US2908040A - Building form - Google Patents

Description

Oct.- 13, 1959 -H. D. SCHNEIDER BUILDING FORM 3 Sheets-Shet 1 Filed Feb. 8, 1954 H. n. SCHNEIDER 2,908,040

' Oct. 13, 1959 BUILDING FORM INVENTOR. fiA/PAY 0. JC/V/Vf/flff? BY m? o I 'V ATTORNEY 3 Sheets-Sheet 2 Filed Feb. 8, 1954 Oct. 13, 1959 H. D. SCHNEIDER BUILDING FORM 3 Sheets-Sheet 3 Filed Feb. 8, 1954 ATTORNEY United States Patent BUILDING FORM Harry D. Schneider, Osceola, Ind., assignor to United States Rubber Company, New York, N.Y., a corporation of New Jersey Application February 8, 1954, Serial No. 408,841

3 Claims. (Cl. 184'1) This invention relates to a depositing form akin to a last and to a method of making the same, and more particularly it relates to a form on which an article is to be formed by deposition of material thereon such as by dipping, spraying, etc., and to a method of making such a form.

Articles, e.g., rubber footwear, are frequently made by a process in which a layer of material is deposited on a building form by dipping, spraying, etc. This layer of material will ultimately form the wall of the completed article, and since the layer deposited on the form takes the configuration of this building form the wall of the article will be shaped to the configuration of the building form. After this layer has been deposited on the building form, the layer may be further treated, either while on or off the form, before the article is completed and ready for use. For example, rubber footwear is he quently made by using a last having the configuration desired in the article of footwean This, last is dipped successively in a bath of a natural or synthetic rubber latex and a bath of acetic acid to deposit a layer of rubber thereon. After the rubber is deposited on the last, the last bearing this deposit is passed through a vulcanizing oven to cure the latex on the last; Thereafter the rubber layer is stripped from the last, and trimmed if necessary to form a completed articleof rubber footwear.

Frequently it is desired to produce articles bearing an attractive design by utilizing such building forms. This can be done by forming a negative of the desired design directly on the building form by carving, machining, etc.,

the surface ofthe building'form. When the layer is de- However it is costly to carve or machine the negatives of these designs in the surface of such building forms, and: this is particularly expensive because any given design may be considered attractive for only a limited time by. the public before it tires of that design. Consequently manufacturers are forced to' devise new designs continually, andv if articles bearing these designs were produced on building. forms having the particular design formed directly in its surface, these building forms need necessarily be discarded or resurfaced at frequent intervals.

The rubber industry has solved this latter problem partially by providing so-called socks of rubberor the like which are adapted to ,fit over building forms. A single master form is provided having in its surface the positive of the ultimate design desired in the article to be produced. This master form may be used to produce many socks bearing the negative of the design by a method of deposition such. as that used to produce the final article. These-socks are'in' turn placed on smooth building forms so that thedesigned surface of the sock is outermost; hence the sock and form together constitute a building formhavi'ng onits surfacethe negative of'the-design to-beproduced in thefinal article. Thereice fore when the public tires of any particular design, the manufacturer need only discard the socks and the single master.

Although the term socks is applied to these form coverings because they are most commonly used over a footwear building last, it should be understood that this term is used to describe the form covering whether his shaped to fit a footwear last or a glove last or tobe used in any similar application, and this term is so used. and should be so understood throughout this specification.

Even when this ingenius practice is used to produce decorated articles, there are many disadvantages in using the building forms heretofore available. Thesev building forms are formed generally of metal although occasionally and for special uses they may be formed of other rigid materials. These rigid forms are subjected. to rough usage in production, and frequently they became chipped or broken so that they are no longer usable and must be discarded. This of course is true whether they are to be used in a process in which material is deposited directly on the form, or the material is deposited on a sock over the form. Furthermore, although designs may be changed by the use of socks in the manner described above, still the basic configuration of these forms, e.g., the configuration for any given foot size, remains the same, and since there are many sizes which a manufacturer must to able to supply if he is to carry a complete line of articles, he must. have on hand a relatively large number of forms of each size even though the demand for any one size form at any given time may be negligible. Consequently a part of the manufacturers capital may be tied up in non-productive equipment, and he may be burdened with excessive storage costs.

Furthermore, although a manufacturer should use only the simplest undecorated building forms, the basic configuration of the form is complex; e.g., a footwear form must be shaped to the configuration of the foot. Metal building forms having such complex configurations are costly to manufacture.

