Patent Application
20090205375
The present invention relates to an apparatus for press-molding optical elements, and particularly, to an apparatus for press-molding optical elements that is used when high-precise optical elements, such as aspheric lenses, are press-molded.
In recent years, it attracts attention a method for precisely press-molding optical glass elements (e.g., glass lenses) in which the faces of the molded grass optical elements can be used as they are without being polished. Generally, in order to execute the above method, it is used a press-molding apparatus that press-molds a glass material in a softened state within a body die by using a molding die that is slid with respect to the body die, to form an optically-functioning face corresponding to a die face of the molding die in the glass material. The important thing herein is that, when products are relatively small, productivity is low if molding is performed by one set of dies by one press-molding apparatus. Thus, a method of producing a plurality of optical elements at the same time by mounting a plurality of dies on one press-molding apparatus is proposed.
When the plurality of dies are pressed at the same time, a contrivance for obtaining optical elements with high molding precision is required. As this method, a method of pressing a plurality of dies using a pressing member, such as a flat plate, which is fixed to an integral pressing shaft so as to be orthogonal to the sliding direction of the dies, is primarily considered. If this method is used, the stroke of all the dies will be determined on the basis of a die having the shortest stroke, among a plurality of dies. For this reason, in order to form optical elements in which the thickness and the face angle are controlled in the order of micrometers, it is necessary to sufficiently control the dimension of each die, the dimension of the pressing member, tilting angle at the time of attachment and pressing of the pressing member, and the wear of a contact portion of the pressing member with the die so that all strokes may fall within standards. However, it is almost impossible in view of the fact that deformation of the molding apparatus is also occurred when the molding apparatus is placed in the hundreds-degrees (Celsius) environment to perform the molding. Therefore, it will be necessary to butt an upper die, which is a die for molding, against a body die, and to guarantee the above precision in terms of the precision of the constructional members of the upper die, the body die, and other dies.
However, since the strokes of all the dies are the same in the above method, it is also almost impossible to always move down all the pressing members thoroughly. Alternatively, there may be a method in which the pressing member is not fixed but is provided with some degrees of freedom to follow the stroke. However, when a plurality of dies, especially four or more dies are pressed at the same time, all the dies cannot be moved down thoroughly unless the heights of the dies are aligned on the same plane when they are moved down thoroughly. Further, since the positions at which pressure application is started and the molding speeds (deformation speeds of glass) are different from one die from another die due to variations in the dimensions of materials to be molded, subtle temperature differences between dies during the application of pressure, or the like, the phenomenon that the dies are pressed in a state where the pressing member is tilted with respect to the sliding direction of the dies occur frequently. For this reason, a pressing force acts in directions other than the sliding direction of the dies, and seizing or damage of the dies are apt to occur. Furthermore, the contact portions between dies and the pressing member are always rubbed together, and are thereby apt to be worn. Particularly under such high temperature, the wear becomes severe. As a result of the wear, the vicious cycle that seizing or damage of the dies is further promoted are repeated.
Further, in the above molding apparatus, it is necessary to heat or cool the body die, the upper die, and the lower die with a fairly high and low temperature difference for the temperature control of a glass material in a press-molding process. Thus, the body die, the upper die, and the lower die are made of a material having almost the same coefficient of thermal expansion, and the clearance for securing sliding of the upper die and the lower die with respect to the body die is provided. For this reason, for example, when a glass material is press-molded between the moved-down upper die and the lower die, if pressing pressure is not applied to the center of the upper die, the upper die is tilted while sliding within the body die. As a result, it is not possible to press-mold a glass material in a state where the upper die and the lower die oppose each other correctly. Furthermore, in an extreme case, seizing occurs between the body die and the upper die, so that the upper die cannot be correctly set with respect to the body die. As a result, normal pressing operation is no longer performed. In other words, the center of the optically-functioning face of the molded optical element will not coincide with its optical axis. Further, when the upper die is pulled up in order to take out a molded element from the dies, if the pull-up force deviates from the center of the upper die, the upper die is tilted, and seizing occurs between the body die and the upper die, so that setting and releasing of the upper die are not allowed. In such molding apparatus, particularly, the clearance of a sliding portion between the body die and the upper die is as small as less than 10 μm in actually used conditions. Moreover, the seizing occurs more easily from the relationship that the apparatus is used under the high-temperature environment.
