This application claims priority to Swiss Application No. 01347/17 filed Nov. 8, 2017, the disclosure of which is incorporated herein by reference in its entirety.
The invention relates to a method and an apparatus for the binding thread-stitching of folded printed sheets or signatures, for which individual signatures are lined up successively, along their flat sides, and are sewn together to form a book block with at least one sewing needle and at least one hook needle.
For this, the at least one sewing needle moves a binding thread from the outside to the inside through the fold of a signature to be sewn, between its legs, thus generating a first, single-strand seam on a fold outside. The binding thread is then stored between the legs of the folded signature and, starting from the sewing needle, is transported in the form of a binding thread loop far enough in the direction of a movement path for the hook needle, so that a closed end of the binding thread loop extends past this movement path. The at least one hook needle is then pushed through an eyelet of the same binding thread, created on the outside of the fold during the sewing of the previous signature, and is moved through the fold of the signature to be sewn, between its legs, to the inside, grips it during a return stroke and moves it from the inside to the outside through the fold of the signature to be sewn and through the eyelet located on the outside of the fold. In the process, a second, double-strand seam is created on the outside of the fold, which is located at a distance to the first, single-strand seam. The hook needle provided with a recess forming a hook on one side for accommodating the binding thread is rotated around its longitudinal axis for sewing the signature and the hook is thus positioned at different rotational positions.
Swiss patent documents CH24452 and the CH55948 disclose binding thread-stitching machines with pre-piercing needles, meaning respectively up and down moving sewing needles and hook needles acting in pairs, as well as binding thread guides that can be moved back and forth between a sewing needle and a hook needle. When operating these types of binding thread-stitching machines, several individual, loose, upright standing folded signatures, lined up along their broad or flat sides to form a stack, are combined into book blocks with at least two seams using the same binding thread. For this, each of the successively provided signatures are first punctured along the fold with two spaced-apart pre-piercing needles, moving up between the two legs from the inside of the fold. Following the pull-back of the pre-piercing needles, a sewing needle with eye is guided from the outside of the fold through the first of the two holes formed by the pre-piercing needles, and a hook needle with the hook open on one side toward the top is guided through the second hole. In the process, a binding thread already located in the eye of the needle and provided, for example, by a binding thread spool and, if applicable, already used for sewing the preceding signature, is inserted between the legs of the signature, thus providing a binding thread supply on the inside of the signature to be sewn at present. A first, single-strand seam is thus formed on the fold outside or a seam of this type, already formed on the fold outside of at least one preceding, stitched (synonymously: sewn) signature is continued in this way.
The binding thread now stored within the signature to be stitched (synonymously: to be sewn) is transported in the form of a loop by the binding thread layer in the direction of the hook needle and is positioned there so as to extend past the needle movement path. During its downward movement, the hook needle moves through the binding thread loop made available by the binding thread layer. The binding thread loop is then tightened around the hook needle and during its subsequent upward movement is gripped by the hook. The binding thread loop is then pulled upward, through the second hole in the fold of the signature to be stitched, and through an eyelet surrounding the hook needle, which is formed by the binding thread loop of the previously stitched signature. In this way, a second, double-strand seam is formed on the fold outside, or a seam is continued on the outside of a fold on at least one previously stitched signature. With the penetrating of the sewing needle and the hook needle into the two holes of the following signature, made available for the binding thread stitching, the above-described process starts anew, wherein this process can be repeated multiple times, depending on the book block to be produced.
During the sewing operation, correspondingly designed control cams or cam disks are used for rotating the hook needle twice around its longitudinal axis by 180°. At the start of the downward movement, the hook needle is rotated such that the hook is subsequently located on the side facing away from the already stitched signature, thus preventing the eyelet formed with the binding thread loop of the previously stitched signature from unhooking. A second rotation occurs no later than during the upward movement of the hook needle, meaning during the upward stroke, so that the hook is facing the side of the already stitched signatures, thereby ensuring that the currently formed binding thread loop is gripped by the hook and is guided through the eyelet of the previously stitched signature, without taking along the latter.
