US3820503A - Apparatus for distributing particulate material - Google Patents

Abstract

An apparatus is disclosed for coating a moving surface with particles in essentially a uniform pattern disposed generally transverse of the direction of movement of the moving surface and for automatically recovering any particles not applied to the surface during coating. Said apparatus comprises an impeller rotatable about its axis to propel the particles towards the walls of a non-cercular hopper so as to produce a substantially uniform disperson of particles on the surface.

Description

United States Patent [191 Tabernacki Y 1.lune 28, 1974 APPARATUS FOR DISTRIBUTING PARTICULATE MATERIAL [75] Inventor: Harry A. Tabernacki, Wonder Lake, Ill.

[73] Assignee: Kraft Corporation, Chicago, 111.

[22] Filed: Apr. 20, 1972 211' Appl. No.: 245,851

[52] US. Cl 118/24, 117/16, 1l7/l0l, 118/312 [51] Int. Cl B04b 3/02, B04b 3/00 [58] Field of Search 117/16, 101, 18,19, 20, 117/21, 23, 24, 26, 29, 30, 32, 33; ll8/24,

, 52, 308, 311, 312, DIG. 4'; 239/687, 689,

[56] References Cited I v UNITED STATES PATENTS 1,966,268 7/1934 Steffen 118/24 3 /l954 Rausc-h 239/687 2,775,532 12/1956 Sallie et a1. 118/308 X 2,955,956 10/1960 Baugh et a1 1. 117/101 X 3,033,159 5/1962 OBrien 118/303 3,582,428 6/1971 Steinberg l l8/D1G. 4 3,650,243 3/1972 Brehm 117/21 X Primary ExaminerWil1iam D. Martin Assistant ExaminerShrive P. Beck Attorney, Agent, or Firm-Fitch, Even, Tabin & Luedeka 57] ABSTRACT An apparatus is disclosed for coating a moving surface with particles in essentially a uniform pattern disposed generally transverse of the direction of movement of the moving surface and for automatically recovering any particles not applied to the surface during coating. Said apparatus comprisesan impeller rotatable about its axis to propel the-particles towards the walls of a non-cercular hopper so as to produce a substantially uniform disperson of particles on the surface.

6 Claims, 5 Drawing Figures APPARATUS FOR DISTRIBUTING PARTICULATE MATERIAL The present invention relates generally to coating with particulate material and, more particularly, relates to the application of particles substantially uniformly across the surface of a moving substrate.

It is conventional to distribute particles over a surface when the particles are contained in a hopper and either the hopper is moved across the surface or the surface is moved beneath the hopper. A vibratory means may be applied to the hopper to stimulate a flow of the particles out of the hopper. To effect a uniform distribution or even spacing of the particles, gating-or other flow impeding means may be utilized.

Some types of particles, such as soft food particles, do not flow freely, however, and difficulties are encountered in effecting an even dispersion of such particles by conventional means. For example, cheese and meat particles do not suitably lend themselves in the first instance to storage in a large hopper, inasmuch as they tend to form a mass by becoming compressed under the accumulation of their own weight. Moreover, such food particles tend to stick to each other to form globules, causing further difficulty in effective particle dispersion. l I

When coating .pizza pies and the like, a solid covering on the pies is usually not wanted. Rather, it is desirable to effect a loose, substantially .uniform distribution of the particles across the surface of the pies. Thus, it is not desirable to merely feed a large quantity of loose particles onto the surface ,of the pies and allow the excess to fall off or be scraped away, leaving essentially a solidly covered surface.

his a primary object of the present invention to pro vide a method and apparatus for coating a moving surface with particles that may be soft and compressible.

These and other objects of the present invention, are

more particularly set forth in the following detailed description and in the accompanying drawings of which:

. FIG. 1 is a schematic side elevational view of a portion of a coating line in which apparatus according to a preferred embodiment of the present invention is employed and in which some parts are shown in simplified form and another part is broken away for clarity of illustration;

FIG. 2 is a schematic plan viewof the apparatus of FIG. 1 with portions omitted for clarity of illustration;

FIG. 3 is an enlarged fragmentary view in elevation of a portion of the apparatus of FIG. 1 taken substantially along the line 3-3 of FIG. 1;

FIG. 4 is a fragmentary plan view of a portion of the apparatus of FIG. 1 taken substantially along the line 44 of FIG. 3; and

FIG. 5 is a graph illustrating a development of onequarter of the curve that is used to form the shape of a portion of the apparatus of FIG. 4.

