LONGITUDINAL SEALING MECHANISM

Abstract

A longitudinal sealing mechanism is adapted to seal an overlapped portion of a packaging material formed into a tubular shape with the overlapped portion extending along a conveying direction of the packaging material. The longitudinal sealing mechanism includes a contact section, a heating section and a receiving member. The contact section comes into contact with the overlapped portion of the packaging material. The heating section heats the contact section to perform longitudinal sealing of the overlapped portion to form a longitudinal seal portion. The receiving member abuts against the contact section with the overlapped portion of the packaging material being disposed therebetween. The contact section, the heating section, and the receiving member are arranged such that an amount of heat per unit time applied to the packaging material from the contact section decreases in a direction toward both sides of the longitudinal seal portion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This national phase application claims priority to Japanese Patent Application No. 2006-280335 filed on Oct. 13, 2006. The entire disclosure of Japanese Patent Application No. 2006-280335 are hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a longitudinal sealing mechanism mounted on a bag manufacturing and packaging apparatus and configured to seal an overlapped portion of a packaging material formed in a tubular shape while the packaging material is being conveyed.

BACKGROUND ART

In recent years, there has been provided a bag manufacturing and packaging apparatus as a device for bag manufacturing and packaging, which manufactures bags and fills the inside of these bags with articles to be packaged such as snack foods. For example, with a longitudinal bag manufacturing and packaging apparatus called a pillow packaging apparatus, a packaging material that is a sheet-like film is formed into a tubular shape by a former and a tube, and overlapped longitudinal ends of the tubular packaging material are thermally sealed (thermal welding) to be made into a tubular packaging material by a longitudinal sealing mechanism. Then, the articles to be packaged are filled from the tube into the tubular packaging material which ultimately becomes a bag. Thereafter, a portion across a top end portion of the bag and a bottom end portion of the next following bag are thermally sealed by a transverse sealing mechanism disposed blow the tube, and then the center of the thermal seal portion (transverse seal portion) is cut by a cutter.

With this type of longitudinal sealing mechanism mounted on the bag manufacturing and packaging apparatus described as above, a sheet-like packaging material is wrapped around the tube to form the packaging material into a tubular shape. Then, an overlapped portion of the tubular packaging material is thermally sealed by causing a heated heater belt to come into contact with the overlapped portion and applying heat and pressure thereto. At this time, as a counterpart of the heater belt to sandwich the overlapped portion of the packaging material therebetween, the tube that forms the tubular packaging material is provided with a pad (receiving member) on the surface facing the heater belt.

For example, Japanese Patent Application Publication No. 2000-72104 A (published on Mar. 7, 2000) discloses a longitudinal sealing device including a heat generating protrusion provided at a heater block and a pair of guide rails provided at an outer surface of a filling tube, in which an overlapped portion of a packing material, i.e., a seal portion, is resiliently deformed by the heat generating protrusion and the guide rails and supported at three points, and heat is applied intensively to the overlapped portion from the heat generating protrusion in order to heat seal the overlapped portion.

DISCLOSURE OF THE INVENTION

However, the above described conventional longitudinal sealing mechanism has the following problems.

Specifically, with the longitudinal sealing mechanism disclosed in the above publication, because a relatively large amount of heat is applied also to the surrounding area of the seal portion, there is a risk that not only the seal portion but also its surrounding becomes contracted, generating wrinkles.

An object of the present invention is to provide a longitudinal sealing mechanism capable of reducing generation of wrinkles, sealing failure, and the like at a surrounding area of a longitudinal seal portion.

A longitudinal sealing mechanism according to a first aspect of the present invention is a longitudinal sealing mechanism adapted to seal an overlapped portion of a packaging material formed into a tubular shape with the overlapped portion extending along a conveying direction of the packaging material. The longitudinal sealing mechanism includes a contact section, a heating section, and a receiving member. The contact section is configured and arranged to come into contact with the overlapped portion of the packaging material. The heating section is configured and arranged to heat the contact section to perform longitudinal sealing of the overlapped portion to form a longitudinal seal portion. The receiving member is configured and arranged to abut against the contact section with the overlapped portion of the packaging material being disposed therebetween while the longitudinally sealing of the overlapped portion. Further, the contact section, the heating section, and the receiving member are configured and arranged such that an amount of heat per unit time applied to the packaging material from the contact section decreases in the direction toward the both sides of the longitudinal seal portion in the direction perpendicular to the conveying direction of the packaging material.

Here, in the longitudinal sealing mechanism which forms a longitudinal seal portion at the overlapped portion in order to manufacture a bag, the contact section, the heating section, and the receiving member which form the longitudinal seal portion are configured and arranged so that the amount of heat applied to the packaging material from the contact section decreases in the direction toward the both sides of the longitudinal seal portion in the width direction. Specifically, in order to prevent excess heat from being applied to the peripheral area of the longitudinal seal portion, for example, a temperature gradient is created in which the temperature decreases in the direction toward the both sides of the contact section in the width direction.

