Device for detecting shape flaws of tubular bag bodies

"FORM ERROR DETECTION"

The invention relates to a device for detecting form defects in tubular sack bodies, in particular sack bodies folded to form cuboid sacks, while the sack bodies are transported along a conveying path on a conveyor, comprising at least one contour sensor for detecting the contour of a sack body, and a comparison device to compare the recorded contour of the bag body with a target contour, wherein the comparison device sends out a form error signal when the discrepancy between the detected contour of the bag body and the target contour exceeds a predefined threshold value. The invention further relates to a device for producing sacks from tubular sack bodies, in particular sack bodies made of a plastic fabric.

Many powdery or pourable consumer goods are nowadays filled, stored and transported in sacks made of plastic fabric. It is essential that the plastic bags used meet the quality criteria appropriate for the respective purpose.

Plastic bags for packaging powdery goods such as cement must be made sufficiently strong and dust-tight to prevent contamination or the escape of dust during the filling process, storage and transport and thus also to make a contribution to environmental protection. Plastic bags for packaging free-flowing chemicals must also meet strict requirements for occupational safety and requirements for the resistance of the material used to the effects of the weather.

Quality assurance is therefore becoming more and more important during the manufacture of sacks made of tubular sack bodies, in particular sack bodies made of a plastic fabric.

From WO 2008/116653 A1, quality assurance measures for a bag filling method are known in which powdery or granular bulk material is filled into plastic bags. In this filling process, measures are taken into account that prevent dust from escaping during the filling process. Furthermore, measures are taken to prevent the filling level in the plastic bags from being higher initially than later during storage due to too rapid filling. If the packaging size of the plastic bags is too large for the content or if the bulk density is too low due to filling too quickly and the filled bags are therefore not sufficiently dimensionally stable, then they cannot be safely stored on pallets, for example. Accidents at work and soiling caused by filled plastic bags falling over or bulk goods escaping can be the result. As a countermeasure to increase the bulk density for powdery bulk goods, a particularly slow, metered filling process for the plastic bags is proposed.

The disadvantage of this bag filling process is that all quality assurance measures are only provided from the beginning of the filling process of a plastic bag. It is accepted or assumed with this filling process that during the filling process, due to a manufacturing defect in the sack body used, the sack can tear or the sacks used can be leaky. The only solution proposed is measures for the early detection of such a case of damage, for example in order to be able to switch off a filling device in good time.

A check of the material quality of the plastic bags to be filled before the filling or - even more advantageous - already during the production of the web-shaped plastic fabric is not considered here at all.

/ 8 Austrian

Patent office

AT508 312 B1 2011-07-15

From EP 677 444 A1 an optical control method of cut parts, for example for cigarette packs, is known. The surface of the cut parts, which are moved along a conveyor, is scanned by means of an analog optical sensor along a scan line which is arranged in the conveying direction and approximately centrally above the cut part.

From the different graphical properties that the sensor determines along the scan line, a signal curve is generated, which is compared with a reference curve. If the comparison results in too great a deviation, an error signal is output. With this arrangement, for example, colors of the surface can be recorded, but not the contour of the cut parts.

From JP 2006 038 458 A a device is known which checks the width of a packaging sack at regular intervals by means of a light barrier line sensor which is arranged transversely to a uniform transport direction of the sack. Based on the distance by which the bag advances per period and the width measured in this period, the cross-sectional area is measured for each period and added up over all periods to form a total cross-sectional area. If the total cross-sectional area deviates from a nominal area, it is concluded from this that the sack is not properly glued. However, JP 2006 038 458 A does not consider evaluating the contour of the sack.

Increasingly, manufacturers or dealers of plastic packaging sacks are faced with the problem that operators of automatic filling systems find a defective sack during random inspections of incoming goods, and thus a whole range or batch of hundreds or thousands of plastic sacks is complained about and taken back by the supplier must become. The resulting economic damage is enormous.

A device that detects shape errors, for example incorrectly folded sack ends or missing reinforcements at the sack ends of a tubular sack body folded into a cuboid sack, and detects deviations between the recorded contour of a sack body and a predefined target contour, is in particular in the known prior art not intended for sack bodies made of plastic.

The present invention therefore has the object of avoiding the disadvantages known from the prior art for a device for detecting form defects in tubular sack bodies of the type mentioned at the outset, which can be used for quality control during the production of sacks.

This object is achieved in a device for form error detection according to the preamble of claim 1 with the features of the characterizing part of claim 1. The subclaims relate to further advantageous embodiments of the invention.

A device according to the invention for detecting form defects in tubular sack bodies, in particular sack bodies folded to form cuboid sacks, while the sack bodies are transported along a conveying path on a conveyor, comprises at least one contour sensor for detecting the contour of a sack body. Such a device further comprises a comparison device for comparing the recorded contour of the bag body with a target contour, the comparison device sending out a form error signal if the deviation between the recorded contour of the bag body and an envelope curve representing the target contour exceeds a predefined threshold value.

