US3640673A

US3640673A - Liquid fuel burner

Info

Publication number: US3640673A
Application number: US56257A
Authority: US
Inventors: Kenya Okamoto; Hajime Satoda
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1969-07-22
Filing date: 1970-07-20
Publication date: 1972-02-08
Anticipated expiration: 1989-02-08
Also published as: GB1277730A; DE2036151A1; DE2036151B2

Abstract

A liquid fuel burner so constructed that a Silocco fan is disposed in a gasification chamber of the burner and an atomizer utilizing the effect of centrifugal force is provided in the center or air-sucking portion of said Silocco fan, whereby a liquid fuel supplied to the atomizer is dispersed radially outwardly under the influence of centrifugal force in the form of particles and further divided into fine particles by the stirring and dispersing actions of the blades of said Silocco fan, said fine particles of liquid fuel being gasified by heated air.

Description

I United States Patent 1151 3,640,673

Okamoto et al. 451 F b, 8, 1972 [S4] LIQUID FUEL BURNER [56] References Cited [72] Inventors: Kenya Okamoto; Hailme Satoda, both of UNITED STATES PATENTS Nara- Japan 1,971,874 8/1934 Perry ..431/168 X 731 Assignee: Matsushita Electric Industrial 00., 1.111., 2905352 6/1935 Branche- 431/168 Osaka, Japan 2,718,919 9/1955 Ray ..431/1e3 x [22] Fi ed: July 20,19 0 3,021,892 2/1962 Brula ..431/168 [21] Appl. No.: 56,257 Primary Examiner-Edward G. Favors Attorney-Stevens, Davis, Miller & Mosher 30 Fore A [1 ti Pri t D ta 1 1 a pp y a [57] ABSTRCT July 22, 1969 Japan ..44/5958l July 22,1969 Japan ..44/59582 A hquld fucl burner constructed that a Silocco fan 15 a July 22,1969 Japan" 44/7165; disposed in a gasification chamber of the burner and an July 22, 1969 Japan ..44/71659 atomizer utilizing the elfect of centrifugal force is Provided in the center or air-sucking portion of said Silocco fan, whereby [52] US. CL... ...431/ 168, 239/2l4.15, 431/208 a liquid fuel supplied to the atomizer is dispersed radially out- [51] Int. Cl ..F23d 11/04 wardly under the influence of centrifugal force in the form of 1 Field of Search 207, 11, particles and further divided into fine particles by the stirring and dispersing actions of the blades of said Silocco fan, said fine particles of liquid fuel being gasified by heated air.

9 Claims, 7 Drawing Figures PAIENIEnrm a ma SHEET 3 OF 3 FIG.7

LIQUID FUEL BURNER The present invention relates to a liquid fuel burner which is so designed that a liquid fuel is burned after it has been completely gasified, whereby the combustion efficiency is enhanced and the combustion noise is minimized.

Various types of liquid fuel burners have been proposed heretofore, of which one is a pot type and the other is a gun type or rotary type wherein fuel is atomized. In the pot type, a fuel stored in the bottom of a combustion cylinder is gasified by the combustion heat and burnt successively. However, since the fuel is gasified only naturally, the combustion capacity is inevitably subjected to a limitation and in addition, the quantity of soot formed becomes large and the funnel construction becomes complicated.

In the type wherein fuel is atomized, the particles of fuel are mixed with air for the first time when they reach a combustion region, so that a red flame tends to occur during combustion and a large quantity of soot is formed.

The red flame combustion may be converted into an efficient blue flame combustion by supplying excess air. However, a type of burner wherein air is supplied in an excessive quantity to obtain a blue flame combustion, has the disadvantages that the combustion is accompanied by a large noise and that carbon monoxide is generated due to incomplete combustion, such as lifting.

The present invention aims to eliminate such disadvantages of the conventional burners, by gasifying fuel completely and mixing the gasified fuel with air thoroughly before the fuel reaches a combustion region.

An object of the invention is to provide a liquid fuel burner wherein a Silocco fan is disposed in a gasification chamber of a burner element and an atomizer utilizing the effect of centrifugal force is provided in the center or air sucking portion of said Silocco fan to disperse the liquid fuel supplied thereto radially outwardly under the influence of centrifugal force in the form of particles, said particles of fuel being further divided into fine particles by the stirring and dispersing actions of the blades of said Silocco fan and gasified by preheated air, whereby the fuel is gasified and burnt efficiently in the form of a blue flame and moreover the combustion noise is minimized.

