US3088147A - Shoe last inserts - Google Patents

Description

May 7, 1963 w. P. FIELD SHOE LAST INSERTS 2 Sheets-Sheet 1 Filed Nov. 2, 1 960 May 7, 1963 w. P. FIELD 3,088,147

SHOE LAST INSERTS Filed Nov. 2, 1960 2 Sheets-Sheet 2 United States Patent 3,988,147 SHOE LAST HJSERTS Walter P. Field, 157 Belmont St, Brochton, Rdass. Filed Nov. 2, 196:), Ser. No. 66,725 1 Claim. (ill. 12l iil) This invention relates to shoe lasts, and more particularly to inserts or plugs for use therewith.

In the manufacture of shoes, one of the first operations ordinarily is to tack an insole to the bottom of the last. In the case of wood-bottom lasts such tacks may be driven directly into the wood of the last, but the resulting nail holes tend to cause early deterioration of the last. Accordingly it is desirable to provide replaceable inserts at such places of tacking in order to increase the life of the last.

In the case of metal-bottomed lasts it is of course necessary to provide inserts at the places of tacking because such metal bottoms, usually steel, are impervious to tacks.

Generally speaking shoe last inserts previously employed have been expensive, difi'icult to apply or replace, have required too frequent replacement, or have not fit adequately, namely flush with the adjacent surface of the last.

To illustrate the matter of fit, if the top of an insert is lower than the adjacent surface of the last, during the processing of the shoe in its manufacture a raised portion will appear in the insole co-rersponding to a depressed surface of an insert. Likewise if the surface of an insert rises above the adjacent surface of the last, a depressed portion will appear in the insole of the resulting shoe.

To illustrate further the matter of poor fit, if the surf-ace of an insert is initially higher than the adjacent surface of the last, and scouring is required to remove the excess material from the insert, such scouring not only involves substantial labor cost but such operation removes anticorrosion material ordinarily applied to metal employed for last bottoms.

By the present invention, there are provided shoe last inserts which obviate difficulties of the prior art indicated above and additionally provide advantages hitherto not available. Shoe last inserts of this invention will be described below, and illustrated in connection with a specific embodiment thereof in the drawings wherein:

FIGURE 1 is a bottom view of a metal bottomed last;

FIG. 2 is a fragmentary sectional view of a last showing a frusto-conical insert of this invention partially inserted in a last cavity;

FIG. 3 is a view similar to FIG. 2 showing the insert completely inserted in the last cavity;

FIG. 4 is an elevation of an insert of this invention;

FIG. 5 is a bottom plan view of the insert shown in FIG. 4;

FIG. 6 is a fragmentary bottom view of a last with an insert of elongate cross-section;

FIG. 7 is an elevation of the elongate insert shown in FIG. 6;

FIG. 8 is a bottom plan of the insert shown in FIGS. 6 and 7;

FIG. 9 is a vertical section taken on line 99 of FIG. 7;

FIG. 10 is a side elevation of a last showing inserts applied to side portions of the last; and

FIG. 11 is a rear elevation of a last showing an insert applied to the rearward portion of the last.

In FIG. 1 is shown a last 16 to the bottom of which is secured a metal plate 12 by means of fasteners 14. Last inserts 16 are shown in place, disposed at places where it is common to drive tacks to hold an insole in place during shoe making operations.

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The shoe last insert of this invention is composed of chemically inert plastic material, specifically polyethylene. It is contoured and for-med to predetermined precise shape and dimension, conveniently by injection molding. As presently preferred the insert is of frustum shape with the larger end of slightly greater cross-sectional dimension than the last cavity to which it is to be applied and with the smaller end of slightly smaller cross-sectional dimension than the shoe last cavity. In one preferred form of the invention, the insert is of frusto-conical shape and circular cross-section. For certain applications, the insert may have a cross-section of elongate character, conveniently with two parallel sides joined by semi-circular arcs. For convenience of insertion the smaller end of the insert is marginally rounded. As illustrated herein, the smaller end of the insert is depressed to form in effect an air trap and the insert is provided with a shallow groove extending from the larger end of the insert along the inclined side thereof and around the smaller end to communicate with said depressed portion. Such groove provides an :air vent, to permit adequate and permanent seating of the insert in desired position.

Referring again to the drawings, particularly FIGS. 4 and 5, insert 16 is of frusto-conical shape with the larger end 18 having a slightly greater diameter than the smaller end 29. The marginal edges 22 of the smaller end 20 are rounded. The central portion of the smaller end 20 is depressed to form the air trap 24. A shallow groove 26 is shown as extending from the larger end 18 along the side of the insert to the smaller end 2! and along and across said smaller end to communicate with said depressed portion 24. As illustrated the insert 16 is of injection-molded polyethylene.

