Abstract:
A hypodermic syringe employing a plunger slidably disposed within a barrel. The plunger has a mounting hole extending through the seal end thereof to receive a mandrel. The mandrel has a flexible flange to be releasably engaged with the plunger. A spring element withdraws the mandrel into a cavity within the plunger upon full extension of the plunger within the barrel. The barrel includes a hub retainer at the forward end thereof and a needle hub retained therein the mandrel includes barbed tines with surfaces having axes of the conical surfaces that are displaced from one another such that movement of the tines toward one another also brings the axes closer. A catch associated with the back end of the spring element coupled with the mandrel at the other end cooperates with shoulders on smooth surfaces within the cavities to retain tension within the bungee. The hub retainer and the needle hub cooperate to insure that the needle hub is constrained to limited motion such that the mandrel will fully engage the needle hub.

Description:
BACKGROUND OF THE INVENTION 
   The field of the present invention is syringes and, more particularly, syringes offering protection against accidental sharps injury. 
   Accidental sharps injuries, in this context needle sticks, have long been recognized as potentially dangerous to health care workers. More recently, the transmission of serious and potentially fatal infections from such sharps injuries have created greater concern. Legislation has been contemplated in a number of States and before the Occupation Safety and Health Administration which would require safe needle technology. 
   A number of approaches have been undertaken to provide protection against such sharps injuries. International Publication WO 01/41843A1 discloses a syringe with a retractable needle which includes a plunger having a cavity extending longitudinally therein. A spring element is located in the cavity and is fixed to a mandrel extending into the syringe barrel from the mandrel which attaches to and retracts a needle into the barrel. The other end of the spring element is associated with a catch which causes the spring element to be placed in tension as the plunger is advanced within the barrel. A retention assembly associated with the end of the plunger receives and secures the catch to retain the spring element in tension. Advancement of the plunger to the end of its stroke results in the capture of the needle assembly by the mandrel and the release of the mandrel from the seal end of the plunger, resulting in retraction. 
   A further refinement of the foregoing design is disclosed in International Publication WO 01/41830A2. Improvements incorporated into this latter device include resilient dogs retaining the needle assembly in the forward end of the barrel. A driver surface is provided on the plunger to move the dogs from engagement for retraction of the needle assembly. Further, teeth are provided along either side of the cavity through the plunger to provide a range of engagements for the catch on the back end of the spring element. The disclosures of the foregoing patent publications are incorporated herein by reference. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a hypodermic syringe including a barrel with a plunger slidably disposed therein. The plunger has a cavity extending longitudinally. A hole extends through the seal end of the plunger and receives a mandrel. A spring element within the cavity is fixed to the mandrel at one end and fixable relative to the plunger in a tensioned state at the other end. A needle hub is releasably mounted in a hub retainer at one end of the barrel. A number of specific features are provided to enhance syringe operation. 
   In a first separate aspect of the present invention, the mandrel positioned within the hole includes an annular flange which is flexible longitudinally of the plunger and engages one or more detents extending into the hole. This flexible flange provides a more uniform release without the need for very close tolerances and flexure of less resilient materials. The detent or detents may each provide an engagement surface which is at an acute angle to the longitudinal direction of the plunger to further enhance the uniformity of mandrel release. 
   In a second separate aspect of the present invention, the mandrel is provided with tines extending longitudinally of the plunger. These tines have a spaced therebetween and each has a barb with a conical surface facing outwardly. The axes of the conical barb surfaces are offset from one another such that they approach one another as the resilient tines are bent toward one another. The arrangement of the barbs is such that, as the barbs move, corresponding elements on the barb surfaces move toward defining a circle. This motion takes place as the tines are forced into an engagement hole on the needle hub. In this way, the center of the barb surfaces define the resistance to insertion within the engagement hole, insuring a more predictable and uniform resistance. 
   In a third separate aspect of the present invention, the barrel includes dogs which retain the needle hub at one end thereof. The barrel also includes a shoulder normal to the longitudinal direction of the barrel facing into the barrel. The needle hub includes a shoulder also normal to the longitudinal direction of the barrel which faces the barrel shoulder. The dogs and the shoulders define two positions, one with the needle hub against the dogs and one with the shoulders engaged. These positions are displaced from one another. The normal aspect of the shoulders provides a fixed position upon engagement of the shoulders advantageous for engagement and retraction of the needle hub by the mandrel. The displacement between positions aids in the assurance of the release of the needle hub by the dogs. It is also possible that an O-ring seal between the needle hub and the barrel is able to bias the hub toward the first position to give stable placement for injection. The location of the shoulders may be advantageously selected along the length of the needle hub. 
