US2756811A - Ignition device for oil burners - Google Patents

Description

July 31, 1956 c, LITTLE 2,756,811

INGITION DEVICE FOR OIL BURNERS Filed May 28, 1951 00000000000000OQw0000o/ INVENTOR. g 50 HARRY (I. Luv-72,5

Fig.5. BY 5W ,1 TTO/PMS Y United States Patent IGNITION DEVICE FOR OIL BURNERS Harry C. Little, San Rafael, Calif.

Application May 28, 1951, Serial No. 228,632

2 Claims. (Cl. 158-91) This invention relates to ignition devices for vaporizing type oil burners, and more particularly to that type of ignition device utilizing an electric coil element for heating, vaporizing and igniting the fuel oil disposed on the bottom of the burner. The invention further constitutes an improvement over the ignition devices disclosed in my Patent No. 1,995,720, issued Match 19, 1935, and in my copending application Serial No. 32,755, filed June 14, 1948, now Patent No. 2,553,975, patented May 22, 1951. s

The general type of ignitor to which this invention relates includes an electrically heated resistance coil disposed in proximity to liquid fuel oil on the bottom of an oil burner. When current of a sufiicient magnitude is permitted to pass through the coil, the latter is rapidlyheaterl to a temperature which will cause local vaporization of the fuel and ignition of the resulting fuel-air mixture.

An object of the present invention is to provide an ignition device of the general type hereinabove described in which means are provided for simply and positively positioning the electric coil element in proper relation to the surface of the oil in the burner.

Another object of my invention is to provide an electric ignitor of the above character in which the coil element is at all times maintained in an oxidizing atmosphere irrespective of the nature of the fuel-air mixture in the burner, whereby the metal coil will consistently have an oxide coating and the usual life thereof will be greatly increased.

A further obiect of the invention is to provide an ignition device of the type above described in which means are provided for thinning out the oil vapor in the vicinity of the coil element so as to facilitate initial combustion of the fuel-air mixture and to prevent the creation of a rich or "reducing" atmosphere adjacent the cell during normal burner operation.

A still further object of the invention is to provide an ignition device of the character described which includes a sheet of wicldng material having a portion thereof immersed in the fuel oil and another portion removed from the oil and lying in a plane substantially parallel and adjacent to the axis of the electric eoil element so as to promote initial combustion of the fuel-air-mixture upon energization of the coil, and at the same time, preventing any immersion of the coil in the liquid fuel oil.

Yet another object of the invention is to provide an ignition-device of the type described which may be readily removed and properly reinstalled in the oil burner for servicing, without requiring taayparticular skill 'or traintag. I 4

Another ebiect of the'lnventlon is to provide'an ignition device of the above character ln'whlch means are rovidedtor preventing the accumulation of carbon in theignitorcoil.

The invention possesses other oble'cts and features of advantage, some of which, with the foregoing, will be set forth-in the following description'ef' the preterredlform of the invention which is lllnstrated-inthe'drawing'aecompartying and forming part of the specification. ltls tube understood, however, that variations in the showing made by the said drawing and description may be adopted within the scope of the invention as set forth in the claims.

Referring to the drawing:

Figure l is a side elevational view of an oil burner with a portion thereof cut away in order to show the ignition device of the present invention in operative position.

Figure 2 is an end view of the ignition device illustrated in Figure 1 taken from exteriorly of the oil burner.

Figure 3 is an end view of the ignition device taken from interiorly of the oil burner.

Figure 4 is a cross-sectional view of a portion of the ignition device and taken along the plane indicated by the line 4-4 of Figure 5.

Figure 5 is a vertical side sectional view of the ignition device, a portion of the oil burner being indicated for purposes of proper orientation, the dot-dash lines indicating the position of the parts when the device is being moved into its proper position within the burner.

Figure 6 is an end view taken in the direction of the arrowed line 6 of Figure 5.

Figure 7 is a cross-sectional view taken along the plane indicated by the line 77 of Figure 5.

