Abstract: A spindle motor comprises a stationary member, a rotor rotatably mounted by bearing means to the stationary member for holding a recording disk, a rotor magnet mounted to the rotor, and an armature mounted to the stationary member to seat opposite to the rotor magnet. In particular, the rotor includes a shaft, a hub extending outwardly and radially of the shaft, and a flange provided circumferentially of the hub which are integrally formed from a metal plate by plastic deformation process.

Abstract: A projection welding method which comprises providing in either one of a first member and a second member to be welded a plurality of projections projecting toward the other member, supplying a current between the first and second members to melt the plurality of projections, and welding the first and second members. The plurality of projections are composed of projections having a plurality of kinds with different heights. Furthermore, with reference to the plurality of projections, concave grooves in which a molten product flows are provided.

Abstract: A low airflow hard disk apparatus comprises a base, a cover member, a rotational portion disposed in a disk chamber, a hard disk held by and rotatable with the rotational portion, a first projection portion disposed on the lower surface of the cover member and facing toward the upper surface of the hard disk, and a second projection portion disposed on the upper surface of the base and facing toward the lower surface of the hard disk. The first and second projection portions, preferably radially extending fins, prevent an air flow from generating by the rotation of the hard disk.

Abstract: A spindle motor having a housing, a hub member rotatable relative to the housing, a bearing means disposed between the housing and the hub member, a rotor magnet mounted on the hub member, and a stator disposed in a facing relationship with the rotor magnet. The hub member includes a supporting wall portion, which cooperates with the stator to constitute an air seal structure. A magnetic fluid seal means is provided at a position outward of the bearing means, and includes a conductive plate for grounding static electricity. The bearing means is comprised of a radial ball bearing, which includes certain improvement.

Abstract: A spindle motor having a housing, a hub member rotatable relative to the housing, a bearing disposed between the housing and the hub member, a rotor magnet mounted on the hub member, and a stator disposed in a facing relationship with the rotor magnet. The hub member includes a supporting wall portion, which cooperates with the stator to constitute an air seal structure. A magnetic fluid seal is provided at a position outward of the bearing, and includes a conductive plate for grounding static electricity. The bearing is comprised of a radial ball bearing, which includes certain improvement.

Abstract: An annular recess is formed in a base which constitutes a disk chamber, and an armature constituting a spindle motor for driving a hard disk and composed of a stator core and a stator coil and a field device composed of a rotor yoke and a rotor magnet are substantially accommodated in the annular recess. As a result, the height of a portion of a hard disk apparatus which constitutes a radial directional gap type spindle motor can be minimized and therefore the overall height of the apparatus can be minimized. Hence, the thickness and the size of a computer apparatus or the like which includes the hard disk apparatus can be reduced.

Abstract: A magnetic disk drive device has a spindle motor for rotatingly driving magnetic disks in a predetermined direction, and a clamp member for mounting the disks on the spindle motor. The spindle motor has a hub rotatably supported through bearings and having a portion for mounting the magnetic disks, a rotor magnet carried by the hub, a stator disposed to oppose to the rotor magnet, and magnetic fluid seal arrangement for preventing scattering of lubricant from the bearing means. The magnetic disk drive device further has a magnetic shield disposed on the radially outer side of the magnetic fluid seal arrangement. One of the bearings rotatably supporting the hub may be charged with a lubricant having a comparatively low viscosity, while the other bearing may be charged with a lubricant having a comparatively high viscosity.

Abstract: A spindle motor has a stationary member, a hub rotatable relative to the hub, a stator mounted on the stationary member and a rotor magnet carried by the hub and facing the stator. The hub is provided with female-threaded holes for receiving screws for fixing a disk clamp member to the hub, and also with communication holes communicating with the female-threaded holes and opening to the exterior of the hub. The hub further has a seal member for sealing the openings of the communication holes. The hub is rotatably supported by the shaft member through a pair of bearings. The stator has a stator stack of a stack height or thickness greater than the spacing of the pair of bearings.

Abstract: A spindle motor comprising a fixed shaft member, a hub member rotatably supported by the fixed shaft member through bearings, and a magnetic-fluid type sealing mechanism arranged between the fixed shaft member and the hub member. The magnetic-fluid type sealing mechanism has a rotary member mounted on the hub member, a stationary member mounted on the fixed shaft member, and a magnetic fluid holding device for holding a magnetic fluid. The magnetic fluid holding is secured to the annular mounting portion of the stationary member. The magnetic fluid holding device and the annular portion of the rotary member cooperate with each other in holding the magnetic fluid therebetween.

Abstract: Separation and recovery of dibenzofuran of high purity is accomplished by distilling a coal tar fraction having boiling point range of 220.degree. to 300.degree. C. thereby producing a dibenzofuran fraction having a dibenzofuran content of not less than 30% by weight, a dibenzofuran/acenaphthene molar ratio of not less than 1.3, and a fluorene/dibenzofuran molar ratio of not more than 0.05, then introducing the dibenzofuran fraction obtained as described above into a continuous crystallization purification unit provided with a cooling zone for crystallization of the feed, a heating zone for melting the purified crystals, and a refining zone for enabling crystals being transferred from said cooling zone to said heating zone to come into counter current contact with a mass of molten crystals midway along the path between said two zones, and subjecting the dibenzofuran fraction to continuous crystallization purification therein.