Abstract:
During the production of cigarette packs having an inner wrapper of thin packaging material, the blank ( 10 ) of the inner wrapper is provided with impressed lines, namely transverse impressed lines ( 19, 20 ) which delimit a base wall ( 11 ) which is first contacted by a cigarette group ( 23 ) when the latter is wrapped in a U-shaped manner. By virtue of the impressed lines ( 19, 20 ), the mechanical load forces exerted on the cigarette group during the U-shaped folding process is reduced. Furthermore, a cigarette conveyor ( 25 ) for transferring the cigarette groups ( 23 ) is driven in a non-uniform manner, i.e. at reduced speed, when receiving a blank ( 10 ), and at a correspondingly greater speed during other conveying operations.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a cigarette pack having an elongate blank which is made of thin packaging material, such as paper, tin foil or the like, and is intended for wrapping a cigarette group such that the blank has a continuous, single-layer base wall which is adjoined by a front wall and a rear wall, the cigarette group, which butts against the base wall by way of end surfaces of the cigarettes, being wrapped in a U-shaped manner in the process, it being the case that the base wall is adjoined laterally by base folding tabs and the front wall and rear wall are adjoined laterally by side tabs for forming folded side walls of the wrapper. The invention also relates to a process and apparatus for producing cigarette packs of the abovementioned type. 
     The types of cigarette pack which are most commonly known throughout the world, namely hinge-lid packs and soft-carton packs, are constructed such that the cigarette group is enclosed by an inner wrapper made of thin packaging material, namely tin foil or paper in particular. The cigarette group is wrapped so as to form a continuous base wall against which the cigarettes butt by way of end surfaces. (Narrow) Side walls and an end wall, which is located opposite the base wall, are formed by overlapping folding tabs. 
     In a first folding step, the blank of the inner wrapper is folded around the cigarette group in a U-shaped manner, said cigarette group being transported by a cigarette conveyor and the blank being held on standby transverse to the conveying plane as a curtain for being carried along by the cigarette group. 
     As the operating speed of the packaging machines increases, the problem of mechanical loading of the cigarettes becomes greater. Pressure and impact loading during the packaging process may result in the quality being impaired. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to propose measures which, despite a relatively high operating speed of the packing machine, avoid, or reduce the risk of, the cigarettes being impaired. 
     In order to achieve this object, the cigarette pack according to the invention is characterized by the following features: 
     a) the base wall is separated off from the front wall and rear wall by transverse impressed lines in the region of right-angled folding edges, 
     b) the transverse impressed lines extend merely in the region of the base wall and front wall and rear wall, but not in the region of the side folding tabs and base folding tabs. 
     According to the invention, it is merely those regions of the blanks which are gripped directly by the cigarette group and/or by the cigarette ends located at the front, as seen in the conveying direction, namely the base wall, which are bounded by preformed and/or pre-impressed folding lines, with the result that, here, the mechanical loading which occurs is reduced on account of the folding of the blank. The transverse impressed lines do not extend into the lateral regions of the blank, especially since, there, another, complex folding formation is provided by base folding tabs and folding gussets. 
     Further pre-impressed folding lines, namely longitudinal impressed lines, are provided for separating off a central, continuous region of the blank from lateral folding tabs. 
     According to the invention, all the folding tabs are provided on a material web for producing the blanks, the longitudinal impressed lines being continuous impressed lines. 
     Further measures are provided according to the invention in the region of the packaging machine. Thus, an endless cigarette conveyor, which removes the cigarette groups from a cigarette magazine and also transports said groups when the latter receive the blank for the inner wrapper, is driven in a non-uniform manner according to the invention such that, when the cigarettes are removed from the magazine and/or when the transversely directed blank is received, the conveying speed is lower and elsewhere the conveying speed is correspondingly higher. Accordingly, the movement characteristics of the cigarette conveyor are non-uniform with acceleration characteristics running in waveform. 
     A further special feature of the apparatus is that assigned to the latter, preferably directly in the region where the blank is fed to the respective cigarette group, is an impressing subassembly which, before the blank has been severed from a material web, provides impressed lines in the formation according to the invention. 
     Further details relate to conveying elements which facilitate the transfer of the blanks to the cigarette group and the U-shaped folding. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Details of the pack, of the process and apparatus are explained more specifically hereinbelow with reference to the drawings, in which: 
     FIG. 1 shows a spread-out blank for an inner wrapper of a cigarette pack, 
     FIG. 2 shows a cross section of part of the blank along section plane II—II, 
     FIG. 3 shows a schematic side view of part of the packaging machine for cigarettes, 
     FIG. 4 shows, on an enlarged scale, a detail of the apparatus according to FIG. 3, and 
     FIG. 5 shows, on a further-enlarged scale, a subassembly for feeding and transferring blanks to cigarette groups. 
