GB2156707A - Methods of and means for enhancing frictional grip between surfaces - Google Patents

Abstract

Frictional grip between two co-operable surfaces is enhanced by coating at least one of the surfaces with an interface material which includes randomly distributed fibrous material. The interface material incorporates an adhesive carrier medium and a fibrous material in divided form or particulate form. The carrier medium can be a polymer. The fibrous can be a material known as Santoweb. The interface material is particularly intended for application to soles and heals of footwear.

Description

SPECIFICATION Methods of and means for enhancing frictional grip between surfaces This invention relates to methods of and means or arrangements for enhancing frictional frip between two surfaces which are required to co-operate with each other and between which surfaces it is desired to be able to reduce relative slip between the surfaces.

It is a common occurance for surfaces which frequently come into contact with each other to be subject to changing ambiant conditions which inherently change or modify the relative friction therebetween so that under certain conditions surfaces which have normally adequate relative friction therebetween do not exhibit adequate relative friction.

Thus, for example, in the case where the surfaces involved are the soles and heels of articles of footwear and surfaces upon which the wearer of the footwear are likely to tread it is frequently the case that the state of wear of the soles and heels and the surface condition of the surfaces upon which the soles and heels are placed may be such that the frictional grip produced therebetween is so reduced that undesired relative slipping can readily occur.

It is well known that under certain weather conditions such as ice, snow, rain, high humidity that road surfaces, shopping area walking surfaces become very slippery so that walking upon such surfaces becomes very dangerous. Furthermore, it is known that the floors of many modern buildings are, for example, for cosmetic reasons very highly polished so that in the event of such surfaces becoming damp for instance by water carried upon the soles and heels of footwear such floors become extremely slippery to an extent that a person finds it difficult to walk or even remain standing.

In so far as ice, and snow are concerned the reduction of the relative friction can have traumatic results. For example, in one recorded period of ice on pavements over four days it was recorded at one hospital that on average seventy four more people per day sustained fractures through accidents arising from slipping on the pavements; this figure representing nearly a three hundred percentage increase over non-icy conditions.

Attention has been drawn above to the fact that articles of footwear become worn at the soles and heels wear, this wear, in practice, is such that the soles and heels become smooth. Such is frequently the condition of plastics material soles and heels. It is also important to note that frequently the surfaces of the soles and heels of new shoes are very smooth so that there is from the onset the possibility of relatively low frictional grip with a surface being trodden upon as compared with soles having roughened and patterned initial surfaces.

Broadly, according to the invention there is provided a method of enhancing the frictional grip between two co-operable surfaces, including the step of providing therebetween qn interface incorporating a fibrous material.

Preferably, the method includes forming the interface by applying a coating or layer containing the fibrous material to at least one of the surfaces of the co-operable surfaces.

Conveniently, the interface is produced by spreading a medium containing the fibrous material, the medium being in a fluid state, over one at least of the co-operable surfaces and then allowing or otherwise enabling the medium to dry or otherwise set into a layer in which the fibrous material is randomly distributed so that fibres are transversely oriented with respect to the said co-operable surface According to a second aspect of the invention a friction enhancing interface material for interpositioning between two co-operable surfaces includes fibrous material randomly oriented with respct to a carrier or material support medium.

Preferably, the interface material is a mixture of an adhesive carrier medium and a fibrous material in particulate or divided form, the mixture being such that the fibrous material is randomly oriented.

Conveniently, the interface material incorporates a polymer as the adhesive and a material which is marketed under the Trade Name SANTOWEB (Registered Trade Mark) A particular form of such Santoweb is known as Santoweb D; and a further form as Santoweb W.

In a further form of the interface material a matrix of rubber includes a suspension of the fibrous material together with an adhesive material.

The adhesive can be a rubber solution form of adhesive.

The polymers used can include Polyurethane or Polyvinylchloride In a particular example, in which it was desired to produce a layer of interface material for subsequent attachment to the sole of an article of footwear and/or the heels thereof the following mixture was used: Santoweb 'D' 10 parts by weight Polyurethane Solution 75 parts by weight Silica VN3 1 5 parts by weight The above mixture was maintained in a well stirred or mixed condition at the time of use.

In applying the mixture to the soles and heels of a shoe having an integral Polyvinylchloride construction the soles and heels were initially washed with warm detergent and water.

After washing the soles and heels were wiped for the purposes of chemical cleaning with Carbontetrachloride.

The above mentioned mixture of fibrous material and adhesive was thoroughly stirred to ensure a thorough mixing of the materials and was spread over the soles and heels to produce an evenly spread layer of a desired thickness.

The shoe having the applied layers of fibrous material were positioned with the layers uppermost and were left to allow the layers to harden or cure. This hardening or curing period was for approximately twelve hours.

An 8mm diameter test sample of the layer forming mixture was allowed to harden for the same time period and upon checking the sample for hardness it was found that the hardened material had a hardness of 60 Shore.

The texture of the material or layers had the visual appearance of a course grit emergy cloth, although the material was resilient to pressure.

On using the shoes in locations at which it was known that slippery conditions were likely to prevail and that accidents had occured it was found by the Inventor who had used the shoes before the application of the material of the invention that the grip exerted between the shoes and the floor had significantly increased. Life testing of the material indicated that wear was surprisingly negligible.

