JPH044932B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to blow molding for manufacturing hollow resin products, and in particular to a method for molding products in which at least one of both ends has an L-shape. .

BACKGROUND ART A hollow resin product having an L-shape at least one of its ends is used as a bumper for a vehicle. This vehicle bumper has an L-shaped part that wraps around the vehicle body at both ends, and the length of the part that curves to the side is about 180 mm or more. Incidentally, such a product is produced by blow molding as shown in FIG. That is, the thermoplastic resin heated to the plastic temperature from the nozzle 1 assumes a cylindrical shape and is suspended between the male mold 3 and the female mold 5. The cylindrical resin extruded from the nozzle 1 in this way is called a parison 7, and air is blown into the inside of this parison 7 from the air supply blowing port 2 provided in the nozzle 1, causing the cylindrical body to expand. It continues to hang down. When the parison 7 reaches the bottom of both molds 3 and 5, the supply of the parison 7 is stopped and the mold is clamped.
After that, at least one of both types 3 and 5,
Here, the air supply blowing port 4 provided on the male mold 3 is introduced into the parison 7, and air is blown into the parison 7 to inflate the parison 7 and make it stick sufficiently to the product surface of the mold. After the mold is cooled and the resin hardens, the mold is opened and the product is removed.

Problems to be Solved by the Invention However, in such a molding method, when the mold is clamped, for example, the parting portions 5a and 5b of the female mold 5 are removed from the parison 7, which is stationary because the supply is stopped. Although it bites in from the side, it does not slip much between parison 7,
The parison 7 is formed while locally stretching its thickness thinner. Therefore, if the part that curves sideways into an L-shape is less than 150 mm, it can be molded into one piece even if the wall thickness is thinner.
When the thickness is 180 mm or more, such as in a vehicle bumper, the thickness is less than 1/3 of the other parts, making it difficult to form one piece in terms of strength.

Therefore, in the past, the sideways curved part and the straight part were molded separately, and then assembled, which increased the number of molds, weight, and assembly man-hours, resulting in high cost and poor appearance. There was a problem that it was also bad.

Means for Solving the Problems Therefore, the first invention incorporates into the blow molding method a step of moving at least the male mold while supplying the parison during mold clamping, and the second invention This involves the process of pinching the tip of the parison and bending it along the male mold.

Effect The first invention employs the above steps,
The parison is not stretched locally, but is supplied by that amount to obtain a resin product having a substantially uniform wall thickness and an L-shaped portion at one end. In the second invention, by similarly adopting the above process, the female mold bites into the parison hanging downward away from the protruding part of the male mold, and before the parison is locally stretched, the male mold is formed in advance. The resin product is bent to fit the shape and has a substantially uniform thickness and L-shaped portions at both ends.

Examples Next, these inventions will be described based on the drawings. FIGS. 1 to 4 show an embodiment of an apparatus for carrying out the method of these inventions, and show the main parts of the blow molding apparatus.

1 is provided on one side of the male mold 3 and the female mold 5, and a thermoplastic resin shaped into pellets or the like is softened and melted in a heating section (not shown) to continuously supply a cylindrical parison 7. It's a nozzle. The nozzle 1 is provided with an air supply blowing port 2 for blowing air into the parison 7. The blow molding mold is a mold for molding a vehicle bumper which is a long hollow body having L-shaped portions at both ends, and is composed of a male mold 3 and a female mold 5. The mold clamping state is the state shown in FIG.
b is formed. And the parting line 6 is the shoulder part 3b, 3c which is connected to the middle and high part 3a of the male die 3.
It is located near the terminal. Male type 3 and female type 5
At least one of them, here male type 3 has 2
Air supply blow-in ports 4 are provided so as to be freely protrusive and retractable into the hollow portion 9, and are connected to an external air supply device (not shown). Further, on the opposite side of the mold from the nozzle 1, a pinching means 11 for pinching the parison 7 is provided. The pinching means 11 may be scissor-shaped with its tips opening and closing, or may be mechanical or manual, but it must be movable.

Next, a molding method using such an apparatus will be explained.

First, molding is performed using the following method.