There is a molding apparatus described in Japanese Patent No. 2815037 (Patent Document 1) as an example in which the drawbacks of the above-mentioned conventional technique are solved to some extent. In the molding apparatus of Patent Document 1, by splitting one pressing shaft that applies pressure to the upper die into an upper shaft and a lower shaft, and stacking and disposing a plurality of disc springs between the upper shaft and the lower shaft, even if the heights of dies during application of pressure differ, pressing pressure is applied to each die uniformly by absorbing the difference of the heights by deformation of the disc springs.
However, in the molding apparatus of Patent Document 1, the disc springs are in a portion near the upper die. Thus, there is a drawback that the disc springs are exposed to high temperature, and loosened. In order to compensate for this drawback, it is necessary to water-cool the portions of the disc springs. In this case, however, the drawback that members are enlarged and complicated for additionally providing a water-cooling mechanism. Furthermore, since the water-cooled members contact the upper die during molding, there is also a drawback that the temperature of the upper die drops rapidly, and the molding become unstable.
Further, since a plurality of upper dies and lower dies are set in one body die for the purpose of cost-down, it is not economical to take a long distance between the die sets. For this reason, even if the distance between the die sets is large, the distance is typically tens of millimeters, and it is necessary to provide a disc spring in each shaft corresponding to this distance. Typically, since the pressure required for press-molding of glass is about 4.9 kN in a metal die of +18, the strength of a spring used for the disc spring needs to be 4.9 kN or more. A spiral spring of 4.9 kN to be received in a space of tens of millimeters does not exist typically. Therefore, although the disc springs are used in Patent Document 1, it is necessary to stack a plurality of disc springs in order to receive a spring of capacity of 4.9 kN in a narrow space even if the disc springs are used. As a result, a drawback that a spring mechanism is considerably lengthened occurs, and consequently the molding apparatus is enlarged. Further, when it is necessary to change the size of a lens to be pressed differently from an original schedule, and to greatly change pressing pressure, it is necessary to replace the disc springs to change a spring constant. In this case, disassembling parts that receive the stacked disc springs and replacing the disc springs require considerable time and efforts. As described above, even in the molding apparatus of Patent Document 1, there is still a problem. In addition, Patent Document 1 has no description about pressure distribution in case the lower die slides in the body die and performs pressing. If pressing is made by the lower die, it is inferred that a mechanism does not perform pressure distribution.
The invention has been made in view of the above circumstances. An object of the invention is to provide an apparatus for press-molding optical elements capable of efficiently manufacturing high-precise optical elements by always causing the force of an operating member applied to a body die to act so as to pass through the center of an upper die, at least when the body die slides with respect to the upper die, and a glass material is press-molded, and when a molded product as an optical element is separated from the dies.
Further, another object of the invention is to provide an apparatus for press-molding optical elements capable of thoroughly pressing all materials to be molded when a body die slides with respect to a plurality of upper dies, and capable of making adjustment in accordance with a difference even if the starting positions of pressure application or the molding speed (deformation speeds of glass) differs between dies due to variations in the dimensions of the materials to be molded, subtle temperature differences between dies during the pressure application, or the like.
In order to achieve the above objects, according to the invention, there is provided an apparatus for press-molding an optical element by pressing a glass material with a plurality pairs of upper dies and lower dies, the apparatus including: a lower die pressure applier, operable to apply pressure to the lower dies; a body die, adapted to guide the upper dies and the lower dies; a pressure generator, operable to lift the body die; and an aligner, operable to slide the body die along the upper dies to align each of the upper dies, the aligner comprising a hunger supporting each of the upper dies in a hanging manner, and operable to cause each of the upper dies to move in a plane which perpendicularly intersects a movement axis of the body die, when the body die is lifted along the upper dies by the pressure generator.
