JPS58131042A - Molding method by ring gate - Google Patents

Abstract

PURPOSE:To mold an annulus like resin product free from a weldline and of excellent strength, appearance making the volume of a runner as small as possible, by injecting a molten molding material into a mold cavity via a hollow cylindrical runner and a ring like gate connected to it. CONSTITUTION:A core 17 having a protruded part 17b is provided to the central part of a molding part 15 provided in a mold 16, meanwhile a runner core 18 is provided at the central part of a mold 19, is fixed by fitting a concave part 18b drilled at its lower end face 18a to said protruded part 17a of the core 17, a hollow cylindrical runner 20 is shaped between the inner face of the mold 19 and the outer face of the runner core 18 and its lower end part is connected to an annulus like gate 22. A molten molding material injected via a vertical runner 26, the horizontal runners 23, 24, the inflow ports 25a, 25b and a flange part 21 joins midway of its flow down in the runner 20 and is filled into the molding part 15 with a uniform flow from the ring gate 22, so a uniform annulus like molded article 29 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection molding method, and is particularly used for molding products that require highly accurate roundness, and products that should not have weld lines from the viewpoint of appearance or strength. This invention relates to a molding method suitable for use in

Conventionally, as shown in Figure 1, in order to mold synthetic resin molded products such as annular parts and gears, runners (1) are formed with several rod-shaped clouds spaced apart at predetermined intervals. Through the inlet (2), the molten synthetic resin material enters the molding section (
3) was injected. For this reason, the injected molding material flows in the direction of the arrows in each molding part (3), creating a butting part, and in this part, a so-called weld line (4), which is a weak joint with insufficient mechanical strength, is created. was. In addition, the inflow pressure of the molding material injected from the several injection ports (2) arranged in a dotted manner as described above is not uniform within the molding part (3). It was extremely difficult to mold products that required highly accurate roundness with accurate shapes.In addition, iron powder etc. were mixed into the synthetic resin material in order to increase the electrostatic charge. In the case of iron powder, the distribution of iron powder tends to be unreliable, and the weight balance tends to be uneven.

In order to solve this problem, a method was proposed in which the molding material is uniformly injected through an annularly formed gate as shown in FIG. That is, according to this 1, a runner (7) is formed in the mold (6) on the fixed side, a molded part (9) is formed in the metal mold W (8) on the movable side, and this molded part (9
) Insert the pins provided at the position corresponding to the opening of the product into the runner (72 #C), and
The structure is such that the runner (71) and the molding part (9) communicate with each other through an annular gate αυ formed between the outer peripheral surface of the mold (71) and the inner peripheral surface of the stationary mold (6). Therefore, the molten molding material flowing into the runner (7) from one or several inlets (not shown) on the outer periphery of the upper part of the runner (7) reaches the annular gate aυ. 7)
After completing the rotation, the radial particles are uniformly injected into the molding part (9) from the annular gate aυ.

In such a method, the above-mentioned weld line does not occur or, on the other hand, the volume of the runner (7) becomes very large, so there is a restriction on the diameter of the gate aυ. That is, as the molded product becomes larger and the diameter of the annular link aυ increases, the diameter of the runner (7) also increases, which not only lengthens the molding cycle but also leaves a large amount of unnecessary synthetic resin in the runner (71P'3). This results in a very disadvantageous and uneconomical material cost.

The present invention has been made from the above-mentioned viewpoints, and its purpose is to provide a molding method that can uniformly inject a molten molding material into a molding part and reduce the volume of the runner as much as possible. It's in Trun.

In order to achieve this object, in the molding method of the present invention, a runner core is used to form an intermediate runner between the outer surface of the runner core and the inner surface of the mold, and the runner core is A ring-shaped gate communicating with the molding part ζ is formed between the outer peripheral surface and the inner peripheral surface of the mold, and the molten molding material l#+ is uniformly distributed from the runner to the molding part f through the ring-shaped gate. It is characterized by being injected into the body.

Hereinafter, a first embodiment of the present invention will be explained based on FIGS. 3 and 4.

