JPH10291235A - Nozzle for mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nozzle for a mold for preventing the backflow of semicured resin from the inside of a cavity into the nozzle. SOLUTION: A nozzle 25 for a mold is provided with a nozzle main body 32 with a gate section 31, a shaft valve 34 movable forward and backward in the nozzle main body 32, a coil spring 38 for energizing the shaft valve 34 in the direction of moving back from the cavity 32 and a valve section 41 provided on the shaft valve 34 and receiving the injection pressure of resin introduced into the nozzle main body 32, moving the shaft valve 34 in the direction to the cavity 22 in resistance to the energizing force of the coil spring 38 and opening the gate section 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle for a mold used for molding a resin, particularly a thermosetting resin such as a liquid silicone rubber.

[0002]

2. Description of the Related Art As a final barrier for introducing a raw material resin into a mold cavity, a gate is an important part that greatly affects the quality of a molded product. For this reason, gates and nozzles having various structures have been developed according to the purpose. For example, when molding liquid silicone rubber, which is a thermosetting resin, the inside of the mold can be made runner-less so that the material is not cured by the heat of the mold until just before the gate, and the vicinity of the material flow path is cooled. Often possible cold type gates and nozzles are used.

Conventionally, this type of mold nozzle is provided with a cooling function in the nozzle itself and a gate in order to prevent the liquid silicone rubber from solidifying during the transfer to the cavity as described above. A cold-type nozzle was incorporated so that it could open directly into the cavity. The opening and closing of the gate of such a cold type nozzle is performed by advancing and retracting a shaft portion having a valve function in the nozzle. As means for performing this operation, there are a hydraulically operated type and a spring. Some of them are used to operate.

FIG. 7 shows a structure of a mold in which a mold nozzle for operating a shaft portion by a spring is incorporated.

[0005] When liquid silicone rubber is molded in this mold, first, liquid silicone rubber injected by an injection molding machine (not shown) is introduced from an introduction section 1, passes through a transfer path 2, and enters a cold nozzle 3. It flows into the resin flow path 4 shown in FIG. The liquid silicone rubber flowing into the resin flow path 4 in which the cooling passage 5 in which the cooling water flows is disposed on the outer periphery is formed by the inner wall of the gate portion 6 located at the tip of the cold nozzle 3 shown in FIG. The resin enters the resin reservoir 8 which is a space between the valve 7 and the concave portion at the tip. The shaft valve 7 that has closed the discharge port 10 of the gate portion 6 by the resilience of the coil spring 9 is moved to the position shown in FIG. 10 by the liquid pressure in the resin reservoir 8 that increases as the liquid silicone rubber is accumulated in the resin reservoir 8. As shown, it is retracted against the elastic force of the coil spring 9.
As the shaft valve 7 is retracted, a gap is formed between the shaft valve 7 and the inner wall of the gate portion 6 as shown in FIG.
It is injected into the cavity 11 of the mold heated to 0 ° C. Thereafter, when the injection of the liquid silicone rubber is completed and the injection pressure from an injection molding machine (not shown) decreases, the shaft valve 7 advances again by the resilience of the coil spring 9 as shown in FIG. 10 is closed.

[0006]

In normal thermoplastic molding, a molded product is obtained by cooling a high-temperature material in a mold cavity. Therefore, in the mold cavity, the material shrinks due to cooling. Conversely, in the molding of the silicone rubber of the thermosetting resin as described above, the material at room temperature is injected into the mold cavity at high temperature in the cylinder, so that the material undergoes thermal expansion. Due to this thermal expansion, the following problems occur in the cold type nozzle. That is, in this cold type nozzle, the shaft valve 7 is pushed backward by the pressure when the liquid silicone rubber, which is a thermosetting resin, undergoes thermal expansion in the cavity 11 of the heated mold, and the gate portion 6 is discharged. Exit 10
Will open. As a result, backflow of the heated liquid silicone rubber from the cavity 11 occurs, and this backflow material is hardened and mixed into the liquid silicone rubber in the nozzle,
There is a problem that the resin flow path in the nozzle is closed.

