The subject invention relates to a disposable syringe which can be used only once.
The object of the invention is to prevent the repeated use of syringes and the resultant spread of certain ineffective illness which currently afflict humanity.
There is known to be an increasingly urgent requirement for syringes which can be used only once, i.e. which are unable to draw in new liquid once the original liquid initially drawn into the syringe has been injected.
The problem of constructing syringes which can be used only once is very urgent, as is demonstrated by the large number of patents offering different solutions, such as those described- in the patents as U.S. Patent No. 4,699,614 and GBP-A- 2,205,750.
Non-reusable syringes as designed in the past have various shortcomings as found in case of non-retractable drive shaft or piston arrangements such as found in U.S.Patent No. 4,493, 703 where the syringes are pre-filled as the syringes were so designed that it was not filled by the user in the conventional manner.
The Patent applications PCT WO 88/10127, GB-A- 2,015,883 and EP-A-0,325,886 describe syringes in which the plunger and its operating shaft are only weakly linked together i.e. can disengage and various expedients are provided to ensure that when the plunger has been pushed to the bottom of the cylinder by the action of the shaft, the shaft disengages from the plunger when the shaft is pulled. To retain the plunger more securely in the cylinder specially designed annular ribs are provided, making the syringe thus made to be very expensive and complicated to use.
To overcome the above referenced problems , the syringe of subject invention has been devised, where the syringe is rendered ineffective to be used for the second time.
The disposable syringe of subject invention is having a hollow cylindrical body, a plunger and a locking mechanism.
The plunger is inserted in the said cylindrical body. One side of the said plunger is flat and is divided into two equal portions, while the other said of the said plunger is having a pair of protrusions. The flat side of the said plunger is having sedations or grooves which are joined on the centrally placed line placed at equidistant from each other.
The sedations or grooves on one side of the said centrally placed line on the flat surface of the said plunger are facing upwards while sedations or grooves on other side of the said line are facing downwards.
A specially designed lock is provided between the plunger and the hollow cylindrical body at the top end of the said hollow cylinder. The said lock is having a pair of protuberances where the first protuberance is held by second protuberance by resilient means which controls the movement of these protuberances in direction inversely proportional to each other. The said lock is fused to the main body and is inserted in the cylinder body in such a way that second protuberance is always in touch with grooves or sedations that are facing downwards. When the plunger is pulled back the flexibility in the second protuberance allows an upward motion along with the plunger as one end of the protuberance is always in touch with the grooves or sedations on the plunger as the first protuberance is held back by second protuberance without interfering with the movement of the plunger. The plunger is pulled back to the extent required. When forward motion is undertaken to deliver the medicine or to inject the fluid out of the hollow cylinder, the second protuberance also undertakes a downward movement because the
downward facing grooves or sedations on plunger ensures that the downward motion is transferred to second protuberance as when it takes downward motion, it releases first protuberance from its grip preventing the said protuberance to come back to its original position and strike the grove which are facing upwards, as the movement of the plunger is downward, the first protuberance does not interfere with the grooves as they are facing upwards. This mechanism allows the syringe to complete its downward movement.
When, the plunger is pulled back for the second time, the first protuberance which is locked into the grooves facing upwards does not allow the upward movement of the plunger for the second time and the syringe is rendered is ineffective second time.
Accordingly the present invention relates to an auto disable syringe comprises a barrel, a plunger having a flat surface on the other side and serrations on the opposite side, locking means provided in the said syringe comprising two parts attached to each other by means of flexible joint around which it can be rotated provided between the said plunger and the said barrel allowing the movement of the said plunger inside the said barrel in a forward and backward direction for few millimeters to allow capability of aspiration of the syringe and then restricting the movement of the plunger undirectionally.
The present syringe consists of the following main parts:

1.

