AUTO RETR CTIL SYRINGE Technical Field This invention relates to a safe syringe having a self-retractable needle for use in the medical or dental profession or in the personal administration of drugs in such a way that the physician, surgeon or needle operator can be protected against damage by the needle after use. The invention in a preferred embodiment refers in particular to a packing facility that facilitates self-retraction of a needle core of the syringe upon completion of the injection. However, the invention is not limited thereto, and it is intended to include any syringe in which the self-retraction mechanism according to the present invention can also be applied. BACKGROUND Recent evidence has grown of needle puncture damage, either in the medical profession or children playing on the beach or in parks. It does not matter if it involves the average man in the street or the professional workers of the greeting, the results are that some will be infected with serious diseases of blood origin, as a result of receiving needle puncture damage. It is well documented the risk of damage and
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Possible HIV infection or hepatitis B virus for medical practitioners who use needles in the normal course of their profession. In addition, people who have the habit of administering drugs to themselves run a severe risk of making contact with any of the specified viruses or in fact making contact with other viruses if a needle, once used, is re-used in a manner not sterilized There are also additional hazards where the needle is required to be replaced in the syringe. 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. Although the following description relates primarily to the use of the invention in connection with the so-called secure interchangeable needle syringe wherein there is a requirement to accommodate various sizes of needles or where a needle change is required between filling the syringe from a vial and applying an injection to a patient, the invention is not limited to this and the use of the invention is also contemplated in any syringe where it is desired to provide self-retraction of the needle after completion of the injection. In this way
it is intended that any syringe requiring a self-retractable needle be encompassed where, by appropriate modification as necessary, the invention can also be used. Objective of the Invention It is an object of the present invention to provide a syringe having a self-retractable surgical needle. It is a further object of the invention to provide a syringe employing such a self-shrinking needle in a sterile manner prior to use and to permanently store that surgical needle, once used, in a substantially secure manner. The invention can be used with so-called interchangeable needle syringes or with other syringes that require self-retraction of water after use. The invention is primarily intended to eliminate needle puncture damage by causing the needle to retract automatically within the barrel when the injection is completed thereby making the syringe safe to handle. Finally, the invention provides the alternative means for accommodating the needle of a syringe used, including an interchangeable needle syringe, to protect against accidental damage arising from unwanted contact with the exposed needle once the syringe has been used.
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Although the following description also generally refers to a syringe of conventional size, such limitation is not intended thereby and the reference to a syringe is intended to encompass any other needle / syringe combination including filiform syringes, wherein, the invention can also be usefully applied, by suitable adaptation. SUMMARY OF THE INVENTION The invention in a broad form provides a secure syringe incorporating a self-retractable needle installation therein, the syringe having securely a barrel syringe which has a hollow plunger loosely located therein, having the hollow plunger a proximal end and a distal end with piston means associated therewith at its distal end in order to be slidably sealed within the barrel, the needle installation comprising a needle and a needle core, with a cavity at the end of the barrel for supporting the needle needle core and a spring disposed on said needle core and acting between the needle core and the end of the barrel, the spring remaining under compression during use, the needle core having airtight means associated therewith to prevent leakage between the needle core and the end of the barrel, said needle core having a slot or cavity therein. around its circumference in which
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the locking means are engaged in order to retain the needle core at the end of the barrel of the syringe during use against the compressive action of the spring and wherein said distal end of the hollow piston has an airtight plug, the plunger making contact in a first stage with said needle installation upon completion of an injection and when further depressed by activating self-retraction of the needle core by acting on the locking means in order to cause said locking means to move away from said slot or cavity to release the needle core upon reaching a second stage, said sealing plug moving from said distal end of the plunger when it reaches the second stage thereby releasing said needle core and thereby allowing the needle and spring to retract into said hollow plunger under the influence of the spring. Preferably, the needle and the needle core are housed in a needle packing, which may be interchangeably connected to the barrel of the syringe. Thus in a particularly preferred form of the invention, the invention in a comprehensive manner provides a secure syringe incorporating a self-retractable needle facility therein, the syringe having securely a syringe barrel which has a localized hollow plunger. slidable in it, having the
