JP3113695B2 - Injection mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold for forming a precision molded product such as an optical element, and more particularly, to a gate sealing mechanism for preventing molten resin from flowing back from a cavity when injection is completed. The present invention relates to an injection molding die provided.

[0002]

2. Description of the Related Art Generally, when injection molding a precision molded product such as an optical element, an injection condition (injection temperature, injection pressure, etc.) from an injection molding machine to an injection mold is appropriately set, and injection is completed. It is necessary to prevent the subsequent resin pressure in the cavity from suddenly changing to prevent uneven distribution of stress, generation of sink marks, and the like. For this reason, some conventional injection molds are provided with a gate sealing mechanism for preventing the backflow of the molten resin from the cavity.

Conventionally, this type of injection mold has been
For example, the one shown in FIGS. In FIG. 4, reference numerals 1a and 1b denote a pair of split molds, and the molds 1a and 1b are clamped to form a cavity 2 and runners 3a and 3b on a mold clamping surface PL of an inner peripheral portion thereof. A cavity 2 is provided with a runner 3 from a sprue 4 formed in one of the split molds 1a by an injection nozzle N.
The molten resin is filled through a and 3b.

Further, as shown in FIG. 5, a groove 5a for forming a runner 3 together with the split mold 1a and the split mold 1b,
A spherical valve element 6 is loosely inserted into 5b, and a square pillar-shaped support member 7 is attached to a portion of the groove 5b of the split mold 1b on the cavity 2 side.
A valve seat 8 on which the spherical valve element 6 is seated is formed in the grooves 5a and 5b on the side of the runner 3a of a and 1b.

[0005] In the injection molding die having such a configuration, when the molten resin is injected from the injection nozzle N,
The injected molten resin (hereinafter simply referred to as injection resin) is supplied to the cavity 2 through the sprue 4 and the runners 3a and 3b. At this time, the spherical valve element 6 is separated from the valve seat 8 by the injection resin pressure from the sprue 4 side, abuts on the support member 7 and is supported by the member 7.

In this state, the molten resin that has passed through the runner 3b from the runner 3a flows into the valve chamber 3V of the runner 3b so as to wrap the spherical valve body 6, and a part of the injection resin that has passed through the spherical valve body 6 is a bearing member. 7, the turbulent flow is generated, and the turbulent flow is merged with the remaining portion to generate shearing heat or the like. Therefore, the flow velocity distribution of the injected resin that has passed through the spherical valve element 6 when being guided by the runner portion 3R of the runner 3b is made uniform, and the molten resin having a uniform flow velocity is supplied to the cavity 2.

When the cavity 2 is completely filled with the injection resin, the resin pressure in the cavity 2 increases to a predetermined value, and the injection of the molten resin from the injection nozzle N is stopped. At this time, the spherical valve element 6 is immediately urged to the valve seat 8 by the resin pressure which is going to flow backward from the cavity 2 side in the runner 3b and is seated, and the runner 3a and the runner 3b
Are shut off liquid-tight. Therefore, when the injection of the molten resin is completed, the molten resin filled in the cavity 2 is prevented from flowing backward, and the pressure in the cavity 2 is prevented from suddenly changing.

When the resin is supplied into the cavity 2 as described above, the support member 7 forms a part of the runner 3b, and the spherical valve body 6 cooperates with the pair of split molds 1a and 1b. Since the passed molten resin is guided in only one direction while being squeezed, the flow rate distribution of the molten resin supplied to the cavity 2 is made uniform by squeezing the portion of the runner 3b on the cavity 2 side from the spherical valve element 6. Thus, uneven distribution of weld and stress can be eliminated, and a highly accurate molded product can be obtained.

[0009]

However, in such a conventional injection molding die, since the bearing member 7 is formed in the shape of a quadrangular prism, the spherical valve body 6 has the bearing member 7.
In addition to the flow path indicated by the arrow a so that the molten resin wraps around the spherical valve element 7 during the injection of the molten resin, the path that flows below the spherical valve element 6 as indicated by the arrow b I took it. For this reason, the molten resin has a spherical valve body 6.
When the two portions of the molten resin join at the junction near the entrance of the support member 7, the flow velocity distribution is not sufficiently uniform, and the uneven distribution of weld and stress is sufficiently reduced. It could not be eliminated.

Accordingly, the present invention can unify the flow path of the molten resin supplied to the cavity through the runner to make the flow velocity distribution uniform, eliminate the uneven distribution of weld and stress, and achieve high precision. An object of the present invention is to provide an injection mold capable of obtaining a molded product of the above.

