US2176132A - Steam boiler regulator - Google Patents

Description

Patented Oct. 17, 1939 UNITED STATES STEAM BOILER REGULATOR James W. Harrie, Oakland, Calif., asslgnor to Westinghouse Pacific Coast-Brake Company, Emeryville, CaliL, a corporation of California Application January 6, 1938, Serial No. 183,670

11 Claims. (01. 122-448) This invention relates to a furnace control system and particularly to improved means for regulating the supply of fluid fuel, such as gas or oil, to the burner of a furnace for heating a steam boiler.

It has heretofore been proposed to provide means responsive to the pressure of the steam in a boiler for regulating the rate of supply. of fuel to the burner of the furnace for heating the boiler. It has also been proposed to provide means responsive to the level of the water in the boiler and operative on a reduction in this level to supply water to the boiler to increase the level of the water in the boiler, and to also provide means responsive to level of the water in the boiler to restrict the rate of supply of fuel to the furnace to a low value until the water in the boiler is restored to the proper level.

As a result of the reduction in-the rate of supply of fuel to a furnace by operation of the means responsive to the level of the water in a boiler there may be a reduction in the pressure of the steam in the boiler, and the means which is responsive to the pressure of the steam in the boiler will then be operated to permit a rapid supply of fuel to the furnace for heating the boiler.

Accordingly on a subsequent restoration of the water in the boiler to the proper level and the removal of the restriction in the rate of supply of fuel by the means responsive to the level of the water in the boiler, fuel will be supplied to the furnace at a rapid rate.

It has been found that the sudden increase in the rate of supply of fuel to the furnace which occurs at this time may cause fuel to be supplied to the furnace firebox more rapidly than the fuel can be burned with the result that unburned gases will accumulate in the firebox and an explosion may result which may damage the furnace.

It is the principal object of this invention, therefore, to provide an improved furnace control system incorporating means operative on a fall in the level of the water in the boiler heated by the furnace to restrict the rate of supply of fuel to the furnace for heating the boiler, the control system being arranged so that on the restoration of the water in the boiler to the proper level, the increase in the rate of supp'y of fuel to the furnace will take place gradually so that the fuel burns as rapidly as it is supplied with the result that explosive gases will not accumulate in the furnace firebox.

A further object of the invention is to provide an improved furnace control system having a control device normally operative to regulate the rate of supply of fuel to a furnace in response to variations in the pressure of the steam in the boiler heated by the furnace, and having means responsive to the level of the water in the boiler for also causing the control device to vary the rate of supply of fuel to the furnace.

Another object of the invention is to provide a control system of the type described which is arranged so that on a predetermined reduction in the level of the water in a boiler the supply of fuel to the furnace will be reduced to a predetermined slow rate, and so that upon a subsequent predetermined increase in the level of the water'in the boiler, the rate of supply of fuel to the furnace will be gradually increased.

A further object of the invention is to provide a furnace control system incorporating a control device having fuel control means operative on the supply of fluid under pressure to restrict the rate of supply of fuel to the furnace for heating a boiler, means operated in accordance with the pressure of the steam in the boiler for supplying fluid under pressure to said fuel control means, and incorporating means responsive to the level of the water in the boiler for also supplying fluid under pressure to said fuel control means.

Another object of the invention is to provide a furnace control system of the type described and incorporating means responsive to the level of the water in the boiler for controlling the communication through which fluid is released from the fuel control means.

A further object of the invention is to provide a furnace control system of the type described in which fluid may be released from said fuel control means only at a restricted rate, whereby said means can only operate to slowly increase the rate of supply of fuel to the furnace.

Another objectof the invention is to provide a furnace control system of the type described and incorporating means operative on operation of means responsive to the level of the water in the boiler to eflect the supply of fluid under pressure to the fuel control means to thereafter maintain the supply of fluid to said fuel control means and to prevent the release of fluid therefrom without attention from the operator.

A further object of the invention is to provide an improved furnace control system of the type described which employs a standard type of furnace regulating device and which necessitates only a minimum of alterations to thedevice.

Another object of the invention is to provide an improved furnace control system of the type described which employs a standard type of furnace regulating device responsive to the level of the water in the boiler of the furnace to be controlled.

A further object of the invention is to provide an improved furnace control system.

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawing in which,

Fig. 1 is a fragmentary diagrammatic view, partly in section, of a furnace equipped with the control system provided by this invention,

Fig. 2 is an enlarged fragmentary sectional view showing a portion of the apparatus employed in the system shown in Fig. 1, and

Fig. 3 is a fragmentary view, partly in section, showing a modified form of apparatus embodying this invention.

Referring to Fig. 1 of the drawing there is shown therein a furnace l which may be of any well known construction and is provided with a flrebox incorporating a burner, not shown, for heating a boiler, not shown.

The burner of the furnace is supplied with fluid fuel, such as gas or oil, through a supply pipe 3. Air is supplied to the furnace firebox through an opening controlled by a draft door 5, and the burned gases escape from the firebox through a smoke pipe 6, while a damper is provided to regulate the rate of flow of gas through the smoke pipe.

The furnace I is provided with a control device responsive to the pressure of the steam in the boiler for regulating the rate of supply of fuel through the supply pipe 3 to the burner, and for also controlling the draft door and the damper 1. The control device is indicated generally by the reference numeral i0, and is shown and claimed in my application Serial No. 100,311, filed September 11, 1936.

The furnace I also has associated therewith means responsive to the level of the water in the boiler of the furnace for controlling the supply of water to the boiler. This means may be of any suitable well known type and my invention contemplates that any suitable commercial form of device may be employed.

As shown in the drawing there is a pressure generator indicated generally by the reference numeral l2, and a valve device |4 operated on a predetermined increase in fluid pressure to open a communication through a pipe l5 through which water under pressure is supplied to the boiler.

The control system associated with the furnace includes a valve device l8 which controls the rate of supply of fuel through the supply pipe 3 to the burner in the furnace firebox. The valve device I8 is responsive to the pressure of fluid supplied by the pressure generator l2, and is operated on a predetermined increase in this pressure to reduce the rate of flow of fuel through the supply pipe 3 to a predetermined relatively the stem 22 extends is sealed by means of suitable packing, while the stem 22 is connected by means of a chain 23, as shown in Fig. 1 of the drawing, with a lever 24 which is pivotally supported by a pin 26 on a bracket 21 secured to the front of the furnace I.

