US3576262A

US3576262A - Rotary particle distributor for minimizing particle size segregation in a bin

Info

Publication number: US3576262A
Application number: US830963A
Authority: US
Inventors: James L Konchesky; Ernest C Oldaker
Original assignee: US Department of the Interior
Current assignee: US Department of the Interior
Priority date: 1969-06-06
Filing date: 1969-06-06
Publication date: 1971-04-27
Anticipated expiration: 1988-04-27

Abstract

A conical chute rotates upon a cylindrical track for distribution of particulate solids within a bin. The vertical axis of rotation of the chute is displaced from the discharge opening of the chute so that the opening traces a circular path in a substantially horizontal plane. The bearing surface of the track has ridges and depressions which cause the chute to oscillate in a generally radial direction as it is rotated. An inverted cone is suspended below the discharge opening for uniform distribution of the particulate in a conical stream. Deflecting baffles, fixed to the bin below the rotating chute and cone, enhance the mixing and distribution of the particulate.

Description

United States Patent Appl. No. Filed Patented Assignee ROTARY PARTICLE DISTRIBUTOR FOR MINIMIZING PARTICLE SIZE SEGREGATION IN A BIN 13 Claims, 3 Drawing Figs.

US. Cl 214/17, 193/3, 239/659, 239/666, 239/684 Int. Cl 865g 65/32 FieldofSearch 214/17.6,

References Cited UNITED STATES PATENTS Aldrich et al.

Primary ExaminerRobert G. Sheridan Attorneys-Emest S. Cohen and Gersten Sadowsky ABSTRACT: A conical chute rotates upon a cylindrical track for distribution of particulate solids within a bin. The vertical axis of rotation of the chute is displaced from the discharge opening of the chute so that the opening traces a circular path in a substantially horizontal plane. The bearing surface of the track has ridges and depressions which cause the chute to oscillate in a generally radial direction as it is rotated. An inverted cone is suspended below the discharge opening for uniform distribution of the particulate in a conical stream. Deflecting baffles, fixed to the bin below the rotating chute and cone, enhance the mixing and distribution of the particulate.

PATENTEDAPRZHHYI 3576.262

' sum 1 [IF 2 IN VE N T0 RS JAMES L. KO/VCHES/(Y ERNEST a. OL 04 KER By W 34 ATTORN I ROTARY PARTICLE DISTRIBUTOR FOR MINIMIZING PARTICLE SIZE SEGREGATION IN A BIN BACKGROUND OF THE INVENTION This invention relates generally to the field of material handling, and more particularly to a bin-charging apparatus including a rotating chute for uniform distribution of solid particles of different sizes.

In the nuclear measurement of impurities in coal, the coal is fed continuously past nuclear sensing instruments which are located in a bin. When the coal is fed directly from a conveyor to the bin by free fall, a conical pile is formed with the fines segregating in the central area of the bin and the coarse material tumbling down the sides of the pile and concentrating close to the bin wall. It is well known that impurities such as moisture, sulfur, and ash in coal generally concentrate in fines and that, therefore, they are also segregated. As the coal flows past the'nuclear instruments, it remains segregated and the instrument response does not represent the total mass of coal. A particle distributor, therefore, is necessary to maintain the level bed and uniform distribution of particles required for accurate measurement.

DESCRIPTION OF THE PRIOR ART Particle distributors are available for use in very large coal bins to obtain a somewhat level bed. In one prior art distributor, particles are discharged into a bin from a belt through a tripper which moves back and forth in the stream of particles. In this operation the particles are distributed in layers with extensive local separation occuring within each layer deposited.

Another prior art particle distributor employs an inclined conveyor on a pivot that reciprocates over an are at the discharge point in the bin. This device serves only to deposit the particles in an elongated pile, resulting in considerable cone tumbling and particle size segregation. Radial mixing arms which aerate and disperse particles from a feed stream have also been employed in a vertical blender to provide continuous mixing as the particles are fed into a bin. The efficiency of these mixing arms for securing uniform particle distribution is nearly as unsatisfactory as free fall.

