Self-Checkout Cart Load Cell Integration for Weight Measurement
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Solution Overview
Problem
Existing self-checkout systems for supermarkets require significant modifications to traditional shopping carts to accurately determine the weight of goods in the basket, and existing solutions are prone to errors and mechanical complexities.
Innovation Solution
A shopping cart design with load cells between the frame and wheels, allowing for weight measurement without exposing cables, which simplifies installation and reduces mechanical stress, and includes a system to differentiate between goods and non-goods weight using center of gravity analysis and strain gauges or Hall sensors for accurate weight determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If load cells are integrated between the frame and wheels with force application elements, then weight measurement accuracy is improved, but device complexity increases due to the need for rigid mechanical connections and cable-free signal transmission
Solution Approach 1:
The patent combines the mechanical force transmission function and electrical signal transmission function into a single integrated load cell component. The force application element serves both to transmit the weight force from the wheel to the frame and to conduct the measurement signal from the strain gauges to the evaluation circuit, eliminating the need for separate cable connections and reducing mechanical complexity.
Solution Approach 2:
The force application element is designed as a multi-functional component that simultaneously acts as a structural load-bearing element, a signal transmission conductor, and a mounting interface. This universal design allows the load cell to be rigidly connected to both the frame and wheel while maintaining electrical connectivity without exposed cables.
2Ease of manufacture
If traditional cable connections are used for load cells, then ease of manufacture is improved, but measurement reliability deteriorates due to force short circuits in cables
Solution Approach 1:
The patent extracts the electrical signal transmission function from the mechanical cable connection and integrates it directly into the force application element of the load cell. This eliminates the separate cable that caused force short circuits, as the signal is now transmitted through the rigid force application element itself rather than through flexible cables that could be affected by mechanical forces.
3Ease of operation
If swivel bearings are rigidly connected to the frame, then ease of operation is improved for turning the cart, but measurement precision deteriorates due to mechanical stress on the load cells
Solution Approach 1:
The patent segments the mechanical connection system into distinct functional zones: the load cell provides a rigid, stress-free connection between the wheel assembly and the frame for accurate measurement, while the swivel bearing provides the necessary rotational freedom for maneuverability. The force application element is positioned to transmit only vertical load forces, separating the measurement function from the maneuvering function.
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 enables accurate weight measurement of goods in the cart without altering the cart's structure significantly, reduces mechanical complexity, and detects anomalies like a child on the cart or items in a bag, improving checkout efficiency and reducing manual errors.
Implementation Method 1
The load cell comprises a spring element with an outer bearing ring, an inner force application element, and an annular deformation section, through which the bearing ring and the force application element are rigidly connected
Implementation Method 2
The load cell includes a transmitter for generating an output signal corresponding to a weight acting on the force application element
Implementation Method 3
Hall sensors for accurate weight determination
Data Source
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Figure 3
Figure 4
AI summary
The present invention relates to a self-checkout system in a supermarket. The system consists of several shopping carts and a checkout device. The checkout device compares weight data received from a shopping cart with expected weight data and verifies the purchase. The invention further relates to a shopping cart for a self-checkout system.