Abstract:
A web of print media dispensable as individual sheets along lines of perforation includes a pattern of ties and slits that provide a more predictable resistance to manually separating the sheets from the web. The lines of perforation extend transversely with respect to a longitudinal dimension of the web and cross a longitudinal centerline between two edges of the web. The ties are weaker near the centerline of the web than near either of the two edges sufficient to relatively increase resistance to tearing along the lines of perforation starting near either of the two edges while relatively decreasing resistance to tearing along the same lines of perforation starting near the centerline of the web.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/248,143, filed on Nov. 13, 2000, which provisional application is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     Perforations provide a mechanism for dividing a web of print media into individually dispensable sheets. 
     BACKGROUND 
     Relevant printing systems dispense individually printed sheets from a continuous web of print media. The individual sheets can be dispensed to recipients by automated cutting or manual tearing of the sheets from the web. However, automated cutting adds mechanical complexity, imposes servicing requirements, and subjects printing systems to mechanical breakdown. Manual tearing shifts some of this burden onto recipients for carrying out the necessary operations. In addition, tearing can produce ragged edges and disturb registration of the print media within the printer. 
     Perforations have been used to assist tearing along designated lines. However, the amount of force required to tear even perforated lines can vary widely depending upon the direction and position at which the tear forces are applied. Braking mechanisms, which add problems similar to those of automated cutting mechanisms, are sometimes needed to maintain proper registration of the print media within the printers. 
     So-called “slits” separated by uncut portions referred to as “ties” form the perforated lines, which can extend from one edge to another through a center of the web. Tearing is accomplished most efficiently by applying tensile forces in offset positions that concentrate the tensile forces through one tie at a time. As each tie breaks, the tensile forces shift to the next adjacent tie. Ordinarily, such tearing starts by breaking ties near one edge of the web and proceeds by breaking ties in succession through the center to the other edge of the web. 
     Other more centered positions for applying tensile forces can distribute the tensile forces through more than one tie at a time. Bursting is accomplished by breaking at least some or all of the ties between both edges of the web at once. The tensile forces required to break all of the ties simultaneously are much higher than those required to break the same ties in succession. Breaking a smaller grouping of the ties simultaneously requires tensile forces intermediate to those required for breaking the ties individually or all at once. 
     Such wide variability in the tensile forces required to manually separate individual printed sheets along lines of perforation also requires a corresponding capacity for high braking forces and imposes inconsistent demands on recipients to perform the tearing operation. The tensile forces required for bursting all of the ties or even some groupings of the ties can easily exceed reasonable levels for performing manual operations of this sort. 
     One solution is to weaken the ties to reduce the maximum tensile force required to burst the ties simultaneously. However, the weakened ties also lower the minimum tensile forces required to tear the ties in succession. Such weakened webs are subject to breakage during in-line manufacture, loading into the printer, and subsequent feeding through the printer. 
     SUMMARY OF INVENTION 
     My invention improves the dispensing of perforated sheets from printers and other dispensing devices by reducing variability among tensile forces required to separate the perforated sheets from webs throughout a range of positions at which the tensile forces can be applied. Initiating tearing actions along lines of perforations at one edge or the other of the webs is made relatively more difficult, while initially bursting ties located near the centers of the webs is made relatively easier. For example, perforation patterns can be arranged in accordance with my invention to support a controlled bursting sequence in which ties break in pairs, starting at the web center and proceeding simultaneously toward both edges. 
     Ordinarily, the minimum tensile forces required to tear lines of perforation are applied from offset positions that initially stress and break the ties located along one of the web edges and proceed by stressing and breaking the remaining ties one at a time. My invention can sustain or even enlarge these minimum tensile forces by maintaining or increasing the strength of ties located near the opposite edges of the webs. 
     The maximum tensile forces ordinarily required to tear lines of perforation are applied through all of the ties at once. My invention reduces the maximum tensile forces by weakening the ties located at or near the centers of the webs so that these ties break in advance of the rest. Due to the flexible nature of webs, tensile forces applied from the same centered positions stress and break the next adjacent ties paired on opposite sides of the web centers. The remaining ties paired on opposite sides of the web centers are stressed and broken in succession. Thus, even where tensile forces are applied in a manner that initially stresses all of the ties, the ties are still broken in a sequence that greatly reduces the maximum tensile forces. 
