Magnetic barrel finishing machine

Abstract: The machine causes multiple different flows or motions of abrasive media and workpieces by varying magnetic fields, thereby repeatedly freeing the workpieces from the abrasive media and subjecting the workpieces to finishing action by the abrasive media. The machine includes a rotator (4) made at least partly of magnetic material, and a plurality of permanent magnets (5) rigidly mounted on the rotator, at least some of the magnets being connected by the magnetic material. A container (11) located above the rotator (4), with a small gap therebetween, contains workpieces (9) and an abrasive medium (10) comprising magnetic material. The permanent magnets (5) are preferably arranged irregularly in such a way that they provide magnetic lines of force acting in both the circumferential direction and the radial direction of the rotator.

Description: The present invention relates to a magnetic barrel finishing machine, as per the preambles of claims 1 and 16. An example of such a machine is disclosed in EP-A-478 805. There has been known a metal finishing machine characterized by regularly arranging permanent magnets on a non-magnetic disk, and changing a magnetic field by rotation of the disk for allowing abrasives and workpieces in a container to flow in the circumferential direction, thereby finishing the free workpieces (Examined Japanese Patent Publication No. HEI 4-26981, and Unexamined Japanese Patent Publication No. SHO 60-118466). When a container filled with workpieces to be finished is placed at a central portion of the non-magnetic rotary disk, the workpieces tend to be finished unevenly, and thereby, extra time is required until the finishing process is completed. Moreover. since poles of the magnets are arranged in the order of N,S:N,S, an alternating magnetic field is generated in the circumferential direction. This regular arrangement of the poles may produce flows of abrasives repeatedly but regularly, and in some cases, this causes the irregular finishing against workpieces or requires a lot of time for completion of the finishing process. Additionally, in the case of using a non-magnetic disk, there presents a disadvantage in generating a magnetic loss. For example, as shown in Fig. 7 or 8, the conventional regular arrangement of poles such as N, S, N, S generates the flows of abrasives along the same circumference (as shown by arrow 21 and loop 22). Accordingly, a container 23 which contains workpieces and media (such as magnetic materials, abrasives, or compounds) must be disposed within a magnetic zone 24 (see Fig. 9). It is apparent that since the magnetic zone 24 is formed in a doughnut shape, the diameter of the container 23 must be set at a value being ½ or less the diameter of a rotary disk 25. In the case where the diameter of the container 23 is substantially equal to that of the rotary disk 25, a loop 22 is not generated at a central portion 26 as shown in Fig. 8, so that the workpieces at the central portion 26 becomes insufficient in finishing, which leads to the uneven finishing of the workpieces as a whole. To cope with this problem, a cylindrical body is sometimes put at the central portion of the container 23. EP-A-0 478 805 discloses a similar machine, in accordance with the preamble of the independent claims 1 and 16. The magnetic force can be reinforced, according to the present invention, by arranging permanent magnets on a magnetic rotator or on magnetic plates on a rotator, preferably with an asymmetrical arrangement of the polarities of the magnetic poles facing the container. The present invention provides magnetic barrel finishing machines as set forth in claims 1 and 16. Preferred embodiments are set forth in the subsidiary claims 2 to 15 and described in more detail below, with reference to the accompanying drawings. With respect to the arrangement of the plurality of permanent magnets according to the present invention, the same function and effect can be obtained by replacement of poles N and S with each other. By the use of the rotary disk made of magnetic material on which permanent magnets are rigidly mounted, it becomes possible to reinforcing the magnetic force by 20% or more as compared with the case where permanent magnets are rigidly mounted on a non-magnetic rotary disk, thus improving the finishing ability and finishing efficiency. As the magnetic material of the rotary disk, there may be used an iron plate or any other plate made of ferromagnetic materials. As the rotator, a disk type is usually used; however, a square plate type or a rotary arm type may be used. For example, in the case of using the rotary arm type, permanent magnets are fixed on arms, respectively. By changing the arrangement of magnets rigidly mounted on the rotator, flows of media and workpieces caused by the rotation of said rotator can be changed somewhat. Accordingly, by replacing the rotator attached with permanent magnets, the workpieces in a container can be finished by different flows of media and workpieces. In other words, the flows of media and workpieces which are suitable for