US2197428A - Automatic stoker - Google Patents

Description

April 16, 1940. F', '5 2,197,428

AUTOMATIC STOKER Filed June 11, 1337 4 Sheets-Sheet 1 INVEN TOR. Clarence E Erb ATTORNEY.

April 16,1940. c. F ERB AUTOMATIC STOKER 4 Sheets-Sheet 2 u u u u a o a a c u DUE:

Filed June 11,

san 5::

INVENTOR. Clarence F Erb AORNEK April 16, 1940. c. F. ERB

AUTDIATIC STOKER Filed' June 11, 19s":

4 Sheets-Sheet 3 INVENTOR Clarence F Erb 16, 1940. c. F. ERB 2,197,428

AUTOMATIC STOKER Filed June 11, 1937 4 Sheets-Sheet 4 Q E szllllllllllllllllllll 1 g x A g a INVENTOR. Clarence EErb BY 1 a i 1 Z TTORNEZ.

Patented Apr. 16, 1940 UNITED STATES PATENT OFFICE AUTOMATIC STOKER stokers and more particularly to stokers of the type utilizing reciprocating devices which move 1 the fuel from the front to the rear of the furnace and supply primary air for combustion. Broadly stated, the objects sought to be accomplished by this invention are the simplification and economy of construction and maintenance of the constituent elements, flexibility of control, and highly eflicient combustion of the fuel. To carry out these objects, the invention includes innovations in the design of the oscillating fuel feeding elements, commonly termed "stoker bars" and in the supporting means therefor, together with an improved apparatus for operating the fuel feeding bars.

Heretofore, in automatic stokers of the general type under consideration, the practice has been to form the entire fuel bed supporting surface of adjacent oscillating stoker bars which practice results in theuse of a large number of elements and a consequent high cost of the installation. Moreover, the tendency of the contiguous bars to warp in use causes them to wedge one against the other, thus interfering with the normal operation of the stoker.

Therefore, the primary object of this invention is to provide an automatic stoker of the type utilizing stoker bars in. which a relatively small number of such bars are used, whereby the initial cost of the installation is reduced and the liability of the system to failure is minimized.

Another object of the invention is to provide an improved support for the stoker bars, which support will not burn out in use and which preheats the primary air for combustion.

A further object of the invention is to provide an improved stoker bar which maintains the fuel bed in better condition for more efficient combustion.

A further object of the invention is to provide improved means for operating the stoker bars whereby the system is rendered more flexible and dependable in use. a

A still further object of the invention is to provide improved means for operating the stoker bars whereby the stoker remains at least partially operative even though some obstruction prevents the normal movement of one of the bars.

The construction of the operating mechanism is such that no damage results from the jamming of any movable parts of the stoker itself, this being achieved without the use of shear pin couplings or other frangible elements which must be replaced by expert workmen to render the stoker again operable.

These and other objects and advantages of the invention will become apparent from a consideration of the drawings and the following detailed specification.

In the drawings:

Figure 1 is a cross-sectional view of a stoker installation constructed in accordance with my invention;

Figure 2 is a top view of the stoker bars, showing their relation to other elements of the furnace and stoker;

Figure 3 is an end view of the stoker;

Figure 4 is a partial cross-sectional view taken along the line 44 of Figure l; and

Figure 5 is a diagrammatic view of the stoker actuating mechanism, parts thereof being shown in section. V

The stoker is illustrated as applied to a boiler furnace of conventional design having a masonry foundation'lll, a front wall l1, water tubes I l connecting with the header l2, and a transverse baflle wall IS. A hopper I 4 having a flat bottom wall is afllxed to the front of the boiler and the stoker bars 25 of my invention are adapted to propel solid fuel from the hopper to the fuel bed within the furnace.

To support the fuel bed and the stoker bars I provide a flat hollow box-like structure 20, horizontally disposed, and extending the entire width of the furnace, which may be conveniently made by casting integrally the top and side walls and welding or otherwise securing thereto a metal plate or sheet to form the bottom wall. As shown in Figure l, the support 20 extends outwardly a considerable distance from the front wall I! of the furnace and thus aids in supporting the hopper l4. To the front wall of the support 20 there is secured the horizontally disposed hydraulic cylinders 40 and 60 which are provided with the pistons 4| and it connected with the rods 32 and 62, respectively,-which extend within the support and connect with the stoker bars 25.