In addition, due to the backflow of the liquid silicone rubber from the cavity into the nozzle, or the clogging of the resin flow path caused by the backflow material being cured in the nozzle,
At the time of injection, a pressure higher than a predetermined injection pressure is applied to the inside of the nozzle, and the stress applied to the nozzle exceeds the allowable stress as a structure of the nozzle, and the nozzle itself is damaged.

[0008] Even in a mold nozzle that operates a shaft portion having a valve function by hydraulic pressure, the pressure for closing the gate is limited depending on the shape of the valve in the shaft portion. Had occurred.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a mold nozzle capable of preventing a backflow of semi-cured resin into the nozzle.

[0010]

According to the present invention, there is provided a mold nozzle having a nozzle body having a gate portion, a shaft valve movably provided in the nozzle body, and retracting the shaft valve from a cavity. Urging means for urging the shaft valve in the direction, and receiving the injection pressure of the resin introduced into the nozzle body, moving the shaft valve in the direction of the cavity against the urging force of the urging means. And a valve portion for opening the gate portion.

In this nozzle, at the time of resin injection, the valve portion of the shaft valve receives the injection pressure of the resin introduced into the nozzle body, and moves the shaft valve toward the cavity against the urging force of the urging means. It acts to open the gate. The action of such a valve section is, for example, to select the shape of the valve section so that the valve section receives the injection pressure of the resin from the opposite side of the cavity, and to apply the urging force of the urging means and the valve section at the time of resin injection. This is realized by setting the balance with the injection pressure of the resin optimally. As a result, the gate portion is opened at the time of resin injection, and is closed by the urging force of the urging means after the completion of resin injection in which the valve portion does not receive the resin injection pressure. Therefore, when a thermosetting resin such as liquid silicone rubber is used as the resin, the valve section receives the thermal expansion pressure from the cavity side after the resin injection is completed. The direction is coincident, and the valve part is only pressed in the direction to close the gate part. Therefore, the resin does not flow backward from the cavity into the nozzle after the resin injection is completed.

In addition, the mold nozzle of the present invention includes a nozzle body having a gate portion, a shaft valve provided to be able to advance and retreat within the nozzle body, and having a resin flow path therein.
Urging means for urging the shaft valve in a direction of retracting from the cavity, and urging means provided on the shaft valve for receiving the injection pressure of the resin introduced into the nozzle main body, and urging the shaft valve with the urging means. In some cases, the apparatus further comprises a valve portion for moving in a direction of the cavity against the urging force to open a resin flow path in the shaft valve with respect to the gate portion.

In this nozzle, when injecting the resin, the valve portion of the shaft valve receives the injection pressure of the resin introduced into the resin flow path and moves the shaft valve toward the cavity against the urging force of the urging means. , And acts to open the resin flow path of the shaft valve with respect to the gate portion. Similar to the nozzle, for example, the action of the valve section is selected by selecting the shape of the valve section so that the valve section receives the injection pressure of the resin from the opposite side of the cavity, and the urging force of the urging means and the valve. This is realized by optimally setting the balance between the unit and the injection pressure of the resin received during the resin injection. As a result, the resin flow path of the shaft valve is opened at the time of resin injection with respect to the gate portion, and is closed by the urging force of the urging means after the completion of resin injection in which the valve portion does not receive the resin injection pressure. Therefore, when a thermosetting resin such as liquid silicone rubber is used as the resin, the valve section receives the thermal expansion pressure from the cavity side after the resin injection is completed. The direction is coincident, and the valve part is only pressed in the direction to close the gate part. Therefore, the resin does not flow backward from the cavity into the nozzle after the resin injection is completed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a mold in which a mold nozzle according to a first embodiment of the present invention is incorporated.

In this mold, for example, an introduction part 21 into which a liquid silicone rubber injected from an injection molding machine (not shown) is introduced, a cavity 22 having an engraved part for forming a molded product, and the introduced liquid silicone rubber. For example, 1
It is mainly constituted by transfer paths 23 and 24 for transferring to the cavity 22 heated to 50 ° C., and a cold nozzle 25 for injecting the liquid silicone rubber supplied through the transfer path 24 into the cavity 22. In order to prevent the liquid silicone rubber being transferred from being hardened by the heat of the cavity 22 being heated, a cooling means such as a cooling water jacket (not shown) is provided around the introduction section 21 and the transfer paths 23 and 24. I have.

