US3027932A - Burner having a thermoelectric safety device - Google Patents

Description

April 3, 1962 G. HUBER BURNER HAVING A THERMOELECTRIC SAFETY DEVICE Fig. 7

Filed Feb. 25, 1960 Fig. 2

Fig. 5

lNVF/VTOR 37 GFORG {ll/86R BY 32 mum 91721 United States Patent Germany Filed Feb. 25, 1960, Ser. No. 11,043 Claims priority, application Germany, Feb. 27, 1959 3 Claims. (Cl. 158-28) The present invention relates to fuel burners in general, and more particularly to a pressure vaporizer burner which comprises an improved thermoelectric safety device adapted to shut off the supply of fuel when the flame is extinguished and to permit return flow of fuel at a given maximum pressure in the vaporizer chamber.

It is already known to utilize thermoelectric safety devices in liquid or gaseous fuel burners. However, many presently known safety devices of such character are rather expensive in that they must be operated by an auxiliary burner which is commonly utilized as an ignition or pilot burner. The latter adds to the bulkiness and weight of the arrangement and, therefore, such de vices have met with little success in actual use. Certain other types of known safety devices for fuel burners already comprise thermocouples which are exposed to the flame produced by the main burner. However, all such safety devices are extremely sensitive to vibrations, and consequently, their life expectancy is too short for use in many types of burners. In addition, many safety devices of presently known design must utilize two or more thermocouples.

An important object of the present invention is to provide a fuel burner comprising. a thermoelectric safety device which does not require a separate burner and which is less sensitive to vibrations or shaking.

Another important object of the invention is to provide a fuel burner comprising a lightweight thermoelectric safety device of the just described characteristics which is inexpensive to manufacture, which maybe readily installed in many types of known liquid burners, which is of rugged construction and has a long life expectancy without requiring frequent maintenance or inspection, and which is of very compact design in that it comprises only one thermocouple with two junctions which may be placed close to each other to produce a strong .thermocurrent.

A further object of the invention is to provide a fuel burner comprising a thermoelectric safety device whose thermocouple may be placed much closer to the main flame than the thermocouples of presently known safety devices whereby a single thermocouple can produce a current of such strength as i necessary to operate the safety device.

An additional object of the invention is to provide a liquid fuel burner comprising a thermoelectric safety device which may be utilized in burners operating with readily vaporizable as well as with hard-to-vaporize fuels.

A concomitant object of the instant invention is to provide a burner embodying a thermoelectric safety device of the above outlined characteristics which is constructed in such a way that it may control the radiation of heat to the thermocouple and which may be readily adapted for use wtih different types of fuel.

Still another object of the invention is to provide a burner provided with a thermoelectric safety device of the above described type wherein the safety device may simultaneously control the delivery of fuel to two or more nozzles.

With the above objects in view, the invention resides bined with a thermoelectric safety device embodying one form of my invention, the section being taken along the line I-I of FIG. 2, as seen in the direction of arrows;

essentially in the provision of a burner including a thermoelectric safety device which comprises a valve installed in the supply conduit that conveys fuel to the nozzle means of the burner, and a thermoelectric generator or thermocouple whose hot junction is exposed to the action of flames produced upon ignition of fuel discharged by the nozzle means. An important feature of the invention resides in the provision of shielding means for the cold junction of the thermocouple which is adapted to direct combustion air to the cold junction and to thereby reduce the temperature of the cold junction even if the latter is located in very close proximity of the hot junction and of the flames. The shielding means preferably assumes the form of a tubular body which surrounds the cold junction and which is located in the path of combustion air so that the air may enter through the intake end and is discharged through at least one opening of the shielding means at a point adjacent to the cold junction. The thermocurrent generated when the hot junction is exposed to the action of flames is conducted to the aforementioned valve which is constructed in such a way that it permits the flow of fuel to the nozzle means when it receives a thermocurrent of given strength but automatically shuts off the supply of fuel when the strength of thermocurrent drops below a given magnitude.

Certain other advantageous features of the invention reside in the provision of flame guiding means for directing additional heat to the hot junction of the thermocouple, in the specific configuration and dimensioning of the shielding means, in the provision of means for adapting the burnerto operation with highly or less readily vaporizable liquid fuels such as petrol and fuel oil, respectively, and in such construction of the valve that it permits return flow of fuel when the pressure at its discharge side reaches a predetermined magnitude.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of two specific embodiments when read in connection with the accompanying drawing, in which:

FIG. 1 is a vertical section through the burner com- FIG. 2 is a section taken along the line II-II of FIG. 1, as seen in the direction of arrows;

FIG. 3 is a greatly enlarged view of a magnet valve for the burner of FIGS. 1 and 2, the magnet valve being combined with a slightly modified safety device and certain parts of the safety device and of the valve being broken away;

FIG. 4 is a transverse section taken along the line IVIV of FIG. 3, as seen in the direction of arrows; and

FIG. 5 is a greatly enlarged longitudinal central section of the thermocouple forming part of the safety device, the section being taken along the line V-V of FIG. 3, as seen in the direction of arrows.