the particular shapes of workpieces (for example, small size plates, small size needles, short-size pieces, complicated pieces and the like) can be obtained by replacing the rotator attached with permanent magnets. As the abrasive media of magnetic material or abrasive media including a magnetic materials, various magnetic materials and non-magnetic materials used for conventional barrel finishing can be used. These materials are suitable for surface finishing of workpieces made of metal, resin or glass. As the magnetic material, there may be used stainless steel pin (diameter: 0.2-1.5 mm, length: 3.0-10.0 mm), stainless steel balls (diameter: 0.5-3.5 mm), and pins or balls made of various hard alloy other than stainless steel. As the non-magnetic material, there may be used SiC, Al 2 O 3 , Fe 2 O 3 , Cr 2 O 3 , Ce 2 O, any kind of diamond powder and various kinds of abrasives. By the use of the above-described magnetic material as the abrasive media independently, the effect of shot-peening can be obtained. On the other hand, by the use of the magnetic material mixed with the above-described non-magnetic material, that is to say, by the use of the abrasive media including magnetic materials, the effect of shot-peening, grinding and polishing can be obtained. As the abrasive media including magnetic material, the magnetic material on which abrasives are bonded or coated, for example, abrasives 83 are bonded at both the ends of the magnetic material pin 84 or coated on the whole surface of the magnetic material pin 84 as shown by Fig. 22 and Fig. 23, may be used. By the use of said magnetic material on which abrasives are bonded or coated, the effect of the grinding and polishing can be obtained. Also, as the abrasive media including magnetic material, the magnetic material 85 in which abrasives 86 are impregnated or mixed as shown by Fig. 24 may be used. Various abrasives which are used in the conventional barrel finishing may be included in the magnetic materials such as ferrite, plastics, etc. By the use of this magnetic material in which abrasives are impregnated or mixed, the effect of the grinding and polishing can be obtained. Further, as the abrasive media including magnetic material, magnetic materials with abrasive powder may be used. By the use of magnetic materials with abrasive powder such as diamond powder, etc., the effect of shot-peening, grinding or polishing can be obtained at the same time. The above-described bonding can be made by using metal bond, resinoid bond, or vitrified bond. Alternatively, abrasives may be bonded on the magnetic material by coating or electro-plating. The above-described abrasives are used in the form of powder or in the form of being bonded on the magnetic material. Moreover, they are used by molding a mixture of abrasives, magnetic materials and non-magnetic materials such as ferrite or plastic. The barrel finishing by the machine of the present invention can perform under a normal pressure in the state without water or in the state where water or the other solution is added. In particular, the addition of water containing a surface active agent in a slight amount (about 0.1%) is effective to increase the finishing effect. According to the each respective kind of workpieces to be finished, the barrel finishing by the machine of the present invention under dry environment may perform good abilities. That is to say, there are some workpieces such as general parts of ordinary machine which may be finished effectively by the machine of the present invention without the use of any water or other solution. A container which contains workpieces to be finished and media is preferably made of non-magnetic material and of a closed type so as to prevent the media and workpieces from being exteriorly discharged during barrel finishing. For example, a synthetic resin made container provided with a lid may be used. The allowance in positional variation (for example, protrusion extent from the concentric circle) of each permanent magnet is specified within the range not to be affected by the adjacent permanent magnet (for example, in the range where the flow of the magnetic lines between the permanent magnets is not changed largely). For example, the positions nearly symmetric to each other relative to the center of the rotator means that the variation from the positions symmetric to each other relative to the center of the rotator is within a value being half the interval between the adjacent permanent magnets. The rotator is not necessarily formed of a circular disk, but hexagonal disk, a member having a plurality of arms radially projecting from the center boss, or a member provided with rings at the outer ends of said arms may be used. Moreover, there may be used a rotator in which a rotary shaft is provided at the center of a rectangular magnetic body, and permanent magnets are disposed symmetrically to each other relative to the rotary shaft. According to an embodiment of the present invention, since a rotator made of a magnetic material is used and a plurality of permanent magnets are rigidly mounted on said