JP2704717B2 - Blow molding method in die accumulator type blow molding machine and material changing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow molding method in an in-die accumulator type blow molding machine and a method for changing the material thereof.

[0002]

2. Description of the Related Art In the prior art, a die head body is disposed with a required annular passage provided on the outer periphery of a mandrel whose vertical position can be adjusted, and the die head body is inserted into the annular passage and the annular body is operated by a hydraulic cylinder. By providing a plunger that rises and falls in the passage, supplies the material through the material supply port provided in the die head body into the annular passage, accumulates a predetermined volume, and presses the molten resin by lowering the plunger. The parison is extruded from the die head. One example is disclosed in
No. 254008. In addition, the blower is provided with a plunger that supplies resin into the spiral groove of the mandrel using a long resin path provided in the axial direction of the mandrel and that also serves to clean the annular passage when injecting a parison and changing materials. A blow molding die head in a molding machine is described in JP-A-3-120025.

[0003]

However, of the above-mentioned conventional techniques, in the former blow molding die head, the material is melted into the passage from a material supply port provided at one or a plurality of locations in the circumferential direction of the die head body. Since the resin is supplied, a portion where the molten resin flows left and right in the passage and joins again, that is, a weld line is generated, and this appears on the parison, so that apparent quality and strength are reduced. Has become a problem. The above problem has been temporarily solved by the latter technique in the prior art. However, the latter prior art embodiment discloses a structure for supplying the molten resin into the spiral groove of the mandrel through a long vertical resin path extending in the axial direction of the mandrel. The molten resin path that reaches the spiral groove is long, the flow of the molten resin is not smooth, and there is a risk that the resin will inevitably accumulate and deteriorate near the wall surface inside this long vertical resin path, In the case where an air blowing tube is provided in a die during molding, the diameter of the tube cannot be increased, and the structure of the die head becomes complicated. The present invention provides a blow molding machine in an in-die accumulator type blow molding machine which can easily clean a spiral groove formed on an outer peripheral surface of a mandrel in a blow molding die head by the same plunger without deterioration of molten resin. It is an object to provide a molding method. Another object of the present invention is to provide a material in an in-die accumulator type blow molding machine capable of smoothly changing materials (that is, changing the material, color, etc.) and performing injection of a parison without a weld line. It is to provide a replacement method.

[0004]

In order to solve this problem, in a specific invention, first, prior to molding, a parison extrusion annular opening of a die head is sealed by relative displacement between a die ring and a core, and a cylindrical plunger is moved to a lower limit position. Then, the extruder connected to the die head is operated, and while the molten resin supplied from the extruder is continuously supplied into the spiral groove of the mandrel in the die head, the cylindrical plunger is moved from the lower limit position. In order to cause the inside of the spiral groove to flow along the outer peripheral surface of the mandrel with the rise of the cylindrical plunger, and the outer peripheral surface of the mandrel extending from the inner peripheral surface of the cylindrical plunger and the spiral groove forming portion to the lower end of the mandrel. The molten resin is formed by a tapered gap that is slightly divergent for the circulation of the molten resin formed between them. Also caused to flow in the axial direction of the Dorell,
The lower end of the tapered gap flows into the accumulator formed at the lower end of the annular passage, and the molten resin corresponding to the volume of the molded product is temporarily stored in the molten resin accumulator. After temporarily storing the desired volume of the molten resin through the tapered gap, the parison extrusion annular opening in the blow molding die head is opened, and at the same time, the cylindrical plunger is pushed down to the lower limit position in the annular passage. The molten resin temporarily stored in the cylindrical port is discharged as a parison having a predetermined thickness from the annular port, and during the elevating period of the cylindrical plunger, the spiral groove has a cylindrical shape with respect to a resin supply port of a die head body. A second long groove communicating with the plunger over the entire vertical stroke, the resin passage hole, and the outside of the mandrel; The molten resin continues to be fed through a first long groove extending upwardly along the axial direction in the plane, further,
When the cylindrical plunger descends, the molten resin located in the first long groove is forcibly fed into the spiral groove due to contact friction with the inner peripheral surface of the cylindrical plunger, and every time the cylindrical plunger moves up and down. The accumulator in a die, wherein the inside of the spiral groove is always replaced with a new resin by the molten resin flowing through the spiral groove, is self-cleaned, and the discharged parison is blow-molded to obtain a desired molded product. This is a blow molding method in a blow molding machine. In order to solve this problem, the related invention is to perform parison molding repeatedly,
When performing the material change, a new material different from the old material is supplied to the molten resin accumulator through the spiral groove and the tapered gap, and the old material remaining in the spiral groove is flushed, and the molten resin accumulate chamber is removed. After having flowed in, the old material in the molten resin accumulator chamber is pushed out of the die head through the annular opening of the parison by means of several vertical movements of the parison injection cylindrical plunger also serving as the resin scraping, and the cylindrical plunger is used. 2. The material change in the accumulator type blow molding machine according to claim 1, wherein the old material adhering to the inner peripheral surface of the die head body is scraped or peeled off to replace the old and new materials. There is a way.

