Thin Weighing Scale Sandwich Structure for Carpet Clearance
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Solution Overview
Problem
Existing bathroom electronic scales face inaccuracies in weight measurement due to insufficient clearance when placed on deep carpets or uneven floors, leading to relative movement between top and bottom plates that distorts measurements.
Innovation Solution
A thin weighing scale design with a thickness of less than 25 mm, featuring a first and second rigid plate with no direct contact, supported by four load cells and a set of linkages that prevent relative movement between the plates in horizontal directions while allowing vertical movement, ensuring accurate weight measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the overall thickness of the scale is decreased, then the scale becomes more compact and aesthetically pleasing, but the height of the feet (clearance) becomes insufficient when placed on deep carpets or uneven floors, causing the underbody to touch the floor and resulting in inaccurate weight measurements
Solution Approach 1:
The scale is divided into two separate rigid plates (top plate and bottom plate) that do not directly contact each other, with load cells positioned between them. This segmentation allows the bottom plate to maintain sufficient clearance from the floor while the top plate remains thin for aesthetic purposes, resolving the contradiction between thin profile and measurement reliability.
Solution Approach 2:
The load cells serve as intermediary elements between the top and bottom plates, providing both structural support and measurement functionality. This intermediary arrangement enables the bottom plate to be elevated above the floor surface through the load cell height, ensuring adequate clearance on carpets and uneven floors while maintaining an overall thin scale profile.
2Strength
If a sandwich structure with rigid top plate and rigid bottom plate is provided, then the structural integrity is improved, but the top plate may rub against the bottom plate causing inaccurate weight measurement
Solution Approach 1:
The direct contact between top and bottom plates is extracted/removed from the design. Instead of a traditional sandwich structure where plates are in direct contact, the invention positions the plates separately with load cells between them, eliminating the rubbing issue while maintaining structural integrity through the load cell support system.
Solution Approach 2:
The solution moves from a two-dimensional contact problem to a three-dimensional arrangement by separating the plates vertically with load cells. This dimensional change allows both plates to maintain rigidity for structural integrity while preventing horizontal rubbing through proper vertical positioning and guidance mechanisms.
3Stability of the object's composition
If load cells provide guidance to prevent movement in horizontal directions, then relative movement between plates is restricted, but parasitic stresses distort the measurement under the stress of a person standing on the scale
Solution Approach 1:
The guidance function is localized to specific regions rather than being uniformly distributed. The linkages provide horizontal guidance at the corners of the scale where they connect to the plates, allowing the central loading area to remain free of guiding constraints that would generate parasitic stresses. This local quality approach maintains horizontal stability without compromising measurement accuracy.
Solution Approach 2:
The linkage structure employs asymmetric arm lengths (first arm longer than second arm in each linkage unit) to optimize the mechanical properties. This asymmetry allows the linkages to provide effective horizontal guidance while minimizing the generation of parasitic stresses during vertical loading, as the longer arm better accommodates the load path.
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 solution provides accurate weight measurements on various floor types, including deep carpets and uneven surfaces, with minimal thickness and improved mechanical properties, enhancing the scale's reliability and design.
Implementation Method 1
Each foot houses a load cell
Data Source
Figure 1~3
Figure 4
Figure 5~6
AI summary
A thin weighing scale (8) having a thickness of less than 25 mm, comprising a first rigid bottom plate (21), extending along a reference plane defined by a first direction X and a second direction (Y), a second rigid top plate (22), at least four load cells 4, interposed between the first and second rigid plates, a set of linkages (1) comprising arms, some arms extend in the first direction X and some other arms extend in the second direction Y, each arm having an elongated shape with a first end (51) attached to the first rigid plate and a second end (52) rigidly connected to the second rigid plate, whereby a movement is provided along a third direction (Z), the set of linkages (1) preventing relative movement between first and second rigid plates along the first and second direction (X, Y).