Patent GB-1161679-A (GB)
Title: Improvements relating to Photographic Apparatus
IPC: G03B15/04
Filed: 1967-09-13
Abstract: 1,161,679. Photographic flash apparatus. INTERNATIONAL POLAROID CORP. Sept. 13, 1967 [Sept.29, 1966], No.41820/67. Heading G2A. A shutter blade 14 is held, against the action of a spring 24, so that it closes an exposure aperture 6, and is retained in that position by an electromagnet 36 engerized from a source EB . When the potential from the source is applied across a flash-bulb 164, and this is energized, the potential across the electromagnet drops so that it is de-energized, and shutter blade 14 is released to initiate the exposure. Blade 14 is held in the "closed" position by a latch 28, which engages a pin 32 on the blade. A keeper 34 on one end of the latch is held by the magnet coil 36 when energized. When the coil is de-energized, latch 28 is pivoted clockwise by a tensioned spring 110, so releasing blade 14. This is then slid to the left by spring 24, so uncovering the exposure aperture 6. An inertia arm 56, pivoted so as to turn anti-clockwise by a spring 58, has been prevented from doing so by a pin 62 on blade 14. When this blade is released for movement, arm 56 is also released, and as it swings about its pivot, one end 64 strikes against an anvil 66 on a second latch member 48, which has been holding back a second shutter blade 12. The second blade is also thus released for movement under the action of a spring 44, and moves across to close aperture 6 and so terminate the exposure. This mechanism provides a fixed speed shutter, the time being determined by the movement of the inertia arm 56. A diaphragm opening is formed by the gap 83 between V-shaped notches in two blades 68, 69 on a common pivot. Adjustment of this opening is effected manually by a control member 70, pivoted at 72 on the supporting base-plate 8. A pin 74 on member 70 engages in slots 76, 78 respectively in blades 68, 69. Thus movement of member 70 causes relative displacement of blades 68, 69 so varying the diaphragm aperture 83. The blades have a further pair of V-shaped notches 84, 86, defining a further aperture 87 which is aligned with a photo-cell 108 forming part of a transistorized switching circuit 94. As member 70 is depressed prior to exposure, both apertures 83 and 87 are gradually opened. When aperture 87 is opened sufficiently, as determined by the light received by cell 108, and the various parameters of the system, circuit 94 is triggered so that coil 36 is de-energized, thus releasing the shutter blades 14, 12 to effect the exposure. If the ambient light is insufficient, depression of member 70 will not trigger the circuit 94, and the shutter does not operate, thus indicating that a flash-bulb is necessary for a satisfactory exposure. If flash is used, it is desirable that the effective aperture is varied according to the subject distance, and the blades 68, 69 may accordingly be coupled to the focusing means for the lens 4. A switching member 138, having thereon an electrically conductive insert 148 with an oblique upper edge 149, can slide horizontally along a supporting strip 140. Its movement is coupled to the focusing movement of lens 4, as for example by mechanical linkage (133, 134, Fig.1, not shown). A wiper type contact 150 is mounted on member 70, and as the member moves downwards, contact 150 will make connection to the conductive insert 148, so closing the flash switch 122, after a distance of movement varying according to the position of member 138 (i.e. the focus distance of lens 4).