Patent Publication Number: US-2011064509-A1

Title: Air delivery apparatus for delivering air to a moving substrate in a printing press

Description:
The present invention relates generally to printing presses and more specifically to an air delivery apparatus for delivering air to a moving substrate in a printing press. 
     BACKGROUND OF INVENTION 
     In printing presses, an air delivery system may deliver air to a web guiding device such as an angle bar or a former by using air generating equipment including a centrifugal or regenerative blower with an appropriately sized heat exchanger and companion plumbing components. The air may eliminate friction between the web guiding device and the web to improve transport of the web through a printing press and to prevent the web guiding device from marking the web. The air delivery system may be inefficient and in order to provide sufficient air flow from an interior of the web guiding device to the surface of the web guiding device, the air generating equipment may require a proportionally large amount of power. Additionally, the air generating equipment may include complex plumbing and may require substantial installation time and cost. 
     BRIEF SUMMARY OF THE INVENTION 
     An air delivery apparatus for providing air to guide a web in a printing press that includes a source of compressed air and a web guiding device coupled to the source of compressed air is provided. The web guiding device includes a body and a guide. The body defines an internal cavity and has an axis, an inner surface, an outer surface, holes extending from the inner surface to the outer surface and an axial end having an opening coupling the internal cavity to ambient air. The guide couples the source of compressed air to the internal cavity and directs the compressed air in an axial direction away from the axial end toward the internal cavity so that the ambient air is forced into the internal cavity. 
     A method of delivering air to guide a substrate moving adjacent to a web guiding device that includes a body defining an internal cavity and having an inner surface, an outer surface, an axis, holes extending from the inner surface to the outer surface and an axial end having an opening coupling the internal cavity to ambient air is also provided. The method includes delivering compressed air that flows in an axial direction to the internal cavity of the web guiding device so that the ambient air flows through the opening into the internal cavity and is passed through the holes to guide the substrate moving adjacent to the outer surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described below by reference to the following drawings, in which: 
         FIG. 1  schematically shows a cross-sectional view of a portion of a web guiding device according to an embodiment of the present invention guiding a moving web; 
         FIG. 2  schematically shows angle bars according to an embodiment of the present invention guiding a moving web; and 
         FIG. 3  schematically shows a former according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically shows a cross-sectional view of a portion of an air delivery apparatus  60  according to an embodiment of the present invention guiding a moving web  12 . Air delivery apparatus  60  includes a web guiding device  10  coupled to an air source  40 . Web guiding device  10  includes a body  13  having an axis  52 , an axial end portion  14  and a body portion  16 . In this embodiment, axial end portion  14  and body portion  16  are not integral and are coupled together; however, in an alternative embodiment, axial end portion  14  and body portion  16  may be integral. Body  13  defines an internal cavity  26  and also includes an outer surface  42  adjacent to web  12  and an inner surface  44 . In the embodiment shown in  FIG. 1 , web guiding device  10  is cylindrical and an axial end  30  of end portion  16  is annular, defining an opening  36  in axial end  30  that couples internal cavity  26  to the ambient air  46 . A compressed air source  40  coupled to end portion  14  via a supply tube  18  provides compressed air to web guiding device  10 . A guide  25  couples the compressed air from supply tube  18  to internal cavity  26  and directs the compressed air in an axial direction away from axial end  30 . In this embodiment, guide  25  is integral with body  13 ; however, in other embodiments, guide  25  may not be integral with body  13 . Guide  25  includes a channel  20  formed in end portion  14  that is coupled to supply tube  18  and a chamber  22  coupled to channel  20  that is formed between end portion  14  and body portion  16 . In this embodiment, chamber  22  is annularly shaped and surrounds internal cavity  26 . Guide  25  also includes a guiding gap  24  coupled to chamber  22  that is formed by an outwardly tapered peak  33  extending towards axial end  30  and an inwardly tapered peak  34  extending away from axial end  30 . Guiding gap  24  is configured to direct compressed air in the axial direction away from axial end  30  of end portion  14  toward internal cavity  26  and holes  32  formed about a circumference of body portion  16 . Holes  32  extend through outer surface  42  and inner surface  44  and allow air to exit internal cavity  26  radially to guide web  12 , which may be adjacent to portions of outer surface  42 . In this embodiment, outwardly tapered peak  33 , inwardly tapered peak  34  and guiding gap  24 , are also annularly shaped and also surround internal cavity  26  of web guiding device  10 . In a preferred embodiment, an axial end of web guiding device  10  that is opposite axial end  30  is closed off from ambient air  46 . 
