US3776478A - Pulverizer with fixed-arm spacer assembly - Google Patents

Abstract

Apparatus is provided for pulverizing raw coal feed stock into comminuted particles which can be conveyed to the combustion chamber of a furnace. A fixed arm spacer assembly is mounted on the pulverizer table such that the pulverizer rollers are separated from each other to prevent skidding.

Description

O Umted States Patent 1191 [111 3,776,478 Gillette et al. Dec. 4, 1973 [54] PULVERIZER WITH FIXED-ARM SPACER 3,458,142 7/1969 Berz 241/103 ASSEMBLY 3,606,179 9/1971 Romanowski et a1 241/103 3,612,418 10/1971 Barton 241/103 X 1 Inventors Robert Gillette, Randolph 1,401,716 12 1921 McCrae 241 104 Township; Henry P. Kunz, Glen Ridge both of Ni FOREIGN PATENTS OR APPLICATIONS 943,176 12/1963 Great Britain 241/117 Asslgneer Foster Wheeler Corporation, 1,361,757 4/1964 France 241/117 Livingston, NJ. 22 Filed: May 4, 1971 Primary Examiner-Robert L. Spruill Attorney-John Maier, 111, Marvin A. Naigur and John [211 App]. No.: 140,173 5 Wilson 52 US. Cl. 241/103 1 1 ABSTRACT [51] Int. Cl. B02c 15/00 Apparatus is provided for pulverizing raw coal feed [58] Field of Search 241/103, 110, 117, stock into comminuted particles which can be con- 241/118, 119, 120, 104, 173 veyed to the combustion chamber of a furnace. A

fixed arm spacer assembly is mounted on the pulver- [56] References Cited izer table such that the pulverizer rollers are separated UNITED STATES PATENTS from each other to prevent skidding.

3,454,231 7/ 1969 Engler 241/103 3 Claims, 3 Drawing Figures PATENTEDBEB MSIS' 3'776'478 SHEET 10F 2 INVENTORS ROBERT P GILLETTE BY HENRY KUNZ ATTORNEY PULVERIZER WITI-I FIXED-ARM SPACER ASSEMBLY BACKGROUND OF THE INVENTION In connection with the operation of relatively large coal fired furnaces which are used in vapor generating systems in the utility industry for production of electricity, it is necessary to supply finely powdered coal to the combustion chamber of the furnace. The raw coal feed stock is usually reduced to comminuted particles in a pulverizer apparatus which generally consists of a rotating grinding table on which there is formed a grinding surface, and relatively heavy rollers are journaled within the apparatus and maintained in contact with the grinding surface by a thrust ring.

There has recently developed a major problem in connection with the pulverizing of coal feed stocks containing particles which cannot easily be pulverized by the apparatus, such as iron pyrite and the like. These relatively hard constituents are more commonly found in many types of coal which are being mined today. The hard particles often prevent the pulverizing apparatus from functioning efficiently, in that skidding action is translated to the rollers. In accordance with the present invention, the skidding of the rollers has been alleviated by providing a fixedarm spacer assembly with contact pads mounted at the end of each arm. In this manner, the rolling action of any two of the pulverizer rollers can restore a jammed or skidding third pulverizer roller back to a rolling mode of operation. By fixing spacer arms and thereby maintaining pulverizer roller separation, it is possible for force to be transmitted from one pulverizer roller through the hub assembly to another roller. Also, the spacer assembly prevents bunching of the rollers which often is caused by either differences in the pulverizer roller size or obstructions to one or more of the pulverizer rollers. This type of condition creates severe breaking action in one of the rollers and often results in the three rollers simultaneously effecting a skidding mode of operation.

In the past, pulverizers have been used with spacer assemblies consisting of a fixed-arm and two pivoted arms, such that the rollers transmit force to each other through wear pads positioned between the rollers, thereby relieving the spacer arms and hub structure of force transmittance. In this type of pivoted spacer design when one of the rollers began to skid, this would cause the remaining rollers to bunch together, and subsequently all of the rollers would enter into a skidding mode of operation. In accordance with the present invention, roller separation is maintained by the fixed arms and when one of the rollers goes into a skid, force is then transmitted from this skidding roller through the hub assembly to one of the other rollers. Depending on the relative speed of the skidding roller, the rotating fixed arms on either side of it will speed it up or slow it down to bring it out of the skid.

SUMMARY OF THE INVENTION In accordance with an illustrative embodiment demonstrating features and advantages of the present invention, there is provided an apparatus for pulverizing material into comminuted particles including a housing and a table having a grinding surface mounted in the housing for rotation. Means are provided for rotating the table and for introducing the material into the housing in contact with the grinding surface. A plurality of rollers are mounted for rotation about their respective axes and each of the rollers have a peripheral grinding face maintained in contact with the grinding surface, and a thrust ring is mounted in contact with the rollers. Mounted on the table is a spacer means which includes a fixed arm between each of the rollers and a contact pad mounted at the end of each fixed arm. In this manner, the rollers are separated from each other and are prevented from skidding, whereby the rollers travel along the table without rotating about their respective axes and slide along the thrust ring.