[0005]

The operation of the first aspect of the present invention will be described together with its method of use. First, prior to molding, the parison extrusion annular port is closed by relative displacement between a die ring and a core, and the cylindrical plunger is set at a lower limit position. On this occasion,
If desired, the parison extrusion annulus need not be open or completely sealed. Next, the extruder connected to the die head is operated, and while the kneaded molten resin is supplied into the spiral groove of the mandrel in the die head, the cylindrical plunger is sequentially raised from the lower limit position, and the inside of the spiral groove on the outer peripheral surface of the mandrel is formed. To flow into the accumulation chamber through the tapered gap,
A molten resin corresponding to the volume of the molded article is temporarily stored in the accumulation chamber. More specifically, the molten resin supplied from the extruder is continuously flowed along the outer peripheral surface of the mandrel along with the rise of the cylindrical plunger without interruption, and the tapered gap is formed. Thereby, the molten resin also flows in the axial direction of the mandrel, flows into the accumulator, and temporarily stores the molten resin corresponding to the volume of the molded product in the accumulator.

In this way, after the molten resin of a desired volume is temporarily stored in the accumulation chamber through the spiral groove and the tapered gap, the annular port is opened and the cylindrical plunger is simultaneously moved to the lower limit position in the annular passage. The molten resin temporarily stored in the annular passage is discharged from the annular opening as a parison having a predetermined thickness.
At this time, the molten resin is continuously supplied to the spiral groove through the second long groove, the resin passage hole, and the first long groove during the vertical movement of the cylindrical plunger. Further, when the cylindrical plunger descends, the molten resin located in the first long groove is forcibly fed into the spiral groove due to contact friction with the inner peripheral surface of the cylindrical plunger. Thereafter, the parison is blow-molded in the same manner as in a usual in-die accumulator type blow molding machine to obtain a desired molded product. At this time, every time the cylindrical plunger moves up and down, the molten resin flowing through the spiral groove always replaces the inside of the spiral groove with a new resin and is self-cleaned.

The operation of the invention described in claim 2 will be described together with its use. The spiral groove into the molten resin accumulator, a new material different from the old material is supplied through the tapered gap, the old material remaining in the spiral groove is flushed, and after flowing into the molten resin accumulator, The old material in the molten resin accumulator chamber is pushed out of this die head from the annular opening of the parison by several vertical movements of the parison injection tubular cylindrical plunger that also serves as resin scraping, and by this cylindrical plunger,
The old material adhering to the inner peripheral surface of the die head body is scraped or peeled off. Thus, the replacement of the old and new materials is completed.

[0008]

Next, a description will be given of a typical embodiment of a blow molding die head in an in-die accumulation type blow molding machine for carrying out the method invention according to the first and second aspects. FIG.
In the above, B is a die head for blow molding in an in-die accumulation type blow molding machine A. The mandrel 10 has a longitudinal axis O extending in the vertical direction, and the die head main body 11 is disposed concentrically with the longitudinal axis O, with a gap provided outside the mandrel 10. The mandrel 10 can be adjusted vertically with respect to the die head main body 11. Has been deployed.

