US3105816A

US3105816A - Rod-type material screening device

Info

Publication number: US3105816A
Application number: US713501A
Authority: US
Inventors: Stanley P Hayden; Cleo B Sheets
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1958-02-05
Filing date: 1958-02-05
Publication date: 1963-10-01
Anticipated expiration: 1980-10-01
Also published as: ES247029A1

Description

S. P. HAYDEN ETAL ROD-TYPE MATERIALTSCREENING DEVICE 2 Sheets-Sheet 1 Fi-lecl Feb. '5, 19 8 1, 1963 s. P. HAYDEN ETAL 5" ROD-TYPE MATERIAL SCREENING DEVICE Filed Feb. 5, 195a ZSheets-Sheet 2 I .umu u m United States Patent 3,105,816 ROD-TYPE MATERIAL SCREENING DEVECE Stanley P. Hayden, Chicago, 111., and Cleo B. Sheets, Hammond, Ind, assignors, by mesne assignments, to Allis-Chaimers Manufacturing Company, Milwaukee,

Wis., a corporation of Delaware Filed Feb. 5, 1953, Ser. No. 713,501 13 Claims. (1. 209-331) This invention relates to screening apparatus. Inone of its forms it is particularly adaptable to screening moist or damp material and selecting the material as to the size of its components.

In adapting the invention to one of its important uses in screening apparatus particularly suited to screening wet iron ore, which normally exerts substantial abrasive action on the screening component, the invention aims to avoid many of the diflicnlties heretofore experienced in attempting to remove for recovery fine particles from sticky iron ore which is high in moisture content.

It usually has been customary in the art to deliver the ore from a bin or hopper and associated conveyor apparatus to a screening mechanism or grating which is subjected to vibration at a reasonably high rate. Then, by moving the ore gravitationally across the screening or grating, a member usually formed of a plurality of bars or rods or of mesh formation, while introducing vibration into the screening frame as a whole the smaller pieces of material moved downwardly over the screening surface are caused to pass outwardly between the bars of the grating or through the interstices of the screen mesh so that any undersized material is separated out and can then be collected by some suitable type of collecting mechanism. Carrying out a process of separation makes possible the recovery of small sizes or the very fine material which then can be sintered and, at a later time, again run through the screening apparatus prior to being supplied to the ore reduction furnace.

Because of the high abrasive characteristics of the ore as it is vibrated upon such a grating or screen for separation as it is moved gravitationally, it has been found that many grating or screen replacements become necessary from time to time due to wear on component parts. It has become almost customary in the past to provide the grating or screening apparatus as a device having numerous rods or bars positioned transversely of a frame in generally equally spaced and parallelly arranged fashion. The spaced bars are held rigidly at opposite sides of the frame and, of course, can be vibrated or moved with the frame proper. By spacing the bars or rods by appropriate distimes it is possible to determine and select the size of the screened particles which can fall therebetween. At the same time, the larger desired material sizes may be removed over the bars or rods to be collected following a passage over the complete series, after which the material is supplied to the ore reduction medium.

At times the gratings or screens have also been formed with a plurality of sets of crossed rods or bars to provide more or less of a mesh, with the bars so arranged both transverse to the path of movement of the ore and also substantially parallel to the gravitational path which the material is to take. Thereover the rigidity of the rod or bar anchoring to the support frame was still maintained so that the screening characteristics were determined by. the formed interstices. Vibrational effects were introduced upon the grating or screening element through a vibrator mechanism. To provide such motion the screen frame is usually spring mounted from a main frame with respect to the vibrating mechanism.

Apparatus of the foregoing type, while heretofore important to the industry, is, nonetheless, expensive to maintain and generally ineflicient because of the high wear factor therein. Accordingly, it is a primary object of the present invention to construct screening apparatus in which the wear factor shall be substantially reduced and the maintenance costs minimized.

