Abstract:
A device for cleaning the outer surface of rotary cylinders and the like ( 2 ) comprising a pair of rotatable members ( 9, 11 ) for unwinding and rewinding a fabric ( 10 ), a presser means ( 12 ) cooperating with the fabric ( 10 ), means ( 50 ) for feeding onto the fabric ( 10 ) a liquid for cleaning the cylinder ( 2 ), and means ( 51 ) for feeding drying air onto the rotary cylinder ( 2 ), in which the pair of rotatable members ( 9, 11 ), the presser means ( 12 ) and the detergent liquid feeding means pertain to a cleaning assembly ( 6 ) movable by pneumatic drive away from and towards the rotary cylinder ( 2 ).

Description:
FIELD OF THE INVENTION 
     This invention relates to a device for cleaning the outer circumferential surface of rotary cylinders or rollers used in printing machines or in other types of machine such as paper and/or film production and processing machines, on which deposits of various materials, such as ink, form and have to be removed for proper machine operation. 
     BACKGROUND OF THE INVENTION 
     The state of the art comprises cleaning devices provided with two shafts for unwinding and rewinding a fabric which is made to adhere to the rotary cylinder or roller by means of a presser member, which can be in the form of an air chamber or a blade of flexible metal or resilient material. 
     Because of their characteristics and method of operation, these conventional devices have drawbacks in use, and do not ensure either adequate cleaning or optimum fabric and detergent consumption. Specifically, in the case of devices comprising an air chamber, this performs two functions, namely those of bringing the fabric into contact with the cylinder and of pressing it against the cylinder. The air is fed into the air chamber and then discharged several times during each cleaning cycle, to the detriment of the elasticity of the chamber, which undergoes variation both because of pressure reduction and leakages, with immediate negative effects on operation, and because of continuing decay in the characteristics of the rubber from which the chamber is constructed. Excessive chamber air pressure or wear involve the risk of chamber bursting with consequent danger to the operator. To this can be added the traction effect exerted by the rotary cylinder on the chamber via the fabric, causing chamber deformation which cannot always be compensated by the pressure exerted by it in the contact region. In the particular case of cylinders which do not have a continuous outer circumferential surface but instead comprise, as for example in the case of blanket cylinders, a gap in the direction of the generating line, this deformation is even more evident, resulting in vibration on passing said gap during rotation, this vibration adversely affecting the quality of the contact offered by the air chamber. 
     In the case of cleaning devices provided with a contact blade, the pressure exerted on the cylinder via the fabric is not always uniform along the entire cylinder length, and any irregularities in its surface or even minimum misalignment between the blade and the cylinder axis prevent its proper cleaning. In the case of the aforesaid discontinuous cylinders the said vibration problem also exists, in that the blade is unable to maintain the fabric in contact with the cylinder surface, not because of deformation but because of its limited flexibility and elasticity. 
     In an attempt to at least partly solve the said problems, it is usual to increase the cleaning time even though this results in greater fabric and detergent consumption. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The main object of the invention is to provide a cleaning device which is quick and simple in use and results in proper and efficient cylinder or roller cleaning and an appreciable saving in fabric and detergent. 
     This and other objects which will be more apparent from the ensuing detailed description are attained by a cleaning device in accordance with the accompanying claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more apparent from the detailed description of a preferred embodiment thereof given hereinafter by way of non-limiting example and illustrated on the accompanying drawings, on which: 
     FIG. 1 is a perspective schematic view of the cleaning device of the invention, together with a cylinder to be cleaned by the device; 
     FIG. 2 is a vertical cross-section through the cleaning device; 
     FIG. 3 is a side view of the device; 
     FIG. 4 is a schematic view, with some parts omitted for representational simplicity, showing the cleaning device of the invention and the means which enable it to be rapidly mounted on and removed from the parts which support it. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the figures, the reference numeral  1  indicates overall the device of the invention. The device is intended to clean the cylindrical surface of a cylinder  2 , for example of a printing machine, without the cylinder having to be removed from the machine which rotates it (not only during printing but also during its cleaning by the device of the invention). 
     The cleaning device is located in front of and parallel to the cylinder as shown in the figures. 
