Buffer Apparatus with Retractable Supports for Sheet Stacking

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Solution Overview

Problem

Conventional stacking systems are inadequate for handling sheets from digital printers, as the sheets are printed in the direction of their longer dimension, leading to the leading edge drooping and potentially damaging the print on lower sheets due to the difference in speed and direction of travel compared to rotary die cut machines.

Innovation Solution

A buffer apparatus with selectively extendable rollers and shelves is introduced to hold sheets above the stack until they can drop vertically, preventing damage and allowing for tamping and squaring of sheets at the accumulator level to form a compact and square stack.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If sheets are printed in the direction of their longer dimension at lower speed, then printing quality is improved, but the leading edge droops and damages the print on lower sheets

Engineering Contradiction:

Improveprinting qualityVSAvoidprint damage

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The buffer holds incoming sheets in a suspended state before they are discharged onto the stack. This preliminary action prevents the leading edge from drooping and scraping against printed surfaces by maintaining the sheet in a controlled position until it is ready to be vertically dropped onto the stack, thus protecting the print quality.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The buffer acts as an intermediary device between the digital printer and the stack. It receives sheets from the printer, holds them temporarily, and then discharges them vertically onto the stack. This intermediary function eliminates the harmful scraping action that would otherwise occur between the printed sheets and the stack.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If sheets are held above the stack until they can drop vertically, then print damage is prevented, but device complexity increases

Engineering Contradiction:

Improveprint damageVSAvoidbuffer structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The buffer is divided into multiple independent roller assemblies that can be selectively extended and retracted. Each roller assembly operates independently to hold and discharge sheets, allowing the system to manage complexity through modular segmentation rather than a single complex mechanism.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The buffer uses dynamically extendable and retractable roller assemblies that adjust their position based on operational needs. When sheets need to be held, the rollers extend; when sheets are discharged, the rollers retract. This dynamic behavior allows the buffer to perform its protective function while maintaining operational simplicity.

Inventive Principle:

Principle #15Dynamics

3Productivity

If sheets are discharged directly onto the stack, then productivity is maintained, but sheets cannot be properly tamped and squared

Engineering Contradiction:

Improvestacking speedVSAvoidstack squareness

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The buffer performs preliminary holding and suspension of sheets before they are discharged onto the stack. This preliminary action allows the sheets to be properly positioned and prepared for stacking, enabling subsequent tamping and squaring operations to be performed effectively without compromising productivity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The buffer operates continuously to receive, hold, and discharge sheets in a controlled manner. This continuous operation maintains productivity by preventing interruptions in the stacking process, while simultaneously enabling proper tamping and squaring actions to be performed on each sheet as it is discharged.

Inventive Principle:

Principle #20Continuity of useful action

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 buffer apparatus effectively prevents print damage and ensures a compact, square stack by holding sheets until they can drop vertically and allowing for tamping and squaring at the accumulator level, improving the stacking process for both digital printer and rotary die cut machine outputs.

Implementation Method 1

allowing the first sheet to fall onto a second set of retractable supports

Methodology Applied

Scientific EffectGravity: Gravitation

Data Source

PatentUS9896295B2Buffer, stacking system including the buffer, and method of buffering

Publication Date: 2018.02.20 AG STACKER INC

AI summary

A buffer apparatus configured to hold a stack of sheets includes an input, first and second side guides each having a face facing transverse to the travel direction, and a backstop facing the input and spaced from the input in the travel direction. The first side guide, second side guide and backstop define a hopper for holding a plurality of the sheets. First and second retractable supports are shiftable from first positions in which a first portion of the respective retractable support projects a first distance into the hopper and a second position in which the first portion of the respective retractable support projects a second distance into the hopper or does not project into the hopper, the second distance being less than the first distance. The at least one second retractable support is located between the input and the at least one first retractable support.