US3034421A

US3034421A - Apparatus for densifying bulky powders

Info

Publication number: US3034421A
Application number: US855123A
Authority: US
Inventors: Henry E Pence
Original assignee: St Joseph Lead Co
Current assignee: St Joseph Lead Co
Priority date: 1959-11-24
Filing date: 1959-11-24
Publication date: 1962-05-15
Anticipated expiration: 1979-05-15

Description

May 15, 1962 H. E. PENCE APPARATUS FOR DENSIFYING BULKY POWDERS 3 Sheets-Sheet 1 Filed NOV. 24, 1959 A M m ||||||1||||||||||||mw|U|l|||||llI IN VENTOR HENRY E PEA/CE ATTORNEYS.

May 15, 1962 H. PENCE APPARATUS FOR DENSIFYING BULKY POWDERS 3 Sheets-Sheet 2 Filed Nov. 24, 1959 INVENTOR HENRY E FENCE ATTORNEYS.

May 15, 1962 H. E. PENCE APPARATUS FOR DENSIFYING BULKY POWDERS 3 Sheets-Sheet 5 Filed Nov. 24, 1959 V H V i V R my .1 E. W m H ATTORNEY$ United States Patent York Filed Nov. 24, 1959, Ser. No. 855,123 8 Claims. (Cl. 1tl943) The present invention relates to the densifying of bulky, finely divided materials and, more particularly, to apparatus for converting a bulky, finely divided material of varying, 10w apparent density into a product of uniform, controlled higher density.

A major difiiculty encountered in the packaging of bulky, finely divided materials into containers, such as bags, is the resistance of such material to the packaging procedures due to their flufiy aerated nature. It will be understood that the term aerated as used in the description refers to the presence of any absorbed gases upon the minute particles of the material and also to the presence of those gases that may be termed merely interstitial. Packing rates of these bulky materials in terms of the weight unit of the product per unit of time with the present conventional methods tend to be low, making packing costs consequently high. Furthermore, apparent densities of these materials tend to vary, causing process upset and lack of finished product uniformity.

One object of this invention is to produce apparatus capable of converting a bulky, finely divided material of varying, low apparent density into a product of uniform, controlled higher density.

The nature of the present invention may be'stated in general terms as relating to an apparatus for densifying a bulky, finely divided material comprising a cylindrical passage having an inlet and an outlet, a first conveyor for transferring the material along the passage toward the outlet, a second conveyor between the output end of the first conveyor and the outlet of the passage for conveying the material to the outlet of the passage, separate motor means for effecting movement of the first and second conveyors, variable speed control means for one of the motor means, means for sensing the power consumption by the other of the motor means, and means responsive to the sensing means connected to the variable speed control means whereby the speed of one of the motor means and its associated conveyor is proportional to the power consumed by the other of the motor means and its associated conveyor.

Now referring to the drawings in which like reference numerals denote similar parts throughout the several views:

FIG. 1 is a fragmentary sectional view of one form of the apparatus of the invention with a diagrammatic illustration of the energizing system;

FIG. 2 is a sectional view of the cutter conveyor illustrated in FIG. 1 taken along line 22;

FIG. 3 is a fragmentary sectional view of the cutter conveyor taken along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary sectional view of a modification of the conveyor showing means for expelling gases from the material being treated;

FIG. 5 is a sectional view of the conveyor illustrated in FIG. 4 taken along line 55;

FIG. 6 is a fragmentary sectional view of another modification of the apparatus wherein the gases from the material being treated are removed at the inlet end thereof;

FIG. 7 is a fragmentary sectional View of still another modification of the apparatus wherein the gases from the material being treated are removed in the region of the outlet end thereof; and

FIG. 8 is an enlarged fragmentary sectional view of the modification illustrated in FIG. 7 taken along line 88 thereof.

Referring to FIG. 1, there is shown a generally elongate cylindrical housing ltl having an inlet opening 12 at one end of the housing and an outlet 14 at the other end thereof. A conveyor screw 16 carried by a hollow shaft 15 is rotatably mounted within the housing 10. The inlet end of the conveyor screw 16 is connected to one end of a shaft 18 which extends through the end wall of the housing It} and is journaled within a bearing assembly 20 secured to the outer end wall of the housing 10. The opposite end of the shaft 18 is provided with a sprocket wheel 22 which is keyed or otherwise suitably secured thereto.

