Watertight Ball-Screw Actuator for Axial and Radial Load Transfer
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Solution Overview
Problem
Existing actuators for trim tab and wake gate assemblies face challenges in providing efficient and watertight operation, particularly in transferring axial and radial loads effectively.
Innovation Solution
The development of a watertight electric actuator with a housing and a drive tube assembly, featuring a piston nut and output shaft, along with bearings for load transmission, and a planetary gear reduction for efficient motor coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional actuator design is used for trim tab assembly, then the structure is simple, but the actuator cannot effectively transfer axial and radial loads while maintaining watertight operation
Solution Approach 1:
The actuator is divided into distinct functional segments: a motor housing containing the motor, a drive tube assembly with threaded drive tube and piston nut, and separate bearing assemblies for axial and radial loads. This segmentation allows each component to be optimized for its specific function while maintaining overall watertight integrity through sealed interfaces between segments.
Solution Approach 2:
Bearing assemblies serve as intermediary elements between the drive tube and housing, mediating the transfer of axial and radial loads. The bearings are positioned as intermediate components that facilitate load transfer without compromising the watertight seal between the motor housing and drive tube assembly.
2Force
If a conventional actuator design is used for trim tab assembly, then the manufacturing process is simple, but the actuator cannot effectively transfer axial and radial loads
Solution Approach 1:
The actuator is divided into distinct functional segments: a motor housing containing the motor, a drive tube assembly with threaded drive tube and piston nut, and separate bearing assemblies for axial and radial loads. This segmentation allows each component to be optimized for its specific function while maintaining overall watertight integrity through sealed interfaces between segments.
Solution Approach 2:
Radial bearings are incorporated to handle radial loads, utilizing curved spherical contact surfaces that efficiently distribute radial forces from the drive tube to the housing. This spherical geometry optimizes load distribution while maintaining compact dimensions.
3Power
If a simple actuator design is used, then the device complexity is low, but the motor coupling efficiency is insufficient
Solution Approach 1:
A planetary gear reduction system replaces direct mechanical coupling between the motor and drive tube. The planetary gears provide high reduction ratios in a compact configuration, efficiently transmitting motor power to the drive tube while reducing the size and complexity compared to alternative mechanical transmission systems.
Solution Approach 2:
The planetary gear system employs a nested configuration where planet gears are positioned around a central sun gear, with ring gears enclosing the entire assembly. This nested arrangement maximizes power density and coupling efficiency within a compact volume, reducing the overall actuator size while maintaining high motor coupling efficiency.
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 actuator achieves efficient and reliable operation by effectively transferring axial and radial loads, ensuring watertightness, and enabling precise movement of trim tabs and wake gates.
Implementation Method 1
There may be a planetary gear reduction coupling the motor to the drive tube.
Implementation Method 2
a threaded surface; a drivable body comprising an output shaft and a threaded surface, the threaded surface of the drivable body threadedly engaged with the threaded surface of the drive body such that rotation of the drive body relative to the housing and around the drive-body axis of rotation causes movement of the output shaft relative to the housing and along the drive-body axis of rotation
Implementation Method 3
a first bearing facing the first thrust-transfer surface and configured to transfer, to the housing, thrust forces from the output shaft in the first direction; and a second bearing facing the second thrust-transfer surface and configured to transfer, to the housing, thrust forces from the output shaft in the second direction
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; 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. The drive body may be engaged with the drivable body through at least one ball such that rotation of the drive body causes movement of the output shaft. The at least one ball may engage with the drive body over a greater extent along an axis of rotation than with the drivable body.