US3790323A

US3790323A - Rotatable material handling drum

Info

Publication number: US3790323A
Application number: US00127715A
Authority: US
Inventors: G Heian
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1971-03-24
Filing date: 1971-03-24
Publication date: 1974-02-05
Anticipated expiration: 1991-02-05
Also published as: CA969327A; JPS511229B1; DE2214592B2; NO129356B; GB1347641A; AU4031572A; BR7201748D0; SE383967B; ES401118A1; DE2214592C3; DE2214592A1; AU443715B2; FR2130602A1; FR2130602B1

Abstract

A balling drum which includes a conventional end discharge preferably of the type shown by U. S. Pat. No. 2,822,076, granted to John F. Baier on Feb. 4, 1958, and which balling drum additionally includes a discharge section intermediate the length of the drum and upstream of the end discharge section, the intermediate discharge section comprising helically extending port means in the form of helical slots through the wall of the drum which slots are so positioned with respect to the angular path of load material flow relative to the internal surface of the balling drum that some predetermined percentage of the entire load passing through the balling drum, preferably about 50 percent of the entire load, is discharged by the intermediate discharge section, the helical slots substantially evenly distributing the discharge flow from the intermediate discharge section onto a classifying screen positioned beneath the intermediate discharge section.

Description

United States Patent [191 Heian Feb. 5, 1974 ROTATABLE MATERIAL HANDLING DRUM [73] Assignee: Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

[22] Filed: Mar. 24, 1971 [21] Appl. N0.: 127,715

[52] US. Cl. 425/222 [51] Int. Cl. C09c 1/56 [58] Field of Search 425/222; 264/117; 198/66, 205,

[56] References Cited UNITED STATES PATENTS 2,728,940 l/l956 Yesberger et al 425/222 X 3,279,592 10/1966 I Kerkviet 198/64 X 3,001,633 9/1961 PrimaryExaminer-Richard E. Aegerter Assistant Examiner- Douglas Watts Attorney, Agent, or Firm-Robert C. Sullivan Heitshu.....'.l 198/64 [5 7] ABSTRACT A balling drum which includes a conventional end discharge preferably of the type shown by U. S. Pat. No. 2,822,076, granted to John F. Baler on Feb. 4, 1958, and-which balling drum additionally includes a discharge section intermediate the length of the drum and upstream of the end discharge section, the intermediate discharge section comprising helically extending port means in the form of helical slots through the wall of the drum which slots are so positioned with respect to the angular path of load material flow relative to the internal surface of the balling drum that some predetermined percentage of the entire load passing through the balling drum, preferably about 50 percent of the entire load, is discharged by the intermediate discharge section, the helical slots substantially evenly distributing the discharge flow from the intermediate discharge section onto a classifying screen positioned beneath the intermediate discharge section.

8 Claims, 14 Drawing Figures PAIENIEU 3.790.323

sum 2 or 4 1 ROTATABLE MATERIAL HANDLING DRUM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to rotatable material handling drums such as a balling drum or the like, and more particularly to an improved discharge arrangement for such drums whereby the material handling capacity of such drums is significantly increased.

2 Description of the Prior Art In the prior art relating to balling drums, as exemplified, for example, by U. S. Pat. No. 2,707,304 issued to Kenneth M. I-Ialey on May 3, 1955, all of the material being processed discharges from the discharge end of the drum onto a vibrating screen or the like, which classifies the discharged material in such manner that the balled or pelletized material of proper size is separated from the material formed in particles which are too small, the latter material being returned to the inlet end of the balling drum for recycling. Another example of a balling drum or the like in which all of the material which has passed through the drum is discharged at a single discharge zone at the discharge end of the drum and hence limit the material handling output capacity of the balling drums in the prior art balling drums constructions in which substantially all of the processed material is discharged at a single discharge zone located at the discharge end of the drum.

While it has been known in the prior art to provide what may be considered an auxiliary discharge section or zone, intennediate the length of the drum and axially spaced upstream of the drum from the discharge end, as exemplified, for example, by the following U. S. Pats. No. 1,921,114 granted to Carl Adolf Brackelsberg on Aug. 8, 1933; No. 2,543,898 granted to Fred D. De- Vaney on Mar. 6, l95l;No. 2,711,557 granted to Robert J. Russell on June 28, 1955; and No. 2,728,940 granted to Lloyd A. Yesberger et al on June 3, 1956, all of the patents to Brackelsberg, DeVaney, Russell and Yesberger et al just referred to show an auxiliary discharge section in which the sole function and capability of the intermediate or auxiliary'discharge section is to discharge undersized balls, pellets, or particles, be-

fore such undersized material reached the main discharge of the balling drum or the like.

STATEMENT OF THE INVENTION Accordingly, it is an object of the present invention to provide in combination with a balling drum or the like an intermediate discharge section or zone located intermediate the length of the balling drum which intermediate discharge section supplements the discharge section conventionally provided at the discharge end of the balling drum whereby to significantly increase the material handling capacity of the balling drum.

It is a further object of the invention to provide a balling drum or the like havinga double discharge arrangement including a conventional end discharge section and additionally an intermediate discharge section upstream of the end discharge section which discharges a predetermined proportion of all of the material entering said intennediate discharge section whereby to significantly increase the material handling capacity of the balling drum.

It is a further object of the invention to provide a balling drum or the like having a plural discharge arrangement which permits a substantial reduction in auxiliary equipment such as fewer feed bins, fewer conveyors, fewer weighing scales, etc., for a given output and which also permits a substantially more efficient utilization of space than prior art balling drum circuits.

In achievement of these objectives, there is provided in accordance with an embodiment of this invention, a balling drum which includes a conventional end discharge preferably of the type shown by U. S. Pat. No 2,822,076 granted to John F. Baier on Feb. 4, 1958, and which balling drum additionally includes a discharge section intermediate the length of the drum and upstream of the end discharge section, the intermediate discharge section comprising helically extending port means in the form of helical slots through the wall of the drum which slots are so positioned with respect to the angular path of load material flow relative to the internal surface of the balling drum that some predetermined percentage of the entire load passing through the balling drum, preferably about 50 percent of the entire load, is discharged by the intermediate discharge section, the helical slots substantially evenly distributing the discharge .flow from the intermediate discharge section onto a classifying screen positioned beneath the intermediate discharge section.

