US 1767248 A
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Description (OCR text may contain errors)
June 24, 1930.
v. G. LEACH MATERIAL FEEDER Filed Oct, 27, 1927 Patented June 24, 1930 UNITED STATES PATENT OFFICE VERNON G. LEACH, F CHICAGO, ILLINOIS, ASSIGNOR TO MODERNCOAL BURNER CO., 0F CHICAGO, ILLINOIS, A CORPORATION 0F ILLINOIS MATERIAL FEEDER application mea october 27, 1927. serial No. 229,056. i i
through a conduit, andfor discharging and distributing the conveyed material in a receiver, such as a furnace;
More particularly, the invention relates to feeding devices for furnaces in which coal 1o is fed from a hopperl at one end into the underside of a bed of coals i-n a furnace at the other. With such an installation there is a superincumbent mass of material upon each end of the conveyor which produces a heavy frictional drag on the conveyor.
A further possible source of friction is in the conduit connecting the feed hopper and l `the furnace. If the diameter and pitch of that portion qf the conveyor within the conduit is of the same diameter as the hopper part of the conveyor adjacent thereto, then the material carried by the conveyor willbe rammed or packed in the conduit as the result of the retarding of movement in the conduit by frictibnal contact therewith.
. It has been proposed toi-makespiral conveyors with greater pitch in the conduit section than in either the receivin'g'r delivery sections. In such case, however, the receiving and delivery sections were of uniforml diameter and pitch throughout.
When the receiving portion of the conveyor has a constant'pitch and constant diameter, the conveyor iills at its outer end with material so that a solid closely packed rotary core is formed. the rotation of which, under the pressure of the superincumbent mass of coal, consumes a large amount of power. When, however, the diameter of theI conveyor 40 gradually increases the forward movement of the material into a part of steadily 'increasing volumeboth loosens the material and 4thereby lessens the friction and als a allows the conveyor to take up more material.
Apart from the loosening effect produced by the steadily increasing volume of the convevor the frictional drag on the conveyor is ureduced by the reduction of its diameter which greatly lessens the area o-f the rotating mass within the receiving hopper.
At the discharge end the material has to -be forced upwards against the weight of superincumbent material. Progressive reduction in the diameter of the conveyor at the dischargey or delivery end has two great advantages, first reduction in frictional losses due to reduction of the area of the rotating mass within the discharge chamber and, second, the deliver instead of being confined to the far end of t e conveyor takes place gradually throughout the entire length of that portion of the conveyor lying within the discharge chamber.
Other and further important objects of this invention will be apparent from the disclosures in the specification and the accompanying drawings.
This invention (in a preferred form) is illustrated in the drawings and hereinafter more fully described.
On the drawings:
Figure 1 shows a suggested application of my device in a coal burning installation with parts in elevation and parts in section.
Figure 2 is a fragmentary sectional view in elevation taken substantially along the line II-II of Figure 1.
Figure 3 is a fra mentary sectional view in elevation taken su stantially along the line III-III of Figure 1.
As shown on the drawings:
Figure 1 shows a suggested application of my device to a stoker for feeding coal to the furnace of a boiler. The numeral 10 indicates a receiver or retort containing a bed of coal in a. furnace to which coal is fed through a conduit 11 by means of a spiral conveyor from a hopper 12. That portion of the conduit connecting the hopper 12 and the receiver 10 that lies between the joints connected at receiver end in a bearing 14 and at the hopper end in a marine bearing 15 to take the thrust of the conveyor shaft 13. The shaft 13 is driven at its front or hopper end by an electric motor or its equivalent.
It will be noted that the conveyor shaft 13 has a plurality of spiral elements 16 within the hopper. The elements 16 are of constant pitch but increase in area towards the rear or conduit end of the hopper as indicated in Figures l and 2. The arrangement shown gives, in effect, a coal pocket increasing in capacity as it moves forward in the hopper and reaching its maximum capacity just before it discharges into the conduit. Were the spiral elements of constant area the effect would be that of a pocket filled at the beginning of the path of travel and pushed through a packed mass of material, with attending serious friction losses. The spiral elements 416 discharge the material into the conduit 1,1 where it is advanced by a plurality of spiral elements 17 It will be observed that the spiral elements 17 have a constant area and have' a pitch steeper than that of the elements 16. Furthermore, the diameter of the spiral elements 17 is substantially the same as the inside diameter of the conduit 11.
Because of the change in pitch the material is swept away, as it were, from the point at which it is lirst engaged by the elements 17 and, as shown in Figure l, the conduit is only partially filled and the material is not rammed as in conveyors heretofore used for a similar purpose. It follows that the friction losses in the arrangement shown are very low, and that the conveyor functions as a truc conveyor, and not in a manner similar to that of a ram.
A plurality of spiral elements 18 on the shaft 13 discharge and distribute the material into the furnace 10. It will be noted-that the spiral elements 18 have a pitch smaller than that 0f the elements 17, andthat the pitch is constant, and that the elements progressively decrease in area towards the rear end of the conveyor.
When the conveyor is discharging intoa receiver, against an accumulated mass of the material, as for instance, when discharging into the furnace of a boiler', the screw is capable of depositing the material in the receiver so that the top of the fuel bed will slope downwards towards the back of the furnace, or of any other desired contour.
It will be understood that it is not intended that the applicant limits himself in his construction to the proportions suggested in the drawings and that the application of the device which is shown lin the drawings is but one of many possible applications.
I am aware that many changes may be made, and numerous details of construction may be varied through a wide range without` departing from the principles of this invention, and I therefore do not purpose limitingthe patent anted hereon, otherwise than necessitated y the prior art.
I claim as my invention.:
1. In an underfeed Stoker, the combination with a coal hopper having a discharge neck, a retort, and a cylindrical conduit connecting the hopper and the retort, the conduit having an internal diameter 'substantially equal to that of the neck, of a screw conveyor extending through the conduit and into the hopper and the retort, the port-ions of the conveyor within the hopper and the retort having vanes with their diameter increasing toward the conduit, and that portion of the conveyor within the conduit having vanes with a pitch materially greater than the pitch of the vanes within the hopper and the retort.
2. In an underfeed Stoker, the combination with a coal hopper having a discharge neck, a retort, and a cylindrical conduit connecting the hopper and the retort with the bottoms of the hopper, the conduit and the retort being substantially in horizontal aline-- ment with each other and the conduit having an internal diameter substantially equal to that of the neck of the hopper, of a screw conveyor extending through the conduit and into the hopper and the retort, the portions of the conveyor within the hopper and the retort having vanes of constant pitch and with their diameter increasing towards the conduit, and that portion of the conveyor within the conduit having vanes with apitch materially greater than the pitch of the vanes within the hopper and the retort.
In testimony whereof I have hereunto subscribed my name at Chicago, Cook County,
VERNON G. LEACH.