Patent Publication Number: US-2003226435-A1

Title: Slitter for slitting a wide sheet into narrow strips and a controller and a controlling method for the slitter

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] This invention relates to a method of controlling arrangements of slitting knives to change the slitting width in a slitter for slitting a wide sheet into a plurality of narrow strips by a plurality of slitting knives arranged at predetermined intervals, and more particularly to a method of controlling arrangements of such slitting knives which can easily provide an additional arrangement of the slitting knives. This invention also relates to a slitter and controller for the slitter which can easily meet the above requirement.  
       [0003] 2. Description of the Related Art  
       [0004] There has been known a slitter for slitting a wide sheet into a plurality of narrow strips by use of a plurality of slitting knives mounted on a shaft extending in a direction substantially normal to the direction in which the wide sheet is fed, as disclosed, for instance, in Japanese Unexamined Patent Publication Nos. 63(1988)-134193 and 3(1991)-245995.  
       [0005] In a slitter of this type, the slitting width can be changed by changing the arrangement of the slitting knives by moving the slitting knives along the shaft so that the spaces among the knives vary. Recently there has been proposed a slitter in which the arrangement of the slitting knives can be automatically changed and examples of systems for controlling the arrangement of the slitting knives are disclosed in the patent publications described above.  
       [0006] As disclosed in the patent publications, when the arrangement of the knives is automatically switched, generally the knives are directly moved from a position for a given slitting width to a position for another slitting width. For example, assuming that each slitting knife is set in positions a, b and c for respective slitting widths A, B and C, any change in slitting width can be dealt with by controlling the knife moving means to be able to move each knife from any one of the positions a, b and c to either of the other two positions.  
       [0007] As means for controlling the knife moving means, a controller storing therein six programs for moving each knife from position a to position b, from position a to position c, from position b to position c, from position b to position a, from position c to position a and from position c to position b, can be suitably employed.  
       [0008] However in such a system where each of the slitting knives is moved directly from one position to another using a selected one of a plurality of predetermined programs, there is a problem that it is difficult to provide an additional arrangement of the slitting knives.  
       [0009] That is, assuming that M sorts of slitting widths are required, programs for moving the slitting knives from M sorts of positions to other (M−1) sorts of positions are necessary, and accordingly M·(M−1) sets of programs are necessary in total. When one slitting width is to be added, (M+1)·M sets of programs become necessary and the number of programs to be created is (M+1)·M−M·(M−1) (=2M).  
       [0010] For example, in the case of a slitter for slitting photographic materials, the sorts of slitting widths sometimes number 40 and when one sort of slitting width is to be added, another 80 sets of programs for controlling the knife moving means must be created. Further when new programs are created, control actions based on the programs must be checked and the accuracy of each control action must be checked. Thus setting an additional knife arrangement has conventionally required a long time.  
       SUMMARY OF THE INVENTION  
       [0011] In view of the foregoing observations and description, an object of the present invention is to provide a method of controlling arrangements of slitting knives which can easily provide an additional arrangement of the slitting knives. It is also an object of the present invention to provide a slitter itself or a controller for the slitter which can easily provide an additional arrangement of the slitting knives.  
       [0012] That is, a controller according to the present invention is a controller for controlling slitting knife arrangements in a slitter for slitting a wide sheet into a plurality of narrow strips by use of a plurality of slitting knives mounted on one or more shafts each extending in a direction substantially normal to a direction in which the wide sheet is fed, comprising: input means for specifying a next slitting width and the number of slitting knives to be used next as input parameters; and arithmetic means which receives the next slitting width and the number of slitting knives to be used next from the input means, and operates to generate a series of signals for moving a plurality of slitting knives to respective positions that effect slitting with the next slitting width and the number of slitting knives to be used next by use of a fixed common program.  
       [0013] In the above controller according to the present invention, the series of signals may be such signals that move a plurality of slitting knives in such an order that movement of each of a plurality of slitting knives is not interfered by the others of a plurality of slitting knives.  
       [0014] Further, in the above controller according to the present invention, the fixed common program can be structured to generate the series of signals based on the next slitting width, the number of slitting knives to be used next, current positions of a plurality of slitting knives and the number of slitting knives currently used. In that case, the controller may further comprise memory for storing the current positions of a plurality of slitting knives and the number of slitting knives currently used, so that the arithmetic means can acquire the current positions of a plurality of slitting knives and the number of slitting knives currently used from the memory.  