     The printing machine comprises a support structure shown schematically as two parallel side walls  3  in which the cylinder  2  is mounted. Two lateral shoulders  4 ,  5 , forming part of the device of the invention and intended for the support and movement of the actual cleaning part  6  of the device, are fixed to said side walls, for example removably, by any known means, for example by screw means. This cleaning part  6  is movable away from and towards the cylinder to be cleaned. The cleaning part  6  comprises at its respective ends two parallel shoulders  7 ,  8 . Between these shoulders  7 ,  8  there is rotatably and removably supported a shaft  9  on which a fabric  10  operating on the cylinder  2  for its cleaning is directly or indirectly wound. Constant lengths of the fabric  10  are unwound intermittently from the shaft  9  at a given frequency. During its unwinding the fabric is wound directly or indirectly onto an underlying removable shaft  11  driven by motor means described hereinafter. 
     During operation, the fabric  10  passes from one shaft  9  to the other  10 , coming into contact with the surface of the cylinder  2  to be cleaned in correspondence with a presser member  12  described in detail hereinafter. 
     As stated, the two shafts  9  and  11  are removably mounted between the two shoulders  7  and  8  by a known rapid-release support system comprising for example support elements having a cavity into which the end of the shafts  9  and  11  is inserted and retained therein by a pin or ball with a counteracting spring. 
     Such an arrangement enables the fabric to wind onto and unwind from the shafts  9  and  11 , not directly but by way of tubes  13 ,  14  for example of plastic or cardboard which are mounted on said shafts (before being mounted between the shoulders  7 ,  8 ), to which the tubes  13 ,  14  can be secured by the action of pneumatic or mechanical radial expansion plugs  15  emerging from the shafts. 
     Using this solution the fabric  10  can be quickly replaced and easily reused, as the shafts  9  and  11  can be quickly removed and the fabric support tubes  13 ,  14  be replaced on the two shafts without having to manually unwind the fabric from one shaft and then rewind it onto the other. 
     The lack of the fabric is indicated by conventional sensors, for example microswitches, not shown, which provide a warning and halt the cleaning operation. 
     The cleaning part  6  also comprises, fixed to the shoulders  7 ,  8 , a crosspiece  16  partially covered with a housing  17 , for example of stainless steel. The presser member  12  comprising a tubular chamber  18  of elastic material, preferably rubber, is fixed to the crosspiece  16 . This tubular chamber comprises a substantially flat base  18 A incorporating a metal plate  19  embedded along its periphery in the elastic material to form a perimetral flange  24  to which, at least at one of its points, there is fixed a projecting nozzle  20  incorporating a non-return valve, to engage in an exit port  21  of a duct  22  passing longitudinally along the crosspiece  16 . A metal frame  23 , fixed to the crosspiece  16  by studs distributed along its perimeter, locks the tubular chamber by securing it to the crosspiece via said flange  24 . 
     The tubular chamber  18  is intended to be filled via the duct  22  with water or another fluid or, for some applications, with a viscoelastic substance, for example a polymer, at a predetermined pressure, to form a presser member (for the fabric against the perimeter of the cylinder  2  to be cleaned) which presents an adequate region of contact against the cylinder to be cleaned, in terms both of dimensions and of elasticity. 
     In contrast to known pneumatic cleaning devices in which the approach and withdrawal of the fabric  10  to and from the cylinder  2  and the application of the fabric against the cylinder are achieved by merely inflating/deflating an air chamber, in the device of the invention the approach and withdrawal of the fabric and its contact pressure are determined by the pneumatic cylinder-piston units  25 ,  26 , whereas the surface optimization in the contact region and the relative degree of elasticity are determined by the hydraulic chamber  18  and are a function of the pressure of the liquid contained in it. 
     It is always possible to find a proper balance between the damping capacity of the chamber  18  and the necessary thrust of the pneumatic cylinder-piston units  25 ,  26 , without having to be excessive with this latter, to the advantage of a considerable reduction in vibration and noise at their source. 
     In this respect, experimental tests have demonstrated the evident advantages deriving from the water or other liquid chamber  18  to reduce and absorb the vibration generated by the rotation of the cylinder  2  and its contact with the device of the invention, and to effectively compensate the pressure differences encountered along the contact region caused by flexure or by minimal misalignment between the device and the axis of the cylinder  2 , and by imperfections in the surface to be cleaned (sometimes deriving from non-uniform deposition of the residues to be removed). 
     The fabric  10  can thus adhere perfectly to the cylinder  2 , to best perform its mechanical action, which contributes to chemical detergent action for cleaning purposes, and to air blowing action for drying purposes. 
