JPH09175828A - Molding equipment for optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the occurrence of shrink mark on the surface of an optical device while holding the accuracy of the inner part in high. SOLUTION: This forming equipment has an upper mold 7 and a lower mold 3 pressing an optical material which is heated and softened, a sensor detecting the end of press of the lower mold 3, a stopper 13 to stop the pressing action of lower mold 3 when the optical material is more thick than the thickness of the forming optical device, a releasing equipment 13a releasing the stoppage of stopper 13 and a delay driver 14 driving stopper 13 at a prescribed delay time after the input of signals from the sensor. The releasing equipment 13a has a curved surface to make the amount of the pressing movement of the lower mold 3 after the releasing of stopper larger at the primary stage than the late stage of driving time of the stopper 13. The stopper 13 suppresses the occurrence of shrink mark at minimum by lowering the applying pressure on the optical material and holding the accuracy of the inner part high, and in late stage of releasing, increases the applying pressure to prevent the occurrence of shrink mark.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding apparatus for softening an optical material such as glass by heating and pressing it with a pair of molding dies.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 4-331728 discloses an optical element molding apparatus capable of ensuring the precision of the molded optical element and preventing sink marks on its surface. This device is a pair of upper and lower molds for pressing the softened optical material, a sensor for measuring the displacement of this mold,
A stop device for stopping the pressing operation of the mold, a driving means for driving the stop device, and sensing an input from the sensor,
Delaying means for driving the stop device after a predefined time. In this device, after a pair of molds presses the heat-softened optical material, a stop device stops the pressing operation of the molds, and then the stop device is released to press the optical material again. . As a result, the stop device can be released at a timing that is neither too early nor too late, and in conjunction with this, pressure processing during shrink molding is performed, so that both the precision of the inside thickness of the optical element to be molded and the surface accuracy can be achieved. It is highly accurate.

[0003]

However, in the case of a thin-walled optical element, the time from the start of press molding until the optical material solidifies is very short. Therefore, even when the stop of the stop device is released at the same timing as the above-mentioned conventional technique, if the speed of the drive means is high, the pressurization at the time of contraction can be sufficiently performed.
The accuracy of medium-sized meat deteriorates. On the other hand, if the speed of the driving means is slow,
When the stopping means is released, the optical material is solidified and the precision of the inside thickness is high, but sink marks occur on the surface portion. Therefore, there is a problem that it is impossible to mold an optical element satisfying both the precision of medium thickness and the precision of surface.

The present invention has been made in consideration of the above-mentioned problems, and provides a molding device for an optical element which can secure the precision of the medium thickness and prevent the sink mark of the surface portion even for the thin optical element. The purpose is to

[0005]

According to a first aspect of the present invention, a pair of dies for pressing an optical material that has been softened by heating, a sensor for measuring pressing stop of the dies, and a wall thickness of an optical element to be molded are used. Also, a stop device for stopping the pressing operation of the mold in a state where the optical material is thick, a stop release means for releasing the stop of the stop device, a signal from the sensor is input,
Delaying means for driving the stopping device after a predetermined time, and the stopping releasing means is a non-linear operation so that the amount of pressing operation of the die by releasing the stopping becomes larger in the latter period than in the initial stage of stopping driving of the stopping device. Then, the stop device is controlled. According to the operation of claim 1, since the stop position of the mold changes non-linearly when the stopping means is released, the amount of pressurization to the optical material is reduced in the initial stage of the release, and the precision of the inner wall is improved, but it is small. However, the pressure is applied, and the amount of pressure applied to the optical material is increased in the latter stage of the release.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 shows a molding apparatus according to Embodiment 1 of the present invention, and FIG. 2 shows a stopper portion thereof. Lower base 6,
A molding chamber 38 is formed by the upper base 10 and the cover 37 that is stretched over the bases 6 and 10.
The upper mold 7 and the lower mold 3 are arranged in the molding chamber 38 so as to face each other. Further, by mounting the lower base 6 on the mount 39, the entire molding chamber 38 is supported by the mount 39.

