US2818220A

US2818220A - Vibrating ball mill having baffle plate for increasing retention time of material in mill

Info

Publication number: US2818220A
Application number: US462298A
Authority: US
Inventors: Guy V Woody
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1954-10-14
Filing date: 1954-10-14
Publication date: 1957-12-31
Anticipated expiration: 1974-12-31

Description

Dec. 31, 1957A G. v. wooDY 2,818,220

VIBRATING BALL MILL HAVING BAFFLE PLATE FOR INCREASING RETENTION TIME OF MATERIAL IN MILL Filed Oct. 14, 1954 du vanYo United States Patent VIBRATNG BALL MILL HAVING BAFFLE PLATE FR INCREASING RETENTION TlME 0F MATE- REAL IN Mill.

Guy V. Woody, Milwaukee, Wis., assignor to Alli.,- Chaimers Manufacturing Company, Milwaukee, Wis.

Application October 14, 1954, Serial No. 462,298

4 Claims, (Cl. 241--175) mill for performing Wet grinding operations, that is, the

grinding of materials in the presence of a liquid.

The wet grinding of materials as contemplated herein includes (l) the reducing by grinding of mineral ores or other solid materials held in suspension in a liquid to more or less finely granulated particles, and (2) the grinding of oleaginous materials of cellular character such as linseed, cottenseed and soybean in the presence of a liquid such as a solvent, water or an aqueous solution, the grinding of the material being effective to crush, rupture, press, cut or break the oil cells of the material .to expose or displace the oil so as to permit the oil to combine with the liquid.

With a continuous grinding operation, as distinguished from a batch operation, the wet grinding of materials involves the continuous feeding of a slurry of the material to be ground to a vibrating ball mill and a continuous discharge of a slurry of material from the mill. In practice a complete or finished grinding operation is effected by recirculating through the mill a portion of the material discharged because in many cases, if the material is passed through the mill only once, the retention v .time of the material in the mill is not sufiicient for the material to be ground to the desired fineness. The recirculating of the material may involve a separating operation in which material which has not been suficiently ground is isolated and returned to the feed opening of the mill or, more simply, merely returning a portion of the discharged material to the mill without a separating operation. ln either case, the recirculated material is continuously supplemented with a fresh slurry of material .to comprise the material which is continuously fed to the mill.v

v In wet grinding operations of the type referred to, the longer the material is retained in the mill before it is discharged, the greater is the opportunity for the material to be acted upon and reduced to the desired degree by the grinding balls. lt is to this end that the "present invention is directed.

In accordance with the present invention a vibrating type ball mill is provided having bathe means for increasing the retention time in the mill of the material passing through the mill. The baffle means also functions to prevent portions of material passing through the mill from taking the shortest route from the feed opening to the discharge opening. The advantage of this latter function is that the discharging from the mill of substantially unground portions of material is avoided. An object of the present invention is to provide a new and improved vibrating type ball mill for continuous wet grinding operations in which the retention time in the "ice creased. Another object, which is realized by increasing the retention time, is to increase the effective capacity of the mill in terms of the amount of material ground to the desired size per hour.

Another object of the invention is to prevent portion of the material passing through the mill from taking the shortest route from the feed opening to the discharge opening.

Another object of the invention is to provide a vibrating type ball mill in which grinding bodies of different sizes may be segregated so that larger grinding bodies are effective to grind material at the feed end of the mill and smaller grinding bodies are effective to grind material at the discharge end of the mill to provide an efficient grinding operation.

rOther objects will become apparent from the following detailed description of the invention and the accompanying drawing which shows one embodiment of th invention.

In the drawing:

Fig. 1 is a vertical sectional view through the longitudinal axis of a vibrating ball mill embodying the present invention; and

Fig. 2 is a cross sectional view taken on line lI-l-l of f lFig. l.

Referring to Figs. l and 2, a suitably shaped container liti, illustrated as having a cylindrical shape and havin-g end walls 1l and 12 is suspended by cables 13 from ya stationary overhead supporting structure ld. Resilient means such as springs are provided between cables 13 and supporting structure 14 to allow container lt) to have a vibrational movement relative to supporting structure 11.4.

