WO1998037367A1

WO1998037367A1 - Ignition control system for igniting a fuel gas burner

Info

Publication number: WO1998037367A1
Application number: PCT/IB1998/000437
Authority: WO
Inventors: Li Ceji
Original assignee: Ranco Of Delaware, Inc.
Priority date: 1997-02-19
Filing date: 1998-02-17
Publication date: 1998-08-27
Also published as: TW401506B; AU6307398A

Abstract

An ignition system for a gaseous fuel burner having an electrical resistance ignitor series wired with the actuator of an electrically operated gas line valve controlling flow to the burner. A normally closed shunt switch by-passes current flow to the valve actuator allowing full line voltage across the ignitor for rapid heating. Upon user closing of a power line switch to light the burner, a time delay means is energized and after lapse of a predetermined interval is operable to open the shunt switch allowing current to flow to the valve operator for opening the line valve. The time interval is chosen to ensure the ignitor heats to ignition temperature before the shunt switch is opened.

Description

IGNITION CONTROL SYSTEM FOR IGNITING A FUEL GAS BURNER

BACKGROUND OF THE INVENTION

The present invention relates to electrical resistance ignitors of the type which are disposed adjacent a fuel gas burner for igniting the fuel air mixture emanating from the burner flame generating ports. In particular, the invention relates to resistance heating ignitors of the type which are employed electrically series connected with a heat motor associated with an electrically operated gasline valve controlling flow to the burner. Burner ignition systems of the latter type require that the ignitor reach ignition temperature of the gas before sufficient current flows m the valve heat motor to cause the valve to open and create flow through the burner ports. It is known to utilize an ignitor formed of a negative thermistor or negative slope resistance material such as silicon carbide having the properties that the resistance decreases with temperature. Negative slope thermistor type ignitors when connected m series with the gas valve heat motor actuator can be tailored such that the resistance maintains a level sufficient to prevent adequate current flow through the valve to cause the valve to open until the ignitor has reached ignition temperature. However, m order to achieve this result m a manner which is predictable and which will accommodate fluctuations m power line voltage, it is required to have tight control of the tolerances on the resistance value versus temperature of the ignitor and of the resistance of the heating element m the gas valve actuator. This has proven to be somewhat costly and created problems m manufacturing of the ignitors and of the heat motor actuator for the gas valve .

It has thus been desired to provide a way or means of utilizing an electrical resistance ignitor m series with a gas valve heat motor actuator and to eliminate the problems of maintaining tight control of the values of resistance for the ignitor and the valve heat motor actuator .

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide an ignition system for igniting a fuel gas burner utilizing a resistance heating ignitor electrically series connected with an actuator m an electrically operated gaslme valve.

It is a further object of the present invention to provide an ignition system for a fuel gas burner having a resistance type ignitor electrically series connected with a heat motor actuator associated with an electrically operated gaslme valve which does not require a negative thermistor type ignitor or tight control of the resistance versus temperature properties of the ignitor.

It is a further object of the present invention to provide a resistance type ignitor for a fuel gas burner of the type series connected with an electrically operated gaslme valve with the valve actuator initially shunted for a predetermined time interval to apply full line voltage across the ignitor to maximize the rate of heating of the ignitor.

The present invention provides a solution to the above described problem of eliminating the need to precisely control the resistance properties of an ignitor and the heat motor for actuating a gaslme valve to control flow through the burner. The present invention utilizes a resistance heating ignitor of the type disposed adjacent a burner for igniting the fuel gas upon impingement of the gas on the hot surface of the ignitor with the ignitor electrically series connected to the heat motor actuator m the electrically operated gas valve and employs a shunt switch for allowing full line voltage to be applied across the ignitor. The ignition system of the present invention employs a time delay which is initiated upon the user closing the line switch to power the ignitor and the time delay maintains the shunt switch closed for a sufficient period of time to allow the ignitor to reach ignition temperature whereupon the shunt switch is opened and the current flowing through the ignitor is allowed to flow through the valve actuator for opening the gas line valve.

The shunt switch may be either electromechanically actuated by a solenoid or the shunt switch and time delay may comprise solid state electronic circuitry or a combination thereof.

BRIEF DESCRIPTION OF THE DRAWING

The sole figure of the drawing is a pictorial schematic of the ignitor of the present invention installed m a typical series connected burner ignition system.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawing, the ignitor of the present invention denoted by reference numeral 10 is indicated as installed m a burner ignition system indicated generally at 10 which has a burner tube 14 with a plurality of flame generating ports 16 disposed adjacent ignitor 12. The burner tube 14 has an mlet end 18 thereof connected via a gas conduit 20 to the outlet 22 of an electrically operated gas valve 24. The valve 24 has an mlet 26 which is adapted for connection to a source of fuel gas (not shown) which provides flow m the direction shown by a black arrow m the drawing. The gas valve 24 has an electrical operator provided therein which is indicated by the resistance R which is connected through one connecting terminal 28 of the valve to junction 30 which is connected to one side of ignitor 12, with the opposite side of the ignitor connected to junction 32 on one side LI of the power line. The opposite side of valve actuator R is connected through terminal 34 of the gas valve to a junction 36 which is connected through a user control switch 38 to a second side L2 of a power line.

Ignitor junction 30 is connected to a terminal 38 of a time delay switch circuit indicated generally at 40; and, terminal 38 is connected to one side of a normally closed switch 42 which has its opposite side connected through terminal 44 to junction 46 on power line L2. The switch 42 is operable m its normally closed condition to act as a shunt for valve 24 such that the full power line voltage is applied across ignitor 12 when the switch 42 is closed.

Switch circuit 40 includes a relay 48 m the form of a solenoid coil which has one side thereof connected through terminal 50 to junction 52 on power line LI. The opposite side of relay 48 is connected to a normally open switch 54 which has its opposite side connected to terminal 56 which is connected to power line junction 58 on power line L2. Power line junctions 52, 58 are each connected to one side of a motorized timing device 60 which is connected to operate switch 54. In operation, upon user closure of switch 38 timing device 60 is energized and after a predetermined time delay preferably on the order of about thirty seconds (30-60 sec.) to one minute operates to close switch 54 which energizes coil 48 to open normally closed switch 42. However, it is anticipated that the delay may be of about ten to about sixty seconds. Opening of switch 42 allows the voltage at junction 30 to be applied to the resistor R to begin heating the valve actuator for opening of the valve. The time delay for opening of switch 42 is chosen to be more than sufficient to ensure ignitor 12 reaches ignition temperature before valve 24 can open thereby preventing a hazardous condition. It will be understood that although device 40 has been illustrated using an electromechanical relay, timer and switches, solid state electronics may be alternatively used to perform the function of device 40.

The present invention thus provides a unique and novel electrical resistance hot surface ignitor for igniting a fuel gas burner and particularly for ignition systems where the resistive ignitor is electrically series connected with an electrical operator m the gas line valve controlling flow to the burner; and, it is not necessary to rely upon the resistance versus temperature properties of the ignitor to control the opening of the valve. If the current flowing in the ignitor is sufficient to operate the valve actuator, when the switch 42 is opened, the valve will be open. It is thus only required that the time delay be chosen to ensure the ignitor will reach ignition temperature at the minimum line voltage.

Although the invention has heremabove been described with respect to the illustrated embodiments, it will be understood that the invention is capable of modification and variation and is limited only by the following claims.