Stacker for stacking sheets, and related method

A stacker for stacking sheets, including:

• a first conveyor, comprising an entrance end and a discharge end for the sheets;
• a first stacking platform, arranged to receive sheets discharged from the discharge end of the first conveyor;
• wherein the first stacking platform is provided with a vertical lifting and lowering movement in a first stacking bay to allow forming stacks of sheets on the first stacking platform;
• along the first conveyor, a device for interrupting a flow of shingled sheets moving forward along the first conveyor;
• a second conveyor, comprising an entrance end and a discharge end for the sheets and arranged in series with the first conveyor;
• a second stacking platform arranged to receive sheets discharged from the discharge end of the second conveyor;
• wherein the second stacking platform is provided with a vertical lifting and lowering movement in a second stacking bay to allow forming stacks of sheets on the second stacking platform;
• a switching device for arranging the discharge end of the first conveyor and the entrance end of the second conveyor selectively:
• in a first position, where the discharge end of the first conveyor is misaligned relative to the entrance end of the second conveyor and positioned to discharge sheets from the first conveyor onto the first stacking platform;
• and
• a second position, where the discharge end of the first conveyor is aligned with the entrance end of the second conveyor to convey the sheets from the entrance of the first conveyor along the first and the second conveyors and to discharge the sheets onto the second stacking platform;
• wherein the stacker further comprises a third conveyor including an entrance end and a discharge end for the sheets;
• wherein the third conveyor is provided above the first conveyor and extends approximately parallel to the first conveyor;
• and wherein the switching device is configured so that, when the discharge end of the first conveyor and the entrance end of the second conveyor are in the second position, the first conveyor, the second conveyor and the third conveyor form:
• a first path for conveying the sheets along the first conveyor, from the entrance end of the first conveyor to the first stacking platform;
• and
• a second path for conveying the sheets along the third conveyor and the second conveyor, from the entrance end of the third conveyor to the second stacking platform.

A method for forming stacks of sheets in sequence, comprising the steps of:

• conveying a flow of shingled sheets along a first conveyor extending from an entrance end to a discharge end for the sheets;
• discharging sheets from the discharge end of the first conveyor onto a first stacking platform, by gradually lowering the first stacking platform moving it away from the discharge end of the first conveyor and keeping the discharge end of the first conveyor in a position where the sheets are supplied to the first stacking platform, and forming a stack of sheets on the first stacking platform;
• forming a first gap in the flow of sheets along the first conveyor;
• when the first gap in the flow of sheets achieves the discharge end of the first conveyor, aligning the discharge end of the first conveyor with an entrance end of a second conveyor;
• conveying a flow of shingled sheets sequentially along the first conveyor and the second conveyor, that are aligned with each other, and discharging the sheets from a discharge end of the second conveyor onto a second stacking platform, by gradually lowering the second stacking platform moving it away from the discharge end of the second conveyor;
• forming a second gap in the flow of sheets along the first conveyor;
• when the second gap in the flow of sheets achieves the discharge end of the first conveyor, moving the discharge end of the first conveyor into a position where the sheets are supplied to the first stacking platform;
• conveying the flow of shingled sheets along the first conveyor and discharging the sheets from the discharge end of the first conveyor onto the first stacking platform, by gradually lowering the first stacking platform moving it away from the discharge end of the first conveyor;
• forming a third gap in the flow of sheets along the first conveyor;
• when the third gap in the flow of sheets achieves the discharge end of the first conveyor, aligning the discharge end of the first conveyor with the entrance end of the second conveyor;
• conveying a flow of shingled sheets sequentially along the first conveyor and the second conveyor, that are aligned with each other, and discharging the sheets from the discharge end of the second conveyor onto the second stacking platform, by gradually lowering the second stacking platform moving it away from the discharge end of the second conveyor;
• wherein, after having formed the second gap, the stack of sheets formed on the second stacking platform remains in position and, after the formation of the third gap, the sheets sequentially conveyed along the first conveyor and the second conveyor, that are aligned with each other, are put over the stack previously formed on the second stacking platform.

A method for forming stacks of sheets in sequence, comprising the steps of:

• conveying a flow of shingled sheets along a first conveyor extending from an entrance end to a discharge end for the sheets;
• discharging sheets from the discharge end of the first conveyor onto a first stacking platform, by gradually lowering the first stacking platform moving it away from the discharge end of the first conveyor and keeping the discharge end of the first conveyor in a position where the sheets are supplied to the first stacking platform, and forming a stack of sheets on the first stacking platform;
• forming a first gap in the flow of sheets along the first conveyor;
• when the first gap in the flow of sheets achieves the discharge end of the first conveyor, aligning the discharge end of the first conveyor with an entrance end of a second conveyor;
• conveying a flow of shingled sheets sequentially along the first conveyor and the second conveyor, that are aligned with each other, and discharging the sheets from a discharge end of the second conveyor onto a second stacking platform, by gradually lowering the second stacking platform moving it away from the discharge end of the second conveyor;
• forming a second gap in the flow of sheets along the first conveyor;
• when the second gap in the flow of sheets achieves the discharge end of the first conveyor, moving the discharge end of the first conveyor into a position where the sheets are supplied to the first stacking platform;
• conveying the flow of shingled sheets along the first conveyor and discharging the sheets from the discharge end of the first conveyor onto the first stacking platform, by gradually lowering the first stacking platform moving it away from the discharge end of the first conveyor;
• wherein, after having formed the first gap and the second gap, the sheets conveyed along the first conveyor and fed to the first stacking platform are put over the stack previously formed on the first stacking platform.