Wedge Sheet Stripper for Printing Press Guidance

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Solution Overview

Problem

Existing sheet guidance systems in printing presses fail to reliably prevent contact between turning and subsequent sheets, especially in large format ranges or with heavy color guidance, leading to sheet encounters and smearing due to insufficient guidance and air volume displacement.

Innovation Solution

A sheet stripping device that temporarily sucks the turning sheet using a suction device on the guide squeegee, combined with a wedge-shaped sheet scraper element that pushes the sheet out of the guide blade's path and into the guide plate's effective area, ensuring the air volume under the sheet is displaced to avoid sheet wave formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a suction device on the guide squeegee is used to temporarily suck the turning sheet, then the sheet is tightened and air volume is displaced, but the guidance is only brief and insufficient for large format sheets or heavy color guidance to avoid sheet wave formation

Engineering Contradiction:

Improvesheet guidance reliabilityVSAvoidguidance duration

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The sheet stripping device is positioned to act on the turning sheet before it completes its reversal and before the following sheet arrives. By preliminarily stripping the sheet from the guide blade and directing it onto the guide plate, the system establishes proper sheet separation in advance, preventing the sheet wave formation that would occur with brief suction-only guidance.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the withdrawing sheet is pressed by a rake out of the feed plane into the effective area of the guide plate, then mechanical separation is achieved, but the guidance is limited by rake length and still insufficient to displace air volume and avoid sheet contact

Engineering Contradiction:

Improvesheet separation reliabilityVSAvoidrake length

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The invention combines the mechanical action of the sheet stripping device with a suction device that uses pneumatic forces. The suction device creates negative pressure to hold and guide the turning sheet, while simultaneously displacing the air volume underneath it. This pneumatic assistance overcomes the length limitation of the rake by creating sufficient separation force and air displacement over a longer interaction distance.

Inventive Principle:

Principle #29Pneumatics and hydraulics

3Object-affected harmful factors

If air cushions are used to prevent smearing on the underside of the sheet, then smearing is prevented, but the air cushion force can press the turning sheet against the following sheet causing smearing between sheets

Engineering Contradiction:

Improvesheet smearing preventionVSAvoidsheet encounter smearing

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The sheet stripping device extracts the turning sheet from the common plane of the guide blade where the air cushion operates. By removing the sheet from this region and directing it onto the guide plate, the system eliminates the turning sheet's interaction with the air cushion that would otherwise press it against the following sheet. This extraction prevents the harmful sheet encounter smearing while the suction device maintains adequate air displacement to prevent underside smearing.

Inventive Principle:

Principle #2Taking out (Extraction)

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 effectively prevents sheet encounters by maintaining the sheet's tension and displacing air volume, thereby avoiding sheet wave formation and ensuring reliable separation of turning and subsequent sheets.

Implementation Method 1

A suction device is advantageously provided on the sheet scraper, with which the turned sheet is temporarily sucked. This tightens this arch. The volume of air under the sheet to be turned is displaced so that the formation of a sheet wave is largely avoided.

Methodology Applied

Scientific EffectSuction: Suction

Implementation Method 2

Methodology Applied

Scientific EffectMechanical Force: Mechanical Force

Implementation Method 3

Another reason for the sheet encounter in the feed level is the use of air cushions to prevent smearing on the underside of the sheet. The force of the air cushion acting in the direction of the turning sheet can lead to the turning sheet being pressed against the following sheet in the feed plane and thus to smearing between the two sheets.

Methodology Applied

Scientific EffectAir cushion: Air Lubrication

Data Source

PatentEP1878569B1Device for supporting sheet guiding in printing presses

Publication Date: 2010.10.13 KOENIG & BAUER AG

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AI summary

The device has a sheet stripping device (8) comprising a sheet stripping unit (10), which is movably arranged in a sheet running direction such that it anticipates the front edge of the subsequent sheet to be turned, which is guided along a guiding scrapper, and scraps the preceding sheet on the periphery of the guiding scrapper. The sheet stripping unit is a wedge-shaped unit. The sheet stripping unit is arranged on traction unit (9) and is movable in a sheet guiding direction.