Abstract:
Fires in kitchen appliances are detected and controlled by a detection and control system that activates a fire extinguishing system when the fire is detected, terminates the supply of electricity and/or gas to the appliances, and initiates audible and visual alarms. The audible alarm can be terminated, while the visual alarm continues until the system is restored to a pre-detection state. The system includes a control circuit, and a fire detection means with a moveable member that engages a normally closed microswitch in the control circuit to open the control circuit. Relays in the control circuit change state upon opening of the control circuit to de-energize the appliance, and audible and visual alarms are activated. The audible alarm can be manually terminated. However, the visual alarm remains activated until the system is recharged and returned to the ready state.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates generally to a system for automatically shutting down cooking appliances and/or associated equipment in accordance with NFDA recommended standards in the event of a fire, and in particular to a fail-safe system of this type that will also shut down in the event of a failure in the system, and which will continue to indicate a failure until corrections are made by authorized personnel. 
     (2) Description of the Prior Art 
     Commercial kitchens and related facilities having a plurality of cooking appliances are normally equipped with a fire extinguishing mechanism that is automatically activated in the event of a fire, such as a grease fire, at one of the appliances. The extinguishing mechanism is usually comprised of a source of an extinguishing chemical that is connected via a piping network to discharge ports that are directed toward the cooking surfaces of the appliance. A discharge valve is used to control the flow of chemicals from the source. The discharge valve is adapted to be opened when an associated mechanism detects a fire. 
     For example, a spring-loaded discharge valve may be held in a closed position by a taut cable, which includes one or more fusable heat links positioned above the cooking appliances. When one of the links is melted by the heat from a cooking fire, the cable is released, opening the discharge valve, and discharging fire extinguishing chemicals onto the surfaces of the cooking appliances to extinguish the fire. 
     An effective, complaint fire extinguishing system must also include means to disconnect the cooking appliances from the energy source when a fire is detected. Otherwise, the fire-extinguishing chemical will be exhausted, and the fire may continue or restart due to the continuing supply of energy, i.e., electricity or gas. In the case of an electrical appliance, the appliance is de-energized by opening the electrical circuit to the appliance. In the case of an gas fueled appliance, the appliance is de-energized by shutting off the gas supply, e.g., by closing a valve, such as a solenoid actuated valve. 
     An effective system should also include an alarm to alert others to the existence of the fire. This alarm can be activated at the time the chemical is discharged, and continues to emit a signal, e.g., a sound and/or a light signal, until manually disconnected. The inclusion of a signal mechanism is mandated by NFPA-17A of the National Fire Protection Codes for “Wet Chemical Extinguishing Systems” used for restaurant canopy hoods. NFPA-17A states: 
     “A signal shall be provided to show that the system has operated, that personnel response is needed, and that the system is in need of recharge. The extinguishing system shall be connected to the fire alarm system, if provided, in accordance with the requirements of NFPA 72, National Fire Alarm Codes, so that the actuation of the extinguishing system will sound the fire alarm as well as provide the function of the extinguishing system.” 
     Various fire extinguishing systems for use with restaurant cooking appliances have been proposed in the prior art. The following patents are representative of prior art systems: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 3,653,443 
                 Dockery 
               
               
                 4,356,870 
                 Gaylord et al. 
               
               
                 4,675,541 
                 Peters et al. 
               
               
                 4,773,485 
                 Silverman 
               
               
                 4,830,116 
                 Walden et.al. 
               
               
                 4,979,572 
                 Mikulec 
               
               
                 5,127,479 
                 Stehling et al. 
               
               
                 5,297,636 
                 North 
               
               
                 5,351,760 
                 Tabor. Jr. 
               
               
                 5,628,368 
                 Sundholm 
               
               
                 5,871,057 
                 Stehling et al. 
               
               
                   
               
             
          
         
       
     
