US2804350A - Fluid current conveyor system for sawdust-like material - Google Patents

Description

Aug. 27, 1957 R. P. VASTINE FLUID CURRENT CONVEYOR SYSTEM FOR SAWDUST-LIKE MATERIAL 4 Shee ts-Sheet 1 Filed Aug. 7, 1946 llllll El? [777 WYEF' HAY MST/NE Aug. 27, 1957 R. P. VAS I'INE 2,804,350

FLUID CURRENT CONVEYOR SYSTEM FOR SAWDUST-LIKE MATERIAL Filed Aug. 7, 1946 4 Sheets-Sheet 2 RAY I? Merl/v5 Aug. 27, 1957 R. P. VASTINE 2,804,350

FLUID CURRENT CONVEYOR SYSTEM FOR SAWDUST-LIKE MATERIAL.

Filed Aug. 7, 1946 4 Sheets-Sheet s BQY MST/IVE Aug. 27, 1957 R. P. VASTlNE FLUID CURRENT CONVEYOR SYSTEM FOR SAWDUST-LIKE MATERIAL Filed Aug. 7, 1946 4 Sheets-Sheet 4 RAY I? k srr/ve United States Patent '0 FLUID CURRENT CONVEYOR SYSTEM FOR SAWDUST-LIKE MATERIAL Ray P. Vastine, Oak Park, 111., assignor, by mesne assignments, to Vastine Engineering; Company, Inc., Forest Park, 111., a corporation of'lllinois The present invention relates to a sawdust. burning system and involves a method of, as well asfor,,bur-ning sawdust as a fuel in a furnace, efficiently andwithout smoke.

The present invention has for an object the provision of a method of efliciently burning sawdustas a fuel in a furnace.

Another object of the invention is to provide a system for burning sawdust and the like as a fuel in a furnace which system operates automatically in accordance with steam pressure conditions in the boiler. f

Another object of the present invention isto provide means for efficiently burning sawdust in a furnace with out the creation of smoke.

A further object of the present'invention is to provide a sawdust burning system in whichthe sawdust is' charged into a furnace in a spread condition so that all of the sawdust will be ignited and burn efliciently and smokelessly.

Another object of the present invention is to provide a sawdust fuel burning system in which the ,sawdust is Withdrawn from a source of supply by suction and delivered-under pressure into a furnace;

A still further object of the present invention is to provide a sawdust fuel burning system in which the rate of delivery of the sawdust to a boiler'furnace is regulated in accordance with the steam pressure conditions in the boiler.

Another and further object of the present invention is to provide a sawdust burning method in which sawdust iswithdrawn from a supply and agitated. The agitated sawdust is removed by suction and delivered in a suspended condition in an air stream under positive pressure into a furnace.

The invention has for a further object-the provision of a nozzle for spreading the sawdust as it is discharged into the furnace.

Another and yet further object of the present invention is toprovide a system as just described in which auto matically functioning controls are provided for operating thesystem in accordance withpressure" conditions in the boiler;

Generally speaking, the invention involves the provision of a supply of sawdust, means for. withdrawing portions of the sawdust of the supply anddelivering it to a pickup compartment wherein air under negative pres sure picks up the sawdust and withdraws it in suspension by means of a suction stream. The suction stream with the suspended sawdust in it is converted to a positive pressure stream and delivered with the sawdust into a furnace. A single instrumentality is employed for cre ating the suction and the positive pressure. Because of thei fact that a high positive pressure is necessary to create suction sufficient to Withdraw the sawdust from the compartment; means are provided for venting the ductwhich carries the sawdust in the positiveair pressure stream-so that the air pressure and velocity in the duct Willbe reduced to avalue suflicient-to carrythe sawdust ice in suspension into the furnace. Also a nozzle is employed which spreads the dust as it enters the furnace to thereby prevent the sawdust from piling upon the floor of the furnace, which spread delivery enables ready combustion of the sawdust without creating smoke, as the dust is burned before reaching the floor of the furnace.

The above, other and further objects of the present invention willbe apparent from the following descrip tion and accompanying drawings.

