there are several preferred embodiments within the instant invention and the preference depends to a great extent on manufacturing and sales choices . the instant invention can be supplied in one of three major forms : there are also several variations for the syringe barrel tip which interact with the three major embodiments and which in themselves increase the overall number of preferred embodiments . there is an alternate syringe barrel design . finally there are several alternate designs for sealing the retractable hollow needle at the barrel tip and within the hollow plunger . the major embodiments will be discussed in reverse order . attention is called to fig1 through 8 which show the preferred pressure sampler embodiment of the safety syringe . these figures also : illustrate a number of the alternative designs which will be discussed in due course . the safety pressure sampler embodiment consists of 10 interrelated parts : the operation of the needle guide wire / valve assembly will be explained first . referring to fig2 the guide wire / valve assembly ( generally 11 ) consists of a guide wire ( 2 ) with a cap ( 1 ). the guide is sized so that it just fits inside the hollow needle ( 4 ) but yet slides easily inside the hollow needle . the hollow needle assembly ( generally 12 ) consists of a needle head ( 3 ) with a lever arm ( 20 ) and a lever arm latch ( 21 ) formed within the lever arm ( 20 ). the needle head ( 3 ) is attached to the hollow needle ( 4 ) and contains an axial opening which aligns with the inside of the hollow needle ( 4 ) thus allowing the guide wire ( 2 ) to pass through the needle head ( 3 ) and into the hollow needle ( 4 ). the hollow needle ( 4 ) contains a port ( 22 ) which is positioned on the hollow needle ( 4 ) so that when the needle is fully extended then the port ( 22 ) is near or at the bottom of the inside of the syringe barrel . ( see fig7 .) the hollow needle ( 4 ) terminates at its distal end in the standard needle bevel or point ( 33 ). retraction of this point ( 33 ) is the purpose of this instant invention . the guide wire ( 2 ) actually serves as a valve and closes off the needle port ( 22 ) whenever the wire passes down the needle towards the beveled end ( or point ) when the hollow needle is retracted . the needle assembly , for the pressure ( or even aspirator ) sampler , is shown assembled in fig3 ( generally 13 ). since the guide wire ( 2 ) is designed to barely fit within the hollow needle ( 4 ), but still be capable of easy movement , the wire will shut off the needle port ( 22 ) from the needle bevel ( 33 ) whenever the wire passes the port ( 22 ) by a reasonable distance . the valve action stems from simple surface tension . the sample fluid exerts surface tension between the wall of the hollow needle ( 4 ) and the guide wire ( 2 ): this surface tension will stop the movement of fluid . the port ( 22 ) and the bevel ( 33 ) will be &# 34 ; shut - off &# 34 ;. this simple mechanism will stop any fluid from exiting the sample chamber through bevel ( 33 ), which will be in the sample chamber whenever the needle is retracted , and out through port ( 22 ) into the hollow plunger ( 5 ). the same action will stop the sample from becoming contaminated ( reverse flow from the port through the bevel ). note how the valve will also stop the fluid sample frown outgasing , thus assuring a true sample when that sample reaches the laboratory . note that it might be possible to design or choose a needle length that would keep the bevel port ( 33 ) on the outside of the barrel and yet within the confines of the luer lock portion of the syringe barrel ( 8 ). this device considers this approach but believes that safety requires complete retraction of the hollow needle ( 4 ) to within the confines of the barrel . the hollow plunger assembly is shown generally as 14 in fig4 . essentially this plunger functions exactly the same as any standard syringe plunger except that first it is hollow , second it has retraction locking ramps ( 34 ), third it has a slot ( 24 ), fourth it has an opening for the needle seal system ( 25 ) and fifth it has a needle seal system ( in general item 7 , but specifically 7a or 7b depending on embodiment ). like the normal syringe plunger it has a piston ( 6 ) which sets the volume of a pressure sample , draws a vacuum for an aspirated sample or causes a pressure for an injection syringe . the thumb flange ( 23 ) allows the thumb to exert the necessary force against the piston or allows the finger to draw the piston backwards within the syringe barrel . slot ( 24 ) is sized to allow lever arm ( 20 ) to pass through it . retraction locking ramps ( 34 ) are essentially molded catches that latch against the needle head ( 3 ) preventing the needle from being extended once the ramps catch the needle head ( 3 ). the needle assembly ( generally 12 ) passes through the opening in the plunger ( 25 ) and then through the enlarged plunger needle seal opening ( 27 ). the plunger needle seal ( generally 7 ) is retained within the opening ( 27 ), against opening ( 25 ), and about the needle ( 4 ). in the pressure filled sampler embodiment , the plunger needle seal consists of a packing formed of &# 34 ; microfilter &# 34 ; material ( 7a ). microfilter material is hydrophobic , in that it will allow entrained air to pass readily through it but will swell and stop fluids from passing through it . thus the microfilter ( 7a ) will seal sample fluids and yet allow the hollow needle ( 4 ) to slide up through so that the needle can be retracted . the completed plunger and retractable needle assembly ( generally 18 ) for the sampler ( pressure or aspirated ) embodiment is shown in fig5 . assembly is a matter of choice but the method used by the inventor is as follows : first , insert the hollow needle assembly ( 12 ) through the slot ( 24 ) and passing the needle through the opening ( 25 ): slightly pry , the slot open and press the needle head ( 3 ) through the slot and into the hollow center of the plunger . third , install the plunger needle seal ( 7 ) [ this could have been done earlier ]. fourth , install the plunger piston ( 6 ) [ this could have been done earlier ]. finally , install the guide wire / valve ( 11 ) assembly by inserting through the plunger opening ( 39 ), guiding it through the hollow needle ( 4 ). guide wire head ( 1 ) is then force fitted into the plunger opening ( 39 ) completing the needle retraction sub - system ( generally 18 ). the barrel assembly ( generally 15 ) shown in fig6 is a standard syringe barrel assembly . a barrel assembly consists of the finger flange ( 28 ) with its associated flats ( 29 ); the barrel itself ( 8 ); and the tip ( not numbered ) in which there is generally a &# 34 ; luer lock &# 34 ; thread ( 35 ) for the receipt of a standard needle . an alternate assembly is shown in fig6 a ; the only difference being in the finger flange ( 28 ) design which has a slot ( 29a ) rather then the flats of a standard barrel . the barrel tip ( not numbered ) also contains a nipple ( 30 ) with an opening through which the hollow needle ( 4 ) can pass . in this instant invention the barrel assembly also includes a barrel cap sub - assembly ( generally 16 ) which consists of the barrel needle seal ( 9 ) and the barrel cap ( 10 ). the barrel cap ( 10 ) has corresponding luer lock tabs [ or flats ]( 36 ) which allow the cap to be drawn up tight against the barrel nipple via the luer lock threads ( 35 ) thus forcing the barrel needle seal ( 9 ) against the barrel nipple and its opening ( 30 ). in discussing the pressure sampler and its preferred embodiment , the preferred barrel needle seal assembly is shown in fig7 a . fig7 a is a cross - section of the barrel cap assembly shown in place on the barrel . the barrel cap ( 10 ) is shown with flange ( 46 ) which is not necessary for the pressure sampler mode , but is shown as most manufacturers would prefer to make one part for use in all versions of the safety syringe . the cap ( 10 ) holds a packing gland ( 38 ) in place against the barrel nipple ( 30 ). after the hollow needle is placed through opening ( 30 ) in the barrel [ during assembly ], packing gland ( 38 ) is squeezed between the barrel nipple and the barrel cap by simply tightening the barrel cap within the luer lock . the tightened packing gland ( 38 ) then forms the barrel needle seal ( 9 ) for the pressure sampler . experience has shown that a tight seal is needed at the barrel end of the needle to stop fluids from escaping around the needle . fig7 d shows an o &# 39 ; ring variation of the barrel needle valve seal . this alternate embodiment will work for all modes of operation of the safety syringe ; however , slight leakage will occur when the needle is retracted . thus in the sampler modes , a packing gland or self sealing rubber seal must be added to prevent leakage or contamination of the sample when the needle is retracted . the packing gland ( 38 ) of fig7 a or the rubber tip ( 41 ) of fig7 b can be utilized . the alternate barrel needle seal assembly consists of the barrel cap ( 10 ) with an o &# 39 ; ring seat ( 46 ) molded within . an o &# 39 ; ring ( 47 ) is placed in the seat and the cap is then placed over the hollow needle ( 4 ) and tightened against the barrel using the luer lock ( 35 and 36 ). it should be realized that the cap ( 10 ) will have to be manufactured to fit different sized needles as needed . the preferred embodiment for the pressure sampler barrel cap assembly will fit a number of different sized needles and would be cheaper and simpler to manufacture . fig7 e shows the barrel needle seal assembly moved to within the barrel itself . this variation of the seal also uses an o &# 39 ; ring ( 49 ) placed within an o &# 39 ; ring seat ( 48 ) molded within the barrel nipple . this variation of the barrel needle seal will function with all embodiments of the safety syringe . the drawback is manufacturing complexity and the fact that the barrel will no longer be a manufactured standard thus increasing its cost . the completely assembled pressure sampler is shown in fig8 a through 