US2149368A - Sifter - Google Patents

Description

March 7, 1939. E. slMPsoN SIFTER 4 Sheets-Sheet 2 'INVENTOR Lana:- I Sw/Psalm BY Filed Nov. .12, 1935 L. E. SIMPSON SIFTER Filed Nov. 12, 1935 l March '7, 1939.

4 Sheets-Sheet 3 INVENTOR. L 041m E. S/MRso/v.

ATTORNEYS.

March 7, y1939. l

L. E. SIMPSON 2,149,368

SIFTER Y Filed Nov. l2, 1935 4 Sheets-Sheet 4 K INVENTOR. Lan/5 'lM/-fsa/v.

ATTORNEYS- Patented Mar. 7, 1939 UNITED STATES PATENT OFFICE 1 Claim.

My invention is directed to controlling the path in which material flows over the sifting or separating surface of that type of sifting or separating machine in which the accustomed modes of 5 operation fall to properly accomplish this. The type of machine with which this invention is concerned is one in which the screen, or cloth,

o r other foraminated sifting or separating surface is substantially in a single plane, and the' agitation which is imparted to it isfin the general direction yci the said plane, but at a slight angle thereto. It is not concerned with sifters in which the sifting surface is agitated or moved in a plane at an angle of more than, say 30 to that at which the vsifting surface is disposed, or sifters in which baflies above the surface serve to control and direct the flow of material thereon.

In the machines With'which I am concerned, the granular or otherwise separable material is introduced onto the sifting surface near one extremity which I will call the receiving extremity, and during operation part of the material passes over the separating surface and off at the opposite, or, discharging extremity. In such 25 machines the agitation is accomplished usually by an eccentric, or by an out of balance weight which causes given points on the sifting surface to move in circular and/or elliptical paths.

These paths may be imparted With identical mo- 30 tions to all points on the sifting surface, or may vary so that, on one surface, there may be cir-` cular motion at one point, Velliptical at another, andfreciprocal or arcuate at still another, and theterm curvilinear path is employed by me to 35` describe this type of motion. This term also implies a continuous movement; for example a circular path as distinguished from a short arcuate movement in one direction followed by a reverse movement in the opposite direction in said arc. 40 g lA difficulty with the forms of devices with which I am concerned, lies in the fact that the flow of material'over the sifting surfaces, therein tends to loc in a path at a slant to the center line o f the sifting surface, or central axis of the sift- 45 ing surface, from the center of the feeding eX- tremity to the center of the discharging extrem ityy thereof. This cuts down the efficiency of such a device because the material crowds to one side of the surface, leaving the other side 50 relatively free of duty, so that the maximum screening or sifting function of the device is not realized.

`My invention relates to overcoming this tendy ency and to causing material on the sifting or 55 separating surface to ow from the feed extremity to the discharge extremity in the most efficient manner.

In explaining my invention, attention should be 'called to the reason for the flow of material in 6,0V such sifters. IThe sifting surfaces, move as stated above, in short paths which I have for convenience termed curvilinear. If the plane of the sifting surface were exactly horizontal and the motion thereof was exactly in the plane of the surface, the siftable material would merely slide f' around on the surface without flowing in any particular direction. With a motion not in the plane of the sifting surface, the surface to Whatever degree the motion is out of the plane, tends to push the material through half of a cycle, 1&0@

While the surface is rising angularly, and pull away from it during the other half. Depending on the weight of the material and its form and consistency and the rapidity of gyration on the surface, the last noted type of movement causes the material to slide about on the screen, but gen-.- erally to move at various rates of speed in the direction ofthe movement at the moment of maximum tractive thrust.

A usual mode of operation of sifters or sepa.- @Si this arrangement, gravity accelerates the flow. 9:5v

However, if the sifting surface is brought to the horizontal and the eccentric path of agitation tipped a like amount from the horizontal, with the angular variation between the plane of the surface and the plane of the path of the eccentric agititation remaining the same, the material being now unassisted by gravity, Will flow over the surface at a lesser rate of speed, but, also, in approximately the same direction.

