Cylinder Lock Key Plug Geometry for Pick-Resistant Machining
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Solution Overview
Problem
Existing cylinder locks face challenges in maintaining security against unauthorized manipulation and unauthorized opening, while facilitating a rational production of locks and keys in large numbers, and rational production of locks and keys in large numbers, with complex geometries that complicate manufacturing and increase the risk of lock-picking.
Innovation Solution
A key plug design with a keyway featuring a narrow, slightly inclined upper part and an interconnecting part that creates a narrow opening passage offset laterally, limiting access to central locking pins, combined with a manufacturing method using a rotating cutter disc at a small angle to simplify production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the keyway has a complex geometry with alternating inclined portions and sharp bends, then security against lock-picking is enhanced, but manufacturing complexity increases and production efficiency decreases
Solution Approach 1:
The patent extracts and eliminates the complex alternating inclined portions and sharp bends from the keyway geometry, retaining only the essential narrow upper part and interconnecting part. This simplification maintains security by preserving the narrow opening passage that limits access to central locking pins, while dramatically reducing manufacturing complexity.
Solution Approach 2:
Instead of creating security through complex geometries that are difficult to manufacture, the patent inverts the approach by using a simple geometry that is easy to manufacture, achieving security through the resulting narrow opening passage that limits access to locking pins. The simplicity itself becomes the security feature.
2Reliability
If the keyway includes a narrow upper part with specific inclination and lateral positioning, then access to central locking pins is limited enhancing security, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies particular parameter values for the upper part inclination (3° to 12°) and lateral positioning (offset distance no more than 15% of maximum lateral width) that optimize the balance between security and manufacturability. These specific parameter ranges ensure the narrow opening passage effectively limits access to locking pins while remaining achievable through standard manufacturing processes.
3Ease of manufacture
If traditional keyway geometries are used, then existing manufacturing processes can be utilized, but production efficiency and cost-effectiveness are reduced
Solution Approach 1:
The patent merges the keyway formation into a single machining operation using a rotating cutter disc, combining what would traditionally be multiple separate operations into one unified process. This approach maintains compatibility with existing manufacturing equipment while dramatically improving production efficiency and cost-effectiveness.
Data Source
Figure 1a~2
Figure 1b~1c
Figure 3~4b
AI summary
A key plug rotatable within a cylindrical bore of a cylinder lock. An upper relatively narrow part of a key way has a small lateral width no more than 33% of the maximum width of a lower relatively wide part of the keyway and extends obliquely upwards along a first direction pointing away from a second lower side wall of a lower part and being inclined at a relatively small angle α, in the interval 3° to 12°, relative to the vertical mid-plane. The sideways or lateral location of the upper relatively narrow part of the keyway is such that an imaginary downward extension thereof, substantially in a second direction opposite to the first direction down to an outer cylindrical contour of the key plug, will fall onto the outer cylindrical contour at a same second side of the vertical mid-plane and inside the second lower side wall of the keyway.