Reference numeral 12 denotes a lower end (tip) of the mandrel 10.
The spiral groove 13 is engraved on the outer peripheral surface of the mandrel 10. The spiral groove 13 is formed in the middle portion of the mandrel 10 as shown in the figure, but may be formed at a position lower than the lower end of the mandrel 10 in accordance with the amount of accumulated molten resin. At the lower end (tip) of the die head main body 11, a die ring 14 which forms a parison extrusion annular opening 19 in cooperation with the core 12 is attached. The annular port 19 is configured to be opened and closed according to the displacement of the mandrel in the vertical direction. An annular passage 23 for a plunger is formed between the mandrel 10 and the die head main body 11, and a cylindrical plunger 15 for parison injection which also moves up and down and is slidable is provided in the annular passage 23. The upper limit position of the cylindrical plunger 15 is such that the lower end of the cylindrical plunger 15 is lower than the lower end of the spiral groove 13 formed on the outer peripheral surface of the mandrel 10 (see FIG. 2). Between the inner peripheral surface of the cylindrical plunger 15 and the outer peripheral surface of the mandrel extending from the portion where the spiral groove 13 is formed to the lower end of the mandrel 10, a slightly divergent tapered gap 24 for flowing the molten molten resin is formed. The lower end of the gap 24 opens into a molten resin accumulation chamber 25 formed at the lower end of the annular passage 23. The tapered gap 24 is provided to prevent a spiral mark from remaining on the surface of the molded product, improve the appearance of the molded product, and prevent deterioration in strength. Accordingly, the flow of the molten resin is a mixed flow of the flow of the spiral groove 13 and the flow of the mandrel 10 in the axial direction due to the gap 24. Above the spiral groove 13, the inner peripheral surface of the cylindrical plunger 15 is in sliding contact with the outer peripheral surface of the mandrel 10, and the outer wall of the cylindrical plunger 15 is in sliding contact with the inner peripheral surface of the die head body 11.

A resin path for supplying molten resin from an extruder (not shown) to a spiral groove 13 formed on the outer peripheral surface of the mandrel 10 through a supply port of the die head body 11 and a supply groove of the cylindrical plunger 15. Is configured as follows. That is, the upstream end of the spiral groove 13 of the mandrel 10 communicates with the lower end of the first long groove 20 extending upward in the direction of the axis 0 on the outer peripheral surface of the mandrel 10, and is connected to the resin supply port 16 of the die head body 11. A second long groove 17 communicating with the cylindrical plunger 15 over the entire vertical stroke is formed along the axial direction on the outer peripheral surface of the cylindrical plunger 15 as a supply groove for the cylindrical plunger 15. The lower end of the second long groove 17 over the entire vertical stroke of the cylindrical plunger 15 communicates with the first long groove 20 via a resin passage hole 21 penetrating through the cylindrical plunger 15 in the radial direction. In addition, as in the embodiment shown in FIG. 3, the shape of the lower portion of the molten resin accumulator 25 and the shape of the lower portion of the plunger 15 may be substantially matched to each other. 15, the molten resin accumulator chamber 25 is almost completely closed by the cylindrical plunger 15, and the resin remaining in the molten resin accumulator chamber 25 not only at the time of extrusion but also at the time of material change. The amount is reduced, and the material replacement effect and the cleaning effect become more remarkable. The operation of the above embodiment is the same as the operation of the first and second aspects of the present invention.

[0011]

According to the first aspect of the present invention,
A desired volume of molten resin can be temporarily stored in the molten resin accumulator chamber sequentially according to the rise of the cylindrical plunger, and a hollow molded product of various volumes can be blow-molded with high quality without a weld line, and its strength can be improved. . Further, each time the parison is formed, the spiral groove can be constantly cleaned and maintained in a clean state by the molten resin flowing in the spiral groove. Further, the molten resin located in the first long groove can be forcibly fed down into the spiral groove along with the downward movement of the cylindrical tubular plunger, and the length of the molten resin path can be reduced by the length of the molten resin path described in the prior art. It can be made shorter to prevent deterioration of the molten resin. The molten resin supplied from the extruder can be continuously flowed without interruption from the spiral groove through the tapered gap into the molten resin accumulation chamber with the rise of the cylindrical plunger, and can be stored smoothly. In addition, no weld line is generated, and the molten resin is caused to flow also in the axial direction of the mandrel by the tapered gap, so that a parison having a uniform material is formed without a spiral mark on the surface of the extruded parison. The molten resin can be discharged from the annular port, and the molten resin does not accumulate in the molten resin path in the die as well as in the spiral groove every time parison molding is performed. Is done. Furthermore, even when the blow tube for blow molding is provided at the center of the die head, the blow tube can be arranged without any trouble, and even when this blow tube is provided, a structure in which a spiral groove is provided using the peripheral surface of the mandrel can be adopted, The structure of the die head can be simplified and its height can be reduced.

