A punching device for a book binding sewing machine

The present invention relates to a punching device for a book binding sewing machine.

Sewing machines are commonly used in book binding systems for making sewn books. A sewn book consists of a block of signatures that are sewn together using continuous threads. Typically, the signatures are supplied in succession to a movable saddle, which is then closed towards a fixed structure bearing a series of needles and corresponding hooked needles (crochets).

Each signature must be punched before sewing, in order not to damage the needles and the crochets. To this end, a punching device is commonly provided inside the movable saddle. The punching device consists of a bar carrying a series of punches, each one associated with a corresponding needle or crochet; the bar is driven with a reciprocating motion towards the signature put astride the movable saddle (and placed below a holding element), so as to cause its piercing.

The same sewing machine is typically supplied with signatures of different format. In this case, it is possible that some holes formed in the signatures are not used during the sewing process, since the corresponding needles or crochets are unpaired and therefore must be excluded. Any resulting free hole allows the glue employed for completing the book to slip between adjacent pages, thereby causing their sticking.

A solution known in the art for solving this problem consists of excluding the punches that are not needed. This operation is commonly carried out disassembling the movable saddle, and loosing a screw that is used to lock any punch that must be excluded. The punch is lowered to a non-operative position and then locked again tightening the corresponding screw. However, the operation described above is very time consuming; the resulting non-working period of the sewing machine strongly reduces its yield.

A different solution is proposed in Italian patent application No.BG2000A000008 filed on 17 February 2000. This document discloses a punching device that may be remotely configured. Particularly, the bar houses one or more pneumatic pistons for corresponding punches. The pistons are controlled by respective valves, so as to lower and raise the punches; the punches are then locked in the desired position by means of a cursor.

A drawback of the solution described above is that the resulting punching device is quite unreliable. In fact, the bar moves to and from the needles and the crochets together with the movable saddle (in addition to moving up and down inside the movable saddle). The very fast movement of the bar may easily damage the small tubes that are needed to convey air under pressure from the valves to the pistons. Moreover, the machined section of the bar features a number of weakness points, which may bring about fatigue failures in the structure.

The pistons and valves required to move the punches are relatively cumbersome, so that their mounting on the bar is difficult. Therefore, in the solution disclosed in the above-mentioned patent application a single tube is used to control two adjacent pistons. As a consequence, both the corresponding punches must be excluded at the same time. However, this restrain prevents using a stagger stitch sewing technique that requires the possibility of excluding each punch individually.

Moreover, only few pistons and valves may be mounted on the bar; the pistons and valves are then placed at opposite ends of the bar for controlling corresponding punches. Therefore, this structure does not allow the use of multiple signatures having two or more pages printed on each layer of the signatures. In fact, the multiple signatures may require the exclusion of one or more intermediate punches (associated with unpaired needles or crochets between adjacent pages).

It is an object of the present invention to overcome the above-mentioned drawbacks. In order to achieve this object, a device as set out in the first claim is proposed.

Briefly, the present invention provides a punching device for a book binding sewing machine including a support structure carrying a plurality of punching elements and means for locking each punching element in an operative position or in a non-operative position, each punching element punching a signature if in the operative position and not affecting the signature if in the non-operative position when the support structure is moved towards the signature during operation of the book binding sewing machine, and first biasing means and second biasing means for biasing each punching element to the operative position and to the non-operative position, respectively, during configuration of the book binding sewing machine, wherein at least one of the first and second biasing means is uncoupled from the support structure during operation of the book binding sewing machine.

The present invention also provides a book binding sewing machine including the punching device. Moreover, the invention provides a corresponding software-implemented method of controlling the punching device, a program for performing the method, and a product storing the program.

