Patent Publication Number: US-9850085-B2

Title: Sheet numbering process and sheet-processing machine for carrying out the same

Description:
This application is the U.S. national phase of International Application No. PCT/162014/059271 filed 26 Feb. 2014, which designated the U.S. and claims priority to EP Patent Application No. 13157342.0 filed 28 Feb. 2013, the entire contents of each of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present invention generally relates to a sheet numbering process and a sheet-processing machine for carrying out such sheet numbering process. The invention is in particular applicable to the production of banknotes and like securities. 
     BACKGROUND OF THE INVENTION 
     Banknotes and like securities are commonly produced in the form of individual sheets (or successive portions of a continuous web which are ultimately cut into sheets) each carrying a plurality of individual imprints arranged in a matrix of rows and columns, which sheets are subjected to various printing and processing steps before being cut into individual notes. Among the printing and processing steps typically carried out during the production of banknotes are offset printing, intaglio printing, silk-screen printing, foil application, letterpress printing and/or varnishing. Other processing steps might be carried out during the production such as window cutting, ink-jet marking, laser marking, micro-perforation, etc. Once fully printed, the sheets have to be subjected to a so-called finishing process wherein the sheets are processed, i.e. cut and assembled, to form note bundles and packs of note bundles. 
     Banknotes and like securities further have to typically meet strict quality requirements, especially concerning the printing quality thereof. Therefore, during the course of their production, banknotes or securities are typically inspected in order to detect, and advantageously mark, defective notes, i.e. notes exhibiting a low printing quality, printing errors, physical damages and the like, such that these defective notes can be sorted out. Inspection can be carried out at various stages of the production, manually, on-line on the printing or processing presses, and/or off-line on dedicated inspection machines. Final inspection of the banknotes is conveniently carried out prior to finishing as this will be explained hereinafter in reference to  FIG. 1  which is illustrative of the prior art. 
       FIG. 1  summarizes a typical process of producing securities wherein a final inspection step is carried out prior to finishing. The production process illustrated in  FIG. 1  is advantageous in that it enables maximisation of the production efficiency by reducing waste to a minimum and enables the production of note bundles and packs of note bundles with uninterrupted numbering sequence. 
     Step  501  in  FIG. 1  denotes the various printing phases which are typically carried out during the production of securities. As mentioned, these various printing phases include in particular an offset printing phase whereby sheets of securities are printed on one or both sides with an offset background, an intaglio printing phase whereby the sheets are printed on one or both sides with intaglio features (i.e. embossed/relief features which are readily recognizable by touch), a silk-screen printing phase whereby the sheets are printed on one or both sides with silk-screen features, such as features made of optically variable ink (OVI), and/or a foil/patch application phase whereby foils or patches, in particular so-called optically variable devices (OVD), holograms, or similar optically diffractive structures, are applied onto one or both sides of the sheets, etc. 
     As a result of the various printing phases of step  501 , successive sheets S are produced. While quality control checks are usually performed at various stages during the production of the securities, a final quality check is typically carried out on the full sheets S after these have been completely printed. This full-sheet quality inspection is schematised by step  502  in  FIG. 1 . Three categories of sheets in terms of quality requirements are generated as a result of this full-sheet quality inspection, namely (i) entirely good sheets S 0  (i.e. sheets carrying imprints which are all regarded to be satisfactory from the point of view of the quality requirements), (ii) partially defective sheets S′ (i.e. sheets carrying a mixtures of imprints which are satisfactory from the point of view of the quality requirements and imprints which are unacceptable, which defective imprints are typically provided with a distinct cancellation mark), and (iii) entirely defective sheets S X  carrying only defective imprints. From this point onward, the three categories of sheets follow distinct routes. More precisely, the entirely defective sheets S X  are destroyed at step  510 , while the entirely good sheets S 0  are processed at steps  503  to  505  and the partially defective sheets S′ are processed at steps  520  to  523 . 
     Referring to steps  503  to  505 , the entirely good sheets S 0  are typically numbered at step  503 , then optionally varnished at step  504 , and finally cut and subjected to an ultimate finishing process at step  505 , i.e. stacks of sheets S are cut into individual bundles of securities (such as banknote bundles)  200 , which bundles  200  are typically banderoled (i.e. surrounded with a securing band) and then stacked to form packs of bundles  210 . While the sheets S are processed in succession at steps  503  and  504 , step  505  is usually carried out on stacks of hundred sheets each, thereby producing successive note bundles  200  of hundred securities each, which note bundles  200  are stacked to form e.g. packs  210  of ten note bundles each. 
     Referring to steps  520  to  523 , the partially defective sheets S′ are firstly cut into individual notes at step  520  and the resulting securities are then sorted out at step  521  (based on the presence or absence of the cancellation mark previously applied on the defective imprints at step  502 ), the defective notes being destroyed at step  510 , while the good notes are further processed at steps  522  and  523 . At step  522 , the individual securities are numbered in succession and subsequently subjected to a finishing process at step  523  which is similar to that carried out at step  505 , i.e. note bundles of securities  200  are formed, which note bundles  200  are banderoled and then stacked to form packs of note bundles  210 . 
     As regards the varnishing operation,  FIG. 1  shows that such varnishing is typically carried out on full sheets at step  504  after full-sheet numbering at step  503 . While this varnishing step is preferred, it is not as such required. Varnishing may furthermore be carried out at a different stage of the production, for example before full-sheet inspection at step  502  or immediately after full-sheet inspection at step  502 , on the entirely good sheets S 0  and partially defective sheets S′ (which other solution would imply that numbering is carried out after varnishing). 
     In case keeping the numbering sequence throughout the notes of successive bundles  200  is not required, the partially defective sheets S′ could follow a somewhat similar route as the entirely good sheets S 0 , i.e. be subjected to a full-sheet numbering step (thereby numbering both the good and defective imprints), then to full-sheet varnishing, before being cut into individual securities, sorted out to extract and destroy the defective securities, and then subjected to an ultimate finishing process to form note bundles and packs of note bundles (in this case single-note numbering would not be required). 
     In all of the above instances, the entirely good sheets S 0  and the partially defective sheets S′ follow distinct routes and are numbered in separate numbering processes. This may create logistical problems in that the entirely good sheets S 0  and the partially defective sheets S′ have to be routed to different locations and handled differently and separately. 
     European Patent Publication EP 1 808 391 A1 discloses, with reference to FIGS. 7A-7E thereof, a sheet numbering process whereby sheets carrying a plurality of imprints that are arranged in a matrix of rows and columns are first inspected with a view to identify specific groups of partly defective sheets where defects are concentrating within single columns of imprints and sorting these sheets in dependence of the relevant column where the defects are located Once sorted, the relevant sheets are numbered by causing the relevant numbering and imprinting machine to omit numbering in the individual columns where one or more defects have been identified or by removing the corresponding numbering devices from the numbering and imprinting machine. 
