Angle Grinder Protective Hood Pocket Stop Design
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Solution Overview
Problem
Existing protective hoods for power tools, such as angle grinders, fail to meet the burst test requirements of IEC-EN60745-2-3 due to stop lugs made of spring-elastic sheet metal bending and allowing the hood to continue rotating past the intended stop positions.
Innovation Solution
Designing a protective hood with a stiffer material and forming stops with a pocket shape to prevent further rotation beyond the intended limit, increasing the distance between the stop element and the free upper edge, and using projections and recesses for secure positioning without tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stop lugs made of spring-elastic sheet metal are used to limit rotation, then the design remains simple and easy to manufacture, but the stop lugs bend under impact allowing the hood to rotate past the 90° limit during burst test
Solution Approach 1:
The patent changes the material parameter from spring-elastic sheet metal to a stiffer material for the stop lugs. This parameter change increases the rigidity of the stop structure, preventing bending under impact forces during burst tests while maintaining the simple integrated design without additional components.
Solution Approach 2:
The stop lugs are segmented into two functional parts: the main body integrated into the protective hood and the extended stop portion that protrudes to contact the bearing shield. This segmentation allows the stop function to be achieved through geometric extension rather than additional components, maintaining simplicity while improving reliability.
2Reliability
If the protective hood is made of stiffer material to prevent stop bending, then burst test compliance is achieved, but manufacturing costs and design complexity increase
Solution Approach 1:
The stop lugs are merged with the protective hood body as an integrated structure rather than separate components. This merging eliminates the need for additional parts, fasteners, and assembly steps, keeping manufacturing simple while the extended geometry of the stop lugs provides the necessary stopping function.
Solution Approach 2:
Instead of making the entire protective hood from stiffer material (which would increase cost and complexity), the patent inverts the approach by using the existing hood material and creating stiffness only where needed through the geometric design of the extended stop lugs that contact the bearing shield.
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 effectively prevents the protective hood from rotating beyond the 90° limit during a burst test, ensuring compliance with IEC-EN60745-2-3 standards without increasing manufacturing costs or complexity.
Implementation Method 1
the stop is provided with a leg extending towards the partial circular arc to form a pocket, so that the stop essentially has the shape of an 'L' in section
Implementation Method 2
several retaining elements are provided on the sector-shaped wall along a partial arc of the circle, coaxial to the sector and thus to the drive spindle or the recess accommodating the drive spindle. These retaining elements can be engaged with a corresponding counter-element
Implementation Method 3
It is generally preferred to mold the stop onto the protective hood itself, which is made of a stiffer material compared to the spring-loaded retaining ring
Data Source
Figure 1
Figure 2
AI summary
A protective cowl (50) for an electric power tool, especially an angle grinder, has a number of holes equidistant to the shaft axis which interact with a catch (18, 19) to lock the cowl into the selected angular setting. A safety end stop comprises an axial fitting (61, 62) shaped as a pocket into which the setting catch locates if the tool is dropped or damaged, ensuring that the cowl displacement remains within safety guidelines. The safety end stop includes a slot to guide the setting catch into the pocket.