The lever 24 has secured on the end thereof a weight 28 which yieldingly urges the lever 24 to move in a clockwise direction, as viewedin Fig. 1, while the lever 24 is connected by means of a link 30 with an arm 32 associated with a valve device .33 interposed in the supply pipe 3 at a point in the supply pipe intermediate the valve device I 8 and the burner of the furnace. On movement of the arm 32, the valve 33 operates to vary the rate of supply of fuel through the supply pipe 3 to the burner of the furnace The lever 24 is connected by means of a chain 34 with an arm for operating the draft door 5, while the lever-24 is connected by means'oi' a chain 38 with a lever 31 for operating the damper I. The arm 31 has secured thereto a weight 38 which yieldingly urges the lever 31 to move in a counterclockwise direction, as viewed in Fig. 1 of the drawing, to thereby move the damper 'l to the full open position.

The control device l0 includes valve means indicated generally by the reference numeral 40 for regulating the supply of fluid under pressure to the chamber 4| at the face of the piston 20, and for also regulating the release of fluid under pressure from the chamber 4|.

As shown in the drawing the valve means 40 comprises a body having a chamber 42 therein which is constantly connected by way of a pipe 43 with a source of suitable fluid under pressure,

such as water supplied from a municipal water supply system. The body of the valve means also has a chamber 44 formed therein which is constantly connected with the chamber 4| by way of a passage having a restriction 45 interposed therein. A ball valve is mounted in the chain ber 42 and is adapted to engage a seat surrounding the chamber 44 to cut off communication between the chamber 42 and the chamber 44. A spring 48 is also mounted in the chamber 42 and operates through a suitable spring seat to press the ball valve 46 towards the seated position.

The valve means 40 includes a valve stem 50, the end of which extends into the chamber 44. The end portion of the valve stem 50 has a passage 5| formed therein and opening on the end of the valve stem 50, while the end face of the valve stem 50 has a seat thereon surrounding the passage 5| which is adapted to be engaged by the surface of the ball valve to prevent flow of fluid from the chamber 44 to the passage 5|.

The body of the valve means 40 has a release chamber 53 formed therein through which the valve stem 50 extends, while the opening between the chamber 53 and the chamber 44 through which the valve stem 50 extends is sealed by means of suitable packing. Likewise the opening in the end wall of the chamber 53 through which the valve stem 50 extends is also sealed by means of suitable packing. A coil spring 54 is mounted in the chamber 53 and extends between a flange 55 on the valve stem 50 and the gland associated with the packing surrounding the stem 50, and yieldingly presses the valve stem 50 upwardly, as viewed in the drawing. The passage 5| in the end portion of the valve stem 50 is open to the release chamber 53, while the chamber 53 is constantly connected to a drain pipe 55. The chamber 51 at the upper face of the piston 2|! is constantly connected to a drain by means of a pipe 58.

The control device In incorporates means responsive to the pressure of the steam in the boiler heated by the furnace for regulating the supply and release of fluid under pressure to an from the chamber 4| by the valve means 40 to effect move ment of the piston 28 in accordance with variations in the pressure of the steam in the boiler.

' tends into a socket formed in one end of a push As shown in the drawing, there is amovable abutment in the form of a diaphragm 6|! which is clamped between a cover 6| and a body 62. The diaphragm 68 and the cover 6| cooperate to form at one face of the diaphragm 6| a chamber 64 which is constantly connectedby way of a pipe 65 with the boiler of the furnace The diaphragm has at the other face thereof a spring seat 61, while a coil spring 68 extends between the spring seat 6'! and a spring seat 69 which is adjustablysupported from the body 62 by means of a threaded member "Ill.

The control device l0 includes a lever I2 having one end pivotally supported by means of bal bearings 13 on a bracket 14, while a push rod 15 extends between the lever I2 and a member associated with the'diaphragm 60. The lever 12 carries an adjusting screw 18, the end of which exrod 19, the other end of which has a socket formed therein which receives the end of the valve stem 58.

The lever I2 also carries an adjusting screw 8| which extends into a socket in a spring seat 82, while a coil spring 83 extends between the spring seat 82 and a spring seat 85 which has a projection thereon which extends into a recess in an arm of a bell crank 81, which is pivotally supported on the bracket 14 by means of a pin 88. The other arm of the bell crank 81 carries a roller 90 which engages a rod 9|.

The upper end of the rod 9| is pivotally secured to the upper end of a rod 93, while the lower end of the rod 9| is adjustably secured with respect to the rod 93 by means of an adjusting screw 94 which is carried by a bracket 96 mounted on the rod 93.

The rod 93 is guided by a roller 98 which is supported in suitable manner from a portion of the bracket 14. The rod 93 is secured to an arm 99 carried by the piston stem 22.

In the operation of the control device In, on an increase in the pressure of the steam in the boiler of the furnace I there is a corresponding increase in the pressure of the fluid in the chamber 64 at the face of the diaphragm 60, and this diaphragm is deflected downwardly against the opposing force of the spring 68. This movement of the diaphragm 60 is transmitted through the plunger or push rod 15 and moves the free end of the lever 12 downwardly from its normal position, thereby compressing the spring 83, while the plunger or push rod 19 exerts forcs upon the valve stem 5|! to move it against the spring 54 with the result that the lower end of the valve stem 58 presses against the ball valve 46 to prevent flow of fluid from the chamber 44 to the passage 5| in the valve stem 58, while the ball valve 46 is moved away from its seat against the spring 48 to thereby permit fluid under pressure supplied by way of the pipe 43 to flow to the chamber 44, and thence at a restricted rate through the choke 45 to the chamber 4| at the face of the piston 20.

On the supply of fluid under pressure to the chamber 4| the piston 28 is moved upwardly, as

viewed in Fig. 2 of the drawing, thereby moving the piston stem 22 upwardly, and on this movement of the piston stem 22 force is exerted through they chain 23 upon the lever 24 to move it in a counterclockwise direction, as viewed in Fig. 1 of the drawing, while the link 38 moves the arm 32 of the valve device 33 in a direction to reduce the rate of flow of fuel through the supply pipe 3 to the burner of the furnace.

In addition upon this movement of the lever 24 in a counter-clockwise direction the draft door 5 is permitted to move towards the closed position to reduce the rate of supply of air to the firebox of the furnace, while force is exerted through the chain 36 upon the lever 31 to move the damper 1 towards the closed position.

On upward movement of the piston stem 22 the arm 99 is moved upwardly, thereby moving the rod 93 upwardly with the result that the rod 9| is also moved upwardly. Because of the inclination of the rod 9|, on upward movement thereof force is exerted upon the roller 98 to move the bell crank 81 in a counterclockwise direction, thereby increasing the degree of compression of the spring 83 and increasing the force exerted by the spring 83 upon the lever 12. As a result of the increase in the force exerted by the spring 33 upon the lever I2, the lever 12 is moved in a clockwise direction, thereby reducin the force exerted through the push rod I9 on the valve stem 59.

