US2173414A - Feeder - Google Patents

Description

Sept. 19, 1939. w. M. FULTON FEEDER Filed Jan. 31, 1939 2 Sheets-Sheet 1 Sept. 19, 1939. w. M. FULTON FEEDER Filed Jan. 31,1939 2 Sheets-Sheet 2 u WIIIIIIIII 'IIIIIIIIII alllllzzdllllllllllllilllllllllllllli IlllluIIlnuIIllllm V III/m i Patented Sept. 19, 1939 UNITED STATES PATENT OFFiCE FEEDER Application January 31, 1939, Serial No. 253,930

Claims.

This invention relates to feeders, and especially to feeders used to handle lumpy solids such as coal, coke, crushed stone and the like. The invention is particularly described hereinafter in 5 connection with a feeder whereby the material being fed is elevated from a lower to a higher level. For example, in the case of over-feed stokers, where coal, coke, or other lumpy fuel is fed into a combustion chamber and distributed over the top of the grates, the fuel is usually elevated and fed onto a fiat surface at the front of the combustion chamber and blown from there over the fuel bed by means of compressed air or steam. Here the feeder is required to elevate the fuel and deposit it on the surface from which it is blown into the combustion chamber. It will be understood, however, that feeders embodying the invention may also be Used to feed fuel and other materials at desired inclinations or horizontally.

Feeders of this type conventionally embody a screw operating in a pipe or casing, the fuel or other material being fed laterally into the pipe as by means of a hopper. Such feeders as heretofore constructed possess a number of defects. For satisfactory results the screw has to fit fairly snugly into the pipe so that the space between the outer surface of the screw and the inner surface of the pipe is quite limited. Hence, feeders of this type can only handle materials which are sufficiently soft to be crushed by the screw when particles are caught between the screw-flights and the entrance end of the pipe. Particles of foreign matter, such as pieces of iron, wood, flint, etc., which find their way into coal during its handling from mine to consumer, become caught between the flights of the screw and the entrance to the feed-pipe and thereby render the feeder inoperative.

To make the feed-screw and feed-pipe of sufficiently rugged dimensions and of sufliciently hard material to handle such foreign matter would excessively increase the cost of manufacture, and consequently various expedients have been resorted to in an effort to overcome these difficulties. For example, a shearing pin has been used in the screw driving mechanism which is sheared whenever the feed screw becomes clogged and offers undue resistance to rotation. In such cases, however, the feeder cannot be put back into operation without, first, removing the cause of the trouble, and second, replacing the sheared pin. These are unpleasant and timeconsuming tasks, especially where the feeder is used on a domestic stoker and the house-owner himself is called upon to do the work without adequate tools and with limited experience in matters of this kind. Another device consists in operating the feed-screw by means of a hydraulic motor, with a relief valve in the oil pressure line feeding process until the foreign matter can be removed from the feeder and at best are quite unsatisfactory makeshifts. In some types of feeders, moreover, if the feeder remains idle for a considerable length of time combustion works its way around the delivery end of the feedscrew and fuses clinker around the screw so tightly that the feeder must be disassembled and the clinker cleaned out. This latter operation not only interrupts the flow of heat from the heater, but, generally, necessitates starting the fire entirely anew.

It is an object of the present invention to avoid the foregoing difiiculties and to provide a feeder of the type characterized above which is simple and inexpensive and at the same time capable of handling lumpy material without amming.

Another object is to provide novel means for insuring passage of materials through the feeder while eliminating the usual closely surrounding pipe or casing. 1

Another object is to provide continuous feeder operation in case of obstruction at its delivery end by by-passing the material fed through the feeder.

A further object is to provide uniform passage of material through the feeder together with regulation of the rate of discharge of material from the feeder.

Other objects will appear hereinafter as the description of the invention proceeds.

One embodiment of the invention has been illustrated in the accompanying drawings, but it is to be expressly understood that said drawings are for purposes of illustration only and are Fig. 1 with the side plate removed to show the interior construction;

Fig. 4 is a horizontal sectional view of the feeder shown in Fig. 1;

Figs. 5 and 6 are detail views showing the screw-flights of the feeder; and

Fig. 7 is a detail view showing means. for mounting the screw-flights on a drive shaft.

