US2200660A - Air control for stokers and the like - Google Patents

Description

May 14, 1940. R. w. sUMAN ETAL AIR CONTROL FOR STOKERS AND THE LIKE Filed March 5l, 1958 5 Sheets-Sheet 1 May 149 194G- R. w. suMAN Er AL 2,20%660 AIR CONTROL FOR STOKERS AND THE LIKE Filed March 31, 1938 5 Sheets-Sheet 2 May 14, 1940. R.' w. sUMAN Er AL AIR CONTROL FOR STOKERS AND THE LIKE Filed March 31, 1938 3 Sheets-Sheet 3 Patented May 14, 1940 2,200.66@ Am common. ron s'roxEas AND 'ma ima Robert W. Suman and Edward Walter Schmidt,

Chicago, Ill., assignors to Link-Belt Company, Chicago, Ill., a corporation of Illinois Application March 3l,

l@ Claims.

Our invention relates to stoker air control and is particularly applicable to the control of the supply of air to a stoker of the retort type for coal and the like.V

In general we propose to control the air supply by controlling automatically th opening of the inlet to the fan so that the fan will only be working against a controlled pressure and so that there will be a free open and unobstructed. ilow n@ of air under pressure from the fan to the tuyres which supply the air to support combustion in the retort.

Especially in connection with house heating stokers, though also in connection with all types,v

1s it frequently happens that the mechanism which generally controls the entire installation is subject to periodic adjustment as a result of change in house temperature or boiler temperature or boiler pressure and sometimes the stoker will be 9,0 supplying coal to the retort and at other times no coal will be fed. Such apparatuses are generally set up so that when the stoker is supplying coal, it supplies it at a somewhat more rapid rate than combustion can take place so that as the stoker 25 operates, a thicker and thicker fuel bed is built up. Then when the stoker temporarily goes out of operation, the coal continues to burn and the thickness of the fuel bed decreases as the combustlon continues. When the stoker starts oper- 30 ating again, the fuel bed is again built up.

To get optimum combustion conditions when coal is being burned, there is an ideal relationship between the coal and the air. The amount of air required to best support combustion varies as the 35 amount of air in the combustion zonevaries and for any stoker design this is ordinarily a function of thickness of the coal bed. Since the fan supplying air to a stoker ordinarily operates at constant speed, being driven by the motor which o drives the coal feeding mechanism, it is very important to provide means to control the rate of air supply independent of motor speed in consonance with variations in the conditions controlling combustion.

'Ihis control is ofthe utmost importance because if too much air is supplied, combustion will be too intense for satisfactory lfurnace operation. On the other hand if too little air is supplied, even if the ilre does not go out, very inefllcient combustlon results and in either case departure from the ideal am'ou/ntrof air supply results in very serious inefficiency in operation of the installation.

A convenient measure for the air control is the M pressure beneath the fuer bed. A thick bed hav- 193s, serial No. 199,132

(on. isi- 153) ing high resistance to air ow gives low pressure. The thicker the bed, the more air needed to support-combustion; the thinner the bed, the less air needed, so we propose to provide automatic means which in consonance with the pressure beneath the fuel bed will control the rate of air supply. Because there is an open and unobstructed passage of air from the ian to the tuyres immediatelyl beneath or adjacent to the fuel bed, We can take the pressure at any suitable point between the fan and the fuel bed because While, of course, there is some pressure drop, it is small and is predictable and measurable and an automatic mechanism taking its pressure at any point between the fan and the fuel bed will give a suitable source of power to operate the control mechanism.

Other objects will appear from time to time throughout the specification and claims.

Our invention is illustrated more or less diagrammatically in the accompanying drawings,

wherein- Figure 1 is a side elevation of a stoker and boiler incorporating our invention;

Figure 2 is an end elevation of the device shown in Figure l;

Figure 3 is a side elevation of the fan housing valve and control mechanism;

Figure 4 is a section along the line 4-3 of Figure 3;

' Figure 5 is a view similar to Figure 3 showing `a modied form;

Figure 6 is a section along the line 6-6 of Figure Figure 7 is a section along Figure 3.

Like parts are indicated by like characters throughout the specication and drawings.

