JPH07290514A - Ring gate mold - Google Patents

Abstract

PURPOSE:To manufacture a cylindrical hollow molded piece wherein weld lines do not appear, while high-level molding precision is maintained. CONSTITUTION:A ring gate 6 and a pair of auxiliary gates 5 communicating with the ring gate 6 from the outside are provided. The auxiliary gates 5 are arranged so as to be opposed to each other at the center of the ring gate 6. The ring gate 6 is formed such that thicknesses of discharging sections 62A, 62B... and 62a, 62b... which form a discharging main body 62 increase in sequence with separation from the auxiliary gates. Thus, weld lines hardly generate nor appear in a cylindrical hollow molded piece.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring gate mold suitable for producing a hollow cylindrical molded product, and more particularly to a ring gate mold in which weld does not become apparent.

[0002]

2. Description of the Related Art Conventionally, when a hollow cylindrical molded product is manufactured by injection molding a thermoplastic resin or ceramics, the flow distance is short and the molded product is deformed due to the orientation or distortion of molecules or particles. Ring gate molds are used because they are difficult. An example of the resin passage formed by the ring gate mold is shown in FIG. The ring gate mold 90 includes a sprue 91, a primary runner 92 communicating with the sprue 91, a substantially semi-circular secondary runner 93 branched from the primary runner 92, and a pair continuous from the secondary runner 93. Of the sub-gate 94 and a ring gate 95 communicating with the sub-gate 94, and a cylindrical hollow molded product-shaped cavity 96 is continuously formed from the ring gate 95. The ring gate 95 is a distribution part forming an outer peripheral part.
95A and a discharge portion 95 formed on the inner peripheral portion of the circulation portion 95A.
It consists of B and. Although 97 and 98 are molds,
A detailed structure such as a protruding pin or a nesting type is omitted for convenience of description. PL is a parting line. A filling material such as a thermoplastic resin injected from an injection molding machine (not shown) in the ring gate mold 90 flows from the sprue 91 to the sub-gate 94 through the primary runner 92 and the secondary runner 93, and the ring gate 95 Is diffused in the circulation direction 95A in the circumferential direction and injected into the cavity 96 from the gate portion 95B. Such a ring gate die 90 is suitable when precision such as the diameter of the hollow tube portion or the thickness of the outer wall portion of the cylindrical hollow molded product is required, and in particular, as shown in FIG. If the number of is increased from 2 to 4, the accuracy can be further improved.

[0003]

In the conventional ring gate mold 90 as described above, when there are two subgates 92, the resulting hollow cylindrical molded article 100 has the subgates as shown in FIG. A weld W is formed at a point where the resin and the like flowing out from 94 merge. Since this weld W extends in the axial direction of the cavity 96, the low-strength portion B is formed in the axial direction of the cylindrical hollow molded product, and particularly when ceramics are injection-molded, the low-strength portion B is Since the shear stress is larger than that of the other portion on the same circumference, there is a problem that the portion is likely to be damaged. This problem becomes more serious when there are four sub-gates 94. Therefore, it is conceivable to use one sub-gate 94, but this causes a problem that the molding accuracy is lowered.

The present invention has been made on the basis of the above problems, and provides a ring gate mold capable of producing a cylindrical hollow molded product in which welds are not exposed while maintaining a high level of molding accuracy. The purpose is to

[0005]

A ring gate mold according to claim 1 of the present invention is a ring gate mold comprising a ring gate and at least two sub-gates communicating with the ring gate. The gate portion is formed so that the thickness of the gate portion gradually increases as the gate portion is separated from the sub-gate.

According to a second aspect of the present invention, the ring gate die is formed such that the width of the sub-gate gradually increases toward the ring gate.

[0007]

In the structure of the first aspect, the injection product such as the resin that has flowed into the sub-gate through the runner is supplied from the sub-gate to the ring gate. In this ring gate, since the thickness of the ejection portion becomes thinner as it gets closer to the sub-gate, it becomes thicker as the distance increases.
Since the difference in the arrival time of the resin in the circumferential direction of the hollow cylindrical product is greatly reduced, welds are unlikely to occur and are not visible.

