Ball Screw Bypass Assembly for High Static Load Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ball screws in applications like Thrust Reverser Actuation Systems require high static load capacity for rare failure forces, leading to the use of expensive hard materials for normal operating conditions, increasing costs and design complexity.
Innovation Solution
A ball screw assembly with a bypass function that allows loads exceeding a predetermined threshold to bypass the ball track, enabling the use of less hard and less expensive materials by incorporating a preloading system between the nut cartridge and actuator, reducing the need for high hardness in the ball screw tracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ball screw tracks are made of hard material to achieve high static load capacity for failure forces, then the ball screw can handle high forces in failure events, but the production cost increases significantly
Solution Approach 1:
The ball screw assembly dynamically switches between two load transmission paths: during normal operation, loads are transmitted through the ball track; during failure events exceeding the threshold, loads bypass the ball track through the bypass mechanism. This dynamic adaptation allows the ball track to be made of less expensive materials while still handling extreme loads through the bypass path.
Solution Approach 2:
The bypass mechanism acts as an intermediary load path that activates when forces exceed the predetermined threshold. This intermediary structure protects the ball track from excessive loads during failure events, allowing the ball track material to be optimized for normal operating conditions rather than worst-case scenarios.
2Strength
If ball screw tracks are made of hard material to achieve high static load capacity, then the ball screw can withstand high failure forces, but material wear increases
Solution Approach 1:
The bypass mechanism serves as a protective intermediary that intercepts excessive loads before they can cause wear damage to the ball track. By diverting failure-level forces away from the ball track, the bypass mechanism significantly reduces wear on the ball track components during abnormal operating conditions.
Solution Approach 2:
The bypass mechanism is pre-configured to activate before excessive forces can cause damage to the ball track. The preloading system establishes a threshold that, when exceeded, automatically engages the bypass path to cushion and protect the ball track from wear-causing extreme loads.
3Reliability
If ball screw assembly is designed for high static load capacity to handle failure forces, then safety is improved, but the design complexity increases
Solution Approach 1:
The load transmission function is segmented into two distinct paths: the primary ball track for normal operation and the bypass mechanism for failure events. This segmentation allows each component to be optimized for its specific function, with the ball track designed for normal loads and the bypass designed specifically for handling extreme loads, thereby managing overall design complexity through functional division.
Solution Approach 2:
The design incorporates dynamic load path selection that automatically activates the bypass mechanism when needed. This dynamic behavior provides safety without requiring complex control systems, as the load redistribution is achieved through mechanical design of the bypass path and preloading system.
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 production costs, minimizes wear, and allows for a targeted life margin of safety, enabling the use of less expensive materials while maintaining adequate performance for normal operating conditions.
Implementation Method 1
The ball screw assembly (10) includes a preloading system arranged to apply a preload to the nut cartridge (2')
Implementation Method 2
arranged such that when a load applied to the ball screw assembly exceeds a predetermined threshold, part of the load applied to the ball screw assembly bypasses the ball track (3, 3') and is transmitted directly from the screw (1) to the nut housing (5)
Data Source
Figure 1A~3
AI summary
A ball screw assembly comprising: a screw shaft (1) along which is formed a first helical groove (3); a nut (2) along which is form a second helical groove (3'); the first helical groove and the second helical groove cooperating to define a track (3, 3'); a plurality of balls (4) arranged in the track and configured to move along the track in response to relative motion between the screw shaft and the nut such that rotational motion of the screw is translated to linear motion of the nut via the balls and vice versa; and further comprising: a bypass shoe (7) arranged between the nut and the track and spaced from the track by a predetermined preload X, wherein when a load applied to the nut exceeds the predetermined preload, the bypass shoe engages with the track such that motion of the screw is transferred to motion of the nut via the shoe and bypasses the balls.