A further specific disadvantage of the building forms heretofore used is met with When these forms are used in conjunction with socks of the type described above. As pointed out above these building forms are subjected to rough usage in production. The metallic forms used are rigid, and when such a building form bearing a sock is abused, as frequently occurs for example by bumping it against a sharp edge, the sock will be cut or marred because the metal form constitutes, in effect, an anvil on which the sock is stretched, and sharp objects will cut through the sock to the form. Consequently the socks must be replaced frequently in production, and frequently the damaged sock may be used to produce one or more defective articles before the damage is discovered.

It is an object of this invention to provide a novel building form and method of making the same wherein the form can be produced cheaply and easily, and bythe use of which a manufacturer may utilize his raw materials to adapt his form supply to the needs of his production with relatively little cost. It is a further object of this invention to provide a novel building form through the use of which a manufacturer will be able to reduce materially his production of defective articles. Further objects and advantages of this invention will be apparent from the following description or will be pointed out more fully hereinafter.

This invention contemplates a building form of the type described and a method of making the same wherein an outer shell having the configuration desired in the article to be produced on the building form is first provided. This shell may be produced by any convenient method; for example it may be produced by a method similar to that used to make the socks above described. However it is preferred to form this outer shell of a vinyl resin and by the Well-known slush casting technique.

To slush cast a shell, a hollow metal mold is first provided having its inner surface formed to the negative of the configuration desired in the shell. Such a hollow metal mold may be made by electroforming, spraying, etc., and preferably it is made by a spraying process such as that disclosed and claimed in U.S. Letters Patent No. 2,629,907, granted to Hugger. In a slush casting technique, the hollow mold is filled with a creamy plastic material that is to form the shell. The material used in casting the shell of this invention preferably is a vinyl plastisol which is prepared by dispersing finely divided polyvinyl resin powder in a liquid plasticizer therefor to form a creamy liquid. The preparation of the plastisols and their use are Wellknown by those skilled in the plastics art, and are described in detail in an article appearing in Modern Plastics 26, 78 (April 1949) by Perrone and Neuwirth.

If the hollow mold is heated when the creamy plastic material is in it, a seamless wall of the plastic material will be deposited on the internal walls of the hollow mold. The thickness of this wall will increase with each passing minute the creamy plastic is in the mold. After a deposit of the desired thickness is built up, the remaining liquid may be poured from the mold. The deposit formed on the internal walls of the mold is then fused by heating it, after which it is stripped from the interior of the mold and suitably trimmed, if necessary, to provide the outer shell.

Thereafter this hollow flexible shell is transferred to a split mold that is adapted to support the shell. The split mold may be conveniently a mold identical to that used to slush cast the shell excepting that it is split in such a manner that the shell may be removed therefrom without bending the shell out of shape. Conveniently the mold may be split along its longitudinal central axis and the two pieces hinged together at its bottom so that the two sides of the split mold may be pulled apart, the shell may be inserted, and the mold may be closed thereabouts.

With the shell thus supported in this split mold, the shell is filled with a molten thermoplastic material. Thereafter the molten thermoplastic is allowed to solidify, after which the split mold is opened, the building form is removed therefrom and its upper surface trimmed if necessary to complete the building form of this invention.

it will be apparent from the foregoing that a building form constructed in accordance with this invention will have many advantages. For example a manufacturer need keep on hand if he so desires no building forms which he is not using or does not contemplate using within a reasonable time. When the manufacturer decides to produce an article of a new design, he need only construct one or a few of the slush casting molds. Thereafter he may slush cast an almost unlimited number of building form shells in these few slush casting molds. These shells may then be filled with the thermoplastic material as described above, to produce the number of building forms which the manufacturer requires. After these building forms are no longer useful, the manufacturer may strip from them the fused hollow shell, and remelt the thermoplastic core, and reuse this core material in making other and different building forms. The only appreciable loss in using such building forms is in the shell.

Furthermore, in the event that the building form is broken in use the manufacturer may remelt it and reuse the thermoplastic material with little or no trouble or loss. A still further advantage flows from the use of a building form in accordance with this invention because the thermoplastic core after it solidifies, although it is rigid enough to give a firm building form, is still resilient enough so that should the building form be bumped against a sharp object the core will yield and the shell will not be cut or marred. Consequently the likelihood that defective articles will be produced on building forms in accordance with this invention is substantially reduced from that which occurs when the metallic building forms of the prior art are used.

