JPH11170352A - Method for biaxially orienting blow molding and its preform heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the temperature of a preform for biaxially orienting blow molding. SOLUTION: In the preform heating line 1 of a biaxially orienting blow molding machine in which preforms P are mounted in turn at prescribed intervals on the upper surface of a transportation route 12 which can be driven intermittently, heating means 5, 5a a are installed on the side of or round the route 12, and the preforms P are transported intermittently while being heated by radiation heat, in the lower part of the route 12, a unit base 120 in which piping 124 equipped with a heating means 123 for heating compressed air is connected with a blowing nozzle 125 is installed on the upper surface of the route 12 elevatably to make the nozzle 125 movable in the preforms P so that the preforms P can be heated from both inner and outer surfaces.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxial stretch blow molding method and a preform heating apparatus, and more particularly to a method for heating a preform from both inside and outside in a preform heating line. The temperature is adjusted. [0002] In recent years, plastic bottles such as PET bottles, which have become popular, are obtained by blow molding a preform as an intermediate material formed of a molten resin by a biaxial stretching blow method using a mold clamping device. However, in this molding method, prior to the main molding, the preform prepared in the pre-molding step is heated to maintain the temperature at an appropriate molding temperature, and is molded. The heating line supports the preform on a transport path sandwiched between a reflector and a heating furnace such as a heater, rotates the intermittently moving preform, and applies radiant heat to the preform to achieve the optimal temperature for biaxial stretching blow molding. The conveying path is formed by a chain conveyor or the like. The preform is a test tube-shaped resin molded product in which a bottle mouth is formed into an opening. Therefore, the chain conveyor is provided with a chuck for holding the support ring formed at the bottle mouth of the preform or a mandrel for fitting the bottle mouth. [0003] However, according to the conventional heating line, heating or temperature control of the preform is always started by applying radiant heat from the outer surface of the preform. The preform has the disadvantage that it takes a long time to heat and lacks uniform heating properties. Therefore, the length of the heating line becomes large, and the installation space becomes a problem. Further, a heater using electricity has a large capacity, so that power consumption becomes excessive. Therefore, an object of the present invention is to solve these disadvantages. According to a first aspect of the present invention, there is provided a biaxial stretching blow molding method comprising a heating line for transferring a preform to a main molding step while heating or controlling the temperature. In the provided biaxial stretch blow molding method, the preform is heated from both inside and outside by sending heated air into the preform in the heating line, so that the preform has a proper molding temperature. According to the preform heating device in the blow molding machine according to the present invention, a plurality of preforms are sequentially placed at predetermined intervals on the upper surface of a transport path that can be driven intermittently. In a preform heating line of a biaxial stretching blow molding apparatus that rotates the preform and provides heating means on the side or periphery of the conveyance path and heats the preform by radiant heat while intermittently transferring the preform, the lower part of the conveyance path In addition, a unit base fixed by connecting a pressure feeding pipe provided with a heating means for heating the compressed air to the blowing nozzle is provided so as to be able to move up and down on the upper surface of the transport path, and the blowing nozzle can advance and retreat into the preform. By doing
The preform can be heated from both inside and outside. [0007] Therefore, since the preform is heated from both the inside and outside, the heating time is about half that of the conventional case, the heating means can be halved, the space can be saved, and the difference between the inside and outside temperatures can be controlled. An embodiment of the present invention will be described below with reference to the drawings. The biaxial stretch blow molding apparatus of the present invention comprises:
As shown in FIG. 1, four sprockets 1
1 are arranged in a substantially quadrilateral shape, and a chain conveyor 1
2 is endlessly wound around the preform heating line 1, and a chain conveyor 30 is wound around a pair of spaced sprockets 29 on the base 28 endlessly to form a substantially elliptical stretch blow line 2. Formed. Preform supply line 3 in heating line 1
Are connected, and a plurality of heating devices 4 and a heater 5 are provided.