At the same time it is a further object of the invention to construct a screening apparatus wherein, through the use of substantially only the same number of component parts as were heretofore used in the prior art, and at a cost which is comparable to gratings or screens now available on the market, both improved screening operation and longer equipment life are assured.

Other and further objects of the invention will suggest themselves from a reading of the following description and claims in connection with the .accompanying drawings in which:

FIG. 1 is an elevational view, largely schematic and partially'in section, to show both the sequence of the operational steps in using the present invention and also to show the structural features thereof;

FIG. 2 is .a plan view of the screening or grating mechanism per se, looking in a direction normal to the plane of the screen as it is shown by FIG. 1;

FIG. 3 is a sectional view, taken along the line 3-3, looking in the direction of the arrows of FIG. 2, and shows the general relationship of the rods and frame members with respect to the apparatus as a whole;

FIG; 4 is also a sectional view through the structure of FIG. 2, taken on the line 44 looking in the direction of the arrows and serves to show the relative arrangement of the vibrating rods, the screen frame; and the drivev unit for introducing vibration;

FIG. 5 is a broken-away view in elevation of a portion of a rack structure for supporting the screening rods, this view being substantially a view of the structure of FIG. 6, looking from right to left on the sheet;

FIG. 6 is a sectional view, taken on the line 6-6 of FIG. 5, to illustrate the relationship between the bar or rod members forming the screen or grating and the posi tioning slots or recesses therefor; and

FIG. 7 is .a vertical section on the shaft center line showing the counter-weight and eccentric drive shaft.

Referring now to the drawings for a further understanding of the invention, it will become apparent that the described screening apparatus utilizes a plurality of rods or bars which are held and located in frame support members having recesses formed in adjacent side walls thereof. The recesses are preferably inthe form of slots having one dimension just slightlylarger than the rod or bar component to be retained therein. The other recess or slot dimension is greater so that by positioning and suitably locating bars or rods in the recesses the supported component is generally freely held and permitted to turn and also to move in the long dimension of the recess. By positioning the support members wherein the recesses or slots are formed at distances from each othersuch that the innermost portion of opposite recesses are spaced by a distance greaterthan the length of the bar or rod to be supported longitudinal movement of the bar is also achieved so that the rods can shift laterally of the support frame. However, even with such rotation and positional shifting the general uniform spacing is retained and if the rods when initially placed in the slots or recesses'are parallelly aligned, that general pattern will be retained even with vibration. Any departures from the precise original alignment will be due to the the material to be screened is usually fed from a supply source to fall upon the screening element. 7 The screening 3 element is usually positioned in sloped relationship to the horizontal so that supplied material falls by gravity along the entire transverse path of the length of the screening element and, in doing so, movestransversely across the various screening bars or rods. Where the screening rods are placed transversely to the downward path of the gravitationally moving material and the frame workis subjected to a shaking motion derived from an appropriate vibrating mechanism the material to be screened rapidly moves from the uppermost 'bar or rod to the lowermost, from which position it is suitably collected by any desired type of collecting component for use elsewhere. Material which is finer than the separation between adjacent bars or rods passes through and between V the bars or rods to be collected as a by-product for recovery. The generally free support arrangement of the bars or rods in the slots or recesses of the supporting frame members permits rod or bar movement longitudinally of the component as well as rotary movement, the latter movement resulting primarily from and being introduced by the falling particles themselves. In addition, movement in a direction having a vertical component is also introduced by vibrating the support frame mechanism.

Referring now particularly to the drawings, and first to FIG. 1 as one particular embodiment which the invention may assume, it will be understood that the invention as described will be directed to a type of mechanism particularly adapted to screen and separate relatively fine and coarse materials. The material'll which will here be considered for illustrative purposes will be ore which is to be reduced to a metal state in a blast furnace, for instance. In this operation, the ore to be screened is contained within a hopper or other suitable component 13 and supplied thereto from any desired source, not shown. The material contained within the hopper then may feed out by moving gravitationally through an exit door, conventionally shown at 15, to'fall upon a conveyor or feeder belt 17, adapted to be moved to pass over rollers 18 and 19, turned by any appropriate form of drive mechanism, not shown. As the material on the feeder belt 17 passes over the end roller 18 it falls by gravity onto a fixed position screen 21, arranged generally in any desired angular position relative to the plane of the conveyor belt,

