Abstract:
A web of film is folded lengthwise, and its superposed sections are joined together along transverse lines to form a series of pockets. A hole is then cut in each pocket near the fold line. The film is shaped and clamped between two curved shaping parts, and a blade in one of the parts is advanced toward a counter blade on the other part. A shoulder element having a pouring spout and a flange is introduced into the pocket and the spout is inserted through the hole, whereafter the flange is joined to the pocket.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage filing under 35 U.S.C. §371 of International Application No. PCT/CH99/00290, which has an international filing date of Jul. 2, 1999 and which designates the United States of America. 
    
    
     BACKGROUND 
     Known bag tubes have a film material of plastic which forms an end-face wall and two side walls of the tube, wherein the side walls are welded (or connected in another manner) to one another along two side sections, and a shoulder piece which comprises a closable outlet piece and a flange fastened on the end-face wall, preferably curved just as the end-face wall. 
     The invention relates to a method for manufacturing bag tubes, wherein a web of film material is folded about a fold line running in its longitudinal direction. The sections of the web are laid on one another, along strips which are arranged at distances from one another and which run transversely to the fold line, and are connected to one another in order to form a row of pockets. A hole is cut in each pocket in the region of the fold line and then a shoulder piece is introduced into each pocket. The shoulder piece comprises a closable outlet piece and a flange projecting from the piece. The outlet piece of the shoulder piece is inserted through the hole, the flange of the shoulder piece is connected to the film material, the outlet piece of the shoulder piece is closed, the pocket then from the open end is filled, and finally the open end is closed. 
     In known methods of this type it is difficult to cut a round hole precisely into the film material forming the end-face wall and to prevent a distortion of the film material which may lead to shoulder pieces seated too obliquely in the bag tubes. 
     SUMMARY OF THE INVENTION 
     The object of the invention lies in avoiding these difficulties, thus to permit a precise cutting of the hole and avoiding a distortion of the film material. 
     According to the invention this object is achieved in that, for cutting the hole into each pocket, the film material of the pocket in the region of the fold line is shaped and clamped between two shaping parts and then in one of the shaping parts a knife is displaced and moved to a counter knife on the other shaping part. 
     The applied shaping parts may usefully be curved, roughly about an axis perpendicular to the connection plane of the two strips limiting the pocket. In the same manner the flange of the shoulder piece to be inserted may also be curved. 
     The pocket may in the axial direction be relatively long. So that the two shaping parts, of which one must be introduced into the pocket, may cooperate precisely despite this, the knife and the other shaping part may usefully comprise a centering pin and a receiving bore. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic of a web of plastic film material, showing how it is initially folded and processed; 
     FIG. 2 shows an individual pocket formed of the film material; 
     FIG. 3 shows, on a larger scale, an axial section through a shoulder piece to be applied into the pocket; 
     FIG. 4 is a schematic representation of the shaping parts used on cutting a hole into the pocket; 
     FIG. 5, on a larger scale, is an axial section through the two shaping parts at a distance to one another; 
     FIG. 6 is the same view as FIG. 5, showing the position in which the two shaping parts cooperate with one another; 
     FIG. 7 schematically represents further processing steps of a pocket after the processing by the shaping parts; 
     FIG. 8 is an axial section through a shoulder piece in a modified embodiment; 
     FIG. 9 is an axial section through a coupling sleeve to be connected to the shoulder piece of FIG. 8; 
     FIG. 10 show the shoulder piece of FIG.  8  and the coupling sleeve of FIG. 9 constructed together and with a screwed-on closure cap; 
     FIG. 11 is an axial section through one variant of the shoulder piece of FIG.  8  and of the coupling sleeve of FIG. 9; and 
     FIG. 12 is an axial section through another variant of the shoulder piece of FIG.  8  and of the coupling sleeve of FIG.  9 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a web  1  of plastic film material which is continuously unwound from a roller  2  and is folded about a fold line  3  running in its longitudinal middle line. The web is moved stepwise in the direction of the arrow P. At a first station, welding jaws are moved towards the folded film web  5  in order to connect to one another the two sections of the film web, which are laid on one another, along a strip running transversely to the fold line  3 . The connection strips  6  which are formed after one another have, in the movement direction of the web  5 , distances to one another so that the film material in each case between two strips  6  neighboring one another forms a pocket  7 . There thus arises a row of pockets. 
