Resin Container Lid With Inverted Cone Fitting Surface
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Solution Overview
Problem
Existing synthetic resin container closures require excessively high initial and secondary torques for unsealing, leading to difficulties in unsealing, particularly for children and females, and often result in the breakage of bridge portions in the circumferential breakable line.
Innovation Solution
Incorporating an inverted truncated cone-shaped fitting surface on the inner peripheral surface of the tamper evident bottom section with a radially outward incline, and setting the axial clearance between the external and internal threads to be equal to or greater than the axial effective width of the locking jaw portion, to reduce torque requirements and prevent breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the locking means is set with a small projection amount to prevent excessive forced extraction from molding die, then the engagement with locking jaw portion becomes insufficient, but increasing projection amount causes excessive initial torque and difficulty in unsealing
Solution Approach 1:
The locking means is divided into two functional parts: a locking protrusion for engagement with the locking jaw portion, and a separate fitting surface (inverted truncated cone shape) for providing interference fit. This segmentation allows each part to be optimized independently - the protrusion maintains small projection for easy manufacturing while the fitting surface provides the necessary interference fit for preventing slipping-out during unsealing.
Solution Approach 2:
The fitting surface acts as an intermediary mechanism between the locking means and the locking jaw portion. Instead of relying solely on the projection amount of the locking means, the fitting surface provides the interference fit function, mediating the relationship between manufacturing constraints and unsealing operation requirements.
2Reliability
If interference fit is applied between inner peripheral surface of tamper evident bottom section and outer peripheral surface of locking jaw portion to prevent slipping-out, then locking reliability improves, but required initial torque becomes excessively high
Solution Approach 1:
The interference fit is localized to a specific region through the fitting surface of inverted truncated cone shape, rather than applying interference fit across the entire inner peripheral surface. This local quality approach provides the necessary anti-slipping function only where needed, while maintaining ease of operation in other regions.
Solution Approach 2:
The fitting surface is designed with an inverted truncated cone shape (curved surface) rather than a flat surface. This curvature allows for gradual engagement and distribution of contact pressure, reducing the peak initial torque required while still providing effective interference fit to prevent slipping-out.
3Manufacturing precision
If axial clearance between external thread and internal thread is small to ensure proper engagement, then threading precision improves, but stress on circumferential breakable line increases causing bridge portion breakage
Solution Approach 1:
The axial clearance between external thread and internal thread is optimized to a specific range (0.05mm to 0.20mm) rather than being minimized. This parameter change balances the competing requirements of threading precision and stress reduction on the breakable line, preventing bridge portion breakage while maintaining adequate engagement precision.
Data Source
Figure 1~2
Figure 3
Figure 4A~4D
AI summary
[Problems to be Solved] A synthetic resin container closure (2) does not render required initial torque and required secondary torque for unsealing excessively high, and but can fully reliably prevent slipping-out, a phenomenon where a locking means (30) ascends while elastically climbing over a locking jaw portion (44), without causing breakage of a circumferential breakable line (16), at the time of unsealing. Such a synthetic resin container closure and a combination of the synthetic resin container closure and a container are provided. [Means to Solve the Problems] An inverted truncated cone-shaped fitting surface (34) extending upwards at a radially outward incline from the base edge of an upper surface (32a) of the locking means is disposed in the inner peripheral surface of a tamper evident bottom section (20) demarcated below the circumferential breakable line (16) formed in a skirt wall (6).