US 3425553 A
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Description (OCR text may contain errors)
Feb. 4, 1969 M. J. SLCVIC GRADING APPARATUS Filed Oct. 23, 1965 Sheet INVENTOR MATTHEW JOHN SLOVIC ATTORNEY Feb. 4, 1969 Filed Oct. .23, 1965 M- J. SLOVIC GRADING APPARATUS I Sheet 3 of2 ATTORNEY United States Patent 2 Claims ABSTRACT OF THE DISCLOSURE Apparatus is disclosed which is capable of very thoroughly screening and separating particulate materials of varying sizes. Several vertically stacked screening units containing screens of different mesh size are suspended by flexible spring-like reeds which are rigidly and nonpivotally connected at each of their ends, i.e., to the apparatus framework and to the screener units to provide a unique, whipping action when moved by a motor driven eccentric. The relationship of the spring-like reeds and the screener units is such that the particulate material is tumbled over and along the screener unit to assure that substantially all of the material is afforded an opportunity to pass through the mesh.
This invention relates to apparatus for grading particulate material into various size gradients, and is especially concerned with a screening apparatus capable of accurately and quickly processing large quantities of particulate materials.
In particular, the present invention is concerned generally with size graders comprised of a vertically disposed series of screens of varying mesh dimensions, each adapted to retain particulate material of a certain size while permitting smaller particles to pass therethrough. The grader apparatus is preferably of the type vibrated by a vibrating mechanism comprised generally of an electric motor, and an eccentric belt driven thereby. The construction of such mechanism is well known in this art and therefore not described hereafter in detail except to the extent the same relates to certain novel aspects of the present invention.
The primary object of this invention is to provide apparatus adapted to thoroughly screen particulate material to a highly accurate degree, i.e. for any given batch of material to be graded into various sizes by the present invention, there will be a resultant high degree of size integrity between the sizes desired with very little, if any, size overlap or spillage from one to the next.
Previously known graders have utilized eccentricvibrator devices to shake a plurality of screens, but in most cases the screens are stacked in spaced relationship vertically, and the material and screens are vibrated until all or part of the material has sifted down through all the screens, with fractions of the material being retained on the various screens. However, these devices, with an essentially vertical movement of the material down through the stack of screens, tend to clog the screens by collecting smaller particles on top of larger ones, the smaller ones being of a size that would otherwise pass the screen. Other grading devices have employed vibrating mechanisms to not only cause the material to pass vertically through the screens but to be jostled across portion of the apparatus as illustrated in U.S. Patent 2,748,942 to Aker, for example. However, these and other graders have not been capable of relatively precise screening in normal operation, without extra time and expense in operating and checking. Such sensitive grading is very important in the tobacco industry, for example, and is particularly critical where the large volumes of material must be handled, as is the case, of course, in many industries, but especially in the tobacco industry where comminuted tobacco of varying size is employed for different products and the individual tobacco particle sizes and weights and the nature of this organic material, make it difficult to size accurately in large quantities. Moreover, in'the tobacco industry, the quality of the product, whether it be cigarettes, filter or nonfilter, pipe tobacco, etc., may be judged by the consumer, depending upon the consistency of the product which depends to a large extent upon particle size uniformity. The latter is an important factor in compaction, draw and burning rate for example. Still another important function in tobacco involves the removal of foreign material such as sand, stems, etc., from the tobacco.
Accordingly, it is a primary object of the preferred embodiment of the present invention to provide a more sophisticated grading apparatus wherein a plurality of stacked screening units are provided, each having a separate screen and collection pan for the smaller fractions (screenings) passing through the screen, and wherein the material being graded is thoroughly agitated and passed longitudinally across theentire length of each screen to atford an opportunity for each particle to pass through the screen if possible. Thus, one of the basic principles of this invention is to improve screening dependability by thoroughly exposing the material being graded to each screen, and this is accomplished primarily by passing the material over the entire length of the screen by a jostlingtumbling vibratory movement, as will be described. The longitudinal movement of the material across the screen as the material is being agitated will eventually provide an opportunity for each particle to pass through the screen if it is small enough. The screening passing through and collected under each screen is conveyed to a point where it may drop onto the next lower screen by the same agitation forces, while the material retained above the screen is conveyed out of the grader by the same forces.
Since the oversize fraction is conveyed out of the apparatus entirely, and the smaller screenings are deposited on another screen, the first screen is completely free from any material and will not become clogged. By continuously removing the material in this manner, new material may be continuously added, whereby a very large volume may be handled with a grader of more or less conventional size screens.
Of course, the present invention is not intended to be limited in any way to any particular type of material or any industry. As will become apparent from the following description, the apparatus may be applied to any particulate material with appropriate adjustment for screen sizes and vibration speed. However, as the tobacco industry has peculiar problems with the lightweight, organic material involved, finely comminuted, the invention has particular applicability thereto.
In addition to the above, another object of the present invention is to provide an apparatus utilizing the principles above-mentioned of continuously sorting particulate material into different sized fractions, including the steps of passing the material through a first sizing zone by vibrating the zone so as to give the material a tumbling motion over the screen, and while collecting oversize material, passing the remaining material longitudinally through said zone and into a subsequent zone, and repeatedly passing the material as aforesaid through subsequent zones until sorted as desired.
