WO2010128862A1

WO2010128862A1 - A stud for a tyre

Info

Publication number: WO2010128862A1
Application number: PCT/NO2010/000162
Authority: WO
Inventors: Hans Husevåg
Original assignee: Husevaag Hans
Priority date: 2009-05-05
Filing date: 2010-05-03
Publication date: 2010-11-11
Also published as: EP2427338A4; NO330285B1; EP2427338A1; NO20091791L

Abstract

A stud for a rubber tyre for a vehicle is described comprising a cylinder-formed capsule (1) in which a spring-loaded, movable core (3) is mounted that has a flange (3B) at the lower end which abuts against a corresponding edge (IB) internally in the capsule (1) when the core (3) is forced outwards in the capsule (1) by a preloaded compression spring (4) which lies inside a hollow space (7) in the lower part (IA) of the capsule (1). The flange (3B) is equipped with at least one slit opening (3C) designed to let through air from the hollow space (7) and to a hollow space (6) that is formed on the other side of the flange (3B) when the core (3) is forced into the capsule (1), and that a counter pressure is created in the capsule (1) which works against the force of the compression spring (4) and which is arranged to provide an inertia against the core (3) being forced out, as said counter-pressure contributes to the core (3), when driving on ice or snow, having a constant protrusion outside the surface (A) of the rubber tyre, but, when driving on harder surfaces such as asphalt or concrete, is automatically forced into the capsule (1) and remains approximately stationary as long as the vehicle is in motion.

Description

A Stud for a tyre

The present invention relates to a stud for a rubber tyre for a vehicle, comprising a cylinder-formed capsule in which a spring-loaded, movable core is mounted which has a flange at the lower end that abuts against a corresponding edge internally in the capsule when the core is pushed outwards in the capsule by a preloaded compression spring that lies inside a hollow space in the lower section of the capsule.

The invention relates in particular to a spring-loaded, compressible core or point of a hard metal which is mounted internally in a capsule of steel or plastic, intended to be inserted in rubber tyres for vehicles to improve the grip on the road during wintery conditions.

Standard studs that have been used up until now are composed of a solid casing of steel, plastic or a light metal moulded to which is a central point of a hard metal and where the point at all times has a certain length, or protrusion beyond the surface of the rubber tyre. Such studs can have a good effect on ice or a compact cover of snow, but have almost no function on loose ground/slushy conditions. The biggest disadvantage is that the studs exert much wear, with resulting unwanted economic and environmental consequences, when they come into contact with the tarmac surface on the road. As much of the car traffic during the winter occurs on dry roads, the authorities have enforced definite restrictions on the use of such studs with respect to the length, weight and number of the studs, and also the length of the season in which studs are allowed. Stud ban/stud fees have also been introduced in large cities. The problem, or the challenge, has been to feasibly construct a functional stud which gives a satisfactory anti-skidding effect in wintery conditions and, at the same time, leads to a minimal wear on the tarmac surface.

Previously, several attempts for solutions are known with studs with a movable or elastic core or point, but none of these can - as far as the inventor of the present invention is aware of - be compared with the present invention with regard to appearance, execution and mode of operation and have none of the advantages of the present invention.

From prior art, reference is made to US 5,198,049 and DE 2204074, among others, and which show solutions where a spring or an elastic element is used to force the core out of the hollow space in the tyre, and which leads to the core, to a larger or smaller extent, being forced in during driving on a hard surface. However, it must be assumed that the core is forced all the way out for each rotation of the wheel, as none of the documents show a device that provides a counter-force or resistance to the pressing out. With the known solutions considerable wear on both the road surface and the stud will still occur.

What is regarded to be characteristic for the stud according to the invention is that the flange is equipped with at least one slit opening designed to let air through from the hollow space where the preloaded compression spring is located and to a hollow space which is created on the other side of the flange when the core is forced into the capsule. This leads to a counter-pressure being created inside the capsule which causes inertia against the core being forced out. In the example shown in the description a gasket is used to provide the counter pressure, but it must be said that other means can be used, for example, the capsule can surround the core so closely that a narrow passage arises which leads to a friction effect against the pressing out.

What is essential with the invention is that an "inertia" against pressing out the core of the stud is provided, where the counter force against the pressing out is somewhat less than the force from the spring, something that leads to the core only, to a limited extent, being forced out in the course of one rotation of the wheel, to be forced inside again the next time the core hits a hard surface. This is contrary to when the road surface is soft, such as with snow or ice, when the force from the road surface is not sufficient to cause the core to be forced into the capsule, i.e. the spring force is much greater than the force from the road surface.

