Patent Publication Number: US-6655435-B2

Title: System for creating linerless pressure sensitive coil of stamps

Description:
RELATED APPLICATIONS 
     This patent application claims the benefit, under Title 35, United States Code, §119(e), of U.S. Provisional Patent Application No. 60/243,155, filed Oct. 25, 2000. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a system for producing pressure sensitive stamps, and more particularly to a method which allows for the production of a coil of such pressure sensitive stamps without a backing or liner on the entire coil. 
     BACKGROUND OF THE INVENTION 
     It has long been known to roll a strip of stamps into a coil to save space and to provide a convenient mechanism for detaching one or more stamps from a plurality of others. However, such a coil configuration had been limited to traditionally known stamps which required moistening on a glue side before being adhered to an envelope. 
     More recently, so-called “self adhesive” stamps have been becoming more and more popular. These stamps do not have to be moistened, but rather are provided with a pressure sensitive adhesive layer which is adhered to the envelope. The pressure sensitive adhesive layer is typically covered with a protective backing, or liner, consisting of a strip of non-adhesive material, generally of the same width of or wider than the strip of stamps, which is peeled away before the stamp is adhered to the envelope in order to expose the adhesive layer. 
     It has been proposed to roll such self-adhesive stamps into a coil in order to enjoy the convenience and space-saving characteristics associated therewith. However, when using known pressure sensitive adhesive stamp designs, rolling them into a coil requires that the entire coil of stamps have a strip of protective liner backing the adhesive layer. This liner is required in order to prevent the adhesive layer from adhering to the printed, unprotected face of the stamp material which is wound immediately beneath the liner which provides a protective barrier. Providing a strip of liner for the entire coil of stamps, however, is undesirable for several reasons. One such reason relates to environmental concerns. The liner strip comprises unnecessary waste, which adversely impacts the environment. Moreover, the liner increases the material costs associated with manufacturing the stamps. Furthermore, when a liner is used, one is required to unroll a stamp off the coil, remove the stamp from the liner, and detach it from the next following stamp before adhering the stamp to the envelope. It would be easier for the user if the stamp could simply be unrolled, detached from the following stamp, and adhered to the envelope without having to remove a liner. 
     In order to remedy the above concerns, and referring to FIG. 1, a coil  10  of stamps has been developed. Coil  10  comprises a continuous strip  12  of stamps rolled on itself, similar to a roll of tape. It should be noted that the strip  12  of stamps does not include a liner, or backing layer, protecting the pressure sensitive adhesive over its entire length. A piece of liner material  14  may be provided, however, at the center (i.e., the end) of coil  10  in order to inhibit lint, dirt, dust and the like from adhering to the stamps at the center of the coil, thereby preventing a sure adhesion of those stamps to the envelope at the time of use, and in order to meet security requirements imposed by the United States Postal Service or any other issuer of the stamps. A piece of liner material  16  may also be provided at the outer portion (i.e., the beginning) of coil  10  in order to facilitate removal of the first stamp or first few stamps from the strip  12  of stamps. However, it should be noted that as the strip  12  of stamps may be several yards, or more, in length the sections of the strip  12  which include a liner layer are relatively very small. 
     While the coil  10  of stamps shown in FIG. 1 is desirable in that it does not include a liner over the entire strip of stamps comprising the coil, the production of coil  10  introduces new problems of its own. More specifically, known methods for manufacturing stamps, even coils of stamps, cannot be used to create a coil of stamps which does not include a liner over the entire strip of stamps. The specific problems encountered using known methods for the production of coils of stamps which include a liner over the entire strip of stamps, and the novel solutions to those problems which comprise the present invention, are discussed in detail below. 
     What is desired, therefore, is a system and method of creating a coil of stamps, which coil does not require a liner layer over the entire strip of stamps comprising the coil, and which avoids the problems associated with known methods for the production of coils of stamps which include a liner over the entire strip of stamps. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a system and method of creating a coil of stamps. 
     A more specific object of the present invention is to provide a system and method of creating a coil of stamps, which coil does not require a liner layer over the entire strip of stamps comprising the coil. 
     A further object of the present invention is to provide a system and method having the above characteristics and which avoids the problems associated with known methods for the production of coils of stamps which include a liner over the entire strip of stamps. 
     These and other objects of the present invention are achieved by provision of a system for creating a coil of stamps from a web of stamp material having an adhesive applied to a side thereof. The system includes a substantially cylindrical anvil and a perforation die cooperating therewith with the web of stamp material passing therebetween in order to perforate the web of stamp material. The web of stamp material is passed between the anvil and the perforation die with the side of the web of stamp material having the adhesive applied thereto facing the anvil. The anvil is chilled so as to inhibit the adhesive applied to the web of stamp material from adhering thereto as the web of stamp material is perforated by cooperation of the perforation die and the anvil. 
