JPH07290515A - 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 and 5A which communicate with the ring gate 6 at about the same face are provided. The auxiliary gates 5 and 5A are arranged in an eccentric state with respect to a center O of the ring gate 6. Further, each of the auxiliary gates 5 and 5A is arranged in a state turned for 180 deg. with base point at the center O of the ring gate 6. Thus, fillers discharged from the auxiliary gates 5 and 5A form spiral flows, which join in the same direction in a state that the flows are most reduced, so that weld lines hardly generate.

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. FIG. 3 shows an example of a passage of resin or the like formed by the ring gate mold. The ring gate die 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. Sub gate 94 and a ring gate 95 communicating with the sub gate 94.
From here, a cavity 96 in the form of a hollow cylindrical product is continuously formed. The ring gate 95 includes a circulation portion 95A forming an outer peripheral portion and a discharge portion 95B formed on an inner peripheral portion of the circulation portion 95A. It should be noted that although 97 and 98 are molds respectively, a detailed structure such as a protruding pin and a nesting mold is omitted for convenience of description. PL is a parting line. The filling material such as thermoplastic resin and ceramics injected from an injection molding machine (not shown) in the ring gate die 90 flows from the sprue 91 to the subgate 94, and flows in the circulation portion 95A of the ring gate 95 in the circumferential direction. It is diffused and injected into the cavity 96 from the gate portion 95B. Such a ring gate die 90 is suitable when molding accuracy 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. When the number of sub-gates 94 is increased from two to four, the molding accuracy can be further improved.

[0003]

In the conventional ring gate die 90 as described above, when there are two subgates 92, the obtained hollow cylindrical molded article 100 has the subgates as shown in FIG. A weld W is generated at the point where the resin, ceramics, etc. flowing out from 94 meet. 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, wherein the sub-gate is The sub-gates are arranged in an eccentric state with respect to the center of the ring gate, and the sub-gates are arranged in a substantially rotating state from the center of the ring gate.

Further, in the ring gate die according to the second aspect of the invention, the sub-gates are arranged in a state in which the sub-gates are rotated by substantially equal angles with respect to the center of the ring gate.

[0007]

In the structure of the first aspect, the filling material such as resin and ceramics which has flowed into the sub gate through the runner is supplied from the sub gate to the ring gate. In the ring gate mold of the present invention, since the sub-gate is arranged in an eccentric state with respect to the center of the ring gate, and the sub-gate is arranged in a state of being rotated about the center of the ring gate. Since the filler discharged from each of the sub-gates forms a spiral flow and does not meet facing each other, welds are unlikely to occur.

Further, according to the second aspect of the present invention, since each of the sub-gates is arranged in a state of being rotated at substantially the same angle with respect to the center of the ring gate, the filler discharged from the sub-gate is disposed inside the ring gate. Since the flow of the filler injected into the cavity while flowing in a spiral in the same direction and discharged from the sub-gates do not face each other, the weld is further unlikely 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 a sprue 2, a primary runner 3 communicating with the sprue 2, a substantially semi-circular 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 5A, and a ring gate 6 that communicates with the sub-gate 5 on substantially the same plane, and a cavity 7 in the shape of a cylindrical hollow molding is formed continuously from the ring gate 6. 8 and 9 are molds, respectively. The sub-gates 5 are arranged so as to be eccentric with respect to the center O of the ring gate 6, and the sub-gates 5 are arranged in a state of being rotated by an equal angle, that is, 180 ° with respect to the center O of the ring gate 6. Has been done. The ring gate 6 is composed of a circulation portion 61 forming an outer peripheral portion and a discharge portion 62 formed on the inner periphery of the circulation portion 61.

