US2569744A

US2569744A - Multiple stand roller mill with worm and worm wheel drive to each roll

Info

Publication number: US2569744A
Application number: US725392A
Authority: US
Inventors: Thomas G Cecka
Original assignee: International Milling Co
Current assignee: International Milling Co
Priority date: 1947-01-17
Filing date: 1947-01-17
Publication date: 1951-10-02
Anticipated expiration: 1968-10-02

Description

Oct. 2, 1951 T. G. cEcKA MULTIPLE STAND ROLLER MILL WITH WORM AND WORM WHEEL DRIVE TO EACH ROLL 5 Sheets-Sheet 1 Filed Jpn. 50, 1947 THOMAS ZE C /ZZ A 7- TOPNE s Oct. 2, 1951 T CECKA 2,569,744

MULTIPLE STAND ROLLER MILL WITH WORM AND WORM WHEEL DRIVE, TO EACH ROLL '5 Sheets-Sheet 2 Filed Jan. 50, 1947 /NI/NTOR THOMAS G. 65cm A TTORNE rs Oct. 2, 1951 'r. G. CECKA MULTIPLE STAND ROLLER MILL WITH WORM 7 AND WORM WHEEL DRIVE TO EACH ROLL Filed Jan. '30, 1947 5 ShaetsSheet 5 L M 3 7 II I. III

lM/ENTM THOMAS G. CEc/m MWM ATTZZQNEYS T. MULTIPLE STAND Oct. 2, 1951 e. CECKA ROLLER MILL WITH WORM AND WORM WHEEL DRIVE TO EACH ROLL 5 Sheets-Sheet 4 Filed Jan. 50, 94?

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NEW ROLLb R S mmww E. m W.W w a A 8 MW 2 w Oct. 2, 1951 T, CECKA 2,569,744

MULTIPLE STAND ROLLER MILL WITH WORM AND WORM WHEEL DRIVE TO EACH ROLL Filed Jan. 30, 1947 5 Shuts-Sheet 5 INVENTOR. 7710/14/15 G. 55004 621, WM MW A TTOHNE rs Patented Oct. 2, 1951 MULTIPLE STAND ROLLER MILL WITH WORM AND WORM WHEEL DRIVE TO- EACH ROLL Thomas G. Cecka, Minneapolis, Minn, assignor to International Milling Company,

Minneapolis,

Minn, a corporation of- Delaware Application January 30, 1947, Serial N 0. 725,392 6 Claims. (Cl. 241-135 This invention relates to roller mills and more particularly to improvements in the construction of roller mills of the type used, in the milling of dry, pulverulent material, such as grain, feeds, mill products, salts, pharmaceuticals and the like.

Roller mills have long been used for the breaking and milling of dry material, and in the grain milling and other industries have been widely used in batteries of many mills operating in parallel. In such installations it has been common to provide a line shaft for supplying power to a battery of mills, each mill or mill stand, as it is sometimes designated, being driven by a belt to the common line shaft, and the mills have been designed to accommodate such drives.

While these mill installationsare satisfactory and have served to mill countless tons of materials they are subject tomany serious defects due to the type of installation required and due to their inherent mechanical construction.

One of the most serious defects in the common belt driven mill stand arises out of the common drive; Since all mills were of necessity belted to a common line shaft any operational defect necessitating servicing of one mill has frequently required a shut-down of the entire drive shaft and all mills connected to it. Furthermore, the belt drive itself, has involved relatively short belts withv consequent highbelt tensions in order to deliver the required horsepower, and this has led to defects in operationvoccasioned by bearing failure, misalignment of the roll, damaged rolls, etc. In addition, heavy stress of the belts is transferred from the mill to the building in which it. is housed.

It is an object of the present invention. to provide an improved roller mill wherein an individual drive is' provided for each mill and furthermore to provide an improved gear drive between the motive power source and the several slow and fast rolls of the mill.

