Device and Method for Controlling the Feed of Polymer Melt to a Plastics Processing Machine

Abstract

The invention relates to a device and a method for controlling the feed of polymer melt, which has been discharged from an extruder, to a plastics processing machine formed from at least two subunits (1, 2), to which the polymer melt discharged from the extruder is fed via a distributor (13) which is positioned downstream of the extruder and which serves for splitting up the polymer melt into partial streams corresponding to the number of subunits. According to the invention, the partial streams are each fed to a subunit by means of a gearwheel pump (11, 12). The volume flows fed to the subunits (1, 2), which are of substantially identical design, can be respectively separately controlled in open-loop or closed-loop fashion through control of the drive rotational speed of the respective gearwheel pump (11, 12) in a manner dependent on operating parameters and/or the configuration of the respective subunit (1, 2).

Claims

1. A device for controlling the feed of polymer melt discharged from an extruder to a plastics processing machine, which is formed from at least two subunits (1, 2) to which is supplied the polymer melt discharged from the extruder via a distributor (13) downstream of the extruder for splitting up the polymer melt partial flows corresponding to the number of subunits, characterized in that the partial flows are each supplied to a subunit by means of a gearwheel pump (11, 12) and that the volume flows supplied to the substantially identically designed subunits (1, 2) are controlled by controlling the drive speed of the respective gearwheel pump (11, 12) depending on the operating parameters, and/or the equipment of the respective subunit (1, 2) can each be separately controlled in open-loop or closed-loop fashion.

2. The device according to claim 1, characterized in that the operating parameters are at least selected from the type and temperature of the polymer melt supplied to the respective gearwheel pump (11, 12), the temperature in the working space of the subunits (1, 2), the filling level and pressure in the respective subunit, and the properties of the products to be processed in the respective subunit.

3. The device according to claim 2, characterized in that the volume flows are controlled in such a way that the pressure in the respective subunit is regulated to a preset target value.

4. The device according to claim 1, characterized in that the plastics processing machine is a device for impregnating fiber bundles with plastic polymer discharged from an extruder, wherein the device is designed to have at least two subunits (1, 2) operated in parallel for an identical or different number or type of fiber bundles.

5. The device according to claim 4, characterized in that the subunits (1, 2) each contain sensors for detecting one or more operating parameters, selected at least from sensors for detecting the temperature of the impregnation chambers of the subunits (1, 2), the temperature of the volume flows, the filling level of the subunits (1, 2), the pressure of the volume flows supplied to the subunits (1, 2), the properties and the number of fiber bundles per subunit, the draw-off speed of the fiber bundles from the subunits (1, 2), the properties of the polymer melt, and that the detected operating parameters are fed to an open-loop or closed-loop control unit via which the drive speed of the respective gearwheel pumps (11, 12) is dynamically adjusted.

6. The device according to claim 1, characterized in that the gearwheel pumps (11, 12) are designed as worm pumps or screw pumps.

7. The device according to claim 1, characterized in that between the extruder and distributor there is a pressure booster pump which can be used to compensate for pressure losses in the polymer melt occurring in the distributor (13), at gearwheel pumps (11, 12), and pipelines (18).

8. The device according to claim 1, characterized in that the gearwheel pumps (11, 12) have a bypass connection between the inlet and outlet, via which part of the supplied polymer melt is fed directly to the subunits (1, 2) of the plastics processing machine, bypassing the pump passage.

9. The device according to claim 4, characterized in that the gearwheel pumps (11, 12) can be operated as pressure boosting pumps with a positive or negative pressure difference between the inlet and outlet by changing the gear bearing with reference to the working pressure of the subunits (1, 2).

10. A method for controlling the distribution of a polymer melt discharged from an extruder over at least two subunits (1, 2) of a plastics processing machine for impregnating rows of fiber strands passing through impregnation chambers of the subunits (1, 2) parallel to one another, in which the fiber strands during their passage through the impregnation chambers are impregnated with the supplied polymer melt, characterized in that the polymer melt discharged from the extruder is split up into at least two partial flows by means of a distributor (13), which are each fed to the subunits (1, 2) by means of a gearwheel pump, wherein the drive speed of the gearwheel pumps (11, 12) is dynamically controlled as a function of the operating parameters of the respective subunits (1, 2).

11. The method according to claim 10, characterized in that the drive speed of the respective gearwheel pump is regulated in such a way that a target operating pressure in the impregnation chamber of the respective subunit is kept constant.

