Patent GB-988722-A (GB)
Title: Machine tool
IPC: B23Q3/157
Filed: 1962-05-30
Abstract: 988,722. Machine tool details. KEARNEY & TRECKER CORPORATION. May 30, 1962 [Nov. 13, 1961], No. 20797/62. Headings B3B, B3C and B3K. [Also in Division G3] A milling, drilling &c. machine tool comprises a work-table 60 carried by a base 57 for rotary movement about two independent axes, a power-driven tool spindle 47, and means for mounting the spindle and table for rectilinear movement relatively to each other in three mutually transverse directions, whereby the position of the spindle relatively to the table may be adjusted to five different paths of travel. The spindle 47, driven by a motor 48, is mounted on a head 43 movable, at a rate determined by a servo-valve, by a screw 38 and an hydraulic motor 44 on a column 32 traversable by a motor 34 also controlled by a servo-valve, in co-operation with a tachometer 907, and a sensing head 906 adjacent a scale 905. The servo-valves receive error signals according to the reading of the sensing heads moving over the energized scales, the motor speeds being controlled by means of the tachometers. A drill 49 in a holder 50 is clamped in the spindle by an hydraulically - actuated collet. The weight of the head is counterbalanced by hydraulic means 51. The table 60 is rotated by a motor 75 on the base 57 which is pivoted at 58 to a saddle 56 traversable by a motor 64 and a screw 63, control being also through a servo-valve 785, a scale 917, a reading head 916 and a tachometer. The base 57 can be rotated about the pivot by a motor 70 controlled by a servo-valve 325 and driving through spiral bevel gearing at each side of the base. The weight of the base is counterbalanced by fluid-pressure piston 499 in pivoted cylinders 496 and the base is frictionally clamped in position on each side by spring-pressed plungers 522 which can be relieved by fluid-pressure. The movements are all determined in direction and speed, through the servo-valves, by a punched tape programme control box 92 which also controls a toolchanging mechanism 80 and the speed of the tool spindle through a tachometer 901. The tool-changing mechanism is of the type described in Specification 946,987 and 916,501. It includes an oscillating tool pick-up arm 107 on a tool-extraction and insertion slide 106, the tool required being selected by a switchmechanism 121 on a storage device 84. The switch mechanism is moved hydraulically to operative position when required, and the toolchange mechanism is operated by fluid-pressure motors and rack-and-pinion gearing. During a tool-change, the tool storage magazine is rotated counter-clockwise until a selected tool is located and is then reversed at a slow speed controlled hydraulically until a roller runs into a recess in a disc rotated with the turret to position the turret precisely. The table 60, Fig. 6, has an annular bearing surface 366 protected by a seal 362. The table is attached by screws 384 to a central spigot 379 and is rotated by a gear 388. A tachometer 420 gauges the speed of the motor 75, which is controlled by a servo-valve 465 and a rotary scale 461, for positioning the table, co-operating with sensing heads 467, 468 on an adjustable mounting 469. Selector switches and pushbuttons are provided to allow the movement to be controlled under manual control, the spindle speed being set by a potentiometer.