JPH06254955A - Biaxially stretched blow molding device - Google Patents

Abstract

(57) [Summary] (Modified) [Objective] To provide a biaxial stretch blow molding machine capable of blow molding a hollow body having a constant wall thickness distribution even if the preform holding temperature varies. [Structure] The preform 1 is arranged in the blow-core mold 20 and the blow-cavity mold 18 that have been clamped, and the preform 1 is longitudinally stretched by a stretching rod 30, and blow air is introduced through the blow core mold 20 to transversely stretch. Then, the hollow body is biaxially stretch blow molded. In order to detect the actual position of the stretching rod 30 while driving the vertical axis, the rod detection device 1
00 is provided. It has a blow air supply control means for determining the introduction start timing of blow air based on the output of the detection means of the apparatus 100.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretch blow molding apparatus for biaxially stretch blow molding a hollow body from a preform, and more particularly to improving the introduction timing of blow air.

[0002]

2. Description of the Related Art In a biaxial stretch blow molding machine of this type, a preform is placed in a clamped blow core mold and Blom cavity cavity mold, and a preform is vertically cut by a drawing rod inserted into the preform. Along with axial stretching,
Blow air is introduced through a blow core mold to laterally stretch the preform to form a hollow body that conforms to the shape of the cavity surface of the blow cavity mold.

Here, the blow air introduction timing from the blow core type is such that the vertical axis drive start command time of the stretching rod is set to 0 point, and the timer outputs the blow start signal after t seconds have elapsed from 0 point. In the case of introducing the primary and secondary air, as shown in FIG. 8, the primary air is introduced after the elapse of t1 seconds after the vertical rod drive start command for the stretching rod and after the vertical rod drive start command for the stretching rod t2 (t2 Secondary air was introduced after> t1) seconds had elapsed. The timing of introducing the secondary air may be determined by operating a timer after the introduction of the primary air is started.

[0004]

According to this conventional method, the quality of blow-molded bottles, especially the thickness distribution thereof, fluctuates with each continuous blowing operation or lot-by-lot operation, and molding stability is improved. There was a fear of worsening.

Generally, the holding temperature of the preform at the time of blow molding is different for each blowing operation or each lot due to a change in the environmental temperature or the temperature control condition of the preform. As for the blow characteristics, if the holding temperature of the preform is high, it is easy to stretch, and if it is low, it is difficult to stretch. Due to this, the drawing resistance of the preform for driving the drawing rod differs depending on the holding temperature. Usually, the stretching rod is usually driven by air which is a compressible fluid, but if the stretching resistance of the preform is large, the driving speed of the stretching rod becomes relatively slow due to the compression of air, and conversely the stretching resistance is increased. If it is small, the driving speed of the drawing rod tends to be high.

However, conventionally, no attention was paid to the difference in the driving speed of the stretching rod, and the introduction timing of blow air was determined by the time from the vertical drive start command of the stretching rod. The vertical axis position of the tip of the rod was different for each blow operation or each lot. In other words, with reference to the actual position of the tip of the stretch rod during vertical driving, the introduction of blow air was delayed or accelerated, and the introduction timing was different. When the introduction of the blow air is delayed, the lower part of the neck part is particularly stretched, and this part becomes excessively thin, while the bottom part becomes thicker. On the other hand, if the introduction of blow air is accelerated, the bottom portion becomes thin. in this way,
Molding stability was poor.

Further, in this type of blow molding apparatus, an air cylinder is often used to drive the longitudinal axis of the stretching rod,
Moreover, this air source is common to other air cylinders.
Therefore, air may be drawn into another air cylinder when the longitudinal axis of the stretching rod is driven, and this may cause the driving speed of the stretching rod to differ for each blow molding, resulting in deterioration of molding stability.

Therefore, the object of the present invention is to make the stretching rod longitudinal even if the holding temperature of the preform is different for each blowing operation or the driving speed of the stretching rod is different for driving reasons. It is an object of the present invention to provide a biaxial stretch blow molding machine that can always introduce blow air at a constant timing based on the axial drive position.

