Fire Door Lock Latch Bolt Immobilizer Mechanism
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Solution Overview
Problem
Current fire door locks with central latch bolts and symmetrically arranged cylinders face issues with excessive torque causing damage to inner mechanisms and potential fraudulent opening due to large clearances, which compromise the function of intumescent joints during a fire.
Innovation Solution
A fire door lock design featuring a lever connected to a rocker and guard that moves horizontally into an immobilizing position when the cam on the lock cylinder is actuated, preventing contact between the follower and rocker, thereby deactivating the latch bolt withdrawal mechanism and preventing excessive torque-induced damage or fraudulent opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the follower is allowed to rotate freely to activate latch bolt withdrawal, then the door can be opened normally, but excessive torque can damage the inner mechanisms and fraudulent opening becomes possible
Solution Approach 1:
The rocker is designed to change its position dynamically between a first position (allowing follower rotation and latch withdrawal) and a second position (preventing follower rotation). This dynamic reconfiguration based on lever position allows the system to adapt its functionality - enabling normal operation when needed while preventing damage and fraud when the immobilizing position is activated
Solution Approach 2:
The rocker acts as an intermediary element between the follower and the latch bolt actuating lug. It mediates the transmission of rotational motion from the follower to the latch bolt, and can selectively block this transmission when in the second position, thus controlling whether the latch can be withdrawn
2Reliability
If the lever is positioned to immobilize the latch bolt, then protection against fraudulent opening is achieved, but the door cannot be opened
Solution Approach 1:
The system transitions between two distinct states: an immobilizing state where the lever is in the second position preventing door opening, and an operational state where the lever is in the first position allowing normal door operation. This dynamic switching capability resolves the contradiction by making the system's behavior dependent on its current state
3Ease of operation
If large clearances are provided for the lever and frame, then ease of installation and operation is improved, but the intumescent joints cannot perform their function correctly during fire
Solution Approach 1:
The system changes the positional parameter of the lever between two discrete positions (first and second positions). When in the second position, the lever's immobilizing face contacts the immobilizing active area of the latch bolt, changing the clearance parameter to near-zero and ensuring proper fire isolation. When in the first position, normal clearances are maintained for operation
Data Source
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AI summary
Fire door lock with a latch bolt immobilizer, of the type which is provided with a lock housing (9) having a central axis of symmetry (14) and equidistant insertion openings for lock cylinders (12) above and below the central axis (14) for use in doors that open on the right or on the left, and a latch bolt (5) which projects beyond the front of the lock (10) at the level of a central axis. The lock incorporates a lever (6) which is connected to the rocker (7) and the guard (8) and is able to move horizontally and in tandem into its immobilizing position when the cam (13) on the lock cylinder (12) is actuated, preventing contact between the actuating end (2a) of the follower (2) and the actuating lug (7a) of the rocker (7) during its rotational movement.