Further objects and advantages of the invention will become apparent from the following description taken BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view of a balling drum in accordance with the invention including an intermediate discharge section in addition to a conventional end discharge section;

FIG. 2 is a perspective view of the drum of FIG. 1 showing both the internal, or intermediate discharge section and the end discharge section;

FIG. 3 is a view in transverse section along line III- III of FIG. 1;

FIG. 4 is a view in longitudinal section along IV-IV of FIG. 7D, illustrating-the angle of repose of the load material in the region of the leading edge of the outlet slots in the intermediate discharge zone;

FIG. 5 is a 360 developed view of the balling drum of FIG. 1;

FIG. 6A is a schematic 360 developed view of the intermediate discharge zone or section of the drum showing the general relation which should prevail between the angle of the leading edge of therespective helical slots and the angular path of load material flow;

FIG. 6B is a schematic 360 developed view of the intermediate discharge zone or section of the drum showing the material flow path relative to the intermediate discharge section, with an angular relation of the leading edge of the respective outlet slots to the angular path of load material flow which causes a predetermined percentage of the total load, in this case approxi- 3 mately 50 percent, to be discharged at the intermediate discharge zone;

FIG. 6C is a schematic 360 developed view of the intermediate discharge zone or section of the drum showing the material flow path relative to the intermediate discharge zone or section with a different angular relation of the leading edge of the respective outlet slots to the angular path of load material flow than in FIG. 6B, whereby to cause a different predetermined percentage of the total load (approximately 66 36 percent in the case of FIG. 6C) to be discharged at the intermediate discharge zone than in the example of FIG. 6B. 1

FIGS. 7A, 7B, 7C, 7D are a series of schematic diagrams showing material flow relative to a plurality of successive positions of the rotating drum, with the drum being shown in a 360 developed view, each successive view being shown with the drum displaced 90 in the direction of rotation of the drum from the previous view;

FIG. 8 is a schematic diagram showing successive 90 displaced positions of the portion of a band of load material which is to be discharged through a given helical slot relative to the given helical slot, with the drum being shown in a 360 developed view; and

FIG. 9 is a schematic diagram, with the drum being shown in a 360 developed view, showing the relation of a modified slot to the angular path of load material flow.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and more particularly to FIG. 1, there is shown a drum generally indicated at 10 in the form of an elongated tubular cylindrical structure open at both ends and supported with its axis of rotation inclined to the horizontal. Drum 10 may have a diameter, for example, of 12 feet, and a length of 50 feet. Suitable supports and framestructure are provided to elevate drum 10 above the level of the floor. Riding rings 12 and 14 encircle and are secured to drum 10 and as seen in FIG. 3 are supported on spaced carrying rollers 16. Suitable thrust absorbing rollers (not shown) are-provided to restrain the drum from movement in an axial direction. Rotation of drum 10 is effected by a motor 18 which drives a pinion 20 through a suitable gear box 22. Pinion 20 meshes with a large ring gear 24 which encircles and is secured to drum 10. Thus, when motor 18 is driven in the proper.

ent material charged into the drum will travel axially therethrough on the lower portion of the inner wall of the drum (FIG. 3), the material proceeding toward the discharge zones and following an angular path of load material flow to be hereinafter defined. In the formation of pellets or ballsof moistened pulverized ore or the like, the pulverent material which is fed into the drum may be either premoistened prior to being charged into drum or may be moistened by a suitable moistening means adapted to spray water on the interior of the balling drum in the active balling area of the drum (zone A to be described). The use of such moistening devices is well known in the balling mill art and is shown, for example, by U.S. Pat. No. 1,775,313 granted to Otto Lellep on Sept. 9, 1930. Also, as is well known in the balling mill art, a suitable scraping means or cutter (not shown) may be supported adjacent the inner wall of the drum to maintain a predetermined coating thickness of the moist mud-like material which is formed on the entire inner surface of the drum in the active balling region thereof, as shown, for example, by U. S. Pat. No. 2,834,043, granted to Kenneth M. Haley et al on May 13, 1958. Such scraping means or cutter would extend for the entire length of the drum including zones A, B, C, D to be described. Also fed into the upper entering end of the drum by a conveyor diagrammatically indicated at 26 which discharges onto conveyor 25 are seed particles or pellets of smaller size than ultimately desired. These seed pellets are undersized particles which are delivered to recycling conveyor 26 by conveyors 29A and 298 from vibrating

screens

28 and 30 which are respectively positioned beneath the intermediate discharge zone B and beneath the end discharge zone D as will be explained hereinafter.

As drum 10 rotates, these seed particles are rolled over the surface of the moist material in the drum and pick up in snowball fashion additional material whereby their size is increased. The pellets travel longitudinally through the drum toward the discharge zones following an angular path of load material flow to be hereinafter defined, and for a given material having particular properties, drum rotary, speed, and inclination of the bottom surface of the drum, these pellets will travel along the drum substantially the same distance for each revolution of the drum.

As best seen in the diagrammatic view FIG. 1, the balling drum generally indicated at 10 comprises four zones respectively designated as zone A, zone B, zone C and zone I). It is assumed for purposes of explanation that the balling drum 10 is 50 feet in total overall length from the beginning of the inlet end to the end of the discharge end thereof. Zone A which may extend, in the given example, approximately 25 feet from the inlet end of the drum in the direction of the discharge end is what may be designated as the active balling length in which most of the balling action of the rotating drum occurs Zone B is the intermediate discharge zone which is an important feature of the present invention and may extend in the present example for a length of approximately 7 feet from the end of the active balling zone A to the beginning of zone C. Zone C is the redistribution region to be explained hereinafter, for the portion of the load which passes through zone B without being discharged in zone B. Zone C may extend approximately 1 1 feet axially of the rotating drum. Zone D is the end discharge section in which the portion of the total load which was not discharged in zone B is discharged. Zone D extends for the remaining'length of the drum or, in the given example, approximately 7 feet lengthwise of the rotating drum. The discharge section of zone D maybe of any suitable typebut preferably is constructed in accordance with the teachings of United States Pat. No. 2,822,076 issued to John F. Baier on Feb. 4, 1958. Drum 10 includes distributing tongues 39 and 39' as taught by the aforementioned U.S. Pat. No.