End walls l1 and l2 are provided with suitably positioned bearing housings and 2i in which

bearings

22 and 23 are mounted. As illustrated herein bearings Z2 and 23 are in coaxial relation to the longitudinal axis 24 of container lil. Rotatably journaled in

bearings

22 and 23 is a shaft 25 with the axis thereof being coincident with the longitudinal axis 24 of container lil. Suitable sealing means and 31 are provided, respectively, between shaft 25 and bearing

housings

20 and 21. A protective tube 26 which surrounds shaft 25 and extends between walls il and l2 of container l0 may be provided.

Weight means 312. and 33 are rigidly attached at opposite ends of shaft 25, preferably in phase with each other, and each of the weight means has a center of mill of the slurry of material fed to the mill is ingravity disposed eccentrically of the axis of shaft 25 and the longitudinal axis 24 of container lll. Upon rotating shaft Z5 the centrifugal forces imparted to shaft 25 by weight means 32 yand 33 are transmitted through

bearings

22 and 23 so as -to cause container 1S to vibrate.

A motor 34 mounted on a stationary support 3a' is provided for driving shaft Z5 of the vibrating bali mill. As the container 1d of the mill is vibrat'able relative to motor 34, a flexible coupling 36 is provided between shaft itl of the motor and shaft 25 of the mill.

A feed inlet al at the top at one end of container lil and a discharge outlet 42 at the bottom at the opposite end of container iti are provided. Means for feeding a slurry of the material to be ground to the mill such as a hopper 413 is also provided and a slurry of material to be ground is continuously fed to the mill through inlet il and a slurry of ground material is continuously withdrawn from the mill through discharge opening 42.

A baffle plate 45 for increasing the retention time of material passing through the mill is provided. Baffie plate 45 extends transversely of the axis of the mill and is mounted in the lower portion of the mill with the upper edge thereof being between the horizontal center line of the mill and the top of the mill. Baie plate 45 may be asiaaeo suitably positioned approximately one-third the length of container from wall 11 thereof.

When the mill is in operation, the ball charge and the material being ground revolves as a whole in a direction opposite the direction of gyration of container lt). Referring to Fig. 2, the gyratory movement of the container 1G is indicated as countercloclrwise and the revolving movement of the ball charge and material is indicated as clockwise.

As seen in Fig. 2, during operation of the mill the upper left portion of container 10 is not contacted by the ball charge and the material. If desired, the partition t5 may therefore be formed, as shown in Fig. 2, with the upper edge thereof disposed at an angle of about relative to a horizontal plane through the axis of the mill.

Material to be ground or otherwise acted upon by the ball charge, which comprises grinding bodies 4o, enters feed inlet 41 in the form of a slurry and flows to the enclosure 47 to the left of baille plate 45. The material is subjected to the grinding action of the ball charge While it is retained in the enclosure 47. As there is a continuous stream of material entering through feed inlet 4l, a slurry of partially ground material continuously overflows baffle plate 45 into enclosure 43 where the material is subjected to further grinding action of the ball charge before being discharged through outlet 42.

A perforated discharge diaphragm or head 49 is positioned near discharge outlet 4Z, the perforations therein being large enough to allow the slurry of material to pass freely therethrough but small enough to prevent the escape of the grinding bodies 46.

ln addition to delaying the flow of the slurry of material through the mill, that is, increasing the retention time, baffle plate 45 prevents portions of material from taking the shortest route through the mill from the feed inlet 41 to the discharge outlet 42. All of the material entering the mill is caused by baffle plate 45 to take a more or less circuitous path before being discharged and all of the material owing through the mill is thereby retained in the mill long enough to receive considerable grinding treating.

A main function of the baffle plate 45 is to prevent oversized particles from passing through the mill without being suiliciently acted upon by the grinding balls. Small perforations in the baflle plate which allow smaller sized particles to pass therethrough may therefore be tolerated without materially affecting the functioning of the baffle plate.

ln a wet grinding operation, apparatus not shown is provided for recirculating through the mill a portion of the material discharged through outlet d2. An overall advantage obtained with the use of the present invention is that a considerably lesser portion can be recirculated without sacrificing the degree of fineness to which the end product of the mill is ground or reduced. The reason is that the baille plate 45' causes the material to take longer to flow through the mill so that there is greater opportunity for the grinding balls to act on the material and, further, portions of material are not allowed to be discharged from the mill without being subjected to a substantial grinding action.

