US1999768A - Screening device - Google Patents

Description

April 30, 1935. c. s. LINCOLN 1,999,768

SCREENING DEVICE Filed March 13, 19:51 2 Sheets-Sheet 1 April 30, 1935. c. s. LINCOLN SCREENING DEVICE Filed MarOh lS. 1951 2 Sheets-Sheerl 2 Em M 4 ,muow

Patented Apr. so, 1935 '1,99$,768

UNITED STATES PATENT OFFICE SCREENING nnvrcn Charles S.-Lincoln, Wauwatosa, Wis... assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application March 13,1931, Serial No. 522,354 11 Claims. (01. 209-326) This invention relates in general to theart of; invention will be apparent from a consideration vibratory screen separators and relates more speof the detailed description and of the drawings ciiically to an improvement in a single drive accompanying the specification and forming a shaft screening device provided with an eccentric part thereof on which like or similar reference having means for mounting a single screen or a characters designate the same or similar parts 5.

plurality thereof and arranged to impart vibraor elements throughout the various views. tory movement to said screen. Fig. Us a plan view of a vibratory, single-drive More specifically this invention has for one of shaft screening device having the improved reits objects to provide a resilient rod support for silient rod support associated with an end portion an end portion of the screen of a vibratory screenof the vibratory screen thereof. 10

ing device as related above, said rod support per- Fig. 2 is a side elevation of the device shown mitting a ready adjustment of the inclinationof in Fig. 1 and clearly illustrates the resilient susthe screen with respect to a frame on which the p n means connected to the four corners of vibratory drive shaft and means cooperating the rectangular frame of the device.

25 therewith is carried. Fig. 3 is a vertical cross-sectional view taken l5.

7 Another object of the invention is' to provide along line III-J11 of Fig. 1, looking in the direca vibratory screening device as related above and tion of the arrows. having a substantially rectangular frame sup- Fig. 4 is a sectional detail view of the means for ported by resilient means and having a motor for adJustably securing the resilient rod support to driving the vibratory shaftthereof mounted at the vibratory screen, taken along line IV-IV of 20 one side of said frame with counter-weights at- Fig. 3, looking in the direction of the arrows. tached to an opposite side of said frame' to Fig. '5 is a vertical central broken cross-section counterbalance the effect of said. motor and retakenalong line V--V of Fig. 1, looking in the lated elements and to. maintain the eccentric drive direction of the arrows. I

shaft in the desired horizontal position. Fig. 6 is an elevational view of a flywheel shown 25 7 Another object of the invention is to provide on the eccentric drive shaft in Fig. 5 and shows 7 asingle shaft vibratoryscreening device adapted the balancing plates attached thereto in dotto carry one or a plurality of screens with im dash lines.

proved balancing flywheels having adjusting Fig. 7 is an elevational view of a modified form means for' selectively counterbalancing the of flywheel assembled for three screen or three 30 screening device to compensate for the particular deck operation of the improved vibratory screen- I number of screens carried by the screening device. ing device.

Another object of the invention is to provide a a Fig. 8 is a cross-sectional view of the flywheel vibratory screening device with improved beartaken on the broken line VIII-VIII of Fig. '7.

3.5 ings for carrying the vibrating shaft mechanism, Fig. 9 is a view of a portion of a side plate of the attached to the vibrating screen body thereof screen body taken substantially in the plane of and to the supporting frame through the use of Fig. 5 and shows a modified form of means for ball and socket, self-aligning housings surrounddetachably securing a. reenforced screen within -ing the anti-friction bearings in which the vithe screen body while simultaneously permitting 40 brating shaft mechanism operates. of the tensioning or stretching of the screen ele- 40 Another object of the invention is to provide ments in the transverse direction. I a vibratory screening device, preferably having a Fig. 10 is a partial plan view of the spring rod as supporting frame, a vibrating shaft mechanism shown in Fig. 1 modified in this that a plurality rotatably associated with said frame, and having a of intermediate clamping means for clamping the screen body secured at substantially its midspring rod to the vibratory screen body are pro- 45 length to said vibrating mechanism in a manner vided. v permitting the dissociation of the vibrating shaft Fig. 11 is a fragmentary side view of the frame mechanism as a unit from the device without disportion ofthe screening device shown in Fig. 1 mantling or disturbing the screen b'ody. provided with resilient means for supporting the I Another object of the invention is to provide a frame at its four corners from an inclined rigid 50 transverse spring rod end-support for a single support.