2,822,076. The construction of the end discharge zone (zone D) per se forms no part of this invention.

Instead of using a discharge end (zone D) similar to that shown in the aforementioned U. S. Pat. No. 2,822,076 to John F. Baier, a trommel discharge section such as that shown by United States Pat. No. 2,834,043, issued to Kenneth M. Haley et al on May 13, 1958, may be used. In the latter case, a vibrating screen 30 is not used at the discharge end (zone D). As seen in the diagrammatic view of FIG. 1, a vibrating screen 28 is positioned beneath zone B to receive the load material discharged through the discharge slots or passages of zone B, to be hereinafter described. Similarly, a vibrating screen 30 is positioned beneath the discharge end section of zone D to receive the material discharged from zone D. As previously explained,

In a similar manner, the other helical slot generally indicated at 32', which is 180 out of phase with the helical slot 32, includes a leading edge 34, a trailing edge 36, and a connecting edge 38' which joins the respective downstream ends of the edges 34 and 36'. The downstream terminus of leading edge 34 is indicated at 40 while the upstream terminus leading edge 34 is indicated at 42. The various slots and slot portions are correspondingly numbered throughout the various figures such as FIGS. 5, 6A-6C, inclusive, 7A-7D, inclusive, and 8. t

In the description of FIG. 6A-6C, inclusive, which follows, reference will be made principally to slot 32 and the relationship of the angular path of load material flow relative to slot 32. However, it will be understood that this discussion applies equally to slot 32',

the undersized material which passes through the vithe proper size productto a desired location for further processing or the like.

DESCRIPTION OF THE INTERMEDIATE DISCHARGE SECTION As best seen in the perspective view of FIG. 2 and in the 360 degree developed view of FIG. 5, the intermediate discharge section of zone B comprises port means in the form of a pair of two separate similar parallel helical slots respectively indicated at 32 and 32, which are 180 out of phase with each other.

Helical slots

32 and 32 each extends in the illustrated embodiment through a peripheral angle less than the entire circumference of the drum, such as a peripheral angle of 270, for example. Slots 32 and 32' are each of the same pitch and extend axially for equal distancesalong the drum length, that is, each of the two slots, 32 and 32 extends for the full length of zone B and from the beginning tothe end of zone B.

The helical slot 32 includes what will be referred to as a leading edge 34, while the helical slot 32' includes a'leading edge, indicated at 34. By leading edge is meant the edge of each respective slot which is first contacted by the material flowing through the drum. In fact, the leading edges 34 and 34' of the respective slots 32 and 32' are-the most significant part of the respective slots since a predetermined percentage of the material being, processed tumbles over the leading edge 34 or 34' through the slot 32 or 32' and the remaining contour and area of the slot is of significance only in that it should be large enough throughout the length thereof to pass therethrough any material which passes over the respective leading edge 34, 34'.

The helical slot 32 seen in FIGS. 5, 6A-6C,'incl., 7A-7D, incl., and 8 in addition having leading edge 34, also includes trailing edge 36 and a connecting edge 38 which connects the downstream terminus 40 of leading edge 34 with the downstream end of trailing edge 36. The upstream terminus of leading edge 34 is indicated at 42.

since

slots

32 and 32 are duplicates of each other and any given position of slot 32 is duplicated by slot 32' with a phase shift of 180.

Referring now to FIG. 6A which diagrammatically shows the general relationship between the angular path of load material flow in the intermediate discharge zone B relative to helical slot 32 it will be noted that the band M of material flow shown in the internal or intermediate discharge zone B is divided into two component paths indicated at M-1 and M-2. The material flowing in path M-l drops through slot 32 at some timeduring the 360 rotation of drum 10, and thus drops onto vibrating screen 28.

By angular path of load material flow is meant the helical path or line which a given particle of material in the load would inscribe on the internal surface of the drum 10 during one revolution of the drum, as such inscription would appear on a 360 developed surface of nent paths M-1 and M-2, and theline X-X all follow and conform to the angular path of load material flow as just defined. Also, in FIGS. 7A-D, inclusive, 8, and 9, the material shown follows and conforms to the angular path of load material flow,

The material dropping through slot 32 is axially distributed onto vibrating screen 28 beneath discharge zone B for an axial distance corresponding to the displacement of downstream terminus 40 and upstream terminus 42 of slot 32 from each other in a direction measured parallel to the longitudinal axis of drum l0.

The material in path M-2 passes through discharge zone B without dropping through either slot 32 or 32' and passes into zone C where it is redistributed; that is, the flow of material in zone C evens out to overcome a banding" type of distribution of the material as it first enters zone C. The material which passes into zone C then passes into zone D where it is discharged onto vibrating screen 30. It will be understood, of course, that at any given moment, the material in zone B only subtends a peripheral angle' 0 (see FIG. 3) relative to the periphery of the balling drum l0, and that due to the rotation of drum 10, the portion of the respective helical slots 32 and 32' lying within the peripheral angle 0 is constantly changing.

Both of the material flow paths M1 and M-2 of FIGS. 6A-6C, inclusive, as best seen in FIG. 6A have a common slope corresponding to the angular path of load material flow as hereinbefore defmd indicated by the line X-X which makes an angle W relative to a line Z-Z which is transverse or perpendicular to the longitudinal axis of the developed surface of rotating drum 10. The leading

edge

34, 34 of the respective he lical slots 32, 32' has a slope designated by the line YY in FIG. 6A. Line YY makes an angle T relative to line ZZ. The angular relationships described are as viewed on the developed surface of the drum. The slope of the line X-Xof the angular path of load material flow relative to line ZZ as indicated by angle W should be greater than the slope of the line YY (angle T) with respect to line Z-Z. By having the slope of the angular path of load material flow greater than the slope of the leading edge 34, 34' as just described, the angular path of load material flow will cross or intersect the leading edge 34, 34' of the slots 32, 32' in a manner which provides proper distribution of the material in both an axial and a transverse direction wih respect to the vibrating screen 28 positioned beneath the discharge zone B.

