US2485206A - Automatically variable air supply control for oil burners - Google Patents

Description

Get. 18, 1949.

J. A. LOGAN AUTOMATICALLY VARIABLE AIR SUPPLY CONTROL FOR OIL BURNERS Original Filed May 24, 1946 5 Sheets-Sheet i INVENTOR Joszpfl Al osmv BY ATTORNEYS Oct. 18, 1949. J. A. LOGAN 2,485,206

. AUTOMATICALLY VARIABLE AIR SUPPLY I CONTROL FOR OIL BURNERS Original Filed May 24, 1946 5 Sheets-Sheet 2 INVENTOR JosEPHALoGA/V ATTORN EYS Oct. 18, 1949. J. A. LOGAN 85,

AUTOMATICALLY VARIABLE AIR SUPPLY CONTROL FOR OIL BURNERS Original Filed Ma 24, 1946 s Sheets-Sheet s INVENTOR \TOSEPII A .Z 06/44 v TTORNEYS Oct. 18, 1949. J. A. LOGAN 2,485,206

AUTOMATICALLY VARIABLE AIR SUPPLY CONTROL FOR OIL BURNERS Original Filed May 24, 1946 5 Sheets-Sheet 4 INVENTOR JASEPHA Loan N ATTORN EYS Oct. 18, 1949. J. A. LOGAN 2,

' AUTOMATICALLY VARIABLE AIR SUPPLY CONTROL *FOR OIL BURNERS 5 Sheets-Sheet 5 Original Filed May 24, 1946 INVENTOR Jon/w A Loan/v JMAT A/VD 51W Rw JEN/1m BY 51: T7706 Q Y/ Z ATTORNEYS Patented Oct. 18, 1949 AUTOMATICALLY VARIABLE AIR SUPPLY CONTROL FOR OIL BURNERS Joseph A. Logan, Hadley, Mass., assignor to G1]- bert & Barker Manufacturing Company, West Springfield, Mass, a corporation of Massachusetts Original application May 24, 1946, Serial No. 672,106. Divided and this application October 22, 1948, Serial No. 56,028

Claims. (01. 158-28) This invention relates to improvements in oil burners, more particularly those adapted for house-heating service.

The invention has for its object the provision in an oil burner of an automatically variable control of the air supply for the purpose of improving the operation of the burner by enabling greater efilciency of combustion to be secured during normal running intervals of operation of the burner, when the air fan and oil pump are running at full speed, without smoky operation during the starting and stopping intervals of operation of the burner, when the fan and pump are respectively accelerating and decelerating.

The invention is capable oi general application for controlling the air supplied to mix with a spray of atomized oil, irrespective of how that spray is produced. The invention will be disclosed by way of illustrative example, in connection with an oil burner of the type in which the spray of atomized oil is produced by a pressure atomizin nozzle. The application of the invention to burners having other forms of oilspray-producing means will be readily apparent from the one example disclosed.

This application is a division of my applicatlon Serial No. 672,106, filed May 24, 1946.

In the accompanying drawings,

Fig. 1 is a diagrammatical view of an oil burner system;

Fig. 2 is a top plan view of the oil burner as arranged in front of a furnace wall;

Fig. 3 is a rear elevational view with parts broken away and parts in section to show one form of air control mechanism embodying the invention;

Fig. 4 is a fragmentary cross sectional view taken on the line 4-4 of Fig. 3 and showing one form of centrifugal clutch for use in the driving transmission between the motor and pump;

Fig. 5 is a diagrammatical view of the fuel supply system including the pressure regulating of a different form of burner, certain parts being broken away and in section to show an air control valve on thepressure side of the fan;

Fig. '12 is a rear elevational view of the burner of Fig. 11; and

Fig. 13 is a fragmentary sectional view taken on the line l3--l3 of Fig. 12.