drive shaft type of vibratory screening device Fig. 12 illustrates the eccentric bearing porwhich is simple in construction, durable and eftion with respect to the remaining concentric fective in accomplishing the desired results. portions of the drive shaft i8, said figure being Other objects and advantages'of the present referred to Fig. 5 and being illustrated as showing eccentric bearings, which the relation when the shaft I8 is viewed looking in the line of its axis from the left end of Fig. 5.

Reference numeral 34 designates a rectangular frame shown including structural steel I-beam side members II and the end members thereof may be L-bars connected by gusset plates at the ends to form a rigid frame. On the frame 34 is mounted at one side thereof, a motor 4| having a drive sheave which receives a plurality of endless V-belts for driving a sheave 3| fixed to one end of an eccentric drive shaft l8 having end bearing portionssecuring the shaft rotatably with respect to the frame 34. These end bearings comprise outer roller bearing-base members I, cooperating roller bearing caps 2, self-alining roller bearing housings 3, inner sealing plates 4, an outer sealingplate 58 shown at the left in Fig. 5, an outer bearing cover 5, outer roller bearing spacing collars 6; a retaining washer l9 at each end of the shaft, a roller bearing 8 at the left end of the shaft, see Fig. 5, of the floating type, a corresponding roller bearing 41 at the right end of the shaft l8, of the retainer ring 10- eating type. A sleeve 30 spaces the sheave 3| from the adjacent spacing collar 6, and said bearings are provided with openings at I to receive "Alemite or other suitable fittings for lubricating the-same. Adjacent the outer bearing portions of the drive shaft l8 are flywheels 20 designed and provided with means for counterbalancing the effect of the eccentric mounting of the drive shaft and the screen body eccentrically carried thereby, and including means for detachably and selectively receiving balancing blocks 2| to adjust said counterbalancing in accordance with the number and weight of screens carried within the screen body. These flywheels will later be described in detail.

Portions of the shaft l8 inwardly of the flywheel shaft portions are provided with eccentric journals having their throws in the same direction which is illustrated as being downwardly in Fig. 5. The bearing for each eccentric of the drive shaft l8 includes an eccentric roller hearing base 9, an eccentric roller bearing cap l0 and aself-aligning roller bearing eccentric housing I I. The eccentric bearings are held spaced, in conjunction with innermost shoulders on the shaft l8, by a sealed spacing tube l4 surrounding the shaft l8. The spacing tube M has integrally formed therewith, as by welds 300, annular flanges I04 engaging with adjacent ends of eccentric bearings l5- and I6 and engaging with the selfaligning roller bearing housings I l to which housings the flanges I04 are bolted, by bolts not shown, to prevent all foreign matter from reaching the bearing ends are located closest to the atmosphere most highly saturated with foreign fine materials about the screen. The spacing collars l3 on the shaft l8 space also each flywheel 20 from the adjacent eccentric roller bearing. Reference numeral I2 thereof against which represents eccentric roller bearing sealing plates cooperating with the spacing collars l3. The ecshown at'the left in Fig. 5 is preferably of the locating type whereas the similar eccentric roller bearing l6 shown at the right of Fig. 5 is preferably of the floating type. Reference numeral 59 designates the eccentric roller bearing inner, spacing collars which abut the innermost shoulders of the shaft l8, the shaft being eccentric only in those portions between these innermost shoulders and the shoulders the hubs 95 of the flywheels 20 are shown to abut in Fig. 5.

