CN101497491B - Method for manufacturing finished product, method for manufacturing preformed member for precise stamping and method for manufacturing optical element - Google Patents
Method for manufacturing finished product, method for manufacturing preformed member for precise stamping and method for manufacturing optical element Download PDFInfo
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- CN101497491B CN101497491B CN200910008442XA CN200910008442A CN101497491B CN 101497491 B CN101497491 B CN 101497491B CN 200910008442X A CN200910008442X A CN 200910008442XA CN 200910008442 A CN200910008442 A CN 200910008442A CN 101497491 B CN101497491 B CN 101497491B
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- 238000000034 method Methods 0.000 title claims abstract description 67
- 230000003287 optical effect Effects 0.000 title claims abstract description 13
- 238000004519 manufacturing process Methods 0.000 title claims description 31
- 238000000465 moulding Methods 0.000 claims abstract description 97
- 239000011521 glass Substances 0.000 claims abstract description 85
- 238000001816 cooling Methods 0.000 claims abstract description 15
- 239000006060 molten glass Substances 0.000 claims description 112
- 238000003825 pressing Methods 0.000 claims description 9
- 238000005498 polishing Methods 0.000 claims description 5
- 239000007789 gas Substances 0.000 description 34
- 230000007246 mechanism Effects 0.000 description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 7
- 238000000137 annealing Methods 0.000 description 6
- 238000007667 floating Methods 0.000 description 6
- 230000001133 acceleration Effects 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000003570 air Substances 0.000 description 2
- 239000000156 glass melt Substances 0.000 description 2
- 238000005339 levitation Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 238000003856 thermoforming Methods 0.000 description 2
- -1 and specifically Substances 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 230000037303 wrinkles Effects 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
- Y02P40/57—Improving the yield, e-g- reduction of reject rates
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- Re-Forming, After-Treatment, Cutting And Transporting Of Glass Products (AREA)
Abstract
A method of producing heat moldings (melted glass blocks), a method of producing preformed piece for fine blanking forming by processing the heat moldings obtained by the method, and a method of producing optical element by fine blanking the preformed piece obtained by the method. The method of producing the preformed piece comprises the steps of: applying wind pressure to the melted glass blocks received by the lower die on the lower die for suspending the same, cooling during the movement in the lower die, and adjusting to the determined viscosity; using the upper die in the determined position for drawing the melted glass blocks on the lower die adjusted to the determined viscosity; finally, cooling the drawing products in the movement of the lower die on the lower die, and taking out the drawing products from the lower die at the determined position. Before taking out from the lower die, the moldings are in contraposition with in non-contact in the determined position on the molding face of the lower die, then taking out after contraposition. The invention further provides a method of producing optical element by fine blanking the preformed piece obtained by the method.
Description
Technical Field
The present invention relates to a method for producing a thermoformed article, a method for producing a preform for precision press molding, and a method for producing an optical element.
Background
As a method for mass-producing glass optical elements such as aspherical lenses made of glass, which are difficult to mass-produce by grinding or polishing, a precision press method is known. In this method, glass called a preform, which is processed into a shape suitable for precision press forming, is press-formed. As a method for producing a preform, various methods are known, and among them, a method of separating an appropriate amount of a molten glass gob from a flowing molten glass and molding the gob into a preform before the glass gob is cooled and solidified has high productivity. This method is called a preform thermoforming method, and although the productivity of a method of producing a glass molded body having a shape similar to that of a preform by a thermoforming method and forming the glass molded body into a preform by a step including grinding is inferior to the above-mentioned method, the productivity can be said to be superior to other methods. In the hot forming method, in order to avoid the formation of wrinkles, voids, or cracks on the surface of the glass, the glass is formed while applying upward wind pressure to the glass mass by blowing gas toward the forming mold. (see patent documents 1 to 5)
[ patent document 1] Japanese patent application laid-open No. 2003-95670
[ patent document 2] Japanese patent application laid-open No. 2004-300020
[ patent document 3] Japanese patent application laid-open No. 2004-284847
[ patent document 4] Japanese patent application laid-open No. 2005-272194
[ patent document 5] Japanese patent application laid-open No. 2007-119335
In the hot forming method, molten glass is continuously poured out, and molten glass gobs are sequentially separated and sequentially formed by a plurality of forming molds. In the methods described in patent documents 1 to 4, the molten glass gob is molded without using a molding die. The forming die used here is only a lower die. In contrast, in the method described in patent document 5, a molten glass gob is press-molded by a molding die. The forming mold used here includes an upper mold in addition to a lower mold.