     One example of my new in-line supply of print media is arranged as a web of printable media having regularly spaced lines of perforation that separate the web into individually dispensable sheets. The lines of perforation extend transversely with respect to a longitudinal dimension of the web crossing a longitudinal centerline between two edges of the web. A pattern of ties separated by slits extend along the lines of perforation. The ties occupy a larger portion of the lines of perforation adjacent to the edges of the web than adjacent to the centerline of the web sufficient to relatively increase resistance to tearing near either of the two edges while relatively decreasing resistance to tearing starting near the centerline of the web. 
     Preferably, the ties located closest to the centerline of the web are weaker than the ties located closest to the edges of the web along the lines of perforation. In addition, the ties are preferably unevenly spaced along the lines of perforation with enlarged spacings separating the ties located closest to the centerline of the web from the remaining ties located closer to the two edges of the web. Once the weaker ties located closest to the centerline of the web have burst, the enlarged spacings encourage the web to pucker, thereby allowing the remaining stronger ties to break in succession from both sides of the web centerline. 
     The print media itself is preferably made of a flexible non-elastic material. The flexibility permits puckering, while the non-elasticity permits the concentration of tensile forces through limited numbers of ties. Each of the sheets of print media can be individually printed by the printer prior to being dispensed from the printer. One example is a thermal paper having a surface coated with a thermosensitive material that forms images in response to the application of heat in patterns. Tensile forces applied along the centerline of the web between adjacent sheets rupture the ties along the intervening line of perforation in a sequence starting with the ties located closest to the centerline of the web and proceeding in opposite directions through the remaining ties located closer to the two edges of the web. Alternatively, tensile forces applied along either edge of the web can rupture the ties in a more usual sequence starting at one edge and proceeding tie-by-tie to the other edge. However, regardless of where the tensile forces are applied between the edges of the web, comparable tensile forces are required to separate the printed sheets from the web. 
    
    
     DRAWINGS 
     FIG. 1 diagrams my printing system tracing a pathway for printing and dispensing sheets from a fan-folded web of print media. 
     FIG. 2 illustrates two of the sheets in the form of scrip broken away from the web and divided from each other by a line of perforation that is enlarged to more clearly show a modified pattern of ties and slits. 
     FIGS. 3A-3D depicts an expected sequence of tearing actions between the two sheets of scrip associated with tensile forces applied along a longitudinal centerline of the web. 
     FIGS. 4A-4D depicts another sequence of tearing actions between the two sheets of scrip associated with tensile forces applied along an edge of the web. 
     FIG. 5 diagrams an in-line system for making the web of print media with lines of perforation dividing the web into separately dispensable sheets. 
    
    
     DETAILED DESCRIPTION 
     An exemplary printing/dispensing system  10  depicted in FIG. 1 dispenses sheets  12  from a web of print media  14  arranged in a fan-folded stack  16 . The web of print media  14  advances through a printer  20  that pinches the web  14  between a print head  22  and a drive platen  24 . Friction generated by this pinching action represented by arrows  26  imparts either a driving force or a braking force on the web  14  for preserving a desired registration of the web  14  with the print head  22 . 
     The printer  20  is preferably a thermal printer under control of a processor  30 . The web of print media  14  is preferably a thermal paper having a thermosensitive coating  32  on a surface adjacent to the print head  22 . Heat applied in patterns by the print head  22  produces images in the thermosensitive coating  32 . Alternatively, ink jet paper or other printable media separable along lines of perforation could also be used in connection with an ink jet or other print-on-demand printer. The printed images can be unique to the individual sheets  12  and related by the processor  30  to local or remote events. 
     Although shown in a fan-folded stack  16 , the web  14  could also be arranged in a roll or other form for supplying an unbroken stream of the sheets  12 . Other printers, including ink jet and laser printers, could also be used with different webs of compatible print media. A separate braking mechanism under the control of the processor  30  could also be used to augment or replace the braking interface of the print head  22  and platen  24 . 
