US3703995A

US3703995A - Screening apparatus

Info

Publication number: US3703995A
Application number: US124849A
Authority: US
Inventors: Paul G Sullivan; Kenneth H Macleod; Joseph E Kempa
Original assignee: Hanna Mining Co
Current assignee: Hanna Mining Co
Priority date: 1971-03-16
Filing date: 1971-03-16
Publication date: 1972-11-28
Anticipated expiration: 1989-11-28
Also published as: CA949946A

Abstract

Screening apparatus includes a main screen deck having a second screen deck attached to the upper surface thereof intermediate its length. The openings in the second screen deck are larger than the openings in the main screen deck for screening out oversize material and allowing the sized material to fall through for normal treatment on the main screen deck. The oversize material is retained on the second screen deck until the vibrations of the second screen deck or a supplemental breaker mechanism breaks or pulverizes the oversize material to a size which allows such material to fall through the second screen deck and main screen deck for recirculation back through a balling apparatus.

Description

United States Patent Sullivan et al.

[ SCREENING APPARATUS [721- Inventors: Paul G. Sullivan; Kenneth H. MacLeod; Joseph E. Kempa, all of Iron Mountain, Mich.

[73] Assignee: The Hanna Mining Company,

Cleveland, Ohio [22] Filed: March 16, 1971 [21] Appl. No.: 124,849

52 us. ..24l/69, 241/81 1 1451 Nov. 28, 1972 1,997,030- 4/1935 Allsweded ..24l/69 Primary Examiner-Robert L. Spruill Attomey-Oberlin, Maky, Donnelly & Renner 57 a ABSTRACT Screening apparatus includes a main screen deck having a second screen deck attached to the upper surface thereof intermediate its length. The openings in the second screen deck are larger than the openings in the main screen deck for screening out oversize material and allowing the sized material to fall through for normal treatment on the main screen deck. The oversize material is retained on the second screen deck until the vibrations of the second screen deck or a supplemental breaker mechanism breaks or pulverizes the oversize material to a size which allows such material to fall through the second screen deck and main screen deck for recirculation back through a balling apparatus.

16 Clains, 4 Drawing figures PATENTED H I 3103,995-

sumtoFz I INVENTORS PAUL 6. SULLIVAN KENNETH H. MACLEOD JOSEPH E. KEMPA @M MQM 6M ATTORNEYS PATENTED I973 3.703.995

SHEEIEDFZ mu T w INVENTORS PAUL 6'. SULLIVAN KENNETH H. MACLEOD JOSEPH E. KEMP/1 BY flhwgm ATTORNEYS SCREENING APPARATUS This invention relates generally as indicated to screening apparatus particularly for use in pelletizing operations for removal of any oversize green balls or goonies" prior to hardening.

During the pelletizing of iron ore concentrates and other materials, a suitable binder such as bentonite is mixed with the concentrates and the material is conveyed to a balling drum or other balling devicewhere it is compacted into green balls. From the balling device the green balls are directed through an induction or other type heating device to harden the balls into pellets. To ensure high quality pellets, it is important that the size of the green balls be closely controlled, since if the green balls are too large they interrupt the air flow through the bed during heating and do not heat uniformly, whereas if the balls are too small, they fill up the interstices between balls and thus afiect air flow and cause non-uniform heating much in the same manner as the oversize balls.

Undersize balls are readily removed by discharging the green balls from the balling device onto a vibrating screen deck which permits the undersize green balls'to fall through the screen onto a conveyor therebeneath for return to the balling device for reprocessing.

Removal of the oversize balls is ordinarily accomplished by providing a larger size screen at the end of the main screen deck or other means and permits the proper size balls to fall through onto a conveyor for transfer to the heating device for hardening, but not the oversize balls. The oversize balls or goonies. are carried along the larger size screen for discharge onto a separate conveyor which returns them to the system for reprocessing. The disadvantage of removing the oversize balls in this manner is that it requires additional costly conveyor equipment to handle the oversize balls.

With the foregoing in mind, it is a principal object of I this invention to provide a screening apparatus which screens out both the oversize and undersize balls and breaks down the oversize balls or goonies within the framework-of the existing equipment for recirculation back to the balling apparatus for reprocessing.

