Patent Publication Number: US-2005119627-A1

Title: Selectively passive forward shielding medical needle device

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a medical device for safe and convenient handling of used needle cannulas. More particularly, the present invention relates to a medical needle device that is adapted to automatically shield a needle cannula during normal use in a medical procedure.  
      2. Description of Related Art  
      Blood collection sets or intravenous (IV) infusion sets typically include a needle cannula having a proximal end, a distal end with a puncture tip, and a lumen extending therebetween. The proximal end of the needle cannula is mounted to a plastic hub having a central passage that communicates with the lumen in the needle cannula. A thin flexible thermoplastic tube is connected to the hub and communicates with the lumen in the needle cannula. The end of the plastic tube remote from the needle cannula may include a fixture for connecting the needle cannula to a separate medical device, such as a holder, a blood collection tube, and the like.  
      In order to reduce the risk of incurring an accidental needle-stick wound, protection of used needle cannulas becomes important. With concern about infection and transmission of diseases, methods and devices to cover used needle cannulas have become important and in great demand. For example, some needle assemblies commonly employ a safety shield that may be moved into shielding engagement with a used needle cannula without risking an accidental needle stick.  
      U.S. Pat. No. 5,505,711 discloses a winged injector needle assembly including a needle cannula attached to a hub and a holder forming a shield portion. The hub is slidable within the shield portion. The needle assembly also includes a latching mechanism between the hub and the shield portion to maintain the hub in a forward position with the needle cannula extending from the shield portion. Upon grasping of and release of the latching mechanism, the shield portion may be moved forward to shield the needle cannula. U.S. Pat. No. 5,928,199 discloses a similar forward shielding needle assembly, which further includes a lock for locking the shield portion in the forward position shielding the needle cannula. Release of the latching mechanism is awkward due to the relation between the latching mechanism extending between the shield portion and the hub. Further, this device requires the operator to exert a substantial force to shield the needle cannula, and is prone to rotation of the needle cannula within the shield portion during the shielding operation.  
      U.S. Pat. Nos. 5,779,679 and 6,210,371 to Shaw disclose winged IV sets with a retracting needle assembly adapted to automatically retract a needle cannula within a safety shield upon release of a latch. The winged IV sets include a pair of latch wings associated with an outer shield that hold the needle assembly in an unretracted position, and which may be released to cause the needle assembly to be retracted rearwardly within the outer shield. A spring drives the needle assembly rearward to the retracted position within the safety shield. However, since retraction of such a device is achieved by holding the safety shield, the user does not hold the needle cannula during retraction and therefore does not maintain control over the needle cannula. Thus, if the latch is released while the needle cannula is inserted in a patient or during withdrawal from the patient, the spring force may cause an undesirable partial or full retraction of the needle cannula, instead of merely passively activating the device to allow for complete retraction upon full removal from the patient.  
      In view of the foregoing, there is a continuing need for a shielding medical needle device adapted to shield a used needle cannula once a medical procedure is completed.  
     SUMMARY OF THE INVENTION  
      The present invention relates generally to a safety needle system in the form of a shielding medical needle device for shielding used needle cannulas. The shielding medical needle device generally includes a hub housing and an elongated shield housing. A needle cannula having a distal puncture tip extends from the hub housing, with at least a portion of the needle cannula extending through the passageway of the shield housing. A biasing member such as a compression spring acts on the shield housing to bias the shield housing from a first biased position adjacent the hub housing toward a second position covering the distal puncture tip of the needle cannula. An engagement mechanism extends dorsally from the hub housing and is in releasable engagement with a portion of the shield housing for releasably retaining the shield housing in the first biased position adjacent the hub housing. Activation of the engagement mechanism releases the engagement mechanism from engagement with the shield housing. As such, the shield housing is released from the biased position, with the biasing member causing the shield housing to move toward the second position. Since the engagement mechanism extends dorsally from the device, activation of the device to shield the needle can be effectively accomplished during removal of the needle device from a patient, thereby providing for a passive activation of the device during normal use.  
