JP2619500B2 - Multi-layer parison molding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention extrudes a multilayer parison composed of a main resin layer and an auxiliary resin layer laminated on the inner side thereof to guide the parison into a cavity of a molding die. The present invention relates to a multilayer parison molding apparatus.

[Conventional technology]

2. Description of the Related Art In recent years, plastic containers have been proposed and put into practical use as containers for storing liquids such as fuel, such as fuel tanks provided in vehicles such as automobiles, in order to reduce the weight of the containers themselves and to facilitate molding. Is being done. Plastics that form this type of container include:
In consideration of moldability, strength, manufacturing cost, and the like, high-density polyethylene is often used.

However, since the high-density polyethylene has a property of permeating a liquid such as gasoline, if the liquid such as gasoline is stored in a container made of only the high-density polyethylene for a long period of time, it is stored. However, there is a problem that the liquid such as gasoline gradually penetrates and permeates the peripheral wall of the container.

Such a problem of the permeation of the contained liquid (gasoline, light oil, etc.) has been particularly emphasized recently, and a high impermeability in a container such as a fuel tank tends to be strongly required.

Therefore, as disclosed in, for example, Japanese Patent Publication No. 58-23212, a main material resin layer made of high-density polyethylene, which maintains the strength of the container, and a nylon resin, which prevents the permeation of a contained liquid such as gasoline. A first sub-material resin layer as a so-called barrier layer and a second sub-material resin layer as an adhesive layer, which is made of modified polyethylene and adheres the main material resin layer and the first sub-material resin layer. A multilayer parison is formed by laminating three types of resin layers, and the multilayer parison is extruded from an extrusion molding device and placed in a cavity of a mold, and then blow molded to form a multilayer hollow molded container having a three-layer three-layer structure. It is generally well known that by forming, a container can be made highly impermeable.

The extrusion molding apparatus for forming the multilayer parison, that is, the multilayer parison molding apparatus is composed of a storage chamber and a plunger. And a supply device for supplying the resin to each resin.

When extruding a multilayer parison with such a multilayer parison molding apparatus, first, each resin is fed into a storage chamber of an accumulator by a supply apparatus. At this time, by keeping the drive cylinder in a floating state, the plunger of the accumulator moves in a direction to push back the piston of the drive cylinder, and the resin is stored and measured in the storage chamber.

When the plunger reaches a predetermined position, the plunger is moved in the direction of extruding the resin by operating the drive cylinder, and the respective resins are extruded almost simultaneously from the nozzle, whereby the respective resins are laminated with a predetermined thickness. To form a multi-layer parison.

[Problems to be Solved by the Invention] However, in the above-described conventional multilayer parison molding apparatus, when resin is fed into the storage chamber of the accumulator, drag such as sliding resistance and own weight due to movement acts on the plunger of the accumulator. Further, even when the drive cylinder is in the floating state, the sliding resistance of the piston of the drive cylinder, the dead weight, and the like also act.

Therefore, the pressure of the resin in the storage chamber of the accumulator may increase, and a part of the resin supplied from the supply device may leak from the nozzle. In this case, a swelling part is partially generated in each layer forming the multilayer parison, and it becomes difficult to form a multilayer parison in which the respective resins are laminated with a predetermined thickness. Therefore, there is a problem that the shape and quality of a tank formed by blow molding a multilayer parison tend to vary.

[Means for solving the problem]

The multi-layer parison molding apparatus according to the first aspect of the present invention, in order to solve the above problems, after measuring the main material resin, pressurized and extruded from the nozzle of the main material resin accumulator,
A multi-layer parison comprising an accumulator for a sub-material resin, which is weighed out and then extruded from a nozzle, and a drive cylinder for driving the accumulator, wherein a main material resin layer and a sub-material resin layer are laminated. In a multi-layer parison molding apparatus for extruding, when at least the auxiliary material resin is supplied to the auxiliary material resin accumulator and measured, in the direction to cancel the drag accompanying the movement of the plunger of the auxiliary material resin accumulator, and An operating force generating means for generating an operating force smaller than the drag is provided.

