JPH07323438A - Method and die for injection molding of net-like product - Google Patents

Abstract

PURPOSE:To improve molding accuracy of synthetic resin-made net-like products by forming a tab in the center of the net part. CONSTITUTION:A net part cavity 13 is formed inside the frame part cavities 11 of a die 10 integrally in communication with the frame part cavities. The net part cavity 13 is provided with an overflow part 14 at its molten resin flowing end. The molten resin is injected from the frame part cavities 11 and filled into the net part cavity 13. A net-like product having the frame and net parts formed integrally and a tab formed in the center of the net part such as air filter is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method and a mold for a mesh product made of synthetic resin such as an air filter for an air conditioner.

[0002]

2. Description of the Related Art As an example thereof shown in FIGS. 12 and 13, a mesh product 1 such as an air filter (hereinafter referred to as a filter) comprises a frame portion 2 and a mesh portion 3 inside thereof. There is. In order to manufacture such a filter 1 by injection molding, a metal or resin net material that has been cut to a predetermined size and shape is inserted into the cavity, and molten resin is injected around the net material frame. The frame portion 2 is molded, and the mesh portion 3 is formed integrally with the mesh material.

[0003]

However, in the insert molding, the outer peripheral edge of the mesh material is easily loosened when the mesh material is cut to a certain size, when it is transported, or when the mesh material is inserted. Also, as shown by the chain line in FIG.
When the mesh portion 3 is processed into an arc shape, the mesh size is likely to be different because the deformation amount of the mesh material is different. Particularly in the case of a resin net material, not only is it difficult to form the shape, but when the filter 1 is required to have heat resistance, there are few types of resin net materials available on the market. The use of metal nets is obligatory.

In addition, in the mold used for insert molding, it is necessary to adjust the pressing margin of the mesh material. If the pressing margin is weak, the resin will flow into the mesh, and conversely, if the pressing margin is strong, the mesh material will be crushed. Furthermore, since resin net materials cannot be positioned in the mold using magnetic attraction, it is necessary to use a fine pin that can be inserted in the mesh to position the net material. Troublesome work is required.

Therefore, it has been attempted to integrally form the frame portion 2 and the mesh portion 3 by injection molding other than insert molding. A mold 10 as shown in FIG. 14 is adopted for the molding in this case. The mold 10 is composed of a cavity 11 for molding a frame portion and a cavity 13 for molding a mesh portion inside the frame portion 11. From a gate 12 such as a pin point gate or a side gate provided on four sides of the frame portion cavity 11 to a frame. A molten resin is injected and filled into the cavity 11 of the part.

Since the cross-sectional area of the frame cavity 11 is larger than the cross-sectional area of the mesh cavity 13, the molten resin P injected into the mold 10 is injected after flowing through the frame cavity 11 first. The center part 1 of the mesh part cavity 13 is drawn so as to form a concentric circle from each gate 12 part with high pressure.
Flow toward 3a. However, since there is no escape area for air in the center 13a corresponding to the flow end of the filled resin, in such molding, a resin unfilled portion is generated in the center 13a of the mesh cavity 13 to cause defective molding.

As a means for solving such a problem, it is conceivable to perform injection filling of the molten resin from the center of the mold 10, that is, the center 13a of the mesh cavity 13.
In this case, since the flow distance of the molten resin becomes long, a large filling pressure is required, and in the case of a large-sized molded product, the mesh on the central side becomes small due to deformation of the mold 10 or insufficient mold clamping force. Molding defects such as crushing tend to occur. Further, since the flow resistance is large, it is difficult to apply injection pressure to the outer peripheral edge of the frame cavity 11, which causes sink marks and voids in the frame of the molded product, so that it is not possible to improve the molding accuracy, and this is avoided. Therefore, if the filling pressure is increased, a new problem arises that the mesh in the central portion is formed small and the aperture ratio is reduced.