     In the enlarged view of FIG. 2, the sheets  12 , which are depicted as sheets  12 A and  12 B of scrip, are separated from each other along the web  14  by lines of perforation  36  that extend transversely with respect to a longitudinal dimension of the web, crossing a longitudinal centerline  38  between two edges  40  and  42  of the web  14 . The scrip sheets  12 A and  12 B are preprinted with repeating indicia  44  and  46 , but also contain unique information  48  added by the printer  20 . For example, the printer  20  can print dollar amounts on the scrip sheets  12 A and  12 B in accordance with instructions from the processor  30 . 
     The lines of perforation  36  contain ties  50 ,  52 ,  54 ,  56 ,  58 , and  60  separated by slits  62 ,  64 ,  66 ,  68 , and  70 . Additional slits  72  and  74  separate the ties  50  and  60  from the two edges  40  and  42  of the web  14  to resist any tendency to scallop the edges  40  and  42  during separation of the sheets  12 A and  12 B. The ties  54  and  56  located closest to the centerline  38  of the web  14  are thinner or otherwise weaker than the remaining ties  50 ,  52 ,  58 , and  60  located closer to the two edges  40  and  42  of the web  14 . For example, the ties  54  and  56  have a width dimension “T 1 ” that is thinner than a width dimension “T 2 ” of the ties  50 ,  52 ,  58 , and  60 . In addition, the ties  54  and  56  are separated from their next closest ties  52  and  58  by slits  64  and  68  that have a width dimension “S” that is much greater that the unlabeled width dimensions of the remaining slits  62 ,  66 ,  70 ,  72  and  74 . 
     After printing, the web  14  is advanced past a burster bar  76  (shown in FIG. 1) into a position at which the closest line of perforation  36  overlies the burster bar  76 . Tensile forces  78  applied manually to the scrip sheet  12 A along the centerline  38 , as also shown in the sequence of drawing FIGS. 3A-3D, are opposed by braking forces applied by the printer  20  to the scrip sheet  12 B lying between the closest line of perforation  36  and the remaining portion of the web  14 . The burster bar  76  provides an edge that concentrates a component of the tensile forces  78  normal to the lines of perforation  36 . 
     The ties  54  and  56  closest to the centerline  36  (see also FIG. 2) are preferably stressed at least as much as the other ties  50 ,  52 ,  58 , and  60  located closer to the two edges  40  and  42  of the web and are weaker than the other ties (e.g., by at least 20 percent). As a result, the ties  54  and  56  tend to rupture (break) in advance of the other ties  50 ,  52 ,  58 , and  60  as shown in FIG.  3 B. The partly separated web  14  is flexible yet sufficiently inelastic to transfer the tensile forces  78  around the extra wide span of the slits  64  and  68  to the next closest ties  52  and  58 . 
     A puckering action through the span of the extra wide slits  64  and  68  distorts the web  14  from a planar form and concentrates the tensile forces  78  through the next closest ties  52  and  58 , thereby rupturing these ties as shown in FIG.  3 C and transferring the tensile forces  78  to the last remaining ties  50  and  60  located closest to the web edges  40  and  42 . An expanded puckering action concentrates the tensile forces  78  through these remaining ties  50  and  60 , resulting in their rupture and a complete separation of scrip sheet  12 A from the scrip sheet  12 B as shown in FIG.  3 D. 
     Although all of the ties  50 ,  52 ,  54 ,  56 ,  58 , and  60  can be initially stressed by the tensile forces  78  applied along the centerline  38 , the relative weakening of the centermost ties  54  and  56  together with a controlled distortion of the web  14  permits the tensile forces  78  to break the remaining ties in a succession of tie pairs  54  and  56 ,  52  and  58 , and  50  and  60 . The breakage of the ties  50 ,  52 ,  54 ,  56 ,  58 , and  60  in the prescribed succession significantly reduces the overall magnitude of the tensile forces  78  required to separate the scrip sheet  12 A from the remaining portion of the web  14  with respect to the overall magnitude of the tensile forces required to achieve the same objective by breaking all of the ties  50 ,  52 ,  54 ,  56 ,  58 , and  60  at once. 
