Die closing unit with retractable tie rods

A die closing unit for an injection molding machine designed to produce plastic or metallic articles through the injection of suitable raw material into a multiplate injection molding die having a cavity, which die is to be opened and closed by means of said unit in a reciprocating straight-line axial motion, whereby the injection molding die is readily removable and interchangeable with another die, said die closing unit comprising in combination:

• a first die carrier member having an axially oriented face for the attachment thereto of a constituent half of said injection molding die;
• a second die carrier member spaced a distance from the face of the first member and having an oppositely oriented face for the attachment thereto of the other constituent half of the injection molding die in axial alignment with said first die half;
• means for forcibly moving one of the two die carrier members towards and away from the other in a reciprocating die closing and opening motion;
• means for axially guiding the movable one of the two die carrier members in relation to the stationary one, said means including at least two tie rods extending parallel to the unit axis, laterally outside and on opposite sides of the space occupied by the cavity of an injection molding die, each tie rod having one extremity rigidly connected to one of the two die carrier members and a central length portion thereof guidingly received in a guide bore of the other die carrier member;
• and wherein
• the rigid connections between the tie rod extremities and said one die carrier member are axially preloaded thread-clamped connections;
• and
• at least one thusly rigid connected tie rod engages a connecting bore in said connected die carrier member with a configuration which permits release of the rigid connection and retraction of the tie rod through its connecting bore;
• said retractable tie rod includes, as part of its releasable connection, an end portion which protrudes from the axially outer side of said connected die carrier member;
• the protruding tie rod end portion defines an axial force transmitting surface which is facing inwardly towards said connected die carrier member and whose maximum diameter is not greater than the diameter of its connecting bore;
• and
• the retractable tie rod further includes, as part of its releasable connection, an abutment member which is axially engaged between said axial force transmitting surface and said connected die carrier member, and threaded means for axially preloading the tie rod against said connected die carrier member in the abutment sense of said abutment member.