DISPOSABLE MEDICAL SYRINGE WITH RETRACTABLE NEEDLE

Abstract: Medical syringe (10) with a needle (40) fixed to a protuberance (35) emerging from a hole (14) in the base of the cylinder (11), fixed to a tightly fitting elastic block (30) inserted inside the cylinder and provided with means (24, 37) for reciprocal automatic conjunction when, at the end of its normal function, the piston (20) is pressed downwards, so that when said piston is drawn back, the pull on the elastic block determines transport of the needle inside the cylinder and elimination of any contact between said needle and the outside.

Description: DISPOSABLE MEDICAL SYRINGE WITH RETRACTABLE NEEDLE The invention concerns disposable syringes for medical use. Medical syringes, namely the hollow cylindrical instruments that include a piston, having at one end a protuberance to which a needle is fitted, are well known for the injection of medicaments, for taking blood samples or for any other purposes . Similarly well known are the serious diseases which can be transmitted by means of syringes where the needles have been used by persons carrying viruses, especially drug addicts, for injecting drugs. Purpose of the invention is to avoid casual contact with a needle already used and often infected, even where packed stocks, as required by law, are kept at hospitals and si i- institutions. This can all be done by simple means and more or less in¬ stincti e gestures as will be explained below. Subject of the invention is a syringe for medical purposes whose needle is fixed to a beak-shaped protuberance emerging from a hole made for it in the bottom of the cylinder of the syringe, fixed to an elastic block tightly fitting inside said cylinder close to its base. Both said block and the internal end of the piston exhibit means for automatic reciprocal conjunction when said piston is pressed inwards. After normal use, therefore and after pressing the piston further down to create conjunction between piston and the block carrying the needle, on pulling the piston back, the block will go with it thus drawing the needle up inside the cylinder where it is stably held and prevented from coming in contact with the outside. The reciprocal means of conjunction between piston and block consist of a small axial head fixed to the end of the piston and of an axial chamber in the block, facing towards the piston, of a diameter substantially corresponding to that of said small head, and an axial mouth whose diameter is less than the diameter of said small head. The external edges of the head and mouth of the block are beveled or rounded to facilitate entry of the head inside the above chamber when the piston iε pressed down to the base of the cylinder, while the internal edges of said head and of said mouth are sharp to prevent accidental separation between piston and block when drawing the needle up inside the syringe. Al ernatively the means of reciprocal association between piston and block consist of an axial head on the end of the block facing towards the piston, and of a chamber made in the head of the piston. Characteristics of said head and of said chamber are similar to those of the first solution. On the block are lateral means for ensuring a moderately tight and elastic association to the walls of the cylinder to keep it stable when the needle penetrates inside the body receiving treatment . Said lateral means of elastic association between the block and the cylinder of the syringe preferably consist of annu¬ lar ridges round the outer cylindrical walls of the block and of annular grooves of a complemen ary shape to said ridges made round the inner walls of the cylinder. Said means do not however impede separation of the block from the bottom of the cylinder when the piston is withdrawn after the injection has been completed. The edges of the block's annular ridges facing towards the piston are beveled or rounded for the very purpose of en¬ suring dtachment of the block from ζhe base of the cylinder when the piston is drawn back after doing the injection, said detachment being facilitated by the fact that the inner edges of the piston head and mouth of the block are sharp. The volume created between the head and end of the piston or of the block is connected to holes, with grooves, made on the top of said head, the purpose of thiε being to allow transfer of liquid, present inside the chamber in the block or in the piston, into said volume. The invention offers evident advantages. Immediately after use , by making a simple movement, he needle is drawn up inside the syringe so that anyone handling it is in no danger of being pricked by it or infected. By means of the invention, infection caused especially by a virus, whose natural habitat is in fact blood, becomes far less likely. Character izt ic s and purposes of the invention will become still clearer from the following example of its execution illustrated by diagrammatically drawn figures. Fig. 1 Longitudinal section of the syringe ready for use . Fig.2 The syringe, longitudinal section, after the injection and when the piston has been pressed ri h down. Fig.3 Longitudinal section of the syringe when the piston is moving back to cause the used needle to enter the syringe . Fig. A Longitudinal section of the syringe when the piston has completed its upward stroke and the needle is entirely inside the syringe. The syringe 10 comprises the cylinder 11 , the piston 20 and the needle-carrying block 30. On the internal end of the piston is a head 21 with a fur- ther small projecting head 22 at the end of a shank 22 said small head being beveled 24. The elastic block 30 exhibits a cylindrical body 31 whose external diameter is substantially equal to the internal diameter of the cylinder of the syringe, and two annular ridges 32,33 that fit into corresponding annular grooves 12, 13 on the wall at the bottom of the cylinder 11 of the syringe (see Fig.3) . On the block 30 is an axial beak-shaped protuberance 35, whose form and size are substantially the same as those of the usual syringes in the same position, for fitting on the needle 40. Said protuberance 35 emerges from the hole 14 made central¬ ly in the bottom of the cylinder of the syringe. In the block 30 there is also a central discoid chamber 37 whose diameter is greater than the external diameter of the small head 22 on the piston 20, diameter of the mouth 38 being less than that of the small head. The external rim of said mouth is beveled 39. Injection of the liquid 36 having been completed, as with an ordinary syringe, and on giving a further short push to the piston, piston and block will become associated as seen in ig. 2. At this point , on pulling the piston back, the block will follo it drawing the needle as well inside the cylinder 1 ! as seen in Fig.3. By pulling the piston back still further, the annular ridges 25,26 on the head 21 , will fit into the annular grooves 17, 18, present close to the external end of said cylinder . In this way the piston is fixed at the end of its stroke and stabilized in this position with the needle inside the syringe thus preventing its coming out accidentally and therefore its accidentally coming into contact with anyone . Even in the presence of infected blood maximum protection against infection by contact is given. The volume between the head 21 and the piston's small head 22 communicates through holes 27 made on the top of the small head and channels 28.

