The invention concerns an electrical heating element for heating a tyre, as set out by the preamble of claim 1.

Background of the invention

When riding a motorcycle, or any vehicle, it is in most cases desirable to have as much friction between the wheels and the ground as possible. The friction is an important factor during acceleration, deceleration and turning, and in order to increase the friction between the tyres and the ground, a number of mechanisms can be optimized. A ground composed of asphalt has more friction than a ground of gravel, the tread of the tyre affects the friction, tyres with a soft and sticky rubber compound generally has a better friction-coefficient than that of hard rubber, etc. Temperature is also one such important factor for maximising friction between a tyre and the ground; a warm tyre has a better friction-coefficient than a cold tyre.

In road racing today, all professional riders pre-heat the tyres of their motorcycles before the race, and a number of devices for pre-heating tyres exist. A common device is a donut-shaped bag which is placed over the tyre and wheel. Such a bag has a heat element and/or is capable of trapping heated air, and as such the tyre will be heated to a predetermined level. In order to fit the wheel into the bag, the motorcycle must be elevated, and a pit support is commonly used. When the bag is removed from the tyre, the tyre has an optimal operating temperature. However, the problem with such devices is that it often takes several minutes from the heating bag is removed from the tyre, to the race actually starts. When the race starts several minutes after the pre-heating device has been removed, the tyre has a less than optimal temperature, resulting in reduced performance during the initial part of a race.

Also, such devices for pre-heating tyres as the above mentioned are expensive and cumbersome to use, partly because they are aimed at a track / racing marked, and as such they are rarely used by commuters or in everyday life. An individual riding his or her motorcycle to and from work rarely bothers to elevate the motorcycle in a pit support, fit the wheels in bags and pre-heat the tyres of his or her vehicle. As such, the tyres are cold when the individual sets out on his or her journey, resulting in less than optimal friction between the tyres and the ground, hence resulting in reduced braking, acceleration and turning properties of the vehicle. In order to overcome these problems, the applicant has devised a heating device which heats the tyre from the inside.

Prior art includes DE 102010048328 A which describes a system with a heating element, e.g. heating wire, heating pad, heatable gel and/or heatable textile and/or gas, mounted on a rim and on an air space side of a flexible tyre. The heating element is guided by a power source unit with power from a vehicle power source. An electronic control unit measures temperature e.g. external temperature, in the tire air space side and automatically switches on or off the heating element depending upon a temperature value.

GB 2511651 describes a tyre warmer for use in warming a tyre of a vehicle, the tyre warmer including: a heating member configured to be secured around a wheel rim within an inflation volume of the tyre such that the heating member is generally adjacent the wheel rim, wherein a temperature of the heating member increases when electric power is supplied to the heating member.

However, there is still room for improvement regarding heating of tyres. In order to more efficiently and less cumbersome heat the tyres of a vehicle, to reduce risk for the person riding the vehicle and increase performance of the vehicle, the applicant has devised a heating device which is easy to use and which accurately heats the tyre to the optimal temperature without the need for much accessories or large equipment. The heating device preserves the heat in the tyre, and the invention is applicable for both professional use and for individuals.

Summary of the invention

The invention is set forth and characterized in the main claim, while the dependent claims describe other characteristics of the invention.

It is thus provided an electrical heating element for heating a tyre, the tyre comprising an inside and an outside, the electrical heating element comprising a heat source and extending at least partially around a centre axis. The heating element comprises a face provided to contact and transfer heat to a surface on the inside of the tyre, the electrical heating element being compressible and expandable in a radial direction relative to the centre axis.

According to one embodiment, the electrical heating element comprises an outer thermal conducting layer positioned in a radial direction on an outside of the heat source.

According to another embodiment, the electrical heating element comprises an inner thermal insulating layer positioned in a radial direction on an inside of the heat source.

According to another embodiment, the thermal insulating layer is made of silicone having flexible properties.

According to another embodiment, the heat source comprises electrical heating wire.

According to another embodiment, the electrical heating element extends 360° about the centre axis.

According to another embodiment, the electrical heating element further comprises electrical wire for connection to an electrical power source.

According to another embodiment, the electrical heating element has a width generally corresponding to that of the surface spanning from a tyre wall to an opposing tyre wall of the tyre.