Another object of the invention is to provide a liquid fuel burner of the character specified above, wherein the Silocco fan is rotated at a relatively low rate at the initiation of combustion so as to avoid supply of a excessively large quantity of air relative to the quantity of fuel supplied, whereby flame lifting can be prevented and the combustion range at the initial stage of combustion is expanded.

Still another object of the invention is to provide a liquid fuel burner of the character specified above, wherein an air suction passage for the Silocco fan is formed adjacent the combustion region, so that in the normal combustion operation the air being sucked may be preheated by the combustion heat, without using a heater, etc., to further promote the gasification of fuel.

Still another object of the invention is to provide a liquid fuel burner of the character described above, wherein the air inlet portion of said air suction passage is shielded from the combustion region, whereby mixing of the combustion gases in the air being sucked is prevented and hence the combustion efliciency is enhanced.

Still another object of the invention is to provide a liquid fuel burner of the character described above, wherein the fuel is supplied to the atomizer from above the center of said Silocco fan, whereby piping of a fuel supply pipe is simplified.

Still another object of the invention is to provide a liquid fuel burner of the character described above, wherein flame holes communicating with the gasification chamber are formed between a mixing rang and a combustion ring and between the combustion ring and a headplate, and the inner edge of the mixing ring is projected into the gasification chamber, whereby mixing of the gasified fuel and air is further promoted and the formation of a red flame or generation of soot due to insufficient mixing can be prevented.

A further object of the invention is to provide a liquid fuel burner of the character described above, which further comprises a fuel supply device comprising a main tank provided with a level-adjusting mechanism to control the level of fuel therein and having an inlet for fuel from a fuel tank, an auxiliary tank smaller in capacity than said main tank communicating with said main tank at a lever above a set level of fuel in the main tank and having an outlet for fuel at a level lower than said communicating level, and a pump for pumping the fuel from said main tank into said auxiliary tank, the pump having a pumping capacity greater than the flow rate of fuel discharged through said outlet, whereby the fuel is supplied to the burner element always at a constant rate even if the pumping capacity of the pump varies, and hence a uniform combustion is obtained at all times.

Other objects, features, and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. I is a sectional view of an embodiment of the liquid fuel burner according to the present invention;

FIG. 2 is a front elevational view of the burner element, with half portion shown in section;

FIG. 3 is an enlarged sectional view of the fuel atomizing portion;

FIG. 4 is a diagram of a combustion control circuit;

FIGS. 5 and 6 are enlarged sectional views of other arrangements of the fuel atomizing portion; and

FIG. 7 is a sectional view of the fuel supply device.

One embodiment of the liquid fuel burner according to the present invention will be described hereunder with reference to FIGS. 1-4.

Referring to FIGS. 1-3, reference numeral 1 designates a mounting frame and 2 designates a burner element mounted on top of said mounting frame. A space 1 is formed between the mounting frame 1 and the burner element 2 by spacers 3 interposed therebetween.

Reference numeral 4 designates a casing of the burner element 2, which consists of an inner casing 5 and an outer casing 6. The inner casing 5 and the outer casing 6 define therebetween a space which is used as an airflow passage 7, and an annular projection 8 is formed extending outwardly from the upper portions of said casings. Reference numeral 9 designates a number of air inlet holes bored through the peripheral wall of the

annular projection

8, and 10 designates the peripheral edges of the inner and outer casings S, 6 which are flexed downwardly so as to cover the air inlet holes 9 from above and outside thereof. Reference numeral 11 designates a heater wound around the outer surface of the inner casing 5,

. and 12 designates a mixing ring fixed to the edge of the opening of the inner casing 5. A combustion ring 14 is provided above the mixing ring 12 with spacers 13a interposed therebetween, and further a headplate 15 is provided above the combustion ring 14 with spacers 13b interspaced therebetween, said spaces 13a, 1312 being respectively spaced from each other so as to define slitlike flame holes 16. The space 17 defined by the inner casing S and the headplate 15 is used as a gasification chamber and the inner peripheral edge of the mixing ring 12 is projecting into said gasification chamber 17.

