Abstract:
A paper cleaning apparatus employs a paper buffing roll which has a lightweight hollow cylindrical core mounted between stub shafts. The stub shafts are mounted to bearings and the hollow core is arranged to be driven at approximately 3,450 to approximately 4,450 RPM. The surface of the cylindrical core is given a rough surface over which a wool cloth jacket is placed. The cloth sleeve is clamped in place by retaining end caps which fit over the stub shafts and clamp the sleeve against the ends of the hollow cylindrical core. The cloth sleeve is shrunk onto the surface of the cylindrical core with hot water or steam. The cloth sleeve is frayed to form a soft outer surface, with radially extending fibers.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
         [0001]    Not applicable.  
         STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT  
         [0002]    Not applicable.  
         BACKGROUND OF THE INVENTION  
         [0003]    The present application relates to apparatus for cleaning a moving paper web in general and particularly to cleaners which affect the boundary layer of air moving with the paper web.  
           [0004]    In a typical web offset press an image to be printed is transferred to a rubber blanket which is brought into contact with a moving web of paper onto which the image is printed. Minute amounts of loose fiber and dust from the paper web stick to the rubber blankets so that over time the blankets become dirty and must be cleaned to maintain image quality. It has been found that the frequency with which the rubber printing blankets must be cleaned can be substantially decreased if the paper web is precleaned before it is printed upon. In my earlier patent, U.S. Pat. No. 6,178,589, which is incorporated herein by reference, I disclosed an apparatus for cleaning the web which used an old but effective type of web cleaning roll. This existing web cleaning roll consisted of a central steel core on which multiple disks of cloth were compressed to form the roll surface. The surface of the roll, i.e. the cloth material was frayed to form a soft outer surface which is then worn in against a moving web. To effectively clean the web, an interaction between the cleaning rolls is uniformly established with the boundary layer of air which attaches to a moving web. This boundary layer which attaches to the paper web is only a small fraction of an inch thick. An ordinary web cleaner using only vacuum to remove fibers and dust from a paper begins to be ineffectual as paper speeds increase above 800 feet per minute (13 fps) because the boundary layer of air which moves with the paper web becomes more difficult to penetrate.  
           [0005]    The buffing rolls are operated at relatively high speeds and, because of space limitations and overall cost, are relatively narrow in diameter—typically between three-and-one-half inches and four-and-one-half-inches in diameter. The fabric rings of the prior buffing rolls were constructed with only relatively narrow diameter cores, for example about 1.5 inches in diameter for a buff diameter of 4 inches. The same buffing rolls typically have a length of between 20 and 60 inches. The construction of the prior art buffing rolls which employ a solid central steel core overlain with disks of cloth results in some difficulty in assuring proper balance so that the cleaning rolls do not vibrate. If the central core is made too large in diameter, it can be difficult for maintenance people to handle the cleaning rolls. Further, renewing the soft outer surface of the rolls requires returning the rolls to the factory with the added cost of shipping to and from the factory.  
           [0006]    What is needed is a paper cleaning roll which is lighter, stiffer, and which has a surface which can be renewed more readily.  
         SUMMARY OF THE INVENTION  
         [0007]    The paper cleaning apparatus of this invention employs a paper buffing roll which has a lightweight hollow cylindrical core mounted between stub shafts. The stub shafts are supported by bearings and the hollow core is arranged to be driven at approximately 3,450 to approximately 4,450 RPM. The surface of the cylindrical core is given a rough surface over which a wool cloth jacket is placed. The cloth jacket is clamped in place by retaining end caps which fit over the stub shafts and clamp the jacket against the ends of the hollow cylindrical core. The cloth jacket is shrunk onto the surface of the cylindrical core with hot water or steam. The cloth jacket is teased to raise fibers on the to form a soft outer surface.  
           [0008]    It is a feature of the present invention to provide a paper cleaning apparatus with a buffing roll which may be easily resurfaced.  
           [0009]    It is a further feature of the present invention to provide a paper cleaning apparatus with a buffing roll which is less subject to damage.  
           [0010]    It is another feature of the present invention to provide a paper cleaning apparatus with a buffing roll which is less subject to vibration.  
           [0011]    It is yet another feature of the present invention to provide a paper cleaning apparatus with a buffing roll which is intrinsically stiffer.  
           [0012]    Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a side elevational view of a paper cleaning apparatus incorporating the buffing rolls of this invention, placed by way of example in a printing press archway.  
