Synthetic resin container lid

Abstract

To provide a new synthetic resin-made container lid which can reduce a used amount of a material while maintaining sufficient rigidity of engagement means 32.SOLUTION: An inner peripheral edge of a main part 34 of engagement means 32 is continuous in a circumferential direction in parallel with an inner peripheral surface of a tamper-evident skirt part 18, and a plurality of lightened parts 44 are formed on not only a fitting upper surface 40 of the main part 34 but also a lower surface 42 thereof at intervals in the circumferential direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a synthetic resin container lid.

[0002] The present invention relates to a synthetic resin container lid in which a locking means consisting of a plurality of locking protrusions extending circumferentially or an annular locking ridge extending continuously circumferentially is formed on the inner surface of the tamper-evident bottom portion of the skirt wall. [Background technology]

[0003] As is well known, a widely used container closure for a container made of glass, synthetic resin, or sheet metal has a cylindrical neck portion on the outer periphery of which a male thread is disposed and a locking jaw located below the male thread. The container closure has a circular top wall and a cylindrical skirt wall depending from the periphery of the top wall, and the skirt wall is formed with a circumferentially extending fracture line consisting of circumferentially extending slits spaced apart along the periphery and bridging portions between the slits. The skirt wall is divided into a main skirt portion above the fracture line and a tamper-evident skirt portion below the fracture line. An internal thread is formed on the inner periphery of the main skirt portion, and a locking means is formed on the inner periphery of the tamper-evident skirt portion. The locking means consists of a plurality of locking projections projecting radially inward and extending circumferentially, or an annular locking ridge projecting radially inward and extending continuously circumferentially. The upper surface of the main part of the locking means is provided with a fitting upper surface whose inner diameter gradually increases upward and which is connected to the inner peripheral surface of the tamper-evident bottom part, and the lower surface of the main part of the locking means is inclined radially outward downward and is connected to the inner peripheral surface of the tamper-evident bottom part.

[0004] When sealing the neck of a container filled with contents, the container lid is fitted onto the neck and rotated in the closing direction, threading the female thread of the lid onto the male thread of the neck. When the container lid is thus attached to the neck as required, the locking means of the container lid elastically overcomes the locking jaw of the neck and is positioned below it. When the locking means elastically overcomes the locking jaw, the lower surface of the locking means is inclined downward and radially outward, allowing the tamper-evident skirt to be smoothly elastically deformed. When the neck is opened to consume the contents of the container, the container lid is rotated in the opening direction. As a result, the container lid is raised relative to the neck as the male thread and female thread are unscrewed. When the container lid is raised slightly, the locking means on the container lid locks into the locking jaws on the neck portion, thereby preventing the tamper-evident bottom from rising. When the locking means locks into the locking jaws, the locking means is firmly held to the locking jaws by the presence of the mating upper surface. When the container lid continues to rotate in the opening direction, the circumferential tear line formed in the skirt wall breaks, and the tamper-evident bottom is separated from the main skirt portion (or, if an axial tear line is formed in the tamper-evident bottom, the axial tear line breaks and the tamper-evident bottom is expanded from an endless ring shape into a band with ends, and the tamper-evident bottom remains connected to the main skirt portion along part of the circumferential direction without being completely separated from the main skirt portion). When the container lid continues to be rotated in the opening direction, the container lid (or the entire container lid including the tamper-evident skirt) is separated from the neck portion, leaving the tamper-evident skirt behind, and the neck portion is opened.

[0005] Recently, from the viewpoint of reducing environmental impact and manufacturing costs, there has been a demand for reducing the amount of material used to manufacture container lids. Patent Document 1 listed below discloses an example of a container lid in which the amount of material used is reduced by providing a plurality of lightening holes at intervals in the circumferential direction on the fitting upper surface of the locking means. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-70031 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, even in the container lid disclosed in Patent Document 1, the reduction in the amount of material used is insufficient, and further reduction is required.

