Blowing molding mechanism and mold apparatus

Abstract

This prevents parts of the stretching rod used to stretch the intermediate molded product during blow molding from coming into contact with the intermediate molded product, except for the tip portion. [Solution] The blow molding mechanism 1 includes a stretching rod 16 that is inserted into the intermediate molded product 200 through the opening 205 when blow molding is performed on the intermediate molded product 200 which is formed into a bottomed cylindrical shape having an opening 205, and stretches the intermediate molded product 200. The stretching rod 16 has a columnar main body portion 161 that stretches inside the intermediate molded product 200, and a tip portion that has a contact portion 162 formed at the tip of the main body portion 161 that contacts the inner wall 206 of the intermediate molded product 200, and the diameter of the contact portion 162 is larger than the diameter of the main body portion 161.

Description

Technical Field

[0001] The present invention relates to an injection molding mechanism and a mold device.

Background Art

[0002] Injection blow molding, which combines injection molding and blow molding, is known. In injection blow molding, first, in injection molding, a bottomed cylindrical intermediate molded product having an opening is molded. Next, in blow molding, the intermediate molded product is stretched by a stretching rod protruding into the interior of the intermediate molded product, and the final molded product is molded by blowing and expanding high-pressure air (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The stretching rod stretches the intermediate molded product by stretching itself while the tip part is in contact with the intermediate molded product. However, during the stretching of the intermediate molded product by the stretching rod, a part of the intermediate molded product may come into contact with a part other than the tip part of the stretching rod. If the intermediate molded product has many parts in contact with the stretching rod whose temperature is lower than its own temperature, the temperature may decrease due to heat exchange and may fall below the temperature required during blow molding. In this case, it leads to a deterioration in the appearance quality of the final molded product. An object of the present invention is to suppress contact of a part other than the tip part of a stretching rod that stretches an intermediate molded product during blow molding with the intermediate molded product.

Means for Solving the Problems

[0005] The present invention, completed with this objective in mind, is a blow molding mechanism comprising a stretching rod that is inserted into the interior of an intermediate molded product, which is formed in the shape of a bottomed cylindrical product having an opening, when blow molding is performed on the intermediate molded product, and the stretching rod has a columnar main body portion that stretches inside the intermediate molded product and a tip portion formed at the tip of the main body portion that contacts the inner wall of the intermediate molded product, wherein the diameter of the contact portion is larger than the diameter of the main body portion. The contact portion may be characterized by being detachable from the main body. Furthermore, the main body portion may be characterized in that it does not come into contact with the inner wall of the intermediate molded product after stretching. Furthermore, the difference between the diameter of the contact portion and the diameter of the main body portion may be greater than the value obtained by dividing the difference between the inner diameter of the stretched intermediate molded product and the diameter of the main body portion by 2. Furthermore, the present invention, completed with this objective in mind, is a mold device comprising a blow molding mechanism, wherein when blow molding is performed on an intermediate molded product that is molded in the shape of a bottomed cylindrical product having an opening, the blow molding mechanism includes a stretching rod that is inserted into the interior of the intermediate molded product through the opening and stretches the intermediate molded product, the stretching rod having a columnar main body that stretches inside the intermediate molded product and a tip portion formed at the tip of the main body that contacts the inner wall of the intermediate molded product, the diameter of the contact portion being larger than the diameter of the main body. [Effects of the Invention]

[0006] According to the present invention, it is possible to suppress contact between the intermediate molded product and any portion of the stretching rod other than the tip portion used to stretch the intermediate molded product during blow molding. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional view showing an example of the configuration of the blow molding mechanism according to this embodiment. [Figure 2] This is a cross-sectional view showing an example of the configuration of the blow molding mechanism according to this embodiment. [Figure 3]Figure 1 is a cross-sectional view showing the stretching rod stretching an intermediate molded product. [Figure 4] This is a cross-sectional view showing an example of the configuration of a conventional blow molding mechanism. [Figure 5] This is a cross-sectional view showing an example of the configuration of a conventional blow molding mechanism. [Figure 6] Figure 4 is a cross-sectional view showing a conventional stretching rod stretching an intermediate molded product. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described in detail below with reference to the attached drawings. <Configuration of the blow molding mechanism 1> Figures 1 and 2 are cross-sectional views showing an example of the configuration of the blow molding mechanism 1 according to this embodiment. Figures 1 and 2 show cross-sectional views of the blow molding mechanism 1 as viewed from the top to the bottom in the vertical direction. Therefore, the front of Figure 1 is the top in the vertical direction, and the back of Figure 1 is the bottom in the vertical direction. Also, Figure 1 shows the blow molding mechanism 1 immediately before blow molding is performed, and Figure 2 shows the blow molding mechanism 1 immediately after blow molding is performed.

