US1474754A

US1474754A - Combustion-controlling system

Info

Publication number: US1474754A
Application number: US317453A
Authority: US
Inventors: Adams Daniel
Original assignee: Individual
Current assignee: Individual
Priority date: 1919-08-14
Filing date: 1919-08-14
Publication date: 1923-11-20
Anticipated expiration: 1940-11-20

Description

Nov. 20, 1923. h flfig D. ADAMS GOMBUST ION CONTROLLING S YSTEM Filed Aug. 14 1919 5' Sheeias-Sheet l v Fig.1.

Inven'i'or.

Daniel Adams b lM3nvMk-fMM Nam 2 1923. 1 474,?54.

D. ADAMS COMBUSTION CONTROLLING SYSTEM Filed Aug. 14 1919 5 Sheets=Sheet 2 a gggg lnvenTov. Danie? 0101 ms Wm N 2O 1923. 11,4?4j3'54 n. ADAMS COMBUSTION CONTROLLING SYSTEM Filed Aug. 14, 1919 5 Sheets-Sheet 5 Nov. 24]) 1923.,

D. ADAMS COMBUSTION CONTROLLING SYSTEM I Filed Aug. 14 1919 5 Sheets-Sheet i 3 VI w M PJWA O S n e a v d n 7 O n 0 Q B .W O 7 v n 7 5 7 6 0 9. Um no.

Nam 20 1923.

D. ADAMS COMBUSTION CONTROLLING SYSTEM Filed Aug. 14', 1919 5 sheefs sheet 5 Patented Nov. 28, 1923.

U NH

DANIEL ADAMS, 0F NEWTON, MASSACHUSE'JE'ES.

COMBUSTION-CONTROLLING SYSTEM.

Application filed August 14., 1919. Serial no. 317,453.

To all whom it may concern:

Be it known that I, DANIEL ADAMS, a citizen of the United States, and resident of Newton, county of Middlesex, State of Massachusetts, and whose post-oflice address is 91 Allerton Road, Newton Highlands, Massachusetts, have invented an Improvement in Combustion-Controlling Systems, of which the following description, in connection with the accompanying drawing, is a specification, like characters on the drawing representing like parts.

This invention relates to a system or apparatus for automatically cont-rolling combustion so as to secure under various and varying conditions a predetermined relation between the amount of fuel fed to the combustion chamber and the amount of air supplied.

The invention is susceptible of a wide 7 range of application but is of particular value in such cases as furnaces to whlch the coal is fed by automatic stokers or oil burning furnaces wherein the rate at which the fuel is fed is under control.

The object of the invention is to secure accurate control of the flow of air through the furnace or combustion chamber by either eliminating or controlling all the variables which affect the flow.

It is usualto regulate the supply of air to the combustion chamber by constricting, as with a damper, at some point the passageway through the furnace forthe air and gases and to vary the area of constriction as by setting the damper at a predetermined position for each load or each rate of flow of the fuel to the combustion chamber. But, such systems fail to take into consideration or to control af number of variable factors. which afi'ect the flow of air. The quantity of air which will pass-a. regulating damper is a function notonly oft-he area of the damper. opening, but also of the differential in pressure at that opening. In order theredraught or the quantity of air' passing 7 ,through the damper opening among which i may be mentioned the weather, the temperature ofthe exit from the combustion chamber, leakage into the combustion :chamber,

wand when a' boiler is being heated such factors as" the extent of y the" collection of soot,

the tightness of the bafies, and the leakage through the boiler setting.

he present invention provides means for automatically correlating the difierential in pressure at the damper opening and the area of the damper opening to secure a predetermined relation between the quantity of air flowing past the. damper opening and the gmount of fuel fed to the combustion cham- Preferably the object of the invention is secured by means for maintaining a substantially constant difierential in pressure at the damper opening whereby the quantity of air passing the damper opening is a function of or proportional to the area of the damper opening alone, and in providing I means for varying the position of the damper or the area. of the damper opening in predetermined relation to the amount of fuel fed which consequently results in the amount of air passing the damper opening having a fixed or predetermined relation to the amount of fuel fed.

More specifically the invention includes means such as a load regulator which acts to set a regulating damper in the passageway for the air and gases through the combustion chamber at a predetermined position for each load together with a draught regulator which acts to control a second damper in the said passageway to maintain a constant differential in pressure at the regulating damper. v

The nature and object of the invention will appear more fully from the accompanying description and drawings and will be particularly defined in the claims.

