GB2064315A

GB2064315A - Anti-static material

Info

Publication number: GB2064315A
Application number: GB7939227A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1979-11-13
Filing date: 1979-11-13
Publication date: 1981-06-17

Abstract

To overcome the effects of static electricity in a room housing electronic equipment the floor is made up of admixtures or alternate portions of materials at the opposite ends of the tribo-electric scale.

Description

SPECIFICATION Anti-static material This invention relates to methods of and arrangements for the reduction of the inconvenient effects of static electricity in electronic installations such as telecommunication exchanges.

One of the main trends in such installations is towards the use of integrated circuitry, which is relatively small in size and uses relatively low voltages.

As a result its susceptibility to static electricity tends to begreaterthan is the case for the moreconven- tional electrical and electromechanical equipment.

Hence great care has been taken in the design and installation of such equipment to avoid trouble due to static electricity.

One of the difficulties which can cause trouble is that human beings and servicing trolleys may become statically charged to relatively high levels without the human beings realising it. Such a charge can cause trouble in an installation with much semiconductor circuitry. It has been found that a human being when charged is equivalent to a charged capacitor of about 120 pf. The voltage level and its polarity depend on the materials which caused the charge, the relative position on the tribo-electric scale of the materials used, and the amount of causal energy. Voltage levels involved vary widely and commonly extend into four orders of magnitude.

If such a charge is discharged, the impedance of the discharge path determines the current which flows, and hence the time taken to dissipate the energy, and a variation within seven or more orders of magnitude can be expected for this impedance. In addition, a static discharge produces a strong radiated electro-magnetic field which can cause trouble by induction.

As is well known the relation between the charge o on a capacitor C and the voltage thereacross is given by Q=CV. Thus if a charged operator moves from floor level to an insulated stool or ladder, his capacity to earth can be significantly reduced, which increases his voltage to earth, so that the voltage hazard increases.

Some of the difficulties due to a charged operator can be minimised by the use of discharging disciplines when the personnel enter an equipment room, but they may acquire charges while in that room.

Further the discharging discipline may not always be fully successful.

An object of the present invention is to provide means to minimise the adverse effects of static due to the movements of human beings and such devices as servicing trolleys.

According to the invention there is provided a floor covering for use in a room which contains electronic equipment, in which the covering is made of admixtures or alternate portions or regions of electrically insulating materials which are widely separated or are at or near to the opposite ends ofthe tribo-electric scale.

To do this the floor covering materials are preferably selected from the opposite ends of the triboelectric scale. This has the result that when a third object whose position on the scale is between those of the materials used moves on such a floor covering, the charges developed as a result of that movement will be opposite polarity and hence will tend to cancel each other out.

One implementation which is especially convenient is for the floor covering to consist of floor tiles or carpet sections iaid in chequer-board fashion, using two tribo-electrically different (as mentioned above) materials. Thus when in contact with, for instance, shoes (the materials of which are usually between the ends of the scale) worn by people walk ins, the charges generated would be of opposite polarity for the two materials. Hence the net charge developed would be very low, and may even be negligible from the point of view of the electronic equipment. In addition, if the person is already charged, some at least of the regions of the floorcovering will tend to reduce his charge.

The tribo-electric scale indicates that nylon is near the positive end, while polypropylene is near the negative end. Hence a floor covering can be made from alternate areas of these materials.

Note that such materials as the vinyls and polyesters, which are used for shoe manufacture, are towards the middle of that scale.

1. A floor covering for use in a room which contains electronic equipment, in which the covering is made of admixtures or alternate portions or regions of electrically insulating materials which are widely separated or are at or near to the opposite ends of the tribo-electric scale.

2. A floor covering as claimed in claim 1, and in which the alternate portions or regions are square, so that the overall result is a chequer-board pattern.

3. A floor covering as claimed in claim 1 or 2, and in which the materials used are nylon (from the positive end of the tribo-electric scale) and polypropylene (from the negative end of the tribo-electric scale).

4. A floor covering substantially as described herein.

5. A method of protecting electronic equipment from the adverse effects of static electrical charges on human beings or maintenance trollies near to that equipment, which includes the application to the floor of the room in which the equipment to be protected is located a covering which includes admixtures or alternate portions or regions of two electrically insulating materials, one of which, e.g.

nylon, is at the positive end of the tribo-electric scale while the other, e.g. polypropylene, is at the negative end of the tribo-electric scale.

