JPH08187750A - Nozzle for injection molding - Google Patents

Abstract

PURPOSE: To provide a nozzle for injection molding unnecessary to replace in both of usual injection molding and the injection molding of a hollow molded article, keeping the stable operation of a needle valve and enabling the desired planning of a mold without being troubled by pressure fluid piping. CONSTITUTION: A control unit 7 has both of a usual molding mechanism and a hollow molded article molding mechanism and can arbitrarily select either one of the mechanisms and can set the operation of a needle valve 5 to either one of them. The opening and closing due to a valve head 52 of a pressure fluid emitting orifice 44 are performed by the separation and contact of a blocking surface 521 and a receiving surface 441 and, since there is no slide part, the penetration of a molten resin can be prevented. Since the inlet 35 of a pressure fluid introducing passage 351 is formed in the vicinity of an injection cylinder 1, pressure fluid piping does not obstruct a mold not shown in a drawing. A loosely fitted sphere 8 can prevent the penetration of a pressure fluid into the injection cylinder 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a hollow mold made of synthetic resin by injecting a pressurized fluid into a molten resin injected into a mold cavity of an injection molding machine to cool and solidify. The present invention relates to an injection molding nozzle used for molding.

[0002]

2. Description of the Related Art A synthetic resin hollow mold is manufactured by injecting a molten synthetic resin into a mold cavity and subsequently injecting a pressurized fluid into the molten resin for cooling and solidification. Injection molding technology for molding is known. In this injection molding, for example, as described in Japanese Patent Publication No. 59-49902, an injection molding nozzle having a built-in needle valve is attached to the front end of the injection cylinder, and the needle valve is moved back and forth. Then, a device is used in which the injection of the molten resin and the injection of the pressurized fluid are alternately performed from the injection port opened at the front end of the nozzle.

However, this injection molding apparatus has a problem that the apparatus is relatively complicated, assembly is troublesome, and the manufacturing cost is high. Therefore, the present applicant has previously developed an injection molding nozzle that has a simple structure with a small number of parts and is easy to manufacture (JP-A-3-6762).
No. 2, JP-A-3-67623).

[0004]

Among these, Japanese Patent Laid-Open No. 3-6
In the technique described in Japanese Patent No. 7622, as shown in FIG. 3, a nozzle device a is attached to a front end portion of an injection cylinder b, a front end opening is made an injection port c, and a rear end opening d is an ejection cylinder b. It has a structure in which a core g having a needle valve f is mounted in a nozzle body portion e communicated with an outlet.

When the screw h advances, the needle valve f closing the rear end opening d of the nozzle body e advances by the resin pressure, and molten resin enters the nozzle body e through the rear end opening d. , Is injected into the mold (not shown) from the injection port c. During this time, the pressurized fluid discharge port h of the core g is closed at the front end of the needle valve f (state shown in FIG. 3). When the screw h is retracted, the needle valve f is retracted by the elastic force of the spring i, closing the rear end opening d at the rear end, and opening the pressurized fluid discharge port h at the front end to pressurize. The fluid flows from the intake port j into the core g, and is injected into the mold from the pressurized fluid discharge port h and the injection port c.

Further, in the technique disclosed in Japanese Patent Laid-Open No. 3-67623, as shown in FIG. 4, when the screw h advances, the needle valve f retracts due to the resin pressure of the screw h and the injection port c.
Open and the molten resin is injected into the mold. At this time, the pressurized fluid passage k in the needle valve f is blocked from the intake port j. When the screw h moves backward, the needle valve f moves forward by the elastic force of the spring i to close the injection port c, and the pressurized fluid is injected into the mold through the injection port c (shown in FIG. 4). Status).

However, even in each of the above-mentioned conventional techniques,
In addition, there was a problem to be solved. One of them is that the injection molding nozzle for molding a hollow mold has a special structure, and when performing normal injection molding,
There is a problem that the injection molding nozzle needs to be replaced each time, which is troublesome.

The other is that when the needle valve moves forward and backward, there is a sliding portion between the needle valve and the tip of the core (for example, A in the case of FIG. 3 and the case of FIG. 4). Is a portion indicated by B), and the molten resin moving at a high pressure enters into the gap (= clearance) of this sliding portion and solidifies to solidify the needle valve f.
May hinder the sliding of the. Still another is that since the pressurized fluid intake port j is close to the injection port c, it may be necessary to modify the mold due to the piping of the pressurized fluid.