Reference numeral 18 designates an air passage hole formed centrally of the bottom wall of the

inner casing

5, and 19 designates a heat insulating material, such as asbestos, surrounding the outer peripheral surface of the outer casing 6 and being held in position by a cover 20. Reference numeral 21 designates a motor secured to the underside of the mounting frame 1 by means of a bracket 22, with the drive shaft 23 thereof extending upwardly through the bottom walls of the cover 20 and the outer casing 6 and further through the air passage hole 18 in the inner casing 5, into the gasification chamber 17. In the gasification chamber 17 is provided a Silocco fan 24. Reference numeral 25 designates an atomizer plate mounted on the drive shaft 23 of the motor 21 in the central portion of the Silocco

fan

24, and 26 designates a fuel supply pipe having one end located above the atomizer plate 25 in opposed relation thereto, with the other end connected to a solenoid valve 27. Reference numeral 28 designates a pipe connecting the solenoid valve 27 with a liquid fuel supply device 29; 30 a cooling fan for the motor 21; and 31 a cooling air inlet hole formed in the mounting frame 1. Reference numeral 32 designates an ignition plug; 33 a heat-sensing element which controls a current conducted through the heater 11 upon sensing the temperature of the casing 4, particularly of the inner casing 5; and 34 a combustion sensing element which senses the combustion state of the burner element 2. The electrical connection and the functions of these elements will be described in detail later.

The liquid fuel burner constructed as described above operates in the following manner: Namely, when the motor 21 is set in motion to rotate the Silocco fan 24 and the atomizer plate 25, and heater 11 is energized and the solenoid valve 27 is opened, air flows into the airflow passage 7 from the outside through the air inlet holes 9 of the casing 4, under the suction produced by the Silocco fan 24. In this case, the inner casing 5 is heated by the heater 11, so that the air is heated by the inner casing 5 and the heater 11 during passage through the airflow passage 7, and flows into the central portion of the Silocco fan 24 through the air passage hole 18 of the inner casing 5 in the heated condition. Thereafter, the air is dispersed within the gasification chamber 17.

On the other hand, a metered quantity of fuel supplied from the fuel supply device 29 passes through the solenoid valve 27 and the fuel supply pipe 26 and is fed onto the rotating atomizer plate 25.

The fuel on the atomizer plate 25 is splashed outwardly as shown in FIG. 3 by the centrifugal force imparted thereto, further accelerated and stirred by the blades of the Silocco fan 24 and finally atomized in the form of fine particles.

Since the Silocco fan 24 is also dispersing the heated air, the fine particles of fuel which are small in heat capacity, are gasified almost entirely as soon as they contact the heated air, and the remaining fuel particles are gasified by contact with the inside surface of the inner casing 5 which is heated by the heater 11.

The gasified fuel and the heated air are thoroughly stirred and mixed within the gasification chamber 17, since the inner edge of the mixing ring 12 projects inwardly of said gasification chamber, and thereafter ejected to the outside through the slit-shaped flame holes 16 defined by the combustion ring 14 and the heat plate 15, etc. By igniting the air-fuel mixture by means of the ignition plug 32, an annular flame A is formed.

The flame A is formed adjacent the annular projection 8 of the casing 4, so that the air flowing into the gasification chamber 17 through the air inlet holes 9 is heated by the flame to a higher temperature than before, without being heated by the heater 11.

The air thus heated gasifies completely the fuel, dispersed by the atomizer plate 25 radially and atomized into fine particles, before the particles reach the inside surface of the inner casing 5. Thus, it will be understood that the current supply to the heater 11 is necessary only at the start of combustion, and not necessary thereafter.

As stated, the combustion flame A is formed adjacent the projection 8 of the casing 4 and the peripheral wall of the projection 8 has the air inlet holes 9 bored therethrough, so that the combustion gases would be mixed in the air flowing into the gasification chamber, unless some means is provided. The mixing of the combustion gases into the air means that the quantity of oxygen per unit volume of air is decreased and a steady combustion cannot be expected due to the development of soot during combustion and in complete combustion. In the burner of this invention, since the peripheral edge of the casing 4 is flexed so as to cover the inlet holes 9 from above and the front side. Therefore, the combustion gases are not allowed to reach the air inlet holes 9 and the air is admitted only from the lower side of the holes.

As a result, no combustion gases are mixed in the air and a steady combustion can be obtained.

The motor 21 is protected from the combustion heat by the heat-insulating material 19 provided along the outer peripheral surface of the outer casing 6, and is cooled by the cooling fan 30. A layer of air flowing in the gap t between the casing 4 and the mounting frame 1 also serves to insulate the motor 21 against the combustion heat.

At the initiation of combustion, the heater 11 heats the inner casing 5 and also the air passing through the airflow passage 7, as stated above, At this point, however, since the burner element 2 has not been sufficiently heated, the temperature of the air flowing into the burner element and the temperature of the inner casing 5 are not so high. Consequently, the fuel dispersed by the atomizer plate 25 and stirred by the blades of the Silocco fan into fine particles is not entirely gasified initially, and a part thereof remains in the bottom of the inner casing 5 in the form of liquid.

