Patent GB-655207-A (GB)
Title: Method and apparatus for generating vane surfaces
IPC: B23C3/18
Filed: 1948-07-09
Abstract: 655,207. Grinding turbine blades. DEHN,S. G. (Thompson Products, Inc.). July 9, 1948, No. 18524. [Class 60] [Also in Groups XXII and XXXVII] A method of generating a vane surface on a workpiece by means of a rotary cutter T consists in effecting the co-operative relationship between the workpiece W and rotating tool in four co-ordinated components comprising rotation of the workpiece about a predetermined axis, relative lineal displacement of the tool and workpiece along said axis, relative lineal displacement of the tool and workpiece in a direction perpendicular to such axis and the axis of the tool, and relative lineal displacement of the tool and workpiece along the axis of the tool. The tool may consist of a sidecutting milling cutter, or be in the form of a grinding element. As shown in Figs. 1 and 4, the work spindle 13 is rotatably mounted in a carriage 12 slidable to and from a pedestal 11 on a bed 10. The tool spindle 16 is journalled in a carriage 15 which is movable vertically on a second carriage 14 adapted to slide along ways 11a, 11b transversely of the pedestal. The relative movements between the work and tool spindle are produced from a motor 20 of two-speed and reversible type through suitable gearing and cams. The lead screw 22 of the carriage 12 is driven from the motor 20 through gearing 20d ... 22a, and the rotation of the spindle 13 is effected by a rack 23b which engages a gear 24 on the spindle and is provided with a follower 23a co-operating with a cam B; this cam is either rigidly mounted on the bed 10 or moved longitudinally relatively to both the bed and carriage by the engagement in a nut portion 21g thereof of the threaded end 21f of a splined shaft 21 which is driven from the motor and so mounted in a bracket 47 on the carriage as to move axially with the latter. Back lash in the drive to the spindle is prevented by a hydraulic unit 25, the piston 25a of which is connected with a rack 26 engaging a second gear 27 on the spindle 13. Initial adjustment of the angular position of the spindle is effected by micrometer mechanism disposed between the cam follower 23a and the rack 23b. The transverse movement of the carriage 14 on the pedestal 11 is produced by a cam C which slides longitudinally on the latter under the action of a rack 30 and pinion 29b operated from the splined shaft 21 through the intermediary of a shaft 28 and gearing 21j, 21k, 28a, 29a. The cam follower 31a is carried by a member 31 secured to the carriage 14, and back-lash is prevented by a hydraulic or pneumatic unit 32, of which the cylinder is fixed in the pedestal 11 and the piston 32b is secured to the carriage; a micrometer adjustment is provided for setting the initial position of the member 31 on the carriage. The carriage 15 is moved vertically by a cam A which is mounted for longitudinal movement on the carriage 14 under the action of a rack 37, gearing 29c ... 29e and splined shaft 29 driven from the shaft 28. The tool spindle 16 is journalled in a plate 70, Fig. 12, which is vertically slidable along ways on a frame 68 adapted initially to be clamped by a gib in correct vertical position along vertical ways on the carriage 14; additional support for the spindle 16 is provided by a driving sleeve 75 which is journalled in the frame 68 and splined to the spindle so as to allow axial movement of the latter with the plate 70. The cam A is engaged by a follower 33 in the form of a bracket adjustably mounted on the plate 70. For generating the hub contour on the vane or impeller, the axial movement of the tool may be eliminated by using a cam A with a horizontal surface. A motor 34 on the carriage 14 drives the tool spindle 16 through a belt drive 35a and gearing 35d ... 35j, Fig. 4. The gear 35j is mounted on the sleeve 75, Fig. 12, and, in order to permit the initial adjustment of the frame 68, the gear 35h is keyed on a splined shaft 35e, Fig. 4, which is journalled at the top in the carriage 14 and projects at its base into a bore in the frame 68. If desired, a pump for supplying pressure fluid to the back-lash units 25. 32 or distributing coolant may be driven from the motor 34. The work spindle 13 is mounted in a sleeve 49, Fig. 7, which is journalled in a hollow casing 48 on the carriage 12 and carries the driving gear 24; the spindle and sleeve are clamped together at the front end by an adjustable ring 50 engaging flared surfaces 13a, 49e on the two members. When the workpiece is in the form of an impeller-wheel blank, an indexing ring 54, Fig. 16, which is provided with a plurality of spaced radial holes 54b, is secured to a hub 53 mounted on the rear end of the spindle. A hub 56 on the rear end of the sleeve 49 engages within the ring 54 and is provided with one or more radial holes 56c; an index pin 55 is inserted in registering holes 54b, 56c. A workholder 51, Fig. 7, having an outwardly-flared flange 51a is clamped against the flared front end 13b of the spindle by an adjustable ring 52. For milling a single-vane element. the indexing mechanism is dispensed with, and the blank W<SP>1</SP> . is supported on a block 82, Fig. 20, which has its top surface conforming to the bottom face of the blank and is rigidly secured to the base of an angle member 80 bolted to an extension 51b of the workholder 51; a screw clamp 81 engages an upstanding arm 80a of the member 80 and is threaded into the stem of the blank. If desired, the positions of tool and work on the spindles may be interchanged. Operation. The main motor 20, the tool spindle motor 34, and, if desired, separate means for driving pumps for supplying pressure fluid to the units and circulating coolant, are included in an electric circuit which is controlled by switches and relays in a low-voltage circuit. For automatic operation, a control switch is suitably set and a circuit of the motor 20 is then closed so as to energize the latter for high-speed operation in the forward direction. A switch situated in the path of the carriage 12 is operated by a dog on the latter just before the work reaches the tool so as to switch over the motor for low-speed operation during milling. A second switch. which is operated by a dog on the carriage at the end of the milling cut, serves to cause reversal of the motor at high-speed, and a third switch is opened by the carriage at the end of the return movement and stops the machine. Additional manuallyoperable switches are provided for effecting automatically the return of the spindles 13, 16 to their initial positions at any desired time in the cycle, stopping the machine at any point, and for controlling the motor 34 and pump-driving motors. When the machine is set for manual control, the machine is de-energized by the second limit switch at the end of the milling operation, and switches must then be actuated manually to return the carriage at high speed to the initial position. Specifications 617,607, [Group XXXVII], and 650,279 are referred to.