Machine for manufacturing flat bottom bags

Abstract

A machine for manufacturing flat bottom bags includes a drum for carrying along at least one blank having a flattened tubular shape in an advancing direction, a first scoring apparatus upstream of the drum for marking on the blank a first folding line which is transverse with respect to the advancing direction, a front gripper on the drum that grips a front edge of the blank on the drum, in an opening step, and and carries along the blank, a first lateral gripping means on the drum that grip the lateral edges of the blank in the region of the first folding line.

Claims

1. A system for making flat bottom bags comprising: a blank of flattened tubular form; a machine that engages the blank, the machine comprising: a rotating drum to drive the blank of flattened tubular form in a direction of advance, wherein the rotating drum comprises: a first element carrying a front pincher that pinches a front edge of the blank on the drum, in an opening stage, and drives the blank; and a second element carrying a first lateral pincher that pinches lateral edges of the blank at the first fold line, wherein the second element is pivotally mounted in relation to the first element around a rotational axis of the rotating drum; and a first scoring apparatus upstream of the rotating drum that marks on the blank a first fold line transverse to a direction of advance; a first adjusting apparatus that introduces an offset into a drive movement between the first element and the second element to adjust, during production, while the rotating drum is rotating and the blank is being processed by the machine, both a distance between the front edge and the first fold line and a relative angular position of the front pincher and the first lateral pincher, wherein the first adjusting apparatus comprises a reduction gear allowing an angular offset to be introduced between a first drive of the first element and a second drive of the second element, wherein the reduction gear comprises: a first planetary gear wheel having a first rotation axis and meshing with a first satellite; and a second planetary gear wheel having a second rotation axis and meshing with a second satellite, wherein the first rotation axis is identical to the second rotation axis and the first satellite and the second satellite are attached to a satellite rotation shaft; a first reduction ratio of the first wheel and the first satellite is different than a second reduction ratio of the second wheel and the second satellite; the satellite rotation shaft is rotatably mounted on a satellite holder, which is pivotally mounted around the first rotation; the first planetary gear receives movement from a motor, and the second planetary gear transmits the movement to one of the first drum element and the second drum element; wherein modification of a position of the satellite holder introduces an offset into the movement between the first element and the second element and the first element and the second element are angularly offset even when the drum is rotating.

2. The system according to claim 1, wherein the first scoring apparatus marks a second fold line on the blank at a distance from the first fold line, the machine further comprising a second adjusting apparatus that adjusts in operation a distance between the first and the second fold line.

3. The system according to claim 2, the machine further comprising a second scoring apparatus that marks, after the opening stage, a third fold line on the blank, wherein the second adjusting apparatus adjusts a distance between the first fold line and the third fold line so that the second fold line will be at mid-distance between the first fold line and the third fold line.

4. The system according to claim 3, wherein the second scoring apparatus marks a fourth fold line at an identical location on the blank as the first fold line.

5. The system according to claim 1, the machine further comprising a second scoring apparatus that marks, after the opening stage, a third fold line on the blank, wherein the second adjusting apparatus adjusts a distance between the first fold line and the third fold line so that the second fold line will be at mid-distance between the first fold line and the third fold line, wherein the second scoring apparatus comprises a first die on a third element of the drum to mark the third fold line, the third element being pivotally mounted in relation to the second element around the rotational axis of the drum, the second adjusting apparatus determining a relative angular position between the second and the third element.

6. The system according to claim 4, wherein the second scoring apparatus comprises a first die on a third element of the drum to mark the third fold line, the third element being pivotally mounted in relation to the second element around the rotational axis of the drum, the second adjusting apparatus determining a relative angular position between the second element and the third element and the second scoring apparatus comprises a second die on the second element to mark the fourth fold line.

7. The machine according to claim 2, wherein the first scoring apparatus includes a first marker roller and a counter roller, which are counter rotative, and with rotational axes parallel to that of the drum and placed on either side of a path for the blanks, the first marker roller comprising a first blade and a second blade extending parallel to the rotational axis to respectively mark the first and the second fold line by pinching between the blade and the counter roller, the angular difference between the blades being adjustable by the second adjusting apparatus.

8. The machine according to claim 7, wherein the counter roller comprises a first and a second indent on a periphery, the indents extending parallel to the rotational axis of the counter roller, the relative angular position of the indents being adjusted by the second adjusting apparatus so that the blades score fold lines by pushing the blank against the respective indent.