     A considerable disadvantage of this known process resides in the fact that it requires a complex sorting operation prior to the numbering operation. A further disadvantage of this known process resides in the fact that imprints that are not considered to be defective but that happen to be located within the same column where a defect is detected are not at all numbered, thus generating unnecessary waste. Furthermore, the process of EP 1 808 391 A1 requires individual and separate numbering of each specific group of partly defective sheets in dependence of the sorting of the sheets. This numbering is carried out on a separate numbering and imprinting machine which is pre-set in dependence of the relevant group of partly defective sheets to be numbered (namely by turning off or removing the relevant numbering devices) prior to undertaking the numbering operation. 
     There is therefore a need for an improved process of numbering sheets, and a sheet-processing machine enabling the same, which simplifies logistics as far as numbering of the sheets is concerned. There is furthermore a need for such an improved process of numbering sheets (and related sheet-processing machine) that is more flexible than the known solutions. 
     SUMMARY OF THE INVENTION 
     A general aim of the invention is therefore to provide an improved process of numbering sheets, and a sheet-processing machine enabling the same. 
     A further aim of the invention is to provide such a process of numbering sheets and related sheet-processing machine that allow a more efficient and centralized handling of the numbering of the sheets, especially of entirely good sheets as well as of partially defective sheets. 
     Another aim of the invention is to provide such a solution that allows more flexibility in the numbering schemes that are to be carried out on the sheets. 
     These aims are achieved thanks to the sheet numbering process and sheet-processing machine as defined in the claims. 
     Further advantageous embodiments of the invention form the subject-matter of the dependent claims and are discussed below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will appear more clearly from reading the following detailed description of embodiments of the invention which are presented solely by way of non-restrictive examples and illustrated by the attached drawings in which: 
         FIG. 1  is a flow chart illustrating a known process for producing notes of securities (such as banknotes) wherein a small part of the production is subjected to single-note processing; 
         FIG. 2  is a schematic illustration of a (yet unnumbered) sheet as used for the production of securities (such as banknotes), which sheet carries a plurality of imprints that are arranged in a matrix of (e.g. eight) rows and (e.g. five) columns; 
         FIG. 3  is a flow chart illustrating an embodiment of the invention as applied in the context of the numbering of sheets which are subjected to full-sheet inspection prior to numbering of the sheets; 
         FIG. 4  is a schematic illustration of an entirely good sheet (i.e. a sheet whose imprints meet quality requirements) which is numbered according to a first numbering scheme; 
         FIG. 5  is a schematic illustration of a partially defective sheet (i.e. a sheet carrying a mixture of good imprints and defective imprints) which is numbered according to first and second variants of a second numbering scheme, different from the first numbering scheme; 
         FIG. 6  is a schematic illustration of a partially defective sheet (i.e. a sheet carrying a mixture of good imprints and defective imprints) which is numbered according to another variant of a second numbering scheme, different from the first numbering scheme; 
         FIG. 7  is a schematic block diagram illustrating the functional components of a sheet-processing machine according to a preferred embodiment of the invention; 
         FIG. 8  is a flow chart illustrating an embodiment of the invention as applied in the context of the numbering of sheets for the purpose of carrying out statistical (or sample) process control of the numbered sheets; 
         FIG. 9  is a schematic illustration of a sheet which is numbered according to a numbering scheme, which is different from the first numbering scheme, for the purpose of carrying out statistical process control of the numbered sheets; and 
         FIG. 10  is an illustrative example of a sheet-processing machine combining the functionalities of final inspection and sheet numbering. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     The present invention will be described in the particular context of the production of banknotes. As already mentioned, banknotes are typically produced in the form of sheets each carrying a plurality of imprints which are arranged in a matrix of rows and columns.  FIG. 2  schematically illustrates a sheet S as used for the production of banknotes, which sheet S bears an effective printed area  100  consisting of multiple (banknote) imprints P which are arranged in a regular pattern of rows and columns. The sheet S exhibits margin portions next to the effective printed area  100 , which margin portions are typically exploited for the purpose of printing control patterns or the like. 
       FIG. 3  is a flow chart illustrating an embodiment of the invention as applied in the context of the numbering of the sheets S, which sheets are subjected to full-sheet inspection prior to numbering of the sheets. 
     Step  601  in  FIG. 3  denotes the various printing phases which are typically carried out during the production of securities (like step  501  of  FIG. 1 ). As a result of the various printing phases of step  601 , successive sheets S are produced, which sheets are subjected to a final quality check as schematised by step  602  in  FIG. 3 . Once again, three categories of sheets in terms of quality requirements are generated as a result of this full-sheet quality inspection, namely (i) entirely good sheets S 0  (i.e. sheets carrying exclusive good imprints), (ii) partially defective sheets S′ (i.e. sheets carrying a mixture of good and defective imprints), and (iii) entirely defective sheets S X  carrying only defective imprints. From this point onward, the three categories of sheets follow distinct routes. 
     More precisely, the entirely good sheets S 0  are subjected at step  603  to a full-sheet numbering process according to a first numbering scheme, designated by reference N 1 , and then sorted to a (first) sheet delivery pile unit at step  604 . The partially defective sheets S′, on the other hand, are subjected at step  605  to a partial-sheet numbering process according to a second numbering scheme, designated by reference N 2 , which is different from the first numbering scheme N 1 , and then sorted to a (second) sheet delivery pile unit at step  606 . The entirely defective sheets S X , which exclusively carry defective imprints, are not numbered and sorted to a (third) sheet delivery pile unit at step  607 . 
     It is to be appreciated that full-sheet numbering at step  603  and partial-sheet numbering at step  605  are performed, according to the invention, at the same numbering location (i.e. on the same sheet-processing machine) without interruption of the numbering process. That is, numbering of the individual sheets S is selectively commutable between a first numbering scheme and at least a second numbering scheme, different from the first numbering scheme, without interruption of the numbering process. This will now be explained in greater detail with reference to  FIGS. 4 to 6  hereof. 
       FIG. 4  schematically illustrates an entirely good sheet S 0 , i.e. an inspected sheet which has been classified, as a result of the full-sheet inspection, as carrying only good imprints, which are designated by reference P 0  in  FIG. 4  for the sake of distinction. As a result of the full-sheet numbering step  603  of  FIG. 3 , each imprint P 0  has been provided with a unique serial number, which is generically identified by reference SN 1 , which unique serial number SN 1  is provided in dependence of the selected first numbering scheme N 1 . 
     This first numbering scheme N 1  can basically be any suitable numbering scheme. The first numbering scheme N 1  is however preferably a so-called non-collating numbering scheme, i.e. a particular numbering scheme that allows continued and uninterrupted finishing of consecutively-numbered documents. Such a non-collating numbering scheme is disclosed in International Patent Publication No. WO 2004/016433 A1, which is incorporated herein by reference in its entirety, and will not be described in great detail here. It suffices to understand that the sheets are numbered in successive runs of e.g. hundred sheets each and in such a way that each run of hundred sheets yields a corresponding number of consecutively-numbered documents. 
     Let us assume for the sake of illustration that one wishes to produce one million numbered notes with serial numbers ranging from “AA 000 000 000” to “AA 000 999 999”. As disclosed in International Patent Publication No. WO 2004/016433 A1, numbering can conveniently be carried out downwards from e.g. the starting number “AA 000 999 999” and by appropriately numbering the sheets as follows. One will assume that each sheet carries forty imprints that are arranged in a matrix of eight rows and five columns as for instance illustrated in  FIG. 4 . The first sheet to be numbered (i.e. the first sheet of the first run of hundred sheets) would be numbered in accordance with the following table (1) where each position in the table corresponds to the relevant imprint position on the sheet: 
     
