WO2022112057A1

WO2022112057A1 - Balloon forming process

Info

Publication number: WO2022112057A1
Application number: PCT/EP2021/081842
Authority: WO
Inventors: Werner Christl; Niels Schilling
Original assignee: Bw-Tec Ag
Priority date: 2020-11-27
Filing date: 2021-11-16
Publication date: 2022-06-02

Abstract

The present invention concerns a method and apparatus for forming a medical device balloon, comprising at least the steps of: placing a tube,having a first diameter and a first length, within an interior cavity of a balloon mold of an apparatus for forming a medical device balloon, blow molding the tube by applying a pressure to a first, inner surface of the tube, heating at least one part of the tube to a first temperature to form the tube into a balloon having a second diameter, heating the balloon to a second temperature, and cooling the balloon to a third temperature, wherein the balloon mold middle part acts as an electric heater.

Description

TITLE

BALLOON FORMING PROCESS

TECHNICAL FIELD

The present invention relates to a method and an apparatus for the manufacture of medical device inflatable members such as for balloon catheters.

PRIOR ART

Balloons used in angioplasty procedures for forcing open previously closed areas of blood vessels, are generally fabricated by molding and have to be suitably dimensioned for their intended use, such as with respect to length, wall thickness and diameter. Other known places of use of balloon catheters include the prostate and urethra. Balloons for balloon catheters are produced by forming thermoplastic material into a mold shape, the raw material normally being a pre-formed tube of thermoplastic material, i.e. parison. The tube is positioned inside the mold, heated, inflated and stretched to form the balloon, as disclosed e.g. in US 6,955,658 B2. A heating system must transfer enough energy into the raw material, e.g. a polymer tube, to allow molding into the final balloon with a defined wall thickness, length and diameters. The mold shape is defined by a main body, a cylindrical tube, with end parts that are conically shaped and lead into the proximal and distal balloon ends. Balloon molds are heated with electrical heating elements, hot air or liquid, such as disclosed in EP 1 737 643 B1. A standard heating process is to guide heated pressurized fluid to the interior of the tube to form the balloon, as disclosed e.g. in US 5,304,240. Differential heating of different areas, such as waist and cone areas of the tube, can be achieved either by multi-segment molds, which can be selectively heated by separate heaters associated with the mold segments. Alternatively, differential heating of different mold areas can also be achieved by varying the coating or texture of the mold while applying uniform temperature to the mold. Mold heating elements include heater cartridges built into the balloon mold body. After the balloon is formed, the mold is normally held at exact temperatures to stabilize the material. The balloon mold is cooled at the end of the process, usually by means of cold air or liquid. The heating and cooling steps are time-consuming. Based on the prior art, an objective of the present invention is to reduce the process time. In order to reduce the overall process time, various steps can be optimized, such as the reduction of time to reach the molding temperature on the raw material, the reduction of time to reach the stabilization temperature on the molded balloon, or the reduction of time to cool the molded balloon. The exchange of the mold tooling also is very time-consuming. For this purpose, the present invention furthermore provides a more flexible mold-tooling, in order to produce different balloon lengths without changing the entire mold tooling.

SUMMARY OF THE INVENTION

The present invention concerns an improved method of forming a medical device balloon, comprising at least the steps of:

- placing a tube having a first diameter and a first length, within an interior cavity of a balloon mold of an apparatus for forming a medical device balloon,

- blow molding the tube by applying a pressure to a first, inner surface of the tube, and

- heating at least one part of the tube to a first temperature to form the tube into a balloon having a second diameter;

- heating the balloon to a second temperature to stabilize the balloon formed from the tube; and

- cooling the balloon to a third temperature.

The inventive method is characterized in that the balloon mold middle part acts as a resistive heater for heating the tube and/or for heating the balloon formed from the tube. This means that at least the heating of the at least one part of the tube to the first temperature, preferably also the heating of the balloon to a second temperature is carried out by directing an electric current to directly flow through the balloon mold middle part. The main mold body of the balloon mold, i.e. the balloon mold middle part is designed and implemented in the machine in such a way that electrical current can flow through it, without the need for separate heating elements or any heating medium. In other words, the balloon mold middle part itself applies heat to at least a part of the raw material, i.e. the tube placed in the interior cavity of the balloon mold middle part and thus is an integral part of a heating system of the balloon forming apparatus. By serving as an electrical heating resistor or heating element, respectively, the balloon mold main body or middle part itself is able to generate the necessary process temperature very effectively.

The tube material preferably comprises or is entirely formed of a polymer, more preferably a bioabsorbable polymer. Optionally, a preformed tube with a cylindrical portion in its middle region and end regions of a reduced diameter, i.e. a "necked" tube, is used as the raw material.

