Patent GB-618878-A (GB)
Title: Improvements in or relating to photographic camera shutters
IPC: G03B9/58
Filed: 1946-05-15
Abstract: 618,878. Switching systems. HEARN, J. W. E., MEECH, F. B., and OPTICAL MEASURING TOOLS, Ltd. May 15, 1946, No. 14708. [Class 38 (iv)] [Also in Group XX] Relates to a photographic shutter and means for operating the same comprising in combination a clock, an electrical circuit with contacts operated by the clock to establish electrical impulses at predetermined intervals of time, a frame plate in which a shutter-opening is formed, two shutter plates, each movable between two positions, in one of which the shutter opening is obscured and in the other of which it is left clear, two electrically-responsive means under the control of the impulses, one for opening the one and one for closing the other of the shutter plates, switch means in the electrical circuit for despatching a first impulse from the clock to one of the electrically-responsive means to operate the shutter plate controlled thereby to open the shutter and changing the circuit to despatch the next impulse from the clock to the other electrically-responsive means to operate the shutter plate controlled thereby to close the shutter and manually operated. means for resetting the shutter plates. The said switch means may include a relay board with a relay for limiting the length of the impulses and interlock contacts operated by the resetting means for disconnecting the shutter from the impulses until it has been completely reset. As shown, a clock mechanism 141 (e.g. an electricallydriven pendulum clock) provides electrical impulses at 1 sec. intervals and also closes a switch 107 at 2 sec. intervals. A relay board 106 carries relays R1, R2, R3, R4. R1, R2, R3. each have six contacts of which the upper and lower contacts in each set of three are normally connected, but when the relays are energized the central and upper contacts are connected instead. R4 has one set of three contacts acting similarly. Two similar shutters (see Group XX), have each electromagnets 72, 82, forming the electrically-responsive means for respectively opening and closing the shutters, and a set of contacts 152, 154, 155 operated by the moving parts of the shutter, contacts 152, 154 being closed when the shutters are set. The shutters are set simultaneously by pulling a cord 36 attached to a point on a pulley 39 having a projection 136 which allows contacts 137, 138 to open when the cord is pulled, but closes them when the cord is released, completing a circuit through the coil of relay R1 which operates to break the circuit but to make a new hold-on circuit. It also makes a circuit whereby, when the switch 107 closes momentarily, relay R2 is operated, provided that the control switch 102 is closed. Operation of relay R2 completes a hold-on circuit and also allows the 1 sec. impulses from the clock to operate the relay R3. The impulse operating the relay is also applied to the electromagnets 72, opening the shutters. The movement of the shutter parts opens contacts 152, 154 and closes contacts 152, 155. The relay R3 operates momentarily to cut short the shutter-opening impulse and to break the holding circuit of relay R1, and drops off at the end of the impulse. The circuit then made enables the next clock impulse to operate the shutter closing magnets 82. The next 2 sec. impulse operates the relay R4, breaking the holding circuit of relay R2. The relays are thus restored to their initial positions, and since the contacts 152, 154 are now open, no further operation can take place until the shutters are reset. Specifications 553,949, and 601,961, [both in Group XX], are referred to.