Patent GB-661869-A (GB)
Title: Improvements in or relating to photographic shutters
IPC: G03B9/22
Filed: 1948-02-26
Abstract: 661,869. Photographic shutters with built-in flashlight synchronizers. KODAK, Ltd. (Eastman Kodak Co., and FUERST, C. C.). Feb. 26, 1948, No. 5867/48. Class 98 (i). A photographic shutter comprising shutter blades pivotally mounted in a casing and a spring-operated blade driving ring movable by manually operable means to a set position, in which it is held by a pivoted latch and having a spring-operated tripping member for the blade driving ring, incorporates a flashlight synchronizer comprising a circuit which includes a first pair of normally open switch contacts adapted to be closed by the tripping member at a predetermined time prior to the release of the shutter for synchronizing lamps of finite lag, and a second pair of contacts in parallel with the first pair, one of these second contacts being stationary and the other carried by the blade ring to engage the stationary contact at the instant the blades are fully opened so as to synchronize lamps of zero lag, and a cam ring oscillatably mounted within the shutter casing for selectively moving one of the contacts of either switch out of the path of movement of the other contact of the switch so that the circuit is controlled in accordance with the type of lamp used. The cam ring may also be capable of moving one contact of each switch out of the path of movement of the other contact of the switch whereby the circuit will not be closed by either switch. As described, the shutter per se is that described with reference to Figs. 1-10 of the second Provisional Specification of Specification 650,874. The shutter is set by moving the member 7<SP>1</SP> attached to the blade ring 23 from the dotted to the full line position, thus tensioning the driving spring 25 attached between the casing at 27 and a pin 26 on the blade ring. The shutter is held set by a latch 33 on a member 32 engaging a projection 34 on the member 7<SP>1</SP>, the member 32 being pivotally mounted at 29 coaxially with a latch member 28 against which a lug 36 on it is urged by a spring 37, the latch 28 itself being latched by a member 39 pivoted at 40 and urged anticlockwise by a spring 126 arranged round the pivot 40 between a pin 116 on the member 39 and a lug 128, which projects through a slot in the member 39 and is carried on a clockwise urged pivoted member 127 held against movement by a pin 125 on the blade ring. On depressing the release trigger 6, the lever 28 is depressed, unlatching the member 39 which then drives the lever 28 to cause the lever 32 to release the blade ring. For synchronizing the shutter with an " instantaneous " flash lamp, e.g. a gaseous discharge lamp, for which the flash circuit is closed only when the shutter blades are fully open, setting of the synchronizer ring 100 so that the index 10 is opposite " X " on the scale 12 allows a spring 104, mounted on but insulated from the casing and connected to the insulated centre pin 1171 of the jack 117, to move into the path of the lug 34 on the setting lever which during exposure strikes it to complete the flash circuit. The spring 104 is normally held clear of the lug 34 by a pivoted lever 103 insulated at 105 and having a lug 106 which rides on a cam surface 102 of the ring 100 except when the index 10 is set to "X " when the lug 106 falls into the depression 101. For lamps of finite lag, the circuit is completed through a pivoted insulated lever 115, connected to the pin 1171 by spring 203 and strip 118, and the pin 116 on the member 39, the position of the arm 115 and hence the lag being determined by a lug, 201 on the lever 115 following an eccentric surface 112 on the ring 100, said surface being rotated by the setting of the index 10 to the scale 11. When the index 10 is set to " X," a cam 112 on the ring causes the lever 115 to be held clear of the pin 116. At the end of an exposure, the latch faces of the lever 28 and the tripping member 39 re-engage so that the switch 115, 116 is open. On setting the shutter therefore, this switch remains open, while the switch 34, 104 is prevented from closing even if the index 10 is set to " X " by an insulated knob 110 pressing the strip 104 out of the path of the lug 34, so that a lamp may be connected to the jack 117 prior to setting. If daylight exposures are to be made with the lamp in circuit, the index 10 is set to "O" on the scale 12, when the cams 102, 112 engage lugs 106, 201 on the levers 103, 115 respectively to render both switches 34, 104 and 116, 115 inoperative. Specification 537,209 is referred to.