| 摘要 |
328,127. Clark, G. M., (Keller Mechanical Engineering Corporation). May 7, 1929. Milling-machines.-In a milling or other machine in which a rotary cutter 12 operates upon a workpiece carried on a reciprocating table 1, electromagnetic means is provided for intermittently interrupting the feed of the table when the load on the cutter reaches a predetermined amount. The cutter 12 is rotated from an electromotor 16 connected to leads 17, 18. In series with the lead 17 is an electromagnet 28 cooperating with an armature 26. The table 1 is fed by a leading-screw 2 rotated from an electromotor 11 through magnetic clutches 6 co-operating with discs 7 on a shaft 5. Reversal of the table is controlled by a tumbler switch 19. In operation, when the load on the cutter 12 reaches a predetermined amount the current in the lead 17 rises' and the armature 26 opens a contact 25 to break circuit through the clutch. The feed is momentarily stopped and the resulting drop in the current in the lead 17 allows the contact 25 to be closed. The variation of current through the magnet 28 causes a vibratory motion in the armature 26 and a reduced speed of the leading screw. In a modification, Figs. 3 and 4, not shown, for the magnet 28 and the motor 16 is' substituted a transmission dynamometer in which overloading of the cutter causes depression of an arm to open the contact 25. In both forms means is provided for adjusting the load at which the feed is interrupted. |
