Patent GB-586125-A (GB)
Title: Improvements in or relating to methods of and apparatus for copying by means of milling or other machine tools
IPC: B23Q35/18
Filed: 1943-02-19
Abstract: 586,125. Copying by milling. RIGID. Ltd. Feb. 19, 1943, No. 2830. Convention date, Jan. 8, 1942. [Class 83 (iii)] [Also in Group XXIX] In a milling or other machine tool for copying by relative co-ordinate movements of the cutter and work slides, the movements are imparted by fluid pressure cylinders under control of valves actuated by two rotary cams, the connection between the cams and valves being resilient and tending to cause movements greater than those allowed by a master pattern and tracer, so as to compensate for reduction in size of the tracer and cutter due to re-grinding of the latter. The pattern 7 and work 5 are mounted on a slide 3 movable horizontally on a vertically adjustable support 2 by means of a fluid pressure cylinder 15 attached thereto, co-operating with a piston-rod 17 secured to the support 2. The control valve 10 for the cylinder 15 is connected to the pattern by a rod 8 secured to the valve rod 9 which carries two pins 19, Fig. 2, actuated through springs 20 by a lever 21 having a roller 23 on its free end, engaging a cam track 24 in a rotatable disc 25. The pattern is capable of a small movement relatively to the slide 3 so that it may partake of the movements of the valve. The disc 25 is driven by worm and bevel gearing from a shaft 31, Fig. 3, which also drives a disc 37 having a cam track 38 engaging a roller 39 on a rod 40 whose collar 41 engages spring-pressed pins 42 on a slide 45 which carries the tracer 47 coacting with the pattern 7. The slide 45 is also connected through a rod 48 to a valveactuating rod 50 slidable within a piston-rod 51 of a stationary cylinder 53 controlled by the valve. The piston-rod 51 is connected to a cross-slide 57 carrying the cutter 58 which is originally the same diameter as the tracer 47, but the latter may be replaced by a roller of smaller diameter when the cutter is ground. In operation, the cam 25 actuates valve 10 to vary the pressure on opposite sides of piston 18 from constant pressure supplies 11, 12 and an exhaust 16, in a manner similar to the control by valve 51, 52 in Specification 544,471. This causes the slide 3 carrying the work and pattern to be traversed longitudinally by the cylinder 15, the body of valve 10 partaking of the movements of slide 3 to give a servo action to the valve. The pattern 7 is thereby maintained in yielding contact with the tracer 47 in the longitudinal direction, but protuberances on the pattern engaging the tracer prevent the pattern from moving with the slide 3 and cause displacement of the valve 10 through the rod 8 so that the movement of the slide will correspond exactly with the shape of the pattern. During this traverse the tracer 47 is pressed transversely against the pattern by the cam 37, and any transverse movement of the tracer allowed by the pattern causes the valve rod 50 to be displaced in the piston-rod 51 to alter the relative pressures on opposite sides of piston 52 and thereby give a corresponding transverse feed to the cutter 58. The tracer is thus given a uniform pressure against the pattern due to the spring connections 20, 42 and this yielding connection also allows the cams 25, 37 to be designed so as to tend to move the pattern and tracer through greater distances than are allowed by the pattern, this greater motion only taking place when a smaller tracer and cutter are in use. A third cam similar to cams 25, 37 may be provided for copying in a third dimension.