rotator, the magnetic force from said plurality of permanent magnets can be reinforced by about 20% or more as compared with the case where permanent magnets are disposed on the rotary plate made of non-magnetic material, thus improving the finishing ability and finishing efficiency. Moreover, since the permanent magnets are disposed such that magnetic forces are directed in the circumferential direction and inwardly and outwardly radial directions, contents in a container are allowed to flow irregularly and to be movable throughout in the container by the rotating magnetic field. Accordingly, abrasives functions against the workpieces in all of the directions can be caused, thus even if the workpieces have any complicated shapes, uniform surface finishing can be conducted. In an arrangement of permanent magnets on the rotator in which the permanent magnets are disposed such that the polarites of the magnetic poles facing the container are arranged asymmetrically the motions of abrasives caused by the rotation of rotator are complicated, and workpieces are irregularly moved, which is effective to uniformly finish workpieces. It becomes possible to eliminate the dead point at the central portion of the rotator, and hence to improve the finishing efficiency. In addition, since permanent magnets are rigidly mounted on a magnetic rotator, it becomes possible to reinforce the magnetic force by about 20% or more as compared with the case where they are rigidly mounted on a non-magnetic rotator, and hence to significantly improve the finishing performance and finishing efficiency. Those and other objects, features, and advantages of the present invention will become apparent from the following detailed description of several preferred embodiments that are shown in the accompanying drawings, in which: Fig. 1 is a plan view of a first embodiment of the present invention, with parts being partially cut-away; Fig. 2 is a front view of the first embodiment, with parts being partially cut-away; Fig. 3 is a side view of the first embodiment, with parts being partially cut-away; Fig. 4 is a diagrammatic front view of the first embodiment in use, showing workpieces and the like in a container; Fig. 5 is a plan view for illustrating the motions of workpieces and media in a container; Fig. 6 is a perspective view for illustrating the motions of workpieces and media in a container; Fig. 7 is a plan view for illustrating the motions of workpieces and media in a container of the prior art magnetic barrel finishing; Fig. 8 is a perspective view for illustrating the motions of workpieces and media in a container of the prior art magnetic barrel finishing; Fig. 9 is a view for illustrating the state that a container is placed in a finishing zone in the prior art magnetic barrel finishing; Fig. 10 is a plan view showing the arrangement of permanent magnets according to a second embodiment of the present invention; Fig. 11 is a plan view showing the arrangement of permanent magnets according to a third embodiment of the present invention; Fig. 12 is a plan view illustrating the moving state of abrasives in a container of the embodiment shown in Fig. 11; Fig. 13 is a plan view showing the arrangement of permanent magnets according to a fourth embodiment of the present invention; Fig. 14 is a plan view showing the arrangement of permanent magnets according to a fifth embodiment of the present invention; Fig. 15 is a plan view showing the arrangement of permanent magnets according to a sixth embodiment of the present invention; Fig. 16 is a plan view showing the arrangement of permanent magnets according to a seventh embodiment of the present invention; Fig. 17 is a plan view of an embodiment in which the outer adjacent permanent magnets are disposed along different concentric circles in the embodiment shown in Fig. 16. Fig. 18 is a plan view showing the arrangement of permanent magnets according to an eighth embodiment of the present invention; Fig. 19 ia a plan view of an embodiment in which poles N and S are disposed at portions different from each other in distance from the center of a rotary disk in the embodiment shown in Fig. 18; Fig. 20 is a plan view showing the arrangement of permanent magnets according to a ninth embodiment of the present invention; Fig. 21 is a front view of the embodiment shown in Fig. 20; Fig. 22 is an enlarged side view of an abrasive medium which can be used in the present invention with parts being partially cut-away; Fig. 23 is an enlarged cut-away side view of another abrasive medium which can be used in the present invention; and Fig. 24 is an enlarged cut-away side view of the other abrasive medium which can be used in the present invention. Embodiment 1 A motor 2 is vertically fixed in a housing 1, and a rotary disk 4 (as a rotator) made of a magnetic material (for example, an iron plate) is fixed to a shaft 3 of the motor 2. Disk-like permanent magnets 5 are rigidly mounted on the rotary disk 4 such that the poles of each magnet 5 are directed vertically (see Figs. 1 and 2). The permanent magnets 5 having the poles N and S being substantially the