Abstract:
The disclosure pertains to a safety syringe having a retractable needle shield which is capable of being retracted to expose the needle for use; being advanced to a needle shielding position; and, if desired, of being removed from the syringe with the shielded needle safely contained within the retractable needle shield via a frangible segment between the syringe barrel and the needle/needle shield components. The disclosure further pertains to a method of using the safety syringe having a retractable needle shield.

Description:
BACKGROUND 
     This disclosure relates to syringes and, in particular, to a hypodermic syringe having a retractable needle guard for the purpose of preventing accidental needle sticks. 
     Most syringes used today for medical or laboratory purposes are sold as disposable items intended to be used only once. Disposal of such syringes has posed a safety hazard for the individuals who use the syringes as well as for those who dispose of them. With the onset of AIDS, the concern for infection due to accidental needle sticks from used syringes has increased and a number of different devices have been proposed to minimize the possibility of spreading infectious disease due to accidents of this type. 
     One approach to this problem is to provide a retractable shield which, after the syringe has been used, can be pulled to an extended position where it covers the needle, making it difficult for an individual to accidentally contact the needle. A common feature of such constructions is that when the shield is pulled to its extended position, it is locked so that it cannot be retracted (thus exposing the needle) except by application of extraordinary force. 
     A number of such constructions have been proposed to satisfy the general requirement that the needle be permanently covered after the syringe has been used. Some of these constructions involve twist-to-lock mechanisms and, in others, locking occurs automatically when the shield is fully extended. These known devices satisfy many of the functional requirements of a needle shield and require, in most cases, modification of the standard syringe construction. 
     Those devices which lock in response to axial movement to the extended position, (i.e., without any rotation) have certain inherent drawbacks that result primarily from the requirement that substantial force be exerted axially to lock the shield in its extended position. In the first place, the likelihood of unintentional and irreversible locking is greater with such devices than with those devices which require rotation to lock. Also, it is difficult to verify that the shield is locked upon such forcible extension without attempting to retract the shield, which increases the possibility of unintended exposure of the needle. Further some of the safety syringes currently available allow the shield to be pulled axially from the syringe with only moderate applied force and or to be removed with moderate wiggling which has been attributed to the use of relatively soft polymers in combination with relatively small protrusions as the engaging elements of the shield and/or other components of the safety syringe. Finally, if the user&#39;s hand should slip from the shield while exerting the force necessary to extend the shield to the locked position, the user&#39;s hand may reflexively rebound back onto the needle point if the shield does not actually lock. 
     Accordingly, it is an object of this disclosure to provide a protective shield of the type described which provides a relatively inexpensive protective shield which satisfies the functional requirements of a needle shield and includes none of the drawbacks mentioned above. 
     Another object is to provide an extendable needle shield for a syringe which performs all of the necessary functions of such a shield and which is particularly well suited to an automated process of manufacture. 
     A further object of the disclosure is to provide an extendable needle shield for a safety syringe which is improved from the points of view of safety, functional utility, and cost of manufacture. 
     SUMMARY 
     This disclosure pertains to a safety syringe comprising: a barrel having a distal and proximal ends; a plunger sealingly slidable within the barrel; a collar having proximal and distal ends; a hollow needle attached to the distal end of the barrel; and an elongate generally tubular needle shield moveable over the barrel, said elongate generally tubular needle shield having a proximal end, a distal end, a lumen therebetween, and a longitudinal axis, wherein the hollow needle is attached to the barrel via a generally tubular needle hub integrally formed with the distal end of the barrel, said generally tubular needle hub having disposed about its external surface a plurality of ribs adapted to join the collar to the generally tubular needle hub; wherein each rib of the plurality of ribs includes an at least partially relieved proximal region to provide a region adapted to be readily frangible when the elongate generally tubular needle shield is positioned distal of the barrel and subjected to a lateral force applied thereto distal of the barrel; further wherein the collar is adapted to be slidably received within the elongate generally tubular needle shield and to be prevented from being withdrawn proximally therefrom. 
