Field of the invention

The invention relates to cannula units for infusion site interfaces and infusion pumps, as well as manufacturing methods for such cannula units.

Background of the invention

Infusion pumps are used for parenterally providing patients with liquid medicaments over longer time periods. Nowadays, infusion pumps with very small dimensions are available that can be carried by the patient on the body. Such small-sized ambulatory infusion pumps are particularly useful for metering small doses of highly effective liquid medicaments, such as insulin for the treatment of diabetes, or analgesics for pain therapy, which are conveyed through a cannula into the tissue of a patient.

In one approach, an infusion pump, carried somewhere on the body, e.g. attached to a belt, is fluidly connected via flexible tubing to an infusion site interface, also called insertion head, that is attached to the body of the patient. The infusion site interface comprises a cannula unit with a cannula to be inserted into the body tissue, a housing to which the cannula is mounted, and connector means for fluidly connecting the cannula with the flexible tubing connected to the upstream infusion pump. The tubing can be repeatedly con- nected and disconnected from the infusion site interface. The connector means may for example comprise a septum sealingly closing the fluid system of cannula and housing. The septum can be penetrated by a hollow needle, for reversibly establishing a fluid connection. The cannula is preferably made of a flexible material. Such cannulas are more comfortable for their users, particularly during body movements. Since flexible cannulas cannot be inserted directly into the tissue, an additional piercing device, e.g. in the form of a rigid pierc- ing needle made from metal, is arranged inside the flexible cannula. A pointed end of the piercing device protrudes from the proximal end of the cannula, the cannula that will be open toward the interstitial fluid. After inserting the piercing device and the stabilized cannula into the body tissue, the piercing device is removed from the cannula. The cannula is now flexible, and remains in the body tissue. Generally, a piercing needle is arranged in such a way that it penetrates a septum, which after withdrawal of the piercing needle sealingly closes the distal end of the now open cannula fluid path. Examples of such infusion site interfaces and insertion heads are shown in WO 02/07804 A1 , US 2008/02881 44 A1 , and US 201 2/296290 A1 , the disclosure of which is hereby included by reference in their entirety In another approach, the infusion pump device is directly fluidly connected with the infusion site interface. Examples of such embodiments are shown in WO 2007/056504 A1 , the disclosure of which is hereby included by reference in its entirety. The fluid connection between pump and cannula is established by a hollow connector needle of the pump, reversibly penetrating a septum of the cannula unit that sealingly closes the distal end of the cannula fluid path. Advantageously, the pump can be repeatedly connected and disconnected from the infusion site interface.

In a common method for manufacturing infusion site interfaces with flexible cannulas, in a first step a stabilizing pin is introduced into the flexible cannula, for simplifying the handling of the flexible cannula during the manufacturing process. The temporary structural unit prepared in this manner is inserted into a previously manufactured housing, the flexible cannula and the housing are permanently connected, for example by a thermal process. The stabilizing pin is then drawn out of the flexible cannula, and is replaced by the actual piercing device. The insertion of the piercing devices sometimes damages the flexible can- nulas, which results in comparably high rejection rates during manufacturing.

In the known manufacturing methods for cannula units, a considerable number of elaborate manufacturing steps are involved, for example injection moulding in very small dimensions and with very small dimensional tolerances. Due to the accumulation of possible deviations from nominal values during the manufacturing steps of the various elements, as well as during the assembly steps, there is a considerably high rejection rate, in order to avoid any risk of malfunction of the manufactured devices, e.g. leakage.