- hollow plunger a proximal end and a distal end with piston means associated therewith at its distal end in order to be slidably hermetic within the barrel, the needle assembly comprising a packing collar, a needle and a needle core, with a cavity in the packing collar for holding the needle needle core and a spring disposed on said needle core and acting between the needle core and the packing collar, the spring remaining under compression during use, having the needle core sealing means associated therewith to prevent leakage between the needle core and the packing collar, said needle core having a groove around its circumference into which the locking means engage in order to retain the needle core in the packing collar during use against the compression action of the spring and wherein said distal end of the hollow plunger has a ta sealing, contacting the plunger in a first step with said needle installation upon completion of an injection and when depressed further activating the self-retraction of the needle core when acting on the needle installation in order to cause said locking means associated with the needle packing move from said groove to release the needle core upon reaching a second stage, said sealing plug moving from
said distal end of the plunger when it reaches the second stage thereby releasing said needle core and thereby allowing the needle and spring to retract into said hollow plunger under the influence of the spring. It will be understood that the needle packing allows the needle installation to be removed interchangeably. However, the invention remains the same, that is to say the use of the blocking means located either in the barrel itself or in the gasket when it is used, in such a way that the action of the plunger causes the blocking means to be released, thereby releasing the needle core retained in the barrel or gasket as the case may be, so that the needle core is caused to enter the hollow piston when released in this manner. The following description relates mainly to the use of a gasket, however it is not intended to be limited by this and any syringe is contemplated to the extent that the gasket is not used, the reference to the gasket should be taken as the reference to the barrel itself, in which otherwise the gasket would hold if it were used. In other words, the use of the gasket in the barrel to provide the interchangeability of the needle should be interpreted simply as a two-part barrel structure and where a gasket is not used, it could be considered as a
simple integral structure. Preferably the locking means are in the form of protrusions or a complete ring located around the inner periphery of the packing collar which engages (or engages as the case may be) with the groove located around the needle core. Alternatively, the locking means may be independent of the packing collar and may include, for example, a centering pin as described in one of the following embodiments. The shape of the components such as the groove in the needle core and the locking means, either in the form of projections or rings in the packing collar itself or an independent element such as a centering pin, can be of any type. Form suitable for the purpose required and includes, but is not necessarily limited to such forms as round, square and triangular. In this way, preferably the needle installation has means for removably attaching the needle to the end of the barrel, in order to provide the so-called interchangeable needle installation for the syringe. In this particular embodiment, preferably the means by which the needle installation is removably attached to the barrel are provided by having
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the packing collar adapted to the end of the barrel by threaded means. The joining means may be a standard torsion adjustment or the so-called luer-lock adjustment. Preferably, the piston means is slidable in the plunger to allow the plunger to move from the first stage to the second in order to activate self-retraction. This movement is preferably achieved by having three edges located around the periphery of the plunger, with only two edges located within the piston seal at any time. When extra pressure is exerted between the plunger and the barrel upon completion of the injection, the piston seal is forced up the plunger. This allows the plunger to protrude through the piston seal and press against the preassembled needle packing assembly to effect self-retraction. Alternatively, the piston means may * be compressible simply under increased pressure exerted at the end of the injection. Preferably a needle core with a protrusion is provided around its perimeter and the inner wall of the cavity is provided in the packing collar with a step, so that the spring is located between the protrusion and the shoulder in such a way that it stays in compression during use. In an embodiment of the invention that uses a