   In a fourth separate aspect of the present invention, the spring element includes a catch which is slidably mounted within the cavity of the plunger. The catch includes elements which are engageable with the barrel as the plunger moves further into the barrel. Additional elements engage shoulders defined within the plunger cavity. There are two opposed smooth walls in the cavity with one shoulder only in each wall. This enables placement of the shoulders to retain the catch such that resistance is not encountered from multiple engaging elements and yet the plunger need not be fully extended within the barrel for engagement. 
   Accordingly, it is an object of the present invention to provide an improved safety syringe with a retractable needle. Other and further objects and advantages will appear hereinafter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is perspective view of a retractable hypodermic syringe. 
       FIG. 2  is an exploded assembly view in perspective of the device of  FIG. 1 . 
       FIG. 3  is a side view of the device of  FIG. 1 . 
       FIG. 4  is a cross-sectional view taken along line  4 - 4  of  FIG. 3 . 
       FIG. 5  is a cross-sectional view as in  FIG. 4  with the plunger moved. 
       FIG. 6  is a cross-sectional view as in  FIG. 4  with the plunger moved. 
       FIG. 7  is a cross-sectional view as in  FIG. 4  with the needle retracted.  4 . 
       FIG. 7A  is a cross-sectional detail as seen in  FIG. 4 . 
       FIG. 7B  is a front view of a bungee with a mandrel and a catch. 
       FIG. 7C  is a side view of the assembly of  FIG. 7B . 
       FIG. 8  is a side view of a mandrel. 
       FIG. 9  is a front view of a mandrel. 
       FIG. 10  is a cross-sectional view taken along line  10 - 10  of  FIG. 8 . 
       FIG. 11  is a front view of a plunger. 
       FIG. 12  is a cross-sectional view taken along line  12 - 12  of  FIG. 11 . 
       FIG. 13  is a cross-sectional view taken along line  13 - 13  of  FIG. 11 . 
       FIG. 14  is a cross-sectional detail of the forward end of the barrel taken along line  4 - 4  of  FIG. 3 . 
       FIG. 15  is a cross-sectional view as in  FIG. 14  with the needle hub advanced. 
       FIG. 16  is a cross-sectional view as in  FIG. 14  of a second embodiment. 
       FIG. 17  is a cross-sectional view as in  FIG. 15  of a second embodiment. 
       FIG. 18  is a cross-sectional view as in  FIG. 14  of a third embodiment. 
       FIG. 19  is a cross-sectional view as in  FIG. 15  of a third embodiment. 
       FIG. 20  is a cross-sectional view of any of  FIGS. 14 through 19  looking forwardly in the barrel. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Turning in detail to the drawings,  FIG. 1  illustrates a syringe with a retractable needle. This view illustrates the device as shipped.  FIG. 2  illustrates the same device in an exploded assembly view as including a barrel  80 , a plunger assembly  30 , a protective needle cap  160  and a needle hub  100  with an associated needle  106 . 
   The plunger assembly is illustrated in various positions within the barrel  80  in  FIGS. 4 ,  5 ,  6  and  7 . Further, the plunger assembly is shown by itself in  FIG. 11 . The plunger assembly  30  includes a molded body  32  having a seal end  34  and an outer end  36 . The outer end  36  defines a thumb button for actuation of the syringe while the seal end  34  acts as a piston with a ring seal  38  extending about a waist  40 . A substantially conical forward surface defines a driver surface  42  which will be described later as interacting with the forward end of the barrel. 
   A cavity  44  lies between the seal end  34  and the outer end  36 . This cavity is shown to be open on two sides and defined by two smooth surfaces  46  which are opposed and extend substantially the length of the cavity  44 . Each of the smooth surfaces  46  has one shoulder  48 . The shoulders  48  in the two surfaces face the outer end  36 . These two shoulders  48  are aligned with one another to receive a catch as will be described below. The smooth surfaces  46  are curved near the middle of the body  32  to constrict the width of the cavity. This may be employed to arrest the motion of the needle as it is being retracted into the syringe as will be discussed below. 
   A mounting hole  50  extends longitudinally of the plunger assembly  30  through the seal end to the cavity  44 . This hole  50  is best illustrated in  FIG. 12 . It is substantially circular in all transverse cross sections but for two detents  52  located diametrically opposed near the seal end  34  of the plunger assembly  30 . The plunger body  32  is relieved around the detents  52  in order that they may have some resilience. As the relief is extended downwardly about the detents  52 , greater resilience is realized. The detents  52  include an engagement surface  54  at an acute angle to the longitudinal direction of the plunger assembly  30 . These engagement surfaces  54  extend inwardly into the otherwise generally cylindrical mounting hole  50 . 
