JP5166011B2 - Method for manufacturing hot press-formed product, method for manufacturing precision press-molding preform, and method for manufacturing optical element - Google Patents

Description

  The present invention relates to a method for manufacturing a hot press-formed product, a method for manufacturing a precision press-molding preform, and a method for manufacturing an optical element.

A precision press molding method is known as a method of mass-producing glass optical elements having poor mass productivity in the method of grinding and polishing an optical functional surface such as a glass aspheric lens. In this method, glass processed into a shape suitable for precision press molding called a preform is press-molded. Several methods are known for producing preforms. Among them, an appropriate amount is separated from the molten glass flowing out to form a molten glass lump, which is then formed into a preform before the glass lump is cooled and solidified. The method boasts high productivity. This method is called a hot forming method of a preform. A method of forming a glass molded body having a shape similar to a preform by the hot forming method, and converting the glass molded body into a preform by a process including polishing is also described above. Although it is inferior in productivity compared to, it can be said that it is superior in terms of productivity compared to other methods. In the hot forming method, molding is performed while jetting gas to the glass lump on the mold and applying upward wind pressure so that the glass surface is not wrinkled, deformed or broken. (See Patent Documents 1 to 5)
JP 2003-95670 A Japanese Patent Laid-Open No. 2004-300020 Japanese Patent Laid-Open No. 2004-284847 JP 2005-272194 A JP 2007-119335 A

  In the hot forming method, the molten glass is continuously discharged, the molten glass lump is separated one after another, and is sequentially formed with a plurality of forming dies. In the methods described in Patent Documents 1 to 4, a molten glass lump is formed without pressing with a forming die. The lower mold is the only mold used here. On the other hand, in the method described in Patent Document 5, a molten glass lump is press-molded with a molding die. The mold used here is the upper mold in addition to the lower mold.

  In the above method, an empty mold (lower mold) is carried into a position where the molten glass lump is received and stopped, and the molten glass lump is supplied at that position. The mold to which the molten glass block has been supplied is unloaded from the above position, and then another empty mold is carried in and stopped. The molten glass gob is formed on a moving mold and then removed from the mold. However, in the method described in Patent Document 5, it is press-molded by the upper mold in the middle of movement, and then removed from the mold. The molding die (lower die) emptied in this way is again carried into the position for receiving the molten glass lump, and the above steps are repeated.

  In order to perform such a process smoothly, for example, there is a method in which a plurality of molds (lower molds) are arranged on a turntable, the table is index-rotated, and each mold is sequentially transferred to a predetermined stopping position. . In this method, acceleration is applied to the glass block on the mold as the mold is moved and stopped. Since this acceleration has a horizontal component, the glass lump is shaken on the mold. In the case of a method in which the mold is transferred and stopped at a constant cycle like index rotation of a turntable, the acceleration is applied to the glass block at a constant cycle, and the glass block shakes greatly. Further, even if the transfer speed of the mold is increased to improve productivity, the acceleration increases and the shaking of the glass lump is promoted.

  In the method of forming the molten glass ingot described in Patent Documents 1 to 4 without pressing with a forming die, even if the glass ingot shakes, there is little direct influence on the forming. However, in the method of press-molding the molten glass ingot described in Patent Document 5 with a forming die (upper die and lower die), in order to obtain a press-molded product of a desired shape, the molten glass ingot with the lower die and the upper die At the time of press molding, the molten glass lump needs to be positioned at the center of the molding surface of the mold.

