JPH04201316A - Exchanging method for material and color in blow molding machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Graduation Field of Application] The present invention forms a cylindrical resin tube called a parison by injecting the resin inside a die, and after sandwiching this between molds, it is poured into the parison. This relates to a material change and color change method in a blow molding machine, etc., which obtains a hollow product by blowing gas such as air and cooling it as it is.

[Prior Art] This type of blow molding machine is conventionally constructed like a molding machine. That is, above the mold, which is divided into left and right parts with a vertical joint surface as the border, and which is opened and closed by a mold opening/closing cylinder, there is a vertical die that injects the parison between the cavities of the opened left and right molds. A resin supply device is attached to this die. FIG. 2 is a schematic cross-sectional view of a conventional resin supply device of this type. This will be explained based on the figure. The die 1 has a cylindrical accumulator 2 connected to the resin passage 3 at the front end. The front end of the accumulator 2 is connected to a resin passage 5 formed at the tip of an extruder 4 orthogonal thereto.

A screw 7 is rotatably fitted into the inner hole 4a of the extruder 4, and a plunger 8, which moves forward and backward by being driven by an injection cylinder (not shown), is fitted into the inner hole 2a of the accumulator 2. There is. 9 is a second on-off valve that opens and closes the resin passage 5, and 10 is a first on-off valve that opens and closes the resin passage 3.

The extruder 4, accumulator 2, die 1, resin passages 3, 5, etc. are heated to a temperature equal to the resin temperature under the molding conditions.

With this configuration, when the second on-off valve 9 is opened and the first on-off valve 10 is closed, resin is supplied from a hopper (not shown) to the inner hole 4a of the extruder 4 and heated. When the screw 7 is rotated, the resin is melted and the molten resin 11 (hereinafter simply referred to as resin 11) is stored in the accumulator 2 while retracting the plunger 8 as shown by the chain line 8a. Next, when the second on-off valve 9 is closed and the first on-off valve 10 is opened to advance the plunger 8, the resin 11 is supplied to the die 1 through the resin passage 3.

Next, the resin 11 hangs down from the die 1 to form a parison, and finally the male and female molds are clamped, cooled, and taken out as a product, completing one cycle. In this way, a desired series of molding is performed.

[Problems to be Solved by the Invention] When changing the material or color of the resin 11 using such a conventional resin supply device, the second on-off valve 9 is opened and the first on-off valve 10 is closed. In this state, when the screw 7 in the extruder 4 is rotated and the plunger 8 is moved back at the same time, the resin 11 is transferred from the extruder 4 side to the accumulator 2.
stored within.

Next, when the on-off valve 9 is closed and the on-off valve 10 is opened to move the plunger forward, the resin 11A that entered the extruder 4 and the accumulator 2 first is pushed by the resin 11 that entered later and is discharged from the die 1. .

Thereafter, the above-described series of operations are repeated again to change the material or color.

However, such a series of operations for changing materials and changing colors is also performed by the extruder 4, the resin passages 3, 5. Replace old resin 11A attached to die 1 and accumulator 2 with new resin 1.
If the resin is not replaced quickly and completely in step 1, it will take a long time to change the resin and color, and a large amount of resin will be wasted. The present invention has been made in view of the above points, and aims to reduce the amount of resin retained in the accumulator and to shorten the time required for changing resins and changing colors.

[Means to solve the problem]

In order to achieve such an object, the present invention includes an accumulator having a front end resin passage joined to a die, an extruder having a front end resin passage joined to this accumulator, and a rotatably fitted into an inner hole of the extruder. a first opening/closing valve that opens and closes a resin passage between the die and the accumulator, the first opening/closing valve having an injection plunger fitted into the inner hole of the accumulator so as to be freely retractable; In a blow molding machine equipped with a second on-off valve that opens and closes a resin passage, the first on-off valve and the second on-off valve are operated when changing materials or colors in the extruder, accumulator, die, and each resin passage. While the screw is kept open and the screw is continuously rotated, the injection plunger is moved forward and backward in small increments at or near the injection plunger advance limit.

[Effect]

When changing the resin material and color, the first on-off valve and the second
While keeping the on-off valve always open and moving the injection plunger back and forth little by little at the injection plunger position at or near the forward limit,
Moreover, when the screw of the extruder is rotated, the new resin from the extruder is smoothly extruded while extruding the old resin remaining in the extruder, the accumulator, and each resin passage.
Materials and colors can be changed in a short time and with less resin.

