Resin Cap
The resin cap addresses the issue of sealing loss by using a female thread with a reduced pressure side flank angle to resist upward forces, ensuring secure attachment under pressure, thus enhancing sealing performance.
Patent Information
- Application Number
- JP2020060019
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2020-03-30
- Publication Date
- 2026-02-05
- Estimated Expiration
- 2040-03-30
AI Technical Summary
Conventional resin caps for carbonated beverage containers risk losing sealing ability due to the internal pressure pushing the cap's internal thread upwards, causing it to tilt and detach from the container's external thread.
The resin cap design features a female thread with a pressure side flank angle smaller than the play side flank angle, typically set between 15 to 25 degrees, to enhance sealing performance by resisting upward forces from increased internal pressure.
The cap maintains effective sealing by minimizing the likelihood of the female thread detaching from the male thread, even under increased internal pressure, thereby improving sealing integrity.
Smart Images
Figure 0007811439000001
Abstract
Description
[Technical Field]
[0001] The present invention relates to a resin cap that is attached to the opening of a container that contains contents such as a beverage (carbonated beverage). [Background technology]
[0002] As shown in Figure 1(A), some resin caps (hereinafter referred to as "caps") are fitted to the mouth of a container such as a PET bottle and used to seal the container, and have a female thread 2 that screws into a male thread M1 provided on the outer peripheral surface of the container mouth M. In this type of conventional cap, in order to emphasize improved mold releasability during molding, as shown in Figure 1(B), the pressure side flank angle (upper surface angle) α of the female thread 2 is made the same as or larger than the play side flank angle (lower surface angle) β (in the example shown in Figure 1(B), both α and β are the same at 30 degrees). Summary of the Invention [Problem to be solved by the invention]
[0003] However, when the above-mentioned conventional cap is used to seal a container whose internal pressure may subsequently increase, such as a carbonated beverage bottle, there is a risk that the internal thread 2 of the cap will be pushed up by the high-pressure gas inside the container, overturning the external thread M1 of the container mouth M, causing the cap to tilt and resulting in loss of sealing ability.The inventors have discovered that the cause of this is the size of the pressure side flank angle α.
[0004] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a resin cap that can improve sealing performance. [Means for solving the problem]
[0005] In order to achieve the above object, the resin cap according to the present invention comprises: It is a carbonated drink bottle container of It has a female thread that screws into the male thread at the mouth. and is used to seal carbonated beverage bottles. A resin cap having a longitudinal cross-sectional shape from one end to the other end. Without changing in the middleThe pressure side flank angle of the female thread is set to be smaller than the play side flank angle, with the play side flank angle being 30 to 40 degrees and the pressure side flank angle being 15 to 25 degrees (claim 1).
[0006] In the resin cap, the female thread may extend intermittently in the circumferential direction via a notched groove (claim 2). [Effects of the Invention]
[0007] The present invention provides a resin cap that can improve sealing performance.
[0008] In other words, in the resin cap of the invention according to each claim of the present application, the pressure side flank angle of the female thread is smaller than the play side flank angle, so that even if the internal pressure of the container increases when attached to the container mouth (capping state), the female thread is less likely to come off the male thread of the container mouth and float up, thereby improving the sealing performance of the container. [Brief explanation of the drawings]
[0009] [Figure 1] (A) is a longitudinal cross-sectional view showing the outline of the configuration of a resin cap according to one embodiment of the present invention and a conventional example, (B) is an explanatory diagram showing the outline of the configuration of the main parts of a conventional resin cap, and (C) is an explanatory diagram showing the outline of the configuration of the main parts of a resin cap according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.
[0011] FIG. 1(A) shows a schematic configuration of a conventional cap, and also shows a schematic configuration of a cap (resin cap) 1 according to one embodiment of the present invention (this example).
[0012] First, the outline of the configuration of the cap 1 of this example will be explained. As shown in FIG. 1(A), the cap 1 comprises a shell 3 and a packing 4 that is held within the shell 3 and seals the opening M of the container.
[0013] The shell 3 has a top wall 5 that is circular in plan view and a substantially cylindrical skirt wall 6 that hangs down from the periphery of the top wall 5, and a female thread 2 that screws into a male thread M1 of the container opening M is formed on the skirt wall 6.
[0014] In addition, the cap 1 in this example is a pilfer-proof cap, and a circular band (tamper-evidence band) 8 is connected to the underside of the skirt wall 6 via a plurality of breakable bridges 7, and the band 8 is provided with a flap 9 that engages with the bead portion M2 of the container mouth portion M.
[0015] On the other hand, the gasket 4 has a top plate 10 that is circular in plan view and covers the container mouth portion M, an approximately cylindrical center foot 11 that is connected to the underside of the top plate 10 and adheres closely to the inner surface of the container mouth portion M, and a folded portion 12 that bends downward from the periphery of the top plate 10 and adheres closely to the outer surface of the container mouth portion M.
