JPH03268913A - Injection molding method and its device for hollow material - Google Patents

Abstract

PURPOSE:To contrive diversification of molding of a hollow material by improving rigidity and load resistance, by a method wherein after injection of the primary molten resin into a mold cavity, the primary fluid is pressed into the mold cavity and after injection of the secondary molten synthetic resin into the mold cavity, the secondary fluid is pressed into the mold cavity. CONSTITUTION:An unfilled quantity of the primary molten synthetic resin PL1 is injected into a mold cavity 4. Then when the compressed primary fluid FL1 is pressed into the cavity 4 from a fluid pressure source through a connecting pipe 30 and sprue 6, the primary molten synthetic resin PL1 is expanded by the primary fluid FL1. Then the secondary molten synthetic resin PL2 is injected into the cavity 4 and positioned within the primary fluid FL1. Then when the compressed secondary fluid FL2 is pressed into the cavity 4, the secondary molten synthetic resin PL2 is expanded and also the primary molten synthetic resin PL1 is expanded. With this construction, the primary molten synthetic resin PL1 is formed as a shell 32 of a hollow material by following after inner contours of the cavity 4 and a reinforcing wall 33 is formed of the secondary molten synthetic resin PL2 within the shell 32. Then when pressure of the secondary fluid FL2 is lowered appropriately under a state where the reinforcing wall 33 is not solidified yet, a hollow material, into which the primary fluid FL1 is enclosed, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for injection molding hollow objects made of synthetic resin.

[Conventional technology]

Conventionally, a method described in Japanese Patent Publication No. 57-14968 has been known as a method for injection molding hollow objects of this type.

This method involves injecting an unfilled amount of molten plastic into the mold cavity, then press-fitting a gas alone or while injecting molten plastic, and then injecting molten plastic as necessary to mold the mold. This is a method of injection molding a hollow object that fills a mold cavity.

Further, as an apparatus for carrying out this injection molding method for a hollow object, there is a nozzle apparatus in which a gas blowing nozzle is disposed at the axial center of the nozzle hole (see Utility Model Application Publication No. 56-91015), A valve body that engages with the inner edge of the nozzle hole is provided in the main body so as to be movable in the axial direction, and a fluid passage having a check valve is provided in the axial center of the valve body (Japanese Patent Application No. 5043385). (see) or a nozzle device in which a valve body is provided in the nozzle body so as to be movable in the axial direction, and a fluid passage is provided in the axial center of the valve body. A needle that closes the outlet is movable in the axial direction (Special Publication No. 59-49902)
Publication No.) is known.

[Problem to be solved by the invention]

However, since the hollow objects produced by the above conventional injection molding method for hollow objects are made of synthetic resin and fluid that form the outer shape, they have a problem of poor rigidity and load capacity. It becomes noticeable.

On the other hand, in the hollow injection molding apparatus described in Japanese Utility Model Application Publication No. 56-91015, there is no means for blocking the relationship between the gas blowing hole and the resin path, so when the molten synthetic resin is injected, the resin flows through the gas blowing hole. The gas enters the cold part and blocks the gas blowing hole, causing it to lose its function.Also, when gas is blown after resin injection, gas enters the resin path, and when reinjecting, the gas mixed in with the melt melts. Since synthetic resin is injected, there is a problem that a product in an undesired state may be molded.

In the injection molding apparatus for hollow objects described in Japanese Patent Application No. 50-43385, since there is a reverse valve in the fluid path, the pressure cannot be controlled to a low level after the fluid is press-in, and the mold clamping energy increases. There's a problem.

In addition, in the hollow injection molding apparatus described in Japanese Patent Publication No. 59-49902, although the problems of those described in Japanese Utility Model Application No. 56-91015 and Japanese Patent Application No. 50-433g5 can be generally solved, There is a problem in that the resin and fluid cannot be injected simultaneously by opening the channel and the fluid channel at the same time, resulting in a lack of diversity in molding.

SUMMARY OF THE INVENTION Accordingly, the present invention aims to provide a hollow article injection molding method and an apparatus therefor, which can produce hollow articles with excellent rigidity and load resistance by various molding methods.

