EP0093865B2 - Feeler for detecting web seams - Google Patents

Description

The invention relates to a scanning device for determining web seams in web processing machines, in particular shearing machines, the control of which is to be influenced in the case of seam detection, with at least two detectors, which scan the web at a distance from one another and are arranged and adjustable perpendicular to the web plane, each with one the probe can be placed on the material web, the signals generated being fed to a control circuit which only issues a control command to the machine control when at least two detectors, possibly at different times, deliver a signal which can be interpreted as a seam.

For reasons of rationalization, a plurality of web sections are sewn or glued to one another for the mechanical processing of webs of goods in order to be able to capture a larger web stock in one goods pass. In almost all cases of processing such a web provided with seams, seam detection is necessary, e.g. B. to lift the shears at a seam passage from the web in a clipper and so to prevent damage to the clipper.

According to the preamble of claim 1, the invention is based on a device as described, for example, in US Pat. No. 4,194,659. Here, the detectors arranged opposite one another on the longitudinal edges of the web consist of electrical switches which are arranged on pivotable holders with respect to the web. Such a switch detector has the disadvantage that it can only react to relatively large elevations on the web, which is due to the mechanics of such switches. On the other hand, a switch is only able to report the two switching states «On» and «Off». As a result, the known device is only able to report relatively strong raised seams. A further disadvantage is that the switches on the other side of the web are still assigned guide rollers, so that the actuation or non-actuation of the switches depends on the thickness of the The web itself is dependent, which can lead to false positives. Finally, it is very difficult to calibrate the two detectors. They are required to react equally to the same change of state. However, this is problematic with mechanical switches, so that it can happen that only one of the two detectors reports a (thin) seam, while the second does not react.

In addition, seam detection has been the subject of numerous considerations on a large scale. For example, B. DE-B-924 323 a device for determining a product seam, in which one side or both sides of the web an electrical conductor, for. B. in the form of a metallic thread, which causes a control pulse when touching two contacts connected to a control circuit. Instead of using z. B. a metal-penetrating or superficially metallized textile thread, DE-B-925 884 proposes that the goods be taken into account at the point to be taken into account, that is to say generally at the seam, with a conductive liquid, for. B. a saline solution or weak acid to short-circuit the control circuit. According to DE-B-930 442, a Geiger tube is used as the seam detector, the fabric being wetted in the seam area with a radioactive liquid. In the device for determining a product connection seam according to DE-B-1 268 575, a thread impregnated with a fluorescent color is sewn into the seam, which is scanned by a photoelectric device comprising several detectors. DE-B-2 428 112 deals with a seam monitor, in which a high-frequency probe is provided with a probe and at least one receiving device which is connected to an electrical conductor incorporated in the seam, e.g. B. appeals to a metal or stanol strip or a conductive film applied to the web.

With the exception of those according to DE-B-924 323, the expenditure on equipment of the known seam detection devices is relatively high. All seam detection devices, without exception, have the essential disadvantage that the seam areas in the web of material must first be prepared in a suitable manner for the seam detection device to respond. These preparations are time-consuming and in any case involve an annoying additional effort. This means that for a long time the experts have tried in vain to avoid the shortcomings of seam detection devices, which in an obvious way have switches as detectors. Apparently, however, this was only possible through considerably more complicated measures, namely through seam preparations.

In contrast, the invention, starting from a scanning device, in particular according to US-A-4 194 659, has the object of creating a device which is very simple in terms of its design, with which web seams of very small thickness can also be scanned, and in which a simple one Calibration of the detectors is possible.

The invention solves this problem in that each detector consists of a potentiometer which is fixed to the machine with its resistance path, and the probe is arranged with little play on a coupling element which is rigidly connected to the sliding contact of the potentiometer and that the potentiometers each have two detectors with opposite polarity the control circuit are connected such that, with the same deflection of the probe heads of the two detectors, the total measuring voltage is zero.

Due to the low-play arrangement of the probe on the rigid and thus play-free with the sliding contact of the coupling element connected to the machine, even the thickness of the web of the order of magnitude of only about 0.05 mm can be registered with the precision of the potentiometer available today. The resistance changing due to the displacement of the sliding contact of the potentiometer can be used in the control circuit for the corresponding evaluation. The advantage that, in contrast to switches, potentiometers can not only assume the "On" and "Off" states, but also detect proportional voltage values, means that the basic values can be easily and correctly calibrated by setting or comparing the measured values of the at least two detectors Detectors guaranteed at all times.