  Therefore, in Patent Document 5, for example, as described in claim 2, the first press molding is performed before the continuous oscillation of the molten glass lump starts. In addition, it is described that the centering of the molten glass lump for press molding is performed before the start of rocking of the molten glass lump (paragraph 0018). However, before the start of continuous rocking is immediately after the molten glass lump is formed, the viscosity of the glass during press molding is low (temperature is high). In order to align the glass lump in such a state with the center of the molding surface of the mold, as in Patent Document 5, a force is applied by directly contacting an alignment tool maintained at a temperature that does not melt to the glass lump. To do. Since the viscosity of the glass is too low, even if a force is applied in a non-contact manner, only the shape of the glass block is deformed and it is difficult to align the glass block. Immediately after the alignment, press molding is performed before the position of the glass lump is shifted again. However, since the glass lump having a high temperature and low viscosity is press molded, wrinkles and undulations occur on the glass surface after molding. However, even if wrinkles are formed on the glass surface during press molding, the glass lump has a considerable amount of heat even after pressing, and the wrinkles formed on the glass surface during press molding are stretched by the heat. In addition to wrinkles, even if waviness is generated, it can be repaired and recovered to a smooth free surface (claim 1). However, on the other hand, since the hot glass lump is press-molded, the shape of the press-molded glass lump slightly returns to the free droplet shape due to surface tension, and the desired shape cannot be maintained. there were.

  Further, in the method described in Patent Document 5, centering for press molding is performed by directly contacting the upper die (paragraph 0018), but the glass lump immediately before pressing has a considerable amount of heat and has a low viscosity. The shape of the glass lump is less likely to deteriorate due to the asymmetry of the temperature distribution. Generally, a temperature distribution is generated in the glass lump when the glass and the upper mold are in partial contact. When the glass has a high viscosity, the portion locally cooled by contact solidifies faster than other high-temperature portions. Thereby, the shape of a glass lump deteriorates. When such a glass lump is viewed from above, the rapidly solidified portion protrudes outward, and the other portions have a concave and distorted shape. That is, the shape of the glass block deteriorates due to the asymmetry of the temperature distribution. The surface shape of the part that solidifies quickly is determined at that point, but the part that solidifies late is determined by the surface tension of the glass so that the surface area is reduced, so a dent is generated compared to the part that solidifies quickly. It will be. However, the glass lump just before pressing in the method described in Patent Document 5 has a considerable amount of heat, and because of low viscosity, it is difficult for the glass lump shape to deteriorate due to asymmetric temperature distribution.

  However, on the contrary, since the upper mold is brought into direct contact with the high-temperature glass block, there is a problem of shortening the life of the upper mold.

  Accordingly, the present invention provides a precision press of a desired shape by positioning the molten glass lump at the center of the molding surface of the mold during press molding, and then press-molding the molten glass lump with a mold including a lower mold and an upper mold. This is a method to obtain hot press-molded products (molten glass lump) that can be used as molding preforms, and can be centered without bringing the upper mold into direct contact with the glass lump, thereby extending the life of the upper mold. The object of the present invention is to provide a method capable of maintaining the desired shape without returning the shape of the glass lump press-molded after pressing to a free droplet shape.

  Furthermore, the present invention provides a method for producing a precision press-molding preform by processing the hot press-molded product obtained by the above method, and an optical element by precision press-molding the preform obtained by each of the above methods. It aims to provide a method.

The present invention is as follows.
[1] Using multiple lower molds that circulate continuously or intermittently,
The molten glass lump is sequentially separated from the molten glass flowing out continuously, and the separated molten glass lump is received at a fixed position by the plurality of lower molds,
While the molten glass lump received by the lower mold is floated by applying wind pressure on the lower mold, it is cooled during the movement of the lower mold and adjusted to a predetermined viscosity,
A glass lump on the lower mold adjusted to a predetermined viscosity is press-molded using the upper mold at a fixed position,
A method for producing a hot press-formed product, including taking out the press-formed product from a lower mold at a fixed position,
In the continuous or intermittent circulation movement of the plurality of lower molds, the turntable on which the plurality of lower molds are arranged is index-rotated so that the plurality of lower molds are synchronized and moved to the respective stop positions in a lump. To do
Prior to press molding, a molten glass lump adjusted to a predetermined viscosity is positioned at a predetermined position on the molding surface of the lower mold in a non-contact manner at a predetermined position for press molding, and after the alignment, press molding is performed using the upper mold. ,
Wherein the alignment uses the position correction member is a porous body, the alignment of the non-contact, the position correction member, a shape similar to the inverted shape the shape of the glass gob upper surface before press-forming A method for producing a hot press-molded product, characterized in that gas is ejected from a position correction surface, and the position correction surface is brought close to the upper surface of the glass lump and wind pressure is applied to the glass lump with the jet gas.
[2] The manufacturing method according to [1], wherein the predetermined viscosity of the molten glass gob is in the range of 10 ³ poise to 10 ^4.4 poise.
[3] The manufacturing method according to [1] or [2], wherein the hot press-molded product is a precision press-molding preform or a glass base material processed into a precision press-molding preform by a method including polishing. .
[4] A method for producing a precision press-molding preform, wherein the glass base material produced by the method according to [3] is processed into a precision press-molding preform by a process including at least polishing.
[5] A method for producing an optical element, in which a preform produced by the method according to any one of [3] to [4] is precision press-molded.

