Variable Density Screed for Non-Planar Subbase Paving

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Solution Overview

Problem

Conventional road paving machines struggle to achieve uniform density and smoothness over non-planar subbases, leading to issues like roller bridging and localized pavement failures, as they cannot effectively compact asphalt in recessed areas to the same density as planar areas.

Innovation Solution

A modified screed design that allows for variable asphalt densities across the paving width by adjusting the angle of attack and using vertically oriented augers to increase material density in specific areas, detected by a vision system and actuated to compensate for lower compaction ratios in recessed regions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional screeds are used to pave over non-planar subbases, then the paving process can proceed, but uniform density and smoothness cannot be achieved due to roller bridging and localized pavement failures

Engineering Contradiction:

Improveuniformity of asphalt densityVSAvoidability to handle non-planar subbases

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The screed is divided into multiple independently adjustable segments or zones, each capable of being raised or lowered to compensate for subbase irregularities in specific areas, allowing uniform asphalt application over non-planar surfaces

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The screed incorporates dynamic adjustment mechanisms that allow real-time modification of screed height and angle in response to detected subbase conditions, enabling adaptation to varying terrain during the paving process

Inventive Principle:

Principle #15Dynamics

2Reliability

If compaction rollers are used on recessed areas, then compaction should be achieved, but roller bridging occurs preventing effective compaction in depressed regions

Engineering Contradiction:

Improveeffectiveness of compactionVSAvoidroller bridging phenomenon

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary detection of subbase irregularities before paving, allowing pre-adjustment of screed height and asphalt application rate in recessed areas to ensure adequate material placement that will compact uniformly without roller bridging

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system modifies paving parameters such as asphalt temperature, application rate, and screed pressure in response to detected subbase conditions, optimizing compaction effectiveness in challenging areas by adjusting these parameters during the paving process

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If uniform asphalt application is used over varying subbase conditions, then the paving process is simple, but density uniformity cannot be achieved in recessed areas

Engineering Contradiction:

Improveconsistency of asphalt densityVSAvoidcomplexity of variable density application

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The system incorporates sensors and detection mechanisms that provide real-time feedback on subbase conditions and asphalt application characteristics, allowing automatic or manual adjustment of paving parameters to maintain uniform density despite varying terrain

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system applies different asphalt application rates, temperatures, or densities to specific local areas based on detected subbase conditions, allowing optimization of each zone's paving parameters to achieve uniform final density across the entire paved surface

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

Ensures uniform final density and smoothness across the entire road surface, enhancing structural integrity and durability by allowing increased asphalt mass in recessed areas, thus preventing frequent repaving needs.

Implementation Method 1

vertically oriented augers to increase material density

Methodology Applied

Scientific EffectMechanical compression: Compression

Data Source

PatentUS11255057B2Screed assembly for road paving machines, and a method for repaving road surfaces

Publication Date: 2022.02.22 GALLAGHER BRIAN

AI summary

A new and improved method and apparatus for use in conjunction with the free floating paving screed used for road paving is disclosed. The method of forming a bituminous mixture into a smooth flat paved mat comprising some areas with a given nominal mat density and some selected areas with a predeterminedly higher mat density is described wherein problems posed by a reduced compaction ratio occurring subsequently to paving the mat where the roller drum bridges over recesses in the subbase are addressed. The modified paving screed described employs a new adjustable screed plate that allows localized areas of increased angle of attack and a device to increased material entry density in localized areas in front of a screed plate leading edge. Either method is used to create an increase in mat density in the desired area. The method and apparatus teach that by pairing differences in compaction ratio that inherently occur due to subbase irregularities with correspondingly predetermined and different mat densities in the paved mat, a good consistent final density can be achieved notwithstanding the limitations of the compaction rolling. A forward looking vision system is described that identifies subbase recesses, a digital controller quantifies the density increase required, and a GPS system maps locations where the mat density increases are to be applied.