Method for manufacturing a braided single-thread stent, device and braiding core therefor, and braided single-thread stent

Abstract

The present invention relates to a method for producing a single-thread stent from a thread (10) with a first end (11) and a second and free end (12), wherein a thread (10) is wound spirally from the first end (11) onto a braided core (2) with a longitudinal axis (X) in turns (13) between at least a first deflection (26) in a proximal end region (21) and at least a second deflection (27) in a distal end region (22), and the thread (10) is alternately placed at a crossing point into a guide (14) and inserted into an underpass (15), characterized by the method steps for forming an underpass (15): - Laying a turn (13) on the braid core (2) until reaching a crossing point, - Inserting and pushing through the second free end (12) of the thread (10) in a insertion direction (S) through a guide recess (25) in the braiding core (2), which is arranged substantially perpendicular to the longitudinal axis (X), and - Receiving and pulling the thread (10) through the guide notch (25).

Description

[0001] The present invention relates to a method for producing a braided single-filament stent having the features of patent claim 1, a braided single-filament stent having the features of patent claim 14, a braided core, in particular a braided core for carrying out the method having the features of patent claim 15, and a device for carrying out the method for producing the braided single-filament stent having the features of patent claim 23.

[0002] Stents in various designs are already known from the state of the art and are primarily used in hollow organs and vessels. Stents are tubular endoprostheses that can be implanted into the hollow organ or vessel, preferably minimally invasively, to stabilize a lumen in the hollow organ or vessel and maintain the functionality of the hollow organ. Such hollow organs include, for example, the respiratory tract, the digestive tract, the urinary and biliary tract, and the cardiovascular system, with their use in these aforementioned organs having proven extremely effective.

[0003] A variety of methods for manufacturing stents are known from the prior art. These manufacturing methods include 2D braiding, 3D braiding, winding, and manual braiding. The manufacturing method used has a significant influence on the final properties of the resulting stent. One example is disclosed in WO 2010 085 794 A2.

[0004] Automatable braiding techniques are characterized by the fact that multiple threads are laid simultaneously on a core and the threads are connected at intersection points, particularly at the stent end, to prevent the stent from coming apart. Due to the complete automatability of 2D and 3D braiding techniques, these fast and cost-effective processes have proven successful in the production of cylindrical stents and dogbone stents. However, the stent ends have proven problematic. At the stent ends, the threads must be connected by welding, which causes traumatic stress on the adjacent tissue, necessitating complex post-processing to prevent this.Furthermore, it has been shown that the stents in the respective hollow organ are subjected to constant dynamic loading, and the welded joints to continuous cyclic loading. There is a risk that the welded joints will break after reaching several tens of thousands of cycles. This reduces the stabilizing effect of the stent, and further interventions in the patient may become necessary.

[0005] A device for mechanically overbraiding a braiding core is known from the document DE 10 2014 016 832 B3.

[0006] Coiled stents are typically single-filament stents that are placed on a winding core in a mostly manual process, known, for example, from DE 10 2016 102 503 A1 or WO 2017 / 137 577 A1. The winding core is typically a cylindrical core with a proximal end region and a distal end region spaced therefrom, with deflection pins arranged in the respective proximal end region and in the respective distal end region. The single-filament stent is made from a filament with a first end and a second end, which is preferably made of a titanium-nickel compound, in particular nitinol.Starting from the first end, the thread is repeatedly applied in spiral turns from the proximal end to the distal end, over the deflection pins and back to the proximal end. At intersection points, i.e. points where two turns intersect at an angle, each laid down turn is placed on top of the first laid down turn, thus forming a so-called bridge. To give the wound single-filament stent sufficient strength and prevent it from falling apart, the two laid down turns are welded together at numerous intersection points. With these single-filament stents, too, it has been proven disadvantageous that the weld points have a detrimental effect on the quality and longevity of the stent and that the stabilizing effect of such stents on the hollow organ is also reduced.

[0007] Manually braided single-filament stents are manufactured using a complex manufacturing process by braiding onto a braided core. These stents are custom-made. For manual braiding, a braided core is used, which is designed similarly to the wound core mentioned above, but has a multitude of guide recesses incorporated into the braided core in a spiral or helical shape. Unlike wound single-filament stents, at the intersection point, the turns are alternately placed over an already laid turn and tucked under an already laid turn, creating a braid. Only the two ends of the thread are connected by a weld.A scientific study entitled "Process Selection for the Production of Metallic Airway Stents" by Kathrin Kurtenbach (2016) compared the processes presented above and concluded that manually braided single-filament stents are far superior to other stents, particularly because they allow for maximum geometric diversity and a particularly flexible stent structure with atraumatic stent ends. Manually braided single-filament stents do not have weld points to maintain the structure, making these stents particularly durable and thus contributing to patient safety.

