Packing unit and method for folding a blank on a packing machine

1. A packing unit ( 10 ) for folding a blank ( 4 ) on a packing machine ( 1 ); the packing unit ( 10 ) comprising:

a packing conveyor ( 17 ) having at least one pocket ( 18 ) for receiving the blank ( 4 ); and

a feed device ( 19 ) for inserting the blank ( 4 ) into the pocket ( 18 ) on the packing conveyor ( 17 );

wherein the packing conveyor ( 17 ) comprises: at least a first conveyor belt ( 23 ), and at least a second conveyor be ( 24 ) separate from, parallel to, and alongside the first conveyor belt ( 23 ), said first and second ( 24 ) conveyor belts forming a bottom wall of the pocket ( 18 ); a first retaining member ( 25 ), which projects perpendicularly from the first conveyor belt ( 23 ) and forms a front wall of the pocket ( 18 ) in the direction of the packing path (P); and a second retaining member ( 26 ), which projects perpendicularly from the second conveyor belt and forms a rear wall of the pocket ( 18 ) in the direction of the packing path (P); and

wherein the length (L) of said pocket ( 18 ) is a distance between said first retaining member ( 25 ) and said second retaining member ( 26 ) in the direction of the packing path (P)

the packing unit ( 10 ) being characterized in that the feed device ( 19 ) comprises:

a first suction pickup head ( 21 ), which engages a first panel ( 11 ) of the blank ( 4 ) inside a store ( 20 );

a second suction pickup head ( 22 ), which engages a second panel ( 13 ) of the blank ( 4 ) inside the store ( 20 ); and

actuating devices ( 33 , 34 ) for moving the pickup heads ( 21 , 22 ) from a withdrawal position at the store ( 20 ) to a release position at the packing conveyor ( 17 ), to insert the blank ( 4 ) inside the pocket ( 18 ) on the packing conveyor ( 17 ), and then release the blank ( 4 ), folded into a ‘U’, inside the pocket ( 18 ) on the packing conveyor ( 17 );

wherein said length (L) is variable according to the format of said blank ( 4 ); and

wherein said actuating devices ( 33 , 34 ) alters the distance between said pickup heads ( 21 , 22 ) and said packing unit at said store ( 20 ) according to the format of said blank ( 4 ).

2. A packing unit ( 10 ) as claimed in claim 1 , wherein said packing conveyor ( 17 ) produces a relative movement between said first ( 23 ) and second ( 24 ) conveyor belts, to move said retaining members ( 25 , 26 ) of said pocket ( 18 ) towards or away from each other according to the format of said blank ( 4 ).

3. A packing unit ( 10 ) as claimed in claim 1 , wherein the packing conveyor ( 17 ) comprises a number of successive pockets ( 18 ), each bounded at the front by a corresponding first retaining member ( 25 ), and at the rear by a corresponding second retaining member ( 26 ); each first retaining member ( 25 ) only forms the front wall of a corresponding pocket ( 18 ); and each second retaining member ( 26 ) only defines the rear wall of a corresponding pocket ( 18 ); and

said pockets ( 18 ) being spaced apart by a spacing distance (S) defined by the distance between said second retaining member ( 26 ) of a pocket ( 18 ) and said first retaining member ( 25 ) of the upstream pocket ( 18 ) in the direction of the packing path (P).

4. A packing unit ( 10 ) as claimed in claim 1 , wherein the packing conveyor ( 17 ) comprises:

two first conveyor belts ( 23 ) having respective first retaining members ( 25 ); and

two second conveyor belts ( 24 ) having respective second retaining members ( 26 ) and alternating with the first conveyor belts ( 23 ).

5. A packing unit ( 10 ) as claimed in claim 4 , wherein said two first conveyor belts ( 23 ) and said two second conveyor belts ( 24 ) are positioned side by side and parallel, and alternate with one another.

6. A packing unit ( 10 ) as claimed in claim 1 , wherein:

the first conveyor belt ( 23 ) is looped about respective first end pulleys ( 27 , 28 );

the second conveyor belt is looped about respective second end pulleys ( 30 , 31 ) parallel to and alongside the first end pulleys ( 27 , 28 ); and

the first end pulleys ( 27 , 28 ) can be operated out of phase with respect to the second end pulleys ( 30 , 31 ) to adjust said length (L) of said pocket ( 18 ) according to the format of the blank ( 4 ).

7. A packing unit ( 10 ) as claimed in claim 6 , wherein the packing conveyor ( 17 ) comprises:

a first motor ( 29 ), which rotates a powered first end pulley ( 28 ); and

a second motor ( 32 ), which is separate from and independent of the first motor ( 29 ), and rotates a powered second end pulley ( 31 ).

8. A packing unit ( 10 ) as claimed in claim 6 , wherein the packing conveyor ( 17 ) comprises one motor ( 32 ), which rotates both a powered first end pulley ( 28 ) and a powered second end pulley ( 31 ).

9. A packing unit ( 10 ) as claimed in claim 8 , wherein at least one powered end pulley ( 28 ; 31 ) can be operated mechanically out of phase with respect to the drive shaft of the motor ( 32 ) to adjust said length (L) of the pocket ( 18 ) according to the format of the blank ( 4 ).

10. A packing unit ( 10 ) as claimed in claim 1 , wherein, as the pickup heads are moved from the withdrawal position to the release position, the actuating devices ( 33 , 34 ) produce a relative movement between the first pickup head ( 21 ) and the second pickup head ( 22 ) to fold the blank ( 4 ) into a ‘U’ before the blank ( 4 ) is inserted into the pocket ( 18 ) on the packing conveyor ( 17 ); and

as said pickup heads move from the withdrawal position to the release position, operation of said actuating devices ( 33 , 34 ) is adjustable to adjust the movements of said pickup heads ( 21 , 22 ) according co the format of said blank ( 4 ).