HOT RUNNER APPARATUS, METHOD FOR BRANCHING MOLTEN RESIN IN THE HOT RUNNER APPARATUS, AND INJECTION STRETCH BLOW MOLDING MACHINE

Abstract

An aim of the present invention is to enable a molten resin to be fed from a hot runner apparatus into preform molding portions of an injection molding mold without a higher temperature and lower viscosity resin being present in a biased manner and to enable preforms having no biased portion of a higher temperature and lower viscosity resin in their circumferential direction.

An introducing runner portion (18) of a hot runner apparatus (9) is bent toward a horizontal runner portion (15) after reaching an elevation plane (A) passing through a position of the horizontal runner portion (15) in an up-and-down direction and continuous with an intermediate portion of the horizontal runner portion (15) in the elevation plane (A).

Claims

1. A hot runner apparatus comprising: a plurality of hot runner nozzles arranged in a row and having an upward injection direction; a horizontal runner portion disposed below the hot runner nozzles along a row direction of the hot runner nozzles; vertical runner portions upwardly extending from the horizontal runner portion for guiding a molten resin flowing through the horizontal runner portion into the hot runner nozzles; and an introducing runner portion continuous with an intermediate portion of the horizontal runner portion for guiding a molten resin from an introducing port, into which the molten resin from an injection apparatus having an injection direction in a horizontal direction is fed, toward the horizontal runner portion, wherein the introducing runner portion has a structure in which the introducing runner portion is bent toward the horizontal runner portion after reaching an elevation plane passing through a position of the horizontal runner portion in an up-and-down direction and continuous with the intermediate portion of the horizontal runner portion in the elevation plane, wherein the hot runner apparatus is provided under an injection molding mold of an injection stretch blow molding machine, the injection molding mold including: a plurality of preform molding portions; and a plurality of gates continuous with the preform molding portions, the plurality of hot runner nozzles are connected to the respective gates, and a molten resin injected by the respective hot runner nozzles is filled into the respective preform molding portions through the gates.

2. The hot runner apparatus of claim 1, wherein the introducing runner portion is continuous with any one of a lower part and an upper part of the horizontal runner portion.

3. The hot runner apparatus of claim 1, wherein a portion at which the introducing runner portion is continuous with the horizontal runner portion is configured as a branching pipe line, and the branching pipe line causes a resin located in an outer peripheral portion of a molten resin slidably in contact with a pipe wall of the introducing runner portion to branch into two directions and causes a moving direction of the branched resin to be biased toward a length direction of the horizontal runner portion along a pipe wall of the horizontal runner portion on a side with which the introducing runner portion is continuous.

4. The hot runner apparatus of claim 1, wherein the structure of the introducing runner portion suppresses temperature unevenness in a molten resin in a circumferential direction of a horizontal cross-section of a pipe line of the vertical runner portion, the molten resin being introduced from the introducing runner portion through the horizontal runner portion into the vertical runner portions.

5. (canceled)

6. A method for branching a molten resin in the hot runner apparatus of claim 1, for branching the molten resin toward the plurality of hot runner nozzles by horizontally feeding the molten resin into the introducing runner portion of the hot runner apparatus by the injection apparatus, the method comprising: changing a moving direction of the molten resin fed into the introducing runner portion and having a higher temperature and lower viscosity resin in an outer peripheral portion thereof due to shear heat generation to a direction along the elevation plane; feeding the molten resin into the intermediate portion of the horizontal runner portion and thereby branching a moving direction of the higher temperature and lower viscosity resin from the intermediate portion of the horizontal runner portion into two directions along the length direction of the horizontal runner portion; and causing the branched higher temperature and lower viscosity resin to be biased toward the length direction of the horizontal runner portion along the pipe wall of the horizontal runner portion on the side with which the introducing runner portion is continuous.

7. An injection stretch blow molding machine comprising: an injection molding section that injects a molten resin from an injection apparatus to injection-mold preforms; a stretch blow molding section that obtains hollow molded bodies by stretch blow molding the preforms, having been released from an injection molding mold of the injection molding section, using a blow molding mold; and an ejecting section that releases the hollow molded bodies from the blow molding mold of the stretch blow molding section and sends the hollow molded bodies to outside of the molding machine, wherein the injection molding section is provided above the hot runner apparatus of claim 1, and the injection molding section has the injection molding mold having preform molding portions corresponding to the hot runner nozzles.

8. The injection stretch blow molding machine of claim 7, wherein the injection molding mold is a molding mold for molding preforms with their mouth portions positioned on an upper side thereof by being injected and filled with a molten resin upwardly fed by the hot runner nozzles.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0050] FIG. 1 is an explanatory diagram illustrating an example of an injection stretch blow molding machine as viewed from the side of an injection molding section.

[0051] FIG. 2 is an explanatory diagram schematically illustrating an arrangement of the injection molding section, a stretch blow molding section, and an ejecting section.

[0052] FIG. 3 is an explanatory diagram illustrating an injection apparatus of the injection stretch blow molding machine.

[0053] FIG. 4 is an explanatory diagram illustrating a cross-section of a conventional hot runner apparatus in a direction along an injection direction of the injection apparatus.

[0054] FIG. 5 is an explanatory diagram illustrating a cross-section of the conventional hot runner apparatus in a direction along a horizontal runner portion of the injection apparatus.

[0055] FIG. 6 is an explanatory diagram schematically illustrating a runner in the conventional hot runner apparatus.

