WO2010101452A1

WO2010101452A1 - An electrostatic dissipative shoe assembly

Info

Publication number: WO2010101452A1
Application number: PCT/MY2009/000045
Authority: WO
Inventors: Kek Hing Kow
Original assignee: Kek Hing Kow
Priority date: 2009-03-30
Filing date: 2009-03-30
Publication date: 2010-09-10
Also published as: CN102438476A; WO2010101452A8; CN102438476B

Abstract

An electrostatic dissipative shoe assembly (10) comprises a conductive strip (13) adhered on the surface of an inner sole (24) at the rear foot region (21) of a shoe (14) and extends toward she base of the internal wall at the farthest end of the back portion of the shoe (14), moves up along the surface of the internal wall, reaching the top of the wall, travels down along the external wall surface and stops at a point just above the bottom shoe sole and a conductive path (15) starting at the bottom of the shoe cover (16) travels underside along forefoot to the rear foot region and continues further until it moves upwards and reaches the stretchable opening rim of the shoe cover (16) so as to form a continual electrical path between the shoe (14) and shoe cover (16) when the shoe cover (16) is worn to the shoe (14) of the wearer (18) to conduct static electricity from the wearer (18) to the floor (19).

Description

An Electrostatic Dissipative Shoe Assembly

Field of the Invention

The present invention relates to an electrostatic discharge (ESD) shoe cover designed as a grounding medium without a need for a ground tail which will lead to efficient utility and effective usage of this unique technology.

Background of the Invention

It is well known to the electrostatic discharge (ESD) industry that ESD shoe covers are becoming an increasingly needed commodity in the combat against ESD damage in an effective ESD control program. Existing prior art and commercial products as-to-date, incorporates the use a conductive tail when designing an ESD shoe cover. Typical layout of the prior art are shown in Figure Ia. The conductive tail is sewn at the bottom of the shoe cover and the sewing extends upwards to the back portion of the shoe cover. When in use, the loose end of the conductive tail is placed into the shoe in order to make electrical contact with a human body when it is stepped upon. It is a known art and has been proven that even wearing a normal insulating sock, the pressure from the weight of our body and the perspiration from our foot inside the shoe create a reliable electrical contact with the conductive tail resting on the surface of the insole as long as the position of the conductive tail is placed in the correct location under the heel of the foot. However, the existing prior art has two weaknesses which makes them very ineffective to be used and is very vulnerable to ESD protection failure. The first shortcoming is that the existing ESD shoe cover with conductive tail requires the taking out of the foot in order to insert the conductive tail under the heel for proper electrical contact whenever such ESD shoe cover is used. This will not only cause inconvenience to the in-house production or factory staff that need to wear shoe cover regularly in daily lunch break, tea break, etc, it also cause great inconvenience to the outside contractors, service providers, visitors etc. especially those shoes with shoe lace. Cumbersome ESD shoe cover can cause delay and crowd jamming during production shift change at the entrance to the production floor.

The second shortcoming is the flaw in the use of the conductive tail. As the conductive tail is only attached to the shoe cover on one end, the opposite end is inserted freely into the shoe, it is found that improper wearing of the shoe cover or movement of the feet during walking might displace the conductive tail, pushing the tail to the side or to the wrong spot(s) of the insole, hi such condition, there will not be proper electrical contact between the conductive tail and the feet, resulting in ESD protection failure. These failure modes are illustrated in Figure Ib.

An earlier PCT application No PCT/MY2009/000015 discloses an electrostatic discharge shoe cover having an envelope with a flexible opening and a conductive strip, whereby during use, the envelope is formed for engulfing a shoe. The conductive strip is sewn on the underside along a substantial length of the shoe envelope. Around the heel section, the conductive strip continues to be sewn upwards and along one side of the flexible opening. The loose end of the conductive strip is finally sewn on the other side of the flexible opening forming a loop which can be pressed down by the heel of the foot of a wearer when the shoe is worn. The loop ensures that the static discharge from the body of the wearer is grounded however this invention lacks practicality for repeated use.

Therefore, there exists an industrial need to invent a more efficient and better ESD shoe cover with the objective of providing a long term solution to overcome the shortcomings of those existing ESD shoe covers with conductive tails.

Summary of the Invention

Disclosed herewith is a unique method to effectively ground the static charge from the foot of a wearer using an ESD shoe cover without the traditional use of a conductive tail attached. The invention consists of a specially designed ESD shoe cover system with unique features consist of the following embodiments:

In the first portion of the present invention, a conductive strip is attached partially inside the shoe and partially outside the shoe. The attachment can be done by means of adhesive coated on one side of the conductive strip or by sewing process. Such conductive strip can be made of cloth, paper, metal foil or plastic materials.