In the above method, an empty forming mold (lower mold) is carried into a position to receive a molten glass gob and is left to stand, and the molten glass gob is supplied to the position. The forming mold that received the molten glass gob is sent out from the above position, and then another empty forming mold is carried in and stopped. The molten glass gob is formed on a moving forming mold and then removed from the forming mold. However, in the method described in patent document 5, press forming is performed by an upper die while the mold is moving, and then the mold is removed from the forming die. The empty molding die (lower die) is then again carried into the position for receiving the molten glass gob, and the above-described steps are repeated.
In order to smoothly perform the above-described steps, for example, there is a method of: a plurality of molding dies (lower dies) are arranged on a turntable, and the turntable is indexed to sequentially convey the molding dies to predetermined stop positions. In this method, acceleration is applied to the glass gob on the molding die as the molding die moves and stops. Since the acceleration has a horizontal direction component, the glass gob is shaken on the forming mold. In the case of the method of conveying and stopping the forming mold at a constant cycle by indexing and rotating the turntable, the acceleration is applied to the glass gob at a constant cycle, and the shaking of the glass gob becomes large. Further, if the conveying speed of the forming mold is increased in order to improve productivity, the acceleration also increases, and the wobbling of the glass gob increases.
In any of the methods for forming a molten glass gob described in patent documents 1 to 5, when a glass gob as a formed article is taken out from a forming mold, the glass gob is sucked and held by the tip of a suction nozzle and taken out from the forming mold. In order to maintain continuous production, it is necessary to reliably perform the operation of sucking and holding the glass gob by the tip of the suction nozzle, and it is necessary to improve the yield without damaging the glass gob. However, as described above, the glass gob moves on the molding die, and the posture of the glass gob on the molding surface of the molding die is not stable.
Disclosure of Invention
Accordingly, the present invention is to provide a method for obtaining a hot-formed article (molten glass gob) which can be used as a preform for precision press forming of a desired shape by forming a molten glass gob, and which can reliably perform suction holding of the glass gob by the tip of a nozzle without damaging the glass gob.
Further, the present invention is directed to a method for producing a precision press-molding preform by processing a thermoformed article obtained by the above method, and a method for producing an optical element by precision press-molding a preform obtained by each of the above methods.
The present invention is as follows.
[1] A method for producing a thermoformed article using a plurality of lower molds that are continuously or intermittently moved in a circulating manner, comprising the steps of:
(1) separating molten glass gobs sequentially from the continuously flowing molten glass, receiving the separated molten glass gobs at predetermined positions by the plurality of lower molds,
(2-1) while applying a wind pressure to the molten glass gob received by the lower mold on the lower mold to suspend the molten glass gob, cooling the molten glass gob while the molten glass gob is moving on the lower mold to adjust the molten glass gob to a predetermined viscosity,
(3) press-forming a glass gob on a lower die adjusted to a predetermined viscosity at a predetermined position by using an upper die, and then further cooling the press-formed product on the lower die while the lower die is moving; or,
(2-2) cooling the molten glass gob received by the lower mold while applying a wind pressure to the molten glass gob on the lower mold to suspend the molten glass gob, and forming the molten glass gob into a predetermined shape by suspending the molten glass gob by the wind pressure without pressing the molten glass gob,
(4) taking out the press-formed product of (3) or the formed product of (2-2) from the lower die at a predetermined position,
before the molded article is taken out from the lower mold, the molded article is aligned with a predetermined position on the molding surface of the lower mold in a non-contact manner, and the molded article is taken out after the alignment.
[2] The production method according to [1], wherein,
the non-contact positioning is performed by applying a wind pressure to the molded article from an upper die.
[3] The production method according to [1] or [2], wherein,
before the press forming in (3), the molten glass gob adjusted to a predetermined viscosity is aligned at a predetermined position for press forming in a non-contact manner with a predetermined position on the forming surface of the lower mold, and after the alignment, press forming is performed using the upper mold.
[4] The production method according to any one of [1] to [3], wherein,
the prescribed viscosity of the molten glass gob in (2-1) is 103Mooring to 104.4The range of poise.
[5] The production method according to any one of [1] to [4], wherein,
the hot-formed article is processed into a glass blank which is a preform for precision press-forming or a preform for precision press-forming by a method including grinding.
[6] A method for manufacturing a preform for precision press molding, comprising processing a glass blank manufactured by the method according to [5] into a preform for precision press molding by a process including at least grinding.
[7] A method for manufacturing an optical element, wherein a preform manufactured by any one of the methods [1] to [6] is subjected to precision press molding.
