Spring-Suspended Threaded Fastener for Heat and Vibration 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 is suspended in a cavity by spring-like members, creating an area of reduced stiffness that allows axial and angular displacement when torque is applied, maintaining pretension and eliminating 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 fastener can be easily installed and removed, but the fastener loses pretension due to heat and vibrations during metal cutting operations, 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 enable the threaded element to move axially and angularly, maintaining constant pretension on the cutting insert despite external disturbances, thus resolving the contradiction between reliability and ease of operation.
Solution Approach 2:
The stiffness of the system is changed by introducing spring-like members that create an area of reduced stiffness. This allows the system to transition from a rigid, fixed-pretension state to a compliant, adaptive state where pretension parameters can automatically adjust to maintain reliability while remaining easy to operate.
2Reliability
If a torque wrench is used to tighten the screw or bolt to a specified torque value, then the pretension can be initially established, but the pretension is still lost during operation due to heat and vibrations
Solution Approach 1:
The fastener system becomes self-regulating through the movable threaded element and spring-like members. The system automatically maintains pretension through elastic displacement and energy storage mechanisms, eliminating the need for external torque wrenches or complex tightening tools while ensuring reliable pretension maintenance during operation.
Solution Approach 2:
The external mechanical control system (torque wrench) is replaced with an internal elastic-mechanical system consisting of spring-like members and a movable threaded element. This substitution enables automatic pretension maintenance through elastic deformation and energy storage, removing the need for complex external tightening tools.
3Manufacturing precision
If the threaded fastener is made rigid to maintain precise torque application, then the torque can be accurately controlled, but the fastener cannot accommodate thermal expansion differences or vibrations, leading to pretension loss
Solution Approach 1:
The system transitions from a static, rigid torque control mechanism to a dynamic system where the threaded element can move and the spring-like members can deform. This dynamic capability allows the system to maintain torque control precision while simultaneously adapting to thermal expansion and vibration conditions, resolving the contradiction between manufacturing precision and adaptability.
Solution Approach 2:
The stiffness parameter of the fastener system is changed by introducing spring-like members, creating an area of reduced stiffness. This parameter change enables the system to maintain precise torque control while gaining the adaptability to accommodate thermal and vibrational effects through controlled elastic deformation.
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 threaded fasteners under temperature and vibration conditions, ensuring the cutting insert remains securely mounted and reducing the need for a torque wrench, with improved resistance to thermal expansion differences between materials.
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 create an area of reduced stiffness... 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.