DE2910041C2 - Screw press for processing polymeric materials - Google Patents

Description

The invention relates to a screw press for processing polymeric materials with a cylindrical housing with hopper and heating elements, with a rotating screw in its cavity axially extending movement, compression and ejection zones and a sleeve are housed, the comprising the screw in the feed zone and with grooves of the polymeric material to the screw through the Hopper is provided.

Such a screw press is z. B. in the article by G. Menges in the journal "Plastverarbeiter", Volume 20, 1969, Issue 2.

This screw press with longitudinal grooves in the loading zone, which allow the sliding of the To avoid polymers in relation to the cylinder in the direction of rotation of the screw has a loading zone with whirring characteristic.

In such a screw press, the coefficient of friction has no influence on the performance in the loading zone. The use of sleeves with longitudinal grooves leads to an increase in the conveying capacity the screw in the loading zone. The following sections of the screw are located however, in the cylinder with a smooth inner surface and consequently less work, whereby they represent a resistance to the material advance. As a result, the solid raw material becomes excessively compacted in these sections, which leads to an overload of the worm drive The object underlying the invention is therefore to create a screw press for Processing of polymeric materials in which the loading and ejection zones are rigid Have characteristic curve, the performance of these zones is matched so that the length of the discharge zone remains constant during processing

The problem posed is achieved in that the Shnecke comprehensive sleeve is designed as a rotatable metering device for the material and a speed controller for the dispenser has a group of openings attached to its circumference, which are consecutive can be brought into congruence with the outlet opening of the filling funnel.

The rotating feeder allows the work of the loading and ejection zones to be coordinated with one another. I the screw press according to the invention run in connection with the fact that the material pressure in the cylindrical housing behind the feeder and the speed of rotation of the screw is always constant, all heat processes of melting and homogenizing without heat fluctuations, and the melt is pressed out at constant temperature and viscosity. The inventive construction of Screw press makes it possible to produce the products of high quality and low thickness difference without Preserve thermal fluctuations.

The attachment of openings of the dispenser on the circumference of the same allows the channels of the Filling the screw evenly with material in the loading zone and preventing it from getting stuck of the material in the bunker. The grooves on the inner surface of the feeder, which run along a helical line, which is opposite to the direction of the thread on the worm makes it possible to adjust the speed of rotation of the feeder and consequently to reduce the performance of the drive as well as the Reduce energy expenditure.

The speed controller of the feeder enables the extrusion process to be automated and facilitates the production of a high-quality product. Expediently, surface sections of the dispenser that separate the openings from one another are positioned at an angle! φ is arranged to the central axis of the screw, which is selected in the range arc tg f <φ < 90 °, where f means the coefficient of friction of the material to be processed on the screw surface.

Such a design of the feeder makes it possible to prevent the destruction (crushing) of the material granules between the housing of the filling funnel and the surface of the feeder and consequently to reduce the energy consumption.
Further embodiments of the invention are from

apparent from the further subclaims.

The screw press according to the invention offers the possibility of the performance of the feed and the Ejection zone on a screw when processing different polymeric materials regardless of to bring the changes in the bulk density of the starting polymer into agreement. The inventive The screw press is suitable for high-quality processing into products with the screw practically all pourable polymeric materials regardless of the grain composition by far Carry out change range of the bulk density of the polymers.

The invention is illustrated by a detailed description of exemplary embodiments with reference to FIG accompanying drawings explained; in the drawings shows

F i g. 1 an embodiment of the invention Screw press (overall view in axial section) with a speed controller of the feeder, with a Pressure transmitter for the polymer material to be processed,

F i g. 2 Section along line H-II of FIG. 1, Fig. 3 View according to arrow D of F i g. 2, fig. 4 part of the screw press with a speed controller of the feeder, with a torque transmitter of the screw,

F i g. 5 Part of the screw press with a speed controller of the feeder with a torque transmitter.

The screw press for processing polymeric materials contains a hopper 1, a cylindrical housing 2 with heating elements (not shown), and a rotating sleeve which is designed as a metering device 3. and a screw 4 with a loading zone A, a compression zone B and an ejection zone C. Longitudinal grooves a are provided on the inner surface of the metering device 3. The depth of the grooves a decreases evenly in the direction of movement of the material. The metering device 3 is mounted in the housing 2 on bearings 5 and is provided with a variable speed drive (not shown in the drawing) for its rotation (2) in relation to the screw 4. The metering device 3 has openings b. which are attached to its circumference and are successively brought to coincide with the outlet opening of the filling funnel 1 during the rotation (0) 2) of the dispenser. The surface sections of the feeder 3, which carry the openings b one below the other (webs c), are at an angle φ to the axis of the screw 4. The angle should be greater than the angle of friction of the polymer material with steel and is aen area arc tg / <<p<90 ^o , where f is the coefficient of friction of the polymeric material with the surface of the meter 3.