A cuboid sack folded from a tubular sack body is expensive to manufacture, depending on the variant. Several work steps are required in which the bag body is folded at its ends, and then a valve sheet is usually attached to one of the two bag ends for later filling the bag with a pourable bulk material and / or a cover sheet to reinforce the bag end. Incorrectly manufactured sacks, in which, for example, cover sheets are not properly applied or the sack ends are folded incorrectly, usually have deviations from a predefined desired contour.

2/8 Austrian

Patent office

AT508 312 B1 2011-07-15

During the individual steps of folding or welding, the bag bodies are flat and usually lie flat on a conveyor. The bag bodies are given their cuboid shape when they are filled as intended.

According to a further feature of the invention, a device for form error detection is designed so that the at least one contour sensor for detecting the contour of the bag body is an optical sensor arranged on the conveying path of the bag body, in particular a line sensor. With a contour sensor, for example designed as a line sensor and coupled to a comparison device, shape errors in the bag body can be detected.

In an advantageous embodiment, a device for form error detection comprises a comparison device which determines the width of the bag body from the recorded contour of the bag body and compares it with a nominal width.

In a further development of the invention, a device for form error detection comprises a comparison device which compares the detected contour with the envelope curve. Particularly when folding the sack ends, it is necessary to produce a conformal fold that conforms to the target contour and thus to avoid errors.

In a particularly advantageous development, a device for form error detection comprises a comparison device that is self-learning and from a plurality of captured contours of bag bodies that are defined as free of form errors, calculates an envelope curve that represents the target contour for subsequent comparisons. In this embodiment variant, for example, with constantly changing contour requirements, as is the case in the production of small series, bags free of defects in shape can be recorded as a reference at any time, the measurement data of which are used to calculate the target contour.

Another useful embodiment of a device for form error detection comprises at least one opening sensor, for example designed as an optical sensor, for detecting whether at least one end portion of the bag body is folded so that it is open, and for sending out an opening error signal when the folding of the bag body did not take place. Advantageously, if an error signal from the opening sensor, for example an optical sensor, occurs, the defective sack body cannot be finished before it is fed to a further processing step and, for example, a valve sheet or a cover sheet is attached to the sack ends of the defective sack body. In this way, the material requirements can be reduced and the production costs can be optimized.

Expediently, two valve leaf sensors for detecting the location, position and presence of a valve leaf attached to the sack body are provided in a device according to the invention for detecting form errors, the comparison device comparing the location and position of the valve leaf with setpoints or setpoint ranges and emitting a valve leaf error signal, if the deviation between the detected position and position of the valve sheet and the setpoints or setpoint ranges exceeds a predefined threshold value. Optical sensors, for example, are used as valve leaf sensors.

In a further variant, at least one cover sheet sensor, for example also an optical sensor, for detecting the position of cover sheets attached to one or both ends of the sack body is provided in a device for form error detection, the comparison device showing the position of the at least one cover sheet with setpoint values or compares target value ranges and sends out a cover sheet error signal, if the discrepancy between the detected position of the at least one cover sheet and the target values ​​or target value ranges exceeds a predefined threshold value.

In order to obtain a compact device according to the invention for form error detection, provision is made in a further development of the invention to provide an excretion station controllable by the form error signal and / or opening error signal and / or valve sheet error signal and / or cover sheet error signal for the elimination of form error-prone sack bodies from the conveying path. The separation station is preferably controlled by the comparison device.

3/8 Austrian

Patent office

AT508 312 B1 2011-07-15

An embodiment of a device according to the invention according to one of the preceding claims comprises a user interface with which a user can set or change the setpoint values ​​or setpoint ranges for the contours of the sack body and / or the valve sheet and / or the cover sheets. In this particularly user-friendly variant, setpoint values ​​of the reference contours can be changed very easily and thus the rate of shape error detection to be achieved can be influenced.

With an expedient variant of a recording device that is suitable for recording statistical data on form defects that have occurred on sack bodies, a device according to the invention can also be used, for example, to monitor manufacturing processes that must meet the strict requirements of a standardized quality management system.

A device according to the invention for detecting form defects in tubular sack bodies can be extremely advantageous for quality monitoring in a device for producing sacks from tubular sack bodies, in particular sack bodies made of a plastic fabric made of tubular round fabric or a flat fabric made of monoaxially stretched polymer -, in particular polyolefin, preferably polypropylene tapes, which are optionally coated on one or both sides with thermoplastic material, in particular polyolefin, are used. Such a device according to the invention for producing sacks from tubular sack bodies comprises, in addition to the device according to the invention for detecting form defects, a conveying device for transporting the sack bodies along a conveying path, wherein along the conveying path one or more sack body folding devices, at least one cover sheet applicator, optionally a valve sheet applicator, and optionally one Separation station are arranged.

Instead of a separation station, it may be sufficient under certain circumstances if a warning display is automatically triggered when a formal error is detected, and the operating personnel is made aware of a defective sack body, for example by emitting a horn signal or by a flashing light. This defective sack then has to be sorted out of production by hand.

Further features of the invention emerge from the following description of exemplary embodiments and with reference to the drawing.

