US1591959A - Screen - Google Patents

Description

July 13 1926. 1,591,959

J. BLAND SCREEN Filed May 17. 1924 njzand 27 Q?" q- G2,,

Jittori'zciypi screen does not do so.

' ticles.

-Patented July 13, 1923.

JOHN BLA ND, OF CHICAGO, ILLINOIS.

SCREEN.

Application filed May 17,

This invention relates to screens, and has for one object to provide means and a process whereby the operation of screens is rendered more etlicient and rapid and whereby the percentage of material of the proper size which fails to go through the screen is greatly reduced.

I have found that in the case of vibratory screens and particularly with screens which vibrate at a very rapid rate, a considerable portion of material small enough to pass through the mesh or perforations of the This is due to many causes, one of the most important being the high rate of vibration of the screen and the vigorous and extreme motion imparted to the particles during screening. In connection with a vibratory screen the particles are frequently thrown into the air a distance equal to several times their thickness. Upon coming down if the particle is just a little smaller than the opening through the screen, unless it strikes exactly in line with the opening it will not pass through it but will bounce and be driven off again. This process will be repeated until the particle which should have passed through the screen passes off at the end.

Another object of my invention is therefore to provide a process and means for damping the degree of movement of the par- Another object is to provide means whereby the particles are held comparatively close to the screening surface, and thus caused to vgo somewhat more readily through'the screen. Other objects will appear from time to time throughout the specification and claims.

7 My invention is illustrated diagrammatically in the drawings, wherein:

Figure 1 is an elevation showing my device applied to a vibratory screen;

Figure 2 is a view similar to Figure 1 showing my device applied to a shaking screen;

Figure 8 is a view more or less accompanying similar to the preceding views showing a modification of my device.

Like parts are designated by like characters throughout.

device in connection with a vibratory and a shaking screen, and it is applicable to both. It is applicable also to practically any other type of screen, although it is probable that it has its greatest I have shown my 1924. Serial No. 713,899.

importance in connection with vibratory screens, because generally in such screens the rapidity of motion is such as to cause the particles of material onthe screen to be out of contact withthe screen throughout a considerable portion of the time within which screening should take place. It is therefore with screens of this type that it is of particular importance to prevent excessive movement of particles away from the screen.

As illustrated in Figure 1 my invention comprises a screen frame A having a screen A fixed in it. As here shown the screen is of metallic cloth but any type of screen might, of course, be used. The screen is pivotally mounted upon a support B, at one end and is carried upon a second support C at its other end. The support G is held at each end against lateral movement and is formed of spring material. One or more such supports may be used. As here shown two such spring supports C would be used but any number might be so used. Mounted upon each of the spring supports 0 is a hearing C within which is mounted for rotation a shaft C This shaft has preferably fixed upon it a pulley G which is driven through a belt G mounted upon a motor C V Mounted upon the shaft G is a fly wheel D. This pulley may be of any suitable form and as shown here is provided with spokes, one of which has mounted upon it an adjustable weight D This weight is provided so that the pulley is slightly out of balance. The degree of this condition may be varied by the variation in the position of the weight D Then the shaft is driven the members 0 are caused to vibrate laterally by reason of the unbalance of the fly wheel D. This lateral vibration sets up a vertical movement at the end of the support and thus a vertical component of vibration is supplied and the screen itself is vibrated.

Mounted on'the screen is a bar or other suitable member -E. Fastened to this memher and trailing loosely from it is a fabric piece E This piece lies on top of the screen and is in contact with the screen fabric or the screening member used. The material to be screened is deposited on the screen fabric at its upper end through a chute F.

As shown in Figure 2 the screen A is mounted for shaking or lateral reciprocation. port G and at the other upon a somewhat longer support G and has connected to it a rod G which is connected to any suitable source of motion whereby the screen is caused to shake or oscillate. The screen has mounted on it a member E like that shown in Figure 1. From this member depends a fabric E which is like that shown in Figure 1. This fabric may be loose at its other end or it may be fastened to a rod E This is not essential, but when the fabric is used in connect-ion with an oscillating screen it is sometimes an advantage, as it overcomes any tendency of the cloth to form into folds which might otherwise occur due to the longitudinal movement of the screen.

As shown in Figure 3 a somewhat different type of screen appears. The screen is carried in a frame H which is mounted for movement on supports H H As here shown the screen is adapted to be shaken in the same manner as is the screen shown in Figure 2. It might also of course be a vibratory screen such as the one shown in Figure 1. The screen cloth I is similar to that shown in the preceding figures although a different construction might be used. In this form'of the screen instead of the fabric shown in Figures 1 and 2 a screen fabric J is used. This is perforated and is preferably provided with perforations somewhat larger than those of the main screening cloth fixed in the frame. his second thickness of screening cloth is mounted for slight movement but is held against excessive movement by means of the flexible connection J Although I have shown an operative device, still it will be obvious that many changes might be made in size, shape and arrangement of parts without departing materially from the spirit ofmy invention; and I wish, therefore, that my showing be taken as in a sense diagrammatic.

The use and operation of my invention are as follows:

As shown in Figures 1 and 2 the fabric which lies over the screening surface proper rests freely upon the screen. Material to be screened passes between it and the screen cloth. 'hen due to the action of the screen material thrown upward from the surface of the screen, it strikes the loosely lying piece of cloth and its movement is greatly limited. By reason of this it has been found that material passes very much more readily through the screen and that a very much smaller percentage of material of a size which should pass through the screen, fails to do so.

The form shown in Figure 2 is practically identical ,with that shown in Figure 1. The operation of the screen is somewhat dif It is carried at one end upon a sup ferent, since its shaking is lateral rather than vertical, but in this case also the maerial on the screen as it is moved from the screen surface proper and thrown upward, comes in contact with the fabric above it and its upward movement is limited, if not entirely prevented and movement of the material through the screen is greatly accelerated. By the use of this construction the size of the screen may be materially reduced because the material moves through the screen very much more readily than is the case without the fabric covering.