       [0015] Similarly, a slitter according to the present invention is a slitter for slitting a wide sheet into a plurality of narrow strips comprising: a plurality of slitting knives mounted on one or more shafts each extending in a direction substantially normal to a direction in which the wide sheet is fed; input means for specifying a next slitting width and the number of slitting knives to be used next as input parameters; arithmetic means which receives the next slitting width and the number of slitting knives to be used next from the input means, and operates to generate a series of signals for moving a plurality of slitting knives to respective positions that effect slitting with the next slitting width and the number of slitting knives to be used next by use of a fixed common program; and knife moving means for moving each of a plurality of slitting knives in the manner specified by the series of signals.  
       [0016] Further, a controlling method according to the present invention is a method for controlling slitting knife arrangements in a slitter for slitting a wide sheet into a plurality of narrow strips by use of a plurality of slitting knives mounted on one or more shafts each extending in a direction substantially normal to a direction in which the wide sheet is fed, comprising the steps of: specifying a next slitting width and the number of slitting knives to be used next as input parameters; generating a series of signals for moving a plurality of slitting knives to respective positions that effect slitting with the next slitting width and the number of slitting knives to be used next by use of a fixed common program; and moving each of a plurality of slitting knives in the manner specified by the series of signals.  
       [0017] In accordance with the present invention, setting of an additional arrangement of the slitting knives is facilitated by executing a fixed common program for controlling the knife moving means in combination with the slitting operation.  
       [0018] That is, in accordance with the present invention, addition of one slitting knife arrangement to M sorts of arrangements can be realized by calculating M sets of position information and moving order information for moving the slitting knives from the positions for the new arrangement to the positions for the M sorts of arrangements, and M sets of position information and moving order information for moving the slitting knives from the positions for the M sorts of arrangements to the positions for the new arrangement. That is, the addition of one slitting knife arrangement to M sorts of arrangements can be realized by only calculating 2M sets of position information and moving order information without changing the program itself or adding new programs.  
       [0019] Calculation of 2M sets of position information and moving order information by use of a fixed common program is much easier than the creation of 2M sets of programs for moving the slitting knives. Thus, according to the present invention, setting of an additional arrangement of the slitting knives is facilitated.  
       [0020] Specifically, it takes about one day to add a slitting knife arrangement to forty sorts of arrangements in the conventional method. In contrast, according to the present invention, the time can be shortened to about one hour. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0021]FIG. 1 is a schematic side view showing an example of a slitter to which the method of the present invention is applied.  
     [0022]FIG. 2 is a schematic front view showing a part of the slitter.  
     [0023]FIG. 3 is a view for illustrating a procedure of switching arrangement of the slitting knives in accordance with an embodiment of the present invention.  
     [0024]FIG. 4 is a flow chart for illustrating initialization of the positions of the slitting knives.  
     [0025] FIGS.  5  to  8  are flow charts for illustrating the processing to obtain positions to which the respective slitting knives are to be moved and the order in which the slitting knives are moved, in accordance with an embodiment of the present invention.  
     [0026]FIG. 9 is a view for illustrating a procedure of switching arrangement of the slitting knives in accordance with an alternative embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0027] A method of controlling the arrangements of slitting knives will be described, hereinbelow. The method of the present invention is applied to, for instance, a slitter shown in FIGS. 1 and 2. In FIGS. 1 and 2, a slitter comprises a pair of pass rollers  1  and  5  around which a wide sheet H in a continuous length such as raw web of photographic paper is passed, a feeding means (not shown) for feeding the wide sheet H in the direction of arrow A in FIG. 1, upper and lower shafts  2 U and  2 L which extend substantially normal to the feeding direction of the wide sheet H respectively above and below thereof, a plurality of upper and lower knife holders  3 U and  3 L (e.g., seven each) respectively mounted on the upper and lower shafts  2 U and  2 L to be movable along the shafts, and a plurality of upper and lower knives  4 U and  4 L respectively mounted on the upper and lower knife holders  3 U and  3 L.  
     [0028] A lower knife moving mechanism  6 L is disposed below the lower shafts  2 L to be movable up and down in the direction of arrow B. The upper shaft  2 U is rotated by a rotating mechanism (not shown) in the direction of arrow D between a slitting position shown by the solid line in FIG. 1 and a retracted position shown by the broken line. An upper knife moving mechanism  6 U is disposed above the retracted position of the upper shaft  2 U to be movable up and down in the direction of arrow C.  