     Despite considerable efforts, there is still a need for a system for effectively de-energizing a plurality of cooking appliances and other restaurant equipment, as required, in the event of a fire, while emitting a signal as required by NFPA-17A. In particular, a system of this type is needed that will not only de-energize appliances in the event of a fire, but which will de-energize appliances in the event of a detected failure in the microswitch or other circuit component. Therefore, the user will not be falsely assured that a functional system is being used to monitor conditions when, in fact, the system is not functioning. 
     A system of this type should also be designed so that the alarm cannot be fully deactivated until the system has been recharged after a discharge of chemical, or has been repaired after a malfunction has been detected. For example, if the alarm system includes both a sound and light emitting components, the operator should be prevented from disconnected both components until the system has be recharged or repaired by authorized and skilled personnel. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a shutdown or control system for de-energizing kitchen appliances in the event of a fire. The system is used in conjunction with a fire extinguishing system comprised of a source of fire extinguishing chemical or other material, a release mechanism for releasing the fire extinguishing material in the event of a fire. 
     Basically, the shutdown system is comprised of a normally closed switch, positioned to be opened when the fire extinguishing system is activated, a plurality of relays that change state when the switch is opened, the relays being capable of de-energizing appliances, and an alarm mechanism that includes an audible component that can be deactivated by an operator, and a visual component that can only be deactivated by repair and recharging of the fire extinguishing system. 
     Preferably, the normally closed switch is positioned in the path of a component of the fire extinguishing system that moves from a ready position to a released position when a fire is detected, so that the component engages the switch to move the switch from a closed state to an open state. For example, the switch can be a microswitch that is positioned adjacent a component of a fire extinguisher discharge valve control mechanism that moves from a restrained position to a released position when a fire is detected, so that the component engages the microswitch when at the released position. 
     More specifically, the fire extinguishing system may be comprised of a control mechanism that includes a pivotal member moveable between first and second positions, with the pivotal member being urged toward the second position by a spring, and held in the first position by a cable that includes a heat fusable link. In the event of a fire, the heat fusable link is severed by the heat from the fire, releasing the cable and allowing the pivotal member to move under the influence of the spring to the second position. 
     A microswitch is positioned at the second position in the path of the pivotal member, so that a component of the pivotal member engages the microswitch to move the switch from the closed state to the open state. The pivotal member also engages a release member, such as a valve, to release fire extinguishing chemicals from a supply source, such as a pressurized tank. 
     The microswitch is in a primary circuit with a plurality of relays that are in secondary circuits with different appliance controllers, e.g., switches or valves. The circuits are designed so that the circuits to the appliances are in a closed or completed state when the microswitch is closed. These circuits may be designed with the relays in an open state or a closed state. Thus, for purposes of description, when the appliances are energized, the relays will be described as being in the energized state, and in the deenergized state when the appliances are deenergized. 
     The microswitch is also in a circuit with an audible alarm, such as a horn, and a visual alarm, such as a strobe light. The audible and visual alarms are in a deenergized state when the microswitch is closed, and are moved to the energized state when the microswitch is opened. The horn is also in a circuit with a switch that can be used to deactivate the horn. 
     During the monitoring cycle, the control system is plugged into a power source, normally a 120 volt AC source, that provides energy to a closed primary circuit including the microswitch and a plurality of appliance control relays that are each connectable to a switch or valve (collectively referred to as controllers) that is interposed between an appliance or other powered device in the kitchen area, and its respective source of energy. The primary circuit is also connected to secondary circuits that include audible and visual alarms. 
     Fires are detected by a fire detection system that includes a tensioned cable positioned above the areas where fires may occur. For example, the cable may be positioned inside a hood that is located over the cooking applicances. The cable includes heat fusable links above each appliance. Such links are known in the relevant art and include means for connecting cable segments to opposite sides of the link, with the link being constructed of a material that melts at relatively low temperatures. 
     When exposed to a cooking fire, the link melts to separate the cable. The cable is attached to a moveable member, preferably a pivotal member that has a pivot end and a distal end. The pivotal member is held at a restrained position when the cable is under tension, and moves to a released position when the cable is released. 
     The fire extinguishing system also includes a source of fire extinguishing chemicals, e.g., a pressurized tank, and conduits or a piping network leading from the fire extinguishing chemical source to discharge nozzles positioned above the cooking appliances. A normally closed control valve is positioned between the chemical source and the nozzles, preventing discharge of chemicals. This valve is positioned in the path of, and engaged by, the moveable member when the movable member is in the released position. 