The heating of the tube and/or in a later step the heating of the balloon formed of the tube is carried out by applying an electric current with a voltage of 0.5 - 48 VAC (volt alternating current, i.e. volts AC power) directly to the balloon mold middle part. Thereby, compared to the prior art, where the balloon mold middle part is heated up indirectly, via heating elements or a heating medium, and/or indirectly by heating the balloon mold end parts or holders, in the present invention, the electric current creates the heat primarily in the balloon mold middle part, which itself functions as an electric heater. More preferably an electric current of a maximum of 1 V and a maximum of 300A is guided to flow through the balloon mold middle part.

Preferably, prior to the step of blow molding, a position of one end part or both of the end parts of the balloon mold is adjusted to a selected position along the longitudinal axis of the balloon mold middle part with respect to the balloon mold middle part. The balloon mold comprises a first, proximal end part, and a second, distal end part disposed along the longitudinal axis at opposite ends of the balloon mold middle part. Preferably, either one or both of the end parts are mounted in a slidably disposable manner along the longitudinal axis, in order to adjust the size of the cavity of the balloon mold and thus enable the manufacture of balloons of different lengths. Therefore, in this preferred step, prior to the step of blow molding, the first, proximal end part and/or the slidably disposable second, distal end part of the balloon mold is adjusted along the longitudinal axis of the balloon mold middle part to a selected position along the longitudinal axis with respect to the balloon mold middle part.

The position of the first, proximal end part and/or the second, distal end part can be adjusted e.g. by sliding at least one end part along the longitudinal axis along or within the cavity of the balloon mold middle part, preferably by means of an actuator, or manually. This sliding action can be realized e.g. by a telescopic arrangement of the end parts within or on the balloon mold middle part.

During the step of blow molding, the tube is preferably stretched in a longitudinal direction along the longitudinal axis of the balloon mold middle part. This stretch blow molding results in a balloon having a second length which is greater than the first length of the original tube placed in the balloon mold.

After the cooling of the balloon, an implantable medical device, preferably a balloon catheter, can be fabricated from the balloon, preferably by attaching the balloon to an implantable catheter shaft.

The present invention furthermore concerns an apparatus for forming a medical device inflatable member from a tube, preferably for forming a catheter balloon. Said apparatus comprises a balloon mold comprising a first, proximal end part, a second, distal end part, and a balloon mold middle part disposed along a balloon mold longitudinal axis between the first, proximal end part and the second, distal end part.

A balloon forming apparatus further comprises a heating system for applying heat to at least one part of the tube having an inner surface and an outer surface and being contained in an interior cavity of the balloon mold. The apparatus according to the present invention is characterized in that the balloon mold middle part itself is adapted to act as a resistive heater for applying heat to the tube contained in an interior cavity of the balloon mold. Therefore, the balloon mold middle part itself functions as an electrical heater, in that the main mold body is designed and implemented onto the machine in such a way that electrical current can flow through it when being guided from a first electric pole to a second electric pole. This allows the balloon mold main body or middle part itself to generate the necessary process temperature very effectively.

For this purpose, the balloon mold middle part is preferably designed as a hollow cylindrical thin walled tube with a wall thickness of in the range of 0.5 mm to 2 mm, preferably between 0.8 mm and 1.8 mm, more preferably between 1 mm and 1.5 mm. The reduced mass compared to the usual mold designs allows this inventive mold to be heated or cooled more quickly compared to conventional balloon forming processes.

According to another preferred embodiment of the invention, the balloon mold middle part has a high thermal diffusion, preferably of 60-80 W m²/kJ and a low electrical conductivity, preferably of at the most 25-35 mS/m.

In a further preferred embodiment, the balloon mold middle part is formed of metal, preferably a metal selected from the group of aluminium, stainless steel, bronze and brass. In addition, the balloon mold middle part preferably comprises, at least partially, a protective coating, preferably a scratch resistant coating, preferably a coating of Nickel, or Chrome or an anodized coating or a coating of ALTEF^®. As a further alternative, also non-metallic materials like glass or plastic with a metallic coating are conceivable. The need for a coating depends on the type of material used for the balloon mold middle part. By applying a coating to a specific region(s) of the mold, the temperature applied to the tube arranged in the interior cavity of the mold can be varied according to the location of the underlying coated regions of the tube in the mold, despite applying a uniform temperature to the balloon mold middle part itself. It therefore is possible, by varying material and coating of the balloon mold middle part and/or the end parts, to achieve a differential heat distribution along the balloon mold and therefore achieve different levels of elasticity in the tube for stretching the tube into the desired balloon shape.

The other parts along the flow of electric current from one pole to the other can be formed of the same material as the balloon mold middle part, preferably of aluminum or stainless steel. The number and shapes of the other parts used within the current flow can vary. However, the electric resistance of the middle part must be higher than any other part within the current flow. This can be achieved by varying the thickness and/or cross-section of the material in dependence on the selected material of the respective parts. For example, if the same material is chosen as the balloon mold middle part, the other parts in the current flow must have a larger thickness and/or cross-section than the balloon mold middle part, so they don't provide a high resistance for the electric current to flow through it and therefore don't generate a lot of heat. This ensures that the heat is mainly generated or concentrated in the balloon mold middle part.