Other defects of the present mills have arisen out of their construction wherein the cooperating fast and slow rolls are situated at equal levels. In such roller mills the entire thrust of the rolls, occasioned by the pressure of the-material being milled between them, has had to be carried by the roll shaft bearings and this bearing load, taken with the added load due to belt tension of the drive, has been the cause of frequent operational di'fficulties. It is an object of the present invention to provide an improved roll mill wherein the thrustdue to material pressure on the rolls while milling is at least partially compensated by theweight of the roll itself so as to relieve in partthe' excessive load on the bearings of the mill.

Another serious objection to conventional mills is the fire hazard and employee hazards occasioned by the belt drives employed for driving the rolls. It is an object of the invention to eliminate these hazards by providing a self-contained gear drive unit in which the roll drive belts are eliminated and which are consequently free from danger due to the ignition of dust by static electricity'on' the belt and free from danger to. employees. It is a further object to provide. an improved self-contained milling unit wherein all working stresses are within the unit itself and not communicated to the building as with belt driven mills and which is free from the vibration which has commonly been encountered due to large rotating pulleys in belt driven mills.

It is also an object of the invention to provide an improved roller mill wherein the rolls are driven by direct mechanical gear connectionfrom a motive power source and at the same time provision made for wide variations in adjustment of therolls to compensate for wear of the rolls with efficient gear drive connection being maintained the while.

It is a further object of the invention to provide an improved mill wherein the fast roll is positioned above and partially overlying the slow roll so as to eliminate the necessity for tramming the rolls (-i. e. maintaining precise parallelism) under milling conditions. It is a further object to provide an improved gear drive wherein shorter shafting is provided. This reduces bowing of the roll shafts and torsional strains which were common causes of, failures with the rather long roll shafts-needed in belt driven mills.

Other and further objects of the invention are those inherent in the apparatus herein illustrated, described and claimed.

The invention is illustrated with reference to the drawings in which Figure 1 is a side elevational view of the machine with certain parts removed;

Figure 2 is an end elevational view taken in:

the direction of arrows 2-2 of Figure 1 showingthe drive gears'exposed and their enclosing housingremoved;

Figure 3 is a sectional' view taken in the direction of arrows 33 of Figure 1;

Figure 4 is a fragmentary sectional view taken along, the lines and in the direction of arrows and in the; direction of arrows 4-4 of Figure 1,

illustrating the rolls after they have been reduced in diameter during their service life;

Figure 6 is an enlarged detail of the adjusting mechanism for moving one of the roll shafts and is representative of the mechanism used for adjusting the ends of the rolls; and

Figure 7 is a fragmentary sectional view through one of the quick throw-out levers and associated cams.

Throughout the drawings corresponding numerals refer to the same parts.

Referring to the drawings the machine comprises a frame and housing generally designated I having end plates II and I2 and side plates I3 and I4. The housing may be cast or fabricated of any suitable materials and is preferably provided with a bolting flange at I5 and I6 by which the machine can be bolted to the millingafloor. The upper portions of the side plates I3 and I4 converge inwardly at I8 and I9 and thenceare shaped in to form the top 23 which is provided with a header 2I which is in turn attached to the supply chute 22.

The interior space of the housing is provided with upwardly converging bafies 24-25 which meet at the point 26. These bafiies, together with the

baffle boards

28 and 29, all extend from one end plate II to the other end plate I2 and form interior hoppers so that the material being fed flows in the direction of arrows 3i] and 3I onto the

feed rolls

32 and 33. The feed rolls are relatively small diameter and serve almost to close the

bottom spaces

34 and 35 formed by the converging baflies 24-28 and 25-29, respectively.

Feed roll 32 is mounted upon the feed roll shaft 36 which is journaled in the end plates II and I2 and extends outwardly beyond rear end plate II and carries a relatively large diameter pulley 38. ,Similarly, the feed roll 33 is carried upon the shaft 48 which is likewise journaled in the end plates II and I2 and extends out beyond rear end plate II, as shown in Figure 1, where it carries the pulley 42. Feed roll 32, its shaft and a shaft 59 carrying a main drive gear 66. Below the housing tunnel there is a central web 56 extending from end plate II to end plate I2 which serves to separate the two streams of milled material falling on opposite sides of the housing 55. In some instances these streams may be different, and the separation 56 thus permits them to be separately withdrawn.

