Abstract:
An air-knife is described in the form of a segmented air distribution bar equipped with control valves along the length of the bar to enable a user to incrementally adjust the air distribution across the width of an inking roller of a printing press.

Description:
This application claims benefit of U.S. Provisional 60/407,367 filed Aug. 31, 2002. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The subject invention relates generally to a segmented air distribution bar and, more particularly, to a segmented air distribution bar having air control valves along the length of the bar to enable a user to incrementally adjust the amount of air that is distributed across the width of a roller in a printing press. 
   2. Background of the Related Art 
   During offset printing it is not uncommon to develop a build-up of excess dampening solution in the ink on the rollers of the printing press. Its occurrence is inherent to the printing process. Such a build-up, however, does not occur evenly across the width of the rollers. When an excessive amount of dampening solution is picked up by ink, it becomes water logged and breaks down. This is commonly called over-emulsification. The results are extreme ghosting and loss of color density in the print, mottled print, ink piling on the inked rollers, and sheet curl resulting in misregistration and paper feed problems. To eliminate the problems, press operators will usually have to clean the entire ink train and dampener and then replenish the ink and dampening solution fountains. This work stoppage results in product delivery delays and measurable economic loss. 
   Attempts have been made to prevent excess dampening solution buildup and/or remove the excess dampening solution from over emulsified ink. One method is to install an air bar that directs a stream of air against the surface of one or more inked rollers to force evaporation of excess solution. Two inventions that exemplify this method are disclosed in U.S. Pat. No. 4,524,689 to Lemaster and U.S. Pat. No. 5,085,142 to Smith. Other attempts have been made to prevent excess dampening solution buildup and/or remove the excess dampening solution from over emulsified ink as exemplified in U.S. Pat. No. 5,454,310 to Hayes. 
   The present invention incorporates a so-called “air-knife” or “air amplifier” of the sort which drives a relatively small volume of air along a wall surface, such that the air adheres to that wall surface. This phenomenon is called the “coanda” effect. This small volume of air creates suction in the adjacent air which pulls in very high volumes of air along with the relatively small volume of air. Amplifications of air volumes on the order of 30 to 1 may be achieved with such air amplifiers. 
   The structure necessary to achieve the coanda effect includes essentially a thin, elongated slot or nozzle formed in a housing member adjacent to a wall face that curves around a bend. Typically, this bend can be up to 90 degrees. A relatively high-velocity, relatively low-volume air flow is driven along that curved wall face from the slot. By maintaining the slot to a desired relatively thin opening, and by controlling the contour of the wall face, it is possible to ensure that the relatively high-velocity, relatively low-volume air adheres to the wall face and is driven around the curve of the wall face. This, in turn, creates a suction adjacent to the slot which entrains a relatively high quantity of air. 
   The structure of the amplifier itself is known to those of ordinary skill in the art, and is commonly available on the market. One such amplifier is available under the trade name Exair Air Knife from Exair Corporation (Cincinnati, Ohio). Those of ordinary skill in the art will be aware of the dimensions and parameters of operation necessary to create the coanda effect and resulting air amplification results. 
   A device that makes use of the coanda effect is disclosed in U.S. Pat. No. 5,313,685, to Sundwiger Eisenhutte, the contents of which are incorporated by reference herein. The device is for removing liquid from the surface of a moving steel strip by means of air blown onto the moving strip from a device having a slot nozzle which is disposed transversely to the direction in which the strip is moving and is directed at the surface of the strip at an angle of between about 45 and 90 degrees opposite to the direction of the strip movement. The device further includes a means for suctioning off any liquid that is removed from the surface of the strip. 
   Another device that makes use of the coanda effect is disclosed in U.S. Pat. No. 5,490,300, to Paul Horn, the contents of which are incorporated by reference herein. The device is disposed adjacent to a web of material that is to be cleaned. A relatively small volume of compressed air is driven from a slot onto a curved wall surface. The coanda effect causes that compressed air to adhere to the wall, and causes a suction creating a relatively high-volume air flow upstream from the slot to be drawn along with the small volume of air adhering to the wall. The high-volume amplified flow of air is drawn along the surface of a web of material to be cleaned to entrain impurities from the web of material to be cleaned. A vacuum source is mounted adjacent to the end of the wall such that impurities are drawn into the vacuum source and removed from the area. In addition, ionized particles are directed into the relatively high-volume air flow to increase the cleaning efficiency of the system. 
   Another device that makes use of the coanda effect is disclosed in U.S. Pat. No. 5,491,602, to Paul Horn, et al., the contents of which are incorporated by reference herein. More particularly, disclosed is an air amplifier system incorporating an ionizing device including a converter driven by the compressed air being directed to an air distributor. The converter provides the power source for the ionizing apparatus. In this way, the air distributor and ionizing apparatus can be an easily contained unit. The system may comprise a turbine which is electrically connected to an ionizing apparatus, such as an ionizing bar. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that those of ordinary skill in the art to which the subject invention pertains will more readily understand how to make and use the segmented air distribution bar described herein, preferred embodiments of the invention will be described in detail with reference to the following drawings. 