Note that the both sides of the longitudinal seal portion in the direction crossing the conveying direction of the above described packaging material refer to both end portions of the longitudinal seal portion in the width direction.

Typically, with this type of conventional longitudinal sealing mechanism, the width of the contact section that comes into direct contact with the packaging material is set larger than the width of the longitudinal seal portion such that the longitudinal seal portion can be formed even when the packaging material is displaced to the left or right during conveyance. Consequently, with the conventional longitudinal sealing mechanism, the both sides of the longitudinal seal portion in the width direction are subjected to the same amount of heat as the longitudinal seal portion is and become contracted. This has been a factor in generating wrinkles and sealing failure.

With the longitudinal sealing mechanism of the present invention, the contact section, the heating section, and the receiving member are configured such that the heat will not be applied more than necessary to the surrounding area of the longitudinal seal portion when the heat is applied from the contact section to the packaging material.

Accordingly, the amount of heat applied to portions other than the longitudinally sealed portion of the packaging material can be reduced compared to the conventional mechanism, and the necessary amount of heat can be applied only to the longitudinal seal portion of the packaging material. As a result, it is possible to prevent the both sides of the longitudinal seal portion from being excessively heated, and thus generation of problems such as wrinkles, sealing failure, and the like along the longitudinal seal portion can be prevented.

A longitudinal sealing mechanism according to a second aspect of the present invention is the longitudinal sealing mechanism according to the first aspect of the present invention, wherein the heating section and the receiving member each have a width substantially equal to a width of the longitudinal seal portion formed on the packaging material. Further, the contact section has a width larger than the width of the longitudinal seal portion.

Here, the widths of the heating section and the receiving member are made equal to the width of the longitudinal seal portion, and the width of the contact section is made larger than the width of the longitudinal seal portion.

Accordingly, a large amount of heat necessary for longitudinal sealing is applied to the area of the contact section where the width is equal to the width of the heating section. At the same time, the amount of heat is gradually reduced toward the areas on both sides of the aforementioned area. As a result, the temperature can be reduced toward the both sides of the contact section that comes into contact with the packaging material, and thus it is possible to prevent generation of wrinkles and sealing failure at the surrounding area of the longitudinal seal portion.

A longitudinal sealing mechanism according to a third aspect of the present invention is the longitudinal sealing mechanism according to the first aspect of the present invention, wherein the receiving member has a width substantially equal to the width of the longitudinal seal portion.

Here, the width of the receiving member is formed according to the width of the longitudinal seal portion.

Accordingly, even when the width of the contact section is larger than the width of the longitudinal seal portion, only the longitudinal seal portion is sandwiched between the contact section and the receiving member and the heat is applied thereto. Consequently, an outer side of the longitudinal seal portion is prevented from being directly subjected to a large amount of heat, and thus generation of wrinkles, sealing failure, and the like along the longitudinal seal portion can be prevented.

A longitudinal sealing mechanism according to a fourth aspect of the present invention is the longitudinal sealing mechanism according to the first aspect of the present invention, wherein the receiving member has a convex contact surface configured and arranged to face the overlapped portion of the packaging material so that both sides of the receiving member in a width direction are spaced apart from the contact section.

Here, the receiving member that sandwiches the packaging material against the contact section and forms the longitudinal seal portion is configured such that a contact surface that contacts the packaging material is formed in a curved shape such that only the longitudinal seal portion is sandwiched between the contact section and the receiving member.

Accordingly, it is possible to reduce the amount of heat applied to the both sides of the longitudinal seal portion from the contact section, and the heat can be applied mainly to the longitudinal seal portion. As a result, it is possible to prevent excess supply of heat to the surrounding of the longitudinal seal portion and generation of wrinkles and sealing failure.

A longitudinal sealing mechanism according to a fifth aspect of the present invention is the longitudinal sealing mechanism according to the first aspect of the present invention, wherein the contact section has a convex surface configured and arranged to face the overlapped portion of the packaging material so that the packaging material is spaced apart from the contact section at an area on an outer side of a contact portion of the contact section that contacts the longitudinal seal portion.

Here, the contact section that sandwiches the packaging material against the receiving member so as to form the longitudinal seal portion has the curved surface whose distance from the packaging material increases toward the both side in the width direction.

Accordingly, the both sides of the longitudinal seal portion of the packaging material are prevented from being directly sandwiched between the contact section and the receiving member. As a result, it is possible to prevent excess supply of heat to the surrounding of the longitudinal seal portion and generation of wrinkles and sealing failure.

