Fire extinguishers – Apparatus which isolates flames from non-burning area
Patent
1997-04-22
1999-09-28
Joyce, Harold
Fire extinguishers
Apparatus which isolates flames from non-burning area
F24F 1102
Patent
active
059572116
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to means for preventing the spreading of gaseous substances in ducts, pipes or like elements, for instance for preventing the spreading of fire or harmful substances in ventilation systems.
BACKGROUND ART
A duct shut-off device which is self-acting in the event of fire and which is intended particularly for use in ventilation ducts is known from SE-B-7602567-5 (Publication No. 401 614). This known shut-off or closure device is comprised of a grating made of supportive cellular material having cells which extend through the grating from one surface to another and which are defined by strip-like cell walls which are coated with a material which will swell when heated. When heated, this material will expand and block the cells, therewith effectively preventing fire from spreading through a ventilation duct in which the device is fitted for instance.
FR-A-2 254 182 teaches a similar device where the grating is comprised of a plurality of parallel ribs which extend over the cross-sectional area of the duct. One drawback with this device is that when the device is closed the resultant increase in pressure of the flowing medium will be concentrated over a short section of the duct with the subsequent danger of the duct rupturing or fracturing.
SUMMARY OF THE INVENTION
With the intention of providing a duct shut-off or closure device which in a non-activated state will offer the lowest possible resistance to flow in ducting, or tubing, a section of a duct is fitted with plates which extend longitudinally in the flow direction and which are coated with an expandable material which reacts when subjected to heat, pressure or some other physical or chemical property of a substance flowing through the duct, above a given threshold level. When this threshold level is exceeded, the shut-off device is activated and the expandable material on the-plates swells and therewith successively reduce the cross-sectional area of the duct, until the duct is completely closed off. The longitudinally extending plates carrying the expandable material ensures that the duct will be closed even when the pressure increases as a result of the decrease in cross-sectional area. Because the pressure exerted by the flowing medium acts both radially and axially within a longer section of the duct, or tube, than in the case of the earlier known technique, the shut-off device will remain fully operative and there is no danger of the device becoming outwardly deformed, such outward deformation, or bulging, being liable to break the device and therewith allow fire smoke and toxic gases to pass through.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A, 1B and 1C is a partial cross-sectional view of an inventive duct shut-off device which comprises internal vertically upstanding plates and a horizontal plate for fixing the vertical plates.
FIG. 2 is a cross-sectional view of a shut-off device for ventilation ducts of rectangular cross-section in accordance with the invention, and shows the expansion of an expandable substance.
FIG. 3 is a cross-sectional view of an inventive ventilation duct shut-off device, and shows the expansion of an expandable substance.
FIG. 4 is a cross-sectional view of a ventilation duct shut-off device in accordance with the invention, and shows the expansion of an expandable substance from inside the duct wall.
DESCRIPTION OF A PREFERRED EMBODIMENT
The drawings illustrate an inventive shut-off device comprised of a tube 1 or a channel 2 of rectangular cross-section for ventilation purposes for instance, having disposed therein longitudinally extending plates 3 which are coated with a layer of an expandable substance. In the case of horizontal ducting, the plates 3 are preferably inserted vertically to prevent any substantial downfall of particles in the duct and to simplify cleaning. In the case of ducting and channelling, shut-off devices can be incorporated therein as a well-defined duct section or channel section, where each section may include one or more plates 3, e
REFERENCES:
patent: 2096271 (1937-10-01), Young
Geuken Stefan
Yllner Niclas
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