Referring to the diagram of Fig. 1, l indicates an electric motor with a transmission 2 to drive an air supplyfan 3 and an oil supply pump 4. The fan 3 blows air at a pressure of usually less than a pound per square inch through tube 5 to mix with oil atomized at a very much higher pressure, for example one hundred pounds per square inch, and issuing from a nozzle 6. The air and oil mix and burn to make the flame in a combustion chamber of a heater having a front wall I. The oil is drawn from-a supply tank 8 through a pipe 9 by pump 4, and delivered through a pipe l0 and a pressure regulating valve 1 II to a pipe l2 the outlet end of which is connected to the nozzle 6. This valve II is set to maintain a constant oil pressure in pipe l2 according to whatever pressure isneeded to enable the atomizing nozzle 6 to operate with good atomizing efficiency. The valve H which is shown schematically in Fig. 5, by-passes excess oil by a pipe Hi, to the inlet side of pump 4, to

keep the atomizing pressure constant in pipe l2,

at a value determined by hand adjustment of screw it to vary the force of a spring l5 which bears on the head of valve l6 and tends to hold the latter and an outlet valve I! closed. The pump 4 works at constant speed and is capable of pumping oil at a greater'rate than is needed by nozzle 6, the excess being by-passed through pipe [3. The arrangement supplies oil to the atomizing nozzle at a constant pressure predetermined by adjustment of screw it, no matter what size nozzle may be used, within a considerable -range of nozzle sizes, each formed for a predetermined oil consumption rate. The rate of air supply is changed by an adjustable shutter or disc valve which is shown, in other figures to be explained and which may control either the inlet or the outlet of the fan. The shutter is adjusted when it is desired to change the air-oil ratio for the mixture makingthe flame.

Such a burner system, indicated in Fig. 1, having the general nature as explained, is well known. The type of burner having this general nature, is one of the types that may be improved by this invention. Its electrical thermostat control T is merely indicated in Fig. 1, because it is so well known that it will be understood by recital of its 7 function, which is to start the motor and ignition system when heat is needed, keep the burner running until the need is satisfied, and then stop the burner until heat is again needed, all automatically. The ignition system is represented by the electrodes I8 positioned adjacent nozzle 6. The ignition system may be turned on and off with the motor but should at least be on when starting the burner. It is generally true of this burner, just mentioned, that it is easy to get a clean oil flre at all times by providing a thin mixture at all times for the flame in the combustion zone. A thin mixture is one with more air than is needed to burn the oil in the mixture. A clean fire made in this easy way is known to be expensive. It does not burn the oil economically in any heating plant. The economical way to burn the oil is in a mixture having a precise and eflicient air-oil ratio, one depending on the character of the oil. The air-oil ratio is usually approximated by adjusting the burner and examining the flame. Theoretically, perfection would occur when the flame mixture has no more air supplied to it than just enough to burn all the air and oil in the sense that all of both enter the chemical decomposition, making the flame, to make the hot products of combustion. Practically, a well informed man tries to make the burner operate close to the most economical air-oil ratio, but he must make comprises. A flame burning with a very economical air-oil ratio, when changed by adding a little more oil to it, will smoke and by adding a little more air to it will begin to waste oil.

The automatic operation is of great importance in the home heating plant. This general type of burner is one that is completely shut down between heating intervals. It usually operates intermittently even in very cold weather. The plan is to maintain approximately even house temperature by intermittent heating operations. There are many separate heating intervals each day and a great many over all the days of a full heating season. Then too, it is common to use such burners with their intermittent heating operations, for domestic hot water heating plants a l the year round. For each of the burner operations or cycles for heating, there is one starting and one stopping operation. Both are short operations or intervals of but a few seconds. Should the burner smoke only a little, in either of these short operations, it is likely to be overlooked. as is also the fact that the great number of such short smoking intervals will add up to a lot of smoke and progressive accumulation of soot on the heat transfer surfaces inside a heater. This will result in waste of oil no matter how efficiently it is burned in the long heating intervals of operation. between starting and stopping intervals. The reason will be explained later on. The problem mentioned has received some attention and burner improvements in the past have been proposed to solve it. It is the problem of this invention. The purpose of the present improvement is to provide a better solution than the prior art burners provide. all things considered.

The type of burner indicated by the diagram of Fig. 1. and the troubles with its operation just outlined. should be kept in mind when the specific features of improvements are described as added to a burner for use according to this invention.

One example of such a burner with the im'- provements of this invention built in, is mainly shown by the top view of Fig. 2 and rear end view of Fig. 3. These flgures indicate the motor I, the multi-vane fan 3 with customary vanes I 9, the

side extension 20 of the fan casing with a plurality of air inlet ports 2| of ample aggregate area, the oil pump 4 with inlet 9, the transformer 22 for the ignition system to be turned on and oil? with the motor, the pressure regulating valve H with regulating screw I4, its inlet pipe l0 and by-pass l3 to pump 4, and the air tube 5 with the oil atomizing nozzle 6 mounted centrally in it near the end, as indicated in Fig. 2 and fed by pipe l2. The parts so far mentioned are well known and need no detailed description because they have been generally available in different forms on the market. The constant pressure regulating valve I l, or means to perform its function, is frequently made in various forms some of which are combined in the pump construction. The drawings show a form easy to explain for the present purpose.

