US2303894A

US2303894A - Control foe heating devices

Info

Publication number: US2303894A
Authority: US
Publication date: 1942-12-01
Anticipated expiration: 1959-12-01

Description

Dec. 1, 1942. w. OLSEN CONTROL FOR A HEATING DEVICE Filed April 29, 1941 Patented Dec. 1, 1942- 2,303,894 CONTROL FOB HEATING 'nnvrcas Ronald w. Olsen, Bloomfield,

N. J., assignor to General Electric Company, a corporation of New York Appueenonnpru 59 1941, Serial No. 390,964

14 Claims.

My invention relates to a control for a heatingdevice, and although not limited thereto, it has particular application to a control for a stoker furnace wherein aresponse to variations in the fuel bedair flow resistance is desirable.

An object of my invention is to provide' an improved automatic control arrangement for controlling the feeding of air and solid fuel to a heating device differentially upon variation in the fuel bed air flow resistance.

Another object of my invention is to provide an improved arrangement for automatically regulating the air flow through a fuel bed of variable I thickness produced upon automatic operation of a fan means and automatically initiating joint operation therewith of a fuel feeding device only when the air flow is above a predetermined minimum, and in addition terminating operation of the fuel feeding device for a furnace in response to a predetermined fuel bed air flow resistance being introduced into the furnace.

A further object of my invention is to provide an improved stoker furnace control for preventing operation of'a fuel feeding device in response to a movement of a constant combustion air flow control damper to a predetermined maximum open position.

A further object of my invention is to provide an improved furnace control arrangement for controlling the rate of fuel feed in response to the level of the outside temperature.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out in the claims annexed to and forming a part of this specification. In the drawing, Fig. 1 illustrates a control for a stoker-flred furnace which is provided-with embodiments of my invention, and Fig. 2 is a sectional side elevation of the air flow control arrangement employed in the furnace control illustrated in Fig; 1. g

In the arrangement illustrated in the drawing, which shows an air flow control for a stokerfired furnace for maintaining a flow of combustion air to the furnace within predetermined limits for varying conditions of the fire in the furnace, Iprovide a fuel feed switch responsive to movement of the air flow control. Thus, the stoker, or fuel feeding device, is deenergized when the air flow control device moves to a predetermined or relatively wide-open position. I may also provide a damper control arrangement in the furnace flue, the movement of which is responsive to outdoor temperatures for further controlling, through the air flow control and fuel feed switch arrangement, the rate of fuel delivery to the furnace.

Referring more particularly toFlg. 1 of the drawing, I have provided a control for a heating device, such as a furnace indicated generally by the numeral I0, having a hopper H into which fuel, such as coal, may be placed, a retort II on which the coal is burned, and a fuel feeding tube l3 connected between the hopper and the retort for conducting the fuel from the hopper to the retort. The fuel may be forced through the-fuel feeding tube l3 in any suitable manner, such as through the movement of a fuel feeding screw it. This screw may be rotated in any suitable manner, such as by a feed motor l5. Any other suitable arrangement may be provided for feeding fuel to the heating device. vIn order to provide an arrangement for conducting combustion air into the retort, a duct i6 is connected to the furnace and there is also provided any suitable air flow control arrangement for controlling the flow of air within predetermined limits, or for maintaining a substantially constant flow of air into the retort for varying The air flow control which I employ with my invention is described and claimed in my copending application Serial No. 390,961 and which is assigned to the same assignee as this present invention. This air flow control is shown in detail in Fig. 2 and includes a damper ll pivotally mounted on a shaft extends through the fire bed conditions.

intake end of the'duct l6 and the duct is open on the sides and on the bottom. With such an arrangement lt is possible to maintain a substantially constant flow of air through the ductl6 for varying back pressure conditions. Thus, the damper I! will rotate around its pivot l8 against the biasing force produced by the weight member between the position indicated in Fig. 2 and the dotted; line position H, for varying conditions of system air flow resistance, in order to control the size of the passageway in the duct. Therefore, for a relatively thick fire bed the damper will assume a position as shown in Fig. 2, while for a relatively thin fire the damper will assume a position as indicated by the dotted lines 11, Any other suitable type of air flow control may also be provided, such as the one described in my co-pending application Serial No. 390,963, and which is assigned to the same assignee as this present invention. In order to provide an outlet for the.

products of combustion from the furnace, a flue l8. The end of the damper.

rotating the fan 23.