     [0029] The lower knife moving mechanism  6 L is fitted on a guide shaft  7 L, extending in parallel to the upper and lower shafts  2 U and  2 L, to be slidable along the guide shaft  7 L. The lower knife moving mechanism  6 L is in mesh with a threaded shaft  9 L and is slid back and forth along the guide shaft  7 L in response to rotation of a motor  8 L. Similarly the upper knife moving mechanism  6 U is fitted on a guide shaft  7 U, extending in parallel the upper and lower shafts  2 U and  2 L, to be slidable along the guide shaft  7 U and at the same time is in mesh with a threaded shaft  9 U and is slid back and forth along the guide shaft  7 U in response to rotation of a motor  8 U. In FIG. 2, the guide shafts  7 U and  7 L are omitted.  
     [0030] A holder detecting means  10 T for detecting the lower knife holder  3 L is mounted on the lower knife moving mechanism  6 L and a holder detecting means  10 U for detecting the upper knife holder  3 U is mounted on the upper knife moving mechanism  6 U. The holder detecting means  10 T and  10 U may comprise, for instance, a photoelectric tube, a contactless switch or a limit switch.  
     [0031] The upper knives  4 U are arranged at regular intervals on the upper shaft  2 U and the lower knives  4 L are disposed in contact with the corresponding upper knives  4 U in said slitting position. While the upper and lower shafts  4 U and  4 L are rotated to rotate the upper and lower knives  4 U and  4 L, the wide sheet H is fed between the upper and lower knives  4 U and  4 L, whereby the wide sheet H is slit into a plurality of narrow strips.  
     [0032] The slitting width of the wide sheet H or the widths of the strips are determined by the intervals between the cutters each formed by the upper and lower knives  4 U and  4 L. Accordingly by switching the arrangements of the cutters so that the intervals between the cutters change, the slitting widths can be changed. The arrangements of the cutters are basically switched in the following manner.  
     [0033] When the arrangements of the upper knives  4 U are switched, the upper shaft  2 U is rotated to the retracted position and then the motor  8 U is energized to rotate the threaded shaft  9 U, thereby moving the upper knife moving mechanism  6 U in the longitudinal direction of the threaded shaft  9 U. A control unit  90  which may comprise, for instance a microcomputer, controls the motor  8 U to control the movement of the upper knife moving mechanism  6 U. When the holder detecting means  10 U of the upper knife moving mechanism  6 U detects one of the upper knife holders  3 U, that is, when the upper knife moving mechanism  6 U comes to be aligned with one of the upper knife holders  3 U, the control unit  90  stops the motor  8 U.  
     [0034] Then the upper knife moving mechanism  6 U is moved to a predetermined position close to the upper shaft  2 U and is brought into engagement with the upper knife holder  3 U. Then the upper knife moving mechanism  6 U releases the upper knife holder  3 U from the upper shaft  2 U and the control unit  90  drives the motor  8 U to move the upper holder  3 U along the upper shaft to a predetermined position by way of the upper knife moving mechanism  6 U. Thereafter, the upper knife moving mechanism  6 U fixes the upper knife holder  3 U (and the upper knife  4 U) to a desired position on the upper shaft  2 U, and then moves away from the upper shaft  2 U. The other upper knife holders  3 U are moved along the upper shaft  2 U and fixed to desired positions on the upper shaft  2 U in the same manner.  
     [0035] The operation of the upper knife moving mechanism  6 U described above is also controlled by the control unit  90 . The mechanism for releasably fixing the upper knife holders  3 U to the upper shaft  2 U and the mechanism for fixing and releasing the upper knife holders  3 U to and from the upper shaft  2 U may comprise, for instance, those disclosed in Japanese Unexamined Patent Publication No. 3(1991)-245995.  
     [0036] The arrangements of the lower knives  4 L are switched in the same manner except that the lower shaft  2 L is not moved and accordingly will not be described here.  
     [0037] A method of controlling the arrangements of slitting knives to switch the arrangements of the cutters from one arrangement (the current arrangement) to another arrangement (next arrangement) in accordance with an embodiment of the present invention will be described, hereinbelow. The method of the present embodiment can be applied to the slitter shown in FIGS. 1 and 2. As switching of positions of the lower knives  4 L may be made in the similar manner, the description below will be made only on the switching of positions of the upper knives  4 U.  