Briefly, there is shown in FIGS. 1 and 2 a portion of an apparatus line 7 for distributing particles on or coating the top surfaces of crusts to form pizza pies and the like. Each pizza pie crust 9 travels in a given direction on a conveyor belt 11. The direction is indicated by an arrow at the belt and is longitudinally of the belt. There may be a plurality of pie crusts 9 across the width of the conveyor belt. These crusts move underneath a discharge opening or slot 13 at the lower end of a hopper l5. Particles 16 are elevated by a series of incline conveyors 17 and 19 and then are dropped into a funnel 21, which directs and controls the fall of the particles toward a rotating impeller 23.-

As will be detailed hereinafter, a stream of particles having essentially a uniform distribution along a line transversely of the belt 11 is discharged across a surface travelling therewith. The surface may be any desired substrate, but in the preferred embodiment, it comprises a plurality of pizza pie crusts 9 in lines abreast of each other. The conveyor belt 11 is endless, but it is not continuous in the horizontal plane of travel of the crusts. A gap 25 transversely of the longitudinal movement of the belt 11 is centered immediately below the discharge slot 13 and spaced therefrom a distance slightly greater than th'e height of the crusts 9. The gap 25 is sufficiently narrow to permit the crusts 9 to easily bridge it and continue in their general horizontal plane of longitudinal movement along the apparatus line. The belt- 11 forms a relatively large loop beneath the gap 25. Through the loop is inserted a recovery conveyor 27. This recovery conveyor moves transversely of the conveyor belt 11. Particles not deposited on or applied to the surfaces of the crusts fall through the gap 25 and onto the recovery conveyor 27. Thereafter, these particles are delivered to the incline conveyor 17 for eventual infeed to the funnel 21. The recovery conveyor 27 not only recovers particles not applied to the pie surfaces, but also serves as an initial feeder conveyor of particles to the incline conveyor 17.

The upper part of the hopper 15 has vertical walls 29 which enclose a shape which appears to be to an ellipse, but which may differ in specific detail therefrom as will be seen hereinafter. This shape is generally seen in FIG. 4, and a development of the curve which forms the shape is seen in the graph of FIG. 5.

For purposes of illustration, the present invention is shown in the drawings for use with a line 7 for coating pizza pies 9 and the like. It should be understood that the invention also could be employed for distributing either other kinds of food particles or non-food particles ontomoving substrates or surfaces to effect an essentially uniform distribution of the particles thereacross.

Moreparticularly, there is shown in FIG. 1 a representation of apparatus for coating substrates or surfaces of articles, such as the crust of pizza pics 9 and the like. An endless belt 11 is applied around a series of drivers and idlers which generally are in the form of long rolls 31. A suitable motor 33 and linkage therefore provides the driving force for moving the conveyor belt 11 in the direction shown. This belt may be any suitable width. In the illustrated embodiment, as can be seen in FIG. 2, the belt is substantially the width of four typical pizza pies abreast of each other on the belt 1 l. The belt could be wider or narrower to accommodate other arrangements or other articles abreast of each other as may be desirable.

The crusts 9 are placed on the belt 11 from the upstream end of the belt, the left end asviewed in FIG. 1. These crusts may be placed there by any suitable means, such as by hand or by transfer from a separate infeed conveyor (not shown). The belt then moves the pies in a generally horizontal plane longitudinally downstream along the lengthwise direction of the belt toward the gap 25. Centered overhead of the gap 25 is the hopper 15.

The hopper 15 is mounted by a suitable means (not shown) and is disposed a sufficient distance overhead of the general horizontal plane in which the crusts 9 move so that the lower terminus of the hopper 15, i.e., the slot 13, is clear of the crusts moving therebeneath. As seen in FIG. 1, at the gap the belt 11 moves through a series of directional changes in a path of deviation that forms a nearly closed delta, the specific purpose of which will be explained hereinafter. The pizza crusts 9 after crossing the gap 25 continue their move to the right or downstream end of the conveyor belt 11 where they may be removed by any suitable means, such as by hand or by transfer to another conveyor (not shown).

For ease of illustration, only a few ranks of crusts or pies 9 are shown. It is understood that in actual practice pies may be closely aligned behind each other and may form continuous lines or rows on the conveyor belt 11.

