US2918703A - Method of producing hollow plastic heels - Google Patents

Description

Dec. 29, 1959 c. L. BEAL METHOD OF PRODUCING HOLLOW PLASTIC HEELS Original Filed Jan. 51, 1957 E N R o "u A United States Patent METHOD OF PRODUCING HOLLOW PLASTIC HEELS Carl L. Beal, Huntington, NY.

Original application January 31, 1957, Serial No. 637,463.

Divided and this application December 30, 1957, Serial No. 706,047

3 Claims. (Cl. 18-58.3)

This invention relates to hollow plastic heels for ladies shoes and especially to a novel construction of such hollow heels, and to the manufacture of such hollow heels from plastic materials, including tall slim high hollow plastic heels for ladies dress shoes, as well as lower types of heels.

One of the requirements of a high quality ladys shoe is that the shoe maintain the trim appearance of a new shoe throughout its useful life. To maintain such an appearance, the heel must show no looseness or pulling away from the area of the shoe bottom to which the heel is attached, and, above all, the complete disengagement of the heel from the shoe under the most severe condition of stress must be prevented. The most destructive stresses imposed on the joinder of the heel to the shoe are lateral stresses which tend, and often do, wrench the heel from the shoe. These stresses are intensified at the heel joinder where ladies shoes are equipped with hollow high heels by reason of the action of the relatively long lever arm which is approximately equal to the height of the heel.

An object of this invention is to provide a novel and highly serviceable hollow plastic heel for ladies shoes that can be attached to a shoe proper by means normally employed in the manufacture of shoes, as by screws or nails or other known fastening means, and meet the severe service requirements above indicated as essential to a high quality shoe.

Another object of this invention is to provide a lightweight hollow and tall slim high plastic heel which will give greater comfort to the wearer and a better balance to the shoe.

Still another object of this invention is to provide a lightweight hollow plastic heel having a space therewithin entirely enclosed by an integral wall structure.

A further object of this invention is to provide a hollow plastic heel having embedded in its upper shoecontacting wall a fastening retaining insert.

Another further object of this invention is to provide a hollow plastic heel having its upper shoe-contacting wall member made, at least in the portion into which the fastening means penetrate, of a less brittle and tougher plastic than that of the remainder of the heel.

A still further object of this invention is to provide a novel and economical method of manufacturing the tall slim high hollow plastic heel with an integral wall structure defining the hollow space and a nail and screw retaining insert integrally cast within the shoe-contacting wall member of the plastic heel.

Other objects will be apparent from the ,following specification and the accompanying drawing, although it is to be understood that changes variations and modifications are to be included within the scope of this invention as herein described and claimed.

Fig. 1 is a cross-sectional view of one form of a mold and of one embodiment of the slim high plastic heel within the mold, the heel being shown completed and ready to be removed from the mold,

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' fied form of attachment insert and the manner in which the heel is attached to a shoe;

Fig. 3 is a view of the heel portion of the shoe taken on line 3-3 of Fig. 2, showing the position of the attaching screw and nails fastening the plastic heel to the shoe;

Fig. 4 is a cross-sectional view of an embodiment of the invention showing still another form of attachment insert;

Fig. 5 is a cross-sectional view on line 55 of Fig. 4;

Fig. 6 is a cross-sectional view on line 66 of Fig. 4;

Fig. 7 is a cross-sectional view on line 7--7 of Fig. 4; and

Figs. 8 and 9 are each a cross-sectional view, similar to Fig. 4, of a modified form of the invention, showing heels of lower heights.

It is here noted that similar cross-sectional views of the embodiments of Figs. 1 and 2 to those shown in Figs. 4, 5, -6 and 7 would vary from the cross-sections of the latter views only in the showing of the nature of the fastening insert.

Referring to the drawing, in all figures of which the same reference numeral indicates the same element, the hollow plastic heel 10 has an integral wall. structure 11 completely enclosing the hollow space 12, a lower groundcontacting portion 13, an upper concave shoe-contacting wall portion 14, a rear and side arcuate wall portion 15, and a front or forward instep wall portion 16. The wall portion 14 contains a fastening insert 17 and a hole 18, left in the upper wall 14 and in the insert. 17 upon removal of the pin on which is mounted fastening insert 17 during the casting of the heel 10, as will be more fully hereinafterdescribed. The plastic of the finished heel 10 is a tough, rigid, resilient plastic of medium hardness and may be manufactured by any suitable process, although the process hereinbelow described seems at present to be preferable.

