EP3482966B1 - Method and device for sewing - Google Patents

Description

The invention relates to a method and a device for thread stitching folded printed sheets, in which individual folded printed sheets are lined up one after the other flatly and sewn with at least one sewing needle and with at least one hook needle to form a book block.

For this purpose, the at least one sewing needle brings a binding thread from the outside through the fold of a printed sheet to be sewn inwards, between its legs, and thereby creates a first, single-stranded seam on an outside of the fold. The binding thread is then stored between the legs of the folded printed sheet and, starting from the sewing needle in the form of a thread loop, is transported so far in the direction of a path of movement of the hook needle that a closed end of the thread loop extends beyond this path of movement. Then the at least one hook needle dips through an eyelet of the same binding thread created on the outside of the fold when sewing the previous printed sheet and through the fold of the printed sheet to be sewn inwards, between its legs in the previously formed thread loop, captures this during a return stroke and conveys it from the inside through the fold of the printed sheet to be sewn and through the eyelet on the outside of the fold to the outside. A second, double-stranded seam spaced apart from the first, single-stranded seam is produced on the outside of the fold. The hook needle, which forms a hook that serves to receive the binding thread and has a recess on one side, is rotated about its longitudinal axis for sewing the printed sheet and its hook is positioned in different rotational positions.

From the CH24452 and the CH55948 are thread sewing machines with pre-piercing needles, sewing needles and hook needles that work in pairs and that can be moved up and down, as well as one between a sewing needle and a hook needle known reciprocating thread layer. During the operation of such thread sewing machines, several loose, standing and folded printed sheets strung together with their broadsides in stack form are connected individually with at least two seams consisting of the same binding thread to form book blocks. For this purpose, each of the printed sheets provided one after the other is first pierced at its fold by means of two pre-piercing needles which are brought up to the fold from an inside at a distance from one another and between its two legs. After retracting the pre-piercing needles, a sewing needle with a needle eye is passed from the outside of the fold through the first of the two holes formed by the pre-piercing needles and a hook needle equipped with a hook open at the top is passed through the second hole. A binding thread located in the needle eye, for example supplied by a thread spool and possibly already sewn to the previous printed sheet, is inserted with the sewing needle between the legs of the printed sheet and a thread supply is created in this interior space of the printed sheet to be sewn. As a result, a first, single-strand seam is formed on the outside of the fold or such a seam that has already been formed on the outside of the fold of at least one previously stapled (synonymous: sewn) printed sheet is continued.

The binding thread now stored within the printed sheet to be stapled (synonymously: the printed sheet to be sewn) is transported by the thread layer in the form of a loop in the direction of the hook needle and positioned there over its path of movement. During its downward movement, the hook needle dips through the loop of the binding thread provided by the thread layer. This thread loop is then pulled taut around the hook needle and captured by the hook during its subsequent upward movement. The thread loop is then pulled upwards through the second hole in the fold of the printed sheet to be stapled and through an eyelet that surrounds the hook needle and is formed from the thread loop of the previously stapled printed sheet. In this way, a second, double-stranded seam is formed on the outside of the fold or such a seam formed on the outside of the fold of at least one previously stitched printed sheet is continued. By dipping the sewing needle and the hook needle into the two holes of the next printed sheet made available for thread stitching, the process described above begins again, which can be repeated several times depending on the book block to be produced.

During the sewing process, the hook needle is rotated twice by 180 ° around its longitudinal axis, for which purpose appropriately designed control cams or cam disks are used. At the beginning of the downward movement, the hook needle is rotated in such a way that the hook is then on its side that is remote from the already stapled printed sheet. This prevents the eyelet formed from the thread loop of the previously stitched printed sheet from unhooking. At the latest during the upward movement of the hook needle, that is to say on its return stroke, a second rotation takes place in such a way that the hook is on its side facing the already stapled printed sheet. This ensures that the currently formed loop of the binding thread is caught by the hook and passed through the eyelet of the previously stapled printed sheet without taking the latter with it.

The EP832758 A2 discloses a similar method for producing thread-sewn book blocks from a stack of printed sheets lined up flat, in which, however, instead of a mechanical thread layer, a gas flow is used to transport the loop-shaped binding thread from the sewing needle to the hook needle. The downward movement of the hook needle is offset in time with respect to the downward movement of the sewing needle, ie later. In this solution, too, the hook needle is rotated by 180 ° for the downward movement and the upward movement. This is done by means of a hydraulic cylinder, which is also like the one in the CH24452 used control cams or how the cams according to the CH55948 exactly two angles of rotation of 180 °, ie two corresponding rotational positions of the hook of the hook needle. In the aforementioned solutions of the prior art, a toothed rack is used in each case as the actuating element for power transmission from the drive to the hook needle to be rotated. The EP832758 A2 discloses the preamble of claim 1 or claim 5.

