JP2016043675A - Production method of bellows, and bellows - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, in the case of producing bellows by using a direct blow molding process, a production method of bellows in which the occurrence of molded-material sagging can be suppressed, and to provide a bellows produced by the production method.SOLUTION: Provided is a bellows production method comprising: setting an extrusion formed tube-shaped parison 54 in a mold 52; inserting an expandable cylindrical member 70 in an opening 63 at an upper end part 54A of the parison 54; inserting a blow pin 53 in an interior space 70A of the cylindrical member 70 inserted in the opening 63, and expanding the diameter of the cylindrical member 70; and blowing air from the blow pin 53 inserted in the interior space 70A of the cylindrical member 70, into the parison 54 to allow the parison 54 to follow along an inner surface 52A of the mold 52, and thus forming the parison 54 into a bellows 15.SELECTED DRAWING: Figure 12

Description

  The present invention relates to a bellows manufacturing method and a bellows manufactured by the manufacturing method.

  A bellows-shaped bellows made of a material such as elastic rubber or resin is known. The bellows, for example, covers a tie rod connected to an end of a rack shaft of a rack and pinion mechanism that constitutes a steering mechanism of an automobile, and a housing that houses the rack shaft. The bellows in this case follows the movement of the rack shaft and the tie rod by expanding and contracting, and prevents foreign matter from entering the gap between the housing and the rack shaft.

  A direct blow molding method is known as a method for molding a hollow body made of rubber, resin, or the like. As shown in Patent Document 1 below, the direct blow molding method is generally used for molding containers for storing daily necessities such as foods and liquid detergents. Unlike a bellows, such a container does not require high dimensional accuracy.

JP 2004-1314 A

When manufacturing a bellows using a direct blow molding method, the manufacturing process assumed is illustrated in FIGS.
First, as shown in FIG. 1, a parison 3 formed in a tube shape by a molten material is extruded toward a lower mold 4 by an extruder 2 constituting a bellows manufacturing apparatus 1. The mold 4 is divided into a plurality of first split molds 5 movable in the horizontal direction and a second split mold 6 movable in the vertical direction.

  As shown in FIG. 2, when the parison 3 is pushed out until the second split mold 6 is accommodated in the lower end of the internal space of the parison 3, the plurality of first split molds 5 move laterally so as to approach each other. By doing so, the mold 4 is closed. Thus, a cavity 7 corresponding to the completed bellows is formed in the mold 4 by the inner surface 4 </ b> A of the mold 4. The upper end portion of the parison 3 is formed in a cylindrical shape by the upper end portion of the inner surface 4A of the mold 4, and an opening portion 3A that faces upward is formed in the upper end portion. The internal space of the parison 3 is closed from below by the second split mold 6.

  Next, the blow pin 8 which comprises the manufacturing apparatus 1 is arrange | positioned above the parison 3 set to the metal mold | die 4. FIG. The blow pin 8 protrudes downward, and a discharge port 8A is formed at the lower end thereof. An air flow path 8 </ b> B is formed inside the blow pin 8. The air flow path 8B extends upward from the discharge port 8A and is connected to an air supply mechanism (not shown) such as a compressor.

Next, as shown in FIG. 3, the blow pin 8 is lowered and inserted into the opening 3 </ b> A at the upper end of the parison 3 from above. Thereby, while the inner peripheral surface of the upper end part of the parison 3 is shape | molded by the outer peripheral surface of the blow pin 8, the internal space of the parison 3 is closed from upper direction.
Next, the compressed air supplied from the air supply mechanism is blown into the parison 3 from the discharge port 8A through the air flow path 8B. Thereby, as shown in FIG. 4, the parison 3 expands and is formed into a bellows along the inner surface 4 </ b> A of the mold 4. Finally, the bellows 9 are completed by removing the flash 9 protruding from the mold 4 in the parison 3.

  Thus, when manufacturing a bellows using a direct blow molding method, when the blow pin 8 is inserted in the opening part 3A of the parison 3, as shown in FIG. 3, the outer peripheral surface of the blow pin 8 is a parison in the opening part 3A. 3 is assumed to be dragged. A portion dragged by the blow pin 8 on the inner peripheral surface of the parison 3 becomes a drooping portion 10 that hangs down so as to protrude from the inner peripheral surface of the parison 3 as shown in FIGS. 3 and 4. Since the sagging portion 10 may be peeled off from the bellows to become a foreign substance, it is not preferable from the viewpoint of the reliability of the bellows.