  According to the present invention, the upper mold can be centered with respect to the upper mold molding surface without bringing the upper mold into direct contact with the glass lump (the center of the upper mold molding surface and the center of the glass lump can be aligned), thereby extending the life of the upper mold. It is possible to provide a method for producing a hot press-formed product that can maintain the desired shape without returning the shape of the glass lump that has been press-formed after pressing to a free droplet shape.

  Furthermore, according to the present invention, a hot press-molded product that can be used as a precision press-molding preform is obtained by the above production method, or a hot press-molded product obtained by the above production method is processed to obtain a precision press. A molding preform can also be produced. Furthermore, the optical element can be manufactured by precision press molding the preform obtained by each of the above methods.

The present invention is a method for producing a hot press-formed product,
Use multiple lower molds that circulate continuously or intermittently,
The molten glass lump is sequentially separated from the molten glass flowing out continuously, and the separated molten glass lump is received at a fixed position by the plurality of lower molds,
While the molten glass lump received by the lower mold is floated by applying wind pressure on the lower mold, it is cooled during the movement of the lower mold and adjusted to a predetermined viscosity,
A glass lump on the lower mold adjusted to a predetermined viscosity is press-molded using the upper mold at a fixed position,
Including removing the press-molded product from the lower mold at a fixed position.
Furthermore, the present invention is a method for producing the hot press-formed product,
Prior to press molding, a molten glass lump adjusted to a predetermined viscosity is aligned with a predetermined position on the molding surface of the lower mold in a non-contact manner at a predetermined position for press molding, and after the alignment, press molding is performed using the upper mold. It is characterized by that.

  The present invention uses a plurality of lower molds that circulate continuously or intermittently. Specifically, a plurality of lower molds are arranged on a turntable, and the turntable is index-rotated to synchronize the plurality of lower molds and move them one after another to each stop position. It can move cyclically. The stop position is a fixed position, at least (1) a position for receiving the separated molten glass block, (2) a position for press molding using the upper mold, and (3) a position for taking out the press molded product from the lower mold. . However, depending on the number of lower molds provided on the turntable, there may be a stopping position without any special operation or operation.

  The molten glass lump is sequentially separated from the molten glass flowing out continuously, and the separated molten glass lump is received at a fixed position by a plurality of lower molds. Thereby, the molten glass lump for shape | molding a hot press molded product one after another from the molten glass which flows out continuously is formed. The molten glass is obtained, for example, by heating, melting, defoaming, and homogenizing a glass raw material. The molten glass continuously flows out of the pipe at a constant flow rate, and flows out of the molten glass flow. Receiving the lower end on the lower mold placed below the pipe, and further lowering the lower mold vertically downward to separate the lower end of the molten glass flow on the lower mold from the molten glass flow, on the molding surface of the lower mold The separated molten glass lump is received.

