Antistatic fiber-foam shoe insoles, and method of manufacturing same

Abstract

To disclose: antistatic shoe insoles that include a flexible foam layer and antistatic filaments of textile material interspersed throughout the foam layer and extending passed or exposed at the surface of the shoe insole; and methods of making such an antistatic shoe insole.SOLUTION: The antistatic filaments are needle punched through the foam layer. The antistatic filaments may be any suitable antistatic material blended with any felt fiber such as wool fiber, cotton fiber, polyester fiber, or the like.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This application claims the benefit of U.S. Patent Application No. 62 / 870,296, filed July 3, 2019, the entirety of which is incorporated herein by reference.

[0002] The present invention relates to an antistatic shoe insole and a method for making an antistatic shoe insole that includes a flexible foam layer and antistatic filaments of a fibrous material that are substantially uniformly distributed throughout the foam layer and that extend beyond or are exposed at a surface of the shoe insole. [Background technology]

[0003] Modern technology requires that various industrial products be produced and / or operated in highly controlled environments, and electrostatic charges in those environments can impair the quality and operation of such products. For example, if charges build up to dangerous levels, electrostatic discharge can reduce the quality of products and even cause associated industrial hazards, such as electric shock.

[0004] For example, electrostatic discharge events cost the electronics industry billions of dollars each year. These costs are the result of the requirement to replace damaged and inoperable equipment affected by electrostatic discharge, and the downtime caused by these failures. Therefore, electrostatic discharge should be minimized or eliminated whenever possible. One of the more common electrostatic discharge events occurs when a person simply walks across a floor surface. In this example, static electricity is generated when the soles of the wearer's shoes touch and release the floor while walking.

[0005] This occurs when two dissimilar materials rub against each other, generating static electricity, creating an electrical charge and upsetting the positive-negative balance. During this rubbing, friction builds up a positive charge on one surface and a negative charge on the other. If the materials are conductive, this charge is easily dissipated. However, if the materials are not conductive, an unpleasant, and possibly dangerous, discharge can occur, resulting in a static shock. This static shock can not only have adverse effects on people, but can also seriously damage electronic devices that are sensitive to static electricity. This has led to the invention of various antistatic devices and equipment, including antistatic shoes.

[0006] When used in conjunction with static dissipative flooring, antistatic shoe insoles and footwear are a very reliable way of removing static electricity from people and the work environment. An example of this is when a charge passes from the wearer's foot, through the antistatic shoe insoles, and out of the wearer's shoes onto the floor. Rather than the charge being discharged onto sensitive electronics, the charge built up on the wearer is passed onto the floor and safely dissipated. In other words, antistatic shoe insoles and static dissipative footwear are designed to reliably transfer static charges away from the body to the floor. For antistatic and ESD shoes to be effective, both the shoe insoles and the shoes themselves must be ESD rated to provide continuous electrical contact of the foot to the ground, as required by global ESD standards.

[0007] However, current antistatic and / or ESD shoes generally include insoles with a thick single seam of conductive fabric at the toe area that the wearer can visually see and physically feel on the top surface of the insole. This previously mentioned thick single seam of conductive fabric in current antistatic and / or ESD shoe insoles is known to be uncomfortable for the wearer because it can directly touch the wearer's toes and can be physically felt directly under the foot. The wearer's discomfort from wearing the current antistatic and / or ESD shoe insoles is exacerbated by the fact that the shoe wearer often wears the antistatic and / or ESD shoe in industrial work environments for many hours at a time. The wearer's extended use of current antistatic and / or ESD shoe insoles significantly increases the likelihood of blisters on the wearer's feet and also increases the likelihood of foot bruising due to foot fatigue from excessive use. Thus, there is a continuing need for improved antistatic and / or ESD shoe insoles and the present invention provides a suitable solution in terms of both improved wearer comfort and higher static dissipation per person. Summary of the Invention

[0008] The present invention is directed to an antistatic shoe insole including a flexible foam having an antistatic layer and antistatic filaments uniformly distributed throughout the foam. More specifically, the antistatic insole comprises a flexible foam having an antistatic felt layer disposed thereon, with a plurality of filaments of the antistatic felt layer embedded in the flexible foam. In some embodiments, the foam is a polyurethane (PU) foam, but may be any other suitable flexible foam, and the antistatic layer is made from a blend of a nonwoven fabric and an antistatic additive. The antistatic additive may be comprised of conductive fibers to allow dissipation of static charges. Additionally, the insole has a portion of the filaments extending through a bottom surface of the insole such that the filaments are exposed to the outside.