     The microswitch in the control circuit is also positioned in the path of the moveable member, and is also engaged by the moveable member in the released position. Thus, when the moveable member is released, the moveable member contacts the fire extinguisher valve, opening the valve to release the extinguishing material. Also, the moveable member contacts the microswitch to open the primary control circuit. As a result, the relays in the primary circuit change state, activating the controller, e.g., opening an electrical switch, or closing a control valve. As a result the supply of energy, e.g., electricity or gas, is terminated. 
     Another relay in the primary circuit is also in a second circuit with a normally open, audible alarm circuit, and a normally open visual alarm circuit. Opening of the primary circuit causes the relay to change state, closing the alarm circuits to activate the audible and visual alarms, thereby alerting appropriate personnel. The audible alarm can be immediately deactivated by a pushbutton switch or another kind of a switch. However, no provision for opening the visual alarm circuit is provided. Therefore, the visual alarm continues to signal until the primary circuit is restored to its closed state. This restoration cannot occur until the microswitch is again closed, which requires authorized personnel to recharge the fire extinguishing system and restore the cable to its tensioned state. 
     Accordingly, one aspect of the present invention is to provide an emergency shutdown system to deenergize appliances upon activation of a fire extinguishing system comprising a microswitch moveable between from a closed position to an open position upon activation of the fire extinguishing system. A plurality of relays are in a first circuit with the microswitch, each of the relays being in a second circuit with an applicance controller. The second circuits are closed when the microswitch is in a closed position, and the relays change from a first state to a second state, opening the second circuits when the microswitch is moved to an open position. An audible alarm is in the circuit with the microswitch, the audible alarm being moveable from an unenergized state to an energized state when the microswitch is opened, the audible alarm also being in a circuit with a silencing switch adapted to return the audible alarm to the unenergized state. A visual alarm is also in the circuit with the microswitch, the visual alarm being moveable from an unenergized state to an energized state when the microswitch is opened, the visual alarm being returnable to the unenergized state only when the fire extinguishing system is returned to the recharged and ready state. 
     Another aspect of the present invention is to provide a fire control system for use with at least one kitchen appliance comprising a fire detection means to activate a fire extinguishing system; a fire extinguishing system activated upon detection of a fire; and a control system. The control system includes a microswitch moveable between from a closed position to an open position upon detection of a fire; a plurality of relays in a first circuit with the microswitch, each of said relays being in a second circuit with an applicance controller; the second circuits being closed when the microswitch is in a closed position. The relays change from a first state to a second state and open the second circuits when the microswitch is moved to an open position. An audible alarm is in a circuit with the microswitch, with the audible alarm being moveable from an unenergized state to an energized state when the microswitch is opened, the audible alarm also being in a circuit with a silencing switch adapted to return the audible alarm to the unenergized state. A visual alarm is also in the circuit with the microswitch, the visual alarm being moveable from an unenergized state to an energized state when the microswitch is opened, the visual alarm being returnable to the unenergized state only when said fire extinguishing system is returned to the recharged and ready state. 
     These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic of a fire detection and extinguishing system joined to the control system. 
     FIGS. 2 and 3 are diagram of the electrical circuit of the preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, terms such as horizontal, upright, vertical, above, below, beneath, and the like, are used solely for the purpose of clarity in illustrating the invention, and should not be taken as words of limitation. The drawings are for the purpose of illustrating the invention and are not intended to be to scale. 
     FIG. 1 illustrates a fire detection system, generally  10 , that includes a tensioned cable  12  positioned above a typical cooking appliance  14 . Cable  12  includes a plurality of heat fusable links  16  positioned above burners  18 . Cable  12  has a fixed end  20  attached to a support, and is strung around pulleys  22  to attach at its opposite end to a pivotal member  24 . Member  24  includes a pivotal end  26 , a first contact element  28  and a second contact element  30 . Spring  32  urges pivotal member  24  in a downward direction toward a released position. Pivotal member  24  is held in a restrained position, as illustrated, by cable  12 . 
     A fire extinguishing system comprises a pressurized container  34  connected by conduit  36  through normally closed control valve  38  to discharge nozzles  39  positioned above burners  18 . Valve  38  is mounted for engagement by contact element  30  of pivotal member  24  when member  24  is in the released position. Microswitch  40  is positioned for engagement by contact element  28  of pivotal member  24  when member  24  is in the released position. 
     Refer now to FIG.  2  and FIG.  3 . The control system, generally  50 , is comprised of a lockable housing  52 , with a strobe light  54  and audible alarm release button  56  on the front panel of housing  52 . A circuit board  58 , audible alarm  60 , and relevant wiring (not shown) are mounted inside housing  52 . 