On this movement of the lever 12 the spring 54 moves the valve stem upwardly, as viewed in Fig. 2 of the drawing, thereby permitting the spring 48 to move the ball valve 46 towards the seated position.

The piston 20 will continue to move upwardly as long as fluid under pressure is supplied to the chamber 4|, and the supply of fluid under pressure to this chamber will continue until the spring 83 has been compressed suificiently to cause movement of the lever 12 to its normal position and thereby permit the valve stem 59 to be moved by the spring 54 far enough to enable the ball valve 46 to be moved to the seated position by spring 48. When the piston 28 has been moved this distance, the valve means 48 will be operated to cut off the supply of fluid under pressure to the chamber 4 I, while the end of the valve stem 50 will be pressed against the face of the ball valve 46 to prevent the escape of fluid from the chamber 4|.

If for any reason there should be a reduction in the pressure in the steam in the boiler of the furnace I there will be a similar reduction in the pressure of the fluid in the chamber 64, and the diaphragm 60 will be moved upwardly, as viewed in Fig. 2 of the drawing, by the spring 68 assisted by the spring 83. On this upward movement of the diaphragm 68 there is a reduction in the force exerted through the push rod 15 upon the lever 12, and the spring 83 thereupon expands and moves the left hand end of the lever 12 upwardly, as viewed in Fig. 2 of the drawing, away from the normal position of the lever. On this movement of the lever 12 there is a reduction in the force exerted through the push rod 19 upon the valve stem 50 and the valve stem 50 is thereupon moved upwardly by the spring 54.

On upward movement of the valve stem 50 the ball valve 46 is pressed to the seated position by the spring 48, if it is not already in the seated position, and upon further upward movement of the valve stem 58, the lower end of the valve stem is moved away from the face of the ball valve 46,

thereby permitting fluid under pressure to flow from the chambers 44 and 4| to the passage 5| in the valve stem. Fluid which flows to the passage 5| flows therefrom to the chamber 53 and thence to the-drain pipe 55. On the release of fluid under pressure from the chamber 4|, the piston 20 and the piston stem 22 are moved downwardly by force exerted thereon by the weights 28 and 30.

Fluid under pressure can only be released from the chamber 4| at a restricted rate because of the restricted flow capacity of the choke 45 with the result that the piston 20 can move downwardly only relatively slowly.

On downward movement of the piston 20, the lever 24 is moved in a clockwise direction, as viewed in Fig. 1 of the drawing, and upon this movement of the lever 24 force is exerted through the link 30 to move the arm 32 in a direction to condition the valve device 33 to increase the rate of flow of fuel through the supply pipe '3 .to the burner of the furnace l.

In addition, upon this movement of the lever 24 force is exerted through the chain 34 to move the draft door 5 to increase the rate of supply of air to the firebox of the furnace, while the weight 38 moves the lever 3'! in a direction to move the damper I towards the full open position.

n downward movement of the piston 20, the arm 99 and the rod 93 carried thereby are moved downwardly, while the rod 9|, which is carried by the rod 93, is similarly moved downwardly.

Because of the inclination of the arm 9|, on downward movement thereof the spring 83 expands and moves the bell crank 81 in a clockwise direction, as viewed in Fig. 2 of the drawing, and maintains the roller 90 in engagement with the rod 9|.

As a result of the expansion of the spring 03 there is reduction in the force exerted thereby upon the lever I2, and through the lever 12 and the push rod I on the diaphragm 60. When the force exerted by the spring 83 upon the diaphragm 60 is reduced to a predetermined amount. depending upon the extent of the reduction in the pressure of the fluid in the chamber 64, and therefore in the boiler of the furnace I, the fluid under pressure present in the chamber 54 will move the diaphragm 60 downwardly, thereby moving the push rod I5 downwardly and causing the lever 12 to be moved in a counterclockwise direction about the balls I3.

On this movement of the lever I2 force is exerted through the push rod 19 upon the valve stem 50 to move the'end of the valve stem towards the ball valve 46.

The piston 20 will continue to move downwardly as long as fluid under pressure is released from the chamber 4|, and the release of fluid under pressure from this chamber will continue until the spring 83 has been permitted to expand sufliciently to enable the lever 12 to be moved to its normal position and thereby cause the valve stem 50 to be moved so that the seat on the end of the valve stem seats upon the ball valve 45.

'When the piston 20 has been moved this distance the valve means 40 will be operated to cut off the release of fluid from the chamber 4|, while the ball valve 45 will be held in the seated position to prevent the supply of fluid under pressure to the chamber 0|. w

The pressure generator I2 comprises a pipe or conduit I05 having one end connected with the boiler of the furnace I at a point therein above the level to which the water in the boiler is normally increased. The other end of the pipe I05 is connected with the boiler at a point therein below the level at which the water in the boiler is normally maintained. The pipe I05 preferably extends at an angle to the vertical so that the pipe has substantial length. As the pipe I05 extends across the water line in the boiler a portion of the pipe is fllled with water and a portion of the pipe is filled with steam, and the relative lengths of these portions will vary with changes in the level of the water in the boiler.

The pressure generator I2 includes a casing I01 which surrounds the pipe I05 and extends throughout most of the length of the pipe I05. The casing I 01 cooperates with the pipe I05 to form a chamber I08 surrounding the pipe I05 and adapted to contain a quantity of volatile liquid, such as alcohol or ether. The casing I01 has mounted thereon a plurality of radially extending heat radiating flns IIO, while a pipe II 2 communicates with the chamber I08 and with the valve devices I4 and I0.

The valve devices I4 and I8 may be of any suitable well known construction and have diaphragms subject to fluid under pressure in chambers to which are connected branches of the pipe II2 leading from the pressure generator I2.

The valve device I4 is arranged so that it is operated on a predetermined increase in the pressure of the fluid supplied thereto to open communication through the pipe I5 to permit water under pressure to flow to the boiler of the furnace I, while the valve device I4 is operated upon a reduction in the pressure of the fluid supplied thereto to close communication through the pipe The valve device I8 is arranged so that on the same predetermined increase in the pressure of the fluid supplied thereto from the pressure generator I2 it is operated to restrict communication through the supply pipe 3, and thereby reduce the rate of supply of fuel to the burner of the furnace I to a low predetermined value which may be just -sufflcient to maintain the fire in the burner. The

valve device I8 is also arranged so that on a reduction in the pressure of the fluid supplied thereto by the pressure generator I2, it will be operated to open communication through the pipe 3 to permit fuel to be supplied to the burner of the furnace I at the rate determined by the valve device 33.

