Force measuring device for measuring tension in a moving material web

Abstract

The present invention relates to a force measuring device (20) for measuring the web tension of a running material web (10) having a longitudinal direction defined by the running direction and a transverse direction, characterized in that the force measuring device (20) comprises a shaft (22) and a measuring roll (30) supported on the shaft and wrapped around by the material web. [Solution] According to the invention, it is provided that the measuring roll is formed as a split measuring roll (30) having two or more measuring segments (32) that are separately slidable on the shaft (22) and that can be locked in a measuring position on the shaft in order to position the measuring segments (32) in accordance with the desired measuring position in the transverse direction of the material web (10) so that each longitudinal portion (12) of the material web is wrapped around one measuring segment (32) in each case.

Description

[Technical Field]

[0001] The present invention relates to a force measuring device for measuring the tension of a running material web in a longitudinal direction defined by the running direction and a transverse direction perpendicular thereto, wherein the force measuring device comprises a shaft and a measuring roll supported on the shaft and wrapped around by the material web. [Background technology]

[0002] In systems for producing or further processing web-like materials, such as paper, plastic foil, or aluminum foil, the material web is processed at a web width of several meters at the beginning of the processing operation. Often, a narrower web is required for further processing, such as label printing or packaging production, and the material web is cut into narrower longitudinal strips of the desired width using a slitter / winder. While conventional force measuring devices measure the web tension throughout the material web across the entire roll width, it would be advantageous to have more accurate information about the distribution of web tension along the transverse direction of the running web for further processing of the cut web.

[0003] That is where the present invention comes in. The object of the present invention, as characterized in the claims, is to provide a force measuring device of the type described above, which is able to measure the distribution of web tension along the transverse direction of a running material web.

[0004] Said object is solved by the features of the independent claims. Further embodiments of the invention are the subject of the dependent claims. Summary of the Invention

[0005] According to the invention, a universal force measuring device is provided, which comprises:

[0006] The measuring roll is formed as a split measuring roll having two or more measuring segments that can be slid separately on the shaft and locked in a measuring position on the shaft in order to position the transverse measuring segments of the material web according to the desired measuring position so that each longitudinal portion of the material web is wrapped around one measuring segment.

[0007] Each of the measurement segments comprises a load cell that contributes to determining the web tension in a longitudinal section of the material web wound on the respective measurement segment and that provides a mount on which the measurement segment is axially positioned; and

[0008] The shaft extends axially over substantially its entire width and is provided with electrical conductors that are contactable at any axial position and that can conduct measurement signals supplied by the load cells of the measuring segment to an evaluation unit located at one end of the shaft.

[0009] The electrical conductors of the shaft can be arranged in an inner shaft chamber, for example in a guide chamber, which will be described in more detail below, but can also be arranged on the outside of the shaft, for example in a groove on the axial outside of the shaft. It is important here that the electrical conductors are accessible in all axial positions at which the measuring segments can be locked, i.e., at virtually any position along the width of the shaft, so that the measurement signals provided by the load cells can be transmitted to the evaluation unit regardless of the respective measuring position of the measuring segments.

[0010] Here, the measurement segment includes not only the load cell but also the roll shell and the bearing for the roll shell supported by the load cell.

[0011] In a preferred embodiment, the load cell comprises, as appropriate, an inner ring arranged on the axis and providing said mount. The load cell further comprises a concentric outer ring that can be displaced slidingly relative to the inner ring under the action of a force, and a measuring part that connects the inner and outer rings at a connection part. When measuring the tension of the web, the outer ring is displaced slidingly radially relative to the inner ring under the action of a force, which generates a stress in the measuring part that can be measured by a strain gauge.

[0012] Particularly advantageously, the inner ring includes a recess in which the connection with the outer ring is accommodated. The recess can extend radially up to half the radius of the inner ring, preferably to the center of the inner ring. The load cell is advantageously guided in an axial guide chamber of the shaft that is provided with the recess in the inner ring. In this way, a particularly compact design of the load cell and force measuring device is achieved, and the load cell is integrated into the shaft of the force measuring device.

