US3099862A

US3099862A - Last for use in making plastic footwear

Info

Publication number: US3099862A
Authority: US
Priority date: 1958-02-05
Filing date: 1958-02-05
Publication date: 1963-08-06
Anticipated expiration: 1980-08-06

Description

United States Patent O 3,099,862 LAST FR USE 1N G PLASTIC FOOTWEAR George H. Bingham, Jr., Westminster, Md., assigner to Cambridge Rubber Company, Taneytown, Md., a corporation of Maryland Filed Feb. 5, 1958, Ser. No. 713,433 7 Claims. (Cl. 18-41) This invention pertains to the manufacture of waterproof footwear, for instance boots, bootees, gaiters, etc., in particular to footwear of the kind in which a synthetic plastic is employed as a waterproofing medium instead of natural rubber, and relates more especially to a novel last for use in making such footwear.

In the co-pendi-ng application of George H. Bingham, lr., Serial No. 707,505, led January 7, 1958, now Patent No. 2,957,188, there is disclosed a method of making a boot whose upper, at least, consists of synthetic resin, and which has an opening extending downwardly from its top with a conventional slide fastener for closing the opening, said application suggesting a novel method of uniting the tapes of such a fastener to the inner surface of the upper and likewise the bonding of a simple rein force tape to the upper. While the method disclosed in said application is much superior to any method which is known to be in commercial use, some difficulties have been experienced in the practice of said method: first, because the plastics employed in making such footwear have no adhesive qualities in the unfused state; and second, because the surface of the boot to which the fastener tapes are to be secured (in particular when the fastener is to be located at the front of 'the boot) is of non-uniform width and is curved both transversely and up and down to varying degrees of curvature, and since the fastener tape is not stretchable, it is very difficult to conform this tape to the inner surface of the boot top so as to insure a strong adhesion between the parts. When herein reference is made to a tape, the term tape is to be understood (unless otherwise dened) as inclusive of a single length of tape or of the two parallel tapes comprised in a slide fastener.

A principal object of the invention is to provide a novel last, which is useful in the practice of the above process whereby it is made possible firmly to attach a tape or tapes (for example the tapes of a slide fastener) to the interior of a plastic boot upper by adhesive means and without recourse to the customary heat-sealing process. A further object is to provide means whereby a shoe upper may be so shaped, without detriment to its salable characteristics, as to facilitate the adhesive bonding of a tape or tapes to the interior of the boot upper. A further object is to provide a novel last which may, if desired, be employed directly in making plastic boots by the dipping method, or which may be employed as a model in the making of a hollow mold for -use in molding a plastic boot by the slush method, or a modification of the slush method, thereby to impart to the mold a shape such as to make possible the making of a boot upper having a specially shaped area or areas to which a woven textile tape may readily be conformed as a step in uniting it adhesively to the inner surface of the upper. Other and further objects and advantages of the invention will be pointed out in the following more detailed description and by reference to the accompanying drawings wherein:

FIG. 1 is a side elevation of a last useful in the practice of the present invention;

FIG. 2 is a front elevation of a last embodying the invention;

FIG. 3 is a rear elevation of the last of FfG. 2;

FIG. 4 is a transverse section in any horizontal plane through that part of the last corresponding to the loca- ICC example on the line 4 4 of FIG. 1; 5-5 of tion `of the tape, fo-r FIG. 5 is a transverse section on the line FIG. 3;

FIG. 6 is a side elevation of a last illustrating another embodiment of the invention;

FiG. 7 is a vertical section on the line 7-7 of FIG. 6;

FIG. 8 is a section in any horizontal piane through that part of the last corresponding to the location of the tape, for example on the line 8 8 of FIG. 7;

FIG. 9 is a transverse section similar to FIG. 8, but illustrating a modification; and,

FIG. 10 is a section similar to modification.

Referring to the drawings, the numeral 16 designates a boot last embodying the present invention. This last comprises the foot por-tion 11 and the leg portion 12. This last is 'of generally conventional construction and, as indicated in FIG. 4, of more or less elliptical shape in transverse section, but, in accordance fwith the present invention, having

areas

13 and 14 at its front and rear, respectively, which are of uniform transverse Width from end-to-end and which, in the illustrated embodiment, are rectilinear in transverse section, although being curved heightwise `of the last. While areas which are transversely at are preferred, it is contemplated that areas of uniform width heightwise `of the last, but which are slightly curved to the same radius at all transverse sections may be employed. Flat areas of uniform width may be formed by taking the ordinary last `and grinding away some of the material, as indicated in dotted lines in FIG. 4, so as eventually to provide the

surfaces

13 and 14. These surfaces, at any horizontal plane of the leg portion of the last section, are rectilinear so that the

surface

13 or 14, as a whole, may be described in geometrical terms as cylindrically curved, that is to say, the surface is such as is generated by the motion of a horizontal straight line in moving downwardly through space while always parallel to itself and while following a directrix line Iwhich may, as respects FIGS. 1, 2 or 3, be considered to be the center line of the usual last at its forward or rear part, respectively. Within said definition, the directrix line may be any curvature or even straight. When hereinafter this surface is referred to as of cylindrical curvature, this term -is to be interpreted in accordance with the above definition.

