Patent Description:
<CIT> discloses a pressure vessel made of resin stores high-pressure gas or high-pressure liquid such as compressed hydrogen or liquefied petroleum gas (LPG). Such a pressure vessel includes a resin liner, a metal cap member, and a fiber reinforced resin layer. The resin liner includes a storage portion to store gas or liquid and a tubular protruding portion (neck portion) protruding outward from the storage portion. The cap member is provided around the neck portion and includes a disk-like contact portion that is in contact with an outer surface of the storage portion. The fiber reinforced resin layer covers outer surfaces of the storage portion of the resin liner and the contact portion of the cap member. In this pressure vessel, to prevent occurrence of a leak path, an O ring is interposed between the neck portion and a valve inserted into the neck portion (see <FIG> of Patent Document <NUM>), between the neck portion and the cap member (see <FIG> of Patent Document <NUM>), and the like.

Further, the applicant proposes in <CIT> a pressure vessel and a manufacturing method thereof, according to the preamble of claim <NUM>, and in which a gas barrier layer is not exposed on a contact surface (a surface that is in contact with a sealing member) provided around a neck portion of a resin liner when the resin liner having multiple layers including the gas barrier layer is manufactured by using blow molding. In this pressure vessel, at least the gas barrier layer and its outer layer are removed from a portion of the neck portion of the resin liner that is in contact with the sealing member, and thus the gas barrier layer is not exposed in the above portion. Accordingly, the degradation of sealing property and the deterioration of the sealing member are prevented.

In the pressure vessel shown in <FIG> of <CIT> in which the O ring is interposed between the neck portion and the valve, the O ring is sandwiched, in the axial direction of the valve, between a fall-prevention wall protruding inward from an inner circumference of the neck portion of the resin liner and a large diameter portion of the valve. Accordingly, the self-sealing function (the function that the sealing property of the sealing member is enhanced as the resin liner receives high pressure inside the vessel) may not be fulfilled, and thus the sealing property may be degraded.

In the pressure vessel shown in <FIG> of <CIT> in which the O ring is interposed between the neck portion and the cap member, the self-sealing function can be fulfilled since the O ring is arranged around the neck portion. However, a parting line, which is formed by a slight gap or step generated on a divisional surface of the molds, appears on an outer circumferential surface of the neck portion formed by using blow molding. Due to the parting line, the sealing property may be degraded and the sealing member may be deteriorated.

Further, in the pressure vessel described in <CIT>, an outer circumference of a portion of the neck portion that is in contact with the sealing member is removed, and thus the parting line does not appear on the above portion. However, to finish the removal surface smoothly, the workload and cost of processing become large.

In view of the above background, an object of the present invention is to provide a blow molding device for manufacturing a resin liner and a manufacturing method of the resin liner using the blow molding device that can suppress the degradation of sealing property of a pressure vessel and the deterioration of a sealing member, and reduce the workload and cost of manufacture.

To achieve the above object, one aspect of the present invention provides a blow molding device for manufacturing a resin liner for a pressure vessel, the resin liner including a tubular neck portion to which a cap member is fitted externally, the blow molding device comprising: a pair of molds configured to be clamped so as to sandwich, from both lateral sides, a parison from which the resin liner is formed, the pair of molds defining a cavity having a shape corresponding to a contour of a main body portion of the resin liner; and a blow pin configured to form the neck portion together with the molds and having an air supply opening to be arranged inside the parison, wherein the blow pin includes: a blow pin body portion provided with an air supply passage that leads to the air supply opening and having an outer circumferential surface of a shape corresponding to an inner circumferential surface of the neck portion; and a ring portion provided coaxially with the blow pin body portion and forming an annular recess portion between the blow pin body portion and the ring portion so as to form an outer circumferential surface of a tip portion of the neck portion, the annular recess portion being recessed in a direction away from the cavity; and wherein the blow pin is provided with an air release passage extending from a bottom of the annular recess portion.

