WO1996004030A1

WO1996004030A1 - Single-use syringe with retractable needle

Info

Publication number: WO1996004030A1
Application number: PCT/IT1994/000133
Authority: WO
Inventors: Paola Danesi
Original assignee: Paola Danesi
Priority date: 1994-08-05
Filing date: 1994-08-05
Publication date: 1996-02-15
Also published as: AU7507694A

Abstract

Single-use syringe with retractable needle (9) including a reservoir (11) defined by the inner wall of a rigid cylinder (7) integral with the outer body (4). A liquid is contained in said reservoir (11) subjected to a pressure so as to be capable of deforming and holding an elastical central rod (5c) operating between an upper head (51) connected to the cylinder (7) and adapted to be pierced at the end of injection in order to allow the liquid to flow out of the cylinder (7), and a lower head (5e) adapted to support the retractable hollow needle (9), both heads (5e, 51) being tight to the cylinder (7) and integral with the same elastic central rod (5c).

Description

Sinσle-use syrinσe with retractable needle

The present invention relates to a single-use syringe with retractable needle for medical purpose.

At the present state of art the following type of syringes of several size and different materials are known. The socalled "disposable syringe" typically made of plastics and having a metal needle may be cited. Such syringes must be used only once, however, they may be incautiously used several times by different people. More particularly, single-use syringes with retractable nee¬ dle are known from EP 0 506 673 disclosing a syringe pro¬ vided with a device preventing it from being reused by means of hooks or fixed joints integral with the plunger which en¬ gage the needle during the backward stroke after the injec- tion and force it back into the body of the syringe. In fur¬ ther embodiments, such syringe is also provided with a plunger having on its rod a predetermined break line al¬ lowing the user itself to break such rod so that the syringe may not be used again. Finally the present Applicant disclosed: a) Single-use syringes with retractable needle disclosed in PT 92 A 000005 and provided with a device allowing the nee¬ dle to be automatically and fully retracted into the syringe after the injection of the medical fluid. The retraction of the needle is caused by the extension of a coil spring which is pressed before and during the use of the syringe by a plunger (carrying the needle) which is subjected to the ac¬ tion of a liquid. As soon as the plunger injecting the medi¬ cal fluid reaches the end of the syringe, a flexible rod provides for emptying the reservoir containing such liquid under the thrust of the pressure spring, which causes the needle to retract into the body of the syringe, thus pre¬ venting the latter from being reused. b) Single-use syringes with retractable needle disclosed in P-T 93 A 000005, in. hich the needle is retracted by means of an elastic- reservoir which is subjected to a drawing action by a plunger carrying the needle along the axis of the syringe and is deformed by the pressure of a liquid. As soon as the plunger injecting the medical fluid reaches the end of the syringe, a hollow rod provides for emptying the elastic reservoir, thus allowing the needle to be retracted. As well known, the useful function of such syringes is of preventing infectious diseases from being given due to the reuse of an infected syringe as it is even more frequently the case. Thus, in order to carry out an effective sanitary prevention, it is necessary that the single-use syringe can be easily usable, economical, and above all absolutely reli¬ able. The known solutions mentioned above are generally safe as far as the offered protection is concerned but they suf¬ fer, however, from the serious problem that they can be hardly proposed for a large scale employment because of the relatively high cost and the involved technical manufac¬ turing problems.

The present invention seeks to provide an absolutely reli¬ able syringe of easy use having a retractable needle which is made of simple economically manufactured pieces in order to be marketed on a large scale at comparable cost as the conventional syringes. To this effect, the present invention provides a syringe comprising a reservoir the sides of which are defined by the inner wall of a rigid cylinder integral with the outer body, in said reservoir a liquid being contained which is capable by its pressure of deforming and holding an elastic central rod operating between an upper head connected to the cylin¬ der and adapted to be pierced so as to allow the liquid to flow down, and a slidable lower head adapted to support the retractable hollow needle, both heads being tight to the cylinder and integral with the same elastic element along with the rod.

The achieved advantages generally consists in the lowering of the manufacturing cost of all of the components of the syringe to the greatest extent while assuring a safe and easy use.

