US2286607A - Apparatus and process for separating particles - Google Patents

Description

June 16, 1942. F. c. DYER HAL 2,286,607

APPARATUS AND PROCESS FOR SERARATING PARTICLES Filed March 6, 1939 I INVENTUHS Patented June 16, 1942 APPARATUS AND PROCESS FoR SEPARATING PARTICLES Frederick Charles Dyer and Harold Langdon McClelland, Toronto, Ontario, Canada Application March 6, 1939, Serial ,No. 260,210 In Canada March '7, 1938 11 Claims.

This invention relates to apparatus and process for separating particles having different characteristics, and is particularly adapted to the Separation of seeds which because of their similarity of size, shape, weight, and/or specific gravity are not readily separable by known methods.

The present invention utilizes primarily a reciprocating or vibrating table, which broadly is old in the art. In using the expression table, it is intended to include a travelling table, which may be in the form of an endless belt. Some of such tables stratify the particles by reason of differences in specific gravity, and advance all the particles in one direction by progressive motion, separation being obtained by reason of the fact that one class ortype of particle moves down the table more rapidly than the other, due to the movement and slope of the table and the difference in specific gravity and size and also, in some cases, owing to differences in shape of the particles. In such tables separation is usually obtained by differences in the rolling or sliding characteristics of the particles. In most of such tables a comparatively long stroke or reciprocating movement of one-quarter inch or more is used. In some cases air forced up through the table is used to keep the mass of particles in a fluid condition.

While such tables are useful for separating certain particles, so far as is known, no such table ha ever made a substantially complete separation of particles of such similarity as to size, shape and weight as, for instance, clover, alfalfa or alsike seeds from common weed seeds such as dodder, catchfiy, foxtail, or campion. To overcome this difiiculty the present apparatus and method was devised, although it is not limited to separation of such closely similar particles, or the seeds referred to above, but may be utilized in the separation of other particles, even such particles as might be separable by other known apparatus or processes.

Broadly speaking, the present invention consists in feeding the particles to be separated to a table having asubstantially flat surface, substantially horizontal at least in its direction of reciprocatiomand covered with fine, closely set, short resilient fibres normally substantially at right angles to said surface, and rapidly reciprocating said table longitudinally in a direction Substantially parallel to the plane of its surface in a series of rapid forward and backward movements with an interval of rest between each double movement in such a manner thatin lieu thereof certain of said particles remain in the position at which they are fed to the surface, or move in one direction, and certain other particles having different characteristics move in the opposite or a different direction over the said surface. It will'appear from the above that by this invention seeds having different characteristics may be positively actuated in opposite or different directions, which action is independent of any Sliding or rolling of the particles due to any slope of the table, such as is obtained in prior constructions.

--A further feature of this invention resides in conditioning to create or accentuate a difference in the-surface characteristics of the seeds. This makes possible or improves the separation of such weed seeds as buckhorn and pepper grass from clover.

The invention is hereinafter more particularly described and is illustrated'in the accompanying drawings in which Fig. l is a diagrammatic side elevation of one embodiment of the invention;

. Fig.'2 a plan view; r

Fig. 3 an end view of the reciprocating mech- A anism;

Fig.4 a graph representing the motion of a standard" table;

Fig. 5 a graph representing the ideal reciproeating movement of the table; and

Fig. 6 a transverse sectional elevation of a modified form of table, on a reduced scale,

In the drawings corresponding numerals in the.

. or other means, although in a case Where a travelling surface is desired for carrying away the separated Seeds, the fabric might be in the form of a belt passing over and around the table from side to side and reciprocable, transversely of its direction of travel, with the table. It is also possible to construct a plurality of articulated tables which travel in an endless chain in a direction at right angles to the direction of the reciprocation or vibration thereof. In the specification and claims, the word table is used broadly to include a table having a travelling surface, such as a belt passing thereover.

Strips 3 preferably extend over the surface of the table transversely thereof, dividing the surface into a plurality of panels.

The table I is mounted for longitudinal reciprocating movement. In the embodiment of our invention illustrated in the drawings resil ient supports 4 are provided for supporting the table on a fixed base 5. The supports 4 may, as illustrated, consist of a plurality of strips of resilient metal, such as thin steel secured to the base 5 and the underside of the table 4 by means of screws. In order to prevent warping or sagging, when the table is made of wood, and to ensure uniform. vibratory movement throughout the a table, a comparatively large number of such supports may be provided, preferably uniformly spaced and located.

