JPH05329919A - Blow molding method and device thereof - Google Patents

Abstract

PURPOSE:To evade the disadvantage due to the drawdown effect in parison, which is injected in the air and droops, in the flow molding of plastic. CONSTITUTION:A self-fused and closed free lower end is produced at an upstream part Y by cutting a parison 1, which consists of the upstream part Y and a downstream part X or X+Y in the previous time run of blow molding. At the present time run, both the processes of the injection for completing the present time parison and of pre-blowing are started at high injection speed and simultaneously without being torn off the cut upstream part from the die 10 of an injection machine. An example, by heating the upstream part Y with a heater 40, the part Y is utilized as the constituent material of a molded article obtained at the prevent time run. Another example, in which the part Y is heated, the part Y is removed at its lower end from the cavity of a mold 50 as the burr in the present time run. Thus, in the case that the material consisting of engineering plastic, which remarkably develops drawdown effect in parison when injected at a slow speed, or the like is used, the productivity, the yield of material and the quality of molded article are respectively improved as compared with those by the prior art.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an improved method and apparatus for blow molding, and more particularly to a method and apparatus for producing blow molded articles made from engineering plastics.

[0002]

Blow molding is a well-known method for molding hollow plastic articles, and according to the prior art, an injection machine equipped with a die defining an annular melt flow path extending downward is described below. Means: Air blowing means; Mold located below the die including two half molds that define the cavities; Parison forming the molded product in one part at the upper part of the mold A product ejector as shown in FIGS. 1 and 2 for pinching and picking the parison when the mold is opened; and the parison at its free end, thereby self-welding the free end. It is used in combination with a pinch device or the like for sealing.

This method comprises the steps of plasticizing and weighing a plastic material in an injection machine; injecting the plastic weighing material into a hollow shape through an annular flow path of a die into a hollow shape; during the injection step, an injection hollow material. Of the long hollow parison that is pre-expanded by blowing low-pressure air from the die into the interior of the. The resulting parison is partially received by the mold and provided to form a molded article within the cavities of the mold. The quality of the parison obtained by injection and pre-expansion is very important because it affects the quality of the molded product.

The mold is cooled while the half mold is clamped with the parison in between, and air is blown into the parison at a relatively high pressure following the pre-blow. When the mold is opened, the parison is pinched, that is, pinched by the product take-out device, and is moved from the mold by the take-out device after the mold is opened. As a result, this parison has its upstream end on the die side from the die to its tip. Will be torn off at.

The next injection is started after the parison of this time (the parison completed by the injection and pre-blowing of this time) is separated from the die, and the molding of the next parison is started.
The material to be the leading part of the next parison, which was injected in the initial stage of the next injection process, is self-welded at its free lower end by the pinch device, so that low pressure air is injected inside the next parison where the free end should be completed. It is closed or sealed for the next pre-blow step of blowing. This pinch operation is performed before the free end hangs down on the mold, and immediately after that, the injection is switched from the low speed to the high speed injection and the material to be the succeeding part of the next parison is continuously injected. At the same time as this post-injection stage, the next pre-blowing process (pre-expansion process) is started, and the next parison molding process is completed.

The above-mentioned conventional blow molding method is shown in FIG.
And (c) and FIG. In these figures, (X + Y) corresponds to the completed parison consisting of the leading part and the trailing part, ΔT is the time of the initial injection stage performed at the low injection speed β, and α is the high injection speed. The low speed β is a speed at a low level such that the pinch sealing action can be sufficiently performed.

The leading portion and the trailing portion of the parison are in a suspended state to form a downstream portion (X) and an upstream portion (Y) as an integral body. The upstream part (Y) of the parison is a material portion extending from the free end of the die to a pinch position above and near the die. The downstream part of the parison (X) is at least the free lower end of the parison, ie the lower end part of the downstream part (X) (Δ
X ₂ ) is removed from the cavity at its lower end, and the upper end local part (X ₁ ) of the downstream portion (X) is removed from the cavity at its upper end and extends upward from the die top end to the die. Partially accepted.

