Patent Publication Number: US-11383950-B2

Title: Longitudinal cutting device

Description:
BACKGROUND 
     The present invention pertains to a device for longitudinally cutting material webs and/or material sheets according to the preamble of claim  1 . 
     It is known to use rotary board cutters, particularly for longitudinally cutting cardboard sheets, wherein said rotary board cutters comprise cutting shafts that extend over the machine width. The individual circular knives of multiple rotary cutters are fastened on these cutting shafts by means of clamping joints. The cutting shafts are permanently connected to a controllable motor in a driving manner via gear mechanisms. The transport of the stock within the cutting mechanism takes place due to the circumferential speed of the circular knives. 
     The cutting position can be varied over the width of the stock by loosening the clamping joints, as well as displacing and subsequently fixing the circular knives of a rotary cutter. Each circular knife has to be positioned individually in this case. The adjustment of the upper and lower knives of the same rotary cutter is particularly important for producing a clean cut on the one hand and for preventing excessive wear of the circular knives on the other hand. This manual setup is correspondingly elaborate and susceptible to errors if the dimensional accuracy of the blanks to be produced is subject to stricter requirements. 
     In addition to the geometry of the individual cutting edges, the overlap of the circular knives of a pair decisively defines the cutting forces. This overlap is adjusted with the distance between the cutting shafts. The overlap of the rotary cutters arranged on the same cutting shaft pair can only be adjusted jointly. This simplifies an overall adjustment of the overlap in order to adjust the device to different properties of the stock. However, an individual correction affecting the individual rotary cutter is not possible. 
     The rotary cutters may be arranged so closely adjacent to one another that their clamping joints touch one another and strips with a width of a few centimeters can be cut out of the sheet. In order to prevent restricting the potential cutting positions and to keep the setup effort low when the cutting positions are varied, the structural spaces of the infeed and delivery transport systems are strictly separated from the cutting mechanism. Consequently, the transport of the stock within the cutting mechanism is realized by means of the driven rotary cutters only. This means that the smallest possible sheet length is essentially defined by the diameter of the rotary cutters used. 
     In contrast, the quality of the cut improves as the diameter of the circular knives increases due to the superior guidance properties. Furthermore, larger diameters of the circular knives allow a more rigid design of the cutting mechanism, which in turn has advantageous effects on the quality of the cut. Today&#39;s rotary board cutters therefore always represent a compromise between a sound quality of the cut and the smallest possible sheet length. 
     SUMMARY OF THE INVENTION 
     The present invention is therefore based on the objective of developing a device that is enhanced in comparison with the prior art and improves the quality of the cut at least for short sheets. 
     According to the invention, this objective is attained by means of a device with the characteristics of claim  1 . Advantageous enhancements of the invention are defined by the characteristics disclosed in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is described below with reference to the figures, to which we refer with respect to all particulars that are not discussed in greater detail in the description. In these figures: 
         FIG. 1  shows a detail of a longitudinal cutting device; and 
         FIG. 2  shows a view of a lower knife holder with integrated transport device. 
     
    
    
