Abstract:
A dust filter bag is in the shape of a flat bag for a vacuum cleaner, which is formed from a first layer and a second layer made of a weldable material. The layers are welded together circumferentially along the circumference thereof.

Description:
FIELD OF INVENTION 
     The invention relates to a dust filter bag in the form of a flat bag for a vacuum cleaner which is formed from a first layer and second layer made of a weldable material, the layers being welded together circumferentially along the circumference thereof. The dust filter bag according to the invention is distinguished in particular in that one of the layers of the flat bag is folded in at least partially at at least one bag side towards the bag interior with formation of a first and second fold member. 
     BACKGROUND INFORMATION 
     A dust bag filter in the form of a flat bag with side folds is known from DE 20 2005 000 917 U1. This flat bag thereby comprises an upper wall and a lower wall which is congruent with the latter, the wall material being formed from a flexible, weldable material and being welded together circumferentially at the circumferential edge thereof. The characteristic feature of this dust filter bag is thereby that a fold-in is provided at at least one bag side towards the interior and has been produced by a fold member formed by the upper wall and a fold member formed by the lower wall. This flat bag hence begins with two substantial congruently large upper and lower walls made of the flexible material and then welding is undertaken at the edge side. In a second step, the fold formation is then implemented so that the weld seam at the side at which the fold-in is effected, when the bag is present folded together, is disposed within the fold. In the operational state the folding can then be turned out. 
     However it is disadvantageous with a dust filter bag of this type that a specific outer fold is formed by the symmetrical construction comprising the approximately congruently large upper and lower wall and the fold-in of the dust filter bag in the operational state, so that adaptation to different vacuum cleaner models is difficult. It is not simple to fold in the side folds in addition in production technology. 
     SUMMARY OF INVENTION 
     The present invention relates to a dust filter bag which has the geometry of the dust collection chamber of the different vacuum cleaner models. The present invention further relates to a method for the production of a flat bag of this type. 
     According to the invention, it is hence proposed that the fold-in at at least one bag side of the flat bag is achieved in such a manner that the fold-in is undertaken in one of the two layers and the fold-in can be turned out. There is thereby understood by “turnoutable” in the sense of the invention, also the folding out of the fold members relative to each other until complete outwardly directed turning out of the side folds is achieved. The folding in is thereby achieved in such a manner that, in the case of the fold member of the layer formed by the folding in, one fold member is larger than the other. The dimensioning is thereby designed such that the larger fold member can then be welded to the second layer at the edge side forming a projection. In the case of the flat bag according to the present invention, no weld seam is hence present in the collapsed state when the fold is situated internally but instead the welding is effected at the edge side between the circumferential edge of the second layer and the projection of the larger fold member of the folded-in layer. As a result of the fact that now no internally situated weld seam is present, as in the flat bag according to DE 20 2005 000 917 U1, it is possible to configure the fold-in such that, in the turned-out state, different geometries, such as a trapezoid or triangle, can be produced. In addition, the turning-in process which is difficult from a production point of view is avoided for the side folds after the welding. 
     In the case of the flat bag according to the invention, it is thereby preferred if a fold-in, as described above, is undertaken at two oppositely situated bag sides. 
     In the case of the dust filter bag according to the invention, it is thereby preferred that the fold-in is configured such that it can be turned out essentially over the entire width of the bag side. The fold-in can thereby be configured such that, in the completely turned-out state, an essentially trapezoidal outer fold is produced. If the fold-in is fixed in addition in all edge regions, then outer folds which deviate from the trapezoidal shape are produced. 
     A further embodiment of the invention proposes that the fold-in which can be turned out is configured in such a manner, for example by fixing on one side, that an external fold, e.g. in the form of a triangle, is formed merely partially over at least a width of the bag side. In this case, a corresponding inner fold is then present at the same time. By means of a corresponding fold-in on two oppositely situated bag sides, different shapes can hence be achieved in the operating state, i.e. if the fold-in is completely turned out. Thus also an offset arrangement inter alia is possible, in which respectively the fixing of the fold-in has been undertaken on oppositely situated sides of the respective bag sides so that the external folds are disposed offset. 
     The dust filter bag according to the invention is chosen preferably in its basic shape such that it has a rectangular or square shape. As weldable air-permeable material for the individual layers of the flat bag according to the invention, in particular nonwoven material is suitable, here also particularly preferred composite materials comprising nonwoven materials with different filter properties. 
     In the case of the flat bag according to the invention, it is of course also possible, as known already to date in the state of the art, that the introduced inlet opening is reinforced by a retaining plate which can be configured also to be sealable. 
     The invention relates furthermore to a method for the production of a flat bag as described above. 
