US2181322A - Measurement and control of the flow of viscous fluids - Google Patents

Description

Nov. 28, 1939.` H. G. GEISSINGER v 2,181,322

MEASUREMENT AND CONTROL OF THE FLOW 0F VISCOUS FLUIDS Original Filed Aug. '23, 1934 l y M ATTORNEYS. l

Patented Nov. 28, 1939 UNITED STATES MEASUREMENT AND CONTROL OF THE FLOW OF VISCOUS FLUIDS Harry G. Geissinger, Cleveland, Ohio Original application August 23, 1934, Serial No. 741.173. Divided and this application January 25, 1937, Serial N0. 122,251

Claims.

My invention relates to the measurement and control of the ow of viscous fluids, and this application is a division of my co-pending application, Serial No. 741,173, filed August 23, 1934 now Patent No. 2,072,204.

The primary object of the present invention is to provide animproved method and apparatus 4 for controlling oil burning equipment for indus- -trial furnaces.

Other objects will be more apparent as 'the description proceeds.

In the drawing: Figure 1 is a'sectional plan view of a fuel input valve embodying one form of my invention; l5 Figure 2 is a vertical section on the line 2-2 of Figure 1;

Figure 3 is a' vertical section on the line 3-3 of Figure l;

Figure 4 is a top planview of a portion of the appazratus as indicated by' the line H of Figure Figure 5 is a vertical section at right angles to the section shown in Figure 2 and is taken on the line 5-5 of Figure 4; Figure 5A is a fragmentary vertical section on line 5A-5A of Figure 4;

Figure 6 is a sectional view on a smaller scale takenon line 6-6 of Figure 1;

Figure 7 is a diagram showing the device of Figure 1 connected to a furnace system;

Figure 8 is a longitudinal section through an equalizer burner valve;

Figure9 is a fragmentary section of the lefthand portion of the device shown in Figure 2 showing a modified form of throttling valve control;

Figure l0 is a section onthe line |0--I0 of Figure 3.

'I'he invention as illustrated is in the form of a 40 fuel input valve adapted to deliver oil to a burner system `determined by the square root of the pressure offthe combustion air supplied to the burners. The construction is of the same general type as illustrated in Figure 6 of my co- 55 Thus the partition wall I4 is retained in the cap pending application, but is provided with addi-- by the annular sleeve |2| which threadedly engaging the boss and having the head end thereof at the upper end of the cap 43 as illus- 5 trated in Figure 5. The metering pin l5 is secured tothe cup-shaped member by fasten'ng means |23. The diaphragm system 9d, I0, 8 is also similar to that shown in my Patent No. 2,072,204 except that the diaphragm 20d is now omitted.

The inlet 2 is provided with a ball valve 34 and seat 35, and the valve is operated by a lever 32 which is connected to an auxiliary diaphragm 36. The casing I is provided with a partition wall |5| forming an inlet chamber |52 into which the iiuid from theinlet 2 first passes. The diaphragm 36 has one side thereof subjected to the pressure in the inlet chamber |52 and is secured to the casing by a cap |53 forming a chamber I |54 on the opposite side of the diaphragm. A passageway |55 connects the chamber |54 with the central cavity ||8 thereby equalizing the pressures in these chambers. Communication between the inlet chamber |52 and the central ,I cavity ||8 is provided by means of the pressure valve 31 which, as shown, comprises a tube |56 extending through the partition wall |5| and having a series of radial ports |51. A slidabl sleeve |58 is arranged Within the tube |56 and is 3 adapted to move within the tube by means of' the lever |59 which in turn is freely mounted on the shaft 40. 'I'he outer end of the lever |59 carries a pin 38 adapted to contact with the center plate of the diaphragm 9d. A spring 39 fixedly g secured to the shaft 4|) bears against the pin 38 and holds the latter in contact with the center plate of the diaphragm. The shaft 40 extends outwardly through the casing I and has iixedly secured `thereto a lever 4| which in turn abuts a push rod 42 extending longitudinally beneath the casing. The push rod 42 is adapted to be moved in accordance with the pressure of the air supply or by any other suitable controlling force and the preferred construction will now be described.