       
         
           
               
             
               
                 TABLE (1) 
               
               
                   
               
               
                 (serial numbers SN1 of first sheet of first run of hundred sheets) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 AA 000 999 999 
                 AA 000 999 199 
                 AA 000 998 399 
                 AA 000 997 599 
                 AA 000 996 799 
               
               
                 AA 000 999 899 
                 AA 000 999 099 
                 AA 000 998 299 
                 AA 000 997 499 
                 AA 000 996 699 
               
               
                 AA 000 999 799 
                 AA 000 998 999 
                 AA 000 998 199 
                 AA 000 997 399 
                 AA 000 996 599 
               
               
                 AA 000 999 699 
                 AA 000 998 899 
                 AA 000 998 099 
                 AA 000 997 299 
                 AA 000 996 499 
               
               
                 AA 000 999 599 
                 AA 000 998 799 
                 AA 000 997 999 
                 AA 000 997 199 
                 AA 000 996 399 
               
               
                 AA 000 999 499 
                 AA 000 998 699 
                 AA 000 997 899 
                 AA 000 997 099 
                 AA 000 996 299 
               
               
                 AA 000 999 399 
                 AA 000 998 599 
                 AA 000 997 799 
                 AA 000 996 999 
                 AA 000 996 199 
               
               
                 AA 000 999 299 
                 AA 000 998 499 
                 AA 000 997 699 
                 AA 000 996 899 
                 AA 000 996 099 
               
               
                   
               
            
           
         
       
     
     In accordance with International Patent Publication No. WO 2004/016433 A1 the subsequent ninety-nine sheets of the same run of hundred sheets are numbered in decreasing sequence, thereby leading to the last sheet of the first run (i.e. the hundredth sheet) being numbered in accordance with table (2) hereafter: 
     
       
         
           
               
             
               
                 TABLE (2) 
               
               
                   
               
               
                 (serial numbers SN1 of last sheet of first run of hundred sheets) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 AA 000 999 900 
                 AA 000 999 100 
                 AA 000 998 300 
                 AA 000 997 500 
                 AA 000 996 700 
               
               
                 AA 000 999 800 
                 AA 000 999 000 
                 AA 000 998 200 
                 AA 000 997 400 
                 AA 000 996 600 
               
               
                 AA 000 999 700 
                 AA 000 998 900 
                 AA 000 998 100 
                 AA 000 997 300 
                 AA 000 996 500 
               
               
                 AA 000 999 600 
                 AA 000 998 800 
                 AA 000 998 000 
                 AA 000 997 200 
                 AA 000 996 400 
               
               
                 AA 000 999 500 
                 AA 000 998 700 
                 AA 000 997 900 
                 AA 000 997 100 
                 AA 000 996 300 
               
               
                 AA 000 999 400 
                 AA 000 998 600 
                 AA 000 997 800 
                 AA 000 997 000 
                 AA 000 996 200 
               
               
                 AA 000 999 300 
                 AA 000 998 500 
                 AA 000 997 700 
                 AA 000 996 900 
                 AA 000 996 100 
               
               
                 AA 000 999 200 
                 AA 000 998 400 
                 AA 000 997 600 
                 AA 000 996 800 
                 AA 000 996 000 
               
               
                   
               
            
           
         
       
     
