US2693849A

US2693849A - Vaporizer-type liquid fuel burning apparatus and electrical ingition means therefor

Info

Publication number: US2693849A
Application number: US168524A
Authority: US
Inventors: Resek Marc; Wilbur A Schultz; Lloyd V Antl
Original assignee: Perfection Stove Co
Current assignee: Perfection Stove Co
Priority date: 1950-06-16
Filing date: 1950-06-16
Publication date: 1954-11-09
Anticipated expiration: 1971-11-09

Description

N v- 9, 1954 M. RESEK ETAL VAPORIZER-TYP 2,693,849 E LIQUID FUEL BURNING APPARATUS AND ELECTRICAL IGNITION MEANS THEREFOR 2 Sheets-Sheet 1 Filed June 16. 1950 TIA 5 w W. w m mm m mfimv m A fin 5w "V. M

Nov. 9, 1954 M. RESEK ETAL 2,693,349 VAPORIZER-TYPE LIQUID FUEL BURNING APPARATUS AND ELECTRICAL IGNITION MEANS THEREFOR Filed June 16, 1950 2 Sheets-Sheet 2 z M IIIge ENTORS dI'L' 531? 74 I 12 M'lburzfl. dcliolz 15 Fe. 4 wwf-vmm struction that facilitates United States Patent APQRIZER T PE L QUID F UEL BURNING APPA- TUS AND ELECTRICAL IGNITION MEANS THEREFOR Marc Resek, Cleveland Heights, Wilbur A. wood, and Lloyd V. Anti, Cleveland, to Perfection Stove Company, poration of Ohio Application June .1 1950, Serial N0. 168,524 3, Claims. (Cl. 158-91) This invention relates, generally, to the liquid fuel burner art; and it has to do more particularly with improvements in pot type vaporizing burners (as distinguished from those of the pressure atomizing gun type) and especially as such vaporizing burners are equipped with electrical igniters and are adapted for use with electrical control systems by which their operation is, rend rc autom ti vaporizing burners of the aforesaid type have several advantages over pressure atomizing burners among which are; multi-stag (high fire and low fire) operation affording even heat regardless of fluctuations in outside temperature and changing weather conditions; capability of operating with high efficiency and with uniform temperatrue at low heat output when installed, for example, in small heating plants; absence of combustion and pump noises that attend operation of pressure atomizing burners, and few mechanical Parts to wear or require service. Heretofore, however, these advantages have been offset in large measure by the inability to use, in vaporizing burners, the heavier types of fuel, especially if the fuel contains large percentages of catalytic cracked stock.

It is the fundamental purpose of our invention to provid a vaporizing pot type burner which will operate in a highly satisfactory manner on various grades of oil that. are now in general use, including those containing large percentages of cracked material.

Other objects of the invention are to provide a vaporizing pot type burner that is capable of being readily controlled throughout its range of multi-stage operation, that functions satisfactorily at all stages, and that operates quietly and with high efficiency and with a clean fire at the different stages; to eliminate the disadvantages of prior vaporizing and pressure atomizing burners while retaining the advantages of both types; to provide a conassembly and disassembly of, and accessibility to, the parts which may require service and attention, and to provide a burner of the aforesaid character that is very durable and requires the minimum of service and attention.

Another object of the invention is to provide a liquid fuel burner of the. vaporizing Pot type wherein the nozzle that delivers fuel to the burner pot is exterior of the com bustion space thereof; to include in such burner provisions for maintaining the nozzle relatively cool, and to so relate the nozzle to the, surrounding parts that define the fuel entrance as to insure against fuel contact with or deposi Upon such parts.

Further objects are to avoid, in vaporizing burners of the pot type, carbon formation at. the fuel inlet to the burner; the building up of carbon on the bottom of the burner pot, and the formation of carbon on the electrical niter.

A still further and very important object of the inven-. tion is to provide, in burners of the class to which our improvements pertain, an electrical igniter of the enclosed, embedded variety. Heretofore, in burners of the Class at hand, either spark gap igniters, or igniters of exposed resistance wir have been employed, These are subject to short circuiting by carbon deposit, and rapid deterioration because of exposure to the high temperaures of combustion during burner operation.

