Patent Application
20050146833
The present invention relates to electrostatic discharge devices, and more particularly to a disposable grounding device for preventing the buildup of excess electrostatic charge.
When sensitive electronic parts are handled or touched by an individual, the sudden discharge of electrostatic charge from the individual can damage or destroy these components. Grounding straps are used in the electronic industry to insure that workers are at the same electrical potential as ground, and thus prevent the buildup of excess electrostatic charge that can harm electronic components. Grounding straps operate by establishing an electrical pathway that is electrically connected from an individual's wrist or other body part to electrical ground. This electrical pathway must be sufficiently electrically conductive to maintain the person at the same electrical potential as ground, while not so electrically conductive as to endanger any person who may come in contact with a charged source. An electrical pathway with a resistance of between 750 kilohms to 10 megohms is typically preferred.
There are numerous wrist straps that provide an electrical pathway coupled with a discrete resistance in the desired range. These wrist straps are typically intended for reuse over and over again. More recently disposable wrist straps have come into being. These wrist straps involve the use of relatively low cost material that is designed to be used once, and then thrown away. Users find this more convenient. Prior art disposal wrist straps may use a conductive plastic material attached to another material. As this conductive plastic material may have a resistance less than the desired range, the conductive plastic may be cut or slit in a number of locations to create a longer, narrower, more convoluted pathway from the individual to ground through the conductive plastic strip. This more convoluted pathway increases the resistance to the desired range. Alternatively, the thickness of the conductive plastic for a given location may be constricted, thus also increasing resistance of the conductive plastic.
Another prior art strap uses a conductive plastic material having an electrically interrupted segment, with the interrupted segment being bridged by a resistor of the desired resistance.
One difficulty with these techniques is that they involve more expensive manufacturing steps. For example, the techniques of slitting the material to create the more convoluted electrical path and incorporating a separate resistor add to the cost of the disposable wrist straps. As cost is a key factor in the manufacturing of a disposable product, the elimination of either of these steps is to be desired.
In accordance with an embodiment of the present invention, a disposable grounding strap is provided. The disposable grounding strap includes an elongate conductive material uniformly conductive along its length. A first outer layer is coated with non-conductive heat sealable plastic on a side disposed adjacent to a first side of the conductive material, with the first outer layer having a width greater than the width of the conductive material. A second outer layer is coated with non-conductive heat sealable plastic on a side disposed adjacent to a second side of the conductive material, with the second outer layer having a width greater than the width of the conductive material. The heat sealable plastic of the second outer layer is partially heat sealed to the heat sealable plastic of the first outer layer along at least a portion of the length of the conductive material.
A more complete understanding of the present invention, as well as further features and advantages of the invention, will be apparent from the following detailed description and the accompanying drawings.
The following detailed description of preferred embodiments refers to the accompanying drawings which illustrate specific embodiments of the invention. Other embodiments having different structures and operations do not depart from the scope of the present invention.
In a preferred embodiment, the uniformly conductive layer 108 is a paper material that has been carbon loaded to provide uniform conductivity throughout its length (BONTEX Inc., Buena Vista Va.). Uniform conductivity simply means that any given section of the conductive layer 108 will have substantially the same resistance as any other section of the conductive layer 108 of the same dimensions. The length of the paper material and the degree of carbon loading may be suitably selected so as to provide a desired degree of resistance from the attachment device 102 to the wrist loop 104. This conductivity is preferably between 700 kilohms and 2.0 megohms.
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Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown and that the invention has other applications in other environments. This application is intended to cover any adaptations or variations of the present invention. The following claims are in no way intended to limit the scope of the invention to the specific embodiments described herein.