The feeder as illustrated in the drawings may be used to elevate coal for an overfed stoker, although as stated above, materials may be fed in any desired direction by inclining the screws at an angle or arranging them horizontally. Broadly stated, the feeding mechanism comprises a main feed screw, a co-acting screw having an axial baflie flange cooperating with the flights of the main screw, and a retention plate fitted around a portion only of the circumference of the main screw. Preferably the two screws rotate in the same direction, that is to say, both rotate clockwise or both rotate counter-clockwise, and in this case the two screws are both threaded alike, that is to say, both have righthand threads or both have left-hand threads. Another important feature of the present invention is that the retention plate does not completely surround the main screw but on the contrary leaves a portion of the circumference of said screw exposed with the edges of the retention plate extending parallel to the axis of the screw, the exposed portion of the circumference being at least suflicient to admit entrance to the screw, in a direction approximately perpendicular to the screw axis, of the largest lump of material being fed. Hence there is no edge perpendicular or approximately perpendicular to the axis of the screw against which lumps of material can be forced in such a way that the screw must shear these lumps apart.

A feeder embodying these features is illustrated in the drawings. The main screw I cooperates with a second screw 2 having an axial baffle flange 3 and with a retention plate 4. The screws are threaded alike and are rotated in the same direction and at the same speed in any suitable manner as by gear wheels 5 and 6 secured to driving shafts I and 8 of screws I and 2 and interconnected by an idler gear 9. These gears may be driven in any suitable manner as by the bevel gear Ill on the gear 5 which meshes with a second bevel gear II on a drive shaft I2.

Each screw may be made as a single unit, or may be made up of a number of separate sections so that screws of different lengths can be assembled from a stock of individual flights. Further, it is desirable that the edge of the flange 3 and the feeding surface of screw I rotate in actual contact or substantially so, and hence screw 2 is preferably composed of individual flights mounted on the shaft 8 in such a manner that each individual flight may slide lengthwise on the shaft while being forced to rotate with the shaft. As shown in Fig. 6, each of these flights comprises a central hub portion I3 and a spiral portion I4 to the outer edge of which is joined the axial baffle flange 3. The hub I3 has a keyway I5 therein and the shaft 8 on which these flights are mounted is provided with a suitable spline or key which loosely engages the key-ways I5 of the flights so that the latter may slide lengthwise on the shaft but are forced to rotate with the shaft. In many cases it is sufficient to have key-ways in none but the top and bottom flights and have these two flights drive the intermediate ones through contact at the ends of the flanges 3. Spaces I6 between flights leave each one free to adjust itself lengthwise of the shaft independently of the neighboring flights.

As shown herein, main feed screw I is also made of individual flights mounted on the shaft '1. As shown in Fig. 5, each of these flights comprises a central hub portion I! having a key-way I8 therein and a spiral portion I9. However, radial elements of the top surface of this spiral portion I9 are not straight lines projecting at I right angles from hub H, as is true of conventional conveyor screws, nor does this surface possess the form of threads found on ordinary machine screws and bolts, but, on the contrary, it is made to conform substantially to the curve described by the lower edge of the flange 3 between its point of intersection with the periphery of screw I and a point adjacent the screw hub I'I. As will be seen in Fig. 5, the top surface of screw I curves upward as it approaches hub I'I, rapidly increasing in curvature as its proximity to hub II increases. The flights of screw I may each be attached to the shaft, or the top and bottom flights may be attached to the shaft and used to drive the intermediate ones through contact of the edges of the spiral portion IS), the hubs I'i snugly abutting against each other. When assembled on its driving shaft I the main screw therefore operates as a single unit, but

due to the spaces IS the flights of screw 2 are free to adjust themselves lengthwise of driving shaft 8 so that they will ride upon the companion flights of screw I and will automatically adjust themselves for wear and thus continually maintain a tight closure between the contacting surfaces of the respective flights.

