Fire Extinguishing System For Cook Stoves And Ranges

Abstract

An automatic fire extinguishing system for a cooking range having top burners includes a hood mountable over the range. A tank containing fire extinguishing fluid is removably mounted in the hood. The tank has a solenoid operated valve connected in circuit with a thermostat and power line to discharge fluid from the tank when the thermostat is operated. The range may have electric or gas burners. A solenoid operated switch or solenoid operated valve is connected in circuit with the thermostat to open the power line to the electric burners or to open the gas main to the gas burners when the thermostat operates. An automatically operated exhaust fan and alarm are also provided. The system includes manually operable set and reset switch means.

Description

This invention relates to an automatically operated fire extinguishing system for an electric or gas cook stove or range, and particularly concerns such a system associated with a hood over the stove or range.

Automatic fire extinguishing systems heretofore known for use in conjunction with cook stoves and ranges have generally been concerned with extinguishing a fire due to burning fat or grease in a pot or kettle. The system was solely concerned with extinguishing the fire and no provision was made for turning off the electric or gas burners of the stove. Frequently the fire extinguishing system extinguished the lighted burners of a gas stove which created a very hazardous condition by permitting fuel gas to flow freely from the burners. Where the system extinguished the fire on an electric stove, the burners were left energized to reignite spilled grease and fat. No provision was made for automatically exhausting smoke and fumes generated during the fire and while it was being extinguished. No provision was made for sounding an alarm. Inadequate provision was made operating the entire system manually in lieu of or in addition to automatic operation.

The present invention is directed at overcoming the above and other shortcomings, deficiencies, objections, and disadvantages of prior systems employed for extinguishing kitchen fires on stoves and ranges and in hoods over the stoves.

According to the present invention a removable and rechargeable fire extinguisher is installed in a hood over an electric or gas range in a kitchen. Strategically located thermostats on the hood are connected in a circuit with a circuit breaker for the electric lines energizing the burners of the electric range. Where a gas stove is employed, the thermostats are connected in circuit with a solenoid operated valve for turning off the gas supply to the stove. Also connected in circuit with the thermostats is a solenoid operated valve which turns on the fire extinguisher to discharge a gaseous or liquid fire extinguishing agent around the hood and on the stove or range. Suitable agents for this purpose are described in U.S. Pat. No. 3,463,233. An exhaust fan may be provided in the system arranged to turn on automatically for exhausting fumes and smoke. An automatically operated audible alarm may also be provided.

It is therefore a principal object of the invention to provide a fire extinguishing system for a kitchen stove or range in which a fire extinguisher is mounted in a hood over the stove or range.

Another object is to provide a system as described, with thermostats connected in circuit with the fire extinguisher to turn it on automatically, and further connected in circuit with a solenoid operated switch or valve for turning off or opening the power or fuel line energizing the burners of the stove or range.

A further object is to provide a fire extinguishing system as described with means for automatically operating an exhaust fan in the event a fire to draw off smoke after the fire is extinguished, and with means for operating a fire alarm.

Other and further features, objects and advantages of the invention will become apparent from the following detailed description taken together with the drawings, wherein:

FIG. 1 is a perspective view of a hood over a cooking stove or range provided with a fire extinguishing system according to the invention.

FIG. 2 is a bottom plan view of the hood taken on line 2--2 of FIG. 1.

FIG. 3 is a vertical sectional view taken on line 3--3 of FIG. 1.

FIGS. 4 and 5 are diagrams of electrical control circuits used in connection with fire extinguishing systems for electric and gas ranges respectively.

Referring first to FIGS. 1-2, there is shown a stove or range 10 having burners 12 on top 14. This may be an electric range having burner control rheostats 16 on the top of the range. Over the range on kitchen wall 18 is a hood 20. This hood has a downwardly and forwardly slanted top wall 22, a wide, vertical rear wall 23, vertical trapezoidal side walls 24, 26 and a vertical, narrow front wall 28. The hood is open at the bottom. Mounted inside the hood on brackets 30 is a tank 32 containing fire extinguishing fluid 34. The fluid is contained under pressure in a known manner. Extending around the inside walls of the hood near the open bottom is an endless pipe 36, supported on brackets 37. This pipe is arranged as a rectangular ring as clearly shown in FIG. 2. The pipe is connected to the tank 32 via a flexible conduit 38 and fittings 40, 42. Fitting 40 is joined to a solenoid operated valve 44 at the head of the tank. Fitting 42 is joined to pipe 36. When valve 44 is operated the fire extinguishing fluid is discharged into pipe 36. Pipe 36 is provided with bottom holes 46 for spraying the fire extinguishing fluid on the top 14 of range 10. Further holes 48 are provided at inner sides of the pipe to spray fluid 34 laterally inside the hood.

