| 摘要 |
PCT No. PCT/JP96/03656 Sec. 371 Date Oct. 27, 1997 Sec. 102(e) Date Oct. 27, 1997 PCT Filed Dec. 13, 1996 PCT Pub. No. WO98/25729 PCT Pub. Date Jun. 18, 1998There are provided a pair of positioning engaging members (27) which are engageable with or disengageable from each other between a base table (10) and a turret (11), and the turret (11) is prevented from rotating when the positioning engaging members (27) engage with each other. The turning of a ball screw (21) or a nut (25) is changed to a linear motion of the turret (11) by a screw feed mechanism comprising the ball screw (21) and nut (25) for performing engagement and disengagement between the positioning engaging members (27). The screw feed mechanism is driven by a first motor (24), and the turret (11) is indexing by a second motor (32). When the second motor (32) is driven to index the turret (11), the first motor (24) rotates in a given rotating direction with a given ratio of rotating speed relative to the rotation of the second motor (32) so as to make the relative turning between the ball screw (21) and nut (25) of the screw feed mechanism zero, thereby preventing the linear motion of the positioning engaging members (27). |
