JP4993195B2 - Blow molding method and mold for blow molding - Google Patents

Description

  The present invention relates to a punching method for forming a through hole in a blow molding die in a solid part protruding from an outer surface of a blow molded product, and a blow molding die used for the punching method.

  In blow molding, a soft parison made of a thermoplastic synthetic resin extruded in a tube shape from a die head of an extruder is sandwiched between blow molding dies, and air is blown into the parison to blow the parison into the blow molding die. This is a blow molded product manufacturing method in which a cavity surface shape is formed and the molded product is removed after cooling and curing, and is widely used as a manufacturing method for various hollow products such as ducts and tanks.

  In the blow molded product, for example, a solid part 71 called a bracket or a flange is formed on the outer surface 72 so as to protrude from the outer surface 72 like a blow molded product 70 for a duct shown in FIG. In some cases, a through hole 73 used for attachment or the like is formed. The solid portion 71 is a portion formed so that the tube walls of the parison are in close contact with each other and do not have a hollow portion inside.

  Conventionally, as a drilling method for forming a through hole in a solid part of a blow molded product, as shown in FIG. 10, a male blade 85 for hole formation is provided in one die 81 of a blow molding die 80 as a cylinder device. The drive device 86 is provided so as to be able to advance toward the other die 83, and the other die 83 is provided with a hole-like female blade 87 into which the male blade 85 can be inserted. Air is blown into the parison sandwiched between blow molding dies 80, the parison is shaped and then cooled and cured to form a blow molded article 90, and then the male blade 85 is advanced as shown in FIG. There is a method of punching the solid portion 91 of the blow molded product 90 with the male blade 85 and the female blade 87 to form the through hole 93. Reference numeral 91 a is a portion punched from the solid portion 91.

  However, the method of punching the through hole 93 using the male blade 85 and the female blade 87 has a clearance (gap) between the outer surface of the male blade 85 and the inner surface of the female blade 87 of 0.1 mm or less on one side, that is, As shown in FIG. 11, the outer diameter a of the male blade 85 and the inner diameter b of the female blade 87 must be a ≦ b ≦ a + 0.2 mm, and high accuracy is required for the hole forming portion in the blow molding die. There is a problem that the mold cost increases. Furthermore, if the clearance accuracy between the outer surface of the male blade 85 and the inner surface of the female blade 87 is lowered during the repetition of blow molding, the through hole cannot be punched well, and burrs are generated around the through hole. As a result, work for removing burrs is required in a later process, and maintenance of the blow molding die is required.

Japanese Utility Model Publication No. 60-83721 JP 2002-178394 A

  The present invention has been made in view of the above points, and when forming a through hole in a blow molded product in a blow molding die, it is difficult to generate burrs around the through hole. There is no need for the hole forming portion to have a high-precision structure, and it is easy to manufacture a blow molding die, and maintenance of the blow molding die is unnecessary or simplified. The purpose is to provide a mold for blow molding.

  According to the first aspect of the present invention, a solid part protrudes from the outer surface by sandwiching a soft parison between blow molds composed of at least two molds, and blowing the air into the parison to shape the parison. In the blow molding product perforating method, a through hole is formed in the solid part in the blow molding die when the formed blow molding product is blow molded, and the through hole of the blow molding die is formed. In the part to be provided, the hole forming blade portion is provided in one mold so as to be able to advance toward the other mold, and the other mold has a receiving portion for the hole forming blade portion at a position facing the hole forming blade portion. The blow mold is closed and the soft parison is sandwiched between the blow molds, and the solid part is formed by the hole forming blade part. Press against the receiving part of the hole forming blade Forming a thin wall portion in the solid portion between the hole forming blade portion and the receiving portion of the hole forming blade portion, and then blowing air into the parison to shape the parison, After cooling and hardening, the thin portion between the hole forming blade portion and the hole forming blade portion receiving portion by moving the hole forming blade portion forward and retreating the hole forming blade portion receiving portion. Is broken to form the through hole in the solid portion, and the blow molding die is opened to release the blow molded product.