Upper part of the lower part of the parison (X) (Δ
The upstream part (Y) of the parison, which is continuous with X ₁ ), the lower end part (ΔX ₂ ) ₁ and the upper end part (ΔX ₁ ) is all discarded as burrs after the product is taken out from the mold by the take-out device. The waste may be recycled and reused as a raw material, but the quality of the blow-molded product made from the recycled material is naturally inferior.

The initial injection stage of low speed β is until the end of the pinch operation,

[Equation 1] , The subsequent injection stage of high speed α and the pre-blowing process are started at the same time,

[Equation 2] Is executed over time. Note that the pre-blowing start time is delayed by Δt ′ + ΔT from the injection start time (low speed).

The lower part of the parison (X) is

[Equation 3] Molded in both the initial and subsequent injection stages for The upper part of the parison (Y) is

[Equation 4] Is molded in a subsequent injection stage at high speed α over time.

However, regarding the above time, there is the following relationship. T: Time of only high-speed injection corresponding to X amount. Δt: Time for only high-speed injection corresponding to Y amount. ΔT + Δt ′: Low speed injection time. ΔT + T: Injection time at low speed and high speed corresponding to X amount.

[Equation 5]

By the way, in recent years, engineering plastic materials have been used as an advantageous raw material for plastic blow molded products because of their heat resistance. However, the physical melt properties cause the thermal parison to be relatively overstretched and thinner, or "drawdown," than that of conventional plastic materials. The drawdown phenomenon becomes more prominent as the parison of a predetermined length is completed, that is, when it takes longer to droop.

From this point of view, high-speed injection is desired in order to provide a high-quality parison that can be received by a mold in a short time for the production of high-quality products. In order to be able to carry out the self-welding of the parison at the open free end of the parison, it has to be carried out at a low speed β which is much lower than the high speed α.

Considering the properties of engineering plastics, the low-velocity β initial injection stage is of course unfavorable for the desired parison molding, and if possible, the parison is produced from the initial stage at a high average speed, whereby the product It is desired to improve quality and shorten the shot cycle time of blow molding runs to improve blow molding productivity.

By the way, the free end of the parison (X + Y) is lifted to some extent when the mold is closed with the mold sandwiched therebetween. Therefore, the upstream part (Y) of the parison (X + Y) reliably ensures that the mold partly receives the downstream part (X) under the following conditions when the mold is closed across the parison. There must be. That is, when the mold is closed, at least the free end of the parison or the lower end portion (ΔX ₂ ) of the downstream portion (X) is excluded from the cavity at its lower end, and at least the upper end portion (ΔX ₁ ) is excluded. The upper end of the mold should protrude from the top of the mold, and the main part to be the product of the downstream part (X) must be properly received by the cavity [Fig. 5 (a),
(See (c)].

Therefore, the appropriate length of the upstream portion (Y) depends on the diameter of the parison of circular cross section or the diameter of the parison of elliptical cross section, especially its minor axis. That is, the larger the circular parison diameter, the longer the upstream portion (Y) must be for the desired blow molding. The upstream part (Y) is further required to have an extra length between the die and the mold to secure sufficient space to allow the parison remainder to be shredded and the product unloading machine to be operated as described above. It

For example, in a circular parison having a diameter of 350 mm or an elliptical parison having a short diameter of 350 mm, the length of the upstream portion (Y) is preferably at least a length corresponding to the parison diameter (350 mm). In this case, the length of the parison local part (ΔZ) as shown in FIG. 5B between the mold and the upstream part (Y) is 100 to 150 mm.

[0018]

SUMMARY OF THE INVENTION It is an object of the present invention that injection can be performed generally at higher speeds, substantially omitting the low speed initial injection stage as used in the prior art examples described above. At the same time, it is to realize an improved blow molding method and apparatus so that pre-blowing can be performed from the start of injection.

A further object of the present invention is to achieve the above object while minimizing the amount of waste plastic material that becomes burrs per molded product.