     Stacking of the thus-numbered hundred sheets of the first run and row-wise and column-wise cutting of the stack thereby allows to produce an uninterrupted sequence of four thousand (forty times hundred) individual notes whose serial numbers form a consecutive sequence of serial numbers ranging from “AA 000 999 999” to “AA 000 996 000”. 
     In accordance with the teaching of International Patent Publication No. WO 2004/016433 A1 the first sheet of the next (i.e. second) run of hundred sheets is numbered with new serial numbers as starting numbers, namely in accordance with table (3) hereafter: 
     
       
         
           
               
             
               
                 TABLE (3) 
               
               
                   
               
               
                 (serial numbers SN1 of first sheet of second run of hundred sheets) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 AA 000 995 999 
                 AA 000 995 199 
                 AA 000 994 399 
                 AA 000 993 599 
                 AA 000 992 799 
               
               
                 AA 000 995 899 
                 AA 000 995 099 
                 AA 000 994 299 
                 AA 000 993 499 
                 AA 000 992 699 
               
               
                 AA 000 995 799 
                 AA 000 994 999 
                 AA 000 994 199 
                 AA 000 993 399 
                 AA 000 992 599 
               
               
                 AA 000 995 699 
                 AA 000 994 899 
                 AA 000 994 099 
                 AA 000 993 299 
                 AA 000 992 499 
               
               
                 AA 000 995 599 
                 AA 000 994 799 
                 AA 000 993 999 
                 AA 000 993 199 
                 AA 000 992 399 
               
               
                 AA 000 995 499 
                 AA 000 994 699 
                 AA 000 993 899 
                 AA 000 993 099 
                 AA 000 992 299 
               
               
                 AA 000 995 399 
                 AA 000 994 599 
                 AA 000 993 799 
                 AA 000 992 999 
                 AA 000 992 199 
               
               
                 AA 000 995 299 
                 AA 000 994 499 
                 AA 000 993 699 
                 AA 000 992 899 
                 AA 000 992 099 
               
               
                   
               
            
           
         
       
     
     The subsequent ninety-nine sheets of the second run of hundred sheets are then likewise numbered in decreasing sequence, thereby leading to the production of another set of four thousand individual notes whose serial numbers form a consecutive sequence of serial numbers ranging this time from “AA 000 995 999” to “AA 000 992 000”, i.e. a set of notes directly following the numerical sequence of the previous set of four thousand notes mentioned above. 
     Production of one million notes according to the above-mentioned numbering scheme therefore requires two-hundred and fifty runs of hundred sheets, with the last sheet of the 250 th  run bearing the last series of serial numbers in accordance with table (4) hereafter: 
     
       
         
           
               
             
               
                 TABLE (4) 
               
               
                   
               
               
                 (serial numbers SN1 of last sheet of 250 th  run of hundred sheets) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 AA 000 003 900 
                 AA 000 003 100 
                 AA 000 002 300 
                 AA 000 001 500 
                 AA 000 000 700 
               
               
                 AA 000 003 800 
                 AA 000 003 000 
                 AA 000 002 200 
                 AA 000 001 400 
                 AA 000 000 600 
               
               
                 AA 000 003 700 
                 AA 000 002 900 
                 AA 000 002 100 
                 AA 000 001 300 
                 AA 000 000 500 
               
               
                 AA 000 003 600 
                 AA 000 002 800 
                 AA 000 002 000 
                 AA 000 001 200 
                 AA 000 000 400 
               
               
                 AA 000 003 500 
                 AA 000 002 700 
                 AA 000 001 900 
                 AA 000 001 100 
                 AA 000 000 300 
               
               
                 AA 000 003 400 
                 AA 000 002 600 
                 AA 000 001 800 
                 AA 000 001 000 
                 AA 000 000 200 
               
               
                 AA 000 003 300 
                 AA 000 002 500 
                 AA 000 001 700 
                 AA 000 000 900 
                 AA 000 000 100 
               
               
                 AA 000 003 200 
                 AA 000 002 400 
                 AA 000 001 600 
                 AA 000 000 800 
                 AA 000 000 000 
               
               
                   
               
            
           
         
       
     
     In contrast to the entirely good sheets S 0  which can conveniently be numbered according to the above non-collating numbering scheme, the partially defective sheets S′ cannot be numbered in the same way due to the presence of defective prints which would break the numbering sequence. One solution is therefore to number the partially defective sheets S′ by skipping the defective imprint(s) and adjusting the numbering sequence accordingly. 
     Let us look at  FIG. 5  which is a schematic illustration of a partially defective sheet S′ which carries defective prints, designated by reference P X  for the sake of distinction, at three different locations, namely on the third row of the second column and the sixth and seventh rows of the fifth column (as schematically illustrated by a corresponding cross in  FIG. 5 ). In this example, all other imprints, which are considered to be good imprints P 0 , are each provided with a unique serial number, which is generically identified by reference SN 2  in this other example. 
     The location of the defective imprints P X  can be indicated by a corresponding cancellation mark provided directly on the relevant defective imprint(s) P X  or appropriately identifying the location(s) of the relevant defective imprint(s) P X . Various solutions are possible, including a specific cancellation mark X 1  provided on the relevant defective imprint (for instance by means of a dedicated marking system) or, more advantageously, a cancellation mark X 2  provided by means of the relevant numbering box (in which case the cancellation mark is located at the same location as the serial numbers SN 2 ). Other solutions are possible, such as cancellation marks X 3 , X 4  which are provided outside of the effective printed area  100  of the sheet S′. 
     Numbering of the partially defective sheet S′ of  FIG. 5  can for instance be carried out as indicated by the following table (5), it being assumed that we are looking at the first sheet of a series of partially defective sheets S′: 
     
       
         
           
               
             
               
                 TABLE (5) 
               
               
                   
               
               
                 (serial numbers SN2 of first partially defective sheet - first variant) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 ZZ 000 999 999 
                 ZZ 000 999 199 
                 ZZ 000 998 399 
                 ZZ 000 997 599 
                 ZZ 000 996 799 
               