[0056] FIG. 7 is an explanatory diagram schematically illustrating resin distributions in the runner of FIG. 6 on an elevation surface a, a planar surface b, and an elevation surface c.

[0057] FIG. 8 is an explanatory diagram illustrating a cross-section of a hot runner apparatus according to an embodiment of the present invention in a direction along an injection direction of an injection apparatus.

[0058] FIG. 9 is an explanatory diagram illustrating a cross-section of the hot runner apparatus according to the embodiment of the present invention in a direction along a horizontal runner portion of the injection apparatus.

[0059] FIG. 10 is an explanatory diagram schematically illustrating a runner in a hot runner apparatus according to a first example of the present invention.

[0060] FIG. 11 is an explanatory diagram schematically illustrating resin distributions in the runner of FIG. 10 on an elevation surface d and an elevation surface e.

[0061] FIG. 12 is an explanatory diagram schematically illustrating a runner in a hot runner apparatus according to a second example.

[0062] FIG. 13 is an explanatory diagram schematically illustrating a resin distribution in the runner of FIG. 12 on an elevation surface f.

[0063] FIG. 14 is an explanatory diagram showing, in a table, values of thicknesses of body portions of PET bottles according to a comparative example.

[0064] FIG. 15 is an explanatory diagram showing, in a table, values of thicknesses of body portions of PET bottles according to an example.

[0065] FIG. 16 shows positions at which thicknesses of a PET bottle are measured: (A) is an explanatory diagram showing measurement positions in a circumferential direction on a cross-section of a body portion; and (B) is an explanatory diagram showing measurement positions in a height direction.

[0066] FIG. 17 shows a runner in a hot runner apparatus according to a third example: (a) is an explanatory diagram schematically illustrating a horizontal runner portion as viewed from the side of a main nozzle; and (b) is an explanatory diagram schematically illustrating the portion of a branching pipe line.

[0067] FIG. 18 shows a runner in a hot runner apparatus according to a fourth example: (a) is an explanatory diagram schematically illustrating a horizontal runner portion as viewed from the side of a main nozzle; and (b) is an explanatory diagram schematically illustrating the portion of a branching pipe line.

[0068] FIG. 19 is an explanatory diagram showing a virtual elevation plane including the position of the horizontal runner portion of the hot runner apparatus and how an introducing runner portion extends toward the horizontal runner portion in the elevation plane so as to be continuous with the horizontal runner portion.

DESCRIPTION OF EMBODIMENTS

[0069] The present invention will be described next in detail with reference to embodiments shown in FIGS. 8 to 19. Note that elements overlapping with those in the conventional example shown in FIGS. 4 to 7 will be denoted by the same reference numerals and the description thereof will be omitted.

FIRST EXAMPLE—HOT RUNNER APPARATUS

[0070] FIGS. 8 and 9 illustrate a hot runner apparatus 9 over which an injection molding mold 4 in an injection molding section 3 of an injection stretch blow molding machine 1 according to the present invention is disposed. In the hot runner apparatus 9, sixteen hot runner nozzles 13 having a vertically upward injection direction are vertically provided on an upper part of a hot runner block 14.

[0071] In the figure, the reference numeral “27” denotes a hot runner fixing plate, and the reference numerals “28” and “29” denote hot runner pressure receiving plates disposed above the hot runner fixing plate 27 for supporting the hot runner block 14.

[0072] A shutoff pin 30 for opening and closing a nozzle orifice of the hot runner nozzle 13 is disposed in a resin passage portion inside the hot runner nozzle 13 so as to pass through the hot runner block 14 in the up-and-down direction from a height position corresponding to a lower side of the hot runner pressure receiving plate 28. At the height position corresponding to the lower side of the hot runner pressure receiving plate 28, a pin fixing plate 32 supported by a shutoff piston 31 is disposed. The pin fixing plate 32 moves in the up-and-down directions by motions of the shutoff piston 31. Note that the hot runner pressure receiving plate 28 is disposed so as not to interfere with the shutoff pin 30.

[0073] The lower end of the shutoff pin 30 is supported by the pin fixing plate 32. The shutoff pin 30 moves in the up-and-down directions by motions of the shutoff piston 31. The nozzle orifice is opened and closed by the up and down movements of the shutoff pin 30.

Basic Configuration of Injection Molding Mold

[0074] FIG. 8 described above also illustrates the injection molding mold 4 attached to an upper part of the hot runner apparatus 9. The injection molding mold 4 shown in the figure is in a mold-closed state. A cavity mold 10 of the injection molding mold 4 is fixed to the hot runner apparatus 9 via a cavity fixing plate 33. A rotary plate 8 is at a descent position during the mold closing as discussed above so that a lip mold 7 supported by the rotary plate 8 is overlaid on the cavity mold 10.

[0075] A core mold 11 supported by an injection core fixing plate 34 is also at a descent position so that a preform inner surface forming part of the core mold 11 is located inside of the lip mold 7 and the cavity mold 10. A gate 12 at the lower end of the cavity mold 10 is opposed to the nozzle orifice of the above-described hot runner nozzle 13, and a molten resin injected upwardly from the hot runner nozzle 13 is filled into a preform molding portion in a direction from its lower side toward its upper side via the gate 12.

