US2201889A - Colloidal mill - Google Patents

Description

y 21, 1940. v L.-M.D|xo- ,201,889

COLLOIDAL MILL Filed July 3, 1937 Patented May 21, 1940 UNITED STATES PATENT OFFICE COLLOIDAL MILL Application July 3, 1937, Serial No. 151,888

3 Claims.

My invention relates to machines for comminuting materials and more particularly to that class of, grinding machines which are used for very fine grinding and are commonly called 001- loidal mills.

The objects of my invention are to provide a mill of very high capacity, simplicity of construction, ease and accuracy of adjustment of the grinding surfaces and low cost of maintenance.

Other objects of the invention will be obvious from the following description or may be learned by practice with the invention.

These objects I attain by means ofv the devices and constructions shown by way of example in the accompanying drawing, which is a section through the center line of the mill.

The shell or casing of the mill is made up of two parts, i and 2; a disc runner 3, consisting of a thin disc of abrasion resistant flexible material, is positioned between the two parts of the casing with a predetermined clearance between casing and runner at the peripheral portion 4 of the runner. A shaft 5 having a circular head 6 and to which is fitted a disc 1 provides a driving means for rotating the disc runner 3. The shaft 5 is provided with a thread II and lock nuts l2 by means of which the shaft head 6 and disc I are caused to clamp and tightly hold runner 3 between their inner surfaces. Bearings 8 and 9 are carried by a sleeve i3 which fits inside the hub of easing member 2 to which it is adjustably attached by cap screws M by means of which the accurate adjustment of the runner 3 midway between casings l and 2 at its periphery 4 is accomplished. Accurate adjustment may be made by varying the thickness of shims l 5. The distance between the two shells of the casing at the peripheral portion 4 of the runner 3 is fixed by the thickness of the shim or gasket [6. In the center of easing member I there is provided a feed opening I! which is threaded for pipe connection. In casing member I is also a discharge connection it, which is also threaded for pipe connection. The runner 3 is provided with a plurality of openings I9 through which material entering through the feed opening I! on one side of runner 3 may pass to the opposite side.

Casing members I and 2 are so shaped as to be internally concave on the inside, thus providing a feeding chamber having a relatively large volume of space at the center of the runner and gradually tapering off toward the peripheral portion of the casing where the casing surfaces are substantially parallel and very close to the disc 3, thus preventing the passage of any granular material having particles larger than the clearance between the disc 3 and the inner surfaces of the casing. By adjusting the clearance between the disc 3 and the casing surface to a very 5 small amount there is strong assurance that no particles of larger size or diameter can pass through. The centrifugal force due to the circular motion of the contents of the mill brought about by the high speed of rotation of the disc '10 3 tends to forcibly feed the material to be comminuted toward the periphery of the internally concave casing members where it is very finely comminuted as a result.

In the past the construction of colloidal mills 15 has been of a relatively complicated nature, involving very close fits and small clearances between co-acting and interacting parts. The result of such close clearances was that when the mill heats up, as they usually do when heavily 20 loaded or grinding extremely fine, unequal expansion of heated parts reduced clearances to zero or actually caused contact between parts and damaging the mill.

It will be obvious upon inspection of. the pres- 25 ent device that no possible amount of expansion of any of the parts can cause damage to any part.

The close and accurate adjustment of clearances in such mills is a matter requiring skill and precision whereas in my new mill the only 30 adjustment necessary to insure proper grinding is the distance between the grinding surfaces of the two parts of the casing and since that distance is controlled by the thickness of the shim or gasket l6, there is no possibility of any change 3 in clearance between grinding surfaces, except as wear takes place, and then a slightly thinner gasket is substituted. Any expansion of the easing or of the disc runner due to temperature changes has no detrimental effect upon the action 4 of the mill.

Another marked advantage possessed by my new device, which is not present, to my knowledge in any previous device, is the self adjusting of the flexible disc 3 midway between the grinding 45 surfaces of the shell by reason of the flexibility of the disc. I have found, for example, in a mill designed to receive a disc twenty-four inches in diameter and one-eighth inch thick, of steel, that the springiness of such a disc is sufficient to permit its peripheral portion to adjust itself or center itself between the two adjacent substantially parallel portions of the surfaces of the casing even when not accurately adjusted to a midposition by means of the shims I5. The disc 3,

when revolving in a fluid material containing solids in suspension, floats between two films of the fluid and centers itself automatically between the two grinding surfaces of the shell.

The disc 3 receives the greatest amount of wear and when the peripheral portion is worn to adegree requiring renewal it is a very simple and inexpensive matter to install a new one as it consists only of a plate of steel with suitable holes punched in it. I find that steel discs such as are used in the manufacture of circular saws answer the purpose admirably.

While I have described my new device as a colloidal mill, and while I believe its peculiar and novel advantages are most pronounced when it is utilized for extremely fine grinding, I find that it can also be used to advantage for coarser grinding, and when run at relatively slow speeds.

I do not therefore restrict the use of my device to extremely fine grading. I use the term colloidal mill as descriptive of the class of grinding machinery to which it belongs and not as limiting the fineness of grinding of the product.

Having described by invention so that one skilled in the art may make and use it, I now state what I believe to be new and novel and for which I pray that letters Patent be granted.

I claim:

1. A colloidal mill characterized by a thin, flexible, smooth surfaced, rotatable disc grinding element having a diameter between one hundred seventy-five and two hundred five times its thickness, rigidly mounted on a shaft, and two internally concave circular casing members each having a ringlike grinding surface closely adjacent to the outer circular portion of one of the two side surfaces of said disc, and in spaced relationship thereto, the order of magnitude oi the spacing being sufliciently close to effect grinding of colloidal material.

2. A colloidal mill characterized by a thin, flexible, smooth surfaced, rotatable disc grinding element having a diameter between one hundred seventy-five and two hundred five times its thickness, rigidly mounted on a shaft, two internally concave circular casing members each having a ringlike grinding surface closely adjacent to the outer circular portion of one of the two side surfaces of said disc, and in spaced relationship thereto, the order of magnitude of the spacing being sufliciently close to effect grinding of a colloldal material, means for feeding material to be comminuted to opposite sides of the disc.

3. A colloidal mill characterized by a thin, flexible, smooth surfaced, rotatable disc grinding element having a diameter approximately one hundred ninety times its thickness, rigidly mounted on a shaft, two internally concave circular casing members each having a ringlike grinding surface closely adjacent to the outer circular portion of one of the two side surfaces of said disc, and in spaced relationship thereto, the order of magnitude oi the spacing being suificiently close to effect grinding of a colloidal material, and means for feeding material to be comminuted to opposite sides of the disc.

LEWIS M. DIXON.

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