  The present invention has been made under such background, and in the case of manufacturing a bellows using a direct blow molding method, the manufacturing method of a bellows capable of suppressing the occurrence of a sagging portion, and the manufacturing method. The purpose is to provide a bellows.

  The invention according to claim 1 is a method for producing a bellows (15) using a direct blow molding method, wherein an extruded tubular parison (54) is set in a mold (52); A step of inserting the extendable cylindrical member (70) into the opening (63) at the end (54A) of the parison, and a blow pin (53) in the internal space (70A) of the cylindrical member inserted into the opening. ) To expand the diameter of the cylindrical member, and air is blown into the parison from the blow pin inserted into the internal space of the cylindrical member so that the parison is aligned with the inner surface (52A) of the mold. Forming the parison into the bellows, thereby producing a bellows.

The invention according to claim 2 is characterized in that a groove (72) extending along the circumferential direction (S) is formed in the outer peripheral surface (70C) of the cylindrical member. It is a manufacturing method.
The invention according to claim 3 is a bellows manufactured by the manufacturing method according to claim 1 or 2.

  In addition, in the above, the numbers in parentheses represent reference numerals of corresponding components in the embodiments described later, but the scope of the claims is not limited by these reference numerals.

  According to the invention of claim 1, when manufacturing the bellows by the direct blow molding method, the extensible cylindrical member is inserted into the opening at the end of the parison set in the mold, and then the blow pin is And inserted into the internal space of the cylindrical member inserted into the opening. When the blow pin is inserted into the internal space of the cylindrical member, the cylindrical member expands in diameter and contacts the inner peripheral surface of the parison at the opening. Thereby, the inner peripheral surface of the parison in the opening is formed by the cylindrical member.

  If the cylindrical member is interposed between the blow pin and the inner circumferential surface of the parison at the opening, the blow pin contacts the inner circumferential surface of the parison at the opening even if the blow pin is inserted into the opening of the parison. do not do. Therefore, it can avoid that the inner peripheral surface of the parison in the opening is dragged by the blow pin. Therefore, generation | occurrence | production of the sagging part in an opening part can be suppressed.

According to invention of Claim 2, the convex part extended along the circumferential direction is formed in the inner peripheral surface of the bellows after completion, when a part of parison enters into the groove | channel of the outer peripheral surface of a cylindrical member. The In the state where the bellows is assembled to the mating part, the convex portion closes the gap between the inner peripheral surface of the bellows and the mating part, so that foreign matter can be prevented from passing through the gap.
According to invention of Claim 3, in the bellows manufactured by the manufacturing method of invention of Claim 1 or 2, generation | occurrence | production of a sagging part can be suppressed.

FIG. 1 is a schematic cross-sectional view showing a manufacturing method according to a comparative example for bellows. FIG. 2 is a schematic cross-sectional view showing the next step of FIG. FIG. 3 is a schematic cross-sectional view showing the next step of FIG. FIG. 4 is a schematic cross-sectional view showing the next step of FIG. FIG. 5 is a schematic perspective view of a bellows according to an embodiment of the present invention. FIG. 6 is a schematic diagram showing a schematic configuration of a steering device in which a bellows is incorporated. FIG. 7 is a schematic diagram showing a schematic configuration of a constant velocity joint in which a bellows is incorporated. FIG. 8 is a schematic cross-sectional view showing a method for manufacturing a bellows according to an embodiment of the present invention. FIG. 9 is a schematic cross-sectional view showing the next step of FIG. FIG. 10 is a schematic cross-sectional view showing the next step of FIG. FIG. 11 is a schematic cross-sectional view showing the next step of FIG. FIG. 12 is a schematic cross-sectional view showing the next step of FIG. FIG. 13 is a schematic cross-sectional view of the completed bellows.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 5 is a schematic perspective view of the bellows 15 according to the embodiment of the present invention. As shown in FIG. 5, the bellows 15 is tubular, and is formed of a material such as rubber or resin having elasticity (for example, an olefin-based thermoplastic elastomer). One end 16 and the other end 17 in the axial direction X of the bellows 15 are formed in an annular shape, and a portion of the bellows 15 between the one end 16 and the other end 17 is a bellows formed in a bellows tube. Part 18. The one end portion 16 and the other end portion 17 may have the same or different dimensions (such as the inner diameter and the length in the axial direction X). Moreover, the dimension of the unevenness | corrugation in the bellows part 18 may be the same in the whole area of the axial direction X, and may differ in the middle.

