WO2024256124A1

WO2024256124A1 - Apparatus for laser welding and respective method

Info

Publication number: WO2024256124A1
Application number: PCT/EP2024/063717
Authority: WO
Inventors: Christian Gimmel; Daniel Wintsch; Sebastian Klaus; Alexander Binder
Original assignee: Biotronik Ag
Priority date: 2023-06-13
Filing date: 2024-05-17
Publication date: 2024-12-19

Abstract

The invention refers to an apparatus for laser welding of an inner workpiece (21, 121, 221, 321, 421) to an outer workpiece (22, 122, 222, 322, 422) of a medical device, for example a catheter, at a welding area, the inner workpiece (21, 121, 221, 321, 421) and the outer workpiece (22, 122, 222, 322, 422) having a longitudinal axis (25), wherein the apparatus comprises a bearing device (10) comprising a bearing element (11, 111), wherein the bearing element (11, 111) is configured to apply pressure onto the outer workpiece (22, 122, 222, 322, 422). Further, the apparatus comprises a laser device (5) emitting electromagnetic radiation for welding, wherein the laser device is configured such that the emitted electromagnetic radiation is transmitted through the bearing element (11, 111) to the welding area.

Description

APPARATUS FOR LASER WELDING AND RESPECTIVE METHOD

The present invention relates to the manufacturing of medical devices, in particular to laser welding of two workpieces (also referred to as shafts or sleeves) of such medical devices, for example catheters, to attach these workpieces at least in one section to one another, wherein one of these workpieces (the inner workpiece) runs at least partly within or underneath the other workpiece (the outer workpiece). The present invention relates to an apparatus for laser welding of an inner workpiece to an outer workpiece of a medical device, a respective method, and a catheter assembly manufactured by such method.

Catheters with two workpieces or shafts that are accommodated within each other are widely used in medical treatment of patients. For example, in percutaneous transluminal coronary angioplasty (PTCA) procedures, a dilation catheter having a balloon on the distal portion thereof is used to dilate lesions in the vasculature of the patient by inflating the balloon with inflation fluid one or more times to a predetermined size at a suitable pressure to compress the stenosis against the arterial wall to open up the vascular passageway. In other cases, a balloon catheter can be used to expand a stent within the patient's vasculature by balloon inflation. Balloon catheters are also used for treatment of other luminal systems throughout the body. Further, other catheters or other medical devices, such as endoscopes, or inlet and outlet elements or cable insulations of medical devices, comprise a tubing where an inner workpiece, for example an inner tube, may be connected to an outer workpiece, for example an outer tube, at least in a section thereof by laser welding because laser welding can be easily automated. With regard to such medical devices, for example, the pushability, trackability and flexibility of the whole device or sections thereof are adjusted to provide a medical device with suitable properties for the specific use of this device. Additionally, as a predetermined pressure is applied to inflation fluid flowing within the tubing of a balloon catheter, for example, the section where one workpiece is fixed to another one should provide a reliable connect! on/fixati on to assure proper function of the medical device.

With regard to the balloon catheter as one example of a medical device, a connection of the distal balloon shaft with the inner shaft or the proximal balloon shaft with the outer shaft has so far been created using a heat shrink layer or heat shrink tube as an additional material and element. An external heat source, for example heating jaws or a long-wave laser beam, heats the shrink layer or shrink tube, thereby causing it to contract and apply contact pressure and heat to the section of the shafts to be connected. As a result, the respective balloon shaft and inner/outer shaft is joined. However, the known method is complicated and costly as the heat shrink layer or heat shrink tube is required as an additional material and element for the joining process. This heat shrink layer or heat shrink tube has to be positioned axially over the section to be connected prior the attachment step. Since there is usually a clearance fit between the shrink layer or tube and the diameter of the respective balloon shaft, it is necessary to reposition the shrink layer or tube directly prior the attachment process is started. After that, the shrink layer or tube is dismantled or peeled off which is a manual process that requires a lot of experience. The last step cannot be automated. Another disadvantage of the known method is that the shrink workpiece is usually longer than the section in which the connection of the balloon and the shaft is to be effected. Accordingly, sometimes non-intended contact pressure and heat is provided to neighboring areas of the balloon and/or the catheter shaft that are not intended to be part of the connection area. This may cause non-intended transition effects to these areas.

Another difficulty has been balancing the effort/costs during manufacturing and often competing characteristics such as strength and flexibility of the workpiece. Another difficulty has been providing a flexibility transition which improves maneuverability of the medical device, yet with a sufficiently strong transition bond. Kinking has also been a known issue for over-the-wire (OTW) catheters as well. As such, there remains a need for a medical device causing less effort/costs during manufacturing and avoiding the above non-intended effect on the balloon and catheter shaft and at the same time having workpieces with an improved combination of characteristics such as strength and flexibility. There is also a need for tubing of a medical device that has improved trackability to facilitate further passage through tortuous anatomy, such as distal coronary and neurological arteries, while maintaining the ability to withdraw from the tortuous anatomy.

The above problem is solved by an apparatus for laser welding having the features of claim 1, a method for attachment of an inner workpiece to an outer workpiece of a medical device with the features of claim 8 and a catheter assembly having the features of claim 15.

