JP2006225225A - Method for designing dropping nozzle for molten glass, dropping nozzle for molten glass using the method, and apparatus for manufacturing glass gob - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for designing a dropping nozzle capable of forming a glass gob having a required mass, a dropping nozzle formed by using it, and an apparatus for manufacturing a glass gob using it. <P>SOLUTION: The method is for designing a dropping nozzle to prepare a molten glass droplet having a required mass. The shape of a molten glass droplet hanging at the tip of a dropping nozzle is calculated and the minimum diameter of the neck of the droplet shape is calculated so as to satisfy the formula: (the maximum volume of a molten glass droplet capable of hanging at the dropping nozzle)×(the density of the molten glass droplet)=(the required mass). The minimum diameter is used as the diameter of the dropping nozzle. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for designing a dropping nozzle for molten glass for producing a glass lump having a desired mass.

  As a method for producing an optical glass element such as a glass lens, attention has been focused on using a glass lump without subjecting it to precision press molding and polishing it. As a press molding method of such an optical glass element, a molten glass lump whose mass is precisely controlled is directly supplied to a press die and press molded, and the molten glass lump is cooled to a temperature at which the molten glass lump is not deformed. The glass preform is then roughly divided into the reheat press method in which the glass preform is supplied to the press mold and heated to the deformation temperature again to perform press molding. In either press method, the shape of the optical glass element is highly accurate. In order to achieve this, it is necessary to strictly control the mass of the molten glass lump as designed.

  That is, when the mass of the molten glass lump is deviated from the design value, the thickness of the optical glass element changes and the optical characteristics and shape accuracy are not satisfied. For example, if the mass is less than the design value, there is a problem that the pressure applied to the glass block, which is the material to be molded, is insufficient and transfer becomes insufficient, and the optical surface needs to be polished or a predetermined shape cannot be secured. On the other hand, if the mass is too larger than the design value, there is a problem that glass overflows from the mold cavity and post-processing is required. Therefore, in order to manufacture an optical glass element with high accuracy, it is important to provide a molten glass lump having a mass as designed.

  As a typical method for producing a molten glass lump, there is a method (hereinafter referred to as a nozzle dropping method) in which molten glass is dropped from the dropping nozzle of a glass lump producing apparatus having a melting crucible and a dropping nozzle. Although the nozzle dripping method has advantages such as simple manufacturing equipment and high productivity, the range of mass control with a single nozzle is narrow, so the optimum nozzle diameter is selected according to the required mass of the molten glass lump. In the past, the selection of the nozzle diameter had to be determined by experience and trial and error.

  It is known that the relationship of Formula 3 is generally established between the molten glass block and the tip radius R of the dropping nozzle (Patent Document 1). However, even if the nozzle calculated from Equation 3 was used, a molten glass lump with a desired mass M (kg) was not actually obtained, and the nozzle radius calculated with this was only a guide.

Therefore, in the nozzle dripping method, the optimum nozzle diameter must be selected experimentally or empirically, and the dripping nozzles with various nozzle diameters are replaced many times until a glass lump with the mass as designed drops. In addition, there is a problem that a dripping experiment has to be performed in advance, and it takes time and labor to obtain a molten glass lump of a desired mass, and there is also a problem in terms of productivity.
R = ((M · g) / (2 · π · σ)) = 0.16 · M · g / σ Equation 3
Japanese Patent Publication No. 4-32772 (2 pages)

  An object of the present invention is to provide a dripping nozzle design method capable of obtaining a glass mass having a desired mass and a dripping nozzle designed therewith.

  The present invention relates to a dripping nozzle design method for producing a molten glass droplet having a desired mass, and calculates a molten glass droplet shape suspended at the tip of the dripping nozzle, Calculate the minimum diameter of the constricted portion of the droplet shape such that the maximum volume of the molten glass droplets) × (density of the molten glass droplets) = (desired mass), and calculate the minimum diameter as the diameter of the dropping nozzle. A method for designing a dropping nozzle for molten glass is provided.

