US3078894A - Rice hulling and polishing machine - Google Patents

Description

Feb. 26, 1963 Filed Sept. 24, 1959 TOSHIHIKO SATAKE RICE HULLING AND POLISHING MACHINE 2 Sheets-Sheet 1 Feb. 26, 1963 TosHlHlKo sATAKE 3,078,894

RICE HULLING AND POLISHING MACHINE Filed Sept. 24, 1959 2-Sheets$heet 2 Unite States The present invention relates to grain cleaning machines for lseparating the bran from and polishing rice or other grains.

In previous grain cleaners, grains have been fed or advanced by a helical formation provided on the peripheral surface of a polishing roll adapted to rotate coaxially with, and interiorly of, a netted cylinder or barrel for removing bran out of the machine. In this case, the roll must be designed to have a circumferential speed of not less than 2,000 feet per minute, taking into consideration both the polishing or cleaning effect and the feeding effect to be provided for.

With such high speeds, there has been a tendency for the grains to be crushed when subjected to a considerable impact due to the helical ridge formation of the roll.

In eliminating the above deficiencies, the grain cleaning machine according to the present invention does not depend upon the rotation of a helical roll for the feed or advance of the grains in the machine, but is adapted to impart advancing movement to the grain along the inner peripheral surface of a cylinder arranged to surround the roll to define a polishing chamber between the outer surface of the roll and the cylinder.

According to the present invention, since feeding movement of the grains within the polishing chamber is not obtained through the polishing roll but is caused by a cylinder surrounding the roll, as described above, the roll acts to impart to the grains no axial impact but only circumferential movement around the roll. The roll is made of a ceramic material such as an artiiicial grindstone having a rough surface. This allows the roll to be rotated at considerably high speeds, thus providing for substantial frictional eect upon the grain, without breaking up the grains through impacts. Grains located close to the periphery of the polishing roll are caused to make revolution or move around the roll with the rotation thereof, and such revolutionary movement of the grains is transmitted successively to outer grains. It will be readily recognized that the speed of such revolutionary movement of grains decreases as the radial distance of the grains from the periphery of the roll increases, with the result that, even when those grains located close to the periphery of the roll are moving at considerably high speeds, the outermost grains move only at much lower speeds. Consequently, the outermost grains or those grains which are in Contact with the inner peripheral surface of the cylinder, which together with the outer peripheral surface of the roll defines a polishing chamber as described above, are not subjected to any crushing effect during revolutionary movement even when the cylinder is provided on the inner peripheral surface thereof with raised ribs or ridges or is formed with a great number of openings,

Accordingly, the present invention provides a grain cleaning machine which comprises a polishing roll having formed on the periphery thereof a plurality of circumferentially extending ridges in parallel to each other, and a bran removing or separating cylinder disposed to surround said polishing roll and having a plurality of relatively narrow elongated slots which extend at an angle such as to advance or conduct forwardly through the polishing chamber those grains coming into engagement with said slots during circumferential movement caused by the rotation of the polishing roll.

l arent According to another feature of the present invention, there is provided a grain cleaning machine which comprises a bran separating cylinder which has formed on the inner peripheral surface thereof with a plurality of ridges instead of through apertures as described above, said ridges serving to impart advancing movement to those grains coming into engagement therewith during revolutionary movement of such grains. In this case, although such ridges also have quite the same effect upon grains as through apertures as described above, it is necessary to form at the same time through apertures in the bran separating cylinder separately from said ridges for the separation and removal of bran from the polishing chamber. The ridges may be formed separately from the cylinder and attached thereto so as to allow adjustment of their inclination exteriorly of the cylinder, which forms a further feature of the present invention.

An object of the present invention is to provide a grain polishing machine which comprises a polishing roll and a bran removing or separating cylinder arranged to surround said roll and to conduct forwardly those grains coming into contact with said cylinder during their revolutionary movement caused by the polishing roll.

Another object of the present invention is to provide a grain polishing machine which comprises a reticulate cylinder or barrel made of thin hard metal plate defining a polishing cham-ber, and a polishing roll disposed in said polishing chamber coaxially with said cylinder, said cylinder being provided over the entire periphery or at least over a portion thereof with a plurality of narrow elongated slots or through apertures arranged in alignment with each other in both longitudinal and transverse directions, said slots being each inclined so as to conduct forwardly grains as they come int-o contact with the slot during their revolutionary movement around the polishing roll caused by the rotation thereof.

