JP4857380B2 - Extrusion head for blow molding hollow bodies with a system of parison wall thickness distribution - Google Patents

Description

  The present invention relates to a part having an extrusion head of a machine for blow molding polymeric materials.

  One of the major problems encountered in blow molding hollow bodies is the precise radial distribution of the polymer that forms the finished product. This problem is much more pronounced when the manufactured product does not have cylindrical symmetry, or when the bottom chamfer radius of the blown product is small.

  In fact, when a tubular parison having a certain thickness is blown in the mold, it can be seen that the semi-molten material is unevenly distributed in the mold. As a result, some of the walls of the finished product are too thin and some are too thick. In order to guarantee a certain dimensional stability and strength of the finished product, it is necessary to increase the weight in order to thicken all the walls of the product, but this leads to excessive use of the material.

  As a system for at least partially solving such drawbacks, for example, the system described in EP1.004.423 filed by Feuerherm Harald is known. The system interferes with the formation of the parison in the extrusion head, thereby obtaining a parison deformed in a preset direction from the head. Thus, the wall thickness is uniformly distributed by blow molding after the parison. The parison deformation is deformed by intervening in a mandrel or male part set in the extrusion head, i.e. by exchanging the mandrel, or by using an intentionally provided plate on the outer skirt of the mandrel Can be obtained.

  The present invention aims to eliminate the disadvantages of the above known techniques by providing an extrusion head for blow molding a hollow body, which can ensure a uniform distribution of the wall thickness of the blown product. .

  The present invention also aims to provide a very versatile extrusion head designed for use with various types of products without any structural changes.

  These objects can be achieved by the extrusion head according to the invention, the characteristics of which are listed in the independent claim 1.

  Advantageous embodiments of the invention are described in the dependent claims.

  An extrusion head according to the present invention for blow molding a hollow body includes a body having a substantially cylindrical chamber configured therein. In the chamber of the main body, a substantially cylindrical push plug is set axisymmetrically so that a cylindrical gap is formed between the outer surface of the male part or mandrel and the inner surface of the main body. ing. The molten plastic material sent by the extruder flows through the cylindrical gap.

  In order to configure the structure of the outer surface of the parison, a die opening is set at the lower end of the main body.

  The bottom part of the male part is set in the die opening so as to form a ring-shaped gap communicating with the first cylindrical gap for discharging the tubular parison from the extrusion head.

  The main feature of the present invention is indicated by the fact that the extrusion head further comprises a plunger which supports an elliptical insert at the bottom. The plunger is mounted so as to be slidable and axisymmetric in a chamber formed at the bottom of the male part, and opens downward. In this way, the plunger is from the stowed stationary position where the lower end of the elliptical insertion portion is located in the chamber at the bottom of the male portion, and the lower end of the elliptical insertion portion is at the bottom from the lower end of the bottom of the male portion. It can be moved to the protruding drawer operating position.

  Thus, the lower end of the elliptical insertion part protruding from the bottom part of the male part at the bottom part can adjust the radial distribution of the polymer inner surface. The lower end of the oval insert is asymmetrical, while the lower end of the die opening is symmetric so that the parison thickness can be properly distributed depending on manufacturing requirements and the subsequent blow molding process in the mold. it can.

  The advantages of the present invention are clear in that the movement of the elliptical insert can be adjusted according to manufacturing requirements by controlling the movement of the plunger.

  Other features of the present invention will become more apparent by referring to the following detailed description in conjunction with the embodiments. These embodiments are shown in the accompanying drawings as merely non-limiting examples. The attached drawings are as follows.

