US2679318A - Bar screen having motion imparting members - Google Patents

Description

y 25, 1954 L. E. SOLDAN 2,679,318

BAR SCREEN x-mvmc uonou IMPARTING MEMBERS Filed Dec. 1. 1948 ATTORNEY Patented May 25, 1954 TENT OFFICE BAR SCREEN HAVING MOTION HVIPARTING MEMBERS Lewis E. Soldan, San Diego, Calif., assignor to Productive Equipment Corporation, Chicago,

111., a corporation of Illinois Application December 1, 1948, Serial No. 62,939

1 Claim.

This invention relates to improvements in vibrating equipment. More particularly, this invention relates to improvements in foraminous screens that can be used with vibratin equipment.

It is therefore an object of the present invention to provide an improved foraminous screen that can be used with vibrating equipment.

In the operation of vibrating equipment it is customary to support a foraminous screen between two spaced side walls and to cause that screen to vibrate by applying a controlled vibration to those spaced side walls. Where this is done, and where mixtures of particles of various sizes are placed on the screen, the vibration of the screen will cause the smaller particles in the mixtures to separate from the larger particles and pass through the openings in the screen. The larger particles will remain on the surface of the screen since they are too large to pass through the Openings in the screen, and thus the desired separation of the smaller particles from the larger particles is effected. The larger particles cannot be permitted to remain on the surface of the screen indefinitely since they would soon begin to occupy those portions of the screen which should be kept clear to receive additional quantities of the mixtures of particles of various sizes. The removal of the larger particles from the surface of the screen by inclining the screen at such an angle to the horizontal that the larger particles will work their way downwardly across the surface of the screen in response to the pull of gravity and fall off into a suitable receptacle. While this practice can be followed in many instances, it has been found that in some installations the available space is not great enough to permit the screen to be set at an angle which is sufficiently steep to insure steady movement of the larger particles across the surface of the screen to the drop off point. The larger particles in such instances tend to remain in position on the surfaces of the screen; and that fact reduces the efficiency of the vibratingequipment by limiting the rate at which additional quantities of the mixtures of particles can be placed on the screen. For these reasons, foraminous screens for vibrating equipment which depend solely on their inclination to the horizontal to cause movement of the larger particles to the drop off point are objectionable. The present invention obviates these objections by providing a foraminous screen which has a number of motion-imparting projections on the surface thereof. These projections is customarily effected i extend upwardly above the surface of the screen and will engage the sides of the larger particles on the surface of the screen. That engagement will, during the forward and upward portions of the movement of the screen, cause the screen to impart an upward and forward component of force to the larger particles. This positive component of force will cause the larger particles on the screen to move steadily across the surface of the screen to the drop off point. The effect of the projections is so pronounced that the larger particles can be forced to move across screens that are horizontal, and they can even be forced to move upwardly across screens that are inclined upwardly relative to the horizontal. It is therefore an object of the present invention to provide a foraminous screen withprojections that extend upwardly from the surface of the screen to engage the sides of particles on the screen.

When screens used with vibrating equipment are inclined upwardly relative to the horizontal and are used to move larger particles upwardly across the screens to the drop off point, the particles tend to remain in position or slide backwards down across the screens. This tendency becomes particularly pronounced when the materials are wet and slippery; since the frictional forces between the particles and the surfaces of the screens are not sufficient to enable the screens to impart upwardly and forwardly directed forces to the particles, and in some cases the frictional forces may be so small that the particles will simply Slide down on of the screens. This tendency can be completely obviated by providing those screens with the motion-imparting projections of the present invention; those projections positively providing upward and forward forces to the particles and also constituting barriers to the downward movement of the particles.

