GB849771A - Improvements in and relating to automatic machining systems - Google Patents

Abstract

849,771. Automatic control systems. GENERAL ELECTRIC CO. Dec. 19, 1956 [Dec. 22, 1955], No. 38754/56. Class 38 (4). In an automatic machine-tool in which the linear dimensions of workpieces are measured when they are in the position in which they have been machined, control is effected only if there is a dimensional deviation greater than a predetermined magnitude on a predetermined number of a series of successively-machined pieces. In one embodiment workpieces of magnetic material are automatically produced in succession by a lathe and after each piece is machined an inductance is automatically brought to a fixed position near the workpiece so that the gap between the workpiece and the U-shaped core of the inductance varies with the size of the workpiece. The inductance is connected in a bridge circuit associated with two meters, one of which operates a two-way switch if the size deviation of the workpiece exceeds a wide limit and the other of which operates another two-way switch if the size deviation of the workpiece exceeds a narrower limit. The occurrence of such wide limit or narrow limit failures causes the operation of indicator lights. One wide limit failure in either sense or a selectable number of consecutive narrow limit failures in the same sense causes one increment of adjustment of the position of the tool in the appropriate sense. Two wide limit failures in the same sense may be arranged to stop the lathe to permit manual correction. In Fig. 5 the gauging of each workpiece after machining is initiated by automatic operation of a switch 195. Meter contacts 101, 102 close upon a wide limit oversize failure to energize a thyratron valve 104 and cause, through a system of relays, the operation of an electromagnetically-operated ratchet 200 to advance the tool one increment, and the operation of means, not shown, to select the appropriate receptacle for wide limit oversize failures. A relay 133 remains energized to memorize the wide limit failure. Then if a second such failure occurs in succession a relay 139 closes contacts 143 to stop the lathe to permit manual correction, after which the relays are reset by operation of a switch 203. If there is no second wide limit failure immediately following the first, the relays are reset automatically. The lathe may, alternatively, be stopped by one wide limit failure or by a number of wide limit failures chosen by a selector switch. The number of narrow limit oversize failures necessary in succession to advance the tool by one increment is chosen by a switch 221 shown set for four. A stepping switch 209 starts at contact 216 and, as each narrow limit oversize failure occurs, the closure of meter contacts 113, 114 energizes a thyratron valve 108 to cause, through another system relays, the advance of switch 209 to its next contact. In the case shown, when contact 220 is reached, ratchet 200 operates to advance the tool. A release solenoid 159 then operates to permit a spring 213 to return switch 209 to the position shown in readiness for a further series of narrow limit oversize failures which may occur. If any one of the gauging operations in a series is not a failure, solenoid 159 operates to reset switch 209. If wide or narrow limit undersize failures occur, meter contacts 101, 103 or 113, 115 close to operate the duplicate relay system shown to give indications, stop the lathe and/or retract the tool by one increment. Specification 837,817 is referred to.