JP4864573B2 - Preform heating method, preform carrier, and biaxial stretch blow molding method - Google Patents

Description

  The present invention relates to a preform heating method for heating a preform (blow molding precursor) manufactured by an injection molding method to a temperature suitable for blow molding, a preform carrier used in the heating method, and the heating method. The present invention relates to a biaxial stretch blow molding method to be used.

For plastic bottles such as PET bottles, the bottomed cylindrical preform produced in advance by the injection molding method is reheated to a temperature suitable for blow molding such as biaxial stretch blow molding, and then blow molded It is manufactured by applying. For example, in the biaxial stretch blow molding method, a preform is supported on a preform carrier in an inverted state, and the preform carrier is conveyed along a conveyance path in which heating elements such as a far infrared heater are arranged. The reform is heated to a temperature suitable for biaxial stretch blow. The preform after heating is fed together with the preform carrier into a blow mold for biaxial stretch blow molding, and after the blow mold is clamped, the stretch rod is pushed up from below through the center hole of the preform carrier and heated. The preform is stretched, and at the same time, the preform is biaxially stretched and blown into the preform by sending compressed air for blow molding, and the molded product is shaped along the inner peripheral surface of the blow mold cavity. Like to get. A biaxial stretch blow molding machine is disclosed in Patent Document 1 below. Further, Patent Document 2 discloses a mechanism for heating while conveying a preform in an inverted state.
WO98 / 003324 brochure JP 2005-28806 A

  Here, when the preform is heated to a temperature suitable for blow molding, the preform is softened. Conventionally, since the thickness of the preform is large, the preform that is fed into the blow mold in an inverted state does not cause thermal deformation that adversely affects blow molding. In other words, before blow molding, an inverted preform that has been softened by heating is deformed into a laterally tilted state, or contracts in the axial direction thereof, resulting in an adverse effect that blow molding cannot be performed properly. Not.

  However, recently, in order to reduce the weight of PET bottles or the like, it is required to reduce the thickness. In order to satisfy this requirement, it is necessary to blow-mold a thin preform. For example, when the thickness of a PET resin preform is reduced, if the preform is heated to a temperature suitable for blow molding, the preform may not be able to withstand its own weight and may lie down. If blow molding is carried out with side-to-side deformation, blow molding is not performed with high accuracy, and there is a high possibility that a defective molded product will be obtained.

  Further, if the preform made of PP resin or PE resin is thinned, the preform is greatly contracted in the axial direction when heated, and the preform is largely deformed as a whole, and blow molding cannot be performed properly. Probability is high.

  In view of such a new problem, an object of the present invention is to perform a preform heating method and a heating method that can prevent or suppress the preform from lying down or shrinking in the axial direction during heating before blow molding. And a biaxial stretch blow molding method using the heating method.

In order to solve the above-described problems, the present invention provides a preform for heating a resin preform having a bottomed cylindrical body and a mouth so that the temperature is suitable for blow molding. In the heating method: the preform is heated in a state where its mouth is faced down, and at the latest, at a time before the completion of heating of the preform, a predetermined length from the mouth of the preform into the body portion thereof. A support rod is inserted, and the support rod prevents or suppresses a lateral fall due to thermal deformation in the body portion of the preform and / or heat shrinkage in the axial direction of the body portion. In addition to this, in the preform heating method of the present invention, in order to prevent excessive stress from acting on the preform by the support rod, a predetermined distance from the preform side is applied to the tip of the support rod. When the above pressing force is applied, the support rod is contracted along the axial direction or moved in a direction to be pushed out from the mouth of the preform.

  Here, at the time before the heating of the preform is started, the support bar may be inserted into the body portion from the mouth portion of the preform.

  Further, in order to prevent the preform from being adversely affected by inserting the support rod, the support rod is heated to a predetermined temperature before being inserted into the preform. It is desirable.

  Furthermore, it is preferable to heat the support rod inserted into the preform and heat the preform from the inside because the preform can be uniformly heated as a whole.

  Next, in order to prevent the preform from falling down and contracting in the axial direction, the support bar is placed in the body of the preform until the tip of the support bar does not hit the bottom of the body of the preform. It is desirable to insert.