In an electrical igniter of the kind herein disclosed, the current. carrying element or wire is embedded. in retract tory insulating material of high heat conductivity encased in a tube, of heat resistant metal, substantially like the sheathed wire electrical heating. nits employed in elec- Sc hultz, Lake- Ohio, assignors Cleveland, Ohio, a coropening 35, and welded 2,693,849 Patented Nov. 9, 1954 tric ranges. Because the current carrying element or wire is completely insulated and sheathed from the fuel and vapor containing space of the burner there is no chance of short circuit or deterioration of the said element or wire. The metallic sheath also supports and protects the current carrying element or wire from injury due to mechanical shock, and, furthermore, permits the use of a high resistance element to which the regular volt house potential can be applied, whereby the need for an ignition transformer is eliminated.

An additional and related object of the invention is to combine with an electrical igniter of the character described a bafile-like member against which the fuel impinges and by means of which flow is retarded in the immediate vicinity of the igniter so as to insurerapid vaporization and ignition. More specifically, we employ a baffle-like member in the form of an open ,end tray which, together with the igniter, is suspended within the burner pot at an elevation slightly above the maximum attainable fuel level in said pot. It will become apparent as this description proceeds that we have provided anigniter that at all times is removed from any accumulation of liquid fuel within the burner.

The objects and advantages above enumerated, with others that will appear as this description proceeds, are attained in the embodiment of the invention illustrated in the accompanying drawings, wherein like reference characters designate like parts in the several views.

In the drawings, Fig. 1 represents a sectional side elevation of liquid fuel burning apparatus embodying our improvements, the view including a diagram of the electrical control system; Fig. 2 is a vertical section through the front portion of the burner, drawn to a scale considerably enlarged over that of Fig. 1; Figs. 3 and 4 are sections on the respective lines 33 and 4-4 of Fig. 2, and Fig. 5 is a fragmentary perspective view of the nozzle guide.

The liquid fuel burning'apparatus includes a burner pot or bowl that is designated, generally, by the reference numeral 1; an air housing, similarly designated 2, and a casing 3, shown in broken lines, that encloses a combustion space or chamber C. The burner pot includes a perforated cylindrical peripheral wall 5 and a slightly dished circular bottom wall 6, the latter being shown in the present instance as formed integral with the peripheral wall. Attached to the exterior of the pot at about the junction of the

walls

5 and 6 is a continuous annular overflow trough 8 which communicates with the interior of the pot through the lowest row of perforations, designated 10. The Wall 5 is provided with a relatively large opening 12, and secured to the wall about said opening, preferably by welding, is the inner end of a cylindrical neck 15 that terminates at its outer end in a flange 16.

Welded or otherwise secured to the outwardly flared upper end of the peripheral wall 5 of the burner pot 1 is a generally upwardly convergent angular top wall 18, and shown as likewise secured to the edge portion of said top wall about the relatively large opening therein is the base flange of a perforated neck 20. This neck is shown as flared outwardly and thence upwardly to provide a peripheral flange that is secured to an upstanding flange of a ring-like member 23. Toward its outer edge said member is stepped abruptly upwardly, to provide a vertical cylindrical shoulder 24, outwardly I beyond which the member is provided with a broad flat flange 25 that is adapted to be engeged with the underside of an annular bottom wall 28 of the casing 3, and to be detachably secured thereto by fastening means of bolts 29.

The air housing 2 includes a cylindrical peripheral wall 30, and a circular bottom Wall 31, formed to fit a suitable distance within the lower end of the peripheral wall. These walls are suitably secured together, by welding or other means, and attached to the upper end of the peripheral wall is a top member 32, shown as extending inwardly and thence upwardly, and as fitted to the shoulder 24 of. the previously describe ringdike member 23.. th parts being f stened. together,v preferably by welding. Opposite the neck 15 f h bumel? not, the wall 30 is provided. with a lar or otherwise secured to said wall about the opening is the inner end of a sleeve 36. A suitable distance from its outer end, the sleeve 36 18 provided with an internal flange 38 formed, in the present instance, of an annular member that is L-shaped in cross section and a cylindrical portion of which is welded or otherwise secured to the sleeve.

