Servovalve Filter Retaining Plug With Tool-Engaging Recesses
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Solution Overview
Problem
Servovalves in aircraft control systems face difficulties in removing and replacing filter screens due to press-fitted plugs, which can cause damage to the servovalve body, necessitating costly repairs.
Innovation Solution
A plug with a radially extending recess and a removal tool featuring offset plug gripping portions with outwardly projecting teeth facilitate easy removal of the plug from the servovalve port, allowing for the replacement of filter screens without damaging the servovalve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a press-fitted plug is used to retain the filter screen, then the filter screen is securely retained in the port, but the plug becomes difficult to remove and may cause damage to the servovalve body
Solution Approach 1:
The plug is segmented by providing recesses in its outer surface, which allow a removal tool to engage with the plug. This segmentation enables the plug to be securely retained during normal operation while allowing for controlled removal when needed, resolving the contradiction between secure retention and ease of removal.
Solution Approach 2:
A removal tool acts as an intermediary between the operator and the plug. The tool engages with the recesses in the plug and uses lever arm action to facilitate removal without directly applying force that could damage the servovalve body. This intermediary mechanism enables easy removal while protecting the servovalve.
2Reliability
If the filter screen is retained by a press-fitted plug, then the filter screen is securely held in place, but removal and replacement of the filter screen becomes difficult and time-consuming
Solution Approach 1:
The plug's outer surface is segmented with recesses that enable tool engagement. This segmentation allows for quick and easy removal of the plug and filter screen assembly, significantly reducing maintenance time while maintaining secure retention during normal operation.
Solution Approach 2:
The recesses are pre-formed in the plug during manufacturing, preparing the plug for future removal operations. This preliminary action ensures that when maintenance is needed, the plug can be quickly removed without requiring complex procedures or excessive time.
3Device complexity
If a standard press-fitted plug is used, then the structure is simple, but the removal process may cause damage to the servovalve body requiring costly repairs
Solution Approach 1:
The plug structure is mildly complexified by adding recesses to the outer surface. This added complexity is minimal but enables tool engagement, allowing for controlled removal that prevents damage to the servovalve body, thus resolving the contradiction between structural simplicity and harm prevention.
Solution Approach 2:
The removal tool serves as an intermediary that mediates between the operator and the plug-servovalve interface. It distributes forces evenly and prevents concentrated loads that could damage the servovalve body, enabling safe removal while maintaining structural simplicity of the overall system.
Data Source
Figure 1~2
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Figure 5
AI summary
A plug (20) for retaining a filter screen (20) in a fluid port (10) of a servovalve (2), comprises an annular body (22), the annular body (22) comprising: opposed first and second axial end surfaces (24, 26), a radially inner surface (28) extending between the first and second axial end surfaces (24, 26), a radially outer surface (30) extending between the first and second axial end surfaces (24, 26) and at least one recess (36) formed in the radially inner surface (28) for receiving a tool (50) for removing the plug (20) from the port (10). A tool (50) for removing the plug (20) comprises a pair of handles (52a, 52b) pivotally mounted to one another about a pivot (54), each handle (52a, 52b) having a plug gripping portion (56a, 56b) extending therefrom beyond the pivot (54), each plug gripping portion (56a, 56b) comprising an outwardly projecting tooth (58a, 58b) for engaging in the recess (36) of the plug (20) when the plug gripping portions (56a, 56b) are moved apart by operation of the handles (52a, 52b).