JP3026679B2 - Heat seal roll - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sealing roll for heat-sealing a packaging film having a hot-melt resin layer, and more particularly to a heat-sealing roll suitable for use as a horizontal sealing roll in an automatic filling bag making machine. Even if the traveling speed of the packaging film is 10 m / min or more, the packaging film can always be properly heat-sealed over the entire width of the heat-sealing blade, and the thickness of the hot-melt resin layer of the packaging film can be reduced. Even if it is effectively reduced, it is possible to provide sufficient heat sealing strength.

[0002]

2. Description of the Related Art Known horizontal sealing rolls widely used in automatic filling and bag making machines are arranged parallel to each other and rotated in opposite directions to each other, as shown in a vertical sectional view in FIG. A pair of driven rolls r, a heater h built in each of the rolls r, and each of the rolls r are provided so as to protrude radially outward, and extend in the axial direction of the roll r. And a heat seal blade s having a surface formed in an arc shape in a circumferential direction, wherein the heat seal blade s formed integrally with or separately from the roll r is a solid having a substantially constant width as a whole. Consists of a structure.

[0003] The horizontal seal roll 1 constructed as described above
For example, a packing film f folded in two in the width direction and subjected to a vertical seal in advance, together with the filling of the object to be packaged between the films, a horizontal seal with a predetermined interval in the length direction. It works to give

The imaginary line in the figure shows the relative positional relationship between the packaging film f and the heat seal blade s when one horizontal seal is applied.

[0005]

By the way, such a horizontal seal roll has a traveling speed of the packaging film f of 10 m / min.
If less than, the film f for packaging can be sufficiently heat-sealed over the entire width of the heat-sealing blade s based on the melting of the hot-melt resin, but the film traveling speed is 10 m In the case of a high speed of / min or more, the heat sealing blade s is, in particular, a film portion that comes into contact with each of the rotation direction front and rear portions due to lack of heat in the respective portions. However, there is a problem that heat seal failure occurs.

This will be described in detail with reference to a plan view shown in FIG. 4, for example. A package which is folded in half from a substantially central portion in the width direction and has a vertical seal v applied to a free end portion in advance. When applying the horizontal seal 1 at a predetermined interval in the length direction of the film f, preferably the horizontal seal portion l
The heat seal blade s has a uniform width corresponding to the width of the heat seal blade s over its entire length, and in the figure, a uniform width sandwiched by imaginary lines. Due to the lack of heat in the portion, the horizontal sealing portion l has a shape in which the central portion in the length direction is constricted as shown by hatching in the figure, and becomes a heat sealing portion having insufficient sealing strength.

On the other hand, in order to solve such a problem, it is only necessary to apply sufficient heat sealing to the film portion in contact with each of the front and rear portions in the rotational direction of the heat seal blade s. In this case, there is a problem that the amount of heat in the central portion in the circumferential direction of the heat seal blade s becomes excessive.

That is, when a horizontal seal is applied to the packaging film f by the heat seal blade s, the film portion that comes into contact with the widthwise center portion of the heat seal blade s receives the supply of heat from the heat seal blade s. In addition to the above, since the heat-melting resin layer comes into contact with the heat-seal blade first, the heat-melted resin layer is also supplied with heat from the heat-melted resin layer. The heat-melted resin layer is sufficiently melted without having to receive a large amount of heat from the s. However, in the conventional heat-seal blade s having a solid structure, the front side portion and the rear side in the rotation direction are used. Assuming that the temperature of the portion is high enough to cope with high-speed running of the packaging film f,
The temperature of the central portion in the circumferential direction of the heat seal blade s rises to be equal to or higher than that of the front portion and the rear portion in the rotational direction. There is a problem that the molten resin layer is excessively melted.