A longitudinal sealing mechanism according to a sixth aspect of the present invention is the longitudinal sealing mechanism according to any one of the first through fifth aspects of the present invention, wherein the heating section has a generally T-shape cross sectional shape in a plane perpendicular to the conveying direction of the packaging material with a side corresponding to a horizontal line of the T-shape being disposed adjacently to the contact section.

Here, the contact section is heated by using the heating section whose cross sectional shape is generally T-shaped. Further, the contact section is heated by the projection-side surface (the side corresponding to the horizontal line) of the generally T-shape.

Accordingly, in the projecting portion of the generally T-shaped heating section, because the heat becomes more easily diffused in the both end portions than in the center portion, it is possible to create a temperature gradient inclined in the direction toward the both sides. As a result, it is possible to reduce the amount of heat applied to the both sides of the longitudinal seal portion and prevent generation of wrinkles, sealing failure and the like along both sides of the longitudinal seal portion.

A longitudinal sealing mechanism according to a seventh aspect of the present invention is the longitudinal sealing mechanism according to any one of the first through sixth aspects of the present invention, wherein the contact section has a rotational belt structure that rotates around the heating section.

Accordingly, it is possible to prevent an excess amount of heat from being applied to the surrounding of the longitudinal seal portion from the rotational belt structure, and thus generation of problems such as wrinkles, sealing failure, and the like along the longitudinal seal portion can be prevented.

A longitudinal sealing mechanism according to an eighth aspect of the present invention is the longitudinal sealing mechanism according to any one of the first through sixth aspects of the present invention, wherein the contact section is integrally formed with the heating section to form a heater block member.

Accordingly, it is possible to prevent an excess amount of heat from being applied to the surrounding of the longitudinal seal portion from the heater block member, and thus problems such as generation of wrinkles, sealing failure, and the like along the longitudinal seal portion can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a bag manufacturing and packaging apparatus equipped with a longitudinal sealing mechanism according to an embodiment of the present invention.

FIG. 2 is an enlarged view showing the longitudinal sealing mechanism included in the bag manufacturing and packaging apparatus in FIG. 1.

FIG. 3 is a cross sectional view taken along an arrow A-A in FIG. 2.

FIG. 4 is a lateral view showing the longitudinal sealing mechanism in FIG. 2.

FIG. 5 is an elevational view showing the longitudinal sealing mechanism in FIG. 2.

FIG. 6 is an elevation view showing the shape of a pulley included in the longitudinal sealing mechanism in FIG. 2.

FIG. 7 is a schematic view showing a transverse sealing mechanism included in the bag manufacturing and packaging apparatus in FIG. 1.

FIG. 8 is a graph showing an example of a widthwise temperature distribution of a heater belt included in the longitudinal sealing mechanism in FIG. 2.

FIG. 9 is a cross sectional view showing a configuration of a longitudinal sealing mechanism according to another embodiment of the present invention.

FIGS. 10(a) and 10(b) are cross sectional views showing the cross sectional shape of a receiving member included in a longitudinal sealing mechanism according to yet another embodiment of the present invention.

FIG. 11 is a cross sectional view showing the cross sectional shapes of a heater belt and a heater block included in a longitudinal sealing mechanism according to yet another embodiment of the present invention.

FIG. 12 is a cross sectional view showing the cross sectional shapes of a heater belt and a heater block included in a longitudinal sealing mechanism according to yet another embodiment of the present invention.

FIG. 13 is a cross sectional view showing the cross sectional shape of a heater block member included in a longitudinal sealing mechanism according to yet another embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A bag manufacturing and packaging apparatus 1 equipped with a longitudinal sealing mechanism 15 according to an embodiment of the present invention is described with reference to FIGS. 1 through 8.

Overall Structure of Bag Manufacturing and Packaging Apparatus 1

As shown in FIG. 1, the bag manufacturing and packaging apparatus 1 according to an embodiment of the present invention is an apparatus that encloses articles C (here, potato chips) such as potato chips in a thermoplastic film (packaging material) F, and manufactures a bag by transversely and longitudinally sealing the film F made into a tubular shape.

In this embodiment, the bag manufacturing and packaging apparatus 1 is configured and arranged to receive potato chips of a predetermined amount that is discharged from a weighing device and the like disposed above the bag manufacturing and packaging apparatus 1.

The bag manufacturing and packaging apparatus 1 includes a bag manufacturing unit 10, a control unit 20, and a film roll holder (not shown).

Film Roll Holder

The film roll holder holds a film roll from which a sheet-like film F is unwound and sent to a former 13a of the later described bag manufacturing unit 10. The film roll is formed by winding the long film F. The tension of the film F unwound from this film roll is maintained in a predetermined range by a dancer roller or the like in order to prevent loosening and meandering during conveyance.

In addition, a film remaining amount detection sensor (not shown) that detects the remaining amount of the film F wound around the film roll is disposed in the vicinity of the film roll holder.