A further object of the present invention is to provide a grain polishing machine which comprises a polishing roll mount-ed rotatably and a bran separating cylinder having a great number of bran passing apertures and a plurality of grain conducting ridges provided on the inner peripheral surface of the cylinder, which, together with the roll, deiines a polishing chamber.

A still further object of the present invention is to provide a grain polishing machine comprising a polishing roll, a bran separating cylinder with the inner peripheral surface thereof defining a polishing chamber together with the outer periphery of said roll, and a pluralityl of grain feeding ridges provided on the inner peripheral surface of the cylinder an-d extending at different angles of inclination so that the grain flow through said polishing chamber has a constant density at respective points there- A further object of the present invention is to provide a grain polishing machine comprising a bran separating cylinder having formed on the inner peripheral surface thereof a plurality of grain conducting ridges which may be set at any adjusted angle of inclination.

These and other objects, features and advantages of the present invention will be best appreciated from the following detailed description, reference being had to the accompanying drawings showing several embodiments, chosen by way of example, of the grain cleaning or polishing machine according to the present invention.

In the drawings:

FIGURE l is a longitudinal cross-sectional view of .a grain polishing machine according to the present invention;

FIGURE 2 is a transverse cross-sectional view of same substantially taken along the line 2-2 in FIGURE l;

FIGURE 3 is a fragmentary plan view on enlarged 'scale showing part of the rice-bran separating cylinder having many elongated openings for separating of the bran, which are inclined to advance grains of the machine shown in FIGURES 1 and 2;

FIGURE 4 is la longitudinal cross-sectional view of `another form of the grain polishing machine according to the present invention, in which the polishing roll has Von its inlet side a conical part arranged to impart to grains some circular or-revolutionary movement before they are engaged by the working surface of the polishing roll; 4

FIGURE 5 is a longitudinal cross-sectional view of -anotlier embodiment of the present invention in which discontinuous vhelical ridges are provided for conducting grains axially forwardly of the machine;

'FIGURE-6 is a vmodified form of the grain polishing machine shown in FIGURE 5 with the ridges formed on the inner peripheral surface of the bran separating `cylinder having an Aangle of inclination to the direction "of `the revolutionary `movement of rgrains progressively reduced;

FIGURE 7 s a transverse crossasectional viewsubstantially `taken along the line 7-7 in FIGURE;

FIGURE 8 is an 'elevational view, partially 'broken `away, `of a further embodiment of the present invention,

'with Ithe 4polishing roll removed to present vthe features 'of the invention more clearly, in which the grain feeding ridges provided on the inner peripheral surface of the cylinder having a plurality of 'rice-'bran separating apertures have an angleof inclination adjustable with respect Vto'thedirectioii of the revolutionary 'movement ofgrains;

"roll 1 3 and also having `a bran separating cylinder 14 arranged to surround the polishing rollin spaced apart relationship therewith. As shown, the shaft of the `polishing roll A13 is rotatably supported at opposite ends in bearingsl and 17 provided lin the respective end walls 11 and 12 of the housing `1t), and projects at oneend beyond the adjacent bearing 17 to carry a pulley 20 fast V'on the projectedportion. j i

Extending downwardly through the top wall 21 of'said housing 10 adjacent to one end thereof to the top portion of 'the cylinder 14 4is a hopper 22 which has 'its lower end `portion fitted into an opening 23 formed in the top por- `tion of said 'cylinder 14. The opposite end walls 11 and 12 of the housing 10, 'the inner surface of said cylinder 1`4, and the peripheral surface of the polishing roll 13 together define a polishing chamber 24 into which grain to be polishedl is charged through the hopper 14. As illustrated, a discharge trough 25 inclined outwardly downwardly is provided at the bottom of the other end wall 11 of said housing 10 for discharging polished grain 'ont of the machine. Provided adjacent to the outlet of the polishing `chamber 24 which 'communicates with the trough 25 is a-flapper plate 26 pivotally secured to the upper portion of said trough by means of apivot shaft having an arm 57 projecting at right angles thereto, said arm carrying a weight '28 adjustable in position along the length of the arm so that the apper plate 26 may provide any desired resistance to the stream of grains owing down said trough 25. The resistance also acts to control the speed of grains liowing through the polishing chamber from its inlet port to its outlet port 27.

