Patent GB-448337-A (GB)
Title: Improvements in milling or like machines for copying or reproducing
IPC: B23Q35/18
Filed: 1934-12-05
Abstract: 448,337. Milling machines; valves. FITZPATRICK, H. J., 94, Hope Street, Glasgow.-(Clearing Machine Corporation; 6499, West 65th Street, Chicago, U.S.A.) Dec. 5, 934, No. 34923. [Class 83 (iii)] [See also Group XXIX] A milling or like machine for copying from a pattern has a tracer and cutter mounted on a carriage which is traversed to-and-fro across the pattern and work, feed mechanism for imparting stepby-step feed to the tracer and cutter in unison after each traverse, means for urging tracer yieldingly against the pattern relatively to the cutter, means tending to move the cutter in one direction to or from the work and fluid pressure means acting on the cutter in opposition thereto, a valve being included in the fluid pressure means and connected to the tracer so as to vary the action of the fluid pressure means in accordance with the shape of the pattern. Copying mechanism.- The machine comprises a base 1, Fig. 1, carrying an upright 13 on which the work and pattern are mounted and provided with guides 3 on which a carriage 78 is horizontally movable. The tracer 14 and cutter 39, Fig. 4, are carried by a slide 74 movable to and from the pattern 8 and work 9 in guides on a slide 113 which is vertically movable on guides 114 on the carriage 78. The cutter is mounted in a spindle 42 rotated by bevel gears and splined shafts 57, a gear box 56 and a belt from an electric motor 55. An annular cylinder 58, Fig. 13, carried by the slide 74 surrounds the rear end of the spindle 42 and contains a piston 64 connected by a yoke 65 to doubleacting thrust bearings 66 on the spindle. Fluid from a continuously rotating pump 67, Fig. 1, is supplied to the cylinder by a pipe 60 so as to tend to urge the spindle and slide 74 towards the work, this motion being resisted by a weight 72, Fig. 1, connected to the slide by a cable 73 passing over sheaves 76, Fig. 4. The tracer 14, Fig. 10, is removably carried by a spindle 20 having a flange 34 which is normally maintained against a shoulder 36 in a cylinder 18 attached to the slide 74 by a bracket 115, by means of a light spring 15 acting through a hollow double piston 23, but may be moved back or tilted slightly by contact with the pattern. Fluid from the pump 67, Fig. 1, is fed by the pipe 60 and opening 27 to a space 25 in the cylinder 18, this pressure acting on the two flanges 21, 24 so as to maintain the piston 23 in a balanced condition. The flange 24 is pressed by the spring 15 against a seat 26 in the cylinder to prevent the flow of fluid, but when the piston is moved to the right in Fig. 10, by the action of a protuberance on the pattern engaging the tracer, fluid is allowed to flow past the seat through apertures 31, 32 in the piston and then to the sump 62 by means of a pipe 61. This lowers the pressure in the pump supply line 60, thereby reducing the pressure on the piston 64 and allowing the weight 72 to withdraw the slide 74 together with the cutter and tracer and reproduce the protuberance on the work. When pressure of the pattern on the tracer is relieved, the flange 24 closes against the seat 26, pressure in the pipe 60 rises and the slide 74 returns against the action of the weight 72. Due to the piston 23 being balanced, movement of the tracer by the pattern is resisted only by the compression of the spring 15, which is adjustable by means of a screwed abutment sleeve 16, so as to make the tracer as sensitive as is desired. The shoulder 36 is adjustable in the cylinder 18 and is locked by a nut 19<b>, a flexible washer 38 being held in the cylinder by a screwed bush 37 to prevent leakage of fluid around the spindle 20. Fluid leaking past the flange 22 may proceed to the exhaust 61 by means of an aperture 35 in the piston. Cutter-slide feeds ; reversing-mechanism.- The carriage 78 is reciprocated horizontally past the work by a fluid pressure cylinder 85 to cause the tracer and cutter to traverse parallel paths along the pattern and work respectively, the slide 113 being initially raised by hand to its uppermost position and then being allowed to descend in steps at the end of each reciprocation by means of a fluid pressure cylinder 138. The cylinder 85, which is attached to the base 1, contains a double-acting piston 84, Fig. 8, connected by a rod 82 to a block 80 attached to the carriage 78. Passages 95, 96 in the block lead through the rod to opposite sides of the piston and terminate in nozzles 93, 94, Fig. 6, located opposite two radial ports in a disc 90 rotatably mounted in a cavity in the carriage. The cavity is supplied with fluid under pressure by a pipe 86, Fig. 1, leading from the pump 67, and the passages 95, 96 are alternately connected by rotation of the disc to the supply and to an exhaust 112 leading to the sump. A spindle 91 having a lost motion connection with the disc is rotatably mounted on the carriage and carries an arm 106 weighted at 107. When the carriage approaches the end of its traverse an arm 92 pivoted on a bush 109 on the carriage engages one of the fixed but adjustable stops 6, 7, Fig. 1, on the bed 1, thereby rocking the arm 92 and causing one of the pins 104, 105 on a plate 110 attached to the arm to strike the arm 106. This rocks the arm 106 and takes up the lost motion between the spindle 91 and the disc 90 and when the weight 107 passes the dead centre the arm 106 falls over and rotates the disc rapidly to the reversed position. A spring 111 maintains the disc against its seat. The stops 6, 7 are secured to the bed 1 by bolts sliding in a T-slot 5 therein and are secured by nuts provided with handles 12. The slide 113 is connected to a rod 136 attached to a single acting piston 137, Fig. 1, sliding in a fixed cylinder 138, an axial passage in the rod leading to the cylinder below the piston and being connected to the central port 141, Fig. 6, of a valve 117 attached to the slide 113. Ports 140, 142 in the valve lead to fluid supply and exhaust respectively. A plunger 121 has a central portion 145 which in the middle position shown closes both ports 140, 142 from the port 141, but in axially displaced positions connects the port 141 to either of the ports 140, 142. The plunger is normally maintained in the middle position by a spring 147 pressing it against a nut 120 slidably mounted in a guide 122 on the carriage 78, this nut being threaded on a screw 119 journalled on the carriage and provided with a handle 126 at the top. The screw may thus be rotated by hand to raise the nut and plunger continuously and connect the port 141 to supply, thereby raising the slide 113 to its uppermost position. At each reversal of the carriage 78 a link 127, Fig. 1, on the plate 110 rocks a linkage 130 carrying pawls 134 acting on ratchets 131, 132 gearing with a pinion 124, Fig. 6, attached to the screw 119, thus rotating the screw and lowering the plunger 121 to cause a downward feed of the slide 113 by connecting the port 141 to the exhaust port 142 until the slide and valve 117 have been lowered sufficiently to close the port 142 again. Stop valves 70, 149 are provided on the fluid supply pipes. Sockets; spindle mountings.-The cutter 39, Fig. 2, is mounted in a split collet 40 which is drawn into the bevelled end of the hollow spindle 42 by means of a rod 41 rotated in the spindle by a bead 43, Fig. 13, at the rear end. The spindle is mounted in bearings 45, 46, Fig. 4, on the slide 74, each bearing consisting of a tapered sleeve 49, Fig. 2, rotating with the spindle in the tapered bore of the bearing. Nuts 50, 51 adjust the sleeves within the bearings and the nut 51 also serves to clamp a split end of each sleeve on the spindle.