Patent GB-631104-A (GB)
Title: Improvements in or relating to photographic timing devices
IPC: G03B15/00
Filed: 1946-06-17
Abstract: 631,104. Timing races. J.D.C. ENGINEERING, Ltd., and COOPER, A. June 17, 1946, No. 11908. [Class 106 (iv)] [Also in Group XX] Means for continuously moving a photographic film past an exposure aperture is combined with an oscilloscope device to mark the film during its passage at regularly timed intervals. As applied to a camera for timing, e.g. races, a film 11, Fig. 1, is led from a supply spool 12 past an exposure aperture 14 by means of guide rollers 13 to a take-up spool, or to a driving sprocket 16, and thence to a processing compartment, not shown. The exposure slot 14 is formed between adjacent edges of plates 26, one of which is fixed and the other is adjustable to vary the width of the slot by means of a screw-threaded rod 27. The fixed edge of the exposure slot lies on the optical axis of the objective 31, which constitutes the finishing line of the race. The film is held flat against the slot by a pressure plate 19 carrying the rollers 13. The sprocket 16 is driven by a variable-speed motor, whereby the film speed is adjusted in accordance with the speed and distance from the camera of the object to give a clear photograph thereof. Light from an oscilloscope device, preferably a cathode-ray tube 35, is reflected as by prisms 38, 33 and focused by a lens 34 on the margin of the film 11, forming a series of marks thereon. The cathode-ray tube normally produces no image since the spot is either displaced from the field of view or blacked out. A quartz-crystalcontrolled pulse generator 36 provides accurately timed pulses at, say, 1/100 second intervals which displace or brighten the spot so that it records a mark at each pulse. Every tenth pulse may be greater than the general level to produce, where the spot is shifted, a longer mark. The pulse generator also provides pulses at 1 second intervals to operate a solenoid 43, Fig. 3, the armature 44 of which carries a lever 45 operating a pawl 47 through a link 46. The pawl 47 engages a ratchettoothed wheel 48 which is moved through a distance corresponding to one tooth at each operation of the solenoid. A dial 49 fast with wheel 48 is made e.g. of blackened glass with transparent numbers thereon. The wheel has e.g. 60 teeth and the numbers then run from 1 to 60. The numbers are brought successively into the light beam reflected as by a prism 53, Fig. 1, from the lamp 42 operated momentarily by the pulse actuating the solenoid. The light beam passes to the reflectors 38, 33 and thence to the film 11, recording thereon a series of numbers corresponding to 1 second intervals. Numbers indicating minute intervals may also be recorded. The timing mechanism is reset by a lever 55, Fig. 3, which turns a cam 56 to raise pawl 47 from wheel 48, and then operates a bell-crank lever 58 which presses a roller 59 against a heart-shaped cam 60 fast with dial 49, which is thereby returned to zero position. In operation, the pulse generator and dial are started as by action of a photo-cell at the start of a race, and the camera motor is started just before the finish preferably the cathoderay tube solenoid, dial and seconds light are transferable to the other side of the camera, and the film drive is reversible. In a modification, Fig. 6, light from the cathode-ray tube 35 is focused on the film by a lens 63 and a reflector 33. Light from a continuously-operated lamp 72 passes through a focusing lens 66 and a reflector 67 to a mirror 68 carried by the armature 69 of a solenoid 70. When the solenoid is operated by 1-sec. impulses the light is reflected through the numbered dial 49 to a semitransparent mirror 64 in the beam from the cathode-ray tube, and thence to the film.