Abstract:
A retractable syringe, comprising a needle having a tip and a base, a needle collar coupled to the needle, the needle collar including at least one groove disposed in a bottom portion of the needle collar and extending from the portion of the needle collar nearest to the base of the needle toward the tip of the needle, a fitting coupled to the needle collar and including a sealing element disposed between a first portion of the fitting and the needle collar, a barrel unit, the barrel unit designed for coupling to the fitting, a plunger unit having a piston on a first end of the plunger unit, the plunger unit and piston being positioned in the barrel unit, an extractor element coupled to the first end of the plunger and having a proximal end adjacent to the plunger and a distal end, the extractor element designed for coupling to the needle collar and encompassing at least a portion of the at least one groove.

Description:
FIELD OF THE INVENTION 
     The field of the present invention relates to safety syringes. 
     BACKGROUND OF THE INVENTION 
     A typical hypodermic syringe includes a transparent cylindrical barrel, generally open at a proximal end, a plunger assembly movable within the barrel to dispense medication, and a needle assembly removably attached to the barrel at a distal end by means of a locking mechanism, such as Luer lock or Luer slip. During usage, medication is sealed within open side of the barrel by means of a rubber piston slipped over the distal end of the plunger. At the distal end of the syringe, sealing is accomplished through a sealant, such as an epoxy resin, extending between the outer surface of the needle and the lock hub carrying the needle. This sealant, and the locking mechanism fastening the needle assembly to the barrel, are also used to transmit the force, which may be as high as several pounds, required to insert the needle into the patient&#39;s body and to remove the needle after the injection process is complete. The applications of hypodermic syringes within a health care facility require the availability of syringes varying particularly in needle length and diameter, and in the dosage capacity of the barrel. To satisfy this need, needles and the remaining portions of syringes are made commercially available both as assembled units, and as separate units allowing the attachment of a selected one of the various needle assemblies to a selected one of various barrels. The Luer lock fittings used to fasten the needle to the barrel form a basis for 
     It is thus desirable that any improved design for hypodermic syringes should include the capability of switching needles among the syringes. It is even more desirable that any improved design for hypodermic syringes should be capable of using standard needle assemblies, and that the new needle assemblies should be usable in standard syringe barrels. 
     Modern medical practice dictates that, in order to eliminate a possible source of contagious disease, hypodermic syringes are used only once. There is a growing concern, even when syringes are discarded immediately after use, that health care workers may be accidentally stuck by a hypodermic needle which has been used in the treatment of a patient having a serious communicable disease, such as AIDS or hepatitis. Used hypodermic needles have become an especially dangerous form of waste material, posing a danger to anyone handling trash from a health care facility and to anyone who might come into contact with such material after it has been dumped, and requiring special puncture resistant containers for disposal. 
     Another problem commonly associated with discarded hypodermic syringes is their potential use by drug abusers, who sometimes search waste material from health facilities for such devices. This practice obviously carries a significant risk of infection to these drug users and to others they may subsequently contact. 
     Conventional hypodermic syringes included an inward extending ring near the proximal opening of the barrel, which forms a stop, preventing the inadvertent removal of the plunger from the barrel. However, this ring is generally not rigid enough to prevent the deliberate, surreptitious removal of the plunger, as by a drug abuser. 
     One prior art solution to the aforementioned problems has been to enclose the needle in a sheath manually slipped over the needle end before and after use of the syringe. However, this technique still exposes health workers to the risk of being stuck with an infected needle as the sheath is slipped on, particularly when the needle is not properly aligned with the sheath opening. Furthermore, this technique does nothing to render the syringe useless to a drug abuser. 
     Another prior art solution to the aforementioned problems is breaking the needle from the syringe once it is used. While this procedure is followed in a number of health care facilities, there are still several disadvantages to this procedure. First, the broken needles are not necessarily enclosed in a way permitting their subsequent safe handling, and second, the additional handling of used needles by health care workers in the process of breaking the needles may increase the risk of their being accidentally stuck by an infected needle. 
     One attractive solution to the aforementioned problems is in providing a syringe/needle assembly in which the needle may be retracted into the barrel of the syringe after use, so that the needle is held in an envelope formed by the barrel during disposal. The patent literature includes descriptions of devices of a first general type, in which a needle is fastened to a needle carrier which travels axially within the barrel. In its distal position, the carrier holds the needle ready for use at the distal end of the barrel. After the plunger assembly is moved to the distal end of the barrel, after dispensing the desired medication, the plunger assembly engages and locks onto the needle carrier. When the plunger assembly is subsequently withdrawn and returned to the proximal end of its travel, the needle is carried with the plunger until it is completely enclosed within the barrel. At this point, the syringe ready for proper and safe disposal. Examples of syringes of this type are found in U.S. Pat. No. 4,710,170, issued to Haber et al on Dec. 1, 1987; in U.S. Pat. No. 4,790,822, issued to Haining on Dec. 13, 1988; and in U.S. Pat. No. 4,883,471, issued to Braginetz et al on Nov. 28, 1989. 
     In the prior art devices, the needle is fastened to the needle carrier by conventional means. For example, needle may be fastened to a Luer lock hub, which, in turn, is screwed onto a threaded hole forming internal surfaces in the needle carrier. Thus, syringes of this kind have the advantage of being capable of using standard needle assemblies of the types widely available for syringes not incorporating the safety feature of needle retraction. If the syringe is provided with its needle carrier at the distal position, an interchangeable needle may be screwed into the syringe from the distal end, in the conventional manner. However, the barrels of syringes of this type, of necessity, have relatively large openings at their distal ends, to accommodate the motion of the needle, together with a portion of the needle carrier as it is retracted into the barrel. This large opening, in turn, significantly increases the complexity and cost of the device by requiring fluid tight sealing around the outside of the needle carrier, so that medicine can be dispensed through the needle without leakage out of the distal end of the syringe. 