While it is possible to form these

surfaces

13 and 14 by grinding away some of the material of the last, a preferred mode of procedure is to set into the substance of the last, at the desired location, a ribbon-like strip 13a or 14a, respectively, of steel or other hard material which has previously been shaped to the desired heightwise curvature. These strips are so set into the substances of the last proper that their exposed surfaces merge smoothly with the adjacent portions of the surfaces of the last proper. Such strips may be made in accordance with a preshaped template having the desired curvature. Such strips, embedded in the material of the last, insure uniformly in the making lof successive lasts. It is contemplated that these strips may be set into the mold in which the last is formed so that the strips are ernoedded in the material of the last during the molding operation.

In FIGS. 1 to 5, the last is shown as having such a cylindrically curved surface, both front and rear, but it is to be understood that fthe last may be provided with such a surface either at front or rear rather than having two such surfaces. The surface at the front yof the last is designed to facilitate the application of a slide fastener at the front of the boot which is fto be made on the last, While that at the rear is particularly intended for use in applying a reinforce tape to the back of the boot.

FIG. 5, illustrating a In FIGS. 6 to S, the last 16 is shown as having a surface such `as above described at its side rather than at the front or rear. Slide fasteners ane often installed at the side of a boot. This surface is indicated at 19 and, as shown in FIG. 8, may be the exposed surface of a preformed strip embedded in the substance of the last, it being noted that in any case in which such an embedded strip is employed, the exposed outer face of this strip will merge smoothly with the adjacent portions of the peripheral surface of the last proper. The strip, as shown in FIGS. 6 and 7, is Kanchored to the Ilast proper by inserted pins or screws although it may be spot welded to the last proper or may be embedded in the material of the last proper and permanently united to the rlatter during the molding of the last.

In FIG. 9, the last 20 is shown as having the surface 2'1 at its side, such surface being -a portion of the last itself, the latter having been ground away as indicated by the dotted line in forming this flat surface.

In the practice of the method set forth in the aforesaid co-pending application for Letters Patent, use is made of an appliance which clamps the tape or tapes to the boot upper to insure iirm contact of the parts while they are being bonded together. No particular d-iiiculty is experienced in preparing a suitable clamping appliance for use in bonding a tape to the side or back of a boot `upper for, at these parts of rthe upper, the curvature of the upper, both heightwise and transversely of the upper, is slight and does not vary greatly among boots of different sizes and styles so that the same clamping appliance is useful in making a substantial variety of boots. However, at the forepart of the yboot upper where slide fasteners are customarily installed, the curvature is substantial and of varying radius, both heightwise and transversely of the boot upper, and varies with different styles and sizes of boot so that ift would seemingly be necessary to provide clamping devices in a great number of shapes in order rto make the above process of general application. In the effort to overcome the difficulty just referred to, extended experiment was made to determine the possibility of providing an embedded strip, such as the strip 13a above referred to, which would be applicable to lasts of different styles and sizes and 'thus make a given clamping appliance of a greater range usefulness. With this in view, a number of lasts were se-lected (those selected being lasts .intended for use in making gaiter-type boots since these are :the mo-st -accurately designed of those employed in the making lof rubber footwear so far as iit is concerned). One of the lasts so selected was of a shape designed for making a gaiter with Ia flat heel, that is to say, one having a heel up to 1 inch in height; a second, for making la shoe having a Cuban heel, that is to say, one having a heel of from 11/2 inches to 2 inches in height; and a third, for use in making shoes having a high heel, that is rto say, for heels of from 21/2 inches to 31/2 inches or higher. Having selected these lasts, a center line was scratched on the front `of each last indicating the position at which the center of width yof a slide fastener should be located `on a shoe made on such a last. A profile was then made of rthe curve formed by this line. Such profile would have the shape of the forward edge of a vertical front-to-rear section of the last in the plane yof its central line. These several profiles were superposed :and from these a composite curve was drawn which was essentially the average shape of the three profiles. A template was then made having Ithe shape of this composite curve. When this template was iitted to lasts of various types and sizes, it Was found that it would iit very closely to the fronts of lasts of many styles and including those designed for womens childrens mens, boys and youths Wear, and designed for making shoes having heels of various heights. Having ascertained this fact, this `template was then employed in making steel strips such as those above referred to for insertion in the front portion of a last; and, upon making lasts having such steel strips embedded therein, it was found that it was possible by the use of the lasts thus prepared to carry out the process :of the aforesaid cowpending application by the use of clamping appliances of a very limited number of sizes, thus making the method wholly practicable from the commercial standpoint. It will be understood that the inserted strips of the last, shown in iFIGS. 2, 3 and 5, are desirably made according -to the above method of procedure; and, likewise, that when the cylindrically curved surfaces of the flast are made by grinding, Ias suggested in FIGS. l and 4, the heightwise curvature of the finished surface will likewise be made according to a template prepared as above suggested.

