Abstract:
A die-cutting device is herein disclosed for performing slots perpendicular to the feeding direction of paperboard sheets used for making boxes, which is mounted on a supporting framework which can be driven in a cross direction with respect to the longitudinal feeding direction of the paperboard sheets.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an improved paperboard sheet die-cutting device. 
     A lot of paperboard sheet die-cutting devices have been already designed, for performing the cutting operations on paperboard sheets, for making paperboard boxes and the like. 
     However, prior paperboard sheet die-cutting devices are affected by several drawbacks, the main of which is that they are not operatively flexible and, moreover, are rather complex construction-wise. 
     SUMMARY OF THE INVENTION 
     Accordingly, the aim of the present invention is to overcome the above mentioned drawbacks of prior paperboard sheet die-cutting devices, by providing a novel improved die-cutting device specifically designed to be directly applied at the outlet of a paperboard sheet slotting machine. 
     Within the scope of the above mentioned aim, a main object of the present invention is to provide such a paperboard sheet die-cutting device which is very flexible in operation and very simple construction-wise. 
     Another object of the present invention is to provide such an improved paperboard sheet die-cutting device which allows to make paperboard boxes with a very high production yield and which, in particular, comprises a plurality of cross rollers, specifically designed for performing, at subsequent operating times, a first and third cross slots, one of said roller supporting cross blades or knives for performing, at different operating times, a second and fourth cross slots. 
     Yet another object of the present invention is to provide such a paperboard sheet die-cutting device which comprises moreover a trimming circular knife or blade, which can be driven toward and away with respect to the paperboard sheet, the driving movement of said trimming knife being controlled by a pneumatic piston, designed for vertically swinging a lever supporting the rotary shafts of the trimming knife or blade, for driving it at a lower position and locking it at a raised position. 
     Yet another object of the present invention is to provide such a die-cutting device comprising a plurality of crumbling cross blades allowing to crumble the excess paperboard material exceeding a rated paperboard amount as required for making a lot of different size boxes. 
     Yet another object of the present invention is to provide such a paperboard sheet die-cutting device in which the trimming knife is directly operated by the paperboard sheet advancing or feeding movement. 
     Yet another object of the present invention is to provide such a paperboard sheet die-cutting device allowing to easily and quickly replace the cutting blades thereof, by a pre-shaped die-cutting unit having wood shells bearing a plurality of contoured blades. 
     Yet another object of the present invention is to provide such a paperboard sheet die-cutting device including two die-cutting assemblies, cooperating with one another to provide a very quick and accurate cutting operation with a consequent very high die-cutting efficiency. 
     According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by a die-cutting device for performing slots perpendicular to the feeding direction of box-forming paperboard sheets having the features of the main claim. 
     Further advantageous features of the device according to the invention are defined in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above mentioned and other features of the die-cutting device according to the present invention will become more apparent hereinafter from the following detailed disclosure of a preferred, though not exclusive, embodiment thereof, with reference to the figures of the accompanying drawings, where: 
         FIG. 1  is a side perspective view illustrating the paperboard sheet die-cutting device according to the present invention, applied to a slotting machine; 
         FIG. 2  is a further detailed side perspective view illustrating the paperboard sheet die-cutting device according to the invention; 
         FIG. 3  illustrates a side view of the die-cutting device, and clearly show the supporting framework of said device, applied to a paperboard sheet slotting machine; 
         FIG. 4  shows the supporting framework of the die-cutting device of the invention, which framework is driven by a worm screw engaging with a female thread formed on a bush applied to the supporting framework. 
         FIG. 4  further schematically shows cross-blade pairs, including cutting blades for performing two cross slots, with respect to be paperboard sheet feeding or advancing direction, this figure further showing a side trimming knife, which is upward and downward operated through a lever by a pneumatic piston; 
         FIG. 5  is a top side perspective view of the above assembly, in which is shown the piston for raising the trimming knife and the two-shaft assembly including two shafts each supporting a pair of cross blades, for performing cross slots, with respect to the paperboard sheet feeding or advancing direction; 
         FIG. 6  shows a side front view of the die-cutting device according to the invention; 
         FIGS. 7 ,  8  and  9  show possible operating steps which can be carried out on flat paperboard sheets to be used for making packaging boxes; and 
         FIG. 10  illustrates a side view of a modified embodiment of the die-cutting device according to the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the number references of the figures of the accompanying drawings, the improved paperboard sheet die-cutting device according to the present invention, which has been generally indicated by the reference number  1 , is provided for mounting at the outlet of the paperboard sheets  60  being processed by a paperboard sheet slotting machine  6 . 
     More specifically, with reference to  FIGS. 1 to 5 , the die-cutting device according to the invention is mounted on a supporting framework  10  of the die-cutting device  1 , which can be transversely driven with respect to the longitudinal feeding or advancing direction of the paperboard sheet  60 . 
     This movement, in particular, is controlled by a gear-motor unit  2  also mounted on said supporting framework  10  and which rotatively drives a worm screw  3  engaging with a female thread of a bush  4  also applied to the supporting framework  10  of the die-cutting device  1 . 
