US 3293494 A
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Description (OCR text may contain errors)
Dec. 20, 1966 J. H. FISCHER I OONDUCTIVE SHOE METHOD OF MAKING SAME Filed April .24, 1964 ww ww BYQMQM ATTORNEY States atent 3,293,494 CONDUCTIVE SHGE METHOD F MAKING SAME Joseph H. Fischer, Woodbury, Conn., assigner to United States Rubber Company, New York, NSY., a corporation of New Jersey Filed Apr. 24, 1964, Ser. No. 362,222 8 Claims. (Cl. 317-2) This invention relates to an electric-ally conductive shoe and, more particularly, .to a sole construction for a shoe that Iprovides an electrical grounding path for the wearer. The invention also relates to novel methods for the production and manufacture of the improved shoe.
Heretofore, the vast majority of conductive shoes were m-ade with entirely conductive soles and/or heels, thus, requiring a great ramount of conductive material. This material, such as conductive rubber, was very expensive and, thus, great-ly increase-d the cost of the shoe.
Successful attempts have been made to produce `a conductive shoe having a non-conductive sole equipped with conductive inserts for providing an electrical path between the ground and the wearers foot. One such shoe construction was shown in United States Patent No. 2,710,366, issued on June 7, 1955, to J. S. Stern, Jr., et al., wherein a thick conductive rubber plug was inserted into a wooden heel to provide contact between the wearer and the ground. The plug was securely held in place by the long bearing surface between the wooden heel and the plug. Furthermore, the rigidity of the heel prevented the plug from bending and working loose from the heel.
A similar type plug was found to be ineffective when adapted for use with a relatively ilexible, thin soled shoe, such as a sneaker or the like. The continual llexing of such a sole provides bending force at the plug and outsole interface that tend -to loosen the bond and may result in a removal of the plug from the outsole.
Accordingly, it is an object of this invention to provide an improved conductive sole construction and method of making same.
Another object is to provide an improved conductive plug for a flexible non-conductive sole construction.
A further object is to provide a conductive sole construction that is extremely simple and inexpensive to fabricate and, yet, results in an integral unit with Iwe-araresisting qualities.
These yand other objects are accomplished in accordance with this invention which comprises a non-conductive outsole having yan aperture extending therethrough, a non-metallic flexible conductive plug in said aperture, the plug having a ground engaging surface and an inner sur-face, the ground engaging s-urface having an inwardly extending groove forming an outer plug portion that is securely bon-ded to the outsole and a central flexible plug portion; and conductive means interconnecting the inner plug surface with the innermost portion of the shoe, so that, the conductive means and the plug form an electrical grounding path for the wearer.
In accordance with the preferred method of making the Iabove sole construction, the plug is placed into the outsole aperture and the -groove is pressed or cut into the plug surface to from an annular plug portion and a central flexible plug portion; the pressing step is effective to force the ann-ular plug .portion firmly against the inner periphery of the -outs-ole aperture and to force the inner plug surface rmly against a gum layer that overlies the inner portion of the outsole. The entire assembly is then vulcanized to form a molecular bond between the conductive plug and the adjacent rubber surfaces.
For a better understanding of the present invention together with other and further objects thereof, reference is made to the following description, taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.
Referring now to the drawing:
FIG. 1 is a cross-sectional View of the shoe embodying the sole construction of the present invention and viewed along line I-I of FIG. 2; and
FIG. 2 is a bottom plan view of a shoe showing the s-ole construction of the present invention.
Referring to the drawing, a shoe, such as a sneaker or the like, is shown generally at 10. Shoe 10 is il1ustrated with a conventional canvas upper 11, however, any suitable material may be used for the upper. A conventional non-con-ductive calendered rubber -outsole 12 is secured to upper 11 around the upper periphery of the outsole. A foxing strip 13 provides an additional bonding means between upper 11 and outsole 12.
Outsole 12 is of unitary construction and is relatively flat from the toe to the .heel portion of the shoe. Outsole 12 is provided with a fabric non-conductive sole binder 14 that is constructed of a combination friction binder stock and overlies the outsole 12 on the inner portion of shoe 10. A circular aperture 15 is cut through both binder 14 and outsole 12 in the ball portion of the shoe and a conductive rubber plug 16, the exact size of aperture 15, is molecularly bonded by v-ulcanization Within the aperture. A circular groove 17 is pressed or cut into the external surface of plug 16 to form an annular plug portion 18 which is in contact with the inner periphery of aperture 15 formed in outsole 12. A relatively ilexible central plug .portion 19 is also formed by groove 17.
