Method and apparatus to maintain the characteristics of a thermoplastic film at constant values
AssigneeA.W.A.X. Progettazione E Ricerca S.r.l.
InventorJoseph Delledonne
Life of this patent
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Abstract
The film, which is cyclically extended in the station for wrapping the product, is acted on by a jet of hot air supplied from a therm-electric generator controlled by a control logic unit which through suitable sensors measures the ambient temperature and the temperature of the film and controls any other inputs, so that the film is kept in optimal and substantially constant conditions to react without tearing to the pre-stretching and/or stretching to which it is normally subjected in the product packaging cycle.
Claims12
A method for maintaining elastic and plastic characteristics of a film of stretchable thermoplastic material at optimal and substantially constant values during packaging of products, comprising the steps of:
- positioning a portion of the film in a packaging system;
- measuring temperature of surrounding environment in which the portion is used and determining whether said measured temperature is lower than an ideal temperature at which the film presents the best deformability characteristics for packaging;
- thermally conditioning said film until the measured temperature of said environment reaches said ideal temperature by blowing hot air onto the portion of film positioned in the product packaging station;
- interrupting thermal conditioning;
- raising the product against the film after said step of interrupting;
- and
- packaging said product.
An apparatus for maintaining elastic and plastic characteristics of a film of stretchable, thermoplastic material at a substantially constant and optimal value during packaging of products, comprising:
- a product packaging station including means for feeding a portion of said film, and means for at least one of pre-stretching and stretching said film;
- generator means for generating at least one flow of hot air with a variable temperature to thermally condition the portion of said film;
- at least one environment sensor for measuring a temperature value of an environment in which the means for feeding the portion of said film operates, and for generating a proportional electrical signal;
- at least one control logic unit which receives as input the electrical signal generated by said environment sensor, and which controls said hot air generator means so that the film acted on by the hot air is stretchable by said pre-stretching and stretching means;
- at least one film sensor for measuring film temperature of said film thermally conditioned by the hot air generator, wherein each of said film sensors sends a proportional electrical signal to said control logic unit for use as a feedback and safety signal to prevent exceeding critical temperatures;
- and
- means for detecting a presence of the film in the product packaging station, for indicating said film presence to said control logic unit, for ensuring conditioning of the film by said hot air generator before pre-stretching and stretching, and for switching said hot air generator off before raising a product up to said film to package the product.
Dependencies are inferred from the claim text.