JPH0444828A - Blow molding of synthetic resin hollow body with rib therein and mold apparatus for its method - Google Patents

Abstract

PURPOSE:To prevent a molded rib from inclining and occurrence of deformation such as strain by blowing a fluid in a parison under a condition wherein cores are forwarded and projected to a molding face side and thereafter retreating successively each divided core at least by two stages. CONSTITUTION:Cores 2a and 2b are forwarded by a specified amt. in the inside of a mold 1a and a compressed air is blown therein. A parison P is tightly adhered to the inner face of molds 1a and 1b and the cores 2a and 2b in such a way that it is tightly pressed against them to all the corners. Then, before the parison P is solidified, the cores 2a and 2b are successively retreated. At first, a free end part 2a' of the core 2a is retreated by actuating a hydraulic cylinder 6a in such a way that it is made at the same plane as the inner face of the mold 1a. Then, by actuating another hydraulic cylinder 6b, the remaining core 2b is retreated in the same way as the core 2a. As the result, a rib is formed by cores 2a and 2b divided into two. In this case, a synthetic resin at a position integrally press-adhered by the previously retreated core 2a supports a synthetic resin at a position of the afterward retreating core and prevents it from deformation such as inclination thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is directed to an automobile gas tank (hereinafter also simply referred to as a tank), which has a baffle inside.
The present invention relates to a method of blow molding a hollow body having ribs such as the above, and a mold device used in the method.

(Prior art, etc.) Conventionally, in blow molding, a parison is placed between a pair of molds (molds), the mold is closed, a pressurized fluid such as compressed air is blown into the mold, and the parison is cooled and solidified. By opening the mold, the desired hollow body is formed.

In this case, it is not easy to mold the hollow body with protruding ribs (7) with high precision.For this reason, conventionally, for example, when blow molding a tank equipped with a wave prevention plate as a hollow body, First, a hollow body (tank body) is manufactured,
After that, separately manufactured 1. A method of attaching a predetermined wave shielding plate (rib) using adhesive or screws is adopted.

In response to this, the applicant of the present application has previously filed an application for the following technology.
Molding 1 and 2 Attach a core that has a shape that corresponds to the wave blocking plate to be used. Then, this core is advanced to the molding 1m side of the mold 1. In the protruding state, a fluid such as compressed air is blown into the inside of the parison, and then the wave breaking plate is integrally formed by moving the T-a back. be.

In this technique, after the mold is closed, when the above fluid is blown into the inside of the parison, the surface of the parison IA mold and It has the shape of a product.

Then, when the core is moved back, the unassimilated synthetic resin that tightly wraps around the core is not compressed by the pressure of the fluid as the core moves back, so it is stopped.

This results in ribs (
A hollow body (tank) is manufactured which is integrally equipped with a wave shielding plate inside.

(Problem to be Solved by the Invention) In the above method, when the core retreats from the inside of the mold (the molding surface side), it comes into close contact with the mold.

At the same time, the synthetic resin that is inside is also subject to the effect of retreating due to friction. In this case, if the core itself is slightly tilted, for example due to poor precision, the synthetic resin that comes into close contact with it will be crimped while being subjected to the force of being twisted due to the tilt. It will be done. For this reason, there is a problem in that the molded ribs tend to tilt to one side or undergo deformation such as distortion.

In other words, the accuracy of the ribs formed by this method greatly depends on the mold used and the accuracy of the lA.
However, there is a problem in that the accuracy is unstable and it is difficult to make it stand upright with high precision.

Furthermore, since the ribs tend to sag somewhat due to their own weight before assimilation, high-precision ribs are molded in this aspect as well.

′: There is a problem that it is difficult.

In the case of a beam-like rib that protrudes in the horizontal J direction with a bias s1i, 1. ,! , this tendency is unsophisticated, especially
The thinner the cross-sectional shape and the longer the rib (may be -2), the more difficult it is to form ribs with high precision. If the mold and ribs are set so that they are not affected by gravity during molding, the ribs that can be molded and the rotation of the hollow body will be limited. In view of these problems, the present invention aims to provide a blow molding technique that can form a hollow body with high-precision ribs inside using a single burr saw and process. .

