Trapezoidal Locking Pins for Folding Devices With Smooth Rotation
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Solution Overview
Problem
Existing baliscissors designs face issues with wear and misalignment due to double square locking pins, leading to excessive play and ineffective locking mechanisms, especially when using tapered handles, and rotating locking pins have complex cross-sections and limited functionality.
Innovation Solution
A balitool design featuring semicylindrical protuberances trapezoidally arranged around the circumference of the pins, with chamfered bases, allows for smooth rotation and secure locking by maximizing contact area between the pins and handles, accommodating tapered handles without full 180-degree rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If double square locking pins are used, then the handles can be locked in scissor-mode or bali-mode, but wear at the corner between the two squares eliminates the ability for the pin to lock into handles
Solution Approach 1:
The locking pin is divided into multiple functional sections: a first square section for initial engagement, a second square section offset from the first, and a circular section. This segmentation allows the pin to provide multiple locking positions while distributing wear across different sections, preventing the complete loss of locking capability.
Solution Approach 2:
The locking mechanism transitions from a two-dimensional square cross-section to a three-dimensional configuration with offset squares and a circular section. This dimensional change creates multiple engagement surfaces and positions, enabling versatile locking modes while maintaining reliability through distributed contact points.
2Ease of operation
If a round pin is used, then the handles can rotate smoothly, but there is excessive play and the pin is not always supported at all four points
Solution Approach 1:
Different sections of the pin have different geometric properties: the circular section provides smooth rotation with minimal friction, while the square sections provide stable support and positioning. This local differentiation of geometric quality allows the pin to simultaneously achieve smooth rotation and stable support.
Solution Approach 2:
The pin features an asymmetric configuration with two square sections offset from each other and a circular section. This asymmetry creates distinct functional zones: the circular portion enables smooth rotation while the offset square portions provide stable support points, resolving the contradiction between rotation smoothness and support stability.
3Stability of the object's composition
If square pin and square hole design is used, then rotation is restricted, but straight handles are required instead of tapered handles
Solution Approach 1:
The locking pin transitions from a static square cross-section to a dynamic multi-section design that adapts its engagement characteristics. The offset square sections and circular section work together to provide rotation control at different positions along the pin's length, enabling the use of tapered handles while maintaining rotation stability.
4Ease of operation
If the pin is made loose enough for rotation, then rotation is easy, but the pin is not always supported at all four points leading to excessive play
Solution Approach 1:
The offset square sections are positioned to provide preliminary support and alignment before rotation occurs. This preliminary action ensures that the pin is properly supported at multiple points during the rotation process, preventing excessive play while maintaining ease of rotation.
Data Source
AI summary
Designs and methods of operation for balitools such as balisongs, butterfly knives, and baliscissors. Two cylindrical locking pins that connect the handles and the tool or blade(s) have semicylindrical protuberances that are trapezoidally arranged. This enables both the use of tapered handles and smooth rotation of the handles with respect to the tool or blade(s) while requiring only a single button assembly to switch between different modes such as pocket mode, in which the handles are locked covering the tool or blade(s); bali mode, in which the tool or blade(s) can swing freely relative to the handles (and, for baliscissors, the scissor blades are locked together); and, for baliscissors, scissors mode, in which each scissors blade is locked to one of the handles.