Patent GB-674958-A (GB)
Title: Improvements in and relating to photographic cameras
Inventor: CLIFFORD THOMAS WILLIAM
IPC: G03B17/14
Filed: 1949-05-24
Abstract: 674,958. Photographic cameras having interchangeable objectives provided with betweenlens shutters. TAYLOR, TAYLOR & HOBSON, Ltd. Aug. 11, 1950 [May 24, 1949], No. 13792/49. Class 98 (i). A photographic camera having an interchangeable lens mount with a between-lens pivoted blade shutter is characterized in that the shutter blades are built into the lens between the lens components and are coupled to shutteroperating mechanism built into the camera body by coupling means mounted within the lens mount. As shown, interchangeable lenses 3 attachable to the camera body 1 by bayonet joints 45 are each provided with an adjustable diaphragm 67, and the blades 4 and bladeoperating means of a between-lens pivoted blade shutter. The blade-operating means comprises a blade ring 5 to which is pin-and-slot connected a lever 6 urged anti-clockwise by a spring 22 to hold the shutter closed and pivoted freely on a shaft 10 journalled in the lens mount. An arm 9, urged clockwise to engage the lever 6, is secured on the shaft adjacent the lever and a second arm 11 is secured to the opposite end of the shaft and when the lens is in place on the camera, projects through a slot 15 in a ring 16 rotatable on the lens mount. When detached from the camera, the arm 11 is held inside the lens mount by the ring 16, which is rotated relatively to the mount by releasing the bayonet joint and cams the arm 11 anticlockwise. To attach the lens to the camera, the bayonet latches and keys 47 on the ring 16 are aligned and seated into key ways 46 on the body 1, and the lens mount is rotated relatively to the body and ring to secure the lens in place by the latches engaging behind the front wall of the body, the arm 11 being freed simultaneously to project through the slot 15 in the ring and a slot 17 in the lens mount-receiving part of the body. The shutter-driving and-controlling means are mounted in the camera body and comprise a master member 19, which is rotatable anticlockwise against a spring 28 to a set position where it is latched by a clockwise-urged bell-crank lever 32, a lug 18 on the master member, when this is released, driving the arm 11 to open the shutter which is closed after the lug has passed clear of the arm by the return spring 22 for the lever 6. To make an exposure, a button 40 is depressed, thereby rotating downwardly about its pivot 37, the arm of a bell-crank lever which cams the bellcrank lever 36 anti-clockwise to release the master member. On re-setting the shutter, the arm 11, together with the arm 9 and against the action of the return-spring 26, is rotated anticlockwise by the lug 18 until the latter slips past it, the shutter blades being held closed by the spring 22. Different exposures may be obtained by means of a conventional retard train 43 and the shutter may be synchronized with a flash-lamp by means of the device described and claimed in Specification 655,511. To avoid fogging of the film when the lens is removed, there is provided a twin flap shutter comprising pivoted pin - and - slot connected members held closed by a joining tension-spring and opened on securing the lens to the camera by a pin 63 on the lens engaging one end of a bellcrank lever 60, which is pin-and-slot connected at its other end to one of the shutter flaps. In known manner, the lens mount may be provided with a key engaging the body to prevent rotation of the mount during rotation of the focusing ring 66 and may be coupled with a range-finder, a ring 68 may be provided for adjusting the diaphragm 67, and the shutter release and film wind may be interconnected to prevent double exposures. The Provisional Specification refers to the known use of cameras having focal-plane shutters and interchangeable lenses having between-lens shutters.