     At a next station, cooling elements  8  act on the connection strips  6  in order to cool the film material heated by the welding process. 
     At a third station, where desired, punching tools  9  in the region of the fold line  3  punch a small section  10  out of the film material in order in the closed end of each pocket  7  to form a small prepunch. 
     At a fourth station, the pockets  7  are separated from one another by cutting through the strips  6  roughly in the middle. Thus individual pockets may arise. It is, however, also possible to form groups of two or more pockets. The pockets of each group may then, where desired, be processed together in the subsequent stations when the tools in these subsequent stations are present doubly or several times. FIG. 2 shows a single pocket  7  formed by the cutting. 
     The shoulder piece  11  is then inserted into the pocket  7 . The shoulder piece  11  has an outlet piece  22  which is provided with a thread and is closable with a screw cap (not shown here), and a flange  13  which projects from the piece  12  and is curved in one direction (according to a cylinder surface). 
     Before inserting the shoulder piece  11 , as shown in FIG. 4, the pocket  7  is opened with suction cups  14  engaging its die walls. Then a first shaping part  15  is introduced through the open end of the pocket  7 . A complementary second shaping part  16 , lying opposite the first shaping part  15 , is applied onto the film material of the pocket  7 . The shaping parts  15  and  16  are shown at a larger scale in FIGS. 5 and 6. 
     The first shaping part  15  has a sleeve whose working end  18  is curved just like the flange  13  of the shoulder piece  11  of FIG.  3 . The axis of curvature (not illustrated) runs in FIGS. 5 and 6 in the plane of the drawing. The sleeve  17  is guided axially displaceable on a rod  19 . The rod  13  carries at one end a circular knife  20 . Furthermore, the rod  19  in the illustrated embodiment carries a centering pin  21  projecting out of the knife  20 . Between the end of the sleeve  17 , this end lying opposite the working end  18 , and a shoulder on the rod  19  there is a compression spring  22 . 
     The second shaping part  16  has a block  23  with a circular opening  24  whose edge  25  forms a counter knife for the knife  20 . A surface section  26  of the block  23 , surrounding the opening  24 , is curved just like the working end  18  of the sleeve  17 . 
     The first shaping part  15 —as described previously with FIG.  4 —is introduced into the open end of a pocket  7 . The centering pin  21  of the first shaping part  15  penetrates through the prepunch which, at the third station in FIG. 1, has been formed by the punching tool  9  in the film material of the pocket  7 . The diameter (or generally the transverse dimension) of the prepunch is preferably somewhat larger than the diameter of the centering pin  21 . If there is no such prepunch, a pointed centering pin  21  may be used which may simply penetrate through the film material. 
     The second shaping part  16 , lying opposite the first shaping part  15 , is applied onto the film material of the pocket  7 . The centering pine  21  of the first shaping part  15  is accommodated in a receiving bore  27  in the second shaping part  16 , by which means the two shaping parts  15  and  16  are aligned exactly with one another. The end-face wall of the pocket  7  which has arisen with the opening of the pocket, as shown in FIG. 6, is clamped and shaped between the curved working end  18  of the sleeve  17  and the equally curved surface section  26  of the block  23 . The sleeve  17  and/or the block  23  when desired may be heated for this. The end-face wall of the pocket thus obtains the same curvature as the flange  13  of the should piece of FIG.  3 . 
     Upon moving the rod  15  towards the block  23  and compressing the spring  22 , the knife  20  is moved to the counter knife  25  on the block  23  and the shaped and clamped film material of the end-face wall of the pocket is cut through. The cut-out film ring may be suctioned away in the second shaping part through a suction bore  28 . 
