Door Lock Trigger Mechanism for Ligature Risk Reduction
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Solution Overview
Problem
Existing door locks in prisons and psychiatric hospitals pose a risk as the bolt can serve as an anchor point for ligatures, allowing individuals to cause harm, especially when the ligature is not visible and cannot be unlocked by moving the bolt with a suspended weight.
Innovation Solution
A door lock design featuring a bolt with a trigger mechanism that automatically retracts into the unlocked position when a rope or cable is looped around it, using a catch system and spring biasing to change the catch's position from engaged to disengaged, preventing the bolt from being used as an anchor point for self-harm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bolt is designed to provide a stable anchor point for security, then the locking reliability is improved, but the risk of ligature creation increases
Solution Approach 1:
The bolt is designed with a trigger mechanism that allows it to dynamically change state from locked to unlocked when activated by the trigger, rather than remaining statically locked. This enables the bolt to automatically respond to ligature attempts by retracting, eliminating the stable anchor point while maintaining security during normal operation
Solution Approach 2:
The trigger mechanism is positioned on the end portion of the bolt such that if a rope or cable is looped around the bolt and pulled, it will actuate the trigger. This converts the harmful ligature force into a beneficial automatic unlocking action, causing the bolt to retract and remove the anchor point
2Reliability
If the bolt is made secure against unauthorized movement, then the security is improved, but the ease of operation in emergency situations deteriorates
Solution Approach 1:
The lock system is designed to automatically unlock itself when a ligature is detected through the trigger mechanism. The bolt self-actuates to the unlocked position without requiring external intervention, keys, or manual operation, enabling automatic emergency release while maintaining normal 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 lock automatically moves into the unlocked position when a ligature is attempted, removing the anchor point and preventing harm, while maintaining security features to ensure the bolt remains locked unless intentionally unlocked.
Implementation Method 1
The catch may be resiliently biased into the engaged position. In particular, the catch may be resiliently biased into the engaged position with a force sufficient to maintain the bolt in the locked position
Implementation Method 2
The retraction mechanism may resiliently bias the bolt into the unlocked position, such that the bolt automatically moves into the unlocked position upon activation of the trigger. For example, the retraction mechanism may comprise a (first) spring configured to urge the bolt into the unlocked position
Data Source
AI summary
The present application provides a lock (100) for a door. The lock comprises a housing (102), a lock mechanism (108), and a bolt (104). An end portion (112) of the bolt comprises a trigger (106). The lock mechanism is operable to move the bolt between a locked position in which the end portion extends through an opening in the housing and projects from the housing, and an unlocked position in which the end portion is within the housing. The lock further comprises a retraction mechanism (110), wherein actuation of trigger causes the retraction mechanism to automatically move the bolt from the locked position into the unlocked position.