Abstract:
An end seal for a fluid chamber which supplies fluid to a roll, includes a generally parallelepiped compressible member having first and second opposite sides and including a first end section having a first inclined planar upper surface, a second end section having a second inclined planar upper surface, and a central section which connects together the first and second end sections, the central section having an arcuate upper surface for receiving the roll, the arcuate upper surface connected to the first and second inclined planar upper surfaces at respective apices; and at least one pressure relieving recess positioned in the compressible member at a position below at least one apex, each pressure relieving recess extending through one side of the compressible member and terminating short of the opposite side of the compressible member so as to define a membrane of the compressible member thereat.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an end seal for an ink chamber of a printing machine, and more particularly, to an end seal having a longer operating life for use with a flexographic printing machine. 
     Conventionally, in printing machines, such as flexographic printing machines, an ink transfer or anilox roll transfers ink to an adjacent plate roll for printing. Ink is supplied to the anilox roll from an ink chamber defined by a chamber housing which partially surrounds the anilox roll. Specifically, ink is supplied through an ink supply tube and then through an ink supply line in the chamber housing, into the ink chamber. In like manner, ink is removed from the ink chamber through an ink return line in the chamber housing and then through an ink return tube. 
     In order to prevent the escape of ink from the chamber, while ensuring that the ink enters the cells in the anilox roll and has a predetermined volume on the anilox roll, doctor and sealing blades are provided at the entry and exit positions of the anilox roll relative to the ink chamber. The blades are fixed to the chamber housing so that the blades overhang the chamber housing and contact the anilox roll. 
     With this arrangement, the outer surface of the anilox roll passes through the ink chamber and picks up ink for printing. The ink is metered by means of the doctor blade held to the outlet end of the chamber housing, and sealed with a sealing blade held to the inlet end, with the free ends of the blades being in contact with the outer surface of the anilox roll. 
     A seal is provided at each end of the blade, that is, at each end of an anilox roll for sealing the ends thereof. Examples of such arrangements are shown in U.S. Pat. Nos. 7,597,761; 6,739,248; 6,672,207; and 5,150,651; and U.S. Patent Publication No. 2004/0261640, the entire disclosures of which are incorporated herein by reference. 
     Each seal is formed by a compressible body. Since the seals provided at each end of the anilox roll function to seal the ends of the ink chamber, each seal must lie against the peripheral surface of the rotating anilox roller. As a result, each seal is therefore exposed to mechanical stresses as well as wear. Further, during the printing operation, the blades, which press against the anilox roll, also wear. The geometry of the sealing function between the anilox roll, the two blades and the end seal changes. 
     Conventionally, each end of a blade sits upon a flat supporting area of the respective seal. As a result, there is not much flexibility at the opposite ends of the blades where they are held by the chamber seals. Because there is more force by the seals on each blade, that is, at the ends of the blades where they are held, the ends of the blades are less capable of flexing or bending at these points. As a result, there is uneven wear on the ends of the blades adjacent the seals, which tends to cause more wear and more leakage of ink at the ends of the anilox roll. Further, ink tends to ride under the blade, that is, between the blade and the flat supporting area of the seal, causing the blade to lift up away from the seal, thereby resulting in still more leakage. Thus, the place where the seal, anilox roll and blades join, is particularly susceptible to leakage. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an end seal which relieves the pressure at a position where the seal and doctor blade meet. 
     It is another object of the present invention to provide an end seal which has less rigidity at a position where the seal, anilox roll and doctor blade meet. 
     It is still another object of the present invention to provide an end seal having a longer operating life. 
     In accordance with an aspect of the present invention, an end seal for a fluid chamber which supplies fluid to a roll, comprises a generally compressible member having first and second opposite sides and including a first end section having a first inclined planar upper surface, a second end section having a second inclined planar upper surface, and a central section which connects together the first and second end sections, the central section having an arcuate upper surface for receiving the roll, the arcuate upper surface connected to the first and second inclined planar upper surfaces at respective apices; and at least one pressure relieving recess positioned in the compressible member at a position below at least one connection of said arcuate upper surface and first and second inclined planar upper surfaces, each pressure relieving recess extending through at least one side of the compressible member and terminating so as to define a membrane of the compressible member thereat. 
     Each pressure relieving recess can take various forms, such as an inverted V-shaped configuration, an inclined planar cross-sectional configuration, a small circular cross-sectional configuration, and a horizontal planar cross-sectional configuration, although the present invention is not limited thereby. 
     Each pressure relieving recess preferably extends below the central section and one end section. 
     A wear pad seats on the upper surface of the central section and at least partially on the upper surfaces of the first and second end sections. Preferably, the wear pad is made from felt. However, other materials such as ultra-high molecular weight polyethylene (UHMWPE) or polyester, may be used as a wear pad. 
     The compressible member is preferably made from a material selected from the group consisting of foam, rubber, plastic and composite materials. 
