JPS60135229A - Preparation of double pipe - Google Patents

Abstract

PURPOSE:To prepare a light wt. double pipe having a strong structure in an extremely efficient and certain manner, by forming a double pipe having a hermetically sealed hollow barrel part between the inner and outer pipes thereof by blow molding. CONSTITUTION:Both molds 5A, 5B approach to each other and matched so as to hold an inner pipe 1 and a parison 4 therebetween to perform clamping. Because the parison 4 is held under a molten state at a high temp. (180-200 deg.C), a sharp contact parts 5a of the molds are contacted with the parison 4 to divide the same into a parison part 4B used in forming an outer pipe and an unused parison part 4A. Therefore, the parison part 4B is integrated with the protruded part 1a of the inner pipe 1 and allowed to fill the grooves 1b, 1b' of the inner pipe 1 to perform the positional determination of the connection part of the inner and outer pipes. After clamping, compressed air is introduced into the inner pipe 1 and the parison part 4B is expanded in the mold hole through the through-hole 1d of the pipe and pressed to the surface of the mold hole to form a hollow barrel part E.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing J1WI, in which an outer tube is tightly fixed on the outer circumferential surface of an inner tube to form a cavity between the two, and in particular, the present invention relates to a method for manufacturing J1WI, in which an outer tube is tightly fixed on the outer circumferential surface of an inner tube to form a cavity between the two. The present invention relates to a manufacturing method for manufacturing a plastic double pipe using the above method.

Internal combustion engines used in automobiles etc. draw in outside air through an air cleaner, etc., and introduce it into a combustion chamber along with atomized fuel, where it is compressed and ignited for combustion, and the combustion gas is sent outside as exhaust gas. Discharge. As described above, an intake pipe is provided on the intake side of the internal combustion engine to take in outside air, and the intake pipe is connected to an air cleaner so that outside air is taken in through the air cleaner.

In particular, when the capacity of an internal combustion engine is increased or when the engine is operated at high speed, a large amount of air passes through the intake pipe. Furthermore, in so-called turbo engines that have been attracting attention in recent years, a larger amount of air is taken in compared to conventional engines, and the amount of air passing through the intake pipe tends to increase. In this way, even if the amount of air passing through the intake pipe increases, the inner diameter of the intake pipe cannot be increased unnecessarily due to various constraints.

Therefore, the flow rate of air passing through the intake pipe increases, and as a result, the level of sound emitted by the air flowing through the intake pipe to the outside tends to increase.

It is possible to use a muffler to absorb the noise emitted from such high-speed flow in the intake pipe.The muffler is a muffler that has a cavity connected to the intake pipe through which gas flows at high speed. It is conceivable to have a structure in which noise is absorbed in a cavity. In order to form such a cavity, two
It is conceivable to use two tubes to surround and form the inner and outer peripheral surfaces between the two. In addition, especially in the case of a silencer used in an automobile's intake pipe, it is necessary to make the silencer as lightweight as possible in order to reduce the weight of the entire automobile, and it is also necessary to have a robust structure. It is.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method for manufacturing a double-layered pipe that is lightweight and has a strong structure and can be manufactured extremely efficiently and reliably. With the goal. Incidentally, the double pipe having a hollow portion manufactured according to the present invention can be applied to various uses other than a silencer.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 8 shows a double tube 7 having a cavity manufactured according to the method of the present invention. 6, and a cavity E is formed in a sealed manner between the inner tube 1 and the outer tube 6. In this embodiment, an appropriate number of through holes 1d are provided in the circumferential direction of the inner tube 1, and the cavity E is communicated with the inside of the inner tube 1 via these through holes 1d. Therefore, when the inner pipe 1 of the double pipe 7 shown in FIG. 8 is connected to the intake pipe of an internal combustion engine, the double pipe 7 can function as a muffler. next,
A method for manufacturing the double pipe 7 shown in FIG. 8 based on the present invention will be described in detail.

First, an inner tube 1 having a configuration as shown in FIG. 1 is prepared. The inner tube 1 has a substantially cylindrical shape, and coupling portions 1A and 1B are formed at the upper and lower portions of the inner tube 1, respectively.
1B, the outer tube 6 and the inner tube 1 are integrally and firmly connected as shown in FIG. The joint portions 1A and 1B of the inner tube 1 are formed with protruding portions 1a and 1a that protrude from the outer circumferential surface of the inner tube 1 and extend in the circumferential direction, respectively. In the illustrated example, a pair of grooves 1b and 1b'' are formed on both sides of the protrusion 1a, but the grooves 1b and 1b- are not formed over the entire circumference like the protrusion 1a; In the example, non-groove portions ic, ic are formed at two opposing locations, and grooves ib, ib- are discontinuous.