It is customary, where the material to be screened tends to resist movement across the surface of the screen, to use screens which are formed from a number of parallel, transverselydisposed wires or bars. Such screen are very useful, but they can not size particles according to length and width; instead, they can only size particles according to width. In those instances where both length and width are to be sized, woven wire screens or woven fabric screens can be used; but those screens are usually incapable of moving the larger particles across the screen to the drop off point unless the screens are steeply inclined relative to the horizontal. However, such inclination is not always possible; and in those installations the woven wire or woven fabric screens can not operate eificiently. Those screens can be made independent of their inclination to the horizontal by providing them with the motion-imparting projections of the present invention. It is therefore an object of the present invention to provide woven screens with motion-imparting projections.

The motion-impartin projections provided by the present invention will be coextensive with one of the dimensions of the screen, and they will extend a sufficient distance above the surface of the screen to engage the size of the particles placed upon the screen. In the case of screens with parallel wires the projections can be welded or soldered to the wires or to the spacers, in the case of the woven wire screens the projections can be welded or soldered to the wires, and in the case of woven fabric screens the projections can be sewn or formed as a rib or seam of the fabric. In each instance, the projections will project above the level of the screen and impart motion to the larger particles on the screen; thereby causing them to move steadily along the surface of the screen.

Where foraminous screens are used to impart controlled vibration to material which is fibrous in character or contains a sizable quantity of fibers or hairs, the fibers or hairs tend to wrap around the transversely disposed wires or bars of the screens. These fibers and hair are hard to remove from the wires or bars of the screen, and they tend to decrease the efiiciency of the screen by progressively decreasing the open areas of the screen. The present invention minimizes the accumulation of hairs and fibers on the screens and yet provides steady motion of the particles across the screens by providing longitudinallyextending sizing wires or bars which underlie transversely-extending, motion-imparting projections on the surfaces of the screens. Because the material moves parallel to the sizing wires or bars, the hairs or fibers will not tend to wrap around the sizing wires or bars but instead will tend to slide off and pass between the wires or bars; and the transversely-extending projec tions, which will cause the material to move, will be so few in number and will be spaced so far apart that the wrapping of hairs or fibers around them will not materially reduce the porosity of the screens. It is therefore an object of the present invention to provide transversely-extending, motion-imparting projections for screens which have longitudinally-extending sizing wires or bars.

'Other and further objects and advantages of the present invention should become apparent from an examination of the drawing and accompanying description.

In the drawing and accompanying description several preferred embodiments of the present invention are shown and described but it is to be understood that the drawing and accompanying description are for the purposes of illustration only and do not limit the invention and that the invention will be defined by the appended claim.

In the drawing,

Fig. 1 is a broken, perspective view of a foraminous screen that is made in accordance with the principles and teachings of the present invenion,

Fig. 2 is a cross-sectional, side view of the screen shown in Fig. 1,

Fig. 3 is a broken, perspective view of another form of foraminous screen that is made in accordance with the principles and teachings of the present invention, and

Fig. 4 is a partial, perspective view of still another form of foraminous screen that is made in accordance with the principles and teachings of the present invention.

Referring to the drawing in detail, the numeral I0 denotes a number of spaced, parallel, transversely-extending wires or bars which are intended to size or grade material placed on the screen, as by permitting the smaller particles to pass between them while preventing the passage the'rebetween of the larger particles. The wires or bars W are elongated, and they extend across the full width of the screen. These wires or bars are spaced apart a distance equal to the diameter or width of the smaller particles which are supposed to pass through the screen, but are positioned closely enough to each other to prevent the passage through the screen of particles withwidths or diameters greater than desired. The wires or rods to are fixedly held in spaced relation by longitudinally-extending spacing bars 12 which are disposed beneath but are connected to the transversely-extending wires or bars Ill. The wires or bars Hi can be secured to the spacing bars H by soldering, welding, brazing or other methods; but soldering is preferred since the low heat required for soldering will not warp or distort the wires or bars l0. The bars l2 not only space the wires or bars in apart the required distance, but they also maintain all of the wires and bars 10 in the same plane; thus providing a uniform surface for the screen. The ends of the wires or bars ID are secured together by end bars 14 which not only maintain the required spacing between the ends of wires or bars l0 but also act to close the ends of the screen and avoid projecting edges.

