GB523199A - Improvements in or relating to metal or other grinding or cutting machines - Google Patents

Abstract

523,199. Grinding and polishing. LUND, J. Dec. 8, 1938, No. 35749. [Class 60] [Also in Group XL] The feed of a grinder 10, Fig. 2, towards work 11 is stopped when the work is reduced to a predetermined size, as ascertained by feeler 38, but grinding continues due to elasticity of the work, and after a further reduction in size, the grinder is withdrawn from the work. The feed of the grinder is effected by pistons 22, 35, Fig. 3, the supply of fluid to which is controlled .by electromagnetically actuated valves 80, 81 controlled over a thermionic valve circuit, Fig. 6, by movement of an armature 43 connected mechanically to the feeler 38. With the valves 80, 81 in the position shown, the piston 22 is urged to the left, to move the slide 15 with a fast initial feed towards the work. Piston 35 is urged to the right, and through rack and pinion gearing rotates piston rod 21 to screw pin 19 to the left, and thus imparts a slow final feed to the slide 15. At the first predetermined size, valve 81 is turned to dotted line position, thus placing both sides of piston 35 to exhaust and so arresting any further movement thereof. At the final size the valve 80 is turned to dotted line position, thus applying pressure to the pistons so as to move 22 to the right and 35 to the left and so withdraw the grinder from the work. Movement of the armature 43 alters the balance of an AC bridge comprising coils 45, 46, 51 and 52, the rectified output being applied to the grid of a pentode 59. The output of the pentode is applied to the grids of valves 60, 61 which are differently biassed by potentiometers 64, 65. These valves become conducting at different positions of the armature 43, and through the intermediary of relays 70, 71 in their anode circuits, and contactors 72, 73 control the electromagnetically actuated fluid valves 80, 81.