GB872597A - Improvements in electrical tracer control devices for use with machine tools - Google Patents

Abstract

872,597. Tracers for copying-machines. HANSENS, A., [trading as DROOP & REIN]. July 24, 1957, No. 23402/57. Class 38 (6). Apparatus for controlling a copying-machine to make it follow the contour of a template comprises a tracer stylus with two sets of switches, the first set comprising four equispaced sets of contacts selectively operated on slight deflections of the stylus in accordance with the direction of deflection to preselect energization of magnetic clutches coupled to the driving motors, and the second set comprising three longitudinal sets of contacts selectively operated in accordance with the extent of the stylus deflection to energize the preselected clutches. The switches may be used to produce a preliminary rough cut of the workpiece. A rod mounted in ball bearings is inserted partially into the rear end of the tracer and the contacts referred to above are adjacent to the upper bearing, a circular spring and adjusting device being provided to maintain the tracer in a central axial position when not touching the template. In Fig. 1 the tracer consists of a stylus 41 supporting a rod 45 in ball joints 6 and 7, the end of the rod engaging a bearing 8. Surrounding the rod 45 are four symmetrically located bars 9, pivoted at 10, each carrying a moving contact 11 co-operating with a fixed contact 12 mounted on a ring attached to the housing 42. The bars are inwardly biased by a circular spring 16 which also tends to maintain the stylus and rods coaxial. When the stylus 41 is deflected, a tubular extension 14 presses against a boss 15 on one of the bars 9 to close the appropriate contacts 11, 12. On further deflection of the stylus 41, bosses 126 on the piece 14 cause the rod 45 to displace the end bearing 8 against a spiral spring 25 and deflect a switch arm 24 to close the second set of contacts 23, 21, 22 in this order in accordance with the extent of the deflection of the stylus. In Fig. 2 the four sets of contacts 11, 12 are designated as I, II, III and IV, and selectively energize relays R1, R2, R3 and R4 which prepare magnetic clutches 117, 18, 19 and 20 for energization by contacts 23, 21 and 22. The clutches 117, 18, 19, 20 produce forward, reverse, right or left movement of the stylus respectively. Contacts 21-23 are connected to the (D.C.) power supply via a reversing switch (not shown) operated by a time relay so that any burning or pitting is shared equally between the two contact elements. In a modification (Figs. 3 and 4, not shown) the tracer and its contacts are used to produce a preliminary rough copy of the template. Each switch 11, 12 controls the energization of four relays, each of which has three normally-open contacts and one normally closed contact, the contacts being interconnected so that when a switch 11, 12 is closed by deflection of the stylus the direction of movement is changed by 90 or 180 degrees to prevent the work being damaged by too deep cutting.