Dispersing and grinding apparatus

Abstract: A dispersing and grinding apparatus in which a material is dispersed by means of a grinding medium such as balls or beads. Inside a grinding vessel (1), a rotor (9) is rotatably disposed in such a manner that a narrow annular flow path (15) is formed between the rotor and the inner wall (14) of the grinding vessel (1). On the outer peripheral surface of the rotor (9), a guiding means (18) is disposed for guiding, in the circumferential direction, the flow of a mixture of the medium and material flowing within the annular flow path (15). Inside the rotor, an inside flow path (10) extending in the dial direction is formed, and a backward screw (21) is disposed for returning the medium in the inside flow path (10) toward the upstream end side. The medium gathering in the downstream end side enters the inside flow path (10) from an inflow conduit (24) provided on the outer peripheral surface of the rotor (1), and returns to the upstream end side by means of the backward screw (2).

Description: BACKGROUND OF THE INVENTION (1) Field of the Invention The present invention relates to a dispersing and grinding apparatus in which a grinding medium such as balls or beads, is agitated together with a material to be ground, and shearing force is applied to the material, thereby finely grinding the material and dispersing it in liquid. (2) Background Information As an apparatus for dispersing a material by means of a medium, various structures are known. In general, an apparatus is widely used wherein disks or rods are protruded on an agitating shaft disposed within a grinding vessel to induce the medium. An annular type dispersing and grinding apparatus is also used wherein a cylinder is disposed within the grinding vessel, and a narrow annular flow path is defined between the cylinder and the inner wall of the grinding vessel, thereby inducing the medium within the annular flow path. In the annular type dispersing and grinding apparatus, the material is fed from an inlet into the grinding vessel by means of a feeding means such as a pump, and dispersed within the annular flow path, and then discharged through the outlet. As mentioned above, the mixture of the material and medium flows through the annular flow path, from the inlet side toward the outlet side, and thus the medium tends to gather near the outlet side. For this reason, the medium is hardly distributed throughout the grinding vessel, and thus the dispersion efficiency becomes poor. Under such circumstances, in order to solve the problem of uneven distribution of the medium, the present inventors have proposed a dispersing and grinding apparatus in which a forward screw is provided on the outer surface of a cylindrical rotor for inducing the medium from the inlet side to the outlet side, and a backward screw is provided on the inner wall surface of the rotor for inducing the medium from the outlet side to the inlet side in U.S. Patent No. 4,856,717. In this apparatus, the medium circulates through the outside and the inside of the rotor and whereby the uneven distribution of the medium occurs a little. Further, the present inventors have proposed a dispersing and grinding apparatus in which a guiding means is formed on the outer peripheral surface of the rotor for guiding the flow of the mixture of the material and medium in the circumferential direction in U.S. Patent No. 4,919,347. In this apparatus, the mixture flows like a plug flow within the grinding vessel, and the material receives sufficient dispersion treatment during the flowing from the inlet side to the outlet side. As mentioned above, these dispersing and grinding apparatuses proposed by the present inventors can attain good dispersion efficiencies. However, for the dispersing and grinding apparatus as indicated in U.S. Patent No. 4,919,347, it is hard to say that there is completely no tendency for the medium in gathering near the outlet side. Further, in the dispersing and grinding apparatus as indicated in U.S. Patent No. 4,856,717, the uneven distribution of the medium can be prevented, but the movement of the medium is mild as compared with the apparatus indicated in U.S. Patent No. 4,919,347, and the treatment time is sometimes very long depending on the type of the material. In addition, in the annular type dispersing and grinding apparatus, the medium moves around the rotor, and thus when the inlet of the medium is located at the center portion of the rotor, the medium is hardly entered therein. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above drawbacks of the prior art. It is another object of the present invention to provide a dispersing and grinding apparatus wherein the material flows through the annular flow path from the inlet side toward the outlet side of the grinding vessel in a substantially plug flow style, and also the medium would not be unevenly distributed. These objects are achieved by the features in claim 1. The above and other objects and features of the present invention will become apparent to persons of ordinary skill in the art upon a reading of the following description of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a vertical sectional view showing an embodiment of a dispersing and grinding apparatus of the present invention. Fig. 2 is an explanatory view showing a guiding means. Fig. 3 is an explanatory view showing another embodiment of the guiding means. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention is explained with respect to embodiments wherein the present invention is applied to a horizontal-type dispersing and grinding apparatus, but it should be mentioned that the present invention can be applied to a vertical-type dispersing and grinding apparatus wherein a grinding vessel is vertically disposed. Fig. 1 shows a vertical cross-sectional view of the dispersing and grinding apparatus of the present invention. In this drawing, a grinding vessel 1 has an inlet 2 for entering a material therein at the upstream end, and an outlet 3 for discharging the dispersed and ground material at the downstream end. At the side of the outlet 3 of the grinding vessel 1, a suitable medium-separating apparatus is provided for separating a medium 4 from the material. In this drawing, a gap-type separator having a stater 5a and a rotor 5b is used, but a screen-type separator of an adequate type may be used. Further, on the outer periphery of the grinding vessel 1, a jacket 8 having an inflow port 6 and an outflow port 7 for a temperature-controlling medium such as cooling water, is disposed. Inside the grinding vessel 1, a cylindrical rotor 9 is disposed. The rotor 9 has an inside flow path 10 extending in the axial direction, and is fixed to a shaft 13 by use of end plates 11, 12 at the both ends and rotated by rotating the shaft 13 by an actuating means (not shown). Between the outer peripheral surface of the rotor 9 and an inner wall 14 of the grinding vessel 1, a narrow annular flow path 15 is defined for permitting the mixture of the material and medium to flow. The width of the annular flow path is required to be of such an extent that, when the rotor 9 is rotated, that the medium 4 in contact with the outer peripheral surface of the rotor is positively induced, and specifically at the size of at least 3 times the diameter of the medium, preferably about 4 times the diameter of the medium. On the outer peripheral surface of the rotor 9, a guiding means is provided for guiding in the circumferential direction the flow of the mixture flowing from the inlet 2 side to the outlet 3 side within the annular flow path 15. Such a guiding means may be provided on an inner wall 14 of the grinding vessel 1. The configuration of the guiding means may be selected from various shapes. The guiding means as shown in Fig. 2 has a plurality of protrusions 18 disposed on the outer peripheral surface of the rotor 9, with a cross section of a parallelogram, each having a forward guide surface 16 facing to the rotational direction of the rotor 9 for putting the mixture forward and guiding it in the rotational direction, and a rearward guide surface 17 facing to the inlet of the grinding vessel 1 for putting the mixture rearward. The forward guide means 16 extends along the axial direction of the rotor 9. The rearward guide surface 17 inclines, but this inclined angle may be variously changed. For example, each surface may be inclined with respect to the axial direction of the rotor 9 as shown in Fig. 3. Further, such protrusions may be formed into various shapes such as a square pillar, a column or a cylindroid. These protrusions are integrally formed on the outer peripheral surface of the rotor, but may be formed as a bead padding by welding, or separately formed so that they may be implanted at the outer peripheral surface of the rotor. The guide means may be made of a metal material having abrasion resistance on its surface or entirely, or may be made of ceramics, engineering plastics, etc. The rotor 9 may be made entirely of a metal material having abrasion resistance, ceramics or engineering plastics. Inside the rotor 9, a jacket 19 is disposed for permitting the temperature-controlling medium such as cooling water to flow, and a flow path 20 communicating to the jacket 19 is formed in the shaft 13. In the inside flow path 10 of the rotor 9, a backward screw 21 is disposed so that it would put the medium 4 backward from the outlet side toward the inlet side. In the drawing, the backward screw 21 is formed on the outer peripheral surface of a cylindrical screw body 22, and the screw body 22 is fitted to the shaft 13 and fixed thereto. On an inner wall 23 of the rotor 9, the backward screw 21 may be formed (not shown). The inside flow path 10 preferably has an aperture at such a portion that the medium 4 gathering near the outlet side may enter easily the flow path. In this drawing, plural inflow conduits 24 communicating to the inside flow path 10, which have apertures on the outer peripheral surface of the end