Separation Roller Break Period Timing for Sheet Feeding
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Solution Overview
Problem
Image reading apparatuses with sheet feeders experience a 'kickback phenomenon' where the front edge of a sheet is curled or stuck due to opposing forces from the separation and feed rollers, leading to inefficient feeding.
Innovation Solution
A medium feeding apparatus with a controller that introduces a break period during feeding operations, preventing the reverse rotation force of the separation roller from affecting the next sheet, and using suppression units to prevent excessive contact between sheet edges and the separation roller, ensuring smooth feeding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separation roller rotates in reverse direction to separate sheets, then sheet separation is achieved, but the front edge of the next sheet is curled up and may be stuck
Solution Approach 1:
The separation roller is driven to rotate in reverse direction periodically only during the period when the rear edge of the currently fed sheet passes the nip position between the feed roller and separation roller. This periodic reverse rotation prevents the front edge of the next sheet from being curled up while still achieving reliable sheet separation when needed.
Solution Approach 2:
The control unit determines the timing of reverse rotation based on feedback about the position of the sheet rear edge passing the nip position. This feedback-controlled timing ensures that reverse rotation occurs only when appropriate, preventing curling of the next sheet's front edge while maintaining separation reliability.
2Reliability
If the separation roller rotates continuously in reverse direction, then sheet separation is maintained, but feeding efficiency decreases due to kickback phenomenon
Solution Approach 1:
Instead of continuous reverse rotation, the separation roller rotates in reverse direction only periodically during specific periods when the rear edge of the fed sheet passes the nip position. This reduces the duration of reverse rotation, eliminating the kickback phenomenon's negative effects on feeding efficiency while maintaining sheet separation reliability.
Solution Approach 2:
The reverse rotation is timed to occur after the sheet has already passed through the nip position, preventing the kickback force from acting on the front edge of the next sheet before it enters the nip. This preliminary timing prevents the harmful effect while maintaining the separation function.
3Ease of operation
If the feed roller and separation roller are made of elastic material, then smooth sheet feeding is achieved, but deformation and kickback phenomenon occur
Solution Approach 1:
The elastic deformation of the feed roller and separation roller, which causes the kickback phenomenon, is converted into a benefit by timing the reverse rotation of the separation roller to occur after the sheet passes the nip. The kickback force then acts on the already-separated sheet rather than curling the next sheet, transforming the harmful effect into a neutral or beneficial one.
Solution Approach 2:
By implementing periodic reverse rotation only during specific periods when the sheet rear edge passes the nip, the system allows the elastic rollers to deform and recover naturally during other periods, maintaining smooth feeding while preventing kickback-related curling of the next sheet.
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 reduces the likelihood of sheet curling and improves feeding efficiency by controlling the timing of the break period and using suppression units to manage sheet interaction with the separation roller, enhancing the reliability and smoothness of the feeding process.
Implementation Method 1
A torque limiter, when rotation torque applied to the separation roller in the first rotation direction exceeds a preset upper torque limit, causes the separation roller to rotate at idle in the first rotation direction, independently of the driving torque
Implementation Method 2
both the separation roller and the feed roller are deformed, because they are each made of an elastic material. Then, when the rear edge of the sheet leaves the nip position, the separation roller and the feed roller return to their original shapes
Data Source
Figure 1
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AI summary
A medium feeding apparatus (1B) includes a feed roller (14) that feeds media. A separation roller (15) nips the media together with the feed roller to separate it and is rotated in a first rotation direction to feed the media to a downstream side in a feeding direction. A motor (51) applies driving torque to the separation roller in a second rotation direction opposite to the first rotation direction. A torque limiter (50), when rotation torque applied to the separation roller in the first rotation direction exceeds a preset upper torque limit, causes the separation roller to rotate at idle in the first rotation direction independently of the driving torque. During feeding operations, including feeding of first and second media, a controller (40) that controls the motor provides a break period in which the motor is not driven. The break period contains the timing when a rear edge of the first medium leaves a nip position between the feeding and separation rollers.