Blade type focal plane shutter

Claim 1

A focal plane shutter, comprising: a shutter base plate having an exposure aperture formed therein; a plurality of auxiliary shutter blades made of opaque laminae and rotatably supported on said base plate by a common shaft to open and close said exposure aperture and having cam slots therein; a first arm rotatably supported on said base plate and having thereon a pin fitted in said cam slots; a second arm rotatably supported on said base plate at a position different from said common shaft and having therin a first portion capable of covering the clearance formed by an adjacent pair of said auxiliary shutter blades when said plurality of auxiliary shutter blades are in a position of covering said exposure aperture and a second portion extending from said first portion so as to form an L-shape in cooperation with said first portion; said second arm being so arranged that said first portion can move by describing substantially the same locus as said plurality of auxiliary shutter blades and said common shaft being placed near to an apparent center of moving locus of said first portion of said second arm; and a main shutter blade pivotably supported on said first and second arms and having therein a tail portion including an edge intersecting the edge of said exposure aperture and capable of forming an exposure slit on said exposure aperture.