RU2558116C2 - Extrusion head, primarily, for extrusion of cellular polycarbonate sheets - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: extrusion head, a mandrel, integrated with mandrel holder, is made of stainless steel and represents the internal part of split spinneret integrated with cellular plastic production line. Invention ensures the mandrel forming part shape by making the chamfers over the entire length of the mandrel forming part at the points of two top angles of mandrel forming part for construction of hexagonal figure. Said chamber represents an equilateral right triangle in cross-section.

EFFECT: higher total load bearing capacity and light translucence.

2 cl, 15 dwg

Description

1. The technical field to which the invention relates.

The extrusion nozzle claimed as an invention is a part of a detachable extrusion head used in an extrusion line. The nozzle is made of metal (mainly steel), is made as a part of the internal part of the demountable die, called a mandrel or mandrel holder. The die has prismatic channels of variable height at the exit point of the melt. Variability of height is provided due to the external part (mouthpiece) and the internal part (body holder) contained in the die. Used for the manufacture of multi-cavity profile polymer sheet products from thermoplastics (mainly for the manufacture of sheets of cellular polycarbonate).

2. The level of technology

The analogues of the invention known to the applicant are mandrel parts of an extrusion head as part of production lines for molding plastics and other materials in a plastic state, commonly referred to in conjunction with a mouthpiece, as an extrusion die. The name of the constituent parts of a demountable extrusion die in the form of two constituent parts: an outer part called a “mouthpiece” and an inner part called a “mandrel” (for a single inner part in a part) or “mandrel” (for several mandrel parts that are identical to each other) fixed on a single holder) is less common (see. "Calculation and design of the forming tool for the manufacture of products from polymeric materials", N.I. Basov, V. A. Braginsky, Yu.V. Kazakov, publishing house "Chemistry", Moscow , 1991).

The die is the forming part of the extrusion head, where the melt is extruded and converted to its final shape. The uniform extrusion of the melt over the cross section of the forming channel largely depends on the location of the forming slit relative to the extrusion axis. (“Extrusion of profile products from thermoplastics”, ed. V.P. Volodin, ed. Profession, St. Petersburg, 2005).

Dies, like their components, are usually made of adhesive and corrosion-resistant alloys (for example, nickel) and stainless steels (Big Soviet Encyclopedia. - M .: Soviet Encyclopedia).

The forming parts forming the die can be made detachable or integral (“Extrusion of profile products from thermoplastics”, ed. V.P. Volodin, ed. Prof., St. Petersburg, 2005).

Permanent dies for the production of thermoplastics do not allow you to adjust the wall thickness of the finished product and mainly contain plates with calibration holes of various shapes that repeat the cross section of the final product (see "Calculation and design of a forming tool for manufacturing products from polymeric materials", N.I. Basov, V.A. Braginsky, Yu.V. Kazakov, publishing house “Chemistry”, Moscow, 1991, “Extrusion of profile products from thermoplastics”, edited by V.P. Volodin, published by the profession, St. Petersburg, 2005).

Given the purpose of the inventive mandrel part of the die as a removable part, mainly used for the production of sheets of cellular polycarbonate, an analogue of the invention is a holder in the form of a detachable die of a casing extrusion head (see Fig. 1). For the production of multi-sheeted plastic sheets, the mandrel with the forming part at the outlet of the melt in the form of a rectangle is most common (callout 15.1, Fig. 1). The body design of the heads is used for the manufacture of continuous sheet or profile products and contains a mouthpiece and a holder that form a melt flow ("Extrusion of profile products from thermoplastics", ed. V.P. Volodin, ed. Prof., St. Petersburg, 2005).

