JP3404108B2 - Manufacturing method of synthetic resin molded products - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a synthetic resin molded product having a hollow portion at least in part.

[0002]

2. Description of the Related Art Conventionally, in order to reduce the amount of burrs in a method of manufacturing a hollow double-walled molded product having one wall and the other wall facing each other with a gap, the applicant will explain the following. Suggested a method.

As shown in FIG. 9, an extruder 101 melts a thermoplastic resin, and a cylindrical parison 103 is extruded from an extrusion head 102 of the extruder 101, which is arranged between split molds 104 and 105. After that, the mold 10
4, 105 are clamped to each other by sandwiching portions 107 provided on the upper and lower ends of one die 104 in the figure and sandwiching portions (not shown) of the other die 105 facing the sandwiching portions 107. A first closing portion is formed at both openings in the axial direction of the parison 103 by sandwiching the parison 103, and then the pre-blowing of the parison 103 is performed to remove a part of the parison 103 near the four corners of the first closing portion. After moving inward of the cavity 110, the parison 10 is spaced from the first closure.
The second closed portion is formed by projecting the moving members 106 provided in the axially inner portion of the third mold 105 near the upper and lower ends of the other mold 105 toward the respective communicating portions 108 of the one mold 104. Along with the formation, a pressurized fluid is further introduced into the parison 103 to carry out main blow and molding along the cavity 110 (Japanese Patent Laid-Open No. HEI 5-1993).
No. 64835).

[0004]

However, in the above-mentioned conventional technique, the cylindrical parison is spaced apart in the axial direction.
Since the second closures are formed inside the first closures formed at the points and between the first closures, respectively, burrs are formed between the first closures and the second closures. Will occur. Further, since it is difficult to arrange the outer surface of the cylindrical parison near both side portions of the cavity, it is not possible to manufacture a synthetic resin molded product having a rising wall as described later, especially in recent years. It has not been possible to manufacture a synthetic resin molded product having a thin wall thickness (thickness measured in a direction perpendicular to the wall surface with respect to one wall and the other wall facing each other) as required.

The present invention has been made in view of the above problems of the prior art, and it is possible to reduce the amount of burrs and to mold a synthetic resin molded product having a thin rising wall. It is an object of the present invention to realize a method for producing a synthetic resin molded product capable of achieving the above.

[0006]

In order to achieve the above object, in the method of manufacturing a synthetic resin molded product of the present invention, a split type mold having a flat cavity whose volume can be changed is opened. , A thermoplastic resin is melted by an extruder, and a cylindrical parison is extruded from the extrusion head, and the cylindrical parison is arranged between the molds opened, and the mold closing is started to set the axial distance of the cylindrical parison. By forming a sealed parison with both axial ends closed by sandwiching the two places, the sealed parison is housed in the cavity, and then negative pressure is applied to the vicinity of the side of the cavity. The side of the sealing parison is brought close to the side of the cavity, and further the mold closing is performed to reduce the volume of the cavity, thereby compressing the sealing parison and increasing the internal pressure. It is characterized in that the hollow molding along the Yabiti.

Further, at least 1 is provided on the cavity surface of the mold.
The recesses are provided, and at least one hollow protrusion is formed on the synthetic resin molded product by the recess, and the portion other than the hollow protrusion compresses the sealed parison when the volume of the cavity is reduced. And close it.

[0008]

In addition, in each of the above-mentioned manufacturing methods, the cavity is shaped such that its peripheral portion has a bent portion bent in the same direction as the opening and closing direction of the mold, and a synthetic resin molded product having a rising wall in the peripheral portion is provided. Mold.

[0010]

When a sealed parison is formed by sandwiching two axially-spaced cylindrical parisons with both axial ends closed, the side of the sealed parison does not pinch off, so the sealed parison is sealed. No burrs on the sides of the parison.
In addition, the side of the sealing parison is brought close to the side of the cavity due to the negative pressure of the peripheral portion of the cavity, and then the inner side of the cavity is closely attached to the side of the cavity with a slight deformation amount due to the increase of the internal pressure of the sealing parison. Therefore, the moldability becomes good.

[0011]

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

First, a split type mold used for carrying out the first embodiment will be described.

As shown in FIG. 1, the split type mold has one mold 3 having a concave cavity surface 6 and a convex cavity surface at the tip of a protrusion 4b protruding from the flange 4a. The other mold 4 provided with 7 and a frame-shaped slide mold 5 surrounding the outer peripheral surface of the protruding portion 4b are provided.

