JPH0343219A - Nozzle device for injection molding - Google Patents

Abstract

PURPOSE:To prevent resin from being solidified at a nozzle end by providing a resin path running through forward and backward on almost the center of a plunger, and an inlet at the rear side and an outlet communicating with the nozzle opening on the front side, also providing a fluid injection path communicating with the nozzle opening when the plunger moves backward on a nozzle cylinder and preventing the nozzle path from opening simultaneously. CONSTITUTION:When injection pressure is applied to molten resin by a screw 2, a plunger 8 resists a compression spring 9 to move forward the front end of a plunger main body 81 until being brought into contact with a supporting surface 72a of a nozzle 72. A rear end rod 83 is removed from a resin fee-in port 5, and a fluid injection path 10 is closed by a front side rod valve 82 to inject the molten resin in the injection cylinder 1 from a nozzle opening 6 into a mold. When the resin of given amount is injected, resin pressure is released and the plunger 8 is moved backward by the force of the compression spring 9, and the resin feed-in port 5 is closed by a recessing rod valve 83 and a fluid injection path 10 is opened to inject the pressurized fluid from a fluid injection path 10 into the resin in a mold cavity through the nozzle opening 6 and mold a hollow molded product.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a nozzle device for injecting molten synthetic resin and fluid into a mold to injection mold hollow molded synthetic resin objects.

(Prior art) Conventionally, as an injection molding technique for molding hollow molded articles of synthetic resin, for example, as described in Japanese Patent Publication No. 59-49902, synthetic resin heated and melted (hereinafter referred to as "molten resin") has been used. Gas injection molding is a method in which a hollow molded object is formed by injecting a gas into a mold, and then press-fitting only a gas body or a gas body and a molten resin to fill the cavity of the mold. Are known.

In the gas injection injection molding method described above, a nozzle device a as shown in FIG. 4 is used. This nozzle assembly Wa is
It is attached to the discharge port C of the injection cylinder b, and the nozzle device a
The valve body e that opens and closes the nozzle hole d on the tip side of the nozzle body g
A passage for injecting fluid such as gas, which has a resin passage i formed by the nozzle wood body g and the valve body e, and has a fine hole j and a sliding insertion hole f communicating with the fine hole j at the tip of the valve body e. Establishment of a
Furthermore, a needle k whose tip end can be freely inserted into the sliding insertion hole f is provided in the fluid injection passage to prevent both passages from being opened at the same time under any condition.

In operation, when the tip of the nozzle device a is engaged with the injection port of the mold (not shown) and resin pressure is applied to the injection cylinder b, the valve body retreats and the nozzle hole d opens. Molten resin is injected into the mold via d.

When the resin pressure in the injection cylinder b is reduced, the nozzle hole d is closed by the advance of the valve body e, and the resin passage i is blocked, and the tip of the needle slides into the insertion hole f due to the advance of the valve body e. A fluid such as gas is injected from the fluid injection passage into the resin filled in the cavity of the mold.

(Problem to be Solved by the Invention) However, in the injection molding nozzle device such as the above-mentioned prior art, when a fluid such as gas close to room temperature is injected, the valve body e is cooled and the valve body e and the nozzle body g are The resin in between solidified and the resin passage i at the nozzle tip was blocked, and even if the discharge pressure of the molten resin from the injection cylinder b was increased, it would not flow and there was a risk of damage to the nozzle device due to the internal pressure. .

In addition, a passage for injecting a fluid such as gas having a small hole j and a sliding insertion hole f communicating with the small hole j may be provided at the tip of the valve body e, or a passage for inserting a fluid such as a gas into the fluid injection passage may be inserted into the sliding insertion hole f. The structure is complicated due to the provision of a removable needle k, and therefore there is a problem in that it takes time and effort to manufacture and assemble, and the manufacturing cost increases.

The present invention has been made in order to solve the above problems, and its purpose is to provide a structure that allows gas injection molding by preventing the resin passage and the fluid injection passage from being opened at the same time. To provide an injection bottom type nozzle device which is free from clogging due to solidification of resin at the tip, has an extremely simple structure with a small number of parts, is easy to manufacture, and is inexpensive to manufacture.

(Means for Solving the Problems) The nozzle device for injection bottom mold according to the present invention includes a nozzle cylinder equipped with a resin inlet at the rear end and a nozzle hole that engages with the injection port of the mold at the front end, A plunger is provided to be able to move forward and backward in the cylinder, and is equipped with a front end rod valve that is slidably inserted into the nozzle port and a rear end rod valve that is inserted into and removed from the resin inlet to open and close, and an injection cylinder. a compression spring that presses the plunger toward the resin inlet until the resin pressure within reaches a predetermined value;
The resin passage is provided with an inlet at the rear and an outlet communicating with the nozzle opening at the front, and the nozzle cylinder is provided with a fluid injection passage which communicates with the nozzle opening when the plunger is retracted, and the resin passage and the outlet are provided in the nozzle cylinder. It is characterized in that it does not open at the same time as the fluid injection passage.