[0011]

According to the first aspect of the present invention,
In order to achieve the above object, a pair of split molds in which a cavity and a runner communicating with the cavity are formed in a mold clamping surface during mold clamping, and formed on at least one mold clamping surface of the split mold. A groove defining the runner;
A sprue formed in the one split mold and supplying the molten resin to the cavity in communication with the groove, a spherical valve element loosely inserted in the runner, and mold clamping of the split mold on the sprue side of the groove; And a valve seat formed on the surface, on which the spherical valve element can be seated, and a mold clamping surface that defines a runner on one side of the split mold, and a mold clamping surface of the other split mold. Bearing means for supporting the spherical valve body while allowing the molten resin to pass through the cavity through the gap, wherein the bearing means makes contact with the spherical valve body at a portion facing the spherical valve body. When the molten resin is supplied from the runner into the cavity, the spherical valve body comes into contact with the corresponding contact portion, so that the molten resin flows between one of the split molds and the spherical valve body. And the other split mold Between the spherical valve body to allow for passage of the molten resin and is characterized by guiding in one direction while squeezing the molten resin between the bearing member and the other of the split molds.

In order to achieve the above object, the invention according to claim 2 is characterized in that the contact portion is formed in a semicircular shape so as to make line contact with the spherical valve body. According to a third aspect of the present invention, in order to achieve the above object, the contact portion is formed to have the same diameter as a part of an outer peripheral portion of the spherical valve body so as to make surface contact with the spherical valve body. It is characterized by.

[0013]

According to the first aspect of the present invention, a contact portion of a predetermined shape is formed at a portion of the bearing member opposed to the spherical valve body so that the spherical valve body contacts with the spherical valve body, and when the molten resin is supplied from the runner into the cavity. By contacting the spherical valve body with the corresponding contact portion, the molten resin is prevented from passing between one of the split molds and the spherical valve body, and the molten resin is prevented from flowing into the other split mold and the spherical valve. It becomes possible to pass between the bodies, and the molten resin is guided in one direction while being squeezed between the bearing member and the other split mold. Therefore, when a part of the molten resin goes under the spherical valve body, the molten resin is not divided into two parts at the boundary of the spherical valve body, and the molten resin does not merge near the entrance of the support member. As a result, the flow path of the molten resin supplied to the cavity after passing through the runner is unified, the flow velocity distribution is made uniform, and the uneven distribution of weld and stress is eliminated, so that a highly accurate molded product is obtained.

According to the second aspect of the present invention, the contact portion is formed in a semicircular shape so as to make line contact with the spherical valve body. Therefore, the processing of the support member is facilitated, and the cost of the support member is reduced. According to the third aspect of the present invention, the contact portion is formed to have the same diameter as a part of the outer peripheral portion of the spherical valve body so as to make surface contact with the spherical valve body. Therefore, when the spherical valve body comes into contact with the contact portion when the resin is injected, the spherical valve body comes into contact with the contact portion with a relatively large area, thereby preventing the bearing member from being damaged by the flow of the high-pressure resin.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
1 and 2 are views showing one embodiment of an injection mold according to the present invention. First, the configuration will be described. In FIG. 1, 21
Reference numerals a and 21b denote a pair of split molds each composed of a fixed mold and a movable mold, and the fixed mold 21a and the movable mold 21b.
The movable mold 21b is supported by an injection molding machine main body (not shown) so that the movable mold 21b can be closed, clamped and opened by abutting, pressing and separating the fixed mold 21a.

The fixed-side mold 21a, which is at least one of the divided dies, has a concave portion 22a and grooves 23a to 25a of a predetermined shape which are open on the mold-clamping surface PL side. A concave portion 22b and grooves 23b to 25b are also formed on the movable mold 21b in opposition to these. When the fixed mold 21a and the movable mold 21b are closed,
Cavity for forming a molded product composed of 22a and 22b
22, a first runner 23 and a second runner 24 (runners) including grooves 23a, 23b, 24a, 24b, and grooves 25a,
A valve seat passage portion 25 made of 25b is defined.

A sprue connected to the injection nozzle N1 of the injection molding machine communicates with the groove 23a in the fixed mold 21a.
A sprue 26 is formed on the first runner 23, the valve seat passage 25, and the second
The cavity 22 is supplied through a runner 24. Further, a spherical valve element 27 is loosely inserted in the second runner 24, and an end of the valve seat passage portion 25 on the second runner 24 side,
That is, the fixed side mold on the sprue 26 side of the grooves 24a and 24b.
The mold clamping surfaces of the movable mold 21a and the movable mold 21b are formed as a valve body 28 on which a spherical valve body 27 can be seated.
The valve seat passage portion 25 is closed or opened by the movement of the spherical valve body 27 which receives the resin pressure (injection pressure) from the cylinder or the resin pressure from the cavity 22. 2nd runner of movable side mold 21b
A support member 31 is attached to a mold clamping surface defining the support member 24. The support member 31 supports the spherical valve body 27 which has received the injection pressure from the sprue 26 side and fixes the resin in the second runner 24. It is arranged so that it can be supplied to the cavity 22 side between the side molds 21a.

