Folding unit for folding a film material to form a tubular wrapping

A folding unit for folding a film material to form a tubular wrapping, wherein a continuous sheet of the film material, which is to be folded to form a tubular wrapping, is fed according to an infeeding direction, the folding unit comprising:

• a base structure having a longitudinal extension, having a first transversal side and a second transversal side and comprising a longitudinal axis and a longitudinal slot which extends, from the first transversal side to the second transversal side, along the longitudinal axis, wherein the folding unit is positionable with the longitudinal axis of the base structure in the infeeding direction of the continuous sheet so that the base structure is longitudinally crossed by the continuous sheet of the film material fed in the infeeding direction;
• a conveying channel, for conveying products to be wrapped according to an advancement direction which longitudinally crosses the base structure and coinciding with the infeeding direction of the continuous sheet, about which a continuous sheet of the film material is to be folded for forming a tubular wrapping during the advancement in the infeeding direction and the crossing of the base structure;
• positioning means of the continuous sheet, arranged superiorly of the conveying channel and configured to receive the continuous sheet of film material and to direct the continuous sheet according to the infeeding direction to longitudinally cross the base structure, and further configured to arrange the continuous sheet above the conveying channel so as to define a central section in the continuous sheet, above the conveying channel, and two lateral sections having respective end flaps, at the sides of the central section and at the sides of the conveying channel;
• a first pair of folding plates, arranged by the sides of the conveying channel and consecutively to the positioning means in the infeeding direction of the continuous sheet, wherein the plates of the first pair of folding plates are profiled in such a way as to comprise folding edges inclined with respect to the base structure and which depart from an upper starting point, situated downstream of the positioning means, down to reaching a lower arrival point, at the base structure, wherein the inclined folding edges of the first pair of folding plates form, with the base structure, an angle comprised between 7 and 14 degrees and are configured to abut the two lateral sections of the continuous sheet and fold them downwards;
• wherein the base structure comprises a pair of lateral slots arranged at the sides of the conveying channel and in a zone at the arrival points of the folding edges of the first pair of folding plates on the base structure, the pair of lateral slots being conformed so as to enable passage of the lateral sections of the continuous sheet folded in a downwards direction by the folding edges of the first pair of folding plates in such a way that a first proximal part of the lateral sections adjacent to the central section, is arranged vertically at the sides of the conveying channel;
• the folding unit further comprising:
• a second pair of folding plates, arranged consecutively to the pair of lateral slots in the infeeding direction of the continuous sheet, inferiorly of the conveying channel and on opposite sides with respect to the longitudinal axis and to the longitudinal slot of the base structure, wherein the plates of the second pair of folding plates are profiled in such a way as to comprise inclined folding edges inclined with respect to the longitudinal axis and which extend starting from a starting point in proximity of the pair of lateral slots up to an arrival point in proximity of the longitudinal axis, wherein the folding edges of the second pair of folding plates form, with the longitudinal axis of the base structure, an angle comprised between 7 and 14 degrees and are configured to abut a second distal part of the folded lateral sections of the continuous sheet comprising the end longitudinal flaps and to fold a first portion thereof in such a way as to arrange the first portion opposite the central section maintaining a second portion comprising the end flaps folded downwards, to form a tubular wrapping with the end flaps facing one another, and wherein the arrival points of the folding edges of the plates of the second pair of folding plates are facing one another in proximity of the longitudinal axis of the base structure defining there-between a passage space for passage of the end flaps of the tubular wrapping that are facing one another;
• wherein the difference between the angle, formed by the folding edges of the plates of the first pair of folding plates with the base structure, and the angle, formed by the folding edges of the plates of the second pair of folding plates with the longitudinal axis of the base structure, is comprised between ±2°.