Torque-Controlled Slipping Clutch for Electric Screwdrivers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing hand-held power tools, such as electric screwdrivers, lack an effective mechanism to control torque transmission, leading to inefficient operation and potential damage when torque exceeds a critical threshold.
Innovation Solution
A torque-controlled slipping clutch system with cam-shaped clutch discs and adjustable engagement depth, utilizing a spring and manually operable mechanism to disengage clutch discs when excessive torque is applied, ensuring robust setting of both low and high threshold values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a torque-controlled slipping clutch is added to control torque transmission, then torque control capability is improved, but device complexity increases
Solution Approach 1:
The patent combines the clutch plates, cams, and spring into a single integrated clutch assembly that is mounted on the existing motor shaft. The first clutch plate is connected to the motor shaft, the second clutch plate is connected to the drive train, and they engage through cam mechanisms, merging multiple torque control functions into one compact unit without requiring separate clutch mechanisms.
Solution Approach 2:
The clutch mechanism is nested within the existing motor housing and drive train structure. The cam mechanisms are positioned between the clutch plates, and the spring is housed within the clutch assembly, creating a compact nested arrangement that minimizes additional space requirements and integrates smoothly with the existing tool structure.
2Force
If the engagement depth is increased to set high threshold values, then torque threshold is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent makes the engagement depth adjustable through a manually operable mechanism that can vary the axial distance between the first clutch plate and the stop. This dynamic adjustment capability allows the user to set different engagement depths corresponding to different torque thresholds, rather than being fixed at a single precision-machined position.
Solution Approach 2:
The patent changes the engagement depth parameter dynamically by allowing axial movement of the clutch plates relative to each other. The manually operable mechanism adjusts the position of the stop or the clutch plates, thereby changing the engagement depth parameter to correspond to different desired torque release thresholds.
3Reliability
If the cam head has large radius of curvature for robust setting, then low engagement depth is achieved, but torque threshold control precision decreases
Solution Approach 1:
The patent combines the robust cam geometry with dynamic adjustability. The cam head maintains its large radius of curvature for robust engagement, while the manually operable mechanism dynamically adjusts the engagement depth to achieve precise torque threshold control. This separates the structural robustness function from the precision control function.
Solution Approach 2:
The patent segments the torque control function into two independent parts: the cam geometry provides robust mechanical engagement with large radius of curvature, while the manually operable adjustment mechanism provides precise control over the engagement depth. This segmentation allows each component to optimize its specific function without compromise.
4Reliability
If the spring force is increased to maintain clutch engagement, then clutch reliability is improved, but the force required to disengage increases
Solution Approach 1:
The patent makes the clutch engagement dynamic rather than static. The spring maintains engagement under normal operating conditions, but the manually operable mechanism can dynamically override the spring force when needed. This allows the spring force to be optimized for reliable engagement without requiring excessively high force for disengagement, as the adjustment mechanism provides mechanical advantage.
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 interrupts torque transmission at a user-set limit, preventing damage and allowing for precise control of torque, enhancing the robustness and reliability of the power tool operation.
Implementation Method 1
The second clutch disc is urged along the axis toward the first clutch disc by the spring
Implementation Method 2
The first clutch plate has cams and the second clutch plate has cams. The clutch discs mesh with each other by means of the cams
Implementation Method 3
The clutch discs mesh with each other by means of the cams
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The tool i.e. electric screwdriver (1), has a tool holder (4) receiving a tool (2), a motor (7) rotating the holder, and a torque-controlled coupling (10) switched in a drive train (6) between the motor and tool holder. A spring force applies a clutch disk in restoring direction to another clutch disk, where the former disk is mounted along an axis (3) parallel to the restoring direction and limited in the direction by a stop unit. An actuating mechanism (11) defines an axial spacing of the latter disk to the stop unit for setting depth of engagement of the latter disk in the former disk.