As shown, the stoker bars 25 are slidably mounted on the upper surface of the support 20, suitable guides 3' being provided to insure .the maintenance of proper position, and are two in number although it should be understood that any number may be used, depending on the width of the furnace and other specific conditions. The bars 25 each consists of a hollow metal body open on the bottom and having on its top wall a multiplicity of upstanding lugs 34 and a multiplicity of adjacent air delivery orifices of comparatively small size. The longitudinal cross-section of the bar 25 in Figure 1 shows a horizontal porthe inward movement of the bar. .10

tion 35 adjacent the furnace wall I1 and a humped portion 21 adjacent the rear end of the bar. Integral with the bar 25 is the wedge-shaped member 29 positioned within the hopper and being provided with a vertically extending shoulder 36 to move the fuel into the furnace. upon The wall ll of the furnace is provided with the openings 88 through which the bars 25 extend. The upper wall of the support 20 is provided with a pair of openings 2| and 22 for each bar which openings provide means for the conduct of air from within the support 20 to within the bars. Tl'he front opening 22 also allows passage of the bracket which is rigidly attached to the bar 25 at its upper end and to the rod 32 or 62 at its lower end by means of the link 3|. It is thus apparent that oscillation of the pistons 4| or 6| within the cylinders 40 or 80 results in oscillating movement of the connected bar 25.

To provide primary air for combustion, I provide the blower 42 driven by motor 44, the blower discharging into the hollow support 20 through the duct 33. Since the support 20 is air tight except for the openings 2| and 22 it follows that the air coming into it will pass through the said openings, into the hollow grate bars 25 and through the orifices thereof to the fuel bed. Since the hollow support 20 underlies the entire fuel bed, a considerable volume of turbulent air is always present which prevents the buming of the upper wall of the support. Moreover, the air passing through the support 20 is heated before it reaches the fuel bed, thus increasing the efficiency of the combustion. If desired, downwardly extending radiating fins may be attached to the upper wall of the support 20 to further the cooling of the upper wall and the preheating of the air.

Each opening 88 in the front wall I! of the furnace is provided with a gate 83 slidably mounted for vertical movement on the outer surface of the wall I! in the guides 81. Gates 83 are operated by the vertically positioned cylinders 80 and I 00 secured to the outer surface of the wall I! above the gates. Pistons 8| and IN within the cylinders are each provided with a downwardly extending rod 82 and I02 the lower ends of which pass through apertures in lugs 84 rigidly attached to the gates 83. Each of the rods 82 and I02 have a cotter pin passed through their lower end below -the lug 84 and a second pin passed through at a point spaced from the upper surface of the lug 84. A washer 86 abuts against the second mentioned pin and a strong helical spring 85, encircling the rod, is positioned between the washer and the upper end of the lug. The arrangement is such that upward movement of the rod results in the positive upward movement of thegate whereas downward movement of the rod results in a spring pressed movement of the gate. If some obstruction prevents the downward movement of the" gate, the rod can continue its movement,

the spring 85 taking up the necessaryrelative movement between the parts but continuing to 20 terminates short of the wall I3 allowing space I9 therebetween for an ash and clinker drop. The pen 24 may be of any desired construction, it may be provided with orifices or slots, it may receive air beneath from the box 20, and a portion thereof may overlie the drop I8. Suitable doors I5 are provided in the side walls of the furnace above the grate bars 25 and an ash cleanout door I5 may be provided below the support 20.

Figure 5 illustrates the operating and control system as applied to a stoker installation utilizing two stoker bars and two gates as described in connection with Figures 1 to 4, inclusive. Rod 32 connected with pistons 4| of cylinder 40 operates the upper bar of Figure 2 and rod 82 connected with piston SI of cylinder operates the lower bar of Figure 2. Rod 82 connected with 8| of cylinder 80 actuates the left gate 83 of Figure 3 which controls the opening about the stoker bar 25 operated by piston 4|. Rod I02 connected with piston IOI of cylinder I00 operates the other of the gates 83. Cylinders 80 and I 00 are identical and cylinders 40 and 80 are identical in construction.