The fuel is completely gasified when the burner element 2 has been sufficiently heated by the combustion heat.

In the burner of this invention, the rate of rotation of the motor 21 is lowered only for a period in which the gasification of fuel is insufficient, so as to decrease the quantity of air blown by the Silocco fan 24. This is because, if the quantity of air blown by the fan is large relative to the quantity of fuel being gasified, lifting tends to occur during combustion resulting in flame out or generation of carbon monoxide clue to incomplete combustion.

Referring to FIG. 4, there is shown an electric circuit for controlling the rate of rotation of the motor 21 and the combustion of fuel.

In FIG. 4, reference numeral 35 designates a primary circuit having a voltage of V. impressed across the

terminals

36, 37 thereof, and 38 designates a secondary circuit arranged with a transformer 39 interposed between it and said primary circuit 35 and impressed with a voltage of about 24 V.

The primary circuit 35 includes the circuit 40 of the heater 11, the circuit 41 of the motor 21, the circuit 42 of the ignition plug 32 and the circuit 43 of the solenoid valve 27. The motor circuit 41 is diverged into a low-speed circuit 41a and a high- Speed circuit 41b.

Reference numeral 44a designates a relay switch inserted in the heater circuit 40; 45b a relay switch inserted in the motor 41; 45b a relay switch inserted in the solenoid valve circuit 43; 46a a bimetal switch to switch the motor circuit 41 from the low-speed circuit 41a to the high-speed circuit 41b or vice versa; and 46b a bimetal switch connected to the motor circuit 41 and operated for engagement with a

contact

47 or 48 of the ignition plug circuit 42. In the secondary circuit 38, reference numeral 49 designates a bimetal switch to ensure safety of the circuit, and the current flowing throughout the circuit 38 is interrupted when said safety switch is opened. Reference nu meral 44b designates a relay switch which switches the electrical connection from a

contact

50 or 51 or vice versa; 450 a relay switch; 52 a switch which is opened and closed by the function of the heat sensing element 33; 53 a switch which is opened and closed by the function of the combustion-sensing element 34; 54, 55 relay coils; and 56, 57 heaters for the bimetal switches. The relay switches 44a, 44b are operated by the relay coil 54, such that when a current flows through the relay coil 54, the relay switch 44a is closed and the relay switch 44b is brought into contact with the contact 51.

The relay switches 54a, 45b, 45c are operated by the other relay coil 55, such that when a current flows through the relay coil 55, all of the

relay switches

45a, 45b, 450 are closed.

The safety bimetal switch 49 is designed to be opened a while after the heater 57 is energized. When the other heater 56 is energized, the bimetal switch 46a is connected to the high-speed circuit 41b and the bimetal switch 46b to the contact 48.

For initiating the combustion operation, with the arrangement described above, a voltage is first of all impressed across the

terminals

36, 37. In the secondary circuit 38, the current flows through the relay coil 54 only, whereby the relay switch 44a of the heater circuit 40 is closed and the other relay switch 44b is contacted with the contact 51. Then, the inner casing 5 is heated to a predetermined temperature by the heater ll, whereupon the temperature of said inner casing 5 is sensed by the heat-sensing element 33 and the switch S2 is closed. Here, the current also passes through the other relay coil 55, so that the

relay switches

45a, 45b, 450 are all closed and the current flows through the low-speed circuit 41a of the motor 21, the solenoid valve circuit 43 and the ignition plug 32. As a result, the burner element 2 starts its operation, with the motor 21 rotating at a low speed. When the flame A is formed in the burner element 2, such state is sensed by the combustionsensing element 34 and the switch 53 is opened. Since the current no longer passes through the relay coil 54, the relay switch 44a is opened to interrupt the current supply to the heater 11. The other relay switch 44b is switched to the contact 50 to deenergize the heater 57 and energize the heater 56. Upon energization of the heater 56, the bimetal switch 460 is switched to the high-speed circuit 41b and the other bimetal switch 46b to the contact 48. Thus, the motor 21 rotates at a high speed and the burner element 2 is brought into the state of normal operation. The current supply to the ignition plug 32 is also interrupted. The heat-sensing element 33 is heated by the combustion heat during normal operation of the burner element, and hence the switch 52 is held closed.

