Knives for cutting packaging materials and vertical form-fill-seal packaging machines

Abstract

To provide a packaging material cutting knife capable of forming a smooth cut area in a packaging material hard to be drawn, and a vertical bag making, filling and packaging machine equipped with the knife.SOLUTION: A packaging material cutting knife 22 for sticking and cutting a packaging material W hard to be drawn comprises: a plate-shaped body 26; a blade 32 formed in the body; and blade slaves 34 formed into V shapes in a plan view and arranged side by side at a prescribed interval D in a width direction X of the blade. Each of the blade slaves is provided with a cutting blade 40 forming a V-shaped pointed end of the blade slave, a blade bottom 42 forming the V-shaped valley of the blade slave and positioned on both sides of the cutting blade in the width direction, a blade tip 44 forming V-shaped two sides of the blade slave and connecting the cutting blade and the blade bottom, a front blade 36 formed on a surface of the blade slave and extending along the blade tip from the blade tip to the blade bottom, and a back blade 38 formed on a backside of the blade slave and having a cutting blade, a blade bottom, and a blade tip similar to those of the front blade. The back blade inclines in a direction where a thickness t2 in a blade thickness direction Z of the front blade decreases.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a knife for cutting packaging material and a vertical form-fill-seal packaging machine equipped with the knife, and more particularly to a knife for cutting low-stretch packaging material and a vertical form-fill-seal packaging machine equipped with the knife. [Background technology]

[0002] Patent Document 1 discloses a cutting knife that is installed in a cutting device of a packaging machine and that thrusts and cuts cylindrically formed sheet material. This knife has a plate-shaped main body, a blade formed on the main body, and cutting blades arranged side by side at a predetermined interval in the width direction of the blade. The cutting blade is shaped like an isosceles triangle, in other words, V-shaped in a plan view, and has a cutting edge, a blade base, a cutting tip, a front blade, and a back blade.

[0003] The cutting edge forms the V-shaped pointed end of the blade. The base is located on both sides of the cutting edge in the width direction and forms the V-shaped valley of the blade. The cutting edge is a linear portion connecting the cutting edge and the base. The front edge is formed on the surface of the blade, includes the cutting edge, extends from the cutting edge to the base, and is inclined in a direction that reduces the blade thickness of the blade. The back edge is formed on the back surface of the blade, and has the same cutting edge, base, and cutting edge as the front edge.

[0004] The front and back blades formed on the knife described in Patent Document 1 have inclined surfaces of the same shape that are inclined in different directions when viewed from the center of the blade's thickness, and are formed symmetrically on the front and back with the same concave angle (see, for example, lines 17 to 20 on page 10 of the publication). As a result, the cross section of the blade in the blade thickness direction from the cutting edge to the base is diamond-shaped. When each blade pushes against the packaging material, diamond-shaped cut edges are formed in the packaging material, lined up in the width direction.

[0005] As the blades continue to thrust, the cut edge of the packaging material gradually becomes larger while forming a similar diamond shape. Then, as the blades continue to thrust, adjacent cut edges in the width direction connect, cutting the packaging material. That is, while the blades of the knife thrust at a portion of the packaging material equivalent to the area of ​​the cut edge (thrust process), the cutting edges of the knife cut the packaging material, gradually enlarging the cut edge (cut process). This cuts the packaging material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Utility Model Application Publication No. 1-176012 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, with the growing momentum for environmental awareness and resource conservation on a global scale, such as through the SDGs (Sustainable Development Goals), and the global social issue of marine pollution caused by discarded plastic, attention has been focused on packaging that reduces the environmental impact. As most conventional packaging materials are sheet-like films made primarily from petroleum-derived plastic, attempts are being made to reduce the amount of plastic used by switching to paper packaging made primarily from paper.

[0008] Because film packaging materials made from plastic materials are thin and flexible, they stretch appropriately during the pushing and pressing process, which, combined with the tearing and slitting process, results in smooth cut edges. On the other hand, paper packaging materials are sheets of entangled fibers, such as wood pulp, which are more difficult to stretch than film packaging materials. Therefore, the paper packaging material is not sufficiently stretched during the pushing and pressing process. This causes the paper packaging material to shred during pressing, resulting in fibers that remain uncut at the cut edges, making it impossible to obtain smooth cut edges.

