WO2003037128A1

WO2003037128A1 - Method for modifying traction surfaces using corundum particles

Info

Publication number: WO2003037128A1
Application number: PCT/US2002/035071
Authority: WO
Inventors: Joseph S. Broz
Original assignee: Old Soles, Llc.
Priority date: 2001-11-01
Filing date: 2002-11-01
Publication date: 2003-05-08

Abstract

A traction-enhanced surface (24) is provided for devices such as shoe or boot soles (23) or for substrates such as stair treads which is capable of providing sufficient traction to avoid slippage, including corundum particles (26) having exposed surface-gripping features, wherein at least a portion of the particles is embedded in the surface (24), or encapsulated in an adhesive coated on at least a portion of the surface. The invention is applicable to a wide variety of footwear (10), including work boots, running shoes, snow boots, hiking boots, trail shoes and waders, and is useful for the aged and infirm as well as for those who work or play outside in slick or slippery conditions. The traction-enhanced surfaces (24) of this invention are also useful for bike tires, conveyor belts, door thresholds, and other surfaces where slipping presents a problem.

Description

METHOD FOR MODIFYING TRACTION SURFACES USING CORUNDUM PARTICLES

BACKGROUND

There have been a number of attempts to provide useful slip-resistant footwear. U.S. Patent No. 5,276,981 discloses applying a mixture of polyurethane and substantially spherical wear-resistant particles having a Mohs hardness of at least 9 for application to regions of shoe soles which are worn down. The patent teaches that the round shape of the particles is "crucial" since with irregular particles, excessive wear occurs because the sharp edges continually break off under impact. This patent also teaches that urethanes unaided do not normally adhere well to materials like aluminum oxide, so it is necessary to treat the particles with a primer such as silane in order to achieve satisfactory adherence. It also teaches that the particles should be relatively large, i.e., 8 to 16 mesh. This patent thus teaches against the use of irregularly-shaped particles.

U.S. Patent No. 3,638,785 discloses a kit and process for applying a slip-resistant surface to shoe soles. This patent teaches the application of adhesive to a shoe sole, followed by application of grit, i.e., aluminum oxide grit, ceramic chips, trisodium phosphate, sodium silicate and silicon carbide, followed by another layer of adhesive, applied until all the grip particles are completely covered. This patent does not disclose or suggest the use of corundum or leaving portions of the particles exposed.

U.S. Patent No. 5,038,500 teaches a boot having a gritted outsole. The grit is disclosed as preferably having a Mohs hardness of at least about 7-9, and as including aluminum oxide. However, this patent teaches coating the grit particles with a primer to make them adhere to a primer-coated rubber sole, or coating the grit particles with a single, ambifunctional monomer having polar and reactive non-polar segments so that a chemical bond is formed between the grit particles and the sole. This patent teaches against the use of grit particles simply glued to a sole bottom with a glue that encapsulates the grit particles rather than forming a chemical bond with the glue particles. U.S. Patent No. 4,160,331 discloses (as prior art to the claims thereof) a shoe having a slip-resistant or gripping surface on the sole in discrete bands, formed as an integral part of the rubber of the sole. The invention of the patent is directed to an improvement for making the grit more durable by placing it within channels in the sole. The grit may be silicon carbide, coarse sand or crushed rock. The shoe sole is provided with an outer rib and a plurality of transverse ribs extending across the sole, leaving channels between. The gripping material is placed in some, but not all, of the channels. This patent teaches that sufficient adhesive should be used to bond the grit in place, but not so much that it would completely encapsulate the grit. This patent does not disclose the use of corundum.

Japanese Patent 7166155 discloses a solid organic polymer such as rubber or plastic mixed in a grinding device in close contact with corundum so that the corundum becomes enwrapped in the polymer to form a non-continuous phase. This non-continuous phase is then mixed with a continuous rubber or polymer phase to produce a non-slip coating in the form of a viscous liquid gel or thixotropic mixture for application to shoe soles, or carpets, mats and the like to produce a non-slip surface. This patent does not disclose the necessity for leaving portions of the particles exposed (not encapsulated in polymer) to increase traction. After-market application of particles is also not taught or suggested.

Soviet Union Patent No. 1669959 discloses the use of a composition containing montana wax, shellac wax, stearic acid, and natural corundum, with the balance being alpha- branched 21-31C monocarboxylic acids as a treatment for leather, such as shoe soles, followed by a further treatment with the non-corundum ingredients. The corundum is not bonded to the leather sole.