A similar aperture 20 is cut through the heel portion of outsole 12 and binder 14 and has a conductive rubber plug 21 located therein. Plug 21 also has a groove 22 pressed or cut into the ground engaging portion thereof to form an outer annular plug portion 23 and a central ilexible plug portion 24.
There are many conductive rubber compounds that are usable with its invention, however, it is preferred t-o use a compound that will be relatively ilexible when vulcanized. The compound preferred for 'use for all of the conductive rubber elements of the present improved sole construction is set forth below, wherein the parts of each compound is represented by the number preceding that compound:
100.0 MBlSH-Brown crepe (natural rubber) #4. 0.31 Lurex (zinc laur-ate).
44.4 Vulcan-XCR Black (carbon black).
13.3 Coray oil #4U-(naphthenic oil).
4.5 Zinc oxide.
.39 Ross wax (hydrocarbon wax).
.25 Flectol H (1,2-dihy-dro 2,2,4-
trimethylquinoline) .25 Aminox (reaction product of diphenylamine and acetone).
.17 ESEN (phthalic anhydride).
.19 Monex (tetramethy-lthiuram m-onosulfied).
.75 MBTS (benzothiozyl disulfide).
.44 DOTG (diorthotolyl quanidine).
A specic insole construction shown generally at 25 in FIG. l is incorporated into shoe 10 to provide a conductive interconnecting means between the inner surfaces 26 and 27 of plugs 16 and 21, respectively, and the bottom of the wearers foot.
Insole 25 has an innermost foot engaging layer of fabric 30. Fabric 30 may be any conventional, non-insulating fabric, such as Osnaburg. The 4only requirement is that the fabric be of a nature that it readily accepts moisture from the wearers -foot thereby becoming conductive and, thus permitting the flow of electrical changes from the foot of the wearer to a layer 31 of conductive rubber cemented or otherwise joined to the underside of fabric 30. A second layer lof conductive rubber 32 directly `overlies fabric 14 and is bonded by vulcan'ization to surfaces 26 and 27. A non-conductive fabric 33 separates conductive layers 31 and 32 over most of the area of the sole construction but the layers 31 and 32 are in intimate contact through an opening 34 cut through fabric 33.
A conventional foam rubber arch cushion 35 is provided in the shank and heel portions of the sole construction.
It will be apparent from the above description that an electrical grounding path is provided bet-Ween the bottom of the wearers foot and the ground via the interstices of fabric 30, conductive rubber layer 31, opening 3a conductive rubber layer 32, and either or both of the conductive -rubber plugs 16 and 21.
All of the rubber components of the improved shoe construction are fabricated before valcanization, therefore, all components are in the gum or unvulcanized state during assembly. Insole 25 is assembled by first securing fabric 3) to conductive gum` `layer 31. The bottom insole fabric layer 33 is then die-cut to provide opening 34 and fitted to the underside of gum layer 31 with arch cushion 3S therebetween. The conductive gum layer 32 is then placed over the bottom portion of fabric layer 33 and the assembly is laminated, thereby pressing gum 32 through opening 34 into intimate contact with conductive gum layer 31.
In the fabrication of shoe 10, the upper 11 is placed on a last and secured to the insole assembly 25. Outsole 12 and `binder 14 with apertures 15 and 20 cut therethrough are then secured to the underside :of the insole 2S and the under-turnedperiphery of upper 11. Foxing strip 13 is then positioned around the juncture of upper 11 and outsole 12. The conductive gum plugs 16 and 21 are then manually placed into apertures 15 and 20, respectively.
Referring t-o FIG. 1, an annular groove cutting tool 36 having a cutting edge 37 andan opening 38 is then brought into position adjacent the gro-und engaging portion of the plugs and pressed into the plugs (as shown in broken lines in FIG. 1) to form grooves 17 and 22. Tool 35 may be heated to provide smoother entry into plugs 16 and 21 and may also be rotated to increase the cutting and pressing ability `of the tool. The action of tool 36 not only forms grooves 17 and 22 but also forces the soft rubber of plugs 16 and 21 firmly against gum layer 32 and forces the annular plug portions 18 and 23 outwardly against the inner periphery of -apertures and 20, respectively, Iformed in outsole 12. Since the rubber is unvulcanized andrelatively tacky, a very strong bond is formed between the plugs and the adjacent rubber surfaces. Upon completion of the 4grooving operation, the entire shoe assembly is vulcanized to form -a completed shoe.
