JP7834352B2 - stirring device - Google Patents

Description

Applicable under Article 30, Paragraph 2 of the Patent Law. Date: December 8, 2022. Meeting Name: Product Technology Briefing for the International Powder Technology Exhibition Tokyo 2022. Venue: Tokyo Big Sight (3-11-1 Ariake, Koto-ku, Tokyo)

This invention relates to a stirring device used in the manufacturing processes of pharmaceuticals, cosmetics, battery materials, fine chemicals, food products, etc., for mixing, emulsifying, dispersing, defoaming, and other treatments of viscous liquids, powders, and other materials.

For example, stirring devices such as those described in Patent Documents 1 and 2 are used to perform processes such as mixing, dispersion, emulsification, and defoaming of materials to be processed. These stirring devices primarily consist of a stirring tank containing the materials to be processed, stirring blades for agitating the materials in the tank, and a homogenizer positioned at the bottom of the tank. The homogenizer has a comb-shaped stator and rotor arranged concentrically. The turbulence effect caused by the rotation of the rotor draws in and pushes out the materials, and the shear action during this process promotes mixing, dispersion, emulsification, etc., of the materials.

Furthermore, Patent Documents 3 to 5 describe a technique in which a rotating blade, such as an impeller or screw, is attached to the rotor rotation axis of a homogenizer, and the material to be processed is pumped towards the homogenizer by the rotating blade that rotates together with the rotor.

Japanese Patent Publication No. 2001-300280 Japanese Patent Publication No. 2021-122784 Patent No. 4888866 Japanese Patent Application Laid-open No. 58-177128 Japanese Utility Model Publication No. 5-26138

When the viscosity of the material being processed increases, the suction action of the homogenizer alone may be insufficient to supply the material to the homogenizer, leading to a decrease in processing efficiency. Furthermore, depending on the viscosity of the material, it may not be supplied to the homogenizer at all, resulting in a complete failure to process.

To avoid the above-mentioned situation, it is conceivable to use a rotating blade, as described in Patent Documents 3-5, to pressurize the material to be processed into a homogenizer. However, the feed blades in Patent Documents 3-5 are mounted on the rotor rotation axis of the homogenizer and rotate at high speed (rpm) at the same rotational speed as the homogenizer (rotor) (the rotational speed of the homogenizer is considerably higher than that of the stirring blades). As a result, the supply flow rate of the material to be processed into the homogenizer may exceed the homogenizer's processing limit (the maximum flow rate of material that the homogenizer can suck in and push out per unit time), disrupting the homogenizer's stable suction and push-out action and potentially preventing the required shearing action from being applied to the material. Furthermore, with high-viscosity materials, the flow of the material may not keep up with the high-speed rotation of the rotating blade, causing the blade to idle, resulting in an insufficient supply flow rate of the material to the homogenizer, or even no material being supplied to the homogenizer at all.

The object of this invention is to provide a stirring device equipped with a mechanism that can stably supply the material to be processed to a homogenizer.

To solve the above problems, the present invention provides an agitation device comprising: a stirring tank for containing a material to be processed; a rotating drive shaft extending in the vertical direction; a stirring blade having a blade portion provided on the rotating drive shaft, which agitates the material to be processed by the rotation of the blade portion in conjunction with the rotation of the rotating drive shaft; and a homogenizer having a stator and rotor arranged concentrically below the rotating drive shaft, which sucks in and pushes out the material to be processed by the turbulence effect caused by the rotation of the rotor, wherein a feed blade is provided at the lower end of the rotating drive shaft, which rotates in conjunction with the rotation of the rotating drive shaft and pressurizes the material to be processed toward the homogenizer.

According to the present invention, the feed blade, provided at the lower end of the rotational drive shaft of the stirring blade, rotates at the same rotational speed as the rotational drive shaft, and pressurizes the material to be processed toward the homogenizer. This prevents the supply flow rate of the material to the homogenizer from becoming excessive or insufficient, enabling a stable supply of the material to the homogenizer.

