GB560741A - Lens focusing devices - Google Patents

Abstract

560,741. Focusing lens mounts. WATSON, W. Feb. 19, 1943, No. 2767. [Class 97 (i)] In a focusing lens mount, e.g. for cameras or projectors, of the type employing a single or multi-start screw engagement between the lens barrel and its mount, the screw thread on the barrel (or one thread in the multi-start case) is formed along its crest with a flat surface carrying a focusing scale co-operating with an index mark on the mount. The screw movement of the barrel in the mount may be effected either directly or through gearing. The lens system may be contained in a tube removably secured inside the barrel. In the drawing, a fixed mount 56 is shown in half section and the movable lens barrel 51 in elevation. The barrel 51 is provided with an external two-start flattopped thread engaging a similar internal thread 50 in the mount 56, one thread element 52 on the barrel carrying a scale 54 co-operating with a mark 66 in a window 65 of the mount, and the other thread element 53 on the barrel having teeth 55 which engage, through an aperture 57 in the mount, with a pinion 58 on a shaft 59 rotatable in bearings 60 on the. external surface of the mount to effect the focusing adjustment by means of a handle (not shown), the shaft being also slidable axially before said rotation by pressure on said handle to release a friction clutch 64 which is normally urged by a spring 61 against the pinion 58 to hold this in adjusted position. The index window 65 may contain a viewing lens.