Patent Publication Number: US-9402964-B2

Title: Passively shielding needle device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a divisional of, and claims priority to, U.S. patent application Ser. No. 11/909,879, filed Sep. 27, 2007, entitled “Passively Shielding Needle Device”, which is a United States national phase application of PCT/US2005/023515, filed Jul. 1, 2005, which is a continuation-in-part of U.S. patent application Ser. No. 10/882,659, filed Jul. 1, 2004, now U.S. Pat. No. 7,201,740, the entire disclosures of each of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a needle assembly including a needle safety shield for protecting users from a used needle tip, such as for use in a blood collection set for safe and convenient handling of needles used in blood collection procedures. 
     2. Description of Related Art 
     Disposable medical devices having medical needles are used for administering medication or withdrawing fluid from the body of a patient. Such disposable medical devices typically include blood collecting needles, fluid handling needles, and assemblies thereof. Current medical practice requires that fluid containers and needle assemblies used in such devices be inexpensive and readily disposable. Existing blood collection devices often employ some form of durable holder onto which disposable medical needles and fluid collection tubes may be mounted. A blood collection device of this nature may be assembled prior to use and then discarded after use. 
     A blood collection device or intravenous (IV) infusion device typically includes a needle cannula having a proximal end, a pointed distal end, and a lumen extending therebetween. The proximal end of the needle cannula is securely mounted in a plastic hub defining a central passage that communicates with the lumen extending through the needle cannula. A thin, flexible thermoplastic tube is connected to the hub and communicates with the lumen of 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 holder or other receptacle. The specific construction of the fixture will depend upon the characteristics of the receptacle to which the fixture is to be connected. 
     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 enclose or cover the used needle cannula have become very important and in great demand in the medical field. For example, needle assemblies often employ a safety shield that can be moved into shielding engagement with a used needle cannula to minimize risk of an accidental needle stick. 
     Some needle safety shields are referred to as “tip guards” and include a small rigid guard that may be telescoped along the length of the needle cannula and extended over the pointed distal end of the needle cannula for protection. Such conventional tip guards may include some form of tether for limiting the travel of the tip guard to the length of the needle cannula. An example of the foregoing is disclosed by U.S. Pat. No. 5,176,655 to McCormick et al. The McCormick et al. patent discloses the use of flexible loop-like straps for limiting the distal movement of a tip guard. 
     Needle shields that incorporate movable tip guards are typically manually actuated. For example, U.S. Pat. Nos. Re. 36,447 and Re. 36,398, both to Byrne et al., disclose a safety device for a hypodermic needle that includes a plastic sheath, which is used to cover the puncture tip of the needle. The plastic sheath incorporates a thumb guard, which the user of the safety device may grasp to move the plastic sheath to a position covering the puncture tip of the needle. U.S. Pat. No. 5,951,525 to Thorne et al. discloses a manually operated safety needle apparatus that includes two pairs of opposed legs adapted to move the tip guard of the apparatus to a position covering the used needle cannula. U.S. Pat. Nos. 5,562,637 and 5,562,636, both to Utterburg, disclose a rectangular needle protector sheath for use with a needle cannula that may be extended over the needle cannula after it is used. Other prior art devices, such as those disclosed by U.S. Pat. No. 5,290,264 to Utterberg and U.S. Pat. No. 5,192,275 to Burns, provide “grippable” members attached to the tip guards to facilitate moving the tip guards to a position covering the puncture tip of a needle cannula. In addition to providing gripping members for moving the tip guards, prior art devices in this area often include flexible wings, which are used as means for securing the needle assemblies to the body of a patient during a medical procedure. Examples of “winged” needle assemblies may be found in U.S. Pat. No. 5,120,320 to Fayngold; and U.S. Pat. Nos. 5,154,699; 5,088,982; and 5,085,639 all to Ryan. Other prior art in this area includes U.S. Pat. Nos. 5,266,072 and 5,112,311, both to Utterberg et al., which also disclose guarded winged needle assemblies. 
     U.S. Patent Application Publication No. 2002/0099339 to Niermann discloses a passive safety blood collection set which includes a tip guard slidably movable along a needle cannula. The tip guard is mounted to a needle hub through a pair of collapsible leaves, which are collapsed onto themselves and held in place by a packaging cover. In use, the practitioner holds the leaves in the collapsed or folded state to remove the cover, and then releases the leaves enabling them to unfold to propel the tip guard distally. 
     Conventional tip guards, such as those discussed hereinabove, often include a structure that lockingly engages over the pointed distal end of the used needle cannula to prevent a re-exposure of the needle cannula. The structure for preventing the re-exposure of the needle cannula may include a metallic spring clip or a transverse wall formed integrally with one end of the tip guard. An example of a metallic spring clip is disclosed by the McCormick et al. patent discussed previously. Conventional tip guards, such as those discussed hereinabove, often further require extensive mechanics for positioning the tip guard over the needle cannula. This results in complex arrangements that are costly to manufacture and assemble. Additionally, operation of the needle assemblies to move the tip guard into the proper position over the pointed distal end of the needle cannula requires substantial manual manipulation by the user of the device, exposing the user to potential needle-stick wounds. 
