US2205494A - Combustion control system fob - Google Patents

Description

June 25, 1940. $H|NDLER 2,205,494

COMBUSTION CONTROL SYSTEM FOR STEAM BOILERS Filed Nov. 29, 1935 5 Sheets-Sheet 1 Q J4 65 75 M; 7 77 m 4% 77 I 57 m Z6 a o A 69 156 Z 1-J35 3/ 0 6 6 1:11- 521. 56 n "7/ 54 7e BLOWER WW "*4 A m 66 W '77 U Caz"? Echmd/aw I'HIIII June 25, c SCHINDLER CDMBUSTIQN CONTROL SYSTEM FOR STEAM BOILERS Filed NOV. 29, 1935 3 Sheets-Sheet 2 Car/ 55/72270752" C. SCHINDLER June 25, 1940.

COMBUSTION CONTROL SYSTEM FOR STEAM BOILERS 3 Sheets-Sheet 3 Filed NOV. 29, 1935 rm; Car], 55272270752" Mama;

Patented June 25, 1940 UNITED STATES PATENT OFFICE COIVIBUSTION CONTROL SYSTEM FOR STEAM BOILERS Carl Schindler, Milwaukee, Wis.,

assignor to Application November 29, 1935, Serial No. 52,143

14 Claims.

This invention relates to combustion controls for steam boilers and has as a general object to provide an automatic control of the fuel feed and draft so as to maintain a, predetermined ratio of fuel and air in rates necessary to maintain a predetermined steam pressure or steam flow.

Another object of this invention is to provide a control of the character described which is governed by and is sensitive to slight fluctuations o in steam pressure.

Another object of this invention is to provide a combustion control of the character described which may be set to maintain any uniform steam pressure within a wide range.

Another object of this invention is to provide a control system of the character described which may be used with any kind of fuel and which is applicable to any type of stoker.

A further object of this invention is to provide a control stem of the character described which is easily adapted for use with either a single boiler of any make, type, or size, or a battery of boilers.

With the above and other objects in view which will appearas the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially.

as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

In its general aspects, the invention embodies a control for the fuel feed actuated by fluid pressure, and a draft control preferably in the form of a damper driven by a reversible electric motor controlled by a switch opened and closed by fluid pressure responsive means. Both the fluid pressure for opening and closing the reversing switch and the fluid pressure for actuating the fuel feed control are variable in correspondence with fluctuations in steam pressure.

The. variation or adjustment of the fluid presmeans of an adjustable relief valve in the pres-n sure feed line, and for the control ofthe draft,

the fluid pressure is adjusted by a ratio valvev actuated in response to fluctuations in steamj pressure.

'of the invention constructed according to the best modes so far devised-for the practical ap- 55 plication of theprinclples thereof, and in which;

Figure 1 is a diagrammatic view illustrating one complete embodiment of this invention;

Figure 2 is an enlarged detail view partly in elevation and partly in section of the ratio valves;

Figure 3 illustrates a development of the two cooperating elements of the ratio valve;

Figures 4 and 5 are detail views illustrating slightly modified embodiments of the fuel feed control per se;

Figure 6 is a diagrammatic illustration of the 10 application of this invention where more than one boiler is involved;

Figure 7 is a diagrammatic view illustrating the application of the invention to a natural draft furnace; and 15 Figure 8 is a detail section view through one of the air supply ducts shown in Figure 6 to illustrate one manner of obtaining a pressure differ ential for the control of draft.

Referring now more particularly to the accompanying drawings in which like numerals indicate like parts throughout the several views, the numeral 5 designates generally the fuel feed control mechanism. In the present instance, a coal flring stoker is shown, but it is to be noted 25 that the system is not restricted to this type of fuel'feed.

The fuel feed control mechanism 5 includes a hopper 6, the discharge end of which drops coal onto a shelf 1 from which it is pushed by a slide 8 to be fed to an impeller 9 which throws the coal onto the flre bed. The slide 8 is reciprocated by means of any suitable stoker engine or driving unit (not shown). The stoker engine or other driving unit employed imparts a constant and 85 uniform reciprocation to a driver I 0, and the driver I!) is connected with the slide 8 through a lost motion connection.

