FR2813551A1 - Line manufacturing extruded plastic has horizontal extrusion head with pipe supplying material directly to calender with two rollers having vertical axes - Google Patents

Abstract

An extrusion line has a horizontal extrusion head (3) with a pipe (12) supplying material directly to a calender (4) with two rollers (21) having vertical axes. The pipe has upstream and downstream parts of different length connected by a bend <= 180 deg . The upstream part forms at least half the length of the pipe and its axis is perpendicular to the axes of the rollers. The upstream part may be two thirds of pipe length and the bend is curved. The head has a blade near the pipe outlet to control the thickness of the extruded material

Description

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The present invention relates to an extrusion line for the manufacture of a flat product in thermoplastic material. This product can be, depending on its thickness and dimensions, a film, a sheet or a plate, and the thermoplastic material can in particular be polystyrene, ABS, polyethylene or polypropylene.

A thermoplastic material extrusion line comprises a thermoplastic material conveying unit, an extrusion head or "die", connected to one end of the conveying unit, and a grille for collecting the extruded material. , located immediately downstream of the extrusion head.

Said conveying unit comprises a hopper at its end opposite to that connected to the extrusion head, by which it receives the thermoplastic material in the form of granules, and comprises heating means to allow the melting of the thermoplastic material in it as well as an endless screw to convey and pressurize this material as it melts.

The extrusion head consists mainly of two assembled parts delimiting between them a flow duct for the thermoplastic material. This conduit flares and thins in the direction of flow of the material, then opens, on the side of the head opposite to the routing unit, between two extrusion lips.

Given the constraints it undergoes, particularly in terms of pressure (2 to 300 bars), the extrusion head is made of metallic material and has a massive structure, so that its total weight can vary from 300 to 1000 kg approximately. according to the extrusion lines.

The extrusion head must be open in certain cases, in particular to clean the flow conduit when it comes to switching from one thermoplastic material to another. This operation is carried out by disassembly and separation of the two parts which constitute the extrusion head.

In addition, the extrusion head comprises a bar transverse to the direction of flow of the material, called "choke bar" or "choke bar" in English, located in the flaring zone of the flow conduit, the height of which in this duct is adjustable. The function of this bar is to distribute the material perfectly over the entire width of the duct and to regulate the flow of this material. The

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 height of this bar is adjustable by means of actuating screws engaged in holes which are arranged in one of the parts forming the extrusion head.

The calender, meanwhile, consists of at least two rollers placed immediately downstream of the lips of the extrusion head, the axes of these rollers being located in a plane perpendicular to the material flow conduit through the extrusion head.

According to a conventional technique, an extrusion line comprises an extrusion head extending generally in a horizontal direction, and the axes of the rollers of the calender are therefore located in a vertical plane.

According to another technique, the extrusion head is positioned so as to extend overall in a direction inclined relative to the horizontal, and the axes of the rollers of the calender are then situated in an inclined plane perpendicular to this direction. This inclination of the extrusion head / calender assembly makes it possible to improve the quality of the extruded product, in particular at the level of the underside thereof, and to obtain greater ease of adjustment of the extrusion head. depending on the extrusion conditions.

In the case of such an inclined extrusion head, the aforementioned operation of opening this head is carried out by dismantling either of the lower part or of the upper part. Said actuating screws are strongly inclined relative to the general direction of the flow conduit, so that the heads of these screws are positioned sufficiently distant from the adjacent roller of the calender to remain easily accessible.

These inclined extrusion heads have the drawback of involving a great deal of effort and care during the abovementioned opening and reclosing operations, taking into account the need to position the lower part in an inclined manner when reassembling it with the upper part, or vice versa. It can happen that damage is caused to the extrusion head during these operations. Another drawback is that the highly inclined actuating screws of these extrusion heads imply, for their operation, to exert forces in an inclined plane. This results in a difficulty of

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 certain maneuver and a difficulty to achieve a precise adjustment of the tightening or loosening of these screws. Perfect control of the positioning of the throttle bar is therefore not obtained.

In addition, there must be sufficient clearance around the extrusion heads to allow opening and closing operations, which leads, taking into account the inclination of these heads, to place the members of the extrusion line in height, particularly the aforementioned routing unit (s), which are heavy and bulky. It follows that these extrusion lines have a large size and that the frames they include to support their organs in height have relatively complex structures.

The present invention aims to remedy all of the aforementioned drawbacks.

Its main objective is to provide an extrusion line whose extrusion head can be opened and closed easily, while retaining the advantages of an inclined extrusion head.

Another object of the invention is to obtain a significantly improved control over the positioning of the throttle bar.

