US2812017A - Automatic burner - Google Patents

Description

Nov. 5, 1957 I l. N. VANT 2,812,017

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AUTOMATIC BURNER Filed Feb. 24, 1953 5 Sheets-Sheet 2 INVENTOR. 54002! AA Mwvr Nov. 5, 1957 l. N. VANT AUTOMATIC BURNER 5 Sheets-Sheet 5 Filed Feb. 24, 1953 m a/i/wm (54002: M l/wr 3) \vll T r 1 1 I I IL U.

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AUTOMATIC BURNER Filed Feb. 24, 1953 5 Sheets-Sheet 4 nvvavrap 6,4002: /V. I m r Nov. 5, 1957 1. N. VANT 2,812,017

AUTOMATIC BURNER Filed Feb. 24, 1953 5 Sheets-Sheet 5 Arrow i) United States Patent AUTOMATIC BURNER Isadore N. Vant, Palo Alto, Calif.

Application February 24, 1953, Serial No. 338,430

2 Claims. (Cl. 158-81) This invention relates to a burner. More particularly it relates to a burner system which employs gasoline or other volatile liquid fuel and which is adapted to operate automatically.

This application is a continuation-in-part of my copending application Serial No. 97,560, entitled Fire Unit, filed June 7, 1949, now abandoned, and of my co-pending application Serial No. 101,43 6, entitled Combined Heater and Prime Mover, filed June 25, 1949, now abandoned.

In burners intended to operate on a volatile liquid fuel such as gasoline, it is necessary to vaporize the fuel before introducing it into the burner. Also, where the fuel is leaded gasoline and the burner is employed in a confined space, as in any army field kitchen, or in a camp stove located in a tent, it is advisable to decompose the lead compounds and to filter out the products of decomposition before the gasoline reaches the burner. By lead compounds are meant compounds such as tetraethyl lead which is generally used to improve the antiknock properties of gasoline.

It is an object of the present invention to provide improved means of vaporizing fuel and of removing lead from leaded fuels.

In burners of the character described, it is also desirable to provide a means for starting the burner which is easy and dependable in operation. This is a problem of some considerable difiiculty where a liquid fuel must first be vaporized, and it is particularly difficult where the vapor must be heated sufiiciently to decompose lead compounds.

It is a further object of the present invention to provide starting means for a gasoline burner or the like which is easily operated, which is dependable and which will rapidly heat a fuel vaporizer or generator sufficiently to vaporize fuel and, if necessary, to also decompose lead compounds contained in the fuel.

It is another object of the invention to provide a starting or priming means for a gasoline burner which is automatic in its operation and will pressurize the system and heat a fuel vaporizer or generator to operating temperature.

A further object is to provide improved means of maintaining the fuel tank of a gasoline burner under constant pressure and of automatically limiting the fuel pressure so as not to exceed a predetermined, safe value.

Yet another object is to provide a means for automatically stopping the feed of liquid fuel to the burner when the pressure in the fuel tank exceeds a certain predetermined value.

A further object is to provide a means of avoiding or minimizing the pulsation of a gasoline burner, especially when the burner is operating at a low pressure.

These and other objects of the invention will be apparent from the ensuing description and the appended claims.

Certain forms of the invention are illustrated by way of example in the accompanying drawings, in which,

Figure 1 is a diagrammatic view of a complete burner system embodying the present invention.

Figure 2 is a view similar to that of Figure 1, but showing a different type of filter.

Figure 3 is a top plan view of a burner assembly embody ing the present invention.

Figure 4 is a side elevation of the burner assembly of Figure 3.

Figure 5 is a perspective view of a portion of the burner assembly of Figure 3, certain parts being broken away for clarity.

Figure 6 is a view in section taken along the line 6-6 of Figure 4, showing the intake of the burner.

Figure 7 is a section taken along the line 7-7 of Figure 3 showing the auxiliary assembly.

Figure 8 is a section taken along the line 88 of Figure 4, showing one of the automatic pressure regulating valves in detail.

Figure 9 is a section taken along the line 9-9 of Figure 3 showing the main burner and the auxiliary assembly.