The outlet end of the conveyor screw 16 is connected to one end of a shaft 24, the other end of which is journaled within a bearing assembly 26 secured to the inner wall of the housing 14 At the outlet end of the housing 19, there is a second conveyor or cutting screw 28 mounted for rotation therein on a shaft 30. The shaft 30 is journaled within spaced

bearing assemblies

32 and 34 located outside the outlet end of the housing 10. The inwardly extending end of the shaft 30 is provided with a pressure plate 36 having a V-shaped notched portion 38 which in turn is adapted to carry a cutter blade 49. The pressure plate 36 and the cutter blade 40 are clearly illustrated in FIGS. 2 and 3 and the function thereof will be described in greater detail hereinafter.

A sprocket wheel 42 is keyed or otherwise suitably secured to the shaft 39' between the

bearing assemblies

32 and 34.

In order to drive the conveyor screw 16, there is provided a constant speed electric drive motor 46 having a sprocket wheel 48 keyed to the armature shaft thereof. A chain Si} is employed to couple. the rotary movement of the sprocket wheel d8 of the electric motor 46 to the sprocket wheel 22 of the conveyor screw 16 and to thereby impart rotational movement to the conveyor. The electric motor 46 is coupled to a source of energizing potential through three power leads 52.

Drive for the cutter or conveyor screw 28 is provided by a variable speed electric drive motor 54 which is coupled to a source of energizing potential through a power lead 56. The motor 54 is provided with a sprocket wheel 55 keyed to the armature shaft thereof, and a chain 57 is employed to couple the rotary movement of the sprocket wheel 55 to the sprocket wheel 42 of the cutter screw 28. The motor assembly 54 may typically be of the type manufactured and sold by The Cleveland Worm and Gear Company and identified as a Cleveland Variator size 6KL6 rated 3 HP. at 870 rpm. This assembly is equipped with volt single phase pilot motor. The motor assembly 54 is a simple drive that provides infinitely variable output speed over a range up to typically 6:1 from a constant speed power source.

To achieve the desired objectives of the invention, that is, to control the speed of the drive motor 54 in relau'on to the power consumed by the constant speed motor 46, there is provided an interconnecting circuit arrangement 58. The circuit arrangement 58 is efiective to receive reduced alternating current from power leads 52, to rectify the current and supply a DC. voltage output. The circuit arrangement comprises a current transformer 6%} which is connected across a suitable full-wave rectifier 62 through leads 64 and 66 which are suitably fused. The rectified output of the rectifier 62 is fed through filter network comprised of

resistors

68, 70 and a condenser 72. The rectified filtered output of the circuit is sensed across a potentiometer 74. A control device 76 for regulating the speed or rpm. of the variable '12 of the housing. 1d.

aosassr 'ing controller and is eifective to energize suitable means in the motor assembly 54 to vary the speed thereof in proportion to an electrical signal received from the control device 76..

In general terms the apparatus thus far described functions in such a manner that the speed with which the cutter conveyor screw 28 is driven is in direct proportion to power consumed by the constant speed'motor as which drives the conveyor screw 1s. More specifically, the conveyor screw 16 is caused to rotate upon the energization of the constant speed motor 4-6, the speed of which is adjusted to the desired level determined by the production demand placed upon the equipment from the standpoint of both the density of the final product and the rate of product output. Therefore, the speed of the conveyor screw 16 is maintained constant irrespective of the load imposed on it by the material fed into the inlet opening As the conveyor screw 16 is rotated, the material is fed toward the outlet end of the housing 16 and enters a dead space area indicated at D and defined by the outlet end of the conveyor screw 16 and the inlet end of the conveyor screw 28. The material being treated tends to pack up against the pressure plate 36 of the cutter screw 28 which provides a resistance to'material flow, thereby effecting the densification of the process material. Manifestly, the densification occurs within the dead space D.

The cutter blade 40 which is aifixed to the pressure plate 36 partially covers the product exit slot 33 formed in the pressure plate 36 and may be set to any desired degree of coverage by a suitable threaded fastener or the like. It will be appreciated that as the cutter screw 28 and its associated pressure plate 36 are revolved, the cutter blade 40 removes the densified product formed within the dead space D. The extent of the cutter blade protrusion into the dead space area and the size of the opening of the product exit slot behind the cutter blade determine the bite, or amount of densified product removed by the cutter, in one revolution thereof. The setting of the cutter blade 46 over the product exit slot 38 is determined by the initial density of the process material; the rate of material throughout, and the degree of densification desired. The best density control is considered to be achieved with the smallest cutter blade which will accordingly readily enable the r.p.m. of the cutter conveyor 28 to increase and decrease over a narrow midsc'ale range.

' To facilitate the description of the automatic operation of the system and interrelationship between the conveyor screw 16 and the cutter screw 28, it is convenient to refer to a null point in the cutter screw operation. The null point: is the equilibrium condition of the process and is determined by the amount of power consumed by the constant speed drive motor 46 that is necessary to prevent a change in the rpm. of the cutter conveyor when the cutter conveyor rpm. is between arbitrary high and low limits.

