Patent Application
20060024607
1. Field of the Invention
The present invention relates to a fluidized bed type pulverization/classification apparatus for manufacturing a powder, which may particularly be a toner powder, and a method of manufacturing the powder using the pulverization/classification apparatus.
2. Discussion of the Background
Background fluidized bed type pulverization/classification apparatuses typically have a cylindrical shape and include a vessel. In addition, plural air nozzles are provided on lower portions of an inner wall of the vessel to discharge a high pressure jetted air. In the cylindrical vessel, particles of a toner raw material (i.e., a toner constituent mixture) are suspended by the high pressure jetted air so as to collide with each other and thereby be pulverized. To efficiently perform pulverization while preventing excessive pulverization, the pulverized toner raw material needs to be rapidly fed to a classifier so that desired toner particles having a small particle diameter in a proper desired diameter range can be extracted.
The toner raw material particles stay within the cylindrical vessel for a predetermined time while circling therein with this operation. After the pulverization is repeated, the pulverized toner raw material particles are fed by an upward current to a classification rotor 3, which is provided on an upper portion of the cylindrical vessel of milling chamber 4.
The classification rotor 3 classifies the toner raw material particles into particles having a particle diameter in a desired particle diameter range (fine particles that can be discharged using a blower) are coarse particles. The particles having a particle diameter within the desired diameter range can be output from the outlet or exhaust tube 2, and then can be used as a toner in the form of a final product. Coarse particles are fed again by the centrifugal force of the classification rotor 3 back into the cylindrical vessel of milling chamber 4 to be again subjected to the pulverization treatment. By repeating these operations, the toner raw material particles can be converted into particles of a desired size for a final toner product.
If the amount of the particles in the milling chamber 4 are stabilized, the system can operate for a continuous pulverization.
When a final toner powder product having a small particle diameter is manufactured using a fluidized bed type pulverization/classification apparatus and method, the following problems tend to occur:
Japanese Laid-open patent publication No. 11-226443 and Japanese Laid-open patent publication No. 2000-005621 disclose pulverization apparatuses for expedited pulverization. As a device to improve crush efficiency, JP 11-226443 discloses an apparatus having an up-and-down movable drawer bottom so that the surface of the particles that have accumulated on the drawer bottom are held at a current air spout position of a nozzle. However, such a structure does not solve the above-noted problems because nothing is changed in the behavior of the particles from other background art. Further, continuing crushing in the milling chamber in such a device is still necessary to obtain the desired particle size.
JP 2000-005621 discloses an apparatus including a collision member at a center of an axis of the milling chamber. Such an apparatus adopts a particle collision member method. However, in such a device for a collision between the collision member and particles the apparatus needs to intensify the pressure and velocity of air output from air nozzles.
Japanese Laid-open patent publication No. 2004-160371 discloses an apparatus to improve efficiency of pulverizing in which compressed air is jetted from air nozzles to cause a first collision with particles. Further, a second collision member is provided above or below the first colliding position. With such an apparatus collision pulverizing efficiency in a crushing chamber improves. In addition, particles within the desired range can be obtained and pulverizing can be performed with high efficiency. However, in such a publication a shape of the rotor or any benefits achieved by using a rotor of a specific shape is not disclosed.
The present inventors have recognized that pulverizing efficiency of a fluidized bed type pulverization/classification apparatus can be improved by optimizing a shape or size of a rotor, which will also operate to improve the accuracy of obtaining particles of a desired size.
The above-mentioned background fluidized bed type pulverization/classification apparatuses can be improved by optimizing a shape or size of a rotor, which will also operate to improve the accuracy of obtaining particles of a desired size.
The above-mentioned fluidized bed type pulverization/classification apparatuses as in Japanese Laid-open patent publication No. 11-226443 and Japanese Laid-open patent publication no. 2000-005621 focus on the air output from air nozzles. Both publications do not disclose specifics of a rotor system or address balance of centrifugal force and centripetal force of the rotor.
The present inventors recognized, for these reasons, that a need exists for a novel pulverizing apparatus that can process particles to be pulverized efficiently, improve efficiency of a collision in a milling chamber and a crush device, shorten the time to provide the crushing device, and crush particles to a desired size range with high efficiency.
Accordingly, an object of the present invention is to realize these and other objects by the present novel pulverization/classification apparatus including a plurality of air nozzles, a milling chamber as a space for pulverizing particles by compressed air jetted particles by the air nozzles, and a rotor installed at an upper part of the milling chamber that classifies powder materials flowing into the rotor from the milling chamber with centrifuging into fine particles and coarse particles. In addition, the present novel pulverizing apparatus includes plural air nozzles that give rise to primary collisions with powder materials, and the width of blades within the rotor are set to be 1/50- 2/25 of the rotor's diameter.
