US3075306A - Overshoe heel - Google Patents

Description

Jan. 29, 1963 F. R. LAPo-RTE 3,075,306

` ovERsHoE HEEL Original Filed Aug. 14, 1959 IN V EN TOR. FERAAA/ l?. A100/97E ATTORNEY United States Patent @hure 3,075,395 Patented Jan. 29, 19E3k August 14, 1959.

The widespread adoption of the spike or French -heel lon womens footwear has been a source of trouble to the. manufacturer of womens oyershoes. vThis heelis characterized by the fact that its cross-sectional area becomes narrower andnarrower from the top of the heel to the base. For example, the -heel shank may taper downwardly so that its lbottom surface or tip may be only one quarter of an inch across. Thus, during walking, the entire weight of a woman would be supported by this very small surface; When overshoes are placedover a shoe having a French heel, extremely high stresses are exerted on the overshoe heel portion, and considerable v wear results Where the heel contacts the overshoe. In fact, the French heel is so narrow that it acts as a spike andpunches `a hole in the overshoe heel base.

Punching is not the only problem caused by wearing a French heel. Cracking or rupturing along the lower sidewalls of the overshoe-also occurs. This cracking is due in part to the excessive stresses placed on the overshoe by the French heel, and in part to shock-the suddenness with which such stresses are applied. It is a common fact that more wear occurs at a surface which is subjected to a repeated, sharp stress than at a surface to which the stress is applied gently.

Attempts to overcome such problems have only been partially successful. In a patent granted October 14, 1930, No. 1,778,592, a flat plate having turned edges is inserted in the heel of a ladies overshoe to overcome the wear problems associated with the French heels. Other patentees have proposed more elaborate wearplates hav-ing vertical side surfaces as well as a bottom surface. As shown in Patent No. 1,119,277, granted December 1, 1914 and `Patent No. 2,108,572, granted February 15, 1938 such wearplates are inserted into the hollow heel portion of the overshoe.

It has been found that the heel of the overshoe still wears through when the yaforementioned wear plate attachments are inserted into the heel. Friction, and wear which necessarily accompanies the friction, remains between the inner side of the overshoe and the surface of the attachment in contact therewith. Further, the attachment can easily be kicked from its proper position.

Since the overshoe is not a rigid body, there is always some latitude in fitting the attachment to the heel. I-f the overshoe fits too snugly about the attachment, excessive stress develops along the overshoe surface that grips the attachment, eventually-* causing a wearing through or a cracking of the overshoe wall.

Also, these attachments do not provide by themselves a cushioning effect. Each step taken produces a sharp, concentrated pressure that pis transmitted through the wearplate to the overshoe surface. Recognizing this problem, cushioning pads have been employed in the past, as shown in the aforementioned Patent No. 2,108,- 572. However such pads wear out rapidly and do not readily remain in a fixed position.

surface to the heel. The French heel'could not remain in one position during walking with respect to the overshoe heel since it is much narrower than the overshoe heel and slides over the Wearplates. This sliding action tends to move the Wearplates, increasing the friction between the inner side of the overshoe and the wearplate surface in contact therewith.

One object of this invention is to provide an overshoe heel that will4 not be punctured or ruptured when used with shoes. having narrow heels.

Another object of this invention is to provide a reinforced overshoe heel having an integral reinforcing lining ofV relatively high wear resistant material as compared with .the material of the overshoe.

4. -Av further ob'jec't of this invention is to provide a reinforced overshoe heel havingv an inner layer. that will vkeep a narrow heel in a iixed position `andwilltend to eliminate heel slipping. v l Y I A still further object of this invention is to provide an innerreinforcing layer .in an overshoe heel 'that will cushion the pressures that are lapplied to the overshoe heelduring walking. y

' In order toprovide' an overshoe having a reinforced 4`heel base and sidewalls, the preferred embodiment of this invention contemplates a liningrof relatively high abrasive material molecularly bonded to the inner sur face of the heel base and sidewalls; the layer will eX- tend across the base of the heel and up along the side- Iwalls thereof. An integral heel will thus be formed which eliminates the vatlorementioned problems associated with loose attachments.

Another object of this invention is to provide a method for making the reinforced heel.

To accomplish this latter objective, during the production of the shoe, a quantity of viscous liquid plast-ic material is poured into the heel of the shoe to the height desired of the sidewall layer and heat is applied to the plastic material. A suction tube is then inserted into this body of plastic and the central portion or core portion is sucked up. The sidewalls remain because the heat has gelled the layer of plastic adjacent the walls ofthe shoe.

The above and other features of thev instant invention will be further understood from the following de.- scription when read in conjunction with the accompanying drawing, wherein:

FIG. 1 is a sectional view of the heel showing the reinforcing lining molded or bonded to the inner overshoe surface;

FIG. 2 is a sectional view of the overshoe heel and shows the heel filled with a quantity of highly viscous liquid plastic and also shows the suction tube being placed in the liquid; v

FIG. 3 shows the suction tube positioned in the tube and illustrates the viscous plastic being drawn up; and

FIG. 4 shows the formation of the viscous plastic in the heel just after the suction tube is removed and illustrates the application of heat to the heel and the gelled plastic reinforcing unit.