The polishing roll 13 is formed of a ceramic or the like material With the peripheral surface of the roll roughened so as to develop a considerable frictional resistance against grains. In addition to this, the roll -is provided around the periphery thereof with a plurality of parallel circumferential ridge-s 29, for example, seven innu'mher as illustrated, at right angles to the longitudinal axis of the roll. There is provided an axial space between the end of the polishing roll 13 adjacent to the inlet port 23 and the end wall 12 of the housing, in which space a helically grooved member 30 made of metal such as steel is aiiixed coaxially to the shaft 15 for feeding grains, abutting closely against the end face of the polishing roll -13 as shown.

Accordingto the present invention, the cylinder 14 for separating bran from polished grains for removal out of the polishing chamber is provided with a `plurality of inclined elongated apertures 31 for converting the circumferential movement of grains under the polishing eiiect at 'least partially into advancing movement in the direction parallel tothe axis of rotation ofthe cylinder to conduct the grains through the polishing chamber, which apertures 31 only allowing 4bran to pass "therethrough pref venting polished grains from passing through such apertures. This construction and configuration of the 'cylinder is illustrated in FIGURES `in anenlargedscale. The separating cylinder is preferably formed of a steel plate, lbeing fitted at opposite ends to opposite annular projec- Vtions 32 and 33 formed integrally with, and on the inside of, the respective'end walls 11 and 12 of the housing `10, as illustrated, and affixed to these 'projections in a suitable manner.

The apertures 31 in the separating cylinder 14 farearranged in alignment with each other in both longitudinal and 'circumferential directions and are each inclined so that the upstream 'portion 34 of the aperture is located Vmore advanced than the downstream portion 35 thereof in a circumferential direction opposite to that of revoluyt'io'nar'ly movement of grains. In FIGURE 3, the arrow A indicates the direction of revolutionary movement of grains caused :by the rotation 'of the roll 13 'while the arrow B indicates the direction in which the 'grains are 'conducted by the provision of the apertures 31.

Grains, charged 'throughthe hopper 22 into the polishing 'chamber 24, are fed toward the roll 13 'by `thehelically ridged lor grooved member 30, and then effect circumferential movement with the rotation 'of the roll as the grains come into contact'with the peripheral surface of the roll. On the other hand, the polishing chamber 224 is always lled with grains continuously fed thereinto with the rcsult that the grains in the polishing chamber cannot effe'ctcompletely free movement therein. Thus, there are relative movements between the grains and the surface of the roll or between the grains themselves, causing frictional 'effect to polish grains. Grainsin the polishing chamber around the roll veliect 'circumferential movement at a 'speed which 'decreases a's the radial distance of the grain from the periphery ofthe 'roll-is increased. The grains effecting 'revolutionary or circumferential movement around the 'polishing roll under the action 'thereof are also subjected 'to the action of the apertures 31 to e'ie'ct advancing movement in a forwardly downward direction Aas indicated by the arrow C in FIGURE 3, as the grains come into contact with the inner peripheral surface vof the cylinder. The advancing movementV is transmitted successively to 'adjacent grains whereby the entire mass of `grain inthe polishing chamber 24 is moved gradually forwardly through the chamber toward the outlet 27 thereof, that is, toward the end wall 11 of thehousing 10. The grain is subjected to polishing action during such movement with the bran separated from the grain being pushed out through said apertures 31 in the peripheral wall of the cylinder 14 to fall upon the bottom of thehousing 10 to be collected in a suitable manner.

As described hereinbefore, the advancing movement of grain owing through the polishing chamber of the grain polishing machine according to the present invention is caused by a plurality of inclined elongated slots 4or apertures provided in the peripheral wall of a cylindrical member constituting the outer wall of the `polishing chamber, and, in order to'cause the grain to pass axially tl'irough the chamber at a suflicient speed to be used in actual practice, it is necessary that grains have a Substantial circumferential or revolutionary speed already at the inlet end of the roll. 'It is desirable from the standpo-int of increasing the output of the machine to cause grains to pass through the polishing chamber at a speed as high as possible without the danger of crushing or breaking the grains. For this purpose, one embodiment of the present invention comprises a conical member 4t) provided at the inlet end of the polishing roll, as illustrated in FIGURE 4. The conical member Ml may be formed separately from or integrally with the main body of the roll 13. In either case, the conical member or portion 46 is preferably made of a similar material and in a similar manner as the roll itself.