If, in the initiation of the combustion operation described above, the combustion flame A is not formed in spite of the fact that all conditions for starting the combustion are satisfied, the combustion-sensing element 34 does not open the switch 53 and the current continues to flow through the relay coil 54. In this case, the relay switch 44b is of course still in engagement with the contact 51 and the heat 57 continues to generate heat, so that the safety bimetal switch 49 is opened. Consequently, no current flows through the secondary circuit 38 and the combustion starting operation is once interrupted. The safety bimetal switch 49 is opened on occurrence of an abnormal condition, such as ignition failure or fuel supply failure. In such a case, the mechanism should be inspected to ensure that the component parts are in a satisfactory condition, because otherwise the condition will possibly lead to malfunction of the mechanism.

In the liquid fuel burner of the invention, as described above, the liquid fuel gasification unit, comprising the Silocco fan and the fuel atomizer plate disposed in the control portion of said Silocco fan, is provided in the casing which has the air flow passage therein adjacent the flame holes, and the motor for driving said Silocco fan is rotated at a relatively low speed at the start of combustion. Therefore, liquid fuel is atomized into fine particles by the centrifugal force of the atomizer plate and the stirring action of the blades of the Silocco fan, and is readily gasified by heating it slightly at the initiation of the combustion operation. The fuel is gasifled and burned from the outset of the combustion operation and thereafter the gasifrcation of fuel is effected by the heated air.

Since the gasifred fuel and air are completely mixed prior to combustion, an excellent blue flame combustion, free of soot, can be obtained. Furthermore, the combustion is not accompanied by a noise since supply of excess air is unnecessary.

At the initiation of combustion, the casing of the burner element is not heated and hence the rate of gasification of fuel is low. In the burner of this invention, the quantity of air blown by the Silocco fan is decreased at this point, by reducing the rate of rotation of the motor. Therefore, occurrence of lifting due to excess air can be avoided and a steady combustion can be obtained from the outset of the combustion. In other words, the range of combustion can be expanded by changing the rate of rotation of the motor.

The table provided below shows the combustion range in the case (B) wherein the quantity of air blown by the Silocco fan is maintained constant without changing the rate of rotation of the motor, and the same in the case (C) wherein the quantity of air blown by the Silocco fan is changed by reducing the rate of rotation of the motor to, e.g., 30 percent of the normal rate of rotation. In this table, the room temperature is -l 0 C. and the flow rate of air blown by the Silocco fan under normal condition is 46.5 mP/hr.

Control of Combustion Rate Motor Rotation (Fuel Quantity) No (B) 3.2-4.2 Llhr. Yes (C) 2.7-4.2 Llhr.

In the above table, the minimum value of the combustion rate is the limit beyond which lifting occurs, and the maximum value of the same is the limit beyond which a red flame occurs.

From the results shown in the table, it will be seen that the combustion range can be expanded 50 percent by reducing the flow rate of air blown by the Silocco fan by 30 percent, by reducing the rate of rotation of the motor, and that thereby a safe combustion free of lifting can be obtained at the initiation of combustion, even if the rate of gasification of fuel is low. Namely, the starting characteristic of combustion can be markedly improved.

The other arrangements of the fuel atomizing portion will be described hereunder with reference to FIGS. 5 and 6.

In the arrangement shown in FIG. 5, an atomizing cap 59 having a large number of atomizing holes 58 perforated through the peripheral wall thereof, is provided by forming a depression at the center of the upper plate of the Silocco fan 24, and the discharge end of the fuel supply pipe 26 is located above said atomizing cap 59 in opposed relation thereto.

The atomizing effect of this arrangement is the same as that in the preceding embodiment. Namely, the fuel fed into the atomizing cap 59 from the discharge end of the fuel supply pipe 26 is ejected in the form of fine particles through the holes 58 under the influence of centrifugal force and further divided by the stirring and dispersing action of the blades of the Silocco fan 24.

In this arrangement, the atomizing cap 59 is formed on the upper plate of the Silocco fan 24, for the following reason:

Namely, the atomizing cap 59 has the effect of radially dispersing the liquid fuel fed therein, under the influence of centrifugal force and dividing the fuel into coarse particles before it is stirred by the blades of the Silocco fan 24.

In this view, it would be satisfactory to connect an atomizer plate to the shaft 20 of the motor 18 in the central portion of the Silocco fan 24, as shown in the arrangement of FIGS. 1-3. However, according to such arrangement, the fuel supply pipe is inevitably extended into the central space of the Silocco fan 24. Consequently, the piping of the fuel supply pipe becomes difficult and the pipe may interfere with the rotation of the Silocco fan 24, and further the diameter of the pipe undergoes a limitation since the pipe is extended into the central space of the fan.