According to the second aspect of the invention, since the width of the sub-gate is formed such that the width of the sub-gate sequentially increases toward the ring gate, the weld is less likely to occur.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described in detail below with reference to FIG. FIG. 1 shows a ring gate mold according to a first embodiment of the present invention. In FIG. 1, a ring gate mold 1 is continuous from a sprue 2, a primary runner 3 communicating with the sprue 2, a secondary semi-arcuate secondary runner 4 branched from the primary runner 3, and the secondary runner 4. A pair of sub-gates 5 and a ring gate 6 communicating with the sub-gate 5.
From the above, a cavity 7 in the shape of a cylindrical hollow molded product is continuously formed. 8 and 9 are molds, respectively. The sub-gate 5 is formed in a substantially fan shape so that its width gradually increases from the boundary with the secondary runner 4 toward the communication part to the ring gate 6. The ring gate 6 is composed of a circulation portion 61 forming an outer peripheral portion and a discharge portion main body 62 formed on an inner peripheral portion of the circulation portion 61. The discharge part main body 62 is
With the center of the ring gate 6 as a base point, the ring gate 6 is divided into 6 parts by 15 ° with respect to 90 ° in the circumferential direction, and the ring gate 6 is divided into 24 parts.
C, 62D, 62E, 62F, the sprue 2 side is the discharge portion 62a,
62b, 62c, 62d, 62e, 62f. For example, the ejection portions 62A, 62B, 62C, 62D, 62 on the side of the sprue 2
The thicknesses of E and 62F are 0.80mm, 0.80mm, 1.00mm,
1.10 mm, 1.20 mm, 1.20 mm, and the thickness of the discharge parts 62a, 62b, 62c, 62d, 62e, 62f on the side opposite to the sprue 2 is 0.80 mm, 0.80 mm, 1.00 mm, 1.10 mm, 1.40 mm, 1.40, respectively. The thickness is mm, and the thickness is gradually increased in the circumferential direction so that the thickness becomes maximum at a position farthest from the sub-gate 5. The discharge part main body 62 is not limited to the one of the present embodiment, and is formed so that the thickness increases gradually or continuously so that the thickness at the position most distant from the sub-gate 5 becomes maximum. If you have. In particular, the ratio of the minimum and maximum thickness of the discharge part body 62 is 1.1 to 2.5.
Is preferred. When the ratio of the minimum value to the maximum value of the thickness of the discharge part main body 62 is less than 1.1, a sufficient weld suppressing effect cannot be obtained, while when it exceeds 2.5, the molding accuracy decreases. It is particularly preferable that the ratio is 1.2 to 2.0. The ratio of the minimum value and the maximum value of the thickness of the discharge part main body 62 is 1.2.
If it is less than 2.0, it becomes difficult to obtain a sufficient weld-suppressing effect, while if it exceeds 2.0, the molding accuracy tends to be lowered.

The operation of the above configuration will be described. A filler such as a thermoplastic resin injected from an injection molding machine (not shown) flows into the subgate 5 from the sprue 2 via the primary runner 3 and the secondary runner 4. The filler that has flowed into the sub-gate 5 flows into the cavity 7 through the discharge portion main body 62 while diffusing in the circulation portion 61 of the ring gate 6 in the circumferential direction. At this time, the ring gate 6 is formed so that the thickness of the discharge portion main body 62 gradually increases so as to become maximum at the position farthest from the sub-gate 5, so that the ring gate 6 is formed in the circumferential direction of the discharge portion main body 62. The difference in arrival time of the filling materials is shortened. For this reason, since the fillers injected from the pair of gates 5 join together at a stage where the temperature of the injected fillers does not drop excessively, welds are less likely to occur because the joined fillers are well joined together. Further, it is possible to suppress the shear stress caused by the merging of the fillers. In particular, in this embodiment, since the sub-gate 5 is formed in a substantially fan shape, it is possible to further reduce the difference in the arrival time of the filling material such as resin in the circumferential direction of the ejection portion main body 62. Further, in the present embodiment, the sprue 2 side discharge portions 62B, 62
The thickness of C ... Is set thinner than the discharge portions 62b, 62c ... on the side opposite to the sprue. This generally corresponds to an increase in the resin flow rate at the gate closer to the sprue 2, and this reduces the difference in the arrival time of the packing material in the circumferential direction of the ring gate 6 and reduces the sprue 2 The difference in the arrival time of the packing between the side and the anti-sprue 2 can also be reduced.

