Boom Stiffening Layout for Lightweight Torsion-Resistant Cut-Off Tools

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Solution Overview

Problem

Existing hand-held cut-off machines face challenges in achieving a balance between high rigidity and low weight for their booms, which are crucial for effective operation and durability.

Innovation Solution

The boom is designed with a stiffening structure that extends both internally and externally, forming a spatially diagonal stiffening element to absorb torsional vibrations, while minimizing weight by strategically placing stiffening structures to optimize force transmission and reduce rigidity in specific areas for increased service life.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If stiffening structures are added to the boom, then rigidity is improved, but weight increases

Engineering Contradiction:
ImproverigidityVSAvoidweight
Core Design Contradiction:
StrengthVSWeight of moving object

Solution Approach 1:

The patent applies local quality by providing stiffening structures only in specific areas where they are most effective. The stiffening structures are arranged to form spatial diagonals primarily in the supporting part of the boom, while other areas remain less stiffened. This localized approach provides necessary rigidity where torsional loads are highest without adding weight throughout the entire boom structure.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent transitions from two-dimensional stiffening (flat plates or simple ribs) to three-dimensional spatial diagonal stiffening structures. By arranging stiffening elements in spatial diagonals that extend through the boom in multiple dimensions, the structure achieves superior rigidity with less material, as the three-dimensional configuration more efficiently resists torsional and bending loads.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Reliability

If stiffening structures are added to absorb torsional vibrations, then durability is improved, but weight increases

Engineering Contradiction:
Improveservice lifeVSAvoidweight
Core Design Contradiction:
ReliabilityVSWeight of moving object

Solution Approach 1:

The patent applies local quality by providing stiffening structures only in specific areas where they are most effective. The stiffening structures are arranged to form spatial diagonals primarily in the supporting part of the boom, while other areas remain less stiffened. This localized approach provides necessary rigidity where torsional loads are highest without adding weight throughout the entire boom structure.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent converts the harmful effect of torsional vibrations into a beneficial design feature by specifically designing stiffening structures that target and absorb these vibrations. The spatial diagonal arrangement of stiffening elements is optimized to counteract the specific vibration modes that occur during cutting operations, transforming the problem of vibration into a design criterion for enhanced durability.

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

3Strength

If uniform stiffening is applied throughout the boom, then rigidity is improved, but manufacturing complexity increases

Engineering Contradiction:
ImproverigidityVSAvoidmanufacturing complexity
Core Design Contradiction:
StrengthVSEase of manufacture

Solution Approach 1:

The patent applies local quality by providing stiffening structures only in specific areas where they are most effective. The stiffening structures are arranged to form spatial diagonals primarily in the supporting part of the boom, while other areas remain less stiffened. This localized approach provides necessary rigidity where torsional loads are highest without adding weight throughout the entire boom structure.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent segments the boom into different zones with different stiffening requirements. The supporting part of the boom receives full spatial diagonal stiffening, while other portions have reduced or no stiffening structures. This segmentation allows each zone to be optimized independently for its specific functional requirements, simplifying the overall manufacturing process.

Inventive Principle:
Principle #1Segmentation

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 effectively absorbs torsional loads, maintains low weight, and extends the service life of the boom by distributing forces efficiently and reducing direct stress on critical components.

Implementation Method 1

the stiffening structures are arranged on the base plate in such a way that they form a stiffening element running diagonally in space. It has been shown that the torsional vibrations occurring during operation on the supporting part of the boom can be absorbed well by stiffening elements running diagonally in space.

Methodology Applied
Scientific EffectStructural damping: Damping

Data Source

PatentEP3338974B1Manually operated work device
Publication Date: 2021.08.18 ANDREAS STIHL AG & CO KG
  • EP3338974B1 patent drawingFigure 1~3
  • EP3338974B1 patent drawingFigure 4~5
  • EP3338974B1 patent drawingFigure 6~7

AI summary

A hand-held tool comprises a motor unit (51), a tool unit (52), and a boom (5) connecting the motor unit (51) to the tool unit (52), with a support element (16). The support element (16) has a base plate (19) with an inner surface (22) and an outer surface (21). A drive shaft (45) and an output shaft (46) are arranged transversely to the base plate (19). The support element (16) has a first stiffening structure (67, 70) that extends from the inner surface (22) of the base plate (19) to a space diagonal (25, 26). On the outside (21) of the base plate (19) a second stiffening structure (60, 61, 62, 65) rises towards the same space diagonal (25, 26), wherein the first stiffening structure (67, 70) and the second stiffening structure (60, 61, 62, 65) form a spatially diagonally extending stiffening element (80, 81).