JP4224741B2 - Blow molding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a blow molding how.
[0002]
[Prior art]
An external contour that conforms to the cavity defined inside the mold by hanging down the parison softened by heating and pinching it between the two molds and forcibly blowing air into the parison Blow molding methods for producing blow molded articles having the following are widely implemented. For example, as shown in FIG. 6, the tube-shaped parison 10 is extruded and suspended by an extruder, and the parison 10 softened by heating is clamped by a pair of blow molding dies 12 and 14 that open and close left and right. By blowing high pressure air into the parison 10, the parison 10 swells inside the cavity 16 defined by both molds 12 and 14, and has a blow contour having an external contour that matches the cavity 16. A molded product 18 is obtained. The blow molded product 18 in the illustrated example is, for example, a bottle as a beverage container.
[0003]
In the example shown in FIG. 6, the suspended parison 10 is completely accommodated in the cavities 16 of both molds 12 and 14, so that a part of the parison 10 protrudes to the outside of both molds 12 and 14. There is no. However, even with the same blow-molded product, for example, a spoiler that is attached to the rear part of a passenger car and suppresses the floating of the vehicle body during high-speed running is a molding die that uses a part of the parison as an extra peripheral part during the blow molding. It is designed to erode out to the outside. The present invention relates to the case where the peripheral edge of the parison protrudes outward from the mold when the parison is clamped by the mold as described above. The procedure for manufacturing the spoiler will be described next.
[0004]
FIG. 7 is a cross-sectional view of blow molding dies 12 and 14 for producing the spoiler 18 as a blow molded product. The molds 12 and 14 are formed with a cavity 16 that matches the outer contour of the spoiler 18 when the mold is clamped. The tube-shaped parison 10 has a size that is considerably larger than the lateral width of the cavity 16 when the parison 10 is flattened. Accordingly, when the parison 10 is clamped by the two molds 12 and 14, the excess peripheral edge portion 10a protrudes outward from the molds 12 and 14, as shown in FIG. The excessive peripheral edge portion 10a is removed from the spoiler 18 as a molded product by trimming after the blow molding is completed.
[0005]
In FIG. 7, circle A indicates a portion where both molds 12 and 14 pinch the parison 10. 8 to 11 show the behavior of the parison 10 with the progress of mold clamping of the molds 12 and 14 with respect to the portion surrounded by the circle A. FIG. That is, as shown in FIG. 8, when the molds 12 and 14 start to tighten, the clamping parts 12a and 14a of each mold start to clamp the parison 10 from the left and right. In addition, although the width dimension of the said clamping parts 12a and 14a is various according to the kind of metal mold | die, generally it is set to about 2 mm. As shown in FIG. 9, when the molds 12 and 14 completely pinch the parison 10 (high-pressure air is blown into the parison 10 at this stage), and the pinching further proceeds as shown in FIG. The resin portions sandwiched between the parisons 10 start to escape to the inside and outside (the side where the excess peripheral edge portion 10a is present) of the blow molded product. Therefore, at the stage where the air blowing is completed, as shown in FIG. 11, a resin escape portion 18 a that slightly protrudes inside and outside the blow-molded product is formed at the die clamping portion of the parison 10.
[0006]
[Problems to be Solved by the Invention]
When the molds 12 and 14 are opened after blow-up in FIG. 11 and the spoiler 18 as a blow-molded product is taken out, the above-described excess peripheral edge portion 10a is still connected to the spoiler 18. An operation of trimming and separating 10a is necessary. FIG. 12 shows a cross section of the spoiler 18 immediately after the trimming. As shown in FIG. 11, a concave relief portion 18 a fitted inside the spoiler 18 is formed at a portion where the peripheral edge portion 10 a is trimmed from the spoiler 18. If there is a concave portion on the outer surface of the spoiler 18 in this way, the design and appearance are inferior, and therefore, for example, there is a step of cutting until the concave portion disappears with sandpaper. In addition, there is an operation of trimming the excess peripheral edge portion 10a from the spoiler 18, which both increases the cost due to bothering the operator's hands.
[0007]
In such a case, it has been found that if the width dimension of the clamping portions 12a and 14a in each mold is changed from the current 2 mm to 1 mm, the above-mentioned defects described with reference to FIG. 12 are alleviated. On the other hand, however, this measure is not effective because it leads to a more serious problem that the strength of the blow molding dies 12 and 14 is reduced due to the thinning of the clamping parts 12a and 14a.