The table I is mounted substantially horizontally, although for specific purposes, it is conceivable that for certain purposes the table might be tilted slightly longitudinally at an angle to the horizontal, and for a purpose hereafter described it may be slightly tilted transversely. However, for the particular purpose for which the device was devised, namely the separation of certain weed seeds from crop seeds, it is essential that the table be as nearly horizontal as possible from one end thereof to the other end. It is also important that the top of the table be a substantially flat plane surface. Unevenness of the surface will introduce the element of gravitational flow which would interfere with proper separation under the influence of the vibratory movement. V

The vibratory movement may be obtained by any one of a number of means. It is necessary that the movement be in theplane of the surface of the table. It must be rapid, and for the purpose of obtaining substantially complete separation of the weed seeds and crop seeds specified above, it is essential that there be a brief interval of rest between each vibratory cycle, comprising a forward and backward movement.

The vibratory movement may be obtained by striking one end of the table with light rapid sharp strokes of a hammer. Such a hammer might be manually manipulated, but for practical purposes automatic mechanism is necessary. The method illustrated has proved to be satisfactory and consists of a weighted hammer head 6 mounted on a shaft 1. Provision is made for varying the weight of the hammer by the addition of discs 8 which may be secured in position by means of a lock nut 9, which also looks the hammer in position on the shaft I. The hammer head 6 may be screwed on to the end of the shaft I, so that its position may be varied.

The shaft 1 is adapted to reciprocate in bearings 22 and 23, and at the end thereof opposite fromthe hammer head is a tappet I0 whose position is adjustable by means of the lock nuts II and I2. A spring I3 is mountedon the shaft I between the bearing 23 and a collar I4 on the shaft I, which spring tends to force the shaft I, and the hammer head 5 against the end of the table I.

A cam I5 having an anti-friction striking roller I5, is mounted on a rotating shaft I6, which may be driven by a motor or other suitable means. The cam I5 is so arranged relative to the tappet ID, that when it rotates it engages the said tappet I0 and forces the shaft 1 backward. When the cam disengages from the tappet ID, the spring I3 forces the shaft 1 forward and causes the hammer 6 to strike the end of the table, causing it to move forward sharply.

Secured to or engaging the other end of the table is a shaft I'I slidable in the bearing I8 and provided with a compression spring I9 between the said bearing I8 and the collar 20 on the shaft. The forward movement of the table compresses the spring, which forces the table sharply backward, the resilient supports I having sufiicient resilience to permit the slight reciprocating movement, which is substantially less than onequarter inch in each direction. The resilient supports 4, however tend to regain a normal vertical position and to hold the table in that position. When the table has been returned by the spring I9, there is a short period, before the cam I5 again engages the tappet I0, or at any rate before it disengages the tappet I0 so that there is an interval of rest before the table is again struck by the hammer. In commercial practice the movement ofthe hammer is, of course extremely rapid, and the period of rest is not visible to the naked eye, but may be traced on a graph. In Fig. 4 there has been represented the ordinary type of vibration, which it will be observed is substantially continuous there being practically no period of rest between the vibratory movements. But, in Fig. 5, there is represented the ideal movement, in which there is a sharp quick forward movement followed immediately by a sharp quick return movement, and with a sharp change of direction at the beginning of each movement a short period between each double movement in which there is no movement at all. This, as explained, is the ideal situation, but in practice the period of rest is not so pronounced, as there is inevitably a certain amount of induced vibration. However, it is believed that the nearer the movement approaches the ideal condition illustrated, the better the separation. The natural tendency of the resilient supports 4 to return to the normal upright position tends to reduce the vibration, as does also the comparatively light pressure of the spring I3, which normally holds the hammer 6 against the end of the table, until it is pulled back by the action of the cam. I5. However, to further dampen the induced vibration, a dampening spring 24 is mounted on the shaft II between the bearing I8 and an adjustable nut 2| on the shaft. It will be observed that when the shaft I! is moved by the forward movement of the table, the tension of the spring 24 is lessened, and when the shaft II moves in the opposite direction under the pressure of the spring I9, the spring 24 is compressed, and it is so adjusted that it tends to prevent the table moving back beyond its normal position, the tensioning, in fact, being such as to hold the shaft I1 in a predetermined normal position.

