US3252573A - Cleaning device for vibrating screens - Google Patents

Description

May 24, 1966 J. J. ASSINCK ETAL 3,

CLEANING DEVICE FOR VIBRATING SCREENS 2 Sheets-Sheet 1 Filed Nov. 28, 1962 ANTON B'. ASS/NCK Al'torn e y y 4, 1966 J. J. ASSINCK ETAL 3,252,573

CLEANING DEVICE FOR VIBRATING SCREENS Filed Nov. 28, 1962 2, Sheets-Sheet 2 Inventors JOHN J. ASS/NCK ANTON B4 ASS/NCK Attorney United States Patent M 3,252,573 CLEANING DEVICE FOR VIBRATING SCREENS Joseph John Assinck and Anton Bernard Assinck,

Markham, Ontario, Canada 1 Filed Nov. 28, 1962, Ser. No. 240,594 2 Claims. (Cl. 209388) This invention relates to a cleaning device for vibrating screens. It is particularly directed to providing a brush assembly which is adapted to maintain the openings of the screen cloth clear of obstruction and clogging or blinding. Vibrating screens are well known and arewidely used for separating granular material of desired particle size from oversize or undersize particles or for classifying granular material according to the size of the particles.

There are a number of types of vibrating screens which are available to industry. In general, they may be divided into two distinct types, the mechanically actuated screen in which the screen frame is oscillated in a circular, elliptical or reciprocating motion by the rotation of an eccentrically mounted or unbalanced shaft assembly which carries, or is carried by, the screen body, and the electrically driven screen in which the screen body of the screen cloth is vibrated at high speed in a vertical plane by the action of an electric motor or by magnetic impulses. The cleaning device of this invention can be employed with advantage in the operation of both mechanically and electrically actuated vibrating screens.

The screen cloth usually is woven or otherwise formed of metal or fabric with holes or openings of a predetermined size. The size of the openings is, of course, determined by the size of the particles to be passed through the screen, the undersize fraction, and the size of the particles to be retained on the screen, the oversize fraction. The size of the screen openings may vary over a very wide range, for example, from several inches to 0.0015 inch, United States standard 400 mesh screen. i

There is a problem in the operation of vibrating screens in that particles of the material being screened tend to become lodged in the screen openings and thus tend to close those openings to the passage of further particles with reduction in the productive capacity of the screen and the efiiciency of the screening operation. This problem is particularly acute in screening wet or damp material and is progressively aggravated as the size of the screen openings is reduced.

We have found that the problem of the clogging, or blinding, of the screen openings can be reduced by the provision of a brush disposed longitudinally with the long axis of the screen and reciprocated laterally across the upper surface of the screen cloth. Thus brush serves to distribute the material to be screened uniformly over the entire screen area to better utilize the full screening area, dislodge particles which may have become lodged in the screen openings, and facilitate the passage of undersized particles through the screen openings.

Also, we have found that even furthercleaning action can be obtained by providing means for the brush to oscillate transversely of its long axis as it reciprocates laterally across the upper surface of the screen cloth thereby providing a beating sweeping action of the brush upon the screen.

Further, we have found that by employing a means for releasably positioning the brush relative to the screen whereby the inter-engagement of the bristles of the b r ush and of the screen fabric is controlled, while allowing complete freedom of disengagement, we obtain reduced wearing of the brush and of the screen.

Moreover, since the present apparatus requires a mini- 3,252,573 Patented May 24', 1966 to co-operate therewith without alteration of the vertical spacing of the decks.

The cleaning device for vibrating screens of this invention comprises, in general, an elongated brush, secured to and carried by a brush holder with the brush extending longitudinally of and in contact with the screen, means for advancing the brush laterally in a reciprocating motion across the width of the screen, and means for adjusting the brush in a vertical plane relative to the screen cloth.

