US1459844A - Vibrating screen - Google Patents

Description

June' 26, 1923.

B. A. MITCHELL VIBRATING SCREEN Filed Dec. 22, 1919- 4 Sheets-Sheet l June 26, 1923.

B. A. MITCHELL VIBRATING SCREEN' Filed Dec. 22 1919 4 SheetsSheet 2 AJune 26. 1923. 1.459.844

B. A. MITCHELL VIBRATING SCREEN Filed Dec. 22, 1919 4 Sheets-Sheet 3 ATTORNEYS June 26, 1923 B. A. MITCHELL VIBRATING SCREEN Filed D60. 22, 1919 4 Sheets-Sheet 4 Patented June 26, 1923.

UNITED STATES BENJAMIN A. MITCHELL, OF GARFIELD, UTAH.

VIBRA'IING SCREEN.

Application filed December 22, 1919. Serial No. 346,751.

To all 'whom t may concern.'

Be it known that I, BENJAMIN A. MITCH- ELL, a citizen of the United States, residing at G-arield, in the county of Salt Lake and State of Utah, have invented certain new and useful Improvements in Vibrating Screens, of which the following is a speciiication.

This invention relates to screening appa-.

ratus for screening crushed ore, coal, or other loose materials with which the machine is adapted to be used.

The purpose of the invention is to provide an improved screening apparatus involving a new method of screening, whereby minute and substantially circular vibrations are set up in the screening medium, such as the ordinary wove-n wire screen cloth. The apparatus comprises a support-ing frame, on

which the screen cloth is mounted, in combination with improved adjusting means for setting up a high degree of tension in the screen cloth. Vibrations are produced in the screen cloth by means of a rotary vibrator embodying one or more unbalanced rotary elements which set up substantially circular vibrations in the vibrator casing. These vibrations are imparted directly to the screen cloth by rigid transmitting elements, thereby causing each particle of the screen cloth to travel in a substantially-circular path of vibration perpendicular to the plane of the screen. An important feature of the invention is the provision of an improved supporting frame and an improved method ot' mounting the vibrator, the frame com` prising cnd plates between which the screen cloth is mounted, and the underlying supporting member connecting the end plates and having the vibrator mounted in iiXed position thereon. This frame is capable of angular adjustment, in order toregulate the flow by gravity of the loose materials thereover, and the screen cloth can be readily detached from the frame to permit replacement thereof when worn without interfering with the vibrating and transmitting mechanism. Other objects of the invention relate to various features of construction, operation, and arrangement which will` be pointed out more fully hereinafter.

The nature of the invention will be understood from the following specification, taken in connection with the accompanying drawings, in which one embodiment is illustrated.

In the drawings- Figure l shows a perspective view of the frame, screen cloth, and vibrator, looking toward the upper 'side thereof;

Fig. 2 is a perspective view of the apparatus illustrated in Fig. 1, looking toward the underside thereof, and illustrating the method of mounting the vibrator on the frame; v

F ig. 43 shows an end elevation vof the screening mechanism, showing the method of mounting the same in position to receive the loose materials from a feeding hopper;

Fig. 4 is an enlarged sectional view through one of the clamping rods and tubes at one end of the screen cloth, showing one means of connecting the screen cloth to the frame and adjusting the tension thereof;

Fig. 5 is an enlarged sectional view, taken in a vertical plane parallel to the path of travel of the materials over the screen, showing somewhat diagrammatically the character of the vibrations set up in the particles of the screen;

Fig. 6 is a longitudinal sectional view, taken on the line 6 6 of Fig. 3;

Fig. 7 shows an end elevation of one of the plates by which the vibrations are transmitted to the screen cloth;

Fig. 8 shows a longitudinal sectional view through the rotary vibrator; and

Fig. 9 shows a sectional view, taken on the line 9-9 of Fig. 8.

The supporting frame 10 in the screening apparatus comprises a longitudinal supporting base member 11 which connects in an integral manner the upstanding end members 12, shown as curving upwardly therefrom. The members 12 are increased in width as their upper edges are approached, and terminate in plates 13 having side plates 14 extending upwardly therefrom flush with the outer surfaces of the portions 12, thus giving the end walls of the frame an angular cross section. The end plates are provided at their upper ends with longitudinally projecting trunnions 15, which are adapt-ed to engage the bearing notches 16 in the brackets 17, secured tothe supporting wall 18. The lower extremities of the end plates 14 are formed integrally with hubs or bosses 20, which are provided with threaded apand of the screen carried thereby in order to secure the desired rate of flow thereover by gravity of the loose materials being screened. The loose materials are discharged onto the upper part of the screening medium from a Lledge or plate28, which is mounted on the upper part of the wall '18 and terminates along a line parallel to the upper edge of the screen cloth. A plate 29 extends upwardly lfrom the rear edge ofthe plate 28, thus forming an intermediate receptacle adapted `to receive crushed ore or other loose materials from a hopper 80, which is mounted above the plate28 and adapted to discharge the loose materials onto a rotary feeding member 3l, which rotates with a shaft 32 and is adapted to discharge the loose materials over the edge of the plate onto the screen,