     Furthermore, the needle carrier of the prior art devices occupies a significant portion of the axial length of the barrel. The conservation of distance along this length is especially important in a syringe having a retractable needle because the space is needed for storage of the needle after use. Conventional syringes are built to particular sizes for convenient handling and use, as well as for various barrel capacities for medication. For example, the barrels of typical syringes having either three cubic centimeter and five cubic centimeter capacities are about 2.5 inches in length, with the difference in capacity being accomplished by varying the diameter. A typical long needle extends 1.5 inches from the end of the Luer hub to which it is attached. Including this hub, the length of the needle assembly is about 2.125 inches. Thus, the use of a needle carrier of the prior art requires lengthening the barrel beyond the length necessary for handling and capacity, thereby decreasing the ease and familiarity with which the syringe is handled and further increasing its costs of manufacture and distribution. 
     The device of U.S. Pat. No. 4,883,471 to Braginetz et al mounts the needle carrier in a second piston. After the medication is dispensed, vent ports are opened by rotating a cap at the distal end of the syringe, so that the atmosphere is allowed to enter the syringe at the distal end of this second piston. The retraction of the piston, with the needle, is then accomplished by the differential pressure established as the plunger is withdrawn. However, rotating the cap in this way presents the health care worker with the inconvenience of an extra step in the process. 
     The patent literature also describes devices of a second general type, in which the needle assembly is loaded into the syringe barrel from inside the barrel, to stick outward through a relatively small opening in the distal end of the barrel. After the injection of medicine by means of the plunger assembly, the needle assembly is attached to the distal end of the plunger assembly to be retracted into the syringe barrel as the plunger assembly is pulled back toward the proximal end of the barrel. 
     While syringes of this type address the concerns expressed above relative to the use of a separate needle carrier, they lack the important ability to use conventional needle assemblies, which are adapted to be screwed into place using Luer couplings from outside the distal end of the barrel. In addition, if interchangeable needles are to be used in any way on the syringes, they must be attached by relatively difficult or complex means within the barrels. Further, by changing a needle through the barrel, the sterility of the barrel can be violated. 
     Some devices of this second general type, in which the needle is loaded from inside the barrel, include couplings between the needle assemblies and the distal ends of the barrels, which are connected and disconnected by the rotation of the needle assembly within the barrel, being described, for example, in U.S. Pat. No. 4,507,i17, issued to Vining et al on Mar. 26, 1985; in U.S. Pat. No. 4,675,005, issued to DeLuccia on Jun. 23, 1987; in U.S. Pat. No. 4,747,830, issued to Gloyer et al on May 31, 65 1988; in U.S. Pat. No. 4,919,652, issued to Alter et al on Apr. 24, 1990; and in U.S. Pat. No. 4,986,813, issued to Blake III et al on Jan. 22, 1991. While DeLuccia, Alter, and Blake III teach the use of threaded screw connections, Vining and Gloyer uses quick release, quarter turn types of connection. Vining also describes means for providing the syringe, before use, with the needle retracted for safe handling. A disadvantage of these syringes is the additional requirement that the plunger must be twisted after an injection is given, before disposal of the syringe with the needle assembly in a retracted position. This twisting is needed to engage the needle assembly to the plunger assembly, and to disengage the needle assembly from the distal end of the barrel. However, this requirement places a burden on health care workers in an emergency situation, and can be expected to result in a failure to properly retract needles in some units before disposal. 
     Other devices of this in which the needle is loaded through the barrel interior include means for engaging the proximal end of the needle assembly with a mechanism extending from the distal end of the plunger assembly as the plunger mechanism reaches the distal end of its travel in dispensing medicine through the needle. Such devices are described, for example, in one of the embodiments of U.S. Pat. No. 4,675,005 to DeLuccia; in one of the embodiments of U.S. Pat. No. 4,692,156 to Haller; and in U.S. Pat. No. 4,804,370, issued to Haber et al on Feb. 14, 1989. In this Haber device, the needle extends outward through a small hole at the distal tip of the syringe barrel. The proximal end of the needle is provided with a flange, and the plunger assembly is provided with a needle capturing receptacle which engages this flange as the plunger assembly is moved to the distal end of the barrel, so that the needle is subsequently retracted into the barrel as the plunger assembly is withdrawn. 
     While such devices are operable without requiring the additional step of twisting the plunger after medicine is dispensed, they are still inconvenient to use, when compared to conventional syringes, because they do not accept conventional needle assemblies, and because, if it is necessary to install any type of needle assembly, the installation procedure is relatively complex and would violate the integrity of the sterility. 
     An important consideration in the design of a hypodermic syringe is the ability of the device to transmit axial forces to the needle from the barrel and plunger. Forces as high as several pounds may be required, both to insert the needle into the patient, and to withdraw the needle from the patient during the process of giving an injection. If the needle is to be retracted into the barrel of the syringe, means must be provided to prevent this retraction during the insertion of the needle into the patient, due to the necessary application of force to the needle as it is inserted. 
