Patent GB-920746-A (GB)
Title: Spiral milling machine
IPC: B23C3/32
Filed: 1959-12-11
Abstract: 920,746. Milling machines. CINCINNATI MILLING MACHINE CO. Dec. 11, 1959 [Dec. 19, 1958], No. 42170/59. Class 83 (3). A milling machine for generating spiral flutes has one or more tool-spindles supported by an adjustable carrier for producing longitudinally extending spiral flutes in one or more workpieces supported by a headstock which is axially movable relative to the tool-supporting spindle, a servomechanism being provided including a tracer and a servomotor for effecting rotational movement of the work relative to the cutting tool, a cam being provided for contact with the tracer for controlling the operation of the servomotor, and adjusting means determining the position of the cam relative to the tracer for varying the rate of the said movement. The machine comprises a bed 31 Fig. 2, on which is mounted a rotatably adjustable table 30 which in turn carries a slide 33 with headstock 50 and tailstocks 51 for three workpieces 52. The table is adjusted by hand against a scale 86, Fig. 3, so that the workpieces are at the correct angle for the flutes being cut. Cutters 43, Fig. 1, are carried by a spindle 42 with flywheel 47 supported by an overarm 46, arbor supports 45 and head 36 which is vertically movable by piston and cylinder means (see below) to adjust the cut. The headstock 50, Fig. 3, has an axially fixed centre spindle and the outside spindles have rack and pinion interconnected quills which are adjusted by worm-gear 95-97, Figs. 3 and 6, so that the spindles may be adjusted in echelon corresponding to the angular setting of the table 30. The spindles are rotated, in timed relation with the movement of the slide 33, by worm and pinion gears from a fluid motor 65, Fig. 3, which also effects the indexing movement between cuts. The slide 33 is moved by a fluid motor 34, Fig. 2, driving a screw 35 which engages a nut on the slide. Dogs 396, 393 on the slide co-operate with switches 2LS and 4LS to stop the movement to the left or right respectively. Control arrangements. The fluid motors 34 and 65, Fig. 18a, and the piston-and-cylinder for the vertical movement (includes fast approach) of the cutter-spindle head 36 are supplied with constant-pressure fluid from pumps controlled by relief valves. Control valves in the hydraulic circuitry are operated by solenoids and in some cases by moving coils forming part of electronic servomechanism. The lead of the flutes and the depth of cut during the axial movement of the workpieces (taper control) are controlled by a pair of cam-bars 110, 140. These are pre-set by hand-mechanism prior to the operation. The arrangement is somewhat similar for both cam-bars, that for cam-bar 110 will be described. A bracket 120, Fig. 6, is secured underneath the table 33 and a lug 109 at one end of the bracket provides a pivoted support 111 for the cam-bar which is of Z-section. The bar is balanced by a spring 115 and is adjusted by a wedge 117 which is moved by a screw 121. The end of the latter is provided with a square for adjustment and a graduated vernier sleeve 127. A worm on the screw rotates a dial 125 which shows the lead setting. After adjustment the free end of the cam-bar is clamped in an arcuate guide slot 113 by a nut 112. A roller 136 is provided on the end of a vertically-movable support 137 which is forced by weights 331, Fig. 18a, to follow the cam-bar. The movement of support 137 is transmitted by a ball-nut and screw mechanism 375 to the rotor of a fine synchro-transmitter CX-3 which drives a coarse synchro-transmitter CX-4 through reduction gearing. The arrangement for cam-bar 140 and the depth-feed is similar, but in this case the cam-follower is moved up and withdrawn (when the cutters are to be retracted) by a fluid-pressure motor 257. The principle of the servo-operation is that the cams drive synchro-transmitters the signals from which are passed through synchrodifferential transmitters to receivers or control transformers. The error signals from the control transformers are amplified and rectified and finally applied to the moving coil of the desired hydraulic control valve. Indexing mechanism is provided housed in a casing 242, Fig. 1, at the side of the machine. Adjustment is provided for cutting up to twenty-four flutes. Operation of a manual switch at the end of a flute-cutting operation causes a rack piston 182, Fig. 18b, to rotate a pinion 225, under ratchet control, driving a synchro-transmitter for indexing the work spindles. Specification 920,745 is referred to.