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centering pin, the plunger acts directly on the needle core to cause self-retraction, the centering pin having a tapered end and the groove around said needle core being a tapered slot on which said tapered end of the needle rests. centering pin, so that upon reaching the second stage, the plunger causes said needle core to be further pressed into said cavity, thereby urging the tapered end of the centering pin out of the tapered slot, said sealing plug moving from said distal end after completion of the injection thereby allowing said needle and spring core to retract into said hollow plunger. In this embodiment, the leak-tight means for preventing leakage between the needle core and the packing collar are preferably a simple O-ring or a similar seal located around the projection of the needle core. Preferably, the centering pin is provided with means by which it is held in position once it has been displaced from the tapered slot, so as not to interfere with the retraction of the needle core under the influence of the spring once it has been moved. released the needle core. Such means include an interference fit, e.g., having a slight taper along the length
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of the centering pin so that it is tightened in the housing after it has been displaced from the needle core. In an alternative embodiment, a bushing is located around the needle core and the spring, the plunger acting on the bushing to cause self-retraction, the centering pin having means by which it can be displaced from the groove around the needle core when the plunger reaches the second stage, the plunger causing said bushing to be further pressed towards said cavity, thereby moving said end of the centering pin of said slot, said sealing plug moving from said distal end after completion of the injection allowing said needle core and spring retract within said hollow plunger. It will be understood in this modality that the pin does not need to have a tapered end, so as to provide a more positive locking of the needle core by retaining it from movement in any direction while in this way it is retained in the packing collar, i.e. before the self-retraction. Preferably in this embodiment, the centering pin is provided with a tapered projection located on its side, against which the end of the bushing acts in order to cause it to move to effect self-regulation.
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retraction. The advantage in this arrangement (i.e. using a bushing located around the core) is that the centering pin is held again by positive means, i.e. under the influence of the bushing, which means that the needle core is free to retract without any possible interference of the centering pin. Preferably in this embodiment, the leak tight means to prevent leakage between the needle core and the packing collar are provided by a hermetic collar which extends between the needle core and the packing collar and therefore through the sleeve which surrounds the needle core and the spring, so that the action of the plunger to cause self-retraction is as a result of the action of the plunger indirectly on the bushing through the hermetic washer. In an alternative embodiment to that described above using a centering pin, the invention uses projections or a ring or other element of projections located around the inner periphery of the packing collar. In this case the needle installation is preferably made of the following parts: 1. Packing collar 2. Sliding spacer collar
3. Packing Seal 4. Needle Core 5. Compression Spring In this mode, the bushing described above in relation to the mode that uses a centering pin, is rather in the form of a sliding spacer collar that is located again around the needle core and the spring, the piston acting in this case again on the sliding spacer collar to cause self-retraction, the projections or rings located on the packing collar being able to move away and thus move away from the slot around the needle core when the plunger reaches the second stage, causing the plunger to press said spacer collar further slidable towards said cavity thereby moving said projections or rings out of said slot, said stopper moving once more from said end distal after the injection is completed allowing said core needle and spring to retract is inside said hollow plunger. It will be appreciated that in the case of a ring, a region of discontinuity such as one or more slits or the like will need to be provided to allow the ring to separate. Preferably the sliding spacer collar
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It has a tapered region around its end to facilitate the separation of the projections or ring as the case may be, allowing a smooth interaction. In contrast, the portion of the packing collar that is engaged by the sliding spacer collar to effect the separation of the projections or ring is tapered in a corresponding manner to facilitate smooth interaction. Once again, the advantage in this arrangement (i.e. using a bushing in the form of a sliding spacer collar located around the core) is that the projections or the ring are held back by positive means, i.e. under the influence of the spacer collar, which means that the needle core is free to retract without any possible interference from the projections or the ring. Preferably in this embodiment, the leak-tight means to prevent leakage between the needle core and the packing collar are again provided by an airtight collar which extends between the needle core and the packing collar and thus through of the spacer collar that surrounds the needle and spring core, so that the action of the plunger when causing self-retraction is the result of the plunger acting indirectly on the spacer collar bushing through the hermetic washer.