In order to simplify the manufacturing process and to reduce the rejection rates during manufacturing, US 201 2/0296290 A1 discloses an advantageous manufacturing method for cannula units. A flexible cannula is threaded onto a piercing needle instead of a temporary stabilizing pin. In one embodiment, the distal end of the cannula has a diameter that increases towards the end, compared to the constant diameter of the rest of the cannula. The housing is injection moulded around the distal end of the cannula, and the directly adjacent piercing pin. As a result, the cannula is form-locked inside the housing body. When the piercing needle is drawn out of the cannula, a channel is formed in the housing body that continues the cannula fluid channel toward a fluid chamber of the housing. While such a cannula unit has many advantages, the necessary injection moulding process is demanding and requires special tooling. Furthermore, the flexible cannula will be compressed to a certain extent during manufacture, due to the high pressures involved in the injection moulding step, and essentially remains in this state after manufacture. The compressed cannula wall exerts a force directed radially inwards onto the insertion needle, which may lead to a considerable while undefined increase of the friction force between the flexible cannula and the insertion needle. This may cause crumpling or even rupture of the flexible cannula during the withdrawal of the insertion needle. At the same time the friction force between flexible cannula and insertion needle should not be too low, in order to avoid problems such as crumpling during insertion of the cannula into the subcutaneous tissue of the patient, which may also be a source for malfunctions and leaks. The involved forces and the influence of the production parameters on the resulting forces are difficult to predict and to control.

There is thus an ongoing need for improvement in the field of cannula units for infusion site interfaces and infusion pumps, and corresponding manufacturing methods.

Objects of the Invention

It is an object of this invention to provide cannula units for ambulatory infusion pumps, and manufacturing method for such cannula units, which overcome one or more of the above- mentioned problems and other problems, and particularly reduce potential malfunctions due to accumulated deviations from nominal production parameters.

It is a further object of the invention to provide a manufacturing method with reduced manufacturing costs, particularly decreased expenditures for tooling and facilities.

It is yet another object to increase the reliability of a manufacturing process for cannula units, and to provide cannula units that are reliable and cost efficient in large scale manufacture. These and other objects are substantially achieved by a cannula unit and a method for manufacturing cannula units, according to the independent claims. Further advantageous embodiments and variants are set forth in the dependent claims and the description.

Summary of the invention

The present invention may comprise one or more of the features recited in the attached claims, and/or one or more of the following features and combinations thereof.

A first aspect of the invention concerns an advantageous method for manufacturing a cannula unit. Such a method for manufacturing a cannula unit according to the invention comprises the steps: providing a flexible cannula with an end area that deviates from the shape of the rest of the cannula; providing a housing; and connecting the end area of the flexible cannula to the housing; wherein the end area of the flexible cannula is positively locked to the housing by clamping.

In the context of the present disclosure, 'clamping' of an object is to be understood in the common technical sense of firmly fastening said object between two or more further objects by friction-lock, or by friction lock in combination with form-lock. The clamped first object is subject to a certain force, in order to achieve the friction lock, which is achieved by moving the further objects into a certain position in regard to the first object, and permanently holding the further objects in that position.

Clamping the cannula to the housing considerably simplifies the assembly process, since e.g. no complex injection molding tooling is needed for connecting the cannula and the housing. Furthermore, clamping a flexible cannula to the housing, which consists of a compressible or even elastic material, allows to achieve a sealing connection with the housing, which would not be possible if the cannula would be made of a rigid material such a steel.

Advantageously, the end area of the flexible cannula is connected to the housing by crimp- ing.

In the context of the present disclosure, 'crimping of an object to another object is to be understood in the common technical sense of firmly fastening said object to the other object, by deforming one or both of the objects, in order to achieve a friction lock and form- lock. Thus crimping can be understood as a special form of clamping. Alternatively, or in addition, the end area of the flexible cannula is connected to the housing by clamping the end area of the flexible cannula between a first part and a second part of the housing.

In such a variant of the method according to the invention, the first part and the second part of the housing are advantageously provided as two separate parts. Even more advan- tageously, after clamping the end area of the flexible cannula to the housing, the first part and the second part of the housing are permanently connected, e.g. by ultrasonic welding and/or adhesive bonding.

Alternatively, the housing is realized as one monolithic element.

In the above-mentioned variants of methods according to the invention, advantageously a piercing element, e.g. a piercing needle, is mounted to the cannula unit, by threading the piercing element or needle on the cannula. Furthermore, advantageously a septum is mounted to the housing, e.g. by crimping.

A second aspect of the invention concerns an advantageous cannula unit. Such a cannula unit according to the invention comprises a housing, and a cannula provided with an end area deviating from the shape of the rest of the cannula. Said end area of the flexible cannula has e.g. a funnel-like shape, or the shape of a flange. The end area of the flexible cannula is positively locked to the housing by clamping.

Advantageously, the end area of the flexible cannula is crimped to the housing.

Alternatively, or in addition, the end area of the flexible cannula is clamped between a first part and a second part of the housing. Even more advantageously, the first part and the second part of the housing are separate parts.

In an advantageous cannula unit as described above, the first part and the second part of the housing advantageously are permanently connected to each other, e.g. by ultrasonic welding and/or by adhesive bonding.

Alternatively, the housing of a cannula unit according to the invention is realized as one monolithic element.

In the above-mentioned embodiments of cannula units according to the invention, advantageously a piercing element, e.g. a piercing needle, is threaded on the cannula.

In further advantageous embodiments of such cannula units according to the invention, a septum mounted to the housing, e.g. by crimping.

Cannula units according to the invention can be manufactured using manufacturing methods according to the invention. Brief description of the drawings

In order to facilitate a fuller understanding of the present invention, reference is now made to the appended drawings. These references should not be construed as limiting the present invention, but are intended to be exemplary only.

Figure 1 schematically shows a cross section of a first embodiment of a cannula unit according to the invention.

Figure 2 schematically shows a cross section of a second embodiment of a cannula unit according to the invention.

Figure 3 schematically shows the cannula unit of Figure 2 , with the piercing needle in place.

Figure 4 schematically shows a cross section of a third embodiment of a cannula unit according to the invention.

Description of embodiments of the invention

Components that are identical, or that are identical at least in terms of their function , are designated below by identical or at least comparable reference numbers.

A first embodiment of a cannula unit 1 according to the invention is disclosed in a cross- sectional view in Figu re 1 . The assembled cannula unit 1 comprises a flexible cannula 3 , of which the distal end, the end opposite to the body of the patient, is visible, and a housing 2, to which the cannula 3 is mounted. The outer shape of housing body 2 is chosen such that the housing body, and thus the cannula unit 1 , can be mounted e.g. to an infusion site interface.

The body of the housing comprises a first part 21 , having a receptacle 21 1 in the form of a conical through-hole along the longitudinal axis 7, and a second part 22, having a cone- shaped bushing 221 with a through-hole along longitudinal axis 7. The two parts 21 , 22 of housing body 2 are advantageously made from a suitable polymer material for medical appliances, advantageously a thermoplastic polymer, such as e.g. methyl methacrylate ac- rylonitrile-butadiene-styrene (MABS), polycarbonate (PC), polymethylmethacrylate (PMMA), polypropylene (PP), polyethylene (PE) and the like, and are advantageously produced by injection moulding. Advantageously, both parts should be manufactured from the same material. The flexible cannula is also advantageously made from a suitable polymer material such as polytetrafluoroethylene (PTFE), linear low-density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), or the like. The housing body, namely in the given embodiment its second part 22, comprises an inner chamber 52 formed by the through-hole, opening on a proximal end, the end facing the body of a patient, toward the fluid channel 51 of cannula 3. An upper, distal end of the fluid chamber 52 is sealingly closed by an essentially cylindrical elastomeric septum 4 arranged in a corresponding seat 26 of second part 22, and is held in place by a crimp con- nection 24. The dimensions of circular septum 4 and the corresponding circular seat 26 of body 2 are chosen such that the septum is radially compressed, thereby achieving a fluid- tight seal between second body 2 / second part 22 and septum 4.

The opening at the distal end of cannula 3 has diameter that is larger than the diameter of the rest of the cannula, and has a funnel-like shape 32. The funnel-like cannula end 32 is clamped between the conical bore 21 1 of first part 21 and the conical bushing 221 of second part 22. The first 21 part and the second part 22 are advantageously permanently connected. In the shown embodiment, the two parts 21 , 22 of the housing body 2 are bonded at two abutting flanges 21 2, 222 of the two parts 21 , 22 by ultrasonic welding 6. Other suitable methods for connecting two such parts are known to the skilled person, e.g. adhesive bonding.

The geometry and dimensions of the bore 21 1 of first part 21 , the bushing 221 of second part 22, and the funnel-shaped distal end 32 of the flexible cannula 3 are chosen such that when the two flanges 21 2, 222 abut each other, the funnel-shaped cannula end 32 is positively locked between the bore 21 1 and the bushing 221 . Advantageously, the thickness of the wall of the cannula 3, particularly of its funnel end 32, is chosen such that the cannula wall is compressed to a certain extent between bore 21 1 and bushing 221 , thereby achieving a fluid-tight sealing connection between flexible cannula 3 and second part 22 of body 2, and thus between the fluid channel 51 of cannula 3 and the fluid cham- ber 52 of body 2. In addition, such a connection provides increased resistance against slipping off of flexible cannula 3 from body 2, due to the increased friction.

The inclination of the surfaces of cones 21 1 and 221 that face each other can be chosen identical. Alternatively, the inclination in regard to longitudinal axis 7 of the outer surface of conus 221 can be chosen a few degrees larger than the inclination of the inner surface of conus 21 1 . As a result, the distance between the two conus surfaces is smallest at the proximal edge of conical bushing 221 , and the cannula end is clamped in a circular area at the end of bushing 221 . This allows to increase the achievable clamping force. In another alternative, one or more circumferential rips or similar protruding structural elements can be provided on conical bushing 221 and/or conical bore 21 1 , in order to increase friction between cannula funnel surface and cone surface.

A cannula unit according to the first embodiment as discussed above allows to realize an assembly process that comprises less steps, and involves less possible sources for leakage and other malfunctions.

In a first step, an end of a flexible cannula 3 is provided with an opening with increased diameter. For example can the opening of an endless cannula be expanded by suitable conical tooling. Form and size of the opening are chosen such that the end of a conical bushing 221 can be placed in the expanded opening of cannula 3. After inserting the conical bushing in the expanded opening of cannula 3, the cannula end is thermally shrunk onto the conical bushing 221 , resulting in a funnel-shaped distal cannula end 32. The mechanical connection between second part 22 and cannula 3 has only to be stable enough for the following manufacturing steps. For the steps above, the cannula may be cut to length before or after expanding the opening, or after mounting the cannula end to the conical bushing. The latter variant has the particular advantage that the trimmed loose cannula does not have to be handled as a separate element, and can be easily handled in the manufacturing process by holding second part 22. The cannula 3 and the conical bushing 221 of second part 22, to which it is attached, are threaded through the through-hole of first part 21 , until the flanges 21 1 , 221 of the two parts of body 2 abut each other. The funnel-shaped cannula end 32, and thus also the conical bushing 221 , is automatically precisely aligned to the longitudinal axis 7 by conical bore 21 1 . The two parts 21 , 22 are then permanently connected, e.g. by ultrasonic welding. The mounting of cannula 3 on body 2 is completed.

In a subsequent step, the septum 4 is inserted into the provided seat 26 in second part 22, and a crimp connection 24 is established, by thermally treating a corresponding cylindrical wall structure of body 2 and crimping the wall over the distal surface of the septum 4, arriving at the state in Figure 1 .

In case the cannula 3 is a flexible cannula, the cannula unit 1 Figure 1 is not yet completed. A piercing needle needs to be threaded into the cannula, in order to obtain the temporary rigid piercing needle/cannula structure. For that purpose, a piercing needle is pierced from above through septum 4 and is threaded through the cannula 3 , until its end protrudes from the proximal end of cannula 3.

In an alternative approach, the above-mentioned manufacturing method can by modified as follows: The piercing needle is threaded onto the flexible cannula directly after expanding one end of the cannula, or after mounting the cannula end to the conical bushing 221 . The following manufacturing steps remain unchanged, expect for the fact that for mounting septum 4 in the corresponding seat of second part 22, the septum is pushed over the piercing means into place in the seat 26, the distal end of the piercing means piercing the septum in this process. Then the crimp connection 24 is completed. This approach has the advantage that the step of threading the piercing means onto the cannula, which has a higher discard rate than other steps, takes place in an early stage, such that the costs involved with discarding damaged intermediate products is minimal. The final cannula unit, however, is identical to a cannula unit where the piercing needle is mounted later, as described further above. Depending on the application of the cannula unit, the body 2 can now be mounted to an overall structure, e.g. of an infusion site interface. The piercing needle can be provided with a handle that allows a user to withdraw the needle after insertion of the needle/cannula structure into the body tissue, or can be connected to a device that allows the automatic withdrawal of the needle, as for example disclosed in US 2008/02281 44 A1 as cited further above.