[0020]

[Means for Solving the Problems] Using the same apparatus and means as those of the above-mentioned prior art example, both the injection and pre-blow steps for the completion of the parison this time are performed in the previous run, that is, the previous shot cycle is performed. The blow molding method of the present invention is characterized in that the plasticizing material remaining in the upstream portion of the parison and the die is not split and is started as it is, at a relatively high injection speed and at the same time. And
To make this possible, the upstream part of the parison was closed,
That is, it is necessary that the upstream part be separated from the downstream part during the previous run and that the separated lower end be sealed by self-welding by pinch so as to have a sealed free lower end.

According to one example of the present invention, immediately after the mold is closed, the upstream part of the parison is self-welded at its lower end over the entire width, and a downstream part continuous with the upstream part is formed from the upstream part. Separately, the lower end of the upstream part is molded into the closed free end in this run in the same manner as the sealing lower end of the parison the previous time. At the same time, following the pre-blowing process, high-pressure air is blown from the mold into the downstream portion where the parison is separated by using an air needle or the like. Meanwhile, the mold is cooled to solidify the resin.

According to the second example of the present invention, after sealing the free end of the upstream part of the parison of the first example and separating it from the downstream part, the upstream part is heated from mold closing to immediately before the next injection. During this heating step, following the pre-blowing step, high-pressure air is blown into the downstream part of the parison from the mold using an air needle or the like,
And the mold is cooled in the meantime.

According to the third example of the present invention, the free end sealing of the upstream part and the separation from the downstream part in the first example are started not when the mold is clamped but when the molded product is taken out from the mold.

The blow molding apparatus of the present invention is a conventional apparatus in which the blow molding apparatus is self-contained in the vicinity of the top end of the die and above the die locally in order to carry out the first, second and third examples. It is provided with means for welding and separating the parison up and down at the welding points.

In addition, the apparatus has the following for implementing the second example:
Means for heating the separated parison upstream portion having a free closed end immediately after self-welding and upper and lower separation until the start of the next injection is provided.

This heating means is preferably incorporated in the means for self-welding and upper and lower separation.

[0027]

According to the blow molding method of the present invention, the injection can be performed at a substantially constant high speed from the beginning to the end. Therefore, the cycle time can be greatly shortened as compared with the past, and the productivity is improved accordingly.

That is, according to the first and third examples of the present invention, it is possible to shorten the cycle time by the time required for the initial injection stage of the conventional low speed β at the maximum. However, the upstream part of the parison and the local part of the lower end of the downstream part are discarded as burrs as in the conventional example, and there is no particular saving in materials in this respect.

According to the second example, the cycle time is shorter than that in the first and third examples. This is because the upstream part of this parison is used to form part of the downstream part that will be completed in the next run. Moreover, because of that, the material is saved only in the upstream portion as compared with the prior art or the first or third example.

In any case, according to the present invention, since the parison can be injection-molded from the die at a high speed from the beginning, not only the shot cycle time is shortened, but also the raw material of the engineering plastic with remarkable drawdown is obtained. Even if used, the pre-expansion of the parison by pre-blowing can be carried out without any problems, and thus the parison of the desired thickness and shape which guarantees the quality of the molded product can be provided before the mold closing.

[0031]

EXAMPLES Three examples of the present invention will be described below with reference to FIGS. 1 to 8 in comparison with a conventional example.

1, FIG. 2 and FIG. 3, the apparatus of the present invention is a conventional injection machine (not shown) equipped with a conventional die 10 having an annular melt flow path extending downward; A pinch cutting device 30 combined with a heater 40 for heating the upstream part of the parison; a die 10
And a mold provided with a cooling device and an air needle; and a mold clamping device (not shown) for the mold.

The product take-out device 20 has a toggle mechanism 21 in combination with a piston type actuator 22 and a pair of horizontally extending movable arms 23 and 24 for holding the parison 1. The pair of arms 23 and 24 are the dice 10
It is a means for gripping the parison 1 ejected downward from the die 10 through the annular flow path toward the die at a position between the die and the die 50.

The pinch cutting device 30 has a pair of movable rods 31, 32 extending horizontally and in parallel, a toggle mechanism 33 and a piston type actuator 34. As shown in FIG. 4A, the pair of rods 31 and 32 have a pressure contact surface for the parison 1, and the rod 31 is provided with a protruding blade 31a. The protruding blade 31a extends horizontally, and is designed to cut off the parison 1 between the pair of rods 31 and 32 over the entire width thereof in the middle region or the lower end region of the pressure contact surface.

