Metal container lid

Abstract

To provide a metallic container lid that can surely ensure the sealing property at the time of resealing.SOLUTION: In a metallic container lid having a metallic shell 3 comprising a circular top surface wall 7 and a cylindrical skirt wall 9 descending from the periphery of the top surface wall 7 and having a screw formation scheduled part 15, and a synthetic resin liner 5 fixed to an inner surface of the circular top surface wall 7, the synthetic resin liner 5 has a circular seal part 5c and a thin-walled peripheral edge part 5d located outside the circular seal part 5c and thinner than the circular seal part 5c, and an inclined step part 5e formed according to a thickness difference between the circular seal part 5c and the thin-walled peripheral edge part 5d. Before the metallic shell 3 is wound around a container mouth part to form a screw, an outer diameter d1 of the circular seal part 5c is set to be larger than an outer diameter D of the container mouth part.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a metal container lid having a synthetic resin liner. [Background technology]

[0002] Although metal container lids are more limited in terms of shape than plastic container lids, they have excellent heat resistance and high strength, and are therefore widely used as lids not only for glass bottles and metal containers, but also for plastic containers.

[0003] Such a metal container lid is formed using a metal shell having a circular top wall and a cylindrical skirt wall that descends from the periphery of the top wall. That is, a synthetic resin liner is disposed inside the metal shell, and by placing the metal shell over the mouth of a container and seaming it using a specified jig, the outer periphery of the circular top wall is squeezed, the liner disposed on the inner surface of the circular top wall is brought into close contact with the mouth of the container, and a thread is formed on the cylindrical skirt wall of the metal shell, making it possible to use it as a container lid. That is, the thread formed on the mouth of the container is transferred to the cylindrical skirt wall of the metal shell by seaming.

[0004] However, such metal container lids are highly rigid and do not adhere closely to the mouth of the container, making it impossible to ensure good sealing. To avoid this problem, as shown in Patent Document 1, for example, a flexible synthetic resin liner is provided on the inner surface of the circular top wall. When attached to the mouth of the container, this synthetic resin liner adheres closely to the upper end surface of the container mouth, thereby ensuring good sealing.

[0005] A structure with a synthetic resin liner is a basic structure when a metal container lid is required to have a tight seal, but this structure has a problem with resealability. That is, when a general consumer removes a metal container lid from the container mouth and then reattaches it to the container mouth, the sealability is insufficient, and the container contents may leak. That is, when the container lid is placed over the container mouth and rotated in the closing direction during resealing, a closing torque is applied continuously from the stage where the liner comes into contact with the container mouth, so that general consumers often think that the closing operation is complete and stop the closing operation.

[0006] As a metal container lid that solves these problems, Patent Document 2 proposes a cap structured such that a relief portion with a reduced thickness is provided on the outer peripheral edge of the liner. With a cap (metal container lid) of this structure, when the cap is rotated in the closing direction during resealing, the liner comes into contact with the mouth of the container and the mouth of the container penetrates into the inside of the cap; however, the thin-walled escape portion formed on the outer edge of the liner acts as a guide, allowing the cap to rotate concentrically without eccentricity, so that there is no temporary increase in torque when the cap is closed, preventing the inconvenience of consumers mistakenly thinking that the cap is closed.

[0007] However, the above-mentioned method of forming a thin-walled relief portion on the outer peripheral edge of the liner does not reliably prevent leakage of the contents during resealing, and there is a need to ensure a more reliable seal, particularly for products such as carbonated beverages that are not heat sterilized after filling with the contents, and which do not experience stress relaxation due to heat in the synthetic resin liner. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2007-45452 A [Patent Document 2] JP 2006-248533 A Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, an object of the present invention is to provide a metal container lid that can reliably ensure hermetic sealing during resealing. [Means for solving the problem]

[0010] The inventors conducted many experiments and studies into the airtightness of metal container lids when they are resealed, and as a result, they discovered that merely providing a thin-walled portion on the outer peripheral edge of a liner cannot reliably prevent airtightness, but that by providing an inclined step portion on the inner peripheral side of the thin-walled portion and arranging an annular seal portion that is in close contact with the container mouth inside this inclined step portion, it is possible to reliably prevent airtightness when resealing, which led to the completion of the present invention.

