US2120046A - Stoker - Google Patents

Description

June 7, 1938. F. c. TRETHEWAY STOKER June 7, 1938. F. c. TRETHEWAY 2,120,046

STOKER Filed May 20, 1957 5- sheets-sheet 2 n ww nv NCQ.

June 7, 1938. F. c. TRETHEWAY STOKER Filed May 2o, `1937 3 sheets-sheet 5 Patented June 7, 1938 PATENT. oFFicE STOKER Frederick C. Tretheway, Wilkes-Barre, Pa., as-

signor of one-fourthv to Charles P. Stewart,

Forty Fort, Pa.

, Application May 20, 1937, serial 10,143,785

16 Claims.

This invention relates to stokers, and more particularly to over-feed stokers, that is, stokers arranged to deliver coal or other solid fuel to a furnace above the lire and to discharge the fuel on top of the fire.

One of the objects of the invention is to provide a stoker which is of simple and inexpensive construction, which is reliable in operation, and which may be connected to existing furnace installations with a minimum of changes or alterations in the furnaces.

Another object is to provide means for efliciently and automatically controlling the operation of a stoker of the kind referred to.

A further object is to provide a stoker adapted to be connected to a furnace in such manner as to permit its being easily moved aside from the furnace charging door so as to permit hand-firing in possible emergencies resulting, for examvple, from failure of the power supply.

Other objects willbecome apparent from a reading of the following description, the appended claims, and the accompanying drawings, in which:

Figure 1 is a view in front sido elevation showing a stoker embodying the invention connected to a furnace of conventional design; Y

Figure 2 is a top plan view of the arrangement shown in Figure 1;

Figure 3 is a view in rear side elevation of the arrangement shown in'Figure 1;

Figure 4 is a top plan view on an enlarged scale showing a charging carrier tray and part of the associated control mechanism; v

Figure 5 is a view in side elevation drawn on an enlarged scale and showing the subject matter disclosed in Figure 4; l

Figure 6 is a transverse sectional view taken on=the line 6 6 of Figure 2;

Figure 7 is a transverse sectional view taken on the line 'l--l of Figure 2;

Figure 8 is a detailed view in side elevation and on an enlarged scale showing driving gears;-

Figure 9 is a sectional view of a drive screw and two of the gears shown in Figure 8;

Figure 10 is a detailed view of controllinkage, shown in one position; and

Figure l1 is a detailed view of the same control linkage shown in a different position;

For the purposes of illustration, a representative embodiment of the invention, is shown con-` Generally stated, the Stoker includes a support or frame B, a carrier tray C mounted for reciprocation on the support B, a hopper D, and means generally designated E for reciprocating the carrier tray so as to move it into and out of the furnace through an opening 2a in the charging door `2.

The support B comprises two longitudinally extending side frame members 6, the inner ends of which are connected to the door 2, and the outer ends of which are joined by a cross frame part. 1. The outer end of the frame is' supported by means of a standard or leg 8 having at its lower end a hoor-engaging wheel 9 having swivel connection to the bottom of the leg 8. All of the tray for reciprocation horizontally on the support B. The tray C comprises vertically extending sides |2|2 and ends la-ls an rigidly connected together, and bottom gates IlK-M Y which are mounted on hinges I5 havingtheir axes extending longitudinally with especthto the direction of movement of the tray, the arrangement being such that the gates, when in horizontal position, form the bottom of the tray, as shown in full lines in Figure 6, the gates, however, being movable downwardly to the dotted line position shown in Figure 6 to discharge the contents of the tray at the proper time. The sides l2-I2 extend outwardly beyond the outermost tray end I3, and are spanned by a at sheet I6 which is shown in Figure '7 and which serves as va hopper valve for preventing flow of fuel from the hopper when thetray has been moved to the position shown in dotted lines in Figures land 2.

