Patent GB-744594-A (GB)
Title: Improvements in and relating to photographic cameras
Inventor: COX NORMAN THOMAS
IPC: G03B17/42
Filed: 1952-02-13
Abstract: 744,594. Electrically-operated photographic roll-film cameras. IMPERIAL TRUST FOR THE ENCOURAGEMENT OF SCIENTIFIC & INDUSTRIAL RESEARCH. May 13,1953 [Feb. 13, 1952], No. 3839/52. Class 98 (1). The camera comprises an electrically-operated device which releases the shutter and is set in action under an external control, and a further electrically-operated device which controls mechanism which winds on a frame of film when an exposure is made, the second device being controlled through two switches in series, one of which is coupled to the shutter so as to be closed when the shutter is closed but open during the whole of the exposure, and the other of which is closed by the first device after the operation of the shutter has proceeded far enough to cause the first-mentioned switch to open. As shown, on manually closing a switch across lines 27, a relay 23 controlling the film winding mechanism is energized through the normally closed switch C5 and thereby a crosspiece 25 on its armature 24 simultaneously closes a hold-on circuit through switch C1 and operates the trigger 26 of a between-lens multiple pivoted blade everset shutter 12. Before the switch C2 is closed by the cross-piece, a cam or lever in the shutter moves a pin 28 radially inwards opening the normally closed contacts C3. When the shutter blades close, the pin 28 moves to close the switch C3 thereby energizing the solenoid 29. A cross-piece 33 on the armature of this solenoid is thereby moved simultaneously to release a notched disc 35 and to close switch C4 which then (1) energizes a motor 19 which worm-drives the shaft 17 of the film feed sprocket 16, this shaft being belt-connected to the take-up spool 14, the decreasing rotation of which at each successive frame feed being allowed for either by a slipping clutch or by slip in the belt drive; and (2) also energizes a slowacting relay 36 which, shortly after the shaft 17 has started to rotate, causes the normallyclosed switch C5 to open, thus breaking the hold-on circuits for the solenoid 23 and hence the solenoid 29. However, the nose 31 on the armature now riding on the periphery of the disc 35 holds the switch C4 closed so that the motor still drives the shaft 17 and the relay 36 remains energized. When the shaft has made nearly one-quarter of a revolution, the nose falls into the next notch 34 in the disc 35, so opening the switch C4 and de-energizing the relay 36, so that the switch C5 re-closes, and also the motor 19. As this idles to rest the sprocket continues to rotate to complete the feeding of the film frame until the nose 31 reaches the far end of the notch when the shaft is arrested without appreciable shock since a friction clutch is provided between the worm drive 18 and the sprocket spindle. Alternatively the shutteroperating circuit may be opened by a further normally closed switch which may replace the switch C5 and which is actuated by the disc 35 or by a four-armed cam rotatable with the disc as soon as the disc has rotated far enough to ensure that the latch 31 will ride on the periphery of the disc. If the disc is replaced by the four-armed cam, the further switch must be opened only at the end of the film-winding cycle. A film-driven sprocket 89 operates a frame counter. The camera may be operated at intervals set by an external time control. In alternative embodiments, a setting type shutter is employed. In Fig. 2, at each film frame feed, a mutilated gear 47 driven from the shaft 17 and having four equally spaced toothed sectors 48 rotates anti-clockwise a toothed drum 51 freely mounted on a fixed shaft to which it is connected by a spring 52. When the parts reach the position shown, a slidably mounted latch 54 spring-urged to ride on the drum falls behind a shoulder 55 and so holds the shutter set. During the setting the link 57 secured to the drum pivots about a pin 61 so that its notch 58 moves clear of the half-round pin 59 on a pivoted arm 45 connected to the pivoted shutter blades 41, 42 without moving it so that the shutter remains closed. On closing the switch across lines 27, the latch 54 is moved to release the drum which is driven clockwise by the spring 52 to cause the notched link 57 to oscillate the half pin 59 so that the arm 45 opens and closes the blades the drum being arrested by a lug 63 engaging a stop 64. In Fig. 3, a shutter comprising an exposure disc 71 and an apertured capping disc 74 are shown in the set position, the capping disc aperture 75 overlying the camera exposure aperture 73. The shutter is released by upward movement of a latch 79 when a wheel 78 is driven anticlockwise by a spring and drives through its teeth 76 a pinion secured to the shutter disc which rotates through 180 degrees to make an exposure, when it is arrested by a pin 82. When the film sprocket shaft rotates, a four-lobed wheel 83 is rotated anticlockwise and one lobe engages a pin 88 on the wheel 78 and drives this clockwise tensioning the shutter driving spring until the latch 79 riding on a concentric shoulder drops behind this to hold the shutter set. During setting, a shoulder 84 on the exposure disc engages a spring catch 85 on the capping disc so that the two discs pass in capping relation across the exposure aperture 73, the connection between being tripped when the cut-out portion of the exposure disc has passed the aperture by the catch 85 striking a pin 86 so that the disc 74 is spring returned to the position shown determined by the stop 90. The switch C3 may be opened by a cam on the exposure disc, or preferably by cams on both the exposure and capping discs, during the exposure movement and closed by a cam on the capping disc during the return movement of the discs.