Eccentric Drive Tool Shaft Rotation Control
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Solution Overview
Problem
Handheld power tools, such as eccentric sanders, often restrict tool selection and safety due to limitations in rotational modes, particularly with polygonal tools, which can cause injuries and are not easily switchable between modes.
Innovation Solution
Integration of rotational angle guide means to stabilize the tool shaft within a limited rotational angle sector, allowing for three eccentric modes: pure eccentric, forced rotation, and free rotation, with braking mechanisms to control speed and prevent unwanted rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the tool shaft is allowed to rotate freely in eccentric mode, then the tool can perform grinding or polishing operations, but polygonal tools may cause injuries to the operator
Solution Approach 1:
The patent implements dynamic control of the tool shaft's rotational freedom through a switching mechanism that can lock or unlock the shaft. In locked position, the tool shaft cannot rotate, preventing injury from polygonal tools. In unlocked position, the tool shaft can rotate freely for grinding/polishing operations. This dynamic state change resolves the contradiction between safety and functionality.
Solution Approach 2:
The patent introduces an intermediary locking mechanism (such as a locking lever or detent system) that mediates between the tool shaft and the housing. This intermediary component can engage to prevent rotation of polygonal tools, or disengage to allow rotation of round tools, thus resolving the safety-functionality contradiction without restricting the tool's operational capability.
2Object-affected harmful factors
If braking torque is applied to prevent tool rotation, then operator safety is improved, but the tool cannot rotate when needed for grinding operations
Solution Approach 1:
The braking torque is made dynamic through a switching mechanism that can engage or disengage the braking force. When the switch is in the locked position, braking torque is applied to prevent tool rotation and ensure safety. When the switch is in the unlocked position, the braking torque is released, allowing the tool to rotate freely for grinding operations. This dynamic control resolves the contradiction between safety and operational capability.
3Object-affected harmful factors
If only round grinding discs are allowed, then operator safety is ensured, but the field of application is limited
Solution Approach 1:
The patent enables dynamic adaptation of the tool shaft's rotational state based on the tool type being used. When a polygonal tool is installed, the locking mechanism engages to prevent rotation, ensuring safety. When a round tool is installed, the locking mechanism disengages, allowing rotation for grinding operations. This dynamic adaptation allows the system to safely accommodate both polygonal and round tools, resolving the contradiction between safety and versatility.
Solution Approach 2:
The locking mechanism acts as an intermediary that mediates between different tool types and the driving system. It detects or responds to the tool type and appropriately engages or disengages the rotation prevention function, thereby enabling safe use of both polygonal and round tools while maintaining operator safety.
4Object-affected harmful factors
If the tool shaft is completely locked to prevent rotation, then operator safety is maximized, but the tool cannot perform any rotational grinding work
Solution Approach 1:
The locking mechanism is designed to be dynamically controllable, allowing the system to switch between a locked state (for safety with polygonal tools) and an unlocked state (for productive grinding operations with round tools). This dynamic capability ensures that productivity is not permanently sacrificed, as the system can adapt its rotational restriction based on the operational needs and tool type.
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
Enables a wider range of tool usage, including cutting and scraping tools, while ensuring operator safety by preventing accidental tool rotation and allowing for various movement patterns and speeds.
Implementation Method 1
a braking torque that exceeds the bearing friction of the tool shaft bearing
Data Source
Figure 1~2
Figure 3~7b
Figure 8~10b
AI summary
The tool (10) has a tool holder performing forced rotation of a drive axis (36) changing rotary angle position to a machine housing (11) of the tool by a forced rotation guide (64) in a forced rotation-eccentric mode. A switch is formed for switching an eccentric gear (27) in a single-eccentric mode. A tool shaft is in contact with a rotary angle-guide (67) for guiding the tool shaft. The tool holder maintains a rotary angular position relative to the machine housing within a rotation angle selector limited by the rotary angle-guide.