Compliant Power Tool Shifting Mechanism for Gear Misalignment
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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 efficient operation.
Innovation Solution
A multi-directional compliant shifting mechanism is introduced, utilizing a camming mechanism with a compression spring and eccentric pin to provide bi-directional compliance, allowing the tool to shift between speeds while compensating for misalignment and reducing the risk of damage to internal components.
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 tool can operate at multiple different speeds to accommodate different types of tasks, but misalignment of internal components during shifting can occur which may lead to damage and hinder efficient operation
Solution Approach 1:
The patent employs compression springs positioned between gear clusters to provide compliant shifting. These springs are pre-loaded to cushion against misalignment forces before damage can occur, allowing smooth transitions between speed ranges by accommodating dimensional variations and thermal expansion during gear engagement.
Solution Approach 2:
The patent utilizes thermal expansion parameters by designing the housing and gear clusters to expand uniformly with temperature increases. This parametric change allows the gear clusters to self-adjust their positioning relative to the housing bore, maintaining alignment during shifting operations even as operating conditions change.
2Strength
If rigid shifting mechanism is used for speed changes, then the structure is simple and strong, but it cannot compensate for misalignment which may cause damage to internal components
Solution Approach 1:
Compression springs are strategically positioned between gear clusters to provide compliant shifting. These springs are pre-loaded to cushion against misalignment forces before damage can occur, allowing smooth transitions between speed ranges by accommodating dimensional variations and thermal expansion during gear engagement.
Solution Approach 2:
The patent introduces compression springs as intermediary elements between the rigid housing and gear clusters. These spring intermediaries absorb misalignment forces that would otherwise be transmitted directly to the gear teeth and shafts, protecting the strong rigid structure from damage while maintaining shifting capability.
3Reliability
If compliant shifting mechanism with compression spring is used, then misalignment effects are absorbed and smooth shifting is enabled, but the device complexity increases
Solution Approach 1:
The patent divides the transmission system into modular gear clusters that can shift independently between speed ranges. Each gear cluster is segmented with its own compression springs, allowing localized compliant shifting without requiring complex mechanisms throughout the entire transmission system. This segmentation maintains reliability while controlling overall complexity.
Solution Approach 2:
The compression springs serve multiple functions simultaneously: they provide compliant shifting to absorb misalignment, maintain gear cluster positioning during operation, and accommodate thermal expansion. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving reliable smooth shifting.
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 enables smooth shifting between multiple operational speeds, reducing the likelihood of damage to internal components and ensuring efficient operation by absorbing misalignment effects, allowing users to freely select and maintain desired operational 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.
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.