     In the devices having needle assemblies connected to the barrels with screw threads or quarter turn fasteners, to be disconnected by rotation of the plunger after the medication is dispensed, these fasteners prevent premature retraction of the needle. These devices are shown, for example, in U.S. Pat. Nos. 4,507,117, 4,675,005, 4,747,830, 4,919,652, and 4,986,813. While this method of holding the needle in place during injection is quite effective, the disadvantages of requiring the performance of the additional manual rotation step and nonstandard components remains. 
     In those devices having means for engaging the proximal end of the needle assembly with a mechanism extending from the distal end of the plunger assembly, the connection between the needle and the barrel must be strong enough to hold the needle in place as it is inserted into the patient. Further, the needle must subsequently be pulled directly out of this connection for retraction. Both of these actions are accomplished by applying an axial force to the needle. In the devices of U.S. Pat. No. 4,692,156 to Haller, the needle is mounted in an aperture within a deformable tapered mounting post, which deforms to slide through a passage in the barrel during retraction. In other devices, as shown, for example in U.S. Pat. Nos. 4,804,370 and 4,826,484 to Haber et al., the needle is retained by a tight fit within a distal hole of the barrel. This means that, for reliable operation, the force which must be applied for needle retraction, to overcome the attachment between the needle and the barrel, must be greater than the highest force expected during the insertion of the needle into the patient, together with a safety factor applied to cover variations in the process of manufacturing the syringe. If the needle is to be retracted during withdrawal from the patient, this force must be even higher. The requirement to apply such a large force places a significant burden on health care personnel and creates a potential danger to the patient. 
     The device described in U.S. Pat. No. 4,710,170 to Haber et al includes a needle carrier which is held in place within the barrel by means of a quick release fastener. After the dispensing of medication is completed, the plunger is manually rotated to release the carrier from engagement with the barrel. Thus, a requirement to perform an additional step is placed on health care personnel. 
     The device described in U.S. Pat. No. 4,790,822 to Haining includes a needle carrier which is held in place at the distal end of the barrel by opposing shoulders extending inward from the interior of the barrel. As the plunger is moved to the distal end of the barrel, a piston at the distal end of the plunger forces these shoulders apart, releasing the carrier to return with the plunger. 
     The patent literature also describes apparatus for causing the needle to be rotated transversely, about its attachment to the plunger as it is retracted into the barrel, to point toward a side of the barrel. This is done to prevent accidental or deliberate extension of the needle through the hole in the distal end of the barrel, by means of pushing the plunger inward. In other words, this feature provides further safety for health care and trash disposal workers, and goes another step toward preventing the subsequent use of the syringe by drug abusers. For example, U.S. Pat. No. 4,804,370, issued to Haber et al on Feb. 14, 1989, describes needle capturing receptacle with legs, for capturing a flange at the proximal end of the needle. Two of the legs are shorter than the others, so the needle is rotated transversely as it is retracted. As described in U.S. Pat. No. 4,986,813 to Blake III et al, a syringe includes a fitting fastening the needle assembly to the distal end of the plunger for retraction with a slot, extending inward from one side of the fitting, which is allowed to expand as the needle is fully retracted, throwing the needle out of alignment with the longitudinal axis of the plunger. 
     Blake III also describes the use of stopping surfaces extending into the barrel near its proximal end, angled to prevent removal of the plunger from the barrel, while allowing its assembly into the barrel as the syringe is fabricated. Such surfaces make it particularly difficult for a drug user to take the syringe apart to make it again operable or to retrieve the needle. 
     Thus, while the feature of needle retraction can be accomplished in a number of ways, the methods proposed in the prior art for providing this feature all have various disadvantages. What is needed is apparatus for providing needle retraction without substantially increasing the size or length of the syringe, as required when a separate needle carrier is employed, and without requiring the performance of an additional step, such as the rotation of the plunger, by health care personnel. Since health care facilities must carry a relatively large inventory of different sizes and types of syringes and needles, it is desirable that an improved syringe should accept the removal and attachment of needles in the standard way, from outside the distal end of the barrel. It is further desirable that the needle be releasibly held in place by positive means, such as a latch or movable abutting surface, rather than by reliance on a tight fit. Also, since conventional hypodermic syringes are low cost items used in large quantities by health care facilities, it is particularly desirable that the feature of needle retraction should be provided by a mechanism which is inherently simple and low in manufacturing cost. In particular, any improved syringe ideally will use existing syringe parts or slight modified parts so that existing mold tooling can be used. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, there is provided a hypodermic syringe including a container for ejecting fluid having an internal cavity between a fluid ejecting end thereof and a proximal end thereof. The container also has a piston assembly having a seal end movable from the proximal end to the fluid ejecting end to eject fluid and retractable towards the proximal end. The syringe further includes a needle attachment assembly affixed to the fluid ejecting end of the container, the needle attachment assembly having a hollow first column with an opening extending therethrough in fluid communication with the cavity. The column is tapered inward at a distal end thereof and has a plurality of slits from the distal end thereof towards the container separating a plurality of segments at the distal end. In addition, the syringe includes a needle subassembly, including a needle with hole extending axially there-through, and a needle flange affixed remote from one end of the needle. A second hollow column extends from the flange towards the one end and is sized to fit within the first column opening such that the end of the segments are juxtaposed to one surface of the flange. The needle subassembly further includes means juxtaposed to the other side of the flange for holding the needle subassembly on the attachment assembly column. Finally, the syringe includes needle extractor means, including a third hollow column affixed to the seal end of the piston assembly. The third column is sized such that the exterior thereof enters the first column and separates the segments so that the ends thereof are spaced from the one surface of the flange. The third column further is sized such that the interior thereof grabs the second column and the needle assembly, including the flange is retracted through the first column upon retraction of the piston assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the subject invention are hereafter described with specific reference being made to the following Figures, in which: 
         FIG. 1  depicts another embodiment of a hypodermic syringe. 
