Abstract:
A blanket wash head for cleaning the blanket cylinder of a printing press comprises a plurality of bristles arranged on a brush that are sized to contact a flicker bar disposed within the blanket wash head. The bristles are arranged to travel along a path and to collect debris and/or moisture. The bristles comprises a leading bristle and a trailing bristle and, in response to rotation of the brush, an end of the trailing bristle swings along an arc caused by contact with a flicker bar. The bristles are spaced on the brush according to a low density cause the trailing bristle to swing though an arc a sufficient distance sufficient to dislodge the debris without interference with the leading bristle.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims priority from U.S. Provisional Application Ser. No. 60/410,600, filed Sep. 13, 2002. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to blanket cylinder cleaning systems used on printing presses and, more particularly, to an improved brush for use with a blanket cylinder cleaning system.  
         BACKGROUND OF THE INVENTION  
         [0003]    On a printing press, the blanket cylinders must be periodically cleaned in order to maintain a desired level of print quality. The blanket cylinders also must be cleaned when changing over to a different print run, especially when changing colors.  
           [0004]    Conventionally, such cleaning operations have been performed manually, with crews using cleaning cloths soaked in volatile solvents to clean the blanket cylinders. Such manual cleaning operations are very labor intensive and time consuming, both of which increase labor costs and lengthen the down time or changeover time of the printing press. Moreover, the printing press environment is often hot due at least in part to heat radiation from the cylinders. The increased physical strain on cleaning and maintenance crews again increases costs and lowers productivity. Finally, the manual cleaning operations also divert the cleaning crew from other cleaning and maintenance operations, such as cleaning the inking systems, cleaning the doctor blades for the dampening brush rollers and other routine tasks.  
           [0005]    Consequently, in an effort to reduce labor costs, shorten down time and/or changeover time, and to increase the overall productivity of the printing press, automatic blanket cylinder cleaning systems were developed. Such automated cleaning systems use a driven and oscillating brush system that reduces or eliminates the need for manual cleaning using solvent-soaked cleaning cloths. Such systems also reduce the consumption of solvents and the associated volatile organic carbon (VOC) emissions often associated with solvent use.  
           [0006]    Unfortunately, some brush designs typically used in such automated cleaning systems may be prone to being clogged with debris, such as lint from the paper web. Such conventional brushes also may be prone to trapping moisture. Trapped moisture and/or trapped debris can eventually make the cleaning brush act more like a solid roller, in which case neither the debris nor the excess moisture is removed from the roller being cleaned. In such situations, the cleaning system may become effectively useless and the brush must be replaced. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a schematic cross-sectional view of an automated blanket cylinder cleaning system employing a rotating brush;  
         [0008]    [0008]FIG. 2 is a fragmentary elevational view of a deteriorated brush of the type conventionally used on the cleaning system of FIG. 1;  
         [0009]    [0009]FIG. 3 is an enlarged fragmentary view in perspective showing a brush similar to that shown in FIGS. 1 and 2 in a deteriorated state and clogged with debris;  
         [0010]    [0010]FIG. 4 is an enlarged fragmentary view in perspective showing a brush similar to that shown in FIG. 3 saturated with moisture;  
         [0011]    [0011]FIG. 5 is an enlarged fragmentary view in perspective showing a brush for use with automated blanket cleaning systems and assembled according to the teachings of the present invention; and  
         [0012]    [0012]FIG. 6 is a schematic plan view of the blanket wash head illustrating the movement of the wash head toward and away from the blanket cylinder and also illustrating an oscillating mechanism;  
         [0013]    [0013]FIG. 7 is an enlarged schematic view of a brush having a spiral or helically flighted bristle arrangement;  
         [0014]    [0014]FIG. 8 is an enlarged schematic view of a brush having transversely oriented rows of bristles;  
         [0015]    [0015]FIG. 9 is an enlarged schematic view of a brush having longitudinally oriented rows of bristles;  
         [0016]    [0016]FIG. 10 is an enlarged fragmentary view of a brush having bristles arranged in clumps;  
         [0017]    [0017]FIG. 11 is an enlarged fragmentary view illustrating an arcuate path traveled by the end of a bristle relative to the base of the bristle in response to contact with the flicker bar. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    The following detailed description is not intended to limit the scope of the invention to the precise form or forms disclosed herein. Instead, the embodiment illustrated herein has been chosen and described in order to best explain the principles of the invention so that others skilled in the art may follow its teachings.  
