Abstract
Disclosed is a pierceable septum for use in drug reservoirs and infusion sets. The pierceable septum has an elastic core made from a core material and a surround made from a surrounding material. The surrounding material is more rigid than the core material. The elastic core is fully embedded in the surround.
Claims
1. A pierceable septum for use in drug reservoirs and infusion sets, the pierceable septum comprising: an elastic core formed from a core material; and a surround formed from a surrounding material; wherein, the elastic core is fully embedded in the surround and the surrounding material is more rigid than the core material.
2. The pierceable septum according to claim 1, wherein the surrounding material has a shore hardness selected such that the expansion of the core material upon penetration of the septum with a cannula is confined.
3. The pierceable septum according to claim 1, wherein the surrounding material has a shore hardness selected from the group consisting of: from 0 to 100 Shore A and from 50 to 80 Shore A.
4. The pierceable septum according to claim 1, wherein the core material has a shore hardness selected from the group consisting of: from 0 to 50 Shore A and from 10 to 40 Shore A.
5. The pierceable septum according to claim 1, wherein the elastic core is overmolded by the surround.
6. The pierceable septum according to claim 1, wherein the core material is an elastomer.
7. The pierceable septum of claim 1, wherein the surrounding material is an elastomer or thermoplastic elastomer.
8. The pierceable septum according to claim 1, wherein the elastic core is radially prestressed by the surround.
9. The pierceable septum according to claim 1, wherein the septum comprises a sealing lip or a circumferential groove.
10. The pierceable septum according to claim 1, wherein the surround comprises first and second different surrounding materials, wherein the first surrounding material is disposed along a piercing path of a cannula and the second surrounding material is disposed aside from the piercing path, further wherein the first surrounding material is less rigid than the second surrounding material.
11. A method for producing a pierceable septum, comprising: providing an elastic core from a core material; fully overmolding the elastic core with a surrounding material to produce a pierceable septum with an elastic core embedded in a surround.
12. The method according to claim 11, wherein the overmolding is performed by injection molding.
13. The method according to claim 12, wherein the overmolding is performed by 2k molding.
14. An infusion set comprising a pierceable septum according to claim 1.
15. The infusion set according to claim 14, wherein the septum is radially prestressed by radial compression.
16. A reservoir for a liquid drug comprising a pierceable septum according to claim 1.
17. The reservoir according to claim 16, wherein the septum is radially prestressed by radial compression.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:
[0041] FIG. 1 shows a cross-sectional view of a pierceable septum in accordance with one embodiment of this disclosure;
[0042] FIG. 2 shows a cross-sectional view of a pierceable septum in accordance with another embodiment of this disclosure;
[0043] FIG. 3 shows a cross-sectional view of a pierceable septum in accordance with another embodiment of this disclosure;
[0044] FIG. 4 shows a cross-sectional view of a pierceable septum in accordance with another embodiment of this disclosure;
[0045] FIG. 5(a) shows a cross-sectional view of a pierceable septum built into a housing in accordance with another embodiment of this disclosure;
[0046] FIG. 5(b) shows a cross-sectional view of a pierceable septum built into a housing in accordance with another embodiment of this disclosure; and
[0047] FIG. 6 shows a cross-sectional view of a pierceable septum built into reservoir for drugs in accordance to another embodiment of this disclosure.
DESCRIPTION
[0048] The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.
[0049] An advantageous embodiment of a pierceable septum 1 according to this disclosure is shown in FIG. 1. The pierceable septum 1 comprises an elastic core 11, from a core material and a surround 10 from a surrounding material. As can be readily seen, the elastic core is fully embedded in the surround. In other words, the elastic core is completely arranged inside the surround. Thus, the elastic core is neither visible nor extends to the surface of the septum nor can be in contact with any other parts, such as a housing or a drug reservoir. The elastic core in the embodiment shown is essentially flat and elongated in the lateral direction of the septum. FIG. 1 also illustrates axis A, which extends along the piercing path of a cannula and which is essentially normal to the lateral direction of the septum.
[0050] FIG. 2 illustrates another embodiment of this disclosure. In addition to elastic core 11 and surround 10, the pierceable septum 1 further comprises circumferential groove 12 (for clarity reasons, no filling of the core and the surrounding is used as in FIG. 1). Typically, if such a septum is used in an infusion set or drug reservoir, the surface of the septum comprising groove 12 is facing the inside of the infusion set or drug reservoir and the opposing flat surface is positioned on the outside of the infusion set or reservoir.
[0051] FIG. 3 shows a septum 1 according to this disclosure, which is penetrated by cannula 21 along a piercing path. As indicated by the arrows, the surround 10 exerts a force F.sub.2 on elastic core 10, upon which the elastic core sealingly engages the cannula (F.sub.1). Thus, a septum according to this disclosure may significantly increase the friction between a cannula and the septum.
[0052] FIG. 4 illustrates a further advantageous embodiment of a pierceable septum 1 according to this disclosure. The surround 10 comprises two different materials. The material along the piercing path of a cannula (see 10a), may be less rigid than the material aside from the piercing path (see 10b). As a result, elastic core 11 is surrounded by two different materials. Such an embodiment has the beneficial effect that it enables smooth piercing of the septum along a predetermined piercing path and still provide the above described sealing effect by laterally engaging a penetrating cannula.
[0053] FIG. 5(a) depicts a pierceable septum 1 according to this disclosure, which is built into a housing unit 20. The housing unit 20 is part of a cannula unit 25, which itself can be part of an infusion set. Additionally, cannula unit 25 may comprise a flexible infusion cannula 23 which can be inserted into the patient's tissue by insertion of a piercing needle through the septum, prior to assembly of removable connector device 24. As can be readily seen, the housing unit 20 and the septum form a compartment 22, which can comprise a liquid drug. For example, the drug can be pumped under pressure into compartment 22 by an infusion pump (not shown), which is in fluid connection with connector cannula 21. Connector cannula 21 is part of connector device 24, which is removably connected to cannula unit 25 and not depicted in greater detail. The state shown in FIG. 5(a) represents the operative state of the infusion set, in which the infusion pump is in fluid connection with flexible infusion cannula 21 via compartment 22 and connector cannula 21.
[0054] FIG. 5(b) shows the cannula unit 25 of FIG. 5(a), in which the user may have disconnected the infusion pump from the connector device 24 by withdrawal of connector cannula 21 from septum 1. Such a process may for example be performed by the user in situations, in which an infusion pump may be unsuitable, for example while taking a shower. As indicated by the curved lines, withdrawal of the connector cannula 21 leaves a puncture or through cut in the septum. Due to the fact that the surrounding material is more rigid than the core material, respectively due to the difference in elastic modulus of elastic core 11 and surround 10, an offset of the through cut is generated, that is, the through cut is not continuous, but the trough cut in the core 11 is laterally displaced as compared to the through cut in the surround 10. This offset significantly decreases the occurrence of any leakage, which becomes even more relevant in the event of multiple piercings.
[0055] FIG. 6 shows a reservoir for drugs 20, for example an insulin cartridge comprising walls 31 and liquid drug 32. A pierceable septum 1 according to this disclosure allows for withdrawal of drug 32 from the reservoir by a cannula and ensures tight sealing of the pierced septum 1 during penetration of the cannula and also after its removal. The particular septum 1 shown comprises core 11 which is fully embedded in surround 10.
[0056] While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