According to the present invention, there can be provided a method of producing a thermoformed article, comprising: the method is capable of surely performing suction holding of the glass gob at the tip of the suction nozzle without damaging the glass gob by making the upper mold opposed to the center of the molding surface of the molding mold (lower mold) without directly contacting the glass gob.
Further, according to the present invention, a thermoformed article usable as a precision press-molding preform can be obtained by the above-described production method, or a precision press-molding preform can be produced by processing the thermoformed article obtained by the above-described production method. Further, the preforms obtained by the above-described methods can be precisely press-molded to produce optical elements.
Drawings
Fig. 1 shows an example of a positioning device used in the present invention.
Fig. 2 is an explanatory diagram of the operation of the aligning device.
Fig. 3 is an explanatory diagram of alignment.
Fig. 4 is a timing chart showing the operation of the molding apparatus for molding a preform from molten glass.
Fig. 5 is an explanatory view showing an example of the turntable.
Detailed Description
The present invention is a method for producing a thermoformed article using a plurality of lower molds that circulate continuously or intermittently, comprising the steps of:
(1) separating molten glass gobs sequentially from the continuously flowing molten glass, receiving the separated molten glass gobs onto the plurality of lower molds at predetermined positions,
(2-1) while applying a wind pressure to the molten glass gob received by the lower mold on the lower mold to suspend the molten glass gob, cooling the molten glass gob while the molten glass gob moves on the lower mold to adjust the molten glass gob to a predetermined viscosity,
(3) press-forming a glass gob on a lower die adjusted to a predetermined viscosity at a predetermined position by using an upper die, and then further cooling the press-formed product on the lower die while the lower die is moving; or,
(2-2) cooling the molten glass gob received by the lower mold while applying a wind pressure to the molten glass gob on the lower mold to suspend the molten glass gob, and molding the molten glass gob into a predetermined shape by the suspension caused by the wind pressure without pressing the molten glass gob,
(4) taking out the press-formed product of (3) or the formed product of (2-2) from the lower die at a predetermined position,
before the molded article is taken out from the lower mold, the molded article is aligned with a predetermined position on the molding surface of the lower mold in a non-contact manner, and the molded article is taken out after the alignment.
The present invention uses a plurality of lower molds that are continuously or intermittently moved cyclically. Specifically, the lower dies can be moved cyclically by arranging the plurality of lower dies on the turntable and indexing the turntable so that the plurality of lower dies are moved to respective stop positions in a batch-by-batch manner in synchronization with each other. The stop position is a predetermined position and is at least (1) a position for receiving the separated molten glass gob and (2) a position for taking out the molded article from the lower mold. However, depending on the number of lower molds provided on the turntable, there may be a stop position where no special operation or operation is performed. Further, in the case of press forming using an upper die, there is a position where press forming is performed using an upper die as a stop position.
Molten glass gobs are sequentially separated from the continuously flowing molten glass, and the separated molten glass gobs are received by a plurality of lower molds at predetermined positions. Thereby, glass melt gobs for forming a hot press-formed article are formed in order from the continuously flowing glass melt gobs. The molten glass is obtained by, for example, heating, melting, defoaming, and homogenizing a glass raw material, continuously flowing out the molten glass from a pipe at a constant flow rate, receiving a lower end portion of the flowing molten glass flow on a lower mold placed below the pipe, rapidly lowering the lower mold vertically downward, separating a molten glass flow-down end portion on the lower mold from the molten glass flow, and receiving a molten glass gob separated onto a molding surface of the lower mold.
In addition to this method, a molten glass gob can be obtained on the molding surface of the lower mold by the following method: a method of receiving the lower end portion of the molten glass flow flowing out by a support member placed below the pipe and vertically and rapidly lowering the support member so that the molten glass flowing-down end portion on the support member is separated from the molten glass flow, and supplying the separated molten glass gob onto the molding surface of the lower mold; or a method in which the lower end portion of the molten glass flow that has flowed out is received by a support member placed below the pipe, the support of the support member is quickly removed, the molten glass flowing-down end portion supported by the support member is separated from the molten glass flow, and the separated molten glass gob is supplied onto the molding surface of the lower mold.
The molten glass gob received by the lower mold is cooled while being moved by applying a wind pressure to the lower mold to suspend the molten glass gob. When a press-formed product is prepared through the steps (2-1) and (3), the product is cooled and adjusted to a predetermined viscosity while the lower die is moving. In this case, the molding surface of the lower mold is a smooth surface on which the shape of the surface is transferred to the glass by pressing, and a plurality of gas ejection ports for ejecting gas for applying wind pressure to the molten glass gob to suspend the molten glass gob are provided. When the molded article is prepared without pressing through the step (2-2), the molten glass gob received on the lower mold is cooled while being moved while applying a wind pressure to the lower mold to suspend the molten glass gob, and the molded article is formed into a predetermined shape by suspension by the wind pressure without pressing. In this case, the molding surface of the lower mold does not need to be formed by a press process and the shape of the surface is not transferred to the glass, but the glass gob is temporarily or instantaneously brought into contact with the molding surface, and therefore, the molding surface is also a smooth surface.