Also, in the multi-layer parison molding apparatus according to the second aspect of the present invention, in the apparatus according to the first aspect of the present invention, the operating force generating means is formed by partitioning the inside by a plunger.
A cylinder having a chamber and a second chamber; first chamber pressure adjusting means for adjusting the pressure in the first chamber; and second chamber pressure adjusting means for adjusting the pressure in the second chamber. Connected to the plunger of the accumulator, the plunger of the accumulator is driven in the direction of the pushing operation by increasing the pressure in the first chamber. The first and second chamber pressure adjusting means supplies the resin to the accumulator. When the pressure is measured and measured, the first chamber pressure adjusting means releases the pressure in the first chamber, while the second chamber pressure adjusting means applies pressure to the second chamber.

(Operation)

With the configuration described above, when at least the sub-material resin is supplied to the accumulator for the sub-material resin and measured, the plunger of the accumulator for the sub-material resin is actuated by the operating force generating means in a direction to cancel the drag caused by the movement of the plunger. ,
In addition, an operating force smaller than the above-described drag acts. Therefore, the increase in the pressure of the sub-material resin inside the accumulator is suppressed to a small value, so that the sub-material resin is prevented from leaking from the nozzle.

Therefore, no bulging portion is generated in each layer forming the multilayer parison, and a multilayer parison in which the respective resins are laminated at a predetermined thickness can be reliably formed.

〔Example〕

One embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 1, an accumulator head 1 constituting a multilayer parison molding apparatus is provided with a cylinder 2 having a concentric cylindrical outer wall 2a and an inner wall 2b. Outer wall 2a
A ring piston 3 slidable in the up-down direction is provided between the ring piston 3 and the inner wall 2b. The ring piston 3 is driven by a first pushing cylinder 15 composed of a hydraulic cylinder via a plunger 14.

The cylinder 2 and the ring piston 3 constitute a main resin accumulator 16 which measures a main resin such as a high-density polyethylene in a molten state, pressurizes the resin, and extrudes the resin from a die slit 11 described later. .

On the inner peripheral side of the inner wall 2b of the cylinder 2, the cylinder 2
A core 4 fixed to the core 4 is provided, and an annular communication passage 7 is formed between the inner wall 2b and the core 4. Also, cylinder 2
A resin storage chamber (resin storage) 5 is formed by the outer wall 2a and the inner wall 2b, the ring piston 3, and the core 4. The resin storage chamber 5 is communicated with the first extruder 6 via a communication passage 7, so that the main resin is continuously supplied. A temperature adjusting device (not shown) is provided near the resin storage chamber 5 in the cylinder 2 so that the resin inside the resin storage chamber 5 is maintained at a predetermined temperature.

At the lower end of the outer wall 2a of the cylinder 2, an annular die 8 is provided.
It is fixed concentrically with the cylinder 2. The lower inner peripheral surface 8a of the die 8 is formed in a conical surface shape.

On the other hand, a core support 9 is fixed to the lower end of the core 4 concentrically with the cylinder 2. This core support 9
A cylindrical portion 9a is formed at the lower part of the cylinder. Core support 9
A core 10 concentric with the cylinder 2 is slidably fitted in the vertical direction in the cylindrical portion 9a. Lower outer peripheral surface of core 10
10a is formed in a conical surface, and the lower outer peripheral surface 10a of the core 10 is formed.
An annular die slit 11 that functions as a nozzle through which the resin is extruded is formed between the die 8 and the lower inner peripheral surface 8a of the die 8. The die slit 11 is formed on the outer wall 2a of the cylinder 2.
The die 8 is communicated with the resin storage chamber 5 through a resin passage 12 formed between the core 4 and the core support 9.

The core 10 is vertically driven by a hydraulic cylinder (not shown) via a rod 13, and the width of the die slit 11, that is, the radial thickness of the parison formed by extruding the resin from the die slit 11, is adjusted. It has become so.

As shown in FIGS. 2 and 3, a ring member 17 having a substantially vertical hexagonal vertical sectional shape is provided in the resin passage 12.
Are provided concentrically with the resin passage 12. The ring member 17 is supported by the four columns 18 at a predetermined distance from the inner peripheral surface of the outer wall 2a of the cylinder 2 while being arranged at a different circumferential position from the columns 18.
The cores 4 are supported by a predetermined distance from the outer peripheral surface of the core 4. That is, the resin passage 12 is divided by the ring member 17 into an inner annular passage 12a and an outer annular passage 12b.

