Patent GB-537543-A (GB)
Title: Machine for milling ships screws, propellers and the like on the pressure and suction sides
IPC: B23C3/16
Filed: 1939-10-24
Abstract: 537,543. Fluid-pressure servomotor control systems. ESCHER WYSS MASCHINENFABRIKEN AKT.-GES. Oct. 24, 1939, No. 28567. Convention date, Oct. 24, 1938. [Class 135] [Also in Group XXII] A machine for milling a series of propeller blades of the same kind of profile employs two patterns only, one for each face of the blades. Movements of the cutter in a vertical direction are controlled by a follower engaging the pattern through a fluidpressure servomotor follow-up device. A throwover member engaging the pattern reverses the direction of rotation of the blank and pattern tables and a second follower device engages the hub portion of the pattern to stop the feed of the blank and pattern slides before the milling cutter can damage the hub of the propeller being machined. The work 11 and the pattern 9 are mounted on rotary tables on slides fed by inter-geared screws 32, 36, driven from the motor shaft 13 through reversing bevels 28. The cutter spindle is carried by an arched arm 4 permitting the machining of overlapping blades. The follower 37 is slid in guides by the pattern and rocks a lever 41 displacing a piston valve 43 to admit pressure from 45 via a passage 47 above a fixed piston 50. The cylinder 49 carrying the follower and its associated control mechanism rises, together with the fulcrum 54 carried by it, working a lever 55 and raising a piston valve 57 to admit pressure from 66 below a piston 70 and causing the cutter slide 3 to ascend, the amount of the movement depending on the angular setting of bar 63 engaged by a follower 62 working a bell crank 59, linked at 56 to the lever 55 to restore the valve 57 to the neutral position. Preventing tracer from overrunning edge of pattern.-The blade and pillion tables are rotated at the same angular velocity from the shaft 13 through reversing bevels 16 and the further bevel and worm gearing indicated. When either the ledge 90 or 91 at the edges of the pattern engages a member 74 this is thrown over displacing a piston-valve 78 and admitting pressure from 80 via a passage 92 or 95 to a cylinder 96 to throw over the clutch 14 and reverse the direction of rotation. The ledge 91 acts at the end of the cutting stroke and on reversal taking place pressure fluid also passes via 82 to the cylinder space 83 moving piston 87 to the left, Fig. 3, and making the cylindrical member 60, on which the bell crank 59 is eventually pivoted, and this acting on the valve 57 to lift the cutter from the work during the return stroke. On reversal of the ledge 90 for the next cutting stroke contrary action takes place and the cutter is restored to operative position. Reversing hand of reproduction.-This is effected by means of the reversing bevels 20 transmitting drive to the work table. Automatic step feeds.-When the platten slide 8 and cutter slide 7 approach the limit of their inward feed fouling of the propeller hub by the cutter 6 is prevented by a feeler 101 that engages the hub portion of the pattern and works a bell crank 104 displacing a piston valve 105 against the action of a restoring spring 107, and admitting pressure from 107 via passage 114 to parts 116, 115 displacing a valve 112 to the right in Fig. 3 against a restoring spring 113. Pressure fluid then passes from 115 to 117 and by the passage 126 tu below the piston 122 which rises throwing the clutch 26 into engagement with the wheel 29 and reversing the feed. As soon as the feeler 101 ceases to touch the pattern the spring 107<SP>1</SP> restores the valves 105 and the piston 122 descends but, owing to lost motion at 140, the clutch is this time only moved to neutral and the feed is stopped. At the end of the down stroke of the piston, a tappet 131 is engaged and moves the valve 130 against the spring 137 admitting pressure from 110 through the passage 133 to the spaces 132, 134 and so to 136 at the other end of the valve 116 causing the valve to return to the left ; both sides of the piston 122 are then in communication via the parts 117, 118, 119, interconnected at 120 and the lever 124 is free to be moved by hand.