The screening medium consists of a woven` wire screen cloth formed, preferably, in two sections 5L and 35, which join along a line 36 midway between the upper and lower edges of the screen. The two sec tions 35a and 35T are relatively inclined, the lower section having a lesser inclination to the horizont-al than the upper section, so that the materials passing downwardly by gravity are retarded asA they approach the discharge edge of the screen The sections of screen cloth are secured to the frame by means of tubes 37 and rods 38. are considerably larger in diameter than the rods, and are provided with longitudinal slots 37a.y through which the screen cloth extends. the rod 38, and the free end thereof carried out again through the slot, so that when a pull is exerted on the tube 37 the edges of the slot exert a snubbing action on the screen cloth and force it against the rod 38, thus securely gripping the screen cloth between the tube and the rod.. as shown at 539. The screen cloth is preferably so arranged that certain parallel strands thereof will. extend longitudinally of the screen, while the other strands extend transversely thereto and parallel to the end plates la. The slotted tubes 37 are formed integrally with or secured to bolts or studs 40, which are adapted to engage and project through slots al. extending downwardly from the upper edges of the end plates 14. Washers l2 engage the projecting ends of the bolts and overlap the These tubes The screen cloth is wound around walls of the slots 4l, and the nuts 43, engaging the bolts and seating against the washers, which are capable of adjustment in order to adjust the tension of the screen 1ongitudinally thereof.

It will. be observed that the end walls of the frame are somewhat angular in shape transversely to the connecting member 11 thereby conforming to the relative inclination of the complementary sections of the screen cloth. lf desired, baille plates nl5 may be mounted at the ends of the screen cloth to prevent loose materials from passing over thetubes 37 at the ends of the screen. These ballles may be mounted in any desired manner, but are preferably provided within-- turned lower edges, which enter the slots 37 in the tubes and are gripped between the rods 38 of the` walls of the slots.

The vibrator 50, utilizes the principle of rotating moments as set vforth in my c0- pending application, Serial No. 275,32l, in producing vibration lt is arranged to be actuated internally and is mounted on the connecting member ll midway between the ends of the supportingframe, and is housed in a casing 5l, which is formed in two parts., each -part including an enlarged central p0rtion 5l, of comparatively large diameter, and a smaller end portion 51h, of small dianieter. wall 52 which connects it with the reduced part 51h, and each part 51b 'has an end wall 53 which is spaced inwardly from the end thereof, leaving a circular depression 54. The two parts of the casing 51 are secured together by means of a series of bolts 55., which extend through apertures in the end walls 52 located just inwardly from the outer cylindrical walls of the parts 51a.' These bolts are engaged at their ends by washers 56 and 57, by which the two parts of the casing are securely clamped together. On its lower side the casing is provided, on the meeting line of the two parts of the casing,.

with an apertured boss having a bearing collar 58 mounted therein. The annular beveled surface of this bearing collar adapted to coact with a similar beveled surface formed on a supporting collar 59, which is adapted to rest upon and be secured to the connecting .member ll of the frame. A strap .60 extends around the vibrator 50 above the collar 59, and the threaded ends of this strap extend through ears ll on the sides of the 'frame member' ll, `thus securely clamping the central part of the casing in position on the frame. For purposes of ventilation the connecting member is provided with an aperture 6l. extending inwardly,Y from one end thereof, and this aperture communicates with the opening 62 formed through the collars 58 and 59, so that air can flow or be forced into the interior of the cen-- trally enlarged portion of the casing.