[0009] The blow molding mechanism 1 shown in Figures 1 and 2 is a mechanism applied to a mold device that molds a final molded product 300 from an intermediate molded product 200 by injection blow molding, which combines injection molding and blow molding. The final molded product 300 is, for example, a bottle container such as a PET bottle. The mold device to which the blow molding mechanism 1 is applied includes a fixed mold, a movable mold, and an intermediate mold positioned between the fixed mold and the movable mold. The fixed mold, the movable mold, and the intermediate mold are each combinations of a mold that performs molding and various devices that operate in conjunction with the mold.

[0010] In injection blow molding, a bottomed cylindrical intermediate molded product 200 having an opening 205 is formed by injection molding with the fixed mold and the intermediate mold closed. In injection blow molding, the final molded product 300 is formed by blow molding onto the intermediate molded product 200 with the movable mold and the intermediate mold closed. In injection blow molding, the intermediate mold alternately performs injection molding and blow molding while moving between a position facing the fixed mold and a position facing the movable mold.

[0011] The blow molding mechanism 1 includes a stretching mechanism 11 that ejects a columnar stretching rod 16 to stretch the intermediate molded product 200 inside the intermediate molded product 200 during blow molding, and also outputs air. The blow molding mechanism 1 also includes a first split mold 12, a second split mold 13, a first bottom mold 14, and a second bottom mold 15 that function as molds during blow molding. Of the blow molding mechanism 1, the stretching mechanism 11 and the first split mold 12 constitute part of the intermediate mold, while the second split mold 13, the first bottom mold 14, and the second bottom mold 15 constitute part of the movable mold.

[0012] Hereinafter, in a mold apparatus to which the blow molding mechanism 1 is applied, the direction in which the fixed mold and the intermediate mold open and close as a whole, and the direction in which the movable mold and the intermediate mold open and close as a whole (the direction of operation of the stretching rod 16) will be referred to as the "opening and closing direction". Furthermore, the root side of the stretching rod 16 in the opening and closing direction will be referred to as the "first side", and the tip side of the stretching rod 16 in the opening and closing direction will be referred to as the "second side". In addition, the direction perpendicular to the axial direction (opening and closing direction) of the intermediate molded product 200 during blow molding (for example, the direction perpendicular to the direction of operation of the stretching rod 16) will be referred to as the "radial direction". Furthermore, the side of the central axis (dotted line) in the radial direction of the intermediate molded product 200 will be referred to as the "inside", and the opposite side will be referred to as the "outside".

[0013] The extension mechanism 11 includes a cylindrical long-axis tube 111 having an outlet 112 at its tip for protruding the extension rod 16. The long-axis tube 111 inserts the outlet 112 into the interior of the intermediate molded product 200 from the opening 205 of the intermediate molded product 200, and protrudes the extension rod 16 from the outlet 112 to the second side in the opening and closing direction, thereby bringing the tip portion of the extension rod 16 into contact with the inner wall 206 of the intermediate molded product 200. Specifically, the extension mechanism 11 brings the contact portion 162 at the tip of the extension rod 16 into contact with the inner wall 206 of the intermediate molded product 200. Then, the extension mechanism 11 extends the intermediate molded product 200 by further extending the extension rod 16 to the second side in the opening and closing direction.

[0014] Further, the extension mechanism 11 expands the intermediate molded product 200 by outputting high-pressure air from the outlet 112 to the second side in the opening and closing direction. The high-pressure air output at this time is output from the gap between the extension rod 16 protruding from the outlet 112 and the inner wall of the long-axis tube 111. FIG. 1 shows the intermediate molded product 200 before extending the extension rod 16 protruding from the outlet 112. Further, FIG. 2 shows the final molded product 300 formed by extending and expanding the intermediate molded product 200 in FIG. 1 by blow molding.

