Synthetic resin container lid

Abstract

To provide a novel synthetic resin container lid allowing a user to clearly recognized that a top lid 6 is opened with respect to a lid body 4.SOLUTION: A to-be-locked piece 40 is inclined downward toward one side of a circumferential direction along an outer face of an attachment wall 12 in a position separated outside in a radial direction from the outer face. If a breakable bridging portion 68 is broken, a locking piece 56 is made movable downward toward the one side of the circumferential direction along the to-be-locked piece 40.SELECTED DRAWING: Figure 9

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 Document 1 discloses an example of a container lid comprising a lid body and a top lid connected to the lid body via a hinge means and rotatable 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 hanging down from the periphery of the closing wall, and the top lid includes a top wall and a skirt wall hanging down from the periphery of the top wall. The skirt wall is provided with a locking piece extending downward via a breakable bridging portion, and the mounting wall is provided with a locking piece to which the locking piece locks when the top lid is rotated to the closed position. When the top lid is rotated from the closed position to the open position, the breakable bridging portion breaks and the locking piece is separated from the skirt wall. This synthetic resin container lid is In such a container lid, when the breakable bridge portion is broken and the locking piece is separated from the skirt wall, it becomes clear to the lid body that the top lid has been opened (tamper-evident function). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5847649 Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, in the container lid shown in Patent Document 1 above, the locking piece is completely separated from the container lid after the breakable bridging portion is broken, so it is difficult for the user to notice the existence of the locking piece itself, and there is a risk that the tamper-evident function will not be fully exerted.

[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 allows the user to clearly recognize that the top lid has been opened relative to the lid body. [Means for solving the problem]

[0006] After careful consideration, the inventors have found that the above-mentioned main technical problem can be solved by tilting the engaging piece downward toward one circumferential side along the outer surface of the mounting wall at a position radially outwardly spaced from the outer surface of the mounting wall, so that when the breakable bridging portion breaks, the engaging piece is caused to move downward toward one circumferential side along the engaging 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 includes a closing wall and a cylindrical mounting wall depending from the periphery of the closing wall, and the upper lid includes 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 locking piece to which the locking piece is locked is disposed on the mounting wall when the top lid is turned to the closed position, and when the top lid is turned from the closed position to the open position, the breakable bridge portion is broken and the locking piece is separated from the skirt wall; the locking piece has a flange portion extending radially outward below the breakable bridge portion, and the locked piece is inclined downward toward one side in the circumferential direction along the outer surface of the mounting wall at a position spaced radially outward from the outer surface of the mounting wall, A synthetic resin container lid is provided, characterized in that when the breakable bridge portion is broken, the lower surface of the flange portion of the locking piece is locked to the upper surface of the locked piece, and the locking piece is moved downward toward one side in the circumferential direction along the locked piece.

[0008] Preferably, the one circumferential side is the direction approaching the hinge means. The upper surface of the engaging piece is preferably divided into a relatively short upper horizontal portion located on the other circumferential side and a relatively long upper inclined portion that continues from one circumferential side end of the upper horizontal portion and slopes downward toward the one circumferential side. A recess with an open top is formed at the upper end of the outer peripheral surface of the mounting wall, and the engaging piece is disposed in the recess, and the outer peripheral surface of the engaging piece is preferably located on the same circumferential plane as the outer peripheral surface of the mounting wall or radially inward therefrom. In this case, both circumferential ends of the engaging piece are preferably connected to the mounting wall at side surfaces that define both circumferential end faces of the recess. Preferably, at least one indicia is disposed on the outer surface of the mounting wall, and the indicia can be selectively viewed depending on the circumferential position of the engaging piece. Preferably, the locking piece has a flange portion extending radially outward below the breakable bridge portion, the radially outer end of the flange portion being located radially outward from the outer circumferential surface of the skirt wall, and the lower surface of the flange portion is formed with a support lower surface that is supported by the upper surface of the locked piece after the breakable bridge portion is broken. The locking piece is preferably provided on both sides in a diameter direction perpendicular to a diameter passing through the circumferential central angular position of the hinge means in a plan view. A removal region is 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, and a tension ring is connected to the upper end of the connecting post. [Effects of the Invention]