In the embodiment discussed above, the distal end area of the cannula has to have a certain shape, in order to achieve the required technical function. While an end area of a flexible cannula can be shaped without problems with corresponding tooling, such shaping would be difficult to achieve or even impossible with rigid cannulas such as steel cannulas, which furthermore would miss the needed compressibility to achieve a sealing connection between the different parts.

A second embodiment of a cannula unit 1 according to the invention is disclosed in a cross- sectional view in Figures 2 and 3 , without and with mounted piercing needle 8. The assem- bled cannula unit 1 comprises a cannula 3, of which the distal end is visible, and a housing 2, to which the cannula 3 is mounted. The body of the housing is realized as one monolithic element 20. The outer shape of housing body 2 is chosen such that the housing body, and thus the cannula unit 1 , can be mounted e.g. to an infusion site interface. A septum 4 is arranged in a seat 26 of the body 2, and is held in place by a crimp connection 24 similar to the cannula unit of Figure 1 . The explanations made further above in regard to suitable materials for body 2 and cannula 3 apply also for this as well as all following embodiments of cannula units according to the invention.

The septum 4 sealingly closes an upper, distal end of an upper bore 21 4 of housing body 2, thereby defining a fluid chamber 52 between septum 4 and the distal end of cannula 3, its fluid channel 51 opening toward the fluid chamber 52. As can be seen in Figure 3 , the piercing needle 8 penetrates septum 4, and is arranged inside the fluid channel of cannula 3 in such a way that the wall of cannula 3 abuts the needle surface, but only with a minimum amount of friction, in order to ensure both an insertion of the cannula/needle struc- ture without wrinkling up of the cannula, and the withdrawal of the piercing needle 8 after insertion into the body tissue.

The cannula unit 1 as shown in Figure 2 differs from the first embodiment particularly in the way the cannula 3 is clamped to the body 2. The cannula 3 is arranged in a lower bore 21 5 of the body, having essentially the same diameter as the cannula. At its distal end, cannula 3 is provided with a flange 31 arranged in a corresponding seat 25 of the body. The flange 31 is held in place in the seat 25 by a crimping connection 23. In order to achieve a fluid-tight connection between inner volume 52 and fluid channel 51 of cannula 3, the crimp connection is prepared in such a way that the outer rim of the flange 31 is compressed by the rim of the crimp 23. The second embodiment of a cannula unit according to the invention as discussed above has the advantage that it comprises one compound less, which further simplifies the assembly process and further reduces potential sources of malfunctions.

For manufacturing a cannula unit according to the second embodiment, in a first step a flexible cannula 3 is provided with a horizontal flange 3 1 , for example by deforming an end of the cannula with an appropriate tool. The cannula is then threaded into the through- hole of body 2, until the flange 31 is located in the circular seat 25 of the body. A suitable crimp structure around the seat 25 is then thermally deformed, in order to make the crimp connection 25. The parameters of this step must be chosen such that after the finalisation of the crimping step, the rim of the crimp structure presses the flange 31 against the body 2, in order to achieve a sealing connection. Now the septum 4 is mounted, similar to the method discussed above in the context of the first embodiment, arriving at the state in Figure 2. The cannula unit as such is completed.

As a next step, the piercing needle is inserted, by penetrating the septum 4 and threading the needle through cannula 3 , until a tipped end of piercing needle 8 protrudes from the proximal opening of cannula 3. Alternatively, and similar to the first embodiment, the piercing needle may already be inserted into the cannula unit directly after the forming of flange 3 1 , or after the completed mounting of the cannula in body 2.

