JP5453896B2 - Stretch blow molding method and apparatus - Google Patents

Description

  The present invention relates to a stretch blow molding method and an apparatus thereof, which can be molded while preventing misalignment during stretching of a bottomed cylindrical preform.

  Conventionally, the general production of bottle-shaped containers is the injection molding of bottomed cylindrical preforms using polyester resins such as polyethylene terephthalate, etc., and heating the resulting preforms in the longitudinal direction with a heated rod. And a biaxial stretch blow molding method in which high-pressure air is blown and stretched in the circumferential direction.

  In stretch blow molding such as a bottle-like container for beverages, misalignment may occur when the preform is stretched with a stretch rod, which causes the stretched state to be uneven and uneven thickness distribution. Occur.

  Therefore, various methods for preventing misalignment during stretching by the stretching rod have been proposed. For example, Patent Documents 1 and 2 provide a receiving rod at a position facing the stretching rod, and the bottom of the preform is stretched by the stretching rod. In a state where the receiving rod is sandwiched between the receiving rod and the receiving rod, a method of performing stretch blow molding with the extending rod while controlling the retreat of the receiving rod through a slide mechanism has been proposed.

  Patent Document 3 discloses a method in which a control core is provided at the center of the bottom mold, is raised to the bottom of the preform, is stretched halfway with a stretching rod, and is then molded only by blow air while being supported by the control core. Proposed.

Japanese Patent Laid-Open No. 05-024099 Japanese Patent Laid-Open No. 10-071641 JP 2002-067131 A

  However, in any of the blow molding methods, a receiving rod that supports the bottom of the preform is provided in the molding bottom mold and controlled to move in synchronization with longitudinal stretching by the stretching rod to prevent misalignment due to stretching. However, there is a problem that the structure of the mold becomes complicated and a large-scale facility for control is required.

  Further, if it is to be applied to an existing stretch blow molding apparatus, there is a problem that a large-scale modification is required and a considerable cost is required.

  The present invention has been made in view of the above-described problems of the prior art, and can be applied to existing facilities without requiring a large-scale modification with a simple structure. It is an object of the present invention to provide a stretch blow molding method and apparatus effective for misalignment.

In order to solve the above-mentioned problem, the stretch blow molding method according to claim 1 of the present invention is directed to longitudinally stretch a bottomed tubular preform with a stretch rod and bias it in the direction opposite to the longitudinal stretch direction in which the preform is kept waiting. In the stretch blow molding method, the bottom center portion of the preform is sandwiched between the presser rod and the stretching rod so as to be longitudinally stretched, and the preform has a different layer configuration at the intermediate portion, and the layer configuration However, it is characterized in that the clamping of the preform by the presser rod is started from a position in the vicinity of where longitudinal stretching of the different parts is started .

  Further, the stretch blow molding method according to claim 2 of the present invention, in addition to the structure according to claim 1, causes the presser rod to protrude from the bottom mold for molding and waits for the presser rod in the middle of the longitudinal stretching. The position is a protruding position shorter than the retreat stroke of the molding bottom mold.

Moreover, the stretch blow molding apparatus according to claim 3 of the present invention projects a bottomed cylindrical preform in the middle of a longitudinal stretching position by a stretching rod that stretches in the longitudinal direction and sandwiches the pressure with the stretching rod. A stretch blow molding apparatus in which a press rod urged in a direction opposite to a direction is provided in a preform mold for molding the preform , wherein the presser after completion of molding by clamping pressure between the stretch rod and the press rod A delay mechanism for delaying the return due to the urging of the rod is provided .

Furthermore, the stretch blow molding apparatus according to claim 4 of the present invention has a structure in which the presser rod is always urged by a spring or a pressurized fluid without being controlled from the outside in addition to the structure of claim 3. It is characterized by.

According to a fifth aspect of the present invention, in addition to the structure according to the third or fourth aspect , the length of the presser rod in the middle of the longitudinal stretching is shorter than the retreat stroke of the bottom mold for molding. It is characterized by being configured as a position.

