LIM-Driven Roller Checkweigher for Continuous Weighing
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Solution Overview
Problem
Conventional checkweighers in conveyor systems require objects to halt or be separated by large gaps for accurate weighing, which slows throughput and limits the ability to measure moving objects simultaneously.
Innovation Solution
A weighing conveyor system using an array of rollers rotated with constant torque to accelerate objects inversely proportional to their weight, determining weight based on changes in spacing caused by the rollers' acceleration, eliminating the need for a weigh scale and allowing continuous object conveyance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If objects halt or are separated by large gaps for weighing, then measurement precision is improved, but productivity deteriorates
Solution Approach 1:
The system applies dynamic acceleration to objects on the conveyor using rollers that can be selectively activated. By controlling the acceleration phase, the system maintains measurement precision while allowing continuous conveyance without requiring objects to halt or be separated by large gaps, thus resolving the contradiction between weighing accuracy and throughput
Solution Approach 2:
The system changes the motion parameters of objects during the weighing process by applying controlled acceleration. The acceleration level is adjusted based on object properties, enabling accurate weight measurement while maintaining continuous flow. This parameter change approach allows the conveyor to transition from passive transport to active measurement without stopping
2Measurement precision
If only one object at a time is conveyed over the scale, then measurement precision is improved, but productivity deteriorates
Solution Approach 1:
The weighing system is segmented into multiple independent measurement zones along the conveyor path. Each zone can measure objects independently, allowing multiple objects to be weighed simultaneously at different positions. This segmentation eliminates the need to separate objects by large gaps while maintaining measurement precision
Solution Approach 2:
The system transitions from a single-point measurement approach to a distributed measurement approach along the conveyor length. By utilizing the spatial dimension along the conveyor, multiple objects can be measured simultaneously at different locations, increasing throughput without compromising accuracy
3Measurement precision
If a weigh scale is used for weighing, then measurement precision is improved, but device complexity deteriorates
Solution Approach 1:
The system extracts the weighing function from a separate physical scale and integrates it into the conveyor system itself. By using the conveyor's existing structure and control systems to measure weight through acceleration effects, the solution eliminates the need for additional weigh scales and reduces overall system complexity
Solution Approach 2:
The conveyor system is given multi-functionality, serving both transport and measurement purposes. The same conveyor infrastructure used for moving objects is also used for weighing, eliminating the need for separate dedicated weighing equipment and reducing device complexity
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
Enables accurate weighing of objects without stopping or large gaps, increasing throughput by using the rollers' effect on object motion to determine weight, and allowing for real-time measurement of object speeds and spacings.
Implementation Method 1
rotating the array of rollers with a constant torque to accelerate each of the objects in the conveying direction to a speed that is inversely proportional to the weight of the object
Implementation Method 2
The array of rollers is rotated by a linear-induction-motor (LIM) stator. The stator produces a magnetic flux wave that passes through the rollers. The flux wave induces eddy currents in the conductive material of the rollers. The eddy currents produce a reaction field that interacts with the stator's magnetic flux wave to create a constant torque on the rollers
Data Source
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AI summary
A weighing conveyor system, a checkweigher, and a method for weighing conveyed objects with a checkweigher comprising LIM-driven rollers positioned in a conveying line and position sensors for determining the objects' weights from the motion of the objects across the rollers. The LIM drives the rollers with a constant torque. The acceleration of an object driven by the rollers is inversely proportional to the object's weight. So an object's weight can be determined by the effect of the rollers on its motion.