GB445105A - Improvements in and relating to metal milling machines - Google Patents

Abstract

445,105. Milling. JERECZEK, V., 8, Wolframstrasse, Tempelhof, Berlin. Oct. 1, 1934, No. 28061. [Class 83 (iii)] A feed drive for the work table of a milling- machine, which is adapted during cutting to move in the same direction as the operative teeth of the cutter, has two screw-threaded members in such driving connection with the table, one being displaceable longitudinally with respect to the other, that the thrust forces set up by the action of the cutter are taken up by brake surfaces and utilized in removing backlash from the screws. The feed mechanism for the work table 6 comprises a pair of oppositehanded screws 4, 5, Fig. 2, which rotate in fixed nuts 2, 3 and are connected together by helical gearing arranged in a housing 22 at the end of the table. The helical wheels 14, 15 are loosely mounted on a sleeve 9 which, by means of end teeth 10 and a keyed sleeve 11, is connected for movement with the screw 4. The sleeve 9 has a star-shaped collar 13, the projections 13<1> of which engage dogs 16 and 17 on the helical wheels 14, 15. A nut 11<1> housing a thrust bearing 30 secures the screw 4 to the table with a limited amount of axial freedom. The toothed wheels 14, 15 engage the toothed peripheries 18<1>, 182 respectively, of the hub 18 arranged on the screw shaft 5 and keyed thereto by dogs on its end engaging similar dogs on a collar 25 secured to the shaft. The screw shaft 4 is driven to effect the feed by means not shown, rotation is in the direction I for feeding the work 7 up to the cutter 8 in the direction of the arrow, Fig. 1. During this movement the drive is transmitted from the shaft 4 through the inclined dogs of the collar 13 to the wheel 15, the inclination of the dog-engaging surfaces is such that the wheel 15 is forced to the right and consequently the shaft is forced to the left to take up backlash in the screwthread ; as the wheel 15 commences to rotate, the reaction between interengaging teeth tends to force the wheel 18<2> and its hub to the right against a thrust washer 28. The toothed wheel 18<1> transmits the drive to the wheel 14 which is thereby forced to the left against thrust collars or brake surfaces 19, 20. As the work reaches the cutter the latter tends to drag the work along and this force is transmitted to the shaft 5 through the thrust bearing 29. The speed of rotation of this shaft during feeding, coupled with the vibrations set up in the machine during milling, are stated to cause the shaft 5 to behave as a reversible screw and thereby tend to increase its rotation. This increased rotation is transmitted to the hub 18 and the wheel 18<2> tends to rotate the wheel 15 to bring about the disengagement of the driving dogs 13<1> and 17, at the same time forcing the wheel to the right. The wheel 18<1> similarly gives an extra rotation to the wheel 14 which is forced with increased pressure against the brake surfaces 19, 20 and its dogs 16 are brought into engagement with the dogs 13<1>, the inclination of these dogs still increasing the pressure of the wheel 14 to the left. The whole of the feeding mechanism is thus tightened up and the feed is still controlled by the rotation of the shaft 4. The return motion of the work table may be used for cutting, the rectangular dogs of the collar 13, Fig. 4, then being used to transmit the drive.