MX2008006350A - Safety syringe with plunger locking means - Google Patents

Abstract

A safety syringe (11) is disclosed. The safety syringe has a retractable needle facility (14/15) incorporated therein, the syringe comprising a barrel (12) and plunger (13) and needle assembly. The needle is caused to retract into the barrel of the syringe upon completion of injection once it has been used, by means of engagement between the needle assembly and the end of the plunger. Locking means (28) preferably in the form of a locking bush is provided in the body of the syringe to engage the plunger once it is retracted after use, so that the syringe is rendered incapable of being used further.

Description

TECHNICAL FIELD This invention relates to a safety syringe having a retractable needle for use in the medical or dental profession or in the personal administration of medicament in such a way that the physician, surgeon or Another needle operator may be protected from damage by the needle after use. In particular it relates to means for retaining the plunger to which the needle is attached and therefore, the needle in the retracted position. Background The danger of harm and possible infection with HIV or hepatitis B virus by medical practitioners using needles in the normal course of their profession is well documented. In addition, people who are in the habit of administering medicines themselves are at a severe risk of contacting either specified viruses or in fact contacting other viruses if an already used needle is re-used in an unsterilized manner. . There have been many proposals aimed at reducing the number of so-called needlestick injuries and several attempts have been made to provide a safe system for the removal of such needles once used, but such previous proposals have had deficiencies.

Several solutions are provided to the above problems for retractable needles. One of the major disadvantages in many of the above proposals is that although the syringe initially becomes safe by having the needle retracted, they commonly do not provide means to prevent further access to the needle. In other words, the plunger may be pressed again causing the needle to re-emerge from the barrel of the syringe or in some other cases be completely removed from the barrel of the syringe thereby having access to the needle. OBJECT OF THE INVENTION It is an object of the present invention to provide a syringe which to some extent resolves or at least diminishes some of the above disadvantages by employing a retractable surgical syringe and permanently storing the surgical needle, once used, in a manner substantially safe. In particular, the present invention provides a positive fixation facility to prevent the plunger, to which the extracted needle is attached, from reactivating or even removing completely, once the syringe has become secure by having the needle retracted. At least the invention provides an alternative means for accommodating the needle of a syringe used to protect against accidental damage arising from unwanted contact with the exposed needle once the syringe has been used.

Although the following description generally refers to a syringe of conventional size, this limitation is not intended by this and the reference to a syringe is understood to encompass any other combination of needle / syringe or single needle including filiform syringes, wherein, by suitable adaptation, the invention can also be applied in a useful manner. Description of the Invention According to the present invention there is provided a safety syringe having a retractable needle facility incorporated therein, the syringe comprising a barrel and a plunger and a needle installation, wherein the needle is caused to retract within the barrel of the syringe upon completion of the injection once it has been used, by means of the clutch between the needle assembly and the end of the plunger and wherein the fixing means is provided in the body of the syringe to engage the syringe. plunger once it has been retracted after use, such that the syringe becomes unable to be used further. In this regard, rendering the syringe incapable of further use means that the plunger can not be pressed down again to reactivate the needle, nor can it be completely removed from the barrel of the syringe to gain access to the needle.

Preferably a region of weakness is provided in the plunger, located on the axis of the plunger in the vicinity of where it extends from the end of the syringe body when it is completely extracted, such that after the needle retracts towards the body of the syringe and the plunger is engaged with the locking means, the plunger is broken in such a way that it can not be pressed again, or easily removed by holding it and exerting a force, thereby further helping to render the syringe incapable of being used again. It will be understood that although this invention is unquestionably improved by the ability to break the plunger, it will also be appreciated that this is an extra stage and one that some users may ignore. Therefore, it is preferable that the fixing means be of sufficient strength to prevent the plunger from being pressed or removed in such a way that it does not matter that the plunger is broken. In other words, even before the plunger is broken, the present invention conceives that the syringe becomes ineffective against deliberate or even accidental re-use if the syringe were struck as if placed on, for example, a syringe. table. Preferably the fixing means is provided by a collar located at the end of the barrel of the syringe from which the plunger extends.

