JP2536580B2 - Glass thread cutting method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a glass thread cutting method for cutting a glass thread generated in a glass droplet when a molten glass is dropped and dropped.

Conventional technology In the droplet method in which gob-shaped molten glass is dropped directly from a nozzle into a mold for press molding, the glass pulls a thread when the molten glass is dropped, and this thread drops into a glass droplet shape. They may overlap and cause striae on the glass surface.

Since this glass stringing occurs due to the relationship between the glass dropping weight and the surface tension of the glass, it is affected by the glass dropping weight, the glass dropping temperature, the glass material, and the like. An example of these relationships will be described with reference to FIG. In FIG. 1, the glass dropping temperature is the tip temperature of the nozzle. The glass dropping temperature is low in consideration of moldability such as adhesion of glass to the mold, oxidation of the mold, and shrinkage of the glass due to a difference from the molding temperature. Although it is more preferable, when it is lowered, the glass becomes easier to pull the thread. When the glass dropping temperature is increased,
The stringiness becomes small but the formability becomes poor, and when it is too high, striae also occurs due to violent evaporation of glass. Even when the weight of the glass dropped is increased, the heat capacity is increased, so that the moldability is deteriorated and the thread is easily pulled.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention And, conventionally, the glass dropping temperature and the glass dropping weight have been determined in consideration of various factors as shown in FIG. 1, particularly striae caused by stringing.

In this case, the glass dropping temperature is often raised to prevent the generation of yarn at the expense of moldability such that the mold is quickly deteriorated by oxidation, which causes an increase in manufacturing cost.

Therefore, the present invention aims to lower the glass dropping temperature in order to improve the moldability.

Means for Solving the Problems Therefore, in the present invention, the glass thread generated in the glass droplets dropped from the nozzle, when the glass thread cutting device sandwiches the glass thread at the timing of passing through the glass thread cutting device, The feature is that the glass thread is cut using the weight of the droplet.

EXAMPLE FIG. 2 shows an example of the present invention, which will be described with reference to this figure.

(1) is a platinum nozzle with an inner diameter of 9.1 mm and a length of 900 mm for dropping glass. A heavy flint glass (SF11) of 1.8 that was heated and melted with stirring in a platinum crucible (not shown) at 1000 ° C above this platinum nozzle (1) weighs about 68.3 mg.
Let it drip naturally. At this time, set the nozzle temperature to 800
Keep the temperature at ± 2 ° C, the middle temperature at 850 ± 2 ° C, and the lower temperature at 900 ± 2 ° C. The glass dropped naturally drops from the droplet part (2) toward the nozzle (1) in a state in which the part (3) where the glass is pulled is connected.

Then, the free fall of the glass is detected by two sets of photodetectors. One set is composed of a light emitter (4A) and a light receiver (4B) facing it, and the other set is similarly composed of a light emitter (5A) and a light receiver (5B). And these photodetectors are arranged at different heights so that the falling glass passes between the light emitter and the light receiver, and the light from the light emitter to the light receiver is blocked only by the glass droplets (2). The signal from the light receiver is lost for a certain period of time. Thereby, the passage timing of each glass droplet (2) is detected. The calculation unit (15) calculates the positions of the glass droplet (2) and the thread (3) after a predetermined time based on the difference in the passage timing of the glass droplets obtained by the two sets of photodetectors.

The thread trimming device comprises a scissor plate (8), a scissor plate operating part (9), a support part (10), a rail (11) and an actuator (12), and the calculation part (15) calculates the result. Operate. The scissor plate (8) is attached to the scissor plate operating part (9), and the scissor plate operating part (9) is attached to the support part (10) so as to be able to open and close. The support (10) is attached to the rail (11) so as to be vertically movable, and the vertical movement is operated by the actuator (12).

Above the scissors plate (8) of the thread cutting device, there is a glass suction device (13), which sucks the yarn (3) cut by the thread cutting device by generating a suction airflow as shown in (14). Then, the thread (3) does not drop into the lower mold.

Below the scissors plate (8), there is a lower mold (7) for press molding that receives the glass droplets (2), and is installed 1 m below the nozzle (1). The lower mold (7) is a set with the upper mold (not shown) with a diameter of 10 mm, a thickness of 0.36 mm, and a radius of curvature.
Used for press molding of 34.9 mm convex lenses, made of stainless steel, mirror-finished and Cr-coated, and heated to 400 ° C, which is lower than the glass softening temperature of 500 ° C.

The glass droplet (2) and the thread (3) that naturally dropped from the nozzle (1) passed through the photodetector and the scissor plate (8), and then the glass liquid liquid (2) reached the lower mold (7), and , The timing at which the thread (3) does not drop onto the glass droplet (2) is calculated by the calculation unit (15)
And the scissor plate operation unit (9) based on this
Is closed and the thread (3) is clamped by the scissors plate (8). When the scissor plate (8) is moved upward by the actuator (12) along the rail (11) while holding the thread (3), the lower glass droplet (2) is heavy and moves together. No, the thread (3) finally breaks.

