Curvilinear Scraper Kinematics for Rainwater Spillway Screening

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Solution Overview

Problem

Existing sieve screens on overflow sills of rainwater relief systems face issues with solids being washed back onto the screen bars due to clumping, leading to increased scraping resistance, jamming, and operational inefficiencies, particularly with plastic materials and hygiene articles, which result in solids being crushed and reintroduced into the water system.

Innovation Solution

The screen design incorporates a downward scraping motion with linear kinematics to gently remove solids from the rake bars, allowing for complete detachment without jamming, and includes a collecting pan to prevent re-introduction of solids into the water flow, with a self-clearing mechanism for blocked scrapers and a water wheel-driven crank system for enhanced operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If comb-like scrapers are pivoted back and forth by a crank drive to scrape solids from rake bars, then solids are removed from the screen, but scraping resistance increases as solids are pressed into spaces between rake bars by overflow flow pressure

Engineering Contradiction:

Improvesolids removal efficiencyVSAvoidscraping resistance

Core Design Contradiction:

ProductivityVSForce

Solution Approach 1:

The scraper movement direction is inverted: instead of the conventional back-and-forth pivoting motion that pushes solids against the overflow flow, the scraper moves in a circular path with the forward motion direction aligned with the overflow flow direction. This inversion allows solids to be scraped off smoothly without being pressed into the rake bar spaces, eliminating the increasing scraping resistance problem.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The scraper mechanism transitions from a simple reciprocating pivoting motion to a dynamic circular motion driven by a cam mechanism. This dynamic motion allows the scraper to follow a curved path that naturally guides solids off the rake bars in the direction of the overflow flow, maintaining low scraping resistance throughout the operation cycle.

Inventive Principle:

Principle #15Dynamics

2Productivity

If scrapers pivot like scissors into spaces between rake bars to remove solids, then solids are scraped off, but plastic materials and hygiene articles wrap around scrapers and rake bars causing jamming

Engineering Contradiction:

Improvesolids removal efficiencyVSAvoidoperational continuity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

Instead of the scraper pivoting into the spaces between rake bars (scissors-like motion), the scraper moves in a circular path that keeps it on the outer side of the rake bars. This inverted motion path prevents plastic materials and hygiene articles from wrapping around the scraper edges, eliminating the jamming problem while maintaining effective solids removal.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The scraper motion is changed from linear reciprocating movement to curved circular movement. This curvilinear motion allows the scraper to glide smoothly along the rake bars without abrupt directional changes that would cause materials to wrap around edges, thereby preventing jamming and improving operational reliability.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Productivity

If solids are scraped off by conventional pivoting motion, then solids are removed from rake bars, but solids are crushed by mechanical effects of scraper and overflow flow pressure, ground up and reintroduced into water

Engineering Contradiction:

Improvesolids removal efficiencyVSAvoidsolids discharge into water

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The scraper motion is inverted to move in the same direction as the overflow flow rather than against it. This alignment allows solids to be gently guided off the rake bars by the flow itself, eliminating the crushing effect caused by opposing forces and preventing solids from being ground up and reintroduced into the water.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The overflow flow, which previously caused harm by pressing solids against the scraper and crushing them, is converted into a beneficial force. By aligning the scraper motion with the flow direction, the overflow flow assists in gently transporting solids away from the rake bars without mechanical crushing, thereby preventing harmful solids discharge into the water.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Productivity

If scrapers are designed to pivot back and forth on rake bars, then solids can be scraped off, but tangles form on scrapers at reversal points that do not detach, leading to increased frictional resistance and malfunctions

Engineering Contradiction:

Improvesolids removal efficiencyVSAvoidscraper maintenance requirements

Core Design Contradiction:

ProductivityVSEase of operation

Solution Approach 1:

The scraper mechanism is inverted from a pivoting motion with reversal points to a continuous circular motion without sharp reversals. This eliminates the points where tangles would form and fail to detach, preventing increased frictional resistance and malfunctions while maintaining effective solids removal throughout the entire operation cycle.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The scraper transitions from a static pivoting mechanism to a dynamic cam-driven circular motion system. This dynamic design eliminates abrupt reversal points where tangles would accumulate, allowing solids to be continuously and smoothly removed without forming persistent tangles that would increase friction and require maintenance.

Inventive Principle:

Principle #15Dynamics

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 design reduces the risk of solids discharge during scraping, increases operational safety, and allows for efficient removal and collection of solids, preventing malfunctions and maintenance issues while enabling a more compact water wheel drive.

Implementation Method 1

The screen rakes according to the invention can be driven in a very space-saving and structurally simple manner by means of a water wheel 9

Methodology Applied

Scientific EffectKinetic energy conversion: Water Turbine

Implementation Method 2

the overflow flow directed onto the scrapers or their carrier element acts as a driving force on the crank drive

Methodology Applied

Scientific EffectHydrodynamic force: Fluid Spray

Data Source

PatentEP2038488B1Screening grid on an overflow spillway of a rainwater relief system

Publication Date: 2011.04.06 GIEHL KLAUS ULRICH DIPL ING FH

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AI summary

In a screening grid (1) on an overflow spillway (21) of a rainwater relief system (20), comprising grid bars (2) extending transversely to the overflow spillway (21) and scrapers (4) engaging in comb-like fashion in the grid bars (2), according to the invention the scrapers (4) are caused, via a crank drive (8) to make a curvilinear circular movement by means of an actuating lever (6) cooperating with a fixed support bearing (7), through which movement the scrapers (4) are guided from above into the gaps (3) between the grid bars (2) and withdrawn again at the bottom of the overflow spillway (21). As a result, the risk of solids being discharged into the waterways due to mechanical action on the solids during the scraping operation is reduced and the operational reliability is increased.