I is a furnace containing a nre box 2. 3 is a retort in the bottom of the lire box having tuyres 4 through which air enters the retort to support combustion. This retort is adapted to receive coal from a spiralv conveyor housing 5, which contains a screw or spiral conveyor 6. 1 is an air box closed at one end by the tuyres 4 and receiving air under pressure from the conduit 8. 9 is a coal bin adapted to supply coal to the screw conveyor, enclosed with the other parts of the mechanism in a. housing I0. II is the cover for the coal bin or hopper 9. I2 is a motor. By means of a belt I3, it drives a gear reducer I4 which in l turn drives the spiral screw conveyor 6. The motor also drives by means of the belt I3, a fan or blower I1 in a blower housing I8, which disclarges air under pressure to the conduit 8. The

the. line 'I-ll of blower housing'l is centrally apertured, this aperture being closed by a perforate cover platev I9, which cover plate has a series of radial wedgeshaped apertures 20, adapted to be closed when desired by a series of radial wedge-shaped shutter blades 2i mounted on an aircontrol or valve shaft 22. It will be understood that when in one position the shutters may leave the ports 20 entirely open and when in another position, they may completely close these ports so that a full range of adjustment of intake for the fan housing i8 is available.

23 is a control lever arm rigidly mounted on the shaft 22. It terminates in a quadrant 24 to the upper portion of which is anchored a chain 25, which extends down and is pivotally attached to the piston rod 26. 2l is a counterbalance lever projecting from the shaft 22 and provided with an adjustable counter-balance weight 28 adapted to be locked in position on the lever 2l by the set screw 29.

3B is a stop having an adjustable screw 3l, whereby if desired the excursion of the shutter blades toward the closed position may be limited to adjustably limit the excursion of the shutters so that at the will of the operator, the shutter may be allowed to close the intake ports completely or the degree of minimum opening may be selected.

32 is an air box or control cylinder. It communicates by means of the pipe 33, with some part of the air pressure system between the fan and the fuel bed, that is, between the fan and the tuyres because the fuel bed is immediately above them. Since when the fan is in operation, the pressure in the system is above atmospheric, that pressure will be eiective in the lower portion of the cylinder 32. 36 is a piston mounted for reciprocation in the cylinder 32 supported by the piston rod 26, the rod 26 being guided in the bearing 35.

3l is a rectangular p ort extending the entire height of the cylinder. Slidable therein is a control plate 38. 39 is a handle which may be manipulated to move the control plate 38 up or down in the guides l5 in which it travels. lill are lock screws which may be used to lock the plate in adjusted position, the plate being slotted as at fil to permit movement of the plate with respect to these screws during adjustment. The plate is apertured as at 42, the side walls of the aperture being out of parallelism with each other. It will be understood that the air which enters under pressure into the cylinder through the passage 33 escapes into the cylinder through the aperture [52, the amount of air escaping being controlled by the total area of the aperture exposed in the wall of the cylinder beneath the piston. The higher up the piston, the larger the area of the aperture. This aperture is shaped to compensate for the peculiar charac- Yteristics of the fan itself so as to give a proper control of air supplied to the fan in consonance with variation in pressure ofthe air in the system supplied by the fan. A change in the characteristics ofthe fan may necessitate a redesign of the aperture in the plate.

The piston rod 26 has an extension having a plurality of bolt holes 453, whereby the distance between the piston and the anchorage of the chain on the quadrant 2B may be adjusted.

There are, therefore, three adjustments in the device shown in Figures 3 and 4. The lever arm to which the counter-balance 28 travels may be adjusted. The distance between the piston.

- trol.

and the point of application of the chain to the quadrant 24 may be adjusted and the apertured control plate in the wall of the cylinder may be adjusted vertically to control the area of escape with respect to piston position whereby to control the i'low of air through the air box.

It will be understood that as the fuel bed builds up in the retort, the resistance to flow of air increases. As the resistance to flow of air increases, pressure in the whole system builds up. As the pressure builds up, the piston is raised. When the piston is raised, the valve opens wider and admits more air into the fan to vincrease the amount of air supplied to support combustion in a thick fuel bed. As the fuel burns down, the fuel bed decreases in thickness, the resistance decreases and so the pressure available to raise the piston decreases and so the piston descends closing off the air intake and decreasing the air. If the fan stops as it does when coal is no longer fed, pressure drops to atmospheric, the piston comes down to the closed position and the intake to the fan chamber is closed entirely or partially depending upon the adjustment desired.

