Patent Grant
9067212
1. Field of the Invention
The present invention relates to a mill configured to grind or pulverize particles of, for example, foods, chemicals and pharmaceutical products.
2. Description of the Related Art
One proposed structure of a conventional jet mill (impact-type airflow grinder) to grind the material accelerates a grinding object in a grinding chamber by the air jet flow from a nozzle and makes the grinding object collide against a collision plate (PTL1). Another proposed structure makes the particles of the grinding object collide with one another by the air jet flow (PTL2). The jet mill is characteristic of finely grinding or pulverizing the particles with limited temperature increase during the grinding action.
PTL1: JP 2002-59024a
PTL2: JP 2003-88773A
The conventional jet mill, however, has the problem of the relatively low throughput per energy cost. The object of the invention is accordingly to provide a mill having the increased throughput per energy cost.
In order to solve at least part of the above problem, according to a first aspect of the invention, there is provided a mill, comprising: a grinding chamber; a rotating shaft located in the grinding chamber; a rotating body structured to have a disk-shaped rotary member fixed to the rotating shaft; and a casing provided to form an outer shell of the grinding chamber. A cylindrical frame member having an inner peripheral surface formed in a corrugated shape along a circumferential direction is arranged coaxially with the rotating shaft in the casing, wherein the corrugated shape has a pitch that is greater than an amplitude. The rotary member has a circular member. A solid-gas two-phase flow of particles and a gas supplied to the grinding chamber is introduced through a gap between the casing and the rotating body into the grinding chamber, is circled in the grinding chamber while being accelerated by the rotating body, and collides against the inner peripheral surface and the circular member to grind or pulverize the particles.
According to one preferable embodiment, the mill further includes a preliminary grinder located at an inlet of the gap and structured to have a shock pin.
The circular member is preferably a ring-shaped member but may be an arc-shaped member. According to another preferable embodiment, the circular member includes a plurality of support plates arranged circularly and protruded in a radial direction, and circular plates linked by the support plates, wherein the solid-gas two-phase flow is circled by rotation force of the circular plates and is collided against the inner peripheral surface in the circumferential direction.
According to another preferable embodiment, the mill further includes a preliminary grinder located at an inlet of the casing and structured to have a shock pin.
The inner peripheral surface is preferably formed to have regular waveform but may include a surface of irregular shape according to the requirements. It is preferable that the entire inner peripheral surface or part of the entire inner peripheral surface is formed in the corrugated shape. It is also preferable that the pitch of the waveform is set to be greater than the amplitude.
This mill is applicable to both an inline particle air-conveying system and a non-inline particle air-conveying system. According to one preferable embodiment of the inline system, the mill is placed in the middle of or at the end of a pneumatic conveying line for the mixture of the particles and the air, and the ground or pulverized material is conveyed pneumatically.
According to one preferable embodiment, the circular member is provided as a blade and includes support plates and circular plates linked by the support plates. The solid-gas two-phase flow is collided against the inner peripheral surface in the circumferential direction, while being circled by the rotation force of the circular plates.
The mill according to the first aspect of the invention reduces the particle size and enhances the grinding effect by diffused reflection of the circled particles by the frame member of the corrugated shape. The mill of this aspect also enhances the throughput per energy cost. The mill of this aspect does not require an air jet nozzle or a collision plate, which are included in the conventional structure, and can thus be downsized.
The mill according to the second aspect of the invention performs preliminary grinding, so as to enhance the grinding effect in the grinding chamber.
The mill according to the third aspect of the invention enhances the circling effect of the solid-gas two-phase flow.
a is a left side view illustrating an annular member and shock pins included in a preliminary grinder;
b is a right side view illustrating an upstream circular disc and shock pins included in the preliminary grinder; and
As shown in
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The rotating shaft 3 is arranged vertically. The rotating speed of the rotating shaft 3 may be, for example, 3000 to 7000 rpm.