     As shown in FIG. 7, a tool  29  then introduces a shoulder piece  11  into the pocket  7  with the precisely cut-out hole in the end-face wall, at a first station. The end-face wall of the pocket is at the same time supported by a counter tool  30 . The outlet piece  12  (FIG. 3) of the shoulder piece  11  enters through the hole in the end-face wall of the pocket. The flange  13  (FIG. 3) of the shoulder piece  11  is fastened on the end-face wall of the pocket, for example by adhesion or welding. The two tools  29  and  30  may simultaneously be designed as welding heads for welding the flange  13  to the end-face wall of the pocket, fox example by ultrasound. 
     In a next station in FIG. 7, a tool  31  for supporting the shoulder piece, fastened on the end-face wall of the pocket, is introduced into the pocket, and a closure cap  32  is screwed or pressed onto the outlet piece  12 . While the closure cap  32  is screwed on, the tool  31  simultaneously serves as a rotational securement for preventing a co-rotation of the shoulder piece and as the end-face wall of the pocket. 
     In a subsequent station, the pocket  7 , closed with the closure cap  32 , is filled from a filling tube  33 . 
     Then in a further station, the open end of the pocket is pulled tight in the direction of the arrows A, and in a subsequent station the edge sections of the two side walls of the pocket in the region of the end of the pocket, this end until now being open, are welded to one another by welding tools  34 . The edge sections welded to one another may then be cooled by cooling elements  35 . The finished bag tube  7 , which is closed with the closure cap  32 , is filled and is sealed all around the edges of the side walls, as represented in FIG. 7 on the far right. 
     In the embodiment described above, the outlet piece  1  (FIG. 3) has an outer thread onto which then the closure cap  32  (FIG. 7) is screwed in order to close the outlet piece  12 . Alternatively, a shoulder piece  41  according to FIG. 8 may be used. This has an outlet piece  42  and a flange  43  projecting from the outlet piece. The outlet piece  42  comprises latching means for holding firm a coupling sleeve  44  (FIG. 9) which may be pressed onto the outlet piece and which comprises an outer thread  45 . In FIG. 10, the coupling sleeve  44  is pressed onto the outlet piece and is shown with a screwed-on closure cap  46 . The screwing (or the pressing) of the closure cap  46  onto the coupling sleeve  44  may be effected before or after the pressing of the coupling sleeve onto the outlet piece  42 . 
     A shoulder piece with a coupling sleeve of the type shown in FIGS. 8 to  10  may alternatively be designed such that the edge of the hole in the end-face of the pocket, though which hole the shoulder piece is inserted, may be clamped between the flange of the shoulder piece and the coupling sleeve. Two such variants are shown in FIGS. 11 and 12, at a larger scale. 
     FIG. 11 shows how an edge of the film material of a pocket is clamped between a flange  53  of a shoulder piece  52  and the end of a coupling sleeve  54 . The coupling sleeve  54 , as described by FIGS. 8 to  10 , is pressed onto an outlet piece  52  of the shoulder piece  51 . Owing to the clamping of the film material, the welding or adhesion of the film material to the flange  53  may be done away with. For improving the sealing between the film material and the flange  53 , the flange may have circular ribs  57  which press the film material into corresponding grooves in the end surface of the coupling sleeve. 
     FIG. 12 shows, similarly to FIG. 11, a shoulder piece  61  with a flange  63 , and a coupling sleeve  64 , wherein the edge of the film material of a pocket  7  is clamped between the flange  63  and the end surface of the coupling sleeve  64 . Between the flange  63  and the film material there is a suitable sealing medium  68 , e.g., a latex. In this case the end surface of the coupling sleeve  64  may have circular ribs  69  which press the film material into the layer  68  of the sealing medium. In place of the layer of sealing medium  68 , or in addition, a sealing medium layer may also be arranged between the film material and the end surface of the coupling sleeve  64 . With such a sealing medium layer, gases or vapors from the contents of the bag tube may be prevented, between the outlet piece of the shoulder piece and the coupling sleeve, from reaching the film material and then, between this and the end surface of the coupling sleeve, from reaching the outside.