The collar can be a split collar or a solid collar, although it has been found particularly advantageous to have a split in the collar for easy adjustment to the barrel. It has been found that a split collar provides an easier fit during manufacture of the syringe, since the collar needs to be adjusted after the plunger is inserted into the barrel. By virtue of the proportioned division, the collar can be made to fit around the axis of the plunger and can be made to be reduced in diameter when pressed to the barrel and will have a rapid adjustment in the inner region of the barrel designed to accommodate it. The collar may use any of a variety of methods to engage the plunger once the plunger engages with the needle and causing it to be drawn into the barrel of the syringe, including, but not necessarily limited to twisting or attracting the plunger through or towards the collar as the case may be. In collars where a torsional movement is required, the collar may be a twist lock collar or a threaded collar or it may be a Luer lock collar. Alternatively in embodiments where a movement of attraction is required, the collar may be a fastening collar by pull or a quick fastening collar. Examples of these collars are illustrated in the accompanying drawings and are discussed below in relation to the description of the respective drawings. As mentioned above, the collar is preferably pressed towards the barrel after the plunger is inserted. A variety of fastening options are also available to retain the collar in the barrel. Any combination of locking mechanism can be coupled to retain the plunger in the locking collar with any such means by which the collar itself is retained in the barrel of the syringe. It will be appreciated that there are several different means available by which the collar can be used to lock the plunger and these are contemplated to be within the scope of the invention. It is also preferred that a vertical or longitudinal projection be provided inside the end of the barrel where the collar is inserted, whereby the collar can be prevented from rotating, particularly in cases where a split collar is used or where it is required a twisting action to block the plunger in the collar. Furthermore, it is preferable that the plunger itself be provided with a flange around its distal end to prevent it from being attracted directly through the fixing means. In this way the syringe will not only become ineffective against the plunger being pressed again, but will also become secure in that the plunger can not retire completely. Thus, once the plunger is locked in the collar, neither the plunger nor the collar itself can be removed to otherwise access the needle located within the barrel after it has been withdrawn into the barrel. Thus, advantageously locking the plunger in the collar is preferably improved by a flange located on the plunger, preferably located just above the piston region of the plunger, allowing the plunger to lock in this way against the bottom of the collar, preventing the plunger It is extracted completely. By providing a break point in the plunger, as discussed above, the possibility of additional hazardous handling will also be avoided or at least minimized, especially by preventing access to the plunger in a manner in which it is allowed to be forced back into the plunger. barrel or hold for withdrawal by excessive force. Thus, for example, a preferred embodiment uses a torsional locking feature that includes corresponding threaded regions in the barrel of the syringe and in the plunger, such that after an injection the plunger is removed and locked in position when the plunger is rotated. to engage the corresponding threaded portions. Alternatively, the fixing means are provided by a fixing feature by torsion including a torsional locking collar having helical grooves in it located in the barrel of the syringe and corresponding projections located in the plunger to engage in the helical grooves, such that after an injection, the plunger is withdrawn and locks in position by rotating the plunger to engage the projections in the corresponding helical grooves. Again, as an alternative, the fastening means may be provided by a torsional locking feature including a twist lock collar having helical grooves therein located in the barrel of the syringe and projections located on the plunger to be engaged in the helical grooves, such that after an injection the plunger is withdrawn and locked in position as the plunger rotates to cause the projections to move through the corresponding helical grooves and pass completely through the collar. Preferably in this embodiment, a permanent fixing installation is provided in the form of an inclination or other projection to prevent the projections from returning through the slots of the collar and thereby preventing the plunger from passing back through the collar towards the collar. barrel of the syringe.