In the arrangement shown in FIG. 5, however, since the atomizing cap 59 is open in the upper plate of the Silocco fan 24, ti is unnecessary to extend the fuel supply pipe 26 into the central portion of the Silocco fan 24 and the pipe can be arranged within the gasification chamber 17. Therefore, the piping of the fuel supply pipe 26 is easy and the rotation of the Silocco fan is not interfered by the pipe at all. In addition, the diameter of the pipe can be made large and clogging of the pipe with dusts, etc., can be avoided.

Fig. 6 shows another arrangement in which the atomizing cap 59 is provided separately from the upper plate of the Silocco fan 24. The effect of this arrangement is identical with that of the arrangement of FIG. 5. In FIGS. 5 and 6,

reference numerals

60, 61 designate a plurality of fuel receiving plates provided on that portion of the fuel supply pipe 26 which extends in the interior of the gasification chamber 17, the diameter of said plates being reduced upwardly. These receiving

plates

60, 61 serve to receive the fuel flowing down onthe outer peripheral surface of the fuel supply pipe 26 and quickly gasifies the same. Namely, a part of the fine fuel particles dispersed by the Silocco fan 24 collides against the fuel supply pipe 26 and flows down in the form of liquid along the outer peripheral surface of said pipe to be accumulated in the

plates

60, 61. The air present in the gasification chamber wherein the receiving

plates

60, 61 are located, is previously heated and maintained at a predetermined elevated temperature by the combustion heat. Therefore, the fuel received by the receiving

plates

60, 61 is gasified is sequence to be served for combustion.

The fuel attached to the wall of the fuel supply pipe 26 is gasified in the process of flowing down on the wall and a very little amount of fuel reaches the receiving

plates

60, 61. In the initiation of combustion, however, the fuel is hardly gasified on the wall of the fuel supply pipe 26, so that the plurality of receiving

plates

60, 61 are provided for the sake of safety and such that the fuel overflowing the upper plate 60 may be received by the lower plate 61, if such overflow occurs.

As may be understood from the foregoing description, the provision of the fuel receiving plates to receive the fuel flowing down along the outer peripheral surface of the fuel supply pipe 26 and to gasify the same, is advantageous, not only in that the fuel dispersed by the Silocco fan 24 can be entirely served for combustion, but also that the accumulation of tar on the surface of the burner casing, particularly on the bottom surface of the inner casing, can be avoided.

Now, the construction of the fuel supply device 29 will be described with reference to FIG. 7. In FIG. 7, reference numeral 62 designates a main tank having a fuel inlet passage 63 formed in the bottom thereof, said fuel inlet passage 63 being communicated with a liquid fuel tank (not shown), and 64 designates a guide cylinder formed integrally with the wall of said fuel inlet passage 63 and having a valve seat 65 formed in the bottom wall thereof at a location where the inside cavity of said guide cylinder communicates with the fuel inlet passage 63. Reference numeral 66 designates a filter removably disposed in the inlet passage 63; 67 a fuel passage hole formed through the peripheral wall of said g$ide cylinder 64; and 68 a valve body vertically slidably fitted in said guide cylinder 64 to open and close the valve seat 65, said valve body being normally urged upwardly by a spring 69 to keep the valve seat 65 open. Reference numeral 70 designates a lever pivotally connected to a projection 71 by a pin 72, which projection 71 extends upright from the flange formed around the open top edge of the guide cylinder 64. One end of the lever 70 is in abutting engagement with the top end of the valve body 68 and the other end thereof is provided with a float 73.

The float 73 maintains the surface of the fuel in the main tank 62 at a predetermined level in cooperation with the lever 70 and the valve body 68. Namely, when the surface of fuel lowers, the float 73 moves downward, causing the lever 70 to rotate in a clockwise direction, whereby the value body 68 opens the valve seat 65. Thus, it will be seen that the fuel is supplied into the main tank 62 through the fuel inlet passage 63, the filter 66, the valve seat 65 and the fuel passage hole 67, until the surface thereof reaches the predetermined level. Reference numeral 74 designates an auxiliary tank formed at the upper portion of one sidewall of the main tank 62. This auxiliary tank 74 is communicated with the upper portion of the main tank 62 through a communication port 75 and is provided with a fuel outlet port 77 on one sidewall thereof, said fuel outlet port 77 having an orifice 76 therein. The capacity of the auxiliary tank 74 is very small as compared with the capacity of the main tank 62. The communication port 75 is positioned at a lever higher than the set level of fuel and the fuel outlet port 77. Reference numeral 78 designates a pump by which the fuel in the main tank 62 is sent into the auxiliary tank 74. The pumping capacity of the pump 78 is set to be greater than the quantity of fuel discharged through the orifice 76 at a predetermined rate. Reference numeral 79 designates a cover. The fuel outlet port 77 is connected to the connecting pipe 28 shown in FIG. 1.