  Further, in order to prevent the preform from deforming and coming into contact with the surface of the support rod and sticking to the surface, the support rod is subjected to a surface treatment, and the preform resin is applied to the surface of the support rod. It is desirable to make it difficult to stick or to improve the sliding property of the preform with respect to the resin. For example, as the surface treatment, the surface of the support bar may be a rough surface such as a satin surface in order to reduce the contact area with the preform. Alternatively, the contact area may be reduced by forming fine slits and protrusions vertically and horizontally.

  Furthermore, when the preform is biaxially stretch blow molded, the stretch rod used during the biaxial stretch blow molding can also be used as the support rod.

  Next, in order to prevent deformation of the preform, it is desirable to keep the inside of the preform in a pressurized state when the preform is heated.

  Here, in the present invention, the preform is heated while being conveyed in an inverted state by a preform carrier provided with an insertion nozzle that can be inserted into the mouth of the preform, and the nozzle hole of the insertion nozzle The support rod can be inserted into the body of the preform from the lower side.

  The preform carrier of the present invention used in this case is characterized by having a carrier body provided with the insertion nozzle and the support bar attached to the carrier body.

  Here, the support rod can be attached to the carrier main body in a state where it can be expanded or contracted or moved in the axial direction thereof, and can be always urged in an extending direction or a direction to be pushed into the preform by an elastic member.

  Next, the present invention provides a biaxial stretching process including a heating step for bringing a preform into a temperature state suitable for biaxial stretching blow molding, and a blow step for obtaining a molded product by biaxial stretching blow of the preform after heating. In the blow molding method, in the heating step, the preform is heated by the preform heating method described above.

  In the present invention, when the preform is heated, a support bar is inserted into the preform. Therefore, when the preform is thin and transported while being heated in an inverted state, the preform is prevented from falling into a sideways state due to its own weight, and is prevented from being thermally contracted in the axial direction. . As a result, it is avoided that defective molding occurs due to thermal deformation in blow molding, which is the next step.

  Moreover, in this invention, since the preform is heated from the inside using the inserted support rod, the preform can be heated uniformly as a whole.

  Furthermore, in the present invention, since the internal pressure of the preform is increased when the preform is heated, deformation of the preform due to heat can be prevented.

  Below, with reference to drawings, the example of the biaxial stretch blow molding machine of the PET bottle to which this invention is applied is demonstrated.

  FIG. 1 is a schematic diagram showing the overall configuration of a biaxial stretch blow molding machine. 2 to 4 are a side configuration diagram, a plan configuration diagram, and a sectional configuration diagram of a biaxial stretch blow molding unit, respectively, of the biaxial stretch blow molding machine.

  Referring to FIGS. 1 to 4, the biaxial stretch blow molding machine 1 includes a preform supply unit 2 for supplying a preform 10, a preform heating unit 3, and a preform 10 after heating. A biaxial stretch blow molding unit 4 that performs stretch blow molding, a collection unit 5 that collects a molded product 20, a closed transport path 6 that sequentially passes through these parts, and a transport path 6 along the transport path 6. A plurality of preform carriers 7.

  The conveyance path 6 has a rectangular closed shape as shown by a thick line in FIG. 3, and the conveyance direction of the preform carrier 7 is indicated by an arrow. The conveyance path 6 includes a first conveyance path portion 62 (from point A in FIG. 3) that conveys the preform carrier 7 carrying the preform 10 via the preform heating unit 3 and the biaxial stretch blow molding unit 4. B) and a second conveyance path portion 64 (Fig. 2) for conveying the preform carrier 7 after the molded product 20 is collected to the preform supply unit 2 through the lower side of the biaxially stretched molding unit 4. 1 and a path from point C to point D in FIG. As can be seen from FIGS. 1 and 4, the second conveyance path portion 64 is configured to pass through a position below the blow mold clamping mechanism 41 of the biaxially stretched blow-molded portion 4.

  Each conveyance path part 62 and 64 is a horizontal conveyance path. Therefore, the transport path part on the preform supply side of these transport path parts is the ascending path part 61 (FIGS. 1 and 3) from the lower second transport path part 64 to the upper first transport path part 62. Path from point D to point A in FIG. Conversely, the conveyance path portion on the molded product collection side is a descent path portion 63 (from point B in FIGS. 1 and 3) from the upper first conveyance path portion 62 to the lower second conveyance path portion 64. Route to C).