The first embodiment of the present invention as described above includes the ring gate 6 and the pair of sub-gates 5 communicating with the ring gate 6, so that the sub-gates 5 face each other at the center of the ring gate 6. The ring gate die is arranged so that the ring gate 6 is formed so that the thickness of the discharge part main body 62 gradually increases in the circumferential direction as the ring gate 6 is separated from the sub gate 5. Since the arrival time of the resin in the circumferential direction of the hollow molded product is greatly reduced, welds are unlikely to occur and do not become apparent. In particular, the minimum thickness 62A, 62a and the maximum thickness 62e of the discharge part of the ring gate 6,
Since the ratio to 62f is 1.1 to 2.5, the weld can be suppressed without impairing the molding accuracy and moldability. Further, in the present embodiment, since the width of the sub-gate 5 is formed in a fan shape so as to gradually increase toward the ring gate 6, the weld is less likely to occur. Further, in the cylindrical hollow molded article 100 obtained by using the conventional ring gate mold 90, the low strength portion B formed due to the weld as shown in FIG. It is possible to obtain a hollow cylindrical molded product having improved dynamic strength.

Next, a second embodiment of the present invention will be described in detail with reference to FIG. In the ring gate mold 1 of the second embodiment, the sub-gate 5 is linearly formed, and the sprue 2 side discharge parts 62A, 62B, 62 are provided.
The thickness of C, 62D, 62E and 62F is 0.70mm and 0.80 respectively.
mm, 1.10 mm, 1.19 mm, 1.40 mm, 1.40 mm, and the thicknesses of the discharge portions 62a, 62b, 62c, 62d, 62e, 62f on the side opposite the sprue 2 are 0.70 mm, 0.80 mm, 1.10 mm, 1.19, respectively. mm, 1.
The structure is the same as that of the first embodiment except that it is 40 mm and 1.40 mm. As described above, the sub-gate 5 does not need to be formed in a fan shape, and the ejection portion main body of the ring gate 6
The ejection portion 62 may have a linear shape as long as it is formed so as to increase in thickness as it is separated from the sub-gate 5.
According to the ring gate mold 1 of the second embodiment as described above, since the arrival time of the resin in the circumferential direction of the hollow cylindrical molded product is reduced, welds are less likely to occur and do not become apparent. In particular, since the ratio of the minimum thickness 62A, 62a and the maximum thickness 62F, 62f of the discharge part of the ring gate 6 is 1.1 to 2.5, the weld can be suppressed without impairing the molding accuracy and the moldability. . Therefore, a cylindrical hollow molded product having improved mechanical strength can be obtained.

The third embodiment of the present invention will be described in detail with reference to FIG. FIG. 3 shows a ring gate mold according to a third embodiment of the present invention. The ring gate mold 1 shown in FIG. 3 is the same as the first except for the sub gate 5 and the ring gate 6.
Since it is similar to the embodiment, detailed description thereof will be omitted.
In this embodiment, the sub-gate 5 is formed on the upstream side of the secondary runner 4 and the sub-gate 5A is formed on the downstream side. Each sub-gate 5, 5A is arranged at an angle of 90 ° with respect to the center of the ring gate 6. It is set up. Further, the upstream side sub-gate 5 is preferably formed so that its thickness is smaller than that of the downstream side sub-gate 5A.
For example, the thickness of the upstream subgate 5 is 0.80 mm, and the thickness of the downstream subgate 5A is 2.25 mm. Further, the sub-gates 5 and 5A are formed in a substantially fan shape so that the width thereof gradually increases from the boundary portion with the secondary runner 4 toward the communication portion to the ring gate 6. The ring gate 6 is composed of a circulation portion 61 forming an outer peripheral portion and a discharge portion main body 62 formed on the inner peripheral portion of the circulation portion 61. The main body 62 of the discharge part is divided into three regions of 45 ° in the circumferential direction by 15 ° with the center of the ring gate 6 as a base point, and the ring gate 6 is divided into 24 parts into discharge parts 62A, 62B and 62C, respectively. There is. The thicknesses of the discharge parts 62A, 62B and 62C are, for example, 1.00 mm, 1.30 mm and 1.40 mm, respectively.
The positions most distant from the individual sub-gates 5 and 5A are ejection portions 62C, respectively, and the thickness thereof is sequentially increased. The discharge part main body 62 is not limited to the one in this embodiment, and is formed so as to increase stepwise or continuously so that the thickness at the position farthest from the four subgates 5 and 5A becomes maximum. If you have. In particular, the ratio of the minimum and maximum thickness of the discharge part main body 62 is 1.1 to
It is preferably 2.5. When the ratio of the minimum value to the maximum value of the thickness of the discharge part main body 62 is less than 1.1, a sufficient weld suppressing effect cannot be obtained, while when it exceeds 2.5, the molding accuracy decreases. It is particularly preferable that the ratio is 1.2 to 2.0. When the ratio of the minimum value to the maximum value of the thickness of the discharge part main body 62 is less than 1.2, it is difficult to obtain a sufficient weld suppression effect, while when it exceeds 2.0, the molding accuracy tends to be deteriorated.

