US2093703A - Pulverizing apparatus - Google Patents

Description

P 1937- A. e. BL'obGETT 2,093,703

PULVERIZING APPARATUS Filed Nov. 9, 1955 Patented Sept. 21, 1937 PATNT OFFICE PULVERIZING APPARATUS Albert G. Blodgett, Worcester, Mass, assignor to Riley Stoker Corporation, Worcester, Mass, a corporation of Massachusetts Application November 9, 1933, Serial No. 697,325

16 Claims.

This invention relates to pulverizing apparatus, and more particularly to apparatus of the type which reduces material to a fine powder by the action of rapidly revolving impact members.

With machines of this type as ordinarily constructed, it is necessary for the impact members to travel at very high linear velocities in order to produce the required fineness of pulverization. This introduces a serious problem in constructing 10 the revolving parts of sufficient strength to withstand the enormous centrifugal forces involved, particularly in the smaller machines in which the rotor diameters are so small as to require high rotational speeds to produce the necessary peripheral velocity. Moreover, these machines are usually driven by direct-connected electric in duction motors supplied with 60 cycle alternating current, and such motors cannot be built to operate at over 3600 revolutions per minute. If a peripheral velocity of 15,000 feet per minute is required and the rotor is to operate at 3600 revolutions per minute, the rotor must be approximately 16 inches in diameter. These facts have seriously limited the use of this type of pulverizing apparatus in installations requiring small pulverizing capacities.

In order to overcome these difliculties it has been proposed to utilize two sets of impact members which revolve in opposite directions about a common axis, thereby obtaining high relative velocities without excessive linear velocities. In some cases the general direction of travel of the material has been outwardly away from the axis, and it has been found that uniformly fine grinding is impossible, since the centrifugal forces act on the coarse particles of material and cause many of them to travel through the pulverizing zone too rapidly to be sufliciently reduced in size. In other cases the attempt has been made to draw the material inwardly past the revolving impact members by means of an air current, and it has been found that the power requirements of such a machine are excessive and that it is extremely difficult to compel any appreciable quantity of material to flow through the machine. Furthermore one of the rotors has been provided with spokes between which the fine material flows as it leaves the machine, and these spokes have been subject to rapid wear caused by contact with the material.

It is accordingly one object of the invention to overcome these difiiculties and to provi-dea pulverizing apparatus which will operate efliciently and produce fine grinding even when built in very small pulverizing capacities.

It is a further object of the invention to provide a pulverizing apparatus having two sets of impact members which revolve in opposite directions, and to so arrange the various parts that a comparatively small amount of power will be required in proportion to the quantity of material pulverized.

It is a further object of the invention to provide a pulverizing apparatus having two sets of impact members which revolve in opposite directions, and to so arrange the various parts that the general direction of travel of the material will be inwardly toward the axis of the machine, and yet coarse particles will recirculate in contact with the impact members until finely pulverized.

It is a further object of the invention to provide a pulverizing apparatus having two sets of impact members which revolve in'opposite directions, and to so arrange the various parts that a free path is provided through which fine material may flow from the peripheral portion of the pulverizing zone to a centrally located outlet.

It is a further object of the invention to provide a pulverizing apparatus having two sets of impact members which revolve in opposite directions, and to avoid the use of rotor spokes subject to excessive wear.

With these and other objects in View, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

Referring to the drawing illustrating one embodiment of the invention, and in which like reference numerals indicate like parts,

Fig. 1 is a vertical section, somewhat diagrammatically shown, of a pulverizing apparatus embodying the invention;

Fig. 2 is a fragmentary section on the line 2-2 of Fig. 1;

Fig. 3 is a View similar to Fig. 1 showing a modified construction; and

Fig. 4 is a fragmentary section on the line 44 of Fig. 3.

The embodiment illustrated in Fig. 1 comprises a hollow casing l0 shaped to provide a preliminary crushing zone I i at one end, a fan chamber 12 at the other end, and a pulverizing zone M located between the crushing zone and the fan chamber. A vertical rotor disk 15 is provided between the crushing zone H and the pulverizing zone I4, these zones being peripherally connected by means of an annular passage I6 around the disk. The disk 15 is mounted on a hub l8 secured to the horizontal shaft IQ of an electric motor 20. A vertical partition 22 is provided between the pulverizing zone I4 and the fan chamber l2, and this partition has a central opening 23 therethrough which forms an outlet for the pulverizing zone.

