Handheld Tool Housing Interlocking Ribs for Fracture Strength

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Solution Overview

Problem

Existing hand-held tool housings are prone to damage, particularly when dropped from hip height, due to insufficient stability and fracture strength.

Innovation Solution

A housing design featuring ribs that project beyond the parting plane, with specific height and spacing ratios, ensuring that the ribs support each other to enhance stability and fracture strength, while avoiding unsightly sink marks and simplifying manufacturing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If thicker ribs are used to increase stability and fracture strength, then the housing becomes more stable and stronger, but sink marks appear on the outside of the housing wall opposite the rib base

Engineering Contradiction:
Improvefracture strengthVSAvoidsurface appearance
Core Design Contradiction:
StrengthVSShape

Solution Approach 1:

The patent applies dimensionality change by having ribs project beyond the parting plane into the opposing housing shell, creating a three-dimensional interlocking structure. The first rib extends into the second housing shell and the second rib extends into the first housing shell, establishing spatial overlap that provides structural reinforcement without requiring increased rib thickness that would cause sink marks.

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

2Stability of the object's composition

If thicker ribs are used to increase stability, then the housing becomes more stable, but the rib structures require coarser mesh design and more complex manufacturing

Engineering Contradiction:
Improvehousing stabilityVSAvoidmanufacturing complexity
Core Design Contradiction:
Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The patent uses dimensionality change by extending ribs into the opposing housing shell across the parting plane, creating stability through spatial interlocking rather than increased rib thickness. This allows for finer rib structures that are easier to manufacture while maintaining housing stability.

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

3Strength

If additional stiffening components are introduced between housing shells, then fracture strength increases, but device complexity increases

Engineering Contradiction:
Improvefracture strengthVSAvoidhousing structure complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The patent applies merging by integrating the stiffening function directly into the housing shell ribs themselves. The first and second ribs form an interlocking structure where each rib provides mutual support, eliminating the need for separate stiffening components and reducing overall device complexity while maintaining fracture strength.

Inventive Principle:
Principle #5Merging (Combining)

4Strength

If ribs are positioned close together to increase stability, then fracture strength increases, but manufacturing precision requirements increase

Engineering Contradiction:
Improvefracture strengthVSAvoidrib spacing precision
Core Design Contradiction:
StrengthVSManufacturing precision

Solution Approach 1:

The patent applies dimensionality change by having ribs extend into the opposing housing shell, creating stability through the third dimension (depth into the shell) rather than relying solely on reduced spacing in the planar dimension. This allows for adequate rib spacing that is easier to manufacture while maintaining fracture strength through the interlocking three-dimensional structure.

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

Data Source

PatentEP3922414B1Housing
Publication Date: 2025.08.27 ANDREAS STIHL AG & CO KG
  • EP3922414B1 patent drawingFigure 1~2
  • EP3922414B1 patent drawingFigure 3~4
  • EP3922414B1 patent drawingFigure 5~6

AI summary

The invention relates to a housing for a hand-held tool (2) comprising two housing shells (10, 20), namely a first housing shell (10) and a second housing shell (20). The first housing shell (10) has a first outer wall (11) and the second housing shell (20) has a second outer wall (21), which at least partially abut each other along a parting line (3). The first housing shell (10) has at least one first rib (13, 33, 53, 54, 55) extending transversely, in particular perpendicularly, to the parting line (3) in a transverse direction (50). The first rib (13, 33, 53, 54, 55) projects beyond the parting line (3) into the second housing shell (20). The first rib (13, 33, 53, 54, 55) has a first rib height (rla, r1b) measured in the transverse direction (50) starting from a first measuring point (M1a, M1b) in the parting plane (3) to one of the first ends (15) of the first rib (13, 33, 53, 54, 55) facing the second housing shell (20).The second housing shell (20) has a second shell height (h2a, h2b) measured in the transverse direction (50) from the same first measuring point (M1a, M1b) in the parting plane (3) to a second inner surface (28) of the second housing shell (20) facing the first housing shell (10). There is at least one first measuring point (M1a, M1b) in the parting plane (3) at which the first rib height (r1a, r1b) is at least 30%, in particular at least 45%, preferably at least 60% of the second shell height (h2a, h2b).