Patent GB-1257912-A (GB)
IPC: G05B19/42
Filed: 1968-01-03
Abstract: 1,257,912. Programme control of machine tools. MORFAX Ltd. Dec. 30, 1968 [Jan. 3, 1968], No.475/68. Heading G3N. A recorded programme for continuous path control of a machine tool is produced by automatically causing a follower device to scan and progressively travel along a representation of an article to be manufactured and recording a train of variable-frequency fluctuating signals generated by the follower movement. A drawing on a co-ordinate table is automatically scanned by a photo-electric line follower which produces sine/cosine signals for the rotation of lead-screws. As shown, Fig. 3, scanning photo-cells 101, 102 of the line follower are mounted on a member 42 and oscillated by a motor 45 in elliptical paths, the major axes of which are maintained transverse to a line D. The output of photo-cell 101 is applied to an amplifier FSA, incorporating filters which reject the first harmonic of the oscillation frequency, feeding a servo-amplifier 5A for a winding W1 of a servomotor M positioning the line-follower on the line D. Rate feedback is applied to the motor M from a tachogenerator T through a potentiomenter P. Rotation of the line-follower positions a sinecosine potentiometer 59 varying the supply to D.C. amplifiers DCX, DCY controlling co-ordinate drive motors 17, 12 which cause the line-follower to travel around the drawing. Feedback is applied to amplifiers DCX, DCY from tachogenerators TX, TY. The supply to the potentiometer 59 is derived from a constant voltage supply T1, T2, and the line-following speed is controlled by a potentiometer SC. An abrupt change in drawing contour is sensed by the photo-cell 102 the output of which, through an amplifier A de-energizes a relay RL. Contacts RL1 of the relay open to remove a shunt from a resistor SR in series with the potentiometer SR and reduce the linefollowing speed. The closure of the relay RL is delayed by circuit DL. The co-ordinate movements of the lead-screws are recorded, Fig.6, on a tape-recorder 131. A lead-screw 111, for X or Y movement, rotates a lamp and photo-cell combination 119, 141 with respect to a slotted disc 115, driven at constant speed by a motor 116. The output of the photocell has a frequency indicative of the relative movement of disc and lead-screw and is recorded on a channel 145, 146 of the tape-recorder 131 together with the reference frequency, on channel 143, from a source 142 which also energizes the motor 116 through an amplifier 144. The Z-axis depth of cut, or other machining parameter, is also programmed by the recording of a pulse train having a rate determined by a rotating disc system, as driven by the lead-screws, and a duration determined by pulses from a photocell responsive to the light through holes in a disc on the drive-shaft for the photo-cell and light source 141, 119. The desired count is set up on decode switches. When the Z-axis system is in operation the co-ordinate drive for the linefollower head is disconnected and may be restarted automatically at the end of the count. The programme is played back by the use of lead-screw transducers, motors rotating the slotted discs being driven in response to the reference frequency. The drawing is prepared with lead-in lines and with marks indicative of stop or Z-axis functions. It is stated that a magnetic toothed wheel may be substituted for the lead-screw transducers and co-ordinate movements imported to the followerlead by hydraulic or pneumatic devices rotary movements of the transducers being obtained through racks and pinions.