Dual-Thread Screw Transmission for Low-Torque Linear Actuation
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Solution Overview
Problem
Existing mechanical transmission systems for aircraft control surfaces, such as spoilers and flaps, face inefficiencies and reliability issues due to high torque and low speed conditions under axial loads, leading to wear and increased weight, and are bulky and heavy, making them unsuitable for aeronautical applications.
Innovation Solution
A compact, lightweight mechanical transmission system utilizing a roto-translational element with different pitched threaded connections between a rotary element and a fixed guide, reducing angular speed and allowing a wide range of reduction ratios without additional gear mechanisms, thereby minimizing torque requirements and enhancing efficiency and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a reduction system with gear box or epicyclic gear mechanisms is used to reduce motor load, then the torque required of the motor is reduced, but the transmission system becomes bulky and heavy
Solution Approach 1:
The patent combines the functions of motion reversal and speed reduction into a single integrated mechanism. The roto-translational element with dual threaded portions performs both the function of reversing motor rotation and providing speed reduction, eliminating the need for separate gear mechanisms and thereby reducing the weight and bulk of the transmission system.
Solution Approach 2:
The roto-translational element serves multiple functions simultaneously: it acts as a motion reverser, a speed reducer, and a motion converter (rotational to linear). This multi-functionality eliminates the need for multiple separate components, achieving weight reduction while maintaining the required torque reduction capability.
2Force
If gear train transmission is used to reduce motor load, then the torque required of the motor is reduced, but the efficiency decreases especially at low temperatures
Solution Approach 1:
The patent replaces traditional gear-based mechanical transmission with a screw-thread-based mechanical advantage system. The screw threads provide torque reduction through mechanical advantage without the sliding friction and efficiency losses characteristic of gear trains, particularly at low temperatures where lubrication effectiveness decreases.
3Force
If gear train transmission is used to reduce motor load, then the torque required of the motor is reduced, but the backlash increases
Solution Approach 1:
The patent combines motion reversal and speed reduction into a single integrated screw-thread mechanism, eliminating the multiple gear meshing interfaces that create cumulative backlash. The direct screw-thread engagement provides more precise motion transmission with reduced clearance.
4Device complexity
If direct-drive with nut screw is used, then the structure is simple, but the motor operates in low efficiency conditions with large torque and low speed
Solution Approach 1:
The patent integrates speed reduction functionality directly into the roto-translational element with dual threaded portions, combining what would traditionally be separate components into one unified structure. This maintains simplicity while enabling the motor to operate at higher speeds with reduced torque requirements, improving efficiency.
5Force
If epicyclic gear mechanisms are used to reduce motor load, then the torque required of the motor is reduced, but the device becomes expensive and technically complex
Solution Approach 1:
The patent consolidates the functions of motion reversal and speed reduction into a single roto-translational element with dual threaded portions, replacing complex epicyclic gear mechanisms with a simpler, more cost-effective integrated design that achieves the same functional outcomes.
6Force
If recirculating ball screw is used to support high axial loads, then the load capacity is increased, but the pitch of the screw must be increased which reduces motor speed
Solution Approach 1:
The patent segments the screw thread into two distinct portions with different pitches: a first threaded portion with a larger pitch for supporting axial loads, and a second threaded portion with a smaller pitch for speed reduction. This segmentation allows the system to handle high loads while maintaining smaller overall pitch dimensions, thereby preserving motor speed.
Solution Approach 2:
Different sections of the screw mechanism have different local properties: the first threaded portion is designed with larger pitch for load bearing, while the second threaded portion has smaller pitch for speed control. This local differentiation allows optimization of each function independently without compromising the other.
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 achieves a wide range of reduction ratios, reduces torque requirements, increases motor speed, and extends the life of the actuator by distributing load, resulting in a more efficient, reliable, and compact transmission system suitable for aeronautical applications.
Implementation Method 1
a first threaded portion (3) and a second threaded portion (4)... The mechanical transmission also comprises a rotary element (5)... equipped with a first thread (8) designed to engage rotatably with the first threaded portion (3)... a second thread (14) which is able to engage with the second threaded portion (4)
Data Source
AI summary
Described is a mechanical transmission (T) comprising a containment structure (1) housing a roto-translational element (2), extending along an axis of rotation (X) and comprising a first and a second threaded portion (3, 4), a rotary element (5) connected or connectable to a drive unit to define a mechanical power input unit and equipped with a first thread (8) designed to engage rotatably with the first threaded portion (3) to the roto-translational element in such a way as to define a first threaded connection, a fixed guide (9) having a second thread (14) designed to engage with the second threaded portion (4) of the roto-translational element (2) in such a way as to define a second threaded connection, and a translating element (10), translating along the axis (X) and defining a power output unit. The translating element (10) is connected to the roto-translational element (2) for translating at the same linear speed as the roto-translational element (2). The roto-translational element (2) is thus simultaneously coupled to the rotary element (5) and to the fixed guide (9) respectively by means of the first and second threaded connections. These connections have different pitches in such a way as to vary the angular speed between the roto-translational element (2) and the rotary element (5).