Synthetic resin container lid

Abstract

To provide a novel synthetic resin container lid in which a locking piece 56 is prevented from being bent radially inward without being elastically locked to a locked piece 40 in a bending step.SOLUTION: A breakable bridge portion 74 is configured to include at least one inscribed bridge 74a that locally connects a lower surface of a skirt wall 48 and an inner surface of the locking piece 56.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a container lid having a lid body and a top cover connected to the lid body via hinge means and pivotable between a closed position covering the lid body and an open position exposing the lid body. [Background technology]

[0002] The following Patent Documents 1 and 2 disclose an example of a container lid including a lid body and a top cover connected to the lid body via a hinge mechanism and pivotable between a closed position that covers the top surface of the lid body and an open position that exposes the top surface of the lid body. The lid body includes a closing wall and a cylindrical mounting wall that hangs down from the periphery of the closing wall, and the top cover includes a top wall and a skirt wall that hangs down from the periphery of the top wall. The skirt wall is provided with a locking piece that extends downward via a breakable bridge, and the mounting wall is provided with a lockable piece. Such a container lid is molded with the top cover in an open position and completed through a bending process in which the top cover is rotated from the open position to the closed position. In this bending process, the top cover is pressed against the lid body with a required pressing force, causing the locking piece to elastically lock onto the lockable piece. When the top lid is pivoted from the closed position to the open position, the breakable bridge breaks and the locking piece separates from the skirt wall. The breakable bridge breaks and the locking piece separates from the skirt wall, clearly indicating to the lid body that the top lid has been opened. The breakable bridge connects the lower surface of the skirt wall to the upper surface of the locking piece in the container lid shown in Patent Document 1, and connects the lower end of the outer surface of the skirt wall to the upper end of the inner surface of the locking piece in the container lid shown in Patent Document 2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4916234 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-237463 Summary of the Invention [Problem to be solved by the invention]

[0004] The container lids disclosed in Patent Documents 1 and 2 have the following problem. In other words, in the bending process, the top lid is pressed against the lid body with a required pressing force, and when the pressing force is applied to the top lid, the locking pieces may be bent radially inward without elastically locking with the locked pieces. If the locking pieces are bent radially inward without elastically locking with the locked pieces, the bending process cannot be completed, resulting in a loss of yield.

[0005] 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 prevents the locking piece from bending radially inward without elastically locking with the lockable piece during the folding process. [Means for solving the problem]

[0006] After careful consideration, the inventors discovered that the above-mentioned main technical problem can be solved by configuring the breakable bridge portion to include at least one inscribed bridge that locally connects the underside of the skirt wall and the inner surface of the locking piece.

[0007] That is, according to the present invention, a synthetic resin container lid that solves the above-mentioned main technical problem comprises a lid body, and a top lid that is connected to the lid body via hinge means and can be rotated between a closed position that covers the top surface of the lid body and an open position that exposes the top surface of the lid body, The lid body has a closing wall and a cylindrical portion hanging down from the periphery of the closing wall. of the upper cover includes a mounting wall, a top wall, and a skirt wall depending from the periphery of the top wall; a locking piece extending downward via a breakable bridge portion is disposed on the skirt wall, and a lockable piece is disposed on the mounting wall, the locking piece is elastically locked to the lockable piece when the top lid is turned to the closed position, and the breakable bridge portion is broken to separate the locking piece from the skirt wall when the top lid is turned from the closed position to the open position, The breakable bridge portion includes at least one inscribed bridge that locally connects the lower surface of the skirt wall and the inner surface of the locking piece, thereby providing a synthetic resin container lid.

[0008] Preferably, the outer peripheral surface of the mounting wall is formed with a relief recess to avoid interference with the inscribed bridge when the upper cover is pivoted to the closed position. The lower end of the locking piece is preferably provided with a protrusion having a radially extending locking upper surface and an inclined lower surface that extends radially inwardly from the radially outer end of the locking upper surface. Preferably, the locking piece has a flange portion extending radially outward, and the radially outer end of the flange portion is located radially outward from the outer peripheral surface of the skirt wall. Preferably, the inner surface of the locking piece is located radially outward from the outer peripheral surface of the skirt wall. Preferably, the locked piece has a band-shaped main portion that extends circumferentially along the outer peripheral surface of the mounting wall and is spaced radially outward from the outer peripheral surface, and a guide surface that is inclined radially inwardly is provided on at least the inner peripheral edge portion of the upper surface of the band-shaped main portion. In this case, the band-shaped main portion has a radially extending lower engaged surface, which is preferably located below the guide surface and in the vertically intermediate portion of the band-shaped main portion. The breakable bridge preferably includes at least one circumscribing bridge locally connecting the lower end of the outer peripheral surface of the skirt wall and the upper surface of the locking piece. In this case, the inscribing bridge is preferably located at both circumscribing ends of the locking piece, and one circumscribing bridge is preferably located at the circumferential center of the locking piece. Preferably, the locking piece and the locked piece are respectively located on opposite sides of a diameter perpendicular to a diameter passing through the circumferential central angular position of the hinge means in a plan view. A removal region is preferably defined in the closing wall by an endless thin-walled breakable line, and a connecting post extending upward is disposed on the upper surface of the removal region, with a tension ring connected to the upper end of the connecting post. [Effects of the Invention]