[0008] However, providing a lightening portion in the locking means to reduce the amount of material used to form the locking means reduces the rigidity of the locking means, which can lead to the following problems. First, when the container lid is released from the molding die, the locking means protruding radially inward is forcibly removed from the molding die. Therefore, if the locking means has low rigidity, the locking means may suffer from molding defects such as sagging. Second, when the neck portion is opened, the locking means must be engaged with the locking jaws of the neck portion to reliably prevent the tamper-evident bottom from rising. Therefore, if the locking means has low rigidity, the locking means may elastically deform and slip over the locking jaws, resulting in a slip-out. Therefore, even if the amount of material used to form the locking means is reduced by providing a lightening portion in the locking means, the locking means must maintain sufficient rigidity.

[0009] The present invention was made in consideration of the above facts, and its main technical objective is to provide a new and improved synthetic resin container lid that can further reduce the amount of material used compared to the container lid disclosed in Patent Document 1 while maintaining sufficient rigidity of the locking means. [Means for solving the problem]

[0010] After extensive research, the inventors discovered that the above-mentioned main technical problem can be solved by making the inner peripheral edge of the main part of the locking means continuous in the circumferential direction parallel to the inner peripheral surface of the tamper-evident bottom part, and by forming multiple lightening portions at intervals in the circumferential direction not only on the upper mating surface but also on the lower mating surface of the main part.

[0011] That is, according to the present invention, a synthetic resin container closure that solves the above-mentioned main technical problem comprises a circular top wall and a cylindrical skirt wall hanging down from the periphery of the top wall, the skirt wall having a circumferentially extending fracture line formed thereon, the circumferentially extending fracture line being made up of a plurality of circumferentially extending slits spaced apart in the circumferential direction and a plurality of bridging portions existing between the slits, the skirt wall being divided into a main skirt portion above the fracture line and a tamper-evident skirt portion below the fracture line, and the inner peripheral surface of the main skirt portion having a female a threaded rib is formed, and a locking means is arranged on the inner peripheral surface of the tamper-evident bottom portion, the locking means consisting of a plurality of locking projections that protrude radially inward and extend circumferentially or an annular locking ridge that protrudes radially inward and extends continuously circumferentially, the upper surface of the main part of the locking means is provided with a fitting upper surface whose inner diameter gradually increases upward and which is connected to the inner peripheral surface of the tamper-evident bottom portion, and the lower surface of the main part is inclined radially outward and downward and is connected to the inner peripheral surface of the tamper-evident bottom portion, The inner peripheral edge of the main portion is continuous in the circumferential direction parallel to the inner peripheral surface of the tamper-evident bottom portion, and a plurality of recesses are formed at intervals in the circumferential direction on the upper and lower mating surfaces of the main portion.

[0012] Preferably, the circumferential width and number of the lightening holes formed on the upper fitting surface are equal to the circumferential width and number of the lightening holes formed on the lower surface, and the lightening holes formed on the upper fitting surface and the lower surface are aligned in the circumferential direction. Furthermore, the circumferential centers of the lightening holes formed on the upper fitting surface and the lower surface may be alternately positioned in the circumferential direction. When the locking means is composed of a plurality of locking protrusions, the inner peripheral edges of both circumferential end portions of the locking protrusions preferably slope radially outward from the circumferential end of the inner peripheral edge of the main portion toward the outside in the circumferential direction and connect to the inner peripheral surface of the tamper-evident hem. In this case, the upper surfaces of the end portions preferably have upper reinforcement portions whose inner diameters gradually increase upward and which are connected to the inner peripheral surface of the tamper-evident hem. Furthermore, a lower reinforcing portion may be provided on the lower surface of the end portion, the inner diameter of which gradually increases downward and which is connected to the inner peripheral surface of the tamper-evident bottom portion. [Effects of the Invention]