same number are irregularly disposed in such a manner as to be slightly spaced from each other for preventing the contact thereof. The permanent magnets 5 must be disposed in a good balance for preventing vibration when the rotary disk 4 is rotated. For example, they are disposed symmetrically relative to the center of the rotary disk 4 as shown in Fig. 1. The rotating magnetic field generated in the above-described construction must upwardly pass through a top plate 7. Accordingly, it is important to use the top plate 7 made of a perfectly non-magnetic material exerting no effect on the magnetic field. The top plate 7 is fitted to a stepped portion 8 of the housing 1. As shown in Fig. 4, a cylindrical container 11 (provided with closing lid 15) made of synthetic resin, in which workpieces 9 (for example, small sized metal parts) and media 10 in a suitable amount are put, is placed on the top plate 7. In the figure 4, reference numeral 16 indicates a finishing solution surface. In Fig. 1, reference numeral 12a indicates an ON switch; 12b is an OFF switch; 13 is a speed adjusting knob; and 14 is a timer. In this embodiment, the media 10(magnetic abrasives or a mixture of magnetic abrasives and non-magnetic abrasives) and the workpieces 9 are put in the cylindrical container 11 (see Fig. 4), and the cylindrical container 11 is placed on the top plate 7. The amount of the media 10 is preferably less than quarter the volume of the cylindrical container 11, and the amount of the workpieces 9 is preferably less than the amount of the media 10. The rotary disk 4 is rotated at a rotational speed of 500-4000 rpm through rotation of the motor. At this time, irregular alternating magnetic fields are generated by the permanent magnets, and the media 10 flows irregularly. The workpieces thus move throughout in the container, and as a consequence, even those workpieces having complicated shapes can be easily and uniformly finished. In this embodiment, as shown in Fig. 5, with respect to abrasives and workpieces, the radial flows (arrow 18) thereof are generated, other than the concentric flows (arrow 17) thereof; that is, as shown in Fig. 6, inward and outward flowing loops 20 thereof are generated, other than circumferential flowing loops 19 thereof. This eliminates the problem in which flows of abrasives and workpieces are not generated at the central portion of container 11, and accordingly, uniform finishing becomes possible even in the case where the cylindrical container 11 is placed at any position or in the case where a large volume of a cylindrical container having a diameter being substantially equal to that of the top plate 7 is placed. In the prior art, the diameter of a container disposed on a rotary disk must be less than half that of the rotary disk; however, in the present invention, such a large volume of a container can be used, which makes it possible to finish large size workpieces which have been conventionally impossible to be finished. In the case where a container having a diameter being the same as that of the container used in the prior art, the diameter of the rotary disk can be reduced, to thus make compact the whole size of the machine. In the container, workpieces and media are suitably moved between the outer peripheral side and the center side of the container, so that the workpieces can be more uniformly finished. Different complicated flows of workpieces and media can be generated by periodically changing the rotational direction of a motor at specified intervals of time. Namely, the flows are changed from the inside to the outside or from the outside to the inside, and thereby the portions of workpieces contacted with media are changed. This is due to the random arrangement of the permanent magnets. The workpieces are, therefore, fully finished in the all directions. In this embodiment, the same effect can be obtained even in the case where poles N and S of the permanent magnets 5 are replaced with each other. According to this embodiment, the magnetic force can be reinforced by about 20% or more as compared with the prior art machine in which permanent magnets are rigidly mounted on a non-magnetic disk, and thereby the finishing ability can be significantly improved. In this embodiment, water or other solutions may be added to the container 11 which contains media and workpieces 9. The water may contain an additive such as a surface active agent or rust preventive agent in a slight amount (for example, about 0.1%). In this case, the finishing ability can be further improved. Alternatively, barrel finishing can be conducted without adding any water or other solution. That is to say, only the media 10 and workpieces 9 are contained in the container 11, and barrel finishing is conducted under dry environment. In this case, good finishing ability can be also obtained. Embodiment 2 This embodiment shown in Fig. 10 is used for a small size finishing machine (for example, diameter of rotary disk: 70-200 mm) In the case where the rotary disk of magnetic material is rotated at a rotational speed of 1000-2400 rpm in the small size finishing