Yet another objective of the invention is to obtain an extrusion line having a reduced bulk compared to the existing extrusion lines and comprising support frames for the constituent members of this extrusion line having a simplified structure.

The extrusion line which it relates comprises, in a manner known per se, an extrusion head, generally oriented in a substantially horizontal direction and delimiting a material flow duct, and a grille for collecting the extruded material , including two rollers located immediately downstream of the extrusion head, the axes of which are contained in a plane substantially perpendicular to the direction of extrusion.

According to the invention, said flow conduit comprises two portions of conduit, namely a portion of upstream conduit and a portion of downstream conduit; these two portions of conduit have different lengths and form an angle less than 180 between them in the plane transverse to the extrusion head which passes through the assembly of this conduit, the portion of upstream conduit extending over more than the half the distance between the upstream and downstream ports of the conduit, while the portion of

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 downstream conduit extends over less than half of this distance and is oriented substantially perpendicular to said plane containing the axes of the rollers of the calender.

The terms "upstream" and "downstream" are of course defined with reference to the direction of flow of the thermoplastic material through the extrusion head.

The extrusion head according to the invention thus comprises a flow conduit in two portions, the upstream conduit portion extending over the major part of the extrusion head, in particular in a horizontal plane, while the portion downstream conduit is inclined relative to this horizontal plane.

It follows that this extrusion head combines the advantages of a horizontal extrusion head, on the one hand, that is to say in particular ease of opening / closing, and no need to raise the members of the extrusion line, and of an inclined extrusion head, on the other hand, that is to say improvement of the quality of the extruded product and ease of adjustment.

In addition, when this extrusion head comprises a throttle bar, the actuation screws which make it possible to adjust this bar can be positioned in a substantially vertical direction, and therefore have a shorter length than the actuation screws d '' a tilted extrusion head. This orientation and this length limitation make it easier to exercise the tightening or loosening forces of these screws. They also make it possible to reduce the deformations or expansions of the latter and therefore to eliminate, or greatly reduce, the inaccuracies in positioning of this choke bar.

The downstream duct portion can be strictly perpendicular to said plane containing the axes of the rollers of the calender, which is the most general case, but can also be oriented at an angle ranging from plus or minus Z0 relative to this perpendicular, without depart from the scope of the invention.

For a good understanding, the invention is again described below with reference to FIG. 3 of the appended schematic drawing, which represents, by way of nonlimiting example, a preferred embodiment of the extrusion line that it relates to.

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 Figure 1 is a simplified side view in longitudinal section of a known type of extrusion line, comprising an extrusion head and an inclined grille; Figure 2 is a top view of this extrusion head, in longitudinal section, and Figure 3 is a simplified view, in cross section, of the extrusion head that includes the extrusion line according to the invention.

FIG. 1 represents an extrusion line 1 for the manufacture of a flat product in thermoplastic material, in particular a film, a sheet or a plate.

The extrusion line 1 essentially comprises a unit 2 for conveying the thermoplastic material, an extrusion head 3, or "die", and a calender 4.

The unit 2 comprises a hopper 5 at its end opposite to that connected to the extrusion head 3, through which it receives the thermoplastic material in the form of granules. It also includes heating resistors 6, arranged along its length and its periphery, to allow the melting of the thermoplastic material in it, and contains an endless screw 7 for conveying and putting this material under pressure as the fusion of this one.

The worm 7 is actuated by a motor 8 and a reduction gear 9.

The extrusion head 3 mainly consists of two assembled metal parts 10, 11, of massive structure. These parts 10, 11 define between them a conduit 12 for the flow of the thermoplastic material.

As shown in FIG. 2, this conduit 12 widens and thins in the direction of the flow of the material, so that it delimits an area 13 serving for admission into the head 3 of the thermoplastic material and a zone 14 used for spreading this material.

Downstream, the conduit 12 opens out between two extrusion lips 15.

The parts 10, 11 are assembled to each other by means of studs and nuts (not shown. These studs and nuts allow the disassembly of the two parts 10, 11 in particular for cleaning the

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 conduit 12 when it comes to switching from one thermoplastic to another.

The extrusion head 3 also comprises a bar 16 transverse to the direction of flow of the material, called "throttle bar". This bar 16 is located in zone 14; its function is to perfectly distribute the material over the entire width of this zone 14 and to regulate the flow of this material.

The height of the bar 16 in the duct 12 is adjustable according to the type of thermoplastic material to be extruded, and this adjustment is carried out by means of actuating screws 20, which are engaged in holes arranged in the part 10. In the case shown in Figure 1 of an extrusion head 3 inclined relative to the horizontal, the actuating screws 20 are strongly inclined relative to the general direction of the conduit 12, so that their heads 20a are positioned sufficiently distant from the adjacent roller 21 of the calender 4 and therefore remain easily accessible.

