JP3240353B2 - Mold for thin-walled molded products and molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for forming an extremely thin molded article such as a speaker diaphragm or a special diaphragm, and a molding method using the mold.

[0002]

2. Description of the Related Art In general, there is known a molding method of an injection molding machine for molding a thin-walled product by injecting and filling a resin plasticized and measured in a heating cylinder into a cavity of a mold by advancing a screw. ing.

In recent years, ultra-thin thin molded products having a thickness of about 0.05 [mm], such as speaker diaphragms, have been injection-molded with synthetic resins. When molding this kind of thin-walled molded product, as shown in FIG. 6, a mold Mo composed of a movable mold Mmo and a fixed mold Mco is usually used.
In addition to providing the cavity Co having the shape of the thin molded product Eso, it is necessary to apply a considerably higher injection pressure to the resin Lo to be injected and filled than the general molded product at the time of injection molding. For this reason, at the time of injection filling, the cavity Co is easily deformed by a high resin pressure, and the area with respect to the thickness of the thin molded article Eso is considerably wide. Therefore, even if the cavity Co is slightly deformed in the thickness direction by the resin pressure. However, its deformation rate becomes considerably large, and it is not easy to obtain high-precision, high-quality thin-walled molded products Eso.

Therefore, such a thin molded product Eso
Is difficult to form by a general molding method including an injection step (speed control area) and a pressure-holding step (pressure control area). Conventionally, after resin Lo is injected and filled into the cavity Co at a high pressure. Then, the pressurization of the screw was immediately stopped, and the pressure in the cavity Co was released.

[0005]

However, such a conventional injection molding method has the following problems.

First, the resin Lo injected and filled in the cavity Co solidifies rapidly because it is extremely thin. If the pressure release is not completely performed, the resin Lo solidifies in a deformed state. As a result, high-precision, high-quality thin-walled molded products cannot be obtained.

Second, as the thickness or the area of the thin molded product Eso becomes thinner, the injection pressure needs to be increased, and the deformation rate of the cavity Co correspondingly increases. The thickness and shape of the molded product are limited, and the thin molded product that can be molded is limited.

The present invention has been made to solve the problems existing in the prior art, and it is possible to obtain a high-precision and high-quality thin-walled molded product, to further reduce the thickness of the thin-walled molded product and to enlarge the area. It is an object of the present invention to provide a mold for a thin-walled molded product and a molding method capable of increasing the versatility and developability by enabling diversification of shapes including the above.

[0009]

SUMMARY OF THE INVENTION According to the present invention, when forming a mold M for a thin-walled molded product comprising a movable die Mm and a fixed die Mc, a regular cavity portion having the shape of a regular thin-walled molded product Es is provided. Cs and the regular cavity portion Cs
A resin reservoir cavity Cf is provided along the entire outer periphery of the terminal portion Cse which communicates with the terminal portion Cse in the resin inflow direction and permits the inflow of the resin L. In this case, according to a preferred embodiment, the movable mold Mm has one or more air holes 2 communicating with the resin reservoir cavity Cf.
Is desirably provided. The resin reservoir cavity C
f may be provided with a regulating portion 3 for setting a flow rate when the resin L flows.

On the other hand, the molding method according to the present invention uses the mold M for thin-walled molded products, injecting and filling the resin L during injection molding so that the resin L partially fills the resin reservoir cavity Cf. After molding, unnecessary portions En... Including a portion corresponding to the resin reservoir cavity portion Cf are cut from the molded product E to obtain a regular thin molded product Es. In this case, according to the preferred embodiment, the movable type Mm
It is preferable to provide one or more air holes 2 communicating with the resin reservoir cavity portion Cf, and to supply the pressurized air A to the air holes 2 at the time of ejection.

Thus, at the time of injection molding, the resin L flowing into the regular cavity portion Cs further flows into the resin reservoir cavity portion Cf so as to partially fill the resin reservoir cavity portion Cf. Is released by the resin reservoir cavity Cf provided in the normal cavity Cs
The deformation in the thickness direction at is almost eliminated. On the other hand, unnecessary portions En... Including the portion corresponding to the resin reservoir cavity portion Cf in the molded product E are cut after the injection molding. If the movable mold Mm is provided with the ventilation holes 2,.
... can be supplied with the compressed air A to prevent the molded product E from adhering to the inner surfaces of the cavities Cs and Cf and deforming the thin portion during the ejector operation, and the restricting portion 3 is provided in the resin reservoir cavity Cf. Then, the flow rate of the resin L flowing into the resin reservoir cavity Cf can be arbitrarily set, so that the resin pressure applied to the regular cavity Cs can be finely adjusted, and as a result, a high thickness relative to the thin molded product Es can be obtained. In addition to the adjustment, the pressure in the regular cavity portion Cs can be made uniform.

[0012]

Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, the mold M for a thin-walled molded product according to the present embodiment
Will be described with reference to FIGS.

