Threaded Tension Rod Structure for Fatigue-Resistant Joints
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Solution Overview
Problem
Conventional tension rod mechanisms have a structurally weak engaging portion that tends to fatigue and break, leading to high maintenance costs and frequent replacements due to the rapid change in cross-sectional area at the jointing area between the engaging member and the rod.
Innovation Solution
A tension rod mechanism with an engaging member and an enveloping member, where the engaging member has an outer threaded portion with a constant major diameter and increasing minor diameters, and the enveloping member has an inner threaded portion with a constant major diameter and increasing minor diameters, which gradually expands to increase structural strength and reduce the likelihood of breakage without additional auxiliary members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the major diameter of the screw rod at the engaging portion is made small to fit within the inner tube, then the engaging portion can be mounted inside the inner tube, but the engaging portion becomes structurally weak and tends to fatigue and break
Solution Approach 1:
The patent transitions from a single-diameter rod design to a threaded rod design, utilizing the radial dimension through thread engagement. The outer threaded portion engages with the inner threaded portion, distributing stress across multiple thread surfaces rather than relying on a single cross-sectional area, thereby increasing structural strength without increasing the overall diameter.
Solution Approach 2:
The patent employs a composite threaded structure where the rod and engaging portion work together as an integrated fastening system. The threaded portions create a composite mechanical connection that combines the rod's tensile strength with the engaging portion's structural support, creating a stronger joint than either component could provide alone.
2Shape
If the cross-sectional area changes rapidly at the jointing area between the engaging member and the rod, then the structure can be compact, but the engaging member becomes prone to fatigue and breakage
Solution Approach 1:
The patent applies different geometric properties to different portions of the rod. The outer threaded portion has a constant major diameter to maintain uniform stress distribution, while the minor diameter increases toward the free end to provide gradual stress transition. This local variation in dimensional properties prevents sudden cross-sectional changes that would cause stress concentration and fatigue.
Solution Approach 2:
The patent gradually changes the minor diameter parameter of the outer threaded portion from the engaging portion toward the free end. This gradual parameter change creates a smooth transition in cross-sectional area, reducing stress concentration and preventing fatigue failure while maintaining a compact overall structure.
3Ease of operation
If the screw rod disengages from the engaging portion, then adjustment can be made, but it becomes difficult to remove the engaging portion out of the inner tube requiring replacement of the entire inner tube
Solution Approach 1:
The patent divides the fixing device into separable components: the engaging member with its engaging portion and the rod with threaded portions. This segmentation allows the engaging portion to be independently removed from the inner tube by disengaging the threaded connection, enabling maintenance and replacement of only the engaging portion rather than the entire inner tube assembly.
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 solution enhances the structural strength of the engaging member, making the fixing device more durable and reducing maintenance frequency by preventing sudden changes in cross-sectional area, thereby prolonging the service life and improving operational reliability.
Implementation Method 1
The outer threaded portion is connected to an end face of the engaging portion. The enveloping member includes an inner periphery having an inner threaded portion engaged with the outer threaded portion.
Data Source
AI summary
A tension rod mechanism includes an outer tube, an inner tube having an end received in the outer tube, and a fixing device. The fixing device includes an engaging member and an enveloping member. The engaging member includes an engaging portion and a rod connected to the engaging portion. The engaging portion is mounted to the end of the inner tube. The rod extends in the outer tube. The rod includes an outer threaded portion formed on an outer periphery thereof. The outer threaded portion is connected to an end face of the engaging portion. The outer threaded portion has a constant major diameter. The outer threaded portion includes increasing minor diameters from the engaging portion toward a free end of the rod. The enveloping member includes an inner periphery having an inner threaded portion engaged with the outer threaded portion.