The calender 4 consists of three rollers 21, two of which are located immediately downstream of the lips 15. The axes of these rollers 21 are located in an inclined plane, perpendicular to the direction of extrusion of the material between the lips 15.

The different members 2, 3, 4 of the extrusion line 1 are supported by frames (not shown), having relatively complex structures. These frames allow these members 2, 3, 4 to be placed in height so that there is sufficient clearance around the head 3 to allow the abovementioned opening and closing operations.

Referring to Figure 3, it appears that the extrusion head 3 of line 1 according to the invention is oriented in a horizontal direction, and that the conduit 12 of this head 3 comprises two portions 12a, 12b connected by an elbow 12c.

These portions 12a, 12b have different lengths and form an angle of the order of 1351 between them in the plane transverse to the head 3 which passes through the assembly of this conduit 12.

The upstream duct portion 12a extends over approximately two thirds of the distance separating the upstream and downstream orifices of the duct 12, and comprises the intake area 13 and a part of the spreading area 14.

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 The downstream duct portion 12b extends over approximately a third of this same distance and is oriented perpendicular to the plane containing the axes of the rollers 21.

The elbow 12c is rounded so as not to cause any break in the continuity of the conduit 12, capable of disturbing the flow of the material.

The head 3 according to the invention also comprises a bar 16 and actuating screws 20. As shown in FIG. 3, the inclination of the calender 21 allows the screws 20 to be arranged in a substantially vertical direction, and not oblique as on the head 3 shown in FIG. 1. These screws 20 thus have a minimum length.

As appears from the above, the invention provides an extrusion line, the extrusion head 3 allows, thanks to the inclination of the duct portion 12b, to improve the quality of the extruded product, in particular at the lower face thereof, and to obtain greater ease of adjustment of the head 3 according to the extrusion conditions, while being able to be opened and closed easily thanks to the fact that this head 3 is oriented generally in a substantially horizontal direction.

This head 3 also allows the actuating screws 20 to be oriented in a vertical direction or close to the vertical, and that they have a limited length, in order to reduce the deformations or expansions of these screws. Significantly improved control of the positioning of the bar 16 can thus be obtained.

In addition, this head 3 eliminates the need to place the organs of the extrusion line in height, and therefore to provide support frames for the organs of this extrusion line having a simplified structure.

It goes without saying that the invention is not limited to the embodiment described above by way of example but that, on the contrary, it embraces all of the variant embodiments thereof. Thus, the extrusion head may not include a choke bar, and the respective orientations of the conduit portions 12a, 12b, as well as the angle formed by these two conduit portions, may vary relative to the orientations and angle. represented.

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Claims (1)

CLAIMS 1 - Extrusion line for the manufacture of a flat product in thermoplastic material, comprising an extrusion head (3) which is oriented generally in a substantially horizontal direction and which delimits a flow conduit (12) of the material, and a calender (4) for collecting the extruded material, which includes two rollers (21) located immediately downstream of the extrusion head (3), the axes of which are contained in a plane substantially perpendicular to the direction d 'extrusion; extrusion line (1) characterized in that said flow conduit (12) comprises two portions of conduit (12a, 12b), namely a portion of upstream conduit (12a) and a portion of downstream conduit (12b); these two portions of conduit (12a, 12b) have different lengths and form an angle less than 180 between them in the plane transverse to the extrusion head (3) which passes through the assembly of this conduit (12), the upstream duct portion (12a) extending over more than half the distance separating the upstream and downstream orifices of the duct (12), while the downstream duct portion (12b) extends over less than half of this distance and is oriented substantially perpendicular to said plane containing the axes of the rollers (21) of the calender (4). 2 - Extrusion line according to claim 1, characterized in that the upstream duct portion (12a) extends over approximately two thirds of the distance separating the upstream and downstream orifices of the duct (12), the duct portion downstream (12b) extending over approximately one third of this same distance. 3 - Extrusion line according to claim 1 or claim 2, characterized in that the two pipe portions (12a, 12b) are connected by an elbow (12c) and in that this elbow (12c) is rounded. 4 - Extrusion line according to one of claims 1 to 3, characterized in that the extrusion head (3) comprises a "throttling" bar (16) transverse to the direction of flow of the material, located in the flaring zone (14) of the flow conduit (12) and the height of which in this conduit (12) is adjustable, and actuating screws (20) engaged in holes which are arranged in the head extrusion (3), these actuating screws (20) being positioned in a substantially vertical direction.