[0009] In the synthetic resin container lid of the present invention, the breakable bridge portion includes at least one inscribed bridge that locally connects the lower surface of the skirt wall and the inner surface of the locking piece, and the locking piece is supported from the radially inner side by the inscribed bridge. Therefore, when the top lid is pressed with a required pressing force in the bending process, the locking piece is prevented from being bent radially inward without elastically locking with the locked piece, which reduces yield. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a plan view of a top cover of a synthetic resin container lid constructed in accordance with the present invention in an open position. [Figure 2] 2 is a bottom view of the container lid shown in FIG. 1 with the top lid in an open position. [Figure 3] FIG. 2 is a front view of the container lid shown in FIG. 1 with the top lid in an open position. [Figure 4] Cross section of line AA in Figure 1. [Figure 5] 2 is a left side view of the container lid shown in FIG. 1 with the top lid omitted in a state where the top lid is in an open position. FIG. [Figure 6] 2 is a right side view of the container lid shown in FIG. 1 with the top lid in the open position, with the lid body omitted. FIG. [Figure 7] 2 is an enlarged vertical cross-sectional view of a locking piece when the top cover of the container lid shown in FIG. 1 is in an open position. FIG. [Figure 8] 2 is an enlarged perspective view of an inscribed bridge of the container lid shown in FIG. 1 in a state where the top lid is in an open position. FIG. [Figure 9] 2 is an enlarged perspective view of the circumscribing bridge when the top cover of the container lid shown in FIG. 1 is in an open position. FIG. [Figure 10] FIG. 2 is a front view of the container lid shown in FIG. 1 with the top lid in a closed position. [Figure 11] 2 is a left side view of the container lid shown in FIG. 1 with the top lid in a closed position. [Figure 12] Cross section of line AA in Figure 10. [Figure 13] 2 is a front view of the container lid shown in FIG. 1 with the top lid pivoted from the closed position to the open position. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in more detail below with reference to the accompanying drawings showing preferred embodiments of a synthetic resin container lid. Unless otherwise specified, the up-down direction in this specification is based on the state in which the lid is in the closed position (described later). Therefore, when the lid is in the open position (described later), the up-down direction is reversed.

[0012] Referring to Figures 1 to 4, the synthetic resin container lid, generally designated by the number 2, comprises a lid body 4 and a top lid 6, and the lid body 4 and the top lid 6 are connected via hinge means 8.

[0013] 1 to 3 as well as FIG. 4, the lid body 4 includes a circular closing wall 10 in plan view and a cylindrical mounting wall 12 that hangs down from the periphery of the closing wall 10. The closing wall 10 is divided into a central portion 14 that is shaped like a downwardly concave bowl and a substantially annular outer peripheral portion 16 that surrounds the central portion 14. The central portion 14 is positioned slightly offset from the center of the closing wall 10 on the opposite side of the diameter from the hinge means 8. A removal area 20 is defined in the central portion 14 of the closing wall 10 by an endless thin-wall breakable line 18. The endless thin-wall breakable line 18 is composed of a so-called score formed by locally reducing the thickness of the closing wall 10. A connecting post 22 extending upward is disposed on the upper surface of the removal area 20, and a tension ring 24 is connected to the upper end of the connecting post 22. A cylindrical pouring guide wall 26 is formed at the boundary between the central portion 14 and the outer peripheral portion 16, extending upward from the upper surface of the closing wall 10. The extending end, i.e., the upper end, of the pouring guide wall 26 is curved radially outward and has a lip shape. A cylindrical engagement wall 28 extending upward and radially outward is provided on the upper surface of the outer peripheral portion 16, more specifically, on the outer peripheral edge of the upper surface of the closing wall 10, and an engagement ridge 30 projecting radially outward is formed at the upper end of the outer peripheral surface of the engagement wall 28. A substantially cylindrical sealing wall 32 hanging downward is formed on the lower surface of the outer peripheral portion 16.

