US1459839A - Vibrating screen - Google Patents

Description

June 26, 1923. 1,459,839

B. A. MITCHELL A VIBRATING SCREEN Original Filed 001:. 16. 1918 4 Sheets-Shet l June 26, 1923. I 1,459,839

B. A.- MITCHELL VIBRATING SCREEN Original Filed Oct. 16. 1918 4 Sheets-Sheet 2 H] WP. l l H 1 I or 2/ 2Q 2 [a ll fi amzjfliz g a I A TTORNEYJ yum 26,1923. Mw'w y B A. NHTCHELL VIBRATING SCREEN ori inal Filed Oct. 16. 1918 4 eets-Sheet 5 June 26, 1923;

B. A. MITCHELL VIBRATING SCREEN Original F iled Oct. '16. 1918 4 Sheets-Sheet 4.

Patented June 26, 1223.

NETF.

FFEQE.

BENJAMIN A. MITCHELL, ST. GEORGE, NEW YORK, ASSIGNOB 0F TWO-THIRDS T0 MINNIE L. MITGEELL, 0F MAGNA, UTAH.

VIBRATING SCREEN.

Application filed October 16, 1918, Serial 310.25%,466. Renewed May 1'7, 1923.

To all whom, it may concern.

Be it known that I, BENJAMIN A. Mrrorn ELL, a citizen of the United States, residing at St. George, Staten Island, in the county of Richmond and State of New York, have invented certain new and useful Improvements in Vibrating Screens, of whic the following is a specification.

This invention relates to vibrating screens and more particularly to screens actuated -for sifting ore, sand, gravel and the like.

This invention has for its general object an improved construction and arrangement of parts which is durable, eflicient, and readily manufactured.

A more specific object of. this invention is to provide improved apparatus of this character for carrying out screening processes without clogging.

Another object is to provide an arrange ment in which the screen for the material to be screened is actuated by a vibrator utilizing the principle of rotating moments.

Another object is to provide improved means for applying to screens under tension, a harmonic motion of constantly changing direction.

Another object is to provide means for setting up vibrations of uniform amplitude throughout the width of screens.

Another object is to provide means for imparting vibrations in different phases to different partsof a screen,

Still another object's to provide improved means for connecting vibrators in operl'ative relation with the screen to be actuate Other objects and advantages will in part be specifically pointed out hereinafter and.

in part obviousfrom the arrangements and constructions here set forth.

The invention'accordingly consists in the features of construction, combinations of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope oftheir ap-- plication will appear in the appended claims.

For a more complete understanding of the nature and advantages of this invention reference should be had to the following detailed description, which describes the best illustrative embodiments of this invention at present known to me, taken in connection with the accompanying drawing in which:

Fig. 1 shows a front elevation of screening apparatus embodying the improvements of my invention;

Fig. 2 shows a vertical sectional view taken on the line 2-2 of Fig. 1, looking in the direction of the arrows;

Fig. 3 shows an enlarged view of the vibrator and the means for connecting the same to the screen, part of the vibrator being shown in longitudinal section:

Fig. 4: shows anenlarged end view of the vibrator, illustrating the means for transmitting vibrations from the vibrator to the screen;

Fig. 5 shows an enlar,ed sectional view of the means for holding t e opposite edges of the screen; I

Fig. 6 shows an enlarged central vertical sectional view through the vibrator taken on the line'66 of Fig. 3;

Fig. 7 shows a vertical sectional view similar to Fig. 2, illustrating a modified arrangement of the apparatus;

Fig. 8 shows a' vertical sectional view tlllfllgh the vibrator-illustrated in Fig. 7, an I Fig. 9 shows a longitudinal view of the vibrator illustrated in Fig. 7.