The portion where the thread (3) is cut from the glass droplet (2) is between the portion where the scissor plate (8) directly contacts and the glass droplet (2), and the glass droplet is directly cooled by the scissor plate (8). Not done. Further, the shape of the glass droplet (2) immediately returns to a spherical shape due to the surface tension, so that distortion due to uneven cooling does not occur,
Of course, no striae occurs due to stringing.

In addition, by pulling, the glass droplet (2) to the thread (3)
It is also possible to cut by shearing instead of cutting. In this case, the thread (3) is cut from the glass droplet (2) at the portion directly contacted by the shearing member, so that the cut portion is cooled (or heated) by the shearing member. Then
This sheared portion has a different cooling rate from other portions and causes distortion, so that an unpolished lens cannot be manufactured.

The portion where the thread (3) is separated from the glass droplet (2) is preferably as much as the glass droplet (2). Considering the size of the glass droplet (2) and the like, the scissors plate (8) The height from the lower die (7) may be determined.

Further, the thread (3) after being cut is sucked so as not to drop into the lower mold (7). That is, scissors (8)
The suction device (13) starts to operate immediately before the yarn (3) is pinched, the scissor plate (8) rises and the yarn (3) is separated from the glass droplet (2), and then the parallel chuck (8) again. 9)
When the open scissors plate (8) releases the thread (3), the thread (3) is completely sucked by the suction device (13).

On the other hand, the glass droplet (2) received by the lower mold (7)
Comes into contact with the lower mold (7), the surface temperature thereof is rapidly lowered below the softening temperature, and press-molding is performed by the lower mold (7) and an upper mold (not shown) to cause defects such as striae on the surface. A lens that does not require polishing is obtained.

The glass material, dripping temperature, nozzle height from the lower mold, lower mold material, lower mold temperature, etc. are closely related, but appropriate only considering the evaporation and moldability of the glass. You can set it to.

Further, the glass droplets may be obtained not by natural dropping in which the droplets become droplets at the tip of the nozzle and then dropping by their own weight, but by a method such as forced dropping in which the molten glass is forcibly dropped under pressure.

Another embodiment of the present invention is shown in FIG. 3, and the difference between the thread cutting device shown in FIG. 2 and the thread cutting device shown in FIG. 3 will be described.

In FIG. 3, the thread cutting device is made up of a pair of rollers (8 '), a supporting portion (10'), and an actuator (12) which are symmetrically installed. The roller (8 ') is supported by the support member (10') and is constantly rotating. The support member (10 ') is attached to the actuator (12) so as to be moved and operated in the horizontal direction.

A glass droplet (2) is dropped from a nozzle (1), and after passing through two sets of photodetectors and a roller (8 '), a lower mold (7).
When the yarn (3) does not drop onto the glass droplet (2), the pair of actuators (12) is operated to close the pair of rollers (8 '), and the roller (8') causes the yarn (8 ') to move. Insert 3). Since the roller (8 ') is constantly rotating, the yarn (3) is pulled upward from the moment when the yarn (3) is sandwiched and the yarn (3) is separated from the glass droplet (2).

 Other operations are the same as those of the embodiment shown in FIG.

EFFECTS OF THE INVENTION As described above, since the stringing of glass droplets, which has been a problem in the prior art by the droplet method, is forcibly removed, striae due to the stringing does not occur and the glass is improved in order to improve the formability. The dropping temperature can be lowered.

It is also possible to increase the glass dropping weight.

Further, since the method of cutting by pulling is selected as a method of removing the thread, the cut portion does not remain as distortion on the lens surface due to uneven cooling.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between glass dropping temperature and glass dropping weight in the droplet method, FIG. 2 is an explanatory view of an apparatus of one embodiment of the present invention, and FIG. 3 is an explanation of an apparatus of another embodiment of the present invention. It is a figure. 1 …… Nozzle 2 …… Glass droplet 3 …… Glass thread 4A, 4B, 5A, 5B, 15 …… Position detection means 7 …… Lower mold 8,9,10,11,12 …… Thread trimmer

Claims (3)

(57) [Claims] 1. A method of dropping molten glass in the form of drops from a nozzle, wherein a glass thread cutting device provided in a dropping path of the dropped glass drops is used to cut the glass threads generated in the glass drops. A glass thread cutting method characterized in that a glass thread cutting device sandwiches a glass thread at a timing of passing through the apparatus, thereby cutting the glass thread by utilizing the weight of the glass droplet. 2. The glass thread cutting method according to claim 1, wherein the timing is determined based on the timing at which the glass droplet passes through a predetermined position and is detected. . 3. The glass thread cutting method according to claim 2, wherein the timing at which the glass droplet passes a predetermined position is detected by a photodetector having a light emitter and a light receiver. .