The coarse material enters the crushing zone ll through an inlet chute 24 which delivers the material into the path of revolving hammers 25 pivotally secured to the periphery of the hub [8. A plate 21 is mounted on the casing wall and extends beneath the hammers 25 to prevent the ma terial from falling directly to the bottom of the casing. This plate is preferably curved on an arc concentric with the shaft l9, and the parts are so arranged that any hard foreign bodies thrown upwardly by the hammers will fall past the end of the plate and be deposited in the space 28 therebeneath. A door 29 is provided in the casing wall to permit access to this space. A few impact members or pegs 30 are preferably mounted on the rotor disk l5 and arranged to revolve outside of the hammers 25, in order to assist in carrying the material through the machine and prevent excessive accumulations of material in the lower portion of the casing.

An annular set of impact members or pegs 32 extends from the outer portion of the disk IE toward the partition 22 and into the pulverizing zone i4, these pegs being revoluble about the outlet 23. A second annular set of impact members or pegs 33 is arranged to revolve close to the pegs 32 but in the opposite direction. The pegs 33 are mounted on the outer portion of a vertical disk 34 which is secured to a hub 36 on the shaft 31 of an electric motor 38. The two shafts l 9 and 31 are aligned. The disk I5 is preferably recessed to receive the disk 34, and the two disks are located closely together. With this construction the length of the pegs 32 is reduced, thus decreasing the stresses due to centrifugal force. Since the two sets of pegs 32 and 33 overlap in a direction parallel to the axis of revolution, and in fact are substantially coextensive, a very effective pulverizing action is ob tained without excessive peripheral speeds.

It will be practically impossible to compel any great quantity of material to travel inwardly toward the axis of revolution and directly through the path of the revolving pegs. In order to avoid the necessity for this mode of operation, both sets of pegs 32 and 33 are spaced from the partition 22 to provide a free passage 40 through which fine material may travel from the peripheral portion of the pulverizing zone to the central or axial portion thereof without contact with the revolving pegs. The material is carried through this passage by means of an air current which in the embodiment illustrated is produced by a rotatable fan wheel 4| mounted on the shaft 3'! within the fan chamber i2. It Will be understood that the fan chamber is provided with the usual peripheral outlet (not shown).

If desired an annular set of stationary pegs 43 may be mounted on the partition 22 .around the outlet opening 23 and arranged to project into the pulverizing zone and close to the revolving pegs 33. These stationary pegs will aid in the pulverization of material, and by varying their number it is believed that the fineness of pulverization can be controlled to some extent, as will be explained hereinafter.

In order to prevent the discharge of coarse particles from the pulverizing zone, I preferably utilize a series of rejector blades 45 which revolve close to the outlet opening 23. These blades may be conveniently mounted on the hub 36, and they may be U-shaped in cross-section, so that coarse particles will be scooped out of the issuing stream of air and hurled back into the pulverizing zone.

The operation of this embodiment will now be apparent from the above disclosure. The shafts l9 and 31 are rotated in opposite directions by their respective motors, and coarse material is deposited in the feed chute 24 by a suitable feeding mechanism. The material falls into the path of the hammers 25 and is crushed and thrown upwardly, any hard foreign bodies dropping into the space 28 at the bottom of the casing. The fan wheel 4! produces an air current through the machine which carries the crushed material through the annular passage l6 into the peripheral portion of the pulverizing zone I4. The particles which are sufiiciently fine will travel with the air current through the passage 40 and the outletopening 23 into the fan chamber [2, whence they may be delivered to a place of use or deposit. The coarser particles, on the Other hand, are more affected by the centrifugal forces set up by the rotation of the various parts in the pulverizing zone, and hence cannot escape so readily to the central outlet. Furthermore, such coarse particles as do approach the outlet will be hurled back by the rejector blades 45. The revolution of the pegs 32 and 33 will produce a powerful air current traveling outwardly through the path of the pegs and returning inwardly through the passage 40. The effect of this recirculating air current, together with the centrifugal forces, will cause the coarse particles which reach the axial region to be drawn toward the disk 34 and into the path of the pegs 33. This is possible because the outlet opening is in direct communication with the region surrounded by the impact members independently of the passage 40. The particles of material will leave the pegs 33 in tangential directions at substantially the linear velocity of the pegs, and immediately thereafter they will collide head on with the pegs 32 which are traveling at high speed in the opposite direction. The result is a very effective pulverization of the material with a minimum of power consumption, since the particles can readily escape from the pulverizing zone as soon as they are sufiiciently fine.

