Importance

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Abstract

An apparatus for heating plastics surface regions of an open end zone of a carton sleeve prior to sealing of the end zone includes a heater head which has a side wall (102) and is closed at its distal end by a wall (106) and is open at its proximal end to receive hot air to flow out sideways via holes (108). The hot air is supplied to the heater head in two separate streams (110) and (112) through two separate ducts (118) and (120). The ducts have their own air-heating arrangements (122) and (124) which can be controlled, insofar as temperature is concerned, to at least some extent independently of each other. The ducts (118) and (120) contain respective air blowers (126) and (128) the speeds of which are adjustable relative to each other. It is thereby possible to adjust the temperature and/or flow rates of the air streams (110) and (112). The streams (110) and (112) enter respective separate compartments (114) and (116) of the heater head which are formed by a partition (130), the compartment (114) occupying most of the interior and the compartment (116) occupying that corner of the interior at which a longitudinal lap seal of the open end zone of the carton sleeve is present. In this manner, the internal plastics surface region at the relevant part of the longitudinal lap seal can be subjected to a level of heating which ensures blocking of channel leakages thereat, whilst the other sealing regions of the end closure are subjected to a lower temperature, sufficient to render them tacky, but such as to minimise the production of heat cracks and of off-taste.

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First Claim