  5 (a) and 5 (b) are a perspective view and a cross-sectional view showing the preform carrier. As shown in these drawings, the preform carrier 7 has a rectangular main body 71, a rotating shaft 72 that passes through the main body 71 in a vertically rotatable manner, and a coaxial state on the upper end surface of the rotating shaft 72. The cylindrical preform insertion nozzle 73 is formed, and external teeth 74 are formed on the protruding portion on the lower end side of the rotating shaft 72. A through hole 75 is formed at the center of the rotating shaft 72 and the preform insertion nozzle 73. A blow air blow-in core can be inserted below the through-hole 75 as will be described later. Further, the extending rod can be inserted into the upper preform 10 through the through hole 75.

  Here, in the through hole 75 of the preform carrier 7, an elongated cylindrical support rod 76 having a small outer diameter is arranged in a coaxial state. The support rod 76 protrudes upward from the preform insertion nozzle 73 by a predetermined length. In this example, in a state where the mouth portion of the preform 10 is inserted into the preform insertion nozzle 73, the length reaches a position near the bottom inner peripheral surface. A large-diameter flange 76 a for receiving a spring is formed at the lower end portion of the support rod 76 located inside the through hole 75. An annular flange 78 protruding inward is formed as a spring receiver at a lower end side portion of the inner peripheral surface portion of the through hole 75. A coil spring 79 is mounted between the large diameter flange 76a and the flange 78. The lower end 76 b of the support rod 76 protrudes downward from the lower end opening 75 a of the through hole 75.

  The preform 10 includes an elongated cylindrical body portion 10a having a bottomed cylindrical shape and a cylindrical mouth portion 10b formed at an end on the opening side. A mouth flange 10c is formed on the outer peripheral surface portion between the mouth portion 10b and the body portion 10a, and a male screw is formed on the outer peripheral surface portion of the mouth portion 10b. The mouth portion 10b remains as the mouth portion of the molded product 20 without being biaxially stretch blow molded, and only the body portion 10a is biaxially stretch blow molded.

  The preform 10 having this shape is supplied to the preform carrier 7 that reaches the point D from the preform supply unit 2 side. The preform 10 waiting with the mouth portion 10 b facing upward is gripped by the turning gripper 22 that can turn around the axis 21. Next, when the gripper 22 turns 180 degrees around the axis line 21, the opening of the mouth portion 10b of the gripped preform 10 faces downward, and is just above the preform carrier 7 waiting at the point D. Positioned.

  In this state, the preform carrier 7 is raised in the Z-axis direction by the biaxial transport mechanism 61A. As a result, the support rod 76 is inserted into the preform 10 from the mouth portion 10b, and then the insertion core 73 is inserted into the mouth portion 10b. As shown by the imaginary line in FIG. 5B, the support rod 76 is inserted into the preform 10 in a substantially coaxial state, and its tip surface 76b is slightly spaced from the inner peripheral surface of the bottom 10d of the preform 10. Become confronted.

  After the preform 10 is carried on the preform carrier 7 in this way, after the gripper 22 is released, the preform carrier 7 moves in the Y-axis direction by the biaxial transport mechanism 61A. A is reached. The preform carrier 7 arriving at the point A is pushed horizontally in the X-axis direction by the push rod 61B, and delivered to the first conveyance path portion 62 from the biaxial conveyance mechanism 61A.

  The first transport path portion 62 includes a pair of rails 62a and 62b on which the rectangular main body 71 of the preform carrier slides. The preform carrier 7 riding on these rails moves along the conveyance path portion 62 each time the preform carrier 7 is pushed out one by one by the push rod 61B. That is, in this transport path portion 62, the feed pitch is defined by the length of the preform carrier 7 in the transport direction, and the preform carriers 7 arranged in a line for each feed pitch are transported intermittently as a whole. It will be.

  Next, in the heating unit 3, heaters for heating the preform are arranged on one side along the conveyance path 62. The heating unit 3 is conveyed while being rotated by a rotating mechanism 62A including a preform 10, a driving pulley, a driven pulley, and a timing belt spanned between them. That is, when the timing belt meshes with the gear 74 of the preform carrier 7 and rotates the gear 74, the rotating shaft 72 to which the gear 74 is integrally attached rotates, and the insertion core 73 on the upper end surface thereof is rotated. The preform 10 inserted in is rotated.

