Rotary Power Tool Clutch With Offset Cam Follower Torque Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional clutch mechanisms in rotary power tools face challenges in accurately limiting torque transmission and maintaining repeatability and efficiency, often resulting in variability and increased size due to frictional forces and complex mechanical designs.
Innovation Solution
A clutch mechanism featuring a cam surface and compression springs that displace a follower along a line of action parallel to the springs' longitudinal axes, allowing for controlled torque transmission and slip at a predetermined value, reducing variability and increasing torque capacity by using dual springs and optimizing the cam surface geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional clutch mechanisms use complex mechanical designs to limit torque transmission, then torque control capability is improved, but device complexity increases
Solution Approach 1:
The patent extracts the essential torque-limiting function from complex mechanical clutch designs and implements it through a simplified cam-follower mechanism with compression springs. The cam surface geometry alone controls torque transmission, eliminating the need for multiple mechanical components while maintaining reliable torque control at a predetermined value.
Solution Approach 2:
The patent changes the geometric parameters of the cam surface to achieve precise torque control. By optimizing the cam profile shape, radius of contact, and spring compression characteristics, the mechanism reliably limits torque transmission without requiring complex mechanical assemblies, thus resolving the contradiction between control capability and device complexity.
2Reliability
If conventional clutch mechanisms use frictional forces for torque limitation, then torque control is achieved, but variability increases
Solution Approach 1:
The patent replaces friction-based torque control with a cam-follower mechanical system where torque limitation is determined by the cam surface geometry and spring force. This substitution eliminates the variability inherent in frictional interfaces, as the cam profile provides consistent, repeatable torque control based on precise geometric relationships rather than variable friction coefficients.
Solution Approach 2:
The patent utilizes the curved cam surface geometry to achieve consistent torque control. The specific curvature and profile of the cam surface ensure that the follower maintains reliable contact while the geometric parameters precisely control the torque limitation, providing superior repeatability compared to friction-based mechanisms.
3Reliability
If conventional clutch mechanisms increase size for torque control, then torque capacity is improved, but tool size increases
Solution Approach 1:
The patent employs a cam surface with an optimized radius of contact that enables high torque capacity within a compact space. The curved cam geometry efficiently converts rotational motion into the required follower displacement, achieving substantial torque control in a small volume, thus resolving the contradiction between torque capacity and tool size.
Solution Approach 2:
The patent optimizes the cam surface parameters, including the radius of contact and profile curvature, to maximize torque capacity relative to the mechanism size. By carefully selecting these geometric parameters, the invention achieves high torque control capability in a compact configuration, reducing overall tool size while maintaining reliable torque capacity.
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 solution achieves more repeatable and efficient torque control, enhances torque-transmitting capacity, and reduces the tool's size and material costs by minimizing the radius of contact, thereby improving the performance and portability of rotary power tools.
Implementation Method 1
first and second compression springs carried by the other of the input member or the output member for co-rotation therewith. The follower is biased against the cam surface by the first and second compression springs
Implementation Method 2
a cam surface formed on one of the input member or the output member... In response to relative rotation between the input member and the output member, the cam surface displaces the follower along a line of action coaxial or parallel with each of the first and second compression springs
Data Source
AI summary
A clutch mechanism is used in a rotary power tool having a motor. The clutch mechanism includes an input member to which torque from the motor is transferred and an output member co-rotatable with the input member. The output member defines a rotational axis. A cam surface is formed on one of the input member or the output member. First and second compression springs are carried by the other of the input member or the output member for co-rotation therewith. A follower has a circular cross-sectional shape and is biased against the cam surface by the first and second compression springs. In response to relative rotation between the input member and the output member, the cam surface displaces the follower along a line of action coaxial or parallel with each of the first and second compression springs. The line of action does not intersect the rotational axis.