These and other advantages will be better understood by those skilled in the art from the following description with reference to the accompanying drawings given by way of a non-limitative example, in which:

Fig. l shows a syringe according to the invention with the needle in retracted position after the use of the same,*

Fig. 2 shows the syringe of Fig. 1 with the needle in the extracted position ready for use,*

Fig. 3 shows a section of the syringe of Fig. 2 along line A-A; Fig. 4 shows a section of the syringe of Fig. 2 along line B-B;

In its general construction a syringe according to the in- vention consists of: an outer cylindrical body 4; a plunger 1 connected to packing 10; an inner hollow cylinder 7 inte¬ gral with body 4 and including the automatic needle 9 re¬ traction device; a rubber member 5 connected to support 8 of hollow needle 9. In the extracted position of the needle, elastic rod 5c of rubber member 5 is kept under drawing by the pressure of the liquid in reservoir 11 between the two terminal heads of rubber member 5 and inner cylinder 7. The sealing of reservoir 11 is assured at the upper side by the tight fit between upper head 51 and cylinder 7, and at the lower side by lip seal 5d integral with lower head 5e and tight to the inner wall of cylinder 7.

The pressure of the liquid acts on lip seal 5d and hence on lower head 5e so as to provide a perfect taper fit between lower end 5f of head 5e and lower end 7a.

Still in the extracted position of needle the medical fluid is sucked in the annulus 6 between the inner wall of cylin¬ drical body 4 and the outer wall of hollow cylinder 7. Plunger 1 slides by the intermediary of ring packing 10 within cylindrical body 4 and runs the medical fluid into annulus 6 between cylinder 4 and cylinder 7 rather than into the whole inner section of body 4.

A ring support 2 provided with a piercing tip 2b is located at the top of plunger 1. As tip 2b pierces head 5a, a slot 2a of tip 2b allows the liquid to flow quickly down from reservoir 11 through con- duit 5b. The shape of conduit 5b may be seen in Fig. 3. In the initial position with the extracted needle, the piercing tip 2b is held in the position shown in Fig. 2 in contact with tapered head 5a of rubber member 5. The pressure of liquid contained in reservoir 11 causes rod 5c to undergo to an elastic deformation so that it is drawn, thus allowing the two tapered surfaces 5f and 7a to per¬ fectly fit to each other and aligning geometrically the two feeding holes 7b with the feeding through hole 5h of lower head 5e. Through hole 5h communicates by the intermediary of through hole 8c with hole 8d which in turn is connected to hollow needle 9.

Holes 7b and 5h communicate always with each other because head 5e has an outer circular groove 5g perpendicular to the axis of head 5e at the height of hole 5h (see Fig. 4) .

Also the through holes 5h and 8c communicate with each other through a circular groove 8b corresponding to the through hole 8c. At the upper side the fixed, not movable position of rubber member 5 within cylinder 7 is kept by the tight fit between head 51 of rubber member 5 and cylinder 7. To this effect head 51 should have before assembling a suitable larger diameter than the inner diameter of cylinder 7.

In operation of the syringe during an injection the fol¬ lowing steps are provided.

The sliding of plunger 1 by the intermediary of ring packing 10 causes the medical fluid to be sucked into annulus 6. During such sliding of plunger 1 by a suitable length such that the requested amount of medical fluid can be sucked in, as soon as ring support passes over the top of head 5a, its axis is naturally aligned with the axis of rubber member 5 owing to its elastic characteristics.

The injection of the medical fluid is made after the latter has been sucked in. Plunger 1 along with ring support 2 slides into annulus 6 by the intermediary of packing 10, -thus pushing the medical fluid towards the two feeding holes 7b and over the latter to holes 5h and then to hole 8c, hole 8d and finally the hollow needle 9. Thus, the flowing cycle of the medical fluid is completed. The above cycle is of course reversed upon sucking in the medical fluid. Imme¬ diately before the end of such operation, i.e. when the ring packing 10 is near the end ^"of the syringe, tip 2b of ring support 2 has already pierced head 5a up to conduit 5b so that the reservoir 11 containing the liquid is quickly emp- tied through slot 2a of tip 2b. The emptying is due to the fact that the slot connects reservoir 11 to the area outside body 5. The emptying of reservoir 11 from the liquid con¬ tained therein causes the force of elastic longitudinal de¬ formation of rod 5c to become inactive so that, upon leaving off such deformation, the rod takes on automatically its original length again, as shown in Fig. 1, and pulls back heads 5e and hence needle 9 by the intermediary of support 8 completely into cylinder 7. Support 8 of needle 9 is tightly fitted to head 5e at 5i. Of course, before and during the injection of the medical fluid, the stability of the outer position of needle 9 is assured by the pressure of the in¬ compressible liquid in reservoir 11 to lip seal 5d and hence to head 5e and needle 9 by the intermediary of support 8. At the upper side the tight fit between body 5 and the upper portion of cylinder 7 through hole 51 assures the stability of the whole system: needle 9, needle support 8, head 5e, reservoir 11. Thus, reservoir 11 may be defined at the upper side by the tight fit with head 51, by the inner wall of cylinder 7 and by the varying position of lip seal 5d of head 5e. The bleed hole 3 has the function of avoiding the compres¬ sion of the air within plunger 1 as the latter begins to inject the medical fluid.

