Torque-Responsive Gear Unit for Automatic Two-Speed Power Tools
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Solution Overview
Problem
Power tools face design challenges due to varying torque and speed requirements during operations, leading to inefficient performance, particularly in tools that require high torque, where manual gear shifting increases complexity and size, and existing two-speed transmissions are cumbersome and require operator intervention.
Innovation Solution
A compact, reliable two-speed power transmission with a torque-responsive gear shift mechanism that automatically adjusts between high torque/low speed and low torque/high speed modes using a planetary gear and coupling elements, with cam mechanisms and springs to manage torque levels and rotational decoupling, allowing for efficient operation without manual intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If planetary gear transmission is used to provide high torque, then torque output is improved, but rotational speed decreases
Solution Approach 1:
The patent implements a two-speed power transmission system that dynamically switches between high torque/low speed mode (using planetary gear) and low torque/high speed mode (direct drive). The system adapts its transmission ratio based on operational requirements, allowing high rotational speed during rundown phase and high torque during tightening phase, thereby resolving the contradiction between torque output and rotational speed
2Force
If manual gear shifting is implemented, then torque control is improved, but device complexity increases
Solution Approach 1:
The patent employs a torque-responsive gear shift mechanism that automatically shifts between transmission modes based on the torque level detected during operation. The system self-regulates the gear selection without operator intervention, using torque-sensing elements and cam mechanisms to automatically engage the appropriate transmission path, thereby maintaining improved torque control while reducing operational complexity
3Productivity
If two-speed power transmission is added, then operational efficiency is improved, but tool size increases
Solution Approach 1:
The patent integrates the two-speed power transmission system within the existing tool housing by nesting the planetary gear mechanism and gear shift components in a compact arrangement. The planetary gear is positioned concentrically around the drive shaft, and the torque-responsive shift mechanism uses space-efficient cam and follower designs, allowing the dual-mode transmission to be incorporated without significantly increasing the overall tool volume while still achieving improved operational efficiency
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 solution provides a compact, reliable power transmission that automatically adjusts to varying torque and speed needs, enhancing operational efficiency and reducing tool size and complexity by maintaining robustness and reliability through efficient rotational decoupling, while allowing for seamless handling of misalignment and torque monitoring.
Implementation Method 1
A first axially acting spring means is arranged for biasing the coupling elements toward the first position of the coupling elements, whereby the action of the first spring means counteracts the axial force developed by the first cam means upon the coupling elements
Implementation Method 2
the driving member comprising an axially acting first cam means for cooperation with the coupling elements in the first position of the coupling elements
Data Source
Figure 1
Figure 2~3
AI summary
The present specification relates to a two-speed power transmission for a power tool comprising a planetary gear (18) and a torque responsive gear shift mechanism (19) for directing torque through the planetary gear in a high torque/low speed mode or past the planetary gear in a low torque/high speed mode, and comprising a driving member, a driven member (27), and a number of coupling elements (30) arranged to intercouple in a first position the driving member (26) and the driven member and in a second position the planetary gear and the driven member, the driving member comprising a number of recesses (39) and axially acting first cam means (35) for cooperation with the coupling elements in the first position forming part thereof. The present specification also relates to power tool comprising such a gear unit and a method for controlling such a power tool.