US2751157A - Grinding mill embodying coaxial oppositely rotating grinding disks - Google Patents

Description

L OPPOSITELY F. MEYER ET A GRINDING MILL EMBODYING COAXIA INDING DISKS April l0. 1953 ROTATING GR Filed ms M m www /W M .CL n I M W/ A EM du F. fw n MQ n RJ @n wv L i Sv y; E.

June 19, 1956 GRINDING MILL EMBODYHYG COAXAL OPPO- SITELY ROTATNG GRBNDING DISKS Fritz Meyer, Busseidorf-Gerresheim, and Friedrich Nicolaus, Dusseldorf, Germany, assignors to Gutehoifnungshiitte (lberhansen Aktiengesellschaft, Oberhausen, Germany The present invention broadly relates to the art of comminuting.

Specifically the invention relates to a grinding mill embodying coaxial oppositely rotating grinding disks.

Still more speciiically the invention relates to a feed for the material to be ground or comminuted.

In the art of grinding, with particular reference to grinding mills which are utilized for the comminution or grinding of granular half-cell material in the manufacture of cellulose, certain problems arise which must be overcome. in connection with this matter it is pointed out that half-cell material is generally produced from wood or woody material by a pretreatment process involving boiling with lye.

It is therefore apparent that fibrous materials are involved. In the grinding of brous materials in a wet state it has been known to utilize disk mills in which the material to be ground is worked on between twol coaxially mounted disks that rotate in opposite directions and which disks are equipped with plate-shaped profiled grinding segments or teeth. The material to be ground is fed adjacent the center of the disks and ground during its travel radially of the center outwardly toward the periphery. Under these conditions the material to be ground moves under the influence of centrifugal force between the grinding segments or teeth and is discharged into a housing that surrounds the disk.

It is also known to have grinding mills utilizing only one disk or stone that is rotatably mounted relative to a stationary coacting disk.

Furthermore and while not connected with the grinding of fibrous materials, there is a known embodiment for comminuting ore including a driven disk and another disk that is freely rotatably mounted relative thereto so that the feed to the disk is, by friction forces, carried along or rotated in the same direction as the driven disk.

Other arrangements embodying conical oppositely rotating grinding disks are known in which these disks or elements are mounted eccentrically relative to one another so that their mutually engaging peripheral surfaces move in the same direction but due to unequal speeds of rotation have some movement relative to one another.

In order to deliver or feed the material to be ground to mills of the aforedescribed type, the feed has been effected in one arrangement by utilization of the centrifugal force of grinding and by feeding material to disks that are rotatable on vertical axes. It has further been proposed to utilize conveying means to convey the material which can be in the form of mechanical means or uid pressure in wet grinding processes where the liquid utilized in grinding is also utilized to convey the material from the source of supply to the grinding disks.

In known grinding mills having oppositely rotating disks, feed recesses are provided between the hub and the grinding segments of one of the disks.

In connection with the present environment, namely the grinding of fibrous material and particularly the grindes atent 2,751,157 Patented June 19, i956 ing of the half-cell material utilized in the production of cellulose, the prior known feed means are not suitable. First of all, material being ground is rather cohesive or adherent and under these conditions it will jam or plug a feed pipe and it cannot be conveyed by gravity or by suction means if safe operating conditions are to be established. Additionally hydraulic conveying of the material to be ground, that is the utilization of water under pressure, is not advisable since under these conditions more water than is required for wet grinding is furnished with the material to be ground and with particular reference to the final state of comminution.

It therefore follows that an important object of the present invention is to provide a mechanical conveying means for a grinding mill of the type having oppositely rotating coaxial disks.

It is an additional object to provide a mechanical conveying means that is driven by power means independent of the drive for either of the disks. Thus this invention provides as a specific feature and in combination with oppositely rotating grinding disks that are adjacent one another and one of which is mounted on a hoilow drive shaft, a worm feed in which the worm is mounted within the hollow drive shaft and drive means independent of the drive for either of the disks are provided for the feed worm or screw so that proper regulation of the rate and quantity of the feed can be maintained.

Inasmuch as the invention is particularly suitable for the wet grinding, it is a further object to provide a unique feed of the liquid that is to be utilized in grinding which Hows in a path such that the liquid does not mingle with the material to be ground until the said material is between the two disks and further in which the liquid in addition to its utilization in the grinding process is utilized as a cooling medium.