FIG. 6 is a schematic diagram showing a schematic configuration of the steering device 20 in which the bellows 15 is incorporated. As shown in FIG. 6, the bellows 15 is incorporated into a vehicle steering device 20 as an example.
The steering device 20 includes a steering shaft 22 to which a steering wheel 21 is connected, and a steering mechanism 23 that steers a steered wheel (not shown) in conjunction with the rotation of the steering wheel 21. The steering mechanism 23 is a rack and pinion mechanism, and includes a rack shaft 24 extending in the left-right direction of a vehicle body (not shown) of the automobile and a pinion shaft 25 connected to the steering shaft 22. The pinion shaft 25 has a pinion 25 </ b> A that meshes with a rack 24 </ b> A provided on the rack shaft 24. The rotation of the steering wheel 21 and the pinion shaft 25 accompanying the steering of the steering wheel 21 is converted into a linear movement of the vehicle body in the left-right direction by the rack 24A and the pinion 25A.

  The rack shaft 24 has a hollow cylindrical shape extending in the left-right direction and is accommodated in a housing 26 fixed to the vehicle body. Each end of the rack shaft 24 in the left-right direction protrudes from the housing 26. A tie rod 27 is connected to each end of the rack shaft 24 via an inner ball joint 28. A tie rod 27 connected to each end of the rack shaft 24 is connected to a steered wheel (not shown) via a knuckle arm (not shown). The steered wheels are steered in conjunction with the movement of the rack shaft 24.

One bellows 15 is provided at each end of the rack shaft 24 in the left-right direction with the axial direction X extending along the left-right direction. The end of the rack shaft 24, the inner ball joint 28, and the end connected to the inner ball joint 28 in the tie rod 27 are accommodated in the bellows 15.
One end portion 16 of the bellows 15 is fitted on the outer peripheral surface of the tie rod 27, and the other end portion 17 of the bellows 15 is fitted on the inner peripheral surface of the housing 26. An annular tightening ring 29 is externally fitted to the one end portion 16 so that the one end portion 16 is in close contact with the outer peripheral surface of the tie rod 27. The bellows 15 seals the gap between the inner peripheral surface of the housing 26 and the rack shaft 24, and prevents foreign matter from entering the gap.

When the rack shaft 24 and the tie rod 27 move as the steering wheel 21 is steered, in the bellows 15, the bellows portion 18 between the one end portion 16 and the other end portion 17 follows the movement of the rack shaft 24 and the tie rod 27. It expands and contracts freely.
FIG. 7 is a schematic diagram showing a schematic configuration of the constant velocity joint 35 in which the bellows 15 is incorporated. The bellows 15 may be incorporated in the constant velocity joint 35 shown in FIG. The constant velocity joint 35 is a component of an automobile and is provided on a drive shaft of the automobile. The constant velocity joint 35 includes an input shaft 36, an output shaft 37, and a plurality of balls 38 that are positioned at a connecting portion between the input shaft 36 and the output shaft 37 and transmit rotation from the input shaft 36 to the output shaft 37.

  In the bellows 15, one end 16 is externally fitted to the input shaft 36, and the other end 17 is externally fitted to the output shaft 37. An annular clamping ring 39 is externally fitted to the one end portion 16, and the one end portion 16 is brought into close contact with the outer peripheral surface of the input shaft 36. An annular clamping ring 40 is externally fitted to the other end portion 17, and the other end portion 17 is brought into close contact with the outer peripheral surface of the output shaft 37. The bellows 15 seals the connecting portion between the input shaft 36 and the output shaft 37, and prevents foreign matter from entering the connecting portion.

The bellows 15 can also be used for devices other than the steering device 20 and the constant velocity joint 35.
Next, a method for manufacturing the bellows 15 will be described. FIG. 8 is a schematic cross-sectional view showing a manufacturing method according to an embodiment of the present invention for the bellows 15. FIG. 9 is a schematic cross-sectional view showing the next step of FIG. FIG. 10 is a schematic cross-sectional view showing the next step of FIG.

First, a manufacturing apparatus 50 for manufacturing the bellows 15 will be described with reference to FIGS. The manufacturing apparatus 50 includes an extruder 51, a mold 52, a cylindrical member 70, and a blow pin 53.
Referring to FIG. 8, extruder 51 has an annular outlet 51A on its lower surface, and pushes the material melted by heating downward from outlet 51A. Thereby, the parison 54 extruded from the material hangs downward from the outlet 51 </ b> A of the extruder 51. The parison 54 is a tube from which the bellows 15 is based, and the axial direction thereof coincides with the axial direction X of the bellows 15. The axial direction X of the parison 54 that hangs down coincides with the vertical direction Z.

