Holder including a hydraulic piston for the detachable assembly of cutting tools

A holder for cutting tools, the holder comprising:

• a housing including an inner cavity defining a longitudinal center axis, the housing including front and rear axial ends, the front end adapted to received a cutting tool;
• a bushing disposed in the cavity and including a surface inclined obliquely relative to the axis;
• and
• a clamping mechanism arranged in the housing and including:
• a clamping element adapted to be received in a cutting tool and movable axially forwardly and rearwardly relative to the bushing between an axially rearward clamping position for clamping a cutting tool, and an axially forward unclamping position for unclamping the cutting tool,
• a piston movable forwardly and rearwardly within the cavity and having an axial projection, the piston arranged to divide the cavity into forward and rearward chambers to and from which hydraulic oil can be fed for moving the piston and the clamping element rearwardly and forwardly between clamping and unclamping positions, respectively, and
• a plurality of wedge bodies arranged around the piston projection for locking the piston in the clamping position, each wedge body having radially inner and outer surfaces each inclined obliquely relative to the axis,
• the piston projection including an outer surface inclined obliquely relative to the axis and arranged to engage the inner surfaces of the wedge bodies when the piston is moved rearwardly, to displace the wedge bodies radially outwardly and produce engagement between the bushing surface and the outer surfaces of the wedge bodies, the bushing surface arranged for displacing the wedge bodies axially rearwardly in response to the engagement between the bushing surface and the outer surfaces of the wedge bodies,
• the piston projection and the wedge bodies being in communication with the forward chamber, wherein pressurized oil fed to the forward chamber to move the piston and the clamping element to the clamping position tends to enter an interface between the outer surface of the piston and the inner surface of the wedge bodies;
• the clamping element arranged to be forwardly and rearwardly displaced in response to forward and rearward movement, respectively, of the piston,
• the outer surface of the piston projection having at least one groove formed therein and extending generally circumferentially therearound for evacuating oil from the interface between the outer surface of the piston and the inner surfaces of the wedge bodies to a location between adjacent wedge bodies.