Pistons 4|, 5|, 8| and IN are hydraulically operated and to supply a quantity of fluid under pressure, I provide the pump I54 having an inlet I55, an outlet I56 and being driven through shaft I53 by the variable speed motor I50. A source of electrical power I5I is provided for motor I50 and a variable resistance I52 is interposed between the power source and the motor so that the speed of the motor and the rate of flow of fluid from the pump may be readily controlled. The change-over valve generally indicated at I20 is provided to reverse the flow of the fluid to the cylinders 40, 50, 80 and I00 to effect the oscillating movement of the stoker bars and gates and consists generally of a cylinder I 2| having therein a piston I24 and an integrally attached valve housing I 22 having a valve I34 therein actuated by the piston I24. A rod I25 is rigidly attached atone end of the piston I24 and extends outwardly through the end wall of the cylinder |2I and into the housing I22. Each end of the cylinder I2I is provided with a port for a purpose to be later described. The lower wall of the valve housing I 22 is provided with three longitudinally spaced ports to which are connected tubes 9|, I51 and I2, respectively, and the end wall of the housing is provided with a port to which is connected the pump outlet tube I56.

Longitudinally slidable on the inner surface of the bottom wall of the housing I22 is the valve I34 which is providedwith an arched recess I35 in its bottom wall to bridge two of the three spaced ports and a longitudinal slot (not shown) on its upper surfac to receive a portion of the rod I25. The upper surface of the valve I34 is further milled to provide shoulders engaged by the spaced collars I26 and |3| rigidly fastened in any suitable manner to the rod I25. Another collar I 30 spaced from the middle collar I3| is rigidly attached to the end of the rod I25 opposite the piston I24. A block I32 having a longitudinally extending bore I33 and being provided with a grooved and milled upper surface similar to that of the valve I34 is positioned between the collars I30 and |3I and between the intervening portion of the rod I25 and the upper surface of the bottom wall of the housing I 22. As shown the block I32 is spaced from valve I34 to allow the port I2 to receive 75 fluid from within housing I22 when'the parts are in the position shown.

Formed integrally with or suitably attached to the upper surface of the rod I2l-between the collars I" and iii is the tooth I having inclined surfaces as shown whichare adapted to be traversed by the complementary inclined surfaces of the wedge I38. The wedge III is carried by the shank I81 which is spring-pressed downwardly by the helical spring I29 housed within the cos-'- ing I2I fastened to the upper wall of the valve housing I 22. The washer I39 secured to the shank I31 transmits the force to the shank and confines the spring. In order that the downward force exerted on the wedge I may be varied, a

screw I28 is in screw threaded engagement with the upper wall of the housing I21 and engages a washer Ill overlying the top of spring I21. Rotation of screw I2l alters the compression of the spring and the force exerted on the shank III.

longitudinal movement of the rod I25 causes the contacting inclined surface of the wedge I" toride up the inclined surface of the tooth I against the expansive force of the spring. Consequently the force required to move the rod is determined by the expansive force exerted by the spring. When the tip of the wedge I38 passes the high point of the tooth I", the spring, acting through the inclined surfaces, will aid the further movement of the rod thus giving a snap action to the movement of the parts. a The block I supports the end of the rod I2! against the force of the spring I29 and is moved along with the rod by the collars I3. and Iii. Likewise, the valve I is held against the inner surface of the bottom wall of the housing I22 by the rod I25 and spring I2! and is moved along with the rod I25 by the collars I2! and iii. In the position of the ports, as illustrated, port ii is connected with port Ii'l by the recess I which does not connect with the general space within housing I22. When the piston I24, valve I" and block I are moved to the right of their strokes,

' port I" is connected with port I2 and port ii control the supply of fluid under pressure to the cylinders II and C0. The valves l9, It, 90 and Ill are one-way valves, allowing fluid to flow through them only in the direction of the arrows.