In particular, the apparatus for laser welding, also referred to as laser beam welding, of an inner workpiece to an outer workpiece of a medical device, for example a catheter, at a welding area, comprises a bearing device and a laser device emitting electromagnetic radiation for welding. The inner workpiece and the outer workpiece having a longitudinal axis. The bearing device comprises a bearing element, wherein the bearing element is configured to apply pressure onto the outer workpiece. Further, the laser device is configured such that the emitted electromagnetic radiation is transmitted through the bearing element to the welding area.

In one embodiment, the inner workpiece may be a tube or an inner shaft or an outer shaft of a balloon catheter and/or the outer workpiece may be a tube or a distal or proximal shaft section of a balloon of the balloon catheter. In particular, in one embodiment a distal section of an inner shaft and a distal balloon shaft of a balloon or a distal section of an outer shaft and a proximal balloon shaft of a balloon may be connected by laser welding using the above apparatus and below described method. The balloon may comprise the following sections in the following order: distal balloon shaft, distal cone portion, working section, proximal cone portion, proximal balloon shaft, wherein in the inflated / expanded state the diameter is greatest in the central working section and smallest in the distal and proximal balloon shaft. The inner and the outer shaft may comprise or consist of at least one thermoplastic material, preferably of at least one thermoplastic material of the following group of materials comprising PA, PEBAX, PET, PC, POM, PEI, ABS, PEEK, PPS, PE and PP. The balloon may comprise or consist of at least one thermoplastic material, in particular of at least one thermoplastic material of the following group of materials comprising PA, PEBAX, PET, PC, POM, PEI, ABS, PEEK, PPS, PE and PP. In the assembly of the medical device the inner workpiece and the outer workpiece may be accommodated concentric or non- concentric but with parallel longitudinal axes to each other. The diameters of the inner workpiece may be 0.1 to 100 mm, preferably 0.3 to 10 mm and of the outer workpiece may be 0.1 to 100 mm, preferably 0.3 to 10 mm, the wand thicknesses of the inner workpiece may be 0.01 to 100 mm, preferably 0.01 to 5 mm, and of the outer workpiece may be 0.01 to 50 mm, preferably 0.01 to 5 mm, wherein the diameter of the inner workpiece, the wand thickness of the inner workpiece and the diameter of the outer workpiece needs to be chosen so that the inner workpiece can be placed inside the outer workpiece.

The apparatus accommodates the assembly comprising the inner workpiece and the outer workpiece of the medical device during laser welding and may allow the relative movement of the assembly and the bearing device, in particular the relative movement of the assembly and the bearing element. To this end, the bearing device and/or the bearing element may be configured to be movable along the longitudinal axis and/or rotatable around the longitudinal axis. Alternatively or additionally, the apparatus comprises a mount which is configured to hold the assembly and to move the assembly along the longitudinal axis and/or to rotate the assembly around the longitudinal axis. Prior welding and accommodation of the assembly, the inner and the outer workpiece may pre-assembled, for example by at least one glue point or welding spot or local pinching. For example, a distal section of an inner shaft and a distal shaft section of a balloon or a distal section of an outer shaft and a proximal shaft section of a balloon are provided and pre-assembled for laser welding. The welding area is usually formed by a longitudinal section of each one of the workpieces to be connected. During preassembling the respective longitudinal section of the outer workpiece is arranged on top of the respective longitudinal section of the inner workpiece, for example, with a clearance fit or, in other words, the respective longitudinal section of the outer workpiece surrounds the respective longitudinal section of the inner workpiece both sections providing a welding area.

The bearing element may comprise a sphere, a cylinder or an element having at least partly a spherical and/or cylindrical outer form, to allow rotation of the outer workpiece and/or the bearing element around the longitudinal axis and/or a movement of the outer workpiece and/ or the bearing element along the longitudinal axis while pressure is applied by the bearing element onto the outer workpiece. According to this feature, the bearing element serves as a low-friction slide bearing.

The apparatus may comprise a motor that is connected to the bearing element and which is configured to drive the bearing element toward the longitudinal axis in order to apply pressure to the outer workpiece. Alternatively, the apparatus may comprise an airstream or a compressed air generator that generates compressed air and which is configured to direct the compressed air to the bearing element in order to move the bearing element toward the longitudinal axis and to apply pressure to the outer workpiece. The applied pressure may be as little as the pressure that results from the slightest touching of the bearing element on the outer shell surface of the outer workpiece in the welding area. The application of pressure leads to a decrease of air pockets and to a strong coupling between molecules within the welded connection of the inner and the outer workpiece. By applying pressure, the welded joint between the outer workpiece and the inner workpiece is improved and the outer shell surface of the outer workpiece can be texturized.

The laser device may comprise a laser beam generating unit producing the laser beam (i.e. is the radiation source) at the pre-defined wavelength, power level and time frame (continuous wave or pulsed mode) and an optical unit that forms the laser beam produced by the laser beam generating unit such that it is directed to the pre-defined area of the inner workpiece and/or outer workpiece and/or a center wire (see below) accommodated within the inner workpiece. The optical unit may comprise at least one optical element of the group comprising lenses, filter, mirrors, prisms, diffraction gratings, apertures. The laser beam emitted by the laser device is transmitted by the bearing element and is thereby directed to the pre-defined area. Accordingly, the material, for example a material comprising or consisting of at least one material of the group comprising quartz glass, sapphire, ruby, spinel, cubic or zirconium oxide, of this bearing element is transparent for the pre-defined wavelength of the laser beam. In one embodiment, the electromagnetic radiation of the laser beam has a wavelength between 0.5 pm and 15 pm, for example between 1.5 pm and 5 pm (near-infra-red range). The laser beam generating unit may comprise a solid state laser. While the assembly with the inner and outer workpiece rotates and/or the bearing element of the bearing device rotates around the longitudinal axis, the laser beam is guided through the laser-transparent rotatable element onto the assembly and heats the workpieces to be welded. Thereby, the contact pressure of the rotatable elements overcomes a possible air gap between the workpieces and the outer contour of the welded assembly may be formed. In one embodiment, the laser wavelength and/or power may be changed during rotation of the assembly and/or the bearing element and/or during below described longitudinal movement of the bearing device. The laser beam may be focused to a point-like form or a line-shape form at the welding area, the line, for example extending parallel to the longitudinal axis of the inner and/or outer workpiece.