The present invention solves the above-mentioned drawbacks of the prior art and eliminates the need to replace the nozzle and stabilizes the needle valve in both normal injection molding and hollow molding. An object of the present invention is to provide an injection molding nozzle capable of maintaining a desired operation and designing a desired mold without being bothered by a pressurized fluid pipe.

[0010]

The injection molding nozzle of the present invention is an "injection molding nozzle attached to the front end of an injection cylinder, in which the front end opening is an injection port and the rear end opening is The injection cylinder has a nozzle main body communicating with a discharge port, and a core supported inside the nozzle main body and having a resin passage around its outer periphery. A cavity serving as an outlet is provided, and a needle valve that is biased rearward by a spring and can be advanced by a pressurized fluid is installed in the cavity, and a valve head is provided at a front end of the needle valve. By advancing and retreating, the valve head separates and abuts against the inner peripheral edge of the fluid discharge port, and opens and closes. In the vicinity of the injection cylinder of the nozzle body,
An inlet of a pressurized fluid introduction path communicating with the cavity of the core is provided, and a sphere capable of closing the rear end opening by fluid pressure is loosely fitted to the rear of the core to introduce the pressurized fluid. -A control device for controlling the stop is attached, and the control device has a mechanism capable of sending a pressurized fluid from the injection port each time after the injection of the molten resin is completed from the injection port, and a pressurization during molding. It also functions as a mechanism that does not supply fluid, and any mechanism can be arbitrarily selected and used. " It

As a material for molding using the injection molding nozzle of the present invention, a molding material mainly composed of a thermoplastic resin or a thermosetting resin used in general injection molding can be used as it is.

As the pressurized fluid, one that can be a gaseous substance at room temperature, such as nitrogen gas, carbon dioxide gas, or air, is used, but a liquid foaming agent or the like may be used.

[0013]

In the injection molding nozzle of the present invention, when the resin is plasticized by the rotation of the screw and a predetermined amount of molten resin is stored in the injection cylinder, the screw is advanced to discharge the molten resin from the discharge port. Let Then, the pressure causes the sphere to open the rear end opening of the nozzle body, and the molten resin is injected from the injection port into the mold cavity of the mold through the resin passage.

During this time, the feeding of the pressurized fluid is stopped by the control device. Since the pressurized fluid does not act, the needle valve is urged rearward by the spring, and the valve head abuts against the inner peripheral edge of the pressurized fluid discharge port and becomes closed.

When molding a hollow mold, a control device is used to set a mechanism capable of feeding a pressurized fluid through the injection port after each injection is completed. Thus, the control device introduces the pressurized fluid from the pressurized fluid introduction passage into the cavity of the core. Then, the needle valve advances against the elastic force of the spring, the valve head separates from the inner peripheral edge of the pressurized fluid discharge port, and the discharge port is opened. Thus, the pressurized fluid is discharged from the pressurized fluid discharge port and injected into the molten resin in the mold cavity through the injection port.

Further, even if part of the pressurized fluid flows back into the resin passage, it does not enter the injection cylinder because it presses the sphere and closes the rear end opening of the nozzle body.
When the injection of the pressurized fluid for the prescribed amount or for the prescribed time is completed, the introduction of the pressurized fluid is automatically stopped by the control device, thus reducing the pressure in the cavity, and the needle valve is biased by the elastic force of the spring. Then, the valve head collides with the inner periphery of the pressurized fluid discharge port, closes it, and completes one cycle.

The opening and closing of the pressurized fluid discharge port by the valve head described above is simply separated from the inner peripheral edge of the pressurized fluid discharge port of the valve head.
Since it is made by abutting, there is no sliding part between the needle valve and the tip of the core, and the valve head at abutting is
There is no room for the molten resin to enter because it is pressed tightly on the inner peripheral edge of the pressurized fluid discharge port.

Further, since the inlet of the pressurized fluid introducing passage is provided in the vicinity of the injection cylinder of the nozzle body, the pressurized fluid pipe can be arranged at a position away from the mold. Furthermore, when the pressurized fluid is discharged, the presence of the sphere housed behind the core prevents the pressurized fluid from intruding into the injection cylinder due to a reverse flow.

Further, the control device for controlling the introduction of the pressurized fluid is, as described above, a mechanism capable of feeding the pressurized fluid from the injection port each time after the injection of the molten resin is finished, and during molding. Since it also has a mechanism that does not feed pressurized fluid, it is possible to select and use one of these mechanisms. If is set to the latter, molding can be performed using the same nozzle.

[0020]

EXAMPLES Examples of the present invention will be described in detail below.

