Watertight Marine Actuator With Bidirectional Thrust Bearings
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Solution Overview
Problem
Existing actuators for trim tab and wake gate assemblies are not watertight, leading to issues with water ingress and inefficiencies in load transfer, particularly in marine vessel applications where both push and pull directions are critical.
Innovation Solution
A watertight electric actuator design featuring a housing with a drive tube or drive shaft assembly, including a piston nut and output shaft, coupled with a motor and planetary gear reduction, and utilizing thrust-transfer and torque-transfer surfaces with bearings for efficient axial and radial load transfer, and a vent tube for pressure management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional actuator design is used for trim tab and wake gate assemblies, then the structure is simpler, but the actuator is not watertight leading to water ingress issues
Solution Approach 1:
The actuator is divided into separate sealed compartments including a motor housing and a drive mechanism housing, with gaskets and seals at interfaces to maintain watertight integrity while allowing modular construction and simpler manufacturing of individual components
Solution Approach 2:
Gaskets and sealing elements are introduced as intermediary components between mating surfaces of the actuator housing and drive tube assembly, providing watertight sealing without requiring complex integrated sealing structures
2Productivity
If conventional actuator design is used, then manufacturing is simpler, but load transfer efficiency in both push and pull directions is insufficient
Solution Approach 1:
The drive tube is designed with integrated thrust-transfer surfaces that combine both push and pull load transfer functions into a single component, eliminating the need for separate mechanisms and improving load transfer efficiency in both directions while maintaining manufacturing simplicity
Solution Approach 2:
The drive tube assembly serves multiple functions simultaneously: it acts as a structural support element, a load transfer mechanism for both push and pull forces, and a sealed compartment boundary, reducing the number of separate components needed
3Reliability
If the actuator is designed to be watertight with sealed housing, then water ingress is prevented, but pressure management becomes more difficult
Solution Approach 1:
A dedicated vent tube is extracted as a separate component from the sealed housing, providing a controlled pathway for pressure equalization while maintaining the watertight seal of the main actuator body, thus simplifying pressure management without compromising sealing integrity
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
The solution provides a reliable, watertight actuator that efficiently transfers loads in both push and pull directions, preventing water ingress and enhancing the operational efficiency of trim tab and wake gate assemblies in marine vessels.
Implementation Method 1
The drive tube assembly includes a drive tube provided with internal threads, a piston nut provided with external threads which threadedly engage the internal threads of the drive tube. A motor rotates the drive tube to cause the piston nut to reciprocate along a length of the drive tube
Implementation Method 2
There may be a planetary gear reduction coupling the motor to the drive tube
Implementation Method 3
There are bearings which transmit axial loads from the drive tube to the housing and transmit radial loads from the drive tube to the housing
Implementation Method 4
There may be a vent tube allowing fluid communication between the atmosphere and an interior of the housing
Data Source
AI summary
An actuator includes a drive body including a torque-transfer surface configured to receive a torque. The actuator further includes: a drivable body including an output shaft such that rotation of the drive body causes movement of the output shaft; a first bearing configured to transfer thrust forces from the output shaft in a first direction; and a second bearing configured to transfer thrust forces from the output shaft in a second direction. At least the first bearing extends in a radial dimension beyond the torque-transfer surface.