[0009] The present invention has been made in consideration of these problems, and aims to provide a packaging material cutting knife that can form smooth cut edges in difficult-to-stretch packaging materials such as paper packaging materials, and a vertical form-fill-seal packaging machine equipped with such a knife. [Means for solving the problem]

[0010] In order to achieve the above object, one embodiment of a packaging cutting knife is a knife for cutting difficult-to-stretch packaging material by pushing it through, and comprises a plate-shaped main body, a blade portion formed on the main body, and cutting edges that are V-shaped in a plan view and are arranged in parallel at a predetermined interval in the width direction of the blade portion, the cutting edges comprising a cutting edge that forms the pointed end of the V-shape of the cutting edge, blade bases that are located on both sides in the width direction of the cutting edge and form the valleys of the V-shape of the cutting edge, cutting edges that connect the cutting edge and the blade base and form two sides of the V-shape of the cutting edge, a front blade that is formed on the surface of the blade and extends along the cutting edge from the cutting edge to the blade base, and a back blade that is formed on the back side of the blade and has the same cutting edge, blade base, and cutting edge as the front blade. A ridge line is formed at the boundary between the adjacent front blades in the width direction and extends from the cutting edge in the direction of extension of the blade, and a valley line is formed at the boundary between the adjacent back blades in the width direction and extends in the direction of extension. The back blade is The valley line is positioned opposite the ridge line in the blade thickness direction, so that it carves out the back side of the front blade. .

[0011] One embodiment of a vertical form-fill-seal packaging machine is equipped with the aforementioned packaging material cutting knife, and forms a difficult-to-stretch packaging material into a tubular shape around a bag-forming tube. As the formed tubular packaging material is unwound in the longitudinal direction of the bag-forming tube, horizontal seals are formed below the bag-forming tube at predetermined intervals in the longitudinal direction of the tubular packaging material, while alternately forming the horizontal seals and filling the tubular packaging material with a filling material. At the same time, the knife cuts the tubular packaging material at the horizontal seals to produce bags filled with the filling material. [Effects of the Invention]

[0012] It is possible to form smooth cut edges on packaging materials that are difficult to stretch. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view of a vertical form-fill-seal packaging machine according to an embodiment. FIG. [Figure 2] FIG. [Figure 3]FIG. [Figure 4] FIG. [Figure 5] FIG. 4 is a cross-sectional view taken along the line AA in FIG. 3. [Figure 6] FIG. 4 is a cross-sectional view taken along the arrow BB in FIG. 3. [Figure 7] FIG. 4 is a cross-sectional view taken along the arrow CC in FIG. 3. [Figure 8] As viewed from the direction in which each blade extends, (a) is a front view of each cutting edge, and (b) to (e) are stepwise cross-sectional views of each blade in the direction approaching the blade base. [Figure 9] These are images taken during the process of cutting a tubular packaging material with a knife: (a) the cut edge of the tubular packaging material as each blade pushes against the tubular packaging material; (b) the cut edge of the tubular packaging material as each blade continues to push against the tubular packaging material; and (c) the cut edge of the tubular packaging material as each blade cuts the tubular packaging material. [Figure 10] This is a front view of the bag, clearly showing the cut edges of the horizontal seals cut with a knife. [Figure 11] FIG. 10 is a diagram showing the fuzzing of fibers at the cut end of a conventional tubular packaging material. DETAILED DESCRIPTION OF THE INVENTION

[0014] FIG. 1 shows a perspective view of a vertical form-fill-seal packaging machine 1 according to an embodiment. This vertical form-fill-seal packaging machine (hereinafter simply referred to as packaging machine) 1 is equipped with a bag-forming tube 2, which extends vertically. The bag-forming tube 2 has a hopper 6 at its upper end, through which it receives a supply of filling material such as powder or granular material. A filling supply device (not shown) is also disposed above the packaging machine 1, and the filling supply device supplies a predetermined amount of filling material into the bag-forming tube 2 via the hopper 6.

[0015] A former 8 is attached above the bag-forming tube 2 and below the hopper 6, and a packaging material payout path extends from the former 8 to the packaging material reel 10. Packaging material W is paid out from the packaging material reel 10 via a plurality of rollers 12. The packaging material W is a difficult-to-stretch packaging material, such as a paper packaging material formed by laminating and bonding a sheet-like paper material used for the exterior of the bag P and a sheet-like heat-sealing material used for the interior of the bag P. The packaging material W paid out from the packaging material reel 10 is guided along the packaging material payout path and led to the outer periphery of the bag-forming tube 2 along the former 8.

