| 摘要 |
<p>PURPOSE:To obtain a contact detector to sense the contact of a tool with a work by detecting the potential difference which occurs before and after the electrical resistance of bearings on the basis of the current flowing along a secondary current path when two objects come into contact with each other. CONSTITUTION:In a circular groove 10a provided in a bearing housing 10a concentric with a spindle 11 is fitted an induction coil 35 comprising an iron core 35a wound with a coil 35b by a pressure plate 36, thereby to produce a magnetic flux surrounding the spindle 11. In the axial direction of the spindle is formed a current path 38 in which a secondary current is induced. The potential difference between the spindle 11 and spindle head 10 which occurs as a result of a voltage drop due to the electric resistance R of bearings 12, 13, 14 is detected by conductors 33, 34 connected via insulating bushes 30, 31, 32. When a tool T comes into contact with a work W, a secondary current begins to flow and consequently a potential difference is caused and this potential difference is detected to sense the contacting condition. The rate of change in the potential difference is so great that the contact can be sensed with a high sensibility by the above arrangement.</p> |
