Compressor Terminal Box Clearance for Flame Containment

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Solution Overview

Problem

Existing compressors face the risk of flames generated inside the terminal box escaping to the outside due to the presence of oxygen in the atmosphere, posing a safety hazard.

Innovation Solution

The compressor design includes a terminal body protruding away from the casing with a tubular portion in the terminal box, allowing flames to pass through a controlled clearance between the terminal body and the tubular portion, ensuring they are extinguished before exiting the terminal box.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the terminal box houses the terminal rod with a simple structure, then the device complexity is reduced, but the flame may escape to the outside causing safety hazards

Engineering Contradiction:
Improveflame containmentVSAvoidterminal box structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The terminal body is nested within the terminal box, with the terminal body protruding into the terminal box's housing space. This nested configuration creates a controlled clearance between the terminal body and the terminal box wall, forming an effective flame barrier while maintaining structural integration.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The clearance between the terminal body and terminal box wall is specifically designed with controlled dimensions (insertion length ≥6mm, clearance ≤0.4mm) to create local flame extinction conditions. This localized structural feature provides flame containment without requiring complex overall redesign.

Inventive Principle:
Principle #3Local quality

2Reliability

If a clearance is created between the terminal body and tubular portion, then flames can be extinguished passing through, but the manufacturing precision requirements increase

Engineering Contradiction:
Improveflame extinctionVSAvoidclearance dimension
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

Specific parameter ranges are defined for the clearance structure: insertion length of the terminal body into the tubular portion is set to ≥6mm, and the clearance between the terminal body and tubular portion is set to ≤0.4mm. These parameter specifications ensure flame extinction while providing manufacturable tolerances.

Inventive Principle:
Principle #35Parameter changes

3Ease of operation

If the terminal body protrudes away from the casing, then the terminal box can house the terminal rod effectively, but the flame may pass through to the outside atmosphere

Engineering Contradiction:
Improveterminal rod connectionVSAvoidflame escape risk
Core Design Contradiction:
Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The controlled clearance between the terminal body and the tubular portion of the terminal box acts as an intermediary barrier. This clearance allows the terminal body to protrude for electrical connection while simultaneously serving as a flame extinction zone that prevents flame escape to the external atmosphere.

Inventive Principle:
Principle #24Intermediary (Mediator)

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

Prevents flames from escaping the terminal box by extinguishing them within the controlled clearance, enhancing safety by minimizing the risk of external ignition.

Implementation Method 1

the flame generated inside the terminal box (120) passes through a clearance between the terminal body (110) and the tubular portion (126) of the terminal box (120) to exit the terminal box (120). The flame may be extinguished while passing through the clearance.

Methodology Applied
Scientific EffectFlame extinction through clearance:

Data Source

PatentEP4729774A1Compressor and refrigeration device
Publication Date: 2026.04.22 DAIKIN INDUSTRIES LTD
  • EP4729774A1 patent drawingFigure 1
  • EP4729774A1 patent drawingFigure 2
  • EP4729774A1 patent drawingFigure 3

AI summary

A compressor includes a compression mechanism, a casing that houses the compression mechanism, a terminal body that is fixed to an outer wall of the casing and holds a terminal rod to which a wire to a device in the casing is connected, and a terminal box that is fixed to the outer wall of the casing and houses the terminal rod held by the terminal body. The terminal body protrudes in a direction away from the casing. The terminal box includes a bottom wall fixed to the outer wall of the casing, a hole formed in the bottom wall and through which the terminal body passes, and a tubular portion extending from a peripheral edge of the hole in the direction away from the casing. The terminal body is inserted into the tubular portion.