MEASUREMENT DEVICE AND METHOD FOR DETECTING LOCAL THICKENINGS IN A FILM WEB

Abstract

Provided is a measurement device (10) for detecting local thickenings in a film web (20), more particularly an extrusion and/or coextrusion film, having a first roll (14) for rolling on the film web (20) that can be moved along, a second roll (18) that can be supported indirectly above the film web (20) on the first roll (14) for rolling on the film web (20) that can be moved along, wherein the second roll (18) is resiliently guided in the thickness direction of the film web (20) that can be moved along, more particularly in the vertical direction, and at least one distance sensor (24) that is stationary with respect to the first roll (14) and/or to the film web (20) that can be moved along, for detecting a distance of the second roll (18). The second roll (18), which can be displaced from a local thickening of the film web (20) in the thickness direction of the film web (20), makes it possible to quickly and easily detect local thickenings in a film web (20).

Claims

1. A measurement device for detecting local thickenings in a film web (20) comprising at least one of an extruded film and a co-extruded film, having a first roll (14) for rolling on the film web (20) configured to be moved along, a second roll (18) that can be supported indirectly above the film web (20) on the first roll (14) for rolling on the film web (20) configured to be moved along, wherein the second roll (18) is resiliently guided in the thickness direction of the film web (20) configured to be moved along in the vertical direction, and at least one distance sensor (24), fixed in position relative to at least one of the first roll (14) and the film web (20) configured to be moved along for detecting a distance of the second roll (18).

2. The measurement device as claimed in claim 1, characterized in that the at least one distance sensor (24) is configured as a sensor measuring without contact, wherein the second roll (18) completely shades at least one of the first roll (14) and the film web (20) from the at least one distance sensor (24).

3. The measurement device as claimed in claim 1, characterized in that the first roll (14) is rotatably mounted in a first frame part (12), wherein the second roll (18) is rotatably mounted and guided linearly in a second frame part (16), wherein the second frame part (16) is coupled to the first frame part (12) configured to be pivoted between a closed position and an open position, wherein, the second frame part (16) is configured to be locked against movement with the first frame part (12) when in the closed position.

4. The measurement device as claimed in claim 3, characterized in that the at least one distance sensor (24) is fixed to the second frame part (16).

5. The measurement device as claimed in claim 1, further including an evaluation device coupled to the at least one distance sensor (24), wherein the evaluation device is configured to output a signal in the event of a distance change of the second roll (18) relative to the at least one distance sensor (24) that exceeds a predefined threshold value, wherein the signal can be further processed by a marking device that is configured to be connected to one of the evaluation device for marking a length section of the film web that is determined to be defective and a cutting device configured to be connected to the evaluation device for severing a length section of the film web (20) that is determined to be defective.

6. A conveying section for conveying a film web (20), comprising one of an extruded film and a co-extruded film, having a forward drive device configured for driving the film web (20) forward, a measurement device (10) as claimed in claim 1 for detecting local thickenings in the film web (10) guided through the measurement device (10), a web cleaning device (28) connected upstream of the measurement device (10) configured for at least one of separating contaminants, neutralizing static charges by means of at least one applied ion cloud and extracting the contaminants, wherein the measurement device (10) is configured to be supported and/or spring-mounted separately.

7. A method for detecting local thickenings in a film web (20), comprising at least one of an extruded film and a co-extruded film, with a measurement device (10) as claimed in claim 1, the method comprising the steps moving the film web (20) between a first roll (14) and a second roll (18) supported on the first roll (14), wherein the second roll (18) is guided resiliently in the thickness direction of the film web (20) configured to be moved along in the vertical direction, detecting a distance change of the second roll (18) relative to the first roll (14), caused by local thickenings, and outputting a signal in the event that a distance change of the second roll (18) exceeding a predefined threshold value is detected, wherein the signal is further processed by at least one of a marking device for marking a length section of the film web (20) that is determined to be defective and a cutting device for severing a length section of the film web (20) that is determined to be defective.

8. The measurement device as claimed in claim 1, characterized in that the at least one distance sensor (24) is a laser rangefinder.

Description

[0014] The invention will be explained below by way of example with reference to the appended drawings and by using preferred exemplary embodiments, wherein the features illustrated below can each illustrate one aspect of the invention individually and also in combination. In the drawings:

[0015] FIG. 1: shows a schematic partly sectioned front view of a measurement device,

[0016] FIG. 2: shows a schematic partly sectioned side view of a conveying section with the measurement device from FIG. 1, and

[0017] FIG. 3: shows a schematic partly sectioned side view of the conveying section from FIG. 2 with the measurement device in an open position.

[0018] The measurement device 10 illustrated in FIG. 1 has a first roll 14 rotatably mounted in a lower, first frame 12, and a second roll 18 rotatably mounted in an upper, second frame 16. A film web 20 can be led through between the first roll 14 and the second roll 18 supported on the first roll 12 by a forward drive device. The second roll 18 is additionally resiliently guided in the thickness direction of the film web 20 which, in the present exemplary embodiment, coincides with the vertical direction, with the aid of a linear guide 22. Should the film web 20 have a local thickening, during the transport of the film web 20 between the rolls 14, 18, this thickening can push the second roll 18 away from the first roll 14 in the thickness direction counter to the direction of the force of gravity. With the aid of at least one distance sensor 24 connected to the second frame 16, this displacement of the second roll 18 can be measured as a distance change. Here, the shortening of the distance of the second roll 18 to the distant sensor 24 corresponds to an enlargement of the distance of the second roll 18 relative to the first roll 14 and/or to the film web 20, caused by the local thickening of the film web 20. If the distance change measured by the distance sensor 24 exceeds a tolerable extent depicted with the aid of a predefined threshold value, the length section of the film web 20 that is identified as defective as a result can be marked and/or cut out.

[0019] As illustrated in FIG. 2, a conveying section 26 provided to transport the film web 20 can have a web cleaning device 28 connected upstream of the measurement device 10. The web cleaning device 28 can suck and/or blow away contaminants on the surfaces of the film web 20. In particular, the web cleaning device 28 can remove electrostatically adhering contaminants in that the web cleaning device 28 applies at least one ion cloud to the surfaces of the film web 20, in order to be able to neutralize and more easily separate off the electrically adhering contaminants.

[0020] The first frame 12 and the second frame 16 can be coupled pivotably to each other via a hinge 30. In the closed position illustrated in FIG. 2, the second frame 16 can additionally be non-detachably connected to the first frame 12, in particular detachably locked, in order that natural vibrations of the measurement device 10 occur identically in both rolls 14, 18. In the open position of the measurement device 10, illustrated in FIG. 3, the second frame 16 is opened through about 90°. Here, the second frame 16 can rest on a rubber buffer 32 defining the end position in the open position. The pivoting movement of the second frame 16 can be damped with the aid of gas pressure springs 34 fixed to the first frame 12 and to the second frame 16.