Referring now ,to the drawing, and to Figs. 1 and 2 in particular, 20 denotes ahopper or other device supported in operative relation with av screen 40 which is adapted to feed the material to be screened through an outlet23 controlled by a gate .24:

onto the upper part of the screening sur' face. The supporting structure for the hopper as shown comprlses aframe composed of members 21 and 22, which in addition supports the screen-frame 30- holding the screen 40 the vibratin means or vibrator 46 for the screen 40a so being supported at tit) one side of the plane of the screen by this structure. The pressure vof the material within the hopper tends normally to open the gate 24, and the degree of opening of the gate is controlled by a bolt-26 whichpasses through oneof the bars 25, and is enga ed atits outer end by a winged-nut 27. he

loose material falling through the outlet.

opening 23 passes onto the screen 40 which is, held his screen-frame 30 the latter being hinged along its upper edge at the'points 31 on the supporting frame of the apparatus. The screen-frame is shown as constructed of angle bar members or other suitable parts, forming a rectangular structure. The lower edges of the screen-frame 3O areprovidedframe members 22. The bolts 35 may be caused to engage any desired aperture34, so

that the lower edge ofthe screen-frame can be raised or lowered to change the incline.-

tion of the screen, as desired. The material passing onto" the screen is screened in the manner hereinafter described, so that the finely divided material passes downwardly into a chute or hopper 36, while the coarse material passing ofl the lower edge of the screen falls into another chute or hopper 37.

The screen 40 is mounted within the rectangular frame. 30, as shown in Fig. 1, and the opposite ends of the screen cloth are secured to the frame by an adjustable device illustrated more particularly in Figs. 3 and 5. The edge of the screen cloth is "wrapped around a circular rod 41 located within a longitudinally slotted tube 42 with the over-. lapping parts of the screen extending outwardly through the slot, as illustrated in ig. 5, so that when the tubes 42*at opposite edges of the screen are pulled apart, the edges 42 of the slots press the screen against the rods 41 and cause the same to be securely gripped. The tubes 42 are engaged by bolts 43 having arms 43 which extend partially around the'tubes 42, as shown in- Fig. 3. These bolts pass through apertures in the. walls of the screen frame 30 and are threadedly engaged by the adjusting members 44, so that the-screen can be stretched tightly within the frame and maintained continuously under relatively great tension, 'substantially similar to a drum-head, through out the screening operation. As the screening process is carried on, it may be desirable from time to time to tighten the screen or to adjustthe tension thereof to secure the most desirable results with the particular material being screened, and it is found in,

practice that the desirable tension of the screen will de end also upon its weight and stifl'ness. Wit particularly heavy'and rigid screens, it is found that it is merely necessaryto support the screen firmly within the frame with suflicient rigidity to prevent any considerable downward bending thereof and to maintain the same in a substantially rigid inflexible condition similar to the condition of a flexible screen stretched to a drum-head tightness. If desired, suitable guards 45 may be mounted along the lateral edges of the screen to prevent the material from passin over these edges.

he screen 40, as indicated, is stationarily supported so asto be vibrated independently of'the screen-frame 30; this being accomcentres and utilizes the principle of rotating I moments to produce relatively minute vibratory movements of constrained amplitude having" a constantly changing direction as set forth in my copending application Serial No. 275,321. As illustrated the vibrator 46 comprises a central casing 47 having bolted thereto the two end casings 48, each of which is reinforced by the longitudinally extending ribs 49. The central housing has its base 47 mounted on a supporting beam 50 which is secured to the middle part of the lower wallof the screen-frame 30 and extends inwardly therefrom over the screen. A shaft 51 passes through the central housing ,50' and has keyed thereon a pulley 52 which is adapted to be engaged by a belt 53 extending to a motor or other driving means. If desired, the housing 47 may be made the casing of a motor and the armature of the motor mounted directly on the shaft, as hereinafter described. The details of the construction here employed are more clearly illustrated in Figs. 3 and 6. So shown it comprises complementary portions secured together to form the housing 48, each portion of which is the same so that one set only willtherefore be described. Mounted within each housing 48 is a bearing ring 54 having a hard metal collar 55 secured to the outer side thereof and adapted to coact with balls '56, which run in a raceway formed by the annular collar 57 secured within the housing 48. Each end of the shaft 51 is reduced in diameter, and the reduced portion is keyed in a suitable recess formed in'an unbalanced rotary member 58 having a lateral projection 59 on one side thereof. The lack of balance of this rotary member is further increased by provlding an eccentrically located aperture 60 therethrough opposite the projection 59. Hard metal bearing collars 61 are secured to the ends of this unbalanced member, and these collars coact with balljections adapted tobear against the rounded I surfaces of the hard metal caps 64, which are secured to the end walls 48 of the housing. The space within each end housing 48 is filled with oil, or other lubricant, which is introduced through aperturesclosed by the plugs 65. The rotation of the shaft 51at high speed produces high frequency vibrations in the casing due to the rotation of the unbalanced members 58.

