US2259845A - Automatic draft regulator - Google Patents

Description

Oct. 21, 1941. s. VALJEAN AUTOMATIC DRAFT REGULATOR Filed Aug 20, 1938 2 Sheets-Sheet 1 .4 40 M o Z 6 9 u. 2.. J 2 M Q HB W 5. Z I. 31.? 1 w H m2 6 {5\ M 4 wafiwxw i b F76 3 INVENTOR.

527V VAL J54/V ATTORNEY.

Oct. 21, 1941. B. VALJEAN AUTOMATIC DRAFT REGULATOR 2 Sheets-Sheet 2 Filed Aug. 20, 1938 F/g. a

1 NVENTOR. 55v 1/44 JEAN ATTORNEY.

Patented Oct. '21, 1941 UNITED STATES PATENT OFFICE AUTOMATIC DRAFT REGULATOR Ben Valjean, Lansing, Mich. Application August 20,1938, Serial No. 225,857

8 Claims.

Thisinvention relates to combustion apparatus, and particularly to oil burners and the means for regulating the draft thereon.

Oil burners of the vaporizing pot type are very sensitive to changes in draft. Therefore, for a given rate of flow of fuel oil, the draft should remain constant. On the other hand, such oil burners do not operate at highest eiiiciency under a uniform draft for all the different rates of flow of fuel oil. Consequently, the draft should be increased or decreased as the oil fiow to the burner increases or decreases, in order to provide the proper quantity of air for combustion. Preferably such regulation should be entirely automatic.

Heretofore the draft on burners of the type mentioned has been controlled by dampers or regulators installed in the flue outlets from the burners, which maintain a constant draft by admitting more or less air to the stacks to cool the same. Such regulators have several disadvantages.

In all types of combustion apparatus there are two ways in which heat is lost in the stack. One of these is the loss due to the warm air of the room in which the burner is installed being drawn into the stack to cool it. While relatively cool in comparison to the gases emanating from theburner, this air contains a considerable quantity of heat units.

The other loss is due to the escape of large quantities of heat units in the exhaust gases from the burner. Some of this last mentioned loss is unavoidable because it is necessary to create the required draft on the burner. Heretofore it has been considered to be necessary to admit a large excess of air to the burner at the lower stages in order that sufficient air for complete combustion would be present at the higher stages of combustion. As a result, considerable heat escapes in this excess air. For maximum efliciency the amount of air admitted should be in direct proportion to the quantity of fuel to be burned;

An object of this invention is to provide a means for automatically maintaining a constant draft in the burner for any given rate of combustion of the fuel. Another object is to provide a means for automatically proportioning the quantity of air to the quantity of fuel admitted to the burner. Still another object is to provide means for automatically admitting an excess of air to the burner during the ignition and warming up periods. A further object of the burner by reducing heat losses in the stack.

These objects are attained by the provision of a spring biased damper at the point of admission of, air to the burner rather than at the exit, with thermo-responsive means for automatically regulating the resiliency of the spring, and the provision of thermo-responsive means to open the damper when theburner is cold.

In the drawings:

Figure 1 is a cross-sectional view of a heater of the circulating type having a damper embodying my invention;

Figure 2 is a cross-sectional view taken on the line 2-2 of Figure 1 and looking in the direction of the arrows;

Figure 3 is a rear elevational view of a portion of the heat chamber of the burner shown in Figure 1 showing my invention in place;

Figure 4 is a fragmentary elevational view of the draft regulator shown in Figure 3;

Figure 5 is a cross-sectional view taken on the line 5-5 of Figure 4;

Figure 6 is a fragmentary sectional view of a portion of the structure shown in Figure 5 but on an enlarged scale;

Figure 7 is a fragmentary elevational view similar to Figure 4, but showing a modification of the invention;

Figure 8 is a cross-sectional view taken on the line 8-8 of Figure 7;

Figure 9 is a fragmentary elevational view similar to Figure 4 showing a still further modified form of the invention; and

Figure 10 is a cross-sectional view on the line I 0-H! of Figure 9.