With the construction described above, when the pump 78 is actuated and the aforesaid solenoid valve 27 is opened, the fuel introduced into the auxiliary tank 74 from the main tank 62 is supplied to the burner element 2 at a predetermined rate established by the orifice 76. Since the pumping capacity of the pump 78 is greater than the quantity of fuel supplied through the orifice 76, the fuel level in the auxiliary tank 74 rises gradually and reaches the level of the communication port 75 but will not rise higher than the communication port because excess fuel is returned into the main tank 62 through said communication port.

Thus, a predetermined quantity of fuel is maintained in the auxiliary tank 74. Therefore, the fuel is supplied to the burner element always at a constant rate through the orifice 76. even when the fuel supply rate of the pump 78 varies due, for example, to a voltage fluctuation or frequency fluctuation.

If the solenoid valve 27 is not closed due to malfunction when the current supply to said solenoid valve and the pump 78 is interrupted, the fuel remaining in the auxiliary tank 74 will flow into the burner element but the quantity thereof is so small that it will not cause any problem.

The conventional liquid fuel burner is unsatisfactory in this point and has the drawback that, once the solenoid valve has failed and is held open, the entire fuel in the fuel tank flows into the burner through the main tank, because in the burner an auxiliary tank is not provided and the main tank is directly connected to the solenoid valve.

According to the present invention, however, the auxiliary tank extremely smaller in capacity than the main tank is provided to store the fuel before the fuel is fed to the burner. Therefore, only a small quantity of fuel flows into the burner even if the solenoid valve is not closed, and the degree of danger can be lessened accordingly.

In addition, the fuel is fed to the burner always at a constant rate even if the pumping capacity of the pump varies, whereby uniform combustion can be obtained.

As may be understood from the foregoing description, according to the present invention there is provided a liquid fuel burner which is capable of burning a liquid fuel efficiently and uniformly, with a minimum noise. The burner of the instant invention can be used in a very wide range of application, e.g., as a stove, a hot water boiler, etc.

Although the present invention has been described and illustrated herein in terms of a specific embodiment thereof, it is to be understood that many changes and modifications are possible without deviating from the spirit of the invention.

What we claim is:

1. A liquid fuel burner comprising a burner casing consisting of an inner casing defining therein a gasification chamber communicating with flame holes and an outer casing surrounding said inner casing and defining an airflow passage between it and said inner casing, a Silocco fan disposed in the central portion of said gasification chamber to suck the air in said airflow passage at the center thereof and disperse the same radially outwardly, a fuel atomizer provided in the central portion of said Silocco fan for rotation therewith and adapted to atomize the liquid fuel under the influence of centrifugal force, means for preheating the air passing through said air flow passage and said gasification chamber, and means for supplying the fuel to said atomizer.

2. A liquid fuel burner as defined in claim 1, wherein means is provided to rotate said Silocco fan at the initiation of combustion at a rate lower than that in the normal combustion operation.

3. A liquid fuel burner as defined in claim 1, wherein said airflow passage formed between the inner and outer casings is located adjacent a combustion region and a heater is provided around that portion of the outer peripheral surface of said inner casing which extends into said airflow passage, said heater being energized only at the initiation of combustion.

4. A liquid fuel burner as defined in claim 3, wherein the airsucking opening of said alrflow passage is shielded form the combustion region by a shielding member and air is sucked into said airflow passage from the side remote from the combustion region with respect to said shielding member.

5. A liquid fuel burner as defined in claim 1, wherein said atomizer is a cup-shaped depression formed at the center of an upper plate of said Silocco fan and having a number of atomizing holes perforated in the peripheral wall thereof and said fuel supply means is a fuel supply pipe extending upwardly and exteriorly of said Silocco fan with the discharge end thereof being spaced above the upper plate of said Silocco fan and extending downwardly toward said atomizer.

6. A liquid fuel burner as defined in claim 5, wherein fuelreceiving plates are mounted on the fuel supply pipe within the gasification chamber for receiving the fuel flowing down on the outer wall of said pipe.

