US3565352A

US3565352A - Ball mill liner having bricks with wear indicators

Info

Publication number: US3565352A
Application number: US797604A
Authority: US
Inventors: Robert F Rea
Original assignee: Champion Spark Plug Co
Current assignee: Federal Mogul Ignition LLC
Priority date: 1969-02-07
Filing date: 1969-02-07
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23

Abstract

A ball mill has a lining of bricks, selected ones of which have colored inserts extending toward the faces of the brick from the backs thereof for a distance of one-eighth to one-third the thicknesses of the bricks. When the bricks wear to the point of possibly failing, the colored inserts are readily visible to show that the liner requires replacement. Preferably the colored inserts are of the same refractory material as the bricks themselves and have a coloring material added thereto. This minimizes contamination of the material being ball milled.

Description

United States Patent Robert F. Rea

Bloomfield Township, Mich. 797,604

Feb. 7, 1969 Feb. 23, 1971 Champion Spark Plug Company Toledo, Ohio Inventor Appl. No. Filed Patented Assignee BALL MILL LINER HAVING BRICKS WITH WEAR INDICATORS 7 Claims, 5 Drawing Figs.

US. Cl 241/182; 52/596; 264/60 Int. Cl B02c 17/22 Field of Search 241/182,

183, 299, 300; 51/164; 52/105, 596; 264/29, 30, 60, (lnquired classes) 220, 106, 110, 259

[56] References Cited UNITED STATES PATENTS 1,775,396 9/1930 Jackman 52/596 2,184,601 12/1939 Konopicky 52/612 3,037,468 6/1962 Snellman 52/105X 3,110,448 11/1963 Landes 241/182 Primary Examiner-Donald G. Kelly Att0rney0wen & Owen ABSTRACT: A ball mill has a lining of bricks, selected ones of which have colored inserts extending toward the faces of the brick from the backs thereof for a distance of one-eighth to one-third the thicknesses of the bricks. When the bricks wear to the point of possibly failing, the colored inserts are readily visible to show that the liner requires replacement. Preferably the colored inserts are of the same refractory material as the bricks themselves and have a coloring material added thereto. This minimizes contamination of the material being ball milled.

BALL MILL LINER HAVING BRICKS WITH WEAR INDICATORS This application is a division of my copending application, Ser. No. 533,033 filed Mar. 9, 1966.

This invention relates to a ball mill with a liner of bricks, selected ones of which have means to indicate when a predetermined amount of wear of the brick has occurred.

A brick according to the invention is particularly useful in the liner of a ball mill container wherein the liner is subjected to wear while the ball mill is operated. In a ball mill, the rate of wear of the liner is difficult to determine and can vary greatly according to such factors as the type and amount of the charge and the percent of solids therein, the size, density, hardness, and quantity of mill balls, and the rate of revolution of the ball mill container. It is also difficult to determine the amount of wear, as by measuring the interior of the ball mill container, because the wear varies considerably for different portions of the container. Such measurements are also difficult to obtain because more than half of the volume of the mill container is normally filled with mill balls. An accurate measurement, consequently, is only possible by removing many of the mill balls. This requires considerable labor and time, particularly in larger mills which may contain several tons of the mill balls. Consequently, it is easy for the liner to wear, before being noticed, to the extent that portions break away and contaminate the charge. The wear also may be enough that the outer wall of the container is exposed and worn by the mill balls to the point of contaminating the charge or even causing .taLitset ila tslst tye The present invention relates to a ball mill liner having marking bricks with indicators .or inserts which, when exposed, indicate to the operator that the liner has worn a predetermined amount. The marking bricks with the wear indicators need not be placed throughout the liner but only in strategic locations where wear is greater, or in a predetermined pattern in the liner to provide a representation of the wear. Either arrangement keeps the cost of the liner at a minimum because the marking bricks, which are more expensive, are used only to the extent necessary. Also, the marked or colored insert of each brick is only a small percentage of the overall brick. This is important where high purity of the charge is required since the contamination from the colored In a preferred form, the colored insert of the marking brick is of a colored ceramic material, the ceramic material being the same as that used in the brick, so that a minimum difference in expansion or shrinkage will occur between the brick and the insert and also so that the colored material will minimize contamination of the charge, being of the same basic material as the brick. V

i It is, therefore, principal object of the invention to provide a liner for a ball mill which indicates when'a predetermined amount of wear has occurred.