In the form shown in Figure 3, in place of the fabric covering a second screen is used. This screen is loose with relation to the main screen and is mounted for movement with relation to it. The material to be screened is deposited on top of it and must pass through to reach the screening surface proper. Once this is done, the action which is carried out in connection with the screening fabric described above is to some extent repeated, that is to say, ma-

terial on the lower screen surface as it driven or thrown up to some extent contacts the upper loose screen and its upward movement is thus limited or prevented and passage of the material through the lower screen is accelerated. There is, however, in connection with this form another action not present in the forms shown in Figures 1 and 2. lVhere very fine material is to be screened it is frequently found that as it moves along the screen it tends to form into balls which are too large to pass through the mesh of the screen and thus move off at the end. \Vhen the double screen is used, the relative movement of the upper and lower screen and the movement of the material which is being screened between the two and from one to the other tends to preventthe formation of these balls and to break them up when formed. Thus the screen shown in Figure 3 in addition to limiting excessive movement away from the screen of the material which is being screened, serves also to prevent the formation of balls of material and break up such balls when once formed.

I claim: I

1.. In combination with a high speed vibratory screen, including a screening surface adapted to be moved to cause screening action, a bafiling element substantially impermeable by the material to be screened, loosely associated with the screening surface and resting upon it to limit the movement of material being screened away from the screen during the screening action.

2. In combination with a high speed vibratory screen, including a screening surface adapted to be moved to cause screening action, a flexible battling element substantially impermeable by the material to be screened and resting upon the screen to limit the movement of material being screened away from the screen during the screening action.

3. In combination with a high speed vibratory screen,'including a screening surface adapted to bemoved to cause screening action, a flexible baffling element substantially impermeable by the material to be screened loosely associated with the screening surface and resting upon it to limit the movement of material being screened away from the screen during the screening action.

4. In combination with a high speed vibratory screen, including a screening surface adapted to be moved to cause screening action, a flexible baffling element substantially impermeable by the material to be screened to limit the movement of material being screened away from the screen and resting upon it during the screening action, said baffling element supported at one end above the screen and resting elsewhere freely upon the screen.

5. In a high speed vibratory screening device a fran'ie in which is mounted screening means, a supporting element of spring material for one end of said frame, means supporting the other end of said frame to permit movement, and means for vibrating said spring member whereby generally Vertical reciprocation of the screening means is effected, in combination with a bafliing element substantially impermeable by the material to be screened to limit the movement of material being screened away from the screen during the screening operation said baffling element resting upon the screening surface.

6. In a high speed vibratory screening device a frame in which is mounted screening means, a supporting element of spring material for one end of said frame, means supporting the other end of said frame to permit movement, and means for vibrating said spring member at a high speed with a hori-' zontal amplitude whereby vertical reciprocation of the screen means is effected, in combination with a baffling element substantially impermeable by the material to be screened to limit the movement of material being screened away from the screen during the screening operation.

7. In a high speed vibratory screening device a frame in which is mounted screening means, a supporting element of spring ma terial for one end of said frame, means supporting the other end of said frame to permit movement, and means for vibrating said spring member at a high speed with a horizontal amplitude whereby vertical reciprocation of the screen means is effected, in combination with a baflling element sub stantially impermeable by the material to be screened to limit the movement of material being screened away from the screen during the screening operation, said element being located above the screen and resting upon the screen surface.

8. In a high speed vibratory screening device, a frame in which is mounted screening means, a supporting element of spring material for one end of said frame, means supporting the other end of said frame to permit movement, and means for vibrating said spring member at a high speed whereby generally vertical reciprocation of the screening means is effected, in combination with a baffling element substantially impermeable by the material to be screened to limit the movement of material being screened away from the screen during the screening operation, said element being located above the screen and resting loosely upon it.

9. In a high speed vibratory screening apparatus, a screen supported in a frame, a member flexible throughout its central part and fixed at one end against lateral movement, and contacting with the screen at the other, a rotating element out of balance and supported upon said flexible member and adapted to vibrate said member at a high speed, in combination with a baflling element substantially impermeable by the material to be screened to limit the movement of material being screened away from the screen during the screening action.

10. In a high speed vibratory screening apparatus, a screen supported in a frame, a member flexible throughout its central part and fixed at one end against lateral movement, and contacting with the screen at the other, a rotating element out of balance and supported upon said flexible member and adapted to vibrate said member at a high speed, in combination with a baffling element substantially impermeable by the material to be screened tolimit the movement of material being screened away from the screen during the screening action, said baffling ele ment being above the screen.

11. In a high speed vibratory screening apparatus, a screen supported in a frame, a member flexible throughout its central part and fixed at one end against lateral move ment, and contacting with the screen at the other, a rotating element out of balance and supported upon said flexible member and adapted to vibrate said member at a high speed, in combination with a baffling element substantially impermeable by the material to be screened to limit the movement of material being screened away from the screen during the screening notion, said baflling element being above the screen and loosely supported upon the screen throughout a portion of its length.

12. In combination with a high speed vibration screen including a frame and a perforated screening surface adapted to be moved at high speed to cause screening ieo action, a flexible balliing element substantially impermeable by the material to be screened adapted to be superimposed upon said screening material above the material to be screened to limitthe movement of said material away from the screen during the screening action, said bafiiing element supported at one end in the screen frame above the screening surface and elsewhere resting freely upon the screening surface.

Signed at Chicago, county of Cook and State of Illinois, this 14th day of May, 192-11 JOHN BLAND.

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