A rotary spreader is used in another prior art device in an attempt to minimize particle size segregation. Three separate spouts are used to discharge particles in three distinct, continuous piles as the spreader rotates. Particle segregation results because of cone tumbling down the sides of the piles. Since this rotary spreader splits one particle feed stream into three streams, the particles must be free flowing for the splitting to occur. Coal containing appreciable amounts of moisture, as with many other solids, is not free flowing and would tend to arch and, therefore, plug the openings where the stream is split. For these reasons the previously available particle distributors were unsuitable for the uniform distribution of all types of particles within a bin.

SUMMARY OF THE INVENTION This invention isa rotary particle distributor for uniformly distributing particulate solids of different sizes into a level bed within a bin. A chute on the particle distributor is positioned within a cylindrical bin, with the central discharge outlet of the chute displaced from the central axis of the bin. The chute is suspended on a cylindrical track which is concentric with the bin, and rotated about the axis of the bin upon four regularly spaced support wheels extending radially from the mouth of the chute. The bearing surface of the track is scalloped in an approximate sinusoid. Diametrically opposite each ridge on the scalloped track there is a depression, so that when one support wheel traverses a ridge, the opposite wheel traverses a depression, causing the chute to tilt from vertical alignment within the bin. As the chute is rotated around the track by a motor through a double universal joint it is alternately tilted in opposite radial directions, superimposing a tilting radial oscillation upon the rotation of the chute.

Below the discharge outlet of the rotary chute an inverted dispersion cone increases the efficiency of the chute by spreading the discharging particulate in a conical stream. Stationary deflecting baffles below the dispersion cone mix and aerate the particulate, further increasing the efficiency of the rotary chute and dispersion cone.

In one embodiment, the rotary particle distributor is fixed within a bin for maintaining a constant height, level bed. This embodiment of the invention is particularly suited for nuclear measurement of coal impurities by sensing instruments within the bin. Alternately the fixed embodiment is suitable for blending solids by recirculating them through the bin in a closed circuit. By removing a side stream of particles and replenishing the circuit with the same amount removed, the circuit also functions as a continuous mixer or blender.

In an alternate embodiment, the rotary particle distributor is independently mounted for raising and lowering the position of the distributor as the height of the particulate bed within a bin changes as the bin is loaded. For most efficient operation, there is an optimum spacing between the dispersion cone, deflecting baffles, and surface of the particulate bed. When the distributor is used to maintain a constant height level bed, this spacing remains constant. When, however, the distributor is used to load a bin for storage, the spacing between the distributor and particulate bed changes as the bin is loaded, requiring a corresponding change in the position of the particle distributor. This change is achieved by raising the distributor as the bin is filled.

Therefore, an object of the invention is to provide a particle distributor for the uniform distribution of particulate solids within a bin.

A further object of this invention is to provide a rotary particle distributor having a discharge chute which is rotated and simultaneously oscillated in a radial direction.

A still further object of this invention is to provide a stationary particle distributor for maintaining a constant height, level bed.

A still further object of this invention is to provide a translatable particle distributor for loading a storage bin.

A still further object of this invention is to provide a rotary particle distributor employing a dispersion cone and deflecting baffles for increased distribution efficiency.

These and other objects of the invention will become more fully apparent with reference to the following specification and drawing which describe the preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an elevation section of one embodiment of a particle distributor situated in a bin.

FIG. 2 is an isometric view of the particle distributor shown in FIG. I.

FIG. 3 is a partial elevation section of an alternate embodiment of a particle distributor situated in a bin.

