US2042170A - Stoking grate - Google Patents

Description

kMay 26, 1936.

45 4f" 47% f- 71H 4Z 1 36 4f 1 G F. L. DUMONT STOKING GRATE Fi1ed Feb. 21, 195s '2 sheets-shewV 2 INVENTO ATTORNEY Patented May 26, 1936 STTES 4 Claims.

The present invention relates to improvements in stoking grates and in methods of stoking fuel carried thereon. It has long been the desideratum in this art to provide a stoking grate or so-called mechanic-al stoker which will feed the solid fuel evenly and uniformly from one end of the furnace grate to the other, without rendering the fuel bed of uneven thickness and producing uneven spots or holes which interfere with the lo combustion process, and without occasioning a substantial loss of fuel through the grate.

In accordance with my present invention, I propose to feed the fuel by successive thrust movements, a small portion thereof at a time, whereis preserved. Preferably, the feeding is accomplished by first moving a small portion of the fuel at the remote or rear end of the furnace rearwardly, such movement being followed by a movement forward of the fuel increment immediately forward the fuel first moved, and these movements repeated in succession until the fuel nearest the front of the furnace has been moved, whereupon the cycle is repeated, freshfuel being added preferably'at the front of the furnace. In this manner, each portion of the fuel is moved easily as a space upon which it is to rest has been prepared for it by the fuel movement which preceded it. At the same time the amount of fuel moved at any one time is insuflicient to disturb the thickness of the fuel bed substantially. In the prior art, so far as I am aware, this uniformity of movement could not'take place since a large fraction of the fuel was moved at each stroke. One reason for this is that heretofore it has been impracticable to provide suicient mech- Y anism for accomplishing any such movement as contemplated by the present invention because the space in the front of the furnace where such mechanism is disposed is necessarily limited.

The practice now common in stokers of various types is to use a single oscillatory actuating shaft in front of and parallel with the front of the furnace for the purpose of imparting movement to the grate bars. An important object of my invention is to utilize this type of actuating shaft by providing an improved electrical coupling between the shaft and the connections to the individual grate bars by means of which this shaft may be caused to actuate any one of the bars in any desired sequence. My improved coupling also involves a timing device of special construction'by means of which not only the 'sequence of operation of the grate bars may be determined but also the frequency of such operation in acby great uniformity of feed and of depth of fuel cordance with a desired combustion rate. A further ob-ject of my invention is to provide grate bars of uniform size and shape which may be interchangeable with any other grate bar in the same furnace.

Other and more specific objects of my invention will be apparent as the description proceeds and the novel features of the invention will be pointed out in the appended claims.

lVIy invention will be best understood by reference to the following detailed description taken with the annexed drawings, in which Figure l is a view, partly in vertic-al section, of a side elevation of a stoking grate to which a preferred embodiment of my invention has been applied;

Figure 2 is a side elevation of an individual grate bar;

Figure 3 is a view taken along the section 3 3 of Figure 2;

Figure 4 is a view, partly in vertical section, of my improved coupling device;

Figure 5 is a diagrammatic view showing the timing device and the electrical connections between it and the coupling devices;

Figure 6 is a View of the timer showing the means for driving same;

Figure '7 is an edgewise view of the timer viewed from the bottom with respect to Figure 6 but with the element 61', Figure 9, removed for-sake of clearness;

Figure 8 shows the actuating shaft and coupling device with the lead-in wires in place; and

Figure 9 is a view taken on line 9 9 of Figure 7.

Referring to Figure 1, a stoking grate l0 is shown as composed of individual inclined grate bars Il, of the type shown in Figures 2 and 3, each of'which is provided with trunnions i3, I3 which rest in sockets of supporting plates of known type, not shown. E'ach grate bar is latticed along the fuel supporting surface as indicated Vat l5, Figures 2 and 3, one vertical side I6 of the bar being longer than the opposite side and having a portion formed of cylindrical shape, the axis 0f which passes through the trunnions I3. The grate bar thus far described is of known type and per se forms no part of the present invention. As indicated in Figures l, 2 and 3, the bar is adapted to be rotated to the position of the third bar from the right in Figure 1, and by such movement advance the fuel from one end of the grate tothe other. For moving the bars, -a lever and link system is provided including a lever i9, one end of which preferably is of a shape fitting between the sides I6 and l1 of the bar and which is attached thereto at a convenient portion thereof, preferably by bolting it, as by bolt 2l, to any one of a plurality of reinforcing fins 22 which are formed at spaced intervals throughout the length of the bar. A link 24 is pivotally attached at 25 to the opposite end of each lever I9, such links 24 extending from the bars Il through the front plate 21 of the furnace where they are attached to the actuating means to be described A dumping section 28, pivoted at 29, is also shown at the right of the series of bars II and also is connected to the front of the furnace by means of link 36.

