Patent GB-594902-A (GB)
Title: Improvements in or relating to machines for milling or grinding any desired kind of curved surfaces
IPC: B23Q35/18
Filed: 1945-04-16
Abstract: 594,902. Copying by milling. ESCHER WYSS MASCHINEN-FABRIKEN AKT.-GES. April 16, 1945, No. 9434. Convention date, April 15, 1944. [Class 83 (iii)] [Also in Groups XXIII and XXIX] Milling screw-propellers and turbine blades.- In a machine for copying curved surfaces by means of a pattern and tracer controlling a milling or grinding tool, the tracer and tool are mounted for pivotal movement about two perpendicular axes so that they may pivot universally in synchronism by contact with the pattern. The machine comprises a longitudinally reciprocated table 64 carrying the pattern A and work B and pillars 5, 6 tied by a beam 7 and having vertical guides 8 for a cross slide 9. A saddle 11 is given a step-by-step feed along slide 9 between reciprocations of the table 64 by means of a screw 12 and electric motor 13, and has arcuate guides 11<1>, Figs. 1 and 4, for a carriage 14 which supports the tracer head 18 and cutter head 19. Each head is mounted on the carriage by arcuate guides 22, 23 arranged about axes perpendicular to the axis of guides 11<1> so that the heads have universal pivotal movement. The cutter consists of a flat milling cutter or grinding disc 1 and the tracer 2 is of similar shape, having two adjustable screws 3, 4, Fig. 5, which, together with an edge 2<1> of the tracer, provide a threepoint contact with the pattern A. The tracer is supported on the head 18 by a centrallylocated rod 24 and ball mount 25, the rod 24 being attached to a valve 32 and also a sleeve 42 in the head. Two other rods 27, 28 are pivoted to the tracer by pins 53, 54<1> located near the periphery thereof at right-angles to each other, these rods being connected to valves 43, 53, respectively in the head. Operation. The screws 3, 4, are adjusted to tilt the tracer 2 according to the curvature of the pattern and provide as long an arc of contact at 2<1> as possible, thus securing a corresponding arc of contact between the cutter and the work. As the pattern is traversed past the tracer, any upward pressure on the latter will cause the rod 24 to displace valve 32 upwards relatively to its sleeve 31 and allow its upper piston to connect a fluid pump 29, through a flexible pipe 45, passage 46<1>, annular part 30 and flexible pipe 34 to the lower end of a servomotor 26 on the beam 7, having a piston-rod 41 connected to the cross slide 9. The slide, together with the cutter and tracer, will thereupon be raised, fluid from the upper end of motor 26 passing to exhaust through a flexible pipe 65, valve 32 and pipe 39. Raising of tracer head 18 will tend to restore valve 32 to neutral position to stop further upward movement unless the tracer 2 continues to rise. Similarly pivoting of the tracer about the balljoint 25 due to rises on the pattern will raise one or both of rods 27, 28, causing their attached valves 43, 53 to admit fluid from pump 29 by pipes 67, 60 to servo-motors 20, 15 respectively. Motor 20 is mounted on carriage 14 and has a piston rod 21 provided with a rack engaging toothed segments 22<1>, 23<1> on the tracer and cutter heads so that these will be oscillated clockwise in Fig. 1. Motor 15 is mounted on saddle 11 and has a piston rod 16 carrying a rack engaging a toothed segment 17 on carriage 14 so that the carriage, together with heads 18, 19 and the tracer and cutter will be oscillated anti-clockwise in Fig. 4. The rocking movements of heat 18 about both axes will tend to restore the neutral positions of valves 43, 53 relatively to their sleeve 42, to stop the rocking movements unless the tracer continues to be deflected and the previously described vertical movement of the tracer 2 and rod 24 will move both the valves and their sleeve 42 by equal amounts so that actuation of servo motor 26 will not affect servo-motors 15, 20. Downward movements of rod 24 due to vertical. downward movement of the tracer, or of rods 27, 38 due to pivoting of the tracer, will actuate the servo-motors in the opposite direction to move the cutter in accordance with the tracer movements these downward movements being caused by a spring (not shown), above the valve, as allowed by depressions in the pattern. Instead of causing the tracer movements to control the cutter through the hydraulic servomotors 15, 20, 26, electric or pneumatic means may be utilised, and a second tracer may be provided to contact the pattern and operate the transverse setting of the saddle 11 automatically.