[0013] According to the present invention, multiple recesses are formed not only on the upper mating surface but also on the lower surface of the main portion of the locking means, allowing the container closure to be manufactured using less material. Furthermore, according to the present invention, the inner peripheral edge of the main portion of the locking means is circumferentially continuous and parallel to the inner peripheral surface of the tamper-evident bottom portion. Therefore, when the locking means is forcibly removed from the molding die during the process of releasing the container closure from the molding die, the entire inner peripheral edge of the main portion of the locking means abuts against the molding die. When the locking means is engaged with the locking jaws during the process of opening the neck portion, the entire upper surface of the inner peripheral edge of the main portion of the locking means abuts against the lower surface of the locking jaws. Therefore, the locking means is less likely to deform, i.e., the locking means has sufficient rigidity. Therefore, despite the container closure of the present invention being manufactured using less material, the rigidity of the locking means is maintained sufficiently, preventing deformation of the tamper-evident bottom portion even when an external force is applied to the locking means. Furthermore, in the present invention, multiple recesses are provided on the upper and lower surfaces of the locking means, thereby increasing the surface area of ​​the locking means, thereby reducing the difference in cooling rate between the upper and lower surfaces of the locking means and enabling the container lid to be cooled efficiently after molding, resulting in improved manufacturing efficiency. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a view showing a preferred embodiment of a synthetic resin container lid constructed according to the present invention, partially in cross section; [Figure 2] FIG. 2 is a bottom view of the container lid shown in FIG. 1. [Figure 3] 2 is a partially enlarged view of the container lid shown in FIG. 1 and the neck of the container to which it is attached. FIG. [Figure 4] 2 is a developed view of the inner peripheral surface of the tamper-evident bottom portion of the container lid shown in FIG. 1. [Figure 5] FIG. 2 is a developed view showing the inner peripheral surface of the tamper-evident bottom portion in a first modified example of a container lid configured according to the present invention. [Figure 6] FIG. 10 is a developed view showing the inner peripheral surface of the tamper-evident bottom portion in a second modified example of a container lid configured according to the present invention. [Figure 7]FIG. 10 is a developed view showing the inner peripheral surface of the tamper-evident bottom portion in a third modified example of a container lid configured according to the present invention. [Figure 8] FIG. 10 is a developed view showing the inner peripheral surface of the tamper-evident bottom portion in a fourth modified example of a container lid constructed according to the present invention. [Figure 9] FIG. 10 is a developed view showing the inner peripheral surface of the tamper-evident bottom portion in a fifth modified example of a container lid constructed according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in more detail with reference to the accompanying drawings showing preferred embodiments of a synthetic resin container lid constructed according to the present invention.

[0016] 1 and 2, a container lid 2, which can be injection molded or compression molded from a suitable synthetic resin such as polyethylene or polypropylene, has a circular top wall 4 and a cylindrical skirt wall 6 depending from the periphery of the top wall 4. A relatively long cylindrical inner seal piece 8 and a relatively short cylindrical outer seal piece 10 depending downward are formed on the inner peripheral edge of the top wall 4. An annular minute rib 12 is also formed between the inner seal piece 8 and the outer seal piece, protruding slightly downward from the inner surface of the top wall 4.

[0017] A circumferentially extending fracture line 14 is formed in the skirt wall 6, and the skirt wall 6 is divided into a main skirt portion 16 above the fracture line 14 and a tamper-evident hem portion 18 below the fracture line 14. The fracture line 14 is composed of a plurality of circumferentially extending slits (kerfs) 20 spaced apart in the circumferential direction and a plurality of bridging portions 22 present between the slits 20, and the tamper-evident hem portion 18 is connected to the main skirt portion 16 via the plurality of bridging portions 22.

[0018] Anti-slip knurling 24 consisting of concave and convex shapes that are alternately arranged in the circumferential direction is formed on the outer peripheral surface of the skirt main portion 16. An internal thread 26 is formed on the inner peripheral surface of the skirt main portion 16 of the skirt wall 6. The internal thread 26 has a plurality of notches 28 spaced apart in the circumferential direction.

