Lock Mechanism Cam Lever Blocking Member Security
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Solution Overview
Problem
Cylinder locks are susceptible to unauthorized actuation, particularly when a thumb bolt actuator is installed on the interior side, as the cam can be freely rotated without requiring a key, making them vulnerable to manual manipulation or removal.
Innovation Solution
Incorporating a blocking member that covers the cam lever and a weakened area on the connecting member to prevent unauthorized access and rotation of the cam, along with a retention member to constrain the cam shaft, and utilizing a push-activated thumb bolt mechanism to secure the lock, ensuring the cam is non-rotatably fixed in a security condition upon removal of an actuator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a thumb bolt actuator is installed on the interior side of the closure, then the lock can be operated from the interior without a key, but the cam can be freely rotated when engaged with the thumb bolt actuator, making it vulnerable to unauthorized manipulation
Solution Approach 1:
The lock actuator system is segmented into two separate actuators: a thumb bolt actuator for interior operation and a key actuator for exterior operation. This segmentation ensures that each actuator serves a specific function with appropriate security characteristics, preventing the cam from being freely manipulated while maintaining ease of interior operation.
Solution Approach 2:
A composite actuator system is implemented where the first actuator (thumb bolt) and second actuator (key actuator) work together through a clutch mechanism. The composite system combines the convenience of thumb bolt operation with the security of key-controlled engagement, resolving the contradiction between ease of operation and security.
2Ease of operation
If the exterior lock actuator is removed to gain access, then the cam can be manually rotated to unlock the lock, but this creates a vulnerability to unauthorized entry
Solution Approach 1:
A blocking member is preliminarily positioned to cover the cam lever before any actuator removal occurs. This preliminary protective measure ensures that even if the exterior actuator is removed, the cam lever remains inaccessible and cannot be manually rotated, preventing unauthorized entry while still allowing legitimate access through the key actuator.
Solution Approach 2:
The blocking member acts as an intermediary protective element between the cam lever and potential unauthorized access. It physically obstructs access to the cam lever, serving as a mediator that prevents direct manipulation of the cam while maintaining the functional integrity of the lock mechanism.
3Reliability
If a blocking member is added to cover the cam lever, then access to the cam is made more difficult, but this increases the complexity of the lock mechanism
Solution Approach 1:
The blocking member is designed to serve multiple functions: it covers and protects the cam lever from unauthorized access, provides structural support within the lock mechanism, and works in conjunction with the clutch mechanism to control cam engagement. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in overall complexity while maintaining enhanced security.
4Reliability
If a predetermined weakened area is provided on the connecting member, then the lock will break at a controlled position under high force, but this reduces the strength of the connecting member
Solution Approach 1:
The predetermined weakened area converts the harmful effect of excessive force into a beneficial controlled failure mode. When subjected to high forces exceeding the lock's security thresholds, the connecting member is designed to break at the weakened area rather than causing catastrophic damage or allowing unauthorized access. This controlled fracture protects the critical cam and blocking member components while providing a clear indication of forced entry attempts.
Data Source
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AI summary
An improved security lock mechanism (100, 200, 400) is provided utilising a blocking member (192) to protect a cam lever (174). Furthermore, a lock barrel (116, 416) is engaged to a first lock actuator housing (114, 414) via a pin instead of a circlip. In addition, a cam(106) is provided whose shaft (172)extends from a lock housing (10). A cam (216) is provided with a radially extending member (302) to bear against the surface of alock casing (10). A thumb turn bolt (300) is provided which can be actuated upon axial movement. A cam (406) can be axially retained against a lock barrel (416)upon actuation of a clutch to a security position.