DUAL CHAMBER DRUG RESERVOIR AND STOPPER THEREFOR

Abstract

The present invention concerns an elastomeric stopper (18, 28, 38) for a drug reservoir, comprising: a stopper body (18.1, 28.1, 38.1) extending along a reference axis between a leading end surface (18.2, 28.2, 38.2) and a trailing end surface (18.3, 28.3, 38.3) and having a generally cylindrical sidewall with an outer body diameter, a circumferential convex rib (18.6, 28.6, 38.6) extending radially outwardly from the sidewall, a non-convex trim edge portion (18.7, 28.7, 38.7) at the trailing end surface (18.3, 28.3, 38.3), the non-convex trim edge portion (18.7, 28.7, 38.7) having an outer trim edge diameter which is greater than the outer body diameter and being axially spaced apart from the circumferential convex rib (18.6, 28.6, 38.6), providing an annular recess (18.9, 28.9, 38.9) therebetween. The elastomeric stopper (18, 28, 38) further comprises a channel structure (18.10, 28.10, 38.10) enabling fluid flow from the trailing end surface (18.3, 28.3, 38.3) to the annular recess (18.9, 28.9, 38.9) through the non-convex trim edge portion (18.7, 28.7, 38.7).

Claims

1. An elastomeric stopper for a drug reservoir, comprising: a stopper body extending along a reference axis between a leading end surface and a trailing end surface and having a generally cylindrical sidewall with an outer body diameter, a circumferential convex rib extending radially outwardly from the sidewall, a non-convex trim edge portion at the trailing end surface, the non-convex trim edge portion having an outer trim edge diameter which is greater than the outer body diameter and being axially spaced apart from the circumferential convex rib, providing an annular recess therebetween, further comprising a channel structure enabling fluid flow from the trailing end surface to the annular recess through the non-convex trim edge portion.

2. The elastomeric stopper according to claim 1, wherein the channel structure comprises at least one bore through the non-convex trim edge portion, the at least one bore having an inlet opening in the trailing end surface and an outlet opening in the annular recess.

3. The elastomeric stopper according to claim 1, wherein the channel structure comprises at least one peripheral cut-out forming a part-cylindrical indentation in the non-convex trim edge portion.

4. A drug reservoir comprising: a reservoir body comprising a generally cylindrical wall with an axially extending bypass channel therein, a proximal end section, a distal outlet end section, an elastomeric stopper according to any of the preceding claims slidably arranged between the distal outlet end section and the proximal end section and initially providing a fluid tight seal with the generally circular cylindrical wall proximally of the bypass channel, a front chamber thereby being defined by the distal outlet end section, a first portion of the reservoir body, and the elastomeric stopper, and a rear stopper slidably arranged between the elastomeric stopper and the proximal end section, a rear chamber thereby being defined by the elastomeric stopper, a second portion of the reservoir body, and the rear stopper.

5. The drug reservoir according to claim 4, further comprising an injection needle with a lumen, the lumen being in fluid communication with the distal outlet end section.

6. The drug reservoir according to claim 4, wherein the distal outlet end section is closed by a penetrable self-sealing septum.

7. A drug delivery device comprising a drug reservoir according to claim 4 together with a drug expelling mechanism, wherein the drug expelling mechanism comprises a plunger rod operable to displace the rear stopper relative to the generally cylindrical wall.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the following the invention will be further described with references to the drawings, wherein

[0029] FIG. 1a is a longitudinal section view of a dual chamber syringe according to the prior art,

[0030] FIG. 1b is a close-up view of a section of the syringe of FIG. 1a,

[0031] FIG. 2 is a longitudinal section view of a conventional type stopper used in dual chamber syringe devices,

[0032] FIG. 3 is a longitudinal section view of the stopper of FIG. 2 in a syringe with a low bypass channel,

[0033] FIGS. 4a and 4b are different views of a stopper according to a first embodiment of the invention,

[0034] FIGS. 5a and 5b are different views of a stopper according to a second embodiment of the invention, and

[0035] FIGS. 6a and 6b are different views of a stopper according to a third embodiment of the invention.

[0036] In the figures like structures are mainly identified by like reference numerals.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0037] When/If relative expressions, such as “upper” and “lower”, “left” and “right”, “horizontal” and “vertical”, “clockwise” and “counter-clockwise”, etc., are used in the following, these refer to the appended figures and not necessarily to an actual situation of use. The shown figures are schematic representations for which reason the configuration of the different structures as well as their relative dimensions are intended to serve illustrative purposes only.

[0038] FIG. 1a is a longitudinal section view of a conventional prior art dual chamber syringe 1 in a pre-use state, i.e. in a state as supplied by the manufacturer (albeit without a rigid needle protector), and FIG. 1b is an enlargement of a section Q thereof.