[0015] Here, each part of the intermediate molded product 200 and the final molded product 300 will be described. As shown in FIG. 1, the intermediate molded product 200 has a fringe portion 201 which is the portion protruding most outward in the radial direction, and a mouth portion 202 which is the portion on the first side in the opening and closing direction from the fringe portion 201. Further, the intermediate molded product 200 has a main body portion 203 and a bottom portion 204 which are portions on the second side in the opening and closing direction from the fringe portion 201.

[0016] Further, as shown in FIG. 2, the final molded product 300 has a fringe portion 201, a mouth portion 202, and a main body portion 303 and a bottom portion 304 which are portions on the second side in the opening and closing direction from the fringe portion 201. The main body portion 303 is the portion where the main body portion 203 of the intermediate molded product 200 is blow molded. The main body portion 303 includes a neck portion 331, a shoulder portion 332, and a body portion 333. The bottom portion 304 is the portion where the bottom portion 204 of the intermediate molded product 200 is blow molded.

[0017] The first split mold 12 is a separable split mold, also called a split and mouth split mold, which grips the mouth portion 202 of the intermediate molded product 200 and the final molded product 300 in the mold-closed state. FIGS. 1 and 2 show the first split mold 12 in the mold-closed state. When the final molded product 300 is molded by blow molding, the first split mold 12 opens the mold from the inner side to the outer side in the radial direction with respect to the final molded product 300. As a result, the mouth portion 202 of the final molded product 300 is released from the first split mold 12.

[0018] The second split mold 13 is a separable split mold, also called a blow split mold, which functions as one of the molds for blow molding and molds the main body portion 303 of the final molded product 300 from the main body portion 203 of the intermediate molded product 200 in the mold-closed state during blow molding. FIG. 1 shows the second split mold 13 in the mold-closed state. When the final molded product 300 is completed by blow molding, the second split mold 13 opens the mold from the inner side to the outer side in the radial direction with respect to the final molded product 300. As a result, the main body portion 303 of the final molded product 300 and the fringe portion 201 are released from the second split mold 13.

[0019] The first bottom mold 14 and the second bottom mold 15 function as one of the molds for blow molding and mold the bottom portion 304 of the final molded product 300 from the bottom portion 204 of the intermediate molded product 200 during blow molding. Among these, the second bottom mold 15 also functions as part of an ejector mechanism that separates the final molded product 300 from itself and the first bottom mold 14 by protruding from the second side to the first side in the opening and closing direction after blow molding.

[0020] <Specific shape of the extension bar 16> FIG. 3 is a cross-sectional view showing the state when the extension bar 16 in FIG. 1 extends the intermediate molded product 200. The blow molding mechanism 1 according to this embodiment is characterized by the tip portion of the stretching rod 16 that stretches the intermediate molded product 200 during blow molding. As shown in Figure 3, the stretching rod 16 has a columnar main body portion 161 that stretches inside the intermediate molded product 200, and a tip portion that has a contact portion 162 formed at the tip of the main body portion 161 and that contacts the inner wall 206 of the intermediate molded product 200. The contact portion 162 has a shape in which a hemispherical portion and a cylindrical portion are integrated, and the hemispherical portion is positioned on the tip side (second side in the opening and closing direction).

[0021] The contact portion 162 may be molded integrally with the main body portion 161, or it may be molded independently of the main body portion 161. If the contact portion 162 is molded independently of the main body portion 161, it may be joined to the main body portion 161, or it may be made detachable. When joining the contact portion 162 to the main body portion 161, it may be joined by methods such as welding or adhesive bonding. When making the contact portion 162 detachable from the main body portion 161, for example, a screw mechanism may be provided between the main body portion 161 and the contact portion 162 to allow for attachment and detachment.

[0022] Here, the stretching rod 16 constituting the blow molding mechanism 1 according to this embodiment is characterized in that the diameter b of the contact portion 162 is larger than the diameter a of the main body portion 161. Specifically, since the diameter b is larger than the diameter a by the length d on one side, the length of the diameter b is longer than the length of the diameter a by length d × 2. Note that as long as the diameter b is longer than the diameter a, the length d is not particularly limited, and the length of the contact portion 162 in the axial direction (opening / closing direction) is also not particularly limited. However, a preferred value for the length d can be determined from the difference between the inner diameter of the stretched intermediate molded product 200, which is calculated from a predetermined stretching ratio of the intermediate molded product 200 during stretching, and the diameter of the main body portion 161 of the stretching rod 16, which is predetermined.

