Electricity: conductors and insulators – Covers or face plates
Reexamination Certificate
1999-02-03
2001-06-26
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Covers or face plates
C220S241000
Reexamination Certificate
active
06252167
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the suppression of fires in electrical boxes and more particularly to the use of an intumescent material to suppress fires within an electrical box.
It is well known that electrical fires are one of the most common sources of fires in the home and elsewhere. In the home, electrical fires may occur within electrical boxes, which may house either electrical devices or electrical connections such as cable splices. A typical electrical box consists of a box made of metal or plastic which may be rectangular or round and which has an open face for access to the inside of the box. Openings are provided in the sides or back of the box for insertion of electrical cables. An electrical device such as a light switch or outlet plug is mounted within the box, and the box is often installed in an opening in a wall. A plastic or metal cover plate is then attached to the electrical device to cover the electrical box and to provide a pleasing outward appearance.
Fires within electrical boxes present particular hazards for the home or other buildings in which they occur. Electrical boxes which contain switches or outlet plugs are typically housed within the walls of the building. If a fire starts in the electrical box, it may spread to the surrounding wood frame and quickly travel throughout the inside wood framing of the structure. Electrical fires also can be hard to detect because they begin within an enclosed electrical box. Thus, they may be well underway before emitting smoke. Further, electrical devices are often placed within the vicinity of plastic or synthetic materials, and thus such fires can produce toxic or hazardous fumes and smoke.
Currently, there are no systems which adequately suppress fires which begin in an electrical box. It has been known generally to use intumescent materials to protect and insulate items from a fire. Intumescent materials are products that “grow” or “thicken” when exposed to heat, creating an insulated layer that separates the protected item from the fire. Conventionally, intumescent materials are applied to the exterior of an item to insulate it from a fire. For example, intumescent materials have been used to create a fire-resistant/retardant wrap suitable for protecting the exterior of conduits and cable trays and the like from a fire. Such a system is described in Kiser, U.S. Pat. No. 5,681,640. In addition, intumescent materials have been applied to large sheets of insulated material for use as an exterior wrap which may be applied to the exterior of a building. However, the exterior application of such intumescent materials, while protecting the material or structure surrounded by such intumescent materials from fire, does not actively suppress fires that begin within an enclosed area, or protect against fires which begin in an enclosed area such as an electrical box.
Accordingly, there is still a need for a system that suppresses fires that begin within an electrical box, that insulates the exterior plate from a fire within an electrical box, that prevents smoke from exiting from an electrical box fire, that is easy to install, and that is cost-effective.
SUMMARY OF THE INVENTION
The present invention overcomes the drawbacks of the prior art by providing a system for suppressing electrical fires within an electrical box. A first aspect of the invention provides an electrical box defining an opening for access to the electrical box and includes therein an electrical device or an electrical cable. A support is sized to cover a majority of the opening. An intumescent material is applied to the support. The support is mounted adjacent to the opening so that the intumescent material covers a majority of the opening.
In addition, the present invention provides a method for suppressing fires in an electrical box. An electrical box is provided which defines an opening for access therein and which contains either an electrical device or an electrical cable. A support is provided which is sized to cover a majority of the opening. An intumescent material is applied to at least one side of the support. The support is mounted adjacent to the opening so that the intumescent material covers a majority of the opening. The intumescent material expands in response to heat generated within the electrical box.
In another aspect of the present invention, an electrical box is provided which defines an opening for access therein and which contains either an electrical device or an electrical cable. A layer of intumescent material covers a substantial portion of the opening.
In still another aspect of the present invention, an electrical box is provided which defines an opening for access therein which contains either an electrical device or an electrical cable. A cover plate is attached to the electrical box and covers the opening. The electrical box contains an intumescent material.
The present invention has at least one or more of the following advantages over the prior art. The present invention, by providing an intumescent material which either covers at least a majority of the opening of an electrical box or is inside the electrical box, actively suppresses a fire within the electrical box by expanding the intumescent material into the electrical box in response to heat generated by a fire in the electrical box. The expanding intumescent material provides an insulated layer which prevents the cover plate from melting or deteriorating. The expanding intumescent material may expand into or over the electrical device or electrical connection, thus directly suppressing the fire at its source. The expanding intumescent material also fills the cracks and voids between the electrical box, surrounding wall and/or the cover plate so as to prevent smoke from exiting the electrical box. Further, by expanding to fill the cracks and voids, the intumescent material cuts off a draft which may accelerate the fire within the electrical box. Because the intumescent material is provided on only a small support, the system is easy to install and is cost-effective due to the small area on which the intumescent material is applied.
The foregoing and other features and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3965629 (1976-06-01), Pearson
patent: 4072316 (1978-02-01), Decker et al.
patent: 4163137 (1979-07-01), Close, Jr.
patent: 4270318 (1981-06-01), Carroll et al.
patent: 4432465 (1984-02-01), Wuertz
patent: 4447484 (1984-05-01), Slosberg et al.
patent: 4573297 (1986-03-01), Benscoter et al.
patent: 4667840 (1987-05-01), Lindsey
patent: 4733330 (1988-03-01), Tanaka et al.
patent: 5675125 (1997-10-01), Hollinger
patent: 5681640 (1997-10-01), Kiser
Chernoff Vilhauer McClung & Stenzel LLP
Reichard Dean A.
LandOfFree
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