Abstract:
A printing unit with removable printing cylinder, comprising two outer shoulders which are adapted to constitute a supporting frame for a printing cylinder, a first pair of arms and a second pair of arms which are pivoted at an upper end of each one of the shoulders and form a seat for accommodating the printing cylinder, elements for locking the printing cylinder being provided in order to retain the printing cylinder so that it rests on the first and second pairs of arms.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a printing unit with a printing cylinder having simplified removal and locking. More particularly, the invention relates to a flexographic printing unit with a printing cylinder which can be easily removed from its seat and can be locked simply. 
     It is known that printing units, for example for flexographic printing, are provided with a plurality of printing cylinders: a first cylinder is an inking cylinder which dips into an ink tray in order to draw ink for printing; a second cylinder is a cylinder on which the print to be transferred to paper or another medium is provided; and a third cylinder is the actual printing cylinder, against which the cylinder that bears the type abuts in order to perform printing on the paper that winds around the printing cylinder. 
     Finally, a fourth cylinder arranged downstream of the printing cylinder allows to transport the printed paper from one printing unit to a subsequent printing unit or to the outlet at the end of the printing cycle. 
     The printing cylinder requires frequent operations for replacing it, in order to pass from one diameter to another, depending of the type of printing to be performed. 
     Replacing the printing cylinder usually takes time, since it is necessary to release the cylinder from its seat and then remove it. These operations are difficult owing to the configuration of the printing unit, and this difficulty, when it is necessary to replace several printing cylinders, entails long replacement times, for example in the case of a plurality of printing units arranged in series. 
     Moreover, the printing cylinder must be adjusted in its position with respect to the cylinder bearing the type, which accordingly abuts against the printing cylinder. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to provide a printing unit with a printing cylinder which can be easily removed and just as easily locked in its seat. 
     Within the scope of this aim, an object of the present invention is to provide a printing unit with a printing cylinder which can be released, and then removed, with a single simple operation without having to disassemble fixed parts of the printing unit. 
     Another object of the present invention is to provide a printing unit with a printing cylinder whose position can be adjusted with respect to the cylinder that bears the type and with respect to an impression cylinder. 
     Another object of the present invention is to provide a printing unit with a printing cylinder which can be adjusted vertically and horizontally with respect to the cylinder that bears the type. 
     Another object of the present invention is to provide a printing unit having a printing cylinder which can be removed easily, is highly reliable, relatively easy to manufacture and at competitive costs. 
     This aim, these objects and others which will become apparent hereinafter are achieved by a printing unit with removable printing cylinder, characterized in that it comprises two outer shoulders which are adapted to constitute a supporting frame for a printing cylinder, a first pair of arms and a second pair of arms which are pivoted at an upper end of each one of said shoulders and form a seat for accommodating said printing cylinder, means for locking said printing cylinder being provided in order to retain said printing cylinder so that it rests on said first and second pairs of arms. dr 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the invention will become apparent from the description of a preferred embodiment thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein: 
     FIG. 1 is a partial perspective view of the means for adjusting and locking the printing cylinder, with the printing cylinder removed; 
     FIG. 2 is a partial side view, with the printing cylinder shown in the removed position; 
     FIG. 3 is a partial side view of the printing cylinder accommodated in its seat and locked thereat; 
     FIG. 4 is a top plan view of the seat for accommodating the printing cylinder and the corresponding locking means; 
     FIG. 5 is a plan view, similar to FIG. 4 but with the printing cylinder arranged in the appropriately provided seat; and 
     FIG. 6 is a partially sectional front elevation view of the arrangement of the printing cylinder in the appropriately provided seat and of its corresponding locking. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the above figures, the printing unit according to the present invention, of which the portion related to the printing cylinder is shown and generally designated by the reference numeral  1 , comprises two lateral outer uprights  2 , only one of which is shown, which form a supporting frame for a printing cylinder  3  which is accommodated in an appropriate seat formed on the top of said outer lateral shoulders  2 . 
     FIG. 1 partially shows a cylinder of the printing unit, designated by the reference numeral  4 , which represents the cylinder that bears the type and is meant to abut against the printing cylinder  3 , which is omitted in FIG. 1 for the sake of simplicity in illustration, so as to transfer the type to the paper that passes over the printing cylinder  3 . 
     The printing cylinder  3  is conveniently provided with means for adjusting its position both in a vertical direction, i.e., at right angles to the footing of the printing unit, and in a horizontal direction, i.e., transversely along the length of the printing unit. 
     Adjustment of the position of the printing cylinder  3  is important in order to adjust its relative position with respect to the cylinder  4  bearing the type and to the cylinder  20 , for example when it is necessary to replace the printing cylinder  3  with a cylinder having a different diameter. 