The closest analogue of the invention (prototype), known on the priority date of the claimed invention, is the shape of the mandrel of the entrance section as part of the invention according to the copyright certificate SU 887236 A (class B29C 47/12, B29F 3/04, published December 7, 1981, to the nearest Fig. 2, BB is assigned to the analogue according to the copyright certificate SU 887236 A). Considered as the closest analogue (prototype) of the invention, the mandrel has the closest shape to the claimed invention and, like the claimed invention, performs the function of forming the melt in the extrusion head. The analogue (prototype) of the invention is a detachable part in the composition of the head of the extrusion line, made in the forming part based on a rectangular mandrel. A rectangular chamfer is made on the upper plane of the forming part of the mandrel, which is the prototype, by cutting off one upper right angle along the length of the forming part of the rectangular mandrel, as a result of which the mandrel in the cross section of the forming part has the shape of a pentagon, in the lower base of which there are two right angles, and in the upper the base is one right angle and two obtuse angles equal to each other (callout 15.2, Fig. 2).

Polycarbonate refers to thermoplastic plastics (thermoplastics) obtained as a result of multistage synthesis of granular raw materials. Cellular polycarbonate is a sheet of plastic, which, in comparison with monolithic, is facilitated by a hollow cellular structure inside a sheet resembling honeycombs. It follows from the well-known prior to the priority date samples of a sheet of cellular polycarbonate that, in its production, detachable dies are mainly used as part of holder supports, which give cells in the finished product quadrangular, rectangular and triangular shapes in the longitudinal section of the sheet. Moreover, each of the internal longitudinal partitions in the sheet, the so-called "stiffeners", forms a right or an obtuse angle with the upper, transverse or lower walls of the sheet, creating the corresponding geometric shapes. Well-known longitudinally shaped sheet cells are shown in FIG. 3 and taken from publicly available information on the Internet (http://www.novattro.ru/products/polycarbonate_novattro).

The cell shapes of multi-cavity profile sheets (honeycomb polycarbonate sheets) known at the priority date allow us to conclude that the mandrel assigned to the closest analogue of the invention is not used directly in the forming part of the extrusion head (at the exit point of the melt).

It is believed that in the development of designs of extrusion nozzles for the production of sheet cellular plastics, the main technological requirement for extrusion nozzles is to ensure the minimum possible wall thickness of the finished product. The performance of the units in the production of thick-walled products is very low due to the low cooling rate, the material consumption of these products is high, the appearance of shrinkable dents and tightening is inevitable on the surface of the finished product. The second technological requirement for the construction of extrusion nozzles is the equal thickness of the walls in the finished product. For equal-thickness walls in the composition of the final product, it is much easier to choose the geometry of the channels, ensuring the equality of the extrusion speeds at different points of the output section of the forming channel. The cooling rate of the profile in the calibrating device and the cooling bath is also the same in different places of the cross section, as a result of which there are practically no internal stresses in the material of the final product, therefore the product does not warp (see “Calculation and design of the forming tool for manufacturing products from polymeric materials”, N. I. Basov, V. A. Braginsky, Yu.V. Kazakov, publishing house “Chemistry”, Moscow, 1991).

Thus, the prototype of the invention can distinguish the following essential features characteristic of the claimed invention:

1) is made of metal (mainly steel);

2) is performed in the form of a mandrel as a part of a holder, as an integral part of the body structure of a detachable extrusion head. The split design of the extrusion head allows you to adjust the wall thickness in the finished product;

3) is a detachable part, forming a prismatic channel of variable height in the places with melt passage together with the mouthpiece of the extrusion head;

4) has right angles of the base in the cross section of the forming part.

At the same time, the use of the prototype of the invention as part of the forming part of the holder for the outlet of the melt does not allow to achieve the technical result provided by the invention, due to the asymmetric thickness of the upper wall in the finished multi-cavity profile sheet product (honeycomb polycarbonate sheet).

3. Disclosure of invention

(1) Information disclosing the essence of the invention.

(1.1) The essence of the invention as a technical solution is expressed in the aggregate of the following essential features of the device, sufficient to achieve the technical result provided by the invention:

1) the execution of the forming part of each mandrel of the forming section as part of the holder in the form of a three-dimensional geometric figure, forming in cross section a hexagon having in the lower base two right angles and in the upper base four obtuse angles equal to each other (Fig. 4 "Extrusion nozzle, claimed as an invention ”, callout 15.3).

