| 摘要 |
934,316. Automatic force control. CINCINNATI MILLING MACHINE CO. Feb. 20, 1962 [March 6, 1961], No. 6474/62. Class 38 (4). [Also in Group XXII] The force on a machine driven tool, e.g. a tap or a reamer, is controlled by adjusting the feed rate in accordance with small axial deflections of the tool against a spring. As shown, a tap 9 is carried in a holder 36 slidable in a sleeve 37 mounted in a rotating head 8, movement being limited by two pins 46 engaging slots 45. The pins are urged apart by a spring 49 so that the tap takes up the central position shown, and the initial force of the spring is greater than that required to start the tap. The work 21 is fed to the tap by an hydraulic motor 18, and an axial force in either direction greater than that of the spring results in a deflection of the tap holder, which is transmitted by a rod 31 to the movable core of a differential transformer 30. The resulting output causes a torque motor 82 to operate a fluid valve 83 to run the feed motor 18 in a direction to reduce the displacement; thus the workpiece is fed to the tap at such a speed that the axial displacement of the tap and hence the force on it is a minimum. At first, a voltage derived from a transformer 69 and adjusted by a potentiometer 74 is applied by closure of a direction switch 72 or 73 to bring the work to the tap. The switch may then be opened, tapping proceeds as above, and when the required depth is reached rotation of the tap is stopped thereby causing the feed to stop also. Reversing the rotation causes reversal of the feed motor and so the tap is withdrawn. The arrangement also causes the feed to stop if the tap is not aligned with the hole. The differential transformer may be replaced by a potentiometer (Fig. 6, not shown), or by a double-throw switch or other arrangement. |
