JP3393940B2 - Cylindrical molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tubular body molding machine for extruding a tubular body such as a parison used for blow molding.

[0002]

2. Description of the Related Art The head of a tubular body molding machine for molding a parison is, for example, as shown in FIG. 6, a housing 1, a screw type extruder 2 for melting a plastic and supplying it into the housing 1, and a housing 1 inside. Mounted on the ring 3, a ring plunger 4 inserted into the ring 3 and movable in the axial direction, a ring die 5 attached to the lower portion of the housing 1, and a shaft inserted into the ring plunger 4. It consists of a rod 6 whose position can be adjusted in any direction, and a core die 7 attached to the tip of the rod 6, and the melted plastic passes through a supply port 8, a ring-shaped space 9 and a ring-shaped slit 10 and in front of the ring plunger 4. Storage room 11
Is temporarily stored in. Then, the ring plunger 4 advances downward to push out the plastic accumulated in the storage chamber 11 through the die hole 12 to form a cylindrical parison. 6 shows a state in which the ring plunger 4 is lowered in the left half and a state in which it is raised in the right half.

The tubular body molding machine of this type is currently the mainstream as a tubular body molding machine for molding a parison in blow molding, but has the following problems. First, when the molten plastic enters the ring-shaped space 9 from the supply port 8, a weld is formed on the opposite side of the supply port 8. The weld means a welded portion which is formed when the left and right plastics entering the ring-shaped space 9 from the supply port 8 meet and weld on the opposite side of the supply port 8. In the case of molding a parison for blow molding, Since the melting temperature is set lower than the melting temperature in general injection molding, for example, the welding may become insufficient and the strength of the portion may be insufficient.

The plastic melted in the screw type extruder 2 and supplied from the supply port 8 is accumulated in the storage chamber 11 through a long flow path (a ring-shaped space 9 and a ring-shaped slit 10) so as to have a uniform cylindrical shape. As a result, the melting temperature is maintained for a long time, and the plastic easily deteriorates due to heat (the deteriorated product is called "burning"). In particular,
It is difficult to use vinyl chloride, nylon, polycarbonate, ABS resin, etc., which easily cause “burn”. At the same time, since there is a long time from when the plastic reaches the melting temperature to when the plastic is extruded in the screw type extruder 2, there is a problem that temperature unevenness in the circumferential direction easily occurs.

Such a "burn" is caused by the ring-shaped space 9
Since it adheres to the side wall on the side opposite to the supply port 8 or the side wall of the ring-shaped slit 10 and is difficult to be discharged, it takes time to replace the kind of plastic (for example, in the case of color change,
The color of old plastic is always mixed with new plastic). It should be noted that the "burn" is likely to occur on the side wall of the flow path where the plastic flow is stagnant, and is unlikely to adhere to the movable part, that is, the ring plunger 4 and its periphery.

Since the flow of plastic in the flow path after the ring-shaped space 9 is all in the vertical direction and the extrusion direction is also in the vertical direction, the molecules of the plastic are oriented vertically and are strong in the pulling in the vertical direction. It is easy to create a parison that is weak against lateral pulling. A parison having such strength characteristics may tear vertically when blown.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the conventional tubular body forming machine, and the tubular body forming machine has no weld and has a uniform perimeter, particularly The objectives are to obtain a parison for blow molding, to suppress thermal deterioration of plastics, to obtain a tubular body having improved lateral tensile strength, and the like.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a tubular body molding machine particularly suitable for molding a blow molding parison,
This tubular body molding machine is provided with a housing having a cylindrical inner wall having a plastic material supply port, a screw provided on the outer periphery, rotatable in the housing, and movable in the axial direction, and supplied into the housing. And a cylindrical screw plunger that melts the plastic and pushes it forward to accumulate it, and then pushes it out from the die hole, a rod that extends through the center of the screw plunger in the axial direction, and the cylinder. Ring die arranged on the extrusion side of the cylindrical housing, a core die attached to the rod and forming the die hole together with the ring die inside the ring die, and a plastic unmelted material is supplied to the supply port. A supply means is provided. The screw may be a screw propeller. Further, a backflow prevention mechanism is provided on the outer periphery of the screw plunger, if necessary.

