USRE23135E - Antiskid rubber tire - Google Patents

Description

July 19, 1949- c. A. GAPEN ET 'AL Re. 23,135

ANTISKID RUBBER TIRE Original Filed Jan. 14, 1947 j l Fay. j.

wuc/n/ow ClarenceA. G51/verz Lonnie apen www@ /M ww @www Reissued July 19, 1949 23,135 AN'rIsnm RUBBER uns Clarence A. Gapen and Lonnie Gapen Morgantown, W. Va. r

original No. 2,434,207, dated January s, 194sse rial No. 722,072, January 14, 1947. Application for reissue December 29, 1948, Serial No. 67.301

e, claims. (c1. 152-211) This invention relates to vehicle tires and surface is not suiciently great to give the best method oi m'aking same. and Athe present applic cation constitutes a continuation-in-part of our abandoned application Serial No. 487,754l,.fl led May 2Q, 1943. l

It has heretofore been proposed to incorporate into rubber used in vehicle tires certaincoarse particles designed to improve the traction-qual#A ties, but such attempts have not met with commercial success due to a number of factors, amongwhich 'are the abnormally high rate of wear which results in some cases and in others from the'factY that in freezing weather or in icy conditions, glazing of the tread from ice is apt to result, making the tire considerably less satisfactory andmore dangerous than a conventional tire. An object of this invention is to provide a ve..

hicle tire or other anti-skid rubber tread "surfa .ce\-

which is devoid ofthe above mentioned disadvantages and which has remarkably high antillid characteristics as well as unusually long Other objects and advantages will become apparent from a study of the following specification taken with the accompanying drawing wherein:

The single gure is a fragmentary perspective view, partly in cross-section, of a vehicle tire having a rubber tread embodying wood particles in accordance with the present invention.

Referring more particularly to the drawing, numeral I denotes an ordinary vehicle tire carcass upon the exterior surface of which is molded a covering body or tread 2 of natural or synthetic rubber or compound thereof having interspersed therein fibrous or ligneous particles inthe form of wood chunks in" accordance with the teachings of thev present invention. Any well known form of tread design may be used such as the circumierentially grooved design illustrated.

We have found that amazing traction qualities can be secured by compounding the rubber with irregularly-shaped wood particles of a predetermined sizeand in an adequate amount. We may use in the neighborhood of 25% by weight of such wood particles, although the exact percentage is not critical, as it may range from somewhere' around 30% by weight to somewhere around 20% by Weight. Since the density of the crude rubber is very much greater than the density of the wood particles, this is equal to about one part of rubber by' volume to four parts of wood particles. It the weight of wood particles is reduced too iar below the optimum of about 25%, the maximum anti-skid qualities are not secured, and the density of wood particles on any exposed area of traction results, whereas if the wood particles are increased much abovethe optimum of 25 the life of the rubber is impaired and it does not have the resilience or toughness to give-,good wearing qualities. We have found. contrary to" expectations, that the use 'of 25% by weight -of wood particles, or one part by volume of rubberto about four parts by volume of wood particles does not detrimentally impair the resilience; l

toughness or wearing qualities 4of the rubber, whereas` the tractioneiect isincreased to an amazing extent. Exhaustive demonstrations hgve proven thattires so prepared give traction 15- lW erino'other materials used on the vehicle tires will possibly hold'. Cars provided withetires -made with rubber compounded according tothe Apresent invention are enabled toascend and descend heavy snow and ice-'coveregrades with much greater facility than cars equipped with conventional tires having chains, and, in fact, cars equipped with tires compounded in accordance with our invention have, in comparative tests, climbed grades where cars equipped with,

conventional chains could not secure traction.

The character of the wood particles .are important; they must be irregular chunks of wood. All of them should be of a size which will pass through a #6 mesh screen, and all or substantially all should be retained and not pass through c than #16 mesh merely act as. an inert-ller much the same Aas wood flour would do, impaiiing the strength of the rubber and adding nothing to its traction-resisting qualities." Normally we take particles produced by a #10 wood cutting saw, removing about 2,0% by weight, so that substantially allv of the particles retained are smaller than a #6 mesh, i. e., will not be retained on a #6 mesh, and are larger than a #16 mesh, i.- e., they will be 4retained on la #16 mesh. It is, of course, probable that notwithstanding careful screening, some nes will be retained, but the mass is predominantly within this range of sizes and not all of the particles are of uniform size, varying between a #6 and a #16 mesh. Particles of both hard and soft woods have been used, and no appreciable dideren'e in results have so far been measured.