The vibrations set up by the vibrator are imparted to the screen 40 by means of transmitting plates or membe s 6.8 whi h are carposite walls of the casing to be en illustratedlin the ried by the collars 69. The ends of the arts 48 of the vibratin casing are tapere as d awings, and these portions. are adapted to be closely fitted by the correspondingly tapered walls of the rings 69. Apertures are provided through the op.- ged by the transverse ke s 70 by which t e rings 69 are securely c amped in position. The rings 69 are rigidly secured to the transmitting members 68 by means of rivets or the like 71, and these transmitting members are in the form of relatigely long plates as illustrated in Figs. 1, 2;? and 4, extending substantially across the screen in a direction transverse to the axis of rotation of the unbalanced rotary members. The lower edges of the transmitting members comprise longitudinally extending blocks or strips 72 of wood, or other equivalent material,-which strips bear directly upon the upper surface of the screen, as illustrated more particularly in Fig. 3, but which strips are not secured to the screen. The parts are so proportioned that the strips 72 bear rigidly against the screen surface, however, when the latter is in a rigid or substantially inflexible condition, as when a flexible screen is stretched to a substantially drum-head tightness, so that the vibrations set u the casing of the vibrator are imparte directly to the screen. The screen thus vibrates a high frequency independently of the frame in which it is mounted, and produces a thorough screening of the material which passes downwardly thereover.

Instead of employing the arrangement illustrated in Figs. 1 to 6, inclusive, it may be desirable in some instances to use the arrangement of apparatus illustrated in Figs. 7 to 9, inclusive, wherein the vibrator and its directly connected parts are mounted beneath the surface of the screen, thus leaving the space above the screen entirely free'and unobstructed. In this modification, a supporting frame, comprising the vertically extending members 7 5 and the horizontal members 76, carries a hopper 7 8 from which the material is fed by a gate 79 onto an inclined screen 80 mounted in the screen frame 81, which is hinged at the points 82'and supported at its lower end by means of adjustvibrator 85 has a central housing 86 which forms a casing of an electric motor, and the base 86 of this motor 'is' secured to a supporting beam 87 which i seemed to th lower part of the'screen frame and'extends upclamping rings 90 mounted on the erfids thereof are transmitted to clamping members 91 which extend upwardly and bear against the underside of the screen b means of the intermediate strips 92 of woo or the like. This arrangement of the apparatus is similar to that previously described, in that thecentral housing is mounted on a part which is rigid with the screen frame, while the projectingand vibrating ends of the easing are operatively connected directly to the screen. The central housing in the last described embodiment is entirelyv closed, however, to prevent the access of dust to the interior of the vibrator, and this construction has the advantage that the screen bears downwardly upon the transmitting members, so that the weight of the material on the screen tends to increase the contact between the screen and the transmitting mem-- bers, whereas, in the first form of the invention described, the weight of the material tends to separate the transmitting members from the screen. The-second invention has the further feature that it leaves the upper surfaceof thescreen entirely unobstructed. If desired, the vibrator of the second form ,of the invention may be further enclosed by a supplementary sheet metal housing '93.