The screen 13 of which a plurality, parallelly spaced, are shown on the figures are carried through means of certain elements, later to be described, by the eccentric roller bearings on the drive shaft l8. In short, the screens 13 may be said to be mounted within a screen body 22 which partakes of the 'gyratory movement set up by the eccentric drive shaft l8 which participates in its support. The screen body 22 comprises spaced side plates 23 carrying at the upper portions thereof and attached to their outer faces angle irons or bars 14. The side plates 23 are suitably reenforced transversely by means of spaced stiffening irons 8|. Within the screen body in spaced relation and rigidly attached thereto are pairs of side angle irons 85, forming slides for the screen frames 24 and 60'. The pairs of angle irons support an upper coarse wire screen 13 and a lower fine wire screen 13, the screens being slid into the screen body 22 from the low end thereof. The opposite end of the screen body may be closed. In order to facilitate ready removal of the screens 13 the screen frames 24 and 60 to which the screens 13 are secured by means of side screen frame bars 29 clamped by means of bolts to the screen frame, are held in place by means now to be described. The side plates 23 of the screen body may be provided with struck-out right angular portions 83 each portion having a vertical slot 84 in one leg thereof for adjustably receiving, to take care of varying thicknesses of screens 13, a carriage bolt 26 carrying a screen frame clamping bar 25 engaging at its lower edge a frame bar 23 and at its upper edge an inner surface portion of the screen body. From this it is evident that by driving home the nuts on the carriage bolts 28 the screen frames 24 and 60 will be rigidly yet detachably supported within the screen body '22. It is, of course, understood that instead of pressing out these right angular portions from the side walls 23 that the same may be provided with openings properly located to be covered by short angle irons 86, preferably welded to the side plates 23, and serving the same purpose as the shown struck-out angular portions 83 in Fig. 5. A modifled means for readily securing the screens I3 within the screen body is shown in Fig. 9. This means contemplates a screen having slotted screen reenforcing side members 88 between which and a pair of bars 29'the side portions of a screen 13 are clamped by means of suitable bolts, the slots in members 89 being provided so that the heads of the clamping bolts are entirely within the cross-section of said members 88 and free from the angle irons 85. A short angle iron 86 having a vertical slot 84 in the lower leg member thereof is positioned to cover each opening in the side plates being preferably welded thereto, said slotted leg portion adjustably receiving, to take care of varying thicknesses of screens 13, a carriage bolt 26 having on it a combined clamping and tensioning bar 81. Each clamping bar 81 is provided with 9. lug 88 welded thereon which precludes the lower end portion of a bar 81 from gouging into the screen 13 when the nuts on the carriage bolts 26 are driven home, to rigidly hold the side members 89 against the supporting angle irons 85, while permitting the tensioning of the screen elements I3 by reason of the outward slidmg movement of said side members 89 on the anglev irons 85.

, Another feature of this invention resides in that the angle irons or bars 14 secured to the upper outer surface portions of the screen bodyside plates 23 detachably receive the eccentric shaft bearing and housing portions to which these parts are attached by means of through bolts 19. The eccentric drive shaft l8 and parts rotating therewith, or in other words the vibrating shaft mechanism is therefore detachable as a unit without disturbing or dismantling the screen body 22. The outer bearings for the shaft l8 are similarly secured to the frame 34 by means of bolts 82, 'so that the vibrating shaft mechanism may readily be detached as a unit from both the screen body 22 and from the frame 34 without disturbing or dismantling the screen body. Reference numeral 80 designates locating bolts for the eccentric bearings. I

The vibrating shaft mechanism suspending the screen body 22 at substantially its midlength from the frame 34 would make the screen body tend to turn with respect to theframe 34. In order to prevent this relative rotation the improved spring rod support which constitutes an important feature of this invention is provided either at the feed'end of the screen body or at its discharge end as shown on the drawings or at both ends. Now referring especially to Fig. 3 and 4 in which the arrangement of the improved spring rod support means for adjustably' and resiliently supporting an end portion of the screen 13 from the frame 34 is shown in detail. The side plates 23 adjacent the low end and inner upper portions thereof are provided with angle irons 64 which support an angle iron crosspiece 62 substantially in the plane defined by the parallel upper edges, the side plates 23 or above said plane to allow of sufficient clearance for large materials to be discharged from the screen. The flange thereof which engages the angle irons 64 is directed away from the shaft l9 and the upwardly directed flange of the angle iron crosspiece 62 is secured to a spring rod 35 through means to be described later. An adjusting plate 63 is substantially centrally secured to the crosspiece 62 and is provided with a vertical slot and the upwardly directed flange of the angle iron cross-piece 62 is provided with cut-away portions bounding said slot to receive a spring rod clamp-.

