US3710925A

US3710925A - Centrifugal stower

Info

Publication number: US3710925A
Application number: US00140904A
Authority: US
Inventors: K Dorman
Original assignee: US Department of the Interior
Current assignee: US Department of the Interior
Priority date: 1971-05-06
Filing date: 1971-05-06
Publication date: 1973-01-16
Anticipated expiration: 1990-01-16

Abstract

A centrifugal stower for propelling fluent solids or slurrys in a continuous stream. In the stower a continuous belt drives a centrifugal accelerator while simultaneously acting as an outer wall of a centrifugal chamber and as a discharge belt. Because the fluent material always travels at approximately the same radial velocity as the adjacent portion of the accelerator, friction and wear are minimal. Through optimized design of the accelerator the need for accelerating vanes is eliminated.

Description

United States Patent [191 Dorman 51 Jan. 16, 1973' 1541 CENTRIFUGAL STOWER [75] Inventor: Knownly Wash.

[73] Assignee: The United States of America as represented by the Secretary of the Interior 22 Filed: May 6,1971

21 Appl.No.: 140,904

R. Dorman, Spokane,

FOREIGN PATENTS OR APPLICATIONS 405,41 1 4/1968 Australia ..222/415 Primary Examiner-Even C. Blunk Assistant Examiner l-l. S. Lane Attorney-Ernest S. Cohen and Albert A. Kashinski [5 7] ABSTRACT A centrifugal stower for propelling fluent solids or slurrys in a continuous stream. In the stower a continuous belt drives a centrifugal accelerator while simultaneously acting as an outer ,wall of a centrifugal chamber and as a discharge belt. Because the fluent material always travels at approximately the same radial velocity as the adjacent portion of the accelerator, friction and wear are minimal. Through optimized design of the accelerator the need for accelerating vanes is eliminated. Y

9 Claims, 7 Drawing Figures PATENTEDJAN 16 1975 SHEET 2 BF 3 mvmron KNOWNLY R. DORMAN (QMJ, f (2, BY arromvsrs When mining operations are completed, backfilling of mined-out underground openings protects the surface environment by reducing any tendency of overburden to collapse. Backfilling is usually accomplished by stowing solid fill into the mine. For this purpose a mechanical stower is used.

Several types of prior art stowers are available. Each has significant unacceptable features. Centrifugal blowers which draw material through rotating fan blades are restricted to use with small particles. Pneumatic stowers are cumbersome, expensive, inefficient, and immobile. Belt-type stowers are cumbersome, inefficient, and are subject to excessive belt wear. To overcome these defects of the prior art, my invention was made.

SUMMARY OF THE INVENTION My invention is a centrifugal stower for propelling fluent solid or semi-solid material in a continuous stream. In addition to use in backfilling mines, other exemplary uses include ejecting material onto stock piles, land fills, or tailing dumps, and applying slurries such as gunite or shotcrete.

In operation of the stower, fluent solids or slurrys are introduced into the chamber of a spinning centrifugal accelerator. The material enters the chamber in a continuous stream near the axis of rotation and migrates outward under the influence of centrifugal force. The chamber is so shaped that the material, as it progresses from the axis to the periphery of the accelerator, remains tightly packed. As it progresses outward, the

' packed material gains linear velocity and always travels at the approximate velocity of the adjacent portion of the accelerator.

When the accelerated material reaches the periphery of the chamber it is separated from the rotating mass by a stationary splitter. The material on the outer side of the splitter discharges along the straight portion of a belt, which also drives the centrifugal accelerator and functions, except in the splitter area, as the outer wall of the accelerator chamber. The material in contact with the inner surface of the splitter ultimately travels to the outer belt wall of the chamber and discharges in the next revolution of the accelerator.