' such as the approximately 45 position indicated by the drawings. The mechanism for supporting the complete component may be carried in any desired fashion, and

here shown for illustration, one suitable l-beam 22. and angle bracket mountings 23 which support the flooring 23' have been illustrated. The remaining support corn ponents for the screening mechanism proper, the chutes to carry the ore, and the feeder belts will not be shown for reasons of clarity of the drawings.

When material is supplied to fall upon the screen 21, which may be in the form of a mesh having the mesh openings of a size such that particles smaller than some selected size fall therethrough, those particles which actually do pass through are caused to fall by gravity upon the chute 24 and thence pass outwardly through the fun nel-shaped element 25 to fall, as in the illustrated form, upon the conventionally represented conveyor belt 26 from which they are carried to any desired utilization points. That part of the" supplied material or ore which is larger than that which will pass through the screen 21 however must be carefully re-screened to remove loose parts and to achieve this eifect'it falls gravitationally from the upper surface of the mesh screen 21 to reach the screening mechanismproper which constitutes the principal component with which this invention is particularly concerned and which component here is designated by the general numeral 30 on the drawings.

In considering the particular arrangement of the screen 30 reference may be had now to the showings of FIGS.

2 and 3 of the drawings in which a multiplicity of rod or bar members 31, all extending parallel to each other, are to provide the components over whichthe ore passes.

The rods or bars 31 are locationally held at opposite sides of a screen frame which comprises a pair of side members 32 and end members 33 which form the device into a generally rectangularly shaped support frame. 7 In one particular form of the invention an angular bracket member 34- extends longitudinally of each side frame member 32 and is adapted to support a bar or rod rack 35.

As can be seen particularly from FIGS. 5 and 6 the rod or bar rack 35 has formed 'in it a plurality of slots or: Q 7 recesses 37 into which the ends of the rods 31 are adapted f to be positioned. As is evident from the showing'of FIGS. 5 and 6 the slots or. recesses 37 have their vertical dimension greater than thediarneter of the rod or bar element held therein. The horizontal or transverse dimension of the slot or recess'is just slightly greater than the end of the bar or rod to be located therein. Illus:

tratively, if the end of the rod or bar 31 be assumedtobe circular and of /2 diameter at the supported point the width of the slot or recess may be considered to be %.2" which provides sufficient freedom for the supported rod or bar to be rotatably (as well as slidably or vertically) movable within the slot or recess.

The supported rods or bars, when held within the". frame Work provided by the side members 32 and the recesses or slots 37 thereof, and where these members are spaced and held by the end spacing members 33 and supporting or reenforcing members 33, are assembled by positioning one end of each rod into one of the slots of the opposite rod or bar racks. 35, held by the brackets 34 from the side members 32. As can be appreciated from the showing of FIG. 6 in particular,

the rod or bar 31 terminates short of the bottom (here considered adjacent to the side member 32) ofithe recess or slot 37 so that, when assembled, therod can be moved transverse to the long dimension of the frame which is in a direction corresponding to its own longitudinal axis.

The rods or bars are secured within the recesses 3 I by means of the endretainer angular strip 40 which fits over the top of the rod orbar rack 35 andcovers the 3 top of the slot while still permitting freedom of move ment of the rods or bars 31 within the slots or recesses 37. Because extremely long rods when vibrated show 7 a substantial amplitude of movement at the center, du

to the rod elasticity, which tends instantaneously to give the effect at the rod ends of rod shortening and thus 5 introduces a tendency for the rodsto slip out of the slots, the effect of possible displacement of the rod due, .to the rod elasticity and rodbending throughout its length, as well as damping of the vibrational amplitude, can be compensated by the use of .an additional rack member in away of locating means and consequently the bars or rods 31 extend completely across and beyond the recesses.

