Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Patent
1994-05-20
1997-03-18
McDermott, Corrine M.
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
604211, 604218, A61M 500
Patent
active
056117833
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to pen shaped syringes comprising a proximal part containing a dose setting and driving mechanism, a piston rod having a non-circular cross section and carrying along one side a cogging engaged by a carrier unidirectonally transmitting axial movements from the driving mechanism to the piston rod, a piston rod guide positioned to maintain the piston rod in a rotational position in the syringe ensuring the engagement between the carrier of the drive mechanism and the cogging of the piston rod, the piston rod guide having a non-circular opening conforming to the cross section of the piston rod, and through which opening the piston rod passes, and a distal part containing a tubular reservoir for medicine, which reservoir at its distal end is closed by a pierceable rubber membrane, and at its proximal end is closed by a piston actuated by the piston rod of the proximal part.
DESCRIPTION OF RELATED ART
Such syringes are used by patients which have to frequently inject themselves. The reservoir contains medicine sufficient for several injections, and when the reservoir is empty, the proximal and the distal part of the syringe may be unscrewed and the reservoir renewed, whereafter the parts are screwed together again.
However, this screwing movement may be difficult to perform especially to patients suffering from diseases reducing their tactile motor function, and this way it may be difficult for these patients to administer the medicine which could just mitigate these symptoms.
SUMMARY OF THE INVENTION
Therefore, it is the object of the invention to provide a pen syringe wherein the medicine reservoir could easily be changed without performing many turns of screwing.
This is obtained by a syringe of the above mentioned kind, which syringe according to the invention is characterized in, that the proximal and the distal part have interlocking bayonet coupling means, and that the bayonet coupling means on the distal part is provided with means engaging the piston guide to rotate this guide and consequently the piston rod during at least part of the rotational movement of the bayonet lock.
When a reservoir is emptied the piston rod is protruding from the proximal part, and the engagement between the piston rod and the drive mechanism has the effect that the piston rod may not immediately be pushed back into the proximal part to be ready for actuating the piston of a new full reservoir. Therefore, a coupling is normally provided to release the engagement between drive mechanism and piston rod when the pen is unscrewed. This coupling is normally operated to reestablish the engagement when the parts are screwed together again, the operation being performed by the reservoir pressing a coupling member when the distal part is screwed onto the proximal part. This arrangement has the disadvantage that the coupling is performed before the parts are screwed totally home, and consequently, if the piston rod is pushed back by the piston of the new reservoir, the movement of the piston rod will be locked and will press the piston into the reservoir during the last part of the screwing. By the pen syringe according to the invention the coupling is performed by rotating the piston rod out of and into is engagement with the drive mechanism, and as this rotation is Performed without any concomitant axial movement the above mentioned disadvantage is avoided.
According to the invention, the bayonet coupling may comprise a stud protruding from a plane distal end surface of the proximal part, this stud being provided with a flange having an outer diameter corresponding to the inner diameter of the tubular distal part and leaving a space between the flange and the end surface, the flange being cut away preferably at diametrically opposite positions, and locking protrusions on the inner surface at the proximal end of the distal part, which protrusions correspond to the cuts of the flange and extend in the axial direction from the proximal end of the distal part to a position a dista
REFERENCES:
patent: 1595424 (1926-08-01), Sather
patent: 4865591 (1989-09-01), Sams
patent: 4936833 (1990-06-01), Sams
patent: 4973318 (1990-11-01), Holm et al.
patent: 5226895 (1993-07-01), Harris
patent: 5304152 (1994-04-01), Sams
Harrington, Esq. James
McDermott Corrine M.
Novo Nordisk A S
Stright Jr. Ronald K.
Zelson Esq. Steve T.
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