     According to the invention, the process thereby takes place such that, diverging from the procedure described in DE 20 2005 000 917 U1, firstly the folding is implemented and that only then is the welding effected subsequently. According to the invention, this is effected in that a first strip-shaped lower strip with a larger surface area relative to a strip-shaped upper strip is prepared and in that the folding-in is then introduced into this lower strip. During folding-in, a fold-in is thereby achieved which comprises a first and second fold member, the second fold member having a larger member length and forming a projection relative to the strip. Subsequently, welding of the upper strip to the lower strip is then effected, the lower strip in the edge region of the projection being welded to the longitudinal edges of the upper strip. In order to form the filter bag, it is then merely required in addition to introduce transverse welds at correspondingly prescribed spacings and to implement a separation. 
     The great advantage of the method according to the invention resides in the fact that, because of the fact that a fold is introduced firstly into the lower strip by introducing stamp-outs into the folding-over and corresponding welds, fold-ins can be formed which then lead, in the turned-out state, to external folds with different geometries. Thus external folds which can be turned out can be achieved in the completely turned-out state in trapezoidal shape and triangular shape so that adaptation of the dust filter bag to the different geometries of the dust collection chambers of different vacuum cleaner models is possible. 
     The method according to the invention can thereby also be developed such that, during the transverse welding to form the flat bag, a separation is performed jointly at the same time. It is also favourable if pre-breaks are jointly introduced into the lower strip in order to assist the fold-ins. In particular ultrasonic welding has proved to be suitable as welding method. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Embodiments of the invention are explained subsequently in more detail with reference to  FIGS. 1 to 8  without restricting the subject of the present invention hereto. 
       There are shown: 
         FIG. 1  a dust filter bag according to the invention in schematic plan view, 
         FIG. 2  the dust filter bag according to  FIG. 1  in cross-section according to the section line I-I in enlarged illustration, 
         FIG. 3  shows schematically in plan view a dust filter bag with two trapezoidal turn-outs, 
         FIG. 4  shows a further embodiment of the dust filter bag according to the invention with triangular turn-outs at both sides, 
         FIG. 5  shows an embodiment in which a triangular turn-out is present only on one side, 
         FIG. 6  an embodiment with oppositely situated triangular turn-outs, 
         FIG. 7  in the Figure sequence  7   a  to  7   g , a first variant of the method for the production of the flat bag, 
         FIG. 8  in the Figure sequence  8   a  to  8   h , a second method variant for the production of the flat bag. 
     
    
    
     DETAILED DESCRIPTION 
     A dust filter bag in the form of a flat bag  1  in rectangular form is shown in  FIG. 1  schematically in plan view. Fold-ins which are not visible in the plan view are symbolised with  2  and  3  and are configured in the case of the example according to  FIG. 1  on the bag sides  4  and  5  in trapezoidal shape. In the embodiment according to  FIG. 1 , an inlet opening  6  is provided furthermore in the centre of the flat bag  1 . The shape of the flat bag  1  which is chosen here to be square can obviously also deviate from the square shape and have a rectangular configuration. The flat bag thereby has a circumferential weld seam  11  which has been produced by means of ultrasonic welding. The material of the flat bag is a multilayer nonwoven material. 
       FIG. 2  now shows the cross-section according to the section line I-I in the embodiment according to  FIG. 1 . In  FIG. 2 , the fold-in  2 ,  3  according to the invention is illustrated particularly clearly. The dust filter bag according to the embodiment according to  FIG. 1  thereby comprises a first layer  8  and a second layer  7  of the multilayer weldable material. The first layer  8  thereby has a fold with the fold members  9 ,  10  or  9 ′,  10 ′. The fold members  9 ,  10  and  9 ′,  10 ′ are thereby configured such that they have an unequal length, the larger of the fold members  9 ,  9 ′ forming a projection relative to the layer  8 . In the dimensioning of the strip-shaped layers  7  and  8 , care must therefore be taken that a corresponding weld can be effected on the outer circumferential edge of the fold members  9 ,  9 ′ or at the outer circumferential edge of the second layer  7 . In order to configure the shown trapezoidal fold-in  2 ,  3 , it is thereby necessary that the fold-in  2 ,  3  is sealed at the short members thereof by an additional weld seam  20 . For production of such a fold-in  2 ,  3 , reference is made to  FIGS. 8   a  to  8   h.    
     The fold-in according to the invention now has the effect, if the filter bag in the inserted state is filled with dust-laden air through the inlet opening  6 , of inflation so that then the fold-ins  2 ,  3  with fold members  9 ,  10  or  9 ′,  10 ′ widen and possibly turn outwards so that an increased volume is produced. 
     In  FIG. 3 , the corresponding shape which then results in the completely turned-out state, is represented schematically in plan view. The circumferential weld seam is in turn thereby designated with  11 , the reference numbers  2  and  3  designate the turned-out fold-ins which form a trapezoidal shape. 