         FIG. 2  depicts one embodiment of a needle collar. 
         FIG. 3  depicts one embodiment of a Luer nut used in a hypodermic syringe. 
         FIG. 4  depicts one embodiment of a Luer nut engaging a barrel, a needle collar and the needle. 
         FIG. 5  depicts another embodiment of a Luer nut and a needle collar. 
         FIG. 6  depicts one embodiment of a plunger. 
         FIG. 7A  depicts one embodiment of the needle collar. 
         FIG. 7B  depicts another embodiment of a needle collar. 
         FIG. 8  depicts a cross section of one embodiment of a piston. 
         FIGS. 9A and 9B  depict one embodiment of bumps on an inner surface of a barrel. 
         FIG. 10A  depicts one embodiment of a syringe. 
         FIG. 10B  depicts another embodiment of a syringe. 
         FIG. 11  depicts one embodiment of a catheter Luer fitting. 
         FIG. 12  depicts one embodiment of a catheter Luer fitting engaging a Luer nut. 
         FIG. 13A  depicts one embodiment of a syringe with a Luer nut attached to the syringe. 
         FIG. 13B  depicts of a top view of one embodiment of the collar. 
         FIG. 13C  depicts one embodiment of the end of the barrel. 
         FIG. 13D  depicts one embodiment of the collar engaging the end of the barrel. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts another embodiment of a hypodermic syringe  100 . The hypodermic syringe  100  includes a needle cover  102 , a Luer nut  104 , a needle  106 , a needle collar  108 , a barrel  110 , a piston  112 , a plunger  114  and an extractor  116 . In one embodiment, the needle  106  is inserted and held by the needle collar  108 . The needle collar  108  is then inserted into the Luer nut  104  which connects to the barrel  110 . The piston  112  connects to one end of the plunger  114  before the plunger  114  is inserted into the barrel  110 . 
       FIG. 2  depicts one embodiment of the needle collar  108 . The needle collar  108  is mostly cylindrical in shape and includes an upper portion  302 , a lower portion  304 , a neck portion  306  which separates the lower portion  304  from the upper portion  302  and a central channel  308  extending through the upper portion  302 , the neck  306  and at least midway through the lower portion  304 . The central channel  308  includes a first portion  307  that is sized to engage and hold the needle  106  and a second portion  309  that has a larger diameter than the first portion  307  to accommodate an adhesive for securing the needing in the central channel  308 . The upper portion  304  includes a first side  310  and a second side  312  with the first side  310  being narrower in cross sectional width than the second side  312  such that the lower portion  304  tapers from the second side  312  towards the first side  310 . The neck portion  306  is positioned at the end of the upper portion  302  closest to the lower portion  304  and the neck portion  306  connects to the lower portion  304  by a shaft  314 . The neck portion  306  has a cross sectional width that is wider than the widths of each of the upper portion  302  and the lower portion  304 . The neck portion  306  has an lower end  316 , a central portion  318  and an upper end  320 . The central portion  318  tapers towards the lower end  316  where it meets the shaft  314  and the central portion  318  includes a tapered section  320  that tapers towards the upper end  322  where it meets the upper portion  302 . The shaft  314  is connected to the second side  312  of the lower portion  304  of the needle collar  108 . 
       FIG. 3  depicts one embodiment of a Luer nut  104  used in a hypodermic syringe  100 . Consistent with this embodiment, the needle  106  is coupled to the needle collar  108  which is inserted into the Luer nut  104 . The Luer nut  104  has a substantially cylindrical shape and includes an upper portion  202  and a lower portion  204  with a first opening  206  on the upper portion  202  and a second opening  208  on the lower portion  204 . The first opening  206  is sized to accommodate the needle collar  108 . The needle collar  108  is held in the Luer nut  104  by the flexible seal  212 . A central channel  216  extends through the Luer nut  104  with the central channel  216  having a larger cross sectional width in the lower portion  204  than in the upper portion  202 . In one embodiment, the Luer nut  104  includes a threaded portion  210  that is coupled to a corresponding threaded portion of the barrel  110 . In another embodiment, the Luer nut  104  is a Luer slip which slips onto the end of the barrel  111  and is held in place by friction. 
     The flexible seal  212  is created at an interconnection of the upper portion  202  with the lower portion  204 . The flexible seal  212  is configured to create a seal between the Luer nut  104  and the needle collar  108  such that fluid in the barrel does not escape when transferred from the barrel  110  to the needle  106 . When the needle collar  108  engages the flexible seal  212 , the flexible seal  212  expands to create a seal with the tapered section  320  of the neck portion  306  of the needle collar  108  the lower portion  302  of which is inserted into the second opening  208 . 
       FIG. 4  depicts one embodiment of the Luer nut  104  engaging the barrel  110 , the needle collar  108 , the needle  106  and the needle cover  102 . Consistent with this embodiment, the tapered section  320  of the neck portion  306  of the needle collar  108  engages the flexible seal  212  of the Luer nut  104  preventing the needle collar  108  from disengaging the Luer nut  104 . To engage the needle collar  108  with the flexible seal  212 , the needle collar  108  is inserted into the second opening  208  of the Luer nut  104  and moved towards the first opening  206 . As the neck portion  306  of the needle collar  108  moves past the flexible seal  212 , the flexible seal  212  is pushed away from the needle collar  108  until the sides of the neck portion  306  engage the flexible seal  212  preventing the needle collar  108  from moving further into the Luer nut  104 . Further, in this position, the flexible seal  212  is in contact with the sides of the neck portion  306  in such a manner as to create a seal between the flexible seal  212  and the neck portion  306  preventing liquid or air from passing through the seal. 