It will be noted that in FIG. 6B, the angular path of load material flow M-l which is intercepted by leading edge 34 of slot 32 and which drops over leading edge 34 into slot 32 is substantially equal in width to the ma- "terial in path M-2 which does not pass into slot 32 but which proceeds beyond intermediate discharge zone B into the subsequent zones C and D. In other words, with the arrangement diagrammatically shown in FIG. 68, approximately equal amounts of material flows in the two paths M-1 and M-2 so'that there is an approximately equal division between the material flowing into the slot'32 and thence to vibrating screen 28 and of the material which does not flow through the slot 32. This approximately equal distribution of flow between the paths M-1 and M-2 is obtained by having the downstream terminus 40 of leading edge 34 of slot 32 spaced from the'upstream terminus 42 of slot 32 in a direction normal to the angular path of load material flow by a distance D-l=%D where D is the total distance in a direction normal to theangularpath of load material flow between the upstream terminus 42 of slot 32' and the upstream terminus 42' of slot 32. The distances 6D and D are as measured on the developed surface of drum l0. 3

It will be noted that the distance D corresponds to the total width in a direction normal to the angular path of load material flow of the flow paths M-l plus M-2 as measured on the developed surface of drum 10. As will be explained hereinafter, the distance D-l of the displacement of the downstream terminus 40 relative to the'upstream terminus 42 relative to the total distance D does not take into consideration a correction factor which should be applied to allow for the effect of the angle of repose of the material adjacent the edges of

slots

32 and 32. (See FIG. 4).

In FIG. 6C, the effect of shifting the distance in a direction normal to the angular path of load material flow of downstream terminus 40 of slot 32 relative to the upstream terminus 42 can be observed. Thus, in FIG. 6C, the distance D-] between downstream terminus 40 and upstream terminus 42 of leading edge 34 of slot 32 is two-thirds the distance D measured in a direction normal to the angular path of load material flow between upstream terminus 42 of slot 32 and upstream terminus 42 of slot 32. The distances D, D-l, D-2 are all as measured on a developed surface of drum 10.

The location of terminus as shown in FIG. 6C causes leading edge of slot 32 to intercept the angular path of load material flow through discharge zone B in a manner such that approximately two-thirds of the material in the band M of material drops over the leading edge 34 into slot 32 and thence passes to vibrating screen 28, while approximately one-third of the total material in band M passes through the discharge zone B without dropping through slot 32 and thence passes to the redistribution zone C and to the final discharge zone D where it drops onto the vibrating screen 30. In other words, in the embodiment diagrammatically shown in, FIG. 6C material flow path M-l which drops into-slot 32 and is thus discharged to screen 28, contains approximately two-thirds of the material flow in path M, while path M-2, which passes through discharge zone B without dropping through slot 32, contains approximately one-third of the material flow in band or path M.

In the previous discussion of proportioning the relative amounts of the total load entering zone B which drops through

slots

32 and 32 and which passes through zone B without dropping through the slots, it can be considered that the distribution of material flow in the respective paths M-l and M-2 is approximately in the same ratio as the distances D-l to D-2. This approximation ignores a correction factor which should be applied in actual practice to provide a more exact proportioning of the material discharged at intermediate discharge zone B relative to the entire load of material passing through drum 10. That is, the angleof repose of the material relative to the slot edge 34 or 34' is such that a slightly greater percentage of closed travel area (path M-2' of FIG. 6A-6C, inclusive) must be allowed than the actual relative percentage of material flowing in the path M-2. That is, for example, in the illustrated embodiment of FIG. 68, where there is theoretically an equal division of material flow between the paths M-1 and M-2, the dimension D-2 should actually be about 55 percent of the total distance D and the distance D-l should be about percent of the total distance D to obtain a more nearly equal division of material flow between paths M-1 and M-2 which is the assumed desired objective in the schematic diagram of FIG. 6B. I

That is, the percentage of the dimension D-2 relative to the total distance D for any given desired percentage flow of load material in path M-2 should be about 10 percent greater than the percentage of the load in path M-2 relative to the total material flow in band M. Thus, in the example cited, where. it was desired to have percent of the total flow of band M in path M4, the dimension D-2 is made percent of dimension D. In a similar manner if it were desired to have 33 ii percent of the material in band M flow in path M-2, then dimension D-2 in FIG. 6C should be approximately 36.6

percent of dimension D. t

Referring now to FIG. 4 which is a sectional view taken along line IV-IV of FIG. 7D, it can be seen that the material M tapers or is inclined relative to the vertical plane by an angle of repose R, contiguous the edges of the slots 32 and 32'. The net effect of this is that distance D-2 which is the dimension of the material flow path M2 of the material which does not drop into the slot 32 or 32' must have a correction factor applied to it as previously explained so that the actual width of the path M-2 (that is, dimension D-2) in a direction measured on a developed surface of the drum in a direction normal to the angular path of load material flow should be about percent greater than the actual relative percentage of material flowing in the path M-2 as previously explained.

Referring now to the diagrammatic sketches of FIG. 7A-7D, inclusive, these sketches show the band of material having an angular span 6 corresponding to the angular span of the material flowing through the balling drum as seen in cross section transverse of the drum (See FIG. 3). In FIG. 7A-7D, inclusive, the drum rotates relative to the band of material M as in actual practice. In FIG. 7A, which represents the starting posi-' beyond

slots

32 and 32 on a previous rotation of drum 10 without dropping through either of the slots. Band portion 2 will pass on to zone C and be discharged at zone D. v

Referring now to FIG. 7B in which drum 10 has rotated 90 from the position of FIG. 7A, it will be'noted that slot 32' has moved to a position in which it isintercepting material band portion 18. In FIG. 7B, slot 32 continues to intercept material band portion 1A, while material band portionZA continues to pass through the intermediate discharge zone B without discharging through either slot 32 or 32'. Band portion 2 in the position of FIG. 2B which has passed beyond slots 32 without dropping through either of these slots continues to advance beyond intermediate discharge zone B into redistribution zone C, from whence it will ultimately pass to end discharge zone D.

Referring now to FIG. 7C, in which drum 10 has advanced 90 beyond the position of FIG. 7B and 180 beyond the position of FIG. 7A, it can be seen that material band 18 continues to be intercepted by slot 32', and'that material band portion 2A has passed beyond slots 32' and 32 and is proceeding toward the redistribution zone C, from whence'it will pass into the final discharge zone D.