The press-molding apparatus may further comprise an upper die pressure distributor, comprising levers respectively pressing the upper dies downward to apply pressure to each of the upper dies independently.
The press-molding apparatus may further comprise a lower die pressure distributor, comprising levers respectively pressing the lower dies upward to apply pressure to each of the lower dies independently.
The upper die pressure distributor may comprise rocking members each of which is rockably supported by a fulcrum, and has one end brought into contact with an upper end of one of the upper dies and the other end coupled with a spring member, so as to press the one of the upper dies downward and pressure applied to the one of the upper dies is adjusted by compressing the spring member.
The lower die pressure distributor may comprise rocking members each of which is rockably supported by a fulcrum, and has one end brought into contact with a lower end of one of the lower dies and the other end coupled with a spring member, so as to press the one of the lower dies upward and pressure applied to the one of the lower dies is adjusted by compressing the spring member.
The fulcrum in the upper die pressure distributor may be displaceable, thereby the pressure applied to the one of the upper dies is variable without replacement of the spring member.
The fulcrum in the lower die pressure distributor may be displaceable, thereby the pressure applied to the one of the lower dies is variable without replacement of the spring member.
The spring member may be a coiled spring.
The press-molding apparatus may further include: an upper die pressure distributor, operable to distribute the pressure generated by the upper die pressure generator to each of the upper dies; and a lower die pressure distributor, operable to distribute the pressure generated by the lower die pressure generator to each of the lower dies.
According to the apparatus for pressing-molding an optical element according to the invention, since the aligner is provided, when press-molding is performed by a plurality of upper dies and lower dies at the same time, the force applied to the upper dies can always support each die in place, and when the body die is lifted, the force can be made to act towards the center of the movement axis of the body die, and high-precision optical element, in which an optically-functioning face is correctly located with respect to an optical axis without no trouble such as seizing, can be manufactured efficiently.
Further, in the present the invention, a pressure distributor having levers is provided. Thus, when a body die having a plurality of guide holes slides with respect to a plurality of upper dies, and a glass material is press-molded, all the upper dies can be pressed thoroughly. Moreover, even if the starting position of application of pressure or the speed (deformation speed of glass) of molding differs between dies due to variations in the dimensions of the molding raw materials, subtle temperature differences between dies during the application of pressure, or the like, adjustment can be made accordingly. Thus, the precision of molded products becomes good, and productivity also improves.
Embodiments of the invention will be described below in detail with reference to the accompanying drawings.
The molding chamber 3 is arranged on a mount 10, and a gate 301 for carrying in a glass material G and carrying out a molded product is equipped with a gate valve 11. The molding chamber communicates with the outside via the gate. Further, an exchanger 4 for performing loading of a glass material G into the molding die 1 and unloading of a molded product is equipped inside the molding chamber 3. The exchanger 4 is constructed by mounting a suction hand 402 serving as a glass loader/unloader on a lower end of a rotary shaft 401 that is vertically penetrating the ceiling of the molding chamber 3, and by providing suction pads 403 at a end of the suction hand 402. The rotary shaft 401 is rotatably connected with a piston rod 14A of an electric cylinder mechanism 14 provided on the ceiling of the chamber 3. The rotary shaft 401 is vertically moved by the operation of the piston rod 14A, and is rotated by an electric motor 15 via a gear train 16 which are provided in the piston rod 14A. In
As shown in
Accordingly, in a state where a glass material G is sucked on the suction pads 403, it is introduced into the molding die 1 by the control of the cylinder mechanism 14, and by the axial operation and rotational operation of the rotary shaft 401 based on the rotational control of the electric motor 15. Further, in a state where a molded product is sucked by the suction pads 403, it is taken out of the inside of the molding die 1 by the reverse axial operation and rotational operation of the rotary shaft 401.
