Tapered Thread Bolt and Nut for Enhanced Self-Locking
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Solution Overview
Problem
Existing threaded fasteners suffer from low self-locking and loading capabilities, leading to easy unthreading and potential security incidents, especially under frequent shocks, due to their geometric structure and thread angles.
Innovation Solution
A bolt and nut with tapered threads featuring a right trapezoidal shape, where the outside and inside helical surfaces form conical surfaces with specific cone angles, ensuring interference fit and enhanced self-locking, loading, and sealing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cylindrical threads with 60° angle are used, then self-locking capability is improved, but loading capability and resistance to unthreading under shock remain insufficient
Solution Approach 1:
The patent changes the geometric parameters of the thread from a conventional cylindrical shape with 60° angle to a tapered conical shape with 30° angle. This parameter change allows the thread to simultaneously achieve high self-locking capability through the optimized angle and high loading capability through the tapered geometry that distributes stress more effectively along the thread engagement length.
Solution Approach 2:
The patent introduces a conical (curved) thread geometry instead of a straight cylindrical thread. The tapered conical shape creates a progressive engagement of thread surfaces, where the contact area increases along the length of the thread, improving both self-locking through friction and loading capability through distributed stress.
2Reliability
If thread angle is increased to improve self-locking, then locking force increases, but loading capability and resistance to shock decrease
Solution Approach 1:
The patent optimizes the thread angle parameter to 30° in the tapered conical geometry, which is different from conventional 60° cylindrical threads. This specific angle parameter, combined with the tapered shape, creates a balance where the normal force between threads provides sufficient friction for self-locking while the gradual taper distributes loads effectively, preventing thread failure under shock.
3Ease of manufacture
If conventional fastener structure is used, then ease of manufacture is maintained, but anti-loosening property and security against unthreading are insufficient
Solution Approach 1:
The tapered conical thread geometry can be manufactured using standard taper turning operations on lathes or through form tooling, maintaining relative manufacturing simplicity. The conical shape provides inherent anti-loosening properties through the progressive thread engagement and friction characteristics, preventing spontaneous unthreading without requiring additional locking mechanisms.
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 tapered thread design provides high self-locking capability, stability, and resistance to unthreading, ensuring secure fastening and connection while maintaining a compact structure and ease of manufacturing.
Implementation Method 1
The increase of the locking force is due to the change of the thread angle which hence makes the angle between the normal force between the internal and external threads and an axis of the bolt to be 60° instead of 30°, i.e. the angle of a standard thread. Obviously, the normal force of Spiralock thread is significantly greater than fasten stress. Thus, the locking friction generated is greatly increased.
Implementation Method 2
a wedge surface with a 30° inclination is defined at the root of a negative thread (internal triangular thread, i.e. female thread). When the bolt is coupled with the nut, a teeth portion of the external thread of a standard bolt abuts against the wedge incline of the internal thread, and hence generating interference screw locking to increase locking force.
Data Source
AI summary
A tapered threaded bolt and nut are provided. The bolt comprises a main body; an outside helical surface and a first end helical surface are defined on the main body; a shape of the outside helical surface is the same as a shape of a lateral surface of a solid of revolution formed by using a right trapezoid as a generatrix, rotating uniformly around a cathetus of the right trapezoid which is coincident with a center axis of the main body, and synchronously, axially and uniformly moving the right trapezoid along the center axis of the main body; a shape of the first end helical surface is the same as a shape of helical end surface with a same direction as an axial moving direction of the solid of revolution. An inside helical surface and a second end helical surface are defined in a screw hole of the nut.