Assume the systemof Figure 5 applied to a stoker installation, viewed from the front, with the cylinders in their proper relative positions. The left stoker bar is in its outward position and the left gate is in its lower position closing oi! the opening 88 above the bar. The right stoker bar is in its inward position and the upper position of piston IIII indicates that the gate above this bar is up. Now, in order that the left bar mayfeedfuelitisnecessarytoflrstraisethe left gate and in order that-the right bar may not withdraw live coals'from the furnace, the right gate should be lowered before the bar begins its outward movement.- This sequence is brought about by the following means. Fluid coming from the pump I" reaches casing I22 through tube II! and enters tube I2 from intotubesllandll. Thefluid into ii and acts against piston same and consequently the left gate. II reaches the upper end of its travel, port it uncovered and the fluid under pressure flows through tube 41 and acts against the outer end of piston 4| to move the piston and the left stoker bar inwardly'to feed a charge of fuel to the bed. At the same time the fluidin branch tube II passes through tube I08 and moves piston IOI downwardly thus closing the right gate and uncovering port Ill. This enables fluid to reach.

the cylinder u and move the stoker bar outwardly.

As piston OI moves upwardly the fluid above it (not under pressure) is discharged through tubes 'I'I, 9i, recess I35, and tube III to the reservoir I". As piston ll moves inwardly, fluid in the inner end of the cylinder ll discharges piston II and right through tube ll, check valve 9., tubes II, 11, ll,

fluid is admitted to-the stoker bar cylinders l0 and ll. If some obstruction prevents the down-' ward movement of the gate, its piston continues its travel, the relative movement being taken up by .the spring 02. Upon removal of the obstruction, by the inward movement of the stoker bar, for example, thespring II will close the gate.

Normally all pistons will reach the end of their strokes and further fluid coming into the dis-- tribution system through'tube 12 will tend to flow through the tube I2. Pressure will build up within the system and an increasing force will be exerted on the head of piston I 24. When this force overcomes the force of spring I20 acting through the inclined surfaces of wedge I" and tooth I36, the piston will move to the right with a snap action, moving valve I" to the right whereby the recess I35 will bridge ports I" and W2 and the port 9i will be open to the general space within the housing I22 so that it may receive fluid coming into I22 through tube I". Since tube 52 is-always connected with port I2, the piston I24 will be moved to the right if suflicient pressure isreached, irrespective of the position of the pistons ll and I. Therefore, even if the movement of the stoker bars is obstructed, the reversing valve will operate. and cause the bars to move in opposite directions. The advantages of this feature should be obvious. In many instances the reversal of movement will free the bar or removetheobstruction, allowing the stoker to continue its normal operation.

No attention is rcquired. Also it should be noted that if one of the bars becomes immovably jammed, the other bar will continue its normal operation, thus maintaining the flre.

Upon shifting of the valve III to the right, fluid passes from the pump I through tube I" and easing I22'into tube ll where it branches into tubes II and II. From tube II, the'fluid flows against piston 8i, moving it down, through tubes II, I4 and into cylinder 40, moving piston II and the left stoker bar outwardly. From tube II, the fluid flows into cylinder Ill, moving piston Ill upwardly; through tube and into cylinder 50, moving piston BI and the right stoker bar inwardly. As piston 8| moves downwardly, fluid below it discharges through tubes H, 13, 12, recess I35 and tube I51 to the reservoir I60. Fluid in front of piston 4I discharges through tube 41, check valve 49, tubes 50, 13, 12, recess I35 and tube I51 to I60. Fluid above piston IOI moves through tubes I03, 1|, 12, recess I05 and tube I51 to I60. Fluid in the rear portion of cylinder GI discharges through tube I05; check valve I04, tubes I03, 1|, 12, recess I35 and tube I51 to reservoir I50. When the pistons all reach the ends of their strokes or when for other reasons no more expansion of the spaces takes place, pressure builds up in lines 9i and 90, exerting an increasing force on the right end of piston I24, moving the piston to the left against the force exerted by the spring I 29, thus operating the reversing valve to cause the gates and bars to move in reverse directions. If desired, a pressure relief valve may be coupled between tubes I 55 and I55 to prevent injury to the system because of excessive pressures.

In operation, the change-over device I20 is adjusted to operate at a pressure approximately twice that required for the normal operation of pistons 4|, 6|, 8| and II. For example, if a pressure of 40 lbs. per square inch is found to be suflicient for the normal operation of the above mentioned pistons, the screw I28 is so set that a pressure of 80 lbs. per square inch is required to move piston;I24 to the other end of its stroke. This arrangement insures the full operation of the stoker bars, if unobstructed, before their direction of travel is reversed. The speed of operation of the stoker is determined by the rate of flow of fluid from the pump I54 which rate may be controlled by manipulation of the rheostat I52. If desired, rheostat I52 may be automatically controlled by any of the known stoker control devices.