[Means to solve the problem]

In order to solve the above problems, the injection molding method for a hollow object of the present invention includes a method for injection molding a hollow object in which a molten synthetic resin and a fluid are pressurized into a mold cavity. After injecting the resin, press the primary fluid, then inject the secondary molten synthetic resin, then press the secondary fluid at approximately the same pressure as the primary fluid, and before the secondary molten plastic solidifies. This is a method of lowering the secondary fluid pressure to inflate a reinforcing wall formed between the primary fluid and the secondary fluid toward the secondary fluid side.

Then, after inflating the reinforcing wall toward the secondary fluid side as necessary, a further small amount of molten synthetic resin is injected.

In addition, in a hollow article injection molding method in which molten synthetic resin and fluid are pressurized into a mold cavity, after injecting an unfilled amount of primary molten plastic into the mold cavity, the primary fluid is press-fitted, and then the secondary molten resin is injected into the mold cavity. After injecting the molten synthetic resin, a secondary fluid of approximately the same pressure as the primary fluid is injected, and the pressure of the secondary fluid is lowered before the secondary molten plastic solidifies, so that the pressure between the primary and secondary fluids is reduced. This method involves destroying part of the reinforcing wall formed between the two.

Then, after destroying a portion of the reinforcing wall as necessary, a further small amount of molten synthetic resin is injected.

Furthermore, in each of the above methods, the molten synthetic resin may be injected in parallel with the injection of the primary and secondary fluids.

On the other hand, a hollow object injection molding apparatus for carrying out each of the above-mentioned methods is a hollow object injection molding apparatus having a mold and a nozzle device for pressurizing a molten synthetic resin and a fluid into a cavity of the mold. The device is connected to the heating cylinder through one end, and has a nozzle body in which a resin passage communicating with the inside of the heating cylinder is formed on the outer periphery. A nozzle cap that forms a resin passage connected to the resin passage, and a nozzle part that protrudes from the other end of the nozzle body and is provided at the tip, are loosely fitted into the nozzle hole of the nozzle cap, and are connected to a fluid pressure source. A nozzle of a nozzle cap on the end face of a hollow piston rod that is fitted to the fluid pipe to be connected and the other end of the nozzle main body so as to be slidable in the axial direction on the outer periphery of the fluid pipe, and that has a tapered outer periphery at the tip end. A first piston is provided to be able to close the resin passage by coming into contact with the periphery of the inner edge of the hole, and a first piston is provided at one end of the nozzle body so as to be movable in the axial direction, and is loosely inserted into the fluid pipe. A second piston configured to be able to close the nozzle hole of the fluid pipe with the tip of one piston rod, and a first biasing means that biases the first piston to open and close the resin passage in response to changes in resin pressure. and a second biasing means that biases the second piston to open and close the fluid passage in response to changes in resin pressure or fluid pressure.

The first biasing means is a compression spring that biases the first piston to approach the nozzle hole of the nozzle cap.

The second biasing means includes a compression spring that biases the second piston away from the nozzle hole of the fluid pipe, and is provided with a diameter larger than the nozzle hole of the fluid pipe in order to resist this spring, and constantly heats the tip. and the other piston rod of the second piston that projects into the cylinder.

Further, the second biasing means may be a pressure fluid that biases the second piston toward the nozzle hole of the fluid pipe.

Furthermore, in each of the above-mentioned devices, the nozzle hole of the fluid pipe may be branched into a plurality of parts.

[For production]

In the above method, the inside of the outer shell of the hollow body formed from the primary molten synthetic resin is divided into a primary fluid chamber and a secondary fluid chamber by a reinforcing wall formed from the secondary molten synthetic resin.

By inflating the reinforcing wall toward the secondary fluid chamber, the primary fluid chamber is sealed in a slightly higher pressure state than the secondary fluid chamber, and by destroying a part of the reinforcing wall, the primary fluid The chamber and the secondary fluid chamber have the same pressure, and the hollow object is sealed by injecting a small amount of molten synthetic resin.

Furthermore, by injecting the molten synthetic resin in parallel with the press-in of the primary and secondary fluids, the formation of the primary and secondary fluid chambers is performed in parallel with the injection of the molten synthetic resin.

This injection of the molten synthetic resin may be carried out in parallel with only the injection of the primary and secondary fluids, or may be carried out consecutively with the injection of the primary and secondary molten plastics, or the injection of the primary and secondary fluids may be carried out consecutively. The injection of the secondary molten plastic resin as well as the injection of the molten plastic resin for sealing may all be carried out consecutively.

