Flexible Plate Scale for AWP Load Weighing
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Solution Overview
Problem
Existing aerial work platforms (AWPs) face challenges in providing accurate load weight measurements due to non-linear slop and stiction effects introduced by pivot bearings in four-bar linkage mechanisms, leading to hysteresis and reduced precision.
Innovation Solution
A load sensing linkage system is introduced, featuring a sole pair of parallel steel load bearing plates and a single load cell, which is stiff in five degrees of freedom and flexible in the sixth, allowing for precise weight determination by flexing upper and lower flex plates to apply pressure to the load cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a four-bar linkage mechanism with pivot bearings is used to support the load, then the structure provides rigidity and load bearing capability, but non-linear slop and stiction effects are introduced that create hysteresis in load measurement
Solution Approach 1:
The patent removes the pivot bearings from the load path by using a four-bar linkage mechanism where the load is applied directly to the linkage without passing through pivots. This extraction of the harmful element (pivot bearings) eliminates the non-linear slop and stiction effects while maintaining the structural rigidity and load bearing capability through the linkage geometry itself.
Solution Approach 2:
The patent replaces the traditional pivot-bearing based mechanical system with a four-bar linkage system that uses geometric constraints and rigid connections. The linkage uses fixed pivots at its joints rather than moving pivot bearings, substituting a different mechanical approach that maintains strength while eliminating the measurement precision problems associated with pivot bearing friction and slop.
2Stability of the object's composition
If a four-bar linkage mechanism is used to support the load, then the structure is stable, but hysteresis is introduced in the load measurement
Solution Approach 1:
The patent extracts the source of hysteresis by removing pivot bearings from the load path. The four-bar linkage maintains structural stability through its geometric configuration and rigid connections, but eliminates hysteresis by applying the load directly to the linkage without the frictional and slop effects introduced by pivot bearings.
3Measurement precision
If multiple load cells are used to measure load weight, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the functions of multiple load cells into a single load cell by using a four-bar linkage mechanism that concentrates all load paths through one measurement point. The linkage geometry ensures that the single load cell captures the total load weight, eliminating the need for multiple separate measurement devices while maintaining precision.
Solution Approach 2:
The single load cell in the patent serves multiple functions: it measures load weight, provides a reference point for the linkage, and integrates the measurement function into the structural system. The four-bar linkage design allows one load cell to perform what would traditionally require multiple cells, reducing complexity while maintaining measurement capability.
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 repeatable and precise load weight measurements, enhances rigidity in the connection to the boom, and is economically efficient, effectively addressing the limitations of prior art AWPs.
Implementation Method 1
a load cell configured to make a weight determination of a load based upon flexing of one of said upper flex plate and said lower flex plate
Data Source
AI summary
An AWP boom is coupled to a platform rotator through a novel load sensing linkage system which provides both structural support and load sensing capabilities of an attached platform support structure. The load sensing linkage system includes an upper flex plate and a lower flex plate and a single load cell for load sensing capabilities. The flex plates provide for stiffness in all directions except where necessary for load sensing.