As illustrated in FIGS. 2 and 3, last 12 is provided with a drilled cavity 23 of precise diameter and depth. In FIG. 2 insert 16 is shown as partially inserted into the cavity 28 which may be done by hand with great ease due to the shape and precise dimensions of the insert. In FIG. 3 the insert 16 is shown as driven to the bottom of the cavity 23 with the larger end of the insert flush with the adjacent surface of the last.

So far as illustrative relative dimensions are concerned, and referring to FIGS. 2 and 3, if the cavity 28 is drilled to a precise diameter of /2", the larger outer diameter of the insert may be 0.515 and the smaller outer diameter of the insert may be 0.495". The vertical dimension of the insert may be made to corerspond to the depth of the last cavity.

The groove 26 performs a highly important and indeed essential function in this invention in permitting the escape of air from the last cavity during the incorporation of the insert therein. Due to the resilient nature of the polyethylene and the precise relative dimensions of the insert and the last cavity, the polyethylene tends to flow and close the groove 26 during the insertion operation and this flow tends to take place to the extent that the polyethylene of the insert fills the cavity 12 snugly throughout its depth. The depressed portion 24 accommodates any additional air at the bottom of the cavity and prevents undue pressure such as might cause the insert otherwise to rise.

Due to the precision character of the insert 16 the larger or upper end thereof lies flush with the adjacent portions of the last and hence requires no scouring in the ordinary situation.

This feature saves labor and time and precludes the removal of any rust-proofing surface from the metal portion of the last. In the event however, that .a last cavity should be of insufficient depth, material of the insert extending above adjacent portions of the last may be removed in any suitable manner.

It Will be noted that when a contoured insert of this invention is driven into a corresponding hole or cavity of the last, any air within the cavity and below the insert is released by means of the air vent or groove. Thus there is prevented any buildup of air pressure beneath the insert which would tend to dislocate the insert from its predetermined position. At the same time, the compressive effect of the walls of the cavity radially inwardly of the upper portion of the insert tends to close tack holes when insole-holding tacks have been withdrawn.

The inserts of this invention may be of cross sections other than the circular cross section specifically illustrated herein. Thus for example, the cross sectional shape may be of generally long oval character, in which case the last cavity will be made of corresponding shape. Other shapes and modifications are within the purview of the invention.

The elongate form of frusto-conical insert illustrated in FIGS. 6 to 11 provides an extended area for the reception of insole tacks. This modification finds highly useful application in the .toe portions of lasts for pointed-toe shoes. Insert 30 is of frustum shape and its larger end 32 has a slightly greater area than the smaller end 34. Insert 30 in cross-section is of elongate character with the two parallel sides 36 and 38 joined by semi-circular arcs 49. The marginal edges 42 of the smaller end 34 are rounded. The central portion of the smaller end 34 is shown as depressed to form the air trap '44. A shallow groove or flute 46 extends from the larger end 32 of the insert down the lateral side 47 thereof and along the smaller end 34 thereof to communicate with depressed portion 44. In FIG. 6, insert 30 is shown in place in pointed-toe last 48. The cross-sectional shape of insert 30 is advantageous because of the relative ease with which a corresponding insert-receiving cavity may be formed in the last.

In FIG. 10, inserts 16 and 30 are shown as incorporated in side portions of last 10, illustrating the possibilities of 4 applying inserts of this invention to any portion of a last which may be damaged and require repair. V

In FIG. 11, an insert is shown as incorporated in the heel end of a last 19, where tacks are frequently driven to assist in holding a shoe upper in place.

The slight flowing tendency of polyethylene tends furthermore to close up to some extent tack holes left upon removal of tacks and thus increases the life of the inserts.

The chemical inertness of polyethylene means additionally that there is no swelling thereof upon the lacquering of the completed last which ordinarily takes places after the incorporation of the inserts. Any swelling characteristic otherwise would tend to cause the insert to rise above the level of the adjacent surface of the last after such lacquering operation.

It will he understood that the last inserts of this invention may be applied to any desired portion of a last for repair or other purposes.

Having disclosed my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

A pressure-formed polyethylene fi usto' conical plug for insertion into a recess in a shoe last comprising polyethylene polymerized to such a state that the material is plastic and slightly resilient to receive tacks and tend to close the tack holes when the tacks are removed.

References Cited in the file of this patent UNITED STATES PATENTS Wells o. May 1, 1883

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