[0008]
OBJECT OF THE INVENTION
The present invention has been proposed to suitably solve the above-described problems, and a part of the parison sandwiched between the molding dies at the time of blow molding protrudes to the outside of the mold as an excess peripheral edge. In the product, the peripheral part is cut off from the blow-molded product at the end of molding, so that the trimming operation is not required, and the part after the peripheral part is cut off is smoothed and a step of grinding with sandpaper or the like is also required. without, therefore an object of the invention to provide a blow molding how that can be cheaply reduce the manufacturing cost.
[0009]
[Means for Solving the Invention]
In order to overcome the above-mentioned problems and achieve the intended object, the present invention is configured to sandwich a heated and softened parison between two molds, and to place an excess peripheral edge of the parison on the outside of the mold. In a blow molding method for producing a blow molded product having an outer contour that matches the cavity of the mold by blowing out and blowing air into the parison and inflating,
In the required timing clamping by the mold has progressed, heating the pressing portions of the mold adjacent to the peripheral edge portion of the excess over the resin softening point of the parison,
The inside of the blow-molded product is forcibly pressed toward the cavity of the mold by the heating of the clamping part in the mold and the pressure of the air blown into the parison, and the heating from the parison together with the heating It is characterized in that the excess peripheral edge is eaten away.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Then attached to the blow molding how according to the present invention, by way of preferred embodiments will be described below with reference to the accompanying drawings. In addition, about the member already demonstrated regarding FIGS. 6-12, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.
[0012]
FIG. 1 is a cross-sectional view of the main parts of blow molding dies 12, 14 for carrying out the blow molding method according to the present invention. The molds 12 and 14 are basically the same as the molds described with reference to FIG. 7, but when the molds 12 and 14 are closed and the parison 10 is clamped, the excess peripheral portion A heating source 20 such as an electric heater is disposed in the clamping portions 12a and 14a of the molds 12 and 14 adjacent to 10a. As the electric heater 20, a sheathed heater in which a heating element such as a nichrome wire is covered with a tube through an insulator, an aluminum embedded tubular heater in which a sheathed wire is embedded in an aluminum shell, or the like is preferably used. By applying a required voltage to the electric heater 20, the vicinity of the pinching portions 12 a and 14 a can be heated above the softening point of the resin constituting the parison 10. As shown in FIG. 1, the electric heater 20 is disposed at the outer peripheral portion located on the opposite side of the cavity 16 from the clamping portions 12 a and 14 a of the blow molding dies 12 and 14. Alternatively, it may be embedded in the clamping parts 12a, 14a or may be externally attached to the clamping parts 12a, 14a.
[0013]
The molds 12 and 14 are provided with a cooling water circulation pipe 22 as shown in FIG. 1, so that the vicinity of the pressing portions 12a and 14a can be rapidly cooled as required. Instead of the cooling water circulation pipe 22, a water jacket may be provided on the molds 12 and 14.
[0014]
A process of manufacturing a blow molded product 18 such as a spoiler from the parison 10 using the molds 12 and 14 configured as described above will be described. FIG. 2 shows an initial stage in which the pre-heated and softened parison 10 is clamped by the molds 12 and 14. At this time, high-pressure air is blown into the parison 10, and the parison 10 swells and comes into close contact with the cavity 16 of the molds 12 and 14 from the inside. At this time, the electric heater 20 is not energized yet.
[0015]
Next, as shown in FIG. 3, energization of the electric heater 20 is started at a required timing when the mold clamping by the blow molding dies 12, 14 has progressed. At this time, the high-pressure air is still blown into the parison 10. When the clamping portions 12a and 14a of the molds 12 and 14 are heated by the heat generated by the electric heater 20, and the temperature exceeds the resin softening point, the parison 10 in contact with the clamping portions 12a and 14a is softened by the resin. To come. Further, the vicinity of the pinched portion where the parison 10 is softened is forcibly pressed toward the pinching portions 12a and 14a by the pressure of the air blown into the parison 10. In this state, when the mold clamping by the molds 12 and 14 further proceeds, the clamping parts 12a and 14a of the molds 12 and 14 bite the excess peripheral edge part 10a from the parison 10. The separation line PL generated on the surface of the blow molded product 18 when the excess peripheral edge portion 10a is cut off becomes extremely smooth as shown in FIG. That is, at the end of blow molding, the surplus peripheral edge is cut off from the blow molded product, so trimming is not necessary, and the part after the peripheral edge is cut off is smoothed, so it is scraped with sandpaper or the like. A post-process is also unnecessary. Therefore, the manufacturing cost can be kept low.