  Instead of this method, the lower end of the flowing molten glass flow is received by a support placed below the pipe, and the support is rapidly lowered vertically to separate the lower end of the molten glass flow on the support from the molten glass flow. The method of supplying the separated molten glass ingot on the molding surface of the lower mold, or receiving the lower end portion of the flowing molten glass flow under the pipe, and removing the support by the support rapidly. Using the method of separating the lower end of the molten glass flow supported by the support from the molten glass flow and supplying the separated molten glass lump onto the lower mold forming surface, etc. A glass lump can also be obtained.

  The molten glass lump received in the lower mold is cooled during the movement of the lower mold and adjusted to a predetermined viscosity while being floated by applying wind pressure on the lower mold. The molding surface of the lower mold is a molding surface that transfers the shape of the surface to the glass by pressing, is a smooth surface, and moreover, a plurality of gas jets for injecting the molten glass lump by applying wind pressure A gas outlet is provided.

  Generally, when manufacturing a hot press-molded product from a molten glass lump, if the temperature of the mold is kept at a temperature that can prevent fusion with the molten glass lump, the temperature difference between the molten glass lump and the mold becomes extremely large. When the molten glass lump directly touches the mold that is kept at a lower temperature than the molten glass lump in this way, the glass is locally cooled and contracted at the contact portion, so that the glass surface is wrinkled and smooth. There is a possibility that a hot press-formed product having a surface cannot be obtained. Further, when the glass whose temperature has been lowered directly touches the mold, the glass may be broken by a phenomenon called can cracking. On the other hand, in the present invention, since the floating molding is performed, the contact between the glass and the lower mold is reduced, so that the above-described problems can be avoided.

  As the gas ejected from the gas ejection port, a gas that does not react with glass is preferably used, and specific examples include air, nitrogen, inert gas, and the like. The amount and pressure of the gas can float the molten glass lump and maintain a stable state so that the molten glass lump does not cause fusion with the lower mold on the molding surface. It is preferable to define. The pressure and flow rate of the gas to be ejected can be appropriately adjusted depending on the volume of the glass block to be molded. Specifically, for example, the pressure is preferably in the range of 0.3 to 0.5 MPa, and the gas flow rate is preferably in the range of 0.25 to 0.45 liters per minute.

  Hereinafter, the upper surface of the molten glass block on the molding surface is defined as the upper surface, and the surface facing the molding surface is defined as the lower surface.

The glass lump supplied to the molding surface of the lower mold is cooled in a floating state, and the viscosity is adjusted so as to have a predetermined viscosity suitable for press molding. The viscosity (predetermined viscosity) of the separated molten glass lump is preferably adjusted by cooling so as to be from 10 ³ poise to 10 ^4.4 poise from the viewpoint that press molding can be relatively easily performed to a desired shape.

  The molten glass lump adjusted to the specified viscosity is positioned in a fixed position for press molding before press molding, aligned in a non-contact position on the molding surface of the lower mold, and press-molded using the upper mold after alignment. To do. Positioning without contact with the molten glass lump can be performed by applying wind pressure to the molten glass lump from the upper side (or position correcting member). At this time, the jet gas pressure is preferably in the range of 0.15 to 0.5 MPa, for example, and the jet gas flow rate is preferably in the range of 0.15 to 0.45 liters per minute, for example.

Hereinafter, the alignment of the glass block will be described with reference to the drawings.
As shown in FIG. 1, a position correcting member 11 made of a porous body is provided at the tip of the rotary arm 10 of the alignment apparatus. The position correction surface 11a of the position correction member 11 facing the molding surface 21 has been processed in advance into a shape that approximates a shape obtained by inverting the shape of the upper surface (the upper surface before press molding) of the glass block G on the molding surface 21. . Air, nitrogen, an inert gas, or the like is supplied to the back surface 11b of the position correction member 11 (the back surface of the position correction surface 11a) through a gas flow path 15 provided in the rotary arm. Air, nitrogen, inert gas, and the like are uniformly ejected from the position correction surface 11a through the position correction member 11 which is a porous body. Position correction is performed by lowering the portion from the position correction member 11 to the shaft 12 of the rotary arm by the lifting device 13 at this position.