The mold 52 is divided into a plurality of (here, a pair) first split molds 55 movable in the horizontal direction Y and a second split mold 56 movable in the vertical direction Z. The manufacturing apparatus 50 includes an actuator (not shown) that moves each of the first split mold 55 and the second split mold 56.
Each first split mold 55 includes an upper arc surface 55A formed in an arc shape when viewed from the vertical direction Z, an irregular surface 55B having irregularities that coincide with the outer surface of the bellows portion 18 of the bellows 15, and a vertical direction Z. A lower circular arc surface 55 </ b> C formed in an arc shape when viewed is formed in this order from above. The second split mold 56 has a circular outer peripheral surface 56 </ b> A that forms an outline of the second split mold 56 when viewed in the vertical direction Z.

  Referring to FIG. 9, the cylindrical member 70 is a cylindrical body having an axis G extending in the vertical direction Z as a circle center. A circular opening 71 is formed at each of the upper end and the lower end of the cylindrical member 70, and the internal space 70 </ b> A of the cylindrical member 70 is exposed to both the upper and lower sides through the opening 71. An inner peripheral surface 70B that divides the internal space 70A in the cylindrical member 70 is formed in a cylindrical shape centered on the axis G, and is connected to the openings 71 at the upper end and the lower end of the cylindrical member 70, respectively. The inner diameter of the inner peripheral surface 70B may be constant throughout the entire area in the vertical direction Z. Alternatively, as in this embodiment, the inner peripheral surface 70B may be a tapered surface that becomes gradually narrower downward.

  The cylindrical member 70 is made of an elastic material such as rubber, and can extend at least outward in the radial direction R of the cylindrical member 70. An annular groove 72 extending along the circumferential direction S is formed on the outer peripheral surface 70 </ b> C of the cylindrical member 70. Although the number of the grooves 72 can be arbitrarily set, in this embodiment, the two grooves 72 extend in parallel in the up-down direction Z with an interval. The cross section of the groove 72 when cut along a plane along both the radial direction R and the vertical direction Z has a substantially semicircular shape that is recessed toward the axis G side. A flange portion 73 projecting outward in the radial direction R is integrally provided at the upper end portion of the outer peripheral surface 70C.

The manufacturing apparatus 50 includes an actuator (not shown) that moves the cylinder member 70 in the vertical direction Z while supporting the cylindrical member 70 from above.
Referring to FIG. 10, blow pin 53 is a metal (for example, copper) pin extending downward. The blow pin 53 has an outer peripheral surface 53A having an axis J extending in the up-down direction Z as a circle center. The lower end portion of the outer peripheral surface 53A is the tip end portion 53B of the blow pin 53, and is rounded so as to be smoothly reduced in diameter as it goes downward. An air flow path 57 is formed in the blow pin 53. One end of the air flow path 57 extends downward along the axis J in the blow pin 53 and is exposed downward from the lower end of the front end 53B of the blow pin 53. A portion of the air flow channel 57 that is exposed downward from the distal end portion 53 </ b> B is a discharge port 58. The other end of the air flow channel 57 is connected to an air supply mechanism (not shown) such as a compressor included in the manufacturing apparatus 50. A cooling passage (not shown) is formed in the blow pin 53. When the bellows 15 is manufactured, the entire blow pin 53 is cooled by the cooling water flowing through the cooling flow path.

The manufacturing apparatus 50 includes an actuator (not shown) that moves the blow pin 53 in the vertical direction Z while supporting the blow pin 53 from above.
The bellows 15 is manufactured by the manufacturing apparatus 50 by the following manufacturing method using the direct blow molding method. Compared with the press blow molding method and the injection blow molding method that have been used for manufacturing the bellows 15 in the direct blow molding method, the equipment cost of the manufacturing apparatus 50 can be kept low. Can be manufactured.

  First, as shown in FIG. 8, in a state where the mold 52 is opened by separating the pair of first split molds 55 from each other, the tubular parison 54 is directed to the lower mold 52 by the extruder 51. Extruded. The extruded parison 54 is disposed between the pair of first split dies 55. The second split mold 56 is inserted into the lower end portion of the internal space of the parison 54 from below.