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In this way, when the plunger is pushed down after the injection, the plunger makes contact with the seal. The downward pressure causes the sliding spacer collar to be clutched with the projections or ring formed inside the packing collar. By continuing to press the plunger, the projections or ring will be forced out which releases the needle core. At the same time the sealing plug, located inside the end of the hollow piston, moves inside the piston and the compression spring forces the needle core to retract within the hollow piston. Preferably two projections are used in the packing collar. Although the centering pin arrangement is useful, it has been found that the use of two protrusions in particular as described in the latter embodiment makes installation much easier and eliminates the more difficult centering pin and the small spring. In addition, the design can be simplified, since there is no need to provide the centering pin with, for example, a free space in the side of any cover used therein. In any of the above embodiments, a needle cover is preferably provided with the installation to protect the needle before use. Before use, the needle cover protect the needle
- of the damage and also acts as a safety cap for the medical personnel that uses the syringe avoiding damage by needle puncture. The presence of the needle cover also means that the needle installation can be conveniently changed in the case of an interchangeable needle mode without the risk of a needle puncture injury which could occur if the needle were unprotected. In the case of an interchangeable needle, the needle packing is preferably held in the needle cover by interference fit. Preferably, there are coupling grooves on the outside of the needle packing that engage with the grooves in the interior of the needle cover. In this way, the needle is preassembled inside a screw in the packing collar and adapted with a safety cap to prevent damage by needle puncture, so that all that is required is to remove the sterile packaging and screw the pre-assembled needle housing in the syringe and remove the safety cap. Then the syringe is ready for use. In this case, after installation, i.e. After the needle packing is assembled with the needle inside and fits the protective needle cap, the installation is screwed into the end of the barrel. A
Hermetic point is ensured by means of tapering between the needle gasket and the inside of the threaded barrel. After the needle packing installation, i.e. With the needle core fitted to it, it is screwed into the barrel and the seal is reached, the needle cover is removed from the installation leaving the needle ready for use. The additional advantage of this syringe is that various sizes of needles can be adapted allowing the health care profession to make a selection of which needle to use. In any of the above embodiments, the barrel of the syringe is preferably transparent plastic and is graduated to read the fluid level. The piston is preferably made of synthetic rubber and is adjusted to the plunger in order to seal by means of an interference fit between the plunger and the barrel, thereby enabling the syringe fluid to be extruded, through the needle, from the common way. BRIEF DESCRIPTION OF THE DRAWINGS The invention can be better understood from the following non-limiting description of a preferred embodiment, in which: Figure 1 is a cross-sectional view of
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the installation of needle packing of a syringe according to a first embodiment of the invention, Figure 2 without a cross-sectional view of the plunger for use with a syringe according to a first embodiment of the invention, Figure 3 is a syringe barrel plunger for use with a syringe according to a first embodiment of the invention, Figure 4 is a cross-sectional view of a syringe assembled according to a second embodiment of the invention in which a cap is used, before use, Figure 5 is a cross-sectional view of the syringe of Figure 4, showing the plunger removed after receiving fluid for an injection, Figure 6 is a cross-sectional view of the syringe of Figures 4 and 5, showing the plunger depressed to the second stage after injection to cause self-retraction of the needle, Figure 7 is a cross-sectional view of the syringe of Figures 4 and 6 showing the needle and spring retracted in the hollow plunger, Figure 8 is a cross-sectional view of the barrel of the syringe (shown in full in Figures 17 to 20), using internal projections located on the collar
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of packing and a slidable spacer sleeve syringe according to a further embodiment of the invention, FIG. 9 is a cross-sectional view of the plunger for use with the syringe of FIGS. 17 to 20, FIG. 10 is the view in FIG. plant of the proximal end of the plunger for use with the syringe of the Figures
17 to 20, Figure 11 is a side cross-sectional view of the end of the plunger of Figure 10, Figure 12 is a cross-sectional view of the cap for the syringe of Figures 17 to 20, Figure 13 is a cross-sectional view of the needle packing for use with the syringe of Figures 18 to 21, the packing being capable of being screwed into the end of the syringe barrel, Figure 14 is a cross-sectional view of the needle core for the use with the syringe of the Figures
18-21 and which is located in the needle packing of Figure 13, Figure 15 is a cross-sectional view of the slidable sleeve for use with the syringe of the
Figures 18 to 21, which is located around the needle core of Figure 14 and inside the packing of Figure 13.