ing block plate 38. It is to be understood, however, that the separate. adjusting plate may be formed as an integral part of the angle iron 62 by extending its height, thuseliminating a separate element. The central portion of the spring rod 35 is shown provided with clamping blocks 36 grooved to receive the spring rod 35. The portion of the rod 35 within the blocks 36 is preferably surrounded by a rubber or other resilient sleeve 16 and permits of a clamping action on the rod 35 by means of clamping bolts 12 received within transverse bores in the blocks 36 to effect said clamping action. The bolts 12 carry the plate 38 which is suflicielntly large to lap the slot in the adjusting plate 63 and to permit of a secure fixation of the clamping blocks 36 to said adjusting plate 63 whenthe nuts on the bolts 12 are driven home. A pair of collars 39 retained on the rod 35 .by set screws is provided on the intermediate portion of the rod 35 to prevent endwise movement of the rod 35 and to prevent displacement of the sleeve 16 within the blocks 36..

the blocks 31 to also prevent endwise movement of the rod 35 and to prevent displacement of the rubber sleeves within the blocks 31.

The width of the screen body may be such as to make it desirable to have a plurality of intermediate clamping connections between spaced adjusting plates 63 forming a part of the screen body 22, and the spring rod 35. Such an arrangement is clearly illustrated in Fig. 10. In this way a sufficiently resilient support may be. provided for a screen body extended in width, without necessarily increasing the diameter of the spring rod as is apparent. 4

The operation of the spring rod 35 and how it permits closed circuit vibrations at the end portions of the screen to conform closely to the gymtory circular closed circuit movements of the cocentric bearings on the drive shaft I8 is readily apparent from the above description of the gyratory screening device, as well as is the means cooperating with the spring rod support for permitting the ready adjustment of the inclination of the screen body 22 and therefore also the upper and lower screens 13 with respect to the supportingframe 34.

Now referring to Fig. 6 in which a flywheel 20 mounted on shaft l8 in Fig. is shown in side elevation. Fig. 5 shows, as stated before, the eccentric throw in the downward direction and therefore the flywheels have their heavy portions above the center of the shaft l8 and Fig. 6 is a related showing and therefore the radially enlargedrim portion 92 of the rim 9| of flywheel 29 is shown at the top. The web portion 90 intermediate the rim 9| and the hub 95 is provided with three relatively large circular bores 96 whose centers may be on the same circle. The intermediate bore has its center in a diametrical line passing through the keyway |91 in the hub, the keyway being shown located diametrically opposite the throw of the eccentrics. The centers of the bores 96 at each side of this intermediate bore are spaced equal distances from said diametrical line and are therefore necessarily spaced equal'distances from a diametrical line at right angles to said diametrical line. Each flywheel 20 machined on these abutments. There are abutments on each side of the web 99 and a pair of like balancing plates cooperates simultaneously with the abutments 91. The radially enlarged rim portion 92 also provides a pair of abutments 94 at each side of the web 90 and these are outlined by an elongated slot 93 to likewise permit satisfactory casting and subsequent machining of said abutments and to similarly secure a complete. and firm engagement therewith of edges of the rectangular balancing plates 2 I. The bores 96 are provided to enhance the unbalance of the flywheels without adding to their weight. The operation of this form of flywheel is as follows: With no balancing plates 2| bearing against either of the stops 94 or 91 or applied to the web portion 99 of the flywheels 29 the screening device is set for two screen or two deck operation. When it is desired to add an intermediate screen or deck to the screen body 22 all that is necessary to be done is to take a pair of like balancing rectangular plates 2| and cause their longitudinal edges to bear firmly against the .is provided with stops or abutments 91 at each side of the intermediate bore 96 and has slots 98 abutments 94 and against which they may be held by means of bolts passing through holes 99. On the other hand, if it is desired to operate the screening device with only one screen I3 or deck in the screen body, the pair of balancing plates is removed from its position just described and similarly associated with the stops 91 as shown in Fig. 6 and held thereagainst by means of bolts passing through other holes 99. A flywheel under the arrangement stated should ordinarily balance when a counter-weight equivalent to a certain number of inch pounds depending upon the weight and arrangement of screen body is placed diametrically opposite the heavy side of the flywheel in line with the key seat. For example, a required counter-weight may amount to 129 divided by12 equals 19 pounds, if placed at a radius of 12 inches.