Another object of this invention is to provide an apparatus as described in the preceding paragraph in which finely comminuted material, particularly tobacco, is supplied continuously to a process while at the same time, it
is passed through the sorting zones by agitating forces applied thereto.
Another object of the present invention is to provide apparatus comprising'a plurality of vertically spaced screen units suspended from a framework by flexible, spring-like reeds, adapting the units to vibrate in such a manner as to cause material being graded or sorted to pass substantially completely across each screen, thereby removing substantially all particles of a pre-determined size range from the bulk thereof and passing said bulk onto the next screen while removing said grade size fraction.
Still another object of the present invention is to provide grading apparatus for a plurality of vertically spaced screens, each having a collection pan underneath for collecting the bulk undersize fraction of the material being graded which the screen will permit to pass, and further providing trough or other means for conveying each retained or oversize fraction from the apparatus as collected and the bulk from each screening unit to the next lower screening unit.
Other objects and advantages of the present invention will become apparent from the appended claims and following description of the best mode of carrying out the present invention and examples and modifications thereof, taken in connection with the accompanying drawings wherein:
FIGURE 1 is a side elevation view of a grader apparatus constructed in accordance with the principles of the present invention;
FIGURE 2 is an end view in elevation of the apparatus shown in FIGURE 1, looking from right to left;
FIGURE 3 is a perspective view of the preferred means for supporting screening units from the framework of the apparatus of FIGURE 1, and
FIGURE 4 is a perspective view of a screening unit of the present invention.
Referring now to the drawings, in particular, the screener shown in FIGURE 1 is comprised of a supporting framework having four vertical posts and rectangular top and bottom frames and respectively. A support column 24 is fixed at one end of the apparatus on approximately the center line between frames 15 and 20, the column being of sufficiently heavy construction to enable it to support a driving mechanism for the screener.
A motor 28 is fixed to rear flange 30 of column 24 and is adapted to belt drive an eccentric vibrator 32 mounted to rotate on shaft 33 which is journaled for rotation in column 24. As the details of construction of the vibratory mechanism are preferably of a well-known type in this art, they have not been illustrated in the drawings. A pair of rocker arms 34 and 36 are pivotally mounted on column 24 on shafts 38 and 40 respectively. The rocker arms are essentially Y-shaped and are connected by rods 42, or the like to eccentric vibrator 32 whereby rotation of the vibrator causes a short rotational stroke of the rocker arms as shown by the arrows on the drawing. The rocker arms are in turn connected by flexible, plastic or metal reeds 44, 46, 48 and 50 to screener units 52, 54, 56 and 58, respectively. As should be apparent, rotative oscillatory movement of rocker arms 34 and 36 will alternately move screen units 54 and 58 in one direction while moving screen units 52 and 56 in the op- 'posite direction, and vice versa.
The screener units are suspended from vertical posts 10 by means of flexible reeds. Thus, taking screener unit 52, for example, four resilient, plastic or metal reeds 60 are secured by bolts to support blocks 62 which are in turn welded or otherwise fixed to posts 10. The reeds extend downwardly at an acute angle from posts 10 and are fixed to second support blocks 64 by bolting or other suitably rigid securing means. The second support blocks 64 are in turn welded or otherwise fixed to angle brackets 66 which are secured to the sides of screener unit 52. The entire supporting assembly, including reeds 60, blocks 62 and 64 and brackets 66 are completely outside the screener unit itself and, therefore, do
.not interfere with the screening process hereafter described. Reeds 60 are preferably resilient plastic such as polyethylene, approximately /2" thick, but may be of any suitably flexible material, preferably sufliciently resilient to spring the screener unit back toward its original position after displacement by the vibrating mechanism. Each screener unit is supported from posts 10 on both sides of the apparatus as shown in FIGURE 2 and accordingly, all of such supporting means are not described with reference numerals.
An important feature of this invention resides in the balance of the apparatus and the supporting arrangement for the suspended screener units. Thus, reeds 60 act as springs and flip the units back toward the normal position shown in FIGURE 1 after displacement in either direction by the vibrating mechanism. Coupled with the vibrating forces, the quick spring return of the screener units, creates a highly effective motion of the material causing it to move horizontally across the screener units (to the right in units 52 and 56, and to the left in units 54 and 58, as shown in FIGURE 1). The motion is of such a nature that the material is tumbled over the screen, thereby assuring that substantially all particles capable of passing the screen will be given an opportunity to do so. Reeds 60 are preferably disposed at an angle which is perpendicular to one of the reeds 44, 46, 48 and 50, as the case may be. Such an arrangement has been found to provide the smoothest operation with satisfactory movement of the material through the units. Since reeds 60 act as springs, and the screener units do not otherwise engage the apparatus framework or other parts, the units swing in a silent rhythmic pattern, counter-balancing each other as each unit has at least one next adjacent unit moving in a substantially opposite pattern. Thus, the unit not only operates quietly, but with very few stresses on the supporting elements and the screener units themselves. Support blocks 62 and 64 prevent reeds 60 from contacting any other elements of the apparatus to eliminate noise and ensure that the rhythmic fluctuations of the screener units are not disturbed.