     As best illustrated in FIG. 2, the circuit of the invention is comprised of first and second DPDT relays R 1  and R 2  that are in a primary circuit with DPDT relay R 3 , and SPST relays R 4  and R 5 . Relay R 1  is connected to terminal blocks TB 4  and TB 5 , and relay R 2  is connected to terminal blocks TB 6  and TB 7 . Pin connector J 1  connects the primary circuit to strobe  54  and horn  60 . TB  2  connects to a 120 volt AC source rated at a maximum of 10 amps. 
     The 120 volt AC input power is connected to terminal block TB 2 , terminals  3 ,  4 , and  5 . These connections are referred to herein by the abbreviations TB 2 - 3 , TB 2 - 4 , and TB 2 - 5 . Other connections will be similarly abbreviated. TB 2 - 3  is used for connection of the hot, 120 volt power source side. TB 2 - 4  is used for connection of the neutral side of the 120 volt power source. TB 2 - 5  is used for connection of the 120 volt AC input ground wire. Terminal block TB 3  connects the primary circuit to microswitch  40 . 
     TB 2 - 3  grounding wire is routed, via a solder joint connection, to the chassis connection between circuit board  58  and housing  52  to allow further connection to earth ground via conduit connections per the National Electric Code requirements. TB 2 - 3  is routed to J 1 - 8  (pushbutton common) and TB 3 - 6  (remote microswitch common). TB 3 - 6  is connected to R 3 - 6  and R 3 - 5 . 
     The 120 volt AC neutral connection, TB 2 - 4 , is routed to TB 1 - 1  (remote contactor), which is connected to J 1 - 3  (power light), J 1 - 7  (horn), and J 1 - 8  (strobe light). TB 1 - 1  is also attached to R 1 - 7  (coil), R 4 - 8  (coil), and to R 2 - 8 , R 3 - 7  and R 5 - 7 . The 120 volt AC ground connection, TB 2 - 5 , is routed to the chassis ground connection located on circuit board  58 . 
     During normal operation, AC current is routed TB 3 - 6  to the common connection of microswitch  40 . The normally closed contact of microswitch  40  is then routed back to TB 3 - 7 , and from TB 3 - 7  to R 1 - 8  (coil) and R 3 - 8  (coil) of R 2  and R 5 . Since a circuit now complete, relays R 1 , R 2 , R 3 , and R 5  are energized. The relay contacts of R 1  and R 2  are routed to terminal blocks located on circuit board  58 . R 1  contacts are routed to TB 4 - 8  (common), TB 4 - 9  (normally open), TB 4 - 10  (normally closed), TB 5 - 11  (normally closed), TB 5 - 12  (normally open), and TB 5 - 13  (common). R 2  contacts are routed to TB 6 - 14  (common), TB 6 - 15  (normally open), TB 6 - 16  (normally closed), TB 7 - 17  (normally closed), TB 7 - 18  (normally open), and TB 7 - 19  (common). 
     TB- 4 , TB- 5 , TB- 6 , and TB- 7  are adapted to connect with connectors (either electrical switches or valves) used to control the flow of energy (either electricity or gas) to appliances. Relay contacts are rated 10 amps at 24 volts DC, 120 and 220 volts AC. Relay R 3 , when energized (the “normal” condition), transfers 120 volt AC hot, from pin R 3 - 4  (normally open when relay R 3  is not energized) to TB 1 - 2 . TB- 1  will then create a 120 volt AC output for remote connection of relays or contactors rated for “normally energized” use. The 120 volt AC output is rated at 10 amps at 24 volts DC, 120 and 220 volts AC. 
     Using normal operating conditions, the contacts of microswitch  40  are in the normally closed position, all relay contacts are in the working position, and the remote contactor/relay output is energized. Upon loss of wiring integrity between TB 3 - 6  and TB 3 - 7 , due to opening of microswitch  40  or a fault in the field wiring, 120 volt AC power will be lost to Relays R 1 , R 2 , R 3 , and R 5 , causing contacts on TB- 4 , TB- 5 , TB- 6 , and TB- 7  to change state. Output on TB 1 - 1  and TB 1 - 2  will drop out. 
     The 120 volt AC hot, connected to R 3 - 6  (common) will now be routed from pin  2  (normally open when R 3  is energized under normal operating condition) to J 1 - 2 . J 1 - 2  is routed to the + input of strobe light  54 . 120 volt AC hot, connected to R 3 - 5  (common) is routed from pin  1  (normally open when R 3  is energized under normal operating condition), to R 4 - 6  (common). R 4 - 6  (common) is routed through R 4 - 2  (normally closed), which is then routed to J 1 - 3 , which is connected to an the + input of horn  60 . The circuit is now in “alarm” condition, shutdown relay contacts have operated, the contactor/relay output is deactivated, alarm horn  60  is sounding, and strobe light  54  is flashing. 
     Depressing momentary pushbutton  56  causes contact closure of a normally open contact block. One side of the contact block is connected to J 1 - 1 , and the other side of the contact block is connected to J 1 - 4 . Closure of the contact block allows 120 volt AC power to pass from J 1 - 1  (120 volt AC hot), to J 1 - 4 , which is connected to R 5 - 6  (common). R 5 - 6  (common) is routed to R 5 - 2  (normally open when R 5  is energized under normal operating condition). R 5 - 2  is connected to R 4 - 3  (normally open when R 4  is energized under normal operating condition), and R 4 - 7  (coil). 
     R 4  is thereby energized, allowing power from R 4 - 6  (via contact pin  3 ) to the coil. This is in turn energizes the relay in a “latched” mode. With R 4  in a “latched” mode (energized), R 4 - 2  (normally open under normal operating condition) returns to a normally open state, and breaks the 120 volt AC Hot connection directed to J 1 - 3 , in turn silencing alarm horn  60 . Even though horn  60  has been silenced, strobe light  54  will still flash, the shutdown contacts will remain in the “off” mode, and the contactor/relay output remain de-energized. Strobe  54  continues to flash until the fire detection system has be repaired, the fire extinguishing systems have been recharged, and the entire system has been returned to its ready state. 
     Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. It should be understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the follow claims.