| 摘要 |
PURPOSE:To prevent a shutter blade from bounding by controlling driving force applied in the open position direction of the shutter blade united with a fan-shaped pattern coil by selecting the shape and arrangement of permanent magnet pieces for electromagnetic drive. CONSTITUTION:When an electric current flows to driving coil 5 in a fan-shaped pattern through shutter release operation, sector ring 6 united with coil 5 rotates counterclockwise. Then, rectangular permanent magnets 4 arranged, with long sides crossing, along the effective side line of the pattern of coil 5 increases gradually the pattern of coil 5 in a magnetic field. Then, the pattern of coil 5 is put off the magnetic fields of magnets 4 and as shutter blades 10 and 11 are open more and more, the electromagnetic driving force increases gradually. After the intermediate opening, it decreases gradually and when they are opened completely, the electromagnetic force nearly balances with the retaining strength by spring 7 and ring 6 stops its rotation smoothly by stopper 8, so that the shutter will be prevented from bounding. |