On the other hand, in the device, the resin pressure between the resin pressure (injection pressure) Pl during injection of the molten synthetic resin and the resin pressure (no-load pressure) P during no load is adjusted in two steps from the injection pressure P1 side to pp (pp). P
The pressure can be adjusted to 1>P2>P3>P4)2゛3, and the urging force of the first urging means is smaller than the force acting on the first piston due to the injection pressure Pl,
and the resin pressure P2 is set to be larger than the force acting on the first piston, and when the urging force of the second urging means is equal to or higher than the resin pressure P3, the nozzle hole of the fluid pipe is closed by the tip of one piston rod. By setting the nozzle hole to a size that opens the nozzle hole when the resin pressure is P4 or less, the opening and closing of the resin path and the opening and closing of the fluid path are performed separately, and the fluid pressure is made equal to the injection pressure P1. As a result, the resin path and the fluid path are simultaneously opened.

The second biasing means includes a compression spring that biases the second piston away from the nozzle hole of the fluid pipe, and is provided with a diameter larger than the nozzle hole of the fluid pipe in order to resist this, and constantly heats the tip. When the second piston is configured with the other piston rod of the second piston that protrudes into the cylinder, the biasing force of the rolling spring is smaller than the force that the second piston receives due to the resin pressure of 23 or more, and is less than the force that the second piston receives due to the resin pressure of P4 or less. The force is set larger than the force that the second piston receives.

Further, when the second biasing means is a pressure fluid that biases the second piston to approach the nozzle hole of the fluid pipe,
The biasing force is caused by the pressure when the fluid is press-fitted.
It is set to be smaller than the force that the piston receives, and larger than the force that the second piston receives due to the pressure when resin is injected.

By branching the nozzle part of the fluid pipe into multiple parts, 1
A plurality of twelfth fluid chambers are formed.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal cross-sectional view of a main part of an injection molding apparatus according to a first embodiment used to carry out a method for injection molding hollow objects.

In the figure, 1 is a mold, and a fixed mold 2 and a movable mold 3 form a mold cavity 4.

5 is a nozzle device that presses the molten synthetic resin 7 and fluid (for example, air, gas such as N2 gas, or liquid such as water) into the mold cavity 4 by contacting and separating from the sprue 6 of the mold 1;
A cylindrical nozzle that is connected to the heating cylinder 8 through one end (the right end in the figure) and has a resin passage 9 in the axial direction (left and right direction in the figure) connected to the inside of the heating cylinder 8 on its outer periphery. It has a main body 10. Nozzle body 1
A nozzle cap 12 that cooperates with the nozzle body 10 to form a resin passage 11 connected to the resin passage 9 is connected to the other end (left end in the figure) of the nozzle body 10 .

At the other end of the nozzle body 10, a fluid pipe 1 is connected to a fluid pressure source (not shown) via a connecting pipe, which will be described later.
3 protrudes, and the nozzle part 13a provided at the tip of the fluid pipe 13 is connected to the nozzle hole 14 of the nozzle cap 12.
It is loosely fitted. Note that the nozzle device 5 is brought into contact with and separated from the mold 1 so as to communicate with the nozzle hole 14 of the nozzle cap 12 or the sprue 6.

Further, a fluid pipe 13 is provided at the other end of the nozzle body 10 at its axial center.
A ring-shaped piston chamber 15 is provided surrounding the fluid pipe 13 , and a first piston 16 is inserted into the piston chamber 15 .
A hollow piston rod 1 is fitted on the outer periphery of the hollow piston rod so as to be slidable in the axial direction.
7, and the first piston 16 is prevented from leaving the piston chamber 15 by a nozzle torpedo 18 attached to the other end of the nozzle body 10 through which the hollow piston rod I7 can be inserted. First piston 16
The hollow piston rod 17 has its end face connected to the nozzle cap 1.
The resin path 11 can be closed by coming into contact with the periphery of the inner end of the nozzle hole 14 of No. 2, and a taper 19 is formed on the outer periphery of the tip portion to serve as a pressure receiving surface when the resin path 11 is opened and closed. The first piston 16 is located in this piston chamber 15.
The resin path 11 is biased to be closed by a first biasing means consisting of a compression spring 20 interposed between the resin passage 11 and the bottom of the resin passage 11.