Based on the technical problem which the present invention solves and which can be regarded as how to provide less wear on tarmac and similar surfaces, and also the stud itself, it does not seem likely that a person skilled in the art would be able to arrive at the present invention, based on US 5,198,049 and DE 2204074, neither individually nor together, as it is defined in the independent claim 1.

Another significant advantage and effect with the present solution is that the effect of the stud on ice or snow is improved, as the core of the stud can be made larger and thicker than today' s stud types and that the number of studs in each tyre can be increased due to the reduced wear .

In the use of the compressible stud according to the invention, the following clear advantages are achieved: 1) Considerable improvement of the anti-skid effect on ice or snow because the core of the stud can be made longer and thicker than today's stud types . 2) Minimal or almost no wear of the tarmac surface or other road surface. 3) Further improvement of the anti-skid effect according to point 1 because of the number of studs in each tyre can be increased as a consequence of point 2.

Said advantages in points 1 and 2 above are achieved in that the compressible stud according to the invention is built up so that the core part or the point of the stud has a constant length at all times when driving on ice or snow, but that it is automatically forced into the capsule or casing of the stud when it hits a harder surface such as tarmac or concrete and that it will remain- approximately stationary in this position as long as the driving on the harder surface occurs. The fact that the core of the stud lies well protected inside the capsule at all times during driving on tarmac means that it is not subjected to wear and will therefore retain its shape and good gripping characteristics over a very long time.

The present invention is based on the basic fact that a road surface of tarmac or concrete has a much higher compressive strength than when it is covered by snow or ice. For ice, one can assume a compressive strength between 1.5 and 3.0 MPa (N/mm²) , dependent on the temperature, while for snow it will, of course, be much smaller. For concrete and/or the hard particles in a tarmac surface one can assume a compressive strength of at least 35 MPa, i.e. at least 10 times higher than for ice. Normally, one can assume that a standard tarmac contains at least 70% hard particles. For a typical car, the load from each wheel will be about 4.0 kN and with a typical wheel diameter of about 550 mm the load surface against the road surface will be about 120x150 mm and the pressure against the road surface about 0.2 MPa. If one assumes about 100 studs in each tyre, about seven of these will, at any time, be in contact with the road surface. With a length, or protrusion, outside the surface of the rubber tyre of, for example, 1.5 mm, one is able to work out that the core or the core of every stud is subjected to a force corresponding to a load surface of about 1200 mm² or about 240 N. A stud core with a thickness of about 2 mm (roughly corresponding to the type of stud used today) will then exert a pressure against the road surface of about 80 MPa, i.e. more than twice of what is considered to be the minimal compressive strength for a tarmac and/or concrete road surface. It is clear that if the stud core does not yield to this pressure it will lead to much wear on the road surface/tarmac and on the core of the stud itself.

A preferred embodiment of the stud according to the invention is given in the independent claim 1, while alternative embodiments are given in the dependent claims 2-7.

The present stud for a rubber tyre for a vehicle is characterised in that the flange is equipped with at least one slit opening arranged to let through air from the hollow space and to a hollow space that is formed on the other side of the flange when the core is forced into the capsule, and that a counter-pressure is formed inside the capsule that works against the force of the compression spring and which is arranged to provide an inertia against the core being forced out, as said counter-pressure contributes to the core having a constant protrusion outside the surface of the rubber tyre during driving on ice or snow, but during driving on harder surfaces, such as tarmac or concrete, is automatically forced into the capsule and remains approximately stationary as long as the vehicle is in motion.

The preloaded compression spring can be conical and the enlarged section at the lower end of the capsule can also be conical, whereupon it is fastened to a base plate ring.

The core has preferably a concave form at the top.

The flange on the core can have several slit openings.

A gasket can be mounted to the flange, arranged to provide said counter-pressure, with the counter-pressure being provided in the hollow space. Said gasket can be an elastic, lamellar gasket which is fixed in a groove in the core at the flange .

To provide a corresponding effect, the capsule can surround the core very closely, whereby a narrow passage is provided which gives an inertia against the pressing out of the core.

The invention shall now be explained in more detail with the help of the enclosed figures, in which:

Fig. 1 shows a stud in a load-free position in a new studded tyre Al.

Fig. 2 shows the same as fig. 1 with the stud core being forced in past the surface of the rubber tyre Al.

Fig. 3 shows the same as fig.l after the rubber surface is worn down to a lower level A2.

Fig. 4 shows the same as fig.3 when the core of the stud is forced all the way in past the rubber surface A2. Fig. 5 shows a cross section of the stud core flange with slit openings. Fig. 6 shows a stud core as it meets a surface of ice B on an underlying tarmac or concrete surface C. The arrow indicates the direction of rotation for the wheel.