         [0014]    [0014]FIG. 2 is an side elevational view, partially broken away in section, and partly cut away, of a buffing roll of the apparatus of FIG. 1. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    Referring more particularly to FIGS.  1 - 2 , wherein like numbers refer to similar parts, a pair of buffing machines  20  are shown in FIG. 1, positioned within an archway  22  formed by a frame  24  of a printing press  26 . A paper web  28  passes between opposed buffing rolls  30  which are mounted within vacuum hoods  32  which are connected to vacuum hoses  34 . The buffing rolls  30  are rotated while air is drawn through the hoods  32 . The rolls are rotated towards each other (one in the clockwise direction and one in the counter clockwise direction) in operation. As shown in FIG. 2, the buffing rolls  30  have a soft surface  36  composed of a profusion of radially extending wool fibers  37  which present a hairy surface. The fibers  37  and the air currents create interact with the boundary layer of air moving with the paper web  28 , causing lose paper fibers and dust containing various components such as clay, starch or fiber particles to becoming entrained in the boundary layer attached to the buffing roll surface  36 . The trapped particles are subsequently removed from the buffing roll  30  by a vacuum supplied by the hoses  34  to the vacuum hoods  32 .  
         [0016]    As shown in FIG. 2, the lightweight buffing roll  30  is constructed from a thin-walled cylinder  38  with a hollow interior  40 . In the case of a 3½-inch diameter thin-walled aluminum cylinder  38  has walls  42  which are approximately ⅜th inches thick, and is joined to two opposed stainless steel stub shafts  44 . The stub shafts  44  are sweated to aluminum plugs  46  which are then welded or bonded to the inside diameter  48  of the cylinder  38 . Sweating refers to the process where one part is expanded by heating relative to another part and assembled so that when both parts are at the same temperature an interference fit is produced. Each stub shaft  44  has a thicker diameter portion  60  as shown in FIG. 2.  
         [0017]    The aluminum plugs  46  are spaced inwardly of the cylinder ends  52 , and are counterbored such that radiused cylindrical edges  52  which project outwardly from the plugs have a diameter of {fraction (3/16)} inches. A wool jacket  54 , about one-quarter inch in thickness, is placed around the cylinder  38 , and the ends  56  of the wool jacket  54  are wrapped about the cylindrical edges  52  which are radiused to prevent cutting of the wool jacket  54 . The wrapped ends  56  of the jacket  54  are clamped to the cylinder  38  by metal caps  58 . Each cap  58  has a central bore  55  which slides along the thicker diameter portion  60  of the stub shafts  44 . Four equally spaced screws  62  extend between the end caps  58  and threaded holes  59  in the aluminum plugs  46 . Tightening the screws  62  draws the caps  58  axially inwardly toward the plugs  46 .  
         [0018]    The end caps  58  have radially protruding circumferential flanges  64  which define circumferential radiused features  66  opening towards the ends  52  of the cylinder  38 . The ends  56  of the wool jacket  54  are clamped between the flanges  64  and the cylindrical edges  52 , to be held in place within the radius conforming features  66 . The wool sleeve or jacket  54  is approximately one-quarter inch in radial thickness and initially fits easily over the surface  68  of the aluminum cylinder  38 . The wool jacket  54  is heated with steam or hot water and dried. This process causes the wool jacket  54  to shrink and grip the aluminum cylinder  38  tightly and to become affixed to the surface without bonding thereto. Following the shrinking process the ends  56  of the wool jacket  54  are bent over the cylindrical edges  52  and clamped in place by the end caps  58 . The surface  68  of the aluminum cylinder  38  may be shot peened to produce a rough surface to which the wool jacket  54  attachment is enhanced when the wool fibers in the jacket shrink. The jacket may be a tubular woven cloth material, for example woven essentially of wool. A suitable wool jacket may be obtained from Edward H. Best &amp; Co., Hanover, Mass., particularly All Wool Endless Jacket products.  