The hopper D is supported on the side frame member .6 of the supporting frame 'B and is provided with a discharge opening Ildlocated directly above the path of the carrier tray and just outside the charging opening yI. In operation, assuming that no fuel need be added to' the flr the parts will be inthe full line positionsshown in .Figure 1, that is', the carrier tray will be in its, retracted position completely outside of the furnace, and will be filled with coal or other'solid fuel. When the fire condition is such that coal should be added, control and driving mechanism later to be described will cause the carrier tray to move inwardly to the dotted line position shown in Figures 1 and 2, at which time the bottom gates I4 will automatically be released so as to fall to their dotted line positions yas shown in Figure 6 and thereby to discharge the fuel evenly over the surface of the fire. It should be noted that, as the outermost end I3 of the charging tray moves past the hopper, the plate or valve I will move under the hopper discharge opening so as to close the latter and to prevent fuel from flowing therefrom. After the contents of the tray have been deposited upon the fire, the carrier tray will be moved outwardly to the position shown in full lines in Figure 2. As soon as the outermost end I3 of the tray has passed undcr the hopper dis- I charge opening, fuel will flow down into the tray preparatory to another charging operation.

Means are provided for releasably holding the gates I4 in vtheir closed positions until the tray has reached the position shown in dotted lines in Figures 1 and 2, such means being adapted to release the gates I4 as soon as the tray has reached its charging position, andimeans also are provided for returning the'gates to their closed l positions in response to outward movement of the carrier tray. In the form shown, each gate is provided with an apertured ear I3 adapted to be releasably held by a U-shaped latch member I3 having legs 20-20 insertable respectively into the ears I8. 'I'he legs 20 of the latch member I9 are slidable in the end I3 of the tray and a cross member 2I at the outer end of the carrier.

A striker plate 22 is connected to the legs 20 of the'latch member and is adapted to engage the furnace door just before the ,charging tray has reachedl the position shown in dotted lines in Figures 1 and 2, so that continued movement .of the chargingv tray will disengage the ears I3 from the respectively associated legs 20, thereby permitting the gates to swing to open position. 'Ihe opening of the gates is limited by means of a stop member 23 which is mounted in fixed relation to the furnace, the location of the stop being such that the gates will swing to an inclined position as shown in Figure 6, but cannot swing all the way down. During return movement of the tray, the gates will engage an inclined cam plate -24 which will cam the gates upwardly-to their closed positions. The carrier tray will then continue to move rearwardly, causing the curved portion of the U-shaped latch I3 to strike the cross frame member 1 of the support. Thereafter, continued rearward movement of the tray will cause the legs 20 of the latch member to be projected into the ears I8 of the bottom gates, thus latching the gates preparatory to theperformance of another charging operation. s

The means E for reciprocating the charging tray comprises a screw shaft 25 journalled at 25-21, and a travelling nut 23 on a cross head 2l connected to the carrier tray by means of bolts 3l. Rotation ofthe screw shaft 25 causes the carrier to travel in a direction depending upon the direction of rotation of the shaft. In order to cause the carrier to move in both directions, means are provided for driving the shaft 25 in either direction. As shown in Figures 8 and 9, this means may include two bevel gears 3i and 32 Journalled on the screw shaft 25 for free rotation relative thereto, both being in mesh 'with a common bevel gear 33 on a drive shaft 34 driven by a motor 35. A 'clutch member 35 disposed between tl'xe bevel gears 3| and 32 lis splined for shifting movements on the shaft 25, but is constrained against rotation relative thereto. 'The clutch 'member 36 is provided at its opposite ends with clutch teeth 38 adapted selectively to engage teeth 39 on the bevel gear 3i and teethffllron the bevel gear 32, dependingv upon the position of the clutch member longitudinally with respect to the screw shaft. For shifting the clutch member so as to engage selectively with the bevel gears 3I-32, there is provided a shiftable control rod 4I extending longitudinally of the screw 25 and provided with a fork 42 adapted to engage opposite sides of a ange 43 surrounding the clutch member 36. 'I'he inner end of the control rod is mounted for sliding movements in a casing 44 housing the gears 3|, 32, and 33 and the clutch` member 36,' and the rearwardly projecting end of the rod extends through an ear 45 on the cross head 29, being mounted for sliding movements in a bracket 44 carried by the cross frame part 1. Fixed to the rod are spaced abutments or collars 46 and 41 located on opposite sides of the ear 45. A cushioning spring 48 is interposed between the collar 46 and the ear 45, and a cushioning spring 49 is interposed between the collar 4'I and the ear 45. Adjacent its outer end the rod is provided with a pin 5I) engaging a toggle lever 5I pivoted as at 5I". A spring-pressed toggle arm 52 cooperates with the lever 5I for yieldably holding the rod 4I in either of two positions to which it is shifted as hereinafter explained.