[0009]

According to the present invention, a preform arranged in a mold-molded blow core mold and blow cavity mold is longitudinally stretched by a stretching rod, and
In a biaxial stretch blow molding apparatus that introduces blow air through the blow core mold to perform a horizontal axis stretch and biaxially stretch blow molds a hollow body, a detection unit that detects the actual position of the stretch rod during vertical axis drive. And a blow air supply control means for determining the introduction start timing of the blow air based on the output of the detection means.

When there are a plurality of simultaneously molded pieces, the plurality of preforms are longitudinally driven by the plurality of stretching rods simultaneously driven by a single driving source, and the preforms are independent for each preform. Blow air supply control means is provided, the detection means detects the common actual position of the plurality of stretching rods, and the plurality of blow air supply control means are independent for each of the plurality of preforms based on the output of the detection means. It is possible to determine the introduction timing of the blow air.

[0011]

According to the present invention, the actual position of the stretching rod is detected while being driven in the vertical axis, and the introduction timing of blow air is determined with reference to the detected actual position. If the holding temperature of the preform is low and its stretching resistance is high,
It takes a long time to reach a position where the stretching rod driven for stretching is located. However, unlike the conventional case where the introduction time of blow air is determined by fixing the arrival time, the tip of the stretching rod can be detected by detecting that the stretching rod has reached a certain position regardless of the variation in the arrival time. Blow air can be introduced at any time when the tip reaches a certain position. Therefore, the position of the stretch rod and the introduction timing of the blow air always match each blow operation,
Molding stability is improved.

When there are a plurality of simultaneous moldings, when a plurality of preforms are longitudinally driven by a plurality of stretching rods simultaneously driven by a single driving source, the detecting means detects the common actual positions of the plurality of stretching rods. Will be detected.
At this time, the blow air supply control means independent for each preform can independently determine the blow air introduction timing for each of the plurality of preforms based on the output of the detection means. Since the preforms that are simultaneously molded do not completely match the blowing conditions, the molding quality of the hollow bodies that are simultaneously molded can be adjusted to be substantially constant by making the blow air introduction timing different.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a blow molding apparatus to which the present invention is applied will be specifically described below with reference to the drawings. First, the structure of the blow molding device will be described with reference to FIGS. 1 and 2. As shown in each figure, a rotatable rotary plate 12 is attached to the upper base 10 of the blow molding apparatus. A neck support plate 13 is attached to each of four regions divided by the rotation angle of 90 ° of the rotary plate 12, and a plurality of neck molds 14 are arranged on the neck support plate 13. The rotating plate 12 is driven to rotate intermittently every 90 °, and an injection molding station, a temperature control station,
A blow station and an eject station are provided. 1 and 2 show an area of a blow molding station, which is provided with a blow cavity mold 18 which is opened and closed by a mold clamping cylinder 16.

On the other hand, above the upper substrate 10 of the blow molding station, there are provided a blow core mold 20, a stretching rod 30, and a drive device for vertically moving them. The first air cylinder 22 drives the blow core mold 20 up and down. A fixing block 24 for fixing the first air cylinder 22 to the upper substrate 10 is provided. This fixed block 24 has rear surfaces 24a, 2
A cylinder fixing plate 24c having a substantially U-shaped cross section having two side surfaces 24b and protruding horizontally from the back surface 24a is provided, and the first air cylinder 2 is provided on the fixing plate 24c.
2 is fixed (see FIG. 2). Further, an elevating block 26 capable of ascending and descending within a region surrounded by the fixed block 24 is provided. The elevating block 26 has an upper surface 26a and a rear surface 26b. A connecting piece 26d protruding outward from a notch 24d provided on the back surface 24a of the fixed block 24 is provided on the elevating block 26, and the connecting piece 26d and the rod 22a of the first air cylinder 22 are connected and fixed. (See Figure 2).