In Fig. l, the heel 10 is shown within a mold 20 and is illustrated with the finished heel 10 in the mold 20, before the opening of the mold and the removal of the heel 10.

The mold 20 is preferably made of a good heat-conductingtmaterial, such as a metal, and as shown is a twosection mold, and, although the mold 20 may be made in a larger number of sections and of a wide variety of materials, a two-section metal mold is preferred. The mold 20 consists of a one-piece lower mold section 21, having its inner wall surfaces 22 of a size and shape to form the lower ground portion 13, rear and side arcuate wall 15 and forward instep wall 16 of the heel 10, and also having an open top 23 into which fits the cover section 24 to close tightly the two-section mold 20'. The inner surface 25 of the cover section 24 is preferably convex so that the upper surface of the wall portion 14 of the heel 10 may conform to the bottom portion of the shoe to which the heel 10 is to be attached. The cover section 24 has a pin 26 secured centrally thereof so as to support in proper position the insert 17 during the manufacture of the heel 10. The two mold sections 21 and 24 may be locked together by any suitable means, as by bolts 27 passing through registering openings 28 in flanges 29 of the mold sections 21 and 24.

The heel 10 is preferably made in the mold 20 by what is sometimes called gyrational casting from a suitable flowable plastic composition capable of being distributed more or less uniformly over the entire inner 3. tion and the heating may be carried out simultaneously, or the mold 20 may be first gyrated to distribute the freely flowable plastic composition within the mold and then heat applied to the outer surfaces of mold 20 while continuing the gyration of the 'mold 20.

A number of freely flowable plastic compositions are suitable as a starting material for producing heels of this application and are not per se a part of the invention of this application, since suitable plastic compositions may be purchased from a number of manufacturers and distributors of plastic compositions. These compositions may be liquids of sufiiciently low viscosity to flow freely at room temperature or they may be materials of higherviscosity that will flow freely under the temperature conditions existing in the mold in the early part of the heating cycle. Any plastic composition that will distribute itself uniformly over the entire inner surface of the mold during the gyrating and heating cycle and will react to produce an article of satisfactory physical properties can be considered as a starting material for this process.

A type of freely flowable composition, sometimes generically called a rigisol, may be used. This may consist of a dispersion of finely divided particles of polyvinyl chloride resin in a liquid mixture of a plasticizer and a liquid dispersant capable of being converted into a rigid plastic by heating, such as a polymerizable rnono-' mer. When such a composition is heated in the gyrating mold, the material is distributed over the entire inner surface of the mold, is gelled in that position, and the composition rapidly becomes a medium-hard, resilient plastic heel, with a hollow space inside. By way of illustration, a flowable 'plastic composition, or rigisol, of the following composition may be The constituents of the above formula are thoroughly intermixed by stirring and/or grinding. The resulting composition isa flowable plastic liquid composition of low viscosity capable of being converted into a rigid plastic by heating.

2 The high molecular weight dispersion-type polyvinyl chlorides, which have been found satisfactory in carry-- ing out the invention of this application, are finely divided or minute particle sized resins, such as are pro-- duced by the polymerization of vinyl chloride in aqueous emulsion, the particle size normally ranging from 0.1 to 10.0 microns. Thus, a high molecular weight polyvinyl chloride resin, marketed by B. F. Goodrich Chemical Company as Geon Vinyl Resin 121, a dispersion-type resin having a particle size ranging between 0.1 and 1.3 microns or, a dispersion-type high molecular Weight polyvinyl resin marketed by Naugatuck Chemical Company as Marvinol Vinyl Resin VR-10, having an average particle size of about 6.2 microns. It may be preferable, however, to use a mixture of two or more dispersion-type polyvinyl resins in varying proportions, since a mixture of the particle sizes of the different dispersiontype resins gives a lower viscosity composition. In practice, equal parts of Geon Vinyl Resin 121 and of Marvinol Vinyl Resin VR-lO have given satisfactory results. It is to be understood that other makes of the dispersiontype high molecular weight polyvinyl resins also may beemployed, such as Bakelite QYNV, Exon 654, Marvinol VR50, and the like. i

