Compliant Power Tool Shifting Mechanism for Misalignment Compensation
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Solution Overview
Problem
Multi-speed power tools face challenges in effectively shifting between operational speeds due to misalignment of internal components, which can lead to damage and hinder smooth operation.
Innovation Solution
A multi-directional compliant shifting mechanism is introduced, featuring a camming mechanism with a compression spring and eccentric pin, allowing the power tool to shift between speeds while compensating for misalignment by providing bi-directional compliance, and a retention device to maintain selected positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a parallel axis transmission system is used to enable multi-speed operation, then the power tool can operate at multiple different speeds, but misalignment of internal components occurs during shifting which can lead to damage and hinder smooth operation
Solution Approach 1:
A compression spring is positioned between the camming mechanism and the selector to provide beforehand cushioning. When the selector is moved to a first position, the spring compresses to absorb misalignment forces before they can damage internal components. This cushioning effect prevents direct transmission of harmful forces during the shifting process, thereby maintaining reliability while enabling multi-speed operation.
Solution Approach 2:
The camming mechanism is configured to change the geometric parameters of force transmission during shifting. By using an eccentric pin and contoured cam surface, the mechanism transforms the linear movement of the selector into rotational movement of the shift member, while the compression spring dynamically adjusts the force parameters to accommodate misalignment, ensuring smooth transitions between speeds.
2Manufacturing precision
If a rigid shifting mechanism is used to ensure precise gear engagement, then shifting between speeds can be accomplished, but binding issues occur due to misalignment that restrict smooth operation
Solution Approach 1:
The compression spring acts as an intermediary element between the selector and the shift member. It mediates the interaction by absorbing misalignment forces and providing compliant coupling, allowing the rigid gear engagement to be maintained while eliminating binding issues during the shifting process.
Solution Approach 2:
The shifting mechanism transitions from a static rigid connection to a dynamic compliant system. The compression spring enables the mechanism to adapt its stiffness characteristics during shifting, providing rigidity when needed for precise engagement and compliance when misalignment occurs, thereby ensuring smooth operation.
3Ease of operation
If misalignment compensation is provided through a compliant mechanism, then smooth shifting between speeds is achieved, but the device complexity increases due to additional components
Solution Approach 1:
The invention merges multiple functions into a single integrated camming mechanism. The eccentric pin, cam body with contoured surface, and compression spring work together as one cohesive unit that provides both the shifting action and the misalignment compensation, rather than requiring separate mechanisms for each function.
Solution Approach 2:
The camming mechanism with compression spring serves multiple purposes: it transfers motion from the selector to the shift member, compensates for misalignment, and provides cushioning during engagement. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity.
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 mechanism facilitates smooth shifting between multiple operational speeds, reduces the likelihood of damage to internal components, and allows users to freely select operational modes without encountering binding issues.
Implementation Method 1
a compression spring positioned between a second end portion of the camming mechanism and the selector. In response to movement of the selector to a first position, interaction of the camming mechanism with the compression spring biases the camming mechanism to provide shifting compliance in a first direction. In response to movement of the selector to a second position, interaction of the camming mechanism with the compression spring biases the camming mechanism to provide shifting compliance in a second direction opposite the first direction.
Implementation Method 2
an eccentric pin fixedly coupled to a first end portion of the camming mechanism and configured to cause a transmission of the power tool to shift between at least a first speed and a second speed
Data Source
AI summary
A compliant shifting mechanism for a power tool includes a selector, a first shift plate rotatable in response to rotation of the selector, a second shift plate rotatable in response to rotation of the first shift plate, a shift member moveable in response to rotation of the second shift plate to shift between a first mode of operation and a second mode of operation, a first torsion spring coupled to the first shift plate, and a second torsion spring coupled to the second shift plate. In response to rotation of the selector in a first direction, the first torsion spring may bias the first shift plate in the first direction for shifting compliance in the first direction. In response to rotation of the selector in an opposite second direction, the second torsion spring may bias the second shift plate in the second direction for shifting compliance in the second direction.