As shown in FIG. 2, the male mold 3 and the female mold 5 are opened, and the nozzle 1 is located above the position between them.
The parison 7 is continuously supplied from the nozzle 1, hangs down between the molds 3 and 5, and is extended to the position shown by the two-dot chain line. During this time, air is constantly blown from the air supply blowing port 2 to prevent the parison 7 from being crushed. Next, as shown in FIG.
Crush it by squeezing it. Then, the tip is bent so as to follow the shoulder 3c of the male die 3, and at least the male die 3 is moved as shown in FIG. 4 while supplying the parison 7 to bring the two dies 3 and 5 closer to each other. In the figure, only the male mold 3 has been moved, and the parison 7 is moved to the left by the middle part 3a, and the parison 7 is successively placed on the shoulder part 3b.
comes into contact with each other. This contact process does not extend parison 7, but rather extends from nozzle 1 to parison 7.
is supplied and only the length necessary to place it on the shoulder portion 3b is replenished. Therefore, the parison 7 is not stretched in the state shown in FIG.
In addition, since air is fed in and the tip is narrowed or completely closed, the parison 7 is sufficiently inflated, and the parts of the parison 7 that are bent along the shoulders 3b and 3c are also prevented from collapsing. do not have. Then, the mold is clamped as shown in FIG. 1, and the air supply blowing port 4 is inserted into the parison 7 so as to break through the resin film of the parison 7, and air is blown from there. By clamping the mold, instead of cutting off the air from the air supply nozzle 2 on the nozzle 1 side, air is supplied from the air supply nozzle 4, increasing the internal pressure of the parison 7, and expanding the shape inside the mold. can be pasted on. At this time, almost the entire surface of the parison 7 is stretched while becoming somewhat thinner, like a balloon inflating. Therefore, the thickness is not localized but uniform throughout, and the thickness does not vary greatly. After cooling and the resin hardens, the mold is opened and the product is removed.

The above method is the second invention itself, and is applied to products with L-shaped portions on both ends, but in the case of products with L-shaped portions on only one side,
If the L-shaped portion is provided on the nozzle 1 side, there is no need for the step of sandwiching the parison 7 on the lower side and bending it toward the male mold 3 side. The first invention eliminates this step.

Effects As explained above, the first invention incorporates at least the step of moving the male mold while supplying the parison into the blow molding method, and the second invention further incorporates the step of moving the male mold while supplying the parison, and the second invention further incorporates the step of moving the male mold while supplying the parison. By incorporating the process of bending it along the curve, the following effects can be achieved.

It has become possible to integrally mold products with L-shaped parts that extend laterally by blow molding. The wall thickness is almost uniform throughout the product, and variations in wall thickness are also reduced, so a parison with an appropriate wall thickness commensurate with strength can be supplied from the nozzle. Therefore, the amount of resin used can be reduced, saving resources and making the product lighter. Furthermore, compared to the conventional method of making products by dividing them, the number of molds, molding time, weight, etc. are all reduced, and the appearance is improved.

[Brief explanation of drawings]

1 to 4 are schematic diagrams showing the main parts of a blow molding apparatus used to carry out the methods of the first and second inventions. Figure 3 shows the state in which the parison is being fed with the mold open, Figure 3 shows the state in which the tip of the parison is being held in the sandwiched state, and Figure 4 shows the state in which the parison is being fed and the lower end of the parison is along the male mold. FIG. 5, which shows a state in which the mold is being bent and clamped, is a schematic view showing the main parts of a blow molding apparatus in a conventional molding state. 1... Nozzle, 2, 4... Air supply blowing port, 3... Male type, 3a... Middle and high part, 3b, 3c...
...Shoulder, 5...Female type, 7...Parison, 11...
pinching means.

Claims (1)

[Scope of Claims] 1. A parison is supplied between the male and female molds while supplying air into the interior from a nozzle provided on one side of the male mold and the female mold, and at least the male mold is supplied with the parison while supplying the parison. The molds are moved to approach each other, and after the molds are clamped, an air supply blowing port provided in at least one of the molds is introduced into the parison to blow air into the parison. Resin molding method in blow molding. 2. Supply a parison between the male and female molds while supplying air inside from a nozzle provided on one side of the male mold and the female mold, sandwich the tip of the supplied parison, and place the tip of the parison between the male and female molds. Bending it along the mold, moving at least the male mold while supplying the parison to bring the molds closer to each other, and after clamping the mold, an air supply blower provided in at least one of the molds. A resin molding method in blow molding, characterized in that a mouth is introduced into the parison and air is blown into the parison.