A longitudinal section of the inner tube 1 including the grooves 1b, 1b- is shown in FIG. 2a, and a longitudinal section of the inner tube 1 including the non-grooved portions ic, ``lc'' is shown in FIG. 2b. In this embodiment, a pair of grooves 1 are provided adjacent to both sides of the protrusion 1a protruding from the outer circumferential surface of the inner tube 1 and carved inside the outer circumferential surface of the inner tube 1.
b, 1b'- are provided, but they may be provided only on one side of the protrusion 1a, or may be provided at a distance from the protrusion 1a.

In this embodiment, the protrusion 1a is formed to have a uniform thickness, but it may be formed into a tapered shape as shown in FIG. 2C, or any other arbitrary shape. As will be described later, since the protrusion 1a functions as a melting margin and ensures the integrity of the inner and outer tubes, it is desirable that the protrusion 1a has a tapered shape as shown in FIG. 2C. Further, as shown in FIG. 2b, in this embodiment, a pair of non-grooved portions 1c and lc are provided facing each other, and such non-grooved portions 1c and 1c are This is provided to correspond to a split mold. For example, when using a quarter mold, four non-grooved portions may be formed on the same circumference corresponding to the parting line. .

The inner tube 1 having the above-described configuration can be molded by injection molding or the like using a plastic material such as polypropylene. Next, as shown in FIG. 3, after pasting release tape 2 on the upper side of the lower joint part 1A and the lower side of the lower joint part 1B of the inner tube 1, the inner tube 1 is placed in a jig 3 that can move up and down. Fix it. This release tape 2 is for preventing the parison for forming the outer tube from excessively adhering to the outer peripheral surface of the inner tube. The release tape 2 is preferably made of a material having a higher melting point than the inner tube 1 and the parison, such as vinyl chloride or Teflon. or,
A release agent may be applied instead of the release tape, and a Teflon cap may be attached to the outer side of the joint of the inner tube 1.

The inner tube 1 temporarily fixed to the jig 3 is placed in a parison pouring machine (
(not shown) below the spout.

In this case, the non-grooved portions ic and 1c in the joint portions 1A and 1B of the inner tube 1 are formed in a mold 5A as shown in FIG.

Orient the inner tube 1 so as to match the dividing lines F, F of 5B.

Next, as shown in FIG. 4, the parison 4 is poured out from a pouring nozzle (not shown) of the parison pouring machine, and the inner tube 1 is inserted. This parison 4 is preferably made of the same material as the inner tube 1 (for example, polypropylene). As shown in FIG. 4, mold holes 5b, 5b are formed in the two-split molds 5A, 5B. When molds 5A and 5B are matched,
A molding space corresponding to the outer shape of the outer tube to be molded is defined by the mold cavities 5b, 5b.
It communicates with the outside through a communication hole 5C drilled in A. In addition, the contact portions 5a, 5 of the molds 5A, 5B with the inner tube 1
a has a sharp edge shape and is configured to come into contact with the release tape 2.

As shown in FIG. 4, the drawing molds 5A and 5B are brought close to each other, the inner tube 1 and the parison 4 are sandwiched, and both molds are brought together and clamped. When the mold clamping is completed, as shown in FIG. 5, the contact portion 5a of the mold 5B contacts the portion of the inner tube 1 outside the protruding portion 1a.

In the illustrated example, the tip of the contact portion 5a is in direct contact with the release tape 2. In this case, the parison 4 is at a high temperature (180~
200° C.), the parison 4 is divided into a parison portion 4B used for forming the outer tube and an unused parison portion 4A by contact with the sharp contact portion 5a. Therefore, the parison portion 4B accommodated in the mold cavity inside the contact portion 5a is integrated with the protruding portion 1a of the inner tube 1, and is filled into the grooves 1b, 1b- of the inner tube 1, so that the inner The joint of the outer tube is positioned. In this case,
The protrusion 1a mainly ensures the sealing of the inner and outer tubes, while the groove 1a
b and 1b' mainly ensure positioning of the inner/outer tube joint. Therefore, it is desirable that the protrusion 1a is melted at the temperature of the parison 4 and the protrusion 1a and the parison 4 are fused.
To do this, the inner tube 1 should be made of the same material as the parison 4,
Furthermore, it is preferable that the protruding portion 1a has the shape shown in FIG.