               
                 ZZ 000 999 899 
                 ZZ 000 999 099 
                 ZZ 000 998 299 
                 ZZ 000 997 499 
                 ZZ 000 996 699 
               
               
                 ZZ 000 999 799 
                 DEFECT 
                 ZZ 000 998 199 
                 ZZ 000 997 399 
                 ZZ 000 996 599 
               
               
                 ZZ 000 999 699 
                 ZZ 000 998 899 
                 ZZ 000 998 099 
                 ZZ 000 997 299 
                 ZZ 000 996 499 
               
               
                 ZZ 000 999 599 
                 ZZ 000 998 799 
                 ZZ 000 997 999 
                 ZZ 000 997 199 
                 ZZ 000 996 399 
               
               
                 ZZ 000 999 499 
                 ZZ 000 998 699 
                 ZZ 000 997 899 
                 ZZ 000 997 099 
                 DEFECT 
               
               
                 ZZ 000 999 399 
                 ZZ 000 998 599 
                 ZZ 000 997 799 
                 ZZ 000 996 999 
                 DEFECT 
               
               
                 ZZ 000 999 299 
                 ZZ 000 998 499 
                 ZZ 000 997 699 
                 ZZ 000 996 899 
                 ZZ 000 996 099 
               
               
                   
               
            
           
         
       
     
     Let us assume that the next partially defective sheet S′ to be detected as a result of the full-sheet inspection includes a single defective imprint P X  located on the fifth row of the third column of the sheet, one could contemplate to number this second partially defective sheet S′ in accordance with table (6) hereafter: 
     
       
         
           
               
             
               
                 TABLE (6) 
               
               
                   
               
               
                 (serial numbers SN2 of second partially defective sheet - first variant) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 ZZ 000 999 998 
                 ZZ 000 999 198 
                 ZZ 000 998 398 
                 ZZ 000 997 598 
                 ZZ 000 996 798 
               
               
                 ZZ 000 999 898 
                 ZZ 000 999 098 
                 ZZ 000 998 298 
                 ZZ 000 997 498 
                 ZZ 000 996 698 
               
               
                 ZZ 000 999 798 
                 ZZ 000 998 999 
                 ZZ 000 998 198 
                 ZZ 000 997 398 
                 ZZ 000 996 598 
               
               
                 ZZ 000 999 698 
                 ZZ 000 998 898 
                 ZZ 000 998 098 
                 ZZ 000 997 298 
                 ZZ 000 996 498 
               
               
                 ZZ 000 999 598 
                 ZZ 000 998 798 
                 DEFECT 
                 ZZ 000 997 198 
                 ZZ 000 996 398 
               
               
                 ZZ 000 999 498 
                 ZZ 000 998 698 
                 ZZ 000 997 898 
                 ZZ 000 997 098 
                 ZZ 000 996 299 
               
               
                 ZZ 000 999 398 
                 ZZ 000 998 598 
                 ZZ 000 997 798 
                 ZZ 000 996 998 
                 ZZ 000 996 199 
               
               
                 ZZ 000 999 298 
                 ZZ 000 998 498 
                 ZZ 000 997 698 
                 ZZ 000 996 898 
                 ZZ 000 996 098 
               
               
                   
               
            
           
         
       
     
     According to this first variant of the second numbering scheme, one shall therefore understand that consecutive numbering sequences are formed in each imprint location, the defective imprints P X  being skipped on a sheet by sheet basis. 
     According to another variant, the second numbering scheme may provide for the skipping of the defective imprints P X  within each sheet as indicated by the following table (7) 
     
       
         
           
               
             
               
                 TABLE (7) 
               
               
                   
               
               
                 (serial numbers SN2 of first partially defective sheet - second variant) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 ZZ 000 999 999 
                 ZZ 000 999 991 
                 ZZ 000 999 984 
                 ZZ 000 999 976 
                 ZZ 000 999 968 
               
               
                 ZZ 000 999 998 
                 ZZ 000 999 990 
                 ZZ 000 999 983 
                 ZZ 000 999 975 
                 ZZ 000 999 967 
               
               
                 ZZ 000 999 997 
                 DEFECT 
                 ZZ 000 999 982 
                 ZZ 000 999 974 
                 ZZ 000 999 966 
               
               
                 ZZ 000 999 996 
                 ZZ 000 999 989 
                 ZZ 000 999 981 
                 ZZ 000 999 973 
                 ZZ 000 999 965 
               
               
                 ZZ 000 999 995 
                 ZZ 000 999 988 
                 ZZ 000 999 980 
                 ZZ 000 999 972 
                 ZZ 000 999 964 
               
               
                 ZZ 000 999 994 
                 ZZ 000 999 987 
                 ZZ 000 999 979 
                 ZZ 000 999 971 
                 DEFECT 
               
               
                 ZZ 000 999 993 
                 ZZ 000 999 986 
                 ZZ 000 999 978 
                 ZZ 000 999 970 
                 DEFECT 
               
               
                 ZZ 000 999 992 
                 ZZ 000 999 985 
                 ZZ 000 999 977 
                 ZZ 000 999 969 
                 ZZ 000 999 963 
               
               
                   
               
            
           
         
       
     
     Assuming once again, for the sake of illustration that the next partially defective sheet S′ to be detected as a result of the full-sheet inspection includes a single defective imprint P X  located on the fifth row of the third column of the sheet, one could contemplate to number this second partially defective sheet S′ in accordance with table (8) hereafter: 
     
       
         
           
               
             
               
                 TABLE (8) 
               
               
                   
               
               
                 (serial numbers SN2 of second partially defective sheet - first variant) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 ZZ 000 999 962 
                 ZZ 000 999 954 
                 ZZ 000 999 946 
                 ZZ 000 999 939 
                 ZZ 000 999 931 
               
               
                 ZZ 000 999 961 
                 ZZ 000 999 953 
                 ZZ 000 999 945 
                 ZZ 000 999 938 
                 ZZ 000 999 930 
               
