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1971 both assigned to the assignee of this application. BACKGROUND OF THE INVENTION Elastic oversho

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OVERSHOES ELASTIC

CROSS REFERENCES TO RELATED APPLICATIONS

The materials used in the practice of this invention are the subject of applications for patent of James Sidles and Raymond C. Srail, Ser. No. 189,026 filed Oct. 13, 1971 and of Gary A. Harpell, Ser. No. 191,118 filed Oct. 20, 1971 both assigned to the assignee of this application.

BACKGROUND OF THE INVENTION

Elastic overshoes which are put on by stretching over the user's street shoes, and which therefore require no fasteners, have been made in two principal constructions. In one construction, these "rubbers" are built on lasts, of an exact size and shape to fit a particular style and size of shoe, and generally with some fabric reinforcement, especially in the sole portion. If fabric is used in the uppers, it has of necessity been a stretchable fabric, such as stockinet. The other construction is a simple molded all-rubber article containing no fabric, often made in small, medium, and large sizes only, so that considerable stretching may be needed to pull it over a shoe not quite large enough to require the next larger size.

The fabric reinforced rubbers will not stretch enough to conform to sizes and shapes other than those of the particular shoes they are made to fit, so they are often purchased too loose, and then shift in position during walking, or even drop off. The all-rubber articles are subject to tearing, and if highly stretched may be uncomfortable to wear.

SUMMARY OF THE INVENTION

We have found that rubber overshoes can be made of a particular kind of elastomeric material which can be reshaped while hot, and which will retain the new size and shape as long as the material is not reheated.

This permits overshoes to be molded in a single size and shape to permit use on a wide range of sizes and styles of shoes. For example, men's rubbers may be molded in a single size and shape, slightly smaller than the smallest normal men's size, and in a neutral shape which is neither a right nor left shape. The user will then heat a pair of these rubbers, quickly pull them over his street shoes, and when cool, they will be the exact size and shape to fit snugly without excessive tension.

THE DRAWINGS

In the accompanying drawings, FIG. 1 shows an overshoe made according to this invention in a small size and neutral shape.

FIG. 2 shoes the same overshoe compressed for storage and shipment.

FIG. 3 shows the same overshoe resized and shaped to fit a particular size and style of men's shoe for the right foot.

DETAILED DESCRIPTION

The material from which the overshoes of this invention are made is one consisting of minute domains of two different polymeric substances, one of which is a vulcanized elastomer, and the other of which is essentially inextensible at room temperature but is either elastomeric or plastic at a higher temperature, and is bonded to the vulcanized elastomer. There are two principal ways in which such a material can be prepared.

One way is to add vulcanizing agents and such pigments and other additives as may be desired to natural rubber, or to any of the vulcanizable synthetic rubbers which are highly elastic at ordinary outdoor temperatures, and also to mix in a substantial quantity of a material which is thermoelastic or thermoplastic, and which will bond to the rubber during vulcanization. For example, trans 1,4 polybutadiene can be described as thermoelastic, since it is a diene polymer which is crystalline and essentially inextensible at room temperature, but is highly extensible at about 200° F, so that it will form a firm bond to the rubber during vulcanization and can be shaped while hot. This mixture is then vulcanized in the desired shape.

The other way to prepare such a material is to make a block copolymer with a central block of thermoplastic and terminal blocks of vulcanizable elastomer. The central block may be polystyrene of molecular weight about 40,000 to as high as 400,000, and the terminal blocks may be elastomeric polybutadiene or polyisoprene of molecular weight about 8,000 to 100,000 or more. Other combinations of synthetic polymers having similar physical properties can be prepared. Vulcanizing agents are added, with or without added vulcanizable elastomer, depending on the proportions of the ingredients in the block copolymer and on the properties which are desired in the finished product, and the material is vulcanized in the desired shape. In all cases the total quantity of elastomer should be at least half of the volume of the material.

In a preferred embodiment of this invention, 100 parts by weight of natural rubber are mixed with 40 parts carbon black, eight parts zinc oxide, one part stearic acid, 0.5 parts sulfur, two parts dithiodimorpholine, 1.25 parts benzothiazyl disulfide, and if desired, small quantities of softener and antioxidant. To this composition is then added one-third of its weight of trans 1,4 polybutadiene, and the mixture is thoroughly blended.

The foregoing mixture is molded and vulcanized in a mold having a cavity the approximate size and shape of the smallest normal men's size of rubbers, except that it is symmetrical rather than right or left shoe shape. The molded rubber shown in FIG. 1 has a sole portion 10 and an upper portion 11, which may have a small bead 12 for reinforcement of the edge. The outside of the sole 10 is preferably somewhat arched under the instep 13, and in addition is made somewhat thinner than the remainder of the sole, so that longitudinal stretching will occur to a greater extent at the instep than elsewhere. The sole under the toe and ball of the foot 14, and also under the heel 15, is formed with a pattern of protuberances or ribs as is usual, to minimize slipping. Preferably, the tread pattern of the sole and heel is extended slightly around the edges so that the pattern will still extend completely across the sole and heel surfaces even after substantial stretching.

One of the molded and vulcanized overshoes is heated to 200° F, dropped into a cold cylindrical plunger mold and quickly compressed under high pressure. Because of the thermoelasticity of the material, the product takes and retains the exact shape, as long as it is kept cool. After cooling in the mold, the overshoe is a dense cylindrical disc 16, as shown in FIG. 2. A pair of these compressed overshoes is then packaged for shipment and sale in a small, conveniently shaped container.

The user removes the discs 16 from the package and reheats them to a temperature of about 200° F, which may be done in boiling water, but preferably in an oven so as to avoid spillage of hot water. As the overshoes heat up, they spontaneously revert to the vulcanized shape shown in FIG. 1, unfolding progressively as the heat penetrates. The user then grasps one of the hot overshoes and quickly slips it over his street shoe, then places the other overshoe over his other street shoe, and allows them to cool to room temperature, which will occur very quickly. Thus, the reshaped overshoe, as shown in FIG. 3, will conform to the size and shape of the shoe, including unsymmetrical distension of the toe portion 17 to fit over the great toe location of the street shoe.

The overshoes can be left on the street shoes as long as may be desired, and will fit snugly without excessive pressure. They may be pulled off whenever they are not needed, as they retain sufficient elasticity for that purpose. They will then be the exactly proper size and shape to be put on the shoes on which they were shaped, or on others of the same size and shape. If the user should wear other shoes of a different style, requiring a different shape, the overshoes are reheated in the oven and reshaped to fit the other shoes.

Although a single style of rubbers is shown, others, designed to fit men's, women's, or children's shoes of various kinds with varying heights of heels, or with or without heel covering, or with varying heights of uppers, can be made in accordance with this invention.

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