FIG. 2 shows an operation explanatory diagram of the alignment apparatus. In (A), alignment is performed so that the center of the position correction surface 11a is positioned directly above the center of the molding surface 21 of the lower mold 20. In (B), closer to the position correcting surface 11a by moving the position correction member 11 is actuated vertically downward the elevating device 13 of the position alignment device in this state to the upper surface of the glass gob G of the molding surface. When the glass lump G is displaced from the center of the molding surface 21 by this operation, the distance between the upper surface of the glass lump G and the position correction surface 11a is closer to the opposite side on the displaced side. Then, the wind pressure received from the gas ejected from the position correction surface 11a is increased on the side where the glass lump G is displaced, the glass lump G is returned to the center of the molding surface 21, and the center of the glass lump G is the center of the molding surface 21. To match. After correcting the position of the glass lump G on the molding surface 21 of the lower mold 20 in this way, the positioning device 11 is raised by operating the lifting device 13 of the positioning device, and the rotating arm 10 is rotated. The position correcting member 11 is retracted from above the lower mold. This series of operations can also suppress the shaking of the glass lump that has been swaying during the ascent.

  Subsequently, in (C), the upper die 30 waiting above the lower die is lowered and the glass lump G on the molding surface is pressed together with the lower die. The entire glass lump is molded by pressing, the molding surface of the upper mold is transferred to the upper surface of the glass lump, and the molding surface of the lower mold is transferred to the lower surface of the glass lump. The outer periphery of the upper surface of the lower mold and the outer periphery of the lower surface of the upper mold are, for example, a structure to be fitted, and the center of the lower mold molding surface and the upper mold molding surface by fitting the lower mold and the upper mold prior to press molding. The glass lump is pressed after aligning the centers of the molds so that the lower mold surface and the upper mold surface face each other. At this time, the pressure of the gas supplied to the lower gas jet port is set to a pressure that does not allow the glass to enter the gas jet port so that the glass is not depressed by the gas pressure.

  Although not shown, after press molding, the glass is released from the upper mold, and the upper mold is retracted upward. Thereafter, the molded glass lump can be further cooled in the state of being floated on the lower mold forming surface, taken out from the lower mold forming surface, and annealed.

  In this manner, rotationally symmetric hot press-formed products can be formed one after another. The shape of the hot press-formed product is not particularly limited. For example, a hot press-formed product having a convex surface on the lower surface and a flat surface on the upper surface, a convex surface on the lower surface, and a rotationally symmetric hot press-formed product having a concave surface on the upper surface. Various hot press-molded products such as a rotationally symmetric hot press-molded product having a convex surface, a flat upper surface and a concave portion at the center can be formed. These shapes can be formed by appropriately selecting the shape of the lower mold surface and the shape of the upper mold surface. Each hot press-molded product is a high-quality molded product with no damage such as cans and cracks.

  The hot press-formed product can be a precision press-molding preform or a glass base material processed into a precision press-molding preform by a method including polishing. When the hot press-molded product is a glass base material processed into a precision press-molding preform by a method including polishing, the produced glass base material is processed into a precision press-molding preform by a process including at least polishing. Thus, a precision press-molding preform can be manufactured. After annealing the hot press molded product, the surface can be polished and finished into a preform. Since the shape of the hot press-formed product is rotationally symmetric, a rotationally symmetric preform can be easily made by polishing.

  Furthermore, an optical element can also be manufactured by carrying out precision press molding of the preform produced by the method of the present invention. Production of an optical element by precision press molding can be performed by a known method. Various preforms such as a concave meniscus lens, a convex meniscus lens, and a biconcave lens can be produced by precision press molding the preform. The lens thus obtained has excellent surface accuracy and does not show defects such as uneven thickness.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example An example will be described with reference to FIG. A molding machine is used in which twelve lower molds are arranged at equal intervals on the circumference around the rotation axis of the turntable that rotates with the index.