Such a constant rotation of the hook needle through 180 ° is easy to implement and proves to be advantageous if the book blocks are always of the same thickness Print sheets are formed. As soon as successive book blocks have printed sheets of different thicknesses, especially when using thin printed sheets, there is a risk that the hook of the hook needle will damage the eyelet formed from the thread loop of the previously sewn sheet, ie it will splice, tear or even sever it. This undesirable effect can be intensified due to manufacturing tolerances of the hook needle, in particular by a slightly different rotational position of the hook.

If printing sheets made of thin material are to be used for the production of relatively thick book blocks, this has the disadvantage that the binding thread spreads in an undesirable manner. In thread sewing, instead of the normal stitch, in which the loop of the binding thread is always formed in the same direction starting from the sewing needle, the alternate stitch is often used, in which the thread loop is formed alternately to the right or to the left. With such a solution, however, the risk of damage to the eyelet formed from the thread loop of the previously stitched printed sheet is increased because this has a smaller distance to the hook of the hook needle with thin printed sheets than with thick printed sheets. In addition to the type of stitches and thus the different directions in which the loops are formed, the different separation of successive book blocks or corrections of errors made in thread stitching must also be taken into account in order to avoid damaging the eyelets of previously stitched printed sheets.

It was therefore the object of the invention to provide a method and a device for thread stitching folded printed sheets with which the quality of the book blocks to be produced is increased and, in particular, the risk of damage to the eyelet formed from the thread loop of a previously stitched printed sheet is reduced even when using thin printed sheets can be.

This object is achieved by a method according to claim 1.

With this method, the hook of the hook needle can be positioned as far away as possible from this eyelet in good time before the inside-out penetration of the eyelet formed from the thread loop of the previously sewn printed sheet. Therefore, the risk of injury to the eyelet can be minimized. In addition, it is ensured that the eye is not picked up again by the hook of the hook needle. In this way, the quality of the book blocks can also be increased compared to book blocks produced according to the prior art.

According to the method, the at least one hook needle is rotated about its longitudinal axis before the thread loop is grasped in such a way that the hook of this hook needle is positioned on its side opposite the sewing needle. As a result of this rotation of the hook needle and the corresponding positioning of the hook, the thread loop can be reliably grasped with the hook during the return stroke of the hook needle. A high quality of the book blocks to be produced can thus be guaranteed.

According to the invention, the at least one hook needle is rotated around its longitudinal axis prior to gripping the thread loop in such a way that its hook is then at an angle of +/- 85 °, preferably at an angle of +/- 50 ° and particularly preferably at an angle of +/- - Is positioned 15 ° in relation to a first vertical plane through the fold of the printed sheet to be stapled. Advantageous areas for the rotation of the hook needle or for the positioning of the hook are thus indicated.

According to a next advantageous embodiment of the method, the at least a hook needle is rotated about its longitudinal axis before penetrating from the outside inwards through the eye of the previous printing sheet and the fold of the printing sheet to be sewn in such a way that its hook is aligned in a second vertical position and at right angles to the fold of the printing sheet to be sewn, imaginary plane, is positioned on a side facing away from the previously sewn printed sheet of the hook needle in a starting rotational position. This position defines a rotation of the hook needle and a positioning of the hook in a first rotational position, which can then advantageously be used as a starting rotational position for the further rotation of the hook needle or for the further positioning of the hook. In addition, the three available and individually adjustable rotary positions can better than the two fixed rotary positions known from the prior art on the three critical process steps of thread sewing, namely the insertion of the hook needles from the outside in through the fold of the printed sheet to be sewn, the grasping of the thread loops with the hooks of the hook needles and the penetration of the hooks of the hook needles from the inside to the outside through the eyelet of the previous printed sheet located on the outside of the fold.

According to a further advantageous embodiment of the method, for each printed sheet to be sewn, based on information stored in a machine control of a device for thread stitching or applied to at least one of the printed sheets to be sewn, information about the type of stitches to be made when thread stitching the printed sheets of a production order and the separation of the stitches to be made Book blocks, based on the starting rotational position of the hook of the at least one hook needle, the corresponding angle of rotation of the at least one hook needle is determined about its longitudinal axis, the at least one hook needle is rotated according to the determined angle of rotation and its hook is positioned accordingly. The information applied to at least one of the printed sheets to be sewn can be, for example, identification by means of a barcode, an RFID transponder or a print mark. In this way, it is possible to react advantageously both to the paper thickness and to further paper properties and to the thread thickness and to further thread properties.