The screw press has a speed regulator of the feeder 3 with respect to the screw 4. This regulator consists of a pressure transducer 6 for the polymeric material (Fig. 1), which is in the cylindrical housing 2 on Exit from the doser 3 is attached. The grooves a of the metering device 3 can be traced along a helical line run opposite to the direction of the thread on the worm 4, thereby inevitable sliding of the polymer in the direction of rotation (ωι) of the screw guaranteed and in this way the speed of rotation of the .ichnecke 3 in comparison to the doser straight nuitn is reduced.

In another variant of the Speed controller of the feeder 3, a torque transmitter 6a (Fig-4) for the screw 4 and a controller 7, which is connected to the pressure transducer 6 and the drive of the dispenser 3

The speed controller of the metering device 3 can contain a torque transmitter 66 (FIG. 5) of the metering device 3 and a controller 7 which is connected to the pressure transmitter 6 and the drive of the metering device 3. The screw press works as follows. A thermoplastic polymeric material in granular, comminuted or powdered state, by the hopper 1 and the openings of the rotating dosing device 3 b of the housing 2 of the screw press fed As a result, in that the webs c between the ports b of the dispenser 3 at an angle φ in are arranged with respect to the axis of the screw, which is greater than the angle of friction of the polymer with steel (the angle φ is limited by the range arc tg f <φ < 90 °), slide the polymer granules reaching between the housing 2 and the webs c through and are not crushed (destroyed). This allows a low power drive for the metering device 3 and the uniform filling of the channel of the screw 4 in the loading zone with material. The most effective angle of inclination of the webs is cp = 15 to 45 °. With these values of the angle φ, almost all polymeric materials show good sliding through. Above 45 ° C, the rigidity of the construction deteriorates because the webs act as springs. At φ = 90 ° the meaning of the construction is lost. Furthermore, the polymer material is advanced by the screw 4 in the direction of the grooves a of the metering device 3. During the processing of the granulated or comminuted polymeric material, the metering device 3 with longitudinal grooves is driven at a speed which is 0.6 to 0.9 the speed of the screw 4 in order to match the work performance of the screw in the feed and discharge zone. Such a high speed of the doser 3 leads to a drive of the doser 3 of increased power, since the drive power according to the equation

xr Μ · Π

71620X1.36
is calculated, where mean:

M - torque (kp / cm),

π - speed of rotation of the feeder (rpm).

so with the aim of reducing energy consumption and reducing the performance of the metering drive the grooves a of the metering device 3 according to a helical line opposite to the direction of the Execute the thread of the worm 4, d. H. an inevitable

bring about figes sliding of the polymer in the direction of rotation of the screw 4 and thereby the Reduce the speed of rotation of the dispenser 3 in comparison with the dispenser 3 which has straight grooves. Reducing the speed of the feeder by twice allows the output of the feeder drive to be increased to be reduced to half, which follows from the equation given above.

The performance in the feed zone of the screw 4 depends on the relative speed of the screw 4 and of the feeder 3 from, which at the constant speed of the screw 4 by changing the speed of the dispenser 3 can be changed. From the dispenser 3, the polymeric material arrives in the

heated housing 2, in which it is heated, compressed, melted and as it moves is homogenized, transformed into a homogeneous viscous mass and by the screw 4 for profiling of a product.

The performance in the discharge zone depends on the speed of the screw and the feed of the Polymer in the feed zone of the screw 4. ·

At a given angular speed of the screw 4, which occurs in all sections of the screw press is constant, the continuity of the work output of the screw press depends on the continuity of the Material feed in the feed zone of the screw 4 is dependent. For the continuity of the material supply in the feeding zone of the screw 4, the grooves a on the inner surface of the feeder 3 contribute. However the material feed can fluctuate over time due to changes in the bulk density of the polymer. Ever according to its size, the output in the loading zone of the screw 4 can be maintained at the same rate The speed of the screw must be higher or lower than the power in the discharge zone of the screw 4. Around the power in the feed zone of the screw 4 to the power in the discharge zone of the screw 4 To coordinate, you select the direction and speed of rotation of the feeder 3. If the Doser 3 rotates at an angular speed which is equal to the speed of rotation of the screw 4, so In this case, the power in the feed zone of the screw 4 is zero because the relative Speed of the screw 4 and the feeder 3 is zero. The enlargement of the supply of the pourable polymeric material is made by increasing the relative speed of auger 4 and Doser 3 made. About the consistency of the work performance of the screw in the feed and the discharge zone is judged by the displays of the pressure transducer 6, which is located in the cylindrical housing 2 on Exit from the doser is attached. If there is no pressure, it means that the performance is in the Feeding zone of the screw is smaller than the output in the discharge zone and the screw press its Operating status has not yet been reached. To increase the capacity, the feed zone of the screw has been increased the relative speed of the feeder 3 with respect to the screw 4 until the beginning of the smooth Portion of the inner surface of the cylindrical housing 2, d. H. a pressure is created at the outlet of the doser 3 The pressure is increased to the required level by further changing the speed of the meter 3 elevated