The inventive apparatus provides a laser welding method of two workpieces that is highly controllable since the heat-affected zone is very limited to contact area and a small vicinity of this contact area of the bearing element transmitting the electromagnetic radiation. The contact area may be determined by the form of the bearing element transmitting the laser beam and by the pressure applied to the bearing element. Further, the above described apparatus eliminates the need of further material such as a heat shrink layer or heat shrink tube. Hence, it is not necessary to assemble and position such heat shrink layer or tube and to remove it after welding. Accordingly, the apparatus allows a medical device production with less costs and complexity. Further, the transition region between the welded and unwelded area can be provided with a more detailed structure.

In some embodiments the apparatus is an apparatus for laser welding of an inner workpiece to an outer workpiece of a medical device within a welding volume. In this case, the laser device is configured such that the emitted electromagnetic radiation is transmitted through the bearing element into the welding volume. The welding volume extends along an interface between the inner workpiece and the outer workpiece, the welding area, into the inner workpiece and/or the outer workpiece.

In one embodiment, the bearing device comprises at least one counter bearing element and each one of the group of the bearing element and the at least one counter bearing element comprises a sphere, a cylinder or an element having at least partly a spherical and/or cylindrical outer form, wherein the bearing element and the at least one counter bearing element are accommodated such that the outer workpiece is clamped pivotable around the longitudinal axis by the bearing element and the at least one counter bearing element.

The assembly comprising the inner and the outer workpiece of the medical device are clamped by the bearing element and the at least one counter bearing element so that the assembly is pivotable or rotatable about the longitudinal axis. The at least one counter bearing element is arranged such that it forms a counter bearing with regard to the one bearing element and therefore is in contact with the shell surface of the outer workpiece. For example, one counter bearing element is arranged opposite with regard to the bearing element with the assembly in between the bearing element and the counter bearing element or two counter bearing elements are arranged in contact to the outer shell surface of the outer workpiece and opposite to the bearing element. Preferably, the bearing element and the two counter bearing elements are arranged at an angular distance of 120 ° to the respective neighboring counter bearing element, respectively, the bearing element. Accordingly, if four rotatable elements are used, they are, for example, arranged with an angular distance of 90 ° in contact to the outer shell surface of the outer workpiece and so on with an angular distance of, for example, 360 °/n, if n rotatable elements are used. In case of two counter bearing elements, preferably in the case of two counter bearing elements with a diameter smaller than the diameter of the bearing element, the angular distance between the two counter bearing elements may be smaller than 120°. The angular distance refers to the longitudinal axis of the inner workpiece and/or outer workpiece.

As indicated above, each one of the bearing element and the at least one counter bearing element is, for example, a sphere (also referred to as ball), a cylinder (also referred to as roller) or an element having at least partly a spherical and/or cylindrical outer form, for example any composite form comprising a cylinder, sphere or cone. In one embodiment, the bearing element and the at least one counter bearing element may have the same form or different forms. Accordingly, the bearing element and the at least one counter bearing element allow rotation of the outer workpiece and/or rotation of the bearing element and the at least one counter bearing element around the longitudinal axis and/or movement of the outer workpiece and/or movement of the bearing element and the at least one counter bearing element along the longitudinal axis while the outer workpiece is clamped in between the bearing element and the at least one counter bearing element. Accordingly, the bearing element and the at least one counter bearing element serve as slide bearing. The diameter of the bearing element and the at least one counter bearing element may be between 0.3 mm and 20 mm, for example between 0.5 mm and 10 mm.

Thus, the welding connection may be provided under laser radiation during pivoting of the inner and outer workpiece assembly relative to the bearing device so that the assembly is at the same time held by the bearing element and the at least one counter bearing element forming the bearing device, correctly positioned with regard to the laser beam emitted by the laser device and moved such that the welding connection of the inner and outer workpiece may be formed along a greater part of or the whole circumference of the inner workpiece. For example, the welding connection may be established over at least 75 % of the circumference of the inner workpiece.

By a bearing device comprising at least one counter bearing element, less rigid outer and inner workpieces can be laser welded as the workpieces are supported by the at least one counter bearing of the bearing device.

In one embodiment, the bearing device and the laser device are configured to be rotatable around the longitudinal axis. According to this feature, a circumferential welding can be achieved without rotation of the outer and inner workpiece. Alternatively or additionally, the apparatus or the bearing device may configured to rotate the outer and inner workpiece around the longitudinal axis in order to achieve a welding along the circumference of the outer and inner workpiece.