(1.2) The claimed invention is aimed at providing a technical result, expressed in a symmetrical partial thickening of the upper wall in the finished product (a sheet of cellular polycarbonate). The technical result affects the improvement of the technical properties of the finished product made using the claimed invention. Including, the technical result is expressed in the following improved technical characteristics of the finished product:

1) increase the total bearing capacity of the final product;

2) an increase in one-sided flexibility of the upper wall of the finished product (bending from the side of the arch);

3) increasing the transmittance area of the visible light spectrum by increasing the total area of the upper wall of each cell.

(2) Signs characterizing the device claimed as an invention. The extrusion nozzle claimed as an invention is a device and is characterized by the following features:

1) is made of metal (mainly steel);

2) is performed as part of the forming section of the holder of the body structure of a detachable extrusion head. The split design of the extrusion head allows you to adjust the wall thickness in the finished product;

3) is a detachable part, forming a prismatic channel of variable height in the places with melt passage together with the mouthpiece of the extrusion head;

4) has a hexagonal cross-sectional shape at the exit of the melt, due to the removal of the second upper right angle along the length of the forming part of the closest analogue (mandrel with a pentagonal cross-section at the exit of the melt).

4. Brief Description of the Drawings

The list of figures attached to the description with brief explanations of what is depicted on each of them:

1. Figure 1. Analogue of the invention. Schematically depicts the composition of a detachable extrusion head and its components, including:

Figure 1A: General view of the design of the extrusion head for the manufacture of a hollow profile. The composition of the drawing includes: 1 - centering shoulder of the flange 23 of the head; 2 - lattice; 3 - thermocouples; 4 - the outer ring-shaped part of the holder; 5 - rib holder; 6 - body holder (central part); 7 - head housing; 8 - pipe drain fluid cooling the calibration device; 9 - channels communicating the cavity G with the cavity D and the atmosphere; 10 - electric heaters; 11 - mouthpiece; 12 - forming channel; 13 - calibrating device; 14 - insulating inserts and gaskets; 15 - mandrel; 16 - rod calibration device and the removal of coolant from it; 17 - the base of the rod 16; 18, 22 - inlet channel; 19 - a bolt for radial displacement of the mouthpiece is relatively mandrel; 20 - a tube for supplying a fluid cooling a calibrating device; 21 - a radial hole in the holder; 23 - head flange; 24 - bolts securing the head to the flange of the cylinder of the extruder.

Figure 1B: construction of a blend extrusion head. The composition of the drawing includes: 25 - Adapter; 7 - Head housing; 6 - Door holder; 15 - mandrel; 11 - Mouthpiece; 26 - Sleeve for mounting a thermocouple; 27, 28 - Heaters.

Figure 1B: construction of an extrusion head for manufacturing a multi-cavity profile sheet. The composition of the drawing includes: 11 - Mouthpiece; 6 - Door holder; 7 - Head housing; 15 - Dorn; 29 - Air channel (indicating the direction of air flow); 30 - place of entry of the melt; callout 15.1 is a cross section of the forming part of the mandrel at the place of exit of the melt.

2. Figure 2. The closest analogue (prototype of the invention). Schematic depicts:

Figure 2A: in the structure of the extrusion head, a General view of the location of the mandrel, which is the closest analogue (prototype) of the invention. The composition of the drawing includes: 7 - Head housing; 15 - Dorn; 30 - the place of entry of the melt, section B-B - the location of the forming part of the mandrel.

Figure 2B: an enlarged view of the location of the mandrel, which is the prototype of the invention, as part of the extrusion head. The composition of the drawing includes: 7 - Head housing; 15 - Dorn; 30 — melt entry point, section B-B — estimated melt exit point in the forming part of the mandrel;

Figure 2B: The composition of the drawing includes: a cross-section B-B with leader 15.2 is a cross-section of the forming part of the mandrel in the composition of the prototype of the invention.