               
                 ZZ 000 999 960 
                 ZZ 000 999 952 
                 ZZ 000 999 944 
                 ZZ 000 999 937 
                 ZZ 000 999 929 
               
               
                 ZZ 000 999 959 
                 ZZ 000 999 951 
                 ZZ 000 999 943 
                 ZZ 000 999 936 
                 ZZ 000 999 928 
               
               
                 ZZ 000 999 958 
                 ZZ 000 999 950 
                 DEFECT 
                 ZZ 000 999 935 
                 ZZ 000 999 927 
               
               
                 ZZ 000 999 957 
                 ZZ 000 999 949 
                 ZZ 000 999 942 
                 ZZ 000 999 934 
                 ZZ 000 999 926 
               
               
                 ZZ 000 999 956 
                 ZZ 000 999 948 
                 ZZ 000 999 941 
                 ZZ 000 999 933 
                 ZZ 000 999 925 
               
               
                 ZZ 000 999 955 
                 ZZ 000 999 947 
                 ZZ 000 999 940 
                 ZZ 000 999 932 
                 ZZ 000 999 924 
               
               
                   
               
            
           
         
       
     
     Yet another possibility is to skip the serial number(s) of the defective imprint(s) P X  altogether as schematically illustrated by  FIG. 6 . This means that rather than adjusting the numbering sequence in dependence of the presence of defective imprints P X , the corresponding serial numbers, which are generically identified by reference SNx, are simply discarded, while the good imprints are provided with a corresponding serial number, which is generically identified by reference SN 2 ′ in  FIG. 6 . The serial numbers may accordingly be provided in accordance with the following table (9): 
     
       
         
           
               
             
               
                 TABLE (9) 
               
               
                   
               
               
                 (serial numbers SN2′ of first partially defective sheet) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 YY 000 999 999 
                 YY 000 999 199 
                 YY 000 998 399 
                 YY 000 997 599 
                 YY 000 996 799 
               
               
                 YY 000 999 899 
                 YY 000 999 099 
                 YY 000 998 299 
                 YY 000 997 499 
                 YY 000 996 699 
               
               
                 YY 000 999 799 
                 DEFECT 
                 YY 000 998 199 
                 YY 000 997 399 
                 YY 000 996 599 
               
               
                 YY 000 999 699 
                 YY 000 998 899 
                 YY 000 998 099 
                 YY 000 997 299 
                 YY 000 996 499 
               
               
                 YY 000 999 599 
                 YY 000 998 799 
                 YY 000 997 999 
                 YY 000 997 199 
                 YY 000 996 399 
               
               
                 YY 000 999 499 
                 YY 000 998 699 
                 YY 000 997 899 
                 YY 000 997 099 
                 DEFECT 
               
               
                 YY 000 999 399 
                 YY 000 998 599 
                 YY 000 997 799 
                 YY 000 996 999 
                 DEFECT 
               
               
                 YY 000 999 299 
                 YY 000 998 499 
                 YY 000 997 699 
                 YY 000 996 899 
                 YY 000 996 099 
               
               
                   
               
            
           
         
       
     
     In the above example, one should therefore understand that serial numbers “YY 000 998 999”, “YY 000 996 299” and “YY 000 996 199” corresponding to the defective imprints P X  are discarded serial numbers (SNx). 
     Assuming once again, for the sake of illustration that the next partially defective sheet S′ to be detected as a result of the full-sheet inspection includes a single defective imprint P X  located on the fifth row of the third column of the sheet, one could contemplate to number this second partially defective sheet S′ in accordance with table (10) hereafter: 
     
       
         
           
               
             
               
                 TABLE (10) 
               
               
                   
               
               
                 (serial numbers SN2 of second partially defective sheet - first variant) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 YY 000 999 998 
                 YY 000 999 198 
                 YY 000 998 398 
                 YY 000 997 598 
                 YY 000 996 798 
               
               
                 YY 000 999 898 
                 YY 000 999 098 
                 YY 000 998 298 
                 YY 000 997 498 
                 YY 000 996 698 
               
               
                 YY 000 999 798 
                 YY 000 998 998 
                 YY 000 998 198 
                 YY 000 997 398 
                 YY 000 996 598 
               
               
                 YY 000 999 698 
                 YY 000 998 898 
                 YY 000 998 098 
                 YY 000 997 298 
                 YY 000 996 498 
               
               
                 YY 000 999 598 
                 YY 000 998 798 
                 DEFECT 
                 YY 000 997 198 
                 YY 000 996 398 
               
               
                 YY 000 999 498 
                 YY 000 998 698 
                 YY 000 997 898 
                 YY 000 997 098 
                 YY 000 996 298 
               
               
                 YY 000 999 398 
                 YY 000 998 598 
                 YY 000 997 798 
                 YY 000 996 998 
                 YY 000 996 198 
               
               
                 YY 000 999 298 
                 YY 000 998 498 
                 YY 000 997 698 
                 YY 000 996 898 
                 YY 000 996 098 
               
               
                   
               
            
           
         
       
     
