Espagnolette Lock Latch Recess Geometry for Jam Prevention
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Solution Overview
Problem
Espagnolette locks often cause the latch of a main lock to jam when the latch excavation engages, due to the narrow protruding edge of the latch head getting caught between the excavation and the recess in the faceplate, especially when the door leaves are opened sequentially.
Innovation Solution
The latch excavation is designed with sections of different widths, where the wider section of the excavation protrudes over the latch head's edge, separating the guide from the outer edge and preventing the latch from getting caught, and the recess has a guide section with a wider area outside the guide section to facilitate smooth movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the latch excavation is designed with a narrow profile to fit precisely in the recess, then the positioning precision is improved, but the latch head's protruding edge gets caught between the excavation and the recess causing jamming
Solution Approach 1:
The latch excavation is designed with varying width along its length: a narrow section in the guide area for precise positioning, and a wider section in the outer area to prevent the latch head's protruding edge from getting caught. This local variation in geometry resolves the contradiction by providing both precise positioning and jamming prevention in different zones of the same component.
2Reliability
If the latch excavation is made wider to prevent the latch from getting caught, then the reliability is improved, but the positioning precision and guidance within the recess deteriorates
Solution Approach 1:
The excavation width is optimized locally: narrow where positioning is critical (in the recess guide section) and wide where prevention of latch engagement is critical (outer section). This resolves the contradiction by applying different geometric properties in different spatial zones.
Solution Approach 2:
The latch excavation can be viewed as segmented into functional zones: a guide section with narrow width for precise positioning, and an outer section with wider width for preventing latch head engagement. This segmentation allows each zone to fulfill its specific function without compromising the other.
3Manufacturing precision
If the recess guide section is made narrower to improve guidance, then the positioning is improved, but the latch head's protruding edge can get caught in the gap
Solution Approach 1:
The solution applies local quality by making the excavation wide in the outer region (where latch engagement prevention is needed) while keeping the guide section narrow (where positioning accuracy is needed). The wide outer section ensures the protruding edge cannot get caught, while the narrow guide section provides accurate guidance.
Data Source
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AI summary
In a counterlock (6) of a rod lock (4) for a double-leaf door, a latch recess (16, 25) has sections (20, 21) of different widths. A guide section (22) of a recess (19) in a faceplate rail (18) guides the narrowest section (20) of the latch recess (16). An edge (23) of the recess (19) is spaced apart from the wider sections (21) of the latch recess (16). This prevents the latch (12) from jamming.