Pluggable Electrical Module Grounding via Captive Screw Segmentation
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Solution Overview
Problem
Existing pluggable electrical modules face challenges in achieving reliable high-current discharge grounding due to the insulating properties of plastic housings and the unreliability of metal elastic tabs, which can lead to increased grounding resistance or loss of grounding, posing risks to electronic components.
Innovation Solution
A pluggable electrical module design featuring a captive screw with a screw rod having distinct thread segments and a housing through-hole with tapered segments, along with an optional resilient washer and spring, ensures a secure and reliable electrical connection between the module and the chassis by expanding the housing through-hole to engage the screw thread securely and accommodate manufacturing and assembly tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If metal elastic tabs are used for grounding, then the structure is simple, but the grounding reliability is poor due to manufacturing tolerances and elastic deformation
Solution Approach 1:
The captive screw is divided into two functional segments: a first thread segment for fastening and a second thread segment for grounding contact. This segmentation allows each segment to perform its specific function optimally, with the second segment providing reliable electrical contact independent of housing tolerances
Solution Approach 2:
The captive screw serves dual functions: it acts as both a fastening element (securing the module to the chassis) and as a grounding element (providing electrical connection through the metal tab). This multi-functionality eliminates the need for separate grounding cables while ensuring reliable grounding
2Reliability
If grounding cable is used, then grounding reliability is improved, but the operation convenience is reduced due to cumbersome installation and removal
Solution Approach 1:
The grounding function is merged with the fastening function through the captive screw mechanism. As the screw is tightened to secure the module, the second thread segment simultaneously establishes the grounding connection through the metal tab. This integration eliminates separate grounding cable installation while maintaining reliable grounding
Solution Approach 2:
The captive screw automatically establishes the grounding connection as part of the fastening process. The screw structure itself provides the electrical path through the metal tab to the chassis, eliminating the need for separate grounding cable connection by the operator
3Ease of manufacture
If the housing is made of plastic material, then manufacturing cost and weight are reduced, but grounding capability is compromised due to insulating properties
Solution Approach 1:
The metal tab acts as an intermediary element that bridges the insulating plastic housing and the conductive chassis for electrical grounding. The metal tab is electrically connected to the PCB ground and extends through the housing to contact the chassis, providing a reliable grounding path through the non-conductive housing material
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 provides a reliable high-current discharge grounding connection with minimal contact resistance, eliminating the need for separate grounding cables and ensuring the module is always grounded, thus preventing damage to electronic components.
Implementation Method 1
the second thread segment presses the metal tab tightly against the chassis, so that a reliable electrical connection with a contact resistance as small as possible is formed between the printed circuit board and the chassis
Implementation Method 2
When the second thread segment is screwed through the tapered through-hole, the thread of the second thread segment engages the inner wall of the tapered through-hole and forces the tapered through-hole to expand, acting similarly to a tapping screw. After the second thread segment completely passes through the tapered through-hole, the inner wall of the tapered through-hole is restored to its initial position under elastic action and restrains the second thread so that it cannot retreat
Data Source
Figure 1
Figure 2
Figure 3a~3c
AI summary
A pluggable electrical module (100), which comprises a printed circuit board; a housing (120) for enclosing the printed circuit board therein, the housing (120) includes at least one housing (120) through-hole; a captive screw (140) comprising a screw head (141) and a screw rod, the captive screw (140) passes through the housing (120) through-hole; a metal tab (130) fixed to the printed circuit board and including a tab through-hole through which the captive screw (140) passes, and in the assembled configuration of the pluggable electrical module (100), the through-hole and the housing (120) through-hole is coaxial with each other. The screw rod includes at least a first thread segment (142A) and a second thread segment (142B), and is used to fasten the pluggable electrical module (100) to the chassis. After the pluggable electrical module (100) is fastened to the chassis, the first thread segment (142A) passes through the tab through-hole, and the second thread segment (142B) presses the metal tab (130) tightly against the chassis.