According to a next advantageous embodiment of the method, the at least one hook needle is rotated by the determined angle of rotation and the hook is positioned accordingly with a drive, in particular with a Servo motor. With such a drive and in particular with a servomotor, in principle every rotation of the hook needle and thus every positioning of the hook can be implemented very precisely and quickly. As a result, the hook needle can be rotated during each sub-process of the thread sewing so that its hook is optimally positioned.

The object is also achieved by a device according to claim 5, in which the hook needle is designed to be rotatable about its longitudinal axis at any angle of rotation and the hook can be positioned in any rotational position. With such a device, the hook of the hook needle can always be optimally positioned, thereby increasing the quality of the book blocks to be produced. In particular, the risk of damaging the eyelet formed from the thread loop of a previously stitched printed sheet can also be reduced when using thin printed sheets. According to an advantageous embodiment, this device has a device, operatively connected to a machine control, for rotating the at least one hook needle about its longitudinal axis, the device having a holder for the at least one hook needle, an adjusting element for rotating the at least one hook needle and a drive for the adjusting element. When using such a device, a large number of hook needles can advantageously be rotated by means of a single drive.

According to a further embodiment of the device, the drive has a servomotor. With such a servomotor, every rotation of the hook needle and thus every positioning of the hook can advantageously be realized.

According to a next embodiment of the device, the adjusting element is equipped with a rack. Such a rack represents a simple, inexpensive component that has proven itself in such applications for transmitting the torque from the drive to the hook needles.

Fig. 1 - 4

eine schematische Darstellung des aus dem Stand der Technik bekannten Nähprinzips einer im Normalstich arbeitenden Vorrichtung,

Fig. 5

eine schematische Draufsicht auf die Näh- und Hakennadel der Vorrichtung gemäß Fig. 1, mit den beiden Drehpositionen der Hakennadel bzw. ihres Hakens,

Fig. 6

eine schematische Seitenansicht der Näh- und Hakennadeln einer für den Wechselstich vorgesehenen Vorrichtung zum Fadenheften des Standes der Technik, mit einer darunter abgebildeten schematischen Draufsicht auf fünf mit dieser Vorrichtung vernähte Druckbogen,

Fig. 7

eine schematische Schnittdarstellung der Hakennadel einer erfindungsgemäßen Vorrichtung zum Fadenheften, welche die Hakennadel mit ihrem Haken in einer erfindungsgemäßen Drehposition beim Durchdringen einer nach rechts ausgerichteten Öse eines vorherigen Druckbogens sowie eine links von der Hakennadel angeordnete Nähnadel zeigt,

Fig. 8

eine Darstellung der gleichen Hakennadel wie in Fig. 7, welche jedoch in einer anderen erfindungsgemäßen Drehposition beim Durchdringen einer nach links ausgerichteten Öse eines vorherigen Druckbogens sowie mit einer rechts von der Hakennadel angeordneten Nähnadel gezeigt ist,

Fig. 9

eine schematische Draufsicht auf die Näh- und Hakennadel einer erfindungsgemäßen Vorrichtung zum Fadenheften, mit weiteren erfindungsgemäßen Drehpositionen der Hakennadel und ihres Hakens zum Erfassen einer von links zugeführten Fadenschlaufe,

Fig. 10

eine schematische Darstellung analog Fig. 9, jedoch mit weiteren erfindungsgemäßen Drehpositionen der Hakennadel und ihres Hakens zum Erfassen einer von rechts zugeführten Fadenschlaufe, und

Fig. 11

eine schematische Darstellung einer Einrichtung zum Drehen von Hakennadeln einer erfindungsgemäßen Vorrichtung zum Fadenheften.

The invention is described in more detail below using an exemplary embodiment. Show:

Figs. 1-4

a schematic representation of the sewing principle known from the prior art of a device operating in normal stitch,

Fig. 5

a schematic plan view of the sewing and hook needle of the device according to FIG Fig. 1 , with the two rotary positions of the hook needle or its hook,

Fig. 6

a schematic side view of the sewing and hook needles of a device for thread basting of the prior art provided for the alternate stitch, with a schematic top view shown below of five printed sheets sewn with this device,

Fig. 7

a schematic sectional view of the hook needle of a device according to the invention for sewing thread, which shows the hook needle with its hook in a rotational position according to the invention when penetrating an eyelet aligned to the right of a previous printed sheet and a sewing needle arranged to the left of the hook needle,

Fig. 8

a representation of the same hook needle as in Fig. 7 which, however, is shown in a different rotational position according to the invention when penetrating a left-facing eyelet of a previous printed sheet and with a sewing needle arranged to the right of the hook needle,

Fig. 9

a schematic plan view of the sewing and hook needle of a device according to the invention for sewing thread, with further rotational positions according to the invention of the hook needle and its hook for grasping a thread loop fed in from the left,

Fig. 10

a schematic representation analog Fig. 9 , but with further rotational positions according to the invention of the hook needle and its hook for detecting a thread loop fed in from the right, and

Fig. 11

a schematic representation of a device for rotating hook needles of a device according to the invention for sewing thread.

