JP3218587B2 - Ring gate mold - Google Patents

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 manufacturing a hollow cylindrical molded product, and more particularly to a ring gate mold in which weld does not appear.

[0002]

2. Description of the Related Art Conventionally, when a hollow cylindrical molded article is manufactured by injection molding of a thermoplastic resin or ceramics, the molded article has a short flow distance and is deformed due to orientation or distortion of molecules or particles. For this reason, a ring gate mold is used. FIG. 3 shows an example of a resin passage formed by the ring gate mold. The ring gate mold 90 includes a sprue 91, a primary runner 92 communicating with the sprue 91, a substantially semicircular secondary runner 93 branched from the primary runner 92, and a pair of continuous runners from the secondary runner 93. And a ring gate 95 communicating with the sub-gate 94, and a cavity 96 in the shape of a cylindrical hollow molded product is continuously formed from the ring gate 95. The ring gate 95 has a flow portion forming an outer peripheral portion.
95A and a discharge part 95 formed on the inner periphery of the flow part 95A.
B. Note that 97 and 98 are molds, respectively.
Detailed structures such as protrusion pins and nests are omitted for convenience of explanation. PL is a parting line. In the ring gate mold 90, a filler such as a thermoplastic resin injected from an injection molding machine (not shown) flows from a sprue 91 to a sub-gate 94 via a primary runner 92 and a secondary runner 93, and to a ring gate 95. Is diffused in the circumferential direction and is injected into the cavity 96 from the gate 95B. Such a ring gate mold 90 is suitable when precision such as the diameter of a hollow tube portion or the thickness of an outer wall portion of a cylindrical hollow molded product is required, and in particular, as shown in FIG. The accuracy can be further improved by increasing the number of symbols from two to four.

[0003]

In such a conventional ring gate mold 90, if there are two sub-gates 92, the obtained cylindrical hollow molded article 100 has the above-mentioned sub-gates as shown in FIG. A weld W is formed at a point where the resin or the like flowing out from the junction 94 merges. Since the weld W extends in the axial direction of the cavity 96, a low-strength portion B is formed in the axial direction of the hollow cylindrical molded product. In particular, when ceramics is injection-molded, the low-strength portion B Since the shearing stress is larger than other portions on the same circumference, there is a problem that breakage or the like is likely to occur in that portion. This problem is 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 reduced.

The present invention has been made on the basis of the above problems, and provides a ring gate mold capable of manufacturing a cylindrical hollow molded product in which weld does not become apparent while maintaining high molding accuracy. The purpose is to.

[0005]

According to a first aspect of the present invention, there is provided a ring gate mold having a sprue, at least two sub-gates communicating with the sprue, and communicating with the sub-gate.
A ring gate mold and a ring gate continuous to the cavity, most of the sub-gate with the thickness of the discharge portion of the ring gate is formed so as to entailment sequential increases away from the sub-gate The thickness of the sprue-side discharge portion at the separated position is set to be smaller than the thickness of the corresponding sprue-side discharge portion.

[0006] In addition, the ring gate mold of claim 2, before
The thickness of the discharge portion of the ring gate is formed so as to increase stepwise.

[0007]

According to the first aspect of the present invention, the injection material such as resin flowing 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 ejection part is thinner as it is closer to the sub-gate, and it is formed so as to gradually increase as it separates.
Since the difference in the arrival time of the resin in the circumferential direction of the hollow cylindrical molded article is greatly reduced, weld is hardly generated and does not appear. In addition, the thickness of the sprue-side discharge portion at the position farthest from the sub-gate is set to be smaller than the thickness of the corresponding anti-sprue-side discharge portion, but this is generally the gate on the side close to the sprue. In response to the increase in the resin flow rate, this aims to reduce the difference in the arrival time of the packing in the circumferential direction of the ring gate,
The difference in the arrival time of the filling between the sprue side and the counter sprue can also be reduced.

