Radial Offset Torque Limiting Unit for Compact Handheld Tools
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing hand-held machine tools have a torque limiting unit design that results in a closed and bulky structure, limiting their range of use due to the axial overlap of the planetary drive and detent support, which restricts the overall length and flexibility of the device.
Innovation Solution
The detent bodies and spring support are arranged radially offset from each other, allowing for the use of longer spring elements and a slim design, with the spring support being adjustable via a bridging member and pressure nut, enabling a compact and reliable torque limiting unit with reduced parts and preventing spring buckling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the detent support and planetary drive are arranged with axial overlap to create a closed design, then the torque limiting unit achieves a compact enclosed structure, but the overall length of the machine tool increases
Solution Approach 1:
The patent transitions from axial arrangement to radial arrangement of components. The detent bodies are positioned radially offset from the spring support, allowing the spring elements to extend radially rather than axially. This dimensional change enables the torque limiting unit to achieve a shorter axial length while maintaining structural integrity and enclosed design.
Solution Approach 2:
The patent implements nesting by positioning the spring support within the radial space of the planetary drive components. The spring elements are arranged to extend radially through the structure, with the detent bodies nested within the radial envelope of the planetary gears. This nesting allows multiple components to occupy overlapping radial zones without increasing axial length.
2Length of moving object
If radial offset arrangement is used with longer spring elements, then the overall length is reduced, but spring buckling risk increases
Solution Approach 1:
The patent introduces guide elements as intermediary components that provide lateral support to the spring elements. These guide elements constrain the springs to follow a defined radial path, preventing buckling while allowing the springs to extend sufficiently to achieve the desired compact axial length. The guide elements act as mediators between the spring elements and the surrounding structure.
Solution Approach 2:
The patent employs thin-walled guide structures and restraining elements that provide lateral confinement to the spring elements. These thin-film-like guide surfaces allow the springs to extend radially while maintaining stability through controlled flexibility and geometric constraint, preventing buckling without requiring bulky support structures.
3Adaptability or versatility
If the spring support is made adjustable with a pressure nut, then the torque limiting capability is improved, but the device complexity increases
Solution Approach 1:
The pressure nut serves multiple functions: it adjusts the axial position of the spring support to set the torque limit, it preloads the spring elements to ensure proper engagement, and it provides a means for user adjustment of the torque threshold. This multi-functionality reduces the need for separate adjustment mechanisms while achieving versatile torque control.
Solution Approach 2:
The patent combines the spring support positioning function with the torque adjustment function in a single integrated mechanism. The pressure nut simultaneously controls the axial position of the spring support and the preload force on the springs, merging what could be separate adjustment systems into one unified component that reduces overall complexity.
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
This configuration achieves a shorter overall length of the torque limiting unit, allowing for a more compact and versatile machine tool design with a reliable locking function and simplified production, while maintaining effective torque limiting capabilities.
Implementation Method 1
the spring elements (16, 17) which, in the exemplary embodiment, are arranged as helical springs over the circumference of the ring gear (8) at a distance from one another
Data Source
Figure 1~3
Figure 4
Figure 5
AI summary
A machine tool (1), in particular a handheld machine tool, preferably in the configuration as a cordless screwdriver, is provided with a torque limiting unit (5) in which the release torque is adjustable via a detent support (6) which is provided with a spring support (13, 14) for detent elements (10) which bear axially against parts of a planetary drive (48) in particular its ring gear (8) or its planet carrier (40) as the last gear stage (7), wherein the spring elements (16, 17) of the spring support (13, 14) and the detent elements (10) are radially offset from each other.