Patent GB-938437-A (GB)
Title: Automatic turret drill
IPC: G05B19/37
Filed: 1961-07-05
Abstract: 938,437. Numerical control systems. CINCINNATI MILLING MACHINE CO. July 5, 1961 [Sept. 6, 1960], No. 24257/61. Class 38 (6). [Also in Group XXII] An automatic turret drill includes a manually adjusted store in which the different distances between the tips of each of the 6 turret mounted tools and a datum line just above the workpiece can be set. The entire numerically controlled system for the machine tool is also disclosed, in which a punched tape carries information regarding the X and Y co-ordinates of each hole in the workpiece, the depth of each hole, the selection of the appropriate tool in the turret, the selection of the desired rotational speed of the tool out of the 16 available, the selection of the desired tool feed rate out of the 100 available, and the selection of either a drilling or a tapping sequence of operations (i.e. whether the tool is pulled out or screwed out). The sequence is determined by a system of electromagnetic relays, Figs. 14a ... 14k (not shown). Tape reader.-The information listed above is recorded sequentially in binary code on a seventrack punched tape. Information for one hole in the workpiece occupies 26 lines, and is read line-by-line by feeler contacts which control latched relays forming a temporary store. A 26-position multi-bank master stepping switch 21 acts as a distributer and advances as the tape is read. Binary/decimal conversion is by a relay " tree." Tool selection.-The tool select signal is applied by the distributer 21 to a 6-position, multi-bank, stepping switch 26, which homes on to the contact marked by the particular tool select signal. Other banks of contacts on switch 26 selectively energize three solenoids, which, Fig. 4 (not shown), cause an hydraulic servomotor 70 to index the tool turret 63. Yet another bank of contacts on switch 26 energize the appropriate bank of manually operated tool length selector switches 71. There are six banks of these switches, one for each tool, each bank having four switches for inches down to thousandths of an inch. These in turn mark the contacts of four more sets of stepping switches. which select tool length analogue voltages from multi-tapped transformers 74, Fig. 8 (not shown). The analogue voltages are such as to cause the tool to advance until the tool tip is just above the workpiece; further movement then being determined by the hole depth signal. X and Y axis control.-Decoded tape signals are applied by the distributer 21 to stepping switches which provide coarse and fine sine and cosine signals from multi-tapped transformers 22, 23. These command signals control X and Y axis hydraulic servomotors 29, 30 by conventional resolver systems, Fig. 5 (not shown). Hole depth.-The hole depth command signal is obtained from transformers 27 similarly the X and Y commands. The hole depth resolver signals are added trigonometrically to the tool length sine and cosine signals by circuits 77, Figs. 8 ... 10 (not shown). As the drill head 62 descends, it drives a resolver 80, Fig. 13 (not shown), the output of which is compared at 75 with the depth command signal, and a feed clutsh. 52 12 (not shown), is disengaged when the position error is zero. A phasesensitive rectifier 81 determines the direction of the feed movement. Spindle speed.-A reversible two-speed, electric motor 46 drives the tool through a gear-box 47, Fig. 1 (not shown), the ratios of which are selected by electromagnets. These are selected by a multi-bank stepping switch 24, the setting of which is determined by the programme tape through the distributer 21. Spindle feed.-The feed rate, in terms of inches per spindle revolution, is read from the tape, and a multi-bank stepping switch selects the required tappings on a transformer 25, Fig. 12 (not shown). The transformer 25 is energized from a tachometer generator 48 driven by the spindle drive motor 46 so that the feed per revolution remains constant. The resultant signal is amplified and compared with the output of a second tachometer generator 50 to control the speed of a reversible 2-phase " pacer motor 49 which therefore runs at a speed proportional to the required feed rate. The speed of the pacer motor controls the speed of an hydraulic motor 59 which actually moves the drill head, through the feed clutch 52 and a resolver system 53, 55, 54, Fig. 3 (not shown), which enables a manual signal to be introduced.