     In this case, serial number “YY 000 997 998” corresponding to the defective imprint P X  would likewise be a discarded serial number (SNx). 
       FIG. 7  is a schematic block diagram illustrating the functional components of a sheet-processing machine, generally designated by reference numeral  1 , according to a preferred embodiment of the invention, by means of which the above embodiments of the numbering process can be carried out. A concrete example of a suitable sheet-processing machine is shown in  FIG. 10 . 
     As illustrated in  FIG. 7 , inspection of the individual sheets S requires a suitable sheet inspection system which is schematically identified by the functional block designated by reference numeral  10 . This sheet inspection system  10  provides feedback as regards the relevant sheet inspection results to a control unit  50 , which control unit  50  in turns controls operation of a suitable sheet numbering system  20 . As is typical in the art, the sheet numbering system  20  includes at least one set (typically two sets) of numbering boxes in a number corresponding to the number of imprints to be numbered (i.e. forty numbering boxes per set). Banknotes are typically provided with two identical serial numbers provided at different locations of the banknote surface, which requires two sets of numbering boxes. In some cases, one of the serial numbers is oriented horizontally, while the other serial number is oriented vertically, which requires one set of so-called horizontal numbering boxes (as identified by reference numeral  21  in  FIG. 7 ) and one set of so-called vertical numbering boxes (as identified by reference numeral  22  in  FIG. 7 ). Two sets of horizontal or, as the case may be, vertical numbering boxes are also possible. 
     In the context of the present invention, the control unit  50  is designed to selectively commute operation of the numbering system  20  between a first numbering scheme (such as the numbering scheme N 1  discussed with reference to tables (1) to (4) and  FIG. 4  hereof) and at least a second numbering scheme (such as the numbering scheme N 2  or N 2 ′ discussed with reference to tables (5) to (10) and  FIGS. 5, 6  hereof). This commutation is performed dynamically, without interruption of the numbering process, in dependence of the sheet inspection results provided by the sheet inspection system  10 . In other words, in this particular example, the control unit  50  performs selection of the appropriate numbering scheme depending on whether the inspected sheet is an entirely good sheet or a partially defective sheet. 
     Advantageously, the control unit  50  further controls a sheet delivery  30  of the sheet-processing machine  1  so as to suitably sort the sheets in corresponding sheet delivery pile units ( 31 ,  32 ,  33 , . . . ) as generally illustrated in the flow chart of  FIG. 3 . 
     As a further refinement, the sheet-processing machine  1  may further comprise a number inspection system  60  adapted to inspect a quality of the serial numbers (SN 1 , SN 2 , SN 2 ′, . . . ) provided on the imprints. This number inspection system  60  could consist of a convenient OCR (Optical Character Recognition) system. However, considering that the serial numbers provided on the imprints are dependent on the relevant numbering scheme (N 1 , N 2 , N 2 ′, . . . ) being carried out by the sheet numbering system  20  (and therefore dependent on the inspection results), it is much more convenient to ensure that inspection of the quality of the serial numbers is carried out in dependence of the operation of the numbering system  20 . That is, the numbering system  20  preferably provides information to the number inspection system  60  as to the serial numbers which are expected to be printed onto the imprints and the number inspection system  60  checks that the actual printed serial numbers correspond to the expected numbers, in addition to other quality measurements such as ink smearing or over-/under-inking. Any quality deviation identified by the number inspection system  60  is fed back to the control unit  50  for appropriate sorting of the numbered sheet. 
       FIG. 10  schematically illustrates an example of a sheet-processing machine combining the functionalities of final inspection and sheet numbering. The illustrated machine is similar to the sheet-processing machines described in International Patent Publications Nos. WO 01/85457 A1, WO 2005/008605 A1 and WO 2005/008606 A1, which are all incorporated herein by reference in their entirety, with the difference that these machines are only designed to number the sheets according to a single predefined numbering scheme. 
     In the illustrated example, reference numeral  2  designates a sheet-feeder which feeds individual sheets S in succession to an inspection system  10 . This inspection system  10  includes in this example three cameras  11 ,  12 ,  13 , one (e.g.  11 ) being designed to advantageously perform transmissive inspection of the sheets, while the other two (e.g.  12 ,  13 ) are designed to respectively perform reflective inspection of the recto and verso sides of the sheets. Appropriate transport drums or cylinders  15  are provided in order to suitably transport the sheets past and in front of the three cameras  11 ,  12 ,  13 . 
     Once inspected, the sheets are transferred via a pair of transfer cylinders or drums (not referenced) to the impression cylinder  25  of a numbering/printing group  3  of the sheet-processing machine  1 . This numbering/printing group  3  includes the aforementioned sheet numbering system  20 , which here takes the form of two numbering cylinder units each carrying a corresponding set of numbering boxes  21 , resp.  22  which are inked by associated inking devices (not shown in  FIG. 10 ). 
     The number inspection system  60  is embodied in this example as an additional camera system that looks at the printed side of the numbered sheets, while those sheets are still supported by the impression cylinder  25 . 
     A chain conveyor system  4  comprising spaced-apart gripper bars (not shown) ultimately takes the numbered sheets away from the impression cylinder  25  and transports these to the sheet delivery  30 , where the sheets are appropriately sorted to corresponding sheet delivery pile units  31 ,  32 ,  33 ,  34 . In this example, four sheet delivery pile units  31 ,  32 ,  33 ,  34  are provided. The first sheet delivery pile unit  31  can suitably be used in production for the delivery of entirely good sheets S 0  which are numbered according to the aforementioned first numbering scheme N 1 . The second sheet delivery pile unit  32  can be used for the delivery of the partially defective sheets S′ which are numbered according to the aforementioned second numbering scheme N 2  or N 2 ′. The third sheet delivery pile unit  33 , on the other hand, can be used for the delivery of entirely defective sheets S X  which are not numbered (as well as for the delivery of any test sheets). This is obviously purely illustrative and more than one sheet delivery pile unit may be assigned to one and a same sheet type. For instance, the first and second sheet delivery pile units  31 ,  32  could be used as production pile units, in an alternate manner, to receive the entirely good sheets S 0  numbered in accordance with the first numbering scheme N 1 , while the third sheet delivery pile unit  33  may be assigned to the partially defective sheets S′ and the fourth delivery pile unit  34  used as reject pile unit for the entirely defective sheets S X . 
     Another embodiment of the invention will now be discussed in reference to  FIGS. 8 and 9 . This other embodiment provides for the ability to carry out so-called statistical (or sample) process control (SPC) of numbered sheets. In a manner similar to the previous embodiments, numbering of the individual sheets S is selectively commutable between a first numbering scheme and at least a second numbering scheme, different from the first numbering scheme, without interruption of the numbering process. While the first numbering scheme can be the same as the aforementioned numbering scheme N 1 , the second numbering scheme consists in this example of a special numbering scheme that appropriately identifies numbered sheets that will be the subject of the statistical process control, i.e. sheets that will be sorted out in a special event pile unit (or SPC pile unit) so as to allow an operator to take the sheets out and pass them to a quality control department for more detailed inspection. 
     In essence, as schematically illustrated by the flow chart of  FIG. 8 , this process implies the ability to selectively run a separate special numbering scheme on the sheets. Steps  610  and  611  in  FIG. 8  could respectively correspond to steps  603  and  604  of  FIG. 3 , while steps  620 ,  621  correspond to numbering of the sheets according to the special SPC numbering scheme and subsequent sorting of the thus-numbered sheets to a special event pile unit (such as e.g. sheet delivery pile unit  34  in  FIG. 10 ). 
     The SPC numbering scheme could be any appropriate numbering scheme which would be differentiable from the numbering scheme used for actual production. As schematically depicted by  FIG. 9 , this could consists in a numbering scheme having a specific prefix identifier, such as “SP” in the illustrated example. 
     It is preferable to run the special SPC numbering scheme exclusively on entirely good sheets, which sheets are identified by reference S* in  FIG. 9  for the sake of distinction, in which case full-sheet quality inspection is carried out at step  602 . In other words, the special SPC numbering scheme could perfectly be implemented as an additional functionality of the numbering process depicted in  FIG. 3 , i.e. by running the special SPC numbering scheme (steps  620 ,  621  of  FIG. 8 ) on the entirely good sheets S 0 , in parallel to steps  603  and  604  of  FIG. 3 . 
     The special SPC numbering scheme may alternately run on any type of sheets, even partially defective sheets, but it is more sensible to perform such numbering scheme on entirely good sheets as these are intended to allow more detailed inspection by a quality control department. 
     In the context of this particular embodiment, full-sheet quality inspection (i.e. step  602  in  FIG. 8 ) is not essential and numbering could be carried out on the sheets S irrespective of their quality. It is therefore to be appreciated that step  602  in  FIG. 8  is optional in this particular context. 
     In the context of this embodiment, it is advantageous to run the special SPC numbering scheme on a periodic basis (for instance every thousand entirely good sheet) so as to perform a representative sampling of the entire production at regular intervals. 
     Once the detailed inspection has been carried out by the quality control department, the statistical process control sheet(s) S* can be returned to production or destroyed, if required. 
     It will be apparent that suitable numbering boxes should be used in order to enable the selective commutation between the various numbering schemes. In that respect, partly or, preferably, fully flexible numbering boxes, such as the partly or fully-motorized numbering boxes disclosed in International Patent Publication No. WO 2007/148288 A2 (which is incorporated herein by reference in its entirety), as sold by the Applicant under the product designation NBX®, are highly advantageous. 
     Various modifications and/or improvements may be made to the above-described embodiments without departing from the scope of the invention as defined by the annexed claims. For instance, in lieu of the partly or fully-motorized numbering boxes mentioned above, one could alternately make use of fully flexible numbering boxes as for instance disclosed in European Patent Publication No. EP 0 718 112 A1. 
     LIST OF REFERENCE NUMERALS USED THEREIN 
     