We shall next describe the means for delivering liquid fuel to the burner pot, and the electrical igniter by which the fuel is initially vaporized and ignited.

Attached, by screws or suitable fastening means 40 to the flange 16 of the neck 15, are the peripheral portions of

circular plates

42 and 44, with a gasket 45 of packlng material interposed between the latter plate and said flange 16. By reason of their function, these plates will be referred to, respectively, as the nozzle plate, and the igniter plate. These plates are provided with relatively large registering openings, and shown as fitted within the opening of the nozzle plate 42 is the outer open end of a cup-like shell 50, which we shall refer to as the outer shell, the shell and plate being secured together, desirably by welding. 52 denotes a nozzle guide. It consists of a cylindrical body that is reduced in diameter adjacent its lower end and said end occupies a circular opening in the lower side of the shell 50, the parts being welded or otherwise rigidly connected together. The nozzle guide 52 has an axial passage enlarged at its upper end to provide an annular shoulder or seat 53; and a distance below said shoulder the passage is downwardly convergent. 55 denotes an inner shell that is provided with a side opening that receives the bottom portion of the larger end of the nozzle guide 52. The inner shell is also welded or otherwise firmly secured to the nozzle guide in spaced, substantially concentric relation to the outer shell 50.

Removably nested within the upper end of the nozzle guide is the relatively deep disc-like part or flange 57 of a fuel nozzle 58, the tubular tip of which depends axially from said flange and terminates at its lower end in a frusto-conical portion that is disposed in spaced substantially concentric relation to the tapered wall of the passage of the nozzle guide 52. Opening into the upper end of said passage are a plurality of air holes 59 of the nozzle flange 57, the portion of the flange outwardly of said holes resting upon the shoulder or seat 53. The nozzle is provided with an axial port 60 that is counterbored and threaded at its upper end for the reception of one end of an elbow 62, to the opposite end of which is communicatively connected. by a conventional coupling 63, the adjacent end of a fuel supply pipe 65. Above its frusto-conical portion, the nozzle 58 is bored transversely to provide lateral openings 67 and below said o enings the nozzle is transversely slotted, thus imparting a bill-like appearance to the lower or fuel discharge end of the nozzle. By so forming the nozzle, it affords better fuel discharge or dripping characteristics at any rate of fuel feed. and insures ample volume at a high rate of flow. Furthermore. it so directs the fuel as to prevent contact of the fuel with the nozzle guide, this being highly important as otherwise residue and carbon would collect and build up about the fuel inlet of the burner, due to the high temperatures prevai ing within the latter during burner operation.

70 denotes an electrical i niter of the embedded sheathed type, previously described, and it is desirably in the form of a coil having terminal portions that extend through aligned holes in the

plates

42 and 44. and are welded to the latter or igniter plate. Forwardly of said plate. the terminal portions of the igniter are provided with

binding posts

74 and 75. The coil of the igniter is preferably inclined downwardly and inwardly from the terminal portions, that are normal to the igniter plate, toward the bottom wall 6 of the burner pot. A sheet metal baflle is applied to the coil of the igniter 70 and the same is in the form of a relatively wide channel or tray including a bottom wall 81, side walls 82 and a relatively steep inclined wall portion 83 against which the fuel impinges as it drops from the nozzle 58. The baffle 80 is held in position on the coil 70 by lugs 84 that extend inwardly over the coil from the side walls 82, and by a lug 85 that is struck upwardly from the bottom wall 81 ad acent the lower edge of the latter and rises within the lower convolution of the coil. The inclined wall portion 83 of the bafile 80 is disposed at such an angle as to divert any splash of the fuel away from the region of the 4 fuel admitting aperture and over or toward the coil of the igniter.