A number of motion-imparting projection 16, which take the form of elongated bars, are spaced along the surface of the screen. These projections are spaced apart distances greater than their own diameters, they have diameters larger thanthe diameters of the sizing wires or bars 10, and they are secured to the spacing bars i2 and the end frame bars l4. One of the projections I6 is preferably provided at each end of the screen, and a number of them are disposed intermediate the ends of the screen. The various projections I6 respond to the movement of the screen to impart forward and upward forces to the particles placed on the top of the screen; thus causing those particles to pass across the screen and be "graded or sized. The ends of the projections l6 extend upwardly from the plane of the screen and have hook-like portions I8 thereon. These hook-like portions are formed to engage the screen-supporting clamps, not shown, of the vibrating equipment and thus support the screen in position between the upstanding side walls of the vibrating equipment.

When the screen of Figs. 1 and 2 is given a controlled vibration, it will cause the material placed thereon to shift about and be graded" or sized; the smaller particles passing through the spaces between the wires or bars i0, and the larger particles remaining on the surface of the screen. These larger particles will not be permitted to remain in one fixed area on the surface of the screen but instead will positively be caused to move progressively along the length of the screen until they reach the drop off" point and fall oil. In this way, room is provided on the surface of the screen for the placing of additional material to be screened.

The motion-imparting projections i 6 are dominantly responsible for the movement of the larger particles along the surface of the screen; and they can provide this motion because they extend sufiiciently far above the surface of the screen to engage the sides of the larger particles, and because they are disposed transversely of the plane of vibrating movement imparted to the screen. As the screen successively moves up wardly, forwardly, downwardly, and rearwardly in a direction parallel to bars 12 during its cycle of vibration, the upward and forward movement of the screen will raise and simultaneously advance the larger particles. In the absence of the projections It, the screen might not present sufficient effective area to the sides of the larger particles to move them, and the particles would then remain in place. With the projections 26, however, the screen presents sufficient effective area to the sides of the particles to force them to move along the screen. Depending on the amplitude of vibration of the screen, the projections it may cause the particles to move past one, two, three or four wires H) at a time; and thus the particles will work their way along the screen until they reach the drop off point and fall into a suitable receptacle.

The projection 66 cannot extend an unlimited distance above the surface of the screen, because if they did they might trap the larger particles and prevent their movement along the screen.

t the same time, the projections must not be so small that they do not effectively move the particles. A good size for the projections i5 is a diameter twice that of the wires or bars I 0.

The efficiency of the motion-imparting projections It is such that they can cause material to move across horizontally disposed screens and can even cause material to move upwardly across the surfaces of screens which are inclined upwardly relative to the horizontal. Stated another way, the projections not only free the screens from complete dependence upon a steep angle of inclination but also enable those screens to move material uphill against the force of gravity. This is very helpful since it increases the time the material spends on the screen and thereby attains more complete separation per unit of area of screen surface. Moreover, the screen achieves this advantage without permitting the material to come to rest in one place and blind the screen. The screen also is fully operative in a downwardly inclined position; and it is thus extremely versatile and useful.

In Fig. 3 another form of foraminous screen is shown. That screen has a number of parallel wires or bars which are secured to the under surface of motion-imparting projections 22; which projections take the form of elongated bars. The ends of the motion-imparting projections 22 extend upwardly from the surface of the screen and have hook-like portions 24 thereon; and the portions 24 facilitate the securement 0f the screen to the vibrating equipment in the same way the portions IS of Figs. 1 and 2 facilitate such securement. The motion-imparting projections 22 cause material to move along the screen, they support and space the wires or bars 23 and they also maintain those wires or bars in the same plane.

