Patent GB-929830-A (GB)
Title: Machine tool control system
IPC: B23Q35/123
Filed: 1959-09-07
Abstract: 929,830. Electric correspondence control systems; electric copying machines. SENECA FALLS MACHINE CO. Sept. 7, 1959 [Sept. 8, 1958], No. 30484/59. Classes 38 (6) and 40 (1). [Also in Group XXII] An automatic copying machine is made to perform a series of rough cuts of the workpiece before accurately following the contour of a template, by means of a group of preset potentiometers whose sliders determine the depth of cut and the length of travel of the tool, a multibank switch being operated cyclically, manually or automatically, to produce the rough cuts in sequence, with the feeler gauge overriding the preset potentiometer signals if the tool should attempt to cut off more than is required by the template. Automatic copying.-A workpiece 1 (Fig. 1) is to be shaped in accordance with a template 3 by a tool 18 located on a slide 17 and a carriage 8, the slide 17 being mechanically coupled to a feeler gauge 35, comprising a stylus tip 39 (Fig. 9) biased by a spring 40 to protrude from the housing, attached to an armature 37 normally located symmetrically inside a differential transformer with an energized primary winding 42, and balanced secondary windings 43, 44. Initially, when the stylus is not in contact with the template, the unbalance voltage from the transformer is amplified at 33 to energize servomotor 20 which drives the slide 17 and feeler gauge 35 until the armature 37 is centrally located in the transformer windings. Prior to balance, a switch LSI at the back of the armature rod, closes a circuit to start the carriage feed. The signal from the feeler gauge 35 now produces a slide velocity which, combined with the normal carriage feed velocity, makes the stylus follow the contour of the template, simultaneously causing the tool 18 to follow the same path. The workpiece may be cut a predetermined amount oversize or undersize by switching from q to r or from q<SP>1</SP> to r<SP>1</SP> respectively on a potentiometer 32<SP>3</SP> across the secondary windings 43, 44 of the transformer. Rough cutting.-To avoid overloading the tool, a series of rough cuts of the workpiece may first be made. The start position for the carriage 8 for each rough cut pass is determined by a potentiometer 22<SP>1</SP> &c. (Fig. 16), the voltage at the slider being compared with that of the slider of a potentiometer 22 driven together with the carriage 8, and used to energize a forward or reverse clutch 11, 12, and a rapid feed clutch 14 which is changed for a normal feed clutch 13 at a predetermined level of difference voltage. The end position for the carriage for each rough cut is similarly predetermined by a potentiometer 46<SP>1</SP> &c. To produce a predetermined depth of cut, the motor 20 driving the slide 17 is coupled to the slider of a potentiometer 32 whose voltage is compared with that at the slider of one of a series of preset potentiometers 32<SP>1</SP> &c., the difference being fed to amplifier 33 instead of the output from the feeler gauge 35. As shown, two predetermined depths of rough cut are established by potentiometers 32<SP>1</SP>, 32<SP>2</SP>. Two further rough cuts are obtained from the template 35 by biasing the feeler gauge signal from potentiometer 32<SP>3</SP>. Selection of the mode of cutting is by a multibank switch A, B, C, Y, Z (Fig. 15), rotated manually or automatically. Relays associated with the end position of carriage 8 may be used to operate a stepping actuator, to move the switch to its next position. Thus the machine automatically proceeds through the rough cuts and ends with an automatic copying of the template. If the predetermined end position for carriage 8, or depth of cut, in one of the rough cut passes causes the stylns to contact the template, switch LSI operates to change over amplifier 33 to automatic following of the template contour. Specifications 686,650,691,897 and 692,173 are referred to.