US3792959A

US3792959A - Method and apparatus for igniting a burner

Info

Publication number: US3792959A
Application number: US00213368A
Authority: US
Inventors: K Mori; T Toue
Original assignee: Volcano Co Ltd
Current assignee: Volcano Co Ltd
Priority date: 1971-08-12
Filing date: 1971-12-29
Publication date: 1974-02-19
Anticipated expiration: 1991-02-19
Also published as: JPS4827867A; JPS5111558B2; GB1377525A

Abstract

A method of igniting a burner in a short period of time. An igniting device is used which has a heating element made of carborundum provided in an outer pipe which is provided movably in the burner. An electric source initially impresses upon the heating element a voltage approximately 1.5 times its rated voltage and the electric current at the secondary side of the transformer at the time when the heating element has reached the desired temperature is detected by a current relay. At this time, taps on the transformer are switched to impress the rated voltage on the element to obtain the desired igniting temperature.

Description

United States Patent [191 Mori et al.

[ Feb. 19, 1974 METHOD AND APPARATUS FOR IGNITING A BURNER Inventors: Keizo Mori; Tutomu Toue, both of Osaka, Japan Assignee: Volcano Co., Ltd., Osaka, Japan Filed: Dec. 29, 1971 Appl. No.: 213,368

Foreign Application Priority Data Aug. 12, 1971 Japan 46/61347 US. Cl 431/6, 317/98, 431/132 Int. Cl. F23n 7/00 Field of Search.. 431/6, 128, 132, 259; 317/98;

Butler, Jr. 317/98 X Mitts et a] 317/98 [5 7] ABSTRACT A method of igniting a burner in a short period of time. An igniting device is used which has a heating element made of carborundum provided in an outer pipe which is provided movably in the burner. An electric source initially impresses upon the heating element a voltage approximately 1.5 times its rated voltage and the electric current at the secondary side of the transformer at the time when the heating element has reached the desired temperature is detected by a current relay. At this time, taps on the transformer are switched to impress the rated voltage on the element to obtain the desired igniting temperature.

10 Claims, 4 Drawing Figures PAIENI mu 91924

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1 or 2 INVENTORS K5 l2 0 Mor i Tuliomu Toug BM ,w QP J ATTORNEE PATENTEB rm 1 a 1914 of svvfac um ert'fure.

SHEET 2 BF 2 200 4.00 m an m I 0 0 (60 I300 INVENTORS Keizo Mori Tu'tomu Toue 'BYmM-m M ATTORNEQ METHOD AND APPARATUS FOR IGNITING A BURNER This invention relates to an improvement in the method of igniting a burner, which uses low voltage and ensures accurate igniting of a burner in a short period of time, with little or no wear of the igniting device and which can be used safely as a portable type.

So far, various methods of igniting a burner which uses liquids or gases as fuel have been disclosed. Most commonly known are the use of a high voltage spark discharge, the method of using electric discharge energy in which electricity is first charged to a condenser and then discharged intermittently by using a semiconductor plug, the method of generating a high temperature by contacting a copper-covered carbon electrode with a carbon plug and impressing l 30V thereto and the method of utilizing nickel-chrome wire.

Each of these methods, however, has substantial defects. In the method which utilizes a high-voltage spark discharge, a secondary voltage of 5,000Vl0,000V is employed which involves considerable danger in handling. In the method in which a condenser is charged and then discharged by using a semi-conductor plug, DC voltage of about 2,000V is employed, which also involves considerable danger in handling. When employing a carbon electrode utilizing low voltage, the electrode is worn considerably and much labor is required for the maintenance thereof and in the case of employing a heating wire such as nickel-chrome wire, more time is required for reaching the desired temperature necessary for ignition.

This invention has been made with the above defects in view and provides a new method by which a burner can be accurately ignited in a short period of time, utilizing low voltage which is free from danger in handling and involves no wearing of parts.

The present invention will be explained hereinafter with reference to the accompanying drawings.

FIG. 1 is a detailed view of an igniting device which is used in igniting a burner by the method according to the present invention. FIG 2 is a circuit diagram of the electric source utilized with the igniting device shown in FIG. 1. FIG. 3 is a curved line diagram showing the relation between the specific resistance of a carborundum (silicon carbide) heating element and its temperature, and FIG. 4 is a rising curve diagram of the temperature of the heating element.

The apparatus of this invention comprises a movable igniting device (carrier member) which effects ignition and an electric source which impresses the required electric current upon said igniting device. The details of the igniting device and the electric source are illustrated in FIG. 1 and FIG. 2 respectively. The igniting device is of the cylindrical type having a desired length which is determined by the size of the burner. The cylinder is applied to one side ofa terminal casing 7 which has a desired shape such as a bottomed cylinder or a box. An outer pipe 2 having one or more cutouts or ports 4 is provided around the top end portion of the igniting device, in which a cap 1 is removably screwed. A support member for a heating element is inserted in said outer pipe 2 and is provided in the above-mentioned terminal casing 7, through the medium of an insulated holding member 6, so that the support member 5 is insulated from the outer pipe 2. A rod-shaped heating element 3 made of carborundum is adapted to be exchangeably held between a recess 1a provided at the inner side of said cap 1 and a recess 5a provided at the end of said support member 5 of the heating element.

While one electric circuit which is led to a lead wire L1 via said cap 1 and said outer pipe 2 is formed at one end of said heating element 3, another electric circuit which is led to a lead wire L2 via a support member 5 is formed at the other end of said heating element 3. These lead wires L1 and L2 are respectively connected to the electric source for effectingignition.