The specified pressure level is then automatically maintained in the following way:. The pressure transmitter 6 (FIG. 1) transmits the signal to the controller 7, which maintains a constant material pressure at the output of the feeder 3 monitored when the bulk weight is increased or decreased of the starting polymer decreases or increases the control device, which is based on the principle of pressure stabilization is built in the smooth cylindrical housing 2, the material feed in the loading zone the screw 4 by constantly changing the speed of the metering device 3 with respect to the screw 4, thus maintaining a steady state of extrusion operation.

In case the feeding of the polymeric material in the feeding zone of the screw after the torque the screw (Fig.4) is regulated, the torque transmitter 6 of the screw 4 sends a signal to the Controller 7, which monitors the maintenance of a constant torque on the screw 4. at Changing the torque on the screw 4 reduces or increases the control system that is based on the principle of stabilizing the torque of the screw 4, depending on the change in torque the material feed in the loading zone by constantly changing the speed of the feeder 3 with respect to the screw 4 and thus maintains a balanced operating condition of the extrusion upright.

In case the feeding of the polymeric material in the feeding zone of the screw after the torque of the doser (Fig. 5) is regulated, the torque transmitter 6 of the doser 3 sends a signal to the Controller 7, which monitors the maintenance of a constant torque of the doser 3. If there is a change of the torque of the doser 3 decreases or increases the control system that is based on the Principle of stabilization of the torque of the screw 4 is built up, depending on the change in torque the material feed in the loading zone by constantly changing the speed of rotation of the Doser 3 with respect to the screw 4 and in this way maintains a balanced operating state of the Extrusion upright

In connection with the fact that the speed of the screw 4 and the power in the feed zone of the screw are constant, all heating processes and homogenization run in the screw press of the melt or thermal fluctuations, and the melt is at a temperature and consistency The viscosity is expressed which contributes to the manufacture of a quality product

The fact that the openings b of the metering device 3 are attached to the circumference of the same and are successively brought into congruence with the outlet opening of the filling funnel when the metering device rotates, makes it possible to fill the helical channel of the screw 4 with the polymer in the charging zone stabilize. .

The arrangement of the surface sections of the feeder, which separate the openings b from one another, at an angle φ to the screw axis, which angle is chosen within the limits of arc ig ί <φ <90 °, prevents the polymer granules from grinding, which increases the power of the rotary drive of the feeder 3 can be reduced considerably.

The grooves a of the metering device 3, made according to a helical line in the opposite direction to the direction of the thread on the screw 4, make it possible to reduce the speed of the metering device 3 and consequently to reduce the power of the drive and to reduce the energy consumption.

For this purpose 3 sheets of drawings

Claims (6)

Patent claims: !. Screw press for processing polymers Materials, with a cylindrical housing S with a hopper and heating elements, in its Cavity a rotatable screw with axially extending loading, compression and Ejection zones and a sleeve are accommodated which comprises the screw in the loading zone and with grooves on its inner surface and with an opening for the supply of the polymeric material is provided to the screw through the hopper, characterized in that the sleeve as rotatable dosing device (3) is designed for the material and a speed controller for the dosing device (3) has, on the circumference of which a group of openings (6) is attached, which follow one another mii the outlet opening of the hopper (1) to Coverage can be brought. 2. Screw press according to claim 1, characterized in that the surface sections of the feeder (3) which separate the openings (b) from one another are arranged at an angle φ to the central axis of the screw (4) which is in the range of arc tg f <φ < 90 ° is chosen, in which / means the coefficient of friction of the material to be processed on the screw surface 3. Screw press according to claim 1 or 2, characterized in that in the rotatable μ metering device (3) the grooves (a) on its inner surface according to a helical line in the direction opposite to the direction of the screw flight of the screw (4) and a continuously decreasing depth in the direction of movement of the material. 4. Screw press according to claim 1, 2 or 3, characterized in that the speed controller of the dispenser (3) is provided with a pressure transducer (6) for the polymeric material to be processed which is arranged in the cylindrical housing (2) at the outlet from the dispenser (3). 5. screw press according to claim 1, 2 or 3, characterized in that the speed controller of the feeder (3) is provided with a torque transmitter (6a) of the screw (4). 6. Screw press according to claim 1 or 2, characterized in that the speed controller of the metering device (3) is provided with a torque transmitter {% b) of the metering device (3). 50