(Means for Solving the Problems) In order to achieve the object described above, the present invention involves closing a parison with a human hand during the molding process, and inserting a mold into the inside of the parison. In a blow molding method in which a predetermined hollow body is formed by blowing a fluid such as air into a pressurized F, a pressure of 2
, has a shape corresponding to the rib to be molded, and can move forward and backward with respect to the molding surface side of the mold,
A core divided into a plurality of pieces is attached along the advance/retreat direction [, 7], and this core is advanced toward the molding surface side (11).
The fluid is blown into the inside of the parison while the parison is in a protruding state, and then the divided individual cores are
This includes sequential retraction in at least two stages.

The molding device used in this method is a molding device that molds a hollow body by blowing a fluid such as air under pressure into the parison. , having a shape corresponding to the rib molded inside the hollow body, capable of moving forward and backward in pairs on the molding surface side of the mold, and divided into a plurality of pieces along the forward and backward direction. Some cores are separated by an angle of 1°, and each of the divided cores is provided with forward and backward drive means for moving forward and retracting sequentially in at least two stages.

(Function) With the above structure, when the fluid is blown into the inside of the parison after the mold is closed, the parison comes into close contact with the surface of the mold and the core, and becomes a hollow product (hollow body) except for the rib portion. It has the shape of

Then, under this condition, the individual divided cores are sequentially retreated.

First, one core is moved back as a first step, and as the core is moved back, the unsolidified synthetic resin that is in close contact with the core is compressed by the pressure of the fluid and fixed together. At the time of this retreat, the other cores still protrude toward the molding surface of the mold, and the unsolidified synthetic resin wraps them in close contact. Therefore, when the previous core retreats, the other core that remains serves to support the synthetic resin that is integrated at that time.

Subsequently, when the other remaining core is retreated in the same manner as described above, the synthetic resin of that part is crimped as it retreats, and becomes integrated with the synthetic resin of the previously retreated part. In this case, the synthetic resin that is crimped and integrated first acts to support the synthetic resin in the core portion that is later retracted.

In this way, the core and the crimped and integrated synthetic resin function to maintain the shape of the part, and therefore, the molded ribs are actively prevented from being tilted or deformed such as distortion.

As a result, in the present invention, a hollow body having internal ribs with high precision can be formed using a single parison and a single process.

(Embodiment) Next, an embodiment embodying the present invention will be described in detail with reference to FIGS. 1 to 5.

First, a case will be described in which the mold 1 in the mold apparatus of this example is attached to a blow molding machine (not shown). However, in this example, the hollow body T is a tank, and the internal ribs R are used as its wave blocking plate (baffle). Incidentally, this wave prevention plate is used to prevent a small amount of fuel from shifting due to centrifugal force during cornering, causing a temporary fuel shortage and resulting engine stoppage, and to prevent the generation of fuel vibration noise. etc.

Now, the mold 1 consists of a pair of left and right molds 1a facing each other.
, 1. An insertion hole 3 for inserting the missing core 2 is opened at a proper position (approximately in the center in this example) of the mold 1a on the left in the figure. Then, the rib (wave breaking plate) R of the hollow body (tank) T to be molded is inserted into this insertion hole 3.
A plate-shaped core 2, which is formed into a flat or substantially rectangular shape according to the conditions, is inserted into the mold in a movable manner so that it can move forward and backward (in and out) by a sliding method, and protrudes from the molding surface side of the mold 1. It is provided. In addition, this core 2 is divided into two pieces in this example along the advancing and retreating direction, and these two cores 2
As shown in FIG. 2, g and 2b are approximately symmetrical on a plane and are attached so as to be in contact with each other. In this example, two ribs R are formed on the hollow body T, so
Although one more set of these two divided cores 2a and 2b is provided, the drawing shows only one of them and omits the other.

