US2373150A - Stoker control system - Google Patents

Description

April 10,1945. v. 'R. TATE 2,373,150

STOKER CONTROL SYSTEM Filed Oct. 13, 1939 INVENTOR.

Patented Arm; l 1945 STATE STOKIER CONTROL Wt Virgil Robins Tate; Milwaukee, is., assior to Perlex Qorporatlon, Milwaukee, Win, a corporatlon of isconsln application (lctoher is, as, denial No. scams (or. lie-loll 2'2 @laims.

Fig. 3 illustrates a modification of the pressure switch of Fig. 1 shown in the normal running ed in the stack of'a stoker-fired furnace and is arranged to open the switch in the event that the stack temperature'falls to too low a value, in-

dlcating that the fire has been extinguished or has been very nearly extinguished. This switch is usually connected in series with the stoker motor in order that the stoker cannot operate with the switch open. Y

Thermal operated devices of this class have I been unsatisfactory in the past because the severe temperatures and the oxidizing atmosphere to which the thermal elements have been exposed leads to their rapid destruction and seriously disturbs their calibration. In order to alleviate these dimculties this invention utilizes the change in pressure conditions in the blast tube or air supply duct of a stoker due to changes in the condition of the fuel bed, to indicate whether or not the firehas become extinguished.

One object of this invention is to provide a new and improved control systenffor stokers'.

Av further object is to providda new and improved pressure operated outfire control switch for stoker control systems.

A further object is to provide an alarm in connection with a pressure operated out-fire, control for indicating that the stoker has been rendered inoperative. J

A further object is to provide a new and improved out-fire mechanism which will deenergize Other objects and advantages reside in certain position.

The preferred circuit shown in Fig. 1 shfiws two line voltage conductors t and 8 connected to a source of power. A transformer choke having a line voltage primary winding it is connected in series with the winding of a high voltage relay l2, and the series combination is connected across the two line voltage conductors B and 8. The

choke is provided with a secondary low voltage winding M. In the choke secondary circuit there is aroom thermostat it and an interval timer switch it connected in parallel therewith. A safety or lockout switch is provided in the choke secondary circuit and is connected in series with the thermostat it and the interval timer switch it. This safety switch has a plurality of elements including a blmetal actuator member 29 mounted at one end to a support it and a bimetal compensator member of blade 22 arranged parallel to the actuator and mounted at one end to the support it. Cooperating with the actuator 20.

on 24 for controlling the circuit through thesafety novel features of construction, circuit arrangement, and operationof the various parts and elements which will be hereinafter more fullyde= scribed in the specification, particularly pointed out in the appended claims and of which a preferred embodiment is illustrated in the accompanying sheet of drawings forming a part thereof:

Fig. 1 shows the component parts and the circuit connections therefore, of a preferred form a of the invention;

Fig. 2 shows a modification of the system shown in Fig. 1;

switch. So long as the distance between the movable ends of the two bimetal members 29 and 22 remains less than a predetermined amount. a circuit connection is maintained through the switch by means of the latch 23, but if the distance between the two members 20 and 2'2 exceeds this pre determined amount, the latch it trips downward and open the circuit through the safety switch. The compensator blade 22 cooperates with the actuator. blade to to compensate the blade 20 for changes in ambient temperature in order that the latch it will release with apredetermined amount of travel of the blade 20 regardless of ambient temperature. A motivating electric heater it for the bimetal actuator member all is connected in the choke secondary circuit in series with the safety switch. This switch may take the general form of several which are commercially available. For more detailed structural information pertaining to the preferred form- 'reference maybe made to Patent No. 2,216,748

issued to Herbert E. Lindemann, on October 8, 1940. While in the preferred form the safety switch operation is obtained by heating a bimeta'l blade, it is to be understood that any other means of operating the switch may be employed without departing from the spirit of the invention.

