A clamping device arranged for releasably holding a tool holder shank, the clamping device comprising:
- a housing;
- a spindle rotatably mounted inside the housing and having a front end, a rear end and a bore, which intersects the front end and extends rearwardly therefrom, wherein a mounting portion arranged for receiving the tool holder shank is provided at a front end of the bore;
- a drawbar slidably mounted inside the bore so as to be reciprocally moveable in the bore along a longitudinal axis thereof between an advanced releasing position and a retracted locking position;
- engagement members arranged around the drawbar at a front end thereof, wherein the engagement members, under the effect of a movement of the drawbar from the advanced releasing position to the retracted locking position, are moveable from a first position, in which the engagement members allow the tool holder shank to move into and out of said mounting portion of the bore, to a second position, in which the engagement members are in locking engagement with the tool holder shank and keep it secured to the spindle;
- an actuating member arranged inside the housing, wherein the actuating member is slidably mounted to the spindle so as to be moveable in relation to the spindle in the axial direction thereof;
- a motion transferring mechanism arranged inside the housing, wherein the motion transferring mechanism is mounted to the spindle and configured to transfer an axial movement of the actuating member in a first axial direction in relation to the spindle into a movement of the drawbar from the advanced releasing position to the retracted locking position;
- and
- a hydraulic actuator arranged for moving the actuating member axially in relation to the spindle, wherein the hydraulic actuator is arranged in the housing and includes a cylinder housing and a piston member, wherein the cylinder housing extends around the spindle and is slidably mounted inside the housing so as to be moveable axially in relation to the spindle between a first end position, in which the cylinder housing abuts against a first shoulder on the spindle that limits the movement of the cylinder housing in relation to the spindle in said first axial direction, and a second end position, in which the cylinder housing abuts against a second shoulder on the spindle that limits the movement of the cylinder housing in relation to the spindle in an opposite second axial direction, wherein the piston member extends around the spindle and is slidably mounted to the cylinder housing so as to be hydraulically moveable axially in relation to the spindle in order to allow the piston member to exert a pulling or pushing force on the actuating member in the first axial direction and thereby effect a movement of the drawbar from the advanced releasing position to the retracted locking position, wherein the piston member includes an annular piston head slidably received in a space in the cylinder housing, wherein a first hydraulic chamber is formed in this space on a first side of the piston head, the cylinder housing being moveable into the second end position and the piston member being moveable in the first axial direction by feeding of hydraulic fluid into this first hydraulic chamber, and
- wherein the actuating member is rotatable in relation to the cylinder housing and the piston member together with the spindle.