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 . fig1 , 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 fig1 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 fig2 , 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 fig3 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 . fig3 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 . fig4 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 . fig5 a , 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 fig5 , 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 fig5 a , 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 fig5 b , 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 and the barrel 100 / plunger 110 of the syringe as shown in fig6 . 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 fig5 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 fig5 b . 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 .
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 .