[0011] That is, according to the present invention, a circular top wall and Round A metal container lid having a metal shell formed of a cylindrical skirt wall descending from the periphery of a top wall, and a synthetic resin liner disposed on the inner surface of the circular top wall, Applicable The synthetic resin liner has an annular seal portion and a thin-walled peripheral edge portion located outside the annular seal portion and thinner than the annular seal portion, and an inclined step portion is present between the annular seal portion and the thin-walled peripheral edge portion according to the difference in thickness between the annular seal portion and the thin-walled peripheral edge portion, Applicable Before the metal shell is wrapped around the container mouth and the screw is formed Applicable The outer diameter of the annular seal portion is set to be larger than the outer diameter D of the container mouth portion, Applicable Metal shell Applicable By tightening the container mouth, Applicable The cylindrical skirt wall is formed with threads that engage with threads formed on the outer surface of the container mouth, Applicable At the mouth of the container ApplicableWhen the metal shell is wrapped around the Applicable The outer peripheral end of the annular seal is in close contact with the outer peripheral wall of the container mouth. Applicable The thin peripheral edge and the inclined step of the synthetic resin liner are spaced apart from the outer peripheral wall of the container mouth, and the inclined step of the synthetic resin liner is inclined downward toward the outside in the radial direction, When resealing, Applicable A metal container lid is provided, characterized in that the inclined step portion of the synthetic resin liner is first brought into contact with the upper end surface of the container mouth.

[0012] The following aspects are preferably adopted in the metal container lid of the present invention. (1) At a stage before the metal shell is fastened to the container mouth and a screw is formed, Synthetic resin The outer periphery of the thin peripheral edge of the liner is located in a flat area on the inner surface of the circular top wall. (2) By wrapping the metal shell around the container mouth, a screw is formed on the cylindrical skirt wall which engages with a screw formed on the outer surface of the container mouth, and when the metal shell is wrapped around the container mouth, the outer peripheral end of the annular seal portion is in close contact with the outer peripheral wall of the container mouth. (3) When resealing, the metal container lid covering the container mouth is rotated in the closing direction, and the upper end surface of the container mouth is Synthetic resin It comes into contact with the sloped step of the liner, Made of synthetic resin The thin peripheral edge of the liner is held away from the outer peripheral wall of the container mouth during resealing. Effect of the Invention

[0013] In the case of the metal container lid of the present invention, when the lid is once removed from the container mouth and is then put back on the container mouth for resealing, the container mouth penetrates into the container lid and comes into contact with the liner as it rotates in the closing direction, but due to eccentricity during rotation, the inclined step portion (the connecting portion between the thin peripheral edge portion and the annular seal portion) formed on the liner comes into contact with the upper end surface of the container mouth, and the container mouth is pushed into the liner. That is, since the outer diameter of the annular seal portion of the liner is set to be larger than the outer diameter D of the container mouth, in a completely sealed state, the annular seal portion is in close contact with the outer peripheral wall that defines the outer diameter D of the container mouth, but when the container lid (metal shell) is rotated for resealing, some eccentricity is inevitably involved. For this reason, when it is rotated in the closing direction until sealing is completed during resealing, the upper end of the outer peripheral wall of the container mouth comes into contact with the inclined step portion located outside the annular seal portion of the liner. In this contact state, the inclined step portion is inclined downward toward the outside in the radial direction, and as a result, the compressive stress that the liner receives from the container mouth is dispersed, and therefore the generation of a large capping torque can be suppressed. That is, the thin-walled peripheral edge portion connected to the inclined step portion is separated from the container mouth and does not function as a guide for concentrically rotating in the capping direction, but does not cause an increase in stress due to contact with the container mouth, and as a result, does not increase the capping torque. Therefore, with the metal container closure of the present invention, there is no risk of a large capping torque being suddenly applied due to contact between the container mouth and the liner during resealing, and even if the container mouth continues to rotate in the capping direction after contact between the container mouth and the liner, no large capping torque is generated, and capping is performed until the container mouth is securely sealed. In this way, the present invention can effectively avoid the inconvenience that ordinary consumers may encounter when completing the resealing process in an insufficient state, and can reliably ensure the hermetic seal during resealing. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a half-sectional side view of the metal container lid of the present invention before being fastened to the mouth of the container. [Diagram 2]FIG. 2 is a half-sectional side view of the metal container lid of FIG. 1 after being fastened to the container mouth portion. [Diagram 3] FIG. 2 is a partially enlarged cross-sectional view showing a main portion of the metal container lid in the state shown in FIG. 1, in comparison with a conventional container lid in which no step is formed in the liner. [Figure 4] FIG. 3 is a partially enlarged cross-sectional view showing a main portion of the metal container lid in the state of FIG. 2, in comparison with a conventional container lid in which no step is formed in the liner. [Diagram 5] 3 is an enlarged partial cross-sectional view showing the process of resealing the metal container lid shown in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Referring to Figure 1, the metal container lid of the present invention, generally designated 1, is in a state before being fastened to the mouth of the container (hereinafter sometimes referred to as the container lid shell), and is composed of a metal shell 3 and a synthetic resin liner 5.