According to the stretch blow molding method of claim 1 of the present invention, a press rod that is vertically stretched with a stretched rod with a bottomed cylindrical preform, and is biased in a direction opposite to the longitudinal stretch direction that is waiting in the middle thereof; A stretch blow molding method in which the bottom center portion of the preform is sandwiched between the stretching rod and the longitudinal stretch, and the preform has a layer configuration that is different in the middle portion and a portion having a different layer configuration. Since the holding pressure of the preform by the presser rod is started from a position in the vicinity of the start of longitudinal stretching, the center of the bottom of the preform is pressed by a presser rod biased by a spring in a standby state in the middle of longitudinal stretching. By longitudinally stretching the part with a stretching rod, it is not necessary to control the operation of the presser rod, and it is possible to prevent misalignment with a simple structure and shorten the overall length, so it can be applied to existing equipment. It can be carried out easily.
Furthermore, since the preform has a different layer configuration at the intermediate portion, and the press of the press rod of the preform is started from the position near the beginning of the longitudinal stretching of the portion having the different layer configuration, Even when the preforms with different layer configurations are stretched longitudinally in the middle part, misalignment is effectively prevented by starting the pinching with the presser rod from the vicinity where the longitudinal stretching of the parts with different layer configurations where misalignment is likely to occur. A molded product can be obtained.

  According to the stretch blow molding method of claim 2 of the present invention, the presser rod is protruded from the bottom mold for molding, and the standby position of the presser rod in the middle of the longitudinal stretching is set to the bottom for molding. Since the projecting position is shorter than the retreat stroke of the mold, even when the molding bottom mold is retracted and the molded product is taken out, the presser rod does not get in the way and can be taken out smoothly.

Further, according to the stretch blow molding device of claim 3 of the present invention, while projecting in the middle of the longitudinal stretching position by the stretching rod that stretches the bottomed cylindrical preform in the longitudinal direction, and pinching with the stretching rod, A stretch blow molding apparatus in which a press rod urged in a direction opposite to a longitudinal stretch direction is provided in a preform mold for molding the preform, and after the molding is completed by clamping pressure between the stretch rod and the press rod Since a delay mechanism for delaying the return due to the pressing of the presser rod is provided, the presser rod biased by a spring or the like that is waiting in the middle of the vertical stretching and the stretching rod are stretched vertically with the bottom center portion of the preform interposed therebetween. Therefore, it is not necessary to control the operation of the presser rod, it can prevent misalignment with a simple structure, and the overall length can be shortened, so it can be easily applied to existing equipment simply by installing it in the bottom mold for molding. Rukoto can.
Further, since a delay mechanism is provided for delaying the return by the biasing of the presser rod after the molding is completed by the clamping pressure between the stretching rod and the presser rod, even if the presser rod is biased forward after the molding is completed. A large force is not applied to the molded product, and the molded product can be easily taken out without damaging the molded product.

Furthermore, according to the stretch blow molding apparatus of claim 4 of the present invention, the presser rod is constantly biased by a spring or a pressurized fluid without being controlled from the outside, thereby preventing misalignment. Therefore, it is possible to easily secure the necessary urging force, simplify the structure, and easily apply to existing facilities.

According to the stretch blow molding apparatus of claim 5 of the present invention, the intermediate position of the presser rod in the longitudinal direction is configured as a position having a protrusion amount shorter than the retreat stroke of the molding bottom mold. When the mold is taken out, it is possible to prevent the press rod and the molded product from interfering with each other by simply retracting the molding bottom mold, and the mold can be taken out easily.

