US3483974A - Bar type screening unit with resilient edge sealing means - Google Patents

Description

Dec. 16, 1969 R. P. PEARSALL 3,433,974

BAR TYPE SCREENING UNIT WITH RESILIENT EDGE SEALING MEANS Filed Feb. 9, 1968 Figure I Figure Rubber Seal S/offed Screen Figure 3 1 Screen Rods Saree/7 Sea/ 57/ Over Ends Figure 4 Rib Support U-Sbaped Edge Seal IV VE/V TOR" Robe/f R Pearsbl/ United States Patent 0 3,483,974 BAR TYPE SCREENING UNIT WITH RESILIENT EDGE SEALING MEANS Robert P. Pearsall, Bloomington, Minn, assignor to Universal Oil Products Company, Des Plaines, Ill., a corporation of Delaware Filed Feb. 9, 1968, Ser. No. 704,340 Int. Cl. B07b l/04 US. Cl. 209-273 5 Claims ABSTRACT OF THE DISCLOSURE An improved form of substantially rigid, knockertype screen unit with resilient edge sealing means. The screen unit is formed of lateral wedge-shaped bar sections providing slots of inverted V-shaped so as to be self-cleaning and longitudinal seals of U-shape crosssection and of resilient material which are elastically clamped over the plurality of opposing ends of the screen bars to thereby provide longitudinal seal means on each side of said panel, whereby the latter may be rapped and vibrated within a circumscribing frame or housing without permitting the passage of finely divided material.

This invention relates to an improved form of screen unit particularly adapted to be rapped or vibrated, when desirable, within an enclosing box or frame. More specifically, the invention is directed to an improved construction for a rigid-type screen panel formed of wedgeshaped bar sections such that there are resulting selfcleaning inverted V-shaped slotted openings and, in addition, longitudinal strips of resilient material are positioned to elastically fit over the plurality of opposing ends of the screen bars to provide seals on each side of the panel section.

Background of the invention The mining industries have recently found that improved methods for screening ores in the very fine size ranges can be of economi advantage over the use of cyclones or more conventional means of making sizing splits. For example, in the treatment of taconite to effect iron concentrate, there is a need to screen material in the 325 mesh range to obtain +325 mesh and 325 mesh material. The approximate 10% +325 mesh material contains most of the natural silica and is preferably eliminated from further processing steps. If cyclone separation means is used for processing the multidensity taconite, the heavier underfiow material may not necessarily comprise the material high in silica. In fact, the high in silica material is usually of middling density and will carry overhead with the light weight material.

As a further aspect of carrying out the improved fine screening operations for taconite, it has been found that it is of advantage to use relatively slow flow rates for the slurry over rigid, structurally strong screen panels which can be periodically rapped to clear blinding or clogging of the screens. For this reason slotted screens that are constructed in a rugged manner of bar members have come into use for this ore treating service.

In a broad embodiment, the invention provides a material screening unit with resilient edge seal means that is adapted to be rapped, which comprises in combination, a slotted screen section formed of closely spaced wedge-shaped bars attached across more widely spaced apart support members to provide slots therethrough of inverted V-shape with an increasing cross-sectional area in direction of flow, and longitudinal edge seal means 3,483,974 Patented Dec. 16, 1969 of resilient material at each side of said screen section and encompassing the ends of said wedge-shaped bars to thereby provide covering means for bar ends as well as opposing longitudinal seal means, whereby the screen section can be rapped and vibrated within a circumscribing housing.

Inasmuch as it is a principal object of the present invention to obtain a unit for use in the screening of extremely fine particles without permitting blinding or clogging, and will be of both rigid and rugged construction, there is therefore provided as part of the present improved design to make use of special wedge-shaped bar members positioned to provide laterally extending inverted V-type slots so that all material which does pass through the slots will continue on in a non-clogging manner. In addition, such bars forming the screen panel will have longitudinal strips of rubber or similar resilient material elastically slip-fit over their opposing ends so as to provide seal means on each side of the resulting composite screen panel unit so that leakage of fines therearound will be prevented.