The cutting means is a pair of heaters 31.
b and 32b as shown in FIG. 4B, a pair of rods 3
It may be provided in each of 1 and 32. The pair of heaters are arranged on the pressure contact surface via the heat insulating materials 31c and 32c, and are locally melted over the entire width of the parison, thereby cutting the parison.

The pair of rods 31 and 32 pinch the parison 1 by the actuator 34 via the toggle mechanism 30, thereby self-welding the local parts of the parison pressed by the pair of rods. Next, the protruding blade 31a or the paired heater 31
b and 32b separate the parison into upper and lower parts at the self-welding point. These self-welding and upper and lower cutting are done by the mold 5.
It is executed immediately after 0 is closed or immediately before mold opening.

Heater 4 in combination with pinch cutting device 30
The 0 is designed to surround the parison 1 and functions to heat the separated upstream part of the parison that is coordinated onto the mold from immediately after mold clamping until the start of the next injection.

The product take-out device 20 includes a toggle mechanism 21,
It has a carrier 25 for driving the unit including the actuator 22 and the pair of arms 23, 24 back and forth in the horizontal direction. After the carrier is opened by the movement of the carrier, the separated downstream portion of the parison that forms the molded product is separated into a pair of arms 2
It functions so as to be taken out from the mold while being gripped by 3,24.

The gripping action by the product take-out device 20 is executed immediately before the self-welding and the vertical separation action by the pinch cutting device 30, and the product take-out action by the carrier 25 is carried out immediately after the mold is opened while the downstream part of the parison is held. ..

In the blow molding method of the present invention, an apparatus or heater 40 having all the means described with reference to FIGS. 1, 2, 3 and 4 (a) or 4 (b) is used. It can be carried out using an apparatus equipped with these omitted means.

Three embodiments of the method of the present invention are referred to as case A, case B and case C, and these are shown in FIGS. 5 (a) and 5 (c).
And in comparison with the conventional example shown in FIG. 8, (a) of FIG.
And (b), (a) and (b) of FIG. 6, and FIG. 7 will be described below.

In the diagrams showing the dynamic injection mode expressing the relationship between the injection speed and the time in FIGS. 7 and 8, the area region (X + Y) is formed by case A or a single run in the conventional example. Corresponding to the plastic material forming the perfect parison or its quantity. On the other hand, the area region (Y + X + Y) is the case B or the case C.
Corresponding to a complete parison molded in a single run or its quantity. The area region (Y) corresponds to the upstream part of the parison molded in a single run of cases A, B, C or the conventional example, and the area region (X) forms the molded product of cases A, B, C or the conventional example. It corresponds to the parison part partially received in the mold.

In each case A, B or C, each injection of the run by the injection machine is such that the upstream part (Y) having the closed free lower end of the parison (X + Y) completed in the previous run has the die 10 at its upper end. In the state where it drooped downward continuously with the plastic melt inside,
After opening the mold, it will be started to complete the parison of this run at high speed. In case A, this injection is started when the heating process of the parison upstream portion (Y) described later is completed.

In the mold operation by the mold clamping device, in case A, B or C, the mold closing and the mold clamping are performed with the downstream part of the parison being coordinated between the pair of mold halves. In cases B and C, (X + Y) is displayed, and in case A
The parison downstream part indicated by (X) is separated from the parison upstream part (Y) in cases A and B at the time of molding by the mold, and in case C,
It is integrated with the upper part of the parison. Such a downstream part of the parison corresponds to at least the case where the closed free lower end is excluded from the mold cavity at the lower end in case A, and at least the previous parison completed in the previous run in cases B and C. The free upper end of the sealed upstream portion (Y) is partially received by the mold under conditions where it is excluded from the mold cavity at its lower end.

Plasticization and metering in the injection machine are case A,
In B and C, it is executed for the next run subsequent to the current injection between the mold clamping and the mold cooling.