Advantageously, the balloon mold is of adjustable length along the balloon mold longitudinal axis. For this purpose, it is preferable to arrange at least one of the first end part and the second end part, preferably both the first end part and the second end part in a displaceable manner along the balloon mold longitudinal axis with respect to the balloon mold middle part. The end parts are preferably mounted in a slidably displaceable manner, preferably along and/or within at least a portion of the middle part, to take various positions along said balloon mold longitudinal axis. The sliding movement is preferably carried out by means of an actuator. Thereby, the length of the cavity of the balloon mold is adjustable to produce balloons with a length in a range from a minimum balloon length of 3 mm to a maximum balloon length of 320 mm. By moving the end parts with respect to the balloon mold middle part or main body, preferably by sliding within the cylindrical or tubular portion of the balloon mold middle part, it is possible to produce a range of different balloon lengths in the same apparatus by using the same balloon mold middle part and end parts, i.e. without changing individual parts of the balloon mold.

Thus, the balloon length can not only be defined by changing individual balloon mold main body parts, but the balloon length can be a software parameter of the balloon forming machine, in that the positioning of the balloon mold end parts are controlled or remote controlled by a computer.The use of adjustable end parts in the balloon mold allows the exchange of the mold tooling to be dispensed with. The end parts preferably are held/gripped and moved along the longitudinal axis of the balloon mold by an actuator or a pneumatic cylinder. The adjustable position of the mold end parts results in a reduced number of necessary mold body parts compared to conventional balloon forming systems. This simplifies mold part management and eliminates tooling changeover time between different balloon mold lengths.

For even more flexibility in different balloon sizes, in addition, a variety of balloon mold middle parts with various different lengths can be selected, fixed to the apparatus, and exchanged according to the specifically desired balloon length.

According to a further preferred embodiment, the balloon mold middle part is clamped at a first, proximal end of the balloon mold middle part by a first, proximal clamping device and at a second, distal end of the balloon mold middle part by a second, distal clamping device. Preferably, at least one of the first, proximal clamping device and the second, distal clamping device is displaceable, preferably slidably displaceable, along the balloon mold longitudinal axis with respect to the balloon mold middle part and can be mounted at various predefined positions on a distance plate.

Preferably both the first, proximal clamping device and the second, distal clamping device are displaceable along the balloon mold longitudinal axis and can be mounted at various defined positions on a distance plate, wherein preferably the displacement of the at least one clamping device is carried out by an actuator and preferably is controlled by a programmable logic controller (PLC).

The balloon mold middle part and at least one of the first, proximal clamping device and the second, distal clamping device are preferably formed in an integral manner and can be exchanged together as one piece, in order to fulfil the requirements of the selected length of the balloon mold middle part. In other words, for example when the end parts are moved to a position as far as possible from the middle of the balloon mold middle part, but an even longer mold form is required, the balloon mold middle part can be exchanged by a longer balloon mold middle part in order to provide a longer cavity for manufacturing a longer balloon therein. It is conceivable that either the one or more clamping devices are part of the apparatus and only the balloon mold middle part is exchanged, or the one or more clamping devices are formed integrally with the respective exchangeable balloon mold middle part and are mounted and exchanged together with the respective balloon mold middle part.

In an especially preferred embodiment, the balloon form middle part has an adjustable inner diameter. For this purpose, the circumference of the cylindrical tubular form of the balloon mold middle part can be altered and adjusted to the desired diameter depending on the selected balloon size.

The apparatus furthermore preferably comprises a temperature sensor, preferably attached or connected to the balloon form middle part.

In an especially preferred embodiment, the first end part and the second end part of the balloon mold each have a conical portion, preferably with inclined inner walls, said respective conical portions preferably having different cone angles and/or diameters from each other. These end regions can also be formed in an exchangeable manner on the mold. This further increases the flexibility in terms of balloon design. In case of the use of a "necked tube" as raw material for the balloon molding, the end regions of reduced diameter of the tube facilitate the insertion of the tube into the conical end parts of the balloon mold.

A further preferred embodiment of the inventive apparatus is characterized in that the first end part and/or the second end part is comprised of at least two parts which differ in material properties. Preferably the first end part and/or the second end part, respectively, comprises a core part and an insulation part covering the core part. Preferably, the core part is composed of a metal and the insulation part is composed of an insulation material, preferably of a thermoplastic polymer, more preferably of PEEK. This also results in a differential heat distribution in the end parts, i.e. that the end parts are heated more or less by the balloon mold middle part through heat transfer and contain their temperature longer than the balloon mold middle part.

