Patent GB-744830-A (GB)
Title: Improvements in photographic shutters
IPC: G03B9/70
Filed: 1953-01-22
Abstract: 744,830. Photographic shutters incorporating flashlight synchronizing switch. GAUTHIER GES., A. Jan. 22, 1953 [Jan. 26, 1952], No. 1910/53. Class 98 (1). A between-lens shutter provided with flash contacts comprises a set of exposure-controlling blades actuated by a primary power system, a set of cover blades actuated by a second independent power system, means for simultaneously setting both power systems, and release means adapted to release the cover blade power system which also operates means closing the flash contacts, the cover blade power system including means for releasing the primary power system, and the arrangement of parts being such that a predetermined time delay is produced between the time of closing the flash contacts and the time at which the exposure-controlling blades are opened. The delay introduced may be varied to synchronize lamps of different lags and the said means for closing the flash contacts rendered inoperative for lamps of zero lag, the flash circuit then being closed by other means when the blades are fully open. As shown, the shutter is set by moving the arm 6a anticlockwise, rotating the master member 6 and tensioning its driving spring 8, a pin 6b on the master member engaging an arm 5b on a rotatable member 5 for driving the cover blade rings 3 to move it clockwise to tension its driving spring 7, a nose 5a sliding over and dropping behind a bevelled lug 3a on the cover blade ring 3, the master member being latched in set position by a lever 14 engaging a shoulder 6e and the member 5 being latched by a lever 12 engaging a shoulder 5d. On operating the trigger 13, the lever 12 releases the member 5 so that it drives the cover blade ring anticlockwise against a return spring to open the cover blades 9 which are held open by a pawl nose on an anticlockwise urged lever 17 engaging in a recess 3b in the ring 3, and also nose 5b engages a pin 14b on the latch lever 14, thereby releasing the master member 6, which by means of the usual driving link 11 oscillates the shutter blade ring 4 to open and close the blades 10. The cover blade ring 3 also carries a pivoted lever 23 urged against a pin 3b on the ring and carrying a pin 23b engaging the movable earthed spring contact 25 of a flashlamp synchronizing switch having a fixed insulated contact 26. Prior to the opening of this shutter the switch is closed, the interval between this closing and the shutter being fully open depending on the speed of the ring 3 which is adjustable by varying the tension of its driving spring 7 by means of a pivoted lever 21 to allow for lamps of different lags M, F. For lamps of zero lag, the lever is set to " X " when a slidable strip 20 to which it is pin-and-slot connected moves clockwise a pivoted plate 29 which pivots the lever 23 so that the pin 23b always remains clear of the spring 25, the switch being closed only when the shutter is fully open by a pivoted lever 30 having a cam 30b engaged by a pin 4b on the shutter blade ring 4, this lever 30 normally only following the spring 25 as this is moved by the pin 23b. The cover blades are closed when the exposure is complete by an arm 6c on the master member 6 as this returns into the rest position shown. In a modification (Fig. 3, not shown) (1) the cover blade ring driving spring is tensioned not by direct engagement of the pin 6b with the lug 5b but by a link pivoted on the member 5 having a recess engaging the pin, this link being disengaged from the pin during the first part of the trigger movement by a lever which follows the trigger; and (2) the flashlamp lag setting means is a ring surrounding the shutter aperture having a cam slot controlling a pin on a lever carrying one end of the cover blade driving spring, and the lever controlling the spring contact for " M " and " F " lag lamps is disengaged for " X " lamps by a lever controlled by a cam on the lag setting ring, the spring contact being moved to close the switch by a lever actuated by the mastermember link-driven pin on the shutter blade ring when the blades are fully open.