[0016] As described above, in conventional caps, the pressure flank angle α of the female thread 2 is equal to or greater than the clearance flank angle β, but in the cap 1 of this example, the pressure flank angle α is made smaller than the clearance flank angle β, as shown in Figure 1(C). In the example shown in Figure 1(C), the pressure flank angle α is 20 degrees and the clearance flank angle β is 30 degrees. Although not shown, it is preferable that the female thread 2 extend intermittently in the circumferential direction via notched grooves in terms of drainage properties, etc.
[0017] In this way, in the cap 1 of this example, in which the pressure side flank angle α of the female thread 2 is smaller than the play side flank angle β, even if the internal pressure of the container increases when it is attached to the container mouth M (capping state), the female thread 2 is less likely to come off and float up from the male thread M1 of the container mouth M, thereby improving the sealing performance of the container.
[0018] In more detail, when the pressure inside the container increases while the cap 1 is attached to the container mouth M, the internal pressure pushes up the cap 1, and as a result, as shown in Figures 1(B) and (C), at the fitting portion between the female thread 2 of the cap 1 and the male thread M1 of the container mouth M, an upward force F is applied from the female thread 2 (female thread pressure side flank 13) to the male thread M1 (male thread pressure side flank M3).
[0019] This upward force F is divided into an inward force F1 perpendicular to the male thread pressure flank M3 and an outward force F2 parallel to the male thread pressure flank M3. Here, F1 = F × cos(α) and F2 = F × sin(α).
[0020] In the example shown in Figure 1(B) where the pressure flank angle α is 30 degrees, F1 = F × cos30° ≒ 0.87F, F2=F×sin30°=0.5F This becomes:
[0021] On the other hand, in the example of Figure 1(C) where the pressure side flank angle α is 20 degrees, F1 = F × cos20° ≒ 0.94F, F2 = F × sin20° ≒ 0.34F This becomes:
[0022] When comparing F1 and F2 in the example of FIG. 1(B) (conventional example) and the example of FIG. 1(C) (this example), the example of FIG. 1(C) has a larger inward force F1 and a smaller outward force F2.
[0023] In this way, if the pressure side flank angle α is changed (reduced) from 30 degrees to 20 degrees, the inward force F1 becomes larger and the outward force F2 becomes smaller, making it more difficult for the internal thread 2 of the cap 1 to escape outward, and preventing the cap 1 from lifting up.
[0024] In fact, five prototypes corresponding to the conventional example in Figure 1(B) and five prototypes corresponding to the present example in Figure 1(C) were created, and a test was conducted in which the internal pressure of the container was increased in the capped state.Four out of the five prototypes corresponding to the conventional example leaked, but none of the five prototypes corresponding to the present example leaked.
[0025] From the above viewpoint alone, the smaller the pressure side flank angle α, the better. However, taking into consideration mold releasability, it is preferable to set the angle to 15 degrees or more.
[0026] In addition, it is thought that the size of the clearance side flank angle β itself does not affect the lift-up or releasability of the cap 1 as much as the pressure side flank angle α, but whether the flank angle, which is the combined pressure side flank angle α and clearance side flank angle β, is too large or too small has a significant effect on the openability, etc., and it is preferable to set it to around 45 to 65 degrees.Based on this, it is preferable to set the clearance side flank angle β to 30 to 40 degrees and the pressure side flank angle α to 15 to 25 degrees.
[0027] It should be noted that the present invention is not limited to the above-described embodiment, and can be practiced in various modified forms without departing from the spirit of the present invention.
[0028] For example, the cap 1 in the above embodiment is a so-called two-piece cap having a shell 3 and a packing 4, but the present invention is also applicable to a so-called one-piece cap in which the shell 3 and the packing 4 are integrated. [Explanation of symbols]
[0029] 1 cap 2 internal threads 3 shells 4. Gasket 5 Ceiling wall 6. Skirt Wall 7 Bridge 8 bands 9 Flap 10. Top plate 11 Midfoot 12 Bend section 13 Female thread pressure side flank M Container opening M1 male thread M2 bead part M3 male thread pressure side flank α Pressure side flank angle β Flank angle on play side
Claims
1. A resin cap having a female thread that screws onto a male thread on the mouth of a carbonated beverage bottle, the resin cap being used to seal the carbonated beverage bottle, The female thread has a constant longitudinal cross-sectional shape from one end to the other end without any change midway, and the pressure side flank angle of the female thread is made smaller than the play side flank angle, A resin cap characterized in that the play side flank angle is 30 to 40 degrees and the pressure side flank angle is 15 to 25 degrees.
2. The resin cap according to claim 1 , wherein the female thread extends intermittently in the circumferential direction via a notched groove.
Citation Information
Patent Citations
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