Thumbwheel Return Mechanism With Zero-Clearance Position Sensing
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Solution Overview
Problem
Existing thumbwheel control devices suffer from residual mechanical clearance around the rest position, which limits their accuracy and prevents precise detection of angular movements.
Innovation Solution
A control device design featuring a body with printed circuit, a pivotable actuator, a torsion spring with end strands supported on actuator surfaces, a magnet, and a magnetic field sensor, along with elastic elements and stops to eliminate residual clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a torsion spring with contact surfaces and stops is used for return-to-center mechanism, then the device can return to rest position, but residual mechanical clearance appears between spring branches and support surfaces
Solution Approach 1:
The patent introduces an elastic element as an intermediary component between the stop and the support surface of the torsion spring. This elastic element acts as a mediator that eliminates the residual clearance by providing continuous contact and force transmission, while allowing for manufacturing tolerances. The elastic element deforms to compensate for gaps, ensuring the torsion spring remains under constant tension without requiring perfect mechanical fit between rigid components.
Solution Approach 2:
The patent changes the mechanical parameter of the connection from rigid fixed contact to elastic deformable contact. By replacing the rigid stop-surface interface with an elastic element, the system can dynamically adjust to manufacturing variations and maintain zero clearance during operation. The elastic element's deformation capability allows the system to adapt to parameter variations while maintaining measurement precision.
2Ease of manufacture
If manufacturing tolerances are relaxed to reduce cost, then production becomes easier, but residual clearance increases between components
Solution Approach 1:
The elastic element serves as a compensatory intermediary that absorbs manufacturing tolerances. Instead of requiring precise fitting between the stop and support surface, the elastic element deforms to fill the gap created by tolerance accumulation. This allows manufacturers to use more relaxed tolerances while still achieving zero operational clearance, significantly easing manufacturing and assembly processes.
Solution Approach 2:
The elastic element provides beforehand cushioning by being pre-installed in a compressed or tensioned state that anticipates and compensates for potential clearance issues. This pre-compression ensures that even with relaxed manufacturing tolerances, the components remain in firm contact during operation, preventing clearance from developing during use.
3Adaptability or versatility
If the actuator is allowed to move freely around the axis, then the range of motion increases, but residual clearance prevents accurate detection near the rest position
Solution Approach 1:
The elastic element acts as a mediator that maintains continuous force transmission between the torsion spring and the stop across the entire range of motion. This ensures that even when the actuator moves freely through large angles, the torsion spring remains under constant tension, eliminating dead zones or clearance gaps that would occur during direction changes or at the rest position.
Solution Approach 2:
The system transitions from a static rigid connection to a dynamic elastic connection that adapts during motion. The elastic element continuously adjusts its deformation state to maintain optimal contact force throughout the actuator's range of motion, ensuring accurate detection at all positions including the rest position, while allowing full freedom of movement.
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 ensures no residual mechanical clearance, enhancing the accuracy of the control device, particularly around the neutral position, and providing a liquid-tight seal.
Implementation Method 1
a magnetic field sensor arranged on the printed circuit facing the magnet, suitable for detecting the angular position of the magnet and for producing an electrical signal depending on said detected angular position
Implementation Method 2
a torsion spring comprising two end strands supported on two respective support surfaces of the actuator, said torsion spring being arranged to drive the actuator in rotation toward a rest position
Implementation Method 3
The branches of said spring are arranged supported on a pair of contact surfaces arranged on the rotor of the movable actuator, and a pair of fixed stops on the lower portion of the body
Data Source
AI summary
A control device comprising: a body comprising a printed circuit, a mobile actuator able to move in pivoting relative to the body about an axis 50 of rotation, a torsion spring comprising two end strands resting against two respective bearing surfaces of the actuator, said torsion spring being designed to urge the actuator to rotate towards a position of rest, at least one magnet rigidly secured to the actuator, a magnetic-field sensor arranged on the printed circuit facing the magnet and designed to detect the angular position of the magnet and to produce an electric signal dependent on the detected angular position, characterized in that it comprises two end-stops rigidly secured to the body, a respective elastic element being arranged between each end-stop and the body, each end-stop comprising a bearing surface bearing on a respective end strand of the torsion spring.