[0016] The metal shell 3 is made of an aluminum alloy having a thickness of, for example, about 0.20 to 0.26 mm, and has a circular top wall 7 and a skirt wall 9 of a substantially cylindrical shape that hangs down from the periphery of the top wall 7. As is clear from Figure 1, a curved portion 10 exists at the boundary between the circular top wall 7 and the skirt wall 9.

[0017] The lower end 9a of the skirt wall 9 is bulged outward in the radial direction, and a tamper-evident (TE) skirt portion 13 is connected to this bulging lower end portion via a plurality of breakable bridges 11.

[0018] The approximate center of the skirt wall 9 is a thread forming region 15 where a thread is formed by tightening, which will be described later, and an annular groove 17 is formed at the upper end of the thread forming region 15. This annular groove 17 is for guiding a jig for thread forming.

[0019] Above the annular groove 17, an uneven portion (knurl) 19 is formed in which recesses 19a and protrusions 19b alternate in the circumferential direction, and a number of circumferentially extending slits 21 are formed at intervals in the circumferential direction at the upper end of the recesses 19a (i.e., near the corner portion connected to the circular top wall 7). Such slits 21 are provided to release the pressure in the container when opening it and to wash the contents that have adhered to the mouth when filling the contents, and usually, the protrusions 19b of the uneven portion 19 are located between the many slits 21. Generally, all of such many slits 21 have substantially the same length, and have a circumferential length of about 2 to 5 mm. That is, gas is released from the inside of the container through the slits 21, preventing problems such as cap flying off.

[0020] In this embodiment, the liner 5 is fixed by dropping molten resin onto the inner surface of the circular top wall 7 and heat fusing it by embossing, and the liner 5 adheres closely to the upper end of the container mouth, which will be described later, ensuring a tight seal. The liner 5 does not have to be fixed to the inner surface of the circular top wall, and may be peeled off after embossing or inserted into the metal shell 3 after injection molding. Such a liner 5 is made of an appropriate synthetic resin such as soft polyethylene, and is formed by supplying a molten synthetic resin to the inner surface of the top wall 7 and then embossing the molten resin into a desired shape. The shape of the liner will be described later.

[0021] The container lid shell 1 having the above-mentioned structure is placed over the container mouth having a thread formed on its side, and the periphery of the circular top wall 7 is pressed from above with a pressing tool to crimp the liner 5 firmly against the upper end surface of the container mouth. In this state, a screw forming roller is introduced into the annular groove 17 formed at the upper end of the screw forming region 15 of the skirt wall 9, and then the screw forming roller is rotated along the thread provided on the container mouth while pressing the skirt wall 9 against the container mouth, thereby transferring the thread formed on the container mouth to the skirt wall 9. In addition, the TE skirt portion 13 connected to the lower end of the skirt wall 9 is pressed against the underside of the jaw formed on the container mouth by the skirt portion rolling roller. Such a screw forming process is known and is shown in, for example, Figures 4 and 5 of Patent Document 1 (JP Patent Publication 2007-45452).

[0022] As described above, the skirt wall 9 of the container lid shell 1 is formed with a screw, and at the same time, it is attached to the mouth of the container. A metal container lid in which the above-mentioned container lid shell 1 is placed over the container mouth and threaded by tightening is shown in Fig. 2. That is, a metal container lid in which threads are formed on the skirt wall 9 of the metal shell 3 is shown at 30 in Fig. 2.