Figs. 1 to 4 show a schematic representation of the sewing principle known from the prior art of a device 1 for thread basting provided for the normal stitch. In Fig. 1 a book block 6 formed from two folded, flatly lined up and already sewn together by means of a binding thread 2 in the form of two spaced seams 3, 4 printed sheets 5 is shown. The folded printed sheets 5, which are conveyed individually one after the other in a feed direction 7 to a stitching saddle (not shown), each have a first leg 8 and a second leg 9 as well as a fold 10 connecting them.

Also shown is a third, folded printed sheet 5, which is transported in the feed direction 7 to the book block 6, with its first leg 8 placed flat against the book block 6 and thus made available for sewing with this book block 6. For a better understanding of the sewing principle, this further printed sheet 5 resting on the stitching saddle, not shown, is shown cut through at its fold 10, ie only the first leg 8 of the third printed sheet 5 is shown, while its second leg 9 has been omitted. In addition, there are two pre-piercing needles 11 arranged at a distance from one another, a sewing needle 13 having a needle eye 12, a hook needle 14 which is arranged at a distance from the sewing needle 13 in the direction of the fold 10 of the third folded printed sheet 5 and has a recess 16 on its circumference that forms a hook 15 ( see also Fig. 7, Fig. 8 ) as well as a blown air nozzle 17 arranged on the side of the sewing needle 13 remote from the hook needle 14 and designed as a transport element for the binding thread 2, as well as a gate 18 of the device 1.

When the device 1 is in operation, the two pre-piercing needles 11 first pierce the fold 10 of the printed sheet 5 to be sewn from the inside in the direction of the movement arrows shown and thereby form two spaced holes 19 in this fold 10 ( Fig. 1 ). After the pre-piercing needles 11 have been withdrawn against the movement arrows, the sewing needle 13, which is initially positioned on an outer side 20 of the fold 10 and guiding the binding thread 2 provided, for example, by a thread spool (not shown), in its needle eye 12 inserted through a first of the two holes 19 into an interior space 21 located between the two legs 8, 9 of the printed sheet 5 to be sewn. A first section 2a of the binding thread 2 located on a first side of the eye of the needle 12 is connected to a first, single-strand seam 3 of the book block 6 formed on the outside 20 of the fold 10, while a second section 2b located on a second side of the eye of the needle 12 of the binding thread 2 is connected to the thread spool, not shown. At this point in time, the hook needle 14 is still on the outside 20 of the fold 10 of the printed sheet 5 to be sewn and is surrounded there by an eyelet 22 formed from a thread loop of the binding thread 2 used to sew the previous printed sheet 5 ( Fig. 2 ).

The two sections 2a, 2b of the binding thread 2 are then acted upon by means of an air blast 23 produced by the blown air nozzle 17 and transported in the direction of a movement path 24 of the hook needle 14, shown in dashed lines. A thread loop 25 with a closed end 26 is formed ( Fig. 3 ). This thread loop 25 is guided into the link 18 and positioned in such a way that its closed end 26 finally extends beyond the movement path 24 of the hook needle 14 onto the side of this movement path 24 facing away from the sewing needle 13. Of course, instead of a pneumatic transport element designed as a blown air nozzle 17 for the binding thread 2, a mechanical transport element known per se, designed as a thread layer, can also be used.

Then the hook needle 14 surrounded by the eyelet 22 on the outside 20 of the fold 10 dips from the outside through the second hole 19 formed by the piercing needles 11 into the interior space 21 of the printed sheet 5 to be sewn between the legs 8, 9 and enters finally also through the thread loop 25. On the return stroke of the hook needle 14, the thread loop 25, which has meanwhile been pulled taut around the latter, is grasped by the hook 15 of the hook needle 14 and guided through the second hole 19 of the fold 10 and through the eyelet 22 located on the outside 20 thereof. In this case, a second, double-stranded seam 4 is formed on this outside 20 of the fold 10, which in the direction of this Fold 10 is arranged at a distance from the first, single-strand seam 3 ( Fig. 4 ). After the next printing sheet 5 to be sewn has been prepared, the thread-stitching process described above begins again.