It is the schematic sectional drawing concerning one Embodiment of the stretch blow molding apparatus of this invention, and explanatory drawing of the biasing means part. It is explanatory drawing of the biasing means part concerning other one Embodiment of the stretch blow molding apparatus of this invention. According to still another embodiment of the stretch blow molding apparatus of the present invention, (a) and (b) are explanatory views of a pressurized air type urging means, respectively. It is explanatory drawing of an example of the shaping | molding object with the stretch blow molding method of this invention, and its apparatus. It is process explanatory drawing of the first half concerning one Embodiment of the stretch blow molding method of this invention. It is process drawing of the latter half concerning one Embodiment of the stretch blow molding method of this invention. It is a graph which shows the experimental result of the effective range with respect to the stroke of the extending | stretching rod by a press rod concerning one Embodiment of the extending | stretching blow molding method of this invention, and its apparatus.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
First, an embodiment of the stretch blow molding apparatus of the present invention will be described with reference to FIG.
In this stretch blow molding apparatus 10, in addition to the mechanism as a normal biaxial stretch blow molding apparatus, a presser rod 12 is provided in a molding bottom mold 11 and slides from the bottom of the molding bottom mold 11 into the mold. The tip of the presser rod 12 is projected so as to be located in the middle of the longitudinal stretching. The presser rod 12 is always provided with an urging means 13 and is urged in a direction opposite to the longitudinally extending direction (upward in the illustrated example) in the mold without being controlled from the outside. It is.

  In this stretch blow molding apparatus 10, a cylindrical holder 15 closed by upper and lower end plates 15 a and 15 b is attached below the bottom mold 11 for molding, and a presser rod 12 is attached to the holder 15. It is supported by the guide and slidable. A spring 14 is mounted between the lower end plate 15b of the holder 15 and the base end side step portion 12a of the presser rod 12, and is constantly biased, and the front end side step portion 12b of the presser rod 12 is moved to the upper end plate 15a. The protruding position is regulated by the contact.

  In such a constant biasing means 13 by the presser rod 12 and the spring 14, when the presser rod 12 is pushed in, the biasing force increases according to the stroke as shown in FIG. For example, as shown in FIG. 2, a second step 12 c is provided in addition to the base end side step portion 12 a of the presser rod 12, and the spring 14 a is applied to the presser rod 12 from the middle of the stroke in addition to the spring 14. By doing so, the constant urging force according to the stroke can be changed in two stages.

  As the urging means 13 for the presser rod 12, as shown in FIGS. 3A and 3B, an air cylinder 16 is provided and the piston rod 16a is connected to the presser rod (or the piston rod 16a The air tank 17a, the pipe 17b, and the safety valve 17c are connected to the base end side cylinder chamber 16b as the air supply means 17 and are in a sealed state. The air tank 17a can be supplied with pressurized air via a regulator 17d. Normally, the air supply means 17 is in a sealed state so that the piston can be operated without external control. The rod 16a is biased.

  When longitudinal stretching is performed while the preform bottom is clamped by the stretching rod and presser rod, the base end side cylinder chamber is compressed, and when the pressure increases from the initial pressurized state to a predetermined pressure, the safety valve opens. The presser rod is urged at a predetermined pressure until is closed.

  The biasing force applied to the presser rod by a spring or pressurized air is effective to apply as much clamping force as possible without causing any trouble in stretch blow molding of the bottom of the preform. For example, the position where the presser rod is pushed in by 10 mm By setting the repulsive force of the spring at 15 to 45 N, misalignment can be effectively prevented.

  Further, the air supply means 16 protrudes when the molding bottom mold 11 is retracted to open the mold after completion of the stretch blow molding, and the piston rod 16a protrudes with a constantly urging force of air. As a delay mechanism 18 for delaying the operation, a throttle valve 18a is provided in the distal end side cylinder chamber 16c so that the exhaust can be performed through the muffler 18b, or air having the same pressure as the proximal end side cylinder chamber 16b is supplied to the distal end side cylinder chamber 16c. By providing the pipe 18c, the protrusion of the piston rod 16a may be delayed so that only the urging force of the integral of the cross section of the piston rod 16a is generated.

  By providing these delay mechanisms 18, the presser rod 12 can be taken out of the way when taking out the molded product. In addition, the external force applied to the molded product during the mold opening is reduced, and scratches can be prevented.

  In such a stretch blow molding apparatus 10, the presser rod 12 is not subjected to longitudinal stretching by sandwiching the bottom center portion of the preform between the stretch rod and the presser rod 12 from the start of the longitudinal stretch of stretch blow molding. As shown in FIG. 6, the holding rod 12 is kept in the middle of longitudinal stretching as shown in FIG. 6, and then the stretching rod 21 and the retaining rod 12 inserted into the preform 20 set in the molding body mold 19. Thus, longitudinal stretching is performed so as to sandwich the bottom center portion of the preform 20.

  The stroke S of the presser rod 12, that is, the protruding amount of the presser rod 12 from the molding bottom mold 11 is preferably smaller than the retreating stroke S1 for taking out the molded product 22 of the molding bottom mold 11 ( In this way, the tip of the presser rod 12 can be prevented from interfering with the molded product 22 when the molded product 22 is taken out.

  The following test was conducted on the effective range of the presser rod in the case where such a presser rod is provided, and the result is shown in FIG. In this test, in order to form a bottle for carbonated beverages having an internal volume of 500 mL using the multilayer preform shown in FIG. 4, the press rod of the present application was applied to the bottom mold of a conventional stretch blow molding device, Effective range of presser rod (presser rod stroke S / stretch rod stroke S2) is 0%, 27%, 32%, 36%. Each of the conditions was changed to 45%, and 30 pieces were molded for each condition. As a result, it was judged that the trace of the drawn rod was completely out of the center of the bottom of the bottle.

  Note that the stroke S of the presser rod corresponds to the protruding amount of the presser rod 12, and the stroke S2 of the stretcher rod 21 is a position at which vertical stretching is completed from the position in contact with the inside of the bottom of the preform 20 (molding bottom mold). It corresponds to the distance to the surface.

  From this test, by setting the effective range of the presser rod S / S2 to a range of 20 to 60%, there is an effect of preventing misalignment when the preform 20 is stretched longitudinally. In particular, the effective range of the presser rod S / S2 By setting the ratio to 27% or more, the defective rate of the molded product can be made less than 20%. More preferably, by setting S / S2 to be 32% or higher, the defective rate of the molded product is set to 0%. be able to.

Further, as a preform 20, as shown in FIG. 4, in the case of stretch blow molding what layer structure in the axial direction intermediate portion has a different multi-layer structure, the opening side 20a of the preform 20 is longitudinally stretched, The bottom center portion of the preform 20 from the vicinity where the longitudinal stretching of the bottom side 20b of the preform 20 having a different layer structure is started (before or after the start of the longitudinal stretching of the bottom side 20b of the preform 20). Misalignment can be effectively prevented by holding the stretching rod 21 and the presser rod 12 that is waiting to continue the longitudinal stretching.

Next, the stretch blow molding method and the operation of the stretch blow molding apparatus 10 configured as described above will be described with reference to FIGS. In FIGS. 5 and 6, the layer structure of the preform of the multi-layer structure is shown only by a solid line different boundaries.

The object to be molded by this stretch blow molding method is a thin-walled bottle-shaped container, and as shown in FIG. 4 in advance, the layer configuration is different from the middle portion between the opening portion side 20a and the bottom portion side 20b of the preform 20, and the opening portion For example, a gas barrier property is improved by inserting a barrier layer only on the side 20a.

  Such a preform 20 is set in a molding body mold 19 of the stretch blow molding apparatus 10, and a presser rod 12 is set in the molding bottom mold 11, and a tip portion is positioned at a predetermined standby position. (See FIG. 5A).

  Thereafter, the stretching rod 21 is inserted from the opening of the preform 20, and the longitudinal stretching by the stretching rod 21 is started so as to be brought into contact with the inner bottom portion, and blow by pressurized air is blown (FIG. 5 ( b) and (c)).

  Then, when the opening side 20a of the preform 20 is longitudinally stretched and the longitudinal stretching of the bottom side 20b is started, the bottom of the preform 20 is placed at the tip of the presser rod 12 waiting in the middle of the longitudinal stretching. The center portion comes into contact with the extending rod 21 and the presser rod 12, and the urging force by the spring 14 of the urging mechanism 13 is always applied to enter the nipping support state (see FIG. 6A).