       FIG. 4  now shows a further embodiment of a flat bag according to the invention. In the case of the flat bag according to  FIG. 4 , the fold-in was thereby configured such that it now was welded jointly on one bag side and in fact as here in  FIG. 4  to the same side  23 , on the edge side to the weld seam  11  so that a turn-out is effected only on one side on the side  24  with formation of an external fold  13 ,  13 ′ and, on the bag side  23  where welding of the fold-ins is effected simultaneously with the circumferential weld seam  11 , an internal fold  14 ,  14 ′ is formed so that altogether a conical configuration of the dust filter bag results in the completely turned-out state. The production method in this respect is explained in more detail in  FIG. 8  (bag side  24 ) and  FIG. 7  (bag side  23 ). 
       FIG. 5  now shows a further modification of the flat bag is which a fold-in, as shown in  FIG. 4 , has now been undertaken on one bag side. 
     Finally,  FIG. 6  shows another embodiment in which an offset arrangement of the external folds  13  and  13 ′ was implemented by corresponding fixing on sides  23  and  24  of the respective side folds so that the external folds  13 ,  13 ′ are disposed offset. 
       FIG. 7  now shows in the Figure sequence  7   a  to  7   g  a first production method for the flat bag according to the invention. 
     In this method, a strip-shaped lower strip made of a nonwoven material is thereby made available in a first step. The dimensioning of this lower strip is thereby chosen in width (designated by b) such that, after completion of the folding-in, a width c is produced ( FIG. 7   c ) which corresponds approximately to the upper strip then to be connected to the lower strip. In  FIG. 7   a , the running direction of the lower strip is designated with the arrow. 
     In order to configure the fold-in according to the invention, the procedure thereby takes place such that folding-over of the strip-shaped lower strip is effected preferably in a first step. This is illustrated in  FIG. 7   b . Subsequently, as shown in  FIG. 7   c , a backward fold is then implemented so that a fold-in is produced with formation of a first fold member  10  and also of a second fold member  9  and  9 ′ or  10 ′. The second fold member  9  or  9 ′ which forms a projection is thereby chosen to be greater in its member length than the fold member  10  or  10 ′. 
     In the next method step, an upper strip is placed on the thus folded-in lower strip. The dimensioning of the upper strip is thereby chosen such that the longitudinal edges extend approximately flush with the edges of the fold members  9  or  9 ′. As shown here in  FIG. 7   d , the upper strip is provided already with a filling opening  6  and a retaining plate (not illustrated). 
     A longitudinal weld is then subsequently implemented ( FIG. 7   e ). 
     It is now required in addition for production of the filter bag merely to introduce transverse welds at a predetermined spacing, as shown in  FIG. 7   f . Finally, separation is then effected in the region of the transverse welds  11  so that then a finished filter bag is produced ( FIG. 7   g ). In the production method of the filter bag according to the invention, as shown in  FIGS. 7   a  to  7   g , a filter bag is now thereby produced in which fold-ins  2 ,  3  are present which are fixed respectively to the bag sides  23 ,  24  by the circumferential weld seam  11 . In the operating state, there is effected then, in the embodiment as produced with the method according to  FIG. 7 , splaying of the fold members or a turn-out. 
     In the Figure sequence  8   a  to  8   h , a variant of the production method of the flat bag according to the invention is shown. As a modification to the previously described method, as shown in  FIG. 8   b , stamp-outs  30  are introduced into the folded-over region after folding-over. These stamp-outs  30  are preferably welded circumferentially with formation of the weld seam  31  (see  FIG. 8   c ). After welding of the stamp-outs  30 , backward folding then takes place as shown already in  FIG. 7   d . Analogously to the method as described in  FIG. 7 , placing of the upper strip ( 8   e ) and welding of the longitudinal edges is subsequently effected with formation of the weld seam  11  ( 8   d ). 
     It is now essential, as shown in  FIG. 8   g , that the transverse weld  11  is chosen such during the transverse welding that it leads respectively through the corresponding stamp-outs  30 . In the production method according to  FIG. 8 , an embodiment is thereby shown in which the stamp-outs  30  are disposed symmetrically and the respective transverse welds  11  are guided centrally through the stamp-outs  30 . As a result, a flat bag is produced, as shown in  FIG. 8   h , which has a trapezoidal fold-in  2 ,  3  which describes additional weld seams  20  of the short members of the trapezium. The flat bag produced with the production method according to  FIG. 8  thereby corresponds to the flat bag according to  FIG. 1 . 
     The Figure sequence  8   a  to  8   h  likewise makes it clear that the method according to the invention has great flexibility. Thus it is possible at all times to produce flat bags in the case of which corresponding dust bags are produced by choice and spacing of the openings  30 , in which the fold-ins, as a modification of the example according to  FIG. 8 , are also fixed on one side. Consequently, dust filter bags can then be produced which, in the turned-out state, have shapes as shown in  FIGS. 4 to 6 . The method according to the invention hence has extremely high flexibility with respect to the dust filter bags to be produced and can be implemented simply at the same time with respect to production technology.