As specific and illustrative embodiments of the invention the drawings show boiler heating furnaces in which the fuel is either coal fed by an automatic stoker or oil fed through a burner all of a familiar type.

In the drawings F ig. 1 is a side elevation largely diagram matic of a boiler, subjacent furnace or combustion chamber, automatic coal stoker, and an apparatus in connection therewith for carrying 'out one form of the invention.

position the second damper.

Fig. '2 isa detail partially in vertical cross Fig. 4 is a detail partially in vertical cross section of a cy inder and plunger shown in Fig. 2 and connected with the blade of the draught regulator. j

Fig. 5. is a View in side elevation partially in vertical cross section of the load regulator shown in Fig. 1.

Fig. 6 is .a view in side elevation of the device through which the governor shown in Fig. 1 acts to position the regulating damper.

' Fig. 7 is a view in front elevation of a pair of boilers provided with subjacent oil heatin furnaces, the one at the left hand being 1llustrated as provided with an apparatus embodying the invention designed to maintain asubstantially constant differential in pressure at the ash pit door by maintaining the pressure in the ash pit substantially constant, and less than that of the atmosphere, while the one at the right hand is ilustrated as provided with an apparatus embodying the invention in which the differential in pressure at the ash pit door is varied to a predetermined amount for each variation in the load.

Fig. 8 is a view in side elevation of the construction shown at the left hand side of Fig. 7.

Fig. 9 is a detail in side elevation and partially in vertical cross section of the draught regulator and connections for the boiler at the right hand side of Fig. 1.

Fig. 10 is aview chiefly in vertical cross section of the Valve for controlling the oil su ply in Fig. 7.

ig. 11 is a view chiefly in vertical cross section ofthe valve for controlling the steam supply in Fig. 7.

Fig. 12 is a view similar to the lower portion of'Fig. 1 showing the mechanism on a larer scale.

ith the present invention embodied in a furnace provided with an automatic stoker where the rate of feeding of the coal is under control, the quantity of air may be correctly proportioned to the amount of coal fed and consequently a high eiiiciency of combustion secured.

Asthe invention is not concerned with the details of construction of the combustion chamber, furnace, boiler. or other devices, and the stoker, these elements have been illustrated chiefly diagrammatically.

In the construction shown in Fig. 1 the combustion chamber 1 is located beneath a' steam boiler 2; air is supplied beneath the fuel bed 3 from a conduit 4 under a pressure greater than atmospheric. Coal is fed to the fuel bed 3 by a. suitable automati stoker. The coal being supplied to the hopper 4 and pushed therefrom by a piston or plunger 5 operating therebeneath and driven by a connecting rod 6 connected to a crank 7 on a shaft 8 geared to a shaft 9 driven in turn by a belt 10 from a pulley 11 rotated by a steam engine '12. y

A device such as a suitable fly ball governor 13 is geared to some element such as a shaft 9 having a movement directly proportional to the amount of fuel fed' and this governor is connected to a regulating damper such as the vertically sliding plate 14 placed in the air conduit 4 in such a manner that the regulating damper is thereby moved to vary the opening of the conduit at the damper in direct proportion to the amount of fuel fed to the combustion chamber. 7

Suitable means are provided for varying the amount of fuel fed to correspond with the requillements such as the load upon the boiler. For this purpose there may be employed and there is herein illustrated a load regulator of the type shown in the'patent to Atchison et a]. reissue No. 13,337 granted December 12, 1911. This load regulator is connected by a pipe 15 to the steam space.

of the boiler 2 and acts to control the valve 16 in the steam admission pipe 17 running to the engine 12. As the load on the boiler rises and falls, the amount of steam fed to the engine is by the load regulator correspondingly increased or diminished and thus the amount of fuel fed to the combustion chamber is similarly increased or diminished.

The load regulator shown in' detail in Fig. 5 and needs no detailed description in view of its disclosure in the aforesaid patent. The steam from the boiler passing through the pipe 15 acts against :1 diaphragm in the chamber 18 moving the rod 19 in opposition to a system of weighted levers. The force of the steam is thus opposed by the

weights

20 and 21. In addition to the provision for varying the amounts of the

weights

20 and 21, a spring 22 is provided which acts to steady' the movement of the parts. When the steam pressure in the boiler rises or falls the rod 19 is moved to. rock the lever-23 and through it the auxiliary lever .24 thus raising or lowering the connecting rod 25 extending to the water valve 26 in the piston 27, in turn causing the water propelled iston 27 to move in the same direction an through'its connection with the lever 28 effect through the flexible connector 29 the operation of the valve 16 todecrease or increase the supply of steam to the engine which operates the stoker.