The flywheel just described being castfrom metal is relatively expensive and therefore the flywheel I29 formed of rolled steel plate and comprising a disk as shown in Figs. '7 and 8 is preferred. This steelplate material makes a flywheel constructed therefrom rather inexpensive as compared to a flywheel cast in the form shown in Fig. 6. The flywheel I29 similarly to the fly-- wheel 29 shown in Fig. 6 is provided with large circular bores I96 winch may be of a smaller diameter than the recessed circular bores I98 located in a diametrical line passing through the keyway I91 and which may have their centers on the same circle as the bores I96. The face of a flywheel I29 opposite the bores I98 is recessed, as shown at 299, to receive the heads of bolts 29I passing through apertures concentric with the bores I99 within the flywheel, each of said bolts 29I selectively securing a balancing disk I99 of a suitable length or lengths of shafting or disks within the desired bore I98. The bores I96 similarly tothe bores 99 of the flywheel 29, shown in Fig. 6, are ,equally spaced from the diametrical line defined by the centers of the bores I98 and' they are likewise equally spaced from a diametrical line at right angles to said diametrical line. The operation of this preferred form of flywheel is apparent from a description of the operation of the flywheel shown in Fig. 6. With two screens I3 within the screen body 22 neither recessed bore I98 will contain a balancing disk I99, while if an intermediate screen is added to the two screens shown within the screen body 22, a balancing disk I99 is inserted in the bore I98 adjacent the keyway I9I. On the other hand, if only one screen I3 is contained within the screen body only the other bore I99 will receive a balancing disk I99.

In order to enhance the efficiency of operation of the disclosed screening device having a single, vibrating shaft and a spring rod-end supported gyratory screen, and for practical reasons, an I- bolt 69 is preferably secured to each corner of the frame 34 to receive the loop portion of a threaded U-bolt 91 carrying disks 98 provided with apertures to receive the leg portions of another inverted threaded U-member 61. The nuts cooperating with the threaded ends of the U-bolts 91 and pressing against the adjacent disks 68 compress a helical compression spring I9 depending upon the weight of the frame 34' and parts carried thereby. A cable I5 is secured to each one of the upper U-bolts 61. The other end of which cable is attached to an overhead support. Should the frame 34 move vertically downward due to unusual shock of falling material on the screen I3 or to improper balancing of the vibrating mechanism the springs I9 would restrain this movement to a certain degree depending upon their strength and the compression provided therein. The springs I9 effect a very desirable cushioning action on the overhead support and prevent dependent vibration of the frame 34 and therefore also of the screens I3, which it is understood may be perforated plates, with respect to the overhead support for the vibratory screening device.

In explanation of the use of springs I9 it may be stated that while the counter-weights 2| or I99 on the flywheels 29 and I29, respectively, ordinarily take care of all unbalancing due to the weight of the eccentrically carried screens I3 and their carrying and supporting elements, the variations of the load carried on the screens during the operation which cannot be maintained uniform at all times will cause some vibrations to be transmitted to the supporting frame 34 and these are taken care of by the springs I9, instead of being transmitted to the overhead support and from there throughout the building.