[0013] According to an advantageous variant of the invention, the inner and outer rings are radially nested and connected at a radial connection by a measuring element. For overload protection, the inner and outer rings are preferably separated outside the connection by a narrow radial gap, the width of which is dimensioned so that in the event of overload, the movable outer ring comes into contact with the inner ring fixed to the shaft. The gap width corresponds, for example, to 110% of the measuring path at rated load, typically in the range of a few tenths of a millimeter.

[0014] In another, likewise advantageous embodiment, the inner ring and the outer ring are spaced apart in the axial direction and connected at an axial connection by a measuring portion.

[0015] The load cell is advantageously equipped with strain gauges for measuring the tension in the web. Preferably, the measuring part connecting the inner ring and the outer ring is equipped with said strain gauges for measuring the mechanical tension occurring in the measuring part.

[0016] In one advantageous embodiment, the measuring part is made in the form of a double-bending beam.

[0017] The inner ring, the outer ring and the measuring part of the load cell are particularly advantageously formed in one piece.

[0018] According to one preferred embodiment, the shaft is formed as an extrusion, preferably comprising a vertical ridge and two horizontal guide rails extending from the vertical ridge, such that the vertical ridge and the two guide rails form a U-shaped axial guide chamber in the extrusion profile of the shaft.

[0019] In this case, axial guide chambers and possibly further recesses such as axial grooves for air hoses and pressure strips are milled into the bar. Manufacturing shafts by milling is simple and cheap, but the lack of a radially closed hollow space generally makes them heavier than extruded material with the same bending stiffness.

[0020] The shaft is preferably provided in a guide chamber with an axially running power rail that can contact the electrical conductor of the load cell of the measuring segment at any axial position and forms the electrical conductor. It is particularly advantageous if the load cell is guided in an indentation of the inner ring and the axially running power rail is arranged in the axial guide chamber.

[0021] Each measuring segment preferably includes an electronic unit for supplying and receiving the strain gauges, preferably for digitizing and preamplifying them, and for introducing the preamplification and, if necessary, the digitized measurement signal into an electrical line, in particular the power rail of the shaft. Digitizing the measurement signal is particularly advantageous when the segmented measuring roll comprises a larger number of measuring segments, for example, four or more or six or more measuring segments, and the digitized measurement signal can then be transmitted to the evaluation unit via a small number of electrical lines, usually two, using a bus protocol. In particular, if the segmented measuring roll comprises only a small number of measuring segments, it is of course also possible to transmit the measurement signal to the evaluation unit in analog form, each via its own electrical line.

[0022] To measure the rotational speed, each measurement segment is advantageously equipped with a device for measuring the rotational speed, which preferably consists of one or more magnets rotating with the roll shell and a static Hall effect generator connected to a load cell. From the Hall voltage generated during rotation, the rotational speed of each measurement segment can be determined in a manner well known to those skilled in the art and is transmitted to the evaluation unit via an electronic unit. Determining the rotational speed of each measurement segment individually makes it possible, in particular, to determine whether slip is occurring in one or more measurement segments during operation.

[0023] In a preferred embodiment, the shaft includes an air hose in an axial groove and a pressure strip for locking the measurement segment on the shaft. The evaluation unit preferably includes a pressure sensor for monitoring the air pressure in the air hose. If the air pressure deviates from a target value, the evaluation unit can, for example, issue a warning signal or initiate other appropriate measures.

[0024] In an advantageous embodiment, each measuring segment is provided with lateral spacers whose size is adjusted to the size of the respective roll shell so that the measuring segments can slide together on the shaft so that the roll shells are next to each other with substantially no gap but without contact with each other. In practice, this means that the clearance between the roll wells in the sliding state is from a few tenths of a millimeter to the order of one millimeter.