The lifting block 26 includes a horizontal core fixing plate 2
6e is provided. A plurality of core fixing plates 26e,
For example, four blow core molds 20 are fixed and can be lifted and lowered integrally with the lift block 26. The stretch rod 30 is
It extends along a blow air introduction path (not shown) that penetrates at the center of the blow core mold 20 and can be inserted from the neck portion 1a side of the preform 1.

The second air cylinder 32 includes the extension rod 3
0 is driven in the preform 1 in the vertical axis, and is fixed on the upper surface 26a of the elevating block 26. The elevating plate 3 is parallel to the upper surface 26a of the elevating block 26.
4 is provided, and the lifting plate 34 is provided with the guide rod 3
It is guided up and down along 6. This lifting plate 34
And the rod 32a of the second air cylinder 32 are connected to each other.

According to the above-mentioned structure, first, the first air cylinder 22 is driven to lower the elevating block 26. Then, the four blow core molds 20 fixed to the elevating block 26 are driven to descend, and the insertion tip ends are inserted in a state in which they are in close contact with the inner wall of the neck portion 1a of the preform 1. At this time, the tip of the stretch rod 30 penetrating the blow core mold 20 is stopped at a predetermined position in the preform 1. Further, by driving the second air cylinder 32, the stretching rod 30 is driven in the vertical axis, and then blow air is introduced into the preform 1 from the blow core mold 20 at a timing described later. By this operation, the preform 1 is biaxially stretched in the vertical axis and the horizontal axis,
The bottle is blow-molded in the blow cavity mold 18 having a cavity surface matching the final shape.

In the present embodiment, the actual position of the stretch rod 30 is detected in order to determine the timing of introducing blow air from the blow core mold 20 into the preform 1. Therefore, the rod position detection shown in FIG. It has a device 100. The rod position detecting device 100 has first and second sensors 102 and 106 at two locations separated in the vertical direction. Each sensor 102, 106 has a movable lever 104, 108, respectively. On the other hand, the second air cylinder 3
The first and second sensors 10 are provided at the end of the elevating plate 34 that is integrally moved up and down with the blow core mold 20 by the driving of 2.
A lever pushing member 35 that pushes the movable levers 104 and 106 is fixed. The lever pushing member 35 comes into contact with and displaces the movable levers 104 and 108 during the longitudinal driving of the stretching rod 20, and the stretching rod 20 is continuously driven to move after the contact, whereby the movable levers are moved downward. The displacement states of 104 and 108 are maintained. Then, the first and second sensors 102 and 106 are turned on while the movable levers 104 and 108 are displaced.

Further, in the present embodiment, the vertical positions of the first and second sensors 102 and 106 are made variable so that the introduction timing of blow air can be changed. For this purpose, first and second screw shafts 110 and 112, which are respectively rotatable by the first and second motors 114 and 116 and extend along the vertical axis direction, are provided. The first sensor 102 is screwed to the first screw shaft 110 and is screwed to the second sensor 106 and the second screw shaft 112. The first and second motors 114 and 11
Reference numeral 6 is composed of, for example, a pulse motor, and by inputting position change information of the first and second sensors 102 and 106 via an operation input unit (not shown), the corresponding number of pulses becomes the first and second pulses. It is input to the motors 114 and 116, and the positions of the first and second sensors 102 and 106 in the vertical axis direction are changed.

In this embodiment, the number of simultaneous moldings is 4, and blow air is supplied to four blow core molds. For this purpose, as shown in FIG.
a to 20d are provided. Blow core molds 20a-2
A common air source 41a for supplying blow air to 0d is provided, and this air source 41a has a maximum pressure of 35 kg / cm ² . An air tank 41b is connected to the air source 41a, and the air tank 41b and the blow core mold 20a are connected.
A primary air supply system 40 and a secondary air supply system 60 are provided as a blow air supply system that connects .about.20d.