8d . all that remains is to explain its operation . the pressure sampler as it would appear when removed from its sanitary container is shown in fig8 a . the hollow needle ( 4 ) is shown in its extended position although it would be possible to package the device with the needle retracted . the hollow needle is latched in its extended position by the lever arm latch ( 21 ) located on the lever arm ( 20 ). the lever arm latch ( 21 ) catches under the finger flange ( 28 ) of the barrel and holds the hollow needle ( 4 ) extended . in the extended position the needle port ( 22 ) is at or near the bottom of the barrel and the guide wire / valve ( 2 ) is located above the port ( 22 ) thus leaving the port in communication with the needle bevel ( 33 ). to use the device in its pressure sampler embodiment , the hollow plunger is withdrawn , as shown in fig8 b , to the required sample volume . the sampler is then inserted and arterial pressure will force the blood sample through the bevel ( 33 ), through the port ( 22 ) and into the barrel . air ( or inert gas ) within the barrel will be displaced through the &# 34 ; microfilter &# 34 ; plunger needle seal assembly ( 7 ) and into the hollow plunger . that air will then flow out of the plunger slot ( 24 ) to the atmosphere . once the blood sample reaches the &# 34 ; microfilter &# 34 ;, it will swell and shut off all flow as well as seal the hollow needle ( 4 ) from the hollow plunger ( 5 ). that is no fluid will escape past the plunger needle seal ( 7 ). the sampler is then withdrawn from the subject , which now exposes the contaminated needle ( 4 ) and the needle bevel ( 33 ). the hollow needle ( 4 ) is easily retracted to its safe position . the worker rotates the plunger assembly so that the needle lever latch ( 21 ) is aligned with the barrel finger flats ( 29 ). in the alternate embodiment shown in fig6 a , the lever latch ( 21 ) would be rotated until it aligns with the slot ( 29a ) at which the latch would clear the finger flange ( 28a ). this means that the latch ( 21 ) is no longer constrained by the flange and the lever arm ( 20 ) may be pulled upwards towards the top of the hollow plunger ( 5 ). the lever arm ( 20 ) slides up the hollow plunger ( 5 ) via the slot ( 24 ) in the plunger . as the hollow needle moves up inside the hollow plunger the needle bevel ( 33 ) moves inside the syringe barrel . at the same time the guide wire / valve ( 2 ), which is fixed , slides within the hollow needle sweeping sample fluid contained within the hollow needle into the barrel via port ( 22 ) which is the shortest flow path . the guide wire / valve ( 2 ) will eventually pass port ( 22 ) and seal it . the needle port ( 22 ) will eventually pass the plunger needle assembly ( 14 ) and position itself within the hollow plunger ( 5 ). if the port ( 22 ) were not valved shut by the needle guide wire / valve ( 2 ) fluid could leak into the hollow plunger ( 5 ) and come out of the slot ( 24 ) and into contact with the world . in a similar manner , the outside world cannot come into contact with the sampled fluid as the communication between the needle port ( 22 ) and the bevel ( 33 ), which is now within the barrel , is cut off by the guide wire / valve ( 2 ). finally , as the hollow needle ( 4 ) retracts past the barrel needle seal assembly ( 16 ) the packing gland ( 38 ) will close about itself and retain the sample fluid within the barrel . as the lever arm ( 20 ) is drawn upwards within the plunger , the needle head ( 3 ) eventually comes in contact with the retraction locking ramps ( 34 ). these ramps allow the needle head to slide inside them but do not allow the head to slide out . thus the retraction ramps ( 34 ) permanently latch the needle ( 4 ) in a retracted position . it should be apparent that the retraction ramps ( 34 ) could be modified to allow a further extension of the needle . the fully retracted and latched needle is shown in fig8 c . the sample contained with the barrel is fully isolated from the outside world by the guide wire / valve ( 2 ), the plunger needle seal ( generally 7 ) and the barrel needle seal ( 9 ). thus the sample cannot be contaminated nor can the sample leak out and contaminate others . all that remains is to eject the sample into an analysis machine . this operation is shown in fig8 d where the plunger ( 5 ) has been pushed back down into the barrel ( 8 ) thus forcing the sample fluid out past the barrel seal ( 7 ), through the cap ( 10 ) and into the machine . if difficulty is experienced in forcing the fluid out the packing gland ( 38 ) can be loosen by unscrewing the cap ( 10 ) or a special form of the gland which incorporates a check valve could be employed . note that the retracted hollow needle ( 4 ) remains within the syringe and does not interfere with the ejection operation . the alternate variations of the barrel needle seal ( 9 ) would work in a similar manner . in the case of o &# 39 ; ring seals ( 47 ) in fig7 d and ( 49 ) in fig7 e there could be contamination of the fluid or some fluid could leak out . the