Dual Ball-Screw Linear Actuator With Single-Motor Coupling
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Solution Overview
Problem
In aircraft applications, the large number of linear ball screw actuators and motors required leads to increased weight and complexity, as each actuator typically has a separate motor, which is inefficient and cumbersome.
Innovation Solution
A linear actuator design where a single electric motor with reduction gearing is used to drive two ball screws with opposite thread directions, mounted in radially enlarged end sections of a drive element, with shield elements and seals to protect against environmental contaminants, allowing for reduced motor count and enhanced operational efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate motor is used for each linear actuator, then the actuator can operate independently and reliably, but the total weight and device complexity increase significantly
Solution Approach 1:
The patent combines two separate actuators into a single integrated unit where one motor drives two ball screws through a differential mechanism. The motor shaft connects to the differential mechanism which distributes rotational motion to two ball screws with opposite thread directions, enabling independent linear motion of two rods from a single motor source.
2Ease of operation
If a separate motor is mounted for each actuator, then each actuator can be controlled independently, but the number of components and device complexity increases
Solution Approach 1:
The patent merges two actuator systems into one by using a differential mechanism that allows independent control of two ball screws from a single motor. The differential mechanism with its pinion gears and bevel gears enables each ball screw to rotate independently while sharing a common motor drive source.
Solution Approach 2:
The differential mechanism acts as an intermediary between the single motor and the two ball screws. It translates the single motor's rotation into two independent rotational outputs with opposite directions, enabling independent actuator control without requiring two separate motors.
3Object-affected harmful factors
If shield elements are added to protect internal components, then protection against environmental contaminants is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent uses flexible sealing elements including O-rings and lip seals to protect the internal components from environmental contaminants. These seals are positioned at critical interfaces such as where the drive element meets the actuator housing and where the ball screws exit, providing effective contamination protection through simple sealing geometries.
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 design reduces the number of motors needed, resulting in a significant weight savings and improved adaptability for various applications by allowing a single motor to efficiently control two ball screws, while maintaining protection against harsh environments.
Implementation Method 1
The ball nut and ball screw are formed with respective grooves that receive ball elements which reduce the friction between the two components
Implementation Method 2
A linear bearing may be provided between a radially outer surface of the drive element and a radially inner surface of the shield element
Data Source
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AI summary
A linear actuator (2) comprises an actuator housing (4) defining a bore (28). A drive element (8) is received in the actuator housing bore (28). The drive element (8) comprises tubular portions (42) receiving first and second ball nuts (12) arranged at respective distal ends (60) thereof. The ball nuts (12) are threaded in opposite directions to one another. The drive element (8) further comprises a drive coupling (44). The actuator (2) further comprises first and second ball screws (14) operatively engaged with the first and second ball nuts (12). Rotation of the drive element (8) and thus the ball nuts (12) relative to said ball screws (14) causes the ball screws (14) to move together in a linear path in opposite directions from one another.