In operation, steam and water from the boiler of the furnace I flows to the pipe I05 of the pressure generator I2, the relative portions of the pipe I 05 fllled with steam and water depending upon the level of the water in the boiler. The steam and water in the pipe I05 causes the volatile liquid in the chamber I08 to be heated, while the extent of the rise in the temperature of this liquid is influenced by the radiation of heat by the fins H0.

The speciflc heat of steam is much greater than that of water at the same temperature with the result that much more heat is transmitted to the fluid in the chamber I08 through the portion of the pipe I05 which contains steam than is transmitted through the portion of the pipe I05 which is filled with water. The extent of increase in the temperature of the fluid in the chamber I08, and therefore the extentoi' the increase in the pressure of this fluid varies withchanges in the relative proportions of the pipe I05 containing steam and water.

'On a reduction in the level of the water in the boiler of the furnace I there is a corresponding reduction in the portion of the pipe I05 which is fllled with water, and a similar increase in the portion of the pipe I05 which is filled with steam. Therefore, on a reduction in the level in the water in the boiler there will be an increase in the temperature and in the pressure of the fluid contained in the chamber I08 of the pressure generator I2.

Likewise, on an increase in the level of the water in the boiler there is a corresponding increase in the portion of the pipe I05 which is filled with water, and a similar reduction in the portion of the pipe I05 which is filled with steam. There will therefore be a corresponding reduction in the pressure and in the temperature of the fluid contained in the chamber I08.

The various parts of the pressure generator l2 and of the valve devices I4 and I8 are arranged and proportioned so that valve device l4 will be closed and the valve device I8 will be opened when the pressure of the fluid present in the chamber I08 of the pressure generator I2 is at that value which is present when the water in the boiler is at substantially the desired level.

On a reduction in the level of the water in the boiler below that which it is desired to maintain in the boiler, the pressure of the fluid in the pressure generator I2 is increased and the valve device I4 is operated to open communication through the pipe I5 to permit water to be supplied to the boiler I, while the valve device I8 is operated to restrict the flow of fuel through the supply pipe 3, and thereby reduce the rate of supply of fuel to the burner of the furnace I.

The reduction in the rate of supply of fuel to the burner of the furnace I prevents possible injury to the boiler of the furnace, which might occur if the furnace continued to be fired heavily at a time when insufficient water was present in the boiler.

As a result of the supply of water to the boiler through the pipe I5 there will be an increase in the level of the water in the boiler and in the pipe I05 of the pressure generator I2, and there will, therefore, be a corresponding reduction in the pressure of the fluid in the chamber I08 of the pressure generator I2.

On this reduction in the pressure of the fluid in the chamber I08 the valve device I4 is operated to cut ofi the further supply of water through the pipe I5 to the boiler I, while the valve device I8 is operated to open communication through the pipe 3 to permit fuel to be supplied to the burner of the furnace I at the rate determined by the valve device 33.

The furnace control system associated with the furnace I includes means responsive to operation of the pressure generator I2 to regulate the control device I0 so that the control device I0 is conditioned to restrict the supply of fuel to the burner of the furnace I to the minimum rate at a time when the valve device I4 is conditioned to permit the supply of water to the boiler of the furnace. This means is also arranged so that on operation of the pressure generator I2 to effect closing of the valve device I4 and opening of the valve device I8, the piston of the control device I0 will slowly return to the position determined by the pressure of the steam in the boiler, and the pistonwill operate the valve device 33 to slowly increase the rate of supply of fuel to the furnace I.

As shown in the drawing there is a valve device indicated generally by .the reference numeral I20 and comprising movable abutments'in the form of diaphragms I2I and I22 which are clamped between body sections I24, I25 and I28.

The diaphragm I2I has secured thereto a valve member I28 having a stem which extends through a bore in the body section I24, and has a seat on the end thereof which is adapted to seat upon a seating face formed on the body I24 to control communication between a chamber I28 to which is connected a branch of the pipe 43, and a chamber I30 which is constantly connected by way of a pipe I32 with the chamber 4| at the face of the piston 20.

A coil spring I33 extends between the body I24 and the head of the valve member I28 and yieldingly presses the valve member to the right, as viewed in Fig. 2 of the drawing, to thereby normally hold the valve in the open position. I

The opening through which the stem of the valve member I28 extends is sealed by means of suitable packing indicated at I34 and held in position by means .of a pack nut I35,

The diaphragm I22 has secured thereto a plunger I38 having a stem which extends through an opening which is sealed by means of packing I39 which is held in position by means of a pack nut I40.

The end of the plunger I38 extends into a chamber I42 to which is connected the drain pipe 56 leading from the valve means 40, while the body section I26 has formed therein a chamber I44 in which is mounted a valve I48 which is yieldingly urged to the seated position by means of a spring I41. The end of the valve I is adapted to be engaged by the end of the plunger I38, while the chamber I44 has connected thereto a suitable drain pipe I49.

The chamber I50 between the diaphragms I2I and I22 is constantly connected by way of a pipe I52 with the supply pipe 3 at a point in the supply pipe intermediate the valve device I8 and the valve device 33.

In operation when the valve device I8 is conditioned to permit flow of fuel under pressure through the supply pipe 3 at a rapid rate, fuel under pressure is present in the portion of the supply pipe 3 intermediate the valve device I8 and the valve device 33. This fuel under pressure flows from the supply pipe 3 by way of the pipe I52 to the chamber I50 of the valve device I20, and exerts force on the diaphragm I2I to maintain the valve I28 seated, and on the diaphragm I22 to hold the valve I46 in the open position.

The supply and release of fluid under pressure to and from the chamber 4| at the face of the piston 20 of the control device I0 is then regulated in the normal manner by the valve means 40.

During operation of the control device I0 to increase or decrease the rate of supply of fuel to the burner of the furnace I as the result of changes in the pressure of the steam in the boiler of the furnace I fuel under pressure will be present in the portion of the supply pipe 3 with which the pipe I52 communicates, and the valve device I20 will operate to cut off the supply of fluid under pressure to the chamber 4| through the pipe I32, while valve device I20 will permit the release of fluid under pressure from the chamber M by the operation of the valve means 40.

On a reduction in the level of the water in the boiler of the furnace I there will be an increase in the pressure of the fluid in the chamber I of the pressure generator I2, and in the pressure of the fluid supplied from the premure generator to the valve devices I4 and I8.

On an increase in the pressure of the fluid supplied by the pressure generator I2 to the valve device I4, this valve device is operated to open communication through the pipe I to permit the supply of water to the boiler of the furnace I.

Likewise, on the increase in the pressure of the fluid supplied by the pressure generator I2 to the valve device I8, this valve device is operated to restrict the rate of flow of fuel through the supply pipe 3 to the burner of the furnace I. This prevents injury to the boiler as a result of overheating of a boiler at a time when the water therein is below the desired level.