The liquid dispersant is one capable of being hardened by heat and/ or chemical action, the dispersion-type polyvinyl resin being first dispersed in the dispersant, with other constituents, and then hardened by heat and/or chemical action. The dispersant is preferably a polymerizable acrylic monomer, preferably a methacrylate diester of an ethylene glycol, such as triethylene glycol dirnethacrylate, marketed by Specialty Resins, Inc, as

v monomer SR #205, or'ethylene glycol dimethacrylate,

marketed by The Borden Company, as EGD, or a commercial acrylic monomer marketed by Carbide and Carbon Corporation under the trade name MG-l, comprising chiefly diethylene glycol dimethacrylate, and having a viscosity of 12.2 centipoises at 25 C., aspecific gravity at 25 C. of 1.078, and a refractive index at 30 C., of 1.459, or other like dispersants.

The plasticizer may also be chosen from a variety of plasticizers known to plasticize high molecular weight polyvinyl chloride resins, as di(2-ethylhexyl)phthalate, dicapryl phthalate, dioctyl sebacate, di-2-ethylhexyl)succina te, and the like.

The catalyst may likewise be any one of the recognized catalysts for the hardening or solidification of the acrylic monomer, such as benzoyl peroxide, acetyl peroxide, lauroyl peroxide and the like.

The cover section 24, having the pin 26 secured in a central portion"thereof'and projecting inwardly therefrom, is first made'ready for the casting operation by supporting the fastening insert 17 on the pin 26 so as to bring the upper surface of the insert 17 generally parallel to the inner surface of the cover section 24 and spaced from the said inner surface a distance approximately that of the thickness of the wall structure 16 at its thinnestpor'tiomso that the plastic during casting will completely fill the space between the upper surface of the insert '17'and the inner surface of the cover section 24, as shown in Fig. 1, and will form on the lower face of the insert17 a'plastic layer somewhat thinner than that of the wall structure 16 at its thinnest portion, since the insert 17 shields somewhat the plastic beneath the insert 17 from the head which the heated walls of the mold 20 transfer to the plastic.

A suitable flowable plastic composition, or rigisol, of the character hereinabove more fully described is introduced into the lower mold section 211, the amount of the rigisol being best determined by experimentation, an amount being selected which gives to the wall structures 11, 13 and 14 of the heel 10 the required thickness at their thinnestwall portions, and leaves a hollow space 12 centrally of the heel 10 as large as is possible, consistent with the strength necessary in the wall portions of the heel 10.

The cover mold section 24 with the fastening insert 17 supported on the pin 26, as above described, is clamped tightly on the lower mold section 21 containing the proper amount of therigisol, as by bolts 27. The assembled mold 20 is then gyrated by any suitable mechanism.

Gyrational casting, as the name implies, comprehends movements of the mold 20 in a variety of ways. Thus, the assembled mold 211, containing a measured amount of a suitable rigisol, may be rotated about a single axis, or simultaneously about two or more axes, or may be oscillated through a wide angle in one or more planes, or may be moved in irregular or zigzag paths, the purpose of any such. gyrating movements of the mold 20 being to spread the freely flowable rigisol all over the inner surfaces of the mold 20 and into the space between the inner surface of the cover section 24 and the fastening insert 17, so as to fill that space. The gyration is accompanied by heating, as by gyrating the mold 20 in a chamber containing a fiuid heating medium, such as heated air, gas or steam. The temperature of the heating medium is such that the heat transferred. through the mold 20 to the rigisol, which has been distributed over the inner surfaces of the mold 20 and insert 17 during the heat-up period, is converted into a tough rigid solid hollow plastic heel 10, such as is shown in Figs. 1 and 4 to 7 of the drawing.

The assembled mold 20 is then cooled, as by passing it through a cold water spray, and when the mold 20 and the tough rigid plastic of the cast heel have been cooled somewhat, the mold sections 21 and 24 are opened, the cover section 24 removed, taking with it the pin 26, leaving the heel 10 with an opening 18 made by removal of the pin 26. The cast plastic heel 10 is then removed from the lower section 21 of the mold 20, with the fastening insert 17 firmly embedded in the shoe-contacting wall 14 of the heel 10.

