Screw head, injection device and injection stretch blow molding machine using same

Abstract

The object of the present invention is to provide a screw head and an injection device capable of improving the stirring performance in the vicinity of the injection position, and an injection stretch blow molding machine using the same. [Solution] A screw head comprising a generally conical head, a neck portion integrally formed on one side of the axial direction of the head, and a connecting portion integrally formed on one side of the axial direction of the neck portion, wherein the head has a plurality of agitating blades which protrude radially outward from the axis of the head and are formed at intervals in the circumferential direction, the agitating blades having a side wall surface extending along the radial direction and a top surface along the circumferential direction, and the intersection of the side wall surface and the top surface forms an acute angle.

Description

[Technical field]

[0001] The present invention relates to a screw head used in an injection unit, an injection unit, and an injection stretch blow molding machine using the same. [Background technology]

[0002] Conventionally, there is an injection stretch blow molding machine that uses a hot parison method to shape a preform into a hollow body as a machine for manufacturing synthetic resin hollow bodies such as PET bottles. This injection stretch blow molding machine has an injection molding section that molds a preform using an injection mold, a blow molding section that places the preform in a blow mold, stretches it, and blows it (by blowing compressed air) into it to shape it into a hollow body, and an ejection section that sends the shaped hollow body out of the molding machine, all of which are arranged in sequence at equal intervals in a circular pattern on a flat surface. In such an injection stretch blow molding machine, an inline screw type injection device is used as the injection device for molding the preform in the injection molding section.

[0003] Incidentally, in recent years, there have been attempts with regard to injection stretch blow molding machines to increase the production efficiency of hollow bodies by early demolding of the preform in the injection molding section, thereby shortening the time required for the injection molding process, blow molding process, and removal process.

[0004] For example, Patent Document 1 discloses an invention in which, in an inline screw type injection device, the screw 2 is rotated throughout the primary injection stroke and the pressure holding stroke, thereby shortening the molding cycle and making the injection amount as large as possible.

[0005] Furthermore, Patent Document 2 discloses an invention in which, in order to shorten the molding cycle, the screw is rotated simultaneously with the start of injection, and the plasticization and kneading process for producing the next shot of molten resin is carried out from the start of injection, and further, the plasticized and kneaded molten resin to be injected in the next injection cycle is not sent to the space in front of the screw during filling.

[0006] As a result, the invention disclosed in Patent Document 2 reliably melts the solid resin material (chips) and sends it out into the space in front of the screw, while preventing poorly melted molten resin from mixing with the shot being filled.

[0007] In an in-line screw type injection device, a screw head is attached to the tip of the screw. Prior art relating to the screw head is disclosed in Patent Document 3.

[0008] Patent Document 3 discloses an invention of a screw head in which, in order to eliminate uneven temperature of the molten resin, a stirring section 3B is formed at the tip of the screw head 3, which is formed by carving a plurality of stirring grooves 3d into the cylindrical outer surface extending along its axis and dividing the outer periphery. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 11-207792 [Patent Document 2] JP 2021-181183 A [Patent Document 3] Japanese Patent Application Publication No. 57-197135 Summary of the Invention [Problem to be solved by the invention]

[0010] An advantage of the rotational injection molding disclosed in Patent Documents 1 and 2 is that the metering time can be shortened compared to conventional injection molding because the screw continues to rotate during injection.

[0011] In addition, in rotational injection molding, the time required for the molding cycle is the same as the metering time, so the metering completion time must be timed to the next injection, so the screw rotation speed is slower than in conventional molding, and the rotation time is longer. This improves the plasticization and kneading of the molten resin, so the temperature of the molten resin to be injected can be lower than in conventional injection molding.

[0012] Focusing on the screw, the screw disclosed in Patent Document 3 has a stirring section 3B formed at the tip of the screw head 3, which extends along the axis of the cylindrical outer periphery surface and divides the outer periphery, in order to eliminate temperature unevenness in the molten resin. The stirring section 3B is formed by carving multiple stirring grooves 3d into the outer periphery.

