Latch Assembly with Automatic Locking and Fire Resistance
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Solution Overview
Problem
Existing double door latch assemblies face issues with reliable automatic locking, as latches can be damaged by improper alignment or heat deformation during fires, leading to potential door opening and fire spread.
Innovation Solution
A latch assembly design featuring a base with movement grooves and engagement holes, a movable member with sliding grooves, and a spring mechanism that automatically aligns and locks the latch with the door frame or ground grooves, preventing damage and maintaining the locked position even during fires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the follower door is not completely closed before closing the primary door, then the second and third latches cannot be moved to the exact latching positions, but this leads to damage to the upper and lower latch assemblies
Solution Approach 1:
A rubber buffer is provided at the end of the actuation latch. When the follower door is not completely closed and the actuation latch contacts the primary door, the rubber buffer absorbs the impact and prevents damage to the latch assembly. This cushioning mechanism allows the primary door to be closed at any time without risking damage to the latch components.
2Reliability
If the latches are made of heat-resistant material to prevent deformation during fires, then the reliability during fires is improved, but the cost and manufacturing complexity increase
Solution Approach 1:
The latch assembly is divided into two functional parts with different material properties: the actuation latch uses a soft, heat-resistant material (such as high-temperature plastic or rubber) that maintains flexibility and resistance during fires, while the second and third latches use hard, heat-resistant materials (such as metal) for structural strength and engagement. This segmentation allows each component to be optimized for its specific function while maintaining overall fire resistance.
3Reliability
If the actuation latch is made soft to prevent damage during improper alignment, then the latch assembly reliability is improved, but the locking strength may be reduced
Solution Approach 1:
The latch system uses different material hardness for different components: the actuation latch is made of soft material (rubber or high-temperature plastic) to absorb impact and prevent damage during improper alignment, while the second and third latches are made of hard material (metal) to provide sufficient locking strength when engaged with the grooves in the door frame and ground.
Solution Approach 2:
The latch assembly incorporates composite construction with the actuation latch made of soft, resilient material and the engagement latches made of hard, strength-providing material. This composite approach allows the system to exhibit both shock-absorbing properties for protection and high strength for secure locking.
Data Source
AI summary
A latch assembly (10) is mounted to a follower door (275) of a double door (257). When the follower door (275) is closed while a primary door (259) of the double door (257) is closed, an actuation latch (131) of the latch assembly (10) is moved from a releasing position to a pressing position to move a latch (231) of the latch assembly (10) to a latching position engaged in a groove (37, 300) in a door frame (31) or in the ground (299). When the actuation latch (131) is moved from the releasing position to the pressing position while the follower door (275) is not in the closed position, the latch (231) is retained in an unlatching position, avoiding damage to the latch assembly (10).