6. A floor covering for use in a room which contains electronic equipment, which covering consists of squares of two different electrically insulating materials arranged in a chequerboard manner, one of the materials, e.g. nylon, being at the positive end of the tribo-electric scale while the other of the materials, e.g. polypropylene, is at the negative end of the tribo-electric scale.

New claims or amendments to claims filed on 8th July 1980.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Anti-static material This invention relates to methods of and arrangements for the reduction of the inconvenient effects of static electricity in electronic installations such as telecommunication exchanges. One of the main trends in such installations is towards the use of integrated circuitry, which is relatively small in size and uses relatively low voltages. As a result its susceptibility to static electricity tends to begreaterthan is the case for the moreconven- tional electrical and electromechanical equipment. Hence great care has been taken in the design and installation of such equipment to avoid trouble due to static electricity. One of the difficulties which can cause trouble is that human beings and servicing trolleys may become statically charged to relatively high levels without the human beings realising it. Such a charge can cause trouble in an installation with much semiconductor circuitry. It has been found that a human being when charged is equivalent to a charged capacitor of about 120 pf. The voltage level and its polarity depend on the materials which caused the charge, the relative position on the tribo-electric scale of the materials used, and the amount of causal energy. Voltage levels involved vary widely and commonly extend into four orders of magnitude. If such a charge is discharged, the impedance of the discharge path determines the current which flows, and hence the time taken to dissipate the energy, and a variation within seven or more orders of magnitude can be expected for this impedance. In addition, a static discharge produces a strong radiated electro-magnetic field which can cause trouble by induction. As is well known the relation between the charge o on a capacitor C and the voltage thereacross is given by Q=CV. Thus if a charged operator moves from floor level to an insulated stool or ladder, his capacity to earth can be significantly reduced, which increases his voltage to earth, so that the voltage hazard increases. Some of the difficulties due to a charged operator can be minimised by the use of discharging disciplines when the personnel enter an equipment room, but they may acquire charges while in that room. Further the discharging discipline may not always be fully successful. An object of the present invention is to provide means to minimise the adverse effects of static due to the movements of human beings and such devices as servicing trolleys. According to the invention there is provided a floor covering for use in a room which contains electronic equipment, in which the covering is made of admixtures or alternate portions or regions of electrically insulating materials which are widely separated or are at or near to the opposite ends ofthe tribo-electric scale. To do this the floor covering materials are preferably selected from the opposite ends of the triboelectric scale. This has the result that when a third object whose position on the scale is between those of the materials used moves on such a floor covering, the charges developed as a result of that movement will be opposite polarity and hence will tend to cancel each other out. One implementation which is especially convenient is for the floor covering to consist of floor tiles or carpet sections iaid in chequer-board fashion, using two tribo-electrically different (as mentioned above) materials. Thus when in contact with, for instance, shoes (the materials of which are usually between the ends of the scale) worn by people walk ins, the charges generated would be of opposite polarity for the two materials. Hence the net charge developed would be very low, and may even be negligible from the point of view of the electronic equipment. In addition, if the person is already charged, some at least of the regions of the floorcovering will tend to reduce his charge. The tribo-electric scale indicates that nylon is near the positive end, while polypropylene is near the negative end. Hence a floor covering can be made from alternate areas of these materials. Note that such materials as the vinyls and polyesters, which are used for shoe manufacture, are towards the middle of that scale. CLAIMS

4. A floor covering substantially as described herein.

6. A floor covering for use in a room which contains electronic equipment, which covering consists of squares of two different electrically insulating materials arranged in a chequerboard manner, one of the materials, e.g. nylon, being: at the positive end of the tribo-electric scale while the other of the materials, e.g. polypropylene, is at the negative end of the tribo-electric scale.

New claims or amendments to claims filed on 8th July 1980.

New or amended claims:

5. A method of protecting electronic equipment from the adverse effects of static electrical charges on human beings or maintenance trollies nearto that equipment, which includes the application to the floor of the room in which the equipment to be protected is located a covering which includes admixtures or alternate portions or regions of two electrically insulating materials, one of which, e.g.