Bag Manufacturing Unit 10

As shown in FIG. 1, the bag manufacturing unit 10 includes: a forming mechanism 13 that forms the sheet-like film F sent from the film roll holder into a tubular shape; a pull-down belt mechanism 14 that conveys the tube-like film F (hereinafter referred to as “tubular film”) downward; the longitudinal sealing mechanism 15 that longitudinally seals an overlapped portion of the tubular film; and a transverse sealing mechanism 17 that transversely seals the tubular film and thereby seals the upper and lower ends of a bag B.

Forming Mechanism 13

The forming mechanism 13 includes a tube 13b, the former 13a, and a surface fastener (receiving member) 13c. Note that, here, the surface fastener 13c is described as a part of the forming mechanism 13, however, it can be regarded as a part of the later described longitudinal sealing mechanism 15.

The tube 13b is a cylindrical shaped member whose upper and lower ends are open. The potato chips C weighed by the weighing device are fed into the opening at the upper end of the tube 13b. In addition, the tube 13b includes the surface fastener 13c on the surface facing a heater belt 16a of the later described longitudinal sealing mechanism 15. Further, an overlapped portion F2 (see FIG. 3) of the film F is sandwiched between the surface fastener 13c and the heater belt 16a, and the overlapped portion F2 is thereby sealed.

The former 13a is disposed so as to surround the tube 13b. The shape of the former 13a is formed such that the sheet-like film F unwound and sent from the film roll is formed into a tubular shape when passing through the former 13a and the tube 13b.

In addition, the tube 13b and the former 13a of the forming mechanism 13 can be replaced according to the size of the bags to be manufactured.

As shown in FIGS. 3 through 5, the surface fastener 13c is detachably and replaceably attached to a flat portion of the surface of the tube 13b, in which the flat portion faces the heater belt 16a of the longitudinal sealing mechanism 15. The surface fastener 13c is disposed in a prescribed position so that heat and pressure is applied to the overlapped portion of the film between the surface fastener 13c and the heater belt 16a and the overlapped portion is sealed. Note that, in view of improvement of sealing performance, as the surface fastener 13c, it is preferable to use a small member such as VELCRO (registered trademark), MAGIC TAPE (registered trademark), or the like, for example, which has elasticity in the direction of contact with the film F and whose contact surface has small frictional resistance. In addition, as shown in FIG. 3, the surface fastener 13c has a width d1 substantially equal to a width d (see FIG. 2) of a longitudinal seal portion F1 of the film F in the plane view, and forms the longitudinal seal portion F1 within this width. Accordingly, when the longitudinal seal portion F1 is formed on the film F, the sealing process is performed by sandwiching an overlapped portion F2 of the film F between the surface fastener 13c having a width substantially equal to the width d of the longitudinal seal portion F1 and the heater belt 16a. Thereby, even when a width d2 of the heater belt 16a is larger than the width d of the longitudinal seal portion F1, heat can be applied intensively to the longitudinal seal portion F1 to accomplish the sealing process.

Pull-Down Belt Mechanism 14

The pull-down belt mechanism 14 is a mechanism that holds the tubular film wound around the tube 13b by suction-adhesion and conveys the same downward. As shown in FIGS. 1 and 5, the pull-down belt mechanism 14 is provided with a belt 14c on each of the left and right sides of the tube 13b. The pull-down belt mechanism 14 rotates the belts 14c having the suction-adhesion function by a driving roller 14a and a driven roller 14b and conveys the tubular film downward. Note that, in FIGS. 1 and 5, the drawing of a roller driving motor that rotates the driving roller 14a and the like is omitted.

Longitudinal Sealing Mechanism 15

As shown in FIG. 1, the longitudinal sealing mechanism 15 is a mechanism that presses, with a constant amount of pressure, the overlapped portion F2 (see FIG. 3) of the tubular film F wound around the tube 13b onto the surface fastener 13c portion attached to the tube 13b, applies heat and pressure thereto, and thereby forms the longitudinal seal portion F1 (see FIGS. 1 and 2) along the longitudinal direction (conveying direction). In addition, the longitudinal sealing mechanism 15 is disposed on the front side of the tube 13b, and is connected to the control unit 20. In addition, as shown in FIG. 2, the longitudinal sealing mechanism 15 includes the heater belt (contact section, rotational belt structure) 16a, a heater block (heating section) 16b and a pulley 16c.