[0008] In the configuration of claim 2, the ring game
Since the thickness of the discharge portion is gradually increased, the difference in the arrival time of the filler such as resin in the circumferential direction of the ring gate is reduced, and no weld occurs.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below in detail 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 includes a sprue 2, a primary runner 3 communicating with the sprue 2, a substantially semi-arc-shaped secondary runner 4 branched from the primary runner 3, and a continuous run from the secondary runner 4. A pair of sub-gates 5, and a ring gate 6 communicating with the sub-gate 5.
, A cavity 7 in the form of a cylindrical hollow molded article is continuously formed. Reference numerals 8 and 9 denote molds, respectively. The sub-gate 5 is formed in a substantially sector shape so that the width thereof is gradually increased from a boundary portion with the secondary runner 4 to a communication portion to the ring gate 6. Further, the ring gate 6 includes a flow portion 61 forming an outer peripheral portion, and a discharge portion main body 62 formed at an inner peripheral portion of the flow portion 61. The discharge unit main body 62 includes:
With the center of the ring gate 6 as a base point, the ring gate 6 is divided into six 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, and the sprue 2 side are discharge portions 62a,
62b, 62c, 62d, 62e and 62f. For example, the discharge units 62A, 62B, 62C, 62D, 62 on the sprue 2 side
The thicknesses of E and 62F are 0.80mm, 0.80mm, 1.00mm,
1.10 mm, 1.20 mm and 1.20 mm, and the thicknesses of the discharge portions 62a, 62b, 62c, 62d, 62e and 62f on the side opposite to the sprue 2 are 0.80 mm, 0.80 mm, 1.00 mm, 1.10 mm, 1.40 mm and 1.40, respectively. mm, and is formed so that the thickness is sequentially increased in the circumferential direction so that the thickness becomes maximum at a position farthest from the sub-gate 5. The discharge unit main body 62 is not limited to the one of the present embodiment, and is formed so that the thickness thereof is increased stepwise or continuously so that the thickness of the position most distant from the sub-gate 5 is maximized. It should just be. In particular, the ratio of the minimum value to the maximum value of the thickness of the discharge portion main body 62 is 1.1 to 2.5.
It is preferred that If the ratio of the minimum value to the maximum value of the thickness of the discharge portion main body 62 is less than 1.1, a sufficient weld suppressing effect cannot be obtained, while if it exceeds 2.5, the molding accuracy is reduced. In particular, the ratio is preferably 1.2 to 2.0. The ratio between the minimum value and the maximum value of the thickness of the discharge portion main body 62 is 1.2.
If it is less than 2.0, it is difficult to obtain a sufficient weld suppressing effect, while if it exceeds 2.0, the molding accuracy tends to decrease.

The operation of the above configuration will be described. The filler such as a thermoplastic resin injected from an injection molding machine (not shown) flows from the sprue 2 to the sub-gate 5 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 via the discharge portion main body 62 while diffusing in the circumferential direction through the flow portion 61 of the ring gate 6. At this time, the ring gate 6 is formed so that the thickness of the discharge portion main body 62 is sequentially increased so as to become the maximum at the position farthest from the sub-gate 5. , The difference in the arrival time of the packing is reduced. For this reason, the fillers injected from the pair of gates 5 merge at a stage where the temperature of the injection filler does not drop too much, and the merged fillers are satisfactorily joined to each other, so that welding is unlikely to occur. Further, the shear stress generated by the merging of the fillers can be suppressed. Particularly, in the present embodiment, since the sub-gate 5 is formed in a substantially sector shape, the difference in the arrival time of the filler such as resin in the circumferential direction of the discharge unit main body 62 can be further reduced. Further, in the present embodiment, the ejection portions 62E and 62E on the sprue 2 side are used.
The thickness of F is set to be thinner than the ejection portions 62e and 62f on the side opposite to the sprue. This corresponds to an increase in the resin flow rate at the gate close to the sprue 2 in general, thereby reducing the difference in the arrival time of the packing in the circumferential direction of the ring gate 6 and reducing the sprue 2. The difference in the arrival time of the filling between the side and the counter sprue 2 can also be reduced.