The air control means of this invention is shown in one embodiment in Fig. 3. It includes a valve disc or shutter 24 of annular form mounted for movement toward and away from the circular air inlet opening 25 of fan 3. This shutter is movable from a relatively wide open position, such as that shown by full lines, to another and much more restricted position, such as that shown by dotted lines. The dotted line position of the shutter is that for normal operations of the burner when motor 1, fan 3, and pump 4 are moving at full speed. This normal position of the shutter may be predetermined with precision by hand-operable means to be described. The shutter occupies the full line position during the initial part of each starting operation and the final part of each stopping operation of the burner. The shutter 24 normally occupies the dotted line position when the burner is at rest and occupies such position until the motor and fan attain high speed when the shutter is automatically moved to its dotted line position by means which include a centrifugal clutch 23. Such clutch also operates during each stopping operation of the burner to cause the shutter to move back from the dotted line position to the full line position after the speed of the motor and fan has decreased below a predetermined and relatively high speed.

The centrifugal clutch may be like that disclosed in my prior Patent No. 1,985,934 dated J anuary 1, 1935. It includes a driving element 26, flxed to the driving portion of the transmission 2 and therefore turning whenever the motor and fan turn. Fixed to element 26 (Fig. 4) are three driving pins 21. These pins 2'! lie in recesses 28 in adjacent radial faces of movable clutch shoes or segments 29. When the pins 21 are rotated they rotate segments 29. The recesses 28, permil; the segments to move in and out radially, while driving pins 21 continue to drive from one constant radial distance from the driving shaft of transmission 2. The segments are biased to their innermost position by a suitable spring 30,- such as the garter spring located in circular grooves 3| in the three segments 29. When the segments 29 are rotated at a sufficiently high speed, they are thrown outwardly by centrifugal force against the force of spring 30 until their circumferential surfaces 32 engage the inner surface of the drum 33, the driven part of clutch 23. This occurs after the fan 3 has attained a predetermined high speed as closely as feasible to full speed. The part 33 will then start suddenly from its rest position and be driven almost instantly at the same constant high speed as the motor. The latter will then begin to drive the oil pump 4 0f the positive displacement type, through -drum 33 and the collar.

the driven portion of transmission 2 to which said clutch drum 33 is keyed. The pump 4 is then driven at full speed without appreciable delay. When the motor current is shut off, the tran mission 2 starts to slow down and the spring 30 moves segments 29 out of driving contact with drum 33. Then the driven part of the clutch and pump 4 stop almost instantly because of the heavy load of pump 4 which load is suflicient to prevent the pump from any substantial amount of coasting. The inertia of the heavy motor rotor, which is substantial, and the inertia of the easily turned fan rotor and driving part of the clutch cause a substantial period of coasting of the driving part of transmission 2, after the motor current is switched off by the usual thermostat. This is the arrangement of the centrifugal clutch element. One type of centrifugal clutch per se, is indicated with its brief description but such element may be any one of many specific kinds and many are available on the market, simply as centrifugal clutches.

The shutter or valve 24 has, as indicated in Fig. 3, an anti-friction mounting in the circumferential groove of a collar 34, which is slidably mounted on the driven part of transmission 2. This collar is automatically movable into and yield-ably held in its illustrated position by means of a spring 35, which is coiled around the driven part of transmission 2 and acts between the hub of The collar is automatically movable to its other position by means of a centrifugal governor which is driven from the driven element of the centrifugal clutch and therefore operates only after the motor and fan 9 have acquired high speed. This governor includes a plurality of pairs of links each pair comprising two links 36 and 31 pivoted together at their adjacent ends. The other end of each link 36 is pivotally connected to the collar 34 and the other end of each link 3! is pivotally connected to the hub of drum 33. The links are provided at their interconnected ends with weights as indicated at 38 and as is usual in governors of this kind. It

will be clear that the governor, when rotated at.

a sufiiciently high speed will draw hub 34 and thus shutter 24 to the right, as viewed in Fig. 3, against the force of spring 35 and reduce the passage area for air to enter the fan casing.

