JP2000264651A - Production of glass gob for molding optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the accurate synchronism of the dropping of a molten glass from a nozzle with the rotation of an index table and efficiently produce a glass gob when mass-producing the glass gob using the index table. SOLUTION: A molten glass passing from a nozzle 3 to a plurality of forming mold members 2 is detected with a passage sensor 10 when the molten glass is dropped from the nozzle 3 onto the forming mold members 2 arranged in an index table 1 capable of indexing and rotating at an interval of a prescribed angle. The interval of average dropping time of the molten glass is determined with a CPU 13 and it is presumed that the dropping of the molten glass is carried out after the passage by the interval of the average dropping time when the dropping of the molten glass is not detected with the passage sensor 10 even if the interval of the average dropping time is passed. Thereby, the index table 1 is rotated by one index.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a glass gob as a material for press-molding an optical element such as a lens.

[0002]

2. Description of the Related Art In recent years, precision optical elements such as lenses have been widely used in a method of manufacturing them by press molding. The press molding is performed by placing a glass lump having a predetermined shape, that is, a glass gob, in a molding die, heating the molding die to soften the glass gob, and applying a predetermined pressing force from above and below. Therefore, prior to the press forming, a glass gob having a predetermined shape must be manufactured. The production of this glass gob is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-14839. That is, as the shape of the glass gob, there are a case where it is formed into a shape relatively close to a lens or the like as a final product, and a case where a spherical glass gob is used. In the former case, the molding surface of the molding die conforms to the shape of the glass gob, and molten glass is poured into the molding die member from a nozzle. In the latter case, a molding tool having a substantially conical molding surface is used and nitrogen gas (N ₂
When a molten glass is dropped from a nozzle disposed on the upper part of the molding die member so as to supply an inert gas such as gas), a gas flow layer is formed between the molten glass mass and the molding surface. As described above, the molten glass mass is held in a state of being floated with respect to the molding surface of the molding die member, whereby the molten glass is molded into a spherical mass, and cooled by this gas flow to form a spherical shape. A glass gob is obtained.

In mass-producing the spherical glass gob formed as described above, an index table is used as shown in Japanese Patent Application Laid-Open No. 7-17725. It is generally known that a mold member is provided, and a nozzle is provided at an upper position of the molding die member so as to face each other, and the molten glass is intermittently rotated by one index every time the molten glass is dropped from the nozzle. . Here, a crucible is used to supply the molten glass to the nozzle, and the temperature for melting the glass in the crucible is an extremely high temperature of around 1000 ° C. Therefore, it is not desirable to use a pump or other means for forcibly feeding the molten glass to the nozzle. To this end, the crucible is arranged at a high place, a nozzle is connected to a pipe from the lower end of the crucible, and the molten glass is supplied to the nozzle using the head pressure in the crucible.

[0004]

By the way, when molten glass is supplied to the nozzle, it grows gradually by the action of surface tension at the outlet, and when it reaches a predetermined weight, the surface tension is broken and the nozzle is broken. It is dripped. Therefore, when the opening area of the outlet of the nozzle is constant, the molten glass is dripped every time it reaches a constant weight, and the manufactured glass gob is uniform in shape and weight. Therefore, even if the supply pressure of the molten glass fluctuates, there is no particular effect on the glass gob as a product, but the time interval of the dropping from the nozzle changes according to the supply pressure of the molten glass. In particular, since glass has a large specific gravity, the supply pressure is extremely high in a state where the molten glass is stored in the crucible to the maximum liquid level state and in a state where the liquid level is lowered to the minimum liquid level state in the crucible. A difference is generated, and a difference of several times or more in a drop time interval occurs.

[0005] From the above, when using an index table, if the index table is set to rotate the index every predetermined time, the timing of the dropping of the molten glass and the rotation of the index table do not coincide. As a result, the molten glass cannot be supplied to a predetermined position with respect to the molding die member, and the molten glass in an extremely high temperature state contacts the surface of the molding die member or falls on the table. And the like.