      Desirably, the engagement mechanism is comprised of a first member extending dorsally from the hub housing, and a second member extending from a portion of the first member moveable with respect to the first member, such as through a fulcrum. The second member releasably engages a portion of the shield housing, such as through a hook element engaged within a recess or opening which extends through a latch element extending dorsally from the shield housing. Activation of the mechanism can be accomplished by movement of the second member with respect to the first member about the fulcrum, so as to release the hook element from engagement within the opening of the latch element of the shield housing.  
      Desirably, the needle system includes a pair of flexible wings extending from opposing lateral sides of the hub housing. In such an arrangement, the engagement mechanism extending dorsally from the hub housing desirably bisects the flexible wings extending from opposing lateral sides of the hub housing, but bending of the flexible wings toward a dorsal position does not cause activation of the engagement mechanism.  
      Additionally, the safety needle system may include a locking mechanism for locking the shield housing in the shielding position, such as by providing the hub housing with at least one flexible cut out portion along a wall thereof for engagement with a portion of the shield housing when the shield housing is in the second position to prevent a return movement of the shield housing to the first position.  
      In a further embodiment, the present invention is directed to a method for passively activating a safety needle system. The method includes providing a safety needle system comprising a hub housing including a needle cannula extending from a distal end of the hub housing toward a distal puncture tip; a shield housing covering at least a portion of the needle cannula adjacent the hub housing; a biasing element for biasing the shield housing toward a shielding position fully covering the distal puncture tip of the needle cannula; and a latch mechanism extending dorsally from the safety needle system for maintaining the shield housing in a biased state adjacent the hub housing. The method further includes inserting the safety needle system into a patient, and withdrawing the safety needle system from the patient by grasping the latch mechanism, thereby releasing the shield housing from the biased state and causing the shield housing to extend toward the shielding position. Desirably, the hub housing further includes a pair of flexible wings extending from opposing lateral sides thereof. In such an arrangement, the inserting step may include bending the flexible wings to a dorsal position for guiding the needle cannula into the patient. Such bending of the flexible wings to a dorsal position does not cause the latch mechanism to release the shield housing from the biased state. Further, the shield housing may be prevented from re-exposing the distal puncture tip of the needle cannula once the shield housing has been extended to a fully shielding position, such as through a locking mechanism.  
      In yet a further embodiment, the present invention is directed to a safety needle system which includes a grippable dorsal housing having distal and proximal dorsal housing portions. The proximal dorsal housing portion supports a needle, and the distal dorsal housing portion extends in an axial direction with respect to the needle from a first position adjacent the proximal housing portion to a second position covering a distal tip of the needle. A planar wing structure is integral to at least one of the proximal and/or distal dorsal housing portions, and extends in a direction which is generally normal to the grippable dorsal housing. A biasing element such as a spring extends between the distal and proximal dorsal housing portions for biasing the dorsal housing portion toward the second position. A release element, such as a release latch on the proximal dorsal housing portion in interference engagement with a recess or opening in the distal dorsal housing portion, selectively retains the distal dorsal housing portion in the first position adjacent the first housing portion against the bias of the biasing element. Activation of the release element causes the biasing element to act on the distal dorsal housing portion to move the distal dorsal housing portion to the second position.  
      Further details and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the drawings, wherein like parts are designated with like reference numerals and lower case letters are included where necessary to identify specific embodiments of the invention. 