The inner and dotted line position of the shutter for normal operations of the burner may be predetermined with precision by the following hand operable means. A screw 39 passes loosely through a hole in shutter 24. This screw has'a bearing inthe fan casing at each end as shown, a slotted head in an outer recess of the outer bearing, a spring 49 tobias the screw 39 inwardly by pressing against a pin driven through the screw all as indicated. Screw 39 can be turned with a screw driver without its moving lengthwise and by so doing a nut 4| on the screw can be moved back and forth. The nut 4| carries a rod 42 pinned to the nut at the left end and having an abutment stop 43 at the right end as shown. This rod 42 passes loosely through an opening in shutter 24 so that the shutter when operated 'bythe centrifugal governor, may slide freely along rod 42 as it does along screw 39, between the full and dotted line positions as shown in Fig. 3. The shutter will engage with stop 43 as an abutment.

It will be seen that the position of stop 43 determines the right hand position of the shutter. Stop 43 can be adjusted with precision by hand turning of screw 39. Its threads are adapted for fine small precision adjustments of nut and stop 43. The shutter has an annular rim which cooperates with an opposite annular rim 44 of the fan casing to determine the effectivepassage area of the air inlet opening of the fan. v

When the motor is started, the fan 3 starts therewith and accelerates with the motor until it reaches its full and high speed. During most of the time of this acceleration, the shutter 24 is in the full line position of Fig. 3 which preferably is such that the shutter does not restrict the fan inlet opening. Thus, in the burner starting interval the fan can have its maximum blast of air going through tube 5 (Fig. 1) to the combustion chamber. As the fan reaches a predetermined high speed c'lose to full speed. centrifugal clutch 23 operates to drive the oil pump 4 and it supplies a full blast of atomized oil to mix with the full blast of air, producing a combustible mixture for ignition in the combustion chamber. Combustion starts with a lean mixture because air is flowing past the nozzle at a. high rate at the time the pump is started and, by the time oil is emitted from the nozzle, air is flowing at its full rate. It should be noted that the centrifugal governor and the shutter will remain in the full line .positions of Fig. 3, while the fan is accelerating until a speed close to full speed is reached in order to establish a high rate of air flow to the combustion chamber. This is because the centrifual governor used to control the shutter 24 is located on the driven side of clutch 23. The shu'ti ter does not start to move towards its hand-adjusted position, the dotted line position of Fig. 3, until the oil pump 4 starts to operate. Then, be-

.cause the pump is positively-acting, the full rate of oil supply is established, practically instantaneously, as the pump starts to turn. The centrifugal governor likewise moves to high speed position and compresses spring 35 practically instantaneously, when the driven part 33 is engaged by the driving part 26 of the clutch. Shutter 24 is moved from full to dotted line position as the centrifugal governor moves to high speed position. In that position, the shutter may be positioned by small increments of precision adjustment by turning screw 39 by hand. When the efflcient oil burning ratio is determined by hand adjustment, the position of that adjustment, or the position of stop 43, may be considered a set one.

In the stopping intervals of operation of the burner, the motor I and fan 3 coast to a stop. But, when their speed starts to slacken, clutch 23 stops driving the centrifugal governor and oil pump. They do practically no coasting. They come to a quick stop. Spring 35 of the governor expands to move shutter 24 into its full line position of Fig.3. This is its position for practically the whole time of the coasting to a stop by the motor and fan. Consequently when the fan is operating at an speeds less said predetermined high speed in the stopping interval, there is'no restriction of the air inlet passage by the shutter. More air is supplied during the stopping intervals by this arrangement. The shutter mechanism, in its preferred arrangement, is adapted to provide no restriction of the air inlet by the shutter, when the fan is movin at less than said predetermined speed and a precision adjusted restriction of the air inlet to exactly determine the air-oil ratio for eflicient oil burning, when the fan is moving at full speed during the heating interval. 01 course substantial benefits can be attained by the same mechanism even though.

starting and stopping intervals but it is preferred to have no restriction in those intervals.

For a given size of fan and supply passage and with a shutter control for changing the air-oil ratio, the species of Fig. 3 has a number of special advantages. It shows a desirable way to automatically provide for the maximum rate of air supply when wanted during the starting and stopping intervals and for hand adjustment to accommodate the need for a precision air-oil ratio to make the burner work efficiently at any one of difierent rates of oil supply during the heating intervals. The oil rate may be changed over a considerable range merely by changing the size of the atomizing nozzle at the end of the oil suppl pipe I 2.