         [0019]    Referring now to FIG. 1 of the drawings, a blanket cylinder cleaning system  10  is shown in FIG. 1 and is positioned closely adjacent to a blanket cylinder  12  to be cleaned. Those of skill in the art will realize that the blanket cylinder cleaning systems actually clean the blanket attached to the blanket cylinder, rather than cleaning the blanket cylinder itself. For purposes of the following discussion, it will be assumed that the blanket cylinder  12  is carrying a blanket to be cleaned. Further, although the cleaning system  10  is shown in conjunction with a blanket cylinder  12 , those of skill in the art will readily understand that the cleaning system  10  may also be used to clean other cylinders or rollers commonly found in a printing press.  
         [0020]    The cleaning system  10  includes a brush  14  rotatably mounted within a blanket wash head or housing  16  and is driven by a suitable drive motor (not shown). Preferably, the brush  14  may also be mounted within the housing  16  so as to be oscillated back and forth along an axis of rotation  18 . The housing  16  includes an opening  20  adjacent the blanket cylinder  12 , and also includes an opening  22  which may serve as a drain or outlet for excess moisture and/or debris from within the housing  16  such that excess moisture and/or debris does not build up within the housing  16 . Preferably, the entire housing  16  may be extended and retracted toward and away, respectively, relative to the blanket cylinder  12  using a carriage arrangement  17  (FIG. 6) in a known manner. Further, the oscillation of the brush along its rotational axis  18  may be carried out using a conventional cam mechanism  19  (FIG. 6) or other suitable mechanisms. In accordance with the disclosed example, the housing  16  may be shifted toward and away from the blanket cylinder  12  along a generally linear path, while only the brush  14 , rather than the entire housing  16 , is oscillated back and forth along the axis  18 .  
         [0021]    The cleaning system  12  also includes a pair of spray bars  26 ,  28  for spraying, for example, water or a cleaning solution. The spray bars  26 ,  28  may be of conventional design and of the type commonly used in blanket cylinder wash heads. The brush  14  includes a central shaft  30  and a plurality of radially extending bristles  32 . Each bristle includes a base  32   a  and an outer end  32   b.  It will be understood that the outer end  32   b  of each bristle  32  travels along a circumferential path designated by the reference arrow A. A flicker bar  33  is mounted closely adjacent to the outward extent of the bristles  32  (i.e., closely adjacent to the outer circumference of the brush  14 ), such that the outer end  32   b  of each bristle  32  makes contact with the flicker bar  33  when the brush is rotated.  
         [0022]    As shown in FIG. 6, the wash head or housing  16  is moveable along the carriage assembly of conventional construction between a retracted position spaced away from the cylinder  12  and an in-use position disposed adjacent to the cylinder  12  such that contact between the brush  14  and the cylinder  12  is possible. A conventional drive motor M may be used to rotate the brush  14 , while the brush  14  is oscillated back and forth along its axis  18  using the conventional cam mechanism  19  or other suitable system.  
         [0023]    Referring now to FIGS. 2-4, a brush  14   a  shown therein in fragmentary form is a conventional prior art blanket cylinder cleaning brush. The bristles B of the prior art brush  14   a  are formed of a Nylon material having a bristle diameter (BD 1 ) of about six thousandths of an inch (0.006″). In the example shown, the bristles B are disposed on the central shaft of the conventional brush  14   a  according to a first density DEN 1 . The Nylon bristles B of the conventional brush  14   a  are known to exhibit an absorbency rate of ABS 1  due at least in part to the conventional Nylon material. Further, the Nylon bristles B of the brush  14   a  will exhibit a stiffness characteristic S 1 , which, for purposes of discussion herein, will generally be acknowledged to be relatively flexible. The flexibility of the bristles B is due, at least in part, to the relatively thin construction of the bristles B and to their material. The brush  14   a  is of the type conventionally employed on blanket cylinder cleaning systems and in all respects is well known to those of skill in the relevant art.  