As shown in FIG. 2, the heater belt 16a is an annularly formed (ring-like) metal belt with a thickness of approximately 0.15 mm. The heater belt 16a is held in a state of maintaining a substantially constant amount of tensional force by the two pulleys 16c disposed in contact with the inner surface of the heater belt 16a. The heater belt 16a is rotated in the longitudinal direction when the pulleys 16c rotate. The heater belt 16a comes into contact with the overlapped portion F2 (see FIG. 3) of the film F in a manner of sandwiching the tubular film F being conveyed at substantially the same speed as the rotation speed of the heater belt 16a between the heater belt 16a and the tube 13b (surface fastener 13c); applies pressure and heat to the overlapped portion F2 in the space between the heater belt 16a and the surface fastener 13c; and thereby longitudinally seals the overlapped portion F2. In addition, as shown in FIG. 3, the heater belt 16a has the width d2 larger than the width d1 of the surface fastener 13c and a width d3 of the heater block 16b which are the widths substantially equal to the width d of the longitudinal seal portion F1. Consequently, as shown in FIG. 8, on the heater belt 16a that comes into direct contact with the overlapped portion F2 of the film F, a temperature gradient is created in which the temperature decreases from the center portion, where the heater block 16b is adjacently disposed, toward the both sides. Accordingly, a sufficient amount of heat and pressure per unit time to perform sealing can be applied to the longitudinal seal portion F1 of the film F, whereas a smaller amount of heat and pressure can be applied to the area surrounding the longitudinal seal portion F1. As a result, it is possible to prevent an excess amount of heat per unit time from being applied to the surrounding of the longitudinal seal portion F1 of the film F due to the contact with the heater belt 16a, and thus generation of wrinkles and sealing failure along the longitudinal seal portion F1 can be prevented.

As shown in FIGS. 2 through 4, the heater block 16b is a rectangular parallelepiped shaped metal block, and has a built-in heater bar 16e that generates heat, on the side where the heater belt 16a and the film F come into contact with each other. Further, the heater block 16b is adjacently disposed to the inner side of the heater belt 16a along the surface of the heater belt 16a in the longitudinal direction, and heats the heater belt 16a to 140 to 150 degrees C. Note that the heater bar 16e is not built in on the back side of the heater block 16b, but the entire heater block 16b is made of a metal having a high thermal conductivity, so that the temperature on the back side is also heated to about 130 degrees C. In addition, as shown in FIG. 3, similar to the surface fastener 13c, the heater block 16b has the width d3 (≈d1) substantially equal to the width d (see FIG. 2) of the longitudinal seal portion F1 of the film F in the plane view. Consequently, from the heater block 16b to the heater belt 16a, a sufficient amount of heat to perform the sealing process is applied only to the portion within the width d of the longitudinal seal portion F1. On the other hand, because the heater block 16b is not adjacently disposed in the areas on the outer sides of the portion of the heater belt 16a corresponding to the width d of the longitudinal seal portion F1, the amount of heat applied to the areas on the outer sides is significantly reduced. Thus, the temperature gradient is created in which the temperature decreases from the center to the both sides on the surface of the heater belt 16a (see the graph in FIG. 8).

As shown in FIGS. 2 and 4, the two pulleys 16c are disposed on the inner side of the heater belt 16a. The transmitted torque from a motor (not shown) causes the pulleys 16c to rotate about a rotation shaft 16f (see FIG. 6), which consequently rotates the heater belt 1 6a in the longitudinal direction.

Note that the inner side of the heater belt 16a refers to the surface inside the endless belt supported by the pulleys 16c, and the outer side of the heater belt 16a refers to the surface on the side where longitudinal sealing is performed by being brought into contact with the film F. In addition, the back side of the heater block 16b refers to the side opposite to the side where the heater bar 16e is built in and longitudinal sealing is performed.

Transverse Sealing Mechanism 17

The transverse sealing mechanism (transverse seal portion) 17 is disposed below the forming mechanism 13, the pull-down belt mechanism 14, and the longitudinal sealing mechanism 15. The transverse sealing mechanism 17 has a pair of sealing jaws 51 each with a built-in heater (see FIG. 7). One of the pair of sealing jaws 51 is located at the front side of the tubular film and the other one at the back side thereof, and as shown in FIG. 7, they circulate so as to produce generally D-shaped trajectories T that are front-to-back symmetric. Further, in the course of the circulatory movement, the tubular film is sandwiched between the pair of sealing jaws 51 as they push against each other. The sealing jaws 51 apply pressure and heat to a portion of the tubular film which becomes the upper and lower ends of a bag in order to seal the portion. One of the sealing jaws 51 located at the front side of the tubular film is supported by a shaft 17c so as to rotate about the shaft 17c. The shaft 17c is rotated via a gear by the operation of a motor for circulation (not shown) and is also horizontally moved front to back via a ball screw mechanism (not shown) by the operation of a motor for movement of the shaft. In addition, similarly, one of the sealing jaws 51 located at the back side of the tubular film is also rotated via a gear by the operation of the motor for circulation and is also horizontally moved front to back by the operation of the motor for movement of the shaft. In this way, as the pair of sealing jaws 51 is rotated and horizontally moved, the generally D shaped trajectories T of the sealing jaws 51 are produced. In addition, through the torque control of the motor for movement of the shaft, the pressure at the time when the pair of sealing jaws 51 sandwiches the tubular film therebetween is adjusted.