Fig. 5 shows a schematic plan view of a sewing needle 13 with the needle eye 12, which is always aligned in the same way, and of a hook needle 14 cooperating with the sewing needle 13. In particular, the two rotational positions of the hook needle 14 and its hook 15 in relation to FIG the fold 10 of the printed sheet 5 to be sewn. Both during the movement of the hook needle 14 from the outside 20 of the fold 10 into the interior 21 of the printed sheet 5 to be sewn and during its return stroke, the hook needle 14 is rotated 180 ° around its longitudinal axis 27 . It is irrelevant whether the rotation is clockwise or counterclockwise. As is illustrated by way of example with the aid of a first and a second movement arrow 28, 29, the hook needle 14 and hook 15 accordingly have a first rotational position 30 and a second rotational position 31, respectively. In its first rotational position 30, the hook 15 is located in a second vertical and at right angles to the fold 10 of the printed sheet 5 to be sewn, imaginary plane 32 and there on a side of the hook needle 14 facing away from the previously sewn sheet 5 Fig. 3 shown. Before it passes through the fold 10 of the printed sheet 5 to be sewn and through the eyelet 22 of the previously sewn printed sheet 5 on the return stroke, the hook needle 14 and thus its hook 15 is rotated into the second rotary position 31, for example according to the second movement arrow 29. The hook 15 then also lies in the second vertical plane 32, but on a side of the hook needle 14 facing the previously sewn printed sheet 5. This position of the hook 15 can also be the Fig. 4 can be removed, the hook needle 14 being shown there, however, after it has penetrated the fold 10 and the eyelet 22.

To rotate the hook needle 14, a correspondingly designed hydraulic cylinder (not shown) is used, the first end position of which is the first rotational position 30 of the hook needle 14 or its hook 15 and the second end position of which is the second rotational position 31 of the hook needle 14 or its hook 15 corresponds. When the hook needle 14 moves from the outside to the inside, it and thus also its hook 15 are in their first rotary position 30. This rotary position 30 of the hook 15 on the side of the hook needle 14 remote from the already stapled printed sheets 5 is maintained at least as long as the hook 15 is still partially on the outside 20 of the fold 10 (cf. Fig. 2, Fig. 3 ). This prevents the eyelet 22 formed from the thread loop of the previously sewn printed sheet 5 from being unhooked from the hook 15 too early. After penetrating the fold 10, but at the latest before the hook 15 reaches the thread loop 25 during the movement of the hook needle 14 from the inside to the outside, the hook needle 14 is rotated so that its hook 15 is in its second rotational position 31, ie on the the side of the hook needle 14 facing the previously sewn printed sheet 5 is located (cf. Fig. 5 above). This ensures that the currently formed thread loop 25 of the binding thread 2 is grasped by the hook 14 and passed through the fold 10 of the printed sheet 5 to be sewn and through the eyelet 22 of the previously sewn printed sheet 5 without taking the latter with you (cf. Fig. 4 ). The next 180 ° rotation of the hook needle 14 and thus of its hook 15, for example in the direction of the first movement arrow 28, takes place before it is again moved from the outside to the inside, that is, before the sewing of a following printed sheet 5 According to the state of the art, a control cam or a cam disk can also be used.

Depending on the design of the book block 6 to be produced, further printed sheets 5 can be added in the same way. Although in the Figs. 1-5 only a single sewing needle 13 and a single hook needle 14 are shown, depending on the length of the fold 10 of the printed sheets 5 to be sewn and on the intended type of stitches generated with the sewing and hook needles 13, 14 - of course, one larger number of such needles are used.

Unlike in the Figs. 1-5 normal stitch shown, in which the binding thread 2 is always transported starting from a sewing needle 13 spaced on the same side of the hook needle 14 to the hook needle 14, a device 1 for sewing folded printed sheets 5 can of course also be provided for the alternate stitch or be switched to this. In order to be able to realize this type of stitches, a sewing needle 13 is arranged on both sides of the respective hook needle 14 and at the same distance therefrom, whereby the supply of the binding thread 2 to the hook needle 14 in the form of the thread loop 25 alternating from the one and the other sewing needle 13 is realized starting from. In Fig. 6 three sewing needles 13 and two hook needles 14 of such a device 1 of the prior art suitable for alternate stitching are shown by way of example, while in FIG Fig. 6 The bottom is a schematic plan view of five printed sheets 5 sewn together at their folds 10 in alternating stitches to form a book block 6. It can clearly be seen here that the eyelets 22 of the second, double-stranded seam 4 are oriented differently, depending on which sewing needle 13 and thus from which side the binding thread 2 has been guided to the hook needle 14.