An embodiment of the present invention is illustrated in the accompanying drawings and the views thereof are as follows: 7

Figure 1 is a side elevational view, somewhat schematically illustrated, of the system of the present invention as arranged for supplying sawdust to the furnace of a boiler;

Figure 2' is a top plan view of the arrangement of Figure 1 showing the manner of supplying sawdust to the furnaces of twoboilers;

Figure 3 is a fragmental side elevational View of th pickup-compartment, with a part in section, showing in dottedlines a. screw conveyor. for moving sawdust from a bin to thecompartment;

Figure 4 is a vertical sectional view taken in the plane of line IV-IV'of Figure 3 V Figure 5 is a. horizontal sectional view, takenin the plane V'V of Figure 3, with some parts in elevation;

Figure 6 is an end view of the pick-up compartment, in section, with some parts in elevation, taken in the plane of line VIVI of Figure 3; and

Figure 7 is a schematic wiring diagram for the reversing motor showing connections of the reversing motor to certain of the operating elements of the'system. v

The drawings will now be explained.

A bin 15 is provided for containing a supply of sawdust. Extending from or formed as a part of the bin is a duct 16 terminating in a pick-up compartment 17.

Means are provided for moving sawdust from the bin 15 to the pick-up compartment 17. The means herein illustrated comprises a spiral or screw conveyor 18 mounted on a horizontal axis having its rear end somewhere within the bin 15 and its front end 18a in the pickup compartment 17. A shaft 19 supports the conveyor and projects through the front'wall 20 of the pick-up compartment to which projecting end ofthe shaft driving means are connected, aswill be later described.

Referring to Figure 4 it will be observed that the duct 16 is preferably rectangular in cross section. The duct, including the pick-up compartment 17, is closed on four sides for a distance from the front wall. 20 through the bin wall 21 and for a short distance into the bin (thereby defining a closed intermediate portion of the casing). Rearwardly of the covered inward portion of the duct the top is open (so as to define a material receiving opening) and inclined side wings 22 and'22a are formed'along the conveyor for receiving sawdust from the 'bin. to direct it to the conveyor 18'. The duct 16 and pickup compartment 17 thus comprise a casing or housing having a material receiving opening adjacent one end, a closed intermediate portion, and a restricted material discharge opening at the other end, which discharge opening 15 will be described in detail hereinafter.

In order to compact the sawdust about the conveyor 18 to prevent the sawdust from falling away along the upper portion of the conveyor a-tube surrounds'the conveyor 18 from its front end 18a to a point-146'ad jacent the rear end of the cover of the duct 1 6 (Figure 3) from that point, rearwardly the tube becomes a semicylindrical trough 147, terminating adjacent the inner end of the conveyor. The interiorof the tube 145 'is radially spaced from the periphery of the conveyor 13 but a-slightdistance which is suflicient to allow pieces of wood, which may be in the trough to the pick-up compartment 17.

By compacting the sawdust in the tube 145, as long as thereis ample sawdust in thebin, the sawdust in 'the tube fills it completely, thereby preventingany from falling away along the top of the tube, which falling away would result in air channels through the sawdust in the tube which would disrupt the effectiveness of the suction air stream in withdrawing sawdust from the pick-up compartment, as the suction air stream passes underneath the bottom of the pick-up compartment.

7 An air duct 23 is erected behind the bin wall 21 and near it, in vertical position, and has its open upper end 24 communicating with the interior of the bin above the supply of sawdust in the bin. A damper 148 is arranged within the duct 23 to control flow of air throughthe duct. The damper is set at the time of installation of the duct.

Referring to Figure 4, it will be noted that the bottom of the conveyor trough 25 is arcuate, which bottom extends from the inner end of the conveyor to the point 26 (Figure 3) adjacent the pick-upcompartment. As will be noted in Figure 3, the point 26 is slightly ahead of the front end 18a of the conveyor. From the point 26 to the front wall 20 of the pick-up compartment the bottom of the compartment is open, as at 155, as may be observed in Figures 3 and 6.

The lower end of the air duct 23 communicates with a hood 27 which in turn communicates with duct means 28 for delivering air from the duct 23 to the pick-up compartment 17, from what is shown in Figure 6 as the right side.

Leading from the lower part of the pick-up compartment 17, and from the left side thereof as viewed in Figure 6, is a duct 29.

