Two-Speed Gear Assembly With Linear Sleeve Shifting for Power Tools
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Solution Overview
Problem
Power tools face challenges in varying speed and torque requirements during different phases of operation, leading to inefficient two-speed transmissions that lack precise control over gear shifting, resulting in potential gear damage and slow rundown phases, especially when tightening large screws.
Innovation Solution
A two-speed power transmission system with a planetary gear and a gear shift assembly using a linear actuator to displace a coupling sleeve between high torque/low speed and low torque/high speed modes, providing precise control over gear shifting through a compact and space-saving design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a planetary gear transmission is used to achieve high torque levels, then the torque output is improved, but the rotational speed decreases correspondingly
Solution Approach 1:
The transmission system is segmented into two distinct speed modes by introducing a two-speed gear shift assembly. The first speed mode provides high torque through the planetary gear, while the second speed mode maintains lower torque but higher rotational speed by bypassing the planetary gear reduction, thus resolving the speed-torque trade-off
2Speed
If a two-speed power transmission is used to provide high rotational speed during rundown, then the speed is improved, but precise control over gear shifting becomes difficult
Solution Approach 1:
A sensor is integrated into the gear shift assembly to detect the axial position of the coupling sleeve and generate a signal indicating whether the coupling is in the engaged or disengaged state. This feedback mechanism provides precise control over the gear shifting operation, allowing the system to know when shifting has occurred and prevent improper shifting that could damage gears
3Measurement precision
If complex mechanisms with synchronizing rings or sensors are used to control gear shifting, then the control precision is improved, but the device complexity and space requirements increase
Solution Approach 1:
The invention extracts and eliminates the complex synchronizing ring mechanism from the design. Instead, it uses a simplified sensor-based detection system that monitors the axial position of the coupling sleeve to determine gear shift status, significantly reducing mechanical complexity while maintaining precise control
4Productivity
If a two-speed gear shift assembly is used to enable high speed during rundown, then the productivity is improved, but the risk of gear damage due to improper shifting increases
Solution Approach 1:
The sensor provides real-time feedback on the coupling sleeve position, enabling the control system to verify that gear shifting has occurred correctly before allowing operation in the high-speed mode. This prevents improper shifting that could lead to gear damage while maintaining the productivity benefits of high-speed rundown
Data Source
AI summary
The present specification relates to a power tool comprising an input shaft and an output shaft and a two-speed power transmission comprising a planetary gear and a gear shift assembly for directing torque through or past the planetary gear comprising a driving member, a driven member and an axially movable coupling sleeve arranged to intercouple in a first position the driving member and the driven member and to intercouple in a second position the planetary gear and the driven member. A linear actuator is arranged to displace the coupling sleeve between the first and second position, wherein the linear actuator comprises a linearly movable push bar arranged for displacing the coupling sleeve. The present specification also relates to a method in and a two-speed power transmission for such a power tool.