In FIGS. 1 and 2, 1 is an injection cylinder, 2 is a screw for plasticizing a resin and injecting a molten resin, 3 is a nozzle main body having a base 31 screwed to its front portion. The front end opening is formed as an injection port 32. The rear end opening 33 is screwed to the injection cylinder 1 and communicates with the discharge port 11 of the injection cylinder 1.

Reference numeral 4 denotes a core, which is a front half 41 and a rear half 4.
2, the outer peripheral wall of each of which is supported by the inner wall of the nozzle body 3 by a spider-shaped bearing wall 43 (one of which is shown in cross section in each drawing). A resin passage 34 is formed between the portion 3 and the inner wall of the portion 3.

Inside the core 4, a cavity having a front end serving as a pressurized fluid discharge port 44 is provided, and a needle valve 5 is mounted in the cavity. The needle valve 5 includes a valve rod 51, a valve head 52 provided at the front end thereof, and a pressure receiving plate 5 fixed at the rear end thereof.
3 and a compression spring 54, which is externally fitted to the valve rod 51, which biases the needle valve 5 rearward when the pressurized fluid does not act.

As shown in FIG. 1B, the valve head 52 has an arrowhead shape, and its rear portion is a closing surface 521 made of a conical surface. The closing end is formed on the inner peripheral edge of the pressurized fluid discharge port 44. A receiving surface 441 corresponding to the surface 521 is formed. Then, as shown in FIG. 1, when the pressurized fluid does not act,
The closing surface 521 closely abuts the receiving surface 441 to close the pressurized fluid discharge port 44, and separates from the receiving surface 441 when the pressurized fluid acts. At this time, there is no sliding part in the abutting / separating operation.

Reference numeral 35 is an inlet of a pressurized fluid introduction passage formed in the nozzle body 3 adjacent to the front end of the injection cylinder 1, and a long pressurized fluid introduction passage 35 is formed in the wall of the nozzle body.
1 is provided, and its front end is opened to the rear end in the cavity of the rear half 42.

Reference numeral 6 is a pressurized fluid source mainly composed of a compressor for sending air as a pressurized fluid, and 7 is a control device having an on / off device for operating the compressor only at the time of injection molding of a hollow mold. , A microcomputer incorporating a predetermined program is incorporated.

At the time of injection molding of the hollow molded article, the pressurized fluid from the compressor 6 is fed into the cavity of the core 4 after the molten resin is injected by the screw 2 in cooperation with a hydraulic mechanism (not shown) that controls the forward and backward movement of the screw 2. Send in. The pressure receiving plate 53 of the needle valve 5 is pressed by this pressurized fluid, and the needle valve 5 is advanced against the elastic force of the spring 54. At this time, a step portion 45 is formed at the boundary between the front half portion 41 and the rear half portion 42 of the core, and the forward movement of the pressure receiving plate 53 is restricted by this step portion 45.

Reference numeral 8 is a sphere, and a narrow portion 331 is provided at the front of the rear end opening 33 of the nozzle body 3, and the core 4 is provided.
The sphere 8 is loosely fitted between the rear end and the narrow portion 331.

Next, the operation of the injection molding nozzle will be described.

First, the control device 7 is set in the forming mechanism of the hollow mold. Then, the main body of the injection molding machine is operated.
In this injection molding machine, resin is preliminarily plasticized and stored in the injection cylinder 1 by the screw 2, and then it is moved forward and backward. At this storage stage, the positional relationship of the needle valve 5 is as shown in FIG. That is, the control device 7 operates so as to stop the feeding of the pressurized fluid core 4 into the cavity.

Therefore, the needle valve 5 is retracted by the elastic force of the compression spring 54, the closing surface 521 of the valve head 52 is pressed by the receiving surface 441 of the pressurized fluid discharge port 44, and the pressurized fluid discharge port 44 is completely removed. Is blocked by. Further, the sphere 8 is in a free state in which it is loosely fitted.

Next, in order to inject the molten resin into the mold,
When the screw 2 is moved forward by a predetermined distance, the sphere 8 becomes the core 4
When pressed by the rear end portion (state shown in FIG. 1), the narrow portion 331 of the nozzle body 3 opens and the molten resin advances in the resin passage 34 and is injected from the injection port 32 into the mold cavity of the mold. To be done.

When the injection of the resin is completed, the control device 7 is actuated by a command from the hydraulic mechanism for advancing / retreating the screw 2, and the pressurized fluid source 6 pressurizes by using a pipe (not shown). The fluid is sent from the inlet 35 of the pressurized fluid introducing passage to the pressurized fluid introducing passage 351 and the pressurized fluid fills the cavity of the core 4.