In the case of very large screws where the flights of screw 2 are massive and might consequently produce undue friction in their contact with the flights of screw I, the flights of screw 2 may be resiliently supported to reduce the friction. One method for accomplishing this is illustrated in Fig. 7. The hubs of adjacent flights of the screw 2 are counterbored to form recesses 20 into which are inserted coil springs 2|, the lower ends of the springs abutting against collars 22 which are suitably secured to shaft 8 as by means of pins, said collars having an outside diameter approximately equal to the inside diameter of the counterbored spaces 20 but with sufficient clearance to permit the flights to slide freely along the shaft. The hub portions above the recesses 20 are provided with key-ways I5 as above described in which are slidably fitted keys 23 which in turn are made fast in keyways 24 in shaft 8. This construction permits the flights to slide freely in the direction of the axis of shaft 8 but forces them to rotate with said shaft, and they are guided in a true rectilinear movement by the hub portions which slide on the shaft 8, and by the collars 22 which fit slidably inside the recesses 29. The springs 2| exert a resilient force tending to raise the flights and by selecting springs of suitable length and resilience the pressure of the flights on the screw I can be relieved to the desired extent while at the same time the springs permit longitudinal adjustments of the flights when in operation.

As shown more clearly in Figs. 3 and 4, the

retention plate 4 may be suitably mounted by attaching one edge, by welding or otherwise, to a frame member 25. The other edge of the retention member, which may be termed its leading edge in the direction of rotation of screw I, flts snugly into the axial line through the points of intersection of the helical peripheries of screws l and 2. At the discharge end the leading portion of the retention member is cut away to provide an opening 26 through which material is discharged from the feeder, and atrough or spout 21 of any desired shape and length is fitted into the opening '26 for conducting the material to any desired place. Opening 26 and spout 21 are thus placed at a lower level than the top of the remainder of the retention member 4. This not only insures that the material will be dis charged through the spout 2'! without danger of overflowing the top of member 4, but as will be presently pointed out it further insures that, in the event spout 2'! becomes clogged or the flow therethrough is restricted, surplus material will be discharged over the edge of the spout and allowed to fall by gravity back to the source from which it is being fed without interfering with the otherwise normal functioning of the feeder.

The feeder mechanism thus far described may be connected to or used with a hopper or storage bin, etc., in any convenient way. As illustrated in the drawings, the feeding mechanism is installed in a hopper 28 having a lid 29 hinged at 3!! to stationary parts of the hopper so that it can be raised to permit charging fuel into the hopper. As shown, a portion 3| of the hopper extends upward above lid 29 and other portions of the hopper to house the upper part of the feeding mechanism, and partition walls 32 and 33 extend down inside the hopper to within a short distance of the bottom 34 and, in conjunction with the two outside walls 35 and 35 of the hopper, constitute an inclosure for the lower part of the feeding mechanism. The feeding mechanism is thus housed in a casing to which fuel is delivered at its bottom by the hopper. In this way the hop-per door 29 can be placed as low as desired so that fuel does not have to be lifted to an inconvenient height, and at the same time the fuel can be delivered at any desired height within practical limits by adding flights to the feeder screws. The frame member 25 is suitably attached as by means of rivets to the bottom 34 and top 3! of the hopper which also provide suitable bearings for the shafts l and 8 of the screws. A frame member 38 connects the top and bottom of the hopper on the side opposite the member 25. The frame side members 25 and 38, and the bottom 34 and top 31 of the hopper which in effect constitute crossp-ieces for the side members, thus carry the entire-feeder mechanism and comprise therewith a feeder unit which can be installed in any hopper, bin, etc. The side walls of the hopper may thus be made of relatively thin sheet metal.

The operation of this improved feeder is as follows:

Fuel such as coal or coke is placed in hopper 28, filling it to the top or as nearly so as desired. Partition walls 32 and 33 allow fuel to flow by gravity past their lower edges and into and around scr ws 5 and 2, but without completely submerging the screws which might cause irregular feed. The bottom flights. of the screws are preferably brought to a fairly sharp edge so as to scrape the surface of the hopper bottom 34. As the screws rotate, being driven by the gearing described above, screw i takes in fuel at its bottom and at that portion of its circumference which is left openly exposed and the fuel thus taken in is carried around until it is confined by the retention plate 4 so that it cannot slide off of the revolving flights. At the same time screw 2 carries material to the screw l at its open side.

