Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2001-10-04
2003-03-25
Mendez, Manuel (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S131000
Reexamination Certificate
active
06537251
ABSTRACT:
THE TECHNICAL FIELD OF THE INVENTION
The invention relates to the design of medication delivery systems with a view to compactness, reliability, weight and production cost.
The invention relates specifically to: A portable medication delivery device comprising a medication cartridge having an outlet and a movable piston, and a housing for holding said cartridge, and a flexible piston rod being operable to engage and displace said piston along an axis of said cartridge, and guiding means for bending said piston rod away from said axis, and actuating means, and driving means for transferring movement from said actuating means to said piston rod, said driving means including a driving wheel for displacing the piston rod, said flexible piston rod comprising regularly spaced first members adapted to mechanically cooperate with corresponding second members on said driving wheel.
DESCRIPTION OF RELATED ART
The following account of the prior art relates to one of the areas of application of the present invention, medication delivery systems for self-treatment of a disease.
In a medication delivery system for self-treatment of a disease such as diabetes, safety and convenience in the handling of the injection or infusion are of major importance. One very important aspect of this is compactness of the device. Another very important aspect for a user is to ensure that a correct intended dose is delivered.
For the manufacturer of the devices aspects such as production control (testability) and economical solutions are important. A handy, i.e. small volume and lightweight, device that is highly reliable and at the same time economical in production is in demand.
U.S. Pat. No. 5,637,095 discloses a medication infusion pump with a flexible drive plunger comprising a spring tape. In one preferred form of the invention, the spring tape is wrapped or coiled onto a take-up spool within the pump housing. Drive means such as a drive capstan roller and associated pinch roller engage and advance the spring tape under control of the pump drive motor to correspondingly engage and advance the piston to deliver medication to the patient in a programmed manner.
EP-A-0 110 687 discloses a portable fluid infusion device including a flexible piston rod assembly. Attached to the piston is a flexible pusher tape, reversely bent in a U-shape at the upstream or open end of the syringe so that the distal end of the tape is adjacent to and in a position to ride upon the cylindrical body of the syringe as the piston is moved within the body of the syringe. The flexible pusher tape is made of a readily flexible plastics material such as a molded polypropylene. A series of parallel grooves are preformed in the face of the plastics tape along the narrow center portion thereof. The outwardly extending face of the tape is engaged by the helical drive screw at the part of the piston rod, which is deflected away from the axis of the cartridge. The rotation of the screw by a DC motor propels the tape in its U-shaped path to drive the piston.
DISCLOSURE OF THE INVENTION
The problems of the prior art are that the driving means are located relatively far from the piston and require a relatively thick piston rod having a relatively high friction with the housing and the cartridge, thus requiring a relatively high power consuming motor to advance it and possibly introducing inaccuracies in the displacement of the piston, or that the means for advancing the tape-shaped piston rod, the take-up spool storing the unused part of the tape, and the drum or wheel that supports the U-shaped path of the tape are individual self-contained functional units, yielding a relatively complex solution.
The object of the present invention is to provide a medication delivery system that combines compactness with an improved accuracy.
This is achieved according to the invention in that said flexible piston rod exhibits a linear or approximately linear path between said driving wheel and said piston.
In the present context, the term ‘medication delivery system’ is taken to mean an injector type device (such as a pen injector or a jet injector) for delivering a discrete dose of a liquid medication (possibly in the form of small drops) or a medication pump for continuous delivery of a liquid medication—in both cases optionally in combination with relevant electronic monitoring and control and possibly communications units.
In the present context the term ‘piston’ is taken to mean a displaceable plate or cylinder that fits tightly against the inner walls of a cartridge. A surface of the piston that faces the inner part of the cartridge and which may be brought into contact with the contents of the cartridge is termed ‘the inner surface of the piston’, and the opposite side of the piston is termed ‘the outer surface of the piston’. In cooperation with a ‘piston rod’ that is engaged with ‘the outer surface of the piston’, the ‘piston’ may be displaced and used to apply pressure to a surface of the contents of the cartridge being in contact with ‘the inner surface of the piston’, thus e.g. delivering a dose through the outlet of the cartridge, if the piston is displaced in the direction towards the outlet. In the present context, the term ‘piston’ may also apply to a movable wall or membrane that engages with a plunger being an integral part of the piston rod.
In the present context, the term ‘piston rod being operable to engage and displace said piston’ is taken to mean that the piston rod may or may not be fixed to the movable wall, but that in both cases it has the ability to displace the piston at least in a direction towards the outlet of the cartridge.
In the present context, the term ‘driving wheel’ is taken to mean the part of the driving means that cooperates with the activating means (e.g. an electromotor) and the piston rod to transfer the movement of the activating means to a displacement of the piston rod. It may take the form of a gear wheel or drum or any other appropriate form that may be adapted to cooperate with the piston rod. A gear box may be inserted between the activating means and the driving wheel.
An advantage of having a linear path of the piston rod between the driving wheel and the piston is that the risk of introducing errors in the displacement of the piston by the rod is reduced because a more direct drive of the piston is provided (i.e. the sources of mechanical inaccuracies from a remotely located driving wheel due to the curved path, extra friction of the guiding means, etc. are eliminated). Related advantages of this are that an improved dose accuracy may be achieved and that the requirements with respect to the power of the activating means are reduced, leading to a possible reduction in weight and volume of the device.
A further improved dose accuracy may be achieved by combining the present invention with the invention disclosed in our co-pending patent application A medication delivery system with improved dose accuracy incorporated herein by reference.
Other advantages of the invention are that it uses a simple principle for transferring rotational movement of the actuating means to translatory movement of the piston rod, a principle that may be implemented in many different ways depending on the design constraints as regards space and materials. It allows the construction of a relatively compact medication device (utilizing e.g. a 180 degrees curve of the path of the piston rod), using a relatively thin piston rod yielding the benefits of a low weight and a potentially economical solution that is suited for large-scale production.
When said flexible piston rod remains in a fully reversible elastic state during cooperation with said driving wheel and said guiding means, it is ensured that the piston rod is able to adjust to the various curvatures of the driving and guiding means and cooperate therewith, without being irreversibly deformed.
When the surface of said flexible piston rod in a transversal cross-section is adapted to follow the surface of said driving wheel fully or partially, it is ensured that the ch
Began, Esq. Marc A.
Bork, Esq. Richard W.
Green, Esq. Reza
Mendez Manuel
Novo Nordisk A S
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