Door Latch Delayed Return Mechanism for Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mortise door locks in institutional environments, such as hospitals, generate noise due to the return movement of the latch mechanism, which is not adequately addressed by existing noise reduction solutions in architectural door latches.
Innovation Solution
A door latch with a delayed return mechanism featuring a housing filled with high viscosity fluid media and a rotatable hub with a fin, allowing controlled flow to resist rotation and reduce noise, including an adjustment element to customize resistance levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a spring is used to return the lever to its original position, then the lever returns quickly to its initial state, but noise is generated due to the lever hitting a stop
Solution Approach 1:
A viscous fluid is introduced as an intermediary damping element between the moving lever and the stop. The fluid resists the lever's motion during return, reducing the impact speed and eliminating the noisy collision while still allowing the lever to complete its return stroke.
Solution Approach 2:
The patent employs a hydraulic damping mechanism where a viscous fluid fills a chamber and resists the motion of a piston or lever component. This hydraulic resistance controls the return speed of the lever, slowing it down to prevent impact noise while maintaining functional performance.
2Object-generated harmful factors
If a damping element is added to decrease the speed of the actuating lever, then impact noise is reduced, but the device complexity increases
Solution Approach 1:
The damping function is merged with the existing return spring mechanism. The viscous fluid chamber is integrated into the same housing that contains the spring, combining the elastic energy storage function with the viscous damping function in a single compact assembly, thereby minimizing additional complexity.
Solution Approach 2:
The viscous fluid serves multiple functions: it acts as a damping element to reduce impact noise, provides friction for controlled motion, and can serve as a lubricant for moving parts. This multi-functionality reduces the need for separate components, offsetting the added complexity with functional consolidation.
3Object-generated harmful factors
If high viscosity fluid media is used to resist rotation of the hub, then noise is significantly reduced, but the resistance to motion increases
Solution Approach 1:
The damping force provided by the viscous fluid is dynamic rather than static. The resistance force varies with the speed of rotation: at high speeds (during normal operation), the fluid provides strong damping to reduce noise; at low speeds (during controlled return), the resistance naturally decreases, allowing smooth completion of the motion cycle.
Solution Approach 2:
The patent utilizes the shear-rate-dependent viscosity characteristic of the fluid. By designing the geometry of the fluid chamber and moving parts, the system operates in a regime where the fluid provides optimal damping at the specific speeds and forces encountered during latch operation, balancing noise reduction with acceptable operating force.
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 mechanism effectively dampens the return movement of the latch, significantly reducing noise levels, making it suitable for noisy environments like hospitals.
Implementation Method 1
a cavity in the housing at least partially filled with a fluid media... a channel through which the fluid media passes during rotation of said hub to control flow of the media about the cavity
Data Source
AI summary
A delayed return mechanism, such as for a door latch, including a housing having a hole with an axis, a cavity in the housing at least partially filled with a fluid media, a hub disposed in the cavity including a spindle hole coaxial with the hole in the housing including teeth within the spindle hole to engage a spindle, the hub being rotatable about the axis and having a fin extending radially outward in the cavity, and a channel through which the fluid media passes during rotation of the hub to control flow of the fluid media about the cavity.