The slide mold 5 has guide rods 8 projecting from four corners of the surface opposite to the cavity surface 5b, and the guide rods 8 are provided in the four corners of the flange portion 4a. 9
It is slidably fitted in and the spring 10 is interposed between the slide die 5 and the flange portion 4a, so that it is always urged toward one of the dies 3 by its elastic force, and when the die is opened. In the state where external force such as
A part of the stepped portion 4d provided on the outer peripheral surface comes into contact with the stepped portion 4d to stop at that position, and when an external force is applied during mold clamping or the like, the stepped portion 4d moves toward the flange portion 4a.

Incidentally, the slide mold 5 may be at least divided into two parts, which are assembled to the protrusion 4b and then integrated by a fixing means such as a screw.

Also, the concave cavity surface 6 of one mold 3
The both ends of the parison 2 in the axial direction (upper and lower ends in the drawing) are formed with pinch-off portions 3a, and the slide die 5 is formed with pinch-off portions 5a facing the respective pinch-off portions 3a. , At least one convex portion 7a and concave portion 7 are provided on the tip surface of the protruding portion 4b of the other mold 4.
A trapezoidal convex cavity surface 7 having b is formed.

Further, as shown in FIG. 3, one die 3, the slide die 5 and the other die 4 are opened at one end side in the vicinity of both sides of a flat-shaped cavity formed by these during die clamping. Many vacuum suction holes 11a, 11
b and 11c are respectively provided along both sides of the cavity, and the vacuum suction holes 11a, 11b and 11 are provided.
The other end of c is configured to communicate with a vacuum generation source such as a vacuum pump (not shown) through communication passages 12a, 12b, 12c, respectively.

In addition, a cavity 4 provided inside the other mold 4
Inside c, there is provided a sliding member 13 having a nozzle 14 which is communicated to the outside by a passage (not shown). It is configured to be movable in the direction. As a result, the tip of the nozzle 14 is attached to the nozzle insertion hole 7c provided between the recess 7b and the space 4c.
It can be made to project in the recessed part 7b through.

Next, each step of the first embodiment of the method for producing a synthetic resin molded product according to the present invention will be described.

As shown in FIG. 1, a split-type mold comprising one mold 3 and the other mold 4 having a slide mold 5 is opened, and a thermoplastic resin is melted by an extruder (not shown). Then, the cylindrical parison 2 is extruded from the extruding head 1, the parison 2 is placed between the molds of the split type that are opened, and the lower end of the parison 2 is welded and sealed by a known means. A so-called pre-blow in which a predetermined amount of pressurized fluid is pressed by a blowing means or the like provided inside the extrusion head 1 is performed.

Then, the mold closing is started and one mold 3 and the other mold 4 having the slide mold 5 are brought closer to each other, whereby the pinch-off portion 3 of the one mold 3 is closed.
a and the pinch-off portion 5a of the slide die 5 sandwich and close the two locations of the parison 2 which are spaced apart in the axial direction,
Form a sealed parison 2a (see FIG. 3) with both ends closed.

After the above steps, by closing the mold, as shown in FIG.
Is pressed and flattened between the concave cavity surface 6 and the convex cavity surface 7, and the tip surface of one mold 3 and the slide mold 5 are
Of the concave cavity surface 6 and the convex cavity surface 7 are sealed by the cavity surface 5b of the slide mold 5 so that the volume can be changed and the peripheral area can be changed. While forming a cavity having a bent portion that is bent in the same direction as the mold opening and closing direction,
The sealed parison 2a is housed in the cavity.
At this time, each of the communication passages 12a, 12b, 12c is communicated with the vacuum generation source so that each of the vacuum suction holes 11a, 11b, 11
Vacuum suction is performed via c and negative pressure is applied to the vicinity of both sides of the cavity whose volume can be changed, so that both sides of the sealed parison 2a are brought close to both sides of the cavity.

As described above, in order to reduce burrs, it is preferable that there is no pinch-off portion on both sides of the sealed parison 2a. However, in the present invention, there is no pinch-off portion on one side of the sealed parison 2a. , It is also possible to vacuum suction that part.

In the present embodiment, the cavity is set to have a shape in which the peripheral portion has a bent portion for forming a rising wall that is bent in the same direction as the opening and closing direction of the mold, but the shape of the cavity is The shape is not limited to this, and may be a shape corresponding to the shape of the synthetic resin molded product.