     The anvil may be chilled from an outer surface thereof, or may be hollow and chilled from an inner surface thereof. In the former case, the system preferably includes a trough holding a chilling material through which at least a portion of an outer surface of the anvil is passed in order to chill the outer surface thereof. Most preferably, the chilling material comprises dry ice. Where the anvil is chilled from an inner surface thereof, a cooling fluid is preferably passed therethrough. 
     The system preferably also includes a liner application mechanism for applying a liner material to no more than a portion of the web of stamp material. Most preferably, the liner application mechanism includes a spool of liner material and a cutting mechanism for cuffing the liner material into a plurality of discrete pieces of liner material having a predetermined length before the liner material is applied to the side of the web of stamp material having the adhesive applied thereto. Preferably, each of the plurality of discrete pieces of liner material includes at least one perforation, and the at least one perforation is aligned with a perforation in the web of stamp material. It is also preferable that the liner application mechanism be located after the anvil and the perforation die. 
     In addition, the system preferably also includes a coiling mechanism for creating discrete coils of stamps from the web of stamp material. Most preferably, the coiling mechanism includes at least one roller around which the web of stamp material is wound in order to place the web of stamp material in tension and a bursting blade extending across a width of the web of stamp material. The bursting blade includes a narrow tip and is movable substantially perpendicular to the web of stamp material such that when moved fully toward the web of stamp material, the bursting blade breaks a plane formed by the web of stamp material. The bursting blade is moved forcefully toward the web of stamp material adjacent to a perforation in the web of stamp material in order to burst the perforation and separate a coil of stamps from the remainder of the web of stamp material. Most preferably, the narrow tip of the bursting blade has a shape selected from a group consisting of sharp, rounded, serrated, or straight shapes or combinations of these. 
     The invention and its particular features and advantages will become more apparent from the following detailed description considered with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a coil of linerless pressure sensitive adhesive stamps which can be created by a system in accordance with the present invention; 
     FIG. 2 is a schematic side view of a system for creating a coil of stamps, which coil does not require a liner layer over the entire strip of stamps comprising the coil, in accordance with the present invention; 
     FIG. 3 is a schematic side view showing in greater detail a cooperating die and anvil for use in the system of FIG. 2; 
     FIG. 4 is a partial side isometric view of the die of FIG. 3; 
     FIG. 5 is a side schematic view illustrating problems associated with known prior art stamp creating systems; 
     FIG. 6 is a top isometric view illustrating a section of a web of contiguous strips of stamps having a liner applied only to a portion thereof; and 
     FIG. 7 is a side schematic view of a portion of the system for creating a coil of stamps, which coil does not require a liner layer over the entire strip of stamps comprising the coil, in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 2, an overall system  18  for creating a coil of stamps, which coil does not require a liner layer over the entire strip of stamps comprising the coil, in accordance with the present invention is shown. A web of contiguous strips of stamps  20  is wound around an input spool  22  and an output spool  24 . Various rollers  26  are provided throughout system  18  in order to direct the web of stamps  20  to the proper positions. It should be noted that the web of stamps  20  has already been printed, and a pressure sensitive adhesive has already been applied to one side thereof. 
     The web of stamps  20  is fed through a cooperating anvil  28  and die  30 , which are provided in order to create perforations  32  in web  20  (see FIG.  6 ). Die  30  essentially comprises a cylindrical drum  34  having a plurality of protrusions  36  shaped so as to form perforations. As die  30  is essentially known in the art, it is not described in further detail herein. 
     Die  30  is pressed against cylindrical anvil  28  with great force with web of stamps  20  passing therebetween in order to create perforations  32  in web  20 . While such a general process is known, the process had heretofore been used only to create perforations in materials not having a pressure sensitive adhesive applied thereto, or if so applied, having a protective backing or liner. As in the present case web of stamps  20  has a pressure sensitive adhesive applied thereto, and does not have a protective liner, special and unforeseen problems may arise. 
     If web of stamps  20  is passed through anvil  28  and die  30  with the adhesive layer A facing the die  30 , as is shown in FIG. 5, when perforations  32  are created, tiny bits of paper and even pieces of adhesive  38  may be forced under pressure to the front surface  40  of web of stamps  20 . This is undesirable, as front surface  40  is specially coated with a material, typically silicone, to protect and inhibit the front side of web of stamps  20  from adhering to the back side thereof when web  20  is rolled onto itself. When tiny bits of paper and/or pieces of adhesive  38  are forced under pressure to the front surface  40  (i.e., past the protective silicone layer) of web of stamps  20 , the benefits of the protective silicone layer in these areas are destroyed, and the web  20  may undesirably indeed stick to itself when rewound into a roll. 