problem could easily be solved by adding a resealable rubber covering of the type used in serum vials . in fact a modified self closing o &# 39 ; ring or a packing gland could be used . these systems would increase the cost of manufacture but are not beyond the scope of this invention or disclosure . turning now to another major embodiment of the invention which also involves sampling but in the form of aspiration sampling . this technique is similar to pressure sampling except that the sample is drawn from the subject by vacuum within the barrel ( 8 ). the vacuum is formed by inserting the sampler with the - plunger ( 5 ) in the full down position and then slowly withdrawing the plunger ( 5 ) until the required sample is drawn into the barrel ( 8 ). the only change needed in the preferred embodiment of the pressure sampler previously described is in the plunger needle seal assembly . this seal must be capable of holding a vacuum . thus the assembly shown in fig4 as item 7b would be a rubber seal rather than the &# 34 ; microfilter &# 34 ; seal ( 7a ). of course the seal could be an o &# 39 ; ring in a seat molded into the plunger opening ( 25 ). an o &# 39 ; ring seal system for the plunger opening ( 25 ) is shown in fig9 . an o &# 39 ; ring seat ( 51 ) is molded into the plunger opening ( 25 ) and an 0 &# 39 ; ring ( 50 ) is placed in that seat . the piston ( 6 ) is shown with a microfilter ( 7a ) and piston spacers ( 52 ). this particular embodiment will now function exactly like a presently available sampling syringe which is designed to operate in both the aspiration mode and the pressure mode . when the syringe is operating in the pressure mode , displaced air within the barrel passes through the microfilter ( 7a ) and between the molded hollow plunger ( 5 ) and the space caused by the piston spacers ( 52 ). when fluid reaches the microfilter , it seals off . to eject the sampled fluid , the plunger is pressed downwards and the piston will press hard against the piston spacers ( 52 ) and the plunger lip ( 54 ) to form a complete pressure seal . when the syringe is used in the aspiration mode a vacuum must be formed within the barrel when the plunger ( 5 ) is withdrawn . this is easily accomplished by the piston ( 6 ), for as it is pulled back , the piston moves downward and seals against the plunger lip ( 54 ). thus it can be seen that this invention can operate very easily in conjunction with an existing combination mode ( pressure and aspiration ) sampler . fig9 also illustrates how an o &# 39 ; ring plunger seal system would operate in the injection mode . it would be possible to mold the o &# 39 ; ring into the needle opening within the piston ( 6 ). these various seal system are considered to be within the scope of this invention . the barrel needle assembly has several more options . the packing gland system of the pressure sampler can still be employed , but the preferred embodiment would be that shown in fig7 b . a minor modification or manufacturing step is added to the barrel cap ( 10 ). the cap ( 10 ) needs a needle guide ( 42 ) which is placed inside the cap opening as shown . in addition an outside rubber cap ( 41 ) is placed over the outside of the barrel cap ( 10 ) and held in place by lip ( 46 ). the rubber cap ( 41 ) is the same material that is used in serum vials which is a self sealing silicon rubber or equivalent . as vacuum is drawn within the barrel , atmospheric pressure will force the rubber against the hollow needle ( 4 ) thus maintaining the seal . after the needle ( 4 ) is retracted the rubber cap ( 41 ) will self seal and stop any chances of contamination . in a similar manner the barrel needle assemblies of fig7 d and 7e could be used . the problems and limitations discussed under the pressure sampler embodiment would also apply to this variant on the seal . the operation of the aspiration sampler follows standard procedure . with the needle extended as in fig8 a the needle ( 4 ) is inserted into the subject . the plunger ( 5 ) is then withdrawn and the sample passes up the needle ( 4 ) into the barrel ( 8 ) in exactly the manner described above . once the required volume is obtained , the needle ( 4 ) is withdrawn from the subject exposing the contaminated bevel ( 33 ). the needle ( 4 ) is then retracted in the manner described above . the port ( 22 ) will seal , the plunger will seal , and the sample will be sealed . turning now to the last major embodiment of the instant invention in which the safety syringe is used for pure injection . the syringe would of course be used with the needle ( 4 ) extended and the retraction scheme is exactly as previously described . there are some major or minor changes as seen fit . first , the safety syringe does not need the needle port ( 22 ) shut off valve as there will be no fluid in the barrel to leak through this port after injection and after retraction of the needle . second the needle head ( 3 ) must be capped ( i . e . the opening passing through it must be closed ) or the opening should not be present because