YFlach central portion has anend lllll lll!) The air introduced into the casing is for the purpose of cooling an electric motor, which comprises a iield winding 6a mounted in an annular metallic casing 65, which, with the casing 5l, serves as the field trame oi? the motor. The armature 66 of the motor is mounted within the ield winding 64 on a shaft 67 which extends longitudinally between the end walls 53. rlhis shaft is journaled in bearing casings 7 0, which comprise enlarged parts 70a located in the parts 5la of .the casing, and the reduced parts 70b located in the end portions 5lb of the casing. The annular walls 7l of the part 70il interlockwith the frame member 65 ot' the motor, as shown at 72, and are provided with apertures 73, through which the air admitted through the aperture 6l is permitted to pass to the motor from the spaces around the bolts 55. The end portion 70b of each bearing casing is provided with a part at its end which closely iits the annular wall oiz the end portion of the casing 5l, and the end walls of thev bearing casings are provided with bearings 76 and 77, in which the shaft 67 is journaled. The reduced part 70b of each end casing is hollowed out between the end walls thereof to form cavities 78 adapted to receive lubricating` oil, which may be inserted through the apertures, which are normally closedfby studs 79 adapted to prevent relative rotation of the bearing casing with respect to the casing 51. The end portions 67a of the shaft project through the bearing casing 70 and are adapted tocarry cages 80, which, with the spherical balls 81,

`form the unbalanced elements by which cir* cular vibrations are imparted to the free ends of the casing. Each cage is provided on opposite sides thereof with a row of recesses 82, of circular cross section and conical formation, these recesses being adapted to receivethe balls 8l. The balls are located in one series r`of recesses only in each cage, leaving the recesses on the diametrically opposite side of the shatvaca-nt. The balls are carried around by the cage during the retation of the shaft, and are adapted to travel on independent raceways 83, which are arranged side by side between the bearing casing and the end Wall of the vibrator casing, and which are secured to the vibrator casing to prevent rotation thereof. These raceways are hollowed out annularly on their inner sides, as shown at 83a, and the balls travell in these hollowed outl portions during the rotation of the cage. Since the balls are located 'only on one side ot the shaft, the rotation of the cage produces an unbalancing` effect by reason of the centrifugal action or' theballs, so that substantially circular vibrations are set up in the casing.

The vibrations so set up in the casing are transmitted to the screen cloth by means ot a pair ot transmitting plates 85. These plates are relatively wideA at their central. portions and taper toward their ends, and the enlarged central portions are provided with apertures 85a which are adapted to cngage the extremities S6 oi the casing These extremities are tapered on their outer suriaces to lit the corresiionding tapered apertures 85a, and after the plates have been driven to position on the casing they are secured thereon by means of transverse tapered keys 87, which engage oppositely dis posed apertures in the parts 86. The plates are thus mounted rigidly with respect to the free ends ot` the vibrator casing, and they extend upwardly therefrom in planes normal to the planes ot' the screen sections and transverse to the direction in which tension is applied in the screen, and engage the under surfaces or' the woven wire screen 35. rlhe plates 85, which are of metal, are preterably provided along their upper edges with wooden transmitting members 88, which are somewhat wider than the plates 85 and which bear directly on the under surfaces of the screen sections. The upper edG'es or' the plates are somewhat angular in contour, so that the wooden transmitting' members 88 on each plate have an angular inclination corresponding to the relative inclination of the two sections 35 and b ci the screen.

The cages 80, which are mounted in opposite ends of the vibrator casing, are preterably mounted in the same plane,-and the balls Si in one cage are preterably mounted diametrically opposite the balls 8l in the other cage. Since the central part oi" the vibrator casing is substantially fixed with respect to the r'rame and the projecting ends through it vibrate, the rotation or the cages in the ends of the casing willV set up circular vibrations therein, and it' the balls in the two cages are on opposite sides otthe shaft the vibrations in one end oif the casing will be out ot phase with those in the other end, so that the casing as a wiole tends to vibrate about its central part with the i'ree ends ot the casing traveling in patl s ot' minute ainplitude.y rlhe vibrations so produced are transmitted to the screen cloth by the plates S5, thereby setting up vibrations oit' small amplitude in each particle or the screen medium. The shatt ot' the vibrator is parallel to the planes or the screen sections so that the vibrations produced are in planes normal to the plane of the screen and transverse to the direction in which tension is applied in the screen. The vertical planes lin which the vibrations taire place also contain the paths of travel of the loose materials passing'downwardly over the screen. The character ot this vibration is illustrated somewhat diametrically in Fig. 5, which shows an enlarged sectional view or the screen ycloth taken in a plane perpendicular to the airisr of the Vibrator and transversely tothe direction in which tension is applied to the screen. Each particle of the screen cloth tends to more in a path 90 slmwn :is substantially circular iii siiape. lilith the vibrator located beneath the casing'in the manner illustrated, the direction ot rotation is preferably in a clockwise direction, as

viewed iii Fig. 3, so that the peripheries ot the rotary elements oit' the vibrator are niovduce an instantaneous or momentary retard-` ation oit the particles ot loose materials passing downwardly over the screen.

