Explosion-Safe Cable Pass-Through for Low-Force-Shunt Weighing
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Solution Overview
Problem
Existing force measuring apparatuses, such as weighing apparatuses, face challenges in achieving explosion-proof designs for current transmission systems, which are costly and require extensive structural modifications to prevent ignition and explosion risks in hazardous environments.
Innovation Solution
A current transmission device with a pressure-resistant housing and a connecting element that passes through the housing wall in an ignition-safe manner, using a moveable cable pass-through with a recess for the cable and a flexible electric contact bridge to minimize force shunt and prevent ignition, allowing the device to be modular and cost-effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire housing is filled with protective gas atmosphere or designed with pressure-resistant housing to prevent explosion, then explosion protection is improved, but structural complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent extracts the explosion protection function from the entire housing system and concentrates it into a localized current transmission device with pressure-resistant housing. This allows the main weighing apparatus housing to remain simple and open, while only the critical current transmission component provides explosion containment and protective gas atmosphere.
Solution Approach 2:
The system is divided into two functional parts: a simple open housing for the weighing apparatus and a segmented pressure-resistant current transmission device. This segmentation allows explosion protection to be applied only where electrical currents are transmitted through the housing wall, rather than requiring the entire housing to be pressure-resistant.
2Reliability
If a tight seal or small gap with labyrinth seal is provided at the passage opening to prevent gas dilution, then explosion protection is improved, but force shunt increases and measurement precision deteriorates
Solution Approach 1:
The patent introduces a bellows as an intermediary flexible sealing element between the load receptor and the passage opening. The bellows provides a tight seal that prevents gas dilution while being sufficiently flexible to transmit force with minimal shunt, thus maintaining both explosion protection and measurement precision.
Solution Approach 2:
The bellows is implemented as a flexible membrane structure that seals the passage opening while allowing force transmission. The flexible nature of the bellows enables it to maintain tight sealing without creating rigid mechanical constraints that would increase force shunt and degrade measurement accuracy.
3Reliability
If the housing is designed to withstand explosion pressure and prevent projectile formation, then explosion protection is improved, but manufacturing cost and structural complexity increase
Solution Approach 1:
The explosion resistance function is extracted from the main housing and implemented in a separate, smaller current transmission device. This localized approach requires pressure-resistant construction only for the current transmission housing, significantly reducing the total volume of pressure-resistant material needed and lowering manufacturing costs.
Solution Approach 2:
Instead of designing a completely new pressure-resistant housing for the entire weighing apparatus, the patent uses a standardized pressure-resistant current transmission device housing that can be integrated into the existing weighing apparatus. This modular approach reduces manufacturing complexity and cost by reusing proven pressure-resistant design elements.
4Reliability
If passage openings are dimensioned with small cross-section and sufficient length to cool exiting gas, then explosion protection is improved, but the design complexity and manufacturing precision requirements increase
Solution Approach 1:
The patent introduces a bellows as an intermediary element that provides both sealing and cooling functions. The bellows structure creates a long, narrow passage that cools exiting gas through extended surface area and length, while the sealing function is provided by the bellows membrane itself, separating these two functions and reducing the precision requirements for the passage opening dimensions.
Data Source
AI summary
The invention relates to current transmission device for a force measuring apparatus, in particular a weighing apparatus, wherein the force measuring apparatus (100) has a housing (102) and a base region as well as a moveable region. The current transmission device has a pressure-resistant housing (202), which can be fixedly connected mechanically to the base region of the force measuring apparatus (100), and a connecting element (216), which, at an outer end region that protrudes from the housing (202), can be fixedly connected mechanically to the moveable region of the force measuring apparatus (100) in an operating state. In an operating state, the connecting element (216) passes through the housing wall (208) in a contactless and ignition-safe manner. The connecting element (216) is embodied as a moveable cable pass-through and directs a first cable (220) into the interior of the housing. A housing-affixed cable feedthrough (206) directs a second cable into the interior of housing. An electrical connection that has a low force shunt is provided in the housing for the two cables. The current transmission device (200) is embodied in such a way that it can be mounted in a housing (102) or externally on a housing (102) of the force measuring apparatus (100). In addition, the invention relates to a force measuring apparatus (100) having such a current transmission device (200).