The cap |60 which retains the diaphragm 8d in position on the casing has a plurality of lugs 54 extending outwardly therefrom. A ring |62 is mounted on' the lugs. A diaphragm |63 ex- 50 tends across the ring |62 and is retained in position by a cap |64 and retaining screws I6| which threadedly engage the lugs 54. The cap |64 is recessed forming a chamber |65 on one side of the diaphragm |63 into which air under pressure may enter through the port 55. The lugs 56 are ,grooved to receive the circumference of a split ring 52. The ring terminates at one end in a lug |66 having a threaded aperture for'receiving a threaded pin 53. The other end of the ring has a laterally extending portion |61 terminating in the lug |68, spaced from the lug |66 and having an aperture |69 for receiving the end of the pin 53.` Thus by adjusting the threaded pin 53 the lugs |66 and |68 may be spread thereby frictionally engaging the ring 52 in the grooved lugs 54. 5| is a hinge arranged between the lugs |66 and |68 and using the pin 53 for its pivot. Extending from the hinge is a member 50 which extends in alignment with the center of the diaphragm |63 and has a return bent portion |10 of arcuate shape. The center plate of the diaphragm |63 `has a projecting portion |1| adapted to bear against the member 50. The push rod 42 hereinbefore described abuts the arcuate member |10.

With the adjustable hinged arrangement as described, it will be observed that by loosening the threaded pin 53 the ring 52 may be rotatably adjusted in the lugs 54 thereby rotatably adjusting the hinge 5| and consequently changing theA effective leverage on the push rod 42. With the.

parts in the position as illustrated, the effective leverage on the diaphragm |63 and the push rod 42 is the same, but by adjusting the hinge rotatively, the leverage effective on the push rod 42 is increased or decreased over that eiectize on the diaphragm. This adjustment makes it possible to compensate for differences in combustion air pressures in the initial setting of the apparatus.

On the cap |64 is arranged a proportioning valve |12 adapted to determine the air pressure in the chamber |65. As shown, this comprises a cylinder |13 having two conduits communicating therewith designated 58 and 59. A piston 60 within the cylinder is so arranged as to simultaneously uncover aportion of each of the conduits and permit communication with the recessed -intermediate portion |14 of the piston. The aperture 51 in the cap also communicates with this recessed portion of the piston. An adjustment screw 62 is adapted to move the piston to vary the proportion of the fluid entering the proportioning valve.

In order to clear the central cavity ||.8 of accumulation of gases a suitable vreliefvalve is provided. As shown, the cap 43 is provided with a shouldered vertical passage |15 extending from the cavity I8 into the passageway 15. The passageway 15, as in the preceding examples, ex-

tends between the chamber P on the outside of the minor diaphragm 8d and the chamber O above the orifice 4, and consequently communicates directly with the discharge 3 by means of the down-turned passageway |16. The valve 45 is actuated by means of a lever 46 arranged within the central cavity ||8 and pivoted on the pin 48. The other end of the lever 46 is provided with a float 41, the arrangement being such that whenever the liquid level falls through an accumulationof gases, the valve 45 is opened and permits such gases to escape through the port 15 and the discharge 3.

There is also provided a manually adjustable by-pass from the cavity H8, this being in the form of an adjustable screw-44, the head of which extends through the top of the cap. The lower end of the screw forms a valve cooperating with the conical valve seat |11 to close or open an auxiliary vertical passageway |18. The upper end slight uctuations.

mais@ uid enters through port 2, flows past ball valve 34 into the inlet chamber |52 and then passes through the pressure valve 31 into the central cavity H8. The -uid then passes downwardly through the variable channels |26 of the resistor into the cup-shaped member |22, then upwardly through the channels |30 of the resistor. It then flows through the orice 4 into the chamber O and out through the discharge 3. 'I'his ow of iiuid creates a tension in the diaphragm system 8d, I0', 9d in the direction of the arrow |05, that is, towards the minorv diaphragm 8d. This pressure is then transmitted through the spring 39 to the rod 40 and tends'to oscillate the same in one direction. This oscillation, however, is resisted by the force transmitted to the rod 40 by the lever 4| and push rod 42 which, as previously explained, is derived fromA the air pressure acting on the diaphragm |63. Thus the pressure due to the liquid iiow and the pressure obtained from the air flow are balanced against each other through the spring 39 Which tends to eliminate The' free lever |53 which actuates the pressure valve 31 is also responsive to the movement due to the balanced forces above mentioned since the pin 38 attached thereto is intermediate the diaphragm 9d and the spring 39, and therefore exerts a throttling effect between the chamber |52 and the cavity ||8. This in turn creates a diierential pressure on the dia.-

-phragm 36 and actuates thelever 32 to open or Figure 7 -illustrates diagranmiatically a pre- 'erred method of utilizing the fuel input valve just described in connection with automatic temperature control mechanism of a metallurgical furnace. It also illustrates two different types of oil burners and the association with a motorized air control energized and directedv by thermometric instruments. The instruments themselves are not illustrated, nor is the furnace, since they may be of any suitable type and are not essential to the understanding of the invention.