BRIEF DESCRIPTION OF THE DRAWINGS The above brief description as well as further objects, features, and advantages of the present invention will be more fully appreciated by referring to the following description of a presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in connection with the accompanying drawings, wherein:

FIG. 1 is a front sectional view of a portion of a pulverizing apparatus embodying features of the present invention;

FIG. 2 is an enlarged sectional view of part of the fixed arm spacer assembly, showing an enlarged portion of the spacer hub; and

FIG. 3 is an enlarged plan view of the rollers and spacer assembly, a portion of which has been sectioned to better show the hub and contact pads.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a pulverizing apparatus is shown which is generally designated by the reference numeral 10. The pulverizing apparatus 10 includes a steel housing 12 which is mounted at ground level for enclosing a rotatably mounted grinding unit 14. Raw coal feed stock is introduced into the housing 12 through a conduit system 16 which is generally positioned above the grinding unit 14.

The grinding unit 14 includes a table 20 on which there is mounted a removable grinding ring 22 formed with an annular groove 24. The table 20 is mounted for rotation on a support and is powered by an electric motor which has not been shown in the drawings for the sake of simplicity.

A plurality of spaced apart pulverizing rollers 26, preferably three in number, are mounted for rotation about their respective axes. Each of the rollers 26 has a peripheral grinding face which is maintained in contact with the outer grinding surface of annular groove 24. The rollers 26 are also formed with a bearing collar 30 which has an annular groove 32. A thrust ring 34 is mounted in housing 12 above the pulverizing rollers 26, and load is applied by means of compression springs 36. The thrust ring 34 is integrally formed with an annular lip 38 which is configurated in accordance with the outer periphery of annular groove 32 in order to achieve smooth mating contact.

In accordance with the present invention a spacer assembly 40 is mounted above the grinding ring 22 by means of a shaft 42 which is fixed to the table 20 for rotation therewith. The spacer assembly 40 includes a hub section 44 having a hollow cylindrical bearing unit 46 on which there is mounted fixed arms 48. As best shown in FIG. 2, hub section 44 includes a lower annular ring bearing 50 and an upper ring bearing 51 mounted on the interior of bearing unit 46 for respectively engaging a lower sleeve bearing 52 and an upper throat bearing 54 which are mounted on the shaft 42. Fron the relatively large bearing clearances shown in FIG. 2, it can be appreciated that spacer assembly 40 is loosely mounted for rotation on shaft 42, such that axial rotation as well as pivotal movement can be achieved by spacer assembly 40 with respect to the central axis of shaft 42.

A contact assembly generally designated 56 is mounted at the ends of each of the fixed arms 48. The contact assembly 56 generally consists of a replaceable contact block 58 having a frustoconical cross-section which is mounted at the end of the fixed arm 48 by means of a shaft 60 formed with a slot 62 for receiving a lower wedge 64 and an upper wedge 66. As shown in FIG. 3, the lower wedge 64 is larger than upper wedge 66, which is secured by a weld connection 68, that can be broken for removing the contact blocks 58. To achieve greater structural stability, the spacer means 40 is provided with an upper spider plate 70 and a lower spider plate 72 which are welded to the fixed arms 48.

During the operation of the pulverizing apparatus 10, it can be appreciated that the spacer assembly 40 rotates on shaft 42 in accordance with the force transmitted by the rollers 26 to the contact assembly 56. Thus, it is possible to operate the pulverizing apparatus with the rollers 26 traveling along the table without rotating about their respective axes and sliding along the thrust ring 34.

A latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features.

What is claimed is:

1. Apparatus for pulverizing material into comminuted particles comprising a housing, a table having a grinding surface defined by a circumferential path mounted in said housing for rotation, means for rotating said table, means for introducing said material into said housing in contact with said grinding surface, a plurality of rollers mounted for rotation about their respective axes and each of the rollers having a peripheral grinding face maintained in contact with said table, and spacer means mounted on said table including a fixed arm between each of said rollers and contact means mounted at the end of said fixed arm for separating said rollers from each other along said circumferential path such that said rollers are prevented from skidding, said spacer means including a shaft fixed to said table and a hub rotatably mounted on said shaft with each of the fixed arms mounted on and extending outwardly from said hub, and said hub formed with an intemal bearing surface for engagement with external bearing means mounted on said shaft, and said internal bearing surface and said external bearing means configurated to afford axial and pivotal movement of said spacer means with respect to said shaft.

2. Apparatus according to claim 1 in which said external bearing means includes a sleeve bearing located in a position spaced apart from the end of said shaft, and a thrust bearing mounted on the end of said shaft.

3. Apparatus according to claim 1 in which said contact means includes a replaceable block having a frusmounted on the end of said fixed arm.

Claims (3)

1. Apparatus for pulverizing material into comminuted particles comprising a housing, a table having a grinding surface defined by a circumferential path mounted in said housing for rotation, means for rotating said table, means for introducing said material into said housing in contact with said grinding surface, a plurality of rollers mounted for rotation about their respective axes and each of the rollers having a peripheral grinding face maintained in contact with said table, and spacer means mounted on said table including a fixed arm between each of said rollers and contact means mounted at the end of said fixed arm for separating said rollers from each other along said circumferential path such that said rollers are prevented from skidding, said spacer means including a shaft fixed to said table and a hub rotatably mounted on said shaft with each of the fixed arms mounted on and extending outwardly from said hub, and said hub formed with an internal bearing surface for engagement with external bearing means mounted on said shaft, and said internal bearing surface and said external bearing means configurated to afford axial and pivotal movement of said spacer means with respect to said shaft.

2. Apparatus according to claim 1 in which said external bearing means includes a sleeve bearing located in a position spaced apart from the end of said shaft, and a thrust bearing mounted on the end of said shaft.

3. Apparatus according to claim 1 in which said contact means includes a replaceable block having a frustoconical crosssection, and said replaceable block is mounted on the end of said fixed arm.

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