It will be noted that the edge of the retention member 4 where the fuel enters the screw I is disposed in a direction parallel with the axis of rotation of the screw and not perpendicular thereto, so that any lumps of material which may be caught between the screw and this vertical edge merely slide along the edge until they become free from the screw and do not have to be sheared. For this reason the feeder is nonclogging and no shearing pins or other safety devices are required. Once the fuel has entered the screw, it is forced upward and around until it contacts the revolving baffle flange 3 of screw 2, whereupon it is confined within a space bounded by retention plate 4 and flange 3 from which it cannot escape. It is then carried upward by the action of screw 1 until it reaches opening 26 whereupon it is swept off through this opening into spout or trough 2'! by the revolution of screw 2.

Fuel is thus being continually elevated from the bottom of screw I and discharged through trough 2'1. The construction is such that if spout 2'! should for any reason become clogged so that fuel would fail to pass through it, then screw I would carry the fuel on up and discharge it over the top of the edge of the spout 21 and allow it to fall by gravity back into the hopper. If the fuel should contain lumps too large to drop through the open space between the screws and the hopper walls, then this space may be enlarged to any desired size by locating screw 2 away from hopper wall 35, all other parts of the feeder remaining undisturbed. As material drops through this space to the hopper bottom it is carried around by screw 2 and delivered to screw l to be again fed upward. As long as opening 26 is clogged or restricted, fuel will be carried up and dropped back, thus merely circulating it, and no damage will be done to the feeder.

Overfeed stokers are usually engineered by combustion experts who predetermine the amount of fuel required per hour, and variations from this requirement do not have to be made with great frequency nor within very wide limits. When, therefore, the feeder just described is used for feeding fuel to an overfeed stoker, necessary variations in rate of feed can be obtained by any well known device for varying the speed of the driving shaft. When, however, this feeder is: used for handling other materials where more fr quent changes in rate of feed are required, and the material must be metered more accurately, this can be accomplished very simply and effectively by any suitable means for regulating the rate of discharge of materials through or from the spout 2?. In the form shown in Fig. 1, a gate 39 is provided in spout 2?, said gate sliding in ways 40 and being operated by a screw 4i threaded in a bracket 42 suitably attached to the top of the spout 21. The screw ll has a suitable swivel connection with the gate 39 and. as here shown extends freely through the upper part of the gate into an opening 43 where it terminates in a head or disk 44. As the screw is rotated, gate 39 is carried up or down with it, thereby enlarging or reducing the size of the opening through the spout 21 and increasing or decreasing the amount of material discharged per hour through the spout 21. This simple and expeditious method of regulating the rate of feed is made possible by the fact that, as previously pointed out, the feeder will continue to deliver material to spout 21, and such portion of this material as does not pass out freely through the spout is carried on up above the opening and discharged back into the hopper.

Since screws I and 2 are not confined within closely fitting housings, but on the contrary are open on all sides except for the fractional portion of screw I inclosed by retention plate 4, this feeder will handle any material whose size does not exceed the pitch of the flights. If any lumps of material greater in size than the pitch of the screw-flights are placed in the hopper, the feeder automatically refuses to take hold of them and they remain in the hopper after all material of proper size has been fed out. It is therefore evident that the feeder cannot become injured by foreign matter at either its intake or discharge ends. Furthermore, since the feeder screws l and 2 are of the open type, friction between the screw and the fuel is greatly reduced, and correspondingly less power is required.

It is to be further noted that since screws l and 2 rotate in the same direction, and since the peripheral speed of the flange 3 is greater than the peripheral speed of the hub or adjacent body portion of screw I, there is a constant tendency for the material being fed to be driven away from the line of contact between the periphery of screw 2 and the hub, or body, portion of screw I, instead of being drawn into it. Hence the wedging and jamming of material between the screws, which is a defect in other feeders, is completely obviated in the present invention.