As a convenient means for securing the operation of the regulating damper 14 from the governor 13 already described, a water cont-rolled piston such as shownin' cross sec tion in Fig. 5 may be employed. Such a de-.

vice is illustrated in side elevation in Fig. 6. The connectingrod 30 of--this device WlllCh corresponds to the connecting rod 25 i the amount ofcoal fed by thestoker, the

lid

is connected by an lL-shaped rod 31 to the vertical sliding collar 32 of the governor 13 while the piston rod 33 extending downward from the Water piston is connected by a flexible connector '34 to the regulating damper. Thus, as the balls of thegovernor 13 move out and in with the increase or decreasein connecting rod rises and falls and the water piston falls and rises to efiect'the opening and closing movement of the regulating damper 14.

Such a mechanism as thus far described thus acts to vary the area of opening at the regulating damper 14 proportional to or in a predetermined ratio With respect to the amount of coal fed to the combustion chamber by the stoker.

As .a simple and preferred means of controlling the differential in pressure at the regulating damper opening a second damper 35 is placed in the 1passageway for the air and gases through t e combustion chamber and is shown as being placed in the air conduit 4 intermediate of the regulating damper and the stoker.

The second damper 35 is controlled by a pressure regulator designed to respond to very small differences in pressures. lln itself it is a familiar device and operates on a similar principle to that of the load regulator already described. In the form herein used, and shown in detail in Figs. 2, 3, and 4, a closed box or casing 36 is connected at opposite sides to the passageway'4 at opposite sides of the'regulating damper 14 so that the pressures at opposite sides of this regulator are conveyed into the opposite sides of the box 36. Within the box 36 and closely fitting the walls is a vertical blade 37 nicely balanced and pivoted with an antifriction pivot at 38. The balancing weight 39 is so formed or adjusted that when the predetermined differential in pressure exists the blade 37 will stand in its central or vertical position. Any slight change in the differential in pressure will therefore cause the blade 37 to swing in one direction or the other. When it thus swings it acts through the arm 40 to raise the rod 41 and with it the valve 42 admitting water from the water pressure system to one or the other of the

pipes

43 and 44 connecting above and below the piston 45 in the cylinder 46, and thus effecting the movement of that piston and through the rod 47 extending therefrom the movement of the damper 35.

Thus, it will be seen that this mechanism acts automatically to maintain a given constant differential in pressure at the opening of the regulating damper 14 at all times and under all conditions, assuming only that the draught out from the combustion chamber is adequate. The quantity of air passing the regulating damper 14 becomes therefore a function solely of the area of the damper opening. Consequently the quantity of air is readily proportioned in any required or predetermined, ratio to the amount of fuel fed to the combustion chamber.

The principles of the invention are further illustrated by the application thereof closed exteriorly by the doors 49. Beneath the combustion chamber is the usual ash pit chamber provided with openings at the front controlled by doors or dampers 50. The smoke box on'the boiler 40 is connected by a flue 51 with a transverse header fine 52.

The oil may be fed to the fire box byany suitable and well known method. As herein shown the oil is fed in and mixes with steam under pressure. The oil pipe 53 leads from a suitable source of oil supply through a controlling valve 54 to the burner 55 projecting into the combustion chamber. The steam pipe 56 leads from a suitable source of steam supply such as the boiler itself through a controlling valve 57 to the burner 55 and acts to inject the oil into the combustion chamber in a well known manner.