The general construction and operation of the burner system of the present invention will be described first with reference to Figure 1, then, in more detail, with reference to Figures 3 to 9.

Referring now to Figure 1, the burner system is generally designated as 10 and it comprises themain burner 11, a fuel tank 12, a combined vaporizer or generator and filter 13, an auxiliary burner 14, a starter burner 15, a main burner valve 16 and a starter Valve 17.

To start and prime the burner system, the main burner valve 16 is closed and the starter valve 17 is opened. Both the valves 16 and 17 are manually operated valves. When the starting valve 17 is opened volatile liquid fuel such as gasoline, shown at 18 in the fuel tank 12, flows by gravity through a line 19 which has a normally open, automatic, pressure regulating valve 20 and is also connected to a pressure gauge 25. Liquid fuel continues to flow by gravity through the line 19 into a straight length of pipe 26 and issues from the end 27 which is formed with a restricted orifice or nozzle. The fuel wets the wick 29 contained in a perforated trough 29. When this occurs, the gasoline in the wick is lighted with a match or other flame. The resulting flame serves to heat the extreme left hand end of the pipe 26 and thereby quickly vaporizes the gasoline in the pipe. The nozzle end 27 of the pipe 26 and the adjacent end 30 of the starter burner 15 form a venturi which mixes the gasoline vapor formed in the pipe 26 and issuing from the nozzle end thereof, with air. The resulting fuel vapor-air mixture passes into the starter burner 15 and emerges from slots 32 formed therein. Due to proximity of the starter burner 15 to the wick 28, the starter burner is immediately ignited by the Wick. The starter burner continues to burn, thereby heating both a pipe 33 and the vaporizer-filter 13. The pipe 33 is connected at one end to the line 19 and at its other end it is connected to the top of the fuel tank 12 so as to communicate with the vapor space 18a in the tank.

Heat from the starter burner 15 accomplishes two functions; as follows: Gasoline flows by gravity into the pipe 33. This gasoline is heated and vaporized and the fuel vapor passes through the pipe 33 to the vapor space 18a in the fuel tank 12. By this means pressure is built up in the fuel tank 12 and in the system as a whole. Meanwhile, heat from the starter burner also heats the vaporizer-filter 13, which may contain a filter medium such as shown at 34. Operation of the starter burner is continued until a predetermined pressure is registered on the gauge 25, e. g., a pressure of 30 p. s. i. When the system has been thus pressurized by means of the starter burner, there exists a sufficient pressure, and the vaporizer-filter 13 is sufiiciently hot, for operation of the main burner. The main burner valve 16 is then opened. Liquid fuel will then pass through a line 35 containing a normally open, automatic, pressure regulating valve to the vaporizerfilter 13. The vaporizer-filter is sufficiently hot to vaporize the liquid fuel and to decompose lead compounds, which are filtered out by the filter medium 34. The filtered fuel vapor then passes through a line 41 and the main burner valve 16 to the burner intake 42, wherein it is mixed with air and introduced into the main burner 11. vapor-air mixture issuing from the burner 11 is then ignited, and the starter valve 17 is closed to extinguish the starter burner 15.

When the starter valve 17 is closed, the starter burner ceases to supply hat to the vaporizer-filter 13 and to the pipe 33, but this function is taken over by the auxiliary burner 14, which is supplied with fuel-air mixture by the main burner 11 through a passage 43.

In the operation of a gasoline burner it is important to maintain the fuel supply in the fuel tank under sufficient pressure for continued, efficient operation of the burner. It is, however, important to prevent the pressure in the fuel tank from becoming excessive. In some prior burner systems the pressure control is such that, as the fuel pressure increases, more fuel is fed to the burner. This makes the flame hotter, which in turn increases the pressure and supplies even more fuel to the burner. As a result, hazardous explosions are possible and have in fact occurred. On the other hand, it is desirable to avoid a control system which cuts off fuel supply to the burner entirely when the fuel pressure exceeds a predetermined value, because complete extinction of the burner is troublesome.