The operation of pinching and cutting by the device 30 is carried out such that the parison 1 is partially self-welded and then bisected into an upstream portion (Y) and a downstream portion each having a closed free lower end. In case C, this operation is started immediately before mold opening, but in cases A and B, it is started immediately after mold closing.

The parison heating operation by the heater 40 is executed only in case A, and heats the separation upstream portion (Y) having the closed lower end.

The air blowing by the pre-blowing device which is the pre-expansion means for the parison incorporated in the die 10 is started simultaneously with the high speed injection at low pressure in the cases A, B and C.

By means of a blowing device with an air needle incorporated in the mould, in cases A, B and C, inside the downstream part of the parison where air has been partially received in the mould, following the end of the pre-blowing. It is blown at high pressure, which causes the product to be molded to the cavity contour within the mold cavity during cooling.

In order to take out the molded product by the product take-out device 20, in the cases A, B and C, the downstream part of the parison is grasped immediately before the mold is opened at the upper end of the parison, which is out of the top end of the mold, and the downstream part is taken out of the mold. It will be taken out immediately after opening.

The upstream part (Y) of the previous parison was Case A.
In this case, the lower part of the product to be molded in the current run is formed, but in cases B and C, the previous upstream portion (Y) is excluded from the product to be molded in the current run.
Therefore, the current downstream portion (X + Y) including the upstream portion (Y) is taken out from the mold and then discarded as burr.

Although the cycle time of the blow molding run is shortened by Δt in Case A compared with Cases B and C, this is longer than that in Cases B and C by ΔT in the conventional example, and compared with Case A. For example, it becomes longer by Δt + ΔT. However,

[Equation 6] Have a relationship.

In the cases A, B and C of the present invention shown in FIG. 7 and the conventional example shown in FIG. 8, for convenience of illustration, the starting point of product ejection and the starting point of injection are the steps shown in FIGS. 7 and 8. As shown in the figure (Chiato), the simultaneous points are set. However, in reality, the injection is started after a slight delay time of the same degree from the time when the product is taken out. In the cases A, B, and C, this delay time is a time difference for ensuring the timing for avoiding the risk of the tip of the hanging parison contacting the horizontally moving product. In the conventional example, the horizontal movement of the product progresses to some extent, and the pulling-off time required for completing the pulling-off from the die of the upstream part (Y) of the parison substantially corresponds to the delay time.

In any case, this delay time is actually
Even so, since it is about the same time, the four types mentioned above
The relative cycle time difference between cases remains virtually unchanged.
Yes. Discarded in each blow molding run in Cases B and C
Plastic material (remaining parison) (W₁): This time Pariso
Part (Y) of the downstream part (X + Y) of the
(Y) was the last run as the upstream (Y) of the previous parison
Molded parison part]; upper end of downstream part (X + Y)
(ΔX₁); And new following the old preceding part (Y)
Lower end of new part (X + Y) (ΔX₂) Consists of. the above
Upper end (ΔX ₁) And the lower end (ΔX₂) Everyone is a mall
It is in a position that is excluded from Doki-aviity. New part
(X + Y) is molded in the current run. That is W
₁= Y + ΔX₁+ ΔX₂Is. The old leading part
(Y) was air-cooled by the atmosphere in the previous run, and was molded in Paris.
It is not preferable because it is deteriorated as a son.
Not used

Corresponding materials (W ₂ ) to be discarded in case A are excluded from the mold cavity either at the upper end (ΔX ₁ ) and at the lower end (ΔX ₁ ).
X ₂ ). That is, W ₂ = ΔX ₁ + ΔX ₂ . The upstream part (Y) molded in the previous run is not discarded, but on the contrary, the downstream part (X) completed in this run by heating sufficiently
To form the preceding effective portion (Y) of. Therefore, this portion is an old parison portion but has not deteriorated, and the lower end portion (ΔX ₂ ) thereof is excluded from the cavity, and the remaining portion is received by the cavity and forms one part of the molded product.