A cover plate is used toprevent the rods or bars from becoming displaced from the central slots 42. cover plate or central retainer 44 functions in "a manner similar to the angle memberil and is represented par: ticularly in FIGS. 2 and 4. The complete framemenk ber 30, as thus formed, is then suspended between a pair of support beams 43 which are located adjacent to; each edge support 32. Spring suspension of the com plete frame in one form particularly suitable to the stru'ctural features ofthe apparatus is achieved by means of a plurality of 'leaf springs 49. One end of the spring I 7 members is anchored to a support member which is secured to the support beam; 43' orforrned as a part thereof. The opposite end of the spring 49 is secured to an extension of the cross member 33 and thus serves to secure and hold the complete frame with the support beam properly spaced from the side members 32.

The construction provides anchoring the supported unit at the support points 50 with spring suspension from the free ends of the generally cantilever type leaf springs 49 so that vibration introduced in any desired manner upon the frame as a whole will be absorbed by the springs and whereby the frame 39, as a whole, may be vibrated relative to the support beams 48.

Various methods and devices for introducing vibration upon the frame as a whole may be provided. in one convenient form of apparatus a motor 51 may be based upon a support bracket 52, extending outwardly from the frame. The motor driven driving pulley 55 (usually secured to the end of the armature shaft) drives a second pulley 55 by way of the indicated driving belt 57.

The driven pulley 55 is keyed to a shaft 59 supported in a suitable bearing conventionally represented at 60, which is held on the support frame member 48. The driven shaft 59 extends transversely of the frame formed by the side members 32 and the end members 33 and is held at its opposite end in a second bearing 62, held upon the opposite support member .8, with the bearing 62 being generally similar to that shown at 60.

If reference now be made to FIG. 7 it will be appreciated that this figure shows the opposite end of the driven shaft from that shown connected to the driven pulley 56. From an inspection .of the drawing it will ecome apparent that the bearing member 62, as shown, includes the self-aligning main bearings 63. The general assembly of this drive and the bearings may be of a type sold by Hewitt-Robin's, Inc, of Passaic, N.I., and which is describedin literature published by such organization. The driven shaft 59 has a section 65 located inwardly from each end and at a region to include each side frame member 32 (see FIG. 7) which is formed eccentric to the main shaft and which is supported within the eccentric bearing 66, as indicated. The bearing 66 is positioned within a tubular vibration housing 67. The tubular vibration housing 67 is then secured to the side member 32 of the frame by any suitable means, such as the indicated bolts 68. The portion of the driven shaft 59 shown by FIG. 7 to the right of the eccentric region 55 and designated at 71 is the usual driven shaft and is concentric with shaft 59. The arrangemerrt of the shaft with its eccentric portion at the opposite end (that is near bearing 6%)) is like FIG. 7 but, of course, reversed so that shaft 71 of FIG. 7 will become apart of the shaft which extends to the left of the side member 32 shown to the left of bearing 60.

The apparatus being so arranged it becomes evident that rotation of the shaft 59 (and of course its section 71) as a whole and with it the eccentric portion 65 causes an eccentric motion of the tubular vibration hous ing 67 which is translated as a vibration or shaking of the side members 32 and the complete frame 30 used to support the transverse rods 31. This vibrational motion causes the rods 31 located within the recesses 37 to move up and down 'as the motor drive is provided.

A counter weight assembly, conventionally shown at 73, is also secured to the shaft 59 at each end. The counter weight device consists preferably of a pair of counter weight arms serving generally similarly to a fly wheel with the arms being tightly secured to the shaft by any appropriate form of clamping mechanism. Structure of this general type is also shown and used in the already mentioned Robins conveyors. .With this arrangement the drive motor 51, driving pulley 56 through the belt 57 causes the shaft 59 to rotate and, of

course, with it, the shaft section 71,- held within the tubular housing 67. The tubular housing has an internal diameter such that allowing for the eccentricities of each shaft section 65 causing movement of the housing relative to the shaft section 71, the shaft section 71 is still maintained free and clear of the inner wall. The counter weight assembly 73 which rotates with the shaft is housed within a counter weight housing 75, shown ateach end of the shaft and positioned adjacent to the bearings 60- and 62, as the case may be, This counter weight thus serves to counter-balance the effect of the eccentric portions 65 of the drive shaft.

