Electromagnetic Beam Scale with Parallel Crank Guidance
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Solution Overview
Problem
Existing electromagnetically compensating bar scales face challenges due to their asymmetrical structure, which compromises the separation of leadership and translation functions, leading to reduced sensitivity and stiffness, making them less suitable for precise mass comparisons.
Innovation Solution
A two-armed, rotatably mounted translation lever with integrated actuators in a closed control loop, utilizing a parallel crank mechanism and solid-state joints to achieve a compliant mechanism with optimized rigidity and sensitivity, allowing for a monolithic, planar construction that minimizes non-linearity and enhances production flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an asymmetrical mechanism is used for electromagnetic force compensation, then the mechanism can be implemented, but the sensitivity and stiffness are reduced
Solution Approach 1:
The patent applies asymmetry in reverse by designing a symmetrical beam balance mechanism. The beam has equal arms with identical structural characteristics, and the heat sources are positioned symmetrically. This symmetrical design compensates for thermal expansions equally from both sides, maintains independence from ambient pressure, and reduces sensitivity to external disturbances while preserving high measurement sensitivity.
2Device complexity
If functional integration is used where one part fulfills both guiding and transmission functions, then the structure is compact, but the joint orientation cannot be optimized for single function leading to compromised performance
Solution Approach 1:
The patent segments the mechanism into distinct functional components: the beam structure handles force transmission between pans, while separate guiding mechanisms (knife edges and supports) handle the guidance function. This separation allows each component to be optimized for its specific function, with joints and supports positioned and oriented appropriately for their respective roles, thereby maintaining high measurement precision without excessive complexity.
3Ease of manufacture
If solid-state joints with semicircular contour are used, then the joints are simple to manufacture, but they are less stiff for lateral loads
Solution Approach 1:
The patent applies different joint designs at different locations based on local requirements. The knife edge joints are designed with specific geometric characteristics optimized for their function. The supports and mounting points are configured to provide appropriate stiffness in lateral directions where needed, while maintaining manufacturability. This localized optimization ensures that each joint has the necessary mechanical properties for its specific position and loading conditions.
4Reliability
If a symmetrical structure is used, then thermal expansion compensation and independence from ambient pressure are achieved, but asymmetrical mechanisms are frequently used which forgo these advantages
Solution Approach 1:
The patent applies asymmetry in reverse by deliberately designing a symmetrical beam balance mechanism. The beam has equal arms with identical structural characteristics, and the heat sources are positioned symmetrically. This symmetrical design compensates for thermal expansions equally from both sides, maintains independence from ambient pressure, and reduces sensitivity to external disturbances while preserving high measurement sensitivity.
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 design achieves high sensitivity and rigidity, enabling precise mass comparisons with reduced influence from thermal expansion, soil vibrations, and electrical/magnetic fields, while allowing for simplified production and material selection.
Implementation Method 1
electromagnetic force compensation (EMF)
Data Source
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AI summary
The present invention introduces an electromagnetically compensating beam balance. The focus is on the design of the mechanism as a compliant mechanism, which can preferably be manufactured monolithically, i.e., from a single semi-finished product. The beam balance can have weighing pans, each arranged on one side of the transmission lever (1). The weighing pans are each mechanically attached to the so-called load-bearing element (70a,b), which is guided relative to a frame (15) by means of a lever mechanism. This lever mechanism consists of four joints and four links and is referred to in gear engineering as a parallel crank. These are the frame (15), the lower parallel link (60a,b), the upper parallel link (61a,b), and the load-bearing element (70a,b), wherein the parallel links are each fixed to the frame and pivotally connected via a coupling element (50a,b).With the help of this arrangement of the parallel crank, a quasi-linear guidance of the weighing pans in the vertical direction can be achieved, following the example of the Roberval platform scale.