Dual-Seal Motor Load Interface for Fluid Ingress Isolation
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Solution Overview
Problem
Existing electric motors used to drive fluidic loads, such as electrohydrostatic actuators, face issues with fluid ingress leading to damage and contamination, necessitating larger, heavier designs with protective sleeves and increased heat dissipation, which is undesirable for applications like aircraft.
Innovation Solution
A sealing arrangement with a rotating shaft and dual seals, including a major flat seal and a minor lip seal, along with drain channels to capture microleakages, effectively isolating the motor from fluid ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective sleeve is added around the motor coils to protect from fluid ingress, then the motor reliability is improved, but the motor size and weight increase
Solution Approach 1:
A seal holder block with integrated seals is introduced as an intermediary component between the motor and pump. This block creates a fluid barrier without requiring protective sleeves around the coils, thus protecting the motor from fluid ingress while avoiding the weight penalty of immersed motor designs.
Solution Approach 2:
The sealing function is segmented into multiple components: a seal holder block, first seal for the shaft, and second seal for the pump outlet. This segmentation allows protection against fluid ingress without enclosing the entire motor in a protective sleeve, reducing overall motor weight while maintaining reliability.
2Reliability
If the air-gap between rotor and stator is increased to accommodate fluid flow, then the motor reliability is improved, but the motor torque capability deteriorates
Solution Approach 1:
The seal holder block acts as an intermediary that manages fluid flow separately from the motor air-gap. This allows the air-gap to be minimized for optimal torque while the seal holder block provides the necessary fluid passage and sealing, decoupling the fluid flow requirement from the air-gap dimension.
3Power
If larger coils are used to compensate for Eddy current losses and air-gap increase, then the motor torque is improved, but the motor heat dissipation requirements increase
Solution Approach 1:
The seal holder block with its fluid passage serves as an intermediary that allows compact coil design by managing fluid flow externally. This eliminates the need for oversized coils required in immersed motor designs, reducing heat generation while maintaining the necessary torque output.
4Reliability
If a seal holder block with dual seals is added to prevent fluid ingress, then the motor protection is improved, but the device complexity increases
Solution Approach 1:
The seal holder block merges multiple functions into a single component: it houses both the first seal (for shaft sealing) and the second seal (for pump outlet sealing), and provides the fluid passage. This integration reduces the number of separate parts compared to alternative sealing arrangements, simplifying the overall device despite the enhanced protection.
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
Enables the use of a smaller, lighter dry motor design by preventing fluid ingress, reducing the need for protective sleeves and heat management features, thus optimizing size and weight.
Implementation Method 1
pressure acting on an axially outer surface of the shoulder causes the first seal to create a seal with the seal holder block against fluid flow past the shoulder
Implementation Method 2
the second seal prevents flow of any fluid that has passed the first seal passing the second seal
Data Source
AI summary
A sealing arrangement for the interface between a fluidic load and a motor. The sealing arrangement includes: a rotating shaft having a shaft body extending along an axis (A) and having a first end, configured to, in use, be in driving engagement with a fluidic load, and a second end configured to, in use, be in engagement with a motor for rotation by the motor, the rotating shaft and a shoulder extending radially outwards from the shaft body at the first end. The sealing arrangement further includes: a first, major seal extending radially around the shaft; a second, minor seal axially spaced from the first seal towards the second end and mounted around the shaft, and a seal holder block located between the first seal and the second seal around the shaft body.