  According to a second aspect of the present invention, there is provided a blow molding mold including at least two molds for forming a blow molded product having a solid portion protruding from an outer surface, wherein the solid portion is formed at one side. The die of the hole is provided with a hole forming blade portion so as to be able to advance toward the other die, and the other die is provided with a receiving portion of the hole forming blade portion at a position facing the hole forming blade portion. The solid portion is pressed against the receiving portion of the hole forming blade portion by closing the solid portion, and the solid portion is interposed between the hole forming blade portion and the receiving portion of the hole forming blade portion. The hole forming blade portion is provided so as to be retractable inwardly of the other mold, and the closed portion that forms the thin portion in the solid portion is formed. When molding, the receiving part of the hole forming blade part is prevented from retreating, while after the thin part is formed, it is retracted. Provided retraction preventing means enabling, receiving portion of the hole forming blade section by advancement of the pore forming blade portion during retractable after formation of the thin portion is characterized in that so as to retract.

  According to a third aspect of the present invention, in the second aspect, the hole forming blade portion can be advanced by a driving device, and the receiving portion of the hole forming blade portion is urged toward the one mold by a spring member. When the receiving portion of the hole forming blade portion is pushed by the hole forming blade portion by the advancement of the hole forming blade portion when the retraction is possible, the hole forming blade resists the elastic force of the spring member. The receiving part of the part is retreated.

  According to the method for perforating a blow molded product in the invention of claim 1, the blow molding mold is closed and the soft parison is sandwiched between the blow molding molds and the soft mold is sandwiched between the blow molding molds. The solid part is pressed against the receiving part of the hole forming blade part of the other mold with the hole forming blade part of one mold, and the solid part is thin between the receiving part of the hole forming blade part and the hole forming blade part. Next, air is blown into the parison to shape the parison, and after the parison is cooled and hardened, the thin-walled portion is sandwiched between the hole-forming blade portion and the hole-forming blade portion receiving portion. By moving the hole forming blade part forward and retracting the receiving part, the thin part is broken to form a through hole in the solid part. The burr around the through-hole that has occurred at the time of cutting can be made difficult to occur.

  Furthermore, according to the method for perforating a blow molded article in the invention of claim 1, unlike the conventional formation of a through hole by punching with a male blade and a female blade, the hole forming blade portion and the receiving portion of the hole forming blade portion High precision is not required, making it easy to produce blow molds, and repeated blow molding can cause failure of the thin-walled part due to the hole forming blade and the receiving part of the hole forming blade. It is difficult, and maintenance of the blow molding die can be unnecessary or simplified.

  On the other hand, according to the blow molding die in the inventions of claim 2 and claim 3, unlike the conventional structure in which punching is performed with a male blade and a female blade, the hole forming blade portion and the hole forming blade portion are received. High precision is not required in the part, making it easy to manufacture a blow molding die, and even if blow molding is repeated, the thin-walled part breaks due to the hole forming blade part and the hole forming blade part receiving part. It is difficult to occur, and maintenance of the blow molding die is unnecessary or simplified, and the blow molded product according to the invention of claim 1 can be perforated satisfactorily.

  Hereinafter, embodiments of the present invention will be described in detail. 1 is a front view of a blow molding die according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1, FIG. 3 is a sectional view when the blow molding die is closed, FIG. FIG. 5 is an enlarged partial sectional view showing a part of FIG. 3, FIG. 5 is an enlarged sectional view of the hole forming blade part and the receiving part of the hole forming blade part of FIG. 4, and FIG. FIG. 7 is a partial cross-sectional view of the blow molding die showing the thin-wall portion after breaking, and FIG. 8 is a partial cross-sectional view of the blow molding die showing the time of demolding.

  A blow molding die 10 according to an embodiment of the present invention shown in FIG. 1 and FIG. 2 is used for blow molding the blow molding 70 for duct shown in FIG. A solid part 71 called a flange or a bracket is formed to protrude from an outer surface 72 of 70, and a through hole 73 can be formed in the solid part 71.