     The disclosure also pertains to a method of using a safety syringe comprising: positioning an elongate generally tubular needle shield relative to a barrel of a safety syringe such that the elongate generally tubular needle shield at least partially covers the barrel and such that at least a portion of a hollow needle associated with the safety syringe extends distal of the elongate generally tubular needle shield; inserting the hollow needle of the safety syringe into a quantity of a fluid to be dispensed; withdrawing a plunger slidable within the barrel, thereby filling the syringe with fluid to be dispensed; removing the hollow needle of the safety syringe from the fluid to be dispensed; ejecting the fluid to be dispensed; positioning the elongate generally tubular needle shield distal of the barrel thereby covering the hollow needle associated with the safety syringe with the elongate generally tubular needle shield; grasping the barrel of the safety syringe thereby substantially preventing transverse motion; and applying a force to the elongate generally tubular needle shield in a direction perpendicular to a longitudinal axis of the elongate generally tubular needle shield sufficient to break an at least partially relieved proximal region between the syringe barrel and a generally tubular needle hub which attaches the hollow needle associated with the safety syringe to the barrel, said at least partially relieved proximal region being adapted to break upon the application of a perpendicularly applied force. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates an embodiment of a safety syringe of the disclosure. 
         FIG. 2  illustrates the safety syringe embodiment of  FIG. 1  with a portion removed. 
         FIG. 3  illustrates a detail of the embodiment of  FIG. 1  prior to final assembly. 
         FIG. 4  illustrates the detail of  FIG. 3  following assembly. 
         FIG. 5  illustrates one of the configurations of the safety syringe embodiment of  FIG. 1 . 
         FIG. 5A  illustrates one of the optional steps in the use of a safety syringe embodiment of  FIG. 1 . 
         FIG. 5B  illustrates one of the optional steps in the use of a safety syringe embodiment of  FIG. 1 . 
         FIG. 6  illustrates a safety syringe embodiment of  FIG. 1  prepared for disposal. 
     
    
    
     DETAILED DESCRIPTION 
     The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The drawings, which are not necessarily to scale, are not intended to limit the scope of the claimed invention. The detailed description and drawings illustrate example embodiments of the claimed invention. 
     All numbers are herein assumed to be modified by the term “about.” The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). 
     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include the plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     It is noted that references in the specification to “an embodiment”, “some embodiments”, “other embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it would be within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described, unless clearly stated to the contrary. 
       FIG. 1 , illustrates a non-limiting exemplary embodiment of a safety syringe of the disclosure. The safety syringe  10  includes a syringe body or barrel  100 , typically including a graduated scale  102  thereon; a plunger  110  sealingly slidable within the barrel  100 ; a hollow needle (not shown in this figure); an elongate generally tubular needle shield  150  moveable over the barrel  100 ; and a distal cap  160  adapted to engage the distal end of the elongate generally tubular needle shield  150 . Distal cap  160 , if present, includes an internal cavity of sufficient depth to accommodate that portion of the hollow needle (not shown) which extends distally from a generally tubular needle hub to be described herein. Distal cap  160  may have a closed distal end. The barrel  100  and elongate generally tubular needle shield  150  are typically sufficiently translucent or transparent to permit the plunger  110  and a scale  102  printed on the barrel to be seen through the elongate generally tubular needle shield. 
     Although the elongate generally tubular needle shield  150  of  FIG. 1  is depicted as having a circular cross-section, it will be appreciated that the function may be provided by elongate generally tubular needle shields having other cross-sectional shapes such as a triangle, a rectangle, a higher polygon, an oval, or the like. In some embodiments, the elongate generally tubular needle shield may have a cross-section which is somewhat elongated along a transverse axis to provide a better gripping surface for translation and/or rotation of the elongate generally tubular needle shield relative to the barrel. In other embodiments, an improved gripping surface may be provided by wings or other flanges extending from the surface of the elongate generally tubular needle shield. In yet other embodiments, the elongate generally tubular needle shield  150  may include, on at least a portion of its outer surface, a textured region  152  adapted to provide an improved finger grip. In certain embodiments, the elongate generally tubular needle shield  150  may include a cooperating key or keyway  154  adapted to guide translation of the elongate generally tubular needle shield relative to other components of the safety syringe, while limiting relative rotation except at selected places along the translation path. Complementary key or keyway  154  may include structures (not shown) which cooperate with collar  120  to provide one or more detents to position and/or lock elongate generally tubular needle shield  150  relative to barrel  100 . The structure of the detents, if present, is not critical and may be provided by structures known in the art such as mutually engaging protrusions and recesses. Some such engagements may be reversible while others may be irreversible. 