[0013] However, the screw disclosed in Patent Document 3 only has a plurality of stirring grooves 3d engraved therein, and while it may be possible to improve the kneading, there is still ample room for improvement.

[0014] An object of the present invention is to provide a screw head and an injection unit that can improve the stirring performance in the vicinity of the injection position, and an injection stretch blow molding machine using the same. [Means for solving the problem]

[0015] The present invention includes a substantially conical head and a neck portion integrally formed on one side of the head in the axial direction; a connecting portion integrally formed on one side of the neck portion in the axial direction, The head is The head has a plurality of stirring blades protruding radially outward from the axis of the head and spaced apart in the circumferential direction, The stirring blade has a side wall surface extending along the radial direction and a top surface along the circumferential direction, A recessed groove is formed in the top surface along the circumferential direction. The screw head is characterized by the above.

[0016] The present invention also provides The side wall surface and the top surface intersect at an acute angle. It is characterized by:

[0017] The present invention also provides an injection device for molten resin, comprising the above-mentioned screw head.

[0018] The present invention also provides an injection stretch blow molding machine having at least an injection molding section for molding a preform, a blow molding section for stretching and blowing the molded preform to form a hollow body, and a removal section for sending the hollow body formed in the blow molding section out of the molding machine, the injection molding section includes an injection mold and an injection device that injects molten resin into the injection mold; The injection device is A substantially conical head; a neck portion integrally formed on one side of the head in the axial direction; a connecting portion integrally formed on one side of the neck portion in the axial direction, The head is The head has a plurality of stirring blades protruding radially outward from the axis of the head and spaced apart in the circumferential direction, The stirring blade has a side wall surface extending along the radial direction and a top surface along the circumferential direction, A recessed groove is formed in the top surface along the circumferential direction. The present invention relates to an injection stretch blow molding machine comprising a screw head having the above-mentioned features. Effect of the Invention

[0019] According to the present invention, the screw head comprises a generally conical head, a neck portion integrally formed on one side of the axial direction of the head, and a connecting portion integrally formed on one side of the axial direction of the neck portion, and has a plurality of stirring blades protruding radially outward from the axis of the head and formed at intervals in the circumferential direction, the stirring blades having a side wall surface extending along the radial direction and a top surface along the circumferential direction, and the intersection of the side wall surface and the top surface is formed at an acute angle.

[0020] By adopting such a configuration, a torque can be applied to the molten resin present between the adjacent stirring blades, so that a strong swirling flow can be generated in the molten resin near the injection position, thereby improving the stirring performance near the injection position.

[0021] According to the present invention, the top surface is provided with a groove extending in the circumferential direction, which generates a strong and complex swirling flow in the molten resin near the injection position, thereby further improving the mixing performance near the injection position.

[0022] Furthermore, according to the present invention, since the injection device includes the screw head described above, it is possible to realize an injection device with improved mixing performance in the vicinity of the injection position.

[0023] Furthermore, according to the present invention, the injection stretch blow molding machine is equipped with an injection device, and the injection device is equipped with the above-mentioned screw head, so that it is possible to realize an injection stretch blow molding machine with improved mixing performance in the vicinity of the injection position. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a plan view illustrating an injection stretch blow molding machine. [Diagram 2] FIG. 2 is an explanatory diagram illustrating an injection device. [Diagram 3] FIG. 2 is a view showing the vicinity of the tip of the screw. [Figure 4] FIG. 2 is a diagram showing the screw as viewed from the tip. [Diagram 5] 5 is a cross-sectional view taken along line AA in FIG. 4. [Figure 6] 5 is a cross-sectional view of FIG. 4 taken along line B-B. [Figure 7] FIG. 2 is an explanatory diagram showing the vicinity of a screw head 14 in a filled state. [Figure 8] FIG. 4 is an explanatory view showing a screw head 14A according to a second embodiment of the present invention. [Figure 9]FIG. 2 is an explanatory diagram showing a cross section of a screw head 14A. [Figure 10] 1 is an explanatory diagram showing the vicinity of a screw head 14A in a filled state. FIG. [Figure 11] FIG. 11 is an explanatory view showing a screw head 14B according to a third embodiment of the present invention. [Figure 12] FIG. 13 is a view of the screw head 14B as seen from the tip side. [Figure 13] 13 is an explanatory diagram showing a cross section of a screw head 14B. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] (Injection stretch blow molding machine) FIG. 1 is a schematic plan view of an example of an injection stretch blow molding machine according to an embodiment of the present invention. The injection stretch blow molding machine 1 has an injection molding section 2, a blow molding section 3, and a take-out section 4 arranged in a circular pattern on a plane of 120°. Degree The 3D images are arranged at angles of 1 to 50°.

