Material web fixing device as part of a filter bag manufacturing installation

A material web fixing device is used as part of a filter bag manufacturing installation. A material web transport device is used to transport at least two material webs, which fixed together at a distance from one another by at least one fixing seam, along a transport direction. A plurality of sewing units each have stitch forming tools configured as a sewing needle and a looper which interact with a thread. The material webs can be passed through between said stitch forming tools in the transport direction. An excess thread production unit is used to lengthen a thread path between the material webs. The excess thread production unit is arranged between the material webs in the thread run during operation. As a result, a material web fixing device is obtained, which allows filter bags to be produced with larger bag openings, particularly with larger opening extensions between the material webs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of German patent application No. DE 10 2016 203 358.1 filed on Mar. 1, 2016, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein.

FIELD OF THE INVENTION

The invention relates to a material web fixing device as part of a filter bag manufacturing installation. The invention further relates to a method of fixing at least two material webs at a distance from one another, and to a filter bag manufacturing installation comprising a material web fixing device of this type.

BACKGROUND OF THE INVENTION

A material web fixing device of the type named at the outset is known from the product brochure “FPS300-High-Speed-Fertigungsinstallation für Filtertaschen” (engl.: “FPS300 High Speed Manufacturing Installation for Filter Bags”), available via the applicant's web pages at the filing date of the application. A multi-needle sewing machine is known from DE 20 2005 014 523 U1.

SUMMARY OF THE INVENTION

An object of the present invention is to further develop a material web fixing device of the type named at the outset in such a way as to allow filter bags to be produced with a larger bag opening, particularly with a larger opening extension between the material webs.

According to the invention, this object is achieved by a material web fixing device as part of a filter bag manufacturing installation, comprising a material web transport device for the transport of at least two material webs to be fixed, by means of a fixing seam, at a distance from one another along a transport direction, a plurality of sewing units with in each case one sewing needle and a looper acting as stitch forming tools between which the material webs can be passed through in the transport direction, the stitch forming tools interacting with a thread to produce the fixing seam, an excess thread production unit to lengthen a thread path between the material webs, the excess thread production unit being arranged in the thread run between the material webs during operation, the excess thread production unit having in each case an oblique surface running at an angle to the transport direction, the oblique surface being arranged between the material webs during operation in such a way that it is passed over by the thread during seam formation due to the transport via the material web transport device, with each sewing unit being associated to a respective one of the oblique surfaces.

It was found according to the invention that an excess thread production unit arranged between the material webs produces the excess thread at the point where it is needed for fixing the distance between the material webs. In other words, the excess thread is produced between the material webs and not outside the material webs. For the excess thread thus produced, it is not necessary to draw said excess thread to a position between the material webs by means of an additional drawing unit. The excess thread production unit may be arranged in direct proximity to the stitch forming tools of a sewing unit. The excess thread production unit may be penetrated by a tip of the sewing needle during operation. One particular excess thread production unit can be associated to a respective one of the sewing units. The excess thread production unit allows excess thread paths to be produced, which provide a distance between adjacent material webs of more than 70 mm, for example of 80 mm, 90 mm, 100 mm and even larger distances. A given filter frame can then be provided with a correspondingly lower number of filter bags having a larger opening width.

The excess thread production unit has an oblique surface running in each case obliquely to the transport direction. During operation, said oblique surface is arranged between the material webs in such a way that during stitch formation, the thread passes over the oblique surface due to the transport via the material web transport device. Each sewing unit is associated to a respective one of the oblique surfaces. Oblique surfaces of this type have proven to be particularly suitable to form excess threads between the material webs in an operationally safe manner. The length of the excess thread produced by means of the excess thread production unit can be defined as a function of the deflection of the thread path produced by the oblique surface in a direction transverse to the transport direction.

Configuring the excess thread production unit as at least one sheet metal part with a plurality of oblique surfaces each, with a respective one of the oblique surfaces being provided for each sewing unit, reduces the manufacturing costs. It is conceivable to use a plurality of sheet metal parts of this type each having a plurality of oblique surfaces. Alternatively, it is conceivable to provide a separate excess thread production unit for each unit.