' The oil controlling valve 54 is shown somewhat in detail in Fig. 10 and the steam controlling valve 57 in Fig. 11. These valves may be operated in any suitable manner to secure the required ratio between the amount of oil and steam mixing in the burner 55. For this purpose a shaft 58 is shown extending at the front of the boiler and mounted in suitable bearings 59. This shaft carries pulleys or

cams

60 and 61 above the oil and steam controlling valves respectively.

connections to these valves are similar. lever 62 is fulcrumed at 63 on a bracket 64 projecting upwardl from the oil valve. This lever is pivota 1y connected at 65 to the valve plunger 66 and at its opposite end 67 is connected to a flexible connector 68 ex tending up over and secured to the pulley or cam 60. A counter weight 69 is hung from the point 67 of the lever. Thus, as the shaft 58 is turned the oil controlling valve is opened and closed at a rate and to an extent depending upon' the proportions of the lever 62 and the size of configuration ofthe pulley or cam 60. In a similar manner the lever 70 of the steam controlling valve 57 operates the plunger 71 by the flexible connector 72 extending over the cam or pulley 61. Any required ratio between the amount of the openings of the oil and steam valves to affect the required ratio between the oil and steam mixing in the burner may be obtained by varying the proportion, size, and

thereto. heretofore, one a regulating damper and the other a damper for maintaining the constant differential in pressure at the opening of the regulating damper. As has already been pointed out, these two dampers may be placed anywhere in the passageway for the air and'gases through the combustion chamber. As herein shown one damper is placed at the ash pit door or at the poin-t where the air' is admitted from the atmosphere and the other is shown as placed in the flue or stack leading out from the combustion chamber.

In this case the doors of the ash pit constitute the regulating damper and operate together. They are operated by flexible connectors 74 extending to levers 75 on the shaft 58. Consequently any required or predeterminedratio between the area of the opening at these dampers and the amount of fuel fed tovthe burner is readily and easily obtained.

In order to maintain the substantially constant differential in pressure the ash pit behind the doors or regulating damper 50 is connected by a conduit 76 with a draught regulator 77 of the type already described.-

As in this case the pressure at the outside is atmospheric,the casing of the draught regulator at one side of the blade is open to the atmosphere and at the other side is closed to form a chamber into which a conduit 76 from the ash pit extends.

This draught regulator 77 acting through a device 78 similar to that shown in Fig. 4 and a device 79 similar to that shown in Fig; 3 operates the damper 80 in the flue to'rnaintain the substantially constant differential in pressure at the regulating dampers with the pressure in the ash pit below atmospheric.

The amount of fuel fed to the combustion chamber is shown as regulated to correspond with the load on the boiler by a load regulator 81 mounted at the side of the boiler and of the type already described and shown in Fig. 5. The connector 82 actuated by the load regulator is shown as extendin to and connected to a pulley 83 on the sha t 58..

Thus, as the load on the boiler rises and falls the shaft 58 is rotated in one direction or the other by the load regulator,

Thus far the principles of the invention -way.- The automatic difi'erential ing damper, but the relation between the quantity of air supplied and the amount of fuel fed may also be controlled by varying the differential in pressure at the regulatin damper with the load. In this case the di erential in pressure at the regulating 7 damper will still be a predetermined amount for each load, but it will'not be the same amount for all loads.

As an illustration of this application of the principles of the invention, a construction, such as shown at the right hand side in Fig. 7 and in Fig. 9 may be employed. The construction illustrated for this purpose is that of an oil burning furnace similar in substantially all respects to that already described excepting the control of the draught, regulator. In order that the differential in pressure at the regulating damper may vary with the load means must be provided to affect the blade 84 of the draught regulator shown in Fig. 9 in accordance with the variation in the load. This may be accomplished in a simple manner by providing a cup 85 secured to the blade 84 and by providing a chainj86 secured to and extending from a cam or pulley 87 on the shaft 88 controlled by the load regulator. These parts are so proportioned that for each change in the load as a result of which the load regulator turns the shaft 88 in one "3 direction or the other, an amount of chain is dropped into or lifted out of the cup 85 sufiicient so to ettect the balance of the blade 84 as to vary the differential in pressure maintaining the blade in its central posi- 1 tion and thus to afiect the control of the flue damper 89 accordingly. The basic principles underlying the main feature of A the invention involving the adjustable regulatingdamper such as 14 and the automatic differential pressure controlling damper such as 35 for regulating the flow of air .or gas under pressure through the passageway or conduit are separately illustrated on a larger scale in Figure 12. The construction 1 -3 here illustrated which, as in theother figures, is more or less diagrammatic. in nature, is the same as that illustrated on a small scale in Figure 1. The passageway is formed by the conduit 4 and the flow of ai'TYI or gas is assumed to be in the direction of the arrow 90. The regulating damper 14 is shown as sliding vertically in the conduit and adjustable b any suitable means to vary the area of t e passageway or in other 1'1 words to rovide at this point a variable or adjusta le'constriction of the passage.

ressure controlling damper 35 is shown in t e same conduit 4 and acts on the principles set rate 14 is automatically controlled and in the,

particular form illustrated automatically maintained at a predetermined constant.