Claims: CL A IH S 1. Medical syringe ( 10) with cylinder ( 1 1 ) and piston(20) characterized in that the needle (40) is fixed to a beak- -like protuberance (35) emerging from a hole ( 14) made in the base of the cylinder ( 11 ), fixed to an elastic block (30)tightly inserted inside the cylinder close to its base and in that said block and the internal head (21) of the piston (20) exhibit means for reciprocal automatic conjunc¬ tion when the piston is pressed down, so that on completion of its normal function, and by further pressing the piston to the bottom of the cylinder, association is determined between piston and needle-carrying block and, therefore, by drawing the piston backward, the elastic block will pull t.he needle up inside the cylinder where it remains in a stable position preventing any contact with the outside. 2. Syringe ( 10) as in claim 1 characterized in that the reciprocal means of conjunction bet en piston and block consist of an axial small head(22) fixed to the internal head (21 ) of the piston (20) , and of an axial chamber in the block facing towards the piston, the diameter of which substantially corresponds to that of said small head, that exhibits an axial mouth whose diameter is less than that of said small head, the external edges of the small head and of said mouth being beveled or rounded to facilitate entry of the small head inside the above cham¬ ber when the piston is pressed against the block, hile the internal edges of said small head and of said mouth are sharp to prevent accidental detachment bet een piston and block when the needle is being dra n up inside the syringe . 3. Syringe ( 10) as in claim 1 characterized in that the means of reciprocal conjunction between the piston (20) and the block (30) consist of an axial head on the block facing towards the piston and of a chamber in the head of said piston, the diameter of which subs antially corresponds to that of the above small head, that exhibits a mouth whose diameter is less than that of said small head, the external edges of the small head and those of said mouth being beveled or rounded to facilitate entry of the small head inside the above chamber when the piston is pressed against the block, while the internal edges of said small head and of said mouth are sharp so as to avoid accidental detachment between piston and block when the needle (40) is being drawn up inside the syringe ( 10) . 4. Syringe ( 10) as in claim 1 characterized in that the block (30) is provided with la¬ teral means for ensuring a moderately elastic tight fitting association to the walls of the cylinder ( 1 1 ) for holding it stable when the needle (40) penetrates the body to be treated but without preventing detachment of said block from the base when the piston (20) is being drawn back on completing the injection. 5. Syringe ( 10) as in claim 4 characterized in that the lateral means for moderately ela ¬ stic asεociation between the block (30) and the cylinder ( 11 ) consist of annular ridges (32, 33) round the external cylindrical walls of the block and of annular grooves ( 12, 13) whose form is complementary to said ridges made on the in ¬ ternal walls of the cylinder, the edges of the annular ridges round the block facing to ards the piston being rounded or beveled to permit detachment of the block from the base of the cylinder when the piston is being dra n back after the injection has been given. 6. Syringe ( 10) as in claim 2 characterized in that the volume created between the small head (22) and the head (21 ) of the piston can communicate through small holes (27) made in the top of said small head and channels (28) so that the liquid present inside the chamber (37) in the block can pass into said volume . 7. Syringe ( 10) as in claim 3 charact rized in that the volume created between the small head and the top of the block can communicate through holes made in the top of εaid small head and channels so that the liquid present inside the chamber in the block pasεeε through to said volume.

Inventors: MUNTONI GUERINO, MUNTONI, GUERINO
Applicants: MUNTONI GUERINO, MUNTONI, GUERINO
Application year: 1996
Main classification: A61M5
IPC codes: A61M5