Dispersing and grinding apparatus

Abstract: A dispersing and grinding apparatus in which a material to be treated and a grinding medium are placed in a grinding vessel and the mixture of the material and medium is provided with motion thereby the material is ground and dispersed into solution. The vessel (1) has an inlet (2) for introducing the material at one end and an outlet (3) for discharging the finished processed material at the other end. The vessel (1) is provided with a cylindrical rotor (10) rotatably therein so as to form a narrow space with the inner wall of the vessel. The outer circumference of the rotor or the inner wall of the vessel is provided with guide members (12) to control the flow of the mixture. The guide members (12) include forward guide (13) surfaces which give forward movement to the mixture and backward (16) guide surfaces which give backward movement. By means of these guide members, the flow of the mixture is possible similar to the plug flow state.

Description: The invention relates to a dispersing and grinding apparatus according to the preamble of claim 1. Such an apparatus is known from EP -A- 206 207. Guide members are provided on the rotor and on the inner wall of the vessel for guiding the flow of the mixture of material and grinding medium, which guide members are provided in the form of rows of individual protrusions in the form of cylindrical pins extending radially on the outer circumference of the rotor and on the inner circumference of the vessel. FR-A 2 293 979 discloses a dispersing and grinding apparatus which is provided with protrusions in the form of a helix on the outer surface of the rotor and on the inner wall of the vessel. Both helixes are provided in a certain distance from each other to provide an angular flowpath therebetween. The helix has a forward and rearward guide surface for the mixture of material to be processed and grinding medium. It is an object of the present invention to provide a dispersing and grinding apparatus of the above-mentioned kind, which makes possible the flow of the mixture consisting of the material and grinding medium in a predominantly circumferential direction along the inner wall of the vessel, and which may provide sufficient motion to the mixture. This object is achieved by the features in the characterizing part of claim 1. The protrusions provide a flow of the mixture in such a manner that the flow does not induce generation of a high velocity gradient, and makes the resulting mixture flow like a plug flow, the mixture may flow mainly in a circumferential direction,and thereby, sufficient motion can be provided to the grinding medium. Further, if the above flow is induced in the narrow space, uniform motion is provided to the grinding medium throughout the vessel, and accordingly, dispersing efficiency can be increased. Other objects and features of the present invention will become apparent from the following description with reference to the attached drawings. Fig. 1 is a cross sectional view in an axial direction of one embodiment of a dispersing and grinding apparatus of this invention; Fig. 2 is a side view showing a portion of the outer circumferential surface of a rotor of the dispersing and grinding apparatus shown in Fig. 1; Fig. 3 is an explanatory view showing operation of a guide member of the dispersing and grinding apparatus of this invention; Fig. 4 is a diagrammatic view of a dispersing and grinding apparatus having two rotors; and Fig. 5 is a cross sectional view in an axial direction of another embodiment of this invention. The present invention may be applicable also to a vertical type of a dispersing and grinding apparatus, however, in the drawing, a horizontal type of a dispersing and grinding apparatus is shown. A grinding vessel 1 has an inlet 2 to supply material at one end thereof and has an outlet 3 to discharge the processed material at the other end. Towards the discharging outlet 3, a proper grinding medium separation unit is provided to separate a grinding medium 4 from the mixture. In the drawing, a screen type separator 5 is used, but a gap type separator may also be utilized. On the outer periphery of the vessel 1, a jacket 6 is provided, and water or another medium for temperature control is introduced at an inlet 7 and issued through an outlet 8. The jacket may be provided within the vessel. A rotor 10 is placed inside the vessel 1 defining a narrow space between itself and the inner wall 9. The rotor 10 is attached to a shaft 11 which is connected with proper driving means (not illustrated) and rotates with rotation of the shaft. In this case, the rotor is designed to be driven directly through the shaft extending to the outside of the vessel. However, it is possible to rotate the rotor indirectly by means of electromagnet inductive action generated by a rotating magnetic field provided on the outer circumference of the vessel or inner circumference of the rotor. In this case, it is possible to generate a transfer magnetic field either by energizing in series the electromagnetic coils which are disposed around the vessel ,or by rotating the permanent magnet which is positioned inside of the rotor or outside of the vessel , whereas the other permanent magnet disposed on the rotor is magnetically connected to the rotating magnet. On the circumferencial surface of the rotor 10, many guide members 12 are formed to induce the mixture of grinding medium and material in the axial direction in accordance with rotation of the rotor. Each of the guide members 12 has a pair of parallelogrammic forward guide surfaces 13 which give a forward movement to the mixture toward the outlet 3, and a pair of parallelogrammic rearward guide surfaces 14 which give a rearward movement to the mixture toward the supply inlet 2. The guide member 12 may be made in various configurations. In the drawings almost parallelogrammic protrusions or preferably nearly diamond shaped protrusions are formed by cutting a right-handed screw and a left-handed screw to overlap one another on the outer circumference of the rotor. In this way the forward guide surfaces 13 and rearward guide surfaces 14 are formed on each side of the parallelogrammic protrusion, and further the forward guide surfaces are aligned in a spiral shape and the rearward guide surfaces are aligned in an spiral shape opposite to the forward guide surface on the outer periphery of the rotor. The forward guide surfaces 13 and rearward guide surfaces 14 are separately disposed in the opposite state so that they can induce the flow of the grinding medium 4 which gathers around the discharge outlet or the supply inlet after abutting and contacting on each of the surfaces, to the opposite direction by movement to the opposite surfaces. The above protrusions can also be formed on the vessel wall, which is made in one body by mechanical processing. Also, they can be formed by an investment casting or other casting process in one body. Thus, by disposing properly the protrusions with fine pitches, it is possible to let the mixture of the material and grinding medium flow in such a manner that a high velocity gradient in the axial direction does not occur, just like in a plug flow. The grinding medium 4 such as glass, ceramic, alumina, zirconium, steel beads and others selected in accordance with the nature of the material to be treated and purposes of treatment, etc., is introduced into the supply inlet for the medium of which illustration is omitted, and is set almost equally along the axial direction of the rotor 10. When the rotor 10 rotates, the mixture of grinding medium 4 and material is directed toward the discharge outlet 3 by striking on the forward guide surfaces 13 of the guide members 12, and next returns toward the supply inlet 2 by striking on the rearward guide surfaces 14. The mixture consisting of grinding medium 4 and material striking on the rearward guide surfaces 14 is again directed toward the outlet 3 by striking the forward guide surfaces 13. As a result, the material including grinding medium 4 is agitated and circulated in the various directions almost within the same limits in the axial direction of the rotor 10, and is maintained almost in a uniform state, and the flow thereof is similar to the flowing state in a plug flow. Therefore, the material entered from the inlet 2 into the vessel 1 with a proper forward pressure by means of a pump (not illustrated) is subjected to uniform shearing force by guide members and medium when it is moving along the circumference of the rotor 10, and, accordingly, it is dispersed efficiently and discharged from the outlet 3. It has been confirmed that the mixture flows in a flowing state of the plug flow which has been proven by experiments in that the height of the above guide member 12 is about 4 mm, the space between the inner wall of the vessel and the protrusions is about 4 mm which distance corresponds to the size of about more than 4 particles of the grinding medium. In the above embodiments, the rotor is designed as a cylinder. The configuration of the rotor is not limited to the above. Other configurations may be utilized. Further, as shown in Fig. 4, a plural number of rotors may be disposed parallel to each other within the vessel. In case plural rotors are provided, the vessel wall of the grinding vessel encircles the rotors 10, 10 so as to form the continuous grinding space around the rotors (see Fig. 4). Fig. 5 is another embodiment in which a jacket is provided within a rotor. In the drawing, a supply conduit 17 used to maintain temperature control with liquid such as cooling water etc is passed through a shaft 16 of a rotor 15. The ends of the supply conduit 17 are connected with a passage 18 provided along the cylindrical wall of the rotor 15 and the passage 18 is also connected with an overflow vent 19 provided on the outer circumference of the supply conduit 17. By this constitution, liquid such as cooling water etc enters the passage 18 through the supply conduit 17 wherein heat exchange operation is performed through the cylindrical wall, and is discharged through the overflow vent 19. The surfaces of both ends of the rotor 15 are preferably designed with conical surfaces 20 so as to guide the mixture consisting of the material and grinding medium to the treatment space. In accordance with the dispersing and grinding apparatus of the invention, the mixture of the grinding medium and the material flows just as in the flowing state of the plug flow in the narrow space provided between the inner wall of the vessel and the rotor by means of the rotation of the rotor,and during such flowing sufficient shearing force is applied to the material by the grinding medium. As a result the mixture performs uniform dispersement through the entire area of the vessel and particle size distribution of the finished ground material becomes uniform.

