JP2000117787A - Die for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a molding material from dripping down at a non-molding time and also to ensure a flow rate of the molding material at a molding time, while simplifying the structure of a gate. SOLUTION: A gate for filling a cavity 31 with a molding material in a flowing state opens in the shape of an annular slit to the inside of the cavity 31. By narrowing the width of the slit, a fluidized molding material can be prevented from dripping down from the gate. Although the slit width is narrowed, the opening area is wide as a whole, since the slit extends long circumferentially, and therefore molding efficiency can be improved by increasing a flow rate of the molding material. Moreover, the structure is simplified in comparison with that provided with an opening-closing mechanism as a means for preventing dripping-down of the molding material and ensuring the flow rate thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a mold for an injection molding machine.

[0002]

2. Description of the Related Art As a mold for an injection molding machine using a thermosetting resin material, a molding material sent from a nozzle of an injection cylinder is passed through a sprue in the mold to fill a cavity from a gate. There is one in which a molding material is cured by heating a mold to obtain a desired molded product.
In such a mold for an injection molding machine, the molding material is always filled in the sprue from the nozzle contact portion of the injection cylinder to the gate, and the molding material in the sprue is close to the gate. It is cured by the heat transmitted from the mold.
However, once the thermosetting resin material has been cured, it cannot be reused thereafter, so that the molding material cured in the sprue is wasted.

Therefore, a mold for an injection molding machine has been developed which has a structure (called a cold runner) in which the entire region from the nozzle contact portion to the gate is kept at a low temperature so that the molding material is not wasted (referred to as a cold runner). Japanese Patent Publication No. Hei 4-52767, Japanese Utility Model Laid-Open No. 4-100823, Japanese Utility Model Laid-Open No. 6-81716, etc.). This is called an open gate type, in which the gate always keeps communicating with the internal communication space of the mold. In this type, the gate diameter is set small in order to prevent the molding material in the sprue from dripping from the gate when the molding material is not filled in the mold.

[0004]

However, in the open gate type, since the diameter of the gate is small, the flow rate of the molding material passing through the gate during molding is small. for that reason,
There is a disadvantage that molding takes time and molding efficiency is poor. As a means for avoiding this drawback, a valve gate type in which a needle valve mechanism is provided at the gate and the gate is opened only when necessary to prevent dripping of the molding material is also considered. However, this not only complicates the structure of the gate, but also requires a drive mechanism for opening and closing the valve, which leads to another problem that the structure becomes complicated as a whole and the cost increases. is there.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and aims to prevent a dripping of a molding material during non-molding and to secure a flow rate of the molding material at the time of molding while making the gate simple. I have.

[0006]

According to a first aspect of the present invention, a flowable molding material injected into a mold from an injection cylinder is filled into a cavity from a gate, and the molding material filled in the cavity is heated. In a mold for an injection molding machine for obtaining a molded product by curing the mold, the gate is opened in an annular slit shape in the cavity.

According to a second aspect of the present invention, in the first aspect of the present invention, a columnar core is fixed in a communication space provided from the nozzle of the injection cylinder to the cavity.
It is characterized in that the gate and a sprue for flowing a molding material from the nozzle to the gate are formed between the outer periphery of the core and the inner wall of the communication space. The invention according to claim 3 is such that a core substantially concentric with the gate penetrates through the cavity, and the molded article having a cylindrical shape is molded in the cavity. A mold for an injection molding machine according to claim 1, wherein said core and said core have mutually corresponding ends, and a positioning portion that engages with each other to keep the end of said core concentric with said core. Is formed.

[0008]

Operation and Effect of the Invention [Invention of claim 1] Since the gate is simply opened like a ring-shaped slit, the structure is simpler than that provided with an opening / closing mechanism. In addition, by reducing the width of the slit, the flowing molding material can be prevented from dripping from the gate. Even if the slit width is reduced, the overall opening area is large because the slit extends long in the circumferential direction, so that the flow rate of the molding material can be increased and the molding efficiency can be improved.

[Invention of claim 2] The molding material injected from the nozzle reaches the gate through the sprue between the inner wall and the core of the communication space, and is filled in the cavity. Since the sprue and the gate, which are the flow path of the molding material from the nozzle to the cavity, are formed so that both are continuous along the inner wall of the communication space and the outer periphery of the core, the flow from the sprue to the gate is Little resistance and good injection efficiency. In addition, the inner peripheral edge and the outer peripheral edge of the annular opening of the gate are formed by the outer periphery of the core and the inner wall peripheral edge of the communication space, respectively, but since the core is fixed in the communication space, The inner peripheral edge and the outer peripheral edge of the annular opening are not misaligned, and the flow rate of the molding material passing through the gate is prevented from fluctuating in the circumferential direction.

