GB822496A - Improvements in or relating to diaphragm adjustment mechanism for photographic lenses - Google Patents

Abstract

822,496. Lens mounts for photographic cameras. BELL & HOWELL CO. May 16, 1956 [May 23, 1955], No. 15306/56. Class 98(1) A diaphragm adjusting mechanism comprises primary and secondary coaxial adjustment members which may be connected for simultaneous rotation in relative positions corresponding to a first exposure factor and ere relatively axially adjustable to select said positions the primary member driving the diaphragm the secondary member moving over a scale representing values of a second exposure factor. In the form shown the lens and diaphragm parts are mounted inside a sleeve 4 which carries on the outside the adjusting elements and a fixed flange ring 6 by which with a securing ring 7, the mount is secured to ahub 2 projecting from the front camera wall being angularly located by an inwardly projecting pin 8 engaging a slot 9 in the mount. Each of the diaphragm leaves carries a pin 15 engaging a bore in the sleeve 4 and a pin 17 engaging a radial slot in a sleeve 18. An external ring 26 carries a screwed stud 28 projecting through an arcuate slot in the sleeve 4 to operate the sleeve 18 and so actuate the diaphragm. The ring 26 is coupled to a secondary ring 33 through pin and slot mechanism, not shown, engageable in a number of different relative angular positions. The two rings carry scales representing values of two exposure factors such as film speed and frame frequency and are angularly adjusted for the combination of factors in use the ring 33 being first disengaged by forward axial movement against a spring 36. In use the diaphragm is adjusted by rotation of the ring 33 which carries a pointer 49 moving over a scale of lighting conditions on the front of the camera.