When the molten glass is actually dropped from the nozzle is detected by a sensor or the like and the rotation of the index table is performed based on the detection signal, the molten glass is accurately supplied from the nozzle to the molding member. it can. However, if the distance between the nozzle and the mold member is large and the molten glass dripping stroke is sufficiently long, the molten glass dripping onto the mold member can be reliably detected by the sensor. If the distance is increased, the acceleration causes contact with the surface of the mold member. Therefore, in order to receive the dropped molten glass in a non-contact state with the molding die member, the dripping distance must be extremely short, such as several mm. As described above, it is extremely difficult to accurately and surely detect the molten glass while the molten glass is dropped for a distance of several millimeters, and there is a possibility that the sensor may overlook the molten glass. If the drop of the molten glass is not detected by the sensor, two or more molten glass blocks are supplied to the mold member. as a result,
Due to the weight of the molten glass, the high-temperature molten glass comes into direct contact with the molding die member, and the heat causes inconveniences, such as a large damage to the molding die member.

The present invention has been made in view of the above points, and an object of the present invention is to mass-produce a glass gob using an index table, and to drop molten glass from a nozzle and reduce the index table. An object of the present invention is to make it possible to accurately synchronize with rotation and to efficiently produce a glass gob.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a mold member provided at every predetermined angle in a circumferential direction of an index table which rotates at an angle every predetermined angle. A method of manufacturing a glass gob by dropping molten glass from a nozzle disposed above the index table while ejecting an inert gas from a lower side of the member, wherein the molten glass is supplied from the nozzle to the molding die member. After detecting that is dropped, the index table is rotated by one index with a predetermined time delay, and an average drop time interval of the molten glass is obtained, and only a predetermined time is calculated from the average drop time interval. If no dripping of the molten glass is detected for a long time, the dripping of the molten glass after elapse of the average dripping time interval Done was estimated as is for its characterized in that the index table to rotate 1 index minute.

Here, the average drop time interval can be, for example, an average value of drop time intervals for one rotation of the index table. Further, when the molten glass is not dropped even after the average dropping time interval has elapsed, the timing for rotating the index table by indexing is necessary to take out the glass gob from the mold member from the end of the average dropping time interval. Set the time earlier than the time.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, FIGS. 1 to 3 show a schematic configuration of an example of a glass gob manufacturing apparatus. 1 and 2, reference numeral 1 denotes an index table. The index table 1 has a through hole 1a at a predetermined angle in a circumferential direction at a position on an outer peripheral side thereof.
(8 indexes in FIG. 1), and a mold member 2 is provided in each of the through holes 1a. The molding die member 2 has a funnel-shaped space provided with a gas flow passage 2b formed in a cylindrical shape below a molding surface portion 2a having a substantially conical shape. And gas flow path 2
At the lower end of b, an opening is formed in a gas chamber 1b formed on the lower surface of the index table 1. The gas chamber 1b is supplied with, for example, nitrogen gas (N ₂ gas) as an inert gas. ing.

Reference numeral 3 denotes a nozzle. The nozzle 3 is arranged at a predetermined position on the index table 1 and at a position separated from the molding die member 2 by a predetermined distance, and the nozzle 3 is not shown. It is connected to a crucible and serves to supply the molten glass supplied from the crucible to the mold member 2. Further, pick and place means 4 is arranged at a position separated by a predetermined number of indexes in the index table 1. Accordingly, the position facing the nozzle 3 is the supply position of the molten glass, the position facing the pick-and-place means 4 is the take-out position of the glass gob, and the position from the supply position to the take-out position is inside the mold member 2. Is a process in which the molten glass is formed into a spherical shape by the action of the nitrogen gas supplied to the glass and cooled to a predetermined temperature.

FIG. 3 shows a state where molten glass is dropped from the nozzle 3 onto the molding die member 2. Thus, the lower end of the nozzle 3 is a glass outlet 3a having a predetermined opening diameter, and the outer periphery of the nozzle 3 is provided with a heater 5 to a position including the glass outlet 3a. I have. Therefore, the temperature of the molten glass flowing out of the nozzle 3 is controlled by the temperature of the heater 5.