    
    
     DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of the safety needle assembly of the present invention in the form of a blood collection set, shown in a ready-for-use position with a packaging cover removed and the needle shield retracted to expose the puncture tip of the needle;  
       FIG. 2  is an exploded perspective view of the assembly of  FIG. 1 ;  
       FIG. 3  is a perspective view of the needle assembly of  FIG. 1  shown with the laterally extending wing members bent into a dorsal position for use during insertion of the needle assembly;  
       FIG. 4  is a perspective view of the needle assembly of  FIG. 1  shown in a fully shielding position covering the puncture tip of the needle;  
       FIG. 5  is a side view of the needle assembly of  FIG. 1  with the needle shield in a retracted position;  
       FIG. 6  is a side view of the needle assembly of  FIG. 4  with the needle shield in a fully shielding position;  
       FIG. 7  is a top view of the needle assembly of  FIG. 1  with the needle shield in a retracted position;  
       FIG. 8  is a top view of the needle assembly of  FIG. 4  with the needle shield in a fully shielding position;  
       FIG. 9  is a top cross-sectional view of the needle assembly of  FIG. 1  with the needle shield in a retracted position;  
       FIG. 10  is a top cross-sectional view of the needle assembly of  FIG. 4  with the needle shield in a fully shielding position;  
       FIG. 11  is a side cross-sectional view of the needle shield in use with a needle in a retracted position;  
       FIG. 12  is a side cross-sectional view of the needle shield in use with a needle in a fully shielding position; and  
       FIG. 13  is a perspective view of a needle clip for use in one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION  
       FIGS. 1-10  generally illustrate a medical device according to the present invention. The medical device of the present invention generally includes a shieldable safety needle system adapted to enclose or surround a used needle cannula at the end of a medical procedure, such as a blood collection procedure. The medical device may be used as part of a fluid collection set used to collect blood or other fluids from the body of a human or animal. While described herein in terms of a blood collection set  10 , it is noted that the medical device of the present invention including the safety needle system may be used with any medical device incorporating a needle, such as a syringe system, a double-ended phlebotomy needle, or the like. Preferably, the medical device includes a portion that is automatically biased to a safety, needle-enclosing position during normal use by a user of the medical device resulting in a passive activation of the safety features of the assembly, as discussed in detail hereinafter.  
      Referring to  FIGS. 1 and 2 , a first embodiment of the medical device is shown in the form of blood collection set  10 . Blood collection set  10  generally includes a shieldable needle device  12 , a flexible tube  14  extending from needle device  12 , a fixture  16  mounted to tube  14 , and a packaging cover  18  removably mounted to portions of needle device  12  opposite tube  14 , such as through a frictional engagement. Shieldable needle device  12  of blood collection set  10  is shown in detail in  FIGS. 2-10 , and generally includes a needle cannula  20 , a hub housing  30 , a shield housing  70 , a biasing element in the form of spring  60  biasing the shield housing away from the hub housing, and a latch mechanism  50  for maintaining the shield housing  70  in a biased state adjacent hub housing  30 . The hub housing  30  is adapted for connection to a receptacle (not shown) of, for example, a blood collection set, by way of fixture  16  extending from hub housing  30  through flexible tube  14  by means and procedures known in the art.  
      Needle cannula  20  includes a proximal end  22  and an opposing distal end  24 , with lumen  26  extending through needle cannula  20  from proximal end  22  to distal end  24 . Distal end  24  of needle cannula  20  is beveled to define a sharp puncture tip  28 , such as an intravenous puncture tip. Puncture tip  28  is provided for insertion into a patient&#39;s blood vessel, such as a vein, and is therefore designed to provide ease of insertion and minimal discomfort during venipuncture. Packaging cover  18  is positioned over the distal end  24  of the needle cannula  20  as a removable protective cover to prevent accidental needle-stick wounds prior to using the blood collection set  10  in a medical procedure and to protect the puncture tip  28  prior to use.  
      Needle assembly  12  further includes hub housing  30 . Hub housing  30  is a unitary structure, desirably molded from a thermoplastic material. Hub housing  30  includes a first, open proximal end  32 , a second, open distal end  34 , and is defined by a rigid tubular wall  36  extending from proximal end  32  to distal end  34 . Tubular wall  36  is characterized by an internal passage  38  extending therethrough from proximal end  32  to distal end  34  of hub housing  30 . Hub housing  30  includes a nub  48  extending from proximal end  32  thereof, which provides structure for connection of flexible tube  14  thereto. Alternatively, hub housing  30  may incorporate structure for attachment to or engagement with an alternate medical device. For example, hub housing  30  may include a luer fitting, such as a female tapering surface at the proximal end thereof for engagement with a male tapering surface of a separate medical device, such as a syringe barrel.  