The primary air supply system 40 includes an air tank 41b.
Has a common air passage 42 whose one end is connected to, and a pressure reducing valve 44 is provided in the middle of the common air passage 42 to reduce the air pressure to, for example, 10 kg / cm ² or less. Four branch air passages 46a to 46d extending toward the blow core molds 20a to 20d are connected to the common air passage 42. In the middle of each branch air passage 26, a first air valve 48 that can be electrically opened and closed, a flow rate regulator 50 that regulates the flow rate of blow air, and a check valve 52 that prevents backflow to the air tank 41b are arranged. ing.
In addition, the common air passage 42 is divided into four branch air passages 46a to
A blow manifold 54 is provided for branching to 46d.

The secondary air supply system 60 includes an air tank 41b.
And four branch air passages 62a to 62d provided between the four blow core molds 20a to 20d. In the middle of each branch air passage 62, a second air valve 64 capable of electrically opening and closing the air passage is provided.

Further, after the blow molding, an exhaust system 70 for exhausting the air in the bottle is provided. This exhaust system has, for example, four branch exhaust passages 72a connected at one end to the four branch air passages 46a to 46d of the primary air supply system 40 and connected to the common exhaust passage 72b by the exhaust manifold 76. ing. A check valve 74 is arranged in the middle of each branch exhaust passage 72a, and the common exhaust passage 72b is also provided.
Is provided with a third air valve 78 that shuts off the passage of the exhaust system 70 when introducing blow air.

Next, the primary air control system 80 and the secondary control system 90 will be described with reference to FIGS. 4 and 5.

First, the primary air control system 80 will be explained. As shown in FIG. 4, during energization of the first air valve 48, the first relay 82, the first timer 84 and the second relay 86 are provided. Is provided. First relay 8
2, the program controller output for executing the blow operation is input, and this ON
The first relay 82 is turned on only during the input.

During energization of the first timer 84, the first timer 84
First relay switch 82a that is closed by the ON operation of the relay 82 and first sensor switch 102a that is open over the ON time of the first sensor 102
And are connected in series. During energization of the second relay 86, the timer switch 84a operated by the first timer 84 and the first relay switch 82a are connected in series. The first timer 84 starts counting from the start of energization of this timer, and the first sensor 102
The delay time t1 set in advance after the actual position of the stretching rod 30 is detected and the primary blow air is introduced is elapsed. This first timer 84 is not always necessary, but as will be described later, when the introduction timing of the primary blow air is changed for every four blow core molds 20,
This can be dealt with by changing the delay time t1 for each blow core type 20.

Then, the timer switch 84a interlocking with the first timer 84 is set to the closed state after the time t1 has elapsed. The first timer 84 is deenergized when the output of the program controller is turned off.
Is set to an open state when the program controller output is turned off. The second relay switch 8 driven by the second relay 86 is energized during energization of the first air valve 48 provided in the middle of the primary air passage 42.
6a is provided.

In the primary blow air control system 80 having the above-described configuration, the second relay 86 is activated after the first sensor 102 is turned on and a predetermined delay time t1 has elapsed, whereby the first air valve 48 is activated. Is opened and the introduction of primary blow air is started.

Next, the secondary air control system 90 will be described with reference to FIG.
Relays 92, 96 and a second timer 94, and switches 92a, 94a, 96a and a second sensor switch 106a operated by the relays 92, 96, respectively.

The third relay 92 includes a first relay 82.
The same output as the program controller output for is input. In the middle of the energizing circuit for the first timer 94, the second timer
The second switch 106a, which is closed while the sensor 106 is ON, and the third relay switch 92a, which is closed by the ON operation of the third relay 92, are connected in series. The second timer 94 starts counting from the start of energization of the timer, and elapses a predetermined delay time t2 from when the second sensor 106 is turned on to when secondary blow air is introduced. A timer switch 94a operated by a second timer 94 and the third relay switch 92a are connected in series in the middle of the energizing circuit for the fourth relay 96. The second timer switch 94a is closed after the second timer 94 has passed a predetermined delay time t2. Further, since the second timer 94 is de-energized when the program controller output is turned off, the second timer switch 94
Also, a is set to the open state by turning off the program controller output. Further, during energization of the second air valve 64 provided in the middle of the secondary air passage 62, the fourth relay switch 9 driven by the fourth relay 96 is driven.
6a is provided.

