FLUID INJECTOR

Abstract: A fluid injector suitable for injecting medicaments into the human body comprises a tube (1) having a piston (3) slidable therein and a slidable sealing member (6) in one end thereof. A cap (10) is located over the one end and has a tubular needle (17) extending from it inwardly of the tube (1), the needle communicating via a fluid passage through the cap to an injector outlet (19) outside the tube. The cap and sealing member are provided with co-operating screw threads whereby rotation of the cap relative to the tube draws the sealing member along the tube and into engagement with the needle, which pierces a thin portion (8) of the sealing member, thereby establishing fluid communication between the interior of the tube and the injector outlet.

Description: FLUID INJECTOR This invention relates to a fluid injector suitable, for example, for use in injecting medicaments. According to the invention, a fluid injector com¬ prises a tube having a piston slidable therein and a slidable sealing member in one end of the tube, and a cap located on the said one end of the tube and having a tubular needle extending therefrom inwardly of the tube, the needle communicating with a fluid passage through the cap to an injector outlet outside the tube, the cap and the sealing member being provided with co-operating screw threads whereby rotation of the cap relative to the tube draws the sealing member along the tube and into engage¬ ment with the needle, the sealing member having a portion thereof pierceable by the needle when the member is drawn on to the needle, thereby establishing fluid communi¬ cation between the interior of the tube and the " injector outlet. Preferably, the tube and the cap are provided with co-operating formations retaining the cap on the tube but allowing rotation relative to the tube. For example, the tube may be provided on its outer surface with a circum¬ ferential groove which receives a corresponding circum¬ ferential rib on the inwardly facing surface of the cap. It is also preferable to mould the cap in a resilient material, such as a plastics material, so that the cap may be pushed on to the tube, the rib then snapping into the groove, or over and into engagement with a rib on the tube. Alternatively, the cap may be provided with a plurality of resiliently deflectable portions each having a rib portion engageable in the groove. The tube is suitably formed of a chemically-inactive glass. The fluid injector of the invention is simple in construction and use. Reference is made to the drawings, in which: Figure 1 is a part-sectioned perspective view of an injector according to one embodiment of the invention; and Figure 2 is a sectional elevation of a portion of the injector shown in Figure 1, after piercing of the seal. The injector comprises a tube 1, suitably of glass, having in one end 2 thereof a piston or plunger 3 retained by an end cover 4 secured over the end of the tube. The opposite end 5 of the tube 1 is closed by a rubber sealing member 6, which has a threaded bore 7 therein, and one end of which includes a thin wall 8, having a thickness of 1 to 2 mm. The tube 1 has a circumferential rib 9 around the outer surface thereof adjacent the end 5. The end 5 of the tube is enclosed within an end cap 10 which has a flange 12, extending therefrom around the circumference thereof, an externally screw-threaded core portion " 13 extending in the same direction as, and coaxially with, the flange 12, and a needle-connecting portion 14 extending in the opposite direction to the core portion 13. The core and needle-connecting portions 13 and 14 are suitably moulded separately from the remainder of the cap and may then have a hexagonal section portion 13a_ which can be an interference fit, or be cemented into a correspondingly-shaped aperture through the cap 10. A rib 15 extends around the inwardly-directed surface of the rim 12, and can engage with the rib 9 to retain the cap 10 on the tube 1. The rib 15 and the rib 9 have tapered ■ profiles on one side only so that the cap may readily be engaged on the tube, but may not readily be removed therefrom. A passage 16 extends along the axis of the cap and communicates at one end with a tubular needle 17 extend- ing from the end face 18 of the core portion 13, and at the other end with an outlet 19 at the end of the needle-connecting portion 14. The needle 17 may suitably be formed of a pharmaceutically inert plastics material. The needle-connecting portion 14 is adapted to receive thereon a hypodermic needle or the like having a moulded socket which fits tightly over the reduced-diameter section 20 of the portion 14. In use, the injector will suitably be provided in two parts, the first of which consists of the tube 1, with the plunger 3 and sealing member 6 closing off opposite ends, the tube containing the liquid medicament to be injected, for example. The second part consists of the cap 10, to which a hypodermic needle may subsequently 5 be fitted. The cap is pushed on to the end 5 of the tube, and being formed of a resilient plastics material, can deform outwardly to allow the rib 15 to be deflected over the rib 9 on the end of the tube 1. The cap 10 is then rotated relative to the tube and the thread thereon o engages with the thread in the sealing member 6 to draw the member 6 along the tube towards the cap. As the sealing member 6 moves along the tube, the needle 17 passes through the thin wall 8, thereby allowing the liquid contained in the tube to be expelled through the 5 passage 16 to the hypodermic needle (not shown) and into the patient, when the plunger 3 is pressed. Figure 2 shows a portion of the injector after the needle 17 has pierced the thin wall 8. Movement of the sealing member 6 along the tube 1 is limited by a shoulder 21 formed by 0 reducing the diameter of the tube 1 over the end portion 5. The injector of the invention may be used for the mixing of measured doses of, for example, a liquid and a powder, without risk of contamination. Two similar in- 5 jectors are used, one containing the liquid and the other the powder. The needle-connecting portion 14 of the cap 10 of the liquid-containing injector is dimensioned so as to be received within the corresponding portion 14 of the cap 10 of the powder-containing injector as a sealing fit, and a retaining clip is provided to hold the two caps in sealing engagement while liquid is injected into the powder-containing injector. After mixing, the resulting liquid may be injected by fitting a suitable hypodermic needle on to the,cap 10 of the powder-con¬ taining injector, after separation of the two injectors.