Tests were also carried out using a mixture in which the Silica was omitted and the frictional grip improvement was also maintained, together with acceptable wear capability.

As a further mixture for the formation of interface layers the previously mentioned quantities of Silica VN3 and Santoweb 'D' were admixed with a chemical curing adhesive known as APASEAL TS98 Code APO 2042 the wet weight of the latter being 1 25 units (producing an estimated dry weight of 35 units). As before the soles and heels were chemically cleaned before the application of the above mixture after the latter had been thoroughly mixed to achieve a uniform dispersion of the Silica and Santoweb material.

To achieve a desired thicknwss of layering two applications of the mixture were applied to the soles and heels.

Slide tests on a wet glass sheet arranged at approximately 30 to the horizontal using a slide length 750mm with the shoes weighted by a 3 125 Kg load indicated that the coefficient of friction increased by a signfican amount following the provision of the interface layer.

In numerical terms it was found that the time required for a slide test increased from a means value of 0 035 seconds to a means value of 0-0252 thereby indicating that the provision of the layers had slowed the rate of slide of the article under test and that the coefficient of friction had correspondingly increased.

In a variation a mixture was formed from the Santoweb material and the Polyurethane solution with the result that the frictional grip was improved.

The misture, i.e., interface material can be formed into a sheet material which is suitably cut into a required shape and then subsequently secured to the interface surface to be covered by means of a suitable adhesive. In other words the interface material can be formed into secondary soles and heels for attachment to footwear.

The operational or working surface of the interface layer can be left 'plane' or can be profiled to simulate or formulate footwear sole profiles.

In addition to the above mentioned enhancement of the frictional grip it has been noted that the application of the interface material resists the spread of the phenomena occuring with plastics material footwear known as cut-growth.

It will be understood that the interface forming material could by applied to floors or other surfaces as desired.

For example, the layer with the fibrous material could be applied to the ferrules or the like of walking sticks or other aids for assisting the mobility of disabled people.

In practice, since the layers may present a roughened surface appearance it may be found necessary to brush the layers following use to remove any entrained foriegn bodies which may have been picked-up during use.

It will be understood that whilst Santoweb has been mentioned as one of the components in view of its fibre content other sourses of fibrous material may be used. In practice, it is useful for the fibres to be relatively short in length, for example, 0 5 to 1 5 mm, so that they become well dispersible throughout the fluid matrix and not arranged as a mono layer or direction. Thus the fibres should be in a random formation. By having the random formation the fibres have been found not only to provide the roughened surface but also to provide additional physical strength to the layer itself and in effects to the substrate sole or heel in withstanding cracking or the like damage to the substrate, sole, heels or other substrate.

An additional feature of the invention is that in the event of wear of the interface it is readily possible to apply a repair or thickening layer to a previously applied layer.

In practice, the selection of fibre thickness in relation to fibre length is thought to be an empirical factor. It is thought that the ratio between fibre length and diameter should lie with the range 80 to 120, with a preferred range centrally located of the overall ranfe.

Claims (12)

1. A method of enhancing the frictional grip between two co-operable surfaces, including the step of providing therebetween an interface incorporating a fibrous material.

2. A material as claimed in claim 1, wherein the interface is formed by applying a coating or layer containing the fibrous material to at least one of the surfaces of the co-operable surfaces.

3. A method as claimed in claim 1 or 2, wherein the interface is produced by spreading a medium containing the fibrous material, the medium being in a fluid state, over one at least of the co-operable surfaces and then allowing or otherwise enabling the medium to dry or otherwise setinto a layer in which the fibrous material is randomly distributed so that fibres are transversely oriented with respect to the said co-operable surface.

4. A method as claimed in claim 1 or 2, wherein the layer is preformed and subsequently secured to the requisite one of the co-operable surfaces.

5. A method as claimed in any one of claims 1, 2, 3 or 4, wherein the interface material is formed from a mixture of SANTOWEB 'D' 10 parts by weight Polyurethane Solution 75 parts by weight Silica VN3 1 5 parts by weight

6. A method as claimed in any one of claims 1, 2, 3 or 4, wherein the interface material is formed from a mixture of Santoweb 'D' 10 parts by weight Silica VN3 15 parts by weight APASEAL TS98 Code APO 2042 75 parts by weight.

7. A friction enhancing interface material for interpositioning between two co-operable surfaces including a fibrous material randomly oriented with respect to a carrier ar material support medium.

8. A friction enhancing material as claimed in claim 7, wherein the interface material is a mixture of an adhesive carrier medium and a fibrous material in particulate or divided form, the mixture being such that the fibrous material is randomly oriented with the carrier medium.

9. A friction enhancing interface material as claimed in claim 7 or 8, wherein the interface material includes a polymer as the adhesive forming medium.

10. A friction enhancing interface material as claimed in claim 7 or 8, wherein the interface material includes a matrix of rubbercontaining a suspension of the fibrous material together with an adhesive material.

11. A friction enhancing interface material as claimed in claim 9, and in which the polymer is a Polyurethane or a Polyvinylchloride.

1 2. An article of footwear when provided with an interface material as claimed in any one of claims 7 to

12.