  Next, the preform 10 heated while rotating in the heating unit 3 is cooled for a certain period after passing through the heating unit 3, and is brought into a temperature state suitable for molding. Thereafter, it is carried into the biaxial stretch blow molding section 4.

  The preform carrier 7 of this example is provided with a support rod 76, and the preform 10 is heated in a state where the support rod 76 is inserted into the body portion. Therefore, even when the thin preform 10 is heated, it is prevented or suppressed that the preform 10 in the inverted state is deformed to the side-down state by its own weight. Further, in the case of a thin preform made of PP resin, PE resin or the like, thermal shrinkage in the axial direction is prevented or suppressed. For this reason, it is possible to reliably avoid the adverse effect that the deformed preform 10 is fed into the biaxially stretched blow-molded portion 4 and a molding defect occurs.

  The support rod 76 is supported by a coil spring 79, and can move downward when a force greater than the spring force is applied. When the preform 10 hits the front end surface of the support rod 76 due to thermal deformation and the support rod 76 is pushed downward, the deformation of the preform 10 is prevented when the pushing force is small. When the pushing force increases, the support rod 76 is pushed downward and can be deformed. Therefore, the support rod 76 can be pushed down before a large force that adversely affects the preform 10 acts on the preform 10. Note that the support rod 76 may be an expandable structure, and may be held in an extended state by a spring force so that the support rod 76 can be compressed and contracted when a predetermined force or more is applied.

  Next, in this example, a feed mechanism 9 for feeding the preform carrier 7 carrying the heated preform 10 one by one into the biaxial stretch blow molding section 4 is provided. The feeding mechanism 9 is for feeding the preform carrier 7 to the biaxially stretched blow molding unit 4 one by one at a feeding pitch wider than the feeding pitch in the heating unit 3.

  FIG. 6 is an explanatory view showing a feeding mechanism for feeding the preform after heating to the biaxially stretched molded part. The feed mechanism 9 includes a pair of grippers 91 and 92 at intervals of a feed pitch L2 toward the transport direction. These grippers are integrally configured to reciprocate at a feed pitch 2 in the transport direction. The preform carrier 7 that has passed through the heating unit 3 and is conveyed at the feed pitch L1 to the point A1 is gripped by the gripper 92. In this state, the front gripper 91 is located at the molding position A <b> 2 in the biaxially stretched molded portion 4.

  After the biaxial stretch blow molding is completed, the grippers 91 and 92 move at the feed pitch L2 in the transport direction. As a result, as shown by a solid line in FIG. 6, the preform carrier 7 held by the rear gripper 92 reaches the biaxial stretching molding position A2, and the preform carrier 7 carrying the molded product 20 is held. The front gripper 91 that reaches the point B reaches the point B.

  The feed mechanism 9 repeatedly performs such a reciprocating operation, thereby conveying the preform carrier 7 fed at the feed pitch L1 to the biaxial stretch blow molding unit 4 at a feed pitch L2 wider than that.

  2 and 4 again, the biaxially stretched blow molded portion 4 includes a set of molds 42, the mold clamping mechanism 41, and a lower end opening 75 a of the through hole 75 of the preform carrier 7. The structure provided with the blow air blowing inlet core 43 inserted, the extending | stretching rod 44 similarly inserted from the lower end opening 75a of the through-hole 75, and the drive mechanism 45 which inserts these blowing air blowing inlet core 43 and the extending | stretching rod 44. It has become.

  At the time of molding, when the preform 10 is carried into the point A2, the mold clamping mechanism 41 clamps the pair of left and right molding dies 42. Thereafter, the blow air blowing core 43 is raised and connected to the through hole 75 of the preform carrier 7, and blowing of blow air into the preform 10 is started. At the same time, the stretching rod 44 rises and is inserted into the preform 10 through the through hole 75. Biaxial stretching is performed by blowing air and inserting the stretching rod 44.