Mounted on a platform 30 supported by posts 31, above the boiler room floor F, isa blower B. The duct sawdust, to pass along the 29 communicates with the inlet of the blower. A duct 3 32 communicates with the outlet of the blower and leads to the furnaces or furnace to be supplied with sawdust as a fuel.

Referring to Figure 2 boilers X and Y are disposed in side by side relation to be fired by sawdust as a fuel. The outlet duct- 32 communicates with a junction box 34 from which a branch duct 35 leads to the furnace 36 of the boiler X. Another branch duct 37 leads to the furnace of the boiler Y. The junction box 34 has means within it for proportioning the amount of fuel delivered to the furnaces of boilers X and Y, shouldthere be need for differential supply to the furnaces.

Each of the branch ducts 35 and 37 discharges into its furnace through a divergent nozzle 38. As maybe noted in Figure 1 the nozzle38 is directed in downwardly inclined position and is arranged to discharge into the furnace 36 through the front wall 39 of the furnace, above In the connection between the shaft 19 and the speed reducer 44 is a shear pin which breaks when some foreign object enters the conveyor and tends to retard the movement of the conveyor. I

As shown, the shift rod 45' of. the drive 43 is pivoted at 46 to a swinging lever 47. The lever 47 is pivoted by i one end at 48 to a lug 49 integral with the casing of V the Reeves drive.

i For swinging the lever 47. to actuate the Reeves drive in a manner to change speeds,,a reversing mot0r50 is employed.

As shown diagrammatically in Figure 7, the reversing motor 50 has a crank 51connected at one end to the motor shaft 52 and at the other end to one end of a link 53. The other end of the link 53 is pivoted at 54 to the lever 47.

The reversing motor 50 is electrically controlled by means responsive to the steam pressure conditions in the boiler. 7

Figure 7 shows a' circuit including a lead-in wire 55 in which is a resistance winding 56 from which a connection is made to the motor 50 by a conductor 57. A swinging contact finger 59 is pivoted at 60, from which pivot electrical connection is made to the motor 50 by a conductor 61. The other lead wire is designated as 58.

For swinging the contact finger 59 steam pressure responsive means are provided. The means herein shown include a pipe 62 communicating with the steam space of the boiler, which pipe enters a Sylphon bellows 63, one end of which 65 is fixed, the other end of which carrying a nose 64, is movable. The nose 64 is suitably connected to the contact finger 59, to move it as the bellows expands and contracts in accordance with steam pressure conditions in the boiler.

7 By means of the arrangement just described the Reeves drive 43 is actuated by the reversing motor 50 in accordance with the rise and fall of steam pressure conditions in the boiler.

Inasmuch as the Reeves drive is operatively connected to the conveyor 18 for rotating it to feed sawdust from the bin 15 to the pickup compartment 17, the rate of feed of the sawdust by the conveyor is thus made responsive to steam pressure conditions in the boiler. As the steam pressure falls the speed of the conveyor is increased, and as the pressure rises the speed of the conveyor is reduced.

Other means responsive to pressure conditions in the boiler are utilized for starting and stopping the conveyor drive motor 42.

Inasmuch as it is necessary to operate the blower. B to create suificient suction in the duct 29'to withdraw sawdust from the pick-up compartment 17 and deliver it to the blower, more pressure is created in the blower than is necessary to discharge the sawdust into a furnace.

In order to reduce the positive pressure and velocity between the blower and the furnace to a value which is sufficient to carry the sawdust into the furnace and discharge it thereinto under proper conditions and pressure, means are provided for venting the duct 32 between the blowertand the furnace.

The illustrated form of such venting means includes a pipe 67 having a plurality of branch connections, three of which are shown as '68, 69 and 70, to the duct 32 and opening into the dust bin. A pipe 71 leads from the pipe 67 and is connected into the duct means 28 adjacent the pick-up compartment 17 as shown in Figure 6. Thus air under positive pressure, in excess of that necessary to discharge the sawdust into the furnace, is withdrawn from the duct 32 and delivered into the pick up compartment 17 or, if desired, into the bin. The branch connection 68, 69 and are provided with dampers or valves 72 (Figure 7) which valves are connected by a -link 73 to the lever 47 and the link 53 of the Reeves drive. Thus, the dampers or valves 72 are connected to be operated by the reversing motor 50 to thereby regulate the valves 72 in accordance with steam pressure conditions inthe boiler. V

The operationof the reversing motor 50 is such that the maximum amount of air under positive pressure is reversing motor will function to reduce the speed of the conveyor drive and to operate the valves 72 in a manner to reduce the pressure and velocity of the air entering the furnace.