[0026] The injection molding section 2 injects molten resin into an injection mold to mold a high-temperature preform. In particular, the injection stretch blow molding machine 1 of this embodiment is configured so that the preform can be quickly released from the mold while being in a state where it can be stretch-blowed in the blow molding section 3.

[0027] The molded preform is held by a lip mold incorporated as part of the injection mold and then released. The released preform is transferred to the blow molding section 3 and placed in a blow mold. The blow molding section 3 stretches the preform held by the lip mold and blows it with high-pressure air or the like to form a hollow body.

[0028] The blow-molded hollow body is transferred to the removal section 4 while being held by the lip mold. The removal section 4 is a section that sends the hollow body formed in the blow molding section 3 out of the molding machine. The injection stretch blow molding machine 1 moves the lip mold from the blow molding section 3 to the removal section 4, opens the lip mold to release the restraint on the hollow body, and removes it from the lip mold.

[0029] The hollow body released from the lip mold is sent out of the molding machine as described above. Then, the lip mold that released the hollow body moves back to the injection molding section 2 and is incorporated as a part of the injection mold for the preform.

[0030] As described above, the injection stretch blow molding machine 1 transfers the preform molded in the injection molding section 2 to the blow molding section 3 using the lip mold, transfers the hollow body blown in the blow molding section 3 to the removal section 4 using the lip mold, and the lip mold releases the hollow body in the removal section 4.

[0031] (Molding cycle) The injection stretch blow molding machine 1 continuously carries out an injection molding process of injection molding the above-mentioned preform, a blow molding process of blow molding the preform molded in the injection molding process into a hollow body, and an ejection process of sending the hollow body molded in the blow molding process out of the molding machine at an ejection section.

[0032] In the injection stretch blow molding machine 1, lip molds are provided at three locations so that the lip molds can simultaneously correspond to three positions: the injection molding section 2, the blow molding section 3, and the removal section 4.

[0033] The three lip molds are attached to a rotating plate, which is rotated 120 degrees in one direction and then stopped, lowered when it stops, and raised after the injection cooling is completed. After that, the plate is rotated 120 degrees in one direction, and the same operation is repeated, thereby sequentially advancing the corresponding positions of the lip molds.

[0034] In the injection stretch blow molding machine 1, three lip molds are simultaneously moved in sequence to different corresponding positions, and the molding cycle for a hollow body and the next molding cycle proceed with a one-step delay.

[0035] (injection device) 2 is an explanatory diagram that shows a schematic diagram of the injection device 6. The injection device 6 is an in-line screw type injection device in which a screw 9 is arranged inside a cylinder 8 of a barrel (heated cylinder) 7 so as to be rotatable and capable of moving forward and backward.

[0036] The injection device 6 supplies chip-like resin material from a feed hopper 10 to a supply section of the screw 9, and the movement of the screw 9 moves the supplied resin material from a compression section to a metering section.

[0037] As the material moves from the compression section to the metering section, shear heat is generated, and the resin material is plasticized and kneaded by the heat from the heater 11 and the stirring caused by the rotation of the screw to produce a molten resin.

[0038] The produced molten resin is sent out in front of the screw 9, and the molten resin located in front of the screw 9 is injected into the injection molding die 5. A heater 11 is disposed on the outer periphery of the barrel 7 to promote the plasticization of the resin material.