Initially, the drive motor 46 is energized to drive the conveyor screw 16; the drive motor 54 is energized to drive the cutter screw 28; and the control device 75 is adjusted to maintain a desired output level to in turn maintain a fixed output speed of the drive motor 54.

Now, we will assume that an increased load is imposed on the conveyor screw 16 which therefore calls for more power consumption by the drive motor 46. The change in power consumed by the motor 46 is sensed by the current transformer 60. The alternating current induced in the transformer 60 is rectified by the rectifier 62., the rectified current is filtered by the filter arrangement of resistors 68, 79, and the condenser 72. The resultant DC. voltage is sensed across the potentiometer '74 and fed to the control device 76 through the

leads

78 and 80. The change in voltage fed to the control device 76 causes change in the output to the variable speed mechanism of the drive motor assembly 54 through lead 82 which effects an increase in the speed of rotation of the cutter screw 28. As the cutter screw 28 increases in speed, more of the densified product is removed from the dead space D and is discharged through the outlet 14 thereby resulting in a decrease in the power necessary to drive the constant speed drive motor 46 at the desired speed. This decrease in the power consumed isaccordingly sensed by the current transformer 66 and in a manner similar to that described hereinabove, reduces the spec of the cutter screw 28 until the predetermined null point" of the system is reached. Upon reaching the null point the motor assembly 54 will drive the cutter screw 28 at a elatively slower speed than the conveyor screw 16 to thereby effect the desired densification of the process material. This condition of operation will continue indefinitely until the power consumed by the motor assembly 46 varies above or below the predetermined null point at which time the motor assembly 56 will be called upon to respectively increase or decrease the speed of the cutter screw 28.

In FIGS. 4-8 there are illustrated various modifications ofv the apparatus illustrated in FIGS. 1-3 wherein means are provided to aid in the removal of adsorbed and interstitial gases from the process material in order to further aid in the densification of the material. It has been found that in the treatment of bulky, finely divided materials such as zinc oxide that there is a presence of adsorbed gases upon the minute particles of the material and also interstitial gases contained within the cavities between the individual particles. Manifestly, to obtain the desired densifica tion of the material, the removal of the adsorbed and interstitial gases therefrom is necessary. While the apparatus illustrated in FIGS. l3 is effective to remove the major portion of these gases, the modifications shown in FIGS. 4-8 may achieve a greater degree of gas exhaustion.

More specifically, the apparatus shown in FIGS. 4 and 5 is similar to the apparatus of FIG. 1 except a hollow shaft 15' is provided with a plurality of radial openings 90. Each of the openings is provided with a hood arrangement 92 being open at the trailing edge when considering the rotation of the associated conveyor 16' to thereby militate against the entrance of the process material into the hollow shaft 15. t

The inlet end of the hollow shaft 15 of the conveyor screw 16 is carried for rotation on the shaft 18' in the same manner as is shown in FIG. 1. The shaft 1-8 differs in that it is provided with a longitudinal bore 94 which is in communication with the hollow shaft 15. The outer end of the shaft 18' is connected to a vacuum fitting as which in turn is connected. to a suitable vacuum pump through a line 98. It will be appreciated in operation that as the material being treated becomes compressed or densified the adsorbed and interstitial gases maybe readily removed through the openings 90, the hollow shaft 15', and the control bore 94 of the shaft 18.

FIG. 6 shows another modification for aiding in the removal of adsorbed and interstitial gases from the material being treated wherein the inlet 12" of the housing 10" is provided with an inverted frusto-conical chamber 1019 having a vacuum line 102 leading to a pump or other suitable means for withdrawing gases from the material being treated. The upper end of the chamber is provided with an inlet hopper 104 for containing the supply of material to be treated. The material leaves the hopper 1&4 and enters and fills the chamber 18% prior to entering the inlet 12 of the housing Gases in the material being treated are in a large degree removed through the vacuum line 102 thereby greatly facilitating the densificationprocess.

Still another modified form of gas removal apparatus of the invention is illustrated in FIGS. 7 and 8. The gas removal apparatus of this form is disposed in the region of the outlet 14" of the housing 10" and comprises a chamber 110 suitably secured to the outer surface of the housing 10" over a housing opening 112. A shield element 114 is secured to the inner surface of the housing 10" and opens toward the outlet end of the housing. A vacuum line 116 is connected to the top of the chamber 110 and provides for communication between the chamber and a source of vacuum.