A rheostat or other suitable means is provided for regulating the speed of the motor driving the shaft I6, which in turn operates the cam I5, and therefore the speed of the action of the hammer may be regulated. Various other factors may be regulated by the adjusting means already described. For instance the position of the tappet Ill may be adjusted, alsothe tension of the springs I3, I9 and 24, and the weight and position of the hammer 6 may be varied. Inasmuch as there are so many variables, and the weight of the blow of the hammer, the length of the blow and its speed, also the length of travel of the table, all vary in accordance with the circumstances, it is not possible to specify exactly and definitely what these variable factors shall be. These factors also depend a great deal on the nature of the particles to be separated, including their weight, shape, and the nature of their surfaces. It is also obvious, that some modification of the nature of the surface of the table, or the stiffness of the spring mounting of the table might be effective. The only way in which these variable factors may be determined in any particular case is by experiment, which, however, is well within the capabilities of any person skilled in the art, who follows the specification of the device herein set forth.

The device is operated as follows: The particles are fed in any suitable manner, in its simplest form manually, but preferably by a discharge trough of some kind to each panel of the separating table and in quantities sufficient that when the separating operation is complete the particles will be spread over each panel not more than one particle deep, and preferably with a substantially clear space, which will be centrally of each panel. The particles will be fed to the panels usually about along the centre line thereof, but since the number and speed of movement of the particles in one direction may be greater than in the opposite direction it may be preferable to feed the particles along a line closer to one side of the panel than the other.. The table is reciprocated, and the particles separate, the heavier particles moving lengthwise of the table in a direction opposite the direction of movement of the table initiated by each hammer blow, and the lighter particles, having the same surface characteristics, travelling in the direction of the initial movement. Similarly, with particles of substantially the same weight, the smoother particles will move in a direction opposite to the direction of initial movement and rougher particles will move in the direction of the initial movement. Separation may also take place owing to differences in shape of the particles to be separated. The strips which separate the panels limit the respective movements of the particles, so that when the separation operation is completed, the particles are arranged across the panels on opposite sides thereof adjacent the dividing strips, and may be removed in any convenient manner, such as by means of suction pipes along the edges of the panels. It is obvious that a continuous feed and continuous removal of the particles may be adopted.

As explained above, the frequency of reciprocation, the speed of movement, and other factors may be adjusted so that the maximum efficiency of separation is obtained. It is found, that other factors being suitable, by increasing the speed of reciprocation and the frequency, all of the particles, or substantially all of them, may travel in one direction. By slowing down the speed of reciprocation and frequency no movement, or a movement in the opposite direction may result. By simple experiment, the critical conditions under which the particles to be separated travel in substantially opposite directions may be obtained.

In the case of separation of red clover, white clover, sweet clover, alfalfa or alsike from weed seeds such as dodder, catchfly or'campion, the slightly smoother, and sometimes heavier, crop seeds travel in a direction opposite to the initial hammer movement of the table, and the weed seeds travel in the direction of the initial movement of the table.

By tilting the table slightly transversely, as shown in Fig. 6, but not suflicient to cause the seeds to roll or slide towards the side of the table, unless the table is reciprocated, the seeds will not only separate longitudinally of the table, but the separated seeds will tend to flow toward the lower edge of the table, and if suitable receptacles are provided below the said lower edge of the table, the separated seeds may continuously flow into such receptacles. This slight tilting, would also improve the separation, since it would give fluidity to the mass of particles. A close observation of the table in operation indicates that particles moving in opposite directions during the separation process frequently collide, and the separating process is thus slowed down. If, however, the particles are not only travelling in substantially opposite directions lengthwise of the table, but are also moving slightly toward one side of the table, instead of the particles striking, so to speak, head on, they strike a glancing blow and may more readily pass one another. 'In this way the separation may be speeded up, but it should be clear that this effect is not analogous to methods of separation whereby differences in the capacity of the particles to slide or roll down an incline is utilized for separation. The movement across the table is primarily to facilitate the discharge.

It will be clear from the above description that by the method proposed particles of quite slight different characteristics may be separated. Larger particles'may be separated from smaller particles, heavier particles from lighter particles, and smoother particles from rougher particles.

