Patent GB-597689-A (GB)
Title: Improvements in or relating to milling machines for copying
IPC: B23Q35/18
Filed: 1944-07-04
Abstract: 597,689. Copying by milling. CINCINNATI MILLING MACHINE CO. July 4, 1944, No. 12735. Convention date, June 10, 1943. [Class 83 (iii)] [Also in Group XXIX] An automatic tracercontrolled milling machine for copying, has a workholder and a cutter head which are relatively movable in three perpendicular directions, two tracers being provided on the cutter head, one of which controls two of the relative movements and the other controls the third movement. The machine comprises a base 10 having horizontal guides for the work table 11 and vertical guides 16 for the cutter carriage 17. The pattern is attached to the face 243 of a bracket 241 which is angularly adjustable in a horizontal plane and also to and from the carriage 17 by a a pivot and screws on the worksupporting bracket 240 on the table 11. This adjustment enables the pattern to be set parallel to the motion of the table after being clamped to the bracket. The cutter 170 is mounted in a head 27 which is slidable on the carriage to and from the work and is driven by a motor 238 on the head. The table 11 is traversed by a hydraulic cylinder 13, Fig. 11, the carriage 17 by cylinder 19 and the head 27 by cylinder 28. Fluid is supplied to the system by a feed pump 137 and a rapid traverse pump 136 whose output is controlled by a selector valve 135, and the fluid may be admitted to any one or more of the cylinders, for normal milling operations or for setting the machine slides, by means of servo valves 46, 48 and 79 respectively, and selector valves 41, 58, 73. As shown, pressure is admitted to both ends of each cylinder and the three slides are held stationary, but rotation of any of the screws 47, 64, 80 will displace the corresponding servo valves and cause feed of the slides so long as the screws are rotated. Rotation of the screws may be effected by hand wheels 81, 83, 82 respectively, or the screws 47, 64 may be rotated by power, as described in Specification 461,596, interlocks controlled by valve 41 being provided to disconnect the screws from the slides and to disconnect the drive from the screws 47, 64. The cylinders 13, 19 are controlled by a valve 103 operated by a tracer 104 to effect copying motion between the cutter and work in a, vertical plane and cylinder 28 is controlled by a valve 105 operated by a tracer 106 for copying motion of the cutter in an axial horizontal direction, A control valve 149 may be moved against the action of a spring 151 by means of a hand-operated lever 152, in which case the cylinders 13, 19 are under hand control and may be actuated by rotation of a hand wheel 169 as described in Specification 581,148 which rotates an eccentric 158 to vary the setting of two reversing and throttle valves 119, 128 connected to the cylinders and thus causes the tracer 104 and cutter to approach the pattern and work respectively. On contact of the tracer with the pattern, the valve 103 is displaced to admit fluid from the pressure line 184 to cylinders 177, 179 to rock latch levers 153, 109. The latter cuts out the manual control and the former allows the valve 149 to be moved down by its spring, and latches it in this position in which a fluid motor 162 for rotating the eccentric 158 is connected. by pipes 163, 164 to ports 174, 189 of the tracer valve 103. The motor 162 is then rotated to cause further approach of the tracer 104 towards the pattern until the pressure on the pattern is balanced by the pressure of a spring 173, the valve 103 then being in a neutral position in which the motor 162 is stopped and the cylinders 13, 19 are actuated to cause the tracer to move tangentially along the pattern. Deviations of the pattern from this direction act on the tracer 104 to move the valve 103 in or out to cause rotation of the motor 162 and eccentric 158, thus setting the valves 119, 128 to give a resultant motion of the table 11 and carriage 17 tangential to the pattern, as described in Specification 581,148. In the neutral position of valve 103, return flow from the valves 119, 128 by pipes 145, 146 is allowed to pass through ports 197, 198 to an exhaust line 199 but movement of valve 103 by the tracer in either direction, throttles the passage through these ports. and so slows down the feed of table 11 and carriage 17 whilst a change in direction of motion is taking place. The lever 152 is operated by a knob on top of the tracer housing 201 and the lever 107 for setting the valves 