European patent document EP832758 A2 discloses a similar method for producing binding thread-stitched book blocks from a stack of signatures, successively lined up along the flat sides, wherein this method uses a gas jet in place of a mechanical binding thread layer for transporting the loop-shaped binding thread from the sewing needle to the hook needle. The downward movement of the sewing needle occurs with a time lag in this case, relative to the downward movement of the sewing needle, meaning it occurs later. For this solution, the hook needle is also rotated by respectively 180° for the downward movement and the upward movement with the aid of a hydraulic cylinder which, in the same way as the control cams used in CH24452, or the cam disks according to CH55948, permits precisely two rotational angles of 180°, meaning two corresponding rotational positions for the hook of the hook needle. A toothed rack is used as actuator for each of the aforementioned solutions according to the prior art for the transfer of power needed for rotating the hook needles.
Rotating the hook needle in the same way always by 180°, can be realized easily and proves to be advantageous if the book blocks are always formed with uniformly thick signatures. As soon as successively arriving book blocks comprise differently thick signatures, in particular when using thinner signatures, there is danger that the hook on the needle damages the eyelet formed with the binding thread loop of the previously stitched signature, meaning the binding thread loop is split or partially torn or even cut. This undesirable effect can be further increased by production tolerances for the hook needle, in particular also caused by a slight deviation in the rotational position of the hook.
If signatures of a thin material are to be used for producing relatively thick book blocks, it has the disadvantage that the binding thread appears bulky in an undesirable manner. In that case, a combined staggered stitch where the binding thread loop is alternately formed on the left or the right is frequently used during the binding thread stitching instead of the normal stitch where the loop of the stitch is always formed in the same direction, starting from the sewing needle. A solution of this type, however, further increases the danger of damaging the eyelet formed by the binding thread loop of the previously stitched signature because the eyelet is located at a shorter distance to the hook of the hook needle with thinner signatures than with thicker signatures. In addition to the type of stitch and thus the differing direction of the loop forming, the differences in the separation of successively following book blocks or corrections of errors that occurred during the binding thread-stitching must also be taken into consideration to avoid damaging the eyelets.
An object of the invention is to create a method and an apparatus for a binding thread-stitching of folded signatures, which permits increasing the quality of the book blocks to be produced and, in particular, reduce the danger of damaging the eyelet respectively formed with the binding thread loop of a previously stitched signature, even when using thin signatures.
The above and other objects are solved with a method for which, prior to penetrating the fold from the inside to the outside of the signature to be sewn as well as the eyelet of the previously sewn signature, the hook needle is rotated around its longitudinal axis in such a way that its hook is positioned in a vertical symmetry plane for this eyelet and on a hook needle side that is facing the previously sewn signature. With this method, the hook of the hook needle can be positioned as far as possible from the eyelet, in a timely manner prior to penetrating the eyelet, formed by the binding thread loop of the previously sewn signature. As a result, the danger of damaging the eyelet can be minimized. In addition, it is ensured that the eyelet 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 relative to the book blocks produced according to the prior art.
According to one advantageous embodiment of the method, the at least one hook needle is rotated around its longitudinal axis, prior to picking up the binding thread loop, in such a way that the hook of this hook needle is positioned on the side opposite the sewing needle. Through this rotation of the hook needle and the corresponding positioning of the hook, the binding thread loop can be gripped securely by the hook during the return stroke movement of the hook needle, thus ensuring a high quality for the book blocks to be produced.
According to another advantageous embodiment of the method, the at least one hook needle is rotated prior to gripping the binding thread loop around its longitudinal axis, such that its hook is subsequently positioned at an angle of ±85°, preferably ±50° and especially preferred an angle of ±15°, relative to a first vertical plane through the fold of the signature to be stitched, thus resulting in advantageous ranges for the rotation of the hook needle and/or the positioning of the hook.