[0009] Unlike the current antistatic and / or ESD insoles mentioned, the present invention has a smooth upper surface, so that the wearer's foot does not come into contact with seams or unpleasant surface changes, and essentially the wearer cannot feel any difference under his feet between a standard non-antistatic and / or ESD insole and that of the present invention, which greatly improves the comfort of the present invention for the shoe wearer over current antistatic and / or ESD insoles. Another advantage of the present invention over current antistatic and / or ESD insoles, as well as those of the prior art, is that the present invention provides a higher amount of conductive fibers per square centimeter covering almost the entire top and bottom surface, which greatly improves the static dissipation capability over those of the prior art, making the insole of the present invention more efficient and reliable during use, especially over long periods of use.

[0010] In another aspect, the present invention is directed to a process for manufacturing an antistatic shoe insole comprising a flexible foam layer and antistatic filaments of fibrous material distributed substantially uniformly throughout the foam layer and extending beyond the surface of the shoe insole, i.e. exposed at the surface. In some embodiments, the method includes disposing an antistatic felt layer on the flexible foam, the antistatic felt layer being a blend of a nonwoven fabric and an antistatic additive, the method further including penetrating the filaments of the antistatic layer into the flexible foam, the filaments being embedded in the foam and some of the filaments extending to a bottom working surface of the foam for external exposure. The antistatic filaments are suitably needle punched into the foam layer using a needle loom. In this method, the needle loom vibrates a needle plate to penetrate into the foam together with the antistatic felt layer. During the vibration, the needles grab some of the antistatic layer and punch the filaments of the antistatic felt layer into the foam, such that some of the filaments extend to a bottom working surface of the foam for external exposure. This exposure of the antistatic filaments allows static discharges to be dissipated up the shoe wearer's foot, through the sole of the footbed, and safely onto the floor.

[0011] The details of one or more embodiments are set forth in the accompanying description below. Other features and advantages will become apparent from the description and claims. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a perspective view of an embodiment of an antistatic insole according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of the embodiment of FIG. [Diagram 3] FIG. 1 illustrates a flexible foam for use in an antistatic insole, according to an embodiment of the present invention. [Figure 4] FIG. 2 illustrates a first step in the manufacture of an antistatic fiber-foam insole according to an embodiment of the present invention. [Diagram 5] FIG. 2 illustrates a second step in manufacturing an antistatic fiber-foam insole according to an embodiment of the present invention. [Figure 6] FIG. 2 shows a cross-sectional view of an antistatic fiber-foam insole during a second step of manufacturing the antistatic fiber-foam insole according to an embodiment of the present invention. [Figure 7] 1 is a cross-sectional view of an antistatic insole according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] As shown in FIG. 1, the antistatic shoe insole 2 includes a body portion 4 constructed of flexible foam 16. The body portion 4 has a bottom work surface 8 and a top surface 12. As known in the art, in some embodiments, the shoe insole 2 can be double-sided so that the top and bottom work surfaces look the same. In other embodiments, the top and bottom work surfaces can be different materials to ensure optimal comfort and design for the shoe wearer. Some non-limiting examples of the top surface of the present invention can be any conductive woven or nonwoven material, such as a steel-polyester felt blend or carbon-containing fibers, while some non-limiting examples of the bottom work surface of the present invention can be constructed of any conductive woven or nonwoven material, such as silver-coated fibers or fine inox wire. In other embodiments, there can be an optional cover layer disposed over the antistatic felt layer. For example, any suitable woven, knitted, or nonwoven fabric can be optionally used as the cover layer, provided it has suitable antistatic properties. The cover layer may be made of an antimicrobial material, a microbial material, a hygroscopic material, or any other suitable material that has inherent antistatic dissipative properties.

[0014] In some embodiments, the foam 6 is comprised of an open-cell polyurethane foam (PU), although other suitable materials such as closed-cell ethylene vinyl acetate (EVA) foam may also be used. Additionally, in certain embodiments, the foam 6 is comprised of a non-woven fibrous fill made from elastomeric polyesters or the like, which may replace traditional foams known in the art.