As shown in
The rotating body 5 includes the rotating shaft 3 and the rotary member 4. The mill 1 receives the air A and the particles PW and joins the received air A with the received particles PW to the solid-gas two-phase flow K. While the linkage pins 10 serve to grind or pulverize the particles, the rotating body 5 circles the solid-gas two-phase flow K, so that the particles collide against the inner peripheral surface 9a of the frame member 9 to be ground or pulverized. The solid-gas two-phase flow K′ containing the ground or pulverized particles is then discharged. The linkage pins 10 are preferably formed to have a round lateral cross section, for example, a circular lateral cross section.
The suction pressure of a suction blower (not shown) and the rotating body 5 rotating at high speed generate the sucking flows via the inlets 7a and 7b into the grinding chamber 2. The solid-gas two-phase flow K containing the particles PW and the air A is accordingly supplied via the inlet 7c into the grinding chamber 2.
As shown in
The inlet 7a serves as an inlet port of the particles PW. The inlets 7b are arranged at a plurality of different positions to serve as inlet openings of the air A and are provided with filters. The mill 1 according to the embodiment has the characteristic rotary member 4 and thereby does not require an air jet nozzle or a collision plate, which are included in the conventional structure.
A suction blower (not shown) is connected with the outlet 8 to suck the air and thereby allow the particles PW and the air A to be supplied via the inlets 7a and 7b.
As shown in
The pitch P (interval between the wave crests or the interval between the wave troughs) is preferably 50 to 200 mm, and the amplitude H (difference between the maximum diameter and the minimum diameter in the radial direction) is preferably 5 to 20 mm. The ratio of the pitch P to the amplitude H is preferably 2.5 to 40, more preferably 5 to 30 or most preferably 6 to 15. The height of the inner peripheral surface 9a of the frame member (length in the axial direction) depends on the number of steps of the circular plates 43b and 43c. The circular plates 43b and 43c are arranged in two steps in the illustrated example of
As shown in
The throughput of the general jet mill using the power of 37 kW (compressor) is approximately 10 to 50 kg/hr with respect to the flour having the particle diameter of 10 μm. The mill 1 according to the embodiment using the power of 40 kW, on the other hand, has the throughput of 100 to 200 kg/hr with respect to the flour having the particle diameter of or below 50 μm. Since the application and the value of the product (ground or pulverized particles) depend on the particle size, the simple comparison is not easy. This, however, proves the increase of the throughput per the energy cost anyway.
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The piping 17 is arranged to transport upward the air A intake from the inlets 7b. The piping 17 is provided with the inlet 7a of the particles. The particles PW are mixed with the air A transported through the piping 17 to form the solid-gas two-phase flow K.
A power distribution unit 18 is connected with the motor 14.
The following describes the operations of the mill 1. During use of the mill 1, the door 15 is closed by the locking device 16. The door 15 is used for maintenance of, for example, the grinding chamber 2, the rotating shaft 3, the rotary member 4 and the rotating body 5.
The suction force is generated at the outlet 8 by the function of the blower (not shown), and the rotating body 5 is integrally rotated by the motor 14. The particles PW as the object material to be ground or pulverized are supplied from the inlet 7a, while the gas A is supplied through the inlets 7b. The gas A supplied through the inlets 7b passes through the filter, which prevents dust or foreign matter from entering the casing 6 and allows only the clean air to enter the casing 6. Part of the gas A passes through the piping 17 and is mixed with the particles PW supplied from the inlet 7a. The remaining part of the air A passes through the passage 6b and joins with the mixture at the location before the linkage pins 10 to form the solid-gas two-phase flow K containing the particles PW. While passing through the rotating linkage pins 10, the solid-gas two-phase flow K is subjected to preliminary grinding to be ground by their impact and granulated to a desired particle size. The preliminarily-ground solid-gas two-phase flow K is then introduced into the grinding chamber 2. At this stage, for example, the flow rate is 31 m/s and the flow volume is 25 m3/min.