By the use of the aforesaid inclined wall portion or extension 83, the igniter 70 can be spaced laterally of and somewhat remote from the fuel inlet of the burner so as to minimize the amount of heat radiated from the igniter to the part of the structure immediately surrounding said inlet during the ignition period, while, at the same time, fuel will be delivered in proximity to the igniter '70 by the baflle 80. It will be observed that the bottom wall 81 of said baflle 80 is inclined downwardly and inwardly, as is the igniter coil, so that although fuel is brought into contact with the igniter coil. such fuel will not accumulate in the vicinity of the igniter at any time. This feature, plus the fact that the igniter 70 and baffle 80 are always above the surface of the fuel in the burner pot, assures against cooling of the igniter during the ignition period by the fuel.

Liquid fuel is supplied to the burner pot through a so-called constant level control valve, shown conventionally in Fig. l and designated 90. It consists of a receptacle to which the fuel is c nveyed from a suitable source (not shown) by a pipe 92, under the control of a valve 93 that is closed by a float 94, wherewith it has the usual operative connections, when fuel rises within the receptacle a given distance. While these float controlled valves are reasonably reliable. they are subject to leakage, and for that reason, as will presently appear, we do not rely upon this float control valve to positively shut off the flow of fuel to the burner. Also incorporated in the unit is a metering valve 98 that reciprocates within a hollow boss that rises from the bottom of the receptacle and through which communicative connection is established between the interior of the receptacle and the reviously mentioned fuel supply pipe 65. As revealed in Fig. l, the metering valve 98 consists of a rod of a diameter to slidably fit within the previously mentioned hollow boss, and the rod has a slot in its lower end. Adiacent its upper end the rod has operative connection with a thermostat that is in the form of a bimetal strip, hereinafter to be described, and by means of this bimetal strip the valve is normally held at an elevation in which the sl t of the rod 98 extends a short distance above the top of the boss. Accordingly, when the metering valve is in normal position, a limited amount of fuel will be permitted to flow past the valve by gravity. Inc uded in the pipe 65 is a so-called fuel release valve 100 of the well known solenoid operated type. The valve is biased toward closed position and accordingly shuts off flow of fuel when the solenoid is deenergized. Reversely, so long as current flows through the coil of the solenoid, the valve will be held open. 102 denotes a similar inlet valve in the pape 92 which functions when the current is cut oif to positively arrest flow of fuel to the constant level control valve 90. As an emergency measure, so that the burner will operate on low fire in case of a general power failure, a by-pass 103 is provided in each of the

pipes

65 and 92 about the

valve

100 and 102 therein, each by-pass, in turn, being equipped with a manual valve 104.

Any liquid fuel that overflows, under abnormal conditions, from the burner pot 1 into the trough 8 is conveyed through a pipe 105 to a closed vessel 106 from which a tube 107 rises through the bottom of the receptacle of the constant level control valve and terminates therein above maximum liquid level. A float 110 operates within the vessel 106 and a rod 111 rises from said float through the tube 107 and is maintained by the latter with its upper end in vertical alignment with a finger 112 on the float 94. Accordingly, when overflow fuel rises sufficiently within the vessel 106, the float 110 lifts the rod 111 so as to engage its upper end with the finger 112 and prevent the float 94 from dropping and lifting the valve 92 from its seat. By this means normal feed of fuel to the burner is prevented until the vessel 106 is drained by the opening of a valve 114 adjacent the bottom of the vessel 106.

designates an air impeller or centrifugal blower that supplies combustion air to the burner. The outlet of the casing of the air impeller or blower 120 ,fits w thin a sleeve 122 that is carried by and extends through an opening in a disc or plate 125, and to which sa d sleeve is rigidly secured, as by welding. The d sc or plate 125 is flanged about its edge and fits within the outer end of the sleeve 36 and against the previously. mentioned flange 38 to which it is secured by a plurality of fastening means 126. These fastening means may consist of screws that are engaged within threaded holes of said flange. The disc or plate 125 is provided with an aperture for the accommodation of the fuel supply pipe 65.

