Antistatic fiber-foam shoe insole, and method for manufacturing the 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 Jul. 3, 2019, the entire disclosure of which is hereby incorporated by reference herein.

[0002] The present invention relates to an antistatic shoe insole including a flexible foam layer and antistatic filaments of a fibrous material that are substantially uniformly dispersed throughout the foam layer and extend beyond the surface of the shoe insole, i.e., are exposed at the surface, and a method of manufacturing the antistatic shoe insole.

Background Art

[0003] In modern technology, various industrial products need to be produced and / or operated in a highly controlled environment, and the electrostatic charges in those environments can impair the quality and operation of such products. For example, when charges accumulate to dangerous levels, electrostatic discharge can degrade the quality of products and even cause related industrial disasters such as electric shock.

[0004] For example, electrostatic discharge events impose billions of dollars in costs on the electronics industry each year. These costs are the result of the need to replace damaged and inoperable equipment affected by electrostatic discharge and the downtime resulting from these failures. Therefore, electrostatic discharge should always be minimized or eliminated if possible. One of the more common electrostatic discharge events occurs when a person simply walks across the surface of a floor. In this example, static electricity is generated when the wearer's shoe sole touches and then leaves the floor during walking.

[0005] This occurs when two different materials rub against each other, generating static electricity and disrupting the balance of positive and negative charges. During this rubbing, friction causes positive charges to accumulate on one surface and negative charges on the other. If the materials are electrically conductive, these charges are easily dissipated. However, if the materials are not electrically conductive, an unpleasant, and possibly dangerous, discharge occurs, which can result in an electrostatic shock. This electrostatic shock can not only harm people but also cause serious damage to electronic devices that are susceptible to static electricity. Therefore, various anti-static devices and equipment, including anti-static shoes, have been invented.

[0006] When used in conjunction with electrostatic discharge flooring, antistatic insoles and footwear are a highly reliable method for removing static electricity from people and the work environment. This example involves charge being discharged from the wearer's feet, through the antistatic insoles, and out of the wearer's shoes onto the floor. Instead of the charge being released to sensitive electronic devices, the charge accumulated on the wearer is transferred to the floor and safely dissipated. In short, antistatic insoles and electrostatic discharge footwear are designed to reliably dissipate static charge from the body to the floor. For antistatic and ESD shoes to be effective, both the insoles and the shoes themselves must be ESD rated to provide continuous electrical contact between the foot and 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 fiber in the toe area that the wearer can visually see and physically feel on the upper surface of the insole. This aforementioned thick, single seam of conductive fiber in the 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 therefore be directly physically felt under the foot. The discomfort experienced by the wearer from wearing the current antistatic and / or ESD shoe insoles is exacerbated by the fact that shoe wearers often wear antistatic and / or ESD shoes for many hours at a time in industrial work environments. Prolonged use by the wearer with the current antistatic and / or ESD shoe insoles significantly increases the likelihood of blisters forming on the wearer's feet, as well as the likelihood of foot bruises resulting from foot fatigue due to excessive use. Therefore, 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 greater electrostatic dissipation per person. [Overview of the project]

[0008] The present invention relates to an antistatic shoe insole comprising a flexible foam having an antistatic layer and antistatic filaments uniformly dispersed throughout the foam. More specifically, the antistatic insole comprises a flexible foam having an antistatic felt layer placed on top of the flexible foam, with multiple filaments of the antistatic felt layer embedded in the flexible foam. In some embodiments, the foam is polyurethane (PU) foam, but may be any other suitable flexible foam, and the antistatic layer is made from a blend of nonwoven fabric and an antistatic additive. The antistatic additive may consist of conductive fibers to allow for the dissipation of static charge. Furthermore, the insole extends through the bottom surface of the shoe insole so that some of the filaments are exposed to the outside.

[0009] Unlike existing antistatic and / or ESD insoles mentioned, the present invention has a smooth top surface, thereby preventing the wearer's feet from coming into contact with seams or unpleasant surface variations. Essentially, the wearer will not feel any difference between a standard non-antistatic and / or ESD insole and one of the present invention, which significantly improves the comfort of the present invention for the shoe wearer compared to existing antistatic and / or ESD insoles. Another advantage of the present invention over existing antistatic and / or ESD insoles, as well as those of the prior art, is that the present invention provides a greater amount of conductive fibers per square centimeter, covering almost the entire top and bottom surface, which significantly improves the electrostatic dissipation capacity compared to the prior art, thereby making the insole of the present invention more efficient and reliable during use, especially over long periods of use.