〔Example〕

FIG. 1 shows an embodiment of a blow molding machine showing a method for changing materials and changing colors in a blow molding machine according to the present invention, and is a schematic side view of a blow molding machine in which the method is implemented.

In the figure, a blow molding machine 20 includes a pair of platens 21 erected on a floor, and molds 22 and 23 each having a vertical joint surface are fixed to each platen 21, respectively. Mold opening/closing cylinders 25.26 are respectively fixed to the cylinder stands 24 provided outside the left and right platens 21, and the piston rods of these mold opening/closing cylinders 25.26 are connected to the molds 22.23. are respectively attached, and the molds 22 and 23 are configured to be opened and closed by moving the piston rods forward and backward.

A vertical die 1 equipped with a control device 27 is provided directly above the joint surface of the mold 22, 23, and a resin supply device, generally indicated by the reference numeral 30, is attached to this die 1. . This resin supply device 30 includes an accumulator 2 formed in a cylindrical shape and having a resin passage 3 at its front end joined to a die 1. The formed resin passage 5 is joined. In this device, the joint of the extruder 4 to the accumulator 2 is set to be located near the retraction limit of the plunger 8, which will be described later. A screw 7 is rotatably fitted into the inner hole 4a of the extruder a4, and the extruder 4 is provided with a hopper 36 serving as a supply port for supplying the resin in the form of an internal heave.

10 is a first on-off valve that opens and closes the resin passage 3;
9 is a second on-off valve that opens and closes the resin passage 5. In addition, the extruder 4, accumulator 2, die 1, resin passage 3.5
etc. are heated to a temperature that is substantially equal to the resin temperature under the molding conditions.

The operation of the blow molding machine configured as above will be explained. With the second on-off valve 9 open and the first on-off valve 10 closed, pellet-shaped resin is supplied from the hopper 36 to the inner hole 4a of the extruder 4 and the screw 7 is rotated while heating it. The resin is melted and the molten resin 11 is stored in the accumulator 2 while the plunger 8 is retracted.

Next, when the second on-off valve 9 is closed and the first on-off valve 10 is opened to advance the plunger 8, the resin 11 is supplied to the die 1 through the resin passage 3. The resin 11 supplied to the die 1 is injected into the cavities of the opened molds 22° and 230 to form a parison, which is a resin cylinder. After this is sandwiched between the molds 22° and 23, When a gas such as air is blown into the parison and the resin is then cooled and fixed, a hollow molded product is obtained.

Next, in the material change and color change operations, the injection plunger 8 is moved forward or close to the forward limit position (for example, the injection plunger 8 is moved forward within a small stroke of about 5 to 20 mm from the forward limit position).
The most effective method is to move the injection plunger 8 forward and backward in small increments.
Additionally, materials and colors could be changed in a short time.

As the above knowledge shows, the basic operations for changing materials and changing colors are to keep the first on-off valve 10 and the second on-off valve 9 open at all times, and can be roughly divided into the following two methods. That is, the first method is carried out with the injection plunger 8 kept at its forward limit. New resin 1 discharged as the screw 7 fitted in the extruder 4 continuously rotates.
1 is a space 12 in front of the resin passage 5 and the accumulator 2 (the forward limit of the injection plunger 8 and the front end inner wall 2b of the accumulator 2).
space created between) The speed of the resin 11 when passing through the resin passage 3 is such that the passing area can be maintained in a state without unevenness, and
It becomes big because it can be made small. As a result, a shearing action is exerted on the wall surface by the circulation of the new resin 11, and the old resin 11A and the new resin 11 on the wall surface can be easily replaced.

The second method is to move the injection plunger 8 forward and backward in small increments near the forward limit position of the injection plunger 8. New resin 11 discharged as the screw 7 fitted in the extruder 4 continuously rotates passes through the resin passage 5 and is then accumulated in the accumulator front space 12. New resin 1 to the accumulator front space 12
1, the injection plunger 8 is forcibly retreated to a desired position, and then the injection plunger 8 is moved forward by a drive source for the injection plunger 8 (not shown).

The distance that the injection plunger 8 moves back and forth is determined by the distance of the resin supply device 3.
A small stroke of about 5 to 20 mm can be selected depending on the amount of the old resin 11A remaining in the cylinder 0, the degree of non-uniformity of the thermal history, etc.

That is, resin 11A with a small amount of residual resin and old
If the degree of non-uniformity of the thermal profile due to the retention of
(for example, 5 plates), and conversely, if the amount of residual resin is large and the degree of non-uniformity of the thermal history due to the retention of old resin 11A is large, the forward and backward stroke of the injection plunger 8 should be made as large as possible (for example, 20 m1+). . As the forward and backward stroke amount of the injection plunger 8 increases, the amount of new resin 11 accumulated in the space 12 in front of the accumulator increases, and the supply speed of the resin 11 sent to the die 1 side by the advancement of the injection plunger 8 increases. As a result, a large shearing action acts on the old resin 11A remaining in the front end inner wall 2b of the accumulator and the resin passage 3, and it can be easily replaced with new resin.

In the first place, in order to improve material and color changes, it is necessary to do the following.

(1) Inside the extruder 4, resin passages 3 and 5, accumulator 2
The inside and the die 1 etc. are shaped so that the resin 11 does not accumulate, and the resin is replaced sequentially in the flow direction of the resin 11.

(2) Peel off the old resin 11A from the wall using a high shearing rate.

Of these, (1) is determined by the shape of each part, and (2) is determined by the procedures and conditions for changing materials and colors, and the type of material.

As described above, in order to make the first method and the second method possible, the present invention can be carried out by the synergistic effect of (1) and (2), and the entire material change and color change are possible. is carried out extremely smoothly, quickly and reliably.

Furthermore, according to the present invention, it is clear that the same effect of promoting material change and color change as described above also extends to the dice 1 located downstream of the accumulator.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, there is provided an accumulator in which a front end resin passage is joined to a die, an extruder in which a front end resin passage is joined to this accumulator,
The extruder is equipped with a screw rotatably fitted into the inner hole of the extruder, and an injection plunger fitted into the inner hole of the accumulator so as to be freely retractable, and the injection plunger opens and closes the resin passage between the die and the accumulator. 1 on-off valve, and a 2nd on-off valve that opens and closes the resin passage between the accumulator and the extruder.
In a blow molding machine equipped with an on-off valve, when changing the material or color inside the extruder, accumulator, die, or each resin passage, the first on-off valve and the second on-off valve are kept open, and the screw is closed. After continuous rotation, the injection plunger is moved forward and backward in small increments at or near the forward limit of the injection plunger, which allows the injection plunger to approach a shape that does not allow resin to accumulate, and also improves the resin speed. Because the shear rate can be increased, the old resin can be easily peeled off and the shear rate can be increased.
In other words, a synergistic effect is exhibited in which the material change and color change effects are enhanced.

Therefore, the time for changing materials and changing colors is shortened, productivity is improved, and resin is not wasted during preparatory work, resulting in a reduction in resin consumption.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of a blow molding machine showing the material change and color change method of the blow molding machine according to the present invention, a schematic side view of the blow molding machine in which this is implemented, and Fig. 2 shows a conventional method for changing the material and color of this type of blow molding machine. FIG. 2 shows a schematic cross-sectional view of the supply device. 1...Dice, 2...Accumulator, 2a...
Accumulator inner hole, 2b... Accumulator front end inner wall, 4... Extruder, 4a... Inner hole of extruder, 3, 5
... Resin passage, 7... Screw, 8... Plunger, 9... Second on-off valve, 10... First on-off valve, 1
1...New resin, 11A...Old resin, 12...
・Accumulator front space, 20... blow molding machine,
21...Platen, 22° 23...Mold, 25.2
6... Mold opening/closing cylinder, 30... Resin supply device. Figure 1

Claims (1)

[Claims] an accumulator whose front end resin passage is joined to the die;
An extruder having a front end resin passage connected to the accumulator, a screw rotatably fitted into an inner hole of the extruder, and an injection plunger fitted into the inner hole of the accumulator so as to be freely retractable. A blow molding machine comprising: a first on-off valve that opens and closes a resin passage between the die and the accumulator; and a second on-off valve that opens and closes the resin passage between the accumulator and the extruder; When changing the material or color in the die and each resin passage, the first on-off valve and the second on-off valve are kept open, and the injection plunger is moved to the forward limit or A method for changing materials and changing colors in a blow molding machine, which is characterized in that the injection plunger is moved forward and backward in small increments at a position near the injection plunger.