A novel pulverizing method uses the above-noted novel pulverizing apparatus.
These and other objects, features, and advantages of the present invention will become apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
Various other objects, features, and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with accompanying drawings in which like reference characters designate like or corresponding parts throughout, and wherein:
The present invention will be explained referring to a pulverization/classification apparatus and method for manufacturing a toner, but the present invention is not limited to such a pulverization/classification apparatus and method.
The present invention realizes an increase in the centrifugal force of a rotor, prevents too much absorption of raw toner particles, and provides accurate classification of particles by the rotor. For a centrifugal force classification, the number of rotors utilized can be either singular or plural. The amount of particle redemption per hour from utilizing plural rotors may be much greater than that utilizing a singular rotor, and thus can provide an advantage.
As discussed below in further detail, in one feature in the present invention a shape and size of rotor blades are selected to provide enhanced operation. In a further feature discussed below a secondary collision mechanism is utilized to achieve a higher probability of pulverizing particles to a desirable size. In one feature also discussed below, the height of a collision member can be made to be adjustable. With such a structure, the present invention can be more flexible to match pulverizing conditions, for example of an average particle diameter and a throughput of particles of the pulverizing apparatus, to provide enhanced flexibility.
In addition, in one feature of the present invention plural air nozzles can be utilized, which can thereby increase the number of primary collisions between particles occurring, making for more efficient pulverizing.
An explanation of different pulverizing apparatuses of the present invention are now provided below.
The background pulverizing apparatus in
One feature in the present invention is to improve on the background rotor such as shown in
In the pulverizing apparatus of the present invention, plural air nozzles 5 are positioned at the milling chamber 4, which provide the function of generating primary collisions between the toner raw material particles fed from the intake 1 by generating collisions between the particles by the compressed air jetted from the plural air nozzles 5.
The number of air nozzles is not restricted, but utilizing 2-8 air nozzles is preferred, and utilizing 3-4 air nozzles is most preferred. A single air nozzle typically cannot sufficiently generate primary collisions from the input jetted compressed air. On the other hand, if there are too many air nozzles, the production process of the entire apparatus becomes more complicated, and there is also the possibility of more inefficient pulverization.
It is also preferable to set the air nozzles 5 at a concentric circle on or around their central axis 17 in the lengthwise direction of the milling chamber 4, as shown for example in
That is, the gradient of the output air from the air nozzles 5 is shown as the angle α for example in
Further, and with reference to
In specific examples of the pulverizing apparatus of the present invention discussed in further detail below, rotor 3 was set not to excessively aspirate raw particles with a particle diameter of 12 μm and above.
One feature in the present invention is to increase the centrifugal force provided by the rotor by controlling settings of an interspace between each blade within the rotor, controlling a width of the blades, controlling the length of the blades, and controlling an angle of the blades. By properly considering these factors, the pulverizing apparatus of the present invention can avoid excessive aspiration of raw particles and can provide precise classification of the particles.
With reference to
The above-mentioned blade width 8 is properly set by factoring in the rotor diameter, the rotational speed of the rotor, the pulverizing particle size used and desired, etc. The rotor diameter used here is an outside diameter of the rotor, see again reference numeral 23 in
Moreover, the present inventors also recognized that the length of the plural blades 6 that form the rotor 3 (see reference numeral 9 in
The above-mentioned blade length 9 is also properly set by factoring in the rotor diameter, the rotational speed of the rotor, the pulverizing particle size desired and used, etc.
As for the spacings between different blades 6 (shown as reference numeral 10 in
The spacings 10 between blades 6 is also properly set considering the rotor diameter, the rotational speed of the rotor, the pulverizing particle size used and desired, etc.
Moreover, the present inventors also recognized that properly setting the width angle of the plural blades 6 can provide increased results. The width angle of the blades 6 of the rotor 3 (shown as reference numeral 7 of
The centrifugal force obtained by the rotation of the rotor 3 can be increased by utilizing such a width angle 7. On the other hand, air resistance of the blades 6 can grow when the above-mentioned angle 7 is too large, and thereby the blades 6 will need to be increased in strength. If the width angle 7 is too large, the rotor 3 may be unsuitable for high velocity revolution. Moreover, a problem that the number of blades 6 cannot be increased also results from too large of a width angle 7.
The width angle 7 of the blades 6 is also properly set based on the rotor diameter, the rotational speed of the rotor, the pulverized particle size used and desired, etc.
