Abstract:
There is disclosed a printer with an arrangement for assuring that a linerless tacky adhesive-backed web is reliably fed. The printer has stripper elements which terminate at tip portions which extend into the platen roll to initially cut grooves in the platen roll, and because the tip portions extend below the outer periphery of the platen roll into these grooves, the stripper elements continue to strip the web reliably from the platen roll during subsequent printing cycles.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to printers for handling webs including linerless webs having tacky adhesive, methods associated with the handling of such webs, rolls including platen rolls, and methods of making rolls. 
   2. Brief Description of the Prior Art 
   The following documents are made of record: U.S. Pat. Nos. 5,267,800; 5,497,701; 5,833,377; 6,585,437; U.S. patent application Ser. No. 10/266,060, filed Oct. 7, 2002; and Linerless Addendum, Monarch Marking Systems, Inc. 1998. 
   SUMMARY OF THE INVENTION 
   The present invention relates to improved method and apparatus to strip a tacky adhesive-backed web from a roll reliably. 
   It is a feature of the invention to provide an improved printer for handling linerless, tacky, adhesive-backed webs wherein the webs are reliably stripped from a roll. 
   It is a feature of the invention to provide an improved printer for printing on a linerless web backed by a tacky adhesive which has a thermal print head and an adhesive-resistant, elastomeric, rotatable platen roll with a web stripper having at least one tip portion to cut at least one circumferential groove in the outer surface of the platen roll upon rotation of the platen roll. Initially, the tip portion or portions are positioned to dig or locally press into the elastomer platen roll. Upon rotation of the platen roll, a circumferential groove or grooves are cut in the surface of the platen roll. From the very beginning, the stripper causes the web to be reliably stripped from the roll. Repeated rotation of the platen roll completes the formation of the groove or grooves as the elastomeric material is cut and/or abraded away. After the groove or grooves have been cut, the linerless web continues to be reliably stripped from the web. 
   It is apparent that the groove or grooves are no wider or deeper than the tip portions that penetrate into the elastomeric material below the outer surface. Indeed, the tip portions “write their own name” in the platen roll, and the grooves are perfectly aligned with the tip portions which formed the grooves. 
   It is a feature of the invention to provide a stripper with one or more tip portions or cutters which serve to help strip the tacky, adhesive-backed web from the roll and which also function to make the groove(s) in the roll. 
   It is a feature of the invention to provide an improved, low friction shelf for a linerless printer which is relatively wide but which is rigid enough to resist flexure during use so that a linerless tacky adhesive-backed web is incapable of bowing the shelf and following the platen roll around. 

   
     BRIEF DESCRIPTION OF THE DIAGRAMMATIC DRAWINGS 
       FIG. 1  is a perspective view of a printer for handling a linerless web backed with tacky adhesive; 
       FIG. 2  is a fragmentary top plan view of the platen roll and the stripper elements initially dug or pressed into the platen roll; 
       FIG. 3  is a fragmentary top plan view similar to  FIG. 2  but showing the platen roll after the platen roll has been rotated to form the grooves in the platen roll; 
       FIG. 4  is a sectional view taken through the stripper, the bar, the platen roll and the print head; and 
       FIG. 5  is an exploded perspective view of a shelf with strippers or stripper elements terminating at tip portions or cutters and a bar for strengthening and mounting the shelf. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to  FIG. 1 , there is shown a portion of a printer generally indicated at  13  for printing on a linerless web generally indicated at  10  in printing cooperation with a print head  16  and a cooperating roll generally indicated at  17 , in particular a platen roll. The web  10  can be either imperforate or it can be provided with longitudinally spaced transverse perforations (not shown) which define labels. The print head  16  is preferably a thermal print head but other types of print heads can be used. The platen roll  17  is composed of an elastomeric material such as silicone rubber and/or outer surface  17 ′ of the platen roll  17  can be coated to be adhesive resistant. An elastomeric material is most preferred for a platen roll used with a thermal print head because it provides slightly yieldable support and counterpressure to the print head  16 , and it is resilient so as to be forgiving particularly in the event of slight misalignment of the print head  16  and the platen roll  17 . 