The first embodiment of the present invention as described above includes a ring gate 6 and a pair of sub-gates 5 communicating with the ring gate 6, such that the sub-gates 5 face each other at the center of the ring gate 6. In the ring gate mold provided, the ring gate 6 is formed so that the thickness of the discharge portion main body 62 is sequentially increased in the circumferential direction as the distance from the sub gate 5 is increased. Since the arrival time of the resin in the circumferential direction of the hollow molded article is greatly reduced, weld is hardly generated and does not appear. In particular, the minimum thickness 62A, 62a and the maximum thickness 62F,
Since the ratio to 62f is 1.1 to 2.5, welding can be suppressed without impairing the molding accuracy and moldability. Further, in this 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, welding is less likely to occur. Further, in the cylindrical hollow molded article 100 obtained by using the conventional ring gate mold 90, for example, the low strength portion B formed due to the weld as shown in FIG. It is possible to obtain a hollow cylindrical molded article having improved mechanical strength.

A second embodiment of the present invention will be described in detail with reference to FIG. FIG. 2 shows a ring gate mold according to a second embodiment of the present invention. The ring gate mold 1 shown in FIG.
Since this is the same as the embodiment, a detailed description thereof will be omitted.
In this embodiment, a sub-gate 5 is formed on the upstream side of the secondary runner 4 and a 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. Has been established. The upstream sub-gate 5 is preferably formed to have a smaller thickness than the downstream sub-gate 5A.
For example, the thickness of the upstream sub-gate 5 is 0.80 mm, and the thickness of the downstream sub-gate 5A is 2.25 mm. Further, the sub-gates 5 and 5A are formed linearly from a boundary portion with the secondary runner 4 to a communication portion to the ring gate 6. The ring gate 6 includes a flow portion 61 forming an outer peripheral portion, and a discharge portion main body formed at an inner peripheral portion of the flow portion 61.
It consists of 62. The discharge unit main body 62 is divided into three parts each of which is 45 ° in the circumferential direction with respect to the center of the ring gate 6 by 15 °, and the whole of the ring gate 6 is divided into 24 parts.
The thickness of the discharge sections 62A, 62B, 62C on the side is 0.80 m each.
m, 1.19 mm and 1.20 mm, and the discharge part 62 on the side opposite to the sprue 2
a, 62b, 62c are 0.80mm, 1.19mm, 1.
The discharge portions 62C and 62c are formed at positions farthest from the four sub-gates 5 and 5A, respectively, and are formed so that their thicknesses are sequentially increased. The discharge unit main body 62 is not limited to the one in the present embodiment, and is formed so as to increase stepwise or continuously so that the thickness of the position farthest from the four sub-gates 5 and 5A becomes maximum. It should just be. In particular, it is preferable that the ratio between the minimum value and the maximum value of the thickness of the discharge portion main body 62 is 1.1 to 2.5. If the ratio between the minimum value and the maximum value of the thickness of the discharge portion main body 62 is less than 1.1, a sufficient weld suppression effect cannot be obtained,
On the other hand, if it exceeds 2.5, the molding accuracy will decrease. In particular, the ratio is preferably 1.2 to 2.0. If the ratio of the minimum value to the maximum value of the thickness of the discharge portion main body 62 is less than 1.2, it is difficult to obtain a sufficient weld suppressing effect, while if it exceeds 2.0, the molding accuracy tends to be reduced.

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 from the sprue 2 into the sub-gates 5 and 5A via the primary runner 3 and the secondary runner 4. In the present embodiment, by setting the thickness of the upstream sub-gate 5 to be much smaller than the thickness of the downstream sub-gate 5A, the discharge amount of the filler from the sub-gate 5 is suppressed,
Control is performed so that substantially the same amount is discharged from the sub-gate 5A. The filler flowing out of the sub-gate 5 flows into the cavity 7 through the discharge part main body 62 while diffusing the flow part 61 in the ring gate 6 in the circumferential direction. At this time, since the thickness of the discharge portion main body 62 is formed so as to increase stepwise so as to become the maximum at the position most distant from the four sub-gates 5 and 5A, the thickness of the resin in the circumferential direction of the ring gate 6 is increased. , The difference in the arrival time of the packing is reduced. Therefore, no weld occurs. In addition, the joining point of the resin where the weld occurs is the position furthest away from the sub-gate 5, that is, the discharge portions 62C and 62c. Since the discharge portion at this point is formed so as to have the maximum thickness in that section. In addition, since the arrival speed time of the resin in the circumferential direction of the hollow cylindrical molded article is greatly reduced, weld is hardly generated and does not appear. In particular, the minimum thickness 62A, 62a and the maximum thickness 62 of the discharge portion of the ring gate 6 are described.
Since the ratio to C and 62c is 1.1 to 2.5, welding can be suppressed without impairing molding accuracy and moldability. Therefore, a hollow cylindrical molded article having improved mechanical strength can be obtained.

