Patent GB-898618-A (GB)
Title: Photographic and cinematographic cameras
IPC: G03B7/085
Filed: 1959-03-09
Abstract: 898,618. Photographic cameras. VOCKENHUBER, K., and HAUSER, C. March 9, 1959 [March 14, 1958; July 22, 1958], No. 8002/59. Class 98(1). [Also in Group XL(b)] A device for controlling the aperture of an objective comprises a first diaphragm arranged to be operated by a galvanometer connected to a photo-electric cell, a second manually controlled diaphragm and means coupled to the latter arranged to reduce the current in the galvanometer controlling the first diaphragm when the second diaphragm is not fully open, thus increasing the aperture of the first diaphragm. In a first embodiment shown in Fig. 3, the first diaphragm comprises two rotatable discs 9, 10 having arcuate slots 11, 12 therein overlapping to form a variable aperture in front of an exposure aperture 22, said discs being coupled to the rotor 2 of a galvanometer coupled to a photo-cell 3 by means of a thread 6 passing round a pulley wheel 5 and having its ends fastened respectively to rollers 7 and 8 rigid with said discs 9 and 10. The second manually controlled diaphragm comprises two slide members 13, 14 having two aperture forming slots 15, 16 therein and having respective racked portions 20, 19 engaged for control of said variable aperture by a pinion 21 which is coupled by way of gear-wheels 23, 24 to a knurled wheel 25. When this wheel is in the position shown, a switch 27 in parallel with the galvanometer is open, the manual diaphragm is in its wide open position and a spring urged lever 40 engages in a notch 39 in a control surface of the wheel 25 thereby bringing a mark A into a window 43 visible when looking through the viewfinder 42 to indicate that the automatic diaphragm is in operation. When the wheel 25 is rotated clockwise for manual setting of the aperture, switch 27 is closed by cam surface 26 thereby rendering the automatic diaphragm ineffective and lever 40 is moved by the cam surface 37 into a position in which the mark H is visible in said window 43. If on the other hand the wheel 25 is rotated anticlockwise from the position shown in Fig. 3, the automatic diaphragm becomes locked in whatever position it happens to be in as a result of the pivoting of a lever 30 by pins 28, 29 into a position in which spring 31 urges pressure lever 32 in the clockwise direction and thereby traps the thread 6 between stop 34 and pressure finger 33. In this case, the lever 40 is positioned by control surface 38 so that the letter B is visible in said window 43. The effect of switch 27 may be over ridden for special effects by a further switch 47 in series therewith. A diaphragm scale visible in said window 43 is provided on a disc 44 moving with said rotor 2 and coloured marks 45, 46 indicate when lighting conditions are unsuitable for exposure. Apertures 11<SP>1</SP>, 12<SP>1</SP> in discs 9, 10 are for counterbalancing purposes. In a second embodiment shown in Fig. 5, the automatically controlled diaphragm is formed by levers 106, 107 having aperture forming recesses 108 at one end and pins 105 at the other engaging in control slots 103 of a disc 104 rigid with the coil 102 of the galvanometer. The manually controlled diaphragm is formed by apertured slides 111, 112 similar to those in the first embodiment and coupled by way of pinion 115 and gear-wheels 116, 117 and 128 to a control knob 129. When the manual diaphragm is in its wide open position, i.e. the automatic diaphragm is in operation, the aperture of iris diaphragm mechanism 119 in front of the photo-cell 101 is determined by the settings respectively of film sensitivity and motor speed setting knobs 125, 126 which are coupled to each other by friction and knob 125 of which is coupled to a first blade control ring by way of gear-wheels 124 and 123. When the manual diaphragm is in any position other than wide open the iris diaphragm is closed down somewhat by way of a second blade control ring coupled to gear-wheel 117 and the automatic diaphragm is correspondingly opened so as to be ineffective. The manual diaphragm aperture may be set according to light conditions by bringing a pointer 131 of a second galvanometer coupled to the photocell 101 into registry with an index mark 133. In a modification the manual diaphragm may be coupled with a variable resistance in the photo-cell circuit instead of being coupled with an iris diaphragm.