| 摘要 |
717,399. Photo-electric machine guards. GENERAL ELECTRIC CO., Ltd. Sept. 28. 1953 [Oct. 9, 1952], No. 25349/52. Addition to 664,797. Class 40 (3) In a photo-electric machine guard comprising photo-cells and means adapted to set the machine in operation when beams of light are facing on each of the cells but to prevent the operation when no beam is falling on any one of the cells, means are provided periodically and automatically to intercept the beams to each of the cells in succession to check the functioning of each cell. As shown, beams of light pass from sources 10a, 10b, 10c across the front of a power press or other machine to be guarded to series connected photo-cells 13a, 13b, 13c respectively. When all the cells are illuminated an anode relay 23 of an A.C. fed triode 20 is energized. Relay 23 in turn operates a relay 26 which energizes a magnet 36 to fix the fu'crum of a foot-operated lever 30 so that the machine may be set in operation. Towards the end of the machines operating cycle contacts 48a are opened and contacts 48d closed by moving part of the machine, thus intercepting the beam of light tc cell 13a. If relay 26 is not de-energized contacts 48d complete the circuit of a relay 42 which locks itself over contacts 46, operates a warning device 45, and breaks the supply to the contacts of relay 23, thereby preventing subsequent energization of relay 26. All the photo-cells may be checked in the same cycle or during successive cycles of the machine operation. A larger number of cells operating through one amplifier or in groups through a number of amplifiers may be used. An alternating current amplifier using two for more valves and operating from modulated light may be used. |
