Patent GB-650279-A (GB)
Title: Method and machine for forming predetermined irregular surfaces
IPC: B23C3/18
Filed: 1948-05-07
Abstract: 650,279. Grinding and polishing. THOMPSON PRODUCTS, Inc. May 7, 1948, No. 12624. Convention date, May 15, 1947. [Class 60] [Also in Groups XXII and XXXVII] A method of machining surfaces of varying side-to-side and end-to-end contour, such as those on impeller blades, comprises moving the workpiece rotatively about a given axis, lengthwise of the axis, and transverse to the axis, and moving a rotating cutter axially and also angularly about a second axis, all the movements being simultaneously performed in a single machining operation. The cutter may be a straight or tapered spiral milling cutter, or it may consist of a polishing tool or grinder. General arrangement.- As shown in Figs. 3 and 4, the cutter head 33 is supported for angular movement about a vertical axis on a platen 36 which is longitudinally and transversely movable on a base 32, cams C, D controlling the angular movement and a cam A the longitudinal movement. The work head 38 is mounted at the top of a vertically-movable column 39 slidable in ways 169, 172, Fig. 3, and the work spindle 42 is arranged for traverse and controlled rotation in the head in timed relation with the vertical movement of the head; a cam B controls the vertical movement, and cams E, F the rotation. The various movements are effected through gear trains from a two-speed motor 44 whereby the workpiece may have a rapid traverse to and from the cutting position and a slow feed during cutting. The main drive shaft 45 may also be driven manually for initial setting by a removable crank, which, when fitted in position, opens the circuit of the motor 44. Cutter mounting.-The cutter spindle 34, Figs. 8 and 10, is journalled on a horizontal axis in a head 33 adjustable longitudinally in a transversely-adjustable saddle 72, Fig. 10, on the platen 36, the spindle being driven by a belt drive from a motor 66 mounted on an adjustably hinged platform 67, on the head 33; the spindle mounting comprises radial and end-thrust bearings 58, 59 and lubricant seals 62, 63. The platen 36 is angularly movable about a vertical post 78, Fig. 8, on a carriage 37 which is longitudinally and transversely movable, the arcuate-shaped outer edge of the platen fitting in ways 86 on the carriage and retained therein by gibs 87. Angular movement of the platen is effected by plate cams C, D, Figs. 4 and 8, which are arranged in parallel horizontal planes and are carried by a slide 113 movable transversely of the carriage 37. Cam followers 115, 116 are provided on slidable racks 117, 118 engaging pinions 125, 126 which are integral with gears 133, 134 meshing with a gear segment 135 secured to the underside of the platen. The cams C, D are operated from the drive shaft 45 through a gear train which includes a telescopic shaft 103, 107 permitting longitudinal movement of the carriage and a gear 109 engaging a rack 112 on the slide 113. The carriage 37 is movable longitudinally on a flat slide 143 and bevel slide 144, Fig. 10, by means of the cam A, Figs. 4 and 8, which is rotated through gearing from the drive shaft 45. The cam acts upon a follower 156 mounted on the carriage and against the action of a spring 158, and a micrometer gauge 165, Fig. 8, permits correct initial adjustment of the carriage. Coolant oil is fed to the cutter by a pump driven by a motor 55, Fig. 3, provided in the base. Work mounting.-The work spindle 42, which carries the work, comprises a circular sleeve slidable and rotatable in a housing 166, Fig. 5, fixed to the work head 38 carried by the column 39; a lubricant seal 168 is provided at the outer end of the housing. Feed of the workpiece is through a screw 43 which is operatively connected to the drive shaft 45, Fig. 4, and threaded into a two-part nut 175 disposed in the interior of the spindle 42. The nut 175 is held against rotation and traverse in the housing 166 by pins and so engages the threads on screw 43 as to prevent lost motion. The screw 43 is carried on a shaft 179, Fig. 4, which is driven from the shaft 45 through gears and shafts 185-206, the shaft 193 being telescopic to permit the vertical movement of the column 39 and work head 38. Rotation of the spindle 42 is also effected from the shaft 45 under the control of the cams E, F each of which is carried by a slide 225 movable transversely of the spindle through a rack 222 and gearing 212, 214, 216 from a gear 209 on the shaft 179. Cam followers 228, 229 are carried by slidable vertical racks 236, 237 engaging elongated pinions 239 which are disposed on opposite sides of the spindle and mesh with a gear 242 on the spindle; back lash is prevented by a spring 244 engaging the rack 237. Vertical movement of the column 39 is effected by means of a cam B which is driven through gearing 245-253 from the slidable portion of the shaft 193; the cam engages a roller 259 mounted on the base 32 and transmits its vertical motion to the column through a roller on the latter. A work holder 299, Fig. 17, secured to the end of the spindle 42 has a bracket 303 provided with ways for receiving a work rest 304 on which the blank 291 is secured by clamps 306, 307; the upper surface of the rest 304 is complementary to the underface of the blank. Control.-The three motors 44, 55, 66 are arranged in a circuit provided with relays, switches &c. to permit an automatic cycle. Limit switches, Fig. 15, (not shown) are adapted to be actuated by dogs, preferably on the slide of the cam E, for (a) starting the cutter and coolant motors 66, 55 at a suitable time after starting the motor 44, (b) altering the winding connections of the motor 44 after a predetermined traverse at high speed of the work towards the cutter so as to feed it at slow speed for the cutting operation, (c) again controlling the motor 44 at the end of the slow feed to withdraw the work at high speed, and (d) stopping the machine at the end of the return movement. A further dog, preferably mounted on the gear 253, Fig. 4, for cooperation with a switch on the column 39, serves to open the main power circuit should over-travel occur. The circuit also includes a time-delay unit which, by the action of one of the limit switches, permits the motor 44 to reverse at high speed for an interval in order to counteract the effect of the kinetic energy of the moving parts and bring the parts to a stop in the correct position. Switches in the circuit provide for stopping the operation or returning the workpiece at any point in the cycle, reversing the direction of drive of the motor 44 so as to determine in which direction of movement of the workpiece cutting should occur, reversing the direction of rotation of the cutter, setting the machine for either manual or automatic operation, and controlling the intermittent rotation of the work spindle when set for manual operation. The act of applying a handcrank to drive manually the shaft 45, instead of employing the motor 44, energizes a relay which opens the circuit of this motor.