JP2900230B2 - Method of manufacturing thermoplastic elastomer bent tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoplastic elastomer bent pipe used as a drain hose, a bypass hose, a transparent pipe for a fuel gauge, a hose for a water purifier and the like of an air conditioner.

[0002]

2. Description of the Related Art A curved tube made of a thermoplastic resin, for example, a hard vinyl chloride resin, is generally known as a blow molding, that is, a resin material plasticized by heating from an extruder is extruded into a tube, and before being cured by cooling, the tube is hardened. The tube (parison) is manufactured by a molding method in which the tube is sandwiched in a mold, air is blown into the tube to inflate the tube, thereby pressing the tube against the inner surface of the mold, and cooling and hardening in this state. However, when trying to manufacture a bent pipe 101 having a shape complicatedly bent in a three-dimensional direction as shown in FIG. 6 by blow molding, such as a drain hose for discharging dew condensation water from an air conditioner, complicatedly divided metal is required. Since a mold is required, in the case of such a drain hose or the like, as shown in FIG. 7, it is manufactured as a two-dimensionally bent curved tube 102 having a bellows portion 102a, and is connected to equipment. In this case, the bellows portion 102a extending in the Z direction is bent in the X direction and the Y direction as shown by a dashed line in the figure.

[0003]

The following problems are pointed out in the above-mentioned method of manufacturing a bent pipe by blow molding. (1) A curved pipe made of hard vinyl chloride resin manufactured by blow molding is inferior in elasticity, so that a problem may occur in the adhesion of a connection end. (2) The wall thickness of the moldable tube is limited. (3) Thickness unevenness in which the wall thickness becomes uneven in the circumferential direction of the pipe cross section is apt to occur, and particularly significant unevenness thickness occurs in a bent portion. (4) Since the divided molds are used, burrs are generated along the mold dividing surfaces (parting lines), and it is necessary to remove burrs after molding. (5) Due to high mold manufacturing costs, it is difficult to provide inexpensive products if a large amount of product supply is not expected, and mold fabrication is impossible depending on the shape of the bent tube.

[0004] The present invention has been made under the above circumstances, and the technical problem thereof is that it does not cause uneven thickness or burrs in the molding process and bends in three dimensions. It is an object of the present invention to provide a method for manufacturing a bent tube that can be easily and inexpensively manufactured even for a tube.

[0005]

Means for Solving the Problems The technical problems described above are:
This can be effectively solved by the present invention. That is, the method for producing a thermoplastic elastomer bent tube according to the present invention comprises:
Thermoplastic elastomer base pipe on an outer periphery of a mandrel made of a metal rod bent shape corresponding to the bent pipe to be molded was softened by preheating press-fitted, in its pipe forming temperature the press-fitted hollow shell A curved tube is formed by heating at a molding temperature of 50 to 80% of the above for a predetermined time and then cooling, and releasing the curved tube while supplying compressed air between the curved tube and the mandrel which are in close contact with each other. Is what you do. In this method, more preferably, when the raw tube is press-fitted onto the outer periphery of the mandrel, the raw tube is softened by preliminary heating in advance, and a surfactant is applied to the inner circumference of the raw tube in the press-fitting direction end. Further, when releasing the bent pipe from the mandrel, a compressed air supply nozzle whose inner peripheral surface of the outlet becomes larger in diameter toward the front end is used, and the outer peripheral edge of the bent pipe located at the front end of the mandrel is used. The bent pipe is pulled out while supplying compressed air by pressing the inner peripheral surface of the outlet.

[0006]

In the above construction, the mandrel is a mold member for deforming the raw tube from the inner peripheral side and holding the raw tube in a bent state during the forming process. Thermoplastic elastomers has a resilient at ordinary temperature, since it has the property of plasticized elasticity decreases upon heating (softening), raw pipe made of the thermoplastic elastomer, the state where press-fitted on the outer circumference of the mandrel 50-80% of the tube forming temperature
By heating to the molding temperature to plasticize and then cooling, a bent tube having a bent shape corresponding to the mandrel is obtained.
If the molding temperature is lower than the above temperature range, thermoplastic elastomer
The plastic tube made of rubber does not plasticize sufficiently,
Return deformation due to ring back increases. Conversely, molding temperature
If the temperature is higher than the above temperature range, cracks may occur.
There is. In addition, at the time of press-fitting into the mandrel, preheating to an appropriate temperature lowers the elasticity, and the application of a surfactant can reduce the frictional resistance with the mandrel and facilitate press-fitting.