It Iwill be apparent fromv the foregoing that, because of the firm bond accomplished by the grooving operation, the plugs will not be appreciably affected by the repeated flexing of the outsole 12 during walking or other movements of the shoe. Furthermore, the central flexible plug portions 19 and 24, which constitute the greater area of the ground engaging portion of the plugs, are free to flex without affecting the bond between the plugs and lthe adjacent rubber surfaces. Although the diameters of grooves 17 and 22 are not critical, it is desirable to form the grooves so that the diameters of the central plug portions are equal to at least one-half the overall plug diameters. This insures that the central plug portions will have sufficient strength to -resist separation from the remainder of the plug, and yet, have sufficient flexibility to reduce the bending stresses between the plugs and the adjacent rubber surfaces to which `the plugs are bonded.
It will be apparent from the foregoing description that the present invention provides an improved conductive shoe construction that is especially useful with flexible, thin-soled shoes; that is inexpensive and simple to fabricate; that is constructed of materials that enable the entire shoe to be .washed without harm to the shoe; and that is completely free of metallic parts.
While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true scope and spirit of the invention.
Having thus described my invention, what I claim and desire to protect by Letters Patent is:
1. A conductive shoe comprising: a non-conductive thin, exible outsole having an aperture extending therethrough; a non-metallic flexible conductive plug in said aperture, said plug having `a thickness approximating the thickness of said outsole, said plug having a ground engaging surface and an inner surface, said ground engaging surface having an inwardly extending continuous groove forming an outer plug portion that is securely bonded to said outsole and a central exible plug portion; and conductive means interconnecting said inner plug surface with the innermost portion of said shoe, so that, said conductive means and said plug form an electrical grounding path fo-r the wearer.
2. A conductive shoe comprising: a non-conductive thin, exible outsole having an aperture extending therethrough; a flexible conductive rubber plug in said aperture, said plug having a thickness approximating the thickness `of said outsole, said plug having a ground engaging surface and an inner surface, said ground engaging surface having an inwardly extending continuous Igroove forming an router plug portion that is securely bonded to said outsole `and a central flexible plug portion; and conductive means interconnecting said inner plug surface with the imiermost portion of said shoe, so that, said conductive means and said plug form an electrical grounding path for the wearer.
3. A conductive shoe comprising: a non-conductive thin, flexible outsole having an aperture extending through the heel portion thereof land an aperture extending through the `ball portion thereof; fiexible conductive rubber plugs in said apertures each of said plugs having a thickness approximating the thickness of said outsole, said plugs having ground engaging surfaces and inner surfaces, each of said ground engaging surfaces having an inwardly extending continuous `groove forming an outer plug portion that is securely bonded to said outsole and a central flexible plug portion; Iand conductive means interconnecting said inner plug surfaces with the innermost portion of said shoe, so that, said conductive means and said plugs form an electrical ygrounding path for the wearer.
4. The conductive shoe of claim 3 wherein said conductive means comprises a layer of conductive rubber overlying and connecting said inner plug surfaces and having a molecular bond directly with said inner plug surfaces.
S. The conductive shoe of claim 3 wherein said outer plug portions have molecular bonds around their peripheries directly with the inner peripheries of said outsole apertures.
6. A conductive shoe comprising: a non-conductive thin, flexible outsole having a circular aperture extending therethrough', a circular non-metallic flexible conductive plug in said aperture, said plug having a thickness approximating the thickness of said outsole, said plug having a ground engaging surface and an inner surface, said ground engaging surface having an inwardly extending circular groove `forming an outer annular plug portion that is securely bonded to said outsole around the inner periphery of said aperture, and a central flexible plug portion; and conductive egos/19a means interconnecting said inner plug surface with the innermost portion of said shoe, so that, said conductive means and said plug form an electrical grounding path for the wearer.
'7. The conductive shoe of claim 6 wherein the diameter of said central iieXible plug portion is equal to at least one-half of the overall diameter lof said plug.
8. In a method of making a conductive shoe the steps of: providing a non-conductive outsole with a circular aperture extending therethrough; positioning a layer of conductive gum over the inner surface of said outsole; placing a circular conductive gum plug into said aperture; pressing a circular groove into lthe surface of said plug to form an annular plug portion and a central flexible plug portion, said pressing step being effective to force said annular plug portion nrnly against the inner Iperiphery of said outsole aperture and to force the inner surface 6 of said plug tirrnly against said gum layer; and vulcanizing said shoe; whereby, said plug is molecularly bonded to said conductive layer and said outsole.
MELTON O. HlRSHFlELD, Prima/y Examiner.
I. A. SLVERMAN, Assistant Examiner.
SAMUEL BERNSTEIN, Examiner.