CH707355B1 - Method for measuring the thickness of wide films. - Google Patents

Abstract

The invention relates to a method for measuring the thickness of wide films, in which a film (10) between two granite crosspieces (20, 30) is conveyed through. With the aid of at least two opposing distance sensors (22, 32) arranged on each of the traverses (20, 30), their distances to the film surface are determined and sent to a data processing device. This calculates the thickness of the film (10) at one point on the basis of measured values of the distance sensors (22, 32), wherein a respective carriage (21, 31) is moved in exact position on the traverses, and one of the slides (21, 31) in each case Distance sensors (22, 32) is assigned, which performs distance measurements at different measuring points during a crossing of the film (10). In the first aspect of the invention, the distance sensors (22, 32) are triangulation laser sensors which are calibrated before crossing the film (10) by means of at least one calibration piece (12, 13) arranged terminally with respect to the crossbars (20, 30), in that a measuring beam (23, 33) of a triangulation laser sensor is emitted and received again in a calibration position at a defined distance of the calibration piece (12, 13) and the defined distance is determined from the transit time of the measuring beam (23, 33), wherein the calibration piece (12, 13) is associated with an optical passage (14). In the second aspect of the invention, in addition to the distance sensors (22, 32), at least one of the carriages (21, 31) is assigned a thermocouple which carries out a temperature measurement in the region of the film (10) and correlates the temperature measured values determined in this way with the distance measured values the data processing device is transmitted, which carries out a normalization of the distance measured values to standard conditions on the basis of the temperature measured values.

Description

Description: The present invention relates to a method for measuring the material thickness of foils, in which a foil is conveyed between two cross members and with the aid of at least two distance sensors arranged on one of the cross members, the distance between them and the surface of the foil is determined and sent to a data processing device are sent, which calculates the material thickness of the film at one point on the basis of measured values from the distance sensors, the crossbeams being granite rails, on each of which a carriage is moved with positional accuracy, the carriage being assigned one of the distance sensors, which during a Crossing the foil distance measurements at different measuring points.

Such a method is already known from CN 2013 64 149 Y. It is already recognized there that a stable and rigid arrangement of the travel rails of the above-mentioned slides is important for a precise measurement of the material thickness. From JP 2002 131 044 A a method of lower accuracy is also known, from DE 10 303 659 A1 the use of granite rails for precise measuring tasks.

In methods known today, the material thickness of the film is usually recorded at two or more static measuring points. If deviations from the quality standard are found at these points, the quality management system takes effect in such a procedure. However, this known procedure is always problematic if there may be deviations between the desired material thickness of a film between the measuring points, which would lead to an elimination according to the criteria of quality management, but which cannot be determined due to the placement of the measuring points.

By arranging a large number of sensors and thus creating a large number of measuring points, the accuracy of the measurement can theoretically be improved as desired, but the cost factor is problematic here, which becomes more and more noticeable with an increasing number of sensors.

Conversely, the desired foils to be produced are technical precision foils, the material thickness of which has a significant share in the quality of the foils, so that special requirements have to be met with regard to the measurement accuracy. These films are typically produced on long belts on production lines and may be cut to the required mass at the end of the manufacturing process. In some cases, however, the intended interfaces are already incorporated into the film strips, so that the films are permanently produced as an endless product and their quality, in particular the material thickness, must be checked using suitable monitoring means at the end of the production line.

A material test for very narrow strips of film is already known in an arrangement which provides a C-shaped truss arrangement which encompasses the film produced on one side and which forms an upper and a lower traverse, on each of which interconnected sensors are moved. Due to the arrangement, it is only possible to check very narrow foil strips, especially because the crossbeams of the C-shaped crossbeam arrangement sag to the ends due to gravity and thus allow a precise measurement at most up to a measuring accuracy of 10 pm.

Against this background, however, a measurement of the material thickness of wider foils is now to be made possible, which also achieves a measurement accuracy of one micron at the same time. At the same time, the costs for a close inspection of the film produced should be kept low.