So arranged, it will be appreciated that the material falling onto the screen 30 from the mesh screen 21 comes to rest at first on one ofthe rods or bars 31 nearest the top of the screen element 30. At this time the screen as a whole is being vibrated by the vibrating mechanism hereinbefore described and the vibration of the screen is absorbed by the spring members 49. With vibration the loaded material tends to move relatively rapidly downwardly over the various rods orbars 33. toward the lowermost end 77 of the screen, there to be discharged into the generally funnel-shaped receiving member 78 from which it may pass to the conventionally represented conveyor 79'. The conveyor 79, here in the form of a belt, may be driven to move forward to any appropriate receiving means or, in the alternative, the material discharged from the end 77 of the screen may fall upon load carriers or platforms for further utilization.

As the material moves from the uppermost end of the screen mechanism 39 toward the lowermost or discharge end 77 thereof and with the screen vibrating as shown, the tendency is for the rods or bars 31 to move I through the slotsor recesses 37 in the direction so that the maximum amount of motion is permitted. Although the slots or recesses as indicated will not extend straight up and down, with the screening device 30 held at the angle shown by FIG. 1, nonetheless it can be appreciated that the movement of the rods or bars 31 includes a vertical component of motion. The bars 31 a l-ways tend to return to the lowermost position in the slot or recess 37 under the force of gravity. At the same time with the material moving downwardly over the bars or rods 31, the looseness of positioning of these elements within the slots or recesses 37 permits the bars or rods both to rotate Within the recesses or slots and, at the same time, to shift axially of the rod or bar members with the amount of shift being determined by the amount of play, within the recess. This ability of the rods both to turn, tomove up. and down, and to shift longitudinally, assists to a substantial extent the progress of the material across the screen. At the same time the several motions tend, by reason of the abrasive action of the material on the rods to make the rods self-cleaning. Further than this, it will be appreciated that the mere turning of the rods or bars, as well as their up and down movement and longitudinal shifting, tends to prevent clogging of any of the spaces between adjacent rods or bars so that small sized material can readily be removed from the upper surface and fall between adjacent bars to be collected on the collector belt or conveyor 26 after passing outwardly through the chute 25.

The arrangement herein provided also insures rapid replacement of worn components in that wornrods may be readily replaced merely by removing theend retainer flanges 40 which uncover the open ends of the various slots or recesses 37. If center retaining strips 44 are used, these likewise can be removed to permit removal and replacement of the rods 31 and then replaced following the replacement of the rods.

The rods 31 individually consist preferably of rolled material'and these may be cut from long stock or they may be made or formed originally to the desired length,

that being a length greater than the distance separating the most closely adjacent edges of the bar or rod racks 34 positioned at opposite sides of the screen frame and less than that distance which separates the screen frame members 32 at opposite sides of the screen. i

It will be appreciated from the foregoing that the recesses or slots 37 are spaced substantially uniformly along the length of the bar or rod rack 35. The centerto-center separation of the slots is, of course, necessarily greater than the diameter of the rods Whose ends are to be supported in the slots or recesses, but depending upon the uses desired may be only slightly greater or considerably greater. Where it is desired that th screening be such as to permit only very fine material to pass between the rods or bars 31 to fall into the chute 25 it is, of course, apparent that the slots or recesses will be closely spaced so that proportional separation may be provided between the rods.

