Abstract:
A needle assembly includes a sheath into which a hypodermic needle is withdrawn in a protected position. Installation of the needle assembly onto a Luer lock causes the needle to be thrust forward out of the sheath. A spring urges the needle to the withdrawn position. An elastomeric ball in the needle assembly provides sealing.

Description:
CROSS-REFERENCE 
   This application relies for priority on my application Ser. No. 60/572,445, filed May 19, 2004. 

   FIELD OF THE INVENTION 
   This invention is directed to hypodermic needle system wherein the needle is retracted into its sheath when the needle assembly is removed from a syringe, to protect personnel against inadvertent needle sticks. 
   BACKGROUND OF THE INVENTION 
   Hypodermic needles are used in medicine both to inject liquid materials into the body and to withdraw samples from the body. The usual withdrawal is the withdrawal of venous blood. Many infectious diseases are carried in the blood. It has become important in the medical arts to protect the practitioners from contact with possibly-infectious blood. Skin surface contact with blood and other body fluids is not particularly harmful, especially when the skin is healthy. The larger danger for medical practitioners is the possibility of being inadvertently stuck by a needle which carries on it elements of another person&#39;s blood. Quite a number of different apparatuses and protocols have been created to minimize risk of inadvertent sticking by a used hypodermic needle. These dangers require the need for advances in the protection from hypodermic needles, and particularly an operative system whereby the hypodermic needle is automatically withdrawn into the retracted position when the needle assembly is unmounted. 
   SUMMARY OF THE INVENTION 
   
       
       
         
           In order to aid in the understanding of this invention,
 
it can be stated in essentially summary form that it is directed to a retractable hypodermic needle which is mounted in an assembly including a needle sheath. The assembly body, which carries the needle sheath, is mountable on a Luer lock syringe. When mounted, the nozzle of the Luer lock extends the needle from its sheath, and when demounted, the needle is retracted into its sheath.
 
         
       
     
  
   It is thus a purpose and advantage of this invention to provide a hypodermic needle which is in the retracted position within a sheath when it is not mounted on a syringe or similar structure.
         It is another purpose and advantage of this invention to
 
provide a needle assembly which mounts on a Luer lock. The needle assembly includes a needle which is retracted into a needle sheath when not mounted. The needle is extended from the needle assembly when the needle assembly is mounted on a Luer lock structure.
   It is another purpose and advantage of this invention to
 
provide a retractable hypodermic needle which is useful both for the injection of medication and for the withdrawal of body fluids, with the needle retracting into its sheath when the needle assembly is removed from its mounting.
   It is another purpose and advantage of this invention to
 
provide a retractable hypodermic needle assembly which is inexpensive to build, reliable to use and maintains the needle when withdrawn into its needle sheath whenever the needle assembly is not mounted.
   The features of this invention which are believed to be
 
novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description,
 
taken in conjunction with the accompanying drawings.
       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view of a syringe with the retractable hypodermic needle assembly of this invention mounted thereon. 
       FIG. 2  is an enlarged side elevational view thereof, in disassembled form with parts broken away and parts taken in section. 
       FIG. 3  is an isometric disassembled view, with parts broken away. 
       FIG. 4  is an enlarged side elevational view, similar to  FIG. 2 , taken generally along a center line section, with parts broken away. 
       FIG. 5  is a view similar to  FIG. 4 , showing the needle assembly attached to the Luer lock nozzle of a hypodermic syringe or the like. 
       FIG. 6  is a view similar to  FIG. 1 , showing the needle assembly attached to a needle holder and a blood collection tube in a phlebotomy set. 
       FIG. 7  is an enlarged view of the phlebotomy set taken substantially along a center line section, with parts broken away. 
       FIG. 8  is an isometric view of the needle assembly of this invention attached to a Luer lock on the end of an intravenous catheter tube, usually used for introducing intravenous fluid. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Syringe  10  is shown in  FIG. 1 . The syringe  10  is of conventional configuration. It has a barrel  12  in which is slidably-disposed plunger  14 . The plunger can slide within the barrel to receive or dispense fluid therefrom. The barrel carries Luer lock  16  thereon. The Luer lock comprises a collar  18  which has interrupted interior threads  20  and nozzle  22  which extends past the collar  18 . Nozzle  22  is tapered and has an interior passage  24  which extends into the interior of the barrel. Thus, depression and retraction of plunger  14  moves fluid through passage  24  into or out of the syringe barrel. This is conventional construction. 
   The retractable hypodermic needle assembly of this invention is generally indicated at  26  in  FIGS. 1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7  and  8 . It comprises a body  28 . In the right hand of the body is formed tube  30  which carries fingers  32 . The fingers are configured to enter into the collar  18  and engage on the interrupted threads  20  therein. It is these fingers which retain the needle assembly  26  on the syringe  10 . This is common Luer lock construction. The other end of the body  28  carries needle sheath  34 . The needle sheath is a tube which slidably carries the needle  36  therein. The needle sheath terminates in a blunt end  38 . The needle has a diagonally-cut sharp end  40 . The sharp end is retracted into the needle sheath  34  in  FIG. 4  and is extended in  FIG. 5 . 
   The needle  36  extends backward through the body  28 . Within the seal cavity  42 , within tube  30 , spring stop collar  44  is part of the needle. Compression spring  46  surrounds the needle, engages against the spring stop  44  and lies within the spring pocket  48  in body  28 . The spring urges the needle to the right, retracted position shown in  FIG. 4 . To the right of spring stop collar  44 , elastic ball  50  engages around the needle tube. In the retracted, right-most position of the needle seen in  FIG. 4 , ball  50  is engaged against circular lip  52  which surrounds the right end of seal cavity  42 . The ball engages against the interior of the seal cavity, engages against the outside of the needle tube and engages against the spring stop collar  44 , as shown in  FIG. 4 . The ball serves as a retracted position stop for the needle, when it is withdrawn into the sheath by compression spring  46  as shown in  FIG. 4 . This is a safe position where the sharp end  40  of the needle is withdrawn into the sheath  34 . The needle will stay in the retracted 
   position until it is forced out into active position. 
   