An oblique surface orientation of at least two oblique surfaces counter to one another such that the resulting forces applied by these oblique surfaces to the material webs in a direction transverse to the transport direction when passed over by the thread act in opposite directions reduces the risk of an unwanted lateral offset between the material webs in the operation of the material web fixing device. A resulting total force applied by the oblique surfaces to the material webs in a direction transverse to the transport direction when passed over by the thread may be 0 or may be approximately 0.

An excess thread production unit, which is adjustable between various default positions to define various thread path lengthening dimensions, allows filter bags to be produced with predefinable opening widths. In order to predefine various thread path lengthening dimensions, the excess thread production unit can be displaceable transversely to the material web transport direction.

An excess thread production unit, which is displaceable during the seam forming process, allows the excess thread produced between the material webs by means of said unit to be lengthened even more. To achieve this additional lengthening, the excess thread production unit can be displaceable transversely to the material web transport direction in the stitch forming process.

An additional excess thread production unit comprising at least one additional excess thread production unit to additionally lengthen the thread path between two stitches of the fixing seam by an additional thread path, the additional excess thread production unit being arranged, during operation, outside the two material webs in the thread run facing the sewing needle, and at least one thread drawing unit to draw the additional thread path, which is first disposed outside the material webs, into the thread run between the material webs provides the possibility of producing a total excess thread, which is longer than the excess thread produced between the material webs by means of the excess thread production unit. The thread drawing unit can be configured as a plurality of thread drawing wires associated to in each case one sewing unit and running obliquely to the transport direction. During operation, these thread drawing wires can be arranged between the material webs in such a way that they are passed over by the thread during stitch formation due to the transport via the material web transport device.

Configuring the additional excess thread production unit as a thread finger, which is drivable to be displaced transversely to the transport direction and is arranged locally between the sewing needle in the top dead center and the material webs, the thread finger being configured such as to initially lengthen the thread path during seam formation, wherein the thread comes out of contact with the thread finger once the thread path has been lengthened due to the transport via the material web transport device, proved to be suitable.

The advantages of a method of fixing at least two material webs at a distance from one another, the method comprising the steps of transporting the material webs along a transport direction to pass through between the stitch forming tools of a plurality of sewing units, producing a fixing seam by means of the stitch forming tools by using a thread with a lengthened thread path, and lengthening the thread path of the fixing seam during seam formation by means of an excess thread production unit arranged between the material webs correspond to those that have already been explained above with reference to the material web fixing device. The method can be carried out using a material web fixing device according to the invention.

The advantages of a filter bag manufacturing installation comprising a material web fixing device according to the invention, a sealing device for sealing the fixing seam formed in such a way that the material webs are permanently fixed at a distance from one another by means of the thread, and a material web edge joining device for closing side seams and/or bottom seam to form a ready-to-use filter bag correspond to those that have already been explained above with reference to the material web transport device according to the invention. A permanent fixing can be carried out with the sealing device by means of hot glue, for example. Connecting the edges can be carried out by sewing and/or ultrasonic welding.

An exemplary embodiment of the invention will hereinafter be explained in more detail by means of the drawing.

DETAILED DESCRIPTION

A material web fixing device1is part of a filter bag manufacturing installation2shown in an extremely schematic view inFIG. 5. The filter bag manufacturing installation2is used to manufacture filter bags the bag walls of which are formed by two material webs3,4shown inFIGS. 2 and 3. In accordance with its orientation when being processed in the material web fixing device1, the material web3is referred to as upper material web while the material web4is referred to as lower material web. A plurality of filter bags thus produced can be inserted into a common filter frame (not shown) at a later point in time, wherein adjacent ones of the filter bags bear against one another with their long bag opening front edges. The short front edges of the filter bag openings have a dimension greater than 70 mm, in particular amounting to 100 mm. A frame with an edge length of 600 mm×600 mm can be filled completely with a total of six filter bags with filter bag openings dimensioned and arranged in this manner (100 mm×600 mm).