In the form of the invention shown in Figs. 6 and 7, a somewhat larger central hole 46 in the annular shutter 45 provides an auxiliary air inlet for the fan casing and valve means are arranged in such opening to vary the passage area therethrough from a maximum when the motor and fan are stopped to a inimurn, when the motor and fan are travelling at high speed. In this case, the shutter is adjustable by means of a screw 47, mounted like the described screw 39 but having a threaded engagement with the shutter. The clutch is mounted on shaft 2 in closer proximity to the pump end of the burner than in the previous example. The driving part 26 of the clutch 23 is provided with a circular flange 4B, the periphery of which is located in the circular opening 46 of shutter 45. In flange 48 are cut a number of openings 49' to provide passages to fan 3 for an additional air inlet area during starting and stopping periods. For each opening 49 a centrifugally operated flap 50 (Fig. '7) one end of which is fastened to the inside of flange 48, the other end of which is bent inwardly as by leaf spring construction and weighted as at 5|, is adapted to progressively close off the additional air inlet area as the motor and shaft 2 gain speed. When high speed is reached and clutch 23 operates the pump 4, the flaps 50 have closed off openings 49. Air then is drawn by fan 3 only through the annular opening formed by adjustment of shutter 45 through the rod 41 as described.

In Figs. 8 and 9, a pair of shutter cups are mounted in the central opening 46 ofthe shutter 45 to control the air flow therethrough. The shutter is adjustable by screw 41 as in Fig. 6. The outer cup 52, keyed to the driven part of transmission 2, is provided with slotted passages 53 registerin with similar passages 54 of an inner cup 55 rotating freely on shaft 2. Inner cup 55 has a stud 56 (Fig. 9) in its outer surface projecting through a slot 51 of cup 521. A tension spring 58 anchored at one end in cup 52 at 59, and at the other end on stud 56 hold the inner cup with the stud 56 at one end of slot 51. In this position when the shaft 2 is idle, the passages of cups 52 and 55 are in registration. Fan 3 thus draws air through these passages until the clutch rotates the drive shaft 2. By driving shaft 2 clockwise, as viewed in Fig. 9, the outer cup 52 is driven while inner cup 55 will lag causing the passages of outer cup 52 tobe closed. The lug portions 60 in cup 55 are turned inwardly to provide resistance to the r tation of inner cup 55. The stud 56 is forced aga nst the spring action to the other end of the slot at, then in the position of Fig. 9, closing 01f the passages 53. The relative spacing of the two cups in Figs. 8 and 9 is exaggerated for purposes of clarity. They are 8 substantially in sliding relationship with just enough clearance to avoid rubbing.

In Fig. 10 an hydraulic arrangement is shown for varying the air inlet to fan 3 upon actuation of the clutch mechanism. In this example, the annular valve or shutter Bl has only a small central hole therethrough just large enough to permit shaft 2 to freely pass therethrough. The shutter has a threaded engagement with an adlusting screw 62 which is rotatable as before to set the shutter with precision in a position, such as that indicated at A, suitable for normal operations of the burner. This screw has an unthreaded inner portion 63 which is Journalled in the inner frame portion of the fan casin and at its outer end an unthreaded portion 64 which extends through a small cylinder 65 and has fixed thereon within the cylinder a piston 66. The cylinder 65 is fixed as indicated to the outer frame 20. This cylinder 65 is supplied with oil under pressure through an inlet 61, which receives it in any suitable way from the outlet of pump 4 as by connection to pipe l2. A compression spring 68 acting between the inner end wall of cylinder 64 and the piston 66 urges piston 86 to the left, as viewed in Fig. 10, carrying with it the shutter 6|. This increases the annular shutter opening to fan 3, when the motor is starting or stopping and no oil pressure is available in the chamber of cylinder 55. When the driven side of the clutch, the drum 33, is engaged for running operation th pump 4 operates as described to place the oil under pressure. This pressure of the oil in cylinder 65 pushes piston 66 to the right, as viewed in Fig. 10, against the force of spring 68 and sets shutter Bl, as in the position A of Fig. 10, in the proper relative position to secure the desired ratio of air flow when fan 3 is operating at full speed durin th normal heating interval of operation. The two positions of the shutter, line A for the running position, and lin B for the starting and stopping position, are indicated in Fig. 10.