The suction pads 403 are configured so as to be able to perform suction or suction release independently in correspondence with four dies, and a suction source is a rotary pump 40 used for substitution of nitrogen (N2) in the molding chamber 3. Sub-lines branched from the rotary pump 40 communicate with the suction pads 403. As shown in
A loader/unloader 17 for a glass material G and a molded product with respect to the molding chamber 3 is located at a side face of the gate 301 of
Thus, when the glass material G or molded product is carried into or carried out of the molding chamber 3, with the glass material G being put on the rest 172, the piston rod 18A is operated by the control of the cylinder mechanism 18 to horizontally move the exchange chamber 171, thereby bringing the opening 171A into airtight contact with the gate valve 11. In this state, after the inside of the exchange chamber 171 is vacuumed by the vacuum pump 40, the atmosphere of the exchange chamber is replaced with nitrogen atmosphere, the gate valve 11 is opened, the molding chamber 3 and the exchange chamber 171 communicate with each other, the rest 172 is introduced into the molding chamber 3 by the horizontal conveyer 173, and transfer of a glass material G and receipt of a molded product are performed with respect to the exchanger 4. Thereafter, the horizontal conveyer 173 is operated reversely, the rest 172 is returned to the exchange chamber 171, the gate valve 11 is closed, the exchange chamber 171 is horizontally moved by the operation of the cylinder mechanism 18, and unloading of a molded product from the rest 172 and loading of a new glass material G thereto are performed.
In the present embodiment, a robot 19 is used for loading of a glass material G to the rest 172, and unloading of a molded product therefrom. The robot 19 transfers a glass material G to the rest 172 from a stocker 20 using a sucking device or the like, and transfers a molded product to a prescribed point from the rest 172. That is, although
Next, a molding apparatus will be described with reference to
A bottom plate 339 that is screw-coupled with the body die 100 via a heat insulator 338 is placed above a body die base plate 337 of
Cutout portions 101E are formed in the bottom 100B2 of the body die 100, and lifters 300 are arranged in the cutout portions 100E, respectively. Each lower die 101 is placed on each of the lifters 300. Each lifter 300 serves to compensate variations in the axial dimensional accuracy of each lower die 101.
In the configuration of the present embodiment, four molded products are at the same time press-formed by die sets of a plurality of, i.e., four upper and lower dies. As will be described later, it is required that a total load of, for example, 19.6 kN is applied to the four upper dies 102, and equal loads are applied to the upper dies 102, respectively. However, the four die sets may deviate to some extent in the movement stroke for glass molding of the body die 100 and the lower dies 101 due to variations in the finishing accuracy of the dimensions of individual members of the upper dies 102, the lower dies 101, and the body die 100. The lifters 300 are provided for adjustment of this stroke.
Meanwhile, a hole that supplies nitrogen gas for cooling is provided in the center of a bottom plate 100D. The nitrogen gas that is blown against the bottom plate 100D is blown against each lower die 101 along a passage provided in the bottom plate 100D, and is further discharged to the outside of the body die 100 by the passage provided in the bottom plate 100D. As shown in
In
As for the aligner 106, as shown in
Further, supporting slots 105C that receive the supporting portions 106B are formed in the hanger 105.
When an upper die 102 is assembled to the hanger 105 and the aligner 106, first, the flange portion 102B of the upper die 102 is inserted through the insertion holes 105B and 106D from below, and is caused to extend upward of the aligner 106. In this state, the flange portion 102B is turned by 90 degrees, and the lower face of the flange portion is caused to be supported by the supporting portions 106A. Thereafter, the relative position between the upper die 102 and the aligner 106 can be held by attaching the rotation stopper 107 to the hanger 105. In this case, the relative position between the hanger 105 and the aligner 106 is ensured as the supporting portions 106B are inserted through supporting slots 105C.