During the outward movement of the stoker bar 25, the wedge-shaped end 29 thereof passes under the fuel in hopper I4, stirring up the fuel and causing a quantity thereof to move over the high point of the wedge and fall on the bar thus insuring that some fuel will be fed with each inward movement of the bar. As the bar begins its outward movement the bed of coals will be squeezed between the gate 83 or wall I1 and the raised portion 21 of the bar which action will break up any incrustation which has begun, thus effectively preventing the formation of clinkers. At the same time some of the bed will be forced about, and over the raised portion 21 where it will receive an increased supply of air to promote the thorough burning of the fuel. Before reaching the ash drop I9, unburnt particles of the fuel must traverse the inclined pan 24 through a region of high temperature, thus insuring the complete combustion of the fuel. Since the bars 25 operate in opposite directions at any one time, the entire fuel bed is periodically agitated. It can readily be seen, however, that the fuel on the bars adjacent the wall I1 is less disturbed than the fuel which has progressed to the raised portions 21. The fuel is at least p rtially coked before it reaches the raised portion 21.

The above specifically described embodiment of my invention should be considered as illustrative only. It is obvious that the basic concepts of my invention may be carried out by apparatus other than that described and that the stoker would be still operative without the use of the gates 03 and their accompanying operating mechanisms.

Having thus described my invention, what I claim is:

1. In an automatic stoker, a hollow oscillating grate bar having side and top walls and an open bottom, said top wall having a raised portion adjacent one end of said bar, a wedge shaped member attached to the other end of said bar, said member being provided with a shoulder whereby fuel may be propelled along said bar towards said raised portion upon oscillation of said bar.

2. A device according to claim 1 further characterized by a multiplicity of upstanding lugs on said top wall.

3. A device according to claim 1 further characterized by a multiplicity of apertures in said top wall.

4. A stoker installation comprising a hollow closed support, a hollow grate bar slidably mounted on said support, apertures in said grate bar, a shoulder adjacent one end of said bar, a fuel hopper supported on said hollow su'pport and encasing said shoulder, means to conduct air into said hollow support, means to conduct air nace, a grate bar slidably mounted on said support and having a portion extending through an aperture in the wall, an upstanding shoulder on said bar on the portion outside said wall, said aperture extending above said bar, a fuel hopper outside said wall encasing the shouldered end of said bar, and a gate slidably mounted on said wall and adapted to close that portion of the aperture extending about said grate bar.

6. A stoker installation comprising a furnace having a front wall, an aperture in said wall, a support within said furnace, a perforated grate bar slidably mounted on said support and having a portion extending through the aperture, an upstanding shoulder on said bar on the portion outside said wall, said aperture extending above said bar, a fuel hopper outside said wall encasing the shouldered end of said bar, a gate slidably mounted onsaid wall and adapted to close that portion of the aperture extending above said grate bar, and means to first move said gate and thereafter move said grate bar.

7. A stoker installation comprising a hollow closed support, a hollow perforated bar slidably mounted on said support, a shoulder on said bar adjacent one end thereof, a fuel hopper about said shouldered end, means to conduct air into said support, means to conduct air from said support into said bar, a cylinder mounted on said support, a piston in said cylinder connected with said bar, and means to supply operating fluid to said cylinder. "L r 8. A stoker installation comprising an oscillating stoker bar, a hopper, a portion of said bar extending into said hopper, an aperture in said hopper through which said bar extends, said aperture extending above said bar, a gate slidably mounted 'on the wall of said hopper adapted to close said extended portion of the aperture, a closed cylinder having a port at either end and a I port in its side wall, apiston within said cylinder connected with said gate, fluid pressure means to operate said bar, a tube connecting said second connected with said fluid supplying means opermentioned port with said fluid pressure means. said piston when in one position closing said second mentioned port, means to supply fluid imder pressure to one of said flrst mentioned ports, the arrangement being such that the piston must first be moved a predetermined distance before fluid can flow through the second mentioned port and the tube into the said fluid pressure means.