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Figure 16 is a cross-sectional view of the piston holder that is installed over the distal end of the plunger of Figure 10 for use with the syringe of Figures 18 to 21, Figure 17 is a detailed cross section of the syringe shown in Figures 18 to 21 in the region where the components of Figures 12 to 16 are used just prior to self-retraction, Figure 18 is a cross-sectional view of the entire syringe according to an additional embodiment of the invention of which Figures 12 to 17 illustrate in detail various components and their interactions, the syringe having the plunger removed and filled with fluid ready for an injection, Figure 19 is a cross-sectional view of the syringe of the Figure 18 showing the depressed plunger used just prior to self-retraction, Figure 20 is a cross-sectional view of the syringe of Figure 18 showing the complete plunger. depressed member to activate self-retraction, and Figure 21 is a cross-sectional view of the syringe of Figure 18 showing self-retraction taking place, the needle core being now located in the hollow plunger. DETAILED DESCRIPTION OF THE DRAWINGS
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Referring generally to FIGS. 1 to 3, the components of a syringe and needle combination generally referred to 11 are shown, which comprises a barrel of syringe 12, a plunger 13 and a needle assembly generally referred to in 14. The installation needle 14 comprises a packing collar 15, which accommodates a needle 16 having a needle core 17 at its upper end. The needle 16 protrudes through the packing collar 15. The needle core 17 is preferably made of medical grade plastic and supports the needle 16. The packing collar 15 has a thread 18 about its periphery for the coupling clutch with a corresponding thread 19 located within the end of the barrel 12. A male tapered portion 20 at the end of the packing collar 15 provides a seal against a corresponding female tapered portion 21 at the end of the barrel 12. The packing collar 15 creates from this Thus, a seal with the barrel 12 prevents leakage between the barrel 12 and the threaded portion 18 of the packing collar 15. The packing collar 15 is preferably made of plastic. A safety cap 23 is preferably made of medical grade plastic and fits neatly in the packing collar 15. The safety cap 23 has edges on its outer surface (not shown) for
- - provide a finger grip to assist in its removal before use and provide guidance when the packing collar 15 is screwed into the body 12 of the syringe 11. The purpose of the safety cap 23 is to prevent puncture damage of needle when adjusting needle installation 14, i.e. by means of the packing collar 15 to the syringe 11 also to present the puncture and sterile needle 16 ready for use. The packing collar 15 has a projection 24 adjacent to the thread 18 to separate the threaded portion 18 from the region where the safety cap 23 rests. The interior of the packing collar 15 has a cavity 25 for holding the needle core 17 around which a spring 26 of stainless steel is located. A protrusion 27 is located around the periphery of the needle core 17, while a step 28 is provided on the interior wall of the cavity 25 in the packing collar 15. The spring 26 is held in compression between the protrusion 27 of the core of needle 17 and the step 28 in the cavity 25 of the packing collar 15. Also on the side of the packing collar 15 is a housing 29 for accommodating a centering pin 30. A corresponding region 45 of free space in the cover 23 to accommodate the housing 29. Around the body of the needle core 17 is
- - finds a tapered groove 31. The end of the tapered centering pin 30 rests on this groove 31. A small spring 32 of stainless steel urges the centering pin 30 towards the locking clutch with the groove 31 in the needle core 17. As the plunger 13 comes into play at the completion of the injection, the needle core 17 is further urged into the cavity 25 of the needle packing collar 15 causing the centering pin 30 to be pressed outwardly, causing the auto retraction of the needle 16, by virtue of the spring 26 operating on the released core 17, since this allows the spring 26 to force the needle 16 towards the retracted position. A slight taper is provided along the length of the centering pin 30 to hold it snugly in the housing 29 when it is removed from the slot 31. The needle core 17 has around the projection 27, a seal 33 to prevent the leak between the core 17 and the cavity 25 inside the gasket 15. A hole 34 is provided through the middle part of the needle core 17 to allow the passage of the fluid that is injected through the needle 16 into the patient . A pin 35 is located in the lower part of the needle core 17 to align the end of the needle core 17 with a female pin 36 located in the seal