The known from the prior art and in Fig. 5 The illustrated second rotational position 31 of the hook needle 14 or its hook 15 when penetrating the fold 10 and in particular the eyelets 22 of the previously sewn printed sheet 5 proves to be disadvantageous because, on the one hand, the alignment of the eyelets 22 is different from that in this second rotational position 31 Hook 15 of the hook needle 14 deviates, that the binding thread 2 of the eyelets 22 can be damaged by the hook 15 and because, on the other hand, the orientation of the eyelets 22 according to the type of stitches (see Fig. Fig. 2 and Fig. 6 ) can change, which can increase the risk of tearing of the binding thread 2.

Fig. 7 shows, in a schematic representation, a section through a hook needle 14 and through a sewing needle 13 of a device 1 according to the invention for sewing thread, arranged to the left of the hook needle 14 and cooperating with it. The thread loop 25 of the binding thread 2, which is also shown, has thus been formed from left to right. This figure shows the hook needle 14 and the hook 15 in each case in a rotational position according to the invention when penetrating the eyelet 22 of the binding thread 2 of the previously sewn printed sheet 5 that rests on the fold 10 of the currently to be sewn printed sheet 5 and is shown here with dashed lines. For this purpose, the hook needle 14 has been rotated about its longitudinal axis 27, that its hook 15 is arranged in a vertical plane of symmetry 33 of this eyelet 22 and is positioned on a side of the hook needle 14 facing the previously sewn printed sheet 5.

In Fig. 8 shows a schematic representation of a section through the same hook needle 14 as in FIG Fig. 7 , but with a different sewing needle 13 arranged to the right of the hook needle 14 and cooperating with it. The thread loop 25 of the binding thread 2, which is also shown, is thus formed from right to left. This figure shows the hook needle 14 and the hook 15 each in a further rotational position according to the invention when penetrating the eyelet 22 of the binding thread 2 of the previously sewn printed sheet 5 lying on the fold 10, not shown here, of the printed sheet 5 currently to be sewn has been rotated about its longitudinal axis 27 that its hook 15 in a vertical plane of symmetry 33 opposite this Fig. 7 is arranged differently oriented eyelet 22 and is positioned on a side of the hook needle 14 facing the previously sewn printed sheet 5.

This means that in Fig. 7 and in Fig. 8 Two different rotational positions according to the invention of the hook needle 14 or its hook 15 are shown, which are dependent on the orientation of the eyelet 22 of the binding thread 2 of the previously sewn printed sheet 5 resting on the fold 10 of the printed sheet 5 currently to be sewn. In addition to the type of stitches used when sewing the respective printed sheet 5, i.e. whether for example normal or alternating stitching is used, the separation of a printed sheet 5 currently to be sewn from the last sewn sheet 5 of a previous book block 6 as well as the type of used Material for the printed sheet 5 and for the binding thread 2 an influence on the alignment of the eyelet 22 of the previous printed sheet 5 and thus on the actual The rotational position of the hook needle 14 or its hook 15 according to the invention to be assumed when the eyelet 22 of the binding thread 2 of the previously sewn printed sheet 5 penetrates from the inside to the outside.

With regard to the also known from the prior art and in Fig. 5 The illustrated first rotational position 30 of the hook needle 14 or its hook 15, it has been shown that this is not optimally aligned for grasping the thread loop 25. Set against it Figures 9 and 10 each a schematic top view of the sewing needle 13 and of the hook needle 14 of a device 1 according to the invention for sewing thread, with further rotational positions according to the invention of the hook needle 14 or its hook 15 for detecting one from the left ( Fig. 9 ) or one from the right ( Fig. 10 ). Accordingly, the hook needle 14 is rotated about its longitudinal axis 27 before the thread loop 25 is grasped in such a way that the hook 15 of the hook needle 14 is positioned on its side opposite the sewing needle 13. The hook 15 is at an angle of +/- 85 °, preferably at an angle of +/- 50 ° and particularly preferably at an angle of +/- 15 ° with respect to a first vertical plane 34 through the fold 10 of the to be stapled Press sheet 5 rotated. With such a rotational position of the hook needle 14 or its hook 15, the gripping of the thread loop 25 by this hook 15 can be improved compared to the prior art. The rotational position of the hook needle 14 or its hook 15 that can be achieved in each case is a compromise between the time available for rotating the hook needle 14, measured in milliseconds, and the optimal gripping of the thread loop 25 by the hook 15.