Further features and the advantages of the solution according to the present invention will be made clear by the following description of a preferred embodiment thereof, given purely by way of a non-restrictive indication, with reference to the attached figures, in which:

• Figure 1 depicts a sewing machine in which the punching device of the invention can be used;
• Figure 2 is a partially cut away view of a movable saddle of the sewing machine,
• Figure 3a and Figure 3b show a particular of the punching device in perspective view and in cross-section, respectively,
• Figure 4 is a schematic block diagram of a PLC controlling operation of the sewing machine, and
• Figures 5a-5c show a flow chart describing the logic of a method used for controlling the punching device.

With reference in particular to Figure 1, a sewing machine 100 for book binding applications is shown. The machine 100 is used to sew together blocks of signatures 105, in order to form corresponding books. Each signature 105 consists of a large printed sheet, which is folded one or more times (so as to define the pages of the book) . The signature 105 may be either a single one (wherein only one page is printed on each layer thereof) or a multiple one (wherein two or more pages are printed on each layer); the multiple signature is commonly referred to as a two-up signature, a three-up signature, and so on (according to the number of pages printed on the layer).

The sewing machine 100 includes a bearing framework 110. A hopper 115 is used to feed the signatures 105 in succession to an opening station 120 (for example, including 4 upper opening heads and 4 lower opening along a feeding direction of the signatures). The signatures 105 are opened in the middle, in order to be placed astride a fixed saddle 125 that conveys the signatures 105 to a sewing station 130.

The sewing station 130 includes a movable saddle 135, which is aligned with the fixed saddle 125 when opened (in a lowered position). Each signature 105 is accelerated, in order to be separated from the following signatures and thrown onto the movable saddle 135. The movable saddle 135 is then closed (to a raised position). The signature 105 loaded on the movable saddle 135 is punched for allowing a series of needles and corresponding crochets (not shown in the figure) to sew the signatures 105 of a block together by means of continuous threads. The sewing machine 100 may use either a normal stitch sewing technique (wherein each needle co-operates only with the adjacent crochet on its right), or a stagger stitch sewing technique (wherein each needle alternatively co-operates with the adjacent crochet on its right and on its left).

Once a last signature 105 of the block has been sewn, the threads are cut and the block of signatures 105 is conveyed to a holder 140 (in order to be supplied to further machines that complete the production of the book). Operation of the sewing machine 100 is remotely managed by means of a programmable logic controller (PLC) 145.

Similar considerations apply if the sewing machine has a different structure or includes other units (for example, a series of trays for pre-loading the signatures or a different number of opening heads), if each needle co-operates with the adjacent crochet on its left in the normal stitch sewing technique, if the PLC is replaced with an equivalent data processing system (for example, a Personal Computer), and the like.

Considering now Figure 2, a pair of driving arms 205 (only one shown in the figure) is operated by a cam to open and to close the movable saddle 135. A square register 210 stops each signature thrown onto the movable saddle 135, so as to place the signature at a desired position along a saddle plate 215. The square register 210 is mounted on a guide 220, in order to be moved along a longitudinal axis of the saddle plate 215 according to the dimension of the signature. A photocell 225 checks the position of the guide 220 along the saddle plate 215.

A punching device 230 is used to punch each signature that is loaded on the movable saddle 135 (when closed). The punching device 230 includes a bar 235 that is mounted inside the movable saddle 135 (below the saddle plate 215). The bar 235 carries a series of punches 240 projecting upwards; the even punches 240 (starting from zero) are associated with a corresponding needle, whereas the odd punches 240 are associated with a corresponding crochet. A tie rod mechanism 245 is used to lower and to raise the bar 235 with respect to the saddle plate 215.

A box 250 houses a pneumatic piston 255 for each punch 240; the box 250 is fixed to the framework 110 of the sewing machine, so that it does not follow the bar 235 in its movement. A pressure reducer 260 provides low-pressure air (for example, at 1 bar), which is used to keep all the pistons 255 in a lowered position. A set of single effect valves 265 is mounted below the box 250. Each valve 265 (when opened) provides high-pressure air (for example, at 6 bar) , so as to raise a corresponding piston 255 towards the bar 235; a hole is formed in the guide 220 for allowing a corresponding piston 255 to pass through. A pair of photocells 270 (receiver and transmitter) checks that all the pistons 255 are lowered.