The operation of the above configuration will be described. The filling material such as thermoplastic resin and ceramics injected from the injection molding machine (not shown) is supplied from the sprue 2 to the primary runner 3.
And sub-gates 5, 5A via secondary runner 4
Flow into. The filler flowing into the subgates 5 and 5A is
In the circulation portion 61 of the ring gate 6, a spiral flow is formed in the same direction as indicated by an arrow in the drawing, and flows into the cavity 7 via the discharge portion 62. Therefore, since the flow of the filling material discharged from the sub-gate 5 and the flow of the filling material discharged from the sub-gate 5A do not substantially merge with each other, a weld is hardly formed. Particularly in this embodiment, since the pair of subgates 5 and 5A are arranged in a state of being rotated by 180 ° about the center O of the ring gate 6, the filler discharged from each of the subgates 5 and 5A is Since a spiral flow is formed and the flows merge in the same direction in the most attenuated state, welds are further unlikely to occur.

The first embodiment of the present invention as described above is a ring gate mold including a ring gate 6 and a pair of subgates 5 and 5A communicating with the ring gate 6, wherein the subgates 5 and 5A are Since the sub-gates 5 and 5A are arranged eccentrically with respect to the center O of the ring gate 6 and are rotated with the center O of the ring gate 6 as a reference point, Since the flows of the filler discharged from the sub-gates 5 and 5A are substantially opposite to each other and do not merge, a weld is unlikely to occur. Particularly, the pair of sub-gates 5 and 5A are connected to the center O of the ring gate 6.
By arranging them in a state of being rotated by 180 ° with respect to the base point, the flow of the filler discharged from each sub-gate 5, 5A can be merged in the same direction in the most attenuated state, so that the weld is further less likely to occur. be able to. Therefore, in a cylindrical hollow molded article obtained by using the conventional ring ring gate die 90, for example, as shown in FIG. 5, a linear portion B having a large shear stress in the axial direction due to the weld is usually used. It is possible to obtain a hollow cylindrical product having improved mechanical strength.

Next, a second embodiment of the present invention will be described in detail with reference to FIG. In the ring gate mold 1 according to the second embodiment, the first sub-gate 5 is provided except that the sub-gate 5 is four pieces.
Since it is similar to the embodiment, detailed description thereof will be omitted.
In this embodiment, the sub-gates 5 and 5A are formed on the upstream side of the secondary runner 4, and the sub-gates 51 and 51A are formed on the downstream side. The sub-gates 5 are eccentric to the center O of the ring gate 6, respectively. The sub-gates 5, 5A, 51, 51A are arranged in a ring gate 6
Are arranged in such a manner that they are rotated at an equal angle, that is, 90 ° each, with the center O of the above as a base point. Also, the upstream subgate 5,
The thickness of 5A is preferably smaller than the thickness of the sub-gates 51, 51A on the downstream side. For example, the thickness of the sub-gate 5 on the upstream side may be about 0.80 mm, and the thickness of the sub-gate 5A on the downstream side may be about 2.25 mm.

The operation of the above configuration will be described. The filling material such as thermoplastic resin and ceramics injected from the injection molding machine (not shown) is supplied from the sprue 2 to the primary runner 3.
And sub-gates 5, 5A via the secondary runner 4,
It flows into 51, 51A. In this embodiment, the thickness of the upstream side subgates 5 and 5A is set to the downstream side subgates 51 and 51.
By setting it to be much thinner than A, the discharge amount of the filling material from the sub-gates 5 and 5A is suppressed,
It is controlled so that the same amount is discharged from 51, 51A. The filling material that has flowed into the sub-gates 5, 5A, 51, 51A forms a spiral flow in the same direction in the flow portion 61 of the ring gate 6 as shown by the arrow in the figure, and the discharge portion.
It flows into the cavity 7 via 62. For this reason, the flow of the filler discharged from the sub-gates 5, 5A, 51, 51A does not merge in a substantially opposed state, so that no weld is formed. Particularly, in this embodiment, since the sub-gates 5, 5A, 51, 51A are arranged in a state of being rotated by 90 ° about the center O of the ring gate 6, the sub-gates 5, 5A, 51, 51A are arranged. Since the filler discharged from the above flows merges in the same direction with the flow being most attenuated, a weld is less likely to occur.