[0025] Advantageously, two or more, three or more, four or more or six or more measuring segments are arranged and fixed on the shaft so that the measuring roll is formed as a divided measuring roll having two or more, in particular three or more, three or more or six or more measuring segments.

[0026] In an advantageous embodiment, the measuring segments are each axially positioned and locked in spaced apart roll shells, such that the segmented measuring roll is particularly adapted and configured for measuring the web tension of cut longitudinal strips of a running material web. The number, position and width of the measuring segments and their roll shells can be conveniently adapted to the number, position and width of the cut longitudinal strips of the material web.

[0027] In another, equally advantageous embodiment, the measuring segments are arranged and fixed on the shaft so that their roll shells are adjacent and substantially tightly spaced without contact with each other. The segmented measuring roll is particularly adapted and configured to measure the web tension in longitudinal sections of an uncut running material web, and thus to measure the tension profile in the transverse direction of the material web. The number, position, and width of the measuring segments are adapted to the resolution required for measuring the tension profile.

[0028] The force measuring device according to the present invention allows for the measurement of the transverse web tension of a running web of material, both in individual longitudinal strips of a cut web and in longitudinal sections of an uncut web. It is understood that during operation of the force measuring device, the slidable, lockable measuring segments are locked in a position corresponding to the desired web tension measurement position. If a different tension profile or a different longitudinal strip configuration of web tension is subsequently measured with the force measuring device, the lock is released, and the measuring segments are slid on the shaft accordingly and locked again. If a different number of measuring segments or measuring segments of a different width are required, the measuring segments can be removed from the shaft and / or additional or different measuring segments of the desired width can be pressed onto the shaft. In this way, the force measuring device can be very flexibly adapted to the respective measuring task and requirements.

[0029] Measuring the longitudinal tension of cut webs allows for individual control of the winding process, eliminating much waste due to improper tension in individual longitudinal strips. Knowing the tension profile can often bring great benefits even for raw materials. For example, in the production of blown film, measuring the tension profile of the produced film tube allows for readjusting the cooling profile of the molten tube and resulting in a uniform tension profile for the film tube.

[0030] Further exemplary embodiments and advantages of the present invention are described below by reference to the drawings, which are not drawn to scale and proportion for the purpose of improving clarity. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 shows a web of material cut into longitudinal strips, the web tension of which is measured individually. [Figure 2]FIG. 2 shows a schematic diagram of a force measuring device according to the invention. [Figure 3] FIG. 3 is a cross-sectional view of the force measuring device according to the invention in a direction corresponding to the line III-III in FIG. [Figure 4] FIG. 4 is a cross-sectional view of the force measuring device in FIG. 3, in which the load cells of the measuring segment are individually measured. [Figure 5] FIG. 5 is a perspective view of the load cell of FIG. [Figure 6] FIG. 6 is a perspective view of the force measuring device in FIG. 3, with the axes thereof separately seen through. [Figure 7] FIG. 7(a) is a cross-sectional view of the shaft of FIG. 6, and FIG. 7(b) is a milled shaft according to a further exemplary embodiment of the present invention. [Figure 8] Figure 8 shows the contact area between the load cell of Figure 4 on the electronic circuit board, the strain gauge, and the power rail of the retracted shaft. [Figure 9] FIG. 9 shows in cross section a load cell according to the invention with a measuring section running axially. [Figure 10] FIG. 10 shows a schematic representation of a force measuring device according to the invention configured for recording the tension profile of an uncut web of material. [Figure 11] FIG. 10 shows the tension profile of the raw web measured with the force measuring device, where the force F is plotted across the transverse dimension x. DETAILED DESCRIPTION OF THE INVENTION

[0032] The invention will be explained below by way of example using a force measuring device for measuring the web tension of a cutting running material web.

[0033] 1 shows, by way of example, a material web 10 whose running direction defines a longitudinal direction L and a transverse direction Q perpendicular thereto. In the exemplary embodiment, material web 10 is cut into n=6 longitudinal strips, i.e., one longitudinal strip 12-1 of average width, two wider longitudinal strips 12-2, 12-3, and three narrower longitudinal strips 12-4, 12-5, 12-6.