  The blow molding die 10 includes two molds 11 and 31 that open and close in the horizontal direction, and one of the two molds 11 and 31 is a movable mold and the other is a fixed mold. In the two molds 11 and 31, cavity surfaces 12 and 32 are formed for shaping the outer surface of the molded product. In the cavity surfaces 12 and 32, the portions formed on the parting surfaces (split surfaces) 14 and 34 of the two molds 11 and 31 constitute the cavity surfaces 13 and 33 for the solid portion 71. Yes.

  In a portion where the through hole 73 is formed in a portion where the solid portion 71 of the two dies 11 and 31 is formed, the hole forming blade portion 41 can be advanced toward the other die 31 in one die 11. The other mold 31 is provided with a hole forming blade receiving portion 51 at a position facing the hole forming blade 41.

  The hole forming blade portion 41 includes an outer peripheral cylindrical portion 42 that matches the inner peripheral shape of the through hole 73 on the distal end side. The cylindrical portion 42 has a thin tip so that it can be easily pushed into the soft resin of the parison. The hole forming blade portion 41 can be advanced toward the other mold 31 by a driving device 45 including an air cylinder device or the like. In the present embodiment, the tip of the hole forming blade portion 41 is located at the rearmost position. 43 is in a state of projecting a predetermined amount from the cavity surface 13 for the solid portion 71 of the one mold 11, and the blow mold 10 is closed (that is, the two molds 11, 31 are When closed, the distance between the tip 43 of the hole forming blade 41 and the receiving portion 51 of the hole forming blade 41 is 0.1 to 0.3 mm. In the mold 11, holes 17 are formed for the arrangement of the hole forming blade 41 and the operation of the driving device 45.

  The receiving part 51 of the hole forming blade part is formed in a disk shape having a diameter larger than the diameter (outer diameter) of the hole forming blade part 41 (2 to 5 mm larger in the present embodiment), and the other mold 31. In the receiving portion slide hole 35 formed perpendicularly from the solid portion cavity surface 33 to the inside of the mold, the receiving portion slide hole 35 is provided so as to be retractable from the solid portion cavity surface 33 to the inside of the die. The receiving portion slide hole 35 includes a large diameter hole portion 36 that allows the receiving portion 51 of the hole forming blade portion to slide from the solid portion cavity surface 33 to a predetermined distance position, and the large diameter hole portion. A portion deeper than 36 is a small-diameter hole portion 37 having a diameter smaller than that of the receiving portion 51 of the hole forming blade portion. The large-diameter hole portion 36 is provided with a spring member 38 that biases the receiving portion 51 of the hole forming blade portion toward the one mold 11.

  A shaft portion 52 is formed on the back side of the receiving portion 51 of the hole forming blade portion, and is inserted into the large diameter hole portion 36 and the small diameter hole portion 37. The shaft portion 52 has a diameter that allows the small-diameter hole portion 37 to slide, and the receiving portion 51 of the hole-forming blade portion has the solid portion cavity in relation to the length of the receiving portion slide hole 35. The length does not hinder retreating from the surface 33. A retraction preventing hole 54 is formed through the shaft portion 52 in the orthogonal direction, and a locking drive device 56 made of an air cylinder device or the like is formed in a direction orthogonal to the small diameter hole portion 37 of the receiving portion slide hole 35. A rod-shaped locking member 57 that is provided and moves forward and backward by the operation of the locking drive device 56 is provided on the distal end side of the locking drive device 56. The locking member 57 has a diameter that can be inserted into the receding prevention hole 54 of the shaft portion 52, and the surface of the receiving portion 51 of the hole forming blade portion is flush with the solid portion cavity surface 33. By being inserted into the receding prevention hole 54 of the shaft part 52 in the state, the receding of the receiving part 51 of the hole forming blade part is prevented, and on the other hand, from the receding prevention hole 54 of the shaft part 52, the locking member By removing 57, the receiving portion 51 of the hole forming blade portion can be retracted. The retraction prevention hole 54 of the shaft portion 52, the locking drive device 56, and the locking member 57 constitute a retraction prevention means 60.

