GB2093975A

GB2093975A - Safety devices for flued gas appliances

Info

Publication number: GB2093975A
Application number: GB8134632A
Authority: GB
Original assignee: TI Domestic Appliances Ltd
Current assignee: TI Domestic Appliances Ltd
Priority date: 1981-02-26
Filing date: 1981-11-17
Publication date: 1982-09-08
Also published as: GB2093975B

Abstract

The safety device comprises a gas control valve (11) in the gas supply line to a main burner (9) of the appliance and a thermocouple (14) heated by a pilot flame. The control valve has a valve member (4) urged on to a seat (3) by a spring (5), a manually operable push rod (12) for opening the valve member, and an electromagnet (13) which is connected to the thermocouple and which holds the valve member (4) in an open position when the pilot flame heats the thermocouple. A normally open temperature sensitive valve e.g. a fusible valve (16) is placed in the gas supply line to the pilot burner and at a position adjacent to an aperture communicating with the flue but not in the normal combustion product flow path of the appliance. If the flue becomes blocked, the combustion products are deflected over the fusible valve (16) which will close to cut off gas supply to the pilot burner. The e.m.f. to the electromagnet (13) will fall and the valve member (4) will close to cut off gas supply to the main burner. <IMAGE>

Description

SPECIFICATION Safety devices for flued gas appliances This invention relates to a safety device for a flued gas appliance.

In the event of a blockage of the chimney or flue of a gas appliance the products of combustion have no alternative but to pass into the room in which the appliance is situated. For a short period of time this condition may not be noticed, but if it is prolonged then the room becomes stuffy and creates a drowsy effect upon the occupants which could eventually become dangerous.

According to the present invention, a safety device for a flued gas appliance having main and pilot burners, comprises a gas control valve for being placed in the gas supply line to the main burner, the control valve having a valve member urged onto a seat by resilient means and an electromagnet for holding the valve member in an open position, a thermocouple for being heated by a pilot flame and electrically connected to the electromagnet of the control valve, and a normally open temperature sensitive valve for being placed in the gas supply line to the pilot burner and at a position adjacent to an aperture communicating with the flue but not in the normal combustion product flow path of the appliance, the arrangement being such that if the flue becomes blocked in use, the combustion products are deflected over the temperature sensitive valve which will close to cut off gas supply to the pilot burner and reduce the heat to the thermocouple with the result that the e.m.f. to the electromagnet falls and the valve member closes against the seat to cut of gas supply to the main burner.

It is a standard requirement of gas appliance construction that in the event of temporary flue blockage such as downdraught the products of combustion pass through an opening in the appliance designed so that the burner can continue to operate in a satisfactory manner.

Under normal flue conditions this opening allows air to be drawn from the room by the up draught caused by hot combustion gases passing up the flue. The temperature of this air stream, despite some effect by radiant and/or conducted heat, is relatively cool. Should down draught occur for any reason and the hot gases are deflected down through this opening the temperature at this position rises significantly. This temperature rise is sensed by the temperature-sensitive valve and used to cut off the fuel supply.

Preferably, the temperature sensitive valve is a fusible valve.

Advantageously, the control valve is provided with a manually operable valve opening arrangement. The valve opening arrangement may comprise a push rod for lifting the valve off of its seat.

The invention also provides a flued gas appliance having a safety device as above described, the control valve being placed in the gas supply line to the main burner and the temperature-sensitive valve being placed in the gas supply line to the pilot burner.

In the accompanying drawings: Figure 1 shows a typical arrangement of a gas fire fitted with a device for cutting off the fuel supply in the event of a blockage of the chimney or flue of the gas fire, and Figure 2 shows the device of Figure 1 in more detail.

As shown in Figure 1, the gas fire has a gas relay or control valve 1 a gas tap 10, and a burner 9 placed such that flames and combustion products pass through radiant block 8, heat exchanger 7 and flue 6.

As shown in Figures 1 and 2, the valve 11 is a thermo electric valve of well known construction where a valve member 4 is opened manually by push rod 12 having a return spring 12' and held in the open position against the action of a spring 5 by electro magnet 13 whose e.m.f. is received from thermo couple 14 heated by pilot flame 1 5.

In the pilot supply line is fitted a fusible valve 1 6 which comprises valve member 17, urged towards a valve seat 18 by a spring 19, and a washer 20, of fusible material, holding the valve member 1 7 in an open position by resting against a shoulder 21.

As shown in Figure 1, the gas fire has a vent space 22 between the radiant block 8 and the flue 6. This is so that, in the event of a downdraught due for example to wind, the combustion products can escape into the surrounding atmosphere without interfering with the burner.

The fusible valve 1 6 is placed just outside so that in normal operation it remains relatively cool and while not exposed to the combustion products it remains open. The fusible valve 1 6 is so designed that if it is exposed to combustion products flowing out from the space 22, for more than a short time, it will close.

However, should the flue become blocked then the flue products are deflected down through the space 22 and pass upwards over the valve 16.

Hence, the valve 1 6 is heated and fusible washer 20 melts thereby allowing valve member 17 to close against seat 18 and shut off the gas to the pilot 1 5. Lack of heat to thermo couple 14 reduces the e.m.f. to electro magnet 13 and the valve member 4 is urged onto seat 3 by the spring 5.

This particular system is readily applicable to flued central heating boilers and similar large consumption appliances which have a thermo electric valve already in the control system. It is, therefore, only necessary to re-route the pilot supply tube and fit a fusible valve as described above to add flue safety features to the appliance.