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or the sealing plug 37 at the end of the plunger 13. The sealing plug 37 seals the interior of the plunger 13 before the final injection is completed. A slot 38 allows the last part of the infected fluid between the needle core 17 and the plunger 13 to escape through the needle 16. The plunger 13 is preferably made of clear medical grade plastic and has a subject on the part outside a piston seal 39. The piston seal 39 is allowed to move in the final injection in order to activate the self-retracting installation by pressing down on the needle core 17 as described above. This movement is achieved by having three edges 40, 41 and 42 on the plunger 13. Only two edges are located within the piston seal 39 at any time. When extra pressure is exerted between the plunger 13 and the barrel 12 upon completion of the injection, the piston seal 39 is forced upwards of the plunger 13, i.e. the piston seal 39 moves from the edges 40, 41 to the edges 41, 42. This allows the plunger 13 to protrude through the piston seal 39 and to be pressed against the pre-assembled needle packing assembly 14, in this case pressing directly on the needle core 17. The plunger 13 is hollow, it has a manual tightening cap 45 located at its proximal end. Plunger 13 is
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hollow to take the needle core 17 and therefore the needle 16 as well as the spring 26 of stainless steel after completion of the injection. The sealing plug 37 is thus displaced when the injection is completed by contacting the pin 35 on the needle core 17. The sealing plug 37 is forced upwards into the piston 13 by the retractable needle core 17 and the spring compression 16 stainless steel. The retraction of the sealing plug 37 is delayed in its travel by the sealing surface inside the barrel 12 which blocks the air which is only allowed to escape slowly through an outlet hole 43 in the upper part of the piston. This slow retraction prevents splashing from the end of the needle 16. Slow retraction can also be achieved by using a slightly tapered hollow region within the plunger 13. As the sealing plug 37 returns inside the plunger 13 after injection, the air can escape in front of plug seal 37 in increasing amounts. This will allow the needle 16 and the plug 37 to return slowly to the start, then increase in speed as the air escapes while the spring 26 causes the movement of the needle 26 and the sealing plug 37 upwardly within the plunger 13. In this way the barrel 12 holds the plunger 13
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which contains the piston seal 39 and the sealing plug 37. The barrel 13 is made of transparent plastic of medical grade and is calibrated to give visual levels of the amount of fluid to be injected. The packing collar 15 containing the needle cover 23 and the needle 16, which is a preassembled unit, is screwed into the barrel 12. Two protrusions 44 in the upper part of the barrel are protruding fasteners to allow the injection of a common way In use, the syringe 11 is removed from the sterile package. The preassembled gasket installation 14 is removed from the sterile package and when held by the safety cap 23, the gasket installation 14 is screwed into the threaded end 19 of the syringe barrel 12. After the cover 23 is removed, the needle 16 is inserted into the jar. The syringe 11 is filled when the plunger 13 is removed. The injection is applied. Upon completion of the injection, the plunger 13 is forced down until the needle core 17 moves downward and releases the centering pin 30 and the sealing plug 37. At this point, the needle 16 retracts into the plunger 13 and therefore inside the barrel 12. The syringe 11 is now safe and inoperable. Now, all the syringe 11 can be safely removed in a responsible manner. If required, a needle change can be made after filling the syringe 11 from a vial