In this embodiment, as in the above described embodiment shown in FIGURES l to 3, a bran separating cylinder 41 is provided around the polishing roll 13 in a spaced apart relationship therewith, according to the invention. As will be observed, however, that portion of the cylinder 41 of this embodiment which is adjacent to the conical portion 40 of the roll 13 is also shaped conically in parallel with the surface of the conical roll portion liti.

A grain feeding hopper 22 extends through the top wall 21 of the cylinder 13 to the conical portion 42 thereof where the hopper 22 opens into the polishing chamber 24. The separating cylinder 41 is provided with a great number of inclined elongated slots or apertures over the entire periphery of the cylinder or at least over a portion thereof as With the first described embodiment for progressively advancing the grains edecting revolutionary movement with the rotation of the roll, it being natural that the conical portion 42 of the cylinder also is provided with similar elongated slots.

In this embodiment, grains charged through the hopper 22 into the polishing chamber 24, are first subjected to frictional eifect of the outer surface of the conical roll portion ft) to start revolutionary movement around the latter. This revolutionary movement is transmitted in succession to outer grains and, as the grains in contact with the inner surface of the conical portion 42 of the separating cylinder effect revolutionary movement, they are deflected toward the diverging side of the conical wall or toward the roll 13 by the engagement with the inner peripheral surface `of said conical portion 42, such dellection being assisted by the tendency for the revolving grains to spread radially outwardly. In addition to this, the conical portion 42 also is provided with a plurality of inclined conducting slots 43 quite the same as those formed in the cylindrical portion of the cylinder, said conducting slots 43 being effective to convert the circumferential movement of the grains along the inner peripheral surface of the conical portion 42 into a spirally advancing movement having an axial component, and such spirally advancing grains act to induce similar movement in adjacent grains. Thus, with this construction, grains will come to have an axial component of movement already when they are in the inlet region of the polishing chamber 24 denn-ed by the inlet end portions of the roll 13 and the cylinder 41, whereby axial advancing movement of the grains after leaving the inlet region will be effectively promoted so that higher grain feeding speeds may be obtained without necessitating any excessive peripheral speed of the roll.

In other Words, the substantial initial speed of grains relative to the polishing roll obtained by the provision of said conical parts di) and 43 makes it possible that the grains pass through the polishing chamber only under the inuence of the conducting apertures in the cylinder wall without any feeding effect of the roll itself upon grains.

Another embodiment of the present invention illustrated in FIGURE 5 has a separating cylinder differing in construction from those employed in the above described embodiments. That is, this embodiment employs a separating cylinder having formed on its inner peripheral surface a plurality of ridges instead of inclined slots for imparting to grains a component movement in the direction of the longitudinal axis of the cylinder.

This embodiment shown in FIGURE 5 is constructed generally similarly to the embodiments shown in FIG- URES 1 to 4 excepting the construction of the polishing roll and the bran separating cylinder. In the grain polishing machine shown in FIGURE 5, grains charged into the polishing chamber are acted on by the polishing roll so as to start revolutionary movement around the polishing roll with the rotation thereof, said revolutionary movement of the grains being converted at least partially into axial advancing movement by inclined ridges arranged around the inner peripheral surface of the separating cylinder for removing the bran formed in the chamber therefrom.

A rotary shaft 15 is rotatably journaled at opposite ends in bearings 16 and 17 carried on respective end walls 11 and 12 of the housing 1t) of the machine. The shaft 115 projects outwardly beyond the bearing means 17 to carry a pulley Ztl fixed to said projecting portion. Affixed to the top of the housing 1t) is an upper wall 21. Provided at the bottom of one of the end walls 11 of the housing is a trough 2S for discharging polished grains out of the machine. These features are substantially identical with those of the machines previously described.

In this embodiment, a bran separating cylinder 50 is provided which is formed of wire gauze 51 and secured at opposite ends coaxially with said rotary shaft 15 to the respective end walls 11 and 12, being fitted to annular projections 52 and 53 formed inside thereof. Secured to said rotary shaft 15 coaxially therewith is a polishing roll 49 made of ceramic or the like material. A polishing chamber S4 is defined by the outer peripheral surface of the roll 1S and the inner peripheral surface of the Wire gauze cylinder 5t). All over the inner peripheral surface of the bran separating cylinder are ixedly arranged a plurality of narrow raised ribs or ridge members 5v5 in alignment with each other in both longitudinal and circumferential directions. These ridge members 55 are each so inclined as to deflect or shift circumferentially moving grains toward the outlet port 29 of the polishing chamber, that is, toward the end wall 11 of the housing as thev grains come into contact with the ridge members.