Thermostats 49 are located at forward outside corners of the hood. Another thermostat 50 is located inside the hood at rear wall 23. A duct 52 is provided at the top of the hood. In this duct is an exhaust fan 54 located in an exhaust path leading from the hood to chimney pipe 56 in kitchen wall 18. Control switches 58 and 60 for the fan are provided on the front of duct 52. A removable filter or screen 61 is mounted on pipe 36 just below tank 32.

A manually operable RESET switch 62 is located at side wall 26 of the hood. A circuit breaker 63 is connected in circuit with the power supply line 65 for burners 12 as explained below in detail in connection with FIG. 4. Another manually operated switch 64 is provided on wall 18 for turning on the fire extinguishing system manually. An electrically operated audible alarm 66 may also be provided for the system. This alarm has a control switch 67.

FIG. 4 shows schematically a control circuit 100 in which parts shown in FIGS. 1 and 2 are connected. Power line 65 includes wires 102, 104 connected via double pole switch 106 to burners 12 which are in series respectively with rheostats 16. The double-pole switch 106 is normally closed but can be opened by plunger 108 of solenoid operated circuit breaker 63. The solenoid 110 of the circuit breaker is connected at opposite ends to contacts 112, 113 of a relay 114. Contacts 112, 113 are normally open with respect to contacts 115, 116. Contacts 115, 116 are connected to wires 104 and 102 respectively. Coil 118 of relay 114 is connected to wire 104 and to terminal 120 of normally closed RESET switch 62. This is a pushbutton switch. Terminal 122 of this switch is connected to contact 124 of relay 114. This contact is normally open with respect to contact 125 which is connected to power wire 102. Also connected to relay contacts 112, 113 are opposite ends of solenoid 126 which operates the valve 44 at the end of tank 32 for discharging fluid into apertured pipe 36.

A time delay relay 130 has a coil 132 connected to relay contacts 112, 113. The relay has contact 133 connected to relay contact 112. Contact 134 is connected to one terminal of fan motor 136. The other terminal of the fan motor is connected via switch 60 to relay contact 113. The terminals of the fan motor are also connected via wires 140 and double-pole switch 58 to power wires 102, 104. Audible alarm 66 is connected at one end via switch 67 to relay contact 113. The other terminal is connected to relay contact 112. Thermostats 49 and 50 are connected in parallel. Open contacts 150 are connected to wire 102. Bimetallic elements 152 are connected to relay coil 118.

The manually operable emergency set switch 64 is a normally open double-pole switch between power wires 102, 104 and points P1, P2 to which are connected solenoids 110, 126, alarm 66 and relay 130. Closure of switch 64 bypasses relay 114 to operate the system instantly under manual control regardless of the open or closed condition of thermostats 49, 50.

In operation of the system including circuit 100, relay 118 is normally deenergized and switch 64 is open. Switch 106 is closed. This enables operation of the burners 12 in a normal way without interference by the fire extinguishing system. If a fire occurs on the stove or range 10, any one or all of the thermostats 49, 50 will be heated to its operating temperature which is above the highest temperature encountered above the range during normal operation. Closure of any thermostat applies power to relay coil 118. This relay closes and is held closed via its holding circuit including closed contacts 124, 125 and RESET switch 62. Thus even if the thermostats subsequently open, relay 114 will remain energized. Closure of relay contacts 112, 115 and 113, 116 energizes solenoid 126 and the valve 44 is operated to discharge fire extinguishing fluid into pipe ring 36 which sprays the fluid on the top of the range and across the hood. Closure of the contacts of relay 114 also actuates alarm 66 and this alarm sounds. Closure of the contacts of relay 114 also energizes relay 130. This relay has a time delay of 5 to 10 minutes to allow time for the fire extinguisher to extinguish the fire. Then the relay closes and the fan motor is turned on to clear the kitchen of smoke and fumes.

It is possible to omit alarm 66 if this component is not desired. Also, the alarm can be turned off if it is automatically operated by opening switch 67, or the alarm can be initially deactivated by opening switch 67.

It is possible to omit the exhaust fan 54, in which case motor 136 and relay 130 can be omitted. Where the fan is provided it is possible to turn the fan on manually at any time. This can be done by closing switch 58 manually. If the fan operates automatically, switch 60 can be opened manually to stop the fan, or switch 60 can be left open to deactivate the fan motor.