U.S. Patent No. 2,732,065 discloses a flexible tape for application to a shoe sole provided with a gritty, sandy, or other friction-producing face. The friction surface may be roughened fabric or sprayed or sprinkled sand, powdered resin or other gritty substance. This patent does not disclose the use of corundum.

U.S. Patent No, 5,380,390 discloses making an abrasive material by coating a substrate with an adhesive and contacting the substrate with a quantity of hard, abrasive particles, then removing all particles not held by the adhesive. Hard particles disclosed are diamonds, carbides, borides, nitrides, pieces of hard metals and pieces of ceramic, but not corundum. This patent relates to abrasive materials, rather than traction surfaces, and thus is from a non-analogous art to that of the present invention.

U.S. Patent No. 5,396,717 discloses a convertible overshoe having an anti-slip carbide grit on its outer surface. This patent does not teach an adhesive for bonding the grit to the sole, nor does it teach corundum.

U.S. Patent No. 4,246,707 teaches a reversible shoe boot which can be turned inside out to expose rock particles embedded in the rubber. Corundum is not disclosed as useful in this invention, nor are the particles taught to be adhesively bonded to the sole.

PCT Publication WO 98/15601 teaches a primer composition for bonding grit to shoe soles. The sole is coated with the primer composition, and then with an adhesive, following which the grit is applied.

U.S. Patent No. 3,629,051 teaches boot soles made with an uncured elastomeric matrix impregnated with waste aluminum particles.

U.S. Patent No. 3,802,951 teaches shoe soles having aluminum pieces cured into a rubber-like matrix for a shoe sole.

A number of patents disclose cleats or stick-on pads or other attachments for providing friction to a shoe sole, including: U.S. Patent No. 1,631,741 to L. Lazzari et al., issued June 7, 1927; U.S. Patent No. 1,796,399 to B.T. Roodhouse, issued March 17, 1931; U.S. Patent No. 2,732,065 to A.S. Marchese, issued January 24, 1956; U.S. Patent No. 2,740,208 to E.R. Dye, issued April 3, 1956; U.S. Patent No. 3,561,140 to F.T. Ludwig, issued February 9, 1971; U.S. Patent No. 3,638,337 to Dollar, Jr., issued February 1, 1972; U.S. Patent No. 3,667,141 to White, issued June 6, 1970; U.S. Patent No. 4,160,331 to Bell, issued July 10, 1979; U.S. Patent No. 4,378,641 to Tarlow, issued April 5, 1983; U.S. Patent No. 4,644,672 to Dassler et al. issued February 24, 1987; U.S. Patent No. 4,702,021 to Cameron, issued October 27, 1987; U.S. Patent No. 5,255,453 to Weiss, issued October 26, 1993; U.S. Patent No. 5,380,390 to Tselesin, issued January 10, 1995; U.S. Patent No. 5,410,823 to lyoob, issued May 2, 1995; U.S. Patent No. 5,485,687 to Rohde issued January 23, 1996; U.S. Patent No. 5,966,840 to Bell et al. issued October 19, 1999; U.S. Design Patent No. 288,262 to Yokoishi, issued February 17, 1987; U.S. Design Patent No. 376,683 to Gaudio et al., issued December 24, 1996; and European Patent No. EP 0 768 048 A2 to Softspikes, Inc., dated April 16, 1997.

Patent No. 6,132,844 issued October 17, 2000 teaches a pressure-sensitive adhesive comprising grit particles, for use in applying to floor tiles. This patent does not teach applying such material to shoes or boots.

U.S. Patent No. 3,609,889 discloses a spiked golf shoe sole wherein the spikes are made of substantially pure corundum for durability. This patent discloses that the corundum is extremely smooth. Thus this patent does not teach the use of corundum particles of irregular shape.

U.S. Patent No. 6,105,282 discloses a spike for a golf shoe sole made of a mixture of polymer and corundum for improved durability. The corundum is 40 to 8,000 grit size. This patent also discloses that the material can be used for the soles of spikeless shoes for increasing the wear of grip surfaces. This patent does not contain any suggestion or motivation for increasing the particle size.