While only one embodiment of the invention has been described and illustrated in the drawings, it Will be understood that the invention is not restricted to this embodiment, and that various changes may be made in the form, details of construction and arrangement of the parts without departing from the spirit of the invention, many of which changes will now be apparent to those skilled in the art. Reference is therefore to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. Feeding mechanism comprising a pair of intermeshing screws threaded in the same direction, means for rotating said screws in the same direction and at the same speed, one of said screws having an axially extending periphery which rotates with its edge substantially in contact with the feeding surface of the other screw, and a retention member partially surrounding said other screw with its edges parallel to the screw axis, said retention member terminating with its leading edge substantially in the axial line through the points of intersection of the helical peripheries of said screws.

2. Feeding mechanism comprising a pair of intermeshing screws threaded in the same direction, means for rotating said screws in the same direction and at the same speed, one of said screws having an axially extending periphery forming a baffle which rotates with its edge in contact with the feeding surface of the other screw, said feeding surface being shaped to conform to the edge of said baffle substantially along a line extending from a point adjacent the hub of said other screw to the point of peripheral intersection of said screws, and a retention.- member partially surrounding said other screw with its edges parallel to the screw axis, said member terminating with its leading edge substantially in the axial line through the points of intersection of the helical peripheries of said screws.

3. Feeding mechanism comprising a pair of intermeshing screws threaded in the same direction, means for rotating said screws in the-same direction and at the same speed, one of said screws being mounted for axial movement and having an axially extending periphery which rotates with its edge in contact with the feeding surface of the other screw, and a retention member partially surrounding said other screw with its edges parallel to the screw axis, said member terminating with its leading edge substantially in the line through the points of intersection of the helical peripheries of said screws.

4. Feeding mechanism comprising a pair of intermeshing screws threaded in the same direction, means for rotating said screws in the same direction and at the same speed, one of said screws comprising sections mounted for individual axial movement and having axially extending peripheries which rotate with their edges substantially in contact with the feeding surfaces of the other screw, and a retention member partially surrounding said other screw with its edges parallel to the. screw axis, said retention member terminating with its leading edge substantially in the axial line through the points of intersection of the helical peripheries of said screws.

5. Feeding mechanism comprising a pair of intermeshing screws threaded in the same direction, means for rotating said screws in the same direction and at the same speed, one of said screws compriisng sections mounted for individual axial movement and having axially extending peripheries which rotate with their edges substantially in contact with the feeding surfaces of the other I screw, resilient means for supporting said sections at least in part, and a retention member partially surrounding said other screw with its edges parallel to the screw axis, said retention member terminating with its leading edge substantially in the axial line through the points of intersection of the helical peripheries of said screws.

6. Feeding mechanism comprising a pair of intermeshing screws threaded in the same direction, means for rotating said screws in the same direction and at the same speed, one of said screws having an axially extending periphery which rotates with its edge substantially in contact with the feeding surface of the other screw, a retention member partially surrounding said other screw with its leading edge substantially in the axial line through the points of intersection of the helical peripheries of said screws, the leading portion being shorter than the remainder of said member at the discharge end of said mechanism to provide a discharge opening, and a; discharge conduit communicating with said opening.

7. Feeding mechanism comprising a pair of intermeshing screws threaded in the same direction, means for rotating said screws in the same direction and at the same speed, one of said screws having an axially extending periphery which rotates substantially in contact with the feeding surface of the other screw, a retention member partially surrounding said other screw with its leading edge substantially in the axial line through the points of intersection of the helical peripheries of said screws, the leading portion being shorter than the remainder of said member at the discharge end of said mechanism to pro- Vide a discharge opening, a discharge conduit communicating with said opening, and means for regulating the rate of discharge of material through said conduit.

