Compliant Shifting Mechanism for Misalignment-Tolerant Power Tools
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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 moves between positions, the spring compresses and expands to absorb misalignment forces before they can damage internal components, thereby maintaining reliability during speed transitions.
Solution Approach 2:
The camming mechanism changes the geometric parameters of force transmission during selector movement. By using an eccentric pin that rotates within an elongated axial slot, the mechanism transforms linear selector movement into rotational cam rotation, changing the alignment parameters dynamically to accommodate misalignment while maintaining reliable operation.
2Manufacturing precision
If a rigid shifting mechanism is used to ensure precise gear engagement, then shifting between speeds can be achieved, but misalignment causes damage and prevents smooth transitions
Solution Approach 1:
The compression spring provides beforehand cushioning by positioning itself between the rigid camming mechanism and selector. During shifting, the spring absorbs misalignment forces through compression, protecting the precisely manufactured gear components from damage while maintaining engagement precision.
Solution Approach 2:
The compression spring acts as an intermediary element between the selector and camming mechanism. It mediates the force transmission during shifting, absorbing misalignment forces and preventing them from reaching the gear components, thereby protecting against damage while maintaining precise engagement.
3Device complexity
If the camming mechanism is directly coupled to the selector without compliance elements, then the structure is simpler, but misalignment cannot be absorbed and component damage occurs
Solution Approach 1:
The compression spring provides beforehand cushioning in the shifting mechanism. It is positioned to absorb misalignment forces before they can cause component damage, adding minimal complexity while significantly improving reliability during speed transitions.
Solution Approach 2:
The compression spring serves as an intermediary compliance element between the selector and camming mechanism. It absorbs misalignment forces through compression, protecting internal components from damage while maintaining relatively simple overall structure.
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 operational speeds, reduces the likelihood of damage to internal components, and allows for efficient operation by absorbing misalignment issues, enabling seamless transitions between high and low speed modes.
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
a camming mechanism provided at a second end portion of the shaft, an eccentric pin fixedly coupled to a first end portion of the camming mechanism. the cam body is coupled to the second end portion of the shaft, such that the cam body is axially fixed with respect to the shaft, and is rotatable relative to the shaft, a contoured cam surface defined on a first side of the cam body, facing the knob, wherein the eccentric pin is coupled to a second side of the cam body, opposite the first side thereof, and a cross-pin coupled to the shaft, such that the cross-pin is axially movable relative to the shaft, wherein the cross-pin is selectively movable along the contoured cam surface of the cam body.
Data Source
AI summary
A multi-directional compliant shifting mechanism for a multi-speed power tool may couple a movable selector to a power transmission system of the tool, for selecting an operational speed of the multi-speed power tool. The complaint shifting mechanism may provide shifting compliance in a first direction in response to movement of the selector in a first direction, and may provide shifting compliance in a second direction in response to movement of the selector in a second direction. In one example, this multi-directional shifting compliance may be provided by interaction of the selector with a camming surface, in combination with a single compression spring. In another example, this multi-directional shifting compliance may be provided by first and second springs, selectively acting to provide compliance in the first and second directions.