The lost motion connection between the driver l0 and the slide 8 comprises levers H and I2 hingedly connected as at l3. Lever I I is attached to the driver l0, and lever I2 is connected through a link M with the slide 8. A book IS on the lever ll is engageable with the free end of the lever 12 to limit movement of the levers apart, but movement of the levers together-is unrestricted except by an adjustable wedge l6 supported on the surface ll of the lever Il' and-with which ftheinner end ofan adjusting screw I 8 carried by 5 The accompanying drawmgs illustrateseveral m' i'ens s scomplete examples of the physical embodiment With the wedge I6 pulled out .all the way, the lost motion in the connection between the driver l0 and the, slide 8 is maximum so that the travel of the slide 8 in proportion to the movement of the driver I9 is slight. Under these circumstances, only a small amount of coal is fed to the impeller 9. As the wedge I6 is moved inwardly between the surface I! and the inner end of the screw I8, the lost motion in the connection between the driver l9 and the slide 8 is reduced thereby making the travel of the slide 8 more nearly equal to the full range of movement of the driver l0 and thus substantially increasing the amount of coal fed to the impeller.

The wedge I6 is automatically moved back and forth to control the fuel feed in response to fluctuations in steam pressure. For this purpose, the wedge is connected through an arm 20 with a piston |9 reciprocating in a cylinder 2|.- The piston I9 is forced outwardly of its cylinder 2| to move thewedge IS in to increase the fuel feed by fluid pressure conducted to the cylinder by a feed line 2|, and a spring 22 acting in opposition to the fluid pressure moves the wedge in the opposite direction.

By varying the effectiveness of the fluid pressure acting on the piston l9, it is thus possible to control the position of the wedge I6, and, as will be hereinafter more fully described, the effectiveness of the fluid pressure is coordinated with fluctuations in the boiler steam pressure.

For the purpose of translating fluctuations in steam pressure into changes in the amount of coal fed, a control unit indicated generally by the numeral 25 is provided. This unit embodies a diaphragm chamber 26 communicated through a steam line 2'! with the steam header of the boiler. By connecting the line 21 with the header rather than with the boiler drum, fluctuation in steam flow as well as pressure are manifested in the diaphragm chamber 26.

Closing the chamber 26 is a diaphragm '28. Movement of the diaphragm 28 in response to fluctuations in pressure within the chamber 26 actuates a switch 29. For this purpose, a beam 39 is fulcrumed on a knife edge 3| through the medium of a head 32 fixed to the lever 38 and bearing against the undersurface of the diaphragm 28. The knife edge 3| is so disposed with respect to the area of the diaphragm 28 that the pressure in the chamber 26 tips the beam 39.

Opposing the pressure on the diaphragm and normally balancing the same to hold the beam in a state of equilibrium is a weight 33 adjustable on the long end of the beam, and a spring 34 attached to the short end of the beam. By adjusting the position of the weight 33 on the beam, the pressure at which a state of equilibrium will be maintained is set.

The switch 29 comprises two stationary contacts 35 and 35' and a movable contactor 36 fixed to the beam 30 and adapted upon rocking of the beam in response to fluctuations in steam pressure to engage either one of the two stationary contacts to close the switch on one side or the other.

The contactor 36 is connected through a conductor 31 to one side of the secondary S of a step-down transformer T, the primary P of which is energized from any suitable external source. The other side of the secondary S is connected through conductor 38 to one pole of a reversible electric motor 39, its other two poles being connected by conductors 40 and 4| to the contacts 35 and 35', respectively. Hence, when the contactor 36 engages the stationary contact 35, the motor runs in one direction and when it engages the stationary contact 35', the motor runs in the opposite direction.