machine, the following arrangement of permanent magnets is preferable for obtaining the good finishing efficiency. Three pieces of permanent magnets 30 are disposed at equal intervals along concentric circles 28, 29 around the center O of the magnetic rotary disk 27 in such a manner that two poles S and one pole N are disposed along the concentric circle 28, and two poles N and one pole S are disposed along the concentric circle 29. Moreover, the permanent magnets 30 on the concentric circles 28, 29 are disposed not to be positioned along the same radius line. For example, the radius lines 41, 42 of the rotary disk passing through the centers of the permanent magnets disposed along the concentric circles 28, 29 are shifted from each other by an acute angle (for example 15 to 60° ). According to this embodiment, the extremely large difference in the density of magnetic lines caused by the rotation of the magnetic rotary disk 27 can be eliminated, and thereby uniform finishing can be obtained. For example, an alternating change in poles (for example, N→S, S→N) is not generated, and consequently the motions of abrasives become more random, to thus achieve the improved finishing. In this embodiment, the same effect can be obtained even by replacement of the poles N and S of the permanent magnets with each other. Embodiment 3 This embodiment shown in Fig. 11 relates to the arrangement of permanent magnets which may be used for a large size finishing machine (for example, diameter of rotary disk: 200 mm or more). Permanent magnets 40 on a rotary disk 31 made of a magnetic material are disposed such that the centers thereof are arranged along four curves 36, 37, 38 and 39 spirally extending at equal intervals in the outer peripheral direction from the center of the magnetic rotary disk 31. The permanent magnets disposed along the spiral curve 37 are symmetric, relative to the center of the rotary disk 31, to those disposed along the spiral curve 39 which is disposed symmetrically to the spiral curve 37 relative to the center of the rotary disk 31.Also, the permanent magnets disposed along the spiral curve 36 are symmetric, relative to the center of the rotary disk 31, to those disposed along the spiral curve 38 which is disposed symmetrically to the spiral curve 36 relative to the center of the rotary disk 31. According to the arrangement of this embodiment, in the case where the area of the rotary disk 31 is partitioned into four zones by radius lines 32, 33, 34 and 35, each of the zones is not divided into either of poles N and S. That is to say, each of the zones contains both poles N and S as shown in Fig. 11. When the magnetic rotary disk 31 on which the permanent magnets are arranged as shown in Fig. 11 is rotated in the direction shown by the arrow 43 in Fig. 12, media and abrasives 45 in a container 44 placed on the top plate of the rotary disk 31 rotate in the direction shown by the arrow 46 in Fig. 12, and thereby excellent finishing effect can be obtained. In the arrangement of permanent magnets according to the embodiment shown in Fig. 11, the finishing efficiency of the surface finishing machine is not essentially changed even in the case where the positions of the permanent magnets are slightly shifted from each other; however, in the case where they are shifted from each other to the extent that the magnetic lines of poles N and S are changed, the finishing effect is changed. In an arrangement of permanent magnets according to an embodiment shown in Fig. 13, four pieces of the permanent magnets on the outermost side in the embodiment shown in Fig. 11 are omitted. As is apparent from Fig. 13, the permanent magnets 49 disposed such that the centers thereof are arranged along four of the spiral curves 36, 37, 38 and 39 are disposed along concentric circles 48, 50, 51, 52 and 53 around the center of the magnetic rotary disk 47. In an arrangement of permanent magnets of an embodiment shown in Fig. 14, four of the permanent magnets along the outermost side in the embodiment shown in Fig. 13 are omitted. Namely, eight of the permanent magnets (four pieces along the outermost side, and four pieces along the next inner side) are removed from those in the arrangement of the embodiment shown in Fig. 11. This is effective for the machine having the reduced size. Like the embodiment shown in Fig. 13, in this embodiment, the permanent magnets 62 having the centers disposed along four of the spiral curves 36, 37, 38 and 39 are disposed along the concentric circles 60, 61, 63 and 64 around the center of the rotary disk 59. An arrangement of permanent magnets according to an embodiment shown in Fig. 15 is a modification of the arrangement of the permanent magnets according to the embodiment shown in Fig. 13. Namely, at portions adjacent to the outermost permanent magnets disposed on the outermost sides of four spiral curves 36, 37, 38 and 39, that is, along the concentric circle 48, permanent magnets having the same poles are disposed. With this arrangement of the permanent magnets, the outer side magnetic fields are reinforced more than in the arrangement shown