In addition, a cutter (not shown) is built-in in one of the pair of sealing jaws 51. This cutter fulfills the role to cut off the bag B from the following tubular film at the central position in the height direction of the transverse seal portion formed by the sealing jaws 51.

Control Unit 20

As shown in FIG. 1, the control unit 20 is connected to the longitudinal sealing mechanism 15 and other components of the bag manufacturing and packaging apparatus 1. Further, the control unit 20 is connected to the heater block 16b (heater bar 16e) included in the longitudinal sealing mechanism 15. In accordance with a detection result of a temperature sensor (not shown) that detects the temperature of the heater block 16b, the control unit 20 adjusts the amount of heat applied to the heater belt 16a from the heater bar 16e (heater block 16b), in other words, the control unit 20 controls the set temperature of the heater block 16b, and also controls the operation of the entire bag manufacturing and packaging apparatus 1.

Characteristics of Bag Manufacturing and Packaging Apparatus 1

(1) With the bag manufacturing and packaging apparatus 1 in this embodiment, as shown in FIG. 3 and the like, the heater belt 16a and the heater block 16b which constitute the longitudinal sealing mechanism 15 and the surface fastener 13c disposed on the forming mechanism 13 side are disposed such that the amount of heat per unit time applied to the areas on both outer sides of the longitudinal seal portion F1 of the film F is reduced.

Accordingly, while a sufficient amount of heat and pressure to perform the sealing process are applied to the longitudinal seal portion F1 of the film F, it is possible to prevent an excess amount of heat from being applied to the areas on both outer sides of the longitudinal seal portion F1. As a result, it is possible to prevent degradation of the appearance of the product caused by generation of wrinkles and the like along the longitudinal seal portion F1 which occurs when an amount of heat and pressure per unit time necessary for the sealing process are applied also to the surrounding of the longitudinal seal portion F1.

(2) With the bag manufacturing and packaging apparatus 1 in this embodiment, as shown in FIG. 3, as the constituent members that apply the amount of heat and pressure to the longitudinal seal portion F1 of the film F to perform the sealing process, the surface fastener 13c and the heater block 16b respectively having the width d1 and the width d3 substantially equal to the width d of the longitudinal seal portion F1, and the heater belt 16a having the width d2 larger than those widths d, d1, and d3 are used.

Accordingly, on the longitudinal seal portion F1 of the film F which is sandwiched between the surface fastener 13c and the heater belt 16a, a large amount of heat and pressure are applied to the area within the width d1 of the surface fastener 13c. On the other hand, although the areas on both outer sides of the width d1 come into contact with the heater belt 16a having the width wider than the surface fastener 13c, the amount of heat and pressure necessary to perform the sealing process are not applied thereto because the temperature gradient as shown in FIG. 8 is created on the heater belt 16a in the width direction and the surface fastener 13c as a counterpart of the heater belt 16a to sandwich the film F therebetween is not present on the heater belt 16a. In particular, in the areas on both outer sides of the surface fastener 13c, the film F wound around the tube 13b whose cross sectional shape is generally circular comes off from the surface of the heater belt 16a, so that the amount of heat and pressure are prevented from being excessively applied to the film F.

As a result, it is possible to prevent generation of wrinkles and the like along the longitudinal seal portion F1 which occurs when an excess amount of heat and pressure are applied to the both outer sides of the longitudinal seal portion F1 from the heater belt 16a, and thus degradation of the appearance of the product can be prevented.

(3) With the bag manufacturing and packaging apparatus 1 in this embodiment, as shown in FIG. 3, the surface fastener 13c has the width substantially equal to the width d of the longitudinal seal portion F1.

Accordingly, because the surface fastener 13c facing the heater belt 16a is not present in the areas on both outer sides of the longitudinal seal portion F1, the amount of heat and pressure per unit time applied to the film F from the heater belt 16a are significantly lower in the areas on both outer sides than in the area of the longitudinal seal portion F1.

In particular, in the areas on both outer sides of the surface fastener 13c, the film F wound around the tube 13b whose cross sectional shape is generally circular comes off from the surface of the heater belt 16a. Thus, the amount of heat and pressure are not excessively applied to the film F.

As a result, it is possible to prevent generation of wrinkles and the like along the longitudinal seal portion F1 which occurs when the same amount of heat and pressure that are applied to perform the sealing process are applied to the both outer sides of the longitudinal seal portion F1 from the heater belt 16a, and thus degradation of the appearance of the product can be prevented.