      Hub housing  30  further includes a pair of stabilizers in the form of flexible wings  40  and  42  extending laterally from tubular wall  36  at opposing sides thereof, desirably forming a planar wing structure. Wings  40  and  42  provide hub housing  30 , and needle assembly  12 , as a butterfly-type wing assembly, for assistance in positioning and placement of needle assembly  12  during a blood collection procedure, and provide a surface for securing needle device  12  to the skin of a patient, such as through taping wings  40  and  42  to the patient&#39;s skin. Wings  40  and  42  may be integrally formed with hub housing  30 , or may be a separate component or components affixed or adhered to hub housing  30 . Wings  40  and  42  may be constructed of a flexible material such that at least one, and preferably both, of the wings  40 ,  42  may be bent toward each other and brought together between the fingers of the user to assist in positioning and placing the needle device  12  during venipuncture.  
      The tubular wall  36  of hub housing  30  includes a pair of cutaway portions adjacent distal end  34  in the form of flexible fingers  44  and  46 . Flexible fingers  44 ,  46  are cutaway sections of tubular wall  36  and are biased radially inwardly of tubular wall  36  into internal passage  38 . As stated, the tubular wall  36  of hub housing  30  is molded of a thermoplastic material, thereby making the flexible fingers  44  and  46  inherently flexible. Flexible fingers  44 ,  46  provide needle assembly  12  with a locking mechanism for preventing re-exposure of puncture tip  28  of needle cannula  20  from shield housing  70 , as will be described in more detail herein.  
      Needle cannula  20  is positioned within internal passage  38  of hub housing  30 , and extends from distal end  34  of hub housing  30 . Desirably, needle cannula  20  and hub housing  30  are separate parts which are fixedly attached and secured through an appropriate medical grade adhesive or the like. More particularly, the proximal end  22  of needle cannula  20  is received within the internal passage  38  of hub housing  30 , with the distal end  24  of needle cannula  20  projecting outward from the distal end  34  of the hub housing  30 . The internal passage  38  communicates with the lumen  26  defined in the needle cannula  20  to enable fluid, such as blood, to pass through the needle device  12  and to the flexible tube  14  connecting the needle device  12  to the blood collection receptacle. The needle cannula  20  is preferably secured adjacent the proximal end  32  of hub housing  30  through the use of an appropriate medical grade adhesive, mechanical means, or the like.  
      A latch mechanism  50  extends dorsally from the top surface of hub housing  30 . Latch mechanism  50  includes a first member and a second member  54  extending from a portion of the first member  52 . First member  52  and second member  54  form generally elongated finger tabs which extending axially toward the proximal position, i.e., toward proximal end  32  of hub housing  30 . Second member  54  includes a forward or distally extending portion with a hook  58  at a distal end thereof, and extends from first member  52  through a lever arm which creates a fulcrum  56 . As such, first member  52  and second member  54  can be squeezed or pinched toward each other about fulcrum  56 , which causes hook  58  at the distal portion of second member  54  to pivot outwardly.  
      As noted, wings  40  and  42  extend from opposing lateral sides of hub housing  30 , generally in a planar fashion. Latch mechanism  50  extends dorsally from the top surface of housing  30  and generally bisects the plane defining wings  40  and  42 , such that wings  40 ,  42  are generally normal to latch mechanism  50 . Moreover, first member  52  and second member  54  of latch mechanism  50  extending in a generally proximal direction such that bending together of wings  40  and  42  in a dorsal manner does not cause first member  52  and second member  54  to be squeezed or pinched together due to the positioning of the finger tabs of first member  52  and second member  54  and of the lever arm or fulcrum  56 , as will be discussed further with respect to use of the device.  
      Needle device  12  further includes shield housing  70 . The shield housing  70  extends between a first, open proximal end  72  and a second, open distal end  74 , and is defined by a generally hollow tubular wall  76  having an internal passage  78 . Shield housing  70  is preferably a unitary structure, which is desirably molded from a thermoplastic material. The internal passage  78  is sized to coaxially receive needle cannula  20 , with shield housing  70  axially slidable thereabout. As such, shield housing  70  is movable along needle cannula  20  between a first proximal or retracted position adjacent hub housing  30 , and a second distal position encompassing and shielding puncture tip  28 , as will be described in more detail herein.  