U.S. Patent No. 4,648,187 discloses an athletic shoe sole with cleats which have caps as gripping elements. A corundum ceramic may be part of the cap in order to provide abrasion resistance. There is no disclosure of the use of large, irregularly-shaped corundum particles and this patent provides no suggestion or motivation for increasing particle size or for using irregularly-shaped corundum particles. U.S. Patent No. 4,061,268 discloses a mat for providing traction under the wheels of a vehicle comprising an open-mesh net of strands that are encased around their individual circumferences with a frictional coating comprising a layer of binder material adhered to the strands and a mono-layer of abrasive granules partially embedded in the layer of binder material. The particle size is specified to be between 400 and 2500 micrometers. This patent makes a point of stating that friction coatings for mats are not analogous to friction coatings for overshoe soles and, in addition, it contains no suggestion or teaching of the use of larger- sized particles.

French Patent 2317109 discloses anti-skid tires produced from rubber compositions containing hard grains such as sand, corundum or ground glass, for use on slippery or icy roads. The grains are added during compounding after mastication of the elastomer/green rubber mixture. A grain size between .5 and 2 mm is disclosed, and it is disclosed that grains project from the rubber. This patent does not disclose the use of particles of a larger size range or patterns of application of grains.

U.S. 5,614,041 discloses a pneumatic tire with an exterior additional layer on the tread strip for reinforcing the tread. Corundum may be used as a component of the reinforcing layer, but the patent contains no teaching of the use of particle sizes large enough to produce traction, nor does it contain a teaching that portions of the particles are deliberately left exposed to enhance traction.

German Patent 2501778 discloses brake and clutch pedals surfaced with non-slip materials, e.g. corundum particles applied by vulcanization for traction and durability. The particle size is not specified. This patent does not disclose use of the material on a shoe sole, and does not provide an enabling disclosure.

None of the foregoing patents provides the advantages of the present invention of providing an easy-to-apply after-market traction-enhancing surface having corundum or other similar particles of a specified size range applied to a surface lacking cleats, channels or other traction-enhancing aids, such that gripping features of the particles (points or sharp edges) are not completely encapsulated within the surface of the adhesive.

A problem with previous attempts to attach grit particles to shoe or boot soles by means of an adhesive has been that even very hard grit particles tend to become rounded over time and therefore to lose their gripping power, yet because of the type of adhesive used to attach the particles, they remain firmly bonded to the sole, making it difficult to apply fresh particles, and making it less likely that the user will realize that the traction-enhancing surface has degraded, thereby delaying the time when the user applies fresh particles and exposing the user to unnecessary danger.

SUMMARY OF THE INVENTION This invention pertains to the modification of traction, preferably of the tread or outsole surface of non-cleated footwear that contacts the ground (possibly covered with ice or snow), and to the application of a high-traction and/or non-slip/slip-resistant layer thereto. This application incorporates by reference, to the extent not inconsistent herewith, the disclosure of U.S. Provisional Patent Application No. 60/187,686 filed March 8, 2000 entitled "Kit and Method for Modifying Footwear Tread Traction" and U.S. Patent Application No. 09/802,015 filed March 8, 2001, entitled "Method for Modifying Footwear Traction." The present invention provides an improvement of the invention described in said applications, specifying a more useful embodiment employing mineral corundum particles or particles of equivalent hardness rather than the metal chips of said prior invention.

A traction-enhancing surface is provided for devices such as ground-contacting devices including footwear (shoes, boots, slippers and the like), foot prostheses. ski attachments, bicycle tires, motor vehicle tires, motor vehicle tread loops (such as those used on tanks and bulldozers), wheelchairs, walkers and canes, or for substrates such as conveyor belts, stair treads, stairwells, door thresholds, and working areas where water (frozen or liquid), lubricants or other slippery materials may be employed. Such traction-enhancing surface is capable of providing sufficient traction to avoid slippage of a device against a slippery surface, and comprises particles (preferably of corundum) having exposed surface- gripping features, wherein at least some of the particles are partially embedded in the surface or partially encapsulated in an adhesive coated on at least a portion of the surface.

The surface to be treated may be that of a device; preferably the device is the sole of an item of footwear, which in use contacts a substrate. Or the surface to be treated may be the surface of a substrate, such as a conveyor belt, which in use contacts another surface, wherein it is desirable that the surface of the substrate prevent slippage of the other surface in contact with it. The surface to be treated may be a standard surface for such device or substrate composed of leather, rubber, mastic, carbon rubber, ethylene vinyl acetate, or any other common shoe outsole material. Preferably the surface has not previously been provided with surface-gripping features such as cleats or channels, but the present invention has usefulness even if such surface-gripping features are already present.