Some seeds are so similar in all their characteristics that separation is difiicult or impossible in their natural state. Such seeds may be successfully separated by the process herein described by conditioning them to create or accentuate a difference in a physical characteristic of some of the seeds relative to the others and in particular by taking advantage of ac'haracteristic not heretofore mentioned. Some weed seeds when moistened develop-a gelatinous outer coating, for example buckhorn and pepper grass. Crop seeds, such as clover seeds, do not have this characteristic or have it in a much less degree. If, for example, seeds containing buckhorn and pepper grass seeds are exposed to moisture which may beeither water or some other liquid either in the liquid state or in the form of mist or steam and then mixed with or sprayed with a finely ground mineral or vegetable substance,

such as sawdust or ground quartz, the gelatinous coating developed by the buckhorn and pepper grass causes the finely ground substance to adhere thereto so that the outer surface of the buckhorn and pepper grass seeds will become rough, whereas the surface of the clover seeds will remain smooth or will not pick up as much of the finely ground substance and therefore will not become as rough as the surface of the weed seeds. The treated seed when dried may be effectually separated by the process and apparatus above described.

It should be noted that a process is in use at present which consists of moistening the seeds to be separated, the consequence of which is that some of the seeds acquire a gelatinous coating. By this process the seeds are then mixed with sawdust and, as a result of the sawdust adhering to one seed in preference to the other, separation may be had by screening or specific gravity methods. This process fails when the gelatinous coating does not develop sufficiently during the time of treatment to allow enough sawdust to adhere to effect the necessary difference in physical characteristics. For instance, immature seeds develop a gelatinous coating more slowly than mature seeds with the result that before screening or specific gravity separation it may be necessary to soak the seeds be yond the allowable wetting time in order to create a sufficient gelatinous coating on the immature seeds, with the result that the crop seeds may be spoiled. It should be understood that if treated for too long a time the moisture will penetrate the inside of the seed and spoil it. The allowable time varies according to the seed treated and the manner in which it is treated, and the allowable wetting time can readily be determined by simple experiment. With the present process it is not necessary that the gelatinous coating be more than incipiently developed, because it is not necessary that any considerable amount of the added dust-like substance shall adhere to the seed, but merely sufficient for the outer coat to become rough to a greater extent in the case of one seed than in the other. Thus a comparatively brief period of moistening is necessary. In screening or specific gravity separation methods there must be sufficient sawdust adhering to the seeds to materially change the size or specific gravity I of those seeds which develop a gelatinous coating. It should be noted that in the present process almost any dust-like substance may be used, but quartz dust or other finely ground mineral or metal substance is preferred.

What we claim as our invention is:

1. Means for separating particles having different characteristics, comprising a table mounted for reciprocation, and having a substantially flat surface, substantially horizontal at least in its direction of reciprocation and covered with fine, closely set, short, resilient fibres normally substantially at right angles to the surface to which surface the particles are fed; and means for rapidly reciprocating said table longitudinally in a direction substantially parallel to the plane of its surface to impart to the table a series of sharp quick forward and backward movements with a sharp change of direction at the beginning of each movement and an interval of comparative rest between each double movement so that certain of said particles remain in the position at which they are fed to the surface or move in one direction and certain other particles having different characteristics move in the opposite or a different direction over the said surface.

2. Means for separating particles having differ ent characteristics, comprising a table mounted for reciprocation, and having a substantially fiat surface, substantially horizontal at least in its direction of reciprocation and covered with fine, closely set, short, resilient fibres normally substantially at right angles to the surface to which surface the particles are fed; means for rapidly reciprocating said table longitudinally in a direction substantially parallel to the plane of its surface to impart to the table a series of sharp quick forward and backward movements with a sharp change of direction at the beginning of each movement and an interval of comparative rest between each double movement so that certain of said particles remain in the position at which they are fed to the surface or more in one direction and certain other particleshaving different characteristics move in the opposite or a different direction overthe said surface; and means for dampening induced vibratory movements in the intervals of rest.

' 3. Means for separating particles having different characteristics, comprising a table mounted for reciprocation, and having a substantially flat surface, substantially horizontal in its direction of reciprocation and covered with fine, closely set, short, resilient fibres normally substantially at right angles to the surface to which surface the particles are fed, and means for rapidly reciproeating said table witha series of sharp quick forward and backward movements, with a sharp change of directionat the beginning and end of each forward stroke, and a period of comparative rest before each forward stroke, the surface of the table being tilted transversely of the direction of its reciprocating movement, sufficiently to impart a movement of the particles across the table to discharge the separated particles at the side of the table, but not sufficient to impart a sliding or rolling movement to the particles independent of the described movement initiated by the reciprocation of the surface.