According to another embodiment, the electrical heating element is fixed to a tubing which is adapted for insertion into the tyre.

According to another embodiment, the electrical heating element is releasably attached to the tubing.

According to another embodiment, the electrical heating element comprises a biasing element, the biasing element extending along at least a portion of the electrical heating element and biasing the heating element outwards in a radial direction.

According to another embodiment, the biasing element is positioned on the inside of the heating element in a radial direction relative to the heating element. According to another embodiment, the biasing element comprises bars connected with plate elements, the bars extending in a circumferential direction.

It is also provided a system for heating an inflatable tyre mounted on a rim, comprising a heating element and a power source, the rim comprising a valve hole with a valve, the tyre comprising an inside and an outside. The heating element comprises a face provided to contact and transfer heat to a surface on the inside of the tyre, the electrical heating element being compressible and expandable in a radial direction relative to the centre axis.

According to one embodiment, the power source is located on the outside of the inflatable tyre.

According to another embodiment, the valve is provided to conduct electric current from the outside to the inside of the tyre through the valve hole.

According to another embodiment, the heating element comprises heating wire.

It is also provided an air valve for an inflatable tyre, the air valve comprising a stem and being provided for mounting in a valve hole on a rim. Two separately insulated electrical conductors conduct electric current through the valve hole from the outside to the inside of the tyre.

According to one embodiment, the electrical conductors extend along the valve stem along at least a portion of the length of the valve.

According to another embodiment, the electrical conductors are electrically insulated from the valve and rim.

According to another embodiment, the electrical conductors are provided with connector points for releasably connection with electrical wire on the inside of the tyre.

According to another embodiment, the electrical conductors are provided with connector areas for contacting an electrical connection.

According to another embodiment, the connector areas extend circumferentially at least a portion around the circumference of the valve. Once installed, the heating device is an integrated part of a wheel and tyre assembly of a vehicle, and it is therefore readily available and has a low threshold for use both on a daily basis for individuals, and on a race track for experienced riders and professionals. The heating device is easily connected to a power output, and the heating device provides heat to the tyres, which in turn enhances friction between tyre and ground right from the start of a daily commute or a track race.

Brief description of the drawings

These and other characteristics of the invention will become clear from the following description of a preferential form of embodiment, given as a non-restrictive example, with reference to the attached schematic drawings, wherein:

Figure 1 is a partially cut perspective view of a motorcycle rim and tyre with the heating device mounted inside the tyre. A biasing element forces the heating device towards the inside of the tyre, and an air valve with electric conductors is mounted in the rim.

Figure 2 is a section view through the assembly shown in figure 1. The assembly is cut where the valve is mounted in the rim. Electrical wires connect the valve to the heating device, the heating device and biasing element are also shown.

Figure 3 is a perspective view of the heating element, biasing element and valve isolated, i.e. not mounted inside a tyre. The heating wire is visible on the inside, shown with dotted lines; it would normally be hidden beneath an inner layer but shown here for visualizing purposes. A transformer is also shown connected to the valve.

Figure 4 is a cross section view of an air valve with electric conductors. The valve has two electrical conductors and is shown mounted in a rim, secured with a nut on the underside. An electric connection is also mounted on the valve.

Figure 5 is a perspective view of another embodiment of a heating element for heating a tyre. The heating element is a heating wire fixed to the outer surface of an annular tubing, for insertion into a tyre.

Detailed description of a preferential embodiment The following description may use terms such as "horizontal", "vertical",

"circumferential", "upper", "lower", "inner", "outer", "forward", "rear", etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader's convenience only and shall not be limiting.

Figure 1 shows, partially cut, a motorcycle tyre 1 mounted on a rim 2. The tyre 1 is for illustration purposes only, and can as such be any inflatable tyre, independent of use, material, shape and size. The wheel or rim 2 is also an exemplified rim and can be any known support for a tyre 1, such as a rim on a vehicle, also independently of material, shape and size. A heating element 3 is positioned on the inside of the tyre 1. The heating element 3 is inserted into the cavity of the tyre 1 when the tyre 1 is disassembled from the rim 2, as is typically done when changing tyres on e.g. a motorcycle. The heating element 3 extends circumferentially in a tangential direction about a centre axis A. The centre axis A is basically coincident with the centre axis of the rim 2 and tyre 1. The heating element 3 has as such a shape which is generally a revolution around the centre axis A, and the heating element 3 thus extends at least partially around the centre axis A.