A blower 28 is provided as part of the stoker mechanism for feeding air to a. combustion chamber 30. An air duct 32 serves to convey the air under pressure from the blower to tuyeres in a retort which serves as the bottom portion of the combustion chamber. A pressure responsive switch such as that shown at A is inserted into" pheric pressure causes the diaphragm 40 to de-' flect up or down. Fastened to the diaphragm at its center is an actuator member 42 having an adjustable cap 44 at its end. Fastened to the housing 38 is a spring blade support 46 carrying two spring blades 48 and 50 and a terminal blade 52. These blades are insulated from each other and the support 46 and are so arranged that the adjustable cap 44 on the actuator member 42 will minimum operating pressure and that the first spring blade 56 will be raised just out of contact with the second spring blade 46 by the actuator member 42 at the selected maximum operating pressure.

With the pressure switch wired as shown in Fig. 1, if the air pressure in the air duct 32 is below the minimum operating value of the pressure switch the actuating member cap 44 will not be in contact with the first spring blade 60 and the normal operating circuit through the pressure switch extending from conductor 54 to conductor 66 will be open. If the minimum pressure'is reached, however, a circuit is established through i just touch thefirst spring blade 66 at the selected tionto the air stream in the combustion chamber 36. If the combustion chamber is practically empty of fuel the static pressure in the air duct 32 will be low. If on the other hand, the combustion chamber is congested and partially full of dense material so that little air can escape from it, the static pressure in the air duct 32 will be high. If the fire in the combustion chamber is burning-properly the burning fuel will be fairly porous and will offer only moderate resistance to the passage of fluid through the fuel bed, and as a result there will be only a moderate pressure in the air duct 32. If on the other hand green fuel is being fed into the combustion chamber faster than the fire can consume it, the chamber will become congested with green fuel, the resistance to the air flow through the fuel bed will increase, and as a result the pressure in the air duct-32 will also increase. If the pressure switch A is adjusted to operate at some pressure below the maximum pressure that the blower can produce with' a heavily congested combustion chamber, the pressure switch will open its contacts only when the air duct pressure increases sufllciently to indicate a congested condition in the chamber. Obviously, the pressure switch may be adjusted to operate on any desired degree of congestion.

Operation lished extending from one side of the choke secthe switch extending from conductor 64, through spring blade 50, through the second spring blade 48, to conductor 56. If the maximum operating pressure is reached the above circuit through the pressure switch is opened by the actuator 42 when the first spring blade 56 and the second spring blade 48 break electrical contact.

Fig. 3 shows a modification of a portion of the pressure switch. It illustrates a method of adlusting the switch to open the electrical circuit through it at selected values of maximum operating pressures. By turning an adjusting screw 63 the compressive force of a. spring 60 against the first spring blade 50 is changed and. hence the amount of effort required bythe actuator 42 to deflect the first spring blade 56 a. sufllcient amount to open the electrical contact between it and second spring blade 46 is likewise changed. In turn the air pressure required on the diaphragm to cause this contact action must change in order. to meet the new restraining force conditions on the first spring blade. Fig. 3 shows gie pressure switch in its normal running posion.

A pair of relay operated contacts 62 connect' and disconnect a stoker motor 64 to the line conductors 3 and 6. An alarm switch 66 is operated responsive to the safety switch latch 24 position by means such as the insulated connecting member 68. An alarm indicator such as the bell I6 ondary l4 through the thermostat i6, the electric heater 26, and the safety switch 20-24-22 to the other side of the choke secondary. The low impedence connected to the choke secondary reflects itself in the choke primary impedance and causes a reduction in its value. This action reduces the impedance of the relay l 2 circuit and causes sufllcient current to flow through the relay l2 to fully energize it and cause it to operate. In response the relay contacts 62 close and energize the stoker motor 64. In a conventional installation this starts the fuel feeding means and the air blower 23. If the fuel in the combustion chamber is burning in a normal manner, the restriction to the air passing through the fuel bed will be nominal as will also be the static pressure in the air duct 32. The pressure will be sufllcient to exceed the minimum operating pressure of the pressure switch however, and a circuit will be established from conductor 54 to conductor 56 through the path 54--554244504856 as has been pointed out. In this way the heater 26 will be shunted and made ineffective. If the fuel being fed into the combustion chamber is consumed at a normal rate the pressure of the air in the air duct 32 will remain above the minimum operating pressure setting but below the maximum operating pressure setting of the pressure switch and the stoker will continue to operate until the space being heated has reached a high motivating heater-2t. in response to the energized heater the bimetal actuator it will slowly travel to the left until such time that the pressure switch'acain closes, or, if this fails to happen, until the latch It is released. The latch may be set to release within any ractical time limit, 5 minutes for example, after the pressure switch ha opened and remains open. When the safety switch opens, the choke secondary circuit is opened and high impedance is reflected in the choke primary causing the relay it to open the contacts or. and shut down the Stoker.