This is a longitudinal cross-sectional view showing the overall configuration of the stirring device according to the first embodiment. This is a side view of the feed blade of the stirring device according to the first embodiment. This is a longitudinal cross-sectional view showing the overall configuration of the stirring device according to the second embodiment. This is a view from above of the feed blade of the stirring device according to the second embodiment. This is a view of the feed blade of the stirring device according to the second embodiment, seen from a diagonal downward angle. This is a partial cross-sectional view of the feed blade of the stirring device according to the second embodiment, as seen from the direction of the line b-b in Figure 4A. This is a longitudinal cross-sectional view showing the overall configuration of the stirring device according to the third embodiment. This figure shows the relationship between the rotation speed (rpm) of the stirring blades and the flow rate of the material to be processed to the homogenizer. This figure shows the relationship between the homogenizer's rotation speed (rpm) and the flow rate of the material being processed into the homogenizer.

The embodiments of the present invention will be described below with reference to the drawings.

Figure 1 is a longitudinal cross-sectional view showing the overall configuration of a stirring device according to the first embodiment. This embodiment of the stirring device consists mainly of a stirring tank 1 for containing the material to be processed, and stirring blades 2 and a homogenizer 3 provided inside the stirring tank 1.

A circulation pipe 4 is installed between the bottom and side of the stirring tank 1. A portion of the circulation pipe 4 is connected to a discharge pipe 4b via an openable/closable discharge valve 4a. Additionally, a baffle 5 is permanently positioned inside the stirring tank 1.

The agitator 2 consists of a rotary drive shaft 2a that extends vertically along the center of the agitator 1 and is rotatable around its central axis X, and a blade section 2b attached to the rotary drive shaft 2a. The blade section 2b comprises a first blade 2b1 attached to the middle of the rotary drive shaft 2a and a second blade 2b2 attached to the lower end of the rotary drive shaft 2. The second blade 2b2 extends outward from multiple positions at the lower end of the rotary drive shaft 2 and further extends towards the upper part of the agitator 1. A scraper 2b3 is attached to the second blade 2b2 to scrape off material adhering to the inner wall of the agitator 1. The rotary drive shaft 2a is driven to rotate around its central axis X by a drive motor (not shown), and the rotation of the rotary drive shaft 2a causes the blade section 2b to rotate, thereby agitating the material in the agitator 1.

The homogenizer 3 is positioned below the rotary drive shaft 2a and, as is well known, has a comb-shaped stator and rotor arranged concentrically. It sucks in and pushes out the material to be processed through the turbulence effect caused by the rotation of the rotor. The rotor is driven by a drive motor (not shown) around an axis coaxial with the central axis X of the rotary drive shaft 2a.

In this embodiment, the rotary drive shaft 2a is formed in a hollow shaft shape, and a raw material supply pipe 7 is inserted inside it along the central axis X of the rotary drive shaft 2a. The upper end of the raw material supply pipe 7 (not shown) communicates with a raw material input section (not shown), such as a hopper, located above and outside the stirring tank 1. The lower end 7a of the raw material supply pipe 7 extends downward through the lower end of the rotary drive shaft 2a and faces the center of the homogenizer 3 with a predetermined gap between them. Raw materials (powder, liquid, mixtures thereof, etc.) introduced into the raw material supply pipe 7 from a raw material input section (not shown) descend inside the raw material supply pipe 7 and are discharged from the lower end of the lower end 7a directly above the center of the homogenizer 3. Due to the turbulence effect associated with the rotation of the homogenizer 3 (rotor), the raw materials are drawn into the homogenizer 3. Raw material introduction into the stirring tank 1 via the raw material supply pipe 7 is performed when initial raw materials are introduced into the stirring tank 1 or when additional raw materials are introduced to materials being processed in the stirring tank 1. The raw material supply pipe 7 may rotate together with the rotary drive shaft 2a, or it may not rotate.

Furthermore, a feed blade 8 is provided at the lower end of the rotary drive shaft 2a. As shown in an enlarged view in Figure 2, in this embodiment, the feed blade 8 comprises a ring-shaped mounting portion 8a attached to the lower end of the rotary drive shaft 2a by appropriate fixing means such as a screw, and a blade portion 8b, one end 8b1 of which is fixed to the mounting portion 8a, and which extends spirally from the one end 8b1 toward the other end 8b2 on the lower side. The blade portion 8b is formed by spirally molding a strip-shaped member made of metal or resin, and has an upper surface 8b3 facing upward and a lower surface 8b4 facing downward. With the feed blade 8 attached to the lower end of the rotary drive shaft 2a, the blade portion 8b extends downward, spirally encircling the lower end 7a of the raw material supply pipe 7, which extends downward through the rotary drive shaft 2a and the attachment portion 8a, from the outer circumference with a predetermined gap δ (the gap between the outer circumference of the lower end 7a and the inner circumference of the blade portion 8b). The other end 8b2 is positioned slightly above the lower end of the lower end 7a. When the rotary drive shaft 2a rotates clockwise (in the direction of the arrow R in the figure) as viewed from above, the feed blade 8 rotates clockwise R in conjunction with the rotation of the rotary drive shaft 2a. This rotation of the feed blade 8 pushes the material to be processed in the agitated tank 1 with the lower surface 8b4 of the blade portion 8b, and pressurizes it downward.