The motor 39 has its drive shaft connected with a gear reduction 42 adapted to slowly move a lever arm 43, one way or the other. The gear connections in the reduction 42 are such that when the contactor 36 engages the contact 35 in response to an increase in steam pressure thus causing operation of the motor 39 in one direction, the lever 43 will be moved upwardly toward a position indicated by the dotted line X, while the operation of the motor 39 in the opposite direction in response to a decrease in steam pressure below the predetermined value causes downward motion of the lever 43 toward a position indicated by the dotted line Y.

The spring 34 which has one end attached to the short end of the beam has its other end fastened to the arm 43. Hence, it will be seen that as the arm 43 moves upwardly in response to an increase in steam pressure, the tension on the spring is proportionally reduced, and when the reduced tension of the spring 34 plus the increased pressure on the diaphragm equals the turning moment of the weight 33, the beam is again brought to a position of balance and the motor 39 stops, leaving the arm 43 in its new position until a further change in steam pressure one way or the other.

The movement of the lever 43 is utilized to vary the effectiveness of the fluid pressure acting upon the piston 9. The fluid pressure may be derived from any suitable source, and in the present instance, a continuously operating constant flow force pump 44 is used. The outlet of the pump is connected to the feed line 2| and its inlet is connected with an oil supply 45.

Also connected with the feed line 2|, is a relief valve 46. The relief valve 46 incorporates a ball 41 yieldingly urged to its seat to close the valve by a spring 48. Oil passing the relief valve is conducted back to the supply 45 through line 49.

The degree of closure of the relief valve determines the effectiveness of the pressure in line 2|, and the degree of closure is proportional to the strength of the spring 48 as the. pump output is constant. Consequently, by determining the strengthof the spring 48, it is possible to govern the eifectiveness of the fluid pressure acting on the fuel feed control. For this purpose, the spring 48 reacts against a plunger 58 connected by means of a link 5| to the lever arm 43 so that the effective force of the spring 48 is dependent upon and controlled by the response of the diaphragm 28 to fluctuations in steam pressure.

With conditions such that the boiler is supplying the desired pressure, for example, one hundred pounds per square inch, the entire fuel feed control system is at rest with the relief valve 46 partially open. Upon a slight increase in steam pressure above one hundred pounds per square inch, the control functions to move the plunger upwardly and thus reduce the effective strength of the spring 48 allowing the relief valve to open farther and reduce the pressure on the piston Hi.

In consequence of the reduction of fluid pressure on the piston i9, the spring 22 acts to move the wedge l6 outwardly and increase the lost motion in the driving connection to the slide 8 which results in a reduction in the amount of coal fed. A decrease in steam pressure effects downward motion of the plunger 50 to increase the effective strength of the spring 48 and produce an opposite result.

Hence, it will be seen that the pressure existing in the feed line 2| and acting upon the piston I8 is dependent upon the compression of the spring 48 and as this compression is determined by the position of the lever 43, it is apparent that the rate of coal feed is directly determined by the steam pressure acting upon the diaphragm and the setting of the weight 33.

Besides controlling the rate of fuel feed, the system also controls the draft or air flow to the furnace so as to at all times maintain the proper proportion of fuel and air for varying load conditions.

This draft or air flow control may be obtained in several different ways, but where the installation involves only a single boiler, an arrangement like that illustrated in Figure 1 has been found desirable. As here shown, a blower 53 open at its sides for the admission of air provides forced draft for combustion. The outlet of the blower is connected to a duct 54 which leads to the combustion chamber of the furnace, and disposed in the duct 54 is a draft control damper 55. This damper 55 is operated by a reversible electric motor 56 having a suitable gear reduction incorporated therein and driving an arm 51 in one direction or the other depending upon the direction of rotation of the motor. The arm 51 is connected through a link 58 with an arm 59 engagable therewith and carried by a beam 64 medially fulcrumed as at 65. With the beam in a horizontal balanced position, the contactor 63 is equispaced from the contacts 6| and 62, but as the beam 64 tips one way or the other, the contactor is engaged with one of the stationary contacts.

The contacts 8| and 62 and the contactor 63 are connected with the motor 56 through con- .ductors 66, 61 and 68, respectively. Current is supplied to the motor by lines 69 which are electrically connected with the conductors 66, 61 and 68 within the motor so that operation of the motor is dependent upon the closure of the switch 68 in one direction or the other.