The particles (also referred to as "chips") are preferably of the mineral corundum, commonly called "corundum," or "emery," "Oregon emery," or 'Turkish emery," having surface-gripping features such as sharp edges or points. Chips of corundum are useful in this invention because of several factors: (1) their hardness, which allows them to be employed in the present invention with reliable durability and with certainty that the particle is harder than the hardest ice likely to be encountered in the envisioned applications (typically Mohs scale 4 - 8) so that the particle digs into the. ice and establishes traction; (2) their toughness, which allows them to be used in the present invention without excessive fracture, thus contributing to their durability; (3) their surface-gripping features, such as sharp edges and points, which allow them to be employed as traction-enhancing particles; and (4) the non-zero aqueous solubility of the particles which allows them to dissolve in cold-water — albeit slowly — into aluminum oxide, silica, titanium oxide, and other compounds naturally found in soils and as constituents of the natural earth's crust at a wide variety of locations around the world. This last property allows for the environmentally-safe use of the invention. As particles become dislodged from the shoe or other device, are worn-away, or ablated, the resulting material loosed into the environment eventually decomposes into natural soil compounds and, as such, does not constitute a significant environmental pollutant or "trash" as would other particulate materials such as metal or ceramic chips that do not dissolve and do not have chemical compatibility with natural soils.

The corundum particles used in this invention may be crushed or sized ad preferably have a largest dimension greater than about 1/16 inch in length (i.e., greater than about 2 mm) and can be up to about ^lΛ inch in largest particle dimension (i.e., up to about 7 mm). Particles useful in this invention have sizes between screen sizes about 6 and about 10 using USA Standard Testing Sieve nomenclature. The hardness of the particles is preferably greater than about 8, more preferably greater than about 8.5, and most preferably 9 or greater than 9 on the Mohs scale.

Suitable adhesives are known to the art, including commercial products such as styrene butadiene rubber cements, e.g., "Shoe GOO^®," urethane adhesives, resin adhesives, solvent cements (such as "Barge^®"), elastomeric adhesive, and epoxies. The adhesive is preferably a single-component adhesive such as "Shoe GOO^®," and the particles are preferably not chemically bonded to the surface being treated or to the adhesive, but rather are partially encapsulated within the adhesive material which is bonded to the surface. The particles are only partially encapsulated so that the gripping features of the particles, e.g., the points or edges, are left exposed.

Non-chemical bonding of the particles to the surface or to the adhesive is useful because virtually all of the major forces on the particles during use are normal to the plane of the treated surface, so there is relatively little shearing force in a direction parallel to the plane of the surface. Non-chemical bonding of the particles is advantageous because in use there is still enough shearing force that eventually the mechanical encapsulation of the particle becomes weakened as the structure of the adhesive degrades, stretches or tears, and particles fall out or are ripped out. Being geo-degradable to natural soil components, the particles do not harm the environment, and the rate at which they fall out (approximately 30 weight percent particle loss on shoe soles after thirty to fifty miles of running) ensures that the user will notice the particle loss and reapply particles to form a new traction surface when needed. If the particles remained embedded in the adhesive until they wore flat, traction would be lost, and they would provide little or no protection for the user.

Reapplying a new gripping surface to a shoe sole or other device after particles have fallen out is much easier than reapplying a new gripping surface to a surface on which the particles have remained embedded and worn down flat because the bonding of the adhesive to the flattened particles is not as strong as to previously-applied adhesive or to the surface being treated (particularly when that surface is rubber).

Methods of making such traction-enhancing surfaces are also provided, such methods comprising rendering at least a portion of a surface of a device or substrate sticky, e.g., by heating to melt the surface or make it tacky, or applying adhesive, and embedding particles having surface-gripping features in the surface or encapsulating them in the adhesive such that at least a portion of the particles has surface-gripping features exposed. Preferably, the particles are corundum particles, and preferably they are pressed into the surface, e.g., by rolling or applying even pressure, before the sticky surface hardens, so that the particles are partially partially encapsulated, leaving a portion exposed to provide superior traction. Preferably a majority of the particles have surface-gripping features exposed; more preferably at least about 85% to about 95% of the particles have surface-gripping features exposed. Surface-gripping features include points and sharp edges of the particles owing to their irregular geometry.

Preferred methods of this invention for applying particles to footwear soles and other surfaces consistently produce a contact surface that provides high-traction on normally slippery surfaces such as ice, snow, packed snow and slimy/mossy surfaces. These methods are amenable to all types of footwear, new or used.