Referring now in greater detail to the drawing, and first to FIGS. 1 and 2, the injection nozzles 1, 1 of the pressure vaporizer burner B are supplied with a suitable liquid fuel through a supply conduit 2 whose intake end is connected to a fuel source, not shown. The conduit 2 conveys fuel to a magnet valve 3 whose discharge port is connected with a further conduit or vaporizer connecting pipe 4 adapted to lead the fuel to an annular vaporizer chamber 5. The latter is connected with the nozzles 1, 1 through a vaporizer pressure conduit 6.

The magnet valve 3 is shown in greater detail in FIG. 3.

It comprises a hand-operated pushbutton or actuating means 7 which is connected to a discoid valve member or seal 26, the latter being normally urged into sealing position against its seat 27 by a helical expansion spring 28. The coaxial stem 7a of the pushbutton 7 carries at its free end an armature plate 30 which, upon depression .of the member 7, moves toward the energizable magnet 36 surrounded by the coil 29, the latter being mounted in the housing of magnet valve 3. Upon depression of the pushbutton and consequent movement of valve member 26 away from its seat 27, the fuel is free to pass from the conduit 2, through the housing of valve 3, and into the conduit 4 to advance into the vaporizer chamber 5. The fuel advancing into, say, the nozzle 1 is discharged in the form of a thin stream onto the bottom 8 of the burner casing 9. The bottom 8, the upwardly extending end plate 10, and the inclined feed plate 11 beneath the nozzles 1, 1' form a shallow pan-shaped receptacle for the fuel discharged by the nozzles 1, 1. This receptacle is shown in FIG. 1. When sufiicient fuel accumulates at the bottom of the burner B, the pushbutton 7 is released and the resilient means 28 immediately returns the valve member 26 into sealing position, i.e. back into abutment with its seat 27. The fuel in the receptacle 8, 10, 11 is thenignited and heats the charged vaporizer chamber sufficiently to raise the pressure of fuel therein to the socalled working pressure. Such working pressure is reached when the nozzles begin to discharge vapors; such vapors are immediately ignited by the fuel burning in the aforementioned receptacle whereupon the ignited fuel vapors heat the chamber 5 without it being necessary to renew the. supply of fuel abovev the bottom 8. Thus, the initial introduction of liquid fuel through one or both nozzles is necessary merely to heat the chamber 5 sufficiently in order to begin the. vaporization of fuel; subsequent'vaporization occurs automatically under the action of flames produced upon ignition of vapors discharged by the nozzles.

The control device for theburner B in addition to the above described magnet valve 3, comprises a thermocouple or thermoelectric generator 12 which is shown in FIG. 2 and is located adjacent to the chamber 5. This thermocouple is now sufficiently heated to produce a thermoelectric current of such magnitude as to supply thenmocurrent to the magnet coil 29 which energizes the magnet 36 in the housing of magnet valve 3 so that the energized magnet 36 may retain the armature plate 30 when the pushbutton 7 is depressed for a second time. As is shown in FIG. 3 in connection with a slightly modified thermocouple 12A, and also in FIG. 5, the thermocouple is electrically connected with the coil 29 by insulated conductor means 32in a tubular member or sheath 31.

If the flame is extinguished for one reason or another, e.g. owing to blocking of a nozzle, the thermocouple 12 is cooled and the magnet 36 is progressively deenergized whereby, in response to a certain temperature of the thermocouple 12, the spring 28 disengages the armature plate 30 from the magnet 36 and returns the valve member 26 into sealing position. The supply of fuel to the vaporizer chamber 5 is now interrupted.

If, during warming up of the vaporizer chamber, a person not familiar with the operating instructions would turn the adjusting wheels 24, 25 into such position as to close the nozzles 1 and 1', excess pressure will build up in the vaporizer chamber. In accordance with one feature of the present invention, the magnet valve 3 is constructed in such a way that the excess pressure of fuel in vaporizer chamber 5 automatically lifts the valve member 26 off its seat 27 whereby the fuel may flow back through the valve 3, thus eliminating the danger of an explosion due to improper operation of the burner B.