A hopper 22 extends through the top wall 21 to Athe separating cylinderSt) to open into the polishing chamber 54. Grains charged through the hopper are first brought into contact with the rotating roll 49, the outer peripheral surface of which is roughened so as to present frictional resistance to the grains thereby to impart to the grainsI revolutionary movement while at the same time causing the grains to rotate about their own axes with the rotation I of the roll 49. Such movements of grains are transmitted in succession to outer grains with the result that all grains are effectively polished by the friction of the grains against the roll surface as well as against each other.

The revolutionary or circumferential movement of grains caused by the rotation of the roll 49 decreases in speed With the distance from the periphery of the roll. For instance, with a high speed machine of this form, even when the roll has a peripheral speed of the vorder of 2,000 feet per minute, those grains located adjacent the cylinder 50 move circnmferentially only at speeds of the order of 1GO to 30() feet per minute. When grains strike against the ridge members 55 at such revolutionary speeds, the grains are suflciently forwardly deflected along the ridges without being crushed thereby. On this occasion, it will be understood that grains effect revolutionary movement upwardly along the illustrated side of the cylinder 50 and are shifted toward the left by the ridges 55. Thus, grains charged through the hopper 22 into the polishing chamber 54 are advanced toward the outlet port 27 While being polished as describedherei'nbefore. Meanwhile, brans are discharged outwardly throughtthe wire gauze cylinder 50. -In the embodiment -show'n in FIGURE 5, the bran separating cylinder -has been described to be formed of Wire gauze, but may also 'take `the form `fof acylindri'cal steel plate having a great' `Vnumber of small apertures-formed therein. Whether the cylinder isformed of wire gauze or made inthe form of -a` cylindrical` perforated plate, the meshes or perforations rare determined `smaller in size than polished grains but `larger than :the brans separated from the grains so `as tot allow the bransto be discharged through such meshes or1 .perforations 1 In Vthis embodiment, asillustrated in FIGURE 5, -the ,polishing roll49comprises a body of a simplecylindrical configuration, :having the outer peripheral surface rough' `cned, but this roll mayalternatively be provided With a `the-cylinder; in other words, the angle made betweenthe Vrespective ridges and the direction of 'revolutionary .movement ofthe grain along the inner periphery of the Acylinder-isdecreased as the axial distance of the respectiveridges from the outlet end of the cylinder is decreased. .In all forms of the polishing machine accordto `the present invention, the bran separated from the grain :by .polishing operation-is removed outwardly ihroughihe apertures ormeshes of the separating cylinder constitutingthe outer wallof the polishing chamber, with theresult that the density of the grain fiow'is pro- .gressively `decreased as `the flow proceeds toward the outlet end of thepolishing'chamber, vwhere the component force acting to impart to the grains advancingmovement through the polishing chamber is uniform throughoutthe length thereof. Such decrease of the flow density from the inlet end to the outlet end is undesirable in 'that thepolishing efficiency is impaired. AIn other words,

it is desirable that the grain flow lin the polishing chamber`has a `constant density .throughout the entire chamber. For this purpose, the;present invention has a further feature as illustrated inFIGURES 6 and 7. Thus, the ridges 59 are ldisposed so that they develop a component force `which decreases with the distance from the outlet end of the polishing chamber. As a result, the grain flow is decelerated while being reduced-in volume as it comes closer to the outlet, so that the grain Vvow may maintain a constant density throughout the entire polishing chamber. I

As illustrated in FIGURES 6 and 7, the polishing roll 60 has on-itsperiphery a plurality of parallel ridges while the bran separating cylinder is `formed with a great number of 4small apertures 62 and, as in the previously described embodiments, is fitted at opposite ends to inside projections 52. and 53 on respective end walls 11 and .12.. In other respects, the construction of this 'embodiment'is identical with that of the previously described embodiments.

As described above, according to one feature of theA present invention, the `bran separating cylinder is provided on its inner surface with a plurality of ridges for 'feeding grains through the polishing chamber, said ridges fhaving different angles of inclination with respect to the longitudinal direction of the chamber for maintaining the density of the grain flow substantially constant throughout the chamber. Grains to be processed may have differentshapes, sizes, surface characteristics, etc. with the difference in their kinds. Therefore, if a variety `of grains having differing qualities be processed all under the same conditions, there will Abe a possibility that the not adequate for others. According to the present invention, means is provided as follows to further assure the elimination of such inconvenience.