[0023] In Fig. 2, the container to which the metal container lid 30 (container lid shell 1) is attached may be a metal container or a plastic container, but here, a mouth 50 of a metal container is shown. The upper end of this metal container mouth 50 is a curled portion 51, and an outer peripheral wall 52 is formed that is connected to the curled portion 51 and extends straight downward. In other words, the outer diameter D of the container mouth 50 (outer diameter of the upper end opening) is determined by this outer peripheral wall 52. A screw 53 is formed below this outer peripheral wall 52, and a jaw portion 55 is formed below that.

[0024] A container lid 1 (container lid shell) before being fastened is placed over such a container mouth portion 50, the outer periphery of the circular top wall 7 is squeezed using the method described above, the liner 5 arranged on the inner surface of the circular top wall 7 is brought into close contact with the curled portion 51, and a screw 15a is formed in the screw formation portion 15, thereby obtaining a metal container lid 30 equipped with a screw 15a.

[0025] In such a metal container lid 30, the liner 5 is in close contact with the curled portion 51 at the upper end of the container mouth 50, thereby ensuring a tight seal. In addition, the screw 15a formed on the skirt wall 9 (the part of the screw forming area 15 in Figure 1) is a transcription of the screw 53 provided on the container mouth portion 50, and therefore is firmly threadably engaged with the screw 53, making it possible to open and close the container by turning it. Furthermore, the TE hem portion 13 is firmly pressed against the underside of the jaw portion 55 of the container mouth portion 50, thereby stably holding the metal container lid 30 so that it does not slip out of the container mouth portion 50.

[0026] When the above-described metal container lid 30 is rotated in the opening direction, the cap 30 rises, but the rise of the TE hem 13 is restricted by the container jaw 55. Therefore, when the metal container lid 30 is rotated in the closing direction, the bridge 11 connecting the skirt wall 9 of the container lid 30 and the TE hem 13 breaks. In other words, general consumers can recognize the opening history of this container lid 30 because the TE hem 13 is separated from the cap 30 (skirt wall 9).

[0027] In the container lid shell 1 used to form the above-mentioned metallic container lid 30, the present invention is characterized in that the liner 5 has a shape as shown in FIG. 3(a). First, referring to FIG. 3(a), the liner 5 is formed, for example, by dropping molten resin onto the inner surface of the top wall 7 of the metal shell 3 held in an inverted state, and spreading the molten resin drop by a punch. As a result, the central portion becomes a circular extremely thin portion 5a, an annular protrusion 5b is formed around the extremely thin portion 5a, and an annular seal portion 5c including an area that is in close contact with the upper end (curl portion 51) of the container mouth portion is formed outside the annular protrusion 5b. The annular protrusion 5b is basically not directly involved in sealing, but it is a portion that is preferable for it to exist in molding the liner 5. That is, when spreading the molten resin, if it is tried to spread it outward all at once, thickness unevenness is likely to occur, so the descending position of the punch is once regulated to form the annular protrusion 5b so that an area where a large amount of molten resin is stored is formed, and the molten resin is spread from such a storage portion (annular protrusion 5b) to the surroundings to form the seal portion 5c, thereby ensuring uniformity of thickness and reliably adjusting the thickness.

[0028] As shown in FIG. 3(a), in the present invention, a thin peripheral edge portion 5d is formed on the outside of the annular seal portion 5c of the liner 5 as described above, and an inclined step portion 5e is formed by this thickness difference. That is, the inclined step portion 5e is a connecting portion between the annular seal portion 5c and the thin peripheral edge portion 5d. If the inclined step portion 5e is the outermost diameter portion of the liner 5, the molten resin may not spread uniformly to the outermost diameter portion during liner molding with a punch, resulting in thickness unevenness. Therefore, by forming the outermost diameter portion of the liner 5 as the thin peripheral edge portion 5d, which has a flat shape, and forming the inclined step portion 5e between the annular seal portion 5c and the thin peripheral edge portion 5d, the thickness unevenness can be eliminated. As shown in FIG. 3(b), in the liner 5 of a conventional metal container lid, the thickness of the sealing portion 5c is uniform, and the edge of the liner 5 is not thin-walled, and therefore no inclined step portion 5e is formed.