       FIG. 5  depicts another embodiment of a Luer Nut  104  and a needle collar  108 . Consistent with this embodiment, the flexible seal  212  is replaced by a ring  414  made of a material having memory characteristics. In one embodiment, the ring is an O-ring. The neck portion  406  of the needle collar  408  tapers towards the shaft  314 , but does not taper towards the upper portion  402 . The ring  414  engages the neck portion  406  of the needle collar  408  where the neck portion  406  meets the upper portion  402 . In addition, the flexible seal  212  of the Luer nut  104  is replaced with an opening  418  in the inner portion of the Luer nut  104  where the lower portion  202  meets the upper portion  204 . The opening  418  includes two ledges with the first ledge  420  positioned between the upper portion  204  and the lower portion  202  of the Luer nut  104 . The first ledge  420  is sized such that the upper portion  402  of the needle collar  408  does not engage the first ledge  420 , but a portion of the neck  406  of the needle collar  408  engages the first ledge  420 . The second ledge  422  is sized to accommodate the ring  414  such that the neck  406  of the needle collar  408  compresses the ring  414  into the second ledge  422 . 
     In one embodiment, the upper portion of the first ledge  420  tapers towards the lower portion of the second ledge  422  and the upper portion of the second ledge  422  tapers towards the upper portion  204  of the Luer nut  104 . Consistent with this embodiment, the ring  414  rests on the second ledge  422 . As the needle collar  108  moves from the second opening  208  of the Luer nut  104  towards the first opening  206  of the Luer nut  104 , the neck portion  406  of the needle collar  408  engages the ring  414  forcing the ring  414  upward towards the upper portion of the second ledge  422 . In addition, the ring  416  is sized such that the ring  416  protrudes into the path of the needle collar  408  which causes the upper portion  402  of the needle collar  408  to press against the ring  414  creating a seal between the ring  414  and the second ledge  422  and also holding the needle collar  408  in the Luer nut  104 . 
       FIG. 6  depicts one embodiment of the plunger  114 . The plunger  114  includes the extractor unit  116  positioned at one end of the plunger  114 , an elongated slide  506  and a gripping unit  508 . The extractor unit  116  includes an opening  504  configured to engage the upper portion  304  of the needle collar  108  of  FIG. 1  when the needle collar  108  is coupled to the barrel  110  by the Luer nut  104 . In one embodiment, the extractor unit  116  tapers towards the opening  504 . The opening  504  has a cross sectional width that is wider than the cross sectional width of the first side  310  of the lower portion  304  of the needle collar  108  and smaller than the second side  312  of the lower portion  304 . A force is applied to the plunger  114  which pushes the extractor unit  116  towards the Luer nut  104  holding the needle collar  108  such that the opening  504  engages lower portion  304  of the needle collar  108 . When the plunger  114  is pulled away from the Luer nut  104 , the needle  106  is pulled into the barrel  110  by the extractor unit  116 . 
     The force required to disengage the extractor unit  116  from the needle collar  108  should be greater than the force required to remove the needle collar  108  from the Luer nut  104 . In one embodiment, the force required to disengage the extractor unit  116  from the needle collar  108  is at least twice the amount of force required to pull the needle collar  108  from the Luer nut  104 . In another embodiment, the force required to disengage the extractor unit  116  from the needle collar  108  is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, 125%, 130%, 135%, 140%, 145%, 150%, 155%, 165%, 175%, 180%, 185%, 190% or more than 190% greater than the amount of force required to pull the needle collar  108  from the Luer nut  104 . In one embodiment, the force required to push the extractor unit  116  over the needle collar  108  is approximately 650 grams. In an additional embodiment, the force required to remove the needle collar  108  from the extractor unit  116  is at least 500 grams and the force required to remove the needle collar  108  from the Luer nut  104  is at least 50 grams. In an additional embodiment, the force required to push the extractor unit  116  over the needle collar  108  is 525 grams, 530 grams, 535 grams, 540 grams, 545 grams, 550 grams, 555 grams, 560 grams, 565 grams, 570 grams, 575 grams, 580 grams, 585 grams, 590 grams, 595 grams, 600 grams, 605 grams, 610 grams, 615 grams, 620 grams, 625 grams, 630 grams, 635 grams, 640 grams, 645 grams or any other force capable of pushing the extractor unit  116  over the needle collar  108 , and the force required to remove the needle collar  108  from the Luer nut  104  is 55 grams, 60 grams, 65 grams, 70 grams, 75 grams, 80 grams, 85 grams, 90 grams, 95 grams, 100 grams, 105 grams, 110 grams, 115 grams, 120 grams, 125 grams, 130 grams, 135 grams, 140 grams, 145 grams, 150 grams, 155 grams, 160 grams, 165 grams, 170 grams, 175 grams or any other force capable of removing the needle collar  108  from the Luer nut  104  without disengaging the extractor unit  116  from the needle collar  108 . This guarantees that the extractor unit  116  will not pull off the needle collar  108  after actuation as the plunger  114  is pulled back. In another embodiment, the force required to pull the needle out of the needle collar is at least 5 Kg. 