The solid-gas two-phase flow K goes upward with being circled in the space between the outer peripheral surface of the rotary member 4 and the inner peripheral surface 9a, so as to be fully ground or pulverized. The solid-gas two-phase flow K moves in the direction M (
The heavier portion or the larger-size portion (further grinding is allowable) of the particles, on the other hand, loses the speed to go downward and is transported outward on the gas flow (pressure difference) from the center to the outward produced by the centrifugal force of the rotation as shown by the arrows K. This portion of the particles collides against the rotating support plates 43a, the circular plates 43b and 43c and the fixed inner peripheral surface 9a to be further ground or pulverized and moves upward.
The waveform of the inner peripheral surface 9a has the wave crests and the wave troughs arranged alternately along the circumferential direction, so as to alternately form wider passages and narrower passages between the blade-like rotary member 4 and the inner peripheral surface 9a. The solid-gas two-phase flow K is pressed outward by the centrifugal force of the rotation of the rotary member 4 and is repeatedly compressed and expanded at very high speed on the inner peripheral surface 9a. Such turbulent motion of the particles PW efficiently grinds or pulverizes the particles PW. The particles PW collide with one another while colliding against the support plates 43a for the rotary member 4, the circular plates 43b and 43c, the linkage pins 10 and the inner peripheral surface 9a, so as to be efficiently ground or pulverized. The inner peripheral surface is preferably formed in a curved shape but may be formed in a jagged shape of straight lines.
The pitch of the waveform of the inner peripheral surface 9a is set to be greater than the amplitude. This reduces the resistance of the solid-gas two-phase flow and prevents the solid-gas two-phase flow from failing to go over the wave crests and from being accumulated in the wave troughs, thus enhancing the circling effect of the solid-gas two-phase flow.
The inner peripheral surface 9a formed as a flat plane produces the homogeneous flow and causes the particles to be ground or pulverized by the linkage pins 10. There is accordingly the possibility that the particles are not sufficiently ground or pulverized. One possible method may machine-form fine grooves on the inner peripheral surface of the frame member 9. Such grooves, however, have the groove width smaller than the pitch of the waveform and are thus likely to be clogged with powder. The mill 1 having the corrugated inner peripheral surface 9a, on the other hand, is easily cleanable and has the corrugated curved surface along the flow direction of the solid-gas two-phase flow. This effectively prevents powder clog.
The door 15 receives the upward lifting force by the action of the spring 15b and rotates about the hinge 15a with moving horizontally to be opened. Without the spring 15b, the door 15 is not readily operable. With the spring 15b, however, the operation of the door 15 is easy and safe.
As described above, the mill 1 according to this embodiment adopts the frame member 9 having the corrugated inner peripheral surface 9a and thereby enhances the throughput per energy cost, compared with the conventional jet mill. The mill 1 of the embodiment does not require an air jet nozzle or a collision plate, which are included in the conventional structure, and can thus be downsized.
The detailed mechanism of the advantageous effects described above is not elucidated, but the inventors have the following presumption. The corrugated shape of the inner peripheral surface 9a of the frame member 9 changes the angle of the inner peripheral surface 9a relative to the circling direction R of the solid-gas two-phase flow K containing the particles. This causes the solid-gas two-phase flow K to be repeatedly compressed and expanded and have significant changes in cross section. The inner peripheral surface 9a generates the periodic turbulent flow and reflects the solid-gas two-phase flow K at random. The particles in the solid-gas two-phase flow K are ground or pulverized by collision against the frame member 9, while colliding with one another to be further ground. This reduces the particles size of the solid-gas two-phase flow K and accelerates grinding. The frame member 9 is made of a non-porous solid, such as metal, that does not allow transmission of the solid-gas two-phase flow K. This ensures the diffused reflection of the particles from the inner peripheral surface 9a and thereby enhances the grinding efficiency per energy cost.
The inner peripheral surface 9a has the wave crests and the wave troughs formed on its whole circumference, but may be partly formed to include a non-corrugated surface, such as flat surface or an inclined surface.
The linkage pins 10 provided as the preliminary grinder are used to preliminarily grind the particles. This reduces the grinding load.