Inside the ring member 17, an annular first auxiliary material resin passage 20 located near the center in the longitudinal sectional shape of the ring member 17 is provided.
Are formed. Further, on the inner peripheral side and the outer peripheral side of the first auxiliary material resin passage 20 inside the ring member 17,
In each case, an annular second auxiliary material resin passage 21 is formed. On the other hand, three concentric annular nozzles 24, 25 and 25 are formed on the lower surface of the ring member 17 and communicate with the resin passages 20, 21 and 21 through annular slits 22, 23 and 23, respectively. ing.

The first auxiliary material resin passage 20 is connected to a second extruder 27 provided outside the accumulator head 1 through a passage 26 formed in one of the columns 18. The second extruder 27 continuously supplies a first sub-material resin which is an impermeable resin as a barrier material for preventing liquid such as gasoline from permeating, such as a molten nylon resin. I have.

The second extruder 27 is provided with a sub-material resin accumulator 33 which measures the molten first sub-material resin, pressurizes it, and extrudes it from the annular nozzle 24 of the ring member 17. The plunger 28 of the auxiliary resin accumulator 33 is driven by a second extrusion cylinder 32 formed of a hydraulic cylinder. The accumulator 33 for the sub-material resin is provided with a temperature adjusting device (not shown) so that the first sub-material resin in the accumulator 33 for the sub-material resin is maintained at a predetermined temperature.

On the other hand, the second sub-material resin passages 21 and 21 are formed by passages 29 and 29 formed on a column 18 different from the column 18 on which the passage 26 is formed.
Is connected to a third extruder 30 provided outside the accumulator head 1. This third extruder 30
For example, a second auxiliary material resin as an adhesive, such as a modified polyethylene in a molten state, is continuously supplied.

The third extruder 30 weighs the second sub-material resin in a molten state, and then pressurizes the resin to form an annular nozzle formed on the ring member 17.
An accumulator 31 for sub-material resin extruded from 25 is provided. Plunger of accumulator 31 for secondary material resin
34 is driven by a third extrusion cylinder 35 composed of a hydraulic cylinder. Further, the accumulator 31 for the sub-material resin is provided with a temperature adjusting device (not shown) similarly to the accumulator 33 for the sub-material resin, and the second sub-material resin inside the accumulator 31 for the sub-material resin is maintained at a predetermined temperature. It is supposed to be.

Upper cylinder chamber 15 of the first extrusion cylinder 15
a and the lower cylinder chamber 15b are each connected to a hydraulic pressure supply device 39 via a first pressure servo valve 36.

In the second extrusion cylinder 32, an upper cylinder chamber 32a as a first chamber is connected to a hydraulic pressure supply device 39 via a second pressure servo valve 37 as a first chamber pressure adjusting means. On the other hand, the lower cylinder chamber 32b, which is the second chamber,
It is connected to a high-pressure air source via an air supply device 50 as a second chamber pressure adjusting means. Air supply device 50
Is a solenoid valve 51, oil separator 52, check valve 5
3, and a pressure reducing valve 54 are connected in order to supply air at a predetermined pressure to the lower cylinder chamber 32b of the second extrusion cylinder 32.

Similarly to the second extrusion cylinder 32, the third extrusion cylinder 35 is configured such that the upper cylinder chamber 32a, which is the first chamber, is connected to the hydraulic supply device 39 via the third pressure servo valve 38, which is the second chamber pressure adjusting means. On the other hand, the lower cylinder chamber 35b, which is the second chamber, is connected to the high-pressure air source via the air supply device 60, which is the second chamber pressure adjusting means. The air supply device 60 includes, similarly to the air supply device 50, a solenoid valve 61, an oil separator 62, and a check valve 6.
3, and a pressure reducing valve 64 are connected in order, so that air at a predetermined pressure can be supplied to the lower cylinder chamber 35b of the third extrusion cylinder 35.

The air supply device 50, the second extrusion cylinder 32 and the second pressure servo valve 37, and the air supply device 60 and the third extrusion cylinder
The first sub-material resin and the second sub-material resin are respectively stored in the accumulator for the sub-material resin by 35 and the third pressure servo valve 38.
When supplied and measured to 33.31, an operating force that generates a working force smaller than the above-described drag in a direction to cancel the drag accompanying the movement of the plungers 28 and 34 of the accumulators 33 and 31 for the auxiliary material resin. A generating means is configured.