The upper die 7 is attached to the lower end portion of a cylindrical upper die support 9 fitted in an opening 10a in the central portion of the upper base 10, and is screwed to a screw portion 9a of the support 9. It is fixed by a matching upper die retainer 8. The lower die 3 is attached to the upper end of the lower die support 5, and is fixed by a lower die retainer 4 that is screwed into a screw portion 5 a of the same support 5. In this case, an opening 6a is formed in the central portion of the lower base 6 described above, and the opening 6a is formed.
The lower die support 5 is attached to the main shaft 11 penetrating through the main die 11 so that the lower die 3 moves up and down together with the main shaft 11.

The main shaft 11 extends in the vertical direction, and a main bearing 16 and a load cell 27 are attached to a lower end 11a of the main shaft 11 and are supported by a pressure device 17 such as an air cylinder. This support is the piston 1 of the pressurizing device 17.
The ball receiver 6 is attached to the upper end portion of 7a.
This is done by the ball 25 on the top 6 contacting the lower surface of the load cell 27 of the main shaft 11. As a result, the main shaft 11 moves up and down as the piston 17a of the pressure device 17 moves up and down.

The main bearing 16 of the main shaft 11 has a pin 2
An arm 21 is rotatably attached via a sensor 9, and a sensor 18 is attached to the arm 21. The sensor 18 outputs a signal to the controller 20. The arm 21 extends in a direction orthogonal to the main shaft 11, and the roller 15 is attached to one side (left side) of the arm 21 and the second stopper 23 is attached to the other side (right side) thereof. These rollers 15 and the second stopper 23
Are provided at symmetrical positions with respect to the pin 29 of the arm 21. Further, the position of the rotary shaft of the roller 15 and the position of the tip of the second stopper 23 can be adjusted in the height direction.

A cylindrical housing 19 hangs from the lower surface of the mount 39 described above. A bearing 28 for guiding the vertical movement of the main shaft 11 is attached at a predetermined position in the length direction of the housing 19. Further, the fixed plate 12 is attached to the lower end of the housing 19, and a stopper receiving portion 24 with which the tip end of the stopper 23 abuts at a portion of the lower surface of the fixed plate 12 facing the second stopper 23.
Is arranged. The stopper receiver 24 is made of a material such as cemented carbide that does not deform even when the second stopper 23 comes into contact with it. The fixed plate 12
A through hole through which the main shaft 11 penetrates is opened in the central portion of the. Further, a first stopper 13 is provided on the lower surface of the fixed plate 12 facing the roller 15.

The first stopper 13 is movable in the direction of arrow 40 along a guide 12a attached to the lower surface of the fixed plate 12. The first stopper 13 is a drive device 1 such as an air cylinder attached to the lower surface of the fixed plate 12.
It is connected to the piston of No. 4 and its movement is performed. The drive timing of the drive unit 14 is controlled by the controller 20, and the controller 20 controls the sensor 1
The drive device 14 is controlled by the input of a signal from the controller 8.

Reference numeral 22 is a stopper adjusting base for regulating the horizontal position of the first stopper 13. The contact surface 13 a of the first stopper 13 contacts the roller 15. The abutment surface 13a of the first stopper 13 is a curved surface central axis 13 that coincides with the end surface of the stopper 13 in the traveling direction 40.
It is molded into an arcuate curved surface having b (see FIG. 2) as a central axis.

In the above structure, the upper mold 7 and the lower mold 3 are heated to the glass transition temperature of the optical material 1 or higher. On the other hand, the optical material 1 heated to a temperature equal to or higher than the softening point temperature in a heating furnace (not shown) provided outside the molding chamber 38, together with the holder 2, is conveyed by an upper mold by a conveying member (not shown). 7 and lower mold 3. Then, pressurizing device 1
7 is operated to raise the piston 17a, whereby the optical material 1 is press-molded by the molding surfaces of the upper mold 7 and the lower mold 3. At this time, the pressing force is monitored by the load cell 27.

The distance between the upper die 7 and the lower die 3 is adjusted in advance by the roller 15 and the second stopper 23 so that the thickness of the optical material 1 becomes a desired value.
By contacting the first stopper 13 with the second stopper 23 and the second stopper 23 with the stopper receiver 24, the raising of the main shaft 11 for raising the lower die 3 is stopped. Further, the arm 21 has a pin 29.
Although it is rotatable about the axis, the force generated when stopping the rise of the main shaft 11 is the roller 15 and the second stopper 2
3 is generated at the same time and is installed at a position symmetrical with respect to the center of the main shaft 11, so that no moment is generated on the main shaft 11.