The use of a potentiometer as a seam tash is known from DE-B-1 075 544. However, only one seam button is provided in the device with snowmaking equipment there, so that the problem of adjusting or calibrating two detectors is important.

Different configurations with special advantages are possible with regard to the arrangement of the detectors. Such an arrangement known per se provides that two detectors are provided at a distance from one another transversely to the direction of travel of the web. This arrangement, which is the simplest in its design, is suitable, for example, for recognizing straight transverse seams in paper webs in particular, the probe heads being deflected at the same time when the seam passes.

An increased measuring accuracy results from the fact that two detectors are arranged both at a distance transversely to the direction of the web and from one another in the direction of the web. These two detectors, too, cannot be excited by the same, locally narrowly defined unevenness at the same time, but it is a prerequisite that the unevenness must occur at the distance from one another which corresponds to the distance of the detectors transversely to the direction of travel of the web. The coincidence of the excitation of the detectors for a given web speed results from the distance between the detectors or from the time difference required at this speed between the excitation of the detector lying behind in the web direction and addressed first and the detector in the web direction at the front and second-most excited.

A universal and therefore particularly advantageous within the scope of the invention scanning device, with which not only bevel seams, but almost all occurring seam shapes can be scanned with outstanding accuracy, consists quasi in a combination of the previously described alternative arrangements of two detectors in that two groups of each two detectors are arranged next to each other transversely to the direction of web travel in such a way that the two detectors of a group are arranged at a distance transversely to the web direction and at a distance in the direction of web travel, and it is also advantageous if the detectors of both groups arranged on a straight line transverse to the web direction each have the same distance from each other In order to trigger a machine control pulse, it is essential that each of the four detectors must be excited. The control circuit essentially has the task of knowing whether all detectors are excited within a permissible time and / or path tolerance. Only if this is the case is it correctly recognized for the seam.

Although a rotary potentiometer could be used as a potentiometer, in which the coupling member could be designed as a pivoting lever carrying the probe, it has proven to be particularly advantageous if the potentiometer has a sliding contact that can be moved in a straight line and if the coupling member, which is essentially rod-shaped, moves in the direction of movement of the Sliding contact extends. The deflection of the probe then leads to a linearly proportional displacement of the sliding contact and thus enables a particularly precise and simple acquisition of the measured values. In addition, with such a “linear potentiometer”, the freedom from play sought for the measuring accuracy can best be achieved in a particularly simple manner. The probe is preferably designed as a low-radial play roller at the end of the coupling member, so that against an otherwise possible design of the probe z. B. as a skid more favorable friction values and thereby in turn more accurate measured values.

Finally, for the purpose of a particularly simple adjustability of the scanning device, the invention provides that two potentiometers with opposite polarity are connected to the control circuit in such a way that, with the same deflection of the probes of these two detectors, the total measuring voltage is zero. This creates a self-adjusting scanning device which only presupposes that all detectors are arranged in a plane parallel to the plane of the web. This can be achieved in a simple manner by arranging all potentiometers at the same distance from a web support.

If, as is provided according to a further advantageous feature, the potentiometers in each case a group or all potentiometers are arranged together in a carrier which is adjustable with respect to the plane of the web, a simple adjustment is possible e.g. B. by adjusting the carrier in such a way that the measuring voltage is to be set to zero, which, for. B. can easily be done with the help of a simple voltmeter.

• Figur 1 eine schematische Seitenansicht einer einfachen Abtastvorrichtung,
• Figur 2 eine Aufsicht auf die Vorrichtung nach Fig. 1,
• Figur 3 eine der Fig. 1 entsprechende schematische Ansicht einer universell verwendbaren Abtastvorrichtung,
• Figur 4 eine Aufsicht auf die Vorrichtung nach Fig. 3 und
• Figur 5 ein Blockschaubild der elektrischen bzw. elektronischen Meßwerterfassung der Einrichtung nach den Fig. 3 und 4.

The invention is explained below with reference to several exemplary embodiments shown in the drawings. The drawings show:

• FIG. 1 shows a schematic side view of a simple scanning device,
• FIG. 2 shows a top view of the device according to FIG. 1,
• FIG. 3 shows a schematic view corresponding to FIG. 1 of a universally usable scanning device,
• Figure 4 is a plan view of the device of Fig. 3 and
• FIG. 5 shows a block diagram of the electrical or electronic measurement value acquisition of the device according to FIGS. 3 and 4.