The combustion air enters through the trunk line 63 from a suitable source and is distributed to the burner 66 through a branch pipe |80 and to burner 66a through branch I8 I. The oil enters the casing of my fuel input valve through the inlet 2 and leaves through the discharge 3, being distributed to the burner 66 by a conduit |82, equalizer burner valve 69 and conduit 13. It is similarly distributed to lburner 66a by conduit |83, equalizer burner valve 69 and conduit 13. The trunk line 63 is provided with a valve 64 mechanically operated by suitable mechanism not illustrated in detail but diagrammatically represented at 65. This form of motor controlled valve is well understood in theart, and the position of the valve is determined by thermometric instruments in the metallurgical furnace.

An air line conduit 61 communicates with the trunk line in advance of the valve 64 and is provided with a manually operable valve 68. One branch from the conduit 61 is connected to the pipe 58 of the proportioning valve previously described. The other pipe 59 of the proportioning valve is connected to the branch air line line pressure and the'pressure of the air flowing' to theburner. 'I'his proportion' may be suitably adjusted by changes of the area of the ports covered by the valve 6 0 of the proportioning valve.

' The equalizer burner valve 69 is shown in detail in Figure 8. It comprises a cylinder |84 in which a piston |85 is longitudinally adjustable by means of a threaded stem |86 engaging the correspondingly threaded head |81. The piston has a spiral groove |88 in the periphery thereof through which the oil is required to fiow from the annular channel |89 to the discharge orice |90. By rotatably adjusting the piston |85 through the handle |9|, the length of the spiral groove between the inlet and discharge may be` varied, consequently varying the resistance to the passage of the oil. 12 is a shut-off valve.

In order to understand the operation of the system as illustrated in Figure 7, it should be remembered that the valve 64 will assume predetermined positions by direction of the ther-l mometric instruments, ranging from a Wide open position during the starting of the furnace to a' closed position when the furnace ceases to bein operation. Intermediate positions of the valve will be obtained in order to exactly regulate the amount of air delivered to the furnace under changing temperature conditions. The quantity of oil passed by the metering control device is determined by some proportion of the combustion air pressure and is not determined solely by the pressure delivered to the burner valve 66. This isv for the reason that at times of low combustion rate in the furnace, external air flows into the furnace through burner port's and other leakag-es. This influx tends to produce an oxidizing atmosphere. To retain the true proportion of air and fuel for ideal combustion, the arrangement which I have illustrated makes it possible to enrich the combustion at low ring rates and to make this i enrichment readily controlled by the operator 'is negligible.

without permitting the operator to alter the normal combustion mixtures during the normal firing of the furnace.

Referring again* to Figure '1, it will be apparent that if the valve 6B were closed, air would iiow through the pipes B1 and 58 to the proporfl tioning valve and thence through pipe 59 and conduit |80 to the burner 66, although the amount of ow through the proportioning valve However, there'would still be a definite pressure in the chamber |65 acting on the-air pressure diaphragm |63 and this pressure would produce a certain. oil flow through the apparatus. It will also be noted that if the valve 64 were Wide open, pressures in 58 and 59 would be substantially equal and the pressure effective on the air pressure diaphragm |63 would be the pressure of the burner system. Due to the square root effect of the air pressure, the enrichment adjustment practically disappears at a 50% to 70% fuel input. Y

In Figure '7 I have also illustrated a second type of burner 66a which is of the dual air type. The secondary air supply is introduced through a conduit |92 from the conduit 68, which in turn receives its supply in advance of the controlling valve 64. The secondary air supply is therefore never under the automatic control.

A modication of the device shown in Figure 2 is illustrated ih I Figure 9. 'I'he only change from the devia @f Fievet 1s a ,me am p f .ne

throttling valve which replaces the diaphragm 36, lever 32 and ball valve 34. As shown in this construction, the partition wall divides the cavity ||8 from an inlet chamber |52 as in the preceding device. The throttling valve 31 is the same as before but is located at a lower portion of the chamber |52. Instead of the diaphragm 36'there 4is nowA provided a piston |93 verticallyslidabl'e in a sleeve I 9|. A port |55 establishes communication between the head of the piston and the central cavity |8. The valve body |95 has an inlet port |96 registering with the uid inlet 2. The valve consists of a rod |91 having a threaded portion |98 engaging the valve body |95. The valve has a groove |99 therein and the arrangement is such that rotation of the same will expose a variable amount of the 'groove and thus vary the amount of uid which can ow from the valve body to the chamber |52. lIhe rotation of the valveis by means of a sprocket 200 on the end of the valve. A chain 20| passes over the sprocket and one end thereof is secured at 202 to the piston, while the otherl'end thereof is attached to a coil spring 203 which in turn is secured to the casing as indicated at 200.