The bottom of the duct 16 between the point 26 and the end plate 20 of the pick-up compartment 17 is provided with an opening 155, shown in Figures 5 and 6 as rectangular. The length of the opening is substantially the diameter of the flight of the conveyor. The width of the opening is such that the area of the opening is equal to one-half, or slightly less, of the cross-sectional area of the passageway 156 in the lower portion of the pick-up compartment 17. a

While the present system has been devised, primarily, for utilizing sawdust as a fuel, it has been found satisfactory for utilizing dust made from Masonite, or like wood products, and could be used in burning feathers as a fuel it a sufficient supply were at hand; Accordingly the word sawdust is herein used generically and not by way of limitation.

The operation of the system is as follows:

At the commencement of firing, the boiler pressure is low, hence the reversing motor 50 is energized to actuate the Reeves drive 43 at high speed which, in turn, operates the conveyor 18 at high speed to supply sawdust for fuel. The blower B operates at constant speed. As soon as the blower B begins to run, a suction is created down through the pipe 23 through the pick-up compartment 17 and up through the duct 29 to the inlet of the blower. The suction stream from the duct or pipe 23 enters the passageway 156 and passes upwardly through the duct 29 thus carrying with it sawdust which has accumulated in the bottom of the passageway and in front of the conveyor, thus picking up the sawdust in suspension and carrying it through the blower where the suction stream is changed to a pressure stream and delivered into the furnace. The Reeves drive, being operable by the reversing motor 50, actuates the dampers 72 to vent the duct 32, between the blower and the furnace, to reduce the pressure and velocity of the air stream in this duct to a point where it is sufficient to carry the sawdust into the furnace but not too high as to efiect proper combustion in the furnace. The air that is thus vented passes downwardly through the duct 71 and into the passageway 156 at the lower end of the pick-up chamber.

By reason of the fact that the sawdust is packed firmly about the conveyor within the tube 145, it accumulates sawdust ahead of the end 18a of the conveyor on the bottom of the passageway 156. Packingtof the sawdust in the tube 145 prevents creation of air channels through the tube. If such air channels were present, then air from Within the bin might pass through the tube and through the opening 155 into the passageway 156 and disturb the air-fuel ratio to the furnace.

The fire in the'furnace once having been started and with a suitable amount of sawdust in the bin the system continues to supply fuel to the furnace as required.

As the steam pressure in the boiler increases, the Sylphon bellows 63, will respond to the increase of pressure. As such pressure increases the bellows will be extended to thusmove the finger 59 to slow the Reeves drive. The reversing motor actuates the swinging lever 47 in accordance with its direction of rotation to change the driving ratio of the Reeves drive to change the speed of rotation of the conveyor shaft 19. When the pressure in the boiler builds up to a predetermined value the reversing motor will stop. As the pressure in the boiler drops, because of the discontinuation of fuel supplied to its furnace, the Sylphon bellows 63 will respond to such drop in temperature and will eventually again operate the reversing motor 50 in a direction to cause rotation of the conveyor 18 to resume the supply of fuel to the furnace.

This continues intermittently as long as the furnace is in operation.

I claim as my invention:

In a fuel burning system for sawdust-like material, a fuel duct having an open end arranged to receive fuel and having a closed end opposite said open end, a conveyor screw in said dust having a terminal end spaced from said closed end of said duct for compaction of the sawdust-like material between said closed end of said duct and said terminal end of said conveyor screw, continuously variable drive means for rotating said conveyor screw, an air duct extending transversely of and below said fuel duct adjacent said closed end and beyond said terminal end of said screw, said fuel duct having a transverse opening aligned above said air duct and having a width less than one-half the width of said air duct for passage of the sawdust-like material into said air duct, and a blower having an outlet for communicating with a fuel burner and having an inlet connected to one end of said air duct, the other end of said air duct being in "communication with the atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS

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