[0015] The antistatic shoe insole 2 further comprises an antistatic felt layer 18 disposed on the foam 6 as shown in FIGS. 1-2. The antistatic felt layer 18 forms the upper surface 12 of the antistatic insole 2. The antistatic layer 18 comprises a fiber fabric blended with an antistatic additive. For example, in some embodiments, the antistatic layer 18 is made from a polyester fabric blended with steel fibers. In other embodiments, depending on the application of the antistatic insole 2, the antistatic layer 18 can comprise a natural fiber fabric such as cotton, wool, jute, hemp, and polylactic acid, or more advanced natural materials such as bio-nylon, blended with an antistatic additive. In the antistatic layer 18, the antistatic additive comprises at least 1% by weight. In other embodiments, the additive can range from 1 to 50% by weight, and more preferably from 5 to 20% by weight. The antistatic additive can be steel fibers, carbon-containing fibers, silver-coated fibers, fine inox wire, or any other suitable conductive fibers.

[0016] 2, the insole 2 further includes filaments 24 of the antistatic layer 18 that penetrate the flexible foam 6. The filaments 24 are embedded in the foam at a given depth such that ends 24a of the filaments 24 extend to the bottom working surface 8 of the foam such that they are externally exposed. This exposure of the antistatic filaments 24 allows electrical static discharges to be safely dissipated through the foot of the shoe wearer, through the sole of the insole, and onto the floor.

[0017] In another embodiment, the present invention is directed to a method of manufacturing an antistatic insole. In some embodiments, the method includes disposing an antistatic felt layer on a flexible foam, the antistatic felt layer being a blend of an antistatic additive and a nonwoven fabric, and the method further includes penetrating a plurality of filaments of the antistatic layer into the flexible foam, the filaments being embedded in the foam and some of the filaments extending to a bottom working surface of the foam for external exposure. Figures 3-7 show various steps in one embodiment of a method of manufacturing an antistatic shoe insole according to the present invention. First, a flexible foam 16 is provided. The foam 16 may be a sheet of foam, but in other embodiments may be a continuous sheet of foam, which may be supplied from a roll or the like.

[0018] Preferably, the foam 16 is constructed of open cell PU foam, although other suitable materials, such as closed cell EVA foam, may be used. The density of the foam 16 is selected as desired for the particular purpose for which the antistatic shoe insole 2 may be used.

[0019] In a first step, an antistatic layer 18 is placed on the foam 16 as shown in FIG. 4. The antistatic layer 18 is a nonwoven fabric formed with an antistatic additive (i.e., a conductive material). The antistatic layer 18 includes a blend of conductive fibers and textile fibers. For example, in some embodiments, the antistatic layer 18 is preferably made from a blend of steel fibers and polyester fibers. In other embodiments, depending on the application of the antistatic insole 2, the antistatic layer 18 can include natural fiber fabrics such as cotton or wool, jute, hemp, and even more advanced natural materials such as polylactic acid, or bio-nylon, blended with an antistatic additive. The antistatic additive can be steel fibers, carbon-containing fibers, silver-coated fibers, fine inox wire, or any other suitable conductive fibers.

[0020] In the antistatic layer 18, the antistatic additive comprises at least 1% by weight. In other embodiments, the additive may range from 1 to 50% by weight, more preferably from 5 to 20% by weight. The antistatic additive may be steel fibers, carbon-containing fibers, silver coated fibers, fine inox wire, or any other suitable conductive fibers.

[0021] Like foam 16, the antistatic layer may be a sheet, as shown in Figures 4 and 5, but in other examples may be supplied onto foam 16 from a continuous roll. In some embodiments, antistatic layer 18 may be optionally affixed to foam 16 using a suitable adhesive to ensure a secure bond therebetween. In other embodiments, antistatic layer 18 may be affixed to the foam by stitching or any other suitable method.

[0022] Following step 100, in step 200, the filaments 24 of the antistatic layer 18 are embedded into the foam 16, as shown in Figures 6 and 7. A needle punch or needle weaving process is used to embed the filaments 24 into the foam 16. A needle weaving machine works by feeding the foam 16 along with the antistatic layer 18 into a needle weaving machine. The sandwiched foam and antistatic layer are fed into the needle weaving machine by an automated transport belt that introduces the two layers into a vibrating needle plate.

