US2235985A - Ball mill - Google Patents

Description

March 25, 1941. DlBBLE 2.235.985-

BALL MILL Filed June 10, 1958 5 Sheets-Sheet l Marion A. DibbZe INVENTOR.

BY M W ATTORNEK March 25, 1941. Mr DlBBLE I Y 2,235,985

BALL MILL Filed June 10, 1958 s Sheets-Skeet 2 Marion A.Dz' 191) e INVENTOR.

M e ATTORNEY March 25, 1941. M DlBBLE I 2,235,985

BALL MILL Filed June 10, 1938 3 Sheets-Sheet 5 Marion A. Dibble IINVENTOR.

7 BY M C 7%? ATTORNEY,

- shell.

.Patented Mar. 25, 1941 BALL MILL Marion A. Dibble, Toledo, Ohio, designer to E. I.

du Pont de Nemours & Company, ,Wilminzt Deb, a, corporation of Delaware Application June10, 1938, Serial No. 212,872

4 Claims.

This invention relates to ball mills and more particularly to a device for increasing the grind ing action in such mills.

lvlills or this type have been known for many I years and several devices have been suggested for increasing their efliciency. Among these are ballle or lifter bars on the shell oi the mill. These bars are usually disposed horizontally and parallel to the axis of rotation. Devices of this type are designed to increase the number of impacts between the balls during one revolution of the mill.

In ball mills with or without baille or lifter bars. there is'usually an area in the mill as it rotates in which there is little if any relative movement between the balls. Consequently, such areas represent lnefliciency and the necessity of a prolonged time in grinding.

Thi invention has as an object a device for increasing the efficiency of ball mills. A further object is the provision of a device within the mill which effects a saving in time and energy in the grinding of the material.

Other objects will appear asthe description of the invention proceeds.

These objects are accomplished by providing a conventional or other type of ball mill with bars, blades, discs, or other forms disposed at right angles to the axis of rotation and which have the effect of reducing the inactive areas of the rotating mill, 7

In the drawings, all ofthe -odd numbered figures represent sections through a ball mill parallel to the axis of rotation. The even numbered figures represent sections through the mill along the lines indicated in the next lower odd numbered figure. In all of the figures, the reference numbers refer to the same elements.

In Figures 1 and 2,1 represents a flat bar extending across the interior of the ballmill in a. perpendicular direction to the axis, 2 represents a similar bar running transversely to bar I. In

Figures 3 and 4, element 2 is disposed at an" angle to produce pitch. Bars 1 and 2 are welded as indicated at 3. However, instead of being welded, th bars may be bolted'o'r attached by any suitable means to each other and'to the mill The mill shell is indicated as 4. Additional bars may be provided as shown in Figures 5 and 6 which extend horizontally and are substantially parallel to the axis of rotation. These are shown as 5.

In Figures 7 and 8, an alternate modification is shown in which the bars are replaced by discs indicated as 6, mounted on a shaft I which is integral with the shell. The discs in this modihcation are of less diameter than the-shell to provide a clearance for passage of the material.

In Figures 9 and 10, the discs 6 are attached to th shell I by means of a tube or rod 9. In

Figures 11 and 12, the discs of the two previous figures are provided with spoke-like radial protuberances from the surface thereof shown as 8. In Figures 13 and 14 there are two discs which are connected by means of four bars welded to them. In Figures 15 and 16, the discs have curved corrugations which are indicated as 9. In Figures 17 and 18,the discs 6 are provided with perforated protuberances shown as Hi.

In the operation of the mill, the balls are placed inside the shell together with the material to be ground through a suitable opening (not shown) and the mill is rotated in the usual way and about at the usual speed.

While no theory of operation and increased efliciency is advanced, it has been found that mills oithe designshownin-I lgures 1 and 2 reduce the grinding time of certain pigments from 47 hours to about 30 hours. In general, it may be expected that mills of the type herein disclosed will reduce the time of grinding by approximately 30%. Those of the type herein disclosed are much more eilicient than mills having bellies or lifter bars attached to the inside of the shell.

The mill herein disclosed was designed primarily for grinding pigments and dispersing the samein vehicles such as oleo-resinous varnishes, synthetic resins, cellulose derivatives, and the like. .The mill may, however, be used for any purpose for which conventional ball mills may be used. It is apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof; and,

therefore, it is not intended to be limited except as indicated in the appended claims.

I claim:

1. A ball mill having an outer shell rotatably mounted on'an axis comprising a cylindrical casing with two closed ends defining a grinding chamber, a plurality of spaced flat members made integral with the said shell, the side of the said fiat members being substantially at right angles to the axis of the shell, said flat mem-' bers being discontinuous near the said shell, thereby forming a passage past the said flat members adjacent to the shell sufliciently large to permit the passage of the charge therethrough.

2. The ball mill of claim 1 in which the flat member is a disc. I

3. The ball mill of claim 1 in which the flat member is perforated with a large number of perforations.

4. The ball mill of claim 1 in which the flat member is a disc having a diameter smaller than the internal diameter of the shell and attached thereto by means of short p MARION A. DIBBLE.

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