Abstract:
A single use syringe ( 10 ) has an outer barrel ( 11 ) and an inner barrel ( 12 ) slidable within the outer barrel. The two barrels are initially latched together to prevent relative movement therebetween whereby the syringe is in a useable condition. A needle ( 16 ) is in fluid communication with the inner barrel and projects initially from a first end of the outer barrel. A plunger ( 21 ) in the inner barrel is connected to a plunger actuating rod ( 22 ) which extends out the other end of the outer barrel. On first depression of the plunger actuating rod a limit catch ( 23 ) prevents full depression thereof but allows sufficient depression to draw fluid into the inner barrel. On the second depression the fluid is ejected and the plunger actuating rod and plunger are allowed full travel whereby latching between the two barrels is disengaged. It is not possible to re-latch the barrels together in the useable condition and therefore further use of the syringe is not possible. The needle retracts into the outer barrel after said first use and is locked therein.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present application is the U.S. national stage application of International Application PCT/AU02/00297, filed Mar. 14, 2002, which international application was published on Sep. 19, 2002 as International Publication WO 02/072182. The International Application claims priority of Australian Patent Application PR 3730, filed Mar. 14, 2001. 

   FIELD OF THE INVENTION 
   The invention relates to syringes and in particular to single use or non-reusable syringes with automatic retracting needle. 
   BACKGROUND OF THE INVENTION 
   The hazards to the general public and medical staff due to needle sticks from used syringes, as well as the problems associated with re-use of syringes by intravenous drug users is well documented. Many prior attempts have been made to provide a syringe which is capable of only a single use and which, after such use is self destructing or provides protection against needle sticks. One such syringe is disclosed in U.S. Pat. No. 5,267,976 for example. Generally speaking the prior art devices suffer one or more disadvantages in that they are too costly to manufacture, are unreliable, are easily tampered with or rely on the user taking some positive action after first use, to ensure that the syringe is disabled from further use. In prior art devices which have an automatically retracting needle such as that disclosed in aforementioned U.S. Pat. No. 5,267,976 there is also the possibility of premature retraction of the needle such as when the plunger is moved from its packaged position in preparation for drawing a drug into the syringe. 
   SUMMARY OF THE INVENTION 
   Accordingly it is an object of this invention to provide a single use syringe with self-retracting needle which overcomes one or more of the aforementioned and other disadvantages of known devices. 
   The invention provides a syringe including an outer barrel having first and second ends, an inner barrel slidable longitudinally within said outer barrel and adapted to support a needle at one end thereof and which needle projects through an aperture in said first end of said outer barrel, said needle being in fluid communication with a fluid retaining chamber of said inner barrel, and a plunger within said chamber and actuable to draw fluid into said chamber and expel fluid from said chamber via said needle, said plunger being connected to an actuating rod extending out from the other end of said inner barrel and the second end of said outer barrel, said outer barrel having first and second spaced retaining means on the inner wall surface thereof, and said inner barrel having latching means for engaging said first or second retaining means and latching said inner barrel in either of two positions relative to said outer barrel, a first said position wherein said needle projects from said outer barrel and is in a useable position, and a second position wherein said needle is fully retracted within said outer barrel, biasing means for biasing said inner barrel towards said second position and said plunger actuating rod having means for contacting said latching means when said plunger is fully depressed to disengage said latching means from said first retaining means whereby said needle moves to said second position wherein said latching means engages said second retaining means and is unable to be re-engaged in said first retaining means. 

