JPH0576901B2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention relates to a blow-molded pipe in which a part of a blow-molded pipe made of synthetic resin is provided with protrusions such as flanges or brackets for connecting or connecting with other parts. Relating to a method of manufacturing a tube.

(Prior art) Conventional methods for manufacturing this type of tube include injection molding and blow molding, especially those with protrusions such as flanges and brackets for attaching the tube to other objects, especially those with complicated shapes. A method for manufacturing a tube, for example, a known automobile manifold (see the shape of FIGS. 7 and 8), is to injection mold the entire tube, or to injection mold the protrusion separately in advance. Then, before blow molding the hollow molded part, set the injection molded protrusion part in a predetermined place in the blow mold, and then blow mold the hollow tube part and place the protrusion in this part. It is known how to insert

There is also a method of performing blow molding and injection molding of the hollow molded part and the protrusion part in the same mold at the same time or with a slight time difference, for example, in
It is known from Publication No. 199218. Alternatively, a method is known in which burrs formed during blow molding are used to form a bracket.

However, when injection molding is used to mold a large or elongated item in its entirety, the mold and injection molding machine become large, inefficient, and costly, making it impractical.

In the method of inserting injection molded protrusions during blow molding, the injection molding must be manufactured with high precision, and the work of setting these into the blow molding mold is quite tedious and difficult to automate. Moreover, since it has already been cooled, it must be heated again in order to fuse it with the blow-molded part, and the bonding force between these two parts is not sufficient.

Therefore, in order to improve the bonding strength, a method is known in which inserts are provided in the joint part of the injection molded product with recesses and holes for engagement, but this method increases the cost of molding this part and is not economical. It is not popular for some reason.

In addition, in the above-mentioned molding method in which injection molding and blow molding are performed simultaneously in the same mold, a part of the parison may expand into the injection mold part during blow molding, or the pressure during injection molding may cause the parison to expand. It may distort the previously formed blow-molded part, so it has not yet reached the point where practical molded products can be efficiently molded.

In addition, the method of using burrs during blow molding as brackets makes it easy to make products that extend in a direction that includes the axis of the hollow molded product, but it is impossible to make products that protrude in other directions, or the mold becomes extremely complicated, and protrusions The thickness is also controlled by the thickness of the parison, and cannot be molded to a desired thickness.

(Problems to be Solved by the Invention) This invention improves the drawbacks of the prior art as described above, uses a blow molding method and an injection molding method in combination, makes it possible to simplify the mold for the injection molded part, and It is an object of the present invention to provide a method for manufacturing a product with high bonding strength between a hollow molded part and a protrusion at a low cost by effectively utilizing thermal energy during blow molding.

(Means for Solving the Problems) The present invention provides that the tube after blow molding is at a solidification temperature sufficient for mold release in the blow molding die, and when the temperature decreases to a temperature close to this solidification temperature, the tube is The tube is released from the blow molding mold, and then the heated tube is fitted into an injection molding mold that has been preheated to an appropriate temperature and is made up of a partial mold that corresponds to the protrusions to be provided on the tube. At least one injection molding space for forming a protrusion is formed by a part of the wall surface of the pipe and the injection mold, and a synthetic resin can be thermally welded to the pipe in the injection molding space before the temperature of the rear pipe substantially decreases. The method for producing a blow-molded synthetic resin tube is characterized by injecting the tube, integrating the tube and the injection molding part in an injection mold, and then releasing the entire molded product from the injection mold.

(Example) A specific method of the present invention will be described below together with its apparatus.

First, blow molding machine A and injection molding machine B are placed close to each other. A blow molding die 20 for molding the tube 10 to be molded is attached to the blow molding machine A. On the other hand, the tube 10 after blow molding can be fitted or positioned in the injection molding machine B, and the tube 10 can be fitted or positioned.
An injection mold 30 is mounted in which an injection molding recess 31 is formed for forming the protrusion 11 to be connected to the holder.

These injection molding molds 30 are injection molding molds 33 that form only the flange portion and/or protrusion portion formed on the tube 10.

To carry out the method of the present invention using these devices, first, the parison P is supplied into the blow molding cavity 21 of the blow molding die 20 by the blow molding machine A, and a predetermined blow molded tube 10 is formed. Then, this tube 10 is inserted into the blow molding cavity 21 in the blow molding mold 20.
When the temperature of the tube 10 and the blow molding mold 20 has decreased to a temperature range (70° C. to 95° C.) that is close to this temperature and can be released from the mold, the tube 10 is released from the mold 20.

In addition, the mold release temperature is controlled by the solidification temperature of the resin to be blow molded, and if the solidification temperature is high,
Release the mold when cooled to around 90℃, or 70℃ for low-temperature products. For example, in the case of polyethylene, the temperature is 75℃ or lower.
A temperature of about 80℃ is desirable.

Next, the waste portions 12 at both ends of the tube 10 are quickly cut off, and the injection mold 30 installed in the injection molding machine B is preheated to at least 50°C.
The still warm tube 10 is fitted into the injection molded recess 31 of the tube.

This tube 10 is released from the blow molding die 20,
The means for moving it to the injection mold 30 may be manually operated by an operator, but a method using a working robot is safer and provides constant work efficiency.