In the operation of the device, fluid entering lthrough the throttling valve |91 passes through the pressure valve 31 which creates a difference of pressure between the chambers |52 and H8, thus moving the piston |98 which in turn rotates the valve* |91 and varies the amount of iiuid entering chamber |52. It will-be noted that the closing of the throttling valve is the result of upward motion of the piston 93 in response to a decrease in the area of the pressure valve 31.

.This upward motion of the piston reduces the ow through the-pressure valve, automatically reducing the effect of the same and anticipates the new position. Such anticipation eliminates hunting in the throttling valve. The closing action alsol creates increase in the counter-pull of the spring 203 cooperating in anticipation eect. It will be noted thatvmovement of the piston |93 does not alter the flow through the metering device of the control.

The fuel input valve of the system connected thereto as illustrated, has many advantages over the prior art. In the rst place, the viscosity effect is eliminated in accordance with the principles described in my Patent, 2,072,204, issued March 2, 1'937. It should also be noted that the throttling valve in actual control of the ow is self-cleaning, automatically opening to produce a definite fiow. The metering orifice and pase sageways are of such size throughout that granu lar carbon (which is present in all modern fuel oil) cannot clog the same in contradistinction to for controlling the oil supply. In my apparatus the quantity of fuel oil delivered to a group of burners is automatically determined by the combustion air pressures whether the variationsvin pressure are accidental or produced bydirect intent. My invention meets the modern tendency towards' a fioating combustion rate. In conjunction with motorized air valves under the `present-day devices using small tapered orifices 8|) d2 may be reduced, larger .metering systems 'equalizing the output.

My device provides for the enrichment of the combustion mixture at low combustion. rates without affecting the adjustment under normal conditions. ing valve 62, but as previously explained, this enrichment is enirely nullied at higher rates because of the equalization of pressures on the opposite sides of the throttling valve 64 where the latter is open. My device further provides izer has `a. back pressure proportioned to the ow and offers material opposition at low rates.

It should be understood that while Figure 7 shows two burners under the same control, the

number of burners may be varied at will, depending upon the furnace construction. A

It will be noted that in the construction illustrated in Figures i and 2, the orifice rod I5 has a variable groove therein and the resistor is made up of two parts, one having variable channels, and the other having channels of fixed dimensions.

It will be evident that the resistance factor R of the orice will vary with the area and stroke of the system, and that the factor r of the resistor must vary in proportion therewith. The resistance developed by the channels |30 is proper-- tional to that of themaximum area of the orifice 'When the rod I5 and the cup-shaped member |22 are in their lowermost positions, the widths of the channels |26 are developed so that the additional resistance, due to the decreasing area of the orifice, will add a proportional resistance to the resistor system. The raising of the rod I5 and the cup-shaped member |22 therefore both increases the length of the resistor and reducesthe primary area of the system. In order to calibrate the instrument shown in Figure 2. the adjustable core I 28, which has the xe'd resistor channels |30 therein', is adjusted longitudinally with respect to the sleeve I2I while the cup-shaped member |22 is in its uppermost position until the proper proportion between the resistance of the fixed channels I30 and the variable channels I26.is obtained,

l this proportion depending upon the maximum and minimum orifice areas due to the extreme movement of the rod I5. When the desired proportion is obtained, the core |28 is suitably secured to the sleeve I2I bysuitable securing means. The rod I5, which is threadedly secured to the cupshaped member I 22, is thereupon adjusted so that theresistance factor R is exactly proportional to the resistance factor r, the latter being the sum-- mation of the fixed resistance of the channels |30 and the variable resistance of the channels |26.

apparatus which will exactly nullify the viscosity effect o'f the fiuid. It is also possible to determine these factors mathematically.-

One of the features of the 1116141119111? YQIYQ'I 'I'his is by means of the proportionstood that the invention is not to be considered as.

limited to the speciflc embodiments herein described, but the scope-of the invention is to be construed by the claims appended hereto.