On the other hand, a circular piston chamber 21 is provided in the axial center of one end of the nozzle body 10, and a second piston 22 is accommodated in this piston chamber 21 so as to be movable in the axial direction.
The second piston 22 is prevented from leaving the piston chamber 21 by a torpedo 23 attached to one end of the nozzle body IO. The piston rod 24 on one side (the left side in the figure) of the second piston 22 is provided with an appropriately smaller diameter than the inner diameter of the fluid pipe 13, and has the same inner diameter as the fluid pipe 13 that communicates the piston chamber 21 with the inside of the fluid pipe 13. The fluid pipe 13 is inserted into the fluid pipe 13 by passing through a communication hole 25 having a large diameter, and its distal end is provided so as to be able to close the nozzle hole 26 of the nozzle portion 13a of the fluid pipe 13. Also, the other (right side in the figure) piston rod 27 of the second piston 22
is provided with a suitably larger diameter than the nozzle hole 26 of the fluid pipe 13, and its tip is slidably inserted into the through hole 28 provided in the torpedo 23 and constantly projects into the heating cylinder 7. . A compression spring 29 is interposed between the second piston 22 and the bottom of the piston chamber 21. This compression spring 29 is connected to the other piston rod 27.
In addition, the distal end of one piston rod 27 constitutes a second urging means for urging the second piston 22 to close the nozzle hole 26 of the fluid pipe I3.

In FIG. 1, reference numeral 30 denotes a connection pipe attached to the nozzle body 10, which communicates with the piston chamber 21 through a communication hole 31.

Note that the pressure of the molten synthetic resin is calculated from the injection pressure P side, between the resin pressure at the time of injection (injection pressure; e.g. 1000 to 2000 kgf/e-) Pl and the resin pressure at no load (no load pressure) P4. Two stages of PP (Pl〉P2〉1 2
' 3 P3>P4), and the biasing force of the compression spring 20 serving as the first biasing means is smaller than the force acting on the first piston 1B due to the injection pressure Pl, and is adjusted by the resin pressure P2. A compression spring 29 that is set to be larger than the force acting on the first piston 16 and also serves as a part of the second biasing means.
The biasing force of the second piston 2 is caused by the resin pressure of 23 or more.
2 is set to be smaller than the force that the second piston 22 receives, and larger than the force that the second piston 22 receives due to the resin pressure equal to or lower than P4.

Next, a case will be described in which a hollow object is injection molded using the injection molding apparatus configured as described above.

First, the pressure of the molten synthetic resin and the fluid are both high pressure P without load.
4. In the case of P'4, as shown in FIG. The resin passage 11 is closed by contact with the inner edge of the hole 14, and the second piston 22 is pushed toward the heating cylinder 8 by the biasing force of the compression spring 29, causing the tip of one piston rod 24 to close. fluid pipe 1
The fluid path is opened by the separation of No. 3 from the nozzle hole 26.

Next, the pressure of the fluid is maintained at the no-load pressure P'4,
When the pressure of the molten synthetic resin is set to resin pressure P3, as shown in FIG. XP, (H.

3 (outer diameter of the other piston rod)], the fluid path is closed, and the first
The force that urges the piston 16 toward the heating cylinder 8 side [-(A-B)XP, (A;
3 outside diameter of the hollow piston rod, B; outside diameter of the tip surface of the hollow piston rod)], the resin passage 11 is maintained in a closed state.

Then, the pressure of the fluid is maintained at the no-load pressure P'4,
When the pressure of the molten synthetic resin 7 is set to the injection pressure P1, as shown in FIG. The force 11 that urges the first piston 16 toward the heating cylinder 8 side due to the injection pressure P1 is released, and as shown in FIG. The liquid is injected into the mold cavity 4 through the nozzle hole 14 and the sprue 6.

By injecting the primary molten synthetic resin PL1, or by opening the mold 1 a small amount after injection, or by using the screw (
By removing the pushing force (not shown) or retracting the screw, the pressure of the molten synthetic resin 7 becomes the resin pressure P2, and the fluid pressure is maintained at the no-load pressure P'4, as shown in FIG. As shown, the biasing force of the compression spring 20 biases the first piston 16 toward the heating cylinder 8 side by the resin pressure P2 2C-(A-C)xP, (C; inner diameter of the hollow screw 2 ton rod)] The resin path 11 is blocked, and
The biasing force of the compression spring 29 is defeated by the nozzle hole diameter of the turnip which biases the second piston 22 toward the nozzle cap 12 side by the resin pressure P2, and the fluid path is maintained in a closed state.