An article of rubber-like footwear 10 is shown in FIG. 1 having a heel 11 and Walls 12. This article can be an overshoe or gaiter having plastic walls formed by conventional slush molding methods. The plastic material used to produce such slush molded footwear is preferably a vinyl plastisol prepared by -dispersing finely divided poly.- vinyl resin powder in a liquid plasticizer. The reinforce ing heel unit 13 is also a plastisol but is compounded so as to be more resistant to wear than the plastic overshoe walls 12..

The reinforcing heel unit 13 has the .same shape as the inner heel wall and is therefore adapted to receive the heel of a shoe. The preferred embodiment is described with reference to womens footwear and therefore the shank of heel 11 is relatively long. The heel unit 13 lplied to the viscous plastic to some extent.

comprises a bottom layer 14 and sidewalls or upright layers 15', oined together. This unit is molecularly bonded or fused at bonding surface 17 to the inner sur- 'fc-.ce of the overshoe wall to provide an integral reinforcing heei unit. That is, because of heat treatment, the plastic overshoe Walls and reinforcing layers coalesce to form an integral mass of single phase plastic material. in etfect, there is no bonding surface 17 as that surface becomes 'part of a continuous medium.

The reinforcing heel unit thus described is not a rigid body and tends to be shock absorbing. Further the top or open surface of this unit which is in contact with the womans shoe heel presents a high friction surface as opposed to metal, or the synthetics such as nylon.

The particular thickness of each layer and the height of the sidewalls can be varied as desired. The following dimensions have been employed in the preferred embodiment and are given here by way of example: the base thickness 18 may be .200 to .250 of an inch; the sidewall height 19 from the inside of the wall base may be .625 of an inch; the thickness 20 of the sidewall 15 may be .G50-.070 of an inch.

A description of the method of making a reinforced heel unit in a plastic overshoe is given hereinbelow. lt is well known to those skilled in the art to make rubberlike or plastic footwear by slush molding. In carrying out this method, a hollow mold is used which has an interi'or surface that defines the exterior contours of the footwear. Liquid plastic material -is then poured into .the 'mold to a predetermined depth. Heat may be applied to "thenold either before or immediately after the plastic material enters the mold.

The plastic material used herein has the physical characteristics of a heavy, viscous cream like consistency in its uncured state. This plastic material is cured by the application of heat as the application of heat changes the viscous liquid into an elastic-like material. Since the duration of the heat controls the amount of elastic-like material that is formed, the heating can be controlled over certain preselected areas when a particular thickness is desired. As heretofore stated, the piastic material used to produce such slush molded footwear is preferably a vinyl plastisol, prepared by dispersing finely divided polyvinyl resin powder in a liquid plasticizer therefor to form a creamy liquid. The slush molding technique and the preparation of plastisols are further discussed in Patent No. 2,880,467, granted April 7, 1959.

In making an overshoe by slush molding, a metal mold is filled to the desired height by the liquid plastic. Heat is applied to the met-al mold 21a to cause the plastic material that contacts the metal wall to adhere thereto. This adheringr plastic, or layer is only a gelled film since the plastic is not completely cured. When the thickness of this iilrn is sufficient, the rest of the liquid plastic is poured from the mold. The overshoe is entirely fused while still in the mold.

The plastic is fused by the further applic-ation of heat. Fusion takes place when the temperature is raised above the softening point of the resin, at which temperature the solvent action of the plasticizer is increased to cause the resin and plasticizer to form a tough homogeneous resinous mass in which the powdered resin and the liquid pl-asticizer have coalesced to form a single phase.

The method of this invention contemplates pouring a quantity of viscous plastic into the heel cavity of the overshoe before the plastic is finally cured or fused. As .shown in FIG. 2, the heel is filled with viscous plastic 2t? to the desired sidewall height. The overshoe remains in the mold that has already been heated, so heat is ap- That is, the heat that has been applied to the mold to gel the over- Lshoe wall remains stored in the mold, meaning simply .that .the mold does not cool instantaneously. The heat retained or stored in the mold is called the latent heat of the mold. lt has been found that the gelling of plastic material 2? is caused by the latent heat, just as soon as it is poured into the heated surface. lf desired, some additional heat may be applied to add to or control the heat applied to the plastic material. If no additional heat is applied, the thickness of the gelled sidewalls and base layer will be proportional to the amount of latent heat in the mold and the time the plastic material 20 is left in the mold. Plastic material 2? is a plastisol compound mixed with a plasticizer and in its cured form is more wear resistant than the plastic material of the overshoe t?. the former having a durometer hardness of 85, the latter, of 70. It has been found that the plastic material of the overshoe should contain from 60 to 80 parts plastici-.zer while plastic material 20 should contain 35 to 40 parts plasticizer. If the plasticizer content of plastic material 2.0 falls below 35, the processing becomes ex.- tremely difiicult; if it is above 40, the abrasion and stiffness characteristics of the reinforcing heel unit is adversely affected. An example of a satisfactory compound -is here given:

Renforcing Heel Unit Compound Mixing time: 30 minutes.

