US2532092A - Roller journal for hot-gas swept bowl mills - Google Patents

Description

Nov. 28, 1950 G. H. FRANGQUIST ROLLER JOURNAL FOR HOT-GAS SWEPT BOWL MILLS Filed Oct. 4, 1946 INVENTOR. Gustav H. Frongqui st (Ma 3&5

Patented Nov. 28, 1950 ROLLER JOURNAL FOR HOT-GAS SWEPT BOWL MILLS Gustav H. Frangquist, Chicago, Ill., assignor to i Combustion Engineering-Superheater, Inc., a

corporation of Delaware Application October 4, 1946, Serial No. 701,096

This invention relates to mill journals and particularly to improvement in bushings forming the bearing surfaces between a mill roller and the shaft upon which it rotates.

In mills, such as the Raymond bowl mills, disclosed in the U. S. patent to Crites No. 2,079,155 (issued May 4, 1937, for Bowl Mill), a multiplicity of large grinding rollers generally rotate in spaced relation with respect to and inside of a ring and the material to be ground is fed between the rollers and the ring to be ground therebetween. Because of the high temperatures that may prevail within a mill when hot gases pass through the mill for the purpose of drying the material being ground, large clearances are provided between the roller bushing and shaft to allow for expansion of the parts. Because of the heavy, unevenly distributed thrust against the rollers and the large clearances in the journal bushings, it has been found that these bushings deform and have actually seized the shaft. It is an object of this invention to provide an improved bearing which will overcome this difficulty.

In the accompanying drawings: Figure 1 is a cross section through a roller and its bearing, showing it mounted within a portion of the mill; and Figure 2' is a cross section of a portion of Figure 1 showing the improved roller bearing of the invention. 7

In Figure 1 a circular bowl Ill having an upwardly projecting wall I I is mounted for rotation around shaft I2. A circular grinding ring I3 is removably mounted within wall H, the inner or grinding surface of the ring being spaced from tangential contact with roller 44. As the bowl and with it ring l3 rotates, the material to be ground, which is continuously fed into the bowl, will move by centrifugal force toward and onto the grinding surface of ring I 3 and thence between the roller l4 and the ring I3 by rotation of the ring. In passing between the roller and ring, the material is ground, which exerts a force against the roller in a general direction radial to the roller, as approximated by arrow I5.

The roller it comprises a wearing ring it. mounted on a lower journal housing H, which is fastened to an upper journal housing I8 by bolts 19 engaging the flanges 26 and 2! of the journal housings. Within lower journal housing I! is bushing 22 and within upper journal housing I8 is bushing 23. Bushings 22 and 23 have their upper edges provided with flanges 24 and 25 respectively, which are fastened to the journal housings I1 and I8 by pins 26 and 21 so that the 4 Claims. (Cl. 241293) I bushing will rotate with the journal housings and rollers. Lower journal housing I! has a recess 28 at its upper end to accommodate an annularly arranged group of roller bearings 29.

The assembled roller, journal, housing and bushings rotate around shaft 30. Shaft is provided with flange 3| which extends into recess 28 and serves as a bottom support for roller bearings 29 which, in turn, support the upper journal housing I 8 and thereby supports the lower journal housing I! and roller ring l6. Shaft 30 is fixedly supported in journal head 32 by means of a tapered shaft end and sleeve 33 held together by a locknut 34 engaging threaded shaft end 35 and the top of journal head 32. The journal head is provided with an integral bearing 31 for rotatably mounting it on a trunnion shaft 38.

Extending from bearing 31 is lever arm 39 whose end 40 bears upwardly against stop bar 4| and downwardly against spring bearing cap 42. Spring 43 bears upwardly against cap 42 and downwardly against spring seat 44. Both stop bar 4| and spring seat 44 are mounted by long threaded bolts 45a in fixed relation to the mill housing 46a.and are vertically adjustable with respect to the housing by means of said bolts. By raising or lowering the stop bar 4|, lever 39 is raised or lowered and rollers 14 are spaced nearer to or farther from grinding ring I3. By raising or lowering spring seat 44 the upward force against lever end 40 may be increased or decreased and thereby the resistance of the rollers E4 to being separated from the grinding surface of ring l3 by the material being ground.

This resisting force is of substantial magnitude and acts in a general direction radial to the roller, as approximately indicated by arrow Hi. The force 15 causes bushing 22 within the lower journal housing E1 to bear against shaft 30 at its lower end and the weight of the upper journal housing I8 causes the bushing 23 to bear against the shaft 30 at its upper end in the opposite direction to force 15. Because of the relatively large clearances provided between the roller bushings 22 and 23 and the shaft 30, the axis JJ of the assembled roller journal housings and bushings will tend to tilt with respect to the axis SS of the shaft as shown in Figure 1. This tilting causes the upper portion of bushing 22 to receive a relatively high bearing pressure where shown by arrow 45. Since this pressure is directly opposite flange 24 of bushing 22 and since the flange is unsupported in the direction of pressure 45, this pressure 45 causes a turning moment around a support at the lower edge of the recess 28 of lower housing 22, the support being approximately shown by arrow 46. It has been found that this turning moment has caused the upper portion of lower bushing 22 to be rolled inwardly toward the shaft as shown by dotted lines 41 and to cause seizure of the bearing where the inwardly extending portion bears against the shaft.

According to the invention, a recess 48 (Figure 2) is provided at the upper edge of bushing 22 which extends downwardly at least to the top of the shoulder 49 of the lower journal housing I! at the bottom of the roller bearing recess 28. By so doing it has been found that all bearin seizures were eliminated, because the turning moment above mentioned no longer exists since the pressure acting at 45 has been removed and the upper portion of the bushing 22 is under direct compression as shown by the opposed arrows .50 in Figure 2. Preferably an additional recess 5| is provided on the top face of flange 24 of bushing :22 which has been found beneficial to the bushing.