it should be noted that the pressure'switch may open at intervals for short periods of time without shutting down the system, but intermittent operation of the pressure switch occurring at and it exceeds or falls short of a certain predetermined amount.

short durations of time will result in a shut down of the system if the bimetel actuator 2t ultimately reaches the necessary temperature above the temperature of the compensator 22 to release the latch til.

it should be further noted that any condition in the combustion chamber it which will offer abnormal restriction to the flow of air through the fuel bed will cause the system to be shut down. For example, the formation of undesirable fuel slag running, down into the tuyeres of the retort and clogging them would shut down the system. "it the circuit of Fig. l is used, the heater it is checked for an open circuit condition upon each operation of the system. As explained when the system is shut down there is an opencircuit between conductors t6 and 5%. Now if the heater is also open because it has been damaged, the choke secondary circuit cannot be completed and hence the relay will not operate.

When the latch 26 trips and drops by gravity or a spring the contacts are closed by the in-' suiating connectortiii and the alarm indicator or signal it is energized.

Alter the latch 25 has been released by the actuator member the system cannot be restarted unless it is manually reset. After the actuator to cools, th latch lid is reset and the circuit is deenergized by raising the movportion of the alarm switch fit by means of the insulating lug it.

The interval timer switch it is wired into the system in the conventional manner and serves to start the atelier at regular intervals through its contacts independent of the thermostat it in order to hold the fire in the combustion chamber. The motor for operating the interval timer switch is continually energized from the switch in this case is somewhat difierent from t shown in Fig. l. Both of the himetal blades and it are provided with an electric heater shown as heaters it and it respectively. The memher Till is arranged to shut down or loci: out the system by opening the circuit through switch when the distance between the free ends of the two himetal' safety switch blades iii The bimetal blade it is slotted at W to receive a projecting lug 8t on the latch it. The lug cs is arranged to slide within the slot 88 with a predetermined amount of travel of the latch it relative to the bimetal blade 2%. If the travel of the latch exceeds the predetermined amount, the lug 8t falls out of the slot til and causes the'latch it to drop. For additional information relative to safety switches of this general type, reference may be made to my Patent No. 2,254,984, dated Sept-2, 19%.

The safety switch heater it for the bimetal blade 22 is connected in parallel with the stoker motor 6 The other safety switch heater it for the other bimetal blade to is normally connected in parallel with the first heater it by the normally closed contacts it-till of the pressure switch A.

A running circuit for the stoker motor extends from the line conductor ii through either or both the interval timer contacts it and the thermostat it, through the first bimetal blade at,

through the safety switch latch it, through the second bimetal blade 22, through the stoker motor heater iii is also energized and causes its associated hirnetai blade 22 to slowly warp toward the left. If the pressure switch A is closed the second heater "it will also be energized and it will cause its associated bimetal blade N to slowly warp toward the left along with the bimetal blade t2,

and the relative distance between the two bimetal relative distance between the two blades will hecome smaller and finally the tip of the first bimetal blade will fail in the slot iii of the latch iii and the circuit through the safety switch' will open when the latch it drops down. The alarm signal it will be energized when the contacts fit close as has been described. Obviously if the second heater i i becomes disabled for any reason,

7 the switch will lock out in the same manner.

ill

However, if the first heater i2 fails, a different action ensues. Under these conditions during a normal operation the second heater it will be energized while the first heater i2 is inoperative. As a result the relative distance between the two bimetel hlades increases until the latch it falls out of the slot lit in the first bimetal blade 3!? and the circuit to the stocker motor is opened.

