Tapered Thread Connection Pair for Anti-Loosening
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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 structure and thread angles.
Innovation Solution
A tapered-thread connection pair is designed with external and internal threads formed by rotating trapezoids around a center axis, creating conical surfaces that interfere fit for enhanced locking and loading capabilities, featuring specific cone angles and transitional guiding surfaces for effective matching and manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional screw threads with triangular cross section are used, then the structure is simple and easy to manufacture, but the self-locking capability and loading capability are low, leading to easy unthreading
Solution Approach 1:
The patent changes the fundamental geometric parameters of the thread by using a trapezoidal cross-section instead of a triangular one, and by employing conical surfaces with specific semi-vertical angles (α1 and α2) rather than cylindrical surfaces. This parameter change fundamentally improves the self-locking capability through increased normal force and friction, while the trapezoidal geometry remains manufacturable with standard tools.
Solution Approach 2:
The patent introduces asymmetry through the trapezoidal cross-section where the two base angles are different (one acute, one obtuse). This asymmetric geometry creates different contact conditions on the two flanks of the thread, optimizing the load distribution and self-locking characteristics. The asymmetric design allows one flank to bear the primary load while the other provides structural support.
2Reliability
If the thread angle is increased to improve self-locking, then the equivalent friction angle increases and self-locking improves, but the loading capability and mechanical sealing performance deteriorate
Solution Approach 1:
The patent applies local quality by having different semi-vertical angles for the external cone (α1) and internal cone (α2). This allows optimization of different regions: the external cone angle is optimized for self-locking and anti-loosening, while the internal cone angle is optimized for loading capability and sealing. Each local region has geometric properties tailored to its specific functional requirement.
Solution Approach 2:
The thread connection is segmented into distinct functional zones: the external tapered thread portion optimized for self-locking, the internal tapered thread portion optimized for loading and sealing, and the transitional guiding surfaces that facilitate assembly. This segmentation allows each zone to be independently optimized for its specific function without compromising overall performance.
3Stability of the object's composition
If conventional cylindrical threads are used, then the manufacturing is simple, but the connection stability and anti-loosening performance are poor under frequent shocks
Solution Approach 1:
The patent transitions from cylindrical thread geometry to conical thread geometry, fundamentally changing the spatial parameters of the thread. The conical surfaces with specific semi-vertical angles create a wedge effect that generates continuous normal force and friction, providing superior anti-loosening performance under shock loads. The manufacturing process uses standard conical surface generation techniques.
Solution Approach 2:
The patent employs curved conical surfaces instead of straight cylindrical surfaces. The conical geometry provides a continuously varying contact angle along the thread length, creating a more stable and forgiving connection that better absorbs shock loads. The curved surfaces also facilitate smoother assembly and reduce stress concentrations.
4Reliability
If the thread structure is optimized for self-locking with larger thread angles, then the locking force increases, but the mechanical sealing performance and compact structure are compromised
Solution Approach 1:
The patent optimizes the semi-vertical angles of the conical surfaces to achieve a balance between locking force and compactness. By carefully selecting α1 and α2 within specific ranges, the design achieves high self-locking capability through the wedge effect while maintaining a compact overall structure. The conical geometry allows for more efficient space utilization compared to conventional threads.
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 connection pair achieves high self-locking, anti-loosening, and loading capabilities, ensuring stable connections and preventing unthreading, with improved mechanical sealing and compact structure.
Implementation Method 1
The basic condition for self-locking thread is that an equivalent friction angle is no less than a lead angle. The value of an equivalent friction angle is related to a thread angle, the bigger the thread angle is, the bigger the equivalent friction angle is, and the more beneficial to self-locking
Implementation Method 2
The wedge thread proposed in recent years, also called 'Spiralock nut', is an improvement to both of the metric screw threads and English screw threads, aiming at improving the self-locking capability of the screw thread defined on a fastener. The structure of 'Spiralock' thread is that a wedge surface with a 30° C. inclination is defined at the root of a negative thread
Data Source
AI summary
A tapered thread connection pair comprises an external thread and an internal thread. The external thread comprises an outside helical surface and a first end helical surface, the shape of the outside helical surface is the same as that of a spiral outside surface of a solid of revolution, and the shape of the first end helical surface is the same as that of a spiral end surface of the end having a moving direction that is the same as an axial movement direction of the solid of revolution. The internal thread comprises an inside helical surface and a second end helical surface. The shape of the inside helical surface is the same as that of the spiral outside surface of the solid of revolution.