     U.S. Patent Application Publication No. 2003/0078540 to Saulenas et al. discloses a retractable push button needle assembly, in which a needle is attached to a hub and extends through a barrel. A push button actuator extends from the hub and is in interference engagement with the barrel. Activation is accomplished with a user actively pushing the push button into the barrel, thereby causing the needle to retract within the barrel based on a spring disposed between the hub and the barrel. 
     SUMMARY OF THE INVENTION 
     A need exists for a shielding needle assembly that achieves secure and effective shielding of a used needle cannula, and which is simple to manufacture and easy to operate. Additionally, a need exists for a needle assembly, such as for use in a blood collection set, that is passively operated during a normal blood collection procedure. 
     In one embodiment of the present invention, a safety needle device comprises a hub including a passageway extending therethrough and a needle cannula having a puncture tip extending from a forward end thereof A shield member is in telescoping association with the hub, with at least one of the hub and the shield member adapted for relative telescoping movement with respect to the other between a first position in which the puncture tip of the needle cannula is exposed from a forward end of the shield member and a second position in which the puncture tip of the needle cannula is encompassed within the shield member. A drive member is disposed between the hub and the shield member, and is capable of biasing the hub and the shield member telescopically away from each other. External pressure applied by a user to at least one of the hub and the shield member provides an engagement therebetween, preventing the drive member from biasing the hub and the shield member away from each other, such as in an axial direction. For example, external pressure applied by a user between corresponding surfaces of the hub and the shield member may provide an interference engagement therebetween, preventing the drive member from biasing the hub and/or the shield member axially away from each other. 
     In one embodiment, the safety needle device further includes a releasable packaging cover disposed about the puncture tip of the needle cannula. The packaging cover is adapted to apply external pressure to at least one of the hub and the shield member to provide an engagement therebetween, thereby preventing the drive member from biasing the hub and the shield member axially away from each other. In this manner, application of external pressure by a user to at least one of the hub and the shield member allows for release of the packaging cover from the needle device, and maintains the engagement between the hub and the shield member to prevent the drive member from biasing the hub and the shield member axially away from each other, thus providing a passive device. 
     One of the hub or the shield member may include at least one release member disposed at least partially within the packaging cover which is adapted to flex radially inward toward a central longitudinal axis of the needle device upon application of external pressure thereto. In this manner, passive release of the packaging cover from the hub or the shield member can be accomplished during normal use when the needle device is grasped by a user. 
     In a further embodiment, a safety needle device comprises a needle cannula comprising a proximal end and a distal end with a puncture tip, a housing defining a passageway extending therethrough, with the puncture tip of the needle cannula extending from a distal end of the housing, and a packaging cover releasably disposed about the distal end of the housing and enclosing the puncture tip of the needle cannula prior to using the safety needle device. The housing comprises at least one release member disposed at least partially within the packaging cover and adapted to flex radially inward toward a central longitudinal axis of the housing upon applying external pressure thereto, allowing passive release of the packaging cover from the distal end of the housing. The at least one release member may be pivotally connected to the housing, and may include a locking tab engaging a locking groove defined within the packaging cover. In this manner, application of external pressure causes the locking tab to disengage from the locking groove to allow passive release of the packaging cover from the distal end of the housing. Desirably, the housing includes a pair of opposing release members each comprising a locking tab engaging a locking groove defined within the packaging cover. A shield member may further be provided, which is axially movable with respect to the housing and which is maintained in a retracted position against a biasing force between the housing and the shield member by external pressure applied to the release member by the packaging cover, which external pressure maintains the shield member in the retracted position in which the puncture tip of the needle cannula is exposed from the shield member. Application of external pressure to the at least one release member, such as through a user&#39;s fingers grasping the at least one release member, causes the packaging cover to release from the housing and further causes the at least one release member to continue to maintain the shield member in the retracted position against the bias. The safety needle device may further be connected to a flexible tube which is adapted for connection to a receptacle, thereby providing a blood collection assembly. 
