Pivoting Handle Friction Control for Contamination-Resistant Power Tools
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Solution Overview
Problem
Handheld work apparatuses with rotary joints suffer from contamination leading to a tightening effect, which adversely affects the feel and functionality, as the annular seal's damping effect is compromised by debris between the handle and housing.
Innovation Solution
A design featuring a handle and housing with contoured surfaces that provide a minimum friction torque in the inoperative position and an increased friction torque in the operative position, utilizing a radial bearing play to prevent contamination and enhance the operator's feel by requiring increased torque to reach the operative position, thus indicating readiness for operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an annular seal is used between the lug and lug receptacle to compensate play and avoid tilting, then the damping effect and feel quality are improved, but contamination occurs between the housing and handle leading to tightening and compromised functionality
Solution Approach 1:
The patent removes the annular seal from the rotary joint between handle and housing. By extracting this sealing element, the design eliminates the contamination problem that caused tightening and functional compromise, while accepting minimal play in the rotary connection.
Solution Approach 2:
The patent introduces a bearing as an intermediary element between the handle and housing. This bearing provides a reliable rotary connection that prevents contamination while maintaining smooth rotation, replacing the problematic seal-based system.
2Ease of operation
If the handle is mounted with minimal friction torque to allow easy pivoting, then ease of operation is improved, but tactile feedback indicating readiness for operation is reduced
Solution Approach 1:
The patent applies different friction characteristics to different positions of the handle rotation. In the retracted position, minimal friction allows easy pivoting, while in the extended operative position, increased friction provides tactile feedback. This local differentiation of friction quality resolves the contradiction.
Solution Approach 2:
The friction torque between handle and housing is made dynamic rather than static. The friction characteristic changes depending on the handle position - low in retracted position for ease of movement, and high in extended position for tactile feedback. This dynamic adjustment resolves the contradiction between ease of operation and feedback quality.
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 enhances the operator's feel by providing a high-quality tactile feedback and prevents contamination-induced blockages, ensuring a smooth and functional pivoting mechanism.
Implementation Method 1
a minimum friction torque M1, which acts about the pivot axis, is provided between the handle and the housing
Implementation Method 2
a further friction torque M2, which acts about the pivot axis, is present between the handle and the housing; the further friction torque M2 in the operative position is greater than the minimum friction torque M1 in the inoperative position
Data Source
AI summary
The disclosure relates to a handheld work apparatus, wherein the work apparatus includes a housing, a drive motor for driving a tool, and a handle disposed on the housing. A contour is provided on the handle and a counter contour is provided on the housing. In the inoperative position of the handle, a minimum friction torque (M1) which acts about the pivot axis is provided between the handle and the housing. In the operative position of the handle, the contour and the counter contour are operatively connected in such a manner that a further friction torque (M2) which acts about the pivot axis is present between the handle and the housing. The further friction torque (M2) in the operative position is greater than the minimum friction torque (M1) in the inoperative position.