         [0024]    As shown in FIG. 2, the conventional brush  14   a  may, under certain circumstances, accumulate debris or clumps of debris indicated as D. As shown in FIGS. 3 and 4, the conventional brush  14   a  may also, under certain circumstances, accumulate moisture M, either alone or in conjunction with the debris D. Based on the above-described circumstances and conditions often encountered in use, in some applications the conventional brush  14   a  may be less stiff and more absorbent than may be desired. Thus the conventional brush  14   a,  in certain situations, may become experience a diminished capacity to effectively remove lint, debris, moisture, or other forms of unsuitable build-up from the blanket cylinder  12 . When this occurs, the brush  14   a  may become clogged and, thereafter, the brush  14  may act more like a solid roller, resulting in a less aggressive cleaning action with no “bite.” Such an undesirable result can be viewed in FIGS. 2 and 3.  
         [0025]    Further, because the conventional bristles B are tightly packed together due to the higher density DEN 1 , water or other moisture from the dampening system or other sources becomes trapped in the brush by capillary action. Such a moisture saturated brush  14   a  can be viewed in FIGS. 3 and 4. This stored or trapped water or moisture may be subject to being transferred to the web when the wash cycle is commenced, which may lead to web breaks and increased downtime and loss of productivity. Finally, the required “flicking” action which ideally helps to keep the brush clean does not occur or is less likely to occur due to the high bristle density of the brush and the overly flexible bristles B. This may cause build up of debris as can be seen in FIG. 2. In such circumstances, a more conventional brush may require more frequent attention in order to return the brush to a suitable condition. Finally, the Nylon bristles have a relatively high water and/or solvent absorbency rate as discussed above, which may cause the characteristics of the bristles to change shortly after the initial use of the brush.  
         [0026]    Referring now to FIG. 5, the brush  14  assembled in accordance with the teachings of a first disclosed example of the present invention is shown. The bristles  32  of the brush  14  are formed of a Polyester material, such as PBT polyester. Other forms of polyester, along with other materials, may be found to exhibit suitable properties of the type hereinafter described. The bristles  32  preferably have a bristle diameter BD 2  of about twelve thousandths of an inch (0.012″), although a thickness in the range of about 9 thousandths of an inch (0.009″) to about 16 thousandths of an inch (0.016″) may prove suitable.  
         [0027]    In the example shown, the bristles  32  are also disposed on the central shaft  30  (FIG. 1) according to a second density DEN 2 . The second density DEN 2  is in the range of about twenty five percent (25%) to about fifty percent (50%) less than the density DEN 1  found on the conventional brush  14   a  discussed above. Also, the polyester bristles  32  of the brush  14  will preferably exhibit an absorbency rate of ABS 2  due at least in part to the polyester material. The absorbency rate ABS 2  is preferably about 0.5%, which is less than the known absorbency rate of Nylon bristles B used in the prior art conventional brush  14   a.  Further, the Polyester bristles  32  of the brush  14  will exhibit a stiffness characteristic S 2 , which, for purposes of discussion herein, will generally be acknowledged to be relatively stiff when compared to the stiffness S 1  of the conventional brush  14  discussed above. Given the greater stiffness S 2  desired for the present bristles  32 , and using the length of the bristle along with the material properties such as the modulus of elasticity for the chosen PBT polyester material, the diameter may be adjusted to account for a change in bristle length. In the disclosed example, the brush  14  may have an outer diameter of about fifty-five millimeters (55 mm) as is commonly found on a conventional brush used in a blanket cylinder wash head system. The brush  14  may also have an exposed bristle length (the distance from the outer surface of the central shaft  30  to the end  32   b  of the bristle) of about twenty-five millimeters to about thirty millimeters (25 mm to 30 mm). Thus, using the central shaft diameter of about 25 mm to about 30 mm, the ratio of the bristle length to its diameter may be expressed as the ratio L/diameter. In its preferred form, and using an bristle length of between 25 mm (0.98 inches) and 30 mm (1.18 inches) for a bristle having a diameter of 0.012 inches, the resultant ration may range between about 81.7 and about 98.3. This ration may be compared to a conventional bristle, using the same length range and a diameter of 0.006 inches, resulting in a ratio range of between 163.3 and about 196.7. Using conventional engineering principles, it will be understood that an element having a lower ratio will be stiffer.  
