Dual-Serration Safety Washer for Stable Bolt Tension
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Solution Overview
Problem
Existing washers fail to consistently induce a well-defined tension in bolts due to varying friction between the washer and the bearing, leading to inconsistent torque and potential sliding during tightening, which affects the untightening torque and residual tension.
Innovation Solution
A washer with distinct serrations on both the bolt under head engaging surface and the bearing engaging surface, featuring a saw tooth structure with boomerang-like edges on the under head surface and inclined teeth on the bearing surface, ensuring high friction with the bearing and controlled movement relative to the bolt head, thereby maintaining a well-defined tension and improved untightening torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a washer with serration on only one surface is used, then the friction between washer and bearing can be controlled, but the washer may still slide on the bearing during tightening and the untightening torque is insufficient
Solution Approach 1:
The washer has different serration patterns on different surfaces: the bearing surface has inclined teeth for high friction and position stability, while the under head surface has saw tooth structure with boomerang edges for controlled movement and tension definition. This local differentiation resolves the contradiction by optimizing each surface for its specific function.
Solution Approach 2:
The serration patterns are asymmetric in design and orientation. The bearing surface teeth are inclined at specific angles to the radial direction, while the under head surface has asymmetric boomerang-shaped edges. This asymmetry creates different friction characteristics on each surface, enabling both position stability and controlled movement.
2Reliability
If the friction between washer and bearing is increased to prevent sliding, then position stability improves, but the complexity of washer design increases
Solution Approach 1:
Instead of making the entire washer complex, only the bearing surface is given inclined teeth for high friction, while the under head surface has a simpler saw tooth pattern. This localized application of complexity resolves the contradiction by providing high friction only where needed.
Solution Approach 2:
The washer is functionally segmented into two distinct surfaces with different serration characteristics. The bearing surface and under head surface are treated as separate functional zones with optimized designs for their respective purposes, avoiding unnecessary complexity in the entire structure.
3Ease of manufacture
If the same serration pattern is used on both washer surfaces, then manufacturing is simplified, but the friction characteristics cannot be optimized for both bearing engagement and bolt tension control
Solution Approach 1:
Different serration patterns are applied to different surfaces of the washer. The bearing surface has inclined teeth optimized for friction with the bearing, while the under head surface has saw tooth structure optimized for interaction with the bolt head. This local differentiation enables precise tension control without sacrificing manufacturability.
4Ease of operation
If the washer is designed to move relative to the bearing during tightening, then easier installation is achieved, but the tension induced on the bolt becomes inconsistent
Solution Approach 1:
The bearing surface is designed with inclined teeth that create high friction to prevent washer movement relative to the bearing during tightening. This ensures consistent tension induction while maintaining ease of installation through the serrated design that guides proper positioning.
Solution Approach 2:
The inclined teeth on the bearing surface create preliminary friction resistance that prevents unwanted washer movement before the bolt is fully tightened. This preliminary anti-action ensures consistent tension from the start of the tightening process.
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 washer achieves a well-defined tension and increased untightening torque, maintaining resistance to bolt loosening even under vibrational stress, with a minimum untightening torque to tightening torque ratio exceeding 1.2, and maintaining residual tension after dynamic stress.
Implementation Method 1
The friction between the washer and the bolt and, on the other hand, the friction between the washer and the bearing
Data Source
Figure 1~2B
Figure 3~4B
Figure 5~6B
AI summary
The present invention relates to a washer having a having central hole (3), a bolt under head engaging surface (4) and a bearing engaging surface (14), wherein - a serration on the bolt under head engaging surface (4) comprises a saw tooth (7) structure, the edges of said saw tooth structure (10) having a boomerang-like shape, - a serration on the bearing engaging surface (14) comprises a plurality of teeth (15) which in top view of the bolt under head engaging surface run in the direction from the inner (5) to the outer (6) circumference of the bearing engaging surface (14) and which are inclined with regard to radially extending straight lines originating from the washer center (2), and - the top sections of the edges of both the teeth (17) and the saw teeth (18) in cross-sectional view of the serrations are rounded.