On the restriction in the rate of flow of fuel under pressure through the supply pipe 3 by the valve device I8 there is a reduction in the pressure of the fuel in the portion of the supply pipe 3 intermediate the valve device I0 and the valve device 33, and a corresponding reduction in the pressure of the fluid in the chamber I50 of the valve device I20,

On this reduction in the pressure of the fluid in the chamber I50 of the valve device I 20, the force exerted thereby upon the diaphragm I2I is insufficient tomaintain this diaphragm against the opposing force of the spring I33 with the result that the valve I28 is moved by the spring I33 so as to open communication from the chamber I to the chamber I30, and thereby permit fluid under pressure supplied through the pipe 43 to flow to the chamber I30, and thence by way of the pipe I32 to the chamber 4| at the face of the piston 20.

Similarly, on the reduction in the pressure of the fluid in the chamber I50 there is a reduction in the force exerted thereby on the diaphragm I22 with the result that the spring I41 moves the valve I46 to the seated position to cut off flow through the drain pipe 56, and thereby prevent the release of fluid from the chamber M by operation of the valve means 40.

As a result of the supply of fluid under pressure through the pipe I32 to the chamber 4| and of the closing of the drain pipe 56, the piston 20 will be moved upwardly in the bore in which it was mounted, and will operate the valve device 33 to reduce the rate of supply of fuel through the supply pipe 3, and to also efiect movement of\ the draft door 5 and the damper towards the closed position.

As a result of this supply of fluid under pressure to the chamber 4I the piston 20 will be moved to the extreme upper end of its range of movement, and will move the valve device 33 to limit the supply of fuel through the supply pipe 3 to the minimum rate permitted by the valvev device 33.

The valve device 33 is arranged so that the minimum rate of flow permitted by this valve device is somewhat greater than the rate of flow permitted by the valve device I0. Accordingly, the pressure of the fuel in theportion of the supply pipe 3 intermediate the valve devices I0 and 33 will not build up after the valve device 33 has been conditioned to restrict the rate of flow of fluid through the supply pipe 3, and the valve device I 20 will not be operated to cut off the supply of fluid under pressure to the chamber H and to permit the release of fluid therefrom.

As a result, therefore, as long as the valve device I8 is conditioned to restrict the rate of supply of fuel through the supply pipe 3, the piston of the control device I0 will be held in its upper position in which it conditions the valve device 5 33 to restrict the rate of supply of-fuel through the pipe 3.

On upward movement of the piston 20 the draft door 5 and the damper I are moved towards their closed positions. In addition, the rods 03 and 9| are moved upwardly and the bell crank 81 is operated to compress the spring 03 to thereby increase the force exerted by this spring upon the lever I2. The free end of the lever I2, therefore, will be moved upwardly and will permit the 15 spring 54 to move the valve stem 50 away from the ball valve 46. Fluid from the chamber 4I may then flow to the passage 5| in the valve stem and thence to the drain pipe 56. However, flow of fluid through the drain pipe 56 is prevented 80 at this time by the valve device I 20.

On a subsequent increase in the level of the water in the boiler of the furnace I, which will be occasioned by the supply of water thereto through the pipe I5, the pressure supplied by the pressure generator I2 to the valve devices I4 and I8 will be reduced, and the valve device I4 will be operated to cut offthe further supply of water to the boiler of, the furnace I.

Likewise, on the reduction in the pressure of the fluid supplied by the pressure generator I2 to the valve device I0, the valve device I8 will be conditioned to permit the rapid supply of fuel through the supply pipe 3, but as the valve device 33 is conditioned to restrict the rate of supply of 35 fuel to the supply pipe 3 at this time, fuel will only be supplied to the burner of the furnace I at the rate determined by the valve device 33. This rate is sufficient to maintain the flre in the burner of the furnace I, but is not a substantial increase over the rate at which fuel is permitted to be supplied through the valve device I8.

When the valve device I8 is operated to permit the rapid supply of fuel through the supply pipe 3 fuel flows to the portion of the supply pipe 3 intermediate the valve devices I8 and 33, and increases the pressure' of the fuel present therein. On this increase in the pressure of the fuel in this portion of the supply pipe 3 there is a corresponding increase in the pressure of the fluid in the chamber I of the valve device I20, and the diaphragm I2I is operated to move the valve I28 to the seated position to thereby cut off the further supply of fluid from the pipe 43 to the chamber H of the control device I0, while the diaphragm I22 is operated to move the valve I46 to the open position against the spring I41 to permit communication through the drain pipe 56.

On this operation-of the valve device I20, fluid is released from the chamber H at a restricted rate through the choke 45, and thence through the passage 5I in the valve stem 50 to the chamber 53, from which it flows by way of the passage and pipe 56 to the chamber I42 in the valve device I20, and thence past the valve I46 to the cligmber I 44 and to a drain by way of the pipe On downward movement of a piston 20 the lever 24 is moved in a clockwise direction, as viewed in Fig. 1 of the drawing, by the weight 20, while force is exerted through the link 30 to move the arm or lever 32 of the valve device 33 in the direction to condition the valve device 33 to increase the rate of flow 01 fuel permitted through the supply pipe 3. In addition, as a 75 result of movement of the lever 24 the draft door 5 is moved towards the open position, while the damper 1 is similarly moved in the direction to open communication through the smoke pipe 6.

As fluid under pressure is released from the chamber H at the face of the piston 28 only at a restricted rate determined by the choke 45, downward movement of the piston 28 will take place only at a slow rate, and there will be. a relatively slow increase in the rate at which fuel is permitted to be supplied to the supply pipe 3 by the valve device 33. Accordingly the fuel which is supplied to the burner of the furnace I can be burned as rapidly as it is supplied, and there will be no increase or accumulation of explosive gases in the firebox of the furnace I.

As a result therefore, there can be no explosion,

of these gases with consequent injury to the furnace I.

On downward movement of the piston 26 the arm 99 and the rods 93 and 9I are moved downwardly, thereby decreasing the degree of compression of the spring 83 with resultant movement of the lever 12 in the direction to cause movement of the valve stem towards the ball valve 46.

The piston 20 will be moved downwardly until it has been moved to a position determined by the pressure of the fluid in the boiler of the furnace I, and when it has been moved to this position the spring 83 will have been expanded sufficiently to permit the lever 12 to be moved to its normal position to cause the end of the valve stem 50 to seat upon the ball valve 46 to cut off the further release of fluid under pressure from the chamber 4I.

The control device II) will operate thereafter to vary the rate of supply of fuel through the supply pipe 3 in response to variations in the pressure of the steam in the boiler heated by the furnace I.