  Next, as shown in FIG. 9, the mold 52 is closed by bringing the pair of first split molds 55 closer to each other. The upper arcuate surfaces 55A of the pair of first split molds 55 are continuous to form a circular upper circumferential surface 60, and the lower arcuate surfaces 55C of the pair of first split molds 55 are continuous to form a circle. A lower circumferential surface 61 of the shape is formed. The second split mold 56 is located at the same position as the lower circumferential surface 61 in the vertical direction Z, and the outer peripheral surface 56A of the second split mold 56 is surrounded by the lower circumferential surface 61 in a non-contact manner.

  The upper circumferential surface 60 corresponds to the outer peripheral surface of the one end portion 16 of the completed bellows 15, and the lower circumferential surface 61 corresponds to the outer peripheral surface of the other end portion 17 of the bellows 15. The outer peripheral surface 56A corresponds to the inner peripheral surface of the other end portion 17 (see FIG. 5). The uneven surfaces 55B of the pair of first split molds 55 are continuous and correspond to the contour of the bellows portion 18 of the bellows 15. The upper circumferential surface 60, the lower circumferential surface 61, and the uneven surface 55B constitute an inner surface 52A of the closed mold 52. In the closed mold 52, a cavity 62 corresponding to the contour of the bellows 15 is formed by the inner surface 52A.

  When the mold 52 is closed, the parison 54 is set in the cavity 62 in the mold 52. In the parison 54, the outer peripheral surface of the upper end portion 54 </ b> A is along the upper peripheral surface 60 of the mold 52, and the lower end portion 54 </ b> B is the outer peripheral surface of the lower peripheral surface 61 of the mold 52 and the second split mold 56. It arrange | positions in the clearance gap between 56A. A portion of the lower end portion 54 </ b> B that protrudes downward from the gap is a flash 64. In the parison 54, a middle portion 54C between the upper end portion 54A and the lower end portion 54B is in the same position as the concave / convex surface 55B in the vertical direction Z, and is not in contact with the concave / convex surface 55B. The internal space of the parison 54 is closed from below by the second split type 56. In the parison 54, a circular opening 63 is formed in an upper end 54 </ b> A that is the end opposite to the second split mold 56 in the axial direction X. The opening 63 is exposed upward from the closed mold 52.

Next, the mold 52 on which the parison 54 is set moves to a position below the cylindrical member 70 described above. The manufacturing apparatus 50 includes an actuator (not shown) that moves the mold 52. In a state where the movement of the mold 52 is completed, the opening 63 of the parison 54 is located immediately below the cylindrical member 70. The inner diameter of the opening 63 is larger than the outer diameter of the outer peripheral surface 70 </ b> C of the cylindrical member 70.
Next, as shown in FIG. 9, the cylindrical member 70 is inserted into the opening 63 of the parison 54 from above in the axial direction X. At this time, since the cylindrical member 70 is fitted into the opening 63 with a gap, the outer peripheral surface 70 </ b> C of the cylindrical member 70 does not contact the inner peripheral surface of the parison 54 in the opening 63. The cylindrical member 70 after the insertion is positioned with respect to each of the mold 52 and the parison 54 by the flange portion 73 being hooked on the first split mold 55 and the upper end portion 54A of the parison 54 from above.

  With the cylindrical member 70 inserted into the opening 63 of the parison 54, the mold 52 moves to below the blow pin 53. When the blow pin 53 has already been kept above the cylindrical member 70, the mold 52 does not have to move. In any case, when the mold 52 is positioned below the blow pin 53 as shown in FIG. 10, the opening 71 at the upper end of the cylindrical member 70 is positioned directly below the tip 53 B of the blow pin 53. The outer diameter of the outer peripheral surface 53 </ b> A (excluding the tip portion 53 </ b> B) of the blow pin 53 is smaller than the inner diameter of the opening 63, but larger than the inner diameter of the inner peripheral surface 70 </ b> B of the cylindrical member 70.

  Next, as shown in FIG. 11, the blow pin 53 is inserted from above in the axial direction X into the internal space 70 </ b> A of the cylindrical member 70 inserted into the opening 63. At this time, the blow pin 53 is lightly pressed into the inner peripheral surface 70 </ b> B of the cylindrical member 70 in a state where the axis G of the cylindrical member 70 and the axis J of the blow pin 53 coincide. Thereby, the cylindrical member 70 is expanded in diameter by being pushed and expanded outward in the radial direction R by the blow pin 53, and contacts the inner peripheral surface of the parison 54 in the opening 63. Thus, the inner peripheral surface of the parison 54 in the opening 63 is molded so as to coincide with the outer peripheral surface 70 </ b> C of the cylindrical member 70. Therefore, a part of the parison 54 enters the groove 72 of the outer peripheral surface 70 </ b> C of the cylindrical member 70.