However, more preferably, it has been found that a fastening collar with a single-flange arrangement is both easy to produce and effective. In this arrangement a flange around the internal perimeter of the collar allows a corresponding flange on the plunger to pass in one direction, but by virtue of the shape of the flanges to prevent its return. In combination with an additional flange on the plunger as described above, the plunger is prevented from being pulled directly through the collar by providing effective blocking against movement in any direction. Instead of a flange around the entire internal perimeter of the collar, it has been found that a pair of fingers function equally efficiently. The movement of the fingers can be achieved to allow passage to the first flange of the plunger when shaping the inner region of the barrel to allow the fingers to bend backwards as the plunger flange passes, immediately receding by virtue of resilience once it has past the first rim. Although much of the following description relates to a particular safety syringe having a retractable needle with certain characteristics, it will be understood that the torsion fixation mechanism can be used with any syringe having any form of installation retractable needle The invention finds application for example in a wide environment to which a safety syringe is provided having a retractable needle facility incorporated therein, so that in a first storage position before use, the safety needle is enclosed securely within the body of the syringe and in a second position in use, the needle is caused to extend from the syringe body in order to function as a useful combination of needle and syringe in a known manner, and where the needle is then made to retract back towards the body of the syringe, once it has been used, in order to return it to the first storage position; the syringe comprising a body and a plunger, wherein the plunger has means associated with the end thereof contained within the body of the syringe to engage in a manner to release an enhancement of the needle located in the body of the syringe in order to retain the needle within the body of the syringe in the first storage position and wherein the body of the syringe has means located at the end thereof opposite to where the plunger extends from the body to retain in a way to release the needle's enhancement in the second position of in use in such a way that the needle extends from the body of the syringe, using the plunger to bring the needle up to the clutch with the end of the syringe body; the plunger then being able to disengage itself from the needle enhancement in order to allow the plunger to be withdrawn and thereby take fluid into the syringe and then used to inject it into a patient in the known manner; and at the end of the injection and having withdrawn the patient's needle, the plunger is brought back to the clutch with the needle enhancement and is removed in order to cause the needle to be released from the end of the syringe body in such a way that the needle retracts back towards the body of the syringe, the needle remaining attached to the end of the plunger. Alternatively, the needle installation may be such that in the initial position, the needle is already extended, ready for use, or it may be a socket arrangement to which a replaceable needle may be adjusted, in any case the needle is protected by a suitable cover or cover before use, in such a way that the end of the plunger only comes into contact with the needle or cap installation as the case may be at the end of the injection, at which point the clutch between the plunger is achieved and the installation or bushing, in such a way that the installation or bushing is extracted together with the needle by itself towards the barrel when retracting the plunger. Then the plunger is made to clutch with the fixing collar and preferably separates instantaneously at the point of rupture to make the syringe safe and ineffective against further use. In this way the invention is of particular benefit in that the needle not only retracts securely after use, but is locked in that position by means of the fixing collar. Instantaneously separating the plunger (if provided) also renders the syringe both ineffective for subsequent use as well as providing additional security in that there is no means by which the needle can be made to re-emerge or cause it to extend from the body of the syringe. BRIEF DESCRIPTION OF THE DRAWINGS The invention can be better understood from the following non-limiting description of preferred embodiments, in which: Figure 1 is a cross-sectional view of one embodiment of the invention using a fixation collar in accordance with an aspect of the invention in which a collar with quick fixation collar is used to retain the plunger after use; Figure 2 is a cross-sectional view of the plunger used in the embodiment of Figure 1, Figure 3 is a cross-sectional view of the barrel used the embodiment of Figure 1, Figure 4 is a cross-sectional view of the end of the barrel of Figure 3 to which a fixing collar can be adjusted, Figure 5 is a cross-sectional view of a preferred embodiment of a fixing collar for use with the syringe and its components as illustrated in Figures 1 to 4, Figure 6 is a plan view of the fixation collar of Figure 5, Figure 7 is a detailed cross-sectional view of the end of the plunger of Figure 2, which is engaged with the clasp of Figures 5 and 6 when the plunger is retracted after it has seized and retracted the needle (not shown), Figure 8 is a cross-sectional view from the end of the plunger and clasp of the previous Figures, after the clutch has been carried out, Figure 9 is a cross-sectional view of a syringe barrel using a torsion fixation collar which is a modal d alternative of the invention to that illustrated in Figures 1 to 8, Figure 10 is a detailed cross-sectional view of a plunger for use with the twist lock collar of Figure 9, FIGS. 11 to 15b show schematically pairs of collars and corresponding pistons in accordance with various alternative embodiments, and FIGS. 16 and 17 show from two perspectives a simplified collar similar to that of FIGS. 5 and 6. according to still a further embodiment of the invention. Detailed Description of the Drawings Referring generally to Figures 1 to 8 and especially to Figure 1, there is shown a syringe according to an aspect of the invention generally referred to in 11, which comprises a syringe or barrel body 12, a plunger 13 slidable therein and a needle 14. The needle 14 is provided with a head 15. The plunger 13 and the barrel 12 are shown separately in Figures 2 and 3 for clarity. The head 15 of the needle is located by interference fit in a bushing 16 which in this embodiment is screwed into the end of the barrel 12 using an internal female thread 17 on the end side of the barrel 12 and a male thread 18 in the cap 16. In this embodiment the needle installation comprising the needle and the head 14/15 and the cap 16 can be replaced or interchanged (or indeed adjusted) before the use of the syringe in order to provide flexibility of choice for example with regarding the caliber of the needle. It will also be appreciated that in the alternative, bushing 16 could be screwed into the outside of the barrel 12, for example in filiform syringes. These modalities allow the replacement of the needle installation in a so-called needle exchange. On the other hand, the needle and the head 14/15 can be used directly at the end of the barrel 12 in an integral arrangement, without a bushing 16, in other embodiments of the invention, where it is not necessary to exchange the needle 14. It is provided a small seal 19 for sealing between the needle head 15 and the cap 16, while a second larger seal 20 is provided for sealing between the cap 16 and the barrel 12. The needle 14 is protected by a cover 21 before the use. The plunger 13 is provided with a clasp means 22 located on a rod 23 at the end of the plunger 13.

