Safe medical syringe with an automatic slowly retractable needle

A needle gradually auto-retractable safety medical syringe includes a hollow barrel, a plunger provided in the barrel, a piston provided on the head of the plunger, a hub provided on the head of the barrel. The hub includes an elastic connecting hub providing with a needle and a hub sheath for fixing the elastic connecting hub, the elastic connecting hub may be disengaged with the head of the barrel and retracted with the effect of a spring after having finished the injection, a regually retractable bracket which are integrated with each other, the regually retractable bracket forms with at least two elastic supporting claws engaged to the inner wall of the pushing tube of the front end of the plunger after the injection finished, the elastic connecting hub allows the regually retractable device to retract in the barrel with the effect of the spring, and allows the needle to be drawn into the barrel.

TECHNICAL FIELD

The invention relates to a medical syringe, in particular, to a medical syringe with a needle which can automatically retract without the withdrawal of a doctor to hide itself after use without hurting people.

BACKGROUND ART

Modern medicine has proved that hypodermic syringes must be disposable and must be treated as medical trash after use to avoid secondary cross infection during the process of in-putting or out-taking medium for people or animals. Presently, the most commonly used disposable syringe consists of a hollow barrel, a needle, and a plunger inside the barrel. The biggest problem of this kind of syringe is that the needle of it is still exposed after use. The sharp needle makes the medical trash inconvenient for transportation or destruction Medical staffs are often hurt by the needles, which unavoidably bring secondary cross infection. Especially, the syringes used for patients with serious infectious diseases (such as AIDS, hepatitis and SARS) are great medical hidden dangers which cannot be ignored. Practices have proved that needle stick injuries caused by unsafe needles are much more than that caused by other accidents.

In recent years, as it was found that disposable syringes were taken back and used by unscrupulous persons, an auto-disposal syringe which would automatically become destroyed or locked and could not be reused, was invented at the end of last century. However, currently some syringes have serious shortcomings. Nurses have to withdraw the needle by hand after injection, which makes the injection process complicated and brings inconvenience for doctors and nurses. There is another kind of syringe, of which the needle is retracted into the cylinder under the action of spring after injection. However, the needle is retracted too fast in a sudden and blood will burst out under the body pressure from the needle hole on the body, which brings secondary cross infection.

CONTENTS OF THE INVENTION

The technical problem that this invention is going to solve is: to provide a safe medical syringe of which the needle can automatically draw back into the barrel slowly after injection. This safe medical syringe will totally solve the secondary cross infection problem of prior art.

In order to solve the above mentioned technical problems, this invention adopts the following technical scheme: a safe medical syringe with an automatic slowly retractable needle which consists of a barrel, a plunger inside the barrel, a rubber piston on the head of the plunger and a hub on the head of the barrel. The front part of the plunger is a push tube. It is characterized in that: the hub consists of an elastic connecting hub providing with a needle and a hub sheath for fixing the connecting hub; there is a spring installed between the elastic connecting hub and the hub sheath; after the injection finished, the elastic connecting hub allows the retractable device to retract in the barrel with the effect of the spring, and slows the needle to be drawn into the barrel; the front of the plunger is provided with a slow retraction device which coordinates with the elastic connecting hub in the axial direction; a backup washer and a slow retraction bracket stick together to form the slow retraction device; the slow retraction bracket consists of at least two elastic bracing claws which cooperate with the inner wall of the push tube on the front part of the plunger.

In order to solve above mentioned technical problems, this invention adopts the following technical schemes: a thru slot is provided on the top of the slow retraction bracket; an outer boss is provided on the head of the bracing claw; a boss on the upper part inside the push tube, superposing the outer boss on the head of the elastic bracing claw.

A nick slot is provided on the head of the backup washer and a protruding circle at the bottom. An inner boss is provided on the head of elastic bracing claw. The outer part of the protruding circle at the bottom of the backup washer joints with the inner boss of the elastic bracing claw.

The outside of the upper part of the backup washer cooperates closely with the piston. The outside of the middle part fits the inner hole of the push tube head movably. At the bottom, the upper surface of the boss joints with the top surface inside the push tube. An inner pocket is provided at the bottom joint with a rubber sealing ring.

An inner pocket is provided on the head of the barrel. At the bottom of the elastic connecting hub, at least two bracing claws are set symmetrically, closely jointed by clips and corresponding with the inner pocket on the head of the barrel. An inner backing pin is set in the hollow space of the elastic bracing claws as support. There are steps at the middle part inside the push tube.