The electrical connections are such that when the contactor 63 engages the stationary contact 62 in response to a clockwise tipping of the beam 44, the motor 56 is caused to operate in a direction to move the arm 51 clockwise and thus carry the damper 55 toward closed position. Operation of the motor in the opposite direction to produce an opening of the damper is effected by engagement of the movable contactor 63 with the stationary contact 6| in response to a counterclockwise tipping of the beam 64.

The right hand end of the beam 64 has the bell 10 of a gasometer attached thereto to move up and down as the beam 64 rocks on its fulcrum. The lower edge portion of the bell is submerged in a suitable liquid seal II. The opposite end of the beam carries an adjustable weight 12 which together with a spring (3 adjustable by means of a screw 14 balances suction tending to draw the bell 10 down so as to maintain the beam 64 horizontal.

A negative pressure or suction is established within the bell ID by connecting the interior thereof with the inlet of the blower 53. For this purpose, a suction pipe 15 having a flared end 16 is arranged with its mouth adjacent the inlet to the blower so that the blower when in operation draws air through the pipe 15. The opposite end of the pipe is connected to a horizontal passage "formed in the housing of the control unit 25 beneath the gasometer and intersecting the axis of its bell 10. The passage 11 opens to the interior of the control housing and is also communicated with the interior of the gasometer bell 18 through a vertical bore 18 formed in an upstanding central stem projecting up into the gasometer bell. The interior of the control unit housing is open to the atmosphere through a port I9.

Mounted in the vertical bore 18 is a ratio valve indicated generally by the numeral 88. This valve controls communication between the suction pipe 15 and the atmosphere and also between the suction pipe and the interior of the gasometer bell so that by the adjustment of this valve it is possible to control the effect of suction upon the bell I0. With the communication between the suction pipe 15 and the atmosphere unrestricted, the effect of suction upon the gasometer bell I is minimum, while upon complete closure of the communication between the suction pipe 15 and the atmosphere, the effect of suction exerts a maximum pull upon the bell 18.

The specific construction of the ratio valve is best illustrated in Figures 2 and 3. The valve consists of a stationary outer sleeve 8| fixed in the bore 18 and rotatably supporting at its lower end a collar 82. The sleeve 8| has two diametrically opposite square holes 83 and 84 in line with the passage 11. v

Slidably and rotatably fitted in the outer sleeve 8| is an inner sleeve 85. This inner sleeve 85 is closed at its lower end and has an irregularly shaped opening 86 formed in its portion adjacent the square holes 83 and 84. The shape of this opening, which is best illustrated in Figure 3, is such that upon relative longitudinal motion between the inner and outer sleeves, the square hole 83 in the outer sleeve may be completely closed without in anywise obstructing the hole 84, and upon relative rotation of the sleeves both holes 84 may be completely covered or uncovered.

To impart. rotation to the inner sleeve 85, a

'stud 8! is fixed to the same with a roller 88 mounted thereon. The roller 88 is adapted to track on the face of a cam 89 depending from the collar 82, the collar 82 being freely rotatable and being held in an adjusted position by a screw 90', the head of which is accessible from the exterior of the control unit housing.

A tension spring 9| having one end attached to the stud 81 and its other end suitably anchored pulls the inner sleeve in a direction to at all times maintain its roller 88 in contact with the face of the cam 89.

Vertical longitudinal motion is imparted to the inner sleeve 85 by having its lower end attached to the link Vertical motion is thus imparted to the valve inner sleeve 85 whenever the arm 43 is moved one way or the other in response to fluctuations in steam pressure acting upon the diaphragm 28.

The quantity of air required for combustion of a given quantity of coal is constant, but because the ratio of minimum coal feed to maximum coal feed is dependent upon the slope of the wedge I6, the characteristics of the springs 22 and 48, and the furnace characteristics, the ratio of minimum to maximum air flow must be adjustable and this is accomplished by the adjusting screw 90. Actuation of the screw 90 effects rotation of the inner sleeve $5 to open or close the ports formed jointly by the square opening 83 and the wide portion of the opening at, and by the square opening 841 and the narrow portion of the opening 06. These ports are respectively designated A and B.