An understanding of the cleaning device for vibrating screens of this invention can be obtained from the following detailed description, reference being made to the accompanying drawings, in which:

FIGURE 1 is a perspective view of a vibrating screen which incorporates one embodiment of our invention;

FIGURE 2 is a perspective view, partly broken away, of the brush supporting means at one end of the screen assembly;

FIGURE 3 isa schematic view of the hydraulic system employed to actuate the drive pulleys; and

FIGURE 4 is a perspective view of another embodiment of our invention, illustrating means which impart an oscillating motion to the brush.

Like reference characters refer to like parts throughout the description and the drawings.

The cleaning device of this invention is described as applied to an electrically actuated vibrating screen in which high speed vibrations are imparted by an electric motor or by magnetic impulses. Such screens vibrate in a plane vertical to the screen cloth, for example, a straight line movement of about $6 of an inch. The vibrations may be at a rate of from about 1,000 to 10,000 per minute. It will be understood, however, that the cleaning device can be applied to other types of screening devices, such as mechanically vibrated screens and bolters. Also, the brush is described as extending the full length of the screen. It can be divided into two or more sections and the frame modified accordingly without departing from the scope of the invention.

The vibrating screen illustrated in the drawing is a conventional electrically vibrated screen and is comprised of a support frame 10 and side plates 11. Screen cloth 12, which is well known in the art, is secured to frame 10 by plates 13. The term screen cloth as used herein is intended to include woven or unwoven materials which are formed with openings of specific sizes and used in screening operations. Usually the screen cloth is formed of woven wire but for extremely fine sizing operations other materials such as natural or synthetic fabric materials may be employed. Bars or rods, not shown, extend the length of the frame and are provided to stretch the screen cloth taut and impart a slight camber or curvature to it according to conventional practice. The screen cloth, or the entire screen frame, is vibrated, either electrically or mechanically according to conventional practice by a conventional vibrating assembly which, as it forms no part of this invention, is not shown.

As illustrated in FIGURE 1, the brush 15 extends above the screen fabric 12 the length of the screen. This brush may be in the form of bristles of fine wire, hair or natural or synthetic fibres or other suitable material having regard to the type of screen cltoh with which it is used. The interior or non-operating ends of the bristles are embedded in and carried by a brush holder 16 which is adjust-able in a vertical plane to position the brush relative to the screen cloth, thus to apply a predetermined pressure on the screen cloth which is suificient to keep the screen openings clear of material being screened with a minimum of wear on the screen cloth.

The brush holder 16 is carried, in a reciprocating motion, across the screen frame in tracks 22-22a which'extend transversely of the screen frame at the ends thereof, the ends of the brush holder being journalled in housings indicated generally by the numerals 2121a. Each housing comprises a pair of spaced plates 17-18 which straddle the track and are secured togetherby spaced pins 20. In the modification of the device ilustrated in FIGURES 1 and 2, three pins are provided, two below the track and one above. A roller 19 is rotatably mounted on each pin and is in engagement with the track. Preferably, each of the tracks 22-22a is shaped to conform with the curvature of the screen such that brush 15 bears uniformly against the surface of the screen throughout its lateral travel.

Each end of tracks 22-22a is adjustab ly secured to a vertical post 24, one post 24 being rigidly secured to each corner of support frame by a fillet weld 25, by means of a sleeve 23. Each sleeve is secured to the end of the track by a lap weld 24a such that the sleeve is vertically aligned and slidably mounted on a vertical post 24. Each sleeve 23 can be movably located in any desired vertical position on post 24 by means of a ring-type set-screw collar 23a mounted therebelow such that brush by gravity bears lightly and uniformly along its length against the screen surface.

In the embodiment of our invention illustrated, brush 15 is reciprocated laterally across screen 12 by means of cable and pulley systems 2 8 and 29 which interconnect a pair of opposed single-acting pistons mounted in cylinders 26 and 27 with housings 21-21a.

FIGURE 3 illustrates schematically a hydraulic system preferably employed to drive the pistons in cylinders 26 and 27. Fluid from fluid pump 28a is fed to one of the two pistons while the second piston is exhausting fluid to sump 2911. A double-acting valve 30, controlled by fluid displacement or the like motor means, regulates the feed and discharge of fluid to and from each piston such that the pistons are driven alternatively.

