JPH02190318A - Blow molding method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a blow molding method for blow molding a parison extruded into a hole formed by a closed mold.

[Prior Art] As shown in FIG. 4, a conventional general blow molding method involves storing plasticized resin in an extruder 1 through a resin passage 3 in a cylindrical wall 2 and then storing it in a resin reservoir 4. , by lowering the ring piston 5 housed in the cylindrical wall 2 by the cylinder 6, the resin in the resin reservoir 4 is pushed out as a parison 10 through the gap 9 between the mandrel 7 and the nozzle 8; The gap 9 between the mandrel 7 and the nozzle 8 is filled with a mandrel support rod 1 integrated with the mandrel 7.
1 is moved up and down by a hydraulic cylinder 12 to change the width of the parison 10, thereby controlling the thickness of the parison 10 pushed out through the gap 9, and furthermore, by the air blown from the air passage 13 through the air pin 14, the thickness of the parison 10 is controlled. A blow molding device is used to carry out blow molding.

However, in the above conventional blow molding method, the parison 10
To adjust the wall thickness of the mandrel support rod 11, use the hydraulic cylinder 1.
This is done by widening and narrowing the gap 9 by moving it up and down with the hydraulic cylinder 12, which not only makes the device complicated and large, but also requires a hydraulic unit for the hydraulic cylinder 12, which makes it expensive and has a large number of parts. There is a problem.

In addition, conventionally, as a method for blow molding bent products, one cavity (half mold cavity) bent in a dogleg shape is formed on the joined surfaces of a pair of molds, and a cavity is formed inside the joined molds. When the parison extruded from the extruder is extruded along the holes inside the joined molds, a blower installed at the bottom of the molds is used to open the openings at the top of the molds. More air is sucked in to create an air flow within the hole, and this air flow guides the parison into the hole formed by both cavities.Then, the parison inside the hole is pinched vertically and blow molded. A blow molding method for obtaining bent products is known (Japanese Patent Publication No. 58-47337).
Publication No.).

[Problems to be Solved by the Invention] However, in the conventional blow molding method described in the above-mentioned Japanese Patent Publication No. 58-47337, air flow is used to extrude the parison along the cavity of the mold. However, this is only for guiding the parison into the mold, and the air flow does not contribute in any way to controlling the thickness of the parison. Therefore, with the method described in Japanese Patent Publication No. 58-47337, it is not possible to control the wall thickness over the entire length of the parison and obtain a molded product with the required wall thickness.

Therefore, the present invention provides blow molding that does not have the problems of the conventional method as shown in FIG. The aim is to control the wall thickness over the entire length of the parison so that the required wall thickness of the molded product can be obtained.

[Means for Solving the Problems] In order to solve the above problems, the present invention forms a caddy on each joining surface of a two-part mold, and joins the two molds together. In the blow molding method, in which a gas flow is used to guide the parison into the hole formed between both cavities, it is used to push the parison into the hole inside the mold. The thickness of the parison is changed by adjusting the flow rate of the gas using a flow rate adjustment device, and then the upper and lower sides of the parison are pinched to blow air into the inside of the parison to perform blow molding.

[Function 1: When pushing the parison into the hole formed inside the mold, if the parison is guided by a gas flow, increasing the intake air flow rate will cause the parison to be pulled into the hole. As a result, the wall thickness can be reduced, and a parison thickness commensurate with the intake air flow rate can be obtained.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show an embodiment of a blow molding apparatus for carrying out the method of the present invention. Similar to the conventional method shown in FIG. 4, a resin passage 3 and a resin reservoir 4 are provided inside. A ring piston 5 is housed in a cylindrical wall 2 that is movable in the vertical direction, and the resin that has passed from the extruder 1 through the resin passage 3 and is stored in the resin reservoir 4 is pushed down by the cylinder 6. In the configuration in which the parison 10 is extruded through the gap 9 between the mandrel 7 and the nozzle 8, the air pin 14 is inserted into the axial center of the ring piston 5 and passed through the air passage 13 so that air can be blown into the parison 10. A certain mandrel support rod 11
is a fixed type.

At the lower position of the cylindrical wall 2, two split molds 15 and 16 are installed. 17b
When the joining surfaces 15a and 16a of the molds 15 and 16 are brought together, the cavity 1 is bent and formed symmetrically.
A hole 17 is formed by 7a and 17b. 18 is on the upper surface of the mold 15.1B and the parison 10
19 is an upper pinch metal fitting which is located on the lower surface of the mold 15.1B and is designed to grip the outlet side of the parison 10, 20 is a mold opening, 21 is a suction cover, 22 is a blower, 23 24 is a connecting pipe connecting the inside of the suction cover 21 and the blower 22, and 24 is a variable flow rate regulating valve as a flow rate regulating device provided in the middle of the connecting pipe 23.