   
     BRIEF DESCRIPTIONS THE DRAWINGS 
     In order that the invention may be more readily understood one particular embodiment will now be described with reference to the accompanying drawings wherein: 
       FIG. 1  is a sectional side elevation of a syringe according to one embodiment of the invention, shown in an initial position; 
     FIG.  1 ( a ) is an enlargement of the portion of  FIG. 1  shown in the circle “A”; 
       FIG. 2  is similar to  FIG. 1  but shows the syringe in a first stage of operation; 
     FIG.  2 ( a ) is an enlargement of the portion of  FIG. 2  shown in the circle “B”; 
       FIG. 3  is similar to  FIGS. 1 and 2  but shows the syringe in a second stage of operation; 
       FIG. 4  is similar to  FIGS. 1-3  but shows the syringe in a third stage of operation; 
     FIG.  4 ( a ) is an enlargement of the portion of  FIG. 4  shown in the circle “C”; 
       FIG. 5  is similar to  FIGS. 1-4  but shows the syringe in a fourth stage of operation; 
     FIG.  5 ( a ) is an enlargement of the portion of  FIG. 5  shown in the circle “D”; 
       FIG. 6  is an exploded perspective view of the syringe of  FIGS. 1-5 ; 
       FIG. 7  is a view similar to  FIG. 1  showing an alternative embodiment of the invention in an initial position; 
     FIG.  7 ( a ) is an enlargement of the portion of  FIG. 7  shown in the circle “E”; 
       FIG. 8  is a view similar to  FIG. 7  but showing the syringe in a first stage of operation; 
     FIG.  8 ( a ) is an enlargement of the portion of  FIG. 8  shown in the circle “F”; 
       FIG. 9  is a view similar to  FIGS. 7 and 8  showing the syringe in a fourth stage of operation; 
     FIG.  9 ( a ) is an enlargement of the portion of  FIG. 9  shown in the circle “G”; 
       FIG. 10  is a view similar to  FIGS. 7-9  showing the syringe in a fifth stage of operation; 
     FIG.  10 ( a ) is an enlargement of the portion of  FIG. 10  shown in the circle “H”; 
       FIG. 11  is an exploded perspective view of the syringe of  FIGS. 7-10  inclusive; 
       FIG. 12  is a side elevation of a syringe as shown in either of the specific embodiments; 
       FIG. 13  is similar to  FIG. 12  but shows the syringe rotated through 90° about its longitudinal axis; and 
       FIG. 14  is an enlarged sectional view of part of a modified flexible arm for use in the described embodiments. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Throughout the drawings like or similar parts have the same reference number. 
   The syringe  10  comprises an outer barrel  11  which apart from openings at each end is a completely aperture free cylindrical barrel. An inner barrel  12  fits within the outer barrel  11  in a manner so as to slide longitudinally back and forth within the outer barrel  11  in engagement therewith. The inner barrel  12  has a narrow neck  13  at one end and is open at the opposite end  14 . The neck  13  is adapted to accommodate a needle housing  15  incorporating a needle  16 . Clearly, the needle  16  is in fluid communication with a chamber  17  within the inner barrel  12 . Once fitted to the neck  13  the needle housing  15  and needle  16  project from a first end  18  of the outer barrel  11 . 
   A spring  20  is located inside the first end  18  of the outer barrel  11  and acts on the inner barrel  12  to bias the inner barrel  12  towards a second end  19  of the outer barrel  11 . 
   A plunger  21  is located within the inner barrel  12  and is mounted at one end of a plunger actuating rod  22 . The plunger actuating rod  22  enters the second end  19  of the outer barrel and the open end  14  of the inner barrel. The outer end of the plunger rod  22  is provided with a limit catch  23  which will be described later. A flange  24  at the second end  19  of the outer barrel facilitates operation of the syringe. An end flange  34  facilitates operation of the plunger actuating rod  22 . 
   The outer barrel has first and second annular grooves  25  and  26 , respectively, in the inner surface thereof. The purpose of the grooves  25  and  26  will become apparent hereinbelow. 
   The above description describes the main components of a syringe according to the embodiment of  FIGS. 1-6  as well as the embodiment of  FIGS. 7-11 . In the first embodiment the inner barrel  12  has a pair of diametrically opposed longitudinal slits  27  (see  FIG. 6 ) at the open end  14  and the slits  27  define a pair of opposed flexible arms  28 . The flexible arms  28  have a lip  29  extending around the extremity thereof for engaging in one or other of the annular grooves  25  and  26 . The slits  27  allow the flexible arms  28  to move slightly towards each other for the purpose of disengaging the lip  29  from one or other of the grooves  25  and  26 . The configuration of the inner barrel and particularly the flexible arms  28  is more evident in FIG.  6 . The plunger actuating rod  22  is provided with an annular skirt  30  having a tapered edge for engaging the respective arms  28  to remove the lips  29  from the respective grooves  25  and  26  as will become apparent hereinbelow. 
   In the embodiment of  FIGS. 7-11 , the flexible arms  28  are much narrower in construction (see  FIG. 11 ) and comprise essentially a pair of opposed fingers which extend from the open end  14  of the inner barrel  12 . The flexible arms or fingers  28  again have lips  29  which engage in one or the other of the annular grooves  25 ,  26 . In addition, the arms  28  have latch members  31  which extend towards the second end  19  of the outer barrel  11 . The actuating rod  22  is provided with an annular skirt  32  similar to the skirt  30  of the previous embodiment but having an inwardly directed ridge  33  extending around the extremity of the skirt. Otherwise, the construction of the syringe in the embodiment of  FIGS. 7-11  is the same as in the earlier embodiment. 