[0016] The packaging material W guided along the former 8 is formed into a tubular shape that surrounds the bag-forming tube 2, and this tubular packaging material Wc is guided downward along the bag-forming tube 2. As it passes through the former 8, both side edges of the tubular packaging material Wc are overlapped with each other in a predetermined shape, for example, a lapped portion L, forming a seam. The packaging machine 1 is also equipped with a packaging material feeding device. The packaging material feeding device has a pair of packaging material feeders 14.

[0017] The packaging material feeders 14 are disposed below the formers 8 on both sides of the outer periphery of the bag-forming tube 2. Each packaging material feeder 14 has an endless suction belt 16, and the tubular packaging material Wc is attracted to the suction belts 14. In this attracted state, the suction belts 14 run in one direction, causing the tubular packaging material Wc to be fed downward along the bag-forming tube 2.

[0018] An openable and closable vertical sealer 18 is disposed near the bag-forming tube 2. The vertical sealer 18 is disposed between the pair of packaging material feeders 14 in the circumferential direction of the bag-forming tube 2, and heat-seals the wrap portion L of the tubular packaging material Wc, bonding both side edges together to form a vertically sealed portion Sv in the bag P. As a result, after passing through the vertical sealer 18, both side edges of the tubular packaging material Wc are completely closed.

[0019] An openable and closable horizontal sealer 20 is disposed below the bag-forming tube 2. The horizontal sealer 20 has a pair of heater blocks 20a, 20b. Each heater block 20a, 20b has a built-in heater. Each heater block 20a, 20b extends horizontally, which is the direction across the tubular packaging material Wc, and moves toward and away from each other in the radial direction of the bag-forming tube 2 within the horizontal plane. This allows the horizontal sealer 20 to open and close.

[0020] The heater blocks 20a, 20b sandwich the tubular packaging material Wc from the front and rear as the horizontal sealer 20 closes, thereby forming horizontal seals Sh in the tubular packaging material Wc. One of the heater blocks 20a, 20b, the heater block 20a, holds a knife 22 for cutting the packaging material. The other of the heater blocks 20a, 20b, the heater block 20b, has a blade receiving groove 24 formed in it to receive the knife 22. As the horizontal sealer 20 closes, the knife 22 slides horizontally toward the blade receiving groove 24, pushing and cutting the horizontal seals Sh.

[0021] The series of operations of the packaging machine 1 configured as described above is described below. The packaging machine 1 forms the packaging material W into a tubular shape around the bag-forming tube 2, and while the formed tubular packaging material Wc is fed in the longitudinal direction of the bag-forming tube 2, i.e., downward, the vertical sealer 18 forms vertical seals Sv. Next, below the bag-forming tube 2, the horizontal sealer 20 forms horizontal seals Sh at predetermined intervals in the longitudinal direction of the tubular packaging material Wc. Meanwhile, the formation of horizontal seals Sh and the filling of the tubular packaging material Wc are alternately performed. At the same time, the knife 22 cuts the tubular packaging material Wc at the horizontal seals Sh. This produces bags P filled with the filling material.

[0022] 2 shows a plan view of the knife 22. The knife 22 thrusts and cuts the tubular packaging material Wc at the horizontal seal portion Sh in the horizontal sealer 20. A plate-shaped main body 26 of the knife 22 is formed with a bolt insertion hole 28 for holding the knife 22 to the heater block 20a and two engagement notches 30. The main body 26 also has a cutting edge 32 formed therein.

[0023] A large number of blades 34 are arranged in the width direction X of the blade portion 32 at a predetermined interval D (for example, a 5 mm pitch). In other words, the width dimension of the blades 34 in the width direction X is the interval D. Each blade 34 is formed with two front blades 36. A back blade 38 (shown by a broken line) is formed on the back surface opposite each of the front blades 36 of each blade 34. The direction perpendicular to the width direction X of the blade portion 32 is defined as the extension direction Y of the blades 34.

[0024] 3 shows an enlarged view of the front blade 36. Each blade 34 has a cutting edge 40, a base 42, and a cutting edge 44. The cutting edge 40 forms the V-shaped tip of the blade 34. The bases 42 are located on both sides of the cutting edge 40 in the width direction X and form the valleys of the V-shape of the blade 34. The cutting edge 44 connects the cutting edge 40 and the base 42 and forms two sides of the V-shape of the blade 34. The front blade 36 extends along the cutting edge 44 from the cutting edge 40 toward the base 42.

