Disposable hypodermic syringe

Abstract: Disposable hypodermic syringe, comprising a tube (1) with its front part (2)narrowed and adapted to receive a hypodermic needle (3) and a hollow piston (4) capable of sliding through the inside of the tube; obturating devices laid across and held in operative position by the head of the needle (5); a spring (6), that tends to push the needle towards the inside of the tube; a closing device of the piston's cavity (11); and irreversible joining devices to fit other complementary joining devices placed at the head of the needle. The afore mentioned obturating devices are composed of a discoid part (7) made of a slightly flexible material, having a central countersinked hole (8) to receive the head of the needle that passes through it. This discoid part has, on its front side, appendages (10) adapted to operate on the retention devices as the discoid part is pushed forward by the front end of the piston, when it completes its operative run. The mentioned retention devices are constituted by many flexible tongues (12) which rise from the wall of the tube in a slanting angle, pointing forward and inward, and which are set so that they become fitted into a ring-shaped external groove (13) made round the outside of the needle's head, from where they are removed as they are bent by means of the pushing action of the appendages of the obturating discoid part previously mentioned.

Description: This invention relates to a disposable hypodermic syringe of the type which is specified in the preamble of claim 1. Technical background The use of disposable hypodermic syringes which are sold in sterilized and sealed packages of one unit each and which are broken and thrown away after they are used once, is well known. However, although these syringes are made and sold to be used only once, the truth is that their structural characteristics allow their repeated use without any difficulty from the mechanical point of view, although this gives rise to obvious and very serious problems in the area of health. These problems have become more acute recently, since the appearance of AIDS, which eventually causes the death of the patient, and for which there is still no known cure or vaccination which will stop it from spreading. Although there have been attemps to come up with disposable syringes to avoid their repeated use, the only ones which really work are those which, automatically and without any subsequent handling by the user, prevent any further use. US-A-4838869, which corresponds to the preamble of claim 1, discloses a disposable hypodermic syringe having means for retaining the needle in an operative position thereof, and releasing means on the piston end releasing the needle when the end of the piston run is attained, so that a spring pushing constantly the needle toward the inside forces the needle to move inwards when these retaining devices are released to conceal the needle in the hollow portion of the piston. However, this known device does not provide means to hold the needle in that concealing position inwards, excepting those constituted by the spring itself. Description of the invention According to the present invention, the posed problem is solved in a simple and efficient way by a hypodermic syringe having the characteristics recited in claim 1. Accoring to a further characteristic of this invention, the interlocking retention appendages in the front part of the tube are made up of a plurality of flexible tongues which rise from the wall of the tube at a slanting angle, facing foward and inward, and which are set so that they become fitted into a ring-shaped external groove made around the outside of the needle's head, from where they are removed as they are bent by means of the pushing action of the appendages of the obturating discoid part previously mentioned. Considering anther characteristic of the invention, the closing device of the piston cavity is constituted by a discoidal button, with its edge pressure-fitted into a ring shaped groove made around the mouth of the piston cavity. This discoid button has a protuberance in its front part, which constitutes said irreversible joining devices, and which has an external stepped protruding edge around it, which will become pressure-fitted into a countersinked hole in the needle head, from where it is impossible to be extracted due to the opposing action of the complementary joining devices, which in turn, consist on an intend step. Another feature of this invention is that piston-retaining devices are arranged at the mouth of the tube cavity which make the total extraction of the piston from the tube impossible. Brief description of the drawings The enclosed drawing show, by way of an example not to be considered as exclusive, a way in which the hypodermic syringe subject of this invention, can be made. Figure 1 is the cross section of an elevational view of a syringe prior of its use; and Figure 2 is a similar view of the one shown in Figure 1, but once the syringe has been rendered useless. The optimum method to make this invention The enclosed drawing show that the disposable hypodermic syringe, which is the subject of this invention, is comprised of a tube 1, having its front part 2 narrowed and adapted to receive a hypodermic needle 3, and a piston 4 capable of sliding through the inside of the tube 1. Obturating devices 7 held in an operative position by the head 5 of the needle 3 are laid across the front inside part of the tube 1. Said head 5 of the needle is pressed by a spring 6, preferentially constituted by a helicoidal compression ring, which tends to push it towards the inside of the tube 1, and is held by means of interlocking retention devices located in the inside part of the tube 1. At the front end of piston 4, there is a closing device of the piston cavity 11, having irreversible joining devices located at the head 5 of the needle 3. Said obturating devices are composed of a discoid part 7 of a slightly flexible material, its edge being in contact with the inside wall of the front end of the tube 1, so accoplishing a tight sealing with the latter. The discoid part 7 has a central countersunk hole 8 to receive the conical end 9 of the head 5 of the needle 3 which passes through it, so accomplising also a tight sealing with said conical end 9. The discoid part 7 has also, at its front side, appendages 10 adapted to operate on the interlocking retention devices in the inside front part of tube 1, as the discoid part 7 is pushed forward by the front part of the piston 4, when it completes its operative run. At this stage, the discoid part 7 and the needle 3 with it, moves slightly foward as they are pushed by piston 4. Said appendages 10, in turn, push the retention devices, thereby releasing the needle 3, which is introduced into the cavity 11 of piston 4, through the action of spring 6. Said interlocking retention devices located at the front part of the tube 1 are made up of a plurality of flexible tongues 12, arising from the wall of the tube 1 at the slanting angle, facing foward and inward, and which are set so that they become fitted into a ring shaped external groove 13 made around the outside of the head 5 of needle 3, from where they are removed as they are bent by means of the pushing action of the appendages 10 of the obturating discoid part 7 previously mentioned. Said closing device of the cavity 11 of the piston 4 is constituted by a discoid button 14 having its edge pressure-fitted into a ring shaped groove 15 made around the mouth of said cavity 11. Said discoid button has a protuberance 16, constituting said irreversible joining devices, and which has an external stepped protruding edge around it 17, to be pressure-fitted into a countersunk hole 18 in the head 5 of needle 3 constituting said complementary joining device, from where it is impossible to be extracted due to the opposing action of said complementary interlocking retention devices, which in turn, consist of an indented step. At the mouth of the cavity of tube 1, there are arranged retaining means for the piston 4, which are preferentially constituted by joining ribs 19 and 20, which make the total extraction of the piston from the tube 1 impossible.

