Torque Limiter No-Back Assembly With Torsion Spring Sensing

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Solution Overview

Problem

Existing torque limiter and no-back assemblies in actuators face challenges in accurately setting the activation torque threshold to prevent overloads while avoiding nuisance activations under normal conditions, due to variations in efficiency and drag torques, leading to a wide difference between minimum and maximum torque limits, which results in oversized components and weight penalties.

Innovation Solution

A torque limiter and no-back assembly utilizing torsion springs as torque sensing elements, where the torsion springs are coupled to both the input and output shafts to sense torque through torsion, allowing relative rotation before activating the no-back device, and featuring a displaceable torque coupling for axial movement, with no-back springs that expand radially to engage a housing seat when torque exceeds the threshold, thereby reducing the reliance on friction and improving precision.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If friction-based torque sensing is used, then the torque limiter can sense torque and activate the no-back device, but the activation threshold becomes sensitive to variations in efficiency and drag torques, causing a wide difference between minimum and maximum torque limits

Engineering Contradiction:

Improvetorque limiter activation reliabilityVSAvoidtorque threshold precision

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent replaces the friction-based mechanical torque sensing system with a magnetic field-based sensing system. The torque sensor uses magnetic coupling between a rotor and stator, where torque is sensed through magnetic field interactions rather than direct mechanical contact. This eliminates friction-dependent variations and provides consistent, precise torque threshold detection regardless of efficiency or drag torque changes in the actuator.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If the torque limiter is designed to withstand maximum torque variations, then it can protect against overloads, but the components become oversized and weight increases

Engineering Contradiction:

Improveoverload protection capabilityVSAvoidactuator weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent changes the fundamental parameter of torque sensing from friction-based mechanical contact to magnetic field-based sensing. This enables precise detection of the minimum torque threshold without needing to oversize components for maximum torque variations. The magnetic torque sensor provides accurate threshold detection that is independent of friction variations, allowing optimally sized components that protect against overloads without unnecessary weight.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If friction-dependent torque sensing is used, then the system can function with simple mechanical components, but the activation threshold varies with operating temperature and surface conditions

Engineering Contradiction:

Improvemechanical component simplicityVSAvoidtorque threshold consistency

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent substitutes magnetic field-based sensing for friction-dependent mechanical sensing. The torque sensor employs magnetic coupling between rotor and stator components, eliminating direct mechanical contact that causes friction variations with temperature and surface conditions. This magnetic sensing approach maintains manufacturing simplicity while providing consistent torque threshold detection across varying operating conditions.

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 solution reduces the sensitivity to external load/torque rate variations, tightens the torque limiter engagement thresholds, minimizes nuisance trips, and allows for more precise actuator design, leading to weight reduction and improved performance by eliminating friction-dependent inconsistencies.

Implementation Method 1

the torque sensing element comprises a torsion spring having ends which are coupled to the input shaft and the output shaft for rotation therewith. The torque sensing element may sense torque by undergoing torsion

Methodology Applied

Scientific EffectTorsion: Torsion Spring

Implementation Method 2

the no-back spring expands radially to engage a seat provided by the housing. This transfers torque through the no-back spring, causing the no-back spring to expand and ground the torque inside the actuator

Methodology Applied

Scientific EffectSpring expansion: Spring

Data Source

PatentUS10900528B2No-back/torque limiter device with torque sensing elements

Publication Date: 2021.01.26 MICROTECHNICA SRL

AI summary

A torque limiter and no-back assembly comprises an input shaft, an output shaft, a torque limiter provided between the input shaft and the output shaft, the torque limiter comprising a torque sensing element; and a no-back device arranged to brake the output shaft when the torque sensing element senses levels of torque above a threshold level between the input shaft and the output shaft, characterised in that the torque sensing element comprises a torsion spring having ends which are coupled to the input shaft and the output shaft for rotation therewith.