Hjertman, Birger; Levander, Gustav; Ljunquist, Olle;

Injection cartridge

An injection cartridge of the dual-chamber type has a bypass connection between its two chambers which is arranged such that the interior wall of the cartridge is modified in a determined area in such a way that the movable wall between the two chambers does not seal completely against the interior wall in said area.

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We claim:

1. An injection cartridge of the dual-chamber type, comprising a tubular barrel which at its front end is sealed by a closure which may be penetrated by an outlet conduit for a liquid preparation from the cartridge, and at its rear end is closed by a piston which may be moved forward, and a movable transversal wall inside said barrel, said movable wall dividing the cartridge into two separate chambers, and a bypass connection between the two chambers, said bypass connection being openable by the displacement of said movable wall to permit a bypass flow of liquid between the two chambers, and characterized in that said connection between the two chambers is arranged as a modification of the surface of the interior wall of the barrel, said modification extending completely around the circumference of the interior wall and comprising a plurality of lands and grooves in said interior wall surface, said lands extending inward from the nominal interior circumference of the barrel and said grooves extending outward from said nominal interior circumference, such that a liquid flow may be arranged around the whole circumference of the movable wall.

2. Injection cartridge according to claim 1, characterized in that the height of the lands and the depth of the grooves, as well as their number, are correlated in such a way that the movable transversal wall has essentially the same cross-sectional area when it is positioned in the area of said lands and grooves as when it is positioned in the smooth-walled part of the barrel.

3. Injection cartridge according to claim 1, characterized in that said modification consists of a pattern of a roughened surface or of small projections in said interior wall surface.

4. Injection cartridge according to claim 1, characterized in that said modified area of the interior wall surface is divided into at least two spaced circumferential areas, and that the movable wall is provided with the same number of peripheral sealing ridges, said ridges and said areas having the same spacing.

5. Injection cartridge according to claim 1, characterized in that the depth of said grooves and/or the height of said lands or projections is between 0.06 and 0.6 mm.

6. An injection cartridge according to claim 2, wherein said modification comprises a pattern of a roughened surface or of small projections in said interior wall surface.

7. An injection cartridge according to claim 2, wherein said modified area of said interior wall surface is divided into at least two spaced circumferential areas, and the movable wall is provided with the same number of peripheral sealing ridges, said ridges and said areas having the same spacing.

8. An injection cartridge according to claim 3, wherein said modified area of said interior wall surface is divided into at least two spaced circumferential areas, and the movable wall is provided with the same number of peripheral sealing ridges, said ridges and said areas having the same spacing.

9. An injection cartridge according to claim 2, wherein the depth of said grooves and/or the height of said lands or projections is between 0.06 and 0.6 mm.

10. An injection cartridge according to claim 3, wherein the depth of said grooves and/or the height of said lands or projections is between 0.06 and 0.6 mm.

11. An injection cartridge according to claim 4, wherein the depth of said grooves and/or the height of said lands or projections is between 0.06 and 0.6 mm.

12. An injection cartridge according to claim 1, wherein said modification of the interior wall surface of the barrel extends completely around the circumference of said interior wall.

13. An injection cartridge according to claim 1, where said modification of the interior wall surface is arranged as a plurality of lands and grooves in said interior wall.

14. An injection cartridge according to claim 13, wherein the lands extend inward from the nominal interior circumference of the tubular barrel, and the grooves extend outwardly from said nominal circumference.

15. An injection cartridge according to claim 14, wherein the height of the lands and the depth of the grooves, as well as their number, are correlated in such a way that the movable transverse wall has essentially the same cross-sectional area when it is positioned in the area of said lands and grooves as when it is positioned in a smooth-walled part of the cartridge.

16. An injection cartridge of the dual-chamber type, comprising:

a tubular barrel which at its front end is sealed by a closure which may be penetrated by an outlet conduit for a liquid preparation from the cartridge, at its rear end is closed by a piston which may be moved forward, and a movable transverse wall inside said barrel, said movable wall dividing the cartridge into two separate chambers, and a bypass connection between the two chambers, said connection being openable by the displacement of said movable wall to permit a bypass flow of liquid between the two chambers, and characterized in that said connection between the two chambers is arranged as a modification of the interior surface of the wall of the barrel along a determined area, such that said movable wall does not seal completely against said interior wall of the barrel within said area.

17. An injection cartridge according to claim 16, wherein said modification of the interior wall surface of the barrel extends completely around the circumference of said interior wall.

18. An injection cartridge according to claim 16, where said modification of the interior wall surface is arranged as a plurality of lands and grooves in said interior wall.

19. An injection cartridge according to claim 18, wherein the lands extend inward from the nominal interior circumference of the tubular barrel, and the grooves extend outwardly from said nominal circumference.

20. An injection cartridge according to claim 19, wherein the height of the lands and the depth of the grooves, as well as their number, are correlated in such a way that the movable transverse wall has essentially the same cross-sectional area when it is positioned in the area of said lands and grooves as when it is positioned in a smooth-walled part of the cartridge.