The synthetic resin used in the present invention is a thermoplastic resin used in general injection molding or extrusion molding, but a thermosetting resin can also be used if necessary.

Further, as the fluid used in the present invention, for example, a fluid that can be a gaseous substance at room temperature such as nitrogen gas, carbon dioxide gas, or air is suitably used, but a liquid blowing agent or the like may also be used.

(Function) The injection bottom type nozzle device of the present invention has the above-described configuration. Before the molten resin in the injection cylinder reaches a predetermined resin pressure, the plunger is pressed in the direction of the resin inlet by the compression spring. The rod valve at the rear end of the plunger is inserted into the resin inlet to close the resin inlet, and at the same time, the opening of the fluid injection passage is removed from the rod valve at the front end of the plunger, and the fluid injection passage and the nozzle port are in communication. . In this state, communication between the injection cylinder and the resin passage of the nozzle device is cut off, and only fluid from the pressurized fluid source can be injected into the mold through the nozzle port.

Also, when the molten resin in the injection cylinder reaches a predetermined resin pressure, the plunger moves forward against the compression spring toward the nozzle opening due to the resin pressure, and the rear end rod valve disengages from the resin inlet and opens the valve. On the other hand, the front end rod valve closes the fluid injection passage. In this state, the injection of fluid is stopped, and the molten resin in the injection cylinder flows out from the inlet of the plunger, through the resin passage, and into the nozzle port.

In this way, the resin passage and the fluid injection passage are alternately opened and closed by the plunger, and under no circumstances will both passages be opened at the same time.

(Example) An example of the injection molding nozzle device of the present invention will be described with reference to the drawings.

In FIGS. 1 and 2, 1 is an injection cylinder, 2 is a screw for injecting molten resin, 3 is attached at its rear end to the discharge port 4 of the injection cylinder 1, and its front end is attached to the injection port of a mold (not shown). The nozzle device is engaged.

The nozzle device 3 includes a nozzle cylinder 7 equipped with a resin inlet 5 at the rear end and a nozzle port 6 at the front end, a plunger 8 provided in the nozzle cylinder 7 so as to be slidable forward and backward, and a resin inlet 5. It is composed of a compression spring 9 that presses the plunger 8 toward the resin introduction port 5 until the pressure reaches a predetermined value.

The nozzle cylinder 7 includes a mounting base 71 that is screwed onto the discharge port 4 of the injection cylinder 1, and a nozzle portion 72 that engages with an injection port of a mold (not shown). The nozzle portion 72 also includes a fluid injection passage 10 communicating with the nozzle port 6.
The fluid injection passage 10 communicates with a hole in a vibrator 11 that is connected to a pressurized fluid source (not shown). The tip of the nozzle port 6 is a pore.

The plunger 8 consists of a plunger body 81, a front end rod valve 82 that is slidably inserted into the nozzle port 6, and a rear end rod valve 83 that can be inserted into and removed from the resin inlet 5. A front end rod 82 and a rear end rod 83 protrude from both ends, respectively. Further, a resin passage 84 is provided approximately at the center of the plunger 8 so as to penetrate in the front-rear direction, and a plurality of inflow ports 85 are provided at the rear end of the plunger body 81 behind the resin passage 84, and at the front end of the plunger 8. Rod valve 8
2 is penetrated by an outlet 86 toward the nozzle port 6 side.

To install the plunger 8 in the nozzle cylinder 7, fit the plunger body 81 into the mounting base 71, insert the rear end rod valve 83 of the plunger 8 into the resin inlet 5 in a slidable manner, and A compression spring 9 that presses the plunger 8 toward the resin inlet 5 side is inserted into the gap 73 between the inner peripheral surface of the mounting base 71 and the outer peripheral surface of the plunger body 81, and the spring 9 is pushed out from the mounting base 71. The front end rod 82 of the section is slidably inserted into the nozzle port 6 of the nozzle section 72,
The nozzle part 72 is fixed to the mounting base 71 with bolts or the like.

In the nozzle device 3 assembled in this way, as shown in FIG. 82 is adapted to close off the fluid injection passageway 10. Also, when the plunger 8 retreats,
During the process, the front end rod 82 connects to the fluid injection passage I.
The rear end rod 83 is inserted into the resin inlet port 5 with the valve closed, and the valve is closed, and when it is moved back, the rear end rod 83 remains closed and opens into the fluid injection passage 10, as shown in FIG.
It looks like it opens.

Next, the operation of the injection molding nozzle device in the above embodiment will be explained based on the drawings.

In advance, the molten resin is introduced into the injection cylinder 1 by the screw 2.
Plasticize it and store it. The positional relationship of the plungers 8 at this time is as shown in FIG. That is, the plunger 8 is pressed in the direction of the resin inlet 5 by the compression spring 9, and the rear end rod 83 is inserted into the resin inlet 5, so that the valve is in a closed state. Due to this valve closed state, the injection cylinder 1 and the resin passage 84 of the nozzle device 3 are disconnected from each other. On the other hand, the front end rod 82 of the plunger 8 is removed from the fluid injection passage 10 and is in communication with the nozzle port 6. That is, the fluid injection passage 10 is open.

