Sheet Separation via Local Overpressure on Curved Sliding Surface
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Solution Overview
Problem
Existing sheet separation systems in printing systems face reliability issues when separating sheets with curled ends due to wet ink, especially when using metal transport belts with large bending radii, leading to inefficient separation processes.
Innovation Solution
A sheet separation system with a metal transport belt featuring a straight section and a curved section, where a local overpressure zone is applied through blow holes in a curved part of a stationary sliding surface to separate sheets from the belt, with the sheet separation guide positioned directly adjacent to the overpressure zone at the downstream end, ensuring reliable separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a large radius roller is used for the metal transport belt to avoid excessive fatigue, then the belt life is improved, but the distance between the blow unit and the paper guide increases, adversely affecting separation reliability
Solution Approach 1:
A curved stationary sliding surface is introduced as an intermediary element between the metal transport belt and the paper guide. This sliding surface is positioned close to the paper guide and provides a curved path that facilitates sheet separation without requiring the metal belt to navigate a tight curve, thus maintaining belt life while improving separation reliability.
Solution Approach 2:
The separation mechanism is moved from the vertical dimension (blow unit height) to the horizontal dimension by positioning the curved stationary sliding surface in close proximity to the paper guide along the transport direction. This allows the blow unit to be positioned much closer to the paper guide, improving separation reliability without affecting the metal belt's bending radius.
2Device complexity
If the blow unit is positioned upstream of the roller for a metal transport belt, then the separation process is simplified, but the large distance from the paper guide adversely affects separation reliability
Solution Approach 1:
The curved stationary sliding surface acts as a mediator that enables the blow unit to be positioned close to the paper guide. This sliding surface provides the necessary geometric transition and facilitates sheet separation in the close proximity, maintaining system simplicity while dramatically improving separation reliability.
3Reliability
If a local overpressure zone is applied through blow holes to separate curled sheets, then separation capability is improved, but the distance from the paper guide must be minimized for optimal performance
Solution Approach 1:
The design transitions from optimizing blow unit height (vertical dimension) to optimizing the horizontal position along the transport direction. By positioning the curved stationary sliding surface close to the paper guide in the horizontal dimension, the system achieves optimal separation capability for curled sheets while minimizing the distance to the paper guide.
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 configuration ensures high reliability in separating sheets with curled ends by positioning the overpressure zone close to the sheet separation guide, reducing the distance between separation and guidance, and maintaining the metal transport belt's integrity by avoiding excessive stress on the belt.
Implementation Method 1
a stationary sliding surface positioned under the metal transport belt and upstream of the sheet separation guide, wherein the metal transport belt slides over the stationary sliding surface... the stationary sliding surface comprises a number of blow holes which define an underpressure zone, the blow holes being connected to a source of underpressure... separate a front end of the sheets from the metal transport belt
Implementation Method 2
the metal transport belt slides over the stationary sliding surface
Data Source
AI summary
A printing system includes an endless metal transport belt for transporting sheets in a transport direction, wherein the metal transport belt comprises multiple through holes through which an underpressure or overpressure may be applied on the sheets, a sheet separation system for separating the sheets from the metal transport belt by applying a local overpressure, and a sheet separation guide which guides the separated sheets away from the metal transport belt. The sheet separation system includes a stationary sliding surface, wherein the metal transport belt slides over the stationary sliding surface, wherein the stationary sliding surface includes a number of blow holes which define the overpressure zone, and wherein the blow holes are configured to apply a local overpressure in the overpressure zone through the metal transport belt onto the underside of the sheets. The overpressure zone is formed in the curved part of the stationary sliding surface, wherein the overpressure zone has an upstream end and a downstream end, which are defined by the location of the blow holes, and wherein the sheet separation guide directly adjoins the overpressure zone at the downstream end thereof.