With each form of the invent on it is found that improved results are obtained in the screening of crushed ore and other ma-v terials, due to the novel combination of the vibrating means and the screen. Due to the action of the rotary vibrator, which is in direct connection with the screening medium, each and every particle of the screen vibrates in an. extremely small circle, so that a vibration is set up in the screen which is in some respects the combination of a vibration transversely of the screen and a vibration in the plane of the screen. This I serves to sift the materials over the screen surface as they pass downwardly thereover by gravity, and to effect a more perfect screening action than is possible with any form of screening device heretofore known. By the use of my improved vibrator it is possible to produce two series of vibrations in the screen through the two transmitting plates which are connected, to opposite ends of the vibrator casing. The unbalanced rotary members in opposite ends of the vibrator casing are pre erably mounted 180 apart on the shaft, so that the vibrations p duced thereby are rm wherebytheactionxsg v: 1mproved. The and secon vibrations produ y in the screen by the operation ofthe rotary vibrator aresu rim upon each other, so that m a rotation at the rate of 3600 revolutions minute it is believed to be easily possible to.

obtain in the screen vibrations of-about 18,- 000 or 20,090 per minute. This hi frequency of the vibrations produced directly in the screen makes, it im terials to become clo v r m the meshes of the screen, and thus t e invention overcomes the difliculty which has been present in all prior screen devices of which ap licant is aware. Even when the wde ore, or other material, iswet, it is found that the high frequency vibrations in the screen prevent the material from adhering to the meshes of the screen and, at the same time,

the materials fed to the screen pass therethrough at a more 'rapid rate than is powble with the ordinary scree" devices. The unbalanced rotar vibrator as the advantage that it pro uces a high frequency vibration without embody' cumbersome or complicated apparatus, an the frequency of vibrations may be readil fiivaried by v the speed of rotation. frequency 0 the vibrations in the screen may also be regulated by adjusting the tension of the screen, and although the desirable degree of tightness of the screen may vary under different circumstances, it ispreferred to stretch it to an extremely tight condition, approximating the tightness of a drum-head. In order to secure the best results with'any given feed Z of material, it is desirable to ad ust the tension of the screen according to the rate of rotation of the vibrator and to the rate of feed of the material. With extremely heavy screens rigidly mounted in the frame, the vibrations produced are similar to those obtained with a lighter screen stretched to and maintained under extremely hi h'tension.

Although I have shown and escribed certain embodiments of the invention for purposes of illustration, .itwill be understood that it may be constructed in various different forms without departing from the scope of the a pended claims.

What I claim is:

L In apparatus of the class described, an inclined screen supported in substantially fixed position, and means for producing in said screen a plurality of simultaneously acting series of minute circular vibrations in planes perpendicular to the plane of the screen.

' 2. In apparatusof the class described, an inclined screen, and means for producing a plurality of series of minute circular vibra. tions directly in said screen in planes perpendicular' to the plane of the screen, said bio for mainclined screen, a vibrator casing, means 'for producing minute circular vibrations in said casing, and means for transmitting a plurality of simultaneously aotiigrzeries of said vibrations to said screen ughout the width of the screen.

4. In apparatus of the class described, a screen, means for hol .said screen in a diff rigid condition, a vibrator casing located outwardly from the plane of said screen, means for producing minute circular vibrations in said casing, and arigid transmitt' plate carried b said vibrator and contacting edgewise wit said screen.

5. In apparatus of the class described, a screen, means for hol said screen ina stifi rigid condition, a vibraton casing located outwardly from the plane of said screen, means for reducing minute circular vibrations in casing, and a pair of transmitting plates connected to the ends of said casing and bearingi edgewise on said screen throughout its W1 th.

6. In apparatus of the class described, a screen, means for hol said" screen and maintaining the same un er a tight drumhead tension, and means for producing a plurality of series of continuous vibrations of uniform amplitude across said screen in means for producing tension in said screen,

and means for producing aseries of continuous circular vibrations in said screen in a plane perpendicular tothe plane of the screen independently of said frame.

8. In apparatus of the class described, a frame, a screen mounted in said frame, a supporting member .pro'ecting from said e substantially para e] to said screen, and a rotating vibrator movably carried'by said supportin member arranged and connected to the intermediate portion of said screen for transmitting thereto harmonic motions executed in a" plane transverse to the plane of said screen.