     In this case, simple adjustment is essential in order to be able to place the printing cylinder  3  in the correct position with respect to the cylinder  4  and the cylinder  20 . 
     The cylinder  3  further has extremely simplified locking means which allow, once the printing cylinder  3  has been arranged in its seat, to lock it very rapidly and with a single operation without modifying the above-cited adjustments. 
     The locking means further allow equally simplified removal of the printing cylinder  3 . 
     In detail, as shown by FIGS. 5 and 6, the printing cylinder  3  has, at its ends, a shaft portion  5  which is arranged along its axis and supports a circular element  6  with raised edges  7  which form an engagement surface for means for locking the printing cylinder  3  in its seat. 
     As shown in detail in FIGS. 1,  2  and  3 , the seat of the printing cylinder  3  is formed by two shaped arms  8  and  9  which are respectively pivoted to the shoulder  2  at points  10  and  11 . There are of course two arms  8  and  9  for each side of the printing cylinder and likewise there are two pivots  10  and  11  for each pair of arms  8  and  9 . 
     The two arms  8  and  9  have a curved shape so that when the arms  8  and  9  are mutually coupled at a flat end region  13  thereof, regardless of the diameter of the printing cylinder the relative position of said printing cylinder with respect to the cylinder  4  and to the cylinder  20  does not change as the diameter of the printing cylinder varies. 
     The coupling between the two arms  8  and  9  is provided by means of an eccentric element  14 , and each arm  8  and  9  ends, at the tip that lies furthest from the coupling to the eccentric element, with the plate-like element  16 , which is accommodated in a slot  17  formed in the shoulder  2 . 
     Each plate-like element  16  constitutes an abutment element for an adjustment screw  19  which allows to adjust the position of the arm  8  and  9  within the slot  17  of the shoulder, so as to transversely vary the relative position of the printing cylinder  3  with respect to the cylinder  4  that bears the type and with respect to a cylinder  20  which lies downstream of the printing cylinder  3  and below it, as shown in FIGS. 2,  3 ,  4 ,  5  and  6 . 
     Conveniently, as shown in FIG. 4, the coupling between the two arms  8  and  9  is provided by way of the fact that the two arms  8  and  9  have an end, formed by the flat region  13 , which is complementarily step-shaped, so that the two arms, once coupled, are arranged so that their sides are parallel and have no discontinuities. 
     The adjustment screw  19  abuts against the plate-like element  16  of each arm and pushes against the respective arm, which rotates about the rotation point  10 ,  11  and about the eccentric element  14 , so as to vary the vertical position of the printing cylinder  3  with respect to the cylinder  4  and the cylinder  20 . 
     This vertical adjustment is necessary, for example, when replacing the printing cylinder  3  with a cylinder having a different diameter, and since it is necessary to maintain a constant distance between said printing cylinder  3  and the cylinders  4  and  20  that must abut against the printing cylinder  3  it is necessary to be able to adjust very easily the position of the printing cylinder  3  with respect to the cylinder  4  and the cylinder  20 . 
     The means for locking the printing cylinder  3 , which are conveniently designated by the reference numeral  25 , comprise for example pneumatic locking means which are provided with engagement means  26  suitable to engage the edges  7  of the disk-like element  6  which is rigidly coupled to the printing cylinder  3 . 
     Substantially, the engagement means  26  can be conveniently constituted, for example, by a tooth which is pivoted about a pivot  27  and by being actuated pneumatically, for example, abuts against the edge  7  of the disk-like element  6 , thus keeping the printing cylinder  3  firmly retained in its seat, i.e., rested on the flat portions  13  of the two arms  8  and  9 . 
     As shown in FIG. 3, the printing cylinder  3  is accommodated on the pair of arms  8  and  9  and is kept raised from the flat portion  13  of the coupled ends of the arms  8  and  9 . 
     FIG. 3 is a view of the printing cylinder  3  in the position for locking by means of the tooth  26 , which engages the raised edge  7  of the disk-like element  6 . 
     In practice it has been observed that the printing unit with removable printing cylinder according to the invention fully achieves the intended aim and objects, since it allows, because of the presence of means for adjusting and locking the printing cylinder, to access the printing cylinder in a simplified manner, in order to be able to remove it and then reposition it, with a very simple operation, without requiring modifications to the adjustment of the relative position thereof with respect to the remaining cylinders, regardless of the diameter of the printing cylinder. 
     The printing unit thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; all the details may also be replaced with other technically equivalent elements. 
     In practice, the materials employed, so long as they are compatible with the specific use, as well as the dimensions, may be any according to requirements and to the state of the art. 
     The disclosures in European Patent Application No. 99830639.3 from which this application claims priority are incorporated herein by reference.