Chainsaw Guide Member Geometry for Chain Passage Chip Discharge

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Solution Overview

Problem

Cutting chips that accumulate in the chain passage of a chainsaw can hinder the rotation of the saw chain and cause damage to the guide bar and sprocket cover.

Innovation Solution

A chainsaw design featuring a guide member with a first and second facing surface, both having an arc shape, positioned to reduce the passage area and facilitate the discharge of cutting chips, with the angle between the connecting line and horizontal plane ranging from -10 to 25 degrees, allowing gravitational discharge and minimizing accumulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the passage area of the chain passage is reduced by the guide member, then cutting chips can be suppressed from advancing deep into the chain passage, but the chain passage may become blocked by accumulated cutting chips

Engineering Contradiction:

Improvecutting chips advancing deep into chain passageVSAvoidchain passage blockage

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The guide member is divided into two distinct facing surfaces: a first facing surface with an arc shape centered on the rotation axis to reduce passage area and suppress chip advancement, and a second facing surface with an arc shape centered on a position offset from the rotation axis to facilitate chip discharge. This segmentation allows each surface to perform its specific function without interfering with the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using a single facing surface that merely reduces passage area, the invention inverts the approach by adding a second facing surface that actively promotes chip discharge. The second surface is positioned and shaped to create a discharge path, effectively doing the opposite of what the first surface does (suppressing advancement vs. facilitating discharge).

Inventive Principle:

Principle #13The other way round (Inversion)

2Object-affected harmful factors

If a single facing surface is used to reduce passage area, then chip advancement is suppressed, but chip discharge is not facilitated

Engineering Contradiction:

Improvechip advancement suppressionVSAvoidchip discharge

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

3Ease of operation

If the angle of the guide member is not optimized, then chip discharge may be inefficient, but manufacturing precision requirements increase

Engineering Contradiction:

Improvechip discharge efficiencyVSAvoidangle precision

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The invention specifies an optimal angle range (−10 degrees to 25 degrees) for the straight line connecting the rotation axis and the connection position of the two facing surfaces relative to the horizontal plane. By defining this parameter range, the invention balances chip discharge efficiency with manufacturing feasibility, avoiding overly strict precision requirements while ensuring effective operation.

Inventive Principle:

Principle #35Parameter changes

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

Effectively suppresses cutting chips from advancing deep into the chain passage and accumulating, ensuring smooth operation and reducing damage to the chainsaw components.

Implementation Method 1

the cutting chips that were prohibited from advancing deep into the chain passage can easily be discharged downward by a gravitational force

Methodology Applied

Scientific EffectGravitation: Gravitation

Data Source

PatentUS12186929B2Chainsaw

Publication Date: 2025.01.07 MAKITA CORP

AI summary

A chainsaw may include a saw chain; a guide bar, a sprocket, a prime mover, a housing, a sprocket cover, and a guide member. The guide bar, the housing and the sprocket cover may define a chain passage. The guide member may include a first facing surface having an arc shape centered on the rotation axis and a second facing surface having an arc shape centered on a position offset from the rotation axis. When the chainsaw is placed on a horizontal mounting surface and viewed in the direction along the rotation axis, an angle between (i) a straight line connecting the rotation axis and a position where the first facing surface and the second facing surface are connected and (ii) a horizontal plane may be in a range of −10 degrees to 25 degrees.