Further, on the back side of the mold 1a, a plate 5 is attached via a spacer block 4 as a means 6 for driving the cores 2a and 2b forward and backward.
The core 2 is provided with hydraulic cylinders 6a and 6b fixed to the rods 7a and 6b for advancing and retracting the rods, and the ends of the rods 7a and 7b are
The outer (left side in the figure) ends of a and 2b are connected. As a result, each hydraulic cylinder 686b is actuated via a control device (not shown), and each core 2a, 2b is moved forward or retreated to the position shown by the two-dot chain line in FIG. Note that the protrusion of the cores 2a and 2b (
The amount of advance (advance) is set to a value obtained by subtracting the thickness of the parison P during molding from the height of the rib R of the hollow body T to be molded, but in this example, the amount of protrusion is 50 mm. There is. Further, the inner surface of the mold 1 is set to have a predetermined hollow T-shape. Note that 8 is a spacer block of the mold 1b on the right side of the figure.

Now, the manufacturing method of this example using the above-mentioned mold apparatus is as follows.

First, for the inside of the molds 1a and lb, although not shown,
A predetermined amount of a predetermined parison P (ultra high polyethylene polyethylene in this example) is fed out toward the cross/\sotho die. At this time, mold 1. a core 2a inside,
The size (circumference, thickness, and length) of the parison P is appropriately selected depending on the shape and size of the hollow body to be manufactured.

After that, in this state, 2
A so-called preliminary blow and a fluid with a pressure of 2L, in this example 41A, are blown from a blowing nozzle (not shown), and the mold is closed via a mold closing device composed of a hydraulic cylinder, etc. ,do.

By doing this, both ends of the parison P are cut off by the pinch-off of the molds 1a and 1b, and the parison P is brought into a "C-nurled" state, as shown by the two-dot chain line in FIG. The cores 2a and 2b are approximately surrounded by the cores 2a and 2b.

After this, a predetermined pressure (approximately 64 c in this example) is applied.
g/cd) of compressed air. This allows the inner surface of the parison pit, metal 1a, lb and core 2a to be removed.
For 2h+, press it tightly against the corner and press it into place. At this stage, the shape of the hollow body T is obtained except for the part that becomes the rib 1.

Next, before assimilation of parison P (synthetic resin),
Each core 2a, 2b is sequentially retreated in the following manner.

First, the hydraulic cylinder 6a is operated to retract the core 2a by a predetermined amount, in this example, until its free (tip) end 2a' comes into contact with the inner surface (molding surface) of the mold a. ,
Due to the retreat, the parison (synthetic resin) Pa that was in close contact with the core 2a is pressed together like a single plate. In other words, the space that is formed as the core 2a retreats is gradually crushed by the internal pressure from the free end 2a', and upon completion of the retreat, the core 2a is fused to the base and integrated (the third Figure (a) (see Ron (c)).At this time, core 2b
still protrudes to the molding surface side of the mold 1a, and the synthetic resin PB at that part before assimilation is tightly wrapped around it. L7 Therefore, when the core 2a retreats, the support 1 maintains its posture and prevents its inclination and deformation until the synthetic resin Pa at that part is integrated. have the effect of

Next, operate the other oil agency shilling-6b, and the remaining 2JA',? ``b'' is moved backward in the same way as ``1a'' 2a.

Sasa, Near 1:? The parison (synthetic resin) Pb that was in close contact with the free end 2b
It is crimped from the ' side and fused to the base. As a result, the ribs -m-"] are formed by the two divided pieces T2a and 2b (Fig. 3 (D) and (Bo)).
reference). At this time, the synthetic resin Pa of the part that is crimped and integrated by the core 2a that retreats first supports the synthetic resin Pb of the core part that retreats later, and prevents deformation such as inclination. perform an action.

In this way, the synthetic resin Pa of the core 28 parts and ``11A2
Two ribs R are molded by integrating the synthetic resin Pb at position b.

Then, cooling the synthetic resin after a predetermined period of time,
After assimilation, open the mold and take out the whole thing. The desired synthetic resin hollow body (tank) T is obtained (see FIG. 5).

In this example, two cores are used to form one rib.
The figure shows the case where the knob is divided into pieces (however, it can be divided into an appropriate number depending on the quality and size of the knob to be molded, or the required precision).