Although the ring gate of the present invention has been described with reference to the accompanying drawings, the present invention is not limited to this, and can be appropriately modified within the scope of the present invention. For example,
The number of gates need not be two or four, but may be three or five or more, but is preferably two or four in terms of design difficulty and moldability. The arrangement is preferably at an equal angle with respect to the center of the ring gate, but the angle 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 resins, thermosetting resins, ceramics, and metals as long as it can be injection-molded. In particular, injection molding of thermoplastic resins and ceramics It is suitable for. In the case of a thermoplastic resin, it is possible to obtain a hollow cylindrical molded product having good mechanical strength without weld or poor gloss. In the case of ceramics, it is possible to obtain a cylindrical hollow molded article having almost no weld, small shear stress in the circumferential direction and good mechanical strength.

[0015]

The ring gate mold according to claim 1 of the present invention comprises a sprue, at least two subgates communicating with the sprue, and a ring gate communicating with the subgate and continuing to the cavity. a is, the thickness of the discharge portion of the sprue side of the farthest position from the sub-gate with the thickness of the discharge portion of the ring gate is formed so as to entailment sequential increases away from the sub-gate Since the thickness is set to be smaller than the thickness of the corresponding discharge portion on the side opposite to the sprue, the ejected material such as resin flowing into the subgate through the runner is supplied from the subgate to the ring gate. In this ring gate, the thickness of the gate portion becomes thinner as it comes closer to the subgate, and it becomes thicker as it gets farther away, so the difference in the resin arrival time in the circumferential direction of the cylindrical hollow molded product is large. Therefore, weld is hardly generated and does not become apparent. In addition, the thickness of the sprue-side discharge portion at the position farthest from the sub-gate is set to be smaller than the thickness of the corresponding anti-sprue-side discharge portion, but this is generally the gate on the side close to the sprue. This corresponds to an increase in the resin flow rate, thereby reducing the difference in the arrival time of the packing in the circumferential direction of the ring gate, and also increasing the difference in the arrival time of the packing between the sprue side and the counter sprue. Can be reduced.

Further, in the ring gate mold according to the present invention,
Since the thickness of the discharge portion of the ring gate is formed so as to increase stepwise, the difference in the arrival time of the filler such as resin in the circumferential direction of the ring gate is reduced, and no weld occurs.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic view of a main part showing a ring gate mold according to a first embodiment of the present invention, wherein (a) is a plan view and (b) is A.
FIG. 4 is a cross-sectional view taken along a line A.

FIGS. 2A and 2B are main part enlarged schematic views showing a ring gate mold according to a second embodiment of the present invention, wherein FIG. 2A is a plan view and FIG.
FIG. 4 is a cross-sectional view taken along line B.

3A and 3B are schematic views showing a conventional ring gate mold, and FIG. 3A is a plan view and FIG. 3B is a cross-sectional view taken along line EE.

FIG. 4 is a schematic view showing a ring gate mold according to another conventional example, in which (a) is a plan view and (b) is a cross-sectional view taken along line FF.

FIG. 5 is a schematic view showing a cylindrical hollow molded product obtained by the conventional ring gate mold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ring gate die 5 Subgate 6 Ring gate 62 Discharge part main body 62A, 62B ... Discharge part

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/26-45/44 B28B 1/24

Claims (2)

(57) [Claims] 1. A ring gate mold comprising: a sprue; at least two sub-gates communicating with the sprue; and a ring gate communicating with the sub-gate and continuing to a cavity. thinner but than the thickness of the discharge portion of the anti-sprue side corresponding to the thickness of the discharge portion of the sprue side of the farthest position from the sub-gate with is formed so as to entailment sequential increases away from the sub-gate Ring gate mold characterized by setting. 2. The ring gate mold according to claim 1, wherein the thickness of the discharge portion of the ring gate is increased stepwise.