Key Blade Undercut Groove Prevents Cross-Keying

Solution Overview

Problem

Conventional lock cylinders face issues with cross-keying, where improper keys can be used to lock or unlock doors due to the lack of unique keyway configurations, leading to security vulnerabilities.

Innovation Solution

The design incorporates a key with a blade featuring an undercut groove on its lateral side, which includes specific surface configurations that align with complementary projections in the lock cylinder's key passageway, ensuring only the correct key can engage and rotate the plug, preventing unauthorized access.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional key and lock cylinder designs are used, then ease of manufacture is maintained, but security reliability deteriorates due to cross-keying vulnerabilities

Engineering Contradiction:

Improvesecurity reliabilityVSAvoidkey and lock cylinder complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by providing an undercut groove on only one lateral side of the key blade, creating an asymmetric key configuration. This asymmetric design ensures that only the correctly oriented key can engage with the corresponding projection in the key passageway, preventing cross-keying while maintaining manufacturing simplicity through single-sided grooving operations

Inventive Principle:

Principle #4Asymmetry

2Reliability

If unique keyway configurations are implemented, then security reliability improves by preventing cross-keying, but manufacturing complexity increases

Engineering Contradiction:

Improvesecurity reliabilityVSAvoidease of manufacture

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies local quality by concentrating the unique identification feature (undercut groove) on a specific local area of the key blade rather than requiring complex configurations throughout the entire key. This localized approach creates security through the specific groove geometry and positioning while leaving the rest of the key structure simple and easy to manufacture using standard processes

Inventive Principle:

Principle #3Local quality

3Reliability

If the key blade includes an undercut groove on one lateral side, then cross-keying prevention is achieved, but key blade complexity increases

Engineering Contradiction:

Improvecross-keying preventionVSAvoidkey blade shape

Core Design Contradiction:

ReliabilityVSShape

Solution Approach 1:

The patent applies asymmetry by providing an undercut groove on only one lateral side of the key blade, creating an asymmetric key configuration. This asymmetric design ensures that only the correctly oriented key can engage with the corresponding projection in the key passageway, preventing cross-keying while maintaining manufacturing simplicity through single-sided grooving operations

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS8800333B2Key and lock cylinder combination

Publication Date: 2014.08.12 SCHLAGE LOCK CO LLC

AI summary

Some embodiments disclosed include keys, lock cylinders, and key and lock cylinder combinations. The keys include a bow and a blade extending from the bow, where the blade includes at least one undercut groove in a lateral side thereof that receives at least one projection defining a keyway passage of a lock cylinder in which the key is positioned.