Abstract:
Cutter for cross cutting of reeled webs comprising a rotary cutting assembly including a blade and a counter blade rotated in synchronism with an advancement assembly of the web. The rotation axes of the blade and of the counter blade are displaceable relative to each other, perpendicularly to the web, and a gear actuator is provided to operate mutual approaching thereof when the blade and the counter blade are placed in a mutually facing angular position for cutting the web. The blade and the counter blade are rotated only at the time of cutting.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is related to cutters for cross cutting of reeled webs, and more particularly of paper, aluminium, coupled paper-aluminium and the like webs. 
     In the field of such web cutters three different systems are presently known. A first system consist of a vertically displacable guillotine knife whose down stroke across the web performs severing thereof. Evidently, descent of the guillotine knife requires stopping the web advancement, whereby this systems involves an excessively long operative time. It has also been proposed to make the cutting assembly movable and to displace it along the advancement direction of the web to avoid stopping thereof upon severing. However this solution is constructively complicated and thus expensive. 
     A second system employs a rotary knife, constituted by a plate mounted on the generating line of a blade-carrier cylinder, co-operating with a stationary counter blade. At each revolution, the blade projecting from the cylinder encounters the stationary counter blade, grazing it so as to cut the web interposed between the blade and the counter blade. This system is affected by precision problems and above all involves imperfections along the cut edges of the web caused by the fact that the counter blade is stationary and, as a consequence, cutting involves a more or less remarkable web tearing effect. 
     The third system, also of a rotary type, includes a blade and a counter blade which are both rotary. More particularly, the cutters of this type comprise a web advancement assembly, a rotary cutting assembly including a blade and a counter blade arranged at opposite sides of the web advancement path and rotatable around respective rotation axes placed transversely of said advancement path, and motor driven means to operate rotation of the blade and of the counter blade around said rotation axes in synchronism with the advancement of the web and to place said blade and counter blade in a mutually facing angular position for cutting the web. 
     This third system, while overcoming the drawbacks linked to the previous systems, does not however enable achieving results in terms of cutting precision and production speed which would instead be desirable. 
     Moreover in the case of the second and of the third system the blade and possibly the counter blade are as a rule continuously rotated during advancement of the web, which involves evident limits in connection with the maximum length of the web, deriving from the maximum diameter of the blade cylinder carrier (and possibly of the counter blade cylinder carrier) which can be applied to the cutter. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a cutter for cross cutting of reeled webs of the above disclosed third type, designed to achieve appreciably improved results both as far as cutting precision, repeatability and uniformity is concerned, and in connection with increased operative speed, and which moreover is not affected by any limits related to the web cutting length. 
     According to the invention, this object is achieved essentially by virtue of the fact that the rotation axes of the blade and of the counter blade are further displaceable relative to each other perpendicularly to the web, of the fact that actuator means are provided to operate mutual approaching between said rotation axes when said blade and said counter blade are located in correspondence of said angular cutting position, and of the fact that said blade and said counter blade are rotated only at the time of cutting. 
     Due to this idea of solution, web cutting carried out between the blade and the counter blade is in practice performed by a shearing action, with a precision which is same and even greater than that afforded by the guillotine systems disclosed in the above, but with an operative speed which is at least same and even greater than that of the rotary systems, without any limits to the cutting length. 
     This result can be achieved not only in connection with cuts perpendicular to the longitudinal edges of the web, but even as far as oblique cuts are concerned, providing a cutting assembly mounting capable to be angularly shifted relative to the web for instance between 0° and 45°. 
     According to a preferred embodiment of the invention, said actuator means comprise a rotary cam system operating against the action of return resilient means. Moreover in the preferred embodiment of the invention the rotation axis of the blade is movable while the rotation axis of the counter blade is stationary. 