This invention also includes a package configured as a kit, the contents of which are in part comprised of: (a) a hard particulate material suitable for being affixed to the bottoms of footwear having normal treaded soles, said footwear bottoms being preferably devoid of cleats or specialized ridges, to provide positive traction; and (b) an adhesive material suitable for bonding said particulate material to the bottoms of footwear. The term "hard" as used to define the particulate material means at least as hard as the ground-contacting surface to be treated therewith. Preferably the particles have a Mohs hardness greater than about 8.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1 A and IB show two proposed commercial-type kits containing the necessary ingredients for application of the high-traction surface of this invention in a unitary package for sale.

Figure 2 shows the application of certain of the kit materials (adhesive and particles), spread more or less uniformly over the forefoot and heel sections of the illustrated footwear sole.

Figure 3 shows another pattern of application of certain of the kit materials (adhesive and particles), spread in a stripe pattern over the forefoot and heel area of a footwear sole.

Figures 4A-4C illustrate the steps for applying particles to a footwear sole. These drawings may form part of instructions furnished with the kit.

DETAILED DESCRIPTION This invention relates, in one embodiment, to the modification of the bottoms of ordinary footwear, said footwear being new or used, through the application of a highly slip- resistant layer of corundum particles which then forms the bottom surface, or modified outsole, of said footwear.

Shoes, athletic footwear, boots, waders and the like that have high traction outsoles of this invention are particularly useful on slippery ground, or slick surface conditions such as ice, snow, packed snow or slimy/mossy terrain. A positive gripping surface on the outsoles of footwear helps prevent slipping on almost any type of surface that has low frictional characteristics. It is the primary focus of this invention to provide a high-traction surface outsole for ordinary footwear and a method of application of corundum particles to conveniently and efficiently fashion the high-traction surface on the outsoles of ordinary footwear.

The high-traction tread surface formed by this invention is durable under most conditions of use; however, the present invention also contemplates periodic replacement and/or enhancement of the high-traction surface through re-application of the corundum particles.

As illustrated in FIG.l A and FIG. IB, the types of kits contemplated by this invention for retail sale and home or commercial application are represented by (but not limited to) the following general elements: A retail display (possibly cardboard) sheet 1 or box 11 onto which the various kit components (items 2-6) can be attached, or into which these items (12- 16) can be placed. The quantity of footwear that can be treated with the kit depends on the size of the kit and quantity of each kit element provided and is variable for the purposes of this disclosure.

A tube (or other container) of adhesive (items 2 and 12) is provided suitable for bonding to the outsole (24 and 34 in FIG. 2 and FIG. 3, respectively), and encapsulating the particulate material (items 3 and 13). This invention contemplates using, but is not limited to the use of styrene butadiene rubber cements (i.e., commercial products such as "Shoe GOO^®"), urethane adhesives, and solvent cements (such as "Barge^®"), elastomeric adhesives, and epoxies. There are a large number of available adhesives beneficial in encapsulating particulate material such as corundum to rubber or neoprene outsoles and other types of outsoles, and the description of the above adhesives is for illustrative purposes only and not intended to restrict the scope of the invention in any manner.

Containers (4 and 14) contain the particulate material (3 and 13); said containers can either be glued to the retail display sheet (1) or placed into the box (11). The corundum particles (3 and 13) useful in this invention have sharp edges such as result from the crushing or grinding of mineral corundum (also called "emery," "Oregon emery" or "Turkish emery" and hereinafter referred to as "corundum") and sorting by size through a sieve. The corundum particles can be constituted from crushed mineral deposits that are mined, or derived from a number of other sources. Other minerals, such as quartz, industrial diamond, aluminum silicates, and the like are also useful in this invention. Most preferred are corundum particles derived from mineral mining which are either sheared to size or crushed in a ball mill to the required width and linear dimensions.

The particles are applied to the bottom outsoles of shoes with an adhesive to form a rugged, non-slip outsole for outdoor use of the footwear, especially on ice or snow. In one embodiment of this invention, corundum may be "diluted" by the use of other minerals or materials utilized in association with the corundum in application.

The size of the corundum particles can range anywhere from about 2 mm to about 10 mm or more, depending on the geometry of the particles. The above dimensions represent the average diameter of a sphere within which a single corundum particle could completely fit. Preferably, the corundum particles are between about 1/16 inch (about 2mm) and about 1/4 inch (about 7 mm) in length, and have a width less than or equal to their length, with a tolerance of ± 10%. Preferably the smallest dimension of the particles is greater than about 2 mm.

Dimension, hardness and/or strength and/or fracture toughness of the mineral corundum particles is important, as particles too thin, too soft, too weak or brittle may crush or crack under the weight of the user, thus diminishing the traction of the surface. The particles must be large enough, hard enough, and strong enough to resist such crushing and destruction during use, and must be harder than the ice or other slippery surface they are designed to be used with.