     [0038] In the present embodiment, an instruction to switch slitting widths is given with input of the next slitting width and the number of slitting knives to be used next through a numeric pad  92  as input means of the control unit  90 . A computer  94  as arithmetic means in the control unit  90  acquires absolute positions X(N) of the upper knives  4 U in the current positions (positions for the current slitting width) from memory  96 , calculates the absolute positions Y(N) of the upper knives  4 U in the next positions (positions for the next slitting width), and allocates those absolute positions X (N) and Y (N) to appropriate blanks in a fixed format of program  20  shown below.  
     [0039] Program  20   
     [0040] {circle over (1)} To move the upper knife holder  3 U in position W(1) to position Z(1).  
     [0041] {circle over (2)} To move the upper knife holder  3 U in position W(2) to position Z(2)  
     [0042] {circle over (3)} To move the upper knife holder  3 U in position W(3) to position Z(3).  
     [0043] {circle over (4)} To move the upper knife holder  3 U in position W(4) to position Z(4).  
     [0044] {circle over (5)} To move the upper knife holder  3 U in position W(5) to position Z(5).  
     [0045] {circle over (6)} To move the upper knife holder  3 U in position W(6) to position Z(6).  
     [0046] {circle over (7)} To move the upper knife holder  3 U in position W(7) to position Z(7).  
     [0047] In the above fixed format of program  20 , W(N) and Z(N) stand for the blanks. That is, the absolute positions X(N) are allocated to W(N) and the absolute positions Y(N) are allocated to Z(N) in such an order that movement of each slitting knife is not interfered by the other slitting knives. The above calculation and allocation by the computer  94  are carried out using a fixed common program preprogrammed in the computer  94 .  
     [0048] The control unit  90  can be either of an integrated unit included in the slitter or a separated unit connected to the slitter via a cable or the like. In addition, although the entire fixed common program is stored in the same control unit  90  in the present embodiment, it is also possible to allot divided portions of the fixed common program to different units or apparatus. For example, it is possible to store the allocating portion of the fixed common program in a control chip or memory within the slitter itself, while storing only the calculating portion of the fixed common program in the separated control unit. In addition, the numeric pad  92  may be replaced with any other type of input means as far as it is capable of specifying next slitting width and the number of slitting knives to be used next. For example, a touch-sensitive screen or wireless input means such as a mobile phone can be used. Also, the computer  94  may be replaced with a programmable logic controller of the slitter, a part of a production control computer of a production line, etc.  
     [0049] Though they will be described in detail later, the absolute positions X(N) and Y(N) are basically obtained in the following manner by use of the fixed common program. The absolute position X(N) can be given as a function of a knife ID number N, the current slitting width A, the next slitting width B and the number of knives currently used S1, X(N)=f{A, B, N, S1}, and the absolute position Y(N) can be given as a function of the knife ID number N, the current slitting width A, the next slitting width B and the number of knives to be used next S2, Y(N)=f{A, B, N, S2}. As described above, the next slitting width B and the number of knives to be used next S2 are input as input parameters by use of the numeric pad  92 . Absolute positions X(N) and Y(N) are defined as distances from the left end of the upper shaft  2 U as seen in FIG. 3. Accordingly, the position of the upper knife  4 U is more rightward in FIG.  3  as the value of the absolute position X(N) or Y(N) increases.  
     [0050] The uppermost one of the upper shafts  2 U shown in FIG. 3 shows the state where all the upper knives  4 U are in position a and lowermost one of the upper shafts  2 U shown in FIG. 3 shows the state where all the upper knives  4 U are in position b. When the upper knives  4 U are to be moved to position b from position a, the absolute positions X(N) and Y(N) are allocated to the blanks in the fixed format of program  20 . Accordingly, the program  20  is converted as follows so that it specifies a series of signals for moving the upper knives  4 U to respective positions that effect slitting with the next slitting width B and the number of knives S2 to be used next.  
     [0051] {circle over (1)} To move the upper knife holder  3 U in absolute position X(7) to absolute position Y(7).  
     [0052] {circle over (2)} To move the upper knife holder  3 U in absolute position X(6) to absolute position Y(6).  
     [0053] {circle over (3)} To move the upper knife holder  3 U in absolute position X(5) to absolute position Y(5).  
