US2874762A - Automatic igniter - Google Patents

Description

Feb. 24, 1959 P. E. DUNSTAN AUTOMATIC IGNITER Filed March 29, 1954 INVENTOR. PHILLIP E. DUNJTHN BY w w wm/ 4 TTOf/VE Y5 United States Patent AUTOMATIC IGNITER Phillip E. Dunstan, Seattle, Wash., assignor to Whirlpool Corporation, St. Joseph, Mich., a corporation of Dela- Ware Application March 29, 1954, Serial No. 419,469

5 Claims. (Cl. 158-28) This invention relates to devices which I have desig nated as automatic igniters. More particularly, it has reference to igniters which are automatically operable under the influence of heat to which they may be subjected, to control an electric circuit whereby an arc is caused to be struck as the means for igniting fuel in the form of oil or gas.

It is the principal object of this invention to provide automatically operating igniters of the character above stated, that are especially adapted for incorporation in the fuel ignition circuits of present day heating systems employing oil as the heat producing fuel.

It is a further object of the present invention to provide an igniter of the above character for use in an ignition circuit, and wherein switch electrodes are moved apart and together to open and close the are producing circuit, and wherein at least one of said electrodes is supported and moved from and against the other by a bimetal strip which is incorporated in the circuit and is heated by flow of current therethrough. It is still another object of the present invention to provide an igniter of the above character and kind, that is especially designed for use with oil burners to effect the ignition of the fuel oil, either as supplied to a pot burner, or as sprayed from a nozzle into a combustion chamber, and which embodies a switch element that automatically adjusts itself, first under the influence of heat as produced by reason of resistance to flow of current in the bi-metal strip, to cause relative adjustment of and arcing between the electrodes for igniting the oil, then under the influence of heat produced by the burning oil, to adjusting the electrodes to a relationship beyond the arcingrange thus to maintain the ignition circuit open.

In accomplishing these and other objects of the invention, I have provided the improved details of construction, the preferred forms of which are illustrated in the accompanying drawings, wherein:

Fig. 1 is a cross-sectional view of an igniter embodied by this invention, and as designed for use in a stove of pot burner type;

Fig. la is a top view of the same with the protective housing removed; and

Fig. 2 is a side view of a device of a modified form.

Referring more in detail to the drawings, and first giving consideration to the igniter shown in Fig. 1:

This device is primarily intended for use in oil burning stoves of those types designated as pot burners. In such stoves, oil is fed in a regulated amount onto the bottom of the pot and is caused to burn in the pot. At the start of any hea'ting operation, ignition of the oil is usually effected by lighting some paper and then dropping it into the pot to set fire to the oil that has been run onto the bottom of the pot. The present igniter, whereby that slow and inconvenient method of ignition is eliminated, will now be described.

The bottom of the pot is designated by reference numeral 10, and it is formed centrally with an opening 11 in which a metal bushing 12 is contained. This bush- J 2,874,762 Patented Feb. 24, 1959 ing has a thin, annular flange 13 projecting from about its upper end and seated against the surface of the bottom 10. A nut 14 is threaded onto the bushing and is tightened against the under side of the bottom about the opening 11; a gasket 15 being disposed between the nut and bottom.

A block 16 of insulating material, such as porcelain, is fitted and secured within the bushing. Its lower end terminates flush with the lower end of the bushing, but its upper portion extends upwardly from the bushing, into the pot. Mounted in the insulating block 16, lengthwise thereof and extending from its opposite ends is a rod 17 of electrically conductive metal. At its lower end, nuts 18-18' are threaded onto the rod and between them is secured the end or terminal clip 19 of a circuit wire 20.

Formed lengthwise of the insulating body or block 16, parallel with rod 17 and spaced somewhat therefrom is a hole or well 25. This well extends from the upper end of the block to near its lower end. Seated in the closed lower end of the hole is an electrode in the form of a graphite block 26 mounted in a cup 27 of electrically conductive metal from which a binding post 27 extends downwardly and from the lower end of the block 16. Nuts 2828' are threaded onto the lower end of this binding post to secure it in place, and a clip 30, on the end of a circuit wire 31, is secured between the nuts thus to provide a circuit connection with the electrode 26.

Extended downwardly into the well 25 is a carbon electrode 35, adapted to be engaged at its lower end against the electrode 26. The upper end portion of the carbon electrode 35 extends substantially from the open upper end of the well, and at its upper end is fitted with a cap 37 of electrically conductive metal. A bi-metal strip 38, bent to a U-form, is mounted upon the block 16, with its legs extending horizontally, and one above the other. One leg is shorter than the other and is secured at its end to the upper end of rod 17 by a nut 17x. The longer leg of the U-shaped strip extends across the base of the cap 37 and is secured thereto by a nut 40. Normally, the parts of the igniter assume the relative positions in which they are shown in Fig. 1. However, when the ignition circuit of the burner, including the bimetal strip 38, is closed, the resistance to flow of electric current through the strip causes it to become heated and under the tendency of its leg portions to spread apart at their ends, the electrode 35 will be lifted, and as it disengages electrode 26, an arc will be established between them as the means for igniting oil on the bottom 10 of the burner pot.

