Electrorheological Fluid Clutch for Electronic Door Lock
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Solution Overview
Problem
Electronic door locks with mechanical locks and electronic controls face issues due to limited battery life and high power consumption, particularly with rheological fluid latches that require large inrushes of power and have bulky designs compromising aesthetic appeal and performance.
Innovation Solution
A low-energy electrorheological fluid clutch is introduced, utilizing a spring, plunger, and electrorheological fluid within a shaft to change viscosity in response to electrical current, providing a hydraulic blocking force for coupling engagement between door handle and lock shafts, reducing power consumption and minimizing moving parts for a more compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a large cylindrical volume of rheological fluid is used in Willats latch, then the latch can provide sufficient viscous resistance to the piston, but the power consumption increases due to the large inrush of power required
Solution Approach 1:
The patent applies local quality by concentrating the rheological fluid in a small chamber rather than using a large cylindrical volume. The fluid is placed in a localized region where it can provide sufficient viscous resistance to the piston through high viscosity state, while the overall volume of fluid remains minimal, thereby reducing power consumption during inrush.
Solution Approach 2:
The patent utilizes parameter changes by controlling the viscosity of the rheological fluid through electrical current application. The fluid transitions from a low viscosity state (allowing easy piston movement) to a high viscosity state (providing resistance), and this transition is controlled locally in a small chamber, achieving the desired force without the power consumption associated with larger fluid volumes.
2Ease of manufacture
If numerous moving parts including linkages and arms are used in Willats latch, then the latch mechanism can be constructed, but the complexity increases and the moving parts are susceptible to dust and wear
Solution Approach 1:
The patent extracts the essential function of the latch mechanism by removing unnecessary moving parts. Instead of using multiple linkages and arms, the invention employs a direct piston-cam mechanism where the piston directly actuates a camming surface that engages with a plunger. This extraction of redundant components simplifies the mechanism while maintaining functionality and improving reliability.
Solution Approach 2:
The patent replaces complex mechanical linkages with a more straightforward mechanical interaction between the piston and camming surface. The camming surface directly converts the piston's linear motion into rotational motion of the plunger, eliminating the need for intermediate linkages and reducing the number of moving parts that could be affected by dust and wear.
3Ease of operation
If a large cylindrical chamber with piston is used in Willats latch, then the latch mechanism can operate, but the size and bulkiness increases requiring housing in escutcheon
Solution Approach 1:
The patent applies local quality by confining the rheological fluid to a small chamber rather than using a large cylindrical volume. This localized approach allows the latch mechanism to operate with sufficient viscous resistance while maintaining a compact overall size that can be integrated directly into the door without requiring separate escutcheon housing.
Solution Approach 2:
The patent utilizes dynamics by employing a camming surface that converts linear piston motion into rotational plunger motion. This dynamic mechanism allows for compact packaging of the latch components, as the camming action enables the plunger to engage and disengage from the camming surface within a small spatial envelope, eliminating the need for large escutcheon housing.
4Productivity
If piezoelectric elements are used as prime mover, then the lock can be actuated, but the capacitive characteristics cause large inrush of power operating as short circuit load
Solution Approach 1:
The patent applies periodic action by using a camming surface that engages the plunger at a specific point in the rotation cycle. The camming surface is positioned such that it contacts the plunger when the rheological fluid has transitioned to its high viscosity state, providing a controlled, periodic actuation that avoids continuous power draw and minimizes inrush current effects.
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 extends battery life by minimizing power draw and reducing the size and complexity of the lock mechanism, enhancing performance and aesthetic appeal by using less energy to maintain coupling engagement and allowing user torque to aid in rotation, thus reducing the need for a large prime mover.
Implementation Method 1
The rheological fluid is capable of changing from a first state in which the fluid has a first viscosity to a second state in which the fluid has a second viscosity in response to the application of an electrical current across the fluid
Implementation Method 2
The plunger is biased by the spring into selective coupling engagement with the first shaft
Data Source
AI summary
A clutch for an electronic door lock includes a first shaft, a second shaft, a spring, a rheological fluid, and a plunger. The second shaft has an aperture therein and is axially co-aligned with the first shaft and is rotatably mounted adjacent the rotatable first shaft. The spring is disposed in the aperture in the second shaft. The rheological fluid is held within the aperture and is capable of changing viscosities in response to the application of an electrical current across the fluid. The plunger is biased by the spring into selective coupling engagement with the first shaft and is capable of selective motion into the aperture in response to contact by a camming surface of the first shaft due to relative rotation of the first shaft with respect to the second shaft.