| 摘要 |
947,729. Machine tool details. BIRFIELD ENGINEERING Ltd. Aug. 28, 1962 [Aug. 29, 1961], No. 31014/61. Heading B3B. In a work-holder comprising a grooved member 8 arranged coaxially with a ball-cage member 13 which is adapted to receive a workpiece, a ring of balls 15 engaging the corresponding grooves in the member 8 and being retained in the cage member by a flat spring 17, the grooves are so formed that the longitudinal axes thereof lie on a conical surface coaxial with the members 8 and 13 and means are provided to produce relative axial movement of said members so that the grooves engage the balls with a wedging action to urge them away from the grooved member to the gripping position. The work-holder is mounted in the sleeve 1 of an indexing head rotatably mounted as by bearings 2 in the body of a machine 3. The indexing head comprises a draw sleeve 19 and indexing sleeve 1, the sleeve 1 being axially fixed. The grooved member 8 is bolted to the flange 4 of the indexing sleeve 1. The draw sleeve 19 is connected to the rear end of the cage member 13 by a claw coupling 25, 26, the other end of the sleeve 19 being screwed to the rear end of the piston-rod 6 of a fluid-pressure piston and cylinder assembly. A ring of return springs 20 urges the piston 6 and hence the cage member 13 forwardly to the non- gripping position. The grooves are of elliptical cross-sectional shape so that each ball has two areas of contact with the flanks of the corresponding groove. The pressure angle subtended by the two areas at the centre of the corresponding ball is of the order of 60 degrees. |
