Tapered Key Coding for Cylinder Lock Anti-Copying
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Solution Overview
Problem
Conventional keys and cylinder locks are vulnerable to easy code reading and copying due to the direct proportionality of milling cuts on the key's surface, which can be measured using high-resolution photography.
Innovation Solution
The key and cylinder lock system features codes that taper from the key's surface towards its longitudinal axis, with varying depths and shapes, including bores and incision millings, which are connected by a continuous groove to obscure the depth and gradient, making it difficult to infer the coding from a photograph.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional milled recesses are used for key coding, then manufacturing is simple and codes can be easily read, but security is compromised because the depth of milled recesses can be easily measured using high-resolution photography
Solution Approach 1:
The invention changes the geometric parameters of the coding from simple depth variations to tapered geometries with specific angle ranges (10-45 degrees). This parameter change makes the coding difficult to measure photographically while maintaining manufacturability through standard milling or boring processes.
Solution Approach 2:
The coding elements are designed with asymmetric tapered shapes rather than symmetric cylindrical or flat recesses. The tapering from a larger diameter at the surface to a smaller diameter at the bottom creates an asymmetric geometry that cannot be accurately reproduced from surface photographs alone.
2Adaptability or versatility
If the depth of milled recesses varies to create different codes, then coding variation is achieved, but security is compromised because the depth is directly proportional to the surface recess and can be easily measured
Solution Approach 1:
The invention transitions from using only depth variation as the coding parameter to using taper angle and taper geometry as the primary coding parameters. This allows for coding variation while preventing easy measurement, as the critical parameters (angle and bottom diameter) cannot be determined from surface photographs.
Solution Approach 2:
The invention adds the dimensional aspect of tapering (creating a three-dimensional angled geometry) rather than relying solely on depth variation (one-dimensional). This dimensional change from simple depth to angled tapering prevents accurate copying from surface images.
3Measurement precision
If core pins with scanning extensions are used to query codes, then code verification is achieved, but the system remains vulnerable because conventional scanning extensions cannot distinguish tapered codes from standard depth codes
Solution Approach 1:
The scanning extensions are designed with complementary tapered geometries that match the key codings. By changing the geometry of the scanning extension from cylindrical to tapered, the system can now distinguish between different taper angles and verify the three-dimensional coding structure, preventing false acceptance of copied keys.
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5b
AI summary
The invention relates to a key for a cylinder lock, the key having coded portions of different depths, which taper from a surface of the key in the direction of a longitudinal axis (18) of the key, wherein at least two coded portions are provided which are substantially identical on the surface and which differ in their depths and in the gradient of their taper in the direction of the longitudinal axis (18), and a cylinder lock comprising pin tumblers projecting into the keyway, wherein the pin tumblers (5) have probing extensions (6) on their ends projecting into the keyway (4) for prompting coded portions of a key, the probing extensions (6) taper in the direction of the keyway (4), and at least two pin tumblers (5, 5', 5'') are provided which have the same diameter but have probing extensions (6, 6', 6'') which differ in the gradient of their taper.