[0010] The core is fixed to the communication space, and the core is positioned with respect to the core by the positioning portion, so that the radial movement of the core in the cavity is regulated, and the molding is performed. The dimensional accuracy of the product can be stabilized and improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first embodiment of the present invention will be described below with reference to FIGS. The mold 10 has an upper mold 10A, a middle mold 10B and a lower mold 10C.
Consists of Explaining the structure of the upper die 10A, an upper plate 14 having an inlet 13 communicating with the nozzle 12 of the injection cylinder 11 is provided at the uppermost portion, and the lower surface of the upper plate 14 is substantially the same as the inlet 13. A concentric holding member 15 is fixed. An elongated communication space 16 having a circular cross section penetrating in the up-down direction is formed in the holding member 15.
The upper end of 6 communicates with the inflow port 13 slightly eccentrically.
A cylindrical core 17 is fixed in the communication space 16, and a spiral groove 18 is formed on the outer periphery of the core 17 between the upper and lower end surfaces, and the spiral groove 18 and the communication space 16 are formed. Between the nozzle 12 and a gate 3 to be described later.
A sprue 19 leading to 0 is formed. This sprue 19
Inside, a fluid molding material (not shown) injected from the nozzle 12 flows toward the gate 30. In the holding member 15, the cooling water inflow passage 2 which extends inward from the outer periphery of the upper end and extends downward along the communication space 16.
0 is formed, and the communication space 16 is formed from the lower end.
A cooling water outflow passage 21 extending upward along the line and opening to the outer periphery of the upper end of the holding member 15 is formed. The cooling water outflow passage 21 is formed in a ring shape surrounding the lower end of the communication space 16. The annular flow path 22 which connects the lower ends of the two is formed.

A cooling member 23 is fixed to the lower surface of the upper plate 14 so as to surround a substantially upper half portion of the holding member 15, and the cooling member 23 communicates with a cooling water supply device (not shown) outside. A cooling water supply passage 24 communicating with the cooling water inflow passage 20 is formed on the inside, and a cooling water communicating with the cooling water outflow passage 21 on the inside and communicating with a cooling water recovery device (not shown) on the outside. A discharge path 25 is formed. Such a cooling member 23
Cools the molding material in the sprue 19 to a predetermined temperature by flowing cooling water around the sprue 19,
Thus, the molding material is kept in a fluid state. The cooling water flow path is sealed by an O-ring 26.

A heat insulating member 27 is fixed to the lower surface of the cooling member 23, and a heating member 28 is fixed to the lower surface of the heat insulating member 27 so as to surround substantially the lower half of the holding member 15. The lower end of the heating member 28 is provided with the communication space 16.
A cylindrical body 29 having a heat insulating property concentric with the cylindrical body 29 is fixed.
The cylindrical body 29 has a slightly smaller inner diameter than the communication space 16 and is provided so as to surround the lower end of the core 17 with a slight gap. The lower end portion of the slight gap space is a gate 30 which has a continuous annular slit shape over the entire circumference. This gate 30
A cavity 31 for molding a molded product as described later.
The molding material in a flowing state is supplied into the cavity 31 through the gate 30. Further, the spiral groove 18 on the outer periphery of the core 17 faces this gap. Therefore, the gate 30 and the nozzle 12 are connected via the sprue 19 which forms a spiral between the core 17 and the communication space 16. Are in communication. The heating member 28 raises the inside of the cavity 31 to a predetermined temperature and hardens the molding material in the cavity 31 as described later.

The middle mold 10B can be moved toward and away from the upper mold 10A, and has a cavity 31 formed therein between the upper and lower end faces. The cavity 31 has a circular cross section that is concentric with the communication space 16 and the core 17 and has an inner diameter that varies in the vertical axis direction. Three enlarged diameter portions 31B are provided. Further, at the time of molding, a core 32 projecting from the upper surface of the lower die 10C is arranged so as to penetrate concentrically in the cavity 31. In the cavity 31, a cylindrical rubber stopper ( (Not shown). Although not shown, the rubber stopper is fitted to a terminal fitting of a wire harness, and when the terminal fitting is inserted into the connector housing, exhibits a function of maintaining waterproofness in the insertion space.

On the upper end face of the core 32, a conical projection 32A (positioning part which is a constituent element of the present invention) concentric with the core 32 is formed. The concave portion 17A (positioning portion, which is a constituent feature of the present invention) is also formed concentrically. Upper die 10
A, in a state in which the middle mold 10B and the lower mold 10C are all in close contact with each other and clamped, the projection 32A is fitted so as to pierce the recess 17A, so that the core 32 is restricted from moving in the radial direction with respect to the core 17. Position.

The lower mold 10C is provided with a heater (not shown) inside and has a heating function. Such lower mold 1
0C is the middle mold 1 between the heating member 28 of the upper mold 10A.
0B, the cavity 3 of the middle die 10B
1 is uniformly heated to a predetermined temperature. Next, the operation of the present embodiment will be described. At the time of molding, all of the upper mold 10A, the middle mold 10B, and the lower mold 10C are clamped, and a predetermined amount of a molding material in a low-temperature flow state is injected into the mold 10 from the nozzle 12 of the injection cylinder 11. The molding material enters the communication space 16 from the inflow port 13, reaches the gate 30 through the spiral sprue 19, and fills the cavity 31. During this time, the molding material in the sprue 19 is kept in a fluid state by the cooling action of the cooling member 23, but is heated from both the upper and lower sides in the cavity 31, whereby the molding material is hardened.