What I claim as my invention is:

1-. A system for controlling combustion of -fiuid lfuel comprising a burner, an air line and a fluid fuel line connected thereto, a valve in said air line adapted to regulate the air supply to said burner,

Va valve in said fluid fuel line. adapted to regulate the uid fuel supply .to said burner, means for regulating said fluid fuel valve bythe unbalanc- 'ing between a pressure derived from the fluid iiow and a pressurederived from said air line, conduits from said air line, on opposite' sides f said air valve connected to said fuel regulating means whereby air pressure anterior to said air, valve is effective on said fuel regulating means in-order to increase the ratio of fuel to air when said air valve approaches the'closed position while maintaining the normal ratio when said air valve is open.

Y 2. A system for' controlling combustion of liquid fuel comprising a burner, an air line anda liquid fuel line connected thereto, a valve in said air line adapted'to regulate the air supply to said burner, 'afvalve in said liquid fuel line' adapted to regulate the liquid fuel supply 'to said burner, said fuel valve comprising a passageway for the liquid fuel having a constricted area. therein` and vhaving means therein for creating a resistance to ow which is a function of length, a movable element having pressure -responsive faces f different effective areas, means for urging said elementv in opposite directions .by the pressures within said passageway on.opposite sides of said 'constricted area on the one hand and-on opposite sides of said resistance means on the other hand, thereby ob- .taining afet force due to the ow of the fluid through said passageway, a pressure responsive element adapted to exert a force on said movable element in opposition to said net force and conduits connecting said pressure responsivemeans y with said air line on opposite sides of said airl valve whereby air pressure anterior to said air valve will be proportionately effective on said movable element when saidair valve approaches closed position thereby enriching the combustion mixture. l l

. 3. In an apparatus of the class described, pressure responsive means, a lever operatively engaging said pressure responsive means, a hinged fu1- Vcruxn for said lever, means for rotatively adjusting said hinged lever, said lever having an arcuate portion extending circumferentially, and a push rod engageable with said arcuate portion and adapted in different rotative positions of said hinge to 'receive a different proportion of the force exerted by said pressure responsive'means.

4. In apparatus of the character described, condition responsivemeans adapted to exert a force I variable in accordance with the value of said condition, movable means associated with said condition responsive means adapted to beacted upon by said condition responsive means, and acb'ustable meanS interposed between| said condition responsive means and said movable means, the

'adjustment of said adjustable means providing for transmitting a predetermined proportion of said variable force to said movable member, said adjustable means comprising a lever having an arcuate arm, and a second arm extending to the. `axis 0f said arcuate arm, and being adjustable about said axis, said condition responsive means said movable means engaging said arcuate arm,

whereby said lever will transmit a reduced or fuel valve, said control means vcomprising pressure responsive means, a conduit providing for a iow of air around said air valve, a regulating valve in said conduit, said pressure responsive means connected to said conduit posterior to said regulating valve.

6. A system for controlling combustion of fluid fuel comprising a burner, an air line and a uid nected to said conduit posterior of said regulating valve. x v

10. A system for controlling combustionv of fluid fuel comprising a burner, an air line anda fluid fuel line Aconnected thereto, a valve in said air line, a valve in said fuel line, control means for said fuel valve, said control means comprising engaging said second arm adjacentsaid aids, and

pressure responsive means, means for applying a pressure to said `pressure responsive means in accordance with lthe iiow and viscosity 'of said fuel, so as to maintain the ilow of\fuel constant irrespective of viscosity, means for applying a second pressure to said pressure responsive means .comprising a conduit connected in parallel to .said air valve, and' providing for a 4iiow'of air therearound, a pair of cooperating valves in said conduit spaced to form a chamber therebetween,

' :saidv pressure responsive means operatively connected to said'chamber.

`1 1. A system :for controlling lcombustion of uid fuel comprising a burner, an air line and a iiuid fuel line connected thereto, a valve in said air line, a valve in said fuel line, ccntrolgmeans for said fuel valve, said control means comprisfuel line connected thereto, a Valve in said air line, a valve in said' fuel line, control means for said fuel valve, said control means comprising pressure responsive means, a conduit providing for a fiow of airaround said air valve, a pair of cooperating valves in said conduit spaced Vto form a chamber therebetween, said pressure responsive means connected to said chamber.

7. A system for controlling combustion of iiuid fuel comprising a burner, an air line and a uid fuel line connected thereto, a valve in said air line, a valve insaid fuel line, control means for said fuel valve, said control means comprising pressure responsive means,'a conduit providing for a flow of air around said air valve, a pair of cooperating valves in said conduit spaced to form a chamber therebetween, said pressure responsive means connected to said chamber, and means for adjusting said cooperating valves to' varytthe pressure in said chamber.

8. A system for controlling combustion of fluidv fuel comprising a burner, an air line and a iiuid fuel line connected thereto, a valve in said air line, a valve in said fuel line, control means for said fuel valve, said control means comprising pressure responsive means, a conduit providing for a ow of air-around said air valve, a pair of cooperating valves in said conduit spaced to form a chamber therebetween; said pressure responsive means connected to said chamber, and means for simultaneously and oppositely adjusting said cooperating valves to vary the pressure in said chamber.

9. A system for controllingv combustion of fluid fuel comprising a burner, an air line" and a fluid fuel line connected thereto, a-,valve in said air vline,'a valve in said fuel line, control Ameans for said fuel valve, said control means comprising pressure responsive means, means for applying a pressure to saidpressure responsive means in accordance with the iiow and viscosity of said fuel, so as to maintain theilow of fuel constant ing pressure responsive means, means for applying a pressure to said pressure responsive means in accordance with the ow and viscosity of said fuel, so as to. maintain the iiow of fuel constant irrespective 'of viscosity, means for applying ya second .pressure to said pressure responsive means comprising a conduit connected in parallel to said air valve, and providing for aow of air therearound, a pair of cooperating valves in said conduit spaced to'form a chamber therebetween, said pressure responsive means operatively connected to said chamber, and means for adjusting said cooperating valves to vary the pressure in said chamber.

12. A system for controlling combustion oi fluid fuel comprising a burner, an air line and a iiuid fuelline connected thereto, a .valve in said air line, a valve in said fuel line, control means for said fuel valve, said control means comprising pressure responsive means, means for applying a pressureto said pressure responsive means in accordance with the iiow andviscosity of said fuel, sc as to maintain the now of fuel constant irrespective of'viscosity, means for applying a air. line, a valve in said fuel line, control means irrespective of viscosity, -means for applying-a second pressure to said pressure responsive means comprising a conduit connected in parallel to said air valve, and providing for a flow of air therearound, a regulating valve in said conduit.

said pressure responsive means operatively con second pressure to said pressureresponsive means comprising a conduit 'connected in parallel to said air `valve, and providing for a flow of air therearound, a pair of cooperating valves in said conduit spaced 4to form a chamber therebetween, said pressure responsive means operatively connected to said conduit intermediate said orifices, and means for simultaneously and oppositely adjusting said lcooperating valves to vary the pressure in said chamber.

-13'.A system for controlling combustion of fluidvfuel comprising a` burner; an air line and a fluid fuel line connected theretc, a valve in said for said fuel valve, said control means compris'- ving pressure responsive means, a conduit providing for a flow cf air around said air valve, a regulating valve in said conduit, said pressure responsive means 'connected to said conduit posterior to said regulating valve, and an adjustable lever connected between said `pressure Yresponsive means and said fuel valve to vary the eiiectiveness of said pressure responsive means.

14. Av system for controlling combustion ci fluid fuel comprising a burner, an air line and a fluid fuel line connected thereto, avalve in said air line, a 'valve in said fuel line, control means 7e for said fuel valve, said control means compris-y a regulating valve in said conduit, said pressure responsive means connected to said conduit pos.

terior to said regulating valve, and an adjustable lever connected between said pressure responsive means and said fuel valve to vary the effectiveness of said pressure responsive means, said lever having an arcuate arm and second arm extending to the axis of said arcuate arm, said lever being adjustable about said axis, said pressure responsivev means engaging said second arm adjacent said axis, a member engaging said arcuate arm and transmitting a controlling forceto said fuel valve.

,areaaaa l5. A system for controlling combustion of iluid fuel comprising a plurality of burners, an air supply means including a trunk with an air valve therein, and 'a branch to-each burner, a fuel supply means including a main, a `fuel valve therein, and a branch to each burner, control means for said fuel valve comprising pressureV responsive means, a conduit providing a flow of air around saidA air valve, a regulating valve in said conduit, said pressure responsive means con- `nected to said conduit posterior to said regulating valve, and means in at least one of said iluel branches providing a tluid channel of variable length but of uniform cross section, and means forv varying the length of said channel.'

HARRY G. GEISSINGER,

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