The index table 1 rotates intermittently by one index every time the molten glass is dropped from the nozzle 3. For this purpose, at a position between the nozzle 3 and the molding die member 2, in order to detect that the molten glass has passed, a passage sensor 10 composed of a photoelectric sensor or the like including a light emitting element 10a and a light receiving element 10b is provided. Is provided. This passage sensor 10 is a nozzle 3
This is for detecting the passage of the molten glass at a stage before the mold glass 2 enters the molding die member 2 after leaving from the mold member 2. Therefore, each time the passage sensor 10 detects that the molten glass is dropped from the nozzle 3 onto the molding die member 2, the index table 1 rotates by an index.

When the molten glass is supplied to the nozzle 3, the molten glass starts flowing out from the outlet 3 a. When the molten glass grows to a predetermined size by the surface tension at the outlet 3 a, the surface of the molten glass is owed to its own weight. The tension is broken, the liquid drops from the nozzle 3, and is dropped on the mold member 2. The index table 1 is positioned so that the nozzle 3 is positioned on an extension of the center axis of the molding die member 2. In this state, the molten glass is dropped from the nozzle 3, but from below the molding die member 2. Since the nitrogen gas is supplied, as shown by the arrow in FIG. 3, the nitrogen gas flows upward between the molding surface 2a of the molding die member 2 and the dropped molten glass. A gas layer is formed on the molding surface portion 2 as shown by G in FIG.
The molten glass mass G is formed into a spherical shape by the action of this nitrogen gas flow while being kept in a non-contact state, that is, in a floating state with a, and the molten glass is cooled by the nitrogen gas. This floating state continues until the index table 1 moves to the position where the pick-and-place means 4 takes out the glass gob, whereby a spherically solidified glass gob is formed. At the take-out position while the index table 1 is stopped, the pick-and-place means 4 is displaced in the direction of the arrow in FIG. 1 so that the glass gob is sucked and stored in a predetermined jig such as a pallet. .

The glass gob is manufactured as described above. In the operation of the index table, the index table 1 needs to be kept stationary at least while the molten glass is dropped from the nozzle 3. The index table 1 must be kept stationary while the glass gob is being taken out by the means 4. However, while the molten glass grows in the nozzle 3, the index table 1
Does not have to be stationary. Therefore, if the index table 1 is rotated one index at a time with a slight delay after the dropping of the molten glass is detected by the passage sensor 10, a glass gob can be formed continuously.

By the way, the passage sensor 10 detects the molten glass that falls only a short distance from the nozzle 3 to the mold member 2. The detection condition is not always good, and therefore, when all the passages cannot be detected accurately. The so-called passage sensor 10 may overlook the passage of the molten glass. However, as long as the molten glass is supplied to the nozzle 3, the molten glass should surely be dropped at certain time intervals.

From the above points, the control of the index table 1 is such that when a predetermined period of time has elapsed and no dripping of the molten glass has been detected, it is assumed that a dripping has occurred and the index table 1 is driven. I am trying to do it. However, since the dropping time interval changes in accordance with the amount of molten glass stored in the crucible, the estimated dropping time interval at the time of the dropping is set to a value during the previous rotation of the index table 1, for example, the index table 1. Is composed of 8 indices, it is set based on the average value of the dropping time intervals for the last eight rotations per rotation. Therefore, if the passage sensor 10 does not detect that the molten glass has been dripped even after a lapse of a predetermined period of time after the average dropping time interval obtained in this way has elapsed, the passage sensor 10 may be overlooked. It is estimated that Here, the average drop time interval is determined because the timing at which the molten glass is dropped from the nozzle 3 slightly varies, and therefore the average value does not necessarily need to be one rotation.

In order to perform the above control, the index table 1 is intermittently rotated at a predetermined index angle by, for example, a pulse motor 11 as its driving means.
The signal from the passage sensor 10 is not directly input to the servo circuit 12 of the pulse motor 11,
(Operation processing unit) 13 is set so as to input a drive signal. Further, the CPU 13 calculates an average drop time interval (DT) based on a signal from the passage sensor 10. Therefore, it is determined whether or not the passage sensor 10 has normally detected the dripping of the molten glass, and if the passage sensor 10 has overlooked the dripping of the molten glass, it is determined at what timing the index table 1 is rotationally driven. ,
This is performed by the CPU 13. Further, the CPU 13 sends a signal to the servo circuit 12 when the dropping of the molten glass by the passage sensor 10 is actually detected, or the passage sensor 1 even after a predetermined time has elapsed after the average dropping time interval.
When a drop is not detected from 0, a pseudo drop signal is input. These drop signals or pseudo drop signals are trigger signals for rotating the index table 1 by one index. In FIG. 3, reference numeral 14 denotes an on-off valve for supplying / cutting off molten glass to the nozzle 3.

