Overload protection device for compressor motor

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Solution Overview

Problem

Conventional overload protection devices for compressor motors experience contact instability and irregular return temperatures due to structural issues with bimetals and movable arms, leading to inconsistent protection against overloads and overheating, and require frequent replacement of resistance heating elements, increasing costs and reducing productivity.

Innovation Solution

An overload protection device with a base formed of insulative material, featuring a conductive terminal with embedded input, output, and intermediate terminals, and an overload protection mechanism including a resistance heating element, a movable arm, and bimetals that ensure constant return temperatures and prevent contact interference, along with a fuse unit for overcurrent protection and a heater holder for easy assembly of various resistance heating elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the embossed portion of the movable arm is offset from the center portion of the second bimetal, then contact instability is avoided, but the return temperature and time become irregular

Engineering Contradiction:

Improvecontact stabilityVSAvoidreturn temperature consistency

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The movable arm is designed with an asymmetric structure where the embossed portion is intentionally offset from the center of the second bimetal. This asymmetric positioning prevents contact instability during the creep-action period while the overall geometry and material properties of the bimetal ensure consistent return temperature and time characteristics

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The embossed portion of the movable arm is positioned at a specific local region rather than the center, creating a localized contact point that optimizes the interaction between the movable arm and second bimetal. This local quality adjustment resolves the contradiction between contact stability and return temperature consistency

Inventive Principle:

Principle #3Local quality

2Device complexity

If a single bimetal is used for overload protection, then the device structure is simple, but the protection reliability decreases when the bimetal fails to operate

Engineering Contradiction:

Improvebimetal structureVSAvoidoverload protection

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The overload protection function is segmented into two independent bimetal elements: a first bimetal for primary overload protection and a second bimetal for auxiliary safety. This segmentation allows each bimetal to operate independently at different temperature thresholds, ensuring that failure of one does not compromise overall system reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second bimetal is pre-positioned on the first bimetal to provide a backup protection mechanism. When the first bimetal fails to operate, the second bimetal serves as a predetermined safety cushion that will activate at a higher temperature to prevent motor damage

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If the movable arm pushes the bimetal at an offset position, then contact instability is prevented, but the pushing force is not uniformly distributed

Engineering Contradiction:

Improvecontact stabilityVSAvoidforce distribution

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The movable arm employs an asymmetric embossed portion design that contacts the second bimetal at an offset position. This asymmetric contact geometry prevents instability during creep-action while the overall symmetric geometry of the bimetal and arm ensures adequate force distribution for reliable operation

Inventive Principle:

Principle #4Asymmetry

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 provides stable and consistent overload protection with constant return temperatures, prevents contact instability, and allows for flexible use with different resistance heating elements, reducing production costs and improving productivity by eliminating the need for frequent component replacements.

Implementation Method 1

a resistance heating element capable of conducting electricity and having a predetermined electrical resistance value; the resistance heating element generating heat when conducting electricity

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

a bimetal placed between the resistance heating element and the movable arm, the bimetal deforming in shape at a predetermined operating temperature and returning to an original shape thereof at a predetermined return temperature

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

a movable arm including a material having electrical conductivity and elastic resilience, the movable arm being placed above the resistance heating element and having a predetermined length

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS10483067B2Overload protection device for compressor motor

Publication Date: 2019.11.19 MICRO CONTACT SOLUTION

AI summary

An overload protection device for a compressor motor and, more specifically, to an overload protection device for a compressor motor, which has an overload protection means and can thus more effectively prevent overload of the compressor motor.