JP7058361B2 - Manufacturing method of container lid - Google Patents

Description

The present invention relates to a container lid composed of a metal thin plate shell and a synthetic resin liner, and more particularly to a metal thin plate shell having a circular top wall and a cylindrical skirt wall hanging from the periphery of the top wall. The present invention relates to a method for manufacturing a container lid composed of a synthetic resin liner having a base layer that is not adhered to the top wall of the shell.

As a container lid suitably applied to a beverage container containing fruit juice or milk, Patent Document 1 below discloses a container lid composed of a shell made of a metal thin plate such as an aluminum-based alloy thin plate and a synthetic resin liner. Has been done. The shell has a circular top wall and a cylindrical skirt wall that hangs from the periphery of the top wall. The liner has a base layer formed of a relatively hard synthetic resin such as polyprolene and a sealing layer formed of a relatively soft synthetic resin such as a styrene-based elastomer. The base layer of the liner is formed by supplying a synthetic resin material to the inner surface of the top wall of the shell and embossing it, and the sealing layer of the liner supplies the synthetic resin material to the lower surface of the base layer, that is, the exposed surface and embossing the synthetic resin material. It is formed by molding. To avoid requiring excessive force during the opening operation of the container lid when opening the mouth and neck of the container, i.e., when rotating in the opening direction, the liner, more specifically its base layer, is of the shell. It is not adhered to the inner surface of the top wall. At the upper end of the skirt wall of the shell, an annular immersion portion is formed inwardly in the radial direction over the entire circumferential direction. At the upper end of the skirt wall of the shell, a knurl is further formed in which concave portions and convex portions alternate in the entire circumferential direction below the annular immersion portion, and a slit is formed at the upper end of the concave portion in the knurl. The upper edge of the portion that is formed and defines the recess is radially inwardly displaced.

Japanese Unexamined Patent Publication No. 2016-26961

In the container lid of the above-mentioned form, since the liner is not adhered to the top wall of the shell, it is necessary to sufficiently prevent the liner from coming off from the shell when the shell is transported. be. Therefore, in the conventional container lid as described above, the inner diameter of the minimum inner diameter region of the annular immersion portion is set to be smaller than the outer diameter of the liner, and the inner diameter of the upper end edge of the portion defining the recess in the knurl is also set to the inner diameter of the liner. It is set smaller than the inner diameter to prevent the liner from coming off the shell due to the annular recess and / or the recess in the knurl. However, when the container lid is in the inverted state, the lower surface of the liner (upper surface in the inverted state) and the annular immersion portion and the concave portion of the knurl are separated from each other in the axial direction, so that the container lid is in the upright state. Alternatively, when the liner is tilted, the liner may tilt with respect to the inner surface of the top wall of the shell, and the liner may be accidentally detached from the shell. In addition, after opening the container lid from the mouth and neck of the container and consuming a part of the contents, if the container lid is reattached to the mouth and neck of the container and sealed, for example, fermentation and putrefaction of the contents occur. The pressure in the progressively sealed container may increase excessively. If the pressure inside the sealed container increases excessively, the container lid cannot withstand the pressure inside the container and causes the lid to fly, damaging people and objects around it, or polluting the surroundings with scattered contents. There was a risk of doing so.

The present invention has been made in view of the above facts, and its main technical problems are that the liner, which is in a non-adhesive state with respect to the inner surface of the top wall of the shell, accidentally separates from the shell. It is an object of the present invention to provide a new and improved method for manufacturing a container lid, which ensures that the pressure in the container is prevented from excessively increasing.

As a result of diligent studies and experiments, the present inventors have formed arcuate slits extending in the circumferential direction at intervals in the circumferential direction in the minimum inner diameter region of the annular immersion portion formed at the upper end of the skirt wall of the shell. The upper cutting edge defining such an arcuate slit is displaced radially inward from the minimum inner diameter region in the arcuate slit non-forming portion of the annular immersion portion, and the inner diameter of the upper cutting edge is smaller than the outer diameter of the liner. It has been found that the above-mentioned main technical problem can be achieved by configuring the upper cutting edge to be located below the free end edge portion provided on the outer peripheral edge portion of the liner.