[0016]
Next, energization of the electric heater 20 is stopped, and cooling water is circulated through the pipes 22 disposed in the molds 12 and 14 as shown in FIG. The parts 12a and 14a are rapidly cooled. As a result, the periphery of the separation line PL in the spoiler 18 after the excess peripheral edge portion 10a is cut off is rapidly cooled below the resin softening point. Therefore, the part of the separation line PL smoothed as described above is cured as it is, and is not deformed again before and after demolding to form a recess. Thereafter, the circulating supply of cooling water to the pipe 22 is stopped, and the molds 12 and 14 are opened as shown in FIG. 5 to obtain the spoiler 18 as the final molded product. As described above, the spoiler 18 does not require trimming work because the excess peripheral edge has already been cut off. Further, since the part of the separation line PL in the spoiler 18 is smooth, there is an advantage that a post-process for cutting with a sandpaper or the like is not required.
[0017]
In the illustrated embodiment, the electric heater 20 is energized at a required timing after high-pressure air is blown into the parison 10. However, the present invention is not limited to this. After clamping, the electric heater 20 is energized in advance to heat the clamping parts 12a, 14a to a temperature higher than the resin softening point, and then high-pressure air is blown into the parison 10 at a required timing. Also good.
[0018]
【The invention's effect】
As described above, according to the blow molding how according to the present invention, in which the following beneficial effects are obtained.
(1) When the blow molding with the mold is completed, the excess peripheral edge portion is cut off from the blow molded product, so that a trimming operation as a post process is not required.
(2) Since the obtained blow-molded product has a smoothed portion after the excess peripheral edge portion is cut away, a post-process for cutting with sandpaper or the like is not required.
(3) By eliminating the need for a post-process in this way, the manufacturing cost for performing the blow molding method can be kept low.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view showing a pinching portion of a blow molding die for performing a blow molding method according to the present invention.
2 is a partially enlarged cross-sectional view showing an initial stage in which a softened parison is clamped by a blow molding die shown in FIG. 1. FIG.
FIG. 3 is a partial enlarged cross-sectional view showing a state in which energization to the electric heater is started at a required timing when mold clamping by a blow molding die proceeds.
FIG. 4 is a partially enlarged view showing a state in which the periphery of the separation line in the spoiler is cooled below the resin softening point by circulating cooling water through a pipe disposed in the mold and rapidly cooling the clamping portion. It is sectional drawing.
FIG. 5 is a partially enlarged cross-sectional view showing a state where a spoiler as a final molded product is obtained by opening a mold.
FIG. 6 is a schematic explanatory view showing a general blow molding method.
FIG. 7 is a cross-sectional view of a blow molding die for producing a spoiler as a blow molded product.
8 is a partial enlarged cross-sectional view showing an initial stage in which the parison is started to be clamped from the left and right sides by the blow molding die shown in FIG. 7;
9 is a partially enlarged cross-sectional view showing a stage in which the mold completely clamps the parison from the stage shown in FIG. 8. FIG.
10 is a partial enlarged cross-sectional view showing a stage in which the clamping pressure of the parison by the mold further proceeds from the stage shown in FIG. 9. FIG.
11 is a partial enlarged cross-sectional view showing a state in which air blowing into the parison shown in FIG. 10 has been completed and a resin escape portion has been formed at a pinched portion of the parison.
12 is a partially enlarged cross-sectional view showing a state after a mold is opened from the state of FIG. 11 and a spoiler is taken out and an excess peripheral edge portion is trimmed from the spoiler.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Parison 10a Excess peripheral part 12,14 Blow mold 12a, 14a Clamping part 16 Cavity 18 Blow molding (spoiler )

Claims (2)

The parison (10) softened by heating is clamped between the two molds (12, 14), and the excess peripheral edge (10a) of the parison (10) is placed on the mold (12, 14). Blow-molded product (18) having an outer contour matching the cavity (16) of the mold (12, 14) is produced by protruding outward and blowing air into the parison (10). In the blow molding method,
At the required timing when the mold clamping by the mold (12, 14) proceeds, the clamping part (12a, 14a) of the mold (12, 14) adjacent to the surplus peripheral edge (10a) is moved to the parison. Heat above the resin softening point of (10),
The inside of the blow-molded product (18) is placed inside the mold (12, 14) by heating the clamping parts (12a, 14a) in the mold (12, 14) and the pressure of air blown into the parison (10). 14) A blow molding method characterized by forcibly pressing toward the cavity (16) of 14) and simultaneously cutting off the excess peripheral edge (10a) from the parison (10) by the heating. Heating is stopped after heating the clamping part (12a, 14a) of the mold (12, 14), and then the vicinity of the clamping part (12a, 14a) of the mold (12, 14) is the parison ( The blow molding method according to claim 1, wherein the blow molding method is rapidly cooled to below the softening point of 10) .

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