   A mandrel  56  is associated with the plunger assembly  30  in the mounting hole  50 . This mandrel  56  includes an annular seal cavity  58  receiving an O-ring seal  60 . The mounting hole  50  is relieved as best seen in  FIG. 12  near the location of the O-ring seal  60  such that retraction of the mandrel  56  from the mounting hole  50  is facilitated. The inner end of the mandrel  56  includes an anchor pin  62  having a varied profile for bonding to a bungee molded in situ on the pin  62 . 
   The mandrel  56  is relieved by annular grooves to define an annular flange  64 . Further the mandrel  56  is preferably of a more resilient material than the body  32  of the plunger  30 . This flexibility of the material along with the geometry of the annular flange  64  makes the flange  64  flexible longitudinally of the plunger. It extends radially outwardly and circumscribes the mandrel  56  at that location. The flange  64  is rounded at its periphery to a substantially semi-circular surface in cross section. This annular flange  64  is held against retraction of the mandrel  56  by the engagement surfaces  54  of the detents  52 . This configuration offers more consistent extraction forces of the mandrel  56  from the mounting hole  50 . 
   Resilient tines  66  are located at the outer end of the mandrel  56 . These tines  66  are spaced apart and each includes a barb  68 . The barbs  68  face outwardly away from one another and are defined by a segment of a truncated conical surface  70 . The surfaces  70  each define a conical axis which extends longitudinally of the mandrel  56 . These conical axes of the two surfaces  70  are offset from one another such that they approach one another as the resilient tines  66  are bent toward one another. In this way, the centers of the conical surfaces rather than their edges define the resistive force to insertion into the needle hub as discussed below. 
   The barrel  80  includes an open end  82  and a hub end  84 . The hub end is illustrated in detail in various embodiments in  FIGS. 14 through 20 . The barrel includes a hub retainer  86  at the hub end  84 . The body of the barrel  80  has an engagement flange  88  about the hub end  84  thereof. This engagement flange  88  receives shoulders  90  on the hub retainer  86  which has periodic longitudinal slits  92  to accommodate assembly. The retainer  86  includes a bore  94  therethrough coaxial with the barrel  80 . Three dogs  96  extend into that bore  94  to retain a needle hub from moving inwardly into the barrel  80 . The dogs  96  are resiliently mounted and have an inclined surface  98  to interact with the plunger assembly  30 . 
   The needle hub  100  is located in the bore  94  of the barrel  80  at the hub end  84 . The needle hub  100  includes a mounting body  102  and a lower engagement body  104 . The mounting body  102  is generally cylindrical with a cavity to receive a needle  106 . The needle  106  may be cemented in place. 
   The engagement body  104  includes an engagement hole  108  concentrically arranged at the inner end of the needle hub  100 . This hole  108  is sized to receive the tines  66  of the mandrel  56 , forcing the barbs inwardly. An engagement shoulder  110  receives the barbs once having passed through the hole  108 . This secures the needle hub  100  to the mandrel  56 . At the inner end of the engagement body  104 , an inner surface  112  is provided for releasable retention by the dogs  96 . An annular space is provided about the intersection between the mounting body  102  and the engagement body  104  and by the main body of the barrel  80  and the hub retainer  86  for an O-ring  114 . The needle hub  100  is able to axially move a small amount within the hub retainer  86 . This movement is resisted by the O-ring  114 . 
   Having generally described the mounting of the needle hub  100  within the hub end  84  of the barrel  80 , specific reference to the differences between embodiments are here addressed.  FIGS. 14 and 15  constitute a first embodiment. In this embodiment, six longitudinally extending ribs  116  are located about the periphery of the mounting body  102 . These ribs define a series of stops as a composite first shoulder  118 . The hub retainer  86  includes an inwardly extending flange  120  having a second shoulder  122  which opposes the shoulder  118 . These shoulders  118  and  122  are normal to the longitudinal direction of the barrel  80 . Through a comparison of  FIGS. 14 and 15 , it can be seen that the needle hub  100  has a first position positioned against the dogs  96 . A second position illustrated in  FIG. 15  has the shoulders  118  and  122  engaged. These two positions are displaced from one another to a small extent. This spacing gives some additional advancement past the engagement of the mandrel  56  with the needle hub  100 . The resistance of the O-ring  114  against movement of the needle hub  100  provides for engagement of the mandrel  56 . However, further advance of the plunger assembly  30  may be needed to release the dogs  96 . The operator will know to push harder until the needle hub  100  is released and the needle  106  retracts. Having the shoulders be normal to the longitudinal direcion of the barrel  80  defines a fixed second position. Without such a fixed limit to movement, the O-ring  114  can get hung up with the hub  100  or the components wedge together and inhibit needle retraction. 