That is, according to the present invention, as a method for manufacturing a container lid that achieves the above-mentioned main technical problem, in a method for manufacturing a container lid composed of a metal thin plate shell and a synthetic resin liner,
The thin metal plate is machined to have a circular top wall and a cylindrical skirt wall that hangs down from the periphery of the top wall, and the upper end of the skirt wall is radial over the entire circumferential direction. A pre-shell molded body forming step for forming a pre-shell molded body in which an annular immersion portion embedded inside is formed, and a pre-shell molded body forming step.
After the shell pre-molded body forming step, a base layer forming step of supplying a synthetic resin material to the inner surface of the top wall of the shell pre-molded body and embossing the synthetic resin material to form a base layer of the liner.
The base layer forming step includes a shell forming step of forming the shell by subjecting the pre-shell molded body to the required machining.
After the base layer forming step, the base layer of the liner is in a non-adhesive state with respect to the inner surface of the top wall.
In the shell forming step, a plurality of arcuate slits extending in the circumferential direction are formed in the minimum inner diameter region of the annular immersion portion at intervals in the circumferential direction, and the upper cutting edge defining the arcuate slit is formed into the annular shape. The inner diameter of the upper cutting edge is smaller than the outer diameter of the liner and the upper cutting edge is placed on the outer peripheral edge of the liner by displacing the inner diameter of the upper cutting edge inward in the radial direction from the minimum inner diameter region in the arcuate slit non-forming portion of the immersion portion. Provided is a method of manufacturing a container lid, characterized in that it is located below the provided free edge portion.

Preferably, the arcuate slit has a circumferential length of 7 to 12 mm. In a preferred embodiment, the arcuate slit is defined when the boundary region between the top wall and the skirt wall of the shell is deformed downward and radially inward for attachment to the mouth and neck of the container. It is preferable that the upper cutting edge is close to or abutted on the lower surface or the outer surface of the outer peripheral edge portion of the liner. At the upper end of the skirt wall of the shell, a portion below the annular immersion portion, a nar is formed in which concave portions and convex portions are alternately repeated over the entire circumferential direction, and the concave portion in the nar is formed. A slit shorter than the arc-shaped slit is formed. The liner has a sealing layer formed by forming the arc-shaped slit in the minimum inner diameter region of the annular immersion portion, supplying a synthetic resin material to the lower surface of the base layer, and embossing the synthetic resin material, and sealing the liner. It is desirable that the outer peripheral edge of the layer is located radially inside the outer peripheral edge of the base layer, and the inner diameter of the upper cutting edge is larger than the outer diameter of the sealing layer.

According to the method for manufacturing a container lid of the present invention, the inner diameter of the upper cutting edge defining the arcuate slit formed in the minimum inner diameter region of the annular immersion portion is smaller than the outer diameter of the liner, and the upper cutting edge is the outer diameter of the liner. By being located below the free edge portion provided on the peripheral edge, the liner is surely prevented from accidentally detaching from the shell. In addition, according to the method for manufacturing a container lid of the present invention, the arc-shaped slit effectively functions as a so-called vent, and the pressure inside the container is increased due to abnormal fermentation of the contents contained in the container. When excessively increased, the shell and liner of the container lid are deformed to release the pressure in the container through the arcuate slit.

The front view which shows the preferable embodiment of the container lid which was constructed according to the manufacturing method of this invention, a part (the position in the circumferential direction in which an arc-shaped slit was formed) in cross-section. The front view which shows the preferable embodiment of the container lid configured according to the manufacturing method of this invention by the cross section which shows a part (the circumferential position where the arc-shaped slit is not formed). The front view which shows the state in which the container lid shown in FIG. 1 is attached to the mouth neck of a container and the mouth neck is sealed, and a part (the circumferential position where the arcuate slit is formed) is shown in cross section. A front view showing a state in which the container lid shown in FIG. 1 is attached to the mouth and neck of the container and the mouth and neck are sealed, and a part (a circumferential position where an arc-shaped slit is not formed) is shown in cross section. A front view showing a part of the pre-shell molded body formed in the manufacturing process of the container lid shown in FIG. 1 in cross section. A front view showing a part of the state before the base layer of the liner formed on the pre-shell molded body shown in FIG. 5 shrinks in cross section. A front view showing a part of the state after the base layer of the liner formed on the pre-shell molded body shown in FIG. 5 has shrunk in a cross section. A front view showing a part of the pre-shell molded body in the state shown in FIG. 7 in a cross-sectional view, which has been appropriately machined.