Similar considerations apply if the movable saddle has a different structure, if the bar carrying the punches is replaced with an equivalent support structure, if the pistons are controlled with different pressures, if the pistons are arranged elsewhere (but in any case so as to be uncoupled from the bar carrying the punches during operation of the sewing machine), if the square register and the photocells are replaced with equivalent means, and the like.

Moving now to Figure 3a, the bar 235 consists of an assembly formed by a lower section 305, a slider 310, a ledge 315 and an upper section 320. These elements are fastened together by a pair of clamps 325 (only one shown in the figure), which are fixed by screws at opposite ends of both the lower section 305 and the upper section 320. The clamps 325 are coupled to the tie rod mechanism, so as to drive the above-described assembly up and down.

Each punch 240 is partially housed in two coaxial through holes 330 and 335 formed in the lower section 305 and in the upper section 320, respectively. A slotted through hole 340 is formed in the slider 310 for each punch 240; the slotted hole 340 has a left narrow section and a right large section. A valve 345 moves the slider 310 along its longitudinal axis. When the slider 310 is moved to the left (release position), each punch 240 can slide axially along the large section of the corresponding slotted hole 340; conversely, when the slider 310 is moved to the right (lock position), the narrow section of each slotted hole 340 engages the corresponding punch 240. A further through hole 350 is formed in the ledge 315 for each punch 240; the hole 350 interferes with the punch 240, so as to prevent the punch 240 from falling down when it is not locked by the slider 310.

As shown in Figure 3b, the hole 335 has a lower large portion and an upper narrow portion defining a shoulder. A plastic bush 355 fits into the narrow portion of the hole 335; the bush 355 is locked by means of a peg 360, which is inserted into a corresponding horizontal hole of the upper section 320 and engages a mating groove formed around the bush 355.

The punch 240 is formed by a needle 365 ending with a lower disc 370 (extending transversally to a longitudinal axis thereof). The disc 370 is closed in a dismountable base, which is formed by an upper bush 375 and a lower cap 380. The bush 375 extends from the hole 335 to the hole 330, and it is provided with a collar 385 that is housed in the large portion of the hole 335; the collar 385 has a diameter larger than the one of the hole 330. An upper groove 390h and a lower groove 3901 are formed around the bush 375; the bush 375 has a diameter mating the hole 330 and the large section of the slotted hole 340 (formed in the slider 310), whereas each groove 390h, 3901 has a diameter mating the narrow section of the slotted hole 340. A lower end of the bush 375 is provided with an external screw for a corresponding internal screw formed in the cap 380. The cap 380 is housed in the hole 330; the cap 380 has a six-sided head (for a corresponding Allen screw), which is formed in its bottom projecting downwards from the lower section 305. A spring 395 is restrained (inside the hole 335) between the bush 355 and the collar 385.

The above-described structure is assembled mounting the bush 355 and then slipping the spring 395 inside the hole 335 from below. The bush 375 is added, and the ledge 315 is fastened to the upper section 320 (by means of a series of screws), so as to close the collar 385 inside the hole 335. The slider 310 and the lower section 305 are fitted onto the bush 375. The lower section 305 and the upper section 320 are then fastened together. The needle 365 is pushed through the bushes 375 and 355, until the disc 370 abuts against the bush 375 (with a tip of the needle 365 that projects from the upper section 320). The cap 380 is then inserted into the hole 330 and is screwed onto the bush 375.

Each needle 365 may be individually removed simply unscrewing the cap 380. The portion of the cap 380 projecting from the lower section 305 is grasped and pulled down. The needle 365 may then be slipped off the bar 235 from below.

