INJECTION SYRINGE

Abstract: A hypodermic syringe provided with a container and an adapter connected to the container and on which a hypoder­ mic needle can be placed with a piston slidable in the container and provided with a closed projecting part which in the extreme position of the piston in the container fills the adapter to leave unoccupied a small space between the inner wall of the adapter and the outer wall of the projection on the piston, the top of the projection then closing the passage of the hollow adapter to the hypodermic needle, and both the hollow space in the adapter and the projection on the piston preferably being tapered, the latter preferably at an angle smaller than the angle at which the hollow space tapers.

Description: Hypodermic syringe The present invention relates to a hypodermic syringe provided with a container with a piston slidable in it and a hollow adapter connected to the container on which a hypodermic needle can be placed. It is generally known that such hypodermic syringes can be applied for medical purposes. In many cases they are intended for use once only, so for injecting a dose of a medical liquid , for instance an insulin liquid. The liquid which remains in the hollow adapter gets lost. This is a drawback when expensive medical liquids or those in short supply are concerned. This is in particular the case with insulin liquids, because insulin is recovered from animal organs, of which only a limited supply is available. On the other hand the number of diabetes patients has been steadily increased of recent years. Despite it, in the application of each dose of 1 ml at an average of for instance an insulin liquid about 9 % of the liquid gets lost in the hollow adapter. For the volume of the hollow space in the hollow adapter cannot be made as small as possible, because air must be able to escape past it before the liquid is injected into the patient. This air which is already present in the unused needle and syringe and which adheres to the walls and the little piston of the hypodermic syringe is removed for the major part as follows; the filled syringe is kept with the needle upwardly and one taps to the hypodermic syringe. By so doing the air rises and escapes from the hypodermic syringe, provided the passage in the hollow adapter is not too small. Now, the#present invention provides for a hypodermic syringe, in which the portion of the medical liquid to be administered, in particular an insulin liquid that gets lost, is limited to a minimum. The invention relates to a hypodermic syringe as mentioned at the beginning, which is characterized in that the piston is provided at its upper side with a closed projecting part, which in the extreme position of the piston in the container fills up the cavity in the adapter to leave unoccupied a small space between the inner wall of the adapter and the outer wall of said projection, the top of the projection then closing the passage of the hollow adapter to the hypodermic needle. The small space between the inner wall of the adapter and the outer wall of the projection on the piston is necessary, because it is not possible to remove the total quantity of air that has got into the container of the hypodermic syringe during sucking in the medical liquid by tapping to the container. There always remains a tiny amount of air. The small space between the inner wall of the adapter and the outer wall of the projection on the piston which is applied according to the invention, however, is sufficient ly big to receive the remaining air, so that same does not get into the hypodermic needle and thereupon into the patient's body. In general the volume of the small space which remains unoccupied after the projection has filled the cavity of the hollow adapter amounts to 10-50 % of the volume of the total hollow space of the hollow adapter. It is preferred that 10-35 % or rather 10-20 % of the hollow space of the adapter is not filled up by the projection of the piston. In practice for instance 14 % of the hollow space of the adapter is not filled up. Though the shape of the hollow space of the adapter for the invention is not vital, as long as one sees to it that this space is largely filled by the projection on the piston, it is in general preferred that the hollow space of the adapter tapers in the direction of the hypodermic needle to be placed on it. This is also the case with the outer side of the adapter, on which the hypodermic needle is placed, but this is the result of international standardization of the coupling between hypodermic syringe and hypodermic needle. It is moreover preferred that the projection on top of the piston also tapers in the direction of the hypodermic needle to be placed on the adapter. In order to obtain an optimum effect as for undesirable loss of injection liquid it is arranged that the tapered portion of the projection on the piston tapers at an angle smaller than the angle of the tapered portion of the hollow space of the cone. In a preferred embodiment of a hypodermic syringe according to the invention the piston rod is provided with notches which correspond to the graduation on the cylinder and which enable the measuring of the dosage of an injection liquid to be injected blindly. Through this provision it is possible that patients with poor eyesight or who are blind can nevertheless inject themselves. Though in general the hypodermic syringe according to the invention will be supplied with a predetermined volume of the container, it is necessary that with this hypodermic syringe variant doses can be injected. The prescribed dose at a time in fact differs from patient to patient. In general the container of the hypodermic syringe is sucked completely, whereupon such an amount of liquid is injected back into the store bottle that the prescribed dose is left in the hypodermic syringe. Even for a blind person it is easy to check in the embodiment just described whether the correct dose is still in the hypodermic syringe before said dose is injected. The invention is further illustrated with the aid of the figures, which relate to an embodiment of a hypodermic syringe according to the invention. Figure 1 shows a piston of a hypodermic syringe according to the invention in side view. Figure 2 is a cross-section of a hypodermic syringe accor ding to the invention when the piston is in a position in which injection liquid is present in the container. Figure 3 shows in cross-section a hypodermic syringe according to the invention with the piston in extreme position. Figure 4 is an enlarged cross-section of the adapter on a hypodermic syringe with in it the projection on the piston in accordance with the invention. The piston consists of a piston body 1, which can slide fittingly in the cylindrical container 6 with a piston rod 2 which is provided with sides 3 which enable an easy sliding of the piston body through the cylinder. At the end of the piston rod 2 there is an end face 4 to which one pushes if one injects injection liquid. The end face 11 of the cylinder makes it possible that the hypodermic syringe can easily be handled during the injection operation. The notches 10 make it possible that also a poor--sighted or blind patient can adjust the correct dose and can inject. In according to the invention on piston body 1 there is a projecting portion 5 which in the extreme position of the piston in the cylinder almost entirely fills the adapter 7 on which the hypodermic needle has to. be placed, with the exception of a small space 8. The figures relate to a preferred embodiment, the cavity 9 in the adapter being tapered at an angle which is a little bit larger than the angle at which the projection on the piston 5 tapers. In result the remaining space 8 is kept as small as possible for a minimalization of the loss of liquid, but is sufficiently big for keeping the last tiny bits of air during the injection operation.

