Planetary Impact Mechanism Torque Control
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Solution Overview
Problem
Existing power tools with impact mechanisms lack an efficient mechanism to switch between continuous rotation and rotary impacting modes, leading to suboptimal torque application and user comfort issues due to inconsistent torque reactions.
Innovation Solution
A power tool design featuring a transmission system with a planetary stage, an impact mechanism that includes anvil lugs and an impactor spring, and an adjustment mechanism to set a switching torque, allowing the tool to switch between direct drive and rotary impact modes, enabling controlled torque spikes for efficient torque application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an impact mechanism is added to provide high torque, then torque application capability is improved, but device complexity increases
Solution Approach 1:
The impact mechanism is nested within the existing transmission system, with the impactor integrated into the planetary gear carrier and the anvil integrated into the ring gear. This nesting allows the impact function to be added without requiring a separate, independent mechanism, thereby improving torque capability while minimizing the increase in overall device complexity.
Solution Approach 2:
The patent combines the impact mechanism with the transmission system by integrating the anvil into the ring gear and the impactor into the planetary carrier. This merging of functions allows the single mechanism to serve both as a transmission element and an impact element, resolving the contradiction between improved torque capability and increased device complexity.
2Power
If the impactor is biased toward the ring gear to enable engagement, then torque transmission is improved, but the tool generates inconsistent torque reactions affecting user comfort
Solution Approach 1:
The impactor is designed with dynamic engagement characteristics, biased toward the ring gear by a spring to enable automatic engagement during operation. This dynamic design allows the impactor to engage and disengage based on operational conditions, improving torque transmission while the controlled engagement mechanism works to reduce inconsistent torque reactions.
Solution Approach 2:
The mechanism incorporates feedback through the spring-biased impactor that automatically engages and disengages based on the operational state. This feedback mechanism allows the system to self-regulate torque transmission, improving power transfer while working to provide more consistent torque reactions for user comfort.
3Productivity
If the impactor is allowed to cam over the anvil lugs to create torque spikes, then productivity is improved, but the mechanism complexity increases
Solution Approach 1:
The impact mechanism operates through periodic engagement and disengagement of the impactor with the anvil lugs, creating controlled torque spikes. This periodic action is achieved through the camming surfaces that naturally guide the impactor into engagement positions, providing high productivity through rhythmic impacting without requiring complex control systems.
Solution Approach 2:
The impactor is designed with self-engaging camming surfaces that automatically guide it into engagement with the anvil lugs based on the rotational motion and spring bias. This self-service mechanism eliminates the need for complex external control systems, allowing the mechanism to generate torque spikes and improve productivity while maintaining relatively simple construction.
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 tool effectively applies torque spikes greater than or equal to 0.2 J and less than or equal to 5.0 J, enhancing user comfort by reducing reaction force while providing high torque to workpieces, and automatically switching between continuous rotation and rotary impacting modes based on predetermined torque thresholds.
Implementation Method 1
The impactor spring biases the impactor toward the ring gear to cause the hammer lugs to engage the anvil lugs
Implementation Method 2
The impactor reciprocates and pivots to permit the hammer lugs to repetitively engage and disengage the anvil lugs and thereby generate a rotary impulse
Data Source
AI summary
A power tool with a housing, a motor, a transmission, a spindle and an impact mechanism. The motor has an output shaft that drives the transmission. The transmission has a plurality of planet gears, a planet carrier journally supporting the planet gears for rotation about an axis, and a ring gear that is in meshing engagement with the planet gears. The impact mechanism has a plurality of anvil lugs, an impactor and an impactor spring. The anvil lugs are coupled to the ring gear and are not engaged by the planet gears. The impactor is mounted to pivot about the spindle and has a plurality of hammer lugs. The impactor spring biases the impactor toward the ring gear to cause the hammer lugs to engage the anvil lugs. A power tool having an impact mechanism with an external adjusting member that can be moved to vary a trip torque of the impact mechanism is also provided.