In accordance with the present invention a safe, dependable automatic pressure control is provided which is efiective to control the fuel pressure and to prevent it from exceeding a safe value, without causing extinction of the burner. The automatic, pressure regulating valve 20 is such that when the pressure in the fuel tank 12, ex-

ceeds a predetermined value, e. g., p. s. i., the valve will close automatically, thereby interrupting the supply of liquid fuel to the pipe 33. This will interrupt the supply of pressurized fuel vapor to the fuel tank 12. Nevertheless, the burnerll will continue to operate because it is supplied with fuel through the line and the other automatic, pressure regulating valve 40. It will thus be apparent that, under most operating conditions, the pressure in fuel tank 12 cannot exceed a predetermined value, but that this control does not interrupt operation of the burner.

The valve provides yet another automatic safety feature, as follows: A burner system such as that illustrated in Figure l is frequently enclosed in a small space, Y e. g., in a cook stove such as employed in army camps.

Such compactness and shielding will necessarily confine the heat from the burner and will heat the fuel tank. Under adverse conditions, such as long continued operation of a burner in a warm climate or in a heated room, the fuel tank may overheat and raise the fuel pressure to a dangerous level.

To overcome this hazard I provide the automatic, pressure regulating valve 40 in the line 35. The valve 40 may be the same as the valve 20. For example, the valve 40 may be set to close at 40 p. s. i. and when the pressure on the left hand side thereof as viewed in Figure l, i. e., on the inlet side of the valve, reaches 40 p. s. i. Thus, should the pressure in the fuel tank 12 become excessive because of the ambient temperature, the valve 40 will automatically close thereby shutting off the supply of liquid fuel to the burner 11. Nevertheless, the burner 11 will not be extinguished because of the following feature:

A pipe is provided which is connected at one end to the line 35 and which extends through the wall of tank 12 and is open at its other end to the vapor space 18a in the fuel tank 12. It will be noted that the pipe 45 connects with the line 35 to the right of the automatic pressure regulating valve 40. The purpose of the pipe 45 is as follows: When the valve 40closes in response to excessive pressure in the fuel tank 12,.the supply of liquid The fuel 4 fuel to the vaporizer-filter 13 is, of course, stopped immediately. However, fuel vapor in the space 18a will pass through the pipe 45 into the line 35, thence through the vaporizer-filter 13 to the burner 11 to support combustion. The excess pressure will be relieved very rapidly, the valve 40 will open again and liquid fuel will be supplied to the vaporizer-filter 13, without extinction of the burner 11.

Referring now to Figures 3 to 9, the burner system 10 is shown as being a compact unit mounted on a base or frame which is slidable into and out of a cookstove or the like. In Figures 3 to 9, elements similar to elements illustrated in Figure l are similarly numbered. As is shown most clearly in Figure 4, the fuel tank 12 is mounted on a sheet metal cradle 51 and is shielded by a sheet metal shield 52 from the burner 11. As shown in Figures 3 and 4 and also in Figure 9, the burner 11 comprises an upright expansion chamber 53 and a burner tip 54 having radial arms 55 formed with slots 56 for escape of fuel-air mixture. The burner 11 also has a central plate 57 and a bolt 58 to clamp the parts together. The burner 11 may be of a conventional construction with suitable modifications as will appear hereinafter.

As shown in Figures 7 and 9, an auxiliary assembly 59 is mounted on or adjacent to the expansion chamber 53 of the main burner 11. This auxiliary assembly comprises the above-mentioned starter burner 15, the pipe 33, the auxiliary burner 14, the vaporizer-filter 13 and the intake 42 of the main burner 11. This auxiliary equipment is very compactly arranged.