[0014] A locking means 34 is disposed on the lower end of the inner peripheral surface of the mounting wall 12. In the illustrated embodiment, as shown in FIG. 2, the locking means 34 is configured as a plurality of (six in the illustrated embodiment) arcuate ridges extending circumferentially at circumferential intervals. If desired, the locking means can also be configured as a continuous annular ridge extending circumferentially. As can be understood by referring to FIGS. 1 and 5 in addition to FIG. 4, an arcuate notch 36 is formed in the upper part of the outer peripheral surface of the mounting wall 12 on the diametrically opposite side from the hinge means 8, and a shallow arcuate recess 38 is also formed below the notch 36. A locking piece 40 is also disposed at a required position on the outer peripheral surface of the mounting wall 12. The locking piece 40 will be described later. As shown in Figure 1, the mounting wall 12 is provided with a known separation mechanism including a bottomed annular groove 42 with an open top and an axial slit 44 (see also Figures 3 and 4), which makes it possible to separate the container lid 2 from the mouth and neck of a container (described later) and discard it by performing the required operation after the container lid 2 has been attached to the mouth and neck of the container. For details of such a separation mechanism, see, for example, Japanese Patent No. 6326472, which was filed by the applicant of the present application prior to this application and has already been granted a patent. A cylindrical thin-walled wall 45 that hangs downward continuously in the circumferential direction is attached to the outer peripheral edge of the lower surface of the mounting wall 12.

[0015] Continuing the explanation with reference to Figures 1 to 3 as well as Figure 4, the top cover 6 includes a circular top wall 46 and a cylindrical skirt wall 48 depending from the periphery of the top wall 46. The lower end of the outer periphery of the skirt wall 48 is connected to the upper end of the outer periphery of the mounting wall 12 of the lid body 4 via hinge means 8, allowing the top cover 6 to freely pivot between a closed position in which it covers the upper surface of the closing wall 10 of the lid body 4 and an open position in which it exposes the upper surface of the closing wall 10 of the lid body 4. The lower surface of the top wall 46 is also formed with an inner cylindrical wall 50 and an outer cylindrical wall 52 depending downward, and two annular shallow grooves 54 are formed between the inner cylindrical wall 50 and the outer cylindrical wall 52. As shown in Figure 3, a downwardly extending locking piece 56 is disposed at a required position on the lower end of the outer periphery of the skirt wall 48. The locking piece 56 will be described later together with the lockable piece 40. 1 and 6 as well as Fig. 4, a flange 58 protruding radially outward is provided at the lower end of the outer peripheral surface of the skirt wall 48 on the diametrically opposite side of the hinge means 8, and a finger can be hooked on the flange 58 when pivoting the top cover 6 to open or close. A thin, arc-shaped protruding piece 60 protruding downward is formed at the diametrically opposite side of the lower surface of the skirt wall 48 from the hinge means 8. An annular engaged ridge 62 is provided at the lower end of the inner peripheral surface of the skirt wall 48. An annular abutting ridge 64 is also provided on the inner peripheral surface of the skirt wall 48 above the annular engaged ridge 62.

[0016] Next, the locking piece 40 disposed on the lid main body 4 and the locking piece 56 disposed on the top lid 6 will be described. In the illustrated embodiment, the locking piece 56 and the locking piece 40 are respectively provided on both sides in a diametric direction perpendicular to a diameter passing through the circumferential central angular position of the hinge means 8 in a plan view (i.e., FIG. 1). As can be understood by referring to FIGS. 1, 3, and 5, the locking piece 40 has a band-shaped main portion 66 that extends substantially horizontally in the circumferential direction along the outer circumferential surface of the mounting wall 12, spaced radially outward from the outer circumferential surface of the mounting wall 12, and a pair of connecting portions 68 that connect the inner circumferential surface of the band-shaped main portion 66 to the outer circumferential surface of the mounting wall 12 at both circumferential ends of the band-shaped main portion 66, and has a U-shape facing radially inward in a plan view. Referring to FIG. 12 together with FIG. 1, a guide surface 70 that slopes downward toward the radially inward direction is provided on at least the inner circumferential edge portion of the upper surface of the band-shaped main portion 66. In the illustrated embodiment, the inner peripheral edge of the entire upper surface of the U-shaped locking piece 40 is inclined downward toward the inside. A radially extending locking lower surface 72 is formed on the band-shaped main portion 66, and the locking lower surface 72 is provided below the guide surface 70 and in the vertical middle of the band-shaped main portion 66.

