JPH0313310A - Mold for injection molding - Google Patents

Abstract

PURPOSE:To enable plastic lenses, etc., with high accuracy to be obtained in which the disturbance of the interference fringes of a molded lens is removed by a method in which a pair of slides are slidably arranged in the groove provided on the surface of a parting line, and the driving member advancing and retracting the slides in the linked relation to the opening and closing operation of the mold, is provided. CONSTITUTION:When a movable mold 9 is moved and clamped, the tips of both slides 33, 34 are brought in contact with each other thereby forming a cavity 31. Next, the cavity 31 is filled with the resin injected from an injecting machine. Then, dwelling is applied thereto, until the resin in a gate 29 made in the slides 33, 34, is solidified. Said condition is kept without applying pressure in the mold and the molded lens 20 is cooled. When the mold is opened the slides 33, 34 are retracted, whereby each tip of the slides 33, 34 is separated from the outer peripheral surface 20a of the molded lens 20 and the gate 19, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection mold for molding plastic lenses and the like.

[Conventional technology]

The mold used in injection molding is designed such that when the plastic (resin) has been filled into the mold and the molded product is cooled and solidified, the molded product is forcibly left on the movable side of the mold when the mold is opened. , is configured to be released from the fixed side of the mold.

The main part of the injection mold whose molded product is a lens is constructed as shown in FIG. 7, and an example of the molded product taken out is shown in FIG.

In the figure, a fixed mold 2 of a mold l has a spool bushing 5 disposed through a fixed mounting plate 3 and a fixed mold plate 4, and a fixed piece 7 is attached to the fixed mold plate 4 via a fixed sleeve 6. are arranged.

In addition, a movable piece 12 is connected to a movable mold plate 10 of the movable mold 9 at a position opposite to the fixed piece 7 via a movable sleeve 11 via a parting line (P/L) 8 of the mold 1. are arranged.

Further, a core bin 14 and a protruding bin 15, 16 which move up and down are disposed through the receiver 13.

After clamping the mold 1 having the above-mentioned components, in order to take out the injection-molded molded product from the mold via the spool bush 5, when the mold is opened, the core bin 14 and each ejecting bin 15, 16 are removed from the protruding plate. (not shown), the spool part 17, launch part 1B, and gate part 1 shown in FIG.
9. The molded lens 20 and cold slug well 21 are integrally projected from the movable mold 9 to complete the molding process.

When the above-mentioned molded product is a plus-thick lens, in order to ensure the surface accuracy of the molded lens 20,
Injection pressure and holding pressure of 4 to 1500 kg/c- are applied.

[1JI to be Solved by the Invention] However, in the injection mold having the above configuration, ``Since the injection pressure and the holding pressure are applied, high pressure is similarly applied to the outer periphery of the lens that becomes the molded product. It will take a while. Therefore, a phenomenon occurs in which the outer peripheral portion 20a of the lens 20 strongly bites into the inside of the movable sleeve 11.

Therefore, a draft angle is formed on the lens outer peripheral portion 20a (that is, the inside of the movable sleeve 11), or the inner surface of the movable sleeve is polished to a tti surface condition to reduce the resistance when the molded product is ejected. It is difficult to completely eliminate the biting, and if you try to protrude with the movable piece 12, the movable sleeve 11 and the lens outer peripheral surface 20a
A shearing stress is generated due to the phenomenon of being caught between the two (a phenomenon caused by biting).

At the same time as internal stress is accumulated within the molded lens 20, the R shape (curvature state) of the lens surface changes, which appears as disturbance of interference fringes on the lens surface (for example, as shown in FIGS. 9a and 9b).
c, d, e) There were problems that made the lens unusable as a highly accurate optical plastic lens.

The present invention has been made in view of the above-mentioned problems, and includes:
Means and operation for solving 9 ciis which aims to provide an injection mold for molding a molded product in which internal stress is not accumulated within the molded product) In order to solve the above purpose In an injection mold that molds a plastic lens by injecting resin into a cavity formed by a fixed mold and a movable mold through a gate, a shape is formed on the parting line surface of the movable mold perpendicular to the direction of the gate. A pair of slides having a forming surface forming the outer peripheral surface of the molded lens at each tip are slidably arranged in the groove provided, and the pair of slides are moved in conjunction with the opening/closing operation of the mold, respectively. It is equipped with a drive member that moves forward and backward with respect to the molding position.

With the above configuration, when the injection mold is closed, the drive member causes the tip of each slide to approach the lens molding position to form a cavity, and in this state, the resin is injected, holding pressure, and cooling and solidifying the molded product. During the subsequent opening operation of the mold, each slide tip is moved away from the outer peripheral surface of the molded lens by the driving member, thereby eliminating the influence of the resin biting into the movable mold.

(Example) The present invention will be explained below based on examples.

In the embodiment, the same reference numerals are used for the same members as those explained in FIG. 7 and the eighth section.