For a better understanding of the nature of this invention and its advantages in use, reference should be had to the following detailed description of specific embodiments thereof, when read in conjunction with the accompanying drawings, wherein:

Fig. l is a front elevational view partially in section of a hollow metal mold illustrating the step of filling this mold in the slush casting process;

Fig. 2 is a side elevational view of the hollow metal mold of Fig. 1 illustrating the step of emptying the mold in the slush casting process and the view shows the shell deposited on the internal walls of the mold;

Fig. 3 is a perspective view of a split mold suitable for supporting the shell of the building form in accordance with this invention showing the shell being inserted therein;

Fig. 4 is a perspective view of the supporting structure of Fig. 3 closed, with the shell inserted therein and illustrating the step of filling this shell with a thermoplastic material;

Fig. 5 is a view similar to' Fig. 4 illustrating the step of immersing a core in the molten thermoplastic;

Fig. 6 is a prespective view partially in section of the completed building form produced by the method illustrated in Figs. 3-5 showing the disposition of the various parts;

Fig. 7 is a sectional view through the building form along the line 7-7 of Fig. 6;

Fig. 8 is a top plan view of a modified building form embodying this invention; and

Fig. 9 is a vertical sectional View along the line 9-9 of Fig. 8 of this modified embodiment of this invention.

Referring now to Figs. 1 and 2, there is illustrated a method of forming the outer shell of a footwear dipping last embodying this invention by a slush casting technique. In these figures, it) indicates a hollow metal mold having its internal surface shaped to the configuration of a boot, which preferably is made in accordance with the method of the above-mentioned Hugger patent. This metal mold 10 may have its internal surface decorated with the negative of any decoration desired on the external surface of the building form, so that the shell formed in this mold may have any desired attractive design imparted thereto which one wishes to impart to the finished article to be produced on the building form. The material 11 which is to form the outer shell of the building form is poured from a source 12 into the hollow mold 10 to fill the same as illustrated. Preferably this material lll comprises a vinyl resin plastisol. After the mold 10 has been filled as illustrated in Fig. l with the vinyl plastisol, it may be heated, or the mold may have been heated previously. As the vinyl plastisol 11 is heated by the hot mold, a thin layer of the plastisol will be deposited in the form of a skin on the internal walls of the mold 10, and the thickness of this layer will become greater with each minute that the plastisol 11 remains in the heated mold. After a skin of the thickness desired in the shell of the building form is deposited on the walls of the mold 10, the still fluid plastisol 11 may be poured therefrom into a suitable container 13 to be reused in forming additional shells. When the plastisol has been poured from the mold 10, the thin skin or shell 14 deposited on the walls of the mold will remain within the mold l0, and this thin skin 14, as pointed out above, will conform accurately to the internal surface of the mold 10. Thereafter, the mold 10 with the weak cheesy skin 14 inside it is subjected to further heat sufficient to fuse the skin 14, as is well-known in the plastics art, into a tough leathery material.

Thereafter, this hollow shell 14 which is to form the outer shell ofthe building form may be stripped from the hollow mold 10. Shell-14-is next-transferred to a sup portingetructure-or mold 15 such as that shown in Fig. 3. The supporting mold 15 is illustrated as a mold identicaliwith the hollow mold excepting only that the mold. has been split along its longitudinal central axis 'andtthetwo halves havebeen hinged: together by means ofihinge 16 fixed'thereto at the sole of the mold. The split mold thus formed is constructed so that the shell 14 may, be inserted therein-and maysubsequently be removed I therefrom without. substantially distorting the shellI14. Although the mold 15 has been illustrated as having decorations that complement those on shell 14, such-for example. as thetread surface, 27 therein, it is not found absolutelyessential that this mold 15 be so decorated;.for its primary purpose ismerely to support thQfiBXIbICSh6l1114-JSO that it may be filled with liquid inva; manner such that the shell will retain its shape while being filled. As illustrated, the mold 15 may have spring.;clasps 16:on one half thereof that are adapted to engage the. other half of the mold 15 whenit is closed to; maintain: the. mold: 15 closed.

Witlr the shell 14 inserted in: the mold 15, the mold 155is=then closed-as illustratedin-Fig. 4. The closed mold 15.-i s then: positioned at a station where. thermoplastic materiahwhichv has been heated: to render it molten may bepouredrfrom'a suitable source such as spout 17 of a caminto'the' hollow shell 14-. In accordance with this invention ,the material that is used to form a core Within the. shell 14: is a thermoplastic material that does not melt substantially at 200 F. Plasticized cellulose acetate-butyrate hasbeenfound excellent for this core material/and is the preferredmaterial for the core. A specific material: comprising 70% cellulose acetate bu,- tyrate and 30% of a suitable plasticizer, for example of the phthalate type, provides excellent results. This material totally. melts at 250 F.,"and incipient melting occurs at 215 F.