The material web fixing device1has a material web transport device5shown only schematically inFIG. 5to transport the two material webs3,4along a transport direction6. InFIGS. 1 and 2, the transport direction6runs perpendicular to the drawing plane and out of the latter.

The material web fixing device1has a plurality of sewing units7. Said sewing units7each have a sewing needle8and a thread looper9serving as stitch forming tools interacting with a sewing thread10.FIG. 1shows an exemplary view of eleven sewing units7arranged adjacent to each other and perpendicular to the transport direction6. The material web fixing device1is actually provided with a total of twelve sewing units7arranged adjacent to each other and perpendicular to the transport direction6.

The thread path of a sewing unit7is shown inFIG. 3, for example: here, the thread runs from a conical thread reel11via an eye12of the needle8and past an additional excess thread production unit13configured as a thread finger. The thread10then passes through the upper material web3and runs past an excess thread production unit14arranged between the material webs3,4, the excess thread production unit14being configured as a thread drawing sheet metal plate. Subsequently the thread10passes through the lower material web4and a stitch plate15of the material web fixing device1. During stitch formation, the thread10then winds around the looper tip of the associated looper9of the sewing unit7.

The looper9is drivable to rotate about a looper shaft16running transversely to the transport direction6. For illustrative reasons, the looper is shown in a view rotated through 90° inFIG. 2. The looper shafts16are each mounted in respective shaft supports17of the material web fixing device1.

The excess thread production unit14serves to lengthen a thread path when forming a fixing seam19between the two material webs3,4. InFIG. 1, the stitches18are marked by an index1,2counter to their order of production.

For each of the sewing units7, the excess thread production unit14has a respective oblique surface20extending at an angle to the transport direction6. In the operation of the fixing device1, said oblique surface20is arranged between the material webs3,4in such a way that it is passed over by the thread10during stitch formation due to the transport via the material web transport device5, causing said oblique surface20to be deflected transversely to the transport direction6. As a result, excess thread21is produced directly between the material webs3and4. In other words, the thread10needs to travel along a path during stitch formation, which—because of the thread drawing sheet metal plate14and the oblique surface20thereof—is longer than it would be if no thread drawing sheet metal plate14was provided. As can be seen directly fromFIG. 1, one of the oblique surface20is in each case associated to a respective one of the sewing units7.

In the embodiment according toFIG. 1, the excess thread production unit14is formed by a total of two sheet metal plates14aand14b. Each of these thread drawing sheet metal plates14a,14bhas six oblique surfaces20each, which are each associated to a respective one of the sewing units7. With respect to their extension in the oblique direction, the six oblique surfaces20of the sheet metal plate14aare oriented counter to the six oblique surfaces20of the sheet metal plate14b. Resulting forces applied to the material webs3,4by these oblique surfaces20of the sheet metal plates14a,14bin a direction transverse to the transport direction6when passed over by the thread then act in directions opposite to each other. A total force applied to the material webs3,4by these oblique surfaces20of the sheet metal plates14a,14btransversely to the transport direction6when passed over by the thread may then be 0 or virtually 0.

The excess thread production unit14may be adjustable to define various thread path lengthening dimensions, in other words various lengths of the excess thread21produced transversely to the transport direction6between various default positions (see double arrow22inFIG. 2). InFIG. 1, the two thread drawing sheet metal plates14a,14bare each shown in the default position “maximum excess thread”. As an alternative or in addition thereto, the excess thread production unit14may be displaceable, in particular drivable to be displaced, transversely to the transport direction6during stitch formation to produce said excess thread.

The additional excess thread production unit13serves to additionally lengthen the thread path between two stitches18i,18i+1by an additional thread path23(seeFIGS. 3 and 4). In the operation of the fixing device1, the additional excess thread production unit13, in other words the thread finger associated to a respective one of the sewing unit7, is arranged outside the two material webs3,4in the thread path facing the sewing needle8. In the orientation of the fixing device1shown in the drawing, both the sewing needle8and the thread finger13are arranged above the upper material web3.