Further, the pressure receiving plate 53 is advanced by the pressurized fluid, collides with the step portion 45, and stops. During this time, the closing surface 521 of the valve head 52 separates from the receiving surface 441 to open the pressurized fluid discharge port 44, and the pressurized fluid discharge port 44 causes the injection port 3 to exit.
Pressurized fluid is injected via 2 into the molten resin in the mold cavity.
If a part of the pressurized fluid flows backward in the resin passage 34, the sphere 8 moves backward and closes the narrow portion 331 (state shown in FIG. 2).

When the injection of the predetermined amount of the pressurized fluid or the predetermined time is completed, the control device 7 is actuated, the feeding of the pressurized fluid is stopped, and the needle valve 5 is retracted and restored (FIG. 1).
State).

In the above-mentioned embodiment, the case of molding a hollow mold is shown. However, when molding a non-hollow mold, the control device 7 is set in the molding mechanism of the hollow mold and the molding is carried out in the usual manner of injection molding. The molten resin may be injected. In this case, the control device 7
Is a mechanism that does not feed the pressurized fluid, the valve head 52
Maintains the closed state of the pressurized fluid discharge port 44,
Keeps playing with being loosely fitted. Furthermore, when molding the hollow mold again, it is possible to simply switch the molding mechanism, and this switching can be repeated.

[0037]

The injection molding nozzle of the present invention has both a molding mechanism for a hollow mold and a molding mechanism for a non-hollow mold, and any one of them can be arbitrarily selected and used. ,
It becomes possible to freely use them properly, only one molding nozzle is required, the preparation work for molding is simplified, the molding speed can be shortened, and the workability can be improved.

Further, when the pressurized fluid discharge port is opened and closed by the needle valve, since there is no sliding portion when opening and closing, there is no defect in the operation of the device due to the intrusion of the resin, and the presence of the sphere prevents the pressurized fluid from flowing. Since there is no intrusion into the injection cylinder, defective products are eliminated and the operating rate is improved.
Products of uniform quality can be manufactured stably and inexpensively.

Furthermore, since the inlet of the pressurized fluid introduction port is provided in the vicinity of the injection cylinder, there is no need to change the design of the die, the design cost does not increase excessively, and the die strength is increased. Is also guaranteed, and in this respect the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the injection molding nozzle of the present invention, in which FIG. 1 (a) is a vertical cross-sectional view for explaining a state in which a needle valve is retracted, and FIG. It is explanatory drawing which takes out only the opening-and-closing part of a needle valve in the same as the above, and shows one part by a cross section.

FIG. 2 is a vertical sectional view showing a state where the needle valve has also advanced.

FIG. 3 is a vertical sectional view showing an example of a conventional injection molding nozzle.

FIG. 4 is a vertical cross-sectional view showing another example of a conventional injection molding nozzle.

[Explanation of symbols]

 1 Injection Cylinder 3 Nozzle Main Body 4 Core 5 Needle Valve 6 Pressurized Fluid Source 7 Control Device 11 Discharge Port 32 Injection Port 33 Rear End Opening 34 Resin Passage 35 Pressurized Fluid Inlet Port 44 Pressurized Fluid Discharge Port 51 Valve rod 52 Valve head 53 Pressure receiving plate 54 Compression spring 351 Pressurized fluid introduction path 441 Receiving surface 521 Closing surface

Claims (1)

[Claims] 1. An injection molding nozzle attached to a front end portion of an injection cylinder, wherein a front end opening portion serves as an injection opening, and a rear end opening portion communicates with a discharge opening of the injection cylinder. There is a core supported in the nozzle main body, the outer periphery of which is a resin passage, and a cavity whose front end is a pressurized fluid discharge port is provided in the core, and the cavity is provided in the cavity. A needle valve that is biased rearward by a spring and that can be advanced by pressurized fluid is installed, and a valve head is provided at the front end of the needle valve. The nozzle main body is provided with an inlet for a pressurized fluid introduction path communicating with the inside of the cavity in the vicinity of the injection cylinder of the nozzle main body. Is a sphere that can close the rear end opening by fluid pressure. Is fitted loosely, and a control device for controlling the introduction / stop of the pressurized fluid is attached, and the control device feeds the pressurized fluid from the injection port each time after the injection of the molten resin is completed from the injection port. The injection molding is characterized in that it has both a mechanism capable of controlling and a mechanism which does not feed the pressurized fluid during molding, and any one of the mechanisms can be arbitrarily selected and used. Nozzle.