The heating element 3 comprises in one embodiment three layers; an outer layer 4, a layer of electrical heating wire 5 and an inner layer 6. I.e. the outer layer 4 is positioned a greater radial distance from the centre axis A than the inner layer 6, relative to the heating wire 5. The heating element 3 could also function without the outer layer 4 and/or the inner layer 6, but a sandwich construction is preferred for durability and resistance against abrasive wear and tear. The outer layer 4 should have good thermal conducting properties, in order to maximize the heat transferred from the heating wire 5 to the tyre 1. The inner layer 6 should have good thermal insulating properties, in order to direct as much heat as possible towards the tyre 1. In another embodiment, instead of heating wire 5, the heat source could be a foil or thin film, adapted to generate heat when connected to a power source. In this embodiment, the heating element 3 could comprise only one single layer; the heat source. The heating element 3 is flexible and malleable such that it adapts the shape of the internal surface 7 of the tyre 1, and does not affect the flexible properties of the tyre 1. The outer layer 4 is provided to contact the internal surface 7 of the tyre 1. The surface 7 extends circumferentially around the centre of the tyre, and as such forms a cylindrical surface with an inner concave shape. As the heating element 3 is flexible, it adapts the shape of the inner surface 7, and in the illustrated embodiment adapts a convex shape, contacting the concave shape of the surface 7. In the case the surface 7 has a different shape, the flexible heating element 3 will adapt to this shape also. The heating element 3 will as such be able to contact and heat basically any surface or shape of an inside of a tyre.

Both the outer layer 4 and the inner layer 6 are made of a flexible material, preferably a rubber material, and more preferably silicon. The layers 4,6 could also be made from a sheet of fabric, or any other material suitable to conduct and preserve heat. The two layers 4,6 could also be made of one piece of material folded, in order to create the two layers, or the two layers 4,6 could be made from different materials with different properties.

The inner layer 6, together with the outer layer 4, sandwiches the heating wire 5 and as such keeps it in place. The heating wire 5 could also be glued, sewn or in any other way known in the art attached to the outer layer 4 and/or inner layer 6. The heating wire 5 has a cross section which is sufficiently small such that the wire is malleable. The heating wire 5 is in the illustrated embodiment positioned in a wave shaped or undulating pattern, such that the wire 5 covers the width of the internal surface 7, preferably without crossing itself. The heating wire 5 could consist of several wires, or it could consist of only one wire, covering the internal surface 7. In order to save weight, and in order to distribute the heat generated by the heating wire 5 to the tyre 1 as evenly as possible, the wire could be placed in a meandering pattern spanning from one tyre wall 8 to the opposite tyre wall (the opposite tyre wall is not visible in the figure). Such an arrangement allows the heating element 3 to be stretched somewhat in the tangential direction. Other arrangements of the heating wire 5 is also possible, one such alternative is to have the electrical wire running in a circumferential direction of the tyre and the heating element (i.e. in a tangential direction around the axis A), in a helical shape. In order to fix the heating element 3 to the internal surface 7, a biasing element 9 is inserted into the cavity of the tyre 1 after the heating element 3 has been inserted. The heating element 3 is made of flexible materials and is as such compressible and expandable in both a radial direction relative to the centre axis A, and to a certain degree also in a tangential and longitudinal direction. The heating element 3 is thus flexible and easy to fit into tyres 1 of different sizes, i.e. with inner surfaces 7 of different diameter and width.

The biasing element 9 comprises two circumferential bars 10 connected to each other with a plurality of curved plate elements 11 extending in a transversal direction between the two bars 10. The bars 10 thus extend in a tangential direction of the axis A. More than two circumferential bars 10 could also be utilized. The plate elements 11 can have a variety of shapes and be straight, curved, have an angle, etc. The circumferential bars

10 and plate elements 11 may be made of the same material, i.e. plastic, metal or any other suitable material, or they may have different material properties. The plate elements 11 preferably positions the circumferential bars 10 a distance apart such that the bars 10 are positioned on the inner layer 6 next to the tyre walls 8. The plate elements 11 may have a length approximately corresponding to the width of the internal surface 7, or the width of the heating element 3. The curved shape of the plate elements

11 biases the heating element 3 towards the internal surface 7, providing an evenly distributed pressure. The biasing element 9 may come in different shapes, such that it can fix the heating element 9 to tyres with differently shaped internal surfaces.

