Rotating magnet focal plane shutter usable in a camera and having an improved device for holding the shutter in a closed position

A focal plane shutter comprising:

• a) first and second shutter curtains movably supported for opening and closing an exposure opening;
• b) first electromagnetic driver means operatively coupled to said first shutter curtain for moving said first curtain between open and closed positions when said first electromagnetic driver means is energized to cause movement in one direction, said first electromagnetic driver means comprising an armature having opposite magnetic poles, a movable magnet operatively associated with said armature having opposite magnetic poles and having a home position where poles of said movable magnet are aligned with opposite poles of said armature and an intermediate position from which said magnetic tends to move toward said home position, and means for energizing said armature to cause selective movement of said magnet in opposite directions;
• c) stop means associated with said first electromagnetic driver means against further movement in said one direction when said first shutter curtain reaches an open or closed position, said stop means being located so as to stop movement of said magnet at a hold position prior to said home position so that said magnet and said first shutter curtain remain at said hold position whereupon said first shutter curtain is in one of the open or closed positions;
• d) second electromagnetic driver means operatively coupled to said second shutter curtain for moving said second shutter curtain between open and closed positions when said second electromagnetic driver means is energized to cause movement in one direction;
• and
• e) stop means associated with said second electromagnetic driver means for physically holding said second electromagnetic driver means against further movement in said one direction when said second shutter curtain reaches an open or closed position.

A focal plane shutter comprising:

• a) first and second shutter curtains movably supported for opening and closing an exposure opening;
• b) first electromagnetic driver means operatively coupled to said first shutter curtain for moving said first shutter curtain between open and closed positions when said first electromagnetic driver means is energized to cause movement in one direction;
• c) stop means associated with said first electromagnetic driver means for physically holding said first electromagnetic driver means against further movement in said one direction when said first shutter curtain reaches an open or closed position;
• d) second electromagnetic driver means operatively coupled to said second shutter curtain for moving said second shutter curtain between open and closed positions when said second electromagnetic driver means is energized to cause movement in one direction, said second electromagnetic driver means comprising an armature having opposite magnetic poles, a movable magnet operatively associated with said armature having opposite magnetic poles and having a home position where poles of said movable magnet are aligned with opposite poles of said armature and an intermediate position from which said magnet tends to move toward said home position, and means for energizing said armature to cause selective movement of said magnet in opposite directions;
• and
• e) stop means associated with said second electromagnetic driver means for physically holding said second electromagnetic driver means against further movement in said one direction when said second shutter curtain reaches an open or closed position, said stop means being located so as to stop movement of said magnet at a hold position prior to said home position so that said magnet and said second shutter curtain is in one of the open or closed positions;

A focal plane shutter comprising:

• a) first and second shutter curtains movably supported for opening and closing an exposure opening;
• b) first electromagnetic driver means comprising an armature having opposite magnetic poles, a movable magnet operatively associated with said armature having opposite magnetic poles and having a home position where poles of said movable magnet are aligned with opposite poles of said armature and an intermediate position from which said magnet tends to move toward said home position, and means for energizing said armature to cause selective movement of said magnet in opposite directions;
• c) first mechanical coupling means operatively connected to said movable magnet and to said first shutter curtain for causing movement of said shutter curtain between open and closed positions in response to movement of said magnet;
• d) first stop means co-operating with said first mechanical coupling means for stopping movement of said magnet in one direction at a hold position prior to said home position so that said magnet and said first shutter curtain remain at said hold position whereupon said first shutter curtain is in one of the open or closed positions;
• e) second stop means spaced from said first stop means and co-operating with said mechanical coupling means for stopping movement of said magnet in an opposite direction at another hold position prior to said home position so that said magnet and said first shutter curtain remain at said another hold position whereupon said first shutter curtain is in the other of the open or closed positions;
• f) second electromagnetic driver means comprising an armature having opposite magnetic poles, a movable magnet operatively associated with said armature having opposite magnetic poles and having a home position where poles of said movable magnet are aligned with opposite poles of said armature and an intermediate position from which said magnet tends to move toward said home position, and means for energizing said armature to cause selective movement of said magnet in opposite directions;
• g) second mechanical coupling means operatively connected to said movable magnet and to said second shutter curtain for causing movement of said shutter curtain between open and closed positions in response to movement of said magnet;
• h) third stop means co-operating with said second mechanical coupling means for stopping movement of said magnet in one direction at a hold position prior to said home position so that said magnet and said second shutter curtain remain at said hold position whereupon said second shutter curtain is in one of the open or closed positions;
• and
• i) fourth stop means spaced from said third stop means and co-operating with said second mechanical coupling means for stopping movement of said magnet in an opposite direction at another hold position prior to said home position so that said magnet and said second shutter curtain remain at another hold position whereupon said second shutter curtain is in the other of the open or closed positions.

A shutter comprising:

• a) a shutter curtain movably supported for opening and closing an exposure opening;
• b) electromagnetic driver means comprising an armature having opposite magnetic poles, a movable magnet operatively associated with said armature having opposite magnetic poles and having a home position where poles of said movable magnet are aligned with opposite poles of said armature and an intermediate position from which said magnet tends to move toward said home position, and means for energizing said armature to cause selective movement of said magnet in opposite directions;
• c) mechanical coupling means operatively connected to said movable magnet and said shutter curtain for causing movement of said shutter curtain between open and closed positions in response to movement of said magnet;
• and
• d) first stop means co-operating with said mechanical coupling means for stopping movement of said magnet in one direction at a hold position prior to said home position so that said magnet and said shutter curtain remain at said hold position whereupon said shutter curtain is in one of the open or closed positions.

A method of operating a focal plane shutter comprising first and second shutter curtains for opening and closing an exposure opening, and first and second electromagnetic drive means operatively coupled to said first and second curtains, respectively, for moving said curtains between open and closed positions, said method comprising the steps of:

• a) energizing said first driver means in one direction in a manner such that said first driver means tends to move from an intermediate operating position toward a home position to cause movement of said first shutter curtain from a position closing said exposure opening to a position opening said exposure opening;
• b) energizing said second driver means in one direction a predetermined time thereafter in a manner such that said second driver means tends to move from an intermediate operating position toward a home operating position to cause movement of said second shutter curtain from a position opening said exposure opening to a position closing said exposure opening;
• c) physically holding said first driver means against further movement when said open position of said first shutter curtain is reached and at a hold position of said first driver means prior to said home operating position so that said first driver means and said first shutter curtain remain at said hold position;
• and
• d) physically holding said second driver means against further movement when said closed position of said second shutter curtain is reached and at a hold position of said second driver means prior to said home operating position so that said second driver means and said second shutter curtain remain at said hold position;
• e) whereby a single exposure is made through said opening.