As a means for preventing the occurrence of sink marks, voids and the like in the frame portion of the molded product and for preventing the central resin unfilled portion, as shown in FIGS. 16 and 17, the center portion 13a of the mesh cavity 13 is also covered. It is conceivable that the gate 12 is provided and the molten resin is simultaneously injected and filled from the four sides of the frame cavity 11 and the central portion 13a. However, in this case, the molten resin P from each gate 12 of the frame cavity 11 and the center 1
The resin p'from the gate 12 of 3a collides with each other to easily cause a weld, and this weld not only lowers the strength of the mesh portion of the molded product but also makes the molding state unstable. It was difficult to adopt any of them for injection molding of mesh products.

The object of the present invention is to solve many problems in forming a mesh product by injection molding by adopting an extremely simple means, and to improve the molding accuracy of the mesh portion more than ever before, and An object of the present invention is to provide a new method for injection-molding a net-like product and a die, which are less likely to produce non-defective products.

[0010]

One of the inventions according to the above object is to integrally have a mesh portion cavity inside a frame portion cavity, and to provide an overflow portion at a portion of the mesh portion cavity which is a flow end of a molten resin. Injecting molten resin from the cavity side of the frame into the mold provided with to form a mesh product in which the frame part and the mesh part are integrated, and the center of the mesh part of the mesh product is filled with the overflow part. It is an injection molding method of a mesh product formed on a tab.

According to another aspect of the present invention, a required number of gates are provided at equal intervals in the frame cavity of a mold having a mesh cavity integrally inside the frame cavity, and the mesh cavity is also provided. In the injection molding die for a mesh product, an overflow portion having a required shape is provided at a portion which is a flow end of the molten resin, and a pressure sensor for the molten resin is arranged at the overflow portion.

[0012]

[Operation] In the above configuration, the molten resin from each gate first fills the frame cavity, then flows from the inner periphery to the mesh cavity, and the air in the mesh cavity is forced to overflow at the center by the resin pressure. The molten resin from each gate also flows into the central overflow portion while drawing an arc shape. Then, at the end, all flow into the overflow portion and are integrated to form a tab. Therefore, there is no unfilled portion in the mesh cavity, and the flow direction of all the molten resin is one from the periphery to the center, so that the occurrence of welds is also prevented.

Further, the filling pressure of the resin in the mesh cavity is detected by the pressure sensor arranged in the overflow portion, and the confirmation of filling and the holding pressure control of the injection pressure can be carried out thereby, so that the molding accuracy can be improved.

[0014]

1 to 9 show an embodiment of the present invention, in which the same parts as those of the filter and the mold shown in FIG. 12 and thereafter are designated by the same reference numerals.

As shown in FIGS. 1 and 2, the mold 10 has a pair of divided molds 10A, which are filter molding cavities in which an annular frame cavity 11 and a mesh cavity 13 inside the cavity communicate with each other. It has a structure formed by closing the mold of 10B. One split mold 10A of the mold 10 is provided with pinpoint gates 12 and 12 that open on the four upper surfaces of the frame cavity 11, and the center of the mesh cavity 13 that serves as the flow end of the molten resin. Has an overflow portion 14 of a required size extending over both of the one split mold 10A and the other split mold 10B.
It is provided so as to be connected to the resin reservoir 14a provided in A.

In the mold 10 having the above structure, each gate 1
When the molten resin P is injected from 2 and 12 at the same time, the molten resin P first fills the frame cavity 11 whose cross-sectional area is significantly larger than the mesh cavity 13. Next, as shown in FIGS. 3 and 4, the molten resin P is applied to each of the gates 12, 1 from the four sides of the inner periphery of the frame cavity 11 to the mesh cavity 13.
It will flow in while drawing an arc shape centered on 2.

Due to the pressure caused by the inflow of the molten resin, the air in the mesh cavity 13 is allowed to flow into the overflow portion 1 in the center.
4 and then the resin pool 14a of one split mold 10A
Will be discharged from. Therefore, the air does not remain in the mesh cavity 13, and the air resistance does not disturb the flow of the molten resin P from the four directions. Therefore, the mesh cavity 13 does not have an unfilled portion.