FIG. 3 is a side view of a completed extrusion head according to the present invention. FIG. 2 is an enlarged detail view of a portion surrounded by a circle A in FIG. 1. It is a top view from the bottom of the die opening of the extrusion head of FIG. FIG. 3 is an axial cross-sectional view showing a state where a die opening of the extrusion head of FIG. 1 is cut along a cross section III-III of FIG. 2. FIG. 4 is an enlarged detail view of a portion surrounded by a circle A in FIG. 3. FIG. 2 is a bottom plan view of an elliptical insertion portion of the extrusion head of FIG. 1. It is a side view of the elliptical insertion part of FIG. FIG. 6 is a side view of an elliptical insertion portion along the direction of arrow A in FIG. 5. FIG. 2 is a side view of the bottom of the head of FIG. 1 when the male part of the extrusion head is in the upper working position and the plunger of the elliptical insertion part is in the retracted rest position. FIG. 7 is an enlarged detail view of a portion surrounded by a circle A in FIG. 6. FIG. 7 is an axial sectional view showing a state cut along a section VII-VII in FIG. 6. FIG. 8 is an enlarged detailed view of a portion surrounded by a circle A in FIG. 7. FIG. 2 is a side view of the bottom of the head of FIG. 1 when the male part of the extrusion head is in the upper operating position and the plunger of the elliptical insertion part is in the retracted operating position. FIG. 9 is an enlarged detail view of a portion surrounded by a circle A in FIG. 8. FIG. 9 is an axial cross-sectional view showing a state cut along a cross section IX-IX in FIG. 8. FIG. 10 is an enlarged detail view of a portion surrounded by a circle A in FIG. 9. FIG. 2 is a side view of the bottom of the head of FIG. 1 when the push plug of the push head is in the lower rest position and the elliptical insertion portion plunger is in the retracted rest position. FIG. 11 is an enlarged detail view of a portion surrounded by a circle A in FIG. 10. It is an axial sectional view showing a state cut along a cross section XI-XI in FIG. FIG. 12 is an enlarged detail view of a portion surrounded by a circle A in FIG. 11.

  Referring to FIG. 1, there is shown an extrusion head according to the present invention, generally designated by the reference numeral 1. The extrusion head 1 has a substantially cylindrical body 2. In the main body 2, a substantially cylindrical male portion 3 is set axisymmetrically.

  A cylindrical gap 4 is formed between the inner wall of the head body 2 and the outer wall of the male part 3. The molten material fed into the head by an extruder (not shown) flows downward through the manifold 5 set in the head through the cylindrical gap 4. The molten material in the cylindrical gap 4 is thus substantially tubular.

  The die opening 6 is disposed at the lower end of the head 1, and the bottom 30 of the male part 3 is set inside the die opening 6. The shape of the parison that must later be ejected from the extrusion head 1 for blowing in the mold depends on the configuration of the die opening 6 and the configuration of the bottom 30 of the male part.

  1A, 2, 3, and 3A, the die opening 6 is fixed to the cylindrical member 7 and a first cylindrical member 7 fixed to the body 2 of the extrusion head. A second ring-shaped member 8. These members are fixed by a fixing screw screwed into a fixing hole 9 formed in the cylindrical member 7 and a disk-like member 8 of the die opening 6.

  A cylindrical gap 10 communicating with the cylindrical chamber 4 is formed between the outer surface of the bottom portion 30 of the male portion and the inner surface of the cylindrical member 7 of the die opening to allow the molten material to pass therethrough. Has been. The cylindrical gap 10 is narrowed in the annular end member 8 of the die opening.

  The ring-shaped member 8 has an inner surface 11 having a tapered shape whose inner diameter decreases downward. The lower end portion of the male end member 30 also has an outer surface 31 having a tapered shape with an inner diameter decreasing downward. Thus, a narrow portion 10 ′ of the cylindrical gap 10 is generated between the two tapered surfaces 11/31.

  In the bottom part 30 of the male part 3, a cylindrical chamber 32 opened at the bottom part is formed. The plunger 20 is slidable axisymmetrically within the male cylindrical chamber 32.

  The plunger 20 has a shaft hole 21 that terminates in the expansion sheet 22. With further reference to FIGS. 1 and 1A, a trunk 25 passes through the shaft hole 21 of the plunger 20. The lower end portion of the trunk 25 is fixed to the plunger 20 by a nut 26 housed in the seat 22 of the plunger 20. As shown in FIG. 1, the plunger 25 extends axially symmetrically within the male portion 3. For this purpose, the male part 3 must show an axial channel designed to allow the plunger stem 25 to pass through.