This secondary air supply system 60 has the above-mentioned configuration, and after the second sensor 106 is turned on, the fourth relay 96 is activated after the elapse of a predetermined delay time t2, and the second air supply system 60 is activated.
When the air valve 64 is opened, the supply of secondary blow air is started.

Next, the operation of the primary air supply system 40 and the secondary air supply system 60 will be described with reference to the timing chart shown in FIG.

When the program controller output shown in FIG. 6 is turned on, the first and third relays 82 and 92 shown in FIGS. 4 and 5 are energized, and the first and third relay switches 82a, 82a, 92a is closed. In addition, in the present embodiment, when the program controller output is turned on, the vertical axis drive of the stretching rod 30 is started. Therefore, the second air cylinder 32 is driven and the rod 32
a, vertical drive of the stretching rod 30 is started via the elevating plate 34. By driving the extension rod 30 in the vertical axis, the first sensor 102 is first turned on. Therefore, the sensor switch 102a in the primary air control system 80 is set to the closed state. As a result, the first timer 84 is energized, and the first timer 84 counts the predetermined delay time t1. When the first timer 84 counts up this time t1, the first timer switch 84a provided during energization of the second relay 86 is closed,
Energization of the second relay 86 is started. As a result, the second relay switch 86a is closed, the first air valve 48 is opened, and the supply of primary blow air is started.

After that, the second sensor 106 is turned on while the extension rod 30 is being driven in the vertical axis. As a result, the second sensor switch 106a of the secondary air control system 90 is brought into the closed state, and the energization of the second timer 94 is started.
The second timer 94 starts counting a predetermined delay time t2 by the start of energization, and after counting up the time t2, the second timer switch 94a is turned on.
To do. As a result, since the fourth relay 96 is energized and the fourth relay switch 96a is closed, the second air valve 64 in the middle of the secondary air supply system 60 is opened and the supply of secondary air is started. .

As described above, according to this embodiment, since the actual position of the stretching rod 30 is detected and the introduction timing of the primary and secondary air is determined based on the detection, the holding temperature of the preform 1 is determined. Even if it differs for each lot or for each blowing operation, the introduction of the primary and secondary air can always be started at the same timing in relation to the actual position of the stretching rod 30. Therefore, the quality of the bottles blow-molded for each lot or each blowing operation, in particular, the thickness distribution does not change. Further, the introduction timing of the primary and secondary air is changed by changing the vertical position of the first and second sensors 102 and 104 by driving the first and second motors 114 and 116 or by changing the first and second sensors. This can be easily dealt with by changing the count times t1 and t2 in the second timers 84 and 94.

In the above embodiment, the number of simultaneous moldings was set to 4 and the introduction timing of the primary and secondary air from the four blow cores 20 was set to the same timing.
The introduction timings of the primary and secondary air may be set differently for each. For this reason, primary and secondary air control systems 80 and 90 are provided for each blow core 20, and the predetermined delay times t1 and t2 counted by the first and second timers 84 and 94 are different values. You can set it to.
By doing so, the quality of the four bottles molded using the four blow core molds 20, in particular, the blow air introduction timing for keeping the thickness distribution constant, can be easily changed.
Moreover, this wall thickness distribution does not change from lot to lot or from blow to blow.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention. In the above-described embodiment, the rod position detecting device 100 detects the actual position of the stretching rod 30 with the mechanical contact type sensor, but the non-contact type sensor is used by using the optical type or magnetic coupling. You can also

Further, in the above embodiment, in order to determine the introduction timing of the primary and secondary air, two different positions in the vertical axis driving direction of the stretching rod 30 were detected, but the vertical axis driving of the stretching rod 30 was detected. It may be configured to detect any actual position therein. FIG. 7 shows an example thereof. In the rod position detecting device 120 shown in FIG. 7, a rack 122 extending in the vertical direction is provided on an elevating plate 34 that is vertically moved by a second air cylinder 32. Further, an encoder 124 composed of a pinion gear that meshes with the rack 122 is rotatably supported by, for example, the fixed block 24.