Since the viscosity of low plasticizer content plastisol is higher than is allowable for the satisfactory operation of the hereindisclosed process, the viscosity being approximately between 10,000 to 20,000 centipoises, a viscosity depressing agent must be added to the compound to reduce the viscosity. That is, the viscosity of the cornpound after the depressing agent has been added must be between 2000 to 4000 centipoises. lt has been found that several types of viscosity depressing agents will do a satisfactory job; however, Sotex CW has proved to be more effective. It has also been found that a satisfactory plastisol (polyvinyl chloride resin) may be made of 70 parts Geon 121 and 30 parts Geon 202. Further the cadmium organic compound used as a stabilizer may be a cadmium ricinoleate `or laurate. it should also be noted that the hardness and the viscosity of the heel compound may be varied by performing steps, adding other compounds and substances according to the practices well known in the art.

The names and addresses of the manufacturers of the components of the heel compound are here listed:

P-363-8 Plasticizer:

Canadian Resins & Chemicals Ltd., 600 Dorchester St. W., Montreal 2, Canada.

Santicizer Monsanto Chemical Co., soo N. 12th Blvd., St. Louis 1, Mo.

Drapex 3.2:

.Argus Chemical Corp., 633 Court St., Brooklyn 31, New York.

tabilizer JCX:

Advmce Solvents & Chemical Corp., 245` Fifth Ave., New York r16, N.Y.

Sotex CW:

Synthetic Chemicals Inc.,

335 McLean Blvd.,

Paterson 4, New Jersey. Calchem Yellow:

Caledonia Co. Ltd.,

751 Victoria Square Montreal, Quebec, Canada. Polyvinyl Chloride Resin (Geon 202 and 121):

B. F. Goodrich Chemical Co.,

3135 Euclid Ave.,

Cleveland 15, Ohio.

After lling the heel cavity with plastic material, a suction tube 21 having positioning probes 22 is inserted into the center of the quantity of plastic to a depth such that the bottom of the probes touch the bottom of the heel base and rest on the mold itself. The correct position is illustrated in FIG. 3. The length of the probes determine the thickness 18 of bottom layer 14. Of course, other means of positioning the suction tube will occur to those skilled in the art.

A suction unit 23 is coupled to the suction tube at its opposite end and begins to suck or draw up the viscous plastic after the suction tube is properly positioned. The core portion of the plastic-the quantity immediately around the suction tube is drawn ol first since the gelled layer of plastic adhering to the sidewalls of the overshoe remains. When the liquid level reaches the level of the bottom of the suction tube, as at 26, suction ceases. Thus the suction tube acts much like a straw in water; when the water level is below the bottom of the straw, water ceases to move up the straw.

When suction ceases, the suction tube is removed, addi- -tional heat may be applied as shown in FIG. 4 to x sidewall layer 24 and bottom layer 27, in position. After layers 24 and 27 are fixed suiciently, the mold containing the overshoe is removed from heating unit 28 and again enters the normal curing station Where heat is applied to the entire mold containing the overshoe to cure the plastic of the overshoe wall 12 as Well as layers 24 and 27. Further, layers 24 and 27 become fused or molecularly bonded to the overshoe wall during this curing step. However, the step of applying heat by the external heating unit 28 may be eliminated and complete fusion may be obtained in the iinal curing step by having suicient heat in the curing oven.

While a preferred embodiment of the reinforced overshoe heel, and a method for making same has been disclosed, it is not intended that the invention be limited to such embodiment as many changes may occur to those skilled in the vart without departing from the essence of the invention.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

An overshoe for high heel shoes comprising a plastisol heel, a plastisol reinforcing insert having a base and sidewall layers shaped and conformed to the inner surface of said plastisol heel, said layers and said inner surface being in direct contact and having a molecular -bond consisting solely of fused plastisol of said layers and said plastisol heel to present an entirely plastisol heel structure, the surface of said layers being non-slippery and being more wear-resistant than the plastisol of said heel, the durometer hardness of said plastisol insert being higher than the durometer hardness of the heel of the overshoe.

References Cited in the file of this patent UNITED STATES PATENTS 920,676 Smith May 4, 1909 1,803,559 Riley May 5, 1931 1,971,456 Manville Aug. 28, 1934 2,108,572 Wilkinson Feb. 15, 1938 2,142,981 Richards Ian. 3, 1939 2,281,321 Olson et al. Apr. 28, 1942 2,880,467 Wibbens Apr. 7, 1959 2,946,139 Slade July 26, 1960 2,966,749 Loewengart et al. Jan. 3, 1961

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