Bit Holder End-Face Machining for Worn Road Milling Drums

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Solution Overview

Problem

Existing road milling machines face inefficiencies in overhauling worn bit holders, as they require precise replacement bit holders of specific lengths, leading to suboptimal results when the wear exceeds the stocked lengths, and the process is complex and costly.

Innovation Solution

A method and apparatus for metal-cutting machining of bit-head-proximal end regions of bit holders, allowing for stepless displacement of end surfaces along the receptacle axis, enabling optimal overhauling at any wear state without the need for precise measurement, using a rotary actuator and material-removing tool positioned by a positioning arbor for accurate machining.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If replacement bit holders of specific lengths are used, then manufacturing precision is improved, but device complexity and loss of time increase due to the need for precise measurement and matching

Engineering Contradiction:

Improvebit holder length precisionVSAvoidoverhaul time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The invention changes the parameter of bit holder length from fixed discrete values to continuously variable values through turning machining. The bit holder length is adjusted by removing material to a specific depth, allowing any length within the machining range rather than being limited to pre-manufactured discrete lengths.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces the mechanical system of selecting from pre-manufactured bit holders with different lengths with a machining system that creates the required length on-site. A turning tool mounted on the milling drum rotates and removes material from the bit holder end face to achieve the precise length required.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If replacement bit holders of specific lengths are used, then manufacturing precision is improved, but device complexity increases due to inventory management and selection processes

Engineering Contradiction:

Improvebit holder length precisionVSAvoidoverhaul process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention extracts the length adjustment function from the bit holder manufacturing process and integrates it into the overhaul process. Instead of managing inventory of bit holders with different lengths, the system extracts material from the bit holder itself during overhaul to achieve the required length.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The bit holder serves its own length adjustment needs through the machining process. The turning tool removes material directly from the bit holder to achieve the precise length, eliminating the need for external measurement, selection, and matching processes.

Inventive Principle:

Principle #25Self-service

3Manufacturing precision

If bit holders are machined to precise lengths, then manufacturing precision is improved, but loss of substance increases due to material removal

Engineering Contradiction:

Improvebit holder length precisionVSAvoidbit holder material

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The invention applies partial action by removing only the minimum necessary material from the bit holder to achieve the required length. The machining process removes material just enough to reach the target length, avoiding excessive material removal while achieving precise dimensional control.

Inventive Principle:

Principle #16Partial or excessive 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

This approach allows for cost-effective and time-efficient overhauling of road milling machine drums by re-establishing uniform cutting circles with reduced diameters, maintaining high-quality milling results, and enabling overhauling at any wear state without the need for extensive measurement or replacement.

Implementation Method 1

apparatus for metal-cutting machining of wear-affected bit-head-proximal end regions of bit holders

Methodology Applied

Scientific EffectMetal-cutting machining: Abrasion

Data Source

PatentUS11273502B2Apparatus for metal-cutting machining of wear-affected bit holders of road milling machines, and use of an apparatus for overhauling such wear-affected bit holders

Publication Date: 2022.03.15 WIRTGEN GMBH

AI summary

An apparatus for metal-cutting machining of wear-affected bit-head-proximal end regions of bit holders of road milling machines encompasses:a rotary actuator having an output member rotating around an actuator rotation axis;at least one material-removing tool, rotatable around a tool rotation axis, which is coupled or couplable to the output member so as to rotate together;a positioning arbor, extending along an arbor axis, which is embodied for introduction into a bit receptacle opening of a bit holder and which comprises an abutment segment, located radially remotely from the arbor axis and facing away from the arbor axis in a direction having a radial component, which is embodied for abutment against an inner wall of the bit receptacle opening.A material-removing region, populated with cutting edges, of the material-removing tool is arranged between the positioning arbor and the output member.