Patent GB-959013-A (GB)
IPC: B23C3/18
Abstract: 959,013. Copy-milling. CINCINNATI MILLING MACHINE CO. April 19, 1963 [Sept. 26, 1962], No. 15501/63. Heading B3K. A machine tool comprises a reciprooable slide 2 (Figs. 1 and 2) carrying a rotatably mounted workpiece 8 on which an irregular contour is to be machined, means 29, 30 to record the position of the slide at a predetermined point in each cycle of movement of a fixture holding the workpiece, the recording means being resettable during each cycle, actuable means 5LS, 6LS energized by the recording means to produce a rate control signal when the slide is a preset distance from a recorded position, and means for changing the rate of movement of the fixture in response to the rate control signals. The table 2 is moved on an inclined guideway by an hydraulic piston. A series of turbine blade blanks 8 are each held for rotation between a headstock 5 and an adjustable tailstock 7. A master blade 11 is rotated in contact with a follower 22 by a headstock 13, all the headstocks being rotated counter-clockwise by a common hydraulic motor 16. The follower 22 controls hydraulic means 23 to move the table 2 to cause cutters 21 to generate the bladeshapes. It is required to reduce the rotational speed of each blade while the concave surface is being machined since, otherwise, the large amount of metal to be removed causes chatter. The point at which the speed is to be varied changes continually due to the twist of the blade. The piston-rods 29, 30 are therefore used to memorize the point at which each crosssection of the blade reaches a leading or trailing edge. The piston-rods are extended by means 31, 32 to engage stops such as 34 which can be advanced by fluid-pressure means. As the table moves in one direction (right, for instance), the stop 33 carries along the rod 29 until the leading-edge of the blade is reached and the table is reversed. The rod 29 remains in its right-hand position. The roller 22 is urged towards the master by a spring 51, Fig. 4, and moves in a sleeve 50, a position of equilibrium being maintained by pressure on the front and rear faces 52, 55 of the sleeve. The position of the sleeve 50 determines the position of a valve 58 which determines the pressure differential in lines 61, 62 leading to the motor which moves the table 2, pressure being supplied through a rate valve 63. Since the valve 58 must move before the slide moves, inaccuracies are prevented by the provision of a compensating valve 69 which causes movement of an hydraulic device 18 to move the cutter-slide 17 laterally in a manner as described in Specification 705,464. Movement of the valve 58 causes a reduction in speed of the motor 16 to compensate for the increased cut. The valve 58 can be adjusted angularly to either of two positions by a fluid-pressure motor 92 and gearing 94, 97 to set notches 82, 83. In operation, after an initial " set-up " cycle, the blades are rotating at a fast rate, the cutters are traversing downwards and the roller 22 is passing over the convex surface 27. When a dog on a disc 45, rotating with the master blade, actuates a switch 3LS, a stop 34, Fig. 2, is retracted. When the table 2 reaches a point previously recorded as the T.E. position, a cam 38 on the rod 29 operates a switch 5LS. This causes extension of a stop similar to the stop 34 and re-setting of the rod 29 thereagainst, sets a circuit for subsequent slowing down of the motor and operates a timer. The table finishes its movement right and is reversed, leaving the rod 29 in its new position. As the switch 5LS is released, a valve 98 is actuated to re-set the device 92 and rotate the valve 58 to slow down the rotational rate of the blades. A similar sequence of events causes subsequent speeding up of the rotational rate. When the blades are finished, a cam on the cutter carrier 19 actuates a valve to cause retraction of the carrier and re-setting of the machine.