[0025] More specifically, the front blade 36 has a rectangular inclined surface. A ridge line 46 is formed on the blade 34 at the boundary between adjacent front blades 36 in the width direction X. The ridge line 46 extends from the cutting edge 40 in the extension direction Y and has a base point 48 at the end opposite the cutting edge 40. The blade base 42 is located on the same line as the base point 48 in the width direction X, or on the cutting edge 40 side of the base point 48 in the extension direction Y. The ridge line 46 extends in the extension direction Y from the base point 48 on the surface of the blade 34 to the cutting edge 40. A first valley line 50 is formed on the surface of the blade 34 at the boundary between adjacent blades 34 in the width direction X.

[0026] 4 shows an enlarged view of the back blade 38. The back blade 38 is formed on the back surface of the cutting element 34, opposite the front blade 36, and has the same cutting edge 40, blade base 42, and cutting tip 44 as the front blade 36. More specifically, the back blade 38 has a triangular inclined surface. A second valley line 52 is formed at the boundary between adjacent back blades 38 in the width direction X on the back surface of the cutting element 34. The boundary between adjacent cutting elements 34 in the width direction X on the back surface of the cutting element 34 forms the apex of the triangle of the back blade 38, and the blade base 42 is located at this apex.

[0027] 5 to 7 are cross-sectional views taken along the lines AA, BB, and CC in Fig. 3, respectively. Fig. 5 shows a cross-section taken along the ridge line 46 of the cutting edge 34. Fig. 6 shows a cross-section at an angle inclined with respect to the extending direction Y at a portion of the cutting edge 34 where both the front cutting edge 36 and the back cutting edge 38 are present. Fig. 7 shows a cross-section taken along the first valley line 50 of the cutting edge 34.

[0028] As is clear from Figures 5 to 7, the front cutting edge 36 is inclined in a direction that reduces the thickness t1 of the cutting edge 34 in the blade thickness direction Z. On the other hand, as is clear from Figures 5 and 6, the back cutting edge 38 is formed so as to hollow out the back side of the front cutting edge 36 due to the presence of the second valley line 52, and is inclined in a direction that reduces the thickness t2 of the front cutting edge 36 in the blade thickness direction Z.

[0029] 8 shows (a) a front view of each blade 34, and (b) to (e) stepwise cross-sectional views of each blade 34 in a direction approaching the base 42, as viewed from the extension direction Y of each blade 34 (specifically, three blades). By reducing the thickness t2 of the front blade 36 in conjunction with the formation of the back blade 38, the area of ​​the cross section S in the blade thickness direction Z, from the cutting edge 40 to the base 42 of the blade 34, is significantly reduced compared to the case of a conventional diamond-shaped cross section S. Specifically, the cross section S is a concave quadrangle in all of the cross sections of FIGS. 8(a) to (e).

[0030] 9 shows captured images of (a) the cut edges 54 of the tubular packaging material Wc when each blade 34 pushes against the tubular packaging material Wc, (b) the cut edges 54 of the tubular packaging material Wc as each blade 34 continues to push, and (c) the cut edges 54 of the tubular packaging material Wc when each blade 34 cuts the tubular packaging material Wc during the process of cutting the tubular packaging material Wc with the knife 22. As each blade 34 pushes against the tubular packaging material Wc, recessed rectangular cut edges 54 are formed in the tubular packaging material Wc lined up in the width direction X, as shown in FIG. 9(a).

[0031] As the blades 34 continue to thrust, the cut edges 54 in the tubular packaging material Wc gradually become larger while taking on similar shapes to the concave square, as shown in Figure 9(b).Then, as the blades 34 continue to thrust, the cut edges 54 adjacent to each other in the width direction X join together, thereby cutting the tubular packaging material Wc, as shown in Figure 9(c).

[0032] That is, while the blades 34 of the knife 22 are thrusting against a portion of the tubular packaging material Wc equivalent to the area of ​​the cut edge 54 (thrust-pushing process), the blades 44 of the knife 22 are used to cut the tubular packaging material Wc, gradually increasing the size of the cut edge 54 of the tubular packaging material Wc (cutting process). The lower part of the cut edge 54 shown in Figure 9 has a shape that corresponds to the recessed part of the blades 34, which have a concave rectangular cross section. Therefore, when the blades 34 thrust against the tubular packaging material Wc in the thrust-pushing process, the tubular packaging material Wc is cut without the blades 34 exerting much pressure on the packaging material W below the cut edge 54.

