GB1560754A - Electric conductive wrist strap - Google Patents

Description

(54) ELECTRIC CONDUCTIVE WRIST STRAP (71) We, DAL INDUSTRIES INC., a corporation organised and existing under the laws of the State of California, United States of America, of 1601 Stierlin Road, Mountain View, State of California 94040, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to an electrically-conductive strap to be worn by a person on some part of his or her body, for grounding the body to prevent the build up of static electricity.

As described very aptly in United States Letters Patent No. 3,857,397, it is often desirable to "ground" an assembly worker, i.e., to connect him to a ground, to prevent the build up of static electric charges. This is not only desirable but also essential for an assembly worker handling or working on certain semiconductor devices. More particularly, some semiconductor devices are so sensitive to electric charges that they could be destroyed by the static electricity to which an ungrounded assembly worker may be charged and to which the device would be exposed when touched.

The electrically-conductive wrist strap as described in above-mentioned United States Letters Patent No. 3,857,397 comprises a pair of plastics strips which sandwich between them a conductive strip. One end of the strap is formed with an opening with the strap being threaded through the opening to form a loop for placing around the wrist.

The loop so formed is secured in its size by a pair of pads of a touch-and-close fastener.

The other end of the strap is provided with a conductive clip to be attached to some suitable grounding post and a snap is provided along the length of the strap, i.e., the strap is formed of two parts interconnected by a snap to allow a quick disconnect should this become necessary.

Even though the above-described strap is fairly suitable for conducting charges of static electricity from the body of the assembly worker to the conductive post, it suffers from at least three deficiencies. One deficiency is that, upon the rapid departure of a worker such as in an emergency, the breaking strength of the strap as such must be adjusted so that it will break, which may be uncomfortable for some people who are not as strong as others. One other problem is that because the strap is made of a flexible plastics laminate, it requires the snap fastening means between its two ends to allow for rotatable adjustment to provide a satisfactory maneuverability of the hand which is wearing the wrist strap. Another deficiency is that such a rotatable snap often causes some electrical problems and if the connection across the snap is not good, the entire purpose of the conductive wrist strap is defeated. Finally, since the wrist strap is made of a plastics material and has a relatively wide end portion around the wrist, some discomfort may be experienced because of perspiration build up thereunder since the material does not breath,- leading to contact dermatitis.

It is therefore an object of the present invention to provide an electricallyconductive wrist strap which will not inhibit the rapid departure from the work site and not hinder or encumber the departing worker. It is a still further object of the present invention to provide a wrist strap that breathes so that it could be placed around any part of the body without being uncomfortable, collecting perspiration or giving rise to a heat or perspiration rash.

It is another object of the present invention to provide a one-piece electrically-conductive wrist strap to ensure good conductivity, which is completely flexible, and whose conductivity or resistivity can be selected over a wide range at the time of manufacture by variations in the impregnating solution.

The electrically-conductive wrist strap nf this invention comprises a long, narrow strip of a breathable material. such as woven cotton, which is impregnated along its length with a latex-based water-soluble coating containing conductive carbon black or a similar conductive compound to make it conductive with a selected degree of conductivity. One end of the strip is provided with a conductive terminal such as the spring clip that may be attached to a grounding post, and the other end has affixed thereto, on opposite sides of the strip, a pair of pads of a touch-and-close fastener, one being at that end and the other one being positioned a distance from that end so that. upon placing one pad over the other into cooperative engagement, a loop is formed of a size dimensioned snugly to encircle the selected body member, such as the wrist, that is to be grounded.

One embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the electrically-conductive wrist strap of this invention in position on a wrist; and Figure 2 is an elevational view, with parts broken away, of the wrist strap as shown in Figure 1.

Referring now to the drawings, there is shown in Figure 1 a portion of a human arm, including the wrist and the hand. Encircling the wrist is one end portion of the electrically-conductive strap 10 of this invention with a conductive terminal 12 attached to the other end portion.

As best seen in the elevational view of Figure 2, electrically-conductive strap 10 is typically four feet long, one-half inch wide and .030 inch thick and may be made of a material such as cotton and which may be woven like a webbing or a ribbon. Such a strip breathes and is flexible and impregnable.

Strap 10 is preferably impregnated with a thermosetting coating of carbon such as for example, latex. The amount of carbon that is impregnated is selected to provide a desired resistivity between the end portions of strap 10 which for some applications may be very low and for others may be very high.

The important point is that the conductivity between the end portion of strap 10 can be selected in very wide limits during the manufacture, depending on the demands to be made on the strap or the function it is to perform.

One ,pad of the touch-and-close fastener 14 is attached to one surface of strap 10 near one end thereof and the other pad of the touch-and-close fastener 16 is attached to the other side of strap 10 at a distance from pad 14 such that, when the strap portion between pads 14 and 16 is looped around so that the pads are put against one another for adherence, the loop formed at the end of strap 10 will easily encircle the wrist or any other preselected body member. The other end of strap 10 has attached to it conductive terminal 12, such as a clamp having a pair of jaws which are biased towards one another under the pressure of a spring (not shown).