As is best shown in FIG. 5, the thermocouple 12 or 12A comprises a first or hot junction 12' which is heated during the operation of the burner, and a second junction 13 which is comparatively cold and which is received in a casing 33. Because the connecting wire 34 between the junctions 12' and 13 is of constantan which is a material with very high resistance to the flow of electric current, the two junctions necessarily must be located rather close to each other, i.e. so close that a heating of junction 13 normally cannot be avoided when the junction 12' is heated, i.e. the junction 13 cannot be placed entirely outside of the radius of action of the flame produced upon ignition of vapors discharged by the nozzle means. In accordance with my invention, undesirable heating of thermocouple 12, i.e. of the junction 13 and its casing 33 is avoided by the provision of protecting or shielding means which assumes the shape of a tubular body 14 (see FIG. 2) and which is mounted on the the'rmocouple 12 with the help of a nut 15 whose internal threads mesh with external threads 35 on the casing 33 (see FIG. 5). The front end portion 14' of tube 14 which is adjacent to the nut or sealing means 15 is formed with one but preferably more axially parallel radially ar= ranged openings or slots 16 for discharge of combustion air which on account of the draft effect flows through the screen 23 in the direction of arrow A (see FIG. 2 i.e. in the axial direction and into the open rear end of shielding means 14. In this manner, the cold junction 13 is al= ways exposed to the cooling action of infiowin'g combus= tion air, while the hot junction 12' is not influenced by' the infiowing combustion air. Consequently, the difler ence in temperature of the junctions 12', .13 is suflicient to generate. an electric current which is capable of ener gizing the magnet 36. The shielding tube 14 partially surrounds the thermocouple 12, and the nut 15 constitutes a front end wall therefor which is perpendicular to the tube axis. The rear end of the tube is open to permit entry of combustion air.

It has been found that the length of tube 14 should be at least 2 cm., preferably at least 3 cm. Tubes of a length between 4.5-5 cm. have been found to be particularly suitable for properly shielding and cooling the junction 13. The diameter of the tube 14 is preferably selected in such a way that its ratio to the length is about 1:2 but preferably somewhat greater. The distance between the sealing means 15 and the hot junction 12 preferably ex ceeds 3 cm.

The provision of shielding tube 14 renders it possible to place the hot junction 12 of thermocouple 12 much closer to the flame, at least by 2 em. but preferably by between 3-4 cm. closer than in heretofore known burners. As a result, the burner may utilize all types of fuel, i.e. a very volatile fuel (petrol) as well as a fuel which is diflicult to vaporize (fuel oil).

The improved burner further comprises a slidable flame guiding pipe 17 (FIGS. 1 and 2) which is shifted into the center of vaporizer chamber 5 when the device is converted for operation with fuel oil. The tubular member 17 is suspended on the straight portion of the vaporizer pressure conduit -6 by means of an element 18 which latter is combined with an elongated bar or guide rod 19 adapted to slide along the upper wall of the vaporizer chamber 5 and to thereby guide the pipe 17 in movements into and out of said chamber. The pipe 17 is formed with a radial opening 20 which is adjacent to the hot junction 12' when the member 17 is in the position of FIGS. 1 and 2, i.e. located externally of the chamber 5. Thus, when the burner is operated with petrol, the hot junction 12' of thermocouple or thermoelectric generator 12 is also affected by heat radiated by flames in the pipe 17. It is preferred to provide an inclined deflecting device or baffle 21 in the open front end of the pipe 17 which directs heat toward the hot junction 12 at the forward end of the thermocouple. The main purpose of the pipe 17 is to guide the concentrated flames against the inner wall of chamber 5 to thereby assist in more rapid vaporization of fuel oil.

As is shown in FIGS. 1 and 2, a cover or lid 22 may be pivoted to the casing 9; this cover is provided with a large intake opening for combustion air which preferably contains a screen 23 of wire netting or the like.

When the flame guiding tube 17 is moved to the right, as viewed in FIG. 1 or 2, i.e. into the vaporizing chamber 5, the flames may pass from the nozzle or nozzles 1, 1 inwardly of the chamber 5 as well as into the annular channel defined by the outer side of the chamber 5 and the wall 9. This is desirable when the chamber 5 is to be heated to a higher temperature, namely, when the fuel is less volatile, e.g. an oil. On the other hand, when the fuel is more volatile, e.g. when the fuel is petrol, the flame guiding tube may be moved to the left, as viewed in FIGS. 1 and 2, whereby the flames are confined to flow through the pipe 17 and heat only the interior of the chamber 5.

When the tube 17 is moved to the right and into the chamber 5, the flames are free to heat the hot junction 12 because the propagation of flames from the nozzle or nozzles 1, 1' to the inner and outer sides of the chamber 5 is unobstructed. On the other hand, when the tube 17 is moved to the left so that it confines the flames to a flow only to the interior of the chamber 5, the flames deflected by the baflle 21 through the opening 20 will heat the hot junction 12 to produce the necessary thermocurrent.

The provision of the opening 20 in the tube 17 renders it possible to mount the thermocouple 12 in close proxim ity of the vaporizer chamber 5 without the danger of overheating the thermocouple. Furthermore, such positioning of the thermocouple facilitates the starting of the burner B because the thermocouple responds more rapidly, and the position of the thermocouple need not be changed when the fuel is changed, i.e. when it is desired to switch from oil burning to a burning with pertol. All that is necessary is to shift the tube 17, whereas the position of the thermocouple 12 remains unchanged.

