Dispersing and grinding apparatus

Abstract: A dispersing and grinding apparatus comprising a vessel (1) which has an inlet (2) for receiving a material to be ground and dispersed at one end and an outlet (3) for discharging the ground and dispersed material at the other end. In the vessel (1), a rotor (9) is rotatably mounted and between the rotor (9) and the inner wall (7) of the vessel a narrow and annular flow path is formed to permit the passage of a mixture of the material and the grinding medium flowing from the inlet toward the outlet of the vessel. The rotor (9) is provided with grooves (13) extending along the axial direction on the periphery surface for guiding the mixture in the circumferential direction. The rotor is partitioned into a plurality of processing zones (17-1,...,17-5) in the axial direction, and the processing zones (17) are arranged with phase difference of the grooves (13) of the respective processing zones (17) adjacent each other in the circumferential direction. When the mixture transfers from one processing zone to another adjacent processing zone, the velocity difference of the mixture is adjusted, and thereby the mixture advances at approximately equal velocity toward the outlet as a whole, during which the material is sufficiently ground and dispersed.

Description: The invention refers to a dispersing and grinding apparatus according to the preamble of claim 1. Such a dispersing and grinding apparatus is known from EP-A-0 322 623. The present invention relates to a dispersing and grinding apparatus for finely grinding materials and dispersing them into liquid by means of grinding medium such as balls, beads, etc. It is supposed that a dispersing and grinding apparatus, which has a plurality of discs or agitating blades disposed within a vessel to disperse a material, applies centrifugal force to a mixture of a grinding medium and the materials by rotation of the discs, circulates the grinding medium between the discs, during which the grinding medium captures the material, and disperses the material by shearing force. However, the flowing of such a mixture is not uniform throughout the vessel. For this reason, the flowing of the grinding medium often causes short pass or dead space, whereby it is difficult to obtain uniform shearing force. Although it has been known to provide an inner cylinder within a vessel of a dispersing and grinding apparatus to apply motion to the grinding medium by rotation of the inner cylinder, it was difficult to move the grinding medium at approximately equal velocity throughout the inner cylinder. The present inventors have proposed a dispersing and grinding apparatus having a rotor disposed within a vessel and having a guiding means, for controlling the flowing of the grinding medium, disposed on the outer periphery of the rotor (EP-A-0 322 623, resp. US-A-4919347). It was confirmed that, according to the dispersing and grinding apparatus, a material-grinding medium mixture flows through a narrow, annular flow path between the rotor and the vessel by means of an array of forward guide surfaces and an array of rearward guide surfaces of the guiding means like a plug flow, and flows around the periphery of the rotor without causing the formation of high velocity gradient. After that, the present inventors have investigated various structures as the above-mentioned guiding means, and also studied a structure in which protrusions and grooves are disposed in the axial direction of the rotor in the shape of a toothed wheel. However, in such a structure, the mixture which entered the grooves of the rotor causes a velocity difference in the axial direction, and the mixture advances straight toward the outlet from the inlet of the vessel so that sufficient dispersion effect sometimes cannot be obtained. An object of the present invention is to provide a dispersing and grinding apparatus which enables efficient dispersion treatment of a material-grinding medium mixture by applying it uniform motion. Another object of the present invention is to provide a dispersing and grinding apparatus which enables sufficient grinding and dispersion of the material-grinding medium mixture, in the course of transfer of the mixture from the inlet to the outlet in the vessel, by applying motion to the mixture in the circumferential direction without causing a velocity difference in the axial direction. According to the present invention, the objects of the present invention can be accomplished by the features in the characterizing part of claim 1. The other objects and features of the present invention will be apparent to those skilled in the art upon reading of the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional side view of an embodiment of the dispersing and grinding apparatus of the present invention. Fig. 2 is a perspective side view showing one of rotor elements constituting the rotor of the present invention. Fig. 3 is an explanatory front view of a part showing an embodiment of the rotor of the present invention. Fig. 4 is an explanatory front view of a part showing another embodiment of the rotor of the present invention. Fig. 5 is a side view of a part showing a further embodiment of the rotor of the present invention. Fig. 6 is a sectional view of a first element of rotor elements constituting the rotor of the present invention. Fig. 7 is a sectional view of a second element of rotor elements constituting the rotor of the present invention. Fig. 8 is a sectional view of a third element of rotor elements constituting the rotor of the present invention. Fig. 9 is a sectional view of a fourth element of rotor elements constituting the rotor of the present invention. Fig. 