Patent GB-1422614-A (GB)
Title: Machine tools
IPC: B23B47/22
Filed: 1973-03-05
Abstract: 1422614 Boring, drilling and tapping machine CARLTON MACHINE TOOL CO 5 March 1973 10534/73 Headings B3B B3C and B3N A machine tool for boring, drilling and tapping operations comprises a head (26) slidable on a column (25, Fig. 1, not shown) and carrying a tool spindle 27 traversable by a feed rack and pinion 52, 51, Fig. 3. Pinion 51 is drivable by two alternative parallel drives; a first including hydraulic motor 64 and clutch 66 and a second including multi-speed gear-box 56, worm-gear 36, 37 and clutch 38a-which as shown in Fig. 3, is connected to pinion 51 via gearing 42-45, 62, 50, 63. A depth sensor and feedback arrangement for setting, sensing and controlling the depth of cut includes sensor 68 with, for example, fine tooth pinion 69 engaging rack 70 on the spindle. In the particular arrangement a third clutch 159 is also provided, control of clutches 159, 38a is hydraulic by solenoid valves 85, 86, Fig. 4, and direction of flow of fluid to hydraulic motor 64 by solenoid valve 90. Clutch 66 is electrically operated. Pressure sensitive switch 93 detects changes of pressure in motor 64, e.g. on contact of the tool with the workpiece. Electric control means such as tape control, not shown, interrelate master control signals with the sensor signals and operates the valves and clutch 66. Drilling.-Clutch 66 is engaged and clutch 38a disengaged and spindle 27 is rapidly traversed by motor 64 until the tool contacts the workpiece whereupon pressure switch 93 operates and causes clutches 38a and 159 to engage and clutch 66 to disengage. Feedback depth sensor 68 is actuated and the rate of feed is determined by gear-box 56. At the preset depth device causes clutches 38a, 159 to disengage, clutch 66 to engage and operates solenoid valve 90 to run motor 64 in reverse and retract the spindle. Boring.-Clutches 38a, 159 are disengaged and clutch 66 engaged to advance the spindle rapidly with its position monitored by the sensor 68. At a preset position clutches 38a, 159 are also engaged and valve 90 operated to run motor 64 in reverse to limit gear backlash but allow tool advance. At the required depth sensor 68 either switches off clutches 38a, 159 to cause retraction or clutch 159 only is disengaged whereupon forward feeding ceases and due to the interaction of worm-wheel and worm 36, 37 retraction is prevented and a dwell occurs so that the borehole is squared out. After the dwell, clutch 38a is disengaged and the spindle retracted. Tapping.-Clutch 38a is disengaged the whole time. The spindle is rapidly advanced by motor 64. On contacting the work with the tap switch 93 causes rotation of the spindle and sensor 68 is switched on. After a slight delay to allow the tap to bite into the work, solenoid valves 89-88 reduce the pressure to motor 64 to a level just balancing frictional forces on the spindle and the tap advances itself into the hole. At the desired depth sensor 68 reverses the flow to motor 64 and the rotation of the spindle is also reversed so that the tap withdraws itself. At the entrance to the hole sensor 68 operates valve 89 to increase the pressure to motor 64 and the spindle is rapidly retracted.