     [0054] {circle over (4)} To move the upper knife holder  3 U in absolute position X(4) to absolute position Y(4).  
     [0055] {circle over (5)} To move the upper knife holder  3 U in absolute position X(3) to absolute position Y(3).  
     [0056] {circle over (6)} To move the upper knife holder  3 U in absolute position X(2) to absolute position Y(2).  
     [0057] {circle over (7)} To move the upper knife holder  3 U in absolute position X(1) to absolute position Y(1).  
     [0058] When the program  20  converted as shown above is executed, the upper knife holder  3 U (upper knife  4 U) in absolute position X(7) is moved to absolute position Y(7) as shown by the second uppermost one of the upper shafts  2 U shown in FIG. 3. Then the upper knife holder  3 U in absolute position X(6) is moved to absolute position Y(6) as shown by the second lowermost one of the upper shafts  2 U shown in FIG. 3. In the similar manner, the seven upper knife holders  3 U are moved respectively to absolute positions Y(7) to Y(1) as shown by the lowermost one of the upper shafts  2 U shown in FIG. 3.  
     [0059] The fixed common program derives absolute positions X(1) to X(7) and Y(1) to Y(7) in the following manner. The following description will be made on a case where one or more of the seven upper knives  4  are sometimes not used in slitting. Initial position setting, that is, processing for setting all the upper knives  4 U and  4 L to the respective origin positions executed by the control unit  90  will be described first with reference to FIG. 4. The initial position setting for the lower knives  4 L is the same as for the upper knives  4 U and accordingly the following description is made only on the upper knives  4 U.  
     [0060] The processing is started in step P 1 . Then a pointer N representing the ID number of an upper knife holder  3 U is set to 1 and the number K of the upper knife holders  3 U on the upper shaft  2 U (seven in this particular embodiment) is set. (step P 2 ) The upper knife holders  3 U are detected one by one from the left side as seen in FIG. 3, by the holder detecting means  10 U on the upper knife moving mechanism  6 U. (step P 3 ) The rightmost upper knife holder  3 U as seen in FIG. 3 is kept stationary irrespective of the slitting width.  
     [0061] When one of the upper knife holders  3 U is detected, the upper knife holder  3 U is moved to origin position G(K−N+1) and fixed there by the upper knife moving mechanism  6 U. (steps P 4  and P 5 ) K−N+1 stands for the ID number of origin position as numbered from the right side in FIG. 3. Steps P 4  and P 5  are repeated until N becomes equal to K with pointer N incremented each time step P 5  is performed. (steps P 6  and P 8 ) In this manner, the upper knife holders  3 U are moved to respective origin positions and fixed there one by one. When all the upper knife holders  3 U are fixed to origin positions (K=N in step P 6 ), flag T is set to 1, which represents that the positions of the upper knife holders  3 U are initialized. (step P 7 ) Then initialization is ended in step P 9 .  
     [0062] Processing after the initialization will be described with reference to FIGS.  5  to  8 , hereinbelow. Processing is started in step P 11  in FIG. 5. Then the current slitting width A, the number S1 of knives used for the current slitting width A, the next slitting width B, the number S2 of knives to be used for the next slitting width B and a reference position Y for the knives are set. Herein, the current slitting width A, the number S1 and the reference position Y are acquired from the memory  96  in the control unit  90 . The next slitting width B and the number S2 are specified by use of the numeric pad  92 . The pointer N representing the ID number of an upper knife holder  3 U is set to 0. (step P 12 )  
     [0063] Herein, in the present embodiment, each of the motors  8 U and  8 L is equipped with an encoder that detects the position of the knife moving mechanism  6 U or  6 L on the threaded shaft  9 U or  9 L. During a set of movements for changing the slitting knife arrangement, the encoder detects each of the positions to which the knife moving mechanism  6 U or  6 L moves and fixes the knife holders  3 U or  3 L, and sends those positions to the memory  96 . In the memory  96 , those positions are recorded as the current positions of the slitting knives for the next set of movements. Preferably, the encoder is such a one that is capable of detecting absolute positions of the knife holders.  
     [0064] Then after pointer N is incremented by 1 in step P 13 , absolute position Y(N) of N−th upper knife holder  3 U is obtained on the basis of the reference position Y and the next slitting width B. (step P 14 ) Then it is determined whether N is equal to S2. (step P 15 ) Thus steps P 13  to P 15  are repeated until N becomes to equal to S2, whereby absolute positions Y(N) for first to S2−th upper knife holders  3 U are all obtained.  