3. Figure 3. Well-known types of internal structure of the finished product (cellular polycarbonate sheet). The figure schematically shows the geometry of the cells of the cross-section of sheets of cellular polycarbonate, well known to the priority date of the invention.

4. Figure 4. Extrusion nozzle claimed as an invention. The composition of the drawing includes: 31 - Chamfer; 15 - Dorn; 6 - Door holder; 29 - Air channel; 32 - collector of air channels; 33 - seal. In the drawing, callout 15.3 shows a frontal image of the forming part of the mandrels as part of the mandrel at the exit point of the melt.

5. Figure 5. Schematic representation of the relative ratio of the amplification sizes of the upper part of the vertical partitions, as a part of the upper part of the finished product (a sheet of cellular plastic). The figure shows the geometry of the cross section of the finished product obtained in the manufacture of the finished product using the nozzle as part of the extrusion head, claimed as an invention.

Figure 5A. The ratio of the amplification sizes of the upper part of the vertical partitions, in which, the parts numbered 34, 35, 36 are equal to each other and each of them is 1/3 of the total cell length in the finished product. At the same time, the reinforcement of the upper part of the partition is accounted for on the part number 1 and 3, and on the part number 2, the thickness of the upper wall in the finished product is intrinsic.

Figure 5B. A schematic spatial representation of the finished product (a sheet of cellular plastic) in a transverse vertical section is given.

6. Figure 6. Schematic representation of the load distribution under pressure on the upper wall of the finished product. The figure shows how one of the components of the technical result manifested when using the nozzle claimed as an invention is manifested, in particular, how the load is distributed on the upper wall in the product, increasing the overall load-bearing capacity of the finished product.

7. Figure 7. Schematic representation of the bend from the side of the thickened wall of the finished product. The figure shows the bending shape of the finished product from the side of the arch.

8. Figure 8. Schematic representation of the length of the places of light transmission in the finished product cell.

Figure 8.1. The image of the length of the light transmission in the arched cell, obtained by using the nozzle, claimed as an invention. The figure shows the place of light transmission in the finished product made using the nozzle, claimed as an invention, where L∂ is the length of the light transmission arc.

Figure 8.2. The image of the length of the light transmission in a square cell, obtained by using the nozzle, which is the prototype of the invention. The figure shows the place of light transmission in the composition of the finished product made using the nozzle, which is the prototype of the invention where Lo is the length of the light transmission arc.

9. Figure 9. Schematic representation of the passage of light rays at a right and oblique angle in a square arched cell of the finished product. The figure schematically shows the passage of light rays through the finished product and an increase in the number of light rays due to their refraction at the points of thickening of the upper wall in the composition of the product.

5. The implementation of the invention

The implementation of the invention is ensured by the two chamfers of the upper corners of each mandrel, instead of one chamfer made as part of the holder, specified as the closest analogue (prototype) of the invention. Chamfers are performed by cutting off the upper two right angles along the entire length of the forming part of each mandrel as part of the mandrel.

To achieve a technical result, certain proportions must be observed:

1) the removed upper corners along the entire length of the forming part of the mandrel should form an isosceles right-angled triangle in the cross-section at the exit of the melt, in addition, the chamfer can have a maximum length of the leg in the transverse section of the forming part of the mandrel, and a smooth narrowing of the leg of the bevel towards the base of the holder ;

2) at the place of exit of the melt (the forming part of the mandrel), the length of the leg of the rectangular triangle cut off from the mandrel when the chamfer is installed is correlated with the total length of the upper base in cross section until the chamfer is cut off, as 1: 5.