Hot Runner Block

[0076] In the injection stretch blow molding machine 1 of the present embodiment, the center of the injection molding section 3 is located on a radial direction of the rotary plate passing through the center of the injection stretch blow molding machine 1 (the arrangement center among the injection molding section 3, a stretch blow molding section 5, and an ejecting section 6) (see FIG. 2).

[0077] In the injection molding section 3, the length direction of the injection molding mold 4 in which preform molding portions are arranged in a row as a 16-cavity mold and the length direction of the above-described hot runner apparatus 9 in which the 16 hot runner nozzles 13 are arranged in a row are set so as to be perpendicular to the above-described radial direction of the rotary plate. The injection direction of an injection apparatus 2 coincides with the above-described radial direction of the rotary plate in the injection stretch blow molding machine 1 passing through the center of the hot runner apparatus 9. An injection nozzle of the injection apparatus 2 is connected to an introducing port 17 located at the center of the hot runner block 14 in its length direction.

[0078] The introducing port 17 of the hot runner block 14 is an opening against which the nozzle of the injection apparatus 2 is allowed to abut as with the above-discussed conventional example. The hot runner block 14 includes: a horizontal runner portion 15 disposed below the hot runner nozzles 13 along the row direction of the hot runner nozzles 13 (the length direction of the hot runner block 14); sixteen vertical runner portions 16 extending upwardly from the horizontal runner portion 15 so as to be continuous with the hot runner nozzles 13; and an introducing runner portion 18, including a passage of a main nozzle 19, for guiding the molten resin from the introducing port 17 toward the horizontal runner portion 15.

[0079] The above-described shutoff pin 30 of the hot runner apparatus 9 completely passes through a pipe line of the horizontal runner portion 15 in the vertical direction (the up-and-down direction) and passes through the center of a pipe line of the vertical runner portion 16 rising from the horizontal runner portion 15 in the vertical direction so as to be disposed in a passage inside the hot runner nozzle 13 (nozzle-axis center) (see FIGS. 8 and 9).

Rod Heater

[0080] In the present embodiment, the hot runner block 14 has a rectangular transverse cross-sectional shape. As shown in the transverse cross-section, the hot runner block 14 is pierced along the length direction of the horizontal runner portion 15 so as to provide insertion holes 35 at a total of four positions: two positions above the horizontal runner portion 15 provided on the side where the introducing port 17 is provided and on its opposite side, and two positions below the horizontal runner portion 15 provided on the side where the introducing port 17 is provided and on its opposite side. Bar heaters 36 are inserted into the insertion holes 35.

[0081] In this hot runner apparatus 9, the bar heater 36 is disposed along the length direction of the horizontal runner portion 15. Furthermore, the bar heaters 36 are disposed at an equal distance from the horizontal runner portion 15. The hot runner block 14 is heated by these bar heaters 36, and the molten resin moving through such a hot runner block 14 is heated by the hot runner block 14 having an increased temperature.

[0082] The present invention is not limited to the shape of the hot runner block 14 shown in the embodiment. For example, its transverse cross-sectional shape may be circular as illustrated in FIG. 4 for the description of the conventional technique. Note that a hot runner apparatus having a hot runner block with a circular transverse cross-section can employ a cover-like heater externally surrounding the hot runner block.

Bent Portion of Introducing Runner Portion

[0083] In the introducing runner portion 18, the direction of the passage of the main nozzle 19 (passage for the molten resin injected by the injection apparatus), which is a part of the introducing runner portion 18, is set to a direction perpendicular to the length direction of the horizontal runner portion 15. A pipe line from the introducing port 17 to the horizontal runner portion 15 extends to a position below the horizontal runner portion 15.

[0084] As shown also in FIG. 19, the pipe line of the introducing runner portion 18 reaches the position below the horizontal runner portion 15 corresponding to a portion of a virtual elevation plane A passing through the position of the horizontal runner portion 15 in the up-and-down direction along the horizontal runner portion 15. The pipe line of the introducing runner portion 18 further bends upwardly toward the horizontal runner portion 15 in an L shape after reaching the portion below the horizontal runner portion 15, i.e., the above-described elevation plane A. The pipe line extends upwardly from a bent portion 37, which is the bent portion of the pipe line, so as to be continuous with a lower part of an intermediate portion 15a of the horizontal runner portion 15 in the elevation plane A. As discussed above, a T-shaped branching pipe line 20 is provided in a connection portion between the upwardly-bent pipe line of the introducing runner portion 18 and the pipe line of the horizontal runner portion 15.

Horizontal Runner Portion and Vertical Runner Portion

[0085] The above-described branching pipe line 20 is placed in the intermediate portion 15a of the horizontal runner portion 15 corresponding to a central portion of the horizontal runner portion 15 in its length direction. Eight vertical runner portions 16 extend upwardly from, and are continuous with, each half of the horizontal runner portion 15 extending from the branching pipe line 20.

Branching of Molten Resin from Introducing Runner Portion

[0086] The molten resin horizontally injected by the injection apparatus 2 is fed into the introducing runner portion 18 through the main nozzle 19. When the molten resin moves through the introducing runner portion 18, a higher temperature and lower viscosity resin 25 is generated in a ring-shaped region 23 corresponding to an outer peripheral portion of the molten resin 21 due to shear heat generation as discussed above. The molten resin 21 in which the portion of a central region 22 where a lower temperature and higher viscosity resin 24 is distributed is surrounded by the higher temperature and lower viscosity resin 25 in the ring-shaped region 23 moves toward the horizontal runner portion 15 and reaches the branching pipe line 20.