     [0065] When it is determined in step P 15  that N=S2, it is determined whether flag T=1 in step P 16 . When it is determined T=1, that is, when the upper knife holders  3 U K in number are all fixed to their respective origin positions, it is determined whether Y(1)−G(1)&gt;0 in order to check whether the system is in normal state. (step P 17 ) When it is determined that Y(1)−G(1)&lt;0, it is determined that the system in an abnormal state. (step P 22 ) When it is determined in step P 17  that Y(1)−G(1)&gt;0, pointer N is set to 0 in step  18 . Then pointer N is incremented by 1 in step P 19  and origin positions G(N) and absolute positions Y(N) of first to S2−th upper knife holders  3 U are allocated to program  20  as positions W(N) and Z(N) in sequence. (steps P 19  to P 21 )  
     [0066] Then processing proceeds to step P 71  shown in FIG. 8. In step P 71 , pointer N is set to 0. Then the absolute positions Y(N) of first to S2−th upper knife holders  3 U are stored in the memory  96  in sequence as current absolute positions X(N) of first to S2−th upper knife holders  3 U. (steps P 72  to P 74 ) Thereafter flag T is set to 2, which represents that the upper knife holders  3 U are in predetermined positions. The knife position setting processing is ended in step P 76 .  
     [0067] When it is determined that flag T is not 1 in step P 16 , processing proceeds to step P 31  in FIG. 6. In step P 31 , it is determined whether flag T=2 and when it is determined that flag T is not 2, it is determined in step P 45  that the system is in an abnormal state.  
     [0068] When it is determined that flag T is 2, that is, when it is determined that the upper knife holders  3 U are in predetermined positions, it is determined whether X(2)−Y(2)&lt;0. (step P 32 ) When it is determined that X(2)−Y(2)&lt;0, that is, in the case of switching where the slitting width is narrowed, pointer N is set to 1 in step P 33  and absolute positions X(N) and Y(N) of a desired number of upper knife holders  3 U are allocated to program  20  as positions W(N) and Z(N) in sequence in steps P 34  and subsequent steps.  
     [0069] That is, absolute positions X(N) and Y(N) of a N−th upper knife holder  3 U allocated to program  20  as positions W(N) and Z(N) in step P 34  while incrementing pointer N by 1 in step P 35  each time step P 34  is performed. In the case of switching where the number of knives used is reduced, that is, S1−S2&gt;0 (step P 36 ), steps P 34  and P 35  are repeated until N becomes equal to S2+1 (step P 37 ), whereby absolute positions X(N) and Y(N) of first to S2−th upper knife holders  3 U are allocated to program  20  in sequence.  
     [0070] In the case of switching where the number of knives used is reduced, after absolute positions X(N) and Y(N) of first to S2−th upper knife holders  3 U are allocated to program  20 , absolute positions X(S1+S2−N+1) and origin positions G(S1+S2−N+1) of (S2+1)−th to S1−th upper knife holders  3 U are allocated to program  20  as positions W(N) and Z(N) in sequence.  
     [0071] That is, absolute positions X(S1+S2−N+1) and origin positions G(S1+S2−N+1) of a (S1+S2−N+1)−th upper knife holder  3 U are allocated to program  20  as positions W(N) and Z(N) in step P 38  while incrementing pointer N by 1 in step P 39  each time step P 38  is performed. Steps P 38  and P 39  are repeated until N becomes equal to S1+1 (step P 40 ), whereby absolute positions X(S1+S2−N+1) and origin positions G(S1+S2−N+1) of (S2+1)−th to S1−th upper knife holders  3 U are allocated to program  20  in sequence.  
     [0072] Thereafter processing proceeds to step P 71  shown in FIG. 8, and flag T is set to 2 in the manner described above, which represents that the upper knife holders  3 U are in predetermined positions. The knife position setting processing is ended in step P 76 .  
     [0073] Thus, when the slitting width is to be narrowed and at the same time, the number of knives to be used is to be reduced from S1 to S2, first to S2−th upper knife holders  3 U out of S1 upper knife holders  3 U in the current position X(N) are moved to the respective next positions Y(N) in this order and S1−th to (S2+1)−th upper knife holders  3 U are moved to the respective origin positions G(N) in this order. By employing this order, each of the upper knife holders  3 U is moved to its desired position without being interfered by the others of the upper knife holders  3 U.  