After the above steps, when the mold closing process is further advanced to bring the one mold 3 and the other mold 4 closer to each other, the volume of the cavity is reduced and the slide mold 5 is moved to the other side. It is pressed against the flange portion 4a by the mold 3, and as shown in FIG. 4, moves to a position where it abuts the flange portion 4a against the elastic force of the spring 10. In the meantime, the sealed parison 2
Since a is compressed and its internal pressure increases, the sealed parison 2a moves (deforms) toward every corner of the cavity whose volume is reduced. At this time, as shown in FIG.
3 is moved by the reciprocating drive means in the direction of the arrow shown in the drawing, and the nozzle 14 is inserted into the projection 21 formed, whereby the excess pressurized fluid in the sealed parison 2a is discharged to the outside through the nozzle 14 and the internal pressure is increased. Lower. By this step, a hollow protrusion 21 is formed in a part of the other wall 20b along the recess 7b, and the other part is compressed to compress the one wall 20a and the other wall 20b.
Is closely adhered, and a synthetic resin molded product having the rising wall 20c is hollow-molded.

After cooling, the mold is opened and the synthetic resin molded product is taken out.

FIG. 5 shows an example of a synthetic resin molded product manufactured according to this embodiment, in which the rising wall 30c has a thin wall thickness D and a hollow foolproof projection 31, a pocket projection 32, and a hollow projection 32. Although it has a bracket protrusion 33, in this case, a concave portion for forming a foolproof protrusion 31, a pocket protrusion 32 and a bracket protrusion 33 is formed on the convex cavity surface. A mold formed on each convex cavity surface is used.

Not only the example shown in FIG. 5 but also various hollow protrusions can be formed by providing a concave portion for forming a hollow protrusion having any desired shape on the convex cavity surface. It is possible to manufacture a synthetic resin molded article having the same.

Next, each step of the second embodiment of the method for producing a synthetic resin molded product of the present invention will be described.

In this embodiment, a synthetic resin molded product having a hollow double-wall structure having one wall and the other wall facing each other with a space as described later is hollow-molded, and is used for carrying out the molding. As shown in FIGS. 6 to 8, in the split type mold, one mold 3 has a concave cavity surface 46 having a relatively large volume, and the other mold 4 has a flat convex cavity surface 47. That is, that is, the reduced volume of the cavity is a size that regulates the outer surface of a hollow double-walled synthetic resin molded product that has one wall and the other wall that face each other at a distance. However, since it is different from the split type mold used for the implementation of the first embodiment and the other parts may have the same configuration, the same reference numerals are given and the description thereof is omitted.

Similar to the first embodiment, a split type mold comprising one mold 3 and the other mold 4 having the slide mold 5 is opened, and the thermoplastic resin is loaded by an extruder (not shown). A cylindrical parison 2 which is melted and is extruded from the extruding head 1 is disposed between the molds of the split type opened, and the lower end of the parison 2 is welded and sealed by a known means, and the extruded head 1 is internally provided. Pre-blow is performed by the blowing means.

Then, the die closing is started and the one die 3 and the other die 4 having the slide die 5 are brought closer to each other, whereby the pinch-off portion 3 of the one die 3 is moved.
a and the pinch-off portion 5a of the slide die 5 sandwich and close the two positions of the parison 2 which are spaced apart in the axial direction,
Form a sealed parison 2a (see FIG. 7) with both ends closed.

After the above steps, by closing the mold, the sealed parison 2a is formed as in the first embodiment.
Is flattened, and as shown in FIG. 7, the tip end surface of one die 3 and the tip end surface of the slide die 5 are brought into contact with each other to form a space portion formed by the concave cavity surface 46 and the convex cavity surface 47. Is sealed by the cavity surface 5b of the slide mold 5, the volume can be changed, and a cavity having a bent portion that is bent in the same direction as the mold opening and closing direction is formed in the peripheral portion, and the sealing parison 2a is Store in the cavity. At this time, each communication passage 12a, 12b,
12c is communicated with the vacuum source and each vacuum suction hole 11
Vacuum suction is performed via a, 11b, and 11c, and negative pressure is applied to the vicinity of both sides of the cavity whose volume can be changed, so that both sides of the sealed parison 2a are brought close to both sides of the cavity.

After the above steps, when the mold closing process is further advanced to bring the one mold 3 and the other mold 4 closer to each other, the cavity is contracted and the slide mold 5 is used for the one mold 3. By flange 4
It is pressed toward a and moves to a position where it abuts the flange 4a against the elastic force of the spring 10, as shown in FIG.

After the above steps, the sealed parison 2a
A pressurized fluid such as air or an inert gas pressurized by a method such as inserting a blowing means such as a blowing needle into the inside is introduced and expanded along the entire surface of the reduced cavity.

By this step, a synthetic resin molded product having a hollow double-wall structure having one wall 60a and the other wall 60b facing each other with an interval in which the hollow portion 60d extends over the whole including the rising wall 60c is obtained. .