       FIG. 7A  depicts one embodiment of the needle collar  108 . Consistent with this embodiment, the lower portion  304  of the needle collar  108  includes at least one groove  612  or depression formed longitudinally in the lower portion  304  of the needle collar  108 . In one embodiment, the groove  612  extends along one portion of the lower portion  304  such that a channel is formed through the lower portion  304 . In another embodiment, two or more grooves  612  are longitudinally formed in the lower portion  304  of the needle collar  108 . In another embodiment, the groove  612  acts to prevent the plunger  114  from becoming hydraulically locked in the barrel  110  by providing a path for fluid to flow from the area between the shaft  314  and the extractor unit  116 , down groove  612  and into the needle through opening  311  when the needle collar  108  is engaged by the extractor unit  116 . 
       FIG. 7B  depicts another embodiment of the needle collar  108 . Consistent with this embodiment, the lower portion  304  of the needle collar  108  is substantially cylindrical in shape and includes a channel  316  extending the length of lower portion  304  and connecting to and allowing liquid to flow through the needle. The channel  316  is sized to accommodate the extractor unit  116  such that the extractor unit  116  extends into the opening and the sides of the extractor unit  116  are in contact with the sides of the channel  316 . In one embodiment, the channel  316  is sized such that the extractor unit  116  is secured in the channel  316  by friction. Consistent with this embodiment, the amount of force required to remove the extractor unit  116  from the channel  316  is approximately twice the force required to insert the extractor unit  116  into the channel  316 . In another embodiment, the interior surface of the lower portion  304  includes a plurality of ridges which engage corresponding ridges on the surface of the extractor unit  116  to secure the extractor unit  116  in the channel  316 . Consistent with this embodiment, the amount of force required to remove the extractor unit  116  from the channel  316  is approximately twice the force required to remove the extractor unit  116  from the channel  316 . In another embodiment, the lower portion  304  includes at least one hole  314  that extends to the channel  316  preventing the extractor unit  116  from being hydraulically locked from entering the channel  316 . In one embodiment the extractor unit  116  is shaped like the lower portion  304  shown in  FIG. 7A , including the groove  612 , to allow for the extractor unit  116  and the lower portion to effectively and more easily mate. 
       FIG. 8  depicts a cross section of one embodiment of the piston  112 . The piston  112  is made from a material having memory characteristics such as, for example, natural rubber, synthetic rubber and latex free rubber. The material may also include silicone, polyethylene, plastic or any other malleable material having memory characteristics. The piston  112  includes a first opening  702 , a second opening  704  and a ridge  706  on the inner surface of the piston  112  between the first opening  702  and the second opening  704 . In one embodiment, the first opening  702  and second opening  704  are sized such that the cross sectional width of the first opening  702  and second opening  704  are substantially identical to the cross sectional width of the extractor unit  116 . The piston  112  is slid over the extractor unit  116  such that the ridge  706  engages the flange  510  on the plunger positioned between the extractor unit  116  and the elongated slider  506  (as depicted in  FIG. 6 ) such that the piston  112  is securely coupled to the plunger  114 . The plunger  114  is sized such that the plunger  114  slides into the barrel  110  with the sides of the elongated slider  506  and the piston  112  contacting the inner sides of the barrel  110 . In one embodiment, the end of the piston  112  closest to the needle  106  is tapered towards the needle  106 . By tapering the piston  112 , the force required to move the piston is reduced. In another embodiment, the extractor unit  116  is tapered such that the end of the extractor unit  116  closest to the plunger  114  has a larger cross sectional width than the portion of the extractor unit  116  closest to the opening  702 . 
       FIG. 9A  depicts one embodiment of a cross section of the inner surface of the barrel  110 . Consistent with this embodiment, the inner surface of the barrel  110  includes a first opening  808  and a second opening  810  and a first row of bumps  802  arranged circumferentially around the inner surface of the barrel  110  with a gap between each of the bumps. In one embodiment, a second row of bumps  804  is arranged on the side of the first row of bumps  802  closest to the first opening  808 . Consistent with this embodiment, each of the bumps in the second row  804  is arranged such that they align with the gap between the bumps in the first row of bumps  802 . In one embodiment, each row includes three to four bumps. In another embodiment each row includes more than four bumps. In yet another embodiment one row includes at least three bumps and the other row includes more than three bumps. 
     The rows of bumps  802  and  804  are configured such that the stop disc  512  disposed between the piston  112  and notch  514  (as shown in  FIG. 6 ) is able to move over the first row of bumps  802  in a direction away from the second opening  810 , but are only able to move over the second row of bumps  804  in a direction away from the second opening  810  with the use of a large amount of force. In one embodiment, the notch  514  separates the piston  112  into an upper portion  516  and a lower portion  518 . Consistent with this embodiment, the depth of the notch  514  is sufficient to allow the piston to be separated into two pieces comprising the upper portion  516  and the lower portion  518  of the piston  112  when the piston  112  is bent at the notch  514 . This can be more easily facilitated when the stop disc  512  engages the second row of bumps  804 . At that position, the piston  112  may be bent using the barrel  110  to provide leverage. With sufficient bending force, the piston can be separated into two portions with the upper portion  516  remaining inserted in the barrel  110  and the lower portion  518  remaining exterior to the barrel  110 . In one embodiment, the notch  514  is continuously formed around the circumference of the piston  112 . In another embodiment, the notch  514  is formed from a plurality of individual notches made around the circumference of the piston  112 . 