Fig. 11 shows in a schematic representation a device 36 connected to a machine control 35 for rotating the hook needles 14 of a device 1 according to the invention for sewing thread. A device 1 with four hook needles 14 is shown here by way of example, the sewing needles 13 cooperating with the hook needles 14 having been omitted for reasons of clarity. The device 36 for rotating the hook needles 14 has a holder 37 for rotatably receiving the hook needles 14, a rack 38 having a rack Adjusting element 39 for rotating the hook needles 14 about their longitudinal axis 27 and a drive 41 having a servomotor 40 for the corresponding actuation of the adjusting element 39. The hook needles 14 and thus also their respective hooks 15 are thus in principle designed to be rotatable about their longitudinal axis 27 at any angle of rotation α and can be stopped in any turning position.

During operation of this device 1, the hook needles 14 for sewing a printed sheet 5 fed to the stitching saddle (not shown) are initially each in an initial rotational position which is the one known from the prior art and shown in FIG Figs. 1 to 3 and 5 first rotational position 30 shown corresponds. In other words, the hooks 15 are each located in the second vertical plane 32 oriented at right angles to the fold 10 of the printed sheet 5 to be sewn and there on the side of their hook needle 14 facing away from the previously sewn printed sheet 5, as is also shown schematically in FIG Fig. 6 above and Fig. 11 is shown.

After the formation and positioning of the respective thread loop 25 in the interior 21 of the printed sheet 5 to be sewn and after the hook needles 14 have dipped into this interior 21, as was also the case for a single hook needle 14 of the prior art Figs. 1 to 4 is described, the hook needles 14 rotatably located in the holder 37 and thus also their hooks 15 are moved out of their starting rotational position after the drive 41 and the actuating element 39, according to the invention, either into one of the in Fig. 9 or in one of the in Fig. 10 rotated second rotational positions shown. This happens depending on whether the thread loop 25 is fed from a sewing needle 13 located on the left or on the right of the respective hook needle 14. During their return stroke, the hooks 15 of the hook needles 14 positioned in this way grasp the respective thread loop 25 and lead them to the outside through the second hole 19 of the fold 10 of the printed sheet 5 to be sewn.

At the latest before the hooks 15 of the hook needles 14 each through the eyelet 22 of the binding thread 2 of the previously sewn on the outside 20 of this fold 10 Printed sheet 5 are moved, these hook needles 14 and thus their hooks 15 by means of the drive 41, for example, in a Fig. 7 or 8 shown third rotational position rotated. Because the hooks 15 are located in this third rotational position on a side of the hook needles 14 facing the previously sewn printed sheet 5 and in the plane of symmetry 33 of the respective eyelet 22 and thus relatively far away from its binding thread 2, it is ensured that these eyelets 22 through the they each penetrating hook 15 are not injured. Subsequently, but at the latest before the hook needles 14 are moved from the outside 20 of the fold 10 of this printing sheet 5 into its interior 21 to sew a next folded printed sheet 5, the hook needles 14 and thus their hooks 15 are returned to the starting rotational position already described above turned.

With this method and the corresponding device 1 - compared to the known prior art with two fixed rotational positions, each offset by 180 ° - a further rotational position of the hook needles 14 and their respective hook 15 is added. The three rotary positions that are now available can better address the three critical process steps of thread sewing, namely the insertion of the hook needles 14 from the outside to the inside through the fold 10 of the printed sheet 5 to be sewn, the grasping of the thread loops with the hooks 15 of the hook needles 14 and the penetration of the hooks 15 of the hook needles 14 occurring from the inside to the outside through the eyelet 22 of the previous printed sheet 5 located on the outside 20 of the fold 10 in each case. In addition, with the solution according to the invention, two of the three rotary positions can be individually and thus flexibly adapted to the respective work situation when thread stitching folded printed sheets 1, which is why the quality of the book blocks 6 produced can be increased and the risk of injury to the binding thread 2 used can be reduced.

