Floating Shaft Cam Assembly for 4 Nm Energy Regulator Torque

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Solution Overview

Problem

Existing infinite switch energy regulators in cooking appliances fail to meet the new torque standard of 4 Nm due to design limitations, leading to potential failures and cracking of the cam, as the neutral break terminal yields under increased push force.

Innovation Solution

The design separates the shaft and cam to be independent, with the cam attaching as a clip-on and the shaft being floating, incorporating a spring to double the push travel distance from 1 mm to 2 mm, using a simple cam ramp activation mechanism instead of cam up/down motion, and allowing interchangeable springs for varying compression strengths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the cam teeth height is limited to 1.2 mm in the single piece or two piece press fitted assembly design, then the neutral break terminal does not yield, but the push travel distance is limited to 1 mm and the torque standard of 4 Nm cannot be achieved

Engineering Contradiction:

Improvepush travel distanceVSAvoidneutral break terminal yielding

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The invention divides the cam and shaft into separate independent components. The cam is separated from the shaft, allowing the cam teeth height to be increased to 2.4 mm without compromising the shaft structure. This segmentation enables the push travel distance to be doubled to 2 mm while maintaining reliability by preventing neutral break terminal yielding through proper force distribution.

Inventive Principle:

Principle #1Segmentation

2Force

If the cam teeth height is increased to achieve 4 Nm torque standard, then the torque requirement is met, but the neutral break terminal yields under increased push force

Engineering Contradiction:

ImprovetorqueVSAvoidneutral break terminal yielding

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

By separating the cam from the shaft, the invention allows the cam to be designed with higher teeth (2.4 mm) to generate 4 Nm torque independently. The shaft and cam follow different mechanical paths, so the increased cam teeth height does not translate to increased push force on the neutral break terminal, thus preventing yielding while meeting torque requirements.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention introduces a spring as an intermediary element between the user input and the cam mechanism. The spring absorbs and moderates the push force, converting it into controlled cam rotation. This intermediary allows the cam to achieve 4 Nm torque through its internal mechanics rather than requiring proportionally higher external push force, preventing neutral break terminal yielding.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If the single piece design of cam and shaft is used, then the structure is simple, but the cam can crack over time and fail before desired full life span

Engineering Contradiction:

ImprovestructureVSAvoidcam cracking

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The invention separates the cam and shaft into independent components that can rotate relative to each other. This segmentation eliminates the stress concentration points that cause cracking in single-piece designs. The cam can rotate freely on the shaft without creating stress concentrations, dramatically improving reliability and preventing cam cracking over time, while the increased complexity is minimal.

Inventive Principle:

Principle #1Segmentation

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 design enhances reliability by eliminating failure modes, reducing cam cracking odds to zero, and ensuring the neutral break terminal does not yield, while meeting the new torque standard of 4 Nm, with a more homogeneous running torque and reduced shaft wobble.

Implementation Method 1

incorporating a spring to double the push travel distance from 1 mm to 2 mm

Methodology Applied

Scientific EffectSpring: Spring

Implementation Method 2

using a simple cam ramp activation mechanism instead of cam up/down motion

Methodology Applied

Scientific EffectCam: Cam

Implementation Method 3

the bimetal element deforms when energy is applied to the internal heater and the resistive load

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 4

when energy is applied to the internal heater and the resistive load

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS11810741B2Increased push travel alternative for energy regulator

Publication Date: 2023.11.07 ROBERTSHAW CONTROLS CO

AI summary

An infinite switch includes a front cover, a back cover, and a base secured between the front cover and the back cover. A floating shaft extending through the front cover and the base. A cam fixed to the base and slidingly receiving an end of the floating shaft. The floating shaft is moveable in an axial direction extending parallel to a longitudinal axis of the floating shaft and the cam is fixed to prevent movement in the axial direction.