In general, when a hot-formed article is produced from a molten glass gob, if the temperature of a forming mold is maintained at a temperature at which adhesion to the molten glass gob can be prevented, the temperature difference between the molten glass gob and the forming mold is large. As described above, if the molten glass gob directly contacts the forming mold kept at a temperature lower than the temperature of the molten glass gob, the glass is locally cooled and shrunk at the contact portion, and hence there is a risk that the surface of the glass is wrinkled and a thermoformed article having a smooth surface cannot be obtained. Further, if the glass after temperature reduction is brought into direct contact with the forming mold, the glass may be broken by a phenomenon called cooling crack. In contrast, in the present invention, since the float molding is performed, the contact between the glass and the lower mold can be reduced, and the above-described problem can be avoided.
The gas ejected from the gas ejection port is preferably a gas that does not react with glass, and specifically, air, nitrogen, an inert gas, or the like can be used. The amount and pressure of the gas are preferably determined as follows: the molten glass gob can be formed in a floating manner, and a stable state in which the molten glass gob does not stick to the lower mold on the forming surface can be ensured. The pressure and flow rate of the gas to be ejected can be appropriately adjusted according to the volume of the glass gob to be formed. Specifically, for example, the pressure is preferably in the range of 0.3 to 0.5MPa, and the flow rate of the gas is preferably in the range of 0.25 to 0.45 liter per minute.
Hereinafter, the upward surface of the glass gob on the molding surface is defined as an upper surface, and the surface facing the molding surface is defined as a lower surface.
The glass gob supplied to the molding surface of the lower mold is cooled in a suspended state, and its viscosity is adjusted in step (2-1) so that it becomes a predetermined viscosity suitable for press molding. From the viewpoint of relatively easy press-forming into a desired shape, it is preferable that the viscosity (predetermined viscosity) of the separated molten glass gob is cooled and adjusted to 103Mooring to 104.4Poise.
In the step (3), the molten glass gob having the viscosity adjusted to the predetermined value in the step (2-1) is press-formed by using an upper mold.
The press forming is performed by lowering an upper die which is standing by above a lower die and pressing a glass gob on a forming surface together with the lower die. The entire glass block is press-molded, and the molding surface of the upper mold is transferred to the upper surface of the glass block and the molding surface of the lower mold is transferred to the lower surface of the glass block. The outer periphery of the upper surface of the lower mold and the outer periphery of the lower surface of the upper mold are fitted to each other, for example, and the lower mold and the upper mold are fitted to align the center of the molding surface of the lower mold and the center of the molding surface of the upper mold before press molding, and the molding surface of the lower mold and the molding surface of the upper mold are opposed to each other, and then the glass block is pressed. At this time, the pressure of the gas supplied to the gas ejection port of the lower mold is set to such an extent that the glass does not enter the gas ejection port, and the glass does not have a dent due to the gas pressure. After press forming, the glass is released from the upper mold, and the upper mold is retracted upward. Then, the molded glass gob is further cooled while being suspended on the lower molding surface.
As described above, in the step (3), the press forming is performed by using the upper die, and it is preferable that the press forming is performed by using the upper die after the non-contact alignment with the predetermined position on the forming surface of the lower die at the predetermined position for press forming before the press forming. The non-contact positioning with respect to the molten glass gob can be performed by applying wind pressure to the molten glass gob from above (or the position correcting member). The pressure of the gas to be ejected is preferably in the range of 0.15 to 0.5MPa, and the flow rate of the gas to be ejected is preferably in the range of 0.15 to 0.45 liter per minute.
The cooling of the molten glass gob while floating by the wind pressure and the forming into a predetermined shape by the floating by the wind pressure without pressing, during the movement of the lower mold in the step (2-2), can be performed in the following manner.
For example, there are the following methods: a method of using a mold as a lower mold, the mold having a concave portion on which a glass gob is placed and formed of a porous material, and ejecting gas through the porous material, and applying wind pressure to the glass gob on the concave portion by the ejection of the gas to suspend the glass gob; or a method of suspending the glass gob by applying wind pressure to the glass gob on the concave portion by ejecting gas from the gas ejection holes by using a forming mold having gas ejection holes formed by a plurality of fine holes in the concave portion on which the glass gob is placed.