In the embodiment of the pulverizing apparatus of the present invention as shown for example in
In the embodiment in
As an alternative embodiment of the present invention shown for example in
In a further embodiment of the present invention shown in
Further, the shape of the colliding members 11, 12 is not limited to specific shapes, but can take on various shapes. The shapes of the colliding members 11, 12 just need to be selected so that the particles collide therewith as needed. One factor to consider in deciding the shapes of such colliding members 11 and 12 is their slip stream from the air jetted from the nozzles 5. With consideration of the interaction of the colliding members 11, 12 with such a slip stream, utilizing colliding members taking the shape of a cone or a cylindrical shape may be preferable.
As shown for example in
In the embodiments shown in
It may also be desirable to make the height of the collision members 11, 12, adjustable, which is the function of the base portions 15 in
In the embodiment of
In the above-noted embodiments bolts have been indicated as a mechanism to secure the colliding members 11, 12 at a desired position. Of course many other types of securing mechanisms can be implemented.
Other methods of adjusting the heights of the colliding members are of course also possible.
In the different embodiments shown in
The conic top of the colliding members 11, 12 is preferably 10-500 mm right above or right below the noted first collision point 18, and is more preferably 10-300 mm above or below, and is most preferably 10-200 mm above or below.
It may also be preferable that the colliding members 11, 12 are detachable, again for example by the bolts 13, 14 in
It may also be preferable to make the faces of the collision members 11, 12 resistant to abrasion. As one example, the collision members 11, 12 can have a hard-face lining with Ti. Abrasion-resistance colliding members may be beneficial in realizing more effective pulverization.
In the embodiments of the present invention noted above, it may be preferable to set the pressure of compressed air supplied from the air nozzles 5 to 0.2-1.0 mPa. If the original air pressure is in such a range, desired pulverizing efficiency may more reliably be obtained. When the original pressure is less than 0.2 MPa, the pressure of the compressed air may be too low, which may give rise to inadequate pulverizing of the particles. Further, if the original air pressure is too high, the ratio of pulverized particles that are in fact too small may increase; that is too high a percentage of the particles may be overpulverized. Further, if the original air pressure is too high, a loss of speed may result by generating collision waves in the flow of air generated from the air nozzles 5.
After the particles are pulverized in the pulverizing apparatuses of the present invention, the particles flow into the rotor 3, which is rotating, and the rotor 3 can classify particles by centrifugal force into fine powder and coarse particles. It is preferable to set the rotor 3 in the upper part of the milling chamber 4 as shown for example in
Particles that have been pulverized will flow into the rotor 3 by virtue of aspiration through the exhaust tube 2, which can include an aspirating fan (not shown). That is, an aspirating fan in the exhaust tube 2 can be activated so that particles move towards the exhaust tube 2, and thereby flow into the rotor 3 set up in the upper part of the milling chamber 4. Then, the particles can be classified by size by the rotating rotor 3.
At that time, pulverized particles that are smaller than a desired particle size can be exhausted through the exhaust tube 2. On the other hand, pulverized particles that are still larger than a desired particle size may be lead outside of the rotor 3 by centrifugal force of the rotor 3, and will move downward along the wall of the milling chamber 4 to then be crushed again.
As for the rotational peripheral velocity of the rotor 3, 20-70 m/s is desirable, and 30-60 m/s may be more desirable. If the rotational peripheral velocity is maintained within such ranges, efficiency of classification can be achieved to an extent desired. When the rotational peripheral velocity of the rotor 3 is less than 20 m/s, the possibility that inefficient classification results is increased. When the rotational peripheral velocity of the rotor 3 is greater than 70 m/s, centrifugal force of the rotor 3 may grow to be too great, and thereby particles that should be exhausted through the exhaust tube 2 will return to the milling chamber 4 again, and then again be crushed. As a result, too many small particles may be generated, that is overpulverizing may result.
In the pulverizing apparatus as discussed above with respect to the present invention, and with reference to
The pulverizing apparatuses of the present invention noted above operate a pulverizing method in which raw particles are supplied by a raw particle feeder 1, crushed fine particles are drained from the exhaust tube 2, and continuous pulverizing is enabled by supplying particles of a quantity corresponding to the quantity of the drained particles appropriately.
Having generally described the present invention, further understanding can be obtained by reference to certain specific examples provided herein for the purpose of illustration only, and that are not intended to be limiting. In the descriptions in the following examples, the numbers represent weight ratios in parts, unless otherwise specified.
In the following examples, the following raw particles were used.