41, 58 to hand control position is connected by linkage 205 to a hand lever on the vertical column 15 which supports the carriage 17. The speed of operation of the table 11 and carriage 17 is controlled by varying the eccentricity of the eccentric 158 by means of an inclined bar which is slid through the mounting of the eccentric by a crank rotated through gearing and a hand-operated shaft 290. For three dimensional copying the axial motion of the cutter to and from the work by means of cylinder 28 is brought into action by feeding the tracer 106 against the pattern. This is effected by operating the handle 82 to feed the head 27 in under control of the servo valve 79 and when the tracer 106 engages the pattern the valve 105 is displaced against its spring 210 to admit fluid below valve 73 which is moved upwards to cut out control by the servo valve 79, connect cylinder 28 to tracer valve 105 and operate a plunger 233 to disconnect the nut 235 from the servo screw 30. The plunger 233 will also be actuated to disengage the nut 235 if, during in feed of the head 27, the tracer 104 is caused to engage the pattern and thereby impart excessive movement to its valve 103. Deflection of the tracer 106 by the pattern connects the supply line 133 to one end or the other of the cylinder 28 to cause the cutter to move in and out as it traverses along the work either by power or manual control through the servo valves 46, 48 or under control of the tracer 104. The tracers are carried by a bracket 245 having a base 246 which is adjustable on the head 27 to and from the table 11 by means of a rack and pinion operated by a handle 251. Tracer 104 is carried by a saddle 253 and tracer 106 by a saddle 254, both saddles being independently adjustable on vertical guideways 252 on the bracket 245 by means of screws 255, 256 rotated through bevel gears &c. from handles 266, 268 on the base 246. The saddle 253 has horizontal guides on which a knee 269 is adjustable by a rack and pinion operated from a handle 273 and a housing 201 carrying the tracer 104, valves 103, 149, 119 and 128, eccentric 158 and motor 162 is laterally adjustable on guides 274 on the knee by a manually operated screw 294. The tracer 106, and valve 105 are mounted in a housing 357 laterally adjustable by a hand-operated screw 359 and capable of being clamped after adjustment on a saddle 358 which is adjustable on guides 361 on the saddle 254 by a handle and screw 363. In order to produce a workpiece having identical horizontal sections from a single laminar pattern, by horizontal traverses of the table 11 with in and out motion of the cutter and step by step vertical feeds of the cutter, the tracer 106 is held against vertical movement so that it will remain in the plane of the pattern and not partake of the stepped feed. For this a goose neck bracket 313 on the column 15 carries a horizontal guide 309 in which may be engaged a roller 308 on a bracket 303 attachable to the saddle 254 by screws 305. When the bracket 303 is placed in position on the saddle a key thereon depresses a spring latch in the saddle to withdraw a half nut from the screw 255 and so allow the screw to move vertically with the bracket 245 and head 27 whilst allowing the guide 309 to maintain the tracer 106 in a constant horizontal position. To prevent a collision between the saddle 254 and the guide 309 a vertical rod in the saddle engages a pivoted cam bar 325 to rock the bar and open a switch 321 on the bracket 313 as the saddle approaches the guide, thereby stopping the motor which drives the pumps 136, 137 and relieving the fluid pressure to stop further upward movement of the head 27. To allow the tracer 104 to follow a laminar pattern it is prevented from moving in and out with the tracer 106 by means of a bracket attached to the carriage 17 having a vertical slot engaging a roller on a plate adjustably clamped to the knee 269, the rack and pinion for adjusting the knee then being disengaged. To withdraw the head 27 from the work and pattern a hand grip 356 on a vertical rod 353 on the machine frame is pulled upwards, this rod being connected by a Bowden wire 342 to the tracer valve 105. Movement of this valve admits fluid to cylinder 28 to withdraw the head and on release of the rod 353 the valve 105 assumes its undeflected position and control of the cylinder 28 is restored to the servo valve 73. Balancing parts.-The saddle 254 is balanced by a chain and a weight sliding in the bracket 245, and the carriage 17 by a chain and a weight sliding in the column 15.