Each screener units is comprised of a rectangular pan having four vertical side walls 68 and a floor 70. The center section of floor 70 is comprised of a screen 72 of any suitable desired mesh size for the particular level at which the screener unit will be utilized. Immediately below the screener 72 is positioned a rectangular collecting pan 74 having an open chute 76 at the end thereof toward which the material being screened will flow. At the same end, a trough 78 is located beneath an opening 80 in pan floor 70. Thus, as material to be screened is introduced as by dropping onto floor 70 on the left hand side of the screener unit as shown in FIGURE 4, the material will pass to the right over screen 72. The fraction retained on the screen continues to pass to the right, falling through opening 80 and is removed from the apparatus from trough 78 while the bulk fraction passing screener 72 is collected in a collection pan 74 and continues to move in pan 74 to the right until it falls through chute 76 onto the next lower screener unit which is reversely situated so as to catch the bulk fraction on its floor 70.
As indicated in FIGURE 1, a feeding device is provided to introduce material, and may be, for example, a funnel or any other suitable device adapted to channel the material onto the top screener unit. As the material 'hits floor 70, it is caused to move toward the right by the vibrating mechanism. Taking unit 52 for purposes of illustration, reed 46 pushes the unit at approximately a 30 angle up and to the right against the resiliency of support reeds 60 as the rocker arm 36 reverses its rotational movement, reed 46 pulls unit 52 down and to the left, supplemented by the internal resiliency of reed 60 to return to its normally straight configuration. Thus, the movement of the material in unit 52 is influenced by longitudinal as well as vertical force components, resulting in longitudinal movement of the material to the right while at the same time, hopping and tumbling along floor 70 and screen 72. As the material progresses across the screen, it is continuously provided an opportunity to pass through the mesh into collecting pan 74. In the meantime, additional material is being introduced from hopper 90, and the process is therefore continuous. Material retained on screen 72 continues to pass to the right and is channeled through the open end of the unit 52, and down slideway 92, which may, of course, be a trough such as 78 shown in FIGURE 4. The bulk material collected in pan 74 after passing through screen 52 is transmitted across unit 52 and allowed to pass through chute 76 into unit 54 on floor 70 thereof. The bulk material then passes left as shown in FIGURE 1, across the screen of unit 54, the part being retained on this screen being channeled out of the apparatus through trough 78 and the bulk fraction passing the screen therein being dropped from chute 76 onto unit 56 and so on until the material has completely passed through the apparatus.
By causing the material to travel completely across each screen while at the same time being tumbled, the material is thoroughly screened and each fraction is then immediately removed from the apparatus to prevent any possible mixing and/ or interference with later screening or smaller particles, while at the same time, however, permitting continuous screening. It has been found that by appropriate speeds, the agitator can move large volumes of material across the various units with relatively little, if any, intermingling of the fractions desired.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of tthe claims are therefore intended to be embraced therein.
What is claimed and desired to be secured by United States Letters Patent is:
1. Apparatus for grading particular material into a plurality of size ranges, said apparatus comprising a supporting framework, 2. series of vertically spaced pairs of screener units, a set of inclined flexible spring-like reeds for each of said screener units, each of said reeds being rigidly, non-pivotally connected at both ends to said framework and a screener unit, at least one such reed being attached on each of two opposed sides of each screener unit and holding said screener units in a normally horizontal position and permitting the units to move in relation to the framework by flexure of said reeds, and vibrating means connected to each of said units to impart oscillatory movement thereto and comprising driven eccentric means and diagonally opposed members interconnecting each of said pairs and said eccentric means, said members engaging said units at a substantial angle to horizontal to impart forces to the units having substantial horizontal and vertical components, said flexible reeds being rectangular in cross-section and fixed to said framework and to said units with the longtudinal dimension thereof facing the direction of movement of said units, and said interconnecting members engaging each screener unit so as to apply forces thereto substantially at right angles to said reeds.
2. Apparatus as defined in claim 1, wherein each of said flexible reeds are rigidly fixed at one end thereof to said framework and at the other end thereof to one of said units, there being four flexible reeds per screener units and a rocker element for each pair of screener units connected to and oscillated by said eccentric means, an interconnecting member extending from said rocker element to each of said screener units and applying forces thereto in alternate directions.
References Cited UNITED STATES PATENTS 252,298 1/1882 Thompson 209390 556,078 3/1896 Anthony 209344 578,067 3/1897 McGarvin 2093l7 610,458 9/1898 Peterson 2093l6 672,420 4/1901 Le Grand 209-344 889,811 6/ 1908 Ruddick 209344 1,344,751 6/1920 Berry 209-344 X 1,531,803 3/1925 McNeal 209-316 X 2,226,503 12/1940 Ramsey 209-316 X HARRY B. THORNTON, Primary Examiner. R. HALPER, Assistant Examiner.
US. Cl. X.R. 209-344, 415