       FIG. 1  is a perspective view of a portion of a printing head (3 inking rollers) of a printing press, a segmented air distribution bar (“air bar”), and a mechanism for attaching the air bar to a printing press; 
       FIG. 2 , taken from  FIG. 1 , is a side view illustrating the air bar (in cross section) assembled to the printing press with an air bar clamping arm (in cross section) and swung into the “on” position; 
       FIG. 3 , taken from FIG.  1  and rotated 180 degrees, is a rear view illustrating the air bar without the air bar clamping arms, tie rod, and inking rollers; 
       FIG. 4 , taken from  FIG. 3 , is a cross-sectional view of the air bar; and 
       FIG. 5  is a perspective view of an air guide plate. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention incorporates a so-called “air-knife” or “air amplifier” of the sort that takes advantage of the coanda effect, which drives a relatively small volume of air along a wall surface, such that the air adheres to that wall surface. This small volume of air creates suction in the adjacent air which pulls in very high volumes of air along with the relatively small volume of air. Amplifications of air volumes on the order of 30 to 1 may be achieved with such air amplifiers. Existing systems that incorporate air-knives, such as disclosed in U.S. Pat. No. 5,490,300 and U.S. Pat. No. 5,491,602, are lacking in that they do not provide a way to alter the flow of the air across the width of the air bar. This is a significant disadvantage in that there are a number of applications that require such control of the air flow in order to benefit from an air bar. One such application is control of excess fountain solution build-up in ink on the rollers of a printing press. It is well known by those having ordinary skill in the art that such buildup does not occur evenly across the rollers. 
   Each printing head of an off-set lithographic printing press consists of several basic components and assemblies: an ink train, a dampening system, a printing plate and plate cylinder, a blanket and blanket cylinder, and an impression cylinder. These components and assemblies cooperate to lay the proper ink image and ink film thickness on the sheet or web. 
     FIG. 1  is a perspective view of three (3) inking rollers  20  from a portion of a printing head. Those of ordinary skill in the art will appreciate that such rollers are attached to the sideframes of the printing head by roller carriers, which may be either fixed to the sideframe or moveable to allow the rollers to be separated when the printing head is not in use. 
   An air bar  22  is mounted adjacent to the inking rollers  20  with two (2) pivot studs  24 , two (2) clamping arms  26  and a tie rod  28 . The tie rod  28  is rigidly mounted to the sideframes of the printing head. Air is supplied to the air bar through air supply tube  30 . An operator controls the flow of air across the width of the rollers using incremental flow control adjusting knobs  32 . 
     FIG. 2 , taken from  FIG. 1 , is a side view illustrating the air bar  22  (in cross section) assembled to the printing head with an air bar clamping arm  26  (in cross section) and swung into the “on” position. The direction of movement that the air bar  22  is moved in order to locate it into the “on” position is identified by arrow “A”. Generally, the “on” position is where the air bar is positioned sufficiently close to an inking roller  20  so that the air flow  34  caused by the air bar  22  tends to evaporate fountain solution from the emulsified ink on the inking roller  20 . The air bar may be moved into an “off” position by moving the air bar  22  in the direction of the arrow identified by arrow “B”. 
   Each clamping arm  26  includes an upper clamp  36  and a lower clamp  38 . The upper clamp  36  and lower clamp  38  are attached to each other with shoulder bolts  40 . Between the head of each shoulder bolt  40  and the bottom of each counterbore in which they reside is a spring  42 . This configuration allows the clamping arms  26  to pivot about the tie rod  28  in the direction of arrows “A” and “B” and also allows the air bar  22  to pivot about pivot studs  24  in the direction of arrows “C” and “D”. This arrangement allows a press operator to precisely position the air bar  22  in a position that is most effective in removing fountain solution from emulsified ink on the inking rollers  20 . 
     FIG. 3 , taken from FIG.  1  and rotated 180 degrees, is a rear view illustrating the air bar  22  without the air bar clamping arms  26 , tie rod  28 , and inking rollers  20 .  FIG. 4 , taken from  FIG. 3 , is a cross-sectional view of the air bar. Considering both  FIGS. 3 and 4 , the air bar  22  is shown to include a body  44  to which is attached an air guide plate  46  with attachment fasteners  48 . The body  44  includes a main air passageway  50  extending its length. Air is supplied to the passageway  50  through air supply tube  30  via an air tube connector  31  The opposite end of the an passageway  50  is closed off with a threaded plug  33 . 
   Body  44  further includes an air supply cavity  52  for each flow control knob  32 . Each air supply cavity  52  is in fluid communication with the air passageway  50  via an air port  54 . The air guide plate includes precision air gap recesses  56 —one for each air supply cavity  52 .  FIG. 5  is a perspective view of an air guide plate showing the precision air gap recesses  56 . 
   In operation, if a press operator decides that he has fountain solution emulsified in an inking roller  20 , the operator adjusts the air bar  22  from the “off” position to the “on” position. The operator then turns the air supply on (and adjusts the pressure as necessary), which provides air through the air supply tube  30  to the air passageway  50  of the body  44 . Using the flow control knobs  32 , the operator may then adjust the flow of air to each segment across the width of the inking roller  20 , depending on where emulsification is occurring. 
   A preferred embodiment of the present invention has been disclosed; however, one having ordinary skill in the art would recognize that certain modifications would come within the scope of this invention.