Padlock Shackle Keying to Block Rotation-Based Theft
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Solution Overview
Problem
Existing padlocks are vulnerable to theft through methods such as cutting the shackle legs and applying twisting forces to rotate the uncut leg, creating a gap for removal.
Innovation Solution
Incorporation of keyed shackle segments and shackle bore segments that interlock to limit rotation of the shackle legs within the bores, preventing rotation beyond a critical angle that would allow gap formation, and use of socket-shaped notches with side wall portions to block shackle rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the shackle is made movable in the axial direction to allow removal, then the ease of operation is improved, but the vulnerability to rotation-based theft methods worsens
Solution Approach 1:
The shackle bore is divided into two distinct segments with different functional qualities: a first shackle bore segment that allows axial movement for normal operation, and a second shackle bore segment with rotational blocking features (such as ridges, grooves, or keyed interfaces) that prevent rotation. This local differentiation enables the shackle to be easily removable along the axial direction while simultaneously protecting against rotation-based theft methods.
2Ease of manufacture
If the shackle leg is made cylindrical for simplicity, then the ease of manufacture is improved, but the ability to block rotation worsens
Solution Approach 1:
The shackle leg maintains a generally cylindrical shape for most of its length, ensuring ease of manufacture. However, specific local regions of the shackle leg incorporate non-cylindrical features such as ridges, grooves, flats, or keyed portions that engage with corresponding features in the shackle bore. These localized modifications provide rotational blocking functionality while minimizing impact on overall manufacturing simplicity.
3Device complexity
If the locking mechanism is placed in the central cavity, then the device complexity is reduced, but the ability to secure the shackle in multiple positions worsens
Solution Approach 1:
The shackle bore is segmented into functionally distinct regions: a first segment that guides axial movement and an second segment that provides rotational blocking. The locking mechanism in the central cavity works in conjunction with these segmented bore regions, where the locking member can engage with features in the second segment to secure the shackle in specific rotational positions, thereby achieving position stability without increasing overall device complexity.
Data Source
AI summary
A padlock includes a lock body, a shackle, and a locking mechanism. The shackle includes first and second cylindrical shackle legs receivable in corresponding first and second shackle bores in the lock body. The locking mechanism is disposed in a central cavity of the lock body and is operable between a locked position securing the shackle in a retracted position and an unlocked position permitting movement of the shackle to an extended position. The first shackle leg includes a keyed shackle segment and the first shackle bore includes a keyed shackle bore segment that is aligned with the keyed shackle segment when the shackle is in the retracted position. The keyed shackle segment and the keyed shackle bore segment are shaped to block rotation of the first shackle leg within the first shackle bore when the shackle is in the retracted position.