In a further preferred embodiment, the balloon mold middle part itself is mountable at various positions along the longitudinal axis of the apparatus. The apparatus preferably comprises a distance plate comprising at least one clamp for clamping the middle part, the at least one clamp being displaceable along the longitudinal axis of said distance plate to take various positions along said longitudinal axis of the distance plate.

Preferably, the apparatus further comprises a pressurization system for applying relative pressure to an inner surface of the tube placed inside the balloon mold middle part, the combined heat and pressure being effective to expand the tube from a first diameter to a second diameter to form said inflatable member.

Advantageously, the apparatus comprises a controller, for controlling at least one of the following parameters selected from the group of: a temperature of the middle part of the balloon mold, a temperature of the first end part and/or of the second end part, a temperature of the tube prior to or during expansion, a temperature of the balloon after expansion of the tube or parison, a length of the balloon to be formed within the balloon mold, an inner diameter of the balloon mold middle part, a position of the first end part and/or of the second end part with respect to the balloon mold middle part, a distance of the first end part from the second end part, a position of at least one clamping device on a distance plate for clamping the balloon mold middle part.

The above mentioned problem of process time reduction is solved on the one hand in that the balloon mold main body or middle part itself functions as an electrical heater. The heating time is reduced due to the reduced material mass of the balloon mold, very effective heating with electrical resistance directly in the mold, and reduced distance between the source of heating and the raw material, i.e. the tube or parison. Thereby, the necessary process temperature is more efficiently generated and no additional heating elements, such as heating cartridges built into the balloon mold, or any heating medium, such as hot air or water, are necessary to generate the process temperatures.

Similarly, also the subsequent cooling is greatly accelerated as only a small mass needs to be cooled down. Thereby, a water cooling can even be dispensed with, and a cooling by air may be sufficient. The cooling time is therefore reduced on the one hand due to reduced material mass of the balloon mold, and on the other hand due to the fact that the cooling air is applicable directly to the balloon mold middle part without having to work through additional parts for heating and cooling on other systems.

As mentioned above, the process time can furthermore be reduced by providing slidably movable end parts, i.e. cones, on either side of the balloon mold middle part, for selecting the length of the balloon without having to change balloon mold component parts. Each of the above mentioned optimizations in the process of balloon forming, alone, and even more in combination with each other, contribute to a minimization of the process time.

Further embodiments of the invention are laid down in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

Fig. 1 shows a perspective view of an apparatus according to a first embodiment of the invention, including a balloon mold, with the path of electricity indicated;

Fig. 2 shows a sectional front view of the apparatus of figure 1 without the end parts of the balloon mold, with the path of the electric current indicated;

Fig. 3 shows an enlarged sectional front view of the apparatus of figure 1 with an indication of three different lengths of balloon mold middle parts and the respective minimum and maximum lengths of possible balloon lengths producible therein.

Fig. 4 shows a perspective view of an apparatus according to a second embodiment of the invention, including a balloon mold;

Fig. 5 shows a sectional front view of the apparatus of figure 4 without the end parts of the balloon mold;

Fig. 6 shows an enlarged sectional front view of the apparatus of figure 4 with an indication of four different positions of each the first and the second balloon mold clamping device;

Fig. 7 shows the sectional front view of the apparatus of figure 5, however, with the path of the electric current indicated.

DESCRIPTION OF PREFERRED EMBODIMENTS

In figure 1 , an apparatus according to a first preferred embodiment of the invention is shown, with a telescopically expandable balloon mold fastened thereto. In figures 4-7, an apparatus according to a second preferred embodiment of the invention is shown. In each case, the hollow-cylindrical balloon mold serves to receive a tube or parison in its interior cavity, preferably a tube or pre-formed tube of plastics material, preferably a polymer, e.g. a bioabsorbable polymer.

The illustrated balloon forming apparatus comprises a transformer 2 mounted on a transformer mount plate 5. Theron, a machine insertion plate 4 is mounted. The balloon forming machine comprises a non conductive base plate 1 , on which a first pole contact plate 6 and a second pole contact plate 3 are mounted and connected to the poles of the transformer, wherein plate 6 is connected to pole 13a and plate 3 is connected to pole 13b. On top of the first pole contact plate 6, a first, proximal balloon clamping device 15a is mounted. The first balloon mold clamping device 15a comprises a first, proximal top clamp 10a for clamping a balloon mold middle part 9, and a first, proximal bottom clamp 11a for clamping the balloon mold middle part 9. On the opposite, distal end of the balloon mold, the balloon mold middle part 9 is clamped by a second, distal balloon mold clamping device 15b, comprising a second, distal top clamp 10b for clamping the balloon mold middle part 9, and a second, distal bottom clamp 11b for clamping the balloon mold middle part 9.