(First embodiment) Fig. 1 is a plan view of the main parts of the injection mold of the first embodiment,
The figure is a sectional view taken along the line A-A of the main part, and FIG. 3 is an explanatory diagram for explaining the main part.

In the figure, a groove 32 is formed on the upper surface of the movable mold plate 10 on the parting line 8 surface of the movable mold 9 in a direction perpendicular to the center line 30 of the runner 28 and the gate 29, with the position of the cavity 31 approximately at the center. A pair of slidable slides 33.
34 are arranged. The thickness of the slides 33, 34 is equal to the height (thickness) of the outer peripheral surface of the molded lens.

The slides 33 and 34 have a forming surface a forming the outer peripheral surface 20a of the lens, a forming surface where the gate 29 is formed, and a forming surface C forming a part of the runner 28 at opposing positions at the tips of each of the slides 33 and 34.

In addition, each end of the forming surface a forming the lens outer circumferential surface 20a of this slide 33, 34 (each joining portion on the gate side and the opposite side of the gate of each slide 33, 34 when forming the cavity 31) is a molded lens. 20 has a straight surface d formed into a D shape by forming a portion of the outer peripheral portion into a strait shape.

The configuration for slidably driving each of the slides 33 and 34 will be explained with reference to an explanatory sectional view (FIG. 3) cut in half at the main parts of the spool bush 5 and the cavity 31.

As described above, the slide 33 (the other slide 34 also has the same configuration) is configured to freely move within the groove 32 formed in the movable mold 9 in a direction perpendicular to the direction of the gate 29. .

A slide core 35 is fixed to this slide 33, and is adapted to engage with an angular pin 36 that is fixed to the fixed side mold plate 4 of the fixed mold 2 at an angle. Therefore, the slide 33 comes into sliding contact with the upper end surface of the movable sleeve 11 disposed on the movable template 10 (the same applies to the slide 34).

In the above configuration, when the movable mold 9 moves and is clamped, the slide core 35 is pressed by the angular pin 36, so the slide core 35 slides in the direction of the cavity 31, and the tips of both slides 33 and 34 They are joined to form a part of the cavity 31, the gate 29, and the runner 28.

Next, the resin injected from an injection molding machine (not shown) passes through a sprue 27, a runner 28, and a gate 29, and then passes through a fixed mold 2.
A cavity 31 for molding a molded lens 20 formed by the fixed side piece 7 of the movable mold 9, the movable side piece 12 of the movable mold 9, and the molding surfaces a and d of the pair of slides 33 and 34.
filled inside.

A holding pressure is then applied until the resin of the gate 29 formed by the slides 33 and 34 is solidified.

When the resin in the two gates solidifies and pressure is no longer transmitted to the molded lens 20 even if the holding pressure is applied from the molding machine, the holding pressure from the molding machine is completed and pressure is applied within the mold. The molded lens 20 is cooled while maintaining this state without causing any damage.

After that, when the molded lens is solidified and does not deform even when taken out from the mold 1, when the mold is opened via P and L8, the slide core 35 moves along the angular pin 36, so the slide 33 .34 retreats, and the outer circumferential surface 20a of the molded lens 20 and the gate portion 19
The tips of the slides 33 and 34 can pass through.

Therefore, the molded product (Fig. 8) is transferred from the mold 1 to the movable piece 12.
When the lens is ejected and taken out using the ejector bins 15, 16, etc., there is no mold release resistance of the lens outer peripheral portion 20a or the gate portion 19, so that the ejector can be ejected smoothly.

As shown in Fig. 4, the interference fringes of the plastic lens molded by the above-mentioned mold are good because there is no distortion caused by biting of the outer periphery, and a highly accurate plastic lens is produced. .

In addition, as shown in FIG.
By cutting the outer circumferential surface 20a of the lens into a D shape, the gate side of the molded lens can be cut inside the circumference of the outside diameter of the molded lens when cutting the gate. This makes it possible to perform gate processing (gate cutting) along the circumferential surface of a molded lens, which is much easier to work with than performing gate processing (gate cutting) along the circumferential surface of a molded lens. For example, when assembling the lens into the lens frame, it is possible to assemble the lens in any rotational direction, and there is no need to provide a gate relief in the lens frame.

Furthermore, since the lens outer peripheral surface is not captured by the movable mold when the molded product is ejected, the effective diameter of the lens can be reduced by taking into account the disturbance of interference fringes on the lens outer peripheral surface. '73'3
! Whereas the outer diameter of l lj is determined, in this embodiment, the effective diameter can be increased to the vicinity of the outer circumferential surface of the lens (D cant portion).

Furthermore, the pair of slides that form the outer periphery of the lens and the gate separate from the outer periphery and the gate when the lens is ejected. Therefore, it is possible to continuously mold good products without staining the mold or adhering to the molded lens.

(Second Embodiment) FIGS. 5a and 5b are a cross-sectional view of a main part showing a second embodiment of an injection mold according to the present invention, and a plan view showing a main part of a slide.