plate 12 fitted to the rotor 9 at the downstream side, are formed, so that the medium would enter the inside flow path through the inflow conduits 24. Outflow conduits 25 of the inside flow path 10 have apertures at the center portion of an end plate 11 fitted to the rotor 9 at the upstream side. The material entering the grinding vessel 1 through the inlet 2 of the grinding vessel 1 by means of an appropriate feeding means such as a pump, etc., moves forward together with the medium 4 toward the outlet 3 within the annular flow path 15. The flow of the mixture of the material and medium, is guided by means of a protrusion 18 as the guide means in the circumferential direction. Since such a flow approximates to a plug flow, the medium is sprung off by the protrusion 18 in the rotational direction, and sandwiched and induced between the outer surface of the protrusion 18 and the inner wall of the grinding vessel 1, whereby sufficient shearing force is applied to the material and the material will be dispersed in the size of fine particles. This dispersion treatment is conducted substantially uniformly from the upstream end side to the downstream end side. In the medium separating apparatus disposed at the outlet 3 of the grinding vessel 1, only the material dispersed as mentioned above passes therethrough and is discharged, and the medium 4 is separated. The medium gathering near the outer peripheral surface of the rotor at the outlet 3 side, enters the inflow conduit 24 of the inside flow path 10 having apertures on the outer peripheral surface, and returns by means of the backward screw 21 from the outflow conduit 25 to the inlet 2 side of the grinding vessel 1. In the present invention constituted as above, the mixture of the material and medium is flown within the annular flow path of the grinding vessel in the circumferential direction, and the material is applied with shearing force by the movement of the medium from the upstream end side to the downstream end side, whereby the material is finely divided securely. Further, the medium is free of partial gathering at the outlet side of the grinding vessel or uneven distribution within the grinding vessel. The medium enters from the inflow conduit 24 having an aperture on the outer peripheral surface of the rotor at the downstream end side, passes through the inside flow path 10, and returns to the upstream end side through the outflow conduit 25 at the center of the upstream end side, whereby the material receives substantially uniform dispersion treatment from the inlet to the outlet, and thus the dispersion efficiency is improved.

Claims: A dispersing and grinding apparatus comprising a grinding vessel (1) having an inlet (2) for permitting a material to enter the grinding vessel (1) at the upstream end, and an outlet (3) for discharging the dispersed and ground material at the downstream end; a cylindrical rotor (9) rotatably disposed within the grinding vessel, which has an inside flow path (10) extending in the axial direction and defines a narrow annular flow path (15) between the outer surface of the rotor and the inner wall (14) of the grinding vessel (1); a guiding means disposed on the outer peripheral surface of the rotor (9) and/or the inner wall (14) of the grinding vessel (1), for guiding in the circumferential direction the flow of the mixture of the material and a medium flowing within the narrow annular flow path (15) toward the outlet side when the rotor (9) is rotated; a backward screw (21) disposed within the inside flow path, for backwardly moving the medium from the downstream end side toward the upstream end side; and an inflow conduit (24) for leading the medium from the outer surface of the downstream end side of the rotor to the inside flow path (10), wherein the guide means is a protrusion (18) with a cross section of parallelogram, having a forward guide surface (16) facing to the rotational direction of the rotor so that the mixture of the material and medium is moved in the rotational direction, and a rearward guide surface (17) facing to the direction toward the inlet of the grinding vessel (1) so that the mixture is moved rearward. The dispersing and grinding apparatus according to Claim 1, wherein end plates (12,11) are fitted to the both ends of the rotor, wherein an end plate (12) at the downstream end side has an inflow conduit (24) having an aperture on the outer peripheral surface, and an end plate (11) at the upstream end side has an outflow conduit (25) having an aperture at the center portion. The dispersing and grinding apparatus according to Claim 1, wherein the backward screw (21) is formed on the outer peripheral surface of a cylindrical screw body (22), and the screw body (22) is fixed to a shaft (13) extending through the central portion of the rotor (1).

Inventors: INOUE YOSHITAKA, KAMIWANO MITSUO, INOUE, YOSHITAKA, KAMIWANO, MITSUO
Applicants: INOUE MFG INC, INOUE MFG., INC.
Application year: 1992
Main classification: B02C17
IPC codes: B02C17, B01F7