These and other objects of the present invention may be achieved by providing in addition to the main screen deck for screening out the undersize material, a second screen deck attached to the upper surface of the main screen deck intermediate its length which has larger openings therein than the openings in the main screen deck for retaining the oversize material while allowing the proper size material to fall through for normal treatment on the main screen deck. The oversize material is retained on the second screen deck until broken down or pulverized by the vibrations of the apparatus or by additional breaker mechanism to a size which allows such material to fall through the second screen deck and main screen deck for recirculation through the system for reprocessing.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the an nexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.

In the annexed drawings:

FIG. 1 is a schematic fragmentary longitudinal section through a preferred form of screening apparatus constructed in accordance with the present invention;

FIG. 2 is an enlarged view of a portion of the main screen deck and partial screen deck and breaker mechanism of FIG. 1;

FIG. 3 is a fragmentary vertical transverse section through the main screen deck and partial screen deck of FIG. 2, taken on the plane of the line 3-3 thereof; and

FIG. 4 is a fragmentary top plan view of the breaker mechanism associated with the partial screen deck as seen from the plane of the line 4-4 of FIG. 2.

Referring now in detail to the drawings and first especially to FIG. 1, there is shown a preferred form of screening apparatus 1 in accordance with the present invention for use in pelletizing of iron ore concentrates and other materials. The screening apparatus 1 generally comprises a main frame 2 which supports the main screen deck 3 directly beneath the discharge end of a balling drum or other balling apparatus 5 for receipt of the concentrates after having been compacted into green balls by the balling device. A suitable binder such as bentonite (but not necessarily limited thereto) is usually mixed with the concentrates prior to enteringthe balling device.

The main screen deck 3 is disposed at a slight inclination as shown and consists of a plurality of closely spaced rows 6 of rod sections 7 each having downwardly bent ends suitably supported in vibrating supports 8. Between rows there is a clearance space 9 (see FIG. 3) of a size which permits the undersize green balls to fall through the main screen deck 3 during vibration onto a conveyor 10 located therebeneath for recirculation through the balling device 5. Preferably, such spacing between rows is approximately threeeighth inch for removal of any green balls of a size less than that.

Retained on the main screen deck 3 between side plates 11 are the larger diameter green balls, including any oversized green balls, generally referred to as goonies, which are undesirable feed for the pelletizing plant since they cause process problems and have an undesirable effect on the quality of the pellets for the reasons previously stated. To separate the oversize green balls or goonies from the proper size balls, there is provided a second screen deck 12 attached to the upper surface of the main screen deck 3 intermediate the ends thereof and extending at a slight angle therefrom.

As best seen in FIGS. 2 and 3, the ends of the rods 13 which comprise the second screen deck 12 are desirably supported by rubber holders or other

suitable mechanisms

14 and 15 containing

holes

16 and 17, respectively, which snugly receive the ends of the rods 13. The rubber holder or other suitable device 14 is confined within a metal support channel 18 welded or otherwise secured to the rod sections 7 of the main screen deck 3 at the joined end portions 19 which are desirably vertically staggered as shown. The vertical height of the support channel 18 is such that the top flange 20 thereof is substantially flush with the adjacent ends of the upstream rod sections 7, such support channel 18 desirably being fabricated from an angle which forms the back 21 and bottom flange 22 of the channel. A separate strip welded to the upper edge of the angle constitutes the top flange 20 which may extend at an angle to provide a narrower opening at the mouth 23 of 1 the channel preventing pull-out of the rubber holder 14. 1

The other rubber holder or suitable device may be clamped to a support channel 24 by a clamp bar 25 using suitable fasteners 26. As shown, the support channel 24 has end plates 27 secured to its ends which are fastened to mounting brackets 28 on the side plates 11 for supporting the downstream ends of the rods 13 which comprise the second screen deck 12 vertically above the main screen deck 3.

The spacing 29 between the rods 13 of such second screen deck 12 is somewhat greater than the spacing between the rods 7 of the main screen deck 3. Such spacing 29 may vary within limits to satisfy the specific size requirements of the product but for this purpose it is desirably approximately three-fourth inch. Accordingly, as the larger diameter green balls are advanced along the incline of the main screen deck 3 onto the second screen deck 12 during vibration of the apparatus, the desired size green balls which are threefourth inch in diameter or less will drop through the second screen deck 12 for continued advancement along the main screen deck 3 and discharge therefrom onto a conveyor 30 which transports such desired size green balls to a heating device (not shown) where they are hardened in the usual manner.