[0023] With the antistatic layer 18 overlying the foam 16, the combined structure is then placed under a number of needles 20, each carrying a number of downwardly extending barbs 22, as seen in FIG. 5. The needles 20 and barbs 22 are used to produce what is commonly referred to as needle punched felt and similar materials known in the art. A needle loom oscillates a needle plate to penetrate into a given thickness of the foam and antistatic layer sandwich. Essentially, the barbs 22 of the needles 20 grab a portion of the antistatic layer 18 and drive the filaments 24 of the antistatic layer 18 into the foam 16. A typical needle penetration is 12mm to 15mm, but can be adjusted depending on the thickness of the foam 16. The needles 20 carry the filaments 24 through the combined thickness of the antistatic layer 18 and foam 16, penetrating deep enough to form a mechanical bond between the foam 16 and the antistatic layer 18. Additionally, the needle penetrates to a sufficient depth such that the ends 24a of the filaments extend to the bottom working surface of the foam, portions 24a being exposed.

[0024] As the needle 20 moves downward through the antistatic layer 18, as shown in Figure 6, the barbs 22 capture a plurality of filaments 24 and pull them downward into the foam 16, causing the filaments 24 to extend from the top surface 12 as shown in Figure 2 and through the foam 16 as shown in Figure 6. Preferably, the ends of the fibers are pulled through the bottom surface 8 of the foam 16, thereby becoming exposed at and extending beyond the working surface 8. The needle 20 is then withdrawn. However, the elongated filaments 24 remain entangled within the foam and remain within the foam, as shown in Figure 7.

[0025] This process can be repeated as many times as desired to increase the density of the antistatic filaments 24 relative to the foam 16 by raising the needles 20, moving the combined antistatic layer 18 and foam 16 through the needle loom, and then moving the needles 20 down again to penetrate additional filaments 24 from the antistatic layer 18 into the foam 16. Thus, the density of the filaments 24 relative to the foam 16 is a function of the number of needles 20, the speed at which the antistatic layer 18 and foam 16 move under the needles 20, and the frequency of the up and down strokes of the needles 20.

[0026] As shown in FIG. 7, after the antistatic filaments 24 are needle punched into and through the foam 16, the composite structure can be cut into a desired insole shape to form an antistatic insole in a finishing step 300. If a single sided antistatic insole is produced, a cover layer can be secured over the antistatic layer 18. If a double sided antistatic insole is produced, two antistatic fiber infused sheets of antistatic layer 18 are secured together with an adhesive between them, as is well known in the art. As will be apparent, the final antistatic insole can be cut into the appropriate shape before or after it is assembled.

[0027] Although certain embodiments have been described in detail above, other variations are possible and may be within the scope of the following claims.

Claims

1. a flexible foam having a top surface and a bottom work surface; an antistatic layer, the antistatic layer being disposed on the foam, a plurality of filaments of the antistatic layer being embedded in the flexible foam, and ends of the plurality of filaments of the antistatic layer extending to a bottom working surface of the foam so as to be exposed to the outside; Antistatic shoe insoles.

2. 2. The antistatic shoe insole according to claim 1, wherein said foam is an open-cell polyurethane foam.

3. 2. The antistatic shoe insole of claim 1, wherein said foam is a closed-cell EVA foam.

4. 10. The antistatic shoe insole of claim 1, wherein the antistatic layer comprises a blend of nonwoven fabric and conductive fibers.

5. 10. The antistatic shoe insole of claim 1, wherein said antistatic layer comprises a blend of polyester cloth and steel fibers.

6. 5. The antistatic shoe insole of claim 4, wherein said conductive fibers comprise at least 1% by weight of said antistatic layer.

7. 5. The antistatic shoe insole according to claim 4, wherein the conductive fibers are in the range of 5 to 20% by weight of the antistatic layer.

8. 10. The antistatic shoe insole of claim 1, wherein the antistatic layer is attached to the foam with an adhesive.

9. 1. A method for producing an antistatic foam insole, comprising the steps of: placing an antistatic layer over the flexible foam, the antistatic layer comprising a nonwoven fabric having an antistatic additive; penetrating a plurality of filaments of the antistatic layer into a given thickness of the flexible foam, embedding the filaments in the flexible foam, with a portion of the filaments extending to a bottom working surface of the flexible foam so as to be exposed to the outside; The method includes:

10. 10. The method of claim 9, further comprising attaching the antistatic layer to the flexible foam with an adhesive.

11. 10. The method of claim 9, further comprising cutting the antistatic layer and the flexible foam into a shoe shape.

Images