     As shown in  FIGS. 3 and 4 , said supporting framework  10  is slidably supported on cross slides  5  applied to the frame of the slotting machine  6  to which the subject the die-cutting device is also coupled. 
     Alternatively, the die-cutting device  1  could comprise an independent bearing construction. 
     The device  1  comprises brushless motor  7 ,  8  and  9 . 
     A first of said motors drives a toothed pulley  11 , thereon is entrained a drive belt  12 , controlled by a belt tension element  19  and a pair of pulleys  20  and  21  rigid with shafts  35  and  36 . 
     The belt  12 , in turn, rotatively drives said shafts  35  and  36  thereon are idly supported the polyurethane ring elements  15  and  16  operating as abutment elements for the cutting operation provided by the cross blades  17  and  18  of the die-cutting device  1 . 
     Said ring elements  15  and  16  can be idly rotatively driven, so as to allow the cross blades  17  and  18  to operate at different cutting positions, thereby preventing the abutment rings  15  and  16  from being quickly worn. 
     The first brushless motor  7  rotatively drives the bottom ring elements or rollers  15  and  16 , the operating speed of which is synchronized with the outlet speed of the paperboard sheet to be processed. 
     Each of the other two brushless motor  8  and  9  drives the advancing or feeding movement of two shafts  33  and  34  supporting a pair of cross blades  17  and  18 , which are designed for performing two cross slots, with respect to the paperboard sheet feeding direction. 
     Alternatively, said two cross blades  17  and  18  can be replaced by a pre-shaped die-cutting unit, having wood shell means bearing the contoured blades. 
     In this connection, it is to be pointed out that the die-cutting devices or assemblies  1 , mounted on the slotting machine, are provided in a number of two. 
     More specifically, they are mounted or coupled to the side portions of the slotting machine frame. 
     In the exemplary embodiment shown in  FIG. 7 , one of the rollers including the cross knives or blades, performs, at subsequent operating times, the first and third slotting operation, a and c, whereas the other two knives, applied on the second roller, perform, at different times too, the second and fourth cross slots b and d. 
       FIG. 8  shows a further working example which can be carried out by using a pair of die-cutting devices, in cooperation with a slotting assembly longitudinally extending with respect to the paperboard sheet feeding direction. 
     This figure, in particular, shows four longitudinal cuts e, f, g, h performed by a longitudinal slotting assembly, and four cross cuts i, l, m, n performed by two die-cutting devices according to the invention. 
     Thus, it is possible to automatically trim or cut away the paperboard portions which has been shown in the drawings by the dashed lines and indicated by the reference numbers  70 ,  71 ,  72  and  73 . 
       FIG. 9  shows another possible working example which can be carried out by the die-cutting device according to the invention. 
     More specifically, this figure shows a paperboard sheet cut by two series of cross cuts o, p, q, r and o′, p′, q′, r′ and two series of longitudinal cuts s, t, u, v and s′, t′, u′, v′. 
     The cross cuts are provided by cutting blades of different lengths. 
     In particular, two shorter blades, applied on a supporting shaft, performs the cuts p, p′ and q, q′, whereas two other longer blades perform the cross cuts o, r and o′, r′. 
     The die-cutting device  1  according to the invention is moreover provided with a circular trimming knife  13  which can be driven toward and away with respect to the paperboard sheet. 
     This circular trimming knife  13  is driven by pneumatic piston  31 , designed for vertically swinging, through a shaft  40  and a pin  41 , a lever  32  supporting the rotary shaft  50  of the trimming knife  13 . 
     As is shown in  FIG. 6 , during its trimming simple operation, the knife  13  can be idly rotatively driven about the shaft  50 , the axis of which is cross-wise directed with respect to the paperboard sheet feeding direction. 
     It is further possible to use the cross blades  17  and  18  for crumbling the paperboard material portion exceeding the rated size. 
     The trimming blade  13  is rotatively driven by the paperboard sheet  60  feeding movement, which drives the counter-pressing top roller  51  rigid with said knife  13 . 
       FIGS. 7 ,  8  and  9  show several operating steps which can be carried out by the die-cutting device according to the invention, i.e. a lot of die-cutting operations performed in a cross direction with respect to the paperboard sheet feeding movement and further longitudinal trimming operations which can be performed by the subject machine. 
       FIG. 10  shows a modified embodiment of the die-cutting device, designed for performing cross cuts instead of cross slots. 
     In this case, the shafts  35  and  36 , which are similar to those shown in  FIG. 4 , instead of supporting the ring elements  15  and  16  and being driven by the motor  7 , support transversal blades  90  and are rotatively driven, in a mechanically synchronized manner, together with the shafts  33  driven by the motors  8  and  9 . 
     Also in this case, the paperboard sheet  60  is evenly driven by the roller  52  and related idle counter-pressing roller, coupled to the motor  7 . 
     While the die-cutting device according to the present invention has been hereinabove illustrated with reference to a preferred embodiment thereof, it should be apparent that it is susceptible to several modifications and variations, all of which will enter the scope of the invention.