As shown in FIG. 2, the cold nozzle 25 has a nozzle body 32 having a gate portion 31 at the tip, a resin flow path 33 formed along the axis inside the nozzle body 32, and a resin flow path. Shaft valve 34 moving forward and backward in 33
A cooling water passage 35 through which cooling water flows around a wall around the resin flow path 33; a shaft bearing 36 and a spring holder 37 for holding a shaft valve 34 so as to be able to move forward and backward.
, A coil spring 38 as urging means for urging the shaft valve 34 backward from the cavity 22 via a spring holder 37, and a holder bearing 39 for holding the spring holder 37 movably forward and backward. ing.

The resin flow path 33 intersects with the transfer path 40 leading from the transfer path 24 at the rear, and the liquid silicone rubber injected from the injection molding machine and introduced from the introduction section 21 passes through the transfer path 40 through the resin flow path. It flows into the gate part 31 through 33.

The shaft valve 34 has a valve portion 41 at its tip for opening and closing the gate portion 31. The valve portion 41 has a conical shape whose diameter is tapered toward the nozzle tip, and forms a liquid pool 43 between the tapered surface and the inner wall surface of the gate portion 31 when the gate portion 31 is closed. It is something to do.

That is, the shaft valve 34 is provided with the liquid 4
The liquid pressure of the liquid silicone rubber flowing into the
1 and moves toward the cavity 22 against the resilience of the coil spring 38 to open the discharge port 42 of the gate portion 31.
As the liquid pressure received by the first tapered surface decreases, the spring moves back from the cavity 22 by the resilience of the coil spring 38 and closes the discharge port 42 of the gate portion 31.

The load of the coil spring 38 needs to be set to an appropriate value in consideration of the resin pressure applied to the valve portion 41 and the like.

The cold nozzle 2 configured as described above
For example, when liquid silicone rubber is molded by the mold having the mold 5, the liquid silicone rubber injected from an injection molding machine (not shown) passes through the introduction section 21, the transfer path 23, the transfer path 24, and the transfer path 40. The liquid silicone rubber that has flowed into the resin flow path 33 in the cold nozzle 25 through the cold nozzle 25 and further flows into the resin flow path 33 is formed between the inner wall surface of the gate portion 31 and the tapered surface of the valve portion 41 of the shaft valve 34. The liquid flows into the pool 43.

As a result, the fluid pressure in the fluid reservoir 43 gradually increases, and the shaft valve 34 receiving the fluid pressure on the tapered surface of the valve portion 41 receives the gradually increasing urging force toward the cavity 22 side. Thereafter, the urging force exceeds the force of urging (pulling) the shaft valve 34 backward from the cavity 22 by the coil spring 38, and the shaft valve 34 is directed toward the cavity 22 as shown in FIG. Move forward. With the advance of the shaft valve 34 (the advance movement of the valve portion 41), the discharge port 42 of the gate portion 31 is opened, and the liquid silicone rubber is filled in the cavity 22. Thereafter, the shaft valve 34 is fixed at the forward position by the injection pressure received on the tapered surface of the valve portion 41 until the injection step is completed.

When the filling of the liquid silicone rubber into the cavity 22 is completed and the injection from the injection molding machine is stopped, the pressure applied to the tapered surface of the valve portion 41 of the shaft valve 34 decreases rapidly, and the shaft valve 34 The spring 38 is moved backward by the urging force. Thereby, the valve portion 41 of the shaft valve 34 returns to the initial position before the injection shown in FIG. 2, and the discharge port 42 of the gate portion 31 is closed.

On the other hand, in the cavity 22, the hardening of the liquid silicone rubber by heating proceeds, and the valve portion 41 of the shaft valve 34 receives the pressure due to the thermal expansion of the liquid silicone rubber. The tapered surface acts in a direction of pressing against the inner wall surface of the gate portion 31, and therefore, the backflow of the liquid silicone rubber from the cavity 22 into the nozzle can be completely prevented.

As described above, according to the mold nozzle of the present embodiment, even if the liquid silicone rubber in the cavity 22 thermally expands and the pressure is applied to the shaft valve 34 of the nozzle,
Since the pressure received by the shaft valve 34 acts to close the valve strongly, the backflow of the liquid silicone rubber into the cold nozzle 25 can be prevented.