This object is achieved by a method for measuring the material thickness of films according to the features of claim 1 and the independent claim 7. Further useful embodiments of this method can be found in the following claims.

According to the invention, it is provided that, as part of a method for measuring the material thickness of films, the film, which is endlessly led out of the production process, is encompassed on all sides by a truss arrangement which realizes an upper and a lower traverse.

The words "above" and "below" will be used in the further course of the description in general, although the position of the film and thus also the trusses can be chosen arbitrarily. For further consideration, it is assumed that the surfaces of the film point upwards or downwards and that a crossbar is set up essentially parallel to the film surfaces above or below the film surfaces. Arrangements with other orientations are just as conceivable as an exchange of the upper with the lower traverse.

The trusses can be laterally connected to one another with the aid of carriers, so that the truss arrangement encloses the film strip. Distance sensors for measuring the distance to the film surface are arranged on the traverses, a sensor on the upper traverse correlating with a sensor on the lower traverse and focusing on the same film coordinates on both sides of the film. A known value of the distance between the correlating sensors and the distance values measured above or below the film make it possible to determine the material thickness of the film at the respective measuring point by simply forming a difference.

In the context of the invention, distance sensors are used in pairs, which are mounted on slides and can be moved along the length of the crossbars. As a result, the same sensors can record several measuring points in succession during the possibly interrupted travel of the sled and thus the task of several

CH 707 355 B1

Take over distance sensors that would otherwise have to be arranged side by side on a crossbar. It is necessary for this that the carriages can be moved so precisely and in a coincident manner that it is guaranteed that both carriages measure exactly at the same coordinates with respect to the film.

Such an exact measurement requires extremely rigid crossbeams, which is ensured in the context of the invention by using crossbeams made of granite. Such granite rails are absolutely rigid and are therefore suitable for spanning a larger distance, such as about a meter in width, without having to expect bending during the movement of the slide. It also makes sense here if the granite rails used are angled in their longitudinal extent, that is to say they have an L-shaped, C-shaped, U-shaped or other angled cross section in cross section. Bending is further avoided by such a shape of the granite rails.

The positionally accurate movement of the carriage, which carries the distance sensors on the traverses, can be accomplished with the aid of a motor drive, which can be designed as a servo motor, linear motor, stepper motor and the like, or as a spindle drive. An exact position determination of the sled is made using a scale that is assigned to the crossbeams. In order to ensure the greatest possible accuracy of the obliteration, the scale is engraved in a glass rod which is connected to the granite rail, preferably incorporated into it. With the help of an optical sensor, which is connected to the carriage, the crossing of each division of the scale of the glass rod is recorded and transmitted to a data processing device, which also receives and processes the distance data from the distance sensors and which, in this respect, participates in the method.

On the basis of the measured distance measurements and the position of the slides on the trusses detected with the aid of the scale, the data processing device is able to assign each point of the film its respective material thickness, so that the arrangement described achieves a largely area-wide monitoring of the material thickness of the film thickness can be.

In order to achieve the greatest possible smoothness of the slide and a precise storage of the same on the crossbeams, they are each mounted on an air cushion, which is created with the aid of air nozzles arranged on the slide. In detail, each carriage has a plurality of wheel chambers. in which wheels are used. However, these wheels are not directly connected to the sled, but are subjected to an air jet from all sides in which they are surrounded by the sled, which ultimately causes the sled to hover over the wheels. By means of an appropriate arrangement from different sides of the crossmember, the carriage is not raised in this way, but is centered in an exact position in that the crossmember is held or clamped between a plurality of wheels which are pushed away from the carriage in this way.

In a first aspect of the invention, the distance sensors used are triangulation laser sensors which emit a laser beam and receive its reflection again, in order then to be able to determine the distance traveled and thus the distance to the film to be measured on the basis of the light propagation time. In order to carry out a calibration with regard to the running time for a distance, the carriers which connect the cross members to one another are assigned calibration pieces, in the area of which the distance sensors connected to the slide can enter before and / or after crossing the film. If the distance sensor of a carriage is then above a calibration piece, the laser beam of the distance sensor is no longer reflected by the film, but by the calibration piece, so that the distance sensor can be adjusted and calibrated based on the defined distance of the calibration piece.

