Resilient tires and wheels – Tires – resilient – Anti-skid devices
Patent
1988-08-17
1990-04-24
Hoch, Raymond
Resilient tires and wheels
Tires, resilient
Anti-skid devices
B60C 1114
Patent
active
049191810
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a fixed spike, or a sleeve-mounted spike, fitted on a vehicle tire.
Increasing traffic load and spike tires in combination have proved to be a remarkable road attrition factor. In some countries this has even led to prohibition of spike tires, or at least to considerable restrictions.
In Nordic conditions, the beneficial effect of anti-slip means on the safety and flexibility of traffic has on the other hand been irrefutably demonstrated, and this effect should not be sacrificed: instead, the drawbacks should merely be eliminated. Good results will be achieved by further developing both the road super-structures and the anti-slip tires.
As a pneumatic automobile tire rolls on an even surface, it is considerably 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.
The longitudinal forces acting on the spike when the tire is rolling are due to bending of the body structure, to longitudinal slipping and to the stress wave in the rubber. The rubber surface pattern of the tire carries the load so that its internal stress state increases. The rubber material is not compressed, but due to its elasticity it changes shape.
When a spike approaches the point of contact with the road, the tire body undergoes bending such that the radius of the bent part is significantly smaller than that of equivalent parts of the load-free tire. This deflects the spike, which has been mounted at right angles against the surface, to assume a vertical position before the contact with the road. Owing to protrusion of the spike tip, however, the spike is not turned into sufficiently upright position: it meets the road surface in an oblique position. At this stage, the forces due to slipping tendency also begin to exert their influence.
As the rotating tire surface and the protruding fixed body (the spike) attached thereto meet the road surface, the spike is pushed into the rubber material on a length dependent on the hardness of the base; on a hard road super-structure the spike is pressed entirely into the rubber material of the tire, while on softer ice and snow surfaces the tip part of the spike remains outside the wear surface of the tire and causes increase of friction. At the same time, the wear surface pattern composed of rubber material is compressed between the body structure of the tire and the road surface, whereby the rubber material is not compressed, but owing to its elasticity it flows and assumes, as it comes under strain, a configuration different from its original shape. The flowing and deformation of the rubber are determined by the load, the rubber material, the dimensions and configuration of the wear surface, and such solid bodies as are embedded in the rubber.
When the rubber is compressed between the forces acting from opposite directions, the deformation is different in different parts of the wear surface pattern. Since the rubber is firmly fixed to the body structure of the tire and the friction against the road surface prevents any horizontal movement of the wear surface, the rubber is forced to flow towards the free surfaces of the wear surface pattern. The vertical displacements are due to flowing of the rubber under the flange of the spike outwards from the central axis, and to the shape of the spike body and the elastic yielding caused by the load. Since the rubber is not compressed, the vertically directed pressure is converted into displacements in the horizontal plane, as rubber molecules flow past each other towards free surfaces, which bulge outwards as a result. Owing to the configuration of the wear surface pattern and the stress caused by the spike, there remains a neutral region within the pattern element, around the spike, where the movement of the rubber is minimal or there is none at all, unless such movement is caused by the shape of the spike.
Traditionally, in designing anti-slip means the rubber flow is not control
REFERENCES:
patent: 3693688 (1972-09-01), Schuman
Linden Unto
Suvanto Erkki
Hoch Raymond
Neste Oy
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