According to this aspect, the tip portion of the neck portion of the resin liner is formed by the annular recess portion, and the shape of an inner circumferential surface of the ring portion is transferred to the outer circumferential surface of the tip portion of the neck portion. Accordingly, it is possible to form the outer circumferential surface of the tip portion of the neck portion into a smooth surface without a parting line. Accordingly, by attaching a sealing member between the neck portion and the cap member such that the sealing member is in contact with the outer circumferential surface of the tip portion of the neck portion, it is possible to prevent the degradation of sealing property and the deterioration of the sealing member. Further, by placing the sealing member outside the neck portion, it is possible to improve the sealing property by virtue of the self-sealing function.

According to this aspect, the parison is more likely to spread over the bottom of the annular recess portion.

Preferably, the ring portion is provided fixedly to the blow pin body portion, and the blow pin is movable in an axial direction thereof with respect to the pair of molds.

According to this aspect, by moving the blow pin toward the cavity, it is possible to cause the parison to spread over the bottom of the annular recess portion even if it is impossible to cause the parison to reach the bottom of the annular recess portion only by clamping the molds. Accordingly, it is possible to increase the axial length of the tip portion of the neck portion on which the parting line does not appear.

Preferably, the ring portion is slidable in an axial direction thereof with respect to the blow pin body portion.

According to this aspect, by sliding the ring portion in the axial direction thereof toward the cavity with respect to the blow pin body portion, it is possible to cause the parison to spread over the bottom of the annular recess portion without moving the blow pin body portion in the axial direction thereof. Accordingly, it is possible to increase the axial length of the tip portion of the neck portion on which the parting line does not appear.

To achieve the above object, one aspect of the present invention provides a manufacturing method of the resin liner using the blow molding device, the manufacturing method comprising: a parison arranging process of arranging the parison on an outer circumferential side of the blow pin and between the pair of molds that are laterally separated from each other; a mold clamping process of clamping the pair of molds such that the pair of molds sandwich the parison; and a blow process of expanding the parison by supplying air to an inside thereof from the air supply opening of the blow pin and transferring a shape of an inner surface of the cavity to a portion of the parison from which the main body portion of the resin liner is formed, wherein between the mold clamping process and the blow process, the parison enters the annular recess portion and a shape of an inner circumferential surface of the ring portion is transferred to a portion of the parison from which the tip portion of the neck portion is formed.

According to this aspect, it is possible to form the outer circumferential surface of the tip portion of the neck portion into a smooth surface without a parting line. Accordingly, by attaching a sealing member between the neck portion and the cap member, it is possible to improve the sealing property by virtue of the self-sealing function and prevent the deterioration of the sealing member.

Preferably, between the mold clamping process and the blow process, the annular recess portion moves toward the cavity along an axial direction of the blow pin.

According to this aspect, by moving the annular recess portion toward the cavity, it is possible to cause the parison to spread over the bottom of the annular recess portion even if it is impossible to cause the parison to reach the bottom of the annular recess portion by the mold clamping process. Accordingly, it is possible to increase the axial length of the tip portion of the neck portion on which the parting line does not appear.

Preferably, the ring portion is provided fixedly to the blow pin body portion and the blow pin is movable in the axial direction, and between the mold clamping process and the blow process, the annular recess portion moves as the blow pin moves in the axial direction.

According to this aspect, by moving the blow pin toward the cavity, it is possible to move the annular recess portion in the axial direction thereof and cause the parison to spread over the bottom of the annular recess portion.

Preferably, the ring portion is slidable in an axial direction thereof with respect to the blow pin body portion, and between the mold clamping process and the blow process, the annular recess portion moves as the ring portion slides in the axial direction thereof with respect to the blow pin body portion.

According to this aspect, by sliding the ring portion toward the cavity with respect to the blow pin body portion, it is possible to move the annular recess portion in the axial direction thereof and to cause the parison to spread over the bottom of the annular recess portion without moving the blow pin body portion in the axial direction thereof.