Referring now to Figures 4 and 5, the ignition assembly, which is generally designated as 65, comprises the abovementioned pipe 26 which is connected at its inlet end to the line 19 and is provided with a needle valve 17 which is operable by means of a stem 66 and a knob 67. The pipe 26 is supported by spaced, upright brackets 68 which are fixed to a box 69 which, in turn, is fixed to the frame 50. Forwardly, or to the left as viewed in Figures 4 and 5, the pipe 26 overlies the trough 29 containing the wick 28. The starter burner 15 is also fixed to the box 69 and, as shown in Figure 7, it is formed with bottom openings 70 communicating the starter burner with the interior of the box. As shown in Figure 5, the box 69 is formed with a series of holes 71 which extend transversely from the starter burner to the vicinity of the pipe 26, thence longitudinally beneath and in registry with the pipe 26.

As described above, the burner system is started by opening the starting valve 17 to allow liquid gasoline to issue from the nozzle end 27 of the pipe 26 and to wet the wick 28, then lighting the wick. The resulting flame heats the overlying end of the pipe 26 and vaporizes gasoline therein. Gasoline vapor mixes with air in the venturi formed by the juxtaposed ends 27 and 30 of pipes 26 and 15, and the resulting gasoline vapor-air mixture passes into the starter burner 15. From an inspection of Figures 5 and 7, it will be apparent that a portion of the fuel-air mixture supplied to the starter burner 15 will find its way into the interior of the box 69 through the openings 70. This fuel-air mixture will issue from the holes 71 formed in the box 69. By reason of the close spacing and arrangement of the holes 71, the fuel-air mixture issuing from the holes adjacent the starter burner 15 will ignite and the flame will travel along the rows of holes 71, thereby igniting the fuel-air ixture issuing from the holes 71 in registry with the pipe 26. By this means an adequate flame is supplied for vaporizing gasoline in the pipe 26, without the necessity of relying upon the wick 28. Also, the fuel-air mixture issuing from the slots 32 in the starter burner 15 will ignite, thus initiating operation of the starter burner.

As described above, operation of the starter burner is continued until a predetermined pressure is registered on the gauge 25. At such time the main burner valve 16 will be opened to admit fuel vapor to the intake 42. The

main burner 11 is then ignited and the starter valve 17 is closed, thus terminating operation of the starter burner 15.

Referring now to Figures 5 and 6, the intake 42 of the burner 11 is shown in detail. It comprises an angular pipe 72 having an air intake branch 73. The main burner valve 16 is a needle valve which is operated by a stem 74 and a knob 75. The valve 16 terminates in a nozzle or restricted orifice 76. An air control shutter 77 is provided which is located at the outer end of the branch 73. It comprises a plate 78 fixed to the branch 73 by means of a screw 79. By adjustment of the screw 79 the spacing of the plate 78 can be controlled to admit more or less air as desired.

Referring now to Figure 8, the valve 40 is there shown in detail. It will be understood that the valve 20 may be identical in structure. The valve 40 comprises a body portion 80 having passages 81 and 82 formed therein which are interconnected by a passage 83 which terminates in a valve seat 84. The valve proper, shown at 85, is urged upwardly toward the valve seat by a light expansion spring 86 and it is urged downwardly, away from the valve seat, by a much stronger expansion spring 87 which bears against a flexible diaphragm 88 which has a grommet hearing against a rod 89 which is fixed to the valve 85. The valve 85 is normally open because of the greater strength of this spring 87, but it will be apparent that if a sutficient pressure is communicated to the chamber 90 beneath the diaphragm 88 through the passage 81 to overcome the force of the spring 87, the valve 85 will be moved to closed position and will remain closed until the pressure in passage 81 diminishes to a predetermined value. This predetermined pressure is determined by adjustment of a screw 91 and by the strength of the spring 87.

Referring now to Figures 3 and 4, a vacuum release valve 92 is there shown which is connected to the fuel tank 12 and is operated by a rod 93. The purpose of this valve is as follows: When the main burner 11 is extinguished and the fuel in tank 12 cools, vapor in the tank 12 will condense and create a vacuum. If this vacuum persists, difficulty will be encountered in obtaining gravity flow of fuel when the burner is started again. The orifice in pipe 26 is too small to admit air to displace fuel flowing by gravity from the fuel tank and to relieve the vacuum in the fuel tank. This difiiculty is obviated merely by manipulating the rod 93 to open the valve 92, allowing air to enter the fuel tank to relieve the vacuum, and then closing the valve 92. The same difiiculty (no gravity flow of fuel) may exist when the tank 12 is filled completely with fuel, and the same manipulation relieves this difficulty.

