Power Tool Terminal Connection Dust Resistance

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Solution Overview

Problem

Existing power tools face issues with dust resistance at terminal connections, particularly during operations like grinding or polishing, where metal chips can enter the motor housing and cause current leakage or short circuits due to vibration loosening the connections.

Innovation Solution

A power tool design featuring a hollow tubular member and a fitting member that maintain the connection between motor-side and switch-side terminals isolated within the tubular member, preventing metal chips from sticking and causing leakage or short circuits, with a plug-and-socket connection mechanism that is securely held even during vibration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the terminal connection is exposed to the internal space for easy connection, then the ease of operation is improved, but the dust resistance deteriorates

Engineering Contradiction:
Improveease of terminal connectionVSAvoiddust resistance
Core Design Contradiction:
Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The terminal connection is nested within the hollow tubular member, which serves as a protective enclosure. The fitting member is inserted into the tubular member to establish the electrical connection, keeping the connection point isolated from external contaminants while maintaining accessibility for connection operations.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The hollow tubular member acts as an intermediary structure between the external environment and the terminal connection. It provides a protected pathway for the fitting member to reach the terminal while isolating the connection point from metal chips and dust particles in the surrounding environment.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the terminal connection is isolated within a tubular member for dust resistance, then the dust resistance is improved, but the device complexity increases

Engineering Contradiction:
Improvedust resistanceVSAvoidstructural complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The hollow tubular member serves multiple functions simultaneously: it acts as a structural support element, a protective enclosure for the terminal connection, and a guiding pathway for the fitting member. This multi-functionality reduces the need for separate protective components, thereby minimizing the increase in device complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The protective enclosure function is merged with the existing structural framework of the power tool. The tubular member is integrated into the housing structure, combining the protective function with the overall structural design rather than adding a separate, standalone protective component.

Inventive Principle:
Principle #5Merging (Combining)

3Reliability

If the fitting member is held in the tubular member during vibration, then the reliability is improved, but the ease of manufacture deteriorates

Engineering Contradiction:
Improveconnection stability under vibrationVSAvoidassembly difficulty
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The fitting member is designed with dynamic retention characteristics that adapt to operational conditions. During vibration, the fitting member remains held within the tubular member due to friction and geometric constraints, ensuring reliable connection. During assembly, the same geometric features allow for straightforward insertion and connection without requiring complex locking mechanisms.

Inventive Principle:
Principle #15Dynamics

Data Source

PatentEP2228179B1Electric tool
Publication Date: 2015.08.12 MAKITA CORP
  • EP2228179B1 patent drawingFigure 1
  • EP2228179B1 patent drawingFigure 2
  • EP2228179B1 patent drawingFigure 3

AI summary

A power tool includes a motor housing (105), a motor (121), a motor-side terminal (163), a switch block (153), and a switch-side terminal (159) provided on the switch block to be connected to the motor-side terminal (163). A hollow tubular member (165) is provided on one of the motor housing (105) and the switch block (153) and extends in a longitudinal direction of the motor housing (105), and a fitting member (169) is provided on the other of the motor housing and the switch block and fitted in the tubular member (165). The motor-side terminal and the switch-side terminal are connected to each other within a hollow of the tubular member. As long as the motor-side terminal (163) and the switch-side terminal (159) are at least connected to each other, the tubular member (165) and the fitting member (169) are held in the fitted state so that a connection between the terminals is isolated from the outside of the tubular member (165).