Electrical Switch Force Segmentation via Torsion Spring

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Solution Overview

Problem

Existing electrical switches face a challenge in achieving a high force on the control lever for safe switching off while maintaining a low force on the latching point for safe unlatching, as the opening spring's force is compromised in meeting both requirements.

Innovation Solution

The opening spring is configured to act on the pivot connecting the control lever and the first intermediate lever, breaking down its force into two components: a smaller partial force directed at the latching point and a larger partial force applied to the control lever, allowing for selective force direction and magnitude adjustment, utilizing a torsion spring that is wound around the stationary axis of the contact carrier to optimize space usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the opening spring acts directly on the control lever to ensure safe switching off, then the force on the control lever is high, but the force on the latching point becomes too high making thermal release difficult

Engineering Contradiction:
Improveforce on control leverVSAvoidthermal release unlatching
Core Design Contradiction:
ForceVSEase of operation

Solution Approach 1:

The force from the opening spring is segmented into two separate functions: one component acts on the control lever to ensure safe switching off, while another component acts on the latching point to enable easy thermal release. This is achieved by having the opening spring act on the pivot connecting the control lever and first intermediate lever, creating a force decomposition that simultaneously addresses both requirements with different force magnitudes.

Inventive Principle:
Principle #1Segmentation

2Force

If a compression spring is used as the opening spring, then it can exert force on the control lever, but it occupies a lot of space and its force direction is fixed

Engineering Contradiction:
Improvespring force on control leverVSAvoidspace occupied by opening spring
Core Design Contradiction:
ForceVSVolume of moving object

Solution Approach 1:

The traditional compression spring mechanism is replaced with a torsion spring that winds around the stationary axis of rotation of the contact carrier. This substitution eliminates the need for a separate compression spring housing, significantly reducing the space occupied by the opening spring mechanism while maintaining the ability to exert the necessary force on the control lever through the pivot connection.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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 configuration enables a high force on the control lever for effective switching off while minimizing the unlatching force, allowing for efficient and safe thermal release, with the torsion spring's linear torque characteristic and adaptable design enhancing spatial efficiency within the switch.

Implementation Method 1

the opening spring is a torsion spring, also known as a leg spring, the first leg of which is supported at a fixed point and the force is applied to the pivot via the second leg

Methodology Applied
Scientific EffectTorsion spring: Torsion Spring

Data Source

PatentEP2097918B1Electrical switch
Publication Date: 2011.04.06 ABB AG(DE)
  • EP2097918B1 patent drawingFigure 1
  • EP2097918B1 patent drawingFigure 2

AI summary

The invention relates to an electrical switch with a main current path, in which a main contact point (10) is located, with a secondary current path having an isolating contact point (37) onto which the current is commutated from the main current path in the event of a short circuit, with a switching lock with which the main contact point (10) and the isolating contact point (37) can be activated, and with a switch knob (24). The main and isolating contact points are opened by using a control lever (17). One end thereof is joined, using an articulated link via a pivot pin (18), to a first intermediate lever (19) which forms a linked chain with a second intermediate lever (21) and the switch knob (24). An opening spring (51) engages on the pivot pin (18) connecting the control lever (17) and the first intermediate lever (19) and acts upon the control lever (17), via the pivot pin (18), in the opening direction of the main contact point (10). The force of the opening spring (51) is introduced to the pivot pin (18) in such a way that a first, smaller partial force (56) acts on the latching point (31), and a second, larger partial force (57) acts on the control lever (17).