Another example of air control means embodying the invention, is shown in Figs. 11, 12 and 13. This example is generally similar to the other examples and especially to the example of Fig. 10. A difference over the other examples is that the air adjusting shutter 10, Fig. 11, to control the rate of the air supply to the combustion zone is on the pressure or outlet side of the air fan rather than the inlet or low pressure side. The motor H, drives the fan 12 and oil pump 13 by a transmission similar to the one of the first example of Fig. 3 and with a centrifugal clutch in it. The transmission arrangement is the same except that the motor H is between the oil pump 13 and fan 12, with its centrifugal clutch positioned to drive the oil pump only when the motor and fan are substantially at their high speed, and to leave the oil pump stopped at other times. This will be understood from the first example.

In the Fig. 11 structure, the fan 12 has an unrestricted inlet at the left of its casing and by its vanes, blows the air into annular chamber 14. Stationary slanting, air directing vanes 15 with spaces between, are adapted to cause whirling of the air in spiral form, as it enters the extension 16, closed at the back and open at the front to cause feeding into air tube 11 corresponding with tube 5 of Fig. 2. The fiat ring or hoop-shaped shutter 10 is adapted for back and forth axial adjustment, to close more or 7 less of the area of the openings between stationary vanes and thus control the rate at which air enters the tube 11 from the fan and on its pressure side. The burner features important here as differing from the other example are, the position of this shutter on the pressure or outlet side of the fan and the way of adjusting this shutter automatically and in relation to its hand adjustment. This example is similar to that shown in Fig. 10.

Referring to Fig. 13, shutter W is carried for adjustment by a yoke 18 hanging from short rod 19, mounted in the spaced depending arms of a sleeve 80, threaded on a screw 8|. An unthreaded portion at one end of this screw has a free bearing in the burner casing permitting the screw to both turn and slide axially. An unthreaded portion at the other end of screw 8! passes through a ower cylinder 82 and has fixed thereto within the cylinder a piston 83. This cylinder at inlet opening 84 is in constant communication by branch pipe 85 (Fig, 12) with the oil delivery line indicated at 86 (Figs. 11 and 12), on its high pressure side from the pump to the atomizing nozzle 81. So whenever the oil pump is turning, the high oil pressure (the oil pressure in both examples may be a high as around one hundred pounds per square inch) is applied as hydraulic pressure on the left of piston 83 (Fig. 13) to move and hold the screw the air tube 11. This will make it simple to get great exactness in the quantity of air going to mix with the oil from the atomizing nozzle for the air-oil ratio in the heating interval of this burner. The oil quantity is constant as has been explained in the first example. The speed of the fan 12 is constant also, as the motor speed in these burners is constant, except in starting and stopping intervals, so the air-oil ratio for the heating interval is constant, and 'by hand adjustment in the installation work may be made constant for a highly eflicient oil burning ratio.

This structure is adapted to automatically shift the shutter 10 to open up a much larger air passage area to the combustion zone for the fiame during the starting and stopping intervals. Coiled pring 88 (Fig. 13) between sleeve 80 and .end wall 89 of cylinder 82 is adapted to bias sleeve 80 and thus screw 8! on which it is threaded, to the left of the position shown. When the oil pump stops, oil pressure in cylinder 82 drops, and spring 88 moves shutter 18 to'the Start and stop setting as indicated by the dot dash line in Fig. 13. It is moved back to the Run setting for the heating interval, when the oil pump starts its operation. For this purpose the piston in cylinder 82 is made to dominate the action of spring 88 when the oil pump is operating as this cylinder 82 contains high oil pressure acting to the left of piston 83 to move it to the right and carry screw 8| against the spring 88. The oil pump is driven, only when the motor and fan are at top speed, by a centrifugal clutch in the motor transmission of this burner as in the first example.

The result is that the operation of the burner in the-example of Figs. 11 to 13 is the same as in the first example or any example where the shutter is on the inlet side of the fan, in these significant respects. During the starting and stopping-intervals a much larger air passage area is automatically made available for the fan than the air passage area that is available under precision adjustment during the comparatively long heating intervals which occur between the short starting and stopping intervals.

