JPH05286022A - Blow-molding method for synthetic resin bottle and shrink device - Google Patents

Abstract

PURPOSE:To make it possible to precisely center a pre-bottle after shrink action and keep the bottom of the pre-bottle smooth. CONSTITUTION:The bottom of a pre-bottle 30 of synthetic resin is held between a receiving rod 17 in the pre-bottle 30 and a pressure rod 38 outside the pre- bottle 30. During a shrink action of the pre-bottle 30, the pressure rod 38 comes down at a speed corresponding to a shrink speed of the pre-bottle 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow molding method for a synthetic resin bottle and a shrink device.

[0002]

2. Description of the Related Art Conventionally, as a method of blow molding a bottle made of synthetic resin such as PET (polyethylene terephthalate), a PET pre-bottle is blow-molded in advance, and then this pre-bottle is shrink-heated and then re-blown. A method of molding is known.

The reason why the pre-bottle is shrunk and then re-blown in this way is that an unstretched portion remains in the pre-bottle at the stage of the pre-bottle, which causes a problem in strength. By shrinking and reblowing the pre-bottle, the unstretched portion of the pre-bottle can be fully stretched to increase strength.

Conventionally, as a shrink device for shrinking a pre-bottle, a device provided with a mouth holding device for holding the mouth of the pre-bottle made of synthetic resin and a receiving rod extending from the mouth holding device into the pre-bottle so that the pre-bottle can freely move back and forth. It has been known. When performing the shrinking work, the pre-bottle held by the mouth holding device is covered with a heating pot from outside and heated. The pre-bottle that shrinks by heating is supported by a receiving rod that extends from the mouth holding device into the pre-bottle, and the shape of the pre-bottle that shrinks is maintained.

[0005]

As described above, the pre-bottle that shrinks by heating is supported by the receiving rod, and the shape in the shrink is maintained.

However, when the pre-bottle is supported only by the receiving rod inside the pre-bottle, slippage may occur between the bottom of the shrinking pre-bottle and the receiving rod, so that the pre-bottle after shrinking may not be surely centered. .. Further, when the pre-bottle is supported only by the receiving rod inside the pre-bottle, if the retracting speed of the receiving rod is slower than the shrink speed of the pre-bottle, traces of the receiving rod may remain at the bottom of the pre-bottle after the shrinking. In this case, a trace of the receiving rod will remain on the bottom of the pre-bottle even if re-blown thereafter.

The present invention has been made in consideration of the above points, and it is possible to surely perform the centering of the pre-bottle after shrinking and to eliminate the trace of the receiving rod at the bottom of the pre-bottle. An object of the present invention is to provide a blow molding method for a bottle and a shrink device.

[0008]

The present invention is a synthetic method in which a pre-bottle made of synthetic resin is blow-molded, then the pre-bottle is shrinked under heating, and then the pre-bottle is put in a blow molding die and re-blown. In the blow molding method of a resin bottle, when shrinking the pre-bottle, a pressure rod that is provided outside the pre-bottle and moves at a speed corresponding to the shrink speed of the pre-bottle, and the bottom portion by the receiving rod inside the pre-bottle. A method for blow molding a synthetic resin bottle characterized by being held, a mouth holding device for holding the mouth of a synthetic resin pre-bottle, and a receiving rod extending from the mouth holding device to the pre-bottle so as to be able to move forward and backward. And movably provided on the outside of the pre-bottle with respect to the mouth holding device, and between the pre-bottle and the pre-bottle Comprising a pressure rod for clamping the bottom, and a heating pot covering the Purebotoru, the pushing rods are shrink apparatus characterized by moving at a speed corresponding to the shrinkage speed of the Purebotoru.

[0009]

[Function] During the shrinking action, the bottom of the pre-bottle is held by the pressure rod and the receiving rod that move at a speed corresponding to the shrinking speed of the pre-bottle, so that the pre-bottle is surely centered after the shrinking action. It is also possible to eliminate the trace of the receiving rod at the bottom of the pre-bottle.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views showing an embodiment of the present invention, and FIG. 5 is a view showing a conventional example for comparison.

First, FIG. 3 shows an outline of a blow molding device for a synthetic resin bottle. As shown in FIG. 3, the blow molding device 10 includes a rotary table 11 to which a mouth holding device 15 described later is attached, and a shrink device 12 and a re-blow molding device 13 are sequentially arranged on the periphery of the rotary table 11. There is.