Solenoids 36a to 38 of the first to third pressure servo valves 36 to 38
a, and the solenoids 51a and 61a of the solenoid valves 51 and 61 are connected to the parison control circuit 40, respectively.
It is controlled by an excitation signal output from 40. The parison control circuit 40 also includes first to third
The first attached to the extrusion cylinders 15, 32 and 35 respectively
To the third plunger position detecting devices 41 to 43, and input a position detection signal corresponding to the elevation position of the ring piston 3 in the accumulator 16 for the main material resin and the plungers 28 and 34 in the accumulators 33 and 31 for the sub-material resin. It is supposed to be.

The parison control circuit 40 further includes a first pressure detector 44 provided in the resin passage 12 of the accumulator head 1 for detecting the resin pressure of the main material resin, and a second pressure sensor 44 provided in the second extruder 27. A second pressure detector 45 for detecting the resin pressure of the second extruder 30 and a third pressure detector 46 provided in the third extruder 30 for detecting the resin pressure of the second sub-material resin are connected.

In the above configuration, when extruding a multilayer parison, first, the first pressure servo valve 38 is held at the neutral position, while the second pressure servo valve 37 and the third pressure servo valve 38 are held.
Are operated in the directions indicated by the arrows C, respectively. Also,
The solenoid valves 51 and 61 are operated in directions indicated by arrows D, respectively.

Then, the first extrusion cylinder 15 becomes a float state,
The main resin sent from the first extruder 6 to the main resin accumulator 16 via the communication path 7 is stored in the resin storage chamber 5 while pushing up the ring piston 3, and is measured.

Also, a second extrusion cylinder 32 and a third extrusion cylinder
The hydraulic oil inside the upper cylinder chambers 32a and 35a in 35 is
Each is drained through a second pressure servo valve 37 and a third pressure servo valve 38 while the lower cylinder chamber 32
b and 35b are provided with the pressure reducing valves 54 of the air supply devices 50 and 60, respectively.
The air reduced to a predetermined pressure by 64 is supplied. As a result, the plungers 28 and 34 of the accumulators 33 and 31 for the sub-material resin act on the plungers 28 and 34 with an operating force that almost cancels the drag caused by the upward movement, such as sliding resistance and own weight. In a state in which no external force is applied, a stationary state is maintained, and a state in which the external force can easily rise when an external force is slightly applied is maintained.

Accordingly, when the first sub-material resin and the second sub-material resin are sent from the second extruder 27 and the third extruder 30 to the sub-material resin accumulators 33 and 31, these sub-material resins are Plunger 28 with almost no increase in pressure
・ Push up 34, stored and weighed. And the first
Since the sub-material resin and the second sub-material resin hardly increase in pressure, they do not leak from the annular nozzles 24, 25, 25.

Eventually, when the ring piston 3 of the main resin accumulator 16 rises to a predetermined position and a predetermined amount of the main material resin is stored, the parison control circuit 40 determines the position output from the first plunger position detecting device 41. The first pressure servo valve 36 is operated in the direction shown by the arrow E based on the detection signal. Then, the hydraulic oil from the hydraulic supply device 39 is supplied to the upper cylinder chamber 15a of the first extrusion cylinder 15, while the hydraulic oil in the lower cylinder chamber 15b is supplied to the first pressure servo valve 3a.
Drain through 6.

Then, the first extrusion cylinder 15 is driven forward to lower the ring piston 3 of the main resin accumulator 16.
With the lowering of the ring piston 3, the main resin stored in the main resin accumulator 16 is pushed out into the resin passage 12, and is once divided into an inner layer and an outer layer above the ring member 17. It merges again below the ring member 17. The joined main resin is further extruded through the die slit 11 to form a single-layer parison.

At this time, the parison control circuit 40 operates based on the signals output from the first plunger position detecting device 41 and the first pressure detector 44 so that the main material resin is extruded at a predetermined ratio. Controls the 15 generated driving forces.

When the single-layer parison extruded from the die slit 11 has a predetermined length, that is, when the ring piston 3 is lowered by a predetermined amount, the parison control circuit 40 detects the position detected by the first plunger position detecting device 41. The third pressure servo valve 38 is actuated in the direction indicated by the arrow E based on the signal. Further, the solenoid valve 61 is operated in the direction indicated by the arrow F.

Then, the upper cylinder chamber 35a of the third extrusion cylinder 35
Is supplied with hydraulic oil from the hydraulic supply device 39,
The air inside the lower cylinder chamber 35b is drained via the solenoid valve 61. At this time, since the oil separator 62 and the check valve 63 are provided in the air supply device 60, the operating oil does not enter the high-pressure air source side.