9. In apparatus of the class described, a screen stationarily supported in screening position, a vibrator having a pair of rotatmg eccentric mass centres disposed in different bases, a support for said vibrator disposed between sa1d centres, and means on said vibrator for-imparting vibrations to said screen.

10. In apparatus of the class described, a

screen stationarily supported in. screening position, a vibrator actuated internally by a rotating moment for producing relatlvely minute vibrations executing a sad orbit a sup ort for said vibrator atone side of the p ane of the screen, and means for n11- parting said vibrations to a plurality of portions of said screen.

said screen, and means for producing and maintaining tension in said screen.

13. In apparatus of the class described, a. frame a screen mounted in said frame m a substantially rigid inflexible condition, a

rotary vibrator carried by said frame between the edges of said screen and having a double oscillatory motion with respectwto its support, and rigid means connecting the end portions of said vibrator with sald screening medium. 0

14. In apparatus of the class described, a screen, a supporting member at one slde of the plane of said screen, a rotating vibrator having a double vibratory movement about its centrally fixed support on sald supporting member, a rigid plate connected to sald vibrator and having one edge bearing against said screen, and means'for operating said vibrator.

15. In apparatus of the class described, a screen frame, a screen detachably mounted on said frame, a rotating vibrator having a double oscillation about its central support mounted opposite the. middle part of said screen, and transmitting means detachably mounted on said vibrator and bearing against said screen and transmitting to said screen circular vibrations in a plane perpendicular to said screen.

16. In apparatus of the class described,

an inclined screen, means for feeding loose materials to the upper partof said screen,

means for producing tension in said screen, a rotating'vibrator mounted independently of said screen, and means for transmitting two series of uniform, circular vibrations forming a continuous operative connection between said vibrator and said screen and per .endicular to said screen.

1 In apparatus of the class described, a screen, a vibrator cas' mounted opposite said screen, said casing avi two tubular parts, a ring secured on each c said tubular arts, and plates carried by said aringlon said screen perpendicular y.

18 apparatus of the class described, a

and,

screen, a rotating vibrator having a double oscillating motion about its central support" mounted opposite the central part of said screen, plates attached to the ends of said vibrator and' bearing on said screen. per- .pendicularly, and means for operating said vibrator.

19. In apparatus of the class described, a screen stationarily supported in screening position, a vibrator having a pivoted cen tral portion and end portions adapted to. execute vibrationsof constrained amplitude and constantly changing directions phases displaced by 180 degrees, rigid means on said end portions for transmitting said vibrations to said screen, and means for iiitroducing material to be upper surface.

20.v In apparatus of the-class described,

a screen, a rotary vibrator comprising an.

electric motor having unbalanced rotary members on each end of its shaft one hundred and eighty degrees apart, and rigid members transmitting the characteristic vibrations of said vibrator to said screen in a plane perpendicular to the plane of said screen.

screened upon its so i 21. In an apparatus of the class described,

a screen, means for stationarily supporting said screen in an inclined position, means for producing minute circular vibrations in the body of said screen, and means for. passin loose materials to the upper part of said screen.

22. In an apparatus of the class described,

directly in said screen and in a plane perpendicular to the plane of said screen.

23. In apparatus of the class described, a screen, means for maintaining said screen in I a stiif rigid condition, means for supporting said screen in an inclined position, means for introducing loose materials onto the upper part of said screen, and means located opposite the plane of said screen and having a connection therewith for producing minute circular vibrations of high frequericy directly in said screen and perpendicular to its plane of support.

24. The combination in a screening machine, of a rotary vibrator, means for supporting said vibrator at its center, transmitting plates connected to the free end portions of saidvibrator and a screen cloth extending over and vi rated by said transmitting plates.

25. combination in a. screening ms leaving the end portions thereof free to vibrute, means for producing minute circular vibrations of frequenc; in the end portions of said casing, transmitting plates con nected to the end portions of said casing, a screen cloth extending over said transmitting plates, and means for retaining said screen. cloth on said plates and producing tension therein. J

In twtimony whereof, I have subscribed my name. 4 7' BENJAMIN A. MITCHELL.

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