Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a fire extinguisher employing an explosive charge for releasing fire extinguishing substance from a container. 
     2. Description of the Prior Art 
     U.S. Pat. Nos. 3,833,063; 3,874,458; 3,884,306; and 3,884,307 disclose prior art fire extinguishers. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved fire extinguisher of the type comprising a closed container, a fire extinguisher substance located in the container, an explosive means located in close proximity to a given portion of the wall of the container for forming an opening through the wall when actuated, and a heat sensitive means for actuating the explosive means to form the opening to allow the fire extinguishing substance to pass out of the opening. 
     In one embodiment, a screen is located across the opening formed to meter the fire extinguishing substance as it passes through the opening. 
     In another embodiment, a vent is provided at a position spaced away from said given portion of the wall to vent to the atmosphere, high pressure in the container resulting from excessive heat and gases which may occur in the container before actuation of the explosive means. 
     In a further embodiment, said given portion of said wall comprises a web with weakened portions selectively formed to facilitate rupture to form a plurality of said openings upon actuation of said explosive means. The web is strengthened to prevent the web from being forced outward due to high pressure in the container. 
     The fire extinguisher is particularly adapted for use with a stove. The heat sensitive means comprises a main fuse extending through the wall of the container to the explosive and having an end extending outward beyond the wall of the container. An extension fuse is provided for attachment to the main fuse if needed in order to locate the fuse closer to the heaters of the stove. 
     In a further aspect, coupling means comprising a magnet is connected to the upper end of the container for attachment to the vent of the stove to allow the lower end of the container with the fuse to hang downward over the stove. A special mechanism is provided to allow the magnet to tilt relative to the container to allow the magnet to be attached to a slanted surface with the container hanging downward. 
     For use on gas stoves, a system including an acoustic detector and circuitry is provided for turning off the gas upon detection of the sound produced upon actuation of the explosive means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial cross-sectional view of one embodiment of the fire extinguisher of the invention. 
     FIG. 2 is a plan view of the bottom of the fire extinguisher illustrating scored lines on its bottom end. 
     FIG. 2A is a cross section of FIG. 2 taken along the lines 2A--2A. 
     FIG. 3 is a plan view of the bottom of the fire extinguisher after its explosive charge has been ignited and its segments forced outward to form openings through the bottom end to allow its fire extinguishing powder to fall out by way of the screen and openings. 
     FIG. 4 is an exploded view of the fire extinguisher components. 
     FIG. 5 is a partial cross-sectional side view of the fire extinguisher showing its coupling magnet and one embodiment of a vent. 
     FIG. 6 illustrates another embodiment of a vent. 
     FIG. 7 illustrates a third embodiment of a vent. 
     FIG. 8 illustrates the connecting end of an extension fuse. 
     FIG. 9 illustrates the extension fuse attached to the main fuse of the container. 
     FIG. 10 is an electrical schematic of a system for shutting off a gas stove upon detection of the noise produced by the explosive of the fire extinguisher upon actuation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1-5, the fire extinguisher illustrated therein is identified by reference numeral 21 and comprises a metal container 23 or can formed by a cup-shaped member having a lower lid 27 sealed to the lower end 23A of the member 23 by a double seam forming a cavity 23C. Located within the container is a fire extinguishing substance 29, preferably a fire extinguishing powder which may be of the A.B.C. type or for example, of the B.C. type. As is well know, the A.B.C. type is formed of about 90% monoammonium phosphate with above 10 percent silicones and other material (silcia, ground mica) added to keep it free flowing to protect it from moisture. The B.C. type is about 90-94 percent sodium bicarbonate. The balance of the material is stearates or silicones and other materials added to keep it free flowing and to protect the sodium bicarbonate from moisture. The top 23B of the container 23 has a magnet 31 attached thereto to allow the fire extinguisher to be attached to a metallic object and hang with its bottom end 27 downward. The fire extinguisher can be attached to the top of a vent-a-hood of a stove for protection against grease fires. The magnet 31 is encased in a case 33 which is moveably attached to the container by an assembly to be described subsequently. 