In operation, assuming the carrier tray to be in the position shown in full lines in Figures l and 2, and assuming that the fire condition calls for the addition of more fuel, the motorl 35 will be started, driving the bevel gears 3|, 32, and 33. The clutch 35 will previously have been shifted into engagement with the bevel gear 3i to cause rotation of the shaft 25 in a direction to move the travelling nut, and with it the carrier tray, into the furnace. inner position, as shown in dotted lines in Figures l and 2, and the gates have been dropped in the manner previously described, the ear 45 will engage the cushioning spring 48 so as to exert pressure upon the collar 49, and move the shiftable control rod to the left. 'I'his will shift the clutch member 36 into engagement with the bevel gear 32, causing the screw shaft.25 to be reversed and driven in the opposite direction, and causing the travelling nut 23 and the carrier tray to be moved to theirouter positions. VWhen the carrier tray approaches its outermost position,

the ear 45 will e'ngage the cushioning spring 43 and shift the control rod 4I to the right so as to move the clutch member 35 4into engagementwith the bevel gear 3i. 'Ihis will cause the screw shaft 25 to be reversed again so as to drive the carrier back into the furnace. operation will be continued automatically until the required amount of fuel has been deposited upon the fire, at which time movement of the carrier will be discontinued by fire-responsive control means hereinafter described, with the carrier in its outermost position.

Means for automatically controlling the tem- After the tray has reached its Such reciprocating i perature in response to low and high temperal door 54, bothpivoted at their top edges in the well known manner. The furnace regulator is provided with the usual regulator beam 55, which moves counterclockwise in response to a high temperature fire condition, and clockwise in response to a low temperature lire condition. A draft door rod 56 connects the regulator beam to the draft door 53, and a check draft door rod 51 connects the check draft door 54 to the regulator beam. A switch 58 in circuit with the motor 35 is connected to the regulator beam by means of a link 59. The arrangement is such that when the fire temperature reaches a predetermined relatively high value the regulator beam will move in a. counterclockwise direction so as to close the 'draft door 53, open the check draft door 54, and

,reaches a predetermined low condition, the regulator beam will move in a clockwise direction,

opening the draft door 53, closingfthe check draft door 54, and also closing the switch 58 so as to start the motor 35. Starting of the motor in response to the low re condition will operate the stoking mechanism so as to feed coal to the fire in the manner already described. When the fire temperature has risen to a predetermined value, the regulator beam will move in a counterclockwise direction, thereby closing the draft door 53, opening the check draft door 54, and opening the switch 58 so as to stop the motor and to discontinue feeding of fuel. Y