     In  FIG. 2 , the distal cap  160  has been removed in preparation for use which may better illustrate additional structures associated with the safety syringe  10 . Hollow needle  140  may be seen extending distally from generally tubular needle hub  130  to which it may be fixedly attached. In this embodiment, generally tubular needle hub  130  is integrally formed with barrel  100 . Generally tubular needle hub  130 , better seen in  FIGS. 3 and 4 , is joined to collar  120  via a plurality of ribs  132  which is integrally formed with the generally tubular needle hub  130 . Each rib of the plurality of ribs  132  includes an at least partially relieved proximal region  134  to provide a region adapted to be readily frangible when the elongate generally tubular needle shield  150  is positioned distal of the barrel  100  and subjected to a lateral force applied thereto at a point distal of barrel  100 . 
     In some embodiments, ribs  132 , adapted to join the collar  120  to generally tubular needle hub  130 , may be deformable and adapted to engage a circumferential inner ridge  122  of collar  120  such that the collar  120  is firmly attached to the plurality of ribs  132  distal of the at least partially relieved proximal region  134  of the plurality of ribs  132 . In other embodiments, the plurality of ribs  132 , adapted to join the collar  120  to the generally tubular needle hub  130 , is fixedly attached to the generally tubular needle hub  130  and by adhesive to the collar  120  distal of the at least partially relieved proximal region  134  of the plurality of ribs  132 . In yet other embodiments, the plurality of ribs  132 , adapted to join the collar  120  to the generally tubular needle hub  130 , is fixedly attached to the generally tubular needle hub  130  and by welding to the collar  120  distal of the at least partially relieved proximal region  134  of the plurality of ribs  132 . It will be appreciated that those deformable ribs  132 , adapted to engage a circumferential inner ridge  122  of collar  120 , may additionally be fixedly attached to the collar by adhesive or welding if desired. In still other embodiments, barrel  100 , collar  120 , generally tubular needle hub  130 , and the plurality of ribs  132 , each including a relieved proximal region  134 , may be integrally formed. These fixation methods may significantly increase the force required to remove elongate generally tubular needle shield  150  from the remaining components of safety syringe  10  by pulling and/or wiggling the elongate generally tubular needle shield  150  relative to the syringe barrel  100 . In each of the above embodiments, the plurality of ribs  132  may include two, three, four, or more ribs  132 . 
       FIG. 3  illustrates a barrel  100 , generally tubular needle hub  130 , ribs  132  with at least partially relieved proximal regions  134 , and a hollow needle  140  prior to assembly with collar  120  having an inner circumferential ridge  122 .  FIG. 4  illustrates the components after assembly in partial detail such that the at least partially relieved proximal region  134  may be seen. Elongate generally tubular needle shield  150  has been omitted from these figures for clarity. Depending upon details of the elongate generally tubular needle shield  150  and collar  120 , which details should not be viewed as limiting in the current disclosure, safety syringe  10  may be assembled by inserting generally tubular needle hub  130  into the proximal end of elongate generally tubular needle shield  150  and advancing generally tubular needle hub  130  until hollow needle  140  extends distally from the elongate generally tubular needle shield  150 . Collar  120  may then be pressed over deformable ribs  132  to engage circumferential inner ridge  122  of collar  120  thereby firmly attaching collar  120  to generally tubular needle hub  130  via the plurality of deformable ribs  132 . If desired, ribs  132  may be fixedly attached to collar  120  as discussed above. In such assemblies, the proximal end of elongate generally tubular needle shield  150  may include one or more projections adapted to prevent collar  120  from being withdrawn proximally through the proximal end of generally tubular needle shield  150 . 
       FIGS. 5, 5A, 5B, and 6  illustrate the use of safety syringe  10 , following the administration of a drug or other fluid. As illustrated, the safety syringe  10  may be operated with a single hand for convenience; however two hands may be used depending on operator preference. In  FIG. 5 , the elongate generally tubular needle shield  150  has been advanced distally along keyway  154 . If an optional detent  124  is present, detent  124  may be engaged by urging the elongate generally tubular needle shield  150  distally with respect to the barrel as shown by the arrow  156 . In some embodiments, detent  124  may also hold elongate generally tubular needle shield  150  in a proximally retracted position during use. If a second optional detent  126  is present, the second detent may be engaged by rotating the elongate generally tubular needle shield  150  relative to the barrel, as shown by curved arrow  158 , thereby locking the collar  120  and generally tubular needle hub  130  near the proximal end of the elongate generally tubular needle shield  150 . 