At times it becomes important that considerably coarser material shall be screened out of the supplied material. For such purpose considerably greater spacing the center-to-center spacing of the recesses. Usually, because of the weight of the material passed over the between the rods 31 must be allowed -which increases rods of the screening device 3%, it is desirable that the openings between adjacent rods shall not exceed, generally speaking, a distance approximating to the rod diameter, although this criterion is not a limitation of the invention. From the practical aspect, however, as the invention is used in the form here disclosed, it is usually preferable to provide the center-to-center spacing of the slots or recesses 57 at a maximum of approximately twice the diameter or" the screen rods 31. This spacing provides a good working embodiment which has been found to be satisfactory, for the coarsest t as of screening. For extreme conditions, however, greater spacing may be allowed, although usually it is to be preferred that such space increases between rods shall be made along with increased sizes of the rods themselves.

Where desired, of course, the recesses can be formed in other fashions than that herein described, provided, of course, that the assembly may be according to a form of arrangement modified slightly from that here disclosed.

The invention has here been described. in a form Where it has been used solely for screening. However, it will be appreciated that without departing from the principles herein set forth the invention is useful for sorting. Illustratively, for some types of sortingor segregating material of different sizes a plurality of devices like that here disclosed may be used with the discharge, for instance, trom the chute 25 then falling into a receiving element analogous to the screen 21 to which the material falls from the conveyor belt 17 and from which element the material may then pass across gratings for screening components like that here described. In such cases the spacingbetween the rod or bar members of the grating or screening elements be comes progressively smaller from unit to unit in order that articles of progressively smaller size may be selected and segregated from a large mass. Illustratively, one form of sorting which may be readily accomplished by duplication of the herein described arrangement may be that of sorting ball bearings formed in various sizes where the largest elements will be collected on a conveyor, such as that shown at 79, the next larger size will be collected, after passing across a grating generally similar to that shown at 39, onto a separate conveyor, and so on, until the sorting has reduced the supplied material into the desired number of size classifications.

Various other modifications, of course falling fairly Within the spirit and scope of that one modification herein set forth and described, may be made. Having now described the invention, what is claimed 1. A screening apparatus comprising a frame; having end and side members secured together, a rod rack supported substantially adjacent to each side member, each rod rack having a plurality of uniformly spaced rod-receiving openings extending inwardly thereof and along the rack for a distance of substantially the rack length, a plurality of screening rods, each rod being positioned with its opposite ends located within opposite frame rod-receiving openings, the plurality of rods extending substantially parallel to each other, the centerto-center spacing of adjacent rod-receiving openings determining the screening of material, each rod-receiving opening being larger than the end of the supported rod held therein by an amount sufiicient to permit free rotary and sliding movement of the rod therein, and a retain} ing member to maintain the rods within the rod-rcceiv ing openings.

2. The apparatus claimed in addition, means to vibrate the frame.

3. A screening structure comprising a pair of racks each having a plurality of substantially equally spaced slots extending along, one side thereof with the long dimension of each slot transverse to the long dimension of the rack and extending for a distance greater than the slot Width, the spacing between adjacent slots being such that adjacent walls of adjoining slots are spaced by a distance less than a slot width, means to space the racks from each other, means to close the remote ends of the slots of each rack, a plurality of removable rods adapted to be located in the slots, each rod having one of its ends located in a slot of one rack and its opposite end located in the corresponding slot of the other rack and all rods being arranged to extend substantially parallel to each other when so located, each rod having a length less than the separating distance between the slot closure members and greater than the separating distance between the open ends of the slots of each rack member, each slot having its small dimension sufiiciently greater than the rod diameter to permit the rod to refate and slide Within the slot substantially without bind-. ing, and a cover plate extending across the top of each.

slot to retain therein the rods positioned within the slots, there-by to permit rolling movement of the rods within the slot as Well-as movement along the rod axis and in p a direction having a ventical component.

