GB1160643A - Variable Lead Device for Line Tracers - Google Patents

Abstract

1,160,643. Cutting by fusion. AIR REDUCTION CO. Inc. 17 April, 1967 [18 April, 1966], No. 17617/67. Heading B3V. [Also in Divisions G1 and G3] A line tracing apparatus comprises a line sensing device operating with a lead distance and a selector controlling the tracing speed and varying the lead distance automatically as a function of the training speed. As shown, Fig. 3, an optical line follower 60 is moved around a line on a template S by a wheel 30 driven at a predetermined speed by a motor 40 and steered by a motor 110 which simultaneously aligns the follower 60 through gearing 22, 48, 52. The position of the follower relative to the line on the template is detected by cadmium sulphide light sensitive elements 154, 156 responsive through a lens 65, to the light reflected from the template. The scanning lead is indicated by A and the elements 154, 156 are proportionally displaced by a distance RA by rotation of a screw 160. The screw is rotated in dependence on the tracing speed as set by manual adjustment of a speed selector 170 for the motor 40 through a servo link comprising a servo 164 responsive to a comparison of selected speed with the signal from an odometer 166 coupled to a motor 62 driving the screw 160, to derive a signal for controlling the motor 62 through a controller 168 whereby the lead A is maintained in correspondence with the selected tracing speed. In a modification, Fig. 7, the line on the template is magnetic and is followed in dependence on the output of coils 204, the lead A being controlled by the movement, through the screw 160, of a rod 202 pivoted about a spherical bearing 208 and slidable in a sleeve 200. It is stated that a knob 172 of the speed selector 170 may be connected to the lead screw 160 by a direct mechanical linkage. The line or edge scanned may be replaced by an elongated shadow. In a guidance system for a metal-cutting torch, a carriage on which the line follower is mounted is connected to a stationary member by pentographic arms and carries on a rigid bracket a torch directed downwardly to propel its flame against a workpiece. Reference is made to the relationship between lead and cutting speed for oxy-thermal flame cutting equipment and for electric arc plasma cutting machines.