[0039] In the injection molding process, the injection device 6 performs the following functions: filling by sending molten resin into the injection mold 5, maintaining pressure on the molten resin sent to the injection mold 5 to prevent backflow of the molten resin, and metering by sending the molten resin forward of the screw 9 to inject a predetermined required amount of molten resin into the injection mold 5.

[0040] The injection device 6 continuously repeats a series of filling, pressure holding, and metering, which is called an injection cycle. One injection cycle is injection (filling + pressure holding) + metering.

[0041] (Injection molding process - injection) In the injection molding process, when the injection device 6 starts filling, the screw 9 is at the injection start position. The injection device 6 advances the screw 9, which is at the injection start position, while rotating it. As the rotating screw 9 advances, the required amount of molten resin is injected into the injection mold 5.

[0042] Filling is performed by rotating the screw 9 with the drive unit and applying hydraulic pressure to the screw 9 in the forward direction (towards the injection mold 5). When it is determined that the screw 9 has reached a predetermined holding pressure switching position, the injection ends by switching the pressure applied to the screw 9 to a holding back pressure.

[0043] During filling, when hydraulic pressure is applied to the screw 9 to move it forward, the resin pressure (injection pressure) in front of the screw 9 increases, causing the ring valve (a ring-shaped flow path opening and closing valve located at the tip of the screw) to close. Therefore, even when the production of molten resin begins with the rotation of the screw 9, the molten resin does not flow from the metering section to the front of the screw 9. In other words, during filling, the molten resin that is plasticized and kneaded to be injected in the next injection cycle is not sent to the space in front of the screw 9.

[0044] In the injection device 6, the screw 9 has been rotating since the start of injection (filling) as described above. The production of molten resin in the next molding cycle is started by the rotation of the screw 9. That is, in the injection device 6, the start of injection and the start of production of the molten resin for the next shot are performed simultaneously.

[0045] (Injection molding process - holding pressure) After the injection unit 6 has finished filling, it continues to rotate the screw 9 from the filling operation to maintain pressure.

[0046] In the injection device 6, during pressure holding, a back pressure set for pressure holding is applied to the screw 9. At this time, the screw 9 continues to rotate from the filling stage, and continues to produce the molten resin for the next shot.

[0047] (Injection molding process - measurement) After completing the dwelling, the injection unit 6 continues the rotation operation of the screw 9 during the dwelling, retreats while rotating the screw 9, and performs metering. The metering operation is set so as to fit within the dry cycle time of the mold opening, rotation, and mold closing in the injection molding section 2.

[0048] In metering, the injection device 6 rotates the screw 9 while retracting it under back pressure. In metering, the rotation speed of the screw 9 is conventionally about 120 RPM, but in this embodiment, it is set to a lower rotation speed than conventionally, for example, 70 RPM to 80 RPM. In metering, the resin material is plasticized and kneaded to send a predetermined required amount of molten resin forward of the screw 9. When the screw 9 retracts and reaches the injection start position, the rotation is stopped, which stops the retraction of the screw 9 and ends the metering.

[0049] When the screw 9 reaches the injection start position (measurement completion position), the injection unit 6 immediately starts the injection molding process without waiting.

[0050] In this embodiment, when the screw 9 retreats to the injection start position, the rotation of the screw 9 stops, but the rotation of the screw 9 may be continued.

[0051] In the injection device 6 of the present embodiment, the plasticization kneading for generating the next shot of molten resin is started from the start of injection, so the generation of the next shot of molten resin can be started earlier than in a conventional injection device that rotates the screw after completion of dwelling pressure. Therefore, the generation of the next shot of molten resin can be completed earlier than in a conventional injection device, and the molding cycle can be shortened.

[0052] In addition, since the time required for metering is the time required for the molding cycle, the screw rotation speed during metering is lower and the rotation time is longer. This improves the plasticization and kneading of the molten resin, so the temperature of the molten resin to be injected can be lower than that of conventional injection molding.