[0008] A particular disadvantage of this process has proven to be that the production of manually braided single-filament stents requires highly qualified personnel who must be able to produce the stents with consistent quality. Maintaining constant wire tension and threading the filament into the guide recesses in the braid core, in particular, requires a high degree of concentration and experience, making the production of such manually braided single-filament stents significantly expensive. Furthermore, it has proven disadvantageous that the filament becomes partially twisted during threading and pulling through the guide recess, and the filament surface suffers surface damage due to contact with the guide recess, which adversely affects the longevity of the stent.

[0009] This is where the present invention comes in.

[0010] The object of the present invention is to provide a method for producing a single-filament stent that expediently enables automated production of a braided single-filament stent while eliminating the other disadvantages of the prior art. In particular, the manufacturing method should be fully or partially automated in order to replace labor-intensive process steps with a suitable manufacturing process in order to produce a consistent and higher quality with less or negligible waste. Furthermore, a braided core and a device for carrying out the method are proposed, which should enable a fully automated process.

[0011] These objects are achieved according to the invention by a method for producing a braided single-filament stent having the features of patent claim 1, by a braided core having the features of patent claim 15, and by a device for carrying out the method according to the invention having the features of patent claim 23. Furthermore, the object is achieved by a braided single-filament stent having the features of patent claim 14.

[0012] To carry out the method according to the invention with the features of claim 1, a thread with a first end and a second end and a braiding core are provided, wherein the braiding core has a proximal end region and a distal end region arranged at a distance from the proximal end region in the longitudinal axis. At least one first deflection is arranged in the proximal end region and at least one second deflection is arranged in the distal end region. Between the proximal end region and the distal end region, the braiding core has at least one guide recess, which is machined or formed substantially perpendicular to the longitudinal axis.Starting from the first end, the thread is laid onto the braiding core in a spiral or helical manner in turns between the at least one first deflection and the at least one second deflection, the thread being laid at crossing points either over a first turn in an overpass or under a first turn in an underpass, the method according to the invention being characterized by the following method steps for forming an underpass:. - Laying a turn on the braiding core until reaching a crossing point, - Inserting and pushing the second end of the thread in a direction through the guide recess in the braiding core, and - Accept and pull the thread through the guide recess.

[0013] According to the invention, the key finding is that when laying the thread to form an underpass, the free end of the thread is not guided along the spiral or helical winding, but essentially perpendicular to the longitudinal axis of the braiding core, thereby significantly facilitating threading, receiving, and pulling through the thread. The guide recess, which is arranged essentially perpendicular to the longitudinal axis, allows the free end of the thread to be inserted through the guide recess along a straight line that is arranged secantial to the braiding core, whereas the braiding cores known from the prior art require the free end of the thread to be inserted through the guide recess along a curved (helical) curve.In the context of this invention, an essentially perpendicular orientation can be understood as an angular tolerance of ±15°, preferably ±10°, more preferably ±5°, and most preferably ±1°. In the context of this invention, secantal can be understood as an arrangement of a straight line formed as a secant, which intersects the lateral surface of the braiding core at two points and is arranged at a distance from the center or the longitudinal axis.

[0014] According to a further advantageous embodiment of the present inventive method, the thread is pulled through the guide recess until the thread winding is applied to the braiding core with a predetermined and preferably constant tension. By pulling on the thread, the thread is preferably positioned on the braiding core such that it rests against it in its final winding position. By pulling, the thread does not lie on the bottom of the guide recess, but bridges or spans the guide recess due to tensile stress, whereby the final positioning on the braiding core can be achieved.

[0015] A further advantageous embodiment of the present invention provides that the insertion direction is aligned parallel to the guide recess. It is further preferred if the free end of the thread is inserted and pushed through the guide recess in the insertion direction, centered on the guide recess. This allows for the thread to be guided in the guide recess with as little contact as possible, without the thread being damaged by frictional contact at the guide recess of the braiding core.

[0016] According to a further advantageous embodiment of the method according to the invention, a first gripper holds the thread at a distance from the free end and inserts the free end into the guide recess in the insertion direction to form an underpass. The distance between the free end and the first gripper corresponds at least to the length of the guide recess (in the insertion direction) or at least one-third of the diameter of the braiding core. Preferably, the distance is greater than the diameter of the braiding core. The first gripper can be CNC-controlled and movable relative to the braiding core, whereby exact positioning of the free end relative to the respective guide recess can take place. Meanwhile, the first gripper holds the thread in such a way that it is fixed in its position and under its control no change in the position of the thread can occur, e.g. undesired displacement or twisting.After the thread has been inserted, the first gripper can release the thread and pick up or receive the thread again on the side located behind the guide recess in the insertion direction.

[0017] Furthermore, it is particularly advantageous if the first gripper or a second gripper is provided, which is configured to receive the free end of the thread in the insertion direction behind the guide recess. The second gripper can contain the first gripper.

[0018] In addition, the second gripper can be designed analogously to the first gripper and can be CNC controlled, whereby an exact positioning relative to the braiding core for receiving the free end of the thread pushed through the guide recess can be carried out on the side of the guide recess opposite the first gripper.

