Method and unit for closing the ends of tubular wrappings on a cigarette packing machine

A method of closing the ends of tubular wrappings enclosing respective groups of cigarettes, each tubular wrapping (5) including a first major wall and a second major wall (6), a first minor wall and a second minor wall (7) perpendicular to said major walls (6), and at least one substantially rectangular-section tubular end portion (8) projecting axially with respect to the relative said group (3), the tubular end portion (8) including two short sides (9) coplanar with respective said minor walls (7), and two long sides (10) coplanar with respective said major walls (6), the method comprising:

• feeding the tubular wrapping (5) in a traveling direction along a path (P) parallel to said major walls (6);
• folding the short sides (9) of each tubular wrapping (5) onto the relative said group (3) to define on the relative said long sides (10) a first tab and a second tab (22) coplanar with said first major wall and said second major wall (6) respectively;
• and
• folding the tabs (22) successively onto the relative said group with a single rocker arm (46) mounted to swing about a hinge axis (49) crosswise to said path (P) and comprising two folding arms (45, 50) located on opposite sides of said hinge axis (49) the folding arms each having a respective folding edge (51;
• 54) for a respective said tab (22), said rocker arm (46) being swung about said hinge axis (49) so that each said folding edge (51;
• 54) interferes with said path (P) in time with said tubular wrapping (5) traveling along the path (P).

A unit for closing the ends of tubular wrappings enclosing respective groups of cigarettes, each tubular wrapping (5) comprising a first and a second major wall (6), a first and a second minor wall (7) perpendicular to said major walls (6), and at least one substantially rectangular-section tubular end portion (8) projecting axially with respect to the relative said group (3) and in turn comprising two short sides (9) coplanar with respective said minor walls (7), and two long sides (10) coplanar with respective said major walls (6);

• the unit comprising:
• first folding means (37, 42) for folding said short sides (9) of each tubular wrapping (5) onto the relative said group (3) to define a tab (22) on each said long side (10);
• second folding means (46) for folding said tabs (22) successively onto the relative said group (3) and one towards the other;
• two flat supporting walls (16, 60);
• actuating means (62, 66, 67) for maintaining said two flat supporting walls (16, 60) parallel to each other and each contacting a respective said major wall (6), at least when folding the tab (22) coplanar with said major wall (6);
• a first folding station and a second folding station (21, 24) located successively along a path (P):
• conveying means (11) for feeding said tubular wrappings (5) successively along said given path (P) and in a given traveling direction (17), said conveying means (11) comprising a number of conveying heads (14), each for housing a respective said tubular wrapping (5), each tubular wrapping (5) being positioned on the relative said conveying head (14) with a longitudinal axis of the tubular wrapping crosswise to said traveling direction (17), wherein a first said supporting wall (16) is a wall of said conveying head (14), and is positioned parallel to and contacting said first major wall (6) coplanar with a first said tab (22);
• and a second said supporting wall (60) is a movable wall common to all the conveying heads (14), and
• said actuating means (62, 66, 67) being connected to said second supporting wall (60) to move the second supporting wall (60) to and from a contact position contacting a said tubular wrapping (5) located at said second folding station (24), and to position said second supporting wall (60), in said contact position, contacting said second major wall (6) coplanar with a respective second said tab (22).

A unit for closing the ends of tubular wrappings enclosing respective groups of cigarettes, each tubular wrapping (5) comprising a first and a second major wall (6), a first and a second minor wall (7) perpendicular to said major walls (6), and at least one substantially rectangular-section tubular end portion (8) projecting axially with respect to the relative said group (3) and in turn comprising two short sides (9) coplanar with respective said minor walls (7), and two long sides (10) coplanar with respective said major walls (6);

• the unit comprising:
• first folding means (37, 42) located at a first folding station (21) to fold said short sides (9) of each tubular wrapping (5) onto the relative said group (3) to define a tab (22) on each said long side (10);
• first actuating means (26, 41) for actuating said first folding means (37, 42);
• second folding means (46) located at a second folding station (24) to fold said tabs (22) successively onto the relative said group (3) and one towards the other;
• second actuating means (26, 56) for actuating said second folding means (46);
• and
• conveying means (11) for feeding said tubular wrappings (5) successively and continuously in a given traveling direction (17) and along a path (P) extending through said first and said second folding station (21, 24);
• wherein said second folding means (46) comprise a single rocker arm (46), which successively folds both said tabs (22) of each said tubular wrapping (5) as the tubular wrapping (5) is fed through said second folding station (24), said rocker arm (46) being mounted to rotate about a hinge axis (49) crosswise to said path (P), and comprising two folding arms (45, 50) located on opposite sides of said hinge axis (49) and each folding arm having a respective folding edge (51;
• 54) for a respective said tab (22), and said second actuating means (26, 56) swinging said rocker arm (46) so that said folding edges (51, 54) interfere with said path (P) in time with said conveying means (11).