In the position of FIG. 7C, material band portions 28 and 1C not shown in FIGS. 7A and 7B have moved into the positions shown in FIG. 7C, In the position of FIG. 7 C, material band portion IC has moved into a position where it will soon be intercepted by slot 32, and material band portion 23 is moving in a region where it will not be intercepted by either slot 32 or 32' and will ultimately pass to discharge zone D.

In FIG. 7D which represents an advance of 90 degrees of drum 10 beyond the position of FIG. 7C and 270 degrees of revolution of drum l0 beyond the position of FIG. 7A, it will be noted that slot 32 has begun to intercept the material band portion 1C; that the material band portion 28 continues to move through the discharge zone B without dropping into either slot 32 or 32'; that the material band portion 18 continues to be intercepted by the slot 32'; and that the material 10 band portion 2A has passed beyond the slots 32 and 32' into the redistribution zone C from whence it will proceed to the end'discharge zone D.

Referring now to FIG. 8, which is another diagrammatic view illustrating the same relationships as shown in FIGS. 7A-7D, inclusive, there is shown a material band portion indicated at l in four different 90 displaced positions relative to slot 32, corresponding to the positions which the band of material which occupies the angle 0 (See FIG. 3) in the drum will have relative to slot 32' at four successive 90 displaced positions of drum 10. Thus, in position I of FIG. 8, slot 32' has not yet intercepted material band portion 1 In position II of the material band portion 1', which represents a 90 rotation of slot 32? in a clockwise direction, slot 32 has begun to intercept the material band portion 1 across the entire peripheral length of the material band portion 1' and some of the material has dropped through slot 32'. Similarly, position III in FIG. 8 shows the relation of material band portion 1 to slot 32' after 180 of rotation of drum 10 relative to the position I. In the same manner, position IV shows the relative position of the material band portion 1 relative to slot 32 after the drum 10 and the slot 32' have rotated through an angle of 270 relative to the starting position (position I).

In the construction and operation of a drum having an intermediate discharge zone in accordance with the invention, the angular path of load material flow as hereinbefore defined can be calculated for a given material having particular properties, a given drum rotary speed, and a given inclination of the bottom surface of r the drum relative to the horizontal plane. With the angular path of load material flow through the drum known (as represented by the angle W in FIG. 6A), slots 32 and 32' can then be designed to have the proper relationship of the respective leading edge 34 and 34' to the angular path of load material flow to sat.- isfy distances D-1 and D-2 as set forth in FIG. 6B and tiC, making sufficient allowance for the angle of repose of the materialas shown in FIG. 4 and as explained hereinbefore. Thus, knowing the angle W of the angular path of load material flow and knowing the percentage of the load which it is desired to discharge at the intermediate discharge zone (this would normally be approximately 50 percent of the total load passing through the drum) the slots 32 and 32' can be laid out in accordance with the principles hereinbefore described to provide a proper distribution of the load as between the intermediate discharge zone B and the final discharge zone D.

In constructing a balling drum or the like having the discharge zone with helical slots as hereinbefore described, the angle'of the leading edge of the slots having the desired relation to the angular path of load material flow are cut into the drum in the intermediate discharge zone in accordance with the principles previously described. It may be necessary after the drum is once installed and in-operation to make some adjustment of the leading edges such as 34 and 34' and of thedistance D4 of FIG. 6B and 6C to conform to actual conditions encountered during .operation of the balling drum. Adjustment of the distance D-l may be provided for example, by slidably adjustable plates (notshown) overlying the leading

edges

34, 34 of slots 32, 32' and extending for the length of the respective leading edges. Such .plates may be adjusted to change the effec- I 6A-6C, inclusive, 7A-7D, inclusive, the edges 34 and tive location of the respective leading edges and thus the dimension Dl. Also, if it is desired to increase the dimension D-l, the wall of drum may be additionally cut at the site of the installation to shift the physical location ofthe leading edge such as 34 or 34'.

While in the illustrated embodiments of F IGS. 5,

34 of the

respective slots

32 and 32 have been shown as the leading edges in intercepting relation to the angular path of load material flow, it is also possible as shown in FIG. 9 in connection with slot 32" to reverse the relative angular positions and relationships of

edges

34 and 36 as compared to those shown in the previous figures so that edge 36" becomes the leading edge and in intercepting relation to material flow path M-l. Normally, in the embodiment of FIG. 9, the angular relation ofleading edge 36 to the angular path ofload material flow would be such as to intercept substantially 50 percent of the total load material entering the intermediate discharge zone B. However, the angular relation of leading edge 36" to the angular path of load material flow could be made such by shifting the location of downstream terminus 43 (FIG. 9) in the same manner as described in connection with downstream terminus 40 in FIGS. 6A-6C, inclusive, and in accordance with the principles previously described so as to intercept any other desired portion of the total material flow in path M of FIG. 9, whereby to cause a desired predetermined percentage of the total load entering intermediate discharge zone B to be discharged to screen 28. I

From the foregoing detailed description of the present invention, it has been shown how the objects of the invention have been obtained in a preferred manner. However, modifications and equivalents of the disclosed concepts such as readily occur to those skilled in the art are intended to be included within the scope of this invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A balling drum or the like comprising an inlet contiguous an end of said drum through which material is charged into the drum, a second discharge means contiguous an opposite end of said drum, and a first discharge means defined by an intermediate discharge zone located intermediate the length of said drum and upstream of said second discharge means, said first discharge means being adapted to discharge therethrough a predetermined proportion of the total load material entering said intermediate discharge zone, said first discharge means comprising two port means in said drum through which material may discharge from said drum, each of said port means extending helically of said drum for the axial length of said intermediate discharge zone, each of said port means being out of phase with the other port means by a predetermined angle peripherally ofsaid drum, each of said port means comprising a downstream terminus and an upstream terminus respectively located at opposite peripheral ends of the respective port means, each of said port means including a corresponding leading edge extending helically and substantially continuously from said downstream terminus to said upstream terminus and adapted to intercept a predetermined proportion of the total flow of load material entering said intermediate discharge zone, the contour and area of each of said port means being large enough to permit passage through said port means of substantially any load material which passes over said leading edge, the downstream terminus of each respective port means when measured on a developed surface of the drum being spaced from the upstream terminus of the corresponding port means in a direction normal to the angular path of load material flow in said intermediate discharge zone by a distance having approximately the same ratio to the distance between the upstream terminus of one of said port means and the upstream terrninus of the other of said port means when measured on said developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone as the ratio which the portion of the total load which it is desired to discharge at said intermediate discharge zone has to the total load entering said intermediate discharge zone.

