Weigh-in-motion scale with flexure and external load cells
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Solution Overview
Problem
Existing vehicle scales face challenges in accurately measuring axle weights due to moments generated during vehicle passage, leading to inaccurate readings, and require complex and costly installation and maintenance processes.
Innovation Solution
A weighing system with a base and a platform structure featuring flexures that inhibit horizontal movement, load cell assemblies with pivotable upper and lower portions, and a configuration where load cells are positioned outside the active surface area to minimize moments and stabilize the platform, allowing for accurate and efficient weighing of moving loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If load cells are positioned under the active section to measure axle weight, then weight measurement capability is provided, but moments are generated during vehicle passage that reduce measurement accuracy
Solution Approach 1:
The load cells are extracted from the traditional position under the active section and relocated to positions outside the active section. This removes the source of moment generation during vehicle passage, as the load cells no longer experience the tipping moments that occur when vehicle tires pass over the active section. The load cells remain positioned to detect vertical forces while eliminating the harmful moment effect.
Solution Approach 2:
The system uses a platform structure with flexures that provide counteracting forces to balance the moments generated during vehicle passage. The flexures create a mechanical counterweight effect that stabilizes the platform and compensates for the moment forces, allowing accurate weight measurement even as vehicles move across the scale.
2Ease of operation
If the platform is allowed to move freely to accommodate vehicle momentum, then the scale can handle moving loads, but forward and downward movement occurs that results in inaccurate weighing
Solution Approach 1:
The system changes the mechanical parameters of the platform by introducing flexures with specific stiffness characteristics. These flexures allow controlled movement in certain directions while restricting movement in others, creating a parameter-based solution that permits vehicle passage while maintaining measurement accuracy through constrained platform motion.
Solution Approach 2:
The platform structure transitions from a static, rigid design to a dynamic system with flexures that adapt to moving loads. The flexures provide dynamic response to vehicle momentum, allowing the platform to accommodate moving loads smoothly while the load cells maintain stable, accurate measurements throughout the vehicle passage.
3Stability of the object's composition
If stops are installed to arrest platform movement, then forward movement is stopped, but stabilization time increases the time required to obtain a weight reading
Solution Approach 1:
The system replaces the traditional mechanical stop-based stabilization approach with a flexure-based passive stabilization mechanism. The flexures provide continuous, smooth resistance to platform movement without requiring discrete stops, enabling faster and more elegant stabilization that reduces the time needed to obtain accurate weight readings.
4Ease of manufacture
If traditional installation methods are used for vehicle scales, then the scale can be installed, but the process is time consuming, cumbersome, and expensive requiring significant construction equipment
Solution Approach 1:
The scale system is segmented into modular components including the platform structure with integrated flexures, load cells positioned outside the active section, and support structures. This segmentation allows for simplified installation where components can be assembled in a more straightforward sequence, reducing the need for complex construction equipment and specialized tools while maintaining structural integrity and measurement accuracy.
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 system provides faster stabilization and improved accuracy in weighing heavy loads, simplifies installation, and reduces maintenance complexity by using prefabricated components and self-stabilizing pendulum motion to dampen lateral forces, resulting in more reliable and efficient weight measurements.
Implementation Method 1
at least one flexure fixedly attached to the platform structure and the base, the at least one flexure configured to inhibit movement of the platform structure along the horizontal plane relative to the base
Implementation Method 2
the load cells 24, 26 are designed to measure a compression force generated by the additional weight of the vehicle axle on the scale
Implementation Method 3
each of the plurality of load cell assemblies including an upper portion pivotably supported by the base through a first pivot assembly and a lower portion pivotably supporting the platform structure through a second pivot assembly
Data Source
AI summary
In one embodiment, a weighing system includes a base, a platform structure movable with respect to the base, at least one flexure fixedly attached to the platform and the base, the at least one flexure configured to inhibit movement of the platform structure along a horizontal plane relative to the base, and a plurality of load cell assemblies, each of the plurality of load cell assemblies including an upper portion pivotably supported by the base through a first pivot assembly and a lower portion pivotably supporting the platform structure through a second pivot assembly, wherein an axis of rotation of the first pivot assembly is parallel to an axis of rotation of the second pivot assembly.