[0053] In the injection device 6 of the embodiment, the screw 9 rotates continuously during filling, pressure holding, and metering, but the number of screw revolutions per unit time does not need to be the same during filling, pressure holding, and metering. The number of screw revolutions per unit time is variable during each of filling, pressure holding, and metering, and can be set appropriately for each of filling, pressure holding, and metering.

[0054] Incidentally, the above-mentioned point of making the screw rotation speed per unit time variable for each of filling, pressure holding, and metering naturally includes changing the screw rotation speed per unit time during each of filling, pressure holding, and metering.

[0055] (screw) Fig. 3 is a diagram showing the vicinity of the tip of the screw 9. Fig. 4 is a diagram showing the screw 9 as viewed from the tip. Fig. 5 is a cross-sectional view taken along line AA in Fig. 4, and Fig. 6 is a cross-sectional view taken along line BB in Fig. 4.

[0056] The screw 9 includes a screw body 12 having a spiral groove formed on the outer surface of the cylindrical body, a seat ring 13 provided at one end of the screw body 12, a screw head 14 attached to one end of the screw body 12, and a ring valve 15 provided at a neck portion 21 of the screw head 14, which will be described later.

[0057] The screw body 12 has a supply section, a compression section, and a metering section (not shown), and transports the molten resin supplied from the feed hopper 10 to the screw head 14. The supply section is a region where the molten resin is transported while being heated. The compression section is a region where the molten resin, which has also been preheated in the supply section, is pressurized and compressed, and mechanical energy is supplied to promote melting. The metering section is a region where the homogenization of the molten resin transported from the compression section is promoted and rectified, and the pressure required for the molten resin to pass through the ring valve 15 is generated. Such a structure of the screw body 12 is no different from that of a full-flight screw of the prior art.

[0058] (Screw head) The screw head 14 has a generally conical head 20, a neck portion 21 formed integrally on one side of the axial direction, which is the direction in which the axis L of the head 20 extends, and a connecting portion 22 formed integrally on one side of the axial direction of the neck portion 21.

[0059] The head 20 has a plurality of (four in this embodiment) agitating blades 30 that protrude radially outward from the axis of the head 20 and are spaced apart in the circumferential direction. A concave groove 31 through which the molten resin passes is formed between adjacent agitating blades 30.

[0060] The agitator blade 30 has two side wall surfaces 40 extending radially, a top surface 41 along the circumferential direction of the head 20, an inclined surface 42 connected to one end of the top surface 41 and inclined toward the tip of the screw head 14, and a back surface 43 connected to the other end of the top surface 41 and extending radially.

[0061] An angle formed by an intersection 44 between the side wall surface 40 and the top surface 41 is set to an acute angle, preferably set to 80 degrees to 90 degrees. As shown in FIG.

[0062] The neck portion 21 is formed in a substantially cylindrical shape. The ring valve 15 is attached to the neck portion 21 so as to be movable in the axial direction. When the ring valve 15 is in the open position (tip side), the neck portion 21 allows the molten resin to move to the injection port through a gap with the ring valve 15. When the ring valve 15 is in the closed position (rear end side), there is no gap between the neck portion 21 and the ring valve 15, and the molten resin does not move to the injection port.

[0063] The connecting portion 22 is a portion that is connected to the screw body 12. The connecting portion 22 is formed in a substantially cylindrical shape, and a male thread is formed on the surface. An attachment portion for attaching the screw head 14 is provided at the tip of the screw body 12. The connecting portion 22 is connected to the screw body 12 by screwing into a female thread formed on the attachment portion formed on the screw body 12.

[0064] 7 is an explanatory diagram showing the vicinity of the screw head 14 in the filling state. As described above, during filling, the injection device 6 applies hydraulic pressure to the screw 9 to move the screw 9 forward. At this time, the resin pressure (injection pressure) in front of the screw 9 increases, so the ring valve 15 (a ring-shaped flow path opening and closing valve located at the tip of the screw) closes. Therefore, even when the generation of molten resin has started due to the rotation of the screw 9, the molten resin does not flow from the metering section to the front of the screw 9 (the injection port side).