Wit-h reference now to FIGURE 1, the cable and pulley systems are most clearly illustrated by system 28 which is identical to system 29. System 28 comprises a doublesheave pulley 31 which is connected to the piston in cylinder 26 by a rod 32, as shown. Cable 3-3, which is secured at one end to the frame by fastener 34, passes over one sheave of pulley 31 and over pulley 3-5 which is pivotally mounted on bracket 36 secured to one end of track 22. An opening 37 formed in track 22 permits passage of cable 33 therethrough. Cable 33 is secured to one side of housing 21 by means of anchor 38.

Cable 39, which is fastened at one end to the frame at the base of pulley 40, passes around the second sheave of pulley 31, over pulley 40 and is reversed to pass over pulley 41 secured to one end of track 22a. Cable 39 is secured to support housing 21a in the manner as described hereinabove with reference to housing 21. Cable and pulley system 29 is identical to system 28 and connects the piston slidably mounted in cylinder 27 to support housings 21 and 21a.

7 In operation, pump 28a supplies fluid under pressure via valve 30 and connecting lines 41 and 42 to cylinder 26 wherein the piston is forced toward rear end 43 of the cylinder. Connecting rod 32 transmits the longitudinal motion of the piston to pulley 31 which in turn transmits the motion to support housings 21 and 21a via cables 33 and 39 such that the brush 15 is drawn laterally.

across the screen tothe right as shown in the drawing. At the end of the travel of the piston in cylinder 26, which corresponds with' the completion of a forward sweep to the right of brush 15, valve 30 is reversed by motor means activated for example, by an electric switch, not shown. Thus fluid under pressure is supplied to cylinder 27 by way of connecting lines 41 and 44 and fluid is exhausted from cylinder 26 to be discharged to sump 29a by way of connecting lines 42 and 45. The piston in cylinder 27 is connected to housings 21 and 21a by cable and pulley system 29 which transmits the longitudinal motion of the piston to a lateral sweep of the brush which is to the left as shownin the drawing. Since both cable and pulley systems are interconnected by housings 21-21a, the rearward motion of the piston in cylinder 27 is transmitted to the piston in cylinder 26 drawing it into a forward position to exhaust the fluid and prepare it for the next positive cycle. The brush is thus reciprocated laterally across the length of the screen to provide a cyclic brushing action on the screen surface.

The speed at which the brush reciprocates can be readily controlled by regulation of the quantity of fluid discharge and the discharge pressure of pump 28a. The screening of different materials such as wet fire brick clay and sand usually require varying brush speeds to overcome blinding problems and thus a vari-speed pump 28a is preferred.

It may be preferred to impart a sweeping motion to the brush as it is reciprocated laterally over screen 12. FIGURE 4 illustrates an embodiment of our invention wherein rod 59, which is rigidly secured to a central portion of the brush holder 51, is pivotally mounted in and carried by housing 52 by means of bushing 53 which is rigidly mounted in spaced side plates 5556. An extension 57 of rod 50, which extends beyond plate 56, is rigidly connected to one end 58 of an elongated strip 59 such that the centre line a of strip 59 substantially parallel with the centre line of the brush, as represented by a." The opposite end 60 of strip 59 is pivotally connected to one end of linkage member 61 by adjustable lock screw62 which is seated in groove 63 formed longitudinally in strip 59 such that the effective length of the strip can be varied as desired.

'The opposite end of linkage member 61 is pivotally connected to an off-centre portion of the face of rotor 64 by means of a connecting pin 65. Rotor 64 is driven by motor 66 mounted on base plate 67 which is rigidly connected to side plate 56, as illustrated. Housing 52 is carried on track 22.

Referring now to FIGURE 3, pump 28a supplies fluid under pressure by way of pipe line 68 to motor 66. The fluid flow is regulated by valve 69 installed in pipe line 68 between the pump and the motor. Line 70 returns exhausted fluid from motor 66 to sump 29a. A by-pass 71 which connects valve 69 to return line 70 permits the by-pass of fluid around motor 66.