Corresponding material to be discarded (W ₃ ) of the conventional example
Is composed of the upper part (ΔX ₁ ) and the lower part (ΔX ₂ ) of the old deteriorated upstream part (Y) and the downstream part (X) formed by the current run excluded from the mold cavity, respectively. That is,
W ₃ = Y + ΔX ₁ + ΔX ₂ .

[0057] Case B, the amount of the lower end of C ([Delta] X ₂₎ may reduce somewhat the lower end of the case A and the conventional example ([Delta] X _2). In the case B, the lower end (ΔX ₂ ) of the case B is connected to the old deterioration leading portion (Y) to be excluded from the cavity on the cavity side, whereas the lower end of the case A and the conventional example is connected. This is because (ΔX ₂ ) itself has a free closed lower end.

As a result, the case A of the present invention, from the viewpoint of both saving plastic material and shortening cycle time,
It is the most economical and the most productive of the four cases.

However, the cases B and C of the present invention can provide a molded product of the highest quality among the four types of cases. This is because in the current run only the fresh thermal parison portion (X-ΔX ₁ -Y) molded by high-speed injection is supplied to the mold cavity.

The conventional example can provide a molded product of the second (secondary) best quality. If the quality deterioration due to the drawdown at the initial low-speed injection is ignored, only the fresh thermal parison part (X-ΔX ₁ -ΔX ₂ ) molded with low injection speed and high injection speed in this run is ignored. This is because it is supplied to the mold cavity.

Case A of the present invention provides a molded product whose quality is slightly lower than that of the conventional example, ignoring the problem of drawdown. This is because the upstream part (Y) that was molded in the previous run and then heated is supplied to the mold cavity together with the fresh subsequent part (X-ΔX ₁ -Y) that was molded in this run. That is, the molded product of the case A contains the old material and the fresh material even though the old material is kept hot in the parison completed in the current run. The improvement of the quality of the molded article of Case A depends only on how to heat the old upstream portion (Y) to maintain a desired level corresponding to the temperature condition of the subsequent fresh portion (X-ΔX ₁ -Y). Depends on.

Apparently, the fresh hot parison part which is molded in the current run at high injection speed and which forms the entire molded part of the current run is subject to the disadvantageous drawdown phenomenon and the parison which occur in the engineering plastic material. It can be said that it is the best for obtaining a high quality molded product in light of both of the required temperature conditions.

From this point of view, it can be said that the molded products of the cases B and C or the conventional example are superior in quality to those of the case A. However, the quality of the molded product of the conventional example is somewhat lower than that of the cases B and C. It is a parison part molded with a low injection speed that accelerates the drawdown phenomenon, even though the molded product of the conventional example was molded in the current run,
That is, this is because the parison portion in which the drawdown remarkably occurs is included as the product constituent material.

In cases B and C of the present invention, the heating step using the heater 40 shown in FIG. 2 is not performed. The self-welding process using the pinch cutting device 30 of Case B and the upper and lower cutting processes are performed when the main blow molding is started by the mold 50.
It is carried out when taking out from.

Therefore, in the product take-out device 20 of FIG. 1, in order to implement the case C, the pinch cutting device 30 equipped with the heater 40 is omitted, and instead, the pair of arms 23 and 24 of the take-out device are pinched. The design may be changed to a configuration in which cutting means is provided.

In order to change the design of Case C, the fourth
The heater 3 provided in the pinch means as shown in FIG.
Such cutting means for cutting the parison with 1b and 31c is preferred. This is because the upstream part (Y) of the parison of the case C is exposed to the atmosphere during the mold clamping and becomes semi-solidified at the time of pinch cutting. Further, for the case C, it is preferable to redesign the pair of arms 23 and 24 in FIG. 3 so as to form the pinch means as shown in FIG.

The heating of the upstream part (Y) of the parison of case A is performed from the outside in the embodiment, but the present invention is not limited to this. A heater that heats from the inside of the parison that extends downward from the center of the die 10
And / or may be used in combination with the illustrated external heater 40.