[0087] Note that the higher temperature and lower viscosity resin 25 and the lower temperature and higher viscosity resin 24 together constitute the molten resin 21 moving through the pipe line. The terms “higher” and “lower” are expressed by contrasting the temperature of resin with the viscosity of the resin. The higher temperature and lower viscosity resin and the lower temperature and higher viscosity resin are not defined on the basis of a particular temperature and a particular viscosity.

[0088] The molten resin 21 is divided when the molten resin 21 reaches the branching pipe line 20 and moves in the length direction of the horizontal runner portion 15. The divided molten resin portions move through the respective halves of the horizontal runner portion 15 so as to move away from each other along the length direction of the horizontal runner portion 15. The branching pipe line 20 causes the portion used to be the central region 22 comprising the lower temperature and higher viscosity resin 24 in the introducing runner portion 18 to branch into two regions 38 and also causes the higher temperature and lower viscosity resin 25 in the above-described ring-shaped region 23 to branch into two. As a result of such branching, two arc-like regions 26 are formed, and the above-described higher temperature and lower viscosity resin 25 is located in these regions (FIG. 11 (elevation surface d)).

[0089] The branching pipe line bends the moving direction of the higher temperature and lower viscosity resin 25 that forms the arc-like region 26 so as to go along a pipe wall of the horizontal runner portion 15 with which the introducing runner portion 18 is continuous, i.e., the pipe wall of a lower part of each half of the horizontal runner portion 15, and thus causes the moving direction to be biased toward the length direction of the pipe wall of such a lower part. In the molten resin 21 immediately after having passed through the branching pipe line 20, the higher temperature and lower viscosity resin 25 is distributed along the pipe wall of the lower part of each half of the horizontal runner portion 15 as the arc-like region 26, and the lower temperature and higher viscosity resin 24 (resin constituting the region 38) is distributed over the remaining region (FIG. 11 (elevation surface e)).

Molten Resin in Horizontal Runner Portion

[0090] When getting to each position of the vertical runner portions 16 provided at intermediate positions, the molten resin 21 moving through each half of the horizontal runner portion 15 in its length direction is branched and fed into the vertical runner portion 16. The molten resin 21 is also fed into the vertical runner portion 16 extending upwardly from an end of each half of the horizontal runner portion 15.

Molten Resin in Vertical Runner Portions

[0091] As the molten resin 21 moves through the half of the horizontal runner portion 15 in its length direction, the ring-shaped region 23 in which the higher temperature and lower viscosity resin 25 is distributed develops in the outer peripheral portion of the molten resin 21 whose lower part has a higher temperature (the temperature of the lower part becomes high since the above-described higher temperature and lower viscosity resin 25 is located along the pipe wall of the lower part of the horizontal runner portion 15). It is believed that for each shot, a part of the molten resin 21 is separated from the laterally moving molten resin 21 and fed into the vertical runner portion 16 while keeping a vertically stacked form in which an upper part thereof is occupied by the lower temperature and higher viscosity resin 24 and the higher temperature and lower viscosity resin 25 is located in a lower part thereof as shown in the above-described elevation surface e. It is also believed that the molten resin 21 passing a branch position without branching moves through the horizontal runner portion 15 also with the distribution shown on the elevation surface e (such resin movement is deduced from comparison results to be described later).

[0092] Furthermore, in the vertical runner portion 16 rising from the intermediate portion in each half of the horizontal runner portion 15, also when the molten resin 21 is fed into an upper part of such a vertical runner portion 16, the ring-shaped region 23 comprising the higher temperature and lower viscosity resin 25 is generated slightly in the outer peripheral portion of the molten resin 21. Since the length of the passage is short, the higher temperature and lower viscosity resin 25 can be prevented from being present in a significantly biased state in the outer peripheral portion in the cross-sectional direction of the pipe line of the vertical runner portion 16.

[0093] The pipe line of the vertical runner portion 16 disposed at an end of the horizontal runner portion 15 is extended upwardly via a bent portion 39 formed by bending the pipe line of the end of the horizontal runner portion 15 upwardly. As the molten resin 21 moves toward the end of the horizontal runner portion 15, a portion transformed into the higher temperature and lower viscosity resin 25 due to shear heat generation increases accordingly in the portion occupied by the lower temperature and higher viscosity resin 24 (in the cross-sectional direction of the pipe line). As discussed above, the portion already occupied by the higher temperature and lower viscosity resin 25 has a small amount of shear heat generation due to its low viscosity. As a result, in the molten resin 21 having reached the end of the horizontal runner portion 15, the proportion of the occupying higher temperature and lower viscosity resin 25 is increased in the cross-sectional direction of the pipe line, and a biased degree of the higher temperature and lower viscosity resin 25 is diminished. It is believed that the molten resin 21 having such a state is fed into the vertical runner portion 16, and thus the higher temperature and lower viscosity resin 25 is not located in a significantly biased manner, or is scarcely present in a biased manner, in the cross-sectional direction of the pipe line also in the vertical runner portion 16. According to the comparison to be described later, uneven thickness is observed in a hollow molded body corresponding to the vertical runner portion at the end, but a degree of such uneven thickness is reduced as compared to the conventional techniques. Thus, it is believed that the higher temperature and lower viscosity resin 25 is not present in a significantly biased manner, or is scarcely present in a biased manner, in the cross-sectional direction of the pipe line in the vertical runner portion 16 disposed at the end as discussed above.