[0017] 1, 3, and 6, the locking pieces 56 are disposed on the skirt wall 48 via breakable bridge portions 74, and the lower ends of the locking pieces 56 are located below the lower end of the skirt wall 48. Also referring to FIG. 7, in the illustrated embodiment, the inner surfaces of the locking pieces 56 are located radially outward from the outer peripheral surface of the skirt wall 48, and a flange portion 76 extending radially outward is provided at the upper end of the locking pieces 56. Therefore, the radially outer end of the flange portion 76 is located radially outward from the outer peripheral surface of the skirt wall 48. If desired, the radially outer end of the flange portion 76 can be located radially inward from the outer peripheral surface of the skirt wall 48 by providing a groove penetrating vertically at a required position on the outer peripheral surface of the skirt wall 48 and arranging the locking pieces 56 in the groove. A protrusion 78 is provided at the lower end of the locking piece 56, and this protrusion 78 has an upper locking surface 80 that extends substantially horizontally in the radial direction, and an inclined lower surface 82 that extends downward and inward in the radial direction from the radially outer end of this upper locking surface 80. The circumferential width of the lower end of the locking piece 56, at least the protrusion 78, gradually decreases downward.

[0018] Explaining with reference to Figures 3, 4, and 6 to 9, it is important that in the container lid of the present invention, the breakable bridge portion 74 includes at least one inscribed bridge 74a that locally connects the lower surface of the skirt wall 48 and the inner surface of the locking piece 56. In the illustrated embodiment, one inscribed bridge 74a is disposed on each circumferential end of the locking piece 56. Due to the presence of the inscribed bridge 74a, a relief recess 84 is formed in the outer peripheral surface of the mounting wall 12, as shown in Figures 3 and 12, to avoid interference with the inscribed bridge 74a when the top cover 6 is pivoted to the closed position. The relief recess 84 is formed by locally reducing the outer diameter of the mounting wall 12 at the upper end of the outer peripheral surface of the mounting wall 12 in a required angular region including the circumferential angular region where the locking piece 40 is present, and the upper side of the relief recess 84 is open. In the illustrated embodiment, the breakable bridge portion 74 also includes at least one circumscribing bridge 74b that locally connects the outer peripheral surface of the lower end of the skirt wall 48 and the upper surface of the locking piece 56. One circumscribing bridge 74b is disposed at the circumferential center of the locking piece 56.

[0019] The above-described container lid 2 is formed by a molding machine with the top lid 6 in an open position relative to the lid body 4. After the formed container lid 2 is removed from the molding machine, it is completed through a folding process in which the top lid 6 is rotated from the open position to the closed position by a required folding machine. In the final stage of the folding process, the protrusion 78 of the locking piece 56 formed on the top lid 6 elastically overcomes the band-shaped main portion 66 of the locking piece 40 formed on the lid body 6, and thus the locking piece 56 is elastically locked to the locking piece 40. For details of the folding process, please refer to the description in the specification of Japanese Patent Application No. 2021-175414, filed by the applicant of the present application prior to this application.

[0020] Here, in the final stage of the bending process, the top cover 6 is pressed against the cover body 4 with a required pressing force by the bending machine, and when the pressing force is applied to the top cover 6, the locking pieces 56 may be bent radially inward without elastically locking with the locked pieces 40, resulting in a loss of yield. If the bottomed annular groove 42 is formed on the top surface of the mounting wall 12 as in the illustrated embodiment, there is also a risk that the locking pieces 56 may be bent radially inward and be guided into the bottomed annular groove 42. However, in the synthetic resin container lid of the present invention, the breakable bridge portion 74 includes at least one inscribed bridge 74a that locally connects the lower surface of the skirt wall 48 and the inner surface of the locking piece 56, and the locking piece 56 is supported from the radially inner side by the inscribed bridge 74a. Therefore, when the top lid 6 is pressed with a required pressing force in the bending process, the locking piece 56 is prevented from bending radially inward without elastically locking with the locked piece 40, which would reduce yield. In the illustrated embodiment, the breakable bridge portion 74 also includes a circumscribed bridge 74b, and the locking piece 56 is supported from the radially outer side by the circumscribed bridge 74b. Therefore, when the top lid 6 is pressed with a required pressing force in the bending process, the locking piece 56 is prevented from bending radially outward without elastically locking with the locked piece 40. Furthermore, in the illustrated embodiment, a guide surface 70 that slopes downward toward the radially inward direction is provided on at least the inner peripheral edge portion of the upper surface of the band-shaped main portion 66 of the engaging piece 40, which also prevents the engaging piece 56 from being bent radially outward.

[0021] When the top cover 6 is rotated to the closed position, as shown in Figure 12, the annular engaging protrusion 62 of the top cover 6 engages with the outer surface or underside of the engaging protrusion 30 of the cover body 4, the annular abutting protrusion 64 of the top cover 6 abuts against the upper surface of the engaging wall 28 of the cover body 4, the outer surface of the inner cylindrical wall 50 of the top cover 6 is brought into close contact with the inner surface of the pouring guide wall 26 of the cover body 4, and the thin-walled arc-shaped protrusion 60 of the top cover 6 is positioned in the notch 36 of the cover body 4, as shown in Figure 11.

[0022] 10 to 13 show, by two-dot chain lines, a container lid 2 constructed according to the present invention as well as the neck of a container to which the container lid 2 is applied. The neck 100 of the container, which can be formed from an appropriate synthetic resin or glass, is cylindrical with an open top, and has a locking ridge 102 formed on the upper end of its outer periphery. The neck 100 also has, on its outer periphery, a support ring 104 located below the locking ridge 102 (this support ring 104 is used when transporting the container).

[0023] When the container lid 2 is attached to the mouth and neck portion 100 to seal the mouth and neck portion 100 after the contents have been placed in the container, the container lid 2, more specifically the container lid 2 with the top lid 6 in the closed position relative to the lid body 4, is fitted over the mouth and neck portion 100 and forced downward, elastically deforming the mounting wall 12 of the lid body 4 so that the locking means 34 formed on the inner surface of the mounting wall 12 is locked below the locking protrusion 102 of the mouth and neck portion 100.

[0024] When the contents of the container are consumed, a finger is placed under the flange 58 of the top lid 6 and an upward force is applied to the flange 58 about the hinge means 8, causing the top lid 6 to pivot from the closed position to the open position, i.e., to pivot open. Referring to Figure 12, in the initial stage of this pivoting open movement, the locking piece 56 provided on the top lid 6 and the locked piece 40 provided on the lid body 4 are engaged with each other, and more specifically, the locking upper surface 80 of the protrusion 78 provided on the locking piece 56 is engaged with the locked lower surface 72 of the band-shaped main portion 66 provided on the locked piece 40, and the upward force applies a vertical tensile force to the breakable bridges 74 (the inscribed bridges 74a and the circumscribed bridges 74b) connecting the locking piece 56 and the skirt wall 48, causing them to break. When the breakable bridge portion 74 breaks and the locking piece 56 is separated from the top lid 6, it is clearly indicated to the lid body 4 that the top lid 6 has been opened, thereby ensuring the so-called tamper-evident characteristics of the container lid 2. After the breakable bridge portion 74 is broken, the lower surface of the flange portion 76 engages with the upper surface of the band-shaped main portion 66 of the locking piece 40, restricting the locking piece 56 from moving downward relative to the locking piece 40. Furthermore, even after the breakable bridge portion 74 breaks and the locking piece 40 is separated from the top lid 6, the locking piece 56 is restricted from moving upward relative to the locking piece 40 because the locking upper surface 80 of the locking piece 56 engages with the locking lower surface 72 of the locking piece 40 (band-shaped main portion 66). Furthermore, the circumferential movement of the locking pieces 56 relative to the locked pieces 40 is restricted by the circumferential side surfaces of the locking pieces 56 engaging with the inner surfaces of the connecting portions 68 of the locked pieces 40. Therefore, in the container lid of the illustrated embodiment, even if the breakable bridge portions 74 are broken and the locking pieces 56 are separated from the top lid 6, the locking pieces 56 are not separated from the locked pieces 40, i.e., the container lid 2, but continue to be held by them, and therefore the locking pieces 56 themselves do not become waste.