[0019] 1 and 2 as well as 3 and 4, a locking means is disposed on the inner peripheral surface of the tamper-evident hem 18. In the illustrated embodiment, the locking means is composed of a plurality of (five in the illustrated embodiment) locking protrusions 32 that protrude radially inward and extend circumferentially. The locking protrusions 32 are divided into a main portion 34 whose inner peripheral edge continues circumferentially in parallel with the inner peripheral surface of the tamper-evident hem 18, and end portions 36 located on both circumferential sides of the main portion 34, whose inner peripheral edges are inclined radially outward from the circumferential end of the inner peripheral edge of the main portion 34 toward the outside in the circumferential direction and connected to the inner peripheral surface of the tamper-evident hem 18. As shown in FIG. 3 , the upper surface of the main portion 34 of the locking projection 32 is divided into an upper locking surface 38 located radially inward and extending substantially horizontally, and an upper mating surface 40 located radially outward, with an inner diameter gradually increasing upward and connected to the inner peripheral surface of the tamper-evident hem portion 18. In the illustrated embodiment, the vertical cross-sectional shape of the upper mating surface 40 extends linearly upward and then slopes radially outward. Meanwhile, the lower surface 42 of the main portion 34 of the locking projection 32 slopes radially outward and downward to connect to the inner peripheral surface of the tamper-evident hem portion 18. As can be understood by referring to FIGS. 1 and 4 , a plurality of recesses 44 are formed at circumferential intervals on each of the upper mating surface 40 and the lower mating surface 42 of the main portion 34. The recessed portions 44 are formed by cutting out the upper and lower mating surfaces 40 and 42 so as to expose the inner circumferential surface of the tamper-evident bottom 18. A circumferentially extending protrusion 46 remains at the corners of the recessed portions 44 formed on the upper mating surface 40. The vertical cross-sectional shape of the protrusion 46 is concave arc-shaped, and its radially inner edge is continuously connected to the radially outer edge of the upper locking surface 38. The concave arc-shaped vertical cross-sectional shape of the protrusion 46 reduces the removal resistance when the container lid 2 is removed from the molding die, thereby preventing deformation of the locking projection 32. Meanwhile, the lower surface of the cutout portion of the lower surface 42 is substantially horizontal. Referring to FIG. 4 , in the illustrated embodiment, the upper mating surface 40 and the lower surface 42 each have four recessed portions 44.The cutouts 44 all have the same circumferential width, and are spaced equally apart in the circumferential direction. Therefore, in the illustrated embodiment, the cutouts 44 formed on the upper mating surface 40 and the lower mating surface 42 are aligned in the circumferential direction. The circumferential width of each cutout 44 is greater than the circumferential width of a remaining portion 50 between two adjacent cutouts 44, and the remaining portion 50 is rib-shaped. The upper surface of the end 36 of the locking projection 32 is provided with an upper reinforcing portion 52a whose inner diameter gradually increases upward and which is connected to the inner circumferential surface of the tamper-evident bottom portion 18. The upper reinforcing portion 52a is not cut out. The lower surface of the end 36 is provided with a lower reinforcing portion 52b whose inner diameter gradually increases downward and which is connected to the inner circumferential surface of the tamper-evident bottom portion 18. The lower reinforcing portion 52b is also not cut out. In the illustrated embodiment, the inner diameter of the lower reinforcing portion 52b gradually increases in the radial direction away from the main portion 34. The lower edge of the lower surface of the end portion 36 is gradually inclined upward toward the circumferential outside. The inner peripheral surface of the tamper-evident bottom portion 18 is also formed with a ridge 54 that extends continuously in the circumferential direction between two locking projections 32 that are arranged adjacent to each other in the circumferential direction. The cross-sectional shape and vertical height position of the ridge 54 are the same as those of the ridge 46, and both circumferential ends of the ridge 54 are connected to the circumferential end faces of the locking projections 32, respectively.

[0020] In Figure 1, the neck 100 of the container is shown by a two-dot chain line along with the container lid 2. The neck 100 of the container, which can be formed from a suitable synthetic resin such as polyethylene terephthalate, glass, or thin metal plate, is generally cylindrical in shape, and the outer circumferential surface of the neck 100 is formed with a male thread 102 and a locking jaw 104 located below the male thread 102. The locking jaw 104 has an arcuate upper surface whose outer diameter gradually increases downward, a cylindrical outer circumferential surface, and a lower surface that extends substantially horizontally. A support ring 106 (such a support ring 106 is used for transporting the container, as is well known to those skilled in the art) located below the locking jaw 104 is also arranged on the outer circumferential surface of the neck 100.