Referring now to Figure 2, a burner system is there shown which is the same as the burner system shown in Figure 1 with the exception of the filter employed to filter decomposed lead compounds from the fuel vapor. Parts in Figure 2 which are similar to parts in Figure l are similarly numbered.

The vaporizer 13a may be of the same construction as the vaporizer-filter 13 in Figure 1 except that it does not function as a filter and therefore requires no filtering medium. The vaporizer 13a is preferably empty and free of any obstruction which would cause a pressure drop. Hot fuel vapor containing decomposed lead compounds is conducted through a line 95 to a filter 96 which is disposed within the fuel tank 12. The filter 96 comprises an outer casing or tube 97 which is disposed within the fuel tank 12 and is immersed in the liquid fuel contained in the tank. The right hand end of the outer casing 97, as viewed in Figure 2, is closed as shown at 98 and the other, or left hand end protrudes through the oppositewall of the tank and is closed by means of a fitting 99. An inner tube 100 is disposed within the outer tube97 and is spaced therefrom to provide an annular space 101. The inner or right hand end of the inner tube 100, as viewed in Figure 2, is closed as shown at 102 and the outer or left hand end extends through'the fitting 9.9.and is provided with a fitting 103. The interior of the inner tube 100 is filled with a suitable filter medium, preferably glass balls as shown at 104, which are preferably about four to six millimeters in diameter. Alternatively ceramic material, pebbles, steel balls and other similar materials may be used instead of glass balls. The particles of filter material are preferably large enough so as not to pack tightly, and to leave adequate voids for passage of fuel vapor. At its inner end the tube 100 is formed with openings 105. The fitting at the outer end of the tube 100 is connected to one end of a line 106, the other end of which is connected to the valve 16 of the intake 42 of the burner 11. The line 106 passes over the burner 11.

In operation the filter of Figure 2 functions as follows: Hot fuel vapor containing decomposed lead compounds which have not as yet been filtered out, pass through the line into the annular space 101 between the outer tube 97 and the inner tube 100. The body of liquid fuel surrounding the outer tube 97 acts as a coolant, thereby effectiveiy cooling the hot fuel vapor. During the starting period some of the fuel vapor will condense, but after the interior of the tube 97, including the inner tube and its contents, have been brought up to operating temperature, no further condensation of consequence occurs. The coolant (i. e., the liquid fuel 18) cools the fuel vapor sufficiently to condense and deposit thermally decomposed lead compounds, but it does not condense the hy drocarbon fuel itself except to the limited extent noted. Decomposition of the lead compounds in the vaporizer 13a requires that the fuel be heated considerably above the end point of the fuel itself; e. g., such thermal decomposition may require a temperature of 800 F. whereas at 300 F. the gasoline will be completely vaporized. Accordingly, a sufficiently wide temperature rangeabout 500 F. in a typical case-is provided for deposition of lead decomposition products without condensation of the hydrocarbon fuel.

The cooled fuel vapor then passes through the openings 105 at the inner end of the tube 100 and then through the tube 100, out through the fitting 103 and into the line 106 where it is reheated by the burner 11. The fuel vapor then passes through the valve 16 and the intake 42 into the burner 11. It is in the tube 100 that filtration of decomposed lead compounds takes place.

It will be apparent that the hot fuel vapors containing decomposed lead compounds are cooled before filtration, and that the cooling medium is the liquid fuel itself. I have found that there are distinct advantages in this mode of operation. A more effective filtering action is obtained by precooling the fuel vapors. Apparently at high temperatures such as prevail in the combined vaporizer and filter 13 shown at Figure 1, it is diflicult for the decomposed lead compounds to filter out and there is some tendency for these compounds to be carried out of the vaporizer-filter and into the burner, where they are dispersed to the atmosphere. Also, there is a tendency for the decomposed lead compounds or products of thermal decomposition of the hydrocarbons, to bake onto the filter medium at the high temperature prevailing in the vaporizer-filter 13. Precooling the hot vapors before filtration obviates these difficulties.

