System for rapidly changing clamping jaws on a machine tool

A workpiece holding mechanism adapted for a rapid interchange of inside and outside clamping jaws which clamp workpieces from the inside and outside, respectively, of the workpieces;

• said mechanism including a locking element having an abutment face against which a respective jaw rests when in a blocked and locked position, said blocking element including first and second bearing faces inclined at first and second angles, respectively, relative to imaginary planes disposed perpendicularly to said abutment face;
• said inside and outside clamping jaws each having an inclined contact face arranged to engage the respective one of said first and second bearing faces when a respective jaw is in a blocked and locked position;
• retaining means for retaining a respective jaw in a blocked and locked position comprising a retaining member having at one end thereof third and fourth bearing faces inclined at third and fourth angles, respectively, relative to imaginary planes disposed perpendicular to said abutment face, each of said inside and outside clamping jaws including an inclined reaction face arranged to be engaged by a respective one of said third and fourth bearing faces such that when said reaction face of said inside clamping jaw is engaged by said third bearing face said contact surface of said inside clamping jaw is urged against said first bearing surface, and when said reaction face of said outside clamping jaw is engaged by said fourth bearing face said contact surface of said outside clamping jaw is urged against said second bearing surface;
• all of said first, second third, and fourth angles being open in the same direction;
• said first and second angles being larger than said third and fourth angles, respectively;
• and means for enabling said retaining means to be released relative to said reaction surface of a respective jaw for unblocking and unlocking said jaw.