On the other hand, the support member 31 protrudes from the movable mold 21b to the fixed mold 21a.
Of the second runner 24 extends in the paper width direction, that is, in the direction perpendicular to the arrow AB direction, and forms a part of the second runner 24 from the sprue 26 through the first runner 23 and the seat passage portion 25. The molten resin supplied to 24 is supplied to cavity 22 through runner portion 24R between support member 31 and fixed mold 21a.

Further, a contact portion 31a of a predetermined shape is formed at a portion of the bearing member 31 facing the spherical valve body 27, and this contact portion 31a is connected to the spherical valve body 27 as shown in FIG. It is formed in the shape of a semicircle so that it may contact. And the contact part 31a
When the spherical valve body 27 comes into contact with the spherical valve body 27, the spherical resin body 27 comes into close contact with the contact portion 31a by linear contact, so that the molten resin supplied from the sprue 26 is supplied to the movable mold 21b and the spherical valve body as described above.
27, without passing through only the runner portion 24R between the fixed mold 21a and the spherical valve element 27. At this time, the molten resin is squeezed between the support member 31 and the fixed mold 21a. It is guided in one direction.

Next, the operation will be described. First, the movable mold
The fixed side mold 21a and the movable side mold 21b are moved by the movement of 21b.
When the mold is closed and the mold is closed, the cavity 22, the first runner 23, the second runner 24, the valve seat passage portion 25 and the like are formed, and the molten resin can be supplied from the sprue 26 to the cavity 22. Next, when the molten resin is injected from the injection nozzle N1 in contact with the fixed mold 21a by the operation of the injection molding machine main body, the injected molten resin (hereinafter simply referred to as injection resin) is sprue 26, the first runner. 23, it is supplied to the cavity 22 through the valve seat passage 25 and the second runner 24.

At this time, the spherical valve body 27 is separated from the valve seat 28 by the injection resin pressure from the sprue 26 side, and linearly contacts the contact portion 31a of the support member 31 to be supported by the member 31. In this state, as described above, the molten resin supplied from the sprue 26 does not pass between the movable mold 21b and the spherical valve body 27, and the runner portion between the fixed mold 21a and the spherical valve body 27
It passes only from 24R, and is guided in one direction while being narrowed between the support member 31 and the fixed mold 21a during this passage. Therefore, the flow velocity distribution of the injected resin that has passed through the spherical valve element 27 when guided by the runner portion 24R of the second runner 24 is made uniform, and is supplied to the cavity 22 at a uniform flow velocity.

When the cavity 22 is completely filled with the injection resin, the resin pressure in the cavity 22 increases to a predetermined value, and the injection of the molten resin from the injection nozzle N1 is stopped. At this time, the spherical valve element 27 is immediately urged to the valve seat 28 by the resin pressure to flow backward from the cavity 22 side in the second runner 24 and is seated, and the first runner 23 and the second runner
24 is liquid-tightly shut off.

Therefore, when the injection of the molten resin is completed, the molten resin filled in the cavity 22 is prevented from flowing backward, and a sudden change in the pressure in the cavity 22 is prevented.
Then, as the pressure in the cavity 22 gradually decreases with the decrease in the temperature of the molten resin in the cavity 22, and the time for the resin in the cavity 22 to solidify elapses, the fixed mold 21a is moved by the injection molding machine body. Then, the movable side mold 21b is opened, and the molded product is taken out.

As described above, in the present embodiment, the first and second
When the molten resin is supplied into the cavity 22 from the runners 23 and 24, the molten resin passes between the movable mold 21b and the spherical valve body 27 by bringing the spherical valve body 27 into contact with the contact portion 31a. While passing through only from between the fixed mold 21a and the spherical valve body 27, and guiding in one direction while squeezing with the runner portion 24R between the support member 31 and the fixed mold 21a. It is possible to prevent a part of the molten resin from going around the lower side of the spherical valve body 27, and to prevent the molten resin from being divided into two parts at the boundary of the spherical valve body 27. Merging can be prevented.
As a result, the flow path of the molten resin supplied to the cavity 22 after passing through the first and second runners 23 and 24 is unified as compared with the related art, so that the flow velocity distribution can be made uniform and the weld and stress can be reduced. Can be eliminated and a highly accurate molded product can be obtained. Further, the contact portion 31a of the support member 31 is
Since the support member 31 is formed in a semicircular arc so as to make line contact with the support member 31, the support member 31 can be easily processed, and the cost of the support member 31 can be reduced.