[0029] In the above-described configuration of the liner 5, in the present invention, as shown in FIG. 3(a), the outer diameter d1 of the annular seal portion 5c of the liner 5 provided on the container lid shell 1 (metal shell 3) is larger than the outer diameter D of the container mouth portion 50 (i.e., the diameter defined by the outer peripheral wall 52) (d1>D).

[0030] 4(a) and (b) show enlarged cross-sectional side views of the main part of the metal container lid 30 in a state in which it is wrapped and fastened to the container mouth 50, so please refer to them in addition to Figs. 3(a) and (b). Fig. 4(a) shows the container lid 30 formed by wrapping and fastening the container lid shell 1 (metal shell 3) of the present invention, in which the liner 5 is provided with a thin peripheral edge 5d and an inclined step 5e, to the container mouth 50, while Fig. 4(b) shows the container lid shell 1 (metal shell 3) of the prior art, which is provided with a liner 5 in which neither the thin peripheral edge 5d nor the inclined step 5e is formed, to the container mouth 50.

[0031] When the container mouth 50 is covered with the container lid shell 1 and the circular top wall 7 is drawn, the thin peripheral edge 5d and the annular seal 5c of the liner 5 are bent downward by drawing. That is, in accordance with this drawing, inflection points P and Q are formed between the flat top wall 7 and the skirt wall 9, but since the outer diameter d1 of the annular seal 5c is set to be larger than the outer diameter D of the outer peripheral wall 52 of the container mouth 50, it is in close contact with the curled portion 51 and also in close contact with the outer peripheral wall 52. In this state, the inclined step portion 5e is inclined radially outward and faces downward. This inclined step portion 5e may be oriented horizontally, but from the viewpoint of resealability, it is preferable that it faces radially outward and faces downward as shown in the figure. Therefore, the thin peripheral edge portion 5d continuing to the inclined step portion 5e extends downward away from the outer peripheral wall 52 of the container mouth portion 50.

[0032] As described above, the liner 5 is in close contact with the curled portion 51 and the outer peripheral wall 52 of the container mouth 50, thereby ensuring a tight seal. In a conventional container lid shell 1 in which the liner 5 does not have a thin-walled peripheral edge portion 5d or an inclined step portion 5e, the thick-walled annular seal portion 5c is simply in close contact with the curled portion 51 and the outer peripheral wall 52 and extends outward and downward.

[0033] By the way, when the metal container lid 30 shown in Fig. 4 is rotated in the opening direction, the TE skirt 13 is cut off and removed from the container mouth 50, and the contents of the container are discharged in this state. If not all of the contents have been discharged after the contents have been discharged, the cap 30 is usually placed again on the container mouth 50 and rotated in the closing direction (i.e., resealing). In the present invention, the inclined step portion 5e of the liner 5 is positioned so that during resealing, the inclined step portion 5e first comes into contact with the upper end (curled portion 51) of the container mouth portion 50, thereby making it possible to reliably prevent poor sealing during resealing.

[0034] That is, referring to FIG. 5 for explaining the resealing process, in resealing, the container lid 30 removed from the container mouth 50 is placed on the container mouth 50 and rotated in the closing direction, but as shown in FIG. 5(a), in the initial stage, the liner 5 does not contact the curled portion 51 at the upper end. By rotating this in the closing direction, the container lid 30 descends. At this time, in the tightening process when forming the screw 15a on the container lid shell 1 to form the container lid 30, the container lid rotates concentrically because it is rotated in the closing direction while being squeezed using a tool, but in resealing, the container lid 30 is simply gripped and rotated by hand, so it rotates slightly eccentrically. For this reason, as shown in FIG. 5(b), the portion A slightly removed from the annular seal portion 5c of the liner 5, i.e., the inclined step portion 5e, comes into contact with the curled portion 51 (the upper end of the container mouth 50) first.

[0035] In this way, when the step 5e first comes into contact with the curled portion 51, the compressive stress applied to the liner 5 at this contact point A is dispersed. The inclined step portion 5e is inclined downward toward the outside in the radial direction, and therefore not only is the thin-walled peripheral edge portion 5d separated from the curled portion 51 and becoming a free end, but the thickness of the liner 5 gradually decreases outside this contact point A, making it easier to disperse the compressive stress. Therefore, a typical consumer performing resealing will continue to rotate in the closing direction without feeling any significant resistance, and eventually, as shown in Figure 5(c), the curled portion 51 at the upper end of the container mouth 50 will bite deeply into the annular seal portion 5c of the liner 5, ensuring a good seal.