  FIG. 3 is a time chart showing the operation of a molding apparatus for molding a preform from molten glass. For the purpose of explaining the operation of the above device, a mechanism for moving the lower mold up and down to separate the molten glass (device name “melted glass separation”) and a mechanism for rotating the turntable carrying the lower mold (device name “molding”). Machine index "), a mechanism for lowering the upper die used for press molding of glass lumps (device name" upper press device "), a mechanism for raising the lower die during the press molding (device name" lower press device ") , A mechanism (device name “Position Correction”) that retreats the porous body that ejects the gas used for non-contact alignment of the molten glass lump to a predetermined position on the molding surface of the lower mold from directly above the lower mold stop position The device 90-degree swivel arm "), and the porous body is divided into a mechanism (device name" position correction device lowering cylinder ") that moves in the vertical direction.

  The apparatus name “start molding machine” at the top of the time chart indicates ON / OFF of the main switch of the entire molding apparatus. First, start the molding device by turning the device name “Start molding machine” from OFF to ON.

  Starting from the timing when the table is stopped by index rotation of the turntable shown in FIG. 4, the next index rotation of the table is performed, and the time until the table stops is defined as one tact, which is represented as h. That is, one tact corresponds to the time from when the lower mold stops at the stop position until it is transferred to the next stop position and stopped. In this embodiment, one tact is set to 6920 milliseconds.

  After stopping at the stopping position 1 (fixed position) below the molten glass from which the lower mold flows out, turn the device name “molten glass separation” from OFF to ON, raise the lower mold, and hold the molten glass at the raised position. Receive the bottom edge. The molten glass that continuously flows out accumulates on the lower mold, and constriction due to surface tension occurs between the glass outlet of the molten glass and the lower mold.

  When 6120 milliseconds · second have passed since the table stopped, turning “melting glass separation” from ON to OFF and dropping the lower mold rapidly, the molten glass below the constricted part separates and melts onto the lower mold. A glass lump can be obtained. Next, the “molding machine index” is turned from OFF to ON, and the turntable is rotated 30 ° around the rotation axis and stopped.

  In this embodiment, the glass block is aligned and press-molded at the next stop position 2 (referred to as a press position) after receiving the molten glass block. The device name “position correcting device 90-degree turning arm” is a rotating arm indicated by 10 in FIG. When this arm is OFF, the position correction member (porous body) 11 is above the press position. This is the state shown in FIG. In this state, when the “position correction device lowering cylinder” is turned on and lowered, the position correction member that ejects gas descends, approaches the glass block on the lower mold, and aligns the glass block without contact. This is the state shown in FIG. The timing for turning on the “position correction device lowering cylinder” is 30 msec (milliseconds) after the lower die stops at the press position. 30 + 480 = 510 msec (milliseconds) after the lower die stops at the press position, turn off the “position correction device lowering cylinder” and raise the position correction member to its original height, the lower die presses 530 msec after stopping at the position, the “position correction device 90 degree turning arm” is turned on, and the arm 10 holding the position correction member is turned 90 ° to move the position correction member horizontally from above the press position. Move and evacuate. In this way, the position correcting member and its holding and moving mechanism are made not to interfere with the press molding, and the upper press device and the lower press device are turned on 550 msec after the lower die stops at the press position. The upper die waiting above the pressing position is lowered, the lower die staying at the pressing position is raised, and the glass block is pressed with the upper and lower dies. This is the state shown in FIG.

  After 3350 milliseconds (550 milliseconds + 2800 milliseconds) after the lower die stops at the press position, the upper press device and the lower press device are turned off, and the upper die and the lower die are raised and lowered to their original heights. End press forming. Next, 3430 milliseconds (530 milliseconds + 2900 milliseconds) after the lower die stops at the press position, the “position correction device 90 degree turning arm” is turned off to return the porous body to the upper side of the original press position. Thereafter, the “molding machine index” is turned ON, the turntable is rotated by 30 °, and each lower mold is moved to the next stopping position.

