Hydraulic chuck

A hydraulic chuck adapted to grip at least one workpiece, comprising:

• a chuck body;
• a fixed seat fixedly mounted to said chuck body, and having a side surface;
• a rotary seat mounted to said fixed seat and rotatable relative to said fixed seat about a central axis, said rotary seat having a side surface that faces toward said side surface of said fixed seat, said side surface of said fixed seat and said side surface of said rotary seat cooperatively defining a gap therebetween that permits pressurized oil to flow therethrough;
• a plurality of flexible seal members each being centered at the central axis and each having a first annular segment that is fixedly mounted to said fixed seat, a neck segment that extends from said first annular segment and through said gap, and a second annular segment that is connected to an end of said neck segment distal from said first annular segment, that is disposed adjacent to said rotary seat and that cooperated with said first annular segment and said neck segment to define at least one oil groove thereamong, said second annular segments of at least one adjacent pair of said seal members being pushed to be in contact with said rotary seat when the pressurized oil is introduced into said gap, said second annular segments of said seal members being spaced apart from said rotary seat when the pressurized oil is ceased to be introduced into said gap;
• and
• a driving seat unit movably mounted to said rotary seat and moved by the pressurized oil for griping or releasing the workpiece.