    
    
     The drawings of the patent concern the configuration and production of cigarette packs which have an inner wrapper made of tin foil, paper or film. Such inner wrappers are used, in particular, for hinge-lid packs and soft-carton packs. FIG. 1 shows a blank  10  for such an inner wrapper, which is designed in accordance with the folded-bottom principle. A continuous base wall  11  is adjoined by a front wall  12 , on the one hand, and by a rear wall  13 , on the other hand. A (top) end wall , which is located opposite the base wall  11 , comprises folded, partially overlapping end folding tabs  14 ,  15 . Upright, narrow side walls likewise comprise folding tabs, namely side folding tabs  16  and  17 . In the region of the base wall  11 , these merge into base folding tabs  42 ,  43 , which adjoin the base wall  11 , and folding gussets  44 , which are arranged alongside the base folding tabs. The base folding tabs and folding gussets are separated from one another by folding lines  45 . 
     Provided in the region of the front wall  12  is a transversely directed perforation  18  which bounds an end-side region of the blank. This end-side region serves as a so-called flap, which, when the pack is opened for the first time, is drawn off by virtue of the end wall tab  14  being gripped. 
     Although it consists of thin packaging material, the blank  10  is provided with impressed lines, namely scores, which constitute a groove-like deformation of the material (FIG.  2 ). The invention provides two parallel, transversely directed impressed lines, namely transverse impressed lines  19 ,  20 . These bound the base wall  11  with respect to the front wall  12  and rear wall  13 . The transverse impressed lines  19 ,  20  form base-side folding edges with a right-angled cross section. 
     Also provided are longitudinal impressed lines  21  and  22  of the same configuration, these running in the longitudinal direction of the blank  10 . These separate off the strip-like side folding tabs  16 , on the one hand, and  17 , on the other hand, from the rest of the blank  10 . In the case of this example, the transverse impressed lines  19 ,  20  extend between the longitudinal impressed lines  21 ,  22 , but they may also, alternatively, extend over the entire width of the blank  10 . 
     The cigarette groups  23  which are to be wrapped are removed from a cigarette turret  24 , which is assigned to a cigarette magazine, and conveyed away. A cigarette conveyor  25  with carry-along elements  26  arranged at regular intervals grips the cigarette groups  23  on the rear side of the latter. The cigarette groups  23  are conveyed on the cigarette path  27 . 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the region of a blank station  28 , blanks  10  are fed one after the other and are held on standby in order to be received by in each case one cigarette group  23 . The blanks  10  are severed from a continuous material web  29  made of paper, tin foil or some other packaging material and are held on standby, as a curtain, in a position transverse to the movement direction of the cigarette groups  23 . 
     In the region of the blank station  28 , the blank  10  is positioned such that the cigarette group  23  grips the blank  10 , by way of end surfaces which are located at the front, and seen in the conveying direction—filter-free cigarette ends—in the region of the base wall  11 , namely precisely between the two transverse impressed lines  19 ,  20 . As the conveying movement of the cigarette group  23  continues, the blank is folded in a U-shaped manner. Arranged in the region of the blank station  28 , for this purpose, is a mouthpiece  30  with guides, namely mouthpiece plates  31 ,  32  above and beneath the movement path of the cigarette group  23 . 
     The blank station  28  is assigned a blank subassembly  33 . The latter is fed the material web  29 —coming from a reel  34 . The blank  10  is severed from the material web  29  by a severing subassembly, namely by a cutting roller  35  with severing cutter  46 , and fed to the respective cigarette group  23 . The cutting roller  35  is also equipped with a perforation cutter  36  for producing the perforation line  18 . 
     The blank subassembly  33  has an impressing element for providing the transverse impressed line  19 ,  20 . This element is an impressing roller  37 . Provided on the circumference of the same are impressing tools, namely two transversely directed rib-like impressing protrusions  38 . The impressing roller  37  is arranged upstream of the cutting roller  35 , as seen in the conveying direction. The transverse impressed lines  19 ,  20  are accordingly provided on the material web  29 . A mating pressure-exerting element, namely a (moveable) pressure-exerting roller  39 , butts against the circumference of the impressing roller  37 , or on the material web  29 , at least during the impressing operation. The pressure-exerting roller  39  can be moved cyclically, e.g. via a crank, and at least partially consists of elastic material, e.g. Vulkolan. The impressing roller  37  has arranged upstream of it a deflecting roller  40 , which produces a large wrap angle on the impressing roller  37 . 
