Improvements in or relating to means for eliminating back lash in transmission mechanisms

摘要

664,824. Machine tool details. VICTORIA MACHINE TOOL CO., Ltd., FRYE, J., and SELBY, J. May 17, 1949 [April 20, 1948], No. 10897/48. Class 83 (iii). [Also in Group XXIV] A screw-and-nut transmission mechanism has means for eliminating backlash. particularly for when the load is in the direction of movement. It is shown applied to a milling-machine in which the table is connected to a non- rotatable traverse screw 1 engaged by two nuts 2, 3, rotatably mounted in a fixed part 23. The nut 2 is rotated by gearing 26, 29 and has projecting tongues 5 engaging slots in the nut 3 so that the two nuts rotate together but may have relative axial movement. The outside of the nut 3 is formed with a coarse helical thread engaging a similar thread in a sleeve 4 in frictional engagement with a rotatably-mounted boss 7 which may be held stationary. The boss 7 has a conical bore and is axially urged into frictional engagement with the conical periphery of the sleeve 4 by springs 12 acting on pins 10 which are slidable in holes 11 in the boss, the pins being secured to a rotatable annulus 9 abutting the face of a collar 8 secured to the sleeve 4. The screw 1 may be moved at two speeds-for " quick traverse " or for " feed "-by separate motors, and as the backlash-eliminating means is required only when feeding, it is automatically effective only on energization of the feed motor. A solenoid 16 is connected, through a switch, across the feed motor terminals and actuates a rod 36 raising a plunger 14 to engage slots 13 in the boss 7 and hold it against rotation. The nut 3 is thus yieldingly urged forward by the coarse helical thread (in co-operation with the slipping connection 4, 7) so that the nut 3 acts as the driving means for the screw 1 and the nut 2 as restraining means. When the solenoid 16 is de-energized the screw 1 is driven by the nut 2. Conventional backlash-eliminating means, comprising a nut 17 rotatable with nut 2, the two nuts being adjustably pressed axially apart, is also provided. Specification 596,147, [Group XXIV], is referred to.