Clamping device for tool holder

A clamping device arranged for releasably holding a tool holder shank, the clamping device comprising:

• a housing 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 moveable in the bore along a longitudinal axis thereof in a first axial direction from an advanced releasing position to a retracted locking position, and further moveable in an opposite second axial direction from the retracted locking position to the advanced releasing 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, to a second position, in which the engagement members are in locking engagement with the tool holder shank and keep the tool holder shank secured to the housing;
• a hydraulically operated actuating member arranged in the bore, wherein the actuating member is axially moveable in relation to the drawbar;
• at least one wedge arranged in the bore and configured to transfer an axial movement of the actuating member in the first axial direction in relation to the drawbar into a movement of the drawbar from the advanced releasing position to the retracted locking position;
• and
• a piston slidably mounted in a space inside the bore and configured to divide this space into a first hydraulic chamber on a first side of the piston and a second hydraulic chamber on an opposite second side of the piston,
• wherein the actuating member is fixed to the piston and moveable together with the piston in the first axial direction by feeding of hydraulic fluid into the first hydraulic chamber and in the second axial direction by feeding of hydraulic fluid into the second hydraulic chamber,
• wherein the at least one wedge is arranged on the outside of the drawbar and is configured to press the drawbar towards the retracted locking position when the at least one wedge is pressed inwards towards a longitudinal center axis of the drawbar,
• wherein the at least one wedge comprises includes an outwardly facing first pressure receiving surface,
• wherein the actuating member has a form of a sleeve and surrounds a part of the drawbar,
• wherein the actuating member on an inner side thereof is provided with a first pressure applying surface which faces inwards for contacting the first pressure receiving surface on the at least one wedge, the first pressure applying surface having a radial distance to the longitudinal axis that increases in the first axial direction;
• and
• wherein the first pressure applying surface is configured to press the at least one wedge inwards towards the longitudinal center axis of the drawbar by pressing against the first pressure receiving surface on the at least one wedge when the actuating member is moved in the first axial direction.