The second embodiment of the present invention as described above is a ring gate mold including a ring gate 6 and four sub-gates 5, 5A, 51, 51A communicating with the ring gate 6, The sub-gates 5, 5A, 51, 51A are arranged eccentrically with respect to the center O of the ring gate 6, and each of the sub-gates 5, 5A, 51, 51A has a center O of the ring gate 6 as a base point. Since the sub-gates 5, 5A, 51, 51 are arranged in a rotated state,
Welds are less likely to occur because the flow of the filler discharged from A does not substantially face and merge. In particular, by arranging the sub-gates 5, 5A, 51, 51A rotated by 90 ° about the center O of the ring gate 6, the filler discharged from the sub-gates 5, 5A, 51, 51A is Since a spiral flow can be formed and the flows can be merged in the same direction in the most attenuated state, welds are further unlikely to occur. Therefore, it is possible to obtain a hollow cylindrical product having improved mechanical strength.

The ring gate mold of the present invention has been described above with reference to the accompanying drawings, but 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 can be 3
The number may be 5 or more, but 2 or 4 is preferable from the viewpoint of design difficulty and moldability. Further, the sub-gate does not need to be arranged in a state of being completely rotated about the center O of the ring gate, but may be in a state of being substantially rotated so as to form a spiral flow. The arrangement is preferably equiangular with respect to the center O of the ring gate, but the angles may be different depending on the case. Further, the shape of the sub-gate does not have to be rod-shaped as in the first and second embodiments, and may be a substantially fan-shaped shape whose width gradually increases from the secondary gate 4 to the ring gate 6. Furthermore, the discharge part
The thickness of 62 can also be changed stepwise or continuously. The ring gate mold 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 it can be injection-molded. Suitable for injection molding. 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 molded product having almost no weld and a small shear stress in the circumferential direction and a good mechanical strength.

[0016]

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, wherein the sub-gate is the ring gate die. It is arranged in an eccentric state with respect to the center, and since each of the subgates is arranged in a substantially rotating state with respect to the center of the ring gate, the resin that has flowed into the subgate through the runner, Filling material such as ceramics is supplied from the subgate to the ring gate. In this ring gate, since the sub-gate is arranged in an eccentric state with respect to the center of the ring gate, and is arranged in a substantially rotating state with the center of the ring gate as a base point,
The filler discharged from the sub-gate forms a spiral flow, and the flows are substantially opposed to each other and do not merge, so that weld is unlikely to occur.

Further, in the ring gate die according to the present invention, since each of the sub-gates is arranged in a state of being rotated at substantially the same angle with respect to the center of the ring gate, the filler discharged from the sub-gate is ring-shaped. Welds are further less likely to occur because the flow of the filler is injected into the cavity while flowing in the same direction in a spiral shape in the gate, and the flows of the filler do not face each other and merge.

[Brief description of drawings]

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

2A and 2B are enlarged schematic views of a main part showing a ring gate mold according to a second embodiment of the present invention, FIG.
It is a B line sectional view.

3A and 3B are schematic views showing a ring gate mold according to a conventional example, FIG. 3A is a plan view, and FIG. 3B is a sectional view taken along line CC.

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

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

[Explanation of symbols]

 1 Ring gate mold 5, 5A, 51, 51A Sub gate 6 Ring gate 62 Discharge part O Ring gate center

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 sub gate is arranged eccentrically with respect to the center of the ring gate. A ring gate die, wherein each of the sub-gates is arranged in a substantially rotating state with the center of the ring gate as a base point. 2. The ring gate mold according to claim 1, wherein each of the sub-gates is arranged in a state in which the sub-gates are rotated at substantially the same angle with respect to the center of the ring gate.