When the slider 310 is in the release position, the bush 375 slides along the large section of the slotted hole 340, until the collar 385 abuts against the ledge 315 under the pressure exerted by the spring 395. The needle 365 (which is integral with the base 375,380) is then lowered and retracted inside the bar 235 (in a non-operative position). The pistons 255 corresponding to the required punches 240 are raised (opening the respective valves). Each raised piston 255 pushes the base 380 inside the hole 330; the resulting pressure exerted by the collar 385 causes the spring 395 to yield elastically, until the collar 385 abuts against the shoulder defined by the narrow portion of the hole 335. As a consequence, the needle 365 is raised and extracted from the bar 235 (in an operative position). The slider 310 is then moved to the lock position, so that the narrow section of each slotted hole 340 engages the upper groove 390h (if the respective punch 240 is lowered) or the lower groove 3901 (if the respective punch 240 is raised). In this way, the slider 310 locks all the punches 240 in the desired position; the pistons 255 are then lowered (closing the respective valves).

Every time the arrangement of the punches 240 must be changed, all the pistons 255 associated with the punches 240 in the operative position are raised. Each raised piston 255 pushes the base 380 upwards, so as to reduce the pressure exerted on the slider 310; the slider 310 is then moved to the release position, and the operations described above are repeated in order to obtain the new desired configuration of the punching device.

When the bar 235 is moved towards the signature (placed astride the movable saddle), the punches 240 in the operative position reach the signature; the signature is then pierced for a respective needle or crochet. Conversely, the punches 240 in the non-operative position do not reach the signature, which is then not affected by the movement of the bar 235.

Similar considerations apply if the bar has a different structure (for example, without any plastic bush), if the slider engages the punches in another manner or it is replaced with equivalent locking means, if each punch has a different structure, if the dismountable base is replaced with equivalent holding means, if different resilient means are provided instead of the spring; alternatively, the structure is assembled with other operations, each needle is individually removed in a different manner, or the punches are locked and released with another procedure.

With reference to Figure 4, the PLC 145 comprises a control unit (CU) 405, which is integrated in a chip of semiconductor material. A working memory 410 (typically a RAM) and a non-volatile memory (typically an E²PROM) 415 are associated with the control unit 405. Moreover, the control unit 405 is connected in a conventional way to a keypad (KP) 420 and to a display (DIS) 425.

During operation of the PLC 145, information (programs and data) stored on the E²PROM 415 is loaded (at least partially) into the working memory 410. Particularly, the working memory 410 includes a program (PGM) 430 for controlling operation of the punching device.

The control program 430 accesses two pre-set tables 435 and 437, which store configuration information for most of the formats of signatures supported by the sewing machine. The table 435 is formed by a series of records for different types of signatures, generally defined according to the number of folds and to the mutual direction (parallel one or transversal one) of the folds (if more than one). The record includes a flag (from Oh₁ to Oh₄) for each upper opening head and a flag (from Ol₁ to Ol₄) for each lower opening head; the flag Oh₁-Ol₄ is asserted to indicate that the corresponding opening head must be actuated for opening the signatures.

The table 437 is formed by a series of records for different heights of the signatures, measured from an upper edge from which reading of the pages starts (head) and an opposed lower edge (foot). The record includes a plurality of fields, each one storing a preferred position of the square register, and then of the signatures, on the saddle plate (with the position measured from zero to the left of a first punch, at a pre-set distance denoted with DP). Each field is associated with a different combination (number of pages of the signatures)-(sewing technique of the machine); for example, the record includes ten fields from POSn₁ and POSs₁ (for single signatures processed with a normal stitch sewing technique and a stagger stitch sewing technique, respectively) to POSn₅ and POSs₅ (for five-up signatures processed with a normal stitch sewing technique and a stagger stitch sewing technique, respectively). The preferred position is defined so as to centre the signatures along the punching device (and then along the needles and the crochets as well). At the same time, the preferred position ensures a minimum margin (for example, 10 mm) between the punches acting on the signatures and their free ends; moreover, the signatures are positioned so as to be associated with an even number of punches (if the normal stitch sewing technique is employed) or with an odd number of punches (if the stagger stitch sewing technique is employed), starting in both cases from a punch associated with a needle.