the guide wire valve assembly is not required . use of the guide wire valve assembly would be a pure manufacturer &# 39 ; s choice -- money could be conserved by leaving this assembly out . this embodiment is shown in fig5 a . here the opening in the top of the plunger head or thumb flange ( 39 ) could be capped with a plug ( 37 ), although this is not strictly necessary , for the comfort of the technician . the plunger needle seal ( 7b ) must be capable of resisting pressure which can be accomplished by a rubber packing or through an o &# 39 ; ring seal . since injection needles are small there is a possibility of fracture at the needle port ( 22 ). safety barbs ( 40 ) will be needed to ensure that a broken needle will come out of the subject . the safety barbs ( 40 ) would be designed to catch against the tip of the barrel needle ( 30 ) and not be able to pass through it . thus if a needle does indeed break at the needle port then it will stay attached to the safety syringe . the barrel needle seal assembly ( 16 ) can take several forms . the original packing gland of fig7 a can be used or the o &# 39 ; ring variations of fig7 d and 7e may be employed . the o &# 39 ; ring variations would be ideal in this case as leakage after the needle is withdrawn is not critical nor is there any requirement for sealing of the sample within the barrel [ there is nothing in the barrel ]. the only disadvantage would be cost . an alternate barrel needle seal assembly is shown in fig7 c . this seal assembly also employs a needle guide ( 45 ) and resealable rubber gasket ( 43 ) as explained for the aspirator sampler . because the pressure is exerted from within the barrel the resealable rubber gasket ( 43 ) must be placed inside the barrel cap ( 10 ). the rubber gasket ( 43 ) is placed over the needle guide ( 45 ) and held in place by tabs ( 44 ) on the needle guide . this assembly is placed within the barrel cap ( 10 ) which in turn is screwed in place on the luer lock ( 35 ). the seal assembly is then held in place between the barrel nipple ( 30 ) and the barrel cap ( 10 ). the hollow needle ( 4 ) passes through the rubber gasket ( 43 ). whenever injection pressure is applied to the device the rubber will force up against the hollow needle ( 4 ) and seal . one more variation of the barrel needle seal is illustrated in fig9 . here the barrel cap ( 10 ) has an 0 &# 39 ; ring ( 47 ) and an 0 &# 39 ; ring seat ( 46 ) molded into its tip . this o &# 39 ; ring will tightly seal the hollow needle ( 4 ). in order to make certain that no sample fluid drips from the barrel and to ensure that the sample fluid cannot be contaminated , a self sealing silicon rubber seal ( 53 ) is placed between the barrel nipple ( 30 ) and the inside of the barrel cap ( 10 ). the action of the luer lock ( 35 and 36 ) will hold this rubber seal in place . operation of the safety syringe as an injection syringe would be the same as a regular syringe . the serum would be drawn into the barrel ( 8 ) via the needle bevel ( 33 ) and the needle port ( 22 ) whenever the plunger is withdrawn . the needle would inserted into the subject and serum would flow in the reverse direction whenever the plunger is depressed . after use , the needle would be retracted in the manner already explained . as can be seen the safety syringe will meet all criteria for a retractable needle safety syringe . the instant invention will serve as a simple injection device and as a sampler device in two modes , pressure or aspiration . the device can serve as its own protector before use by packaging it with the needle retracted . the device can be manufactured from mostly standard syringe components , but variations in seal arrangements are available to improve the device . it would be possible to package the device with preloaded serum or to supply the device &# 34 ; heparinized &# 34 ; when used for arterial blood gas sampling . it should be apparent that the descriptions in this invention show three uses for the device but the use is only limited by the imagination of the user . the device is designed for medical use but could easily find use in the laboratory ; for example , in gas chromatography .
three versions of a safety syringe are disclosed which can be used as a pressure sampler syringe , an aspiration sampler syringe , or a regular hypodermic injection syringe . the device has a manually retractable needle which withdraws to inside the syringe after use ; thus , protecting the user from accidental stabbing by an exposed used needle . the syringe plunger can still function to expel entrained fluids after the used needle is retracted to the &# 34 ; safe &# 34 ; position , which allows the syringe to be used as a blood gas analysis sampler . additionally the sampler versions of the syringe will completely seal the sampled fluid from the atmosphere , thus assuring no contamination of the sample . the device consists of three basic parts , a retractable needle and seal assembly , a standard syringe barrel , and a modified plunger which stores the retracted needle .