This invention has the following advantages in comparison with prior art: 1. After injection, the hub cooperates with slow retraction device, and under the action of the spring, the elastic connecting hub springs the slow retraction device to retract into the barrel slowly and hides the needle inside the barrel. It solves the problem of secondary cross infection when the needle is drawn back too fast in a sudden and blood bursts out under the body pressure from the needle hole on the body; 2. The structure of the syringe is reasonable. Pushing is easy. The syringe is reliable and easy to operate. It is suitable to be applied widely.

MODE OF CARRYING OUT THE INVENTION

It is showed inFIG. 1that: this invention consists of a hollow barrel1, a plunger2installed inside the barrel1, a rubber plunger3installed on the head of plunger2, a hub installed on the front part of the barrel1, a push tube21on the front part of the plunger2. It is showed inFIG. 9that hub4consists of an elastic connecting hub42which is installed with an injection needle and a hub sheath41for fastening the elastic connecting hub42. There is a spring44between the elastic connecting hub42and the hub sheath41. The elastic connecting hub42can break away from the head of barrel1after pushing liquid and draw back with the action of the spring44. On the front part of the plunger2is a push tube, slow retraction device is installed along the axis of the elastic connecting hub42and cooperates with it. The slow retraction device slowly and automatically draws the elastic connecting hub42back into the barrel. The slow retraction device is formed by a backup washer23and a slow retraction bracket24. The backup washer23acts as support of the slow retraction bracket24. There are at least two elastic bracing claws242cooperating with inner wall of the push tube21to form the slow retraction bracket24. The bracing claw242with self springing action touches the inner wall of the push tube21and produces frictional resistance. After liquid is pushed, under the springing action of the spring44, the elastic connecting hub42draws back and springs the slow retraction bracket24and the backup washer23, which makes the bracing claw with springiness242of the slow retraction bracket24slide down along the inner wall of the push tube21. The elastic connecting hub42and the injection needle draws back into the push tube21. The elastic connecting hub42does not draw back in a sudden but draws back slowly against the frictional resistance between the bracing claw242and the inner wall of the push tube21.

The following is further detailed illustration in combination with each figure:

It is showed inFIG. 20that the plunger2consists of a push tube21, a handle22and a backup washer23, a slow retraction bracket24and an airproof rubber ring25.

It is showed inFIG. 21that the hub4consists of a hub sheath41, an elastic connecting hub42, an inner backing pin43, a spring44and a rubber sealing ring45. A thru slot433is provided at the middle part inside the backing pin43(seeFIG. 18). A protection sheath5is installed outside the hub4.

It is showed inFIG. 19that there is a boss11outside the head of the barrel1. An inner pocket12is inside the head. A circle14is provided at the bottom. A big protection sheath6is provided outside the circle14to avoid wrong operation. An inner boss13is provided at the bottom of the barrel1.

It is showed inFIG. 10that the push tube21is a hollow tube. A boss211is provided outside the top of it. There is a top surface215inside the tube. An inner boss212is provided inside the upper part. A step213is provided inside the middle part. The step213is inclined or straight. The step213is set in the middle part of the push tube21to enlarge the inner diameter of the push tube21. An inclined step boss214is provided at the bottom inside push tube21.

It is showed inFIG. 11that boss221on the upper part of handle22closely joints with the inclined step boss214by clips at the bottom inside the push tube21. At the middle part, there is a boss222. The boss surface224touches the bottom of the push tube21. More than two clips223are symmetrically set at the bottom. After injection, it joints with the boss13at the bottom of the barrel1by clips.

It is showed inFIG. 12that there is a nick slot231on the head of the backup washer23and a protruding circle236at the bottom. The outside of the upper part is closely jointed with the piston3. The outside of the middle part fits the inner hole216of the push tube21movably. At the bottom, there is an upper surface232of the boss jointing with the top surface215inside the push tube21. At the bottom, an inner pocket233jointing with a rubber sealing ring25is provided. The outside of the protruding circle236at the bottom joints with the inner boss2422of the elastic bracing claw242of the slow retraction bracket24.

It is showed inFIG. 13that a thru slot241is provided on the top of the slow retraction bracket24. Slow retraction bracket24joints with backup washer23and fits it movably. More than two elastic bracing claws242are provided outside the bottom of it. On the head of it, an outer boss2421superposes with the upper boss212inside the push tube21. At this time, the boss212fastens and locates the elastic bracing claw242. The inner boss2422joints with the outside of the protruding circle236at the bottom of the backup washer23.