[0021] After the contents are filled into the container, the container lid 2 is fitted onto the mouth and neck portion 100 and the container lid 2 is rotated in the closing direction, i.e., clockwise as viewed from above in Fig. 1, so that the female thread 26 of the container lid 2 is threaded onto the male thread 102 of the mouth and neck portion 100. When the female thread 26 is threaded onto the male thread 102 to the state shown in Fig. 1, the inner seal piece 8 of the container lid 2 enters the mouth and neck portion 100 and is in close contact with the inner circumferential surface of the mouth and neck portion 100, the outer seal piece 10 is in close contact with or adjacent to the outer circumferential surface of the mouth and neck portion 100, and the annular minute ridge 12 is in close contact with the top surface of the mouth and neck portion 100, thus sealing the mouth and neck portion 100. The locking protrusion 32 disposed on the inner peripheral surface of the tamper-evident skirt 18 elastically overcomes the locking jaw 104 of the mouth and neck part 100 (i.e., by elastic deformation or displacement of the tamper-evident skirt 18) and is positioned below the locking jaw 104. When the locking protrusion 32 elastically overcomes the locking jaw 104 of the mouth and neck part 100, the lower surface 42 of the locking protrusion 32 is inclined downward and radially outward, which allows the tamper-evident skirt 18 to be smoothly elastically deformed. In this state, as can be understood by referring to Figures 3 together with Figure 1, the fitting upper surface 40 of the locking protrusion 32 is in contact with or closely fitted to the lower end of the outer peripheral surface of the locking jaw 104 of the mouth and neck part 100.

[0022] When opening the neck / mouth portion 100 to consume the contents, the container lid 2 is rotated in the opening direction, i.e., counterclockwise as viewed from above in Fig. 1. This gradually disengages the male thread 102 from the female thread 26, and the tamper-evident skirt portion 18 together with the skirt main portion 16 is raised relative to the neck / mouth portion 100 as the container lid 2 is rotated. At this time, as can be seen from Fig. 2, the upper mating surface 40 of the locking projection 32 on the tamper-evident skirt portion 18 is brought into close contact with the lower end of the outer circumferential surface of the locking jaw portion 104 of the neck / mouth portion 100, gradually increasing the resistance torque due to friction. When the container lid 2 is raised relative to the neck portion 100 by a predetermined amount, the upper locking surface 38 of the locking projection 32 locks against the lower surface of the locking jaw 104, preventing the tamper-evident hem 18 from moving upward in the axial direction. At this time, the upper mating surface 40 of the locking projection 32 is also in close contact with the lower end of the outer circumferential surface of the locking jaw 104 of the neck portion 100, so that the tamper-evident hem 18 is held by the locking jaw 104. Then, because the tamper-evident hem 18 is prevented from moving upward in the axial direction, stress is generated in the bridging portion 22 of the break line 14, causing the bridging portion 22 to break, and the tamper-evident hem 18 is separated from the main skirt portion 16. After the break line 14 is broken, the top wall 4 of the container lid 2 and the main skirt portion 16 of the skirt wall 6 are rotated and freely moved upward in the axial direction to separate from the neck portion 100, leaving the tamper-evident bottom portion 18 in place, thereby opening the neck portion 100. If desired, an axial break line can be formed in the tamper-evident bottom portion 18, so that when the neck portion 100 of the container is opened, the axial break line is broken, while a portion of the circumferentially extending break line 14 remains unbroken, causing the tamper-evident bottom portion 18 to expand from an endless annular shape into an ended annular shape, and the entire container lid 2 together with the tamper-evident bottom portion 18 can be separated from the neck portion 100.

[0023] According to the present invention, a plurality of lightening portions 44 are formed not only on the upper fitting surface 40 but also on the lower surface 42 of the main portion 34 of the locking projection 32, allowing the container lid to be manufactured using less material. Furthermore, in the present invention, the inner peripheral edge of the main portion 34 of the locking projection 32 is circumferentially continuous and parallel to the inner peripheral surface of the tamper-evident bottom portion 18, so that when the locking projection 32 is forcibly removed from the molding die in the process of releasing the container lid from the molding die, the entire inner peripheral edge of the main portion 34 of the locking projection 32 abuts against the molding die, and when the locking projection 32 is engaged with the locking jaw portion 104 in the process of opening the neck portion 100, the entire upper surface of the inner peripheral edge of the main portion 34 of the locking projection 32 abuts against the lower surface of the locking jaw portion 104, so that the locking projection 32 is less likely to deform, i.e., the locking projection 32 has sufficient rigidity. Therefore, the container lid of the present invention can be manufactured using less material, yet the rigidity of the locking protrusion 32 is maintained sufficiently, preventing deformation of the tamper-evident bottom portion 18 even when an external force is applied to the locking protrusion 32. Furthermore, in the present invention, the locking protrusion 32 has a plurality of recesses 44 on each of its upper and lower surfaces, thereby increasing the surface area of ​​the locking protrusion 32. This reduces the difference in cooling rate between the upper and lower surfaces of the locking protrusion 32 and enables the container lid to be efficiently cooled after molding, improving manufacturing efficiency. Furthermore, the rigidity of the locking protrusion 32 is maintained satisfactorily by providing an upper reinforcing portion 52a on the upper surface of the end 36 of the locking protrusion 32 and a lower reinforcing portion 52b on the lower surface.