Hereinafter, the description will be described in more detail with reference to the attached drawings.

Before explaining a suitable mode of the method for manufacturing a container lid of the present invention, for convenience, a container lid configured according to the manufacturing method of the present invention will be described. Explaining with reference to FIGS. 1 and 2, the container lid indicated by No. 2 as a whole, which is configured according to the manufacturing method of the present invention, is composed of a metal thin plate shell 4 and a synthetic resin liner 6.

The shell 4, which can be formed from an appropriate metal sheet such as an aluminum-based alloy sheet, has a circular top wall 8 and a cylindrical skirt wall 10 hanging from the periphery of the top wall 8. The boundary region between the top wall 8 and the skirt wall 10 has an arc shape in the cross section. At the upper end of the skirt wall 10, an annular immersion portion 12 embedded inward in the radial direction is formed over the entire circumferential direction. The annular immersion portion 12 will be further described later. At the upper end of the skirt wall 10 below the annular immersion portion 12, a knurl 18 in which the concave portion 14 and the convex portion 16 alternately repeat over the entire circumferential direction is formed. A slit 20 is formed at the upper end of the recess 14 in the knurl 18, and the upper edge of the portion defining the recess 14 is displaced inward in the radial direction. A circumferential breakable line 22 is arranged at the lower end of the skirt wall 10, and the skirt wall 10 has a main portion 24 above the circumferential breakable line 22 and a temper below the circumferential breakable line 22. It is divided into the evidence skirt 26. The circumferential breakable line 22 in the illustrated embodiment has a plurality of bridging portions 30 remaining between the plurality of hem slits 28 extending in the circumferential direction at intervals in the circumferential direction and the hem slits 28. The tamper evidence hem 26 is connected to the main portion 24 via a plurality of bridge tie portions 30.

A plurality of arcuate slits 32 extending in the circumferential direction are formed in the minimum inner diameter region 13 of the annular immersion portion 12 at intervals in the circumferential direction. The upper cutting edge 34 defining the arc-shaped slit 32 is displaced inward in the radial direction from the minimum inner diameter region 13 in the portion of the annular immersion portion 12 where the arc-shaped slit 32 does not exist (the arc-shaped slit non-forming portion) (the arc-shaped slit 32 is not formed). (Refer to FIG. 1 and FIG. 2 for comparison), the inner diameter of the upper cutting edge 34 is smaller than the outer diameter of the liner 6, and the upper cutting edge 34 is a free end portion described later provided on the outer peripheral edge portion of the liner 6. It is important to be located below 46. The circumferential length of the arcuate slit 32 is preferably 7 to 12 mm. It is preferable that three or more arc-shaped slits 32 are formed at equal intervals in the circumferential direction.

The liner 6 has a base layer 36 formed of a relatively hard synthetic resin such as polypropylene and a sealing layer 38 formed of a relatively soft synthetic resin such as a styrene-based elastomer. The base layer 36 is in a non-adhesive state with respect to the inner surface of the top wall 8 of the shell 4, but the sealing layer 38 is in a non-adhesive state with respect to the lower surface of the base layer 36. The process of forming the liner 6, that is, the base layer 36 and the sealing layer 38 will be described later.

The base layer 36 extends along the inner surface of the outer peripheral edge portion of the circular thin-walled central portion 40 extending along the inner surface of the top wall 8 of the shell 4, the outer peripheral edge portion of the top wall 8 of the shell 4, and the inner surface of the upper end portion of the skirt wall 10. It has a ring-shaped thick outer peripheral edge portion 42. The thin-walled central portion 40 has an annular thickness variation region 44 in which the thickness gradually decreases outward in the radial direction (thus, the lower surface extends inclined upward in the radial direction). .. The outer peripheral edge of the thickness variation region 44 is located in the radial direction of the sealing layer 38 in the vicinity of the annular protrusion 52 described later. In the outer peripheral edge region of the thick outer peripheral edge portion 42, a free end edge portion 46 whose wall thickness gradually decreases downward is formed. In the illustrated embodiment, the lower end of the free edge portion 46, i.e., the free edge, is located close to above the upper cutting edge 34 of the shell 4.

The sealing layer 38 is laminated on the thin central portion 40 of the base layer 36. That is, the outer peripheral edge of the sealing layer 38 is located radially inside the outer peripheral edge of the base layer 36, and is radially inside the upper cutting edge 34 defining the arcuate slit 32 provided in the skirt wall 10 of the shell 4. Located (in other words, the inner diameter of the upper cutting edge 34 is larger than the outer diameter of the sealing layer 38). The sealing layer 38 has a circular thin-walled central portion 48 and an annular-shaped thick-walled outer peripheral edge portion 50. In the radial inner region of the thick outer peripheral edge portion 50, there is an annular projecting portion 52 projecting downward.

According to the container lid manufactured by the manufacturing method of the present invention described later, the inner diameter of the upper cutting edge 34 defining the arcuate slit 32 formed in the minimum inner diameter region 13 of the annular immersion portion 12 is the liner 6 (more specifically, the inner diameter of the liner 6). The upper cutting edge 34, which is smaller than the outer diameter of the base layer 36), is located below the free end edge portion 46 provided on the outer peripheral edge portion of the liner 6 (more specifically, the thick outer peripheral edge portion 42 of the base layer 36). This ensures that the liner 6 is prevented from accidentally detaching from the shell 4.

In FIGS. 1 and 2, the mouth neck 54 of the container to which the container lid 2 is applied is illustrated by a two-dot chain line. The mouth and neck 54 of the container, which can be formed from a suitable metal sheet such as a chromic acid-treated steel sheet, a tin plate or an aluminum-based alloy sheet, which is a well-known form in itself, has a substantially cylindrical shape as a whole. An outer winding curl 56 is formed at the upper end portion where the outer diameter gradually decreases toward the upper side. A male screw 58 and a locking jaw portion 60 located below the male screw 58 are formed on the outer peripheral surface of the main portion of the mouth neck portion 54.

When the container lid 2 is attached to the mouth and neck 54 of the container to seal the mouth and neck 54, the container lid 2 is fitted to the mouth and neck 54 and pressed downward to press the sealing layer 38 of the liner 6 downward. The state of being in close contact with the top of the mouth neck 54, more specifically, the outer peripheral surface of the annular protrusion 52 of the sealing layer 38 and the radial outer region of the thick outer peripheral edge 50 located radially outside the annular protrusion 52. While maintaining the lower surface of the mouth neck 54 in close contact with the upper or upper surface of the inner peripheral surface of the outer winding curl 56, the boundary region between the top wall 8 and the skirt wall 10 of the shell 4 is downward and inward in the radial direction. Deformation, that is, the shape as shown in FIGS. 3 and 4. In this way, the outer peripheral surface of the annular protrusion 52 of the sealing layer 38 of the liner 6 is brought into close contact with the upper part of the inner peripheral surface of the outer winding curl 56, and the thick outer peripheral edge portion 50 located radially outside the annular protrusion 52. The lower surface of the radial outer region of the outer winding curl 56 is brought into close contact with the upper surface or the outer peripheral surface of the outer winding curl 56. At this time, the upper cutting edge 34 defining the arcuate slit 32 is brought close to or in contact with the lower surface or the outer surface of the outer peripheral edge portion of the liner 6. Further, the main portion 24 of the skirt wall 10 of the shell 4 is deformed along the male screw 58 formed on the mouth neck 54 of the container to form the female screw 62, and the skirt wall 10 of the shell 4 is formed. The lower end of the tamper evidence hem 26 is deformed inward in the radial direction to be locked to the locking chin 60 at the mouth and neck 54 of the container.

According to the container lid manufactured by the manufacturing method of the present invention described later, the arc-shaped slit 32 formed in the minimum inner diameter region 13 of the annular immersion portion 12 effectively functions as a so-called vent and is housed in the container. When the pressure inside the container is excessively increased due to abnormal fermentation of the product or the like, the shell 4 and the liner 6 of the container lid 2 are deformed and the pressure inside the container is released through the arcuate slit 32.