[0034] During the subsequent winding process of the longitudinal strips, it is advantageous to know the web tension in each strip individually. While conventional measuring devices are only capable of measuring the web tension of the entire web 10 across the entire roll width, the force measuring device 20 of the present invention, described below, makes it possible to measure the web tension of each of the multiple longitudinal strips 12-i (i=1...6) of the material web 10 individually.

[0035] 2 shows a schematic representation of a force measuring device 20 according to the invention. The force measuring device 20 comprises a flexible shaft 22, the ends of which rest on a substructure (not shown). Supported on the shaft 22 is a measuring roll 30 which, in operation, is wrapped around by the material web 10 to be measured.

[0036] According to the present invention, the measuring roll is formed in an exemplary embodiment as a segmented measuring roll 30 that serves to measure the web tension of six longitudinal strips 12-i of the material web 10 of FIG. 1 and therefore consists of n=6 measuring segments 32-i (i=1...6) adapted to the longitudinal strips 12-i.

[0037] 2, the measuring segments 32-i may differ in their width, in particular in the width of their roll shells, but are otherwise preferably identical in their structural features. Therefore, the following description of the measuring segments relates to all measuring segments 32-i of the measuring roll 30, and the index i may be omitted for simplicity.

[0038] The measuring segments 32 are individually slidably arranged on the shaft 22 and lockably arranged in a measuring position on the shaft so that they can be positioned to a desired measuring position in the transverse direction Q of the material web 10, so that a longitudinal strip 12-i of the material web 10 lies on and is wound around the roll shell 34 of the respective measuring segment 32-i. The roll shell 34 of a measuring segment is in each case connected via a roller bearing 38 to a load cell 36, which serves to determine the web tension in the longitudinal section 12 of the material web 10 wound around the respective measuring segment 32. Furthermore, the load cell 36 provides a mount for seating each measuring segment 32 on the shaft 22.

[0039] The width of the roll shell 34 of the measuring segment 32 is adapted to the width of the associated longitudinal strip 12 of the material web, as depicted in Figures 1 and 2. Thus, in the exemplary embodiment, the measuring roll 30 is composed of a measuring segment 32-1 with a roll shell of average width, two measuring segments 32-2, 32-3 with wider roll shells, and three measuring segments 32-4, 32-5, 32-6 with narrower roll shells.

[0040] The shaft 22 is provided with an electrical conductor 26 which extends axially over substantially its entire width, is contactable at any axial position, and conducts the measurement signals supplied by the load cells 36 of the measuring segment 32 to an evaluation unit arranged at the shaft end 28. The electrical conductor 26 can here be arranged outside the shaft 22, for example in an axial groove, but can also advantageously be present in a guide chamber within the shaft, which will be explained in more detail below. The measuring segment 32 further comprises a spacer 40, the function of which is explained in more detail in FIG. 10.

[0041] One advantageous design of the measuring segment 32 and the axis 70 of the force measuring device according to the invention will now be explained in more detail with reference to Figures 3 to 7. Figure 3 shows a cross section through the force measuring device 20 in a direction corresponding to line III-III in Figure 2. The load cell 36 of only the measuring segment 32 is depicted in cross section in Figure 4 and in perspective in Figure 5, and the axis 70 only is depicted in perspective in Figure 6 and in cross section in Figure 7.

[0042] 3, the measurement segment 32 includes, radially from outside to inside, a roll shell 34, a roller bearing 38, and a load cell 36. The longitudinal strip 12 of the material web 10 wrapped around the measurement segment 32 is shown in dashed lines.