[0068]

According to the method and apparatus of the present invention, since the high speed injection and the pre-expansion of the parison are allowed at the same time from the start of injection, the blowdown phenomenon of the engineering plastic, in which the drawdown phenomenon remarkably appears in the low speed injection, is blow molded. In comparison with the conventional example, the productivity can be improved by shortening the molding cycle time, the quality of the molded product can be improved, the material loss can be reduced, and the yield can be improved.

Further, according to one aspect of the present invention [Case A], the parison part [upstream part (Y)], which should originally be discarded as burrs, can be effectively used as the constituent material of the molded article in the next run. In this case, the material yield is greatly improved.

Incidentally, the parison portion which is conventionally discarded as burr is recycled depending on the material and reused as a raw material. In comparison with this, however, in the case A, the cost reduction can be at least equivalent to the recycling cost. ..

[Brief description of drawings]

FIG. 1 is a front view showing a product take-out device of a blow molding device according to the present invention, a pinch cutting device equipped with a heater, and a die of an injection molding machine.

2 is a bottom view showing a pinch cutting device including the heater of FIG. 1. FIG.

FIG. 3 is a bottom view showing the product extracting device of FIG. 1.

4 (a) and 4 (b) are explanatory views showing examples of the pinch cutting device of FIG. 2, respectively.

FIG. 5 is an explanatory view showing an example of the present invention and a conventional example of the blow molding method, (a) and (b) together show the case A of the present invention, and (a) and (c) together. An example is shown.

FIG. 6 is an explanatory view showing another example of the blow molding method of the present invention, and (a) and (b) together show case B and case C of the present invention.

FIG. 7 is a process time chart showing the processes of cases A, B, and C of the present invention in combination with diagrams showing respective dynamic injection modes.

FIG. 8 is a process time chart corresponding to FIG. 7 showing a process of a conventional example in combination with a diagram showing a dynamic injection mode thereof.

[Explanation of symbols]

 1 ... Parison 10 ... Die 20 ... Product removing device 30 ... Pinch cutting device 40 ... Heater 50 ... Mold α ... High injection speed β ... Low injection speed X, Y ... Parison part 21,33 ... Toggle mechanism 22,34 ... Piston Expression operator 23, 24 ... 1 pair arm 25 ... Carrier 31, 32 ... 1 pair rod 31a ... Projecting blade 31b, 32b ... 1 pair heater 31c, 32c ... Insulation material

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Claims (2)

[Claims] 1. A mold having a die defining a downwardly extending annular melt flow path, a mold including a pair of mold halves defining a cavity arranged below the die and having cooling means. And a blow molding method for producing a hollow plastic molded product to be used in combination with an air blowing means: plasticizing and measuring a plastic material in an injection machine; Injecting into a hollow shape during mold opening; blowing low pressure air from a die into the inside of the injection hollow material during the injection step so that the injection material is partially received later in the cavity In such a blow molding process, which includes a pre-blowing process for forming a long hollow pre-expanded good parison to be formed into a finished product, the parison is completely finished. Both the injection and pre-blowing processes to achieve a relatively high cost under the condition that the previous upstream part with the closed free lower end of the previous parison molded in the previous molding run is integrally suspended with the material remaining in the die. Blow molding method characterized by starting simultaneously at injection speed. 2. A plastic metering material is injected into the atmosphere through an annular melt flow path extending downward from the injection machine, the injection machine having a die having such a flow path; air is injected inside the injection material. A pre-blowing means incorporated in the die for shaping the injection material into a good pre-expanded hollow parison to be subsequently formed into a finished article; a pair of halves having cooling means and defining cavities A mold disposed below the die containing the mold; mold clamping means for closing the mold with the parison partially received; and gripping the parison portion excluded from the mold at its top end, In a blow molding machine for producing a hollow plastic article comprising means for removing the parison portion and the series of articles from the die when opened, the parison is placed on top of the die with its apex. Self-welding the entire width in the adjacent region, and at least the free lower end of the lower part of the parison is excluded from the cavity at its lower end, while the lower part of the parison is partially received by the mold. Means for separating and separating the parison up and down so that the resulting top of the parison has a closed free lower end; and means for heating the top of the parting parison after completion of self-welding and cutting of the parison until immediately before the next injection. A blow molding device characterized by being configured to include.