The control program 430 further manages an array (CONF) 440, which stores a current configuration of the punching device. Particularly, the configuration array 440 includes a flag for each punch; the flag is asserted when the punch is raised, whereas it is deasserted when the punch is lowered. A variable (CUR_POS) 445 is used to store a current position of the square register on the saddle plate.

Similar considerations apply if the PLC has a different structure or includes other units (for example, if the keypad and the display are integrated in a touch-screen), if the programs and data are structured in a different manner, if other configuration information is stored for each format of signatures, if the preferred position is set in a different way (for example, without considering any minimum margin), if the configuration array is replaced with equivalent information (for example, consisting of a list with only the numbers of the punches that are raised), and so on.

As shown in Figures 5a-5c, when the sewing machine is turned on, the PLC loads the control program from its E²PROM. Whenever the format of the signatures is changed, the program performs a method 500. The method starts at block 502 and then passes to block 504, wherein an operator of the sewing machine sets a series of configuration parameters for the new job; for example, the operator selects the mode of operation of the control program (automatic one or manual one), the number of signatures forming each book, the possible use of a blind stitch (for improving closing of the sewing), and the like. Proceeding to block 506, the operator selects the sewing technique (normal stitch or stagger stitch) employed by the machine. The operator is then prompted at block 508 to input the number of pages (from 1 to 5) printed on each layer of the signatures.

A test is made in decision block 510 to determine the mode of operation of the control program. If the control program is set to the automatic mode of operation the blocks 512-518 are executed, whereas if the control program is set to the manual mode of operation the blocks 519-520 are executed; in both cases, the method then passes to block 521 (described in the following).

Considering now block 512 (automatic mode of operation), the PLC displays a graphical representation of the different types of signatures supported by the sewing machine, so as to enable the operator to select the desired one. A signature production process, which involves the setting of a number of operative parameters of the sewing machine, is started at block 514. During this process, a first signature is extracted from the hopper, and its length (measured transversally to a spine of the signature) is detected; the signature is then opened, placed astride the fixed saddle, and conveyed towards the sewing station (being stopped before reaching the movable saddle near the end of the fixed saddle); while the signature moves along the fixed saddle, its height (H) is detected at block 516. Continuing to block 518, the preferred position of the square register on the saddle plate is extracted from the record associated with the height of the signature (according to the number of pages and to the sewing technique); the position so obtained is stored into the respective variable (CUR_POS).

With reference to block 519 (manual mode of operation), the operator selects the heads to be actuated for opening the signatures. The operator is then prompted at block 520 to input the length and the height of the signatures, and the position of the square register on the saddle plate.

Moving now to block 521, a loop defined by the blocks 521-538 is executed a number of times equal to the number of pages PG printed on each layer of the signatures (with PG=1 if the signatures are simple). In detail, the j-th loop (with j=1...PG) starts calculating the number of the first punch (Pf_j) to be raised; denoting with PTH the distance between two adjacent punches (for example, 19 mm), the number of the first punch Pf_j is given by the formula: The method verifies at block 522 whether the first punch is associated with a needle (that is, whether Pf_j is even) . If not, the number of the first punch Pf_j is incremented (Pf_j=Pf_j+1) at block 524; the method then continues to block 526. Conversely, if the first punch is correct the method descends into block 526 directly.

The number of a last punch (Pl_j) associated with the current page is likewise calculated at block 526 applying the formula: The method verifies at block 528 whether the number of the last punch Pl_j is odd (for the normal stitch sewing technique) or even (for the stagger stitch sewing technique). If not, the number of the last punch Pl_j is decreased (Pl_j=Pl_j-1) at block 530; the method then continues to block 532. Conversely, if the last punch is correct the method descends into block 532 directly.