Suitably journaled at the front of the furnace (journal 3 l) is an actuating shaft 33, means being shown in the form of arm 34, link 34a and rotative disk 34h, Figure 1, for oscillating this shaft by an amount which will give the desired throw to the bars Il. Shaft 33 is connected to each of the links or rods 24 by means of a coupling device denoted generally by 35 and forming a part of my present invention. This device', which is best shown in Figure 4, is pivotally connected to a link 24 through a pair of ears, one of which, 35, is seen in Figure 4. It is the function of each coupling device 35 to operatively join the link 24 associated therewith to the shaft 33 at such times as may be desired and which are predetermined in advance. To accomplish this I have provided the following mechanism: A key 31 is disposed within a collar 39 surrounding the shaft 33, such key being adapted to register within a spline way or slot 39 formed within the shaft 33 and extending preferably continuously with the shaft. The collar 38 is bolted to the shell 46 of the coupling by means of suitable bolts (bolt 4|). Within the shell 46 of the coupling 35 is a solenoid winding 42 having a fixed core 43 of soft iron and a movable core 44 also of this material. A pin of non-magnetic material 45 extends from the key 31 to the core 44 through a bore in the core 43. The solenoid comprising the various parts mentioned is held within the shell without vibration, preferably by means of a spring Y 43 which causes the top of the winding 42 to press i against a collar 41 of the core 43 which in turn causes the latter to be pressed within a slight recess 48 within the collar 33. A suitable space is provided between the shell 49 and the collar 41 for the electrical cable 5 supplying current to the winding 42.

It is apparent from the foregoing that when the current is turned on the movable core 44 will be drawn upwardly and will press the pin and hence the key 31 into the slot 39 upon registry therewith. This will cause the coupling 35 to be pinned tothe shaft 33 and to be oscillated by it until such time as the current is released and the key 31 is allowed to drop by gravity out of the slot 39. In operation it is desirable to have the current on until after the bar l! has completed device by means of which the several coupling devices are actuated. Referring to Figure 5, a commutator is provided consistingof a conducting not shown, before the handle is moved.

ring 56 and contact areas 51 of a number equal to the coupling devices. A rotatable switch arm 59 connects in sequence the contacts 51 with the ring 56 whereby circuit is established from the source of E. M. F. 60 through the solenoids of the 5 coupling devices 35. VThe switch arm 59 is connected to shaft 6| which is driven in timed relation with the shaft 33 by a connection comprising an arm 62 on shaft 33, a link 63 and a lever 64 pivoted to shaft El and driving this shaft and 10 the contact arm 59 attached thereto through the pawl 64 and ratchet wheel 65 splined to shaft 6l. The arrangement is such that depending upon the adjustment of plate 61 the electric circuit through any given solenoid is established when 15 the slot 39 is directly over the key 31 and preferu ably slightly before this event. Means are also provided for varying the speed of rotation of the arm 59, and consequently the rate of fuel feed, by varying the effective throw of the pawl 34. For this purpose a plate E1 is rotatably mounted 0n shaft 6I and is held in position by a spring pressed detent 61', Figure 9, in such a manner that it can be rotated slightly by means of the handle 63, plate 61 having a portion cut away from the periphery so as to permit the pawl to engage the ratchet wheel E5 while the non-cut portion prevents the pawl from engaging the ratchet wheel 65, such number of teeth skipped depending upon the position of the plate. In one extreme position a single throw of the pawl will advance the ratchet wheel 65 by three or more teeth whereas in the other extreme position, obtained by moving plate 61 by a handle 68, the pawl will ride over all but one tooth on each forward movement. By means of handle 69 attached to shaft 6l it is also possible to move the arm 59 manually so as to operate any grate bar desired. The manual operation of handle 59 should occur when the slot 39 and the shaft 33 40 (as revealed by the position of the coupling then in connection with the shaft) is away from the vertical so as to obviate the connecting up of the bar 33 with coupling devices intermediate the one in action and the one it is desired to put into 45 action. Since the movement of the shaft 33 is very slow, this operation is readily performed. Or, if desired, the circuit involving the source of E. M. F. 6 may be broken by means of a switch,