Thus, according to the above aspects, it is possible to provide a blow molding device for manufacturing a resin liner and a manufacturing method of the resin liner using the blow molding device that can suppress the degradation of sealing property of a pressure vessel and the deterioration of a sealing member, and reduce the workload and cost of manufacture.

In the following, an embodiment of the present invention will be described in detail with reference to the drawings.

<FIG> is a vertical cross-sectional view (partially cut cross-sectional view) showing a pressure vessel <NUM> according to the embodiment. As shown in <FIG>, the pressure vessel <NUM> includes a resin liner <NUM> defining a storage chamber 2a that stores gas or liquid, a metal cap member <NUM> attached to an outer surface of the resin liner <NUM>, and a reinforcement layer <NUM> externally stacked on the resin liner <NUM> and the cap member <NUM>. An attachment is attached to the cap member <NUM>. In the illustrated example, as the attachment, a valve <NUM> for injecting and discharging high-pressure gas or high-pressure liquid is attached such that the valve <NUM> is inserted into the cap member <NUM>.

The resin liner <NUM> includes a main body portion <NUM> having a hollow cylindrical shape so as to form the storage chamber 2a, and a tubular neck portion <NUM> formed continuously with the main body portion <NUM> so as to protrude outward from the main body portion <NUM>. The resin liner <NUM> has a single-layer structure in the present embodiment. The material of the resin liner <NUM> is selected according to the gas or liquid to be stored therein and the filling condition (for example, filling pressure) thereof. For example, polyethylene (PE), high density polyethylene (HDPE), polyamide, polyketone, or polyphenylene sulfide (PPS) can be used as the material of the resin liner <NUM>. In the present embodiment, the resin liner <NUM> is made of high density polyethylene (HDPE).

In another embodiment, the resin liner <NUM> may have a multi-layer structure. For example, the resin liner <NUM> may have a laminated structure of three or more layers including a gas barrier layer and two resin layers sandwiching the gas barrier layer. Ethylene vinyl alcohol copolymer resin (EVOH resin) is suitable for the material of the gas barrier layer. Also, high density polyethylene (HDPE) into which fine plate-shaped polyamide sheets are mixed may be used as the material of the gas barrier layer.

The cap member <NUM> has a cylindrical cap tubular portion <NUM> externally fitted to the neck portion <NUM> of the resin liner <NUM>, and an annular flange portion <NUM> protruding radially outward from a base end of the cap tubular portion <NUM> on a side of the resin liner <NUM>. The cap tubular portion <NUM> and the flange portion <NUM> are formed integrally and continuously with each other. In a state where the cap tubular portion <NUM> is externally fitted to the neck portion <NUM>, the flange portion <NUM> is arranged along an outer surface of the main body portion <NUM> of the resin liner <NUM> around the neck portion <NUM>.

The reinforcement layer <NUM> consists of, for example, fiber reinforced plastic (FRP) so as to reinforce the compressive strength of the resin liner <NUM>. The reinforcement layer <NUM> is provided so as to cover outer surfaces of the main body portion <NUM> of the resin liner <NUM> and the flange portion <NUM> of the cap member <NUM> by using, for example, a filament winding method to wind a fiber bundle impregnated with a resin and then cure the resin. The method of stacking the reinforcement layer <NUM> is not limited to this, and other methods such as a sheet winding method to wind a resin sheet in which fibers are embedded may be used.

When the reinforcement layer <NUM> is formed, the cap member <NUM> functions as one of a pair of chucking portions to support the resin liner <NUM>. An engagement portion (for example, a screw portion; not shown) for attaching a boss that functions as the other of the pair of chucking portions is formed at the other end of the resin liner <NUM> on a side opposite to the cap member <NUM>. Alternatively, a member (not shown) having a similar configuration to the cap member <NUM> may be attached to the other end of the resin liner <NUM>.