Claims: CLAIMS 1. A fluid injector, comprising a tube having a piston slidable therein and a slidable sealing member in one end of the tube, and a cap located on the said one end of the tube and having a tubular needle extending therefrom inwardly of the tube, the needle communicating with a fluid passage through the cap to an injector outlet outside the tube, the cap and the sealing member being provided with co-operating screw threads whereby rotation of the cap relative to the tube draws the sealing member along the tube and into engagement with the needle, the sealing member having a portion thereof pierceable by the needle when the member is drawn on to the needle, thereby establishing fluid communication between the interior of the tube and the injector outlet. 2. A fluid injector according to Claim 1, wherein the tube and the cap are provided with co-operating formations retain¬ ing the cap on the tube but allowing rotation thereof relative to the tube. 3. A fluid injector according to Claim 2, wherein the tube is provided on the outer surface thereof with a circumferen- tial groove which receives therein a corresponding circum¬ ferential rib on an inwardly facing surface of the cap. 4. A fluid injector according to Claim 2 , wherein the tube is provided on the outer surface thereof with a circumferen¬ tial rib which engages with a corresponding circumferential groove or rib on an inwardly facing surface of the cap. 5. A fluid injector according to Claim 3 or 4, wherein the cap is formed of a resilient material whereby the cap is res- iliently expandable to fit the cap on to the tube. 6. A fluid injector according to Claim 3 or 4, wherein the cap is provided with a plurality of resiliently deflectable portions each bearing a portion of the rib or groove, thereby permitting the cap to be fitted on to the tube. 7. A fluid injector according to any of Claims 3 to 6, wherein the rib or ribs or the groove is shaped so as to resist removal of the cap from the tube. 8. A fluid injector according to any preceding claim, where¬ in the tube is formed of a chemically-inactive glass. 9. A fluid injector according to any preceding claim, where¬ in the sealing member is formed of rubber, the pierceable portion thereof being in the form of a thin wall. 10. A fluid injector according to Claim 9, wherein the thin wall has a thickness of 1 to 2 mm. 11. A fluid injector, substantially as described with ref¬ erence to, or as shown in, the drawings.

Inventors: SMITH FRANK, SMITH, FRANK
Applicants: ANGLO INFUSER SYST, ANGLO INFUSER SYSTEMS LIMITED
Application year: 1985
Main classification: A61M5
IPC codes: A61M5