50 In the embodiment shown, the commutator 55 forms both the functions of a distributor and a timer but obviously these functions may be performed by a separateY timer and a separate distributor, as is well known in the art, if desired. 55 In operation, the shaft 33 is oscillated at such a speed that several oscillations will be required to move the switch arm from one contact to another for the slowest fuel movement desired. By regulating the position of the plate 61 from 60 the position of slowest speed, less oscillation of the shaft 33 will be required to move the switch arm from one contact to the other and hence the frequency of operation of the grate bars will be increased. When contact is made by the switch 65 arm 59, the current will be on until the ratchet is again moved, an interval long enough to have the current on throughout the upward movement 4of the coupling (Figure 1) and for a short interval thereafter. It will be noted, however, that what- 70 ever frequency is used the time required for one complete movement of each grate bar is the same. From the foregoing it will be evident that I have provided coupling means between the main actuatingshaft 33 and the links 24 which may 75 be actuated in any desired sequence and preferably so as to effect a progressive feed of the fuel by actuating successive grate bars starting with the one nearest the back of the furnace. By means of this progressive movement, tendency to disrupt the fire bed is reduced to a minimum. On the other hand, if for any reason .a portion of the fuel bed becomes overloaded or a portion becomes too thin, it is possible to immediately remedy this situation by bringing into play those grate bars in the region concerned. Or, should it be desirable to operate any two or more of the grate bars together, -as for example successive bars, this can be effected by connecting to the same commutator segment the solenoids of the grate bars whose simultaneous operation is desired. It will further be seen that the utmost flexibility has been achieved, all with maintaining the same economy of space as has been obtained in the prior art where half of the grate bars have been operated .at one time. It is also apparent that I have provided a new method of fuel feed which makes for the least disturbance of the fuel bed and for this reason requires less power than has been previously the case.

My improved stoker is adapted both for mechanical feed of the fuel into the furnace as well as for hand feed. When applied to mechanical feed, it will be understood that the fuel admitting apparatus will be operated in synchronism with the stoker mechanism as is usual in the art.

It is to be understood that the principle of my invention may be embodied in other specific mechanism than that shown.

I claim:

l. In combination with a furnace, a stoker comprising a series of grate bars mounted for movement of a nature to feed the fuel through the combustion area, a common actuating shaft for said bars, automatic means for operatively connecting said bars to said shaft in a regular sequence and means for varying the frequency of actuation of said bars independently of the frequency of movement of said shaft.

2. In a furnace grate, a series of grate bars disposed beneath the combustion space of the furnace and adapted to support fuel undergoing combustion, each of which bars is mounted for a movement of a nature. such as to advance fuel from one end of the furnace to the other, said bars having a common actuating, oscillatory shaft with linkages between said bars and said shaft adapted to impart said movement to the bars and including coupling devices, each comprising a movable key and an electromagnetic device for moving the key into a slot in said shaft, thereby establishing an operative connection between the linkage and the shaft, and an electric current switching device controlled by said shaft for actuating said electromagnetic devices and hence the grate bars in predetermined sequence.

3. The combination recited in claim 2 in which said switching device includes means for manually interrupting said predetermined sequence and for operating any grate bar out of turn.

4. In a furnace grate, a series of grate bar elements, each of which is mounted for movement of a nature to .advance fuel through a combustion zone, means for moving said elements including a rod connected to each element in a manner so as to cause actuation thereof when said rod is moved back and forth, means for so moving each of said rods independently of the others, said means comprising a shaft having a movement of oscillation, means linking each of said rods to said shaft and comprising a coupling device adapted when actuated to lock said linking means to said shaft and thereby actuate a particular grate bar element, means for actuating said coupling devices in any desired sequence and means for varying the frequency of actuation of said bar elements independently of the frequency of movement of said shaft.

FRANK Il.` DUMONT.

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