The stationary pegs 43 tend to stop the movement of the coarse particles just before they are struck by the inner pegs 33, and in this way they aid the pulverization. It is believed, however, that the machine will produce finer grinding (perhaps at some sacrifice of capacity) if the stationary pegs are removed, since these pegs by decreasing the whirl in the axial region will probably allow somewhat coarser particles to escape than would otherwise be the case. By varying the number of these pegs, the fineness of the ground product can probably b arie as sired within certain limits.

It will be noted that by mounting the rotor disks I5 and 34 close to each other and at the same side of the pulverizing zone, I have avoided the necessity for utilizing rotor spokes subject to the abrasive action of the material being pulverized.

In Fig. 3 I have illustrated a modified construction comprising a casing shaped to provide a preliminary crushing zone 5| at one end, a fan chamber 52 at the other end, and a pulverizing zone 54 located between the crushing zone and the fan chamber. A vertical rotor disk 55 is provided between the crushing zone 5| and the pulverizing zone 54, these zones being peripherally connected by means of an annular pas sage 56 around the disk. The disk 55 is mounted on a hub 58 secured to the horizontal shaft 59 of an electric motor 50. Avertical partition 62 is provided between the pulverizing zone 54 and the fan chamber 52, and this partition has a central opening 63 therethrough which forms an outlet for the pulverizing zone.

The coarse material enters the crushing zone 5| through an inlet chute 64 which delivers the material into the path of a series of impact members 65 projecting intothe crushing zone from the outer portion of the rotor disk 55. A plate 6'! is mounted on the casing wall and extends beneath the impact members 65 to prevent the material from falling directly to the bottom of the casing. This plate is preferably curved on an arc concentric with the shaft 59, and this are is comparatively short so that any hard foreign bodies entering the machine can drop past the end of the plate into the bottom of the casing, whence they can be removed through a door 68.

An annular set of impact members or pegs 10 extends from the outer portion of the disk 55 toward the partition 62 and into the pulverizing zone 54, these pegs being revoluble about the outlet 63. A second annular set of impact members or pegs H is arranged to revolve close to the pegs Til but in the opposite direction. The pegs H are mounted on an .annular rotor plate 12 located between the disk 55 and the partition 52, and these pegs extend toward the disk 55 and overlap the pegs ID in a direction parallel to the shaft 59. The plate 12 is connected by means of radial spokes M to a central hub 15 which is secured to the shaft 15 of an electric motor H. The two shafts 59 and 16 are aligned.

The annular plate 112 and the ends of the pegs 10 are spaced from the partition wall 62 to provide a free passage 19 through which fine material may travel from the peripheral portion of the pulverizing zone to the central or axial portion thereof without contact with the revolving pegs. The material is carried through this passage by means of an air current which in the embodiment illustrated is produced by a rotatable fan wheel 88 mounted on the shaft 16 within the fan chamber 52. It will be understood that the fan chamber is provided with the usual peripheral outlet (not shown).

In order to prevent the discharge of coarse particles from the pulverizing zone, I preferably utilize a series of rejector blades 82 which revolve close to the outlet opening 63 and extend between the spokes E i and into the space between the plate 12 and the disk 55. These blades may be supported by the hub 75 and the spokes l4, and they may be fastened to the spokes by means of screws 83. The rejector blades are preferably U-shaped in cross-section, so that coarse particles will be scooped out of the air stream and hurled back for further pulverization. It will be noted that the outlet opening 53 is in direct communication with the region surrounded by the impact members through the central portion of the annular rotor plate '52 and independently of the passage 19.

