GB370142A - Circuit for testing electrically-operated photographic flashlamps - Google Patents

Abstract

370,142. Flashlight photography. SASHALITE, Ltd. and HARKER, J. A. M., Westminster House, Great George Street, London. Feb. 28, 1931, No. 6317. [Class 98 (i).] In order to test the filament of a photographic flashlamp of the type in which oxidizable material in a bulb or vessel is ignited when current is passed through a filament, a small electric lamp having a filament of high resistance is connected, in series with a testing switch, across the main switch of the circuit so that, if the flashlamp filament is intact, the test lamp lights up, but the current in the circuit is insufficient to cause the flashlamp filament to glow. One construction of flashlamp unit is shown in Fig. 4, the connections being shown diagrammatically in Fig. 7. A metal container 11 has on its underside a flanged plate 12 adapted to slide into a fitting on the top of the camera, brackets 13, 14 being provided at the top for supporting a reflector 15. A block 16 of insulating material is secured within the container 11 by screws 17 and is provided with a recess to take a socket 18 into which fits the cap 19 of the flashlamp 2. The socket 18 is connected to a metal strip 20 which at one end has an upwardly bent portion 20a received in a recess 16a, and at the other end is bent up at 20b at the end of the block 16. A screw 21 engaging the centre contact of the flashlamp 2 is connected to a metal strip 23, insulated from the strip 20 and bent down to make contact with one terminal of a battery 27. The other terminal of the battery is bent over to make contact with the container 11, and thence, through a spring conducting strip 30, with a socket 29 adapted to take a small test lamp 31 and having a perforated protecting cap 32. The battery 27 is held in position by an insulating plate 33 which is held between lugs 11b and a spring 34. The plate 33 carries a conducting strip 35 making contact at its upper end with the end 20b of the strip 20 and at its lower end adapted to engage a contact piece 36 on the camera connected to a switch 38, which may be controlled by the camera shutter as described in Specification 363,050. On pushing in the test lamp 31, this is placed in series with the flashlamp 2 and battery 27 and lights up if the filament of the flashlamp is complete. Alternatively, the test lamp 31 may be connected to a two-way switch so arranged that the test lamp may be connected either across the main switch or across the flashlamp socket. In the latter position, by removing the flashlamp and closing the main switch, the test lamp glows if the rest of the circuit is complete. In a modification, the battery is contained in a hollow handle carrying a press-button switch for completing the main circuit. A two-pin plug connection may be provided for connection to a shutter-controlled switch with or without additional flashlamps in series.