The reason why the pseudo drop signal is output is as follows.
By that time, the molten glass should have been dripped from the nozzle 3 without fail.
After rotation of one index, until the next index rotation is performed, a time (PPD) in which the pick-and-place means 4 can reliably take out the glass gob is left. Therefore, after detecting the drop of the molten glass by the previous passage sensor 10, the average drop time interval (D
Glass gob removal time (PP)
D) is subtracted, that is, 2DT-PPT = Tset is set as the generation timing of the pseudo drop signal. In addition, 2
If the passing sensor 10 is overlooked consecutively, the first false drop signal is output when the time Tset is reached, and the second false drop signal is output when (3DT-PPT) has elapsed. Output.

As described above, by continuously supplying the molten glass to the nozzle 3 and rotating the index table 1 intermittently, the glass gob can be continuously produced. Therefore, a method of manufacturing a glass gob will be described based on the flowchart of FIG.

First, before starting the production of the glass gob, predetermined initial values are set in the CPU 13 (step 1). As the initial value, the initial average drop time interval is set as the average drop time interval (DT). The initial average dropping time interval is determined from the amount of molten glass stored in the crucible and its viscosity, etc., by actually measuring the time interval from the start of supply of the molten glass to the nozzle 3 to the dropping by actual measurement or the like. The average drop time interval is set in the CPU 13.
Therefore, the first rotation of the index table 1 is
This initial average drop time interval is the average drop time interval (DT).
Becomes Further, the glass gob take-out time (PPT) required for taking out the glass gob from the molding die member 2 by the pick and place means 4 and the passage sensor 10
A time delay from the start of driving of the index table 1 after the detection of the dripping of the molten glass due to the above is set. This time delay is a time required for the molten glass to be stabilized after being taken into the mold member 2.

When the above initial values are set, dripping of the molten glass from the nozzle 3 is started (step 2). The start of the dropping is performed, for example, by operating the nozzle 3 and the on-off valve 14 provided in the pipe to the nozzle 3. At the start of the dropping, the initial average dropping time interval is set to the average dropping time interval (DT) until the index table 1 makes one rotation.
2DT−PPT = Tset, which is obtained by subtracting the glass gob removal time (PPT) from twice the average drop time (DT), is set in the CPU 13 as the pseudo drop signal generation time interval (step 3). Here, the pseudo drop signal generation time interval Tset is variable,
After one rotation of the index table 1, Tset is based on the average drop time interval (DT) consisting of the actually measured values.
Is updated.

Then, the passage sensor 10 is set within the time Tset.
It is determined whether or not the passage of the molten glass has been detected (step 4), and the time from the previous dropping time of the molten glass (at the time of the first dropping, the dropping start time) is measured, and the passage sensor is detected within the time Tset. It is determined whether or not the passage of the molten glass is detected by 10 (step 5). If the drop of the molten glass is detected by the passage sensor 10 within the time Tset, the CPU 13 sends the servo circuit 12 with a predetermined time delay. And a drop time interval is measured (step 6). The pulse motor 11 with a predetermined time delay is triggered by the dripping signal output from the CPU 13.
Is activated (step 7), and the index table 1
Is stopped, the pick-and-place means 4 is operated to take out the glass gob (step 8).

Here, the pseudo drop signal generation time interval Tse
t is updated every one rotation of the index table 1. When the index table 1 makes one rotation, a flag of a Tset change request is set, and it is determined whether or not this request has been made. (Step 9) If the index table 1 has less than one rotation,
Return to step 4. Also, index table 1 is 1
When the rotation is completed, the CPU 13 calculates the average value of the drop time intervals for one rotation, calculates the Tset for the next one rotation from the average drop time interval (step 10), returns to step 3, and updates the Tset. At the same time, the next drop of molten glass is detected.