More specifically, the arc-shaped slit 32 will be described in more detail. In a container lid having a nominal diameter of 38 mm, three arc-shaped slits 32 are formed at intervals in the circumferential direction, and the circumferential length of the arc-shaped slit 32 is 7 to 12 mm. The arcuate slit 32 is preferably located 1.5 to 2.5 mm below the lower surface of the top wall 8. When opening the container lid, it is preferable that the pressure inside the container is released at a predetermined value set at 0.6 to 1.0 MPa. If the circumferential length of the arc-shaped slit 32 is too small, the pressure inside the container cannot be released at a predetermined value and so-called lid skipping may occur, and the circumferential length of the arc-shaped slit 32 is excessive. In that case, the pressure inside the container may be released at a value lower than a predetermined value.

When opening the mouth and neck 54 to consume the contents of the container, put a finger on the skirt wall 10 of the shell 4 to open the container lid 2 in the opening direction, that is, counterclockwise when viewed from above in FIGS. 3 and 4. Rotate clockwise. In the initial stage of this rotation, the liner 6, more specifically, the base layer 36 thereof is in a non-adhesive state with respect to the inner surface of the top wall 8 of the shell 4, and only the shell 4 rotates with respect to the liner 6, so that an excessive force is applied. The container lid 2 can be easily rotated with respect to the mouth neck 54 without the need. When the shell 4 is rotated with respect to the mouth neck 54, the female screw 62 formed on the main portion 24 of the skirt wall 10 moves along the male screw 58 of the mouth neck 54, so that the container lid 2 Is moved upward with respect to the mouth and neck 54. At this time, the shell 4 is moved upward with respect to the mouth neck 54, and the liner 6 is also provided with a free end edge portion 46 provided on the thick outer peripheral edge portion 42 by the upper cutting edge 34 of the arcuate slit 32. Since the outer surface to the lower surface of the sill is surely supported, it is moved upward with respect to the mouth neck 54 without tilting and falling off. At this time, when three arc-shaped slits 32 are formed in the annular immersion portion 12 at equal angular intervals in the circumferential direction, the liner 6 cuts upward regardless of which direction the liner 6 tilts in the radial direction with respect to the shell 4. It can be supported by the edge 34.

When the container lid 2 is moved upward with respect to the mouth and neck 54, the tamper evidence hem 26 of the skirt wall 10 is upward because its lower end is formed on the locking chin 60 of the mouth and neck 54. The movement to the skirt wall 10 is prevented, stress is generated in the bridge tie portion 30 in the circumferential ruptureable line 22 formed on the skirt wall 10, and the bridge fold portion 30 is broken. After that, the container lid 2 moves upward with rotation, leaving the tamper evidence hem 26, and is detached from the mouth and neck 54, and the mouth and neck 54 is opened.

Subsequently, with reference to FIGS. 5 to 8, the preferred mode of the manufacturing process of the container lid 2 will be described as follows as a preferred mode of the method for manufacturing the container lid of the present invention. First, a thin metal plate to which a weak adhesive is previously applied to one side is appropriately machined to form the pre-shell molded body 64 shown in FIG. 5 (pre-shell molded body forming step). The weak adhesive is applied to the inner surface of the pre-shell molded body 64, that is, the surface on the side that will later become the inner surface of the shell 4. As the weak adhesive, those mainly composed of known components such as paints containing a polypropylene adhesive component can be used. Only the annular immersion portion 12'is formed on the outer peripheral surface of the skirt wall 10'of the pre-shell molded body 64, and the arcuate slit 32'is not formed (the numbers indicated by' are the completed shells. It is the number of each corresponding part in 4. The same applies hereinafter). Next, as shown in FIG. 6, a synthetic resin material is supplied to the inner surface of the top wall 8'of the shell preformed body 64 (that is, the inner surface of the top wall of the shell in which the annular immersion portion is already formed), and the synthetic resin material is embossed. The base layer 36 of the liner 6 is formed by molding (base layer forming step). More specifically, the base layer 36 holds the pre-shell molded body 64 in an inverted state on a base (not shown), and supplies a softened and melted synthetic resin material to the central portion of the top wall 8'. It is formed by pressing an embossing member (not shown) having a required shape against such a synthetic resin material with a required pressure. Immediately after the base layer 36 was formed on the inner surface of the top wall 8'of the pre-shell molded body 64, as clearly shown in FIG. 6, the above-mentioned weak adhesive applied to the inner surface of the top wall 8'was used. The base layer 36 is in an adhesive state with respect to the inner surface of the top wall 8'. However, after the base layer 36 is formed on the inner surface of the top wall 8'of the pre-shell molded body 64 and a predetermined time elapses, the base layer 36 cools and shrinks as shown in FIG. 7, and the above-mentioned weakness The adhesive peels off. As a result, the base layer 36 is in a non-adhesive state with respect to the inner surface of the top wall 8'. After that, the pre-shell molded body 64 is appropriately machined to form the shell 4 as shown in FIG. 8 (shell forming step). At this time, an arcuate slit 32'is formed at the immersion end edge of the annular immersion portion 12'of the shell preformed body 64. After that (in other words, after forming a slit at the immersion end edge of the annular immersion portion), the sealing layer 38 of the liner 6 is formed by embossing the synthetic resin material supplied to the lower surface of the base layer 36 of the liner 6. Form (Fig. 1). More specifically, the sealing layer 38 holds the shell 4 on which the base layer 36 is formed in an inverted state on a base (not shown), and supplies a softened and melted synthetic resin material to the central portion of the base layer 36. The synthetic resin material is formed by pressing a stamping member (not shown) having a required shape with a required pressing force.