Other Embodiments

An embodiment of the present invention has been described as above, however, the present invention is not limited to the above embodiment, and various changes and modifications can be made herein without departing from the scope of the invention.

(A) The above embodiment is described, as shown in FIG. 3, taking an example in which the width d1 of the surface fastener 13c and the width d3 of the heater block 16b are set substantially equal to the width d (see FIG. 2) of the longitudinal seal portion F1, and the width d2 of the heater belt 16a is set larger than these widths d, d1, and d3. However, the present invention is not limited thereto.

For example, as shown in FIG. 9, the width d1 of the surface fastener 13c may be set substantially equal to the width d of the longitudinal seal portion F1, and the width d2 of the heater belt 16a and a width d4 of a heater block 116b may be set larger than these widths d and d1.

Also in this case, because the width d1 of the surface fastener 13c is set substantially equal to the width d of the longitudinal seal portion F1, the width of the overlapped portion F2 sandwiched between the heater belt 16a and the surface fastener 13c is substantially equal to the width d of the longitudinal seal portion F1. As a result, because the amount of heat is locally applied to the portion corresponding to the longitudinal seal portion F1 from the heater belt 16a, generation of problems such as wrinkles, sealing failure, and the like in the surrounding of the longitudinal seal portion can be prevented, and thus the same effect as described above can be obtained.

However, in view of the fact that creating the above described temperature gradient on the surface temperature of the heater belt 16a can prevent the amount of heat per unit time from being excessively applied to portions other than the longitudinal seal portion F1, it is preferred that the width d3 of the heater block is set substantially equal to the width d of the longitudinal seal portion F1, as is the case with the above embodiment.

(B) The above embodiment is described taking an example in which the surface fastener 13c whose contact surface that contacts the film F is flat is used as the receiving member that sandwiches the overlapped portion F2 of the film F against the heater belt 16a and performs the sealing process. However, the present invention is not limited thereto.

For example, as shown in FIG. 10(a), a surface 113ca corresponding to the contact surface that contacts the film may be formed in a curved convex shape, as the cross sectional shape of a surface fastener 113c, and the overlapped portion F2 of the film F may be sandwiched between this curved surface 113ca and the heater belt 16a for the sealing process. By providing the convex surface, both sides of the surface fastener 113c is spaced apart from the heater belt 16a when the surface fastener 113c abuts against the heater belt 16a with the film F being disposed therebetween.

In this case, a sufficient amount of heat and pressure per unit time are applied to the film F in the area near the center portion corresponding to the width d of the longitudinal seal portion F1, and at the same time, it is possible to reduce the pressure applied to the areas on the outer side of the longitudinal seal portion F1. As a result, it is possible to prevent an excess amount of heat and pressure from being applied to the surrounding areas of the longitudinal seal portion F1 of the film F by the shape of the surface fastener 113c, regardless of the width of the heater belt and the heater block that the surface fastener 113c faces. Thus, generation of wrinkles and sealing failure in the surrounding of the longitudinal seal portion can be easily prevented by a simple configuration.

Further, as the convex cross sectional shape of the receiving member, as shown in FIG. 10(b), the center portion of the curved surface 113ca of the surface fastener 113c may be formed as a flat surface 213ca, and curved surfaces 213cb may be formed on both sides of the flat surface 213ca.

In this case, the amount of heat and pressure can be evenly applied to the area having a width corresponding to the longitudinal seal portion F1, and at the same time, the amount of heat and pressure applied to the surrounding areas on both sides can be reduced. Thus, generation of wrinkles and sealing failure in the surrounding of the longitudinal seal portion can be easily prevented by a simple configuration.

(C) The above embodiment is described taking an example in which a generally rectangular parallelepiped heating element is used as the heater block 16b disposed adjacently to the heater belt 16a. However, the present invention is not limited thereto.

For example, as shown in FIG. 11, a heater block 116c whose cross sectional shape is generally T-shaped may be used, and a portion 116ca whose width of the generally T-shape is wider (i.e., the side corresponding to the horizontal like of the T-shape) may be disposed adjacent to the heater belt 16a on the side that comes into contact with the overlapped portion F2 of the film F.

In this case, with the portion 116ca whose width is wider, the temperature at both ends that are not continuous with a portion 116cb on the narrow width side tends to be lower than the temperature at the center portion. Consequently, a temperature gradient in which the temperature is reduced from the center portion to the both ends can be created on the generally T-shaped heater block 116c. As a result, generation of wrinkles, sealing failure, and the like in the surrounding of the longitudinal seal portion can be easily prevented by a simple configuration.

(D) The above embodiment is described taking an example in which the heater belt whose contact surface that contacts the film F is flat is used as the heater belt 16a that sandwiches the overlapped portion F2 of the film F against the surface fastener 13c as the receiving member and performs the sealing process. However, the present invention is not limited thereto.