The clasp has a tongue 24 which engages with the inner region 25 of the needle center 15 when the plunger 13 is brought into contact with the needle head 15 at the end of the injection. Plunger 13 is also provided with a piston region 26 around its lower periphery which seals against the interior of body 12 of the syringe, when insert in it. A rupture groove or a region of weakness 27 is provided at a suitable location on the plunger 13, such that it can be broken after the needle 14 has been retracted into barrel 12 of the syringe, that is, after use as described below. A locking collar 28 is located in the upper region of the barrel 12. Details of the locking collar 28 and the relevant portions of the syringe 11 pertinent to its use are illustrated in detail in Figures 4 to 8. The fastening collar 28 has a division region shown schematically at 29 in Figure 6 for easy adjustment of the collar 28 with the barrel 12. A flange 30 is located around its periphery and a pair of fingers 31 depend on the collar 28 for engaging a circumferential groove region 32 located between the circumferential flanges 33 and 34 located near the end region of the plunger 13. The flange 33 and the fingers 31 are suitably tilted on one side to provide ease of passage, but they have surfaces on the other side which are effectively parallel to each other, in order to avoid the return. The profile of the inner region 35 of the end of the barrel 12 similarly allows adjustment and retention of the collar 28 specifically therein providing a groove 36 in which the flange 30 for the coupling clutch is located with the proper inclination where required to assist in adjustment. In particular, a recess 37 is provided behind the fingers 31 of the collar 28 when it is in place (as shown in Figure 1), so that the fingers 31 can be deformed as the end of the plunger 13 clutches with it. A rim 38 is also located around the periphery of the collar to reinforce and assist in aligning the collar 28 when it fits with the barrel 12. Specifically, the first ridge 33 is capable of passing through the fingers 31 when pressed towards the nose. cavity 37 as the region of the plunger 13 passes through the fingers 31 of the collar 28. The second ridge 34 is provided with larger diameter than that of the rim 33 in order to prevent it from passing through the fingers 31, thereby blocking the plunger 13. when the fingers 31 engage the groove 36 in this way. The plunger 13 can not be further attracted through the collar 28 by virtue of the flange 34, nor can it be pressed again under the flange 33. Returning to Figure 1, a pin is located 39 in the hole 40 in the upper region of the plunger 13. The pin 39 acts as a deep stop to prevent the Accidental clutch of the plunger 13 with the head 15 of the needle before use. When the syringe is about to be used, the pin 39 can be easily pressed so as to allow full travel of the plunger 13 in the barrel 12. In this manner in use, after the injection has been completed, the plunger 13 press towards the clutch with the needle head 15. Then the plunger 13 with the needle 14 engaged retracts, thus withdrawing the needle 14 towards the barrel 12, the plunger 13 being completely withdrawn back in order to engage with the fixing collar 28 by means of the flanges 33 and 34 preventing the plunger from moving in any direction once the fingers 31 have been engaged in the groove 36 located between them. Then the plunger 13 breaks rapidly at the breaking point 27. With the plunger 13 disabled and the needle 14 retracted into the body 12 of the syringe 11, it becomes completely useless and can then be disposed of safely. Figures 9 and 10, wherein the similar features common to Figures 1 to 8 are referred to with the same reference numerals, show in detail specifically an alternative embodiment of the invention in the form of a locking collar 41 by twisting and a corresponding plunger 13 for use therein. This combination it can be used for example in any syringe including that of Figure 1, where a fixing mechanism is required to retain a retracted needle 14 located at the end of a plunger 13 and whereby it is desired to render the syringe 11 completely unusable after use by locking the plunger 13 and breaking it at a breaking point 25 and therefore leaving the needle 14 in the barrel 12 of the syringe 11 and otherwise inaccessible. The plunger 13 is provided with projections 42 which may be of any suitable cross-sectional shape. Three particular sections are shown in detail at 43, 44, 45, which are respectively round entry with a flat base, a simple rounded and threaded segment. In this embodiment the projections 42 are located in the grooves of the plunger 13, while the corresponding characteristic of the previous embodiment, ie the rim 33 was formed in that embodiment, circumferentially (and thus described) around the plunger 13, instead of being an extension of a groove element of the plunger 13. The collar 41 can be divided to wrap around the plunger 13 as in the previous embodiment. Alternatively it can be solid and screwed on the plunger 13 before adjusting the piston 26 thereto. The collar 41 has two internal helical grooves 46 for feeding the projections 42 as the plunger 13 is rotated through the collar 41. When the projections 42 pass through the collar 41 they rise over the permanent retainer 47 and thereby the plunger 13 is locked within the barrel 12. With the plunger 13 blocked, the piston 26 is displaced by tormenting it within the barrel 12. As the piston 26 reduces in depth it expands its diameter. The twist lock collar 41 is held in the barrel 13 within the slot 48 as shown. Figures 11 to 15 show a variety of means by which the collars 41 can be used with corresponding pistons 13. The characteristics already described use the same reference numerals for convenience. Figs. 11, 11b show a combination of locking collar 41 / plunger 13 in which generally the collar 41 has two helical grooves 46. The two projections 42 on the plunger 13 engage the helical grooves 46 when the plunger 13 is retracted by blocking Plunger 13 as it is turned. The fixing is carried out when the projections 42 ascend to the upper part of the collar 41, at the same time the flange 49 located on the piston 26 is locked in the base 50 of the twist fixing collar 41, preventing the movement of the plunger 13. either up or down.