Particles formed by a coarse saw, such as a #10 wood saw, are irregular in shape, as well as in size, which is distinctly advantageous in the present invention. Whereas normally the tread Re. i23,1354

sans

surface of the tire made in accordance with our invention feels reasonably smooth and of uniform texture to the touch under ordinary circumstances, the vtread surface in contact with the ground or with the ice. due toA the weight of the car at the place where the tire is resting or contacting the ground, has a tremendous number of rough wood surfaces projecting or protruding from it, being the ends, corners, and edges of irregularly-shaped wood particles exposed at the surface of the tire. these creating a unique surface condition at that instant which is effective to give tremendous traction and holding power. As the wheel moves around, shifting the point of compression, the wood particles tend to draw back into the surface as the tire resumes its normal shape.

The irregular shape of the particles not only increases the effectiveness oi' the particles to give traction and resist skidding. but itis eifective in more securely anchoring the particles in the rubber, and holds them in. In all cases. the wood particles are kiln dried before they are introduced into the rubber. Additionally. they may be treated with some chemical which will increase the adhesion between the wood and the rubber. Forexample, a solution of pine tar used totreat the wood particles will cause the rubber in being curced to attach itself more rmly to the wood particles. The active ingredient of the pine tar is a terpene which causes; the rubber to wetandadheretothewood.`

In the practice of our invention, the wood particles are niiormly-j'mixed throughout the to be used in making the tread of the tire by adding the wood particles along withpther ingredients to the Banbury mixer which isthe mechanism commonly employed for mixing ingredlents with rubber in preparing rubber for its final cming, Also. the wood particles, insteadcf being incorporated at the mixing' macliirie,.zriay be calendered into the rubber on the mlendering rolls. It makes no difference which operation is employed, although. because of the greater bulk of the wood particles. it is somewhat more. eiective and cheaper to mix the wood particles into the rubber in the Banbury or similarmi-xing machine.

Rubber to which the wood particles have been added may be used in forming the outer layers or treads of new automobile tires, or it may be formed into strips for use in retreading tires as is well understood in the art. Also, while the invention has primary application to rubber for use in tires, such rubber also may be very effectively used in rubber shoes, and particularly rubber shoes intended for use on wet surfaces; as for example. on the decks of ships. or for walking on wet ice. or for other purposes where nonslipping qualities are especially needed.

The term rubber'l as used in the present applicationis used in its generic sense as comprehending both natural rubber of the type used in tires, shoes. and shoe treads, as well as synthetic rubber and combinations of synthetic and natural. rubber, and the term is not used in the limited sense oi meaning natural rubber alone. We. of course, recognize that the so-called synthetic rubbers are actually not rubber, but are a substitute. However, they are spoken of in the art as rubber, and our invention includes both the natural and synthetic materials. Except for the wood particles, the rubber is compounded in all respects the same as for tires or like articles according to well known practices in the art.

Not only are the wood particles highly euective in improving the traction qualities of the tire, but because of the surprisingly large proportion of wood. from the standpoint of volume to rubber.`a given quality of rubber is extended substantially so that less rubber need be used in any tread, and an improvement of quality ac'- compa'nied by a saving of rubber. which. of course, is more expensive than the wood particles.

While we have described our invention in detail, it will be understood that 25% by weight oi' wood to 75% by weight of rubber is about the optimum, but the invention is not limited to any exact proportion. However, as hereinbeiore indicated, any increase of wood particles very much beyond 25% or above about 30% impairs the resilience and the toughness of the rubber and its wearing qualities, whereas very much less than 25%, and say about 20% as a minimum does not give the most desirable tread qualities. Certainly. by volume, the wood particles should be at least of the rubber, and preferably more. Also. while the particle sizes are predominantly smaller than #6 mesh, i. e., capable of passing through a #6 mesh screen, and larger than #16 mesh. still there may be a. small percentage of zparticles vvlhlch'are out-.e je this range. As herein indicated, the amasing traction eiect and gripping-or anti-skid properties are due to the slight projection of many irregulansmall wood surfaces when a. pressure is applied to the rubber.