Once the relay 114 is energized, the fire extinguisher discharges its contents until exhausted. Switch 106 is opened by circuit breaker 63 and remains open. The fan and alarm also stay on. The system can be deactivated entirely by momentarily pressing the RESET switch 62 to open it. This will open the holding circuit for relay 114. As a safety provision the system will automatically operate again if any one of the thermostats 49, 50 is closed, indicating excessive temperature in the hood 20 or over the range 10.

If an attendant happens to be present when a fire breaks out, the emergency switch 64 can be closed manually should relay 114 fail to operate for any reason, or should thermostats 49, 50 fail to respond at once. This will apply power to solenoids 110 and 126, and to relay 130 and alarm 66 independently of the relay 114.

The circuit 100A shown in FIG. 5 is similar to circuit 100 except that solenoid operated valve 160 is provided for opening gas main 162 automatically in case of a fire on the range where gas burners 12a controlled by hand valves 16a are installed. All parts mounted in the hood 20 shown in FIG. 1 apply equally well to circuit 100A, so that parts of circuit 100A corresponding to those of circuit 100 are identically numbered. Power to operate the system is provided via wires 102', 104'.

Valve 160 has a solenoid 110a which actuates plunger 108a of the valve. The solenoid is energized by operation of relay 114 in the same manner as described above. Solenoid 126 which operates valve 44 of tank 32, the fan motor 136, alarm 66, the time delay relay 130 and thermostats 49, 50 all operate as described above. Emergency switch 64 is provided to operate the system manually when necessary.

The systems described are adapted for installation in kitchens of households, restaurants, hotels, hospitals, etc. The systems are adapted for operation automatically in the absence of or in the presence of an attendant. However, they also have provisions for manual operation. The systems can be installed on hoods of existing ranges with very minor alterations, or they can be installed as original equipment when newly manufactured. They fulfill a long felt need for automatic effective protection against fire at kitchen ranges and stoves.

While a limited number of embodiments of the invention have been described this has been by way of example only. Many modifications and variations are possible without departing from the invention.

Claims

What is claimed is:

1. An automatic fire extinguishing system for a cooking range having top burners comprising a hood mountable over the range, said hood having a closed top, vertical side walls and an open bottom; a tank containing fire extinguishing fluid removably disposed inside the walls of the hood; a solenoid operated valve on said tank for releasing said fluid when the solenoid is energized; at least one thermostat set to operate at a predetermined temperature and disposed for sensing the temperature of a fire between the range and hood; an electric power line; and circuit means interconnecting the thermostat, solenoid and power line for actuating the valve when the thermostat operates upon the occurrence of a fire between the range and hood, and relay means in said circuit connected between the power line and said solenoid and arranged for energizing the solenoid and keeping the solenoid energized regardless of the temperature sensed by the thermostat after the thermostat is once operated.

2. An automatic fire extinguishing system as defined in claim 1, further comprising an apertured pipe arranged as a rectangular ring inside the hood and connected to said tank via said valve for spraying said fluid on the range and across the hood.

3. An automatic fire extinguishing system as defined in claim 1, wherein said range includes electric burners, said system further comprising switch means connected in said power line for cutting off power supplied to the burners, and another solenoid connected in said circuit and arranged to open said switch means when the first named solenoid is energized by operation of said thermostat.

4. An automatic fire extinguishing system as defined in claim 3, further comprising relay means in said circuit connected between the power line and both solenoids and arranged for energizing the solenoids and keeping the solenoids energized regardless of the temperature sensed by the thermostat after the thermostat is once operated; and reset switch means connected in circuit with said relay means for resetting the same to deenergized condition and for deenergizing the solenoids to close the first named switch means and to close said valve on the tank.

5. An automatic fire extinguishing system as defined in claim 1, further comprising reset switch means connected in circuit with said relay means for resetting the same to deenergized condition and for deenergizing said solenoid.

6. An automatic fire extinguishing system as defined in claim 5, further comprising a motor driven fan arranged to draw fumes and smoke from the hood; and time delay relay means connected in circuit with said first named relay means and said fan for operating the fan only after a predetermined time has elapsed following operation of said solenoid to discharge said fluid from said tank.

7. An automatic fire extinguishing system as defined in claim 6, further comprising an alarm connected in circuit with the first named relay means for actuation thereby when said first relay means is energized.

8. An automatic fire extinguishing system as defined in claim 1, wherein said range includes gas burners and a gas main connected to said burners, said system further comprising another solenoid operated valve connected in said circuit and arranged to close said gas main when the first named solenoid is energized by operation of said thermostat.

9. An automatic fire extinguishing system as defined in claim 1, further comprising reset switch means connected in said circuit for deenergizing said solenoid after the same has become energized; and manually operable set switch means connected in said circuit and arranged to energize said solenoid independently of the temperature sensed by said thermostat.