Claims (8)

1. Method for sewing threads, in which individual folded printed sheets (5) are placed successively in a manner in which they lie flat against one another and are stitched to form a book block (6) by means of at least one stitching needle (13) and by means of at least one hook needle (14), wherein

   • the at least one stitching needle (13) introduces a binding thread (2) from the outside, through the fold (10) of a printed sheet (5) to be stitched, inwards between the limbs (8, 9) of said printed sheet (5), in the process creating a first, single-strand seam (3) on an outer side (20) of the fold (10),

   • the binding thread (2) is stored between the limbs (8, 9) of the folded printed sheet (5) and, proceeding from the stitching needle (13), is transported in the form of a thread loop (25) far enough in the direction of a path of movement (24) of the hook needle (14) that a closed end (26) of the thread loop (25) extends beyond this path of movement (24),

   • the at least one hook needle (14) dips into the previously formed thread loop (25), through a lug (22) of the same binding thread (2) that has been produced on the outer side (20) of the fold (10) during the stitching of the preceding printed sheet (5) and through the fold (10) of the printed sheet (5) to be stitched, inwards between the limbs (8, 9) of said printed sheet, captures said thread loop (25) during a return stroke travel, conveys said thread loop (25) from the inside outwards, through the fold (10) of the printed sheet (5) to be stitched and through the lug (22) located on the outer side (20) of the fold (10), and in the process creates a second, double-strand seam (4), which is spaced apart from the first, single-strand seam (3), on the outer side (20) of the fold (10),

   • the hook needle (14) has a recess (16) on one side, which recess (16) forms a hook (15) which serves to receive the binding thread (2), which hook needle (14) is rotated about its longitudinal axis (27) for the purpose of stitching the printed sheet (5) and in the process the hook (15) is positioned in different rotary positions,

   • before the penetration from the inside outwards of the fold (10) of the printed sheet (5) to be stitched and of the lug (22) of the previously stitched printed sheet (5), the hook needle (14) is rotated about its longitudinal axis (27) in such a way that its hook (15) is positioned in a vertical plane of symmetry (33) of said lug (22) and on a side of the hook needle (14) that faces the previously stitched printed sheet (5),

   characterized in that, before the capturing of the thread loop (25), the at least one hook needle (14) is rotated about its longitudinal axis (27) in such a way that the hook (15) of said hook needle (14) is positioned, on its side which is opposite the stitching needle (13) and at an angle of +/- 85°, preferably at an angle of +/- 50° and particularly preferably at an angle of +/- 15° with respect to a first vertical plane (34) through the fold (10) of the printed sheet (5) to be sewn.
2. Method according to Claim 1, characterized in that, before the penetration from the outside inwards of the lug (22) of the preceding printed sheet (5) and of the fold (10) of the printed sheet (5) to be stitched, the at least one hook needle (14) is rotated about its longitudinal axis (27) in such a way that its hook (15) is positioned in a starting rotary position in a second vertical plane (32), which is oriented at right angles to the fold (10) of the printed sheet (5) to be stitched, on a side of the hook needle (14) that faces away from the previously stitched printed sheet (5).
3. Method according to Claim 2, characterized in that, for each printed sheet (5) to be stitched and on the basis of information stored in a machine control system (35) of a device (1) for sewing threads or applied to at least one of the printed sheets (5) to be stitched, which information relates to the type of stitches to be performed during the operation of sewing the threads of the printed sheets (5) of a manufacturing order and relates to the separation of the book block (6) to be produced, proceeding from the starting rotary position of the hook (15) of the at least one hook needle (14) corresponding rotational angles (α) of the at least one hook needle (14) about its longitudinal axis (27) are determined, the at least one hook needle (14) is rotated in a manner corresponding to the determined rotational angles (α) and its hook (15) is positioned correspondingly.
4. Method according to Claim 3, characterized in that the rotation of the at least one hook needle (14) about the determined rotational angles (α) and the respective positioning of the hook (15) are carried out by a drive (41), in particular by a servomotor (40).
5. Device for sewing threads, in which individual folded printed sheets (5) are placed successively in a manner in which they lie flat against one another and are stitched to form a book block (6) by means of a binding thread (2), wherein the device (1) has at least one stitching needle (13) with a needle eye (12) and at least one hook needle (14) which is arranged such that it is spaced apart from the stitching needle (13) and has a recess (16) on one side, which recess forms a hook (15) which serves to receive the binding thread (2), and the hook needle (14) is designed such that it can rotate about its longitudinal axis (27) for the purpose of stitching a printed sheet (5), characterized in that the hook needle (14) is designed such that it can rotate about its longitudinal axis (27) at any desired rotational angle (α) and the hook (15) is designed such that it can be positioned in any desired rotary position.
6. Device according to Claim 5, characterized in that the device (1) has a mechanism (36), operatively connected to a machine control system (35), for rotating the at least one hook needle (14) about its longitudinal axis (27), wherein the mechanism (36) has a mounting (37) for the at least one hook needle (14), an actuating element (39) for rotating the at least one hook needle (14) and a drive (41) for the actuating element (39).
7. Device according to Claim 6, characterized in that the drive (41) has a servomotor (40).
8. Device according to Claim 6, characterized in that the actuating element (39) has a toothed rack (38).

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