Further, the sensor 18 senses the moment when the rise of the main shaft 11 is stopped by the roller 15 and the second stopper 23, and the controller 20 receives the signal and operates the drive unit 14 at a predetermined timing. The sensor 18 is
For example, a proximity switch is used, and the roller 15 is the first
The second stopper 23 is attached to the stopper 13 of
The arrangement position such as the height is adjusted so that a signal is output at the position where it abuts against No. 4.

The first stopper 13 and the roller 15 are
Since it is supported by a ball bearing or the like, it is possible to move in the horizontal direction with a comparatively small force even if it receives a force generated when the main shaft 11 is stopped by rising. Therefore, the first stopper 13 can be easily moved in the horizontal direction 40 in synchronism with the movement of the driving device 14 without any time delay. And the pressed optical material 1
In the process of cooling and solidifying and contracting, the sensor 18
It is moved by the drive device 14 in the horizontal direction and removed at a timing which is neither too early nor too late from when it is sensed. As a result, the optical material 1 is pressed by the pressing device 17, and the pressure is applied during contraction.

The contact surface 13a of the first stopper 13 with respect to the roller 15 is such that the contact surface with the roller 15 is a curved center axis 13b.
Since the first stopper 13 is moved in the horizontal direction at a constant speed by the driving device 14 because it is an arcuate curved surface centered on the center of the roller 15, when the first stopper 13 starts to move, it moves in the height direction of the roller 15. Although the change in the position is small, the amount of movement of the first stopper 13 becomes long and the change in the position of the roller 15 in the height direction also becomes large. Therefore, when the first stopper 13 starts to move, the optical material 1 is not pressed because the roller 15 and the first stopper 13 are in contact with each other. However, as the amount of movement of the first stopper 13 increases, the change in the position of the roller 15 increases, and the first stopper 13 is removed.
Is pressurized again.

Next, the timing of delay until the lower die 3 presses the optical material 1 again after sensing the signal from the sensor 18 for measuring the displacement of the main shaft 11, that is, the lower die 3 will be described. If the timing of delay is too early, the optical material 1 is pressed again in a temperature state having sufficient fluidity, and the thickness of the optical material 1 varies in the process. On the contrary, if the delay timing is too late, even if the optical material 1 is cooled to the mold temperature (the temperature at which the deformation of the optical material 1 does not substantially occur = the glass transition point temperature or less), the pressing operation of the mold is still prevented. It has been stopped. As a result, when the optical material 1 shrinks as it cools and solidifies, no pressure is applied from the lower mold 3, sink marks occur, and a highly accurate surface shape cannot be obtained.

Here, the width of the first stopper 13 is set to 10
mm and the radius of curvature R of the contact surface 13a of the first stopper 13 with the roller 15 is 57 mm and the 5 ° tapered surface shown in the prior art, the diameter is 10 mm and the wall thickness is 0. 5 optical elements on both planes of 9.9 mm each
Under the condition that 0 pieces are molded and the wall thickness accuracy is within ± 0.05 mm, when the former is used, the drive amount of the first stopper 13 is started 0.1 seconds after the spindle 11 is stopped. Although it was 0.2 μm, when the latter was used, it was necessary to start driving the first stopper 13 1.0 second after the spindle 11 was stopped, and a sink mark of 3 μm occurred. on the other hand,
When the sink amount is set to 0.2 μm by molding 50 pieces, in the latter case, it is necessary to start driving the first stopper 13 0.1 seconds after the main shaft 11 is stopped, and the wall thickness accuracy is ± 0.08 mm. . Generally, it is desired that the wall thickness accuracy is ± 0.05 mm and the sink mark amount is 2 μm or less. Therefore, this embodiment is more effective.

As described above, in the process of adjusting the distance between the upper mold 7 and the lower mold 3 so that the optical material 1 has a desired thickness, and the compressed optical material 1 shrinks as it cools and solidifies,
The controller 18 and the driving device 14 are provided so that the first stopper 13 can be moved at a timing that is neither too early nor too late by detecting the moment when the rise of the main shaft 11 stops by the sensor 18, and further the first stopper 13 is provided. The contact surface 13a of the first stopper 13 with the roller 15 is an arcuate curved surface having a curved central axis 13b which coincides with the end surface of the first stopper 13 on the advancing direction side. The amount of pressure applied to the material can be reduced to increase the precision of the inside thickness, and even a slight amount of pressure can be applied to minimize the occurrence of sink marks. By increasing the number, it is possible to prevent the occurrence of sink marks on the surface, thereby ensuring the precision of the inside thickness at the end of molding, and it is possible to mold a highly accurate optical element without sink marks on the surface.