In operation, valve 69 is adjusted to regulate the throughput of the fluid through motor 66 such that rotor 64 rotates at a desired speed. As rotor 64 rotates, in a clock-wise direction as illustrated by FIGURE 4, linkage 61 converts the rotational movement of rotor 64 to the lateral reciprocal movement of the effective end 60 of strip 59. This reciprocal movement is then converted to rotational movement of rod 50, which is rigidly connected to brush holder 51, to impart a sweeping or oscillating motion to the brush 72.

The angular displacementof brush 72, as illustrated by letters [2 and c, is controlled by the positioning of lock screw 62 in groove 63. Since the amplitude of reciprocal travel of screw 62 is constant, the reduction of effec tive length of strip 59 maximizes the angular displacement of rod 50 imparting a maximum oscillating motion to the brush connected thereto. Conversely, the lengthening of the distance between screw 62 and the center of rod 50 has the effect of minimizing the oscillating motion of the brush.

Thus, in this latter embodiment of our invention, not only can the brush be reciprocated laterally across the screen surface, but also the brush can be concurrently oscillated in a sweeping motion. The speed of lateral travel of the brush and the amplitude and rate of oscillation of the brush can each be controlled independently to provide an optimum cleaning action on the screen.

Brush 15 is preferably adjusted to exert a bearing pressure upon screen 12 such that the brush bristles ride light- 1y on the screen fabric to minimize fabric wear while providing maximum cleaning of fabric openings. The brush bristles can be formed of metal or other conventional natural or synthetic material as is customarily used. In the case of screen cloth in the form of drilled or perforated plates, bars and woven wire, metal bristles usually would be employed. It the screen cloth is in the form of woven fabric, bristles of softer material would be employed in the brushes.

We have found that the use of the cleaning device of the present invention in the operation of vibrating screens has many important advantages. Heretofore, the blinding of screen fabrics by oversize particles was the rule rather than the exception. Now, by means of this invention, we have found that the throughput of sized material can be increased manyfold for a standard-sized vibrating screen and, also, can be maintained constant; both factors of which are important in the design and operation of material handling and sizing plants where material balances must be maintained.

Further, the apparatus of the present invention can be readily installed on most single or multi-deck vibrating screens with a minimum of alteration, thereby permitting its use with existing equipment.

Also, it is found that the useful life of the screen cloth is extended by the use of this device. In the use of a vibrating screen, the strands which define the screen openings frequently Wear and break to the extent that the screen cloth must be replaced. It may be that particles which become lodged in the screen openings cut or deform the strands which define the openings. It is found that when screen openings are kept clear of obstructions, the useful life of the screen cloth is extended.

It will be understood, of course, that modifications can be made in the preferred embodiment of this invention as described herein without departing from the scope of the invention as defined by the appended claims.

What we claim as new and desire to protect by Letters Patent of the United States is:

1. A cleaning device for a vibrating screen comprising in combination a brush in contact with the upper surface of the screen, a first hydraulic power means for moving said brush over the upper surface of said screen, at least one cable and sheave system actuated by the hydraulic power means for reciprocally moving said brush from side to side over said screen transversely of the long axis of the brush, tracks disposed over said screen in spaced apart relationship transversely to the long axis of the brush, means movably mounted on said tracks including a brush holder supporting said brush, the ends of said brush holder being journalled in the means movably mounted on said track, a second independent hydraulic power means in the form of a variable speed motor, said motor including a rotor, a link eccentrically mounted on one side of the rotor, a crank fixed to one end of an extension of the brush holder the link and crank being connected together whereby the rotation of the rotor causes the brush through its holder to oscillate transversely of its long axis, oscillation of the brush taking place as the brush moves from side to side of the screen, and means to position the brush to control the degree of inter-engagement of the brush on the upper surface of the screen.