<FIG> is an enlarged view of a main portion of <FIG>. As shown in <FIG>, the cap tubular portion <NUM> includes a cap large diameter portion <NUM> and a cap small diameter portion <NUM>. The cap large diameter portion <NUM> is arranged on a side of the flange portion <NUM>, and has an inner diameter substantially the same as an outer diameter of the neck portion <NUM>. The cap small diameter portion <NUM> is arranged on a tip end side of the cap tubular portion <NUM>, and has an inner diameter substantially the same as an inner diameter of the neck portion <NUM>. An annular first sealing groove <NUM> that receives a first sealing member <NUM> interposed between the resin liner <NUM> and the cap member <NUM> is formed in a portion of the cap large diameter portion <NUM> on a side of the cap small diameter portion <NUM>. A cap sealing surface <NUM> that consists of an inner circumferential surface (an annular smooth surface) is formed in the cap small diameter portion <NUM> on a side of the cap large diameter portion <NUM>. A cap coupled portion <NUM> to which the valve <NUM> is coupled is formed on a tip end side of the cap small diameter portion <NUM>. The first sealing member <NUM> may consist of, for example, an O ring. The cap coupled portion <NUM> consists of a female screw in the illustrated example, but is not limited to this embodiment.

The valve <NUM> includes a valve inserted portion <NUM> inserted into the cap tubular portion <NUM>, and a valve exposed portion <NUM> arranged outside the cap tubular portion <NUM> and exposed to an outside. A valve coupled portion <NUM> coupled to the cap coupled portion <NUM> of the cap member <NUM> is formed in the valve inserted portion <NUM> on a side of the valve exposed portion <NUM>. In the present embodiment, the valve coupled portion <NUM> consists of a male screw. A tool engagement portion 22a (for example, a hexagonal portion) for coupling (fastening) the valve coupled portion <NUM> to the cap coupled portion <NUM> is provided integrally with the valve exposed portion <NUM>. A portion of the valve inserted portion <NUM> on a tip end side of the valve coupled portion <NUM> has an outer diameter substantially the same as an inner diameter of the neck portion <NUM> and an inner diameter of the cap small diameter portion <NUM>. In a state where the valve <NUM> is attached, the valve inserted portion <NUM> has a length to reach the cap large diameter portion <NUM> and enters an inside of the neck portion <NUM>. An annular second sealing groove <NUM> that receives a second sealing member <NUM> interposed between the valve <NUM> and the cap member <NUM> is formed on an outer circumferential surface of a portion of the valve inserted portion <NUM> corresponding to the cap sealing surface <NUM>. The second sealing member <NUM> may consist of, for example, an O ring.

<FIG> is a perspective view of a main portion of the resin liner <NUM> shown in <FIG>. As shown in <FIG>, a coupled structure <NUM> coupled to the cap member <NUM> so as to prevent the rotation of the cap member <NUM> around an axis thereof is formed on a base end side of the neck portion <NUM> of the resin liner <NUM>. The coupled structure <NUM> has a polygonal shape (a hexagonal shape in the illustrated example) in the present embodiment, and is a large diameter portion whose diameter is larger than a tip end side of the neck portion <NUM>. A corresponding coupled structure <NUM> (<FIG>) coupled to the coupled structure <NUM> is formed inside the cap member <NUM>. The corresponding coupled structure <NUM> has a polygonal shape (hexagonal shape) in the present embodiment, and consists of a recessed portion formed on a bottom surface of the cap member <NUM>.

In another embodiment, as shown in <FIG>, the coupled structure <NUM> may consist of a male screw formed on a base end side of the neck portion <NUM>. An outer diameter of the male screw is set larger than an outer diameter of the tip end side of the neck portion <NUM>. In this case, the corresponding coupled structure <NUM> provided in the cap member <NUM> may consist of a female screw engaging with the male screw. Accordingly, it is possible to prevent not only the rotation of the cap member <NUM> around the axis thereof with respect to the neck portion <NUM> of the resin liner <NUM> but also the movement of the cap member <NUM> in an axial direction thereof with respect to the neck portion <NUM> of the resin liner <NUM>.

