Sleeve Shaft Clamping Fixture for Thermal Expansion
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Solution Overview
Problem
Conventional metal holding fixtures in the Danner process experience increased frictional resistance due to thermal expansion, leading to weakened clamping force and deviations in coaxiality, which hinders the production of high-quality glass tubes or rods with consistent dimensional accuracy.
Innovation Solution
A sleeve design with a metal holding fixture featuring a reduced area of contact between its inner circumferential surface and the sleeve shaft, utilizing an annular undercut or multiple undercuts to minimize frictional resistance and ensure smooth sliding, even during thermal expansion, thereby maintaining the clamping force and coaxiality of the metal tip, refractory tube, and fixture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inner circumferential surface of the metal holding fixture is in close contact with the outer circumferential surface of the sleeve shaft over the whole region, then the metal holding fixture can be firmly held, but the frictional resistance increases when the sleeve shaft undergoes thermal expansion
Solution Approach 1:
The inner circumferential surface of the metal holding fixture is divided into multiple contact regions separated by non-contact regions (undercuts). This segmentation allows the fixture to maintain firm holding through distributed contact points while reducing overall frictional resistance during thermal expansion sliding.
Solution Approach 2:
Different regions of the inner circumferential surface are given different properties: contact regions provide firm holding through close contact, while non-contact regions (undercuts) provide reduced friction zones. This local differentiation resolves the contradiction between firm holding and low friction.
2Reliability
If the metal holding fixture slides smoothly along the axial direction during thermal expansion, then the clamping force is maintained, but the manufacturing complexity increases due to the need for undercuts
Solution Approach 1:
The inner circumferential surface is segmented into contact and non-contact regions using undercuts. While this adds some structural complexity, it ensures smooth sliding during thermal expansion and maintains reliable clamping force, making the added complexity worthwhile for performance.
Solution Approach 2:
The geometry of the inner circumferential surface is modified by introducing undercuts that change the contact parameters between the fixture and sleeve shaft. This geometric parameter change enables smooth sliding while maintaining firm holding, balancing complexity and performance.
3Temperature
If the distance between the metal tip and metal holding fixture increases due to thermal expansion, then the sleeve shaft expands freely, but the clamping force weakens and coaxiality deviations occur
Solution Approach 1:
The metal holding fixture is designed to slide dynamically along the axial direction during thermal expansion, maintaining constant contact with the metal tip through the urging force of the urging member. This dynamic adjustment prevents distance increase and maintains both clamping force and coaxiality during temperature changes.
Solution Approach 2:
The urging member (spring) provides continuous feedback force that pushes the metal holding fixture toward the metal tip, compensating for any distance increase due to thermal expansion. This feedback mechanism ensures constant clamping force and maintains coaxiality despite temperature variations.
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 reduced frictional resistance allows for continuous formation of high-quality glass tubes or rods with high dimensional accuracy by preventing the weakening of the clamping force and ensuring coaxiality, even with thermal expansion of the sleeve shaft.
Implementation Method 1
the area of contact between the inner circumferential surface of the metal holding fixture and the outer circumferential surface of the sleeve shaft is large, resulting in increase in frictional resistance between the metal holding fixture and the sleeve shaft when the metal holding fixture slides
Implementation Method 2
The temperature of the molten glass guided onto the sleeve is as high as about 1,000[° C.] or more, and the sleeve undergoes thermal expansion as a whole. At this time, the amount of thermal expansion of the sleeve shaft in the axis direction is large
Data Source
AI summary
Provided is a sleeve for glass tube molding, the sleeve being capable of: preventing the weakening of clamping force between a metal tip and a metal holding fixture even if the distance between the metal tip and the metal holding fixture increases due to the thermal expansion of a sleeve shaft; and ensuring the coaxiality, on the sleeve shaft, of the metal tip, the metal holding fixture and a refractory tube. This sleeve for glass tube molding comprises: a sleeve shaft; a refractory tube into which the sleeve shaft is inserted in a coaxial manner; a metal tip which is at one end of the refractory tube, and is fixed to the tip of the sleeve shaft; and a metal holding fixture which, at the other end of the refractory tube, is slidably inserted in the sleeve shaft, and clamps and holds the sleeve shaft together with the metal tip. A part of the inner circumferential surface of a through-hole, which is in the metal holding fixture and through which the sleeve shaft is inserted, is in close contact with the outer circumferential surface of the sleeve shaft.