Timber Joint Staple Geometry for Shrinkage and Withdrawal Resistance
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Solution Overview
Problem
Existing fastening systems for structural timber components, such as gang-nail connectors, face challenges in maintaining strength over time due to rust and require complex alignment for replacement, while conventional connectors cannot accommodate repetitive load cycles and timber shrinkage.
Innovation Solution
A staple with specific angular dimensions and material properties, driven into timber components with a fastening gun, creates pre-tension and resistance to withdrawal, allowing for secure connection and accommodation of timber movement, and can be used to reinforce existing joints without removing old connectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional connectors (gang-nail connectors) are used to connect structural timber components, then initial connection strength is achieved, but the connection strength deteriorates over time due to rust and the connectors cannot accommodate timber shrinkage and expansion
Solution Approach 1:
The patent changes the material parameter from conventional steel connectors to corrosion-resistant steel with minimum yield strength of 1300 MPa and minimum tensile strength of 1500 MPa. This material parameter change ensures the connector maintains strength over time without rusting, directly resolving the contradiction between initial connection strength and long-term durability
Solution Approach 2:
The connector incorporates a crown portion that can deform and bends at least partially into the timber component. This dynamic capability allows the rigid connector to accommodate timber shrinkage and expansion movements while maintaining connection integrity, resolving the contradiction between structural rigidity and adaptability to timber movement
2Ease of manufacture
If conventional connectors are used for structural connections, then initial assembly is achieved, but replacement requires complex alignment and specialized equipment
Solution Approach 1:
The connector is segmented into distinct functional portions: two spikes for insertion, a crown portion for deformation and embedding, and a stem portion for connection. This segmentation allows the connector to be driven in sequentially and enables replacement by simply driving new connectors through the timber without requiring removal of old ones or complex alignment equipment
Solution Approach 2:
The connector design enables self-installation through the timber component using a simple fastening gun. The spikes self-align as they are driven into the timber, and the crown self-bends into the timber to complete the connection, eliminating the need for complex alignment equipment during both installation and replacement
3Strength
If high-strength wire is used for the staple, then connection strength and corrosion resistance are improved, but the wire becomes more difficult to drive into timber
Solution Approach 1:
The connector has non-uniform geometry with spikes that are thinner at the tips and thicker at the base, and a crown portion with specific curvature radius (0.5-2 times the wire diameter). This local variation in geometry concentrates stress at the spike tips during driving, enabling high-strength wire to be driven into timber more easily while maintaining overall connection strength
Solution Approach 2:
The crown portion is formed with a specific curvature radius that is 0.5 to 2 times the wire diameter. This curvature allows the crown to bend smoothly into the timber during installation, reducing resistance and enabling easier driving of high-strength wire connectors into the timber component
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
The staple provides a secure, corrosion-resistant connection that maintains strength under repetitive loads and accommodates timber shrinkage and expansion, allowing for efficient assembly and refurbishment of structural assemblies without the need for complex alignment or equipment.
Implementation Method 1
the crown is bowed into the adjoining workpieces. This sets up a pretension in the staple
Implementation Method 2
Each spike (14) includes a sharpened tip portion (18) for embedding in the timber component
Data Source
Figure 1~5
Figure 6~8
Figure 9~10
AI summary
A staple includes a length of metal wire shaped to form a crown and two spikes. Each spike depends from a respective end of the crown and includes a shoulder at each end of the crown, a sharpened tip portion and an elbow interposed between each tip portion and shoulder, the elbow comprised of a proximal limb and a distal limb such that the tip portions depend from respective distal limbs. An included angle between each shoulder and the crown is between about 91° and 96°, an included angle between each proximal limb and the crown is between about 60° and 85° and an included angle between each distal limb and the crown is between about 95° and 130°.