Patent GB-637439-A (GB)
Title: Improvements in or relating to photographic recording devices
IPC: G03B15/00
Filed: 1946-11-08
Abstract: 637,439. Photographic race-timing cameras. WILLIAMSON, S., ODLE, J. E., and LAWS, F. C. V. Nov. 8, 1946, No. 33285. [Class 98 (i)] In a camera for photographing moving objects comprising an optical system having a slit-form of aperture, and a drum which is driven to advance a film continuously past the slit in a direction normal to its length, and which is positioned in register with the slit to support the film at the zone whereat the image is formed, the drum is driven by a variable-speed electric motor coupled to the drum through a single-stage worm reduction gear. The motor may be housed in the same casing as the drum, said casing having externally operated motor controls comprising selector switches to run the motor at different set speeds, and a regulator to adjust the set speeds. As shown, Fig. 2, a drum 3 is driven about a vertical axis by an electric motor (not shown) through a worm reduction gear and draws the film 1 from a magazine 9 round an idler drum 10, carries it past a slit in member 2 on the optical axis of an objective lens in a mount 2<SP>1</SP> and feeds it to a take-up magazine 12. Drums 10, 3 are rubber covered, and the film is pressed into contact with them by rollers 29 on arms 30 swingable to facilitate film-threading. The motor circuit includes speed-controlling resistance, comprising a resistance variable in steps by press-buttons 15 and a continuously-variable resistance controlled by a knob 17. The direction of the motor is reversible by a switch 8<SP>1</SP>; the film is then fed from the magazine in an alternative position 9<SP>1</SP> to a second magazine 12<SP>1</SP>. Each take-up magazine has a fixed blade 22, Fig. 9, a blade 23 pivoted at 24 and actuated by a lever 32 against action of a return spring 26, a guard plate 27 normally masking blade 22, and film deflectors 30, 31. The slit unit 2, Fig. 8, has two plates 40 in a frame 39 urged by springs 46 to rest positions where their edges intersect the optical axis. For recording race finishes, the optical axis lies on the finishing line, and either the left-hand or the right-hand plate 40 (according to the direction of travel of the contestants) is moved to form the slit by a lever 48 pivoted at 47 and having a finger 46 bearing on a pin 44 or a lug 45 on the plates 40. To align the optical axis with the finishing line and for focusing the objective, a retractable mirror is swung into the objective field to reflect light rays to form an image on a ground glass screen which has a sighting line and is viewed by an eye-piece. After alignment the mirror is retracted by a return spring. A supplementary sighting tube is also provided. An arcuate runner bolted to the bottom of the casing rests in an arcuate cradle. The runner has an arcuate rack meshing with a pinion journalled in the cradle and rotatable to tilt the camera about an axis perpendicular to the slit. The camera is clamped in any tilted position by a clamp on the cradle. The slit and the objective iris diaphragm are controlled through flexible cables by knobs 50, 77 respectively mounted on a panel 13, Fig. 2, which also carries the selector switches 15, a film speed indicator 71 and a footage indicator 73. The motor is started and stopped by a switch connected thereto by a flexible cable.