The biasing element 9 may not extend around the entire circumference, but can in one embodiment extend about three quarters (270°) around the circumference of the heating element 3. The biasing element 9 could extend from 180° to 360° of the circumference of the heating element, depending on the material properties of the circumferential bars 10. If the biasing element 9 extends 360°, it should either be made of a material which allows the biasing element 9 to be collapsed and inserted into the cavity of the tyre 1, and which, when inserted, will expand and still provide sufficient pressure on the heating element 3 towards the internal surface 7, or, the circumferential bars 10 of the biasing element 9 could have one open portion (i.e. a portion of the circumferential bars 10 is cut away) , such that the biasing element 9 could be collapsed to allow for insertion into the cavity of the tyre 1. The main function of the biasing element 9 is to provide contact between the heating element 3 and the tyre 1 when the motorcycle is standing still. The centrifugal forces when the wheel is rotating will force the heating element 3 towards the internal surface 7. Alternatively, the biasing element 9 can be an integrated part of the heating element 3.

Another alternative is to glue the heating element 3 to the internal surface 7, or anywhere on the inside of the tyre 1. Such glue or other sticky substance should allow the heating element 3 to be removed and transferred to a new tyre if the old tyre is worn and needs to be replaced.

The heating wire 5 is connected to two electrical wires 12 which are connected to a valve 13. The valve 13 has the same thread as a common air valve for vehicles, and is installed in the existing valve hole 14 of a rim 2. The valve 13 is described in more detail with reference to figure 4. Electric energy is provided through the valve 13, via the electrical wires 12 to the heating wire 5. When provided electrical energy, the heating wire 5 generates heat, as is commonly known in the art. Because the heat is provided on the inside of the tyre 1, it is easier to control and no external bag or similar device to trap the heat is needed. When the power to the heating element 3 is cut and the motorcycle is ready to ride, the heating element 3 traps heat in the tyre 1, and the effect of the heat element 3 will wear more slowly off than that of a tyre warmed from the outside. As the friction generated between the ground and the tyre generates heat once the motorcycle is moving, the tyre will shortly gain equilibrium with an optimal and constant temperature. Wear and tear of a tyre is significantly more present if there is a large difference in temperature through the thickness of the tyre. This can occur if the tyre is not heated enough from the outside (e.g. in a "heating bag"). With a heat source located on the inside of the tyre, the temperature from both the heating element 3 and the friction generated between the tyre 1 and the ground will contribute to an evenly distributed temperature through the thickness of the tyre 1. In addition, the inner and outer layers 4,6 of the heating element 3 will significantly contribute to maintaining the heat in the tyre, even after the power to the heating element has been turned off.

Figure 2 shows the valve 13 mounted in a rim 2. The valve 13 is inserted into an existing valve hole 14 of a rim 2 and secured to the rim 2 by means of a nut 15, as is commonly known in the art. Two types of valve holes are commonly used today, 8.3 and 11.3mm. When riding a motorcycle, or any other vehicle, only the outer surface 16 of the tyre 1 is intended to contact the ground, unless riding in extreme conditions. Therefore, the temperature of the portion of the tyre 1 located between the internal tyre surface 7 and the outer tyre surface 16 influences the properties of the tyre 1 the most. As the heating element 3 is situated next to this portion of the tyre 1, the heating effect is direct, resulting in rapid heating of the tyre 1 while keeping energy consumption to a minimum.

The layer 4 preferably contacts the internal surface 7 along most of the width of the surface 7. The undulating pattern of the heating wire 5 also preferably covers the width of the tyre 1, stretching from one tyre wall 8 to an opposing tyre wall 8. The circumferential bars 10, defining the outer edges of the biasing element 9, could be positioned such that when inserted into the tyre 1, they are positioned close to the tyre walls 8. The middle portion of the tyre 1, i.e. the portion in the middle between the two tyre walls 8, is the portion of the tyre most often in contact with the ground, at least for individuals commuting, and as such is the portion which is most important to provide with sufficient temperature. If a heating element 3 and biasing element 9 is intended for use with tyres of different width, this middle portion will always contact the heating element 3 directly, independently of the width of the tyre 1.