Claims: CLAIMS 1. A hypodermic syringe provided with a container with a piston slidable in it and a hollow adapter connected to the container on which a hypodermic needle can be placed, characterized in that the piston is provided at its upper side with a closed projecting part, which in the extreme position of. the piston in the container fills up the cavity in the adapter to leave unoccupied a small space between the inner wall of the adapter and the outer wall of said projection, the top of the projection then closing the passage of the hollow adapter to the hypodermic needle. 2. A hypodermic syringe according to claim 1, charactezized in that the volume of the small space which remains unoccupied after the projection has filled the cavity of the adapter amounts to 10-50 % of the volume of the total hollow space of the adapter. 3. A hypodermic syringe according to claim 2, characterized in that the volume of the small space which remains unoccupied after the projection has filled the cavity of the adapter amounts to 10-35 % of the volume of the total hollow space of the adapter. 4. A hypodermic syringe according to claim 3, characterized in that the volume of the small space which remains unoccupied after the projection has filled the cavity of the adapter amounts to 10-20 % of the volume of the total hollow space of the adapter. 5. A hypodermic syringe according to any of the preceding claims, characterized in that the hollow space of the adapter tapers in the direction of the hypodermic needle to be placed on the adapter. 6. A device according to any of the preceding claims, characterized in that the projection on top of the piston tapers in the direction of the hypodermic needle to be placed on the adapter. 7. A device according to claim 5 and 6, characterized in that the tapered portion of the projection on top of the piston occurs at an angle smaller than the angle of the tapered portion of the hollow space of the adapter. 8. A hypodermic syringe according to any of the preceding claims, characterized in that the piston rod is provided with notches, which correspond with the graduation on the container, which enable the measuring of the dosage of an injection liquid to be injected blindly.

Inventors: MULLER, ROBERT HANS
Applicants: COOPERATIEVE APOTHEKERS VEREENIGING "DE ONDERLINGE PHARMACEUTISCHE GROOTHANDEL" U.A.
Application year: 1981
Main classification: A61M5
IPC codes: A61M5