By using a core of plasticized cellulose acetate butyrate, it is found that a dipping last may be produced which is-especially useful for dipping articles of rubber footwear from apre-vulcanized latex in which the finished article is-tobear adesign on its external surface. In one specific processof th-is'type, the decorated building form -isdippedalternately in a bath of pre-vulcanized rubber latex and abathof coagulant to'deposit a layer of rubber upon the building form. After the rubber layer of the desired thickness is deposited thereon, the building form bearing the layer is conducted to a drying oven where it is subjected to a temperature of 190-200 F. to dry the layer of rubber. Thereafter the layer of rubber is stripped from the building form, turned inside out to dispose the decorated surface exteriorly of the footwear, and then placed on a curing last. Thereafter the article on the curing last may be subjected to further heat to finish the cure of the article.

Referring again to the drawings, the molten plasticized cellulose acetate butyrate 19 from the source 17 is poured into the shell 14 until it fills the same to the height desired, which will depend in part upon the specific construction of thebuilding form desired. For example in making the building form illustrated in Figs. 5, 6 and 7, there is provided a hollow body 18 of metal or the like that is immersed in the cellulose acetate butyrate 19 while it is molten. This body 18, as will be apparent, is designed to occupy much of the internal volume of the shank of the finished last, so that the quantity of cellulose acetate butyrate used in constructing the building form may be minimized. Accordingly the shell 14 is filled with cellulose acetate butyrate to a height such that when the hollow body 18 is immersed therein, the cellulose acetate butyrate will fill the shell 14 to the height desired in the finished building form.

As shown in Fig. 5, the hollow body 18 may have a rod 20 fixed in its upper end by which the building form may be attached to a dipping-machine: During the pro ductionof thebuilding form, a stop block 21 having an openingtherein-is fitted. over the rod 20 and positioned thereon whereupon the screw 22 may betightenedto fix the block 21 tothe rod 20. When the body 18 is immersed. inthe molten cellulosev acetate butyrate, the blockzl will rest upon the upper endof the mold 15 to position the body 18-aocurately in its desired vertical position within the completedrbuildingform and hold it thereuntil the cellulose acetate butyrate 19 solidifies.

The cellulose acetate butyrate is then allowed to cool to solidify it withinthe shell 14- and thus form a firm core within shell 14: Thereafter, the building form is removed from the support 15, its top may be trimmed if necessary, and the building form-is then ready for use.

As best shown in Figs. 6 and 7-, the completed building form will have an outer surface forming shell 14, pref: erably of fused vinylresin, which may have an irregular surface as indicated at 27' for the tread of the'footwear. Within this shell 14-there is disposed a core 19 ofsolidified cellulose acetate butyrate which'conforms accurately tothe interior contours of the shell 14 and substantially fills the same. In the embodiment thus far described, there is provided immersed in this core of solidified-cellulose acetate butyrate a hollow body 18 adapted to occupy much of the internal volume of the shell 14 so as to minimize the quantity of cellulose acetate butyrate which must be usedin producing the building form.

Referringto Figs. 8 and 9 there is shown an embodis ment of this invention in a dipping last designed'to make a childs decorated; boot orgaiter. This embodiment comprises a hollow outer shell 14 which preferably is formed by slush casting a vinyl resin-in a hollow, metal mold. As'best shown in-Fig. 8 this shell 14 may haveits outer/surface provided with any suitable. attractive decoration such as that shown at 23. Such a design is; quite easily achieved in the slush casting technique above described; This shell 14 is filled with acore 1? of solidi+ fied cellulose acetate butyrate which has a support immersed therein. In this embodiment the support come prises a flat relatively thin metallic plate 24, at the upper portion of the last immersed in the cellulose; acetate butyrate. There is depending from this plate 24 a hollow sleeve which has its. lower end closed. As shown, the sleeve 25'may be screwediin'the plate'24; This sleeve25 andv plate 24; comprises a. supporting means inywhich a post from a dipping machine may be inserted to support the completed building form on the machine. As shown, the sleeve 25 may have interiorly thereof the locking shoulders 26 so that the building form may be locked on the dipping apparatus. The building form shown in Figs. 8 and 9, as will be obvious, may be made in essentially the same manner as the form illustrated in Figs. l7. Thus the shell 14' may be slush cast, the shell 14' may then be supported in a split mold and the cellulose acetate butyrate 19' may be poured therein whilein a molten condition, whereupon the sleeve 25 and plate 24 are immersed in the cellulose acetate butyrate. Thereafter the cellulose acetate butyrate 19' is allowed to solidify to form the firm core for the building form.