[0009] the cylindrical body molding machine, e Bei advancing and retracting mechanism for advancing and retracting the rotating mechanism and axially rotating the screw plunger, said reciprocating mechanism by forward and backward the rotary mechanism connected to the rotating mechanism, It is configured to allow the screw plunger to rotate and move back and forth. Further, if the position of the rod inserted through the inside of the screw plunger can be adjusted in the axial direction, or conversely, the position of the ring die can be adjusted in the axial direction (both combinations may be used),
The distance between the ring die and the core die can be adjusted, and the wall thickness of the tubular body extruded from the die hole can be adjusted. The housing is preferably heated by a heater.

[0010]

In the above tubular molding machine, unmelted plastic material (pellets, powder, granules, etc.) supplied into the cylindrical housing from the supply port by an appropriate supply means (eg screw system, chute system, etc.) Is gradually melted by the shearing heat generated by the rotation of the screw plunger and the heat transfer from the heated inner wall of the housing, and at the same time, it is deaerated by the strong compressive force and stirring action. The plastic melted in the housing is pushed forward by the pressure of the screw rotation, and at the same time, the screw plunger retracts in the housing under the pressure of the pushed plastic, and the molten plastic is pushed forward of the screw plunger. Accumulates. At this time, in order to prevent the screw plunger from freely retreating and make the molten state of the plastic uniform, it is preferable to apply back pressure to the screw plunger by the advancing and retracting mechanism.

When the molten plastic has accumulated once in front of the screw plunger, the screw plunger is advanced by the advancing / retreating mechanism and pushed out through the die hole to form a tubular body. At this time, the backflow prevention mechanism provided on the outer periphery of the screw plunger has a function of preventing the accumulated plastic from flowing back to the side of the screw plunger. Since the high plastic itself has a function of preventing backflow, a special backflow prevention mechanism may not be needed when, for example, a thick cylindrical body is extruded. On the other hand, during the above operation of the screw plunger, the plastic is more viscous or unmelted in the upper part of the housing, which prevents the molten plastic from flowing back and leaking to the upper part of the housing. After extrusion, it is preferable that the amount of plastic remaining in front of the screw plunger be as small as possible (particularly, in the case of plastic that easily deteriorates due to heat).

In the conventional tubular molding machine, molten plastic was supplied into the housing. However, in the tubular molding machine of the present invention, the molten plastic is directly melted in the housing, so that no weld occurs and the circumferential direction is increased. It is possible to obtain a uniform tubular body. Further, since the melted plastic does not pass through the long flow path, the time to be maintained at the melting temperature is short and the thermal deterioration can be prevented. Further, since the time from melting to extruding can be shortened, temperature unevenness hardly occurs.

The plastic in the housing is kneaded by a screw so that the molecules are helically oriented and subsequently oriented vertically when extruded through a die hole. In the conventional tubular body molding machine, it was oriented only in the vertical direction through a long flow path, but in the tubular body molding machine of the present invention, since it is oriented in a spiral shape (horizontal direction) and then oriented in the vertical direction, It is possible to obtain a tubular body that is strong against pulling in the direction.

Further, in the above-mentioned tubular molding machine, heat deterioration is less likely to occur and at the same time, there are few places where "burn" adheres (does not adhere to the screw plunger portion), so that the plastic in front of the machine can be kept in the flow path forever. It does not remain on the surface, and the color change of the plastic is completed in a short time.