7 Another object of the invention is to provide a ball mill liner having marking bricks with wear indicators, I IVIariy other objects and advantages of the invention will be apparent from the following detailed description of preferred embodiments thereof, reference being made to the accompanying drawing, in which:

FIG. 1 is a view in perspective, with parts broken away and with parts in section, of a ball mill having a liner embodying the invention;

FIG. 2 is a fragmentary view in perspective of a container of the ball mill of FIG. 1;

FIG. 3 is a view in perspective of a brick for the liner of the ball mill, which brick has a colored section therein;

FIG. 4 is a view in perspective, with parts broken away and with parts in section, of a slightly modified mill liner brick embodying the invention; and

FIG. 5 is a view in perspective of a modified brick for the liner of the ball mill, which brick has another type of colored section therein.

A ball mill ofthe general type for which the brick according to the invention is particularly useful is shown in FIG. 1. The ball mill basically includes a drive unit 10 for rotating a ball mill container 12 which is rotatably mounted on

bearing units

14 and 16. The container 12 has an outer metal wall 18 and a liner 20 and circular end walls 22 which also can include outer metal walls and an inner ceramic liner similar to the liner 20.

A particularly useful application for the ball millis in the mixing and grinding of ceramic batch material for spark plug insulators. Such insulators require a high degree of purity as well as a high degree of uniformity. Consequently, the materials must be mixed for long periods of time and must be subjected to minimum contamination from the ceramic liner 20. In the event that the liner 20 becomes too thin during use, portions thereof can break away and contaminate the ceramic batch material so as to impair the quality of the final spark plug or other product made with the ceramic material. The wear also can be excessive to the point that the outer metal wall 18 is exposed with small pieces of metal being worn away and contaminating the batch. Over a period of time this wear even can cause failure of the outer wall 18 and result in expensive repairs for the ball mill. The extent of the wear of the liner 20 cannot be accurately determined by the length of time the ball mill is in use because the wear varies greatly. As pointed out previously, the degree of wear will depend on the type and amount of the charge and percent of solids, as well as the size, density, hardness, and quantity of the mill balls employed. The rate of revolution of the ball mill container 12 also is a factor in the rate of wear. Attempts have been made heretofore to determine the amount of wear of the liner by taking diametrical measurements in the container 12. This has not been reliable or practical, however, because the wear in the container is not at all uniform and because the measurements are difficult and time consuming to obtain, due to the presence of the mill balls,

To overcome the above problems, marking bricks 24 are used as part of the liner 20. In one form of the invention, the brick 24, as shown in FIG. 3, is of generally rectangular configuration with slightly tapered sides to fit properly in the and mixed. The height of the section will be from one-eighth to one-third the height of the brick 24 and usually will be from about one inch to about three inches thick. The width and length of the colored section 28 are not critical but these dimensions should be small to minimize contamination, and yet be clearly visible when exposed. If desired, however, the colored section can constitute a layer extending over the entire back of the brick.

The colored section 28 is preferably made of the same material as the brick but with a colorant, preferably a strong one, added. By way of example, cobalt oxide or chromium oxide are desirable for alumina brick. However, small amounts of oxides of manganese, iron, or nickel, or any combination, can also be used. Other colorants also can be used but are usually more costly than those just set forth. Examples are titanium, vanadium, and copper compounds. The colored sections can also be made by adding carbon or metals to the ceramic and firing in an inert atmosphere. Amounts of about one-half percent to about 2 percent, by weight, of the colorants added to the ceramic material are usually sufficient. By making the section 28 of the same material as the brick, the effect of contamination is minimized since the contaminating colored material is the same as that of the brick except for the additional colorant,

By way of example, the brick and the insert can have the following compositions:

Moisture in the amount of 9-12 percent by weight can be added to the batches and the final shaped brick and insert then fired to cone 16, for example, for vitrification.

The brick 24 of FIG. 3 can be extruded in a continuous body and then cut transversely to the predetermined brick length. The colored section 28 also can be extruded separately and then cut transversely into sections equal substantially to the width of the slot 26. The slots 26 are then cut in the larger surface of the brick 24 and the colored sections cemented in by means of a thick slip made from crushed, raw brick. The extrusion pressures and other conditions for the brick 24 and the colored section 28 should be alike and the orientation of the brick 24 and the section 28 should be the same to prevent shrinkage cracks which otherwise can occur, particularly since extruded pieces tend to have a high degree of shrinkage. Consequently, if the brick 24 is extruded lengthwise, then the colored sections 28 should be extruded in widths equal to the widths of the brick 24 or the length of the slot 26. The extruded colored section is then cut transversely into sections equal to the widths of the slots 26.

The bricks 24 need not be used throughout the liner but can be employed only at strategic positions or in a predetermined pattern as shown in FIG. 2. In this manner, a minimum number of the more expensive marking brick 24 need be employed and contamination by the exposed coloring section is a minimum. By way of example, it is sufficient to have less than one out of ten ofthe bricks in the liner be a marking brick. The mill lining wear is usually considered to be about one percent of the charge being milled. Further, if the marking section 28 includes 2 percent of the colorant and occupies ten percent of the area of the brick, the resulting contamination, even if all of the colored section 28 were exposed, would only be 0.0002 percent. As a practical matter, the liner would be replaced when only a relatively few of all of the colored marking sections 28 were exposed.

Another suitable marking brick 30 is shown in FIG. 4. This brick has a cylindrical recess 32 in which a cylindrical marking section or insert 34 is located. The section 34 can be pressed to shape under a predetermined pressure and then placed centrally in a larger mold cavity with the uncolored ceramic material pressed around it. By shaping both pieces at the same pressure, the problem of shrinkage cracks again can be minimized.

LII

' l 2. Aball mill according to claim 1 wherein said colored A marking brick 36 of FIG. 5 has a recess 38 in which a marking section or insert 40 is located. The brick 36 can be either extruded in accordance with the method discussed for the brick 24 or can be molded in accordance with the method discussed for the brick 30. The important feature of the brick 36 is that the sides of the insert 40 extending toward the face of the brick taper so that more of the colored section is exposed as more of the brick wears. in this manner, the amount of wear can be determined by the width of the exposed colored section. The thickness of the section 40 may exceed that of the

sections

28 and 34 but again will not normally exceed approximately one-third the thickness of the overall brick.

While the section 40 is shown in an elongated shape, it also can be made in the form of a cone or pyramid, if the brick is molded similarly to the brick 30. The sides of the section 40, rather than tapering toward one another, in a direction toward the face of the brick, can taper in the opposite direction so that the exposed portion narrows as wear increases.

various rriodmations of the above described embodiments of the invention will be apparent to those skilled in the art, and

his to'be understood that such modifications can be made without departing from the scope of the invention, if they are within the spirit and the tenor of the accompanying claims.

lclaim: 1. A ball mill comprising wall means forming a generally cylindrical chamber, a ceramic liner for said chamber, and means for rotating said wall means, said ceramic liner for said chamber comprising a plurality of bricks lining said chamber and located in contiguous relationship, said plurality including a predetermined number of marking bricks disposed among said plurality in predetermined positions, each of said marking bricks having a recess in the back thereof extending inwardly toward the face, said recess being filled with a colored material which, when exposed, is readily distinguishable to the eye from the remainder of the brick, said colored material being substantially of the same size and shape as said recess.

material is a ceramic material.

3. A ball mill according to claim 1 characterized by said colored material having a thickness from one-eighth to onethirdthe oyer all thickness of themarking brick.

4. A ball mill according to claim 1 wherein said colored material includes a coloring agent present in an amount not exceeding about 2 percent by weight. 7

s. A ball mill accordin g to claim 1 wherein each of said marking bricks comprises ceramic material constituting at least percent alumina, by weight.

6. A b all mill according to claim 4 wherein said coloring agent consists of an oxide selected from the group consisting of cobalt, nickel iron, chromium, and manganese.

7. A ball mill according to claim 5 wherein said colored material comprises alumina and a colorant not exceeding about 2 percent of the colored material, by weight.

Claims

1. A ball mill comprising wall means forming a generally cylindrical chamber, a ceramic liner for said chamber, and means for rotating said wall means, said ceramic liner for said chamber comprising a plurality of bricks lining said chamber and located in contiguous relationship, said plurality including a predetermined number of marking bricks disposed among said plurality in predetermined positions, each of said marking bricks having a recess in the back thereof extending inwardly toward the face, said recess being filled with a colored material which, when exposed, is readily distinguishable to the eye from the remainder of the brick, said colored material being substantially of the same size and shape as said recess.

2. A ball mill according to claim 1 wherein said colored material is a ceramic material.

3. A ball mill according to claim 1 characterized by said colored material having a thickness from one-eighth to one-third the overall thickness of the marking brick.

4. A ball mill according to claim 1 wherein said colored material includes a coloring agent present in an amount not exceeding about 2 percent by weight.

5. A ball mill according to claim 1 wherein each of said marking bricks comprises ceramic material constituting at least 85 percent alumina, by weight.

6. A ball mill according to claim 4 wherein said coloring agent consists of an oxide selected from the group consisting of cobalt, nickel, iron, chromium, and manganese.