The present invention is not concerned with 3'5r the type of sifting or separating machine in which the plane of the motion of the separating surface is perpendicular, or normal, to the surface, because in this type of machine there is no motion lateral to the desired direction of the flow of lIna-f 40 terial and the problem here presented is not en countered.

Reverting to the example of a sifting surface at a small angle to the plane of the curvilinear agitation, with which my invention is concerned, the tendency of material in moving is to follow the general direction of a point in the arc of movement occurring in the last half of the thrust stroke. Thus in sifters as constructed hereto fore, a. surface moved generally in a clockwise circle, or ellipse, will cause material to move along in the direction of thrust and to the right side of the surface as viewed from its feed extremity. If the direction of agitation is changed to counter-clockwise, the movement is again along the surface in the direction of thrust, and, then, to the left. 'Ihus in the rst instance, material will move in a slanting path from the feed toward the discharge extremity of the surface, and toward the right hand side Vof the surface;

in the second instance, it will tend instead to move to the left hand side of the surface, as it progresses. It will be simpler to describe this owing action from diagrams, and this will be done in the specification to follow. So far as this introductory matter is concerned, it should be noted that with a sifting surface which is held level as to its lateral components, and along which material is owed by reason of an agitation in a curvilinear path whose plane is at a fairly low angle to the lengthwise components of the surface, material will not ow in the direction of a line from the middle of the feeding to the middle of the discharging extremities of the surface, but will move over the surface at a slant thereto, due, as I believe, to the occurrence of the moment of greatest tractive push being at a point, in the cycle of gyratory motion, past the middle, but before the end, of the rising, or thrust, portion of the motion, at which moment the agitating motion is directionally at a slant to the center line of the surface from its feeding to its discharging extremities.

By my improvement this defect in the ow is avoided by arranging the plane of the path of movement to be at an angle to the plane of the surface not only as to its lengthwise but also as to its lateral components. This results, as will be described, in the latter portion of the thrust stroke of the surface being approximately axial of the surface, rather than at a. slant to its central axis in the feeding direction, by which I mean, lengthwise as extending in the direction of s a center line drawn through the sifting surface a from the middle of its receiving to the middle of its discharging extremity, sifting surfaces being usually, but not always, longer in this direction.

' In the drawings:

Fig. 1 is a diagram illustrating movement of the sifting surface of a sifting machine.

Fig. 2 is a plan diagram of such movement.

Fig. 3 is an end view of one type of `sifting machine.

Fig. 4 is a side view thereof.

Fig. 5 is a sectional plan view and diagram thereof taken along the line 5 5 of Fig. fl.`

Fig. 6 is a sectional end view of another type of sifting machine and is taken along the line 6-6 of Fig. '7. l

Fig. 7 is a side view of the machine shown in Fig. 6.

Fig. 8 is a sectional plan View and diagram thereof being taken along line 8 3 of Fig. 7.

Fig.y 9 is a plan View of another type of sifting machine and has part of the cover broken away to obtain better view of the sifting surface.

Fig. 10 is a longitudinal sectional View thereof.

Referring first to Fig. l of the diagrams, it should be noted that the slanting lines are intended to indicate the lengthwise components of a sifting surface with the feeding extremity Vat X vand the discharging extremity at Y, the lateral components of which surface are horizontal. The elliptical figure indicates the path of a point on the surface as agitated by an eccentric or out of balance device of some kind. If, instead of as illustrated, the agitated point were moved in the same plane as the lateral components of the surface, i. e., remained truly horizontal, then its path would be indicated by the straight line drawn between points A and D, in ther diagram. In such a case, since the sifting surface is longitudinally at an angle to the plane AD of a horizontally moving point on the surface, it is apparent that when the surface, in the position of the line passing through A, is moved to the position of a line passing through D, that there has been a thrust stroke of the surface against the siftable material thereon. So when the surface is moved from position D back to position A, there is a withdrawal of the surface from under the material, which, due to its inertia, does not follow back with the surface to the same extent as it moved forward.

