US1947953A - Beater bar mill with two beater bar disks rotating rapidly in opposite directions - Google Patents

Description

Feb. 20, 1934. J. o

HEATER BAR MILL WITH TWO BEATER BAR DISKS ROTATING RAPIDLY IN OPPOSITE DIRECTIONS 2 Sheets-Sheet 1 Filed June 12, 1931 U I e Feb. 20, 1934.

J. o'r'r 1,947,953 HEATER BAR MILL WITH TWO BEATER BAR DISKS ROTATING RAPIDLY IN OPPOSITE DIRECTIONS Filed June 12. 1931 2 Sheets-Sheet 2 gym newton Patented Feb. '20, 1934 UNITED STATES PATENT OFFICE BEATER BAR MILL WITH Two BEATER BAR DISKS ROTATING RAPIDLY IN OP- POSITE DIRECTIONS Josef Otto, Cologne-Lindenthal, Germany 7 Claims.

Applications for patent filed in Germany June 13, 1930, and August 5, 1930.

In beater bar mills for grinding material finely which are provided with two grinding disks rapidly rotating with respect to each other on a horizontal shaft the main difficulty resides in effecting the introduction of the material to be ground in such manner that it is distributed uniformly over the entire periphery of the rotating beater bars or mill teeth. It is only when the material is uniformly distributed that a high performance and a constantly good grinding is ensured because otherwise only a part of the beater bars is operative and at the overloaded points larger particles can readily slip through without being pulverized by beating. Also if the material to be ground is not uniformly distributed the wear of the machine is increased and its operation is unsteady. In the case of moist and sticky material it is only possible to grind it when it is uniformly distributed over the entire grinding chamber as otherwise the machine im-- mediately jams at the overloaded points.

It has already been proposed to provide the rotating grinding disks with centrifugal vanes. In this way however it is not possible to obtain a general distribution of the material as it can fall from the charging hopper directly into the lower part of the grinding zone between the vanes which are directed downwardly. No improvement can be obtained by providing a distributing cone for the material which cone is disposed between the centrifugal vanes with a view to affording uniform distribution, as in this case also the material is free to pass beyond the cone into the lower portion of the grinding zone.

All the disadvantages above set forth are overcome in the present invention in that the centrifugal vanes or scoops disposed close to the row of bars are mounted helically on a deflecting cone of a hub assisting the introduction of the material, the cone being disposed on the shaft of the mill and tapering conically towards the point at which the material is introduced and the vanes dividing in an approximately radial direction the inlet passage of approximately constant annular cross section formed at the hub. In this arrangement the material supplied vertically from above from the supply hopper is directed axially by the centrifugal scoops which in consequence of their conical arrangement deflect it in the radial direction and scatter it and at the same time effect a distribution over the entire length of the beater bars. In this way a stop is provided at the same time by the distributing arrangement between the supply hopper and the grinding zone so that the material supplied cannot fall directly into the grinding chamber in a non-uniform manner.

One embodiment of the invention is shown by way of example in the drawings in which:

Fig. l is a vertical section through the beater bar mill (partly broken away),

Fig. 2 shows a perspective view of the hub serving for guiding the material introduced,

Fig. 3 shows also in perspective a ring of guide scoops, a part of the guide scoops being omitted.

Fig. 4 shows a vertical section through a somewhat modified beater bar-mill (partly broken away).

The beater bar mill consists of the two grinding disks b and s which are equipped with concentric rings of beater bars and are secured on the two shafts n and 0 which are rotated in opposite directions. The introduction of the material from the supply hopper 1 into the grinding zone is effected by the hub a of the grinding disc b. The hub is provided with centrifugal scoops c which are arranged in such manner that the material supplied axially from the annular trough e cannot fall directly between the scoops into the lower part of the grinding chamber but that the material is drawn up by the scoops c and deflected in such manner that it is scattered on all sides in the radial direction and at the same time is distributed over the entire length of the beater bars. The angle of the scoops is chosen in accordance with the peripheral speed of the scoop wheel so that the material to be ground passes with the initial speed determined by the height which it has fallen and without impacts between the scoops in the axial direction.

When adhesive and plastic material is being ground, the axial speed with which the material enters the space between the blades 0 of the centrifugal wheel may become very much reduced. In order to insure, under such circumstances, a smooth and uniform flow of the material, the blades 0 must be inclined toward the wall of the casing in which the supply channel (2 is arranged at a very small angle. But when so constructed, the blades will be of excessive length and involve great frictional losses for the material to be ground. Such long blades, moreover, would result in large oblique cross-sections for the blades at the side where the material enters, whereby the space through which the material enters would be considerably reduced in size and whereby naturally also the capacity of the mill would be correspondingly reduced. To overcome the aforementioned disadvantages, a guide blade ring as shown in Fig. 3 may be disposed in that portion of the supply channel e which faces the blade wheel, the blades of the guide blade ring being inclined in a direction opposite to that of the blades 0 of the centrifugal wheel. When so arranged, the material to be ground enters through supply hopper f and passes under pressure into channel e where by means of the guide blades 9 it is-uniformly distributed over the whole of the centrifugal wheel and smoothly fed between the blades 0.