The gas ejected upward from the gas ejection port for levitation may be clean nitrogen, air, or inert gas. The flow rate of the ejected gas can be set to a value sufficient to maintain a stable floating state of the glass gob in the recess of the forming mold, for example. The softened glass gob is shaped into a glass gob of a desired shape while being cooled and solidified in the concave portion of the shaping mold.
Further, the temperature of the gas supplied to the gas ejection port needs to be adjusted with attention to the following points. First, the temperature is not heated by the gas ejected from the mold, and the molten glass is prevented from adhering to the concave portion of the molding die. Therefore, the temperature of the supplied gas is preferably set to 300 ℃ or lower. The temperature of the gas is preferably adjusted within a range of-50 to 300 ℃ in accordance with the properties of the glass to be molded, the weight of the preform, and the like.
Further, since the forming mold is recycled, a mechanism for cooling the forming mold may be provided in order to prevent the temperature of the forming mold from rising due to heat conduction from the glass.
In this way, in step (3) or step (2-2), a rotationally symmetric thermoformed article can be sequentially molded. In the step (3) or the step (2-2), the molded article cooled to the predetermined temperature may be taken out from the molding surface of the lower mold, and may be subjected to an annealing step.
In the present invention, before the molded article is taken out from the molding surface of the lower mold, the molded article is aligned with a predetermined position on the molding surface of the lower mold in a non-contact manner, and after the alignment, the molded article is taken out. The molded article can be aligned in a non-contact manner by applying wind pressure to the molded article from above (or the position correcting member). The pressure of the gas to be ejected is preferably in the range of 0.15 to 0.5MPa, and the flow rate of the gas to be ejected is preferably in the range of 0.15 to 0.45 liter per minute.
The positioning of the molded article will be described below with reference to the drawings.
As shown in fig. 1, a position correcting member 11 made of a porous material is provided at the tip of a rotary arm 10 of the aligning device. The position correcting surface 11a of the position correcting member 11 facing the molding surface 21 is formed to have a concave surface, is larger than the upper surface of the molded article G, and is formed to have a size capable of covering the entire upper surface area of the molding surface G. Air, nitrogen gas, inert gas, or the like is supplied to the back surface 11b (the back surface of the position correcting surface 11 a) of the position correcting member 11 through a gas flow path 15 provided in the rotary arm. Air, nitrogen, inert gas, or the like is uniformly ejected from the position correcting surface 11a through the porous position correcting member 11. The part from the position correcting member 11 to the axis of the rotating arm 12 is lowered at the position by the lifting device 13, thereby performing the position correction.
Fig. 2 is an explanatory diagram of the operation of the alignment device. In the step (a), the positioning is performed so that the center of the position correction surface 11a is positioned just above the center of the molding surface 21 of the lower die 20. In (B), the lifting device 13 of the positioning device is operated in this state, and the position correcting member 11 is moved vertically downward so that the position correcting surface 11a approaches the upper surface of the molded article G on the molding surface.
By this operation, as shown in fig. 2(a), if the molded article G is offset from the center of the molding surface 21, the upper surface of the molded article G is closer to the position correction surface 11a than to the opposite side. Thus, the wind pressure of the gas ejected from the position correcting surface 11a to which the molded article G is subjected is large on the offset side of the molded article G, and the molded article G returns to the center of the molding surface 21, and the center of the molded article G coincides with the center of the molding surface 21. After the position of the molded article G on the molding surface 21 of the lower mold 20 is corrected in this way, the lifting device 13 of the positioning device is operated to lift the position correcting member 11, and the rotary arm 10 is rotated to retract the position correcting member 11 from above the lower mold. The shaking of the molded article that is shaken during the levitation process can be suppressed by such a series of operations.
Next, as shown in (C), the front end of the suction nozzle 31 provided at the front end of the conveyance robot 30 waiting above the mold 20 is brought close to the upper surface of the molded article G, and the molded article G is sucked and held at the front end of the suction nozzle 31 and taken out from the mold 20. The formed article G after taking out can be appropriately annealed.
The position correcting operation is preferably performed on the glass piece staying at the removal position. By performing the position correction in this way, the suction nozzle can be closely sucked to the upper surface of the glass block subjected to the position correction and the adjustment, and the glass block can be more reliably taken out from the forming mold.
The thermoformed article illustrated in fig. 3 has a shape in which both the lower surface and the upper surface are convex (may be formed without using a press). The outer peripheral portion of the thermoformed article on the molding die in a plan view does not contact the molding die even in a non-floating state. Since the outer periphery of the molded article having such a shape is not restricted by the molding die, the glass gob is likely to move during conveyance of the molding die, and is likely to be displaced from the correct position on the concave portion of the molding die. As described above, the present invention is particularly suitable for producing a thermoformed article having a shape in which the lower surface is in contact with the molding die but the outer peripheral portion is not in contact with the molding die in a non-floating state.