The heater shown in Figures 1 to 3 comprises an outer casing ID of any conventional type enclosing a heat chamber II in which a burner I2 is secured. The'outer casing I I! is rectangular in plan and consists of four upright corner posts l3 and four side panels l4 intermediate the corner posts. At the top of the casing is a grille l5 allowing heated air to escape from the interior of the casing.-

The heat chamber ll consists of a cylindrical sheet metal jacket it closed at its top by a wall l1, and provided with a flue outlet l8 which connects to the usual chimney l9. Rigidly attached.

to the lower end of the jacket I6 are a plurality of legs 20 which are supported on the corner posts I 3 of the outer casing. Within the jacket I6 is the burner it. The burner shown is of the type disclosed in my application Serial No. 171,640, filed October 29, 1937, although the invention the invention is to increase the efllciency of the herein disclosed is not limited to that type of burner. The invention is particularly useful with burners having a plurality of compartments, such as the one ,shown, wherein combustion may be localized in any of the compartments. This burner l2 comprises a bottom pan 23, and a side wall 24 having a plurality of primary air inlet openings 25. Intermediate the top and bottom edges of the wall 24 is a partition 28 having a centralopening 21. A top wall 28 having anopening 38 is also provided. Above the top wall 23 are a plurality of secondary air inlet openings 38. The side wall of the burner is provided with a. bead 2| which fits snugly against a complementary bead 22 on the jacket I8 thereby forming an air tight joint. Between the bottom pan 23 of the burner and the side wall I8 of the jacket is an annular ring 24a. This ring 241: fits snugly between the outer wall of the burner and the wall l8 of the jacket to prevent the entrance of air to the burner except through the draft opening.

A conduit 3| connects the burner to a fuel tank (not shown) and the amount of fuel admitted .is controlled by a conventional metering valve plate is flanged about its periphery in order to stiffen the same. Secured to the wall of the jacket l6, preferably by welding, is a block 31. A blade spring 38 is secured rigidly thereto by means of screws 39. The lower end of the spring 38 is riveted by rivets 48 to the upright arm 38 of plate 35.

Intermediate the block 31 and the spring 38 is a bimetallic strip 4| composed of two dissimilar metals 42 and 43. It will be noted that this bimetallic strip 4| extends downwardly adjacent the spring 38 a substantial distance. The strip is so constructed that upon increase in its temstrip 44 is heated by radiation from the jacket l8, whereby the strip 44 bends away from the jacket, to allow the regulator to function normally. .Thestrip 44 moves relatively quickly so that it becomes inoperative in a rather short time. The radiant heat from the jacket l8 also causesthe bimetallic strip 4| to bend to the left, as viewed in Figure 5, thereby decreasing the effective length of they spring 38, and requiring afgreater draft to move the regulator toward its closed position.

As long as the burner. is warm the auxiliary bimetallic strip 44 will be ineifective. Thus if the flow of oil is reduced to the smallest quantity sufllcient to maintain combustion in the burner, and the fire is thereby reduced, it is possible that the strip 4| may allow the regulator to become nearly completely closed. In other words the draft allowed by the regulator may be less when the burner is slightly-warmed than when it is cold. This effect is due to the presence of the auxiliary bimetallic strip 44, which, as above stated, is effective only during the initial stage of burner operation just after the same has been ignited.

, It will be readily apparent that the temperature of the jacket varies with the rate of combustion and oil flow, and that correspondingly the position of the strip 4| changes with the temperature of the jacket. Thus, as the oil flow is increased and the draft rises, the strip 4| increasingly resists closing of the plate 35, and as the velocity of air fiow through the regulator increases due to the increased draft, the quantity of air adperature it will bend to the left, as shown in 7 Figures 5 and 6, or from the position shown in Figure 5 to that shown in Figure 6. Consequently,

as the temperature of the bimetallic strip rises it tends to shorten the effective length'of the spring 38 and thereby stiffen the same.-

In addition, a second bimetallic strip 44, composed of two dissimilar metals 45 and 46, is secured to the plate 35 and the spring 38 by the rivets 40. This bimetallic strip operates in the same direction as the strip 34, or in other'words,

as it cools it moves toward the heat chamber and eventually contacts the-same. The purpose and operation of these strips will appear presently.