By reference to the diagram of Fig. 2, in which the sifting surface is represented by the rectangle i, and the circle shows the path of movement of a point on the surface, shown for convenience as lying in the plane of the sifting surface, it will be noted that if the agitated point moved in the same plane as the lateral components of the surface, the tendency of the thrust movement from point A to D, when the rotation of the eccentric is clockwise, (with the arrows as shown), is to cause the particles of material on the surface to travel in the direction indicated by the arrow 2. Regarding the circle illustrating the path of movement, it will be noted that this is in conformance with the movement at a point in the cycle between the middle and the end of the thrust stroke, B to D.

With the plane of the path of movement in the plane of the lateral components of the surface, that portion of the path of movement constituting the last half of the thrust stroke, from B through C to D, is preponderatingly more at a lateral slant to the longitudinal direction of the surface, than parallel thereof. 'I'his results in the flow being at the angle noted, probably because the early part of the thrust stroke is necessary to overcome the inertia of the material, or the tendency of the material to stand still and allow the screen surface to move under it, while the latter part of the thrust stroke is that which actually imparts the motion to the material in the direction of the flow.

Now, if, as before, we regard the lines passing through A and D1 in Fig. l as positions of the surface at the extremes of the thrust stroke, when the path of a point on the surface is in a horizontal plane with the surface slanting longitudinally, but, we tip the plane of the path of movement so that the arc of movement of the path is no longer level laterally, we have the situation actually depicted in the diagram, by the elliptical lines A, Bl, D and E. Now by drawing slanting lines representing positions of the surface during this path, with the plane of its arc of movement at an angle both laterally and longitudinally of the surface as drawn, we find that the thrust stroke begins at point F and continues to point C, during which period the surface is rising against the material. Then the withdrawal stroke begins. It is no longer true that position D in the arc of movement is the most advanced point in the thrust.

Coming back to Fig. 2, it will be noted that the latter part of the thrust stroke, which ends at C, is no longer generally transverse to, but is now principally parallel to, the lengthwise component of the sifting surface. 'I'he result is that the last part of the frictional push on the granular material on the surface, which determines its direction of flow, is preponderatingly in line with the lengthwise components of the surface as indicated in line 2a.

The material will therefore ow along the surface without any marked tendency to travel at an angle to the lengthwise component of the surface.

Another way of expressing the matter is to refer to the high point in the motion of the surface. Where the circular or elliptical shaped path imparted to a point on the surface is in a plane which is longitudinally, but not laterally, at an angle to the planey of the surface, then the highest point ofk movement will be at the end of the thrust stroke at D, which is the point nearest the discharge extremity of the surface. What I have done in my invention is then to so arrange the angularity of the plane of the 'path of movement, that the high point of the sifting surface'movement is not in the length- Wise central axis of the surface, which extends in the desired direction of Aow, but, instead, is at an angle thereof, preferably for most materials from thirty to seventy degrees in advance in the path of movement from this central axial line, the exact advance in angularity, for perfect results, depending on the tractive properities of the particular material being sifted. The term high point is somewhat confusing because the relationship of the parts to the force of gravity is not so much involved as their relationship to each other. For this reason extremity of thrust stroke is believed to be clearer.

Referring to Fig. 1, it is noted that the highest of the parallel lines, representing a longitudinal component of the sifting surface, intersects the path of movement at point C which, therefore, is the high point in the motion of the surface, and the end of the thrust stroke, in which position, on Fig. 2, the sifting surface is represented by the rectangle Ic. In Fig. 2, it can be seen that v point C, or the high point of path of movement as shown on the drawings, is in advance of the central axial line in an amplitude of approximately sixtydegrees. y

- While the above diagrams show a circular movement, it will loe understood that the principle applies to any curvilinear movement as I have defined it. Thus in the typeof sifting machines wherein the movement is in a circular path as imparted by an eccentric at one end, and has a sliding movement in a fairly straight line at the other, the same considerations apply as above; the paths of movement on such a surface change through various stages of ellipse from the feed to the discharge extremity of the surface, so that, at the very discharge extremity, the movement is nearly in a straight line. This type of sifter is a very widely used one because of its mechanical simplicity. Finally, it is the practice in Some sifting machines to impart a crown or slight rounding to the sifting surface for retarcling and flow-control purposes. Such surfaces present'like problems to plain, flat ones, and are classed as flat surfaces.

