Sheet Feeder Positive Pressure Inversion for Double Feed Prevention

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Solution Overview

Problem

Conventional sheet feeders using negative pressure to separate and convey sheets often result in double feeding and require users to wait for the end-of-feeding sheet to fall before drawing out the feed tray, leading to inefficiencies and potential damage or loss of sheets.

Innovation Solution

A sheet feeder with a feed tray, sheet suction unit, air suction unit, sheet conveying unit, and positive pressure generating unit, where the positive pressure unit generates a positive pressure in the sheet suction unit after the feeding operation ends to release the end-of-feeding sheet, allowing immediate tray removal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the sheet conveyor belt continuously conveys sheets using negative pressure suction, then sheet feeding speed is improved, but double feeding occurs when the trailing edge of the first sheet passes through the suction area

Engineering Contradiction:

Improvesheet feeding speedVSAvoidfeeding accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent inverts the conventional approach by using positive pressure to push sheets onto the conveyor belt instead of negative pressure to pull them. The blowing unit blows air toward the leading edge of sheets to separate and lift the topmost sheet, then the sheet conveyor belt conveys it. This inversion prevents double feeding because the positive pressure mechanism naturally separates sheets rather than attracting multiple sheets simultaneously.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The blowing unit performs preliminary action by separating and lifting the topmost sheet before the conveyor belt picks it up. This preliminary separation ensures that only one sheet is positioned to be conveyed at a time, preventing double feeding while maintaining continuous operation.

Inventive Principle:

Principle #10Preliminary action

2Loss of time

If the feed tray is drawn out immediately after feeding operation ends, then user wait time is reduced, but the end-of-feeding sheet may fall into unreachable areas or be damaged

Engineering Contradiction:

Improveuser wait timeVSAvoidsheet damage or loss

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The patent inverts the sheet handling mechanism from negative pressure suction to positive pressure blowing. The blowing unit blows air toward the leading edge of sheets to separate and push them onto the conveyor belt. This positive pressure mechanism ensures that the end-of-feeding sheet is pushed onto the belt and conveyed properly, eliminating the risk of the sheet falling into unreachable areas or being damaged when the tray is removed.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The blowing unit and conveyor belt work together to automatically convey the end-of-feeding sheet to a safe position before the feed tray is removed. The sheet is pushed by air flow and conveyed by the belt without requiring manual intervention or waiting time, allowing immediate tray removal without risk of sheet damage.

Inventive Principle:

Principle #25Self-service

3Ease of operation

If negative pressure suction is used to attract sheets on the conveying member, then sheet separation is achieved, but the end-of-feeding sheet remains attracted to the belt requiring user waiting time

Engineering Contradiction:

Improvesheet separationVSAvoidtray removal delay

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The patent inverts the suction mechanism to a blowing mechanism. Instead of using negative pressure to attract sheets to the conveyor belt, the blowing unit uses positive pressure to push sheets onto the belt. This inversion means that when the feeding operation ends, there is no negative pressure holding the end-of-feeding sheet to the belt, allowing immediate tray removal without waiting time while still achieving effective sheet separation during operation.

Inventive Principle:

Principle #13The other way round (Inversion)

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 prevents double feeding, reduces user wait time, and enhances productivity by enabling immediate tray replacement and sheet handling after the feeding operation.

Implementation Method 1

an air suction unit connected to the sheet suction unit via an air flow passage and configured to suck air from the sheet suction unit side to generate a negative pressure in the sheet suction unit

Methodology Applied

Scientific EffectNegative pressure: Pressure Drop

Implementation Method 2

a positive pressure generating unit configured to generate a positive pressure in the sheet suction unit

Methodology Applied

Scientific EffectPositive pressure: Pressure Increase

Data Source

PatentUS8408533B2Sheet feeder and image forming apparatus

Publication Date: 2013.04.02 RICOH CO LTD

AI summary

A sheet feeder attracts a topmost sheet on a sheet conveyor belt as a conveying member and conveys the sheet toward an image forming unit in a subsequent step. The sheet feeder includes a vane rotation direction control unit that serves as a suction direction control unit controlling a direction in which a suction blower as an air suction unit sucks air to be reversed as a positive pressure generating unit that generates a positive pressure in a sheet suction unit. The vane rotation direction control unit controls the direction in which the suction blower sucks air to be reversed immediately after a feeding operation ends to generate the positive pressure in the sheet suction unit.