The hopper 15 is one part of a particle spreader 35, which further includes the funnel 21, the impeller 23, and an impeller drive 37. The impeller drive 37 comprises a driven pulley 39, a driving pulley 41, a belt 42 between the two pulleys, and a suitable motor 43. The driven pulley 39 is engageably mounted at the upper end of a shaft 45 for rotation thereof. The impeller 23 is engageably mounted at the lower end of the shaft 45 and rotates therewith. The funnel 21 and all of the members of the impeller drive 37 are mounted for support in an appropriate disposition with respect to each other by suitable mounting means (not shown). The operation of the particle spreader 35 will be described in detail hereinafter.

Referring now to FIG. 2, the source of particles is a particle dispenser 47. This particle dispenser may be in the form of a cheese shredder, a cooked meat applicator, such as a sausage applicator, or other suitable food applicator. Particles are formed in the dispenser 47 and are discharged therefrom through a chute 49 onto the conveyor 27. The particles are loose as they are discharged from the dispenser 47 and they are carried on the conveyor 27 in substantially the same manner. After reaching the limit of the conveyor, the particles transfer to the incline conveyor 17. The incline conveyor l7 is disposed substantially parallel to the conveyor belt 11, but it is inclined to elevate the particles above the general plane of travel of the pies 9, as is best seen in FIG. 1. The particles then fall onto the incline conveyor 19, which is disposed at an angle to the longitudinal direction of the incline conveyor 17 and the conveyor 11. The incline conveyor 19 elevates the particles to a point overhead of the funnel 21, which itself is overhead of the conveyor belt 11 (FIGS. 1 and 2). Both incline conveyors receive their motive power from suitable sources, such as motors 51 and 53 which drive the incline conveyors 17 and 19 respectively.

As the particles 16 fall free of the incline conveyor 19 into the funnel 21, they are directed in their fall by the funnel toward the shaft 45 and through a constricted end 55 of the funnel 21 along the shaft 45. Suitable means (not shown), such as a stirring rod or paddle, may be employed internally of the funnel 21 to prevent compaction of the particles and to regulate the discharge of the particles. From the end 55, the particles fall onto the impeller 23. When the impeller is caused to rotate by the impeller drive 37, the falling particles strike the impeller surface and are propelled centrifugally in outwardly directed adjacent paths that emanate essentially from the axis of impeller rotation, or the shaft 45. The particles move outwardly along these paths until they are intercepted by the vertical walls 29 of the upper end of the hopper 15. The impeller 23 is generally saucer shaped with an upwardly extending lip 57 on its periphery. This lip, among other purposes, helps retain the particles to support a column thereof back into the constricted end 55 when operation is shut down.

The vertical walls 29 are in the form of a non-circular curve 58 having the general appearance of an elongated curve or ellipse, as best seen in FIG. 4. The curve has a major axis 60a in the direction of elongation and a minor axis 60b normal thereto in the direction of the short or narrow portion of the curve, the two axes intersecting at the center 62 of the curve. As will be understood hereinafter during the description of a development of the curve, the curve is symmetrical with respect to the major axis 60a, and it is symmetrical with respect to the minor axis 60b. It is noted, however, that the curve 58 is not precisely an ellipse. For example, it can be seen that opposing sides 58a, 58b intersect in an angular manner at points 58c, 58d rather than merge in an arcuate manner.

The path that the curve 58 follows is developed to disperse the particles substantially uniformly in the direction of elongation after they are centrifugally propelled outwardly. As the generally outward movement of each particle 16 is intercepted in its path of travel by a portion of the walls 29, the particle is deflected and directed toward the discharge slot 13. The boundaries of interception are determined by the opposing sides 58a, 58b of the closed curve 58 and their points of intersection 58c, 58d.

For laying out the shape of the vertical walls 29 of the hopper 15, a theoretical environment is assumed to illustrate and define the closed curve 58 to which the walls 29 conform. If the curve 58 were to be divided into arcuate increments between points of interception of adjacent propelled particles around the curve, the increments would successively increase in length from the minor axis 60b toward the major axis 60a (FIG. 4). The hopper 15 is so disposed relative to the impeller 23 that the center 62 of the curve 58 of the walls 29 is concentric with the center of rotation of the impeller 23 about its axis or shaft 45. Thus, the axes 60a, 60b of the curve 58 pass through and intersect at the center 62, which is also the center of rotation of the impeller 23 and the point from which the centrifugally propelled particles 16 emanate. Further, by disposing the hopper 15 so that the elongation of the walls 29 lies transversely of the conveyor belt 11, the particles will be distributed substantially uniformly in the direction across their ends (a) intercepting equal angles emanating from a common axis or shaft 45 and (b) projecting equal distances or lengths on the major axis 60a in the transverse direction. The particles respond to the interception by the walls 29 defined by the curve 58 so that they are dispersed in the transverse direction in substantially equally spaced apart distances. 7