From this state, when the pressure of the molten synthetic resin 7 passes through the resin pressure P and reaches the no-load pressure P4 due to the removal of the force pushing the screw or the retraction of the screw, the compression spring of the first biasing means is activated as shown in FIG. 20 closes the resin path 11,
Also, the fluid path is opened by the compression spring 29 of the second biasing means. Then, the compressed primary fluid FL1 (for example, 1
50～! 80 kgf/cd) is supplied from a fluid pressure source to the fluid pipe 13 through the connecting pipe 30, the communicating hole 31, the piston chamber 21, and the communicating hole 25, and then through the nozzle hole 26, the nozzle hole 14 of the nozzle cap 12, and the sprue 6. When press-fitted into the mold cavity 4, the primary molten synthetic resin PL is swollen by the primary fluid FL, as shown in FIG. 6(b).

After pressurizing the primary fluid FL, when the pressure of the molten synthetic resin 7 is set to the resin pressure P2, the biasing force of the compression spring 20 moves the first piston 16 toward the heating cylinder 8 side due to the resin pressure P2, as shown in FIG. The resin roadwork 1 is closed by the force that urges the second piston 22 toward the heating cylinder 8 due to the urging force of the compression spring 29 and the press-in pressure P'l of the primary fluid FL. The fluid path is blocked by the exerting force C-(H2)xPE. After the fluid path is blocked, the fluid pipe 13
The connection with the fluid pressure source is cut off, and the inside of the fluid pipe 13 is brought to the no-load pressure P'4.

Next, when the pressure of the molten synthetic resin 7 is set to the injection pressure P1,
As shown in FIG. 4, the resin path 11 is opened while the fluid path is closed, and as shown in FIG. 6 into the mold cavity 4 and located in the primary fluid FL.

The pressure of the fused synthetic resin 7 becomes resin pressure P2 (see Figure 5).
When the pressure of the molten synthetic resin 7 passes through the resin pressure P (see Fig. 3) and reaches the no-load pressure P4 due to the removal of the force pushing the screw or the retraction of the screw, as shown in Fig. 1,
The resin passage 11 is closed by the compression spring 20 of the first biasing means, and the fluid passage is opened by the compression spring 29 of the second biasing means. Next, when the compressed secondary fluid FL2 is supplied from the fluid pressure source to the a-body pipe I3 and press-fitted into the mold cavity 4 through the nozzle hole 26 etc., as shown in FIG. 6(d), the secondary fluid FL2 is Molten synthetic resin PL2 or secondary fluid FL2
The primary molten synthetic resin PL
, is similarly inflated, and as shown in FIGS. 1 and 7, the primary molten synthetic resin PL is formed as the outer shell 32 of the hollow object following the inner contour of the mold cavity 4, and
The inside of this outer shell 32 is divided by a reinforcing wall 33 formed from a secondary molten synthetic resin PL2 into a primary fluid chamber 34 filled with the primary fluid FL and a secondary fluid chamber 35 filled with the secondary fluid FL2. Ru. This press-fitting of the secondary fluid FL2 is performed in a state where the primary and secondary molten synthetic resins PL and PL2 are not solidified.

Then, the secondary molten synthetic resin PL2, that is, the reinforcing wall 33
When the pressure of the secondary fluid FL 2 is appropriately reduced in a state where it has not yet solidified, the primary fluid FL is enclosed in a state of a slightly higher pressure than the secondary fluid FL 2 , and the reinforcing wall 33
is solidified in a swollen state toward the secondary fluid FL2 side. Next, after the primary and secondary molten synthetic resins PL and PL2 are solidified, the pressure of the fluid path is lowered to the no-load pressure P'4, and the mold is opened and demolded, and the primary fluid FL is enclosed. A hollow object is obtained.

In this case, if the synthetic resin has a high tensile strength and can withstand internal pressure sufficiently, it may be left as is, or if not, a hole may be made later to drain the primary fluid FL.

On the other hand, when the reinforcing wall 33 is not yet assimilated, the pressure of the secondary fluid FL2 is lowered to, for example, atmospheric pressure, and as shown in FIG. (occurs in a weak part when
The pressure becomes the same as that of the secondary fluid F L 2. Next, after the primary and secondary molten synthetic resins PL1 and PL2 are solidified, the mold is opened and demolded to obtain a hollow object from which the primary and secondary fluids FL and FL2 have flowed out. Since most of the reinforcing wall 33 remains in this hollow, its effect is not lost.

