Thermostat Metal Compensator Dimple Design for Circuit Breakers

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Solution Overview

Problem

Existing thermostat metal actuated devices face challenges in providing ambient temperature compensation for a series of devices with different current ratings, as changing thickness or length of thermostat metal compensators is costly and increases sensitivity to shock and vibration, with impractical packaging constraints.

Innovation Solution

The effective length of the thermostat metal compensator is modified through the formation of dimple or rib configurations in thinner material, allowing for varying levels of compensation without changing the overall length, reducing mass and increasing shock and vibration resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If different thickness thermostat metals are used to obtain different levels of compensation, then compensation levels can be varied for different current ratings, but manufacturing cost increases and shock and vibration sensitivity increases

Engineering Contradiction:

Improvecompensation level variationVSAvoidshock and vibration sensitivity

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating non-uniform thickness variations in the thermostat metal compensator through dimple patterns. Instead of using uniformly thick compensators of different overall thicknesses, the invention introduces localized thin regions (dimples) in a uniform thickness compensator. This allows different compensation levels for different current ratings while maintaining consistent overall mass and shock resistance characteristics.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If different thickness thermostat metals are used to obtain different levels of compensation, then compensation levels can be varied for different current ratings, but manufacturing cost increases

Engineering Contradiction:

Improvecompensation level variationVSAvoidmanufacturing cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent applies parameter changes by modifying the dimensional parameters of the thermostat metal compensator through dimple formation. By changing the depth, diameter, and distribution of dimples in a standard thickness compensator, different compensation levels are achieved without changing the base material thickness. This allows a single compensator thickness to serve multiple current ratings, reducing manufacturing complexity and inventory requirements.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If the length of the thermostat metal compensator is changed to provide different compensation levels, then compensation can be adjusted, but packaging constraints prevent accommodating devices of different sizes

Engineering Contradiction:

Improvecompensation level adjustmentVSAvoidcompensator length

Core Design Contradiction:

Adaptability or versatilityVSLength of moving object

Solution Approach 1:

The patent applies local quality by creating localized dimensional variations (dimples) in the compensator rather than changing the overall length. This allows different compensation levels to be achieved through local thickness modifications while maintaining a uniform compensator length that fits standard packaging requirements across all device variants.

Inventive Principle:

Principle #3Local quality

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

This approach provides cost-effective ambient temperature compensation with improved shock and vibration resistance across different current ratings, reducing actuation forces and enabling effective use with low force piezo-resistive actuators.

Implementation Method 1

thermostat metal, such as bimetal, compensator to provide relatively constant levels of hold and trip currents as a function of ambient temperature

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

different types metals for the thermostat metals are used to obtain varying levels of bimetal activity (movement per degree Fahrenheit)

Methodology Applied

Scientific EffectBimetallic effect: Bi-Metallic Strip

Data Source

PatentUS7397339B2Method for ambient temperature compensating thermostat metal actuated electrical devices having a plurality of current ratings

Publication Date: 2008.07.08 SENSATA TECHNOLOGIES MASSACHUSETTS INC

AI summary

A thermally actuated device, such as an electrical circuit breaker (10) is provided with an ambient temperature compensation thermostat metal member (38) selected so that it bends when subjected to changes in temperature and compensates for ambient temperature effects on a thermostat metal trip arm for a selected current rating. Movement of such thermostat metal member is directly proportional to the flexivity of the material and to the square of the length of the member and indirectly proportional to the thickness of the member. Since packaging constraints make changes in length impractical, compensation members used to provide temperature compensation for different current ratings of the device typically have been made by using members of different thickness. In accordance with the invention, ambient temperature compensation members for a family of devices having a plurality of different current ratings is provided by changing the effective length of respective blank thermal compensation members by stamping selected deformations (48c, 50c) appropriate for each current rating in respective blank compensation members.