' closing the contacts II and 33 .;,-the relay 21 may move to tion. The relay the retort for varying conditions I3 is connected to the furnace and a fan 23 is placed therein in order to induce the draft, or to provide a pressure diflerence between the outside or intake end or the duct I3 and the end connected to the retort. Instead of employing an induced draft, a forced 'drait, a natural draft. or any other drait producing arrangement may be employed. A ten motor In order that the fan and feed motors may be energized from a suitable source of power, a transformer 22 is provided having its primary winding connected to incoming lines 23 and 24. Its secondary winding 25 has one side thereof connected to an operating coil 23 of the relay indicated generally by the numeral 21 through a conductor 28. In order that the coil 26 may be energized when an increase in indicated generally by the nube placed in the. room suitable place. This ondary winding 25 through

conductors

33 and 36, while the stationary contact 34 is connected to the opposite side of the transformer winding 25 through

conductors

31 and 28. thermostat 29 calls for heat it will be seen that the bimetallic strip 33 will move to the left thus so that the coil 26 will be energized through the circuit including one side of the transformer secondary winding 25, conductor 23, coil 26, bimetallic strip 30, contacts 3i and 33, and

conductors

35 and 36. When the call for heat has been satisfied the thermostat w'ill move to its open circu1t position and then to the right so that the coil 23 will be short circuited through the

contacts

32 and 34 so that its inoperative posi- 21 is provided with a

core

33 and 33 and 34 are provided, the conv 2| is provided for g the heat of the provide a suitable temperature bimetallic strip 30 with contherein. when low resistance to the new of air I! need only be open a slight amount in order to allow a predetermined rate of air fiow into the retort. However, if the fuel bed is very thick it will provide a much higher resistance to the flow 0! air so that the damper l1 must move to a relatively wide open position in order to maintain the same rate of air flowing to the retort. In-order to control the feed motor in response to fuel bed thickness any suitable circuit breaker arrangement, such as the switch 49, may be provided, the operation of which is responsive to movement of the constant only a relatively and the damper air flow control arrangement which is employed.

The switch will remain closed when the fan motor is running and the fire sistance, is below any predetermined maximum amount, but it opens when the air flow control which may be connected to the conductors 43 and 53, a pool of mercury 52 in the interior of the switch, and a central portion which has a hole the hole is below the surface 0! the mercury it will flow therethrough and make a" closed circuit between the hole 53 will be above the when the damper has asmaximum the level a and remain so within any

predetermined range contacts

39 and 40 which are operable to a circuit be energized. The energizing circuit for the fan motor may be traced from the line 24 through conductor 43, contacts 43,

conductors

44 and 44,

through the fan motor, conductor 43, conductor The circuit for the feed line 24 through the conductor 43, contacts 43, conductor 44, ductor 48, a switch 43 which is operated by movement of the damper l1 and the function of which will be described in'more detail below, conductor 50, feed motor l5, conductors and 41, back to the line 23.

Instead of employing a thermostat in the space to be heated for initiating the tion of the fan and fuel feed motors, any other such as a thermostat responsive to furnace plenum temperature, or an aquastat responsive to boiler water temperature, may be employed.

As described above and in my above first-mentioned copending application S. N. 390,961, the air flow control arrangement will move so as to maintain a, substantially constant fiow of air into of the fire bed. Thus, if the fire bed is very light it will provide 41, back to the line 23.

' through the of damper movement. Thus, the switch will close its contacts when the damper has moved from the postion shown in Fig. 2 to a position as indicated by the dotted lines 54 and will remain-closed during movement of the damper between this position and the dotted line position ll, or minimum opening position. Itxwill be noted that a mercury switch of the balanced disk or water type, which may be mounted on an axis passing through its center of gravity, is a desirable type to employ when an air flow control of the type described above is employed.

since movement of the switch with the damper will not change the center of gravity of the damper counter weight combination. Thus. air flow control, the fuel feed motor on and off in order that no new coal will be fed into the furnace if the bed has reached a predetermined maximum thickness,- this thickness being any suitable. value, such as that which the fan can just handle with the damper almost wide open. Thus, operation of the fuel feeding device is prevented when the may be turned damper is operated to a predetermined maximum open position.

It will also is employed as shown that it assumes a position of mum opening when the fan is deenergized, that at the moment the thermostat calls for heat the fan will be actuated first and the fuel feeding motor will be actuated after the damper I] has moved into the range between the positions indicated by the dotted lines 54' and H. with in Fig.2, which is biased so bed thickness, or reswitch contacts. The switch need only be suitably placed on the substantially maxiconditions. .In order to accomplish this a bellows 58 may be provided which has a bulb 51 responsive to outdoor temperature conditions. A rod 58 and a suitable linkage 59 are provided so that movement of the bellows may cause corresponding movement of the damper 55, When the damper 55has moved to a relatively closed position it will be in effect throttling or reducing the eflectiveness of the fan 20, as it will be increasing the back pressure whichthe fanmotor must overcome. Conversely, if the damper 55 is moved to a wide-open position it will present substantially no impediment to the movement of the products of combustion through the flue. I

havefound that by moving the damper 55 from a wide-open position to a position which throttles the fan motor, I am able to control the rate at which the fuel will be fed from the hopper to the retort. The rod and linkage are, therefore,

the outdoor temperature is relatively cold, while the damper will be moved to a relatively closed position during relatively warm weather.