As already suggested, while a surface which, at any transverse section, is rectilinear, is preferred, some of the advantages of the invention may be obtained, especially at the front or back of the last, if fthe surface of the uniformly wide area be sl-ightly bowed or curved in transverse section, to the same radius at all such sections. Such an arrangement is illustrated in FIG. 10, wherein the last 22 is shown as having, at its front and rear, inset strips Z2 and Z3, which like the strips 139' and 14a extend heightwise of the last at locations corresponding to those at which tapes are to be placed in fthe shoe upper, and which `are tof uniform width from end-to-end, but which are slightly bowed, to the same radius, at all transverse sections, the longitudinal curvature to the strips corresponding to those of strips y13a and 14a.

However, it should be noted that, while the above procedure is desirable and preferred, ythe cylindrically curved surfaces may he vformed in accordance with other procedures within the scope of the appended claims.

I claim:

1. A last for use in the manufacture of an article of footwear such as a boot whose upper, at least, is of a synthetic plastic and which includes a length of textile tape adhesively bonded at the inner surface of the upper, the peripheral surface of the leg portion of the last comprising Va cylindrically curved area which, at any transverse section of the last, is rectilinear, said area being of substantially the uniform Width of said tape heightwise of the last and of a curvilinear length approximating the length of the tape which is to be `adhered to the boot upper, the edges of said area merging smoothly with the adjacent peripheral surface of the last proper at all points heightwise of the last.

2. A last, according to claim 1, wherein said cylindrically curved area is of a transverse width approximately yequal to the total width of a conventional slide fastener.

3. A last, according to claim 1, wherein said cylindrically curved area is located at the front of the leg portion of the last.

4. A last, according to claim 1, wherein said cylindrically curved `area is located at the side of the leg portion of the last.`

5. A last, according to claim 1, wherein said cylindrically curved area is located at the rear of the leg portion of the last.

6. A last for use in the manufacture of an article of footwear such as a boot whose upper, at least, is of a synthetic plastic and which includes a length of textile tape adhesively bonded at the inner surface of the upper, the leg portion of said last being of approximately elliptil transverse section but varying in transverse area from point-to-point heightwise and having a ribbonlike strip of hard material embedded in the substance of the last at the location at which the tape is applied to the boot upper, said strip approximating in width and length the tape which is to be used in the boot to be lasted upon said last, said strip being curved heightwise of the last to conform to the curvature of the latter and being rectilinear at the surface at any transverse section therethrough, the edges of the exposed surface of said strip merging smoothly with the adjacent peripheral surface of the last proper 5 6 at all points heightwise of the last, said last having means 228,664 Miller June 8, 1880 securing the strip to the last proper. 1,247,550 Larkin Nov. 20, 1917 7. A last, according to claim 6, wherein said strip is 1,495,136 Wilson May 20, 1924 located at the front of the leg portion of the last, and 1,679,016 Ashton July 31, 1928 wherein the surface of the strip is of a transverse Width 5 1,735,598 Creelman Nov. 12, 1929 approximately equal to the total width of a conventional 2,247,818 Nast July 1, 1941 slide fastener. 2,320,732 Laierty June 1, 1943 2,330,260 Baxter Sept. 28, 1943 References Cited in the file of this patent 2,759,206 Vinng Aug. 21, 1956 UNITED STATES PATENTS 10 FOREIGN PATENTS 24,830 Squire July 19, 1859 539,049 Italy Feb. 3, 1956

Claims

1. A LAST FOR USE IN THE MANUFACTURE OF AN ARTICLE OF FOOTWEAR SUCH AS A BOOT WHOSE UPPER, AT LEAST, IS OF A SYNTHETIC PLASTIC AND WHICH INCLUDES A LENGTH OF TEXTILE TAPE ADHESIVELY BONDED AT THE INNER SURFACE OF THE UPPER, THE PERIPHERAL SURFACE OF THE LEG PORTION OF THE LAST COMPRISING A CYLINDRICALLY CURVED AREA WHICH, AT ANY TRANSVERSE SECTION OF THE LAST, IS RECTILINEAR, SAID AREA BEING OF SUBSTANTIALLY THE UNIFORM WIDTH OF SAID TAPE HEIGHTWISE OF THE LAST AND OF A CURVILINEAR LENGTH APPROXIMATING THE LENGTH OF THE TAPE WHICH IS TO BE ADHERED TO THE BOOT UPPER, THE EDGES OF SAID AREA MERGING SMOOTHLY WITH THE ADJACENT PERIPHERAL SURFACE OF THE LAST PROPER AT ALL POINTS HEIGHTWISE OF THE LAST.