For this purpose, the calibration piece can provide at least two calibration positions by being configured in two stages, so that a level formed by the calibration piece represents a maximum distance, the second level formed represents a minimum distance. In addition, the calibration piece can be arranged on both sides of the film and can also be designed equally for the slides and distance sensors of the two traverses in that the integrated steps are present on both sides. It is provided, although not absolutely necessary, that the distance sensors are calibrated in both directions after each crossing of the film.

In order to be able to take into account the reflection behavior of the film to be measured during the calibration, the calibration pieces each have a receptacle in the area of their calibration positions in which calibration patterns can be used. These calibration patterns are made of a material corresponding to the material of the film, so that the reflective properties of the film are simulated at this point and an exact calibration is possible.

[0020] In addition, the calibration pieces can each have an optical passage, through which two mutually opposite distance measuring sensors can be compared with one another. For this purpose, each of the distance sensors will emit a measuring beam which strikes the other distance sensor and is thrown back by the latter. One distance sensor will amplify the measuring beam compared to normal operation and the other distance sensor will weaken the measuring beam. Ideally, the first-mentioned distance sensor will use the measuring beam at maximum strength, while the other distance sensor operates the measuring beam at the lowest possible energy. This makes it possible to distinguish the reflected own beam from the foreign beam to be reflected by comparing the transmitted beam with the received beam.

CH 707 355 B1 In the course of a mutual position adjustment in the area of the optical passage of the calibration, an adjustment with respect to the feed position on the crossmember is also advantageously carried out by the respective position on the scale of the glass rod in this position being 0 or on the highest value is set.

In a second aspect of the invention, in addition to the distance sensor, at least one of the slides is assigned a thermocouple, which is held on the sled in the area of the film. In this way, the ambient temperature of the film can be recorded, so that the actual temperature of the film can be inferred from the recorded temperature and, using this information, which is forwarded to the data processing device, a conversion of the actual measured material thickness to normal conditions under a predetermined temperature can be provided by the data processing device.

In addition to this normalization, the possible deformation thereof is also recorded in advance of the use of a cross member and checked as part of a measurement as to whether the respective cross member has a pitch or not. Any deformations are stored in connection with the respective position on the crossbar at the data processing device and taken into account when calculating the material thickness of the film.

The invention described above is explained in more detail below using an exemplary embodiment. Show it

1 shows an endlessly produced film converted from a truss arrangement in a more schematic representation transverse to the film,

Fig. 2 shows one of the trusses shown in Fig. 1 with an attached slide in a schematic cross-sectional view, and

3 shows one of the calibration pieces shown in FIG. 1 in a lateral, schematic cross-sectional illustration.

Fig. 1 shows a film 10 in a cross-sectional view, a truss arrangement being constructed around this film 10, which consists of an upper cross member 20, a lower cross member 30 and two supports 11 holding them in position. An upper slide 21 and a lower slide 31 are each movably arranged on the cross members 20 and 30, which can detect the entire width of the film 10 with a distance sensor 22 and 32 arranged on the slide 21 and 31. The crossbeams 20 and 30 are made of granite, so that despite the large width of the film 10, which is overlapped by the crossbeams 20 and 30, the latter keep their shape exactly during the movement of the slide 21 and 31.

So while the film 10 is being produced and conveyed, the slides 21 and 31 move back and forth over the film 10 or below and measure the distance between the distance sensors 22 and 32 and that of the respective distance sensor in a large number of measuring points 22 and 32 facing surface of the film 10. In a calibration position, ie in the area of the calibration pieces 12 and 13 arranged laterally on the supports 11, the distance between the two distance sensors can also be determined, so that the material thickness of the film 10 in every measuring point can be determined. The detected distance values of the distance sensors 22 and 32 are sent to a remote data processing device, which is not shown in the picture. The data processing device processes the recorded measurement data and, based on the production specifications, decides whether the specifications regarding the material thickness and the permitted deviations have been met. If this is not the case, at least a part of the film 10 is marked as a scrap.