[0094] As just described, in each of the vertical runner portions 16, the higher temperature and lower viscosity resin 25 is not present in a significantly biased manner in the cross-sectional direction of the pipe line. The molten resin 21 is injected and filled into the respective preform molding portions of the above-described injection molding mold 4 from the above-described vertical runner portions 16 via the hot runner nozzles 13.

Preform Molding Portions of Injection Molding Mold

[0095] The injection molding mold 4 is a molding mold for molding preforms with their mouth portions positioned on an upper side thereof. The molten resin 21 is injected into sixteen preform molding portions by corresponding hot runner nozzles 13, respectively. The molten resin 21 is injected and filled upwardly via the gate 12.

[0096] As discussed above, in each of the vertical runner portions 16, the higher temperature and lower viscosity resin 25 is scarcely present in a biased manner in the circumferential direction of the cross-section of the pipe line. Thus, the higher temperature and lower viscosity resin 25 is not located in a significantly biased manner in the circumferential direction of the horizontal cross-section of the preform molding portion. Therefore, a preform having no significant temperature unevenness in the circumferential direction can be molded in every preform molding portion. According to the comparison to be described later, temperature difference tends to increase in the circumferential direction in each of preforms corresponding to the positions of the vertical runner portions 16 at both ends, but such temperature difference can be regarded to fall within a range manageable on the part of the injection molding mold.

SECOND EXAMPLE—HOT RUNNER APPARATUS

[0097] In the first example, the pipe line of the introducing runner portion 18 is continuous (in the elevation plane A) with the pipe wall of the lower part of the central portion of the horizontal runner portion 15 after reaching the elevation plane A and bending upwardly in an L shape. The present invention, however, is not limited to the introducing runner portion 18 continuous with the lower part of the horizontal runner portion 15.

[0098] FIG. 12 shows a second example in which an introducing runner portion 18 is continuous with a central portion of a horizontal runner portion 15. The second example differs from the first example in that the introducing runner portion 18 is continuous with a pipe wall of an upper part of the horizontal runner portion 15 as will be described below. The other elements in the second example are the same as those in the first example.

[0099] In the second example, the direction of the introducing runner portion 18 is set so as to be perpendicular to the length direction of the horizontal runner portion 15 as with the first example. A pipe line of the introducing runner portion 18, into which a molten resin 21 is fed by an injection apparatus 2 injecting the resin in a horizontal direction, extends toward a position above the horizontal runner portion 15.

[0100] Furthermore, the pipe line of the introducing runner portion 18 reaches an elevation plane A, and then extends downwardly in the above-described elevation plane A from a bent portion 40 bent in an L shape at the position above the horizontal runner portion 15, so as to be continuous with the pipe wall of the upper part of the central portion of the horizontal runner portion 15. A T-shaped branching pipe line 20 is provided in a connection portion between the pipe line of the introducing runner portion 18 and a pipe line of the horizontal runner portion 15 as with the above-described first example.

Branching of Molten Resin from Introducing Runner Portion

[0101] The molten resin 21 horizontally injected by the injection apparatus 2 is fed into the introducing runner portion 18 through a main nozzle 19, and the molten resin 21 reaches the branching pipe line 20.

[0102] Upon reaching the branching pipe line 20, the molten resin 21 is divided when the molten resin 21 moves into the length direction of the horizontal runner portion 15. The divided molten resin portions move through respective halves of the horizontal runner portion 15 so as to move away from each other along the length direction of the horizontal runner portion 15. The branching pipe line 20 causes the portion used to be a central region 22 comprising a lower temperature and higher viscosity resin 24 in the introducing runner portion 18 to branch into two regions 38 and also causes a higher temperature and lower viscosity resin 25 in the above-described ring-shaped region 23 to branch into two. As a result of such branching, two arc-like regions 26 are formed, and the above-described higher temperature and lower viscosity resin 25 is located in these regions (FIG. 13 (elevation surface f)).

[0103] Furthermore, the branching pipe line 20 bends the moving direction of the higher temperature and lower viscosity resin 25 that forms the arc-like region 26 so as to go along the pipe wall of the upper part of each half of the horizontal runner portion 15, and thus causes the moving direction to be biased toward the length direction of the pipe wall of the upper part. In the molten resin 21 immediately after having passed through the branching pipe line 20, the higher temperature and lower viscosity resin 25 is located along the pipe wall of the upper part of each half of the horizontal runner portion 15 as the arc-like region 26, and the lower temperature and higher viscosity resin 24 (resin constituting the region 38) occupies the remaining region.

Molten Resin in Horizontal Runner Portion

[0104] When getting to each position of the vertical runner portions 16 provided at intermediate positions, the molten resin 21 moving through each half of the horizontal runner portion 15 is branched and fed into the vertical runner portion 16. The molten resin 21 is also fed into the vertical runner portion 16 extending upwardly from an end of each half of the horizontal runner portion 15.

Molten Resin in Vertical Runner Portions

[0105] In the second example, the moving direction of the higher temperature and lower viscosity resin 25 that forms the above-described arc-like region 26 is biased toward the length direction of the horizontal runner portion 15 along the pipe wall of the upper part of each half of the horizontal runner portion 15.