[0065] In this state, the screw 9 continues to rotate, so that the molten resin to be injected (the molten resin located on the tip side of the ring valve 15) is pushed out to the injection port while being accompanied by a swirling flow. That is, the molten resin being injected is pushed out to the injection port while being plasticized and kneaded, and is injected into the injection mold 5.

[0066] As shown in Fig. 7, the screw head 14 has an agitating blade 30, which has a side wall surface 40 and a top surface 41, and the intersection portion 44 is formed at an acute angle. As a result, the molten resin present in the concave groove 31 formed between adjacent agitating blades 30 receives torque in the rotational direction from the side wall surface 40 due to the rotation of the screw 9. The screw 9 advances toward the injection port while rotating, so that a swirling flow can be generated in the molten resin.

[0067] By forming the intersecting portion 44 at an acute angle, a torque can be applied to almost all of the molten resin inside the groove 31, generating a strong swirling flow. This improves the plasticization and kneading of the molten resin, suppressing temperature unevenness and allowing the temperature of the injected molten resin to be lower than in conventional injection molding.

[0068] In this way, by using the screw head 14 of this embodiment, it is possible to improve the plasticization and kneading of the molten resin, suppress temperature unevenness, and make the temperature of the molten resin to be injected lower than that of conventional injection molding. Therefore, it is possible to reduce the waiting time of the preform in the blow molding die, which is required in the conventional blow molding process to even out the temperature unevenness of the preform. This makes it possible to shorten the molding cycle.

[0069] In the prior art, when polypropylene is used as the molding material, it was necessary to provide a long waiting time for the preform in the blow molding die in order to eliminate temperature unevenness. However, by using the screw head 14 of this embodiment, the molten resin can be sufficiently kneaded to provide a molded preform with suppressed temperature unevenness, so that the waiting time for the preform in the blow molding die can be reduced or eliminated.

[0070] Furthermore, for example, when the molding material contains granular pellets containing a filler, the screw head 14 of this embodiment can sufficiently knead the molten resin during filling, making it possible to provide a preform molded from molten resin without uneven mixing. This allows the desired molded product to be manufactured with a good yield.

[0071] Therefore, according to the present invention, it is possible to realize a screw head and an injection device that can improve the stirring performance in the vicinity of the injection position, and an injection stretch blow molding machine using the same.

[0072] Next, another embodiment of the present invention will be described. Fig. 8 is an explanatory diagram showing a screw head 14A according to a second embodiment of the present invention, and Fig. 9 is an explanatory diagram showing a cross section of the screw head 14A. Fig. 10 is an explanatory diagram showing the vicinity of the screw head 14A in a filled state. To avoid duplication of explanation, the same reference numerals are used for the same parts as in the above-mentioned embodiment, and explanations will be omitted.

[0073] The screw head 14A has an agitating blade 30A. The agitating blade 30A has a top surface 41A. A groove 45 having a generally V-shaped cross section extending along the circumferential direction is formed on the top surface 41A. The groove 45 is a groove recessed toward the radially inward direction of the screw head 14, and the cross-sectional shape is not limited to a V-shape. Since the groove 45 is formed on the top surface 41A in this manner, the agitating blade 30A has a front blade portion 50 located on the tip side of the groove 45 and a rear blade portion 51 located on the rear end side of the groove 45.

[0074] When the screw head 14A is rotated, as shown in Figure 10, an annular gap having the cross-sectional shape of the groove 45 is formed between the molten resin stirred by the front wing portion 50 and the molten resin stirred by the rear wing portion 51, and the torque applied to the molten resin located in the annular gap is different from the torque applied to the molten resin located between each front wing portion 50 and between each rear wing portion 51.

[0075] Therefore, the molten resin stirred by the stirring blade 30A receives a torque that is more dispersed than that of the stirring blade 30, and a complex swirling flow is generated in the molten resin. This can further improve the plasticization and kneading of the molten resin.

[0076] Furthermore, since the reaction force acting on the screw head 14A is reduced by the groove 45, the rotation speed of the screw 9 can be increased, and further, durability can be improved due to the reduced load.

