Glued Timber Truss Joint Design for Robust Assembly

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Solution Overview

Problem

Existing timber truss joints with metal connectors lack robustness, reliability, flexibility in spacing, and shoring, limiting the use of glued timber trusses in demanding construction projects.

Innovation Solution

A novel glued timber truss joint design featuring chords and diagonals with specific routing and groove configurations, including tapering fingers, unique bit usage, and automated assembly, allowing for increased strength, flexibility, and cost-effectiveness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If metal connectors are used to join timber trusses, then assembly is simple and quick, but the joint robustness, reliability, and flexibility are insufficient

Engineering Contradiction:

Improveassembly simplicityVSAvoidjoint robustness

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces metal mechanical connectors with a glued joint system using finger joints and routing grooves. The timber components are joined through precisely routed grooves and fingers that interlock and are bonded with adhesive, eliminating the need for metal plates or fasteners while achieving superior joint strength and reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the joining mechanism from external metal fasteners to internal wood-to-wood bonding through routed grooves. The groove depth, width, and positioning are precisely controlled to optimize the glued joint's mechanical properties, transforming the connection method from mechanical interlocking with metal to chemical bonding between timber surfaces.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If glued joints are used instead of metal connectors, then fire resistance and moisture resistance improve, but the joint strength and reliability are insufficient

Engineering Contradiction:

Improvefire and moisture resistanceVSAvoidjoint strength

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The patent creates a composite joint system combining timber, adhesive, and precisely engineered geometric features (fingers and grooves). The combination of the glued bond and the interlocking finger geometry produces a joint that leverages both the chemical bonding strength and the mechanical interlocking, achieving superior strength while maintaining the fire and moisture resistance benefits of solid timber connections.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent employs tapered fingers with varying cross-sectional areas along their length, creating a wedgelike geometry that concentrates stress and enhances bonding. The tapered shape allows for progressive load transfer from the smaller end to the larger end of the finger, optimizing the distribution of forces and maximizing joint strength.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Strength

If fingers are embedded deep in the chord, then joint strength increases, but chord routing complexity and difficulty increase

Engineering Contradiction:

Improvejoint strengthVSAvoidrouting complexity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent incorporates routing grooves directly into the timber components during the manufacturing process, before assembly. The grooves are precisely cut to match the finger dimensions, ensuring perfect fit and maximum bonding surface area. This preliminary preparation eliminates the need for complex field adjustments or additional routing operations during assembly.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies different groove depths and geometries at different locations along the chord based on local requirements. The routing varies to accommodate the specific finger configurations needed at each joint location, optimizing both strength and manufacturability for each specific connection point rather than using a uniform approach throughout.

Inventive Principle:

Principle #3Local quality

4Reliability

If multiple diagonal bars are used in parallel or succession, then joint strength and reliability improve, but the number of routing operations and manufacturing complexity increase

Engineering Contradiction:

Improvejoint reliabilityVSAvoidrouting operations

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple diagonal bars into a single integrated timber component with internally routed grooves for multiple fingers. Instead of separately routing and assembling multiple independent diagonal members, the design merges them into one piece that engages the chord through coordinated finger-groove interfaces, reducing assembly steps while maintaining the cumulative strength of multiple diagonals.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11680405B2Glued timber truss

Publication Date: 2023.06.20 PATENTTITOIMISTO T POUTANEN

AI summary

A glued timber truss (FIGS. 1, 3), comprising chords (1, 2) and therebetween a first diagonal bar (3) and a second diagonal bar (4), which is crosswise relative to the first one, or a web panel (9) connected to each other with an adhesive and a finger joint (FIG. 3), whereby the first diagonal bar is present alongside the second diagonal bar or the web panel.