According to the second aspect of the present invention, the old material remaining in the spiral groove, the tapered gap, and the molten resin accumulating chamber is removed from the die head by the vertical movement of the cylindrical plunger when changing the material. At this time, the old material adhering to the inner peripheral surface of the die head body can be scraped or peeled off by the cylindrical plunger. In this way, material change can be performed quickly, and the amount of material loss at the time of material change can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of an embodiment.

FIG. 2 is a schematic longitudinal sectional view showing a state where a cylindrical plunger in FIG. 1 is located at an upper limit position.

FIG. 3 is a schematic vertical sectional view showing a main part of another embodiment in which the shape of the lower end of the cylindrical plunger is different.

[Explanation of symbols]

 13 Spiral Groove 15 Cylindrical Plunger 17 Second Long Groove 20 First Long Groove

Claims (2)

(57) [Claims] First, prior to molding, the parison extrusion opening of the die head is sealed by the relative displacement between the die ring and the core, and the cylindrical plunger is set at the lower limit position. The cylindrical plunger is actuated and the molten resin supplied from the extruder is continuously fed into the spiral groove of the mandrel in the die head, and the cylindrical plunger is sequentially raised from the lower limit position. Through the inner circumferential surface of the mandrel, and a portion of the annular molten resin formed between the inner circumferential surface of the cylindrical plunger and the outer circumferential surface of the mandrel extending from the spiral groove forming portion to the lower end of the mandrel. The molten resin flows also in the axial direction of the mandrel by the tapered gap extending at the end of From the lower end, it flows into the accumulator formed at the lower end of the annular passage, and the molten resin corresponding to the volume of the molded product is temporarily stored in the molten resin accumulator. In this way, the molten resin always flows through the spiral groove and the tapered gap. After temporarily storing a volume of molten resin, the parison extrusion annular opening in the blow molding die head is opened, and at the same time, the cylindrical plunger is pushed down to the lower limit position in the annular passage, and is temporarily stored in this annular passage. The molten resin is discharged from the annular port as a parison of a predetermined thickness, and during the vertical movement of the cylindrical plunger, the spiral groove has a full vertical stroke of the cylindrical plunger with respect to a resin supply port of a die head body. A second long groove communicating over
The molten resin is continuously supplied through the resin passage hole and the first long groove extending upward along the axial direction on the outer peripheral surface of the mandrel, and further, when the cylindrical plunger descends, the molten resin contacts the inner peripheral surface of the cylindrical plunger. Due to the contact friction, the molten resin located in the first long groove is forcibly fed into the spiral groove, and every time the cylindrical plunger moves up and down, the molten resin flowing through the spiral groove always causes a new resin in the spiral groove. A blow-molding method in an in-die accumulator type blow-molding machine, wherein a blow-molding of the discharged parison is performed to obtain a desired molded product. 2. When the material is changed after the parison molding is repeatedly performed, a new material different from the old material is supplied to the molten resin accumulating chamber through the spiral groove and the tapered gap. After the old material remaining in the melted resin accumulator chamber is flushed and flows into the molten resin accumulator chamber, the old material in the molten resin accumulator chamber is extruded by several vertical movements of the parison injection cylindrical plunger also serving as the resin scraping. In addition to pushing out the die head from the annular opening to the outside of the die head, the cylindrical plunger scrapes or peels off the old material adhering to the inner peripheral surface of the die head main body, and replaces the old and new materials. A method for changing materials in an in-die accumulator type blow molding machine according to claim 1.