The resin liner <NUM> is formed by blow molding. As shown in <FIG> and <FIG>, a parting line <NUM>, which appears at a dividing position of a pair of molds <NUM> (see <FIG>), is formed on an outer surface of the resin liner <NUM>. The parting line <NUM> is a linear protrusion protruding from the outer surface of the resin liner <NUM>. The parting line <NUM> is formed on an entire circumference of the outer surface of the main body portion <NUM> of the resin liner <NUM> and an outer surface of the base portion of the neck portion <NUM> including the coupled structure <NUM>. The parting line <NUM> is not formed on an inner surface of the resin liner <NUM> and an outer surface of a tip portion <NUM> of the neck portion <NUM>.

An annular burr <NUM> is generated between the tip portion <NUM> of the neck portion <NUM> on which the parting line <NUM> is not formed and the base portion of the neck portion <NUM> on which the parting line <NUM> is formed. The burr <NUM> is removed after the blow molding. The method of removing the burr <NUM> is not limited. For example, a cutting process, a grinding process, a laser process, or the like can be used therefor. By contrast, the shape of the blow pin <NUM> (see <FIG>; the detailed structure thereof will be described later) that functions as another mold is transferred to the outer surface of the tip portion <NUM> of the neck portion <NUM> on which the parting line <NUM> does not appear. Accordingly, the outer surface of the tip portion <NUM> of the neck portion <NUM> is formed smoothly in the blow molding, and the secondary process after the blow molding is not performed.

As shown in <FIG>, the first sealing member <NUM> is in contact with an outer circumferential surface of the tip portion <NUM> of the neck portion <NUM> on which the parting line <NUM> does not appear. If the parting line <NUM> appears on a surface of the neck portion <NUM> with which the first sealing member <NUM> is in contact, the sealing property may be degraded and the first sealing member <NUM> may be deteriorated due to the parting line <NUM>. By contrast, in the present embodiment, the parting line <NUM> does not appear on the surface of the neck portion <NUM> with which the first sealing member <NUM> is in contact. Accordingly, it is possible to prevent the degradation of the sealing property and the deterioration of the first sealing member <NUM>. Further, as the first sealing member <NUM> is arranged outside the neck portion <NUM>, the first sealing member <NUM> fulfills the self-sealing function. Accordingly, it is possible to improve the sealing property between the resin liner <NUM> and the cap member <NUM>.

Next, an outline of a manufacturing method of the resin liner <NUM> configured in this way will be described with reference to <FIG>. The resin liner <NUM> is manufactured by using the blow molding device <NUM> shown in <FIG>. Prior to the description of the manufacturing method, an outline of the configuration of the blow molding device <NUM> will be described.

As shown in <FIG>, the blow molding device <NUM> includes a die device <NUM>, a pair of molds <NUM> arranged below the die device <NUM>, a blow pin <NUM>, and an air supply source <NUM>. The die device <NUM> is supplied with a resin, which is heated and melted by an extruder, as a material of the resin liner <NUM>. The die device <NUM> shapes the resin supplied from the extruder by using a die and a core, and thus supplies the resin downward. The resin extruded downward from the die device <NUM> is a tubular parison <NUM> from which the resin liner <NUM> is formed.