In addition to measuring the distance of a distance sensor 22 or 32 to the surface of the film 10, a thermocouple 29 is arranged on at least one of the slides 21 and 31, which detects the temperature in the region of the film 10. The temperature measurement values are also transmitted to the data processing device, which normalizes the measured distance values to a desired normal temperature on the basis of the temperature values. The upper measuring beam 23 and the lower measuring beam 33 are laser beams which are emitted by the distance sensors designed as triangulation laser sensors.

As can be seen in Fig. 2, the carriage 21 and 31 on the cross members 20 and 30 are movable. In FIG. 2, the upper carriage 21 is shown by way of example in a cross-sectional view, so that it can be seen that the upper carriage 21 is supported on a total of three wheels 27 in the plane shown. For this purpose, the wheels are accommodated in wheel chambers 28 of the upper carriage 21 and are illuminated from all sides with the aid of air nozzles 26, so that ultimately the arrangement of several such wheels 27 from different directions holds the upper carriage 21 on the crossmember and transports them on an air cushion becomes. This enables exact positioning on the crossbeam 20, which is only in contact with the wheel arches.

In the upper cross member 20, a glass rod 25 is incorporated, which has a scale. The scale is read using an optical sensor 24, so that the data processing device can use the readings to draw conclusions about the position of the upper carriage 21 on the upper cross member 20. In detail, the markings on the glass rod 25 are engraved notches, which are detected by the optical sensor 24

CH 707 355 B1. Starting from a zero point, the position of the slide 21 on the crossmember 20 can then be deduced by counting the detected, crossed graduation marks and the current direction of movement of the drive.

3 shows a calibration piece 12 which is arranged on a carrier 11. As soon as the distance sensor 22 or 32 extends beyond the edge of the film 10, it will enter the area of the calibration piece 12 or 13 which has a first calibration position 15 and a second calibration position 15. The first calibration position 15 represents a minimum distance which the film occupies in the course of the measurement to be carried out, while the second calibration position 16 represents the maximum distance of the film. At both calibration positions 15 and 16 there is a receptacle 17, into which a calibration pattern can be inserted. This is simulated in the material of the film 10, so that the reflection properties of the film can be taken into account in the calibration. An optical passage 14 of the first calibration piece 12 can be used to measure the distance between the distance sensors 22 and 32 above this optical passage 14 or below. The first calibration piece 12, as well as its counterpart on the opposite carrier 11, namely the second calibration piece 13, are each designed so that calibration of the two opposite distance sensors 22 and 32 can take place simultaneously. A calibration is carried out before and after each crossing of the film 10 on both sides of the film 10 on the respective calibration pieces 12 and 13.

A method for measuring the material thickness of foils is thus described above, which allows an arrangement of traversing sensors to be used despite the foil width, which is made possible by extremely rigid material, in the form of granite traverses. Their use also enables high measuring accuracy. With the use of traversing distance sensors, it is possible to dispense with the arrangement of a large number of sensors in spite of a close-meshed covering with measuring points.

Claims (12)