Examples of other shapes of the hot-formed product include a hot-press formed product having a rotationally symmetric shape with a convex lower surface and a flat upper surface, a hot-press formed product having a rotationally symmetric shape with a convex lower surface and a concave upper surface, and a hot-press formed product having a rotationally symmetric shape with a convex lower surface and a flat upper surface and a concave portion at the center. Each of the hot-formed articles is free from damage such as cooling cracks, and a high-quality formed article can be obtained.
The thermoformed article may be a precision press-molding preform or a glass blank processed into a precision press-molding preform by a method including grinding. When the hot-formed article is a glass blank processed into a precision press-forming preform by a method including polishing, the produced glass blank is processed into a precision press-forming preform by a process including at least polishing, and the precision press-forming preform can be produced. After annealing the hot formed article, the surface may be ground to finish the preform. Since the shape of the hot press-formed article is a rotationally symmetric shape, a preform having a rotationally symmetric shape can be easily produced by polishing.
Further, the optical element can also be produced by precision press-molding the preform produced by the method of the present invention. The optical element can be manufactured by a known method using precision press molding. Various aspherical lenses such as a concave lens, a convex lens, and a biconcave lens can be manufactured by precision press-molding a preform. The lens thus obtained has excellent surface accuracy and is free from defects such as thickness unevenness.
[ examples ]
The present invention will be described in further detail below with reference to examples.
Examples
An embodiment is described with reference to fig. 3. A molding machine in which twelve lower molds are arranged at equal intervals on a circumference around a rotation axis of an index-rotating turntable is used.
Fig. 4 is a time-series view showing the operation of a molding apparatus for molding a preform from molten glass.
For convenience of explanation, the operation of the above apparatus is divided into the following mechanisms: a mechanism for separating molten glass by vertically moving the upper mold and the lower mold (referred to as "molten glass separation"); a mechanism (device name "molding machine index") for rotating the rotary table for conveying the lower mold in an index manner; a mechanism (apparatus name "adsorption nozzle") for adsorbing the solidified glass gob by negative pressure; a mechanism (apparatus name "conveying apparatus") having an adsorption nozzle with a negative pressure mechanism for taking out the solidified glass gob from the molding die and conveying it to the annealing step; a mechanism for ejecting gas from the porous body to align the solidified glass gob with a predetermined position on the molding surface of the lower mold without contact (the apparatus name "position correcting member"); a mechanism (device name "position correcting device 90-degree rotating arm") for retracting the upper die from just above the position where the lower die is stopped; and a mechanism (device name "cylinder for lowering position correcting device") for moving the porous body in the vertical direction.
The device name "molding machine start" in the uppermost column of the timing chart indicates the on/off of the main switch of the entire molding machine. Initially the apparatus name "former start" is changed from off to on to start the forming apparatus.
The time when the turn table shown in fig. 5 is indexed to rotate and stopped is defined as a starting point, and the time until the turn table stops after the next indexing rotation of the turn table is defined as one tact, which is denoted by h. That is, one tact corresponds to the time from when the lower mold stops at the stop position to when the lower mold moves to the next stop position and stops. In the present embodiment, one tact is set to 6920 milliseconds.
After the lower mold is stopped at a stop position 1 (predetermined position) below the molten glass flowing out, the apparatus name "molten glass separation" is changed from closed to open, and the lower mold is raised and held at the raised position to receive the lower end of the molten glass. The continuously flowing molten glass is stored in the lower mold, and a neck is formed between the glass flow outlet of the molten glass and the lower mold by surface tension.
When 6120 milliseconds has elapsed since the stop of the turn table, the lower mold is rapidly lowered by changing the "molten glass separation" from open to closed, and the lower molten glass is separated from the constricted portion, whereby a molten glass gob can be obtained on the lower mold. Next, the "former indexing" is changed from off to on, and the turntable is rotated about the axis of rotation by 30 ° and stopped.