Claims: Disposable hypodermic syringe, of the type which is rendered unusable after it has been used once, comprising a tube (1) with its front part narrowed and adapted to receive a hypodermic needle (3), the head (5) of which is pressed by a spring (6) tending to push it towards the inside of the tube (1); a hollow piston (4), which slides through the inside part of the tube (1); interlocking retention devices (12) placed in the front inside part of the tube (1) holding the head (5) of the needle (3); a closing device (14) of the cavity (11) of the piston (4) at the front part of the piston (4); and appendages (10) which press on the interlocking retention devices (12) of the inside front part of the tube (1) when the piston (4) completes its operative run thereby releasing the needle (3), which, forced by the spring (6), is made to enter the cavity (11) of the piston (4) characterised in that an obturating device (7) constituted by a discoid part (7) made of a slightly flexible material is arranged across the front inside part of the tube (1) and held in an operative position by the head (5) of the needle (3); the edge of the discoid part (7) is in contact with the inside wall of the front part of the tube (1), accomplishing with a tight sealing; the discoid part (7) has a central counter-sunk hole (8) to receive the conically enlarged end (9) of the head (5) of the needle (3) passing through the hole (8) accomplising also a tight sealing between the conical surface of the end (9) of the head (5) and the surface of the countersunk hole (8); said discoid part (7) is pushed forward by the front of the piston (4) when the piston completes its operative run; said appendages (10) are arranged on the front side of the discoid part (7); and that said closing device (14) of the piston cavity (11) comprises an irreversible joining device which fits into complementary joining devices placed at the head (5) of the needle (3) intended to work together when they come into contact once the piston has completed its operative run. Disposable hypodermic syringe according to claim 1, characterized in that said interlocking retention devices of the front end of the tube are made up of a plurality of flexible-tongues, arising from the wall of the tube (1) at a slanting angle, facing forward and inward, being adapted so that they become fitted into a ring-shaped external groove (13) made around the outside of the head (5) of needle (3), from where they are removed as they are bent by the pushing action of the appendages (10) of said obturating discoid part (7). Disposable hypodermic syringe, according to claim 1, characterized in that said closing device (14) of the piston cavity is constituted by a discoid button, with its edge pressure-fitted into a ring-shaped groove (15) made around the mouth of the cavity of the piston (4), said discoid button having a protuberance (16) in its front part which constitutes said irreversible joining device and which has an external stepped pro-truding edge (17) around it whish is to be pressure-fitted into a countersunk hole (18) of the head (5) of needle (3) constituting said complementary joining devices, from where it is impossible to be extracted due to the opposing action of said complementary joining devices, which, in turn, consist of an indent step. Disposable hypodermic syringe according to claim 1, characterized in that the piston-retaining devices (19) are arranged at the mouth of the cavity of tube (1), so that the total extraction of the piston (4) from the tube (1) is impossible.

Inventors: CARALT BATLLE JAIME, CARALT BATLLE, JAIME
Applicants: CARALT BATLLE JAIME, CARALT BATLLE, JAIME
Application year: 1991
Main classification: A61M5
IPC codes: A61M5