Power Screwdriver Overload Protection Using Interlocking Ball Rings
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Solution Overview
Problem
Existing power wrench overload protection devices suffer from wear and damage at high torques, requiring radial shaft bearings and often becoming unusable, while lacking precise and repeatable torque interruption without destructive mechanisms.
Innovation Solution
A power wrench overload safety device utilizing two interlocking ball rings under spring pretension, where balls from the drive part roll or slide over balls in the driven part to interrupt torque transmission at the limit torque, eliminating the need for radial shaft bearings and minimizing wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional overload protection devices (slip clutches, spur gears, ball-and-socket mechanisms) are used to interrupt torque transmission at high torques, then torque interruption function is achieved, but the components are exposed to wear and damage that reduces service life and may render the device unusable
Solution Approach 1:
The patent introduces an intermediary mechanism consisting of two ball rings that mediate the torque transmission between the drive shaft and driven shaft. These ball rings engage and disengage smoothly under spring pretension, preventing direct contact and wear between the shafts and the overload protection mechanism, thereby eliminating component damage while maintaining reliable torque interruption functionality
Solution Approach 2:
The invention replaces traditional mechanical overload protection mechanisms (slip clutches with friction rings, spur gears, ball-and-socket joints) with a refined ball ring system that uses spring pretension and controlled rolling/sliding motion. This substitution eliminates the wear-prone elements of traditional mechanisms while maintaining the torque interruption function, significantly extending device service life
2Strength
If radial bearings are added to support shafts in traditional torque limiting devices, then adequate bearing capacity is achieved, but device complexity and the need for precise bearings increase
Solution Approach 1:
The ball rings serve multiple functions simultaneously: they transmit torque during normal operation, provide controlled slip at overload conditions, and inherently support the shafts without requiring separate radial bearings. This multi-functionality eliminates the need for additional bearing components and reduces precision requirements, simplifying the overall device structure while maintaining adequate bearing capacity
Solution Approach 2:
The invention extracts and eliminates the radial bearing components from the traditional torque limiting device design. The ball ring mechanism itself is designed to provide the necessary support function, removing the need for separate radial bearings and reducing device complexity while maintaining adequate shaft bearing capacity through the spring-pretensed ball engagement geometry
3Measurement precision
If friction rings are used in slip clutch mechanisms to define friction and ensure reproducible limit torque, then torque repeatability is improved, but the friction mechanism causes wear and becomes destructive at very high torques
Solution Approach 1:
The invention changes the fundamental parameter of torque transmission from friction-based sliding contact to ball-based rolling contact under spring pretension. This parameter change maintains the ability to define and reproduce limit torque through controlled mechanical engagement while eliminating the wear-causing friction between surfaces, allowing the mechanism to handle very high torques without destructive wear
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
Enables non-destructive, almost wear-free torque interruption with precise repeatability at high torques without radial shaft bearings, ensuring reliable operation and extended service life.
Implementation Method 1
zwei Kugelläufen, die unter Federkraft stehen
Implementation Method 2
die Kugeln des Antriebs Teils über die Kugeln des Abtriebs Teils rollen oder gleiten
Implementation Method 3
die Kugeln des Antriebs Teils über die Kugeln des Abtriebs Teils rollen oder gleiten, wodurch die Kraftübertragung unterbrochen wird
Data Source
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AI summary
A power screwdriver overload prevention means (100), which is arranged between an input drive part (110) and an output drive part (102, 121) and which interrupts the transmission of torque between the input drive part (110) and the output drive part (102, 121) when a threshold torque is exceeded, is characterized in that the input drive part (110) has at least one ring of balls (130) that is arranged in a rotationally fixed manner in the input drive part, in that the output drive part (102, 121) has at least one ring of balls (140; 141, 142) that is arranged in a rotationally fixed manner in the output drive part (102, 121), and in that the ring of balls (130) that is arranged in the input drive part (110) is spring-preloaded via the ring of balls (140; 141, 142) arranged in the output drive part (102, 121) such that the balls (130) of the input drive part (110) are located in each case between two balls (140; 141, 142) of the output drive part (102, 121) and thus transmit a torque, and such that, when the threshold torque is exceeded, the balls (130) of the input drive part (110) roll over the balls (140; 141, 142) of the output drive part (102, 121) and thus interrupt the transmission of torque.