[0106] In the same manner as that discussed above, as the molten resin 21 moves through the half of the horizontal runner portion 15 in its length direction, the ring-shaped region 23 in which the higher temperature and lower viscosity resin 25 is located develops in the outer peripheral portion of the molten resin 21. It is believed that for each shot, a part of the molten resin 21 is separated from the laterally moving molten resin 21 and fed into the vertical runner portion 16 while keeping a vertically stacked form in which a lower part thereof is occupied by the lower temperature and higher viscosity resin 24 and the higher temperature and lower viscosity resin 25 is located in an upper part thereof (the vertically inverted form of the distribution shown on the elevation surface e). It is also believed that the molten resin 21 passing a branch position without branching moves through the horizontal runner portion 15 while keeping the vertically stacked form in which the lower part thereof is occupied by the lower temperature and higher viscosity resin 24 and the higher temperature and lower viscosity resin 25 is located in the upper part thereof.

[0107] Furthermore, in the vertical runner portion 16 rising from the intermediate portion in each half of the horizontal runner portion 15, also when the molten resin 21 is fed into an upper part of such a vertical runner portion 16, the ring-shaped region 23 comprising the higher temperature and lower viscosity resin 25 is generated slightly in the outer peripheral portion of the molten resin 21. Since the length of the passage is short, the higher temperature and lower viscosity resin 25 can be prevented from being present in a significantly biased manner in the outer peripheral portion in the cross-sectional direction of the pipe line of the vertical runner portion 16.

[0108] As explained in the above-described first example, in the molten resin 21 having reached the end of the horizontal runner portion 15, the proportion of the occupying higher temperature and lower viscosity resin 25 is increased in the cross-sectional direction of the pipe line, and a biased degree of the higher temperature and lower viscosity resin 25 is diminished. It is believed that the molten resin 21 having such a state is fed into the vertical runner portion 16 at the end, and thus the higher temperature and lower viscosity resin 25 is not located in a significantly biased manner, or is scarcely present in a biased manner, in the cross-sectional direction of the pipe line also in the vertical runner portion 16.

Preform Molding Portions of Injection Molding Mold

[0109] As just described, also in each of the vertical runner portions 16 in the second example, the higher temperature and lower viscosity resin 25 is not present in a significantly biased manner in the cross-sectional direction of the pipe line. The molten resin 21 is injected and filled into respective preform molding portions of an injection molding mold 4 from the above-described vertical runner portions 16 via hot runner nozzles 13. Furthermore, the higher temperature and lower viscosity resin 25 is not located in a significantly biased manner in the circumferential direction of the horizontal cross-section of the preform molding portion as with the first example. Therefore, a preform having no significant temperature unevenness in the circumferential direction can be molded in every preform molding portion.

Comparative Example and Example

[0110] Values obtained by measuring thicknesses of body portions of PET bottles molded according to a conventional example are shown in a table of FIG. 14, and values obtained by measuring thicknesses of body portions of PET bottles molded according to an example are shown in a table of FIG. 15.

[0111] The conventional example employs a hot runner apparatus 9 in which an introducing runner portion 18 is continuous with a central portion of a horizontal runner portion 15 in its length direction from a traverse direction perpendicular to the horizontal runner portion 15. The PET bottles were produced using an injection stretch blow molding machine 1 in which the hot runner apparatus 9 was disposed in an injection molding section 3.

[0112] The example employs a hot runner apparatus 9 in which a pipe line of an introducing runner portion 18 is bent in an L shape and the pipe line extending from the bent portion is continuous with a central portion of a horizontal runner portion 15 in its length direction from below so as to be perpendicular to the horizontal runner portion 15. The PET bottles were produced using an injection stretch blow molding machine 1 in which the hot runner apparatus 9 is disposed in an injection molding section 3.

[0113] An injection molding mold 4 used in the comparative example and the example is a molding mold for obtaining sixteen preforms arranged in a row.

Used Resin Amount

[0114] Used resin amounts for the PET bottles in the comparative example and the PET bottles in the example were each 24.0 g.

Molding Procedure of PET Bottles

[0115] In both of the comparative example and the example, the PET bottles were produced, using the three-station injection stretch blow molding machines, by: injecting a molten resin into preform molding portions of the injection molding mold; releasing the preforms early at a stage not impairing the shapes of the preforms and directly conveying the preforms to a stretch blow molding section from the injection molding section; and stretch-blow molding the preforms while being cooled.

Measurement Positions for Thicknesses of PET Bottles

[0116] Thicknesses of a body portion X of a PET bottle produced as a hollow molded body were measured at eight positions in the circumferential direction thereof. Numbers 1 to 8 shown in the tables represent thickness measurement positions in the horizontal cross-section of the body portion. As shown in FIG. 16(A), the number “1” corresponds to the side of an injection apparatus, and thicknesses are measured at an interval of 45 degrees in the circumferential direction. As shown in FIG. 16(B), thicknesses are also measured at four positions along the height direction of the body portion X of the PET bottle. A line at the center of the cross-section of the body portion in FIG. 16(A) and a line at the center of the side surface of the container in FIG. 16(B) both indicate a parting line position in a blow mold.

Molding Positions of PET Bottles

[0117] In the conventional example and the example, the measured PET bottles are those molded from preforms molded in eight preform molding portions corresponding to a half of the horizontal runner portion in the hot runner apparatus among the sixteen preform molding portions of the injection molding mold. In these tables, a molding position corresponding to the side of the above-described branching pipe line in the hot runner apparatus is denoted by H. Molding positions are denoted by I, . . . , P so as to correspond to the arrangement order of the preform molding portions of the injection molding mold.

