US2985390A - Beater mill - Google Patents

Description

May 23, 1961 P. RAETZ BEATER MILL F'il ed Dec. 19, 1958 FIG. I

FIG. 2

1N VENTOR.

PAU L R A ETZ Y @/(M @ZZ/ AGENT BEATER lVIILL Paul Raetz, Stuttgart, Germany, assignor to Kohlenscheidungs-Gesellschaft m.b.H., a corporation of Germany Filed Dec. 19, 1958, Ser. No. 781,657

4 Claims. (Cl. 241-486) The invention relates to a beater mill having a'beater paddle wheel fixedly supported on the end of a horizontal shaft mounted forrotation and having an uprightvconduit for axially feeding into the wheel thematerial to be ground together with a gaseous conveying medium.

One well known type of construction of this mill has the lower portion of the vertical supply .duct through which the mill receives the material together with heated gas or air, organized in the form of an access door. Such construction offers the advantage of providing ready access to the beater paddle wheel by merely swinging the access door away from the mill housing, whereby easy and quick replacement of the beater' plates or the entire beater wheel is greatly facilitated. This is especially important in installations operating in'connection with pulverized furnaces of steam boilers or in industrial furnaces, where the mill not only functions as a pulverizer but also as a blower in conveying the pulverized fuel to the burners. In installations of this type. great stress must be placed on continuous and troublefree delivery of large quantities of coal. Since, however, a large pulverizing capacity causesa correspondingly heavy wear of the beater wheel, the replacement of the beater wheel paddles becomes necessary at frequent intervals. For reasons of economy therefore, both with respect to material as well as With respect to outage time and maintenance costs, it is highly desirable that the wear of the beater wheel platesor paddles be distributed as uniformly as possible. 1

It is accordingly the main object of the invention to co'ntrol the attrition of the beater plates in such a manner that this wear is uniformly distributed over the entire surface that is subject to such wear. sive and fullest use is made of the beater plate material and, above all, the operating time of the mill can thereby be lengthened considerably before replacement of the beater wheel paddles becomes necessary.

In accordance with the invention a considerable improvement in obtaining such uniformity is achieved by providing that end of the supply duct or chute which joins the mill housing with a cylindrical guide or deflector ring, which ring surrounds a radial rotary distributor and extends into the inner space of the beater paddle wheel. This improved construction causes the material which descends through the supply chute and accumulates on the bottom thereof in front of the beater wheel, to be seized and lifted up by the radially extending rotary arms of the distributor. In this manner the material is, by centrifugal force, thrown against and deflected by the deflector ring and is uniformly distributed about the axis of rotation while entering the beater wheel. Thus the cylindrical guide or deflector ring contributes in a substantial degree to the improvement by maintaining uniform distribution of the material over the entire cross sectional flow area. This results in a simultaneous feeding of the mill material to all beater wheel paddles along their entire length parallel to the mill axis, with a uniformity of nite States Patent the beater wheel plates became necessary. At the same time it was possible to increase the mill capacity to a considerable extent.

It has already been proposed to install in the material supply duct of a paddle wheel mill a beater rotor acting as a pre-pulverizer for the purpose of increasing the mill capacity of the entire pulverizing assemblage. In these cases the material to be pulverized was extensively retained in the ante-chamber of the beater rotor, so that it arrived at the beater paddle wheel only after having already undergone a substantial degree of pulverization. Accorddisintegration of the material.

drical guide cause rapid how of the material through the distributor and into the inner space of the beater paddle wheel, whereby the beater paddle wheel is caused to perform a predominantly large portion of the work of pulverization.

Further. details and objects of the invention will become apparent from the drawing and from the following description thereof.

In this manner exten- In the drawing: 7

Fig. 1 shows an elevational cross section through a beater paddle mill;

Fig. 2 is an inside view of the mill door; Fig. 3 is an elevational view of the rotary distributor wheel;

Fig. 4 is an elevational View of the wheel; 1 Fig. 5 is a view similar to that of Fig. 1 but on a larger scale and of another embodiment of theinvention; and

Fig. 6 shows the end of a beater mill shaft when not equipped with the herein disclosed improvements. 7

Referring nowto Fig. 1, the mill comprises a spirally formed housing 1 supporting a mill classifier 2 of conventional design. A paddle wheel 3 arranged for rotation within housing 1 is fixedly mounted on the end of shaft 5 which is rotatably supported by a double bearing 4. Shaft 5 is organized to be driven by an electrical drive (not shown) or other driving means, by way of coupling 6. The beater wheel 3 comprises a circular disc 7 which is joined to a ring-like disc 8 by means of bars 9a which are circumferentially spaced. Bars 9a are protectively provided with beater blades 9 which also serve as blower blades. The rear wall of housing 1 is, in part, formed by disc 7, whereas the front of housing 1 has an opening faced by a hinged door 10. This door is hung to swing about a vertical axis 10a. The door 1%) also forms the lower portio'n 11a of a chute 11 by way of which the material to be ground and the conveying air are axially introduced into the beater paddle wheel 3. Ring shaped disc 12 of the door 10 when swung against the housing 1 can be pressed against the latter by means of screws 12a or similar means to make an airtight connection. The ring shaped disc 12 has attached thereto removable deflector ring 13, which when the door is closed, extends into the inner space 3a of the beater paddle wheel 3. A rotary distributor comprising paddle arms or spokes 15 is fixedly mounted on the very end of shaft 5 for rotation therewith, and in such a position that it is closely surrounded by circular defiector ring 13.