For purposes of illustration, it may be assumed that to maintain a normal condition at which the boiler supplies steam at one hundred pounds per square inch, the inner sleeve 05 is located at a position substantially half way between its range of rotational adjustment. With this setting, the damper 55 remains stationary as long as normal conditions obtain, but in the event of fluctuations in the load causing fluctuations in steam flow, or in variations of the combustion conditions producing fluctuations in steam pressure, and also changes in the condition of the fire, adjustments are automatically made to the damper 55.

In the event the thickness of the coal bed decreases so that the resistance to the air flow diminishes, the increased rate of air flow through the blower is also manifested in the suction pipe it. As a result, the degree of vacuum under the gasometer bell rises and the bell is drawn downwardly to engage the switch contactor fit with the stationary contact to cause operation of the motor 56 and move the damper toward closed position.

Moving the damper toward closed position reduces the air flow as required and when the air flow is again normal, a balanced condition is reestablished and the switch 60 opens, stopping the motor 58 and leaving the damper in its re-adjusted position. In this manner, changing conditions in the fire per se act to maintain the draft proportionally correct at all times.

In the event of fluctuations in steam pressure above or below the predetermined one hundred pounds per square inch, the resulting response of the diaphragmflil and the movement of the lever arm 33 carries the inner sleeve 85 up or down to open or close the port A as the case may be, which in turn causes a proper response of the gasometer bell W and a closing of the switch in the direction necessary to effect an adjustment of the damper 55 to coordinate the draft conditions with the altered fuel feed.

So that the complete operation of the system may be more clearly understood, assume that the steam pressure has dropped below the predetermined one hundred pounds per square inch. To restore the pressure, a higher rate of fuel feed and a coordinated higher draft is required. The system effects these changes in the following manner.

With a decrease of the steam pressure on the diaphragm 28, the weight 33 tips the beam 30 in a counter-clockwise direction closing the switch 29 to run the motor in the direction required to move the link i downwardly. The motor 30 operates until the arm 43 has moved to a position at which the combined increased tension of the spring 34 plus the decreased steam pressure acting on the diaphragm 20 balances the weight 33. When these forces acting upon the beam 30 balance, the switch 29 is opened and the arm 43 remains in its re-adjusted position holding the link 5| and consequently the plunger 50 down from its central neutral position a distance corresponding to the decrease in steam pressure below the required one hundred pounds per square inch.

As a result of the readjustment of the position of the plunger 50, the strength of the spring 48 is effectively increased. Consequently, the fluid pressure in the line 2i rises to move the wedge 86 in against the action of its spring 22 and thus increase the rate of fuel feed.

concomitantly with the increased rate of fuel feed, the draft is also increased. This is effected by the downward movement of the inner sleeve 05 with the link til. Such downward movement of the sleeve 85 augments the opening of port A bleeding in more air and reducing the degree of vacuum under the gasometer bell I0. Immediately the beam it is unbalanced and tips in acounter-clockwise direction to close the switch 60 and operate the motor 56 in a direction to open the damper 55. As the damper 55 opens, the rate of air flow through the blower and to the combustion chamber of thefurnace is stepped up and as a result of this increased rate of air flow, the negative pressure in the suction pipe 715 and consequently under the gasometer bell rises to the point where it balances the weight 12 and the spring F3 to again restore the beam 64 -to its state of equilibrium.

These readjusted conditions of fuel feed and draft obtain until the steam pressure rises to its predetermined normal when the system again functions to restore the parts to their initial normal positions.

While in the embodiment of the invention so far described the draft has been produced positively by means of a blower, the system is also applicable to installations using a natural draft, and Figure 7 diagrammatically illustrates the invention so applied. In its general aspects the functioning of the system in this embodiment of the invention is identical with that described. The fuel feed control is the same, but the manner in which the gasometer bell is actuated to efiect draft control is different.