[0023] For example, suppose the difference between the outer diameter and inner diameter in the axial direction (opening / closing direction) of the intermediate molded product 200 is constant, and the stretching ratio of the intermediate molded product 200 during stretching is approximately 2 times. Also, suppose the stretching rod 16 is in the state before the contact portion 162 is formed at its tip (i.e., only the main body portion 161 is formed). In this case, the inner diameter of the intermediate molded product 200 after stretching becomes approximately 0.4 times smaller than before stretching. For example, if the inner diameter of the intermediate molded product 200 before stretching is 17.6 mm, the inner diameter of the intermediate molded product 200 after stretching will be approximately 7.4 mm. In contrast, suppose the diameter of the stretching rod 16 is 8 mm. In this case, the diameter of the stretching rod 16 will be approximately 0.6 mm larger than the inner diameter of the intermediate molded product 200 after stretching, so the intermediate molded product 200 will come into contact with the stretching rod 16 during the stretching process.

[0024] Therefore, when forming a contact portion 162 at the tip of the stretching rod 16, a contact portion 162 is prepared that exceeds the length d value on one side. In the above case, it is necessary to prepare a contact portion 162 in which the length d value exceeds at least approximately 0.3 mm, which is the difference between the inner diameter of the stretched intermediate molded product 200 and the diameter of the stretching rod 16, divided by 2 (approximately 0.6 mm).

[0025] <Comparison with conventional extension rods> As described above, the blow molding mechanism 1 according to this embodiment is characterized by the tip portion of the stretching rod 16 that stretches the intermediate molded product 200 during blow molding. The characteristics of the tip portion of the stretching rod 16 and its effects will be described below with further reference to Figures 4 to 6, which are examples of the configuration of a conventional blow molding mechanism.

[0026] Figures 4 and 5 are cross-sectional views showing an example of the configuration of a conventional blow molding mechanism. Figures 4 and 5 show cross-sectional views of a conventional blow molding mechanism, viewed from the top to the bottom in the vertical direction. Therefore, the front of Figure 4 is the top in the vertical direction, and the back of Figure 4 is the bottom in the vertical direction. Furthermore, Figure 4 shows the conventional blow molding mechanism immediately before blow molding is performed, and Figure 5 shows the conventional blow molding mechanism immediately after blow molding is performed.

[0027] The configuration of the conventional blow molding mechanism shown in Figures 4 and 5 is basically the same as the configuration of the blow molding mechanism 1 according to the embodiment shown in Figures 1 and 2 above. That is, the conventional blow molding mechanism stretches the intermediate molded product by stretching the stretching rod protruding from the protruding port of the stretching mechanism to the second side in the opening and closing direction, as shown in Figure 4. Figure 4 shows the intermediate molded product before the stretching rod protruding from the protruding port is stretched. Figure 5 shows the final molded product formed by stretching the intermediate molded product from Figure 4 and further expanding it with high-pressure air.

[0028] However, when comparing the configuration of the conventional blow molding mechanism shown in Figures 4 and 5 with the configuration of the blow molding mechanism 1 according to this embodiment shown in Figures 1 and 2, the configuration of the stretching rod in the conventional blow molding mechanism and the configuration of the stretching rod 16 in the blow molding mechanism 1 according to this embodiment are different. Specifically, the shape of the stretching rod contact portion at the tip of the stretching rod in the stretching mechanism of the conventional blow molding mechanism is different from the shape of the contact portion 162 at the tip of the stretching rod 16 in the stretching mechanism 11 of the blow molding mechanism 1 according to this embodiment.

[0029] As shown in Figures 1 and 2, the stretching rod 16 of the stretching mechanism 11 of the blow molding mechanism 1 according to this embodiment has a contact portion 162 at its tip that is larger in diameter than the main body portion 161. In contrast, as shown in Figures 4 and 5, in the stretching mechanism of a conventional blow molding mechanism, the diameter of the stretching rod contact portion at the tip and the diameter of the main body portion of the stretching rod are the same. In this case, the intermediate molded product is more likely to come into contact with the stretching rod during the stretching process. The reason for this will be explained below with reference to Figure 6.

[0030] <Specific shape of conventional extension rods> Figure 6 is a cross-sectional view showing the conventional stretching rod from Figure 4 stretching an intermediate molded product. As shown in Figure 6, the stretching rod of a conventional blow molding mechanism has a columnar stretching rod body that stretches inside the intermediate molded product, and a stretching rod contact portion formed at the tip of the body that contacts the inner wall of the intermediate molded product. The stretching rod contact portion has a shape in which a hemispherical portion and a cylindrical portion are integrated, and the hemispherical portion is positioned on the second side in the opening and closing direction.