The pair of molds <NUM> are configured to be openable and closable. In an opened state shown in <FIG> in which the pair of molds <NUM> are laterally separated from each other, the parison <NUM> is supplied from above between the pair of molds <NUM>. The pair of molds <NUM> are clamped so as to sandwich, from both lateral sides, the parison <NUM> from which the resin liner <NUM> is formed. Accordingly, a closed state shown in <FIG> is generated. In the closed state, the pair of molds <NUM> define a cavity <NUM> having a shape corresponding to a contour of the main body portion <NUM> of the resin liner <NUM>. Further, the pair of molds <NUM> define a blow pin insertion hole <NUM> extending from an outside to the cavity <NUM>. In the present embodiment, the blow pin insertion hole <NUM> is formed at lower ends of the pair of molds <NUM>. In another embodiment, the blow pin insertion hole <NUM> may be formed at upper ends of the pair of molds <NUM> or at both the upper and lower ends of the pair of molds <NUM>.

The blow pin <NUM> is arranged at a position corresponding to the lower ends of the pair of molds <NUM> such that the axial direction of the blow pin <NUM> matches the up-and-down direction. The blow pin <NUM> is movable in the axial direction thereof. That is, the blow pin <NUM> is movable in the axial direction thereof with respect to the pair of molds <NUM>. In another embodiment, the pair of molds <NUM> may be movable in the axial direction of the blow pin <NUM>. In the closed state of the molds <NUM> shown in <FIG>, the blow pin <NUM> penetrates the blow pin insertion hole <NUM>, and is arranged at a height that an upper portion of the blow pin <NUM> is located inside the cavity <NUM>. A tip portion of the blow pin <NUM> is provided with at least one air supply opening <NUM> located inside the parison <NUM> in the closed state of the molds <NUM>. An air supply passage <NUM> that leads to the air supply opening <NUM> is formed inside the blow pin <NUM>. The blow pin <NUM> supplies air, which is supplied from the air supply source <NUM>, from the air supply opening <NUM> to an inside of the parison <NUM>.

The manufacturing process of the resin liner <NUM> by using the blow molding device <NUM> configured in this way includes a parison arranging process shown in <FIG>, a mold clamping process shown in <FIG>, a blow process shown in <FIG>, and a mold opening process shown in <FIG>. In the parison arranging process, as shown in <FIG>, the die device <NUM> forms the tubular parison <NUM> from which the resin liner <NUM> is formed, and the parison <NUM> is arranged on an outer circumferential side of the blow pin <NUM> and between the pair of molds <NUM> that are laterally separated from each other. In the mold clamping process, as shown in <FIG>, the pair of molds <NUM> are clamped so as to sandwich the parison <NUM>. In the blow process, as shown in <FIG>, the air is supplied from the air supply opening <NUM> of the blow pin <NUM> to the inside of the parison <NUM>, and thus the parison <NUM> expands. Accordingly, the shape of an inner surface of the cavity <NUM> is transferred to a portion of the parison <NUM> from which the main body portion <NUM> of the resin liner <NUM> is formed.

In the mold opening process, as shown in <FIG>, the pair of molds <NUM> are opened so as to be laterally separated from each other, and are removed from the parison <NUM> having a shape of the resin liner <NUM>. Further, the blow pin <NUM> is removed from the parison <NUM> having the shape of the resin liner <NUM>. Either the opening of the pair of molds <NUM> or the removal of the blow pin <NUM> may be performed first. The burr <NUM> is removed by using a cutter.

After the manufacturing process of the resin liner <NUM> is completed, the cap member <NUM> is attached to an outer circumference of the neck portion <NUM> in a state where the first sealing member <NUM> is interposed therebetween as shown in <FIG> and <FIG>. After that, the outer circumferences of the resin liner <NUM> and the cap member <NUM> are covered with the reinforcement layer <NUM>, and thus the pressure vessel <NUM> is manufactured. Further, as needed, the attachment such as the valve <NUM> is attached to the cap member <NUM>.