The electrical systemby which the operation of the burner is automatically controlled (although constituting no part of the invention that forms the subject matter hereof) is shown in the diagram that forms a part of Fig. l, and it includes, besides the solenoids of the

valves

100 and 102, the following parts: a transformer 130, the primary and secondary windings of which are designated 131 and 132, respectively; a room thermostat 135 that is shown conventionally as comprising a thermosensitive element of the bimetal variety 136 through which, and a leaf 137 that is carried thereby, current is adapted to be conducted to the low fire contact 138, and the high fire contact 139; a so-called Micro switch 140, the movable element 141 of which is biased in a direction to engage a contact 142, and which is moved into engagement with a contact 143, through the intervention of a push rod 144, by a leaf spring 145. 150 designates, generally, a switch including blades 151 and 152 that are mechanically connected by an extension 153 of the core of a solenoid 155. A bimeta'l strip 158'has operative connection with the metering valve 98 and serves, when cold, to retain the valve open sufficiently to pass enough fuel to maintain low fire burner operation. Associated with said bimetal strip is an electric resistance heater 160, and when this heater is energized it causes the bimetal strip to warp in a direction to lift the metering valve to wide open position, therebyto pass sufiicient fuel to maintain high fire operation of the burner. Associated with the previously mentioned leaf spring 145 is a thermostatic element in the form of a bimetal strip, designated 165. When this element or strip is cold it contacts the free end of the leaf spring 145 and holds the latter under tension in a position to maintain, through the intervention of the push rod 144, the movable element 141 of the Micro switch in engagement with the contact 143 thereof. When heat is imparted to the element or strip 165 by an electrical resistance heater 167, said element or strip will warp in a direction to relax the leaf spring 145 and thereafter withdraw from said spring and engage a contact 168, the latter occurring after a suitable interval of time. Relaxing of the spring 145 permits the movable element 141 of the Micro switch 140 to snap over into engagement 170 designates a so-called top limit switch, asafety feature usually employed in domestic furnaces and other similar apparatus, to open the control circuit in case the apparatus becomes overheated, such switch, obviously, being disposed in intimate suitable part of the apparatus.

The usual house circuit, furnishing electrical energy at a potential of say 110 volts, is represented by a conductor 175 that leads to the primary winding 131 of the transformer 13!), and a conductor 176 that leads from said winding. The circuits of higher potential or voltage are shown in heavy lines, and those of comparatively low voltage, in light lines. The motor 180 of the air impeller or blower 120, and the igniter 70, which may have a capacity of say 500 watts, are in high voltage circuits, as will presently appear. Current is carried from the conductor 175, through a conductor designated 182, to the movable element 141 of the Micro switch 140. The contact 143 of said switch is placed in electrical connection with one side of the motor 180 through a conductor 183. The other contact 142 of said switch has electrical connection with the terminal 75 of the igniter 70 through a conductor 184. Current returns from the motor and igniter to the other side of the high voltage circuit through a conductor 185 and its respective branches 186 and 187. The low voltage circuits, say of 24 volts. that have as their source of current the secondary winding 132 of the transformer, will be described in connection with the operation of the apparatus.

As illustrated in Fig. 1, the apparatus is inactive excepting for the operation of the air impeller or blower. it being assumed that the temperature of the space to which the room thermostat 135 is subjected is above that requiring immediate low fire operation. Upon decline of said temperature to the upper limitof a temperature with the contact 142. r