Claims

1. A safety device for a flued gas appliance having main and pilot burners comprising a gas control valve for being placed in the gas supply line to the main burner, the control valve having a valve member urged onto a seat by resilient means

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Safety devices for flued gas appliances This invention relates to a safety device for a flued gas appliance. In the event of a blockage of the chimney or flue of a gas appliance the products of combustion have no alternative but to pass into the room in which the appliance is situated. For a short period of time this condition may not be noticed, but if it is prolonged then the room becomes stuffy and creates a drowsy effect upon the occupants which could eventually become dangerous. According to the present invention, a safety device for a flued gas appliance having main and pilot burners, comprises a gas control valve for being placed in the gas supply line to the main burner, the control valve having a valve member urged onto a seat by resilient means and an electromagnet for holding the valve member in an open position, a thermocouple for being heated by a pilot flame and electrically connected to the electromagnet of the control valve, and a normally open temperature sensitive valve for being placed in the gas supply line to the pilot burner and at a position adjacent to an aperture communicating with the flue but not in the normal combustion product flow path of the appliance, the arrangement being such that if the flue becomes blocked in use, the combustion products are deflected over the temperature sensitive valve which will close to cut off gas supply to the pilot burner and reduce the heat to the thermocouple with the result that the e.m.f. to the electromagnet falls and the valve member closes against the seat to cut of gas supply to the main burner. It is a standard requirement of gas appliance construction that in the event of temporary flue blockage such as downdraught the products of combustion pass through an opening in the appliance designed so that the burner can continue to operate in a satisfactory manner. Under normal flue conditions this opening allows air to be drawn from the room by the up draught caused by hot combustion gases passing up the flue. The temperature of this air stream, despite some effect by radiant and/or conducted heat, is relatively cool. Should down draught occur for any reason and the hot gases are deflected down through this opening the temperature at this position rises significantly. This temperature rise is sensed by the temperature-sensitive valve and used to cut off the fuel supply. Preferably, the temperature sensitive valve is a fusible valve. Advantageously, the control valve is provided with a manually operable valve opening arrangement. The valve opening arrangement may comprise a push rod for lifting the valve off of its seat. The invention also provides a flued gas appliance having a safety device as above described, the control valve being placed in the gas supply line to the main burner and the temperature-sensitive valve being placed in the gas supply line to the pilot burner. In the accompanying drawings: Figure 1 shows a typical arrangement of a gas fire fitted with a device for cutting off the fuel supply in the event of a blockage of the chimney or flue of the gas fire, and Figure 2 shows the device of Figure 1 in more detail. As shown in Figure 1, the gas fire has a gas relay or control valve 1 a gas tap 10, and a burner 9 placed such that flames and combustion products pass through radiant block 8, heat exchanger 7 and flue 6. As shown in Figures 1 and 2, the valve 11 is a thermo electric valve of well known construction where a valve member 4 is opened manually by push rod 12 having a return spring 12' and held in the open position against the action of a spring 5 by electro magnet 13 whose e.m.f. is received from thermo couple 14 heated by pilot flame 1 5. In the pilot supply line is fitted a fusible valve 1 6 which comprises valve member 17, urged towards a valve seat 18 by a spring 19, and a washer 20, of fusible material, holding the valve member 1 7 in an open position by resting against a shoulder 21. As shown in Figure 1, the gas fire has a vent space 22 between the radiant block 8 and the flue 6. This is so that, in the event of a downdraught due for example to wind, the combustion products can escape into the surrounding atmosphere without interfering with the burner. The fusible valve 1 6 is placed just outside so that in normal operation it remains relatively cool and while not exposed to the combustion products it remains open. The fusible valve 1 6 is so designed that if it is exposed to combustion products flowing out from the space 22, for more than a short time, it will close. However, should the flue become blocked then the flue products are deflected down through the space 22 and pass upwards over the valve 16. Hence, the valve 1 6 is heated and fusible washer 20 melts thereby allowing valve member 17 to close against seat 18 and shut off the gas to the pilot 1 5. Lack of heat to thermo couple 14 reduces the e.m.f. to electro magnet 13 and the valve member 4 is urged onto seat 3 by the spring 5. This particular system is readily applicable to flued central heating boilers and similar large consumption appliances which have a thermo electric valve already in the control system. It is, therefore, only necessary to re-route the pilot supply tube and fit a fusible valve as described above to add flue safety features to the appliance. Claims

1. A safety device for a flued gas appliance having main and pilot burners comprising a gas control valve for being placed in the gas supply line to the main burner, the control valve having a valve member urged onto a seat by resilient means and an electromagnet for holding the valve member in an open position, a thermocouple for being heated by a pilot flame and electrically connected to the electromagnet of the control valve, and a normally open temperature sensitive valve for being placed in the gas supply line to the pilot burner and at a position adjacent to an aperture communicating with the flue but not in the normal combustion product flow path of the appliance, the arrangement being such that if the flue becomes blocked in use, the combustion products are deflected over the temperature sensitive valve which will close to cut off gas supply to the pilot burner and reduce the heat to the thermocouple with the result that the e.m.f. to the electromagnet falls and the valve member closes against the seat to cut off gas supply to the main burner.

2. The safety device of claim 1, wherein the temperature sensitive valve is a fusible valve.

3. The safety device of claim 1 or claim 2, wherein the control valve is provided with a manually operable valve opening arrangement.

4. The safety device of Claim 3, wherein the valve opening arrangement comprises a spring loaded push rod for lifting the valve off of its seat.

5. A safety device for a flued gas appliance substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

6. A flued gas appliance having a safety device according to any one of the preceding claims, the control valve being placed in the gas supply line to the main burner and the temperature-sensitive valve being placed in the gas supply line to the pilot burner.