   As mentioned above, the outer end of the plunger actuating rod  22  incorporates a limit catch  23 . Essentially, the limit catch prevents the plunger actuating rod  22  and hence the plunger  21  from moving to the forward or needle end extremity of the inner barrel  12  on the first operation of the syringe. Once the plunger actuating rod  22  is forced inwardly towards the needle end of the syringe on the initial occasion the limit catch changes its construction whereby on the next depression of the plunger actuating rod, the plunger is able to move to the forward most extremity of its movement in the inner barrel. 
   More specifically, on initial depression of the plunger rod  22  fingers  36  of the limit catch  23  engage with the end  19  of the outer barrel  11  and are pivoted from the position shown in  FIG. 1  to the position shown in  FIG. 2  whereby further movement (depression) of the plunger is prevented. This pivoting is facilitated by a flexible joint between the ends of each finger. The fingers  36  are then locked in this pivoted position. This pivotal movement of the fingers  36  severs a thin membrane  38  (see FIG.  2 ( a )) which initially holds arms  37  of the limit catch  23  inwardly on the body of rod  22 . Consequently, on withdrawal of the plunger rod  22  the arms  37  spring outwardly or spread to the position shown in  FIG. 3  wherein tongue and groove  39  locks the arms  37  in the new position. On the next depression of the rod  22  the fingers fail to engage the end of the outer barrel  11  and hence extended depression of the plunger (to the end of inner barrel  12 ) is facilitated. 
   Operation of the syringe is as follows. The syringe is packaged after manufacture in a sealed package without the needle housing  15  and needle  16  and is in a condition where the inner barrel and plunger are in a position substantially as shown in  FIGS. 1 and 7 , respectively. The user removes the syringe from the package and installs a needle housing  15  with attached needle  16  onto the neck  13  of the inner barrel  12 . The plunger actuating rod  22  is then depressed by applying thumb pressure on end flange  34  whilst holding the outer barrel  11  between first and second fingers until the actuating rod  22  is fully depressed into the inner barrel  12  and the limit catch  23  prevents further movement. In this position the plunger  21  is almost to the neck  13  of the inner barrel and only a very small chamber exists in the inner barrel between the plunger  21  and the neck  13 . It should be noted that at this point movement of the inner barrel  12  relative to the outer barrel  11  is prevented by means of the lip  29  engaging in the annular groove  25  of the outer barrel (see FIGS.  1 ( a ) and  7 ( a ), respectively). Once this initial actuation has taken place, the syringe is in the condition shown in  FIGS. 2 and 8  respectively. The purpose of the limit catch is to prevent the lip  29  from being released from the groove  25  on the initial depression of the plunger actuating rod as this would prevent use of the syringe, as will become evident hereinbelow. 
   The next action is to draw a drug into the inner barrel  12  via the needle  16 . The needle  16  is placed in the drug and the plunger is drawn outwardly to a position shown in FIG.  3 . The inner barrel still remains firmly fixed relative to the outer barrel. 
   The next action is to depress the plunger to expel the drug and on this actuation of the plunger actuating rod  22  the plunger moves all the way to the end of the inner barrel  12  as shown in FIG.  4 . In other words the limit catch  23  does not restrict the inner movement of the actuating rod  22  on this second depression. In regard to the first embodiment, when the plunger  21  has reached its inner most extremity the protrusions  30  on the rod  22  engage the flexible arms  28  and cam the lip  29  on each arm  28  out from the annular groove  25  as is evident in FIG.  4 ( a ). At this point, as soon as pressure is released from the plunger rod  22 , the spring  20  forces the inner barrel towards the second end  19  of the outer barrel, since there is nothing to stop relative movement between the two barrels. Of course this movement relies on the user releasing pressure on the plunger actuating rod  22 . 
   The movement of the inner barrel relative to the outer barrel continues until the inner barrel assumes a position as shown in  FIG. 5  wherein the lip  29  of each flexible arm  28  locates in the second annular groove  26 . In this position the needle  16  is fully retracted within the outer barrel  11 . 