     In another embodiment, the height of the bumps  802  and  804  are set such that the piston  112  cannot move back towards the needle  102  once the piston is pulled over the bumps  802  or  804  or can only be moved back with a large amount of force In one embodiment, the portion of the bumps  802  and  804  nearest to the first opening  808  rise to a higher level above the inner surface of the barrel  110  than the portion of the bumps  802  and  804  furthest from the first opening  808 . In another embodiment, the bumps  802  and  804  taper from the higher point to the lower point. In another embodiment, the first row of bumps  802  are lower than the second row of bumps  804 . In one embodiment, the force required to pull the piston  112  over the first row of bumps  802  is 1.2-1.6 Kg. In another embodiment, the force to pull the piston  112  over the second row of bumps  804  is at least 5 Kg. 
       FIG. 9B  depicts another embodiment of the barrel  110  that includes a first row of bumps  802  along the inner wall of the barrel  110 , a third row of bumps  806  and a second row of bumps  804  arranged between the first row of bumps  802  and the third row of bumps  806 . Consistent with this embodiment, the bumps  806  in the third row are raised higher above the inner surface of the barrel  110  than the second row of bumps  804  and the second row of bumps are raised higher than the bumps  802  in the first row. In another embodiment, the bumps  806  in the third row are raised above the inner surface of the barrel  110  such that the piston assembly is prevented from passing over the bumps  806 . 
       FIG. 10A  depicts one embodiment of a syringe. Consistent with this embodiment, the barrel  110  includes a rim  900  which engages a flange  902  on a fitting in the form of a securing cap  904 . In one embodiment, the rim  900  of the barrel  110  and the flange  902  of the securing cap  904  are welded together. In another embodiment, the rim  900  and the flange  902  are secured together by an adhesive. In yet another embodiment, the rim  900  and the flange  902  are secured using a pressure fit. In a further embodiment, as shown in  FIG. 10B , the rim  900  and the flange  902  are secured using offset ridges or locking ridges  908  on the exterior of the tip of the barrel  110  and corresponding offset ridges or locking ridges  910  on the interior of the securing cap  904 . 
       FIG. 10B  depicts one embodiment of a securing cap  904  engaging a barrel  110 . Consistent with this embodiment, the tip of the barrel  906  includes one or more ridges  908  arranged around the external surface of the barrel tip  906 . The ridges  908  taper away from the rim  900  such that the portion of each ridge  908  closest to the rim  900  extends further from the surface of the barrel tip  906  than the portion of the ridge  908  furthest from the rim  900 . The securing cap  904  includes corresponding ridges  910  which are arranged on the inner surface of the securing cap  904 . The securing cap  904  ridges taper towards the flange  902  such that the portion of each ridge farthest from the flange  904  extends further from the inner surface of the securing cap  904  than the portion of each ridge  910  closer to the flange  904 . The ridges  908  are arranged on the barrel tip  906  and the ridges  910  are arranged on the securing cap  904  such that the ridges  910  are positioned between the ridges  908  when the rim  900  is in contact with the flange  902  with the high points of the ridges  908  and  910  contacting each other thereby securing the securing cap  904  to the rim  900 . 
     In one embodiment, the syringe is a 1 cc syringe used with an intravenous needle system. In another embodiment, the syringe is marked with an insulin scale. In yet another embodiment, the syringe is a ½ cc syringe. In one embodiment, the piston  112  and/or the inside of the barrel  110  are treated with a silicone lubricant to provide for smooth motion relating to the movement of the plunger  114  through the barrel  110 . 
       FIG. 11  depicts one embodiment of a catheter  1000 . The catheter  1000  includes a catheter fitting  1002  having an opening  1004  at one end of the catheter fitting  1002  and a plastic tube  1006  at the opposing end of the catheter fitting  1002 . In one embodiment, the opening  1004  is sized to accommodate the upper portion  202  of a Luer nut  104  (as shown in  FIG. 3 ) or the upper portion  910  of the securing nut  904  (as shown in  FIG. 10A ) and the plastic tube  1006  is sized to accommodate a needle  106 . Consistent with this embodiment, the Luer nut  104  engages the catheter fitting  1002  allowing the needle  106  to enter into the plastic tube  1006 . The length of the plastic tube  1006  is sized such that the end of the needle  106  extends beyond the end of the plastic tube  1006  allowing the needle to pierce the skin of a patient before the plastic tube  1006  is inserted into the patient and to also allow extraction of the needle  106  from the plastic tube  1006  after the plastic tube  1006  is inserted below the patient&#39;s skin. 
       FIG. 12  depicts one embodiment of the catheter fitting  1002  engaging a Luer nut  104 . Consistent with this embodiment, the upper portion  202  of the Luer nut  104 , which is coupled to the barrel  110 , is inserted into the opening  1004  of the catheter fitting  1002 . In addition, the needle  106  extends through the plastic tube  1006  to a point beyond the end of the plastic tube  1006  to expose the sharpened end of the needle  1008 . Accordingly, to insert the catheter  1000 , the needle  106  first pierces the skin of the patent allowing the tube  1006  to be inserted into the patient. In one embodiment, the catheter fitting  1002  is configured to accommodate an intravenous connector which allows an IV bag to be coupled to the catheter fitting  1002 . 
     Retraction of the needle may be accomplished in the same manner as retraction of the needle described above. However, upon retraction of the needle, the plastic tube will remain intact in the patient. After retraction of the needle, the catheter fitting  1002  may be disengaged from the Luer nut  104  to allow the catheter fitting  1002  to be coupled to an IV bag or another object. 
