Electricity: conductors and insulators – Covers or face plates
Reexamination Certificate
2000-09-29
2002-09-17
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Covers or face plates
C174S067000, C220S241000, C220S242000
Reexamination Certificate
active
06452100
ABSTRACT:
FIELD OF THE INVENTION
My invention is directed to enclosures for electrical equipment utilizing devices having screw-type electrical terminals.
BACKGROUND OF THE INVENTION
It has long been common practice in the design of enclosures for electrical equipment to equip the enclosure with an access panel attached to a chassis of the enclosure by hinges or fasteners in such a manner that the access panel may be opened or removed to facilitate manufacture, maintenance, and repair of the enclosure and equipment included as part of the enclosure. It has also long been a practice to mount electrical devices such as push-buttons, switches, or indicator lights in such access panels so that the electrical devices can be actuated or viewed from outside of the enclosure.
Electrical devices mounted in access panels are often equipped with screw-type wire terminals for connecting the electrical device to a wire extending out of the enclosure when the access panel is opened or removed. During assembly, maintenance, or repair of the enclosure, it is sometimes necessary to operate the enclosure with the access panel open and electrical current or voltage applied to the screw-type terminal of an electrical device mounted in the access panel.
In the past, electrical codes applicable to such enclosures did not require screw-type terminals of electrical devices mounted in access panels to be electrically insulated. During the year 2001, however, Underwriters Laboratories Standard 508 will become effective requiring that screw-type terminals on electrical devices mounted in access panels must include some sort of electrically insulative protection against inadvertent electrical contact by personnel who might come into contact with the terminals while the access panel is open.
Traditional methods of providing electrical insulation of such screw-type terminal has been accomplished by wrapping exposed metal surfaces of the terminal with electrician's tape, or encapsulating exposed metal surfaces of the terminal in an electrically insulative coating such as glyptol or RTV. These traditional methods suffer from a number of drawbacks. Applying electrical tape or such coatings is also time consuming and labor intensive, thereby driving up the cost of initial manufacture and repair or maintenance of the enclosure. Taping and coatings are also undesirable in that they provide no access to the electrical terminal for test probes of diagnostic or trouble shooting equipment, thereby making it necessary to destroy or compromise the protective covering of the terminal during troubleshooting and repair operations. Because the taping and coating cannot be removed without destroying its effectiveness, it cannot be reused, thereby necessitating a complete re-application of tape or coating after troubleshooting or repair-operations to ensure that electrical insulation protection of the terminal is maintained.
What is needed, therefore, is an improved electrical enclosure capable of meeting the requirements of UL Standard 508 and solving one or more of the drawbacks and problems recited above associated with the prior methods of insulating screwed-type terminals in enclosures subject to the requirements of UL 508.
SUMMARY OF THE INVENTION
My invention provides such an improved electrical enclosure through the use of a reusable cover of electrically insulative material for surrounding a portion of a screw-type electrical terminal of an electric device mounted in an access panel of the enclosure. My protective cover includes an integral clamp for attaching the cover to the terminal and also includes an opening for passage of a wire through the cover to the terminal.
According to one aspect of my invention, the cover is adapted to be removed or installed on the terminal regardless of whether a wire is attached to the terminal.
In some embodiments of my invention, a test probe access hole is provided for passage of a test probe through the cover and into contact with the terminal when the cover is installed on the terminal.
Some embodiments of my invention include a cover configured to cover two or more terminals. In some embodiments, the integral clamp for attaching the cover to the terminal is provided by snap tabs that grip a portion of the terminal. In other embodiments, the cover is formed of a first and a second part which clamp together to surround the terminal. Some embodiments of my invention include a cover having a flexible hinge to facilitate installation and removal of the cover.
In a preferred embodiment of my invention, the cover is formed of two or more parts capable of providing electrical protection for two or more terminals, with one of the parts of the cover being configured so that it may be cut in pieces, and the pieces interlocked to form a cover for a single terminal.
Other aspects and advantages of my invention will be apparent to those having skill in the art upon review of the attached drawings and the following detailed description.
REFERENCES:
patent: 3283062 (1966-11-01), D'Entremont
patent: 3618804 (1971-11-01), Krause
patent: 3824555 (1974-07-01), Klein et al.
patent: 3864005 (1975-02-01), Klein
patent: 4146289 (1979-03-01), Kirrish
patent: 5147219 (1992-09-01), Gilberts et al.
patent: 5944210 (1999-08-01), Yetter
Patel Dhiru R
Reichard Dean A.
Siemens Energy & Automation
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