Recessed Last and Method of Lasting and Molding a Shoe Sole to Upper Including Positioning Insole in Recessed Last

This invention relates to the art of manufacturing footwear with molded soles.

In the production of machine-made footwear with in situ injection or compression molded outsoles of plastic or elastomeric material, a continuing source of trouble has been the task of inserting the insole component into such an item of footwear so as to be properly and securely positioned in the same throughout the expected service life thereof. One known method of making such footwear of which we are aware involves the steps of lasting the upper on a last, placing the last with the upper thereon over the open top of a mold cavity, injection molding or compression molding the sole-forming composition directly to the bottom margin of the lasted upper in the mold cavity, and, after the solidification and/or curing of the outsole, removing the upper and sole combination from the last, inserting the insole, and securing it in place in the interior of the footwear item by means of an adhesive.

One of the disadvantges of this manufacturing method is that it is necessary for the operator, when inserting the insole, to handle the virtually completed footwear item, which in the case of footwear with light-colored fabric uppers greatly enhances the likelihood of the finished item becoming soiled. Another disadvantage is that an operator requires a considerable amount of practice and experience in order to be able to properly position the insole in the footwear, i.e. so as to be sure that the exposed upper surface of the outsole is adequately covered and to keep the relatively flexible insole from becoming wrinkled. Yet another disadvantage is that the securing of the insole in place generally requires a cold setting or drying adhesive, which, it has been found, frequently results in an adhesive bond of less strength than is required.

It is an object of the present invention, therefore, to provide means by which the aforesaid disadvantages and drawbacks can be efficaciously avoided.

A more specific object of the present invention is the provision of means enabling an accurate positioning of the insole relative to both the lasted upper and the outsole during the molding of the latter, so as to enable a firm, practically indestructable bond to be created therebetween by virtue of the molding of the outsole and without any need for further manual operations.

Generally speaking, the objectives of the present invention are attained by the provision, in the botton of the last, of a recess dimensioned and contoured in accordance with the shape of the insole, so that when an insole is positioned in the recess, it will be retained therein by the marginal regions of the upper drawn over the peripheral rim bounding the said recess. This ensures that there will be no displacement of the insole relative to the last while the mold is being closed, and that the insole will be in its proper location relative to the upper during the molding of the outsole to the upper and the insole.

The foregoing and other objects, characteristics and advantages of the present invention will be more clearly understood from the following detailed description thereof when read in conjunction with the accompanying drawing, in which:

FIG. 1 is a perspective illustration of an open footwear sole mold utilizing a last constructed in accordance with the principles of the present invention;

FIG. 2 is a transverse vertical section through the mold in closed condition, preparatory to the solemolding operation;

FIG. 3 is a detail illustration, on an enlarged scale, of the circled portion of the structure shown in FIG. 2; and

FIG. 4 is a fragmentary transverse section through an article of footwer manufactured by means of the mold shown in FIGS. 1 to 3.

Referring now to the drawing in greater detail, conventionally the basic elements of a footwear sole mold 10 are a last 11 and a cavity structure 12, the latter essentially consisting of a bottom plate 13 and a pair of complementary side plates 14 and 15. In the usual arrangement of these elements, see FIG. 2, the bottom plate 13 is arranged for vertical reciprocal movement, as indicated by the arrow A, on a suitable ram or other support (not shown), the side plates 14 and 15 are arranged for horizontal reciprocal movement toward and away from each other and the bottom plate 13, as indicated by the arrows B and C, and the last 11 is arranged for angular and vertical reciprocal movement, as indicated by the arrows D and E, between its illustrated upright position and an inverted position (not shown). The inwardly directed surfaces 14a and 15a of the side plates 14 and 15 are contoured so as to define, when the latter are in the illustrated positions thereof, the side walls of a cavity 16 the dimensions and shape of which are those of the footwear outsole to be molded. Suitable heating means (not shown), may be provided in or in association with the cavity structure 12 and the last 11.

The present invention resides in a modification of the last 11 to enable an insole to be accurately located and supported thereon during the sole-molding operation. To this end, there is provided in the bottom of the last a recess 17 the dimensions and shape of which are essentially those of the insole to be incorporated in the footwear item being manufactured. Preferably, the depth of the recess should be either equal to or slightly greater than the thickness of the insole.

In use, generally while the last is inverted from the position shown in FIGS. 1 and 2, an insole 18, which may be made of sponge rubber, non-cellular rubber, bonded cork, fiberboard, etc., is placed into the recess 17 and an upper 19 is then lasted on the last, the lower marginal regions 19a of the upper being drawn over the peripheral rim 20 bounding the recess 17. The rim may be as narrow as feasible, subject only to the requirement that it be sufficiently strong to resist collapse under the lasting forces applied thereto. We have found a rim thickness of about .030 inch to be a practical minimum. In the illustrated arrangement, the opposed edges of the marginal regions 19a of the upper are shown as drawn under the last by means of a string 21, but other lasting arrangements, utilizing a net or mesh fabric or the like providing an adequate amount of strike-through space for the molding composition, and other means for retaining the insole in the recess preparatory to the molding operation, may be used.

The last 11 is then moved to its upright position and lowered against the cavity structure 12 until the top edges 14b and 15b of the side plates 14 and 15 engage the last, with a suitable amount of a sole-molding composition being introduced into the cavity 16 either prior or subsequent to the closing of the cavity, depending on the particular method of compression molding or injection molding used. Either of the side plates 14 and 15 or the bottom plate 13 may also be provided with a suitable inlet orifice or passageway (not shown) to enable injection of the molding composition. The molding composition may be polyvinyl chloride, polyurethane, natural or synthetic rubber, or the like, and if desired may include a blowing agent to provide a foam or cellular sole. With the mold closed under appropriate pressure, the molding composition will then solidify by fusion, cooling or curing, as the case may be, and the resultant outsole thereupon will be intimately bonded to the bottom portions of the upper 19 confined in the mold cavity as well as to the insole 18 confined in the recess 17. If desired, the strength of the bond between the outsole and the insole may be further enhanced by providing a fabric facing integral with the insole on the lower surface thereof or by precoating the latter with a heat-activatable adhesive material such as a thermoplastic urethane.

At the end of the molding operation, the mold is opened and the completed footwear item 22 (FIG. 4) having an outsole 23 molded directly to the insole 18 and upper 19 removed from the last. There will, accordingly, be no further need for additional treatment of the insole, which is found to be firmly bonded to the outsole in precisely centered location and free of wrinkles or other deformations, whereby the possibility of the footwear becoming soiled is greatly reduced.

It will be understood that the foregoing description of a preferred embodiment of the present invention is for purposes of illustration only, and that the various structural and operational features herein disclosed are susceptible to a number of modifications and changes none of which entails any departure from the spirit and scope of the present invention as defined in the hereto appended claims. Thus, although the invention has so far been described as applying to the incorporation of an insole in the article of footwear, the principles herein disclosed are applicable as well to the (incorporation of such items as arch cushions, heel pads, shank stiffeners, half insoles and the like in footwear, requiring in each case, of course, an appropriately shaped and dimensioned recess in the bottom of the last. Wherever the term "insole" is used in the specification and claims, therefore, it is to be interpreted in the broader sense of referring to any such footwear component.