  Blow molding and perforation using the blow molding die 10 will be described. As shown in FIG. 1, a softened parison P1 extruded in a tube shape from a die head 61 of an extruder is disposed between the molds 11 and 31 of the blow molding die 10 as shown in FIGS. 2 to 4. And the softened parison P1 is sandwiched between the molds 11 and 31.

  In the present embodiment, in the present embodiment, the hole forming blade portion 41 is set to the rearmost position, and the hole forming blade portion 41 projects a predetermined amount from the cavity surface 13 for the solid portion 71 in the die 11. ing. In addition, the receiving portion 51 of the hole forming blade portion has a surface 51a that is flush with the cavity surface 33 for forming the solid portion of the mold 31, and in this state, the receding prevention hole 54 of the shaft portion 52 is provided. The retaining member 57 is inserted into the hole forming blade portion to prevent the receiving portion 51 of the hole forming blade portion from moving backward.

  By the closed mold, the tube wall of the parison P1 in the soft state is brought into close contact with the solid portion cavity surfaces 13 and 33, and a solid portion 71 is formed. The formed solid part 71 is in a softened state. When the mold is closed, the tip side of the hole forming blade 41 protruding from the cavity surface 13 for the solid part 71 of the one mold 11 replaces the solid part 71 with the hole forming blade. The thin portion 74 is formed in the solid portion 71 between the hole forming blade portion 41 and the hole forming blade portion receiving portion 51 as shown in FIG. The thin portion 74 has a thickness of 0.1 mm because the interval between the hole forming blade portion 41 and the receiving portion 51 of the hole forming blade portion is set to 0.1 to 0.3 mm when the mold is closed. It becomes a film shape of 1 to 0.3 mm. The thin portion 74 corresponds to a weak portion having low strength.

  Next, air is blown into the softened parison P1 from a blow pin (not shown) to inflate the parison P1, and the parison P1 is brought into close contact with the cavity surfaces 12 and 32 as shown in FIG.

  After the formed parison P1 is cooled and hardened by natural cooling or the like to form the blow molded product 70, the locking drive device 56 is operated to move the locking member from the receding prevention hole 54 of the shaft portion 52. 57 is extracted, and the receiving portion 51 of the hole forming blade portion can be retracted. In this state, as shown in FIG. 7, the hole forming blade 41 is advanced by the operation of the driving device 45. By advancement of the hole forming blade part 41, the receiving part 51 of the hole forming blade part is pushed by the hole forming blade part 41 through the thin part 74, so that the hole forming blade part 41 advances. Accordingly, the spring member 38 moves backward against the spring member 38. The thin-walled portion 74 is broken between the hole-forming blade portion 41 and the hole-forming blade portion receiving portion 51 by the advancement of the hole-forming blade portion 41 and the retreat of the hole-forming blade portion receiving portion 51. And the through-hole 73 is formed in the part after a fracture | rupture. Reference numeral 76 denotes a portion that is broken by the thin portion 74 and removed from the solid portion 71.

  After that, as shown in FIG. 8, the blow molding die 10 is opened and the blow molded product 70 is removed. As shown in FIG. 9, the blow molded product 70 obtained in this way has a through-hole 73 formed in a solid portion 71 protruding from the outer surface. In order to facilitate the demolding of the blow molded product 70, it is preferable to retract the hole forming blade 41 to the position before the mold closing when demolding. Further, the hole forming blade part 41 and the hole forming blade part receiving part 51 are returned to the positions before the mold closing, and the locking member 57 is inserted into the receding prevention hole 54 of the shaft part 52 and the next Provided for blow molding.