In this example, the glass gob was positioned at the 9 th stop position 10 (take-out position) from the position where the molten glass gob was received. After the molding machine was started, 9 molten glass separation operations were performed, and the molding die estimated by the indexing was stopped at the stop position 10. After a period of 30m seconds (msec), the "position correcting device-lowering cylinder" is lowered 480m seconds (msec). After 30+480 seconds (milliseconds) of 510m, the "position correction device lowering cylinder" is closed to raise the position correction member to the original height, the "position correction device 90-degree turning arm" is opened after the lower die is stopped at the take-out position for 530m seconds, the arm 10 holding the position correction member is turned 90 °, and the position correction member is moved and retracted horizontally from above the take-out position. In this way, the position correcting member and the holding and moving mechanism thereof do not hinder the removal of the preform, and after 570m seconds, the suction nozzle of the conveying device is moved to above the forming die to generate negative pressure to suck the preform and convey the preform to the annealing process.
The "90 degree swivel arm of the position correction device" is then closed, returning the position correction member above the removal position. The "former indexing" is then turned on, the turret is rotated through 30 °, and each lower die is moved to the next dwell position.
This operation is repeated to correct the position of the preform, and the solidified glass gobs are sequentially adsorbed and conveyed to the annealing step.
The device name "position correction device 90 degree swivel arm" is the rotating arm shown at 10 in fig. 1. In a state where the arm is closed, the position correcting member (porous body) 11 is positioned above the takeout position. Namely, the state shown in fig. 2 (a). In this state, if the "cylinder for lowering the position correcting device" is turned on and lowered, the position correcting member from which the gas is discharged is lowered, and the molded article is positioned in proximity to the glass gob on the lower mold without contact. Namely, the state shown in fig. 2 (B). The timing of turning on the "cylinder for lowering the position correcting device" is 30m seconds (milliseconds) after the lower die is stopped at the take-out position. After the lower die is stopped at the take-out position 30+480 for 510m seconds (milliseconds), the "position correction device lowering cylinder" is closed to raise the position correction member to the original height, and after the lower die is stopped at the take-out position 530m seconds, the "position correction device 90-degree rotation arm" is opened to rotate the arm 10 holding the position correction member by 90 degrees to move and retract the position correction member horizontally from above the take-out position. Thus, the position correcting member and the holding and moving mechanism thereof do not interfere with the taking-out, and the upper surface of the molded product is sucked and lifted upward. Namely, the state shown in fig. 2 (C).
After the removal, the workpiece is moved to an annealing (slow cooling) step to be slowly cooled. The molten glass gob is supplied again to the lower mold from which the molded article was taken out and emptied, and molding is performed.
Thus, a preform having a shape of a revolution with a flat upper surface and a convex lower surface is formed. In the state of fig. 2(C), by designating the center of the suction nozzle 31 of the conveying device 30 of the molded article at the center of the molding die in advance, it is possible to suction the preform whose position is corrected to the center of the molding die by the position correcting device in hundreds of operations without occurrence of a removal failure or the like.
The preform thus obtained is subjected to precision press molding by a known method to produce an aspherical lens having a convex lens shape with a uniform thickness.
Comparative example
The "position correcting device 90-degree rotating arm" was always turned on, and a preform having a flat upper surface and a convex lower surface was formed under the same conditions as in the above-described embodiment except that the position correcting member was retracted from above the press position. In a state before the preform is corrected in position with respect to the molding die as shown in fig. 3, the suction nozzle 31 of the conveying device 30 is lowered, and there is a case where a removal failure occurs with a state where the preform is pressed by one side edge of the suction nozzle at a considerable frequency. The glass material to be processed is not damaged on the upper surface of the preform, but may be damaged by the pressing operation depending on the kind of the glass material.
[ industrial applicability ]
Is useful in the field of production of optical elements such as glass lenses.
Claims (7)
1. A method for producing a thermoformed article using a plurality of lower molds that are continuously or intermittently moved in a circulating manner, comprising the steps of:
(1) separating molten glass gobs sequentially from the continuously flowing molten glass, receiving the separated molten glass gobs at predetermined positions by the plurality of lower molds,
(2-1) while applying a wind pressure to the molten glass gob received by the lower mold on the lower mold to suspend the molten glass gob, cooling the molten glass gob while the molten glass gob is moving on the lower mold to adjust the molten glass gob to a predetermined viscosity,
(3) press-forming a glass gob on a lower die adjusted to a predetermined viscosity at a predetermined position by using an upper die, and then further cooling the press-formed product on the lower die while the lower die is moving; or,
(2-2) cooling the molten glass gob received by the lower mold while applying a wind pressure to the molten glass gob on the lower mold to suspend the molten glass gob, and forming the molten glass gob into a predetermined shape by suspending the molten glass gob by the wind pressure without pressing the molten glass gob,
(4) taking out the press-formed product of (3) or the formed product of (2-2) from the lower die at a predetermined position,
the method for manufacturing a thermoformed article is characterized in that before the thermoformed article is taken out from the lower die, a position correcting member having a position correcting surface facing the thermoformed article and covering the entire upper surface of the thermoformed article is used at a predetermined position on the molding surface of the lower die, and wind pressure is applied to the thermoformed article from the position correcting surface of the position correcting member, whereby the centers of the thermoformed article and the lower die are aligned without contact, and the thermoformed article is taken out after the alignment.