A strip or" insulating material 92 is fastened to the end oi the himetal blade to to prevent the latch it from getting into such a position under the first bimetal hlade 2t that the lug iii? would engage the end of the blade and prevent the latch iii from sliding up on the the slot With the modification shown in Fig. 2 the correct operation of the heaters iii and it is checked with every oneration of the system regardless of how the pressure switch A is connected into the circuit. a

lie the disclosure given herein shows a relay controlled by a choke circuit, those skilled in blade it and falling int the art will recognize that other types of relay control circuits may be used without departing from thespirit of the invention. Further it will be recognized that the safety switch illustrated in connection with Fig. 2 might be substitutedfor the safety switch of Fig. 1 and vice versa with equally satisfactory results. Further it is to be understood that any pressure switchof suitable characteristics may be substituted for the pressurssggitch A disclosed in the drawing. Since only preferred illustrations of the invention have been disclosed, it is conceivable that other modifications thereof may be readily perceived by those well versed in the art and it is therefore desired that the invention be not limited to the precise structure illustrated and described but only to the extent of the appended claims.

What is claimed is:

1. In a control system for a fuel burner having means for feeding fuel and means for feeding combustion air, the combination of, control meals for controlling the fuel feeding means, air pressure actuated means actuated by the air passing to the burner and responsive to abnormal combustion air conditions for actuating said control means in a manner to place said fuel feeding means out of operation, means operative upon placing of the fuel feeding means out of operation to retain the same out of operation irrespective of the combustion air conditions, and resetting means for replacing said fuel feeding means into operation.

2. In a control system for a fuel burner having means for feeding fuel and means for feeding combustion air, the combination of, control means for controlling the fuel feeding means, air pressure actuated means actuated bythe air passing to the burner and responsive to abnormal combustion air'conditions for actuating said control means in a manner to place said fuel feeding means out of operation, means normally retaining the fuel feeding means out of operation when placed out of operation by said pressure actuated means, and manual .reset means for actuating said control means in the opposite direction for replacing the fuel feeding means into operation.

3. In a control system for a fuel burner having means for feeding fuel and means for feeding combustion air, the combination of, control means rection for replacing the means for feeding into operation.

5. In a control system for a fuel burner having means for feeding fuel and means for feeding combustion air, the combination of, control means for controlling the means for feeding air, and means including air pressure actuated means actuated by the air passing to the burner for placing said means for feeding air out of operation in response to abnormal combustion air condir tions and for then maintaining the air feeding means out of operation irrespective of the combustion air condition.

, 6. In a control system for a fuel burner having means for feeding fuel and means for feeding combustion air, both driven by a single motor, the combination of, switching means for controlling said motor, and air pressure actuated means actuated by the air passing to the burner and responsive to abnormal combustion air conditions A for actuating said switching means in a manner to place the motor out of operation in response to an abnormal combustion air condition.

7. In a control system for a fuel burner having means for feeding fuel and means for feeding combustion air, both driven by a single motor,

the combination of, switching means for controlling said motor, air pressure actuated means actuated by the air passing to'the burner and responsiveto abnormal combustion air conditions for actuating said switching means in a manner to place the motor out of operation in response to an abnormal combustion air condition, means air feeding means, pressure actuated means for for controlling the means for feeding air, air

pressure actuated means actuated by the airpassing to the burner and responsive to abnormal combustion air conditions for actuating said control means in a manner to place said means for feeding air out of operation, means normally retaining the-means for feeding air out of operation means in a manner to place said means for feeding air out of operatiommeans normally retaining said means for feeding air out of operation when placed out of operation by said pressure actuated means, and manual reset means for actuating said control means in the opposite diactuating said control meansin a manner to place said air feeding means out of operation upon rise or fall in combustion air pressure above or below normal values, means normally retaining the air feeding means out of operation when placed out of. operation by said pressure actuated means, and resetting'means for actuaating said control means to replace the air feeding means into operation.