8. Feeding mechanism comprising a pair of intermeshing screws threaded in the same direction, means for rotating said screws in the same direction and at the same speed, one of said screws having an axially extending periphery which rotates with its edge substantially in contact with the feeding surface of the other screw, a retention member partially surrounding said other screw with its leading edge substantially in the axial line through the points of intersection of the helical peripheries of said screws, the leading portion being shorter than the remain der of said member at the discharge end of said mechanism to provide a discharge opening, a discharge conduit communicating with said opening, and an adjustable gate for regulating the effective cross-sectional area of said conduit.

9. Apparatus of the class described comprising a casing, means for delivering material to be fed to one end of said casing, feeding mechanism in said casing comprising a pair of intermeshing screws threaded in the same direction, means for rotating said screws in the same direction and at the same speed, one of said screws having an axially extending periphery which rotates with its edge substantially in contact with the feeding surface of the other screw, and a retention member partially surrounding said other screw with its edges parallel to the screw axis, said retention member terminating with its leading edge substantially in the axial line through the points of intersection of the helical peripheries of said screws, the leading portion being shorter than the remainder of said member at the discharge end of said mechanism to provide a discharge opening, and a discharge conduit communicating with said opening and extending outwardly of said casing.

10. Apparatus of the class described comprising a casing, means for delivering material to be fed to one end of said casing, feeding mechanism in said casing comprising a pair of intermeshing screws threaded in the same direction, means for rotating said screws in the same direction and at the same speed, one of said screws having an axially extending periphery which rotates with its edge substantially in contact with the feeding surface of the other screw, and a retention member partially surrounding said other screw with its edges parallel to the screw axis, said retention member terminating with its leading edge substantially in the axial line through the points of intersection of the helical peripheries of said screws, the leading portion being shorter than the remainder of said member at the discharge end of said mechanism to provide a discharge opening, a discharge conduit communicating with said opening and extending outwardly of said casing, and means for regulating the rate of discharge of material through said conduit.

11. Apparatus of the class described comprising a receptacle for material to be fed, feeding mechanism in said receptacle and spaced from the walls thereof, said mechanism comprising a pair of intermeshing screws, one of which has an axially extending periphery rotating substantially in contact with the feeding surface of the other screw, a retention member partially surrounding said other screw with its edges parallel to the screw axis and its leading edge substantially in the axial line through the points of intersection of the peripheries of said screws, the leading portion of said retention member adjacent the discharge end of said mechanism being shorter than the remainder to provide a discharge opening, and a discharge conduit communicating with said opening and extending outwardly of said receptacle, whereby material is fed to said discharge conduit and excess material is discharged over the top of said retention member into the space between said mechanism and the walls of said receptacle.

12. Apparatus of the class described comprising a receptacle for material to be fed, feeding mechanism in said receptacle and spaced from the walls thereof, said mechanism comprising a pair of intermeshing screws, one of which has an axially extending periphery which rotates substantially in contact with the feeding surface of the other screw, a retention member partially surrounding said other screw with its edges parallel to the screw axis and its leading edge substantially in the axial line through the points of in-. tersection of the peripheries of said screws, the leading portion of said retention member adjacent the discharge end of said mechanism being shorter than the remainder to provide a discharge opening, and a discharge conduit communicating with said opening and extending outwardly of said receptacle, and means for regulating the rate of discharge of material throughsaid conduit, whereby material is fed to said discharge conduit and excess material is discharged over the top of said retention member into the space between said mechanism and the walls of said receptacle.

13. In a feeder, the combination of two intermeshed screws, on one acting as a feeder screw and the other as a baflie, and a retention member partially surrounding said feeder screw, said feeder screw being open on its intake side throughout the entire distance through which material is fed, whereby shearing of lumps by the feeder screw is obviated.

14. In a feeder, the combination of two intermeshed screws, one acting as a feeder screw and the other as a baffle, and a housing partially surrounding the feeder screw with its edges lying approximately in the direction of'travel of the material fed, whereby shearing of lumps by the feeder screw is obviated.

15. In a feeder, the combination of a feed screw, a baffle screw coacting therewith comprising a plurality of individual flights, and means for mounting said flights for rotation in unison but for free individual movement in the direction of the axis of rotation.

WESTON M. FULTON.

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