Also, did you give an example of a case in which a core divided into two pieces is retreated in two steps by - pieces?For example, a core for molding seven ribs is divided into six pieces (7, each of those pieces is Ribs can be divided into 1 set and made into 3 silks, and each set can be divided into 3 stages and retracted sequentially. If the size is large, divide it into many parts 11, for example, divide it into 2 sets with 1 set for each jump, and set it back by 2 steps.The support of the synthetic resin will also be averaged, and the precision will be higher. In that case, if one set of cores among the divided individual cores is held by one hydraulic cylinder,
The number of hydraulic cylinders can be reduced, and the forward and backward drive means can be simplified.

Additionally, in this example, after one core has completed its retreat,
Although we have decided to retreat the other cores, depending on the number of divisions and the number of retreat stages, it is also possible to sequentially retreat the following cores while the previous core is being retreated. These conditions are
It is appropriately selected depending on the shape of the rib, the accuracy required for the rib, etc.

In addition, by providing the core at an appropriate part of the mold in an appropriate protruding direction, the rib can be molded at an appropriate part and in an appropriate protruding direction. Of course, in that case, the means for driving the core forward and backward (hydraulic cylinder, etc.) is appropriately provided so as to correspond to the direction of movement.

In addition, in this example, the forward and backward drive means is a direct-acting type using a hydraulic cylinder, but a pneumatic cylinder can also be used, or a link device such as a trouble mechanism can be interposed. It is not limited.

(Effects of the Invention) As is clear from the above description, the present invention has the following effects.

■The manufacturing process of ribs and hollow body are not separate processes,
Not only can a hollow body with integral ribs be manufactured using a single blow molding process, but also the core can be retracted sequentially.
Since it is possible to actively prevent the molded rib from being tilted or deformed such as distortion, it is possible to mold the rib with high precision.

■Also, compared to conventional technology in which ribs are manufactured in a separate process, the number of manufacturing steps can be reduced, which can be expected to improve productivity and reduce manufacturing costs. Furthermore, since the ribs and the hollow body can be manufactured integrally with a single parison, there is no lack of strength due to the attachment of the ribs, which is effective in improving durability.

■Since it is effective in preventing deformation during rib forming and deflection due to its own weight, it can be applied to a wide range of hollow bodies, and is particularly effective in forming ribs that tend to be significantly bent due to their own weight.

[Brief explanation of the drawing]

Figures 1 to 5 are process diagrams for explaining one embodiment of the present invention, and Figure 1 shows the process of introducing lysone into the inside of the mold, closing the mold, and blowing fluid. FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1, and FIG. 3 is an explanatory diagram of the process of retracting the core after closing the mold. Figure (a) shows before both cores have retreated, figure (b) shows one core in the middle of retreat, figure () 1) shows when the same core has finished retreating, figure ( d) shows the other core in the process of retreating, and the same figure (
E) is an enlarged longitudinal sectional front view showing the main parts of both cores when they are completely retracted; FIG.
FIG. 5 is a partially cutaway schematic sectional view of the hollow body (tank) molded in this example. 1...Mold 2 (2a, 2b)...Core 6...Advance/retreat drive means Pol, parison T...Hollow body (tank) R...Rib (wave removal plate)

Claims (2)

[Claims] (1) A blow molding method in which a parison is placed between molds, the mold is closed, and a fluid such as air is blown into the parison under pressure to form a predetermined hollow body. A core that has a shape that corresponds to the rib to be molded, that can move forward and backward with respect to the molding surface of the mold, and that is divided into a plurality of pieces along the forward and backward direction is installed. The fluid is blown into the inside of the parison in a state in which the parison is advanced and protruded toward the molding surface, and then the individual divided cores are sequentially retreated in at least two stages. and
A blow molding method for a synthetic resin hollow body with internal ribs. (2) In a mold device that molds a hollow body by blowing a fluid such as air under pressure into the inside of a parison, the mold has a shape corresponding to a rib to be molded inside the hollow body; , is provided with a core that can move forward and backward with respect to the molding surface side of the mold, and is divided into a plurality of pieces along the direction of movement, and each of the divided cores can move forward and backward in at least two stages. A molding device used in a blow molding method for a synthetic resin hollow body having internal ribs, characterized in that it is equipped with a forward and backward drive means that sequentially retreats.