     The cutter according to the invention can be advantageously employed for cutting reeled webs made of aluminium, paper, coupled paper-aluminium and the like, and can be installed in lines along with printing machines, spreading apparatus, spraying machines, coupling devices etc. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be disclosed in detail with reference to the accompanying drawings, in which: 
     FIG. 1 is a diagrammatic lateral elevational view of a cutter for cross cutting of reeled webs according to the invention, 
     FIG. 2 is a partially cross sectioned and enlarged view along line II—II of FIG. 1, 
     FIG. 3 shows in a larger scale a detail of FIG. 1, 
     FIG. 4 is a cross sectioned and enlarged view along line IV—IV of FIG. 2, 
     FIG. 5 shows in a larger scale a first detail of FIG. 4, 
     FIG. 6 is an enlarged partially sectioned view of a second detail of FIG. 4, shown in a first operating condition, 
     FIG. 7 is a view same as FIG. 6 in a second operating condition, 
     FIG. 8 is a perspective view of a part of FIG.  6  and 
     FIG. 9 is an exploded view of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to FIG. 1, reference numeral  1  generally designates a cutter according to the invention, designed to be employed in the case of the shown example for cross cutting of a web N made of aluminium. The cutter  1  comprises an unwinding station  2  including in the case of the shown example two reels  3  from which the web N, drawn through a joining unit  4  and a traction control device  5  of the web N, is unwound by a motor-driven drawing assembly  6 . 
     Downstream of the drawing assembly  6  the web N advances along a straight horizontal path, shown by the arrow F, towards a rotary cutting assembly generally designated as  7 , followed by an acceleration roller unit  8  and by a guide channel  9  of the cut sheets. 
     Referring now in more detail to FIGS. 2,  3  and  4 , the rotary cutting assembly  7  comprises a pair of vertical bearing walls  10  supporting for rotation a first shaft  11  rotatable around a horizontal axis A arranged above the advancement path F of the web N, a second shaft  12  rotatable around a horizontal axis B located beneath the advancement path F, and a counter shaft  13  rotatable around a horizontal axis C arranged above the axis A. 
     The shaft  11  carries a radially projecting and axially elongated support  14 , to which a blade or knife  16  is releasably secured, for instance by means of screws  15 . The conformation of the blade  16 , which has a tapered cross section, can be seen in more detail in FIGS. 4 and 5. 
     On the diametrically opposite side to the support  14 , the shaft  11  carries a counterweight  17 . 
     Reference numerals  18  designate two cylindrical gears fixed in proximity of the ends of the shaft  11 , designated as  19   a  and  19   b . These ends  19   a ,  19   b  are rotatably mounted through respective sliding blocks  20 , in turn slidably guided vertically within respective apertures  21  formed in the bearing walls  10 . The sliding blocks  20 , and thus the ends  91   a  and  91   b  of the shaft  11 , are normally placed in a raised position shown in the drawings (and particularly in FIG.  3 ), and are capable to move downwardly, such as clarified herebelow, against the action of respective return springs  22 . In the case of the shown example the springs  22  consist of helical compression springs: however these springs may be replaced by elastomeric material pads or the like. 
     The lower shaft  12  is actually constituted by two axial shaft portions whose ends, designated as  23   a ,  23   b , are rotatably supported by the vertical bearing walls  10 . The two portions of the shaft  12  coaxially support a cylindrical jacket  24  formed with an axial slot  25  in correspondence of which a channel support  26  is fitted, to which a counter blade  28  is secured for instance by means of screws  27  (FIGS.  4  and  5 ). On the diametrically opposite side to the support  26  with the counter blade  28 , the cylinder  24  carries an axial counterweight bar  29 . 
     The horizontal path F of the the web N is generally tangential to the jacket  24  carried by the shaft  12 . As it will be apparent in the following, this path F is never affected—namely never deflected or deviated—by the cutting operation of the web which is thus not tensioned upon cutting. 
     The counter shaft  13  is rotatably supported at its ends  30   a ,  30   b  by the vertical bearing walls  10  and carries, near to these ends  30   a ,  30   b , a pair of cylindrical gears  31  whose diameter is same as the diameter of the gears  18  of the shaft  11 , and meshing therewith. 
