Ball screw centering devices for injection molding apparatuses

A ball screw centering device comprising:

• a center bearing housing to be connected to a center mold block;
• a rotatable shaft extending through a channel of the center bearing housing and rotatably mounted to the center bearing housing, the rotatable shaft having a first side ball track and a second side ball track;
• a first nut to be coupled to a stationary mold block, the first nut including a track portion cooperating with the first side ball track to define a passage for a first set of ball bearings to traverse;
• a second nut to be coupled to a distal mold block, the second nut including a track portion cooperating with the second side ball track to define a passage for a second set of ball bearings to traverse;
• a first nut housing to be fixed to a stationary mold block;
• and
• a first sleeve to be connected to and extendable between the center bearing housing and the first nut housing to circumscribe an exposed portion of the first side ball track and an exposed portion of the first nut between the center bearing housing and the first nut housing, the first sleeve being positionable between an unexpanded position and an expanded position.

A method comprising:

• translating a distal mold block of a stack mold tool in a first longitudinal direction to rotate a rotatable shaft of a ball screw centering device coupled to the stack mold tool in a first rotation direction, wherein:
• a first nut housing of the ball screw centering device is fixed to a stationary mold block of the stack mold tool;
• a center bearing housing of the ball screw centering device is fixed to a center mold block of the stack mold tool;
• a second nut housing of the ball screw centering device is fixed to the distal mold block of the stack mold tool;
• and
• a first sleeve is connected to and extendable between the center bearing housing and the first nut housing to circumscribe an exposed portion of a first side ball track and an exposed portion of a first nut between the center bearing housing and the first nut housing, the first sleeve being positionable between an unexpanded position and an expanded position.