Figures 12a, 12b show a collar 41 which has a thread 51 (which can be any thread). As the plunger 13 retracts and the thread 51 engages with the corresponding thread 52 on the plunger 13, rotation will stop when the edge 53 is reached on the collar 41. At the same time the rim 49 on the piston 26 is it locks on the lower part 50 of the threaded collar 41. In FIGS. 13 a, 13 b a collar 41 is shown, which is a tension fixing collar. The collar 41 has two slots 54 inside the collar 41 as shown. The fastening is carried out as the plunger 13 retracts through the slots 54 and is rotated, the projections 42 on the plunger 13 engage with the internal slots 54 in the collar 41. In this way the projections 42 fit into the lower horizontal slots 55 in a bayonet fit manner. At the same time, the projection 49 on the piston 26 is locked again in the lower part 50 of the fixing collar 41 by attraction. A quick fastening collar 41 is shown in Figures 14a, 14b in which the interior has tapered locking fingers 56 and a step 57. As the plunger 13 retracts through the tapered flange 58 for immediate fixation in the plunger 13, engages the tapered locking fingers 56 by separating them to allow the plunger 13 pass through them. The tapering fingers 56 move rapidly around the taper 58 of the plunger and the two steps, the 59 on the plunger 13 and the other 57 on the upper part of the fingers 56 within the collar 41, thereby making the retainer impossible for the plunger 13 Press down. Figures 15a, 15b depict a plunger 13 which has two grooves 60 similar to a needle head engaging the Luer lock design 61 within the collar 41. As the torque of the plunger 13 is carried out, the plunger 13 it moves upwards blocking between the flange 49 and on the piston 26 and the lower part 50 of the collar 41. In each of the above cases the plunger 13 breaks at the breaking point 27 thus avoiding any reuse without authorization or accidental of the syringe 11. A simplified version of the quick-fix collar shown in Figures 14, 14b is shown in Figures 16 and 17, where the fingers 51 can be as few as two. Although not shown, the collar 41 can also be divided to allow ease of installation, such that the distal end of the plunger 13 is first pressed into the barrel 12 of the syringe 11. The collar 41 can then be placed around the plunger 13 during the installation of the syringe 11 and pressed into its position before the plunger 13 rests in its starting position, before, but ready for use. It will be appreciated by those skilled in the art that various modifications and variants of the embodiments described herein may be made without departing from the spirit or scope of the invention. Through the specification the word "comprises" and its derivatives are intended to have an inclusive rather than exclusive meaning unless the context otherwise requires. The invention described herein has utility in that it provides an alternative means for a safety syringe having a retractable needle installation which can become useless after injection by locking the plunger and breaking it.