Another advantage which may be obtained with the use of the present invention is that large and small grinding balls may, if desired, be segregated to obtain a more efficient grinding operation. lf one inch and one-half inch balls are utilized, for example, the one inch balls may be disposed to the left of baffle plate 45 at the feed end of the mill and the one-half inch balls may be disposed to the right of bafe plate 45 at the discharge end of the mill. Suitable grating (not shown) or the like could be provided above the upper edge of bale plate 45 which would allow material being ground to flow over the baffle plate but would prevent the segregated grinding balls from doing so. With this arrangement the material to be ground first comes into contact with the larger balls at the feed end of the mill and the relatively larger pieces of material are reduced in size. When the material flows over bafe plate 45 and comes in contact with the smaller balls a liner grinding of the material is effected. With this arrangement the larger grinding balls act upon the large particles of the material being ground and the smaller grinding balls act upon the smaller partially ground particles to provide a very eiicient grinding operation.

While only one embodiment of the invention is described and illustrated herein, it is to be understood that other embodiments and modications of the invention may be made and used Without departing from the spirit and scope of the invention as set forth in the appended claims.

l t is claimed and desired to secure by Letters Patent:

l. A vibrating type ball mill for continuous wet grinding operations comprising a container with a substantially horizontally disposed longitudinal axis and an arcuately formed bottom portion, said container being adapted to be supported for gyratory movement transversely of its axis for advancing material to be ground through said container along a generally spiral path relative to said container axis, an inlet opening disposed at one end of said container at the top thereof and a discharge opening disposed at the other end of said container at the bottom thereof, and a baffle plate for increasing the retention time of material passing through the mill extending transversely of said axis in the lower portion of said container and positioned intermediate said inlet and discharge openings, said baffle plate having a continuous upper edge inclined upwardly in the direction of the transverse component of the generally spiral path of material flow relative to said container.

2. A vibrating type ball mill for continuous wet grinding operations comprising a container with a substantially horizontally disposed longitudinal axis and an arcuately formed bottom portion, said container being adapted to be supported for gyratory movement transversely of its axis for advancing material to be ground through said container along a generally spiral path relative to said container axis, a feed opening disposed at one end of said container at the top thereof and a discharge opening disposed at the other end of said container at the bottom thereof, and a baffle plate for increasing the retention time of material passing through the mill extending transversely of said axis in the lower portion of said container and positioned intermediate said inlet and discharge approximately one-third the length of said container from the feed end thereof, said baffle plate having a continuous upper edge inclined upwardly in the direction of the transverse component of the generally spiral path of material ow relative to said container.

3. A vibrating type ball mill for continuous wet grinding operations comprising a container with a substantially horizontally disposed longitudinal axis and an arcuately formed bottom portion, said container being adapted to be supported for gyratory movement transversely of its axis for advancing material to be ground through said container along a generally spiral path relative to said container axis, a shaft iournaled in said container concentrically with said axis and having eccentric weight means associated therewith for imparting a gyratory movement to said container, a cylindrical casing disposed in said container and surrounding said shaft in concentric relation thereto, an inlet opening disposed at one end of said container at the top thereof and a discharge opening disposed at the other end of said container at the bottom thereof, and a baffle plate for increasing the retention time of material passing through the mill extending transversely of said axis in the lower portion of said container and positioned intermediate said inlet and discharge openings, said baffle plate having a continuous upper edge inclined upwardly in the direction of the transverse cornponent of the generally spiral path of material ilow re1- ative to said container.

4. A vibrating type ball mill for continuous wet grinding operations comprising a container with a substantially horizontally disposed longitudinal axis and an arcuately formed bottom portion, said container being adapted to be supported for gyratory movement transversely of its axis for advancing material to be ground through said container along a generally spiral path relative to said container axis, an inlet opening disposed at one end of said container at the top thereof and a discharge opening disposed at the other end of said container at the bottom thereof, and a baffle plate positioned intermediate said inlet and discharge openings for increasing the retention time of material passing through the mill which extends transversely of said axis in the lower portion of said container and has a continuous upper edge at an angle of about 15 degrees relative to a horizontal plane and the inclination of said edge being upwardly in the direction of the transverse component of the generally spiral path ot material flow relative to said container. 5

References Cited in the le of this patent UNITED STATES PATENTS 926,441 Shatter June 29, 1909 10 983,069 Lindhard Jan. 31, 1911 2,019,454 Larsen Oct. 29, 1935 2,208,077 Linke July 16, 1940 2,298,015 Lincoln Oct. 6, 1942 FOREIGN PATENTS 15 685,226 Germany Dec. 14, 1939