Patent GB-880908-A (GB)
Title: Improvements in and relating to photographic shutters
IPC: G03B9/48
Filed: 1957-11-15
Abstract: 880,908. Photographic shutters. VOIGTLANDER A.G. Nov. 15, 1957 [Nov. 17, 1956], No. 35684/57. Class 98(1). A photographic slit shutter, comprising a double blind focal plane shutter, is provided with an auxiliary shutter, which additionally covers the same image window as the slit shutter when the two shutters are mounted in a camera and which by actuation of the release member of the slit shutter is opened immediately before the slit shutter starts to run down and is locked in the open position, this locking being released at the end of the running down operation of the slit shutter by a member which is connected with the following part of the slit shutter which closes the image window after an exposure, whereupon the auxiliary shutter under spring action returns again to its closed position. As shown in Fig. 1 the opening slider group 4, 400, 401 and the closing slider group 5, 500, 501 of a focal plane slit shutter slide between walls 1 and 3 in known manner to provide an exposure slit of adjustable width between sliders 4, and 5 which moves over the image window 6 under which is the film 2. In the wound up condition, the opening slider group cover the aperture in partially overlapping relation as shown and the closing slider group are stacked clear of the window A rectangular foil 13 comprising the auxiliary shutter also covers the image window 6, is slidable between guides 14, 15, and is secured at one end to a rotatable roller 17 journalled in side walls 18, 19. When the release member 26 is depressed against the force of a spring 28 it positively rotates a bell-crank lever 30 against the tension of a spring 31 and by means of co-operating toothed segment 36 and pinion 24 coupled to the roller 17, rotates the roller 17 against the tension of a spring contained within said roller. As a result, the foil 13 is wound on to the roller from the region of the window 6 When the winding is complete, the roller is locked by means of the lever 39 engaging a toothed wheel 25, and a flat lever 33 slides over the curved surface of the bell-crank to obviate further winding. Further depression of member 26 causes-through intermediate members 41, and 42-the raising of the member 9 and hence the release of the opening slider group which is closely followed by the closing slider group, to effect exposure. When the member 5 has reached the position occupied originally by slider 401 an arm 43 thereon engages the lever 39 at 44 to release the drum 17 from its locked position and cause the foil 13 to unwind and recover the window 6. When member 26 is released, the bell-crank 30 returns to its original position by moving the flat lever 33-pivoted to 36-out of the way against the loading of its spring 38. The shutter sliders are returned to their original positions under cover of the foil 13 by means not shown. In the embodiment shown in Fig. 6, the slit shutter means are as before, but depression of the release lever 62 causes the latch 60 to engage a lug 59 to rotate the wheel 58-which-by means of rods 55, 56 causes the shutter doors 45, 46 comprising the auxiliary shutter to open and uncover the window 6 under which the film passes. The doors are held open by the pin 59 engaging a locking lever 68 and further movement of the actuating member 2 releases the slider groups in the known manner. At the conclusion of the running down motion the arm 71 of the slider 5 co-operates with the lever 69 to unlock the wheel 58 and the doors shut under the action of springs 50. In a third embodiment the auxiliary shutter comprises a pair of pivoted plates which swing away from each other in a common plane to uncover the aperture, the motion being provided by a slotted cam plate actuated by a manual release member engaging pins in the plates which are locked in their open positions until the exposure is completed in a manner similar to that described above.