     DETAILED DESCRIPTION 
     The apparatuses of the longitudinal cutting device for cardboards illustrated in  FIG. 1  are arranged in a common machine frame  200 . This machine frame  200  is essentially formed by a pair of sidewalls  201  that are arranged opposite of one another and connected to one another by crossbeams  202 . Several of these crossbeams  202  comprise guide rails of linear guides  203  that serve as a support for the rotary cutters  220 . 1 ,  220 . 2 ,  220 . 3  of the cutting device. 
     An infeed  11 , the cutting mechanism with the rotary cutters  220 . 1 ,  220 . 2 ,  220 . 3  and a delivery  15  are arranged behind one another in this machine frame  200  referred to the process flow direction  6 . These apparatuses are jointly driven by a drive  210 . This drive  210  is likewise arranged on the machine frame  200  and respectively comprises a shaft  211  extending transverse to the transport direction  6  above and underneath the transport plane  5 . Both sides of these two shafts  211  are supported in the sidewalls  201  of the frame  200 . They respectively have a multi-spline profile and form sliding seats  212  with the rotary cutters  220 . 1 ,  220 . 2 ,  220 . 3 . 
     The infeed  11  and the delivery  15  respectively comprise a pair of cooperating transport rollers  16 ,  17 . Both sides of these transport rollers are respectively supported in the sidewalls  201 . The lower transport rollers  16  are arranged directly underneath and parallel to the transport plane  5  illustrated in  FIG. 2 . The upper transport rollers  17  are aligned parallel to the lower transport rollers  16  and arranged above the transport plane  5 . The distance between the rollers of each pair can be adjusted to the thickness of the stock. A not-shown adjusting device of conventional design is provided for this purpose. 
     The cutting mechanism comprises multiple rotary cutters  220 . 1 ,  220 . 2 ,  220 . 3  of the same type. Each of these rotary cutters  220 . 1 ,  220 . 2 ,  220 . 3  comprises an upper knife holder  221 . 1 ,  221 . 2  with a respective upper circular knife  223  and a lower knife holder  222 . 1 ,  222 . 2  with a respective lower circular knife  225 . The upper circular knives  223  of the rotary cutters  220 . 1 ,  220 . 2 ,  220 . 3  are respectively arranged coaxial to one another analogous to the lower circular knives  225 . 
     The knife holders  221 ,  222  can be displaced transverse to the transport direction  6  of the stock along the linear guides  203  in the form of rotary cutters  220  and fixed by means of clamping devices  205  such that the cutting position is adjustable. 
     An exemplary lower knife holder  222  is described below. 
     The lower knife holder  222  illustrated in  FIG. 2  has two linear guides  203  that extend parallel to one another. These linear guides  203  are arranged on the carrier  237  at a significant distance from one another and turned relative to one another by 90°. These linear guides  203  serve for receiving the knife holder  222  in the base frame  200  of the device. A respective clamping apparatus  205  is arranged on the carrier  237  adjacent to each of the two linear guides  203 . The position of the knife holder  222  along the linear guides  203  and therefore the cutting position are fixed by activating these clamping apparatuses  205 . 
     The circular knife  223  is coaxially fastened on a pulley  216  and supported on a knife receptacle  227  so as to be rotatable about the common axis  224  together with this pulley. This knife receptacle  227  is arranged in the carrier  237  so as to be rotatable eccentric to the circular knife  223  and can be fixed with respect to its rotational position in this carrier. 
     The circular knife  223  is driven by means of an endless revolving toothed belt  214 . This toothed belt is wrapped around the pulley  216  connected to the circular knife  223  on the one hand and around an additional pulley  215  on the other hand, wherein said additional pulley forms a sliding seat  212  with the drive shaft  211  fixed in the frame. For this purpose, the hub of this pulley  215  has a multi-spline profile  213 . A belt tensioner  217 , which is supported in the carrier  237  and spring-loaded relative to the toothed belt  214 , ensures a suitable tension of the toothed belt  214  regardless of the position of the eccentric knife receptacle  227 . 
     The lower knife holder  222  furthermore comprises a transport apparatus  240  that takes hold of the stock with a conveying effect in the region of the cutting mechanism. A first transport belt  241  is provided for this purpose, wherein said first transport belt moves in the transport direction  6  and is wrapped around a first deflection roller  243  and a second deflection roller  245 , as well as a transport pulley  242 . The deflection rollers  243 ,  245  and the transport pulley  242  are supported in a receptacle  249 . This receptacle  249  is rigidly connected to the carrier  237  of the knife holder  222 . 
     The deflection rollers  243 ,  245  are respectively arranged upstream and downstream of the circular knife  223  referred to the transport direction  6  in such a way that the first transport belt  241  bridges the cutting mechanism and provides a planar support surface for the stock in this region. Multiple backup rollers  244  are provided between the deflection rollers  243 ,  245  in order to prevent sagging of the first transport belt  241 . These backup rollers  244  are likewise supported in the receptacle  249  of the first transport belt  241 . 
     The first transport belt  241  is driven by means of the aforementioned transport pulley  242 . This transport pulley has a coaxial second toothing, around which the toothed belt  214  of the knife holder  222  is wrapped such that the transport pulley is driven together with the circular knife  222 . The respective effective diameters of the pulleys  215 ,  216 ,  242  and the circular knife  223  are adapted to one another in such a way that the transport speeds of the infeed  11 , the delivery  15 , the rotary cutter  220  and the associated transport apparatus  240  are identical. 
     A second transport belt  246  is arranged opposite of the first transport belt  241  referred to the circular knife  223 . This second transport belt is wrapped around the correspondingly extended second deflection roller  245  of the first transport belt  241  and driven thereby. The sections of the two transport belts  241 ,  246  with a conveying effect extend parallel to one another such that the stock is taken hold of with a conveying effect to both sides of the respective rotary cutter  220 . The deflection rollers  243 ,  245 ,  227  and backup rollers  244 ,  248  of both transport belts  241 ,  246  are supported in the common receptacle  249 . 
     The receptacle  249  is realized in the form of a housing  250  in the region located downstream of the circular knife  223  referred to the transport direction  6 . The housing  250  is open on its side that faces the transport plane and comprises a connection piece  252 . A suction mechanism  253  of conventional design is connected to this connection piece  252 . A brush  251  is provided in order to already remove dust accumulating during the cutting process from the stock in the region of the cutting mechanism. This brush is arranged in the housing in the region of its opening with its bristles pointing upward such that it sweeps along the stock. 
     Instead of a transport belt, the upper knife holders  221  comprise rollers that are freely rotatable about their axes and press the stock against the respective transport belts  241  of the lower knife holder  222 .