From the foregoing it will be seen that the control system provided by this invention provides means automatically operative on a reduction in the level of the water in the boiler of a furnace to supply water to the boiler, and to also reduce the rate of supply of fuel to the furnace for heating the boiler until the waterin the boiler is restored to the desired level. This prevents injury to the boiler which might result if the furnace were fired heavily at a time when the water in the boiler was below the desired level.

It will be seen also that the control system provided by this invention is arranged so that on the restoration of the water in the boiler to the proper level, the increase in the supplyof fuel to the furnace takes place gradually so that the fuel can burn as rapidly as it is supplied to the furnace firebox. This prevents the accumulation of unburned gases in the furnace firebox, and eliminates the possibility of injury to the furnace as a result of an explosion of these gases,

In addition, it will be seen that the control system provided by this invention employs a standard type of furnace control device, and that only a minimum of changes are required in the device. Furthermore, the system contemplates the use of a standard type of a device responsive to the level of the water in the boiler, and does not require any changes in the construction and operation of this device.

In Fig. 3 of the drawing there is shown a portion of a modified form of apparatus which may be employed in the control system provided by this invention. The system of which the apparatus shown in Fig. 3 forms a part is the same as the system shown in Fig. 1 except as hereinafter pointed out in detail. The system ofwhich the apparatus shown in Fig. 3 forms a part does not employ a valve device I26 as is employed in the system shown in Fig. 1.

The apparatus shown in Fig. 3 includes a control device Illa which is similar to the control device I8 shown in Figs. 1 and 2 of the drawing. The control device Illa has a lever 12a which carries a hollow adjusting screw 180. which extends into a socket in the end of the push rod 18 for operating the valve means 48.

The control device IIIa has associated therewith an actuating device I for effecting operation of the valve means 40 of the control device. The actuating device I68 comprises a body I 6I which is supported on the body 62 of the control device IIIa. A flexible diaphragm I63 is clamped between the body I6I and a cover I64, and has at the face thereof a chamber I65 which is constantly connected byway of a pipe I52a with the fuel supply pipe 3 at a point intermediate a valve device I8 and the valve device 33.

The diaphragm I63 has at the other face there- 'of a plunger I66 having a large head which engages the face of the diaphragm. The stem of the plunger I66 extends through an opening in the body I6I and engages a lever I68 which is pivotally supported by means of a pin I69 on a bracket carried by the body I6I. The other end of the lever I68 is engaged by a spring seat I10, while a compression spring I12 extends between the spring seat I10 and the body I6I so as to yieldingly urge the lever I68 to move in a clockwise direction about the pin I69.

The portion of the lever I68 on the side of the pin I69 adjacent the spring I12 is engaged by one end of a push rod I14, the other end of which has a socket formed therein into which extends one end of a push pin I15 which extends through the opening in the hollow adjusting screw 18a and into the socket in the end of the push rod The actuating device I60 has associated therewith latch mechanism comprising a latch element I15 which is pivotally supported on the body I6I by means of a pin I16. The latch element I15 has a projection I18 thereon which at certain times extends beneath the end of the lever I68 to prevent movement of the lever I68 by the diaphragm I63.

The latch element I15 also has formed thereon an arm I19, while a spring I80 extends between the arm I19 and the body I6I and yieldingly urges the element I15 in a counterclockwise direction, as viewed in Fig. 3 of the drawing. When the lever I68 is in the position in which it is shown in Fig. 3 of the drawing, the end of the projection I18 on the element I15 is pressed against the end of the lever I68, but does not interfere with movement of the lever I68 by the diaphragm I63 or by the spring I12. However, upon upward movement of the left hand end of the lever I 68, the element I15 is moved by the spring I88 so that the projection I18 extends beneath the end of the lever I68 and prevents movement of the lever I68 by the diaphragm I63.

The various parts of the actuating device are arranged and proportioned so that when fluid is present in the chamber I65 at the pressure present in the portion of the supply pipe 8 intermediate the valve device I8 and the valve device 33 when the valve device I8 permits flow of fuel through the supply pipe 3 at a rapid rate, the diaphragm I63 holds the plunger I66 in engagement with stops formed on the body I6I, and thereby holds the lever I68 in a position in which the end of the lever I68 is engaged by the projection I16 on the latch element I15.

In this position of the lever I66 no force is exerted by the spring I12 on the plunger I14, and through this plunger on the valve stem 56 of the valve means 40 of the control device I6.

At this time the lever 12a of the control device Ia may move the stem 19 and permit it to be moved without interference by the actuating device I60. Accordingly the control device Illa will be operated in the usual manner in response to variations in the pressure of the steam in the boiler with which it is associated.

If the water in the boiler should fall below the desired level, the pressure generator I2 will operate as described in detail above to supply fluid at an increased pressure to the valve devices I4 and I8 to condition the valve device I4 to permit the supply of water to the boiler, and to condition the valve device I8 to restrict the rate of supply of fuel through the supply pipe 3 to the furnace l.

After the valve device I6 is operated to restrict the rate of supply of fuel to the supply Pip 3 there is a reduction in the pressure of the fuel in the portion of the supply pipe 3 with which the pipe |52a communicates, and there is a corresponding reduction in the pressure of the fluid present in the chamber I65 of the actuating device I60. On this reduction in the pressure of the fluid in the chamber I65 the force exerted by the fluid on the diaphragm I63 is insufllcient to maintain the diaphragm against the opposing force of the spring I12, and, as a result, the lever I68 is pivoted about the pin I69 until it is moved to a point in which the end of the lever is no longer engaged by the projection I16 on the latch element I65.

0n movement of the lever I66 to this point the spring I60 moves the latch element I15 in a counterclockwise direction about the pin I16 so that the projection I18 extends beneath the end of the lever I68 and prevents return movement of the lever I66 by the diaphragm I63.

On movement of the lever I66 by the spring I12 force is exerted on the plunger I 14 to move it downwardly and this force is transmitted through the push pin I15 to the plunger 18 and moves the plunger away from the adjusting screw 18a.

0?: this downward movement of the plunger 19 force is exerted to move the valve stem 50 downwardly against the spring 54 with the result that the valve stem presses against the face of the ball valve 46 so as to prevent the release of fluid under pressure from the. chamber H at the face of the piston 20, while the ball valve 46 is moved away from its seat to permit fluid under pressure supplied through the pipe 43 to flow at a restricted rate through the choke 45 to the chamber 4I. As a result of the flow of fluid under pressure to the chamber 4 I, the piston 20 will move upwardly at a slow rate, and on this movement of the piston the valve device 33 will be conditioned to restrict the rate of supply of fuel through the supply pipe 3, while the draft door and the damper 1 will be moved to their closed positions.

