Patent GB-774852-A (GB)
Title: Diaphragm for photographic cameras
Inventor: NOACK ROLF
IPC: G03B9/07
Filed: 1955-08-18
Abstract: 774,852. Photographic lens diaphragms. VEB ZEISS IKON DRESDEN. Aug. 18, 1955, No. 23840/55. Class 98(1) In a diaphragm comprising pivoted blades operable by means of a spring- loaded driving ring which can be held in a cocked position by locking members, the blades being set to a preselected aperture value on the release of the driving ring, one of the blades and a stop member are both operatively connected with the driving ring and the stop member, after the actuation of the locking members to release the driving ring, abuts on a cam of the diaphragm setting means so that the travel of the driving ring is limited to obtain the preselected aperture value. As shown in Fig. 1, the control ring 2 is urged counterclockwise by the spring 16 and the diaphragm driving ring 3 is urged clockwise by the weaker spring 13. The control ring 2 has a toothed segment 5 meshing with a pinion 15 having a shaft 44 projecting from the shutter casing which shaft may be rotated to turn the ring 2 clockwise until the pawl 46 on the lever 25 falls behind the projection 26, when the shutter is set. A projection 12 on the ring 2 drives the shutter bladedrive ring through the pin 47. Near the end of the setting movement, a pin 6 on the ring 2 strikes the arm 45 of the pawl 39 engaging the projection 4 on the ring 3 and allows the latter to move to the preset position determined by the engagement of the end 11 of the bell-crank lever 8 coupled to the ring 3 with the cam surface 14 of the diaphragm setting-means 23, the extension 37 of which may be set to the desired value of diaphragm opening along the scale 38. Operation of the shutter release lever 33 through the shaft 57 propecting from the shutter casing moves the pawl 46 to free the ring 2 to move counterclockwise to effect the exposure until the nose 41 on the lever 25 is engaged by the step 43 on the ring 2. Release of the lever 33 allows the lever 25 to move to free the control ring 2 to drive the ring 3 by engagement of the projection 12 with the projection 4 until this projection is engaged by the pawl 39. The nose 41 engages the end of the step 42, and, since it rests against the step 43, operation of the release lever 33 is impossible. Where the shutter has a retarding mechanism including a toothed segment 53 movable into the path of the projection 12 to obtain different exposure times by delaying the movement of the control ring 2 when it has reached the shutter open position, the member 12 is provided with an extension 51 to engage the projection 52 of the toothed segment 53 so that the projection 12 does not engage the projection 4 to close the diaphragm until the shutter blades have closed. As shown in Fig. 4, when the control ring 2 is released, the cam-surface 48 thereon strikes the projection 40 of the member 27 which has a nose 34 engaging a pin 32 on the toothed segment 17. As the member 27 rotates clockwise, the spring 49 pulls the lever 28 to push the contact spring 29 against the contact 35 and close the flash-light circuit 50. As the toothed segment 17 moves, the pin 30 thereon moves the locking member 22, which has arrested the projection 4 of the diaphragm driving ring 3, and permits the ring 3 to rotate clockwise to its pre-set position determined by the engagement of the end 11, Fig. 1, of the lever 8 with the cam-surface 14. In a modification, one diaphragm blade is provided with a pair of symmetrically disposed pins, one of which engages the cam-surface 14 and so limits the closing movement of the diaphragm to obtain the pre-selected aperture value, the other pin performing the same function when the diaphgragm blades are reversed for use in a reflex camera shutter where it is desired that the diaphragm should be completely open outside the duration of the exposure.