The present invention concerns an apparatus and method for thermoforming a plastic article from a sheet of plastic material heated to a predetermined forming temperature. The apparatus includes a mold having forming surfaces defining a forming cavity generally conforming to the shape of the plastic article to be formed. The heated plastic sheet is urged into contact with the forming surfaces of the mold to form the plastic article. The mold includes at least one undercut forming element moveable between an advanced position wherein the element projects into the forming cavity to form an undercut portion in the plastic article and a retracted position wherein the element is withdrawn from the forming cavity to enable the formed plastic article to be removed from the forming cavity. After the plastic article has been formed, the undercut forming element is moved to the retracted position and a stripper plate is utilized to remove the formed plastic article from the forming cavity. In the preferred embodiment of the invention, the undercut forming element is retracted simultaneously with the stripping movement of the stripper plate to minimize the cycle time associated with producing the plastic article.

An apparatus and method for forming thermoplastic containers having a male locking member. The apparatus includes a cavity defining a shape of the container, a stripper movable in a longitudinal direction relative to said cavity, and a retractable lock adjacent to an edge of the cavity. The retractable lock is movable in a transverse direction relative to the cavity between a retracted position and an unretracted position and movable in a longitudinal direction between a first position and a second position. The containers are formed through a process in which the apparatus is sequentially placed in a ready mode, lift mode, disengage mode, and back to the ready mode. In the ready mode, the retractable lock is placed in the unretracted position and first position in order to receive a sheet of plastic material and form a locking member thereon. In the lift mode, the retractable lock is moved in a longitudinal direction from the first position to the second position in order to lift the container from the cavity. In the disengage mode, the retractable lock is moved in a transverse direction from the unretracted position to the retracted position in order to disengage itself from the locking member.

An apparatus and method for forming thermoplastic containers having a male locking member. The apparatus includes a cavity defining a shape of the container, a stripper movable in a longitudinal direction relative to said cavity, and a retractable lock adjacent to an edge of the cavity. The retractable lock is movable in a transverse direction relative to the cavity between a retracted position and an unretracted position and movable in a longitudinal direction between a first position and a second position. The containers are formed through a process in which the apparatus is sequentially placed in a ready mode, lift mode, disengage mode, and back to the ready mode. In the ready mode, the retractable lock is placed in the unretracted position and first position in order to receive a sheet of plastic material and form a locking member thereon. In the lift mode, the retractable lock is moved in a longitudinal direction from the first position to the second position in order to lift the container from the cavity. In the disengage mode, the retractable lock is moved in a transverse direction from the unretracted position to the retracted position in order to disengage itself from the locking member.