Particles of rubber or other similar elastomeric material may be used in one embodiment of this invention, by themselves or in addition to the particles having a Mohs hardness greater than about 8 to improve traction on such surfaces as smooth floors, e.g. marble and tile. These particles are preferably slightly larger than the corundum particles described above, and preferably are between about 5 and about 8 mm in size (size being as defined above). Preferably, these elastomer particles constitute no more than about 10% of the total particulate material.

The particulate material used herein may also or alternatively include particles of metal such as titanium particles as described in U.S. Patent Application Serial No. 09/802,015 incorporated herein by reference. These particles act as guards for the other particulate materials, since they generally extend further from the surface being coated with the particles and prevent extreme wear on the other particles. Also, they are somewhat more durable. Preferably such metal chips constitute no more than about 10% of the total particulate material. This invention provides an urban embodiment which may comprise metal chips or other non-soluble particles as described above, and a trail embodiment in which the particulate material is degradable, as is corundum.

Other items in the kit are the applicator devices (5 and 15) as shown in FIG. 1 A and FIG. IB. These are devices or tools of various types such as brushes, spatulas, spreaders and the like, useful in the application of the adhesive to the footwear outsole (24 and 34, Figures 2 and 3); or in spreading the particulate (3 and 13) onto the adhesive-coated outsole tread to render a specific pattern of fixed particulate (25 and 35, FIG. 3); or said applicators may comprise a sponge or other wiping means to ensure that the individual particles (noted as 26 and 36, Figures 2 and 3) are not completely covered or coated with adhesive, so that at least a portion of each particle is exposed to contact the slippery ground surface (e.g., ice). This is considered an important feature of the present invention as it allows the particle to come into direct contact with the slippery surface, thus enhancing traction. A sharp-edged piece of particulate that is partially encased in adhesive and which has an exposed portion that is ground- or surface-contacting, provides a point of much higher traction than a piece of particulate that is completely encapsulated in adhesive. Instructions (6) and (16) in FIGs. 1 A and IB give the kit purchaser exact directions for the consistent application of the kit ingredients for a superior, high quality, high-traction sole. The kits, and all items pictured in FIG. 1 A and FIG. IB, are intended to be sold commercially with all or some of the items as described packaged and sold as a unit.

Figure 2 shows shoe 10 having an outsole 23 with an outsole contact surface 24, having a heel area 21 and a forefoot area 25, on which fixed particulates 26 are adhered.

The outsole 23, specifically the outsole contact surface 24, is treated to obtain a gripping, high-traction surface.

The outsole contact surface 24 of the outsole 23 is first roughened by scuffing on pavement or by using sandpaper or a wire brush, or any other method of physically or chemically roughening the surface to provide a superior adhering surface for the adhesive to stick to firmly.

Following this roughening process, the outsole contact surface 24 of the footwear is cleaned and dried so that there is no grease, wax, dirt or other foreign matter that could come between the adhesive and the outsole contact surface 24.

The footwear is inverted and, using an applicator tool, e.g., a spatula, or by squeezing adhesive from a tube, a generous coating of adhesive is spread uniformly on the outsole contact surface 24 on forefoot and heel areas 21 and 25 of the outsole contact surface 24 of the footwear outsole 23.

It is desirable to keep a small margin 22 of clear area that is free of adhesive around the edges of the outsole. In these adhesive-free areas, the corundum particles that are later applied will not adhere, which allows the edges to be free of particles that could cut or injure the opposite leg or another person or object. The amount of adhesive applied is typically gauged by the size of the area to be covered and should be sufficient to create a layer of adhesive that is approximately half the dimension of the particles so that approximately 50% of any individual particle is embedded into the adhesive, and half of the particle is exposed to the slippery surface on which it is to be used. This is a rough "rule-of-thumb" and does not limit the patent in any manner but is to be construed as guidance so that not too little adhesive is applied (leading to insufficient adhesion), nor too much applied (thereby leading to fully-encapsulated particulate with sub- optimal traction properties compared to exposed particles). Once the adhesive is applied in the desired pattern, the particles are spread evenly on the heel area 21 and forefoot area 25 where the adhesive has been placed. The particles should be placed quickly enough so that the adhesive is at most tacky and has not dried or cured fully. The particles are spread in an amount sufficient to fully cover the desired pattern areas, but no so much as to substantially pile up. The areas without adhesive allow an application that easily excludes particles from the edges of the outsole and other areas of the outsole where they are not desired.