In addition, upon upward movement of the piston 20, the arm 99 and rod 93 will be moved upwardly, thereby moving the rod 6| in a direc-' tion to effect movement of the bell crank 61 to increase the degree of compression of the spring 63. On this compression of the spring 63 the lever 12a is moved so that the hollow adjusting screw 18a is spaced somewhat farther from the end of the plunger 19. The. position in which the plunger 19 is held by the actuating device I60 is not affected by this movement of the lever 12a.

The piston 20 will continue to move upwardly, therefore, until it has been moved to the extreme upper end of its range of movement, in which position it conditions the valve device 33 to reduce the rate of supply of fuel through the supply pipe to the minimum rate permitted by this valve device.

0n subsequent operation of the pressure generator I2 to reduce the pressure of the fluid supplied to the valve devices l4 and I8, the valve device I4 is operated to cut off the supply of water to the boiler of the furnace I while the valve device I8 is operated to again permit flow of fuel through the supply pipe 3 at a rapid rate. On this opening movement of valve device l8, however, the valve device 33 is conditioned to restrict the rate of supply of fuel through the supply pipe 3 with the result that there is not an immediate rapid increase in the rate of supply of fuel to the flre box of the furnace I.

On opening movement of the valve device I8 fuel under pressure flows at a rapid rate to the portion of the supply pipe 3 with which the pipe I524: communicates, and increases the pressure of the fuel in this portion of the supply pipe and in the chamber I65 of the actuating device I60.

0n the increase in the pressure of the fluid in the chamber I65 there is an increase in the force exerted by this fluid upon the diaphragm I63 and through the diaphragm upon the lever I68. At this time, however, the projection I18 on the latch element I68 extends beneath the end of the lever I66 and prevents movement of the lever I66 by'the diaphragm I63.

Accordingly, the lever I66 will not be moved against the spring I12, but will remain in the position in which the plunger, I14 presses upon the plunger 19 and causes the valve stem 50 of the valve means 40 to be held in the position to permit the supply of fluid under pressure to the chamber 4I.

As a result, therefore, the control device I0 will not be operated to change the adjustment of the valve device 33 to increase the rate of supply of fuel to the furnace I until the latch element I15 device I60 has been released by an operator.

Since the rate of supply of fuel to the furnace continues to be restricted by the valve device 33,

ator that the furnace requires attention.

If the operator finds everything in proper con dit on he can restore the furnace control system to its normal operation by moving the latch element I15 against the spring I80, thereby releasing the lever I 68.

Upon the release of the ..lever plunger I66 into engagement with the stops or projections on the body I6I while the lever I68 is pivoted about the pin I 69 and is moved against the opposing forcev of the spring I12.

As a result of this movement of the lever force is no longer exerted by the spring through the plunger ill upon the plunger 19, and on the release of force exerted upon the plunger 19, the spring 54 expands and moves the valve stem 50 upwardly until the end of the plunger 19 engages the hollow adjusting screw 180..

As a result of this movement of the valve stem 50, the end of the valve stem is moved away from the face of the ball valve 46 to thereby permit fluid under pressure to flow' from the chamber 4| to the passage 5| and thence to the drain pipe 56, while the ball valve 46 is moved to the seated position to cut off the further supply of fluid under pressure from the pipe 43 to the chamber 4|.

Fluid under pressure will be released from the chamber 4| only at a restricted rate determined by the choke 45 and the piston 20 willbe moved downwardly only at a slow rate. Accordingly the valve device 33 will be slowly conditioned to increase the rate of supply of fuel to the furnace I, and the fuel can be burned as rapidly as it is supplied.

On downward movement of the piston 20 the arm 99 and the rods 93 and 9| are moved downwardly, while the bell crank 91 is permitted to move in a direction to permit the spring 83 to expand, thereby reducing the amount of force exerted by the spring 99 on the lever 12a.

The piston 20 will continue to move downwardly until it is moved toa position in accordance with the pressure of the steam in the boiler of the furnace l, whereupon the lever 12a will be moved downwardly far enough so that the hollow adjusting screw 18a will press upon the plunger I9 and operate to the plunger to move the valve stem 50 against the spring 54 until the end of the valve stem presses against the ball valve 46 to cut off the further release of fluid under pressure from the chamber 4|.

The control system shown in Fig'. 3 of the drawing prevents injury to the boiler in the event of failure of the water supply system to supply water to the boiler when the valve device I is opened. At the time that the valve device I4 is opened the valve device I8 is operated to restrict the rate of supply of fuel to the furnace. Because of this restriction in the supply of fuel to the furnace there will be a decrease in the temperature of the steam and water in the boiler of the furnace. As a result of this reduction in the temperature of the steam and water in the boiler, if it continues for an unusual period of time, the pressure of the fluid present in chamber I08 of the pressure generator [2 will decrease, and it may be decreased to such a value as to effect movement of the valve device 14 to the closed position and the valve device l8 to the open position, even though the water in the boiler remains below the desired level.

If at a time when the water in the boiler is below the intended level the valve device 18 is operated to again permit the rapid supply of fuel to the furnace I, overheating and injury to the boiler may result.

The system shown in Fig. 3 operates to prevent an increase in the rate of supply of fuel to the furnace subsequent to a restriction in the rate of supply of fuel to the furnace as a result of a reduction in the level of the water in the boiler below the desired point until the operator restores the control system to its normal method of operation. Before the operator releases the latch element I15 he should ascertain whether there is sufficient water in the boiler, and if there is not he should not condition the system to increase the rate of supply of fuel to the furnace until the water in the boiler is restored to the proper level.

It will be seen that the control system shown in Fig. 3 of the drawing makes use of a standard type of furnace control device and requires only a minimum of changes in this device.

It will be seen also the control system shown in Fig. 3 of the drawing is simple and positive in operation and prevents possible serious injuries to a boiler.

While two embodimen s of the improved steam boiler regulator provided by this invention have been illustrated and described in detail, it is to be understood that the invention is not limited to these details of construction, and that-numerous changes and modifications may be made without departing from the scope of the following claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a control system for a furnace having a boiler and having a burner for heating said boiler, a communication through which fluid fuel may be supplied under pressure to said burner, means operated on the supply of fluid under pressure to a chamber to reduce the rate of flow of fuel through said communication and operated on the release of fluid from said chamber to increase the rate of flow of fuel through said communication, said means being operative to vary the rate of flow of fuel through said communication in accordance with the rate of supply and release of fluid to and from said chamber, means responsive to a heat condition in said boiler for supplying fluid under pressure to said chamber and for also controlling a release passage through which fluid may be released from said chamber only at a restricted rate, and means responsive to the level of the water in said boiler for also supplying fluid to said chamber and for controlling said release passage.