After cooling, the mold is opened and the synthetic resin molded product is taken out.

Although the pre-blowing is performed before the mold is closed in each of the above-mentioned embodiments, the pre-blowing is not necessarily required when the expansion ratio of the parison is small.

In the present invention, the type of thermoplastic resin, the use of the molded product, the cross-sectional shape of the cylindrical parison (circular, flat,
The partially thick-walled shape) and the like are not limited to those in the above-mentioned embodiment. In the present invention, it is useful as a method for producing a synthetic resin molded product that is required to have appearance, rigidity, and lightness, as well as to improve appearance by preventing burr removal traces. Particularly, ABS resin, polyphenylene ether resin, polycarbonate It is useful as a method of manufacturing a housing panel of an electronic device such as an air conditioner, a printer, a copying machine, a computer, which is made of a hard thermoplastic resin such as polyamide or polypropylene.

[0040]

Since the present invention is configured as described above, it has the following effects.

Since the amount of burrs generated is significantly reduced, the yield of the molding material is improved and a synthetic resin molded article having a good appearance can be obtained.

Further, by making the side of the cavity negative and vacuuming the parison, the side of the parison is brought closer to the side of the cavity and the amount of deformation of the pressurized fluid due to the internal pressure is reduced. The moldability is improved, and as a result, it becomes possible to hollow-mold a synthetic resin molded product having a thin wall and a rising wall.

[Brief description of drawings]

FIG. 1 is a schematic front view showing one step of the first embodiment of the present invention and showing a state in which parison is extruded from an extruding head between molds of a split type in which molds are opened.

FIG. 2 is a plan view of the mold showing a state immediately after starting the mold closing of the split type mold after performing pre-blowing after the step shown in FIG. 1;

FIG. 3 shows a state in which a cavity whose volume can be changed by further closing the mold after the step shown in FIG. 2 is closed is sealed,
It is a principal part sectional drawing which follows the AA line of FIG.

FIG. 4 is a cross-sectional view of a main part taken along the line AA of FIG. 1, showing a state where the mold closing is completed and the volume of the cavity is reduced after the step shown in FIG.

FIG. 5 is a schematic plan view showing an example of a synthetic resin molded product manufactured according to the first embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view showing one step in the second embodiment of the present invention and showing a state in which parison is extruded from an extruding head between molds of a split type in which the molds are opened.

FIG. 7 is a sectional view taken along the line BB of FIG. 6, showing a step in the second example of the present invention, showing a state in which a cavity whose volume can be changed by advancing mold closing is closed.

8 is a cross-sectional view of main parts taken along the line BB of FIG. 6 showing a state where the mold closing is completed and the volume of the cavity is reduced after the step shown in FIG. 7.

FIG. 9 is a schematic perspective view of a blow molding machine for explaining a conventional example.

[Explanation of symbols] 1 extrusion head 2 Parisons 2a sealed parison 3 One mold 3a, 5a Pinch off section 4 Other mold 5 slide type 5b Cavity surface 6,46 concave cavity surface 7,47 Convex cavity surface 8 guide rod 9 guide holes 10 springs 20a, 60a One wall 30,60 Synthetic resin molding 20b, 30b, 60b The other wall 20c, 30c, 60c Rising wall 31 Proof part for foolproof Projection for 32 pockets 33 Projection for bracket

Claims (3)

(57) [Claims] 1. A mold in which a split type mold having a flat-shaped cavity whose volume can be changed is opened, a thermoplastic resin is melted by an extruder, and a cylindrical parison is extruded from an extrusion head of the mold. It is arranged between the opened molds, and the mold closing is started to sandwich two axially spaced intervals of the cylindrical parison to form a sealed parison with both axial ends closed. The sealed parison is housed in the cavity, and then a negative pressure is applied to the side of the cavity to bring the side of the sealed parison close to the side of the cavity, and further mold closing is performed to advance the mold closing. A method for producing a synthetic resin molded product, characterized in that the volume of the cavity is reduced to compress the sealed parison to increase the internal pressure and hollow molding is performed along the cavity. 2. A cavity surface of a mold is provided with at least one recess, and the recess forms at least one hollow protrusion on the synthetic resin molded product, and a portion other than the hollow protrusion is formed. 2. The method for producing a synthetic resin molded article according to claim 1, wherein the sealed parison is compressed and brought into close contact when the volume of the cavity is reduced. 3. The cavity is shaped so that a peripheral portion thereof has a bent portion that is bent in the same direction as the opening and closing direction of the mold, and a synthetic resin molded product having a rising wall in the peripheral portion is molded. The method for producing a synthetic resin molded article according to claim 1 or 2 .