On a designated 10 frame of a web processing machine, for. B. a clipper, two carriers 11 for each detector 12 and 13 are arranged such that they are both adjustable in height (double arrow 14) and pivotally adjustable about an axis 15 (double arrow 16). Each carrier 11 is located with the associated detector 12 or 13 above a table 18 provided with a fabric support 17, over which a web 19 is guided in the web running direction 20. The web 19 shows two sections 21 and 22 which are connected by a seam 23.

The detectors 12 and 13 each comprise a linear potentiometer 22 with a resistance track (not shown) fixed in the housing and thus fixed on the carrier 11 and a sliding contact indicated by 25. This is rigidly connected to a rod-shaped coupling member 26, on the free end of which a preferably roller-mounted roller 27 is arranged as a probe head 28. Each change in the thickness of the web 19, in particular the seam 23, causes a deflection of the probe head 28 and, associated therewith, a displacement of the sliding contact 25 upwards. The resulting change in resistance influences the electrical values of the control circuit to which the respective detector is connected at 29.

As FIG. 2 shows, two detectors 12 and 13 are arranged at a distance 30 transversely to the direction of web travel 20. The control command to the machine control is given when the scanning signals of these two detectors 12 and 13 coincide, i.e. H. that is, when both detectors are excited simultaneously by an unevenness of the material web in the arrangement shown in FIG. 2. This very simple device according to FIGS. 1 and 2 is very well suited for the seam detection on essentially smooth surface webs with seam 23 arranged perpendicular to the web running direction 20, in particular thus z. B. for paper web processing machines.

The arrangement described is less suitable for scanning such webs, the regular patterns, z. B. cross grooves or waffle pattern on the back (which is usually scanned). Straight seams of such webs could, however, be scanned, for example, by arranging one of the two detectors 12 or 13 offset with respect to the other detector 13 or 12 in web direction 20. This is illustrated in FIG. 2 with the detector 13 'taking the place of the detector 13, which is offset by the distance 31 in the direction of web travel 20 relative to the other detector 12. With this arrangement, transverse seams can also be detected on patterned or profiled webs, the only requirement being that the pattern repeat has a dimension different from the distance 31. The electronics here has to hold on to the pulse generated by the first-responding detector 12 by changing the resistance until, in accordance with the set goods running speed, the time has elapsed that a seam would at least need to reach the second detector 13 '. Then speaks to this second detector 13 ', is detected on the seam; if it does not respond, no control impulse is passed on to the machine control. In many cases, even with such a device, cross seams of the type of seam 23 can be detected with sufficient reliability.

The detector arrangements described above also have the disadvantage that oblique or special seams cannot be detected, at least not with sufficient reliability. However, this is easily possible with the device shown in FIGS. 3 and 4. Here, two groups 32 and 33 of two detectors 34, 35 and 36, 37 are arranged in such a way that the detectors 34 and 35 and the detectors 36 and 37 are at a distance 38 from one another in the direction of web travel 20 and in each case in the direction transverse to the web direction of travel Distance 39 are offset. An arrangement is provided in the vicinity of both web edges, as corresponds to that last described with reference to FIG. 2.

The mode of operation is understood as follows with reference to FIG. 5. As soon as the diagonal seam 40 excites the detector 34 and, as a result of the change in the resistance set by its potentiometer, this supplies the differential logic 41 with a pulse, the path / pulse generator 42 keeps the pulse caused by the detector 34 usable at least until the seam - if it is is one - the detector 35 should have reached. The same happens with regard to the detector group 33 having the detectors 36 and 37, in whose circuit a differential logic 43 is also connected, which is also linked to the path / pulse generator 42.

The following explains the following characteristic conditions:

1st example

At the designated 50 and 51 and lying in line with the detectors 34 and 35, the web has bumps in the device according to FIGS. 1 and 2, provided that it is in line with the detectors 12 and 13 or 13 ' Detection of a straight seam would result. Here is the case that first the detector 34 and with time Delay the detector 35 are excited. The differential logic connected to these two detectors 34 and 35 initially recognizes on standard seam. However, since neither the detector 36 nor the detector 37 are energized, the differential logic 43, which is connected to these detectors, cannot detect at the seam. The link logic 44, which only receives a seam detection from the difference logic 41, can no longer detect seams due to the missing message from the difference logic 43 and does not give a control pulse to the machine controller 45.