2. In a control system for a furnace having a boiler and having a burner for heating said boiler, a communication through which fluid fuel may be supplied under pressure to said burner, means operated on the supply of fluid under pressure to a chamber to reduce the rate of flow of fuel through said communication, means responsive to a heat condition in said boiler for supplying fluid to said chamber, a valve device for also controlling the rate of flow of fuel through said communication, means responsive to the level of the water in said boiler for operating said valve device, and means responsive to the pressure of the fuel in said communication at a point intermediate the valve device and the burner for also' supplying fluid under pressure to said chamber.

3. In a control system for a furnace having a boiler and having a burner for heating said boiler, a communication through which fluid fuel may be supplied under pressure to said burner, means operated on the supply of fluid under pressure to a chamber to reduce the rate of supply of fuel through said communication and operated on the release of fluid from said chamber to increase the rate of flow of fuel through said communication, means responsive to a heat condition in said boiler for supplying fluid to said chamber, a valve device for also controlling the rate of flow of fuel through said communication, means responsive to the level of the water in said boiler for operating said valve device, and means responsive to the pressure of the fuel in said communication at a point intermediate the valve device and the burner for also supplying fluid to said chamber and for controlling the release of fluid from said chamber.

4. In a control system for a furnace having a boiler and having a burner for heating said boiler, a communication through which fluid fuel may be supplied to said burner, means operated on the supply of fluid under pressure to a chamber to restrict the rate of flow of fuel through said communication, said means being operated on the release of fluid from said chamber to permit an increase in the rate of flow of fuel through said communication, valve means controlling the supply of fluid under pressure to said chamber, and also controlling a communication through which fluid may be released from said chamber only at a restricted rate, means responsive to a heat condition in said boiler for operating said valve means, and means responsive to the level of the water in said boiler for also operating said valve means.

5. In a control system for a furnace having a boiler and having a burner for heating said boiler, a communication through which fluid fuel may be supplied to said burner, means operated on the supply of fluid under pressure to a chamber to restrict the rate of flow of fuel through said communication and operated on the release of fluid from said chamber to increase the rate of flow of fuel through said communication in accordance with the rate at which fluid is released from said chamber, means responsive to a heat condition in the boiler for supplying and releasing fluid to and from said chamber, a movable member having a normal position in which it permits release of fluid from said chamber only at a restricted rate and being movable therefrom to an operating position in which it effects the supply of fluid to said chamber and also prevents the release of fluid from said chamber, means responsive to the level of the water in the boiler for effecting movement of said member from its normal position to its operating position, an element operative on movement of said member to its operating position to prevent movement thereof to its normal position and manually controlled means for releasing said element to permit said member to be moved to its normal position.

6. In a control system for a furnace having a boiler and having a burner for heating said boiler, a communication through which fluid fuel may be supplied under pressure to said burner, a control device having a chamber therein, means operative on the supply of fluid to said chamber for effecting a decrease in the rate of supply of fuel through said communication, said means being operative on the release of fluid from said chamber to effect an increase in the rate of supply of fuel through said communication in accordance with the rate of release of fluid from said chamber, and means responsive to the level of the water in said boiler for controlling the supply and release of fluid under pressure to and from said chamber, said means being operative on a predetermined reduction in the level of the water in the boiler to effect the supply of fluid to said chamber and thereby eifect a reduction in the rate of supply of fuel to said burner, said means being operative on a predetermined increase in the level of the water in said boiler to gradually release fluid from said chamber and thereby effect a gradual increase in the rate of supply of fuel to said burner.

7. In a control system for a furnace having a boiler and having a burner for heating said boiler, a communication through which fluid fuel may be supplied to said burner, a control device having a chamber to which fluid under pressure may be supplied and from which fluid under pressure may be released, means operative in accordancewith therate of change in the quantity of fluid in said chamber for varying the rate of supply of fuel through said communication ,means responsive toaheat condition in said boiler for supplying fluid to and for releasing fluid from said chamber, and means operative on a predetermined reduction in the level of the water in said boiler to effect a sudden change in the quantity of fluid in said chamber which will cause a reduction in the rate of flow of fuel through said communication, said last named means being operative on a predetermined rise in the level of the water in said boiler to eflect a gradual change in the quantity of fluid in said chamber which will cause a gradual increase in the rate of flow of fuel through said communication.

8. In a control system for a furnace having a boiler and having a burner for heating said boiler, a communication through which fluid fuel under pressure may be supplied to said burner, valve means operative on a predetermined change in the quantity of fluid in a chamber to effect a reduction in the rate of supply of fuel through said communication, a valve device for also controlling the rate of flow of fuel through said communication, means responsive to the level of the water in the boiler for controlling said valve device, and means subject to and operated on a predetermined reduction in the pressure of the fuel in said communication at a point intermediate the valve device and the burner for effecting said predetermined change in the quantity of the fluid in said chamber.

9. In a control system for a furnace having a boiler and having a burner for heating said boiler, a communication through which fluid fuel under pressure may be supplied to said burner, valve means operative on one predetermined change in the quantity of liquid in a chamber to effect a reduction in the rate of supply of fuel through said communication and operative on the opposite predetermined change in the quantity of fluid in said chamber to effect an increase in the rate of supply of fuel through said communication, a valve device for also controlling the rate of flow of fuel through said communication at a point therein on the side of said valve means remote from the burner, and means subject to and operated on a predetermined reduction in the pressure of the fuel in said communication at a point therein intermediate the valve device and the valve means for eflecting said one change in the quantity of fluid in said chamber, said last named means being operative on a predetermined increase in the pressure of the fuel in said communication at said point therein intermediate the valve device and the valve means for effecting said opposite change in the quantity of fluid in said chamber.

10. In a control system for a furnace having a boiler and having a burner for heating said boiler, a communication through which fluid fuel under pressure may be supplied to said burner, valve means for controlling the supply of fuel through said communication, a valve device for also controlling the supply of fuel through said communication, means responsive to the level of the water in said boiler for controlling said valve 7 device, and means responsive to the pressure of the fuel in said communication at a point therein intermediate the valve device and the burner for controlling said valve means.

11. In a control system for a furnace having a boiler and having a burner for heating said boiler, a communication through which fluid fuel under pressure may be supplied to said burner, valve means for controlling the supply of fuel 10 through said communication, a valve device for also controlling the supply of fuel through said communication at a point therein on the side of the valve means remote from the burner, means responsive to the level of the water in the boiler for controlling-said valve device, and means responsive to the pressure of the fuel in said communication at a point therein intermediate the valve device and the valve means for controlling said valve means.

JAMES W. HARRIE.

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