To protect the bi-metal strip from direct flame of burning oil, it is enclosed in a metal case 41 which is applied to the upper end portion of the block 16 and also encloses its upper portion therein.

To permit the oil to get to the arc, the block 16 is formed with a deep recess 42 opening to a side thereof, and extending inwardly through and beyond the well 25. The bottom surface of this recess is horizontal and is flush with the top surface of the electrode 26.

In order that oil can be readily ignited in the pot, I have disposed a fiat sheet of asbestos wicking 45 on the pot floor about the block 16, and with a part thereof extended into the recess 42 and about the lower end of electrode 35. Oil will be drawn by this wick close to the vicinity of the are. In burners of this kind, if operation is under thermostatic control, the thermostat usually operates to cut off flow of oil to the pot when the area being heated reaches a designated degree. Then when the room or area has cooled down below a designated degree, the oil supply line is again opened.

Assuming this igniter to be made and installed in the manner illustrated and described, it operates in the following manner: Upon closing" the ignition circuit through wires 20 and 31, current flows through the bi-metal strip 38 and the engaged electrodes 26 and 35. The strip has a ure-established electrical resistance that causes the stripto become heated. This heat instantly influences the strip to move the electrode 35 slightly upwardly and as this takes place an electric arc is momentarily established between its lower end surface and the top surface of electrode 26. This are will generate heat sufficient to ignite the oil as supplied by the wick. Then, the ignited fuel oil produces more heat whereby the bimetal strip is caused to separate the electrode well beyond the arcing gap, and thus the igniter circuit is automatically opened beyond arcing gap and remains open as long as fuel is burning. When the fuel supply is shut off, the fire soon goes out, andthe bi-rnetal strip cools oil and returns to normal position.

The control of fuel supply is generally under thermostatic control, and when the circuit is re-established by the thermostat, the arcing circuit is re-established.

It is to be understood that suitable means is provided in connection with this igniter for so controlling the flow of oil that it will not rise above a desired level in the pot.

In Fig. 2, I have shown an igniter of modified form, like that above described except that I employ a two part bi-metal strip 38x of 8 form and supported in the vertical plane of electrode 35 with its lower end fixed to cap 37 and its upper end fixed to asupporting bracket 38a fixed rigidly to the block 16 and to the upper end of rod 17. The bi-metal of the two curved end portions of the strip 8 are oppositely arranged so that one will not counteract the other.

Having thus described by invention, what I claim as new therein and desire to secure by Letters Patent is:

1. In a pot burner adapted to receive fuel oil for'burning therein, a fuel igniter mounted in the pot, said igniter comprising a fixed electrode, a movable electrode, a thermostatic arm supporting the movable electrode and whereby it is caused to be moved into and from contact with the fixed electrode, an electric circuit including the electrodes and thermostatic arm therein and through which current can be caused to flow when the electrodes are engaged to heat said arm and thus eiiect adjustment of the electrodes apart to establish an arcing gap between them,.and a wick in the pot positioned to conduct fuel from the bottom of the pot to the vicinity of the said gap for ignition by the are when established between the separated electrodes.

2. A combination as recited in claim 1 wherein the igniter comprises an electrically non-conductive body mounted in the burner and mounting thesaid fixedelectrode therein and supporting the thermostatic arm thereon within the burner pot for heating by the burning fuel.

3. In a pot burner, or the like, having a bottom wall and adapted to receive fuel oil onto said bottom wall for burning, and a fuel igniter mounted within the pot, and comprising an electrically non-conductive block mounted in said bottom wall toextend into the pot and below it, an electrode fixedly mounted inv the block, a thermostatic arm mounted on the block within the pot, a movable electrode mounted by said arm and movable there with from and against the fixedly mounted electrode, an electric circuit including the said electrodes and thermostatic arm therein and through. which current can be caused to fiow when the electrodes are engaged to heat said arm to cause it to effect separation of the electrodes and the momentary establishing of an electric arc between them, and a wick within the pot positioned to conduct fuel from the bottom of the pot to the arcing gap for ignition by the are thus produced.

4'. A combination as in claim 3 wherein the thermostatic arm operates to move the electrode apart under heat of burning fuel to a distance beyond the arcing gap.

5. An igniting system for a fuel burner comprising means tosupply fuel to said burner, a first electrode, a thermostatic arm, a second electrode carried by said am and normally in contact with said first electrode, said arm when heated to predetermined extent being effective for moving said second electrode away from said first electrode a distance efiective for drawing an are between 'said electrodes, said arm when heated to a further extent being effective for moving said second electrodea further distance away from said first electrode effective for breaking the are, said electrodes being disposed in igniting relation to said burner, and an 'elec tric circuit including said electrodes and arm and effective when energized for heating said arm to said predetermined extent for drawing an arc between said electrodes, said arm being exposed to heat from said burner and heated thereby to said further extent elfective for moving said second electrode said further distance away from'said first electrode and thereby breaking the arc.

References Cited in the file of this patent UNITED STATES PATENTS 346,430 Cutten July27, 1886 651,067 Cram June 5, 1900 761,379 Heany May 31, 1904 2,076,418 Smith Apr. 6, 1937 2,500,663 Cleveland Mar. 14, 1950

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