Reference numeral 212 of
A number of molding processes are at the same time performed by a plurality of sets of upper dies 102 and lower dies 101. In the molding apparatus of the present embodiment, after glass is press-molded by four upper dies 102 and four lower dies 101 to form lenses, the operation of moving down the body die 100 and taking out a molded product remaining on each lower die 101 through the opening 101A of the body die 100 is performed in order to take out a lens as a molded product from between each set of upper and lower dies.
In the present embodiment, alignment of each of the four upper dies 102 is performed by the aligner 106. That is, if the body die 100 is moved downward, the flange portion 105F of the hanger 105 will hit the lower end hook portion 212B, and the hanger 105 will not move downward from there.
In
When the body die 100 is moved downward in a state where each upper die 102 is held by the hook member 212 of
In a state where the body die 100 is moved downward, each upper die 102 is held by the hanger 105 and the aligner 106 with the two planes X-X and Y-Y orthogonal to the axis O-O of
Reference numeral 104 of
The lever rod 230 is rockably supported by a fulcrum member 231, and the other end 230B which is an end opposite to the end 230A adapted to come in contact with the upper end 202A of the upper die pressing rod 202 is fixed to the chamber 3 via a compression spring 232. The upper die pressing rod 202, the lever rod 230, the fulcrum member 231, and the compression spring 232 constitute a pressure adjuster for an upper die 102. Further, reference numeral 233 designates nitrogen cooling pipe provided in the middle of the four upper die pressing rods 202. An upper end of the cooling pipe is coupled with a cooling-medium supplying port 234 provided in the chamber 3, and a lower end thereof faces the upper center of the body die 100, so that nitrogen gas cooling can be performed along a groove for nitrogen gas provided in the body die 100.
A pressure adjuster (upper die pressure distributor) 208 of an upper die 102 is comprised of the upper die pressing rods 202, the lever rods 230, the fulcrum members 231, and the compression springs 232. One of the objects of the invention is to provide an apparatus that obtains a number of molded products at the same time by a plurality of sets of upper and lower dies. For that purpose, it is necessary to cause the pressing load required for four die sets to act uniformly. In the apparatus shown in
In order to heat and press a glass material and to form a high-precision optical element, it is necessary to cause high pressure (3.92 to 5.88 kN) to be generated in each upper die 102, and to transmit the pressure to each upper die 102 via the above individual members from the body die lifting cylinder 210. Furthermore, in an apparatus using a method of repeating the process of taking out a molded product after a glass material is heated and press-molded to a predetermined temperature (400 to 800° C.) within the die, it is required that a heating-cooling-heating cycle is shortened in order to repeat heating and cooling of the molded product, die members, the body die, etc. Thus, it is necessary to reduce the heat capacity of the whole molding apparatus, and therefore, it is necessary to miniaturize the apparatus.
Each upper die 102 is pressed by the upper die pressing rod 202 and the ascending body die 100, which are shown in
The whole upper end face 10a of the body die 100 hits the four upper dies 102 via the spacers 102C. This is a condition that is required to obtain the same molded products, for example, lenses having the same thickness, by four die members. For that purpose, it is necessary to cause a pressing force to independently act on the four upper dies 102, to cause the upper end face 10a of the body die 100 to completely hit each upper die 102, and to cause a sufficient pressing force to act on the upper dies 102.