     [0074] In the case of switching where the number of knives used is increased, that is, when it is not determined that S1−S2&gt;0 in step P 36 , steps P 34  and P 35  are repeated until N becomes equal to S1+1 (step P 41 ), whereby absolute positions X(N) and Y(N) of first to S1−th upper knife holders  3 U are all allocated to program  20  in sequence.  
     [0075] In the case of switching where the number of knives used is increased, after absolute positions X(N) and Y(N) of first to S1−th upper knife holders  3 U are allocated to program  20 , origin positions G(N) and absolute positions Y(N) of (S1+1)−th to S2−th upper knife holders  3 U are allocated to program  20  as positions W(N) and Z(N) in sequence. (steps P 42  to P 44 )  
     [0076] Thereafter processing proceeds to step P 71  shown in FIG. 8, and flag T is set to 2 in the manner described above, which represents that the upper knife holders  3 U are in predetermined positions. The knife position setting processing is ended in step P 76 .  
     [0077] Thus, when the slitting width is to be narrowed and at the same time, the number of knives to be used is to be increased from S1 to S2, first to S1−th upper knife holders  3 U out of S1 upper knife holders  3 U in the current position X(N) are moved to the respective next positions Y(N) in this order and (S1+1)−th to S2−th upper knife holders  3 U in the respective origin positions G(N) are moved to the respective next positions Y(N) in this order. By employing this order, each of the upper knife holders  3 U is moved to its desired position without being interfered by the others of the upper knife holders  3 U.  
     [0078] When it is determined in step P 32  in FIG. 6 that X(2)−Y(2) is not smaller than 0, that is, in the case of switching where the slitting width is widened, processing proceeds to step P 51  in FIG. 7. In step P 51 , it is determined whether X(2)−Y(2) is larger than 0. When it is determined that X(2)−Y(2) is not larger than 0, it is determined in step P 60  that the slitting width is not changed.  
     [0079] When it is determined in step P 51  that X(2)−Y(2) is larger than 0, pointer N is set to 1 in step P 52  and then it is determined in step P 53  whether S1−S2&gt;0. When it is determined that S1−S2&gt;0, that is, in the case of switching where the number of knives used is reduced, absolute position X(S1−N+1) and origin position G(S1−N+1) of a (S1−N+1)−th upper knife holder  3 U, i.e., X(S1−N+1) and G(S1−N+1), are allocated to program  20  as positions W(N) and Z(N) in step P 54  while incrementing pointer N by 1 in step P 55  each time step P 54  is performed. In the case of switching where the number of knives used is reduced, that is, S1−S2&gt;0 (step P 53 ), steps P 54  and P 55  are repeated until S1−S2 becomes equal to N−1 (step P 56 ), whereby absolute positions X(N) and origin positions G(N) of S1−th to (S2+1)−th upper knife holders  3 U are allocated to program  20  in sequence.  
     [0080] In the case of switching where the number of knives used is reduced, after absolute positions X(N) and origin positions G(N) of S1−th to (S2+1)−th upper knife holders  3 U are allocated to program  20 , absolute positions X(N) and Y(N) of S2−th to first upper knife holders  3 U, i.e., X(S1−N+1) and Y(S1−N+1), are allocated to program  20  as positions W(N) and Z(N) in sequence.  
     [0081] That is, absolute positions X(S1−N+1) and Y(S1−N+1) of a (S1−N+1)−th upper knife holder  3 U are allocated to program  20  as positions W(N) and Z(N) in step P 57  while incrementing pointer N by 1 in step P 58  each time step P 57  is performed. Steps P 57  and P 58  are repeated until N becomes equal to S1+1 (step P 59 ), whereby absolute positions X(N) and Y(N) of S2−th to first upper knife holders  3 U are allocated to program  20  in sequence.  
     [0082] Thereafter processing proceeds to step P 71  shown in FIG. 8, and flag T is set to 2 in the manner described above, which represents that the upper knife holders  3 U are in predetermined positions. The knife position setting processing is ended in step P 76 .  
