Thermal Flow Meter Sealing with Resin Ferrules
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Solution Overview
Problem
Thermal flow meters face challenges in securely fixing the end portions of tubular measurement tubes with small diameters to prevent liquid leakage, especially when measuring small flow rates.
Innovation Solution
A thermal flow meter design that includes a measurement tube with a temperature detecting substrate bonded to it, using inlet and outlet-side bodies with nuts and ferrules to create seal areas, and fillers to securely fix the temperature detecting substrate, ensuring no liquid leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a tubular measurement tube with a straight tube portion is used to measure small flow rates, then measurement precision and flow rectification are improved, but securing the end portions and preventing liquid leakage becomes difficult
Solution Approach 1:
The connection structure is divided into separate components: a connection body, a nut, and a ferrule. The ferrule is inserted into the connection body, and the nut is threaded onto the connection body to secure the measurement tube. This segmentation allows each component to perform its specific function - the ferrule provides sealing, the nut provides clamping force, and the connection body provides structural support - thereby reliably preventing liquid leakage while maintaining measurement precision.
Solution Approach 2:
The ferrule acts as an intermediary component between the measurement tube and the connection body. It is inserted into the connection body and secured by the nut, creating a reliable sealing interface. The ferrule mediates the connection between the small-diameter measurement tube and the larger connection body, enabling secure fixation and leakage prevention without compromising the measurement tube's dimensional integrity.
2Measurement precision
If the measurement tube has a small diameter to improve measurement accuracy, then measurement precision is improved, but the ease of securing and assembling the tube decreases
Solution Approach 1:
The measurement tube is inserted into the connection body, and the ferrule is nested within the connection body to secure the measurement tube. The nut is then threaded onto the connection body to clamp the ferrule and measurement tube assembly. This nested structure allows the small-diameter measurement tube to be securely fixed within the larger connection body, maintaining measurement precision while simplifying assembly through a standardized threaded connection mechanism.
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 design effectively secures both end portions of the measurement tube, preventing liquid leakage and enhancing the adhesiveness of the temperature detecting substrate while maintaining measurement accuracy across temperature changes.
Implementation Method 1
a heating resistance element and a temperature detecting resistance element formed on a detection surface
Implementation Method 2
the inlet-side ferrule being deformed to form a seal area as the inlet-side nut is fastened to the inlet-side body, and an outlet-side ferrule of resin formed in a cylindrical shape and fitted between the outer circumferential surface of the measurement tube and an inner circumferential surface of an end portion of the outlet-side body facing the inlet, the outlet-side ferrule being deformed to form a seal area
Data Source
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AI summary
Provided is a thermal flow meter including an inlet-side body 16 into which an inlet 11a of a measurement tube 11 is inserted, an outlet-side body 17 into which an outlet 11b of the measurement tube 11 is inserted, an inlet-side nut 15a having internal threads 15g fastened to external threads 16b formed on the inlet-side body 16, an outlet-side nut 15b having internal threads 15h fastened to external threads 17b formed on the outlet-side body 17, an inlet-side ferrule 18 of resin being deformed to form a seal area as the inlet-side nut 15a is fastened to the inlet-side body 16, and an outlet-side ferrule 19 of resin being deformed to form a seal area as the outlet-side nut 15b is fastened to the outlet-side body 17. The end portions of a temperature detecting substrate 12 are fixed to the inlet-side nut 15a and to the outlet-side nut 15b by a filler charged in a first recess 15e on the end portion of the inlet-side nut 15a facing the outlet 11b and in a second recess 15f on the end portion of the outlet-side nut 15b facing the inlet 11a. The temperature detecting substrate 12 and the measurement tube 11 are preferably made of glass and bonded together with an adhesive.