In the present embodiment, in order to solve the above problems, the pressure adjuster (upper die pressure distributor) 208 in which a spring member, particularly, the compression spring 232 shown in
If a pressing force acts on the body die 100 from the body die lifting cylinder 210 (refer to
Next, a specific example of each compression spring 232 will be described. That is, one rectangular wire spring made of silicon chrome steel wire having an external diameter of φ18 mm, an internal diameter of φ9 mm, a spring constant of 44.1 Ns/mm, a maximum load of 568 N, and a free height of 45 mm was used, a fulcrum member 231 supporting a lever rod 230 was set so that the ratio of the distance to an upper die pressing rod 202 and the distance to a compression spring 232 may be set to 1:10, and individual members were assembled. As a result, a pressure adjuster that endures a load of 10 times the maximum load of the compression spring 232 by the lever's principle (5.68 kN in this case) was constructed. By constructing four such compression springs so as to correspond to the upper dies 102, four pressure adjusters are completed (they endure up to 22.7 kN in total pressure). Consequently, since it is not necessary to provide a lot of disc springs as in the molding apparatus of Patent Document 1 in which disc springs are assembled into a chamber, there is no need for adjustment. Further, since the compressing springs are installed outside the chamber, there is a margin of space, and design becomes easy. Further, it is not necessary to cool the compression spring 232.
The same configuration is allowed even in a compression spring 232 using an ordinary piano wire. Specifically, one rectangular wire spring made of a piano wire having an external diameter of φ28 mm, an internal diameter of φ4.5 mm, a spring constant of 68.6 Ns/mm, a maximum load of 862 N, and a free height of 40 mm was used, the position of a fulcrum member 231 supporting a lever rod 230 was set so that the ratio of the distance to an upper die pressing rod 202 and the distance to a compression spring 232 may be set to 1:6, and individual members were assembled. As a result, a pressure adjuster that endures a load of 6 times the maximum load of the compression spring 232 by the leverage principle (5.17 kN in this case) was constructed. By constructing four such compression springs so as to correspond to the upper dies 102, four pressure adjusters are established (they endure up to 20.7 kN in total pressure). In this state, when the thrust (the total of the pressing force applied to the four upper dies 102) of the body die lifting cylinder was set to 19.6 kN, and the pressure variation between the upper die pressing rods 202 was measured, it was confirmed that the variation falls within a range of 98 N. Thereafter, using a die set in which the variation of the height to the abutment piece 104 was adjusted to less than 0.2 mm, lenses for video cameras having a finish dimension of φ10 mm, a center thickness of 3.5 mm, and a lens face curvature of 15 or 20 mm were formed under a body die ascent pressure of 19.6 kN that is one of molding conditions. As a result, pressing can be completely performed at the same time without any troubles such as seizing in the four dies, and molded products that coincident with the cavities formed by individual dies and sufficiently satisfy thickness accuracy and the allowed value of an optical face were obtained.
A pressing mechanism (lower die pressure distributor) for the lower die is shown in
A pressure adjuster for the lower die 101 is comprised of the lower die pressing rods 302, the lever rods 330, the fulcrum members 331, the compression springs 332, and the compression spring holders 334 as shown in
One of the objects of the invention is to provide an apparatus that obtains a number of molded products at the same time by a plurality of sets of upper and lower dies. For that purpose, it is necessary to cause the pressing load required for four die sets to act uniformly during cooling. In the apparatus shown in
In order to heat and press a glass material of the invention and to form a high-precision optical element, it is necessary to cause high-pressure (0.98 to 3.92 kN) to be generated in each lower die 101, and to transmit the pressure to each lower die 101 via the above individual members from the lower die lifting cylinder 340. Furthermore, in an apparatus using a method of repeating the process of taking out a molded product after a glass material is heated and press-molded to a predetermined temperature (400 to 800° C.) within the die, it is required that a heating-cooling-heating cycle is shortened in order to repeat heating and cooling of the molded product, die members, the body die, etc. Thus, it is necessary to reduce the heat capacity of the whole molding apparatus, and therefore, it is necessary to miniaturize the apparatus.
Furthermore, in the molding apparatus of the present embodiment, in order to obtain the same molded products, for example, lenses having the same thickness, by four die members, molded products are pressed in the upper dies 102 and the lower dies 101 by the lower die pressing rods 302 and the ascending lower dies 101, which are shown in
For that purpose, it is necessary to cause equal pressing forces to act on the four lower dies 101 independently, and to cause sufficient pressing force to act on each lower die 101.