Claims (28)

1. CLAIMS 1. A safety syringe having a retractable needle facility incorporated therein, the syringe comprising a barrel and a plunger and a needle assembly, wherein the needle is caused to retract toward the barrel of the syringe to the syringe. termination of the injection once it has been used, by clutch means between the needle assembly and the end of the plunger and wherein fixing means are provided in the body of the syringe to engage the plunger once it retracts after the use, in such a way that the syringe becomes incapable of being used additionally. A safety syringe according to claim 1 in which the syringe is unable to be used additionally since the plunger can not be pressed down again to reactivate the needle, nor can it be completely removed from the barrel of the syringe to gain access to the needle. 3. A safety syringe according to either of claim 1 or claim 2 wherein a region of weakness in the plunger is provided, located on the axis of the plunger in the vicinity of the place where it extends from the end of the body of the plunger. the syringe when fully retracted, such that after the needle is retracted into the body of the syringe and clutched the plunger with the fixing means, the plunger may be broken in order to render the syringe unable to be used again. A safety syringe according to any of the preceding claims wherein the fixing means is provided by a collar located at the end of the barrel of the syringe from which the plunger extends. 5. A safety syringe according to claim 4 wherein the collar is a solid collar. 6. A safety syringe according to claim 4 wherein the collar is a split collar. A safety syringe according to claim 6 in which the collar is adapted after the plunger is inserted into the barrel and pressed into position in the barrel, where the division is made to fit around the shaft of the plunger and is reduced in diameter when pressed into the barrel and clutched by a quick adjustment in the inner region of the barrel. 8. A safety syringe according to any of claims 4 to 7 in which the collar is pressed towards the barrel after the plunger is inserted. 9. A safety syringe according to any of claims 4 to 8, wherein any suitable fixation mechanism for retaining the The plunger in the clamping collar engages with any suitable means by which the collar itself is retained in the barrel of the syringe. A safety syringe according to any of claims 4 to 9 in which a vertical or longitudinal projection is provided within the end of the barrel where the collar is inserted, whereby the collar is prevented from rotating. 11. A safety syringe according to any of claims 4 to 10 in which the plunger is provided with a rim around its distal end to prevent it from being attracted directly through the fixation means. 12. A safety syringe according to claim 11 in which the plunger is able to lock against the lower part of the collar, preventing the plunger from being completely extracted. A safety syringe according to any of the preceding claims 4 to 12 in which the collar uses the torsion or attraction of the plunger through or towards the collar. 14. A suitable safety syringe with claim 13 wherein the collar is a twist-lock collar and the twist is provided by a threaded collar or a Luer lock collar. 15. A safety syringe according to either claim 13 or claim 14 in which the syringe uses a torsional locking feature including corresponding threaded regions in the barrel of the syringe and in the plunger, such that after an injection the piston is extracted and locked in position by twisting the piston to engage the corresponding threaded portions. 16. A safety syringe according to either claim 13 or claim 14 in which the syringe uses fixation means in the form of a torsional locking feature including a torsional locking collar having helical grooves in the same located in the barrel of the syringe and corresponding projections located in the plunger for the clutch in the helical grooves, in such a way that after an injection, the piston is extracted and locked in position when rotating the plunger to engage the projections in the corresponding helical grooves. 17. A safety syringe according to either claim 13 or claim 14 wherein the fastening means is provided by a torsional locking feature including a torsional locking collar having helical grooves therein located in the the barrel of the syringe and projections located in the plunger for engaging in the helical grooves, such that after an injection the plunger is withdrawn and locked in position as the plunger rotates to cause the projections to move through the corresponding helical grooves and pass completely through the collar. 18. A safety syringe according to either claim 13 or claim 14 in which the fastening means is provided by a collar having two helical grooves, which engage with two projections on the plunger which engage the grooves helical when the plunger is retracted by locking the plunger as it is turned. 19. A safety syringe according to either claim 13 or claim 14 in which the fastening means is in the form of a collar having a thread and wherein as the plunger retracts and engages the thread with a corresponding thread on the plunger, the rotation will stop when the edge is reached on the collar, while at the same time the flange on the piston is blocked at the bottom of the threaded collar. 