  In this way, if the cylindrical member 70 is interposed between the blow pin 53 and the inner peripheral surface of the parison 54 in the opening 63, the blow pin 53 can be opened even if the blow pin 53 is inserted into the opening 63 of the parison 54. No contact is made with the inner peripheral surface of the parison 54 at 63. Therefore, the inner peripheral surface of the parison 54 in the opening 63 can be prevented from being dragged by the blow pin 53. Therefore, generation | occurrence | production of the drooping part 10 (refer FIG. 3) in the opening part 63 can be suppressed. Therefore, even the manufactured bellows 15 can suppress the occurrence of the sagging portion 10.

The inner peripheral surface 70B of the cylindrical member 70 is the aforementioned tapered surface (see FIG. 10), and the tip 53B of the blow pin 53 is rounded, so that the blow pin 53 is smooth in the internal space 70A of the cylindrical member 70. The cylindrical member 70 is surely expanded in diameter. In the blow pin 53 after insertion, the distal end portion 53B protrudes downward from the internal space 70A.
The blow pin 53 inserted into the internal space 70A of the cylindrical member 70 is cooled as described above. Therefore, the inner peripheral surface of the parison 54 in the opening 63 is cured by being cooled. Further, the internal space of the parison 54 is closed from above by the cylindrical member 70 and the blow pin 53.

  Next, compressed air is supplied to the air flow path 57 of the blow pin 53 from the air supply mechanism (not shown) described above. As a result, air is blown into the parison 54 from the discharge port 58 of the blow pin 53 inserted into the internal space 70 </ b> A of the cylindrical member 70, as indicated by a solid arrow in FIG. 12. As a result, the parison 54 is formed into the bellows 15 by expanding and along the inner surface 52 </ b> A of the mold 52. Thus, in the parison 54, the upper end portion 54A becomes the one end portion 16 of the bellows 15, the lower end portion 54B becomes the other end portion 17 of the bellows 15, and the midway portion 54C becomes the bellows portion 18.

Next, the flash 64 protruding from the mold 52 in the cured parison 54 is removed, and the cylindrical member 70 and the blow pin 53 are pulled upward from the opening 63 of the parison 54, whereby the bellows 15 is completed. When the mold 52 is opened, the completed bellows 15 is taken out.
FIG. 13 is a schematic cross-sectional view of the completed bellows 15. As described above, a part of the parison 54 enters the groove 72 of the outer peripheral surface 70C of the cylindrical member 70 during molding, so that the inner peripheral surface 16A of the one end portion 16 of the completed bellows 15 has a circumferential direction (cylindrical member). The same number of protrusions 74 as the grooves 72 are formed. In a state where the bellows 15 is assembled to a mating part such as the tie rod 27 (see FIG. 6) or the input shaft 36 (see FIG. 7) described above, the convex portion 74 is a gap between the inner peripheral surface 16A of the bellows 15 and the mating part. Therefore, foreign matter can be prevented from passing through the gap.

  The present invention is not limited to the contents of the above embodiments, and various modifications can be made within the scope of the claims.

DESCRIPTION OF SYMBOLS 15 ... Bellows, 52 ... Mold, 52A ... Inner surface, 53 ... Blow pin, 54 ... Parison, 54A ... Upper end part, 63 ... Opening part, 70 ... Cylindrical member, 70A ... Internal space, 70C ... Outer peripheral surface, 72 ... Groove, S ... Circumferential direction

Claims (3)

A method for producing a bellows using a direct blow molding method,
Setting the extruded tubular parison in a mold;
Inserting an extensible cylindrical member into an opening at the end of the parison;
Inserting a blow pin into the internal space of the cylindrical member inserted into the opening to expand the diameter of the cylindrical member;
Molding the parison into the bellows by blowing air into the parison from the blow pin inserted into the internal space of the cylindrical member and causing the parison to follow the inner surface of the mold;
A method for producing a bellows, comprising:   The method for manufacturing a bellows according to claim 1, wherein a groove extending along a circumferential direction is formed on an outer peripheral surface of the cylindrical member.   A bellows manufactured by the manufacturing method according to claim 1 or 2.

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