Blown film line and method for operating a blown film line

Abstract

A blow film line and a method for operating the same relates to improving the flow rate in conventional blow film lines without compromising the production quality. The inner cooling body shows an air outlet path, with a cooling ring being embodied in a height-adjustable fashion, with a controller positioning the cooling ring in a lower area of the inner cooling body for the start-up of the facility. The cooling ring is positioned in the upper area of the air outlet path of the inner cooling body in order to achieve the steady-state production.

Claims

1. A blow film line comprising an inner cooling body with an air outlet path, the inner cooling body being embodied at least over an overwhelming part of the air outlet path in a monotonously or strictly monotonously expanding fashion, and a height-adjustable cooling ring that cools a blow film hose from outside the inner cooling body, the height-adjustable cooling ring traveling along a displacement path that extends along the entire inner cooling body during the operation of the blow film line, wherein the cooling ring is positioned in an upper half of the air outlet path during a steady-state production, and wherein the cooling ring is positioned in a lower half of the air outlet path during a start-up phase; wherein a controller is provided, which is connected to a height adjusting means of the cooling ring, wherein the controller is embodied to position the cooling ring during the start-up phase of the blow film line underneath the upper area and/or in a lower area, and to move it for the steady-state production into the upper area and/or to move it upwards within the lower area.

2. A blow film line comprising an inner cooling body with an air outlet path, whereby the inner cooling body is embodied at least over an overwhelming part of the air outlet path in a monotonously or strictly monotonously expanding fashion, and whereby a height-adjustable cooling ring is provided for cooling a blow film hose from the outside during the operation of the blow film line, wherein the height-adjustable cooling ring traveling along a displacement path that extends along the entire inner cooling body during the operation of the blow film line, whereby the blow film line is embodied to position the cooling ring in the lower half of the air outlet path during the steady-state production, particularly preferred in the lower third; and a controller is provided, which is connected to a height adjusting means of the cooling ring, wherein the controller is embodied to position the cooling ring during the start-up phase of the blow film line underneath the upper area and/or in a lower area, and to move it for the steady-state production into the upper area and/or to move it upwards within the lower area.

3. A blow film line according to claim 1, wherein the blow film line is implemented to allow the blow film hose to travel upwards and to pull it off.

4. A blow film line according to claim 1, wherein the inner cooling body shows a structured surface.

5. A blow film line according to claim 1, wherein the inner cooling body further includes a plurality of annular grooves which are embodied as a plurality of air outlets.

6. A blow film line according to claim 1, wherein the inner cooling body comprises a perforated sheet at its surface.

7. A blow film line according to claim 1, wherein the inner cooling body comprises a functionally modified surface.

8. A blow film line according to claim 7, wherein the inner cooling body comprises a coating.

9. A blow film line according to claim 1, wherein the height adjusting means is provided for the cooling ring, which shows a drive.

10. A blow film line according to claim 9, wherein the height adjusting means is connected to a manual switch, with the switch comprising a rising setting, a lowering setting, and a holding setting.

11. A blow film line according to claim 9, wherein the height adjusting means is connected to a manual switch, and the manual switch includes a spring-loaded rising setting and a spring-loaded lowering setting.

12. A blow film line according to claim 9, wherein the height adjusting means is connected to the controller, and the controller is connected to a recipe database in a data transmitting fashion, wherein the controller is embodied to read data from the recipe database regarding a target height position of the cooling ring, primarily regarding precisely two target height positions, and the height adjusting means being appropriately addressed or regulated.

13. A blow film line according to claim 1, wherein the controller is provided, which is connected to the height adjusting means of the cooling ring, wherein the controller is embodied to keep the cooling ring locally fixed during the steady-state production.

14. A blow film line according to claim 1, wherein the controller is provided, which is connected to the height adjusting means of the cooling ring, wherein the controller is implemented to keep the cooling ring in motion during the steady-state production based on continuous measurements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the disclosure is explained in greater detail based on an exemplary embodiment with reference to the drawing.

(2) FIG. 1 is a schematic in a longitudinal cross-section the upper edge of a blow head with an annular nozzle, the lower part of an inner cooling body, as well as a height-adjustable cooling ring, each at a blow film line.

DETAILED DESCRIPTION OF THE DRAWINGS

(3) The blow film line 1 in FIG. 1 (shown only partially) comprises with regards to the extrusion of a plastic melt essentially the blow head 2 with an annular shaped die 3, which is arranged rotationally-symmetrical around an extrusion axis 4, as well as an inner cooling body 5 located upstream thereof, and a cooling ring 6. During operation of the blow film line 1 a plastic melt is extruded through the annular shaped die 3 in a direction of extrusion 7, thus vertically upwards. In its diameter, perpendicular in reference to the axis of extrusion 4, the blow film expands then along the direction of extrusion 7 around the inner cooling body 5, preferably without contacting it.

(4) Air outlet sections are arranged along the height of the inner cooling body 5, for example air outlet grooves or perforated sheets 8 with pressurized air flowing behind them (shown as an example).

(5) From a lowest height 9, at which cooling air is blown out of the inner cooling body 5, to an uppermost height 10, here for example represented by an air outlet groove 11, an air outlet path 12 extends parallel in reference to the axis of extrusion 4.

(6) The cooling ring 6 shows air outlet nozzles 13 (numbered as examples). The cooling ring 6 is additionally positioned along a displacement path 14 in a manner adjustable in height along the inner cooling body 5. A height adjusting means 20 is effectively connected to a controller 22 so that within certain maximal limits the controller can displace the cooling ring 6, more precisely its area at the air outlet nozzles 13 projected to the axis of extrusion 4.

(7) The preferred embodiment of the disclosure provides that the air outlet nozzles 13 of the cooling ring 6 or in case of several cooling rings of at least one cooling ring, preferably however of all cooling rings, preferably during the start-up phase of the equipment are positioned in a lower area 15 of the air outlet path 12, in any case however during the steady-state production in an upper area 16.

(8) The inner cooling body 5 may, as shown in the present example, be provided with different angles of incline 17 of its jacket, here for example initially showing a strictly monotonously expanding angle of incline 17, then a bend 18, followed again by a stronger, strictly monotonously increasing area in its diameter, and finally a strictly monotonous, less increasing area in the diameter. Prototype tests of the inventor have shown that the diameter of the inner cooling body 5 should expand strictly monotonously or at least monotonously, with preferably at least one section being provided with strictly monotonous expansion, thus a non-cylindrical area with an incline angle 17 of the jacket being 90, with the angle potentially changing rapidly or steadily over the vertical extension. Any small recesses in the surface of the inner cooling body 5 potentially formed by air outlets, such as caused by each recess 19 in the perforated sheet 8, are not considered, here. Rather, the actual surface contour is being discussed.

(9) When the diameter expands in a strictly monotonous fashion along the direction of extrusion, here the blow film hose is subject to tensile stress over the entire distance due to the also strictly monotonous expansion, which can prevent the formation of creases.