      The proximal end  72  of shield housing  70  is sized to be received within the distal end  34  of hub housing  30  and extend within internal passage  38  thereof. Accordingly, tubular wall  76  of shield housing  70  may include a portion of reduced diameter at stepped down portion  84 , which extends toward the proximal end  72  of shield housing  70 . This stepped down portion  84  slidably cooperates within the internal passage  38  of hub housing  30 . Shield housing  70  may further include a neck  86  extending radially about the stepped down portion  84 , forming a shoulder  88  facing the proximal end  72  of shield housing  70  for interference engagement with flexible fingers  44 ,  46  to providing a locking mechanism, as will be discussed in more detail herein.  
      Shield housing  70  is generally movable between a first or retracted position adjacent hub housing  30  with at least a portion of shield housing  70 , such as proximal end  32  thereof, coaxially contained within internal passage  38  of hub housing  30 , and a second, extended or needle-shielding position, wherein the needle cannula  20  is enclosed or disposed within shield housing  70  fully covering the needle cannula  20  and, in particular, the puncture tip  28 . The first or retracted position of the shield housing  70  is shown in  FIGS. 1, 5 ,  7  and  9  and the second or extended position of the shield housing  70  is shown in  FIGS. 4, 6 ,  8  and  10 . In the first retracted position, the distal end  24  of needle cannula  20  projects outward from the shield housing  70  for use in a fluid collection procedure.  
      A latch element  80  extends dorsally from the top surface of shield housing  70 , forming a dorsal wing-like structure. Latch element  80  includes a recessed portion within the surface thereof, or an opening such as opening  82  extending through the surface thereof. Opening  82  of latch element  80  is provided for establishing releasable engagement with hook  58  of latch mechanism  50  of hub housing  30 . As such, the engagement between hook  58  of latch mechanism  50  within recess or opening  82  of latch element  80  establishes a dorsally extending engagement mechanism for releasably retaining shield housing  70  in the proximal or retracted position adjacent hub housing  30 .  
      The needle device  12  preferably further includes a biasing member such as compression spring  60  extending between the hub housing  30  and the shield housing  70 . Spring  60  is adapted to act on the shield housing  70  to bias the shield housing  70  from the first retracted position adjacent hub housing  30  toward the second shielding position in which shield housing  70  encompasses puncture tip  28  of needle cannula  20 . The biasing member or spring  60  is disposed within internal passage  38  of hub housing  30  about needle cannula  20 , and extends between the internal surface within internal passage  38  at the proximal end  32  of hub housing  30  and shoulder  88  of neck  86  extending circumferentially about the proximal end of shield housing  70  extending within hub housing  30 . Spring  60  is maintained in a compressed state by engagement of the hook  58  of the second member  54  of latch mechanism  50  within the recess or opening  82  in the latch element  80  of shield housing  70 . If desired, the proximal end  62  of the spring  60  may be secured to the proximal end  32  of hub housing  30  by a suitable medical grade adhesive known in the art or by a fixed mechanical connection. Likewise, the distal end  64  of the spring  60  may be adhesively or mechanically secured to the shield housing  70 , such as at shoulder  88 . Once the spring  60  is released by disengaging the hook  58  from the corresponding opening  82 , the spring  60  exerts an axial expansion force against the shield housing  70 , and in particular, against the proximal end  72  or shoulder  88  of shield housing  70 , relative to the hub housing  30 . The shield housing  70  is urged by the spring  60  to the second, needle-shielding position, wherein the shield housing  70  covers the needle cannula  20  (i.e.,  FIG. 4 ). The spring  60  also substantially prevents the shield housing  70  from moving proximally back toward the first position within hub housing  30  by providing a counter-acting biasing force against such a movement.  
      In one embodiment, shield housing  70  may further include a protective clip  90  for locking out puncture tip  28  of needle cannula  20  and preventing re-exposure thereof. As best seen in  FIGS. 11-13 , clip  90  may be unitarily stamped and formed from a resiliently deflectable metallic material. Clip  90  includes a planar spring leg  92  extending between a proximal end and an opposed distal end. A mounting aperture  94  extends through clip  90  at a location near the proximal end. A lock out leg  96  extends angularly from the distal end of clip  90 , and is bent back toward the proximal end of clip  90 . The bends in lock out leg  96  enable secure protective engagement with puncture tip  28  of needle cannula  20  and further enable smooth axial sliding movement of shield housing  70  along needle cannula  20 , as described in further detail herein.  