     The longitudinal impressed lines  21 ,  22  are produced in the material web  29  by an independent impressing subassembly which, in the case of the present exemplary embodiment, is arranged upstream of the blank subassembly  33 , as seen in the transporting direction. A separately arranged impressing subassembly  49  has two impressing rollers  55 ,  56  which constantly butt against one another and of which one—e.g. the impressing roller  55 —has two encircling, annular impressing ribs (not shown) corresponding to the position of the longitudinal impressed lines  21 ,  22 . The other impressing roller  56  may serve as a pressure-exerting roller, preferably likewise with an elastic casing. The material web, which is impressed constantly by the impressing subassembly  49 , is fed to the abovedescribed blank subassembly  33  over deflecting and guide rollers. 
     A special feature is that the blank subassembly  33 , including impressing element, is driven independently, that is to say not by the central driving mechanism of the packaging machine, but in coordination therewith. The blank subassembly  33  is assigned a motor, namely a servomotor  41 . The latter drives a central drive wheel. 
     The drive of the blank subassembly  33  is controlled in dependence on the position of the fed cigarette groups  23 . This measure achieves the situation where the blank  10  is held on standby in a precise relative position—as far as the transverse impressed line  19 ,  20  is concerned—for being received by the cigarette group  23 . Arranged above the conveying path for the cigarette group  23  is a sensing element, namely an optoelectronic sensor  47 . The latter senses the front side of a cigarette group  23  by way of a light barrier and controls the servomotor  41  and thus the feeding of the blank  10  in precise coordination with the cigarette groups  23  which actually arrive. If it is thus the case that no cigarette groups are fed to the blank subassembly  33 , or detected by the sensor  47 , the feeding of the packaging material is also stopped. 
     However, the blank subassembly  33  is driven by the servomotor  41  in coordination or synchronously with the timing of the machine. For this purpose, a sensor, namely an initiator  58 , is assigned to the blank subassembly  33 . Said initiator interacts with a (metallic) marking  59  of the blank subassembly  33 . The marking  59  is provided on the cutting roller  35  and controls the drive of the blank subassembly  33  in coordination with the timing of the machine. 
     A special feature of the apparatus is that the cigarette groups  23  are conveyed in a non-uniform manner, namely at an increasing and correspondingly decreasing conveying speed. The drive is selected such that, as a cigarette group  23  is received in the region of the cigarette turret  24 , the cigarette conveyor  25  has a reduced speed. Equally, a reduced speed of the cigarette conveyor  25  is provided as a blank  10  is received by a cigarette group  23 . During the rest of the conveying phase, the cigarette conveyor  25  is driven at a correspondingly higher speed. The procedure is preferably such that one cigarette group  23  is gripped in the region of the cigarette magazine  24  at the same time as a blank  10  is gripped by another cigarette group  23 . In this case, the cigarette conveyor may be driven, for example, in accordance with DE 1 288 970, that is to say at a speed which alternates cyclically. 
     The movement characteristics of the blank subassembly  33  are adapted to the movement characteristics of the cigarette conveyor  25 , that is to say they are non-uniform and surge and subside. The characteristics of the conveying movement are selected such that, as a blank  10  is received by a cigarette group  23 , the conveying speed of the blank  10  is reduced, but is otherwise correspondingly increased. This conveying movement of the material web  29  and/or the blank  10  is brought about by the impressing roller  37 , which is designed and mounted as an eccentric roller, that is to say with an eccentric axis of rotation  48 . The arrangement is such that the impressing roller  37  is conveyed at reduced speed during the impressing operation, that is to say during the time over which the transverse impressed line  19 ,  20  is being provided, and at a correspondingly higher speed thereafter. 
     The blank  10 , which is severed from the material web  29 , is transferred from the cutting roller  35  to rotating suction discs  51 . The suction discs  51  are provided along the circumference with suction bores and grip the blank at lateral borders. The cigarette groups  23  can be conveyed through between the suction discs  51 , the blank being gripped by the cigarette group  23 , and drawn off from the suction discs  51 , in the region of the base wall  11 . 
     Arranged in the region of the mouthpiece  30  are further auxiliary elements which help the blank  10  to be carried along by the cigarette group  23  in a manner which is free of loading. These elements are suction rollers  53 ,  54  which have their axes positioned transversely to the conveying direction of the cigarette groups  23 , above and beneath the movement path of the same, said suction rollers specifically being in the form of inlet elements of the mouthpiece  30 . The cigarette group  23  is conveyed, with the blank  10 , between the top and bottom suction rollers  53 ,  54 . 
     The specific method of driving the cigarette conveyor  25  may also be used in some other context, that is to say independently of the operation for impressing the inner wrapper.