As shown in Figure 3, the eect of the weight of the lever 23, the chain 25, piston 34 and piston rod 25 is opposed to the effect of the counterweight 28, the relationship being such that the piston @ll remains normally at the lower extremity of its excursion and the air valve to the fan housing is closed. When air pressure is applied to the underside of the piston, the eective forces on the right hand side of the shaft 22 are reduced by an amount equal to the upward pressure on the piston and the counterweight is then enabled to open the valve.

Because the two lever arms 21 and 23 are very close to the horizontal angular movement of these arms within the range of operation of the y device produces a negligible change in effective radius through which the weights are applied and so the position of the piston is substantially directly responsive to variation in air pressure and variation in escape of air under pressure through the port Q2 so that raising or lowering the plate 38 with the port 42 furnishes an effective and accurate control of -the response of the air valve to pressure variation.

As a result of this arrangement, the operation of the fan in so far as the amount of air supplied to the combustion zone is concerned, is concentrated at the parted plate or orifice con- The fan generates pressure in the system. Some of the air is bled off into the control cylinder by a fixed connection which for any given set of conditions will be a constant. This pressure will tend to raise the piston until a point is reached at which the control orifice is opened sulciently to permit a balance -of pressure in the control cylinder between the air and the effective weight of the piston and associated parts.

Change in the position of the control orifice will change the position of the piston at which this equilibrium is reached. Actual change in pressure drop between the main air system and the control cylinder resulting from changes in pressure or velocity may be compensated for by design of the orice; in the iirst instance by adjustment of the position of the orifice, in the second instance by adjustment of the relationship between the position of the valve and the position of the piston.

In the modiiled form shown in Figures 5 and 6, 75

is a handle projecting outwardly from the valve. 5| is a threaded adjustable anchorage for a chain 52, which is pivoted to a piston rod 53. The piston rod 53 is guided in a bearing 54 in the air box 55. The box is closed and receives air through a passage 56 from the pressure side of the system discharging into the box beneath the piston 5l on the piston rod 53. Extending from top to bottom of the air box, which is in this case square, are guide rods 58. These rods extend through the piston. 59 is a carrier on the piston rod 53, 60 is a stepped supporting frame contained within the box. v0n this frame rest a series of. separate spaced varying weights 6|. These weights are strung upon the piston rod 53 and the guide rods 58. As the `air pressure beneath the piston increases, it forces it up, the

carrier 59 picks up successive weights thereby offering an increasing resistance to the upward movement of the piston. The valve blades and their associated parts are in inherent unbalance or themselves counterweighted so that as the, piston rises, the valve tends to open and vice versa. By this arrangement, variation in pressure in the system is directly eiective to vary the degree of opening of the valve just as it wasv in the device of Figures' 3 and 4.

Since the output characteristics of fans available for this kind of service vary and usually vary irregularly with respect to variations in speed and pressure and the like, the mass of the various weights must' vary in consonance to maintain proper control. When designing for a new fan then, the design of the weights must" be 'more or less empirical to produce the desired result and so the variation between the different weights will usually be an irregular one.

While we have shown our invention associated with a well-known type of air valve, wherein the rotation of a shaft causes radially disposed vanes to open and close radial ports, it will be understood that al wide range of air valves might be used interchangeably with the type disclosed.

Such valves may or may not be rotatable valves tothe extentv that they differ in detail from the specific form we have shown. It would become e necessary to interpose between the valve and the Y box. When the box is square, guide rods are used because rotation of the square or polygonal shaped lbalance weights' would cause binding. The weights are made square because it is easy and cheap to shear offplates from a. lead sheet to provide a close control of weight. So far as `operation is concerned, Vthe device might just as well have a cylindrical control cylinder, in which case the 4guide rods would not be needed.

In'our drawings and description, wel haveshown two forms of mechanisms having a variable moment response to pressure variations.

Many other types of mechanism might be used without departing from the spirit of our invention so long as the device or arrangement is such thatstraight line variations in the air pressure give other than straight line variations in valve control.

