Electricity: conductors and insulators – Covers or face plates
Reexamination Certificate
2000-08-25
2003-02-18
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Covers or face plates
C174S067000, C220S241000, C220S242000, C439S138000
Reexamination Certificate
active
06521834
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to fire stopping devices and, more particularly, to a cover plate for electrical outlets, switches, or the like which includes a fire stopping mat arranged on the inside surface of the cover plate which serves to form a fire barrier in the event of a fire.
BACKGROUND OF THE INVENTION
One mechanism by which fire may spread from one compartment of a structure to another is through passages in the walls. Such passages or through-penetrations include electrical outlets, electrical switches, and the like. Current methods used to prevent the spread of fire and passage of smoke through such openings include providing intumescent compound either on the outside of the outlet or switch box, or on the inside surface of the back wall of the box.
While providing intumescent compound on the outside of the outlet or switch box is generally satisfactory for resisting the spread of fire and preventing the passage of smoke from one compartment to another, this technique has certain drawbacks. For example, to arrange intumescent compound on the outside of the box, the compound must be installed during the framing of the structure because retrofitting the intumescent compound on the outside of the box is difficult, costly, and requires the wall structure to be torn apart. Providing the intumescent compound on the inside of the back surface of the box also has certain drawbacks and disadvantages, most notably, that the intumescent compound must be installed by a licensed electrician.
In addition, providing an intumescent mat on the inside surface of the faceplate allows electrical boxes such as electrical outlets, switches, and the like to be quickly and easily inspected to determine whether the electrical box has been properly fire stopped.
Techniques for insulating electrical outlets are known in the prior art. The U.S. Pat. No. 4,293,173 to Tricca for example, discloses a thermal insulation system for electrical outlets. The system includes a large plate of thermal insulation which is secured behind the faceplate of the outlet, smaller plates of thermal insulation which are placed over the receptacles of the electrical outlets, and dummy plugs which are used to seal the slots of the receptacles and hold the small insulation plates in position. The thermal insulation plates are constructed of a thermal insulating material, such as a resilient closed cell foam material, having low thermal conductivity, and good compressibility and resilience.
The U.S. Pat. No. 4,447,484 to Slosberg et al discloses a flame resistant vinyl-foam gasket material for use as an insulating draft shield in electrical outlets and switch boxes. The gasket material comprises a layer of a flexible vinyl-foam sheet material suitable for use as a gasket material, and a dimensionally stable glass-fiber tissue sheet material integrally positioned and secured within the foam layer.
The insulating articles described in these patents, however, serve only to prevent air infiltration though electrical outlets and switches, thereby conserving energy and increasing the thermal efficiency of buildings. They do not expand when exposed to a fire and are not intended to create a fire barrier.
Accordingly, there exists a need in the industry for a fire stopping mat which can be positioned on the inside surface of a faceplate adapted for mounting on an electrical box which is capable of resisting the spread of fire through the electrical box. It would therefore be desirable to provide a faceplate for an electrical outlet or switch box which includes a fire stopping mat capable of resisting the spread of fire through the outlet or switch box.
SUMMARY OF THE INVENTION
The present invention provides a fire stopping faceplate assembly for an electrical box comprising a faceplate having an inner surface, and a fire stopping mat arranged adjacent the faceplate inner surface. The fire stopping mat provides an active system which forms a fire barrier capable of preventing an excessive temperature rise on the wall side opposite the fire by providing either an intumescent compound which expands to provide additional insulating properties and otherwise stops the spread of fire, smoke and hot gases, by providing an endothermic compound which withdraws heat from the system, or both. By an active system, it is meant that the fire stopping mat undergoes a physical change when exposed to fire-like conditions, and the physical change enhances the thermal characteristics of the fire stopping mat, thereby allowing it to more effectively stop the spread of fire and prevent temperature rise on the wall side opposite the fire. In one aspect of the invention, the fire stopping mat has an activation temperature of no greater than 365° F. (185° C.).
The fire stopping mat may include an intumescent compound, an endothermic compound, or both an intumescent compound and an endothermic compound. Alternatively, the fire stopping mat may comprise a layer formed integrally with the faceplate or may be applied to the faceplate as a coating. In addition, the fire stopping mat may include a layer of an infrared blocking material formed of, for example, a metal or a ceramic fiber material. The fire stopping mat preferably has a thickness of no greater than about {fraction (3/16)} inches so that it can be positioned within faceplates used to cover conventional electrical outlets and switches.
In another aspect of the invention, the fire stopping faceplate assembly provides fire stopping performance such that a wall including an electrical box with the fire stopping faceplate assembly can achieve fire and temperature ratings when tested according to the test method for fire tests of through-penetration fire stops set forth in ASTM E119 sufficient to pass a test for a time period of at least one hour.
In a specific embodiment, the invention provides a fire stopping faceplate assembly adapted to cover an electrical box mounted in a wall. The assembly includes a faceplate having an inner surface and a fire stopping mat having an activation temperature of no greater than 365° F. (185° C.) arranged adjacent the inner surface of the faceplate. The fire stopping faceplate may include a fire stopping mat formed of a plurality of layers. The layers may include a layer of intumescent compound, a layer of endothermic compound, and a layer of an infrared blocking material arranged adjacent said faceplate inner surface. In one embodiment, the infrared blocking material is formed of a ceramic fiber material. In a specific embodiment of the invention, the layer of infrared blocking material is arranged adjacent the faceplate inner surface, the layer of endothermic compound is arranged adjacent the layer of infrared blocking material, and the layer of intumescent compound is arranged adjacent the layer of endothermic compound.
In yet another embodiment, the fire stopping faceplate includes a fire stopping mat including a moldable putty which may include an intumescent compound.
The fire stopping mat generally has a density of at least about 30 lbs/ft
3
in its pre-expanded state, that is, prior to being exposed to fire-like conditions, preferably at least about 40 lbs/ft
3
, more preferably at least about 50 lbs/ft
3
, and most preferably at least about 60 lbs/ft
3
.
In another embodiment, the faceplate is formed of a metal, and the faceplate provides a fire stop which allows a wall including an electrical box having the metal fire stopping faceplate to pass the test method for fire tests of through-penetration fire stops set forth in ASTM E119 for a time period of at least two hours.
In another embodiment, the faceplate is formed of a synthetic polymeric material, and the faceplate provides a fire stop which allows a wall including an electrical box having the synthetic polymeric fire stopping faceplate to pass the test method for fire tests of through-penetration fire stops set forth in ASTM E119 for a time period of at least one hour.
In another aspect, the present invention provides a fire stopping faceplate assembly for fire s
Boros Robert J.
Dykhoff Michael G.
Harshbarger D. Max
Patchett David B.
Patel Dhiru R
Reichard Dean A.
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