Deck Fastener With Reverse Threads Prevents Back-Out
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Solution Overview
Problem
Conventional wood fasteners tend to back out of decks over time due to repeated freezing and thawing cycles, leading to unsightly protrusions and potential tripping hazards, as well as material separation and reduced deck lifespan.
Innovation Solution
A fastener design featuring a shank with a combination of right-handed threaded and reverse threaded sections, where the reverse threaded section includes left-handed threads, which counters the back-out force by reaming the opening and providing additional holding strength, thereby resisting compression and weather-related deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wood fasteners are used to assemble deck structures, then the fasteners can initially secure the decking boards, but over time the fasteners back out of the wood due to freezing and thawing cycles, causing protrusions and material separation
Solution Approach 1:
The fastener shank is divided into distinct functional sections: a first threaded section for initial engagement and pulling substrates together, a reverse threaded section for reaming and preventing back-out, and an unthreaded section. This segmentation allows each section to perform its specific function optimally, with the reverse threaded section specifically addressing the back-out problem caused by freezing and thawing cycles.
Solution Approach 2:
The patent applies reverse threading (left-handed threads) in the reverse threaded section, which rotates in the opposite direction compared to conventional right-handed threads. This inversion creates a reaming action that prevents the fastener from backing out, directly counteracting the harmful effect of freezing and thawing cycles that cause conventional fasteners to loosen.
2Ease of operation
If the fastener uses only conventional right-handed threading, then installation is straightforward, but the fastener cannot resist the back-out force generated by elastic material recovery and weather cycles
Solution Approach 1:
The threading is segmented into a first threaded section with right-handed threads for easy installation and a reverse threaded section with left-handed threads for resisting back-out force. This segmentation allows the fastener to maintain ease of installation while gaining resistance to loosening forces.
Solution Approach 2:
Different sections of the shank have different threading properties: the first threaded section has conventional right-handed threads optimized for installation, while the reverse threaded section has left-handed threads optimized for preventing back-out. This local differentiation allows each section to excel at its specific function.
3Strength
If the reverse threaded section is made longer to improve back-out resistance, then holding strength increases, but the fastener may not properly align with the substrate interface and may reduce installation precision
Solution Approach 1:
The reverse threaded section is given a specific moderate length that is sufficient to provide back-out resistance without being excessive. This localized optimization ensures the reverse threaded section performs its function while maintaining proper alignment with the substrate interface.
Solution Approach 2:
The patent specifies particular dimensional parameters for the reverse threaded section length and positioning to optimize both back-out resistance and interface alignment. By carefully controlling these parameters, the fastener achieves both strength and precision.
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 fastener effectively prevents back-out and enhances the durability of deck assemblies by creating a self-locking mechanism that maintains secure attachment between wood substrates, reducing the risk of tripping hazards and extending deck lifespan.
Implementation Method 1
The reverse threaded section may provide additional holding strength, thereby resisting compression and weather-related deformation
Data Source
AI summary
A fastener configured to couple a first substrate to a second substrate may include a head, a shank, and a tip. The shank may have a generally constant diameter between the head and tip, and the shank may include an unthreaded portion proximate the head, a threaded portion proximate the tip, and a reverse threaded portion therebetween. The threaded portion may include a plurality of right handed threads that continue onto the tip, and the reverse threaded portion includes a plurality of left handed threads. The unthreaded portion may have an axial length greater than an axial length of the reverse threaded portion. In addition, the fastener may include one or both of a cut extending radially inward toward the fastener axis proximate the tip and serrations on at least one of the plurality of right handed threads.