Fig. 1 shows a schematic representation of an embodiment of a device 1 according to the invention for detecting form defects in tubular bag bodies 2, which are provided in particular for forming cuboid bags. For this purpose, the sack bodies 2 are transported along a conveying path 3 on a conveying device 4, for example on a conveyor belt. In Fig. 1 two optical contour sensors 5 are shown, which, designed as line sensors, detect the contour 6 of a sack body 2 and send the recorded measurement data to a comparison device 7, which compares the recorded contour 6 of the sack body or the completely folded sack with the data of a target contour and emits a form error signal 8, if there are deviations between the recorded contour 6 and the target contour, a predefined threshold value should be exceeded.

The comparison device 7 is able to determine the width 9 or 9 'via the contour sensors 5 and to compare this measurement data with a nominal width.

In addition, the comparison device 7 automatically compares the detected contour 6 of the sack body with an envelope curve 30 which was obtained by measuring several desired contours.

At the entrance of the conveying path 3 of the conveying device 4, two opening sensors 15 are present. These opening sensors 15 are used to check whether a folding 31 of the bag body 2 has been carried out in such a way that it can be used for further processing in accordance with regulations. If the bag body 2 has not been folded, an opening sensor 15 detects a faulty fold 31, for example, and sends an opening error signal 16 to the Ver4 / 8 Österreichisches

Patent office

AT508 312 B1 2011-07-15 equalization device 7. This prevents additional, unnecessary

Manufacturing steps are carried out.

The device 1 for form error detection further comprises two valve leaf sensors 17, which detect the position, position and the presence of a valve leaf 18 previously attached to one of the two folds 31 of the bag body 2. The location, position and presence of the valve sheet 18 are compared with setpoint values ​​by the comparison device 7; if one or more setpoint ranges are exceeded by a predefined threshold value, a valve sheet error signal 19 is then sent out.

Furthermore, two cover sheet sensors 20 are provided for detecting the position of the cover sheets 21 attached to both folded ends of the bag body 2. After comparison of the position of the recorded cover sheets 21 with setpoint values ​​by the comparison device 7, a cover sheet error signal 22 is also triggered when deviations by a predefined threshold value are exceeded.

Each individual error signal, the form error signal 8, the opening error signal 16, the valve sheet error signal 19 and the cover sheet error signal 22 lead to the separation station 23 being actuated and a sack body 24 with a form error, which has, for example, a cover sheet 21 attached at an angle protruding at an end section 14 , is withdrawn from conveyor route 3.

Design variants of a device 1 according to the invention for form defect detection are also conceivable: For example, several separation stations 23, 23 ', 23 can be provided, each individual separation station for separating a defective bag body 24 exclusively on the basis of a single, bes specific error signal 8, 16, 19 or 22 is used. In this way, for example, bags in which only the position of a fixed cover sheet 21 deviates from its permissible position by at least a predefined threshold value can be collected separately in a single separation station for bag bodies with defective cover sheets and sold as a second bag quality after a visual check.

The device 1 is equipped with a computing unit with a user interface 25, the computing unit also serving as a recording device 25 for recording statistical data of sack bodies 24 with form errors.

A method according to the invention for manufacturing sacks from tubular sack bodies 2 advantageously makes use of a previously described device 1 for detecting defects in shape for checking the quality. In addition, a device for producing sacks from tubular sack bodies 2 comprises a conveying device 4 for transporting the sack bodies 2 along a conveying path 3, wherein along the conveying path 3 one or more sack body folding devices 27, at least one cover sheet applicator 28, possibly a valve sheet applicator 29, and optionally a separation station 23 are arranged.

As is shown schematically in FIG. 1, two opening sensors 15 are provided on or near the conveyor 4 at the beginning of the conveyor path 3 in such a manufacturing method according to the invention for bags from tubular bag bodies 2. When the tubular sack body 2 is opened, it is suitably folded by a plurality of sack body folding devices 27, in particular the two free end sections 14 of the sack body 2 being folded into preferably rectangular end surfaces. A valve leaf 18 is attached to the bag body 2 by a valve leaf applicator 29 at a fold 31, the position, position and presence of the valve leaf 18 being checked by the valve leaf sensors 17. In the same way, cover sheets 21 are then respectively attached to the two end sections 14 of the bag body 2 by a cover sheet application device 28. To check the position of the attached cover sheets 21, two cover sheet sensors 20 are provided.

Finally, two contour sensors 5, each designed as line sensors, are provided for the final inspection. When the detected contour 6 of the sack produced 26 the

5/8 Austrian

Patent office

AT508 312 B1 2011-07-15 preset conditions of the target contour are met, then the manufacturing process is completed and the sack 26 is checked for form errors.

If one or more criteria deviate from preset threshold values ​​of the desired contour, the bag body 2 is recognized as a faulty bag body 24 and is separated from the ongoing production in the separation station 23.

Instead of the separation station 23, it may be sufficient, depending on customer requirements, if a warning device, for example a horn signal or a flashing light, is triggered as soon as a defective bag body 24 is detected. This then has to be separated from the ongoing production by the operating personnel.