2. A balling drum or the like as defined in claim 1 in which each of said port means comprises a slot through the wall of said drum, each said slot extending helically of said drum substantially continuously from said downstream terminus to said upstream terminus of the respective port means.

3. A balling drum or the like as defined in claim 1 in which each of said port means is out of phase with the other of said-port means by an angle of substantially peripherally of said drum.

4. A balling drum or the like as defined in claim 1 in which the spacing of said downstream terminus of each respective port means from the upstream terminus of the corresponding port means is compensated for the angle of repose of the load material adjacent said port means to obtain discharge through said intermediate discharge'zone of said predetermined proportion of the total load by making the ratio D,/D approximately 10 percent greater than the ratio of the load material passing through said intermediate discharge zone without discharging to the total load material entering said intermediate discharge zone, where:

D the distance between the upstream terminus of one of said port means and the upstream terminus of the other of said port means D the distance from the upstream terminus of one of said port means to the downstream terminusof said one of said port means;

all of said distances being as measured on a developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone.

5. A balling drum or the like comprising an inlet contiguous an end of saiddrum through which material is charged into the drum, a second discharge means contiguous an opposite end of said drum, and a first discharge means defined by an intermediate discharge zone located intermediate the length of said drum and upstream of said second discharge means, said first discharge means being adapted to discharge therethrough a predetermined proportion of the total load material entering said intermediate discharge zone, said first discharge means comprising two port means in said drum through which material may discharge from said drum, each of said port means extending helically of said drum for the axial length of said intermediate discharge zone in substantially axially coextensive relation to the other port means each of said port means comprising a downstream terminus and an upstream tenninus respectively located at opposite peripheral ends of the respective port means, each of said port means comprising a slot through the wall of said drum, each said slot extending helically of said drum substantially continuously from saiddownstream terminus to said upstream terminus of the respective port means, each slot including a leading edge extending substantially continuously from said downstream terminus to said upstream terminus of the respective port means, the material which dischargesthrough each respective slot dropping over said leading edge of the respective slot to pass through the respective slot, the contour and area of each slot being large enough to permit passage through said slot of substantially any load material which passes over said leading edge of the respective slot, the slot of each respective port means being out of phase with the slot of the other port means by an angle of substantially 180 degrees peripherally of said drum, the downstream terminus of each respective port means when measured on a developed surface of the drum being spaced from the upstream terminus of the corresponding port means in a direction normal to the angular path of load material flow in said intermediate discharge zone by a distance having approximately the same ratio to the distance between the upstream terminus of one of said port means and the upstream terminus of the other of said port means when measured on said developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone as the ratio which the portion of the total load which it is desired to discharge at said intermediate discharge zone has to the total load entering said intermediate discharge zone.

6. A balling drum or the like comprising an inlet contiguous an end of said drum through which material is charged into the drum, a second discharge means contiguous an opposite end of said drum, and a first discharge means defined by an intermediate discharge zone located intermediate the length of said drum and upstream of said second discharge means, said first dis- I entering said intermediate discharge zone, said first discharge means comprising two port means in said drum through which material may discharge from said drum, each of said port means extending helically of said drum for the axial length of said intermediate discharge zone and in substantially axially coextensive relation to the other port means, each of said port means being out of phase with the other port means by a predetermined angle peripherally of said drum, each of said port means comprising a downstream terminus and an upstream terminus respectively located at opposite peripheral ends of the respective port means, each of said port means including a corresponding leading edge extending helically and substantially continuously from said downstream terminus to said upstream terminus and adapted to intercept a predetermined proportion of the total flow of load material entering said intermediate discharge zone, the contour and area of each of said port means being large enough to permit passage through said port means of substantially any load material which passes over said leading edge, the slope of said leading edge relative to a line which is normal to the longitudinal axis of the developed surface of the drum being less than the slope of the angular path of load material flow in said intermediate zone relative to said line all as measured on said developed surface of the drum, whereby the angular path of load material flow will intersect said leading edge, the downstream terminus of each respective port means when measured on a developed surface of the drum being spaced from the upstream terminus of the corresponding port means in a direction normal to the angular path of load material flow in said intermediate discharge zone by a distance which is a function of the ratio of the load which it is desired to discharge at said intermediate discharge zone relative to the total load entering said intermediate discharge zone, the spacing of said downstream terminus of each respective port means from the upstream terminus of the corresponding port means being compensated for the angle of repose of the load material adjacent said port means to obtain discharge through said intermediate discharge zone of said predetermined proportion of the total load by making the ratio D /D approximately 10 percent greater than the ratio of the load material passing through said intermediate discharge zone without discharging to the total load material entering said intermediate discharge zone, where:

D the distance between the upstream terminus of one of said port means and the upstream terminus of the other of said port means D the distance from the upstream terminus of one of said port means to the downstream terminus of said one of said port means; all of said distances being as measured on a developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone.

7. A balling drum or the like comprising an inlet contiguous an end of said drum through which material is charged into the drum, a second discharge means contiguous an opposite end of said drum, and a first discharge means defined by an intermediate discharge zone located intermediate the length of said drum and upstream of said second discharge means, said first discharge means being adapted to discharge therethrough a predetermined proportion of the total load material entering said intermediate discharge zone, said first discharge means comprising two port means in said drum through which material may discharge from said drum, each of said port means extending helically of said drum for the axial length of said intermediate discharge zone, each of said port means being out of phase with the other port means by a predetermined angle peripherally of said drum, each of said port means comprising a downstream terminus and an upstream terminus respectively located at opposite peripheral ends of the respective port means, the downstream terminus of each respective port means when measured on a developed surface of the drum being spaced from the upstream terminus of the corresponding port means in a direction normal to the angular path of load material flow in said intermediate discharge zone by a distance having approximately the same ratio to the distance between the upstream terminus of one of said port means and the upstream terminus of the other of said port means when measured on said developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone as the ratio which the portion of the total load which it is desired to discharge at said intermediate discharge zone has to the total load entering said intermediate discharge zone, the spacing of said downstream terminus of each respective port means from the upstream terminus of the corresponding port means being compensated for the angle of repose of the load material adjacent said port means to obtain discharge through said intermediate discharge zone of said predetermined proportion of the total load by making the ratio D /D approximately percent greater than the ratio of the load material passing through said intermediate discharge zone without discharging to the total load material entering said intermediate discharge zone, where:

D DD D the distance between the upstream terminus of one of said port means and the upstream terminus of the other of said port means D, the distance from the upstream terminus of one of said port means to the downstream terminus of said one of said port means; all of said distances being as measured on a developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone.