     [0083] Thus, when the slitting width is to be widened and at the same time, the number of knives to be used is to be reduced from S1 to S2, S1−th to (S2+1)−th upper knife holders  3 U (S1−S2 in number) out of S1 upper knife holders  3 U in the current position X(N) are moved to the respective origin positions G(N) in this order and S2−th to first upper knife holders  3 U are moved to the respective next positions Y(N) in this order. By employing this order, each of the upper knife holders  3 U is moved to its desired position without being interfered by the others of the upper knife holders  3 U.  
     [0084] When it is determined in step P 53  that S1−S2 is not larger than 0, that is, in the case of switching where the number of knives used is increased, origin position G(S1+N) and absolute position Y(S1+N) of a (S1+N)−th upper knife holder  3 U, i.e., G(S1+N) and G(S1+N), are allocated to program  20  as positions W(N) and Z(N) in step P 61  while incrementing pointer N by 1 in step P 62  each time step P 61  is performed. Steps P 61  and P 62  are repeated until S2−S1 becomes equal to N−1 (step P 63 ), whereby origin positions G(N) and absolute positions Y(N) of (S1+1)−th to S2−th upper knife holders  3 U are allocated to program  20  in sequence.  
     [0085] In the case of switching where the number of knives used is increased, after absolute origin positions G(N) and absolute positions Y(N) of (S1+1)−th to S2−th upper knife holders  3 U are allocated to program  20 , absolute positions X(N) and Y(N) of S1−th to first upper knife holders  3 U, i.e., X(S2−N+1) and Y(S2−N+1), are allocated to program  20  as positions W(N) and Z(N) in sequence.  
     [0086] That is, absolute positions X(S2−N+1) and Y(S2−N+1) of a (S2−N+1)−th upper knife holder  3 U are allocated to program  20  as positions W(N) and Z(N) in step P 64  while incrementing pointer N by 1 in step P 65  each time step P 64  is performed. Steps P 64  and P 65  are repeated until N becomes equal to S2+1 (step P 66 ), whereby absolute positions X(N) and Y(N) of S1−th to first upper knife holders  3 U are allocated to program  20  in sequence.  
     [0087] Thereafter processing proceeds to step P 71  shown in FIG. 8, and flag T is set to 2 in the manner described above, which represents that the upper knife holders  3 U are in predetermined positions. The knife position setting processing is ended in step P 76 .  
     [0088] Thus, when the slitting width is to be widened and at the same time, the number of knives to be used is to be increased from S1 to S2, (S1+1)−th to S2−th upper knife holders  3 U (S2−S1 in number) in the origin positions G(N) and S1−th to first upper knife holders  3 U in the current positions X(N) are moved to the respective next positions Y(N) in this order. By employing this order, each of the upper knife holders  3 U is moved to its desired position without being interfered by the others of the upper knife holders  3 U.  
     [0089] In this embodiment, an additional arrangement of the slitting knives can be easily provided. That is, in this embodiment, an additional arrangement of the slitting knives can be provided by calculating positions to which the respective slitting knives are to be moved and order in which the slitting knives are moved without the necessity of revising the common program or creating new programs.  
     [0090] In addition, although described above is an embodiment that is applied to the mode where the rightmost slitting knife in FIG. 3 is fixed at the same position and all of the other slitting knives are moved in the same direction, it is obvious that those skilled in the art can easily modify the above embodiment into an alternative embodiment that is applied to a mode where the slitting knives are moved with respect to a reference point in the center of the slitting knife arrangement. Illustrated in FIG. 9 is an example of such a mode. When changing the slitting knife arrangement, the controller  90  checks the ID number of a slitting knife at which the sign of X(N)−Y(N) changes. In the illustrated case where there are seven slitting knives and the slitting width is to be widened while keeping the number of the knives to be used unchanged, X(N)−Y(N)&lt;0 for N=1 to 3 and X(N)−Y(N)&gt;0 for N=4 to 7. The calculation explained in above in reference to FIGS.  5 - 8  can be modified so that it is applied separately for the knives of N=1 to 3 and the knives of N=4 to 7, so that the knives of N=1 to 3 are moved from the one having a smaller ID number and the knives of N=4 to 7 are moved from the one having a larger ID number.  
     [0091] Further, in either of the modes illustrated in FIGS. 3 and 9, the entire pass rollers  1  and  5  carrying the wide sheet H can be moved in parallel after the slitting knife arrangement is changed, so that the center of the entire set of active slitting knives in use is matched with the center of the width of the wide sheet H.