beater paddle Patented May 23,v 1961 When the mill is inoperation the grinding material fallingnthroughchute 11 and accumulating inthe lowen re-.

gion of inlet 14, is seized by the rotary distributor paddles 15, hurled upward against the guide ring 13, to be deflected .th'erefrom.

ingnthrough the. beaterwheelthe.material is ground by the beaterQplates thereof, and.is,.,while being retained in the conveying air, carried into the wind sifter or classifier.

Zby wayv of an .outlet duct 16 which tangentially branches o'iifrom the. mill housingand leads into the interior space.-

material is..discharged with the. conveying air by wayoi.

outlet .19 intoa duct .(no't shown) leading to .astorage bin or place of use.

By opening door 10 deflector ring 13 as Wellas dis-.

tributor. arms 15 are readily accessible, and can if neces sary, be removed and replaced. Furthermore, beater plates:9v can'likewise be replaced through door 10 with.

relativeease. It.is even possible to withdraw through the housing 1 the. complete beater wheel unit including rotary distributor '15, shaft and bearing 4, if replacement thereof should become. necessary.

The embodiment of Fig. 5 illustrates how an. existing beater millcanadditionally be equipped with the herein disclosed inventive. devices. The retaining nut. 2.0a as indicated in Fig. 6, is conventionally employed to secure.

the beater wheel 3 to shaft 5 in a mill not equipped. with the herein disclosed improvement. In converting a.con-. ventional mill retaining nut 20a is replacedby memberlt) which serves as an extension of shaftpS. After being threaded on theshaft in place ofnut 20a, member-20: is secured to beater paddle wheel 3 by means of a set screw 21. The end of extension member 20 is organized for attachment thereto, of, rotary distributor spokes. 15. by means of pins 22 which, in turn, are secured by cover plate 23 and bolt 24. Providing an existing, mill with the rotary distributor 15 in the above manner, and adding the deflector ring 13 by securing the sameto the ring shaped disc 12 such as by bolts 25, will impart to an existing mill all the advantages resulting, from the herein disclosed invention.

While I have illustrated and described a preferred embodiment of my invention it is to be understood that such is merelyillustrative and not restrictive and that variations andmodifications may be made therein without departing from the spirit and scope of the invention. I therefore. do not wish to be limited to the precise details set forth but In this manner it;is introduceiurii-v formly into the beater paddle Wheel 3. By radially. pass- 4, desire to avail myself'of such changes as fall within the purview of-my invention.

What is claimed is:

1. In a beater mill having a heater paddle wheel fixedly supported on the end of a horizontal shaft mounted for rotation and a removable duct portion for axially conducting into said wheel byway of said annular inlet the material to be ground together with a gaseous transporting medium; the combination of said paddle wheel having a rear. wall of disc shape and a front wall of ring shape; a circular axial material inlet opening into the interior of said wheel, said inlet being bounded by the inside diameter of said ring-shaped front wall; a plurality of circumferentially spaced beater platesmounted in a radial position between said rear wall and said front wall; an annular open space within said beater wheel defined by a cylindrical surface encircled by the edges of said heater plates facing the axis of rotation, said rear wall, said front Wall, and said axial material inlet; arotary radial distributor mounted atithe .endof said'shaft, said distributor having radial .armsiof. sufficient length to sweep over a substantial area of said. circular inlet while said distributor is rotating, thereby permitting limited entry of said material between said. arms into said annularopen space in directions; parallelto the axis of rotation; and a guide integral withsaid removable. ductportion and in enveloping relation with said. radial rotary distributor for deflecting into said open space material thrown thereagainst by said distributor; arms;

2. The apparatusas defined in claim 1, wherein said removable .guide is replacably attached to the removable duct.portion..

3. The apparatus as defined in claim 1 wherein said shaft is provided with a nut for retaining said paddle wheel on, said shaft, said. nut having an axialjexte'nsion upon Whichsaidflrotary distributor is mounted.

4; The apparatusas. defined in claim.3 wherein said removable guide is replacably attached to the removable duct portion.

References Cited in the file of this patent UNITED STATESPATENTS 794,785 Cox July .18, 1905 1,773,906 Klagsbrunn Aug. 26, 1930 1,801,842 Briggs Apr. 21, 1931 1,820,462. Kittay Aug. 25, 1931 FOREIGN PATENTS 143,333 Austria... Nov. 11, 1935 273,577 Germany May 14, 1914 881,748 Germany July 2, 1953 7 695,030 GreatBritain Aug. 5, 1953 1,131,438, France Oct. 22, 1956

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