      In use, blood collection set  10  is provided with needle device  12  assembled and including flexible tube  14  extending from needle device  12  and connected to fixture  16 . Blood collection set  10  is preferably packaged with the shield housing  70  in the first retracted position, as shown, for example, in  FIG. 1 . After removing blood collection set  10  from its package, it can be assembled with other appropriate medical equipment for use. For example, a non-patient needle assembly and a needle holder may be connected to blood collection set  10  through fixture  16 .  
      To prepare for use of blood collection set  10 , the user grasps wings  40  and  42  at opposing lateral sides of hub housing  30  between a thumb and forefinger, and bends wings  40  and  42  dorsally toward each other, with latch mechanism  50  extending therebetween, as shown in  FIG. 3 . Packaging cover  18  is then grasped and urged distally to disengage from needle cannula  20  and/or shield housing  70 , thereby exposing puncture tip  28  of needle cannula  20 .  
      The overall design and profile of latch mechanism  50  is configured such that bending of the wings  40  and  42  to the dorsal position for positioning and placement does not cause activation of the latch mechanism  50 . In other words, bending of wings  40  and  42  together does not cause pinching movement of the finger tabs of first member  52  and second member  54  relative to each other, which would disengage the hook  58  from interference engagement with opening  82 . This may be accomplished by maintaining the lever arm or fulcrum  56  at a position directly adjacent the point of contact between bent wings  40  and  42 . As such, shield housing  70  is maintained in the first retracted position with latch mechanism  50  unactivated during bending of wings  40  and  42  for positioning and placement of needle device  12 . Desirably, wings  40  and  42  are of sufficient length to extend dorsally beyond latch mechanism  50  when wings  40  and  42  are bent together, thereby providing further assurance that latch mechanism  50  will not be activated to release shield housing  70  during positioning and placement.  
      After packaging cover  18  is removed, the medical practitioner can then urge puncture tip  28  at distal end  24  of needle cannula  20  into a targeted blood vessel of a patient with wings  40  and  42  bent inwardly toward each other between the user&#39;s fingers to act as a structure for guided placement, as is known in the art. After the targeted blood vessel has been accessed, the medical practitioner can release the grip on wings  40  and  42 , and wings  40  and  42  can thereafter be taped to the patient&#39;s skin to prevent movement of the needle device  12  during use.  
      Upon completion of the procedure, such as when all desired samples have been drawn, needle cannula  20  can be withdrawn from the patient. As opposed to conventional techniques for withdrawing wingsets by again bending the wings together in a dorsal manner, withdrawal of needle device  12  is preferably accomplished by grasping latch mechanism  50 , that is by grabbing the finger tabs of first member  52  and second member  54  between a user&#39;s thumb and forefinger. This grabbing causes first member  52  and second member  54  to move toward each other in a direction of arrows A in  FIG. 1 , with fulcrum  56  acting as a pivot point for movement thereof. This movement toward each other in turn causes the distal end portion of second member  54  to pivot outwardly, which causes hook  58  to disengage from interference engagement within opening  82  of latch element  80  of shield housing  70 . Once the interference engagement between hook  58  and opening  82  is released, the bias from spring  60  causes shield housing  70  to be propelled distally in a direction of arrow B in  FIG. 4 , away from hub housing  30  along needle cannula  20 . At this point, the puncture tip  28  of needle cannula  20  may still be positioned within the patient. As such, shield housing  70  is propelled forward to a position in which it contacts the patient&#39;s skin. The user can then remove the needle device  12  from the patient, during which the shield housing  70  continues to move forward under the bias of the spring  60 , until the needle cannula  20  is fully withdrawn from the patient, at which point the shield housing  70  extends to the fully shielding position completely encompassing puncture tip  28 . After shield housing  70  is moved along needle cannula  20  past the puncture tip  28 , lockout leg  96  of clip  90  will pass distally beyond puncture tip  28  of needle cannula  20 . The inherent resiliency of spring leg  92  of clip  90  will urge lockout leg  96  over puncture tip  28  of needle cannula  20 . Thus, a return movement of shield housing  70  is prevented through clip  90  acting as a locking mechanism. Hence, puncture tip  28  of needle cannula  20  is safely shielded. Blood collection set  10  may then be appropriately discarded.  