First, the mold apparatus used in this first implementation will be explained. Reference numeral a9 is a molding part formed in the movable mold 06), and in the center of this molding part Q5 there is an upper end (8) (17a) of the same size and shape as the opening of the molded product.
A core Q7)f's having a protrusion (17b) is provided at the center of the core Q7), and its upper end surface (17) is approximately on the same level as the upper surface of the mold αe.

On the other hand, the lower end surface (18a) of the runner core α is Mt+
=t=core Q? ) has a small truncated conical shape with a nerber having the same shape as the upper end surface (17), but the lower end surface (18a) has a recess (18b) bored therein.
The protrusion (17a) on the upper end surface of the core tI7) is fitted into the core tI7) so that it is coaxial with the core On, and is coupled with high precision.

Next, a fixed mold 1 (11) having a predetermined thickness surrounds the runner core θ81, and a cylindrical runner snare is formed between the outer peripheral surface of the runner core a8 and the inner peripheral surface of the mold 1lI9. An upper runner flange portion Cυ is formed, and a link-shaped gate (221) communicating with the molded portion α4 is formed at the bottom of this runner (201).

- A straight horizontal runner (C), a semicircular horizontal runner branching from one end (24J, and this horizontal runner C)
Inflow ports (258X25b) connecting the ends of 241 to the runner flange portions Qυ are formed on the upper surface of the mold 0 wing of the fixed mantle 1. Then, a vertical runner (A) is formed on the inside, one end of which is connected to the upper sprue (not shown), and the other end is connected to the end of the horizontal runner (C). A mold (5) is placed on the first mold (2) and fixed.

In the acid-containing mold device as described above, the flow of molten molding material flowing from the sprue into the runner flange portion 3υ via the runners (A), (C), (2) (25aX25b) lr flows downward while going around the periphery. Since it is a flowing flow, the flow at the upper part of the runner (4) is a combination of a circumferential flow and a unidirectional flow, and a part of the flow remains in the circumferential direction. However, at the lower part of runner 4, the above-mentioned molding material completes its rotation around the runner core 081 and flows in the direction of the ring gate.

Therefore, the melt molding material is
It flows radially uniformly into the molding part (19) through the molding part 19, and is completely filled into the molding part (into) with a strong pressure, forming a ring-shaped molded product.

After molding, the molds Qi19 and H are connected to the protrusions of the core u (
Press off at part 17b) and remove the molded product from the molded part (l”)
What is shown in FIGS. 5 and 6 is a second embodiment of the present invention, and is a highly accurate small product. molding (this is preferred).
Since the embodiment differs from the first embodiment in the mold device,
First, I will explain the details of the mold assembly.

A molding part @l is formed on the movable side mold C31H, and a rod-shaped core C3'lI of a size and shape corresponding to the opening of the molded product is provided at the center of this molding part (to). , the core passes upward through the molded portion Q.

- 10,000, the runner core (2) is a conical rond with a small taper with an obtuse conical surface formed on its lower end surface (33a), or a recess (36b) bored in the center of its lower end surface (33a). The core gear is fitted into the core gear 4 to make it coaxial with the core gear 4, and then fixed vertically with a predetermined gap provided between the core gear and the molded part.

Next, the runner core (c) is surrounded by a first mold (b) fixed at a predetermined bank, and the lower end surface (33a) of this runner core (to) and the inner circumferential surface of the mold are connected. A conical runner eel is formed between them. Then, a gap is formed between the lower part of the runner can, that is, the lower end of the molded part and the runner core, and the protruding cores G are used as auxiliary runner cores. (a link-shaped game connected to the molding am) between the inner peripheral surface of the mold drawing and the molding am)
136) is formed.

- 10,000, At a position opposite to each other at the upper end of the conical runner (C), there is a runner core (to) connected to this runner (to).
Runners (37a) (37b) are formed along the outer circumferential surface of the runners (37a) and (37b), respectively, extending upwardly with a predetermined width and a predetermined pitch.