In use, the production worker attaches conductive terminal 12 to a suitable grounding post and places end portion 18 around the wrist by placing pad 14 after winding it around the wrist on pad 16. When a quick departure of the worker is necessary, such as occasioned by an emergency, the pull exerted by the wrist on the touch-and-close fastener will open the same and will release the worker without having a strap hanging around his wrist.

The strap of this invention is extremely convenient to use, is very safe because it disengages very easily by pressure on the touch-and-close fastener pads, and is most reliable from an electrical point of view since there are no breaks, joints, or other discontinuities in the strap which may give rise for failure.

One example of the touch-and-close fastener which can be used in the present invention is that made of the material known commercially as "Velcro" (Registered Trade Mark).

WHAT WE CLAIM IS: 1. An electrically-conductive wrist strap comprising: a continuous, narrow strip of a flexible, breathable, and impregnated material having first and second end portions; conductive material impregnated into said strip to make said strip conductive between said first end and said second end; a conductive terminal means connected to said first end portion; a first part of a touch-and-close fastener affixed to one surface of said strap at said second end portion; and a second part of a touch-and-close fastener for cooperating with said first part, affixed to the other surface of said strip at a distance along said strip from said first part such that the strap snugly encircles a predetermined portion of the human anatomy when said first and second parts are brought in cooperative fastening relationship around said portion of the human anatomy.

2. An electrically-conductive wrist strap in accordance with Claim 1 in which the amount of conductive material impregnated into said strip is selected to provide a predetermined conductivity between said first and second end portions.

3. An electrically-conductive wrist strap substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. with a latex-based water-soluble coating containing conductive carbon black or a similar conductive compound to make it conductive with a selected degree of conductivity. One end of the strip is provided with a conductive terminal such as the spring clip that may be attached to a grounding post, and the other end has affixed thereto, on opposite sides of the strip, a pair of pads of a touch-and-close fastener, one being at that end and the other one being positioned a distance from that end so that. upon placing one pad over the other into cooperative engagement, a loop is formed of a size dimensioned snugly to encircle the selected body member, such as the wrist, that is to be grounded. One embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of the electrically-conductive wrist strap of this invention in position on a wrist; and Figure 2 is an elevational view, with parts broken away, of the wrist strap as shown in Figure 1. Referring now to the drawings, there is shown in Figure 1 a portion of a human arm, including the wrist and the hand. Encircling the wrist is one end portion of the electrically-conductive strap 10 of this invention with a conductive terminal 12 attached to the other end portion. As best seen in the elevational view of Figure 2, electrically-conductive strap 10 is typically four feet long, one-half inch wide and .030 inch thick and may be made of a material such as cotton and which may be woven like a webbing or a ribbon. Such a strip breathes and is flexible and impregnable. Strap 10 is preferably impregnated with a thermosetting coating of carbon such as for example, latex. The amount of carbon that is impregnated is selected to provide a desired resistivity between the end portions of strap 10 which for some applications may be very low and for others may be very high. The important point is that the conductivity between the end portion of strap 10 can be selected in very wide limits during the manufacture, depending on the demands to be made on the strap or the function it is to perform. One ,pad of the touch-and-close fastener 14 is attached to one surface of strap 10 near one end thereof and the other pad of the touch-and-close fastener 16 is attached to the other side of strap 10 at a distance from pad 14 such that, when the strap portion between pads 14 and 16 is looped around so that the pads are put against one another for adherence, the loop formed at the end of strap 10 will easily encircle the wrist or any other preselected body member. The other end of strap 10 has attached to it conductive terminal 12, such as a clamp having a pair of jaws which are biased towards one another under the pressure of a spring (not shown). In use, the production worker attaches conductive terminal 12 to a suitable grounding post and places end portion 18 around the wrist by placing pad 14 after winding it around the wrist on pad 16. When a quick departure of the worker is necessary, such as occasioned by an emergency, the pull exerted by the wrist on the touch-and-close fastener will open the same and will release the worker without having a strap hanging around his wrist. The strap of this invention is extremely convenient to use, is very safe because it disengages very easily by pressure on the touch-and-close fastener pads, and is most reliable from an electrical point of view since there are no breaks, joints, or other discontinuities in the strap which may give rise for failure. One example of the touch-and-close fastener which can be used in the present invention is that made of the material known commercially as "Velcro" (Registered Trade Mark). WHAT WE CLAIM IS:

1. An electrically-conductive wrist strap comprising: a continuous, narrow strip of a flexible, breathable, and impregnated material having first and second end portions; conductive material impregnated into said strip to make said strip conductive between said first end and said second end; a conductive terminal means connected to said first end portion; a first part of a touch-and-close fastener affixed to one surface of said strap at said second end portion; and a second part of a touch-and-close fastener for cooperating with said first part, affixed to the other surface of said strip at a distance along said strip from said first part such that the strap snugly encircles a predetermined portion of the human anatomy when said first and second parts are brought in cooperative fastening relationship around said portion of the human anatomy.

2. An electrically-conductive wrist strap in accordance with Claim 1 in which the amount of conductive material impregnated into said strip is selected to provide a predetermined conductivity between said first and second end portions.

3. An electrically-conductive wrist strap substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.