[0015]

Embodiments of the present invention will be described below with reference to FIGS. The tubular molding machine shown in FIGS. 1 to 4 includes upper and lower fixing plates 20, 21 and four rods 22 for connecting and fixing them, and a central portion of the lower fixing plate 21 connected to the lower fixing plate 21. A cylinder 24 having an inner wall connected to the formed hole 23, a cylindrical screw plunger 25 arranged in the cylinder 24, and a rod 2 inserted in the center of the screw plunger 25 and extending in the axial direction.
6, a ring die 27 attached to the pushing side of the cylinder 24, and a ring die 2 attached to the rod 26.
7, a core die 28 and the like disposed inside 7. In addition,
In the present embodiment, the lower fixing plate 21 and the cylinder 24 form the housing of the present invention.

A sleeve 30 is fixed to the upper portion of the screw plunger 25, and a rotating mechanism 31 for rotating the screw plunger 25 is arranged around the sleeve 30.
The rotating mechanism 31 includes a reduction gear box 32, a plurality of gears arranged therein, that is, a large diameter gear 33 fixed to the outer periphery of the sleeve 30, and a drive motor 34 fixed to the gear box 32. 35, and a gear 3 that is pivotally supported by the gear box 32 and connects the gear 33 and the gear 35.
It consists of 6 mag. The sleeve 30 and the gear box 32 are connected via a cylindrical roller bearing 37 and a tapered roller bearing 38 so that they can rotate relative to each other, but they do not move relative to each other in the axial direction. In addition, 2 on the outside of the gear box 32
One guide member 39 is attached, and its guide hole is slidably fitted in the rod 22 to guide the vertical movement of the gear box 32 and also serves as a stopper for preventing the gear box 32 from rotating.

A hydraulic cylinder 40 is mounted on the upper fixing plate 20, and a piston rod 41 of the hydraulic cylinder 40 extends downward through the upper fixing plate 20 and is connected to a gear box 32, which move the screw plunger 25 forward and backward. Configure the mechanism. That is, when the piston rod 41 expands and contracts, the gear box 32 moves up and down,
The screw plunger 25 moves back and forth in the axial direction.

The screw plunger 25 is a rod 26.
Is rotatable around and axially slidable. The piston 42 is attached to the upper end of the rod 26.
The piston 42 is supported in the cylinder 43 so that its vertical position can be adjusted, and the vertical position of the core die 28 can be adjusted to adjust the distance between the ring die 27 and the core die 28 to adjust the wall thickness of the parison. ing.

In the lower fixing plate 21, a horizontal through hole 45 connecting the hole 23 and the outside is formed, in which a feed screw 46 is rotatably installed, and a hopper 47.
The plastic pellets can be supplied from the inside into the housing. In addition, 48 is a check ring for preventing backflow, 49 is a heater, and 50 is a feed screw 4.
6 is a motor for driving 6.

Next, the operation of the tubular body molding machine will be described. Assuming that the screw plunger 25 is at the position shown in FIG. 1, first, the screw plunger 25 is rotated under the back pressure applied by the cylinder 40, and the plastic pellets are supplied from the hopper 47 through the through hole 45 into the hole 23. To do. The plastic pellets are heated by the heat transfer from the inner wall and screw plunger 25
Is sent downward by the rotation of the
It is heated by heat transfer from the inner wall and self-heated and melted by the shearing action accompanying the rotation of the screw plunger 25. As the plastic is plasticized and the pressure increases as it is sent downward in the cylinder 24, the plastic is pushed out through the check ring 48 into the storage chamber 51 in front of the screw plunger 25, where it accumulates, The accumulated plastic pressure causes the screw plunger 25 to retreat against the back pressure.

When a predetermined amount is stored in the storage chamber 51 (see FIG. 3)
State), the screw plunger 25 is lowered by the pressure of the cylinder 40, and the plastic accumulated in the storage chamber 51 is extruded through the die hole 52 to form a parison. At this time, it is desirable to design so that the plastic remaining in front of the screw plunger 25 is reduced as much as possible.