[0025] After the breakable bridge 74 is broken, the top cover 6 is pivoted from the closed position to the open position, exposing the upper surface of the closing wall 10 of the cover body 4. The pull ring 24 of the cover body 4 is then pulled upward with a finger, breaking the endless thin-walled breakable line 18 and removing the removal area 20 from the closing wall 10, thus creating a discharge opening. The contents of the container are then discharged through the discharge opening by tilting the container appropriately. After the contents have been discharged, the top cover 6 is pivoted back to the closed position and reattached to the cover body 4.

[0026] The synthetic resin container lid of the present invention has been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiment, and various modifications are contemplated within the scope of the present invention. For example, in the illustrated embodiment, the endless thin-walled breakable line 18 is broken by the tension ring 24 to create a discharge opening in the closing wall 10. However, a suitable method for creating a discharge opening in the closing wall may be used instead of a tension ring. For example, as shown in Japanese Patent Application No. 2021-137189 filed by the applicant prior to this application, the closing wall of the lid body and the top wall of the upper lid may be connected by a suitable connecting means, so that the endless thin-walled breakable line breaks simultaneously when the upper lid is pivoted open from the closed position. [Explanation of symbols]

[0027] 2: Container lid 4: Lid body 6:Top lid 8: Hinge means 10:Occluded wall 12: Mounting wall 40: Locked piece 46: Top wall 48: Skirt Wall 56: Locking piece 74: Breakable bridge 74a: Inscribed bridge 74b: Circumscribed bridge 84:Relief recess

Claims

1. The container comprises a lid body, and a top lid connected to the lid body via a hinge means and rotatable between a closed position that covers an upper surface of the lid body and an open position that exposes the upper surface of the lid body, the lid body includes a closing wall and a cylindrical mounting wall that hangs down from the periphery of the closing wall, and the upper lid includes a top wall and a skirt wall that hangs down from the periphery of the top wall, a locking piece extending downward via a breakable bridge portion is disposed on the skirt wall, and a lockable piece is disposed on the mounting wall, the locking piece is elastically locked to the lockable piece when the top lid is turned to the closed position, and the breakable bridge portion is broken to separate the locking piece from the skirt wall when the top lid is turned from the closed position to the open position, The rupturable bridge portion includes at least one inscribed bridge that locally connects the lower surface of the skirt wall and the inner surface of the locking piece.

2. 2. The synthetic resin container lid according to claim 1, wherein the outer peripheral surface of the mounting wall is formed with a recess for preventing interference with the inscribed bridge when the top lid is pivoted to the closed position.

3. A synthetic resin container lid as described in claim 1 or 2, wherein the lower end of the locking piece is provided with a protrusion having a radially extending locking upper surface and an inclined lower surface extending radially inward from the radially outer end of the locking upper surface downward.

4. A synthetic resin container lid as described in any one of claims 1 to 3, wherein the locking piece has a flange portion extending radially outward, and the radially outer end of the flange portion is located radially outward from the outer peripheral surface of the skirt wall.

5. 5. The synthetic resin container lid according to claim 1, wherein the inner surface of the locking piece is located radially outward of the outer circumferential surface of the skirt wall.

6. A synthetic resin container lid as described in any one of claims 1 to 5, wherein the engaging piece has a band-shaped main portion that is spaced radially outward from the outer peripheral surface of the mounting wall and extends circumferentially along the outer peripheral surface, and at least the inner peripheral edge portion of the upper surface of the band-shaped main portion is provided with a guide surface that slopes downward toward the radially inward direction.

7. 7. A synthetic resin container lid as described in claim 6, wherein the belt-shaped main portion has a radially extending engaging lower surface formed thereon, the engaging lower surface being located below the guide surface and in the vertically middle portion of the belt-shaped main portion.

8. 8. The synthetic resin container lid according to claim 1, wherein the breakable bridge portion includes at least one circumscribing bridge that locally connects the lower end of the outer peripheral surface of the skirt wall and the upper surface of the locking piece.

9. 9. The synthetic resin container lid according to claim 8, wherein the inscribed bridges are arranged at both circumferential ends of the locking piece, and one circumscribed bridge is arranged at the circumferential center of the locking piece.

10. A synthetic resin container lid as described in any one of claims 1 to 9, wherein the locking piece and the locked piece are respectively provided on both sides of a diameter perpendicular to a diameter passing through the circumferential central angular position of the hinge means when viewed in a plane.

11. A synthetic resin container lid as described in any one of claims 1 to 10, wherein a removal area is defined in the closing wall by an endless thin-walled breakable line, and a connecting pillar extending upward is arranged on the upper surface of the removal area, and a tension ring is connected to the upper end of the connecting pillar.

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