In the present invention, the desired mass of the molten glass droplet is M (kg), the surface tension of the molten glass is σ (N / m), the acceleration of gravity g (m / s ² ), and the diameter of the dropping nozzle is 2R (m). Then, the design method of the dripping nozzle for molten glass is provided, in which the tip radius R of the dripping nozzle is calculated by Equation 4.
R = c · M · g / σ Equation 4
Where c is a constant and c = 0.20 to 0.29.

  By using the dripping nozzle designed by the design method according to the present invention, the mass of the dripping nozzle with different nozzle diameters can be changed many times or the dripping experiment can be carried out in advance. It is possible to easily produce a molten glass lump in which the above is strictly controlled. Therefore, a high-precision glass lens can be easily and stably manufactured using the glass block controlled to a desired accuracy obtained by the present invention.

  In addition, since it is not necessary to change the nozzle diameter many times in order to determine the nozzle diameter, the production preparation period is short, and the delivery time can be shortened and the production volume can be expected to increase. In addition, since no extra nozzles are prepared, the development cost can be reduced. Further, when manufacturing molten glass lumps having different masses, the selection of nozzles can be easily performed, so that job change is facilitated.

  The present invention relates to a dripping nozzle design method (hereinafter referred to as the present design method) for producing molten glass droplets having a desired mass, and calculates a molten glass droplet shape suspended from the tip of the dripping nozzle. Then, calculate the minimum diameter of the constricted portion of the droplet shape such that (maximum volume of the molten glass droplet that can be suspended by the dropping nozzle) × (density of the molten glass droplet) = (desired mass), The minimum diameter is the diameter of the dropping nozzle. The conceptual diagram of a dripping nozzle and a molten glass droplet is shown in FIG. In FIG. 1, 1 is a molten glass droplet, N is a dropping nozzle, and 2R is a diameter of the dropping nozzle. In the present specification, the nozzle radius and nozzle diameter refer to values at the tip of the dropping nozzle.

The molten glass droplet shape is preferably calculated based on the balance between the liquid pressure of the molten glass at the tip of the dropping nozzle and the surface tension of the molten glass. In this case, the liquid pressure of the molten glass is represented by the resultant force of the liquid pressure due to gravity and the liquid pressure from the upstream of the dropping nozzle. This relationship is shown in FIG. In Figure 2, 1 is the molten glass droplets, N is the dropping nozzle, P _L is the molten glass in the dropping nozzle tip hydraulic, P _G is the hydraulic by gravity, P _N is the hydraulic pressure from the dropping nozzle upstream, the Shown respectively. It is a _P L _{= P} G + _{P N} from FIG, since the balance the fluid pressure _{P L} of the molten glass and the surface tension _{P S} of the molten glass, after _all, a _{P G + P N = P S} .

  In this design method, the calculation for calculating the maximum mass that can be suspended at the tip of the dropping nozzle in the shape of a molten glass droplet is preferably performed using Equation 5.

However, in Equation 5, y and z are variables that determine the interface position of the molten glass droplet shape that is symmetric with respect to the z axis as the target axis. As shown in FIG. 3, the y axis is horizontal and the z axis is vertical. Take in each direction. y (z) is a function representing the shape of the molten glass droplet, and y ′ (z) and y ″ (z) represent a first-order derivative and a second-order derivative with respect to z, respectively. P is the hydraulic pressure (N / m ² ) (P _{N in} FIG. 2) from the upstream of the dropping nozzle at the tip of the molten glass droplet, σ is the surface tension (N / m) of the molten glass, and g is The gravitational acceleration (m / s ² ) and ρ represent the density of molten glass, respectively.

The calculation procedure gives an arbitrary P, derives the relationship between y (> 0) and z (> 0) for which Equation 5 is established, and when drawn on an axis object, a molten glass droplet shape as shown in FIG. Calculated. In FIG. 3, reference numeral 11 denotes a virtual molten glass droplet obtained by calculation. When the distance Δy _neck of the first constricted portion of the molten glass droplet shape is the diameter of the dropping nozzle 2R, the volume of the molten glass droplet suspended by the dropping nozzle is maximum (hereinafter referred to as the maximum suspended volume). The mass multiplied by the density is also the maximum (hereinafter referred to as the maximum suspended mass).