Therefore the invention specifically provides, in combination with a rotatable hollow shaft for one grinding disk and within which shaft is arranged the feed worm, a tubular means mounted between the worm and the inner periphery of the shaft and constituting a fluid channel through which the liquid can flow and means for feeding liquid to the channel to flow therethrough to the space between the cooperating oppositely rotating grinding disks.

It is believed clear than an important object of this invention is to provide for the proper cooling of the journals or bearings for the hollow shaft since the liquid grinding medium, which can be water, flows through the hollow shaft and is isolated from the material being fed to the grinding disks until it reaches the space between the disks. This is of particular importance if the material to be fed for any reason, such as a pretreatment process, has an extremely high temperature since under these conditions the liquid flowing about the tube within which the material to be ground is fed will act as a refrigerant and cool the material.

It is further to be pointed out that if the material to be ground is highly active from a chemical standpoint the structural parts that are contacted by the same are to be made of rust resistant steel or a suitable non-metallic material that will be insensitive to any corrosive action of the material being ground. Synthetic resins, due to their low specific weight, are ideally suited as the material from which the conveying worm or screw and the tube surrounding the same are made. This is particularly true if both the worm and the tube surrounding the same are supported at only one end and are mounted on a horizontal axis so that the terminal ends of these elements are not supported and constitute free ends.

Further and more specific objects will be apparent from the following description taken in connection with the acompanying drawing which isa fragmentary View partly in longitudinal section and partly in elevation illustrating a grinding mill for the flue comminution of material.

In the drawing the grinding mill includes a base denoted at 19. On the base is carried two facing, oppositely rotatable plate like disks between which material to be comminuted is fed. The base, therefore, supports two spaced bearing supports 20 and 21 respectively carrying ball and roller bearing means 31 and 3U that journal a hollow shaft 26 splined or otherwise suitably rigidly fastened to the left hand rotor 25. A casing 22 that is closed at the sides and top and open at the bottom to communicate with an outlet 22 has an aperture in one wall thereof through which the shaft 26 is passed. A facing aperture in the opposite wall in alignment with the axis of shaft 26 receives a shaft 24 for the right hand rotor 23. The base 19 is extended to the right as shown and supports bearing means including a bearing support denoted generally at 44 that journals shaft 24. Suitably splined to hollow shaft 26 is a drive pulley 32. This pulley and the shaft 26 are rotated in one direction by a suitable belt drive not shown. A drive pulley 45 is keyed or splined to shaft 24 so that by means of a suitable belt drive not shown the shaft 24 can be rotated in a direction opposite to the direction of rotation of shaft 26. Each of the rotors or disks 23 and 25 are provided with an annular groove in the respective faces thereof and shearing means in the form of castings 27 and 28 are bolted to the respective rotors or disks. Each rotor includes a depressed central portion so that when the rotors are in facing relation as shown, a space or chamber 29 is provided between the rotors. Suitable Alemite ttings or other lubricating means are provided in association with the housings of the bearing supports to furnish lubrication to the respective ball and roller bearing means.

The hollow shaft 26 terminates at the side 32' of the bearing support 20 that is remote from the rotors or grinding disks. Secured to the side 32 is a flanged ring 33 having packing ring means 34 therewithin in engagement with a hollow tube 35 that is within the shaft 26. To one side of the bearing support 20 and carried by the base 19 is an inlet reservoir means denoted generally at 36'. The hollow tube 35 extends from the inlet reservoir means to which it is connected through the full length of the hollow shaft and terminates in a free end at the inner end of this shaft. The external diameter of tube 35 is less than the internal diameter of hollow shaft 26 so that there is an annular space or passage 36 between the tube and shaft for the full length of the shaft. One end of this space or passage is closed by the flanged ring 33 which forms an annular chamber around the tube 35. A liquid inlet pipe 37 communicates with this annular chamber. Thus liquid, such as water, or other low temperature liquid, can be supplied under pressure to the annular chamber within the ring to ow through the annular passage 36 into the space 39 between the disks. The liquid will there mix with the material to be ground which is fed through the tube 35. In flowing through the space or passage 36, the liquid will cool the material flowing through tube 35 and help cool the bearings for the hollow shaft. The cooling effect on the material being fed eliminates the likelihood of the feed material backing up within the feed tube 25 or plugging within the space between the disks 23 and 25.

