The present invention concerns a vehicle tyre .Intended to be fitted with spikes.

Increasing traffic load and spike tyres in αxπbination have proved to be a remarkable road attrition factor. In s ne countries this has even led to prohibition of spike tyres, or at least to con¬ siderable restrictions.

In Nordic conditions, the beneficial effect of an anti-slip means on the safety and flexibility of traffic has on the other hard been irrefutably demonstrated, and this effect should not be sacrificed: instead, the associated drawbacks should be eliminated. Good results will be achieved by further developing both the road superstructures and the anti-slip tyres.

As a pneumatic automobile tyre rolls on an even surface, it is con¬ siderably flattened radially, owing to its flexibility, whereby in the contact region longitudinal as well as transversal forces are generated owing to changes of the rolling radius.

T e longititdinal forces acting on the .spike when the tyre is rolling are due to bending of the body structure, to longitudinal slipping and to the stress wave building up in the rubber.

When a spike approaches the point of contact with the road, the tyre body undergoes bending such that the radius of the bent part is significantly smaller than that of equivalent parts of the load-free tyre, ϊhis deflects the spike, which has been inounted at right angles against the surface, to assume a vertical position before contact with the road. Owing to the protrusion of the spike point, however, the spike is not turned sufficiently: it meets the road surface in an oblique position. At this stage, the forces due to

slipping tendency also begin to exert their influence.

'Traditionally, the shape of the spike has been symmetric and it has been mounted in a hole, perpendicular against the wear .surface of the tyre, whereby it meets the read in a slightly oblique position, as described above. Ihe oblique contact of the spike with the road, as well as its being pushed deeper into the tyre in oblique position during the initial part of road contact, cause damage to the rubber and to the spike which impairs the friction properties of the spike, detracts from the durability of the spike and increases its road attrition properties.

The aim of the invention is to achieve an i-iprovement in currently known vehicle tyre designs intended to be fitted with .spikes. Ihe more specific aim of the invention is to provide a. vehicle "tyre intended to be fitted with spikes which may be fitted with fixed spikes, respectively with sleeve^mounted spikes, and in which the drawbacks embarrassing designs of prior art have been avoided.

ihe aims of the invention are achieved by means of a vehicle tyre intended to be fitted with spikes which is mainly characterized in that the -tye comprises asymmetric or inhcmogeneous regions which have been disposed to produce a force component tending to turn the fixed spike, respectively the sleeve-mounted spike, fitted on the tyre in such manner that the fixed spike, respectively the sleeve- ircuπted spike, is arranged at first contact with the road surface to meet the road surface in a substantially perpendicular position.

The rest of the characteristic features of the vehicle tyre of the invention are presented in claims 2-13.

The invention is described more in detail by referring to some advantageous embo iments of the invention, presented in the figures of the drawing attached, yet to which the invention is not meant to be exclusively confined.

In Fig. 1 is schematically presented the force αsnpαnent turning the spike, the force cαrponent lifting the spike and the resultant of the read contact force.

Fig. 2 presents an advantageous eπtoodi ent of the vehicle tyre in¬ tended to be fitted with .spikes of the invention, in schematic sec¬ tional projection.

Figs 3a and 3b present another advantageous embodiment of the vehicle tyre intended to be fitted with spikes of the invention, in schematic sectional projection and in elevatiαnal view.

Fig. 4 presents a third advantageous embodiment of the vehicle -tyre intended to be fitted with spikes of the invention, viewed from the direction of the plane of the wear surface.

Fig. 5 presents a fourth advantageous embodiment of the vehicle tyre intended to be fitted with sspikes of the invention,' viewed from the direction of the plane of the wear surface.

Fig. 6 presents a fifth advantageous embodiment of the vehicle tyre intended to be fitted with spikes of the invention, in sc-ematic sectional projection.

Fig. 7 presents a sixth advantageous embodiment of the vehicle tyre intended to be fitted with .spikes of the invention, in schematic sectional projection.

Fig. 8 presents a seventh advantageous a±odiment of the vehicle tyre intended to be fitted with spikes of the invention, in sche¬ matic sectional projection.

Fig. 9 presents an eigth advantageous eiribodiment of the vehicle tyre intended to be fitted with spikes of the invention, in schematic sec±iαnal projection.

As illustrated in Fig. 1, in a static situation and at low speeds, the pressure effect originating in the contact angle K of the rubber is uniform and its resultant R is very close to vertical. The rear margin of the rubber piece 12 bulges out rearwards and the contact surface, forward against the road. As the speed increases, the pressure resultant turns forward in the direction Rτ_, and the pressure pattern becomes more pronouncedly oval. The pressure resultant is also turned forward because in the region D the press¬ ure in the rubber is lower since no compressive force is present there. Owing to rotation of the -tyre 10 and compression of the rubber 11, the pressure resultant also moves forward to the point R ₂ e∞cuπtering the flange 22 of the spike 20, and imparts to it an upward acceleration, with the ccπpαneπt F _] _, at the same time taαrning it from the position as installed to a position more nearly perpendicular against the road surface 13, with the ccsrponent F ₂ . The spike 20 is enabled to turn since there is no compression on the front side thereof. Ey the mode of installing the spike 20, and by its shape, the utilization of the forces mentioned can be influenced. In Fig. 1, for spike 20 is used a fixed spike 20, its tip being indicated by reference numeral 23.

