in <FIG> is provided with a round covering material <NUM>.

<FIG> shows a thirty third embodiment of the invention in a radial view wherein the covering material <NUM> applied along outer circumferential surface <NUM> of the first layer <NUM> of the embodiment in <FIG> is provided with a round covering material <NUM>.

<FIG> shows a thirty fourth embodiment of the invention in a radial view wherein the covering material <NUM> applied along outer circumferential surface10 of the first layer <NUM> of the embodiment in <FIG> is provided with a round covering material <NUM>.

<FIG> shows a thirty fifth embodiment of the invention in a radial view wherein the covering material <NUM> applied along outer circumferential surface <NUM> of the first layer <NUM> of the embodiment in <FIG> is provided with a round covering material <NUM>.

<FIG> shows a thirty sixth embodiment of the invention in a radial view wherein the covering material <NUM> applied along outer circumferential surface <NUM> of the first layer <NUM> of the embodiment in <FIG> is provided with a round covering material <NUM>.

<FIG> shows a thirty first embodiment of the invention in a radial view wherein the covering material <NUM> applied along outer circumferential surface <NUM> of the first layer <NUM> of the embodiment in <FIG> is provided with a hole which allows the conducting material <NUM> to protrude to the outer circumferential surface <NUM> of the first layer <NUM>. In this embodiment in order to allow the flow of charge between the conducting material <NUM> and the ground a direct connexion between the conducting material <NUM> and the ground is provided through the hole.

<FIG> shows a thirty second embodiment of the invention in a radial view wherein the covering material <NUM> applied along outer circumferential surface <NUM> of the first layer <NUM> of the embodiment in <FIG> is provided with a hole which allows the conducting material to protrude to the outer circumferential surface <NUM> of the first layer <NUM>. In this embodiment in order to allow the flow of charge between the conducting material <NUM> and the ground a direct connexion between the conducting material <NUM> and the ground is provided through the hole.

<FIG> shows a thirty third embodiment of the invention in a radial view wherein the covering material <NUM> applied along outer circumferential surface <NUM> of the first layer <NUM> of the embodiment in <FIG> is provided with a hole which allows the conducting material <NUM> to protrude to the outer circumferential surface 10of the first layer <NUM>. In this embodiment in order to allow the flow of charge between the conducting material <NUM> and the ground a direct connexion between the conducting material <NUM> and the ground is provided through the hole.

<FIG> shows a twenty second embodiment of the invention in a radial view wherein the conducting material <NUM> is applied solely along the tire sidewall <NUM>, throughout the first layer <NUM>, on both tire sidewalls <NUM> in an opposed configuration.

<FIG> shows a twenty third embodiment of the invention in a radial view wherein the conducting material <NUM> is applied solely along the tire sidewall <NUM>, throughout the first layer, on both the tire sidewalls <NUM> in an interdigited configuration.

<FIG> shows an twenty fourth embodiment of the invention in a radial view wherein the conducting material <NUM> is applied as in <FIG>, in an opposed configuration and merely in the axial direction.

Claim 1:
A non-marking anti-static solid rubber tire for a vehicle wheel (<NUM>) comprising electrically conducting means (<NUM>) such as a rim, the tire (<NUM>) comprising a tread surface (<NUM>) delimited by two opposing tire sidewalls (<NUM>), the tire (<NUM>) comprising a first cylindrical layer (<NUM>) provided for contacting the ground, the first layer being of a first material, and comprising a first outer circumferential surface (<NUM>) and a first inner circumferential surface (<NUM>), the first inner and first outer circumferential surface (<NUM>, <NUM>) being interconnected by opposing first layer sidewalls (<NUM>) and together delimiting the first layer (<NUM>), wherein the first material is a non-conducting and non-marking rubber material, wherein the tire comprises at least one further cylindrical layer comprising an outer circumferential surface and an inner circumferential surface, the inner circumferential surface being arranged to contact the electrically conducting means (<NUM>) of the wheel, and wherein the tire (<NUM>) further comprises a rubber conducting material (<NUM>) having an electrical resistance which is smaller than the electrical resistance of the first material, wherein the conducting material (<NUM>) extends from the first outer circumferential surface at least up to the first inner circumferential surface so that the conducting material (<NUM>) is electrically connected to the layer having the inner circumferential surface arranged to contact the electrically conducting means (<NUM>) of the wheel, and wherein the material of the layer having the inner circumferential surface arranged to contact the electrically conducting means (<NUM>) of the wheel is sufficiently electrically conducting to conduct electric charges from the electrically conducting means towards the ground, and characterized in that the conducting material (<NUM>) is applied along at least one of the tire sidewalls (<NUM>).