[0019] When carrying out the method according to the invention, it is particularly advantageous if the first gripper holds the thread at least until the second gripper also holds the free end of the thread. As soon as the second gripper has taken over and is holding the free end of the thread, the first gripper can release the thread. This ensures that control over the thread is maintained uninterrupted during the implementation of the method according to the invention and, for example, prevents unwanted twisting of the thread.

[0020] A further advantageous development of the method according to the invention provides that the thread is pulled through from the free end by winding it onto a spool around a second axis. It is preferred if at least one of the grippers, preferably the second gripper, which receives the free end behind the guide recess, rotates together with the spool around the second axis to pull the thread through the guide recess and wind it up, whereby complete control over the position of the thread can be maintained even when the thread is being wound up. Furthermore, it is particularly preferred if the second gripper first pulls the free end of the thread through the guide recess in the insertion direction and the first gripper follows the feed movement of the second gripper and picks up and holds the thread again, also in the insertion direction behind the guide recess.The first gripper can then be rotated together with the second gripper and the spool around the second axis to pull the thread completely through the guide recess and wind the thread up.

[0021] It is particularly preferred if, when the thread is wound onto the spool or when the thread is laid onto the braiding core, the predetermined tension of the thread on the braiding core is monitored, for example by at least one force and / or torque sensor, by means of which the torque applied to the spool or the tension or the tensile force on the thread is detected.

[0022] A particularly advantageous embodiment of the present invention provides that the second axis is either aligned parallel to the longitudinal axis of the braiding core, or that the second axis is arranged perpendicular to the longitudinal axis of the braiding core.

[0023] When carrying out the method according to the invention, it can also be advantageous if the thread is held on the braiding core after being pulled through the guide recess to form an underpass. It is particularly preferred if at least one holding means is provided that is designed to apply a holding force to the winding of the thread. The at least one holding means can fix at least one winding deposited on the braiding core and secure the laying of the winding until the next underpass is reached.

[0024] It has also proven advantageous if the thread is completely unwound from the spool before the free end of the thread is inserted and pushed through to form the underpass. After unwinding the spool, the free end of the thread is positioned in the insertion direction in front of the next guide recess to form another underpass. For this purpose, the braiding core can preferably be twisted along its longitudinal axis and a corresponding lateral movement along the longitudinal axis between the proximal end region and the distal end region of the braiding core can be performed in order to position the free end of the thread in front of the corresponding guide recess according to the pitch of the winding.

[0025] Furthermore, it is advantageous if a guide device which is more rigid than the thread is arranged at the second end of the thread. The guide device can guide the thread, for example, according to the needle and thread principle, wherein the first gripper and the second gripper can hold the guide device rather than the thread, thereby considerably simplifying handling of the thread when carrying out the method according to the invention. It is particularly preferred if the shape of the guide device is adapted to the shape of the guide recess. The guide device and the guide recess can, for example, have a polygonal cross-section. As a result, the guide device cannot be twisted in the guide recess due to a positive fit (with a clearance fit), thereby preventing unwanted twisting of the thread when creating an underpass.The guide device can be attached to the thread when the thread is provided.

[0026] A further advantageous embodiment of the present invention provides that the first end and the second end of the thread are connected to one another in a common winding. Particularly preferably, the weld is arranged centrally between the proximal end region and the distal end region. Even more preferred is when the weld is arranged in an underpass. The weld can preferably be produced by means of electron beam welding, laser welding, resistance welding, friction welding, or microplasma welding. After welding, the free end regions of the first end and the second end of the thread beyond the weld can be severed. Thus, on the one hand, the weld is located in an area with low mechanical stress, and on the other hand, the weld is positioned atraumatically.

[0027] It has proven particularly advantageous that the laid thread is pulled out of the respective guide recess due to the thread tension and bridges or spans the guide recess. This releases the guide recess and the thread can be pushed through the at least one guide recess several times along the turns according to the method described above to form an underpass. In this turn, at least two sections of the thread then lie directly next to one another. In particular, the connection of the first end and the second end of the thread in a common turn with two sections is considerably simplified. The sections can also be twisted together in one or more turns. Furthermore, it is advantageous if the braided single-thread stent is post-treated after braiding by tempering and / or electropolishing.The tempering process step is preferably performed before the single-filament stent is removed from the braided core. Furthermore, it is advantageous if the single-filament stent is electropolished after removal from the braided core, thereby removing even the slightest surface damage, especially scratches. This increases the fatigue strength of the braided single-filament stent.

[0028] It has also proven advantageous to use a metallic or polymer thread to manufacture the braided single-thread stent.

[0029] The thread can particularly preferably be a single thread. Alternatively, the thread can be made from multiple individual threads (strands), whereby the strands can be made from different materials. The following materials or material groups are preferably used for the thread: nickel-titanium alloys, in particular nitinol, magnesium alloys, stainless steel, in particular medical-grade stainless steel (e.g., 316LVM), chromium alloys, cobalt-chromium alloys, cobalt alloys, niobium-containing alloys, platinum alloys, platinum-chromium alloys, tantalum alloys. A thread made from a polymer or polymer mixture can also be used to manufacture the braided single-thread stent.