[0043] Here, the load cell 36, again depicted separately in FIGS. 4 and 5, consists of an outer ring 50, a concentric inner ring 52, and a measuring section 54 with an H-shaped recess 56. The outer ring 50 has notches 58 (FIG. 5) for holding the roller bearing 38 via a retaining ring (not shown), while the inner ring 52 rests on the shaft 70 and provides the aforementioned mount. In the exemplary embodiment, the inner ring 52 and the outer ring 50 are radially nested and are connected at a radial connection area by the measuring section 54. For this purpose, the inner ring 52 defines a radially extending indentation 66 in the center of the inner ring 52. On the one hand, the indentation 66 accommodates the connection area with the outer ring, and on the other hand, it serves to reliably guide the load cell into the axial guide chamber 80 (FIG. 7) of the shaft 70.

[0044] The outer ring 50, inner ring 52 and measuring portion 54 are integrally formed, and the different hatching in FIGS. 3 and 4 is merely to illustrate the different functional areas 50, 52, 54 of the load cell 36.

[0045] Outside the connection area, the inner and outer rings are separated by a radial gap 60, the width of which is dimensioned to avoid destruction of the load cell 36 in the event of overload, such that the movable outer ring 50 stops plastically deforming relative to the inner ring 52 fixed to the shaft 70. In an exemplary embodiment, the width of the gap 60 is designed to be 110% of the measurement path at rated load.

[0046] The H-shaped recess 56 causes the measuring portion 54 to form a double-bending beam, on the upper side of which, in the illustrated exemplary embodiment, a strain gauge 62 is disposed to measure the mechanical tension on the surface of the material caused by the application of force. It is understood that the strain gauge 62 can also be disposed on the lower side of the double-bending beam, or on both the upper and lower sides.

[0047] When the measuring segment 32 is wrapped with the longitudinal strip 12 of material web, a force 64 that depends on the wrapping angle and the web tension is generated, which presses the movable outer ring 50 of the load cell 36 downwards against the fixed inner ring 52, thus causing bending of the double bending beam of the measuring section 54. This bending is measured by the strain gauges 62 and a corresponding electrical signal is generated, which is pre-amplified by an electronic unit in the measuring segment 32 and transmitted in an appropriate form to the evaluation unit 28 via the power rail of the shaft 70.

[0048] 3, 6, and 7(a), in the illustrated exemplary embodiment, the shaft 70 is formed as an extruded profile that can accommodate multiple individual measurement segments 32 across its width, as shown generally in Figures 2 and 10. Forming the shaft 70 as an extruded profile allows for a flex-resistant formation that does not deform, or only minimally deforms, even under maximum loads due to high web tensions, and therefore does not affect either the geometry of the measurement segments across the width or the measurement of web tension.

[0049] In the exemplary embodiment, the extruded profile shaft 70 is formed with a circular cross-sectional circumference 75. It includes a central vertical ridge 72 that ensures the stability of the shaft, from which extend two horizontal guide rails 74, 76 and a guide curve 78. The horizontal guide rails 74, 76, together with the ridge 72, form a U-shaped axial guide chamber 80 in the shaft 70 that is open on one side and into which the recess 66 of the inner ring protrudes for guiding and electrically connecting the load cell (FIG. 3). The curvature of the guide curve 78 and the radially outer surfaces of the guide rails 74, 76 is adapted to close tolerances to that of the inner ring 52 so that, on the one hand, the measuring segment 32 can easily slide on the shaft, but, on the other hand, it can be easily and reliably locked, for example by a mechanical or pneumatic locking mechanism.

[0050] In order to conduct the electrical signals generated by the strain gauges 62 of the load cells of the measuring segment 32 to the evaluation unit 28, the lower horizontal guide rail 76 of the shaft 70 is provided in a recessed area with an axially running power rail 82 that facilitates electrical contact between the power supply and the measuring segment 32, regardless of its position on the shaft 70. It will be understood that the power rail may also be provided elsewhere within the guide chamber, for example on the upper guide rail 74 or on both guide rails 74, 76.