According to a further feature of the present invention, a grain polishing machine is provided with a means for adjusting freely and exteriorly of the machine the angle of inclination of discontinuous helical ridges disposed on the inner surface of the bran separating cylinder. As illustrated in FIGURE 8, ridge members 66, 67 -and 68 are pivotally secured at one end to the inside of the -bran separating cylinder 65 for rocking movement along the inside surface thereof and at the other end to respective adjusting or operating rods 69, 7() and 71 at the adjacent end thereof. Each of the operating rods 69, and 71 extends at the other end through one of the end walls ofthe machine and is releasably fixed by rod fixing means provided von the outside of this lend wall. The rod fixing means 72 comprises a plurality of block members and a set of set screws carried by each of the block members. Each of the block members is formed with bores through which the 'outer end portions of rods 69, 70 and 71 extend. The rods may be rmly held in any adjusted position by said set screws, which extend transversely to said bores. When these set screws are loosened, the operating rods are freely movable longitudinally through said bores in the block for adjusting `the angle of inclination of the associated ridge members. After proper inclination has been selected, the set screws are again `threaded inwardly to fix the respective rods in the selected positions.

Thus, by longitudinal movement'of the operating rods, the ridge members pivotally secured to the respective rods are rocked to have their angle of Yinclination correspondingly changed. Such adjusting operation may be effected even during the polishing operation of the machine while observing the state of the finished grain delivered out of the machine.

In the embodiment of FIGURE 8, a pair of ridge members are pivotally secured to each of the adjusting rods as illustrated so as to effect the same rocking movement by operation of the associated rod. In FIGURE 8, there are shown six of such adjusting rods together with six pairs of ridge members respectively secured thereto; that is, only those rods and ridge members disposed'on the rear half of the bran separating cylinder are illustrated. It goes without saying that similar adjusting rods and ridge members are also disposed on the other half of the separating chamber. In the actual practice, ridge members in each row, disposed in the same axial position 4and in circumferential alignment with each other, are adapted to have at all times one and the same angle of .inclination with respect to the circumferential direction, which angle decreases with the decrease of the distance of the row of ridges from the outlet of the cylinder.

Referring to FIGURE 9, there are illustrated ridge members each pivotally secured to a separate `operating rod. A separating cylinder 73 is shown provided with a great number of small circular apertures 74, which have an area smaller than the grain size so that only bran separated from the grain may pass through the apertures. A number of ridge members 75, extending closely along the inner surface of the cylinder, are each lpivotally secured at one end to the inner surface of the replaced by the roll assembly shown in FIGURE 1 or 4. 'Ille number of grain feeding ridges and the number of sets in which they are arranged may also be selected as desired. Further, the bran separating cylinder may selectively take the form of a cylindrically-shaped wire gauze, perforated steel sheet or the like, but, where the separating perforations or apertures themselves are utilized for imparting feeding or advancing movement to the grain, a perforated or apertured steel plate is generally preferable.

What is claimed is:

A grain cleaning machine comprising a polishing roll of a ceramic material adapted for rotation about a longitudinal axis, a bran separating cylinder surrounding said roll, the outer periphery of said polishing roll and the innerrperiphery of said bran 4separating cylinder defining a space constituting a polishing chamber, means providing a grain inlet and a grain outlet for said polishing chamber, means for rotating said polishing roll, guide means `on ysaid bran separating cylinder to advance grain toward said outlet from said inlet as the grains come into engagement with said guide means when said polishing roll is rotated, said bran separating cylinder having a plurality of openings through which bran is removed from grain in said chamber, said openings being elongated and inclined at an angle to the axis of said roll, to constitute said guide means, and a plurality of circumferential parallel ridges on the outer peripheral surface of said polishing roll extending perpendicular to the axis of said roll, whereby the area for contacting grain is increased.

References Cited in the le of this patent UNITED STATES PATENTS 644,774 Matthews Mar. 6, 1900 1,156,640 Stern Oct. l2, 1915 1,814,398 McKain July 14, 1931 2,499,590 Konupek Mar. 7, 1950 2,667,905 Tanner Feb. 2, 1954

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