The resin plasticized in the extrusion 11 passes through the resin passage 3 of the cylindrical wall 2 and is stored in the resin reservoir 4.

Next, when the ring piston 5 is lowered by the cylinder 6, the resin stored in the resin reservoir 4 passes through the gap 9 between the mandrel 7 and the nozzle 8 and is pushed out as a parison 10. The extruded parison 10 is inserted into the hole 17 formed by joining the joining surfaces 15a, 16a of the molds 15, 1B. At this time, the blower 22
By applying a suction force through the connecting pipe 23, the suction cover 21, and the hole 17, air is forced into the hole 17 through the mold 15.1 and the upper mold opening 20. Guided by the flow, the above parison 10
is housed in the hole 17 as shown in FIG. In this state, a gap is provided between the parison 10 and the cavities tza, ob forming the holes 17.

When the parison 10 is placed in the hole 17 inside the mold 1-5.16 as shown in FIG. 1 while being guided by the air flow,
In the present invention, the variable flow rate control valve 24 provided in the middle of the connecting pipe 23 is adjusted to adjust the flow rate of air sucked by the blower 22. In this case, if the velocity V of the extruded parison 10 and the intake air flow ff1Q by the blower 22 match, the maximum thickness can be achieved, and if the intake air flow mO is increased within a range that does not break the parison 10, the parison 10 can be Since it is stored in the hole 17 while being pulled, a parison thickness commensurate with the intake air flow rate O can be obtained.

Therefore, the wall thickness in the longitudinal direction of the parison can be controlled by the flow control valve 24, and the required wall thickness of the molded product can be easily adjusted to 1.
You will be qed.

When the thickness of the parison 10 housed in the hole 17 in the molds 15 and 1B is controlled by adjusting the intake air flow rate Q as described above, the thickness of the parison 10 is controlled by the upper pinch metal fitting 18 and the lower pinch metal fitting 19. Pinch the top and bottom, and then remove the air pin 14 from the air passage 13 in the mandrel support rod 11.
The parison 10 is pressed against the cavities 17a, 17b by the pressure of the air blown into the parison 10 through the parison 10, and is blow-molded (see FIG. 3). As a result, a product having the required wall thickness is molded in the molds 15, 16.

Note that the present invention is not limited to the above-mentioned embodiments; for example, in FIG.
Although the case where a and 16a are made into a flat surface is shown, if the product is bent back and forth and left and right, the bonding surface 15
a, 16a may be formed into an uneven surface, and it goes without saying that various changes can be made without departing from the gist of the invention.

[Effects of the Invention] As described above, according to the blow molding method of the present invention, a parison formed by extruding resin from a resin reservoir in a cylindrical wall is guided into a hole in a mold by a gas flow. After the parison has been stored, the thickness of the parison is controlled by adjusting the intake gas flow rate to guide the parison when blow molding is performed by pinching the top and bottom of the parison. Compared to a method in which the wall thickness of the parison is changed by changing the gap between Easily 1 for any wall thickness! ? It is possible to achieve excellent effects such as:

[Brief explanation of the drawing]

FIG. 1 is a side view of the mold joining surface showing an example of a blow molding apparatus used for carrying out the method of the present invention, and FIG. 2 is a side view of the mold joint surface shown in FIG.
3 is a side view of the joint surfaces of the molds showing the state during blow molding, and FIG. 4 is a sectional view showing an example of a conventional blow molding apparatus. 1... Extruder, 2... Cylindrical wall, 4... Resin reservoir,
5...Ring piston, 7...Mandrel, 8...
・Nozzle, 9... Gap, 10... Parison, i5,
1&...mold, 15a, 16a...bonding surface, 17
... Hole, 17a, 17b... Cavity, 18... Upper pinch hardware, 19... Lower pinch hardware, 21... Suction cover, 22... Blower, 23... Connection pipe, 24...Flow rate control valve (flow rate control device) Patent applicant Ishikawajima-Harima Heavy Industries Co., Ltd.

Claims (1)

[Claims] (1) A cavity is formed on each joint surface of a two-part mold, and when the joint surfaces of both molds are joined, the hole formed between both cavities is filled from the exit side. In order to guide the parison into the hole in the method of blow molding by pinching the top and bottom of the parison after the parison is sucked to create a gas flow and the parison is guided by the gas flow and stored in the hole. A blow molding method characterized in that the wall thickness of the parison is controlled by adjusting the flow rate of gas flowing into the parison using a flow rate adjustment device.