Next, when a predetermined injection pressure is applied to the molten plasticized resin by the screw 2 in order to inject the resin into the mold, this resin pressure causes the plunger 8 to advance toward the nozzle port 6 against the compression spring 9. do.

The front end of the plunger body 81 is the receiving surface 72 of the nozzle part 72.
When the rear end rod 83 moves forward until it comes into contact with point a, the rear end rod 83 comes off from the resin introduction port 5, and the front end rod valve 82 closes the fluid injection passage 10. That is, in this state, the resin passage 84 is open and the fluid injection passage 10 is closed, and the molten resin in the injection cylinder 1 passes through the resin inlet 5 and flows through the inlet 85 of the plunger 8, the resin passage 84, and the outlet. The molten resin enters the nozzle port 6 through the nozzle port 86, and is injected into the mold from the nozzle port 6.

Next, when a predetermined amount of resin is injected into the mold, the resin pressure by the screw 2 is removed, and the plunger 8 is moved from the state shown in FIG. It retreats to the state shown in FIG. 3(c), but during the retreat, it goes through the process shown in FIG. 3(b). Figure 3 (b
), the fluid injection passage 10 remains closed by the front end rod valve 82 and the resin inlet 5 is closed by the rear end rod valve 83. That is, in this state, both the resin passage 84 and the fluid injection passage 10 are closed.

When the plunger 8 is further retreated to the state shown in FIG. 3(C), the resin inlet 5 is closed by the rear end rod valve 83, as explained based on FIG. The fluid injection passage 10 remains open. Therefore, pressurized fluid from a pressurized fluid source is injected into the resin of the mold cavity from the fluid injection passage 10 through the nozzle port 6, and a hollow molded object is molded.

At this time, even if a fluid such as gas at room temperature is used, the fluid passing through the fluid injection passage is injected into the mold without cooling and solidifying the molten resin in the resin passage within the plunger.

After molding, the pressurized fluid source may be switched to a low pressure fluid source to cause the fluid in the hollow mold to flow directly back through the fluid injection passage.

The conditions for realizing the states shown in FIGS. 3(a) to 3(c) are such that in the state shown in FIG. 3(a), the maximum moving distance of the plunger 8 is α, and the plunger 8 is T indicates the position where the plunger 8 moves backward from the most advanced position to the tip of the nozzle part 72 until the resin inlet 5 is closed by the rear end rod valve 83; Letting β be the distance that the fluid injection passage 10 moves backward until the opening of the fluid injection passage 10 is disengaged from the front end rod valve 82 and communicates with the nozzle port 6, then α>β>γ.

(Effects of the Invention) Since the injection molding nozzle device of the present invention is constructed as described above, unlike conventional nozzle devices, there is no passage for injecting fluid such as gas into the valve body. The resin in the resin passage does not solidify as a result of this, and the resin passage does not become clogged with solidified resin. Therefore, molding production can be continued under good flow conditions without increasing the discharge pressure of the molten resin from the injection cylinder, and there is no fear that the nozzle device will be damaged.

In addition, unlike conventional structures that require a needle in the fluid injection passage, the structure is extremely simple and requires only a small number of parts.Therefore, manufacturing and assembly requires little effort and manufacturing costs are low. It is.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing one embodiment of the injection molding nozzle device of the present invention and illustrating the state in which the plunger is advanced;
The figure is a longitudinal sectional view illustrating a state in which the plunger is retracted, FIGS. 3(a) to 3(c) are diagrams illustrating the operation of the plunger, and FIG. 4 is a longitudinal sectional view of an injection molding nozzle device illustrating a conventional example. It is a front view. Explanation of symbols 1. Injection cylinder 2. Screw 3. Nozzle device, 4. Discharge port, 5. Resin introduction port, 6. Nozzle port, 7. Nozzle cylinder 71. Mounting base, 72
...Nozzle part, 8.. Plunger, 81.. Plunger body, 82.. Front end rod valve, 83.. Rear end rod valve, 84.. Resin passage, 85.. Inlet, 86.. Outlet. , 9... Compression spring, 10... Fluid injection passage. 7 Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A nozzle cylinder equipped with a resin introduction port at the rear end and a nozzle hole that engages with the injection port of the mold at the front end; A plunger has a protruding front end rod valve that is slidably inserted and a rear end rod valve that can be inserted into and removed from the resin inlet, and the plunger is inserted into the resin inlet until the resin pressure in the injection cylinder reaches a predetermined value. The plunger has a resin passage penetrating in the front-rear direction approximately in the center thereof, an inlet at the rear of the resin passage, and an outlet communicating with the nozzle opening at the front. An injection molding nozzle, characterized in that the nozzle cylinder is provided with a fluid injection passage that communicates with the nozzle port when the plunger is retracted, and the resin passage and the fluid injection passage are not opened at the same time. Device.