For example, as shown in FIG. 12, the heater belt 16a whose surface on the side that comes into contact with the overlapped portion F2 of the film F is formed as a curved surface 116aa may be used.

In this case, the amount of heat and pressure per unit time applied to the film F from the center portion of the curved surface 116aa can be made larger than the amount of heat and pressure applied to the both ends thereof. As a result, by positioning the center portion of the longitudinal seal portion based on the center portion of the curved surface 116aa, while a sufficient amount of heat and pressure are applied to the longitudinal seal portion, such sufficient amount of pressure can be prevented from being applied to the surrounding areas at both ends of the longitudinal seal portion.

Further, as is the case with a surface fastener 213c in FIG. 10(b), the heater belt 16a having a flat surface formed in the vicinity of the center portion of the curved surface may also be used.

(E) The above embodiment is described taking an example in which the sealing process is performed in a manner that the overlapped portion F2 of the film F is sandwiched between the surface fastener 13c and the heater block 16b. However, the present invention is not limited thereto.

As a mode to perform the sealing process, for example, the sealing process may be performed in a manner that the seal portion is sandwiched by fins. Also, as the overlapped portion, a portion where films simply overlap with each other without having a folded portion formed thereon may be subjected to the sealing process.

(F) The above embodiment is described taking an example in which the surface fastener 13c that sandwiches the overlapped portion F2 of the film F against the beater belt 16a is disposed on the forming mechanism 13 side instead of the longitudinal sealing mechanism 15 side. However, the present invention is not limited thereto.

Because the surface fastener is an element used during the longitudinal sealing process according to the illustrated embodiments, it can be considered as a part of the longitudinal sealing mechanism 15.

(G) The above embodiment is described taking an example in which the heater belt 16a is used as the contact section that comes into contact with the longitudinal seal portion of the film F and thermally seals the portion. However, the present invention is not limited thereto.

For example, as shown in FIG. 13, it may be a type of longitudinal sealing mechanism in which a heater block member 216b integrally formed with the heating section of the heater and the like is intermittently operated in a manner that a contact surface (contact section) formed on the heater block member 216b is pressed against the overlapped portion F2 of the film F so as to longitudinally seal the portion.

The longitudinal sealing mechanism according to the illustrated embodiments is capable of preventing the both sides of the longitudinal seal portion from being excessively heated, so that the effect of preventing generation of problems such as wrinkles, sealing failure, and the like along the longitudinal seal portion is obtained. Thus, the longitudinal sealing mechanism according to the illustrated embodiments is widely applicable to various types of sealing devices that perform sealing while conveying packaging materials.

Claims

1. A longitudinal sealing mechanism adapted to seal an overlapped portion of a packaging material formed into a tubular shape with the overlapped portion extending along a conveying direction of the packaging material, the longitudinal sealing mechanism comprising:

a contact section configured and arranged to come into contact with the overlapped portion of the packaging material;

a heating section configured and arranged to heat the contact section to perform longitudinal sealing of the overlapped portion to form a longitudinal seal portion; and

a receiving member configured and arranged to abut against the contact section with the overlapped portion of the packaging material being disposed therebetween while the longitudinal sealing of the overlapped portion;

the contact section, the heating section, and the receiving member being configured and arranged such that an amount of heat per unit time applied to the packaging material from the contact section decreases in a direction toward both sides of the longitudinal seal portion in a direction perpendicular to the conveying direction of the packaging material.

2. The longitudinal sealing mechanism according to claim 1, wherein

the heating section and the receiving member each have a width substantially equal to a width of the longitudinal seal portion formed on the packaging material, and

the contact section has a width larger than the width of the longitudinal seal portion.

3. The longitudinal sealing mechanism according to claim 1, wherein

the receiving member has a width substantially equal to a width of the longitudinal seal portion.

4. The longitudinal sealing mechanism according to claim 1, wherein

the receiving member has a convex contact surface configured and arranged to face the overlapped portion of the packaging material so that both sides of the receiving member in a width direction are spaced apart from the contact section.

5. The longitudinal sealing mechanism according to claim 1, wherein

the contact section has a convex surface configured and arranged to face the overlapped portion of the packaging material so that the packaging material is spaced apart from the contact section at an area on an outer side of a contact portion of the contact section that contacts the longitudinal seal portion.

6. The longitudinal sealing mechanism according to claim 1, wherein

the heating section has a generally T-shape cross sectional shape in a plane perpendicular to the conveying direction of the packaging material with a side corresponding to a horizontal line of the T-shape being disposed adjacently to the contact section.

7. The longitudinal sealing mechanism according to claim 1, wherein

the contact section has a rotational belt structure that rotates around the heating section.

8. The longitudinal sealing mechanism according to claim 1, wherein

the contact section is integrally formed with the heating section to form a heater block member.