One-Piece Coil Body for Compact Direct Measuring Systems

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Solution Overview

Problem

Existing electromagnetic force compensation direct measuring systems face challenges in compactness, assembly complexity, and zero point drift due to mechanical connections and thermal expansion, particularly in low-load ranges where precision and robustness are critical.

Innovation Solution

The system redesigns the force transmission linkage as a one-piece coil body, integrating electrical conductor tracks and using a multi-part parallel guide with conductive surfaces, eliminating the need for additional mechanical connections and simplifying assembly, while maintaining robustness and precision through optical scanning and a compact design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the coil is electrically connected to the adjustable circuit via thin wires, then the electrical connection is established, but the wires create additional mechanical connections and spring constant that distort measurement results

Engineering Contradiction:
Improvemeasurement accuracyVSAvoidmechanical connection complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the electrical connection function with the mechanical force transmission function by making the force transmission linkage itself electrically conductive. The coil body is formed as an integral part of the force transmission linkage, eliminating the need for separate wire connections. This combines two previously separate functions (mechanical force transmission and electrical signal transmission) into a single integrated component, thereby eliminating additional mechanical connections and spring constants that would distort measurements.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The force transmission linkage is designed to serve multiple functions simultaneously: it transmits mechanical force from the load cell to the parallel guide, provides structural support, and conducts electrical current to the coil. This multi-functional design eliminates the need for separate wire connections, reducing mechanical complexity and improving measurement accuracy by removing additional spring constants.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Measurement precision

If delicate thin wires are used to minimize additional spring constant, then measurement precision is improved, but the wires are difficult to secure and easy to come loose

Engineering Contradiction:
Improveweighing result precisionVSAvoidwire connection reliability
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent eliminates the separate wire connection by merging the electrical conduction function into the force transmission linkage itself. The coil body is formed as an integral part of the linkage, creating a robust, permanent connection that cannot come loose while maintaining the low spring constant requirement for precision measurements.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent replaces the fragile, difficult-to-secure thin wires with a durable, integral construction. The coil body is formed as a permanent part of the force transmission linkage, eliminating the need for separate wire connections that are prone to coming loose and requiring replacement.

Inventive Principle:
Principle #27Cheap short-living objects (Disposable)

3Volume of moving object

If the direct measuring system is made compact, then space is reduced, but assembly complexity increases

Engineering Contradiction:
Improvesystem compactnessVSAvoidassembly complexity
Core Design Contradiction:
Volume of moving objectVSEase of manufacture

Solution Approach 1:

The patent combines multiple components into integrated structures: the coil body is formed as an integral part of the force transmission linkage, and the parallel guide elements are designed as single-piece components with built-in conductive surfaces. This integration reduces the number of separate parts that need to be assembled, simplifying manufacturing while achieving a compact overall system design.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The force transmission linkage serves multiple functions (mechanical force transmission, structural support, electrical conduction) in a single integrated component, reducing the number of separate parts needed. This multi-functional design simplifies assembly while maintaining system compactness.

Inventive Principle:
Principle #6Universality (Multi-functionality)

4Reliability

If additional mechanical connections are added for electrical connection, then electrical connectivity is ensured, but zero point drift increases due to thermal expansion

Engineering Contradiction:
Improveelectrical connection stabilityVSAvoidzero point stability
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The patent merges the electrical connection with the existing mechanical force transmission linkage, eliminating additional mechanical connections that would be subject to thermal expansion. The coil body is formed as an integral part of the linkage, so no separate connection elements are needed, thereby preventing zero point drift caused by thermal effects in additional mechanical joints.

Inventive Principle:
Principle #5Merging (Combining)

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 approach enhances the compactness of the direct measuring system, reduces assembly complexity, and minimizes zero point drift, ensuring high repeatability and precision in low-load range measurements.

Implementation Method 1

the force exerted by a load on the scale pan or load cell is compensated by a force compensation device consisting of at least one permanent magnet and a coil. The current flowing through the coil to generate the compensating force is measured.

Methodology Applied
Scientific EffectElectromagnetic force: Lorentz Force

Implementation Method 2

The coil's position after the load is applied is determined by a position sensor, and the current through the coil is increased until the load-induced displacement of the coil relative to the permanent magnet is compensated.

Methodology Applied
Scientific EffectOptical scanning:

Data Source

PatentEP3708978B1Compact direct measurement system
Publication Date: 2023.05.03 METTLER TOLEDO GMBH
  • EP3708978B1 patent drawingFigure 1
  • EP3708978B1 patent drawingFigure 2A~2C
  • EP3708978B1 patent drawingFigure 3A~4

AI summary

An electromagnetic force compensation direct measuring system (100) is known, comprising a load sensor (101) connected to a force compensation device (120) via a force transmission linkage, and a multi-part parallel guide comprising at least two parallel guide elements (131, 132) spaced apart by the force transmission linkage, wherein the force compensation device (120) comprises at least one permanent magnet (121) and a coil (122) electrically connected to a controllable circuit, and wherein at least one parallel guide element (131, 132) is electrically integrated into the controllable circuit. According to the invention, the force transmission linkage is designed as a one-piece coil body (110) such that the coil (122) is arranged on it between the parallel guide elements (131, 132) and is electrically connected to the controllable circuit.