[0030] It is advantageous if a thread with a diameter in the range of 1 µm to 1000 µm is used to manufacture the single-filament stent, preferably in the case of a blood vessel single-filament stent in the range between 10 µm and 350 µm and preferably in the case of a pulmonary, tracheal, laryngeal, ureteral, gastrointestinal or bile duct single-filament stent in the range between 10 µm and 500 µm.

[0031] Preferably, the spiral windings are placed on the winding core in such a way that a crossing angle α, at which two windings intersect or cross at a crossing point, lies in the range between 10°≤ α ≤ 80°, preferably in the range between 30° ≤ α ≤ 60°.

[0032] A second and further aspect of the present invention relates to a single-filament stent produced by a method according to the invention.

[0033] A third aspect of the present invention relates to a braiding core, in particular a braiding core for carrying out the method according to the invention, comprising a core with a longitudinal axis, a proximal end region, and a distal end region, wherein the proximal end region is arranged at a distance from the distal end region in the longitudinal axis. Furthermore, the braiding core comprises at least one first deflection and at least one second deflection, wherein the at least one first deflection is arranged in the proximal end region and the at least one second deflection is arranged in the distal end region. According to the invention, at least one guide recess is arranged between the proximal end region and the distal end region, which guide recess is arranged substantially perpendicular to the longitudinal axis.In the context of this invention, an arrangement which is oriented substantially perpendicular to the longitudinal axis is understood to mean an angular tolerance of ±15°, preferably less than ±10°, even more preferably less than ±5° and most preferably less than ±1° between the orientation of the at least one guide recess and the longitudinal axis. The guide recess is machined or molded into the core and is designed in the manner of a secant and as a groove oriented perpendicular to the longitudinal axis. The depth and width of the guide recess are adapted to the size of the thread and are at least as large as the thread to be passed through the guide recess. The width of the guide recess is limited by a mesh size, wherein the mesh size describes the distance between two intersection points parallel to the longitudinal axis.

[0034] According to a further advantageous embodiment of the present invention, the core is cylindrical. It is particularly preferred if the core has a constant diameter between the proximal end region and the distal end region, or if the core initially has a decreasing and then increasing diameter between the proximal end region and the distal end region, thereby allowing the production of a braided single-filament stent in a dogbone shape.

[0035] According to a further advantageous embodiment of the present invention, the at least one deflection is formed by a deflection pin protruding from the core, preferably radially. The deflection pins can be releasably attached to the core of the braided core, whereby, for removing the braided single-filament stent, the deflection pins in the proximal end region and in the distal end region can be removed, and the single-filament stent can be pulled or removed from the braided core. The deflection pins can be designed as a clamp, arch, T-shaped pin, or the like.

[0036] Furthermore, it has proven advantageous if a number i of deflections is arranged in each of the proximal end region and the distal end region. It is particularly preferred if deflections in the proximal end region and in the distal end region are arranged circumferentially symmetrically. The number i of deflections in the proximal end region and in the distal end region can preferably be an even number. A particularly preferred embodiment of the braiding core provides that ten or twelve deflections (i = 10 or i = 12) are arranged circumferentially symmetrically in each of the proximal end region and in the distal end region.

[0037] It is advantageous if the at least one guide recess is a recess which runs perpendicular to the longitudinal axis around the core and / or if the at least one guide recess is a recess which is machined or formed secantally into the core.

[0038] The recess can be incorporated into the core particularly easily and cost-effectively by means of an appropriate machining process, e.g. turning, or it can be formed into the core during the reshaping or primary forming of the core.

[0039] It may also be advantageous if the guide recess is a secantally machined recess in the core, i.e., a recess oriented in a tangential direction. The respective recess can be molded or machined into the core.

[0040] It is preferred if a number j of guide recesses is formed over the circumference of the core in a plane transverse to the longitudinal axis. The guide recesses can be spaced apart from one another, whereby the applied windings between the guide recesses are not influenced. Furthermore, it is advantageous if the guide recesses are arranged in rows in a number k along the longitudinal axis.

[0041] It is advantageous if the at least one guide recess has a rectangular, U-shaped, or V-shaped cross-section, or combinations thereof. In particular, it has proven advantageous if the guide recess has a variable width. Particularly preferably, the width of the guide recess increases from a center point of the guide recess, more preferably in both directions, thereby simplifying the threading and insertion of the free end of the thread and further reducing the positioning effort required when inserting and inserting the free end of the thread.