One development of the curve is seen in FIG. 5. There an arc 59 represents one-quarter of the curve 58 and is shown in graphical form, limitedby the horizontal or baseside OT and the vertical side CV of aright angle whose vertex is O. In the'illustrated embodiment, OV corresponds to the longitudinal direction of surface movement and OT to the transverse direction. Approximately onehalf the width of the conveyor belt 11, the

distance (/W), is laid out on the graph along the line OT at a suitable scale and is divided into an arbitrary number of equal segments. For example, in the illustration 'rW on the base line OT is divided into 16 equal segments,- and the end of each successive segment outwardly from O is sequentially designated A through 0. It is noted that the letter O is omitted in the sequence of segment designations since it is used for the origin or vertex of the graph. Lines are then drawn parallel to the vertical line OV (the direction of surface movement) from each of the points A through on the base line OT.

Next, the right angle having'the vertex 0 is divided into the same number of equal angles between the sides 0V and OT as the number of segments on the line OT, which in the present illustration is 16. The sides of each of the equal angles are extended outwardly from O and are sequentially designated A through 0' to correlate with the'designatio ns of the equal segments along the line OT. These extended angle sides represent a few of C, etc., are a selected few of a possible infinite number of lines that represent vertical, parallel, equally spaced apart planes that intersect the equal angles emanating from O. The selected planes intersect in succession the sides of the equal angles to define the ends of the aforementioned theoretical arcuate increments. The total of these increments define the curve 58. These points of intersection also represent a few of the points of partithe adjacent paths emanating from the shaft and travelled byv the propelled particles. There are, of course, an infinite number of paths travelled by the particles.

Thus, for purposes of illustration, it may be assumed that the particle will travel along lines such as OA', DB, etc. It is recognized that as a practical matter a particle travelling from, for example, 0 to A may not follow a straight line as illustrated: The effect is the same, however, as long as the particles travel uniformly outwardly fromthe axis 45 to the walls 29. Stated otherwise, if a particle travels from O to A in the same way that a particle travels from O to B, the effect, for

purposes of the illustrated embodiment, is the same as if they both travelled their respective paths in straight lines. It is noted that the impeller is not a point source as is the vertex 0, but a point'source is suitable for lay out purposes and'it simplifies the development of the curve.

The are 59 is drawn by joining the points formed by the intersection of the correspondingly lettered lines, e.g., A, A; B, B; C, C; etc., and by the extrapolation in the counterclockwise direction of 'the arc portion from the point A, A to the line OV terminating at the designation R on the graph. The illustrated lines A, B,

cle interception. Thus, the extent of outward movement of each particle, depending upon the path each particle is travelling, is provided by the walls 29 when the walls conformv to the curve 58. The equal spaces between planes or the equal distances along OT illustrate the substantially uniform spacing of the intercepted particles along a transverse line. As mentioned previously, OT represents in the specific embodiment a line or vertical plane in the transverse direction relative to the surface movement. I

The are 59 thus drawn is onequarter of the curve 58. The curve 58 is symmetrical about the line 0V and about the line OT. Hence, the entire curve 58 is determinable by graphical construction of the arc 59. It can be seen that the lengths of the arcuate increments successively increase from the line OV (representative of a line or vertical plane in the longitudinal direction) toward the line OT (representative of a line or vertical plane in the transverse direction). For example, compare arcuate increments 59a and 59b.

Thus it is graphically illustrated that a configuration of equal angles emanating from a center of a closed, non-circular curve is intercepted by the curve in such a manner as to effect-a projection of equal segments onto the major axis of the curve, and these equal segments represent the substantially uniform distribution of particles in the direction of the major 'axis. The curve may be used as the pattern for a form to shape the vertical walls 29 in the manufacturing of the upper portion of the hopper 15 for uniformly spacing the particles across the moving surface.