The insert 17 may be made of a variety of materials. Thus, fibrous sheets or slabs of various types have been found to be effective. These may range from soft cardboard to wall boards and other fibrous bodies. The insert 17 in Fig. 1 represents a fibrous sheet insert, such as cardboard. Again, the insert 17 may be made of plywood or cross-plied fiber boards and may have a considerable thickness, the better to anchor screws and nails and other fastening devices. Such a thick plied construction is shown in Fig. 2. Further, the insert may be made of a metal sheet, such as aluminum and aluminum alloys, copper and copper alloys, and a sheet iron and tinned sheet iron insert has also proven to be effective in certain cases. Such a metal insert is shown in Fig. 4.

While the fastening insert 17 of the finished heel 10 serves primarily as an anchoring means for the fasteners employed in securing the heel 10 to the shoe, it may also be desirably employed to modify the properties of the rigid plastic in the region of the heel penetrated by the fasteners. Thus, it has been found in certain cases to be advantageous to embody in the preformed insert 17, by incorporation into the insert 17 in course of its construction or later by impregnation, or otherwise, or by coating the insert 17 on its upper surface with, a material that exerts a softening influence on the rigid plastic of the heel contiguous to the insert 17. Such a material may be a solid or liquid plasticizer, or both, that, during the heating of the mold 20 and its rigisol contents, migrates into portions of the plastic contiguous to the insert, and thus makes the rigid plastic in the nailable top of the heel softer, less brittle, and more readily penetrated by the fasteners which attach the heel to the shoe and also reduces any tendency to crack or split the rigid plastic of the heel during the driving of the fasteners. It is to be understood, however, that satisfactory attachments of the heel 10 to a shoe may be attained without the embodiment of a plasticizer on or in the insert 17.

As an example of the use of solid plasticizers in the production of inserts having the plasticizer distributed throughout the insert, powdered dicyclohexyl phthalate, a commercial solid plasticizer having a, melting point of about 58-65 C., is added to paper pulp at the heater in proportions ranging from 10 to 40 weight percent of the dry fiber weight, and thoroughly admixed therewith. Sheets of a thickness of heavy cardboard are made therefrom on a paper-making machine and sections of the size and shape of the insert 17 for any desired size heel are cut from said cardboard and either as a single board section or a plurality of plied-up sections are utilized as an insert. Upon gyrational casting of the rigisol and heating of the mold to the temperature necessary for conversion of the rigisol to a hard tough rigid plastic, that is, from 300 to 500 F., the dicyclohexyl phthalate plasticizer fuses and migrates into contiguous portions of the plastic, producing a tougher and less brittle plastic portion in the region of the insert. Other plasticizers which are solid at normal temperatures may be similarly employed, such as triphenyl phosphate, glycerol monostearate, N-ethyl p-toluene'sulfonamide, and the like.

Plasticizers which are liquid at normal temperatures, such as didecyl phthalate, tricresyl phosphate, and the like, may serve a like purpose by impregnating or coating the inserts with the liquid plasticizer before placing the inserts in the mold 20. Upon the heat formation of the plastic solid about the impregnated insert, the plasticizer gyrated in heated chambers.

will migrate into the contiguous portions of the plastic heel, producing a less brittle plastic adjacent the insert.

For a comprehensive list of plasticizers, both solid and liquid, useful in the invention of this application, consult the 1956 Modern Plastics Encyclopedia, pages 534 to 549, published by Breskin Publications, Inc., Bristol, C0nnecticut, which plasticizers are incorporated in this application by reference.

It will be understood that this invention is not limited to the specific inserts hereinabove described but that any solid sheet or slab of any material that will provide an adequate anchorage for screws, nails or other fastening devices is within the scope of this invention.