[0024] In the above-described embodiment, the circumferential width and number of the lightening holes 44 formed on the upper fitting surface 40 of the locking projection 32 are equal to the circumferential width and number of the lightening holes 44 formed on the lower surface 42, and the lightening holes 44 formed on the upper fitting surface 40 and the lower surface 42 are aligned in the circumferential direction, but as in the modified examples shown in Figures 5 to 8, the circumferential width, number, and circumferential positions of the lightening holes formed on the upper fitting surface and the lower surface may be changed as appropriate. In the following description, the same parts as in the above-described embodiment are designated by the same numbers with the addition of letters a to e in the first to fourth modified examples, respectively.

[0025] In the first modified example shown in Figure 5, the number of cutouts 44a formed on the upper mating surface 40a of the locking projection 32a is equal to the number of cutouts 44a formed on the lower surface 42a, but the circumferential width of the cutouts 44a formed on the upper mating surface 40a is slightly wider than the circumferential width of the cutouts 44a formed on the lower surface 42a, and the circumferential center positions of the cutouts 44a formed on the upper mating surface 40a and the cutouts 44a formed on the lower surface 42a are arranged alternately in the circumferential direction with respect to the circumferential center position.

[0026] 6, the number of lightening holes 44b formed on the upper fitting surface 40b of the locking projection 32b is equal to the number of lightening holes 44b formed on the lower surface 42b, but the circumferential width of the lightening holes 44b formed on the upper fitting surface 40b is slightly narrower than the circumferential width of the lightening holes 44b formed on the lower surface 42b. In this modification, the circumferential width of the remaining portions 50b left on the upper fitting surface 40b is wider than the circumferential width of the remaining portions 50b left on the lower surface 42b, and the circumferential center positions of the remaining portions 50b left on the upper fitting surface 40b and the circumferential center positions of the remaining portions 50b left on the lower surface 42b are aligned in the circumferential direction.

[0027] 7, the number of lightening holes 44c formed on the upper fitting surface 40c of the locking projection 32c is four, while the number of lightening holes 44c formed on the lower surface 42c is three, and the circumferential width of the lightening holes 44c formed on the upper fitting surface 40c is wider than the circumferential width of the lightening holes 44c formed on the lower surface 42c. In this modification, the circumferential width and circumferential center position of the remaining portion 50c left on the upper fitting surface 40c correspond to the circumferential width and circumferential center position of the lightening holes 44c formed on the lower surface 42c.

[0028] In the fourth modified example shown in Figure 8, the number of cutouts 44d formed on the upper mating surface 40d of the locking projection 32d is four, while the number of cutouts 44d formed on the lower surface 42d is three. However, the circumferential width of the cutouts 44d formed on the upper mating surface 40d is approximately the same as the circumferential width of the cutouts 44c formed on the lower surface 42d, the circumferential width of the remaining portions 50d left on the upper mating surface 40d is approximately the same as the circumferential width of the remaining portions 50d left on the lower surface 42d, and the circumferential center positions of the remaining portions 50d left on the upper mating surface 40c and the circumferential center positions of the cutouts 44d formed on the lower surface 42d are aligned.

[0029] For example, as in the third and fourth modified examples, when the cutouts 44c, 44d formed on the mating upper surfaces 40c, 40d and the cutouts 44c, 44d formed on the lower surfaces 42c, 42d are arranged alternately in the circumferential direction, it is possible to avoid as much as possible the cutouts being formed at the same circumferential position on both the mating upper surfaces 40c, 40d and the lower surfaces 42c, 42d, and therefore the rigidity of the locking protrusions 32c, 32d is further improved compared to the rigidity of the locking protrusions 32 in the embodiment shown in Figures 1 to 3.