In this embodiment, the valve portion 4 of the shaft valve is used.
Although the conical shape is selected as the shape 1, as shown in FIG. 4, the valve portion 44 may have a columnar shape, and the shape of the valve portion interference portion of the gate portion may be changed accordingly.

Next, a second embodiment of the present invention will be described.

FIG. 5 is a sectional view of a mold nozzle used in the second embodiment.

A cold nozzle 51 shown in the figure is incorporated in a mold similarly to the cold nozzle 31 described in the first embodiment, and includes a nozzle body 53 having a gate portion 52 at a tip, and a cold nozzle 51 inside. A shaft valve 55 having a resin flow passage 54 for moving forward and backward in the nozzle body 53; a cooling water passage 56 for flowing cooling water; a shaft bearing 57 and a spring holder 58 for holding the shaft valve 55 movably forward and backward; Shaft valve 55 via holder 58
For example, a coil spring 60 as biasing means for biasing the cavity 59 heated to 150 ° C. in a retracting direction, and a holder bearing 61 for holding the spring holder 58 movably forward and backward. I have.

The shaft valve 55 branches radially in the vicinity of the center, and a resin flow path 54 formed therein is connected to a transfer path (not shown) through which the liquid silicone rubber injected from the injection molding machine flows. It passes through the inside of the shaft branched in the radial direction of the shaft valve 55 and continues to the branch point of the shaft valve 55. Then, the resin flow path 54 extends from the branch point of the shaft valve 55 along the axis to the gate portion 52, inclines while branching in the radial direction of the shaft valve 55 at the distal end portion, and passes through the discharge port 62 to the shaft valve 55. To the outside. Cavity 59 at the branch of resin flow path 54
The inner wall on the side serves as a pressure receiving portion 63 as a valve portion, and opens and closes the discharge port 62 by the forward and backward movement of the shaft valve 55.

More specifically, the shaft valve 55 receives the liquid pressure of the liquid silicone rubber flowing into the branch portion of the resin flow path 54 at the pressure receiving portion 63, and thereby the shaft valve 5
5 moves in the direction of the cavity 59 against the resilience of the coil spring 60 and opens the discharge port 62 by exposing the discharge port 62 from the inner wall of the gate section 52. At the end of the injection, the pressure receiving section 63 receives the discharge port 62. As the hydraulic pressure decreases, the spring moves backward from the cavity 59 due to the elastic force of the coil spring 60, and the discharge port 62 of the resin flow path 54 is closed by the inner wall of the gate 53. The load of the coil spring 60 needs to be set to an appropriate value in consideration of the resin pressure or the like that the pressure receiving portion 63 receives.

The cold nozzle 5 configured as described above
For example, when liquid silicone rubber is molded using No. 1, liquid silicone rubber injected from an injection molding machine flows into a resin flow path 54 in a shaft valve 55 via a transfer path in a mold (not shown). The liquid silicone rubber that has flowed into the resin flow path 54 is located at the tip end of the shaft valve 55, and the cavity 5 at the branch portion of the resin flow path 54
It flows toward the pressure receiving portion 63 which is the inner wall on the ninth side.

Then, as the injected liquid silicone rubber flows one after another, the liquid pressure received by the pressure receiving portion 63 gradually increases, and the shaft valve 55 receives the gradually increasing urging force toward the cavity 59 side. Thereafter, the biasing force is applied to the shaft valve 5 by the coil spring 60.
5 is pushed (pulled) in a direction to retract from the cavity 59.
The shaft valve 55 advances toward the cavity 59 as shown in FIG. As the shaft valve 55 advances, the discharge port 62 of the resin flow path 54 opens, and the liquid silicone rubber fills the cavity 59. Thereafter, the shaft valve 55 is fixed at the forward position by the injection pressure received by the pressure receiving portion 63 until the injection step is completed.

When the filling of the liquid silicone rubber into the cavity 59 is completed and the injection from the injection molding machine is stopped, the pressure received by the pressure receiving portion 63 of the shaft valve 55 decreases rapidly.
The shaft valve 55 is moved rearward by the urging force of the coil spring 60. Thereby, the shaft valve 55
Returns to the initial position before the injection shown in FIG. 5, and the discharge port 62 of the resin flow path 54 is closed.