The closed box or casin 36 as already described is connected by the feeler pipes 91. to the passageway 4 at opposite sides ofthe point of constriction or damper 14. Thus the pressures at the opposite sides of the damper are conveyed into the, casing 36 to opposite sides of the vertical blade 37 pivoted at 38 and adjustably balanced by the weight 39. As alread pointed out the wei ht 39 is preferably a justed so that the blade 37 will stand in a central or vertical position when the predetermined difi'erem tial in pressure exists. All the parts would be in substantially the position illustrated under these circumstances. Tn this'position it will be noted pressure controlling damper stands midwa of its opened and closed posit-ions and t 'e valve 42 stands 'so as to close the end of

pipes

43 and 44. Thus the water or fluid under pressure fed into the valve casin 92 through the pipe. 93 is cut 0d from. t e pipes 43. and 44. Consequently the piston is held against vertical movement by the water there beneath in the cylinder 46, consequently the damper 35 is maintained in its midway position.

If now for example the pressure is re-' duced at the left hand side of the damper 14 the blade 37 .will swing to the left depressing the piston 42 until the pocket 94 therein extends over the ends of the

pipes

43 and 44 and serves to connect them. This permits the water beneath the piston 45 to escape or be forced out throu h the waste 95 or into the space above t e piston 45 allowing the piston 45 and its connecting rod 47 which, if not suficiently heavy, may be weighted to sink swinging the damper 35 toward its closing position. This 1mmediately acts to restore the required differential in pressure.

If the differential in pressure atthe damper 14 is disturbed so asto swing the plate 37 to the right,- then' the iston'42 is raised until it closes the end 0 the pipe 43 and uncoversthe end of thepipe 44 allowing the water-or fluid under pressure to pass into the pipe 44 and thence beneath the piston 45' forcing the piston up and opening the damper 35. Any water above the piston 45 in the cylinder the vent;95.-

Jlheby-pass 96 shown connecting the pipes 46 may waste out through are I 7 53 or balancing the pressure in the two pipes, 7

and allowing the piston 45 and the connected parts to sink closing the damper 35. This by-pass .and valve are useful, as for ex ample when the device is applied to. a furnace and the furnace is banked whereupon the damper 35 should be closed.

The foregoing constructions are resented for the purpose of illustrating t e broad principles of this invention and it will be understood that the invention is not to be restricted by reasons of the specific applications disclosed nor otherwise than as by the claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is- 1. A combustion controlling system comprising a combustion chamber, a passageway for the air and gases through and includ ing said chamber, a damper in said passageway regulating the flow of air to the combustion chamber, and means for controlling the differential in pressure at the damper whereby the quantityof air flowing past the damper is controlledf.

2. A combustion controlling-system comprising a combustion chamber, a passageway for the air and gases through and including said chamber, a damper in said assage- WayreguIating the flow of air to t e oombustion chamber, and means for controlling the relation between the differential in pres sure at the damper and the area of the damper opening;

3. A combustion controlling system compr1s1ng a combustlon chamber, a passageway for the air and gases through and including said chamber, a damper in said passageway regulating the flow of air to the combustion chamber, and means for automatically correlating the difierential in ressure at. the damper and the area of t e damper opening to secure apredetermined relation between the quantity of air flowing past the damper and the amount of fuel fed.

4. A combustion controlling system comprising a combustion chamber, a passageway for the air and gases through and including said chamber, and means for automatically correlating the difierential in pres T25" sure at a given point in the said passageway with the area of the said passageway at a said given point to secure a predetermined relation between the quantity of air fiowin past that fed to thercom ustion chamber.

5. A combustion controlling system comrising a combustion chamber, a passageway or the air and gases through and including said chamber, a damper, inseid passage- 13c oint and the amount of first way regulating the flow of air to the combustion chamber, and means for maintaining a 6. A combustion controlling system comprising. a combustion chamber, a passageway for the air and gases through and including said chamber, means for feeding fuel to the combustion chamber, a damper in said passageway, means for varying the position of "the damper in accordance with the amount of fuel fed, 'and means for maintaining a substantially constant differential in pres sure at the damper :opening whereby the quantity of'flow through the damper opening is in directproportion to the damper opening alone and is consequently proportional to the amount of fuel fed.

