Boots – shoes – and leggings – Boots and shoes – Made of material other than leather
Patent
1994-01-21
1995-06-27
Foster, Jimmy G.
Boots, shoes, and leggings
Boots and shoes
Made of material other than leather
36 87, 36 30R, 36 25R, 361223, A43B 1302, A43B 1304, A43B 1312
Patent
active
054268702
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an antistatic shoe sole.
In the manufacture of some products, for example electronic devices, stray static electricity can damage or significantly disrupt the operation of the products. Sensitive computers, integrated circuits and computer software and data which are stored on magnetic tape or disk may even be destroyed by stray static electricity. Consequently, extensive measures are taken during the manufacture and use of these products in order to reduce the risks of damage by stray static electricity. People using and manufacturing the products are usually one of the most significant sources of stray static electricity. Consequently, it is essential to discharge static electricity from people who may come in contact with products which may be adversely effected by static electricity. Usually working areas in which such products can be found have a grounded floor or grounded mats which are able to discharge the static electricity from people walking on the floor or mats by conducting the static electricity from the people to the floor. The only contact people have with the floor is usually through their shoe soles, but static electricity does not readily discharge through conventional shoe soles since the shoe soles do not adequately conduct static electricity from the body of the person to the floor. Therefore, in order to improve static electricity discharge it is desirable to have an antistatic shoe which readily discharges static electricity.
DISCUSSION OF PRIOR ART
It is known to produce antistatic shoes with rubber soles, but these shoes suffer from a number of disadvantages. Rubber soles are often heavy and may mark floors. In order to overcome these problems, it is preferably to use polyurethane rather than rubber, since polyurethane is a lighter product which lasts longer and is non-marking. However, polyurethane is not within the desired range of electrical resistance for conducting static electricity. Antistatic shoes usually have an electrical resistance property of between 75 kOhms and 50 MOhms, (as measured by the standard test specified in British Standard 2050). Polyurethane does not have these resistance properties and it is therefore necessary to enhance the antistatic properties of the polyurethane by the introduction of additives to the polyurethane. However, polyurethane is a blown material and the dispersion of additives within the material is not homogenous due to the poor mixing characteristics of polyurethane. Furthermore, in order to achieve adequate antistatic properties it is necessary to add a large amount of additives, but this deteriorates the quality of the polyurethane. Consequently, simply adding antistatic additives to polyurethane to make an antistatic polyurethane shoe sole is not possible.
SUMMARY OF THE INVENTION
The present invention attempts to overcome one or more of the above problems.
According to the present invention there is provided a shoe sole comprising:
a polyurethane outer sole having predetermined electrical resistance characteristics, and
a rubber sole insert having predetermined electrical resistance characteristics positioned adjacent the outer sole,
wherein, static electricity in the sole insert is capable of discharging from the sole insert along a path of least resistance through the outer sole.
It is preferred that the shoe sole further comprises a conductive inner sole positioned adjacent the sole insert so as to improve the discharge of static electricity from a wearer of a shoe having the shoe sole through the inner sole, the sole insert and the outer sole.
DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which;
FIG. 1 is a perspective view of a preferred embodiment of the present invention,
FIG. 2 is a top view of the sole of FIG. 1, and
FIG. 3 is a preferred embodiment of a shoe having an antistatic sole of FIG. 1.
DETAILED DESCRIPTION OF THE PREFER
REFERENCES:
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patent: 4858337 (1989-08-01), Barma
patent: 4858340 (1989-08-01), Pasternak
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Derwent Abstract Accession No. 78-35932A/20 Class A83 JP,A, 53-038453 (Hiroshima Kasei KK) 8 Apr. 1978.
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Derwent Abstract Accession No. 88-351049/49 Class P22 JP,A, 63-264002 (Seiaicho Rubber KK) 31 Oct. 1988.
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Purnell Andrew T.
Purnell Robert D.
Foster Jimmy G.
Patterson Marie Denise
Phurness Pty. Ltd.
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