[0051] Instead of an extruded shape, the shaft can also be formed as a milled shaft 170 with a U-shaped axial guide chamber 80 and axial groove 84 milled in, as depicted in Figure 7(b). Here, the shaft body 172 includes a central vertical support structure ensuring the stability of the shaft, from which extend two horizontal guide rails 174, 176, which together with the shaft body 172 form in the shaft 70, within the cross-sectional periphery 175, a U-shaped axial guide chamber 80 into which protrudes an inner ring recess 66 for guiding and electrically connecting the load cell.

[0052] 8, the load cell 36 includes, in addition to the mechanical elements already described, a circuit board 90 having electrical couplings that are connected to the strain gauges 62 at contact areas 92 and that can establish contact with the power rail 82 at any axial position of the shaft 70 via electrical conductors 94 to supply and receive measurement signals. In the exemplary embodiment shown, the electrical couplings on the circuit board 90 include a preamplifier that amplifies and digitizes the measurement signals of the strain gauges 62 and relays the digitized measurement signals to an internal bus for signal processing.

[0053] Arranged at the end of the shaft is an evaluation unit 28, which communicates with the measurement segments 32-i on the shaft 70 and receives and further processes their measured values. For this purpose, in the exemplary embodiment, the power rails 82 include two power rails for the power supply as well as two further power rails for data transmission to the evaluation unit 28, for example according to the RS-485 standard. If the measuring roll includes only a small number of measurement segments or if digitization is not performed for other reasons, it is of course also possible for the pre-amplified measurement signals to be transmitted to the evaluation unit in analog form via each own power rail.

[0054] The evaluation unit 28 communicates via a standardized bus protocol with a higher-level controller which triggers appropriate actions based on the measurements provided by the different measurement segments 32, for example running the drive slower or faster, issuing an alarm signal, etc.

[0055] In the exemplary embodiment, the secure locking of the measuring segment 32 on the shaft 70 is achieved with the help of an axial air hose 86 and an axial pressure strip 88 (FIG. 3), both of which are embedded in a groove 84 formed in the guide curve 78 of the shaft 70.

[0056] When the air hose 86 is in a relaxed state, the measuring segments 32 can slide freely along the shaft and can be positioned in any desired number at any desired location on the shaft. When the air hose 86 is then inflated, it presses the pressure strips 88 with a force dependent on the air pressure, which pushes the pressure strips 88 slightly radially out of the grooves 84. As a result, the pressure strips 88 clamp the positioned measuring segments 32 against a defined stop on the shaft 70, thus simultaneously locking all measuring segments 32 in their correct position. When the air hose 86 is relaxed, the lock is released again, allowing the measuring segments to be slid and / or replaced. The air pressure in the air hose 86 is monitored by a pressure sensor located in the evaluation unit 28 at the end of the shaft.

[0057] In another variant of the invention, it is provided that instead of air hoses and pressure strips, the measuring segments 32 each have a mechanical locking device via which they can be individually fixed on the shaft.

[0058] 3 to 8, the measuring section 54 runs radially between the inner and outer rings, which is currently preferred due to its simpler construction and high positive tension. However, it is equally possible to have the measuring section of the measuring segment run axially, as will be explained below with reference to the exemplary embodiment of FIG. 9, in which a measuring segment 100 according to the invention is shown diagrammatically in side view.

[0059] The measuring segment 100 includes a load cell 102 consisting of an outer ring 110, an axially spaced concentric inner ring 112, and an axial measuring portion 114. The inner ring 112 is seated with close tolerance on the shaft 22, shown in dashed lines in the drawing, so that it can slide along the shaft when not under tension. The outer ring 110 houses the bearing retainer of the roller bearing 38, which has the roll shell 34 mounted on its outer periphery.

[0060] The outer ring 110 and the inner ring 112 are connected by an axial measuring section 114 which in the exemplary embodiment consists of a substantially H-shaped recess 1116 and forms a double bending beam equipped with strain gauges 62 for measuring the tension in the measuring section 114. The tolerance of the outer ring 110 relative to the axis 22 is dimensioned so that in the event of an overload, the outer ring rests relative to the axis 22, thus preventing any destruction of the load cell 102.