The embodiment shows a mold M for forming a speaker diaphragm (a regular thin molded product Es). The mold M includes a movable mold Mm and a fixed mold Mc, and has a radial flow type cavity C in a parting line. The cavity C is a regular thin molded product Es, that is, a regular cavity portion Cs having the shape of a speaker diaphragm, and a resin that allows the resin L to flow in by communicating with a terminal Cse in the resin inflow direction of the regular cavity portion Cs. It consists of a reservoir cavity Cf.

In this case, since the regular cavity portion Cs has a circular outer shape as shown in FIG. 3, the resin reservoir cavity portion Cf is formed in a ring shape (donut shape) along the outer periphery of the regular cavity portion Cs. . Therefore, the entire outer periphery of the regular cavity portion Cs communicates with the resin reservoir cavity portion Cf. As an example, as shown in FIG. 4, if the thickness Xs of the speaker diaphragm is about 0.05 [mm] and the diameter of the speaker diaphragm is about 6 [cm], the thickness in the resin reservoir cavity Cf is increased. The dimension Xf in the vertical direction is 0.5 to 1 [m
m] and the dimension Xw in the radial direction can be selected to be about 1 [cm].

On the other hand, in FIGS. 3 and 4, Po and Pi indicate cutting lines for cutting after injection molding. After the injection molding, the molded product is cut along these cutting lines Po and Pi. Therefore, the resin reservoir cavity portion Cf has a constant dimension Xr in the radial direction as it is with the end portion Cse of the regular cavity portion Cs in the resin inflow direction. An extended portion is included, and a resin reservoir cavity portion Cf having the above-described dimension Xf is formed at the tip thereof.

As shown in FIG. 3 (FIGS. 1 and 2), the movable mold Mm has four (generally one or two or more) ventilation holes 2 communicating with the resin reservoir cavity Cf. ... is provided. Each of the ventilation holes 2 faces the resin reservoir cavity Cf at a right angle, and is connected to a pressure air supply unit (not shown) so that the pressure air A can be supplied. Further, an ejector mechanism 10 is provided at the center of the movable mold Mm, and the ejector pin 11 is moved forward and backward to be able to protrude the molded product. Reference numeral 12 denotes an undercut-shaped portion for attaching a molded product to the movable mold Mm when the mold is opened, and reference numeral 13 denotes a sprue 13 provided at the center of the fixed mold Mc. On the other hand, a virtual line indicates an injection device 20 in the injection molding machine, 21 indicates a heating cylinder, 22 indicates an injection nozzle, and 23 indicates a screw.

Next, a molding method according to the present embodiment using such a mold M for a thin molded product will be described with reference to the drawings.

First, at the time of injection molding, the mold M is clamped.
The measured resin L is injected and filled into the mold M.
In this case, as shown in FIG. 2 to FIG. 4, the amount of the resin L to be filled in the cavity C is measured so as to fill a part of the resin reservoir cavity Cf. Therefore, the resin L that has flowed into the regular cavity portion Cs by injection filling further flows into the resin reservoir cavity portion Cf, and fills a part of the resin reservoir cavity portion Cf.

When the injection filling is completed, the mold is opened. At this time, the molded product E is opened by being attached to the movable mold Mm by the undercut-shaped portion 12 provided on the movable mold Mm. After the mold is opened, the ejector pin 11 of the ejector pin mechanism 10 is advanced to the cavity C side from the position shown in FIG. In this case, since the molded product E includes the thin portion of the speaker diaphragm, if the ejector pin 11 is provided only at the center, an excessive force acts on the thin portion of the speaker diaphragm to cause deformation or the like. For this reason, at the time of ejection, the pressurized air A is supplied to the ventilation holes 2 facing the resin reservoir cavity Cf to release the molded product E from the movable mold Mm. The pressure air A
The supply of the pressurized air A exhibits an auxiliary ejector function.

On the other hand, after injection molding, unnecessary portions En including portions corresponding to the resin reservoir cavity portions Cf are removed from the molded product E.
To obtain a regular thin-walled molded product Es. In FIG. 3, Po is a circular cutting line for removing an unnecessary portion En on the outside, and Pi is a circular cutting line for removing an unnecessary portion En including a sprue portion located on the center side.

As described above, according to the mold M for a thin-walled molded product and the molding method using the mold M according to the present embodiment, the resin L flowing into the regular cavity portion Cs at the time of injection molding.
Further flows into the resin reservoir cavity Cf so as to fill a part of the resin reservoir cavity Cf, so that the resin pressure is released by the newly provided resin reservoir cavity Cf, and the thickness in the normal cavity Cs is reduced. Deformation is almost eliminated. Therefore, it is possible to obtain a high-precision and high-quality thin-walled molded product Es, and it is possible to further reduce the thickness of the thin-walled molded product and to diversify the shape including an increase in area, thereby improving versatility and development. .