An essential feature of my invention is the multiple functions performed by the accelerator drive belt. A single belt drives the accelerator, serves as the outer wall of the centrifugal chamber, and serves as a material discharge belt. Another important feature is that, from the point of entry to the point of exit, the fluent material always travels at approximately the same speed as that part of the accelerator it contacts. Friction is minimal and wear is essentially limited to the splitter, which is easily and inexpensively replaced. Because the accelerating chamber is progressively restricted from the center to the periphery, material compression alone is sufficient to provide the necessary accelerating friction, and complicated accelerating vanes are unnecessary. Employing these features, the stower has few moving parts, is compact, mobile, and efficient for use in any attitude with a wide variety of fluent materials.

Therefore, one object of my invention is a centrifugal stower with a multiple function drive mechanism.

Another object of my invention is a centrifugal stower with minimum frictional resistance.

Another object of my invention is a centrifuga stower of simple construction. These and other objects of the invention are apparent in the following specification and drawing.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENT A centrifugal stower 10 is shown in FIG. 1. Generally, the stower consists of a stationary conical hopper 12 for feeding fluent material into a rotating centrifugal accelerator 14. The term fluent material applies to any solid or semi-solid mass with sufficient interparticle separation to permit discrete flow and sufficient interparticle resistance to permit acceleration. Within the centrifugal accelerator the material is accelerated to a hightangential velocity before ejection as a continuous stream 16 through a discharge nozzle 18.

Power for rotating centrifugal accelerator 14 is transferred from a motor 20 to a drive shaft 22 through a belt and pulley combination 24. A drive pulley 26, turned by the drive shaft 22, pulls a flat, continuous belt 28 which, in combination with four idler pulleys 30-36, rotates the centrifugal accelerator, as best seen in FIG. 3.

The centrifugal accelerator 14 is shown in cross-sectional detail in FIG. 2. From the hopper 12, a continuous stream of fluent material flows in a downward direction, as shown by an arrow 38, into a feed tube 40 integrally fixed to the hopper mouth. At the discharge end of the tube the material enters a centrifugal chamber 42, spreading radially outward under the influence of centrifugal force, as shown by arrows 44. As

the centrifugal accelerator 14 rotates, the material migrates laterally toward the periphery of the centrifugal chamber where it ultimately discharges through nozzle 18.

As seen in FIG. 2, centrifugal accelerator 14 consists of two independent

concentric rotors

46 and 48, spaced a short distance from one another with opposed concave faces that together form the centrifugal chamber 42. The lower rotor 46 rotates freely upon a spindle 50 secured within two

flange bearings

52 and 54 that are bolted back to back on a lower supporting plate 56. The upper rotor 48 rotates freely while supported from above by an integral support tube 58, secured within two flange bearings 60-62 that are bolted back to back on an upper supporting plate 64. To optimize loading efficiency when fluent material flows from stationary feed tube 40 into the rotating accelerator, the inner walls of support tube 58 and upper rotor 48 blend smoothly to produce an unobstructed opening into chamber 42. Below this opening a concentric conical projection 66 blends gradually into the concave face or rotor 46 to direct fluent material outward toward the periphery of the accelerator 14. The two rotors of the'accelerator are so shaped that the thickness of the centrifugal chamber 42 decreases toward the periphery to maintain the material in a constant state of compression as it proceeds outward. Pipe spacers 68, bolted between upper and

lower plates

64 and 56, as seen in FIG. 1, insure constant spacing between the upper and lower rotors to counteract any tendency toward separation under normal operating pressures.

As the fluent material migrates outward from feed tube 40, friction forces move it at the same tangential speed as the adjacent portions of the rotors. Since the tangential velocity of the rotors increases as the distance from the axis of rotation increases, the velocity of the fluent material also increases. Because compressional forces continually compact the material as it flows outward, accelerating vanes or similar devices are unnecessary. Because, from the point of entry to the point of exit, the material always travels at approximately the same tangential speed as the adjacent rotors, abrasion and wear are minimal. As shown by arrows in FIG. 3, the fluent material continues outward in a spiral path until it reaches discharge nozzle 18.

