Dynamic buffer for a continuous envelope stuffing system

A dynamic buffer for a continuous envelope stuffing system, of a type for supplying piles formed by one of more sheets to the stuffing system, the sheets coming from a cutting station provided in a supply line arranged upstream, the continuous stuffing system being of a type in which a film of flexible material is unwound, supplied stretched on a horizontal plane such as to receive thereon a sequence of the piles, and then progressively wound in a tube fashion in order to wrap the piles and subsequently cut in spaces separating each of the piles from a next pile, the buffer being comprising:

• at least a storage level, comprising a plurality of parking cells, arranged in series, suitable for receiving, retaining and dispensing the piles, within each cell being provided:
• at least two lower rollers having horizontal axes that are parallel and distanced by an amount which is less than a dimension of the piles and parallel to the advancement direction, the lower rollers being synchronously motorized, independently of the lower rollers of remaining parking cells;
• at least two upper rollers, idle on axes thereof, each of which is suitable for forming, with the corresponding lower rollers, a roller-counter-roller pair able to adheringly grip and draw one of the piles;
• sensor means suitable for detecting whether each parking cell is free or occupied by one of the piles;
• an electronic managing and command unit, suitable to receive the signals supplied by the sensor means of each parking cell and to pilot a flow of the piles in inlet to the storage level up to bringing each of the piles to a most downstream parking cell, transferring the piles to the successive cells and finally allowing exit of the piles from the storage level, the electronic managing and command unit acting in phase relation with the cutting station and the stuffing system, such that the supplying of the piles thereto is done with a cadence that is proportional to an operating velocity thereof,
• wherein two superposed storage levels are provided, respectively an upper level and a lower level, and switcher means positioned upstream thereof, destined to direct the piles in inlet towards one or another of the storage levels,
• wherein a buffering station is located in each of the superposed storage levels upstream of the relative parking cells, which buffering station is suitable for receiving a predetermined succession of single sheets, supplied in inlet to the buffer, for superposing the sheets in order to form a corresponding pile, and for transferring the pile to the parking cell situated immediately downstream, and
• wherein each of the storage stations comprises:
• at least a lower drive roller, coupled to at least an idle upper roller, for sending sheets in arrival to a tray arranged at a lower level with respect to the level with which the rollers engage the sheet;
• elastic plates, suitable for directing the sheets in arrival in a downwards direction and for maintaining the pile in formation on the tray;
• sensor means suitable for detecting arrival of each of the sheets and sending a corresponding signal to the electronic managing and command unit;
• a carriage, which bears the tray made horizontally mobile between a retracted position in chase relation with the formation of the pile, and an advanced position, for delivery of the pile once it is completed;
• a roller transport group arranged downstream of the tray, suitable for receiving the just-complete pile and for transferring the said pile to the parking cell immediately downstream, maintaining unaltered the reciprocal position of the sheets making up the pile.