The processing of the material to be processed in the agitated tank 1 is carried out by rotating the agitator blade 2 (rotary drive shaft 2a) and the homogenizer 3 (rotor). The rotation speed (rpm) of the agitator blade 2 is set to a considerably lower rotation speed (rpm) than that of the homogenizer 3. The rotation of the agitator blade 2 agitates the material to be processed in the agitated tank 1. At the same time, the feed blade 8, which is provided at the lower end of the rotary drive shaft 2a, rotates at the same rotation speed as the agitator blade 2, so that the material to be processed in the agitated tank 1 is pushed downward by the helical blade portion 8b of the feed blade 8 and pumped towards the homogenizer 3. The material to be processed, which has been pumped downward by the feed blade 8 and has reached the vicinity of the homogenizer 3, is drawn into the homogenizer 3 by the turbulence effect associated with the rotation of the homogenizer 3 (rotor). The material to be processed, after being mixed, emulsified, and dispersed within the homogenizer 3, is pushed out of the homogenizer 3 into the circulation pipe 4 and returned to the inside of the stirring tank 1 via the circulation pipe 4. The material returned to the stirring tank 1 is stirred by the stirring blades 2 and pumped downwards by the feed blades 8, and then drawn back into the homogenizer 3. After the processing of the material is complete, the material pushed out of the homogenizer 3 is discharged as a product through the discharge pipe 4b (with the discharge valve 4a open) connected to the circulation pipe 4.

Figure 3 is a longitudinal cross-sectional view showing the overall configuration of the stirring device according to the second embodiment. The difference between the stirring device according to the second embodiment and the stirring device according to the first embodiment described above is that a feed blade 18, with a different configuration from the feed blade 8, is provided at the lower end of the rotary drive shaft 2a.

As shown in Figures 4A to 4C, the feed blade 18 used in the second embodiment comprises a ring-shaped mounting portion 18a attached to the lower end of the rotary drive shaft 2a by appropriate fixing means such as screws, a plurality of, for example, four support rods 18b fixed to the mounting portion 18a, and a plurality of block-shaped blade portions 18c attached to the support rods 18b. Each blade portion 18c is formed in the same shape from a metal or resin material, and both sides in the circumferential direction are fixed to two circumferentially adjacent support rods 18b. Between the circumferentially adjacent support rods 18b, there are a plurality of, for example, four sets of blade portions 18c arranged in the vertical direction, and four such sets of blade portions 18c are arranged at equal intervals along the circumferential direction. The sets of circumferentially adjacent blade portions 18c are arranged with the positions of the blade portions 18c shifted vertically between them. With the feed blade 18 attached to the lower end of the rotary drive shaft 2a (see Figure 3), the set of blade sections 18c surrounds the lower end 7a of the raw material supply pipe 7, which extends downward through the lower end of the rotary drive shaft 2a and the attachment portion 18a, from the outer circumference side, with a predetermined gap (the gap between the outer circumference of the lower end 7a and the inner circumference of the blade section 18c). The lowest blade section 18c is positioned slightly above the lower end of the lower end 7a.