7. A combustion controlling system comprising a combustion chamber, a passageway for the air and gases through and-including said chamber, means for feeding fuel to the combustion chamber, a damper in said passageway, means for varying the position of the damper, and means forficontrolling the differential in pressure at the damper open 'ing whereby the quantity of flow through the damper opening may be regulated to correspond with the amount of fuel fed.

8. A combustion controlling system comprising a combustion chamber, a passageway for the air and gases through and including said chamber, means for feeding fuel to the combustion chamber, a pair of dampers 10- cated at different points in said passageway means for varying the position of one of said dampers to cause the damper opening to vary in accordancefwith the amount of fuel fed, and means, controlled by the differential in pressure effecting the flow through said damper opening, acting to vary the position of the other damper to maintain constant the said difi'erential in pressure.

9. The method of regulating furnaces which consists in controlling a constrictionin the passageway for the air and gases through the furnace and in controllin the differential in pressure at the point 0 constrlctlon.

1 The method of regulating furnaces which consists in coiitrolling a constriction m the passageway for the air and gases through the furnace and in maintaining a substantially constant differential in pressure at the point of constriction.

1 1. The method of regulatin furnaces which consists in'regulating the ow of air to'the furnace by varying a constriction in the passageway for the air and gases throughthefurnace and in maintaining a substantially constant differential in pressure at the point ofv constriction.

ply of air to the furnace .by varying in accordance with the amount of fuel fed a constriction in the passageway for the air and gases through the furnace at a given point, and in maintaining a substantially constant differential in pressure at that point.

14. The method of regulating furnaces which consists in feeding fuel to the furnace, in supplying air to the furnace, in controlling the feeding of the fuel'in accordance with'the work performed, in regulating the supply of air to the furnace by varying a constriction in the passageway for the air and gases through the furnaceat a given point, and in controlling the differential pressure at the point of constriction.

15. The method of regulating furnaces which consists in feeding fuel to the furnace, in supplying air to the furnace, in controlling' the feeding of the fuel in accordance with the work performed, in varying in accordance with the amount of fuel fed a constriction in the passageway for the air and gases through the furnace at a given point, and in maintaining a substantially constant differential in pressure at the point of constriction.

16. The method of re latin furnaces which consists in feeding 5111 to t e furnace,

in supplying air to the furnace, in control- '18. The method of regulating furnaces which consists in regulating the amount of fuel fed to the furnace in accordance with the amount of'work performed, in supply ing air to the ash pit of'the furnace throu h an orifice varying in accordance with t e amount of fuel fed, and in maintaining a substantially constant differential in pressureat the said orifice.

19. The method of regulating the flow of gas under pressure through a passageway 1 'WhlCh consists in controlling a constriction in the passageway for the gas and in controlling the differential in pressure at the point of constriction.

20. The method of regulating the flow of gas under pressure through a passageway which consists in controlling a constriction in the passageway for the gas and ,in main taining a substantially constant differential in pressure at the point of constriction.

21. The method of regulating the flow of gas under pressure through a passageway which consists in regulating the flow of gas by varying a constriction in the passageway and in maintaining a substantially constant differential in pressure at the point of constriction.

22. The method of regulating the flow of gas under. pressure. through a passageway which consists in regulating the flow of gas by varying a constriction in the passageway and in controlling the differential in pressure at the point of constriction.

23. An apparatus of the class described comprising a conduit, a damper in the conduit, means to adjust the position of the damper to vary the area of the conduit at the damper, and means forcontrolling the differential in pressure at the damper whereby the quantity is controlled.

24. An apparatus of the class described comprising a conduit, a damper in said conduit regulating the flow of gas therethrough, and means for controlling the relation between the differential in pressure at the damper and the area of the damper opening.

25. An apparatus of the class described comprising a conduit, a damper in the conduit regulating the flow of gas therethrough, and means for maintaining a substantially constant difierential in pressure at the damper whereby the quantity of gas flowing past the damper is in direct proportion to the damper opening alone.

26. An apparatus of the class described comprising a conduit, a pair of dampers located at different points in the conduit, means for varying the position of one of said dampers to vary the damper opening, and means controlled by the differential in pressure efiecting the fiow through said damper opening, acting to vary the position of'the other damper to maintain constant the said difierential in pressure.

In testimony whereof, it have signed my name to this specification.

DANIEL ADAMS.

of gas flowing past the damper