[0042] A fourth aspect of the present invention relates to a device for carrying out the method according to the invention for producing a braided single-filament stent. The device for carrying out the method comprises a first axis and a second axis, wherein the first axis is configured to hold or receive a braiding or winding core, in particular a braiding core according to the invention. Furthermore, the device comprises at least one arm with at least one gripper, wherein the at least one gripper is configured to grip and hold a thread. The at least one arm and the at least one spool are arranged rotatably about the second axis. According to the invention, the braiding core is held rotatably about the first axis, wherein the device preferably controls the rotation of the braiding core about the first axis.Furthermore, the device controls the second axis such that the spool and the arm rotate together along the second axis. During rotation about the second axis, the arm or at least one of its grippers can hold the free end of the thread while simultaneously winding the thread onto or unwinding it from the spool.

[0043] According to a further advantageous embodiment of the present invention, the at least one arm comprises the first gripper and a second gripper, which are arranged at a distance from one another and are rotatable together about the second axis. The first gripper and the second gripper can each be controlled separately by a controller of the device, so that the first gripper and / or the second gripper can each independently perform a movement for picking up, gripping, and holding the thread.

[0044] According to an advantageous embodiment of the device according to the invention for producing a braided single-filament stent, the first axis and / or the second axis have / have at least one force sensor which is configured to determine the torque or a transverse force applied to the first axis and / or the second axis. By determining the torque or the transverse force applied to the first axis and / or the second axis, it is possible to determine the tensile stress with which the thread is pulled when it is laid on the braided core, whereby it can be ensured that the thread is laid on the braided core with a constant and predetermined tensile stress when it is laid on the braided core.

[0045] According to a further embodiment of the present invention, it can be advantageous for the at least one arm to be movable relative to the first axis. The at least one arm is preferably CNC controlled by the control system of the device, whereby the respective at least one gripper can be positioned precisely. This is necessary, for example, in order to position the gripper in a plug-in direction in front of the braiding core and the guide recess, and in the plug-in direction behind the braiding core in order to receive the free end of the thread. While the first gripper is preferably designed to guide a free end of the thread protruding from the gripper to form an underguide at an intersection point, the second gripper is preferably designed to receive the thread or its free end after the underguide has been formed and to pull it through the underguide.In a particularly preferred embodiment of the present invention, the first gripper and the second gripper can hold the thread together after formation of the underpass and can be rotated together with the spool about the second axis, whereby the thread is secured against a change in position when wound around the spool and it can be prevented that the thread is twisted.

[0046] It is preferred if the first axis and the second axis are aligned parallel to each other or if the first axis and the second axis are arranged perpendicular to each other.

[0047] Furthermore, a provision of the present invention provides that the device comprises at least one holding means which is designed to apply a holding force to the braiding core. In particular, it is preferred if the holding means can fix a turn placed on the braiding core on the braiding core, so that the tension of the thread of the turns already placed on the braiding core is not lost. It is particularly preferred if the at least one holding means is rotatable about the first axis, wherein it is further particularly preferred if the at least one holding means can be rotated about the first axis together with the first axis or with the braiding core arranged in the first axis.

[0048] An embodiment of the present invention will be explained in detail below with reference to the accompanying drawings. They show: Fig. 1 a highly simplified representation of a device according to the invention for producing a braided single-thread stent with a braided core, wherein the braided core has a plurality of guide recesses which are formed vertically in the braided core to form an underpass at an intersection point, Fig. 2a to 2g schematic and simplified detailed representations of individual process steps for forming the underpass with the device according to Fig. 1, and Fig. 3 an enlarged plan view of a guide recess according to Fig. 1 or Fig. 2, and Fig. 4a to 4c schematic sectional views through the guide recess.

[0049] The same reference numerals designate the same or similar parts in the different illustrations. For clarity, not all reference numerals are shown in all figures.

[0050] Fig. Figure 1 shows the device 5 for producing a braided single-thread stent from a thread 10. The device 5 comprises a first axis 51 and a second axis 52, which are oriented perpendicular to each other in the illustrated and exemplary embodiment, but can also be oriented parallel to each other. The first axis 51 and the second axis 52 can correspond to machine axes and can each be controlled independently of each other by a controller of the device 5.

[0051] To produce the braided single-thread stent, a braiding core 2 is coupled to the device 5 in the first axis 51, whereby the braiding core 2 in the device 1 is drivingly coupled to the corresponding machine axis of the device and is held rotatably about the first axis 51.

[0052] In the second axis 52 are an arm 54, see Fig. 2a to 2g, and a spool 55 are rotatably supported, with the second axis 52 being movable relative to the first axis 51. The arm 54 comprises a first gripper 61 and a second gripper 62, which can be controlled independently of one another by the control system of the device and are configured to grip and hold the thread 10. The arm 54 allows the grippers 61, 62 to be positioned relative to one another and, together with the arm 54, relative to the first axis 51. The braided core 2 comprises a cylindrical core 20 with a longitudinal axis X, a proximal end region 21, and a distal end region 22. The proximal end region 21 and the distal side 22 are arranged parallel and spaced apart along the longitudinal axis X. The proximal end region 21 has a plurality of first deflections 26, and the distal end region 22 has a plurality of second deflections 27, wherein the respective deflection 26, 27 is formed as a deflection pin 28 protruding from a lateral surface of the cylindrical core 20. The respective deflection pin 28 can be a clamp, a bow, a bracket, or a T-shaped pin.