Claims: A dispersing and grinding apparatus comprising: a vessel (1) for receiving a material to be processed and a grinding medium, the vessel (1) having an inlet (2) at an upstream end for admitting the material into the vessel and an outlet (3) at a downstream end for discharging processed material from the vessel, a rotor (10) mounted rotatably within the vessel (1) and being positioned relative to the vessel to define an annular flow path between an inner wall (9) of the vessel (1) and the outer peripheral surface of the rotor (10); and guide members (12) disposed on the outside surface of the rotor (10) or on the inner wall of the vessel (1) for guiding the flow of the mixture of material and grinding medium, wherein said guide members (12) are provided in the form of rows of individual protrusions, the side surfaces of which define, as seen in the axial direction of the rotor, forward and rearward guide surfaces (13, 14) respectively, to impart forward and rearward motion to the mixture in response to the rotation of the rotor, characterized in that each of said forward and rearward guide surfaces (13, 14) being defined by flat surfaces disposed at an angle to the axial direction. A dispersing and grinding apparatus according to claim 1, wherein said forward guide surfaces (13) are disposed on the outer surface of the rotor (10) in a spiral shape, and said rearward guide surfaces (14) adjacent to the forward guide surfaces (13) are disposed in an opposite spiral shape. A dispersing and grinding apparatus according to claim 1 wherein said guide members (12) are protrusions of parallelogrammic cross-section each side surface of the protrusion defining the forward or rearward guide surfaces (13, 14), respectively. A dispersing and grinding apparatus according to claim 1, wherein said rotor (10) has a passage (18) in which temperature control liquid flows along the wall of the rotor. A dispersing and grinding apparatus according to claim 1, wherein many rotors (10) are disposed parallel to each other in the vessel (1) and the wall of the vessel encircles the rotors so as to form the continuous grinding space around the rotors. A dispersing and grinding apparatus according to claim 1, wherein the rotor (10) is of a cylindrical configuration, and both end surfaces (20) of the rotor are conical in shape so as to guide the material and medium toward the grinding space.

Inventors: INOUE YOSHITAKA, KAMIWANO MITSUO, INOUE, YOSHITAKA, KAMIWANO, MITSUO
Applicants: INOUE MFG, INOUE SEISAKUSHO (MFG) CO., LTD.
Application year: 1988
Main classification: B02C17
IPC codes: B02C17, B01F7