The suction pipe 75 in this instance opens to the combustion chamber as at I00 where the suction is proportional to the draft requirements of the fire, and the draft control damper MI is mounted in the flue leading to the chimney, but these changes do not in anywise alter the functioning of the system so that further description of this embodiment of the invention is not required.

The invention is also applicable to a battery of boilers as shown in Figure 6. In this embodiment of the invention there is of course a separate fuel feed control for each boiler and also a separate draft control for each boiler. All of the fuel feed controls are connected to a single feed line 502 which corresponds to the feed line 25' in the embodiment illustrated in Figure 1.

- The control of the pressure on this line I02 by the steam pressure is the same as it is when only a single boiler is being controlled, but besides providing the medium for the operation of the fuel feed control mechanism, specifically the movement of the Wedge I6 back and forth, the pressure on the line I02 is also utilized to coordinate The pistons I05 are connected to the movable element of the ratio valves or the air control units I06 and produce vertical up and down movement thereof in correspondence to fluctuations in steam pressure in the same manner as the link 5| does in the embodiment shown in Figure 1.

The manner in which a pressure differential is obtained for the operation of the gasometer bells is different, however, for it would not do to have all of the draft controls responsive to a single source of pressure differential. Hence, instead of having a suction line leading to the blower, each air duct I01 which leads to the combustion chamber of the furnace and in which the draft control dampers I08 are mounted has a restriction I09 to produce a pressure differential at opposite sides thereof, as best shown in Figure 8. At the pressure side of the restriction I09, the air pressure is high, while at the opposite side of the restriction the pressure is considerably lower and the differential is proportional to rate of flow.

Tapped into the ducts I01 at the pressure sides of their restrictions I09 are tubes H which are communicated with the ports A of the ratio valves, and tapped into the ducts I01 at the opposite sides of the restrictions I09 in line with the low pressure zones are ducts III which take the place of the suction pipe 15. Inasmuch as the pressure differential in the ducts H0 and III is proportional to the rate of air flow through the ducts I01, the conditions are the same as described hereinbefore with the control units I06 functioning to govern the operation of the damper control motor in the same manner as hereinbefore described.

The relationship of the area of the port A to the air flowing in the -main duct 54 which supplies the draft to the combustion chamber is fairly accurate, but in the event it is desired to correct for unavoidable losses of air as it enters port A the face of the cam 89 may be curved as shown or maybe of any other suitable shape. Through the selection of the shape employed for the face of the cam 89, certain degrees of rotation may be imparted to the inner sleeve 85 as it is adjusted vertically so as to correct for entrance losses in the port A and also to allow for more or less excess air at various boiler ratings.

For instance, if normal air flow is desired at one hundred per cent boiler rating, a boiler rating of two hundred per cent might call for twenty-five per cent excess air and this can be easily obtained by shaping the face of the cam 89 to impart rotation to the inner sleeve 85 as it is moved vertically to open the port A, so as to turn the same the necessary amount to increase the air supply.

In the embodiment of the invention illustrated in Figure 1, the wedge I6 is shown with its face engageable by the screw I8 fiat. If found desirable, this shape may be curved as shown in Figure 4 or may be irregular as shown in Figure 5. By the selection of the shape of the wedge IS, the gradient of the change in fuel feed may be properly coordinated with different load conditions.

To illustrate, with a straight faced wedge, as shown in Figure 1, the rate of fuel feed changes uniformly as the fluctuations in steam pressure adjust the wedge. This construction would be suitable where the load conditions vary uniformly, but in the event the load conditions suddenly increase or decrease, it is necessary to likewise alter the rate of fuel feed abruptly and this is possible through the proper selection of shape for the wedge l8.

It may also be found desirable to so mount the wedge l6 as to preclude the transmission of shock to the operating piston, and in Figures 4 and 5 two methods of connecting the wedge with the piston to attain this end are illustrated.