In accordance with .an important feature of the invention, the control mechanism includes means for preventing opening of the switch 58 to stop the motor except when the carrier tray is in its retracted position-outside of the furnace 'so as to prevent the stoking mechanism. fromI being stopped when the carrier tray is in thefurnace directly above the fire. In the mechanism disclosed for the Apurposes of illustration, there is provided a latch 60 pivoted as at 6| on the support B and having an arm 62 engageable by the outer or rearmost edge of the cross head 29 when the latter approaches its outermost position. The latch also is provided with a trigger portion 63, the arrangement being' such that, when the cross head moves rearwardly, a leg 64 thereon will engage the arm 62 so as to swing the latch in a clockwise direction as viewed in Figures 3, 10, and 11, and will engage the trigger 63 when the cross head is moved in the opposite direction or towards the furnace, so as to swing the latch 60 in a counterclockwise direction. A link 65 is pivoted at one of its ends as at 66 to the latch 60, and at its other end is pivoted as at 61 to one arm of a bell crank lever 68, itself pivoted to the support B as at 69. A chain or draw member 10 is connected to the other arm of the bell crank lever 68, and passes over a pulley 1| and thence down for connection to the regulator beam as at 12.

In operation, assuming that the re condition does not call for the addition of coal, the draft door 53 will be closed, the check draft 54 will be open, the switch 58 will be open, the carrier tray will bein its outermost position, and the latch 60, the link 85, and the chain 10 will be in the position shown in Figure 1l. Asv soon as the fire reaches a predetermined low temperature condition, Ithe regulator beam will swing in a clockwise direction, and this will open the draft door 53, close the check draft door 54, and close the switch 58 so as to start the motor 35. Operation of the motor 35 will cause theV carrier tray to be moved into the furnace to deposit a charge of coal on the're. The lspeed of the motor and pitch of the feed' screw is such that the tray will move slowly, the speed depending upon the type of coal used and upon draft conditions. In one installation, from ten to fifteen minutes for a complete charging and return stroke of the carrier has been found to be the proper speed. If, however, the draft or other re conditions should be such that the `predetermined high-limit temperature is reached while the carrier tray is still in the furnace, or partially therein, it. will be impossible for the motor to stop until after the carrier tray has been returned to its outermost position. This is due to the fact that, when the carrier tray starts to move inwardly from its outermost `or retracted position, the trip lug 64 on the cross head 29 will engage the trigger 63, thereby moving the latch 60, the link 65, and the bell crank lever 68 to the positions shown in Figure 10. This causes a tightening of the chain 10, which has the eifect of holding the regulator beam against counterclockwise movement. Thus, even Y though the regulator should have a tendency, in

response to high fire condition, to open the switch 58, it will not be able to do so because of the restraining effect of the chain 10. Thus, the motor circuit must remain closed until the carrier tray has returned to its outer position, at which time the cross head 29 will engage the arm 62 of the latch 66 so as to move the latch, the link 65, and the bell crank lever 68 to the positions shown in Figure 11. Such movement of the bell crank lever 68 slackens, the chain or draw member 10, thereby permitting the regulator beam to move in a counterclockwise direction so as to close the draft door 53, open the check draft door 54, and'open the circuit 58, thereby discontinu-v thereby giving the fire a chance to burn at an increased rate just before fresh coal is added. This maybe accomplished in various ways, and in the form' shown is accomplished by arranging the switch 58 to have a small amount'of. movement before the contacts actually engage one another to close the circuit, the switch constituting a delayed action device for starting operation of the carrier after the draft door 53 has been opened.

Although the stoking mechanism and controls shown for the purposes of illustration` embody the invention in a form which has been found to be practical in actual use, and is the at present preferred form, it will be understoodthat various changes may be made without departing from the invention as defined in the claims.

I claim:

1. In an overfeed stoker for a furnace or the like, the combination of a Support; a fuel carrier reciprocably mounted on said support for movements into and out of the furnace; a tray to said carrier; means for causing the gate to open when the carrier reaches a'predetermined position within the furnace; means for closing the gate in response to movement of the carrier to its retracted position; a screw extending longitudinally of the path of travel of the carrier; a travelling nut connected to said carrier and op- `eratively engaging the screw; and means for rotating the screw sequentially in opposite directions for effecting reciprocation of the carrier.