[0053] In the illustrated embodiment, a number i of twelve deflection pins 28 are arranged circumferentially symmetrically around the circumference of the lateral surface in both the proximal end region 21 and the distal end region 22, wherein the deflection pins 28 are detachably fastened to the cylindrical core 20. The number i can be chosen arbitrarily, and the number i of first deflections 26 and second deflections 27 should be identical, with the number i preferably being an even number. The deflection pins 28 are preferably cylindrical and preferably protrude radially from the lateral surface of the core 20.

[0054] Furthermore, Fig. 1 shows that between the proximal end region 21 and the distal end region 22, between the first deflection 26 and the second deflection 27, a plurality of guide recesses 25 are arranged in columns, which are aligned substantially perpendicular to the longitudinal axis X. The respective guide recess 25 is formed along a secant in the core 20, wherein the secant, by definition, intersects the lateral surface of the preferably cylindrical core 20 at two points and is accordingly arranged between a tangent and the longitudinal axis X. A number j of guide recesses 25 are arranged circumferentially symmetrically around the longitudinal axis X in a plane perpendicular to the longitudinal axis, wherein the number j corresponds to half the number i of deflections 26, 27, i.e. j = i / 2.

[0055] The guide recesses 25 are arranged in columns along the longitudinal axis X in a number k, wherein the number k depends on a mesh width W and a distance between the proximal end region 21 and the distal end region 22, which distance corresponds to a length of the single-thread stent to be braided.

[0056] The respective guide recess 25 can be machined or formed into the lateral surface of the core 20 as a tangential or secantial groove or recess perpendicular to the longitudinal axis X or alternatively as a circumferential recess (not shown).

[0057] The respective guide recess 25 has a width B and a depth T and can have any shape in cross section, whereby three typical cross sections for the guide recess 25 are shown in the Fig. 4a to 4c. The guide recess 25 may, for example, have a U-shaped cross-section, shown in Fig. 4a. The guide recess 25 can also have a V-shaped cross-section - see Fig. 4b - or a rectangular cross-section - see Fig. 4c. The width B and depth T of the guide recess 25 are adapted to the size of a thread 10 used to form the braided single-thread stent. The width B is at least as large as the diameter of the thread 10 used, with the maximum width B being limited by the mesh size W and thus preferably not exceeding 0.9*W. Furthermore, the Fig. 3 that the width B of the guide recess 25 does not have to be constant, but the width B in the respective guide recess 25 can be variable. It is preferred if the width B increases from the center of the guide recess 25 to the ends of the guide recess 25, where the guide recess 25 merges into the lateral surface of the core 20.

[0058] To form the braided single-filament stent, the filament 10 is placed on the braided core 2, wherein the filament 10 has a first end 11 and a second end 12. The filament 10 can be made of a metallic material or a synthetic material, for example, polymer fibers, and can have a diameter between 1 µm and 1000 µm, depending on the intended use of the tubular braided single-filament stent.

[0059] It is particularly preferred if the thread 10 is made of a titanium-nickel alloy, for example Nitinol, and has a diameter of approximately 350 µm.

[0060] The thread 10 is, as shown below using the Fig. 2a to 2g, starting from the first end 11, the braided core 2 is placed in spiral or helical windings 13, wherein a guide device 16 can be arranged at the second end 12 to improve the handling of the thread 10. The guide device 16 can be coupled to the second end of the thread 10, for example, by means of a positive, non-positive, or material-locking connection, wherein the guide device 16 has a higher rigidity than the thread 10. In particular, the guide device 16 can also have a larger cross-section, even with a non-rotationally symmetrical cross-section, preferably a square cross-section, thereby improving the handling of the thread 10.

[0061] For this purpose, the first end 11 is attached to the braiding core 2 at the proximal end region 21 and, starting from the first end 11, the free end 12 is placed on the braiding core 2 until a deflection pin 28 of the second deflections 27 in the distal end region 22 is reached. The thread 10 is then placed around one of the deflection pins 28 and guided in a further turn 13 in a spiral or helical manner around the core 20 to one of the first deflections 26 in the proximal end region 21. This process is repeated until the turn 13, during laying, crosses an already laid turn 13 at a so-called crossing point, wherein at this crossing point either the free end 12 is placed in an overpass 14 onto the first turn 13 or is guided in an underpass 15 under the first turn 13, thereby forming a braid.The two turns 13 intersect at the intersection point with a crossing angle α, which, depending on a predetermined pitch of the turns 13, is approximately 10° ≤ α ≤ 80° and preferably 30° ≤ α ≤ 60°.