In other words, when the hot-melt resin layer is uniformly and properly melted in the entire contact portion of the packaging film f with the heat seal blade s, the resin is filled between the packaging films. Wrapped items, such as liquids,
Based on the pressing force of the film by the heat sealing blade s, the film is gradually pushed upward in FIG. 3 under the action of the hot-melt resin layer having an appropriate viscosity, and the liquid remaining between the films is completely prevented. In other words, the packaging film f
If the amount of heat supplied to the heat-melting resin layer is too large, in addition to the melting depth of the hot-melting resin layer becoming too deep, the melt viscosity of the hot-melting resin layer becomes too low, so that the liquid filled between the packaging films can be reduced. Due to the action of the molten resin layer, it is impossible to completely remove the resin. As a result, as shown in FIG. Mixed and remaining packaging film f
Will hinder heat sealing.

In addition, since the residual liquid w expands as steam during heat sealing, it is relatively easy to visually recognize from the outside. By the time, the residual liquid w has already cooled down and returned to the liquid state, and it is extremely difficult to visually recognize the residual liquid w from the outside. Therefore, it is practically impossible to detect a heat seal failure in the inspection process. .

Further, the heat seal blade s of the prior art is
It has a constant radius of curvature over its entire width, and the thickness of the heat-melted resin layer g in the heat-sealed portion is substantially uniform over the entire width of the heat-sealed portion. The thickness of the hot-melt resin layer g is selected for the purpose of setting the heat seal strength, which increases in proportion to the thickness, to a required value, and therefore, in the portion of the packaging film that is not heat-sealed, In addition to a problem in terms of material yield that the thickness of the hot-melt resin layer far exceeds the required thickness, there was also a problem in terms of excessive packaging. An object of the present invention is to provide a heat seal roll that solves all of the problems of the prior art.

[0012]

SUMMARY OF THE INVENTION A heat seal roll according to the present invention has a heat seal blade itself, particularly on a side surface on the rotation direction front side of a heat seal blade formed integrally with or separately from the roll. A different material having a higher thermal conductivity is attached, for example, in close contact with the roll surface, and a hollow portion having a lower thermal conductivity than the heat seal blade itself is provided inside the circumferential center portion of the heat seal blade. , A heat-insulating material-filled portion, etc., and at least the surface of the heat-sealing blade provided on one of the rolls has the same radius of curvature on both the front side and the rear side in the rotational direction. The radius of curvature at the center in the circumferential direction of the blade surface is somewhat larger than the radius of curvature of the other portions.

[0013]

In this heat seal roll, a different material having a high thermal conductivity, such as copper or aluminum, attached to the side surface on the front side in the rotation direction of the heat seal blade is used for heat sealing from the roll having a built-in heater. It transmits more than the blade itself, which heats the heat seal blade's front portion in the rotational direction, and thus its surface, to a higher temperature than the other surfaces of the heat seal blade.

Therefore, the traveling speed of the packaging film is 10 m /
Even if the contact time between the heat sealing blade and the packaging film is shortened by setting the high speed of min or more, the surface part on the front side in the rotation direction of the heat sealing blade will be sufficient from the beginning of contact with the packaging film. The heat-melting resin layer of the packaging film can be melted to the required depth by supplying a sufficient amount of heat. It will be heat sealed.

On the other hand, the surface temperature of the central portion in the circumferential direction of the heat sealing blade, in other words, the surface temperature of the central portion in the width direction is reduced by, for example, a decrease in thermal conductivity due to the hollow portion, and the end of the heat sealing blade on the front side in the rotation direction. It does not become as hot as the surface of the part, so the amount of heat supplied to the packaging film from the surface part at the center in the width direction is effectively reduced, and the overmelting of the hot-melt resin layer is effective. Will be prevented.

In other words, the film portion which comes into contact with the surface of the central portion in the width direction of the heat seal blade receives an appropriate total amount of heat supplied from each of the heat seal blade and the already melted portion of the packaging film. Therefore, the hot-melt resin layer in the film portion can completely remove the filling liquid under the molten state, and can provide excellent heat-sealing strength.