We claim:

1. An air control for stokers and the like including in combination, an air box, a piston mounted for reciprocation therein and in contact throughout its entire periphery with .the walls thereof,means for supplying motive fluid under .pressure to one side of the pistn to move it in one direction and yielding means tending to move it in the opposite direction, a control port through which the motive iluld escapes'from'the box, located in the wall thereof and extending throughout substantially the entire range of piston movement, the port being so shaped that piston movement effects an irregular change in the effective area of the' port and a power transmission member operated by the piston and adapted to transmit power to the. unit upon which the control is applied.

2. An air control for stokers and the like including in combination, an air box, a piston mounted for reciprocation therein, means for supplying motive fluid under pressure-to one side of the piston to move it in one direction and yielding means tending to move it in the oppositedirection, a control port through which the motive fluid escapes from the box, located in the wall thereof and extending throughout substantially the entire range of piston movement, the port being so shaped that piston movement effects anirregular change in the eiective area of the port and means for manually adjusting the effective shape and area of the port irrespective of piston movement and a power transmission member operated by the piston and adapted to transmit power to the unit upon which the control is applied.

3. An air control for stokers and the like including in combination, an air box, a piston mounted for reciprocation therein, means for supplying motive fluid under pressure to one side of the piston to move it in one direction and yielding means tending to move it in the opposite direction, a control port through which the motive eld escapes from the box, located in the wall thereof and extending throughout substantially the entire range of piston movement, an apertured adjustable clousure for theport, so shaped that changes in piston position effect varying changes in opening area and a power transmission member operated by the piston and adapted to transmit power to the unit upon which the control is applied. v

4. An air control-for stokers and the like including in combination, an air box, a piston mounted for reciprocation therein, means for supplying motive uid under pressure to one side of the piston to move itin the opposite direction, a control port through which the motive iiuid escapes from the box, located in the wall thereof and extending throughout substantially the entire range of piston movement, an aperturedv closure for the port, so shaped that changes in piston position eii'ect varying changes in opening area, means for manually adjusting the position of the apertured closure with respect to the position of the piston irrespective of piston movement and a powerv transmission member operated-by the pistonand adapted to transmit power to the unit upon which the control is applied.

5. An air control for stokers and the like comprising an air box, a piston movable therein, means for supplying air under pressure to the box below the piston, a control element responsive to the movement of the piston, an aperture vin the wall of the box, the total cross sectional area of which varies variably in response to different of the box, means for adjustably moving the plate' along a line generally parallel with the line of movement of the piston, the side Walls of the aperture in the plate being out of parallelism and a power transmission member operated by the piston and adapted to transmit power to the unit upon which the control is applied.

7. An air control for stokers and the like including in combination, an air box, a piston movable therein, means for supplying air under pressure to the box on one side of the piston to -move it, the wall of the box being apertured, an

apertured plate closing the aperture in the wall of the box, means for adjustably moving the plate along a line generally parallel with the line of movement of the piston, the aperture in the plate being so shaped that the piston as it moves is adapted variably and irregularly to change the effective cross sectional area of the aperture inthe plate and a power transmission member operated by the piston and adapted to transmit power to the unit upon which the control is applied.

8. An air control for stokers and the like including in combination, an air box, a piston mounted. for reciprocation therein, means for supplying air under pressure to one side of the box and an exhaust port associated with the same side of the box, means responsive to change in piston position for varying irregularly the eective area of the exhaust port and a power transmission member operated by the piston and adapted to transmit power to the unit upon which the control is applied.

9. A11 air control for stokers and the like including in combination, an air box, a piston mounted for reciprocation therein, means for supplying air under pressure to one side of the box and an exhaust port associated with the same side of the box, means responsive to change in piston position for varying irregularly the effective area of the exhaust port, and manual means for adjusting, independent of piston position, the variation of the port in response to the piston movement and a power transmission member operated by the piston and adapted to transmit power to the unit upon which the control is applied.

10. An air control for stokers and the like comprising an air box, a piston movable therein, means for supplying air under pressure to the box below the piston, a control element respon sive to the movement of the piston, an aperture in the wall of the box, the effective opening of which varies as a result of piston movement in coordination with the inordinately variable delivery characteristics of the air supplying means under varying circumstances to maintain volume and pressure characteristics necessary for the proper operation of the unit upon which the control is applied.

ROBERT W. SUMAN. EDWARD WALTER SCHMIDT.

Images