4'.' Means for separating particles having different characteristics, comprising a table mounted for reciprocation, and having a substantial flat surface formed by a short-pile fabric, substantially horizontal at least in its direction of reciprocation; and means for rapidly reciprocating said table with a series of sharp quick forward and backward movements, with a sharp change of direction at the beginning and end of each forward stroke, and a period of comparative rest before each forward stroke.

5. Means for separating particles having different characteristics, comprising a table having a substantially flat surface substantially horizontal at least in its longitudinal direction and covered with fine, closely set, short resilient fibres normally substantially at right angles to the surface, to which surface the particles may be fed; resilient supports for said table adapted to permit longitudinal reciprocation to and from its normal position; and'means for imparting to the table a series of sharp quick forward and backward movements with a sharp change of direction at the beginning of each movement and an interval of comparative rest between each double movement.

6. Means for separating particles having different characteristics, comprising a table mounted for reciprocation, and having a substantially fiat surface, substantially horizontal at least in its direction of reciprocation and covered with fine, closely set, short, resilient fibres normally substantially at right angles to the surface to which surface theparticles are fed; reciprocatin'g means for periodically forcing the table to move iii one direction with a sharp quick movement; and spring means adapted to return the table in the .opposite direction with a sharp quick movement, whereby a rapid vibratory movement in a direction parallel to the plane of the surface of the table is imparted thereto, the stroke and frequency of the reciprocating means and the strength of the spring means being relatively adjustable and adapted to provide a desired length, speed and frequency of movement of the table and to provide a sharp change of direction at the end of each forward movement and an interval of rest at the end of each return movement of the "table.

7. Means 'for'separating particles having difed for reciprocation, and having a substantially flat surface, substantially horizontal at least in its direction of reciprocation and covered with fine, closely set, short, resilient fibres normally substantially at right angles to the surface to which surface the particles are fed; reciprocating means for periodically forcing the table to move in one direction with a sharp quick movement; spring means adapted to return the table in the opposite direction with a sharp quick movement, whereby a rapid vibratory movement in a direction parallel to the plane of the surface of the table is imparted thereto, the stroke and fre quency of the reciprocating means and the strength of the spring means being relatively adjustable and adapted to provide a desired length, speed and frequency of movement of the table and to provide a sharp change of direction at the end of each forward movement and an interval of rest at the end of each return movement of the table; and a damper for dampening induced vibratory movements in the intervals of rest.

8. Means for separating particles having different characteristics, comprising a table having a substantially fiat surface substantially horizontal in its direction of reciprocation and slightly tilted transversely thereof, and having its surface covered with a short-pile fabric; supporting means for said table adapted to permit a horizontal vibratory movement; means for imparting to the table a rapid series of sharp quick movements in one direction; spring means for returning the table in the opposite direction with a sharp quick movement, the movement imparting means being adjusted so that there is a sharp change of direction at the end of each forward movement and a period of rest after the return movement of the table before imparting the next forward movement thereto; and means for dampening induced vibratory movements in the period of rest.

9. Means for separating particles having different characteristics, comprising a substantially horizontal table mounted for longitudinal reciprocation in the plane of its upper surface; a surface covering for the table of fabric having a short-pile of fine, closely set, resilient fibres; resilient means tending to maintain the table in a predetermined initial position; and positive means for imparting a series of sharp quick movements to the table in one direction from its initial position, a sharp quick return being effected by the resilient means aforesaid, and the said positive means being timed to allow a short period of rest between each double movement of the table.

10. Process of separating particles having different characteristics on a table having a substantially fiat surface substantially horizontal at least in its direction of reciprocation, and covered with fine, closely set, short resilient fibres normally at substantially right angles to the surface, comprising feeding the particles tothe table, and rapidly reciprocating said table in a direction substantially parallel to the plane of its surface in a series of sharp quick forward and backward movements with a sharp change of direction at the end of each forward movement and a brief interval of rest between each double movement whereby certain of said particles remain in the position at Which they are fed to the surface or move in one direction and certain other particles having different characteristics move in the opposite or a different direction over the said surface.

11. Process of separating particles having different characteristics, as set forth in claim 10, in which induced vibratory movements in the intervals of rest are dampened.

his FREDERICK CHARLES DYER.

mark HAROLD L. MCCLELLAND. Witnesses to mark of Frederick Charles Dyer:

F. FRANK DYER, MRS. N. MAoKINNON.

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