Next, the injection mold 30 is clamped, and the tube 1 is sealed.
An injection molding cavity 32 for forming a protrusion is formed by a part of the tube 10 and the injection mold recess 31, and the injection molding space 32 is filled before the temperature of the tube 10 falls too much from the temperature range. An injection molding machine B injects a synthetic resin of the same quality as the tube 10 or a material that can be thermally welded, and integrally fuses and molds the protrusions 11 on a part of the tube 10 by injection molding. After cooling, the entire hollow molded product 15 with projections is removed from the injection mold 30 to obtain the desired hollow molded product 15.

In order to improve the adhesion between the tube 10 and the injection molded part, the present invention is the same even if an adhesive is applied to the joint surface before the tube 10 is set in the injection mold 30.

The injection mold 30 described above is a partial mold 33 that forms only a cavity 32 in which a protrusion and/or a protrusion 11 such as a flange is to be provided on the blow-molded pipe 10. A desired portion of the tube 10 is fitted into the mold 33. An intake manifold of an automobile engine or flanges 11 at both ends of a long pipe 10 and an intermediate 10
When forming the protrusion 16, both ends of the tube are fitted into two sets of injection molding partial molds 33 for flange molding, and an injection molding partial mold 33 for protrusion molding is fitted in the middle of the tube 10. (See Figures 5 to 8).

In the injection molding machine B described above, when there are several places to inject, the injection nozzle 38 at the tip 36 of the flexible pipe 35 connected from the extruder 34 is sequentially moved by a work robot to form the injection mold 30. Injection may be performed through the injection port 37, or the extruder 34 may be provided with several groups of injection nozzles 38 and the injection may be performed all at once.The present invention is the same.

(Effects) In the method of the present invention configured as described above, since the tube 10, which constitutes the main part of the molded product 15 to be molded, is molded by blow molding, a core is not required for molding this part. Unnecessary, then injection mold 3
Since the tube 10 is the main part of the hollow molded product 15 having the protrusion, the size of the part is generally large, and the special hollow molded product 1 is fitted into the hollow molded product 1.
With the exception of 5, even if there are several injection molded parts, only the work of fitting the only tube 10 into the injection mold 30 is required, even if the work is done manually.
Even if it is automated, the work hours will be extremely simplified.

Furthermore, since the injection molding die 30 is a partial mold 33 having only the portion where the protrusion 11 is located, the size of the injection molding die 30 can be reduced, and the manufacturing cost of the injection molding die 30 can be reduced. Furthermore, since a part of the injection molding cavity 31 is always constituted by the tube 10, the number of molds is smaller than that of the conventional injection molding mold in which the injection molded product is first molded and then inserted during blow molding. good.

In particular, in this method, since thermal energy during blow molding is effectively utilized, thermal economy is excellent and the bond between the blow molded part and the injection molded part is strong.

Therefore, in the method of the present invention, flanges at both ends of the tube, brackets that are flat in a direction perpendicular to the axis of the tube, or a part of the tube have a wall thickness of 16 mm, or a branch tube with a wall thickness of 17 mm.
can be easily molded.

[Brief explanation of the drawing]

The drawings show things related to the present invention, in which Fig. 1 is an external layout diagram showing an example of an apparatus for carrying out the method of this invention, and Fig. 2 shows a parison inserted into a blow molding die. 3 is a longitudinal sectional side view showing the state after blow molding, FIG. 4 is a longitudinal sectional side view of the hollow molded product released from the blow molding mold after blow molding, and FIG. 5 is a longitudinal sectional side view showing the state after blow molding. 6 is a longitudinal side view of the tube fitted into the partial mold.
The figure is a perspective view showing an example of a hollow molded product with projections to be molded, FIGS. 7 and 8 are perspective views showing examples of other flanges and a hollow molded product with projections, respectively.
9 is a partially vertical side view taken along the line 9-9 in FIG. 7. FIG. Main symbols in the diagram: A...Blow molding machine, B...
Injection molding machine, P... parison, 10... tube, 12
... Waste meat, 13 ... Flange, 14 ... Bracket, 15 ... Hollow molded product with protrusions, 20 ... Blow molding mold, 21 ... Blow molding cavity, 30
...Injection mold, 30a...Lower mold, 30b...
Upper mold, 31... Injection molding recess, 32... Injection molding cavity, 33... Partial mold.

Claims (1)

[Claims] 1. When the tube after blow molding is at a solidification temperature sufficient for mold release in the blow molding mold, and the temperature has decreased to a temperature close to this, the tube is removed from the blow molding mold. After the mold is released, the heated tube is fitted into an injection mold that has been preheated to an appropriate temperature and is made up of a partial mold only for the portion corresponding to the protrusion to be provided on the tube. At least one injection molding space for forming a protrusion is formed by the wall surface and the injection mold, and then a synthetic resin that can be thermally welded to the pipe is injected into the injection molding space before the temperature of the pipe substantially decreases. A method for manufacturing a synthetic resin blow molded tube, which comprises integrating the tube and the injection molding part in an injection mold, and then releasing the entire molded product from the injection mold. 2. The temperature at which the tube solidifies in its blow molding mold is sufficient for release from the mold, preferably between 75°C and 95°C.
A method for manufacturing a synthetic resin blow-molded tube according to claim 1, characterized in that the temperature is 80°C to 90°C.