While the preferred embodiment of the invention has been shown and described, it will be understood that minor changes in construction and arrangements of parts and equivalent applications of the invention may be made without departing from the spirit of the invention as claimed.

What I claim is:

1. In a bowl mill for grinding relatively cool material and for drying said material by exposure to relatively hot gases, the combination of a substantially vertical shaft exposed to an atmosphere of said hot gases; a roller surrounding the lower portion of said shaft for rotation with respect thereto and being in close contact with and cooled by the aforesaid cool material; a journal housing within said roller serving as a mounting for the roller; a bushing positioned in said'journal housing intermediate it and said shaft to rotate within the housing on the shaft and protruding at the upper end beyond the surrounding housings contacting wall, said bushing fitting loosely over said shaft to provide clearance between the bushing and shaft for thermal expansion of said shaft; and a circumferential recess at the protruding end of said bushing and on the interior side thereof, said recess extending downwardly adjacent said shaft for at least the axial length of the bushing protrusion, whereby side thrusts on said roller which are set up by grinding said cool material in the bowl mill and which impose concentrated forces on said bushings upper portion adjacent its protruding end are prevented from deforming the bushing wall in a Way that otherwise might occur with resultant seizure of said shaft.

2. In a bowl mill for grinding relatively cool material and for drying said material by exposure to relatively hot gases, the combination of a nonrotating substantially vertical shaft exposed to an atmosphere of said hot gases; a roller surrounding the lower portion of said shaft for rotation with respect thereto and being in close contact with and cooled by the aforesaid cool material; a journal housing within said roller serving as a mounting for the roller and having means forming a circumferential recess in its upper portion; a bushing positioned in said journal housing intermediate it and said shaft to rotate with the housing on the shaft, said bushing fitting loosely over said shaft to provide clearance between the bushing and shaft for thermal expansion of said shaft; a circumferential flange on the top of said bushing extending outwardly into said housing recess; and means forming a circumferential recess at the 'top end of said bushing and on the interior side thereof, said recess extending downwardly adjacent said shaft for at least the axial thickness of the aforesaid flange, whereby side thrusts on said roller which are set up by grinding said cool material in the bowl mill and which impose concentrated forces on said bushings upper portion adjacent the flange are prevented from deforming the bushing wall in a way that otherwise might occur with resultant seizure of said shaft.

3. In apparatus of the class described comprising a casing that defines a chamber through which hot gases flow for the purpose of drying low temperature material to be ground therein; a bowl rotatably mounted within said casing and having annpwardly extending side wall terminating in a bowl rim; a shaft and means for suspending it at its upper end above said bowl in .a substantially upright position and for holding the shaft against rotation about its axis, the lower portion of said shaft extending inside said bowl and below said bowl rim, the upper portion extending above said bowl rim and being exposed to the stream of the aforesaid hot gases flowing through said chamber and past said upper shaft portion; a roller surrounding the lower portion of said shaft for rotation with respect thereto and being in close contact with and surrounded by the aforesaid low temperature material being pulverized within said rotating bowl; a journal housing within said roller serving as a mounting for the roller; a bushing positioned said journal housing intermediate it and said shaft to rotate with the housing on the shaft and protruding at the upper end beyond the surrounding housings contacting wall, said bushing having an inside diameter suflicientiy larger than said shafts diameter to provide clearance for thermal expansion of said shaft; and means forming a circumferential recess at the protruding end of said bushing and on the interior side thereof, said recess extending downwardly adjacent said shaft for at least the length of the bushing protrusion, whereby side thrusts on said roller which are set up by a grinding of said material between the roller and said rotating bowl and which impose concentrated forces on said bushings upper portion adjacent its protruding end are prevented from deforming the bushing wall in a way that otherwise might occur with resultant seizure of said shaft.

4. In apparatus of the class described comprising a casing that defines a chamber through which hot gases flow for the purpose of drying low temperature material to be ground therein; a bowl rotatably mounted within said casing and having an upwardly extending side wall terminating in a bowl rim; a shaft and means for suspending it at its upper end above said bowl in a substantially upright position and for holding the shaft against rotation about its axis, the lower portion of said shaft extending inside said bowl and below said bowl rim, the upper portion extending above said bowl rim and being exposed to the stream of the aforesaid hot gases flowing through said chamber and past said upper shaft portion; a roller surounding the lower portion of said shaft for rotation with respect thereto and being in close contact with and surrounded by the aforesaid low temperature mate- 5 rial being pulverized within said rotating bowl; a journal housing within said roller serving as a mounting for the roller and having means forming a circumferential recess in its upper portion; a bushing positioned in said journal housing intermediate it and said shaft to rotate with the housing on the shaft and having an inside diameter sufficiently larger than said shafts diameter to provide clearance for thermal expansion of said shaft; a circumferential flange on the top of said bushing extending outwardly into said housing recess; and means forming a circumferential recess at the top end of said bushing and on the interior side thereof, said recess extending downwardly adjacent said shaft for at least the axial thickness of the aforesaid flange, whereby side thrusts on said roller which are set up by a grinding of said material between the REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Numf'cer Name Date 1,184,417 Capen May 23, 1916 1,921,044 Sparrow Aug. 8, 1933 2,100,734 Crites Nov. 30, 1937 2,112,359 Crites Mar. 29, 1938 2,124,132 Bate et a1. July 19, 1938

Images