Door Latch Lock Mechanism Resolving Bush Interference
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Solution Overview
Problem
The existing door latch device fails to reliably switch the child lock mechanism during operation of the inner handle due to interference between components, preventing the mechanism from switching between unlocked and locked states.
Innovation Solution
A door latch device with a first lock mechanism that includes a rotating lever system, a connection spring, and a holding spring, allowing the connection member to move between unlock and lock positions, enabling reliable switching even during inner handle operation by using a rotating lever system connected by a connection spring and held by a stronger holding spring, ensuring the mechanism can switch states after handle operation is completed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the child lock mechanism is driven during inner handle operation, then the lock state should be switched, but the bush interferes with the inside lever preventing switching
Solution Approach 1:
The switching lever is divided into a first rotating lever and a second rotating lever that can rotate relative to each other. The first rotating lever controls the bush position while the second rotating lever controls the inside lever engagement. This segmentation allows the bush to be positioned away from the inside lever during handle operation, eliminating interference while maintaining reliable lock switching.
Solution Approach 2:
A connection spring is introduced as an intermediary element between the first and second rotating levers. This spring allows controlled relative rotation between the two levers, enabling the bush to be positioned in non-interference locations while still transmitting the switching command from the motor to the lock mechanism.
2Reliability
If the bush is moved to prevent interference, then switching reliability improves, but the mechanism complexity increases
Solution Approach 1:
The first and second rotating levers are combined into a single switching lever assembly that performs multiple functions. The first rotating lever controls bush positioning while the second rotating lever controls inside lever engagement, and both are integrated into one component structure. This merging reduces the number of separate parts while maintaining the complexity-needed functionality.
Solution Approach 2:
The connection spring introduces dynamic flexibility between the two rotating levers, allowing them to rotate relative to each other as needed. This dynamic capability enables the system to adapt its configuration during operation - keeping the bush away from the inside lever during handle operation, but allowing engagement when appropriate - without requiring complex mechanical linkages.
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 solution allows for reliable switching of the lock mechanism during inner handle operation, enhancing the safety and functionality of the door latch device by ensuring the lock can be switched between states without interference, thus addressing the issue of the child lock mechanism not switching correctly.
Implementation Method 1
a connection spring that rotatably connects the second rotating lever to the first rotating lever, allows rotation of the second rotating lever to the second rotation position with respect to the first rotating lever at the first working position and biases the second rotating lever toward the first rotation position
Implementation Method 2
a holding spring that has a biasing force stronger than a biasing force of the connection spring, biases the first rotating lever rotated to the first working position side beyond a specific position between the first working position and the second working position to the first working position and holds the first rotating lever
Data Source
AI summary
A door latch device includes a latch mechanism, an inner lever having a connection lever and an actuation lever, and a lock mechanism switching between unlocked and locked state. The lock mechanism includes a connection member capable of transmitting operation of the connection lever to the actuation lever, a first rotating lever rotated by a motor to first and second working positions, a second rotating lever rotatable to a first rotation position where the connection member is moved to an unlock position and a second rotation position where the connection member is moved to a lock position, a connection spring connecting the first rotating lever and the second rotating lever while allowing relative rotation of them, and a holding spring having a biasing force stronger than a biasing force of the connection spring and holds the first rotating lever at the first and second working positions.