     Each pressure relieving recess terminates so as to define the membrane of the compressible member thereat. The membrane functions and is defined to prevent ink from flowing from the inside of the chamber to the outside through the recess. 
     The above and other objects, features and advantages of the invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a conventional doctor and sealing blade seal in association with an anilox roll; 
         FIG. 2  is a perspective view of an end seal according to a first embodiment of the present invention; 
         FIG. 3  is a side elevational view the end seal of  FIG. 2 ; 
         FIG. 4  is a cross-section view of the end doctor seal of  FIG. 2 , taken along line  4 - 4  thereof; 
         FIG. 5  is a side elevational view of an end seal according to a second embodiment of the present invention; 
         FIG. 6  is a side elevational view of an end seal according to a third embodiment of the present invention; 
         FIG. 7  is a side elevational view of an end seal according to a fourth embodiment of the present invention; and 
         FIG. 8  is a side elevational view of an end seal according to a fifth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings in detail, and initially to  FIG. 1  thereof, there is shown a conventional doctor and sealing blade sealing assembly  10 . Conventionally, in printing machines, such as flexographic printing machines, an ink transfer or anilox roll  12  transfers ink to an adjacent plate roll (not shown) for printing. Ink is supplied to anilox roll  12  from an ink chamber  14  defined by a chamber housing  16  which is adjacent to and may partially surround anilox roll  12 . Anilox roll  12  rotates in the direction of arrow  12   a.    
     In order to prevent the escape of ink from ink chamber  14 , while ensuring that the ink enters the cells in anilox roll  12  and has a predetermined volume on anilox roll  12 , sealing and doctor blades  18  and  20  are provided at the entry and exit positions of anilox roll  12  relative to ink chamber  14 . Blades  18  and  20  are fixed to chamber housing  16  by a blade holder (not shown) so that blades  18  and  20  overhang chamber housing  16  and contact anilox roll  12 . Blades  18  and  20  are placed at an angle against the periphery of anilox roll  12  and help to define ink chamber  14  which extends along the length of anilox roll  12 . 
     Seals  22  are provided at each end of anilox roll  12  to seal the ends of ink chamber  14 . Each seal  22  has an upper concave surface  22   a  which lies against the peripheral surface of the rotating anilox roll  12 . The edges of upper concave surface  22   a  continue in downwardly sloping flat supporting surfaces  22   b  and  22   c  which support blades  18  and  20 , respectively. 
     With this arrangement, the outer surface of anilox roll  12  passes through ink chamber  14  and picks up ink for printing. The ink is metered by means of doctor blade  20  held to the outlet end of chamber housing  16 , and sealed with sealing blade  18  held to the inlet end, with the free ends of blades  18  and  20  being in contact with the outer surface of anilox roll  12 . 
     Each seal  22  is formed by a compressible body. Since the seals  22  provided at each end of the anilox roll  12  function to seal the ends of the ink chamber  14 , each seal  22  must lie against the peripheral surface of the rotating anilox roll  12 . As a result, each seal  22  is therefore exposed to mechanical stresses as well as wear. Further, during the printing operation, the blades  18  and  20 , which press against the anilox roll  12 , also wear. The geometry of the sealing function between the anilox roll  12 , the two blades  18  and  20  and the end seals  22  change. 
     Conventionally, each end of a blade  18 ,  20  sits upon a flat supporting area  22   a ,  22   b  of the respective seal  22 . As a result, there is not much flexibility at the opposite ends of the blades  18 ,  20  where they are held by the chamber seals  22 . Because there is more force by the seals  22  on each blade  18 ,  20 , that is, at the ends of the blades  18 ,  20  where they are held, the ends of the blades  18 ,  20  are less capable of flexing or bending at these points. As a result, there is uneven wear on the ends of the blades  18 ,  20  adjacent the seals  22 , which tends to cause more wear and more leakage of ink at the ends of the anilox roll. Further, ink tends to ride under the blade  18 ,  20 , that is, between the blade  18 ,  20  and the flat supporting area  22   a ,  22   b  of the seal  22 , causing the blade  18  to lift up away from the seal  22 , thereby resulting in still more leakage. Thus, the place where the seal  22 , anilox roll  12  and blades  18 ,  20  join, is particularly susceptible to leakage. 