The ignition device of the present invention, generally indicated by the numeral 11, is arranged for operative positioning in an oil burner 12, here shown as an elongated updraft type wherein fuel oil is introduced through an inlet 13 at the front 14 of the burner for passage onto and over the burner bottom 16. As is well known in the art, the fuel oil thus introduced is vaporized and mixed with primary air introduced through openings 17 in -the-sidewalls 18 of the burner, the admixture of fuel vapor and air then passing upwardly through a burner throat 19 whereat secondary air may be admitted. A flame spreader 21 may be mounted immediately over the burner throat for converting and modifying the normally circular flame shape. It is usually desirable in burners of this type; to have the bottom 16 provided with a slight downward incline toward the rear of the burner and under theburner throat so that the oil will gravitate in a thin sheet over the entire bottom and afford maximum vaporization. To effectthe proper slope of the bottom, leveling screws 22-or similar devices are usually provided. and the level of the oil on the burner bottom is-controlled and maintainedat a constant height by means of an external float controlled valve which forms no part of this invention and has therefore not been illustrated in the drawing. While 'the ignition device of this invention is shown in conjunction with a burner as hereinbcfore described, it will be evident that the same may be similarly used in most-types of conventional vaporizing types of oil burners.

The ignition device 11 includes an elongated tubular metal supporting member 23 which is arranged to bc supported -at one end 24 thereof-adjacent the front wall 14 of the burner, and -to enter the burner on a downward slope, as will be bestseen-in Figure 5 of the drawing. Normally the other end '25 of member-23 -is positioned just above the bottom 16 of the burner, and-is arranged for axial movement and positioning relative 'to front wall 16 as indicated by the tlo't-dns'lr'lines of Figure-:5 whereby the member may be mitomaticallypositioned in its proper location aswill be 'here'inafter'explained in'detail. it is also desirable to permit the eiitire ignitiondeviee 'to be entirely removable from the burner for replacement of the wicking material, cleaning or other reasons. .'Ihe-' fo'regoing positioning and removability feature rnziy'b'e accom- 'plished in the following'manner. As is well known in the art, the casing comprising the burner? housingflis generally constructed "of'relatively light :gauge' metal. Therefore, to insure 'nn'adeqttate'support for this igni- *t'io'n deviceyfrent-wiill -14 is provided with anmpermte 26 bounded by a heavier metal flange 27 extending forwardly of the front wall from the periphery of the aperture. The aperture is normally covered by a door or coverplate 28 releasably secured to the leading edge of flange 27 by means of screws 29 engageable with threaded apertures in the latter. The plate is provided with a boss 31 through which an angularly disposed aperture 32 extends having a diameter sufiicient to permit sliding movement of member 11 thercthrough. In this manner, member 11 may be axially moved relative to plate 28 and front wall 14 as aforesaid so as to permit repeated automatic positioning thereof relative to the burner bottom 16 and the oil thereon. To secure the member in position, a set screw 33 is provided in an aperture 34 of the plate boss 31, the aperture 34 intersecting the aperture 32 at substantially right angles, and it will be readily understood that as the screw 33 is tightened, the distal end thereof will bear against and releasably hold the member 23 in selected positions of axial movement. It will be noted that aperture 32 has its axis sloping toward the burner bottom whereby the member 23, when installed, will be disposed in angular relation to the bottom 16.