The operation of this embodiment will now be apparent from the above disclosure. The shafts 59 and 16 are rotated in opposite directions by their respective motors, and coarse material is deposited in the feed chute 64 by a suitable feeding mechanism. The material falls into the path of the pegs 65 and is crushed. The fan wheel 85 produces an air current through the machine which carries the crushed material through the annular passage 56 into the peripheral portion of the pulverizing zone 54 and thence through the passage #9 to the outlet opening 63. The particles which are sufficiently. fine will travel with the air current through the opening 63 into the fan chamber 52, whence they may be delivered to a place of use or deposit. The coarser particles, on the other hand, will be held back by centrifugal forces, and they will be carried through the openings between the spokes "M by the recirculating air current produced by the revolving pegs. The rejector blades 82 will assist in transporting the coarse particles through these openings. The particles of material will be struck by the pegs H and given a high tangential velocity, and immediately thereafter they will collide head on with the pegs NJ which are traveling at high speed in the opposite direction. This action results in a very effective and efficient pulverization of the material. If a particle is not sufficiently reduced in size by one passage through the path of the pegs, it will return for further pulverization, and yet all particles which are sufficiently fine are immediately carried away by the air current. There is no useless and power wasting pulverization of particles to unnecessary fineness, and there is ample provision for free flow of air through the machine without interference with the action of the oppositely revolving pegs.

The invention can be built to operate successfully in comparatively small sizes, since the oppositely revolving pegs will give high relative speeds at 3600 revolutions per minute even though the rotor diameters are in the neighborhood of say 8 inches. Moreover, the invention has many practical advantages in large sizes also, as will be apparent to those skilled in the art. While I have shown a preliminary crushing zone in each instance, this is not essential and can be omitted. Furthermore, the type of crushing means illustrated in Fig. 3 can be readily applied to the machine illustrated in Fig. l, and vice versa.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A pulverizing apparatus comprising two cooperating annular sets of impact members surrounding a central space and arranged to revolve in opposite directions about a common axis, one of said sets. overlapping the other set in a direction parallel to the axis, the impact members producing a current of air which flows outwardly from the central space, through the path of the impact members, and thus to the region outside zeir path, means providing a passage through which the air current returns freely to the central space and thus continues to circulate in a closed path, means to introduce coarse material into the circulatingair current, and means to withdraw fine material from the central space.

2. A pulverizing apparatus comprising two cooperating annular sets of impact members surrounding a central space and arranged to revolve in opposite directions about a common axis, one of said sets overlapping the other set in a direction parallel to the axis, the impact members producing a current of air which flows outwardly from the central space, through the path of the impact members, and thus to the region outside their path, means providing a passage through which the air current returns freely to the central space and thus continues to circulate in a closed path, means to deliver coarse material to the region outside the path of the impact members, such coarse material being thus introduced into the circulating air current, andmeans to withdraw fine material from the central space.

3. A pulverizing apparatus comprising means providing .a pulverizing zone having an outlet opening in one wall thereof, two cooperating annular sets of impact members located within the zone and arranged to revolve in opposite directions about a central space which communicates directly with the outlet opening, one of said sets overlapping the other set axially, the impact members producing a current of air which flows outwardly from the central space, throughv the path of the impact members, and thus to the region outside their path, both of said sets of impact members being spaced from said wall to leave a passage through which the air current returns freely to the central space and thus continues to circulate in a closed path, means to introduce coarse material into the circulating air current, and means to withdraw fine material through the outlet opening.

4. A pulverizing apparatus comprising means providing a pulverizing zone, two cooperating annular sets of impact members located within the zone in surrounding relation to a central space and arranged to revolve in opposite directions about a common axis, one of said sets overlapping the other set in a direction parallel to the axis, one wall of said zone having an outlet opening therein near said axis and in direct communication with the central space, the impact members producing a current of air which flows outwardly from the central space, through the path of the impact members, and thus to the region outside their path, both of said sets of impact members being spaced from said Wall to leave a passage through which the air current returns freely to the central space and thus continues to circulate in a closed path, means to deliver air and coarse material to the circulating air current, and means to withdraw air and fine material through the outlet opening.