3. In an overfeed stoker for a furnace or the like, the combination of a support; a fuel carrier reciprocably mounted on said support for movements into and out of the furnace; a gate in the bottom of said carrier; means for supplying fuel to said carrier; means for causing the gate to open when the carrier reaches a predetermined position within the furnace; means for closing the gate in response to movement of the carrier to its retracted position; a screw extending longitudinally of the path of travel of the carrier; a travelling nut connected to said carrier and operatively engaging the screw; means for rotating the screw sequentially in opposite directions for effecting reciprocation of the carrier; and control means responsive to movement of the carrier for reversing the vdirection of movementl thereof at the ends of its reciprocating movements.

4. In an overfeed stoker for a furnace or the like, the combination of a support; a fuel carrier reciprocably mounted on said support for movements into and out of the furnace; a gate in the bottom of said carrier; means for supplying fuel to said carrier; means for causing the gate to open when the carrier reaches a predetermined position within the furnace; means for closing the gate in response to movement of the carrier to its retracted position; a screw extending longitudinally of the path of travel of the carrier; a travelling nut connected to said carrierr and operatively engaging the screw; a shiftable clutch member splined for sliding movements on said screw; two gears journalled for free rotation about and with respect to the screw and' being respectively provided with clutch elements selectively engageable with said clutch member; power driven means for operating said gears in mutually'reverse directions; and'means for selectively engaging said clutch member with one or the other of the first two named gears.

5. In an overfeed stoker for a furnace or the like, the combination of a support; a fuel carrier reciprocably mounted on said support for movements into and out of the furnace; a gate in the bottom of said carrier; means for supplying fuel to said carrier; means for causing the gate to open when the e'arrier reaches a predetermined position within the furnace; means for closing the gate in response to movement of the carrier to its retracted position; a screw extending longitudinally of the path of travel of the carrier; a travelling nut connected to said carrier and operatively engaging the screw; a shiftable clutch member splined for sliding movements on said screw; two gears journalled for free rotation about and with respect to the screw and being respectlvely provided with clutch elements selec- @tively engageable with said clutch member; power driven means for operating said gears in mutually reverse directions; and means responsive to movement of the carrier for selectively engaging said clutch member with one or the other of the rst two named gears.

6. In an overfeed stoker for a furnace or the like, the combination of a support; a fuel carrier reeiprocably mounted on'said support for movements into and out of the furnace; a gate in the bottom of said carrier; means for supplying fuel to said carrier; means for causing the gate to open when the carrier reaches a predetermined position within the furnace; means for closing the gate in response to movement of the carrier to its retracted position; a screw extending longitudinally of the path of travel of the carrier: a travellingv nut connected to said carrier and operatively engaging the screw; a shiftable clutch member splined for sliding movements on said screw; two gears journalled for free rotation about and with respect to the screw and being respectively provided with clutch elements selectively engageable with said clutch member; power driven means for operating said gears in mutually reversedireetions; a shiftable control rod extending longitudinally ofthe screw and being connected to said clutch member; spaced abutments on said rod; and means movable with said carrier and adapted to engage said'abutments for shifting the rod.

7. In an overfeed stoker for afurnace or the like, the combination of va support; a fuel carrier reciprocably mounted on said support for movements into and out of the furnace; a gate in the bottom of said carrier; means for supplying fuel to said `carrier; means for causing the gate to open when the carrier reaches a predetermined position within the furnace; means for closing the gate in response to movement of the carrier to its retracted position; a screw extending longitudinally of the path of travel of the carrier; a travelling nut connected to said carrier and operatively engaging the screw; a shiftable clutch member splined for sliding movements on Asaid screw; two bevel gears journalled for free rotation about and with respect to said screw and being respectively provided with clutch elements selectively engageable with said clutch member; a power driven third bevel gear in mesh with both of said rst named two bevel gears; and

means for selectively engaging said clutch mem` ber with one or the other of said first named bevel gears.

