Patent GB-828438-A (GB)
Title: Improvements in and relating to apparatus for taking photographs in explosive atomospheres
IPC: G03B15/00
Filed: 1955-09-02
Abstract: 828,438. Photographic cameras. HOLLINGSHEAD, D. Sept. 3, 1956 [Sept. 2, 1956], No. 25281/55. Class 98(1) Apparatus for use in taking photographs in an explosive atmosphere comprises two gas-tight containers which are joined by a flexible tube and can be filled with an in-  ert gas, one container supporting or being adapted to support a camera and including, therein means for operating a camera flashlight and means for operating a camera shutter and the second container including electrical equipment, powered from the mains or from batteries in the container, for operating said means in the first container. As shown in Fig. 1, the apparatus comprises a container 1 on which a camera body 2 is permanently mounted and a power pack 4 joined by a flexible tube 3 to the container 1 and having therein a filling valve mounting 25 adapted for attachment to a cartridge of compressed inert gas. Divergent lugs 6, 7 project from the: rear upper corners of the container 1 and  depending therefrom are handles 8, 9. Accommodated within the lug 6 is a train of gears (Fig. 4) for driving the film sprocket 55 in the camera body 2, this gear train including a pinion 48 carried by an -arm 47 frictionally connected to a pinion 44 so that pinion 48 is adapted to mesh with  a pinion 49 and transmit the drive to .sprocket 55 only when the handle 8 is rotated (against a torsion spring) in the right direction for winding on the film in the camera. The other lug 7 accommodates .a slidable trigger bar 17 which, when it is pushed inwards, rocks a pivoted arm 70 so that a lever 102 extending downwardly into the container 1 through gas-tight bellows closes a switch 73 in the container 1. The closure of this switch energizes a solenoid 85 in container 1 from the power pack 4. As a result lever 81 (Fig. 5) is pivoted so that a member 80 thereon rocks a lever '74, housed in gas-tight bellows 77, to trip the shutter in the camera body 2, and flash contacts 90 are closed by a projection 89 from the solenoid armature to fire flash bulbs in containers 5 on top of the container 1. At the same time as switch 73 is closed, the arm 70 rocks a two armed lever 57, 61 about a pivot 59 to disengage a snail cam 56 on film sprocket 55 so that the film may be wound on with the arm 57 resting on the cam surface under the control of a spring 60. The new position taken up by lever 57, 61 is such that a latch 63 extending from the arm 61 engages a shoulder 67 - on the trigger bar, when the latter again moves outwardly on being released by the operator, and so prevents a further shutter operation until the film has been wound on one frame. An arm may project from one wall of the power pack so that, when the container 1 is rested on this arm, a micro-switch in power pack 4 is opened and the whole circuit de-energized. A pressure indicator observable from the exterior of container 1 and comprising a slidable lever, operated by gas-tight bellows against a spring, may be provided in container 1, which may also have a safety valve, the mounting of which has a screwed closure  member with lugs so disposed therein that the member can also serve as a key for removing the plug of the filler valve mounting 25.