9. Apparatus for the sequential operation of oscillating elements comprising fluid pressure motors connected with said elements, means to supply fluid under pressure to said motors, means controlled by the actuation of one of said motors in control of the flow of fluid to the other of said motors, and a pressure responsive element able to reverse the direction of flow of the flui through said motors. I

10. A stoker installation for a furnace comprising .a hollow closed support having a horizontally disposed upper surface extending through the front wall of the furnace, a plate inclined toward the rear of the furnace and mounted on the rear portion of said support, a hollow grate bar havins side'and top walls and an open bottom slidably mounted on said support forwardly of said plate,

said top wall being apertured and having a raised portion adjacent the end nearest the plate, said top 'wall sloping downwardly from the top of said raised portion toward said plate, a fuel hopper above the outer end of saidsupport, means to longitudinally oscillate said grate bar, means on said bar to propel fuel from said hopper toward said raised portion upon oscillation thereof,

means to supply air-to within said support, and means .to conduct air from said support to said grate bar.

11. A stoker installation for a furnace comprising a hollow closed support having a horizontally disposed upper surface extending through the front wall of the furnace, a hollow grate bar having side and top walls and an open bottom slidably mounted on said support, said top wall being apertured and having a raised portion adjacent the one end thereof, said top wall sloping downwardly from the top of said raised portion to the end of said bar, the other end of said bar being wedge shaped and having an upwardly extending shoulder, a fuel hopper supported on the outwardly extending end of said support and encasing said shoulder, means to supply air to within said support, means to conduct air from said support to said grate bar, and means to oscillate said grate bar longitudinally.

12. A stoker installation for a furnace having a front wall comprisingza hollow closed support having a horizontally disposed upper surface extending through the front wall of the furnace, a fuel hopper supported on the outwardly extend- & ing end of said support, a hollow grate bar slidably mounted on said support, apertures in said grate bars, a'shoulder adjacent the outer end of said bar within said hopper, means to supply air to within said support. means to conduct air from saidsupporttosaidbanandmeanstooseiilate saidbarlonsitudinally.

itAstohsrinstallationeom a'isingasupport in control of said valve;

having a horizontally disposed face and a contiguous upwardly inclined surface,

' a grate bar having side and top walls and an open bottom slidably mounted on said horizontal surface, said bar extending in the direction of said inclined surface, the end of said bar adjacent said surface having a raised portio said top wall sloping downwardly from the top of said raised portion to the end of said bar, a series of apertures in said top wall, means to oscillate said.

bar longitudinally, means adjacent the other end of said bar to propel fuel toward said raised porshoulder on the portion within the hopper, an

opening in said wall extending above said bar, a slidable gate for said opening, a fluid presure operated motor for operating said gate comprising a cylinder having a port at either end and a third port in its side wall, a piston in said cylinder yieldably connected with said gate, a second fluid pressure operated motor to oscillate said bar, means to conduct fluid under pressure to one of the flrst mentioned ports, and means to connect the third port with said second motor.

15. A stoker installation for a furnace comprising a fuel hopper adjacent one wall of the furnace, a grate bar extending from within said hopper to within said furnace and having a shoulder on the portion within the hopper, an opening in said wall extending above said bar, a slidable gate for said opening, a fluid pressure -operated motor yieldingly connected with the gate and movable between two definite limiting positions, a second fluid pressure operated motor for oscillating said bar, means to conduct fluid under pressure to the first of said motors and thence to said second motor, the arrangement being such that the first of said motors must move to one of its limiting positions before the fluid to the second motor.

-i8.Astructureaccordingtoclaim l4further characterized by a fluid pressure responsive valve connected with the said means to conduct fluid under pressure to the first of said motors for reversing the direction of flow offluid throuah said motors.

1'1. A stoker installation comprising a pair of grate bars each provided with means 'to propelsolid fuel therealong upon oscillation thereof, a fluid pressure operated motor for each of said bars, a source of fluid pressure, means connecting said source with said motors whereby said bars will move in opposite directions, means connecting said source with said motors whereby said bars will move in reversed opposite directions, a reversing valve determining the means connected, and fluid pressure responsive means connected with said first and second mentioned means cmnmcanm;

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