   The web  10  has an upper face  11  with the usual coatings such as a thermal coating, an optional barrier coating and a silicone coating. The underside of the web  10  has a coating of adhesive  14  which can be uniform and continuous as shown, which is known as a “full gum” coating, but the coating of adhesive  14  can be patterned or a “part gum” coating which is useful in certain applications. The adhesive  14  is of the tacky type also known as “pressure sensitive adhesive” because it adheres to a surface when pressure is applied. Tacky adhesive is sticky or tacky without activation by heat, water or other medium. 
   Because rolls that are to be in contact with adhesive on one side of a linerless web are typically adhesive resistant, when such rolls become worn the adhesive on the linerless web adheres more tenaciously to the worn roll and the linerless web has a tendency to follow the roll around. The web may bunch up or buckle between the platen roll and a stripper even though the stripper is immediately adjacent to or touches the platen roll. When the linerless web adheres to the platen roll there is also a tendency of the buckled linerless web to push against the stripper or to bow the stripper to make an easier throat between the platen roll and the stripper through which the linerless web can pass. 
   According to the invention, there is provided a support  18  with parallel support elements or members  19  which, as shown in  FIG. 4 , support the web following printing by the print head  16 . The support elements  19  have tip portions  20 . The tip portions  20  are preferably both sharp and pointed and terminate at laterally aligned points  21 . The tip portions  20  are used to cut circumferential grooves  22  in the outer surface or periphery  17 ′ of the platen roll  17 , and thus the tip portions are cutters that cut the grooves  22 . The tip portions  20  are those portions of the elements  19  that extend into the grooves  22 . The tip portions  20  act initially as cutters. The elements  19  including their tip portions  20  act as strippers that help strip the web  10  from the platen roll  17 .  FIG. 4  shows that the elements  19  enter the grooves  22  essentially tangent to the surface of the outer surface  17 ′, and more particularly, near the top of the outer surface  17 ′. 
   Initially, the support  18  is positioned so that the points  21  depress and dig into the outer surface  17 ′ of the platen roll  17  as illustrated in  FIG. 2 . Upon rotation of the platen roll  17 , the tip portions or cutters  20  cut the grooves  22  as best shown in  FIGS. 1 and 3 . Once positioned as indicated above, the tip positions  20  can remain positioned in the grooves  22  throughout use of the printer  13 . The tip portions  20  are slightly below the outer surface  17 ′ of the roll  17 . Because the tip portions  20  are below the outer surface  17 ′ in the grooves  22 , the linerless web  10  cannot go between the roll  17  and the element  19 . Yet the grooves  22  are small enough so that the grooves  22  do not degrade the print quality. The grooves  22  are narrow enough and the web  10  is thick enough so that the web  10  remains well supported, and there is no tendency of the web  10  to take on an undulating configuration. It is preferred that the grooves  22  are of equal width and depth. The grooves  22  are no wider than the tip portions  20 . There is no clearance between the sides of the tip portions  20  and the grooves  22 , and there is no clearance between the tips  21  and the bottoms of the grooves  22 . Once the tip portions are positioned to cut the grooves  22 , they are in perfect alignment with the grooves formed by the tip portions  22 , and there is therefore no need to adjust or reposition the stripper  18  with respect to the roll  17 . By way of example, not limitation, the grooves are most preferably about 0.125 mm wide and about 0.125 mm deep. A typical web  10  is about 0.1 mm thick. The stripper elements  19  are blades or are blade-like in construction. The upper configuration of each element  19  is preferably inverted V-shaped as shown and terminates in a longitudinally extending linear or straight line-shaped edge as indicated at  19 ′. The elements  19  terminate at the points  21 . The sides  23  of the elements  19  that face the platen roll  17  are arcuate and terminate at the points  21 . The elements  19  are preferably equally spaced. The adhesive  14  of the web  10  contacts the edges  19 ′ and the web  10  is accordingly supported by the edges  19 ′ which exert only minimal drag on the web  10  as the web  10  advances. 
