US3071817A

US3071817A - Overshoe heel

Info

Publication number: US3071817A
Application number: US833828A
Authority: US
Inventors: Fernand R Laporte
Original assignee: United States Rubber Co
Current assignee: Uniroyal Inc
Priority date: 1959-08-14
Filing date: 1959-08-14
Publication date: 1963-01-08
Anticipated expiration: 1980-01-08
Also published as: FR1263633A; DK100092C; CH395793A; GB903374A

Description

Jan. 8, 1963 F. R. LAPORTE 3,071,817

' OVERSHOE HEEL Filed Aug. 14. 1959 INVENTOR. fE/MMfl A. 14/ 0/275 ATTORNEY weight of a woman would be supported small surface.

astral? l atented Jan. 8, 1.963

" Flee 3,071,817 OVERSHOE HEEL Fernand R. Laporte, St. Jerome, Quebec, Canada, asslgnor to United States Rubber Company, New York, N.Y., a corporation of New Jersey Filed Aug. 14, 1959, Ser. No. 833,828 2 Claims. (Cl. 18-58) This invention relates to an overshoe having a reinforced inner heel base and to a method for making such a heel base.

The widespread adoption of the spike or French heel on womens footwear has been a source of trouble to the manufacturer of womens overshoes. This heel is charracterized by the fact that its cross-sectional area becomes narrower and narrower from the top of the heel to the base. For example, the heel shank may taper downwardly so that its bottom surface or tip may be only one quarter of an inch across. Thus, during walking, the entire by this very When overshoes are placed over a shoe having a French heel, extremely high stresses are exerted on the overshoe heel portion, and considerable wear results where the heel contacts the overshoe. In fact, the French heel is so narrow that it acts as a spike and punches 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 shockthe 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 stressis 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 having 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 wearpl ates are inserted into the hollow heel portion of r the overshoe.

It has been found that the heel of the overshoe still wears through when the aforementioned wear plate attachments are inserted into the heel. Friction, and wear which necessarily accompanies the friction, remains be tween 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. If the overshoe fits too snugly about the attachment, excessive sress 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 is transmit-ted 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.

In addition, wearplates generally present a slippery surface to the heel. The French heel could not remain in one position durink walking with respect to the overshoe heel since it is much narrower than the overshoe heel and slides over the wear-plates. 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 a method for making an overshoe heel that will not be punctured or ruptured when used with shoes having narrow heels.

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

A further object of this invention is to provide a method for making a reinforced overshoe heel having an inner layer that will keep a narrow heel in a fixed position and will tend to eliminate heel slipping.

A still further object of this invention is to provide a method for making an inner reinforcing layer in an overheel that will cushion the pressures that are applied to I the overshoe heel during walking.

In order to provide an overshoe having a reinforced heel base and sidewalls, this invention contemplates a lining of relatively high abrasive material molecularly bonded to the inner surface of the heel base and sidewalls; the layer will extend across the base of the heel and up along the sidewalls thereof. An integral heel will thus be formed which eliminates the aforementioned problems associated with loose attachments.

To accomplish these objectives, during the production of the shoe, a quantity of viscous liquid plastic 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 of the shoe.

The above and other features of the instant invention will be further understood from the following description 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;

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 illus trates 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 have 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 polyvinyl resin powder in a liquid plasticizer. The reinforcing 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 comprises a bottom layer 14 and sidewalls or upright layers 15, joined together. This unit is molecularly bonded or fused at bonding surface 17 to the inner surface of the overshoe wall to provide an integral reinforcing heel 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 effect, 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 050-070 of an inch.

A description of the method of making a reinforced heel unit in a plastic overshoe is given hereinbelow. It 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 interior 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 the mold 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 which 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 plastic 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 for a creamy liquid. The slush molding technique and the preparation of plastisols is further discussed in Patent No. 2,880,467 to V. l. Wibbens granted April 7, 1959.

in making an overshoe by slush molding, a metal mold Zia is filled to the desired height by the liquid plastic. Heat is applied to the metal mold 21a to cause the plastic material that contacts the metal wall to adhere thereto. The adhering plastic layer is only a gelled film since the plastic is not completely cured. When the thickness of this film is sufficient, the rest of the liquid plastic is poured from the mold and the overshoe is entirely fused thereafter while still in the mold by the further application 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 plasticizer 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 inFIG. 2, the heel is filled with viscous plastic 20 to the desired sidewall height. The overshoe remains in the mold that has already been heated, so heat is applied to the viscous plastic to some extent. That is, the heat that has been applied to the mold to gel the overshoe 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. It has been found that the gelling of plastic material 20 is caused by such latent heat, just as soon as it is poured into the mold. If 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 d to the amount of latent heat in the mold and the time the plastic material 20 is left in the mold.

