JP2773429B2 - Material change and color change method of blow molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention forms a cylindrical resin tube called a parison by injecting a resin in a die, inserts this in a mold, and then inserts it into the parison. The present invention relates to a material change and color change method in a blow molding machine or the like that obtains a hollow product by blowing a gas such as air and then cooling it.

[Conventional technology]

This type of blow molding machine is conventionally configured as follows. That is, a vertical die for injecting the parison into the space between the cavities of the opened left and right dies is provided above the dies which are divided into right and left divided by the vertical joint surface and opened and closed by the opening and closing cylinders. This die is provided with a resin supply device. FIG. 2 is a schematic cross-sectional view of a conventional resin supply apparatus of this type. Referring to FIG. 2, a cylindrical accumulator 2 is provided in a die 1 with a resin passage 3 at a front end. Further, a resin passage 5 formed at the front end of the extruder 4 orthogonal to the accumulator 2 is connected to the front end of the accumulator 2. A screw 7 is rotatably fitted in the inner hole 4a of the extruder 4, and a plunger 8 which is driven by an injection cylinder (not shown) to advance and retreat is fitted in the inner hole 2a of the accumulator 2. I have. Reference numeral 9 denotes a second opening / closing valve for opening / closing the resin passage 5, and reference numeral 10 denotes a first opening / closing valve for opening / closing the resin passage 3. Note that the extruder 4, the accumulator 2, the die 1, the resin passages 3, 5, and the like are heated so as to have a temperature substantially equal to the resin temperature under the molding conditions.

With this configuration, the second on-off valve 9
Is opened and the first on-off valve 10 is closed, a resin is supplied from the hopper (not shown) to the inner hole 4a of the extruder 4 and the screw 7 is rotated while heating the resin. Molten resin 11 (hereinafter simply referred to as resin 11) is stored in accumulator 2 while retreating plunger 8 as shown by chain line 8a. Next, when the second on-off valve 9 is closed and the first on-off valve 10 is opened to move the plunger 8 forward, 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. Finally, the male and female molds are clamped, cooled, taken out as a product, and one cycle is completed. Thus, a desired series of molding is performed.

[Problems to be solved by the invention]

When the material or the color of the resin 11 is changed using such a conventional resin supply device, the screw in the extruder 4 is opened with the second on-off valve 9 opened and the first on-off valve 10 closed. When the plunger 8 is simultaneously retracted while rotating the resin 7, the resin 11 is stored in the accumulator 2 from the extruder 4 side. Next, when the on-off valve 9 is closed and the on-off valve 10 is opened to advance the plunger, the resin 11A that has entered the extruder 4 and the accumulator 2 is pushed by the resin 11 that has entered later and is discharged from the die 1. . Thereafter, the material change or the color change is performed again by repeating the above-described series of operations.

However, the series of operations for material change and color change can be performed quickly, completely and completely by replacing the old resin 11A adhering to the extruder 4, the resin passages 3 and 5, the die 1 and the accumulator 2 with the new resin 11. Otherwise, a long time is required for resin change and color change, and there is a problem that a large amount of resin is wasted. The present invention has been made in view of the above points, and has as its object to reduce the stagnation of resin in an accumulator and to shorten the time for resin change and color change.

[Means for Solving the Problems] In order to achieve such an object, in the present invention, 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, A first opening and closing mechanism for opening and closing a resin passage between the die and the accumulator, comprising: a screw rotatably fitted to an inner hole of the machine; and an injection plunger fitted to advance and retreat to the inner hole of the accumulator. In a blow molding machine provided with a valve and a second opening / closing valve for opening and closing a resin passage between the accumulator and the extruder, the extruder, the inside of the accumulator, the die and the material change and color change in each of the resin passages may be replaced with the second one. While the first and second on-off valves and the second on-off valve are kept open and the screw is continuously rotated, the forward end of the injection plunger or the vicinity thereof is not changed. The injection plunger is advanced and retracted little by little at the injection plunger position.

[Action]

At the time of resin material change and color change, the first on-off valve and the second on-off valve are always opened, and the injection plunger is moved back and forth in small increments at or near the forward end of the injection plunger and at the same time as the extruder. When the screw is rotated, new resin from the extruder extrudes old resin remaining in the extruder, accumulator and each resin passage, and in a short time, material change and color change are performed with less resin in a short time. It is.