' 8. A balling drum or the like comprising an inlet contiguous an end of said drum through which material is charged into the drum, a second discharge means contiguous an opposite end of said drum, and a first discharge means defined by an intermediate discharge zone located intermediate the length of said drum and upstream of said second discharge means, said first discharge means being adapted to discharge therethrough a predetermined proportion of the total load material entering said intermediate discharge zone, said first discharge means comprising two port means in said drum through which material may discharge from said drum, each of said port means. extending helically of said drum for the axial length of said intermediate discharge zone and in substantially axially coextensive relation to the other port means, each of said port means being out of phase with the other port means by a predetermined angle peripherally of said drum, each of said port means comprising a downstream terminus and an up.

stream terminus respectively located at opposite peripheral ends of the respective port means, each of said port means including a corresponding leading edge extending helically and substantially continuously from said downstream terminus to said upstream terminus and adapted to intercept a predetermined proportion of the total flow of load material entering said intermediate discharge zone, the contour and area of each of said port means being large enough to permit passage through said port means of substantially any load material which passes over said leading edge, the downstream terminus of each respective port means when measured on a developed surface of the drum being spaced from the upstream terminus of the corresponding port means in a direction normal to the angular path of load material flow in said intermediate discharge zone by a distance which is a function of the ratio of the load which it is desired to discharge at said intermediate discharge zone relative to the total load entering said intermediate discharge zone, the spacing of said downstream terminus of each respective port means from the upstream terminus of the corresponding port means being compensated for the angle of repose of the load material adjacent said port means to obtain discharge through said intemiediate discharge zone of said predetermined proportion of the total load by making the ratio D,/D approximately 10 percent greater than the ratio of the load material passing through said intermedaite discharge zone without discharging to the total load material entering said inter mediate discharge zone, where:

,D the distance between the upstream terminus of one of said portmeans and the upstream terminus of the other of said port means D the distance from the upstream terminus of one of said port meansto the downstream terminus of said one of said port means;

0 1 l I I

Claims

1. A balling drum or the like comprising an inlet contiguous an end of said drum through which material is charged into the drum, a second discharge means contiguous an opposite end of said drum, and a first discharge means defined by an intermediate discharge zone located intermediate the length of said drum and upstream of said second discharge means, said first discharge means being adapted to discharge therethrough a predetermined proportion of the total load material entering said intermediate discharge zone, said first discharge means comprising two port means in said drum throuGh which material may discharge from said drum, each of said port means extending helically of said drum for the axial length of said intermediate discharge zone, each of said port means being out of phase with the other port means by a predetermined angle peripherally of said drum, each of said port means comprising a downstream terminus and an upstream terminus respectively located at opposite peripheral ends of the respective port means, each of said port means including a corresponding leading edge extending helically and substantially continuously from said downstream terminus to said upstream terminus and adapted to intercept a predetermined proportion of the total flow of load material entering said intermediate discharge zone, the contour and area of each of said port means being large enough to permit passage through said port means of substantially any load material which passes over said leading edge, the downstream terminus of each respective port means when measured on a developed surface of the drum being spaced from the upstream terminus of the corresponding port means in a direction normal to the angular path of load material flow in said intermediate discharge zone by a distance having approximately the same ratio to the distance between the upstream terminus of one of said port means and the upstream terminus of the other of said port means when measured on said developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone as the ratio which the portion of the total load which it is desired to discharge at said intermediate discharge zone has to the total load entering said intermediate discharge zone.

3. A balling drum or the like as defined in claim 1 in which each of said port means is out of phase with the other of said port means by an angle of substantially 180* peripherally of said drum.

4. A balling drum or the like as defined in claim 1 in which the spacing of said downstream terminus of each respective port means from the upstream terminus of the corresponding port means is compensated for the angle of repose of the load material adjacent said port means to obtain discharge through said intermediate discharge zone of said predetermined proportion of the total load by making the ratio D2/D approximately 10 percent greater than the ratio of the load material passing through said intermediate discharge zone without discharging to the total load material entering said intermediate discharge zone, where: D2 D-D1 D the distance between the upstream terminus of one of said port means and the upstream terminus of the other of said port means D1 the distance from the upstream terminus of one of said port means to the downstream terminus of said one of said port means; all of said distances being as measured on a developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone.

5. A balling drum or the like comprising an inlet contiguous an end of said drum through which material is charged into the drum, a second discharge means contiguous an opposite end of said drum, and a first discharge means defined by an intermediate discharge zone located intermediate the length of said drum and upstream of said second discharge means, said first discharge means being adapted to discharge therethrough a predetermined proportion of the total load material entering said intermediate discharge zone, said first discharge means comprising two port means in said drum through which material may discharge from said drum, each of said port meAns extending helically of said drum for the axial length of said intermediate discharge zone in substantially axially coextensive relation to the other port means each of said port means comprising a downstream terminus and an upstream terminus respectively located at opposite peripheral ends of the respective port means, each of said port means comprising a slot through the wall of said drum, each said slot extending helically of said drum substantially continuously from said downstream terminus to said upstream terminus of the respective port means, each slot including a leading edge extending substantially continuously from said downstream terminus to said upstream terminus of the respective port means, the material which discharges through each respective slot dropping over said leading edge of the respective slot to pass through the respective slot, the contour and area of each slot being large enough to permit passage through said slot of substantially any load material which passes over said leading edge of the respective slot, the slot of each respective port means being out of phase with the slot of the other port means by an angle of substantially 180 degrees peripherally of said drum, the downstream terminus of each respective port means when measured on a developed surface of the drum being spaced from the upstream terminus of the corresponding port means in a direction normal to the angular path of load material flow in said intermediate discharge zone by a distance having approximately the same ratio to the distance between the upstream terminus of one of said port means and the upstream terminus of the other of said port means when measured on said developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone as the ratio which the portion of the total load which it is desired to discharge at said intermediate discharge zone has to the total load entering said intermediate discharge zone.