In the first embodiment of the present invention, shown in figures 1-3, the apparatus comprises only one distance plate 12a, mounted on the pole contact plate 3 with a cut-out for the pole 13b in order to not touch the pole 13b. The distal balloon mold clamping device 15b can be slidably mounted at different positions 14a-d along the distance plate 12a. The predefined positions 14a-d are spaced apart at regular distances and allow a slidable displacement along a longitudinal axis S of the distance plate 12a, which is preferably parallel to the longitudinal axis A of the balloon mold middle part 9, and to allow a fastening/mounting of the balloon mold clamping device 15b at various predefined distances from the middle of the balloon mold middle part.

An electric current of 0.5-48 VAC takes, in the first preferred embodiment of figures 1-3, the following route between the transformers poles: from the first pole 13a to the first pole contact plate 6, via the first bottom clamp 11a and top clamp 10a on to and through the balloon mold middle part 9 along the balloon mold longitudinal axis A, then into the second top clamp 10b and bottom clamp 11b, and on into the distance plate 12a and via the second pole contact plate 3 to the second pole 13b. Electricity runs in both directions.

The balloon mold middle part 9 is designed as a thin wall tube or hollow cylinder to create resistance to the electric current. The range of the wall thickness of the thin wall tube or hollow cylinder lies between 0.5 mm and 2 mm. Thereby, the balloon mold middle part 9, is heated up very effectively. The middle part 9 essentially causes a short-circuit between the two poles 13a and 13b. Like a filament lamp, the middle part 9 heats up with the electric current running through it. A temperature sensor (not shown) connected to the balloon mold middle part 9 measures the heat of the balloon mold middle part 9. By means of controlling the current flow through the balloon mold middle part 9, the temperature can be controlled as well. The temperature sensor causes the primary power of the transformer to turn on and off by means of a PID-Controller (proportional-integral-derivative controller) to achieve the set temperature.

The balloon mold middle part 9 is preferably made out of aluminum, having very good heat transfer coefficients, e.g. of about 200 W/m²K. This ensures a consistent temperature across the entire balloon mold middle part 9. The aluminum requires a protective coating to prevent scratches and eliminate contact of bare aluminum with the product, the coating preferably being an anodized coating ora coating of ALTEF^® ora metallic coating like nickel or chrome. As an alternative, other materials, such as stainless steel, bronze or brass can be used to form the balloon mold.

The electric resistance of the middle part 9 must be higher than any other part within the current flow, i.e. parts 6, 11a, 10a, 10b, 11b, 12a, 3. This is achieved by varying the thickness and/or cross-section of the material in dependence on the selected material of the respective parts. Their function is to connect the balloon mold middle part 9, which serves as a resistor, to the poles 13a, 13b of the transformer 2.

The balloon mold is made up of three parts: a first, proximal end part 7a, a middle part 9, and a second, distal end part 7b. The balloon mold middle part 9 can be formed of different lengths (Lm, Lmin, Lmax), of which three are shown in Fig. 3. The end parts 7a, 7b may be of the same size and/or shape. The end parts 7a, 7b preferably vary in their respective cone angle and diameter, as the distal and proximal end of a formed balloon are usually different. The end parts 7a, 7b may be made up from two parts, which differ in material properties. The conical end parts 7a, 7b normally need to transfer heat onto the tube material and therefore are formed of a metal. The end parts 7a, 7b are preferably passively heated by the heat of the middle part. To keep the mass that needs to be heated small, the conical end parts 7a, 7b are each inserted into a first, proximal insulation part 8a and a second, distal insulation part 8b, respectively. The insulation parts 8a, 8b preferably are formed of a thermoplastic polymer, more preferably of PEEK, as PEEK has a very good heat resistance of 260°C. Alternatively, it is possible to combine the proximal end part 7a with the proximal insulating part 8a by forming one piece of the same material(s). Equally, it is possible to combine the distal end part 7b with the distal insulating part 8b by forming one piece of the same material(s). Such a combined single piece can be made of a single material, i.e. either only of metal or only of insulating material, or of an insulating material with a thin coating of metal e.g. copper, nickel, chrome or other.

In the first preferred embodiment of the present invention, as shown in figures 1-3, the second, distal clamping device 15b for the balloon mold middle part 9 on the distance plate 12a can be mounted in different positions, depending on the selected length (Lmin, Lm, Lmax) of the balloon mold middle part 9, which again depends on the desired length of the balloon to be molded therein. Each length of balloon mold middle part 9 allows the molding of balloons with a range of lengths. For example, in a balloon mold middle part 9 of a length Lm, balloons of a length from Lbm min to Lbm max can be molded, whereas in a balloon mold middle part 9 of a length Lmin, balloons of a length from Lbn min to Lbn max can be molded, and in a balloon mold middle part 9 of a length Lmax, balloons of a length from Lbx min to Lbx max can be molded. In figure 3, the second, distal clamping device 15b is shown in a default first position 14a on the distance plate 12a, and with dotted lines as a displaced, second, distal clamping device 15bi with displaced top and bottom clamps 10b', 11b' in a fourth position 14d on the distance plate, at a maximal possible distance to the first, proximal clamping device 15a. Two intermediate positions 14b, 14c for further displacement of the second, distal clamping device 15b between the first position 14a and the fourth position 14d are indicated in figure 1 , however, without any example of a clamping device 15b fastened thereon. The second, distal clamping device 15b could also be fastened on a rail with infinite, i.e. non-defined displacement positions along the distance plate 12a. In figure 1 , the distance plate 12a is shown in a sectioned manner in order to allow a view of the second pole 13b for which a cut-out 16 is provided in the distance plate 12a.