It has been found that the use of the edge seals of rubber or other resilient material also provide improved vibration characteristics for the screen panel when it is being periodically rapped While mounted in knockerbox or suitable encompassing frame. Actually the preferred design for the rubber seal means of the screen unit embodies longitudinal seal strips of U-shaped cross section. Along each edge portion of the screen unit, the U-shaped seal material will be elastically slipped onto or frictionally held in place over the multiplicity of ends of the wedge-shaped bar members so that each longitudinal edge portion of the screen unit can have a tight fit within a suitable enclosing frame or rapping box. Thus, the interior portion of each of the U sections will be sized to provide a tight slip fit over the ends of the bars and be capable of holding itself in place before as well as after mounting within the supporting frame or box.

It is not intended to limit the invention to the use of any one type of rubber or other resilient material as the edge seal means for the unit; however, in each instance the seal strips should be of sufiicient cross section and of an elasticity or deformability which will insure maintaining a close contact with the inside face of the encompassing frame or box. In lieu of various forms of rubber, certain types of plastics, such as the polyurethanes or polyvinyl chlorides, may serve to effect a satisfactory seal member. As noted hereinbefore in connection with using the present improved type of screen for the processing of taconite in the mining industries, there is the need to effect screening of ores in the 325 mesh range. This means that the screen will have a 0.004" and smaller slot and, consequently the seal between the screen and the enclosing box should have an opening no larger than about 0.004. Still further, the resilient seal strip shall be one that does not interfere with the periodic rapping of the composite screen unit to assist in releasing the blinding or clogging of the screen by the fine particles. Present experience has shown that rubber seals, of the U-shape cross section, will not interfere with a periodic mechanical rapping and, in fact, tend to increase vibration characteristics for the screen unit, particularly as compared with rigid metal edge strips. At the same time the resilient rubber seal means vastly improve the seal to prevent particle flow around the periphery of the screen unit.

Reference to the accompanying drawing and the following description thereof will serve to better describe the improved construction of the composite screening panel as well as point out the advantageous operational features thereof for the processing of finely divided materials.

Description of the drawing FIGURE 1 of the drawing indicates diagrammatically a partial plan view of a composite slotted type of screen section with the end portions of closely spaced bars being encompassed in opposing U-shaped rubber seal members.

FIGURE 2 of the drawing shows, in a partial sectional view, the construction of the end portion of the screen panel, as indicated by line 22 in FIGURE 1.

FIGURE 3 of the drawing shows, in an enlarged partial sectional view, the construction and arrangement of the screen panel along its side with the rubber seal strip in place over the ends of the transverse bars, as shown by line 33 in FIGURE 1.

FIGURE 4 of the drawing is a diagrammatic sectional view indicating the mounting of the present improved form of screen section within a separating and collecting box and means for effecting a periodic rapping.

FIGURE 5 indicates, in a diagrammatic view, the formation of a screen panel into a curved configuration.

Referring now particularly to FIGURES 1, 2 and 3 of the drawing, there is shown a panel unit 1 which comprises a multiplicity of wedge-shaped bar members 2 extending laterally across spaced longitudinal support rods 3. The wedge-shaped bars 2 have their lower edges welded or otherwise fixedly connecting with the top portions of the longitudinally extending rods 3 so as to maintain uniform narrow slots extending laterally across the entire screen unit. The Wide portions of the bars 2 will be along the upper surface, or upstream with respect to a slurry or material flow, whereby there are resulting slots, each in the nature of an inverted V-shape that has a cross-sectional area increasing in the direction of flow. In other words, the slotted portions are of a self-cleaning nature so that all material which does pass through the screen will readily continue on through the entire screen unit and minimize clogging or blinding of the screen surface.

In the present embodiment, as best shown in FIGURE 2, the end portion of the screen panel has the ends of rods 3 and the ends of additional support ribs 4 welded or otherwise joined to the back of a support angle 5. The latter is normally used to advantage in supporting the entire screen panel within a suitable frame or housing which will receive the slurry to be screened over the top surface of a panel section. Both edge portions of the screen section 1 are provided with longitudinal seal strips 6 of rubber or other equivalent resilient material. As best indicated in FIGURE 3, the seal strips 6 are square or rectangular in nature and of a U-shape sized to slip-fit over the end portions of the multiplicity of wedge-shaped bars 2. There are thus provided longitudinal resilient strips that can be held tightly against the inside face of an encompassing frame or box adapted to hold the entire knockertype screen panel. Inasmuch as the seal strips 6 will be encompassed within a suitable framing section, there is no need to have the longitudinal strips actually bonded or bolted to the ends of the bars 2. The partial cross-sectional view of the unit, as shown in FIGURE 3, also indicates rectangular rib support members 4 as being placed directly under and welded, or otherwise attached to longitudinal rod members 3. This construction insures that there is a substantially rigid, non-sagging form of screen section that can take abuse and rapping for long periods of time within a suitable slurry receiving box.