According to this heat seal roll,
The end surface on the rear side in the rotation direction of the heat seal blade is lower than the end surface on the front side in the rotation direction under the heat conductivity inherent to the heat seal blade itself, and is lower than the surface temperature of the central portion in the circumferential direction. Heated to a high temperature, the film portion in contact with the end surface on the rear side in the rotation direction receives a relatively large amount of total heat supply from each of the heat sealing blade and the melted film portion. Will be. Therefore, a part of the heat supplied to the hot-melt resin layer for the packaging film is absorbed by the filling liquid inscribed in the hot-melt resin layer, and the remaining portion of the heat is supplied to the high-speed running packaging film. The hot melt resin layer can be melted to an extent sufficient to provide proper heat sealing.

Further, in this heat seal roll, the radius of curvature of the surface of the heat seal blade provided on at least one of the rolls is adjusted at the central portion in the circumferential direction to the front end portion in the rotation direction and the rear end portion having the same radius of curvature. By making them larger than those at the side end portions, the heat pressing force of the film in the circumferential central portion is particularly increased during heat sealing, and thereby, a part of the molten resin in the molten state is moved forward in the rotation direction of the heat sealing blade. And displacing the part and the rear part respectively.

According to this, at the heat seal portion displaced farthest from the packaging space defined by the heat seal, that is, at the portion heat sealed by the center portion in the circumferential direction of the heat seal blade, the heat melting resin layer While the total thickness is thinner than that of the packaging film, the heat seal blade is heat-sealed by the front and rear portions in the rotational direction of the heat seal blade, and the total heat is displaced adjacent to the packaging space. The thickness is much larger than the total thickness of the hot-melt resin layer of the packaging film.

Therefore, according to such a configuration of the heat sealing blade, that is, the horizontal sealing blade, the thickness of the hot-melt resin layer of the packaging film itself is determined by taking into account only the proper packaging proper excluding the heat sealing strength. In addition, the heat-sealed part located adjacent to the packaging space can secure a total thickness sufficient to provide the required heat-sealing strength. And the problem of over-packaging can be completely eliminated.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention for two heat seal rolls. here,
Two rolls 1 extend in parallel with each other, and each of the rolls 1 driven to rotate in opposite directions has a built-in heater 2 as a heat source. The heat seal blades 3 are integrally formed with or protrude outward and extend in the length direction. The heat seal blades 3 are separately formed in the figure, and the outer surface of each heat seal blade 3 is formed in an arc shape in the circumferential direction. I do. In addition, in this example, the base of the heat seal blade 3 which is configured separately forms a part of the roll 1.

Each of the heat seal blades 3 shown in FIG. 3 provided with three rolls at equal intervals in the circumferential direction for one roll 1
Based on the synchronized rotational movement of the two rolls 1, in cooperation with another heat-seal blade 3 opposed thereto at an appropriate interval, the length of the packaging film, which has been subjected to a vertical seal, is added. At intervals in the direction, heat sealing in the width direction thereof, that is, horizontal sealing is performed to make the packaging film a continuous packaging bag in the length direction.

In the illustrated example, on each of the heat sealing blades 3, a different material 4 having a higher thermal conductivity than the heat sealing blade itself, for example, copper, aluminum, or any of them, Is tightly attached, and preferably, the dissimilar material 4 is brought into close contact with the surface of the roll 1. In the illustrated example, the radially inner peripheral surface of the dissimilar material 4 is adhered only to the roll surface formed by the base of the heat sealing blade 3.
Of course, it is possible to extend the contact surface to the base beyond the base of the heat seal blade 3, and according to this, it is
Accordingly, a larger amount of heat can be transmitted from the roll surface to the side surface of the heat seal blade 3.

By the way, the attachment of the dissimilar material 4 to the heat seal blade 3 and the roll 1 can also be performed by brazing with a material having high thermal conductivity, for example, silver braze. , Dissimilar material 4,
In order to interpose an air layer acting as a heat insulating layer between the roll 1 and the heat sealing blade 3, a dissimilar material 4 having a brazing material previously adhered to the entire joint surface is completely applied to them under pressure and heat. It is preferable to join them.