[0009] In the container lid of the present invention, the engaging piece is inclined downward toward one side in the circumferential direction along the outer surface at a position radially outwardly spaced from the outer surface of the mounting wall, and when the breakable bridging portion is broken, the engaging piece is moved downward toward one side in the circumferential direction along the engaging piece, allowing the user to clearly recognize that the top lid has been opened relative to the lid body, and providing good tamper-evident properties. [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] FIG. 2 is a front view of the container lid shown in FIG. 1 with the top lid in a closed position. [Figure 8] Cross-sectional view of line AA in Figure 7. [Figure 9] 2 is a front view showing an initial stage of a process in which the top cover of the container lid shown in FIG. 1 is pivoted from a closed position to an open position. [Figure 10] 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 may 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. As shown in FIG. 3, a locking piece 40 is also disposed at a required position on the outer 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 underside 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 locking piece 56 extending downward is disposed at a required position on the underside 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 locked pieces 40 disposed on the mounting wall 12 of the lid main body 4 and the locking pieces 56 disposed on the skirt wall 48 of the top lid 6 will be described. First, the locking pieces 56 will be described. In the illustrated embodiment, the locking pieces 56 are provided, one on each side in a diameter 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 shown in FIG. 3, in the circumferential portion where the locking pieces 56 are provided, the lower surface of the skirt wall 48 is displaced slightly upward, so that a rectangular notch 66 extending in the circumferential direction is formed in the lower end of the skirt wall 48, and the upper end surface of the locking piece 56 is connected to the lower surface of the skirt wall 48 at this notch 66 via a pair of breakable bridges 68. 3 and 6, the locking piece 56 has a flange portion 70 extending radially outward below the breakable bridge portion 68, with the radially outer end of the flange portion 70 located radially outward from the outer circumferential surface of the skirt wall 48, and a substantially horizontal supporting lower surface 72 formed on the underside of the flange portion 70. A protrusion 74 is provided at the lower end of the locking piece 56, and this protrusion 74 has an upper locking surface 76 extending substantially horizontally radially outward and an inclined lower surface 78 extending radially inward from the radially outer end of the upper locking surface 76, with the circumferential width of the protrusion 74 gradually decreasing downward. A required degree of clearance exists between the upper locking surface 76 and the supporting lower surface 72 of the flange portion 70.

[0017] Next, the engaging pieces 40 will be described. In a plan view (i.e., FIG. 1), one engaging piece 40 is provided on each of the front and rear surfaces of the mounting wall 12. As will be described later, when the top cover 6 is rotated to the closed position, the engaging pieces 56 disposed on the top cover 6 are elastically engaged with the engaging pieces 40, and therefore the circumferential positions of the engaging pieces 40 correspond to the circumferential positions of the engaging pieces 56. The positions of the engaging pieces 40 will be further discussed later. In a container cover constructed according to the present invention, it is important that the engaging pieces 40 are positioned radially outwardly from the outer surface of the mounting wall 12 and incline downward toward one circumferential side along the outer surface. As can be understood by referring to FIG. 3, in the illustrated embodiment, the one circumferential side is the direction approaching the hinge means 8. The upper surface of the locking piece 40 is divided into a relatively short upper horizontal portion 80 located on the other circumferential side and a relatively long upper inclined portion 82 that slopes downward from one circumferential end of the upper horizontal portion 80 toward one circumferential side. The lower surface of the locking piece 40 is divided into a lower horizontal portion 84 located on the other circumferential side and a lower inclined portion 86 that slopes downward from one circumferential end of the lower horizontal portion 84 toward one circumferential side. The circumferential lengths of the lower horizontal portion 84 and the lower inclined portion 86 are approximately the same. The upper inclined portion 82 and the lower inclined portion 86 are parallel. If desired, the upper and lower surfaces of the locking piece 40 may be entirely inclined downward toward one circumferential side. As shown in FIG. 8 , the upper surface of the locking piece 40 is entirely inclined downward toward the radially inward direction to form a guide surface 88. The "outer surface" of the mounting wall 12 will be referred to later.

[0018] 1, 3, 5, and 8, in the illustrated embodiment, an upwardly open recess 90 is formed at the upper end of the outer peripheral surface of the mounting wall 12, and the locking piece 40 is disposed in the recess 90. Therefore, in the above description, "The locking piece 40 is inclined downward toward one circumferential side along the outer peripheral surface of the mounting wall 12 at a position spaced radially outward from the outer peripheral surface of the mounting wall 12," the "outer peripheral surface" of the mounting wall 12 refers to the bottom surface 91 of the recess 90 in the illustrated embodiment. The outer peripheral surface of the locking piece 40 is located on the same circumferential plane as the outer peripheral surface of the mounting wall 12, and both circumferential ends of the locking piece 40 are connected to the mounting wall 12 at side surfaces 92 that define both circumferential end surfaces of the recess 90. The side surfaces 92 extend linearly in the vertical direction. A lower surface 94 of the recess 90 extends somewhat horizontally from the other circumferential end toward one circumferential side, and then slopes downward toward one circumferential side along the upper surface inclined portion 82 and the lower surface inclined portion 86 of the locking piece 40. As shown in FIG. 3 , at least one marking is disposed on the outer surface of the mounting wall 12 at the recess 90. In the illustrated embodiment, the markings are the Chinese characters "open" (denoted by reference numeral 96a) and "closed" (denoted by reference numeral 96b), which are printed by an appropriate printing method on the outer surface of the mounting wall 12 after the container lid 2 is molded. Both the markings 96a and 96b are disposed below the locking piece 40, with the marking 96a disposed at the other circumferential end of the recess 90 and the marking 96b disposed at one circumferential end of the recess 90, and the markings 96a and 96b spaced apart in the circumferential direction.