FIG. 5 shows a modified embodiment. In this modified embodiment, a regulating portion 3 for arbitrarily setting the flow rate of the resin L when flowing is provided in the resin reservoir cavity portion Cf.
Thereby, the regulating portion 3 exhibits a pressure adjusting function, and can adjust the resin pressure applied to the regular cavity portion Cs. Therefore, by the delicate pressure setting that is difficult on the injection device 20 side, a high degree of thickness adjustment for the regular thin molded product Es is possible, and the pressure in the regular cavity Cs can be made uniform. In this case, the height Xh of the regulating portion 3 in the thickness direction can be arbitrarily set according to a regular thin molded product.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment,
The detailed configuration, shape, numerical value, method, and the like can be arbitrarily changed, added, or deleted without departing from the gist of the present invention. For example, although one or more air holes 2 communicating with the resin reservoir cavity Cf are provided, an ejector mechanism similar to the ejector mechanism 10 may be provided. That is, if the resin reservoir cavity Cf is not provided, the ejector pin may break through the speaker diaphragm even if the ejector mechanism is provided. Therefore, the ejector mechanism cannot be provided. Since the ejector pin does not hit the thin portion, an ejector mechanism can be provided. In addition, although the speaker diaphragm is illustrated, the present invention can be applied to the molding of various articles having similar properties such as a special diaphragm.

[0025]

As described above, the mold for a thin molded product according to the present invention has a regular cavity portion having the shape of a regular thin molded product, and a resin that communicates with the end of the regular cavity portion in the resin inflow direction. A resin reservoir cavity is provided along the entire outer periphery of the terminal end to allow the inflow of the resin. Also, the molding method according to the present invention uses this mold so that the resin is injected into the resin reservoir cavity during injection molding. In addition to injection-filling to fill a part of the product, after injection molding, unnecessary portions including the portion corresponding to the resin reservoir cavity are cut from the molded product to obtain a regular thin-walled molded product. Has a remarkable effect.

It is possible to obtain a high-precision and high-quality thin-walled molded product, and it is possible to further reduce the thickness of the thin-walled molded product and to diversify the shape including an increase in area, thereby improving versatility and developability. .

According to a preferred embodiment, if a vent is provided in the movable mold, pressurized air can be supplied to the vent, and during ejection, a molded product adheres to the inner surface of the cavity portion and the thin portion is deformed. Problems can be avoided.

According to the preferred embodiment, if the regulating portion is provided in the resin reservoir cavity, the pressure of the resin applied to the regular cavity can be adjusted. By setting the pressure, it is possible to perform a high-level thickness adjustment for the thin-walled molded product and to make the pressure in the regular cavity portion uniform.

[Brief description of the drawings]

FIG. 1 is a sectional side view of a mold according to a preferred embodiment of the present invention;

FIG. 2 is a cross-sectional side view showing a state in which the mold is filled with resin.

FIG. 3 is a front view showing a movable mold cavity constituting the mold;

FIG. 4 is an enlarged sectional view of a resin reservoir cavity in the mold.

FIG. 5 is an enlarged sectional view showing a modified embodiment of the resin reservoir cavity portion in the mold.

FIG. 6 is a sectional side view of a mold according to the related art;

[Explanation of symbols]

 2 ... Ventilation hole 3 Restriction part M Mold for thin-walled molded product Mm Movable type Mc Fixed type Cs Regular cavity portion Cse Resin inflow direction end portion Cf Resin cavity portion Es Regular thin-walled molded product E Molded product En ... Unnecessary portion L resin A pressure air

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-246634 (JP, A) JP-A-7-119104 (JP, A) JP-A-9-262869 (JP, A) 245891 (JP, A) JP-A-7-40389 (JP, A) JP-A-8-112840 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/03-45 / 84

Claims (5)

(57) [Claims] In a mold for a thin-walled molded product comprising a movable die and a fixed die, a regular cavity having the shape of a regular thin-walled molded product is communicated with an end of the regular cavity in a resin inflow direction. A mold for a thin-walled molded product, comprising a resin reservoir cavity along the entire outer periphery of the terminal end to allow inflow. 2. The mold for a thin-walled molded product according to claim 1, wherein the movable mold has one or more air holes communicating with the resin reservoir cavity. 3. The mold for a thin-walled molded product according to claim 1, wherein said resin reservoir cavity has a regulating portion for setting a flow rate when the resin flows. 4. A regular cavity portion having the shape of a regular thin molded product, and a resin reservoir along the entire outer periphery of the regular cavity portion, which communicates with a terminal portion of the regular cavity portion in the resin inflow direction to allow the resin to flow therein. Using a mold for a thin molded product consisting of a movable mold and a fixed mold with a cavity,
The resin is injected and filled so as to fill a part of the resin reservoir cavity, and after injection molding, unnecessary portions including a portion corresponding to the resin reservoir cavity are cut from the molded product to obtain a regular thin molded product. A molding method characterized in that: 5. The molding method according to claim 4, wherein the movable die is provided with one or more air holes communicating with the resin reservoir cavity, and pressurized air is supplied to the air holes at the time of ejecting. .