The dissimilar material 4 functions to transmit a larger amount of heat from the roll 1 to the rotation-side front side surface of the heat seal blade 3 in the heat sealing operation than the heat seal blade itself. As a result, the surface temperature of the front portion of the heat seal blade 3 in the rotation direction becomes higher than the surface temperature of the other portions, so that the heat seal blade 3, especially the front end portion in the rotation direction, runs at high speed. Immediately upon contact with the packaging film, the hot-melt resin layer is melted to a sufficient depth to provide a proper and strong heat seal at the contact start end between the heat sealing blade 3 and the packaging film.

Here, a portion having a lower thermal conductivity than the heat seal blade itself, for example, a heat insulating material filled portion, a hollow portion as shown in the drawing, is provided inside the central portion in the circumferential direction of each heat seal blade 3. A portion 5 is provided to reduce the amount of heat transfer from the roll side to the heat seal blade side. Note that, here, the circumferential length of the hollow portion 5 is preferably １ ／ to ／ of the circumferential length of the heat seal blade 3.

According to this, from the heater 2 to the roll 1
The heat transmitted to each heat seal blade 3 via the heat seal blade 3 is hindered by the hollow portion 5 at the circumferential central portion of the heat seal blade 3, and as a result, the heat during the heat seal operation is The surface temperature of the seal blade 3 is lowest at the center in the circumferential direction. By the way, when the heat seal blade 3 having a circumference of 15 mm is made of S45C steel and the length of the hollow portion 5 in the circumferential direction is 7.5 mm,
When performing heat sealing to a packaging film traveling at 12 m / min, when the temperature of the end surfaces on the front side and the rear side in the rotation direction of the heat sealing blade 3 is 165 ° C. and 170 ° C., respectively, The surface temperature at the center was stabilized at 155 ° C.

Therefore, according to the heat seal blade 3,
From the respective end surfaces on the front side and the rear side in the rotation direction thereof, a sufficient and sufficient amount of heat can be supplied to the packaging film as needed, while the surface of the central portion in the circumferential direction of the heat seal blade 3 is provided. Can supply only the insufficient amount of heat in consideration of the amount of heat transfer in the packaging film,
For this reason, it is possible to effectively prevent overheating of the film portion in contact with the surface of the central portion in the circumferential direction of the heat seal blade 3.

Further, in the illustrated example, in each heat seal blade 3 provided on each roll 1, the radius of curvature R of the central portion surface 6 in the circumferential direction is changed to the front portion surface 7 and the rear portion surface 8 in the rotation direction. Radius of curvature R of
_Make it larger than ₀ . Here, the difference between the respective radii of curvature and the respective partial surfaces 7,
The circumferential length of 8 can be appropriately selected in relation to the heat sealing strength required for the packaging bag.

In this example, all the heat seal blades 3 provided on each roll 1 are provided with a difference in the radius of curvature. However, three heat seal blades 3 provided on one roll 1 are provided. And the heat sealing blades 3 which cooperate with each other
Can be alternately provided in the circumferential direction.

According to such a heat-sealing blade, when heat-sealing the packaging film thereby, the central part surface 6 which is located farthest from the defined packaging space is melted of the packaging film. The hot melted resin layer is particularly strongly pressed, whereby a part of the resin layer is moved to the respective partial surface sides on the front side and the rear side in the rotation direction. For this reason, in the portion adjacent to the packaging space, which is heat-sealed by each of the front side surface 7 and the rear side surface 8 in the rotational direction, the total thickness of the hot-melt resin layer is reduced by the inherent heat of the packaging film. The thickness can be made sufficiently large with respect to the total thickness of the molten resin layer, and the expected heat seal strength can be obtained. On the other hand, the total thickness of the hot-melt resin layer at a portion that is heat-sealed by the central portion surface 6 and does not significantly affect the heat-sealing strength of the packaging bag is smaller than the total thickness of the hot-melt resin layer of the packaging film itself. Become.