[0030] Furthermore, in all of the above-described embodiments, the locking means is composed of a plurality of locking projections that protrude radially inward and extend circumferentially, but as in the fifth modified example shown in Fig. 9, the locking means may be composed of a single annular locking rib 32e that protrudes radially inward and extends continuously circumferentially. When the locking means is composed of the annular locking rib 32e, the entire annular locking rib 32e serves as the main portion 34e of the locking means. In this case, too, the number, circumferential width, and circumferential position of the lightening holes 44e formed on each of the upper and lower mating surfaces 40e, 42e may be changed as appropriate.

[0031] While preferred embodiments of the container lid of the present invention have been described above in detail with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, and further modifications are possible within the scope of the present invention. For example, in the illustrated embodiment, the upper surface of the locking means includes a substantially horizontally extending locking upper surface, as well as a mating upper surface whose inner diameter gradually increases upward and connects to the inner peripheral surface of the tamper-evident bottom portion. However, the locking upper surface may be omitted, and the entire upper surface of the locking means may serve as the mating upper surface. Furthermore, while the shape of the recessed portion 44 is rectangular in the examples and modifications, it may also be curved, such as connecting the upper ends of the remaining portions together in an arc shape (arch-shaped) when viewed circumferentially. [Explanation of symbols]

[0032] 2: Container lid 4: Top wall 6: Skirt wall 14: Break line 16: Main part of skirt 18: Tamper evident bottom 20: Slit 22: Bridge section 26:Female thread 32: Locking protrusion (locking means) 34: Main part (of the locking projection) 40: (Main part of the locking projection) fitting upper surface 42: Lower surface (of the main part of the locking projection) 44: Hollowed-out section

Claims

1. The device comprises a circular top wall and a cylindrical skirt wall hanging down from the periphery of the top wall, and the skirt wall has a circumferentially extending fracture line formed therein, the circumferentially extending fracture line being made up of a plurality of circumferentially extending slits spaced apart from one another and a plurality of bridging portions existing between the slits, the skirt wall being divided into a main skirt portion above the fracture line and a tamper-evident skirt portion below the fracture line, and a female thread is formed on the inner peripheral surface of the main skirt portion, and the tamper-evident skirt portion a locking means is disposed on the inner peripheral surface of the bottom portion, the locking means being composed of a plurality of locking projections that project radially inward and extend circumferentially, or an annular locking ridge that projects radially inward and extends continuously circumferentially, the upper surface of the main portion of the locking means is provided with a fitting upper surface whose inner diameter gradually increases upward and which is connected to the inner peripheral surface of the tamper-evident bottom portion, and the lower surface of the main portion is inclined radially outward downward and is connected to the inner peripheral surface of the tamper-evident bottom portion, A synthetic resin container lid characterized in that the inner peripheral edge of the main portion is continuous in the circumferential direction parallel to the inner peripheral surface of the tamper-evident bottom portion, and a plurality of recessed portions are formed at intervals in the circumferential direction on the mating upper and lower surfaces of the main portion.

2. 2. A synthetic resin container lid as described in claim 1, wherein the circumferential width and number of the cutouts formed on the upper engaging surface are equal to the circumferential width and number of the cutouts formed on the lower surface, and the cutouts formed on the upper engaging surface and the cutouts formed on the lower surface are aligned in the circumferential direction.

3. 2. The synthetic resin container lid according to claim 1, wherein the circumferential center positions of the recesses formed on the upper engaging surface and the circumferential center positions of the recesses formed on the lower engaging surface are alternately arranged in the circumferential direction.

4. A synthetic resin container lid as described in any one of claims 1 to 3, wherein when the locking means is composed of a plurality of locking protrusions, the inner peripheral edges of the ends on both sides of the circumferential direction of the locking protrusions are connected to the inner peripheral surface of the tamper-evident bottom portion, inclining radially outward from the circumferential end of the inner peripheral edge of the main portion toward the outside in the circumferential direction.

5. 5. The synthetic resin container lid according to claim 4, wherein an upper reinforcing portion is provided on the upper surface of the end portion, the inner diameter of which gradually increases upward and which is connected to the inner peripheral surface of the tamper-evident bottom portion.

6. 6. A synthetic resin container lid according to claim 4 or 5, wherein a lower reinforcing portion is provided on the lower surface of the end portion, the inner diameter of which gradually increases downward and which is connected to the inner peripheral surface of the tamper-evident bottom portion.

Images