JPH0143689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for cutting a stream of molten low viscosity glass to form striae-free gobs.

[Prior art] When molding optical glass into a lens shape, molten glass is flowed down from an outflow tube, cut with a shear blade, and press-formed before the glass cools and solidifies, similar to the molding of conventional container glass. method has been adopted. This method is called the old type for optical glasses, and is effective for glasses that have a low liquidus temperature and can be cut and formed without causing devitrification even at high viscosities of several hundred poise or more. . However, if this method is directly applied to a new type of optical glass that has a high liquidus temperature and a low melting viscosity, the following problems will occur. In other words, when cutting low-viscosity molten glass with a shear blade, the molten glass not only scatters in small beads, but also clumps on the closed blade due to the high flow rate, and when the shear blade opens, the glass clumps onto the shear blade. The problem arises that the glass is scattered and does not flow down to the center of the mold.

Therefore, in U.S. Pat. No. 3,352,658,
A large number of molds with edges are circulated endlessly under the glass outlet, a flow of molten low-viscosity glass is sequentially supplied into the moving molds, and the glass flow is cut at the tip of the edge while moving. However, a method is disclosed for supplying a predetermined amount of glass to each mold. Furthermore, Japanese Patent Publication No. 52-24525 proposes a method of cutting low-viscosity glass with a blade while suppressing scattering. In that case, molten low-viscosity glass is injected into the mold while flowing down through a frame, and this glass flow is divided by a blade installed directly under the frame, and while the mold can be handled, the blade After the mold change is completed, the blade is moved back and the retained glass flow is injected into a new mold to obtain a gob of molten low-viscosity glass. be.

[Problems to be Solved by the Invention] Although there are conventional techniques that meet the above requirements, there are the following problems.

First, the U.S. patent is improved in that it tries to mold a gob of low viscosity glass without using a shear blade, but because the mold is moved during the glass flow, the gob is large compared to the size of the outlet. When making glass, there is a great risk that glass with a surface that has undergone compositional changes due to volatilization after being exposed to air will fold in and cause striae. Furthermore, when the mold is moved, small beads of molten glass are scattered, which causes defects. Furthermore, in order to obtain gobs of optical glass, it is necessary to form the gobs into the desired shape and to keep the mold temperature high to avoid defects such as surface cracking due to overcooling. Since the heat capacity of the edge part of the movable type is small, the temperature becomes too high when it comes into contact with molten glass.
Resistance due to wetting occurs between the mold and the glass, making it impossible to cut the glass.

On the other hand, the above-mentioned Japanese Patent Publication No. 52-24525 is characterized in that the glass flow is temporarily maintained on the blade.
It is excellent in that it is not affected by the movement of the mold, but since the temporarily held glass is fed into the mold by sliding the bottom surface of the frame, if this operation is repeated for a long time, the frame will be damaged. The lower part becomes high temperature or a part of the frame is oxidized, and the molten glass adheres to the lower part of the frame, and this glass falls into the molten glass in the mold, causing striae.

[Means for Solving the Problems] The present invention was made to solve the above-mentioned drawbacks, and its object is to form a molten low-viscosity glass gob without striae or the like.

To achieve this objective, the present invention involves injecting a stream of molten low-viscosity glass into a mold, breaking this glass stream with a blade, and having the blade hold the glass stream while changing the mold, and then:
In the method of retracting the blade and supplying molten glass into a new mold, an upper plate is provided on the blade, and the glass held on the blade is moved by sliding the blade in the mold closing direction along the lower surface of the upper plate. It is designed to be extruded at the tip of the upper plate and fed into the mold.

As described above, in the present invention, even if the molten low-viscosity glass is cut, it can be fed to the center of the mold without scattering, so that gobs without defects such as striae can be molded. Since the tip of the upper plate pushes out the holding glass, a portion of it may stick. In that case, it is necessary to remove it using various methods to prevent it from getting into the mold, but it can be easily and effectively removed by sliding the plate member against the tip of the upper plate.

[Example] The present invention will be described below based on the drawings. FIG. 1 is a cross-sectional view of an apparatus for carrying out the method of the present invention, in which a flow of molten low-viscosity glass 2 flowing down from an outlet 1 is injected into a mold 3, and a piston 4 descends as the glass is injected to inject the required amount. When this is completed, the blade 5 placed above the mold is moved forward in the mold closing direction to break up the glass flow. An upper plate 6 is disposed above the blade 5, and a plate-like member 9 is attached to the side of the upper plate, as shown in FIG. There is.

When the required amount of glass flow is injected as shown in FIG. 2, the blade 5 advances in the direction of the arrow to divide the glass flow 2 and hold the glass flow on the upper surface of the blade. The glass flow is divided using the surface tension and viscous flow of the glass, and the cutting speed of the blade is adjusted depending on the surface tension and viscous flow rate of the glass. During this time, the mold 3 is moved and the new mold change is completed. When the new mold 13 is fixed, the blade 5 is moved back while sliding against the lower surface of the upper plate as shown in FIG. Due to the retreat of blade 5,
The glass held on the blade 5 is pressed by the upper plate tip 7 and fed to the center of the mold to form a glass gob 10.
In this case, when the upper plate 5 is slightly advanced in the opposite direction to the blade retreat direction and then moved back in the same direction as the blade to open the mold, the holding glass is pushed out to a large extent, so it is necessary to pour the holding glass even more. It can be done reliably.

When a portion of the holding glass adheres to the top plate tip 7, the cylinder 8 shown in FIG. do. The plate member 9 is constantly cooled by water flowing from the side cooling pipes 12. On the other hand, molten glass is injected into the new mold 13, and when the required amount has been injected, the blade 5
The mold is divided by the mold, and the same operation as before is repeated to sequentially inject into a new mold.

[Effects of the Invention] As described above, by using the method of the present invention, it is possible to divide the flow of molten low-viscosity glass to smoothly form gobs, and it is also possible to change the mold without disturbing the flow of the glass. In addition to being able to inject into the center of the mold, the glass held on the blade that adheres to the tip of the blade is removed and does not mix into the mold, making it possible to mold glass without defects such as striae. be able to.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a gob forming apparatus that carries out the method of the present invention, FIGS. 2 and 3 are cross-sectional views during operation, and FIG. 4 is a perspective view showing the relationship between the tip of the upper plate and the plate-like member. It is. 1... Outlet, 2... Glass flow, 3... Mold,
4...Piston, 5...Blade, 6...Top plate,
7... Upper plate tip, 8... Cylinder, 9... Plate member, 10... Gob, 11... Adhesive glass, 12
...cooling pipe.

Claims (1)

[Claims] 1. The glass flow injected into the mold is divided by a blade advanced so as to close the upper part of the mold, and after the mold is changed while the glass flow is maintained on the upper surface of the blade, the blade is removed. A method for supplying molten glass to the inside of a new mold by retracting the blade, the method is characterized in that an upper plate is provided above the blade, and when the blade is retracted, the held glass is pushed out with the tip of the upper plate and supplied to the inside of the mold. A method for forming molten low-viscosity glass gobs. 2. The method for molding a molten low-viscosity glass gob according to claim 1, wherein the upper plate is slightly advanced when the blade is retracted to extrude the holding glass into the mold, and then retracted in the same direction as the blade. 3. A method for forming a molten low-viscosity glass gob according to claim 1 or 2, wherein the glass adhering to the tip of the top plate is removed by a plate-like member that slides against the tip of the top plate.