5. A pulverizing apparatus comprising means forming a pulverizing zone having a centrally located outlet, two rotors mounted within the pulverizing zone, means to rotate the rotors in opposite directions about a common axis which is adjacent to the outlet, each rotor having an annular set of impact members thereon and the two sets overlapping each other in an axial direction, the various parts being so constructed and arranged as to provide a passage for the flow of fine material from the peripheral portion of the pulverizing zone to the outlet without contact with the impact members, means to introduce coarse material into the pulverizing zone, and means to produce an air current through the passage and thence through the outlet to carry away the fine material in suspension.

6. A pulverizing apparatus comprising means forming a pulverizing zone, one wall of the zone having a centrally located outlet, two rotors mounted within the pulverizing zone, means to rotate the rotors in opposite directions about a common axis which is adjacent to the outlet, each rotor having an annular set of impact members thereon and the two sets overlapping each other in an axial direction, both sets of impact members being spaced from said wall to provide a passage for the flow of fine material from the peripheral portion of the pulverizing zone to the outlet without contact with the impact members, means to introduce coarse material into the pulverizing zone, and means to produce an air current through the passage and thence through the outlet to carry away the fine material in suspension.

7. A pulverizing apparatus comprising means forming a pulverizing zone having a centrally located outlet, two rotors mounted within the pulverizing zone, means to rotate the rotors in opposite directions about a common axis which is adjacent to the outlet, each rotor having an annular set of impact members thereon, the two sets overlapping each other in an axial direction and surrounding a central space which communicates directly with the outlet, the various parts being so constructed and arranged as to provide a passage for the flow of fine material from the peripheral portion of the pulverizing zone to the outlet without contact with the impact members, means to introduce coarse material into the pulverizing zone, and means to produce an air current through the passage and thence through the outlet to carry away the fine material in suspension.

8. A pulverizing apparatus comprising means forming a pulverizing zone, one wall of the zone having a centrally located outlet, two rotors mounted within the pulverizing zone, means to rotate the rotors in opposite directions about a common axis which is adjacent to the outlet, each rotor having an annular set of impact members thereon, the two sets overlapping each other in an axial direction and surrounding a central space which communicates directly with the outlet, both sets of impact members being spaced from said Wall to provide a passage for the flow of fine material from the peripheral portion of the pulverizing zone to the outlet without contact with the impact members, means to introduce coarse material into the pulverizing zone, and means to produce an air current through the passage and thence through the outlet to carry away the fine material in suspension.

9. A pulverizing apparatus comprising means forming a pulverizing zone having a peripheral inlet and a centrally located outlet, two oppositely rotatable rotors mounted within the pulverizing zone at the side opposite the outlet, each rotor having an annular set of impact members thereon which project into the pulverizing zone toward the outlet and revolve about the outlet, one set of impact members overlapping the other set in an axial direction, means to introduce coarse material into the pulverizing zone through the inlet, and means to produce an air current through the pulverizing zone and thence through the outlet to carry away the fine material in suspension.

10. A pulverizing apparatus comprising means providing a pulverizing zone having a centrally located outlet, two rotors mounted within the pulverizing zone at the side opposite the outlet and arranged to rotate in opposite directions about a common axis which is adjacent to the outlet, each rotor having an annular set of impact members thereon which project into the pulverizing zone toward the outlet and revolve about the outlet, one set of impact members overlapping the other set in an axial direction means to introduce coarse material into the pulverizing zone, and means to produce an air current through the pulverizing zone and thence through the outlet to carry away the fine material in suspension.

11. A pulverizing apparatus comprising means forming a pulverizing zone having a centrally located outlet, two oppositely rotatable rotors mounted within the pulverizing zone at the side opposite the outlet, each rotor having an annular set of impact members thereon which project into the pulverizing zone toward the outlet and revolve about the outlet, one set of impact members overlapping the other set in an axial direction, said parts being so constructed and arranged as to provide a passage for the fiow of fine material from the peripheral portion of the. pulverizing zone to the outlet without contact with the impact members, means to introduce coarse material into the pulverizing zone, and means to produce an air current through the passage and thence through the outlet to carry away the fine material in suspension.

