WO1989010766A1

WO1989010766A1 - A syringe

Info

Publication number: WO1989010766A1
Application number: PCT/EP1989/000498
Authority: WO
Inventors: Michael Alexa
Original assignee: Gerum Ag
Priority date: 1988-05-09
Filing date: 1989-05-05
Publication date: 1989-11-16
Also published as: GB8810955D0

Abstract

A syringe comprising a barrel (1) in operative interconnection with a hollow needle (4) and a piston (2) therefor, said piston and barrel assembly being provided with cooperating surfaces adjacent the base of the hollow needle to reduce residual volume; characterised in that the piston is provided with a projection (7) adapted to fill the hollow space between the base of the needle and the cooperating surfaces when said cooperating surfaces are in abutment.

Description

A SYRINGE

DESCRIPTION

The present invention relates to a syringe, and particularly, although not exclusively, to a hypodermic syringe.

As is well known in the art hypodermic syringes, or syringes of other types but of similar form, are provided with a barrel in which a piston slidingly cooperates. At the end of the barrel remote from the piston is an outlet which may, for example, be connected to a hypodermic needle. In use the piston is depressed by means of a plunger into the barrel whereupon liquid or other fluid material within the barrel is expressed from the outlet thereof.

The syringes have been known for a number of years but only recently has it become apparent that a significant amount of pharmaceutical material was being left in the barrel after the piston had been pushed home thereby wasting this drug on each occasion. This is because the space between the end of the piston and the base of the needle is in fact a dead space hereinafter referred to as the residual space.

Attempts to alleviate the problem of the residual space have been made. In particular one form of syringe has been provided with a conical piston end made of a resilient material. This conical piston end presses against the concave end of the barrel adjacent to the base of the needle and if enough pressure is placed on the plunger most of the residual space is eliminated by means of the residual cone.

Arrangements in accordance with this disclosure are used in the art but suffer from the problem that the space immediately adjacent the base of the needle cannot be reached by such an arrangement and accordingly a small residual space still subsists immediately adjacent the base of the needle. Further because of the need to provide a resilient material at the end of the piston a certain amount of valuable drug material will be absorbed by the conical piston end and hence be lost.

Accordingly therefore the prior art provides a syringe comprising a barrel in operative connection with a hollow needle, and a piston for cooperation within said barrel, the piston in the barrel being provided with cooperating surfaces adjacent the base of the hollow needle to reduce residual volume. The invention is characterised in that the piston is provided with a projection adapted to fill the hollow space between the base of the needle and the cooperating surfaces when said cooperating surfaces are in abutment.

It will be appreciated that this projection may be either coaxial with the piston, or may be eccentric of it depending on the position of the base of the needle relative to the barrel. Preferably the projection and the cooperating surfaces are formed of a hard plastics material which are moulded to have as near a precise abutment with each other as can be achieved through ordinary moulding techniques. Preferably the operating surface of the piston is formed of a material which while being resilient is also non-absorbent.

An aspect of this invention will now be described, by way of illustration only, with reference to the accompanying drawing which shows in vertical cross-section an arrangement in accordance with the present invention.

A hypodermic syringe 10 is provided with a clear plastics body 1 of a generally cylindrical configuration. A piston 2 is provided a slidable cooperation with the internal faces of the barrel 1; said piston being provided with a plunger 3 which can be optionally interengaged with the piston 2.

Extending coaxially of the barrel 1 and remote therefrom is a needle 4 having a base secured at a needle seating 5 to the terminal end of the barrel 1 The needle seating 5 is formed of a plastics material in standard fashion. The piston 2 is formed of a moulded plastics material with annular ribs extending thereabout for sliding sealed engagement with the inner walls of the barrel 1.

The piston 2 carries on its terminal face adjacent the base of the needle 4 a generally conical piston cone 6 formed of a relatively hard, or at least non absorbent plastics material. The conical faces of the piston cone 6 are adapted for abutment with corresponding internal faces of the barrel 1 immediately adjacent the base of the needle 4. Disposed coaxially of the piston 2 is an upstanding projection 7. The upstanding projection 7 is adapted to just fit within the residual space 9 immediately adjacent the base of the needle 4.

In use the barrel 2 is filled with a pharmaceutical substance by drawing the said substance through the needle 4 by withdrawing the piston 2 relative to the barrel 1. In accordance with standard practice the hypodermic syringe is then turned upwardly and the piston is driven into the barrel 1 until the liquid drug is emitted from the end of the needle 4 thereby removing any air. The needle 4 is then inserted into its site of operation and the plunger 3 is depressed thereby pressing the piston 2 towards the needle base 4. At the end of the piston the residual space 8 is eliminated by contact of the piston cone 6 with the internal conical surfaces of the barrel 1. Simultaneously the projection 7 enters the residual space 9 immediately adjacent the base of the needle 4 thereby eliminating any residual volume in that area as well.

Although the residual space eliminated by means of the projection 7 is comparatively small there is a significant saving in liquid drug caused not only by the elimination of the residual space 9 but also because of the cooperating surfaces of the cone 6 and the reciprocal surfaces of the barrel 1 eliminate waste It will be appreciated that the extra costs from moulding the piston in accordance with the present invention is far outweighted by the value of the drug saved. The advantages in accordance with the present invention have been described with reference to a hypodermic syringe. Obviously any syringe can make use of the arrangement as shown above.

Further it would appreciated that although the above description relates to an axially disposed needle, eccentric needles can also be utilised on the same basis so long as the projection and the residual space 9 extend in the same direction as the piston.

Accordingly the present invention relates to a syringe as hereinbefore described.

Claims

C LAIMS

1. A syringe comprising a barrel in operative inter-connection with a hollow needle and a piston therefor, said piston and barrel assembly being provided with cooperating surfaces adjacent the base of the hollow needle to reduce residual volume; characterised in that the piston is provided with a projection adapted to fill the hollow space between the base of the needle and the cooperating surfaces when said cooperating surfaces are in abutment.