Impact Tool Barycenter Shift and Vibration Reduction
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Solution Overview
Problem
Conventional impact tools, such as hammer drills, suffer from increased vibration during striking operations due to an off-center barycenter, leading to reduced operability and workability, and existing solutions to address pressure issues within sealed impact units complicate the tool structure and increase costs.
Innovation Solution
The impact tool design positions the motor closer to the axis of the tool holder, with an intermediate reduction shaft and reduction shaft configuration that shifts the barycenter forward and upward, reducing vibration and allowing easy air release without oil leakage, using a vent hole and labyrinth seal to manage pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor, crank mechanism and shaft are disposed in a rear-side space of the housing, then the impact mechanism can be sealed and filled with oil to ensure smooth impactor motion, but the barycenter shifts to the rear side causing increased vibration during striking operation
Solution Approach 1:
The patent repositions the motor from a rear-side arrangement to a front-side arrangement, changing the spatial dimension of component layout. This dimensional change moves the barycenter forward, reducing the moment arm and consequently the vibration during striking operation while maintaining the sealed impact mechanism for reliable operation
2Reliability
If a sealed impact unit filled with oil is used to ensure smooth impactor motion, then the impact mechanism operates reliably, but pressure rise from temperature increase cripples the air spring and causes oil leakage
Solution Approach 1:
The patent extracts air from the sealed impact unit by providing a vent hole that allows air to escape during compression strokes. This removes the harmful accumulated air pressure that would otherwise cripple the air spring and cause oil leakage, while maintaining the sealed oil-filled environment for reliable impact mechanism operation
3Reliability
If additional casings are mounted to form air chambers or pressure equilibrating chambers, then pressure issues are addressed, but the tool structure becomes complicated and housing size increases
Solution Approach 1:
The patent merges the pressure management function with the existing housing structure by integrating a vent hole directly into the housing rather than adding separate casings. This combining approach achieves pressure relief and prevents oil leakage while avoiding increased structural complexity and housing size
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
This design improves weight balance, reduces vibration, enhances operability, and maintains adequate lubrication while minimizing tool height and cost by simplifying the structure and preventing oil leakage.
Implementation Method 1
a vent hole which opens to the outside of the rotation and impact unit is formed in a surface of the proximity portion opposed to the end face of the output shaft so that air inside the rotation and impact unit can be released through the vent hole
Implementation Method 2
a labyrinth seal is formed by the output shaft and the proximity portion so that oil inside the rotation and impact unit is prevented from flowing out through the vent hole
Implementation Method 3
an impactor configured to move in synchronization with the piston by the action of an air spring
Data Source
Figure 1
Figure 2
AI summary
Vibration entailed during a striking operation of an impact tool is reduced thereby achieving improved operability and workability. In a hammer drill (1), between a reduction shaft (32) configured to transmit a rotatory motion to a tool holder (7) and an output shaft (9), an intermediate reduction shaft (31) configured to reduce a rotation speed of a rotatory motion of the output shaft (9) and transmit a speed-reduced rotatory motion to the reduction shaft (32) is disposed in a position frontward of the output shaft (9) and parallel to the output shaft (9), so that the reduction shaft (32) is disposed frontward of the intermediate reduction shaft (31), whereas a motor (8) is disposed in a position such that the output shaft (9) protrudes upward beyond a third gear (37) of the reduction shaft (32), whereby the motor (8) is positioned closer to the axis of the tool holder (7). Thus, the barycenter of the hammer drill (1) is in a position shifted frontward and upward, with the result that the moment to be produced around a tip end of a bit (20) in the hammer drill (1) during a drilling or other operation will become small.