Lock mechanism for stage apparatus

1. A lock mechanism for a stage apparatus, comprising:

a movable stage which is provided on a stationary member movable in a reference plane;

a pair of engaging members provided on said movable stage;

a pair of lock members which are positioned between said engaging members and are movable so as to engage and disengage with corresponding said engaging members, said lock members being movable along a straight imaginary line passing through said engaging members;

a first link member which is movable in a plane parallel to said reference plane in a direction along a reference straight line which passes through a central position of pair of said engaging members and is orthogonal to the moving direction of said lock members;

a pair of second link members symmetrically arranged with respect to said reference straight line, wherein one end of each of said second link members is rotatably mounted on said first link member via a first rotational axis, and the other end of each of said second link members is rotatably mounted on a corresponding said lock member via a second rotational axis, said first and second rotational axes extending normal to said reference plane;

a lock driving device which moves said lock members to an engaged position wherein said lock members mutually move away from each other and engage with said corresponding engaging members by moving said first link member in one direction along said reference straight line; and

an unlock driving device which moves said lock members to a disengaged position wherein said lock members mutually move toward each other so as to disengage with said corresponding engaging members by moving said first link member in the other direction along said reference straight line.

2. The lock mechanism for the stage apparatus according to claim 1 , wherein each of said second link members comprises a linear shaped member; and

wherein said lock members are positioned at said engaged position when axial lines of said link members extend in a common straight line which is aligned in a direction of said straight imaginary line passing through said lock members.

3. The lock mechanism for the stage apparatus according to claim 1 , wherein said lock driving device comprises:

a magnetic-force generator provided on one of said first link member and said stationary member; and

a drive coil fixed to the other of said first link member and said stationary member, said drive coil generating a linear drive force in a direction along said reference straight line upon receiving electric current while receiving a magnetic force from said magnetic-force generator;

wherein said linear drive force in said direction along said reference straight line is converted into a linear drive force along said straight imaginary line passing through said lock members via said first link member and said second link members.

4. The lock mechanism for the stage apparatus according to claim 1 , wherein said unlock driving device comprises:

a biasing device, each end of which is connected to said first link member and said stationary member, respectively, so as to exert a biasing force in said reference straight line direction.

5. The lock mechanism for the stage apparatus according to claim 1 , further comprising:

a first retaining device for holding said lock members at said engaged position upon said lock members being moved to said engaged position; and

a second retaining device for holding said lock members at said disengaged position upon said lock members being moved to said disengaged position.

6. The lock mechanism for the stage apparatus according to claim 5 , wherein said first retaining device comprises:

a magnet fixed to one of said first link member and said stationary member; and

a magnetic plate which is magnetically attracted to said magnet so as to contact each other when said first link member and said second link members are positioned at said engaged position.

7. The lock mechanism for the stage apparatus according to claim 5 , wherein said second retaining device comprises:

a biasing device which biases said first link member and said second link members to said disengaged position.

8. The lock mechanism of the stage apparatus according to claim 5 , wherein said second retaining device comprises:

a magnet which is fixed to one of said first link member and said stationary member; and

a magnetic plate fixed to the other of said first link member and said stationary member, said magnetic plate being magnetically attracted to said magnet so as to contact each other when said first link member and said second link members are positioned at said disengaged position.

9. The lock mechanism of the stage apparatus according to claim 1 , wherein at least one of said lock members resiliently engages with a corresponding said engaging member.