2. The manufacturing method according to claim 1,
the non-contact positioning is performed by applying a wind pressure to the molded article from an upper die.
3. The manufacturing method according to claim 1 or 2,
before the press forming in (3), the molten glass gob adjusted to a predetermined viscosity is aligned at a predetermined position for press forming in a non-contact manner with a predetermined position on the forming surface of the lower mold, and after the alignment, press forming is performed using the upper mold.
4. The manufacturing method according to claim 1 or 2,
the prescribed viscosity of the molten glass gob in (2-1) is 103Mooring to 104.4The range of poise.
5. The manufacturing method according to claim 1 or 2,
the thermoformed article is a glass blank which is processed into a precision press-molding preform or into a precision press-molding preform by a method including grinding.
6. A method for manufacturing a preform for precision press molding, comprising processing a glass blank manufactured by the method according to claim 5 into a preform for precision press molding by a process including at least polishing.
7. A method for manufacturing an optical element, comprising precision press-molding the preform manufactured by the method according to claim 6.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2008017136A JP2009179486A (en) | 2008-01-29 | 2008-01-29 | Method for producing hot-molded article, method for producing preform for precision press molding, and method for producing optical element |
| JP2008-017136 | 2008-01-29 | ||
| JP2008017136 | 2008-01-29 |
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| CN101497491A CN101497491A (en) | 2009-08-05 |
| CN101497491B true CN101497491B (en) | 2013-08-07 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US8806893B2 (en) * | 2011-02-18 | 2014-08-19 | Hoya Corporation | Manufacturing method of a glass blank for magnetic disk and manufacturing method of a glass substrate for magnetic disk |
| JP5654383B2 (en) * | 2011-02-25 | 2015-01-14 | Hoya株式会社 | Manufacturing method of glass preform for precision press molding and manufacturing method of optical element |
| CN102757168B (en) * | 2011-04-27 | 2016-01-27 | Hoya株式会社 | Precise punch forming preformed glass part manufacture method and Optical element manufacturing method |
| JP6127868B2 (en) * | 2013-09-24 | 2017-05-17 | 日本電気硝子株式会社 | Glass material manufacturing method and glass material manufacturing apparatus |
| JP6641923B2 (en) * | 2015-11-25 | 2020-02-05 | 日本電気硝子株式会社 | Glass material manufacturing method and glass material manufacturing apparatus |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1535252A (en) * | 2001-10-06 | 2004-10-06 | 舱壁玻璃公司 | Non-contact molding method and device for molten glass blank |
| CN1880249A (en) * | 2005-06-06 | 2006-12-20 | Hoya株式会社 | Precision mould-pressing forming prefoamer production method and optical component production method |
| CN101062827A (en) * | 2006-04-27 | 2007-10-31 | Hoya株式会社 | Method for manufacturing glass molded body and method for manufacturing optical element |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000001321A (en) * | 1998-06-15 | 2000-01-07 | Canon Inc | Method for producing glass optical element or glass lump as glass material for producing the same |
| JP2001019444A (en) * | 1999-06-29 | 2001-01-23 | Canon Inc | Optical element molding method |
| JP3712575B2 (en) * | 1999-12-10 | 2005-11-02 | Ｈｏｙａ株式会社 | Glass gob manufacturing method and manufacturing apparatus |
| JP4359169B2 (en) * | 2004-03-24 | 2009-11-04 | Ｈｏｙａ株式会社 | Press molding preform manufacturing method, manufacturing apparatus, and optical element manufacturing method |
| JP4847781B2 (en) * | 2005-07-13 | 2011-12-28 | Ｈｏｙａ株式会社 | Press molding preform manufacturing method and molding apparatus, and optical element manufacturing method |
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2008
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1535252A (en) * | 2001-10-06 | 2004-10-06 | 舱壁玻璃公司 | Non-contact molding method and device for molten glass blank |
| CN1880249A (en) * | 2005-06-06 | 2006-12-20 | Hoya株式会社 | Precision mould-pressing forming prefoamer production method and optical component production method |
| CN101062827A (en) * | 2006-04-27 | 2007-10-31 | Hoya株式会社 | Method for manufacturing glass molded body and method for manufacturing optical element |
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| CN101497491A (en) | 2009-08-05 |
| JP2009179486A (en) | 2009-08-13 |
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