Patent GB-477456-A (GB)
Title: Improvements in or relating to pattern controlled milling machines
IPC: B23Q35/18
Filed: 1936-06-30
Abstract: 477,456. Milling-machines. CINCINNATI MILLING MACHINE CO. June 30, 1936, No. 18155. Convention date, July 10, 1935. Addition to 461,596. [Class 83 (iii)] [Also in Group XXIX] A milling, profiling, &c. machine described in the parent Specification includes the provision of a tracer-slide whose movements to and from a pattern are capable of being manually controlled through the servo-mechanism, and also of means responsive to a predetermined displacement of the tracer, such as is caused by contact of the tracer with the pattern, for rendering the manual control ineffective. The machine comprises a horizontally movable table 10, carrying a pattern 12 and workpiece 11, and a horizontal ram 17 having vertical guideways 16 for a carriage 15 which supports the cutter 13 and the tracer 14. The carriage 15 is movable vertically by means of a cylinder 18, Fig. 3, and a piston 20 attached to the ram 17, fluid being admitted to either end of the cylinder by pipes 23, 24, Fig. 7, leading from a distributing valve 27. Fluid is supplied by a pump 36 to a servo-valve 43 by pipe 37, and thence by either of the pipes 30, 31 to the valve 27. The screwed stem 44, Fig. 3, of valve 43 has two nuts 45, 46 thereon, separated by a spring 47 to prevent backlash, and held from rotation by a sleeve' 48 on the ram 17. In order to move the tracer and cutter to or from the pattern and work, the valve and screw are rotated by a hand wheel 55 and bevel gears 51 so as to displace the valve from its central position and allow fluid to flow from the pipe 37 to one of the pipes 30, 31 and thence by one of the pipes 23, 24 to the lower or upper end of the cylinder 18. Movement of the valve casing 56 with the slide 15 restores the neutral position of the valve 43 unless the handle 55 is continuously turned. The bevel gear 51 may also be rotated by power through gearing 94, a reversing bevel drive 72, Fig. 6, and a variable speed friction drive 61, 63 rotated through worm gearing from an electric motor 57, Fig. 7. The movable disc 63 of the variable drive is adjusted by a yoke 65 and a screw 68 rotated by a hand wheel 69 in co-operation with a graduated dial 70. The reversing clutch 72 is controlled by a yoke 81 and a vertical shaft 82 moved by a crank 86 on a shaft 84 rotatable by a hand lever 83. The shaft 82 may be moved automatically at opposite ends of the traverse of the slide 15 by dogs 87, 88, Fig. 1, on the ram 17 engaging a lever 89, Fig. 6, carrying a second crank 92 acting on the rod, thus disengaging the clutch after a predetermined traverse. For tracer control, the cylinder 18 is connected to the tracer valve 107, Fig. 7, by means of pipes 103, 104 leading to the distributer valve 27, this position of the valve 27 being produced automatically when the tracer engages the pattern, in order to prevent damage to the tracer mechanism by excessive pressure thereon due to hand control. When the tracer is free from the pattern the valve 107 therein moves downwards, due to a spring constantly acting on the top thereof, and fluid flows from the pump 36 to pipe 103 and thence by pipe 112 to the left-hand end of valve 27, thereby pushing the plunger 28<1> of this valve to the right so as to connect servo-valve 43 with cylinder 18 for hand control, but as soon as the tracer engages the pattern and is deflected, pressure on the opposite ends of plunger 28<1> is equalized and that acting on the larger right-hand end moves the plunger to the left to connect cylinder 18 with the tracer valve 107 for automatic copying control and simultaneously cutting out the hand control. Thereafter, movement of the valve 107 up or down by contact with the pattern moves the piston 20 and cutter a similar amount by allowing fluid to flow through either of pipes 103, 23 or 104, 24. The plunger 28<1> is connected by a lever 117, Fig. 3, to a shaft 118 carrying another lever 119 which controls the axial position of a gear 121. A spring normally acts to rotate the shaft 118 so that the gear 121 occupies an idle position and the plunger 28<1> is in the handcontrol position, but when the plunger is displaced to the left in Fig. 7 by action of the tracer, the gear 121 is moved upwards to engage a gear 123, on the shaft of a hydraulic motor 125, with a gear 122 connected to the bevel pinion 51 which rotates the screw 44 of valve 43. Simultaneously, the plunger 28<1> puts the pipes 126, 127, Fig. 7, leading to the motor 125 in circuit with the supply from the servo-valve 43, so that when the slide 15 moves up or down under tracer control and carries with it the casing 56 of valve 43, fluid is admitted to one side or other of the motor 125, thus rotating the screw 44 to make the valve 43 follow this motion. The hand wheel 55 is also rotated by the gears 51 so that it cannot be rotated at any other speed by hand, but serves to indicate the position of the tool and tracer by means of its dial 130. The end of shaft 118 has flattened portions 131, Fig. 6, lying within a slot in the yoke 81 which controls the reversing clutch 7 to allow actuation of the yoke when the machine is under hand control, but when the plunger 281 moves to tracer-control position, the larger diameter of the shaft 118 locks the clutch in neutral position so that the screw 44 cannot be rotated by the motor 57. The tracer may be disengaged from the pattern at any time by manually displacing the tracer a maximum amount, thereby raising the slide 15 and moving the plunger 28<1> to hand-control position.