In the present embodiment, in order to solve the above problems, the pressure adjuster in which a spring member, particularly, the compression spring 332 shown in
Next, a specific example of the compression spring 332 will be described. That is, one rectangular wire spring made of silicon chrome steel wire having an external diameter of φ18 mm, an internal diameter of φ4.9 mm, a spring constant of 23.5 Ns/mm, a maximum load of 382 N, and a free height of 45 mm was used, the position of the fulcrum member 331 supporting the lever rod 330 was set so that the ratio of the distance to an upper die pressing rod 202 and the distance to a compression spring 232 may be set to 1:7, and individual members were assembled. As a result, a pressure adjuster that endures a load of 7 times the maximum load of the compression spring 332 by the lever's principle (2.68 kN in this case) was constructed. By constructing four such compression springs so as to correspond to the lower dies 101, four pressure adjusters are established (they endure up to 10.7 kN in total pressure). Consequently, since it is not necessary to provide a lot of disc springs as in the molding apparatus of Patent Document 1 in which disc springs are assembled into a chamber, there is no need for adjustment. Further, since the compressing springs are installed outside the chamber, there is a margin of space, and design becomes easy. Further, it is not necessary to cool the compression spring 332.
The same configuration is allowed even in a compression spring using an ordinary piano wire. Specifically, one rectangular wire spring made of a piano wire having an external diameter of φ25 mm, an internal diameter of φ3.5 mm, a spring constant of 28.4 Ns/mm, a maximum load of 0.49 N, and a free height of 40 mm was used, the position of a fulcrum member 330 supporting a lever rod 331 was set so that the ratio of the distance to a lower die pressing rod 302 and the distance to a compression spring 332 may be set to 1:6, and individual members were assembled. As a result, a pressure adjuster that endures a load of 6 times the maximum load of the compression spring 332 by the leverage principle (1.96 kN in this case) was constructed. By constructing four such compression springs so as to correspond to the lower dies 101, four pressure adjusters are completed (they endure up to 7.84 kN in total pressure). In this state, when the thrust (the total of the pressing force applied to the four lower dies 101) of the lower die lifting cylinder 340 was set to 6.86 kN, and the pressure variation between the lower die pressing rods 302 was measured, it was confirmed that the variation falls within a range of 98 N. Thereafter, using a die set in which the variation of the height to the abutment piece 104 was adjusted to less than 0.2 mm, lenses for video cameras having a finish dimension of φ10 mm, a center thickness of 3.5 mm, and a lens face curvature of 15 or 20 mm were formed under a body die ascent pressure of 19.6 kN that is one of molding conditions. As a result, pressing can be completely performed at the same time without any troubles such as seizing in the four dies, and molded products that coincident with the cavities formed by individual dies and sufficiently satisfy thickness accuracy and the allowed value of an optical face were obtained.
Thus, when a glass material G is press-molded using the pressing mechanism 2 of
Next, when the upper die pressing rod 202 is moved upward by the cylinder mechanism 210 to raise the body die 100, the glass material G will be pressed against the upper die 102 as shown in
Next, when the body die 100 is further moved upward by the cylinder mechanism 210, as shown in
Accordingly, even if clearance required for sliding exists in a sliding portion between the body die 100 and the upper die 102, the body die 100 can be moved upward in a state where the posture of the upper die 102 is kept vertical. As a result, there is no positional deviation of the die faces of the upper die 102 and the lower die 101 in the horizontal direction, and molding can be made in a state where the position of an optically-functioning face with respect to the optical axis of a molded optical element is held correctly.
In particular, in the present embodiment, it is necessary to drive the body die 100 by the common cylinder mechanism 210 and to absorb the dimensional errors of the upper die 102 and the upper die pressing rod 202 from the relationship that pressing is at the same time made by the four upper dies 102. However, since the upper die pressing rod 202 is resiliently held by the pressure adjuster 208, as shown in
Further, if the body die 100 is moved downward by the operation of the cylinder mechanism 210 in order to perform die opening after molding, as shown in
In addition, in the present embodiment, the pressure distributor are provided in both the upper die 102 and the lower die 101. However, the invention is not limited thereto. Any pressure distributor may not be provided on both sides, or one pressure distributor may be provided in either the upper die 102 or the lower die 101.