       
       
         
           When it is desired to use the syringe to inject liquid,
 
the needle assembly  26  is assembled onto the Luer lock of syringe  10 . As seen in  FIG. 5 , the nozzle  22  of the syringe engages against the ball  50  and presses the ball leftward in the seal cavity  42  until it engages against the left end of the cavity. At this point, the stop collar  44  is at the entrance of the spring pocket  48 . In this position the sharp end  40  of the needle  36  extends past the blunt end  38  of the needle sheath  34 . The hypodermic syringe and the needle assembly are now ready for insertion and injection. Immediately after injection, the needle is withdrawn from the patient. Thereupon, the needle assembly is removed from the syringe. Upon removal, the nozzle  22  no longer holds the needle to the exposed, left position, but the compression spring  46  moves the needle  36  and ball  50  to the right to the retracted position shown in  FIG. 4 . Now the needle is thrown away. As soon as the needle is retracted into the sheath, the needle is safe. The various dimensions can be established in accordance with the amount of needle exposure which is required. Only the needle touches the patient, and as soon as the tip of the needle is retracted into its sheath, the needle is safe.
 
         
       
     
  
     FIGS. 6 and 7  illustrate a structure where the retractable hypodermic needle  26  of this invention is used in connection with a phlebotomy set  54 . The phlebotomy set is configured for the direct withdrawal of blood from the patient to a blood collection tube  56 . The needle holder  58  of the phlebotomy set is of similar configuration to the syringe barrel  12 . It carries a nozzle  22  with a Luer lock thereon which is the same as the Luer lock  16  on syringe barrel  12 . The difference is internal of the phlebotomy set and does not affect the operation of the needle assembly  26 . The blood collection tube  56  has an elastomeric cap thereon and the blood collection tube has a vacuum therein. The blood collection tube may contain chemicals for preserving the blood or for other purposes with respect to the blood. Thus, the blood collection tube  56  is an independent structure. Interiorly of the needle holder  58  is a tubular needle directed toward the blood collection tube  56 . The interior tubular needle is in line with and is connected to the nozzle  22  and its passage  24 . The phlebotomy set is used by placing the needle assembly  26  on the needle holder  58 . This extends the needle tip from the needle sheath  34  as shown in  FIG. 7 . The medical person then inserts the needle into the vein. When in position, the blood collection tube  56  is thrust down into the needle holder  58 . Thereupon the puncture needle in the needle holder punctures the rubber cap on the blood collection tube  56 . The vacuum in the blood collection tube withdraws blood from the patient, through the needle, through the sealed Luer connection, through the puncture tube into the blood collection tube. The hypodermic needle must be first inserted into the patient, before the advance of the blood collection tube so that the vacuum in the blood collection tube is not lost due to premature puncturing of its cap. After the collection is completed, the blood collection tube  56  is removed from the needle holder and the needle assembly  26  is removed from the needle holder. The removal of the needle assembly withdraws the needle  36  into its sheath  34 . Thereupon, the needle assembly can be disposed. The blood collection tube goes to the laboratory and the needle holder can be sterilized for re-use, or disposed. 
   The needle assembly  26  can also be used with an intravenous drip tube, as shown in  FIG. 8 . The intravenous tube  60  comes from an IV fluid bag and through a dispensing pump. The end of the IV tube is provided with a Luer lock  62 , the same as the Luer lock  16 . When IV fluid is to be administered, the needle assembly  26  is attached to the Luer lock  62 . This extends the needle  36  out of its sheath  34  so that the needle can be inserted into the patient&#39;s vein. The system remains in place until completion of the fluid transfer. Thereupon, the needle is withdrawn from the patient and the needle assembly is released from the Luer lock. The release from the Luer lock permits the spring to withdraw the needle into its sheath, therefore protecting personnel against inadvertent needle sticks. An effective protection of needles has been created. 
   This invention has been described in its presently contemplated best modes and it is clear that it is susceptible to numerous modifications, modes and embodiments within the ability of those skilled in the art and without the exercise of the inventive faculty. Accordingly, the scope of this invention is defined by the scope of the following claims.