GB509552A - Improvements in and relating to driving gearing for planing or other machine tools - Google Patents

Abstract

509,552. Grinding-machines. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 22, 1938, No. 27656. Convention date, Sept. 24, 1937. [Class 60] [Also in Groups XXII and XL] A machine tool such as a milling, planing, slotting or grinding machine has the working and traversing speeds and the reversal controlled by scanning a pattern of the same shape as the work-piece by a scanning device whose position on the pattern always corresponds with the position of the tool on the work. In the application to a planing machine, the table 2 carrying the work is reciprocated by a motor 10, while the tool 4 is fed horizontally or vertically by motors 9, 8 respectively. Control for planing a piece of the shape shown by the continuous vertical lines in Fig. 4 is effected by means of a photo-electric cell 14 operating in conjunction with a templet consisting of a scale drawing of the work having different translucence in different parts. For example the surface corresponding to machining areas may be shaded grey, quick traverse areas may be white and the margins where reversal of the stroke is to be effected may be black. The cell is moved so that its position always corresponds with the position of the tool on the work. For this purpose a block carrying the cell may be moved by screws 17, 18 driven from splined shafts 21, 22 respectively, these shafts being driven by motors 23, 24 coupled by the Selsyn system with the table motor 10 and the feed motor 9. Where the tool passes over gaps in the work-piece as shown by dotted lines in Fig. 4, the high-table speed is effective. Suitable allowances may be made on the templet to ensure that the correct cutting speed becomes effective before the tool engages the work. Alternatively, the scale of the templet may be enlarged or a modified transmission ratio of say 1 : 1.1 may be employed between the scanning-cell drive and the machine drive. In a modification, the scanning may be effected mechanically. For instance, the templet may have sections cut to different depths and be scanned by a ball device 28, Fig. 6, actuating contacts 31 which control the speed and direction of the driving motor. Alternatively, electrical measuring heads may effect the control. The transmission of the scanning movement may be through toothed gearing or. by pantographs, the motors 23, 24 being dispensed with.