       FIGS. 13A through 13C  depict one embodiment of a syringe  1100  with a Luer nut  1102  attached to a barrel  110  of the syringe  1100 . Consistent with this embodiment, the end of the barrel  111  closest to the needle collar  108  (not shown) includes a plurality of extensions  1104  approximately evenly spaced around the periphery. A removable collar  1106  includes a lower portion  1108 , an upper portion  1110 , a flat bottom portion  1112  and an open upper portion  1114 . The lower portion  1108  is formed with a plurality of notches  1116  located on the inside of the lower portion  1108  that are each designed to engage a corresponding extension  1104  at the bottom portion of the end of the barrel  111 . The engagement of the extensions  1104  with the notches  1116  prevents the removable collar  1106  from rotating around the center axis of the barrel  110  as shown in  FIG. 13D  below. 
     The barrel  110  includes a ridge  1120  adjacent to the lower portion of the end of the barrel  111  which is configured to engage a portion of the notches  1116  on the removable collar  1106  when the notches  1116  are engaged with the extensions  1104  on the end of the barrel  111 . Each notch  1116  rises above an inner surface of the lower portion  1108  of the collar  1106  such that a portion of each notch  1116  closest to the upper portion  1110  of the removable collar  1106  engages the ridge  1120  on the end of the barrel  111 . The ridge  1120  is of sufficient height to secure the notches  1116  and the collar  1106  to the barrel  110  as discussed in  FIG. 13B  below. 
     The inside of the upper portion  1110  of the removable collar  1106  includes a spiral groove  1122  that correspond to ridges  1124  on the lower end of the Luer Nut  1102 . In one embodiment, the ridges  1124  are formed around the entire circumference of the lower portion of the Luer Nut  1102 . In another embodiment, the ridges  1124  are formed around a portion of the circumference of the lower portion of the Luer nut  1102 . In another embodiment, the Luer nut  1102  includes two tabs extending from the lower portion of the Luer nut  1102  on opposing sides. In one embodiment, the spiral grooves  1122  on the inner surface of the upper portion  1110  of the removable collar  1106  are angled in relation to the bottom of the Luer nut  1102 . In another embodiment, the spiral grooves  1122  have an upper portion which taper away from the collar  1106  such that the ridges  1124  are pushed over the spiral grooves  1122  in a direction towards the barrel  110 , but cannot be pushed over the grooves in a direction away from the barrel  110 . In another embodiment, a Luer slip is used where the Luer slip is held in place on the barrel by pressure and/or friction. The grooves may be other than spiral depending on the design of the Luer nut  1102 . 
       FIG. 13B  depicts a top view of one embodiment of the collar  1106 . Consistent with this embodiment, a plurality of notches  1116  extend around the periphery of the inside of the lower portion  1108  of the collar  1106 . The notches  1116  have a rectangular or square base that extends from about the lower third of the upper portion  1110  towards the flat bottom portion  1112  with the end of each notch  1116  that is closest to the flat bottom portion  1112  converging to a point. In addition, the base extends above the inside surface of the lower portion  1108  such that a portion of the base closest to the upper portion  1110  engages the ridge  1120  on the tip of the barrel  110  to prevent the collar  1106  from disengaging the barrel  110 . In one embodiment, the collar  1106  includes four notches  1116  that are approximately equally spaced and separated from each other by four separating gaps with the separating gaps being sized to accommodate the extensions  1104  on the end of the barrel  111 . 
       FIG. 13C  depicts one embodiment of the end of the barrel  111 . Consistent with this embodiment, a plurality of extensions  1104  are arranged around the periphery of the end of the barrel  111  with the bottom surface of each extension  1104  being substantially flush with the top surface of the barrel  110 . The extensions  1104  have a rectangular or square base that extend from the top of the barrel  110  at ridge  1120  towards the upper portion of the end of the barrel  111  with the end of each extension  1104  converging to a point. The number of extensions  1104  on the barrel  110  is equal to the number of notches  1116  on the collar  1106 . Further the extensions  1104  are substantially equally spaced from each other and are separated by gaps. The extensions  1104  are sized to engage the gaps between the notches  1116  on the collar  1106 . In addition, the gaps between the extensions  1104  are sized to engage the notches  1116  on the collar. The ridge  1120  is positioned on the barrel tip such that the pointed ends of the notches  1116  contact the ledge of the barrel  110  while the end of each notch  1116  opposite the pointed end engages the ridge  1120 . 
       FIG. 13D  depicts one embodiment of the collar  1106  engaging the end of the barrel  111 . Consistent with this embodiment, the notches  1116  are pushed over the ridge  1120  such that the non pointed end of each notch  1116  is in contact with the bottom of the ridge  1120  preventing the collar  1106  from disengaging the barrel  110 . In addition, the extensions  1104  engage the gaps between the notches  1116  and the notches  1116  engage the gaps between the extensions  1104  such that the collar is prevented from rotating around the center axis of the barrel  110 . 
     Another hypodermic syringe with needle retraction can be found in U.S. Pat. No. 5,336,198, titled “HYPODERMIC SYRINGE WITH NEEDLE RETRACTION FEATURE,” which is incorporated in its entirety herein by reference. 
     While various embodiments of the present invention have been described, it will be apparent to those of skill in the art that many more embodiments and implementations are possible that are within the scope of this invention. Accordingly, the present invention is not to be restricted except in light of the attached claims and their equivalents.