2nd example

The special seam 40 'shown in Fig. 4' passes through the scanning device. This means that the detectors are excited by the thickenings 50 to 53 in the order 34, 36, 35 and 37. Accordingly, the difference logic 41 first detects a seam, with a slight time delay the difference logic 43 also determines a seam. Since the logic logic 44 has now received a seam message from the two difference logics 41 and 43, it also recognizes the seam and responds to the machine control 45.

It is understandable that, of course, diagonal seams of the type of diagonal seam 40 can also be recognized with the device according to FIGS. 3 and 4. The path / pulse generator 42 merely has to ensure that bumps in the material web which are too far apart in terms of time or distance, do not more than seam can be recognized.

The linking logic essentially has the task of not accepting a seam as reported by only one detector group 32 or 33 via the associated difference logic 41 or 43, unless the other difference logic at a later point in time corresponding to the setting of the path / pulse generator Seam reports. On the other hand, it has the task of recognizing a seam when the difference logics 41 and 43 report a seam, either at the same time or with a time delay.

The detectors 34 and 35 on the one hand and the detectors 36 and 37 on the other hand are each connected to the control circuit with different polarities. If the detectors 35/35 and 26/37 of a group 32 or 33 are acted upon in the same direction, the resistance of one detector is to be reduced thereby, while that of the other is increased by the same amount. An adjustment of a detector group 32 or 33 is therefore possible in a simple manner by adjusting the total measurement voltage to zero. This is possible in a simple manner by the pivot adjustment arrangement of the supports 11 for the corresponding detectors described at the beginning.

Claims (8)

1. Scanning apparatus for the determination of fabric web seams (23; 40; 40′) in machines processing fabric webs (19), in particular shearing machines, the controls of which are to be influenced in the event of seam detection, with at least two detectors (12, 13), which scan the fabric web (19), arranged at a distance (30) from each other and can be set and adjusted perpendicular to the plane of the fabric web and each have a probe (28) which can be placed on the fabric web (19), the generated signals being fed to a control circuit which only emits a control command to the machine controls if at least two detectors deliver a signal interpretable as a seam, possibly at different times, characterised in that each detector (12, 13, 13′, 34, 35, 36, 37) consists of a potentiometer (24) arranged mechanically-fixed to its resistor path, and the probe (28) is arranged with little play on a coupling link (28), which is rigidly connected to the sliding contact (25) of the potentiometer (24), and that the potentiometers (24) of each two detectors (34, 35; 36, 37) are connected with opposite polarity to the control circuit (29) in such a way that if there is equal deflection of the probes (28) of the two detectors (34, 35; 36, 37), the total measuring voltage is equal to zero.

2. Scanning apparatus according to claim 1, characterised in that -  in a known arrangement -  two detectors (12, 13) are provided at a distance (30) from each other, transverse to the direction in which the fabric web runs (20).

3. Scanning apparatus according to claim 1, characterised in that two detectors (12, 13) are arranged both at a distance (30) transverse to the direction in which the fabric runs (20) and at a distance (31) from each other in the direction in which the fabric runs (20).

4. Scanning apparatus according to claim 2 or 3, characterised in that two groups (32; 33), each of two detectors (34, 35; 36, 37) are arranged alongside each other transverse to the direction in which the fabric runs (20), in such a way that in each case the two detectors (34, 35; 36, 37) of a group (32, 33) are arranged at a distance (39) transverse to the direction in which the fabric runs (20) and at a distance (38) in the direction in which the fabric runs (20).

5. Scanning apparatus according to claim 4, characterised in that the detectors (34, 36; 35, 37) of both groups (32; 33), arranged on a straight line lying transverse to the direction in which the fabric runs (20), in each case have the same distance (46) from each other.

6. Scanning apparatus according to claims 1 to 5, characterised in that the potentiometer (24) has a linearly-moveable sliding contact (25) and that the substantially rod-shaped designed coupling link (26) extends in the direction of movement of the sliding contact (25).

7. Scanning apparatus according to claim 6, characterised in that a probe (28) is designed as a feeler roll (27) mounted in a rolling bearing with little radial play at the end of the coupling link (26).

8. Scanning apparatus according to one of the preceding claims, characterised in that the potentiometers (24) of each group (32; 33), or all potentiometers (24), are arranged together in a carrier (11) which can be adjusted with respect to the plane of the fabric web.

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