[0019] If desired, the outer peripheral surface of the locking piece 40 may be located radially inward from the outer peripheral surface of the mounting wall 12. Also, the recess 90 may be omitted and the locking piece 40 may be disposed on the outer peripheral surface of the mounting wall 12, with the outer peripheral surface of the locking piece 40 located radially outward from the outer peripheral surface of the mounting wall 12. In this case, the locking piece 56 is connected via the breakable bridge portion 68 to the outer peripheral surface of the skirt wall 48 rather than the lower surface thereof, and the entire locking piece 40 is located radially outward from the outer peripheral surface of the skirt wall 48.

[0020] The container lid 2 described above is formed by a molding machine with the top lid 6 in an open position relative to the lid body 4, and after the formed container lid 2 is removed from the molding machine, it is completed by 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 74 of the locking piece 56 formed on the top lid 6 elastically climbs over the lockable piece 40 formed on the lid body 4, and thus the locking piece 56 is elastically locked to the lockable piece 40. When the locking piece 56 is locked to the lockable piece 40, the guide surface 88 formed on the upper surface of the lockable piece 40 cooperates with the inclined lower surface 78 formed on the protrusion 74 of the locking piece 56 to allow the protrusion 74 to climb over the lockable piece 40 smoothly and smoothly. For details of the folding process, please refer to the specification of Patent Application No. 2021-175414, which was filed by the applicant prior to this application.

[0021] 7, in the illustrated embodiment, when the locking piece 56 is elastically locked to the locked piece 40, the lower horizontal portion 84 of the locked piece 40 is positioned vertically opposite the upper locking surface 76 of the locking piece 56. The other circumferential end of the locked piece 40 is positioned slightly spaced apart on the other circumferential side from the locking piece 56, while the one circumferential end of the locked piece 40 is positioned sufficiently spaced apart on one circumferential side from the locking piece 56. The locking piece 56 covers the Chinese character "open" indicia 96a disposed on the outer surface of the mounting wall 12, making it invisible, and only the Chinese character "close" indicia 96b is visible.

[0022] At this time, as shown in Figure 8, the annular engaging protrusion 62 of the top cover 6 engages with the outer peripheral 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 peripheral surface of the inner cylindrical wall 50 of the top cover 6 is brought into close contact with the inner peripheral surface of the pouring guide wall 26 of the cover body 4, and at the same time, as shown in Figure 7, the thin-walled arc-shaped protrusion 60 of the top cover 6 is positioned in the notch 36 of the cover body 4.

[0023] 7 and 8 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).

[0024] 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.

[0025] 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, thereby pivoting the top lid 6 from the closed position to the open position, i.e., pivoting it open. Referring to FIG. 8 , in the initial stage of this pivoting open movement, the locking piece 56 on the top lid 6 and the lockable piece 40 on the lid body 4 engage with each other. More specifically, the locking upper surface 76 of the protrusion 74 on the locking piece 56 engages with the lower horizontal portion 84 of the lockable piece 40. This upward force exerts a vertical tensile force on the breakable bridge 68 connecting the locking piece 56 and the skirt wall 48, thereby breaking it. It is important to note that in a container lid constructed according to the present invention, when the breakable bridge 68 is broken, the locking piece 56 is moved downward along the lockable piece 40 toward one side in the circumferential direction. When the breakable bridge portion 68 is broken, the locking piece 56 is separated from the skirt wall 48, the lower support surface 72 of the locking piece 56 (flange portion 70) is locked onto the upper inclined portion 82 of the locked piece 40, and the locking piece 56 is caused to move (slide) to one side in the circumferential direction by gravity along this upper inclined portion 82. Then, when the locking piece 56 is slid to one end in the circumferential direction, as shown in Figure 9(c), the locking piece 56 covers the Chinese character "close" mark 96b arranged on the outer surface of the mounting wall 12, making it invisible, and only the Chinese character "open" mark 96a becomes visible.

