| 摘要 |
980,851. Numerical control of machine tools. D. SCIAKY. Dec. 13,1960 [Dec.24, 1959], No. 42796/60. Heading G3N. [Also in Divisions G4 and H2] The worktable of a drilling machine is moved from point to point by electric motor driven leadscrews which carry apertured discs so that rotation of the leadscrews produce incremented pulses from photo-cells. These pulses are counted until they approach a number pre-selected either manually or by a binary coded punched tape when the speed of the leadscrew is reduced. The counting is completed on an auxiliary counter and the motor is then stopped. The work-table 10, is movable in two directions at right-angles by leadscrews 11, 12 driven by motors 15, 75 through clutches 16, 76. Considering only the control of leadscrew 11, as the other is identical, a disc 17 with two rows of apertures, is secured to the leadscrew and controls a pair of photo-cells 21, 22 and the two valves 24, 25 of a multivibrator so that an outer aperture switches the multivibrator to produce a pulse and the inner aperture which follows, resets it. The pulses may alternatively be generated electro-magnetically. The pulses are applied to a main counter consisting of five cold-cathode counter tubes 35, 36, 37, 38, 39 which, with transfer networks, count units, tens, hundreds &c. The cathodes of each counter tube can be selectively connected to an undisclosed coincidence circuit 50 which produces an output when the selected count has been reached. The selection can be made either manually, or Fig. 6 (not shown) by diode gating networks-one network per tube-each controlled by four change-over switches. The switches are actuated by a punched tape 34 having 5 decimal ranks each in standard four digit binary code. The motor 15 runs at full speed, energized by a control 59 because a thyratron 56 has been fired by a sequence circuit 52. An output from the coincidence circuit momentarily cuts off a valve 58 which extinguishes thyratron 56 and fire a thyratron 57. This causes the control 59 to run the motor slowly. The change of grid voltage when thyratron 56 is extinguished opens a gate 31 to admit pulses from the multivibrator 24, 25 to an auxiliary counter consisting of 3 cold-cathode counter tubes 65, 66. 69. This is always reset to a pre-determined number. When the auxiliary counter has counted back to zero an output signal is applied to momentarily cut off valve 58, which extinguishes thyratron 57 and fires a thyratron 55 to disengage clutch 16 through a control 72. A circuit 52 now causes the drilling operation to be carried out, the tape recorder head 53 to be lifted out of contact with the tape, the punched tape 34 to move on, and the reader head to re-engage the tape. Completion of the drilling operation is said to cause the next positioning cycle to commence |
