Background of the Screw Extruder (3)
German Patent 35 03 911 has disclosed a hydraulic pin adjustment which permits the pins to be driven all the way in and backed all the way out, each pin being constituted by the plunger of a hydraulic cylinder. For each pin a separate hydraulic cylinder is provided. The possibility of achieving specific, defined pin depth settings has been practically unattainable on account of the immensely great complexity of the controls required. Even the complete plunging and extraction of the pins is so structurally complex that such hydraulic pin control has not become established to any great extent.
A pin adjuster that appears to be mechanically very simple, and which theoretically also offers the possibility of any desired depth adjustment, has been disclosed by German Patent 35 06 424. The disadvantage of this type of construction using Kellen drives for the screw movement producing the axial movement of the pins lies in the fact that extremely great friction is involved, which renders unfunctional any design based on this principle, and therefore it has never been used in actual practice.
The present invention avoids the disadvantages of the state of the art. It is the aim of the invention to create a practically usable and economical possibility for rapid pin movement and depth adjustment on screw extruders.
A pin adjuster that appears to be mechanically very simple, and which theoretically also offers the possibility of any desired depth adjustment, has been disclosed by German Patent 35 06 424. The disadvantage of this type of construction using Kellen drives for the screw movement producing the axial movement of the pins lies in the fact that extremely great friction is involved, which renders unfunctional any design based on this principle, and therefore it has never been used in actual practice.
The present invention avoids the disadvantages of the state of the art. It is the aim of the invention to create a practically usable and economical possibility for rapid pin movement and depth adjustment on screw extruders.