4. The apparatus claimed in claim 3 comprising, in additi0n,-rneans to vibrate the frame.-

5. A screening structure comprising a material receiving screen member supported in a plane bearing in angular relationshipless than to a vertical, the receiving screen member comprising a frame having end and side members, the side members having a plurality of rodreceiving recesses formed in adjacent Walls facing toward each other, each of the recesses being elongated with its long dimension extending transverse to the side member length, a plurality of screen rods having end diameters approximating the recess widths and slightly less than said widths, each rod being of a greater length than theseparating distance between adjacent edges of the ho ing side members and of a length less than the sum of the widths of the side members and the spacing distance between'f acing edges thereof, the ends of the rods being positioned in opposite recesses to locate the rods in substantially coplanar uniformly spaced parallel array, the

assembly being such that material placed upon the rods gravitationally moves transverse to the rod length and across the rods, so that material of a size smaller than the rod spacing passes through between the rods and larger material passes over all of the rods to be discharged in the lowermost rod of the plurality, and means for vibrating the assembly to provide movement of the rods within the slots, rotary movement of the rods, and lon gi- I tudinal movement of the rods within the recesses. V

6. The apparatus claimed in claim 5 comprising, in addition, means located between the rod-locating slots for limiting the amplitude of vibration of the rods, t

7. The apparatus claimed in .claim 6 wherein the vibration limiting means comprises a slotted member having rod-receiving slots spaced to correspond to the rod spac claim 1 comprising, in

ing and adapted to have one rod of the plurality positioned in each slot of the slotted member and means to prevent the located rods from moving without the central slotted member with vibration.

8. A screening apparatus comprising a frame having end and side members secured together, a rod rack supported substantially adjacent to each side member, each said rack having a plurality of uniformly spaced recesses extending inwardly thereof for substantially the rack length and each adapted to receive and locate one end of a screening rod, a plurality of screening rods each positioned with opposite ends located in opposite recesses and each rod extending substantially parallel to each other rod, the recesses being spaced from each other so that the center-towenter spacing of adjacent recesses is less than twice the diameter of each supported rod and greater than the diameter of each supported rod, each slot width being larger than the diameter of each supported rod held therein only by an amount sufficient to permit free movement of the rod within the slot, and a retaining member covering the top of each slot to prevent rod movement out of the slot.

9. The apparatus claimed in claim 8, comprising, in addition, means to vibrate the frame.

10. A screening structure comprising a pair of racks each faced toward each other, means to hold the racks in the said facing position, each of the racks having a plurality of substantially equally spaced elongated slotted recesses formed therein and extending along the length thereof with the long dimension of each slotted recess being transverse to the rack length, a plurality of screening rods each having an end diameter less than the width of each slotted recess, one end of each rod being located in a slotted recess of one rack and the opposite end located in the slotted recess of the other rack, all of the rods being located to extend substantially parallel to each other, each rod having a length greater than the separating distance between the near surfaces 'of the pairs of rack members and less than the separating distance between the innermost portion of each slotted member so that when the rods are positioned within the slotted recesses they are retained in a position wherein rolling movement of the rods within the slotted recesses as well as longitudinal and vertical movement of the rods therein is achieved with screen structure vibration and gravitational movement of material thereover in a directiontransverse to the rod axes.

11. A screening structure comprising a pair of racks each faced toward the other, means to hold the racks in the said facing position to form a rod-support frame, each of the racks having a plurality of substantially equally spaced elongated slotted recesses, the recesses being arranged in aligned formation and extending along the racks substantially from end to end with the long dimension of each slotted recess transverse to the rack length, a plurality of screening rods each having an end diameter less than the width of each slotted recess, one end of each rod being located in a slotted recess of one rack and the opposite end of each rod located in a slotted recess of the other rack and all rods being positioned to extend substantially parallel to each other and in substantially coplanar relationship when at rest, each rod having a length greater than the separating distance between the near surfaces of each pair of rack members and a length less than the slot regions of maximum spacing apart so that, when the rods are positioned within the slotted recesses, they are retained in a position wherein rolling movement of the rods within the slotted recesses as well as longitudinal and vertical movement of the rods therein is achieved with screen structure vibration and gravitational movement of material thereover occurs in a direction transverse to the rod axes to produce rotary rod motion.