     Referring to FIG. 2, the bottom lid 27 has grooves or scored lines 41A-46A selectively formed on the outside thereof to facilitate breaking or rupturing of the bottom end into separate tear-open segments 41-46 without fragmentation to forte openings 41B-46B only in the bottom end or bottom wall portion when the free ends of the segments are forced outward to allow the fire extinguishing powder to fall or pass outward from the container onto the fire. Although the scoring is illustrated on the outside surface of the lid it can be on the inside surface thereof. 
     The explosive charge for rupturing the bottom end along the weakened or scored lines for forcing the free ends of the segments outward comprises a small amount of explosive charge 51 deposited on the inside of the lid 27. The charge 51 is deposited as a thin layer in the area defined by the dotted circle 53 as seen in FIG. 2. Extending through the lid 27 and to the explosive layer 51 is a heat sensitive fuse or firetrain 61. On the inside, the fuse is held in contact with the explosive 51 by means 51A. The fuse 61 may be held in place by a ferrule and a push on friction nut as shown in U.S. Pat. No. 3,884,307. The fuse 61 ignites when the temperature outside of the fire extinguisher reaches a certain level to explode the charge 51. When this occurs, the force of the explosion ruptures the scored or weakened lines and forces the tear open segments 41-46 outward to form the openings 41B-46B. In addition, the force of the charge pushes the fire extinguishing powder upward in the container, loosening any caking. The fire extinguishing powder then falls out of the can by gravitational force to extinguish any fire below which may be in a frying pan, for example. The explosive charge 51 and fuse 61 may be of the type disclosed in U.S. Pat. No. 3,884,307 which patent is herein incorporated by reference. Although the fire extinguisher of this patent is effective, some problems have occurred in that the fire extinguishing powder sometimes drops down in a manner which causes splashing of the grease. In addition the pressure in the container resulting from excessive heat before activation of the explosive may cause the container to &#34;puff up&#34; which affects formation of the openings 41B-46B. 
     In accordance with one aspect of the invention, there is provided a metal metering screen 71 formed of members 71A and 71B which is located in the container and secured to the inside of the lid 27 over the explosive 51. The screen 71 has a central opening to receive the means 51A. The screen is round and extends outward beyond the explosive where its outer edge 73 is secured to the inside of the lid 27 between the edges 23E and 27E of the can and lid when they are bent together to form the seam. When the openings 41B-46B are formed, the non-erupting portions or web 27W of the lid 27 hold the central portion of the screen 71 in place. The screen 71 meters the flow of powder through the openings 41B-46B and causes it to fall down in an even distribution and prevents splashing of the grease which may be in a pan below the fire extinguisher. The screen 71 can be a 1/8 inch, 1/4 inch, 3/8 or 1/2 inch mesh size screen. 
     Tests were conducted with and without the screen 71 using a container having a diameter of about 3 3/8 inches and height of about 2 inches and wherein six openings 41A-46B in the lid 27 were formed with the lid 27 located 32 inches above a flat surface onto which the powder was dropped. 
     Without the screen 71, the container was emptied in 5 seconds depositing about 75% of the powder in a 10 inch diameter circle. Using a 1/2 inch mesh screen 71, the container was emptied in 6 seconds with 75% of the powder deposited on the lower surface in a 10 inch diameter circle. Using a 1/4 inch mesh screen 71, the container was emptied in about 7 second with 75% of the powder deposited in a 8 inch diameter circle on the lower surface. With a 1/8 inch mesh screen, the container was emptied in about 16 seconds with 75% of the powder deposited in a 10 inch circle. These test showed that the screen allowed the powder to flow out of the container sufficiently fast with an even distribution on the surface below to minimize any splashing of grease in a pan located on a burner of the stove below. The screen 71 also allows use of the deeper container 23 which holds more fire extinguishing powder 29. For the container size described above, a 3/8 inch mesh size screen is preferred. 
     Referring to FIGS. 4 and 5, the assembly for connecting the magnet 31 and case 33 to the top 23B of the container 23 comprises a hollow eyelet 91, a resilient O-ring 93, a washer 95, a hollow eyelet 97 and a hollow eyelet 99. The top 23B of the container 23 has a central aperture 23BA formed therethrough and the case 33 has a central aperture 33A formed therethrough. The eyelet 91 is inserted through the O-ring 93, and through the aperture 23BA. The eyelet 97 is located around the eyelet 91. The case 33 has a central aperture 33A formed therethrough. The eyelet 99 is inserted through the aperture 33A, around the eyelet 91 and into the eyelet 97. The edge 91E of the eyelet 91 crimped over to secure the assembly together. The eyelet 99 is longer than the eyelet 97 and the space between the rims 97R and 99R of the eyelets 97 and 99 allows the case 33 to tilt relative to the wall 23B of the can 23. This allows the magnet 31 to be attached to a slanted surface of the metal vent-a-hood with the container 23 hanging generally straight down. 