Within the main housing there are also positioned two pairs of milling rollers 6I-52 and 3364, each roller being provided with a shaft upon which it is journaled. The shaft 65 carries roll BI and extends through

stuffing boxes

85 and 61 in the end plates and is journaled upon pillow block 68 which is mounted upon end plate II and pillow block 69 which is mounted upon plate I2. Similarly, shaft Ill of roll 63 likewise .extends through the stuffing boxes in the end plates II and I2 and is likewise journaled in suitpulley rotate in the direction of arrow 43, and

feed roll 33, its shaft and pulley 42 rotate in the direction of arrow 44, being belt driven as hereinafter described. Likewise, within the housing there are a pair of downwardly extending and converging bafiies 46 and 41 which extend from the side walls I3 and I4, respectively, and at their lower ends form a chute space 48 which is connected to delivery chutes leading to classifying machinery below the milling floor. The converging chute formed by the bafiles 46 and 41 collects the milled material as hereinafter described and thus delivers it from the mill.-

Within the space between the

baflies

46 and 4! there is a motor housing enclosure 0r tunnel 50 which extends from end' plate II to end plate I2. The housing has a bottom portion 54 and sides 52 and 53 which converge upwardly at their top portions 5I--5I at an angle such that the milled material will not lodge thereon. The motor housing tunnel 5D is formed integrally with the end walls I I and I2 and is suitably supported by interior bracing not illustrated. The end walls I I and I2 are, of course, provided with opening plates on the ends of the tunnel 50 and these plates are provided with louvers 55 so as to allow through ventilation from one end to the other for cooling the drive motor therein. The motor 58 which is mounted in tunnel 50 is thus completely isolated from the milled material falling downwardly within the hopper space formed between the baflles 46 and 41. From motor 58 there extends able bearings fastened on the end plates, one of the bearings I2 on end plate I2 being illustrated in Figure 3. The bearings carrying the shafts 65 and III and hence the rolls GI and 63, respec-' tively, are journaled upon fixed journals which do not move in respect to the end plates II and I2. Hence, the axis of rotation of the rolls BI and 63 remains fixed throughout their service life.

Roll 62 is supported. upon shaft I4 which-likewise extends out through stuffed boxes in the end plates II and I2 and is supported by journals I5 illustrated in Figure 3 and a corresponding journal at the other end of the machine. These journals are mounted upon a frame I6 having a T- slot connection to a correspondingly shaped slide TI attached to the end plates and I2. Similarly, roll 54 is mounted upon shaft 19 which likewise extends out through suitable stuffing boxes in the end plates II and I2 and is carried by journals mounted upon each end plate, as hereinafter described. One of the journals is illustrated in Figure 3 and there is a corresponding journal at the other end of the machine. The journal 80 is likewise mounted upon the frame 8I which has a T-slot connection to the correspondingly shaped slide 82 which is solidly fastened to the end plate I2. The journals at each end of the machine carrying the roll shafts I4 and I9 of rolls 52 and 64, respectively, are thus permitted to move in a plane transverse to the machine, the plane being at lines 8383. Suitable sliding stufiing boxes are provided at each end of each shaft I4 and I9 where they pass through the end plates II and I2 and thus keep dust from the milling operation from passing out of the mill around .the shafts. The stufiing boxes are either split diametrically or are made so as to lift from the machine frame, so as to allow removal of the rolls and their shafts and gears when the mill frame is opened as hereinafter described.

Figure 3 shows the two

slides

11 and 82 which are permanently fastened to end plate I2. Figure 1 shows the slide 82 which carriesjournal 80 adjacent end plate I2 and also shows the slide 84 carrying the journal 85 at the other end of the machine upon which the shaft I9 is mounted.

It is to be understood, of course, that the journal,

not illustrated adjacent rear end plate I I and at the far end of shaft I4, is likewise mounted upon a slide exactly similar to that shown at IT and 82 in Figure 3. The journal constructions for the shafts I4 and I9 and their adjustments hereinafter described are identical at each end of the machine and therefore it is only necessary to,

seed-744 describe in detail the. construction adjacent-the end plate I 2.