In Figure 4, the wedge I6 is attached to the piston carried arm 20 through a flexible strip H5 and in the construction illustrated in Figure 5, the wedge I6" is connected to the arm 20 by having a spherical head H6 fixed to the base of the wedge l6 riding in a correspondingly shaped hole Ill formed in the arm 20. A stem H8 projects from the spherical head H8 through the arm 20 and has a compression spring H9 coiled thereabout and confined between the arm 20 and a spring seat I 20 carried by the outer end of the stem H8. Both the constructions shown in Figures 4 and 5 provide a non-shock transmitting connection between the wedge and its operating means.

It is to be observed that the fuel feed control is not restricted to a coal firing equipment, and it is to be understood that where fuel is used in the specification and claims, gas, oil, or any other suitable medium as well as coal is intended. For a gas or oil fired boiler, it is only necessary to properly connect the piston IS with the fuel valve so that reciprocation of the piston opens and closes the valve.

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art to which this invention appertains, that this invention provides a completely automatic control system for insuring optimum conditions of combustion for steam boilers.

What I claim as my invention is:

1. In a fuel feed mechanism, a movable member adapted to feed. fuel in amounts dependent upon its distance of travel, a driver for said member having a definite range of travel, a lost motion connection between the driver and said member comprising pivotally connected levers unrestrictedly movable toward each other but held against separation beyond a predetermined distance, and a wedge movable between said levers for determining the lost motion in said connection and thereby regulating the distance of travel of said fuel feed member.

2. In a fuel feed mechanism, a movable member adapted to feed fuel in amounts dependent upon its distance of travel, a driver for said member having a fixed range of motion, a lost motion connection between the driver and said member comprising pivotally connected levers, one of which is connected to the driver and the other to the fuel feed member, said levers being readily movable toward each other but restrained against separation beyond a predetermined distance, a wedge movable between the levers to determine the lost motion in the connection and consequently the distance of travel of the fuel feed member in response to the motion of the driver, and fluid pressure actuated means for controlling the position of the wedge with respect to the levers.

3. In a fuel feed mechanism, a movable member adapted to feed fuel in amounts dependent upon its distance of travel, a driver for said member having a fixed range of motion, a lost motion connection between the driver and said member comprising pivotally connected levers,v

one of which is connected to the driver and the other to the fuel feed member, said levers being readily movable toward each other but restrained against separation beyond a predetermined distance, a wedge movable between the levers to determine the lost motion in the connection and consequently the distance of travel of the fuel feed member in response to the motion of the driver, a spring yieldingly urging the Wedge in one direction, and fluid pressure actuated means operable against the spring for moving the wedge in the opposite direction.

4. In a combustion control system for the furnace ofa steam boiler, a duct communicating with the furnace and through which air moves to provide draft for the furnace, a damper in said duct to control the air flow therethrough, a reversible electric motor for opening and closing the damper, an electric switch for controlling the operation of the motor, normally balanced fluid pressure responsive means for opening and closing said switch, and means responsive to steam pressure for varying the effect of fluid pressure on said means to cause the same to function and close the switch for operation of the motor in one direction or the other as determined'upon a rise or fall in steam pressure.

5. In a combustion control system for the furnace of a steam boiler, a duct communicating with the furnace and adapted to provide draft therefor, a draft damper in said duct, a reversible electric motor for opening and closing the draft damper, a reversing switch for connecting the reversible motor with a source of E. M. F. to cause the same to operate in one direction or the other, fluid pressure operated means for actuating the switch, means for producing fluid pressure proportional to the draft for operating said fluid pressure operated means, and means responsive to steam pressure for controlling the effectiveness of the fluid pressure so that the response of the means controlling the functioning of the reversing switch is dependent upon steam pressure.

