GB555792A - Improvements to precision machine tool with automatic control of its slides - Google Patents

Abstract

555,792. Drilling. SOC. GENEVOISE D'INSTRUMENTS DE PHYSIQUE. Dec. 4, 1941, No. 15658. Convention date, Dec. 28, 1940. [Class 83 (iii)] [Also in Group XL] The work table of a precision centre-punching machine which is driven at a high speed towards the desired position by a motor is slowed down before it reaches the desired position by mechanically or electrically controlled devices and is then stopped accurately by a photoelectrically controlled device. The tool, which is adjusted transversely over the work table, may be positioned by similar automatic means or by hand. The work table 31, Fig. 3, is moved by a feed screw 35 driven by a motor 41 through a gear box 13, shaft 14 and gearing 33, 34. A hand wheel 24 is provided for independent or preliminary adjustment of the work table. The gear box 13 includes a clutch 27, Fig. 2, having upper and lower positions for low and high speed respectively and an intermediate disengaged position, the member 27 being actuated by an armature 26 pivoted at 28 and operated by two electromagnets 11, 12 controlled by a relay 10. The preliminary slowing down is controlled by an index member 16 attached to the table adapted at the proper moment to trip a lever 18 to open a switch 19 connected to the relay 10. The final stopping is controlled by a photo-electric cell 9 connected to the relay device 10 and subjected to light from a lamp 40 through an optical system including groups of marks 2a on a scale 1 attached to the work table and a corresponding screen 8 adjustable by a micrometer screw 37. The control circuit of the cell is normally cut off by a switch (not shown) which is automatically operated to prepare the circuit for operation just before the work table reaches its desired position. The scale 1 also carries marks 3a for observation by a microscope 7, when making hand adjustments. In operation, the pointer 16 is set to a mark on the scale 15 just short of the desired position and the screen 8 is adjusted for the additional travel required. The motor is started to drive the work table at high speed towards the desired position. Just before that position is reached, the pointer 16 trips the lever 18 and opens the switch 19 whereupon the relay device 10 throws the clutch 27 to the slow driving position and the circuit of cell 9 is prepared for action by its switch. When the work table reaches the exact position desired, the image of the groups of marks 2a coincides with the corresponding groups of marks of the screen 8, and the sudden change of illumination on the cell 9 causes the relay device 10 to switch off both magnets 11, 12 whereupon the clutch member 27 takes its mid position and the work table stops. The photo-electric device is similar to that described in Specification 558,848, [Group XL].