DESCRIPTION OF THE PREFERRED EMBODIMENT A rotary particle distributor I0 is shown in FIG. I mounted upon a cylindrical bin I2 for uniformly distributing a stream of particulate matter I4l into a level bed 16. The particulate I4 is fed into the distributor 10 by a suitable feeder, such as a conveyor belt I8, rotating on a wheel 20. After leaving the conveyor belt I8, the particulate l4 enters a chute 22 which changes the angular path of the particulate stream I4 into a vertical path. As the downward moving stream of particulate I4 emerges from the chute 22 it encounters a dispersion cone 36 that spreads the particles evenly in a conical pattern.

Below the dispersion cone 36, the particulate encounters a concentric array of circular deflection baffles 90. The baffles mix and aerate the particles before they reach the bed 16. As the particulate discharges into the bin, the chute 22 and dispersion cone 36 are rotated about a vertical axis which is displaced from the discharge opening 29 in the chute and concentric with the longitudinal axis of the bin 12. As the chute 22 and cone 36 are rotated a radial oscillation is imparted to the chute 22 so that the opening 29 traverses a path approxi mating a circular sinusoid. The resulting interaction of this rotation and oscillation with the mixing by the deflection baffles evenly distributes the particulate stream and maintains a level surface on the bed 16.

The chute 22, which the particulate enters after leaving conveyor belt 18, is constructed from three hollow sections. The upper, or deflecting, section 24 is shaped as an inverted frustum of an oblique cone; the central, or transition, section 26 is shaped as a cylinder, and the lower, or focusing, section 28 is shaped as an inverted frustum of a cone. The upper and

central sections

24 and 26 are joined at their edges by a continuous welded seam 30, while the central and

lower sections

26 and 28 are joined by suitable fasteners at radially extending

flanges

32 and 34, respectively.

The dispersion cone 36 is suspended below the focusing section 28 by three equilaterally spaced suspension rods 38. Each suspension rod 38 has a dogleg extension 40 which is attached to the upper surface of the flange 32 on the transition section 26. The lower portion of each rod 38 has external screw threads extending a distance upward from the end of the rod. Threeequilaterally spaced eyebolts 42 extend radially from the lower edge of the dispersion cone 36 and are fastened to the threaded portion of suspension rods 38 by nuts 44 above and below the eyebolts. The screw threads on each rod 38 are long enough to permit optimum placement of the dispersion cone 36 relative to the focusing section 28. The dispersion cone 36 is locked in a position close enough to the focusing section 28 to cause the center of the particulate stream 14 to hit the apex of the cone and spread evenly over the cone surface, and far enough away to prevent obstruction in flow in the particulate stream. A uniform vertical drop of the particulate stream 14 onto the dispersion cone 36 is achieved with the aid of a vertical deflection plate 46 which extends from just below the top of the deflecting cone 24 to the lower end of the transition section 26. The deflectionplate 46 is narrower than the diameter of the transition section 26, yet is wide enough to deflect a portion of the particulate 14 to one side of the focusing section 28, while permitting an equal portion to pass to the other side of the section.

The chute 22 is suspended within the cylindrical bin 12, and on a cylindrical track 48, by four support wheels 50 and axles 52. The axles 52 extend radially from a hub 54 within the deflecting section 24, through apertures in the section, to the cylindrical track 48. Each axle 52 is connected to the chute 22 and is braced on the outside wall of the chute by a gusset plate 53. A support wheel 50 is mounted for free rotation on the end of each rigidly mounted axle 52.

The upper edge 56 of the cylindrical track 48 has a smooth series of scallops, resembling a sine wave. Diametrically opposite each ridge on the track 24 there is a depression, causing the chute 22 to tilt from vertical alignment within the bin 12. As the chute 22 is rotated around track 48 on the support wheels 50, the alternate ridges and depressions in the track 48 tilt the chute, first in one direction, and then in the opposite direction, superimposing a tilting radial oscillation upon the circular rotation. This rotation and oscillation evenly distributes the particulate 14 across the bed 16.