     In  FIG. 5A , operator  170  has used a thumb and forefinger of one hand to slide elongate generally tubular needle shield  150  distally with respect to barrel  100 , held by the remaining fingers, thereby optionally engaging a detent (not visible in this view) and further has rotated elongate generally tubular needle shield  150  to lock elongate generally tubular needle shield  150  to collar  120  via a second optional detent (not visible in this view). In  FIG. 5B , operator  170  has started to apply a force, perpendicular to the barrel  100 , to elongate generally tubular needle shield  150 , which is being held by the remaining fingers. Further application of force will cause generally tubular needle hub  130  and plurality of ribs  132  to break at the at least partially relieved region  134  allowing separate disposal of the protected used needle  140 , contained within lumen  151  of elongate generally tubular needle shield  150 , and the barrel  100 /plunger  110  of the syringe as shown in  FIG. 6 . Separate disposal of the barrel  100 /plunger  110  of the syringe allows recycling of those parts thereby reducing the volume of medical waste. 
     In use, elongate generally tubular needle shield  150  is initially retracted proximally relative to the barrel  100  to expose the tip and a portion of the shaft of hollow needle  140  and typically a portion of generally tubular needle hub  130 . In some embodiments, the elongate generally tubular needle shield  150  may be releasably held in the retracted position by cooperation between optional detent components associated with elongate generally tubular needle shield  150  and collar  120 . Plunger  110  is advanced fully distally. Hollow needle  140  may then be inserted into a fluid to be dispensed, often by passing the tip of hollow needle  140  through the septum of a vial containing a drug or other fluid to be dispensed. Withdrawing plunger  110  relative to barrel  100  causes fluid to be drawn through hollow needle  140  to fill a portion of the barrel with the fluid to be dispensed. The amount of fluid contained within the barrel may be determined by reference to scale  102  in the conventional manner. Scale  102  on barrel  100  as well as plunger  110  can be viewed through translucent or transparent elongate generally tubular needle shield  150 . 
     Once the fluid has been delivered to the desired site through needle  140  by moving plunger  110  distally, the elongate generally tubular needle shield  150  may be advanced distally over barrel  100  to a stop or optional detent thereby covering hollow needle  140 . This may be accomplished as a single-handed operation if desired. In some embodiments, the combination of elongate generally tubular needle shield  150  and collar  120  may also include a second detent capable of being engaged by rotating the elongate generally tubular needle shield  150  relative to barrel  100  thereby locking the collar  120  proximate the proximal end of the elongate generally tubular needle shield  150 . The optional locking operation also may be accomplished with one hand if desired. See  FIGS. 5 and 5A . 
     With elongate generally tubular needle shield  150  advanced distally and optionally locked to collar  120 , the operator may then apply a force in a direction perpendicular to the longitudinal axis of the elongate generally tubular needle shield  150  sufficient to break the safety syringe at the at least partially relieved proximal region between barrel  100  and elongate generally tubular needle shield  150 , thereby separating the used hollow needle  140  component from the barrel  100 /plunger  110  component to allow separate disposal of the respective components in an approved medical waste container. For an added measure of protection, cap  160  may be reinstalled. Operator  170  may separate the used hollow needle  140  component from the barrel  100 /plunger  110  component with a single hand, if desired, by grasping the barrel  100  with the fingers while pressing laterally on the elongate generally tubular needle shield  150  distal of the barrel  100  as illustrated in  FIG. 5B . 
     Although the illustrative examples described above relate to a specific exemplary embodiment of a single use safety syringe, use with other safety syringes is also contemplated. In such embodiments, details of elements corresponding to the collar, elongate generally tubular needle shield, and ribs may be modified while preserving the enhanced ability to break reliably and predictably at a region adjacent to the distal end of the syringe barrel. 
     Various modifications and alterations of this invention will become apparent to those skilled in the art without departing from the scope and principles of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth hereinabove. All publications and patents are herein incorporated by reference to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference.