Pyrotechnical Interface Undercuts via Injection Molding

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Solution Overview

Problem

The existing manufacturing processes for pyrotechnical connecting interfaces are complex and cost-intensive due to the difficulty in producing radially circumferential undercuts using single injection molding, which are necessary for a water-tight and cost-efficient interface.

Innovation Solution

A pyrotechnical connecting interface with a housing having three radially spaced undercuts produced by injection molding, where the pins are embedded within the housing, and a manufacturing process using angular ejectors in the injection molding tool to create axially and radially closed undercuts, allowing for a single injection molding process and cost-effective production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a radially circumferential continuous undercut is formed in the socket, then water-tight coupling and reliable engagement with latching fingers are achieved, but manufacturing complexity and cost increase due to inability to use single injection molding process

Engineering Contradiction:

Improvewater-tight couplingVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The continuous radially circumferential undercut is segmented into multiple discrete undercuts (first, second, and third undercuts) spaced around the peripheral wall. This segmentation allows each undercut to be independently formed by separate injection molding operations, enabling the use of a single injection molding process while maintaining the water-tight coupling and reliable engagement functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The injection molding process is designed to form the undercuts as integral features of the housing during the molding operation itself, rather than requiring subsequent machining operations. The mold includes features that create the undercuts in the plastic material as it is injected, eliminating the need for post-molding material removal and simplifying the manufacturing process.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If material-abrading machining is used to create radially circumferential undercut, then the undercut geometry is achieved, but manufacturing cost and complexity increase

Engineering Contradiction:

Improveundercut geometry precisionVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The mechanical material-abrading machining process is replaced with an injection molding process that forms the undercut geometry by injecting molten plastic material into a mold cavity with the desired geometry. This substitution eliminates the need for subsequent machining operations, reducing manufacturing cost and complexity while maintaining precise undercut geometry through mold design.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If pins are exposed at the end face of the housing, then electrical connection is simplified, but moisture protection and water-tight coupling are compromised

Engineering Contradiction:

Improveelectrical connection simplicityVSAvoidmoisture exposure

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The pins are nested within the housing structure, with pin receiving bores formed in the peripheral wall that extend axially to receive the pins. The pins are positioned inside the housing rather than exposed at the end face, protecting them from moisture while maintaining electrical connection capability through the wall structure.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The peripheral wall with integrated pin receiving bores acts as an intermediary structure that protects the pins from moisture exposure while still allowing electrical connection. The bores provide a protected pathway for the pins to pass through the wall, shielding them from the external environment while maintaining their electrical function.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11296476B2Pyrotechnical connecting interface, pyrotechnical connecting device, and process for manufacturing a pyrotechnical connecting interface

Publication Date: 2022.04.05 ZF AIRBAG GERMANY GMBH

AI summary

A pyrotechnical connecting interface of a pyrotechnical vehicle safety device comprises a socket which includes a housing with a plug-in port for accepting a plug, the pyrotechnical connecting interface further comprising pins which end in the plug-in port and via which electricity for activating a pyrotechnical charge can flow, the housing being an injection-molded housing and being provided with a peripheral wall which surrounds end portions of the pins at a distance therefrom and which ends in an end face on the side facing the plug; three radial undercuts for interlocking engagement with three associated latching fingers that are part of the plug are formed on the inner face of the peripheral wall, are spaced apart from each other in the peripheral direction, are entirely closed axially as well as radially outward, and are made in an injection-molding process.