   The elements  19  are molded integrally with a bar portion  24  having ribs  25 . The side of the bar portion  24  opposite the ribs  25  has spaced ribs  26 . The bar portion  24  has three laterally spaced, oversize through-holes  27 . The support or stripper  18  has a groove  28  disposed between the elements  19  and the ribs  25 . A rigid metal bar generally indicated at  29  is received in the groove  28 . The bar  29  is a composite comprised of a bar member  30  and a bar member  31  welded to the bar member  30 . Internally threaded fasteners  32  pass through and are secured in aligned holes  33  and  34  in the bar members  30  and  31 . Screws  35  pass through the holes  27  and are threaded into the threaded fasteners  32 . The bar portion  24  and the composite bar  29  are clamped together by the head of the screw  35  and the fastener  32 . Because of the clearances between the groove  28  and the bar  29  and between the holes  27  and the screws  35 , the stripper  18  can be precisely positioned or adjusted manually so that the tip portions  20  penetrate or dig into the outer surface  17 ′ to the desired depth. While the one-piece molded stripper  18  is rigid, the bar  29  adds rigidity and thus helps to maintain the tip portions  20  positioned in the grooves  22 . As shown, the bar  29  is mounted in frame plates  36  and  37  of the printer frame  38 . End portion  39  of the bar  29  hooks into the frame plate  36 , and end portion  40  snaps into a clip  41  screwed to the frame plate  37 . Further aspects of the printer  13  are shown in U.S. Pat. No. 5,833,377 incorporated herein by reference. The frame plates  36  and  37  in the present application correspond to walls  126  and  127  in U.S. Pat. No. 5,833,377. 
   The platen roll  17  is preferably comprised of a metal shaft  42  on which an elastomeric sleeve  43  is secured. The shaft is  42  preferably driven as illustrated in U.S. Pat. No. 5,833,377 while the thermal print head  16  prints in the web  10 . As the platen roll  17  rotates, the web  10  is stripped from the roll  17  by the stripper elements  19 , and the printed, stripped web  10  passes over the elements  19  with the adhesive  14  in contact with upper edges  19 ′ of the elements  19 . As shown in  FIG. 4 , the web  10  preferably follows a slightly downward trajectory as it is stripped from the platen roll  17  and is supported by elements  19 . 
   The tip portions or cutters  20  cut the circumferential grooves by wearing away quite narrow circumferential zones of the outer portion of the sleeve  43  with relatively few rotations of the roll  17 . 
   While the invention is applied to a platen roll  17  it is also useful when stripping adhesive-backed webs for various rolls other than platen rolls. 
   By way of example, not limitation, for a web which is about 102 mm wide, it is most preferred to use  14  stripper elements, however a greater or lesser number can be used. It is also within the spirit of the invention to have less than all the elements  19  extend into the grooves  22 . 
   While the stripper  18  is stiffened or strengthened by the bar  29 , the stripper  18  could be made stronger by making it from thicker plastics material and suitably mounting it to the frame plates  36  and  37 . While the stripper  18  is preferably of one-piece molded plastics construction, the stripper  18  can be made in multiple parts. 
   The preferred illustrated shape of the tip portion  20  is such that if the platen roll  17  is to be rotated in the reverse direction from that shown by arrow A in  FIG. 1  to bring the web  10  to the top-of-form position, no harm will come to the platen roll  17 . 
   While the invention is particularly useful for use with linerless, tacky adhesive-backed, printable webs, the method and 
   While the invention is particularly useful for use with linerless, tacky adhesive-backed, printable webs, the method and apparatus of the invention can also be used with adhesive webs having siliconized release liners. 
   Other embodiments and modifications of the invention will suggest themselves to those skilled in the art, and all such of these as come within the spirit of this invention are included within its scope as best defined by the appended claims.