heat exchange relation to a 6 range for which the thermostat is set, and which may be referred to as the comfort range, the element 136 thereof will swing in a direction and only far enough to engage the leaf 137 with the contact 138. This will close a circuit (starting with the secondary winding 132 of the transformer) through a conductor 190, the winding of the solenoid of inlet valve 102, conductor 191, the beforementioned parts of the room thermostat, and a conductor 192, including the limit switch 170, back to the source. This will result in the opening of valve 102, insuring ample fuel supply to the constant level control valve 90. Current will also flow from the conductor 190 through a conductor 195, the blade 152 of the switch 150 and a conductor 197 to the electrical resistance heater 167 and thence, through a conductor 198, to the previously mentioned conductor 191 and back to the source. Very shortly, or about ten seconds, after the energization of the heater 167, the element or strip 165 will warp enough to relax the spring and permit the movable element 141 of the micro switch 140 to snap into engagement with the contact 142, whereupon current will flow through the conductor 184 to the igniter 70, returning through the conductors designated 187 and 185 to the negative side of the main circuit. Withdrawal of the element 141 from 1 the contact 143 will, of course, cut off the supply of current to the motor 180 of the air impeller or blower, thus interrupting the air supply to the burner during the ignition phase and accordingly accelerating the preheating of the igniter and adjacent parts of the burner due to the absence of the cooling effect of the air. Until the element or strip 165 is warped sufliciently to engage contact 168, the igniter 70 will continue to build up heat in itself and in the adjacent parts of the burner bowl. After an interval of time, say one and one-half minutes, said element or strip 165 will engage the contact 168 and close a circuit including, besides said element and contact,

conductors

200 and 201, the winding of the solenoid 155, and a conductor 202 that leads back to the previously mentioned conductor 191. Upon energization of the solenoid 155, the blades 151 and 152 of the switch will be swung into engagement with the respective contacts 205 and 206, the latter blade 152 withdrawingfrom a contact 2117 that controls the previously described circuit including the electrical resistance heater 167, thereby opening said heater circuit. By engagement of the blade 152 with the contact 206, a circuit is established from the beforementioned conductor 195, through the blade 152, contact 206 and a conductor 208 that joins the previously mentioned conductor 201 thereby to insure continued flow of current to the solenoid after the element or strip cools and withdraws from contact 168. During the interval of time that represents the cooling off period of the element or strip 165, approxiinately one and one-half minutes, which is measured from the time said strip withdraws from contact 168 until it engages and deflects the spring 145, the igniter 70 will remain energized. There is, however, an appreciable fraction of this time, say ten seconds, when electrical contact is made between the element or strip 165 and said spring 145 before the latter yields enough to effect operation of the micro switch. During this dwell cur- 'rent will flow through the conductor 210, the switch blade 151, contact 205, a conductor 212, the winding of the solenoid of the fuel release valve 100 and a conductor 213 to the previously mentioned conductor 262 and thence to the source, thus opening said valve to permit oil to flow, under the control of the metering valve 98, from the fuel supply of the constant level control valve 90 to the burner. I

Now, with the igniter and adjacent parts of the burner, including the bafiie 80, highly heated, the liquid fuel that drops from the nozzle 58 will impinge against the steeper inclined portion of the bottom wall 81 and practically instantaneously flash into vapor and be ignited, such fuel as remains liquid rapidly vaporizing as it flows over the bottom wall of said baflie 80, in contact with the igniter, or, if not before reaching this point, from the bottom of the burner pot, suiiicient air being supplied through the perforations of the peripheral wall of the pot to support such combustion as now occurs.

By this time the continued movement of the element I or strip 165- will have fully deflected the leaf spring 145 and, through the mediumof the rod 144, operated the micro switch 140, causing the element 141 thereof to withdraw from the contact 142 and resume engagement with the contact 143. This will cut ofi supply of current to the igniter and reestablish the circuit through which current is delivered to the motor 180 of the air impeller or blower 120. Air will now be supplied to the burner, desirably under the control of a damper 220, shown as positioned within the discharge opening of the impeller or blower, and which may be set to provide the proper amount of air to the burner to produce the best results. It will be observed that the discharge opening of the impeller or blower casing is so related to the

shells

50 and 55 as to insure air circulating through the space between the shells and about the nozzle. The constant flow of air will keep said shells and the nozzle and nozzle guide relatively cool, notwithstanding their proximity to the intense heat within the burner pot. Part of the air entering the shell 55 will pass through the holes 59 of the nozzle about the nozzle tip and through the passage of the nozzle guide. This will have the effect of preventing contact of the liquid fuel with the surrounding portion of the guide, which is important from the standpoint of keeping these parts clear of residue and carbon, as already pointed out, and, at the same time, of providing primary air in the vicinity of the i niter.

