Movable Threaded Fastener for Heat- and Vibration-Stable Pretension
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Solution Overview
Problem
Threaded fasteners in cutting tools lose pretension due to heat and vibrations, causing the cutting insert to become loose during metal cutting operations, and require the use of a torque wrench for proper tightening.
Innovation Solution
A movable threaded element with spring-like members is suspended in a cavity to create an area of reduced stiffness, allowing axial and angular displacement when torque is applied, which maintains pretension and eliminates the need for a torque wrench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional threaded fastener is used to mount the cutting insert, then the structure is simple and easy to manufacture, but the fastener loses pretension due to heat and vibrations causing the cutting insert to become loose
Solution Approach 1:
The threaded element is made movable rather than fixed, allowing it to dynamically adjust its position in response to thermal expansion and vibration forces. The spring-like members provide dynamic support that maintains pretension under varying operating conditions, resolving the contradiction between reliability and structural simplicity.
Solution Approach 2:
The fastener system is divided into separate functional components: a movable threaded element, spring-like members for elastic support, and a cavity structure. This segmentation allows each component to perform its specific function optimally while maintaining overall system reliability without excessive complexity.
2Reliability
If torque is applied to tighten the screw or bolt to a specified torque value, then the cutting insert is securely mounted, but a torque wrench is required adding operational complexity
Solution Approach 1:
The fastener system is designed to self-regulate the tightening process through the elastic displacement of the threaded element supported by spring-like members. The system automatically achieves proper pretension without requiring external torque measurement tools, eliminating the need for torque wrenches and simplifying operation.
Solution Approach 2:
The system changes the stiffness parameter of the mounting structure by introducing spring-like members that provide elastic compliance. This allows the fastener to achieve proper pretension through controlled elastic deformation rather than requiring precise torque control, improving ease of operation while maintaining reliability.
3Reliability
If the threaded element is made movable with spring-like members to maintain pretension, then reliability under thermal and vibrational conditions is improved, but the device complexity increases
Solution Approach 1:
The threaded element and spring-like members are combined into an integrated movable assembly that functions as a unified pretension-maintaining mechanism. This merging reduces the number of separate components and simplifies the overall structure while achieving improved reliability under thermal and vibrational 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 effectively maintains pretension of the threaded fastener, preventing loosening due to temperature variations and vibrations, and allows for secure mounting of the cutting insert without the need for a torque wrench, even under thermal fluctuations.
Implementation Method 1
one or more spring-like members extending from an exterior surface of the movable threaded element... allowing the internally threaded movable element to move axially and/or angularly... to store elastic potential energy
Data Source
AI summary
A hardware fastener with a movable threaded element suspended within a cavity formed in a body. The movable threaded element has an internal surface with threads for cooperating with a threaded fastener. The movable threaded element is suspended in the cavity by the one or more spring-like members such that an area, A, of reduced stiffness is created in the cavity proximate the movable threaded element, thereby allowing the movable threaded element to move a predetermined distance within the cavity when torque is applied to the threaded fastener. The one or more spring-like members store elastic potential energy to prevent the loss of pretension of the threaded fastener that can be caused by heat or vibration. The invention also eliminates the need for a torque wrench when tightening the threaded fastener to a specified torque value.