Patent GB-1158008-A (GB)
Title: A Tracer Arrangement for Copying Machine Tool
IPC: B23Q35/34
Filed: 1966-12-19
Abstract: 1,158,008. Copy-milling. NASSOVIA WERKZEUGMASCHINENFABRIK G.m.b.H. 19 Dec., 1966 [24 Dec., 1965], No. 56748/66. Heading B3K. [Also in Division G3] A tracer control apparatus for a copying machine tool comprises a freely mounted tracer connected to a biased stationary reference member and a control unit, having a head rotatable about the stationary member, which is adjustably displaceable relative to the stationary member to allow adjustment of the rotary head along a surface portion of varying cross-section of the stationary member to vary the radial separation of the stationary member and rotary head and thereby vary the tracer lead. As shown, Fig. 1, a tracer bar 1 is mounted, for universal movement in forked levers 4, 4<SP>1</SP> and co-ordinate movement of pin 2 or workpiece and template is determined by hydraulic control valves 5, 6, 7. Biasing force is applied at the top end of the tracer bar through a spherical element 10 attached to the bar by an arm 9 and is provided by a spring 20 acting through a lever 21 bearing a pressure roller 22<SP>1</SP>. The roller 22<SP>1</SP> co-operates with a roller 23<SP>1</SP> which, through a lever 23 loaded by a spring 30, determines the position of a bar 25. The bar 25 sequentially operates a switch 5 controlling the energization of a motor 19 rotating a member carrying the levers 22, 23 so that the tracer pin 2 is biased in a direction tangential to the contour of the template. The biasing assembly is adjustable in bearing and azimuth, about the spherical member 10 and is axially positionable by a knob 35 bearing an eccentric pin 36 to adjust the biasing force. The switch S comprises a contact 26 which is initially closed by axial movement of bar 25 to energize relays Z, Y, the motor 19 being de-energized and a brake 21 applied since the biasing force is tangential to the contour. An inclined portion of the template causes additional movement of the bar 25 to open a contact 32 to de-energize relay Y to cause a counter-rotation of the motor 19 until the tangential direction of the biasing force is restored. Limit switches on the worktable, not shown, reverse the feed movement and de-energize relays Z, Y through a switch 25X having a time delay such that the motor 19 rotates the levers 22, 23 to the lead position. In an alternative arrangement, Fig. 3, (not shown), rollers engage a coned surface attached to the tracer bar and are positionable in coordinate axes by bayonet joints. In an alternative arrangement, Fig. 5, a precontrol force is applied to the member 10 by a roller 22<SP>1</SP>, loaded by a spring 45, which cooperates with a roller 23<SP>1</SP> positioning through a lever 46 a piston 48 in an hydraulic valve body 18. A counter-force to the pre-control force is applied through a spring 49 and is adjusted by a set-screw 50. The bearing of the lever 46 on the piston 48, and consequently the location of the control edges of the valve, is adjusted by a setscrew 51. An hydraulic motor 52 drives the valve body through a shaft 53 and is supplied from a fluid container 54 by a pump 55 through electromagnetically actuated valves 57, 62. The effective lead of the tracer is adjusted by positioning the valve body 18 by an eccentric pin 35. The valve 57 is electrically connected to a time switch ZSX which is switched by end switches 63 actuated by the work slides of the machine to reverse the line direction. The valve 62, also connected to the time switch ZSX, has the same control effect as the relay Y, Fig. 1.