   As will be evident in  FIG. 5  it is possible to depress the plunger actuating rod  22  and cause the inner barrel to disengage the annular groove  26  whereby the needle can be moved outside the first end  18  of the outer barrel. However, such action does not enable the syringe to be re-used because it is not possible to latch the inner barrel, or more specifically the lips  29 , into the annular groove  25 . This is because the spring  20  holds the inner barrel against the protrusions  30  or ridge  33  whereby the lips  29  remain in a position cammed away from the groove  25 . 
   A notch  35  in the actuating rod  22  enables the part of the actuating rod projecting from the outer barrel to be broken off as a means of preventing further depression of the plunger but even if this action is not performed it is not possible to re-use the syringe. 
   Operation of the syringe shown in the embodiment of  FIGS. 7-11  is very similar in that depression of the actuating rod  22  for the purpose of expelling a drug in the chamber of inner barrel  12  causes the ridge  33  of annular skirt  32  to engage the latch members  31  to again cam the lips  29  from the first annular groove  25  (see FIG.  8 ( a )). Again the spring  20  causes the inner barrel to move towards the second end  19  of the outer barrel whereby the lips  29  engage in the second annular groove  26  of the outer barrel  11  as is shown more clearly in FIGS.  10  and  10 ( a ). FIGS.  9  and  9 ( a ) show the position of the inner barrel in transit between the two positions. 
   As will be evident from FIGS.  10  and  10 ( a ), once the inner barrel is latched in the second annular groove  26  it cannot be removed by depressing the plunger actuating rod  22  since engagement between the annular skirt  32 , or more particularly the ridge  33  thereon, and the latch member  31  is such that depression of the rod  22  will not cam the latch member  31  from the groove. Therefore further actuation of the plunger or movement of the inner barrel relative to the outer barrel is prevented and the needle is safely retracted within the outer barrel  11 . The notch  35  in the actuating rod  22  enables the part of the actuating rod projecting from the outer barrel to be broken off although such action is hardly necessary. 
   In a modification to the above described embodiments some of the flexible arms  28  on the inner barrel differ to those previously described. A profile of a modified flexible arm  28  is shown in FIG.  14 . As well as some of the arms having the modified profile the total number of arms  28  on the inner barrel  12  is increased and preferably comprises a total of at least four such arms comprising at least two of the modified arms. The modified arms  28  are shorter than the other arms which have a profile the same as those shown in  FIGS. 1-6  but are thin fingers as in the embodiment of  FIGS. 7-11 . In the case of a total number of four arms they are uniformly spaced around the barrel  12  with the two long arms being diametrically opposed and the two short arms likewise. 
   The longer arms are initially latched in the annular groove  25  and are released therefrom in the manner described above, on the first full depression of the plunger. It will be appreciated that the shorter arms  28  are not engaged by the protrusions  30  or skirt  32  as the case may be. Such engagement is with the longer arms. As the plunger retracts the shorter of the arms  28 , which are not located in the groove  25  must pass over the groove  25  in moving towards the second end  19 . This is achieved by the angled surface  39  being cammed over the edge of the groove  25  nearest the second end  19 . In other words, the shorter arms  28  are deformed inwardly towards the longitudinal axis of the syringe as the plunger retracts under the bias of the spring  20  and they glide over the groove  25 . 
   At the second end  19  the longer arms  28  are held away from the groove  26  since they are engaged with the plunger protrusions  30  or skirt  32  under bias from spring  20 . The shorter fingers are under no such influence and are able to spring outwardly and engage the groove  26  when the inner barrel reaches its furthermost position towards the second end. Once engaged in the groove  26  the right angled lip  40  of the shorter arms is firmly located in the groove  26  and the inner barrel is thus prevented from ever moving within the outer barrel towards the first end  18 . The needle is thus permanently retracted within the outer barrel and the syringe cannot be re-used. 
   It should be evident that by a combination of the novel latching arrangement between the inner barrel and the outer barrel and the limit catch  23 , there is provided a safety syringe which is extremely reliable, relatively inexpensive to manufacture and does not require any positive action to be taken on the part of the user in order to ensure that the syringe is disabled from further use. 
   Clearly of course many variations may be made to the embodiments described above without departing from the spirit and scope of the invention. Persons skilled in the art will readily envisage alternative mechanisms for latching and de-latching the inner barrel from movement relative to the outer barrel. Various arrangements of the plunger will also be envisaged for the purpose of disengaging the latching mechanism.