Referrin to Figure 3 the slide TI carries the frame 16' so that the frame 16 carryingthe journal I5 may move ina-translatorymotion back and forth in the direction of the double arrow 86;. Similarly, the slide 8.2 which mounts the frame 81 carrying the journal 8!) permits the frame. 81: and journal 80 to be moved in the direction of the double arrow 81).. Thus, both. the

journals. 7.5.. and 80 can moveback and forth. and.

hence carrying; the shafts I4 and 19. inc. trans.- verse. plane at thelevel of line 8.3-83. The degree of. such, movement: permitted in the machine suflipientto accommodate not: only the desiredop nins. lithe-mac n for clearing; an jamsthat may occur, b t also sufiici nta o-permit the. mov ment of

rolls

62 and 64 more closely adjacent the rolls B21 and 63;, respectively, so as, to maintain the desired close clearance for milling as, the rollsare reduced in size. during their service life. It.

may be. pointed; out at this juncture that. in ordinary miling practice for flour milling ma.- chine-ry, the rolls SI and 63, 62 and 64 are: approximately nine inches in diameter as initially manufactured. The rolls may be smooth. or corrugated trough) depending upon the type of milling effect desired, As the milling takes place, there is some wear on the roll and it iscustomalsy to. remove the rollsfrom the machine from time, totime andre-finish them to true and accurate diameter throughout their length and to re-corrugate them when. corrugations are deired. This, cffectsfan overall reduction in the diameter, of the roll and compensatory adjustment must therefore be provided to maintain desired close clearance for milling. Figure 4 represents the position of the rolls set. close as during aniling when the rolls are of maximum diameter when new. Figure 5 in the full line position illustratesthe position of the rolls. likewise set. close for milling but after they have been reduced in diameter during the service life. The dotted lines in Figure 5 illustrate the position of therolls-when they are new and corresponds thus. to the full lineshowing of Figure 4.

Figure 3- and Figure 6; which is an enlarged view of the mechanism for shaft I 6, illustrate the mechanism for-adjustment of each of the adj ustable rolls 62 and 64. For this purpose there is provided a shaft 88 and. another shaft coaxial with it at the other end of the machine. Both shafts are mounted on their adjacent end plates.

Upon the shaft there is mounted an oscillatabl'e lever 89 having a handle portion 99; the lever carries two eccentrics SI and 92 towhich there are

attachedeccentric links

93 and 94; respectively. Link 93' serves roll 64 and link 23 serves roll 62.

The link 93"has athreaded' connection at95 to the.

rod 96, and rod 96 extends through a cylindrical space 51 in the bearing frame 8| and thence to termination at the hand wheel; I whichis solidly mounted: on rod 96. By turningthe hand wheel Ills the rod may be threaded more or less into the threaded connection 95. Upon the rod 96 there is mounted sleeve IBI which is threaded at IOS' uponthe rod 96. The threads 95 are-fine threads and I are coarse threads. Hence, by rotating rod 98" by means. of hand wheel I00 the sleeve canbe' moved axially in respect to eccentric. link 93.- A locking nut hand wheel I92 is threaded on shaft. 96 at threads I05 and by turning wheel I32. tight, any adjustment of; the sleeve I6! on rod 3% can be fixed. Sleeve II". has a nut. at I185; and an internalcollar at I'U'l. Spring I04 bears against the collar I'DT and against. the end weir I08 of the cylinder- 91. By initially turning up nut I08 the spring IMwmay be adjusted to agiven compression. A cover plate IE9 serves as a journal around sleeve MI and closes the.- cy-llne drical space 91. Cover plate i09 is held onto: the cylinder 91: by. several cap screws.

The hand lever is first. moved against rights hand stop 98; to roll closed position in which the eccentric links 93- and a4 are moved" towards each other. Then by rotatingthe hand wheels m0; it is possible to vary the position of sleeve ID I for: example, with reference to: link 153 and move the periphery: of. roll 6d. towards the pert...

