Surge Arrestor Module Bladder Compaction for Void-Free Curing
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Solution Overview
Problem
Existing methods for manufacturing surge arrestors using shrink film to compact fiberglass and epoxy resin are limited by fixed compaction levels and leave surface imperfections, requiring additional smoothing operations.
Innovation Solution
A method involving a flexible bladder and controlled pressure application during the curing process to eliminate air gaps and ensure consistent surface quality, using a flexible bladder to apply both radial and axial compressive forces to the epoxy-fiberglass layer around the MOV blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shrink film is used to compact fiberglass and epoxy resin during curing, then compaction force is applied to eliminate air voids, but the compaction level is fixed and cannot be varied, and surface impressions are left requiring additional smoothing operations
Solution Approach 1:
The patent replaces the static shrink film with a dynamic bladder system that can be inflated to varying degrees. The bladder is inserted into the mold cavity and inflated with air or fluid through a valve, allowing the compaction force to be adjusted and controlled during the curing process. This enables variable compaction levels to be applied according to specific manufacturing requirements, resolving the contradiction between fixed compaction and the need for adaptability.
2Reliability
If shrink film is used to compact fiberglass and epoxy resin, then air voids are eliminated, but surface impressions are created that require additional smoothing operations
Solution Approach 1:
The patent uses a flexible bladder as an intermediary compaction element that conforms to the mold cavity shape. Unlike rigid shrink film that leaves impressions, the bladder's flexible nature allows it to distribute pressure evenly and be removed without leaving surface marks. The bladder is designed to be smooth on the inside surface to prevent impressions, and can be deflated and removed cleanly after curing, eliminating the need for additional smoothing operations while maintaining reliable void elimination.
3Strength
If multiple layers of pre-impregnated fiberglass are wrapped around MOV blocks, then desired wall thickness and strength are achieved, but air voids between layers increase requiring higher compaction force
Solution Approach 1:
The patent employs pneumatic or hydraulic inflation of the bladder to apply uniform compaction pressure on all sides of the stacked MOV blocks and fiberglass layers. This multi-directional pressure effectively eliminates air voids between multiple fiberglass layers without requiring excessive force in any single direction. The gradual inflation process allows air to be progressively displaced, ensuring complete void elimination while maintaining the structural integrity and strength of the multi-layer fiberglass construction.
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
The method achieves consistent surface quality without the need for post-curing smoothing, reduces air voids, and allows variable compaction forces, resulting in a more reliable and efficient surge arrestor production process.
Implementation Method 1
applying pressure to the flexible bladder to generate a compressive force to the epoxy-fiberglass layer and the stack
Data Source
AI summary
The present disclosure is directed to a method of producing a surge arrestor module, comprising the acts of (i) providing a plurality of MOV blocks arranged in a stack, (ii) applying an epoxy-reinforced structural layer to an outer surface of the stack, (iii) after the applying, inserting the stack into a flexible bladder, and (iv) curing the epoxy-reinforced structural layer with elevated temperatures while the flexible bladder applies radially aligned pressure to the stack and a tool applies axially aligned pressure to the stack. The present disclosure also includes an apparatus for performing the methods described herein. The apparatus includes an outer case structure and a flexible bladder that fits within the outer case structure. A hollow inner region of the outer case structure is pressurized to force the flexible bladder against the surge arrestor module as the surge arrestor module is curing.