GB521370A - Improvements in or relating to grinding and abrading machines - Google Patents

Abstract

521,370. Grinding-machines. ROWLAND & CO., Ltd., F. E., and ROWLAND, F. E. Nov. 17, 1938, No. 33394. [Class 60] Electrically-driven machines of the type in which the work is applied to the wheel by hand have the rest interconnected with change speed gearing and with a finger adapted' to make contact with the wheel and with switch mechanism so that on the one hand the wheel cannot be driven at an unsafe speed and on the other cannot continue to be driven at an uneconomical speed after the wheel diameter has become reduced. The rest 28, is movable towards and from the wheel centre on a bracket 27 adjustable vertically on the frame, and as the rest is reset from time to time following the wheel as it becomes reduced in diameter, a cam projection 33, Fig. 7, eventually engages the plunger 32 of a switch 31 and stops the driving motor. When the belts have been shifted on the line pulleys to give the next higher speed, the motor having a pivoted mounting 21 for this purpose, the movement of the belt forks 36, through links 44, 45 and bell crank 43 moves a slide 29 carrying the switch away from the projector 33 to permit a further range of inward adjustment of the rest. The bell crank is connected through bevel gearing 41 to an arm 46 linked to the finger 48, so that the finger is moved towards the wheel and prevents the belts from being moved more than one step on the cone pulleys. To prevent the motor from being restarted after backward movement of the rest to an unsafe distance from the wheel a bar 49 carried by links 50 rests on the switch plunger 32 and if such movement be attempted the frictional engagement between the bar and plunger will cause the bar to ram the plunger down. A catch and resetting finger may be provided for the bar accessible only from within the frame. The machine as shown has two motors driving separate but aligned shafts 13 each carrying a wheel 17 mounted in antifriction bearings 18 on a fixed sleeve 15 through which the driving- shaft passes with clearance, drive being communicated to the wheel at 19. One motor may drive the two spindles, independent belt tensioning being provided for by means such as jockey pulleys.