   In  FIGS. 16 and 17 , another embodiment is employed where a first shoulder  124  is found at the outer end of the needle hub  100  and the flange  120  includes a second shoulder  126  receiving that shoulder  124 .  FIGS. 18 and 19  represent yet another embodiment where the first shoulder  128  is defined at the intersection between the mounting body  102  and the engagement body  104  while the resisting second shoulder  130  forms the lower end of the upper portion of the bore  94 . A further embodiment is contemplated where an entire circular shelf is created at a location similar to that defined by the ribs  116  about the full periphery of the mounting body  102 . 
   A spring element in the form of a bungee  140  is located within the cavity  44  of the plunger assembly. The bungee  140  is molded about the anchor pin  62  of the mandrel  56  at one end. At the other end, the bungee  140  is molded onto another anchor pin  142  of a catch  144 . The catch  144  includes elements  146  which extend outwardly from the anchor pin  142 . The barrel  80  includes an inwardly extending shoulder  148  which engages the elements  146  to prevent the catch from moving into the inner portion of the barrel  80 . 
   The catch  144  also includes side elements  150  extending to a lesser extent outwardly from the anchor pin  142 . These side elements  150  slide along the smooth surfaces  146  defining the cavity  44 . There is some spring resilience to the plunger at the surfaces such that, in a relaxed position, the side elements  150  will be engaged by the two shoulders  48  and yet the catch  144  can move fairly easily within the cavity  44  toward the shoulders  48 . This single set of shoulders  48  helps define a point at which the plunger assembly  30  is cocked the shoulders  48  can be positioned such that the thumb button can be grasped and the plunger easily retracted to charge the barrel  80 . Likewise, the force profile in advancing the plunger assembly  30  provides clearer transition such that premature needle retraction can more easily be avoided. 
   In operation, the syringe comes as illustrated in  FIG. 1  with the plunger assembly  30  partially inserted into the barrel  80 . A protective needle cap  160  isolates the needle  106 . The configuration of  FIG. 1  is also illustrated in  FIG. 4 . As can be seen, the bungee  140  can be in a relaxed or substantially relaxed condition to avoid any long term creep, thereby extending the shelf life of the syringe. 
     FIG. 5  illustrates an advance of the plunger  30  substantially fully into the barrel  80 . As the catch  144  is prevented from entering the barrel because of the elements  146  engaging the shoulder  148 , the bungee  140  is stretched and tensioned by this insertion. Further, the catch  144  comes into engagement with the shoulder  148  on the smooth surfaces  46  of the cavity  44 . 
   With the shoulders  148  engaging the catch  144 , the bungee will remain in tension until such time as the mandrel  56  is extracted from the mounting hole  50 . The bungee will not lose tension as the plunger assembly  30  is drawn back to intake the substance to be injected. 
   Once the appropriate amount of fluid is drawn into the syringe, the injection may be given until the plunger assembly  30  again is fully within the barrel  80 . The syringe may then be withdrawn from the injection site and further pressure exerted against the thumb button of the outer end  36  of the plunger assembly  30 . This action drives the resilient tines  66  into the engagement hole  108  of the needle hub  100  to the point that the barbs  68  engage the engagement shoulder  110  within the engagement body  104 . Concurrently, the driver surface  42  on the seal end  34  of the plunger assembly  30  engages the inclined surfaces  98  of the dogs  96  and forces them outwardly to release the needle hub  100 . The engagement of the needle hub  100  with the mandrel  56  requires less force than and precedes the release of the mandrel  56  from the mounting hub  50 . 
   With the dogs  96  retracted and the mandrel  56  engaged with the needle hub  100 , the mandrel  56  is released from the seal end  34  of the plunger assembly  30  and tensioned bungee retracts the needle hub  100  and the needle  106  into the cavity  44  of the plunger assembly  30 . This last condition can best be seen in  FIG. 7 . In the retraction, the annular flange  64  is flexed longitudinally by being dished toward the outer end of the mandrel  56 . This releases the mandrel  56  from the detents  52  to permit retraction of the bungee  140  and withdrawal of the mandrel  56 . Once the mandrel has been separated from the mounting hole  50 , the assembly cannot be reused as a syringe without full disassembly of the device. 
   Accordingly, an improved syringe having a retractable needle is disclosed. While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein. The invention, therefore is not to be restricted except in the spirit of the appended claims.