[0036] On the other hand, in the liner 5 without the inclined step portion 5e as shown in Figure 3(b) and Figure 4(b), as shown in Figure 5(b'), the initial contact point A is not a part where the liner thickness gradually decreases, so the stress on the liner 5 is not sufficiently distributed and a large resistance is applied. For this reason, general consumers stop rotating the cap in the closing direction, assuming that the cap is completely closed, even though the cap is not closed properly, resulting in poor sealing and leakage of the contents.

[0037] In this way, in the present invention, when resealing, the initial contact point A between the liner 5 and the upper end (curled portion 51) of the container mouth 50 is set to be the inclined step portion 5e, so that the capping operation can be reliably performed up to the capping completion position during resealing, ensuring airtightness.

[0038] 3 and 4, in the container lid (shell) 1 of the present invention, it is desirable that the outer peripheral end of the liner 5, i.e., the outer peripheral edge of the thin peripheral edge portion 5d, is located on the inner surface of the flat top wall 7, in other words, that this thin peripheral edge portion 5d does not extend to the inner surface of the bent portion 10 (see FIG. 3(a)). This is because, when the screw 15a is formed by the fastener, i.e., when the fixing tool presses the circular top wall 7 from above, the bent portion 10 is further squeezed and inflection points P and Q are formed (see FIG. 4(a)), and the deformation of the end portion of the liner 5 during this fastening becomes large, making it extremely difficult to set the inclined step portion 5e to be the first contact portion A during resealing.

[0039] In the present invention, the thickness of the annular seal portion 5c and the thin peripheral edge portion 5d of the liner 5 is not particularly limited as long as the stress dispersion at the inclined step portion 5e is effectively generated, but in order to ensure that the inclined step portion 5e becomes the first contact portion A, it is preferable to set the thickness difference between them (the height of the step 5e) to 0.15 mm or more and 0.35 mm or less. If this thickness difference is small, the surface of the thin peripheral edge portion 5d will come into contact with the inclined step portion 5e during resealing, and the step 5e will not become the first contact portion A. That is, in this case, although the thin peripheral edge portion 5d acts as a guide and the rotation in the closing direction becomes concentric as in Patent Document 2, the stress dispersion effect is almost lost. Also, if this thickness difference is excessively large, the thickness unevenness will become large, and molding defects will be easily caused. Furthermore, the inclination angle of the inclined step portion 5e is preferably 10 to 50 degrees. If the inclination angle is less than 10 degrees, the thickness difference between the annular seal portion 5c and the thin peripheral edge portion 5d cannot be ensured, and as described above, the inclined step portion 5e comes into contact with the surface of the thin peripheral edge portion 5d. If the inclination angle exceeds 50 degrees, after the cap is tightened around the mouth of the container, the inclined step portion 5e becomes thicker toward the inner diameter. During resealing, when the cap first comes into contact with the curled portion 51 and the capping operation is further advanced, a force is applied to the corner portion formed by the inclined step portion 5e and the seal portion 5c to overcome the curled portion 51, which increases the capping resistance and may cause the capping operation to be stopped before completion of the capping operation. EXAMPLES

[0040] <Evaluation materials and methods> A metal cap with a nominal diameter of 38 mm and a metal container with a nominal diameter of 38 mm and a capacity of 300 ml are used. A metal bottle was filled with 300 ml of liquid with a product temperature of 5 degrees and a gas volume of 3.6 vol, and then a metal cap was placed on top and rolled up to resemble the state shown in Figure 2. The rolled container was showered at 30°C for 8 minutes. After the shower treatment, the bottles were stored in a cold room at 5 degrees for one week, and the reseal torque (the torque required to complete sealing) of five bottles was measured and the average values ​​were compared. Pass criteria: Reseal torque is 30 N·cm or less and there are no problems with formability.

[0041] <Example 1> Outer diameter of curled part 51: φ33.5mm Outer diameter of seal part 5c: φ34.3mm Thickness of seal part 5c: 0.8mm Thickness of thin peripheral edge 5d: 0.6 mm Angle of inclined step portion 5e: 40 degrees Reseal torque: 19N cm There is no problem with formability.