l. A rubber tread surface lcomprising approximately 20%n to' 30% by weight of irregularly shaped wood chunks and approximately 80% to by weight, respectively, of a cured rubber matrix, said wood chunks being uniformly and intimately dispersed throughout said rubber ma trix, said wood chunks consisting substantially oi' a screen size 'between a No. 6 standard mesh screen as a maximum and a No. 16 standard mesh screen as a minimum and being substantially of the configuration of sawdust produced by a No. 10 wood cutting saw, which sawdust is in the form of chunks having projecting' ends, corners and edg.

2. A vehicle tire including an anti-skid rubber tread surface comprising approximately 20% to 30% by weight oi irregularly shaped, hard wood chunks and approximately to 70% by weight, respectively, of cured rubber in the -form of a matrix, said wood chunks being uniformly and intimately dispersed throughout said rubber matrix, said wood chunks consisting substantially of a screen size between a No.; 6 standard mesh screen as a' maximum and a No. 16 standard mesh screen as a minimum, and being substantially of the configuration of sawdust produced by. a No. 10 wood cutting saw, which sawdust is in the form of chunks having projecting ends, corners and edges.

3. In a pneumatic tire, a tread comprising a rubber composition having particles of hard fbrous material interspersed therein of such size 'that all will pass through a No. 6 standard mesh screen and most will be, retained by a No. 16

screen and comprising ofV the order of 20% by weight of said composition, said particles being in the form of irregularly shaped chunks -having projecting ends, corners and edges.

4. An anti-skid rubber tread composition for vehicle tires having particles of hard cellular material interspersed'therein of irregularly shaped chunks substantially in the form of three dimensional blocks whose lengths vary from one to several times their widths and oi such size that all will pass through a No. 6 standard mesh screen and most will be retained by a No. 16

screen.

5. A rubber tread surface comprising approximately 20% to 30% by wei'ght of irregularly shaped chunks of woody material and approximately 80% to 10% by weight, respectively, of a cured rubber matrix, said chunks being uniformly and intimately dispersed throughout saidrubber matrix, said chunks consisting substantially of a screen size between a No. 6 standard mesh screen as a maximum and a No. 16 standard mesh screen as a minimum and being substantially of the conguration of sawdust produced by a No. 10 wood cutting saw, which sawdust is in the form f chunks having projecting ends, corners and edges.

6. A vehicle tire including an anti-skid rubber tread surface comprising approximately 20% to 30% by weight of irregularly shaped chunks of hard cellular material and approximately 80% to 70% by weight, respectively, of cured rubber in the form' of a matrix, said chunks being uniformly and intimately dispersed throughout said rubber matrix, said chunks consisting substantially of a screen size between a. No. 6 standard mesh screen as a maximum and a No. 16 standard mesh screen as a minimum and being substantialy of the conguration of sawdust produced by a No. wood cutting saw, which sawdust is in the form of chunks having projecting ends, corners and edges.

l 7. A vehicle tire including an anti-skid rubber tread composition having particles of hard material interspersed therein of such size that all willpass through'a No. 6 standard mesh screen and a substantial portion will be retained by a No. 16 standard mesh screen, and being of the configuration of irregularly shaped, substantially block-like chunks having projecting ends, corners and edges similar to sawdust produced by a No. 10 Wood cutting saw.

8. A rubber composition having particles of hard, ligneous material interspersed therein of such size that all will pass through a No. 6 standard mesh screen and most will be retained by a No. 16 standard mesh screen, Yand being of the conguration of irregularly shaped, block-like chunks having projecting ends. corners and edges similar to sawdust produced by a No. 10 wood cutting saw.

CLARENCE A. GAPEN. LONNIE GAPEN.

REFERENCES CITED The following references are of record in the ille of this patent:Y

UNITED STATES PATENTS Number Name Date 1 647,112 Pearson Apr. 10, 1900 2,056,558 Beldam Oct. 6, 1936 `2,274,855 Wallace Mar. 3, 1942 FOREIGN PATENTS Number Country Date 368,411 Great Britain Mar. 10, 1932 472,118 Great Britain Sept. 13, 1937 '184,938 France July 29, 1935

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