As shown in Figure 4B, each blade portion 18c has a first side surface 18c1 on one side in the circumferential direction and a second side surface 18c2 on the other side in the circumferential direction. The first side surface 18c1, located on the front side in the right rotation direction (arrow direction R) when viewed from above, is formed as an inclined surface (inclined plane or inclined curved surface) that slopes forward in the right rotation direction R from its lower end to its upper end, and the second side surface 18c2, located on the front side in the left rotation direction (arrow direction L), is formed as an inclined surface (inclined plane or inclined curved surface) that slopes forward in the left rotation direction L from its lower end to its upper end. Therefore, when the rotation drive shaft 2a rotates in the right rotation direction R, and the feed blade 18 rotates in the right rotation direction R as the rotation drive shaft 2a rotates, the material to be processed in the stirring tank 1 is pushed downward by the first side surface 18c1 on the front side in the rotation direction of each blade portion 18c. Furthermore, when the rotary drive shaft 2a rotates in the leftward direction L, and the feed vanes 18 rotate in the leftward direction L in conjunction with the rotation of the rotary drive shaft 2a, the material to be processed in the agitated tank 1 is pushed downward by the second side surfaces 18c2 on the forward side in the direction of rotation of each vane portion 18c. Therefore, in the agitator according to the second embodiment, in which the feed vanes 18 are provided at the lower end of the rotary drive shaft 2a, the material to be processed in the agitated tank 1 can be pumped toward the homogenizer 3 regardless of whether the rotary drive shaft 2a rotates to the left or right. Other matters are the same as in the first embodiment, so redundant explanations are omitted.

Figure 5 is a longitudinal cross-sectional view showing the overall configuration of the stirring device according to the third embodiment. The difference between the stirring device according to the third embodiment and the stirring device according to the first embodiment described above is the elimination of the raw material supply pipe 7 inserted inside the rotary drive shaft 2a. By eliminating the raw material supply pipe 7, the inner circumference of the blade portion 8b of the feed blade 8 becomes hollow. Raw material is introduced into the stirring tank 1, for example, by installing a raw material supply valve on the lower side of the stirring tank 1 and introducing the raw material from the raw material supply valve to a position directly above the homogenizer 3.

In the first embodiment of the agitator shown in Figure 1, the lower end 7a of the raw material supply pipe 7 is positioned on the inner circumference side of the blade portion 8b of the feed blade 8. In contrast, in the third embodiment of the agitator shown in Figure 5, the inner circumference side of the blade portion 8b of the feed blade 8 is hollow. Comparing the two, it can be said that the agitator of the first embodiment has a higher pumping effect of the material to be processed by the feed blade 8 compared to the agitator of the third embodiment. This is thought to be because, when the inner circumference side of the blade portion 8b is hollow, a phenomenon occurs in which a portion of the material to be processed, which is pumped downward by the blade portion 8b, flows back upward through the inner circumference side of the blade portion 8b. By positioning an axial member such as the lower end 7a of the raw material supply pipe 7 on the inner circumference side of the blade portion 8b of the feed blade 8, the above backflow phenomenon is suppressed by the axial member, and the material to be processed is pumped more effectively. Considering these circumstances, in a configuration where the raw material supply pipe 7 is eliminated, the axial member positioned on the inner circumference of the blade portion 8b may be integrally formed with the lower end of the rotary drive shaft 2a.

Although not shown in the illustration, the stirring apparatus according to the second embodiment shown in Figure 3 may also have a configuration in which the raw material supply pipe 7 is eliminated, similar to the above.

A comparative test was conducted using the stirring device according to the first embodiment (example) shown in Figure 1 and a comparative example stirring device obtained by removing the feed blade 8 from the stirring device of the first embodiment. The comparative test was performed by operating the stirring device under the conditions shown in Tables 1 to 3 below {viscosity of the material to be processed (mPa·s), rotational speed of the stirring blade 2 (rotating drive shaft 2a) (rpm), rotational speed of the homogenizer 3 (rotor) (rpm)}, and measuring the flow rate (L/min) of the material discharged from the homogenizer 3 (the material pushed out from the homogenizer 3 and discharged from the discharge pipe 4b). The flow rate (L/min) of the material discharged from the homogenizer 3 can be considered equivalent to the supply flow rate (L/min) of the material to be processed to the homogenizer 3.

As shown in Tables 1 and 2, when compared under the same conditions, it was confirmed that the agitator in the embodiment equipped with feed vanes increased the flow rate of the material to be processed to the homogenizer compared to the comparative example agitator without feed vanes. This increase in the flow rate of the material to be processed to the homogenizer is due to the pumping force exerted by the feed vanes, which rotate in conjunction with the rotation of the agitator vanes (rotary drive shaft), pushing the material towards the homogenizer. Furthermore, it was confirmed that increasing the rotation speed of the agitator vanes in the embodiment equipped with feed vanes also increased the flow rate of the material to be processed to the homogenizer.