Referring to Figs. 2 and 3, in which the reference numerals heretofore applied to heel 10 are also applied to the heel of Figs. 2 and 3, the upper 31 of the shoe 30 is attached to and made a part of the mid-sole 32 and the sole 33 of the shoe in any of the well-known shoe constructions. An inner sole 34 is attached to the midsole 32 in any suitable manner. As is usual in applying a heel to a proper part of the sole construction of the shoe, the upper shoe-contacting surface of the heel 10 and the contacting surface of the shoe sole may be coated with an adhesive and the heel attached to the shoe in its proper position by means of adhesion. Usually the shoe and heel are held in position in a jig constructed for that purpose, and then placed in well-known machines for mechanically setting the screw, and/or for driving the nails, through the sole of the heel portion of the shoe into the plastic heel 10 and the fastening insert 17. Normally, different machines are employed for driving the screws and for driving the nails. As shown in Figs. 2 and 3, a central screw 35 and five nails 36 which are firmly anchored in the insert 17 are normally adequate, although a less or greater number of fastening means may be used. In some instances, forked or barbed nails, whose projecting points catch in the insert and resist the withdrawal of the nails may be used to effect a stronger anchorage of the nails 36 in the insert 17. Extensive tests have demonstrated that the tall slim high plastic heel 10 having an insert 17 of the nature hereinabove described may be most firmly attached to the proper portion of a shoe in the above described manner, so as to produce a high quality ladys shoe having the desirable characteristics hereinabove more fully described.

It has heretofore been proposed to manufacture tall slim plastic heels for ladies shoes by the high pressure injection of cellulose acetate and other plastics into multiple cavity molds, a process which requires expensive high pressure injection machinery as well as expensive multiple cavity high pressure molds, that is, molds that Will withstand the high plastic pressures necessary for multiple cavity injection molding. Further, such prior injection processes produce heels which lack the central hollow space of the heels of this application and which consequently are heavier, less resilient and more expensive in the use of plastic material.

On the other hand, the tall slim ladies heels of this application are made in lightweight inexpensive molds, and without the use of heavy expensive machinery, since the plastic molding is done at substantially atmospheric or relatively low pressures with the lightweight mold Further, the heels are molded with a hollow space in the central portion of the heel. The volume of the'hollow portion 12 of the heel 10 will vary with the strength of the plastic employed, and the size and style of the heel. For tall slim high heels the volume of the hollow portion will range from 10 to 30% of volume of the whole heel, the smaller sizes being in the lower ranges and the larger sizes being in the upper part of this range. In case of high heels,

not as slim or tall, as the heel of Fig. 8, the volume of the hollow portion 12 will range from 40 to 60%, and in case of lower heels, such as that of Fig. 9, the volume of the hollow portion will range as high as 70% of the total volume of the heel. The of the hollow portion 12 to the total volume of the heel makes possible not only a substantial economy in the quantity of plastic needed for the manufacture of the heel, but, what is more important, produces a lighter and more resilient heel and a more comfortable shoe.

The further features of the insert embedded in the plastic to anchor the fasteners of the heel to the shoe and the modified softened, tougher and less brittle plastic adjacent the insert and through which the fasteners must be driven in attaching the heel to the shoe, make the rigid resilient hollow plastic heel of this application superior in quality. i H

From the above detailed description, it is apparent that the heel of this application is the result of a fundamentally novel conception which has made available a novel, practical, highly useful and greatly improved heel construction for ladies shoes embodying a singly unitary hollow rigid plastic heel, light in weight and economical to manufacture.

The rigid hollow heel comprises a relatively thin arcuate side and back wall, a thin forward or instep wall, a heavier and thicker ground-contacting portion, and a novel upper or shoecontacting wall portion reinforced by an insert in which the fastening means for attaching the heel to the shoe are anchored. In certain embodiments, the heel has a portion of the upper wall member, through which pass the fastening means attaching the heel to the shoe, composed adjacent the insert of a tougher, less brittle rigid plastic, but at the same time integral with the more rigid plastic of the rest of the heel. This permits the fastening means, whether nails or screws or other fastening elements, to penetrate the toughened, less brittle rigid plastic portion more readily and to minimize the cracking or splitting of the heel during its attachment to the shoe by means of the specialized machinery now commonly used in the shoe manufacturing industry.

It will be obvious that in addition to the advantages above indicated, other advantages accrue to both the manufacturer of shoes and to the wearer of shoes which embody the invention of this application.

To the manufacturer, the utilization of the standard machines for attaching the hollow plastic heels of this invention to the proper sole portion of the shoe brings about substantial economies, and further, the hollow plastic heels of this invention are more economical to manufacture, making a double economy to the manufacturer in the utilization of the heels of thisapplication.