in Fig. 13, thus obtaining an increased magnetic fields. Accordingly, the excellent finishing efficiency can be obtained. In this embodiment, the permanent magnets are disposed along four of the spiral curves 36, 37, 38 and 39; however, the number of the spiral curves may be changed from 4 pieces to 3, 6 or 8 pieces. Embodiment 4 In this embodiment shown in Fig. 16, along a concentric circle 55 on the outer peripheral side of a rotary disk 54 made of a magnetic material, eight pieces of permanent magnets 56, 56 are disposed at equal intervals such that the poles thereof are arranged in the order of (N, N, S, S, N, N, S, S). Moreover, along a concentric circle 57 on the inner side, four pieces of permanent magnets are disposed at equal intervals such that the poles thereof are arranged in the order of (N, S, N, S). In this case, the centers (for example, O1, O2) of the permanent magnets along the inner and outer sides are preferably disposed along the different radius lines (for example, lines r1, r2) of the magnetic rotary disk 54. In the embodiment shown in Fig. 16, three pieces of the permanent magnets (one piece on the inner side, two pieces on the outer side) are substantially positioned at vertexes of a triangle 58. An arrangement of permanent magnets according to an embodiment shown in Fig. 17 is a modification of the arrangement of permanent magnets according to the embodiment shown in Fig. 16. Namely, the permanent magnets 56 on the outer side in the embodiment shown in Fig. 16 are divided into two groups, the one is indicated by 56 and the other is indicated by 56a, and the adjacent permanent magnets 56, 56a are disposed such that the centers thereof are arranged along different concentric circles 55, 55a. With this arrangement, the flows of media are changed between the cases where the magnetic rotary disk 54 is rotated in the direction shown by the arrow 72 and 73 in Fig. 17. Accordingly, by rotation of the rotary disk 54 connected to a transmission capable of being reciprocally rotated, thus improving the finishing efficiency. In this embodiment, the non-magnetic rotary disk of the known prior art barrel finishing machine on which permanent magnets are mounted, is replaced with the magnetic rotary disk. The present invention, therefore, is not limited to the number of the permanent magnets used, and is applicable for all of the known machines. Namely, as shown in Fig. 16, the area of the rotary disk 54 is partitioned into four zones and permanent magnets are regularly arranged in the zones. Each of the zones contains only pole N or pole S. Therefore, the motions of workpieces and media caused by the rotation of the magnetic rotary disk 54 become regular, like the known prior art finishing machine. However, since the machine of the present invention uses the magnetic rotary disk 54,replacing the non-magnetic rotary disk of the prior art finishing machine, a strong magnetic force can be obtained, so that relatively weak permanent magnets can be used for arranging and mounting them on the magnetic rotary disk 54. Also, in the barrel finishing machine of the present invention, the structure is simplified comparing with the prior art finishing machine. Embodiment 5 In this embodiment shown in Fig. 18, the area of a magnetic rotary disk 68 is partitioned into zones A, B, C and D by partitioning lines 69, 70 passing through the center of the rotary disk 68 made of a magnetic material, and permanent magnets 71 are disposed in these zones such that the poles thereof are arranged in order of (N, S, N, S) and that they are symmetric to each other relative to the center of the rotary disk 68. An arrangement of permanent magnets according to an embodiment shown in Fig. 19 is a modification of the arrangement of permanent magnets according to the embodiment shown in Fig. 18. In an embodiment shown in Fig. 19, the permanent magnets are disposed such that distances L1, L2 between the adjacent permanent magnets 71, 71a and the center O of the rotary disk are different from each other. In this case, the permanent magnets must be arranged so as to be held in a preferable dynamic balance upon rotation. With this arrangement, the flows of the media can be significantly changed depending on the rotational direction (such as arrows 74, 75 in Fig. 19) of the rotary disk 68. Consequently, by the reciprocating rotation of the rotary disk 68 connected to a transmission capable of being reciprocally rotated, the finishing efficiency can be improved. In this embodiment, the non-magnetic rotary disk of the known prior art barrel finishing machine on which permanent magnets are mounted is replaced with the magnetic rotary disk 68. The present invention, therefore, is not limited to the number of the permanent magnets used, and is applicable for all of the known machines. Namely, as shown in Fig. 18, the area of the rotary disk 68 is partitioned into four zones and permanent magnets are regularly arranged in the zones. Each of the zones contains only pole N or pole S. Therefore, the motions of workpieces and media caused by the rotation of the magnetic rotary disk 68 become