     The overall magnitude of the tensile forces  78  is comparable to the overall magnitude of tensile forces  80  applied manually along the edge  40  of the web for rupturing the ties  50 ,  52 ,  54 ,  56 ,  58 , and  60  according to a more conventional tearing action depicted in the drawing FIGS. 4A-4D. Here, the tearing begins at the tie  50  located closest to the edge  40  and proceeds one-by-one through the remaining ties in their listed order  52 ,  54 ,  56 ,  58 , and  60  without regard to the relative strengths of the ties. In fact, the relatively weakened ties  54  and  56  have little or no effect on the overall magnitude of the tensile forces  80  because the relatively stronger ties  50 ,  52 ,  58 , and  60  are also separately broken in the same sequence. Similar results can be expected for tensile forces applied along the opposite edge  42 . 
     Thus, the tensile forces  78  applied along the centerline  38 , which would otherwise be unacceptably high, are significantly reduced; and the tensile forces  80  applied along either of the edges  40  or  42 , which are ordinarily much lower, are substantially maintained. The similarity of the overall magnitudes of the tensile forces  78  and  80  without regard to the positions at which these forces are applied between the edges  40  and  42  allows the script sheet  12 A to be gripped through the same range of positions and separated from the remaining portion of the web  14  by a more consistent and predictable exertion of manual force. 
     Many other combinations and patterns of ties and slits following these general practices can be arranged to achieve similar goals. For example, more or less ties can be used. The ties could also be made progressively stronger approaching both edges  40  and  42  of the web to further promote a controlled bursting sequence starting near the centerline  38  and proceeding towards both edges  40  and  42 . Relatively strengthening the ties  50  and  60  closest to the edges  40  and  42  of the web  14  can be used to relatively increase resistance to tearing actions starting at either edge  40  or  42  without unduly increasing resistance to tearing starting near the centerline  38 . 
     The web  14  of print media is preferably manufactured by an inline press  84  such as shown in FIG. 5. A roll  86  unwinds the web  14  of print media into the press  84  for a sequence of processing operations. A printing station  88 , which is representative of a plurality of printing and surface treating stations, applies the repeating indicia  44  and  46  to the web  14 . A die cutting station  90  cuts the lines of perforation  36  into the web  14  at regularly spaced intervals in registration with the printing operations for dividing the web into the individually dispensable sheets  12 . A folding station  92  folds the web into the fan-folded stack  16  that can be inserted into the printing/dispensing system shown in FIG.  1 . 
     Additional or replacement operations can be performed along the in-line press for adapting the sheets  12  for a variety of purposes, including couponing and labeling. During manufacture, the webs can contain more than one width of the sheets  12  and can be longitudinally sliced into multiple webs of dispensable sheets. The printing operations are preferably performed flexographically; but other in-line printing processes can also be used, such as variable imaging, letterpress, rotogravure, and screen printing. The web of print media  14  is preferably a thermal paper, but other paper or media products, such as conventional bonded or ink jet paper, having the requisite flexibility and inelasticity can also be used. The in-line press operations can be performed on a single press, or the operations can be divided among a plurality of presses. For example, the printing operations can be performed on one press, and the perforating and folding functions can be performed on another press. Registration marks printed on the webs can be used to synchronize the presses. 
     The web of print media  14  can be printed in advance of being mounted in the dispensing system  10  or can be printed just prior to dispensing. Examples of such dispensable print media include tags, tickets, coupons, and labels. For most such uses, at least some printing is preferably completed before the media is loaded into the dispensing system  10 . Links between the processor  30  and internal or external information systems can be established to print unique information on the sheets  12  within the dispensing system  10  prior to the intended separation of the sheets  12  from the remaining print media  14 . In place of a printer within the dispensing system  10 , a stand-alone braking mechanism can be used to prevent the sheets from being prematurely dispensed before the sheets have been separated from the web  14  along the lines of perforation  36 .