In some cases it may be desirable to support the frame 34 resiliently from inclined fixed supports I99 as illustrated in Fig. 11. This may be accomplished by locating an inclined upper telescoping socket member lol and a lower cooperposition the drive shaft I8 out of the horizontal and thereby effect unequal screening actions in transverse portions of the screens I3. In order to preclude this possibility and to maintain a uniform transverse disposition of the screening material on the screens I3, counter-weights 19 are attached to the web portions of the I-beam II opposite the I-beam II which directly supports the motor 4 I. It will be noted that the center of gravity of the counter-weights I8, at the preferred inclination of the frame 34, is in a vertical plane parallel to the axis of the drive shaft I8 and passing substantially through the center of the driving motor, to properly effect said counterbalancing action thereby, since the supporting frame 34 must necessarily be operated in z. position longitudinally inclined to the horizon- A feed hopper 11 shown in dot-dash lines at the elevated -or feed end of the gyratory screening device in Fig. 2 may be employed to conduct the material to be graded on to the upper screen I3 whereupon the gyratory action of the screen body 22 will effect the classified grading desired depending as to whether one, two or three or more screens I3 are carried within the screen body.

The disclosed gyratory screening device permits ready disociation of the eccentric drive shaft body. The improved flywheels effect and facilitate a selective balancing against the eccentriccarried screen body with the screen body carrying one or a plurality of screen frames. The spring rod support permits of-readily adjusting the inclination of the screen body with respect to the supporting frame while permitting in-each adjusted position a desired closed circuit vibration of the screen body and therefore also the screens 13 at that end portion of the screens and effectively precludes the relative rotation of the screen body with respect to the frame 34 when the screening device is in operation. The resilient support means for the frame 34 prevents dependent vibration between the supporting members for the screening device and the frame 34 and-the counter-weights l8 cooperate with such supporting means for the screening device to maintain the single gyratory shaft of the screening device in the desired horizontal position. Each of these features is conducive of enhancing the efficiency and value of this screening device and is separately set forth in the following claims.

It should be understood that it is not desired to limit the invention to the exact details herein shown and described, for various modifications within the scope of the claims may occur to persons skilled in the art.

It is claimed and desired to secure by Letters Patent:

1. In a vibratory screening device, in combination, a screen frame, an operating eccentric about which said frame may pivot longitudinally and which participates in its support, a frame support for said eccentric, transverse resilient supporting means for said screen frame located at a distance from and generally parallel to the axis of rotation of said eccentric, said means being secured at its ends to said frame support and at its middle to said screen frame and permitting of a closed circuit movement of said screen frame in a longitudinal plane thereof and means for rotating said eccentric.

2. In a vibratory screening device, in combination, a screen member, an operating eccentric about which said screen member may pivot longitudinally and which participates in its support,

a frame support for said eccentric, transverse resilient supporting means for said screen member located at a distance from and generally parallel to the axis of rotation of said eccentric, said means being secured at its ends to said frame and at its middle to said screen member and permitting of a closed circuit longitudinal movement of said screen, means connected with said screen member-supporting means permitting of adjustment of the inclination of said screen member with respect to said frame, and means for rotating said eccentric.

3. A gyratory screening device comprising, a frame, vibrating means including a shaft provided with an eccentric, rotatably associated with said frame, means connected with said eccentric and partaking of its motion, a screen member secured to said means, flexible means comprising a rod located remote from and generally parallel to said shaft and secured to said screen member and to said frame, and permitting of a substantially circular movement of said screen member, means connected with an intermediate portion of the rod of said flexible means, permitting adjustment of the inclination of said screen member with respect to said frame, and means for rotating said shaft.

4. A gyratory screening device comprising, a

frame, vibrating means including a shaft provided with an eccentric, rotatably associated with said frame, means connected with said eccentric and partaking of its motion, a screen member secured to said means, means comprising a flexible rod located remote from and generally parallel to said shaft and clamped at an intermediate portion to said screen member and at its ends to said frame and permitting of a closed circuit movement of said screen member, means connected with an intermediate portion of the rod of said remote means, permitting adjustment of the inclination of said screen member with respect to said frame, and means for rotating said shaft.