[0039] The syringe 1 comprises a generally cylindrical syringe barrel 2 with a bypass channel 3 and a narrowed distal end portion 4. An injection needle 5 is fixed to the distal end portion 4 and establishes fluid communication to an outlet portion 6. A front stopper 8 is arranged in the syringe barrel 2 between the outlet portion 6 and an open proximal end 7, and a front chamber 10 is thereby defined by the outlet portion 6, a front portion of the syringe barrel 2 comprising the bypass channel 3, and the front stopper 8. A rear stopper 9 is arranged in the syringe barrel 2 between the front stopper 8 and the open proximal end 7, and a rear chamber 11 is thereby defined by the front stopper 8, a middle portion of the syringe barrel 2, and the rear stopper 9. The rear stopper 9 has a cavity 13 adapted to receive an end portion of a plunger rod (not shown), which is then actuatable to advance the rear stopper 9 through the syringe barrel 2. The front chamber 10 holds a first liquid substance 20, and the rear chamber 11 holds a second liquid substance 30.

[0040] As can be seen from FIG. 1b the bypass channel 3 is defined by a bypass length L.sub.b and a bypass height h.sub.b. The generally cylindrical syringe barrel 2 has an inner diameter d. However, at the bypass channel 3 the inner diameter is accordingly d+h.sub.b.

[0041] FIG. 2 is a longitudinal section view of the front stopper 8 which comprises a stopper body 8.1 extending along a longitudinal stopper axis and having a leading end face 8.2 and a trailing end face 8.3. The stopper body 8.1 further has three convex circumferential sealing ribs, a leading rib 8.4, an intermediate rib 8.5, and a trailing rib 8.6, as well as a non-convex trim edge 8.7. The three circumferential sealing ribs are axially spaced apart by respective annular recesses 8.8 and serve to seal against an interior wall of the syringe barrel 2. Hence, the transversal dimension of the front stopper 8 varies along the longitudinal stopper axis between a rib diameter D.sub.r and a stopper core diameter D.sub.c. The trim edge 8.7, which serves no functional purpose but is inherently present due to the separation of the stopper body 8.1 from a batch rubber sheet, is axially spaced apart from the trailing rib 8.6 by a trailing annular recess 8.9. In the present example the trim edge 8.7 has a maximum diameter approximately of the size of the rib diameter D.sub.1, and a potential sealing length, L.sub.s, of the front stopper 8 is thus defined as the axial distance between a leading curved portion of the leading rib 8.4 and a trailing face of the trim edge 8.7.

[0042] A design prerequisite for liquid flow past the front stopper 8 is that L.sub.s<L.sub.b. However, as illustrated in FIG. 3, which sketches a version of the syringe 1 where the bypass channel 3 has a low bypass height h.sub.b, when the second liquid substance 30 is pressurised due to an advancement of the rear stopper 9 a pressure p is resultantly exerted onto the trailing end face 8.3 which at first causes the front stopper 8 to advance towards a position within the bypass channel 3, but which when the trailing end face 8.3 reaches the bypass channel 3 may cause the trim edge 8.7 to deform thereinto and prevent the second liquid substance 30 from entering an otherwise established flow passage 12 between the exterior of the front stopper 8 and the syringe barrel 2 (the bypass channel 3 has a limited circumferential extent which prevents any of the three circumferential sealing ribs from entering, but the trim edge 8.7 is a much more easily deformable structure). The desired transfer of the second liquid substance 30 to the front chamber 10 can thus not be realised, leading to a malfunction of the syringe 1, as only the first liquid substance 20 is then administrable.

[0043] This problem can be overcome by employing a specially designed front stopper where liquid flow into the passage 12 is guaranteed even if the trim edge is deformed into the bypass channel 3.

[0044] One such is shown in FIG. 4, where FIG. 4a is a perspective view and FIG. 4b a longitudinal section view of a front stopper 18 according to a first exemplary embodiment of the invention. In FIG. 4a the front stopper 18 is depicted from a proximal perspective, i.e. seen from a trailing end, and like the conventional front stopper 8, which the front stopper 18 is supposed to replace, it comprises a stopper body 18.1 extending along a longitudinal stopper axis and having a leading end face 18.2, a trailing end face 18.3, three axially spaced convex circumferential sealing ribs including a trailing rib 18.6, and a non-convex trim edge 18.7. A trailing annular recess 18.9 is present between the trailing rib 18.6 and the trim edge 18.7.