9. In a control system for a fuel burner having air feeding means and fuel feeding means, the combination of, control means for controlling the fuel feeding means, and pressure actuated means for actuating said control means in a manner to place the fuel feeding means out of operation upon rise or fall in combustion air pressure above or below normal values.

10. In a control system for a fuel burner having means for feeding fuel and means for feeding combustion air, both driven by a single motor, the combination of, switching means for controlling said motor, pressure actuated means for actuating said switching means in a manner to place the .motor out of operation upon rise or fall in combustion air pressure above or below normal values, and reset means for replacing the motor into operation.

11. In a control system for a stoker having means for retaining a bed of fuel, fuel feeding means and combustion air feeding me the combination of, control means fo ontrolling the fuel feeding means, means nsive to the resistance of the fuel bed to passage of combustion air for actuating said control means in as'raico the resistance to flow of combustion air through the fuel bed for actuating said control me for placing said one portion out of operation when the fuel bed resistance rises above or falls below normal values. A

13. In a control system for a stoker mechanism having means for retaining a bed of fuel, air feeding means and fuel feeding means, the combination of a. ontrol device responsive to the demand for operation and non-operation of the stoker mechanism for placing said mechanism into and out of operation, and control means for the air feeding means, said control means comprising a means responsive to the resistance to air flow through the fuel bed for reduci the air flow upon fall in resistance of the fuel bed. said control means also comprising a time delay device controlled by said control device ior rendering the control means ineffective to control the feeding of air until a, timed period after the stoker mechanism is placed into operation by said control device.

it. In a control system for a stoher mecha- I nisrn having means forreta'ining a bed of fuel, a fuel feeding portion and an air feeding portion, the'combination of control means for placing at least the fuel feeding portion out of oporation, means influenced by the thickness of the fuel bed for actuating said control means to place said portion out or operation when the thickness of the fuel bed increases to a point indicating that the fire is probably out, and re set means for replacing the fuel feeding portion into operation at least temporarily irrespective of the thickness of the fuel bed.

15. In a control system for a stoker mecha nism having means for retag a bed of incl,

dill

tuating said switching mechanism to place said a fuel feeding means and an air feeding means,

said air feeding means and said fuel fee means being driven by a single motor, the com bination of switching mechanism for placing said motor out of operation, means influenced by the thickness of the fuel bed for actue said switching mechanism to place said motor out of operation when the thickness of the fuel hedin creases to a point indicating t the fire is probably out, lock-out meanaior maintaimng. paced out of the motor out of operation when operation by said switching m and m set means for said lockout means for replacing ing said motor into operation.

17. In a control system for a stoker mechanism having means for retaining a bed of fuel, a fuel feeding means and an air feeding means, said air feeding means and said fuel feeding means driven by a single motor, the combination of a control device responsive to the demand for operation and non-operation of said stoker mechanism for placing said motor into and out of operation, a switching'mechanism for placing said motor out of operation irrespective of sad control device, and means influenced by the thickness ofthe fuel bed for actuating said switching mechanism to place the motor out of operation when the thickness of the fuel bed increases to a point indicating that the fire is probably out.

18. In a control system for a stoker mechanism having means for retaining a bed of fuel, a fuel feeding portion and an air feeding portion, the combination of control means for placing the air feeding portion out of operation, and means influenced by the thickness of the fuel bed for actuating said control means to place the air feeding portion of the stoker mechanism out of operation when the fuel bed becomes toothin.

19. In a control system for a Stoker mechanism having means for retaining a bed of fuel, a fuel feeding portion and an air feeding portion, the

combination of control means for'placing said stoker mechanism, out of operation, and means influenced by the thickness of the fuel bed for actuating said control means for placing the stolser mechanism out of operation when the fuel bed becomes either too thick or too thin.

, 20. In a control system for a stoker mechanism having means for retaining a bed of fuel, a fuel feeding portionand an air feeding portion, the combination of,' a first responsive device responsive to the demand for operation and nonoperation of the stoker mechanism for placing said mechanism into and out of operation, a lock-out device for locking at least one portion of the stolrer mechanism out of operation, means including a second responsive device arranged to respond generally to the thickness of the fuel bed, and a time delay device controlled by said second responsive device for controlling said lock-out device.

21. In a control system for a stoker mechanism. having means for retaining a bed of fuel, a fuel feedingportion and an air feeding portion, the combination oi, a first responsive device re" sponsive to the demand for operation and non operation of the stoker mechanism for placing said mechanism into and out of operation, a locir-= out device for locking at least one portion of the stoker mechanism out of operation, timing means controlled by said first responsive device for actuating said lock-out device a period of time after the stoker mechanism is placed into operation, and means including a second re sponsive device arranged to respond generally to the thickness of the fuel bed for arresting ac tion of said timing means if the fuel bed thiclzness is at a desired value.

22. In a control system for a Stoker mechanism having means for retaining a bed of fuel, a fuel feeding portion and an air feeding portion, the

combination of, a first responsive device re= sponsive to the demand for operation and non operation of the stolze'r mechanism for placing sponsive device for actuating said lock-out device a period of time after the stoker mechanism is placed into operation, and a second device responsive to the pressure of the combustion air a lock-out device for placing at least one portion of the stoker mechanism out of operation, timing means controlled by the first responsive device for actuating said lock-out device a period of time after the stoker mechanism is placed into operation, and a second device responsive to the pressure of the combustion air fed to the fuel bed for arresting action of the timing means I when the air pressure is within a predetermined range of values while .permitting action of said timing means when the air pressure is above or below said range of values.

24. In a control system for a stoker having means for retaining a bed of fuel, fuel feeding means and combustion air feeding means, the

' combination of,*control means for controlling the fuel feeding means, means responsive to the resistance of the fuel bed to passage of combustion air for actuating said control means in a manner to place the fuel feeding means out of operation when the fuel bed resistance varies to a predetermined value, means normally retaining said fuel feeding means out of operation when said fuel feeding means is placed out of operation by said responsive means, and means including manual reset means for replacing said fuel feeding means into operation.

25. In a control system for a stoker mechanism having means for retaining a bed of fuel, a fuel feeding portion and an air feeding portion, the 'combination of, a responsive device responsive to the demand for operation and non-operation of the stoker mechanism for placing said stoker mechanism into and out of operation, a control device for placing at least one portion of the stoker mechanism out of operation, timing means adapted-when actuated to actuate said control device a period of time thereafter for placing said one portion of the stoker mechanism out of operation, and means influenced by pressure of the combustion air fed to the fuel bed for arresting the action of said timing means when the fuel bed thickness is satisfactory while actuating said timing means when the fuel bed becomes too thick.

26. In a control system for a stoker mechanism having means for retaining a bed of fuel, a fuel feeding portion and an air feeding portion, the combination of, a responsive-device responsive to the demand for operation and non-operation of the stoker mechanism for placing said stoker mechanism into and out of operation, a control device for placing at least one portion of the stoker mechanism out of operation, timing means adapted when actuated to actuate said control device a period of time thereafter for placing! said one portion of the stoker mechanism out of operation, and means influenced by the resistance of the fuel bed to flow of combustion air I therethrough for arresting the action of said timing means when the fuel bed resistance is satisfactory while actuating said timing means when the resistance of the fuel bed to flow of combustion air becomes improper.

27. In a control system for a stoker mechanism having means for retaining a bed offuel, a fuel feeding portion and an air feeding portion, the combination of, a responsive device responding to the demand for operation and non-operation of the stoker mechanism for placing the same into and out of operation, a control device for placing at least one portion of the stoker mechanism out of operation, timing means controlled by the responsive device'and arranged to beactuated thereby when the stoker mechanism out of operation, and means influenced by the resistance of the fuel bed to flow of combustion air therethrough for arresting the action of said timing means when the fuel bed resistance is satisfactory while permitting action of said timing means when the resistance of the fuel bed to flow of combustion air becomes improper.

VIRGIL ROBINS TATE.

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