GB667174A - Improvements in or relating to machine tools having gear shift control mechanism - Google Patents

Abstract

667,174. Change-speed control; shaft couplings. BROWN & SHARPE MFG. CO. Jan. 11, 1949 [Jan. 24, 1948], No. 735/49. Class 80 (ii). The drive from the control member 64, Fig. 1, of a machine tool change-speed gear to the executive speed-changing members 52 is through a connection 80, 82 which normally drives solid but which contains an element 82 yieldable upon overload, due to non-meshing abutment of the teeth of relatively-shiftable gears to be engaged, in order to actuate a device for imparting a gearsynchronizing start-and-stop impulse to the power source of the machine tool drive. As shown applied to the sliding wheel cascade train of a milling machine spindle drive, the sliding wheels are controlled from cam drums 52 mountec on a shaft 40 and a further shaft (not shown) geared there to. A coupling element 8( rotatable on the shaft 40 has tapered teeth coacting witl similar teeth on an element 82 slidable on the shaft 40 througl a pin 90 engaging a slot therein and spring biassed to engage fully the element 80 during normal drive of the drums 52 from a manual control handle 64 via gearing 68, 70, 74, 76. The arrangement is such that each complete revolution of the handle 64 initiates a further one in a progressive series of gear changes, and, to prevent the handle 64 and drums 52 getting out of step, the element 82 has only a range of axial movement insufficient to allow complete disengagement of the elements 80, 82. When the operative drum 52 encounters excessive resistance due to end-on abutment of the gears to be meshed, the member 82 yields axially and, through a plunger 98, fast with the pin 90, and a further spring loaded plunger 100, actuates a two-way switch 96, which is incorporated in an electrical control circuit, Fig. 5 (not shown), for the machine in such a manner that a relay controlling the spindle motor is temporarily energized to give a momentary impulse to the spindle drive.