GB857004A - Machine-tool - Google Patents

Abstract

857,004. Drilling-machine details. SOC. GENEVOISE D'INSTRUMENTS DE PHYSIQUE. Dec. 24, 1957 [Sept. 10, 1957], No 40038/57. Class 83 (3). In a machine-tool of the type wherein a member 11 is positioned in two stages, firstly by hydraulic means 13,14, and then by a screw- and-nut gear 15, 16, mechanism 26 is provided to return the nut 16 into its medial position relatively to the screw 15 to avoid jamming of the nut at the ends of the screw arising from a succession of operations of the screw-and-nut gear. As applied to positioning the table 11 of a jig-borer along a path perpendicular to the direction of traverse of the boring-head 12, the screw 15 is on the end of the rod of piston 14, and cylinder 13 is fixed to the machine-bed 10. The nut 16, formed as a bevel-gear, is driven from a shaft 20 by a sliding bevel-gear 19 and bevel-gears 18, the nut 16 and gears 18, 19 moving with the table. A hand-lever 39 controls admission of liquid to the cylinder 13, and the hydraulic traverse, which may be effected at a variable speed, is terminated at a few mm. or a fraction of a mm., short of the desired position, by means which are not described. A reversing electric motor, which may have two speeds in each direction is then started and completes the table traverse by rotating the nut 16 on the screw 15, which is held stationary by the hydraulic system, the motor driving shaft 20 by a worm-gear 22, 23, bevel gears 24 and an electro-magnetic clutch 25. Alternatively, the traverse may be completed by a hand wheel 35, driving the shaft 20 through an electromagnetic clutch 38 which is disengaged automatically and an electromagnetic brake 37 applied when the motor 21 or the hydraulic jack 13, 14, is operative. The return mechanism, operated by depression of a push-button 34 when a warning lamp 33 is illuminated and indicates that the nut is adjacent either end of the screw, consists of bevelgears 26 coupled to the shaft 20 by an electromagnetic clutch 27 and driven by the motor 21 the direction of rotation of which is decided by one or, as illustrated, a pair of cams 28c, 28d, operating switches 31. Operation of the button 34 de-energizes clutch 25 and energizes the clutch 27. The cams, rotated from shaft 20 by gears 30, turn through about 270 degrees as the nut traverses the operative length of the screw, and further cams 28a, 28b are provided to control the warning lamp 33, cam 28a causing intermittent illumination of the lamp when the nut is adjacent the ends of the operative part of the screw, and cam 28b a continuous illumination if the nut reaches the end positions. When the nut reaches the medial position, the cams 28c, 28d de-energize the motor. In a modification, the gears. 22-24 may be duplicated in a different ratio to provide a second speed for the final part of the traverse. The nut may be returned to the medial position automatically by a switch energizing the motor 21, the switch being operated by the hand-lever 39 each time the hydraulic traverse is operated, or by a tachometer driven by the table.