Anti-pick Latch Assembly for Double Door Security
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Solution Overview
Problem
Double doors are vulnerable to being forcibly opened due to the risk of the follower door latch being picked or deformed by heat, leading to potential fire spread.
Innovation Solution
A latch assembly with a base, movable member, limiting member, and actuation latch system that ensures the latch remains in a locked position even when the primary door is aligned with the follower door, using springs and pins to prevent movement from the latching to the unlatching position, and safety pins that extend during a fire to maintain the latch in the locked position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional latch assembly is used on the follower door, then the door can be easily operated and locked, but the latch is vulnerable to being picked or deformed by heat
Solution Approach 1:
The latch assembly is divided into multiple independent components: a movable member with lateral walls, a base with sidewalls, pins extending through engagement holes, and spring members. This segmentation allows each component to perform its specific function while collectively providing anti-pick protection through the aligned engagement holes that prevent manual manipulation.
Solution Approach 2:
The movable member is nested between the sidewalls of the base, with pins extending through both the sidewalls and lateral walls. The spring members are nested within the engagement holes, creating a compact integrated structure where components are housed within each other to form a unified anti-pick locking mechanism.
2Device complexity
If the latch is designed to be simple and accessible, then it can be easily operated, but it becomes vulnerable to picking and heat deformation
Solution Approach 1:
The latch assembly features asymmetric design elements including the specific arrangement of engagement holes at different positions on the lateral walls, the oriented positioning of spring members, and the asymmetric configuration of the movable member relative to the base. This asymmetry prevents standard picking tools from effectively manipulating the latch while maintaining operational functionality.
Solution Approach 2:
The spring members are pre-loaded within the engagement holes to maintain constant biasing force on the movable member. This preliminary action ensures that the latch components remain under controlled stress, making them more resistant to heat deformation and picking attempts before any manipulation occurs.
3Reliability
If the latch assembly uses multiple engagement holes and pins, then picking resistance increases, but the structure becomes more complex
Solution Approach 1:
The engagement holes serve multiple functions: they provide structural alignment between the base and movable member, house the spring members for biasing force, and create the anti-pick barrier through their specific positioning. The pins simultaneously connect components and prevent lateral movement. This multi-functionality reduces the need for separate dedicated anti-pick features.
Solution Approach 2:
The anti-pick mechanism is merged with the basic locking mechanism by integrating the engagement holes and pins into the primary latch structure. The spring members are combined with the engagement holes, and the movable member integrates both locking and anti-pick functions, creating a unified design rather than adding separate anti-pick components.
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 effectively prevents the double door from being opened by picking or heat deformation, ensuring reliable locking and reducing the risk of fire spread by maintaining the latch in the locked position even during a fire.
Implementation Method 1
A spring member is mounted between the movable member and the base. The spring member is biased from the disengagement position to the engagement position
Implementation Method 2
A first pin extends through the first engagement holes of the sidewalls of the base and the first sliding grooves of the lateral walls of the movable member. A second pin extends through the second engagement holes of the sidewalls of the base and the second sliding grooves of the lateral walls of the movable member.
Data Source
AI summary
An anti-pick latch assembly (10) is mounted to a follower door (275) of a double door (257). The latch assembly (10) includes an actuation latch (131) normally extending beyond an end face (291) of the follower door (257) and a latch (231) movable between an unlatching position received in the follower door (275) and a latching position extending out of the follower door (275) into a groove (37) in a door frame (31). When the follower door (275) is closed while a primary door (259) of the double door (257) is closed, the actuation latch (131) is actuated to move a limiting member (90) to a locking position, moving the latch (231) of into the groove (37) of the door frame (31). The limiting member (90) in the locking position prevents the latch (231) from moving out of the groove (37) while the latch (231) is picked.