[0077] Next, a third embodiment of the present invention will be described. Fig. 11 is an explanatory diagram showing a screw head 14B according to the third embodiment of the present invention, Fig. 12 is a diagram of the screw head 14B seen from the tip side, and Fig. 13 is an explanatory diagram showing a cross section of the screw head 14B. To avoid duplication of explanation, the same reference numerals are used for the same parts as in the above-mentioned embodiment, and explanations will be omitted.

[0078] The screw head 14B has an agitating blade 30B. The agitating blade 30B is formed such that the circumferential interval between adjacent agitating blades 30B is narrower than that of the agitating blade 30A, and the circumferential thickness dimension is also small. In other words, the screw head 14B has an agitating blade 30B in which eight agitating blades 30A with a reduced thickness dimension are formed in the circumferential direction.

[0079] The grooves 31 formed in the screw head 14B are spaced closer together than the grooves 31 formed in the screw head 14A.

[0080] When the screw head 14B is rotated, the mixing blade 30B is divided into a front blade portion 50 and a rear blade portion 51 due to the presence of the concave groove 45. When the mixing blade 30B rotates, an annular gap having the cross-sectional shape of the concave groove 45 is formed between the molten resin mixed by the front blade portion 50 and the molten resin mixed by the rear blade portion 51.

[0081] In addition, since the intervals between the grooves 31 are narrower than those of the screw head 14A, the molten resin that enters the grooves 31 is dispersed more than in the screw head 14A.

[0082] At this time, the molten resin stirred by the stirring blade 30B receives a torque that is more dispersed than that of the stirring blade 30A, and a more complex swirling flow is generated in the molten resin. Therefore, the plasticization and kneading of the molten resin can be improved.

[0083] In the above description, the injection stretch blow molding machine 1 that continuously performs the injection molding process, the blow molding process, and the removal process in a series has been taken as an example of the injection stretch blow molding machine, but the present invention is not limited to this. The present invention can also be used in an injection stretch blow molding machine that includes a temperature adjustment process that adjusts the temperature of the injection-molded preform. [Explanation of symbols]

[0084] 1. Injection stretch blow molding machine 2 Injection molding section 3 Blow Molding Section 4. Extraction section 9 Screw 12 Screw body 13 Seat ring 14 Screwhead (Torpedo) 14A Screw Head 14B screw head 15 Ring Valve 20 Head 21 Neck 22 Connecting part 30 Stirring blade 30A stirring blade 30B Agitator blade 31 Groove 40 Side wall 41 Top 42 Slope 43 Back 44 Intersection 50 Front wing 51 Rear wing

Claims

1. A substantially conical head; a neck portion integrally formed on one side of the head in the axial direction; a connecting portion integrally formed on one side of the neck portion in the axial direction, The head is The head has a plurality of stirring blades protruding radially outward from the axis of the head and spaced apart in the circumferential direction, The stirring blade has a side wall surface extending along the radial direction and a top surface along the circumferential direction, The screw head is characterized in that a groove is formed on the top surface along the circumferential direction.

2. 2. The screw head according to claim 1, wherein an intersection between said side wall surface and said top surface forms an acute angle.

3. 3. An injection device for molten resin, comprising the screw head according to claim 1 or 2.

4. An injection stretch blow molding machine having at least an injection molding section for molding a preform, a blow molding section for stretching and blowing the molded preform to form a hollow body, and a take-out section for sending the hollow body formed in the blow molding section out of the molding machine, the injection molding section includes an injection mold and an injection device that injects molten resin into the injection mold; The injection device is A substantially conical head; a neck portion integrally formed on one side of the head in the axial direction; a connecting portion integrally formed on one side of the neck portion in the axial direction, The head is The head has a plurality of stirring blades protruding radially outward from the axis of the head and spaced apart in the circumferential direction, The stirring blade has a side wall surface extending along the radial direction and a top surface along the circumferential direction, 13. An injection stretch blow molding machine comprising: a screw head, the top surface of which is formed with a recessed groove along the circumferential direction.

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