When the molding material in the cavity 31 is cured, first, the mold is released between the upper mold 10A and the middle mold 10B, that is, at the gate 30, and the cured molding material in the cavity 31 and the fluidized state in the sprue 19 are removed. Separate from the molding material. Thereafter, the core 32 is extracted by releasing the lower mold 10C from the middle mold 10B, and the cavity 3 is further removed.
Take out the cured molded article in 1. When the middle mold 10B is separated from the upper mold 10A, the gate 30 remains open downward, and the molding material in a flowing state remains in the sprue 19 above the gate 30. However, since the gate 30 is opened in a slit shape and the opening width is narrow, the molding material in a flowing state in the sprue 19 does not drop from the gate 30.

Even if the width of the slit is narrow to prevent dripping as described above, since the slit extends long in the circumferential direction, a wide opening area is secured as a whole. Therefore, the flow rate of the molding material passing through the gate 30 does not decrease, and the molding efficiency does not decrease due to the decrease in the flow rate. Further, the structure is simpler and the cost can be reduced as compared with a method in which an opening / closing mechanism such as a needle valve is provided as a means for preventing the molding material from dripping and securing the flow rate at the gate 30.

The sprue 19 is a flow path until the molding material injected into the mold 10 reaches the cavity 31.
And the gate 30 are formed so as to be continuous along the inner wall of the communication space 16 and the outer periphery of the core 17.
There is almost no flow resistance from 9 to the gate 30 and the injection efficiency is excellent. In addition, since the sprue 19 forms a spiral flow path, the injection pressure becomes uniform over the entire circumference, and in this regard, a good injection molding can be performed.

The inner peripheral edge and the outer peripheral edge of the annular opening of the gate 30 are formed by the outer periphery of the core 17 and the inner wall peripheral edge of the communication space 16, respectively. Since it is fixed, the inner peripheral edge and the outer peripheral edge of the annular opening of the gate 30 are not misaligned, and the flow rate of the molding material passing through the gate 30 can be kept uniform over the entire circumference. Since the core 17 is fixed to the communication space 16 and the core 32 is positioned with respect to the core 17, radial movement of the core 32 in the cavity 31 is restricted, and the size of the molded product is reduced. Accuracy can be stabilized and improved.

<Other Embodiments> The present invention is not limited to the embodiments described above with reference to the drawings. For example, the following embodiments are also included in the technical scope of the present invention. In addition, various changes can be made without departing from the scope of the invention. (1) In the above embodiment, the gate is continuously opened over the entire circumference. However, according to the present invention, a plurality of arc-shaped slit-shaped openings are arranged so as to be circular as a whole. Is also good.

(2) In the above embodiment, the gate is opened in a perfect circle, but according to the present invention, the gate may be opened in a shape other than a perfect circle such as an ellipse or an oval. (3) In the above embodiment, the gate is opened in a single annular shape. However, according to the present invention, a plurality of annular openings having different diameters may be arranged concentrically. (4) In the above embodiment, the core is fixed by bringing the outer circumference of the core into surface contact with the inner circumference of the communication space. However, according to the present invention, the outer circumference of the core or the inner circumference of the communication space is fixed. A plurality of radially projecting ribs may be arranged at appropriate intervals in the circumferential direction, and the ribs may restrict the radial movement of the core.

(5) In the above embodiment, the sprue is formed on the outer periphery of the core, but according to the present invention, the sprue is formed inside the core and the sprue is opened to the outer periphery of the core near the gate. You may do so.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a mold clamping state according to a first embodiment.

FIG. 2 is an enlarged sectional view showing a gate portion.

FIG. 3 is a bottom view showing the shape of a gate opening;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Die 10A ... Upper mold 10B ... Middle mold 10C ... Lower mold 11 ... Injection cylinder 12 ... Nozzle 16 ... Communication space 17 ... Middle core 17A ... Depression (positioning part) 19 ... Sprue 30 ... Gate 31 ... Cavity 32 ... Core 32A ... projection (positioning part)

Claims (3)

[Claims] 1. A molding material in a flowing state injected into a mold from an injection cylinder is filled into a cavity from a gate, and the molding material filled in the cavity is heated and cured to obtain a molded product. A mold for an injection molding machine, wherein the gate is opened in an annular slit shape in the cavity. 2. A column-shaped core is fixed in a communication space provided from the nozzle of the injection cylinder to the cavity, and the gate and the gate are disposed between an outer periphery of the core and an inner wall of the communication space. 2. A mold for an injection molding machine according to claim 1, further comprising a sprue for flowing a molding material from said nozzle to said gate. 3. The molded product according to claim 2, wherein a core substantially concentric with the gate penetrates through the cavity, and the molded article having a cylindrical shape is molded in the cavity. A mold for an injection molding machine, wherein a positioning portion is formed at a corresponding end of the core and the core to keep the end of the core concentric with the core by engaging with each other. A mold for an injection molding machine, which is characterized in that: