Power Tool Output Device with Pawl-Actuated Ratchet Protection
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Solution Overview
Problem
Conventional power tools with axial vibration functions are prone to mechanical stress and damage due to the high stress encountered when the movable and stationary ratchet teeth catch against each other during reverse rotation.
Innovation Solution
An output device with a protection mechanism featuring a stationary ratchet gear with inclined ribs and a locking member with pawls, where the pawls engage or disengage from the ribs to control the rotation and vibration modes, ensuring the ratchet teeth are protected from damage by releasing axial vibration during reverse rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the movable ratchet gear is engaged with the stationary ratchet gear to output axial vibration, then the power tool can tighten or loosen bolts effectively, but the ratchet teeth are subjected to high mechanical stress and are likely to break during reverse rotation
Solution Approach 1:
A control element with pawls is introduced as an intermediary between the movable and stationary ratchet gears. The pawls engage with the ribs on the stationary ratchet gear to control the engagement state. During reverse rotation, the pawls disengage the stationary ratchet gear from the movable ratchet gear, preventing direct tooth-to-tooth contact and high stress, while still allowing the power transmission function to operate normally during forward rotation.
Solution Approach 2:
The control element is designed to dynamically change the engagement state between the movable and stationary ratchet gears based on rotation direction. During forward rotation, the stationary ratchet gear is fixed through pawl engagement with ribs for vibration output. During reverse rotation, the pawls automatically disengage, allowing the stationary ratchet gear to rotate freely and avoiding tooth damage. This dynamic adaptation resolves the contradiction between power transmission and durability.
2Adaptability or versatility
If the stationary ratchet gear is fixed to output axial vibration, then the output function is enhanced, but the structure becomes more complex due to the addition of control elements
Solution Approach 1:
The control element with pawls serves multiple functions: it acts as a locking mechanism to fix the stationary ratchet gear during forward rotation for vibration output, serves as a releasing mechanism during reverse rotation to prevent tooth damage, and provides structural support within the housing. This multi-functionality reduces the need for separate control mechanisms, thereby limiting the increase in device complexity while enhancing output adaptability.
3Stability of the object's composition
If the pawls are constantly engaged with the ribs to fix the stationary ratchet gear, then the vibration function is maintained, but the ratchet teeth are susceptible to damage during reverse rotation
Solution Approach 1:
The control element operates with periodic engagement and disengagement based on rotation direction. During forward rotation, the pawls are engaged with the ribs to maintain stationary gear fixation for vibration output. During reverse rotation, the pawls automatically disengage to allow free rotation and prevent tooth damage. This periodic action pattern resolves the contradiction between maintaining stability during useful operation and preventing damage during reverse operation.
Data Source
AI summary
An output device for a power tool includes an output unit, a stationary ratchet gear unit, a spring disposed between the output shaft unit and the stationary ratchet gear unit, a locking member having pawls, a case accommodating the aforementioned parts and a control device threadedly connected to the case. The output unit includes an output shaft with a first bearing and a movable ratchet gear which have movable ratchet teeth facing stationary ratchet teeth of a stationary ratchet gear. The stationary ratchet gear includes ribs and each rib has an inclined surface. When the pawls are not engaged with the ribs, the output shaft can outputs power in a form of rotation in both directions. When the pawls are engaged with the ribs, the output shaft outputs power in a form of rotation in a forward direction combined with vibration or rotation in a reverse direction without vibration.