V phery" of roll 63 for proper grinding. During this} adjustment spring IU' lholds web- I508 against nut I016; The adjustment may be locked. by tightening hand wheel #02. As: millin pressure (i. e. the pressure exerted by the material: being ground) develops. this may be sufficient to. c'om:-= press: spring I 94 further and move the entire journal: Bflioutwardly from the vertical center line; of the machine and? along: rod 96. When this: occurs a clearance will develop between nut.- 1108; and web". me; To maintain a given fineness of? grind. a readjustment of the wheel I00 maybe re quired so as to change the position of journal while the mill is operating and the milling pres-= sure is on. In any event spring; I04 will com. press and permit hard obstacles to be cleared by the rolls. In order tosmove the

rolls

64 and 82 quickly away from rolls 63. and: 6Il, respectively; handle 98- is moved in the direction: of arrow 0 against left-hand stop-98. When. the handle 90 moved in the direction of arrow MD, the entire bearing support 15 isqui'c-kly moved towards the sidewall 13 of the machine by action of eccentric 92 through link 94 and rod H4, and thus roll- 6-2 is. thus quickly moved away from roll 6.I- so to clear any: obstruction thatmay have developed on that side of the machine and at the sametime bearing Bills moved toward side wall M and roll 64 is moved away from roll 63. The bearin-gcomstruction on the far; end of the machine (plate H): is exactly analogous and by means of'its handlever, not illustrated, the rolls 62. and 6 maybe quickly moved to clear position at that end;- Usually the hand levers at the two ends of the machine areconnected together by linkages for simultaneous movement so that by pulling the leveron either end of the machine, the rolls may-- be quickly separated. Since the adjustments at the two ends of the machine are independent. it is possible to maintain accurately theuniform clearance between the

rolls

63 and 64, regardless of irregularities in operation of the mill. This is called tramm-ing, i. e. maintaining. the rolls parallel. Since the fixed, fast speed rolls BI and 63 of the present mill diagonally overlie" the ad-= justable slow-speed rolls 62 and; andtherolls B2 and 64" are movable in a horizontal plane through the machine, much less critical parallel adjustment or tramming is required; as cornpared with older mills in which the, rolls are on the same level. One of the hand wheels III of the bearing support is' shown in Figure 1,, Iti's understood that the bearin support 85 is; precisely the same as that previously described for. bearing support 8|.

Likewise the shaft I4 carried on the bearing support 16 and the corresponding bearing support. at the opposite end of the machine for'shaft'll; are provided with adjusting hand wheels 'I I2- II3 which permits variation. in the closenessof the rolls and the pressure 'necessaryto move the tension shaft attached to link 94 is illustrated at H4 and it extends through the housing H5 and terminates at wheel II2. Each end II and I2 is preferably provided with stops 98 for limiting the movement of lever 90 in its open and operating positions.

Within the machine housing there are provided adjustable baffles H6 and Ill which serve to direct the downwardly falling material directly into the nip ofeach pair of rolls 63-64 and 6I-62. The grain falls downwardly from the feed rolls 32; and 33 in the general direction of arrows H8 and H9 and are directed by the boards -I I6 and III into the nip space between the differentially revolving rolls.

r .The mechanism for rotating the rolls is illustrated in Figures 1 and 2. The motor shaft 59 is provided with a spiral gear 60 mating with a corresponding spiral gear I26 on countershaft I2I'. The shaft [H is supported in a plurality ofbearings I22 and is therefore rotated by the gears 66 and I26 at approximately motor speed. Upon shaft I2I there is a herringbone gear I24 which mates with a corresponding herringbone gear I25 upon the countershaft I26 which is likewise'supported by the bearings I21. Since the gears I24 and I25 are approximately the same diameter the countershaft I26 is likewise rotated at approximately motor speed. At the ends of the shaft I26 there are provided worm gears I28 and I29 which mate, respectively, with the worm wheels. I36 and I3I on the ends of roll shafts I6 and 65,'respectively'. The-gear pairs I28-I36 and I26'I3i afford approximately a 1 to 1 gear ratio-and therefore the rolls BI and 63 ,are rotated at approximately motor speed. By suitably selecting the angle of the gears I28I36 and I 1I29 -I3I, the fast roll 6! may be caused to rotate in the direction of arrow I32 and at the same time fast roll 63 may be caused to rotate in the direction of arrow I33. With such rotation the countershaft I26 rotates in the direction of arrow I34 and countershaft I2I rotates in the direction of arrow I35, the motor being rotated in the direction of arrow I46; The thrust caused by gears I28'and I28 reacted with gears I36 and I3I,- respectively, is therefore approximately balanced and relatively little end thrust is transmitted by shaft I26 to the bearings I2! in which it operates.