         
         S individual (printed) sheets 
           100  effective printed area of the sheets/matrix arrangement of rows and columns of imprints P 
           200  note bundle(s) (e.g. banknote bundle(s)) 
           210  pack(s) of note bundles  210   
         P imprints on effective printed area  100  of the sheets S 
         P 0  inspected imprints P meeting quality requirements/good imprints 
         P X  inspected imprints P not meeting quality requirements/defective imprints 
         S 0  inspected sheets S carrying only good imprints P 0 /entirely good sheets 
         S′ inspected sheets S carrying mixture of good imprints P 0  and defective imprints P X /partially defective sheets 
         S X  inspected sheets S carrying only defective imprints P X /entirely defective sheets 
         N 1  (first) numbering scheme 
         SN 1  serial numbers of (first) numbering scheme N 1   
         N 2  (second) numbering scheme 
         SN 2  serial numbers of (second) numbering scheme N 2   
         X 1  cancellation mark for defective imprint P X  (first example) 
         X 2  cancellation mark for defective imprint P X  (second example)/provided by means of corresponding numbering box 
         X 3  cancellation mark for defective imprint P X  outside of effective printed area  100  (first margin location) 
         X 4  cancellation mark for defective imprint P X  outside of effective printed area  100  (second margin location) 
         N 2 ′ (second) numbering scheme (alternative) 
         SN 2 ′ serial numbers of (second) numbering scheme N 2 ′ (alternative) 
         SNx discarded serial numbers of (second) numbering scheme N 2 ′ (alternative) 
         S* statistical (sample) process control (SPC) sheet 
         N* (second) numbering scheme/statistical (sample) process control (SPC) numbering scheme 
         SN* serial numbers of (second) numbering scheme N* 
           1  sheet-processing machine 
           2  sheet feeder 
           3  numbering/printing group 
           4  chain conveyor system with spaced-apart gripper bars 
           10  sheet inspection system 
           11  (first) inspection camera (e.g. for transmissive inspection) 
           12  (second) inspection camera (e.g. for reflective inspection of the recto side of the sheets S) 
           13  (third) inspection camera (e.g. for reflective inspection of the verso side of the sheets S) 
           15  (three) inspection drums or cylinders 
           20  sheet numbering system 
           21  (first set of) numbering boxes (e.g. horizontal numbering boxes) 
           22  (second set of) numbering boxes (e.g. vertical numbering boxes) 
           25  impression cylinder 
           30  sheet delivery station 
           31  (first) sheet delivery pile unit (e.g. production pile unit) 
           32  (second) sheet delivery pile unit (e.g. production pile unit) 
           33  (third) sheet delivery pile unit (e.g. reject pile unit) 
           34  (fourth) sheet delivery pile unit (e.g. statistical process control pile unit) 
           50  control unit 
           60  number inspection system