- before the injection. Referring generally to Figures 4 to 7, there is illustrated a syringe generally referred to in 11 wherein each of the components, refer to the same reference numerals as those of Figures 1 to 3, wherein the components are substantially identical However, in this embodiment the end of the plunger 13 does not act directly on the needle core 17 as is the case with the embodiment shown in Figures 1 to 3, but rather there is a bushing 48 located around both the spring 26 and the core 17. A seal 49 extends through the opening between the needle core 17 and the inner wall of the packing collar 15. In this case the plunger 13 effects self-retraction by acting on the cap 48, through of the seal 49. The centering pin 50 is urged towards the mating contact with the slot 51 by the spring means 52. The pin 50 is provided with a tapered projection 54 on its side against which the end of the bushing 48 is pressed when the plunger 13 is depressed upon completion of the injection, ie as it moves from the first stage to the second stage as discussed above. Thus, in Figures 4 to 7 there is shown a combination of syringe and needle generally referred to in 11, which comprises a barrel of syringe 12 a plunger 13 and a
needle installation generally referred to in 14. The needle assembly 14 comprises a packing collar 15, which accommodates a needle 16 having a needle core 17 at its upper end. The needle 16 protrudes through the packing collar 15. The needle core 17 is preferably made of medical grade plastic and supports the needle 16. The packing collar 15 has a thread 18 about its periphery for the coupling clutch with a corresponding thread 19 located within the end of the barrel 12. A male tapered portion 20 at the end of the packing collar 15 provides a seal against a corresponding female tapered portion 21 at the end of the barrel 12. The packing collar 15 creates a this way a seal with the barrel 12 preventing leakage between the barrel 12 and the threaded portion 18 of the packing collar 15. The packing collar 15 is preferably made of plastic. A safety cap 23 is preferably made of medical grade plastic and fits neatly on the packing collar 15. The safety cap 23 has on its outer surface edges (not shown) to provide finger grip to assist in its removal before use and provide driving when the packing collar 15 is screwed into the body 12 of the syringe
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11. The purpose of the safety cap 23 is to prevent needle puncture damage when adjusting the needle installation 14, i.e. by means of the packing collar 15 to the syringe 11 and also to present the sharpened and sterile needle 16 ready for use. The packing collar 15 has a projection 24 adjacent to the thread 18 to separate the threaded portion 18 from the region where the safety cap 23 rests. The interior of the packing collar 15 has a cavity 25 for holding the needle core 17 around which a spring 26 of stainless steel is located. A protrusion 27 is located around the periphery of the needle core 17, while a step 28 is provided on the inner wall of the cavity 25 in the packing collar 15. The spring 26 is maintained in compression between the protrusion 27 of the core of needle 17 and the step 28 in the cavity 25 of the packing collar 15. Also on the side of the packing collar 15 is a housing 29 for accommodating the centering pin 50. A corresponding region of clearance 45 is provided in the cover 23 to accommodate the housing 29. Around the body of the needle core 17 is a slot 51. The end of the centering pin
50 rests on the slot 51. A small spring 52 of stainless steel drives the centering pin 50 towards the
- - locking clutch with the slot 51 in the needle core 17. Between the needle core 17 and the wall of the packing collar 15 there is a seal 53 to prevent leakage between the core 17 and the cavity 25 inside the packing 15. As the plunger 13 comes into play at the completion of the injection, the plunger acts on the seal 53 so that the bushing 48 is further pressed into the cavity 25 of the needle packing collar 15 causing the centering pin 50 is pressed outwardly by virtue of the action of the end of the bushing on the tapered surface of the projection 54 on the side of the centering pin 50, causing self-retraction of the needle 16 by virtue of the spring 26 which operates on the core released 17, since this allows the spring 26 to force the needle 16 into the retracted position. A sealed plug 37 seals the interior of the plunger 13 before the final injection is completed. The plunger 13 is preferably made of medical grade clear plastic and has a piston seal 39 on the outside. The piston seal 39 is allowed to move in the final injection in order to activate the self-retracting facility by pressing downwardly. on bushing 48, through seal 53 as described above. East