The fixing device1further has a thread drawing unit24associated to the respective sewing unit7to draw the additional thread path23, which is first provided outside the two material webs3,4, into the thread run between the material webs3,4. The thread drawing unit24is configured as a plurality of thread drawing wires extending obliquely to the thread direction6, the thread drawing wires being associated to a respective one of the sewing units7. In the operation of the fixing device1, these are arranged between the material webs3and4(seeFIG. 3). This arrangement is such that the respective thread drawing wire24is passed by the thread10during stitch formation due to the transport via the material web transport device5. Once the thread has passed by the respective thread drawing wire24, the excess thread21produced by the excess thread production unit14and the additional thread path23produced by the additional excess thread production unit13add up to form a total excess thread25between the material webs3and4.

The additional excess production unit13is configured as a thread finger drivable to be displaced transversely to the transport direction6(see double arrow26inFIG. 2). This thread finger displacement may be an oscillating movement synchronized with the stitch formation. As an alternative or in addition thereto, it is conceivable for the thread fingers13associated to the sewing units7to be displaced in a direction perpendicular to a web plane of the material webs3,4(see double arrow26a) in the seam forming process. This allows the additional thread path23produced during seam formation to be varied along the fixing seam19.

The thread fingers13are each arranged locally between the needle8in the top dead center and the material webs3,4. The thread finger13is configured such as to lengthen the thread path during stitch formation; once the thread path has been lengthened by means of the thread finger13, the thread10comes out of contact with the thread finger13, which is not transported together with the material web3,4, due to the transport via the material web transport device5.

In addition to the material web fixing device1, the filter bag manufacturing installation2further includes a sealing device27for sealing the stitches formed such that the material webs3and4are permanently fixed at a distance from one another by means of the thread10. The sealing device27is configured as a pair of hot glue nozzles28,29associated to a respective one of the sewing units7via which glue30(seeFIG. 3) is applied to the fixing seam19from above and to the material webs3,4from below after the total excess thread25has been produced.

The filter bag manufacturing installation2further includes a material web edge joining device31to close side seams and bottom seam of the filter bag comprising the two material webs3,4. Joining the edges can be performed by sewing and/or ultrasound welding.

When fixing the two material webs3,4at a distance from one another by means of the material web fixing device1and the other components of the filter bag manufacturing installation, the material webs3and4are passed through between the stitch forming tools8and9of the sewing units7along the transport direction6. The stitches18iare produced by means of the sewing needle8, with the thread10being transported through the two material webs3,4to the looper9. A thread loop is then picked up by the looper and wound around another thread portion10′ running below the lower material web4. This causes knots32(seeFIG. 3) to form between the thread10transported through the material webs3and4and the thread portion10′.

When producing the fixing seam19, the thread path is lengthened on the one hand between the material webs3and4by means of the excess thread production unit14and between two stitches18i,18i+1by means of the additional excess thread production unit13on the other. The additional thread path23produced by the additional excess thread production unit13is drawn, by means of the thread drawing unit24, between the material webs3and4as well, with the result that for each stitch18, there is a total excess thread path25between the respective knot32and the associated needle entry into the upper material web3, said total excess thread path25providing a distance of 100 mm between the two material webs3,4when the thread10is tensioned.

The total excess thread path25can be varied by correspondingly setting the excess thread production unit14and/or the additional excess thread production unit13along the fixing seam19, with the result that a filter bag is obtained that has a conical shape in the direction of a bag bottom. Having produced the total excess thread path25, the thread10and the thread portion10′ are sealed together below the upper material web3and below the lower material web4by means of the two hot glue nozzles28,29of the sealing device27to permanently secure the thread10,10′ to the material webs3and4. Subsequently, side seams and bottom seams of the filter bag are closed by means of the material web edge joining device31. The filter bag is now ready for use and can be inserted into the pre-fabricated filter frame together with other filter bags.