Next, the detailed structure of the blow pin <NUM> and the details of the manufacturing method of the resin liner <NUM> will be described with reference to <FIG> is a cross-sectional view of a main portion of the blow molding device <NUM> shown in <FIG>. The blow pin <NUM> includes a blow pin body portion <NUM> provided with the air supply passage <NUM> that leads to the air supply opening <NUM> and having an outer circumferential surface of a shape corresponding to an inner circumferential surface of the neck portion <NUM> of the resin liner <NUM>. Further, the blow pin <NUM> includes a ring portion <NUM> provided coaxially with the blow pin body portion <NUM> and forming an annular recess portion <NUM> between the blow pin body portion <NUM> and the ring portion <NUM> so as to form the outer circumferential surface of the tip portion <NUM> of the neck portion <NUM>. The annular recess portion <NUM> is recessed away from the cavity <NUM>.

The ring portion <NUM> is provided integrally with the blow pin body portion <NUM>, and is provided fixedly to the blow pin body portion <NUM>. The blow pin <NUM> is provided with an air release passage <NUM> extending from the bottom of the annular recess portion <NUM>. The air release passage <NUM> may be provided in either the ring portion <NUM> or the blow pin body portion <NUM>.

As the blow pin <NUM> is configured in this way, the parison <NUM> enters the annular recess portion <NUM> between the mold clamping process of <FIG> and the blow process of <FIG>, more specifically, during the mold clamping process. The shape of an inner circumferential surface of the ring portion <NUM> is transferred to a portion of the parison <NUM> from which the tip portion <NUM> of the neck portion <NUM> is formed. Accordingly, as shown in <FIG> and <FIG>, the outer circumferential surface of the tip portion <NUM> of the neck portion <NUM> is formed into a smooth surface without the parting line <NUM>. Accordingly, it is possible to prevent the degradation of the sealing property of the first sealing member <NUM> and the deterioration of the first sealing member <NUM>, which is interposed between the neck portion <NUM> and the cap member <NUM>.

<FIG> are explanatory diagrams showing a molding method of the neck portion <NUM> by using the blow molding device <NUM> shown in <FIG>. In the parison arranging process, the blow pin <NUM> is arranged in a prescribed position for the blow molding. As shown in <FIG>, as the pair of molds <NUM> are clamped, the parison <NUM> enters the annular recess portion <NUM> and spreads over the bottom of the annular recess portion <NUM>. Accordingly, the shape of the inner circumferential surface of the ring portion <NUM> is transferred to the parison <NUM>. At this time, as the air release passage <NUM> extending from the bottom of the annular recess portion <NUM> is formed in the blow pin <NUM>, the parison <NUM> is more likely to spread over the bottom of the annular recess portion <NUM>. Alternatively, as a negative pressure is applied to the air release passage <NUM>, the parison <NUM> is more likely to spread over the bottom of the annular recess portion <NUM>.

After that, as shown in <FIG>, in the blow process, the air is supplied from the air supply opening <NUM> of the blow pin <NUM> to the inside of the parison <NUM>. Accordingly, the parison <NUM> expands and comes into close contact with the inner surface of the cavity <NUM>, and thus the shapes of the pair of molds <NUM> (the shape of the inner surface of the cavity <NUM>) are transferred to the parison <NUM>.

<FIG> are explanatory diagrams showing a molding method according to a modified embodiment of the neck portion <NUM> by using the blow molding device <NUM> shown in <FIG>. As shown in <FIG>, this modified embodiment differs from the above embodiment in that the blow pin <NUM> is moved in the axial direction thereof between the mold clamping process and the blow process. More specifically, in the parison arranging process, as shown in <FIG>, the blow pin <NUM> is arranged slightly below the prescribed position for the blow molding. Then, between the mold clamping process and the blow process, as shown in <FIG>, the annular recess portion <NUM> moves toward the cavity <NUM> (moves upward) along the axial direction of the blow pin <NUM>. As described above, the ring portion <NUM> is fixed to the blow pin body portion <NUM>. Accordingly, in the present embodiment, the annular recess portion <NUM> moves as the blow pin <NUM> moves upward along the axial direction thereof.