The operation of the above configuration will be described. A filling material such as a thermoplastic resin injected from an injection molding machine (not shown) flows into the subgates 5 and 5A from the sprue 2 via the primary runner 3 and the secondary runner 4. In this embodiment, by setting the thickness of the upstream side sub-gate 5 to be significantly smaller than that of the downstream side sub-gate 5A, the discharge amount of the filling material from the sub-gate 5 is suppressed,
The sub-gate 5A is controlled so that approximately the same amount is discharged. The filling material flowing out from the sub-gate 5 flows into the cavity 7 through the discharge portion main body 62 while diffusing the ring gate 6 in the circulation portion 61 in the circumferential direction. At this time, since the thickness of the discharge part main body 62 is formed so as to gradually increase so as to become maximum at the position farthest from the four sub-gates 5 and 5A, resin or the like is formed in the circumferential direction of the ring gate 6. The difference in arrival time of the filling materials is shortened. Therefore, no weld occurs. Particularly, in this embodiment, since the sub-gate 5 is formed in a substantially fan shape, the difference in the arrival time of the resin can be further reduced.

The third embodiment of the present invention as described above includes a ring gate 6 and a pair of sub-gates 5 and 5A communicating with the ring gate 6 from the outside, and the sub-gates 5 and 5A are connected to the ring gate 6. A ring gate mold arranged at an angle of 90 ° to the center,
Since the ring gate 6 is formed such that the thickness of the discharge portion main body sequentially increases in the circumferential direction as the ring gate 6 is separated from the sub gate, the flow resistance of the filling material differs depending on the portion. The confluence point of the resin where the weld occurs is the position farthest from the sub-gate 5, that is, the discharge portion 62C, and the thickness of the discharge portion at this point is formed to be the maximum in that section. Since the arrival time of the resin in the circumferential direction of the product is significantly reduced, welds are less likely to occur and do not become apparent. Particularly, the ratio of the minimum thickness 62A and the maximum thickness 62C of the discharge portion of the ring gate 6 is 1.1 to 2.5.
Therefore, the weld can be suppressed without impairing the molding accuracy and moldability. Further, in the present embodiment, since the width of the sub-gate 5 is formed in a substantially fan shape so as to gradually increase toward the ring gate 6, the weld is further unlikely to occur. Therefore, a cylindrical hollow molded product having improved mechanical strength can be obtained.