9. The system according to claim 1, the machine further comprising an opening roller to open the blank, the opening roller being placed opposite the drum downstream of the first scoring apparatus, the opening roller being rotative around an axis parallel to that of the drum in an opposite direction, the opening roller comprising a sucker to suck and move away an upper skin of the blank on an outer side of the drum near to the front edge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of an installation for making flat bottom bags according to the invention;

(2) FIG. 2 is a schematic view of a machine for making flat bottom bags in compliance with the invention;

(3) FIG. 3 is a kinematic diagram of the elements of the machine of FIG. 2;

(4) FIG. 4 is a cross-sectional view of the first scoring means;

(5) FIG. 5 is a schematic view of a reduction gear used for the adjustment means;

(6) FIGS. 6 to 11 are perspective views of the bag blank at different manufacturing stages.

DETAILED DESCRIPTION

(7) An installation for making flat bottom bags comprises in a classical manner a feed roller 1 of a reel B of film such as paper, a take-up device 2 to store a strip of unwound film, an envelope forming machine 3, a cutting device 4 and a machine 5 for forming flat bottom bags 6. A stacking device, not shown, can also be provided to receive the bags produced and form stacks. The envelope forming machine 3 folds the strip to join and glue the two edges together. At outlet, the envelope has two skins 61, 62 connected together along two opposite edges by two bellows 63. The cutting machine 4 makes a transverse cut of the envelope to form blanks 6a with a constant transverse section, therefore of tubular form, as shown on FIG. 6. The blank 6a is presented with the bellows 63 folded between the two skins 61, 62 thus with a flattened form. In a conventional manner, it is considered that one of the skins 61 is the lower skin and the other the upper skin 62. The blank is identified below by reference 6 completed by a letter to distinguish between the various bag 6 manufacturing stages.

(8) The machine 5 forming bags 6 comprises a drum 50 rotationally mounted around a drum transverse axis A and on the periphery of which the blank 6a is gripped and submitted to the transformations detailed below. The blank follows a path in the machine which in part follows the periphery of the drum 50 in a so-called direction of advance.

(9) The machine 5 first comprises in the direction of the path first scoring means 51 upstream of the drum 50. The first scoring means 51 comprise a first marker roller 510 and a counter-roller 511 which are counter-rotative with rotational axes C, D parallel to the axis of the drum 50 and placed on either side of the path of the blanks 6a. The first marker roller 510 comprising a first blade 5101 and a second blade 5102 extending parallel to the rotational axis C to respectively mark a first and a second fold line on the blank 6b by pinching between the blade 5101, 5102 and the counter-roller 511. As shown on the detail of FIG. 4, the first marker roller 510 comprises a centre shaft 5103 inserted into a partially open tube 5104. The centre shaft 5103 carries the first blade 5101 whereas the tube carries the second blade 5102. The first blade 5101 protrudes from the periphery of the tube passing via the open part of the tube 5104. The tube 5104 is pivotally mounted on the centre shaft 5103 in such a way that the angular difference between the blades 5101, 5102 is adjustable, in a manner detailed below. The counter-roller 511 also comprises a centre shaft and a partially open tube which respectively carry a first indent 5111 and a second indent 5112 extending parallel to the rotational axis of the counter-roller 511. The first indent 5111 is carried by a quadrant which is flush with the periphery of the tube and which protrudes into the open part of the tube. The first blade 5101 in cooperation with the first indent 5111 allow the first fold line 64 transverse in relation to the direction of advance to be marked on the blank at a predetermined distance from the front edge 68 of the blank 6b, whereas the second blade 5102 in cooperation with the second indent 5112 allow a second fold line 65, parallel to the first fold line 64, to be marked on the blank 6b at a distance from the front edge 68 higher than the first fold line 64, as shown on FIG. 7.

(10) The drum 50 is formed by three elements 501, 502, 503, each pivoting in relation to the other. Each element is driven by a shaft with drum axis 50 as axis. Each element also comprises four regularly spaced branches in order to form four stations for the transformation of the blank as shown on FIG. 2. Thus, on reach rotation of the drum 50, four bags 6 are formed, one per station.