To militate against the slot 112 and its associated shield 114 from becoming plugged or blocked by the deposition or build-up of the material being processed, there is provided an oscillating arm 118 having a pin 120 pivotally mounted in the chamber 110. Anarm 122 is connected at one end thereof to the extended end of the pin 120 and the other end of the arm is pivotally coupled to one end of a linkage 124. The opposite end of the linkage 124 is eccentrically pivotally mounted on a rotary wheel 126. As the wheel 126 rotates oscillatory movement is imparted to the extended end of the arm 118. The oscillatory movement of the arm 118 causes the re moval of any material which does collect in the slot 112 and the shield 114 and thereby maintains proper communication between the inner portion of the housing 10' and the vacuum line 116.

From the foregoing description, it will be seen that new improved apparatus for converting a bulky, finely divided material of varying low apparent density into a product of uniform, controlled higher density has been produced thereby resulting in a uniform product density and the attained high product density.

Although in the preferred embodiment of the invention there is a pressure plate assembly 36 provided with a cutter member 40, in certain applications it may be desired to use the machine without the pressure plate and associated cutter 40. In such an embodiment, the relative difference in the speed of revolution between the conveyor screw 16 and the cutter screw 28 is effective to achieve the desired density and also the cutter screw 28 only may be effective to discharge the densified product through the outlet 14. In such an arrangement for the best results the dead space between the outlet end of the deaerator or conveyor screw 16 and the inlet end of the cutter and conveyor screw 28 would be somewhat longer than inthe instance where a pressure plate assembly were employed.

As will be apparent to those skilled in the art, satisfactory densification of the process material may be achieved with certain modifications of the apparatus such as a reversal of the manner in which the

conveyors

16 and 28 are coupled to the drive motor means. For example, the variable speed drive motor means 54 could be coupled to the conveyor and deaerator screw 16 and the constant speed drive motor means 46 could be coupled to the cutter and conveyor screw 28. In such an arrangement, the power consumed by the motor means driving the cutter and conveyor screw 28 will be sensed and, in turn, will control the speed of the motor means driving the conveyor and deaerator screw 16.

According to the provisions of the patent statutes, I have explained the principle and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiments. How- 8 ever, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. Apparatus for treating a bulky, finely divided material comprising a cylindrical passage having an inlet and an outlet, a first screw conveyor for transferring the material along said passage toward the outlet, a second screw conveyor between said first conveyor and the outlet of said passage for conveying the material to the outlet of said passage, a pressure plate assembly having at least one slot formed therein disposed on the end of said second conveyor adjacent said first conveyor, constant speed electric motor means for effecting movement of said first conveyor, variable speed electric motor means for effecting movement of said second conveyor, and means for continuously sampling the electrical power consumption of said constant speed motor means, said means being effective to vary the speed of said variable electric motor to thereby efiect densification of the material between the inlet and the outlet of said cylindrical passage.

2. Apparatus as defined in claim 1 wherein said pressure plate is provided with a cutter element attached thereto adjacent the slot and effectively controls the material passing through the slot.

3. Apparatus as defined in claim 1 wherein said first conveyor screw is carried by an apertured hollow shaft co-extensive with said screw, and a vacuum producing means is connected to one end of said hollow shaft.

4. Apparatus as defined in claim 3 wherein a plurality of hood-like members are carried by said shaft and positioned over the apertures therein.

5. Apparatus as defined in claim 1 wherein the inlet of said housing is provided with an outwardly extending chamber having means for communication with a source of vacuum.

6. Apparatus as defined in claim 1 wherein means are provided between the outlet end of said first conveyor and the inlet end of said second conveyor to create a vacuum within said housing.

7. Apparatus as defined in claim 6 wherein said means includes a chamber mounted on the outer surface of said housing, said chamber having communication with a source of vacuum and with the interior of said housmg.

8. Apparatus as defined in claim 7 wherein said chamber is provided with agitating means for maintaining the communication of said chamber with the interior of the housing.

References Cited in the file of this patent UNITED STATES PATENTS 859,506 Morton July 9, 1907 1,334,492 Hindshaw Mar. 23, 1920 1,792,216 Fahnestock Feb. 10, 1931 1,990,632 Bowling Feb. 12, 1935 1,999,241 Kiergard Apr. 30, 1935 2,078,565 Durst et a1. Apr. 27, 1937 2,178,714 Anderson Nov. 7, 1939 2,280.880 Anderson Apr. 28, 1942 2,340,009 Meakin Jan. 25, 1944 2,547,336 McDaniel et a1 Apr. 3, 1951 2,556,391 Hawk June 12, 1951 2,714,490 Prechter Aug. 2, 1955 FOREIGN PATENTS 568,094 Great Britain Mar. 19, 1945 739,509 Great Britain Nov. 2, 1955