20. A safety syringe according to any of claims 4 to 12 wherein the collar is an attachment clamp collar or a quick clamp collar. 21. A safety syringe according to the claim 20 in which the fixing means has a permanent fixing facility provided in the form of a tilt or other projection to prevent the projections from returning through the slots of the collar and thus preventing the plunger from passing back to through the collar to the barrel of the syringe. 22. A safety syringe according to claim 21 in which a flange is located around the internal perimeter of the collar which allows a corresponding flange in the plunger to pass in one direction, but by virtue of the shape of the flanges it is avoided to return and where in combination with an additional flange on the plunger as described above, the piston is prevented from being pulled straight through the collar providing an effective lock against movement in any direction. 23. A safety syringe according to claim 21 in which a pair of fingers cooperate with the first flange of the plunger allowing it to pass by virtue of the shape of the ridges in the inclined installation and by the shape of the internal region of the barrel to allow the fingers to curve backward as the plunger flange passes, rapidly retracting under the resilience once the flange has passed. 24. A safety syringe according to claim 20 in which the fixation collar is a quick-fix collar in which the interior has a fixing taper and a step, so that as the plunger is retracted through the tapered quick-clamp flange, it engages the tapered clamping fingers upon detachment to allow the plunger pass through them and where the tapered fingers retract rapidly around the taper of the plunger and the two steps, one on the plunger and the other on the upper part of the fingers inside the collar, making the retainer by this impossible for the Plunger is pressed down. 25. A safety syringe having a retractable needle facility incorporated therein, such that in a first storage position before use, the needle is securely enclosed within the body of the syringe and in a second position in use, the needle is caused to extend from the body of the syringe in order to function as a useful combination of needle and syringe in the known manner and wherein the needle is then made to retract back towards the body of the syringe. the syringe, once it has been used, in order to return it to the first storage position and the syringe comprising a body and a plunger, wherein the plunger has means associated with the end thereof contained within the body of the syringe for releasably engage a needle enhancement located in the The body of the syringe in order to retain the needle inside the body of the syringe in the first storage position and wherein the body of the syringe has means located at the end thereof opposite to where the plunger extends from the body. to releasably hold the needle in the second position in use in such a way that the needle extends from the body of the syringe, the plunger being used to bring the needle up to the clutch with the end of the body of the needle. syringe; the plunger then being able to disengage from the enhancement of the needle in order to allow the plunger to be withdrawn and thereby take a fluid into the syringe and then be used to inject it into a patient in the known manner; and at the end of the injection and when the needle has been withdrawn from the patient, the plunger is brought back to the clutch with the needle enhancement and is removed in order to cause the needle to be released from the end of the body of the needle. the syringe in such a way that the needle retracts back towards the body of the syringe, the needle remaining attached to the end of the plunger. 26. A safety syringe according to claim 25 wherein the needle installation is located such that in the initial position, the needle is already extended, ready for use or it can be a socket configuration to the which fits a needle replaceable, protecting the needle in any case by a suitable cover or cover before use in such a way that the end of the plunger only comes into contact with the installation of needle or cap as the case may be at the end of the injection, at which point the clutch between the piston and the installation or bushing is achieved, in such a way that the installation or bushing is extracted together with the needle itself towards the barrel when the piston is retracted. 27. A safety syringe according to claim 25 or claim 26, wherein the plunger is then engaged with the locking collar and preferably breaks immediately at the breaking point to make the syringe safe and ineffective against additional use. 28. A safety syringe having fastening means for locking the plunger therein after use to prevent further use of the syringe substantially as described herein in conjunction with any of Figures 1 to 8 of the drawings, Figures 9 and 10 of the drawings or each of Figures 11 to 15 of the drawings.