JPH06834A - Molding method of product made of synthetic resin - Google Patents

Abstract

PURPOSE:To mold a product which is made of synthetic resin and has a water path inside, without using a core. CONSTITUTION:After casting of a synthetic resin material under a molten state within a molding space 5, pressurized gas is blown into the molding space 5 through a resin rich area 5b provided by connecting with a gate part 4b of a mold 1 and simultaneously with forming of a resin layer 11 having almost a uniform thickness by stretching the synthetic resin material over the whole of a molding surface 5a, a space 12 for a water path is formed on the inside of a resin layer 11. With this construction, since molding can be performed without making use of a core, a degree of freedom in setting-up a form of the water path becomes high. Then since the thickness of the resin layer becomes almost uniform, a defect such as a sink dose not occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a product having a water passage inside a shower head or the like without using a core when molding a synthetic resin material.

[0002]

2. Description of the Related Art As a device for molding a shower head for a hand shower with a synthetic resin material, an injection molding machine 30 as shown in FIG. 7 is conventionally known. In general, this type of injection molding machine 30 is equipped with a mold 31 including a movable mold 32 and a fixed mold 33, and presses a heated and melted synthetic resin material into a molding space formed in the mold 31. The injection device 30a for injection and the movable mold 32 are moved to move the mold 31.
It includes a mold clamping device 30b for opening and closing, and a drive mechanism and a control mechanism thereof.

The structure of the mold 31 will be described. As shown in FIG. 8, the movable mold 32 molds the lower surface side of the shower head, and the fixed mold 33 molds the upper surface side of the shower head. A runner 33a for introducing the synthetic resin material into the molding space 34 is formed therein, and a nozzle 35 provided at the tip of the injection device 30a is connected to the opening on the outer surface side thereof. On the other hand, the movable die 32 is provided with an extrusion mechanism 38 including a push rod 36 and an extrusion plate 37 for taking out a molded product from the die 31. The pushing mechanism 38 is configured to operate in conjunction with the mold clamping device 30b described above.

Next, a procedure for molding a shower head using the injection molding machine 30 will be described with reference to FIG. First, as shown in the figure, the movable die 32 and the fixed die 33 are united to form a molding space 34. In this molding space 34,
A core 39 for forming a water passage in the shower head is arranged, and a middle mold 4 for forming a water discharge port and a screw pilot hole for fixing a water sprinkler to the water discharge port on the movable mold 32.
Wear 0. Subsequently, the heated and melted synthetic resin material is injected under pressure from the nozzle 35 of the injection device 30a into the molding space 34 to fill the space. After that, when the synthetic resin is hardened, the core 39 is removed, the movable die 32 is retracted to divide the die 31, and the push rod 3 of the extrusion mechanism 38 is removed.
By extruding the molded product at 6, as shown in FIG.
A shower head product 41 is obtained.

[0005]

When the shower head 41 is molded by the conventional injection molding method, there are the following problems. First of all, as shown in FIG. 10A, the shower head 41 is formed in a shape that is slightly curved from the base portion to the tip end in consideration of usability. Therefore, since the water passage 42 inside the shower head 41 is also curved, the core 39 (see FIG. 7) forming the water passage 42 must also be curved. However, in order to allow the core 39 to be removed from the molded product, the curvature of the water passage 42 in the shower head 41 must be set to a constant value, so the degree of freedom in design is very narrow.

The second problem is that the shower head 41 is generally formed so that the front end side is wider than the base side, while the water passage 42 is formed as shown in FIG. 10 (B). The water passage 42 is tapered so as to provide a slight draft for facilitating the removal of the core 39.
As a result, the side wall 43 near the tip of the water passage 42 has an extremely large thickness. A thicker portion takes a longer time to complete curing, resulting in a delay in the molding cycle. Moreover, if the water passage 42 is tapered, it also becomes difficult to obtain a desired discharge flow rate.

Thirdly, the conventional shower head 41
The thickness of the synthetic resin layer differs depending on the portion, and the inside of the portion having the largest layer thickness remains uncured until the end.
For this reason, there is a problem that when the portion is cured, it affects the already-cured peripheral portion and causes defects such as sink marks on the surface of the product. In the shower head 41 shown in FIG. 10, sink marks were easily generated on the surface of the side wall 43 having the largest thickness shown in FIG.

[0008]

SUMMARY OF THE INVENTION The present invention is a method for molding a synthetic resin product, which was devised in view of the above-mentioned problems, and the gist of the present invention is to provide a molten state from a gate portion of a mold to a molding space. After injecting the synthetic resin material, a pressurized gas is blown into the molding space from the resin reservoir portion connected to the gate portion to spread the synthetic resin material on the entire molding surface of the mold to make it substantially uniform. At the same time as forming a resin layer having a thickness, a space for a water passage is formed inside the resin layer.