Accordingly, the parison <NUM> spreads over the bottom of the annular recess portion <NUM>, even if the parison <NUM> does not reach the bottom of the annular recess portion <NUM> in the mold clamping process as shown in <FIG>. Further, the blow pin <NUM> is movable in the axial direction thereof with respect to the pair of molds <NUM>, and the manufacturing method of the resin liner <NUM> includes a process of moving the blow pin <NUM> in the axial direction thereof. Accordingly, it is possible to increase the axial length of the tip portion <NUM> of the neck portion <NUM> on which the parting line <NUM> does not appear.

<FIG> is a cross-sectional view of a main portion of another embodiment of the blow molding device <NUM> shown in <FIG>. Elements that are the same as or similar to those of the above embodiment are provided with common reference numerals, and duplicate explanations will be omitted. In this embodiment, the ring portion <NUM> is formed separately from the blow pin body portion <NUM>, and is slidable in the axial direction thereof with respect to the blow pin body portion <NUM>. The air release passage <NUM> is formed between the ring portion <NUM> and the blow pin body portion <NUM>.

When the resin liner <NUM> is manufactured by the blow molding in which the blow pin <NUM> of this embodiment is used, it is preferable that the resin liner <NUM> is manufactured as shown in <FIG>, while the resin liner <NUM> can be manufactured as shown in <FIG>, <FIG>. <FIG> are explanatory diagrams of the molding method of the neck portion <NUM> by using the blow molding device <NUM> shown in <FIG>. In the parison arranging process, as shown in <FIG>, the ring portion <NUM> is arranged slightly lower than the blow pin body portion <NUM>. Then, as shown in <FIG>, the ring portion <NUM> slides toward the cavity <NUM> (slides upward) with respect to the blow pin body portion <NUM> between the mold clamping process and the blow process. Accordingly, the annular recess portion <NUM> moves toward the cavity <NUM>.

Thus, the parison <NUM> spreads over the bottom of the annular recess portion <NUM> without moving the blow pin body portion <NUM> in the axial direction thereof, even if the parison <NUM> does not reach the bottom of the annular recess portion <NUM> in the mold clamping process as shown in <FIG>. Accordingly, it is possible to increase the axial length of the tip portion <NUM> of the neck portion <NUM> on which the parting line <NUM> does not appear.

Claim 1:
A blow molding device (<NUM>) for manufacturing a resin liner (<NUM>) for a pressure vessel (<NUM>), the resin liner (<NUM>) including a tubular neck portion (<NUM>) to which a cap member (<NUM>) is fitted externally, the blow molding device (<NUM>) comprising:
a pair of molds (<NUM>) configured to be clamped so as to sandwich, from both lateral sides, a parison (<NUM>) from which the resin liner (<NUM>) is formed, the pair of molds (<NUM>) defining a cavity (<NUM>) having a shape corresponding to a contour of a main body portion (<NUM>) of the resin liner (<NUM>); and
a blow pin (<NUM>) configured to form the neck portion (<NUM>) together with the molds (<NUM>) and having an air supply opening (<NUM>) to be arranged inside the parison (<NUM>),
characterized in that the blow pin (<NUM>) includes:
a blow pin body portion (<NUM>) provided with an air supply passage (<NUM>) that leads to the air supply opening (<NUM>) and having an outer circumferential surface of a shape corresponding to an inner circumferential surface of the neck portion (<NUM>); and
a ring portion (<NUM>) provided coaxially with the blow pin body portion (<NUM>) and forming an annular recess portion (<NUM>) between the blow pin body portion (<NUM>) and the ring portion (<NUM>) so as to form an outer circumferential surface of a tip portion (<NUM>) of the neck portion (<NUM>), the annular recess portion (<NUM>) being recessed in a direction away from the cavity (<NUM>); and
wherein the blow pin (<NUM>) is provided with an air release passage (<NUM>) extending from a bottom of the annular recess portion (<NUM>).