In a further embodiment, each one of the bearing element and the at least one counter bearing element is rotatable along an axis parallel to the longitudinal axis of the inner workpiece and/or the outer workpiece. For example, the bearing element and the counter bearing element may be a rolling bearing or an air bearing. Accordingly, the friction between the outer workpiece and the bearing element and the counter bearing element during rotation of the outer workpiece and/or rotation of the bearing element and the counter bearing element around the longitudinal axis can be reduced. In one embodiment, at least one of the bearing element and the at least one counter bearing element is configured to be moveable along a radial direction of the inner workpiece and/or the outer workpiece. This movement of several mm or cm may be helpful when accommodating and removing the assembly with the inner and outer workpiece prior and after welding. By the movement of the at least two rotatable elements in the radial direction, the distance between the rotatable elements may be increased thereby allowing easy accommodation and removal of the assembly within/from the bearing device.

In a further embodiment, at least one of the bearing element and the at least one counter bearing element are configured to direct an airstream toward the welding area. For example, the bearing element and/or the at least one counter bearing element may comprise an opening through which an airstream is directed to the welding area. Alternatively or additionally, an airstream may be directed toward the welding area from the air bearings itself in case the bearing element and/or the counter bearing element are embodied as air bearings.

In one embodiment, at least one of the bearing element and the at least one counter bearing element comprise a contouring relief for contouring an outer workpiece shell surface and/or an inner workpiece shell surface. For example, the contouring relief comprises a projection or recess running along at least a part of a circumference of the respective bearing and/or counter bearing element and/or extending along at least a part of the (longitudinal) axis of the respective bearing and/or counter bearing element, wherein the (longitudinal) axis of the respective bearing and/or counter bearing element is parallel to the longitudinal axis of the inner workpiece and/or outer workpiece. The projection or recess may have any kind of circumferential contour or a straight contour running, for example, along the (longitudinal) axis of the respective rotatable element (e.g., having at least partly the form of a cylinder) parallel to the longitudinal axis of the inner workpiece and/or the outer workpiece. Alternatively, the projection may have a helical contour. Accordingly, each kind of project! on/recess forms a respective groove/protrusion within the shell surface of the outer workpiece and, if applicable, alternatively or additionally within the shell surface of the inner workpiece projection from the outer workpiece. The inner workpiece may form a tip at some distance. For example, a groove running parallel to the longitudinal direction of the inner and/or outer workpiece may reduce the cross sectional area of the inner and/or outer workpiece and thereby ease the introduction into a lesion. A helical notch/groove may improve bending flexibility of the respective area, e.g. also within a tip portion of the inner workpiece. At the same time, pushability keeps in the same range as without the helical notch. Additionally, with regard to some applications, the introduction into a lesion may be eased when a rotational movement is provided during this introduction. If a circumferential notch is created, for example at the outer shell surface of the inner and/or outer workpiece or directly at the end of the outer workpiece by a respective projection at at least one of the bearing and/or counter bearing element, the bending flexibility of the respective section of the inner workpiece (e.g. forming a catheter tip) is increased while maintaining good pushability and the form of the inner workpiece (e.g. the tip). Furthermore, a tapered section at the inner workpiece with the highest wall thickness at the interface to the stouter workpiece forms a transition area in which mechanical properties seamlessly merge into the ones of the welded area.

In one embodiment, the bearing element and the at least one counter bearing element are rotatable about an axis perpendicular to the longitudinal axis of the inner workpiece and/or the outer workpiece. By such rotation of the bearing and counter bearing elements a weld may be created that has a pre-defined length along the longitudinal axis of the inner and/or outer workpiece. Alternatively or additionally, the laser device may be controlled such that a beam of electromagnetic radiation is moved along the bearing element transmitting the electromagnetic radiation, for example along the longitudinal axis of the inner and/or outer workpiece. By this beam movement, the welding area may be extended along the assembly of the inner and outer workpiece.

In one embodiment, the apparatus further comprises a center wire that is configured to be accommodated within the inner workpiece. The center wire may be introduced into the inner workpiece prior accommodation within the bearing device and welding. It may stabilize, hold and/or move (rotate) the inner workpiece and thereby the whole assembly of the inner and outer workpiece. Further, the center wire may support the (homogenous) heating of the inner and outer workpiece as it reflects the electromagnetic radiation emitted by the laser. Alternatively or additionally, the center wire may absorb at least part of the electromagnetic radiation emitted by the laser, which may lead to a heating of the center wire. Thus, the laser welding joint between the inner and the outer workpiece can be improved. The diameter of the center wire may be equal to or less than the inner diameter of the inner workpiece. The center wire may comprise or consist of a metal material (for example silver or gold or any alloy of these materials) or of a polymer material or of fiberglass. The surface of the center wire may be configured to increase the reflectivity of the center wire with respect to the electromagnetic radiation emitted by the laser. Alternatively, the surface of the center wire may configured to increase the absorptivity with respect to the electromagnetic radiation emitted by the laser.

In one embodiment, the electromagnetic radiation of the laser device is configured to heat the inner workpiece and/or the outer workpiece and/or the center wire. For example, the optical unit of the laser device focuses the laser beam such that it heats a pre-defined area at the inner workpiece and/or the outer workpiece, e.g. the interface between the inner and outer workpiece or that it heats the center wire. By heating the inner workpiece and/or outer workpiece the respective workpiece material absorbs the electromagnetic radiation and directly melts and joins with the respective other workpiece under the contact pressure provided by the bearing element. After cooling the inner and outer workpiece are fused together. This method is also called penetration welding. Alternatively, the center wire absorbs the electromagnetic radiation and is thereby heated. Accordingly, the center wire applies the high temperature indirectly from the inner side to the inner workpiece and the outer workpiece to fuse these two elements together.

