Vertical Screw Conveyor Retention Step Design
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Solution Overview
Problem
In vertical screw conveyors, wood chips or piece goods tend to slide back due to gravity during discontinuous conveying processes, leading to increased lead times and energy consumption when the conveying operation is restarted.
Innovation Solution
An ascending screw conveyor with a spirally rotating screw blade and a retention step that rises opposite to the conveying direction, utilizing the screw blade's weight absorption and frictional forces to prevent sliding, and featuring offset blade segments for structural simplicity and constant speed maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a vertical screw conveyor is used in discontinuous conveying process, then the conveyor can be operated with clocked operation at constant screw speed, but the material slides back due to gravity causing lead times when conveying is restarted
Solution Approach 1:
The retention step is positioned ahead of the material flow in the conveying direction, creating a preliminary stop that prevents material from sliding back during interruptions. This advance preparation eliminates the need for lead times when restarting conveyance, as material is already held in position by the retention step.
Solution Approach 2:
The gravity force that causes material to slide back is converted into a beneficial retention mechanism. The retention step utilizes the material's own weight and the gravitational force to create a natural stopping point, where material accumulates against the retention step during interruptions and is automatically released when conveying resumes.
2Reliability
If the retention step height is increased to prevent material sliding back, then material flow stability improves, but the height loss during conveying increases impeding transport
Solution Approach 1:
Instead of increasing the overall screw blade height or retention step height significantly, the invention applies a localized retention feature at a specific position on the screw blade. The retention step creates a localized stop that prevents sliding back without requiring substantial height increases that would impede material transport during active conveying.
Solution Approach 2:
The invention optimizes the retention step height parameter to achieve the minimum necessary height that effectively prevents material sliding back. By carefully selecting this parameter, the system achieves reliable material flow stability while minimizing the height loss during conveying operations.
3Device complexity
If the screw blade is designed with offset blade segments to form retention stage, then structural simplicity and constant speed maintenance are achieved, but manufacturing complexity increases
Solution Approach 1:
The screw blade is divided into multiple blade segments that are offset relative to each other in the longitudinal direction. This segmentation creates the retention stage functionality while allowing each segment to be manufactured separately and assembled, potentially simplifying production despite the offset requirement.
Solution Approach 2:
Instead of creating a complex curved or three-dimensional retention structure, the invention uses a simplified approach where flat blade segments are offset in one dimension (longitudinal direction) to create the retention effect. This inverted approach achieves the retention function with simpler manufacturing requirements compared to traditional curved retention designs.
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 ensures a constant material flow without lead times, reducing energy consumption and noise, particularly beneficial for domestic heating systems, while allowing for efficient operation at various screw angles.
Implementation Method 1
the frictional forces acting within the conveyed material flow are sufficient to brake the conveyed material flow as a whole and to prevent it from sliding back
Implementation Method 2
a vertical screw conveyor (2) with an ascending screw (1) for conveying wood chips or piece goods (9) with a screw blade (5) circulating spirally around a screw core (4)
Data Source
Figure 1
Figure 2
AI summary
A screw conveyor (1) for conveying wood chips or block material (9) for a vertical screw conveyor (2) is described, featuring a screw blade (5) spirally rotating around a screw core (4). To design such a screw conveyor (1) to ensure a constant material flow during a discontinuous conveying process with varying cycle times, it is proposed that the conveying flank (6) of the screw blade (5) has at least one retention step (8) sloping downwards in the conveying direction (7).