6. A balling drum or the like comprising an inlet contiguous an end of said drum through which material is charged into the drum, a second discharge means contiguous an opposite end of said drum, and a first discharge means defined by an intermediate discharge zone located intermediate the length of said drum and upstream of said second discharge means, said first discharge means being adapted to discharge therethrough a predetermined proportion of the total load material entering said intermediate discharge zone, said first discharge means comprising two port means in said drum through which material may discharge from said drum, each of said port means extending helically of said drum for the axial length of said intermediate discharge zone and in substantially axially coextensive relation to the other port means, each of said port means being out of phase with the other port means by a predetermined angle peripherally of said drum, each of said port means comprising a downstream terminus and an upstream terminus respectively located at opposite peripheral ends of the respective port means, each of said port means including a corresponding leading edge extending helically and substantially continuously from said downstream terminus to said upstream terminus and adapted to intercept a predetermined proportion of the total flow of load material entering said intermediate discharge zone, the contour and area of each of said port means being large enough to permit passage through said port means of substantially any load material which passes over said leading edge, the slope of said leading edge relative to a line which is normal to the longitudinal axis of the developed surface of the drum being less than the slope of the angular path of load material flow in said intermediate zone relative to said line all as measured on said developed surface of the drum, whereby the angular path of load material flow will intersect said leading edge, the downstream terminus of each respective port means when measured on a deVeloped surface of the drum being spaced from the upstream terminus of the corresponding port means in a direction normal to the angular path of load material flow in said intermediate discharge zone by a distance which is a function of the ratio of the load which it is desired to discharge at said intermediate discharge zone relative to the total load entering said intermediate discharge zone, the spacing of said downstream terminus of each respective port means from the upstream terminus of the corresponding port means being compensated for the angle of repose of the load material adjacent said port means to obtain discharge through said intermediate discharge zone of said predetermined proportion of the total load by making the ratio D2/D approximately 10 percent greater than the ratio of the load material passing through said intermediate discharge zone without discharging to the total load material entering said intermediate discharge zone, where: D2 D-D1 D the distance between the upstream terminus of one of said port means and the upstream terminus of the other of said port means D1 the distance from the upstream terminus of one of said port means to the downstream terminus of said one of said port means; all of said distances being as measured on a developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone.

7. A balling drum or the like comprising an inlet contiguous an end of said drum through which material is charged into the drum, a second discharge means contiguous an opposite end of said drum, and a first discharge means defined by an intermediate discharge zone located intermediate the length of said drum and upstream of said second discharge means, said first discharge means being adapted to discharge therethrough a predetermined proportion of the total load material entering said intermediate discharge zone, said first discharge means comprising two port means in said drum through which material may discharge from said drum, each of said port means extending helically of said drum for the axial length of said intermediate discharge zone, each of said port means being out of phase with the other port means by a predetermined angle peripherally of said drum, each of said port means comprising a downstream terminus and an upstream terminus respectively located at opposite peripheral ends of the respective port means, the downstream terminus of each respective port means when measured on a developed surface of the drum being spaced from the upstream terminus of the corresponding port means in a direction normal to the angular path of load material flow in said intermediate discharge zone by a distance having approximately the same ratio to the distance between the upstream terminus of one of said port means and the upstream terminus of the other of said port means when measured on said developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone as the ratio which the portion of the total load which it is desired to discharge at said intermediate discharge zone has to the total load entering said intermediate discharge zone, the spacing of said downstream terminus of each respective port means from the upstream terminus of the corresponding port means being compensated for the angle of repose of the load material adjacent said port means to obtain discharge through said intermediate discharge zone of said predetermined proportion of the total load by making the ratio D2/D approximately 10 percent greater than the ratio of the load material passing through said intermediate discharge zone without discharging to the total load material entering said intermediate discharge zone, where: D2 D-D1 D the distance between the upstream terminus of one of said port means and the upstream terminus of the otheR of said port means D1 the distance from the upstream terminus of one of said port means to the downstream terminus of said one of said port means; all of said distances being as measured on a developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone.

8. A balling drum or the like comprising an inlet contiguous an end of said drum through which material is charged into the drum, a second discharge means contiguous an opposite end of said drum, and a first discharge means defined by an intermediate discharge zone located intermediate the length of said drum and upstream of said second discharge means, said first discharge means being adapted to discharge therethrough a predetermined proportion of the total load material entering said intermediate discharge zone, said first discharge means comprising two port means in said drum through which material may discharge from said drum, each of said port means extending helically of said drum for the axial length of said intermediate discharge zone and in substantially axially coextensive relation to the other port means, each of said port means being out of phase with the other port means by a predetermined angle peripherally of said drum, each of said port means comprising a downstream terminus and an upstream terminus respectively located at opposite peripheral ends of the respective port means, each of said port means including a corresponding leading edge extending helically and substantially continuously from said downstream terminus to said upstream terminus and adapted to intercept a predetermined proportion of the total flow of load material entering said intermediate discharge zone, the contour and area of each of said port means being large enough to permit passage through said port means of substantially any load material which passes over said leading edge, the downstream terminus of each respective port means when measured on a developed surface of the drum being spaced from the upstream terminus of the corresponding port means in a direction normal to the angular path of load material flow in said intermediate discharge zone by a distance which is a function of the ratio of the load which it is desired to discharge at said intermediate discharge zone relative to the total load entering said intermediate discharge zone, the spacing of said downstream terminus of each respective port means from the upstream terminus of the corresponding port means being compensated for the angle of repose of the load material adjacent said port means to obtain discharge through said intermediate discharge zone of said predetermined proportion of the total load by making the ratio D2/D approximately 10 percent greater than the ratio of the load material passing through said intermedaite discharge zone without discharging to the total load material entering said intermediate discharge zone, where: D2 D-D1 D the distance between the upstream terminus of one of said port means and the upstream terminus of the other of said port means D1 the distance from the upstream terminus of one of said port means to the downstream terminus of said one of said port means; all of said distances being as measured on a developed surface of said drum in a direction normal to the angular path of load material flow in said intermediate discharge zone.