open to a relatively wide open.position to try to maintain the air flow constant and thus will cycle the fuel feed motor on and on, thus reduc'ing the total flow of fuel. In this manner I may control the rate of fuel feed to the furnace by varying the position of the damper 54,

since this in turn controls the, position of [the air flow control damper 11. Such a control of the rate of fuel feed is particularly desirable during mild seasons of the year, since in the spring and the fall a lesser amount of fuel feed is needed than in the cold weather. Thus. the bellows may be set so as to throttle the fan in the spring and the fall and still provide relacold season of the year.

Although I have shown and describedparticular embodiments of my invention, I do not desire to be limited to theparticular embodiments described, and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A control for a furnace including .a fuel feeding device, a duct for introducing combustion air into said furnace, fan means for producing a flow of air through said duct, air control means for maintaining a substantially constant quantity of air flow through said duct for varying conditicns within said furnace, means for initiating operation of said fan means when an increase in the amount of heat from said furnace is desired, means responsive to movement of said air control means to predetermined positions for initiating and terminating operation of said fuel feeding means, and means responsive to changes in outdoor temperature for varying the effectiveness of said fan means so as to control the rate of fuel feed to the furnace in response to outdoor temperatures.

2, A control for a furnace including a fuel feed- When 1 the damper 55 is nearly closed, damper i! will access in: device. a duct for introducing combustion air into said furnace, fan means for producing a now of air through laid duct, air control means for producing a substantially constant quantity of air flow through said ductfor varying fire conditions within said furnace, this means connected to said furnace. means for initiating operation of said fan means when an increase in the amount of minating operation of said fuel feeding means,

- and damper means within said flue, said damper means being movable in response to variations in outdoor temperature for controlling the rate of feed of said fuel feeding means. v 3. A control for a furnace including a fuel feedconnected so that the damper is wide open when tively no impediment to its during the relatively ing device, a duct for introducing combustion air into said furnace, fan means for producing a flow of air through said duct, air control means for producing a substantially constant quantity of air flow through said duct for varying fire conditions within said furnace, flue means connected to said furnace, means for initiating op-, eration of said fan means when an increase in the amount of heat from said furnace is desired, means responsive to movement of said air control means to predetermined positions for initiating and terminatingoperation of said fuel feeding means, damper means within said flue, and thermostat means responsive to changes in outdoor temperature for controlling the position of said flue damper means.

4. In combination, a combustion heating device having a fuel bed, stoker means for feeding fuel to increase the thickness of said fuel bed, independently operable fan means for producing a flow of combustion air through said fuel bed dependent upon the thickness thereof, an automatic flow responsive damper movably mounted in the path of said air flow for maintaining the flow within predetermined limits and having biasing means for maintaining said damper in'a predetermined position until said air flow in- 45.

creases above the minimum limit, an automatic stoker control device responsive to movement of said damper to said predetermined position for, preventing operation of said stoker means, and automatic control means having connections for independently operating said fan means and havlng other connections under the control of said stoker control device foroperating said stoker means jointly with said fan means only upon movement of said damper from said predeter-;

mined position.

5. In combination, a combustion heating dcvice having a fuel bed, stoker means for feeding fuel to increasevthe thickness of said fuel bed, separately operable fan means for producing a flow of combustion air through said fuel bed dependent upon the air flow resistance thereof, a

damper having automatic operating means reoperated by said automatic means for preventing operation of said stoker. means when .the flow resistance of said fuel bed exceeds said range, and

' automatic control means having connections for independently operating said fan means and hav-- ing other connections under the control of said mediate predetermined open and closed positions to maintain a substantially constant air flow through said fuel bed upon variation in the thickness thereof, and condition responsive means for controlling joint operation of said fan means and said stoker means including means for preventing operation of said stoker means jointly with said fan means when said damper is operated to said predetermined open position.