In order to identify the broken part of the reinforcing wall 33, as shown in FIG. It may be made to solidify quickly. Protrusion 36
are provided within a range that does not interfere with the shape or use of the hollow object.

Incidentally, after the reinforcing wall 33 is deformed or partially destroyed, a small amount of molten synthetic resin may be injected as necessary, and by doing so, a sealed hollow object can be obtained.

Furthermore, in the injection molding of the hollow object described above, we have described the case where the primary and secondary fluids FL and FL2 are press-fitted after injecting the primary and secondary molten synthetic resins PL and PL2, respectively. However, as shown in FIG. 9, the pressure of the molten synthetic resin is reduced to the injection pressure P1 with the pressure of the resin 7 reduced to the injection pressure P1 and the resin passage 11 opened. The press-in pressure P' is the same as
1 to open the fluid path, and the primary and secondary fluids FL, FL
The molten synthetic resin 7 may be injected in parallel with the press-fitting in step 2. This injection of the molten synthetic resin 7 may be performed, for example, in parallel only with the injection of the primary and secondary fluids FL1 and FL2, or consecutively with the injection of the primary and secondary molten synthetic resins PL and PL2. Alternatively, all of the injection of the primary and secondary molten synthetic resins PL, PL2 and the injection of the molten synthetic resin 7 for sealing may be performed continuously, and by doing so, The molding cycle can be sped up, and the thickness of the reinforcing wall and partial destruction can be controlled.

Furthermore, the injection of the molten synthetic resin and the press-in of the fluid are not limited to the second order, but may be performed in the third or higher order.By doing so, a large number of fluid chambers can be partitioned, and the rigidity and load-bearing properties of the hollow object can be improved. etc. can be further increased.

FIG. 10 is a longitudinal cross-sectional view of the main parts of the injection molding apparatus of the second embodiment used to carry out the injection molding method for hollow objects.

The injection molding apparatus of this embodiment uses the second biasing means for biasing the second piston 221 to open and close the fluid path according to changes in the resin pressure or fluid pressure in the nozzle device 501, as compared to the first embodiment. It is something that is different from the original. The other structural members, etc. are almost the same as those of the first embodiment, so the same structural members, etc. are given the same reference numerals, and the explanation thereof will be omitted.

That is, on the heating cylinder 8 side of the piston chamber 2I into which the second piston 221 is slidably inserted in the axial direction, a supply/discharge hole 37 for supplying and discharging the pressure fluid serving as the second urging means is opened. This supply/discharge hole 37 is provided so as to be connectable to an operating fluid pressure source (not shown) via a connecting pipe 38.

Therefore, by supplying a pressure fluid higher than the pressure of the fluid in the fluid pipe 13 from the operating fluid pressure source to the heating cylinder 8 side of the piston chamber 21, the second piston 221 is moved to the nozzle cap 12 as shown in FIG. The piston chamber 2 is slid to the side to close the fluid path, and a pressure fluid lower than the pressure of the fluid in the fluid pipe 13 is transferred from the operating fluid pressure source to the piston chamber 2.
1 to the heating cylinder 8 side of the piston chamber 21, or by setting the heating cylinder 8 side of the piston chamber 21 to atmospheric pressure when the pressure of the fluid in the fluid pipe 13 is press-in pressure, as shown in FIG. In this way, the second piston 221 can be slid toward the heating cylinder 8 to open the fluid path, and can be used to carry out the injection molding method for hollow objects similar to that of the first embodiment.

FIG. 12(a) and FIG. 13(a) are longitudinal cross-sectional views of main parts of injection molding apparatuses of the third and fourth embodiments used for carrying out the injection molding method for hollow objects, respectively.

The injection molding apparatuses of the third and fourth embodiments have primary and secondary fluids FL and FL2 in the nozzle devices 502 and 503.
The nozzle hole 26 of the nozzle part 13a of the fluid pipe 13 into which the
It is a branch of . Since the other structural members, etc. are substantially the same as those of the first embodiment, the same structural members, etc. are given the same reference numerals, and the explanation thereof will be omitted.