Such precooling of the fuel vapors can, of course, be accomplished by atmospheric cooling, as by leading the hot vapors through a coil exposed to the atmosphere. However, atmospheric temperature is more variable than the temperature of the liquid fuel. Also, atmospheric cooling requires coils or some equivalent structure presenting a heat exchange surface to the air, and this structure must be external to the burner system. Thus extra space is required for atmospheric cooling, and the provision of extra space may be difficult or impossible. Thus, the designer may be required to install the extra system within a small space in a cabinet, with no allowance for external coils.

'Yet another advantage of. the cooling system of Figure 2 is as follows: Heat is absorbed by the liquid fuel in tank 12 from the fuel vapor. Should the fuel vapor become excessively hot, it will heat the liquid fuel correspondingly and will raise its pressure. When the pressure exceeds a predetermined value, e. g., 40 pounds per square inch, the valve 40 will close. Excess pressure will be bled off through the pipe 45 and will be burned. This will rapidly relieve the excess pressure, as explained above.

I have also found that glass balls such as those shown at 104, or other like filter medium, provides a more effective filtering medium and/ or is more easily cleaned than conventional filtering media such as steel wool. Thus, from time to time it is sufficient merely to unscrew the fitting 99, remove the inner filter unit, and hold it with the inner end down to allow drainage of condenser fuel therefrom. The fuel will carry with it a deposit of filtered lead compounds. This is apparent from the dirty, black color of the liquid flowing out of the holes 105 at the end of the tube 100. A more thorough cleaning and re juvenation can be accomplished by removing the end fitting 103, pouring out the glass balls 104 and rinsing them with clean gasoline. By way of contrast, steel wool is diflicult or impossible to clean and rejuvenate. It is commonpractice to discard a steel wool filter when it has become clogged and fouled. My preferred filter material can be rejuvenated and re-used indefinitely.

In the systems of Figures 1 and 2, starting can be facilitated by minimizing the surface area of liquid fuel in the fuel tank 12, e. g., by employing a tank of relatively great vertical length and relatively small horizontal diameter. A smaller surface area minimizes condensation of fuel vapor, which is a source of trouble in starting a burner.

Yet another advantage of the systems of my invention, is the minimization or elimination of pulsations. During the operation of a burner in which liquid fuel is vaporized, then supplied to the burner in the form of vapor, difficulty is encountered, especially during starting by pulsations. These pulsations arise because, as the pressure increases in the vaporizer, it passes back through the fuel line into the tank. This occurs because of the restricted character of the nozzle or orifice at the outlet end of the fuel line. The restricted character of this orifice does not permit relief of pressure through the outlet; hence pressure backs up into the fuel tank.

This phenomenon causes pulsation of the flame and may extinguish the flame. It is troublesome during starting when the vapor pressure is low.

In accordance with my invention, hot fuel vapor is supplied to the fuel tank to pressurize the fuel supply. It has been proposed heretofore to supply fuel vapor from the vaporizer to the fuel tank, e. g. in Stein U. S. Patent No. 2,450,025, granted September 28, 1948, entitled Gasoline Field Stove. However, in such prior design, the vapor is taken off at the inlet of the vaporizer, and no automatic control means is provided to diminish the fuel supply when the flame becomes too hot.

A connection between the vaporizer inlet and the fuel tank is not adequately effective in evening out pulsations, and it has the further disadvantage that the vapor at the vaporizer outlet is relatively cool, hence condenses more readily in the fuel tank. And when the fuel vapor condenses it is no longer effective to pressurize the fuel supply. By connecting the outlet of the vaporizer to the fuel tank, these difficulties are overcome; pulsations are greatly reduced or eliminated and the fuel supply is effectively pressurized.