     As stated, two pneumatic cylinder-piston units  25 ,  26  are provided for moving the cleaning part  6  away from and towards the cylinder  2 . These cylinder-piston units are visible in FIGS. 3 and 4, and rotate the cleaning part  6  in such a manner as to apply it to or withdraw it from the cylinder. Each pneumatic cylinder-piston unit  25 ,  26  is rigid with the fixed shoulders  4 ,  5 . A U-piece or fork  30 A is provided at the end of the relative rod  30 . In each U-piece  30 A there is provided a pin  31  projecting outwards from each of the shoulders  7 ,  8 . These have a further pin  32  acting as a pivot for the movable cleaning part  6  and arranged as described hereinafter in a seat provided in the fixed shoulders  4 ,  5 . By operating the pneumatic cylinder-piston units  25 ,  26  the cleaning part  6  is made to approach or withdraw from the cylinder  2 . 
     Advantageously, as described hereinafter, the connection between the cleaning part  6  and the fixed shoulders  4 ,  5  is such (see FIG. 4) as to enable it to be removed. 
     On the hydraulic chamber  18  there is superposed a diaphragm  37 , for example of nylon or rubber, which becomes interposed between said chamber and the fabric  10  to facilitate, by virtue of its low coefficient of friction, the sliding of the fabric by being resistant to abrasion and to the detergents used. As can be seen in FIG. 2, the diaphragm is fixed along its perimeter to the crosspiece  16 , between this and the housing  17 , by means of the same screws  40  which fix the housing to the crosspiece. 
     If cleaning blanket cylinders of printing machines, it has been found to be effective to use for example the same rubber as the blanket for the chamber covering diaphragm, by virtue of its gauged thickness, its perfect surface finish, its tear resistance and its total compatibility with the detergents used on it. The filling liquid is fed into the tubular chamber  18  on installation, via the non-return valve mounted in the nozzle or nozzles  20 , until attaining the required pressure, indicated by a pressure gauge (not shown). After a number of wash cycles and several months of operation it may be necessary to restore the correct liquid pressure, easily done by using any source having the required pressure. 
     In an advantageous variant of the device, the operating pressure of the liquid contained in the chamber  18  is automatically restored after a predetermined time and/or after a given number of wash cycles, this being achievable for example by means of a sensor, for example a pressure switch, operating via a circuit on a feed valve for the pressurized liquid. 
     In the top of the crosspiece  16  there is located a detergent distributor consisting of a tube  50  having a series of holes of suitable diameter and distance apart, extending in the longitudinal direction of the crosspiece  16  within an outwardly open channel  50 A. To ensure good distribution the detergent liquid is fed from both ends and/or at several points of the distributor tube  50  through valves from a pressurized feed source, not shown. The exit holes for the detergent liquid face the outer housing  17 , adjacent to them, so that the detergent is not sprayed directly onto the fabric but instead reaches it “by reflection” and in this manner well distributed and without soiling adjacent machine parts. 
     A tube  51  with holes along its entire length and arranged between the fixed shoulders  4  and  5  feeds drying air against the surface of the cylinder  2  at the end of the cycle, this tube being connected to a valve-controlled compressed air source. 
     To produce constant intermittent advancement of the fabric  10  there is provided (see FIG. 3) on one of the shoulders  7 ,  8  a further pneumatic cylinder-piston unit  40 A of fixed stroke. The rod  41  of this unit acts on a lever  42  via a transverse pin  43  thereof. The lever  42  rotates the support for the shaft  11  (which carries the soiled fabric), to which it is connected by a “freewheel” anti-return device. A second lever  44  is connected to a mechanical feeler  45  which under the action of a spring (not shown) adheres to the clean fabric present on the shaft  9 . This lever  44  varies its position (by rotating) on the basis of the position assumed by the feeler  45 . 
     When in operation, the cylinder-piston unit  40  rotates (clockwise) the lever  42  which, under the action of a spring (not shown), then returns to its initial rest position to halt against the lever  44 . 
     The position of the feeler  45 , the position of the lever  44  rigid with it, and consequently the rest position in which the lever  42  lies prior to its rotation vary according to the quantity (diameter) of fabric wound on the feed shaft  9 . 
     As the fabric advancement depends on the degrees of (clockwise) rotation which the lever  42  undergoes from its initial rest position by the action of the cylinder-piston unit  40 , it varies on the basis of the position assumed by the lever  42  when in its rest position. 