In the calculation, it is preferable to use values at the temperature dropped from the nozzle as the surface tension σ (N / m) and density ρ (kg / m ³ ) of the molten glass. The gravitational acceleration may be a general value, but is preferably corrected as appropriate in an environment where an external force such as a centrifugal force is applied.

Molten glass to be actually dropping, since it is when the balance between the surface tension P _S of the hydraulic P _L and the molten glass of the molten glass in the dropping nozzle tip is no longer achieved, the mass of molten glass droplets dripping is It can be regarded as almost the same as the maximum suspended mass. Therefore, if the diameter 2R of the dropping nozzle when the mass of the desired molten glass droplet is the maximum suspended mass is employed, the molten glass droplet having the desired mass can be manufactured with high accuracy.

Furthermore, the approximation of Formula 6 is obtained from the relationship between the nozzle radius R obtained by calculation and the mass M of the molten glass droplet to be dropped. c is a constant appropriately selected depending on the type of glass, the nozzle material, and the like, and preferably takes a value of c = 0.20 to 0.29. The lower limit of c is more preferably 0.21 and particularly preferably 0.22. The upper limit of c is more preferably 0.26, and particularly preferably 0.25.
R = c · M · g / σ Equation 6

  Since an actual dropping nozzle has a thickness, the diameter of the dropping nozzle includes an outer diameter, an inner diameter, an average value of the inner diameter and the outer diameter (hereinafter, simply referred to as an inner and outer diameter average value), and the like. In this design method, the diameter 2R of the dropping nozzle may be any of the outer diameter, inner diameter, and inner / outer diameter average value of the dropping nozzle. When the wettability between the molten glass and the dropping nozzle is good, the diameter 2R of the dropping nozzle is preferably the outer diameter of the nozzle, and conversely, when the wettability between the molten glass and the dropping nozzle is poor, the diameter 2R of the nozzle is set. The inner diameter is preferred.

This relationship is shown in FIG. In FIG. 4 N is a dropping nozzle, d _I is the inner diameter of the dropping nozzle tip, d _O is the outer diameter of the dropping nozzle tip, d _IO is a not shown inner and outer diameters the mean value of the dropping nozzle tip, respectively.

  The dripping nozzle of the present invention (hereinafter referred to as the present nozzle) is not particularly limited except that it has the nozzle diameter calculated by the present design method. The material of the nozzle is not particularly limited as long as it has corrosion resistance to the molten glass and can drop the molten glass as droplets, but a noble metal such as Pt and / or Au is a preferable material.

  In addition, in this nozzle, if the thickness is made as thin as possible within the range where mechanical strength without problems in use can be obtained and the difference between the inner diameter and outer diameter of the dropping nozzle is reduced, the compatibility between the molten glass and the nozzle material This is preferable because the influence of the above can be reduced. In manufacturing this nozzle, it is preferable to process the tip of the nozzle to have a sharp edge.

  In the present invention, a glass lump manufacturing apparatus (hereinafter referred to as the present manufacturing apparatus) includes a glass melting crucible (hereinafter simply referred to as a crucible) provided with the nozzle if it has the nozzle, and a temperature measuring means for the molten glass. However, it is preferable to have a means for stirring the inside of the crucible because the quality of the molten glass becomes uniform.

  In this manufacturing apparatus, the mounting position of the nozzle on the crucible is not particularly limited, but a bottom surface portion and a side surface portion can be cited as preferable mounting positions. If this nozzle is provided on the side of the glass melting crucible and on the bottom of the tip of the glass, the distance from the nozzle tip to the molten glass liquid surface can be shortened while ensuring a sufficient amount of molten glass. This is preferable because variations in quality can be suppressed and nozzles can be easily manufactured.

