Propeller Blade Counterweight with Stop Member for Pitch Control

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Solution Overview

Problem

Existing propeller rotor designs face challenges in maintaining the pitch angle of blades when the hydraulic pitch change mechanism fails, as counterweights must be positioned to maximize radius while allowing for movement from reverse to feather positions without interfering with adjacent blades, limiting the radius from the blade rotational axis.

Innovation Solution

A movably mounted counterweight on each blade with a stop member to prevent rotation beyond the feather position, allowing the counterweight to transmit torque and maintain pitch angle when the hydraulic mechanism fails, and enabling a longer arm length by avoiding the need to pass through the hub envelope.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the counterweight is positioned at a larger radius from the blade pitch change axis, then the counterweight can more effectively increase the pitch angle and maintain blade position during hydraulic failure, but the counterweight may interfere with adjacent blades during movement from reverse to feather positions

Engineering Contradiction:

Improvepitch angle maintenance during hydraulic failureVSAvoidblade movement range from reverse to feather position

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The counterweight is made movable relative to the blade through a pivot connection, allowing it to dynamically adjust its position. During normal operation, the counterweight remains stationary relative to the blade. During blade movement from reverse to feather position, the counterweight can rotate independently on the blade to avoid interfering with adjacent blades, thus enabling the blade to achieve full feather position without collision

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

A stop member is introduced as an intermediary element between the counterweight and the blade. This stop member limits the rotation of the counterweight on the blade, preventing it from rotating too far while still allowing sufficient movement to avoid adjacent blades. The stop member acts as a mechanical constraint that mediates between the counterweight's need to move and the blade's need to maintain proper positioning

Inventive Principle:

Principle #24Intermediary (Mediator)

2Force

If the counterweight arm length is increased to maximize radius, then the counterweight produces greater torque to increase pitch angle, but the counterweight requires more space to pass adjacent blades during position transitions

Engineering Contradiction:

Improvetorque production for pitch angle increaseVSAvoidspace required for counterweight to pass adjacent blades

Core Design Contradiction:

ForceVSArea of stationary object

Solution Approach 1:

The counterweight arm is designed with rotational freedom on the blade, transforming it from a rigid fixed structure to a dynamic component. This allows the counterweight to rotate on its pivot point during blade position transitions, effectively reducing the swept area and space required to pass adjacent blades, while maintaining the long arm length for optimal torque production

Inventive Principle:

Principle #15Dynamics

3Device complexity

If the counterweight is fixed to the blade, then the structure is simple and reliable, but the counterweight cannot avoid adjacent blades during blade movement, limiting the maximum safe radius

Engineering Contradiction:

Improvecounterweight mounting structureVSAvoidcounterweight operation during position transitions

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The counterweight mounting structure transitions from a fixed rigid connection to a pivot-based movable connection. This simple pivot mechanism allows the counterweight to rotate independently on the blade, avoiding complex multi-component mechanisms while providing the necessary movement capability to prevent interference with adjacent blades during position transitions

Inventive Principle:

Principle #15Dynamics

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 ensures the counterweight can effectively increase the pitch angle and maintain blade position during hydraulic failure, allowing for a more optimized counterweight placement and reduced interference with adjacent blades, enhancing the propeller rotor's operational range and efficiency.

Implementation Method 1

the counterweight is designed to be attached to a base of the blade and produce a twisting moment on the blade when the propeller rotor rotates, such that in that moment on the blade is in a direction to increase pitch

Methodology Applied

Scientific EffectTorque: Torque

Implementation Method 2

A stop member stops rotation of the counterweight as the blade moves to a feather position

Methodology Applied

Scientific EffectMechanical constraint: Mechanical Force

Data Source

PatentEP2774842B1Propeller blade with relatively movable counterweight

Publication Date: 2017.03.08 HAMILTON SUNDSTRAND CORP

AI summary

A propeller rotor (99) has a hub (112) mounting a plurality of blades (106). A counterweight (100) is movably mounted on the blade (106). A pitch change mechanism (108; 110) for changing an angle of incidence of an airfoil is associated with each of the blades (106). The counterweight (100) twists the blades (106) toward an increased pitch direction should the pitch change mechanism (108; 110) fail. A stop member stops rotation of the counterweight (100) as the blade (106) moves to a feather position.