Mounted within member 11 and rigidly supported therein in spaced insulated positions as by means of a suitable ceramic insulating material 36, are a pair of electrical conductors 37 and 38. These conductors are preferably formed as rods of low resistance material such as copper or the like for the rigid support for the parts attached thereto and project from the end 24 of the member to provide exposed ends 39 and 41 for connection to a source of electrical potential. As here shown, these ends are connected to suitable insulated lead wires 42 and 43 arranged 'in series with a battery 44 or other source of electric current and a switch 46. The ends 39 and 41 are preferably threaded for receipt of electrical binder nuts 47 for facilitating connection of the external electrical leads. The opposite ends of conductors 37 and 38 are connected to the ends of high resistance heater wires 48 and 49 which are extended longitudinally from the end 26 of the tubular member 11, the latter wire extending for a greater distance than the former to provide therebetween a helical ignitor coil 51 disposed in axially aligned relation with the longitudinal axis of member 11. The aforesaid ends may be inserted into the rod apertures, and by crimping the rod ends, a suitable mechanical and electrical connection will be effected between the rods and the coil wires. From the foregoing, it will be understood that by closing the switch 46, the coil 51, due to its high resistance, will rapidly heat up for initial vaporization and ignition of the fuel oil.

Incorporated in the present device is a sheet or strip of wicking material 52 which is composed of any suitable non-combustible material capable of conveying small quantities of liquid fuel oil, through capillary action, from the oil pool at the burner bottom to a position adjacent the coil 51. By placing one portion of this material along the burner bottom and immersed in the liquid fuel oil thereon, and having another portion outside of the oil pool and adjacent the ignitor coil, it will be understood that this latter portion will, by capillary action, attract a limited quantity of oil which will be in a condition for rapid vaporization and ignition upon energization and heating of the coil.

As an important feature of the present invention, means are provided for positioning the wicking material in the aforementioned relationship, and which, at the same time, provides for proper positioning of the member 23 and coil 51 within the burner. Such means preferably includes a substantially rectangular metal foot plate 50 being flat or slightly curvate in cross-sectional form and having an angular bend along its longitudinal axis to provide angnlarly related portions 53 and 54. As will best be seen in Figure of the drawing, the portion 53 is secured by welding or the like to the lower surface of the end 25 of member 23 in predetermined relationship to coil 51,

and when so secured forms a parallel extension of the member immediately subjacent the coil for substantially the entire length of the latter. The portion 54 is disposed in the same degree of angular relationship to portion 53 as the member 23 and coil 51 bear to the bottom 16 of the burner. Because of this arrangement, the ignitor may be easily installed in the burner by merely inserting the mem ber 23 through the apertures 32 and 26 until the base of the foot portion 54 strikes the burner bottom. It is then only necessary to tighten the set screw 33 to secure the device in position. To insure proper radial orientation, one or more indexing marks 45 may be located on the end of the member 23 and on the boss 31 so as to properly locate the foot plate onthe lower surface of the device. The position of the coil relative to the foot plate is fixed by the manufacturer, and the installer does not have to possess any particular skill to properly position the coil with respect to the fuel oil.

The foot plate 53, besides providing for accurate positioning of the burner, also serves as a support for the wicking sheet 52. The latter is preferably formed by folding the same upon itself so as to provide upper and lower layers 56 and57 which may be fastened together by rivets or staples 58, and is arranged to be inserted in a sleeve-like manner over the plate 53. As will best be seen in Figure 5, with the wicking strip so positioned, the enclosed end portion of the sheet will contact the burner bottom and be immersed in the oil thereon, the portions of the strip enveloping portion 53 of the foot plate being raised above the oil level and relying on capillary action for oil saturation thereof. It is this latter portion which acts as a source of fuel oil for local vaporization and ignition .by the coil.

