JPS6137414A - Manufacture of two-layer product by blow molding - Google Patents

Abstract

PURPOSE:To make perfect the joint of an inner cylinder and an outer cylinder, by welding the inner cylinder and the outer cylinder when the outer cylinder is molded by blow molding. CONSTITUTION:An inner cylinder 1 of a synthetic resin that has been previously molded by blow molding, injection molding or the like is placed on a second holding device 13, a parison 10 is supplied between molds 11, and the forward end of the parison 10 is pressed to a cylindrical section 12b of the holding device 13 to seal it. Then auxiliary air is fed into the parison 10. When a second auxiliary device 13 is lifted, the inner cylinder 1 is also lifted. As the parison 10 has been expanded by the auxiliary air, the inner cylinder 1 can be lifted without touching the parison 10. A sealing film 14 in the shape of a bellows is progressively contracted. When the molds 11 are further moved toward each other, the parison 10 and the inner cylinder 1 are pinched at recessed sections 11b, 11 of the molds 11. At this moment, the parison 10 is pinched between the inner cylinder 1 and the mold 11. Then if air is fed, the air is passed through small holes 1a in the inner cylinder 1 into the parison 10, and the parison is formed into the shape of the recesses 11a of the molds 11 thereby forming an outer cylinder 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for forming two-layer products, such as silencers, by blow molding.

A silencer used in an automobile air duct, etc. has an inner cylinder 1 having a large number of small holes 1a, as shown in FIG.
and an outer cylinder 2 arranged to surround this. Silencers with such a structure are relatively expensive because they are made of metal. Therefore, it is possible to reduce the cost by forming this silencer from a synthetic resin. In that case, an inner tube 1 having a small hole 1a and an outer tube 2 having a hole passing through the inner tube 1 are formed on each side and assembled as shown.

After this, the parts indicated by A must be bonded by heat welding or adhesive, which poses problems such as the process is time-consuming and it is difficult to achieve complete bonding.

The present invention has been made in view of the above circumstances, and includes supplying a parison to a mold for forming an outer cylinder, and
This parison is inflated by supplying auxiliary air and then blow molded inside.

The present invention provides a method for producing a two-layer product by blow molding, in which an inner cylinder made of synthetic resin formed by injection molding or the like is placed, and then the mold is closed and air is blown into the product to form an outer cylinder. .

The manufacturing method of the present invention will be explained in detail below based on the illustrated examples. FIG. 1 is a diagram showing a mold used in the "manufacturing method" of the present invention, which includes a recess 11a for forming the outer cylinder 2, recesses 11b and llc shaped to match the outer shape of the inner cylinder 1, and It has a structure with Although only one of the molds 11 is shown in the drawing, in reality, molds having symmetrical shapes are arranged so as to face each other. The flange 12 is used to hold the tip of the parison as will be explained later.
A first holder 13 is used to hold the inner cylinder 1 as shown in FIG.
3a and a step 13b; 14 is a bellows-shaped holder having one end joined to the flange 12a of the first holder 12 and the other end joined to the flange 13a of the second holder 13; It is a flexible sealing membrane.

Next, a manufacturing method of the present invention using a mold having such a structure will be described. 3 to 6 are diagrams showing the manufacturing method of the present invention in the order of steps. First, as shown in FIG.
o is supplied between both molds 11, and its tip is inserted into the first holder 12.
This part is sealed by pressing it against the cylindrical part 12b.

Subsequently, when auxiliary air is fed into the parison 10, the tip thereof is sealed so that it does not leak out of the parison 10, and the Varisin 1O swells as shown in FIG. This auxiliary air is blown from above by making a small hole in the portion of the second auxiliary auxiliary tool 13 shown at 13c in FIG.

You can also blow in from here.

If the second auxiliary tool 13 is raised here, the inner cylinder 1 will also be raised. When the second holder 13 is raised, the parison 10 is inflated by the auxiliary air, so the inner cylinder 1 rises without adhering to the parison 1=0.

Further, the bellows-shaped sealing membrane 14 is being contracted. Therefore, the inner cylinder 1 rises while maintaining airtightness, and is located between the two molds 11 within the parison 10, as shown in FIG.

If the mold 11 is further tightened, the parison 10 and the inner cylinder 1 will fit into the recesses Jlb, llc of the mold 11, as shown in FIG.
I was caught in the middle. At this time, the parison 10 is sandwiched between the inner cylinder 1 and the mold 11.

If air is blown here, the air is blown into the parison 10 through the small hole 1a of the inner cylinder 1, and the parison is molded into the shape of the recess 11a of the mold 11 to form the outer cylinder 2.

Molding is performed in this manner, and at this time, as described above, the parison 10 is formed into a recess 11 by the mold 11 and the inner cylinder 1.
b. They are sandwiched and brought into close contact at the llc points. in this case,
Since the parison is at a high temperature, the parison IQ and the inner cylinder 1 are welded together at the recesses 11b and llc. Therefore, when the molding process is completed and the mold is opened, the outer cylinder 2 is molded to surround the inner cylinder 1, and at the same time the recess 11b of the mold is formed.
The inner tube 1 and the outer tube 2 are welded together at the portion llc and taken out from the mold. In this way, a synthetic resin silencer is formed.

The sealing membrane 14 does not have to be bellows-like, but may have any shape as long as it is non-permeable and deformable.

Although the above detailed description of the present invention has been made using the production of a silencer as an example, the production of two-layer products other than silencers can be molded in exactly the same manner. In that case, when manufacturing a product that does not require a small hole in the inner cylinder, it is necessary to form a hole for air to pass through in advance and close this hole after forming the two-layer product. Bye.

As explained above, according to the manufacturing method of the present invention, the inner cylinder and the outer cylinder are welded together when the outer cylinder is formed by blow molding, so manufacturing is simple and the joining of the inner cylinder and the outer cylinder is easy. It can be done perfectly.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a device used in the manufacturing method of the present invention, FIG. 2 is a cross-sectional view of a second holder used in the device, and FIGS. 3 to 6 illustrate the steps of the present invention. The sequentially drawn diagrams and FIG. 7 are diagrams showing an example of a product manufactured by the apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Inner cylinder, 2... Outer cylinder, 10... Parison, 11... Mold, 12... First holder,
13...Second holder, 14...Sealing membrane.

Claims (1)

[Claims] A parison is supplied to a mold for forming an outer cylinder, and after the parison is inflated by supplying auxiliary air, a pre-formed synthetic resin inner cylinder is placed inside the parison, and then the mold is tightened. A method for manufacturing two-layer products using blow molding, in which air is supplied to form an outer cylinder.