Abstract: A spindle apparatus comprises a rotary body and at least a pair of magnetic bearings for levitating the rotary body by magnetic forces. A combined motor and magnetic bearing device is disposed between the magnetic bearings for imparting a rotational torque to the rotary body and for positionally controlling the rotary body by magnetic forces. A control circuit outputs and exciting current to the magnetic bearings and the combined motor and magnetic bearing device and for makes an adjustment of the exciting current of the magnetic bearing and the combined motor and magnetic bearing device to hold the rotary body afloat in a predetermined position.

Abstract: An armature stator comprises an iron core and a coil directly mounted on the iron core. The coil is composed of wound electric wire which has a coating comprising an inorganic material, such as ceramic. A bonding material of the inorganic material is formed over the coil and iron core for filling any gaps and adhering the coil and iron core together into a unitary structure. To improve the reliability of the coil, after the electric wire is wound to form the coil, a filling material comprised of the inorganic material is formed over the coil by vacuum impregnation, and then sintered so as to repair defects in the coating disposed on the electric wire. After the bonding material is formed over the coil, which is directly mounted on the iron core, it is cured under high temperature. The armature stator thus constructed can be used with high reliability in high temperature and high vacuum applications.

Abstract: An apparatus for detecting machining conditions in a machine tool has a magnetic bearing for magnetically supporting a work spindle or a tool spindle. An exciting current detector is provided for detecting an exciting current of an electromagnet of the magnetic bearing. The exciting current corresponds to various machining conditions including the conditions when the machine tool starts operating, the tool contacts the workpiece to follow various unfinished faces, and a machining face condition of the workpiece during machining. The detection signals from the exciting current detector are inputted to a plurality of frequency band pass filters to discriminate the machining conditions. Comparators are provided to compare the output signals from the frequency band pass filters with a predetermined set of reference values, and comparative judgment signals are inputted to a control unit, thereby controlling the machine tool to automatically perform appropriate machining operations.

Abstract: A machining apparatus having a main spindle supported by magnetic bearings which controls machining conditions by controlling electric current values flowing in electromagnets according to predetermined conditions, thereby obtaining an optimum machining condition and thus improving accuracy and machining efficiency. The machining apparatus comprises a spindle having a tool at its one end, electromagnets for radially and axially supporting the spindle by magnetic force without contact to the spindle, position detecting means for detecting radial and axial positions of the spindle, control means responsive to outputs from the position detecting means for controlling current flowing in the electromagnets, current measuring means for measuring current values flowing in at least one of the electromagnets, and machining control means for controlling machining conditions by controlling current values at the electromagnets according to the measured current values.

Abstract: A lubricating and cooling system for a spindle bearing assembly in which the spindle is rotatably mounted in bearings in a closed spindle housing comprises means for supplying lubricating oil to the bearings and cooling oil to the bearings and spindle, the lubricating admission passages and cooling oil admission passages being separate from one another and being supplied from separate lubricating oil and cooling circuits so that the lubricating and cooling are controlled individually and selectively.

Abstract: A preloaded bearing comprises a spindle which is rotatably supported in the bore of a housing by a pair of ball bearings near one end of the bore and a second pair of ball bearings near the other end of the bore. One pair of ball bearings is axially slidable in the bore and is preloaded by a compression spring acting between the bearings and an abutment in the bore. The spindle is driven by a belt which runs on a pulley at one end of the bore and thereby subjects the spindle to a radial load. A recess is provided in the wall of the bore on the radially loaded side of the slidable pair of bearings and pressurized fluid is supplied to the recess so as to exert fluid pressure in a direction opposing the load applied by the belt. The pressurized fluid is preferably lubricating oil and is supplied not only to the recesses but also to the bearings in order to lubricate them.

Abstract: A sealing structure for protecting the bearing of a high speed spindle such as a grinding wheel spindle comprises a bearing cover having an opening that receives and closely surrounds the spindle adjacent the bearing. Three annular recesses provided in the opening of the bearing cover open inwardly to the spindle. An annular channel in the bearing cover radially outwardly of the opening is supplied with pressurized lubricating fluid and is connected by angularly spaced passages with the first and third of the annular recesses so as to supply the pressurized lubricating fluid to them, while the second of the recesses located between the other two is provided with exhaust passages so as to carry off the pressurized lubricating fluid together with any chips or other impurities entering between the spindle and the opening in the bearing cover. The annular channel in the bearing cover is also connected with the bearing so as to supply the pressurized lubricating fluid to the bearing.

Abstract: A spindle assembly has a rotatable spindle which is electrically insulated from its housing by means of a moulded synthetic resin layer surrounding bearing holders. Electric current for effecting electrolytic grinding is supplied by a brush member which is in contact to the rear end of the spindle, the contact portion of the spindle and the brush having air circulating pathes for cooling and ejecting out powdered-brush-material and have radiating surfaces exposed to cooling air flow.

Abstract: A spindle device has pre-loaded anti-friction bearings which are so lubricated with oil jet accelerated through jet nozzles facing thereto that very high speed rotation with lower levelled vibration is permitted for the spindle.The spindle assembly has a rear bearing holder longitudinally slidable in the housing for pre-loading and cooling oil flows in the bearing holder. The spindle assembly further has a high frequency electric motor therein and is sealed up against dust penetration from outside.Air or oil vapor is prevented from staying in the sealed spindle assembly by a gas outlet which is provided in the assembly. Jetted oil toward the bearings and bearing holder cooling oil are recollected through a suction pump into a reservoir, and are fed by a pressurizing pump from the reservoir to the spindle assembly. Oil is there cooled by a cooling device.The circulating oil temperature and oil amount are detected by sensors to be observed.