The raw particles were a compound in styrene acrylic copolymer resin 85 weight part and carbon black 15 weight part that was melt kneaded, cooled, and pulverized with a hammer mill roughly.
Preparation of Pulverizing Apparatus:
A pulverizing apparatus as shown in
Rotor:
The air nozzles were placed at equal intervals (equiangular degree) along the wall of milling chamber 4. To be suitable for 0° from horizontal direction, the direction of the exit of air nozzles 5 was set.
With the above-mentioned crushing device in this example, air nozzles 5 were set at the position of the first collision such that point 18 (
One rotor was set above the centerline of the air nozzles 5 about 450 mm.
Particles of the above-mentioned composition were supplied on the following conditions, and the particles were pulverized.
Former pressure of compressed air supplied to air nozzles 5: 0.5 MPa
Particles of the above-mentioned composition were supplied on the following conditions, and the particles were pulverized.
Original pressure of compressed air supplied to the air nozzles 5: 0.5 MPa
Volume average particle size: 6.05 μm (MULTICIZER by Coulter Electronics)
The same device as in example 1 except also including a first secondary collision member 11.
The centerline of the air nozzles 5 set up below the first collision member 11 from the intersecting position (the position 18: compressed air first collides mutually attended with particles) right under 60 mm mutually as shown in
Particles of the above-mentioned composition were supplied on the following conditions, and the particles were pulverized.
Original pressure of the compressed air supplied to air nozzles 5: 0.5 MPa
The same device as in example 1 except including secondary collision member 12.
As shown in
Particles of the above-mentioned composition were supplied on the following conditions, and the particles were pulverized.
Original pressure of the compressed air supplied to air nozzles 5: 0.5 MPa
Volume average particle size: 5.88 μm (MULTICIZER by Coulter Electronics)
The same device as in example 1 except including both a first secondary collision member 11 and a second secondary collision member 12, as shown in
The centerline of the air nozzles 5 set up the first collision member 11 from the intersecting position (The position 18: compressed air first collides mutually attended with particles) right under 60 mm mutually as shown in
Particles of the above-mentioned composition were supplied on the following conditions, and particles were pulverized.
Original pressure of compress air supplied to air nozzle 5: 0.5 MPa
Volume average particle size: 5.75 μm (MULTICIZER by Coulter Electronics)
The procedure for preparation of the pulverizing apparatus in Example 2 was repeated except that the first collision member 11 was replaced with a detachable first collision member.
After the pulverization, the chamber was cleaned.
The time required for cleaning was reduced by about 10% in comparison with the apparatus in Example 2.
The procedure for preparation of the pulverizing apparatus in Example 3 was repeated except that the secondary collision member 12 was replaced with a detachable secondary collision member.
After the pulverization, the chamber was cleaned.
The time required for cleaning was reduced by about 10% in comparison with the apparatus shown in Example 3.
The procedure for preparation of the pulverizing apparatus in Example 2 was repeated except that the first collision member 11 was replaced with an abrasion-resistant first collision member.
Preparation of abrasion-resistant first collision member 11 dispensing lining method with Ti.
Pulverization particles with a pulverization apparatus with abrasion-resistant first collision member 11, resulted in the effect of the abrasion resistance doubled roughly compared with a background apparatus.
The procedure for preparation of the pulverizing apparatus in Example 3 was repeated except that the second collision member 12 was replaced with an abrasion-resistant second collision member.
Preparation of abrasion-resistant second collision member 12 including dispensing a lining method with Ti.
Pulverization particles with a pulverization apparatus with abrasion-resistant second collision member 12, resulted in the effect of the abrasion resistance has doubled roughly compared with a background apparatus.
The procedure for preparation of the pulverizing apparatus and pulverization condition in Example 1 were repeated except that: width of each blade of the rotor: 1/50 of rotor diameter=2 mm, Length of each blade: 1/20 of rotor diameter=5 mm, Pagination of blades: 50,
The procedure for preparation of the pulverizing apparatus and pulverization condition in Example 1 were repeated except that: width of blade which construct rotor: rotor diameter of 1/50=2 mm, Length of blade: rotor diameter of 1/20=5 mm,
Obtained fine particles were as follows.
Volume average particle size: 6.53 μm (MULTICIZER by Coulter Electronics)
The present application claims priority and contains subject matter related to Japanese patent application No. 2004-219990 filed on Jul. 28, 2004, the entire contents of which are hereby incorporated herein by reference.
Obviously, numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-219990 | Jul 2004 | JP | national |
| 2005-205915 | Jul 2005 | JP | national |
