Elastically Deformable Joint for High Precision Weighing Sensors
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Solution Overview
Problem
Existing monolithic lever mechanisms in weighing sensors face limitations in achieving high transmission ratios due to geometric constraints and manufacturing parameters, leading to sensitivity to static and dynamic forces, which impairs measuring accuracy and rigidity.
Innovation Solution
The use of an elastically deformable joint with two bending areas whose longitudinal extension planes enclose an angle of 45 to 135 degrees, providing improved rigidity and reduced sensitivity to unwanted forces, allowing for a high transmission ratio with a small size and improved bending stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If several levers are connected in series to achieve high transmission ratio, then the transmission ratio is improved, but the device complexity and sensitivity to unwanted forces increases
Solution Approach 1:
The joint is segmented into two separate bending areas (first and second bending areas) that are arranged at angles to each other. This segmentation allows each bending area to handle specific force components independently, achieving high transmission ratio functionality without requiring multiple separate levers connected in series.
Solution Approach 2:
The joint transitions from a single-plane bending structure to a three-dimensional structure with bending areas arranged at angles (45-135 degrees) relative to each other. This dimensional change enables the joint to achieve high transmission ratio while maintaining compact size and reducing sensitivity to unwanted forces in directions perpendicular to the bending planes.
2Measurement precision
If the shorter lever arm is reduced to increase transmission ratio, then the transmission ratio is improved, but the manufacturing precision and structural stability deteriorate
Solution Approach 1:
The joint structure moves from a two-dimensional single-plane bending design to a three-dimensional configuration with bending areas oriented at angles to each other. This allows the shorter lever arm to be reduced to minimal values without compromising manufacturing feasibility, as the angled arrangement provides inherent structural stability and force distribution.
3Force
If the elastically deformable joint is designed to transmit large forces, then the force transmission capability is improved, but the rigidity in unwanted directions increases causing sensitivity to vibrations
Solution Approach 1:
Different regions of the joint (first and second bending areas) are designed with specific orientations (45-135 degrees to each other) to provide localized rigidity in specific directions. This allows the joint to transmit large forces effectively while maintaining low rigidity in directions perpendicular to the bending planes, thereby reducing sensitivity to vibrations and unwanted forces.
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
This configuration significantly enhances the rigidity and stability of the lever mechanism, reducing sensitivity to disruptive forces and maintaining high measuring accuracy and long-term stability.
Implementation Method 1
an elastically deformable joint with two bending areas whose longitudinal extension planes enclose an angle of 45 to 135 degrees, providing improved rigidity and reduced sensitivity to unwanted forces
Data Source
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AI summary
The invention relates to a crank mechanism, in particular, for a weighing sensor on a balance working on the electromagnetic force compensation principle, comprising at least one crank (23) connected to a fixed base body (3) or an element connected thereto, the at least one crank arm being connected to the base body (3) or the element connected thereto by means of an elastically-deformable joint (28), defining a pivot axis of the at least one crank (23) and a load force (FL) corresponding to the weight force (FG) or a derivative thereof acts on a first crank arm of the at least one crank which generates a reaction force (FR) on a second crank arm of the at least one crank. According to the invention, the elastically-deformable joint (28) comprises two thin elastically-deformable flexible regions (29), connecting the crank directly or indirectly to the base body (3) or the element connected thereto, each flexible region (29) being flexible in a direction perpendicular to a longitudinally extending plane defined by the geometry of the flexible region (29) to generate a pivot movement of the at least one crank (23), the longitudinally-extending planes of the flexible regions (29) including an angle (α) which is not zero and a virtual pivot axis (D) for the at least one crank (29) is defined by the two elastically-deformable flexible regions (29).