It has been the general fabricating practice to construct the self-cleaning type of screen panels, having the wedge-shaped bars, in a manner where they are automatically welded to rather widely spaced apart rods, such as 3, that are of a size or cross section not greatly different than the bar members themselves. As a result, suitably sized support rib members 4 must be placed in combination with rods 3 in the longitudinal direction so as to provide a non-sagging screen panel. Thus, the depth of the strip members 4 will vary and will be greater for longer finished screen units.

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In the diagrammatic processing arrangement of FIG- URE 4, there is indicated within a box or tank 7, an angularly mounted screen panel such as 1 within FIGURE 1. The box is indicated as having a low interior wall or partition 8 which serves to support the panel 1 from a lower angle member 5' while an upper box portion 9 serves to hold the upper end support angle 5. It is generally conventional to position the screen panels in a sloping position such that the slurry stream passing downwardly over the face of such screen will strike the laterally positioned slots of the panel section at a right angle thereto and at a slope to minimize direct impact against any given portion of the slotted face of the screen unit. In this instance, the slurry outlet 10 is indicated as being available to dis charge a slurry stream 11 down over the face of the panel 1 whereby oversize material will carry to the section 12 at the front end of box 7 and undersize material will carry through the screen panel into section 13 within the back portion of the box. An outlet means 14 with valve 15 provides for carrying separated material from the front end of the box 12, while a similar outlet 16, with valve means 17, provides for the withdrawal of material from the rear zone 13 of the box 7.

Where the panel unit 1 is to effect the screening of finely divided material, then such panel section and longitudinal rubber seal sections 6 will be installed within the box 7 so that the seal members are tightly adjacent the interior faces or the side walls of the box 7 and thus preclude the passage of any particulates around the edge of the screen panel. For example, where the screen unit is effecting the screening of the taconite ore in the 325 mesh range and the slots between bars 2 are less than about 0004, then of course the seal members 6 shall be tightly adjacent the walls of box 7 to likewise minimize any opening to less than .004".

Also, as mentioned hereinbefore, in effecting the fine screening operations it has been found good practice to periodically rap the rigid screen panel to loosen any blinding effect of any fine particulates along the face of the screen. In this instance there is diagrammatically shown a rapper hammer 18 suspended from a shaft means 18 and the use of a weighted actuating means 20 connecting thereto so that there is a periodical mechanical rapping of the underside of the screen panel 1 at any given frequency, which may be 5 to 10 times a minute, or more. The hammer or rapped portion 18 is shown in this case to effect impact against a lateral bar member 21, which in turn may be attached to the longitudinal support rib members such as 4, as indicated in FIGURE 1 of the drawing.

Through the use of the present improved screen member, where the multiplicity of Wedge-shaped bars provide increasing sized V-shaped slots that extend laterally across the unit, with respect to slurry flow, there is a definite increase in efficiency for effecting the desired sizing splits for fine screening operations. Still further, by the use of the resilient, rubber type of seal means over the multiplicity of free ends of the bars 2, there is effected a highly improved and desired form of edge seal means for the entire composite screening panel whereby particles are preeluded from bypassing the panel, even during periodic rapping operations on the panel to eliminate blinding of the screen surface. In fact, it appears that the lateral bar arrangement with the U-shaped rubber seal sections effecting a frictional or elastic clamping over the ends of the bars tends to improve the vibrational characteristics of the screen panel when under rapping conditions in a slurry box.

FIGURE 5 of the drawing merely shows that a panel section with the plurality of laterally extending bars, such as 2', may be formed into a curved configuration for mounting in a slurry handling box or frame. However, in this modified construction the edge seal means 6' will still utilize rubber or other resilient material in a U-shaped cross-sectional configuration and the interior of such U- shape is sized to provide a tight slip fit over the multiplicity of ends of the laterally portioned bars 2, whereby particle bypassing may be precluded along the entire longitudinal edges of the screen panel.