FIG. 2 is a cross-sectional view of a packaging bag illustrating this. For example, a packaging film 11 is formed by a base film layer 12 made of a biaxially-rolled nylon film having a thickness of 15 μm.
And a laminate of a heat-melt resin layer 13 of a total thickness of 40 μm made of polyethylene and EVA, the total of the heat-melt resin layer 13 in the heat seal portion 15 located far from the packaging space 14 By setting the thickness to 60 μ under the action of the central portion surface 6 of the heat sealing blade 3, the heat sealing portion 16 located adjacent to the packaging space 14 has a thickness of 60 μm.
For example, the total thickness of the hot-melt resin layer 13 can be set to 120 μ by the action of the front partial surface 7 in the rotation direction.

The cross-sectional view shown in FIG. 2 shows that each of the packaging bags which are heat-sealed by the horizontal sealing rolls and which are continuous in the vertical direction are sealed by the heat-sealing portion 15 which is sealed by the central portion surface 6 of the heat-sealing blade 3. FIG. 5 is a vertical cross-sectional view showing a state of being cut and separated at a central position.
Therefore, the packaging space of the packaging bag adjacent to the right side of the figure is
The heat-seal blade 3 is defined by a heat-seal portion by the rear surface 8 in the rotation direction.

[0034]

As described above, according to the heat seal roll configured as described above, the heat seal blade is rotated on the front side in the rotation direction of the heat seal blade based on the action of the different material having a high thermal conductivity attached to the heat seal blade. By sufficiently increasing the temperature of the part, the heat-melting resin layer of the packaging film is sufficiently melted as soon as the heat-sealing blade comes into contact with the packaging film running at a speed exceeding 10 m / min. Heat sealing can be applied.

Further, by the action of the portion having a low thermal conductivity provided inside the central portion in the circumferential direction of the heat seal blade,
By effectively suppressing the temperature rise of the central portion surface, it is possible to prevent over-melting of the hot-melt resin layer and to almost completely prevent the packaged material from remaining in the heat-sealed portion,
Heat sealing strength can be further increased.

Further, according to the heat seal roll,
The heat seal blade adjacent to the packaging space is provided by making a necessary difference between the radius of curvature of the heat seal blade at the front and rear portions in the rotation direction and the radius of curvature of the heat seal blade at the center in the circumferential direction. The total thickness of the hot melt resin layer in the part, regardless of the thickness of the hot melt resin layer of the packaging film itself, can be made sufficiently thick to provide the expected heat seal strength, and therefore In addition, the material yield of the hot-melt resin layer can be sufficiently improved, and the problem of excessive packaging can be effectively eliminated.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention for two pairs of heat seal rolls.

FIG. 2 is a vertical cross-sectional view of a main part showing a state in which respective packaging bags that are continuous in the vertical direction are cut and separated at a central portion of a heat sealing portion.

FIG. 3 is a longitudinal sectional view showing a conventional horizontal seal roll.

FIG. 4 is a plan view illustrating a heat sealing portion using a conventional horizontal sealing roll.

FIG. 5 is a vertical cross-sectional view illustrating a state in which an article to be packaged remains in a heat seal portion.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Roll 2 Heater 3 Heat seal blade 4 Dissimilar material 5 Hollow part 6 Central part surface 7 Front part surface 8 Back part surface R, _R0 Curvature radius

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 65/02-65/78 B65B 51/10-51/32

Claims (1)

(57) [Claims] 1. A pair of two rolls arranged close to each other and driven to rotate in opposite directions to each other, a heater built in each roll, and provided on each roll and projecting outward in the radial direction. And a heat-sealing roll extending in the axial direction and having an arcuate surface in the circumferential direction. Attach a different material with high conductivity and heat seal blade inside the circumferential center,
A portion having a lower heat conductivity than the heat seal blade itself is provided, and the surfaces of the heat seal blade provided on at least one of the rolls have the same radius of curvature for both the rotational front portion and the rotational rear portion. In addition, a heat seal roll in which the radius of curvature of the central portion in the circumferential direction of the surface of the heat seal blade is slightly larger than the radius of curvature.