[0031] In conventional stretching rods, as shown in Figure 6, the diameter f of the stretching rod contact portion is the same as the diameter e of the stretching rod body. Therefore, when the stretching rod is extended to the second side in the opening / closing direction with the stretching rod contact portion in contact with the inner wall of the bottom of the intermediate molded product, the intermediate molded product is also extended to the second side in the opening / closing direction, generating stress that deforms the shape of the main body of the intermediate molded product. Specifically, when the intermediate molded product is extended to the second side in the opening / closing direction, the main body of the intermediate molded product is pulled towards the end point of the contact portion between the stretching rod contact portion and the intermediate molded product, bringing it closer to the stretching rod. As a result, the diameter of the main body of the intermediate molded product gradually decreases and approaches the diameter of the stretching rod. Consequently, the main body of the intermediate molded product comes into contact with the main body of the stretching rod in the area enclosed by the dashed line in Figure 6.

[0032] In contrast, the stretching rod 16 according to this embodiment differs from conventional stretching rods in that the diameter of the contact portion 162 at the tip is larger than the diameter of the main body portion 161. Therefore, even if stress is generated when the intermediate molded product 200 is stretched and the main body portion 203 approaches the main body portion 161 of the stretching rod 16, as shown in Figure 3, contact between the main body portion 203 of the intermediate molded product 200 and the main body portion 161 of the stretching rod 16 can be suppressed by a length d.

[0033] <Variation> In the above-described embodiment, the contact portion 162 at the tip of the extension rod 16 has a shape in which a hemispherical portion and a cylindrical portion are integrated, as shown in Figures 1 to 3, but is not limited to this. As long as the diameter of the contact portion 162 is larger than the diameter of the main body portion 161, for example, a spherical contact portion 162 may be formed at the tip of the extension rod 16.

[0034] In summary, the blow molding mechanism to which the present invention is applied only needs to have the following configuration, and various embodiments can be adopted. In other words, the blow molding mechanism 1 according to this embodiment includes a stretching rod 16 that is inserted into the interior of an intermediate molded product 200, which is formed in the shape of a bottomed cylindrical intermediate molded product 200 having an opening 205, when blow molding is performed on the intermediate molded product 200, and stretches the intermediate molded product 200. The stretching rod 16 has a columnar main body portion 161 that stretches inside the intermediate molded product 200, and a tip portion that has a contact portion 162 formed at the tip of the main body portion 161 that contacts the inner wall 206 of the intermediate molded product 200, and the diameter b of the contact portion 162 of the stretching rod 16 is larger than the diameter a of the main body portion 161 of the stretching rod 16.

[0035] As a result, the diameter of the contact portion 162 at the tip of the stretching rod 16 is larger than the diameter of the main body portion 161. Therefore, even if stress is generated during the stretching of the intermediate molded product 200 and the main body portion 203 of the intermediate molded product 200 approaches the main body portion 161 of the stretching rod 16, contact is suppressed. Consequently, a decrease in the appearance quality of the final molded product 300 that may occur due to the temperature dropping when the intermediate molded product 200 comes into contact with the stretching rod 16 can be suppressed.

[0036] Here, the contact portion 162 of the extension rod 16 may be characterized by being detachable from the main body portion 161 of the extension rod 16. This allows the contact portion 162 to be replaced to match the shape of the intermediate molded product 200, thus improving the efficiency of the replacement work compared to replacing the entire stretching rod 16.

[0037] Furthermore, the main body portion 161 of the stretching rod 16 may be characterized in that it does not come into contact with the inner wall 206 of the intermediate molded product 200 after stretching. This makes it possible to suppress the deterioration of the appearance quality of the final molded product 300 that may occur when the intermediate molded product 200 comes into contact with the stretching rod 16 and its temperature drops.

[0038] Furthermore, the device may be characterized in that the difference between the diameter b of the contact portion 162 of the stretching rod 16 and the diameter a of the main body portion 161 of the stretching rod 16 is greater than the value obtained by dividing the difference between the inner diameter of the intermediate molded product 200 after stretching and the diameter a of the main body portion 161 of the stretching rod 16 by 2. This makes it possible to improve the efficiency of the design of the contact portion 162 of the extension rod 16.