On the other hand, in the cavity 59, the hardening of the liquid silicone rubber by heating progresses, and the end face of the shaft valve 55 receives the pressure due to the thermal expansion of the liquid silicone rubber. It acts in the direction of retracting from 59, that is, in the direction of closing the discharge port 62, so that backflow of the liquid silicone rubber from the cavity 59 into the nozzle can be completely prevented.

As described above, according to the mold nozzle of the present embodiment, even if the liquid silicone rubber in the cavity 59 is thermally expanded and the pressure is applied to the shaft valve 55 of the nozzle,
Since the pressure received by the shaft valve 55 acts to strongly close the discharge port 62, the backflow of the liquid silicone rubber into the cold nozzle 25 can be prevented.

[0038]

According to the mold nozzle of the present invention,
For example, even if liquid silicone rubber, which is a thermosetting resin, undergoes thermal expansion in the cavity of a heated mold and receives pressure in a direction in which a shaft valve having a valve function is retracted, the resin outlet is strongly forced. Since it acts in the closing direction, backflow of the resin can be prevented. Therefore, there is no risk that the semi-cured resin flows back into the nozzle and mixes with the raw resin before curing, or blocks the flow path of the raw material.

Further, since there is no influence from the backflow of, for example, liquid silicone rubber from the cavity into the nozzle, or the clogging of the resin flow path due to the hardening of the backflow in the nozzle, the nozzle is not affected at the time of injection. No pressure higher than a predetermined injection pressure is applied to the inside of the nozzle, and there is no possibility that the nozzle may be damaged.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a mold in which a mold nozzle used in a first embodiment of the present invention is incorporated.

FIG. 2 is a sectional view of a mold nozzle according to a first embodiment of the present invention before resin injection.

FIG. 3 is a cross-sectional view of the mold nozzle immediately after resin injection according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a mold nozzle in which a shaft valve having another shape according to the present invention is incorporated.

FIG. 5 is a cross-sectional view of a mold nozzle according to a second embodiment of the present invention before resin injection.

FIG. 6 is a sectional view of a mold nozzle according to a second embodiment of the present invention immediately after resin injection.

FIG. 7 is a sectional view of a mold in which a conventional mold nozzle is incorporated.

FIG. 8 is a sectional view of a conventional mold nozzle before resin injection.

FIG. 9 is an enlarged view of a conventional mold nozzle before resin injection.

FIG. 10 is a sectional view of a conventional mold nozzle immediately after resin injection.

FIG. 11 is an enlarged view of a conventional mold nozzle immediately after resin injection.

[Explanation of symbols]

22 · 59 cavity, 25 · 51 cold nozzle, 31 · 52 gate part, 32 · 53 nozzle body, 33 · 54 resin flow path, 34 · 55 shaft valve, 35 · 56 ... Cooling water channel, 36/57 ... Shaft bearing, 37/58 ... Spring holder, 38/60
…… Coil spring, 39 ・ 61 …… Holder bearing, 4
0: transfer path, 41, 44 ... valve section, 42, 62 ... discharge port, 43 ... pool, 63 ... pressure receiving section.

Claims (3)

[Claims] 1. A nozzle body having a gate portion, a shaft valve movably provided in the nozzle body, a biasing means for biasing the shaft valve in a direction to retract from a cavity, and the shaft valve. A valve portion for receiving the injection pressure of the resin introduced into the nozzle body, moving the shaft valve in the direction of the cavity against the urging force of the urging means, and opening the gate portion. A nozzle for a mold, comprising: 2. A nozzle body having a gate portion, a shaft valve provided to be able to advance and retreat within the nozzle body, and having a resin flow path therein, and a biasing means for urging the shaft valve in a direction to retract from the cavity. Urging means, provided on the shaft valve, receiving the injection pressure of the resin introduced into the nozzle body, moving the shaft valve in the direction of the cavity against the urging force of the urging means, And a valve portion for opening a resin flow path in the shaft valve. 3. The mold nozzle according to claim 1, wherein a coolant flow path is formed in the nozzle body.