There is a well known type of sifting machine in Which there is mounted below the sifting surface a tray divided into chambers by angular cross section strips, the chambers having balls in them which strike the sifting surface during agitation. My invention is well applicable to such sifters because it results in preventing the balls from tending to group themselves oiT to one side. in the compartments, for the same reason that the particles on the surface tend to move laterally. y

It now remains to describe the several examples which have been illustrated in the drawings to show the general application of my invention to various types of sifting machines, it being understood that by giving a series of examples Y I do not wish to exclude others.

In Figs. 3 to 5, I have illustrated a type of sifting device in which the sifting surface is level and suspended by suitable cords, or the like, with the prime mover fast to a foundation. The sifting surface is indicated at I0, and the supporting cords at Il. An eccentric l2, is so positioned as to cause the lower ends of the cords to swing the sifting surface through a movement which is longitudinally angular with respect to the plane of the sifting surface, as is indicated by the arrow I3 in the side elevational view, Fig. 4. It is also positioned so as to cause the cords to swing the sifting surface through a movement which is laterally angular with respect to the plane of the sifting surface, as is indicated by the arrow I4 in the end elevational view, Fig. 3.

In other words, the position of the eccentric with regard to the supports for the cords is such as to prevent the screen from swinging equal amounts to each side of a truly vertical position of the cords, but instead permanently holds the screen in an unnatural position. In order that there may be a minimum of misalignment, with consequent objectionable sliding or oscillatory movement between the eccentric pin and its I bearing seat connected to the sifting surface, I have so inclined the prime mover as to cause the path of the driving eccentric to lie in a plane substantially parallel in every direction with the plane of the path of movement of the sifting surface. For best results the eccentric pin and its bearing seat may be made slidable and selfaligning, as shown, for example, in the cross sectional view, Fig. 6. The direction of rotation of the eccentric in this case is clockwise.

Therefore, by reference to the diagrams of which explanation has been made, particles depcsited near the feeding extremity of the surface at A, in the three views, will move in a straight line, or approximately straight line, over the surface to the discharge extremity indicated at B, without tendency to crowd the particles toward either side.

The thrust stroke is indicated on the plan view as beginning at F and ending at C, so that the latter portion of the thrust stroke, which imparts the greatest directional thrust to the particles on the sifting surface, is generally parallel with the axial line of the surface from the feed to the discharge extremity and in the direction of desired flow, as distinguished from being generally at a slant thereof, as would be the 'case were another portion of the path of movement to impart the greatest thrust.

Referring now to Figs. 6 to 8, the sifting surface as indicated at 2t, is suspended by cords 2l, so that it will be at a slant from the feed extremity A to the discharge extremity B. The eccentric 22 is again fast on the oor. As indicated, the surface has a ball socket joint 23 with the eccentric, Here the eccentric is so positioned as to cause the lower ends of the cords to swing the sifting surface through a movement which is level in a direction parallel to the longitudinal axis of the sifter, but angular with respect to the plane of the sifting surface longitudinally, which angularity is indicated by the arrow 24 in the side elevational view, Fig. 7.

The plan view is so taken as to be identical with the plan view of the first illustrated form, Fig. 5, with the exception that the eccentric is now offset longitudinally toward the feeding extremity of the sifting surface with respect to the stationary upper attachment ends, 2Ia, of the suspension cords, 2l. It is so made as to show that the same forces` apply in each instance so far as the sifting surface movement is concerned. However, in this second form gravity assists the now of material from the feeding extremity A to the discharge extremity B of the sifting surface. As before, the thrust stroke, so far as its relations to the sifting surface are concerned, begins at F and extends to C, being so arranged, as explained, to cause the particles to move lengthwise of the surface in` straight lines parallel with the sides of the surface, or approximately so.

Were the invention to be applied to a reaction operation type of sifting machine in which an out-of-balance weight actuates the sifting surface, and causes the surface to move by reaction, then it would be necessary to hold the surface in some way to vforce it to follow the movement noted. The angularity would remain the same. It would also be possible to let the path of the actuating movement and sifting surface be in parallel planes with each other, Whether of the reaction type, or of the fixed eccentric type, and provide for the angularity of movement of the surface by other means than as here described for guiding the surface with the movement desired. As, for example, by using an eccentric With a fixed axis not operating on a reaction principle, it would be practical to have the eccentric connected to the surface by a sliding connection in addition to a ball joint as shown in Fig. 6, and to employ guides on Which the sifting surface rests, which will require it to move with the desired angularity.