[0039] Furthermore, the mold apparatus to which the present invention is applied only needs to have the following configuration, and various embodiments can be adopted. In other words, the mold apparatus according to this embodiment is a mold apparatus comprising a blow molding mechanism 1, wherein when blow molding is performed on an intermediate molded product 200 formed in the shape of a bottomed cylindrical object having an opening 205, a stretching rod 16 is inserted into the interior of the intermediate molded product 200 through the opening 205 and stretches the intermediate molded product 200, and the stretching rod 16 has a columnar main body portion 161 that stretches inside the intermediate molded product 200 and a tip portion having a contact portion 162 formed at the tip of the main body portion 161 that contacts the inner wall 206 of the intermediate molded product 200, and the diameter b of the contact portion 162 of the stretching rod 16 is larger than the diameter a of the main body portion 161 of the stretching rod 16.

[0040] <Other> Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above. Furthermore, the effects of the present invention are not limited to those described in the embodiments described above. For example, the stretching mechanism 11, the first split mold 12, the second split mold 13, the first bottom mold 14, and the second bottom mold 15 that constitute the blow molding mechanism 1 shown in Figures 1 and 2 are merely illustrative examples for achieving the objectives of the present invention and are not particularly limited. Similarly, the configuration of the stretching rod 16 shown in Figure 3 is also merely illustrative examples for achieving the objectives of the present invention and is not particularly limited.

[0041] Furthermore, although the final molded product is a bottle container in the above-described embodiment, the final molded product does not have to be a bottle container. It can be anything that can be molded by injection blow molding.

[0042] Furthermore, the final molded product does not necessarily have to be a product molded by injection blow molding. It is sufficient for the molding of the intermediate molded product and the molding of the final molded product to be carried out using different molds. For example, the final molded product may be a product molded by so-called two-color molding, in which different resins or materials are combined and integrated. Alternatively, for example, the final molded product may be a product molded by so-called insert molding, in which metal inserts such as screws or terminals are placed in a mold beforehand, and molten resin is injected around them to form a single integrated product.

[0043] Furthermore, the injection blow molding described above may be performed using the hot parison method, in which the intermediate molded product is blow-molded while maintaining the preheating from injection molding. Alternatively, it may be performed using the cold parison method, in which the intermediate molded product is cooled once, then reheated, and blow-molded. [Explanation of symbols]

[0044] 1... Blow molding mechanism, 11... Stretching mechanism, 12... First split mold, 13... Second split mold, 14... First bottom mold, 15... Second bottom mold, 16... Stretch rod, 200... Intermediate molded product, 206... Inner wall, 112... Output, 111... Long axis tube, 1 61...Body part, 162...Contact part, 205...Opening part, 300...Final molded product, 201...Fringe part, 202...Mouth part, 203,303...Body part, 204,304...Bottom part, 331...Neck part, 332...Shoulder part, 333...Body part

Claims

1. When blow molding is performed on an intermediate molded product that is formed in the shape of a bottomed cylinder with an opening, a stretching rod is inserted into the interior of the intermediate molded product through the opening and stretches the intermediate molded product. The stretching rod has a columnar main body that stretches inside the intermediate molded product, and a tip portion formed at the tip of the main body that has a contact portion that contacts the inner wall of the intermediate molded product. The diameter of the contact portion is larger than the diameter of the main body portion. Blow molding mechanism.

2. The contact portion is characterized in that it is detachable from the main body portion. The blow molding mechanism according to claim 1.

3. The main body portion does not come into contact with the inner wall of the stretched intermediate molded product. The blow molding mechanism according to claim 1.

4. The difference between the diameter of the contact portion and the diameter of the main body portion is greater than the difference between the inner diameter of the stretched intermediate molded product and the diameter of the main body portion divided by two. The blow molding mechanism according to claim 3.

5. Equipped with a blow molding mechanism, The aforementioned blow molding mechanism, When blow molding is performed on an intermediate molded product that is formed in the shape of a bottomed cylinder with an opening, a stretching rod is inserted into the interior of the intermediate molded product through the opening and stretches the intermediate molded product. The stretching rod has a columnar main body that stretches inside the intermediate molded product, and a tip portion formed at the tip of the main body that has a contact portion that contacts the inner wall of the intermediate molded product. The diameter of the contact portion is larger than the diameter of the main body portion. Mold equipment.

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