12. A screening apparatus comprising a rectangular frame having end and side members secuned together, each side member having a plurality of uniformly spaced rod-receiving openings extending inwardly thereof for the major portion of its length, a plurality of screening rods each having [one end positioned in one opening of one side member and its opposite end positioned in an opening of the opposite side member so as to extend substantially parallel to the end members, the outer diameter of each rod at its end portion which is positioned within the side member openings being sufii-ciently smaller than the side member opening to permit movement therein with each rod being held in a position substantially parallel to each other rod when so positioned within the openings, the center-to-center spacing of the rod-receiving openings being greater than the maximum diameter of the screening rods and determining the screening characteristic, each rod being shorter than the distance between the outer ends of each side member and longer than the least distance between the inner edges of opposite side members so that the rods may move 1ongitudinally-along their axes when held within the openings and may vibrate in a plane normal to the longitu dinal rod axis and also may rotate Within the rod-re ceiving openings, and means to vibrate the assembly to induce combined rod movement in the said two directions and rod rotation.

13. A screening apparatus comprising a rectangular frame having end and side membens secured together, a plurality of elongated grid members extending in the same general direction, a journaled coupling between each grid member and each side member, a journal for each coupling having a given inside diameter, a journaled element for each coupling fitted into its respective journal and of substantially less outside diameter than the given diameter of its co-operating journal, each journaled element being free to rotate with respect to its journal to permit the grid member associated therewith to rotate and be freely shiftable transverse of its axis, the center-to-center spacing of said grid members being greater than the maximum dimension of said members transverse of their axes, each grid member being free to move longitudinally of its journaled couplings, and means to vibrate the assembly to induce combined grid member movement transverse and longitudinal of the grid member axes.

References Cited in the file of this patent UNITED STATES PATENTS I 510,642 Hurst Dec. 12, 1893 781,493 Clements et al. Jan. 31, 1905 1,025,791 Donges May 7, 1912 1,343,292 Turner June 15, 1920 2,080,884 Anderson May 18, 1937 2,458,887 Winters Jan. 11, 1949 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 105,816 October 1, 1963 Stanley P. Hayden et a1.

It is hereby certified that error appears in the above numbered patent req'iiring correction and that the said Letters Patent should read as corrected below.

Column 7, line 19 strike out "between the rods 31 must be allowed which increases" and insert the same after "spacing" in line 16, same column 7.

Signed and sealed this 14th day of April 1964.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims

1. A SCREENING APARATUS COMPRISING A FRAME HAVING END AND SIDE MEMBERS SECURED TOGETHER, A ROD RACK SUPPORTED SUBSTANTIALLY ADJACENT TO EACH SIDE MEMBER, EACH ROD RACK HAVING A PLURALITY OF UNIFORMLY SPACED ROD-RECEIVING OPENINGS EXTENDING INWARDLY THEREOF AND ALONG THE RACK FOR A DISTANCE OF SUBSTANTIALLY THE RACK LENGTH, A PLURALITY OF SCREENING RODS, EACH ROD BEING POSITIONED WITH ITS OPPOSITE ENDS LOCATED WITHIN OPPOSITE FRAME ROD-RECEIVING OPENINGS, THE PLURALITY OF RODS EXTENDING SUBSTANTIALLY PARALLEL TO EACH OTHER, THE CENTERTO-CENTER SPACING OF ADJACENT ROD-RECEIVING OPENINGS DETERMINING THE SCREENING OF MATERIAL, EACH ROD-RECEIVING OPENING BEING LARGER THAN THE END OF THE SUPPORTED ROD HELD THEREIN BY AN AMOUNT SUFFICIENT TO PERMIT FREE ROTARY AND SLIDING MOVEMENT OF THE ROD THEREIN, AND A RETAINING MEMBER TO MAINTAIN THE RODS WITHIN THE ROD-RECEIVING OPENINGS.