A mill according to a second embodiment of the invention is a transverse mill that has the horizontally-arranged rotating shaft 3 and does not use a spring to lift up the door 15, but otherwise has the similar or common configuration to that of the mill 1 according to the first embodiment. The description and the illustration of the first embodiment are thus applicable to the mill according to the second embodiment of the invention. The like components are expressed by the like numerals in the 100s. The advantageous effects of the second embodiment are similar to those of the first embodiment, except that the force of gravity is applied to the solid-gas two-phase flow K in a different direction.
A mill 101 according to a third embodiment of the invention has the solid-gas two-phase flow K formed differently from the first embodiment and has the horizontally-arranged rotating shaft like the second embodiment. As shown in
As shown in
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The rotating body 105 includes the rotating shaft 103 and the rotary member 104. When the mill 101 receives the solid-gas two-phase flow K, the rotating body 105 circles the solid-gas two-phase flow K, so that the particles collide against the inner peripheral surface 109a of the frame member 109 to be ground or pulverized. The solid-gas two-phase flow K′ containing the ground or pulverized particles is then discharged.
The suction pressure of a suction blower (not shown) and the rotating body 105 rotating at high speed generate the sucking flow via the inlet 107 into the grinding chamber 102. The solid-gas two-phase flow K containing the particles PW is accordingly supplied via the inlet 107 into the grinding chamber 102.
As shown in
The inlet 107 is arranged to receive the solid-gas two-phase flow K pneumatically transported through a piping (not shown) and introduce the received solid-gas two-phase flow K into the feed port 102a. The mill 101 according to the embodiment does not require an air jet nozzle or a collision plate, which are included in the conventional structure.
A suction blower (not shown) is connected with the outlet 108 to suck the air, so that the solid-gas two-phase flow K is supplied via the inlet 107.
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The following describes the operations of the mill 101. The solid-gas two-phase flow K containing the particles to be ground or pulverized is supplied via the inlet 107 and is introduced into the feed port 102a. The solid-gas two-phase flow K supplied to the feed port 102a is then introduced into the preliminary grinder 112. The solid-gas two-phase flow K entering the preliminary grinder 112 runs between the first pins 110 and the second pins 111 to be ground by the impact of the stationary first pins 110 and the rotating second pins 111 and to be granulated to a desired particle size and is then introduced into the grinding chamber 102. The solid-gas two-phase flow K moves leftward in
According to one modification shown in
The force of gravity is applied parallel to the rotating direction of the particles contained in the solid-gas two-phase flow K. The particles may be accumulated in a partial area, for example, on the bottom, of the simple cylindrical structure. According to the embodiment, however, the corrugated inner peripheral surface 109a has the effect of lifting up the particles by the circular plates 143b and 143c, compared with the simple cylindrical surface. This diffuses the particles upward and prevents accumulation of the particles.
The invention is not limited to the above embodiments but may be altered, modified, substituted, replaced or omitted in various ways without departing from the scope of the invention. Such modifications and alterations are also included in the scope of the invention. For example, the diameter, the pitch, the amplitude and the height of the inner peripheral surface 109a of the frame member may be changed according to the requirements. The rotating shaft 103 is arranged horizontally or vertically according to the above embodiments but may be inclined in some situations.
The mill of the invention is applicable to grind or pulverize particles of, for example, foods, chemicals, pharmaceutical products and toners of copying machines or more specifically flours, buckwheat flours, soy beans, red beans, coffee beans, corns, dried noodles, rice snacks and noodle offcuts.
This application is a continuation-in-part of International Patent Application No. PCT/JP2011/007059 with an international filing date of Dec. 18, 2011, designating the United States, now pending. The contents of the aforementioned application, including any intervening amendments thereto, are incorporated herein by reference. Inquiries from the public to applicants or assignees concerning this document should be directed to: Matthias Scholl P. C., Attn.: Dr. Matthias Scholl Esq., 14781 Memorial Drive, Suite 1319, Houston, Tex. 77079.
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| Number | Date | Country | |
|---|---|---|---|
| 20130186990 A1 | Jul 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2011/007059 | Dec 2011 | US |
| Child | 13791959 | US |