Barrel

2. Plunger
3. Locking system
The plunger is flat on one side and grooved and on the other. ■ The flat side has serrations and a rough portion. This side of the plunger will be inserted in the barrel in such a manner so that the side having the serrations will face inside of the barrel.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will be described with reference to the accompanying drawings:
The lock has a special type of structure which consists of two main portions as shown in Fig. 1
& Fig. II. Figure I shows the lo'ck in its open position and figure II shows it in the closed
position.
Parts number 1, 2, 3 & 4 make portion A of the lock whereas numbers 5, 6, 7 & 8 collectively
make portion B of the lock. Portion B is attached to portion A with the help of number 5,
around which it can be rotated and closed on to portion A, as shown in figure II.
The lock & plunger have following parts as marked in the figures:
1: ears of the top portion which will be welded with the main body of the parrel;
2: A small ridge meant for keeping the part II of the lock in its place when closed;
3: Another small ridge which will lock in at number 7 during the downward movement of
portion B of the lock . 4: Slightly protuberant portion meant to push part number 6 towards the plunger. 5: Flexible joint which will hold part II of the lock in the closed position. 6: Protruded portion which will fit in with the serrations ( 11) in the plunger 7: A small ridge which will get locked by number 4. 8: A slightly thin portion which will induce flexibility in portion B and allow it to move
forward during its downward movement. 9: A rough longitudinal wall on the outer side of portion B which will touch part number 10
of the plunger when inserted in the barrel. 10: A rough portion on the plunger which will impart downward movement to the portion B
of the lock through friction with part 9. 11: Serrations, facing upwards. These will hold part number 6 and will not allow the plunger to move upwards second time. 12: A vacant portion which will not interfere with the lock during the initial small movement
of the plunger and therefore will provide space for aspiration. 13: Lower portion of the plunger where the piston will fit in.
14: A serrated portion meant to weaken the joint between number 15 and the plunger. 15: Top part of the plunger.
The plunger is inserted in the barrel like in an ordinary syringe. The side having serrations v face inside of the barrel, as shown in figure 4. Thereafter the lock is inserted from the above, closed position (figure 2) in such a manner that number 9 and 10 face each other. It is then ' fused with the barrel by part number 1.
Working of the Syringe.
The plunger is drawn out for medication or for the extraction of blood when the syringe is usee for the first time. During the initial few millimetres part numbers 9 and 10 are not in close toucl with each other and hence do not interfere with the working of the locking mechanism. This is done to introduce the capability of aspiration in the syringe. Aspiration is the ability of the syringe to be used and reused until the blood enters the syringe from the vein. Once this is achieved, the plunger is drawn out and the blood or the medicine is extracted. The parts number 9 & 10 have the rough surface and are so sized, so as to touch each other closely. At this point portion B of the lock is held in its place by part number 2 and it does not allow portior B to move upwards along with the plunger as it would have in normal circumstances because 9 & 10 are closely touching each other and movement in 10 would have been automatically transferred to number 9 by way of friction. Once the extraction part is over, the plunger is pushed downwards for delivering the medicine or pushing the fluid or blood out of the barrel. When the downward motion of the plunger takes place, it imparts the same motion to portion B of the lock downwards by transferring motion to part 9. Portion B of the lock slides downwards over number 4, which is so designed that while moving downwards, portion B also experiences a small forward motion towards the plunger, which results in to part 6 coming in direct contact with the serrations (part No. 11). At the same time part numbers 3 & 7 get locked onto one another. Now portion B of the lock can neither be pushed upwards or downwards. Number 11 can slide past number 6 because the serrations are facing upwards . After the first downward movement of the plunger is complete and the syringe has been used, the plunger can not be drawn second time because part number 6 has now been securely locked with part number 11. Part 5 & 8 help portion B of the lock to experience downward and forward motions respectively by providing flexibility. In the initial phase part 6 is so designed that it is just short of part 11. When portion B of the lock slides downwards it gets a small forward motion because part number 4 has been so designed. This forward motion results into part 6 getting so close to part 11 that both of them are now engaged to each other. Hereafter only downward motion is possible because of the angle of the serrations and shape of part 6. Once the downward motion is complete, no second upward motion can be made. Hence the syringe can not be used twice.

I CLAIM:
1. An auto disable syringe comprising a barrel, a plunger having a flat surface on the other side and serrations on the opposite side, locking means provided in the said syringe comprising two parts attached to each other by means of flexible joint around which it can be rotated provided between the said plunger and the said barrel allowing the movement of the said plunger inside the said barrel in a forward and backward direction for few millimeters to allow capability of aspiration of the syringe and then restricting the movement of the plunger undirectionally.
2. An auto disable syringe as claimed in claim 1, wherein the said plunger comprises serrations on its one side, facing the inside barrel.
3. An auto disable syringe as claimed in claim 1, wherein the said locking means comprises two parts, joined to each other by means of a flexible joint holding the second position of the said locking means in a closed position.
4. An auto disable syringe as claimed in claim 1, wherein the inside surface of the barrel and out cover of the plunger are provided with rough surfaces.
5. An auto disable syringe as claimed in claim 1, wherein the said first part of the said locking means comprises ears of the top position welded with the main body of the barrel, a small ridge meant for keeping the lock in its place when
closed, a second small ridge provided in the second part of the locking mean locking during the downward movement of the second part of the said locking means; and a protuted portion fitted in the said serrations in the plunger allowing only downward motion and no second upward motion because of angle of serration and conforming sape of said protuded portion.
6. An auto disable syringe as claimed in claim 1, wherein the said part of the said locking means comprises protruded portion fitted with the serration in the plunger and a thin position allowing the plunger to move forward during its downward movement.
7. An auto disable syringe as claimed in claim 1, wherein the said serrations are provided with a angle of inclination allowing only downward motion of the plunger.
8. An auto disable syringe, substantially as hereinbefore described with reference to the accompanying drawings.