According to the structure shown in FIG. 7, when the second air cylinder 32 is driven and the elevating plate 34 is downwardly driven, the rack 122 is integrally downwardly driven, which causes the encoder 124 to rotate, Any actual position of the stretch rod 30 can be detected. This encoder 12
4 is configured to generate a pulse for each predetermined rotation angle,
If the pulse position corresponding to the introduction timing of the primary and secondary air is set in advance, the introduction timing of the primary and secondary air can be determined based on the output of the encoder 124. When the number of simultaneous moldings is plural, after the predetermined pulse is detected by the encoder 124, the delay time t set for each blow core mold 20 is counted and the timing set for each blow core mold 20 is counted. It is possible to set the introduction timing of the primary and secondary air.

The present invention is not limited to introducing primary and secondary air. For example, when molding a bottle having a small volume or a simple shape, it is sufficient to introduce blow air at a constant pressure. In this case, only the introduction timing should be decided once.

[0041]

As described above, according to the present invention, the actual position of the stretching rod is detected even if the descending speed of the stretching rod fluctuates due to variations in the preform holding temperature during blow molding. By determining the blow air introduction timing, the blow air can be introduced at a constant timing in relation to the actual position of the stretching rod.
It is possible to prevent the quality of the molded container, particularly the thickness distribution thereof, from varying from lot to lot or from blow operation to blow container.

[Brief description of drawings]

FIG. 1 is a schematic front view in which a part of a blow molding device to which the present invention is applied is cut away.

FIG. 2 is a schematic side view in which a part of the blow molding device shown in FIG. 1 is cut away.

FIG. 3 is a block diagram of primary and secondary air supply systems of the embodiment apparatus.

4 is a circuit diagram showing a valve control system of the primary air supply system shown in FIG.

5 is a circuit diagram showing a valve control system of the secondary air supply system shown in FIG.

6 is a timing chart showing an operation of the valve control system shown in FIGS. 4 and 5. FIG.

FIG. 7 is a schematic front view for explaining a modified example of the rod position detection device.

FIG. 8 is a timing chart for explaining a conventional example of vertical axis drive of a stretching rod and introduction timing of primary and secondary air.

[Explanation of symbols]

 20 blow core type 30 stretch rod 32 second air cylinder 35 lever pushing member 80 primary air control system 90 secondary air control system 100 rod position detection device 102 first sensor 104, 108 movable lever 106 second sensor 120 rod Position detector 122 Rack 124 Encoder

Claims (2)

[Claims] 1. A hollow body is biaxially shaped by vertically stretching a preform arranged in a mold-clamped blow core mold and a blow cavity mold by a stretching rod and introducing blow air through the blow core mold. In a biaxial stretch blow molding apparatus for stretch blow molding, a detection unit that detects the actual position of the stretch rod while driving the vertical axis, and a blow air supply control unit that determines the introduction start timing of the blow air based on the output of this detection unit. And a biaxial stretch blow molding device. 2. The blow air supply control according to claim 1, wherein the plurality of preforms are longitudinally driven by the plurality of stretching rods simultaneously driven by a single drive source, and each preform is independent. Means for detecting the common actual position of the plurality of stretching rods by the detection means, and the plurality of blow air supply control means independently of the blow air for each of the plurality of preforms based on the output of the detection means. A biaxial stretch blow molding apparatus, characterized in that the introduction timing of the is determined.