Patent GB-940481-A (GB)
Title: Control of machine tools by coded tape or the like
Inventor: BATEMAN WILLIAM HENRY
IPC: G05B19/42
Filed: 1960-06-01
Abstract: 940,481. Milling. WICKMAN Ltd. June 26, 1961 [June 1, 1960; Aug. 16, 1960; Nov. 17, 1960], Nos. 19345/60, 28321/60 and 39474/60. Heading B3K. [Also in Divisions G3 and G5] A three dimensional template is automatically scanned along three orthogonal axes, and the dimensional data recorded on a magnetic tape for subsequent replay. The Specification also states that a template need not be used, the axes need not be mutually perpendicular, and that the record may be a disc or perforated tape. Recording.-A hollow template, of conductive material, representing a die, is mounted on the work-table 33. It is moved to and fro in the X direction by a motor 37 and lead-screw, and is stepped in the Y direction by a further motor and lead-screw so as to be scanned by a probe mounted on a head 36. The probe automatically rises and falls under the control of a third motor so as to explore the cavity in the template. As the table moves in the X direction, so by a direct mechanical drive it rotates the capstan of a magnetic tape recorder, Figs. 2 and 3 (not shown). Reversing clutches ensure that the tape always moves in the same direction even ,though the table reverses. The magnetic tape carries three sets of signals, the first of which records both the X and the Y movements, the second, the Z, i.e. probe rise and fall movement, and the third is a synchronizing signal in case the tape becomes stretched. The X movement is defined by a pre-set pair of trip dogs and reversing switches secured to the machine bed, Fig. 4 (not shown), a time delay relay ensuring that the table pauses at the end of each X traverse before reversing. During this pause, further relays energize the Y traverse motor to move the table by a selected increment. The motor, Fig. 5 (not shown), also drives geared rotary switches until they coincide with a manually selected line. The particular increment (six are available) is recorded by energizing a selected combination of four magnetic tape recording heads. Thus the code indicates the Y increment of movement and the distance along the magnetic tape between successive code blocks indicates the X movement. During each X traverse, the probe, Fig. 8 (not shown), is energized at high voltage so that sparking occurs between the probe and the template when the probe is at the required distance from the template. The presence or absence of sparking current energizes a relay to control a reversible motor effecting the Z movement of the probe so that the probe follows the contour. The same motor drives a rotary switch, Fig. 6 (not shown), which produces an output pulse for every 2-thousandths of an inch of Z movement and these are recorded on another track of the magnetic tape, together with a sense signal. Whenever the Z movement necessitates one or more of the 0.002 inch increments, time delay relays provide a pause in the X and Y movements, and since this stops the magnetic tape, a separate stepping motor moves the tape slightly after each Z increment pulse. The extent of the Z movement may be limited so that several successive runs are necessary to reach the bottom of the template cavity, to prevent overloading the cutter on subsequent replay. Equispaced synchronizing pulses are applied to the tape by another head under the control of contacts cam-actuated by the capstan drive. Playback.-A workpiece replaces the template and a rotating cutter replaces the probe. The Y code pulses energize relays to select the appropriate line to which the Y axis switches are driven. The X axis motor is disconnected during this movement. Each Z axis pulse causes the Z axis switch to be rotated one contact step. For synchronizing, the timing pulses on the tape are compared with the cam-actuated timing contacts and any error causes an auxiliary motor to advance or retard the tape feed.