[0009]

According to the present invention, the synthetic resin material in a molten state is injected into the molding space in the mold, and then the pressurized gas is blown.
Then, since it is in a molten state, the synthetic resin material having fluidity spreads almost uniformly over the entire molding surface to form a resin layer that follows the shape of the molding surface. This resin layer is held by being pressed against the molding surface by gas pressure,
The pressure acting on this is equal in all parts. Therefore, the thickness of the resin layer formed on the molding surface is substantially uniform.

[0010]

EXAMPLES The present invention will be described in detail below by taking a case of molding a shower head made of synthetic resin as an example.

FIG. 1 is a schematic view of a mold part of an injection molding machine A used for carrying out the method of the present invention. The basic structure of the injection molding machine A is almost the same as the conventional one. That is, a mold 1 composed of a movable mold 2 for molding the lower surface side of the shower head and a fixed mold 3 for molding the upper surface side thereof, a mold clamping device (not shown) for controlling opening / closing of the movable mold 2 and the fixed mold 3, An injection device 6 for injecting a synthetic resin material into a molding space 5 in the mold 1, an extruding mechanism 8 including a push rod 8a and an extruding plate 8b for demolding a molded product, which interlocks with the above-mentioned mold clamping device, and their driving. It is composed of a device, a control device, and the like. However, the injection molding machine A for carrying out the method of the present invention is different from the conventional one in that a gas injection device 7 for injecting a pressurized gas into the molding space 5 is provided. In the present embodiment, the blowing nozzle 7a of the gas press-fitting device 7 is arranged at the base portion of the shower head. Further, the movable mold 2 is the middle mold 3 for forming a screw pilot hole for fixing the water sprinkling plate to the spout of the shower head.
However, the shape is different from the conventional example. The middle mold 3 may be manufactured integrally with the movable mold 2.

The practice of the molding method according to the present invention using the molding machine A will be described with reference to FIGS. First, Figure 2
As shown in FIG. 3, the movable die 2 and the fixed die 4 are united to form a molding space 5 inside the die 1. A resin reservoir 5b is provided at a location corresponding to the base of the shower head in the molding space 5, and the tip of the resin reservoir 5b is made to face the blowing nozzle 7a of the gas injection device 7.
Are arranged. A runner 4 a for introducing the synthetic resin material into the molding space 5 is formed on the dividing surface 1 a of the fixed die 4 and the die 1. That is, as shown in FIG.
Grooves are provided in both the movable die 2 and the fixed die 4 on the divided surface 1a of the die 1, and by combining the two, the resin pool portion 5b is continuously formed from the runner 4a of the fixed die 4.
The runner 4a is formed so as to reach the gate portion 4b that opens at the bottom.

Next, as shown in FIG. 4, the synthetic resin material heated and melted into the molding space 5 formed in the mold 1 from the injection device 6 through the runner 4a and the gate portion 4b as described above. Inject 10. At this time, the synthetic resin material 10 does not fill the molding space 5, but is injected in an appropriate amount according to the thickness of the intended product, as described later.

Subsequently, pressurized gas is blown into the molding space 5 by the gas injection device 7. Then, as shown in FIG. 5, the synthetic resin material 10 having fluidity in a molten state.
Are spread along the molding surface 5a by the gas pressure, and the molding surface 5a
A synthetic resin layer 11 having a surface shape following a is formed.
Since the pressure for pressing the synthetic resin layer 11 against the molding surface 5a and holding it is a gas pressure, an equal force acts on any part. Therefore, the thickness of the resin layer 11 becomes substantially uniform. Further, since the total area of the molding surface 5a is constant, the thickness of the resin layer 11 is determined according to the set value of the injection amount of the synthetic resin material 10 into the molding space 5.

The space 12 formed inside the resin layer 11 is a space that should be a water passage for the shower head after molding. In addition, an inlet of the water passage is inevitably formed on the base side of the shower head, which the blowing nozzle 7a of the gas injection device 7 faces.

In this way, after forming the substantially uniform resin layer 11 on the molding surface 5a, the gas pressure is maintained until the resin layer 11 is cured. The wall thickness of the shower head molded according to the present invention can be made much thinner than the case of molding by the conventional injection molding, so that the time to complete the curing becomes very short.

When the curing of the resin layer 11 is completed, the valve 7d at the base of the blowing nozzle 7a of the gas injection device 7 is closed, and the valve 7 of the deaeration part 7c provided in the middle of the nozzle 7a.
b is opened and the pressurized gas in the resin layer 11 is discharged. Note that the pressurized gas can be discharged by pulling out the blowing nozzle 7a, in addition to the above-described valve operation.