Blind hole 2c formed in ring support 2 is used in the assem¬ bling step of the syringe for exactly positioning tip 2b on the tapered wall of head 5a of body 5.

It is then self-evident that, after the end of the injection and without intervention of the user, the syringe cannot be used any longer. Advantageously, circular flange 5m has a diameter such as to prevent packing 10 from slipping off along with plunger 1, thus providing a further safety.

Additionally, in order to vary the amount of fluid that can be sucked in, it is sufficient to change the dimension of the outer body 4 leaving cylinder 7 and body 5 unchanged.

The construction details may be changed as far as the form, size, arrangement of the components is concerned without de¬ parting from the scope of the present invention.

Claims

1. A single-use syringe with retractable needle formed of an outer cylindrical body (4) , a plunger (1) with packing (10) , a hollow needle (9) , and comprising a pressure reservoir (11) containing a liquid acting to an elastic element (5) carrying the needle (9), also including means (2, 2a) to let the liquid flowing down from said reservoir (11) , charac¬ terized in that the sides of said reservoir (11) are defined by the inner walls of a rigid cylinder (7) integral with the body (4) , in said reservoir a liquid being contained which is capable by its pressure of deforming and holding an elastic central rod (5c) operating between an upper head (51) connected to the cylinder (7) and a slidable lower head (5e) adapted to support the retractable needle (9) , both heads (51, 5e) being tight to the cylinder (7) and integral with the same elastic element (5) along with the rod (5c) .

2. The syringe according to claim 1, characterized in that said plunger (1) and said packing (10) have an annulus- shaped section and slide in said annulus (6) defined at the inner side by cylinder (7) and at the outer side by the in¬ ner wall of the cylindrical body (4) .

3. The syringe according to claim 1, characterized in that cylinder (7) has at the lower side a inner tapered profile (7a) , in which a through hole (7b) is formed for the flowing in/flowing down of the medical fluid in order that cylinder (7) communicates with annulus (6) .

4. The syringe according to the preceding claims, charac¬ terized in that said upper head (51) is tightly fitted to cylinder (7) and has a circular flange (5m) , said head (51) being further provided with a conduit (5b) through which the liquid of the reservoir under pressure flows down to the outside.

5. The syringe according to the preceding claims, charac¬ terized in that said lower head (5e) is provided with a lip seal (5d) which is tight to the inner wall of cylinder (7) and with a terminal tapered surface (5f) which fits at the lower side to the surface (7a) of cylinder (7) , said surface (5f) being diametrically crossed by a through hole (5h) for the flowing in/flowing down of the medical fluid which is in turn connected to the outside through a circular groove (5g) formed at the same height as head (5e) , and to the inside through a hole (8c) coaxial thereto and formed in support (8) of needle (9) .

6. The syringe according to the preceding claims, charac¬ terized in that the circuit for the flowing in/flowing down of the medical fluid is formed of the following members com¬ municating with one another and crossed in succession during the sucking step: a hollow needle (9); a vertical hole (8d) formed in support (8) of the needle,* said hole (8c) of sup¬ port (8); a circular groove (8b) formed in support (8); said hole (5h) of head (5e) ,- said outer circular groove (5g) of the lower head (5e) ; said through hole (7b) of cylinder (7) ; said annulus (6) between body (4) and cylinder (7) , such flowing direction being reversible during the step of injec¬ tion of the medical fluid.

7. The syringe according to the preceding claims, charac¬ terized in that said means (2, 2a) for the flowing down of the fluid of the reservoir (11) under pressure are formed by a piercing rod (2) integral with the head of plunger (1) and provided with a s ot (2a) and a tip (2b) which rod, in the initial extracted position of the needle, is held in a de¬ viated position engaged with the upper head (51) of the rub¬ ber member (5) , and disengages from said position during the sucking step of the plunger (1) so that during the next in¬ jection step the tip (2b) is aligned with reservoir (11) and can pierce said conduit (5b) , thus allowing the liquid to flow down through slot (2a) and the rod (5c) to resiliently take on its original length so that needle (9) is retracted into cylinder (7) .

8. The syringe according to the preceding claims, charac¬ terized in that said rod (2) is provided with a blind hole (2c) having the function of allowing the rod itself to be fitted against said upper head (51) .

9. The syringe according to the preceding claims, charac¬ terized in that said flange (5m) of the upper head (51) has a somewhat larger diameter than the outer diameter of cylin- der (7) in order to prevent packing (10) from being ex¬ tracted.