  The upper end portion of the trunk 25 is disposed at the uppermost portion of the extrusion head 1 and is connected to the actuator 26. As a result, axial translation of the trunk 25 becomes possible. The actuator 26 is controlled by a controller 27 provided intentionally.

  An elliptical insertion portion 40 is fixed to the bottom surface of the plunger 20. The oval insertion portion 40 has a plurality of fixing holes 41. These fixing holes 41 are designed to be aligned with the fixing holes of the plunger in order to receive fixing screws.

  As shown in FIGS. 4, 5 and 5A, the oval insert 40 has a substantially disc shape and its outer diameter slides within the male chamber 32. It is substantially equal to the outer diameter of the plunger 20 so that it can. The outer lower end 48 of the oval insert 40 has an asymmetric shape and the four arc portions 48a, 48b, 48a ′, 48b of the circle whose corresponding angle is 90 ° in the center. It is divided into '. More precisely, as shown in FIGS. 5 and 5A, two parts of the outer lower end with raised shapes 48a and 48a ′ arranged in diametrically opposite positions, and diametrically opposed positions. There are two portions at the outer lower end with indentations 48b and 48b.

  Referring to FIGS. 6, 6A, 7 and 7A, the plunger 20 is in the retracted rest position and the male part 3 is in the lower operating position. In this state, the plunger 20 is stored in the chamber 32 of the bottom portion 30 of the male portion, and the lower end 48 of the elliptical insertion portion 40 protrudes outward with respect to the lower end 38 of the bottom portion 30 of the male portion. Yes. The male part 3 is pulled up, and the bottom part 30 of the male part is inside the die opening 6. As a result, the lower end 38 of the bottom of the male part does not protrude outward with respect to the lower end 88 of the die opening 6.

  The molten material can pass through the narrow portion 10 ′ of the gap 10 so as to form a substantially constant thickness tubular parison at the discharge of the die opening 6. This is because the lower end 38 of the male part and the lower end 88 of the die opening 6 are both circular and symmetric. As a result, the parison thickness is not controlled.

  If the objective is to control the thickness of the parison, the controller 27 (FIG. 1) controls the actuator 26, which actuates the stem 25, thereby causing the plunger 20 to translate downward.

  After the translational movement (see FIGS. 8, 8A, 9, and 9A), the plunger 20 is in its retracted operating position and the male bottom 30 is in the upper operating position. In this state, the lower end 48 of the elliptical insertion portion 40 protrudes outward and downward with respect to both the lower end 38 of the bottom portion 30 of the male portion and the lower end 88 of the die opening 6.

  The molten material can pass through the narrow portion 10 ′ of the gap 10. However, in this case, the inner surface of the molten material comes into contact with the outer lower end 48 of the elliptical insertion portion 40.

  The outer lower end 48 of the oval insert is asymmetric and has raised portions 48a, 48a ′ and recessed portions 48b, 48b ′ so that the inner surface of the parison at the discharge from the die opening 6 is oval. become. As a result, the thickness of the parison is thicker at the raised portions 48a and 48a 'of the elliptical insertion portion 40 and thinner at the depressions 48b and 48b' of the elliptical insertion portion.

  Later, when a parison having a non-uniform thickness is blown into the mold, the thickness of the sidewall of the finished product is evenly distributed.

  The male part 3 closes the narrow part 10 'of the gap 10 so as to prevent the molten material from passing from the upper working position where the narrow part 10' of the gap 10 is open so that the molten material can pass. It should be noted that it is possible to translate the head 1 in an axially symmetrical manner to a lower stationary position.

  See FIGS. 10, 10a, 11, and 11a. When production needs to be stopped, the plunger 20 is returned to its retracted rest position inside the chamber 32 of the male bottom 30 and the male 3 is a die-shaped outer wall 31 of the male bottom 30. Actuated in a downward translational motion so as to contact the tapered inner wall 32 of the opening 6. Thus, the narrow portion 10 ′ of the gap 10 is closed, and the molten material cannot be discharged from the die opening 6.