All of the molten resin P flowing through the mesh cavity 13 is almost at the same time in the final stage at the overflow portion 1.
4 and integrated into one, and an excess amount is accumulated in the resin reservoir 14a.
Flow into. As a result, the tab 15 is formed in the overflow portion 14 as shown in FIGS. Further, since the flow direction of all the molten resin P is one from the periphery to the center, the weld is unlikely to occur, and the molded product obtained by opening the mold after the completion of injection is the frame part 2 and the mesh part 3 integrally molded. The filter has a tab 15 in the center.

FIG. 7 shows a mold 10 provided with a gate 12 on the side of a frame cavity 11 and a mold clamping device 20 of an injection molding machine.
It also shows an example in which it is mounted on the mold and molded. In this mold 10 as well, the gates 12 are provided at a plurality of places at regular intervals, but they are omitted at one place in the figure. The gate 12 is provided on the parting surface on the side of the other split mold 10B so as to be connected to the spool 27 provided at the center of the one split mold 10A via the runner 28. The mold clamping device 2 is divided into a movable platen 22 side that moves back and forth with respect to the fixed platen 21 of the mold clamping device 20 and one of the split molds 10A divided into the fixed platen 21 side.
It is open and closed at 0.

The other split mold 10B is fixed to the surface of the movable plate as it is, but one split mold 10A is used.
Is provided on the front surface of an overtab stopper plate 24, which is attached to a base die 21a attached to a fixed platen 21 by a stop bolt 23 with a spring interposed, and is connected to the overtab stopper plate 24 by a pulling link 25. Over tab stopper plate 24 and one split mold 10A when opened
As shown in FIG. 8, the resin pool 14a
After the over tab 14b is pulled out by adhering to the over tab stopper plate 24, the split mold 10A is opened by pulling the pull link 25. As a result, the overtab 1 generated in the resin pool 14a at each molding
4b is released so as not to hinder the subsequent molding.

Further, the portion of the overtab stopper plate 24 facing the resin reservoir 14a provided on the one split mold 10A,
A lock pin 29 is movably inserted from the fixed plate 21 side, and a lower end portion 29a of the lock pin 29 has a resin pool 1
It is located at 4a. Further, the pressure sensor 30 is in contact with the upper end portion 29b of the lock pin 29 located in the fixed board 21, and the lock pin 29 is charged from the movable amount which is movable by the resin pressure of the resin reservoir 14a connected to the overflow portion 14. By detecting the pressure, it is possible to determine whether the resin filling confirmation, the injection pressure holding control, or the molding state is good or bad by the route shown in FIG.

The judgment by the pressure sensor 30 is shown in FIG.
As shown in 0, it can be performed by monitoring the output distribution A at the time of completion of the resin filling and the completion of the holding pressure.
If the output at the time of completion of resin filling is within the monitor width W, it is determined to be good, and if it is outside the allowable range of the monitor width W, the holding pressure is controlled up and down with respect to the standard injection pressure distribution B. Further, when the output at the completion of the holding pressure is out of the monitor width W, an alarm is output.

In the above embodiment, the single mesh portion 3 is integrally formed inside the annular frame portion 2.
Like the filter 1 shown in (A) and (B), a filter in which a partition frame 2a is provided inside a rectangular frame portion 2 and a plurality of mesh portions 3 and 3 are integrally molded is also a filter having a single mesh portion 3. 1. Injection molding can be performed by the same means. In this case, a mold is formed so that the tabs 15 and 15 are formed in the centers of the mesh portions 3 and 3, and the frame 2 and the frame portion 2 are formed so that the positions of the tabs 15 and 15 are the flow ends of the molten resin. A required number of gates 12 and 12 are set in the partition frame 2a.

The shape of the tab 15 is not limited to the circular shape as shown in the figure, but may be any shape such as a cross shape, a square shape, a polygonal shape, a star shape, an elliptical shape, etc. By providing the shape of 14 in the center of the mesh portion cavity 13, it can be easily molded. It is also possible to provide the overflow portion 13a only on one side of the mesh portion cavity 13 so that it is exposed on the front side or hidden on the back side.