regular, like the known prior art finishing machine. However, since the machine of the present invention uses the magnetic rotary disk 68 replacing with the non-magnetic rotary disk of the prior art finishing machine, a strong magnetic force can be obtined, so that relatively weak permanent magnets can be used for arranging and mounting them on the magnetic rotary disk 68. Also, in the barrel finishing machine of the present invention, the structure is simplified comparing with the prior art finishing machine. Embodiment 6 In this embodiment shown in Fig. 20, magnet connecting plates 67, for fixing different poles of permanent magnets 66 disposed in the inner and outer sides, are buried in a non-magnetic rotary disk 65 in such a manner as to keep the rotational balance. Each of the magnetic connecting plates 67 is partially or wholly buried in the non-magnetic rotary disk 65 or fixed on the non-magnetic rotary disk 65. The other permanent magnets 66 are rigidly mounted on the non-magnetic rotary disk 65 without magnetic connecting plates 67 as shown in Fig. 20 and Fig. 21. In each case, the upper surfaces of all of the permanent magnets are preferably adjusted at the same level. An iron plate, or other ferromagnetic plates,may be used as the magnetic connecting plate 67. The presence or absence of the magnetic connecting plates causes about 20% difference in the strength of magnetic force produced by the permanent magnets. That is to say, the magnetic force which is produced by the permanent magnets fixed on the magnetic connecting plates 67 is reinforced by about 20% or more as compared with the magnetic force produced by the other permanent magnets which are rigidly mounted on the non-magnetic rotary disk 65 witout magnetic connecting plates 67. Thus caused difference in the strength of magnetic force is effective to form irregular magnetic fields under the rotation of the non-magnetic disk 65 and hence to impart complicated motions to magnetic abrasives. This makes it possible to easily and uniformly finish workpiece having relatively complicated shapes. Although the present invention has fully been described by referring to the particular preferred embodiments of the present invention, it should be understood that various changes and modifications may be made without departing from the scope of the appended claims.

Claims: A magnetic barrel finishing machine comprising: a container (11) for containing workpieces to be finished as well as an abrasive medium comprising magnetic material; a rotator (4; 27; 31; 68) arranged under the container (11), with a gap between the rotator and the base of the container; and a plurality of permanent magnets (5; 30; 40; 71) rigidly mounted on the rotator (4; 27; 31; 68), each magnet having a pole (N or S) facing the base of the container (11), the magnets being spaced apart and arranged so as to provide magnetic lines of force acting circumferentially, radially inwardly, and radially outwardly; characterised in that the rotator (4; 27; 31; 68) is made of magnetic material which connects the magnets (5; 30; 40; 71). A magnetic barrel finishing machine as claimed in claim 1, wherein poles of opposite polarity (N,S) facing the base of the container (11) are arranged asymmetrically relative to the axis of rotation of the rotator. A magnetic barrel finishing machine as claimed in claim 1, wherein the number of north poles equals the number of south poles, and the magnets are arranged substantially symmetrically relative to the axis of rotation. A magnetic barrel finishing machine as claimed in claim 1, wherein the magnets (5) are disposed along three concentric circles (6a-c) around the axis of rotation of the rotator (4) in such a manner that three poles of first polarity and three poles of second polarity are disposed at substantially equal intervals along the outermost concentric circle (6a) substantially symmetrically relative to the axis of rotation, two poles of the first polarity are disposed along the intermediate concentric circle (6b) substantially symmetrically relative to the axis of rotation, and two poles of the second polarity are disposed along the innermost concentric circle (6c) substantially symmetrically relative to the axis of rotation. A magnetic barrel finishing machine as claimed in claim 1, wherein the magnets (30) are disposed along a plurality of concentric circles (28,29) around the axis of rotation of the rotator (27), and the centers of the magnets at least along the adjacent concentric circles are arranged on different radius lines of the rotator. A magnetic barrel finishing machine as claimed in claim 5, wherein the magnets (30) are disposed such that one pole of first polarity and two poles of second polarity are arranged at substantially equal intervals along an inner concentric circle (28), and two poles of the first polarity and one pole of the second polarity are arranged at substantially equal intervals along an outer concentric circle (29). A magnetic barrel finishing machine as claimed in claim 1, wherein the magnets (40) have centers disposed along curves (36-39) spirally extending