It should be noted also that the structure to get this result is quite simple. Such structure is adapted for application to existing forms of burners already in use, to convert them to the improved form for more economical operation in the use of oil. It is adapted for use in the manufacture of new burners with a little extra expense in merely adding the new elements to make the new burner combination.

The manner of automatically changing the eifective' area of the shutter-controlled airinlet passage to vary the rate at which air is supplied by the fan to the combustion chamber to adjust the air-oil ratio is both cheap and efiicient. Men accustomed to install the prior art burners are accustomed to adjust the shutter of each burner to get the air-oil ratio for its operation. One practice is to provide enough air to avoid smoke altogether; but a thin enough mixture to do this in the starting and stopping intervals, will waste a lot of oil in the heating intervals. Another practice is to let the prior art burner smoke just a little but only in the starting or stopping interval or both. This will give better combustion efficiency in the heating intervals when checked by gas analysis instruments, but will result in soot deposits and consequent insulation of heat transfer surfaces. The installation men usually check for any smoking by simply looking at the flame but sometimes a smoke detector instrument is used. In any case, they follow the practice, when installing, of adjusting the shutter until they get a little smoke and then again adjusting it for just enough more air. to stop the smoke. It is a fine adjustment and has to be made when the burner is operating at full speed at the place installed and necessarily an adjustment to be made in the field and not in the factory.

Under these circumstances, consider the utility of burners containing the present invention and furnished by a factory to the men, usually independent dealers, who will install them in all kinds of heating plants. ter with a fine adjustment to avoid smoking in the heating interval, that adjustment need not be compromised by further adjusting to avoid smoking in the starting and stopping intervals. The air passage area is automatically increased during the stopping and starting intervals so much that the installing men neednever adjust the shutter to avoid smoke.

The additional air inlet area provided for use in the starting and stopping intervals should be large enough to accommodate different sized atomizing nozzles. For any given oil pressure, the size of the orifice in the nozzle determines the rate of oil supply. Assuming that the factory furnishes a dealer with a given size burner, he may use it either for a heating plant requiring a certain oil consumption rate or one requiring several times that given rate or any rate between. All the dealer needs to do in order to adapt the burner for the desired oil rate over a substantial range is to use an atomizing nozzle with an orifice size to determine the rate. The same burner will operate with different size oil When theyadjust the shutnozzles. It will be apparent that as the oil consumption rate is increased more air is needed in order to maintain the proper air-oil ratio. The dealer will adjust the shutter to get the economical air-oil ratio during the heating interval for a given size nozzle. The automatic increase in air passage area for the starting and stopping intervals will be sufiicient to get the results wanted for a range of oil consumption rates. In the installation of the improved burners, the dealers will just naturally make a more efllcient adjustment of the shutter to save oil. This saving will be made every day the burner operates. The dealer can now confine his attention to merely setting the air adjustment for the heating intervals. Plenty of air is provided by simple automatic means to avoid smoke in the starting and stopping intervals. The improved burner results in very eflicient use of oil, while maintaining a clean fire at all times.

The invention is characterized by the arrangement for automatically increasing the air passage area of the fan during the starting and stopping intervals of operation of the burner. The purpose is to establish a high rate of air flow more quickly than would otherwise be possible during the starting interval of operation and to maintain a high rate of air flow longer than would otherwise be possible during the stopping interval of operation of the burner. A clean fire can be had at all times and the burner can operate at higher efificiency during its normal running intervals of operation because the extra air needed during the starting and stopping intervals of operation in order to avoid smoke is provided by the means of this invention.

The invention is useful regardless of how the oil spray is produced and whether the spray is composed wholly or only partly of oil. The invention has been disclosed in its most difficult application, .wherein high oil pressures are required for atomization of oil by pressure. Here, the load of the pump is great and it is desirable to use the clutch in the drive to the oil pump in order to unload the motor to get faster starting of the fan and to get greater coasting of the fan after the motor circuit is opened. In other types of burners, the clutch in the pump drive may not be needed and the flow of oil to the nozzle can be otherwise controlled. However, the automatic means for increasing the air passage area during the starting and stopping intervals will have value, as before stated, in providing the extra air needed during such intervals to avoid smoky operation and yet enable operation of the burner during its normal running intervals at high efiiciency.