Considering now block 532, the configuration array is updated accordingly (after making a copy); particularly, the flags from the one associated with the first punch to the one associated with the last punch are asserted.

The method verifies at block 534 whether the first punch and the last punch ensure a minimum margin (for example, 5 mm) from the respective free ends of the page (with this margin given by the formulas Pf_j·PTH-CUR_POS-(j-1)·$\frac{\mathit{\text{H}}}{\mathit{\text{PG}}}$+DP and CUR_POS+j·$\frac{\mathit{\text{H}}}{\mathit{\text{PG}}}$-DP-Pl_j·PTH, respectively). If not, the flags in the configuration array associated with the first two punches and/or with the two last punches are deasserted at block 536; the method then continues to block 538. Conversely, the method descends into block 538 directly.

A test is made in decision block 538 to determine whether the last page of the signatures has been processed. If not, the method returns to block 521 for repeating the operations described above for a next page.

On the contrary, the method enters block 544 wherein the movable saddle is opened. The square register is moved at block 546 to a position that does not interfere with any piston (if necessary). The method then passes to block 548, wherein the pistons associated with the punches that are raised (respective flags asserted in the copy of the configuration array) are actuated. The slider is moved to the release position at block 550. Proceeding to block 552, the pistons associated with the punches to be raised (respective flags in the configuration array asserted) are actuated. The slider is moved to the lock position at block 554, so as to obtain the desired configuration of the punching device. Continuing to block 556, all the pistons are lowered. The method enters an idle loop at block 557, waiting for completion of the movement of the pistons. As soon as the pistons are uncoupled from the bar, the square register is placed again at block 558 to the position stored in the corresponding variable.

Considering now block 560, the first signature is placed on the movable saddle; the movable saddle is then raised approaching the closed position wherein the operator can check the position of the signature with respect to the needles and the crochets.

Moving to block 574, a test is made to determine whether the operator confirms the configuration of the punching device. If not, the method enters block 576, wherein the operator may update the position of the square register and/or may select one or more punches to be moved (raised or lowered). For example, the configuration of the punching device is changed to take into account printing scraps on the signatures; alternatively, the position of the signatures on the saddle plate is moved towards the fixed saddle to make easier their throwing onto the movable saddle (for example, when the signatures feature a high number of open layers or are made with very light paper). The new configuration of the punching device is actuated at block 578 (repeating the operations described with reference to the blocks 544-558). The method then returns to block 574. As soon as the operator confirms the configuration of the punching device (block 574), the method ends at the final block 580.

Similar considerations apply if an equivalent method is performed (for example, with error routines that are called when the number of punches associated with each page of the signatures falls below a threshold value), if the configuration of the punching device is established in a different manner, if the control program supports different formats of signatures, if the sewing machine only operates in the automatic mode, if the sewing machine employs different sewing techniques, if the configuration of the punching device cannot be updated by the operator, if the first punch and the last punch are fixed (and cannot be excluded). Alternatively, the number of the intermediate punches to be excluded (for multiple signatures) is pre-set and stored in a further table, or the configuration of the punching device is calculated with an algorithm, and the like.

More generally, the present invention provides a punching device for a book binding sewing machine. A support structure is used to carry a plurality of punching elements. The punching device includes means for locking each punching element in an operative position or in a non-operative position; each punching element punches a signature if in the operative position and does not affect the signature if in the non-operative position when the support structure is moved towards the signature during operation of the book binding sewing machine. First biasing means and second biasing means are used to bias each punching element to the operative position and to the non-operative position, respectively, during configuration of the book binding sewing machine. In the punching device of the invention, at least one of the first and second biasing means is uncoupled from the support structure during operation of the book binding sewing machine.