For large radius curved sections of screen panel, the rubber seal sections 6 will not have to be of any premolded or precut construction other than to provide a U-shape, since the longitudinal strip will generally conform to the screen panel edge profile, as provided by the end portions of the bars 2. However, where small radius screens are constructed or where panels may have sharp angular configuration, then edge seal members may have to be prefabricated or cut and rebonded along their length to in turn provide a suitable matching configuration with the end profiles effected by the bars 2' in the resulting panel section. Although the drawing, particularly in FIG- URE 3 thereof, indicates the seal members 6 to be of a square or rectangular cross section, it is to be noted that modifications may be made within the scope of the present invention Without unduly interfering with a satisfactory screen panel operation. For example, the outer peripheral cross section may be oval or substantially circular. In another instance, the cross section may be of a wedge or trapezoidal shape, particularly where it is desired to have a substantially fiat surface in contact with the inner faces of the box or framing section which will encompass the screening panel. It may still further be pointed out that the size of each of the seal members 6 shall be sufiicient to insure a self-holding arrangement when installed Within a particular frame or box. For example, the rubber seal section should be of at least about /4" x such that there is adequate material to encompass the end portions of the lateral bar members 2 and preclude a rapid wearing through or splitting during the severe operational conditions in effecting screening of ores or other abrasive materials.

While the foregoing description has been particularly directed to a screen construction for use in a knockertype box or frame, it is to be noted that for certain types of ores, as for example in the lead and zinc industries, there may be no need to utilize rapping operations. However, the present improved screen construction may still be used to advantage in conventional boxes or holding frames to provide highly efficient screening and/ or sizing.

I claim as my invention:

1. A material screening unit with resilient edge seal means that is adapted to be rapped, which comprises in combination, a rigid slotted screen section formed of closely spaced laterally extending wedge-shaped bars p0- sitioned across and fixedly connecting with the top portions of more widely spaced apart longitudinally extending support members, said bars being uniformly positioned to provide slots of inverted V-shape with an increasing cross-sectional area in the direction of material flow, and each of said bars having opposing free ends which overhang the outermost of said support members, a continuous longitudinal edge seal strip of resilient material of U-shape cross-section at each longitudinal side of said screen section encompassing and slip fitting tightly over the free ends of said wedge-shaped bars to thereby provide both coverings for bar ends and opposing longitudinal seals on the sides of said screen sections, and mounting means for said screen spaced from said longitudinal edge seals, whereby the screen section can be held within a circumscribing housing.

2. The screening unit of claim 1 further characterized in that said screen section has widely spaced apart longitudinal support ribs coextensive with and fixedly attached to said longitudinal su port members below said spaced wedge bars whereby to provide a longitudinally rigid screening unit capable of being rapped without deformatron.

3. The screening unit of claim 1 further characterized in that said slotted screen section is curved and said edge seal material encompassing the ends of the wedge-shaped bars in turn continuously cover the latter to follow the edge profiles of the screen section.

4-. The screening unit of claim 1 further characterized in that said seals are generally square or rectangular and have a slot from one side to provide said U-shape for a slip fit over the end portions of said wedge-shaped bars and the external side faces of said seals are substantially fiat to provide an extended surface contact within a circumscribing housing.

5. The screening unit of claim 1 further characterized in that said mounting means are provided at the end portions of said screen section to permit the latter to be rapped and vibrated within the circumscribing housing.

References Cited UNITED STATES PATENTS 1,380,289 5/1921 Childers 209-382 X 2,374,775 5/1945 Parks 209-395 2,910,180 10/1959 Parks 209-395 2,924,334 2/1960 Hendrickson 209-395 X 2,942,730 6/1960 Fontein 209-273 X 3,042,206 7/1962 Olender 209-405 X 3,194,397 7/1965 Taege 209-394 3,259,244 7/1966 Kaljo et a1. 209-281 X 3.363,769 1/1968 Wilmot et a1. 209-405 X FOREIGN PATENTS 476,880 9/1951 Canada.

TIM R. MILES, Primary Examiner U.S. Cl. X.R. 209-282, 382, 395

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