When the tyre 1 is mounted on the rim 2, the two parts enclose and define an air tight space, into which air is inflated through the valve 13 when the tyre 1 is inflated. This space 26 is also referred to as the inside 26 of the tyre 1 or rim 2. The outside 27 is defined as the portion of the tyre 1 or rim 2 exposed to ambient air, i.e. not in contact with the pressurized air on the inside 26 of the tyre 1. The outside 27 of the tyre 1 and rim 2 is generally the surfaces of the tyre 1 and rim 2 which are visible when the tyre 1 is mounted on a rim 2.

Figure 3 shows the heating element 3 isolated, i.e. without a rim or tyre. The biasing element 9 is shown on the inside of the heating element 3, and the heating wire 5 is also visible on the inside, shown with dotted lines; the heating wire 5 could normally be hidden beneath an inner layer but shown here for visualizing purposes. When mounted inside a tyre, the outer face 31 of the heating element 3 contacts the inside of the tyre. The outer face 31 is flexible and malleable, and provides physical contact between the heating element 3 and the inside of the tyre, independent of the shape of the tyre.

Connected to the valve 13 is an electric connection 28, which connects the valve 13 to a transformer 29. The electric connection 28 is releasably attached to the valve 13 and is shaped like a donut, such that it can be tread down on the valve stem. Such a design enables the valve 13 to be utilized (i.e. to inflate/deflate air) while electric current is provided to the heating element 3. The electric connection 28 could also be shaped like a cap designed to be tread on the valve 13, or have an open profile, such that is could be entered the valve 13 from the side. The electric connection 28 is described in further detail with reference to figure 4.

The electric transformer 29 is connected with an electric wire 30 to a power outlet, and advantageously reduces the electric current from the power outlet (normally about 230 volt) to 12, 24, 48 volt or any voltage required to heat the heating element 3. The transformer 29 could be equipped with on/off buttons, or, if the heating element 3 is equipped with a thermostat, indicators indicating when the tyre is sufficiently warm, etc. A tyre, depending on several factors such as the compound of the tyre, riding

conditions, personal preferences, etc, could be heated to any temperature, but preferably between 40° and 200°C and more preferably between 80° to 130°C. The preferred maximum temperature could be set on the transformer 29. The heating wire 5 could also be self-regulating, i.e. when a maximum temperature has been reached, the heating wire 5 turns off.

Figure 4 shows the air valve 13 mounted in a valve hole 14 in the rim 2. The valve hole 14 is as described above a standard valve hole 14, which comes prefabricated with any rim 2. The valve 13 is fitted in the valve hole 14 and secured with a nut 15 on the inside of the rim 2, as is commonly known in the art. The valve 13 has inner valve components 17 generally corresponding to those of a regular air valve for tyres. The valve stem 19 is preferably made of aluminium, as is common in the art, but may also be made of any suitable metal or other material. The valve stem 19 extends in the shown embodiment along the entire length of the valve 13.

In order to conduct electric current from the outside 27 of the wheel to the heating element located on the inside 26 of the tyre, the valve 13 comprises a connection cap 18 and electric conductors 20,21. The connection cap 18 is preferably made of plastic, or other non-conductive material, but may also be made of a metal, provided the conductors 20,21 are insulated. The connection cap 18 comprises the electric conductors 20, 21, connected to the electrical wires 12 on the lower part of the valve 13 (i.e. the part of the valve 13 located on the inside 26 of the rim 2, when installed in a rim 2) at two connector points 24. The electrical wires 12 may be removably fitted to the connector points 24, such that when installing the heating element and valve 13 in a wheel, the valve 13 is fitted in the valve hole 14, after which the electrical wires 12 are connected to the connector points 24. The connector points 24 may also be located a distance away from the valve 13, and connected to the valve 13 by electrical wires, in order to ease the connection of the electrical wires 12 to the connector points 24 when the tyre is partly mounted on the rim 2 and access to the lower part of the valve 13 might be limited.