[0062] The braid can be formed in any desired sequence, with the thread 10 being alternately placed at an intersection point in an overpass 14 and inserted into an underpass 15. This results in particularly good mechanical properties for the braided and tubular single-thread stent. Such fabrics can be referred to as plain weave. Alternatively, fabrics with twill weaves, satin weaves, or warp-thickness fabrics are possible.

[0063] To produce the single-thread stent, the thread 10 is held at a distance from the second end 12 by at least one of the grippers 61, 62, and then the thread 10 is wound onto the spool 55 starting from the second end 12. To place the thread 10 onto the braiding core 2, the braiding core 2 is rotated about the first axis 51, during which the spool 55 unwinds the thread 10 under a constant thread tension in the second axis 52, and the spool 55 is moved along the longitudinal axis X, whereby the winding 13 receives a corresponding pitch.

[0064] Upon reaching a crossing point where an underpass 15 is to be created under an already laid first turn 13, the already laid turn 13 is fixed by a holding means 65. Subsequently, the thread 10 is completely unwound from the spool 55 and the first gripper 61 is positioned in a plugging direction S in front of the corresponding guide recess 25, wherein the first gripper 61 positions the thread 10 in the plugging direction S coaxially to the orientation of the guide recess. The second gripper 62 is - as in Fig. 2a - positioned in the insertion direction S behind the guide recess 25 for receiving the free end 12 of the thread 10 and then the free end 12 of the thread 10 is pushed through the guide recess 25 and under the first winding 13 and received on the opposite side of the guide recess 25 by the second gripper 62. Only when the second gripper 62 has received the free end 12 of the thread and securely holds the free end 12 of the thread 10, the first gripper 61, as shown in Fig. 2c, the thread 10 is released so that the thread 10 can be completely pulled through the guide recess and the underpass 15. For this purpose, the second gripper 62 can first exert a pulling force on the free end 12 of the thread 10 and then, as shown in the Fig. 2d and Fig.2e, the free end 12 of the thread 10 is wound onto the spool 55, whereby the thread 10 is pulled completely through the guide recess 25.

[0065] The first gripper 61 and / or second gripper 62, as well as the first axis 51 and / or the second axis 52, can have force sensors (not shown) by which a tensile stress applied to the thread 10 can be determined. It is particularly preferred if the force sensor detects a torque applied to the spool 55 or to the first axis 51.

[0066] After the thread 10 has been completely pulled through to form the underpass 15, the winding 13 is further laid onto the braiding core 2 as already described above, with the holding means 65 being positioned behind the underpass 15 and applying a holding force to the winding 13 so that the tensile stress of the thread 10 in the already laid winding 13 is not lost when the spool 55 is unwound to create a further underpass 15. Preferably, the thread 10 is held under a predetermined and preferably constant tensile stress when laying the winding 13.

[0067] The thread 10 is wound in turns 13 onto the braiding core 2 until the wound turns 13 are arranged parallel to a first turn 13. These two turns 13 are preferably connected by means of a welded joint, and then the free end regions of the thread 10 located between the welded joint and the ends 11, 12 are cut or removed.

[0068] Finally, the braided core 2 can be removed from the device together with the braided and tubular single-filament stent and subjected to further processing steps. In a first further processing step, the single-filament stent can be thermally post-treated, preferably on the braided core 2, by tempering at approximately 500°C.

[0069] Subsequently, the deflection pins 28 can be detached from the core 20, and the single-thread stent can be stripped from the core 20. In a further process step, the surface of the thread 10 can be reworked, for example, by electropolishing. List of reference symbols 2 braided core 5 Device 10 threads 11 first end 12 second end 13 turns 14 Transfer 15 Underpass 16 Guide device 20 braided core 21 proximal end region 22 distal end area 25 Guide recess 26 first diversion 27 second diversion 28 Deflection pin 30 guide recess 51 first axis 52 second axis 54 Arm 55 coil 61 first gripper 62 second gripper 65 holding devices B width of 25 S Plug direction T depth of 25 X Longitudinal axis