When hydraulic oil is supplied to the upper cylinder chamber 35a, the third extrusion cylinder 35 is driven forward together with the first extrusion cylinder 15 to lower the plunger 34 of the accumulator 31 for the auxiliary material resin. With the lowering of the plunger 34, the second sub-material resin stored in the sub-material resin accumulator 31 passes through the passage 29
The resin is extruded between the inner layer and the outer layer of the main resin divided from the annular nozzles 25 through the second sub-resin passages 21 and the slits 23.

The parison control circuit 40 also controls the third plunger position detecting device 43, as in the case where the main resin is extruded.
And based on the signal output from the third pressure detector 46, so that the second auxiliary material resin is extruded at a predetermined ratio,
The driving force generated by the third extrusion cylinder 35 is controlled.

After the parison control circuit 40 drives the third extrusion cylinder 35 forward, the parison control circuit 40 drives the second extrusion cylinder 32 forward with a slight delay. That is, the second pressure servo valve 37 is operated in the direction indicated by arrow E, and the solenoid valve 51 is operated in the direction indicated by arrow F.

Then, similarly to the third extrusion cylinder 35, the operating oil from the hydraulic pressure supply device 39 is supplied to the upper cylinder chamber 32a of the second extrusion cylinder 32, while the air inside the lower cylinder chamber 32b is Drained through 51. And
The second extrusion cylinder 32 is driven forward together with the first extrusion cylinder 15 and the third extrusion cylinder 35 to lower the plunger 28 of the accumulator 33 for the auxiliary resin. Plunger
With the lowering of 28, the first sub-material resin stored in the sub-material resin accumulator 33 passes through the passage 26, the first sub-material resin passage 20,
The resin is extruded from the annular nozzle 24 between the inner layer and the outer layer of the second auxiliary material resin through the slit 22.

Also at this time, the parison control circuit 40 outputs the signals output from the second plunger position detecting device 42 and the second pressure detecting device 45 similarly to the case where the main material resin and the second auxiliary material resin are extruded. Based on this, the driving force generated by the second extrusion cylinder 32 is controlled so that the first sub-material resin is extruded at a predetermined ratio.

In this way, following the single-layer parison consisting only of the main material resin layer, the first sub material resin is interposed between the two main material resin layers of the inner layer and the outer layer via the second sub material resin layer. A three-layer, five-layer multilayer parison with layers interposed is extruded.

When the ring piston 3 further descends by a predetermined amount and the multilayer parison reaches a predetermined length, the parison control circuit 40
The second pressure servo valve 37 is returned to the neutral position based on the position detection signal output from the first plunger position detection device 41.
After a short delay, the third pressure servo valve 38 is returned to the neutral position.

Then, the second extrusion cylinder 32 and the third extrusion cylinder 35 are locked, the extrusion of the first sub-material resin and the second sub-material resin is stopped, and after the multilayer parison, again, only the main material resin layer is used. The resulting single-layer parison is extruded.

When the single-layer parison has a predetermined length, the parison control circuit 40 returns the first pressure servo valve 36 to the neutral position based on the position detection signal output from the first plunger position detection device 41. Thereby, the forward drive of the first extrusion cylinder 15 is stopped, the extrusion of the main resin is stopped, and the extrusion of the parison in one process is completed.

In this way, a parison having a single layer at both upper and lower ends and a multilayer at the center is extruded. The parison is blow-molded into a desired shape such as a fuel tank by introducing a pressurized gas into a cavity of a mold (not shown). Further, the upper and lower single layers can be removed as burrs after blow molding and recycled as a recycled material of the main resin.

Thus, the first accumulators 33 and 31 for the secondary material resin
When supplying the sub-material resin and the second sub-material resin, a multi-layer parison is formed by applying an operating force to the plungers 28 and 34, such as sliding resistance and own weight, which substantially cancels the drag caused by the upward movement. The occurrence of partial bulges in each layer can be prevented, and a multilayer parison in which the respective resins are laminated with a predetermined thickness can be reliably formed.

In this embodiment, the operating force generating means is provided for the first sub-material resin and the second sub-material resin. However, the present invention is not limited to this, and only one of the sub-material resins may be provided as necessary. Or may be provided for the main resin.

Further, the configuration of the multi-layer parison is not limited to the three-layer five-layer configuration. For example, the same effect can be obtained even when a multi-layer parison having various configurations such as a three-layer three-layer configuration is extruded.