[0033] Figure 10 shows a front view of the bag P, clearly showing the cut edges 54 of the horizontal seals Sh cut by the knife 22. The cut edges 54 in the tubular packaging material Wc at the horizontal seals Sh are formed at the top and bottom ends of the bag P. The cut edges 54 have a wavy pattern with peaks and valleys that follow the outer edges of the concave rectangular cross sections of each blade 34. Both the peaks and valleys of this wavy pattern are smooth, and as is clear from Figure 9(c), no uncut portions such as frayed fibers of the tubular packaging material Wc remain at the cut edges 54.

[0034] 11 shows fiber fluffing 56 that occurred at the cut edge 54 of the conventional tubular packaging material Wc. At the cut edge 54 of the conventional tubular packaging material Wc, fiber fluffing 56 of the tubular packaging material Wc occurs at the peaks of the corrugated peaks and the corners of the valleys. This is because the packaging material W is more difficult to stretch than film packaging, and in the conventional case where the cross section S of the blade 34 is diamond-shaped, the tubular packaging material Wc is not stretched sufficiently during the pushing process, causing the tubular packaging material Wc to be torn apart by pushing.

[0035] Specifically, as the thrusting process of knife 22 progresses, the portion of tubular packaging material Wc shown in Figure 11 where incision 54 will be formed (the upper end of bag P) is pushed into place by blade 34, and is pulled by blade 34 while being pulled downwards by blade 34. The tubular packaging material Wc, which is made from low-stretch packaging material W, is pulled by blade 34 to a point where the tensile strength of the packaging material W is exceeded before cutting is complete, and the tubular packaging material Wc is torn by blade 34, causing fuzz 56 at incision 54.

[0036] Such fluff 56 not only prevents the formation of a smooth cut edge 54, but also reduces the quality of the bag P by causing other objects to get caught on the fluff 56 when they come into contact with it, and by causing paper dust when the fluff 56 falls off.

[0037] As described above, in the packaging material cutting knife 22 of this embodiment, the thickness t2 of the front blade 36 is reduced by forming the back blade 38, so that the front blade 36 and the back blade 38 have inclined surfaces that are inclined in the same direction when viewed from the center of the thickness of the blade 34, and are formed asymmetrically with different cutting angles on the front and back sides. This reduces the area of ​​the cross section S in the blade thickness direction Z from the cutting edge 40 to the blade base 42 of the blade 34.

[0038] By reducing the area of ​​the cross section S of the blades 34, the tubular packaging material Wc is cut without each blade 34 pressing too hard against the packaging material W below the cut edge 54. In other words, because the area of ​​the cut edge 54 of the tubular packaging material Wc is smaller than before, the importance of the pushing and pushing process described above can be reduced. Therefore, when the tubular packaging material Wc is cut with the knife 22, the importance of the slicing process described above becomes relatively greater, and a smooth cut edge 54 can be formed in the tubular packaging material Wc.

[0039] Specifically, the cross section S in the blade thickness direction Z from the cutting edge 40 to the blade base 42 of the blade 34 is a concave rectangle. This allows the cut edge 54 of the tubular packaging material Wc to be formed into a wavy, peak-valley pattern without fuzz 56 that follows the outer edge of the concave rectangular cross section of each blade 34. The blade base 42 is located on the same line as the base point 48 of the ridgeline 46 in the width direction X, or is located closer to the cutting edge 40 than the base point 48 in the extension direction Y.

[0040] As a result, when the blade base 42 of the cutting edge 34 reaches the tubular packaging material Wc during the process of cutting the tubular packaging material Wc with the knife 22, the ridge line 46 is reliably positioned at the top of the peak of the cut edge 54 of the tubular packaging material Wc. Therefore, as shown in Figure 9(c), the cut edges 54 are connected, making it possible to maintain the cross section S as a concave rectangle until the tubular packaging material Wc is cut. This makes it possible to more reliably form smooth cut edges 54 in the tubular packaging material Wc.

[0041] Furthermore, the spacing D between the blades 34 arranged side by side in the width direction X of the blade portion 32 is preferably 5 mm. By arranging the blades 34 side by side at a spacing D that is shorter than conventional spacing, fuzzing 56 on the cut edge 54 can be prevented even more effectively.

[0042] This concludes the description of the embodiment, but the present invention is not limited to the above embodiment and various modifications can be made without departing from the spirit of the present invention. For example, knife 22 can cut hard-to-stretch packaging materials other than paper packaging materials, and can be used to cut packaging materials W of all shapes other than tubular packaging material Wc. Furthermore, if used to cut packaging material W, knife 22 may be used in packaging machines of packaging types other than the vertical form-fill-seal packaging machine 1 shown in the embodiment.

