Impact Tool Radial Run-Out Reduction via Elastic Biasing
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Solution Overview
Problem
Impact tools experience noise due to radial run-out of the tool bit during operation, caused by reaction forces from the workpiece, leading to metal-against-metal contact with the tool holder and barrel.
Innovation Solution
An impact tool design featuring a tool holder with a barrel, a striking element, and an intermediate element that comes into point contact with the tool bit, along with an elastic element between the tool holder and tool bit to prevent radial run-out, minimizing noise by applying a biasing force and preventing movement in directions other than the axial direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the tool bit is driven to perform hammering operation, then the hammering operation can be performed on the workpiece, but the tool bit undergoes radial run-out causing noise
Solution Approach 1:
An elastic element is introduced as an intermediary component between the tool bit and the tool holder. This elastic element acts as a mediator that absorbs radial run-out movements and prevents direct metal-against-metal contact, thereby reducing noise while allowing the hammering operation to continue effectively
Solution Approach 2:
The elastic element is installed in advance between the tool bit and tool holder to provide cushioning before radial run-out occurs. This pre-positioned cushioning mechanism absorbs radial movements and prevents the harmful noise-generating contact between the tool bit and tool holder during operation
2Force
If the intermediate element is in contact with the tool bit, then the driving force can be transmitted to the tool bit, but radial run-out of the tool bit causes metal-against-metal sound
Solution Approach 1:
The elastic element serves as a mediator between the intermediate element and the tool holder, allowing force transmission while preventing direct metal contact. The elastic element absorbs radial run-out movements and provides a compliant interface that eliminates metal-against-metal sound generation
Solution Approach 2:
The introduction of the elastic element changes the mechanical parameters of the contact interface between the intermediate element and tool holder. The elastic element provides compliance and damping, transforming the rigid metal-against-metal contact into a compliant contact that transmits force while reducing noise
3Ease of operation
If the tool bit is allowed to move freely in axial direction, then the hammering operation is effective, but radial run-out occurs causing noise
Solution Approach 1:
The constraint system is segmented into two independent functions: the tool holder provides axial guidance and force transmission, while the elastic element provides radial constraint. This segmentation allows the tool bit to move freely in the axial direction for effective hammering while preventing radial run-out through the elastic element
Solution Approach 2:
Different parts of the tool bit are given different degrees of freedom: the axial direction is free for hammering operation, while the radial direction is constrained by the elastic element. This local differentiation of movement freedom allows effective operation while reducing noise
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
Effectively reduces noise generated by tool bit run-out by minimizing radial movement and preventing contact with the tool holder, thereby reducing metal-against-metal sounds released externally.
Implementation Method 1
an elastic element that is disposed between an inner circumferential surface of the tool holder and an outer circumferential surface of the tool bit in an end region of the tool bit on the barrel side and connected in close contact with the tool holder and the tool bit over a predetermined length of the tool bit in the axial direction
Data Source
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AI summary
It is an object of the invention to reduce noise caused by run-out of a tool bit in an impact tool. The representative impact tool according to the invention includes a tool holder 137 that houses a tool bit 119 in such a manner that the tool bit can linearly move in its axial direction, and a barrel 108 that is integrally connected to the tool holder 137 The impact tool further includes an elastic element 155 that is disposed between an inner circumferential surface of the tool holder 137 and an outer circumferential surface of the tool bit 119 in an end region of the tool bit 119 on the barrel side and connected in close contact with the tool holder 137 and the tool bit 119 over a predetermined length of the tool bit 119 in the axial direction. The elastic element 155 applies a biasing force to prevent a run-out of the tool bit 119 in a direction transverse to the axial direction. Further, an intermediate element 145 comes in point contact with the tool bit 119 on its axial center line.