After clamping the mold, as shown in Figure 6, pressurized gas is
The parison portion 4B is introduced into the inner tube 1 at a pressure of ~9 Kg/m2, and is expanded in the mold cavity through the through hole 1d of the inner tube 1, and is pressed against the surface of the mold cavity to form a cavity E. During this blow molding, the communication hole 5C provided in the mold splitter 5A
Since the air in the mold cavity is exhausted to the outside through the mold cavity, the parison portion 4B is blow-molded accurately into the external shape defined by the surface of the mold cavity. As shown in FIG. 7, pinholes are usually likely to occur at the parting line F, where the forming molds 5A and 5B are aligned, and the contact part H between the inner tube 1 and the inner tube 1, but in the embodiment, As shown in the figure, since a non-groove portion 1C21C is provided corresponding to this portion, it is possible to prevent pressurized gas from leaking.

After blowing in the pressurized gas, the parison is cooled. A flow path (not shown) is provided in the molds 5A and 5B for flowing cooling water, and the concentration of the mold is 8 to 8.
The structure allows the temperature to be maintained within a range of 15°C. Therefore, the parison is cooled by contacting the molds 5A and 5B, and the molded shape of the parison is maintained.

After sufficient cooling, pressurized air is released, and the mold is then opened to take out the double tube thus molded. In this case, as shown in FIG. 5, since a release tape 2 is attached to the inner tube 1, unnecessary parison parts can be easily removed by peeling off the release tape. The time and effort required for removal work can be omitted.

As described in detail above, according to the present invention, it is possible to easily form a double tube having a sealed cavity between the inner tube and the outer tube by blow molding.

In addition, it is possible to manufacture a double pipe in which the joint between the inner tube and the outer tube is reliably sealed, and the strength of the joint between the inner tube and the outer tube is high.

It should be noted that the present invention should not be limited to the specific embodiments described above, and it goes without saying that various modifications can be made within the technical scope of the present invention.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the inner tube, Figures 2a and 2b are sectional views showing different longitudinal sections of the inner tube shown in Figure 1, and Figure 2C is a deformation of the protrusion of the inner tube. A partial sectional view showing an example, FIG. 3 is a schematic diagram showing a state in which the inner tube is fixed to a jig, and FIG. 4 is a schematic diagram showing a state in which the parison is extrapolated to the inner tube.
Fig. 5 is a schematic diagram showing the mold clamped state, Fig. 6 is a schematic diagram showing the blow molding state, Fig. 7 is a schematic diagram showing the plane of the mold in the mold clamped state, and Fig. 8 is a schematic diagram showing the mold clamped state. The figure is a perspective view showing a double pipe manufactured based on the present invention. (Explanation of symbols) 1: Inner tube 1a: Projection 1b, lb': Groove 1d: Through hole 2: Release tape 4: Parison 5A, 5B: Molding mold 5a: Contact portion 50: Communication hole 6: Outer tube Patent Applicant: Eli Cell Co., Ltd. Figure 3 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. A cylindrical inner tube with an appropriate number of through holes is held in a predetermined position, a parison is inserted into the inner tube, and the mold is divided into an appropriate number of pieces. The inner tube and the parison are placed in the mold cavity and the mold is clamped, and pressurized gas is sent through the inner tube and the through hole to blow the parison into an external shape defined by the mold cavity. 1. A method for manufacturing a double-walled tube, comprising: forming an outer tube to form a cavity between the inner tube and the outer tube. 2. The method for manufacturing a double pipe according to item 1 above, wherein the inner pipe is made of plastic. 3. In the above item 2, the inner tube is provided with a connecting portion having a predetermined shape along the circumferential direction, and the inner tube and the outer tube are integrally connected at the connecting portion. Features: A manufacturing method for double tubes. 4. The method for manufacturing a double pipe according to item 3 above, wherein the coupling portion extends along the outer periphery of the inner tube and has a protruding portion that protrudes in the radial direction from the outer circumferential surface. . 5. The method for manufacturing a double pipe according to item 4 above, wherein the protrusion has a tapered shape. 6. The double pipe according to the above item 3 or 4, characterized in that the coupling part extends along the outer periphery of the inner pipe and has a groove carved on the outer peripheral surface. Production method. 7. The method for manufacturing a double pipe according to item 6 above, characterized in that the grooves are provided discontinuously. 8. The method for manufacturing a double pipe according to item 6 above, characterized in that the grooves are provided on both sides of the protrusion.