- Upon shaft I2! there are provided worm gears I36 and I31 of equal diameter which mate with relatively larger worm wheels I38 and I39 causing the latter and the roll shafts and rolls which they drive to be rotated in the direction of arrows I46 and MI, respectively, but at a much lower speed than the rotation of rolls 6| and 63. By appropriate selection of the gear ratio of the gear pairs I'36I38 and I3'II39, the

rolls

62 and 64 can be caused to rotate at any desired speed relative tothe speed of rolls 6| and B3 and accordingly the desired relatively peripheral velocity for adequate grinding of various ma-. terials can be varied to suit the conditions needed in the particular grinding operation under cons'ideration. It will be noticed also that the rotation of shaft I2I in the direction of arrow I35 causes the rotation of gears I36 and I39 in opposite directions. Therefore, the end thrust pro duced by each of the gears I36 and I3! upon III the shaft m is substantially balanced. The only.

appreciable end thrust on this shaft is that produced by the gears reacting against gear I20.

The gears I36 and I3! are made relatively long and since they are of uniform pitch diameter throughout their length, they mate precisely with the gears I38 and I39, respectively, regardless of the adjustment position of the latter gears as determined by the position of their bearing blocks I5 and 86.. Therefore, the bearing blocks 15 and and the correspondingbearings at the opposite end of the machine may be moved by the quickopening handle and their position maybe adjustedby the hand wheels I66, I62, H2 and H3 and the correspondingadjustment wheels at the opposite end of the machine as desired, without disturbing the precise mating of the gears I36 and I31 with the corresponding gears I38 and I39, respectively. Furthermore, as the rolls are reduced in diameter as shown in Figures 4 and 5, thus requiring the closer together setting, depicted in Figure 5, this fact likewise does not effect the accurate mating of the gears I36 and I39 upon their driving gears I36 and I31, respectively, since the gears I38 and I39 simply operate at positions on gears I36 and I3! which are a little closer to the center of the mill. 7

Referring to Figures 4 and 5, particularly, the pressure caused by the grinding of material between the rolls 6i and 62, for example, is in the direction of arrows I42 and I43. The force of arrow I42 has an upward component I44 which therefore merely tends to lift the weight of the roll 6|, or stated another way the weight of the roll 6| tends to maintain the milling pressure upon the cooperating roll 62. Similarly, the weight of roll 63 tends to maintain the milling pressure upon its cooperating roll 64. This is a distinct advantage as compared with earlier mills wherein the entire milling pressure had to be sustained by the bearings carrying the roll shafts. In addition, the elimination of the drive belts and the provision of a geared drive reduces bearing pressure, permits the use of shorter shafts which consequently distort less under load. re-

duces fire hazard and employee hazard, and at the same time greatly reduces vibration and the transmission of vibratory and belt stress to the building carrying the mill.