[0042] <Example 2> Outer diameter of curled part 51: φ33.5mm Outer diameter of seal part 5c: φ34.4mm Thickness of seal part 5c: 0.8mm Thickness of thin peripheral edge 5d: 0.6 mm Angle of inclined step portion 5e: 15 degrees Reseal torque: 21N cm There is no problem with formability.

[0043] <Example 3> Outer diameter of curled part 51: φ33.5mm Outer diameter of seal part 5c: φ34.4mm Thickness of seal part 5c: 0.8mm Thickness of thin peripheral edge 5d: 0.5 mm Angle of inclined step portion 5e: 40 degrees Reseal torque: 20N cm There is no problem with formability.

[0044] <Comparative Example 1 (conventional product, no step)> Outer diameter of curled part 51: φ33.5mm Outer diameter of seal part 5c: φ34.4mm Thickness of seal part 5c: 0.8mm Thickness of thin peripheral edge 5d: 0.8 mm Inclined step portion 5e: None Reseal torque: 31N cm There is no problem with formability.

[0045] <Comparative Example 2> Outer diameter of curled part 51: φ33.5mm Outer diameter of seal part 5c: φ34.4mm Thickness of seal part 5c: 0.8mm Thickness of thin peripheral edge 5d: 0.4 mm Angle of inclined step portion 5e: 40 degrees Reseal torque: 20N cm In terms of moldability, uneven thickness occurred in the liner, so the evaluation was poor.

[0046] Because the metal container lid of the present invention maintains good sealing properties during resealing, it is suitable for use as a lid to be attached to the mouth of a container from which the contents are not discharged all at once but in multiple batches, such as a medium- or large-capacity container with a content of 200 ml or more. [Explanation of symbols]

[0047] 1: Metal container lid precursor 3: Metal shell 5: Synthetic resin liner 5a: Circular extremely thin section 5b: Ring-shaped protrusion 5c: Annular seal part 5d: Thin circumferential edge 5e: Inclined step part 7:Circular top wall P,Q: point of inflection 9: Skirt wall 10: Bend 11: Bridge 13: Tamper evident (TE) hem 15: Screw formation area 15a: Screw 17: Annular groove 30: Metal cap 50: Container mouth 51: Curl part (upper end of container mouth) 52:Outer wall 53: Spiral 55: Container jaw A: First contact point B: void

Claims

1. A metal container lid having a metal shell consisting of a circular top wall and a cylindrical skirt wall descending from the periphery of the circular top wall, and a synthetic resin liner disposed on the inner surface of the circular top wall, The synthetic resin liner has an annular seal portion and a thin-walled peripheral edge portion located outside the annular seal portion and thinner than the annular seal portion, and an inclined step portion is present between the annular seal portion and the thin-walled peripheral edge portion according to the difference in thickness between the annular seal portion and the thin-walled peripheral edge portion, The outer diameter of the annular seal portion before the metal shell is fastened to the container mouth portion to form a screw is set to be larger than the outer diameter D of the container mouth portion, By tightening the metal shell onto the container mouth, the cylindrical skirt wall is formed with threads that engage with threads formed on the outer surface of the container mouth, When the metal shell is wrapped around the container mouth, the outer peripheral end of the annular seal is in close contact with the outer peripheral wall of the container mouth, but the thin peripheral edge and the inclined step of the synthetic resin liner are spaced apart from the outer peripheral wall of the container mouth, and the inclined step of the synthetic resin liner is inclined downward in the radially outward direction. A metal container lid, characterized in that, at the time of resealing, the inclined step portion of the synthetic resin liner is first brought into contact with the upper end surface of the mouth of the container.

2. A metal container lid as described in claim 1, wherein, before the metal shell is wrapped around the container mouth and a screw is formed, the outer peripheral end of the thin-walled peripheral edge portion of the synthetic resin liner is located in a flat area on the inner surface of the circular top wall.

3. 3. The metal container lid according to claim 1 or 2, wherein when resealing, as the metal container lid placed over the container mouth is rotated in the closing direction, the upper end surface of the container mouth comes into contact with the inclined step portion of the synthetic resin liner, but the thin peripheral edge portion of the synthetic resin liner is kept away from the outer peripheral wall of the container mouth while being resealed.

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