[0010] In another embodiment, the present invention is directed to a process for manufacturing an antistatic shoe insole comprising a flexible foam layer and antistatic filaments of a fibrous material substantially uniformly dispersed throughout the foam layer and extending beyond the surface of the shoe insole, i.e., exposed on the surface. In some embodiments, the method comprises placing an antistatic felt layer on top of the flexible foam, the antistatic felt layer being a blend of a nonwoven fabric and an antistatic additive, and the method further comprises penetrating the filaments of the antistatic layer into the flexible foam, the filaments being embedded in the foam, and a portion of the filaments extending to the bottom working surface of the foam so as to be exposed to the outside. The antistatic filaments are optimally 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 grasp a portion of the antistatic layer and punch the filaments of the antistatic felt layer into the foam, so that a portion of the filaments extends to the bottom working surface of the foam so as to be exposed to the outside. This exposure of the antistatic filament dissipates electrostatic discharge so that it travels through the foot of the shoe wearer, through the insole of the sole, and safely dissipates to the floor.

[0011] Details of one or more embodiments are described in the appendix below. Other features and advantages will become apparent from this specification and the claims. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view of one embodiment of an antistatic insole according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view of the embodiment shown in Figure 1. [Figure 3] This figure shows a flexible foam used in an antistatic insole according to an embodiment of the present invention. [Figure 4] This figure shows the first step in the production of an antistatic fiber-foam insole according to an embodiment of the present invention. [Figure 5] This figure shows a second step in manufacturing an antistatic fiber-foam insole according to an embodiment of the present invention. [Figure 6] This figure shows a cross-sectional view of an antistatic insole during a second step of manufacturing an antistatic fiber-foam insole according to an embodiment of the present invention. [Figure 7] This is a cross-sectional view of an antistatic insole according to an embodiment of the present invention. [Modes for carrying out the invention]

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

[0014] In some embodiments, the foam 6 is composed of open-cell polyurethane foam (PU), but other suitable materials such as closed-cell ethylene vinyl acetate (EVA) foam can also be used. Furthermore, in certain embodiments, the foam 6 is composed of a nonwoven fiber filling made from elastomer polyester or the like, which can replace conventional foams known in the art.

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

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

[0017] In other embodiments, the present invention is directed toward a method for manufacturing an antistatic insole. In some embodiments, the method comprises placing 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 comprises penetrating a plurality of filaments of the antistatic layer through the flexible foam, the filaments being embedded in the foam, and some of the filaments extending to the bottom working surface of the foam so as to be exposed to the outside. Figures 3-7 show various steps in one embodiment of a method for 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, it may be a continuous sheet of foam that can be supplied from a roll or the like.

[0018] Preferably, the foam 16 is composed of open-cell PU foam, but other suitable materials such as closed-cell EVA foam may also be used. The density of the foam 16 is selected to be desirable for the specific purpose for which the antistatic shoe insole 2 may be used.

[0019] In the first step, an antistatic layer 18 is placed on the foam 16, as shown in Figure 4. The antistatic layer 18 is a nonwoven fabric formed together with an antistatic additive (i.e., a conductive material). The antistatic layer 18 includes a blend of conductive fibers and woven 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 may include a blend of natural fiber fabrics such as cotton or wool, jute, or hemp, and an antistatic additive with more advanced natural materials such as polylactic acid or bionylon. The antistatic additive can be steel fibers, carbon-containing fibers, silver-coated fibers, fine inox wire, or any other suitable conductive fiber.

[0020] In the antistatic layer 18, the antistatic additive constitutes at least 1% by weight. In other embodiments, the additive can be in the range of 1 to 50% by weight, more preferably in the range of 5 to 20% by weight. The antistatic additive can be steel fiber, carbon-containing fiber, silver-coated fiber, fine stainless wire, or any other suitable conductive fiber.

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

[0022] Following step 100, in step 200, as shown in FIGS. 6 and 7, the filaments 24 of the antistatic layer 18 are embedded in the foam 16. To embed the filaments 24 in the foam 16, a needle punching or needle weaving process is performed. The needle loom functions by feeding the foam 16 together with the antistatic layer 18 into the needle weaving machine. The foam and the antistatic layer stacked like a sandwich are supplied to the needle loom by an automatic conveyor belt that introduces the two layers into a vibrating needle plate.