The feature of this embodiment is that a tab forming surface is provided at each tip of each slide 43.44 so as to form a protruding tab 45 at a position 180 degrees opposite to the gate 29 formed by each slide 43.44. e, e are provided, the molded protrusion tab 45 is protruded by an ejection pin 46, and the movable piece 47 is fixed within the movable mold 9.

The operation of the injection mold having the above-mentioned structure until the mold opening after completion of injection is the same as that in the first embodiment, but when ejecting the molded product after completion of the mold opening, the molded product is ejected and the pins 15, 16
．． 46 will protrude. At this time, since the movable piece 47 is fixed to the movable sleeve 11, it does not operate at the time of protrusion.

In this embodiment as well, the same effect of tS as in the first embodiment can be obtained.

(Third Embodiment) FIG. 6 is a plan view of a main part of a third embodiment of an injection mold according to the present invention.

The feature of this embodiment is that in the multi-cavity mold ζ in which a large number of molded lenses are molded (the number of molded lenses), a slide is disposed on the same side with respect to one lunch 2g and the gate 29. 53 and 54 are configured in an integrated state.

According to this embodiment as well, the same effects as in the first embodiment can be obtained, and since the width of the slides 53 and 54 (or the width of the groove) is increased, the sliding movement of the slide' can be stabilized. .

In addition, in the pair of slides of each of the above embodiments, if a ring-shaped protrusion with a ■-shaped (or rectangular) cross-sectional shape is provided on the forming surface that forms the lens outer peripheral surface of the pair of slides, the molded lens A V-shaped (or U-shaped) groove is formed on the outer peripheral surface.

If this groove is filled with black dye or the like, it can be used for squeezing, etc.

(Effects of the Invention) As described above, according to the injection molding mold of the present invention, when the molded product is ejected from the mold, the outer periphery of the molded lens is not removed by the movable mold (cutting r=t). Therefore, there is no disturbance of interference fringes in the molded lens, and a high-precision plastic lens can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the main parts of an injection mold according to the first embodiment of the present invention, Fig. 2 is a sectional view taken along line A-A of the main parts, and Fig. 3 is an explanation for explaining the main parts. Figures 4 and 4 are state diagrams of interference fringes of the plastic lens, Figures 5a and b are longitudinal sectional views of the main parts of the second embodiment and a plan view showing the main parts of the slide, and Figure 6 is the third embodiment. A plan view of the main part of the example, Fig. 7 is an explanatory diagram of the main part of a conventional injection mold, Fig. 8 is a perspective view of a molded product of a plastic lens, and Fig. 9 a + b + c + d, e shows the interference of a conventional plastic lens. It is a state diagram of a stripe. 2...-Fixed mold 4...Fixed side template 6...Fixed side sleeve 7...Fixed side piece 8...Parting line 9...Movable mold 10...Movable side die cutter 11 ...Movable side sleeve 12.47...Movable side piece 15, 16.46...Protrusion bottle 20...Molded lens 28...Runner 29...Gate 32...Groove 33.34, 43, 44. 53, 54...Slide Figure Figure 35...Slide Core 36 Anguilla Bin 47...Protrusion Tab Figure 6 Figure Figure Figure 1, Incident Display 1999 Patent Application No. 148948 Name of the λ invention Injection molding mold 3, Relationship to the case of the person making the amendment Patent applicant address 2-43-2 Hatagaya, Shibuya-ku, Tokyo Name Name
(037) Representative of Olympus Optical Industry Co., Ltd.
Satoshi Yama, Department 4, Agent 105 Address: 2-2-15-6, Hamamatsucho, Minato-ku, Tokyo Contents of amendment (1) “Straight side d” on page 7, lines 16 to 17 of the specification ``It has a straight surface d.'' It is also possible to provide a draft angle to this straight surface d to facilitate the release of the slides 33 and 34. ” he corrected. (2) The description of "slide" in the second line of page 8 of the same book is corrected to "slide." (3) The statement "in a ring shape on the forming surface" on page 13, line 20 of the same book is corrected to "in a ring shape on the forming surface." e4) The description "movable side mold cutting" in the 15th line 11th line of the same place is corrected to "movable side mold plate". “Detailed Description of the Invention” column of the above description

Claims (1)

[Claims] (1) In an injection mold that molds a plastic lens by injecting resin into a cavity formed by a fixed mold and a movable mold through a runner and a gate, a part of the movable mold is arranged perpendicularly to the direction of the gate. A pair of slides each having a forming surface that forms the outer circumferential surface of the lens is placed in a groove formed in the molding line surface, and the pair of slides are moved in conjunction with the opening and closing operations of the mold, respectively. A driving member is provided that moves forward and backward with respect to the molding position, and when the mold is closed, the tips of the slides approach each other to form the lens cavity, and when the mold is opened, the slides move away from each other. An injection molding mold characterized in that it is configured to be separated from the outer peripheral surface of a lens.