     In accordance with a first aspect of the present invention, as shown in  FIGS. 2-4 , a blade/ink chamber seal  122  for use in a sealing assembly according to a first embodiment of the present invention for use with an anilox roll  12  and sealing blade  18  and doctor blade  20 , includes a unitary, single-piece compressible member  124  of a generally parallelepiped configuration and made from a compressible material such as foam, rubber, felt, plastic or composite material. Compressible member  124  includes a first end section  126  and a second end section  128  connected together by a central section  130 . The upper surface  130   a  of central section  130  has an arcuate configuration which conforms to the arcuate outer surface of anilox roll  12 , while the upper surfaces  126   a  and  128   a  of first and second end sections  126  and  128  meet upper surface  130   a  of central section  130  at raised apices  129  and  131 , respectively, and include flat surfaces that slope downwardly from upper surface  130   a  of central section  130 . Generally, upper surface  128   a  on which doctor blade  20  seats has a greater inclination than upper surface  126   a  on which sealing blade  18  seats. Although not limited thereby, an example of dimensions of compressible member  124  are a length of 96.5 mm, a depth of 12.5 mm and a height ranging from 21.8 mm at the extreme end of upper surface  128   a  and 33.4 mm at the opposite end of upper surface  128   a . Compressible member  124  further includes at least one through opening  132  therein for mounting compressible member  124  onto mechanical elements (not shown) of a holder (not shown) of the ink chamber, as is well known in the art. 
     Seal  122  preferably also includes a wear pad  134  fixed along upper surfaces  126   a ,  128   a  and  130   a , as is also well known in the art, for example, as included in the seal sold by All Printing Resources, Inc. of Glendale Heights, Ill. under the designation APR TEAMFLEXO. Wear pad  134  is relatively thin, for example, on the order of about 6.35 mm (0.25 inch), although the present invention is not limited thereto. Wear pad  134  can be made of any suitable material that resists the wear of anilox roll  12  as anilox roll  12  rotates, for example, felt or the like. However, the present invention is not limited to the use of wear pad  134 , and in fact, wear pad  134  can be eliminated. 
     Thus, while wear pad  134  resists wear as anilox roll  12  rotates, the compressible material of compressible member  124  compensates for tolerances in the system for frictional wear of the blades  18 ,  20  as they run again anilox roll  12 . 
     However, the above construction is relatively stiff, in order to hold everything in place as anilox roll  12  exerts force on seal  122 . This, however, is disadvantageous because it creates a higher force on blades  18 ,  20 , and in particular, on the end of doctor blade  20  where seal  122 , anilox roll  12  and doctor blade  20  meet. 
     As a result, because there is more force by seal  122  on each blade  18 ,  20 , that is, at the ends of blades  18 ,  20  where they are held, the ends of blades  18 ,  20  are less capable of flexing or bending at these points. As a result, there is uneven wear on the ends of blades  18 ,  20  adjacent seal  122 , which tends to cause more wear and more leakage of ink at the ends of anilox roll  12 . Further, ink tends to ride under blades  18 ,  20 , that is, between blades  18 ,  20  and the flat supporting areas  126   a ,  128   a  of seal  122 , causing blades  18 ,  20  to lift up away from seal  122 , thereby resulting in still more leakage. Thus, the place where seal  122 , anilox roll  12  and blades  18 ,  20  join, is particularly susceptible to leakage. 
     In order to overcome this problem, the present invention provides a feature which relieves the pressure or force only a positions of blades  18 ,  20  where they meet anilox roll  12 . Specifically, the present invention, as shown in  FIGS. 1-3  provides a narrow hollow space or pressure relieving recess  136  in compressible member  124  immediately below positions where blades  18 ,  20  meet anilox roll  12 . In the embodiment of  FIGS. 1-3 , each hollow space  136  is provided in the form of a thin recess  138  of a semi-circular cross-section, that extends transversely through a first side  124   a  of compressible member  124  but does not extend entirely through the opposite second side  124   b  of compressible member  124 , thereby forming a thin membrane  124   c  at the opposite second side  124   b  of compressible member  124 , in order to prevent leakage of fluid therethrough. In other words, recess  138  is closed at second side  124   b . Semi-circular recess  138  preferably has a curvature such that it curves upwardly from ends thereof. 
     Hollow space  136  thereby functions as a pressure relief that reduces the pressure on blades  18 ,  20 , when needed, and thereby reduces the uneven wear on blades  18 ,  20 . 
     Although the present invention has been discussed in relation to hollow spaces  136  being in the form of semi-circular recesses  138 , the present invention is not limited thereto, and any other suitable shape can be utilized. For example, other configurations, such as recesses  140  having an inverted V-shaped cross-section ( FIG. 5 ), recesses  142  having an inclined planar cross-section ( FIG. 6 ) or even recesses  144  having a small circular cross-section ( FIG. 7 ) can be provided. 
     A still further configuration is shown by the recesses  146  in  FIG. 8  having a horizontal planar cross-section. In this seal, a wear pad recess  148  is provided in central section  130  and extends only partially into first and second end sections  126  and  128 . 
     Preferably, each pressure relieving recess  136  extends below said central section  130  and one end section  126 ,  128 . 
     In each case, however, thin membrane  124   c  would always be provided. 
     Having described specific preferred embodiments of the invention with reference to the accompanying drawings, it will be appreciated that the present invention is not limited to those precise embodiments and that various changes and modifications can be effected therein by one of ordinary skill in the art without departing from the scope or spirit of the invention as defined by the appended claims.