Fig 7 shows the position of the studs in a studded tyre A that is either standing still or is in motion on a surface of ice or snow B.

Fig. 8 shows the same as fig. 7 as the vehicle starts on a surface C of tarmac or concrete. The arrow indicates the direction of rotation of the wheel. Fig. 9 shows the same as fig. 7 for a studded tyre A which is in motion on a surface C of tarmac or concrete.

Fig. 10 shows the same as fig. 7 for a studded tyre A that is standing still on a surface C of tarmac or concrete . Fig. 11 shows the stud according to the invention.

The stud according to the invention has a core 3 which will yield for a force ^"corresponding to the preload of the conical compression spring 4. This force can, for example, be around 15 N. At the moment the stud meets a surface of ice (see the illustrations in fig. 6), the concave form 3A of the core head will result in that pressure of penetration will be at least 2-3 times higher than the maximum compressive strength of ice. This will immediately lead to crushing of the ice underneath and in the vicinity of the stud core 3, so that the ice loses its compressive strength, and the stud core 3 will then be forced all the way down into the layer of ice almost without meeting further resistance. If the surface is snow, the stud core 3 will not meet any noticeable resistance, but when it hits a hard particle in a tarmac surface it will be forced into the capsule 1 with a force that, for example, can be at least 10-15 times greater than the outwardly directing spring force from the preloaded compression spring 4. When the core 3 is forced into the capsule 1, a part of the air in the hollow space 7 will be forced through the slit openings 3C in the flange 3B to the hollow space 6 that is formed on the other side of the flange 3B. At the moment the stud leaves the tarmac, the spring force will force out the core 3 again. But - as a consequence of an elastic lamellar gasket 5 which is fastened to the core 3 all the way in against the flange 3b - the volume of air that has entered the hollow space 6 will not be forced back again but instead create a counter-pressure that prevents the core 3 from being forced out into its extreme position (fig. 1) and the next time the core 3 meets the tarmac, it will be forced in again. This "bicycle pump" effect leads to the air pressure in the hollow space 6 finally becoming greater than the outwardly directing spring force. It will only take a few in/out movements by the core 3 before this occurs.

During driving on tarmac at a speed of, for example, 20 km/h every stud will be "hit" against the surface 2-3 times a second and it will only take a few seconds from the vehicle starting before all the studs are in their approximate constant inner position, as shown in fig. 2, fig. 4 and fig. 9.

At higher speed the movement of the core when driving on tarmac will be further affected. The distance between the innermost and outermost position of the core 3 is about 3 mm. If one assumes that the core 3, when it is not subjected to a load, is forced out in the course of, for example, 30 seconds, the movement will be about 0.1 mm per second. When driving on tarmac or concrete at, for example, 60-70 km/h, the core 3 will be "hit" against the surface 8-10 times per second and the movement of the core beyond each "hit" will consequently be only about 0.01 mm. i.e. practically zero. Thus, the inertia against being forced out, either due to a gasket or friction, constitutes an essential aspect of the present invention.

The capsule 1 of the stud according to the invention can, for. example, be made from Teflon, a plastic material that has a self-lubricating effect and minimum friction against steel. The opening for the core 3 at the top of the capsule 1 can be adjusted so that a permanent pressure force/pressing force that ensures a compact, airtight and approximately friction-free connection between these two parts is established. On the other hand, the elastic lamellar gasket 5 does not need to be tightly mounted, but is adapted so that it lets in air into the hollow space 8 back to the hollow space 7 during a certain time - for example 30 seconds - when the compression spring forces the core 3 outwards when it is in a load-free stat.

When driving on ice or snow all studs will have a constant length or protrusion beyond the surface Al and A2 of the rubber tyre all the time, as shown in figs. 1, 3 and fig. 7. This is also the case when the vehicle is standing still on this surface, and also for all the studs that are load-free when the vehicle is stationary on a harder surface such as tarmac or concrete (fig. 10) .

During driving on asphalt or concrete all the studs will all the time lie within the surface Al and A2 of the tyre as shown in fig. 1, fig. 2 and fig.9, but when the vehicle stops, the studs that are not in contact with the road surface will slowly come "out of the tyre" until they, for example, in the course of 30 seconds, reach their extreme position as shown in fig. 1, fig. 3 and fig. 10

In a wheel that rotates, all parts i.e. the whole of the wheel mass will be affected by a centrifugal force or a dynamic "slinging force". This slinging force increases proportionally with the square of the speed and is greatest for the peripheral part of the wheel, i.e. in this case the stud core 3. A core 3 of a hard metal and a size as given in the preceding drawings will have a mass of about 1.0 g. At a speed of about 50 km/h this mass will be subjected to an outwardly directed dynamic slinging force of about 5 N. At 80 km/h, this force will increase to about 15 N and at 100 km/h to about 23 N. This slinging force, together with the built-in preloaded force from the compression spring 4, will give the stud core 3 even greater penetration effect on a road surface of hard ice or snow. This increased penetration effect will be particular relevant at great speeds, i.e. when there really can be a need for the largest possible resistance to skidding.

Another advantageous characteristic with the stud according to the invention is that the thickness of the ^"stud core 3 can be much greater than for today's studs without it affecting- the ability of the stud to penetrate into a road surface of hard ice or snow. The reason for this is the concave shape of the top surface 3A of the core which ensures that the penetration ability on ice will be at least as great as for a stud core with only half the thickness. The core 3 of the stud can be manufactured, for example, with a thickness of about 4.6 mm and this will lead to a doubling of the resistance to skidding on ice or snow compared to today's studs which have a core thickness of only about 2 mm.

As the tyre rubber is worn down, the protrusion of the stud core 3 beyond the rubber surface Al and A2 will increase correspondingly and thereby provide at least the same resistance to skidding on ice or snow as for a new stud tyre. If one assumes that the stud, when it is inserted into a new studded tyre has a mounting depth of, for example, about 12 mm, the protrusion of the core 3 will be about 1.5 mm. After the rubber surface has been worn to a level A2, as shown in fig. 3, the protrusion of the stud core 3 will be twice as long. As can be seen in fig. 4, the rubber surface A2 together with the surface of the capsule 1 could be worn down even more before the stud loses its effect.

Thus, the object of the invention is that means to at least partially counteract that the core 3 is driven out, are provided in the capsule 1, after the core 3 is forced into the capsule 1 during driving on a harder surface, as the reaction from said means is less than the pressure from the surface of ice or snow. This can be obtained as in the example shown above, or in that another form for counter-active force is provided. An alternative is, therefore, that the capsule 1 is shaped so that it surrounds the core 3 very snugly, whereby a narrow passage is provided that offers the desired inertia against pressing out the core 3. Thus, a "friction resistance" is provided between the contact surfaces of the capsule and the core, in contrast to what is explained above in connection with the first example and which is adapted to provide sufficient counter-acting force. The two described solutions can also be combined.

Claims

C L A I M S

1. A stud for a rubber tyre of a vehicle, comprising a cylinder-formed capsule (1) in which a spring-loaded, movable core (3) is mounted that has a flange (3B) at the lower end which abuts against a corresponding edge (IB) internally in the capsule (1) when the core (3) is forced outwards in the capsule (1) by a preloaded compression spring (4) which lies inside a hollow space (7) in the lower part (IA) of the capsule (1), c h a r a c t e r i s e d i n that the flange (3<S) is equipped with at least one slit opening (3C) designed to let through air from the hollow space (7) and to a hollow space (6) that is formed on the other side of the flange (3B) when the core (3) is forced into the capsule

(1), and that a counter pressure is created in the capsule (1) which works against the force of the compression spring (4) and which is arranged to provide an inertia against the core (3) being forced out, as said counter- pressure contributes to the core (3) , when driving on ice or snow, having a constant protrusion outside the surface (A) of the rubber tyre, but, when driving on harder surfaces such as tarmac or concrete, is automatically forced into the capsule (1) and remains approximately stationary as long as the vehicle is in motion.

2. The stud according to claim 1, c ha r a c t e r i s e d i n that said preloaded compression spring (4) is conical and the enlarged section (IA) at the lower end of the capsule (1) is also conical, whereupon it is fastened a bottom plate ring (2).

3. The stud according to claim 1, c h a r a c t e r i s e d i n that the core (3) has a concave form at the top (3A) .

4. The stud according to claim 1, c h a r a c t e r i s e d i n that the flange (3B) on the core (3) has several slit openings (3C) .

5. The stud according to claim 1, c h a r a c t e r i s e d i n that a gasket (5) is arranged against the flange (3B) arranged to provide said counteracting pressure, as the counteracting pressure is provided in the hollow space (6).

6. The stud according to claim 5, c h a r a c t e r i s e d i n that said gasket is an elastic, lamellar gasket (5) which is fixed in a groove (5A) in the core (3) at the flange (3B) .

7. The stud according to claim 1, c h a r a c t e r i s e d i n that the capsule (1) surrounds the core (3) snugly, whereby a narrow passage is provided that offers an inertia against pressing out the core (3) .