Spring Head Screw Assembly for High-Temperature Preload Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing spring head screws experience a decrease in preload force due to creep deformation under high temperatures, leading to potential screw joint failures and reduced assembly safety.
Innovation Solution
A washer is arranged between the threaded shank and the conical skirt of the spring head screw, with a cylindrical region between the support plane and the shank transition, reducing contact pressure and creep deformation, and a tangential transition to ensure homogeneous stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spring head screw is exposed to high temperatures for a prolonged period, then the preload force decreases due to creep deformation, but the assembly safety and reliability deteriorate
Solution Approach 1:
A washer is introduced as an intermediary element between the clamping part and the spring head screw. The washer distributes the contact pressure over a larger area, reducing the contact pressure intensity that causes creep deformation in the clamping part when exposed to high temperatures, thereby maintaining preload force retention.
Solution Approach 2:
The washer modifies the local pressure distribution at the contact area between the screw and the clamping part. By creating a more uniform pressure distribution across the contact surface, the washer reduces localized high-stress regions that would otherwise accelerate creep deformation under thermal exposure.
2Force
If the shank transition comes to bear against the washer during tightening, then the screw-in torque increases excessively, but the assembly process becomes difficult
Solution Approach 1:
The cylindrical region is designed to extend beyond the support plane, creating a preliminary geometric constraint that guides the washer's position during the tightening process. This preliminary geometric arrangement ensures that the washer is properly positioned before the shank transition comes into contact with it, preventing premature contact and excessive torque.
Solution Approach 2:
The shank transition is designed with a rounded radius that tangentially connects the cylindrical region and the conical skirt. This curved geometry allows for a smoother transition of contact during tightening, enabling the washer to be gradually engaged without creating sudden torque spikes or binding conditions.
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 maintains preload force retention under high temperatures, enhancing assembly safety and reliability by minimizing creep deformation and preventing torque increases during assembly.
Implementation Method 1
Particularly when exposed to a change in temperature, some materials undergo significant creep deformation under the preload force applied in each case
Data Source
AI summary
The invention relates to a spring head screw assembly (8) incorporating a spring head screw (10) having a head (12) with a conical skirt (14) that widens towards the free end of a threaded shank which adjoins the head (12), wherein the spring head screw assembly (8) has a washer (30) which is located between the skirt and the threaded part (20) of the shank (16) in an unthreaded part (18) of the shank that has a bolt diameter (d0). The inner surface (22) of the skirt transitions into the shank at a radius (Ru), wherein the inner surface (22) forms a contact angle (α) with a support plane (EA). The support plane is defined by the end of the skirt facing the free end of the screw and is orthogonal to the screw axis. The shank has, between the support plane and the radius in the transition to the skirt, a cylindrical region having the bolt diameter.