In the second portion of the invention, a conductive path is provided on a shoe cover starting at the bottom of the shoe cover and extends upwards until the stretchable opening rim of the shoe cover and connected to a conductive thread which is sewn along the stretchable opening of the shoe cover. The conductive path is a continuous ink or paint printed or silkscreened on the shoe cover or a continuous conductive strip made from one or a combination of the materials from paper, plastic, cloth and metallic foil. Specifically, upwards extension of the conductive path is made to overlap slightly with the conductive threads sewn along the stretchable opening rim of the shoe cover. This will ensure electrical continuity from the conductive path to the conductive thread.

The electrostatic dissipative shoe assembly of the present invention is an unique system that allows reliable drainage of static charge from a human body via the shoe, through the ESD shoe cover to the ESD floor ground, eliminating all the shortcomings as experienced by the ESD shoe cover with a conductive tail attached. Therefore a useful and practical solution for the ease of implementing the ESD control is achieved.

Brief Description of the Drawings

Other objects, features, and advantages of the invention will be apparent from the following description when read with reference to the accompanying drawings. In the drawings, wherein like reference numerals denote corresponding parts throughout the several views:

Figure 1 illustrates the layout of a typical prior art and the possible failure modes;

Figure 2 shows a perspective view of a shoe with a conductive strip of the present invention illustrating the location of the conductive strip placed on the shoe;

Figure 3 illustrates a perspective view of a shoe cover of the present invention;

Figure 4a is a side view of an electrostatic discharge shoe assembly of the present invention by combining the shoe and cover of Figures 2 and 3; and Y2009/000045

Figure 4b is a pictorial view of the electrostatic discharge shoe assembly of Figure 4a.

Detailed Description of the Preferred Embodiments

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known methods, procedures and/or components have not been described in detail so as not to obscure the invention. Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

An electrostatic dissipative shoe assembly (10) of the preferred embodiment of the present invention comprises of a conductive strip (13) placed inside and outside on a shoe (14) and a conductive path (15) provided on a shoe cover (16) as shown in Figures 4a and 4b. hi the first portion of the present invention, the objective is to provide a conductive strip as a common electrical contact point for both the human body and shoe cover (16). This is done by the conductive strip (13) adhering onto the inner sole of the shoe (14) at the heel region and extend the electrical continuity to the outer side of the back portion of the shoe (14) above the heel as shown in Figure 2, so that the conductive strip (13) will not be displaced or shifted even when subjected to vigorous movement or motion of the feet inside the shoe (14). However, the exact type and style of the shoe is not critical as long as the shoe makes contact with the ground and supports a wearer's foot. MY2009/000045

The conductive strip (13) is made from one or a combination of materials selected from plastic, paper, cloth and metal foil. It can be affixed onto the shoe (14) through adhesive means or by sewing process. The conductive strip (13) is preferably comprises of one adhesive side (13a) which is coated with an adhesive layer which can be water based or solvent based depending on the condition of use and the specific requirements and the other side (13b) is a non-adhesive side as shown in Figure 2.

For repeated use of the shoe cover (16) to achieve economical advantage, the conductive strip (13) can be permanently or semi permanently adhered onto the shoe (14). In this manner, whenever grounding of a human body through the feet is required, there is no need to take out the foot from the shoe (14) to insert a conductive strip or ribbon. As the conductive strip is already adhered onto the shoe (14), the personnel will only require to put on the external conductive shoe cover (16). In the absence of free movement unlike a grounding tail, there will be no displacement of conductive strip inside the shoe (14) during walking and there is less tendency of stretching which alleviate the problem tearing or breakage of the grounding tail. This will ensure reliable electrical continuity providing continuous ESD protection from body to ground.

In the second portion (12) of electrostatic dissipative shoe assembly (10), the conductive path (15) includes a conductive thread (15a) sewn along a stretchable opening (17) of the shoe cover (16). Such conductive thread connects to the rest of the conductive path extending from the external surface of the heel region of the shoe cover (16) to the bottom sole of the shoe cover (16) as shown in Figure 3. The material for the conductive thread (15a) is typically metal coated thread or made from stainless steel fiber, carbonized or carbon nanotube material. When the shoe cover (16) is worn, the stretchable opening (17) of the shoe cover (16) will gently grip the body of the shoe (14) as shown in Figures 4a and 4b. The metallic thread (15a) along the stretchable opening (17) of the shoe cover (16) ensures good electrical contact with the exposed conductive strip (13) affixed on the external surface of the heel region of the shoe (14) as described earlier. This will facilitate reliable electrical continuity to allow static charges to flow from the conductive strip (13) through the conductive thread (15a) to the remaining conductive path (15) of the shoe cover (16) and finally to ground when step on a static dissipative or conductive floor.