A glass heating mechanism is comprised of a glass heater 600 and a driving unit 604, as shown in
Next, the process of molding a molded product as an optical element will be described in detail in order of loading, molding, and unloading mainly about the glass material G, using the press-molding apparatus according to the present embodiment. In addition, the molded optical element is an aspheric lens used for a camera, a video camera, etc.
The glass material G, which is a glass blank that is formed in advance in a spherical shape, is first placed on a pallet 20C of a stocker 20 of
If the glass material G is introduced into the molding die 1, a glass material alignment mechanism 500 shown in
Then, the glass heater 600 held at 900° C. by the cartridge heater 602 is inserted between above the lower die 101 and the glass material G and below the upper die 102 through a window of the body die 100 by the operation of the cylinder mechanism 604. Further, the upper die 102 and the lower die 101 are heated to, for example, a temperature of about 109 poises in glass viscosity by the cartridge heater provided in the body die 100. Meanwhile, the glass material G is heated to, for example, a temperature of about 107 poises in glass viscosity by the glass heater 600. After the glass material G, the upper die 102, and the lower die 101 are warmed during a desired period of time (for example, 90 seconds), the cylinder mechanism 604 is operated to draw out the glass heater 400 through the window of the body die 100, and therefore, the body die lifting cylinder 210 is moved upward, for example, with the pressure of 196 MPa, thereby performing press-molding. After the flange portion 102A comes into contact with the upper end of the body die 100 via the spacer 102C sufficiently (for example, after 10 seconds), the heater of the body die 100 is turned off, a cooling medium is introduced into cooling-medium introducing portions 101B and 102D of the upper die 102 and the lower die 101, and pressing pressure is applied from below by the lower die 101 (for example, 98 MPa in total pressure) while the temperature of the upper die 102 and the lower die 101 is between about 1010.5 and 1013 poises in glass viscosity. Meanwhile, a sticking prevention member 700 (refer to
Thereafter, the molded product is returned to the rest 172 by the reverse operation of the exchanger 4, is taken out from the molding chamber 3 by the loader/unloader 17, and is further returned to the pallet 20C by the operation of the robot 19.
In the present embodiment, the molding die 1 is such that four (sets) upper dies 102 and lower dies 101 are operated within the common body die 100. However, the structure of the aligner 106 as mentioned above may be adopted for one upper die 102 and one lower die 101. In addition, in the present embodiment, the molding die 1 is such that four (sets) upper dies 102 and lower dies 101 are operated within the common body die 100. However, as shown in
As described above, the hanger 105 corresponds via the abutment piece 104 so that the pressing pressure parallel to a sliding face with the body die 100 may act at least in the axial center of the upper die 102, and the hanger 105 hung and supported by the hook member 212 is interlocked via the aligner 106 so that a pull-down force may act in the axial center of the upper die 102. Thus, when a glass material G is press-molded, or when a molded product as an optical element is separated from the die, the force of body die upper and lower members applied to the upper die 102 can be made to act so as to pass through the center of the upper die 102, and a high-precision optical element in which an optically-functioning face is correctly located with respect to an optical axis can be manufactured efficiently.
According to the invention, it is possible to provide a molding die for an optical lens suitable for a precision press-molding method having excellent durability or die-releasing property from the optical lens. Further, since it is possible to press-mold an optical lens using the die of the invention, thereby manufacturing various optical elements after molding without performing polishing, etc., it is possible to provide an optical element manufacturing method having mass productivity, and having advantages in terms of cost.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-290260 | Oct 2006 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP07/70850 | Oct 2007 | US |
| Child | 12429780 | US |