Is installed, and a transfer device 6 is provided for supplying a preform from the heating line 1 to the stretching blow line 2. The stretching blow line 2 is provided with a mold clamping device 7 and a product take-out device 8. In the heating line 1, temperature sensors A and B are provided near the preform supply line 3 and near the transfer device 6, respectively. Is arranged. A carrier 17 (see FIGS. 2 and 3) having a mandrel 18 (see FIGS. 2 and 3) on which the preform P is placed is fitted to the coupling shaft 14 of each chain of the chain conveyors 12 and 30. As shown in FIG. 2, a pair of link plates 12a, 12a having a predetermined length are opposed to each other at a predetermined interval, and both ends of the chain conveyor 12 are rotatable about a connecting shaft 14, as shown in FIG. A pair of link plates 12a, 12a
As shown in FIG. 3, guide rails 15, 15 enter between facing upper and lower link plates 12a, 12a. The guide rails 15, 15 are fixed to the upper surface of a base 16 fixed to at least two orthogonal sides of the base 10, so that the chain conveyor 12 is horizontally supported without bending downward, and the link plates 12a, The reference numeral 12a can slide on the upper and lower surfaces of the distal end portions of the guide rails 15, 15. The chain conveyor 12 is provided with a tension sprocket 11a in pressure contact therewith. As shown in FIGS. 2 and 3, a carrier 17 is rotatably engaged coaxially with the coupling shaft 14 of the chain conveyor 12, and a mandrel 18 for fitting the preform P is crowned on the upper end of the carrier 17. A sprocket 19 is rotatably mounted on the lower end of the base 16 at a lower end thereof. The carrier 17, the mandrel 18 and the sprocket 19 have shaft holes 17a, 18a and 19a, respectively.
Are drilled. The sprocket 19 is engaged with a chain or a timing belt 20 fixed or moved inside the base 16 in the longitudinal direction (the depth direction in the drawing) of the base 16. It is wrapped around the supported pulley 21. The pulleys 21 are installed near both ends of the base 16 having a predetermined length.
One of the chain or the timing belt 20
Can be moved in the moving direction of the heating line 1 or in the opposite direction, and the preform P is rotated. A guide 21a supports the chain or the timing belt 20 in a straight line.
The base 16 is the link plate 1 of the chain conveyor 12
The base 16 is a hollow body in which a concave portion 22 for accommodating 2a, 12a is formed on the upper surface, and a groove 24 for fitting the roller 23 of the carrier 17 is formed substantially in the center of the concave portion 22.
The guide groove or the guide hole 16 corresponding to the groove 24
a has been established. A shaft hole 23 a is formed in the roller 23, and a shaft portion of the carrier 17 is inserted into the shaft hole 23 a. The shaft portion of the carrier 17 extends to a shaft hole 19 a of the roller 19. Further, a bush 25 is interposed in order to improve the rotation between the coupling shaft 14 and the carrier 17 and to prevent the occurrence of backlash (misalignment). Below the chain conveyor 12, a unit base 120 is provided with a piston 122 of a cylinder 121.
And is arranged to be able to move up and down. A piping 124 for feeding compressed air having a heater 123 is fixed to the unit base 120, and a blowing nozzle 125 is connected to the piping 124 for feeding compressed air. This blowing nozzle 12
5 is the guide hole 16a, shaft holes 17a, 18a, 19a
And can be stretched into the preform P. The blowing nozzle 125 is a bottomed cylindrical body made of a porous material, or a metal pipe having a plurality of axial slits formed in the circumferential direction. The heater 123 is advantageous because the electric heat can be easily controlled. The heating device 4 is provided in advance by appropriate means, and the heating heater 5 is a group of heaters vertically installed on the base 10 so as to face the chain conveyor 12, and includes a chain. The preform P, which is conveyed while rotating on the carrier 17 of the conveyor 12, is uniformly heated, and does not need to be described in detail because it is sufficient to use a known one. Next, the operation of the preform heating device will be described. The preform P descends from the chute formed between the guide plates 40 of the preform supply line 3 and is received by the gripping reversing device 43 to be gripped. In the reversing device 43, the mandrel 18 in the carrier of the heating line 1
On the other hand, the chain conveyor 12 is intermittently rotated by a drive source 13 such as a servomotor in the direction indicated by the arrow (a) in FIG. Then, when the preform P is conveyed to the heating line 1, the temperature sensor A measures the temperature and stores it in a computer. The preform P intermittently moves to the area of the heater 5 and stops. Therefore, the unit base 120
Rises and the blowing nozzle 125 enters the preform P from the shaft hole 17a of the carrier 17 and the shaft hole 18a of the fitting mandrel 18 via the guide groove or guide hole 16a of the base 16, and passes through the pressure feeding pipe 124. Blow nozzle 125
Supplies heated compressed air. Preform P
Is rotated by the rotating means. Blow nozzle 125
Since the whole is porous or formed with slits in the axial direction, high-temperature heating air blows out of the holes or slits into the preform P to heat the inner surface evenly. Thereafter, the preform P is transferred while maintaining the heated predetermined temperature, and is supplied to the stretching blow line 2 by the transfer device 6. When the preform P is conveyed to the transfer device 6, the temperature sensor B measures the temperature, compares the measured temperatures of the temperature sensors A and B, and sets the temperature to a temperature required for forming in the stretch blow line 2. For this purpose, a command necessary for driving the heating device 4 and the heater 5 in accordance with the difference is automatically given. In the stretch blow line 2, the preform P is transferred from the transfer device 6 to the chain conveyor 30 which is intermittently driven in the direction shown by the arrow (b) in FIG. Supported mold 70,
70 are pinched so as to match each other, and as shown in FIGS.