  The present invention is not limited to a blow molded product for a duct, and can be applied to various blow molded products in which a solid part called a flange, a bracket, or the like protrudes from the outer surface of a hollow part. is there. Further, the hole shape is not limited to a round hole, and can be applied to a long hole, a modified hole, or the like.

It is a front view of the metal mold | die for blow molding which concerns on one Example of this invention. It is 2-2 sectional drawing of FIG. It is sectional drawing at the time of mold closing of the metal mold | die for blow molding. It is a fragmentary sectional view which expands and shows a part of FIG. It is an expanded sectional view in the receiving part of the hole formation blade part of FIG. 4, and the hole formation blade part. It is a fragmentary sectional view of the metal mold | die for blow molding which shows after air blowing. It is a fragmentary sectional view of the metal mold | die for blow molding which shows after the fracture | rupture of a thin part. It is a fragmentary sectional view of the metal mold | die for blow molding which shows the time of mold removal. It is a perspective view of the blow molded product for ducts. It is a fragmentary sectional view of the conventional mold for blow molding. It is a fragmentary sectional view which shows the hole formation part in the metal mold | die for blow molding of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Blow molding die 11 One type | mold 31 The other type | mold 38 Spring member 41 Hole formation blade part 45 Drive device 51 Receiving part of the hole formation blade part 60 Retraction | retraction prevention means 71 Solid part 73 Through-hole 74 Thin part P1 Parison

Claims (3)

A blow molded product in which a solid part protrudes from an outer surface by sandwiching a soft parison between blow molds composed of at least two molds, and blowing the air into the parison to shape the parison. In blow-molding method of blow-molded product, when blow-molding, a through-hole is opened in the solid part in the blow-molding mold,
In the portion of the blow molding die where the through hole is formed, one die is provided with a hole forming blade portion capable of moving forward toward the other die, and the other die is provided with the hole forming blade portion. Receiving the receiving part of the hole forming blade part in the opposite position so as to be retractable into the other mold,
The blow molding mold is closed and the softened parison is sandwiched between the blow molding molds, and the solid part is pressed against the receiving part of the hole forming blade part by the hole forming blade part. Forming a thin part in the solid part between the hole forming blade part and the receiving part of the hole forming blade part;
Next, air is blown into the parison to shape the parison,
After the parison is cooled and hardened, the hole forming blade portion is advanced and the receiving portion of the hole forming blade portion is retracted, so that the hole forming blade portion and the hole forming blade portion are received between the receiving portions. Breaking the thin part to form the through hole in the solid part,
A blow molding product punching method, wherein the blow molding product is removed by opening the blow molding die. In a blow molding die consisting of at least two molds for forming a blow molded product having a solid part protruding from the outer surface,
In the portion that forms the solid portion, a hole forming blade portion is provided in one mold so as to be able to advance toward the other mold, and a hole is formed in the other mold at a position facing the hole forming blade portion. The hole forming blade portion and the hole formation are provided by providing a receiving portion of the blade forming portion, and the hole forming blade portion presses the solid portion against the receiving portion of the hole forming blade portion by a closed mold at the time of blow molding It is configured to form a thin part in the solid part between the receiving parts of the blade part,
The hole-forming blade portion receiving portion is provided so as to be retractable inward of the other mold, and the hole-forming blade portion receiving portion of the hole-forming blade portion is closed when the thin portion is formed in the solid portion. The hole forming blade is provided by advancing the hole forming blade portion when it is possible to retreat after the thin wall portion is formed, and provided with a retraction preventing means for preventing the retreat and forming the thin wall portion. Blow molding die characterized in that the receiving part of the part is retracted. The hole forming blade portion can be advanced by a driving device;
The receiving part of the hole forming blade part is urged toward the one mold by a spring member, and the receiving part of the hole forming blade part forms the hole by the advance of the hole forming blade part when the retreat is possible. 3. The blow molding die according to claim 2, wherein when pressed by the blade part, the receiving part of the blade forming blade part moves backward against the elastic force of the spring member.

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