Ball Screw Tabs for EMA Housing Retention
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Solution Overview
Problem
Conventional electromechanical actuators (EMAs) with ball screws require additional retaining structures like snap rings, which add weight, are prone to failure, and complicate assembly, while also increasing costs.
Innovation Solution
The EMA design incorporates a ball screw with three tabs extending from its inner surface, allowing the ADU housing to be retained without a snap ring, using a gear train assembly with a carrier plate and receptacles for ball bearings to maintain axial retention and facilitate assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a snap ring is used to retain the ADU housing in conventional EMAs, then the housing is retained, but the weight increases and the device becomes more complex
Solution Approach 1:
The snap ring is completely removed from the EMA design. The ADU housing retention function is transferred to an integrated retention feature formed directly on the ball screw, eliminating the separate retaining component and reducing overall weight.
Solution Approach 2:
The retention function is merged into the ball screw structure itself through the formation of a retention feature (such as a tab or protrusion) that directly engages with the ADU housing, combining the screw's fastening function with the housing retention function.
2Reliability
If a snap ring is used to retain the ADU housing, then the housing is retained, but the device complexity increases and assembly is complicated
Solution Approach 1:
The snap ring and its associated installation tools, positioning features, and assembly steps are completely removed. The retention feature is formed as an integral part of the ball screw, simplifying the overall device structure and assembly process.
Solution Approach 2:
The retention function is merged into the ball screw structure itself through the formation of a retention feature (such as a tab or protrusion) that directly engages with the ADU housing, combining the screw's fastening function with the housing retention function.
3Reliability
If a snap ring is used to retain the ADU housing, then the housing is retained, but the cost increases
Solution Approach 1:
The snap ring component and its associated inventory, storage, and handling requirements are completely removed. The retention feature is formed as an integral part of the ball screw during manufacturing, eliminating the need for separate retaining components.
Solution Approach 2:
The retention function is merged into the ball screw structure itself through the formation of a retention feature (such as a tab or protrusion) that directly engages with the ADU housing, combining the screw's fastening function with the housing retention function.
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 eliminates the need for separate retaining structures, resulting in a lighter, more durable, and cost-effective EMA with reduced assembly complexity and potential for failure points.
Implementation Method 1
the ball screw may be rotated to translate a ball nut situated concentrically (i.e., coaxially or substantially coaxially) over the ball screw
Implementation Method 2
An inner surface of the ball screw may be threaded to mate with a threaded portion of an outer surface of the ADU housing
Implementation Method 3
The ball bearings may be received by the at least one receptacle through a slot formed in the ball screw
Data Source
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AI summary
An electromechanical actuator ("EMA") may comprise a ball screw (204) having at least one tab (208) extending from an inner surface thereof and/or an actuator drive unit ("ADU") housing (202) that interfaces with the at least one tab (208). The ball screw (204) may include three tabs (208a, 208b, 208c) extending from the inner surface thereof. An outer surface of the ball screw (204) may be threaded to mate with a threaded portion of an inner surface of the ADU housing (202), and/or the ADU housing (202) may interface with the at least one tab (208), and the ball screw (204) may be rotated to translate a ball nut (206) situated concentrically over ball screw (204) axially. The ADU housing (202) may include a gear train assembly (102) having a carrier plate (104), wherein the carrier plate (104) includes at least one receptacle (106).