Referring to FIG. 4, as the impeller 23 rotates and causes a propelling force to be imparted to each of the particles falling thereupon from the constricted end 55 of the funnel 21, the particles are propelled generally outwardly by centrifugal force to the vertical walls 29 of the hopper 15. As mentioned previously, a stream of loose particles fall downwardly onto the impeller 23.

they strike the vertical walls 29 in a continuous succession of points of impingement around the inside of the wall.

As the particles fall after impingement, they are directed along the transverse direction toward the discharge slot 13 by lower portions of the hopper 15. It will be seen that the particles are directed inwardly toward the discharge slot 13 by a pair of sides 61, 63 sloping inwardly toward each other and terminating in the slot 13. The planes of these inwardly sloping sides intersect the vertical walls 29 of the hopper to produce the configuration shown in FIG. 3. Here also may be seen the approximate elevation of the impeller 23 with respect to the vertical walls 29 and the inwardly sloping sides.

In the illustrated embodiment, it may be seen in FIG.

I 4 that ends 13a, 13b of the slot 13 are substantially coterminous with the ends 58c, 58d of the curve 58. The long dimension of theslot 13 is substantially equal to the widthof the conveyor belt 11. Hence, the long dimension of the curve 58 is also substantially equal to the width of the belt 11. The ends 13a, 13b of the slot 13 are directly under the ends 58a and 58b of the curve 58 shaping the walls 29. The short dimension of the slot 13 preferably is sufficient to accommodate the specific particles contemplated for use in the coating line. The slot is centered under the impeller 23 such that a vertical plane containing the center of the slot would also contain the curve center 62 and the axis 45.

It has been seen that the particles 16 are dispersed from a rather narrow path in which they are conveyed to a substantially uniform distribution across the width of the travelling conveyor belt 11 on which a plurality of abreast rows of pizza pies 9 travel beneath the slot 13. As mentioned previously, the conveyor belt 11 could be wider or narrower than that illustrated. Hence, four pies abreast is not intended as a limitation. On the contrary, by using the principle of the invention, the belt and the particle spreader 35 could be adapted not only for the width desired, but for a purpose other than the conveying of pizza pies for coating with food particles. The principle of the present invention could also be utilized for applying particles to any moving substrate, which could include non-food material. Further, it should be understood that more than one such particle spreader 35 could be used on a given coating line. For example, in coating pizza pie crusts, one spreader could be utilized to apply cheese particles, another like spreader in tandem with the first along the same coating line could apply sausage particles, and yet another in tandem could apply olive, mushroom and pimento particles. Application of still other food particles could be similarly arranged as desired.

It was mentioned earlier that the recovery conveyor 27 is used to initially carry the'particles 16 from the particle dispenser 47 (FIG. 2). Also, as may be seen in FIG. 1, the recovery conveyor 27 is disposed beneath the gap 25 so that the center of the conveyor is approximately beneath the center of the gap. Thus, as is illustrated, when the pizza pies 9 are round, it will be seen that the particles being discharged fromthe slot 13 will not all be deposited on the pies travelling therebeneath, since interstices between the pie perimeters will not intercept particles. The discharged particles not so deposited will continue downwardly through the gap 25 and land on the moving recovery conveyor 27. Thus, the particles not applied to the pies are added to any new supply of particles that may be travelling on the conveyor 27 and are fed back to the incline conveyor 17 for recirculation through the spreader system described earlier.

Summarizing, there has been set forth a method and apparatus for coating a horizontally moving substrate or surface by spreading particles substantially uniformly across the moving substrate. A particle spreader 35 accepts particles 16 from a dispenser 47 by means of a series of conveyors, including a recovery conveyor 27, an incline conveyor 17, and an incline conveyor 19. As the particles are discharged from the upper end of the incline conveyor 19, they fall into a funnel 21 and are generally controlled thereby. The particles are discharged from a constricted end 55 of the funnel. Below the constricted end is a rotatable impeller 23 which imparts substantially a uniform propelling force centrifugally to the particles along paths emanating from the impeller. A hopper having upper vertical walls 29 is disposed outwardly of the impeller. The vertical walls 29 are in the form of a non-circular curve elongated in one direction and having the general appearance of an ellipse. The curve is formed to cause the particles striking the walls to be intercepted in their generally outward paths of movement so that they are substantially uniformly spaced apart along a line or plane in a single direction. The hopper is disposed relative to the moving surface so that the single direction is transversely of the direction of the moving surface. inwardly sloping sides 61, 63 of the hopper 15 direct the particles to the discharge slot 13 and onto the moving surface therebelow in substantially their uniformly spaced relation.