The cylindrical track 48 is mounted within the bin 12 on a support ring 58 which is secured to the outer wall of the track and the inner wall of the bin. Horizontal pilot wheels 60 are suspended by a framework 62 from an axle 52 adjacent each support wheel 50. The pilot wheels maintain the alignment of the axis of rotation of the chute 22 with the axis of the track 48 and prevent interference between the support wheels and the interior of the bin 12.

The chute 22 is driven by a motor 64 through a variable speed transmission 66, a sprocket gear 68, a chain 70, a sprocket gear 72, an upper drive shaft 74, a double universal joint 76, and a lower drive shaft 78. The double universal joint 76 permits the tilting radial oscillation of the chute 22 at the same time the chute is driven for rotation by motor 64. The motor 64 and the variable transmission 66 are supported on a suitable framework outside the bin 12. A cover plate 82, with a central flanged inlet opening 84, extends across the top of the bin 12. A roller bearing 86 is supported above, and in alignement with the opening 84 by four regularly spaced supporting rods 88. The spacing of the rods 88 permits discharge of the particulate 14 into the bin, while simultaneously supporting the bearing 86. The upper drive shaft 74 extends through and is attached to the bearing 86 for the free rotation of the shaft about a vertical axis. The lower end of the shaft is fixed to one end of the double universal joint 76. The upper end of the lower drive shaft 78 is secured to the other end of the universal joint 76. The lower end of the lower drive shaft 78 is rigidly secured within the hub 54. In this way a part of the combined weight of the chute 22 and supporting structure is supported by the roller bearing 86, and a part is supported by the track 48.

Below the dispersing cone 38, a concentric array of circular deflection baffles 90 extends diametrically across the bin 12. Each baffle is shaped as a frustum of a hollow cone. The baffles 90 are supported in two parallel layers by slots in radial spider plates 92. The spider plates are bolted to vertically slotted channels 94 which are attached to the inner wall of the bin 12, providing independent vertical adjustment for each layer of baffles 90. The optimum deflection angle for each baffle is dependent upon the nature of the particulate 14, as is the spacing between the layers of baffles, and is best detennined by experiment with each type of particulate distributed.

The particle distributor 10 shown in FlGS. 1 and 2 is fixed within a bin 12 for maintaining a constant height, level bed 16 as the particulate 14 is simultaneously charged into and discharged from the bin. As previously explained, this operation is useful for the nuclear measurement of the particulate 14 within the bin, among other applications. For the best operation of the particle distributor 10, the particulate is maintained at a constant distance from the dispersion cone 36 and baffles 90. When a bin is used for storage, the height of a particulate bed changes as the bin is filled. For best operation in this case an alternate particle distributor 110, as partially shown in FIG. 3, is employed to change the position of the dispersion cone and baffles as the height of the bed 116 changes.

The particle distributor 110, fragmentarily shown in FIG. 3, is similar in general detail to the distributor 10 shown in FIGS. 1 and 2. A cylindrical track 148 and a support ring 158 are secured within a cylindrical casing, or framework 113 for supporting a rotatable duct 122. At the lower end of the casing 113, deflecting baffles 190 are adjustably suspended from spider plates 192 and slotted channels 194, as in the embodiment shown in FIGS. 1 and 2.

The cylindrical casing 113, in which the chute 122 and deflecting baffles 190 are mounted, is supported within a bin 112 by bearings which are spaced evenly on the wall of the casing within suitable supports 117. The outer wall of the casing 113 is spaced slightly from the inner wall of the bin 112, and the separation is maintained by the bearings 115 to enable relative longitudinal displacement of the casing and bin. As the bin is filled, raising the level of the bed 116, the casing is raised to maintain a constant distance between the bed and the deflection baffles 190. in this way, particle size segregation is minimized.

Power for raising the casing 113 is provided by the same motor 164 and transmission 166 that is used to drive the chute 122. An auxiliary power takeoff on the transmission 166 drives a pinion gear 167 through a gear 169, a chain 170, a pair of

concentric gears

171 and 173, a chain 175, and a gear 177 fixed to the pinion. The pinion gear 167, which is fixed to casing 113 by a rigid framework 180, engages a vertical rack 179. The rack 179 is secured to the outer wall of bin 112, and when the pinion gear 167 is rotated by motor 164, the pinion translates along the rack, raising the attached casing 113 within the bin 112. The speed at which the casing is raised is adjusted to equal the rate of filling of the bin 112 for maintaining the correct spacing between the bed 116 and the baffles 190 and dispersion cone (not shown in H0. 3).

In a test comprising the operation of free fall, a vertical blender, and the particle distributor of this invention, the superiority of the particle distributor was demonstrated with particulate coal. The largest degree of particle size segregation was found to exist within a .-l-4-mesh coal. Therefore, particle size segregation was based on the percentage of this size fraction in samples taken from the bin, in comparison with a standard amount in the input feed stream.

In the free test the central area of the bin, extending to twothirds of the radius, contained less +4-mesh coal than in the feed, with a deviation in the range of 20 percent to 25 percent. The outer area near the bin wall, covering about onefourth of the radius contained more +4-mesh coal than in the feed stream, and the deviation was as much as +40 percent. The remaining area of the bin showed a sharp transition from less +4-mesh coal near the center, to more as the distance from the center increased. The unbiased standard deviation of the +4-mesh fraction in the bin samples from that in the feed samples was 26.2 percent.

The segregation that resulted from use of the prior art vertical blender was nearly as poor as that resulting from the freefall test for the reasons given in the description of the prior art. The +4-mesh coal in the horizontal cross section of the bin deviated greatly in a random pattern in a range of 24 percent more to 33 percent less than that in the feed. The unbiased standard deviation of +4-mesh fraction in the bin samples from that in the feed was 20.2 percent.

In the test of the particle distributor of this invention the chute was rotated at rpm. The horizontal cross section of the bin charged by the particle distributor contained +4-mesh coal that did not deviate by more than about 8 percent from that in the feed. Moreover, about two-thirds of the samples deviated by not more than about 4 percent. The unbiased standard deviation of the +4-mesh fraction in the bin samples from that in the feed was 4.3 percent. It is apparent that the particle distributor considerably decreased particle size segregation relative to the results achieved with free fall or a vertical blender. it is, therefore, apparent that a useful apparatus has been provided for uniformly distributing difi'erent size particles within a bin. in adapting the present exemplary disclosure to a specific distribution environment, numerous modifications within the scope of the invention will become apparent to those skilled in the art.

The dimensions and operating speed of the particle distributor 10 are dependent upon the specific nature of the particulate distributed. The speed of rotation of the chute 22 is limited only by the effect of centrifugal force upon the particulate. The number and height of the scallops in the track 48 can be varied to change the gyratory characteristics of the chute 22. The track 48 can be rotated relative to the bin 12 and chute 22 to establish a changing pattern of gyration. In the embodiment shown in FIG. 3, additional racks 179 and pinions 167 can be spaced around the bin 112 to raise the casing 112 where the weight of the particle distributor 110 overloads the single rack and pinion. Alternatively, the particle distributor can be suspended within a bin by the cable of an overhead crane and transferred to other bins when the loading process is completed.

displaced horizontally from the outlet opening of the chute; the horizontal track further comprising a scalloped bearing surface for contacting the wheels at said spaced points; and

a drive shaft concentric with the axis of rotation, coupling the chute to a source of motive power through a universal joint for rotating the chute upon the track,

whereby, as the chute rotates, a tilting radial oscillation is superimposed upon the rotation of the chute.

2. The particle distributor claimed in claim 1 further comprising dispersion means secured for rotation with the chute below the outlet opening for dispersing a particulate stream emitted by the chute.