Preferably, in order to optimize the heat distribution, the clamping devices 15a, 15b are positioned symmetrically with respect to the middle of the balloon mold middle part 9 along the longitudinal axis A.

For this purpose, in the second preferred embodiment of the invention according to figures 4-7, not only one of the clamping devices 15a, 15b, but both, i.e. also the first, proximal clamping device 15a for the balloon middle part 9 is displaceable and mountable in different defined positions along the longitudinal axis S of the distance plate(s) 12a, 12b. Compared to the first preferred embodiment, this second, preferred embodiment, comprises two distance plates 12a, 12b, along which both the first balloon mold clamping device 15a and the second balloon mold clamping device 15b can be displaced. In figure 5, it can be seen that in this particular embodiment, the balloon mold arrangement is symmetrical, in the sense that the two clamping devices 15a, 15b are moved symmetrically along two distance plates 12a, 12b of equal length along the longitudinal axis S, parallel to the longitudinal axis A of the balloon mold middle part 9. In this particular preferred embodiment, the top clamp 10 and bottom clamp 11 of the clamping device 15a, 15b are integrally formed, contrary to the first embodiment. In figure 4, the second distance plate 12b is shown in a sectioned manner in order to allow a view of the second pole 13b for which a cut-out 16 is provided in the second distance plate 12b.

As mentioned above, the displaceability of the at least one clamping device 15a, 15b allows the use of balloon middle parts 9 of the same or different outside diameter to be of very different lengths (Lmin, Lm, Lmax). Also, the inside diameter of the balloon form middle part 9 can vary in a certain range to allow different balloon diameters with the same set up. The end parts 7a, 7b are not in a fixed position but held each by a further clamping device (not shown) and are brought into position with an electric drive or an electric or pneumatic actuator with adjustable end stops. It is possible that, for this purpose, either the end parts 7a, 7b or corresponding insulating parts 8a, 8b adjoining the core of the respective end parts 7a, 7b are gripped by said further clamping device. In case the insulating parts 8a, 8b are formed as integral parts of the respective end parts, the insulating parts 8a, 8b can be clamped. If no insulating parts are present, the end part 7a, 7b itself can be clamped. The various possible positions (7ai-7a₄; 7bi, -7b₄) of the end parts 7a, 7b allow the production of balloons with a wide range of balloon lengths. The combination of the selection of different lengths of the balloon middle parts 9 and the possibility to change the position of the clamps 15a, 15b on the distance plates 12a, 12b to reach different positions (15a, 15ai-15a₃, 15b, 15bi-15b₃) of the clamps 15a, 15b, together with the adjustment of the position of the end parts 7a, 7b, allows the production of balloons with any length between Lbn min and Lbx max. The variation in length between Lbn min and Lbx max is preferably programmable as a machine parameter if an electric drive is used, or it can be carried out manually by adjusting a stop. Referring to figures 3 and 6, various minimal and maximal possible balloon lengths (Lbn min, Lbn max, Lbm min, Lbm max, Lbx min, Lbx max) are illustrated. For example, in the first embodiment of figure 3, a balloon mold middle part 9 of a length of Lm, a minimal possible balloon length Lbm min and a maximal balloon length Lmb max are indicated, in that for the maximal possible balloon length Lbm max, the first, proximal end part 7a is shown in a default position 7a and the second, distal end part 7b is shown in a default position 7b, and that for the minimal possible balloon length Lbm min, the first, proximal end part 7a is shown in a position displaced to the right and the second, distal end part 7b is shown in a position displaced to the left. For a balloon mold middle part 9 of a length of Lmin, a minimal possible balloon length Lbn min and a maximal balloon length Lbn max are indicated, in that for the maximal possible balloon length Lbn max, the first, proximal end part 7a is shown in a default position and the second, distal end part 7b is shown in a default position, and that for the minimal possible balloon length Lbn min, the first, proximal end part 7a is shown in a position displaced to the right and the second, distal end part 7b is shown in a position displaced to the left. For a balloon mold middle part 9 of a length of Lmax, a minimal possible balloon length Lbx min and a maximal balloon length Lbx max are indicated, in that for the maximal possible balloon length Lbx max, the first, proximal end part 7a is shown in a default position, and the second, distal end part 7b is shown in a position displaced to the right, and that for the minimal possible balloon length Lbx min, the first, proximal end part 7a is shown in a position displaced to the right, and the second, distal end part 7b is shown in a position displaced to the left. Similarly, the respective insulation parts 8a, 8b, are positioned together with their respective end parts 7a, 7b.