The axial stretching device 90 and the bottom mold elevating device 110 are connected to the molds 70 and 70.
The stretch rod 95 stretches the preform P at the time of blowing, and high-pressure air is blown into the preform P to form a product along the cavity 70a. The driving speed of the stretch rod 95 at this time is controlled, and the position, speed, and time of the stretch rod 95 can be arbitrarily set on the setting screen of the molding apparatus. When the stretch rod 95 is drawn into the head portion 91 and the stretch blowing is completed, the molds 70 and 70 are separated from each other, and the pair of molded products are separated from the mold clamping device 7 by the intermittent movement of the chain conveyor 30, and the product take-out device. 8 is held by the chuck 130 rotating with the shaft 131, removed from the stretch blow line 2, and transferred to the product outlet. According to the present invention described above, since the preform is heated from both the inside and outside in the heating line, the time required to raise the temperature to an appropriate temperature for the main molding can be reduced by half. Therefore, the number of heaters can be reduced by half, and the installation space can be reduced. In addition, since it is desirable that the inner surface temperature of the preform is higher than the outer surface temperature of the preform, such a state can be easily controlled and formed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall plan view showing an embodiment of the present invention. FIG. 2 is a cross-sectional side view of a main part of a heating line. FIG. FIG. 5 is a front view of the stretching apparatus. [Description of reference numerals] P: Preform 1: Heating line 2: Stretching blow line 3: Preform supply line 4 ... Heating mold 5 ... Electric heater 5a ... Reflector 6 ... Transfer device 7 ... Molding device 8 ... Product take-out device 12,30 ... Chain conveyor 14 ... Coupling shaft 16 ... Base 16a ... Guide hole (groove) 17 ... Carrier 18 fitting mandrel 19 sprocket 23 rollers 17a, 18a, 19a, 23a shaft hole 120 unit base 121 cylinder 122 piston 123 heater 124 supply pipe 125 blowing nozzle

Claims (1)

Claims: 1. A biaxial stretch blow molding method having a heating line for transferring a preform to a main molding step while heating or adjusting a temperature of the preform. A biaxial stretching blow molding method characterized in that the preform is maintained at an appropriate molding temperature by heating from both inside and outside by feeding heated air. 2. A method according to claim 1, wherein a plurality of preforms are sequentially placed at predetermined intervals on an upper surface of the transport path that can be intermittently driven, and a heating unit is provided on a side portion or around the transport path while rotating the preform. In a preform heating line of a biaxial stretching blow molding apparatus that intermittently transports a preform while heating it with radiant heat, a pressure feeding pipe having a heating means for heating compressed air to a blowing nozzle is connected to a lower portion of the transport path. A fixed unit base is provided so as to be able to move up and down on the upper surface of the transport path so that the blowing nozzle can advance and retreat into the preform, so that the preform can be heated from both inside and outside surfaces. A preform heating device in a biaxial stretch blow molding device. 3. The preform heating apparatus in a biaxial stretching blow molding apparatus according to claim 2, wherein said blow nozzle is formed of a bottomed cylindrical body having a predetermined length from a porous material. 5. The preform heating apparatus according to claim 2, wherein said blowing nozzle is formed of a bottomed cylindrical body having a predetermined length and having an axial slit formed in a peripheral wall portion. apparatus.