7. A liquid fuel burner as defined in claim 1, wherein a mixing ring, a combustion ring and a headplate for closing the open top end of said gasification chamber are provided on the open top edge of said inner casing one on another in the order mentioned with circumferentially spaced spacers interposed between each other, the resultant slit-shaped gaps being utilized as flame openings, and the inner edge of said mixing ring is projected into the gasification chamber.

8. A liquid fuel burner as defined in claim 1, which further comprises a fuel supply deice comprising a main tank provided with a level adjusting mechanism and having an inlet for fuel from a fuel tank, an auxiliary tank smaller in capacity than said main tank communicating with said main tank at a level above a set level of fuel in the main tank and having an outlet for fuel at a level lower than said communicating level, and a pump for pumping the fuel from said main tank into said auxiliary tank, the pump having a pumping capacity greater than the flow rate of fuel discharged through said outlet; and a fuel supply pipe for supplying the fuel to said atomizer is communicated to said outlet through a solenoid valve.

9. A liquid fuel burner comprising an inner casing defining a gasification chamber therein and having an air passage hole formed in the bottom wall thereof; said inner casing further having a mixing ring smaller in inner diameter than said inner casing, a combustion ring and a closure headplate mounted on the open top edge thereof with circumferentially spaced spacers interposed between each other so as to form slitshaped flame openings; an outer casing surrounding said inner casing; an airflow passage formed between said inner and outer casings with a portion thereof located adjacent the flames formed at said flame openings and with an air-sucking end thereof being covered by the flexed edges of said inner and outer casings from above and the radially outside thereof; a heater wound around the outer peripheral surface of said inner casing within said airflow passage; a Silocco fan disposed in the center of said gasification chamber to suck the air in said airflow passage through said air passage hole in the bottom wall of said inner casing at the center thereof and disperse the same radially outwardly by the blades thereof; an atomizer rotating integrally with said Silocco fan to disperse the liquid fuel supplied thereto radially outwardly under the influence of centrifugal force; a mounting frame provided beneath said outer casing with a space therebetween; a motor mounted on said mounting frame with the drive shaft thereof extending upwardly and connected directly to said Silocco fan; and a fan fixedly mounted on the drive shaft of said motor for rotation therewith to cool said motor and form a layer of airflow in the space between said outer casing and said mounting frame.

Claims

4. A liquid fuel burner as defined in claim 3, wherein the air-sucking opening of said aIrflow passage is shielded from the combustion region by a shielding member and air is sucked into said airflow passage from the side remote from the combustion region with respect to said shielding member.

6. A liquid fuel burner as defined in claim 5, wherein fuel-receiving plates are mounted on the fuel supply pipe within the gasification chamber for receiving the fuel flowing down on the outer wall of said pipe.

8. A liquid fuel burner as defined in claim 1, which further comprises a fuel supply device comprising a main tank provided with a level adjusting mechanism and having an inlet for fuel from a fuel tank, an auxiliary tank smaller in capacity than said main tank communicating with said main tank at a level above a set level of fuel in the main tank and having an outlet for fuel at a level lower than said communicating level, and a pump for pumping the fuel from said main tank into said auxiliary tank, the pump having a pumping capacity greater than the flow rate of fuel discharged through said outlet; and a fuel supply pipe for supplying the fuel to said atomizer is communicated to said outlet through a solenoid valve.

9. A liquid fuel burner comprising an inner casing defining a gasification chamber therein and having an air passage hole formed in the bottom wall thereof; said inner casing further having a mixing ring smaller in inner diameter than said inner casing, a combustion ring and a closure headplate mounted on the open top edge thereof with circumferentially spaced spacers interposed between each other so as to form slit-shaped flame openings; an outer casing surrounding said inner casing; an airflow passage formed between said inner and outer casings with a portion thereof located adjacent the flames formed at said flame openings and with an air-sucking end thereof being covered by the flexed edges of said inner and outer casings from above and the radially outside thereof; a heater wound around the outer peripheral surface of said inner casing within said airflow passage; a Silocco fan disposed in the center of said gasification chamber to suck the air in said airflow passage through said air passage hole in the bottom wall of said inner casing at the center thereof and disperse the same radially outwardly by the blades thereof; an atomizer rotating integrally with said Silocco fan to disperse the liquid fuel supplied thereto radially outwardly under the influence of centrifugal force; a mounting frame provided beneath said outer casing with a space therebetween; a motor mounted on said mounting frame with the drive shaft thereof extending upwardly and connected directly to said Silocco fan; and a fan fixedly mounted on the drive shaft of said motor for rotation therewith to cool said motor and form a layer of airflow in the space between said outer casing and said mounting frame.