6. In a combustion control system for the furnace of a steam boiler, a duct counicating with the furnace and adapted to provide draft therefor, a draft damper in said duct, a reversible electric motor to open and close the damper, a reversing switch for connecting the reversible motor with a source of E, M. F., fluid pressure responsive means for actuating the reversing switch, an air duct connected with said fluid pressure responsive means and with suction producing means so that the effect of suction is transmitted to said fluid pressure responsive means so as to tend to close the reversing switch in one direction, means to normally oppose and balance the force of suction on said fluid pressure responsive means, and valve means operable at the dictation of fluctuations in steam pressure beyond a predetermined value to correspondingly alter the effect of suction on said fluid pressure responsive means whereby the reversing switch is opened and closed in one direction or the other in accordance with fluctuations in steam pressure in excess of predetermined limits.

'7. In a combustion control system for the furnace of a steam boiler, a duct communicating with the furnace and adapted to provide draft therefor, a damper in said duct for controlling the flow of air therethrough, a reversible electric motor for opening and closing the damper, an electric switch for controlling the operation of the motor, suction responsive means for conmember and said rockable means upon rocking of said rockable member for regulating the degree of rocking of said rockable means; spring operated means for moving said projectible means in one direction; and an arm, operable by the pressure of a boiler with which used, for moving said projectible means in the opposite direction.

9. In combination, a fuel feed for feeding fuel to the furnace of a steam boiler in varying amounts per unit of time, fluid pressure actuated means for controlling the fuel feed to thereby regulate the amount of fuel fed per unit of .time, a pump for producing fluid pressure for the operation of said fuel feed control means, draft producing means, fluid pressure operated means for controlling the draft, means responsive to fluid pressure other than that produced by the pump for the operation of said draft control means, and means responsive to steam pressure for governing the efiectiveness of the fluid pressure in each instance.

10. In combination, a fuel feed for feeding fuel to the furnace of a steam boiler in varying amounts per unit of time, fluid pressure actuated means for controlling the fuel feed to thereby regulate the amount of fuel fed per unit of time, draft producing means, fluid pressure actuated means for controlling the draft, means for producing hydraulic'pressure for the operation of the fuel feed control, a duct between said draft control means and said draft producing means providing air pressure for the operation of the draft control, electrically operated instrumentalities for regulating the effectiveness of both. of said pressures, and means responsive to steam pressure for controlling said electrically operated instrumentalities.

ii. In combination, a fuel feed for feeding fuel to the furnace of a steam boiler in varying amounts per unit of time, fluid pressure actuated means for controling the fuel feed so as to regulate the amount of fuel fed per unit of time, draft producing means, fluid pressure actuated means for controlling the draft, said draft control means being actuated in response to the air pressure produced by the draft producing means, separate means for providing fluid pressure for said fuel feed control, electrically operated instrumentalities for simultaneously varying the effectiveness of said two fluid pressures, and means responsive to steam pressure for controlling the functioning of said electrically operated instrumentalities.

12. In combination, constantly operated means for feeding fuel to the furnace of a steam boiler in varying amounts per unit of time, fluid pressure actuated means for controlling said fuel feeding means to effect adjustment of the amount of fuel fed per unit of time, a pump for providing fluid pressure forsaid fuel feed control, electrically driven means for varying the effectiveness of the fluid pressure, and means responsive to steam pressure for governing the functioning of said electrically driven means.

13. In combination with the furnace of a steam boiler, a fuel feed for feeding fuel to the furnace in varying amounts per unit of time, fluid pressure actuated means for controlling the fuel feed so as to regulate the amount of fuel fed per unit of time, a pump for providing fluid pressure for said fuel feed control, control mechanism for varying the effectiveness of said fluid pressure produced by the pump, electrically driven means operable in either of two directions for actuating said control mechanism, and means responsive to steam pressure for controlling the operation of said electrically driven means.

14. In combination, a fuel feed for feeding fuel to the furnace of a steam boiler in varying amounts per unit of time, fluid pressure actuated means for controlling the fuel feed to thereby regulate the amount of fuel fed per unit of time, a pump for providing said fluid pressure, a feed line constantly connecting the pump with the fuel feed control, control mechanism associated with the feed line for determining the effectiveness of the fluid pressure therein, electrically operated instrumentalities for actuating said mechanism, and means responsive to steam pressure for controlling the functioning of said electrically operated instrumentalities.

CARL SCHINDLER.

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