Optionally, various lengths of distance plates 12a, 12b can be used depending on the desired length of the balloon mold middle part, either by exchange of the respective distance plate 12a, 12b for a plate of a smaller or larger length, or, in case of a modular system, by adding or detaching an elongation part fastenable to the respective distance plate 12a, 12b. The preferred possible range of a balloon length (in a molded state, prior to inflation in the body) is from an Lbn min of 3 mm to an Lbx max of 320 mm. The possible range of a balloon diameter (in a molded state, prior to inflation) in its finished, molded state (prior to inflation in the body after implantation) is from 2 to 50 mm.

In the second preferred embodiment of figures 4-7, the electric current of 0.5-48 VAC takes the following route between the transformers poles: from the first pole 13a to the first pole contact plate 6, through the second distance plate 12a via the first clamping device 15a on to and through the balloon mold middle part 9, across the balloon mold middle part 9 along the balloon mold longitudinal axis A, and on through the second clamping device 15b, then on into the second distance plate 12b and via the second pole contact plate 3 to the second pole 13b. Electricity runs in both directions. LIST OF REFERENCE SIGNS non conductive base plate 13b second pole transformer 14a first position of 15b on 12 second pole contact plate 14b second position of 15b on 12 machine insertion plate 14c third position of 15b on 12 transformer mount plate 14d fourth position of 15b on 12 first pole contact plate 15a first balloon mold clampinga first, proximal balloon mold device end part 15ai-a₃ alternative positions of 15aai-a₄ alternative positions of 7a 15b second balloon moldb second, distal balloon mold clamping device end part 15bi-b₃ alternative positions of 15bb b₄ alternative positions of 7b 16 cut-out in 12a, 12b for 13a,a first, proximal balloon mold 13b insulation part A balloon mold longitudinalb second, distal balloon mold axis, sliding axis insulation part Lmin balloon mold minimal length balloon mold middle part, Lm balloon mold middle length main body Lmax balloon mold maximal length0a first, proximal top clamp Lbn min balloon minimal length within0b second, distal top clamp Lmin 0b' displaced second, distal top Lbn max balloon maximal length within clamp Lmin 1a first, proximal bottom clamp Lbx min balloon minimal length in1b second, distal bottom clamp Lmax 1b' displaced second, distal Lbx max balloon maximal length in bottom clamp Lmax 2a first distance plate S longitudinal axis of 12a, 12b2b second distance plate 3a first pole

Claims

1. Method of forming a medical device balloon, comprising at least the steps of: placing a tube having a first diameter and a first length within an interior cavity of a balloon mold of an apparatus for forming a medical device balloon, blow molding the tube by applying a pressure to a first, inner surface of the tube, and heating at least one part of the tube to a first temperature to form the tube into a balloon having a second diameter; heating the balloon to a second temperature (to stabilize the balloon formed from the tube); and cooling the balloon to a third temperature, characterized in that the balloon mold middle part (9) acts as a resistive heater for heating the tube and/or for heating the balloon formed from the tube.

2. Method according to claim 1, characterized in that the heating of the tube and/or the balloon is carried out by applying an electric current directly to a balloon mold middle part (9), such that an electric current, preferably with a voltage of 0.5 - 48 VAC, more preferably of a maximum of 1 V and 300A, is guided to flow through the balloon mold middle part (9) and therebyelectrically heats the balloon mold middle part (9).

3. Method according to one of the preceding claims, characterized in that the method further comprises, prior to the step of blow molding, a step of adjusting a position of a slidably disposable first, proximal end part (7a) and/or a slidably disposable second, distal end part (7b) of the balloon mold along a longitudinal axis (A) of the balloon mold middle part (9) to a selected position along the longitudinal axis (A) with respect to the balloon mold middle part (9), wherein preferably the position of at least one of the first, proximal end part (7a) and the second, distal end part (7b) is adjusted by sliding the at least one end part (7a, 7b) along the longitudinal axis (A) within the cavity of the balloon mold middle part (9), preferably by an actuator.

4. Method according to one of the preceding claims, characterized in that the method further comprises, during the step of blow molding, a step of stretching the tube in a longitudinal direction along the longitudinal axis (A) of the balloon mold.

5. Method according to one of claims 1-4, further comprising, after the cooling of the balloon, a step of fabricating an implantable medical device, preferably a balloon catheter, from the balloon, preferably by attaching the balloon to an implantable catheter shaft.