〔Example〕

FIG. 1 is a schematic side view of a blow molding machine showing an embodiment of a blow molding machine showing a material change and a color changing method of the blow molding machine according to the present invention. In the drawing, a blow molding machine 20 includes a pair of platens 21 erected on a floor, and each platen 21 has a mold having a vertical joining surface.
22,23 are fixed respectively. Each cylinder table 24 provided outside the left and right platens 21 has a mold opening / closing cylinder 2
The molds 22 and 23 are respectively mounted on the piston rods of the mold opening / closing cylinders 25 and 26, and the molds 22 and 23 are moved by moving the piston rods back and forth. Are configured to be opened and closed.

A vertical die 1 provided with a control device 27 is provided directly above the connection surfaces of the dies 22 and 23.
A resin supply device generally indicated by reference numeral 30 is provided. The resin supply device 30 includes an accumulator 2 which is formed in a cylindrical shape and has a resin passage 3 at a front end joined to a die 1. The accumulator 2 is provided at a tip end of an extruder 4 orthogonal to the accumulator 2. The formed resin passage 5 is joined. In the present apparatus, the joint of the extruder 4 to the accumulator 2 is set so as to be located near the retreat limit of the plunger 8 described later. A screw 7 is rotatably fitted in the inner hole 4a of the extruder 4,
Further, the extruder 4 is provided with a hopper 36 as a supply port for supplying the resin in the form of pellets to the inside thereof.

Reference numeral 10 denotes a first opening / closing valve for opening / closing the resin passage 3;
Reference numeral 9 denotes a second on-off valve for opening and closing the resin passage 5. Note that the extruder 4, the accumulator 2, the die 1, the resin passages 3, 5, and the like are heated so as to have a temperature substantially equal to the resin temperature under the molding conditions.

The operation of the blow molding machine configured as described above will be described. When the second opening / closing valve 9 is opened and the first opening / closing valve 10 is closed, the 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 them. 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 move the plunger 8 forward, the resin 11 is supplied to the die 1 through the resin passage 3. Resin supplied to die 1
11 is injected aiming at both cavities of the opened molds 22 and 23, and a parison which is a resin cylinder is formed.After being sandwiched between the molds 22 and 23, air or the like is injected into the parison. Gas is blown in. After that, when the resin is cooled and fixed,
A hollow molded article is obtained.

Next, in the material change and color change operations, the injection plunger 8 is used.
The most effective method is to advance or retreat the injection plunger 8 in small increments at or near the forward limit position (for example, advance or retract within a short stroke of about 5 to 20 mm from the forward limit position of the injection plunger 8). With a small amount of resin 11, material change and color change could be performed in a short time.

As described above, the basic operations for material change and color change both involve keeping the first opening / closing valve 10 and the second opening / closing valve 9 always open, and are roughly classified into the following two methods. That is, the first method is performed with the injection plunger 8 kept in the forward limit state. New resin 11 discharged with the continuous rotation of the screw 7 fitted in the extruder 4
The velocity of the resin 11 when passing through the resin passage 3 is as follows: the space 12 formed between the accumulator front space 12 (the forward end of the injection plunger 8 and the front end inner wall 2b of the accumulator 2).
The passage area can be kept in a state without irregularities and can be made small, so that it becomes large. As a result, new resin 11
With the circulation of, a shearing action acts on the wall surface, and the old resin 11A and the new resin 11 on the wall surface are easily replaced.

In the second method, the injection plunger 8 is advanced and retracted little by little near the forward limit position of the injection plunger 8. New resin 11 discharged with the continuous rotation of the screw 7 fitted into the extruder 4 passes through the resin passage 5 and is temporarily accumulated in the accumulator front space 12. In order to encourage the accumulation of new resin 11 in the accumulator front space 12, the injection plunger 8 is forcibly retracted to a desired position as appropriate, and then the injection plunger 8 is advanced by a driving source of the injection plunger 8 (not shown).

The forward and backward travel distance of the injection plunger 8 is determined by the resin supply device.
A small stroke of about 5 to 20 mm can be selected depending on the amount of the old resin 11A remaining in the resin 30 and the unevenness of the heat history.

That is, the residual resin amount is small and the old resin 11A
In the case where the degree of non-uniformity of the thermal history due to stagnation is small, the forward / backward stroke of the injection plunger 8 is reduced as much as possible (for example, 5 mm). If the degree of non-uniformity is large, the forward / backward stroke of the injection plunger 8 is made as large as possible (for example, 20 mm). As the forward / backward travel stroke of the injection plunger 8 increases, the amount of new resin 11 accumulated in the accumulator front space 12 increases, and the resin sent to the die 1 side as the injection plunger 8 advances.
As a result, the old resin 11A staying in the accumulator front end inner wall 2b and the resin passage 3 has a large shearing action, and is easily replaced with a new resin.

In the first place, to improve the material change and color change, the following is necessary.

(1) In the extruder 4, the resin passages 3 and 5, the accumulator 2, the dies, and the like are formed in a shape in which the resin 11 does not stay.
It is recommended to change the resin in the flow direction 11 afterwards.

(2) The old resin 11A on the wall surface is peeled off at a high shear rate.

Of these, (1) is determined by the shape of each part, and (2)
Is determined by the procedure and conditions of material change and color change, and the type of material.

Then, as described above, the present invention provides (1) and (2) for enabling the first method and the second method.
Can be performed by the synergistic effect of
Color change is performed very smoothly, quickly and reliably.

In addition, according to the present invention, it is apparent that the same effect of promoting material change and color change as described above is exerted on the die 1 located downstream of the accumulator.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, the accumulator in which the front end resin passage is joined to the die, the extruder in which the front end resin passage is joined to the accumulator, and the inner hole of the extruder are rotatable. A first opening / closing valve for opening and closing a resin passage between the die and the accumulator, and a first opening / closing valve for opening and closing the resin passage between the die and the accumulator; In a blow molding machine provided with a second opening / closing valve for opening / closing a resin passage between machines, the first opening / closing valve and the second opening / closing are used when exchanging materials or changing colors in the extruder, the accumulator, the die and each resin passage. After the valve is kept open and the screw is continuously rotated, the injection plunger is moved to the injection plunger limit at or near the injection plunger advance limit. By making the jaws move forward and backward in small increments, it is possible to approach the shape where the resin does not stay, and because the resin speed can be increased, the shear rate can be increased, and the old resin can be easily peeled off, that is, The synergistic effect of increasing the material changing and color changing effects is exhibited.

For this reason, the time for material change and color change is shortened, the productivity is improved, and the resin consumption is reduced without wasting the resin during the preparation work.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a blow molding machine showing a material change and color changing method of the blow molding machine according to the present invention, and FIG. 2 is a schematic side view of the blow molding machine implementing the method. FIG. FIG. 2 shows a schematic cross-sectional view of the supply device. 1 ... die, 2 ... accumulator, 2a ... accumulator inner hole, 2b ... accumulator front end inner wall, 4 ... extruder, 4a ... extruder inner hole, 3, 5 ... resin passage, 7 ...
Screw 8 Plunger 9 Second on-off valve 10
… First open / close valve, 11… New resin, 11A… Old resin, 12… Accumulator front space, 20… Blow molding machine, 21… Platen, 22, 23… Mold, 25, 26… ... mold opening / closing cylinder, 30 ... resin supply device.

──────────────────────────────────────────────────の Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) B29C 49 / 02,49 / 04,49 / 42 B29C 47 / 08,47 / 92 B29B 11/10 B29L 22: 00

Claims (1)

(57) [Claims] 1. An accumulator having a front end resin passage joined to a die, an extractor having a front end resin passage joined to the accumulator, and a screw rotatably fitted in an inner hole of the extruder. An injection plunger fitted to the inner hole of the accumulator so as to be able to move forward and backward,
In a blow molding machine provided with a first on-off valve for opening and closing a resin passage between the die and the accumulator, and a second on-off valve for opening and closing the resin passage between the accumulator and the extruder,
When exchanging materials or changing colors in the extruder, the accumulator, the die and each resin passage, the first on-off valve and the second
While the on-off valve is kept open and the screw is continuously rotated, the injection plunger is advanced and retracted little by little at the injection plunger advance limit or at the injection plunger position near the injection plunger. Material changing method and color changing method for blow molding machine.