(11) Each station comprises front pinching means 52 carried by the first element 501 of the drum 50 to pinch a front edge 68 of the blank on the drum 50, in an opening stage, and drive the blank. The second element 502 of the drum 50 carries first lateral pinching means 53 to pinch the lateral edges of the blank 6b at the first fold line 64.

(12) The machine 5 comprises an opening roller 54 to open the blank 6b. It is placed opposite the drum 50 downstream of the first scoring means 51, tangent to the path followed by the blank 6b. The opening roller 54 rotates around an axis E parallel to that of the drum 50 in an opposite direction. The opening roller 54 comprises at least one sucker 540 to suck and move away the upper skin 62 of the blank 6b on outer side of the drum 50 near to the front edge 68. The opening roller 54 is driven by a specific motor 542 with a variable speed during a given rotation. The opening roller 54 also comprises second lateral pinching means 541 substantially on the same generatrix as the sucker 540 to grip the lateral edges of the blank and to tension the blank between the first and second lateral pinching means 53, 541. The pinching means 52, 53, 541 are controlled to grip and release the blank 6c at positions detailed below.

(13) The machine 5 also comprises spatulas 55 which are placed in a fixed manner, on the periphery of the drum 50, tangent to the drum 50, oriented in a pinching direction in the movement of the drum 50. The second element 502 has a table 5020 of semi-cylindrical form adjusted to the periphery of the drum 50, the table 5020 being drilled with suction holes connected to a suction line, not shown. A distributor controls the communication between the holes and the line to cut the suction when the bag must leave the drum 50.

(14) The machine 5 also comprises second scoring means 56 to mark, after the opening stage, a third and a fourth fold line 66, 67 on the blank 6. The third fold line 66 is placed symmetrical to the first fold line 64 in relation to the second fold line 65. The fourth fold line 67 passes via the same location as the first fold line 64 in order to mark the parts of the blank which have been pressed down over the first fold line 64. The second scoring means 56 comprise a second marker roller 560 of same composition as the first marker roller 510 and comprising a third and fourth blade 5603, 5604 carried respectively by a shaft 5601 and a tube 5602. The second scoring means 56 also comprise a first die 561 on the third element 503 of the drum 50 to mark the third fold line 66 in cooperation with the third blade 5603 and a second die 562 on the second element 502 of the drum 50 to mark the fourth fold line 67 in cooperation with the fourth blade 5604. The second die 562 comprises tightening means, not shown, to pinch the blank along the fourth fold line 67.

(15) The machine 5 also comprises downstream of the second marker roller 560 an adhesive application station 57 and two press down stations 58 which will not be detailed here.

(16) In order to do an adjustment in operation of certain bag characteristics, the machine 5 comprises first adjustment means 7 and second adjustment means 8. The first adjustment means 7 are provided to adjust in operation both the distance between the front edge 68 and the first fold line 64 and the relative angular position on the drum 50 of front pinching means 52 and lateral pinching means 53. The second adjustment means 8 are provided to adjust also in operation the distance between the first and the third fold line 65, 66 so that the second fold line 65 will be at mid-distance between the first and the third fold line 64, 66.

(17) In detail, the first adjustment means 7 determine the relative angular position between the first and the second element 501, 502. For this, a drum motor 505 drives a main shaft 506, which is connected to the second element 502 by a first set 91 of pulleys and a notched belt. The first element 501 is driven by the main shaft 506 by means of a first reduction gear 71 belonging to the first adjustment means 71.

(18) By referring to FIG. 5, which shows in a schematic and general manner the composition of the first reduction gear 71, it can be seen that the reduction gear comprises two planetary gear wheels 711, 712 with same rotational axis, each wheel 711, 712 meshing with a satellite 713, 714, the satellites being attached to the same rotation shaft 715. The reduction ratios between one and the other of the wheel/satellite pairs are different. The shaft 715 of the satellites is rotationally mounted on a satellite holder 716, which is pivotally mounted around the same rotational axis as the planetary gears 711, 712. If:

(19) Z1 is the number of teeth of the first planetary gear 711;

(20) Z2 is the number of teeth of the secondary planetary gear 712;

(21) Za is the number of teeth of the satellite or satellites 713 of the first planetary gear 711;

(22) Zb is the number of teeth of the satellite or satellites 714 of the second planetary gear 712;

(23) and

(24) $=\frac{Z_1.Math.Z_b}{Z_2.Math.Z_a},$

(25) then, when the satellite holder 716 is stationary, .sub.2=..sub.1, where 2 and 2 are the rotational speeds of the first and second planetary gear 711, 712 respectively. When the first planetary gear 711 is stopped, the rotation of the satellite holder 716 drives the rotation of the second planetary gear 712 according to the following relation:
.sub.2=(1)..sub.ps

(26) where .sub.ps is the rotational speed of the satellite holder 716. In this relation, it can be seen that an angular offset between the elements driven respectively by the first and second planetary gear 711, 712 can be obtained by turning the satellite holder 716. This angular offset is produced, even if the drum is rotating.