[0007] The formed bent tube is in close contact with the surface of the mandrel, and thus cannot easily come out of the mandrel as it is. Since it is separated from the mandrel, it can be easily released. For the supply of compressed air in this case, for example, a compressed air supply nozzle whose inner peripheral surface becomes larger in diameter toward the tip is used. The compressed air is interposed between the mandrel and the mandrel so as to slightly expand the wall surface of the bent tube by pressing the peripheral surface to supply compressed air to the front space of the mandrel and the outer periphery of the bent tube. So pull out the bent tube in this state.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, as one embodiment of a method for manufacturing a thermoplastic elastomer bent pipe according to the present invention, a method for manufacturing a three-dimensionally bent bent pipe used as a drain hose of an air conditioner will be described with reference to FIGS. This will be described with reference to FIG.

First, FIG. 1 shows a pipe 1 around the mandrel 2.
FIG. Mandrel 2
Has a three-dimensional bent shape in which a round bar made of stainless steel (SUS) is bent at a plurality of positions, that is, the first portion 21 that extends in the X direction and has a spherical tip 21a.
And Z from the first portion 21 via the R-shaped bent portion 22.
The second portion 23 extends in the direction, the third portion 25 extends in the X direction from the second portion 23 via the R-shaped bent portion 24, and the R-shaped bend from the third portion 25. A fourth portion 27 extending in the Y direction via the portion 26 and fixed to the base 3
And a plurality of them are arranged on the base 3 (only one is shown in the figure). The fourth portion 27 includes a base 3
The base end 27a on the side is formed to be larger in diameter than the other parts via the tapered step 27b. The bending angle of the mandrel 2 is set in consideration of the return deformation of the bent tube 1 ′ (see FIGS. 2 to 4) formed from the raw tube 1 due to the springback after the mold release.

The raw tube 1 is made of a transparent flexible vinyl chloride resin which is a thermoplastic elastomer, and its inner diameter is compared with the outer diameter of the mandrel 2 other than the base end portion 27a and the tapered step portion 27b. A small diameter of about 0.2 to 0.5 mm is selected. The raw tube 1 is cut in advance into a length substantially equal to that of the mandrel 2.

Before press-fitting the pipe 1 into the mandrel 2,
While preheating to 5 to 75 ° C, a surfactant is applied to the inner peripheral surface of the end 1a in the press-fitting direction. As the surfactant, for example, a household liquid detergent is also suitable. As described above, the raw tube 1 made of a flexible vinyl chloride resin
Although the inner diameter is slightly smaller than the outer diameter of the mandrel 2, the elasticity is reduced (softened) by the preheating, so that the diameter can be easily expanded with press-fitting to the outer peripheral surface of the mandrel 2. At the same time, the surfactant intervenes between the outer peripheral surface of the mandrel 2 and the inner peripheral surface of the raw tube 1 to form a lubricating film. Press-fit easily due to frictional resistance. Further, since the distal end portion 21a of the first portion 21 of the mandrel 2 has a spherical shape, the operation of aligning the inner circumference of the end portion 1a in the press-fitting direction of the raw tube 1 with the distal end portion 21a is extremely easy.

FIG. 2 shows a step of heating the raw tube 1 to form a bent tube 1 '. That is, in the above-described press-fitting step, when the base tube 1 is press-fitted to each mandrel 2 on the base 3 until the end 1a in the press-fitting direction substantially abuts the base 3, for example, in this state, The raw tube 1 is housed in a pressure vessel (not shown) such as a vulcanizing can for rubber vulcanization molding, and heat pipe is heated at a predetermined temperature for a predetermined time by supplying hot steam into the pressure vessel. The forming temperature by the hot steam at this time varies slightly depending on the material and thickness of the raw tube 1, but as shown in FIG.
The temperature is between 0 and 80%, more preferably between 60 and 73%. This is because, if the molding temperature is too low, the flexible vinyl chloride resin constituting the raw tube 1 is not sufficiently plasticized, and the return deformation due to springback after the completion of molding becomes large. Is too high, cracks occur.