FIGS. 3 and 4 show a slightly modified thermocouple 112A comprising a shielding tube 37 whose front end portion is flattened, as at 38, and is welded to the nut 15 which latter is centrally received in said end portion. In this manner, the end portion 3 8 defines two passages or channels 40, 41 at the opposing sides of retaining nut 1'5, the combustion air entering through the open rear or intake end 39 of tube 37 and being discharged through the passages 40, 41. The front end face 38 of the end portion 38 is preferably flush with the exposed side of nut 15.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a fuel burner, in combination, nozzle means; conduit means for supplying fuel to said nozzle means; a vaporizer chamber in said conduit means disposed in such proximity of said nozzle means as to be heated by flames produced upon ignition of fuel discharged by the nozzle means; flame guiding means provided between said nozzle means and said vaporizer chamber for directing flames to said chamber, said flame guiding means having at least one opening through which a portion of the flames may be deflected from the direction of flame propagation to said chamber; and a thermoelectric safety device for controlling the flow of fuel to said chamber and to said nozzle means, said device comprising valve means in said conduit means adapted to permit the flow of fuel to said chamber when receiving a thermocurrent of given strength and automatically shutting off the flow of fuel when the strength of thermocurrent drops below the given value, a thermocouple connected with said valve means, said thermocouple having a hot junction located adjacent to and adapted to be heated by the portion of flames deflected through the opening of said flame guiding means and a cold junction, and shielding means located in the path of combustion air for the flames and adapted to direct combustion air against said cold junction whereby the latter may be placed in immediate proximity of the flames and the thermocouple still produce a thermocurrent of such strength as is necessary to maintain the valve in fuel flow permitting position.

2. In a fuel burner, in combination, nozzle means; conduit means for supplying fuel to said nozzle means; an annular vaporizer chamber in said conduit means disposed in such proximity of said nozzle means as to be heated by flames produced upon ignition of fuel discharged by the nozzle means; tubular flame guiding means provided between said nozzle means and said vaporizer chamber for directing flames into the interior of said chamber, said flame guiding means having at least one radial opening through which a portion of the flames may be deflected from the direction of flame propagation to said chamber, and said flame guiding means further comprising baffle means located forwardly of said opening for deflecting the flames in said flame guiding means; and a thermoelectric safety device for controlling the flow of fuel to said chamber and to said nozzle means, said device comprising valve means in said conduit means adapted to permit the flow of fuel to said chamber when receiving a thermocurrent of given strength and automatically shutting off the flow of fuel when the strength of thermocurrent drops below the given value, a thermocouple connected with said valve means, said thermocouple having a hot junction located adjacent to and adapted to be heated by the portion of flames deflected through the opening of said flame guiding means and a cold junction, and shielding means located in the path of combustion air for the flames and adapted to direct combustion air against said cold junction whereby the latter may be placed in immediate proximity of the flames and the thermocouple still produce a thermocurrent of such strength as is necessary to maintain the valve in fuel flow permitting position.

3. In a fuel burner, in combination, nozzle means; conduit means for supplying fuel to said nozzle means; a vaporizer chamber in said conduit means disposed in such proximity of said nozzle means as to be heated by flames produced upon ignition of fuel discharged by the nozzle means; flame guiding means movable between said nozzle means and said vaporizer chamber for directing flames into the interior of said chamber when moved toward said nozzle means and for permitting the flames to heat the exterior of said chamber when moved toward and into the chamber, said flame guiding means having at least one opening through which a portion of the flames may be deflected from the direction of flame propagation to said chamber; and a thermoelectric safety device for controlling the flow of fuel to said chamber and to said nozzle means, said device comprising valve means in said conduit means adapted to permit the flow of fuel to said chamber when receiving a thermocurrent of given strength and automatically shutting off the flow of fuel when the strength of thermocurrent drops below the given value, a thermocouple connected with said valve means, said thermocouple having a hot junction located adjacent to and adapted to be heated by the portion of flames deflected through the opening of said flame guiding means when the latter is moved toward said nozzle means and a cold junction, said hot junction heated by the flames heating the exterior of said chamber when the flame guiding means is moved into the chamber, and shielding means 7 8 located in the path of combustion air for the flames and References Cited in the file of this patent adapted to direct combustion air against said cold junction UNITED STATES PATENTS whereby the latter may be placed in immediate proximity of the flames and the thermocouple still produce a thergf ggf f g y g tfh th J 16 mocurren o suc s reng as 1s necessary to mam am 5 2,303,807 Wilson Dec. 1942 the val f lfl 'tt' o to V6 ue ow Perm mg P 2,322,410 Alfery June 22, 1943

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