Bag making and packaging machine

1. A bag making and packaging machine comprising:

a conveying unit configured and arranged to continuously convey a tubular packaging material;

a transverse sealing mechanism having a pair of sealing jaws configured and arranged to revolvingly move while following annular loci to seal the tubular packaging material in a transverse direction with respect to a conveyance direction of the tubular packaging material, the transverse sealing mechanism further having shutter members configured and arranged to touch the tubular packaging material before the sealing jaws touch the tubular packaging material to prevent entry of contents from above into a space inside a transverse sealing target portion of the tubular packaging material at which the tubular packaging material is sealed by the sealing jaws immediately after the shutter members touch the tubular packaging material;

a gusset forming mechanism having a pair of folding members configured and arranged to be pressed against side portions of the tubular packaging material to form gussets in the side portions of the tubular packaging material while the folding members move along the conveyance direction of the tubular packaging material before the transverse sealing mechanism seals the tubular packaging material, the gusset forming mechanism being configured and arranged to annularly move each of the folding members and parts supporting each of the folding members, the gusset forming mechanism further being configured and arranged to revolvingly move each of the folding members so as to match a conveyance speed of the tubular packaging material while revolvingly moving them along the conveyance direction on the tubular packaging material continuously conveyed when forming the gussets, lower ends of the folding members are positioned lower than the shutter members when the shutter members have reached the first state; and

a control unit configured to control operations of the transverse sealing mechanism and the gusset forming mechanism, the control unit being configured to control the operation of the transverse sealing mechanism and the operation of the gusset forming mechanism so that the gussets are formed in the side portions of the tubular packaging material by the folding members before the shutter members reach a first state where the shutter members prevent entry of the contents from above into the space inside the transverse sealing target portion of the tubular packaging material.

2. The bag making and packaging machine according to claim 1 , wherein

the gusset forming mechanism is configured and arranged to move the folding members along circular trajectories.

3. The bag making and packaging machine according to claim 1 , wherein

when the folding members are contacting the tubular packaging material, the gusset forming mechanism is configured and arranged to move the folding members at a speed that is substantially equal to or slightly faster than a conveyance speed of the tubular packaging material.

4. The bag making and packaging machine according to claim 1 , wherein

the gusset forming mechanism further has a servo motor configured and arranged to drive the folding members, and the gusset forming mechanism is configured and arranged to vary an angular velocity of the servo motor between when the folding members are contacting the tubular packaging material and when the folding members are not contacting the tubular packaging material.

5. The bag making and packaging machine according to claim 1 , wherein

the gusset forming mechanism is configured and arranged to move the folding members away from the tubular packaging material when the sealing jaws seal the tubular packaging material in the transverse sealing mechanism.

6. The bag making and packaging machine according to claim 1 , wherein

the folding members include thin plate-shaped members.

7. The bag making and packaging machine according to claim 1 , wherein

the transverse sealing mechanism further has a pair of stripper members configured and arranged to touch the tubular packaging material at substantially the same time as or after the shutter members touch the tubular packaging material, and before the sealing jaws touch the tubular packaging material, and to move along the conveyance direction of the tubular packaging material at a faster speed than a conveyance speed of the tubular packaging material before the sealing jaws seal the tubular packaging material, and

the control unit is configured to control the operation of the transverse sealing mechanism and the operation of the gusset forming mechanism so as to maintain a state where the folding members that press against and have formed the gussets in the side portions of the tubular packaging material are contacting the tubular packaging material at least until the stripper members reach a state where they sandwich the tubular packaging material in a state where the stripper members are closest to each other.

8. The bag making and packaging machine according to claim 7 , wherein

at least a part of one of the stripper members is recessed away from the other one of the stripper members at a portion corresponding to a central portion between the side portions of the tubular packaging material than portions that press against the side portions and the vicinity thereof of the tubular packaging material in which the gussets are formed.

9. The bag making and packaging machine according to claim 1 , wherein

the folding members are configured and arranged to revolvingly move while following annular loci separate from those of the sealing jaws, and

the control unit is configured to set revolving speeds of the folding members after the shutter members have reached the first state to zero or a value smaller than the revolving speed of the folding members when the folding members are forming the gussets in the side portions of the tubular packaging material.

10. The bag making and packaging machine according to claim 1 , wherein

the lower ends of the folding members and the sealing jaws become as close to each other as 10 mm or less when the shutter members have reached the first state.

11. The bag making and packaging machine according to claim 1 , wherein

the shutter members have a pair of body portions that are rigid bodies and a pair of auxiliary portions that are elastic bodies, and

in the first state, the body portions sandwich the tubular packaging material including the side portions of the tubular packaging material that the folding members are touching in a state where there is a clearance between the body portions that is larger than a thickness dimension of the folding members while the auxiliary portions sandwich the tubular packaging material so as to press against the folding members.

12. The bag making and packaging machine according to claim 1 , wherein

the control unit is configured to lower the conveyance speed of the tubular packaging material via the conveying unit around a point in time when the folding members contact the tubular packaging material.

13. The bag making and packaging machine according to claim 12 , wherein

the transverse sealing mechanism further has a pair of stripper members configured and arranged to touch the tubular packaging material at substantially the same time as or after the shutter members touch the tubular packaging material, and before the sealing jaws touch the tubular packaging material, and to move along the conveyance direction of the tubular packaging material at a faster speed than a conveyance speed of the tubular packaging material before the sealing jaws seal the tubular packaging material.

14. The bag making and packaging machine according to claim 13 , wherein

the control unit is configured to set a speed of the sealing jaws along the conveyance direction of the tubular packaging material slower than the conveyance speed of the tubular packaging material when the sealing jaws seal the tubular packaging material.

15. The bag making and packaging machine according to claim 1 , wherein

the folding members have

first surfaces configured and arranged to press against the side portions of the tubular packaging material,

second surfaces disposed adjacent to the first surfaces and diagonally oppose the tubular packaging material immediately before the sealing jaws start sealing the tubular packaging material, and

air blowout ports formed in the first surfaces and in the second surfaces, with air being blown out from the air blowout ports when the folding members form the gussets in the side portions of the tubular packaging material.

16. The bag making and packaging machine according to claim 15 , wherein

the folding members further have heaters fixed onto surfaces on opposite sides of the first surfaces to heat the folding members.

17. The bag making and packaging machine according to claim 1 , wherein

the folding members have

first surfaces configured and arranged to press against the side portions of the tubular packaging material,

second surfaces disposed adjacent to the first surfaces and diagonally oppose the tubular packaging material immediately before the sealing jaws start sealing the tubular packaging material, and

heaters fixed onto surfaces on opposite sides of the first surfaces to heat the folding members.

18. The bag making and packaging machine according to claim 1 , wherein

each of the pair of folding members including a plate-like member having a first surface, each of the first surfaces being straight, the folding members being configured and arranged such that the first surfaces are pressed against side portions of the tubular packaging material to form gussets in the side portions of the tubular packaging material while the folding members move along the conveyance direction of the tubular packaging material before the transverse sealing mechanism seals the tubular packaging material.