at substantially equal intervals in the outer peripheral direction from the axis of rotation of the rotator (31), and the magnets (40) disposed along one spiral curve (e.g. 36) are substantially symmetric, relative to the axis of rotation, with respect to those disposed along another spiral curve (38) which is substantially symmetric with respect to the said one spiral curve (36) relative to the axis of rotation. A magnetic barrel finishing machine as claimed in claim 7, wherein four said curves (36-39) spirally extend at substantially equal intervals and the magnets (40) are arranged along the curves (36-39) such that sets of magnets with poles in the order of N-N-S-N outwards alternate with sets of magnets with poles in the order of S-S-N-S outwards A magnetic barrel finishing machine as claimed in claim 7, wherein four said curves (36-39)spirally extend at substantially equal intervals, and the magnets (49) are arranged along the curves (36-39) such that sets of magnets with poles in the order of N-S-N outwards alternate with sets of magnets with poles in the order of S-N-S. A magnetic barrel finishing machine as claimed in claim 7, wherein four said curves (36-39) spirally extend at substantially equal intervals and the magnets (62) are arranged along the curves (36-39) such that sets of magnets with poles in the order N-S outwards alternate with sets of magnets with poles in the order of S-N. A magnetic barrel finishing machine as claimed in claim 1, wherein the magnets have centers disposed along curves (36-39) spirally extend at substantially equal intervals in the outer peripheral direction from the axis of rotation of the rotator; the magnets disposed along one spiral curve (e.g. 36) are substantially symmetric, relative to the axis of rotation, with respect to those disposed along another spiral curve (38) which is substantially symmetric with respect to the said one spiral curve (36) relative to the axis of rotation; and near the outermost magnet (82) of each spiral curve, a permanent magnet is disposed having the same pole facing the base of the container. A magnetic barrel finishing machine as claimed in claim 11, wherein there are four said curves (36-39), and an arrangement of the poles in the order of N-S-N outwards alternate with an arrangement of the poles in the order of S-N-S. A magnetic barrel finishing machine as claimed in claim 1, wherein the magnets (56) are disposed along inner and outer concentric circles (57,55) around the axis of rotation of the rotator (54) in such a manner that two north poles and two south poles are alternately disposed at substantially equal intervals along the inner circle (57) and four north poles and four south poles are alternately disposed at substantially equal intervals along the outer circle (55); the magnets are disposed on the inner and outer concentric circles such that the centers thereof are not positioned on the same radius line; and poles of the same polarity face the base of the container in each of four zones partitioned by imaginary partitioning lines passing through the axis of rotation. A magnetic barrel finishing machine as claimed in claim 13, wherein the eight magnets disposed along the outer concentric circle have the centers of the adjacent magnets (56,56a) disposed on concentric circles (55,55a) having different diameters respectively. A magnetic barrel finishing machine as claimed in claim 1, wherein the magnets (71,71a) are arranged in each of four zones (A-D) of the rotator partitioned by imaginary partitioning lines passing through the axis of rotation; the magnets (71,71a) in the respective zones are disposed substantially symmetrically relative to the axis of rotation in such a manner that the poles facing the base of the container are in N-S order; and the distance (L 1 ) between one set of symmetrically disposed magnets (71) and the axis of rotation is different from the distance (L 2 ) between another set of symmetrically disposed magnets (71a) and the axis of rotation. A magnetic barrel finishing machine comprising: a container (11) for containing workpieces to be finished as well as an abrasive medium comprising magnetic material; a rotator (65) arranged under the container (11), with a gap between the rotator and the base of the container; and a plurality of permanent magnets (66) rigidly mounted on the rotator (65), each magnet having a pole (N or S) facing the base of the container (11), the magnets being spaced apart and arranged so as to provide magnetic lines of force acting circumferentially, radially inwardly, and radially outwardly; characterised in that the rotator (65) includes a plurality of connecting plates (66) made of magnetic material, each of which is adapted to fix spaced-apart magnets (66) having different poles facing the base of the container, at a specified interval, other spaced-apart magnets (66) being fixed to parts of the rotator made of non-magnetic material.

Inventors: IMAHASHI TAKAHIRO, IMAHASHI, TAKAHIRO
Applicants: IMAHASHI MFG CO LTD, IMAHASHI MFG. CO., LTD.
Application year: 1995
Main classification: B24B1
IPC codes: B24B31, B24B1