On the other hand, in step 5, if the dropping of the molten glass is not detected by the passage sensor 10 even after the lapse of the false drop signal generation time interval Tset, the false drop signal is output to the servo circuit 12 when the Tset has elapsed (step 5). Step 11). Then, the pulse motor 11 is operated based on the pseudo drop signal to rotate the index table 1 by one index (step 12), and the pick-and-place means 4 takes out the glass gob (step 13). Return to 4. It is assumed that this dropping is performed when the average dropping time interval has elapsed, and from that time, a determination is started as to whether or not the passage of the molten glass has been detected by the passage sensor 10 within the time Tset. In this case, since the drop is estimated, it is excluded from the calculation of the average drop time interval. When the index table 1 is rotated based on the pseudo drop signal while the flag of the Tset change request is set, the flag is set until the next drop signal is actually output without changing Tset. In the state.

As described above, the index table 1
By controlling the operation of the
Does not overlook the dripping of the molten glass, the molten glass is not dripped twice into the same mold member 2. In addition, since the work of taking out the glass gob by the pick-and-place means 4 can be performed smoothly, the glass gob does not move to the position facing the nozzle 3 with the glass gob remaining in the molding die member 2. That is, even if there is an oversight by the passage sensor 10, the nozzle 3
The synchronization of the dropping of the molten glass from the glass table, the operation of the index table 1, and the removal of the glass gob by the pick-and-place means 4 are reliably maintained.

When the passage of the molten glass by the passage sensor 10 is not detected for more than a predetermined number of times, for example, three times or more, whether or not a trouble has occurred, the supply of the molten glass from the crucible has been stopped, or the like, is caused by the nozzle 3 in the first place. It is desirable to determine that the molten glass is not dripped, and to close the on-off valve so as to shut off the supply state of the molten glass to the nozzle 3. In addition, the average drop time interval is calculated every rotation, but the average drop time interval may be calculated each time the passage sensor 10 detects a drop. Further, at the index position next to the take-out position of the glass gob facing the pick-and-place means 4, a sensor for detecting whether or not the glass gob remains in the molding die member 2 is provided, and the pick-and-place means 4 removes the glass gob. When it is detected that the glass gob remains in the molding die member 2 even after the removal position, the on-off valve 14 is closed and a predetermined alarm is generated. However, the index rotation of the index table 1 is continued until all the glass gobs existing in the mold member 2 are taken out.

[0028]

As described above, the present invention is constructed as described above. In mass-producing glass gobs using the index table, it is possible to accurately synchronize the dripping of the molten glass from the nozzle with the rotation of the index table. There is an effect that no glass gob can be efficiently produced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for performing a method for manufacturing a glass gob for molding an optical element according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a sectional view of a nozzle and a mold member.

FIG. 4 is a flowchart relating to operation control of an index table.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Index table 2 Mold member 3 Nozzle 4 Pick and place means 10 Passage sensor 11 Pulse motor 12 Servo circuit 13 CPU

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[Procedure amendment]

[Submission date] April 8, 1999 (1999.4.8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (3)

[Claims] 1. A mold member is provided at a predetermined angle in a circumferential direction of an index table which rotates by an index at a predetermined angle, and while the inert gas is ejected from a lower side of each of the mold members, the index table is rotated. A method of manufacturing a glass gob by dropping molten glass from a nozzle disposed above the, wherein after detecting that the molten glass has been dropped from the nozzle to the molding die member, the index with a predetermined time delay The table is rotated by one index, and the average dropping time interval of the molten glass is obtained. When the dropping of the molten glass is not detected for a predetermined time longer than the average dropping time interval, the average dropping time interval is set. It is presumed that the dripping of the molten glass has been performed after elapse of only Claim 1 process for producing an optical element molding glass gob of wherein the rotating index minute. 2. The method according to claim 1, wherein the average drop time interval is an average value of drop time intervals for one rotation of the index table. 3. When no drop of molten glass is detected after the lapse of the average dropping time interval, the timing of rotating the index table by an index is such that the glass gob is taken out of the molding member from the end of the average dropping time interval. The method for producing a glass gob for molding an optical element according to claim 1, wherein the time is set earlier than a necessary time.