Further, the type of the sub-material resin layer is not limited to the barrier material layer or the adhesive layer, and may be, for example, a resin layer for improving strength.

[Effect of the Invention] As described above, the multilayer parison molding apparatus according to the first aspect of the present invention measures the main resin and then measures the accumulator for the main resin that is pressed and extruded from the nozzle, and the auxiliary resin is measured. A multi-layer parison for extruding a multi-layer parison in which a main material resin layer and a sub-material resin layer are laminated, the sub-material resin accumulator being pressed and extruded from a nozzle, and a drive cylinder for driving the accumulators described above. In the molding apparatus, at least when the sub-material resin is supplied to the accumulator for the sub-material resin and weighed, in a direction to cancel the drag caused by the movement of the plunger of the accumulator for the sub-material resin, and an operating force smaller than the above-described drag. This is a configuration provided with an operating force generating means for generating the force.

Also, in the multi-layer parison molding apparatus according to the second aspect of the present invention, in the apparatus according to the first aspect of the present invention, the operating force generating means is formed by partitioning the inside by a plunger.
A cylinder having a chamber and a second chamber; first chamber pressure adjusting means for adjusting the pressure in the first chamber; and second chamber pressure adjusting means for adjusting the pressure in the second chamber. Connected to the plunger of the accumulator, the plunger of the accumulator is driven in the direction of the pushing operation by increasing the pressure in the first chamber. The first and second chamber pressure adjusting means supplies the resin to the accumulator. The first chamber pressure adjusting means releases the pressure in the first chamber, and the second chamber pressure adjusting means applies pressure to the second chamber when the measurement is performed.

This prevents at least the sub-material resin from leaking from the nozzle when supplying and measuring the sub-material resin to the accumulator for the sub-material resin, so that the bulging portion is partially formed in each layer forming the multilayer parison. Does not occur, and a multilayer parison in which the respective resins are laminated at a predetermined thickness is reliably formed.

Therefore, for example, there is an effect that variation in shape and quality of a tank formed by blow molding a multilayer parison can be easily reduced.

[Brief description of the drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is an explanatory view showing the structure of a multilayer parison molding apparatus, and FIG. 2 is a cross-sectional view taken along the line AA in FIG. FIG. 3 is a sectional view taken along the line BB in FIG. 11 is a die slit (nozzle), 15 is a first extrusion cylinder,
16 is an accumulator for the main resin, 24 and 25 are annular nozzles,
28 is a plunger, 31 and 33 are accumulators for auxiliary resin,
32 is a second extrusion cylinder (operating force generating means), 32a and 35a are upper cylinder chambers (first chamber), 32b and 35b are lower cylinder chambers (second chamber), 34 is a plunger, and 35 is third extrusion. Cylinder (operating force generating means), 37 is a second pressure servo valve (first chamber pressure adjusting means), 38 is a third pressure servo valve (first chamber pressure adjusting means), 50 and 60 are air supply devices (operating force) Generating means, second chamber pressure adjusting means).

Claims (2)

(57) [Claims] 1. An accumulator for a main material resin which is measured and then extruded from a nozzle by pressurizing the main material resin, and an accumulator for a sub material resin which is extruded from a nozzle after measuring and pressing the sub material resin. A multi-layer parison molding apparatus comprising a drive cylinder for driving an accumulator and extruding and forming a multi-layer parison in which a main material resin layer and a sub material resin layer are laminated, wherein at least the sub material resin is supplied to the sub material resin accumulator When weighing, in the direction to cancel the drag caused by the movement of the plunger of the accumulator for secondary material resin, and
A multi-layer parison forming apparatus comprising an operating force generating means for generating an operating force smaller than the drag. 2. The operating force generating means includes: a cylinder having a first chamber and a second chamber formed by partitioning the inside thereof by a plunger; and a first chamber pressure adjusting means for adjusting a pressure in the first chamber. And a second chamber pressure adjusting means for adjusting the pressure in the second chamber, wherein the plunger is connected to the plunger of the accumulator, and the plunger of the accumulator is pushed out in the direction of operation by pushing up the plunger of the accumulator by increasing the pressure in the first chamber. The first and second chamber pressure adjusting means release the pressure in the first chamber when the first chamber pressure adjusting means releases the pressure in the first chamber when the resin is supplied to the accumulator and measured. The multilayer parison molding apparatus according to claim 1, wherein the two-chamber pressure adjusting means applies pressure to the second chamber.