     The opening 91A extending through the eyelet 91 is filled with a lower temperature melting solder 101 which will melt to provide a vent through the top wall 23B of the container if the inside of the can 23 gets too hot before the explosive 51 is actuated. This relieves the pressure in the container and prevents the container wall from &#34;puffing up&#34; which may occur due to the heat and gases released in the can 23 before the explosive 51 is actuated. 
     If the can 23 does puff up or swell the web 27W may be pushed outward before the explosive 51 is actuated preventing the vanes or segments 41-46 from opening outward since the resulting openings 41B-46B may be smaller than the segments 41-46. 
     FIGS. 6 and 7 show different embodiments of vents which also may be formed through the top wall of the container. In the embodiment of FIG. 6, the vent is a one-way &#34;duckbill&#34; valve 103 allowing flow only in the direction of the arrow 105. In the embodiment of FIG. 7, the vent comprises a hollow vent 107 having its opening 109 filled with wax 111 which melts in the presence of heat allowing pressure release from the container 23. 
     Embossed reinforcing ribs 27WR also are formed on the web 27W to make the web 27W stiffer which prevents the web from being pushed outward which also minimizes the problem of the segments or vanes not opening outward. The ribs 27WR are formed by bending the web 27W outward after the score lines 41A are formed which tends to pull metal away from the score lines 41A-46A faciliting opening of the segments 41-46. 
     Referring now to FIGS. 8 and 9, there is shown an extension fuse 161 adapted to be attached to the main fuse 61 if needed The main fuse 61 extends out of the lower lid 27 about 1/2 of an inch and has a diameter of about 3/32 of an inch. The extension fuse 161 is formed of the same material as fuse 61 and has the same diameter. Its length is about 51/2 inches. It has two sleeves 163 and 165 with an opening 167 formed at its end 161U on one side of the fuse 161 between the fuse 161 and the sleeve 163 for receiving the lower end of the fuse 61 and clamping the fuse 161 to the fuse 61. By attaching the fuse 161 to the fuse 61, the effective fuse will be closer to the fire source and will result in the fire extinguisher being actuated sooner than if only the shorter main fuse 61 were used. 
     Referring to FIG. 10 there is disclosed an acoustic detector 127 and circuitry for closing a solenoid actuated valve 123 in a gas pipe 125 leading to a stove 127, when the detector 121 and circuity detects the sound produced upon actuation of the explosive charge. 120 A.C. voltage is taken from leads 131A and 131B and applied by way of a 12 volt transformer 135 to a full wave rectifier 137 which converts the A.C. to D.C. voltage. The D.C. is applied to operate the detector 127 and a filter comprising a capacitor 143 and a potentiometer 145. The filter is a high pass filter and passes a voltage representative of the sound produced upon explosion of the explosive charge 51 for producing an output for controlling a triac 139 for allowing passage of A.C. to lead 141A for closing the normally open valve 123. The purpose of the filter is to prevent lower frequency background noise from actuating the valve 123. 
     More details of the circuit of FIG. 10 now will be described. Member 151 is a 5 volt regulator which produces 5 volts at its output for operation some of the circuity. Member 153 is an operational amplifier for amplifying the output of the microphone 127. The gain of the amplifier is controlled by potentiometer 155 and its frequency response is controlled by potentiometer 145. Members 161A, 161B, 161C, and 161E are nand gates of a single chip. Gates 161A and 161B are inverters and gates 161C and 161D form a set-reset flip-flop. Member 171 is an optical coupler. Five volts on its left side as shown, turns on two SCRs which turns on the triac 139 to close the solenoid valve 123. In one embodiment the representative of sound frequencies above about one Khz. and blocks lower frequencies. 
     The electrical valves and other information of the components of the circuitry are set forth on FIG. 10.

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