' Having disclosed my invention, I claim:

1. An oil burner for starting, running and stopping operations under thermostatic control, comprising, an air supply fan, a casing for said fan having an inlet and an outlet opening, an air tube connected to said outlet opening and through which the air for combustion is supplied, an atomizing nozzle in said tube to supply oil at a constant rate to mix with the air supplied through said tube, a pump to supply oil to said nozzle, a motor, driving means connecting the fan to the motor to start and stop coincidentally therewith, driving means connecting the pump to the motor and including a centrifugal clutch operable to drive the pump only when the motor and fan are operating at or above a predetermined high speed, valve means associated with one of said openings to control the passage area for the flow of air to said tube, hand-operable means for actuating said valve means to determine a precision adjustment of the passage area for normal operation of the burner, yieldable means for actuating the valve means to increase the passage area, and means operatively connected to said clutch to operate only while the motor and fan are moving at or above said predetermined speed for actuating said valve means to counteract said yieldable means and decrease the passage area to that for normal opertion of the burner.

2. An oil burner for starting, running and stopping operations under thermostatic control, comprising, an air supply fan, a casing for said fan having an inlet and an outlet opening, an air tube connected to said outlet opening and through which the air for combustion is supplied, an atomizing nozzle in said tube to supply oil at a constant rate to mix with the air supplied through said tube, a pump to supply oil to said nozzle, a

motor, driving means connecting the fan to the motor to start and stop coincidentally therewith, driving means connecting the pump to the motor and including a centrifugal clutch operable to drive the pump only when the motor and fan are operating at or above a predetermined high speed, a valve for one of said openings and movable from one position to another to vary the effective air passage area, means tending to hold said valve in its position of greater passage area, hydraulic means operatively connected to the pump to move said valve into its position of lesser passage area whenever the pump is in operation, and handoperable means for adjusting said valve and predetermining with great accuracy its last-named position.

3. An oil burner for starting, running and stopping operations under thermostatic control, comprising, an air supply fan, a casing for said fan having an inlet and an outlet opening, an air tube connected to said outlet opening and through which the air for combustion is supplied, an atomizing nozzle in said tube to supply oil at a constant rate to mix with the air supplied through said tube, a pump to supply oil to said nozzle, a motor, driving means connecting the fan to the motor to start and stop coincidentally therewith driving means connecting the pump to the motor and including a centrifugal clutch operable to drive the pump only when the motor and fan are operating at or above a predetermined high speed, a valve for one of said openings and movable from one position to another to vary the effective air passage area, means tending to hold said valve in its position of greater passage area, means operatively connected to the driven element of said clutch to move said valve into its position of lesser passage area whenever the pump is in operation, and hand-operable means for adjusting said Valve and predetermining with great accuracy its last-named position.

4. An oil burner for starting, running and stopping operations under thermostatic control, comprising, an air supply fan, a casing for said fan having an inlet and an outlet opening, an air tube connected to said outlet opening and through which the air for combustion is supplied, an atomizing nozzle in said tube to supply oil at a constant rate to mix with the air supplied through said tube, a pump to supply oil to said nozzle, a

motor, driving means connecting the fan to the motor to start and stop coincidentally therewith, driving means connecting the pump to the motor and including a centrifugal clutch operable to 13 drive the pump only when the motor and fan are operating at or above a predetermined high speed, a valve for one of said openings and movable from one position to another to vary the efiective air passage area, means tending to hold said valve in its position of greater passage area, and a centrifugal governor connected to the driven element of said clutch to be rotated thereby and operable when rotated at or above a predetermined speed to move said valve into its position of lesser passage area, and hand-operable means for adjusting said valve and predetermining with great accuracy its last-named position.

5. An oil burner for starting, running and stopping operations under thermostatic control, comprising, an air supply fan, a casing for said fan having an inlet and an outlet opening, an air tube connected to said outlet opening and through which the air for combustion is supplied, an atomizing nozzle in said tube to supply oil at a constant rate to mix with the air supplied through said tube, a pump to supply oil to said nozzle, a motor, driving means connecting the fan to the motor to stop and start coincidentally therewith, driving means connecting the pumpto the motor and including a centrifugal clutch operable to drive the pump only when the motor is operating at or above a predetermined high 'speed, an an-- 14 nular disc valve associated with one of said openings to control the passage area for the flow of air to said tube, said valve having a central opening, hand-operable means for effecting a precision adjustment of the rim of said disc in spaced rela- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,012,037 Drew Aug. 20, 1935 2,464,698 Logan Mar. 15, 1949 2,465,125 Schulz Mar. 22, 1949

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