Patent GB-1110476-A (GB)
Title: Photographic camera with an automatic exposure regulating device
IPC: G03B7/081
Filed: 1966-05-06
Abstract: 1,110,476. Automatic exposure control. AGFA-GEVAERT A.G. May 6, 1966 [May 6, 1965], No.20086/66. Heading G2A. A camera has an automatic exposure-regulating device including two electrical time-delay circuits controlled by a photo-resistor, one of the circuits including a solenoid for arresting a diaphragm aperture setting member during the running down thereof from a tensioned position, and after its running down has been arrested at the predetermined setting, as controlled by the first time-delay circuit, the shutter is opened under the control of the second time-delay circuit. In the form shown, the diaphragm 1 is controlled or set by a ring member 2, which is urged by a spring 3 into a rest position in which a cam 4 on the ring abuts against a fixed stop 5. A pinion 7 on a manually operated shaft 8 engages with a toothed portion 6 of ring 2, and so rotates the ring against the tension of spring 3. When ring 2 has been rotated (anti-clockwise) into its fully tensioned position, a lug 30 latches (in the position shown in broken lines) behind a tooth 29 on a release lever 27, and is retained there. Two retarding switching circuits 34, 35 are provided. When the release 27 is pressed, it pivots about pin 28 in direction c, so releasing ring 2 to run down, and also closing contacts 31, 32, which makes retarding circuit 34 operative. In this circuit, controlling the rundown time, is a photo-resistor 46, in front of which may be provided an iris diaphragm 47 for adjustment of various exposure factors. After the ring 2 has run down an amount predetermined by the prevailing illumination, as registered by photo-resistor 46, an electromagnet 63 is energized, which causes the diaphragm to be held at this particular aperture value by a lever 54, which pivots in direction d, a tooth 58 engaging and locking a toothed portion 59 on ring 2. At the same time, lever 54 pivots a pawl 60 out of latching engagement with the first shutter blade 17, so that it is free to be pivoted by its tensioning spring 20 into the "shutter open" position (direction a). Also at the same time, lever 54 operates a changeover switch which breaks retarding circuit 34 and makes retarding circuit 35 operative. After a predetermined time again dependent on the photoresistor 46, a further electromagnet 71 is energized, which pivots a pawl 74 out of latching engagement with the second shutter blade 18, so freeing it to be pivoted in direction b by its tensioning spring 21. This terminates the exposure when it rotates into the light path A-A. Attached to ring 2 is an index carrier 11 having four index ranges 12-15 laid out in different colours, which are visible in the view-finder 16, and read against a fixed mark 98 therein. The arrangement may be such that range 14 may indicate that handheld exposures may be made, while range 13 indicates that a tripod is necessary. If the illumination is too high (range 12) or too low (range 15), either cam 4 or cam 9 is under tooth 58, so preventing full movement of lever 54 and thus preventing an exposure being made. (These can be made ineffective by a manual over-ride). A manual reversing switch 37 can change over the apparatus from the normal operating position (in which contacts 39 and 41 are closed) into a battery-testing position (in which contacts 39 and 40 are closed). This is the position shown in Fig. 1, and causes the photo-resistor to be switched out of circuit and replaced by a fixed resistor 44. The condition of the battery is shown by the position of a pointer 216 on the index carrier 11 with respect to pointer 98. In this battery-testing position, a safety latch automatically comes into operation to prevent an exposure being made.