.ln practice, the motor, or other driving ineans, which is employed to operate the yi bratoi, should preferably drive the shati; ata relatively high speed. For example, a-

Aspeed of thirty-.six hundred revolutions per minute has been round to give satisfactory results in the screening crushed ore. The screen cloth should, preferably, be 4under high tension, or in a substantially stili' and rigid condition. l Where relatively coarse screens are used the tension therein may be considerably decreased, or eliminated altoget-her, andthe amount or' tension ifor the most satisfactory 'vibration ot the screen cloth Will Vary, dependii'ig upon .the character of 'the material being screened, the speed ot vibration, andtl'ienature or vthescreen cloth used. The proper conditions can best be determined by trial. `When the parts ot the mechanism are properly adjusted, the rotation ol' the ifibrator will result in the settinol u i oit liioh ifreui'iencf Vibrations in thev n n l .l

screen cloth. `These Vibrations, although they are minute, are Very pronounced in their effect upon the materials being screened, and.

' l )ueftothc novel coi'istructjion ol" 'the iframe and method oi mounting the vibrator, all of the parts olf' the vil 'ating mechanism are llo-` cated beneath 'the screening medium, leaving the upper surface oil1 'thescreeii cloth entirely ilrec, as well as the region beneath the screen at the upper and lower edges thereof. This maires it possible to mount the screening` apparatus conveniently, and tooperate it under all conditions with the highest el'liciei'icy.

i-llthouglil l have shown and described one iorni oi the invention it'or purposes oit illustration, it Willbe i'inderstood that it may be constructed in various other embodiments without departing from the scope oit the appeiided claims.

inenibi-rf a horizontal siipporting base membei' ai ged to'connect integrally said end nienibe and :means it'or piyotally supportingsaid traine. l

f2. In ricrceiiing apparatus, a supporting traine comprising opstanding parallel end members, a horizontalsupporting base inem- Je' i gsd to connect integrally said'end incnibei -1 said end members having edges adapted to support a screen frame, and ineaiis'ifor pivotally supporting said frame.

3, lhe combination in screening apparasubstantially parallel end frame mem# i single connecting member extending ciitlie central parts ot said end VVtrame ibers, a screening iiiiedium mounted bei said end .trame members, the lateral oite said screening medium being unrtcd and Vibrating means mounted on said connecting member and connected to screening medium to transmit vibra- 'i ons thereto.

et. The combination in screening appara- ,fas olvl an integrally 'lornied trame comprisj end walls and a connecting member, a een cloth mounted between said end frame members, and vibrating means mounted on said connecting member andconnected to sind screen cloth to transmit Vibrations` thereto. p n

5. 'llie combination in screeninguppara tus ot parallel end trame members,` a single connecting member `extending between the ral parts ol said end trame members and a i `ne parallel to the plane of said. end iti-aine members, ascreeningl medium mountcd between said end trame members, a yibrator mounted on the body portion oi' said connecting member, and means for operatively connecting said vibrator to said screeiiinv in num to transmit vibrations thereto. G. The combination inscreening apparatus ol an integrally termed supporting trame comprising upstanding end members anda hoi. intal connecting member, a screenclotli incurred between said endinembers, and` means tor mounting said trame with said screen cloth in an inclined position.

7. he combination in screening apparatus ol" an integrally formed supporting frame con'iprising opstanding end members and a horizontal connecting member, a screen clot-h mounted between said end members a vibra fing the body portion thereotl located in Slt).

lll() tor, means for mounting said frame With said screen cloth in an inclined position, and

`means for changing' the angular position of insonne end wallssubstantiall;T parallel'to said connectma'v member, and 'a vibrator mounted on said connecting member' midwa7 betweeny said end walls and operatively connected to said -screen cloth, said vibrator and saidconnccting member' being located beneath said screen cloth.

9. The combination in screening' apparatus of substantially parallel end frame members, a longitudinal frame member extending; between the central parts 'of said end frame members, means connected 'to said end frame members for 'iounting' them in an inclined position, a screening medium extending tween said end frame members, and a Y' tor mounted on said longitudinal member and operatively connected to sai screening' medium on the uncerside thereof.

l0. The combination in screenin(r apparatus of substantiall;7 parallel `end i' e neinbers mounted in an inclined position, a screen lcloth mounted in an inclined position between said end frame members, a lon midinal frame member located beneath said screen cloth and having' the ends thereof upturned and connected to said end trame members, a. vibrator mounted on said longjgi- 'tudinal frame member, and a transmitting' Vmember extending upwardl;rv from said vibrator in a members.' 1 y 11. rllhe combination in screening apparatus of substantially parallel end frame memplane parallel to said end frame `bers mounted in an inclined position, a

screen cloth mounted in an inclined position between said end frame members, a longitudinal frame member located beneath said screen cloth and having the ends thereof upturned and connected to said end frame members, a vibrator mounted on said lonnitudinal fra-me member, a vibrator casina' having),` itsl central part rigidly,7 secured to said longitudinal frame member and having the end portions thereof free to vibrate, and' plates secured to tie free end portions of said vibrator casing;- and extending' upwardly therefrom to engage said screen cloth.

