Radially Expanding Spring Clutch for Torque Limiting
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Solution Overview
Problem
Existing overdrive clutches in power tools are complex and costly due to their high part count, which can lead to damage and torque overload issues when a threshold torque is surpassed, necessitating a more efficient and cost-effective torque regulation mechanism.
Innovation Solution
A radially expanding spring clutch system with a shaft member featuring longitudinal grooves and rolling members that engage and disengage based on torque levels, using clutch springs to manage torque transmission by moving rolling members between grooves and the outer cylindrical surface, thereby reducing torque when it exceeds a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional overdrive clutch is used to prevent torque overload, then torque protection is improved, but device complexity increases due to high part count
Solution Approach 1:
The patent combines multiple clutch functions into a single integrated mechanism. The radially expanding spring clutch merges the torque limiting function, the overdrive clutch function, and the centrifugal clutch function into one unified assembly, eliminating the need for separate clutch components and reducing overall device complexity while maintaining torque protection
Solution Approach 2:
The spring clutch assembly serves multiple functions simultaneously: it acts as a torque limiter during engagement, provides overdrive protection during operation, and functions as a centrifugal clutch at high speeds. This multi-functionality reduces the need for separate specialized components
2Reliability
If a traditional overdrive clutch is used to prevent torque overload, then torque protection is improved, but manufacturing cost increases due to high part count
Solution Approach 1:
By merging multiple clutch functions into a single spring clutch assembly, the patent reduces the total number of parts that need to be manufactured, assembled, and quality-checked. This integration directly lowers manufacturing costs while maintaining comprehensive torque protection
3Productivity
If rolling members are held in longitudinal grooves, then torque transmission is efficient, but torque threshold control becomes limited
Solution Approach 1:
The spring clutch assembly is designed to dynamically adjust its radial position based on operating conditions. The spring can expand and contract radially, allowing the rolling members to move between the longitudinal grooves and the outer cylindrical surface, thereby providing variable torque threshold control while maintaining efficient torque transmission when engaged
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 reduces torque transmission when necessary, preventing damage and maintaining user control while minimizing complexity and cost by using a simpler design that maintains low torque loss during normal operation.
Implementation Method 1
A first clutch spring holds a first set of rolling members between lobes that extend from a first output gear
Implementation Method 2
move longitudinally along the shaft member to a position where at least one of the first gear assembly and the second gear assembly is engaged for rotation with the shaft member
Data Source
AI summary
A transmission generally includes a shaft member having a cylindrical outer surface in which longitudinal grooves are formed. Rolling members are disposed in the longitudinal grooves. A gear member having lobes the lobes is disposed between the rolling members and over the shaft member. A clutch spring that at least partially encircles the rolling members and the lobes is also disposed. The clutch spring includes a reduced torque condition that at least defines the clutch spring stretching to accommodate the rolling members leaving the longitudinal grooves and moving to the outer cylindrical surface such that the clutch spring forms a generally elliptical shape in the reduced torque condition.