By performing steam heating at the above-described molding temperature for a predetermined time, the raw tube 1 is uniformly heated around the entire circumference, plasticized and almost loses elasticity, and therefore, is plastically deformed into a bent shape corresponding to the mandrel 2. . When the inner diameter of the base tube 1 is larger than that of the mandrel 2, the cross-sectional shape of the bent portion corresponding to the bent portions 22, 24, and 26 of the mandrel 2 changes, causing uneven thickness. Since the inner peripheral surface of the raw tube 1 is entirely in close contact with the outer peripheral surface of the mandrel 2 by press-fitting, such uneven thickness does not occur. When the supply of the hot steam is stopped after a predetermined molding time has elapsed, the hot steam is taken out of the pressure vessel in the fitted state shown in FIG. 2 and immediately transferred to a cooling shower device (not shown).
Cool with a cold water shower at ℃. For this reason, the base tube 1 is crosslinked and hardened in a bent shape corresponding to the mandrel 2 to recover elasticity, and becomes a bent tube 1 ′. During this cooling, the transparent curved tube 1 'becomes cloudy, but this cloudiness can be eliminated by drying described later.

FIG. 4 shows a step of releasing the bent tube 1 ′ formed by the above-described steps from the outer periphery of the mandrel 2. In this release step, an air gun 4 connected to an air compressor (not shown) is used. The compressed air supply nozzle 41 is detachably attached to the tip of the air gun 4.
Has an outer diameter larger than the outer diameter of the bent pipe 1 'and an inner diameter smaller than the outer diameter of the bent pipe 1', and the inner peripheral surface 42 of the outlet has a larger diameter toward the tip. Is formed on the tapered surface.

That is, when releasing the bent pipe 1 'from the outer periphery of the mandrel 2, as shown in FIG. 4 (A), first hold the air gun 4 with one hand and press the compressed air supply nozzle 41 thereof.
The inner peripheral surface 42 of the tapered outlet is closely contacted with the outer peripheral edge 1b of the end of the bent pipe 1 'located on the outer periphery of the distal end portion 21a of the mandrel 2 while supplying compressed air from the air compressor in this state. Then, pull out the bent tube 1 'with the other hand. As shown in FIG. 4B, the compressed air acts so that the pressure P pushes the inner peripheral surface of the bent pipe 1 ′, so that the bent pipe 1 ′ and the mandrel 2 that have been in close contact with each other. The bent tube 1 'made of a flexible vinyl chloride resin is easily elastically deformed. Can be typed. A plurality of types of compressed air supply nozzles 41 having different sizes are prepared, and are appropriately selected and used according to the outer diameter of the bent tube 1 'to be formed.

The released bent tube 1 ′ has a three-dimensional bent shape corresponding to the shape of the mandrel 2, as shown in FIG.
That is, one end 11 extending in the X direction, and R
Part 13 extended in the Z direction via a bent part 12
A portion 15 extending from the portion 13 in the X direction via an R-shaped bent portion 14; and a portion 15 extending from the portion 15 in the Y direction via an R-shaped bent portion 16 via a tapered portion 17b. And the other end 17 having a large-diameter portion 17a whose diameter is enlarged. This bent tube 1 'is cut at both ends 11, 17 to a predetermined product size, and then washed for 5 to 7 minutes to remove cloudiness of the bent tube 1' generated at the time of cooling by the above cold water shower. To a drying oven for drying. The temperature inside the drying oven is
The temperature is controlled at 41 to 45 ° C. by a temperature sensor in order to prevent the deformation of the bent tube 1 ′, and by drying at this temperature for 2 hours, the cloudiness is completely eliminated.

According to the manufacturing method of this embodiment, the wall thickness of the formable tube is infinite, depending on the shape of the bent tube to be formed, and uneven wall thickness also occurs at the bent portions 12, 14, and 16. In addition, since there is no burr generated by the mold dividing surface as in the case of blow molding, a high quality product can be provided at low cost. In addition, mandrel 2 which is a core type
Can be manufactured only by bending a round bar made of stainless steel, so that the mold cost is extremely low as compared with a blow molding die.