Although the air filter in which the cross-sectional areas of the frame portion 2 and the mesh portion 3 are remarkably different has been described in the above embodiment, the application of the present invention is limited to the molding of the mesh product having such a structure. Needless to say, the present invention can also be applied to injection molding of mesh products in which the cross-sectional areas of both parts are similar or the same.

[0026]

As described above, according to the present invention, the molten resin is injection-filled from the frame cavity side to the overflow portion provided at the portion of the mesh cavity where the molten resin flows, and the frame and the mesh are filled. Part is formed as a mesh product and the center of the mesh part of the mesh product is formed as a tab, so the injection molding of the molten resin is performed from the periphery of the mesh part cavity to form the mesh part. Even if it is a resin, no unfilled portion of the resin is generated, and since the resin is filled in the frame cavity, molding defects such as sink marks and voids are unlikely to occur in the frame portion of the mesh product.

Furthermore, since the flow direction of the molten resin is one direction from the periphery to the center, no weld is generated and the filling pressure in the mesh cavity is easily maintained, so that the fine mesh is well formed, and the whole is excellent. A product with high molding accuracy can be obtained. Moreover, since it is possible to confirm the resin filling, control the injection pressure, or determine the quality of the molding state by the pressure sensor provided in the overflow portion, it is possible to obtain various quality mesh products by injection molding with high quality.

[Brief description of drawings]

FIG. 1 is a plan view schematically showing a positional relationship between a cavity of a mold used in an injection molding method of a mesh product according to the present invention, a gate, and an overflow portion.

FIG. 2 is a schematic vertical sectional side view of a mold according to the present invention.

FIG. 3 is a plan view of a mold schematically showing a flow state of molten resin.

FIG. 4 is a schematic vertical sectional side view of the above.

FIG. 5 is a plan view of a mold that schematically shows a state where the molten resin has been completely filled.

FIG. 6 is a schematic vertical sectional side view of the above.

FIG. 7 is a schematic vertical sectional view at the time of injection molding when a mold is attached to the mold clamping device.

FIG. 8 is a schematic vertical cross-sectional view when the mold is opened in the above.

FIG. 9 is a flowchart for performing judgment control by monitoring the quality of the confirmation of filling by the pressure sensor of the overflow portion and the holding pressure control of the injection pressure.

FIG. 10 is an explanatory diagram showing a monitor width of the quality of resin filling confirmation and injection pressure control.

FIG. 11 is a schematic plan view of two types of mesh products (air filters) that can be molded according to the present invention.

FIG. 12 is a schematic plan view of a mesh product (air filter) to be molded by the present invention.

FIG. 13 is a schematic vertical sectional view of the above.

FIG. 14 is a schematic plan view of a mold showing a flow state of molten resin when injection is performed from the frame cavity side.

FIG. 15 is a vertical sectional side view of the above.

FIG. 16 is a schematic plan view of a mold showing a flow state of molten resin when injection is performed from both the frame cavity side and the mesh cavity center.

FIG. 17 is a vertical sectional side view of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 filter 2 frame part 3 mesh part 10 mold 10A one split mold 10B other split mold 11 frame part cavity 12 gate 13 mesh part cavity 13a center of mesh part cavity 14 overflow part 14a resin pool 15 tab 20 injection molding device 29 Lock pin 30 Pressure sensor P Molten resin

Claims (2)

[Claims] 1. A mold having a mesh cavity integrally connected to the inside of the frame cavity and having an overflow portion at a portion of the mesh cavity that serves as a flow end of the molten resin. It is characterized in that the molten resin is injected and filled from the above to form a mesh product in which the frame portion and the mesh portion are integrated, and the center of the mesh portion of the mesh product is formed in the tab by the overflow portion. Injection molding method for mesh products. 2. A frame cavity of a mold having a mesh cavity integrally communicating with the inside of the frame cavity,
A required number of gates are provided at equal intervals, and an overflow portion having a required shape is provided at a portion of the mesh portion cavity which is a flow end of the molten resin, and a pressure sensor for the molten resin is provided at the overflow portion. An injection mold for mesh products.