Focal plane shutter for cameras

Abstract

A camera shutter mechanism for opening and closing a shutter aperture to effect an exposure comprises a group of opening blades movable, when released, from a closed position covering the shutter aperture to an open position uncovering the shutter aperture to thereby initiate an exposure, and a group of closing blades movable, when released, from an open position uncovering the shutter aperture to a closed position covering the shutter aperture to thereby terminate the exposure. A release mechanism releases the opening blades thereby enabling them to move to the open position for initiating the exposure, and subsequently releases the closing blades thereby enabling them to move to the closed position for terminating the exposure. A driving member automatically operates immediately after completion of the exposure to move the group of opening blades back towards the closed position so that the aperture is at least partially covered thereby so as to improve the light-shielding capability of the shutter mechanism.

What is claimed is: 
     
       1. A camera shutter mechanism .Iadd.for a camera having a view finder.Iaddend.for opening and closing a shutter aperture to effect an exposure comprising: .Iadd.a base plate having therein a shutter aperture, the base plate having a vertical height dimension and a horizontal width dimension and having a widthwise extending recess at the upper part thereof at a location vertically above the shutter aperture, the recess being dimensioned to accommodate therein the lower part of the view finder;.Iaddend.a group of opening blades movable, when released, from a closed .Iadd.charged.Iaddend.position in which they cover the shutter aperture to an open position in which they do not cover the shutter aperture to initiate an exposure.Iadd., said group of opening blades being arranged to be stowed in a space provided in the lower part of the camera;.Iaddend.a group of closing blades movable, when released, from an open .Iadd.charged.Iaddend.position in which they do not cover the shutter aperture to a closed position in .[.with.]. .Iadd.which .Iaddend.they cover the shutter aperture to terminate the exposure.Iadd. , said group of closing blades being arranged to be stowed in a space provided in the upper part of the camera beneath the view finder such that the stowed closing blades do not obstruct the optical path of the view finder; said group of opening blades having better light-shielding effectiveness than said group of closing blades when in the closed position;.Iaddend.release means for releasing the opening blades thereby enabling them to move to the open position for initiating the exposure, and for subsequently releasing the closing blades thereby enabling them to move to the closed position for terminating the exposure; and means including a driving member automatically operable immediately after completion of the exposure for moving the group of opening blades back towards the closed position so that the aperture is at least partially covered thereby .Iadd.so that after termination of the exposure, though before charging of the shutter, the aperture is at least partially covered by the opening blade group which has better light-shielding effectiveness than the closing blade group.Iaddend.. 
     
     
       2. A camera shutter mechanism as defined in claim 1; wherein said last-mentioned means comprises means for effecting at least partial covering of the shutter aperture by said group of opening blades within a predetermined period of time after completion of the exposure. 
     
     
       3. A camera shutter mechanism as defined in claim 1; wherein said last-mentioned means comprises means for displacing at least one of said groups of opening and closing blades in the shutter charging direction to an extent such that the opening and closing blades sufficiently overlap one another to attain a good light-shielding effect within a predetermined period of time after completion of the exposure. 
     
     
       4. A camera shutter mechanism as defined in claim 3; wherein said last-mentioned means comprises means for applying sufficient driving force to said driving member to displace said group of closing blades and/or said group of opening blades in the shutter charging direction within a predetermined period of time after completion of the exposure. 
     
     
       5. A camera shutter mechanism as defined in claim 4; including a hook member operable to hold said driving member under a charged condition. 
     
     
       6. A camera shutter mechanism as defined in claim 5; further including a closing arm having a curved portion engageable with said driving member to effect actuation thereof. 
     
     
       7. A camera shutter mechanism as defined in claim 1; wherein said group of closing blades is composed of divided blades which can be stowed in a space smaller than the space required for stowing said group of opening blades. 
     
     
       8. A camera shutter mechanism as defined in claim 7; wherein said group of closing blades is composed of a greater number of divided blades than the number of divided blades of said group of opening blades.