Under the now prevailing conditions fuel will continue to flow to the burner in proper amount to maintain low fire. In the event the temperature of the space to which the room thermostat is subjected rises as a result of the low fire condition to a value beyond the upper limit of the comfort range for which the room thermostat is set, the element 136 will swing toward the position shown in Fig. 1, withdrawing the leaf 137 from the contact 138, thus opening all circuits and allowing the burner to resume the condition assumed at the beginning of the description of operation. On the other hand, should the temperature of said space, notwithstanding low fire operation, drop below the comfort range, the element 136 of the room thermostat will swing still further in its former direction, maintaining engagement of the leaf 137 with the contact 136 and, at the same time, engaging its terminal portion with the contact 139 thereby to close the circuit that branches off from the previously described circuit represented in part by the conductor 212 and through which current is supplied to the solenoid of the fuel release valve 100. The present circuit includes a conductor 225 that leads from the conductor 212 to the electrical resistance heater 160 that is associated with the thermosensitive element or bimetal strip 158. Continuing on from this heater, the current returns to the source through a conductor 226, contact 139, the element 136 ofthe room thermostat, and the conductor 192 which, as previously mentioned, contains the limit switch When the heater 160 is energized, the element or strip 158 will warp in a direction to move the metering valve 98 to wide open position, under which circumstances fuel in sufficient quantity is delivered to the burner to maintain high fire. When, under these circumstances, the temperature to which the room thermostat is exposed rises to somewhere within the comfort range, under which conditions low fire operation is suiiicient, the element 136 will withdraw from contact 139 and open the circuit including the heater 160, after which the element or strip 158 will cool and resume its former condition to return the metering valve to the position shown in Fig. l.

The

valves

100 and 102, when the solenoids thereof are deenergized, serve to positively shut off the flow of fuel to the burner thereby insuring against fuel drip when the room thermostat is not calling for heat. However, when said thermostat is in either of its effective positions, said

valves

100 and 102 are open, under which circumstances the fuel supply to the burner is regulated by the constant level control valve 90, which includes the metering valve 98.

By reason of the novel manner in which the liquid fuel is admitted to the vaporizing and carbureting zone of our improved burner, carbon formation about or within the fuel inlet is entirely avoided. This results in part from the fact that the fuel is maintained at relatively low temperature (below 200 F.) until it is entirely clear of the inlet passages. Instantly upon reaching the burner it drops into the aforesaid zone where it quickly attains a temperature high enough to completely vaporize it and to burn it without carbon formation. Furthermore, carbon does not form on the bottom of the burner pot be cause of the rapid vaporization of the fuel due to the high 8 temperature that prevails within the burner. Incidentally, in this connection, it may be pointed out that the parts of the burner subjected to combustion temperatures are made of material which will not deteriorate at the high temperatures maintained during operation.

Important advantages of our improved burner arise from use of the sheathed, embedded type of igniter, as distinguished from the conventional spark gap igniter, and the exposed hot rod or wire igniter, and from the latter when encased only in a coating of quartz or the like. Either of these spark gap or exposed wire types of igniters will be shorted by even small amounts of carbon, resulting in ignition failure and in deterioration or destruction of the ignition elements. Furthermore, with conventional electrical igniters, ignition is so slow or the zone of ignition so confined that a long time is required for the burner to reach full fire, resulting in a lengthy period of smoky operation each time the burner is started, and lack of heat for some time after heat is needed. Also, by reason of our improvements, no pilot burner is required. As generally known by those acquainted with the art, pilot burners cannot be kept hot enough to prevent formation of carbon when burning the heavier grades of oil. Our improved igniter provides enough heat to accomplish three things, namely: (1) preheat the burner parts hot enough to vaporize the liquid fuel the instant the fuel enters the burner; (2) heat the resultant mixture of vapor and air hot enough to cause instant ignition, and (3) accelerate the heating of the metal parts of the burner so that the fuel vaporizes fast enough to produce a clean hot fire shortly after the oil is ignited.