Care should be taken to make sure that at least some of the sharp or pointed portions of the corundum particles remain free of adhesive and protrude from the adhesive layer.

Using an applicator such as a spatula or another stick or object, good contact between the adhesive and the particles should be ensured by gently pressing down on the particles to make sure that they are partially embedded into the adhesive. This can also be accomplished by (and should be followed by) turning the shoe or footwear right side up and gently rolling the outsole on a protected surface to embed (or implant) the particles into the adhesive and to also ensure the grip tread is even and provides a reasonably-contoured and usable outsole surface for the intended application. If desired, adhesive can be applied in a pattern as in Figure 3, which shows a straight stripe 37 on the forefoot, and a "horseshoe"-shaped stripe 38 on the heel.

In all patterns, it is also desirable to keep a small margin of clear area that is free of adhesive around the edges of the outsole. The adhesive should then be allowed to dry or cure fully before handling and use. This time varies from adhesive to adhesive, as is known to the art.

The high-traction, non-slip/skid-resistant surface thus applied is very effective in a wide variety of slippery and/or slick conditions.

Figure 4 shows the steps used to apply the particles of this invention to a footwear sole. The instructions caution the user to apply the product in a well-ventilated area, and for best results, to roughen the surface before use by scuffing soles on pavement, or with sandpaper or a wire brush. Soles should be clean, dry and free of dirt. The instructions further instruct the user to puncture the seal in the neck of the tube using the pointer cap furnished with the adhesive and to spread the adhesive in an inverted "N" on the forefoot and a "V" on the heel area of the sole, and recommend keeping a one-fourth inch to one-half inch clear margin around the sides for running shoes to prevent accidental injury to the opposite foot, leg or clothing while running. The user is next instructed to, within 3-5 minutes of spreading the adhesive, sprinkle the corundum particles evenly over the adhesive-applied surface, taking care to have the particles protruding out of the adhesive. Next, the user is instructed to gently press down on the sprinkled particles using a popsicle stick or the like to ensure good contact with the adhesive. After the glue is "tacky" (about twenty minutes at room temperature), the shoe sole can be turned over and gently "rolled" on a (protected) surface for guarantee of an even grip tread. The user is cautioned not to roll the treated surface on wood floors, tile or carpet. The user is further instructed to allow the treated surface to fully dry for twenty-four hours before handling. For maximum strength, the user is instructed to allow seventy-two hours drying time before use. The user is advised to store unused portions of the kit at room temperature in a dry area, and is further cautioned that misuse of the product can cause serious personal injury or death or damage to property, and that the tread produced by the proper application of the kit materials is not intended for use on certain flooring or surfaces, especially indoors, such as wood, tile or carpet. Severe injury could be caused by slipping or falling while using the product if the user attempts to walk on hard, polished surfaces such as ceramic tile, stone tiles or marble. Over-confident use on icy surfaces can also constitute misuse of the product as, while the product provides excellent traction enhancement, it is not one hundred percent slip-free and should never be a substitute for good judgment. Additional product warnings are also provided regarding keeping the product away from heat, spark and flame while vapors are present, and obtaining first aid if breathing difficulty is experienced.

Corundum is comprised substantially of alumina (aluminum oxide of a particularly hard crystalline form), silicon oxide (silica), titanium dioxide, and possible other minerals in the matrix of the corundum as noted here in an analysis of typical "Oregon emery" and has the following physical and chemical properties summarized in Table 1 below:

TABLE 1

CORUNDUM AND OREGON EMERY DATA AND PROPERTIES

(Source: Advanced Surfaces and Processes, Inc. Forest Grove, OR)