Arriving at the periphery of

rotors

46 and 48, the fluent material is ultimately restrained by belt 28 from further outward migration. As seen in FIG. 2, belt 28 seats within a circumferential track 70 formed by radial flanges 72-74 on the upper and lower rotors. The belt envelops a substantial portion of the periphery of the rotors, forming an outer barrier to migration while simultaneously driving the rotors in unison. From drive pulley 26 the belt travels around four rectangularly positioned idler pulleys 30-36, and then around the accelerator rotors before returning to the drive pulley. As seen in FIGS. 1 and 3, a portion of the rotors adjacent to discharge nozzle 18 is not enveloped by the belt. In this portion radial migration of material is prevented by a discharge splitter 76, shown in detail in FIGS. 4-7.

In addition to restraining migration of fluent material, discharge splitter 76 performs the additional function of separating a fraction of the material from the rotating mass for discharge through nozzle 18. Separation occurs at the chisel point 78 of a splitting knife 80. As seen in FIGs. 6 and 7, the chisel point 78 seats against the inner wall 82 of a splitter track 84, located radially inward from belt track 70. As the accelerator rotors turn, a portion of the fluent material adjacent to belt 28 is split from the rotating mass. The remainder is restrained by thecurved inner edge 86 of the splitter knife until the rotating belt 28 is again encountered at the tail end of the splitter. From the chisel point to tail, the splitter tapers on an arc toward the periphery of the rotors, permitting gradual migration of the fluent material for discharge during the next revolution. Because at this point the belt and rotating mass have the same tangential speed, abrasion occurs only at the inner edge 86 of the splitter knife, and wear is minimal.

By the time the fluent material passes through discharge chamber 88, its trajectory is established and belt 28 is no longer needed. At this point the belt is withdrawn from the tangential path. To accomplish this result without loss of fluent material, drive pulley 26 is nested within a curved opening 104 that bisects the wall of discharge nozzle 18 closest to the discharge chamber. As seen in FIG. 3, the belt conforms closely to the wall of the opening as it contacts the pulley, permitting a change of direction without disrupting flow. From drive pulley 26 the belt again travels around the idler pulleys in a continuous cycle.

As my invention is suitable for operation with a wide variety of fluent'materials, operating speeds will vary according to the particular material used. For small particulate solids, exiting tangential velocities on the order of ft/sec have proved successful. While the invention is described with the accelerating chamber oriented horizontally, operation in other attitudes without adverse effects is possible if sufficient material flow into the accelerator is maintained. While the invention is shown with a single belt for simultaneously driving the rotors and acting as the outer wall of the accelerator, independent belts could easily be substituted. Because my invention is easily adaptable to diverse environments and materials, additional modifications within the scope of this disclosure are expected. For this reason the invention should not be limited by the particular details of the disclosure, but only by the scope of the following claims.

I claim: 1. A centrifugal stower comprising: first and second concentric rotors of similar diameter mounted in spaced facing relationship for rotation about a common axis,

a flat, continuous belt simultaneously enveloping a substantial portion of the periphery of each rotor to form a substantially closed chamber between the rotors,

stationary means mounted near the periphery of the rotors and cooperating with the continuous belt for closing the chamber between the rotors except for a small discharge opening,

means for rotating the rotors and belt in unison,

means for continuously introducing a mass of fluent material into the chamber between the rotors in an area near the common axis to substantially fill the chamber,

means mounted at the discharge opening for separating a small fraction of the total fluent material from the mass between the rotors while the stationary means and belt retain the remaining mass for discharge during subsequent rotation of the rotors, and

means for directing the separated fraction in a con- .tinuous stream.