[0118] The table entry title “Height” represents a height measured from the bottom of a PET bottle in its height direction, the table entry title “unit” represents a unit for a measured value, the table entry title “Ave.” represents an average value, and the table entry title “Differ.” represents a difference between a maximum value and a minimum value. Furthermore, for each of the PET bottles, a numerical value in the last line under the above-described table entry title “Differ.” represents an average “Differ.” value of the four measured heights.

For PET Bottles Molded According to Comparative Example

[0119] On the basis of the table shown in FIG. 14, the PET bottles molded according to the comparative example are evaluated as follows. [0120] (a) A degree of increase in temperature in a portion on the side closer to the injection apparatus when in the form of a preform is large. [0121] (b) A temperature difference between the portion on the side closer to the injection apparatus and a portion on the side opposite to the injection apparatus when in the form of the preform is large. [0122] (c) A difference (Differ.) between a maximum value and a minimum value among thicknesses of a body portion of a PET bottle at the eight positions in the circumferential direction thereof is generally large. [0123] (d) An average value of differences (Differ.) between large values and small values at the four positions along the height direction of a PET bottle fluctuates in the PET bottle molding arrangement direction, and a degree of such fluctuation is large.

For PET Bottles Molded According to Example

[0124] On the basis of the table shown in FIG. 15, the PET bottles molded according to the example are evaluated as follows. [0125] (a) A degree of increase in temperature in a portion on the side closer to the injection apparatus when in the form of a preform is extremely small. [0126] (b) A temperature difference between the portion on the side closer to the injection apparatus and a portion on the side opposite to the injection apparatus when in the form of the preform is extremely small. [0127] (c) A difference (Differ.) between a maximum value and a minimum value among thicknesses of a body portion of a PET bottle at the eight positions in the circumferential direction thereof is generally small. A degree of thickness unevenness is small in the circumferential direction of a body portion. [0128] (d) An average value of differences (Differ.) between large values and small values at the four positions along the height direction of a PET bottle does not fluctuate in the PET bottle molding arrangement direction, and only exhibits a tendency to change in one direction toward an end (toward the position P) in the PET bottle molding arrangement direction.

[0129] In contrast with the comparative example, the above-described example employs the hot runner apparatus 9 in which the introducing runner portion 18 is continuous with the horizontal runner portion 15 from below in an elevation plane A. It is believed that the similar results can be obtained also by employing the hot runner apparatus 9 in the above-described second example since the introducing runner portion 18 is continuous with the horizontal runner portion 15 from above in the elevation plane A, and the molten resin 21 fed from the introducing runner portion 18 branches and the branched portions of the molten resin 21 move along the length direction of the horizontal runner portion 15 so as to move away from each other.

[0130] As a result of comparison between the thicknesses of the body portions of the PET bottles molded according to the comparative example and the thicknesses of the body portions of the PET bottles molded according to the example, it can be concluded that favorable PET bottles can be produced by molding PET bottles according to the example.

THIRD EXAMPLE

[0131] The hot runner apparatuses exemplified in the first example and the second example are those manufactured for obtaining an even number of preforms. It has been described that the introducing runner portion is continuous with the central portion of the horizontal runner portion from below (the first example) or from above (the second example). The present invention, however, is not limited to the configurations shown in the first example and the second example. The present invention can be applied also to a hot runner apparatus in which an odd number of hot runner nozzles are vertically provided on a hot runner block.

[0132] FIG. 17 illustrates a hot runner apparatus 9 including an odd number of hot runner nozzles 13 as a third example. FIG. 17(a) schematically illustrates the hot runner apparatus 9 including the five hot runner nozzles 13 as viewed from the side of a main nozzle. FIG. 17(b) schematically illustrates the portion of a branching pipe line 20. In the hot runner apparatus 9 of the third example, a single hot runner nozzle 13 is provided vertically at a central portion of a horizontal runner portion 15 in its length direction.

[0133] An introducing port 17 of the hot runner apparatus 9 is located at a central portion of a hot runner block 14 in its length direction. A pipe line of an introducing runner portion 18 extends from the side of the introducing port 17 in a direction perpendicular to the length direction of the horizontal runner portion 15, bends in an oblique direction toward one end side immediately before reaching an elevation plane A, and reaches a position below the horizontal runner portion 15 on the above-described elevation plane A from the bent portion 41.

[0134] The pipe line of the introducing runner portion 18 further bends at the portion having reached the elevation plane A, and extends from the bent portion 42 toward the horizontal runner portion 15 in the elevation plane A, so as to be continuous with a portion of a pipe wall of a lower part of the horizontal runner portion 15. As with the above-described first example and second example, the portion at which the introducing runner portion 18 is continuous with the horizontal runner portion 15 is configured as the T-shaped branching pipe line 20.

[0135] As illustrated in the figure, the branching pipe line 20 in the third example is not located in the central portion of the horizontal runner portion 15 in its length direction. The above-described branching pipe line 20 is provided so as to be displaced toward the one end side of the horizontal runner portion 15 from the central portion of the horizontal runner portion 15 and be located at an intermediate portion 15a between two vertical runner portions 16.