10 is a sectional view of a fifth element of rotor elements constituting the rotor of the present invention. Fig. 11 is an enlarged perspective side view of a part of the rotor of the present invention. Fig. 12 is a cross-sectional side view showing another embodiment of the dispersing and grinding apparatus of the present invention. Fig. 13 is a perspective side view showing a rotor element constituting the rotor of the present invention shown in Fig.12. Fig. 14 is an enlarged sectional view of a part of the rotor of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMETNS Fig. 1 shows a horizontal-type dispersing and grinding apparatus of the present invention. The present invention is also applicable to a vertical-type dispersing and grinding apparatus. A vessel 1 has an inlet 2 at one end for supplying a material by using a supplying pump (not shown) and an outlet 3 at the other end for discharging the ground, dispersed material. A grinding medium separating means 4 such as a screen, a gap type separator, etc. is provided at the outlet to prevent fine medium such as glass beads, ceramic, alumina, zirconia, steel, etc. from flowing out. The grinding medium can be drained out by opening a drain port 5. A jacket 6 is provided on the outer periphery of the vessel 1 to control the temperature in the vessel. A rotor 9 is disposed to define a narrow, annular flow path 8, through which the material-grinding medium mixture circulates, between the rotor and an inner wall 7 of the vessel 1. The rotor 9 is mounted to a rotating shaft 10 and rotated by a suitable driving means not shown in the figure. In the figure, the rotor is formed in a cylindrical shape, but, instead of the cylindrical shape, it may be formed into polygonal column shape having a cross-section of approximate triangle, quadrilateral, etc. or into cylindroid. It may be constructed so that cooling water is circulated in the rotor. As shown in Fig. 2, the rotor is constructed by preparing a plurality of rotor elements 12 having an uncircular through hole 11 to be engaged with the rotating shaft 10 at the center, combining them and inserting the rotating shaft 10 into the through hole .11 The rotor may be molded into one integral body. The annular flow path 8, which is formed in an appropriate width depending on the processing conditions and the size of the grinding medium, has the width of at least four pieces of the grinding medium in order not to interfere with the motion of the rotor. On the outer peripheral surface of the rotor 9 , a groove 13 is formed, extending in the axial direction to positively guide the material-grinding medium mixture supplied into the annular flow path 8 in the circumferential direction. In the figure, since the groove 13 is formed between the protrusions 14 and 14 in a toothed-wheel shape, it can be prepared like a gear or a spline shaft. The groove is formed into an involute configuration, but may be formed in a quadrilateral-shape groove 15 as shown in Fig. 3. A groove 16 shown in Fig. 4 is an embodiment formed into a L-letter shape in cross-section. The groove may be formed in other various configurations. The groove can be prepared by a casting method such as lost wax process or the like. In the case of the rotor element 12 as shown in Fig. 2, the groove 13 may be prepared by machining. The pitch of the grooves is appropriately determined depending on the number of revolution of the rotor and properties of the material to be processed. The groove is provided in parallel with respect to the axial direction, but may be provided with a slight obliquity to the axial direction like a helical gear (Fig. 5). The rotor 9 is partitioned in a plurality of processing zones 17 ... in the axial direction. The processing zones are arranged with phase difference of the grooves of the processing zones adjacent each other. For example, the rotor shown in Fig. 1 is partitioned into five processing zones, 17-1, 17-2, 17-3, 17-4 and 17-5, by respective rotor elements. As shown in Fig. 6 to Fig. 10, the phases of the grooves of respective processing zones are each shift by 6 degrees. The aperture width of a communicating section 18 between the grooves of the processing zones adjacent each other (Fig. 11) varies depending on the shift angle. The aperture width of respective communicating sections 18 is preferably formed into the size through which at least one grinding medium is permitted to pass while applying friction to the flows of the grinding medium. The phases of the grooves may occasionally be shifted in such a condition that the communicating section 18 does not exist. In the instance where the rotor 9 is comprised of the rotor elements 12 as shown in Fig. 2, since the pitch of the grooves 13 is constant, the rotor 9 can be prepared by providing rotor elements of which the position of the uncircular through hole 11 and the position of the grooves 13 are little by little shifted in the circumferential direction, as shown, for example, in Fig. 6 to Fig. 10, and inserting the rotating shaft 10 through these rotor elements. In Fig. 12, another embodiment of the rotor of the present invention is shown. In the figure, the construction in which the rotor 9 is rotatably disposed within a vessel 1 defining an annular flow path 8, grooves 13 are provided on the rotor 9 in the axial direction, and the processing zones 17-1,17-2, 17-3, 17-4 are formed, is the same as that of the embodiment shown in Fig. 1. Thus, the same portions are indicated with the same numerals. In this embodiment, it is different from the embodiment shown in Fig. 1 that annular grooves 19 extending in the circumferential direction are formed between respective processing zones. The annular