Buckle With Detent And Reentrant Lips For Theft Resistance
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Solution Overview
Problem
Existing buckles that connect straps to bags are vulnerable to accidental release due to tension loss or twisting, making them unsuitable for preventing casual theft without increasing costs.
Innovation Solution
A buckle design featuring a male and female coupler with a detent mechanism, including a latch and actuator, and lips and inwardly-extending faces that enhance strength and security, along with a tapering slot and internal web for secure strap connection, and the option to lock with a padlock for added security.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional buckle design is used, then the cost is low, but the security against casual theft is insufficient due to vulnerability to accidental release
Solution Approach 1:
The buckle is divided into distinct functional components: a bar portion with flange for strap connection, a hollow body with slot opening, a detent mechanism with latch and actuator, and lips with inwardly-extending faces. Each segment performs a specific function, allowing the complex security features to be modular and manageable without prohibitive cost increase
Solution Approach 2:
The lips extend reentrantly along the slot part to engage the inwardly-extending faces before the flange fully enters the hollow body. This preliminary engagement prevents accidental release by establishing security constraints during the insertion process itself, rather than requiring additional active locking steps
2Reliability
If a detent mechanism with latch and actuator is added, then the security is improved, but the manufacturing complexity increases
Solution Approach 1:
The detent mechanism integrates the latch, actuator, and spring into a compact assembly within the bar portion. The latch is biased by the spring to automatically engage with the hollow body, while the actuator provides manual control. This merging of functions into a single integrated mechanism achieves enhanced security without proportionally increasing manufacturing complexity
Solution Approach 2:
The spring-biased latch automatically engages with the hollow body when the flange is inserted, providing self-latching security without requiring manual intervention. The system serves itself by using the insertion motion to trigger the latching action, reducing the need for complex manual operation mechanisms
3Strength
If lips with inwardly-extending faces are added to resist tensile loads, then the strength is improved, but the device complexity increases
Solution Approach 1:
The lips extend reentrantly along the slot part, creating a curved, encompassing geometry that engages the inwardly-extending faces on the bar portion. This curved configuration allows the lips to effectively resist tensile loads by distributing forces around the engagement point, achieving high strength with a relatively simple geometric feature
Solution Approach 2:
The inwardly-extending faces are positioned asymmetrically on the bar portion, allowing the lips to engage only in the intended loading direction. This asymmetric design provides strong resistance to tensile loads while maintaining simplicity by not requiring symmetric features on all sides
Data Source
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Figure 8
AI summary
A buckle (10) comprising a male coupler (11) including a bar portion (15) with an external surface (16), a first flange (17) protruding from the external surface (16), the first flange (17) being adapted for connection of a strap (13, 14) thereto; a female coupler (12) with a hollow body (20) having an opening (44, 48) therein, the opening (44, 48) including an end part at a first axial end of the hollow body (20) and a slot part extending generally axially from the end part of the opening (44, 48), the slot part having opposing lips (28) extending along the slot, the hollow body (20) having an internal surface (23) complementary to the external surface (16) of the bar portion (15), such that the bar portion (15) can be entered through the end part of the opening (44, 48) as the flange (17) slides through the slot part of the opening (44, 48); a detent (36) for releasably holding the bar portion (15) in the hollow body (20); and wherein the lips (28) extend reentrantly and each lip (28) is adjacent a respective inwardly-extending face in the bar portion (15).