Patent GB-932906-A (GB)
Title: Machine tools
Inventor: HADEKEL RUBEN
IPC: B23Q35/121
Filed: 1958-09-12
Abstract: 932,906. Automatic programme control systems for machine tools. SPERRY GYROSCOPE CO. Ltd. Aug. 21, 1959 [Sept. 12, 1958], No. 29353/58. Divided out of 932,905. Class 38 (6). [Also in Group XXII] A lathe or other machine tool (see Group XXII), has means for controlling the speed of rotation of a work-spindle 11 as the radial distance of a tool-slide (14 or 15) from the spindle varies. Electrical means are also provided for correlating the speed of the spindle 11 and the linear rate of movement of a toolslide 15, moved perpendicularly to the workaxis, a copying tool slide 14 moved at an angle to the work-axis and a longitudinal slide 13 carrying the copying slide. The speed of the spindle motor 12 is controlled to maintain constant the product of this speed and the distance of either of the slides 14, 15 (whichever is in use), from the lathe axis, in the following manner. The copy-slide 14 and the slide 15 have two-part inductive piak-offs PO3, PO7 respectively, each providing an output varying with the relative displacement of its two parts and the excitation of a winding on one of the parts. The two parts are displaced as the slide moves and the winding is excited by the output of a tachometer 36 driven by the spindle 11. The signals for the pick-offs are compared with set signals derived from respective potentiometers 73 and 74 and the difference is fed to the amplifier 28 controlling the spindle motor 12. Only one signal is used at a time depending on which slide is being used. The slide 15 may be moved proportionally to the spindle speed 11, the output from tachometer 36 being fed through indicator 46 and adjustable potentiometer 47 to the primary of transformer 48, the secondary of which is centre-tapped and connected to change-over relay contacts D3. The movable contact is connected through a resistor to the input of amplifier 49 whose output controls an electric motor 51 which drives a generator 52 whose. output provides a feed-back component of the input to amplifier 49 so that the motor 51 runs at a rate proportional to the speed of spindle 11. Motor 51 also drives a pick-off PO6 through a normally disengaged clutch 54 which is spring-centred when the clutch is disengaged. The pick-off output is connected as one component of the input of amplifier 35 controlling a fluid cylinder 19 for moving the slide 15. The other two input components are provided by the output of an adjustable A/C energized potentiometer 61 through a normally closed relay contact C2 and normally closed push-button 62 to set a fast-feed,or withdrawal signal for the slide and by a position-responsive pick-off PO5 driven by cylinder 19. The input to amplifier 35 is also fed as an input to an amplifier 55 whose output is fed through a discriminator 56 to oppose a source of positive voltage which tends to excite a solenoid 57 for engaging the clutch 54 provided that normally-open contacts C3 are closed. The clutch remains open until the input to the amplifier drops low enough to allow the solenoid 57 to be energized to cause the feed rate to be applied to the amplifier inputs. The copy-slide 14 has a stylus 71 deflected by contact with a template, fixed to the machine bed, to balance a suitable bias signal obtained from an A/C energized adjustable potentiometer 72. The copy-slide is mounted on a longitudinal slide 13 which is moved proportionally to the spindle speed by a velocityservo system. A signal proportional to the spindle speed is fed as an input to amplifier 31 whose output controls the speed of motor 17 which drives a lead-screw 16 to feed the slide 13. The signal is fed through normally-open contact of change-over relay contact B1 and is derived as the output signal of a settable potentiometer 37 across which the output signal of tachometer 36, driven by spindle 11, is applied. A signal proportional to the output of a tachometer 38 driven by the lead screw 16 is fed degeneratively into the amplifier 31 to ensure that the speed of the lead-screw is kept proportional to the set feed and the speed of spindle 11. When the copy-slide is moving along shoulders and sharp bends the feed of slide 13 is compensated to the rate of feed of slide 14 by a slide position responsive pick-off PO8, of a known type, whose output is connected to an amplifier 41 of a position follow-up servomotor control system including a motor 42, a speed generator 43 and motor displacement pick-off PO9. The motor 42 drives a tachometer 44 which gives an output signal proportional to the rate of movement of copy-slide 14 and is fed as a third component of the input to amplifier 31 controlling the feed motor 17 for slide 13. The slides are arranged to move forwards and return to their starting positions by position responsive pick-offs, stops and switches.