GB487065A - Improvements in and relating to photo-electric exposure meters - Google Patents

Abstract

487,065. Photo - electric exposure meters. MACADIE, H. S., and AUTOMATIC COIL WINDER & ELECTRICAL EQUIPMENT CO., Ltd. Dec. 22, 1936, No. 35183. [Class 40 (iii)] [Also in Group XX] In a meter wherein the sensitivity may be changed by moving a mask or masks in front of the cell, two or more alternative scales of exposure times are borne by a movable element operatively connected to the mask or masks so that when a particular scale is moved into effective position, the cell is appropriately masked. In the form shown the pointer d, Fig. 1, of the measuring instrument is seen against a scale through a window b below which are pivoted three concentric discs ; one l is fixed and bears a plate speed scale l<1>; another m is rotatable and bears an arrow co-operating with the plate-speed scale, and also bears a diaphragm aperture scale m<1> ; and the third n is rotatable and bears two exposure-times scales n<1>, n<2> co-operating alternatively with the diaphragm scale, and also bears two coloured spots s, r adjacent to the two scales, these spots co-operating with guide-lines leading to the pointer scale in the window b. On the pivot of disc n is a cam o, Fig. 3, co-operating with a hump j<2> on a spring-urged bar j pivoted at j<1> and connected by a link i to an apertured mask f hinged at h in a passage between a window in the top of the meter and the photoelectric cell. When the disc n is turned to bring the scale n<1> into co-operation with the scale ml, the cam o is free from the hump j<2> and the mask f obscures the window ; and when the disc is turned to bring scale n2 into co-operation with scale ml, the cam o depresses the hump and causes the link i to turn the mask f down, against the wall of the aforesaid passage, out of operative position. A modification using three scales and two masks is referred to.