The electric source, as shown in FIG. 2, is connected to a transformer 10 via a switch 9 and a fuse F from an input terminal 8. This transformer 10 has a primary winding having end taps Tb and an intermediate tap Ta. A current relay contact switch 11 is provided between said taps Ta and Tb so that either tap Ta or Tb can be selected. Provided at the secondary side of said transformer are an output terminal 12 which connects to the lead wires L1 and L2 of the igniting device and a current relay 13 which detects the output current of the secondary side.

The characteristics of the carborandum constituting the heating element are shown in FIG. 3. From the figure it can be seen that its specific resistance changes according to the surface temperature. Specifically, the device exhibits a negative temperature coefficient (resistance decreases in proportion to the rise in temperature) up to about 800 C., but a positive temperature coefficient (resistance increases in proportion to the rise in temperature) at about 800 C. or higher. With this in view, the current relay contact 11 is connected to the intermediate tap Ta of the transformer so that the voltage applied to the heating element is about 1.5 times the voltage rating of the element, until the temperature reaches about 800 C.

It is known that the abrupt heating of a heating element adversely affects the life of the heating element. The result of experiments, however, has revealed that a voltage of about 1.5 times the rated voltage is applied until the surface temperature reaches the highest point in the negative temperature coefficient range and then when the voltage is switched to the rated voltage, the life of the heating element is not adversely affected, and the igniting part reaches the desired temperature within several seconds. Of course, the value at the intermediate tap Ta and the value of the operating current of the current relay will vary with the size of the heating element.

When igniting a burner with the above apparatus, the current relay contact 11 is first connected to the intermediate tap Ta of the transformer, whereupon a voltage about l.5 times the rated voltage is generated at the secondary side and the heating element is heated. Then, current at the secondary side of the transformer is detected by the current relay l3 and the current relay contact 11 is switched to the tap Tb. As described above, the electric relay is set at a current value which is shown when the surface temperature of the heating element reaches 800 C and at this current value, the switch is changed.

When the switch is changed from the tap Ta to the tap Tb in the above-described manner, the rated voltage is supplied to the heating element and in l or 2 seconds, the heating element temperature reaches about l,600 C, which is the burner igniting temperature,

whereby the ignition is effected.

The curve of the heating element temperature in this case is shown at C in FIG. 4. The curve line A in this figure shows the case when the rated voltage is supplied to the heating element initially from the beginning of the operation and the curve line B shows the case when the switch is not changed, in which case the surface temperature continues to rise and the heating element finally fuses.

Carborundum is employed as a heating element in the embodiment of this invention but any other substance having the same performance and action as carborundum can also be employed.

According to the present invention, the characteristic of carborundum or its equivalent is utilized in such a manner that aproximately 1.5 times the rating voltage is impressed at first and when the surface temperature of the heating element reaches the desired value, the current relay detects the current value and is actuated, whereby the switch is automatically changed from the tap Ta over to the tap Tb to obtain the rated voltage.

Furthermore, this invention has such advantages that the ignition can be ensured at the low voltage of -5OV and in a short'period of time, by a simple operation and without any wearing of the heating element.

What is claimed is:

l. A method of igniting a burner with an igniting device utilizing a Carborundum heating element comprising the steps of initially supplying said heating element with a first voltage approximately equal to one and onehalf times the rated voltage of said element, sensing the electric current passing through said element, supplying said heating element with a second voltage substantially equal to the rated voltage of said element when said current reaches a predetermined value, said predetermined current value corresponding to a predetermined temperature of said heating element.

2. The method of claim 1 wherein said steps of supplying said voltages comprises providing a transformer having a primary winding with an intermediate tap and a secondary winding, and connecting said secondary winding across said heating element.

3. The method of claim 2 wherein said step of supplying said first voltage comprises connecting a voltage source to said intermediate tap of said transformer.

4. The method of claim 3 wherein the step of sensing the electric current passing through said element comprises sensing the current flowing through said secondary winding.

5. A device for igniting a burner comprising a hollow pipe member and a terminal casing supporting said pipe member at one end of said pipe member, a carborundum heating element located within said pipe member adjacent the other end thereof, means supporting said heating element, a closure means closing said other end of said pipe member, at least one hole formed in the wall of said pipe member adjacent said heating element and means for supplying electric power to said heating element.

6. The device of claim 5 wherein said means for supplying electric power to said heating element comprises means for supplying a first voltage to said heating element, said first voltage being equal to approximately one and one-half times the rated voltage of the element, means for sensing the current flowing through said element, and means for supplying a second voltage to said element when said current reaches a predetermined value, said second voltage being substantially equal to the rated voltage of said element.

7. The device of claim 6 wherein said means for supplying said first and second voltages comprises a transformer having a tapped primary winding, the secondary winding of said transformer being connected to said heating element.

8. The device of claim 7 wherein said means for sensing said current comprises a current relay, said relay being adapted to be activated when said current reaches said predetermined value, said relay carrying switching means connected to said primary winding for changing the taps thereof when said current reaches said predetermined value.

9. The device of claim 8 wherein said pipe member is cylindrical.

10. The device of claim 9 wherein said support means comprises an elongated support member secured to said one end of said pipe member and extending coaxially within said pipe toward said closure member at said other end of said pipe, a recess formed in the end of said supporting member and a recess formed in said closure member, said heating element being supported between said two recesses.

Claims

1. A method of igniting a burner with an igniting device utilizing a carborundum heating element comprising the steps of initially supplying said heating element with a first voltage approximately equal to one and one-half times the rated voltage of said element, sensing the electric current passing through said element, supplying said heating element with a second voltage substantially equal to the rated voltage of said element when said current reaches a predetermined value, said predetermined current value corresponding to a predetermined temperature of said heating element.

9. The device of claim 8 wherein said pipe member is cylindrical.