(27) In the setup of the first reduction gear 71, the first planetary gear 711 is directly driven by the main shaft 506, the second planetary gear 712 is connected to the first element 501 by means of a second set 92 of two pulleys and a notched belt. The satellite holder 716 is connected to a control knob 72 which can be operated manually to determine the relative angular position between the first and the second element 502. The various transmission ratios between the main shaft 506 and the second element 502, and that of the first reduction gear 71 and of the second set 92 of pulleys and belt are chosen so that the first element 501 and the second element 502 rotate at the same speed.

(28) So that the second adjustment means 8 can adjust in operation the distance between the first and the second fold line 64, 65, they in particular determine the relative angular position between the second and the third element 502, 503. For this, a third set 93 of pulleys connects the main shaft 506 to the first planetary gear of a second reduction gear 82 similar to the first reduction gear 71. The second planetary gear is connected by a fourth set 94 of pulleys and belt to a shaft 5030 of the third element 503. The various transmission ratios are also chosen so that the third element 503 is driven at the same speed as the first and the second element 502. The satellite holder of the second reduction gear 82 is normally stationary, but it can be pivoted to introduce an angular offset between the main shaft 506 and the shaft 5030 of the third element 503. It is connected to a second control knob 85 which can be operated manually.

(29) The second adjustment means 8 in addition allow the angular difference to be adjusted between the blades 5101, 5102 of the first marker roller 510 of the first scoring means 51 and thus the angular difference between the first and the second indent 5111, 5112 of the counter roller 511. For this, the centre shaft 5103 of the first marker roller 510 is connected to the centre shaft 5113 of the counter roller 511 by a first pair of gears in such a way that the roller and the counter roller 511 are counter rotative and always synchronised in such a way that the first blade 5101 and the second indent 5111 coincide during the rotation. Also, the tube 5104 of the first marker roller 510 is connected to the tube 5114 of the counter roller 511 by a second pair of gears 513 in such a way that the second blade 5102 and the second indent 5112 coincide during the rotation. In addition, a third reduction gear 83, similar to the first reduction gear 71, connects the centre shaft 5103 and the tube 5104 of the first marker roller 510. The centre shaft 5103 is connected by a fifth set 95 of pulleys and belt to the first planetary gear of the third reduction gear 83, whereas the tube 5104 is connected by a sixth set 96 of pulleys and belt to the second planetary gear of the third reduction gear 83. The satellite holder of the third reduction gear 830 is controlled by the second control knob. The transmission ratios of the third reduction gear 83, of the fifth and of the sixth set 95, 96 of pulleys and belt are chosen so that when the satellite holder is stationary, the centre shaft 5103 and the tube 5104 of the first marker roller 510 rotate at the same speed. The pivoting of the satellite holder of the third reduction gear 83 induces an angular offset between the centre shafts 5103, 5113 and the tubes 5104, 5114 of the first marker roller 510 and of the counter roller 511. The centre shaft 5103 is driven by a first scoring motor 515.

(30) The second adjustment means 8 also allow the angular difference between the blades 5603, 5604 of the second scoring means 56 to be adjusted. For this, a fourth reduction gear 84, similar to the first reduction gear 71, connects the centre shaft 5601 and the tube 5602 of the second marker roller 560. The centre shaft 5601 is connected by a seventh set 97 of pulleys and belt to the first planetary gear of the fourth reduction gear 84, whereas the tube 5602 is connected by an eighth set 98 of pulleys and belt to the second planetary gear of the fourth reduction gear 84. The satellite holder of the fourth reduction gear 84 is controlled by the second control knob. The transmission ratios of the fourth reduction gear 84, of the seventh and eighth set 97, 98 of pulleys and belt are chosen so that when the satellite holder is stationary, the shaft 5601 and the tube 5602 of the second marker roller 560 rotate at the same speed. The pivoting of the satellite holder of the fourth reduction gear 84 induces an angular offset between the shaft and the tube of the second marker roller 560. The centre shaft 5601 is driven by a second scoring motor 563.