In this embodiment, the contact portion of the support member 31
31a is formed in a semicircular arc shape, but is not limited to this.
As shown in FIG. 7, the contact portion 41a is formed in the same diameter as a part of the outer peripheral portion of the spherical valve body 27 so as to make surface contact with the spherical valve body 27, and the spherical valve body 27 is brought into contact with the contact portion 41a. By this, the molten resin is prevented from passing between the movable mold 21b and the spherical valve body 27, and is allowed to pass only from between the fixed mold 21a and the spherical valve body 27, and the molten resin is supported. The guide may be guided in one direction while being squeezed by the runner portion 24R between the 41 and the fixed mold 21a.

In this manner as well, it is possible to prevent a part of the molten resin from wrapping around the spherical valve body 27 and dividing the molten resin into two parts at the boundary of the spherical valve body 27. The same effect as the example can be obtained. In addition to this effect, when the spherical valve body 27 comes into contact with the contact portion 41a at the time of injection of the resin, the spherical valve body 27 can be brought into contact with the contact portion 41a with a relatively large area. The support member can be prevented from being damaged by the flow.

[0027]

According to the first aspect of the present invention, it is possible to prevent a part of the molten resin from going around the lower side of the spherical valve body and dividing the molten resin into two parts at the boundary of the spherical valve body. Thus, it is possible to prevent the molten resin from joining near the entrance of the support member. For this reason, the flow path of the molten resin supplied to the cavity after passing through the runner can be unified, and the flow velocity distribution can be made uniform, and the uneven distribution of weld and stress can be eliminated to obtain a highly accurate molded product. be able to.

According to the second aspect of the present invention, since the contact portion is formed in a semicircular shape so as to make linear contact with the spherical valve body, the support member can be easily processed, and the support member can be easily processed. Cost can be reduced. According to the third aspect of the present invention, the contact portion is formed to have the same diameter as a part of the outer peripheral portion of the spherical valve body so as to make surface contact with the spherical valve body. Can contact the contact portion with a relatively large area when contacting the contact portion, and it is possible to prevent the bearing member from being damaged by the flow of the high-pressure resin.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an injection mold according to the present invention.

FIGS. 2A and 2B are views showing a part of a spherical valve body and a bearing member in FIG. 1, wherein FIG. 2A is a cross-sectional configuration view of a main part thereof, and FIG.

3A and 3B are diagrams showing another embodiment of the injection mold according to the present invention, wherein FIG. 3A is a cross-sectional view of a main part showing a spherical valve body and a part of a bearing member, and FIG. It is a BB arrow line view of (a).

FIG. 4 is a sectional view showing a conventional injection mold.

5A and 5B are diagrams showing a part of the spherical valve body and the bearing member in FIG. 4, wherein FIG. 5A is a sectional view of a main part thereof, and FIG. 5B is a view taken along the line CC of FIG.

[Explanation of symbols]

 21a Fixed mold (one mold) 21b Movable mold (the other mold) 22 Cavity 23 First runner (runner) 23a Groove 24 Second runner (runner) 24a Groove 26 Sprue 27 Spherical valve body 28 Valve Seats 31, 41 Bearing members 31a, 41a Abutment part PL mold clamping surface

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Suji Hatakeyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company Limited (72) Inventor Akira Fukushima 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Wataru Otani 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd. (56) References JP-A-4-282218 (JP, A) 156020 (JP, U) Fully open sho 63-77721 (JP, U) Fully open sho 55-83328 (JP, U) Fully open sho 56-76424 (JP, U) (58) Fields investigated (Int. ⁷ , DB name) B29C 45/26-45/44

Claims (3)

(57) [Claims] 1. A pair of split molds having a cavity and a runner communicating with the cavity formed on a mold clamping surface during mold clamping, and the runner formed on at least one mold clamping surface of the split mold. A sprue formed in the one of the divided molds and communicating with the groove to supply the molten resin to the cavity; a spherical valve element loosely inserted in the runner; and a sprue side of the groove. The spherical mold is formed on the mold clamping surface of the split mold, and the spherical valve element is provided on a mold seat defining a runner on one side of the split mold. Bearing means for supporting the spherical valve body while allowing the molten resin to pass through the cavity between the mold clamping surface of the mold, and a bearing opposed to the spherical valve body. Predetermined shape contact where spherical valve body contacts When the molten resin is supplied from the runner into the cavity, the spherical valve body abuts on the corresponding contact portion, thereby preventing the molten resin from passing between one of the split molds and the spherical valve body. And allowing the molten resin to pass between the other split mold and the spherical valve body, and guiding the molten resin in one direction while squeezing the molten resin between the bearing member and the other split mold. Mold for injection molding. 2. The device according to claim 1, wherein said contact portion is formed in a semicircular arc so as to make line contact with the spherical valve body.
The mold for injection molding according to the above. 3. The injection molding according to claim 1, wherein said contact portion is formed to have the same diameter as a part of an outer peripheral portion of said spherical valve body so as to make surface contact with said spherical valve body. Mold.