The portion of the conductive path after the conductive thread can be constructed from printed or silkscreened conductive ink or paint; conductive strip adhered on or sewn on made from one or a combination of the materials from paper, plastic, cloth and metal foil. Such conductive path (15) is preferably printed or silkscreened at the external surface of the bottom sole region of the shoe cover (16) to provide electrical contact with the ESD flooring (19) when the shoe cover (16) is worn. ESD flooring (19) refers to flooring having static dissipative property of approximately 10⁵ - 10¹¹ ohm or conductive property less than approximately 10⁵ ohm which is electrically grounded and to protect microchip from electrostatic discharge (ESD) damage in a manufacturing environment. The conductive path (15) printing at the bottom sole region is then extended backwards and upwards along the external surface of the heel region of the shoe cover (16) as shown in Figure 3. The conductive path (15) extension is made to slightly overlap with the conductive thread (15a) at the stretchable opening (17) of the shoe cover (16). This will provide reliable electrical continuity from the conductive thread (15a), via the conductive path (15), to the ESD flooring (19). The preferred printed conductive path (15) can be formulated from water based system or solvent based system commonly available from the market with the incorporation of conductive carbon powder, conductive carbon fiber, metallic powder or carbon nanotube material etc. to impart various electrical, mechanical, cosmetic and other desirable properties as needed commercially.

Such preferred printed or silkscreened conductive path (15), when covers a broader surface area at the bottom sole region of the shoe cover (16), can impart skid-resistance property. In other words, the area of the conductive path (15) at the bottom sole of the shoe cover (16) can be enlarged not only to provide improved contact surface coverage, it also provides better safety feature to a wearer. A typical example is a "fish-bone" pattern printed or silkscreened with the head or tail of the fish-bone pattern electrically connected to the conductive thread (15a) at the opening rim of the shoe cover (16).

The electrostatic dissipative shoe assembly (10) of the present invention is an unique system where static charges will be effectively drained from the body of the wearer (18) to the ESD flooring (19). The electrical charges travel from the sole of the feet, to the uniquely place conductive strip (13), to the conductive thread (15a) sewn at the stretchable opening (17) of the shoe cover (16), then to the conductive path (15) at the external surface of the heel and sole regions of the shoe cover (16) and finally to ground as shown in Figures 4a and 4b. The invention disclosed herewith has overcome all the shortcomings and problems associated with electrostatic discharge shoe cover with conductive tail and provides a useful and more practical method to drain static charges from body to ground.

In general, although this invention has been described in connection with specific forms and embodiment thereof, it will be appreciated that various modifications other than those discussed above may be resorted to without departing from the spirit and scope of the invention.

Claims

1. An electrostatic dissipative shoe assembly (10) comprising of: a conductive strip (13) adhered on the surface of an inner sole (24) at the rearfoot region (21) of a shoe (14) and extends towards the base of the internal wall at the farthest end of the back portion of the shoe (14), moves up along the surface of the internal wall (22), reaching the top of the wall, travels down along the external wall surface (23) and stops at a point just above the bottom shoe sole of said shoe (14); and a conductive path (15) starting at the bottom of the shoe cover (16) travels underside along forefoot to the rearfoot region and continues further until it moves upwards and reaches the stretchable opening (17) rim of said shoe cover (16) so as to form a continual electrical path between said shoe (14) and shoe cover (16) when said shoe cover (16) is worn to said shoe (14) of said wearer (18) to conduct static electricity from said wearer (18) to the floor (19).

2. The electrostatic dissipative shoe assembly (10) as claimed in claim 1, wherein said conductive path (15) is a continuous conductive ink or paint printed or silkscreened on said shoe cover (16) or a continuous strip made from one or a combination of the materials from paper, plastics, cloth and metal foil.

3. The electrostatic dissipative shoe assembly (10) as claimed in claim 2, wherein said conductive path (15) is preferably printed and said path (15) is formulated from water based or solvent based system with the incorporation of conductive carbon powder, conductive carbon fiber, metallic powder or carbon nanotube material.

4. The electrostatic dissipative shoe assembly (10) as claimed in claim 1, wherein said conductive path (15) is further connected to a conductive thread (15a) sewn along a stretchable opening (17) of said shoe cover (16).

5. The electrostatic dissipative shoe assembly (10) as claimed in claim 4, wherein said conductive thread (15a) is metal coated thread or made from stainless steel fiber, carbonized or carbon nanotube material.

6. The electrostatic dissipative shoe assembly (10) as claimed in claim 1, wherein said conductive strip (13) can be permanently or semi permanently adhered to said shoe (14).

7. The electrostatic dissipative shoe assembly (10) as claimed in claim 6, wherein said conductive strip (13) is made from one or a combination of materials selected from plastic, paper, cloth and metal foil.

8. The electrostatic dissipative shoe assembly (10) as claimed in claim 7, wherein said conductive strip (13) can be affixed onto said shoe (14) with adhesive means or by sewing process.