[0061] When the tension in the web causes a force 64 to press against the roll shell 34 of the measuring segment 100, the force is transmitted via the roller bearing to the outer ring 110, which rests against the inner ring 112 via the measuring element 114. The tension thus generated at the measuring element 114 is measured by the strain gauges 62, and the resulting electrical signal is pre-amplified, possibly digitized, as already generally mentioned, and passed on to the power line of the shaft 22. The fixing of the measuring segment 100 to the shaft can be effected, for example, mechanically or pneumatically, as also already mentioned above.

[0062] In addition to measuring the web tension of cut longitudinal strips of a material web, the force measuring device according to the invention also makes it possible to record the tension profile of an uncut material web through an independent web tension measurement of a measuring segment.

[0063] 10, the measuring segments 32 of the force measuring device 20 are positioned and locked on the shaft 22 so that their roll shells 34 are adjacent and substantially tightly spaced without contact with each other (reference numeral 120). To ensure this, the measuring segments 32 are provided with lateral spacers 40 (FIG. 5) whose size is adjusted to the size of the respective roll shells 34 so that, when the measuring segments 32 are moved together, the desired side-by-side arrangement 120 is achieved with a mutual clearance of the roll shells of a few tenths of a millimeter, substantially tightly spaced.

[0064] Because every measurement segment 32 measures the local web tension Bz(x) at its respective measurement segment position x along the transverse direction Q of the material web, multiple measurement segments 32 can be used to measure the tension profile 122 of the material web, as illustrated diagrammatically in FIG. 11. In the tension profile diagram shown there, the local web tension Bz(x) is plotted over the spatial coordinate x in the transverse direction of the material web. Knowledge of the tension profile can lead to appropriate countermeasures. For example, in the case of an inhomogeneous profile, control measures can be implemented to achieve a more homogeneous tension profile. Furthermore, by displaying the time course of the local web tension, e.g., as a waterfall diagram, periodic signals, such as supply reel non-roundness or periodic wrinkles, can be easily identified.

[0065] Although the width of the measurement segments 32 used for tension profile measurements can be the same, as in the exemplary embodiment of Figure 10, it is also advantageous to use measurement segments 32 of different widths. For example, in the middle region of the material web, measurement segments having narrower roll shells can be used than in the end regions of the material web.

[0066] By measuring the rotational speed of each measurement segment 32, it is possible to determine whether slippage is occurring in one or more measurement segments. The fastest-rotating segment in each case provides the reference value. To determine the rotational speed of the measurement segments 32, for example, two magnets 132 offset by 180° from each other can be attached to each measurement segment via mounts 130 on the roll shell 34, as depicted in FIG. 3 . The load cell 36 includes a Hall-effect generator at a suitable position, through which the magnets 132 periodically pass as the roll shell 34 rotates. This generates a Hall voltage in the Hall-effect generator, the rotational speed of which can be determined from its temporal progression. The Hall-effect generator signal is transmitted to an evaluation unit via an electronic unit (FIG. 8) and evaluated. For example, the rotational speed of the fastest-rotating measurement segment can be used as a reference value, and slippage can be indicated for measurement segments whose rotational speed falls below the reference value by a predetermined threshold.

Claims

1. A force measuring device for measuring the tension of a running material web, the tension being in a longitudinal direction defined by the running direction and a transverse direction, the force measuring device comprising a shaft and a measuring roll supported on the shaft and wound by the material web, the measuring roll is formed as a segmented measuring roll having two or more measuring segments that can be slid separately on the shaft and locked in a measuring position on the shaft in order to position the measuring segments according to desired measuring positions in the transverse direction of the material web so that each longitudinal portion of the material web is wrapped around one measuring segment, each measuring segment serving to determine web tension in a longitudinal portion of the material web wound on the respective measuring segment and comprising a load cell providing a mount on which the measuring segment sits on an axis; A force measuring device characterized in that the shaft extends axially over substantially its entire width, is contactable at any position in the axial direction, and is provided with electrical conductors through which measurement signals provided by the load cells of the measuring segments are transmitted to an evaluation unit arranged at the end of the shaft.

