| 摘要 |
1302333 Grinding; headstocks TOYODA KOKI KK 19 April 1971 [10 March 1970] 22855/71 Headings B3D and B3T A headstock device for a grinding-machine is usable selectively as a dead-centre drive or live centre drive for the spindle 7 of the machine. The device has a base 1 in which is secured a sleeve 2 carrying bearings 4 for a belt-driven pulley 3 bolted to a transmission member 6. The spindle 7 is rotatably supported by bearings 14a, 14b, 15a, 15b in the sleeve and at its outer end receives a centre 8. A notch 7a is formed in the spindle and houses a pawl 9 which is movable about a pivot 10 from the position shown when the device is used as a dead centre drive to a position engaging a notch 6a in the transmission member 6 when the device is used as a live centre drive. During dead centre driving, a dog is fixed to a face-plate 11 for driving the workpiece and a seal 12 is mounted at the end of the spindle. During live centre driving, the faceplate is replaced by a chuck (13, Fig. 2, not shown). The bearings 14a, 14b, 15a, 15b are preloaded by a spring 16 adjusted by a nut 18. The preload on the bearings is increased for dead centre drive by axial thrust on the spindle 7 being applied by a clamping mechanism. The mechanism has inner and outer clamping members 27, 28 formed with tapered faces 27a, 28a, the outer member being mounted on a screwthread on a member 23 secured to the sleeve 2 and connected to a ring 29 having a handle 35, and the inner member being connected to the end of the spindle. When the ring 29 is rotated to cause the tapered faces to engage, the spindle acts through a shoulder 7b to apply the axial thrust to the preloaded bearings to increase the stiffness of the bearings when the spindle does not rotate during dead centre driving. When the tapered surfaces are disengaged, the bearings are only bonded by the spring 16 during rotation of the spindle for line centre driving. The disengaging of the tapered surfaces is effected automatically when the spindle is rotated after retraction of the latch 9 into the notch 7a. |