The above problem is further solved by a method for attachment of an inner workpiece to an outer workpiece of a medical device, for example a catheter, by laser welding at a welding area, the inner workpiece and the outer workpiece having a longitudinal axis, with the following steps:

• Accommodating the inner workpiece and the outer workpiece at a bearing device comprising a bearing element;

• Applying pressure onto the outer workpiece through the bearing element; and

• Emitting electromagnetic radiation for laser welding by a laser device and transmitting the emitted electromagnetic radiation through the bearing element to the welding area, thereby providing laser welding of the inner workpiece to the outer workpiece.

As indicated above, the above method is a cost efficient method to permanently join an inner workpiece and an outer workpiece of a medical device. In one embodiment, the inner workpiece is an inner tube or shaft or an outer tube or shaft of a catheter and the outer workpiece is a proximal balloon shaft or a distal balloon shaft as described above in more detail.

In one embodiment, the method further comprises the step of rotating the bearing element and/or the outer workpiece and the inner workpiece around the longitudinal axis while pressure onto the outer workpiece is applied through the bearing element and while emitting electromagnetic radiation. By this step, a circumferential or partly circumferential laser welding joint between the inner and outer workpiece can be achieved.

In a further embodiment, the bearing device comprises at least one counter bearing element and each one of the group of the bearing element and the at least one counter bearing element comprises a sphere, a cylinder or an element having at least partly a spherical and/or cylindrical outer form, and the method comprises the step of clamping the outer workpiece by the bearing element and the at least one counter bearing element, wherein the outer workpiece is clamped pivotable around the longitudinal axis by the bearing element and the at least one counter bearing element. Accordingly, less rigid outer and inner workpieces can be laser welded as the workpieces are supported by the at least one counter bearing of the bearing device.

It was also described above in more detail, that in one embodiment of above method, at least one of the bearing element and the at least one counter bearing element may be additionally moved along a radial direction of the inner workpiece and/or the outer workpiece, for example to ease and accommodation with higher accuracy of the assembly formed by the inner workpiece and the outer workpiece within the bearing device. In one embodiment, the bearing element comprises a contouring relief. By applying pressure onto the outer workpiece through the bearing element a contour structure may be provided onto the outer workpiece during and/or shortly after application of the electromagnetic radiation by the laser device. Then, the inner workpiece and/or the outer workpiece are softened and/or molten. After cooling, the relief structure is fixed at the respective surface(s). The contouring relief of the bearing element is the negative form of the contour structure of the outer workpiece.

The following method steps are also explained above in detail. For example, in one embodiment, each of the bearing element and the at least one counter bearing element are rotated about an axis parallel to the longitudinal axis of the inner and/or outer workpiece. In another embodiment, the bearing element and the at least one counter bearing element are rotated about an axis perpendicular to the longitudinal axis of the inner workpiece and/or the outer workpiece. Alternatively or additionally, the laser device may be controlled such that a beam of electromagnetic radiation is moved along the bearing element transmitting the electromagnetic radiation, for example in a direction parallel to the longitudinal direction of the inner and/or outer workpiece. Further, in one embodiment, a center wire is accommodated within the inner workpiece prior to laser welding. In another embodiment, the method further comprises the step of directing an airstream toward the welding area.

After cooling, the assembly comprising the inner workpiece and the outer workpiece is cooled and removed from the bearing device. Further, the center wire is removed from the assembly. Prior to laser welding and accommodation within the bearing device the assembly comprising the inner workpiece and the outer workpiece may be pre-assembled, for example, by gluing.

The above problem is further solved by a catheter assembly having an inner workpiece and an outer workpiece directly attached to each other by laser welding, preferably by the above method. In one embodiment of the catheter assembly, the inner workpiece is an inner shaft or an outer shaft of a catheter and the outer workpiece is a proximal balloon shaft or a distal balloon shaft as described above in more detail. It is also explained that in one embodiment, the shell surface of the inner workpiece and/or the shell surface of the outer workpiece comprises a relief structure, for example a groove running into the longitudinal direction of the assembly, a groove running into the circumferential direction, a helical groove and/or a tapered section.

The material of the inner workpiece and/or the outer workpiece may comprise or consist of a thermoplastic material, preferably of a thermoplastic material of the group of materials comprising PA, PEBAX, PET, PC, POM, PEI, ABS, PEEK, PPS, PE and PP.

The various features and advantages of the present invention may be more readily understood with reference to the following detailed description and the embodiments shown in the drawings. Herein schematically and exemplarily,

Fig. 1 depicts a first embodiment of an apparatus for laser welding and a first embodiment catheter assembly both in a top view,

Fig. 2 depicts a second embodiment of an apparatus for laser welding and a first embodiment catheter assembly both in a top view,

Fig. 3 shows the embodiment of the apparatus of Fig. 1 in a side view and the embodiment of the apparatus of Fig. 2 in a side view, but in case of the latter for clarity reasons with only the bearing element and without the counter bearing elements of the bearing device, with the first embodiment of a catheter assembly also in a side view,

Fig. 4 depicts a third embodiment of an apparatus for laser welding and a second embodiment catheter assembly both in a side view,

Fig. 5 shows a third embodiment of a catheter assembly in a perspective side view,

Fig. 6 shows the embodiment of Fig. 4 in a perspective view of a longitudinal section, Fig. 7 shows a fourth embodiment of a catheter assembly in a perspective side view,

Fig. 8 shows the embodiment of Fig. 6 in a perspective view of a longitudinal section,

Fig. 9 shows a fifth embodiment of a catheter assembly in a perspective side view, and

Fig. 10 shows the embodiment of Fig. 8 in a longitudinal section.