Because the current carrying element of our improved igniter is completely insulated and sheathed from the fuel and vapor there is no chance of short circuit or deterioration of the element.

Having thus described our invention, what we claim is:

l. A liquid fuel vaporizing burner comprising a burner pot including a peripheral wall and a bottom wall, the peripheral wall of the burner pot being provided with an opening, an open end shell projecting through said opening into the pot and having its open end substantially sealed to said peripheral wall about the aforesaid opening, said shell having an aperture in the bottom thereof, a nozzle guide having its lower end within the aperture and secured to the shell about the same, an inner shell having an opening in its lower side wherein the nozzle guide is fitted, said inner shell being secured to said guide and supported thereby in spaced relation to the first mentioned shell, said guide having a vertical passage, a nozzle nested within the guide and provided with a fuel discharge tip located adjacent the bottom of said passage substantially centrally thereof, a fuel supply pipe having communicative connection with the nozzle, an air housing surrounding and enclosing the burner pot, and means for supplying air to said housing and so arranged as to project a part of the air into said shells.

2. A liquid fuel vaporizing burner comprising a pot including a perforated peripheral wall and a bottom wall, the peripheral wall having a relatively large opening, a neck surrounding said opening and extending outwardly from said wall, a nozzle plate disposed across and secured to the outer end of the neck, said plate having a relatively large opening, an open end shell projecting inwardly through thelast mentioned opening and having its open end secured to the nozzle plate about the opening therein, an aperture in the bottom of said shell, a nozzle guide having its lower end within said aperture and secured to the shell about the same, an inner shell having an aperture in its lower side wherein the nozzle guide is fitted, said inner shell being secured to the guide and supported thereby in spaced relation to the first mentioned shell, said guide having a vertical passage, a nozzle nested within the guide and provided with a fuel discharge tip located adjacent the bottom of said passage substantially centrally thereof, a fuel supply pipe having communicative connection with the nozzle, an air housing surrounding and enclosing the burner pot, and means for supplying air to said housing and arranged to project a part of the air into said shells.

3. In a liquid fuel vaporizing burner, a walled struc ture enclosing a carbureting chamber and provided with means for admitting air to the latter, a high wattage electrical igniter comprising a resistance element embedded in insulating material encased in a tubular metallic sheath, the igniter being formed intermediate its ends to provide a coil and having itsend portions arranged in laterally spaced relation to each other and extended outwardly through and secured to a wall of said structure so as to support said coil within said chamber in spaced relation to the walls thereof and in a plane slightly inclined to the horizontal, a baffle including bottom and side walls applied to the igniter so that said bottom wall underlies and is closely adjacent and substantially parallel to the aforesaid coil and so that the side walls rise on opposite sides of the coil, the baffle including also a wall portion that is inclined upwardly from the high side of the bottom wall in obtuse angular relation thereto, holding means attaching the baffle to the igniter, means for delivering fuel to the chamber above the bafi le in such relation to said wall portion as to impinge thereagainst, and means supplying electrical energy to said resistance element of sufiicient potential to cause said element to impart to the sheath a fuel igniting temperature.

References Cited in the file of this patent UNITED STATES PATENTS Number e Da 974,795

Number 10 Name Date Johnson June 23, 1914 Grotenhuis July 12, 1927 Meyers Oct. 23, 1928 Ravenor June 3, 1930 Haden July 26, 1932 Babb Aug. 30, 1932 1935 Dalen Mar. 15, 1938 Unser Apr. 22, 1941 Holthouse June 16, 1942 Breese et al. Apr. 18, 1944 Tate Feb. 27, 1945 De Lancey May 15, 1945 Hotchkiss Oct. 2, 1945 Miller et al. Mar. 4, 1947 De Lancey July 8, 1947 Resek et a1 Mar. 30, 1948 Tramontini Sept. 13, 1949 Fiedler Nov. 15, 1949 Long Aug. 29, 1950 Little May 22, 1951 Chadwick et al. Oct. 21, 1952 Budlane May 5, 1953