(Second Embodiment) FIG. 3 shows a second embodiment, in which the same elements as in the first embodiment are designated by the same reference numerals and correspond to each other. In this embodiment, the contact surface 13c of the first stopper 13 with the roller 15 is formed into a three-step stepped surface 13c. All the stepped portions on the contact surface 13c are processed vertically. The number of steps is 2
Any number of steps is possible as long as it is equal to or more than a step. The first stopper 13 in this embodiment can also be moved in the direction indicated by the arrow 40 by the drive device 14.

In this structure, since the contact surface 13c of the first stopper 13 with the roller 15 is a three-step step surface, even if the first stopper 13 is driven by the drive device 14 to move at a constant speed in the horizontal direction. The position of the roller 15 in the height direction does not change while the roller 15 is in contact with the horizontal surface of the contact surface 13c. However, the position of the roller 15 in the height direction changes until the roller 15 stops contacting the stepped portion of the contact surface 13c and contacts the next horizontal surface having a different height. Therefore, even if the first stopper 13 starts moving, pressure is not applied to the optical material 1 until the roller 15 comes into contact with the first step protrusion of the contact surface 13c, and the roller 15 moves to the step surface. The optical material 1 is pressed from the time when it contacts the first stepped portion of 13c to the time when it contacts the next horizontal surface having a different height. This operation is similarly performed in the next stepped portion, and the optical material 1 is repressurized.

In this embodiment, the width of the first stopper 13 is set to 10 mm, and the roller 15 contacts the contact surface 13c 0.1 second after the first stopper 13 starts moving.
Finish contact with the first stepped part of the
By contacting after 2 seconds and ending contact with the next stepped portion after 0.6 seconds, the optical element having the same shape can be made to have the same thickness accuracy and sink amount as in the first embodiment.

In such an embodiment, since the contact surface 13c of the first stopper 13 with the roller 15 is a stepped surface having three steps, even if the first stopper 13 starts to move. The pressure is not applied to the optical material 1 until the roller 15 contacts the stepped portion of the contact surface 13c, and the height after the roller 15 contacts the first stepped portion of the contact surface 13c. The optical material 1 is pressed until it touches another horizontal plane different from. Therefore, immediately after the movement of the first stopper 13 is started, it is possible to minimize the occurrence of sink marks by intermittently applying pressure to the optical material to increase the accuracy of the medium thickness and even applying a small amount of pressure. In the latter stage of releasing, the amount of pressure applied to the optical material can be increased to prevent the occurrence of sink marks on the surface. As a result, at the time of completion of molding, there is an effect that the precision of the medium thickness is ensured and a highly accurate optical element having no sink mark on the surface can be molded.

[0025]

According to the present invention, when the stopping means is released, the stop position of the mold is gradually changed, so that the initial stage of the release is as follows.
Minimize the occurrence of sink marks by increasing the amount of pressure applied to the optical material to increase the precision of the inside thickness and applying a slight amount of pressure, and increase the amount of pressure applied to the optical material in the latter stage of release. By preventing the occurrence of sink marks on the surface, it is possible to ensure the accuracy of the inside thickness at the end of molding and to eliminate sink marks on the surface.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a first embodiment of the present invention.

FIG. 2 is a front view of a main part of the first embodiment.

FIG. 3 is a front view of a main part of the second embodiment.

[Explanation of symbols]

 1 Optical Material 3 Lower Mold 7 Upper Mold 11 Spindle 13 First Stopper 15 Roller 17 Pressurizing Device 18 Sensor 20 Controller

Claims (1)

[Claims] 1. A pair of molds for pressing the heat-softened optical material, a sensor for measuring the pressing stop of the mold, and the metal in a state where the optical material is thicker than the thickness of the optical element to be molded. A stop device for stopping the pressing operation of the mold, a stop release means for releasing the stop of the stop device, and a delay means for receiving a signal from the sensor and driving the stop device after a predetermined time, The stop releasing means controls the stop device by performing a non-linear operation so that the amount of pressing operation of the mold due to the stop release becomes larger in the latter stage than in the initial stage of the stop drive of the stop device. .