Therefore, in the injection molding apparatuses of the third and fourth embodiments, as shown in FIG. 12(b) and FIG. 13(b), two
342, 352 primary and secondary fluid chambers and 3 primary,
The secondary fluid chambers 343 and 353 can be formed simultaneously, and the primary fluid chambers 342 and 343 and the secondary fluid chambers 35
2.353, as well as a plurality of primary fluid chambers 342, 343, a plurality of reinforcing walls 3321, 3331 and a plurality of secondary fluid chambers 352.3.
Reinforcing walls 3321, 333 that can form reinforcing walls 3322, 3332 that partition each other, and partition the primary fluid chamber 342, 343 and the secondary fluid chamber 352, 353.
1 can be deformed by expanding it toward the secondary fluid chambers 352 and 353, or a part of it can be destroyed.

〔Effect of the invention〕

As described above, according to the method of the present invention, the inside of the outer shell of the hollow body made of the primary molten synthetic resin is divided into the primary fluid chamber and the secondary fluid chamber by the reinforcing wall formed of the secondary molten synthetic resin. Therefore, it is possible to make the hollow object excellent in rigidity and load resistance, and it is particularly effective for large hollow objects.

By inflating the reinforcing wall toward the secondary fluid chamber, the primary fluid chamber is sealed under a slightly higher pressure than the secondary fluid chamber, making it possible to further improve the rigidity of the hollow object. , by destroying a part of the reinforcing wall, the primary fluid chamber and the secondary
Since the next fluid chamber has the same pressure, the rigidity of the hollow object can be made uniform, and the fluid can be drained and reused. Since it is sealed, the uses of hollow objects can be further expanded.

In addition, by injecting the molten synthetic resin in parallel with the injection of the primary and secondary fluids, the formation of the primary and secondary fluid chambers can be carried out in parallel with the injection of the molten synthetic resin in step 1. As a result, the molding cycle can be speeded up, and the thickness of the reinforcing wall and partial failure can be controlled.

On the other hand, according to the device of the present invention, the resin path and the fluid path are opened and closed separately, and the resin path and the fluid path are simultaneously opened by making the fluid pressure equal to the injection pressure. , the invention of the method can be carried out without damaging the function of the fluid path, contaminating the molten synthetic resin, or being unable to control the fluid pressure as in the past, and also controlling the fluid pressure after press-fitting. Therefore, the mold clamping force can be lowered, and the manufacturing cost of the hollow product can be reduced.

In addition, by branching the nozzle hole of the fluid pipe into a plurality of parts, a plurality of primary and secondary fluid chambers are formed. Reinforcing walls are formed between each other and between the secondary fluid chambers, thereby making it possible to further improve the rigidity, load resistance, etc. of the hollow body.

[Brief explanation of drawings]

FIGS. 2, 3, 4 and 5 are longitudinal sectional views showing the operation of the nozzle device of the injection molding apparatus, and FIGS. ) and (d) are sectional views showing the injection molding method for hollow objects using the injection molding apparatus of the first embodiment, respectively, and FIG. 7 is a cross-sectional view showing ■-■ in FIG.
8 is a sectional view showing another injection molding method for hollow objects, FIG. 9 is a vertical sectional view showing another function of the nozzle device of the injection molding apparatus of the first embodiment, and FIG. 11 is a longitudinal sectional view of the nozzle device of the injection molding apparatus of the second embodiment, FIG. 11 is a longitudinal sectional view showing its operation, FIG. 12(a) and FIG. 13(a)
) are sectional views of the main parts of the nozzle devices of the injection molding apparatuses of the third and fourth embodiments, respectively, and FIGS. 12(b) and 13(b) are injection molding of hollow objects by the respective apparatuses. It is an explanatory diagram showing a method. 1... Mold 4... Mold cavity 5... Nozzle device 7... Molten synthetic resin 9
Resin passage 11 Resin passage 13 Fluid pipe 14 Nozzle hole 17 Hollow piston rod 20 Compression springs 22, 221 Second piston 24 One side piston rod 28, 262.283...nozzle hole 27...other piston rod 29...compression spring 33, 332, 333.3321.3322.3331
゜34, 342, 343...Primary fluid chamber 35, 35
2, 353... Secondary fluid chamber 37... Supply/discharge hole
38... Connection pipe PL i... Primary molten synthetic resin PL2... Secondary molten synthetic resin FLl... Primary fluid FL2 10... Nozzle body 12... Nozzle cap 13a... Nozzle part I6...First piston 19...Cheetsma 3332...Reinforcement wall...Secondary fluid tg2 Fig. 83-14 Fig. 7 Fig. 6 Fig. 9 Fig. 10 Fig. 112