To provide for the proper feed, a` feed worm 38 is mounted within the tube 35. The shaft for the feed worm is supported at one end by axially spaced bearings 39 and 41. A spider means such as shown diagrammatically at 3S can be associated between the interior of the tube 35 to journal the free end of the feed worm shaft. However, such spider means can be eliminated if desired. ln any event, both the tube and feed worm have associated therewith supporting means at the ends thereof remote from the disks or rotors and each of said tube and worm have greater axial extent than the hollow ,shaft 26. The total extent of the worm and tube that i is within the hollow shaft is freely supported by the supporting means in cantilever fashion in spaced relation to the interior of shaft 26. The bearing 39 is in the form of a bushing mounted in the end wall of the inlet reservoir 36', that is remote from the disks or grinding rotors. The bearing or bushing 41 is mounted on a pedestal 42, supported by a shelf or bracket 43, secured to the inlet housing 36. Since the inlet housing is carried by the base 19, the axially spaced bearings 39 and 41 include supporting means carried at least in part by the base 19. The portion of the feed worm shaft between bearings 39 and 41 has secured thereto a pulley 40. This pulley is driven by a belt from a motor 17 carried by a suitable supporting means, not shown. Thus the drive for the feed Worm, the drive for disc 25 and the drive for disc 23 are all independent with respect to one another.

lf desired, the feed worm shaft can be driven directly by an electric motor. Likewise, shaft 24 can be directly driven by an electric motor. The rotation of the rotors 23 and 25 in opposite directions is utilized in connection with the shredding of alkali cellulose material and certain other grinding actions. However, this opposite rotation of the rotors is not to be considered a limitation since under certain conditions it is desirable to rotate both rotors in the same direction.

lt is therefore clear that this invention provides, in a mill for the purposes set forth hereinbefore, facing rotors each embodying shearing means or other suitable cornminuting means and provided with a central space therebetween and in which the shearing means are in closely spaced relation relative to one another, a housing surrounds or encloses the rotors and is provided with an outlet for the material that has been ground, emulsified, shredded, homogenized, or is in another suitable state of comminution. One of the rotors is mounted for rota- 'l tion with a hollow shaft and is driven in a direction opposite to that of the other rotor. The hollow shaft in turn is journaled in spaced bearings and a drive pulley is mounted between the bearings. Within the hollow shaft extends a feed tube which is of smaller external diameter than the internal diameter of the shaft and provides communication between the grinding chamber between the rotors and an inlet reservoir. A feed worm with means for driving the same independently of the drive means for either rotor is embodied within the feed tube and means is provided for feeding cooling liquid to the space between the tube and the hollow shaft.

Obviously this structure immediately aforedescribed can be arranged along a vertical axis, that is the grinding disks will rotate on a vertical axis. The manner of feeding the cooling liquid independent of the feed of the material and the feed of the material independent of the rotation of either disk is a very important aspect as regards safety of operation with particular reference to the utilization of disks that rotate in opposite directions at high speed. This is further important since in-a fine grinding operation or where the particle size to be completed is of colloidal magnitude, that is, the grinding teeth or segments are spaced apart to a distance amounting to 'only a fraction of a millimeter, the independent feed of fibrous material and liquid minimizes the danger of blockage or of plugging in the grinding process. Furthermore, `since the speed of rotation of the feed worm is independent of the rotary speed of the two grinding disks, the structure of the type aforedescribed is ideally suitable and adaptable to grinding conditions arising out of fthe utilization of different materials to be ground.

What we claim is:

l. In a comminuting apparatus, two coaxially arranged grinding disks and between which material to be cornminuted is fed, one of said disks having an aperture therethrough, a lhollow shaft secured in the aperture and constituting a drive shaft for rotating said one disk, a drive shaft for the other disk, a feed worm for feeding the -material to the space between the disks and mounted coaxially within said hollow drive shaft, drive means independent of the drive means that rotate the said shaftsfor rotating the feed worm, a feed tube arranged within the hollow shaft between the interior thereof and the feed worm, said tube having a length such to extend at least passage along the tube and shaft to cool the same.

2. In a comminuting apparatus as defined in and by claim l, and supporting means for supporting the tube ported by said supporting means 1n cantilever fashion and in spaced relation to said shaft.

3. In a comminuting apparatus, two coaxially arranged gnnding disks and between which material to be corntending at least the full length of the hollow shaft so as the tube and communicating with the space between the ing axially spaced bearings both disposed outwardly of tation of both said disks.

5. In a com inuting machine as defined in and by being mounted on said base, said means constituting an including supp the base.

References Cited in the le of this patent UNITED STATES PATENTS

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