grooves 19 are, as shown in Fig. 13, formed by providing rotor elements 20 provided with a groove 13 and protrusions 14, 14 extending in the axial direction and an uncircular through hole 11, and a cylindrical-shape section 21 on the side portion of the rotor element 20, and by inserting in order the rotating shaft 10 through the rotor elements 20. When the rotor 9 is molded as one integral body, the annular groove 19 may be formed by machining the rotor in the circumferential direction. By forming the groove 19 in the circumferential direction between respective processing zones 17, a material-grinding medium mixture which passed through a certain processing zone enters the annular grooves 19, and circulates in the circumferential direction before advancement to the next processing zone. Thus, the velocity difference of the mixture can be corrected. The grooves and processing zone as mentioned above may be formed on the inner wall 7 of the vessel. The surface of the rotor 9 and the dinner wall 7 of the vessel 1 are preferably composed of anti-corrosion material. As the anti-corrosion material, ultra rigid material such as ceramic, tungsten carbide, etc. are available. These ultra rigid materials are used for the formation of the whole body, or used for the formation of only the surface layer portion which is to be coated. As shown in Fig. 14, these ultra rigid materials may also be flame-sprayed by deflagration type (explosion type) flame-spraying on a substrate 22 to form a protection layer 23 containing the anti-corrosion material. The material which was thus supplied in the vessel 1 through the inlet 2 by suitable charging pressure by using a supplying pump not shown in figure, is mixed with numerous grinding mediums 24 housed in the vessel and supplied to the annular flow path 8. The mixture is then circulated around the rotor by rotation of the rotor 9 and is further guided in the circumferential direction by the groove 13 formed on the outer peripheral surface of the rotor, thereby flowing like a plug flow. In this instance, even if a velocity difference occurs in the axial direction, the grooves of respective processing zones are arranged with phase difference, thereby high velocity flowing is inhibited when the flow transfers from a processing zone to another processing zone. Accordingly, the mixture transfers to adjacent processing zone at approximately equal velocity as a whole. The mixture flows out from the annular flow path 8 through respective processing zones and discharges through the outlet 3 during which the material is applied with sufficient shearing force by the grinding medium and thus finely ground. The present invention is constructed as mentioned above. The material charged in the vessel flows without causing a large velocity difference in the axial direction during the passage through the annular flow path, and the flow thereby approximates a plug flow. Therefore, the material receives uniform shearing force during the operation and is uniformly dispersed thereby attaining sharp particle size distribution to improve the dispersion efficiency.

Claims: A dispersing and grinding apparatus comprising a vessel (1) for receiving a material to be processed and a grinding medium, the vessel having an inlet (2) for admitting the material into the vessel and an outlet (3) for discharging the processed material from the vessel; and a rotor (9) rotatably disposed within the vessel (1) and positioned to define a narrow, annular flow path (8) for permitting the passage of a mixture of the material and the grinding medium with the inner wall of the vessel characterized in that said rotor (9) is provided with grooves (13) along the axial direction on the outer periphery surface of the rotor, the rotor (9) is partitioned into a plurality of processing zones (17-1 to 17-5) in the axial direction, and the processing zones are arranged with phase difference of the grooves (13) of the respective processing zones adjacent to each other in the circumferential direction. A dispersing and grinding apparatus according to Claim 1, wherein the grooves (13) are arranged with a slight obliquity to the axial direction. A dispersing and grinding apparatus according to Claim 1, wherein the rotor (9) comprises an anti-corrosion material. A dispersing and grinding apparatus according to Claim 1, wherein the rotor (9) has a protective layer formed thereon and consisting of an anti-corrosion material. A dispersing and grinding apparatus according to Claim 1, wherein the rotor (9) consists of a combination of a plurality of rotor elements (17-1 to 17-5) having grooves (13) extending in the axial direction on the periphery surface of the rotor (9) and the rotor elements each of which constitutes the processing zones. A dispersing and grinding apparatus according to Claim 1, wherein the grooves (13) of the processing zones (17-1 to 17-5) adjacent each other are communicated with an aperture width of the communicating section 18 which permits the passage of at least one grinding medium. A dispersing and grinding apparatus according to Claim 1, wherein the rotor (9) is provided with annular grooves (19) between the processing zones (17-1 to 17-5) adjacent each other. A dispersing and grinding apparatus according to Claim 7, wherein the rotor (9) consists of the combination of rotor elements (20) having the grooves (13) extending in the axial direction on the periphery surface and having a cylindrical section (21) on the side portion.

Inventors: INOUE YOSHITAKA, KAMIWANO MITSUO, INOUE, YOSHITAKA, KAMIWANO, MITSUO
Applicants: INOUE MFG, INOUE SEISAKUSHO (MFG) CO., LTD.
Application year: 1990
Main classification: B02C17
IPC codes: B02C17, B01F7