  Such an operation is repeated, and the molten glass is press-formed one after another to form a desired shape. The glass molded product obtained while the lower mold is stopped at the stop position three times before returning to the molten glass supply position 1 (position 10 in FIG. 4 or the position where the cooling of the glass is completed) is taken out from the lower mold. For removal, the upper surface of the molded product is adsorbed, lifted upward, moved to a slow cooling device, and slowly cooled. The molded product is taken out and the molten glass lump is supplied again to the empty lower mold and molded.

  Thus, a rotating body-shaped preform having a flat upper surface and a convex lower surface was formed. A photograph of the preform obtained in the example taken from directly above is shown on the left of FIG. The preform surface was smooth, the outer diameter (arithmetic mean of the major axis and the minor axis) was 15.0 mm, and the difference between the major axis and the minor axis was less than 0.2 mm when viewed from the rotationally symmetric axis direction.

  The preform thus obtained was precision press-molded by a known method to produce a convex meniscus aspherical lens without uneven thickness.

(Comparative example)
A preform with a flat top surface and a convex bottom surface under the same conditions as in the above example, except that the “position correction device 90-degree swivel arm” is always ON and the porous body is retracted from above the press position. Molded. A photograph taken from directly above the preform obtained in the comparative example is shown on the right side of FIG. The outer diameter was 15.0 mm, the difference between the major axis and the minor axis was 0.9 mm, and the roundness decreased.

  Using this preform, a convex meniscus aspherical lens was precision press-molded in the same manner as in the above example. As a result, the lens had a large thickness deviation and a low surface accuracy.

  This is useful in the field of manufacturing optical elements such as glass lenses.

An example of the alignment apparatus used for this invention. Explanation of the operation of the alignment device. The operation | movement of the shaping | molding apparatus which shape | molds a preform from a molten glass is shown as a time chart. Explanatory drawing which shows an example of a turntable. The photograph which image | photographed the preform obtained in the Example (left) and the comparative example (right) from right above.

Claims (5)

Use multiple lower molds that circulate continuously or intermittently,
The molten glass lump is sequentially separated from the molten glass flowing out continuously, and the separated molten glass lump is received at a fixed position by the plurality of lower molds,
While the molten glass lump received by the lower mold is floated by applying wind pressure on the lower mold, it is cooled during the movement of the lower mold and adjusted to a predetermined viscosity,
A glass lump on the lower mold adjusted to a predetermined viscosity is press-molded using the upper mold at a fixed position,
A method for producing a hot press-formed product, including taking out the press-formed product from a lower mold at a fixed position,
In the continuous or intermittent circulation movement of the plurality of lower molds, the turntable on which the plurality of lower molds are arranged is index-rotated so that the plurality of lower molds are synchronized and moved to the respective stop positions in a lump. To do
Prior to press molding, a molten glass lump adjusted to a predetermined viscosity is positioned at a predetermined position on the molding surface of the lower mold in a non-contact manner at a predetermined position for press molding, and after the alignment, press molding is performed using the upper mold. ,
Wherein the alignment uses the position correction member is a porous body, the alignment of the non-contact, the position correction member, a shape similar to the inverted shape the shape of the glass gob upper surface before press-forming A method for producing a hot press-molded product, characterized in that gas is ejected from a position correction surface, and the position correction surface is brought close to the upper surface of the glass lump and wind pressure is applied to the glass lump with the jet gas. The manufacturing method according to claim 1, wherein the predetermined viscosity of the molten glass gob is in the range of 10 ³ poise to 10 ^4.4 poise.   The manufacturing method according to claim 1 or 2, wherein the hot press-molded product is a precision press-molding preform or a glass base material processed into a precision press-molding preform by a method including polishing.   A method for producing a precision press-molding preform, wherein the glass base material produced by the method according to claim 3 is processed into a precision press-molding preform by a process including at least polishing. The manufacturing method of the optical element which carries out precision press molding of the preform produced by the method in any one of Claims 3-4 .