         [0019]    The wool jacket  54  has an outer surface  36  from which multiple radially extending fibers  37  project. The number of radially extending fibers  37  may be increased by teasing or brushing the surface  36  of the roll  30  with, for example, a wire brush. In use, the ends of the fibers  37  should be tangent to the web  28 . Correct positioning of the fibers  37  with respect to the web  28  is accomplished by positioning the rolls so that they contact the paper web  28  and allowing the paper web over a period of four to twenty-four hours to seat in or wear away the fibers which actually frictionally engage the surface of the paper web  28 , after which the buffing rolls  30  can be considered to be in noncontact with the paper web, because no further wearing against the paper occurs. The buffing roll surface  36  is noncontact with the moving paper web. Surface  36  moves in a direction opposite to the direction of the paper web  28 . In practice a gap between the roll surface  36  and the paper web  28  of as much as a {fraction (1/32)}th or even {fraction (1/16)}th of an inch, will not prevent the cleaning action. A contact roll on the other hand moves in the same direction with the same or similar speed as the web the contact roll is in contact with, or the contact roll produces significant frictional engagement with the web because of the contact combined with the relative motion between the contact roll and the web.  
         [0020]    To create the proper buff boundary layer of air it is important that the surface velocity of the roll surface  36  be approximately in the range of 60 to 80 fps, in a direction opposite that of the paper web  28  which is moving typically at a velocity in excess of 25 fps to typically about 40 fps. For a roll with a total diameter of approximately four inches, this implies a rotation speed of between 3,450 RPM and 4,600 RPM. For a buffing roll  30  with an overall diameter of four and one half inches, the rotational speed may be proportionately about 12½ percent less. Rotating a cylinder sixty or more inches long at upwards of 4000 RPM without significant vibration is difficult. The tendency of a rotating core to vibrate depends on the square root of the spring constant of the system divided by the mass of the system.  
         [0021]    By increasing the diameter of the core over the prior art and substantially decreasing the mass by constructing the core of lightweight materials and by making the core hollow, the buffing roll is rendered substantially stiffer and substantially of lower mass, thus increasing the spring constant, of the spring mass system which represents the spinning core, and decreasing the mass. Increasing the spring constant and decreasing the mass both contribute to decreased vibration.  
         [0022]    To replace the the wool jacket  54 , the screws  62  are loosened to allow the end caps  58  to slide away from the edges  52  of the roll cylinder  38  and unclamp the ends  56  of the wool jacket  54 . Once the old wool jacket  54  is no longer clamped at its ends, it is removed by slitting it axially with a utility knife. A new jacket is then slid over the surface  68  of the aluminum cylinder. The wool jacket  54  is heated with steam or hot water and dried. This process causes the wool jacket  54  to shrink and grip the aluminum cylinder. Following the shrinking process, the ends  56  of the wool jacket  54  are bent over the cylindrical edges  52  and clamped in place by the end caps  58  . The surface  36  of the roll  30  is then developed as necessary by wire brushing, and the buffing rolls  30  are installed and worn in.  
         [0023]    It should be understood that the roll could be constructed of any relatively strong lightweight material, particularly a composite hollow core could be used, in particular one constructed of graphite epoxy. Other roll surface coatings or jackets of other fibers could be used, either natural plant or animal fibers or synthetic fibers. Various methods of clamping or otherwise holding a fiber jacket to the surface of the roll could be employed.  
         [0024]    It should also be understood that the buffing rolls  30  should be balanced to a relatively high degree. The balancing of rotating or spinning objects is well understood by those skilled in the art. The rolls  30  shown in FIG. 2 may, for example, be balanced by removing material from the aluminum plugs  46  along the radial surface  70  through which the threaded holes  59  are drilled, although other techniques known to those skilled in the art could be used.  
         [0025]    It should be understood that the term “thin-walled” when used to describe a cylinder or pipe is used in its ordinary technical meaning of a wall thickness which is less than or around {fraction (1/10)} the diameter of the cylinder or pipe.  
         [0026]    It should be understood that two buffing rolls  30  may be placed opposite each other as shown in FIG. 1 to clean both sides of the paper web  28  or a single buffing roll may be positioned opposite a backing roll to clean one side of a paper web. A second single buffing roll opposite a second backing roll can then be used to clean a second side of the paper web.  
         [0027]    It should be understood that the vacuum hood  32  preferably will include a number of vacuum slots which are positioned adjacent axially extending bars which closely approach the surface  36  of the buffing rolls  30  and interact with the boundary layer of the buffing roll to knock fibers and dust from the buffing roll. These bars may be spaced at 60, 90 or 180 degrees from the point at which the roll  30  is tangent to the web  28 , and oriented tangent or perpendicular to the buffing roll  30 .  
         [0028]    It is understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces all such modified forms thereof as come within the scope of the following claims.