  Here, FIG. 7 shows a state when the stretching rod 44 is raised. As shown in this figure, when the extending rod 44 is lifted, the tip end surface of the extending rod 44 comes into contact with the lower end surface of the support rod 76 protruding downward from the lower end opening of the through hole 75 of the preform carrier 7. After this, it rises together with the support rod 76. The stretching rod 44 and the support rod 76 function as one stretching rod. In other words, the support rod 76 functions as a stretching rod in the biaxial stretch blow molding section 4.

  As a result, it is not necessary to raise and lower the stretching rod 44 with a large stroke as in the prior art, and it can be raised and lowered with a stroke similar to that of the blow-air blowing inlet core 43, as compared with the case where it is raised and lowered with a large stroke. Thus, the time required for the lifting and lowering can be greatly reduced, and the processing efficiency can be improved.

  Next, the molded product 20 obtained by the biaxial stretch blow molding is conveyed to the point B by the above-described feed mechanism 9. At this point B, the preform carrier 7 is delivered to the biaxial transport mechanism 63A.

  When the preform carrier 7 is delivered to the biaxial transport mechanism 63 </ b> A, the turning gripper 5 </ b> A of the molded product collection unit 5 grips the neck portion of the molded product 20 on the preform carrier 7. In this state, the biaxial transport mechanism 63A lowers the preform carrier 7 (moves in the Z-axis direction). As a result, the support rod 76 and the insertion core 73 on the preform carrier 7 side are pulled out from the mouth portion 12 of the molded product 20. Thereafter, the turning gripper 5A turns to collect the molded product 20. An extraction mechanism for extracting the molded product 20 from the preform carrier 7 side using the lowering by the biaxial conveyance mechanism 63A is configured. Therefore, the molded product 20 can be collected by a simple mechanism.

  The biaxial transport mechanism 63A transports the preform carrier 7 emptied by being lowered toward the start point C of the second transport path portion 64 (transports in the Y-axis direction). When the point C is reached, the preform carrier 7 is pushed out from the biaxial transport mechanism 63A side by the push rod 63B in the X-axis direction, and a pair of left and right transport belts 64a constituting the second transport path portion 64 is reached. , 64b. The preform carrier 7 is conveyed by these conveyance belts toward the preform supply unit 2 through the lower side of the mold clamping mechanism 41 of the biaxially stretched molding unit 4.

  Thereafter, similarly, the preform carrier 7 repeatedly moves on the conveyance path 6 to perform biaxial stretch blow molding of the preform 10.

(Other embodiments)
In this example, it is conveyed with the support rod inserted into the preform from the beginning. The time point at which the support rod is inserted may be a time point before the start of heating the preform as in this example, but may be a time point at which heating is started or a time point during heating. Depending on the case, it may be at the end of heating or after heating.

  In addition, the support bar 76 may be heated to a predetermined temperature before the support bar 76 is inserted into the preform 10. If the inside of the preform 10 is not sufficiently heated by inserting the support rod 76 and there is a possibility that the whole will be in a non-uniform heating state, it is desirable to heat the support rod 76 in advance.

  Further, the support rod 76 may be actively used to heat the preform. That is, if the support rod 76 is heated after the support rod 76 is inserted into the preform, the preform can be heated from the inside. As a result, the preform can be heated uniformly as a whole, which is preferable.

  Next, it is desirable that the support rod is subjected to a surface treatment so that the resin of the preform does not easily stick to the surface of the support rod, or the slipperiness with respect to the resin is improved. For example, the support rod can be formed from a metal rod, and surface treatment such as Teflon (registered trademark) coating can be applied to the surface. Moreover, what is necessary is just to reduce a contact area with a preform by making the surface of a support rod into a satin surface, or forming the vertical and horizontal fine groove | channel.

  Furthermore, in this example, the support rod is used as a stretching rod. Alternatively, the support rod may be formed from a hollow member and penetrated therethrough to push the stretch rod into the preform.

  Next, in this example, the support rod 76 is used to prevent or suppress the deformation of the preform. Alternatively, when the preform is heated, compressed air may be supplied into the preform to increase its internal pressure so that it does not deform. Of course, the support rod may be inserted, and the preform internal pressure may be increased to reliably prevent the deformation of the preform.