Claims (10)

[Claims] (1) In a hollow object injection molding method in which a molten synthetic resin and a fluid are pressurized into a mold cavity, after an unfilled amount of primary molten plastic is injected into the mold cavity, the primary fluid is pressurized, and then a second molten plastic is injected into the mold cavity. After injecting the secondary molten synthetic resin, a secondary fluid of approximately the same pressure as the primary fluid is injected, and the pressure of the secondary fluid is lowered before the secondary molten synthetic resin solidifies to separate the primary and secondary fluids. A method for injection molding a hollow article, characterized by expanding a reinforcing wall formed between the two toward the secondary fluid side. (2) In the method for injection molding a hollow article according to claim 1,
A method for injection molding a hollow object, which comprises injecting a small amount of molten synthetic resin after inflating a reinforcing wall toward a secondary fluid. (3) In a hollow article injection molding method in which molten synthetic resin and fluid are pressurized into a mold cavity, after injecting an unfilled amount of primary molten plastic into the mold cavity, the primary fluid is pressurized, and then the second molten plastic is injected into the mold cavity. After injecting the secondary molten synthetic resin, a secondary fluid of approximately the same pressure as the primary fluid is injected, and the pressure of the secondary fluid is lowered before the secondary molten synthetic resin solidifies to separate the primary and secondary fluids. A method for injection molding hollow objects, characterized by destroying a part of the reinforcing wall formed between the two. (4) In the method for injection molding a hollow article according to claim 3,
A method for injection molding hollow objects, which comprises injecting a small amount of molten synthetic resin after partially destroying a reinforcing wall. (5) The method for injection molding a hollow object according to claim 1, 2, 3 or 4, characterized in that the injection of the molten synthetic resin is carried out in parallel with the injection of the primary and secondary fluids. Molding method. (6) A hollow article injection molding apparatus having a mold and a nozzle device for pressurizing a molten synthetic resin and a fluid into a cavity of the mold, the nozzle device being connected to a heating cylinder via one end, a nozzle body having a resin passage formed on its outer periphery that communicates with the inside of the heating cylinder; a nozzle cap that is connected to the other end of the nozzle body and cooperates with the nozzle body to form a resin passage that communicates with the resin passage; A fluid pipe protrudes from the axial center of the other end of the nozzle body, a nozzle part provided at the tip is loosely fitted into the nozzle hole of the nozzle cap, and is connected to a fluid pressure source; is fitted to the outer periphery of the fluid pipe at the portion so as to be slidable in the axial direction,
a first piston that is capable of closing the resin passage by abutting the end surface of a hollow piston rod having a tapered outer circumference with the inner edge of the nozzle hole of the nozzle cap; and an axial center portion of one end of the nozzle body. is provided so as to be movable in the axial direction,
A second piston is provided so that the nozzle hole of the fluid pipe can be closed by the tip of one piston rod loosely inserted into the fluid pipe, and a first piston is provided to open and close the resin passage according to changes in resin pressure. A hollow object characterized by comprising a first urging means for urging, and a second urging means for urging a second piston to open and close a fluid passage in accordance with changes in resin pressure or fluid pressure. Injection molding equipment. (7) In the hollow article injection molding apparatus according to claim 6,
An apparatus for injection molding hollow objects, wherein the first biasing means is a compression spring that biases the first piston toward the nozzle hole of the nozzle cap. (8) In the hollow article injection molding apparatus according to claim 6 or 7, the second biasing means includes a compression spring that biases the second piston to move away from the nozzle hole of the fluid pipe, and a compression spring that biases the second piston to move away from the nozzle hole of the fluid pipe. 1. A hollow injection molding device comprising a second piston and the other piston rod of a second piston, which is provided with a diameter larger than that of a nozzle hole of a fluid pipe and whose tip end constantly projects into a heating cylinder. (9) The hollow article injection molding apparatus according to claim 6 or 7, wherein the second urging means is a pressure fluid that urges the second piston fluid pipe to approach the nozzle hole. Equipment for injection molding of objects. (10) The injection molding apparatus for hollow objects according to claim 6, 7, 8 or 9, wherein the nozzle hole of the fluid pipe is branched into a plurality of parts.