     After air source  40  is turned on, an accumulation of air in chamber  22  forces a stream of air through guiding gap  24  into internal cavity  26  at a junction  28  between guiding gap  24  and internal cavity  26 . Outwardly tapered peak  33  and inwardly tapered peak  34  are configured closely enough to each other such that the air stream exits guiding gap  24  at junction  28  at a sufficiently high velocity that the air stream at junction  28  creates a boundary-layer flow in web guiding device  10  that induces flow of the ambient air  46  through opening  36  at axial end  30  into internal cavity  26 . After ambient air  46  enters opening  36 , this air and the air stream flowing from guiding gap  24  create an air stream in internal cavity  26  that flows out of web guiding device  10  through holes  32 . The air exiting holes  32  then acts on web  12  to assist in guiding web  12 . 
     In other embodiments, one or more additional supply tubes  18  may supply compressed air to end portion  14 , via air source  40  or additional air sources, such that air is introduced into chamber  22  at locations circumferentially spaced about axis  52 . Also, if air is supplied to web guiding device  10  at locations circumferentially spaced about axis  52 , at least one of chamber  22  and guiding gap  24  may not be a continuous annular ring and may be divided into sections circumferentially spaced about axis  52 . 
     Air delivery apparatus  60  does not require blowers, heat exchangers and plumbing components and may reduce energy and equipment costs. Compressed air may be delivered at a lower temperature and may not require any additional cooling or treatment. Additionally, installation time and cost may be reduced and because air delivery apparatus  60  does not include any moving parts, reliability may be improved. 
       FIG. 2  schematically shows angle bars  110 ,  111  according to an embodiment of the present invention guiding a moving web  112 . Angle bars  110 ,  111  are each configured as web guiding device  10  shown in  FIG. 1 . Air sources  140 ,  141  provide compressed air to respective guides  25  ( FIG. 1 ) in respective angle bars  110 ,  111  via respective supply tubes  118 ,  119 . In another embodiment, a single air source may supply air to both angle bars  110 ,  111 . Respective guides  25  ( FIG. 1 ) of angle bars  110 ,  111  provide compressed air axially into respective internal cavities  26  ( FIG. 1 ), which causes ambient air  146  to enter through respective openings  136 ,  137  formed at axial ends  130 ,  131  of angle bars  110 ,  111 , respectively. The air in internal cavities  26  ( FIG. 1 ) is then forced out of holes  132 ,  133  towards moving web  112 . Holes  132 ,  133  may be formed around the entire circumferences of angle bars  110 ,  111  or may only be formed in areas directly adjacent to where web  112  passes each angle bar  110 ,  111 . 
       FIG. 3  schematically shows a former  200  according to an embodiment of the present invention. Former  200  includes an RTF  250 , former bars  210 ,  220  and a former tip  260 . A former board can fit over bars  210 ,  220 . Former bars  210 ,  220  are each configured as web guiding device  10  shown in  FIG. 1 . An air source  240  provides compressed air to respective guides  25  ( FIG. 1 ) in respective former bars  210 ,  220  via respective supply tubes  218 ,  219 . In another embodiment, each former bar  210 ,  220  may be supplied with compressed air from a separate air source. Respective guides  25  ( FIG. 1 ) of former bars  210 ,  220  provide compressed air axially into respective internal cavities  26  ( FIG. 1 ), which causes ambient air  246  to enter through respective openings  236 ,  237  at axial ends  230 ,  231  of former bars  210 ,  220 , respectively. Air is then forced out of holes  232 ,  233  formed in respective former bars  210 ,  220  towards a web that is transported over RTF  250  past former bars  210 ,  220  and is longitudinally folded by former tip  260 . Holes  232 ,  233  may be formed around the entire circumferences of former bars  210 ,  220  or may only be formed in areas directly adjacent to where a web passes each former bar  210 ,  220 . 
     In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.