3. The particle distributor claimed in claim 1, further comprising deflecting means which are stationary relative to the rotation of the chute and positioned below the opening of the chute for deflecting a particulate stream emitted by the chute is diverse directions.

4. The particle distributor claimed in claim 2, further comprising deflecting means which are positioned below the dispersion means and stationary relative to the rotation of the chute and the dispersion means for deflecting the particulate stream in diverse directions.'

5. The particle distributor claimed in claim 2 in which the dispersion means includes a cone having a vertex and a base, with the vertex positioned below the chute, between the opening of the chute and the base of the cone.

6. The particle distributor claimed in claim 3 in which the deflecting means includes at least one concentric array of deflecting baffles shaped as frustums of hollow cones.

7. The particle distributor claimed in claim 4 in which:

the dispersion means includes a cone having a vertex and a base, with the vertex positioned below the chute between the opening of the chute and the base of the cone, and

the deflecting means includes at least one concentric array of deflecting baffles shaped as frustums of hollow cones.

8. The particle distributor of claim 1, further comprising means for securing the substantially horizontal track permanently in a fixed position within a bin.

9. The particle distributor claimed in claim 1, further comprising means for securing the substantially horizontal track for vertical translation within a bin, whereby the chute may be raised and lowered as the bin is charged and discharged.

10. The particle distributor claimed in claim 4, further comprising means for securing the substantially horizontal track and the deflecting means permanently in fixed positions within a bin.

11. The particle distributor claimed in claim 4, further comprising:

means for securing the substantially horizontal track and deflecting means for interdependent vertical translation within a bin,

whereby the spacing between the dispersion means, the deflecting means and a particulate bed can be maintained constant while the chute and deflecting means are raised and lowered as the bin is charged and discharged.

12. The particle distributor claimed in claim 7, further comprising means for securing the substantially horizontal track and the concentric array of deflecting baffles permanently in fixed positions within a bin.

13. The particle distributor claimed in claim 7, further comprising:

means for securing the substantially horizontal track and the concentric array of deflecting baffles for interdependent vertical translation within a bin,

whereby the spacing between the cone, the deflecting baffles and a particulate bed can be maintained constant while the chute and baffles are raised and lowered as the bin is charged and discharged.

Claims

1. A rotary particle distributor comprising: a substantially vertical chute, having an upper inlet opening and a lower outlet opening, supported by wheels at spaced points upon a substantially horizontal track for rotation on the track about a substantially vertical axis displaced horizontally from the outlet opening of the chute; the horizontal track further comprising a scalloped bearing surface for contacting the wheels at said spaced points; and a drive shaft concentric with the axis of rotation, coupling the chute to a source of motive power through a universal joint for rotating the chute upon the track, whereby, as the chute rotates, a tilting radial oscillation is superimposed upon the rotation of the chute.

4. The particle distributor claimed in claim 2, further comprising deflecting means which are positioned below the dispersion means and stationary relative to the rotation of the chute and the dispersion means for deflecting the particulate stream in diverse directions.

7. The particle distributor claimed in claim 4 in which: the dispersion means includes a cone having a vertex and a base, with the vertex positioned below the chute between the opening of the chute and the base of the cone, and the deflecting means includes at least one concentric array of deflecting baffles shaped as frustums of hollow cones.

11. The particle distributor claimed in claim 4, further comprising: means for securing the substantially horizontal track and deflecting means for interdependent vertical translation within a bin, whereby the spacing between the dispersion means, the deflecting means and a particulate bed can be maintained constant while the chute and deflecting means are raised and lowered as the bin is charged and discharged.

13. The particle distributor claimed in claim 7, further comprising: means for securing the substantially horizontal track and the concentric array of deflecting baffles for interdependent vertical translation within a bin, whereby the spacing between the cone, the deflecting baffles and a particulate bed can be maintained constant while the chute and baffles are raised and lowered as the bin is charged and discharged.