The electric conductors 20,21 extend from the connector points 24 along the valve stem 19 a distance at least corresponding to the thickness of the rim 2. On the outer side 27 of the rim 2, the conductors 20,21 are led radially outwards through the connection cap 18, and ends in two circular connection areas, 22,23 respectively. The connection areas 22,23 protrude from the outer surface of the connection cap 18, and extend around the circumference of the connection cap. As such, the electric connection 28 can be mounted on the valve 13 and connection cap 18, whereupon two electric conductors 30 are connected to the two connector areas 22,23. The connector areas 22,23 may not extend around the entire circumference of the connection cap 18, but may also extend in a circumferential segment, or might even be only a connection point on the connection cap 18.

As is shown in figure 4, if the connector areas 22,23 extend around the entire circumference of the connection cap 18, the areas 22,23 should be positioned at different heights, such that the two connectors 22,23 are separated. The two connector areas 22,23 should also preferably be positioned a distance apart, to prevent electric shortcut. Similarly, the electric conductors 30 might extend around the entire circumference of the valve stem 19, or a portion. The electric connection 28 has a donut shape such that it must be guided from the top of the valve stem down to the portion where the connector areas 22, 23 are located. Alternatively, the electric connection 28 could also have an open portion, such that is could be entered onto the valve 13 sideways, i.e. in a radial direction onto the connection cap 18. The open portion should be large enough to allow the connection cap 18 to enter the electric connection 28, and be small enough such that the electric connection 28 is secured to the connection cap 18. The electric connection 28 and electric conductors 30 must as such be flexible.

As the connection cap 18 is made of plastic, being an electric non-conducting material, the electric conductors 20, 21 could simply be a piece of metal wire, metal plate or similar. They should, however, be insulated from the outside of the valve 13 (except at the connector areas 22,23 and the connector points 24) in order to prevent the electric conductors 20,21 to come into contact with the rim 2, nut 15, etc, which are commonly made of metal.

The valve 13 acts as a conductive member for electricity and as an air valve. Along the center of the valve 13 is an air channel 25 through which air can be inflated into the tyre (and escaped, if necessary), and the valve 13 has also, as previously mentioned, valve components 17 corresponding to those of a regular valve, and which do not need to be disclosed further. In order for the air channel 25 to have an as large cross section as possible, i.e. to minimize reduction in air flow through the air channel 25, the portion of the electric conductors 20,21 running parallel to the valve stem 19 could have a semicircular cross section, with the centre of the semi-circular shape being coincident with the centre of the valve stem 19.

Figure 5 shows another embodiment of a heating element for heating a tyre. In this embodiment, the heating element 3', in the illustrated embodiment shown as a heating wire 5', is fixed to the outer surface of an annular tubing 32. When the tubing 32 with the heating element 3' is inserted inside a tyre of a vehicle, and inflated, the tubing 32 will bias the heating element 3' towards the inside of the tyre such that the heating element 3' contacts the inside of the tyre. The outer surface of the tubing 32 is thus defined as the surface which will contact the inside of the tyre of a motorcycle or other vehicle. The outer face of the heating element 3' is as such adapted to contact and transfer heat to the inside of a tyre. The heating element 3' is in this embodiment glued or welded to the tubing 32, and can expand and contract corresponding to the tubing 32. In the illustrated embodiment, such expanding and contracting is in the illustrated embodiment made possible due to the undulating pattern of the heating wire 5'. The heating element 3' could also comprise a thermal conductive layer (not shown) positioned on the outside of the heating element 3', and/or a thermal insulating layer (not shown) positioned between the heating element and the tubing 32. Alternatively, the tubing 32 could also have thermal insulating properties.

In yet another embodiment of a heating element mounted on a tubing, the heating element could advantageously be a thin film or foil, which could also be adapted to expand and contract correspondingly to the tubing 32 and the tyre. This heating element could be releasably attached to the tubing 32, such that heating elements of various types could be interchanged, or if a heating element is broken, it could easily be replaced. The releasable connection between the heating element and the tubing could be by means of velcro, glue, a sticky substance, or by other means known in the art. The heating element could even be supported between the tubing and the inside of the tyre by means of friction, as there is a high amount of friction between elements made of e.g. rubber, silicone, fabric, etc.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive and it is not intended to limit the invention to the disclosed embodiments.