12. The method according to claim 10, characterized in that the drive speed of the respective gearwheel pump is determined by determining one or more operating parameters of the subunits (1, 2), which are selected from the parameters of the temperature of the impregnation chambers of the subunits (1, 2), the temperature of the volume flows, the filling level of the subunits (1, 2), the pressure of the volume flows supplied to the subunits, the properties and the number of fiber bundles per subunit, the draw-off speeds of the fiber bundles from the subunits (1, 2), as well as the physical or chemical properties of the polymer melt.

13. The method according to claim 10, characterized in that the gearwheel pumps (11, 12) are designed as worm pumps or screw pumps.

Description

[0023] The invention is explained in more detail below using an exemplary embodiment for two subunits. In the following:

[0024] FIG. 1 shows a simplified perspective view of a plastics processing machine with melt feed,

[0025] FIG. 2 shows a bottom view of a machine according to FIG. 1,

[0026] FIG. 3 is a front view of a machine according to FIG. 1.

[0027] The plastic processing machine shown in FIG. 1 serves to impregnate fiber strands with plastic polymer. The fiber bundles are fed in parallel to each other into a gap of the machine and become saturated with plastic polymer as they pass through the gap. The machine comprises two subunits 1 and 2 which are arranged parallel to one another and can be operated essentially independently of one another. Such a plastics processing machine is disclosed in EP 3470196 A1, the content of which is referred to.

[0028] The invention is not limited to use on two subunits, but also includes a larger number of subunits. The invention is also suitable for a large number of plastics, such as polymers, in particular polyamides (PA), polyolefins (PP), polyesters and other engineering plastics.

[0029] In FIG. 1, subunit 1 has a nozzle outlet 3 and subunit 2 has a nozzle outlet 4, from which the impregnated fiber bundles leave the subunits.

[0030] The polymer melt to be fed to the subunits is supplied by an extruder, not shown. The polymer melt reaches a distributor 13 via a flange 19, the pipeline 18, a deflection 17, and a flange 16, in which it is split up into two partial streams which enter two gearwheel pumps connected to the distributor. The distributor 13 is a passive distributor which splits the incoming melt and directs it to separate outlets to which feed pumps are connected. The distributor has inspection covers 20 and 21 for maintenance.

[0031] The gearwheel pumps 11 and 12 connected to the outlets of the distributor 13 are driven via motor drives with electric motors 5, 6 and gears 7, 8. To compensate for mounting tolerances or for local adjustment, the motor drives can contain cardan shafts 9 and 10, via which the gearwheel pumps 11 and 12 are driven.

[0032] To cool the shafts 22 and 23 of the gearwheel pumps, these have front cooling seals 14 and 15, which are designed as liquid-cooled shaft seals.

[0033] FIG. 2 shows a view from below of the device according to the invention, which shows the arrangement of the distributor 13 below the two subunits of the plastics processing machine.

[0034] FIG. 3 shows a front view of the device. The figure shows the compact structure, in which the distributor 13, the gearwheel pumps 11 and 12 and the subunits 1 and 2 of the plastics processing machine are directly interconnected over a short distance to keep the path of the polymer melt as short as possible.

[0035] To regulate the drive speed of the gearwheel pumps, which is preferably between 5 and 150 rpm, an open-loop or closed-loop control unit, not shown, is provided which is connected to a series of sensors which are arranged in the distributor, the gearwheel pumps and the subunits, in particular for recording the working pressures, temperatures, and relevant properties of the products to be processed and to regulate the delivery volume of the pumps and the pressure there. Furthermore, target values and fixed parameters for the type and quantity of the products to be processed can be set in the open-loop or closed-loop control unit.

REFERENCE SYMBOLS

[0036] 1 Subunit [0037] 2 Subunit [0038] 3 Nozzle outlet [0039] 4 Nozzle outlet [0040] 5 Electric motor [0041] 6 Electric motor [0042] 7 Gears [0043] 8 Gears [0044] 9 Cardan shaft [0045] 10 Cardan shaft [0046] 11 Gearwheel pump [0047] 12 Gearwheel pump [0048] 13 Distributor [0049] 14 Cooling seal [0050] 15 Cooling seal [0051] 16 Flange [0052] 17 Deflection [0053] 18 Pipeline [0054] 19 Flange [0055] 20 Inspection cover [0056] 21 Inspection cover [0057] 22 Shaft [0058] 23 Shaft