When the moving surface comprises a plurality of pizza pies moving in rows abreast of each other beneath the discharge slot 13, the pies intercept most of the particles falling therefrom. Any discharged particles not intercepted by the pizza pies passing therebeneath fall through a gap 25 in the horizontal plane of article travel onto the recovery conveyor 27 disposed under the gap. The recovered particles may join an initial supply of particles moving from the dispenser 47. The particles then are elevated to the infeed or starting point overhead of the funnel 21 of the particle spreader 35.

Thus, it is apparent that there has been provided, in accordance with the present invention, a method for spreading particles and a particle spreader. While the invention has been described in connection with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in view of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and scope of the appended claims.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. Apparatus for distributing particles on a generally horizontal surface moving in a given direction by arranging the particles substantially uniformly in a relatively narrow path disposed generally transverse to the direction of movement of said surface, said apparatus comprising an impeller rotatable about its axis to propel the particles centrifugally along paths emanating essentially from the center of said impeller, means for supplying said particles to said impeller, a hopper having non-circular walls disposed outwardly of said impeller to intercept said particles in their paths such that the points of interception when projected onto a plane containing said impeller axis and lying transversely of said given direction are equally spaced apart, said hopper further having wall means defining a relatively narrow discharge slot disposed generally transverse to said direction of movement of said surface, said wall means being adapted to guide particles intercepted by said non-circular walls toward said discharge slot in a manner to provide a substantially uniform dispersion of the particles on said surface transversely of said given direction, and conveyor means disposed longitudinally of said given direction and beneath said discharge slot.

2. The apparatus in accordance with claim 1 wherein said non-circular walls are in the fonn of a curve comprising arcuate increments which successively increase in length from a line in said given direction toward a line transversely thereof, both of which pass through the center of said impeller, the lengths of said increments being determined by the increment ends (a) in- 10 is discontinuous, the discontinuity being in the form of a transversely extending gap, said gap being disposed directly below said discharge slot of said hopper to permit any of said particles not deposited on said surface to fall below said plane of movement of said surface.

6. The apparatus in accordance with claim 5 further comprising a recovery conveyor means disposed beneath said gap to collect and remove said particles passing through said gap for subsequent return to said means for supplying said particles to said impeller.

Claims (6)

1. Apparatus for distributing particles on a generally horizontal surface moving in a given direction by arranging the particles substantially uniformly in a relatively narrow path disposed generally transverse to the directiOn of movement of said surface, said apparatus comprising an impeller rotatable about its axis to propel the particles centrifugally along paths emanating essentially from the center of said impeller, means for supplying said particles to said impeller, a hopper having noncircular walls disposed outwardly of said impeller to intercept said particles in their paths such that the points of interception when projected onto a plane containing said impeller axis and lying transversely of said given direction are equally spaced apart, said hopper further having wall means defining a relatively narrow discharge slot disposed generally transverse to said direction of movement of said surface, said wall means being adapted to guide particles intercepted by said non-circular walls toward said discharge slot in a manner to provide a substantially uniform dispersion of the particles on said surface transversely of said given direction, and conveyor means disposed longitudinally of said given direction and beneath said discharge slot.

2. The apparatus in accordance with claim 1 wherein said non-circular walls are in the form of a curve comprising arcuate increments which successively increase in length from a line in said given direction toward a line transversely thereof, both of which pass through the center of said impeller, the lengths of said increments being determined by the increment ends (a) intercepting equal angles emanating from said impeller center and (b) projecting equal distances on said transverse line.

3. The apparatus in accordance with claim 1 wherein said discharge slot is disposed along a transverse line located under the center of said impeller and in a vertical plane which passes through the impeller center.

4. The apparatus in accordance with claim 3 wherein the length of said slot is substantially equal to the width of said moving surface.

5. The apparatus in accordance with claim 1 wherein said longitudinal conveyor means beneath said hopper is discontinuous, the discontinuity being in the form of a transversely extending gap, said gap being disposed directly below said discharge slot of said hopper to permit any of said particles not deposited on said surface to fall below said plane of movement of said surface.

6. The apparatus in accordance with claim 5 further comprising a recovery conveyor means disposed beneath said gap to collect and remove said particles passing through said gap for subsequent return to said means for supplying said particles to said impeller.

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