US2252304A - Vibrating screen - Google Patents

Description

Aug. 12, 1 941. G. A. OVERSTROM ETAL VIBRATING SCREEN Filed Jan. 6, 1959 2 Sheets-Sheet l m mmTM K S. ommm H Wwas M W R mfiww A X. m r s n u 0 GGC Y B Aug. 12, 1941.

G. A. OVERSTRQM ETAL VIBRATIN G SCREEN Filed Jan. 6, 1939 2 Sheets-sheaf 2 INVENT OR ve A oversH-orn e 0 Vera!- d Over m ATT r-om gram EYS. 3

Gear Can 2 Patented Aug. 12, 1941 olreo STATES TENT OFFICE Eagle Rock, and Conrad Calif.

Overstrcm, Pasadena,

Application January 6, 1939, Serial No. 249,548

3 Claims.

This invention relates to improvements in screening devices of the power driven vibratory type as particularly designed for the treatment of rotary mud, pottery clay, and the like, wherein the screen box has movements in a vertical plane so as to have downward and backward motion at the discharge end during a portion of its cycle.

This invention is concerned with an improvement in screens of this type discovered as a result of practical experience therewith, particularly in the screening of sticky materials where for one reason or another it is not possible to employ a stream of water to wash away the waste. Under these conditions the over-size material which is discharged from the screen cloth at the delivery end of the screen piles up in front of the screen un'tilit reaches the level of the screen cloth. The cross tie members or braces at the discharge end of the screen box cause a backward scraping movement of the over-size material in under the screen box and cloth so that it becomes mixed with the under-size material, that is the material recovered by the screening process for re-use.

This action is particularly true in vibrating screens of the type having a screen box which is resiliently supported for and subjected to free vibration in a vertical plane so that the motion thereof is oval. In a structure of this type a space of course must be left around the screen box to permit such movement thereof, which space provides the place of entry or return of the oversize material by reason of the movement of the screen box back into the troughcommonly used under such screen boxes to collect the under-size or recovered material.

The general object of this invention is to provide a construction in vibratory screens of this type which will prevent the above undesired action while at the same time leave the screen box entirely free for its vibratory screening movement.

Other objects of this invention will be apparent from the following detailed'description thereof.

This invention resides substantially in the construction, arrangement and relative location of parts, all as will be described in full detail below.

In the accompanying drawings,

Figure 1 is a side elevational view of a power driven vibratory screenof the type in which the screen box and cloth are supported for substantially free vibration in a verticalplane and adapted to have an oval motion;

Figure 2 is a front elevational view thereof;

Figure 3 is an enlarged detail cross-sectional view taken on the line 33 of Figure 2, showing the structure of this invention;

Figure 4 is a vertical, cross-sectional view through the flexible element of this invention;

Figure 5 is a front elevational view of a portion thereof;

Figure 6 is a similar cross-sectional view of a modification of the invention herein; and

Figure '7 is a still further modification of the invention herein.