Plastic material 20 is a plastisol of resin and plasticizer and in its cured form is more wear resistant than the plastic material of the overshoe 12 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 parts plasticizer for parts resin while plastic material 20 should contain 35 to 40 parts plasticizer for 100 parts resin. If the plasticizer content of plastic material 20 falls below 35 parts, the processing becomes extremely diificult; if it is above 40 parts, the abrasion and stiffness characteristics of the reinforcing heel unit is adversely affected. Therefore, as used herein, the term a harder reinforcing plastisol means the plastisol used to form the heel unit 20 which is more wear-resistant than the plastic material of the overshoe and contains from 35 to 40 parts plasticizer for 100 parts resin. An example of a satisfactory compound is here given:

Reinforcing H eel Unit Compound Batch 52 2 5 Ingredients Base Lbs. ozs.

10.00 30 00 P-3038 (60 percent DiOctyl RhthalageAO percent Di-Octyl dipate 19.00 57 0o swimmer (Butyl Phcnyl mas/um Phthalatc). 11.00 33 00 Drapcx3f2 0ctylEpoxyStcarate). 3.00 9 00 Stabilizer .TCX (cadmium organic compound). 2.00 6 O0 Viscosity Depressing Agent-Sotex V. 100.00 300 Polyvinyl Chloride Resin 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 compound after the depressing agent has been added must be between 2000 to 4000 centipoises. It 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 Goon 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:

84 Chemical Corp.

Sotex CW: I

Synthetic Chemicals Inc.

335 McLean Blvd.

Paterson 4, NJ. 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 filling the heel cavity with plastic material, a suction tube 21 having positioning probes 22 is inserted into the center of the quantity of plastic and adjusted to a depth such that the bottom of the probes touch the bottom of the heel base and rest on the upper surface of the mold heel cavity. 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 plasticthe quantity immediately around the suction tube is drawn otf 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, and additional heat may be applied as shown in FIG. 4 to fix sidewall layer 24 and bottom layer 27, in position. After

layers

24 and 27 are fixed suificiently, 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 final curing step by having sutficient 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 art without departing from the essence of the invention.

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

1. A method of forming a plastic overshoe having a heel portion separately walled from the sole portion comprising the steps of pouring a quantity of plastisol into an overshoe mold, applying heat to the mold to gel a layer of plastisol adhering to the inner wall of said mold, removing the remaining liquid plastisol from the mold, pouring a predetermined amount of plastisol solely into said heel portion while allowing the walls of said heel portion to serve as a mold While the plastic of the overshoe is gelled but before it is cured, applying a specific degree of heat for a specific duration to gel the plastisol adjacent the base and sidewalls of said heel portion, removing the remaining liquid plastisol leaving only the base and sidewall layers thereof, and then curing the entire overshoe, whereby the overshoe plastic and the base and sidewall layers of plastic in said heel portion fuse forming a reinforcing heel base.

2. The method of claim 1 wherein the last-mentioned liquid plastisol is removed from the heel portion by suction.

References Cited in the file of this patent UNITED STATES PATENTS 1,536,866 Kamborian May 5, 1925 1,630,762 Randall May 31, 1927 1,896,123 Schweitzer Feb. 7, 1933 2,142,981 Richard Jan. 3, 1939 2,237,835 LHollier et al. Apr. 8, 1941 2,535,123 Demick Dec. 26, 1950 2,880,467 Wibbens Apr. 7, 1959 2,915,788 Engel Dec. 8, 1959 2,923,029 Harris et a1. Feb. 2, 1960

Claims

1. A METHOD OF FORMING A PLASTIC OVERSHOE HAVING A HEEL PORTION SEPARATELY WALLED FROM THE SOLE PORTION COMPRISING THE STEPS OF POURING A QUANTITY OF PLASTISOL INTO AN OVERSHOE MOLD, APPLYING HEAT TO THE MOLD TO GEL A LAYER OF PLASTISOL ADHERING TO THE INNER WALL OF SAID MOLD, REMOVING THE REMAINING LIQUID PLASTISOL FROM THE MOLD, POURING A PREDETERMINED AMOUNT OF PLASTISOL SOLELY INTO SAID HEEL PORTION WHILE ALLOWING THE WALLS OF SAID HEEL PORTION TO SERVE AS A MOLD WHILE THE PLASTIC OF THE OVER-