Referring to Figure 1 the entire gear train for driving the rolls from the motor, together with the countershafts is preferably enclosed in a suitable gear housing shown by the dotted lines I45 which is suitably supported from the end plate I2 of the mill. The housing has not been shown in detail since it will be understood adequately to enclose the gears so as to permit their complete lubrication during operation. Likewise the bearings of the various countershafts are intended merely as illustrative, it being understood that adequate bearing supports will be provided on one or both sides of each gear in order to sustain the loads encountered during service. At the rear end of themill the shafts 65 and i6 protrude outwardly beyond their hearing and are provided with V-belt pulleys I48 and I49 which serve to drive the belts I56 and I5I and thus propel the material feed roll pulleys 38and 42, respectively. The feed rolls thus are operated at relatively low speeds whenever the mill is in operation. The main housing of the mill and also the gear drive housing I45 are provided with removable sections which separate along the planes I52, I53, I54 and I5 so as to permit the rolls 6 E454, their shafts and drive gears, to be lifted bodily from the mill for renewal or replacement.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments herein except as defined by the appended claims.

What I claim is:

1. A roller mill comprising a frame, a first pair of rollers positioned in an elevated transverse plane through the frame and substantially symmetrically about a vertical center plane through the frame, a second pair of rollers journaled on the frame and positioned in a lower transverse plane and more widely spaced than said first rollers from said center plane, means for moving each of the second rollers toward and away from the center plane of the frame so as to position the periphery of each of said second rollers closer or farther away from the position of the more elevated first roller to which it is adjacent, a first transverse countershaft journaled in the frame and worm gear means conmeeting said shaft to each of the first pair of rollers, a second transverse countershaft journaled on the frame and worm gear means connecting said second shaft to each of said second pair of rollers, a power source on the frame and drive means connecting it to the first and second countershafts.

2. The apparatus of claim 1 further characterized in that the worm gear means connecting the first countershaft and the first pair of rollers drives said first rollers in opposite directions and the worm gear means connecting the second countershaft to the second pair of rollers drives said second rollers in opposite directions.

3. The apparatus of claim 1 further characterized in that the power means is an electric motor having a gear connection to the second countershaft, said second countershaft being geared to the first countershaft.

4. A roller mill comprising an enclosing housing, a material feed chute having means therein for providing separated flows of grain to each of a pair of spaced feed rolls cooperating therewith for feeding material downwardly in spaced planes extending substantially the length of the housing, a pair of cooperating grinding rolls situated beneath each feed roll in the path of falling material fed thereby, each pair of grinding rolls comprising an elevated roll, journal means for said elevated roll, and a lower roll, journal means for said lower roll, said lower rolls being posi- 10 tioned beneath each feed roll and mounted for movement in a horizontal plane toward and away from its cooperating more elevated slow roll through a range of movement sufficient to position the peripheries of the rolls in spaced relation or in grinding relation regardless of reduction of diameter of the cooperating rolls during their service life, a first countershaft, worm gear means connecting the countershaft to each of the slow rolls and a second countershaft, worm gear means connecting said second countershaft to each of the fast rolls, and a motor mounted on the housing and gear means connecting it to each of the countershafts.

5. The apparatus of claim 4 further characterized in that the motor is mounted within the housing in a ventilated enclosed space separated from the spaces below the cooperating pairs of rollers.

6. The apparatus of claim 4 further characterized in that the slow rollers are mounted on slidable journals and adjustment means is provided at each end of the housing for moving them directly towards and away from each other while gear connected to their countershaft drive.

THOMAS G. CE'CKA.

REFERENCES CITED The following references are of record in the file of this .patent:

UNITED STATES PATENTS Number Name Date 199,605 Wegmann Jan. 22, 1878 240,453 Oexle Apr. 19, 1881 255,860 Holt Apr. 4, 1882 335,257 Van Gelder Feb. 2, 1886 411,404 Wagner Sept. 17, 1889 447,951 Kapler Mar. 10, 1891 459,352 Wagner Sept. 8, 1891 1,130,365 Altheide Mar. 2, 1915 1,199,938 Sorenson Oct. 3, 1916 1,713,487 Torrance May 14, 1929 2,022,135 Newhouse Nov. 26, 1935 2,293,670 Sickman Aug. 18, 1942 FOREIGN PATENTS Number Country Date 1,179 Great Britain Mar. .5, 1883 1,107 Great Britain Jan. 24, 1888 6,990 Austria Mar. 10, 1902 12,087 Great Britain of 1909 344,019 Italy Oct. 221, 1936 487,759 Great Britain June 24, 1938