| 摘要 |
The internal depressurization of thermoformed containers (C) is performed by means of the secondary suction circuit of a Venturi meter or ejector (15), the primary circuit of which is passed through by compressed air at pressure values regulated by a proportional valve (19) controlled by an electronic control unit (10) which detects the internal pressure or vacuum of the containers by means of a transducer (9) which is programmed by means of a special apparatus (11) and which, upon reaching of the predetermined vacuum inside the containers, activates means (Z) for closing the end portion of the said thermoformed containers. By means of a barometric sensor (21), the electronic control unit is also able to detect the atmospheric pressure of the working environment of the thermoforming machine, and the said control unit, upon a variation in the atmospheric pressure, automatically corrects the vacuum value associated with operation of the said closing means (Z), following a law whereby the said vacuum varies in an inversely proportional manner with respect to the variations in the atmospheric pressure.
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