Dosage unit for dosing a number of measured quantities of a liqu

Details Dosage unit for dosing a number of measured quantities of a liqu Dosage unit for dosing a number of measured quantities of a liqu

1989-10-05

1991-05-21

Pellegrino, Stephen C.

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

604208, 604209, 604110, A61M 500

Patent

active

050171909

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The invention relates to a dosage unit for dosing a number of measured quantities of a liquid, such as an insulin preparation, from a container, preferably a separate cartridge, said dosage unit comprising a cylindrical casing for the container, the distal end of the casing being provided with means for fastening a double-pointed injection needle, one point thereof being provided to pierce a membrane closing one end of the container, and said dosage unit comprising a piston rod for exerting a force on a piston closing the other end of the container, and an adjustment means provided with an internal thread, said adjustment means being in rotatable engagement with an external thread on the casing and adapted to adjust the length of the stroke of the piston rod according to the dosage needed in each case, the dosage being adjusted to be readable on a scale.


BACKGROUND ART

U.S. Pat. No. 4,475,905 discloses a dosage unit comprising a casing with an external thread over its entire length and a ring screwed on said thread. The ring is adjusted in relation to a measuring scale on the external surface of the casing, simultaneously serving as a retainer for a pin protruding through a slot of the casing, said pin being in solid connection with the piston of a syringe mounted in the casing.
U.S. Pat. No. 2,826,195 discloses a dosage unit for receiving a cartridge, the distal or front end of said cartridge being provided with a pierceable closure, through which one end of a double-pointed needle is pierced. After the cartridge has been inserted the needle is screwed to the distal end of the dosage unit one point passing through the adjacent closure of the cartridge.
Cartridges with different concentrations of insulin are used for the injection of insulin in dosage units of the above type. Usually, such cartridges contain 1.5 ml and the concentration of insulin herein can be 100 insulin units per ml, whereby the cartridge can contain 150 insulin units. In use a predetermined quantity is to be delivered by means of the dosage unit, preferably up to 40 insulin units per injection. By means of the dosage unit each cartridge can thus be used for several injections. Prior to each injection the dosage unit is adjusted to deliver exactly the amount of injectable preparation required in the particular case.


DISCLOSURE OF INVENTION

The present invention is characterised in that the dosage unit is provided with a first ratchet means between the casing and the piston rod, said ratchet means allowing the displacement of the piston rod in a direction towards the distal end of the casing and preventing the displacement in the opposite direction, and with a second ratchet means between the adjustment means and the casing or a second part of the dosage unit, which is unturnable in relation to the casing, and in relation to which the adjustment means is rotatable, said second ratchet means allowing the rotation of the adjustment means in a direction forward towards the distal end of the casing and preventing the rotation in the opposite direction.
Hereby it is ensured that the adjustment means and the piston remain in the positions they occupy subsequent to an injection until a new adjustment of the dose is performed. This is especially due to said ratchet means ensuring a stable locking of both the piston and the adjustment means in the position set up during premeditated use. Simultaneously the ratchet means prevent the piston rod and adjustment means from moving in a direction opposite to the desired one, the latter increasing the risk of a user either drawing air into the container or misjudging the amount of insulin remaining in the container.
According to the invention the first ratchet means is formed by circumferential, radial shoulders on the piston rod, each shoulder being bounded by conical surfaces tapering in a direction towards the front end of the piston rod, seen in the direction of movement during use, and where said shoulders and surfaces cooperate with a circumferential collar acting as a pawl,

REFERENCES:
patent: 2826195 (1958-03-01), Ashkenaz
patent: 4246898 (1981-01-01), Travalent et al.
patent: 4413760 (1983-11-01), Paton
patent: 4444335 (1984-04-01), Wood et al.
patent: 4475905 (1984-10-01), Himmelstrup
patent: 4583978 (1986-04-01), Porat et al.
patent: 4865591 (1989-09-01), Sams

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