Power Tool Decoupling Mechanism for Rapid Blade Stop
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power tools, particularly circular saws, pose safety risks due to exposed rotating blades, with current safety systems being costly, inconvenient, and often destructive to the blade, and lacking in early detection and graduated protective actions.
Innovation Solution
A decoupling mechanism that includes a shaft gear with shallow and deep receiving structures, a spring assembly, and a cam system to frictionally transfer motor torque to the blade, allowing for rapid decoupling of the motor from the drive shaft when a dangerous condition is detected, thereby preventing injury.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a decoupling mechanism is added to protect against blade failure, then reliability is improved, but device complexity increases
Solution Approach 1:
The decoupling mechanism is nested within the existing drive shaft assembly. The cam is positioned on the drive shaft, the shaft gear engages with the cam, and the spring assembly is contained within the same spatial envelope as the drive components. This nesting allows the protective function to be added without significantly increasing the overall device footprint or complexity.
Solution Approach 2:
The decoupling mechanism operates automatically through self-service principles. The spring assembly is pre-biased to engage the shaft gear, and when blade failure occurs, the cam automatically disengages from the shaft gear through the existing rotational motion, causing immediate decoupling without requiring external sensors, actuators, or control systems.
2Ease of operation
If a friction-based decoupling mechanism is used, then ease of operation is improved, but loss of energy increases due to friction
Solution Approach 1:
The friction connection is made dynamic through the cam mechanism. During normal operation, the cam maintains a friction-based pressure connection between the shaft gear and drive shaft, allowing smooth torque transmission. Upon blade failure, the cam's geometric profile automatically reduces the friction pressure, enabling rapid decoupling. This dynamic adjustment optimizes both operational ease and energy efficiency.
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 decoupling mechanism effectively stops the blade within 0.05 seconds of operator contact, minimizing the risk of injury and preventing tool failure by isolating the motor's inertia from the drive shaft during braking events.
Implementation Method 1
The spring assembly is disposed on the drive shaft on a second side of the shaft gear and is configured to apply a normal force on the shaft gear to frictionally transfer motor torque from the shaft gear to the pressure plate
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A decoupling mechanism (200,300) for a power tool having a motor driving a drive shaft (128) that drives a rotating component includes a shaft gear (210,310) disposed around the drive shaft (128). The shaft gear (210,310) has a first side (212,312) and a second side. The second side has at least one shallow receiving structure (222,320) and at least one deep receiving structure (226,326). At least one friction plate (214,314) is disposed on the drive shaft adjacent to the first side (212,312). At least one pressure plate (216,316) is disposed on or integrally part of the drive shaft (128) adjacent to the friction plate and configured for rotation with the drive shaft. A spring assembly (236,336) is biased against the shaft gear (128). The spring assembly (226,336) includes a plate disposed around the drive shaft and a spring member. At least one cam (228,366) is disposed between the plate and the shaft gear (210,310), and is configured to engage with the shallow and deep receiving structures (222,320,226,326).