According to a different advantageous embodiment of the method, prior to penetrating the eyelet of the preceding signature and the fold of the signature to be sewn from the outside to the inside, the at least one hook needle is rotated around its longitudinal axis, such that its hook is located in a second, vertical imaginary plane, arranged at a right angle to the fold of the signature to be sewn, on a side of the hook needle that is facing away from the previously sewn signature and serves as a starting rotational position. This position defines a rotation of the hook needle and positioning of the hook in a first rotational position, which can then advantageously be used as starting rotational position for the further rotation of the hook needle and/or for the further positioning of the hook. In addition, the three available and individually adjustable rotational positions can thus be divided easier than the two fixed rotational positions according to the prior art into the three critical method steps of binding thread stitching, namely the inserting from the outside to the inside of the hook needles through the fold of the signature to be sewn, gripping of the binding thread loop with the hook of the hook needles, and penetrating from the inside to the outside of the hook on the hook needle through the eyelet of the preceding signature respectively located on the outside of the fold.
According to another advantageous embodiment of the method, corresponding rotational angles for the at least one hook needle around its longitudinal axis are determined for each signature to be sewn, beginning with the starting rotational position of the hook for the at least one hook needle and based on information stored in a machine control of a thread-stitching apparatus, or based on information affixed to at least one of the signatures to be sewn and relating to the type of stitches used for the binding thread-stitching of signatures for a production order or the separating of the book block to be produced. The at least one hook needle is then rotated corresponding to the determined angle of rotation and the hook is positioned accordingly. The information affixed to the at least one signatures to be sewn can, for example, be a barcode marking, a RIFD transponder marking or a print mark. In this way, it is advantageously possible to react to the paper thickness and other paper characteristics, as well as the binding thread thickness and additional binding thread characteristics.
A different advantageous embodiment of the method requires a drive, in particular a servomotor, for the rotation of the at least one hook needle around the determined angle of rotation and the corresponding positioning of the hook. With such a drive, in particular with a servomotor, any rotation and thus also any positioning of the hook needle in principle can be realized very quickly and precisely. As a result, the hook needle can be rotated for each partial process of the binding thread stitching in such a way that its hook is optimally positioned.
The object is furthermore solved with an apparatus having a hook needle that can be rotated at an optional angle of rotation around its longitudinal axis and for which the hook can be positioned at an optional rotational position. With an apparatus of this type, the hook of the needle can always be positioned optimally and the quality of the book blocks to be produced can thus be increased. The danger of damaging the eyelet respectively formed with a binding thread loop from a previously stitched signature can be reduced even when using thin signatures.
According to one advantageous embodiment, this apparatus is provided with a device that is operatively connected to the machine control for rotating the at least one hook needle around its longitudinal axis, wherein the device comprises a holder for the at least one hook needle, an actuator for rotating the at least one hook needle and a drive for said actuator. When using such an apparatus, a large number of hook needles can advantageously be operated with a single drive.
A servomotor is used as the drive for yet another embodiment of the apparatus, which advantageously allows realizing any rotation of the hook needle and thus any positioning of the hook.
According to a different embodiment of the apparatus, the actuator is provided with a toothed rack which represents a simple, cost-effective and for such uses also proven component for transferring torque from the drive to the hook needles.
