Sash Lock Delay Cam Mechanism for Forced Entry Resistance
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Solution Overview
Problem
Traditional window locks are not sufficiently resistant to forced entry, as they can be easily manipulated by lock-picking devices, and the mechanism for securing the sash is not robust enough to prevent unauthorized access.
Innovation Solution
A window latch system comprising a housing, a shaft, a locking cam, a delay cam, and a locking spring, where the delay cam selectively engages and drives the locking cam between locked and unlocked positions, requiring approximately 85-90 degrees of rotation to lock and 90-95 degrees to unlock, incorporating protrusions and chamfered recesses for secure engagement and disengagement, thereby enhancing resistance to forced entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional window locks are used, then the device complexity is low and ease of operation is high, but forced entry resistance is insufficient
Solution Approach 1:
The lock mechanism is divided into two independent cams: a locking cam that performs the locking function and a delay cam that controls the timing and sequence of operations. This segmentation allows each component to be optimized for its specific function while collectively providing enhanced forced entry resistance through coordinated operation.
Solution Approach 2:
The delay cam is designed to rotate approximately 90 degrees before the locking cam begins to rotate, creating a preliminary action sequence. This delay prevents lock-picking devices from immediately manipulating the locking cam, as the user must first complete the full rotation sequence including the delay portion, thereby enhancing security against forced entry.
2Reliability
If the locking mechanism requires substantial rotation (85-90 degrees to lock, 90-95 degrees to unlock), then forced entry resistance increases, but operation time increases
Solution Approach 1:
The lock mechanism utilizes dynamic cam profiles with varying radii that convert the substantial rotation requirement into a smooth, continuous motion sequence. The cam geometry is designed to provide mechanical advantage at critical points, allowing the user to complete the required 85-95 degree rotation with controlled effort rather than brute force, making the extended operation time acceptable while maintaining enhanced security.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system significantly increases the resistance to forced entry by requiring substantial rotation and engagement of multiple components, making it difficult for lock-picking devices to operate and ensuring the latch remains locked until intentionally unlocked, thus enhancing security.
Implementation Method 1
A locking spring being installed in the housing cavity... The biased locking spring may engage a first opening in the locking cam to lock the locking cam relative to the housing upon the locking cam reaching the second position
Implementation Method 2
a locking cam being rotatably mounted upon the shaft within a cavity of the housing... a delay cam being fixedly mounted to the shaft... The delay cam selectively engaging and driving the locking cam may comprise, upon rotation of the shaft and delay cam from the first position to the second position
Data Source
AI summary
An improved forced entry resistant sash lock comprises a housing, a shaft rotatably mounted thereto, a locking cam and a delay cam rotatably and fixedly mounted to the shaft, respectively, and a locking spring. The delay cam selectively engages and drives the locking cam between a locked position and an unlocked position. Locking spring biasing causes engagement with a locking earn opening to lock the cam when in the latch-locked position, with engagement to a depth permitting releasable detent engagement in a delay cam recess. Selective engagement and driving of the locking cam comprises a first portion of delay cam rotation being without driven locking cam rotation, and a second portion causing driven locking cam rotation from a retracted position into a protruding position. Selective engagement is by contact between corresponding protrusions on the delay and locking cams. Shaft/delay cam counter-rotation to unlock the latch proceeds in a reverse manner.