l2'. The combination in screening appara.- tus of sub'stantialljvfv parallel end frame meinbers mounted in an inclined position, a screen cloth mounted in an inclined position between said end frame members, a longitudinal frame member located between said screen cloth and having' the ends thereof upturned and connected to said end frame members, a. vibrator mounted on said longitudinal frame member, ay vibrator casing having' its central part rigidly secured to said longitudinal frame member and having' the end portions thereof free to vibrate. platessecured to the free end portions of said vibrator casing and extending upwardly7 therefrom to engage said screen cloth, and means in said vibrator casing for producing substantially. circular' viln'ations in the free end portions thereof.

rThe combination in screening apparatns ofparallel end frame members. a screen cloth stretched between said end frame members, a longri'tudine.l frame member connecting said end frame members and located beneath said screen cloth. and vibrating' means mounted on said longitudinal'frame members and operativelyv connected to said screening' cioth for producing minute circular vibrations therein.

Af. The combination in screening' apparatus of parallel end frame members. a screen cloth mountechin an inclined position and stretched between said end fram members,

longitudinal frame member extending' beween said cnd frame members beneath said `ns ca fied bv said lonnembei' n mi lar vibrations cloth. the .direction of mov said screen ent of each ticle of the screen cloth ben' toward the edge of the screen cloth when in the .ier part of path of vibration.

i5. The combination in screening' apparatus of parallel end frame members. a screen'cloth mounted in an inclined position between said end frame Ymembers, a longitudinal frame member extending' between said end frame members'beneath said screen cloth, means carried by said longitudinal frame member for producing' minute circular vibrations in said screen cloth, the direction of movement of each particle of the screen cloth being' toward the upper edgre of the screen cloth when in the upper part of its path of vibration, and means for causing' loose materials to pass downwardly over said screen cloth.

16. The combination in screening' apparatus of end frame members, a screen cloth mounted in an inclined position between end frame members, means for causing loose materials to pass downwardl7 over said screen cloth transversel;7 to the direction in which tension is applied. a longitudinal frame member extending between said end frame members beneath said screen, and vibrating mea-ns mounted on said longitudinal frame member and connected lo said screen cloth for producing' circular vibrations in said screen cloth in planes normal to the plane of the "screen and transverselj.7 to theA direction in which tension is applied.

17. rl`he combination in screening' apparatus of end frame members, a screen cloth mounted in an inclined position between end frame members, mea-ns for maintaining' tension in said screen cloth longitudinall7 thereof, means for causing loose`V materials to pass downwardly over said screen cloth transversely to the direction in which tension is applied, a longitudinal frame member extending between said end frame memproducino' :-1.

llt)

bers beneath said screen, and vibrating means mounted on said longitudinal frame fiember and connected in operative engagement with said screen cloth for producing circular vibrations in said screen cloth inv planes normal to the plane of the screen and transverselyto the direction in which tension is applied, the direction of movement of each particle of the screen cloth in the upper part of its path-oi. vibration being toward the upper part of' said screen cloth.

18. The combination in screening apparatus oit parallel end frame members, a screen cloth mounted in an inclined position between said yend frame members and having tension maintained therein in a longitudinal direction, a longitudinal frame member extending between said end frame members beneath said screen cloth, a vibrator casing having the central part thereoie` mounted in substantially fixed position on the central part of said longitudinal 'frame member, said vibrator casing having free end portions, means comprising unbalanced rotary elements in said end portions forproducing minute circular vib'ations therein, and plates mounted on the free end portions of said casing and' extending `upwardly therefrom in planes normal to ythe plane of the screen and transversely to the direction in which tension is applied in said screen cloth for transmitting said circular vibrations to said screen cloth;

19. The combination 1n screening apparatus of parallel end frame members, a

screen clothfmounted in an inclined position between said end frame members and having tension maintained therein in a longi-` tudinal direction, a longitudinal frame member extending between said end frame members beneath said screen cloth, afvbrator casing; having` the central part thereoi' mounted in substantially fixed position on the central part of .said longitudinal frame member, said vibrator casinghaving free end portions, means comprising unbalanced l rotary elements in said end portions for In testimony whereof, I have subscribed my name.

BENJAMIN A. MITCHELL.

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