6. Apparatus for forming a medical device inflatable member from a tube, preferably for forming a catheter balloon, said apparatus comprising a balloon mold comprising a first, proximal end part (7a), a second, distal end part (7b), and a balloon mold middle part (9) disposed along a balloon mold longitudinal axis (A) between the first, proximal end part (7a) and the second, distal end part (7b), characterized in that the balloon mold middle part (9) is adapted to act as an electric resistive heater for applying heat to the tube contained in an interior cavity of the balloon mold.

7. Apparatus according to claim 6, characterized in that the balloon mold middle part (9) is designed as a hollow cylindrical thin walled tube with a wall thickness of in the range of 0.5 mm to 2 mm.

8. Apparatus according to one of claims 6 to 7, characterized in that the balloon mold middle part (9) is formed of metal, preferably a metal selected from the group of aluminium, stainless steel, bronze and brass, and wherein the balloon mold middle part (9) preferably comprises a protective coating, preferably a scratch resistant coating, preferably a coating of Nickel, or Chrome or an anodized coating or a coating of ALTEF^®.

9. Apparatus according to one of claims 6 to 8, characterized in that the balloon mold is of adjustable length along the balloon mold longitudinal axis (A), wherein preferably at least one of the first end part (7a) and the second end part (7b), preferably both the first end part (7a) and the second end part (7b), are arranged in a displaceable manner along the balloon mold longitudinal axis (A) with respect to the balloon mold middle part (9), preferably in a slidably displaceable manner, preferably along and/or within at least a portion of the middle part (9), to take various positions along said balloon mold longitudinal axis (A), preferably by means of an actuator, such that the length of the cavity of the balloon mold (Lmin, Lm, Lmax), is adjustable to produce balloons with a length in a range from a minimum balloon length (Lbn min) of 3 mm to a maximum balloon length (Lbx max) of 320 mm.

10. Apparatus according to claim 9, characterized in that the balloon mold middle part (9) is clamped at a first, proximal end of the balloon mold middle part (9) by a first, proximal clamping device (15a) and at a second, distal end of the balloon mold middle part (9) by a second, distal clamping device (15b), and wherein at least one of the first, proximal clamping device (15a) and the second, distal clamping device (15b) is displaceable, preferably slidably displaceable, along the balloon mold longitudinal axis (A) with respect to the balloon mold middle part (9) and can be mounted at various predefined positions on a distance plate (12), wherein preferably both the first, proximal clamping device (15a) and the second, distal clamping device (15b) are displaceable along the balloon mold longitudinal axis (A) and can be mounted at various defined positions on a distance plate (12), wherein preferably the displacement of the at least one clamping device (15a, 15b) is carried out by an actuator and preferably is controlled by a programmable logic controller.

11. Apparatus according to claim 10, characterized in that the balloon mold middle part (9), and at least one of the first, proximal clamping device (15a) and the second, distal clamping device (15b) are formed in an integral manner and can be exchanged together as one piece depending on the selected length (Lmin, Lm, Lmax) of the balloon mold middle part (9).

12. Apparatus according to one of claims 6 to 11, characterized in that the balloon form middle part (9) has an adjustable inner diameter.

13. Apparatus according to one of claims 6 to 12, characterized in that the apparatus comprises a temperature sensor, preferably attached or connected to the balloon form middle part (9).

14. Apparatus according to one of claims 6 to 13, characterized in that the first end part (7a) and the second end part (7b) each have a conical portion, said respective conical portions preferably having different cone angles and/or diameters from each other.

15. Apparatus according to one of claims 6 to 14, characterized in that the first end part (7a) and/or the second end part (7b) is comprised of at least two parts which differ in material properties, wherein preferably the first end part (7a) and/or the second end part (7b), respectively, comprises a core part composed of a metal and an insulation part (8) covering the core part, wherein the insulation part (8) is composed of an insulation material, preferably of a thermoplastic polymer, more preferably of PEEK.

16. Apparatus according to one of claims 6 to 15, characterized in that the balloon mold middle part (9) is mountable at various positions along the longitudinal axis (A) of the apparatus, wherein preferably the apparatus comprises a distance plate (12) comprising at least one clamp (10, 11) for clamping the middle part (9), the at least one clamp (10, 11) being displaceable along the longitudinal axis (A) to take various positions along the longitudinal axis (A).

17. Apparatus according to one of claims 6 to 16, further comprising a controller, controlling at least one of the following parameters selected from the group of: a temperature of the middle part (9) of the balloon mold, a temperature of the first end part (7a) and/or of the second end part (7b), a temperature of the tube prior to or during expansion, a temperature of the balloon after expansion of the parison, a length (Lbn min, Lbn max, Lm min, Lm max, Lbx min, Lbx max) of the balloon to be formed within the balloon mold, an inner diameter of the balloon mold middle part (9), a position of the first end part (7a) and/or of the second end part (7b) with respect to the balloon mold middle part (9), a distance of the first end part (7a) from the second end part (7b), a position of at least one clamping device (15a, 15b) on a distance plate (12) for clamping the balloon mold middle part (9).