2. A centrifugal stower as claimed in claim 1, in

which:

the facing surfaces of the first and second concentric rotors. are substantially concave and form a chamber of decreasing thickness from the axis of rotation toward the periphery,

the flat continuous belt, as it envelops the rotors, is guided by an array of pulleys spaced outward from the rotors,

the stationary means for closing the chamber includes a flat, arcuate plate abutting the rotors between two spaced points where the belt comes which: a into and departs from contact with the rotors, and the means for rotating and the means for directing inthe means for separating includes a chisel blade nestclude the flat continuous belt that envelops the roing in a portion of the space between and extendtOrS- v ing in a direction against the rotation of the con- 5 7- A Centrifugal tow as Claimed in claim 2 in centric rotors. which: 3. A centrifugal stower as claimed in laim 2 i the means for rotating includes the flat continuous which: belt that envelops the rotors, for transfering power the means for directing includes a discharge to the rotors from one pulley of the array of pulchamber, one side of which is formed by a section 10 y and y of the continuous belt that extends i ll the means for directing includes a portion of the belt from the rotors at the spaced point adjacent to the Substantially tangential to the [0mm chisel blade. 8. A centrifugal stower as claimed in claim 3 in 4. A centrifugal stower as claimed in claim 2 in which! hi h; the means for rotating includes the flat continuous the stationary means and the means for separating that envelops the rotors, for transferring are f d as a unit power to the rotors from one pulley of the array of 5. A centrifugal stower as claimed in claim 3 in Pulleys which; 9. A centrifugal stower as claimed in claim 5 in the stationary means and the means for separating whch:

are f d as a unit, and the means for rotating includes the flat continuous the discharge chamber includes a pair of opposed belt that envelops the rotors, for transferring channels seated at one end against the periphery of power to the rotors 'P one pulley of the array of the rotors. p y 6. A centrifugal stower as claimed in claim 1 in

Claims

1. A centrifugal stower comprising: first and second concentric rotors of similar diameter mounted in spaced facing relationship for rotation about a common axis, a flat, continuous belt simultaneously enveloping a substantial portion of the periphery of each rotor to form a substantially closed chamber between the rotors, stationary means mounted near the periphery of the rotors and cooperating with the continuous belt for closing the chamber between the rotors except for a small discharge opening, means for rotating the rotors and belt in unison, means for continuously introducing a mass of fluent material into the chamber between the rotors in an area near the common axis to substantially fill the chamber, means mounted at the discharge opening for separating a small fraction of the total fluent material from the mass between the rotors while the stationary means and belt retain the remaining mass for discharge during subsequent rotation of the rotors, and means for directing the separated fraction in a continuous stream.

2. A centrifugal stower as claimed in claim 1, in which: the facing surfaces of the first and second concentric rotors are substantially concave and form a chamber of decreasing thickness from the axis of rotation toward the periphery, the flat continuous belt, as it envelops the rotors, is guided by an array of pulleys spaced outward from the rotors, the stationary means for closing the chamber includes a flat, arcuate plate abutting the rotors between two spaced points where the belt comes into and departs from contact with the rotors, and the means for separating includes a chisel blade nesting in a portion of the space between and extending in a direction against the rotation of the concentric rotors.

3. A centrifugal stower as claimed in claim 2 in which: the means for directing includes a discharge chamber, one side of which is formed by a section of the continuous belt that extends tangentially from the rotors at the spaced point adjacent to the chisel blade.

4. A centrifugal stower as claimed in claim 2 in which: the stationary means and the means for separating are formed as a unit.

5. A centrifugal stower as claimed in claim 3 in which: the stationary means and the means for separating are formed as a unit, and the discharge chamber includes a pair of opposed channels seated at one end against the periphery of the rotors.

6. A centrifugal stower as claimed in claim 1 in which: the means for rotating and the means for directing include the flat continuous belt that envelops the rotors.

7. A centrifugal stower as claimed in claim 2 in which: the means for rotating includes the flat continuous belt that envelops the rotors, for transfering power to the rotors from one pulley of the array of pulleys, and the means for directing includes a portion of the belt substantially tangential to the rotors.

8. A centrifugal stower as claimed in claim 3 in which: the means for rotating includes the flat continuous belt that envelops the rotors, for transferring power to the rotors from one pulley of the array of pulleys.

9. A centrifugal stower as claimed in claim 5 in which: the means for rotating includes the flat continuous belt that envelops the rotors, for transferring power to the rotors from one pulley of the array of pulleys.