Angle Grinder Protective Hood Locking Mechanism

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Solution Overview

Problem

Existing power tools, such as angle grinders, often require a large space for locking devices, limiting the arrangement of other functional groups and making it easy for users to improperly remove protective covers.

Innovation Solution

A compact securing device using a retaining ring and cover ring is integrated into the power tool, which secures the protective hood in place, making it difficult to remove without destruction, and allows for flexible use of the through-opening in the receiving flange.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a locking device is provided to secure the protective cover, then the protective cover cannot be removed improperly, but the locking device requires a relatively large amount of space in the area of the spindle passage

Engineering Contradiction:
Improveprotective cover securityVSAvoidspace requirement of locking device
Core Design Contradiction:
ReliabilityVSVolume of moving object

Solution Approach 1:

The securing device is nested within the receiving flange structure, utilizing the existing flange geometry to house the locking mechanism. The radial projections are integrated into the flange's cylindrical inner surface, and the retaining ring engages with grooves formed in the flange itself, minimizing the space occupied by the securing device while maintaining its protective function.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The locking mechanism transitions from a two-dimensional planar arrangement to a three-dimensional radial configuration. The radial projections extend along the inner circumferential direction, creating a circumferential distribution of locking points around the spindle passage. This radial arrangement optimizes space utilization by distributing the locking function around the circumference rather than requiring linear space along a single axis.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If the through-opening of the receiving flange is made larger for tool holder arrangement, then more functional groups can be arranged, but less space remains for the securing device

Engineering Contradiction:
Improvetool holder arrangement flexibilityVSAvoidsecuring device functionality
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The receiving flange is designed with differentiated local properties: the cylindrical inner surface contains radial projections specifically positioned to engage with the retaining ring, while the outer structure provides a large through-opening for tool holder access. The annular groove is locally formed at a specific radial position to accommodate the retaining ring, separating the securing function from the tool holder mounting area. This local differentiation allows both functions to coexist without interference.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The receiving flange structure is segmented into distinct functional zones: the cylindrical inner surface with radial projections for securing, the annular groove for retaining ring engagement, and the through-opening area for tool holder arrangement. This segmentation allows each zone to be optimized independently - the securing zone maintains compact dimensions while the tool holder zone provides ample space, resolving the spatial conflict between these two functional requirements.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP4414129B1Electric power tool with protective cover
Publication Date: 2025.06.18 C & E FEIN GMBH & CO KG
  • EP4414129B1 patent drawingFigure 1~2
  • EP4414129B1 patent drawingFigure 3
  • EP4414129B1 patent drawingFigure 4~5

AI summary

The invention relates to a power tool (1), in particular an angle grinder (2), with a tool spindle (7) having a tool holder (8), which is rotatably received in a spindle passage (11) of a bearing plate (10) about an axial direction, wherein the bearing plate (10) has a receiving flange (12) on which a protective hood (13) can be rotatably mounted, the disassembly of which is at least made more difficult by a locking device (21) which has a retaining ring (27), in particular a snap ring element, which in the locking position is in engagement with an annular groove (18) and is arranged between the receiving flange (12) and a mounting flange (17) of the protective hood and which forms a stop for at least a first radial projection (16) of the mounting flange, which blocks an axial outward movement of the protective hood (13) away from the bearing plate.