The lack of an automatic pressure control in prior systems is disadvantageous for reasons noted above; when the flame becomes excessively hot, a greater fuel pressure is communicated to the fuel supply, and this greater fuel pressure feeds more fuel to the burner, hence makes the flame hotter. This difficulty is obviated in accordance with the present invention by providing an automatic valve at 40 which cuts off the supply of liquid fuel to the vaporizer Cir and burner when the fuel pressure exceeds a predetermined value.

It will thus be apparent that the burner systems of the present invention achieve the several objects set forth hereinabove. They are adapted to operate on a volatile liquid fuel such as gasoline,.to vaporize the fuel and to decompose and filter out lead compounds. They are simple to start, require a minimum number of starting operations and the problem of pulsation is eliminated or greatly diminished.

The starting system shown in Figures 1 to 9 is substantially automatic in its operation. It provides the heat necessary to vaporize the gasoline which is burned during the starting operation, and it also pressurizes the fuel tank and heats the fuel vaporizer to operating temperature.

The entire unit is compact. Also certain important safety features are provided which are automatic in their operation. Thus the valve 20 is such that the fuel pressure is not allowed to exceed a predetermined value. Yet the valve 20 operates in a manner to avoid interruption of the main burner. If, because of heat from the burner and a high ambient temperature, the fuel in the tank 12 becomes overly heated, the valve 49 operates to automatically shut off the flow of liquid fuel to the main burner, but the burner is not extinguished.

Among other features, a novel and advantageous filter, and a novel means for reheating and rte-evaporating condensed fuel vapor are provided.

I claim:

1. A burner system comprising a fuel tank for volatile liquid fuel, a main burner and a main fuel vaporizer connected to the fuel tank to receive liquid fuel therefrom and to said main burner to supply fuel vapor thereto; an auxiliary burner connected to receive a combustible fuel and air mixture for operation thereof from the cornbustible mixture supplied to said main burner for heating said main fuel vaporizer during normal operation of the main burner; a second vaporizer having an inlet connected to the fuel tank to receive liquid fuel therefrom and an outlet remote from said inlet and connected to said tank to apply the pressure of the vapor generated in said second vaporizer to said tank; said second vaporizer being heated by said auxiliary burner; a starter burner for heating said main fuel vaporizer and said second vaporizer during starting of the burner system, and a third vaporizer connected to the fuel tank to receive liquid fuel therefrom, said third vaporizer supplying vaporized fuel to the starter burner.

2. In a burner system of the type comprising a fuel tank, a burner and a main vaporizer, and means including conduit forming means interconnecting said elements to supply liquid fuel from the tank to the main vaporizer and to supply fuel vapor from the main vaporizer to the burner; a second vaporizer having an inlet connected to the fuel tank to receive liquid fuel therefrom and an outlet remote from said inlet and connected to said tank to supply fuel vapor thereto for pressurizing the tank, means for heating said second vaporizer, a first automatic valve operable automatically to terminate flow of liquid fuel to said main vaporizer when the fuel pressure in the fuel tank reaches a first predetermined value, a second automatic valve operable automatically to terminate flow of liquid fuel to said second vaporizer when the pressure in the fuel tank reaches a second predetermined value which is less than said first value and means including conduit forming means for supplying vaporized fuel from said tank to said burner during the portion of the period of operation of said burner system when said first automatic valve means is closed.

References Cited in the file of this patent UNITED STATES PATENTS 211,997 Harris Feb. 4, 1879 (Other references on following page) 10 UNITED STATES PATENTS 2,397,142 Howard Mar. 26, 1946 2,448,235 Rasmussen Aug. 31, 1948 639,197 Loeben 12, 1899 2,450,025 Stein Sept. 28, 1948 778,443 capell 27, 1904 2,586,416 Buckley Feb. 19, 1952 968,233 Best 23, 1910 5 2,586,935 Gerson Feb. 26, 1952 1,223,141 Boyd Apr. 17, 1917 1,230,735 Logan June 19, 1917 FOREIGN PATENTS 1,338,361 Doran Apr. 27, 1920 1,653,867 McKeoWn Dec. 27 1927 336,654 Great Bntam O 17, 1930 1,807,521 Foulk May 26, 1931 10

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