     Referring in more detail to FIG. 2, a driving unit generally designated as  32  is operatively associated to the rotary cutting assembly  7 , which includes an electrical motor  33  conveniently of the brushless type driving in rotation, through a first gear pair  34  and a second gear pair  35 , the end  23   a  of the shaft  12  of the counter blade  28 , and the end  91   a  of the shaft  11  of the blade  16 , respectively, via a cardanic shaft  36 . 
     The electrical motor  33  is operated by means of an electronic control unit (not shown), in a programmable way and in synchronism with the driving motor of the drawing assembly  6 , and rotates the shaft  11  and the shaft  12  not continuously, but instead in an intermittent timed way as a function of the desired cutting length of the web N, which accordingly is not subjected to any limitation. 
     The arrangement is such that the shaft  11  and the shaft  12  are driven in rotation by the motor  33 , whenever cutting is to be performed, with same peripheral speed, whereby following each complete revolution the blade  16  and the counter blade  28  are placed in a mutually facing angular position at opposite sides of the web N, such as depicted in FIGS. 2,  4  and in better detail in FIG.  5 . 
     According to the fundamental feature of the invention, in correspondence of the above angular positioning the blade  16  is linearly displaced with respect to the counter blade  28  so as to penetrate with its cutting edge, in immediate proximity of the corresponding edge of the counter blade  28 , into the cavity of the channel support  26 . This displacement, upon which transverse cutting of the web N is carried out, is operated through the counter shaft  13  and the downward motion of the sliding blocks  20 , against the action of the respective springs  22 . To such effect each pair of meshing gears  18 , 31  is operatively associated to a respective cam system, shown in detail in FIGS. 6 through 9. This cam system simply comprises a shim or bar member  37  fitted within the space between two adjacent teeth of the corresponding gear  18 , in an immediately proximal angular position to the counterweight  17  of the shaft  11 , i.e. at an almost diametrically opposite position with respect to the blade  16 . As shown in detail in FIGS. 8 and 9, the shim member  37  is secured to a pair of mounting plates  38  fitted within corresponding opposite recesses  39  of the gear  18  and fixed to the latter by means of axial screws  40 . 
     In operation, the gears  18  and  31  are regularly meshing with one another until the shim members  37  of the gears  18  reach the angular meshing position with the gears  31  (FIG.  6 ). Starting from this condition, corresponding to the position in which the blade  16  is facing towards the counter blade  28  (FIG.  5 ), meshing of the gears  18  with respect to the gears  31  takes place irregularly owing to the presence of the shim members  37 , thus performing downward displacement of the gears  18 , and thus of the whole shaft  11  against the action of the return springs  22 , and consequently partial penetration of the blade  16  into the cavity of the channel support  26  of the counter blade  28 . By virtue of this displacement the web N is cut by a shearing action between the blade  16  and the counter blade  28 , in a sharp and precise way. While rotation proceeds, the shim members  37  are disengaged from the gears  31 , whereby the gears  18  and thus the shaft  11  as a whole can be moved back to the previous raised position, due to the thrust action of the return springs  22 . 
     As already pointed out the horizontal path F of the web N, which is generally tangential to the jacket  24  carried by the shaft  12 , is not deflected or deviated appreciably during the cutting operation, whereby the web N is not tensioned or stretched upon cutting. This ensures achievement of best results in terms of cutting precision, repeatability and uniformity. 
     Naturally the details of construction and the embodiments may be widely varied with respect to what has been disclosed and illustrated, without thereby departing from the scope of the present invention such as defined in the appended claims. Thus for example, and as already pointed out in the above, the rotary cutting assembly  7  may be designed to perform a cut oriented obliquely instead of perpendicularly to the longitudinal edges of the web N, providing that mounting thereof enables its angular shifting with respect to the web N for instance between 0° and 45°.