2: Container lid 4: Shell 6: Liner 8: Top wall 10: Skirt wall 12: Circular immersion 13: Minimum inner diameter 32: Arc-shaped slit 34: Upper cutting edge (which defines the slit) 36: Base layer 46: Free edge (of liner)

Claims (5)

In the method of manufacturing a container lid composed of a metal thin plate shell and a synthetic resin liner,
The thin metal plate is machined to have a circular top wall and a cylindrical skirt wall that hangs down from the periphery of the top wall, and the upper end of the skirt wall is radial over the entire circumferential direction. A pre-shell molded body forming step for forming a pre-shell molded body in which an annular immersion portion embedded inside is formed, and a pre-shell molded body forming step.
After the shell pre-molded body forming step, a base layer forming step of supplying a synthetic resin material to the inner surface of the top wall of the shell pre-molded body and embossing the synthetic resin material to form a base layer of the liner.
The base layer forming step includes a shell forming step of forming the shell by subjecting the pre-shell molded body to the required machining.
After the base layer forming step, the base layer of the liner is in a non-adhesive state with respect to the inner surface of the top wall.
In the shell forming step, a plurality of arcuate slits extending in the circumferential direction are formed in the minimum inner diameter region of the annular immersion portion at intervals in the circumferential direction, and the upper cutting edge defining the arcuate slit is formed into the annular shape. The inner diameter of the upper cutting edge is smaller than the outer diameter of the liner and the upper cutting edge is placed on the outer peripheral edge of the liner by displacing the inner diameter of the upper cutting edge inward in the radial direction from the minimum inner diameter region in the arcuate slit non-forming portion of the immersion portion. A method for manufacturing a container lid, characterized in that it is located below the provided free end portion. The method for manufacturing a container lid according to claim 1, wherein the arcuate slit has a circumferential length of 7 to 12 mm. When the boundary region between the top wall and the skirt wall of the shell is deformed downward and radially inward for attachment to the mouth and neck of the container, the upper cutting edge defining the arcuate slit is said to be The method for manufacturing a container lid according to claim 1 or 2, wherein the container lid is brought into close contact with or in contact with the lower surface or the outer surface of the outer peripheral edge portion of the liner. At the upper end of the skirt wall of the shell, a portion below the annular immersion portion, a nar is formed in which concave portions and convex portions are alternately repeated over the entire circumferential direction, and the concave portion in the nar is formed. The method for manufacturing a container lid according to any one of claims 1 to 3, wherein a slit shorter than the arc-shaped slit is formed. The liner has a sealing layer formed by forming the arc-shaped slit in the minimum inner diameter region of the annular immersion portion, supplying a synthetic resin material to the lower surface of the base layer, and embossing the synthetic resin material, and sealing the liner. The container lid according to any one of claims 1 to 4, wherein the outer peripheral edge of the layer is located radially inside the outer peripheral edge of the base layer, and the inner diameter of the upper cutting edge is larger than the outer diameter of the sealing layer. Manufacturing method.

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