2. 2. A force measuring device according to claim 1, characterized in that the measuring segment comprises, in addition to the load cell, a roll shell and a bearing for the roll shell supported by the load cell.

3. 3. A force measuring device according to claim 1 or 2, characterized in that the load cell comprises in each case an inner ring lying on the shaft and providing the mount, a concentric outer ring slidable relative to the inner ring, and a measuring part connecting the inner ring and the outer ring at a connecting region.

4. 4. The force measuring device according to claim 3, wherein the inner ring has a recess in which a connecting region with the outer ring is accommodated.

5. 5. A force measuring device according to claim 4, characterized in that the load cell is guided in an axial guide chamber together with a recess in the inner ring.

6. 6. The force measuring device according to claim 3, wherein the inner ring and the outer ring are arranged in a radially nested manner and are connected by the measuring unit at a radial connecting region.

7. 6. The force measuring device according to claim 3, wherein the inner ring and the outer ring are spaced apart in the axial direction and connected to each other at an axial connecting region by the measuring unit.

8. 8. The force measuring device according to claim 3, wherein the load cell is provided with a strain gauge for measuring the tension of the web, and a measuring section connecting the inner ring and the outer ring is provided with the strain gauge for measuring the mechanical tension generated in the measuring section.

9. 9. The force measuring device according to claim 3, wherein the measuring section is formed in the shape of a double-bent beam.

10. 10. The force measuring device according to claim 3, wherein the inner ring, the outer ring and the measuring portion of the load cell are integrally formed.

11. 11. A force measuring device according to claim 1, wherein the shaft is formed as an extruded profile.

12. 11. A force measuring device according to claim 1, wherein the shaft is formed as an extruded profile including a vertical ridge and two horizontal guide rails extending from the vertical ridge, the vertical ridge and the two guide rails forming a U-shaped axial guide chamber in the extruded profile of the shaft.

13. 13. The force measuring device according to claim 12, characterized in that the shaft in the axial guide chamber is provided with an axially running power rail which can contact the electrical conductor of the load cell of the measuring segment at any axial position and forms said electrical conductor.

14. the measurement segments for supplying and receiving the strain gauges, respectively; 9. A force measuring device according to claim 8, characterized in that it comprises an electronic unit for passing the preamplified measuring signal onto an electric line for preamplification.

15. 14. A force measuring device according to claim 2, wherein the measuring segments each comprise a device for measuring the rotational speed.

16. 14. A force measuring device according to claim 2, wherein each of the measuring segments comprises a device for measuring the rotational speed, the device comprising one or more magnets rotating together with the roll shell of the measuring segment and a static Hall effect generator connected to a load cell of the measuring segment.

17. 15. A force measuring device according to claim 1, wherein the shaft comprises, in an axial groove, an air hose and a pressure strap for locking the measuring segment on the shaft.

18. 15. The force measuring device according to claim 1, wherein the shaft comprises an air hose in an axial groove and a pressure strip for locking the measuring segment on the shaft, and the evaluation unit comprises a pressure sensor for monitoring the air pressure in the air hose.

19. 11. A force measuring device according to claim 1, wherein two or more measuring segments are arranged on an axis and locked together.

20. 20. A force measuring device according to claim 19, characterized in that the measuring segment for measuring the web tension of a longitudinal strip of a cut running material web is arranged on an axis with spaced apart roll shells and locked.

21. 20. The force measuring device according to claim 19, wherein the measuring segments for measuring the web tension of longitudinal strips of an uncut running material web are arranged and locked on the shaft so that their roll shells are adjacent to each other without contact and with substantially no gaps.

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