         [0028]    The lower bristle density may be achieved in a number of additional ways. Referring now to FIGS. 7-10, the bristles  32  may be arranged in a spiral or helically flighted pattern P 1  (FIG. 7), a pattern P 2  consisting of a series of rows oriented transversely relative to the axis  18  of the brush  14  (FIG. 8), or a pattern P 3  consisting of a series of rows oriented parallel elative to the axis  18  of the brush  14  (FIG. 9). Further, as shown in FIG. 10, the bristles  32  may be grouped in clumps  40 . Other suitable arrangements may prove suitable.  
         [0029]    Referring now to FIG. 11, one of the bristles  32  is shown, along with a bristle  35   a  that is disposed in front of the bristle  32  relative to the path A, and a bristle  35   b  that is disposed behind the bristle  32  relative to the path A. Although only a single bristle  32  is shown, it will be appreciate that, and viewing FIG. 11 in conjunction with FIG. 5, the bristles  32 ,  35   a,  and  35   b  may comprise a clump or group of bristles spaced away from each other. When the brush  14  is rotated, it will be appreciated that the end  32   b  of the bristle  32  will be delayed in its progress along the path A due to contact with the flicker bar  33 , causing the end  32   b  to deflect along an arc AA relative to where the end  32   b  would be had no contact been made. Upon ceasing contact with the flicker bar  33 , and owing to the relative stiffness of the bristle  32 , the end  32   b  will swing forward along the arc AA, catching up and perhaps passing the position the end  32   b  would be had no contact been made with the flicker bar  33 . Should the end  32   b  swing forward enough to pass it&#39;s initial position, the end  32   b  will do so along the path of an arc AB. It will be appreciated that at no time does the end  32   b  actually travel backward along the path A, but instead its normal progress along the path A is delayed due to contact with the flicker bar  33 .  
         [0030]    When assembled according to the teachings of the disclosed example, the brush  14  may exhibit one or more advantageous characteristics. For example, the Polyester construction absorbs virtually no water or solvent due to the lower absorbency characteristic ABS 2 . In some applications this may allow the bristles  32  to remain in their original condition for a longer usage period. Further, the increased stiffness S 2  and lower bristle density D 2  relative to the stiffness and density of the conventional brush  14  act to increase the “flicking” action of the bristles  32  as the bristles  32  pass over the flicker bar  33 . Generally speaking, according to the disclosed example the bristles  32  may both snap back more aggressively after passing over the flicker bar  33 , and the tips or ends  32   b  of each bristles  32  may have more room to travel before contacting another bristle such as, for example, the leading bristle  35   a  or the trailing bristle  35   b  (FIG. 11). Thus, the brush  14  tends to remain cleaner and, as a result, requires less maintenance, because the brush  14  can more readily dislodge debris and/or moisture.  
         [0031]    These density and stiffness characteristics also serve to promote the removal of water from the bristles when the bristles pass over the flicker bar. The brush therefore remains dryer, again resulting in significantly reduced web breaks. These same density and stiffness characteristics further inhibit the build up of debris on the brush  14 , as debris is better able to escape from between the bristles because the bristles have more room to deflect and swing as they pass over and then are freed from the flicker bar. Again, this helps to maintain the brush in it&#39;s original condition for a longer period of time. Finally, these stiffer bristles provide a more aggressive “bite” and a better cleaning action.  
         [0032]    It will be appreciated that the brush  14 , except for the above-mentioned properties and characteristics involving bristle material, length, diameter, absorbency and spacing, may be constructed using conventional brush construction techniques. Such techniques are known and typically employed by a number of commercial suppliers generally known in the art. One such supplier is OXY-DRY® GmbH.  
         [0033]    Various details and aspects of the various arrangements disclosed may be freely interchanged and/or combined with other details and aspects disclosed herein. No example or embodiment need be considered as mutually exclusive with another example.  
         [0034]    The foregoing description is not intended to limit the scope of the invention to the precise form disclosed. It is contemplated that various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention.