Document Feeder Sheet Overlap Prevention via Actuator Sensor
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Solution Overview
Problem
Conventional document feeders for image forming devices face issues with overlapping sheets during conveyance, leading to image formation failures and reduced productivity due to the use of costly optical sensors and inadequate sensing of heavy paper sheets.
Innovation Solution
A document feeder system utilizing a first conveyor that picks up sheets with the rear edge of a preceding sheet overlapping the front edge of a succeeding sheet, combined with a second conveyor and an actuator-type front edge sensor that adjusts its position to ensure precise sensing of sheet edges, reducing component costs and improving productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical sensors are used to sense the front edge of the succeeding sheet, then sensing precision is improved, but component costs increase
Solution Approach 1:
The patent replaces the optical sensing system with a mechanical sensing system. A sensor arm with a sensor tip mechanically contacts the front edge of the sheet to detect its position. This mechanical substitution eliminates the need for expensive optical sensors while maintaining sensing capability, directly resolving the contradiction between measurement precision and component cost.
2Measurement precision
If transmitted light sensing is used for heavy paper, then sensing capability is improved, but sensing fails due to insufficient transmitted light
Solution Approach 1:
The patent replaces transmitted light sensing with mechanical contact sensing. The sensor arm extends and the sensor tip contacts the front edge of the sheet directly, providing mechanical detection that is independent of the sheet's optical properties. This resolves the contradiction by making sensing capability reliable for heavy paper that blocks transmitted light.
3Productivity
If sheet feeding with short intervals is performed, then productivity is improved, but sheet overlap occurs causing image formation failure
Solution Approach 1:
The patent implements a feedback control system where the sensor detects the front edge of the succeeding sheet, and the controller adjusts the conveyance timing of the first conveyor based on this detection. When the sensor detects the succeeding sheet, the controller stops the first conveyor to prevent overlap, then resumes conveyance after the preceding sheet passes. This feedback mechanism enables high-speed sheet feeding while preventing overlaps that would cause image formation failures.
Solution Approach 2:
The patent uses preliminary detection of the succeeding sheet's front edge before it reaches the conveyance path. The sensor arm extends to detect the upcoming sheet in advance, allowing the controller to prepare the conveyance timing and prevent overlap before it occurs. This preliminary action enables precise control at high feeding speeds.
4Reliability
If sheet feeding with increased intervals is performed, then sheet overlap is prevented, but productivity decreases
Solution Approach 1:
The feedback control system dynamically adjusts the sheet interval based on real-time detection. When the sensor detects the succeeding sheet, the controller stops the first conveyor only for the brief moment needed to prevent overlap, then immediately resumes conveyance. This minimizes the interval extension while maintaining reliable sheet separation, preserving productivity compared to static increased interval approaches.
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 system achieves low-cost, precise sensing and control of sheet conveyance, preventing overlaps and enhancing productivity by using an actuator-type sensor to detect sheet edges effectively, even with heavy paper, thus minimizing image formation failures.
Implementation Method 1
an actuator-type front edge sensor that adjusts its position to ensure precise sensing of sheet edges
Data Source
AI summary
A document feeder includes: a first conveyer that picks up sheets from a sheet bundle sheet by sheet, where rear edge of a preceding sheet overlaps front edge of a succeeding sheet; a second conveyer that conveys each sheet picked up by the first conveyer; a front edge sensor that is disposed on a conveyance path from the first conveyer to the second conveyer, and senses whether the sheet falls within a sensing range; and a shift unit that shifts, while the first and second conveyers convey the sheet, positional relation between the sheet and the front edge sensor by increasing distance therebetween in a direction crossing a sheet conveyance direction, such that the sheet falls outside the sensing range. When the preceding sheet falls outside the sensing range, the first conveyer picks up the succeeding sheet such that the front edge of the succeeding sheet enters the sensing range.