Chopper Pump Impeller with Sharpened Shearing Fingers

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Solution Overview

Problem

Centrifugal pumps used for pumping liquids and slurries with solid matter often experience motor overloading and clogging due to inefficient chopping, leading to increased motor power consumption and downtime, as well as issues with stringy material wrapping around impeller parts.

Innovation Solution

An improved impeller assembly with sharpened cutting blades, a cutter bar plate featuring shearing fingers with aggressive edges, and an external tool with cutting wings, designed to create a shearing action that reduces debris build-up and clogging, maintaining a clear cutting area and reducing wear on cutting parts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional impellers with radial vanes and inlet apertures are used, then the pump can handle solid matter, but motor overloading occurs during heavy chopping and chopping efficiency is poor

Engineering Contradiction:

Improvechopping efficiencyVSAvoidmotor power consumption

Core Design Contradiction:

ProductivityVSPower

Solution Approach 1:

The impeller is segmented into multiple functional zones: an external tool with cutting wings for preliminary cutting, a cutter bar plate with shearing fingers for intermediate processing, and impeller vanes with sharpened edges for final chopping. This segmentation allows each component to perform a specific cutting function, improving overall chopping efficiency and reducing motor power consumption by preventing overload during heavy chopping operations

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The external tool with cutting wings performs preliminary cutting of solid material before it enters the main impeller chamber. The cutter bar plate with shearing fingers provides intermediate processing. This preliminary action reduces the size and complexity of material chunks before they reach the main chopping zone, preventing motor overloading and improving overall chopping efficiency

Inventive Principle:

Principle #10Preliminary action

2Reliability

If conventional impellers are used, then the pump operates continuously, but stringy material wraps around impeller parts causing plugging

Engineering Contradiction:

Improvecontinuous operationVSAvoidmaterial wrapping and plugging

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The harmful wrapping action is eliminated by removing the conventional impeller design that allows material to wrap around vanes. Instead, a cutter bar plate with shearing fingers and an external tool with cutting wings are introduced to perform cutting operations without creating wrapping conditions, thus preventing plugging and ensuring continuous reliable operation

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The design converts the potential harmful wrapping action into a beneficial shearing and cutting action. The shearing fingers and cutting wings are positioned to create shearing operations that aggressively reduce and eliminate stringy material buildup, transforming what would be a plugging problem into an efficient material reduction process

Inventive Principle:

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

3Productivity

If conventional cutting edges are used, then the pump can cut solid matter, but cutting part wear increases reducing operational efficiency

Engineering Contradiction:

Improveoperational efficiencyVSAvoidcutting part service life

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

Different cutting components are provided with locally optimized properties: the external tool cutting wings, cutter bar shearing fingers, and impeller vane edges are all sharpened to specific geometries suited for their respective cutting zones. This local quality optimization ensures efficient cutting while distributing wear across multiple components, extending overall system service life and maintaining operational efficiency

Inventive Principle:

Principle #3Local quality

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 solution effectively reduces motor power load, minimizes chopping downtime, and prevents the accumulation of stringy material, enhancing operational efficiency and reducing maintenance costs by ensuring continuous pump operation.

Implementation Method 1

the first sharpened edge creates a shearing operation in combination with the sharpened edge of the cutting blades of the impeller during use

Methodology Applied

Scientific EffectShear stress: Shear Stress

Implementation Method 2

Centrifugal pumps used for pumping liquids and slurries containing solid matter

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS11028850B2Chopper pump with double-edged cutting bars

Publication Date: 2021.06.08 VAUGHAN CO INC

AI summary

An impeller assembly with an impeller and a cutter bar plate is used in a chopper pump system which handles liquid material sometimes entrained with large debris and stringy matter. The debris and matter present clogging hazards, which are reduced by a combination of scissoring between sharpened impeller blades and shearing fingers, and between cutting wings and shearing fingers. To make the cutting feature more aggressive, sharpened edges along two of the scissoring edges of the shearing fingers are utilized. Preferably, the sharpened edges are either the result of machined v-notches on the cutting surface of the shearing fingers or of a casted part having a cupped surface. Generally speaking, the impeller assembly comprises an impeller attached to a rotatable pump shaft and includes a back shroud.