Output Mode Switching Device for Electric Tools
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Solution Overview
Problem
Conventional output-mode switching devices for electric tools are overly complex, leading to high manufacturing costs and potential damage to motor components when the operating bit is forced to rotate in the opposite direction.
Innovation Solution
The device incorporates an output shaft unit with a movable ratchet wheel and a fixed ratchet unit, along with a function switch unit that includes a switch ring and pawls, allowing for switching between continuous rotation, single-direction rotation, and axial impact during rotation, while preventing the output shaft from rotating in the opposite direction to protect the motor and other components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional output-mode switching device is used to switch among continuous rotation, single-direction rotation, and rotation with axial impact, then the electric tool can perform multiple functions, but the structure becomes complicated with too many components resulting in high manufacturing expense
Solution Approach 1:
The patent combines multiple ratchet units (fixed ratchet unit and movable ratchet unit) and their corresponding pawls into a single integrated switching device. The fixed ratchet unit with pawl controls continuous rotation versus single-direction rotation, while the movable ratchet unit with pawl controls single-direction rotation versus rotation with axial impact. This merging of multiple switching mechanisms into one unified structure reduces the number of separate components and simplifies the overall device complexity while maintaining full output mode switching capability.
2Productivity
If the switching device allows rotation in specific direction with impact function, then the tool can effectively tighten/loosen nuts, but when the operating bit is forced to rotate in opposite direction, the motor and components may be damaged due to lack of stop means
Solution Approach 1:
The patent incorporates a stop means that preliminarily prevents the operating bit from rotating in the opposite direction before damage can occur. The stop means includes a stop member that engages with a corresponding stop surface when the output shaft attempts to rotate counter to the designated rotation direction. This preliminary blocking action stops the reverse rotation before it can transmit damaging forces to the motor and internal components, thereby protecting the system while allowing full impact function effectiveness during proper rotation.
3Device complexity
If multiple ratchet units and pawls are integrated into one switching device, then the structure is simplified reducing manufacturing cost, but the reliability of mode switching may be compromised
Solution Approach 1:
The patent segments the switching mechanism into functionally independent but structurally integrated units: the fixed ratchet unit with its pawl for controlling continuous versus single-direction rotation, and the movable ratchet unit with its pawl for controlling single-direction versus impact rotation. Each ratchet-pawl pair operates as a reliable independent switching mechanism, and their integration into one device maintains reliability through functional segmentation while achieving structural simplification and reduced manufacturing cost.
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 simplifies the structure, reducing manufacturing expenses and preventing damage to the motor and other components by ensuring the output shaft only rotates in the intended direction, thus enhancing operational safety and efficiency.
Implementation Method 1
a plurality of compression springs, the torque cover being mounted rotatably on the outer casing
Implementation Method 2
a plurality of pawls and a plurality of torsion spring which are mounted pivotally within the switch ring
Implementation Method 3
a fixed ratchet wheel sleeved around the shaft and has ratchet teeth for meshing with movable ratchet teeth of the movable ratchet wheel
Data Source
AI summary
A switching device for an electric tool includes: an output shaft unit disposed in an outer casing, having an output shaft, a movable ratchet wheel mounted such that the movable ratchet wheel is movable axially along the output shaft and is non-rotatable therewith; a fixed ratchet unit having a fixed ratchet wheel sleeved around the output shaft and having ratchet teeth for meshing with ratchet teeth of the movable ratchet wheel; and a function switch unit having a switch ring mounted rotatably on the casing. Rotation of the switch ring about its axis results in rotation of pawls within the switch ring, thereby driving the pawls about its pivot points and meshing and/or non-meshing of the pawls with external ratchet teeth of the fixed ratchet wheel, thereby switching the output shaft among a continuous rotation, rotation in a single direction and simultaneously providing an axial impact during the rotation.