     It has also been found that when the adhesive layer A is provided on the web of stamps  20  facing anvil  28 , the adhesive A may undesirably adhere to anvil  28 . It has been suggested that this problem may be avoided by providing the surface of anvil  28  with a protective coat of some type of oil or other lubricant. However, when such coating is provided, it has been found that this coating can contaminate adhesive A, thereby disadvantageously affecting its adhesive characteristics. 
     Therefore, in accordance with one novel aspect of the present invention, the outer surface of anvil  28  is chilled to a temperature well below standard room temperature. The exact temperature to which anvil  28  is chilled is dependent on the characteristics of adhesive A. The outer surface of anvil  28  may be chilled from the outside, such as by providing ice, dry ice or the like in a trough which contacts the outer surface, or by chilling the outer surface from the inside, such as by flowing a cool liquid through anvil  28 . By so chilling the outer surface of anvil  28 , adhesive A is inhibited from adhering thereto. This may be caused by the adhesive A in contact with the outer surface of the chilled anvil  28  essentially becoming inert at the contact point therewith, and may also be caused by a thin layer of moisture condensate being created by the chilled anvil on its outer surface. 
     Web of stamps  20  is also fed past a mechanism  42  by which a small amount of liner material  44  may be affixed thereto. Liner material  44  is provided on a spool  46 , and is passed through a cutting device  48  which cuts liner material into appropriate sized pieces. It should be noted that the web of stamps  20  does not include a liner over its entire length. As discussed above, and in reference to FIG. 1, a piece of liner material  14  may be provided at the center (i.e., the end) of coil  10  and another piece of liner material  16  may be provided at the outer portion (i.e., the beginning) of coil  10 . 
     It should be appreciated that the length of the piece of liner material  44  is the sum of the lengths of the pieces of liner material  14 ,  16 . For purposes of illustration, and not limitation, and as illustrated in FIG. 6, piece of liner material  14  may be three stamps in length, while piece of liner material  16  may be one stamp in length. Piece of liner material  44  would thus be four stamps in length. It should be noted that liner material  44  includes a perforation  45  between pieces of liner material  14 ,  16 , and that such perforation is precisely aligned so as to be proximate to a perforation  32  in web  20 . Piece of liner material  14  may or may not include perforations therein. 
     Mechanism  42  may be provided either after anvil  28  and die  30  (as shown in FIG. 2) or therebefore. The former is preferable so as to reduce wear on die  30  by not requiring it to form perforations through web  20  and liner material  44 . Moreover, as it is preferable that liner material  14  not include perforations therein, it is preferable that mechanism  42  be provided after anvil  28  and die  30 . 
     Referring now to FIG. 7, a mechanism  46  is shown for creating discrete coils of stamps  10  from web of stamps  20 . Web  20  may be fed to mechanism  46  directly from mechanism  18  (shown in FIG.  2 ), or as shown in FIG. 7, may first be wound into roll  24 , and then later fed to mechanism  46 . Web  20  is wound into coil  10 , and may be passed around rollers  54 , such that web  20  is in moderate tension, and a bursting blade  50  is provided proximate to coil  10 . Bursting blade  50  extends across the entire width of web  20 , and has a narrow tip which may be sharp or rounded, and serrated or straight. Bursting blade is movable substantially perpendicular to web  20  (indicated by arrow  52 ) and when moved fully toward web  20 , breaks a plane formed thereby. Thus, after an appropriate number of stamps have passed by bursting blade  50 , bursting blade  50  is moved forcefully toward web  20  at the appropriate time such that it strikes perforation  45  between pieces of liner material  14 ,  16 , thereby bursting the perforation  45  and the perforation  32  to which it is adjacent, thereby separating coil  10  from the remainder of web  20 . This break occurs precisely along the perforation  45  in the liner material  44 , thereby severing the liner which is adhered to the web of stamps  20  in such a way as to create starting tab  16  on the finished coil  10  and inner liner  14  on the coil  10  which is about to begin. 
     The present invention, therefore, provides a system and method of creating a coil of stamps, which coil does not require a liner layer over the entire strip of stamps comprising the coil, and which avoids the problems associated with known methods for the production of coils of stamps which include a liner over the entire strip of stamps. 
     Although the invention has been described with reference to a particular arrangement of parts, features and the like, these are not intended to exhaust all possible arrangements or features, and indeed many other modifications and variations will be ascertainable to those of skill in the art.