The general screen structure illustrated in Figures 1 and 2 will only be described generally in order that the type of screen to which the invention is applicable may beunderstood without going into the details of the construction thereof. Such a screen usually includes some form of base or supporting frame which is illustrated as a pair of side members I made of any suitable material and connected together by cross braces or ties l2, as well as by the remaining structure as will appear later. These base framers may be made of steel for example and the cross ties welded thereto. The screen box 2 is shown supported on the top of the frame by means of springs 3 of any suitable form to permit vibration of the box in a vertical plane. As is frequently the case, the screen box 2 is made up of side members connectedtogether by cross ties or braces I2 which in this case have been illustrated as angle irons. The box is further braced transversely by reason of the unbalanced rotary vibrating member 4 interconnecting the sides thereof in accordance with well known practice. The screen cloth is shown at 5 mounted in the box and arranged for being placed under tension lengthwise thereof, as will be explained later. At 6 is generally indicated the hopper structure by means of which material is fed into the screen box. The trough under the box is illustrated as comprising a central portion 1 and two extending portions Band 9 so that all the material that falls through the screen is collected in the trough. The trough is provided with one or more side exit chutes it which may be closed by means of sliding doors I l. The screen cloth is attached at the feed end that is the left hand end in Figure 1, to the screen brace 12 in any suitable manner, as is well known in practice. It may be provided for examplewith a U-shaped strip extending across the width thereof attached to the end edge of the screen cloth and hooked overoneside of the angle iron l2 in a manner somewhat similar to that illustrated in Figure 3 for the discharge end of the cloth. Thus at l3 there is shown a U- shaped or hooked metal strip l3 secured to the end of the cloth as for example by welding in those cases where the screen cloth is metal. The hooked end of the member l3 fits over a plurality of stretching devices I4 which may consist of a continuous bar or individual members which have the pieces l5 resting against sockets IS on one flange of the angle iron 12. These stretching devices have a plurality of screws ll threadedly mounted therein and positioned to engage the other flange of the angle iron l2 so that screws I! are driven towards it the screen cloth 5 will be longitudinally stretched in a manner which will be apparent. This is but one commercial way of effecting arrangement and stretching of the screen cloth, there being many other ways equivalent thereto.

It will be seen from Figure 3 that there is a space between the bottom of the lower flange of the angle iron i2 and the upper edge of the trough extension 9 which must be provided to permit free vibration of the screen box. It is through this space, as will be explained later, that the discharged over-size material OS is undesirably worked back into the under-size or collected material collected in the trough under the screen box.

One method of overcoming this diihculty in accordance with this invention is illustrated in Figures 3, 4 and 5. A strip of flexible material l8, which may be fabric, rubber, metal, or the like, is provided along a pair of opposite edges with a strip or bar of some suitable material such as metal, as illustrated at l9 and 2|. In order to minimize wear of th strip l8 the bars l9 and 2| are preferably rounded along their inner edges, and one way of getting this result is to form the bars l9 and 2| from thin strips of metal folded back on themselves as illustrated in Figure 4. On the opposite faces of the strip l8, that is, in alignment with the strips [9 and 2|, are-the bars and 22 which likewise may be of any suitable material, but which do not necessarily require, although they may have rounded edges as previously explained in connection with the strips I9 and 2|. The strip I8 is secured to the strips I9, 20, 2| and 22 by means of rivets for example, as illustrated at 25. Other equivalent and suitable means are available for securing these parts together.

As illustrated in Figure 3, one edge of this strip combination is bolted to the lower flange of the angle iron l2 by means of the bolts 24. The other edge is secured in the following manner. The extension 9 of the trough at the discharge end of the screen is provided with a more or less downwardly extending lip 9' which extends to the cross brace 12 of the base. Secured along the terminal edge of this lip is a reinforcing bar 26 to the outer face of which is secured a series of arms 29. These parts may all be welded to the cross brace I2 and otherwise secured so as to firmly hold them in place. Secured to the outer face of the strip 2|, in any suitable manner as by means of welding for example, are a series of wedge shaped blocks 23 which are positioned to be aligned with the arms 21. Thus this edge of the combination strip 18 is secured in place by positioning it so that the wedges 23 can be driven down into the space between the lip 9' and the arms 21, as clearly illustrated in Figure 3.

A modified method of attaching the strip I8 is illustrated in Figures 9 and 10. The arrangeiii ment of these figures is one wherein the screen cloth, as is frequently the case, is secured in the screen box and stretched transversely instead of longitudinally. In the structure of Figure 9 the cross brace I2 is shown in a different position than one commonly used. In this case as before the upper edge of the strip I8 is bolted to one flange of the cross brace I2 but the other edge is secured to the lip 9' by means of bolts as indicated at 24'. In Figure 7 is illustrated a slightly modified arrangement wherein the strip I8 is applied so as to be curved towards the feed end of the screen box and is secured to the cross brace l2 of the box and the lip 9 of the trough in a manner quite similar to that illustrated in Fig. 6.

