Weighing Plate with Free Rollers for Dynamic Mail Measurement
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Solution Overview
Problem
Dynamic scales in franking machines face challenges with vibrations and shocks due to the load cell supporting the entire conveyor, which complicates weight measurement and limits throughput when processing letters of varying thicknesses.
Innovation Solution
The load cell is affixed to a weighing plate above the envelope transport path, with a movable conveyor pressing the envelope against the plate, ensuring constant loading and minimizing friction, using counterweights, tension springs, or spiral springs to maintain a constant or sensibly constant load, and a dashpot to reduce shocks and vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the load cell supports the complete conveyor, then the conveyor can transport letters at consistent speed, but vibrations and shocks complicate weight measurement and limit throughput
Solution Approach 1:
The system is divided into two independent functional parts: the conveyor mechanism (with motor, pulleys, belts) that handles transportation, and the weighing mechanism (load cell with weighing plate) that handles measurement. The conveyor is no longer supported by the load cell, separating the transportation function from the measurement function. This segmentation eliminates vibrations and shocks from the weighing process while maintaining consistent transport speed through the conveyor's independent drive system.
Solution Approach 2:
The weighing plate and load cell are extracted from the conveyor support structure. The load cell now only supports the weighing plate, not the entire conveyor. This extraction removes the source of vibrations (conveyor motor, pulleys, belts) from the weighing measurement, allowing accurate weight determination without compromising throughput since the conveyor continues to operate independently at required speeds.
2Adaptability or versatility
If the conveyor supports varying envelope thicknesses, then adaptability is improved, but loading consistency deteriorates affecting measurement accuracy
Solution Approach 1:
A movable drive mechanism with counterweight applies a constant downward force (load) on the weighing plate regardless of envelope thickness. This counterbalancing mechanism ensures that the loading on the load cell remains consistent even when handling envelopes of varying thicknesses, thereby maintaining measurement precision while preserving adaptability to different mail item dimensions.
Solution Approach 2:
The system changes the parameter of applied load from variable (dependent on envelope thickness) to constant (independent of envelope thickness). The movable drive mechanism with counterweight adjusts its position and force application to maintain a constant loading parameter on the weighing plate, ensuring measurement accuracy across varying mail item thicknesses while maintaining adaptability.
3Speed
If rollers or flaps are added to press the letter against the belt, then speed consistency is improved, but device complexity and weight increase
Solution Approach 1:
Instead of modifying the conveyor with rollers or flaps to press letters against the belt, the patent uses a separate weighing plate that copies the pressing function. The movable drive mechanism with counterweight applies pressure on the weighing plate, which then presses the envelope against the plate during weighing. This copying of the pressing function to a dedicated weighing component simplifies the conveyor structure while maintaining speed consistency through the conveyor's independent drive system.
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
This arrangement stabilizes the weight measurement process, reducing errors and increasing throughput by maintaining consistent loading regardless of envelope thickness, while minimizing vibrations and shocks, thus improving the accuracy and efficiency of weight determination.
Implementation Method 1
a weighing sensor (18) attached to the weighing plate (16) for measuring the weight of the mail item
Implementation Method 2
The conveyor (12) is adapted to move vertically in order to press the flat object in motion against the weighing plate (16)
Implementation Method 3
The weighing plate (16) comprises a set of free rollers (160) for receiving the flat objects
Implementation Method 4
a dashpot to reduce shocks and vibrations
Data Source
AI summary
Device for weighing flat objects in motion comprising a conveyor (12) with drive rollers (22A, 22B) for conveying the flat objects along a transport path (14), a weighing plate (16) facing said transport path and comprising a set of free rollers (160) for receiving the flat objects, and a weighing sensor (18) attached to the weighing plate for measuring the weight of the flat objects during their passage between the conveyor and the weighing plate, wherein the weighing sensor is arranged above the transport path and the conveyor is adapted to move vertically in order to press the flat objects in motion against the weighing plate.