  It should be noted that in this state, the lower end 38 of the bottom portion 30 of the male portion protrudes slightly downward with respect to the lower end 88 of the bottom portion 8 of the die opening 6.

  Numerous variations and modifications can be made to the specific nature of the embodiments of the invention. All of these variations and changes can be made by those skilled in the art and are within the scope of the present invention in any case as set forth in the claims.

Claims (8)

An extrusion head (1) for blow molding a hollow body,
A body (2) having a substantially cylindrical chamber configured therein;
A substantially cylindrical indentation plug (3) having a cylindrical shape in which a molten plastic material fed by an extruder can flow between the outer surface of the indentation plug and the inner surface of the body. A push plug (3) set axisymmetrically inside the cylindrical chamber of the main body so that a gap (4) is formed;
A die opening (6) set at the lower end of the body (2);
Set in the die opening (6) so that a ring-shaped gap (10) communicating with the cylindrical gap (4) for the discharge of the tubular parison from the extrusion head is constructed. Including the bottom (30) of the pusher plug (3),
The extrusion head is
Plunger (20) supporting an elliptical insertion part (40) at the bottom, slidable into a chamber (32) formed in the bottom (30) of the push plug and shaft The lower end (48) of the elliptical insert is mounted symmetrically and opens from the retracted rest position where the lower end (48) of the elliptical insert is located inside the chamber (32) at the bottom of the push plug. The lower end (48) of the shaped insert includes a plunger (20) that can be displaced to a pull-out operating position protruding at the bottom with respect to the lower end (38) of the bottom of the push plug. An extrusion head (1), characterized in that   The elliptical insertion portion (40) has a substantially ring shape, and its lower end (48) is asymmetrical, with a portion having a raised shape (48a, 48a ′) and a hollow shape (48b, Extrusion head (1) according to claim 1, characterized in that it shows a part with 48b ').   The oval insert (40) has two parts having raised shapes (48a, 48a ′) arranged at diametrically opposite positions and a recessed shape (48b, 48b ′) arranged at diametrically opposite positions. 3. Extrusion head (1) according to claim 2, characterized in that it has two parts.   4. Each part having a raised and recessed shape (48a, 48a ′, 48b, 48b ′) has the shape of a circular arc with a corresponding angle of 90 °. Extrusion head (1) as described.   The plunger (20) is connected to a trunk (25) crossing the push plug (3) in an axisymmetric manner and is operated in translation by an actuator (26) set in the uppermost part of the push head (1). 5. Extrusion head (1) according to any one of claims 1 to 4, characterized in that   The push plug (3) is mounted so as to be capable of translational movement in an axially symmetrical manner inside the main body (2) of the head, and the bottom (30) of the push plug and the die opening (6). Formed between the bottom (30) of the push-in plug and the die opening (6) from the upper operating position where the annular gap (10, 10 ') formed between 6. Extrusion head (1) according to any one of claims 1 to 5, characterized in that said annular gap (10, 10 ') made passes through to a lower stationary position where it remains closed. . The die opening includes a bottom (8) having a tapered inner surface (11) with a radius decreasing downwards;
The bottom (30) of the pusher plug is reduced in diameter downward so that a restriction (10 ′) of the annular gap (10) is created for the passage of the molten plastic material. 7. Extrusion head (1) according to any one of the preceding claims, characterized in that it comprises a tapered outer surface (31). A method for controlling the wall thickness of a parison discharged from an extrusion head (1) according to any one of the preceding claims,
Sending the molten material into the extrusion head (1);
A plunger (20) supporting an elliptical insert (40) set in a chamber (32) formed in the bottom (30) of the push plug (3) of the push head is inserted into the elliptical insert. The lower end (48) of the part is lowered so as to protrude at the bottom part with respect to the lower end (38) of the bottom part (30) of the push plug, and the inside of the parison discharged from the extrusion head is made elliptical A method comprising the steps of:

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