[0026] In the container lid of the present invention, the engaging piece 40 is inclined downward toward one side in the circumferential direction along the outer surface at a position spaced radially outward from the outer surface of the mounting wall 12, and when the breakable bridge portion 68 is broken, the engaging piece 56 is caused to move downward toward one side in the circumferential direction along the engaging piece 40, so that the user can clearly recognize that the top lid 6 has been opened relative to the lid body 4, and the container lid has good tamper-evident properties. After the breakable bridge portion 68 breaks and the locking piece 56 is separated from the top cover 6, the lower surface of the flange portion 70 engages with the upper inclined surface portion 82 of the locking piece 40, restricting downward movement of the locking piece 56 relative to the locking piece 40. Upward movement of the locking piece 56 relative to the locking piece 40 is restricted by the locking upper surface 76 of the locking piece 56 engaging with the lower inclined surface portion 86 of the locking piece 40. Furthermore, circumferential movement of the locking piece 56 relative to the locking piece 40 is restricted by the circumferential side surface of the locking piece 56 abutting against the side surface 92. Therefore, in the container lid of the illustrated embodiment, even if the breakable bridge portion 68 breaks and the locking piece 56 is separated from the top lid 6, the locking piece 56 will not separate from the locked piece 40, i.e., the container lid 2, but will continue to be held by it, so the locking piece 56 itself will not become waste.

[0027] After the breakable bridge 68 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, as shown in FIG. 10 . 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.

[0028] While the synthetic resin container closure of the present invention has been described in detail above with reference to the accompanying drawings, 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 engaging piece 40 is inclined downward toward the hinge means 8, i.e., one circumferential side is in a direction approaching the hinge means. However, by appropriately selecting the inclination angle, the engaging piece can also be inclined downward in a direction away from the hinge means. Furthermore, in the illustrated embodiment, the outer surface of the mounting wall is provided with indicia 96a and indicia 96b, but one or both of these may be omitted. Furthermore, in the illustrated embodiment, the endless thin-walled breakable line 18 is broken by the tension ring 24 to form a discharge opening in the closing wall. However, any other suitable method may be used to form a discharge opening in the closing wall. For example, as shown in 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 can be connected by an appropriate connecting means so that the endless thin-walled breakable line breaks at the same time as the upper lid is pivoted open from the closed position. [Explanation of symbols]

[0029] 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 68: Breakable bridge 70: Flange part 72: Support bottom surface

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 depending from the periphery of the closing wall, and the upper lid includes 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 locking piece to which the locking piece is locked is disposed on the mounting wall when the top lid is turned to the closed position, and when the top lid is turned from the closed position to the open position, the breakable bridge portion is broken and the locking piece is separated from the skirt wall; the locking piece has a flange portion extending radially outward below the breakable bridge portion, and the locked piece is inclined downward toward one side in the circumferential direction along the outer surface of the mounting wall at a position spaced radially outward from the outer surface of the mounting wall, A synthetic resin container lid characterized in that, when the breakable bridge portion is broken, the lower surface of the flange portion of the locking piece is locked to the upper surface of the locked piece, and the locking piece is moved downward toward one side in the circumferential direction along the locked piece.

2. 2. The synthetic resin container lid according to claim 1, wherein said one side in the circumferential direction is a direction approaching said hinge means.

3. A synthetic resin container lid as described in claim 1 or 2, wherein the upper surface of the engaging piece is divided into a relatively short upper horizontal portion located on the other side of the circumference and a relatively long upper inclined portion that slopes downward from one circumferential side end of the upper horizontal portion toward that side of the circumference.

4. A synthetic resin container lid as described in any one of claims 1 to 3, wherein an open recess is formed at the upper end of the outer peripheral surface of the mounting wall, the engaging piece is arranged in the recess, and the outer peripheral surface of the engaging piece is located on the same circumferential plane as the outer peripheral surface of the mounting wall or radially inward therefrom.

5. 5. The synthetic resin container lid according to claim 4, wherein both circumferential ends of the engaging piece are connected to the mounting wall at side surfaces that define both circumferential end faces of the recess.

6. 6. A synthetic resin container lid according to claim 1, wherein at least one marking is provided on the outer surface of the mounting wall, and the marking is selectively visible depending on the circumferential position of the locking piece.

7. A synthetic resin container lid as described in any one of claims 1 to 6, wherein the locking piece has a flange portion extending radially outward below the breakable bridge portion, the radially outer end of the flange portion is located radially outward from the outer peripheral surface of the skirt wall, and the lower surface of the flange portion has a support lower surface formed thereon that is supported by the upper surface of the lockable piece after the breakable bridge portion is broken.

8. 8. The synthetic resin container lid according to claim 1, wherein the locking pieces are provided on both sides in a diameter direction perpendicular to a diameter passing through a circumferential central angular position of the hinge means in a plan view.

9. A synthetic resin container lid as described in any one of claims 1 to 8, 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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