The projections 22 will cause material placed on the screen to move longitudinally of that screen; and this arrangement is particularly 6. beneficial where the material to be screened is of a fibrous character or has fibers or hairs in it. In those instances, the fibers and hairs will move along the wires or bars 20 and will not tend to wrap or wind around them; consequently, the screen will remain remarkably free of hairs or fibers, and will thus not have its open areas closed to any appreciable degree. some hairs and fibers may tend to wrap around the motion imparting projections 22, but those projections are spaced suificiently far apart so the screen as a whole remains porous; and the reduction in the open areas of the screen will be far less than the reductions in area experienced with prior screens. The motion-imparting action of the projections 22 also helps keep the screen free from twisted hairs and fibers since that action keeps the material from coming to rest and having time enough to wind around portions of the screen. The projections 22 will not be as large in diameter relative to the wires or bars 20 as the projections E6 of Figs. 1 and 2 were to the Wires or bars l0, because the projections 22 are wholly above wires or bars 20 instead of being partially coextensive with them. However, the diameters of projections 22 should be between one and two times the diameters of the wires or bars 20.

In Fig. 4, still another form of foraminous screen is shown; and that screen has longitudinally-disposed elements 26, transversely-disposed elements 28, and transversely-disposed motionimparting projections 30. The elements 26 and 28 may be made of metal, fabric, fiber, plastic or the like, and they are woven together to provide a number of openings of uniform size in the screen. The projections 39 will preferably be made of the same material as the elements 26 and 28; metal projections preferably being secured to the tops of elements 26 and 28 by soldering, fabric projections preferably being secured to the elements 26 and. 28 by stitching or by being formed directly from those elements as ribs or seams, and fiber or plastic projections preferably being cemented to the elements 2% and 23. In each case, the projections 30 will extend above the surface of the screen and engage the sides of the larger particles so those particles can be forced to move. This type of screen operates somewhat similarly to perforated-plate screens in the sense that both types size and grade particles for length and width; and perforated-plate screens can easily be equipped with motion-imparting projections.

With the constructions provided by the present invention, blinding of the screen is minimized, and continuous movement of the larger particles of material along the surface of the screen is assured even though the screen is horizontal or is inclined upwardly. This greatly adds to the versatility of the screen by keeping them from being completely dependent on a steep inclinaion.

Whereas several preferred embodiments of the present invention have been shown and described in the drawing and accompanying description, it should be obvious to those skilled in the art that various changes may be made in the form of the invention without aifecting the scope thereof.

What I claim is:

In a vibrating screen having a substantial horizontal screening surface and means to impart vibrating movement thereto in a predetermined plane to move particles longitudinally along said screen, said screening surface comprising a plu rality of spaced, parallel, sizing elements which define a particle-supporting surface and a plurality of motion-imparting members extending across the screen and being straight throughout their length, said members being used with said surface to impart motion to particles on said surface which said sizing elements could not impart to those particles, said members extending upwardly from said surface of said screen to a level above said surface presenting a straight unobstructed surface to impart an advancing force to said particles, said motion-imparting members being parallel to each other and spaced apart a distance greater than the spacing between said sizing elements and being disposed transversely of said plane of vibrating movement imparted to said screen, said sizing elements being disposed in a direction parallel to said plane of vibrating movement imparted to said screen, each of said motion-imparting memhers having a vertical dimension above the screen surface between one and two times the thickness of said sizing elements and extending above said sizing elements to constitute the uppermost screening parts of said screen.

8 References Cited in th file of his patent UNITED STATES PATENTS Number Number Name Date Wulfert Sept. 29, 1885 Scott May 25, 1886 Bestlofl Dec. 12, 1893 Behringer Sept. 24, 1895 Maag May 19, 1903 Ditsworth Aug. 4, 1914 Mitchell -1 June 26, 1923 Somers Nov. 24, 1925 Herrman Nov. 10, 1931 Wettlaufer Nov. 17, 1931 Bradford Jan. 11, 1938 Wantling Dec. 21, 1948 FOREIGN PATENTS Country Date Great Britain Feb. 5, 1920 Italy Sept. 13, 1938

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