Patent GB-498486-A (GB)
Title: Improvements in or relating to light-actuated control means
IPC: H01J40/14
Filed: 1937-07-09
Abstract: 498,486. Photo - electric apparatus; thermionic valve relay circuits. GILBERT, V. H., and RADIOVISOR PARENT, Ltd. July 9, 1937, No. 19091. [Classes 40 (iii) and 40 (v)] In photo-electric apparatus for controlling the filling and emptying of hoppers or similar to-and-fro movements, two photo-electric cells 1, 2, Fig. 4, are arranged at different levels and are connected in parallel with each other and alternately in series with a relay 4, Fig. 1, the arrangement being such that when the relay is energized, the circuit of the light sensitive element 2 located at one level is closed and the other element 1 is isolated until the light conditions of both elements are reversed, whereupon the relay is de-energized and is again re-energized when the light conditions of both elements are restored, the relay also serving to control the circuit of a controlling or signalling device. In the form shown in Figs. 1 and 4, when a hopper 15 is empty and both cells 1, 2 are exposed to light from lamps 46, 47, the relay 4 is energized and both arms 5, 6 thereof are lifted up to contacts 9, 12 respectively. A device 14 is thus energized and gives a signal or causes a motor 16 to operate a conveyer 17 to fill the hopper. When the hopper is full and therefore both cells are screened off, the relay is de-energized the arms 5, 6 move down to contacts 8, 11 respectively and the device 14 is de-energized. The various devices remain in this condition until the hopper is emptied, when the operation mentioned above is repeated. In the form shown in Fig. 3, the photo-electric cells 1, 2 and adjustable resistances 35, 36 in series therewith are fed in parallel from the secondary 37 of a mains transformer, the primary of which is indicated at 23. The points 41, 42 of connection between the cells and the resistances are connected to contacts 33, 34 co-operating with the armature 32 of a relay 19 in the anode circuit of a thermionic valve 18, the grid 26 of which can be connected through a grid current limiting resistance 27 and a plug 28 to socket 29 of armature 32. The filament of the valve is heated by a secondary 25 of the mains transformer, and the anode current is supplied by the secondary 24. The secondary 37 feeding the cells is provided with a potentiometer 39, the rider 40 of which is connected to the mid point of the secondary 25 feeding the filament to determine the grid bias. The rectified anode current produced by the action of the cells is smoothed by a condenser 49 across the relay 19. Another armature 43 of the relay is in circuit with a source of power 45 and a signalling or controlling device 44. The plug 28 can be connected to either of two sockets 30, 31 to facilitate preliminary adjustments of the circuits of each cell or if apparatus is required for use with a single cell ; but in working according to the invention, the plug 28 is connected to socket 29. Assuming the device 44 is the motor 16 of Fig. 4, and the hopper 15 is empty. The light on the cells causes the relay 19 to operate. The armatures 32, 43 then make contact with 34, 48 respectively and motor 16 drives conveyer 17 to fill hopper 15. When the filling is completed, light from lamp 47 is cut off from cell 2, relay 19 is de-energized, and motor 16 stops. If now hopper is emptied, first cell is lighted ; but this cell is out of circuit with armature 32, and the valve circuit, Fig. 3, remains inoperative until level has fallen below cell 1. When this cell is lighted the valve circuit is again operated and the filling operation repeated. In a modification, the valve circuit is fed from batteries.