Next, a fourth embodiment of the present invention will be described in detail with reference to FIG. In the ring gate mold 1 of the fourth embodiment, the sub-gates 5 and 5A are formed in a linear shape, and along with this, the ejection portions 62A, 62B and 62C on the side of the sprue 2 are formed.
Are 0.80 mm, 1.10 mm, 1.19 mm, 1.20 mm, respectively, and the discharge portions 62a, 62b, 62c on the side opposite to the sprue 2 are 0.80 mm, 1.19 mm, 1.40 mm, respectively. Except for this, the third embodiment has the same structure as that of the third embodiment. In this way, the discharge portion of the discharge portion main body 62 of the ring gate 6 is connected to the sub-gates 5, 5
The sub-gates 5 and 5A need not be fan-shaped and may be linear as long as they are formed so that the thickness increases sequentially with the distance from A. According to the ring gate mold 1 of the fourth embodiment, the subgates 5, 5 are
Since the thickness of the discharge portion main body is gradually increased in the circumferential direction as the distance from A is increased, the weld arrival time is increased because the arrival time of the resin in the circumferential direction of the hollow cylindrical molded article is significantly reduced. Difficult to reveal. In particular, the minimum thickness 62A, 62a and the maximum thickness 62C, 62c of the discharge portion of the ring gate 6 are
Since the ratio is 1.1 to 2.5, the weld can be suppressed without impairing the molding accuracy and moldability. Therefore, a cylindrical hollow molded product having improved mechanical strength can be obtained.

Although the ring gate of the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to this and can be appropriately modified within the scope of the gist of the present invention. For example,
The number of gates does not have to be 2 or 4, and may be 3 or 5 or more, but is preferably 2 or 4 in terms of design difficulty and moldability. Further, the arrangement is preferably equiangular with respect to the center of the ring gate, but the angles may be different depending on the case. The ring gate of the present invention as described above can be applied to various materials such as thermoplastic resin, thermosetting resin, ceramics, and metal as long as injection molding is possible, but in particular, injection molding of thermoplastic resin and ceramics. Suitable for In the case of a thermoplastic resin, it is possible to obtain a hollow cylindrical molded product having good mechanical strength, not only a weld but also no poor gloss. Further, in the case of ceramics, it is possible to obtain a hollow cylindrical product having almost no weld and a small shear stress in the circumferential direction and a good mechanical strength.

[0018]

The ring gate die according to claim 1 of the present invention is a ring gate die including a ring gate and at least two sub-gates communicating with the ring gate, and the ring gate die has a discharge part. Since the thickness is formed so as to gradually increase with the distance from the sub-gate, the injection product such as resin that has flowed into the sub-gate through the runner is supplied from the sub-gate to the ring gate. In this ring gate, the thickness of the gate part becomes thinner as it gets closer to the sub-gate, and it becomes thicker as it goes away, so there is a large difference in the arrival time of the resin in the circumferential direction of the hollow cylindrical product. Weld is less likely to occur and does not become apparent.

According to the ring gate mold of the second aspect, since the width of the sub-gate is formed such that the width of the sub-gate sequentially increases toward the ring gate, the weld is less likely to occur.

[Brief description of drawings]

FIG. 1 is an enlarged schematic view of a main part of a ring gate mold according to a first embodiment of the present invention, in which (a) is a plan view and (b) is A.
FIG.

FIG. 2 is an enlarged schematic view of a main part showing a ring gate mold according to a second embodiment of the present invention, in which (a) is a plan view and (b) is B.
It is a -B line sectional view.

FIG. 3 is an enlarged schematic view of a main part of a ring gate mold according to a third embodiment of the present invention, in which (a) is a plan view and (b) is C.
It is a -C line sectional view.

FIG. 4 is an enlarged schematic view of a main part showing a ring gate mold according to a fourth embodiment of the present invention, in which (a) is a plan view and (b) is D.
It is a -D line sectional view.

5A and 5B are schematic views showing a ring gate mold according to a conventional example, FIG. 5A is a plan view, and FIG. 5B is a sectional view taken along line EE.

6A and 6B are schematic views showing a ring gate mold according to another conventional example, in which FIG. 6A is a plan view and FIG. 6B is a sectional view taken along line FF.

FIG. 7 is a schematic view showing a hollow cylindrical product obtained by the conventional ring gate mold.

[Explanation of symbols]

 1 Ring gate mold 5 Sub gate 6 Ring gate 62 Discharge part main body 62A, 62B ... Discharge part

Claims (2)

[Claims] 1. A ring gate mold comprising a ring gate and at least two sub-gates communicating with the ring gate, wherein the thickness of the discharge portion of the ring gate increases as the distance from the sub-gate increases. A ring gate mold, which is characterized in that 2. The ring gate mold according to claim 1, wherein the width of the sub-gate is formed so as to increase gradually toward the ring gate.