The operation of the device is'substantially as follows: when the burner is cold the parts will be in the position shown in Figure 5, with the strip 44 contacting the wall of the jacket |6,-and with the strip 4| in its position farthest from the spring 38. In that position the spring 38 tends to hold the plate 35 relatively close to the bezel 33, but spaced slightly therefrom. If the fuel in the burner is ignited it soon creates a draft through the regulator which would normally tend to close the latter and cut off the air supply. However, due to the position of the bimetallic strip 44, closing of the regulator is prevented. As the burner heats up, the bimetallic mitted to the burner rises.

The mounting of the regulator plate 35 on the spring metal strip 38 allows the plate 35 to move back and forth relative to the bezel 33 to cooperate for fluctuation in the stack draft. There- .fore, it the stack draft changes because of a change in outside air conditions, such as a change in temperature or a variation in wind velocity or direction, the plate moves to vary the air inlet opening. In this way the burner draft is maintained at a constant value for any fuel flow setting of the control valve.

The modification shown in Figures 7 and 8 is similar to that shown in Figures 1 to 6 except for the location of the bimetal strip for biasing the spring 38. The plate 35 is secured by rivets 40 to a flat spring 38 and this spring 38 is in turn connected by screws 38 to a block 31 secured to the jacket 6. Instead of mounting the bimetal strip as in the previous modification, a bimetal strip 48 is secured in a horizontal position by rivets 49 to an angle bracket 41 welded or otherwise securedto the jacket I 6. One edge of the strip 48 contacts the inner face of the spring 38. The strip 48 is so designed that upon an increase in its temperature it will bend downwardly from the full line position in Figures 7 and 8 to the dotted line position, thus decreasing the effective length of the spring 38. The spring thus functions, the same as the spring 38 in the previous device.

The regulator of Figures 7 and 8 is also provided with a second bimetallic strip 44 identical to the jacket l6 of the heater. In this device the strip 52 performs the functions of both the spring mount and the bimetallic strips of the previous devices. This strip 52 is resilient, thus allowing the plate 50 to move to and from the opening in the jacket IE, but as the temperature of the strip 52 is increased it tends to bend away from the jacket, and thereby resist the tendency of the plate 50 to close upon an increase in draft on the burner.

The regulator shown in these figures is also provided with a bimetallic strip 55 which is identical in construction and arrangement with the strips 34 shown in the modifications of Figures 1 to 8. It acts in the same manner also, or in other words, prevents closing of the regulator when the burner is cold.

It will thus be seen that this invention provides for an excess of air during the starting and warming up period of the burner by means of an auxiliary bimetal strip. It compensates for fluctuations in draft by providing a flexible resilient mounting for the regulator plate. It also proportions th air to the oil by means of the main bimetal strip which is responsive to combustion chamber temperature, the latter in turn being in direct proportion to the quantity of air admitted.

The scope of the invention is indicated in the appended claims.

I claim:

1. Combustion apparatus including, in combination, a burner of the vaporizing pot type, an air compartment for supplying combustion supporting air to the burner, said air compartment having an air inlet opening for the admission of air thereto, a cover for said air inlet opening, means including a spring for normally holding said cover in an open position and adapted to permit the cover to close in response to a predetermined pressure differential between the inside and the outside of the air compartment, and thermo-responsive means associated with the spring and located in a position to absorb heat from the burner for regulating the stiffness of the spring and thereby automatically varying said predetermined pressure differential in response to variations in the temperature of the burner.

