Segmented Wood Truss Fastener Prevents Lumber Splitting

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Solution Overview

Problem

Conventional fasteners cause splitting, splintering, cracking, and fracturing when used to assemble laminated wood truss assemblies, leading to cosmetic and structural damage.

Innovation Solution

A truss fastener with a shaft featuring interrupted threading and oblique projections, such as wings, that displace and ream lumber material to prevent damage during embedding, allowing for secure fastening without splitting or splintering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional fasteners are used to assemble laminated wood truss assemblies, then fastening is achieved, but splitting, splintering, cracking, and fracturing occur causing cosmetic and structural damage

Engineering Contradiction:

Improvefastening reliabilityVSAvoidmaterial damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The threading on the fastener shaft is divided into multiple separate threaded sections by unthreaded portions. This segmentation allows the fastener to engage the wood material in discrete locations rather than continuously, reducing the cumulative stress and preventing splitting and splintering while still providing reliable fastening through multiple engagement points.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The fastener features varying thread characteristics along its length, with different threaded sections having different properties. The unthreaded portions create localized zones of reduced stress concentration, while the threaded sections provide localized gripping force. This local variation in fastener quality allows effective fastening without causing damage to the laminated wood material.

Inventive Principle:

Principle #3Local quality

2Force

If continuous threading is used on the fastener shaft, then strong gripping force is achieved, but splitting and cracking of laminated elements occur

Engineering Contradiction:

Improvegripping forceVSAvoidcracking and fracturing

Core Design Contradiction:

ForceVSObject-affected harmful factors

Solution Approach 1:

The continuous threading is broken into discrete threaded sections separated by unthreaded portions. Each threaded section provides localized gripping force, while the unthreaded sections act as stress relief zones that prevent the propagation of cracks and fractures through the laminated wood material, thereby maintaining strong overall gripping force without causing damage.

Inventive Principle:

Principle #1Segmentation

3Productivity

If standard fasteners are used for laminated building elements, then assembly is achieved, but cosmetic damage occurs significantly impacting the structure

Engineering Contradiction:

Improveassembly efficiencyVSAvoidcosmetic damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The segmented threading design allows the fastener to be driven into laminated wood material without causing splintering or surface damage. The unthreaded portions prevent the fastener from continuously engaging and damaging the cosmetic surface of the laminated elements, while still providing sufficient holding power for assembly.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The unthreaded portions of the fastener shaft act as a preliminary cushioning zone that prepares the wood material for the subsequent threaded sections. This preliminary action prevents the immediate concentration of stress at the entry point, thereby preventing cosmetic damage while maintaining assembly efficiency.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7686556B2Wood truss fastener

Publication Date: 2010.03.30 HANDY & HARMAN

AI summary

A truss fastener which includes a shaft having a head and a tip. Threading extends along the shaft from the tip end toward the head end of the shaft. The threading is interrupted, abbreviated, and/or otherwise separated by wings projecting from the surface of the shaft. The interrupting projection extends in a generally oblique orientation to the center axis of the fastener.