8. In an overfeed stoker for a furnace or the like, the combination of a support; a fuel'carrier tray reciprocably mounted on said support for movements into and out of the furnace; a bottom gate in said carrier tray hinged about an axis extending longitudinally of the direction of movement of the tray; means for causing the bottom gate to swirg downwardly to open position when the tray reaches a4 predetermined position within the furnace; a cam surface fixed with respect to the furnace and'being engageable by said gate while the tray is being moved toward its retracted position for camming the gate upwardly; means for supplying fuel to said tray; and means for reciprocating said tray.

9. In an overfeed stoker for afurnace or tlie like, the combination of a. support; a fuel carrier tray eciprocably mounted on said support for movements into and out of the furnace; two bottom gates in said carrier tray hinged about an axis extending longitudinally of the direction of movement of the tray and centrally of the tray; releasable means for holding said gates upwardly in closed position and responsive to movement of the tray to a predetermined position within the furnace for releasing the gates and permitting them to drop to open position; cam means fixed with respect to said furnace and being positioned to be engaged by said gates when the tray is moved toward its retracted position for camming-the gates upwardly; means for re-setting said releasable means to hold the gates in closed position; means for supplying fuel to said tray; and means for reciprocating said tray.

10. Combination as defined in claim 8 and in which there also is included a xed gate stop for limiting opening movement of the gate to an inclined position.

11. Combination as defined in claim 9 and in which there also is provided a xed gate stop for limiting downward opening movement of the gates respectively to oppositely inclined positions.

12. In a stoker for a furnace or the like having a charging opening, thecombination of a charging device mounted for reciprocation through said opening into the furnace over the grate thereof and out of the furnace; driving means for effecting reciprocation of said device; means for starting said driving means in response to low fire condition; means for stopping said driving means in response yto relatively increased re condition; and means for rendering said stopping means inoperative to stop the driving means while the charging device is over the grate.

13. In a stoker f'or a furnace or the like having a charging opening, the combination of a charging device mounted for reciprocation through said opening into the furnace over the grate thereof and out of said furnace; driving means for reciprocating said device; means responsive to low re condition for increasing the rate of combustion and for starting said driving means; and means responsive to increased fire condition for decreasing the rate of combustion and stopping said driving means and including an element movable in response to outward movement of the charging device for limiting stoppage of the driving means in a position whenv the charging device is retracted from over the grate.

14.-In an overfeed stoker for a furnace or the like, the combination of a support; a fuel carrier reciprocably mounted on said support for movements into and out of the furnace, a gate in the bottom of said carrier; means for supplying fuel to said carrier; means forcausing the ygate to open when the carrier reaches a predetermined position within the furnace; and a cam fixed with respect to said furnace and adapted to cooperate with said gate for closing the latter in response to movement of the carrier to its retracted position outside the furnace.

l5. In an overfeed stoker for a furnace or the like, the combination of a support; a fuel carrier tray reciprocably mounted on said support for movements into and out of the furnace; hinged bottom gate means in said carrier tray; releasable latch means for holding said gate means upwardly in closed position and responsive to movement of the tray to a predetermined position Within the furnace for releasing the gate means and permitting it to drop to open position; means responsive to travel of the carrier to its retracted position for moving the gate means upwardly; means for resetting said releasable latch means to hold the gate means in closed position; means for supplying fuel to said tray; and means for reciprocating said tray.

16. In a stoker for a furnace having a charging opening; a charging device; means mounting said device for reciprocation through said opening into the furnace over the grate thereof and to retract the said device from over said grate; electrical driving means to effect said reciprocation including a switch; draw mechanism controlled by movement of the charging device; and means constraining the drav:r mechanism to slacken when the charging device is retracted from over said grate "to permit said movement of the control element to open said switch.

FREDERICK C. TRETHEWAY.

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