After that, if the movable die 2 is retracted and the molded product is demolded by the extrusion mechanism 8, a shower head 20 as shown in FIG. 6 can be obtained. However, in the above-described molding method according to the present invention, the resin layer 11 that is uniform over the entire surface is formed except for the water passage port 21 formed at the position where the pressurized gas is blown in. 11 will be provided. Therefore,
As shown in FIG. 6A, after removing the molded product, the shower head 20 as shown in the drawing can be obtained by cutting off the resin layer 11a at the portion that will become the water discharge port 23 of the shower head 20. Reference numeral 22 is a water passage formed by pressurization of pressurized gas, and 24 is a screw pilot hole for attaching a sprinkler plate to the water outlet 23. The screw pilot hole 24 is formed by the middle mold 3 attached to or integrally formed with the movable mold 2 (see FIG. 5). Further, in the above embodiment, the resin reservoir 5b is provided on the base side of the shower head 20.
Since the resin layer 11b formed in 1 is attached, the extra resin layer 11b is also cut off after the mold release.

The embodiment of the present invention is not limited to the above. In the above embodiment, the injection of the synthetic resin and the injection of the pressurized gas were performed from the base side of the shower head, but it is also possible to perform this from the water outlet side of the shower head. The present invention can also be applied to the molding of products other than shower heads, for example, synthetic resin faucets. In addition, the present invention does not prevent appropriate modification according to the embodiment.

[0020]

As is apparent from the above description, according to the present invention, when molding a product having a water passage inside with a synthetic resin material, a core is not required at all. Greater freedom of setting. Therefore, in the case of molding the shower head, the water passage can be expanded from the base side toward the tip side, so that it is easy to secure the water discharge amount.

Further, in the molded product according to the present invention, since the thickness of the synthetic resin layer can be made substantially uniform, unevenness of curing time due to difference in parts is eliminated, and thus defects such as sink marks may occur. There is no.

Further, according to the present invention, since the thickness of the synthetic resin layer can be made thinner than before, it is possible to shorten the time required to complete the curing of the molded product, accelerate the molding process, and at the same time, to carry out the synthesis. It is possible to reduce the amount of resin material used and bring about a reduction in manufacturing cost.

In addition, in the present invention, since the resin layer having a uniform thickness is formed on the molding surface and the pressurized state is maintained until the resin layer is cured, air bubbles mixed in the resin layer can be eliminated. You can Therefore, an excellent product having no defects such as pinholes and cavities can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a mold part of an injection molding machine for molding a shower head according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing a main part of a mold in the injection molding machine shown in FIG.

3 is a cross-sectional view taken along the line (ii)-(ii) of FIG.

FIG. 4 is an enlarged view showing a main part of a mold in the injection molding machine shown in FIG. 1, and is a cross-sectional view showing a state where a synthetic resin material is injected into a molding space.

5 is an enlarged view showing a main part of a mold in the injection molding machine shown in FIG. 1, and is a cross-sectional view showing a state in which a pressurized gas is being pressed into a molding space.

6A and 6B show a shower head molded according to the present invention, in which FIG. 6A is a side sectional view and FIG. 6B is a drawing seen from the lower surface side.

FIG. 7 is a side view showing an entire conventional injection molding machine.

FIG. 8 is a cross-sectional view showing a mold part in a conventional injection molding machine for molding a shower head, which is taken out and shown.

9 is an enlarged sectional view showing a main part of a mold in the injection molding machine shown in FIG.

FIG. 10 is a view showing a conventional shower head,
(A) is a side sectional view, and (B) is a drawing seen from the lower surface side.

[Explanation of symbols]

 A injection molding machine 1 mold 2 movable type 3 medium size 4 fixed type 4a runner 4b gate part 5 molding space 5a molding surface 5b resin reservoir part 6 injection device 7 gas injection device 7a blowing nozzle 7b degassing part 7c valve 7d valve 10 Synthetic resin material 11 Synthetic resin layer 12 Water passage space 20 Shower head 21 Water passage 22 Water passage 23 Water outlet

Claims (1)

[Claims] 1. A method for molding a synthetic resin product having a water passage inside, wherein a synthetic resin material in a molten state is injected into a molding space from a gate portion of a mold, and then connected to the gate portion. The synthetic resin material is spread over the molding surface of the mold to form a resin layer having a substantially uniform thickness by blowing a pressurized gas into the molding space from the resin reservoir portion, and at the same time, inside the resin layer. A method for molding a synthetic resin product, characterized in that a space for a water passage is formed in the.