Increasing the bearing capacity of the finished product made using mandrels included in the invention is achieved by strengthening the junction of the upper wall and the vertical partitions (stiffeners) of the finished product. Strengthening is achieved due to the roundness of the junction of each vertical partition (stiffeners) to the upper horizontal wall of the sheet. Due to the indicated adjacency method, when considering a vertical section of a sheet made across the width of the finished product, a rectangular cell image with arched rounding of the corners in the upper part of the structure is visually created (Fig. 5 "Schematic representation of the relative ratio of the reinforcement sizes of the upper part of the vertical partitions, as a part of the upper parts of the finished product (cellular plastic sheet) "). At the same time, observing the proportions when cutting off the upper right angles along the length of the forming part of the mandrel allows achieving the following proportions of the thickening of the upper wall in the finished product: the own thickness of the upper wall of the sheet in each of the individual cells accounts for 1/3 of the distance between two vertical partitions. The remaining distance between two vertical partitions along the upper wall of the sheet falls on the thickening of the nodes of the intersection of the upper wall and the vertical partitions of the finished product. Thus, due to the roundness of the junctions of each vertical partition to the upper horizontal wall of the sheet, the total thickness of the upper wall in each cell is increased by 2/3 of the distance between two vertical partitions (stiffeners). Strengthening the junction of the upper wall and stiffening ribs in the finished product allows you to increase the overall bearing capacity of the finished product due to the redistribution of the load on the thickening of the junction in the area of vertical partitions, since the support area on the vertical partition increases (Fig. 6 "Schematic representation of the load distribution at pressure on the upper wall of the finished product ").

Redistribution of the material into the region of the reinforced junction increases the one-sided flexibility of the upper wall of the finished product. Bending strength from the side of the arch (Fig. 7 "Schematic representation of bending from the side of the thickened wall of the finished product") is confirmed by the test report of samples of a sheet of cellular polycarbonate with an arched cell structure and a rectangular cell structure. The tests were carried out on a tensile testing machine P-05 m. The test results showed that the flexural strength on the side of the arch was increased in comparison with products made using a body holder specified as the closest analogue of the invention in a ratio of 1: 1.8. This improvement in the technical characteristics of the finished product allows more widespread use of the finished product, made using the nozzle, claimed as an invention, in construction, including the installation of arched structures. In addition, the ability to visually determine the upper wall in the composition of the finished product, due to the peculiar thickening of the junction points, avoids errors in the installation of finished products, since the upper wall of the sheets of cellular polycarbonate is usually coated with a UV layer that protects the finished product from the damaging effects of UV rays.

Given the roundness of the junctions of the upper wall and the internal vertical partitions in the finished product, the transmittance area of the visible light spectrum increases due to an increase in the total area of the upper wall of each cell (see the designation of the arch arc L∂ in Fig. 8 "Schematic representation of the length of light transmittance points in cell of the finished product ”, in contrast to the finished product, sheets of cellular polycarbonate made with a rectangular cell having a length of the light transmission surface Lo). The increase in the length of the upper wall inside the arch cell of the finished product, allows you to increase the overall light transmission of the finished product. The effect is achieved due to the fact that a focused stream of refracted light is added to the possibility of a direct stream of light, in areas of arched rounding at the edges of the cell, in a wider range of the angle of incidence of sunlight (Fig. 9 "Schematic representation of the passage of light rays at right and oblique angles in square arched cell of the finished product "). An increase in the light transmittance of the finished product is an important component of the achieved technical result, since the most widely finished product in the form of sheets of cellular polycarbonate is used for the construction of easily erected structures in the form of greenhouses, street canopies, roof lamps of natural light.

Claims (2)

1. An extrusion nozzle for molding thermoplastics, which is a mandrel as part of a mandrel of a detachable extrusion head, the forming part of which is made in the form of a volumetric geometric figure, characterized in that a rectangular chamfer is made on the upper plane of the forming part of the mandrel by cutting off the upper right angle along the entire forming parts of a rectangular mandrel, as a result of which the mandrel in the cross section of the forming part has the shape of a hexagon, in the lower base of which two right angles at the top and base are four obtuse angles equal to each other. 2. The extrusion nozzle according to claim 1, characterized in that the length of the leg of the rectangular chamfer cut off from the mandrel in cross section at the exit point of the melt has a ratio with the length of the upper base - the forming part of the mandrel formed after cutting the corners of the forming part of the mandrel, as 1 :5.

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