Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Patent
1995-08-14
1998-03-17
Buiz, Michael Powell
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
604224, A61M 550
Patent
active
057280754
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention refers to improvements in injection devices for adminstering a liquid preparation by injection. More particularly, the invention refers to improvements in injection devices for injection cartridges, and especially then in injection devices for multi-chamber injection cartridges. Still more particularly, the invention refers to a novel device in a piston rod for use in an injection device employing an injection cartridge.
2. Background Art
Injection devices using injection cartridges have been known for a long time and have been appreciated for their ease of handling and their lessened risk of contamination of the preparation to be injected. An injection cartridge is essentially shaped as a cylinder which is filled with the liquid injectable preparation. The front end of the cylinder is sealed by a closure which may be pierced by an outlet conduit, such as an injection needle, when the preparation is to be injected. The rear end of the cartridge is sealed by a piston which may be urged forward by means of a piston rod acting thereon. This piston will then expel the preparation from the cartridge through the outlet conduit. The cartridge is usually arranged in a holder device which comprises the piston rod for acting on said piston. The holder device may also comprise a mechanism for setting and delivering one or more predetermined doses of the preparation to be injected.
A further development of the injection cartridges has been the so-called multi-chamber cartridges. Such cartridges are intended to be used for injectable preparations where the ready-to-use preparation is not stable for any extended time, and are divided into a front chamber and a rear chamber, which are separated by an intermediate movable wall. The front chamber usually contains a solid component of an injectable preparation, while the rear chamber contains a liquid component of said preparation. At a suitable position in the cartridge, a bypass connection is arranged in the interior wall of the cartridge, such that the liquid component may flow around and bypass the intermediate wall, to be mixed with the solid component.
When the mixing of the two components is to be carried out, pressure is applied to the piston by means of a piston rod, to urge it forward. The pressure is transmitted through the liquid in the rear chamber such that the intermediate movable wall is also urged forward. When the intermediate wall has been moved forward for a predetermined distance, it will be positioned at the bypass connection, making it possible for the liquid component to bypass the intermediate wall to flow into the front chamber. Further movement forward of the piston will cause the liquid component to flow over into the front chamber until all of the liquid has been transferred into the front chamber, and the front face of the piston rests against the rear face of the intermediate wall. The liquid component will now be mixed with the solid component to be dissolved or suspended in the liquid phase.
Further forward pressure on the piston will now move it together with the intermediate wall forward together to expel the mixed injectable preparation from the front chamber of the cartridge through the outlet conduit in the front closure of the cartridge.
The design and function of injection cartridges of the single-chamber and the multi-chamber type is well-known to those skilled in the art and does not have to be described here in greater detail.
When a dual-chamber injection cartridge is to be readied for injection, it is important that the piston is displaced smoothly without any uneven movements. Furthermore, it is important that the forward movement is stopped just at the exact position where the piston and the intermediate wall contact with each other and all the liquid has passed over into the front chamber. For this, the piston rod is often provided with a thread which cooperates with a corresponding internal thread in a nut element provided in a holder device for the cartridge. Thus, the pi
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Buiz Michael Powell
Nguyen A. T.
Pharmacia & Upjohn Aktiebolag
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