Regarding the shrink device, FIG. 1 and FIG.
Will be described in detail. As shown in FIG. 2, the shrink device 1
2 includes a mouth portion holding device 15 attached to the rotary table 11 via a holding base 23, and a receiving rod 17 extending from the mouth portion holding device 15 so as to be able to move upward and backward. Of these, the mouth portion holding device 15 holds the mouth portion 30a of the bottle 30 made of synthetic resin such as PET, and is a fastener 20.
The mouth portion 30a of the bottle 30 is held and fixed by the. The pre-bottle 30 has a cylindrical shape, and its bottom has a spherical shape.

Below the rotary table 11, an air cylinder 21 for driving the receiving rod 17 is arranged.
The lower end of is fixed to the piston 16 that slides in the air cylinder 21. Further, a cylindrical guide 18 that guides the receiving rod 17 from the outside is fixed to the holding base 23 that supports the mouth portion holding device 15, and the cylindrical guide 18 and the receiving rod 17 are fixed.
There is a gas flow path 19 between and. Further, a communication passage 22 that communicates with the gas passage 19 is formed on the side wall 21 a of the air cylinder 21.

On the other hand, a bearing 32 fixed to a support bracket 31 is provided above the receiving rod 17, and a pot 33 having a heater (not shown) is rotatably supported on the bearing 32. The pot 33 covers the pre-bottle 30 as the support bracket 31 descends. A driven gear 34 is fixed to the outer periphery of the pot 33, and the driven gear 34 is driven by a drive gear 36 via an idle gear 35. The drive gear 36 is driven by a drive motor 37, and both the drive gear 36 and the idle gear 35 are rotatably supported by the support bracket 31.

Above the pot 33, the pot 33
A pressure rod 38 that can penetrate therethrough is disposed so as to be vertically movable. A driven gear 40 is axially slidably mounted on the outer periphery of the pressure rod 38, and the driven gear 40 is engaged with a drive gear 39 that is rotationally driven by a stepping motor 42. The rotation of the stepping motor 42 causes the pressure rod 3 to pass through the drive gear 39 and the driven gear 40.
8 and the external thread 3 formed on the outer circumference of the pressure rod 38.
8a engages with the fixed female screw 41, so that the pressure rod 38
Is descending.

The pressurizing rod 38 is in contact with the center of the bottom portion of the pre-bottle 30 and holds the pre-bottle 30 between it and the receiving rod 17, and the descending speed of the pressurizing rod 38 corresponds to the shrinking speed of the pre-bottle 30. There is. That is, pre-bottle 3
The shrink speed of 0 is determined in advance by an experiment or the like, and the pressurizing rod 38 descends at a speed corresponding to this shrink speed.

On the other hand, the receiving rod 17 is pressed downward by the downward movement of the pressure rod 38, and is lowered at the same speed as the pressure rod 38 against the air pressure in the air cylinder 21.

The fixed female screw 41 for rotatably supporting the pressure rod 38 and the stepping motor 42 are supported by the support bracket 31 as a whole through an intermediate bracket (not shown).

Next, the operation of this embodiment having such a configuration will be described.

First, the mouth holding device 1 for the rotary table 11
5, pre-blown synthetic resin pre-bottle 30
The mouth portion 30a of the above is attached and the mouth portion 30a is held and fixed to the mouth portion holding device 15 by the fastener 20. In this case, the bottom of the pre-bottle 30 is formed into a spherical shape.

Next, the rotary table 11 is rotated to bring the pre-bottle 30 to the shrink device 12. When the pre-bottle 30 reaches the shrink device 12, the support bracket 31 descends and the pot 33 covers the pre-bottle 30 from the outside. As the support bracket 31 descends, the pressure rod 38 also descends and comes into contact with the bottom of the pre-bottle 30.

On the other hand, in the air cylinder 21, the piston 16
Rises and the catch bar 17 contacts the bottom of the pre-bottle 30,
The bottom portion of the pre-bottle 30 is held between the receiving rod 17 and the pressure rod 38.

Subsequently, the inside of the pot 33 is heated by the heater, and the pot 33 is rotated by the drive motor 37 via the drive gear 36, the idle gear 35 and the driven gear 34. By rotating the pot 33 in this manner, heat unevenness in the pot 33 is prevented.