In the following, the invention is described in further detail with the aid of an exemplary embodiment, showing in:
Also shown is a third, folded signature 5, which has been transported in feeding direction 7 to the book block 6 and fits with its leg 8 flat against the book block 6, so that it can be sewn together with the book block 6. To better understand the sewing principle, this additional signature 5 which rests on the non-depicted stitching saddle is shown while cut along the fold 10, meaning only the first leg 8 of the third signature 5 is shown while the second leg 9 is not shown. Furthermore shown are two spaced-apart pre-punching needles 11, a sewing needle 13 with an eyelet 12, a hook needle 14 arranged at a distance to the sewing needle 13 in the direction of the fold 10 on the third signature 5, which is provided along the circumference with a recess 16 forming a hook 15 (see also
During the operation of the apparatus 1, the two pre-punching needles 11 initially penetrate the fold 10 of the signature 5 to be sewn, from the inside in the direction of the movement arrows shown, thus forming in this fold 10 two spaced-apart holes 19 (
The two segments 2a, 2b of the binding thread 2 are subsequently admitted with an air stream 23 from the compressed air nozzle 17 and transported in the direction of the hook needle 14 movement path 24, shown with a dashed line. In the process, a binding thread loop 25 with closed end 26 is formed (
Following this, the hook needle 14 which is surrounded on the outside 20 of the fold 10 by the eyelet 22 dips from the outside through the second hole 19, formed by the pre-punching needles 11, into the inside space 21 between the legs 8, 9 of the signature 5 to be sewn and finally also through the binding thread loop 25. During the return stroke of the hook needle 14, the binding thread loop 25 that is in the meantime pulled tight by said hook needle is gripped by the hook 15 of the needle 14 and guided through the second hole 19 of the fold 10, as well as through the eyelet 22 on its outside 20. In the process, a second, double-strand seam 4 is formed on this outside 20 of the fold 10, arranged in the direction of this fold 10 at a distance to the first, single-strand seam 3 (
A correspondingly embodied hydraulic cylinder, not shown here, is used to rotate the hook needle 14, wherein its first end position corresponds to the first rotational position 30 of the hook needle 14 and/or its hook 15, and its second end position corresponds to the second rotational position 31 of the hook needle 14 and/or the hook 15. During the movement of the hook needle 14 from the outside to the inside, this needle and thus also its hook 15 are located in the first rotational position 30. This rotational position 30 of the hook 15, on the side of the hook needle 14 located on the previously stitched signature 5, is maintained at least as long as the hook 15 is still partially on the outside 20 of the fold 10 (see also
Depending on the configuration of the book blocks 6 to be produced, additional signatures 5 can be joined in the same way. Even though
Deviating from the normal stitch shown in
The second rotational position 31 of the hook needle 14 and/or its hook 15, known from the prior art and shown in
Concerning the first rotational position 30 of the hook needle 14 and/or its hook 15, also known from the prior art and shown in
When operating this apparatus 1, the hook needles 14 used for sewing the signatures 5, supplied by the non-depicted stitching saddle, are initially in a starting rotational position, which corresponds to the first rotational position 30 known from the prior art and shown in
Once the respective binding thread loop 25 is formed on the inside 21 of the signature 5 to be sewn, and after the hook needles 14 dip into this inside space 21 in the same way as described in the above for a single hook needle 14 according to the prior art, in connection with
At the very latest before the hooks 15 of the hook needles 14 are moved respectively through the eyelet 22 formed by the binding thread 2 of the previously sewn signature 5 and located on the outside 20 of this fold 10, these hook needles 14 and thus the hooks 15 are rotated with the aid of the drive 41, for example to a third rotational position shown in
In contrast to the known prior art with two fixed rotational positions, respectively offset by 180°, this method and the corresponding apparatus 1 add another rotational position for the hook needles 14 and their respective hooks 15. The now available three rotational positions can be divided easier into the three critical method steps of thread-stitching, namely the inserting from the outside to the inside of the hook needles 14 through the fold 10 of the signature 5 to be sewn, gripping of the binding thread loops with the hooks 15 of the hook needles 14, and penetrating from the inside to the outside of the hooks 15 of the needles 14 through the eyelet 22 that is respectively located on the outside 20 of the fold 10 for the previous signature 5. In addition, the inventive solution permits adapting two of the three rotational positions individually and thus flexibly to the respective working situation during the thread-stitching of folded signatures 5. The quality of the produced book blocks 6 can therefore be increased and the danger of damaging the binding thread 2 used for this can be reduced.
It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and that the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.
Number | Date | Country | Kind |
---|---|---|---|
01347/17 | Nov 2017 | CH | national |