[0136] Although the portion at which the introducing runner portion 18 is connected to the horizontal runner portion 15 preferably corresponds to the central portion of the horizontal runner portion 15 in its length direction, such a portion may be located at a position displaced from the central portion as needed. Also when the introducing runner portion 18 is continuous with a portion of a pipe wall of an upper part of the horizontal runner portion 15 as in the second example, the introducing runner portion 18 may be connected to a position displaced from the central portion of the horizontal runner portion 15.

[0137] The hot runner apparatus 9 of the third example also works in a manner similar to when the hot runner apparatuses 9 shown in the first example and the second example are incorporated into the injection stretch blow molding machines 1 and hollow molded bodies are produced at advanced timing for releasing preforms. More specifically, by disposing the T-shaped branching pipe line 20 in the intermediate portion displaced from the central portion of the horizontal runner portion 15 so that a molten resin 21 from the introducing runner portion 18 is fed thereinto, branching of the molten resin 21 can be made as with the first example and the second example. Thus, favorable hollow molded bodies can be produced also when the hot runner apparatus 9 shown in the third example is incorporated into an injection stretch blow molding machine 1 and hollow molded bodies are produced at advanced timing for releasing preforms.

FOURTH EXAMPLE

[0138] FIG. 18 illustrates a fourth example. FIG. 18(a) schematically illustrates a hot runner apparatus 9 including an odd number of hot runner nozzles 13 as viewed from the side of a main nozzle. FIG. 18(b) schematically illustrates the portion of a branching pipe line 20.

[0139] As with the third example, an introducing runner portion 18 in the hot runner apparatus 9 shown as the fourth example is provided so as to be displaced toward one end side of a horizontal runner portion 15 from a central portion of the horizontal runner portion 15 and be continuous with an intermediate portion 15a between two vertical runner portions 16. In the hot runner apparatus 9 of the fourth example, a pipe line of the introducing runner portion 18 extends from the side of an introducing port 17 in a direction perpendicular to the length direction of the horizontal runner portion 15 and reaches a position below the horizontal runner portion 15 on an elevation plane A. The pipe line of the introducing runner portion 18 bends at the portion having reached the elevation plane A, and extends from the bent portion 43 in an obliquely upward direction in the elevation plane A, so as to be continuous with a portion of a pipe wall of a lower part of the horizontal runner portion 15.

[0140] In the fourth example, the branching pipe line 20 is provided in a Y shape in the portion where the introducing runner portion 18 is continuous with the horizontal runner portion 15 in the intermediate portion 15a of the horizontal runner portion 15 so as to conform with the introducing runner portion 18 extending in the obliquely upward direction. The branching pipe line 20 provided in the portion where the introducing runner portion 18 is continuous with the horizontal runner portion 15 in the present invention is not limited to those having a T shape as shown in the first to third examples. The branching pipe line 20 may have a Y shape as shown in the fourth example.

[0141] As discussed above, in the hot runner apparatus 9 of the fourth example, the Y-shaped branching pipe line 20 is provided in the intermediate portion displaced from the central portion of the horizontal runner portion 15, and the introducing runner portion 18 is continuous with the horizontal runner portion 15 at the above-described intermediate portion 15a. By causing a molten resin 21 from the introducing runner portion 18 to be fed into the branching pipe line 20, branching of the molten resin 21 can be made as with the above-described examples. Thus, favorable hollow molded bodies can be produced as with the first to third examples also when the hot runner apparatus 9 of the fourth example is incorporated into an injection stretch blow molding machine 1 and hollow molded bodies are produced at advanced timing for releasing preforms.

Other Examples of Hot Runner Nozzle

[0142] With regard to the hot runner nozzles 13, a passage for a molten resin, with which the vertical runner portion 16 is continuous, is located in a nozzle-axis center portion, and the shutoff pin 30 is provided so as to pass through the vertical runner portion 16 and the above-described passage in the nozzle-axis center portion. The hot runner nozzle that can be employed in the present invention, however, is not limited to those constructed in such a manner that the position of the shutoff pin is overlapped with the entire length of the passage for a molten resin. For example, it is also possible to employ a hot runner nozzle constructed in such a manner that a passage for a molten resin is provided in a portion displaced from a nozzle-axis center portion and the passage is overlapped with the position of a shutoff pin on the tip side of the nozzle as described in Japanese Patent Application Laid-Open No. Hei. 06-182815.

[0143] Although the hollow molded bodies produced for contrasting the comparative example with the example were PET bottles, a resin material used when carrying out the present invention is not limited to PET.

REFERENCE SIGNS LIST

[0144] 1 . . . injection stretch blow molding machine

[0145] 2 . . . injection apparatus

[0146] 3 . . . injection molding section

[0147] 4 . . . injection molding mold

[0148] 9 . . . hot runner apparatus

[0149] 10 . . . cavity mold

[0150] 11 . . . core mold

[0151] 12 . . . gate

[0152] 13 . . . hot runner nozzle

[0153] 14 . . . hot runner block

[0154] 15 . . . horizontal runner portion

[0155] 16 . . . vertical runner portion

[0156] 17 . . . introducing port

[0157] 18 . . . introducing runner portion

[0158] 20 . . . branching pipe line

[0159] 21 . . . molten resin

[0160] 22 central region

[0161] 23 Ring-shaped region

[0162] 24 lower temperature and higher viscosity resin

[0163] 25 higher temperature and lower viscosity resin

[0164] 26 arc-like region

[0165] 37, 39 to 43 bent portion

[0166] 38 region

[0167] X body portion of PET bottle

[0168] A elevation plane