5. A vibratory screening device, comprising a frame supported at a plurality of points, vibrating means including a shaft journaled to said frame, means connected with said vibrating means and partaking'of its motion, a screen secured to said connected means, flexible means positioned generally parallel to and located remote from said shaft and secured to said frame and to said screen, intermediate portions of said flexible means being flexible in directions transversely of said shaft, said means permitting of a closed circuit movement of said screen transversely of said shaft, means connected with said flexible means remote from said shaft permitting adjustment of the inclination of said screen relative to said frame, and means for rotating said shaft.

6. A vibratory screening device, comprising a frame suspended at a plurality of points, vibrating means including a shaft journaled to said frame, means connected with said vibrating means and partaking of its motion, a screen secured to said connected means, means comprising'a resilient rod located, remote from and generally parallel to said shaft and secured at an intermediate portion to said frame and at its ends to said screen and permitting of a closed circuit movement of said screen transversely of said shaft, means connected with an intermediate portion of the rod of said means remote from said shaft, permitting adjustment of the inclination of said screen relative to said frame. and means for rotating said shaft.

'7. A vibrating screen mechanism, comprising a frame adapted to carry three screens, a shaft having eccentric portions operatively connected to impart vibratory motion to said frame, means for rotatably supporting said shaft and for supporting said frame to permit vibration thereof, unbalanced flywheels secured on said shaft said unbalanced wheels being so proportioned that they effectively counterbalance said frame when it is carrying two screens and being shaped to receive counterweights at two predetermined positions, and counterweights for said unbalanced flywheels said-counterweights being so proportioned that when attached to said flywheels at one of said predetermined positions the flywheels become so unbalanced as to effectively counterbalance said frame when it is carrying three screens and when attached to said flywheels at the other of said predetermined positions the flywheels are so adjusted as to effectively counterbalance said frame when it is carrying only one screen.

8. A vibrating screen mechanism, comprising a frame adapted to carry three screens, a shaft having eccentric portions operatively connected to impart vibratory motion to said frame, means for rotatably supporting said shaft and for supporting said frame to permit vibration thereof, unbalanced flywheels secured on said shaft said unbalanced wheels being so proportioned and having their heavy sides so disposed that they effectively counterbalance said frame when it is carrying two screens and being shaped to receive counterweights at their heavy sides and at their light sides, and counterweights for said unbalanced flywheels said counterweights being so proportioned that when attached to said flywheels at their heavy sides the flywheels become so unbalanced as to eifectively counterbalance said frame when it is carrying three screens and when attached to said flywheels at their light sides the flywheels are so adjusted as to effectively counterbalance said frame when it is carrying only one screen.

9. A vibratory screening apparatus, comprising a supporting frame, a screen vibrating shaft rotatably mounted on said frame, a screen element pivotally carried by said screen vibrating shaft, and resilient supporting means for said screen element including a resilient rod disposed substantially parallel to said shaft and spaced therefrom said rod being attached at its ends to opposite sides of said frame and connected to said screen element near the middle thereof.

10. A vibratory screening apparatus, comprising a supporting frame, a screen vibrating shaft rotatably mounted on said frame, a screen element pivotally carried by said screen vibrating shaft, and resilient supporting means for said screen element including a resilient rod disposed substantially parallel to said shaft and spaced therefrom said rod being attached at one end to said frame and connected to said screen element near the middle thereof.

11. A vibratory screening apparatus, comprising a supporting frame, a screen vibrating shaft rotatably mounted on said frame, a screen element pivotally carried by said screen vibrating shaft, resilient supporting means for said screen element including a resilient rod disposed substantially parallel to said shaft and spaced therefrom said rod being attached at one end to said frame and connected to said screen element near the middle thereof, and means associated with said rod for effecting adjustment of the inclination of said screen element relative to said frame.

CHARLES S. LINCOLN.

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