It has been determined that if the ignitor coil is immersed in the fuel oil, relatively rapid erosion of the metal coil may result because of impurities in the oil. The metals most commonly used for the coil wire are alloys of chromium, nickel, iron and cobalt; and particularly in the catalytic fuel oils, copper compounds may be present which are highly injurious to these alloys. In the device of the present invention, all portions of the coil are always positioned above the liquid fuel oil level. Through extensive research, I have also found that when the ignitor coil is subjected to alternating oxidizing and reducing atmosphere, erosion of the metal and resulting short life of the coil is experienced. In conventional electrical ignition systems, these deleterious results cannot be avoided as the atmosphere initially surrounding the coil consists substantially of air, that is, a very lean or oxidizing mixture. However, when the coil is energized, local vaporization of the oil occurs and the vaporized oil is admixed with the air, gradually increasing the fuel concentration and approaching a richer fuel-air mixture, and when the proper temperature and fuel-air ratio conditions are reached, ignition occurs. Such ignition results in a greatly increased vaporization rate of the fuel oil and increased local temperatures until the vaporization of fuel is so great that the fuel-air ratio surrounding the ignitor coil becomes too rich to support combustion, and combustion then occurs at the burner throat. This latter occurrence is the so-called normal operation of the burner. When the mixture surrounding the coil becomes very rich as above mentioned, the atmosphere becomes reducing and tends to remove the protective oxide coating on the surface of the ignitor coiL In accordance with the teachings of the present invention, means are provided to maintain an oxidizing atmosphere in the vicinity of the coil and to prevent the accumulation of carbonaceous deposits on the ignitor coil irrespective of the richness of the fuel-air mixture in the burner. This may be effected by providing one or more air tubes 59 disposed within member 23 for the complete length of the latter, and at least one of such tubes being positioned in substantial alignment with the axis of the helical coil 51. Also, preferably at least two additional air tubes 61 extend through suitable apertures in the coverplate 28 and terminate adjacent the coil 51 which function to admit air from exteriorly of the burner and conduct it for discharge near the coil. These tubes all operate to provide a lean or oxidizing mixture around the coil at all times. The admission of air through the tubes is not sufiicient to affect the ignition of the mixture, and even when normal combustion is occurring at the burner throat and a subsequent draft is induced in the burner, the increased amount of air introduced through the tubes will only serve to provide a lean mixture adjacent the coil and not support combustion of any appreciable amount. If desired, the tubes 61 could be secured to other side wall portions of the burner, but it has been found more practical to mount such tubes directly on the front cover as above described.

It should also be pointed out that having the coil 51 in parallel adjacent relation with the unimmersed wicking material, together with the ever present oxidizing atmosphere, results in complete combustion of all the carbon and prevents carbon deposits forming on the coil.

From the foregoing, it will be clear that I have provided a simple, inexpensive ignition device which may be readily installed in proper operating position within an oil burner, and which will permit long periods of use without requiring any servicing due to formation of carbon deposits or due to the presence of rich fuel-air mixtures around the resistance coil.

I claim:

1. In an oil burner having a bottom and side Walls, the combination with said burner of an ignition device comprising, an exposed helix of relatively high resistance wire, means adapted for supporting said helix within said burner with the axis thereof forming an actute angle with the burner bottom and with the innermost end of said helix spaced from said bottom, means-for securing said helix in selected positions along a path substantially coinciding with the axis thereof, a relatively fiat sheet of wicking material supported subjacent said helix and having a first portion thereof in parallel spaced relation thereto, and said sheet including an angularly related second portion extending axially beyond said innermost end of said helix and arranged to lie on the bottom of said burner.

2. An ignition device for an oil burner comprising, an elongated tubular member, a pair of electrical conductors mounted and insulated within said member and having portions thereof providing a helical coil extending beyond and in axial alignment with said member, the axis of said member and said coil adapted to form an acute angle with said burner bottom, a plate secured to the lower surface of said member subjacent and in parallel relationship to said coil, said plate including an angularly disposed extension adapted to rest upon the bottom of the burner whereby said member and said coil may be readily positioned within the burner, a sheet of wicking material on said plate and extension, and means forming a passage in said member adapted to direct air from exteriorly of the burner to adjacent said coil, said air passage adjacent said coil being in substantial axial alignment with the axial passage of said coil.

References Cited the file of this patent UNITED STATES PATENTS 2,025,074 Roe Dec. 24, 1935 2,286,854 Holthouse June 16, 1942 2,438,823 Resek et al. Mar. 30, 1948 2,553,975 Little May 22, 1951

Images