The upper ends of these runners (37aX37b) are respectively connected to semicircular horizontal runners (to). Linear horizontal runners connected to this semicircular runner (to) and vertical vertical runners (4 (l) and fixed side second gold p (411) are the same as in the first embodiment. All (same, h is the runner (37a) (37) of the mold device configured as above)
The molten molding material that has flowed into b) flows into a conical runner (c). Even in this second embodiment, the inflowing molding material finishes turning around the lower end surface (33a) of the runner core (g) before reaching the ring gage (Gljl), and flows only in the direction of the ring gage. The flow is the same as in the first embodiment. Further, although the shape of the runner is slightly different from that of the first embodiment, it is similar to the first embodiment that it has a hollow shape as shown in FIG. Therefore, also in this second embodiment,
The same effects as in the first embodiment can be achieved.

In addition, since the common cylindrical molded part (151 (to)) and the runner core a81 in the first and second embodiments are configured to have the same axis, the roundness of the molded product (c) is It will be very expensive.

In addition, in these embodiments, the ring gate C24
Although the shape of □□□ is circular, this shape may also be polygonal, and it is clear that C can achieve the same effect as described above.

As explained above, according to the molding method of the present invention, the molten molding material is injected radially and uniformly into the molding part from the hollow runner through the ring gate, so that the molding material that has flowed in is uniformly injected. The molded part is filled with pressure. Therefore, of course, there are no weld lines in the molded product, and
The molded product is uniform in its internal filling,
A product with an accurate shape that guarantees high precision roundness and shape is molded.

However, as mentioned above, the runner is hollow and has a very small volume, which is advantageous in that the molding cycle is short and the material quality of the synthetic resin can be significantly reduced.

Since there are few restrictions on the diameter of the ring gate, it is easy to realize a large gate, and a large molded product can be formed with high precision.

[Brief explanation of drawings]

Fig. 1 shows the conventional molding method, T for explanation is the wheel load, Fig. 2 is a longitudinal cross-sectional view of the molding part of the previously proposed mold device, and Fig. 6 is used for the embodiment of Ml of the present invention. FIG. 4 is a vertical sectional view of the mold product device, FIG. 4 is a perspective view of the molding runner, FIG. 5A is a vertical sectional view of the mold device used in the N2 embodiment of the present invention, and FIG. 5B is a FIG. 6 is a vertical circle view taken by cutting the mold apparatus shown in FIG. SA in a direction perpendicular to the mold apparatus shown in FIG. In addition, in the symbols used in the drawings, α5 (to)...
・Molding part - (to)・・・・・・・・・・・・・・・・・・
・・・・Ranna Core■(2)・・・・・・・・・・・・
・・・・・・・・・ Fixed side first mold (To) (To)
(37th (37b)... Runner (2) (to)...
・・・・・・・・・・・・ Ring Gate G3z...
・・・・・・・・・・・・ Song core (auxiliary runner core). Agent Masaru Ueya Yoshio Tsuneko Toshiki Sugiura flute 2 @ -21:2- // , Z! 0) Procedural amendment 1984 4 Yesterday, Mr. Commissioner of the Patent Office 1, Indication of the case Relationship to the 1981 Patent Application No. 13794 Patent applicant 6, Number of inventions increased by the amendment 7, Subject of the amendment, (1) In the specification, [Page 5, lines 18 to 19] "Fixed to the mold of Fixed Takao 2..." is changed to "Fixed Takao 2." 2 runner stripper (2) is placed on the first metal utensil.'' and corrected t T . (2), page 6, lines 13 to 14 of the specification: ``Then, after molding, the 11 gold rings and the goose...''
1T0 (3), and changed ``Runner stripper'' on page 6, line 16 of the specification to ``Then, press the molded product (2)'' to ``And after molding, the molded product (c)''. Runner stripper (2)” and correction stripe To (4)
, "Mold 0" on page 8, line 8 of the specification is corrected to runner stripper (4DJ), "Material quality" on page 10, line 1 of the specification is changed to "material cost". ”. (6) Please correct the symbol aυ of figure #!4 of the drawing so that it is not placed in the attached corrected drawing.

Claims (1)

[Claims] From the hollow runner formed between the outer circumferential surface of the runner core and the outer circumferential surface of the runner core (the inner circumferential surface of the mold in which this is placed),
The bath melting bottom material is injected into the molding part through a ring-shaped gate formed between the inner peripheral surface of the mold and the outer peripheral surface of the runner core or an auxiliary runner core connected to the runner core. A link gate forming method characterized by the following.