Operation

(31) During the operation of the machine 5 for making flat bottom bags, the main motor 505 drives the drum 50 at a constant speed, except during transitory phases. The first and the second scoring means 51, 56 and the opening roller 54 are rotationally driven by their own respective motors 515, 563, but in a synchronised speed and position manner in relation to the drum 50. The synchronisation is done for example electronically. The marker rollers 510, 560 and the opening roller 54 rotate in the opposite direction to the drum 50, whereas the counter roller 511 rotates in the same direction.

(32) The blank 6a, from the cutting device arrives between the first marker roller 510 and the counter roller 511. The first scoring means 51 make a first fold line 64 and a second fold line 65 at a predetermined distance from the first fold line 64, in a direction perpendicular to the bellows 63, as shown by the blank 6b represented on FIG. 7. By progressing, the front of the blank 6b passes between the drum 50 and the opening roller 54. The lower skin 61 of the blank is sucked against the table 5020 of the second element 502 whilst the upper skin 62 is sucked by the sucker 540 of the opening roller 54. When the upper skin 62 is separated from the lower skin 61, the front pinching means 52 pinch the front edge 68 of the lower skin 61 against the table 5020 to maintain the blank 6b on the drum 50 and drive it. When the opening of the bellows 63 is sufficient, the first lateral pinching means 53 pinch the lateral edge of the blank at the junction between the bellows 63 and the lower skin 61 in the alignment of the first fold line 64. Symmetrically, the second lateral pinching means 541 pinch the lateral edge of the blank at the junction between the bellows and the upper skin 62 in the alignment of the first fold line 64. When the blank 6a continues its passage between the roller and the drum 50, the lateral pinching means 541, 53 move away from each other, open the blank 6c and form a fold on the bellows 63, as shown on FIGS. 8 and 9. The second lateral pinching means 541 then release the blank 6c whereas, in the remainder of the movement of the drum 50 which drives the blank 6c, spatulas 55 press down the part thus opened towards the centre and the rear. The upper skin 62 is folded towards the rear at the second fold line 65, as shown by the blank 6d on FIG. 10.

(33) Concerning the operations, the second scoring means 56 mark on the blank 6d a third and a fourth transverse fold line 66, 67 on either side of the second fold line 65. The fourth fold line 67 coincides with the first fold line 64. Then, adhesive is applied to the two flaps 60, 69 delimited by these fold lines 66, 67 at the adhesive application station 57. A rear flap 69, beyond the third fold line 66 is pressed down towards the front. The front pinching means 52 release the front flap 60 so that it is pressed down around the fourth fold line 67 onto the rear flap 69 at the press down stations 58 to close the flat bottom and thus form the bag 6, as shown on FIG. 11.

(34) When the format of the bags to be produced is to be changed, the first adjustment means 7 can be acted upon to modify the position of the front pinching means 52 in relation to the second element 502, by rotating the first knob, and therefore the satellite holder of the first reduction gear 71. At the same time, in an automatic manner or manual manner, the relative angular position of the first scoring means 51 can be acted upon to adjust the distance between the front edge 68 of the blank 6a and the first fold line 64 which determines the length of the front flap 60.

(35) The second adjustment means 8 can also be acted upon to adjust the distance between the first fold line 64 and the third fold line 66, which determines the width of the flat bottom, by acting on the second scoring means 56. Acting on the second knob, causes the rotation of the satellite holder of the second, of the third and of the fourth reduction gear 82, 83, 84, and therefore the relative angular offset between the second and the third element 502, 503, between the first and the second blade 5101, 5102 of the first marker roller 510 and between the first and the second indent 5111, 5112 of the counter roller 511, and between the third and the fourth blade 5603, 5604 of the second marker roller 560. The position of the second fold line 65 which must be found at mid-distance from the first and the third fold line 64, 66 is also moved by acting on the first scoring means 51.

(36) The invention is not limited to the embodiment described above as an example. The offset between the rotationally driven elements can be introduced by other means, such as the axial offset of a helical-toothed sprocket.