12. A pulverizing apparatus comprising means forming a pulverizing zone, one wall of the zone having a centrally located outlet, two rotors mounted within the pulverizing zone at the side opposite the outlet and arranged to rotate in opposite directions about a common axis which is adjacent to the outlet, each rotor having an annular set of impact members thereon which project toward the outlet and part way only into the pulverizing zone so as to leave a passage between the ends of the impact members and said wall, one set of impact members overlapping the other set in an axial direction, means to introduce coarse material into the pulverizing zone, and means to produce an air current through the passage and thence through the outlet to carry away the fine material in suspension.

13. A pulverizing apparatus comprising means forming a pulverizing zone, one wall of the zone having a centrally located outlet, two rotors mounted within the pulverizing zone at the side opposite the outlet and arranged to rotate in opposite directions about a common axis which is adjacent to the outlet, each rotor having an annular set of impact members thereon which project toward the outlet and part way only into the pulverizing zone so as to leave a passage between the ends of the. impact members and said wall, one set of impact members overlapping the other set in an axial direction, an annular set of impact members mounted on the wall around the outlet and projecting into the pulverizing zone, means to introduce coarse material into the pulverizing zone, and means to produce an air current through the passage and thence through the outlet to carry away the fine material in suspension.

14. A pulverizing apparatus comprising means forming a pulverizing zone, one wall of the zone having a centrally located outlet, a rotor mounted within the pulverizing zone at the side opposite the. outlet and arranged to rotate about an axis which is adjacent to the outlet, an annular set of impact members on the rotor and projecting part way only toward said wall, an annular rotor plate located between the wall and the. rotor and spaced from each, said rotor plate being arranged to rotate in the opposite direction from the rotor, an annular set of impact members. on the rotor plate to cooperate with the first mentioned set, one of said sets overlapping the other in an axial direction, means to produce a current of air from the peripheral portion of the pulverizing zone through the space between the rotor plate and the wall and thence through the outlet, and means to introduce coarse material into the pulverizing zone, the parts being so constructed and arranged as to produce a circulation of air through the central portion of the annular rotor plate, thence outwardly through the path of the revolving impact members and inwardly through the. space between the rotor plate and the wall.

15. A pulverizing apparatus comprising means forming a pulverizing zone, one wall of the zone having a centrally located outlet, a rotor mounted within the pulverizing zone at the side opposite the outlet, an annular set of impact members on the rotor and projecting part way only toward said wall, an annular rotor plate located between the wall and the rotor and spaced from each, means to rotate the rotor and the rotor plate in opposite directions about a common axis adjacent the outlet, an annular set of impact members projecting from the rotor plate toward the rotor, one of said sets overlapping the other in a direction parallel to the axis, means to produce a current of air from the peripheral portion of the pulverizing zone through the space between the rotor plate and the wall and thence through the outlet, and means to introduce coarse material into the pulverizing zone, the parts being so constructed and arranged as toproduce a circulation of air through the central portion of the annular rotor plate, thence outwardly through the path of the revolving impact members and inwardly through the space. between the rotor plate and the wall.

16. A pulverizing apparatus comprising means forming a pulverizing zone, one wall of the zone having a centrally located outlet, a rotor mounted Within the pulverizing zone at the side opposite the outlet, an annular set of impact members on the rotor and projecting part way only toward said wall, an annular rotor plate. located between the wall and the rotor and spaced from each, means to rotate the rotor and the rotor plate in opposite directions about a common axis adjacent the outlet, an annular set of impact members projecting from the rotor plate toward the rotor, one of said sets overlapping the. other in a direction parallel to the axis, means to produce a current of air from the peripheral portion of the pulverizing zone through the space between the rotor plate and the wall and thence through the outlet, means to introduce coarse material into the pulverizing zone, and rejector blades revoluble adjacent the outlet and arranged to transfer coarse particles through the. central portion of the annular rotor plate and into the space between the rotor plate and the rotor.

ALBERT G. BLODGETT.

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