A special arrangement to protect the guide blade ring against displacement is not needed, since the lateral edge p of channel e which is turned toward the shaft n is provided with radial recesses in which engage the guide blades 9.

The aforementioned disadvantages which present themselves when adhesive material is being ground can also be overcome by modifying the arrangement as shown in Fig. 4. According to Fig. 4, the blades c are-provided with extended portions 2' which project into the supply channel e at the side at which the material enters the mill. In all its other details, the form of construction shown in 4 corresponds to that shown in Fig. 1.

The inlet hub a, the centrifugal scoops c of which serve at the same time as spokes for the grinding disk I), is preferably adapted to be interchangeable so that a centrifugal wheel with centrifugal scoops c of suitable obliquity can be used to suit the material to be pulverized.

What I claim is:

i. In a mill of the kind described, a pair of coaxial and independently rotatable shafts adapted to rotate in opposite directions, a hub on one of said shafts provided with an annular peripheral channel. and with an opening leading from channel through an end of the hub, helical feeder means extending from the openin the end face of the hub to the other end of the hub, a disk carried by said hub, a second disk carried by the remaining shaft and spaced from the first disk, and beater bars carried by the proximal faces of said disks with the bars of one disk interposed betyeen the bars of the other disk.

2. In a mill of the kind described, a pair of coaxial and independently rotatable shafts adapted to rotate in opposite directions, a frustoconoidal hub having a concave surface and mounted on one of said shafts, helical feeder blades extending from said hub, a flange on one end of the hub supported by said blades in spaced relation to the body of the hub to provide material inlet openings, a disk carried by said hub, a second disk carried by the remaining shaft and spaced from the first disk, and beater bars carried by the proximal faces of said disks with the bars of one disk interposed between the bars of the other disk.

3. In a mill of the kind described, a pair of coaxial and independently rotatable shafts adapted to rotate in opposite directions, a hub on one of said shafts provided with helical feeder means extending from one end face of the hub to its periphery, a disk carried by said hub, a second disk carried by the remaining shaft and spaced from the first disk, beater bars carried by the proximal faces of said disks with the bars of one disk interposed between the bars of the other disk, a casing having an annular feeder channel wherewith said feeder means constantly com- I municate, and fixed guide members disposed between said hub and channel to direct material to said feeder means.

4. In a mill of the kind described, a pair of coaxial and independently rotatable shafts adapted to rotate in opposite directions, a frustoconoidal hub having a concave surface and mounted on one of said shafts, helical feeder blades extending from said hub, a disk carried by said hub, a second disk carried by the remaining shaft and spaced from the first disk, beater bars carried by the proximal faces of said disks with the bars of one disk interposed between the bars of the other disk, a casing having an annular feeder channel having an open side adjacent the smaller end of the hub, and fixed guide members disposed between said hub and channel and arranged to direct material to said blades.

5. In a mill of the kind described, a pair of coaxial and independently rotatable shafts adapted to rotate in opposite directions, a hub on one of said shafts provided with helical feeder means extending from one end face of the hub to its periphery, a disk carried by said hub, a second disk carried by the remaining shaft and spaced from the first disk, beater bars carried by the proximal faces of said disks with the bars of one disk interposed between the bars of the other disk, a casing having an annular feeder channel open toward said hub, and feeder extensions on said feeder means extending into said channel to force material from said channel and deliver it to the main portions of said feeder means.

6. In a mill of the kind described, a pair of coaxial and independently rotatable shafts adapted to rotate in opposite directions, afrustoconoidal hub having a concave surface and mounted on one of said shafts, helical feeder blades extending from said hub, a disk carried by said hub, a second disk carried by the remaining shaft and spaced from the first disk, beater bars carried by the proximal faces of said disks with the bars of one disk interposed between the bars of the other disk, a casing having an annular feeder channel open towards the hub at the smaller end thereof, and extensions on said blades entering said channel to force material from said channel and deliver it to the main portions of said blades.

7. In a mill of the kind described, a pair of coaxial and independently rotatable shafts adapted to rotate in opposite directions, a hub arranged on one of these shafts and provided with an annular channel beginning at one of the front faces of the hub and extending in arelike formation to the periphery of the hub, said annular channel being subdivided by helical blades, a disk carried by said hub, a second shaft supporting a second similar opposed disk, each of the disks being provided with a plurality of concentric, lattice-like collars of stationary beater bars, the beater bar collars of the two oppositely arranged disks rotating in opposite directions coacting with each other in such fashion that they are not in immediate contact with each other, said beater bars extending across the entire width of the space between the disks forming the grinding area.

JOSEF OTTO.

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