Patent ID: 7011509

Claim:
In a calibration device for a plastic extrusion system comprising: a. a housing to receive the coolant, through which a plastic profile may be transported and thereby cooled by the coolant, b. calibration guides in the housing through which the plastic profile passes, c. inlet and drainage openings in the housing with connected lines for the coolant, d. wherein the coolant level in the housing lies above the apex of the plastic profile to be calibrated and is so adjusted that a liquid-free, air-filled volume remains above the coolant level, and e. an air extraction aperture in the housing above the coolant level through which air may be extracted and a partial vacuum of Pu=Pa−ΔP may be created in the liquid-free, air-filled volume above the coolant level with respect to ambient air pressure, whereby Pu is the partial vacuum prevailing in the calibration device, Pa is the ambient air pressure prevailing outside the calibration device, and ΔP is the difference between the two pressure values, each of which is measured in height units of a coolant column, the improvement wherein f. the drain opening for the coolant is positioned in a wall of the housing at the coolant level so that the coolant may drain without an additional pump, g. and that a drain line connected to the drain opening extends essentially vertically and ends below a level corresponding to ΔP into a coolant supply tank exposed to the ambient atmosphere, whereby a compact fluid column with a height h corresponding to ΔP is formed.