2. Combustion apparatus comprising a burner of the vaporizing pot type, a jacket surrounding the burner, an opening in the jacket for admitting air to the burner, a cover for the opening, a leaf spring connected at one nd to the jacket and at the other end to the cover and adapted to permit the cover to close in response to a predetermined pressure diiferential between the inside and the outside of the jacket, and thermores'ponsive means associated with the spring and located in a position to absorb heat from the burner for increasing or decreasing the effective length of the spring upon increase or decrease in the heat generated in the burner.

3. Combustion apparatus comprising a burner of the vaporizing pot type, a jacket surrounding the burner,. an air inlet opening in the jacket for admitting air to the burner, a cover for the opening, a spring connected at one end to the cover and at the other end to the jacket and adapted to permit the cover to close in response to a predetermined pressure differential between the inside and the outside of the jacket, a bimetallic strip connected at one end to the jacket and extending freely away therefrom, said bimetallic strip contacting the spring and forming a fulcrum about which the spring may bend,

said bimetallic strip being movable under the infiuence of heat generated by the burner to vary the position of the fulcrum.

4. Combustion apparatus comprising a burner of the vaporizing pot type, a jacket member surrounding the burner, an opening in the jacket member for admitting air to'the burner, a cover member for the opening, means connecting the cover member to the jacket member to allow movement of the cover member toward and away from the opening under the influence of changes in air pressure on the cover member, thermoresponsive means associated with said connecting means and located in a position to receive heat from the burner for controlling the move ment of the cover member whereby to increase or decrease the quantity of air admitted to the burner upon increase or decrease respectively of the heat generated in the burner, and auxiliary thermo-responsive means connected to one of said members and movable from a position contacting the other member to a position free of the latter upon increase in the heat generated by the burner.

5. Combustion apparatus comprising a burner of the vaporizing pot type, a jacket surrounding the burner, an opening in the jacket for admitting air to the burner, a cover for said opening,

a leaf spring connected at one end to the jacket and at the other end to the cover to allow movement of the cover toward and away from the.

opening under the influence of changes in air pressure on the cover, thermo-responsive means associated with said spring for increasing or decreasing the effective length thereof upon increase or decrease, respectively, of the heat generated by the burner, and auxiliary thermoe responsive means secured to the cover and movable from a position contacting the jacket to a position free of the jacket upoh increase in temperature of the latter.

6. Combustion apparatus including, in combination, a burner of the vaporizing pot type, means for supplying liquid fuel to the burner in regulatable quantities, means for supplying air to the burner comprising an air compartment having an air inlet opening therein for the admission of air thereto, and means for automatically maintaining a predetermined ratio of air and fuel admitted to the burner, said last named means comprising a cover for the opening, means for normally holding the cover in open position but permitting it to close in response to an increase in the pressure difierential between the inside and outside of the air compartment, and thermo-lresponsive means in heat exchanging relation to the apparatus for automatically varying said predetermined pressure differential in response to variations in the temperature of the apparatus.

7. Combustion apparatus including, in combination, a burner of the vaporizing pot type, means for supplying liquid fuel to the burner in regulatable quantities, means for supplying air to the burner comprising an air compartment having an air inlet opening therein for the admission of air thereto, and means for automatically maintaining a predetermined ratio of air and fuel admitted to the burner, said last named means comprising a cover for the opening, spring means for normally holding the cover in open position but permitting it to close in response to an increase in the pressure differential between the inside and outside of the air compartment, and thermo-responsive means in heat exchanging relation to the apparatus for automatically varying said predetermined pressure differential in response to variations in the temperature of the apparatus.

8. Combustion apparatus including, in combination, a burner of the vaporizing pot type and a combustion chamber thereabove, means for supplying liquid fuel to the burner in regulatable quantities, means for supplying air to the 10 burner comprising an air compartment having an air inlet opening therein for the admission of air thereto, and means for automatically main-

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