  In the above example, the biaxially stretched molded part has a so-called single-piece configuration including a set of molds. Instead of this, for example, it is possible to adopt a two-piece configuration. In this case, instead of the feed mechanism 9, a feed mechanism that transports the preform carriers two by two may be employed. In this case, a mechanism for widening the interval between the two pallets may be added in conjunction with the transport operation.

It is a schematic diagram which shows the whole structure of the biaxial stretch blow molding machine to which this invention is applied. It is a side lineblock diagram of a biaxial stretch blow molding machine to which the present invention is applied. It is a plane block diagram of the biaxial stretch blow molding machine of FIG. It is a cross-sectional block diagram of the biaxial stretch molding part of the biaxial stretch blow molding machine of FIG. It is the perspective view and sectional drawing of the preform carrier in the biaxial stretch blow molding machine of FIG. It is explanatory drawing which shows the feed mechanism for sending the preform after the heating in the biaxial stretch blow molding machine of FIG. 2 to a biaxial stretch blow molding part. It is explanatory drawing which shows a state when pushing a support bar with an extending | stretching rod.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Biaxial stretch molding machine 2 Preform supply part 3 Preform heating part 4 Biaxial stretch molding part 5 Collection | recovery part 6 Carriage path 7 Preform carrier 73 Push core 76 Support rod 76a Flange 79 Coil spring 9 Feed mechanism 10 Preform 10a Body part 10b Mouth part 10d Bottom part 62 First conveyance path part 64 Second conveyance path part 91, 92 Gripper L1, L2 Feed pitch 10 Preform 20

Claims (10)

In a preform heating method for heating a resin preform having a bottomed cylindrical body portion and a mouth portion to a temperature state suitable for blow molding,
Heat the preform with its mouth down,
At the latest, at the time before the completion of heating the preform, a support rod having a predetermined length is inserted into the trunk portion from the mouth of the preform,
The support rod prevents or suppresses the lateral collapse due to thermal deformation in the body portion of the preform and / or the thermal contraction in the axial direction of the body portion,
When a predetermined or more pressing force is applied to the tip of the support rod from the preform side, the support rod is shrunk along its axial direction or pushed out from the mouth of the preform. A preform heating method characterized by moving in a direction. In claim 1,
The preform heating method, wherein the support rod is inserted into the body portion from the mouth portion of the preform at a time before the heating of the preform starts. In claim 1 or 2,
A preform heating method, wherein the support rod is heated to a predetermined temperature before being inserted into the preform. In claim 2,
A preform heating method, wherein the support rod inserted into the preform is heated to heat the preform from the inside. In any one of claims 1 to 4,
The preform heating method, wherein the support rod is inserted into the preform body until the tip of the support rod does not contact the bottom surface of the preform body. In any one of claims 1 to 5,
A preform heating method, wherein the support rod is subjected to a surface treatment so that the resin of the preform does not easily stick to the surface of the support rod, or the slip property with respect to the resin is improved. In any one of claims 1 to 6,
A preform heating method, wherein the preform is maintained in a pressurized state when the preform is heated. In any one of claims 1 to 7,
Heating the preform while conveying the preform in an inverted state by a preform carrier equipped with an insertion nozzle that can be inserted into the mouth of the preform,
A preform heating method, wherein the support rod is inserted into a body portion of the preform from the lower side through a nozzle hole of the insertion nozzle. A preform carrier used for the preform heating method according to claim 1 , wherein the preform is transported in a state where the preform mouth is laid down ,
A carrier body having an insertion nozzle into which the mouth of the preform can be inserted;
Has said support rod attached to the carrier body,
The support bar is coaxially disposed in a through hole formed at the center of the insertion nozzle, and protrudes upward by a predetermined length from the insertion nozzle.
The support bar is attached to the carrier body in a state where it can be expanded and contracted or moved in the axial direction,
The preform carrier is always urged by an elastic member in an extending direction or a direction of being pushed into a preform in which a mouth portion is inserted into the insertion nozzle . A heating step for bringing the preform into a temperature suitable for biaxial stretch blow molding;
In a biaxial stretch blow molding method having a blow step of obtaining a molded product by biaxial stretch blow of a preform after heating,
The biaxial stretch blow molding method characterized in that the heating step heats the preform by the method according to any one of claims 1 to 8.

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