Torque-Controlled Clutch with Eccentric Springs for Hand-Held Power Tools
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Solution Overview
Problem
Existing hand-held power tools lack effective mechanisms to manage torque overload, leading to potential damage and user safety issues when exceeding a critical torque threshold.
Innovation Solution
A torque-controlled clutch system with a spring device that connects the input and output shafts in a non-positive manner, allowing for torque transmission in one direction and reversing direction when the critical torque is exceeded, utilizing eccentrics and springs to manage rotation and counter-torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional rigid coupling is used to connect input and output shafts, then torque transmission is continuous and reliable, but the tool cannot protect itself when exceeding critical torque threshold
Solution Approach 1:
The clutch mechanism dynamically changes its state based on torque conditions. Under normal operation, the spring device maintains a first state for continuous torque transmission. When critical torque is exceeded, the system transitions to a second state where the spring device exerts counter-torque to protect the tool. This dynamic state change enables automatic protection without complex control systems.
Solution Approach 2:
The spring device utilizes elastic deformation parameter changes to respond to torque variations. The spring's physical state (compression, extension, angular position) changes in response to applied torque, automatically triggering protection when torque exceeds the critical threshold. This parameter-based response eliminates the need for electronic sensors or complex mechanical switches.
2Productivity
If the clutch continuously transmits torque in one direction, then productivity is maintained, but the output shaft cannot rotate backwards to release stored energy when overload occurs
Solution Approach 1:
The clutch operates in periodic cycles: normal forward torque transmission, overload detection, reverse rotation for energy release, and recovery. This periodic action allows the system to maintain productivity during normal operation while periodically checking for and responding to overload conditions, preventing cumulative energy buildup that could cause damage.
Solution Approach 2:
The system converts the harmful effect of stored kinetic energy during overload into a beneficial protective action. When torque exceeds the critical threshold, the output shaft rotates backwards under spring influence, deliberately releasing stored energy in a controlled manner to prevent damage to the tool or workpiece. The harmful energy buildup is transformed into a protective energy release mechanism.
3Reliability
If a spring device is added to enable torque control and reverse rotation, then tool protection is improved, but the device complexity and potential energy loss increase
Solution Approach 1:
The spring device is self-actuating and requires no external power source, control electronics, or additional actuators. The spring automatically responds to torque conditions through its elastic properties, providing torque control and reverse rotation functions without consuming additional energy. This self-service approach minimizes energy loss compared to electronically-controlled clutches that would require motors, sensors, and power supply.
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 system effectively prevents damage by interrupting torque transmission and reversing the rotation direction when the critical torque is reached, ensuring tool safety and reliability.
Implementation Method 1
The clutch has a spring device (26) which connects the input shaft (21) and the output shaft (22) in a non-positive manner
Implementation Method 2
The spring device (26) is permanently, inseparably suspended on an eccentric (27, 29) of the output shaft (22) and on an eccentric (27, 29) of the drive shaft (21)
Implementation Method 3
The spring exerts permanently, preferably parallel to a line connecting the two eccentrics, in a first direction a spring force on the driven-side eccentric and in a second direction opposite to the first direction an opposite spring force of equal strength on the drive-side eccentric
Data Source
Figure 1
Figure 2~5
Figure 6
AI summary
The tool i.e. drilling hammer (1), has a driven shaft (22) coupled with a tool receiver (2). A motor (5) is coupled with a drive shaft (21). A rotational torque-controlled coupler (20) comprises spring elements (26) i.e. spiral springs, for connecting the drive- and driven shafts with each other in a force-fit manner. The elements are inseparably suspended at eccentric cams of the drive- and driven shafts, where rotating movements of ends of the elements and the shafts are synchronous with each other. The driven shaft is provided coaxial to the drive shaft. An independent claim is also included for a method for operating a hand-held power tool.