Self-Locking Spoke Nipple With Intermediate Insert Positioning
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Solution Overview
Problem
Existing self-locking nipples for spoked wheels require unnecessarily long spokes and result in material waste, increased wheel weight, and undesirable inertia effects, as well as requiring disassembly of the wheel for adjustment.
Innovation Solution
A self-locking nipple design featuring a deformable insert with a discontinuous mantle, applied in an intermediate axial position, which allows for a shorter spoke length and enables adjustment without disassembling the wheel, using a radially contractile insert with a metal core for improved precision and repeatability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insert is applied to the axial end of the nipple furthest from the rod, then self-locking is achieved, but the spoke must be needlessly long resulting in material waste and increased wheel weight
Solution Approach 1:
The insert is positioned in an intermediate axial region of the nipple rather than at the extreme end, creating a localized self-locking zone that is optimally positioned to engage the spoke thread. This local positioning reduces the required spoke length while maintaining the self-locking function, thereby reducing wheel weight and material waste.
2Reliability
If the insert is applied to the axial end of the nipple, then self-locking is achieved, but excessive energy and tool wear occur due to processing spoke portions that do not contribute to mechanical resistance
Solution Approach 1:
By positioning the insert in an intermediate axial region, the self-locking function is achieved at a location that does not require excessive processing of the spoke. This reduces the length of spoke that must be threaded and processed, thereby reducing energy consumption and tool wear during manufacturing.
3Reliability
If the insert is over-dimensioned with respect to the diameter of the threaded hole, then engagement with the spoke thread is ensured, but substantial difficulties arise in the axial insertion process
Solution Approach 1:
The insert is designed with a radially contractile capability, allowing its external diameter to be temporarily reduced for insertion into the threaded hole. Once positioned in the intermediate axial region, the insert returns to its original diameter, ensuring adequate engagement with the spoke thread while facilitating easy insertion during manufacturing.
Solution Approach 2:
The insert incorporates a discontinuous mantle structure that provides radial contractility, enabling the insert to be compressed radially for insertion and then expand to its full diameter for proper engagement. This flexible design allows for easy axial insertion while maintaining the necessary engagement dimensions.
4Productivity
If the insert is made radially contractile with a discontinuous mantle, then rapid and precise application is achieved, but the structural integrity must be maintained
Solution Approach 1:
The discontinuous mantle is designed with specific geometric features that allow radial contraction for insertion while maintaining sufficient structural integrity. The mantle's configuration ensures that when expanded, it provides the necessary strength for engagement with the spoke thread, while during insertion, it can be compressed radially to pass through the threaded hole.
Solution Approach 2:
The insert is made from deformable resin material that combines flexibility for radial contraction with sufficient strength for structural integrity. The material properties are selected to allow the mantle to be radially contractile during insertion while maintaining adequate strength for engagement and repeated screwing and unscrewing operations.
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 design achieves a self-locking connection with reduced material waste and weight distribution issues, allowing for spoke tension adjustment without disassembling the wheel, while maintaining mechanical resistance and ease of manufacturing.
Implementation Method 1
the insert is bored so as to define a passage, the internal diameter of which is less than the crest diameter of the thread of the spoke. In this manner, when the spoke is screwed in the nipple, it deforms the walls of the passage of the insert while being inserted therein with an interference fit.
Implementation Method 2
the insert, in order to be able to be introduced from the exterior inside the threaded hole of the nipple up to the seat formed in an intermediate position of said hole, is made radially contractile
Data Source
Figure 1
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AI summary
A nipple for spokes of spoked wheels includes a rod with an axial development, a threaded hole which is formed axially in the rod, the thread of the hole defining a root diameter and a crest diameter, a head which is widened with respect to the rod and a deformable insert which is inserted in a seat which is axially aligned with the hole and which is constructed in an axially intermediate position thereof. The insert, at least when it is inserted in the seat, has a passage for a threaded spoke end, the internal diameter of which is less than the root diameter of the thread of the hole so as to interfere with the thread of the spoke when it is screwed into the threaded hole.