[0023] Next, with the antistatic layer 18 overlapping the foam 16, the combined structure is placed under a plurality of needles 20 each carrying a plurality of downwardly extending barbs 22 as seen in FIG. 5. The needles 20 and barbs 22 are used to manufacture what is commonly referred to as needle punch felt and similar materials known in the art. A needle loom vibrates a needle plate to penetrate into a sandwich of the foam and antistatic layer of a given thickness. Basically, the barbs 22 of the needles 20 grasp a part of the antistatic layer 18 and drive the filaments 24 of the antistatic layer 18 into the foam 16. A typical needle penetration is from 12 mm to 15 mm, but it can be adjusted according to the thickness of the foam 16. The needles 20 carry the filaments 24 through the combined thickness of the antistatic layer 18 and the foam 16 and penetrate to a depth sufficient to form a mechanical bond between the foam 16 and the antistatic layer 18. Further, the needles penetrate to a depth such that a plurality of ends 24a of the filaments extend to the bottom working surface of the foam and that part 24a is exposed externally.

[0024] As shown in FIG. 6, when the needles 20 move downward through the antistatic layer l8, the barbs 22 capture a plurality of filaments 24 and draw them downward into the foam 16, whereby the filaments 24 extend from the upper surface 12 as shown in FIG. 2 and extend through the foam 16 as shown in FIG. 6. Preferably, the ends of the fibers are drawn to pass through the bottom surface 8 of the foam 16, thereby being exposed at the working surface 8 and extending beyond the working surface 8. Thereafter, the needles 20 are pulled up. However, the elongated filaments 24 become entangled within the foam and remain within the foam as shown in FIG. 7.

[0025] This process can be repeated a desired number of times to increase the density of antistatic filaments 24 in the foam 16. To do this, the needle 20 is raised, the combined antistatic layer 18 and foam 16 are moved within the needle loom, and then the needle 20 is moved downward again to penetrate additional filaments 24 from the antistatic layer 18 into the foam 16. Thus, the density of filaments 24 in 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 Figure 7, the antistatic filaments 24 are needle-punched into the foam 16 and through the foam 16, and the composite structure can be cut into the desired shoe insole shape to form an antistatic shoe insole in the finishing step 300. When manufacturing a single-sided antistatic shoe insole, a cover layer can be fixed on top of the antistatic layer 18. When manufacturing a double-sided antistatic shoe insole, the antistatic layers 18 of two antistatic fiber-injected sheets are fixed together with an adhesive between them, as is well known in the art. As is obvious, the final antistatic shoe insole can be cut into the appropriate shape before or after assembly.

[0027] While several embodiments have been described in detail above, other modifications are possible. Other embodiments may fall within the scope of the following claims.

Claims

1. A flexible foam having an upper layer and a bottom working layer, Antistatic layer and Equipped with, The antistatic layer is disposed on the upper surface of the upper layer of the flexible foam, Multiple filaments made of substantially the same material as the antistatic layer are dispersed throughout the flexible foam and embedded in the flexible foam. Each of the plurality of filaments extends through the flexible foam to the lower surface of the bottom working layer such that the end of each of the plurality of filaments is exposed to the outside of the flexible foam. Antistatic shoe insoles.

2. The aforementioned flexible foam is an open-cell polyurethane foam. The antistatic shoe insole according to claim 1.

3. The aforementioned flexible foam is closed-cell EVA foam. The antistatic shoe insole according to claim 1.

4. The antistatic layer comprises a blend of nonwoven fabric and conductive fibers. The antistatic shoe insole according to claim 1.

5. The antistatic layer includes a blend of polyester fabric and steel fibers. The antistatic shoe insole according to claim 1.

6. The conductive fibers constitute at least 1% by weight of the antistatic layer. The antistatic shoe insole according to claim 4.

7. The conductive fibers make up 5 to 20% by weight of the antistatic layer. The antistatic shoe insole according to claim 4.

8. The antistatic layer is attached to the flexible foam with an adhesive. The antistatic shoe insole according to claim 1.

9. A method for manufacturing an antistatic foam insole, An antistatic layer containing a nonwoven fabric with an antistatic additive is placed on the upper surface of a flexible foam, The method involves inserting a plurality of filaments made of substantially the same material as the antistatic layer into the flexible foam of a given thickness, dispersing the filaments throughout the flexible foam, and embedding them in the flexible foam, wherein each of the plurality of filaments extends through the flexible foam to the bottom working layer such that the end of each of the plurality of filaments is exposed to the outside of the flexible foam. Methods that include...

10. The antistatic layer is further attached to the flexible foam with an adhesive. The method according to claim 9.

11. The antistatic layer and the flexible foam are further cut into the shape of a shoe. The method according to claim 9.

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