With the arrangement of this invention it will be apparent that the objects sought are completely secured without in any way interfering with the action of the screen and in a manner which permits detachment of the projecting strip very quickly when necessary. For example, if it is desired to loosen the lower edge of the strip I8 in the arrangement of Figure 3, it is only necessary to loosen the wedges with a hammer. In the other arrangements the bolts need merely to be removed. It may b noted that the strips 20 and 22 in addition to reinforcing the edge of the flexible strip I8 serve the useful purpose, in the case where that strip is made of rubber or rubberized fabric, of preventing th strip I8 from sticking to the lip 9 and the flange 12. It has been found that with some of these materials when the strips 20 and 22 are not used so that the strip I8 is directly bolted to the angle iron l2 and the lip 9 and left there for a time, that it sticks so badly as to tear when removed.

It will be apparent to those skilled in the art that the details of this invention may be readily varied without departing from the true and novel scope thereof. We do not, therefore, desire to be strictly limited to the disclosure as given for purposes of illustration, but rather to the scope of the appended claims.

What we seek to secure by United States Letters Patent is:

1. In a vibratory screen structure of the type described, the combination which comprises a longitudinally extending screen box mounted for vibratory movement in a closed curved path in a vertical plane and provided with a screen cloth and having a delivery end at which over-size material is discharged therefrom, said vibratory movement being such that said delivery end moves downward and backward at the lower portion of its path; a trough disposed under the screen box to receive under-size material passing through the screen cloth and having a portion whose upper edge is spaced from and below said delivery end of the screen box; and a strip of flexible material extending across the space between said delivery end of the screen box and said upper edge of the trough portion; means detachably securing said strip along one edge to the screen box; a lip extending downwardly from said upper edge of the trough portion; a plurality of arms secured to and spaced from said lip; a pair of reinforcing bars extending along the opposite edge of said strip on the inner and outer faces thereof and rigidly secured together to hold the strip therebetween; and a plurality of outwardly projecting wedge shaped blocks secured to the outer one of said bars, said blocks tapering toward the adjacent edge of the strip and being driven into the spaces between the respective arms and said lip, whereby said flexible strip is held in position to close the space between the delivery end of the screen box and the upper edge of the trough portion and prevent discharged over-size material from being scraped by said delivery end, in its said downward and backward movement, back through said space and into said trough.

2. As an article of manufacture, an elongated narrow imperforate flexible strip having a pair of reinforcing bars secured along each of its longitudinal edges on opposite faces of the strip, one of said bars having wedge shaped members secured to its outer face, each of said wedge shaped members tapering in a direction transverse to the length of the strip and toward the adjacent edge thereof.

3. In a vibratory screen structure of the type described, the combination which comprises a longitudinally extending screen box mounted for vibratory movement in a closed curved path in a vertical plane and provided with a screen cloth and having a delivery end at which over-size material is discharged therefrom, said vibratory movement being such that said delivery end moves downward and backward at the lower portion of its stroke, a trough disposed under the screen box to receive under-size material passing through the screen cloth and having a front wall whose upper edge is spaced from and below said delivery end of the screen box, a strip of flexible material extending across the space between said delivery end of the screen box and said upper edge of the front wall, means detachably securing said strip along one edge to the screen box, a plurality of arms secured to and spaced from said front wall, a pair of reinforcing bars extending along the opposite edge of said s ip on the inner and outer faces thereof and rigidly secured together to hold the strip therebetween, and a plurality of upwardly projecting wedge shaped blocks secured to the outer edge of said bars, said blocks tapering towards the adjacent edge of the strip and being driven into the spaces between the respective arms and said front wall, whereby said flexible strip is held in position to close the space between the delivery end of the screen box and the upper edge of the trough portion and prevent discharged oversize material from being scraped by said delivery end in its downward and backward movement back through said space and into said trough.

GUSTAVE A. OVERSTROM. GEORGE OVERSTROM. CONRAD OVERSTROM.

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