Linear Actuator Rod-Screw Connection Preventing Spontaneous Disconnection
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Solution Overview
Problem
Existing linear electromechanical actuators (EMAs) with roller screw drives face issues of spontaneous disconnection due to vibration, torque, and axial forces, leading to reduced manufacturability and working life, as well as increased production line downtime.
Innovation Solution
The EMA design features a connecting section with embedded teeth on the RSD screw and a tapered opening in the rod, along with a retainer system, to prevent relative rotation and longitudinal movement, ensuring a gapless connection and improved load distribution, thus eliminating spontaneous disconnection and enhancing manufacturability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the RSD screw and rod are connected by a threaded connection, then the assembly is simple and manufacturable, but the connection is prone to spontaneous disconnection under vibration and torque
Solution Approach 1:
The connection is divided into two functional parts: a threaded connection for simple assembly and a separate retainer component for preventing disconnection. This segmentation allows each part to perform its specific function optimally while maintaining overall manufacturability and reliability.
Solution Approach 2:
The retainer acts as an intermediary element between the RSD screw and rod, providing additional security against spontaneous disconnection without interfering with the threaded connection's assembly simplicity. The retainer mediates the conflicting requirements by adding reliability without significantly complicating manufacturing.
2Strength
If through hardening is applied to the rod to increase hardness, then cyclic load resistance is improved, but machining speed decreases and tool wear increases
Solution Approach 1:
Instead of through hardening the entire rod, the invention applies local quality enhancement only at the critical connecting section where the RSD screw attaches to the rod. This localized hardening provides the necessary cyclic load resistance at the connection point while leaving the rest of the rod soft enough for efficient machining.
Solution Approach 2:
The connecting section is pre-hardened before the final assembly, allowing the rod to be machined efficiently first, then selectively hardened at the connection point. This preliminary action sequence optimizes both machining productivity and subsequent connection durability.
3Adaptability or versatility
If the RSD screw and rod are manufactured as separate parts, then adaptability for various rod strokes is improved, but the complexity of ensuring reliable connection increases
Solution Approach 1:
The retainer is designed as a universal component that can be used with RSD screws and rods of various lengths and configurations. This multi-functional retainer maintains reliable connection across different rod stroke applications without requiring design modifications, thus managing complexity while preserving adaptability.
4Ease of operation
If a threaded connection is used between RSD screw and rod, then assembly is simplified, but the connection is susceptible to self-unscrewing under axial forces and vibration
Solution Approach 1:
The connection system is segmented into the threaded connection for assembly and the retainer for stability. This segmentation maintains assembly simplicity while adding a dedicated component for preventing self-unscrewing under axial forces and vibration.
Solution Approach 2:
The retainer is installed in advance to counteract the harmful effects of vibration and axial forces before they can cause self-unscrewing. This preliminary anti-action prevents the problematic effect without complicating the assembly process.
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 significantly increases the working life and manufacturability of the EMA, allowing for higher force generation and reduced production line downtime by preventing self-unscrewing and improving the uniformity of load distribution.
Implementation Method 1
a connecting section with a plurality of teeth which are embedded (depressed) into the surface of the opening in the rod and cause plastic deformation of the surface
Data Source
Figure 1
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Figure 4
AI summary
Disclosed is a linear electromechanical actuator comprising a housing, an electric motor, an output member and a roller screw drive arranged within the housing. The roller screw drive comprises a rod and a screw, wherein the rod being connected to the screw to form the output member. The rod has an axial opening at the end proximal to the screw, and the screw comprises a connecting section at the end proximal to the rod with a plurality of longitudinal teeth arranged along the perimeter of the connecting section and embedded into the surface of the axial opening. The actuator further comprises a retainer engaged with the rod and the screw and configured for preventing relative longitudinal movement thereof. Further disclosed are methods for assembling the output element of the claimed actuator. The proposed invention allows to eliminate the possibility of spontaneous disconnection of the rod and the screw of the roller screw drive under the effects of vibration, torque and axial force, and to improve manufacturability of the electromechanical actuator.