In the embodiment of Fig. 2, the vehicle tyre intended to be fitted with spikes of the invention in general is indicated by reference numeral 10. The tyre rubber is indicated by reference numeral 11 and the wear surface, by reference numeral 12. The road surface is indi¬ cated by reference numeral 13. In this embodiment a sleeve-mounted spike, in general indicated by reference numeral 15, has been in¬ stalled in the tyre 11. The sleeve-mcunted spike 15 comprises the rivet 16, the rivet head 17, the tip 18 and the sleeve 19.

As taught by the basic idea of the iπveπticjn, in this embodiment eπ nences 14 have been provided on the wear surf ce 12 of the tyre 10. Only one such eminence 14 has been depicted in Fig. 2, but it is understood that the entire wear surface 12 of the tyre is pro¬ vided with similar eminences 14, the wear surface of every sleeve- mσunted spike 15 being similar in kind.

' In the embodiment depicted in Figs 3a and 3b, the wear surface 12 has been shaped to be an intended pattern element 14a. In this em¬ bodiment, fixed spikes 20 are used, comprising a body part 21, a flange 22 and a tip 23. The other reference numerals are equivalent to those in Fig. 2.

In the embodiment of Fig. 4, the wear surface 12 is shaped to present knob patterns 14b.

in the embodiment of Fig. 5, the wear surface 12 comprises longi¬ tudinal configurations 14c.

In the embodiment of Fig. 6, the rubber 11 is hardened in the region indicated by reference numeral 14d, with the aid of heat, radiation, chemicals, etc., so that a region 14d, harder than the rest of the rubber material, leads from the contact angle of the pattern element 12 to the hole of the sleeve^mounted spike 15, or naturally simi¬ larly to the hole of a fixed .spike 20, and which by mediation of the impact from the road surface 13 delivers, immediately before the moment of road contact, a turning and lifting force ccm-ponent to the sleeve-mounted spike 15, respectively to the fixed spike 20. Said hardening may be accomplished in the manufacturing step of the tyre 10 or thereafter, or not until in' conjunction with spike installation, e.g. by age-hardening the rubber material 11 with a rotating drill and by injecting curable vulcanizing material into the hole.

The embodiment of Fig. 7 is the same as that of Fig. 6 in other respects, except that in the embodiment of Fig. 7 one entire half of the pattern element 12, that is, the region 14e, has been hard¬ ened in order to produce a pressure effect, and a fixed spike 20 is used.

In the embodiment of Fig. 8, the effect which turns and lifts the sleeve-mounted spike 15 is accxaπplished hy placing a piece 14f of some material other than rubber inside the patterned element 12

which is to be fitted with a spike, said piece being arranged to transmit the impact frαn the contact angle to the sleeve-mounted spike 15. It goes without saying that a fixed spike 20 may equally be used instead of the sleeve-mounted spike 15. In the embodiment of Fig. 8, a substantially rod-shaped body 14f e.g. of plastic is inserted in the pattern element 12 which is meant to receive a spike, by cementing or in another way, said body resting with one end against the sleeve 19 of the sleeve-mounted spike 15, respect¬ ively against the flange 22 of the fixed spike 20, or against the rubber region 11 substantially close thereto. The other end of this rod-shaped body 14f is located in the contact angle of the pattern element 12. The deformation of the rubber 11 is transmitted with the aid of the rod-shaped body 14f e.g. to the flange 22 of the fixed spike 20, thus turning the fixed spike 20 to vertical position and also imparting to the fixed spike 20 before road contact an upward acceleration, which reduces the dynamic inpact.

In the embodiment of Fig. 9, a body 14g has been installed inside the pattern element 12, which poriduced around itself in the rubber ii _a stress field, indicated by C. Said stress field C meets the stress field, indicated by B, which was produced at installation of the sleeve-mounted spike 15, respectively of the fixed spike 20, and turns the fixed .spike 20, respectively the sleeve-mounted spike 15, to a more upright position than that seen in the figure. Such a stress field C also transmits the pressure resultant Ro-R-i produced at road contact of the pattern element 12 more rapidly e.g. to the flange 22 of the fixed spike 20, whereby the force ccaiponent, des¬ cribed above, "turning and lifting the fixed sspike 20, respectively the sleeve-mounted spike 15, is produced.

In the foregoing merely scene of the advantageous etobodiments of the invention are presented, and it is obvious to a person skilled in the art that numerous modifications thereof can be ccmtemplated within the scope of the inventive idea stated in the claims en- closed.