FIG. 5 shows another embodiment of the core die 28a.
The upper and lower positions are fixed and the ring die 27a can be vertically adjusted (the other configurations are almost the same). That is, the rod 26a that supports the core die 28a is fixed to the fixed plate 20a, while the ring die 27a penetrates the fixed plates 20a and 21a and extends vertically through the adjustment rod 55, and the hydraulic cylinder 43.
It is attached to the piston rod 56 of a. Cylinder 4
By the action of 3a, the ring die 27a slides up and down within the cylinder 24a within a predetermined range, and the ring die 27a and the core die 2
The thickness of the parison can be adjusted by adjusting the interval of 8a.

[0023]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a tubular body having no weld and uniform temperature around the entire circumference, particularly a parison for blow molding. Further, the thermal deterioration of the plastic can be suppressed, the plastics such as the color change can be replaced in a short time, and the plastic material which easily deteriorates can be used. Further, it is possible to obtain a tubular body having an improved tensile strength in the lateral direction.

[Brief description of drawings]

FIG. 1 is a half sectional view of a tubular body molding machine when a screw plunger is lowered.

FIG. 2 is a sectional view taken along line AA of FIG. 1 (partially omitted).

FIG. 3 is a half sectional view of the tubular body molding machine when the screw plunger is retracted.

FIG. 4 is a plan view of the tubular body molding machine.

FIG. 5 is a half sectional view of another embodiment.

FIG. 6 is a cross-sectional view of a conventional tubular body molding machine.

[Explanation of symbols]

24 cylinders 25 screw plunger 26 rod 27 ring die 28 core dies 31 rotation mechanism 32 gearbox 39 Guide member 40, 43 cylinders 48 Check ring for backflow prevention

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) B29C 49/00-49/80 B29B 11/10

Claims (2)

(57) [Claims] 1. A housing provided with a plastic material supply port and having a cylindrical inner wall, and a screw provided on the outer periphery of the housing, which is rotatable and axially movable back and forth in the housing. A cylindrical screw plunger that melts and pushes forward to accumulate, and then pushes it out of the die hole.
A rod inserted through the screw plunger and extending in the axial direction, a ring die arranged on the extrusion side of the cylindrical housing, and a die hole attached to the rod and inside the ring die together with the ring die. And a supply means for supplying a plastic unmelted material to the supply port , further comprising the screw plan
A rotating mechanism that rotates the jar and an advance and retreat that advances and retracts in the axial direction.
A mechanism, the advancing / retreating mechanism is connected to the rotating mechanism,
It is designed to move the rolling mechanism back and forth, and fixed bottom play
Screw plunger between the top and the upper fixing plate
The rotating mechanism is arranged on the upper part of the
A tubular body forming machine characterized in that an advancing / retreating mechanism is attached to a fixed plate . 2. A housing provided with a plastic material supply port and having a cylindrical inner wall, and a screw provided on the outer periphery of the housing, which is rotatable and axially movable back and forth in the housing, and supplies the plastic supplied into the housing. A cylindrical screw plunger that melts and pushes forward to accumulate, and then pushes it out of the die hole.
A rod inserted through the screw plunger and extending in the axial direction, a ring die arranged on the extrusion side of the cylindrical housing, and a die hole attached to the rod and inside the ring die together with the ring die. And a supply means for supplying a plastic unmelted material to the supply port , further comprising the screw plan
A rotating mechanism that rotates the jar and an advance and retreat that advances and retracts in the axial direction.
A mechanism, the advancing / retreating mechanism is connected to the rotating mechanism,
It is designed to move the rolling mechanism back and forth, and fixed bottom play
Screw plunger between the top and the upper fixing plate
The rotating mechanism is arranged on the upper part of the
The lower fixing plate and a system connected to the lower fixing plate.
It consists of a Linda, and further moves back and forth on the upper fixed plate
A tubular body molding machine having a structure attached thereto.