In the following, the inventive apparatus for laser welding and the respective method are exemplarily described with regard to a catheter assembly, in particular with regard to the attachment of an inner shaft as an inner workpiece to a distal balloon shaft as an outer workpiece. The inventive method and apparatus may similarly be used with regard to the fixation of an outer shaft of the catheter to the proximal balloon shaft, workpiece assemblies of other catheter types or workpiece assemblies or other medical devices such as endoscopes, or inlet and outlet elements or cable insulations of medical devices.

Fig. 1 and 3 show the first embodiment of a laser welding apparatus comprising a laser device 5 and a bearing device 10 for laser welding of an inner shaft 21 to a distal balloon shaft 22 of a balloon catheter, wherein the inner shaft 21 is accommodated within the distal balloon shaft 22. The bearing device 10 comprises a sphere 11 which is transparent for the electromagnetic radiation (i.e. the laser beam) provided by the laser device 5. For laser welding the first sphere 11 is accommodated such that it is in contact with an outer shell surface of the distal balloon shaft 22 providing a contact pressure to this surface. Further, the catheter assembly is stabilized and rotated by a center wire 30 that is accommodated within the inner cavity of the inner shaft 21. The sphere 11 is rotatable about a longitudinal axis that is parallel to the longitudinal axis 25 of the inner shaft 21 and the distal balloon shaft 22 shown in Fig. 3. The sphere 11 is rotatable held by an airstream between the two supporting/retaining jaws 14, wherein the airstream is directed toward the sphere 11. The necessary thermal energy for welding is provided by the laser device 5. The laser device comprises a laser beam generating unit 6, e.g., a solid state laser, and an optical unit 7 that forms and focuses the laser beam 8 generated by the laser beam generating unit 6 to the predefined area of the catheter assembly or the center wire using the above mentioned optical elements in a known way. The solid state laser provides, for example, a laser beam 8 having a wavelength of 1.725 pm. As one can derive from Fig. 1 and 3 the first sphere 11 contributes to optical focusing of laser beam 8 by diffraction at the surface of the sphere 11. In the shown first embodiment of the apparatus, the laser beam 8 is focused to the center wire 30 outer surface thereby heating the inner shaft 21 that is in contact with the center wire 30 outer surface and accordingly also the distal balloon shaft 22. Accordingly, the distal balloon shaft 22 is welded to the inner shaft 21 in the region/welding area 100 where the laser beam 8 transmits thermal energy to the center wire 30. The thermal energy for welding is provided by laser beam 8 along the whole circumference to the center wire 30 to produce the welding connection along this area by rotation of the center wire 30 thereby causing a rotation of the spheres 11, 12 around an axis parallel to the longitudinal axis 25 of the catheter assembly. The dimension of the region/welding area 100 may vary from a very thin region which extends only little into the inner shaft 21 and/or the distal balloon shaft 22 to a very pronounced region which extends through the whole thickness of the inner shaft 21 and/or the distal balloon shaft 22 depending for example on the material of the inner shaft 21 and/or the distal balloon shaft 22, the deposited energy of the laser light and the applied pressure. In one embodiment, the catheter assembly and/or the apparatus may be moved into longitudinal direction (i.e. axis 25) to provide a welding connection between the inner shaft 21 and the distal balloon shaft 22 that extends in longitudinal direction.

The balloon of the catheter further comprises a distal cone section 23, a working section 24 (see Fig. 3) and (not shown in Fig. 1 and 3) a proximal cone section and a proximal shaft section. The proximal shaft section may be laser welded to a proximal shaft (not shown) of the catheter in similar way. For example, the inner shaft 21 may have an inner diameter of 0.40 mm and an outer diameter of 0.55 mm, the distal balloon shaft 22 may have an inner diameter of 0.60 mm and an outer diameter of 0.90 mm The distal balloon shaft 22 and the proximal balloon shaft may have a length (in longitudinal direction) of 1.5 mm, the distal and proximal cone sections may have a length (in longitudinal direction) of 5 mm and the working section 24 may have a length (in longitudinal direction) of 20 mm.

For laser welding at first the center wire is slid into the inner cavity of the inner shaft. Prior to that or afterwards, the balloon is positioned such that the distal balloon shaft is located within a pre-defined distance from the distal tip of the inner shaft and is pre-assembled in this position, for example, by gluing. Then, the assembly with the center wire is accommodated within the bearing device 10. This may be facilitated in an easy way, for example, by opening the bearing by moving, e.g., the first sphere 11 perpendicular to the longitudinal axis 25 (opposite direction of arrow 15), accommodation of the assembly within the bearing and moving the first sphere 11 back in the way that a pre-defined contact pressure is provided by each of the spheres 11, 12 to the shell surface of the distal balloon shaft 22. Then, the laser welding is provided by the laser device 5, wherein the laser beam is transmitted through the first sphere 11 to the center wire 30. The welding is provided under rotational movement of the center wire 30 and, accordingly, the catheter assembly and, if applicable, movement of the center wire 30 in longitudinal direction to provide the welding connection within the pre-defined welding area.

