REDUCED SPUTTERING SYRINGE

Abstract

A medical syringe which is suitable for dispensing and injecting medical foams is described and claimed. The syringe has a standard syringe plunger and barrel arrangement but comprises a flexible annular flange on the inner surface of the barrel. The annular flange extends inwards and forwardly from a base portion, affixed to the inner surface of the barrel to contact the plunger shaft and form a seal. The shape and orientation of the annular flange enables injection of medical foam with reduced sputtering of the syringe contents which make administration of sclerosing foams more controllable.

Claims

1. A syringe for dispensing medical foam comprising: a substantially cylindrical barrel comprising a nozzle at its forward end; and a plunger comprising a substantially cylindrical shaft disposed within the barrel, characterised in that: a flexible, annular flange is provided on the inner surface of the barrel and extends toward the nozzle to contact the shaft and form a seal between the barrel and the plunger.

2. A syringe according to claim 1 wherein the flange is mechanically fixed to the inner surface of the barrel.

3. A syringe according to claim 1 wherein the flange is flexible over its entire surface area.

4. A syringe according to claim 1 wherein the flange is tapered from a thicker base to have reduced thickness at the point at which it contacts the shaft.

5. A syringe according to claim 1 wherein the flange extends generally forwards and generally inwards and contacts the shaft at an angle which is less than 90°.

6. A syringe according to claim 1 wherein the flange has a generally frustoconical shape.

7. A syringe according to claim 1 wherein the flange extends to an annular edge having a circumference that is equal to or less than the outer circumference of the shaft.

8. A syringe according to claim 1 wherein the flange extends to an annular edge having a circumference that is greater than the outer circumference of the shaft such that foam within the barrel deforms the flange to contact the shaft and form the seal between the barrel and the plunger.

9. A syringe according to claim 1 further comprising a guide means arranged to align the plunger within the barrel.

10. A syringe according to claim 9 wherein the guide means comprises a non-sealing spacer.

11. A syringe according to claim 1 further comprising a stop guard that stops removal of the plunger from the barrel.

Description

[0033] Further features and advantages of the invention will be apparent from the following description of specific embodiments, which is made with reference to the accompanying drawings.

[0034] FIG. 1 shows a schematic view of an embodiment of the invention.

[0035] FIG. 2 shows an enlarged cross-sectional view of part of a kinked flange of a syringe of the invention.

[0036] A syringe of the invention is shown in FIG. 1 having a barrel 1 with a plunger 2 disposed coaxially within it. A flange 3 is provided around the inner surface of the barrel 1 and makes continuous contact with the lateral surface of the plunger 2 around its entire circumference to form an annular seal such that together, the barrel 1, the plunger 2 and the flange 3 contain the syringe contents 5 within the syringe. Movement of the plunger 2 to a more withdrawn position within the barrel 1 reduces the pressure on the syringe contents 5 and leads to aspiration of foam into the syringe through the syringe nozzle 6. Conversely, depression of the plunger 2 within the barrel 1 leads to increased pressure on the syringe contents 5 and expression of foam from the syringe through the nozzle 6.

[0037] The flange 3 is tapered from a base and has a decreasing thickness along its length, having its narrowest profile at the point in contact with the plunger 2. This tapering provides a reliable seal between the flange 3 and the plunger 2 while generating reduced breakout and glide forces to resist the plunger 2 being moved within the barrel 1.

[0038] The syringe also includes an optional guide means comprising a non-sealing spacer consisting of two O-rings 4 that serve to position the plunger 2 centrally within the barrel 1 and ensure that the flange 3 remains in continuous contact with the plunger 2 about its entire circumference.

[0039] An angled flexible flange 3 within a syringe of the invention is shown in FIG. 2 having a kinked surface 13 oriented toward the forward end of the barrel (not shown). The flange 3 is provided as a molded extension of the syringe barrel wall 1, and it extend inward to contact the plunger 2. The flange 3 has a kinked surface 13 oriented forward, the kink comprising an angle in the surface of the flange 3.