As explained further above for the first embodiment, the body 2 and/or the piercing needle 8 can now be connected with other functional structures.

A third embodiment of a cannula unit 1 according to the invention is shown in Figure 4. The body of housing 2 comprises a first part 21 and a second part 22. The first part 21 comprises a through-hole consisting of two cylindrical bores 21 4, 21 5 with different diameters, and an outer circumferential flange 21 2. A cannula 3 having a flange 3 1 at its distal end is mounted to body 2. The cannula 3 protrudes through a lower bore 21 5 of first part 2 1 , and the flange 3 1 abuts the bottom 21 3 of an upper bore of the first part 21 . The second part 22 comprises a bushing 220 with a through-hole, and an outer circumferential flange 222. The bushing 220 is arranged in the upper bore 21 4 of first part 21 , and the flange 222 of second part 22 abuts the flange 21 2 of first part 2 1 . In the assembled can- nula unit 1 , the two parts 21 , 22 are permanently connected to each other, in the given exemplary embodiment by ultrasonic welding points 9 between the two flanges 21 2, 222. A septum 4 is arranged in seat 26 of second part 22 , and held in place by crimp connection 24, as discussed above for the previous embodiments. The septum 4 sealingly closes an upper end of an inner bore of second part 22 , thereby defining a fluid chamber 52 that is fluidly connected with fluid channel 51 of cannula 3. The dimensions of the two parts 2 1 , 22 and the flange 31 of cannula 3 are chosen such that a proximal edge 223 of bushing 220 presses the cannula flange 3 1 against bottom 21 3, thereby compressing flange 3 1 and sealingly connecting the inner bore of second part 22 and cannula 3. The manufacturing method for this third embodiment of a cannula unit according to the invention is similar to the methods discussed further above. After providing a cannula 3 with a flange 31 on its end, and placing the cannula into first part 21 , the bushing 220 is inserted into the upper bore 21 4 of first part 2 1 , until the two flanges 21 2, 22 abut each other. The bushing 220 is aligned to longitudinal axis 7 by cylindrical upper bore 21 4. After permanently connecting the two flanges 21 2, 222 by ultrasonic welding 6, septum 4 is put in place, and the crimp connection 24 is completed. As for the other discussed method variants, the piercing needle 8 may be inserted into cannula 3 directly after the formation of cannula flange 3 1 , after the fixation of cannula 3 and the permanent connection of the two parts of the housing body 2, or after the mounting of the septum 4 to the housing body 2.

The embodiments of cannula units as discussed so far have been equipped with only one septum, which can be used both for withdrawing the piercing means, and for establishing a fluid connection with an infusion pump. However, cannula units according to the invention can also be equipped with a separate connection element for connecting the cannula unit to an upstream infusion pump. For example can the cannula unit be provided with a further connector port with septum, fluidly connected to the fluid chamber by a fluid channel in the housing body. Examples of such cannula units are disclosed e.g. in Figure 1 B of US 201 2/0296290 A 1 , and in Figure 21 of US 2008/02281 44 A1 . The cannula units according to the invention as discussed so far can be adapted by a skilled person to such complex cannula unit structures. The same applies for the manufacturing methods for such cannula units.

The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the present invention, in addition to those de- scribed herein, will be apparent to those skilled in the art from the foregoing description and accompanying drawings. Thus, such modifications are intended to fall within the scope of the appended claims. Additionally, various references are cited throughout the specification, the disclosures of which are each incorporated herein by reference in their entirety.

List of Reference Numerals

1 cannula unit

2 housing body, housing

20 single part of body

21 first part of body

21 1 receptacle, conical bore

21 2 flange

21 3 bottom of upper bore of first part

21 4 upper bore

21 5 lower bore

22 second part of body

220 bushing

221 conical bushing

222 flange

223 proximal edge of bushing

23 crimp connection for fixation of tube

24 crimp connection for fixation of septum

25 seat for cannula flange

26 seat for septum

3 cannula

31 flange

32 funnel-shaped end of cannula

4 septum

51 fluid channel

52 fluid chamber

6 ultrasonic welding point

7 longitudinal axis

8 piercing needle