I have not illustrated all of these forms of structure, for the sake of brevity, since the principle involved is shown in the diagrams.

It should be noted that the angularities in movement in the illustrations, and in the diagrams, as well, have in some respects, been exaggerated over what would normally be provided, so as to bring out the point involved. Ordinarily an angularity of movement up to fifteen degrees from the longitudinal plane of the sifting surface, and up to ten degrees from the lateral components of the surface, will be sufficient. The exact angles and the orientation of the device to the horizontal plane will be determined for various materials and requirements of flow, and length of time desired for treatment, matters which are ones of design well within the skill of the sifting machine builder. .Also adjustable arrangements can be provided winch will permit the user to obtain the desired results on any given material, and compensate for the divergence of flow for this material, merely shifting the angularities about, and changing the orientation of the machine for use of the additional force of gravity to the extent desired,

I have illustrated my invention, in Figs. 9 and 10, as applied to a type of sifting machine having motion imparted at the feeding extremity of the sifting surface by an eccentric, but held to move in a fairly straight line at the discharge extremity. The behavior of materials on such amachine is like that on machines which have but one arc of movement throughout.

I have also illustrated in this machine the use of balls for cleaning the meshes of the sifting surface, although this is not intended to limit the application of my invention only toball cleaner type sifters of this general style.

In this illustration the sifting surface is shown as consisting of two elements and 3l, held in a frame which also `contains the ball trays 32.

The ball trays have partitions 33, dividing them up into compartments, with balls 34 in the trays. The action of the balls is to hit the partitions and due to their angularity, to bounce and strike the under side of the sifting cloth, or surface. As noted, in the machines of today operating with balls, and of the type illustrated, the balls Will accumulate at the sides of the partitioned chambers in which they are located, thus cutting down their efficiency.

In the case here illustrated the sifting surface elements are inclined longitudinally to the horizontal at a normal angle for such machines, say around four degrees, and are horizontal laterally. However, the eccentric 35 is inclined to the crosswise components of the sifting surface at an angle of around six and one-half degrees. Here, unlike the diagrams previously explained, the eccentric drive bearing is the guiding means by which the angular motion is imparted to the sifting surface.

The result is to bring this machine into line with the diagrams, already explained. The sifting surface is moved in a path which varies from circular or nearly so, at the extremity nearest the point of power application, through various elliptical forms grading to the rectilinear movement of the surface on the shoes 36 which support its discharge extremity. This path of surface movement is at an angle to the plane of the surface such that the thrust stroke begins and ends at an angle to the longitudinal axis of the surface, which results in materials flowing in straight lines parallel with the sides, over the surface from the feeding extremity A to the discharge extremity B, and also results in the balls bouncing around uniformly throughout their compartments rather than crowding to the side.

It will be apparent that instead of obtaining the compound angularity by adjusting the plane of the eccentric in the illustration, that the screen itself could be given the compound angularity and the eccentric arranged to operate in a truly horizontal plane.

It will be understood that if the rotation of the eccentric devices in any of the illustrations were counter-clockwise instead of clockwise, then the lateral tip of the plane of motion imparted to the sifting surface would be the opposite to that shown.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

In combination a screen having a rectangular screen surface, means for feeding material to one end of the screen surface, said screening surface being supported to be inclined downwardly from the feed end and being supported in a horizontal plane in a direction laterally of the direction of inclination, means for imparting a gyratory motion to the feed end of the screen, said means comprising an element mounted for rotation, said element being mounted in a vertical plane transverse to the direction of feed and being inclined in said plane and an element constraining the screen surface to move in a plane normal to said element and means for rotating said element in such direction that the highest point to which the screen is moved is short of the furthest position to which the surface is moved in the direction of forward movement of material downwardly of said surface and means for constraining the movement of the discharge end of the table to a linear path.

LOWE E. SIMPSON.

Images