To the wearer ofquality shoes having the hollow plastic heels of this invention, the lighter heel is not only more comfortable, but also the strength of the joinder of the heel to the shoe insures a trim neat appearance of a new shoe throughout the useful life of the shoe by the maintenance of the original lines of the heel and shoe, a very desirable feature in high quality ladies shoes.

This application is a division of my pending application Serial Number 637,463, filed January 31, 1957.

The invention of this application may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the embodiments hereinabove set forth are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

What is claimed is;

1. The process of manufacturing a rigid resilient hollow plastic heel for ladies shoes which comprises placing in a heel mold a measured quantity of a flowable plastic composition comprising finely divided polymerized vinyl resin and a plasticizer for said resin, suspending within the mold a solid insert embodying a plasticizer, said insert being spaced a short distance from the inner surface of that portion of the mold which shapes the shoerelatively large volume surfaces of the heel mold and to embed the insert, heat-,

ing the heel mold to a temperature at which the flowable plastic composition is converted into a rigid resilient plastic, whereby the said insert is embedded in the said.

rigid plastic and the plasticizer migrates from the insert into the said rigid plastic adjacent the insert during the 1 conversion of the flowable plastic composition to the said rigid plastic, then cooling the heel mold and the molded heel within the heel mold, and removing the molded plastic hollow heel from the heel mold.

2. The process of manufacturing a rigid resilient hol-v low plastic heel for ladies shoes in aconventional two-v piece heel mold having a side-and-ground-walls-forming bottom section and a top cover section, which process comprises pouring into the said bottom section a quantity less than needed to fill the said bottom section of a flowable rigisol comprising a dispersion-type polyvinyl resin powder, a plasticizer for said resin powder and a liquid dispersant capable of being solidified by heat and/or,

chemical action, suspending from the cover section an insert plate somewhat smaller than, and spaced a short distance from, the inner molding surface of the cover section, the insert plate embodying a plasticizer for the rigisol, placing the two mold sections in closing contact, then gyrating the closed two-piece mold to distribute the flowable rigisol over all the inner surfaces of the twopiece mold and to embed the insert plate in the flowable plastic, heating the said mold, while continuing the gyrating, to a temperature at which the rigisol is converted into a rigid resilient plastic and the plasticizer of the said insert plate migrates from the insert plate into the rigisol as it is being converted into a rigid resilient plastic, whereby the said insert plate is embedded in the said rigid plastic and the rigid plastic adjacent the said insert plate is less brittle than the remainder of the converted rigisol,v then cooling the heel mold and the heel within the heel. mold, and removing the rigid resilient hollow plastic heel from the heel mold.

3. The process of manufacturing a rigid resilient hollow plastic heel in a conventional heel mold having a side-and-ground-wails-forming bottom portion and a shoe-.

contacting-wall-forming top cover portion, which process comprises introducing into the said bottom portion a quantity less than needed to fill the said bottom portion of a flowable rigisol capable of being solidified by heat to a rigid resilient plastic, suspending from the said cover portion a plate somewhat smaller than, and spaced a short distance from, the inner molding surface of the said cover portion, the said plate embodying a plasticizer for the rigisol, closing the heel mold, then gyrating the closed heel mold to distribute the flowable rigisol over all the inner surfaces of the heel mold and to embed the plate in the flowable plastic, maintaining the heel mold, while continuing the gyrating, at temperatures at which the rigisol is converted into a rigid resilient plastic and the plasticizer of the plate migrates into the rigisol, whereby the said plate is embedded in the said rigid resilient plastic and the said rigid resilient plastic adjacent the said plate is less brittle than the remainder of the rigid resilient plastic, then cooling the heel mold and the heel within the heel mold, and removing the rigid resilient hollow plastic heel from the heel mold.

References Cited in the file of this patent UNITED STATES PATENTS 1,174,054 B utterfield Mar. 7, 1916 1,402,872 Langford Jan, 10, 1922 2,629,134 Molitor Feb. 24, 1953 2,839,788 Dembiak June 24, 1958 FOREIGN PATENTS 606,936 Great Britain Aug. 23, 1948

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