The larger diameter green balls or so-called goonie balls are retained on the second screen deck 12 until the impact of the vibrations of the second screen deck or a supplemental breaker mechanism 31 breaks or pulverizes the oversize balls .to a size which allows them to pass through the second screen deck 12 and main screen deck 3 onto the conveyor 10 therebeneath for recirculation through the system. As shown in FIGS. 1, 2 and 4, such breaker mechanism 31 desirably consists of an elongated pipe 32 loosely supported crosswise on the second screen deck 12adjacent the downstream end thereof by a plurality of inverted U-shape retainer rods 33 secured to the upper edge of the support channel 24. Preferably, three such retainer rods 33 areprovided, equally spaced across the width of the second screen deck 12, and such retainer rods 33 are of a size to permit the pipe 32 to bounce up and down due to the vibrations of the second screen deck 12 while confining the pipe to the downstream end of the second screen deck. Any oversize material which reaches the downstream end of the second screen deck 12 is consequently crushed between the pipe 32 (commonly referred to as a masher) and the rods 13 of the second screen deck 12, the broken particles then passing through the second screen deck 12 and main screen deck 3 for return to the system by the conveyor between said rods is reduced. V 3. The screening apparatus of claim I wherein said screen deck as shown to provide a dam for retaining the oversize balls on the second screen deck until sufficiently reduced in size to pass through the second screen deck as aforesaid.

From the foregoing, it will now be apparent that the screening apparatus disclosed herein provides a unique and efi'ective means for removing and breaking down the oversize green balls to permit recirculation through the system for achieving high quality pellets at reduced cost and increased efficiency.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Screening apparatus comprising a first screen deck, a second screen deck disposed above said first screen deck in overlying relationship therewith, said first screen deck being inclined relative to said second screen deck, said secondscreen deck having openings therein of a size for retaining the larger size material deposited thereon and permitting the smaller size material to pass therethrough onto said first screen deck, and a breaker mechanism for reducing the size of the material retained by said second screen deck for passage therethrough thus to obtain a desired size product with minimum oversize which affects both quality and production and cost ofproduction, said breaker mechanism comprising an elongated pipe loosely supported on said second screen deck across the width thereof adjacent the end furthest from said first screen deck, and means for vibrating said second screen deck tocause the larger size material retained on said second screen deck to move toward said pipe and said pipe to bounce up and down for crushing the larger size material between said pipe and said second screen deck.

2. The screening apparatus of claim 1 wherein said second screen deck comprises a plurality of spaced apart rods defining said openings therebetween, said rods in the region of said pipe being covered by tubing to provide a restricted zone in which the spacing elongated pipe is loosely supported on said second screen deck adjacent the end furthest from said first screen deck by a plurality of transversely spaced inverted U-shape retainer rodssecured to said second screen deck, said retainer rods being of a size to permit said pipe to bounce up and down while confining said pipe therebetween.

4. The screening apparatus of claim 1 further comprising means for preventing discharge of the oversize material from the end of said screen deck furthest from said first screen deck.

5. Screening apparatus comprising a first screen deck onto which the material to be screened is discharged, a second screen deck having one end connected to the upper surface of said first screen deck intermediate the ends of said first screen deck, said first screen deck being inclined relative to said second screen deck, means for advancing the material retained by said first screen deck onto said second screen deck for retention of the larger size material on said second deck and passage of the smaller size material through said second screen deck back onto said first screen deck, and a breaker mechanism on said second screen deck remote from the end connected to said first screen deck for reducing the size of the material retained on said second screen deck for passage through said second screen deck thus to obtaina desired sized product with minimum oversize;

6. The screening apparatus of claim 5 wherein said means for advancing the material retained by said first screen deck comprises a vibrator which vibrates said first screen deck.

7. The screening apparatus of claim 5 wherein said breaker mechanism comprises an elongated pipe loosely supported crosswise on said second screen deck remote from the end connected to said first screen deck, and means for vibrating said second screen deck to cause said pipe to bounce up and down for crushing the larger size material between said pipe and said second screen deck, and means for retaining said-pipe on said second screen deck remote from the end connected to said first screen deck without interfering with such bouncing thereof.