It is showed inFIG. 15that the top surface411is set inside the hub sheath41touching the upper surface of spring44. A middle boss surface412closely jointing with the rubber sealing ring45is provided in the middle part. A pocket413is provided at the middle bottom part inside, closely cooperating with the outer boss11of the head of the barrel1.

It is showed inFIG. 16that at the bottom of the elastic connecting hub42; more than two elastic bracing claws242are set symmetrically. The outer shapes of them correspond with the inner pocket12of the head of barrel1and closely joint with it by clips. The inner part4213of the elastic bracing claw421and the lower inside hole424joint with the outer wall of the inner backing pin43. A step boss422is set in the middle of the elastic connecting hub42, superposing with the bottom of the spring44. The outer circle423of the elastic connecting hub42fits the inner hole of spring44movably. The upper inner hole425of the elastic connecting hub42cooperates with the injection needle.

FIGS. 1,2,3,4,5,6,7and8show the whole process of using this invention.FIG. 1shows the cutaway view in the state before use. At this time, the elastic bracing claw242on the slow retraction bracket24is fastened and located by an inner boss212of upper part inside the push tube21.FIG. 2is the cutaway view of preparing to draw liquid. At this time, the outside sheath5of the hub4and the big sheath6at the bottom of the barrel have been taken off.FIG. 3is the cutaway view after finishing drawing liquid.FIG. 4is the cutaway view in the state of liquid not being pushed to the bottom and drawing back and self destroying having started. The top of the slow retraction bracket24just touches the bottom of the inner backing pin43. Liquid can flow through the thru slot241on the head of the slow retraction bracket24.FIG. 5is the cutaway view of the state at the end of the first step of the needle drawing back and destroying itself. At this time, the backing pin43is pushed into half of the hollow space of the elastic connecting hub42by the slow retraction bracket24. The top of the backup washer23touches the bottom of the elastic bracing claw421on the elastic connective hub42, preparing for the next action.FIG. 6is the cutaway view in the state at the end of the second step of the needle drawing back and destroying itself. When the liquid is pushed forward, the slow retraction bracket24is pushed forward again because of movable fit between the backup washer23and the slow retraction bracket24. At this time, the bottom of the backup washer23has relatively moved to the inner root part of the elastic bracing claw242of slow retraction bracket24, which makes inner part of the head of the elastic bracing claw242lose support. Meanwhile, the inner backing pin43has been totally pushed into the elastic connecting hub42. The elastic bracing claw421loses support and transfigures towards inside.FIG. 17shows the transfiguration. Therefore, the elastic bracing claw421breaks away from the pocket12which cooperates with the head of barrel1and the elastic bracing claw421takes hold of the head of the slow retraction bracket24, getting ready for drawing back the needle.FIG. 7is the cutaway view in the state of the end of the third step of the needle drawing back and destroying itself after injection and beginning to draw back. When the liquid is pushed forward, inner part of the head of the elastic bracing claw242of the slow retraction bracket24is squeezed because of losing support and breaks away from the upper boss212inside the push tube2. Later on, the elastic bracing claw242of the slow retraction bracket24transfigures through self springing, which is showed inFIG. 14, and touches the inner wall of the push tube21. Liquid pushing is finished and drawing back starts.FIG. 8is the cutaway view in the state of the needle drawing back into the push tube21. When liquid pushing finishes, the elastic connecting hub42springs the slow retraction bracket24and the backup washer23under the springing force of the spring44, which makes the elastic bracing claw242of the slow retraction bracket24slide down back to the push tube21along the inner wall of the push tube21. At this time, because the elastic bracing claw242of the slow retraction bracket24has been transfigured and the elastic bracing claw242opposes to cooperate with the inner wall of the push tube21, the elastic connecting hub42does not draw back in a sudden but slowly draws back against the frictional resistance between the elastic bracing claw242and the push tube21. When the elastic bracing claw242goes down and slips to the middle part of the push tube21, the inner diameter of the push tube21will become bigger due to a step set in the middle of the push tube, which reduces the resistance against the inner wall of the push tube21from the elastic bracing claw242. Therefore, the frictional resistance between the elastic bracing claw242and the inner wall of the push tube21becomes less, cooperating with declining force of the spring, makes the elastic connecting hub42draw back and destroy itself successfully.

The above example is only to illustrate this invention and does not limit this invention. Ordinary technicians of related technical field can make more changes and transfiguration without breaking away from the spirit and scope of this invention. Therefore, all equivalent technical schemes belong to the scope of this invention.