Imaging Device Stack Height Measurement via Pressure Plate Compression
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Solution Overview
Problem
Existing imaging devices face inaccuracies in determining stack height due to surface finish, reflectance properties, and air pockets between media sheets, leading to inconsistent and unreliable measurements, and are prone to wear and tear with complex mechanical systems.
Innovation Solution
The use of a pinch roller and pressure plate combination to compress the media stack, preventing air pockets and measuring the distance between the pressure plate and pinch roller to determine the instantaneous stack height, with a non-contact sensor measuring the pressure plate's position to accurately assess the stack height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical distance sensor is used to measure stack height by detecting reflection from media surface, then measurement can be performed, but measurement accuracy deteriorates due to surface finish variations, reflectance property differences, and air pockets between media sheets
Solution Approach 1:
The pressure plate is positioned to contact and compress the media stack before the optical sensor performs measurement. This preliminary compression action eliminates air pockets and ensures consistent media contact, creating optimal conditions for accurate optical measurement of stack height.
Solution Approach 2:
The pressure plate acts as an intermediary element between the media stack and the measurement system. By applying controlled pressure through the pressure plate, the system achieves consistent media compression and eliminates the harmful effects of air pockets, enabling reliable optical measurement.
2Measurement precision
If a mechanical flag system is used to measure stack height, then measurement accuracy improves, but device complexity and wear increase due to additional moving parts
Solution Approach 1:
The patent replaces the mechanical flag system with an optical sensing system. Instead of using physical flags that move and contact the media stack, an optical sensor non-contactingly measures stack height, eliminating the mechanical moving parts while maintaining measurement capability.
Solution Approach 2:
The optical sensor creates an optical measurement of stack height that substitutes for the mechanical flag's physical measurement. The light-based measurement copies the function of the mechanical flag without requiring physical contact or moving mechanical components.
3Ease of operation
If air pockets are present between media sheets, then handling becomes easier, but measurement accuracy deteriorates due to inconsistent contact and reflection
Solution Approach 1:
The pressure plate applies compression to the media stack before measurement occurs. This preliminary action removes air pockets from between the media sheets, ensuring consistent contact and reflection properties for accurate optical measurement while maintaining ease of media loading.
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 method provides accurate and repeatable stack height measurements, reducing variations caused by media reflectance and air pockets, and minimizes wear and tear with fewer moving parts, making the system more reliable and cost-effective.
Implementation Method 1
the IR sensor, using an intensity of a signal reflected from media to the IR sensor, ascertains the stack height of the media stack
Implementation Method 2
The use of a pinch roller and pressure plate combination to compress the media stack, preventing air pockets
Data Source
AI summary
Examples relating to determining stack height in imaging devices are described herein. According to one example, an imaging device includes an input roller assembly to transport a print medium towards an image-forming assembly of the imaging device. The input roller assembly can include a pinch roller for drawing the print medium from a media stack. The imaging device further includes a pressure plate movably coupled to a body portion of the imaging device and biased towards the pinch roller. The pressure plate may hold the media stack between itself and the pinch roller and is movable by a first distance from a neutral position when the media stack is there between. The first distance is measured from a fixed point to a measurement region on the pressure plate and can indicate an instantaneous stack height of the media stack.