claims 1. A method for measuring the material thickness of foils, in which a foil (10) is conveyed between two cross members (20, 30) and with the aid of at least two mutually opposite distance sensors (22, 30) arranged on one of the cross members (20, 30). 32) whose distances to the film surface are determined and sent to a data processing device which calculates the material thickness of the film (10) at one point on the basis of measured values of the distance sensors (22, 32), the trusses (20, 30) being granite rails acts, on each of which a carriage (21, 31) is moved with positional accuracy, one of the distance sensors (22, 32) being attached to one of the carriages (21, 31) which, during a crossing of the film (10), measures distance at various Carries out measuring points, characterized in that the distance sensors (22, 32) are triangulation laser sensors which are used before the film is crossed (10) are calibrated with the aid of at least one calibration piece (12, 13) arranged terminally with respect to the crossbeams (20, 30), in that a measuring beam (23, 33) of a triangulation laser sensor in at least one calibration position at a defined distance of the calibration piece (12, 13 ) is transmitted and received again and the defined distance is determined from the transit time of the measuring beam (23, 33), the calibration piece (12, 13) having an optical passage (14) through which two opposite distance sensors (22, 32) can detect their mutual distance, which they transmit to the data processing device. 2. The method according to claim 1, characterized in that the calibration piece (12, 13) is designed such that the distance sensors can assume at least two calibration positions (15, 16), a first calibration position (15) a minimum distance and a second calibration position ( 16) represent a maximum distance which the film can occupy in the course of the measurement to be carried out. 3. The method according to any one of claims 1 or 2, characterized in that the calibration piece (12, 13) for the sled (21, 31) of both traverses (20, 30) is used, the at least one calibration position for the calibration of the two Distance sensors (22, 32) is formed. 4. The method according to claim 2, characterized in that on the calibration piece (12, 13) in the calibration positions (15, 16) receptacles (17) for inserting calibration patterns are arranged which match the material of the film (10). 5. The method according to any one of the preceding claims, characterized in that, for mutual distance measurement, a distance sensor (22, 32) increases the intensity of its measuring beam (23, 33), the other distance sensor (32, 22) increases the intensity of its measuring beam (33, 23 ) and for verifying the reception of the other measuring beam (23, 33) a difference between emitted and received light intensity is evaluated. 6. The method according to any one of the preceding claims, characterized in that a calibration of the at least one position is carried out along a scale of a glass rod (25) at the at least one calibration position in the region of the optical passage (14). 7. A method for measuring the material thickness of foils, in which a foil (10) is conveyed between two cross members (20, 30) and with the aid of at least two distance sensors (22, 32) whose distances to the film surface are determined and sent to a data processing device which determine the material thickness of the film (10) at one point on the basis of CH 707 355 B1 Measured values of the distance sensors (22, 32) are calculated, the crossbeams (20, 30) being granite rails, on each of which a carriage (21, 31) is moved with positional accuracy, one of the distance sensors (22, 32) each one of the slides (21, 31) is attached, which carries out distance measurements at different measuring points during a crossing of the film (10), characterized in that the data processing device in each case has a position of the slides (21, 31) from the distance sensors (22, 32) received on the crossbeam (20, 30) and distance values of the sensors and for each measuring point on the film (10) their material thickness is determined by forming the difference between a calibrated distance and the sum of the distances measured in the measuring point, at least one of the slides being a thermocouple (29), which carries out a temperature measurement in the area of the film (10) and the temperature measurements thus determined in correlation are transmitted with the measured distance values to the data processing device, which uses the measured temperature values to normalize the measured distance values to predetermined normal conditions. 8. The method according to claim 7, characterized in that the carriages (21, 31) on the crossbeams (20, 30) are each moved by means of a motor drive, with an exact obliteration of the carriages (21, 31) over each of the crossbeams (20, 30) assigned scale is carried out. 9. The method according to claim 8, characterized in that the scale is engraved into a glass rod (25) incorporated into the granite rail and, with the aid of an optical sensor (24), a position signal from the optical sensor (24) is indicated each time a division mark of the scale is exceeded the data processing device is transmitted. 10. The method according to claim 8, characterized in that each carriage (21, 31) has wheels (27) which run on the corresponding crossmember (20, 30) and are mounted on an air cushion relative to the respective carriage (21, 31) , 11. The method according to claim 10, characterized in that a plurality of air cushions interact with the wheels (27) for mounting a carriage (21, 31) on its cross member (20, 30) by the air cushions on pairs of wheels (27) with oppositely oriented running surfaces , or act on wheels (27) with the traverse (20, 30) contacting contact surfaces in the direction of gravity. 12. The method according to any one of claims 7 to 11, characterized in that any deformations of the crossbeams (20, 30) recorded by a one-time measurement, transmitted to the data processing device and included by this in determining the material thickness of the film (10) , CH 707 355 B1 22 - 20