8. The screening apparatus of claim 7 wherein said last-mentioned means comprises a plurality of transversely spaced inverted U-shape retainer rods secured to said second screen deck in overlying relation to said pipe.

9. The screening apparatus of claim 7 further comto provide a restricted zone in which the spacing between said rods is reduced.

11. The screening apparatus of claim 5 further comprising means for preventing discharge of the oversize material from the end of said second screen deck furthest from said first screen deck.

12. The screening apparatus of claim 5 wherein said second screen deck comprises a plurality of parallel spaced apart rods defining said openings therebetween, the ends of said rods being supported at one end by said first screen deck.

13. The screening apparatus of claim 12 further comprising a rubber holder for the ends of said rods at one end of said second deck, anda support channel for said rubber holder, said support channel being supported by said first screen deck at the upstream end of said second screen deck.

14. The screening apparatus of claim 13 wherein said first screen deck comprises a plurality of rows of rod sections having vertically staggered end portions, said support channel being secured to said rod sections at said end portions.

15. The screening apparatus of claim 14 wherein said support channel includes a top flange which is substantially flush with the adjacent end portions of the upstream rod sections.

16. The screening apparatus of claim 15 wherein the opening to said support channel is narrower than the back wall thereof to resist pull-out of said rubber holder therefrom.

Claims

1. Screening apparatus comprising a first screen deck, a second screen deck disposed above said first screen deck in overlying relationship therewith, said first screen deck being inclined relative to said second screen deck, said second screen deck having openings therein of a size for retaining the larger size material deposited thereon and permitting the smaller size material to pass therethrough onto said first screen deck, and a breaker mechanism for reducing the size of the material retained by said second screen deck for passage therethrough thus to obtain a desired size product with minimum oversize which affects both quality and production and cost of production, said breaker mechanism comprising an elongated pipe loosely supported on said second screen deck across the width thereof adjacent the end furthest from said first screen deck, and means for vibrating said second screen deck to cause the larger size material retained on said second screen deck to move toward said pipe and said pipe to bounce up and down for crushing the larger size material between said pipe and said second screen deck.

2. The screening apparatus of claim 1 wherein said second screen deck comprises a plurality of spaced apart rods defining said openings therebetween, said rods in the region of said pipe being covered by tubing to provide a restricted zone in which the spacing between said rods is reduced.

3. The screening apparatus of claim 1 wherein said elongated pipe is loosely supported on said second screen deck adjacent the end furthest from said first screen deck by a plurality of transversely spaced inverted U-shape retainer rods secured to said second screen deck, said retainer rods being of a size to permit said pipe to bounce up and down while confining said pipe therebetween.

5. Screening apparatus comprising a first screen deck onto which the material to be screened is discharged, a second screen deck having one end connected to the upper surface of said first screen deck intermediate the ends of said first screen deck, said first screen deck being inclined relative to said second screen deck, means for advancing the material retained by said first screen deck onto said second screen deck for retention of the larger size material on said second deck and passage of the smaller size material through said second screen deck back onto said first screen deck, and a breaker mechanism on said second screen deck remote from the end connected to said first screen deck for reducing the size of the material retained on said second screen deck for passage through said second screen deck thus to obtain a desired sized product with minimum oversize.

7. The screening apparatus of claim 5 wherein said breaker mechanism comprises an elongated pipe loosely supported crosswise on said second screen deck remote from the end connected to said first screen deck, and means for vibrating said second screen deck to cause said pipe to bounce up and down for crushing the larger size material between said pipe and said second screen deck, and means for retaining said pipe on said second screen deck remote from the end connected to said first screen deck without interfering with such bouncing thereof.

9. The screening apparatus of claim 7 further comprising a rubber covering on said elongated pipe.

10. The screening apparatus of claim 7 wherein said second screen deck comprises a plurality of spaced apArt rods defining said openings therebetween, said rods in the region of said pipe being covered by tubing to provide a restricted zone in which the spacing between said rods is reduced.

13. The screening apparatus of claim 12 further comprising a rubber holder for the ends of said rods at one end of said second deck, and a support channel for said rubber holder, said support channel being supported by said first screen deck at the upstream end of said second screen deck.