"I; In combination, a combustion heating device asoasos the air flow-produced upon operation of said fan means for maintaining the rate of said air flow substantially constant upon variation in the flow resistance of said fuel bed within a predetermined range, separate air flow control means for controlling said air flow to predetermine said range, a stoker control device operated by said automatic means for preventing operation of said stoker means when the flow resistance of said fuel bed exceeds said range, and automatic control means having connections for operating said fan means and having other connections under the control of said stoker control device for operating said stoker means Jointly with said fan means when the flow resistance of said fuel bed is within said predetermined range. 10. In combination, a combustion heating del vice having a fuel bed, stoker means for feeding having a fuel bed, stoker means for feeding fuel to increase the thickness of said fuel bed, separately operable fan means for producing a flow of combustion air through said fuel bed dependent upon the thickness thereof, means including a damper biased to a predetermined open position and having cooperating air flow directing means for varying the position of said damper upon operation of said air flow producing means to maintain the rate of air flow through said fuel bed substantially constant upon variation in j, the thickness of said fuel bed, stoker control switch means operated upon movement of said damper to said predetermined open position for preventing operation of said fuel feed means, and automatic control means having connections for operating said fan means and having other connections under the control of said stoker control switch means for operating said stoker means jointly with said fan means only upon movement of said damper from said predetermined open position.

8. In combination, a combustion heating device having a fuel bed, stoker means for feeding fuel to increase the thickness of said fuel bed, separately operable fan means for producing a flow of combustion air through said fuel bed dependent upon the thickness thereof, means including a centrally pivoted damper having balancing means for biasing said damper to the open position and having cooperating air flow directing means for varying the position of said damper upon operation of said air flow producing means to maintain the rate of air flow through said fuel bed substantially constant upon variation in the thickness of said fuel bed, balanced switch means operated upon movement of said damper to said open position for preventing operation of said stoker means, and automatic control means having connections for operating said fan means and having other connections, said balanced switch means for operating said stoker means jointly with said fan means upon movement of said damper from said predetermined open position.

fuel to increase the thickness of said fuel bed, separately operable fan means for-producing a flow of combustion air through said fuel bed dependent upon the air flow resistance thereof,

means including a damper biased to a predetermined position and having operating means for varying the position of said damper upon operation of said air flow producing means to maintain the rate of air flow through said fuel bed substantially constant upon variation in the flow resistance of said fuel bed within a predetermined range, separately operable damper means for restricting the flow of air through said fuel bed to predetermine said range, stokercontrol switch means operated upon movement of saiddamper to said predetermined position for preventing operation of said stoker means, and automatic control means having connections for operating said fan means and having other connections under the control of said stoker control switch means for operating said stoker means jointly with said fan means upon movement of said damper from said predetermined open position.

11. In combination, a furnace having a fuel bed, stoker means for feeding fuel to increase the thickness of said fuel bed, separately operable fan means for producing a flow of combustion air through said fuel bed dependent upon the air flow resistance thereof, automatic means for energizing and deenergizing said fan means and having connections for controlling the joint operation of said stoker means with said fan means, a damper having automatic operating means responsive to the flow of air through said fuel bed produced upon operation of said fan for positioning said damper intermediate the open and closed positions thereof for maintaining said flow of air through said fuel bed substantially j constant upon variation in the flow resistance of under the control of said fuel bed within predetermined limits, and switch means for controlling said connections responsively to movement of said damper to the maximum open position for preventing operation of said stoker means, said automatic operating means being biased to move said damper to said maximum open position when said fan is inactive.

12. In combination, a furnace having a fuel bed, stoker means for feeding fuel to increase the thickness of said fuel bed, control means for 9. In combination, a combustion heating device combustion air through said fuel bed dependent upon the air flow resistance thereof, a damper having automatic operating means responsive to controlling the operation ofsaid stoker means and operating means for said control means ineluding an automatic flow responsive damper for maintaining the flow of combustion air through said fuel bed substantially constant upon variation of the fuel bed flow resistance within a prerange, and means responsive to variations in the outdoor temperature for-separately varying the flow of air through said fuel bed to predetermine said range.

13. In combination, a furnace having a fuel bed, s'toker means for feeding fuel to increase the thickness of said fuel bed, separately operable fan means for producing a now of combustion air through said fuel bed,.a damper having automatic operating means responsive to the air flow produced upon operation of said fan means for maintaining the rate of said air flow substantially constant upon variation in the flow resistance of said fuel bed within a predetermined range,

means responsive to variations in the outdoor bed stoker means for feeding fuel to increase 7 the thickness of said fuel bed, a fan for producing temperature for separately varying the rate of air flow through said fuel bed to predetermine said range, and means responsive to movement of said damper to the maximum open position for preventing operation of said stoker means 'when theflow resistance of said fuel bed exceeds said range.

14. In combination, a furnace having a fuel a flow of combustion air through said fuel bed, condition responsive means for starting and stopping operation of said fan, means. including a centrally pivoted damper having balancing means for biasing said damper to the open position and having cooperating air flow directing means for