Attachment mechanism for interchangeable injection molding dies

A mechanism for the clamping attachment of interchangeable injection molding dies to the die carrier plates of an injection molding machine, which machine has a die closing unit defining a horizontal center axis and including a stationary and a movable die carrier plate with radially oriented parallel opposite die mounting faces for the attachment thereto of a stationary and a movable die half, the movable die carrier plate being guided on a plurality of horizontal tie rods and driven for opening and closing movements along said center axis, the die attachment mechanism comprising in combination:

• at least two axially movable clamping plungers arranged in each die carrier plate in axial guide bores which are located on opposite sides of the center axis of the die closing unit, the clamping plungers having forward extremities protruding a distance from the die mounting faces of the associated die carrier plates;
• a standardized back plate on the axially outer side of each die half, the back plate having an outer face adapted to be clamped to the die mounting face of the corresponding die carrier plate and radial dimensions which permit radial insertion and retraction of the back plate between the protruding extremities of said oppositely located clamping plungers, in a movement in which the outer face of the back plate moves along the die mounting face of the die carrier plate with minimal clearance, thereby making it possible to insert and attach a closed injection molding die, while the die carrier plates remain in a virtually closed position;
• means defined by the back plates of the die halves and by the associated clamping plungers for clamping each back plate to the die mounting face of the corresponding die carrier plate, when the clamping plungers are retracted in the direction of the die mounting plate;
• and
• means for forcibly retracting the clamping plungers in the direction of the die mounting plate so as to operate said back plate clamping means;
• and wherein
• the plunger retracting means includes a transverse bore in each clamping plunger and a wedge rod extending transversely to the clamping plunger so as to reach through its transverse bore;
• the transverse bore of the clamping plunger defines an axially forwardly facing tapered face and an opposite, axially rearwardly facing extension drive taper;
• the wedge rod portion reaching through the transverse bore of the clamping plunger has an axially rearwardly facing tapered face which is inclined to the axis of the wedge rod and cooperates with the tapered face of the transverse bore to translate an axial displacement of the wedge rod into a much smaller retracting displacement of the clamping plunger, while applying to said clamping plunger a retraction force which is correspondingly greater than the axial force applied to the wedge rod;
• and
• the wedge rod portion reaching through the transverse bore of the clamping plunger further includes an axially forwardly facing drive protrusion which cooperates with the extension drive taper of the transverse bore to forcibly translate an opposite axial displacement of the wedge rod into a corresponding extension displacement of the clamping plunger.