Patent GB-626295-A (GB)
Abstract: 626,295. Photo-electric gauges. HURLEY, S. C. Aug. 28, 1945, No. 22080. Convention date, Sept. 23, 1944. [Class 40 (iii)] [Also in Group XL (c)] A gauging device comprises an electronic tube containing two control grids, one of the grids being connected in a control circuit responsive only when the article being gauged is correctly positioned in the inspection zone, the other grid being connected in a photoelectric control circuit responsive to the size of the article, and indicating means responsive to the tube anode current. As shown, Fig. 2, for inspecting and testing the diameter of round or cylindrical electrically conducting articles, the test piece is positioned in a V block 60 where it connects the side portions 14 separated by insulation 13, and permits a large current to flow through resistor 11 to ground, thereby lowering the potential on the grid 35 of a valve 26 and biassing it back to cut-off or substantially so. In the inspection zone, the test piece 64, Fig. 9, depending on its diameter intercepts a certain portion of the light projected from a source 101, through a condenser system 102 and focusing lens 104, on to a magnifying mirror 105 and reflected thereby on to photo-cells 18, 19. The arrangement is such that photo-cell 19 is in light and 18 is in shadow when the diameter of the test piece 64 lies within the allowable tolerances, the permissable tolerance being adjustable by varying the relative positions of the photo-cells and optical system. The photo-cells 18, 19 are arranged in a bridge circuit 2, Fig. 2, which when balanced applies earth potential to the grid of a valve 40. -When a test piece within the permissible tolerances is in the inspection zone, the bridge is unbalanced in such a way as to make point 25 negative, and bias the valve 40 back to cut-off. For bridge balance or unbalance in the opposite direction valve 40 conducts. When a test piece 64 of permissible size is located correctly in the inspection zone both valves 26, 40 are as above described, biassed to cut-off, thereby correspondingly and simultaneously raising the potentials on the control grids 55, 56 of a normally blocked power tube 50, for example, of the gas-filled type. Tube 50 then conducts and operates a relay 5 to actuate an interpreter 4 which may be an indicator, recorder, or sorting mechanism. The tube 50 is de-ionized prior to the next inspection by opening a switch 59 in its anode circuit, the switch 59 being actuated, e.g. by the mechanism feeding the test pieces into the inspection zone. Figs. 3 to 7 (not shown) show other arrangements for positioning test pieces of differing shapes in the inspection zone, correct positioning shortcircuiting the leads 16, 17, Fig. 2, as above described to cut-off tube 26. In another arrangement, Fig. 8, the photo-cell bridge circuit which includes voltage regulating glow discharge tubes 78, 87 controls the potential of grid 35 of tube 26 while the test piece positioning device 60 controls the grid potential of a tube 88. The anodes of the two tubes are fed in series with the relay coil 5 from A.C. mains 97 through a transformer 95. Normally both tubes are biassed to or beyond cut-off, the control grid potentials being simultaneously raised to permit anode current to flow and operate relay 5 provided that the test piece is correctly positioned in the inspection zone and that its size lies within the permissible tolerances. The tubes 26, 88 may both be of the gas-filled type. Actuation of relay 5 energizes a solenoid-controlled air-valve 100, Figs. 8 and 9, to " accept " the test piece, the " reject " air-valve 99 being operated if the relay 5 is not operated. A cam 94 synchronized with the test piece feeding mechanism closes the circuit to the appropriate solenoid 99, 100 during the appropriate time in the test cycles. The test piece positioning control and the photo-electric control may operate on separate control grids in one valve, Fig. 11 (not shown), and two or more such valves may be provided, Fig. 10 (not shown, for sorting test pieces of two or more sizes. Fig. 12 shows three tubes 138, 139, 140 in series, the tube 139 being controlled by an arrangement such as the test piece positioning device of Fig. 2, while the other tubes are each controlled by lightsensitive control circuits, the arrangement being such that the grids of all three valves must go positive simultaneously to pass anode current to actuate the interpreter 4.