The tests shown in Table 3 used a high-viscosity cream with a viscosity of 300,000 MPa·s as the material to be processed. In the comparative example's stirring device, which lacked a feed vane, the supply flow rate (g/min) of the material to the homogenizer was zero, making processing impossible. In contrast, the stirring device of the example, equipped with a feed vane, was able to stably supply the material to the homogenizer. This test result confirmed that the stirring device of the example with a feed vane is capable of stable processing even with high-viscosity materials such as 300,000 MPa·s. Furthermore, as shown in Figure 6, it was confirmed that the supply flow rate of the material to the homogenizer was proportional to the rotation speed of the stirring vane (i.e., the rotation speed of the feed vane).

The tests shown in Table 4 below used the same high-viscosity cream as the tests shown in Table 3, and were conducted in a stirring apparatus equipped with feed blades. The rotation speed of the feed blades was kept constant, while the rotation speed of the homogenizer was varied. As shown in Figure 7, it was confirmed that the supply flow rate (g/min) of the material to the homogenizer increased exponentially and rapidly with increasing homogenizer rotation speed.

Generally, the shear force of a homogenizer acting on a material being processed is proportional to the homogenizer's rotational speed (rpm), provided that the viscosity of the material and the homogenizer's configuration (including the clearance between the rotor and stator) are the same. As shown in the test results in Table 4 (Figure 7), while it is possible to adjust the supply flow rate of the material to the homogenizer by adjusting the homogenizer's rotational speed, the supply flow rate changes exponentially and rapidly with respect to the homogenizer's rotational speed, making it difficult to adjust to a desired flow rate. Furthermore, changing the homogenizer's rotational speed alters the shear force acting on the material, affecting the processing quality. In contrast, in the stirring apparatus of the embodiment equipped with a feed vane, as shown in the test results in Table 3 (Figure 6), the supply flow rate of the material to the homogenizer changes proportionally to the rotational speed of the stirring vane, making it easy to adjust to a desired flow rate. Additionally, since it is not necessary to change the homogenizer's rotational speed when adjusting the supply flow rate, the shear force acting on the material can be maintained at a desired value.

1. Agitation tank 2. Agitator blade 2a. Rotary drive shaft 2b. Blade section 3. Homogenizer 7. Raw material supply pipe 7a. Lower end 8. Feed blade 8a. Mounting section 8b. Blade section 18. Feed blade 18a. Mounting section 18b. Support rod 18c. Blade section 18c1. First side surface 18c2. Second side surface δ. Gap.

Claims (5)

A stirring tank containing the material to be processed,
A stirring blade having a rotating drive shaft extending in the vertical direction and a blade portion provided on the rotating drive shaft, the stirring blade agitates the material to be processed by the rotation of the blade portion in conjunction with the rotation of the rotating drive shaft,
A homogenizer having a stator and rotor arranged concentrically below the aforementioned rotary drive shaft, which sucks in and pushes out the material to be processed by the turbulence effect caused by the rotation of the rotor,
In a stirring device equipped with,
A stirring device characterized in that a feed blade is provided at the lower end of the rotary drive shaft, which rotates in conjunction with the rotation of the rotary drive shaft and pressurizes the material to be processed toward the homogenizer. The stirring device according to claim 1, wherein the feed blade has a blade portion that extends spirally from above to below. The stirring device according to claim 1, wherein the feed blade has a plurality of blade sections arranged at predetermined intervals in the circumferential direction, and each blade section has a first side surface located on the front side in the direction of rotation of the rotary drive shaft with respect to rotation in one direction, and formed on an inclined surface that slopes forward from the lower end to the upper end in the direction of rotation; and a second side surface located on the front side in the direction of rotation of the rotary drive shaft with respect to rotation in the other direction, and formed on an inclined surface that slopes forward from the lower end to the upper end in the direction of rotation. The stirring device according to claim 2 or 3, wherein a shaft-shaped member extending in the vertical direction is arranged on the inner circumference side of the blade portion of the feed blade with a predetermined gap between them. The stirring device according to claim 4, further comprising a raw material supply pipe coaxially inserted inside the rotary drive shaft, wherein the lower end of the raw material supply pipe extends downward through the lower end of the rotary drive shaft and is positioned as the shaft-shaped member on the inner circumference side of the blade portion of the feed blade.