- movement is achieved by having three edges 40, 41 and 42 on the plunger 13. Only two edges are located within the piston seal 39 at any time. When extra pressure is exerted between the plunger 13 and the barrel 12 upon completion of the injection, the piston seal 39 is forced upwards of the plunger 13, i.e. the piston seal 39 moves from the edges 40, 41 to the edges 41, 42. This allows the plunger 13 to protrude through the piston seal 39 and to be pressed against the pre-assembled needle packing assembly 14, by pressing in this case indirectly on the bushing 48 through the seal 53. The plunger 13 is hollow, it has a manual tightening cap 45 located at its proximal end. The plunger 13 is hollow to take the needle core 17 and therefore the needle 16 as well as the stainless steel spring 26 after completion of the injection. The airtight plug 37 is thus dislodged when the injection is completed. The airtight plug 37 is forced upwardly into the plunger 13 by the retractable needle core 17 and the compression spring 16 of stainless steel. The retraction of the sealing plug 37 can be delayed as described above in relation to the embodiment of Figure 1, to avoid splashing from the end of the needle 16. In this way the barrel 12 keeps the piston 13 containing the piston seal 39 and the hermetic plug 37.
The barrel 13 is made of clear medical grade plastic and calibrated to provide visual levels of the amount of fluid to be injected. The packing collar 15 containing the needle cover 23 and the needle 16, which is a preassembled unit, is screwed into the barrel 12. Two protrusions 44 at the top of the barrel are finger restraints to allow injection in a common way In use, the syringe 11 is removed from the sterile package. The preassembled gasket installation 14 is removed from the sterile package and when held by the safety cap 23, the packing assembly 14 is screwed into the threaded end 19 of the syringe barrel 12 as shown in Figure 2. After the Removal of the lid 23, the needle 16 is inserted into the bottle. The syringe 11 is filled when the plunger 13 is removed, as shown in Figure 3. The injection is applied. Upon completion of the injection, as shown in Figure 4, the plunger 13 is forced down until the bushing 48 moves downward and releases the centering pin 50 and the sealing plug 37. At this point, the needle 16 is it retracts into the plunger 13 and therefore into the barrel 12 as shown in Figure 5. The syringe 11 is now safe and inoperable. Now, all the syringe 11 can be safely removed in a responsible manner. If required, a change can be made
of needle after filling syringe 11 from a bottle before injection. The advantages of the invention in any embodiment are found in the locking centering pin and the pre-assembled gasket. The invention also provides slow retraction of the needle core by controlling the escape of air. Advantageously, the location of the plug that seals the plunger to the needle core is facilitated by the use of the spike. Using a movable piston allows the complete escape of the fluid at the completion of the injection while allowing the piston to travel further to execute the retraction of the needle. Returning to Figures 8 to 21, a further embodiment of the invention is shown in which components similar to those already described use the same reference numerals. The sliding spacer collar 64 has a tapered conductive end 65. The packing collar 15 is shown so that the shape of the projections 62 is discernible. Referring to Figures 17 to 21, when the plunger 13 (not shown) is pressed downwards after the injection, the plunger 13 contracts the seal 53 by pressing it downwards. This will cause the sliding spacer collar 64 to be clutched with the two molded projections 62
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inside the packing collar 15. By continuing to press the plunger 13 the two projections 62 will be forced out which releases the needle core 17. At the same time the sealing plug 36 (not shown), located inside the end of the hollow plunger 13, moves within the plunger 13 and the compression spring 26 forces the needle core 17 to retract within the hollow plunger 13. The other aspects of the general operation of this embodiment are similar to those described above in relation to Figures 1 3 and Figures 4 7. It will be appreciated by those skilled in the art that many modifications and variations may be made to the embodiments described herein without departing from the spirit or scope of the invention. Throughout the specification the word
"comprises" and its derivatives are proposed to have an inclusive meaning rather than an exclusive one unless the context otherwise requires.