The proposed punching device is very reliable, since the number of elements carried by the support structure moving fast to and from the needles and the crochets together with the movable saddle (and up and down inside the movable saddle) is strongly reduced.

Moreover, the solution of the invention makes it possible to control the position of all the punches individually (even if the combined control of sets of punches or the control of a reduced number of punches is not excluded). In this way, the punching device may be easily configured also for use with a stagger stitch sewing technique and/or with multiple signatures.

The preferred embodiment of the invention described above offers further advantages.

Particularly, an additional support structure for the biasing means uncoupled from the bar (i.e., the box for the pistons) is fixed to the bearing framework of the sewing machine.

This configuration is particularly simple and robust.

In a particular embodiment of the invention, a series of springs housed in the bar are used for retracting the needles.

The proposed feature results in a very compact structure of the bar carrying the punches.

Advantageously, a series of pistons are used to raise the punches through corresponding holes formed in the bar.

The devised solution makes it possible to configure the punching device in a very simple manner.

Moreover, the pistons are driven by means of corresponding single effect valves.

The use of these valves strongly reduces the cost of the whole punching device.

Alternatively, the box for the pistons is not fixed to the bearing framework, different valves for the pistons are employed, or the springs and/or the pistons are replaced with other biasing means (even with both of them that are uncoupled from the bar during operation of the sewing machine); for example, each punch is biased to the non-operative position only by its weight, the pistons are not pneumatic, or each piston ends with a magnet for lowering the respective punch.

Preferably, the needles of the punches are individually removable from below the bar.

In this way, maintenance operations on the punching device (for example, for replacing a defective needle) may be carried out without removing the saddle plate.

As a further improvement, each cap (holding a needle) has a grasping end that projects downwards.

This feature makes it easier to access and remove the cap (for replacing the needle).

Advantageously, the pistons are raised against the bar before moving the slider to the release position.

In this way, the respective springs are unloaded, so as to help the movement of the slider.

Preferably, the square register is moved during configuration of the sewing machine so as not to interfere with the pistons.

The proposed feature prevents any risk of damage to the sewing machine.

Moreover, operation of the sewing machine is disabled until all the pistons are lowered.

This ensures that the movable saddle is operated only when all the pistons are uncoupled from the bar.

However, the punching device according to the present invention leads itself to be implemented even holding the needles in a different manner (for example, with respective screws), with the needles that are not individually removable from the bar, with the caps that do not project from the bar, without raising the pistons against the bar before moving the slider to the release position, moving the square register to its position only after completion of the configuration process, or even without checking that the pistons are lowered.

Advantageously, the punching device is controlled by means of a program, which is stored on the E²PROM of the PLC.

Alternatively, the program is provided on floppy-disk, is stored on a different data processing system readable medium, or more generally is provided in any other form directly loadable into a working memory of a data processing system. However, the proposed method of controlling the punching device is also suitable to be carried out with a hardware structure (for example, integrated in a chip of semiconductor material).

In a preferred embodiment of the invention, the configuration of the punching device is automatically defined as a function of the format of the signatures.

This feature simplifies operation of the sewing machine, strongly reducing the intervention of the operator.

As a further improvement, the configuration of the punching device is defined according to both the dimension of the signatures and to the number of pages printed on each layer of the signatures.

The proposed solution makes it possible to use either simple signatures or multiple signatures transparently to the operator.

Moreover, the configuration of the punching device is further updated according to the sewing technique employed by the machine.

In this way, different sewing techniques may be automatically supported.

Alternatively, the configuration of the punching device is defined manually, the punches to be excluded with multiple signatures are selected by the operator, the sewing machine only supports simple signatures or multiple signatures (of a pre-set type), a single sewing technique is employed, and the like.

Naturally, in order to satisfy local and specific requirements, a person skilled in the art may apply to the solution described above many modifications and alterations all of which, however, are included within the scope of protection of the invention as defined by the following claims.