      In addition to or instead of the locking mechanism established through clip  90 , a further locking mechanism may be provided through the interference interaction between flexible fingers  44 ,  46  and shoulder  88  of neck  86  on shield housing  70 . More particularly, as spring  60  propels shield housing  70  distally in the direction of arrow B, neck  86  of shield housing  70  passes beyond flexible fingers  44 ,  46 , which are biased radially inwardly against the outer surface of shield housing  70 . Once neck  86  passes beyond flexible fingers  44 ,  46 , the flexible fingers  44 ,  46  abut against shoulder  88 , thereby preventing shield housing  70  from movement backward in the opposite direction, as seen in  FIG. 10 . As such, shield housing  70  is locked in the shielding position encompassing puncture tip  28 . It will be appreciated that the location of the flexible fingers and corresponding shoulder may be reversed in accordance with the present invention. In addition, neck  86  of shield housing  70  may be trapped by the distal end of hub housing  30  to prevent movement beyond hub housing  30 , such as through a return portion within the distal end  34  of hub housing  30  which prevents the passage of neck  86  therebeyond.  
      Alternatively, if desired, activation of latch mechanism  50  to release shield housing  70  can be accomplished immediately after needle cannula  20  is placed within the patient&#39;s blood vessel, as opposed to waiting for withdrawal of needle device  12  from the patient.  
      Alternatively, activation of latch mechanism  50  may be delayed until after needle cannula  20  is fully removed from the patient. For example, wings  40  and  42  may be bent together in a dorsal manner to create a structure for holding needle device  12  and withdrawing needle cannula  20  from the patient. After the needle cannula  20  is withdrawn in this manner, activation of latch mechanism  50  can be accomplished to release shield housing  70  and effectively shield the used puncture tip  28 . As such, the needle device of the present invention is selectively passive.  
      The inner surface of the hub housing  30  and the outer surface of the shield housing  70  may interact such that any axial rotation of the hub housing  30  with respect to the shield housing  70  is inhibited during the sliding movement of the shield housing  70  from the first retracted position to the second shielding position. For example, a surface feature may be provided on one of the outer surface of the shield housing  70  or the inner surface of the hub housing  30 , such as a plurality of spline grooves or detents. Alternatively, the hub housing  30  and shield housing  70  may each have a non-circular cross section, for example, with one planar side, desirably a bottom flat surface, to prevent relative rotation between these elements.  
      The needle device of the present invention is particularly innovative since it involves a passive activation of the safety shielding feature through the ergonomic layout of the device. In particular, when in the retracted position, the shield housing interengages with the hub housing to form a grippable dorsal housing structure with the hub housing forming a proximal housing structure and the shield housing forming a distal housing structure, and incorporating a latch mechanism extending dorsally therebetween. Moreover, the shield housing is automatically activated to shield the needle cannula during the typical steps involved in a venipuncture procedure. For example, the device is easily insertable within a patient using a normal technique with bent wings forming a dorsal structure for guiding, positioning, and placement of the device. The shield housing can remain retracted during the blood sampling procedure, thereby preventing the shield housing from interfering with the user during the sampling procedure, and preventing the patient from being startled by activation of the shield against the patient&#39;s skin prior to the sampling procedure. Moreover, activation is easily accomplished during a typical procedure for removing the needle device from the patient, i.e., by grasping the device in a dorsal manner, through the latch mechanism extending dorsally from the device. This grasping automatically passively activates the device during removal, thereby avoiding any active step for shielding of the assembly by the user, and preventing any unnecessary exposure to the used needle cannula. The selectively passive activation affords a greater degree of safety to the user with minimal or no change in technique, as compared with conventional safety needle mechanisms.  
      While the medical device of the present invention is described in terms of several preferred embodiments for use in connection with bodily fluid collection systems and like devices, the present invention may take many different forms. The preferred embodiments shown in the drawings and described hereinabove in detail are to be considered as exemplary of the principles of the invention and are not intended to limit the invention to the embodiments illustrated. Various other embodiments will be apparent to and readily made by those skilled in the art without departing from the scope and spirit of the invention. The scope of the present invention will be measured by the appended claims and their equivalents.