Sheet Size Detection with Dual Arms and Single Sensor
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Solution Overview
Problem
Existing sheet size detecting apparatuses in image forming devices often result in wrong size detection, leading to temperature rise issues and potential damage, especially when small size sheets are incorrectly identified as large, due to the lack of sensors on both sides of the conveyance reference.
Innovation Solution
A sheet size detecting apparatus with first and second arms disposed on both sides of the conveyance path, where the output of the sensor changes only when both arms are moved by the sheet, preventing incorrect detection by mimicking the behavior of a single arm setup without increasing the number of sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sheet size detecting means are disposed only on one side of the conveyance reference, then the device complexity is reduced, but the measurement precision deteriorates causing wrong size detection
Solution Approach 1:
The patent applies asymmetry by configuring the two arms at different positions relative to the conveyance reference in the width direction. The first arm is positioned at a first distance from the conveyance reference, while the second arm is positioned at a second distance, creating an asymmetric detection arrangement. This asymmetric configuration allows the system to accurately detect sheet size by comparing the differential movement of arms at different positions, resolving the contradiction between simplified device structure and accurate measurement.
2Measurement precision
If arms are disposed on both sides of the conveyance path, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent merges the functions of multiple detection points into a single sensor system. By using one sensor to detect the combined state of both arms (through their differential movements), the system achieves accurate sheet size detection without requiring separate sensors for each arm position. This merging approach resolves the contradiction by maintaining high measurement precision while avoiding the increased device complexity that would result from adding multiple sensors.
3Device complexity
If a single arm setup is used, then the device complexity is low, but the reliability deteriorates due to wrong detection when sheet position varies
Solution Approach 1:
The patent segments the detection function by dividing it into two separate arms positioned at different locations relative to the conveyance reference. This segmentation allows the system to independently monitor sheet presence at multiple positions, thereby improving reliability without significantly increasing overall device complexity. The segmented approach ensures that variations in sheet positioning do not lead to wrong detections, as the differential arm movements provide redundant verification.
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 solution accurately detects sheet sizes without increasing sensor costs, preventing temperature-related issues and ensuring proper temperature control and process speed adjustments for image forming devices.
Implementation Method 1
the sensors 101b and 102b are photointerrupters each having a light emitting portion and a light receiving portion
Data Source
AI summary
An image forming apparatus has a sheet size detecting unit with first and second arms each moved by contact with a moving sheet, the arms disposed at differing locations in a direction orthogonal to sheet movement. An actuator which acts on the sensor is not moved when only one arm is moved by sheet contact, but is moved when both arms are moved by sheet contact so that the sensor output level when only one arm is moved is the same as when neither arm is moved, and the output level of the sensor when both of arms have moved differs from when neither arm moves. The first and second arms have first and second regulating portions, respectively, for regulating actuator movement, and the actuator is moved only when both regulating portions are moved from contact of both arms with the moving sheet.