The pre-bottle 3 is heated by heating the pot 33.
0 shrinks. This shrink device is obtained by an experiment in advance, and the stepping motor 42 is used by the stepping motor 42 at a descending speed corresponding to the shrink speed of the pre-bottle 30.
8 drops. As the pressure rod 38 descends, the receiving rod 17
Is pressed downward, and the receiving rod 17 descends against the air pressure in the air cylinder 21 at the same descending speed as the pressurizing rod 38.

The pre-bottle 30 is heated by heating the pot 33.
After shrinking, the support bracket 31 is pulled up. After that, the pre-bottle 30 is conveyed to the re-blow molding device 13 as the rotary table 11 rotates, and is re-blow molded in the mold 44 of the re-blow molding device 13. In this case, pressurized air flows into the pre-bottle 30 through the gas flow path 19 from the communication flow path 22 formed in the side wall 21 a of the air cylinder 21, and the pressurized air causes the pre-bottle 30 to flow.
Are re-blow molded.

Next, the shrinking action of the pre-bottle will be described in detail with reference to FIGS. 4 and 5. As shown in FIG. 4A, the bottom of the pre-bottle 30 has a spherical shape,
During the shrinking operation, the central portion of the bottom portion of the pre-bottle 30 is held by the receiving rod 17 and the pressure rod 38. Further, during the shrinking action, the pressing rod 38 and the receiving rod 17 descend at a descending speed corresponding to the shrinking speed of the pre-bottle 30. Therefore, the center of the pre-bottle 30 can be reliably performed during the shrinking action, and the spherical shape of the bottom of the pre-bottle 30 can be maintained. Therefore, FIG.
As shown in FIG.
The re-blow molding can be performed accurately within the number 4.

That is, in the case of the conventional device (see FIG. 5), since the pre-bottle 30 is guided during the shrinking action only by the receiving rod 17 in the pre-bottle 30, the slip between the bottom of the pre-bottle 30 and the receiving rod 17 is caused. May occur, and the pre-bottle 30 may not be reliably centered. Further, when the receiving rod 17 is lowered by the shrinking force of the pre-bottle 30, or when the descending speed of the receiving rod 17 is slower than the shrinking speed of the pre-bottle 30, the receiving rod trace 45 remains at the bottom of the pre-bottle 30 (see FIG. 5). ).

As described above, according to this embodiment,
Since the pre-bottle after the shrinking action can be surely centered and the spherical shape of the bottom of the pre-bottle can be maintained smooth, the re-blowing can be performed accurately after the shrinking action.

[0029]

As described above, according to the present invention,
The pre-bottle can be surely centered after the shrinking action, and the receiving rod mark at the bottom of the pre-bottle can be eliminated. Therefore, it is possible to accurately re-blown the pre-bottle after the shrinking action to form a highly accurate synthetic resin bottle that matches the shape of the mold.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a shrink device according to the present invention.

FIG. 2 is a side view showing a lower portion of the shrink device.

FIG. 3 is a schematic plan view showing the entire blow molding device for a synthetic resin bottle.

FIG. 4 is a diagram showing a shrink action of a pre-bottle in the case of the present invention.

FIG. 5 is a diagram showing a shrinking action of a pre-bottle in the case of a conventional example.

[Explanation of symbols]

 10 Blow Molding Device for Synthetic Resin Bottle 11 Rotating Table 12 Shrinking Device 15 Mouth Holding Device 17 Receiving Rod 33 Pot 38 Pressure Bar

Claims (2)

[Claims] 1. A pre-bottle made of synthetic resin is blow-molded,
After that, shrinking the pre-bottle under heating, then in a blow molding method of a synthetic resin bottle in which the pre-bottle is put in a blow molding die and re-blown, when shrinking the pre-bottle, it is provided outside the pre-bottle. A blow molding method for a synthetic resin bottle, characterized in that the bottom portion is held by a pressure rod that moves at a speed corresponding to the shrink speed of the pre-bottle and a receiving rod inside the pre-bottle. 2. A mouth holding device for holding a mouth of a pre-bottle made of synthetic resin, a receiving rod extending from the mouth holding device so as to advance and retract into the pre-bottle, and the mouth holding outside the pre-bottle. A pressure rod that is movably provided with respect to the device, and that holds the bottom portion of the pre-bottle between the receiving rod,
A shrink device comprising: a heating pot that covers the pre-bottle; and the pressure rod moves at a speed corresponding to a shrink speed of the pre-bottle.