Valve Lockout Screw Retention Against Vibration Loosening
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Solution Overview
Problem
Existing valve assemblies in turbine engines, particularly those used in aircraft, face issues with locking mechanisms that can be loosened or damaged due to vibration, leading to unreliable control of bleed air flow, as manual locking fasteners can be liberated or detached from their positions.
Innovation Solution
A valve assembly with a lockout mechanism that utilizes self-stored lockout screws with threaded engagement and tapered necks, which are retained within receivers, providing secure positioning and resistance to vibration-induced disengagement, ensuring the valve remains locked in desired positions without the need for external tethers or specialized tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual locking fasteners are used in valve assemblies, then the valve can be locked in desired positions, but the fasteners can be loosened or damaged due to vibration, leading to unreliable control
Solution Approach 1:
The lockout screw is nested within a receiver cavity in the actuator, with only the head portion extending through an opening. This nesting configuration prevents the screw from being completely removed or misplaced while still allowing it to engage with the valve stem for locking. The receiver acts as a protective container that guides and constrains the lockout screw's movements.
Solution Approach 2:
The lockout screw is pre-positioned within the receiver and aligned with the valve stem before vibration occurs. The threaded engagement between the lockout screw and valve stem is established in advance, creating a pre-loaded locking condition that resists vibration-induced loosening. The spring mechanism is also pre-compressed to provide continuous locking force.
Solution Approach 3:
The receiver serves as an intermediary component between the lockout screw and the external environment. It provides a controlled interface through which the screw can engage the valve stem while preventing direct exposure to vibration and other harmful factors. The receiver's opening acts as a gateway that allows necessary movement while filtering out harmful external influences.
2Productivity
If lockout screws are allowed to move freely between stowed and locked positions, then quick position changes are enabled, but the screws may become misplaced or detached due to vibration
Solution Approach 1:
The lockout screw is nested within a receiver cavity that provides a defined path for movement between stowed and locked positions. The receiver's opening allows the screw to move in and out for positioning while preventing lateral displacement or complete removal. This nested configuration enables quick position changes while maintaining screw retention.
Solution Approach 2:
The receiver acts as an intermediary structure that mediates between the need for free movement (for quick positioning) and the need for secure retention (to prevent misplacement). It provides a controlled environment that allows axial movement while constraining radial displacement, thus resolving the contradiction between productivity and reliability.
3Reliability
If external tethers or specialized tools are used to secure lockout screws, then vibration-induced disengagement is prevented, but device complexity increases
Solution Approach 1:
The receiver and lockout screw are merged into a single integrated component system, eliminating the need for separate tethers or external securing mechanisms. The receiver's cavity and opening are designed to work in conjunction with the screw's head and shaft, creating a self-contained locking system that is both reliable and simple.
Solution Approach 2:
The receiver serves multiple functions simultaneously: it houses the lockout screw, guides its movement between positions, prevents misplacement, and provides the interface for tool engagement. This multi-functionality eliminates the need for additional specialized components, reducing overall device complexity while maintaining reliability.
Data Source
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AI summary
An assembly for use with a valve having a valve element disposed within a valve body flow passage, the assembly comprising an actuator (130) and a lockout mechanism configured to maintain the position of the actuator in an opened position or a closed position. The lockout mechanism includes a receiver (156), at least one lockout screw (153) contained in the receiver and self-storing therein and a cover (140) disposed over the receiver and comprising an aperture (142), wherein a head (154) of the at least one screw is smaller in width than the aperture and a first set of threads (152) of the at least one lockout screw is wider than the aperture such that the at least one lockout screw is retained within the receiver by the cover.