Clamping device

A clamping device configured to clamp a member having a shank part in which a recess is formed, comprising:

• a body, a clamping mechanism and a driving mechanism, wherein:
• the body has a first body interior space, a second body interior space and a communication passage,
• the clamping mechanism has a first movable member that is movable along an extending direction of the first body interior space, a first chamber having a volume that changes in response to movement of the first movable member, a first elastic member that generates an elastic force that urges the first movable member to move relative to the body in a first direction that reduces the volume of the first chamber, and a collet having a first projection that is engageable with the recess of the member to be clamped,
• the collet is settable to a clamping mode in which the first projection becomes engaged with the recess in response to movement of the first movable member in the first direction, and is also settable to an unclamping mode in which the engagement between the first projection and the recess is released in response to movement of the first movable member in a second direction that increases the volume of the first chamber,
• the driving mechanism has a second movable member that is movable along an extending direction of the second body interior space, and a second chamber having a volume that changes in response to movement of the second movable member,
• the communication passage fluidly connects the first chamber and the second chamber,
• a power transmitting medium is filled in the first chamber, the second chamber and the communication passage,
• the first chamber has a first cross-sectional area that is larger than a second cross-sectional area of the second chamber, and
• the clamping device is configured such that:
• movement of the second movable member in a third direction that increases the volume of the second chamber causes the first movable member to move in the first direction due to the elastic force of the first elastic member, and thereby causes the collet to be set to the clamping mode,
• movement of the second movable member in a fourth direction that reduces the volume of the second chamber causes the first movable member to move in the second direction against the elastic force of the first elastic member and thereby causes the collet to change to the unclamping mode.