[0045] The inventive idea is to enable liquid flow to the trailing annular recess 18.9 through the trim edge 18.7. To this end a plurality of channels 18.10 (FIG. 4b) have been established by penetration of the trim edge 18.7. A plurality of inlet openings 18.11 in fluid communication with a corresponding plurality of outlet openings 18.12 are thereby provided, and when the second liquid substance 30 becomes pressurised a volume thereof will flow through the channels 18.10 and into the trailing annular recess 18.9.

[0046] As long as the trailing rib 18.6 is in sealing contact with the syringe barrel 2 proximally of the bypass channel 3 the second liquid substance 30 will apply a driving force to the front stopper 8, advancing the front stopper 8 distally in the syringe barrel 2. However, as soon as the trailing rib 18.6 enters the bypass channel 3 the pressure in the rear chamber 11 will force the liquid in the trailing annular recess 18.9 into the flow passage 12 between the stopper exterior and the syringe barrel 2. At this point the front stopper 18 will stop advancing and as the rear stopper 9 continues to advance the second liquid substance 30 is forced through the channels 18.10 into the trailing annular recess 18.9 and from there on into and through the flow passage 12, as indicated by flow arrows F.

[0047] The transfer of the second liquid substance 30 to the front chamber 10 continues until the rear chamber 11 eventually is completely collapsed, at which point the rear stopper 9 abuts the front stopper 8 and further advancement of the rear stopper 9 by means of the plunger rod causes a gradual collapse of the front chamber 10, all expellable liquid thereby being forced through the outlet portion 6 and the injection needle 5.

[0048] Hence, the presence of the channels 18.10 through the trim edge 18.7 ensures a path from the rear chamber 11 to the flow passage 12 which the second liquid substance 30 can flow through, regardless of the size and deformability of the trim edge 18.7. A fail-safe liquid transfer from the rear chamber 11 to the front chamber 10 is thereby provided, even in a syringe with a minimised bypass height h.sub.b.

[0049] The same basic principle is utilised in two alternative embodiments shown, respectively, in FIGS. 5 and 6.

[0050] FIG. 5a is a perspective proximal view, and FIG. 5b a longitudinal section view, of a front stopper 28 according to a second embodiment of the invention. Like the embodiment of FIG. 4 the front stopper 28 comprises a stopper body 28.1 extending along a longitudinal stopper axis and having a leading end face 28.2, a trailing end face 28.3, three axially spaced convex circumferential sealing ribs including a trailing rib 28.6, and a non-convex trim edge 28.7. A trailing annular recess 28.9 is present between the trailing rib 28.6 and the trim edge 28.7, and a plurality of channels 28.10 (FIG. 5b) have been established by penetration of the trim edge 28.7. A plurality of inlet openings 28.11 in fluid communication with a corresponding plurality of outlet openings 28.12 are thereby provided, and when the second liquid substance 30 becomes pressurised a volume thereof will flow through the channels 28.10 and into the trailing annular recess 28.9. The working principle is the same as that described above with respect to the front stopper 18 according to the first embodiment of the invention, the only significant difference from the first embodiment, apart from the number of inlet openings and outlet openings, being the establishment of the channels 28.10. The tool used to establish the channels 28.10 has a geometric cross configuration and is thus more robust when penetrating the trim edge 28.7 than for example six separate thin sticks used to penetrate the trim edge 18.7 in the establishment of the channels 18.10 in the front stopper 18.

[0051] FIG. 6a is a perspective proximal view, and FIG. 6b a longitudinal section view, of a front stopper 38 according to a third embodiment of the invention. Like the previous embodiments the front stopper 38 comprises a stopper body 38.1 extending along a longitudinal stopper axis and having a leading end face 38.2, a trailing end face 38.3, three axially spaced convex circumferential sealing ribs including a trailing rib 38.6, and a non-convex trim edge 38.7. A trailing annular recess 38.9 is present between the trailing rib 38.6 and the trim edge 38.7, and a plurality of circumferentially spaced apart channels 38.10 (FIG. 5b) have been established as semi-cylindrical cut-outs 38.13 in the periphery of the trim edge 38.7. This ensures that the rim of the trim edge 38.7 cannot seal completely against the syringe barrel 2 and that the second liquid substance 30 accordingly can flow through the trim edge 38.7 between the rim of the trim edge 38.7 and the syringe barrel 2 and enter the trailing annular recess 38.9 from where it can pass to the flow passage 12 when the trailing annular recess 38.9 reaches the bypass channel 3.

[0052] It is noted that even though each of the specifically disclosed embodiments of the invention has three circumferential sealing ribs it is understood that the exact number of such ribs is irrelevant to the inventive concept of establishing a permanent flow path through the trim edge to the trailing annular recess. This solution is thus equally applicable to other types of stoppers having, for example, one, two or four circumferential sealing ribs.