     Specifically, the closer the lever  42  lies to the rod  41 , the more its stroke is utilized and the greater the rotation of the lever, hence the greater the advancement of the fabric. 
     The shape of the levers  42  and  44  and their relative position are chosen to provide constant fabric advancement. 
     In a modified embodiment, the mechanical system for advancing the fabric can be replaced by one or two electric or pneumatic motors rotating one or both the fabric-carrying shafts. 
     The detergent reaches the tube  50  of the cleaning part  6  via an automatic plug-in connector comprising a male part  70  rigid with the outer face of the shoulder  7  (see FIG.  4 ), close to the pivot pin  32 , and plugging into a corresponding female part  71  elastically secured to the inner side of the fixed shoulder  4  in such a manner as to be able to follow the (limited) movements of the cleaning part  6  and hence of the connector part  70  relative to the fixed shoulders  4 ,  5 . 
     A second automatic plug-in connector similar to the preceding and similarly positioned, comprising the mutually insertable components  80 ,  81 , performs the function of automatically filling the hydraulic chamber  18  to the required pressure via the duct  22 . 
     As already stated and as shown in FIG. 4, the cleaning part  6  is removable. In this respect, as already indicated, the cleaning part  6  is provided, for each of the lateral shoulders  7 ,  8 , with a cylindrical rear pin  32  and a cylindrical front support pin  31 , whereas each of the fixed shoulders  4 ,  5  comprises, on its inner side, flat support and guide surfaces  83 ,  84 , support and fixing elements  82 , and the already stated U-pieces  30 A relative to the pneumatic cylinder-piston units  25 ,  26 . 
     To mount the removable cleaning part  6  of the device of the invention on the machine for which it is intended, it is brought into contact with the fixed shoulders  4 ,  5  rigid with the machine, by resting its rear support pins  32  on the flat support and guide surfaces  83  of both the fixed shoulders  4 ,  5 , then the entire part  6  is rotated about the pivots in the form of the rear pins  32  until the front support pins  31  enter into contact with the support and guide surfaces  83 ,  84 . The movable part  6  is then thrust in the direction of the cylinder  2  until the rear pins  32  enter the hollow support elements  82  and the front pins  31  enter the U-pieces  30 A. 
     For each side, the arm  90  of an outer slidable ring  91  mounted on the support element  82  is then slid axially towards the part  6  to close the hollow region of the support element  82  previously used for inserting the pin  32  into it. This ensures that the pin  32  is retained in the support element  82 , the aperture of which is closed by the ring  91  and by the entire movable part  6  against the shoulders  4  and  5  fixed to the machine. 
     Operating the pneumatic cylinder-piston units  25  and  26  causes the cleaning part  6  to move about its rotation pivots in the form of the rear support pins  32 , to cause it to move towards or away from the surface of the rotary cylinder  2 . 
     On mounting the cleaning part  6  in the aforedescribed manner, when thrusting said part in the direction of the cylinder  2  the two male and female components of the plug-in connectors  70 ,  71  and  80 ,  81  automatically engage each other without the operator having to act on them. 
     According to a particular aspect of the invention, one and the same device can be used to clean two or even three adjacent cylinders or rollers. For this purpose it is sufficient, for example, to make the device movable (together with the shoulders  4 ,  5 , no longer fixed) along rectilinear guides parallel to the cylinders, either manually or by motors, for example pneumatic. 
     Alternatively it can be made rotatable about a support axis parallel to the axis of the crosspiece. 
     When in operation the device performs four main functions, namely detergent feed and distribution, fabric advancement, approach to and withdrawal from the cylinder, and cylinder drying. 
     On cycle commencement the detergent is fed in the correct quantity to the distributor tube  50  which sprays it onto the fabric along its entire length. 
     The fabric wetted in this manner is made to adhere to the rotary cylinder  2  in the region in front of the chamber  18 , under the action of the pneumatic cylinder-piston units  25  and  26  which move the movable part  6 . 
     During the next stage these latter retract the movable part  6  from the cylinder so that the fabric is no longer in contact with it and can be advanced by unwinding it from the feed shaft  9  and winding it onto the take-up shaft  11 . Detergent is again sprayed to wet the fabric  10  prior to its advancement. 
     The cycle comprising detergent distribution, fabric advancement and approach/withdrawal is repeated a number of times in accordance with the program chosen on the basis of the quantity of impurities and residues to be removed from the cylinder. 
     After washing, an air blast from the tube  51  dries the cylinder  2 .