In the above embodiment, the method of manufacturing the three-dimensionally bent pipe 1 'used as the drain hose of the air conditioner has been described. The present invention is similarly applicable to the manufacture of a bent tube used as a device hose, for example, a bent tube having a two-dimensional bent shape, and a thermoplastic elastomer (eg, a polyester-based material) other than a flexible vinyl chloride resin is also applicable. It is. Also, in this embodiment,
Although hot steam is used for heating in the forming step, a heating method using an electric furnace or hot water immersion may be employed, and the subsequent cooling and drying may be natural cooling and natural drying.

[0019]

According to the method for manufacturing a thermoplastic elastomer bent pipe according to the present invention, the following effects are realized. (1) A bent tube with excellent adhesion and elasticity at the connection end can be obtained. (2) The wall thickness of the moldable tube is infinite. (3) There is no uneven wall thickness in which the wall thickness becomes uneven in the circumferential direction of the pipe cross section. (4) Since burrs are not generated on the surface of the bent pipe, it is necessary to remove burrs after molding, and the quality is improved. (5) Since it is formed by an inexpensive mandrel made of a metal bar, products can be provided at a low cost even with a small number of products.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a step of press-fitting a raw pipe to an outer periphery of a mandrel in one embodiment of a method for manufacturing a thermoplastic elastomer bent pipe according to the present invention.

FIG. 2 is a perspective view showing a step of forming a bent tube by heating and cooling a raw tube press-fitted to the outer periphery of a mandrel in the embodiment.

FIG. 3 is a diagram showing a relationship among a pipe forming temperature, a forming temperature, and a heating time of a raw tube in the above example.

FIG. 4 is an explanatory view showing a step of extracting and releasing the bent pipe while supplying compressed air between the formed bent pipe and the mandrel in the embodiment.

FIG. 5 is a perspective view showing a bent tube manufactured in the embodiment.

FIG. 6 is a perspective view showing a bent pipe made of a rigid vinyl chloride resin having a shape bent in a three-dimensional direction manufactured by a conventional method.

FIG. 7 is a perspective view showing a bent pipe made of a hard vinyl chloride resin having a bellows manufactured by a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw pipe 1 'Curved pipe 2 Mandrel 4 Air gun 41 Compressed air supply nozzle 42 Inner peripheral surface of outlet

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B29K 101: 12 B29L 23:00 (56) References JP-A-63-54214 (JP, A) JP-A-1-133705 (JP) JP-A-60-260318 (JP, A) JP-A-6-210759 (JP, A) JP-A-6-137468 (JP, A) Shoji Matsuzaki, "Thermoplastic Elastomer", February 1991 Published by Chemical Daily on March 15 (58) Fields investigated (Int.Cl. ⁶ , DB name) B29C 53/00-53/84 B29B 13/02 F16L 9/12 F16L 11/04-11/12

Claims (3)

(57) [Claims] 1. A step of press-fitting a tube made of a thermoplastic elastomer around an outer periphery of a mandrel made of a bent metal bar corresponding to a bent tube to be formed, and said element press-fitted into said mandrel. Tubes are made at their tube making temperature
Forming a bent tube by heating at a forming temperature of 50 to 80% of the temperature for a predetermined time and then cooling; forming the bent tube while supplying compressed air between the bent tube and the mandrel in close contact with each other; And releasing the mold. A method for producing a thermoplastic elastomer bent pipe, comprising: 2. The method according to claim 1, wherein when the raw tube is press-fitted onto the outer periphery of the mandrel, the raw tube is softened by preliminary heating in advance, and a surfactant is applied to the inner circumference of the raw tube in the press-fitting direction end. A method for producing a thermoplastic elastomer bent tube, characterized by coating. 3. The curved pipe according to claim 1, wherein, at the time of releasing the mold, a compressed air supply nozzle whose inner peripheral surface has a larger diameter toward the distal end is used, and a distal end of the curved pipe located at the distal end of the mandrel. A method for manufacturing a thermoplastic elastomer curved pipe, wherein the curved pipe is pulled out while supplying compressed air by pressing the inner peripheral surface of the outlet to an outer peripheral edge.