Shutter blade drive system

Photographic apparatus for controlling the opening and closing of a photographic shutter during an exposure interval, comprising:

• a photographic shutter including a pair of blades mounted for movement between a closed orientation and an open orientaion in which scene light may pass to a focal plane as said blades are moved between said closed and open orientations;
• means for connecting said blades for simultaneous movement;
• a linear motor including a field coil, a bobbin for supporting the windings of said field coil, an armature mounted for reciprocating movement within a passageway in said bobbin, said armature including a first permanent magnet at one end thereof and an output member coupled to said connecting means, a second permanent magnet fixedly secured within said passageway such that the same magnetic poles of each of said magnets face each other thereby producing a magnetic field therebetween having a force sufficient to move said armature in a first direction into a closed shutter position, and means for biasing said armature in a second direction opposite to said first direction and toward said first permanent magnet, said biasing means providing a force less than the force created by said magnetic field;
• and
• means for energizing said field coil in a manner so as to create a magnetic field in opposition to the magnetic field naturally occurring between said first and second permanent magnets to reduce its force to a level below that of said biasing means whereby said biasing means moves said armature in said second direction to thereby move said blades from said closed orientation toward said open orientation.

A linear motor comprising:

• means for supporting electrically conductive means, said supporting means including means defining a passageway extending axially of said supporting means;
• a first permanent magnet fixedly mounted within said passageway with its magnetic poles orientated along said passageway;
• an armature including a second permanent magnet and an ouput member mounted within said passageway for axial movement between first and second opposite positions, the magnetic poles of said second permanent magnet being orientated along said passageway such that common poles of said first and second permanent magnets face each other and create a magnetic field having a force sufficient to move said armature into said first position;
• means for resiliently biasing said armature toward said second position, said biasing means having a force less than that created by said magnetic field;
• electrically conductive means wound upon said supporting means;
• and
• means for energizing said electrically conductive means in a manner so as to create a magnetic field in opposition to the magnetic field naturally occurring between said first and second permanent magnets to reduce its force to a level below that of said biasing means whereby said biasing means moves said armature in said second direction.

A positioning device comprising:

• a linear motor including an armature having first and second output members and electrically conductive means selectively energizable to move said armature in first and second directions, respectively;
• an electromagnet fixedly secured to said first output member;
• a link adapted to be coupled to a positionable member;
• means for mounting said link for movement in said first and second directions, said mounting means maintaining said link adjacent to said electromagnet as said link is moved in said first and second directions;
• and
• means for simultaneously energizing the winding of said electromagnet and said electrically conductive means to thereby magnetize said electromagnet and magnetically draw said link in said first direction as said armature is moved in said first direction and for alternatively energizing said electrically conductive means so as to move said armature in said second direction so as to move said second output member into engagement with the positionable member.

Photographic apparatus for controlling the opening and closing of a photographic shutter during an exposure interval comprising:

• a photographic shutter including a pair of blades mounted for movement between a closed orientation and an open orientation in which scene light may pass to a focal plane;
• means for connecting said blades for simultaneous movement between said closed and open orientations;
• a linear motor adapted to be coupled to said connecting means for incrementally moving said blades from said closed orientation toward said open orientation, and for rapidly returning said blades to said closed orientation, said linear motor including an armature having a first output member;
• means for coupling said linear motor to said connecting means, said coupling means including a rod having one end secured to said connecting means and an electromagnet fixedly secured to said first output member in close proximity to said rod;
• and
• means for generating a sequence of electrical pulses to energize said linear motor in a first directional sense to displace said blades from said closed orientation toward said open orientation and for generating an electrical pulse to energize said linear motor in an opposite directional sense to rapidly return said blades to said closed orientation thereby terminating the exposure interval, said generating means being adapted to energize the winding of said electromagnet each time said linear motor is driven in said first directional sense thereby magnetically drawing said rod in the same direction so as to move said blades toward said open orientation.