[0043] The knife 22 can also be used to cut packaging material W in devices other than packaging machines. The cross section S of the cutting edge 34 is not limited to a concave rectangle. Specifically, the thickness t2 of the blade 36 may be reduced in accordance with the formation of the back cutting edge 38. In other words, the front cutting edge 36 and the back cutting edge 38 may have inclined surfaces that are inclined in the same direction when viewed from the center of the thickness of the cutting edge 34, and may be formed asymmetrically on the front and back sides with different cutting angles.

[0044] As long as these conditions are met, the cross section S of the blade 34 can be changed to various shapes depending on the required shape of the cut edge 54 of the packaging material W. For example, the cross section S in the blade thickness direction Z from the cutting edge 40 to the blade base 42 of the blade 34 may have arc-shaped corners instead of a concave rectangle with acute corners.

[0045] Alternatively, the cross section S may be triangular with the blade base 42 positioned on the same line in the width direction X as the base point 48 of the ridge line 46, or on the cutting edge 40 side of the base point 48 in the extension direction Y. This reduces the area of ​​the cross section S of the cutting edge 34 compared to when the cross section S is at least diamond-shaped. Furthermore, because the cut edges 54 are connected, the cross section S can be maintained in a triangular shape until the tubular packaging material Wc is cut, and smooth cut edges 54 can be formed in the tubular packaging material Wc. [Explanation of symbols]

[0046] 1 Vertical form-fill-fill packaging machine 2. Bag-making tube 22 Knife 24 Blade receiving groove 26 Main Unit 32 Blade part 34 Blade 36 Front blade 38 Back Blade 40 cutting edge 42 Blade base 44 cutting edge 46 Ridgeline 48 base point D interval P bag S cross section Sh Horizontal seal part t2 thickness W packaging material Wc cylindrical packaging material X Width direction Y extension direction Z Blade thickness direction

Claims

1. A knife for cutting packaging material that pushes and cuts difficult-to-stretch packaging material, A plate-shaped main body; a blade portion formed on the body; cutting edges arranged side by side at predetermined intervals in the width direction of the blade portion and having a V-shape in a plan view; Equipped with The cutting tool is a cutting edge forming the V-shaped pointed end of the cutting tool; a blade base that is located on both sides of the cutting edge in the width direction and forms the V-shaped valley of the cutting edge; a cutting edge that connects the cutting edge and the blade base and forms two sides of the V-shape of the blade; a front edge formed on a surface of the cutting tool and extending from the cutting edge toward the base along the cutting edge; a back blade formed on the back surface of the cutting element and having the same cutting edge, blade base, and cutting edge as the front blade; a ridgeline formed at a boundary between the front blades adjacent in the width direction and extending from the cutting edge in the extending direction of the blade; a valley line formed at a boundary between the back blades adjacent in the width direction and extending in the extension direction; Equipped with The back blade is formed so as to gouge the back side of the front blade by arranging the valley line opposite the ridge line in the blade thickness direction.

2. 2. The packaging material cutting knife according to claim 1, wherein the front blade and the back blade have inclined surfaces that are inclined in the same direction when viewed from the center of thickness of the blade, and are formed asymmetrically with different cutting angles on the front and back sides.

3. 3. The packaging material cutting knife according to claim 2, wherein a cross section of the blade in the blade thickness direction from the cutting edge to the blade base is a concave quadrangle.

4. A base point that is an end of the ridgeline opposite to the cutting edge is provided. The packaging material cutting knife according to claim 1 , wherein the blade base is located on the same line as the base point in the width direction or on a side of the cutting edge relative to the base point in the extension direction.

5. The packaging material cutting knife according to claim 1 , wherein the spacing between the cutting edges arranged in parallel in the width direction of the blade portion is 5 mm.

6. 6. The packaging material cutting knife according to claim 1, wherein the front blade has a rectangular inclined surface, and the back blade has a triangular inclined surface.

7. A vertical form-fill-seal packaging machine equipped with the packaging material cutting knife according to any one of claims 1 to 6, A vertical form-fill-seal packaging machine that forms the packaging material into a tubular shape around a bag-forming tube, and while the formed tubular packaging material is fed out in the longitudinal direction of the bag-forming tube, forms horizontal seals below the bag-forming tube at specified intervals in the longitudinal direction of the tubular packaging material, alternately forms the horizontal seals and fills the tubular packaging material with a filling material, and simultaneously cuts the tubular packaging material at the horizontal seals with the knife to produce bags filled with the filling material.

Images