Fig. 2 shows a second embodiment of an apparatus for laser welding. The bearing device 110 comprises three spheres 11, 12 with an angular distance of 120 °, wherein the first sphere 11 is transparent for the electromagnetic radiation (i.e. the laser beam) provided by the laser device 5. For laser welding the first sphere 11 and the two second spheres 12 are accommodated such that they are in contact with an outer shell surface of the distal balloon shaft 22 providing a contact pressure to this surface. Further, the catheter assembly is stabilized and rotated by a center wire 30 that is accommodated within the inner cavity of the inner shaft 21. Each of the spheres 11, 12 is rotatable around a longitudinal axis that is parallel to the longitudinal axis 25 of the inner shaft 21 and the distal balloon shaft 22 shown in Fig. 3. Each of the spheres 11, 12 are rotatable held by a respective airstream between two respective supporting/retaining jaws for each sphere 11, 12, wherein the airstream is directed toward each respective sphere 11, 12. For clarity reasons, only the supporting/retaining jaws 14 for sphere 11 are shown in Fig 2. Fig. 4 to 10 refer to further embodiments of laser welding apparatus and catheter assemblies. The components of the apparatus or catheter assembly that are similar to the ones of the respective first embodiments described above are denoted with same reference numbers increased by multiples of 100. For these components it is therefore referred to the above explanation with regard to the first embodiments.

Fig. 4 shows a third embodiment of an apparatus for laser welding. In contrast to the first and second embodiment, the third embodiment comprises a cylinder 111 as rotatable element, which transmits the electromagnetic radiation emitted from the laser. The cylinder 111 has a basically cylindrical/conical form. The cylinder 111 can also be combined with spheres 12 of the second embodiment shown in Fig. 2 or with two further cylinders comparable or identical to the cylinder 111 instead of the spheres 12. In this case the two further cylinders or the spheres 12 are located in a similar way compared with the two second spheres 12 of the second embodiment. Further, the cylinder 111 comprises a certain surface relief in order to form the shell surface of the inner shaft 121 and the outer shaft 122 in a pre-defined way and as described above during welding. In this embodiment, a proximal section I l la and a distal section 111b of the cylinder 111 have a conical form. Further, a cylindrical center section 111c is provided. Thereby, the distal end 122a of the distal balloon shaft 122 is formed conical thereby providing a transitional section from the inner shaft 121 to the balloon. The distal section 111b of the first cylinder forms a conical tip of the inner shaft 121 at its distal end. The cylindrical rotatable elements 111 do not move in longitudinal direction.

As one can derive from Fig. 4 the laser beam 108 is not focused in a point-like way but has a line shape and is focused to the interface of the inner shaft 121 and the distal balloon shaft 122 (the laser beam 108 travels along the direction 115). For clarity reasons, the rectangular area representing the laser beam 108 is not drawn all the way to this interface. The line shape of the laser beam 108 has the advantage, that welding and forming of the shell surface of the distal balloon shaft 122 and distal end of the inner shaft 121 is provided along a pre-defined dimension along the longitudinal direction (for example a length of 2 mm) at the same time without moving the center wire 130 or the laser device in longitudinal direction. This is less time consuming and leads to a more accurate laser welding connection. Additional precise forming of the above mentioned shell surfaces is possible.

Fig. 5 to 10 show further examples of laser connected catheter assemblies having different profiles or contour structures at their shell surfaces (of the distal end of the inner shaft 221, 321, 421 and of the distal balloon shaft 222, 322, 422), all created by a bearing element (for example the first sphere or the cylinder) or by a respective projection at the bearing element used during welding.

The embodiment of Fig. 5 and 6 comprises four grooves 221a, 222a extending in longitudinal direction at the outer shell surface of the inner shaft 221 and the distal balloon shaft 222. The grooves 221a, 222a reduce the cross sectional area of the inner shaft and distal balloon shaft and thereby ease the introduction into a lesion.

A helical groove 321a, 322a is formed at the outer shell surface of the inner shaft 321 and the distal balloon shaft 322 of the embodiment shown in Fig. 7 and 8 thereby improving bending flexibility of the respective area.

Referring to Figs. 9 and 10, a circular groove 421a extending along the full circumference of the inner shaft 421 is provided in the outer shell surface of the inner shaft 421 at the position just distal from the very distal end of the distal balloon shaft 422 which comprises a tapered section 421b. By this specific form the bending flexibility of the respective section of the inner shaft (e.g. forming a catheter tip) is increased while maintaining good pushability at this section (including the transition section to the balloon).

The embodiments of Fig. 5 to 8 have a tapered section 221b, 321b at the inner shaft 221, 321 providing a transition section to the balloon, as well. In these sections 221b, 321b, 421b, the wall thickness of the inner shaft increases into proximal direction.

All above embodiments may be manufactured using the method explained with regard to the first embodiment. The respective method is only adapted with regard to the form/power of the laser beam or the movement of the apparatus relative to the catheter assembly/center wire as well as the form of the at least two (e.g. three) rotatable elements of the bearing device to realize the specific properties of the laser welding connection of the inner shaft and the distal balloon shaft and the specific properties of the shell surface profile. The above method has the advantage that it is less complicated and cost effective. It is fully automatable. Further, with regard to the welding connection it was proven that it is more precise and provides a defined transition for the welded area to the unwelded area.