A gold container having an inner diameter of about 80 (mm) at the upper end, an inner diameter of about 60 (mm) at the lower end and a height of about 90 (mm) and an inner volume of about 350 (mL) is prepared as a glass melting crucible. A dropping nozzle described later is provided on the bottom surface, and a tellurite glass material (surface tension 0.165 N / m, density 5169 kg / m ³ , gravitational acceleration 9.80665 m / s ² ) is melted and dropped at a melting temperature of 900 ° C., and target dropping is performed. A test for producing a mass of 104 mg of glass was conducted. The surface tension was measured by the ring method, and the density was measured by the Archimedes two-sphere method.

  Using the physical properties of the glass material and calculating the nozzle radius using Equation 4, a value of 1.40 mm was obtained. Therefore, two Au-containing noble metal dripping nozzles having nozzle outer diameters of 2.80 mm and 3.00 mm, a thickness of 0.5 mm, and a length of 8 mm were produced, and the glass lump production was actually performed about 40 times. When the average mass of the glass block was determined, when the nozzle outer diameter was 2.80 mm (c = 0.23 in Equation 5), 103 mg, and the nozzle outer diameter was 3.00 mm (c = 0.24 in Equation 5). It was confirmed that a glass lump could be produced with an accuracy of 105 mg.

  By using this design method, it becomes easy to design an optimum dropping nozzle, and by using this nozzle based on this design method, a glass lump whose mass is strictly controlled can be easily produced.

The conceptual diagram of the largest droplet shape of the molten glass suspended by the nozzle. The conceptual diagram which shows balance of the force which acts on a molten glass droplet. The conceptual diagram of the coordinate system at the time of calculating the droplet shape of a molten glass. The partial enlarged view of the nozzle tip.

Explanation of symbols

1: molten glass droplet 11: molten glass droplets calculated by obtained virtual d _I: inner diameter of the dropping nozzles d _O: outer diameter of the dropping nozzle N: dropping nozzle P _G: the hydraulic pressure due to gravity P _L: dropping nozzle tip of the molten glass in the fluid pressure _{(= P} G ₊ P S)
P _N : Liquid pressure from the upstream of the dropping nozzle P _S : Surface tension of molten glass (= P _L )
R: Radius of tip of dropping nozzle Δy _neck : Distance of first constricted portion of molten glass droplet shape (= 2R)

Claims (6)

  A method of designing a dropping nozzle for producing a molten glass droplet having a desired mass, wherein a molten glass droplet shape suspended at the tip of the dropping nozzle is calculated, and (a molten glass that can be suspended on the dropping nozzle) Calculate the minimum diameter of the constricted portion of the droplet shape such that (maximum volume of droplet) × (density of molten glass droplet) = (desired mass), and use the minimum diameter as the diameter of the dropping nozzle. Design method of dripping nozzle for molten glass.   The molten glass droplet nozzle design method according to claim 1, wherein the shape of the molten glass droplet is calculated based on a balance between a liquid pressure of the molten glass at a tip of the dropping nozzle and a surface tension of the molten glass. When the desired mass of the molten glass droplet is M (kg), the surface tension of the molten glass is σ (N / m), the acceleration of gravity g (m / s ² ), and the diameter of the dropping nozzle is 2R (m) The method for designing a dropping nozzle for molten glass according to claim 1 or 2, wherein the radius R of the dropping nozzle is calculated by the following formula 1.
R = c · M · g / σ Equation 1
Where c is a constant and c = 0.20 to 0.29. When the desired mass of the molten glass droplet is M (kg), the surface tension of the molten glass is σ (N / m), the acceleration of gravity g (m / s ² ), and the diameter of the dropping nozzle is 2R (m), A method of designing a dropping nozzle for molten glass, wherein the radius R of the dropping nozzle is calculated by the following formula 2.
R = c · M · g / σ Equation 2
Where c is a constant and c = 0.20 to 0.29.   The dripping nozzle for molten glass which has the nozzle diameter computed by the design method of the dripping nozzle for molten glass in any one of Claims 1-4. The glass lump manufacturing apparatus which has the dripping nozzle for molten glass of Claim 5.

Images