  In this way, when the longitudinal stretching is continued in a state where the bottom center portion of the preform 20 is sandwiched and supported by the stretching rod 21 and the presser rod 12, the presser rod 12 is pushed back against the spring 14 and the longitudinal stretching and pressurized air are performed. Blow molding is completed, and a molded product 22 without misalignment can be molded (see FIG. 6B).

  In general, at the same time (or just before or immediately after) the end of the longitudinal stretching, the pressurized air is switched to a higher pressure so that the shape of the mold is transferred more accurately.

  After the stretch blow molding is completed in this way, in order to take out the molded product 22, the mold is opened and the molding bottom mold 11 is retracted, and the protruding amount (stroke S) of the presser rod 12 is set to the molding bottom mold 11. Since it is shorter than the retreat stroke S1, even if the presser rod 12 returns so as to protrude forward by the spring 14, a gap is formed between the molded product 22 and the molded product 22 is not damaged and interferes. Can be taken out without.

  According to such a stretch blow molding method, it is possible to prevent misalignment even in the case of a multilayer bottle-shaped container combining light weight of different bottle-shaped containers and different resins, and to make the distribution of the wall pressure uniform. In addition, the influence of slight variations in the heating temperature of the preform 20 can be avoided.

  Further, in this stretch blow molding apparatus 10, it is only necessary to always install the presser rod 12 together with the biasing means 13 in the molding bottom mold 11, and it can be easily applied to an existing molding apparatus to prevent misalignment. Can do. Further, it is not necessary to control the urging force by the presser rod 12, so that no large-scale equipment is required, and the range of modification to the existing equipment can be minimized.

DESCRIPTION OF SYMBOLS 10 Stretch blow molding apparatus 11 Molding bottom metal mold 12 Holding rod 12a Base end side step part 12b Front end side step part 12c The second base end side step part
13 Constant urging means 14 Spring 14a Added spring 15 End plate 15b Upper end plate 15b Lower end plate 16 Air cylinder 16a Piston rod 16b Base end side cylinder chamber 16c Front end side cylinder chamber 17 Air supply means 17a Air tank 17b Piping 17c Safety valve 17d Regulator 18 Delay mechanism 18a Throttle valve 18b Muffler 18c Pipe 19 Molding body mold 20 Preform 20a Opening side part 20b Bottom side part 21 Stretching rod 22 Molded product S Presser rod stroke S1 Retraction of bottom mold Stroke S2 Stretch rod stroke

Claims (5)

A bottomed cylindrical preform is longitudinally stretched with a stretching rod, and the bottom center portion of the preform is sandwiched between the presser rod biased in the direction opposite to the longitudinal stretching direction that is waiting in the middle and the stretching rod. A stretch blow molding method for longitudinal stretching ,
The preform has a different layer structure at an intermediate portion, and the pressing of the preform by the presser rod is started from a position in the vicinity where longitudinal stretching of a portion having a different layer structure is started. Stretch blow molding method.   The presser rod protrudes from the bottom mold for molding, and the standby position of the presser rod in the middle of the longitudinal stretching is set to a projecting position shorter than the retreat stroke of the bottom mold for molding. The stretch blow molding method according to claim 1. A bottomed cylindrical preform protrudes in the middle of a longitudinal stretching position by a stretching rod that extends in the longitudinal direction and is clamped by the stretching rod, and a presser rod that is biased in a direction opposite to the longitudinal stretching direction is attached to the preform. A stretch blow molding device provided in a molding bottom mold ,
A stretch blow molding apparatus , comprising a delay mechanism for delaying the return due to urging of the presser rod after completion of molding by the clamping pressure between the stretch rod and the presser rod . The stretch blow molding apparatus according to claim 3 , wherein the press rod is constantly biased by a spring or a pressurized fluid without being controlled from the outside. Longitudinal stretching of the middle position, stretch blow molding apparatus according to claim 3 or 4, wherein the configured as a position shorter than retraction stroke of the molding bottom mold projecting amount of the pressing rod.

Images