From the foregoing it will be seen that a multiplicity of building forms may be made with great ease in accordance with this invention. Should it be decided that a different style of building form is desired, the building form in accordance with this invention need not be discarded, for it is a simple matter to cut the shell 14 from the building form, re-heat the cellulose acetate butyrate 19 to remelt 'it and pour it into new shells having the desired design. So also should the building form be broken by extreme abuse, it need not be discarded for the cellulose acetate butyrate may be reused.

Although it is believed that the building form in accordance with this invention will find its greatest use as a dipping last for such articles as rubber footwear, it will be obvious that it will lend itself to other allied uses. It

is contemplated that it will be of particular value as a building form on which a decorated article is to be deposited because of the ease with which the slush casting process lends itself to making decorated shells. Furthermore, the building form in accordance with this invention may be used as an electroforming form to produce internally decorated hollow metal molds of the type illustrated at 10, for the hollow metal mold may be electrodeposited on the building form of this invention after which the cellulose acetate butyrate may be removed by melting or otherwise and the flexible shell 14 may be collapsed and withdrawn from the mold.

The building form in accordance with this invention will have special advantages when used in a dipping process in substitution for the rigid lasts covered with socks of the prior art described above. Thus in the finished product the core 19 of cellulose acetate butyrate, although it is rigid to provide a firm dipping last, is still somewhat resilient and soft so that should the dipping last strike a sharp object such as a corner, the core will yield under the force of the blow so that the outer shell 14 is not damaged. As contrasted with this when the socks of the prior art are used as heretofore over metallic building forms, these socks are readily cut when they strike a sharp object. A still further advantage as compared with the metal dipping forms having socks thereon, flows from the fact that the shell 14 is accordance with this invention need not be stretched over the core. Therefore the likelihood of the shell 14 being torn while covering the dipping last is substantially eliminated to provide savings in their manufacture. Furthermore there is no likelihood that the shell 14 will be placed improperly on the form as sometimes occurs when a rubber sock of the type heretofore described is used. A still further advantage exists when the dipping form of this invention is compared to the forms covered by a sock heretofore used. In these forms of the prior art it was necessary that both the internal and external surface of the sock be accurately formed. The design bearing surface thereof obviously must be accurately formed to the design desired in the finished article. And if a sock is to be stretched on a pre-shaped building form, the other side of this sock must also be accurately formed. Thus there can be no runs on the inner surface of the sock, i.e., no raised lumps or veins may be permitted on this inner surface of the sock because when such an imperfectly formed sock is stretched over a smooth building form such lumps will cause the external surface to bulge out of shape to destroy the contour of the article produced on the form. By contrast the internal surface of the shell 14, may be made very irregular during its formation and yet when the molten thermoplastic 19 is poured therein it will flow around these irregularities to absorb them, so that the external surface of the shell 14 is in no Way distorted by any irregularities in the sock.

A further incidental advantage flows from the use of the building form as a dipping and drying last in a process such as that described above using pre-vulcanized latex. This flows from the fact that the core of cellulose acetate butyrate expands somewhat under heat and therefore when the deposited layer of latex is being heated to dry it the building form of this invention will expand within this layer to provide a good design transfer to the latex.

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

1. A building form comprising an outer hollow vinyl shell the external surface of which constitutes the external surface of the building form, whereby the configuration of the external surface of said shell may determine the configuration of articles built on said form, and a sturdy inner core of plasticized cellulose acetate butyrate filling said shell to render said shell substantially rigid.

2. A building form in accordance with claim 1 including a sturdy hollow body adapted to occupy a large portion of the volume of said shell, said hollow body being embedded in said cellulose acetate butyrate and fixed thereto.

3. A building form in accordance with claim 1 comprising a footwear dipping and drying last in which said outer hollow vinyl shell is shaped to the configuration of an article of outer footwear.

References Cited in the file of this patent UNITED STATES PATENTS 1,282,260 Merritt Oct. 22, 1918 2,203,421 Stevenson et a1 June 4, 1940 2,320,583 Forro June 1, 1943 2,345,977 Howald et al. Apr. 4, 1944 2,473,723 Nelson June 21, 1949 2,476,994 Milton et al July 26, 1949 2,748,435 Hackett June 5, 1956

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