Claims

[1] Method for producing a single-thread stent from a thread (10) having a first end (11) and a second and free end (12), wherein a thread (10), starting from the first end (11), is wound spirally in turns (13) onto a braided core (2) having a core (20) and a longitudinal axis (X) between at least one first deflection (26) in a proximal end region (21) and at least one second deflection (27) in a distal end region (22), wherein the thread (10) is alternately laid at a crossing point into an overpass (14) and inserted into an underpass (15), characterized by the procedural steps for the formation of an underpass (15): - Placing a turn (13) on the braided core (20) until reaching a crossing point, - Inserting and pushing through the free end (12) of the thread (10) in a pushing direction (S) substantially perpendicular to the longitudinal axis (X) into a guide recess (25) of the braiding core (2), wherein the guide recess (25) is machined or formed into the core (20) and is designed in the manner of a secant and substantially perpendicular to the longitudinal axis groove, and - Accept and pull the thread (10) through the guide recess (25). [2] Method according to claim 1, characterized by that the thread (10) is pulled through the guide recess (25) until the winding (13) of the thread (10) is laid on the braiding core (2) with a predetermined tension. [3] Method according to claim 1 or 2, characterized by that the plug-in direction (S) is aligned parallel to the guide recess (25). [4] Method according to one of the preceding claims, characterized bythat a first gripper (61) holds the thread (10) at a distance from the free end (12) and inserts the free end (12) into the guide recess (25) in the insertion direction (S). [5] Method according to one of the preceding claims, characterized by that a second gripper (62) receives the free end (12) of the thread (10) in the insertion direction (S) behind the guide recess (25). [6] Method according to claims 4 and 5, characterized by that the first gripper (61) holds the thread (10) at least until the second gripper (62) holds the free end (12) of the thread (10). [7] Method according to one of the preceding claims, characterized by that the thread (10) is held on the braiding core (2) after being pulled through the guide recess (25). [8] Method according to one of the preceding claims, characterized bythat the thread (10) is pulled through from the second free end (12) by winding the thread (10) on a spool (55) around a second axis (52). [9] Method according to claim 8, characterized by that after winding the free end (12) of the thread (10) onto the spool (55), the thread (10) is laid on the braiding core (2) until reaching a next crossing point with an underpass (15). [10] Method according to claim 9, characterized by that the thread (10) is placed on the braiding core (2) with a predetermined tensile stress. [11] Method according to one of claims 8 to 10, characterized by that the thread (10) is completely unwound from the spool (55) before the free end (12) of the thread (10) is inserted and pushed through to form the underpass (15). [12] Method according to one of the preceding claims, characterized bythat a guide device (16) is arranged at the second end (12) of the thread (10), which has a greater rigidity than the thread (10). [13] Method according to one of the preceding claims, characterized by that the first end (11) and the second end (12) of the thread (10) are connected to one another in a common winding (13). [14] Braided core (2) for carrying out the method according to one of claims 1 to 13, comprising: - a core (20) having a longitudinal axis (X) and a proximal side (21) and a distal side (22), and - at least one first deflection (26) and at least one second deflection (27), - wherein the at least one first deflection (26) is in the proximal end region (21) and the at least one second deflection (27) is in the distal end region (22), - wherein at least one guide recess (25) is arranged between the proximal end region (21) and the distal end region (22), which is arranged substantially perpendicular to the longitudinal axis (X) - wherein the guide recess (25) is machined or formed into the core (20) and is designed in the manner of a secant groove oriented substantially perpendicular to the longitudinal axis. [15] Braided core (2) according to claim 14, characterized by that the core (20) is cylindrical. [16] Braided core (2) according to claim 14 or 15, characterized by that the respective deflection (26, 27) is formed by a deflection pin (28) projecting perpendicularly from the core (20). [17] Braided core (2) according to one of claims 14 to 16, characterized bythat a number (i) of deflections (26, 27) is arranged at the proximal end region (21) and the distal end region (22), wherein the number (i) of deflections (26, 27) is preferably even. [18] Braided core (2) according to one of claims 14 to 17, characterized by that the at least one guide recess (25) is a recess tangentially aligned in the core (20). [19] Braided core (2) according to one of claims 14 to 18, characterized by that the at least one guide recess (25) has a rectangular, triangular or rounded cross-section. [20] Braided core (2) according to one of claims 14 to 19, characterized by that a number (j) of guide recesses (25) are arranged circumferentially symmetrically over the circumference of the core (20) in a plane perpendicular to the longitudinal axis (X), and / or that a number (k) of guide recesses (25) are arranged parallel and spaced from the longitudinal axis. [21] Device (5) for carrying out the method according to one of claims 1 to 13 with a braiding core (2) with the features according to one of claims 14 to 20, comprising - a first axis (51) and a second axis (52), - at least one arm (54) with at least one gripper (61) which is arranged to grip and hold a thread (10), and - at least one coil (55) - wherein the braiding core (2) is arranged in the first axis (51), and - wherein the arm (54) and the at least one coil (55) are arranged to be rotatable about the second axis (52). [22] Device (5) according to claim 21, characterized by in that the at least one arm (54) comprises a first gripper (61) and a second gripper (62) which are arranged parallel and spaced from one another and are rotatable together with the spool (55) about the second axis (52). [23] Device (5) according to claim 21 or 22, characterized bythat at least one force sensor is provided by which the torque applied to the first axis (51) and / or the second axis (52) can be determined. [24] Device (5) according to one of claims 21 to characterized by that the arm (54) is arranged to be movable relative to the first axis (51). [25] Device (5) according to one of claims 21 to 24, characterized by that the first axis (51) and the second axis (52) are aligned parallel to each other, or that the first axis (51) and the second axis (52) are perpendicular to each other. [26] Device (5) according to one of claims 21 to 25, characterized by that at least one holding means (65) is provided which can apply a holding force to the first axis (51), in particular to the braiding core (20). [27] Device (5) according to one of claims 21 to 26, characterized by that the at least one holding means (65) is rotatable about the first axis (51).

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