2. A cleaning device for a vibrating screen comprising in combination a frame supporting said screen, a brush in contact with the upper surface of said screen mounted on said frame, a first power means in the form of hydraulic mechanism for controlling the position of said brush on said screen, at least one cable and sheave system actuated by said hydraulic mechanism for reciprocally moving the brush side to side over said screen transversely of the long axis of said brush, at least two tracks disposed above said screen in spaced apart relation transversely to the long axis of the-brush, means movably mounted on the tracks comprising a brush holder for supporting said brush, the ends of said brush holder being journaled in the movable track, a second power means in the form of a variable speed hydraulic motor including a rotor, a link eccentrically mounted on the end of said rotor, a crank fixed to one end of an extension, said extension being attached to said brush holder, the link and crank being connected together whereby the rotation of the rotor causes the brush to oscillate transversely of its long axis, oscillation of the brush taking place as the brush moves from side to side of the screen, posts generally vertically disposed and fixed to said frame, sleeves slidable upon the posts and secured to the tracks, rings slidable upon and securable to the posts under said sleeves whereby the securing of the rings will releasably position the sleeves and thereby locate the track and brush to control the degree of inter-engagement of the brush on the upper surface of the screen.

References Cited by the Examiner UNITED STATES PATENTS 162,269 4/1875 Brown 209-386 564,776 7/1896 Bunden 210-414 887,436 5/1908 ,Smith 209-388 1,536,961 5/1925 McMillen 210-413 1,908,788 5/1933 Pulliam 15-21 2,183,033 12/1939 Segrin 15-21 X 2,537,878 1/1951 Coon 209-388 2,596,518 5/1952 Bahnson -296 2,609,064 9/ 1952 King 55-296 FOREIGN PATENTS 724,773 l/ 1932 France.

1,192,638 3/1958 France.

HARRY B. THORNTON, Primary Examiner.

Claims (1)

1. A CLEANING DEVICE FOR A VIBRATING SCREEN COMPRISING IN COMBINATION A BRUSH IN CONTACT WITH THE UPPER SURFACE OF THE SCREEN, A FIRST HYDRAULIC POWER MEANS FOR MOVING SAID BRUSH OVER THE UPPER SURFACE OF SAID SCREEN, AT LEAST ONE CABLE AND SHEAVE SYSTEM ACTUATED BY THE HYDRAULIC POWER MEANS FOR RECIPROCALLY MOVING SAID BRUSH FROM SIDE TO SIDE OVER SAID SCREEN TRANSVERSELY OF THE LONG AXIS OF THE BRUSH, TRACKS DISPOSED OVER SAID SCREEN IN SPACED APART RELATIONSHIP TRANSVERSELY TO THE LONG AXIS OF THE BRUSH, MEANS MOVABLE MOUNTED ON SAID TRACKS INCLUDING A BRUSH HOLDER SUPPORTING SAID BRUSH, THE ENDS OF SAID BRUSH HOLDER BEING JOURNALLED IN THE MEANS MOVABLY MOUNTED ON SAID TRACK, A SECOND INDEPENDENT HYDRAULIC POWER MEANS IN THE FORM OF A VARIABLE SPEED MOTOR, SAID MOTOR INCLUDING A ROTOR, A LINK ECCENTRICALLY MOUNTED ON ONE SIDE OF THE ROTOR, A CRANK FIXED TO ONE END OF AN EXTENSION OF THE BRUSH HOLDER THE LINK AND CRANK BEING CONNECTED TOGETHER WHEREBY THE ROTATION OF THE ROTOR CAUSES THE BRUSH THROUGH ITS HOLDER TO OSCILLATE TRANSVERSELY OF ITS LONG AXIS, OSCILLATION OF THE BRUSH TAKING PLACE AS THE BRUSH MOVES FROM SIDE TO SIDE OF THE SCREEN, AND MEANS TO POSITION THE BRUSH TO CONTROL THE DEGREE OF INTER-ENGAGEMENT OF THE BRUSH ON THE UPPER SURFACE OF THE SCREEN.

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