Claims

1. An apparatus for laser welding of an inner workpiece (21, 121, 221, 321, 421) to an outer workpiece (22, 122, 222, 322, 422) of a medical device, for example a catheter, at a welding area, the inner workpiece (21, 121, 221, 321, 421) and the outer workpiece (22, 122, 222, 322, 422) having a longitudinal axis (25), wherein the apparatus comprises a bearing device (10) comprising a bearing element (11, 111), wherein the bearing element (11, 111) is configured to apply pressure onto the outer workpiece (22, 122, 222, 322, 422); and a laser device (5) emitting electromagnetic radiation for welding, wherein the laser device is configured such that the emitted electromagnetic radiation is transmitted through the bearing element (11, 111) to the welding area.

2. The apparatus of claim 1, wherein the bearing device (10) comprises at least one counter bearing element (12) and each one of the group of the bearing element (11, 111) and the at least one counter bearing element (12) comprises a sphere, a cylinder or an element having at least partly a spherical and/or cylindrical outer form, wherein the bearing element (11, 111) and the at least one counter bearing element (12) are accommodated such that the outer workpiece (22, 122, 222, 322, 422) is clamped pivotable around the longitudinal axis (25) by the bearing element (11, 111) and the at least one counter bearing element (12).

3. The apparatus of claim 1 or 2, wherein the bearing device (10) and the laser device (5) are configured to be rotatable around the longitudinal axis (25).

4. The apparatus of one of the previous claims, wherein each one of the bearing element (11, 111) and, when dependent on claim 2, the at least one counter bearing element (12) are rotatable about an axis parallel to the longitudinal axis (25).

5. The apparatus of one of the previous claims, wherein at least one of the bearing element (11, 111) and, when dependent on claim 2, the at least one counter bearing element (12) are configured to direct an airstream toward the welding area.

6. The apparatus of one of the previous claims, wherein at least one of the bearing element (11, 111) and, when dependent on claim 2, the at least one counter bearing element (12) comprise a contouring relief (1 I la, 11 lb, 111c) for contouring an outer workpiece shell surface and/or an inner workpiece shell surface.

7. The apparatus of any one of the previous claims, wherein the apparatus further comprises a center wire (30) that is configured to be accommodated within the inner workpiece (21, 121, 221, 321, 421).

8. A method for attachment of an inner workpiece (21, 121, 221, 321, 421) to an outer workpiece (22, 122, 222, 322, 422) of a medical device, for example a catheter, by laser welding at a welding area, the inner workpiece (21, 121, 221, 321, 421) and the outer workpiece (22, 122, 222, 322, 422) having a longitudinal axis (25), with the following steps:

Accommodating the inner workpiece (21, 121, 221, 321, 421) and the outer workpiece (22, 122, 222, 322, 422) at a bearing device (10) comprising a bearing element (11, 111);

Applying pressure onto the outer workpiece (22, 122, 222, 322, 422) through the bearing element (11, 111); and

Emitting electromagnetic radiation for laser welding by a laser device and transmitting the emitted electromagnetic radiation through the bearing element (11, 111) to the welding area, thereby providing laser welding of the inner workpiece (21, 121, 221, 321, 421) to the outer workpiece (22, 122, 222, 322, 422).

9. The method of claim 8 further comprises the step of:

Rotating the bearing element (11, 111) and/or the outer workpiece (22, 122, 222, 322, 422) and the inner workpiece (21, 121, 221, 321, 421) around the longitudinal axis (25) while pressure onto the outer workpiece (22, 122, 222, 322, 422) is applied through the bearing element (11, 111) and while emitting electromagnetic radiation.

10. The method of claim 8 or 9, wherein the bearing device (10) comprises at least one counter bearing element (12) and each one of the group of the bearing element (11, 111) and the at least one counter bearing element (12) comprises a sphere, a cylinder or an element having at least partly a spherical and/or cylindrical outer form, and the method comprises the following step:

Clamping the outer workpiece (22, 122, 222, 322, 422) by the bearing element (11, 111) and the at least one counter bearing element (12), wherein the outer workpiece (22, 122, 222, 322, 422) is clamped pivotable around the longitudinal axis (25) by the bearing element (11, 111) and the at least one counter bearing element (12).

11. The method of any one of the claims 8 to 10, wherein the bearing element (111) comprises a contouring relief (1 I la, 11 lb, 111c).

12. The method of any one of the claims 8 to 11, wherein each of the bearing element (11, 111) and, when dependent on claim 11, the at least one counter bearing element (11, 12, 111) are rotated about an axis parallel to the longitudinal axis (25).

13. The method of any one of the claims 8 to 12, wherein the method comprises the step of:

Directing an airstream toward the welding area.

14. The method of any one of the claims 8 to 13, wherein a center wire (30) is accommodated within the inner workpiece (21, 121, 221, 321, 421) prior to laser welding.

15. A catheter assembly having an inner workpiece (21, 121, 221, 321, 421) and an outer workpiece (22, 122, 222, 322, 422) directly attached to each other by laser welding by the method of any one of the claims 8 to 14.

16. The catheter assembly of claim 15, wherein the shell surface of the inner workpiece (121, 221, 321, 421) and/or the shell surface of the outer workpiece (22, 122, 222, 322, 422) comprises a contour structure, for example a groove (221a, 222a) running into a longitudinal direction, a groove (421a) running into a circumferential direction, a helical groove (321a, 322a) and/or a tapered section (221b, 321b, 421b).