Component Chemistry: Wt. %

Aluminum Oxide (A12O3): 67%

Iron Oxides (Fe2O3): 25%

Silica (SiO2): 3.5%

Titanium Oxide(TiO2): 3%

Other Minerals: 1.5%

Hardness: Mohs 8 - 9

Other ordinary minerals, such as quartz (silicon dioxide, Mohs scale 4-6), do not provide sufficient hardness, strength or toughness to ensure the durability and functionality of the particles in use. Other minerals tested in the application (including quartz) suffered from fracturing, breakage, excessive wear, and rapid deterioration under conditions of normal use. The specified use of corundum has as an advantage in its ability to dissolve in cold water (CRC Handbook, 1964, Solubility of Compounds), thus providing a particle that not only can stand up to rugged use, but that can also decompose into common compounds present in natural soil, thus saving the natural environment from needless pollution or litter as particles become dislodged or wear off the shoe during use. In comparison to other materials tested for this application, the use of corundum is superior to titanium metal particles or aluminum particles. Such metals will stay noticeably in the environment in metallic form for a considerable length of time without degradation, dissolution, or decomposition. The noticeable presence of such metallic particles, for example, would by most accounts constitute "litter," whereas the presence of a corundum particle would appear like a small piece of natural rock or gravel and be virtually unnoticeable. After some time, depending upon local conditions, the particle would dissolve into common chemical compounds that are ubiquitously present in the environment and constitute the general background inorganic chemistry of soil, i.e., Aluminum Oxide (Al₂O₃), Silica (SiO₂), Hematite (Fe₂O₃) (Means, R.E. Physical Properties of Soils. Oklahoma State University, Merrill Books, Inc. 1963, Lib. Congress: 63-14199). All other materials tested or contemplated for this application either lacked the required physical properties of hardness, strength, or toughness, or if they had these properties, lacked the ability to dissolve in water under the types of conditions contemplated for the environment in which the application will generally be used which is out-of doors on sidewalks, streets, or trails. Some of these alternate materials tested or contemplated but ultimately rejected for one or both of the cited reasons are: quartz (too soft), silicon carbide (zero solubility), flint (too soft and fractured easily).

Various aspects and elements of the invention may be used independently and for applications other than footwear where a high-traction surface would be beneficial, such as application of a high-traction surface to tires (especially mountain bike tires), conveyor belts, stair treads, stairwells, door thresholds, and other stationary surfaces.

It should be apparent that this invention could take many forms, particularly in the choice of adhesives and variations to the method of application, and the invention should not be considered to be restricted to the preferred embodiment described in detail herein.

Claims

1. A traction-enhanced surface for a device or a substrate comprising:

(a) non-metallic particles having exposed surface-gripping features and having a Mohs hardness greater than about 8;

(b) at least a portion of the particles being partially embedded in the traction- enhanced surface, or in encapsulated in an adhesive coated on at least a portion of the traction-enhanced surface.

2. The traction-enhanced surface of claim 1 wherein said particles have a size greater than about 2 mm.

3. The traction-enhanced surface of claim 1 wherein said particles comprise corundum particles.

4. The traction-enhanced surface of claim 1 wherein said particles comprise up to about 10% elastomeric particles.

5. The traction-enhanced surface of claim 1 wherein said particles comprise up to about 10% metal chips.

6. The traction-enhanced surface of claim 1 wherein said substrate is part of a ground- contacting device.

7. The traction-enhanced surface of claim 6 wherein said substrate is part of a device selected from the group consisting of footwear, foot prostheses, ski attachments, bicycle tires, motor vehicle tires, motor vehicle tread loops, canes, walkers and wheelchairs.

8. The traction-enhanced surface of claim 1 which is part of the substrate.

9. The traction-enhanced surface of claim 8 which is part of a substrate selected from the group consisting of conveyor belts, stair treads, stairwells, and door thresholds.

10. Footwear comprising the traction-enhanced surface of claim 1 on a sole thereof.

11. Footwear of claim 10 wherein said sole does not comprise cleats or ridges.

12. The traction-enhanced surface of claim 1 wherein said particles have a largest dimension of about 1/16 inch (about 2 mm) to about ^lΛ inch (about 7 mm) or less.

13. The traction-enhanced surface of claim 3 wherein the corundum particles are made by grinding, shearing, or crushing natural corundum or corundum-bearing minerals.

14. A method of making a traction-enhanced surface of claim 1 comprising:

(a) rendering at least a portion of a surface of a substrate sticky; and

(b) encapsulating the particles in said surface such that at least a portion of the particles has surface-gripping features exposed.

15. The method of claim 14 wherein the maj ority of said particles have surface-gripping features exposed.

16. The method of claim 14 wherein said surface is rendered sticky by partially melting said surface or portion thereof.

17. The method of claim 14 wherein said surface is rendered sticky by applying an adhesive to said surface or portion thereof.

18. The method of claim 14 also comprising the step of pressing said particles into said sticky surface.

9. A kit comprising, packaged in close proximity to each other:

(a) an adhesive;

(b) a particulate material having exposed, surface-gripping features and a Mohs hardness of at least about 8;

(c) optional applicators for said adhesive; and

(d) optional instructions for use of said kit.

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FIG. 1A

FIG. 1B 2/4

CM 3/4

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