     In one particular embodiment of the invention, the needle device includes a shield member which may be movably associated with a hub between a first position in which the shield member is retracted within the hub and a second position with the shield member extended for shielding the puncture tip of a needle cannula. In such an embodiment, the hub may include at least one release member pivotally connected thereto, for maintaining the shield member within the hub against a biasing force provided by a drive member, such as a coil spring. A releasable packaging cover may also be disposed about the puncture tip of the needle cannula when the shield member is in the first position retracted within the hub, with the packaging cover engaged with the at least one release member to maintain radial pressure against the at least one release member, thereby maintaining the shield member within the hub against the bias of the drive member. Application of radial pressure by a user to the at least one release member causes the at least one release member to pivot radially inward, disengaging from any packaging cover which may be present to release the packaging cover from the hub, and further causing the at least one release member to engage the shield member and maintain the shield member in the retracted position. Release of the radial pressure applied by a user releases the engagement between the at least one release member and the shield member, thereby enabling the drive member to move the shield member from the first position retracted within the hub to the second position shielding the puncture tip of the needle cannula. In such an embodiment, the at least one release member may be pivotally connected to the hub, for example, substantially at the hub proximal end. Desirably, a pair of opposing release members is pivotally connected to the hub, for example, substantially at the hub proximal end. A finger tab may be provided on each of the release members for applying the radial inwardly directed pressure to the release members. The release member may further include at least one resiliently deflectable locking member such as a locking tab adapted to engage a locking recess in the safety shield member when it is in the extended position. Further, the release member may include a locking tab engaging a locking groove in the packaging cover, generally preventing removal of the packaging cover until radial pressure is applied to the at least one release member, causing the at least one release member to pivot radially inward and disengage the locking tab from the locking groove. 
     In another particular embodiment, the shield member includes a forward end and a rearward end defining a passageway extending therethrough, such as a barrel, with the hub disposed within the passageway of the shield member. In such an embodiment, the hub includes a release member, such as a button protrusion, extending toward the forward end thereof, and the shield member includes at least one release tab adapted for engagement with a surface of the release member of the hub and adapted to deflect radially outwardly from the shield member out of engagement from the release member when in a relaxed, unbiased state. External pressure maintains the release tab in the biased state in interference engagement with at least a portion of the release member of the hub, thereby maintaining the hub in the first position against the bias of the drive member. Sufficient release of the external pressure from the release tab permits the release tab to move to the unbiased state out of interference engagement with the release member, allowing the drive member to move the hub toward the second position wherein the puncture tip of the needle cannula is encompassed by the shield member. Desirably, a pair of release tabs extends longitudinally from opposing lateral sides of the shield member in a rearward direction, cooperatively defining an opening for receiving the release member in the interference engagement in the biased state of the release tabs. The at least one release tab preferably extends outward from the shield member when in the relaxed, unbiased state, and is adapted to deflect radially inward for engagement with the release member of the hub when external pressure is applied thereto. In such an embodiment, the drive member, desirably a coil spring, is disposed in the shield member and is associated with the hub for moving the hub toward the proximal position of the needle device. At least one resiliently deflectable locking member may also be associated with the shield member and adapted to engage the hub when the hub substantially reaches the proximal position for preventing re-exposure of the needle cannula. For example, the shield member may further include at least one flexible cutout portion or locking tab along a wall thereof, with the flexible cut out portion biased inwardly, such that the flexible cut out portion is adapted for interfering engagement with a portion of the hub when retracted to prevent a return movement. 
     In yet a further particular embodiment, the hub includes a dorsal member extending from an external surface thereof, and the shield member includes a grip structure extending dorsally therefrom adapted for corresponding engagement with the dorsal member at the external surface of the hub when the shield member is in a first retracted position, thereby forming a dorsal grasping structure. External pressure applied between the grip structure of the shield member and the dorsal member of the hub prevents the drive member from biasing the hub and the shield member axially away from each other. In such an embodiment, the shield member preferably telescopes within the passageway of the hub and the grip structure extends dorsally from the shield member toward the dorsal member of the hub, such that external pressure applied between the grip structure of the shield member and the dorsal member of the hub establishes frictional engagement therebetween. The shield member is thereby maintained in a retracted position within the passageway of the hub against the bias of the drive member with the puncture tip of the needle cannula exposed. Release of the external pressure between the grip structure of the shield member and the dorsal member of the housing releases the frictional engagement, allowing the drive member to bias the shield member toward an extended position in which the puncture tip of the needle cannula is encompassed within the shield member. A packaging cover may be provided in such an embodiment for releasably covering the forward end of the puncture tip when the shield is in the retracted position. Such a protective cap may provide for external pressure between the grip structure of the shield and the dorsal member of the housing to maintain the shield in the retracted position against the bias of the drive member. 
     Desirably, the dorsal member of the housing comprises a generally planar spine extending dorsally from the external surface of the housing in a plane corresponding to a longitudinal axis defined by the needle cannula, and the grip structure comprises generally planar structure for corresponding engagement with the spine of the housing. For example, the grip structure may define a pair of flexibly resilient planar leafs extending from a forward end of the shield in a plane corresponding to the longitudinal axis defined by the needle cannula. The pair of planar leafs may be spaced from each other to define an opening therebetween for accommodating the spine of the housing, with the pair of planar leafs joined at a forward surface of the shield at a bridge, and with at least a portion of the shield extending coaxially within the passageway o the housing. Moreover, the planar leafs and the spine may include corresponding structure adapted for interference engagement therebetween when external pressure is applied between the pair of planar leafs and the spine. For example, an external surface of the spine may include a detent and at least one of the pair of planar leafs may include a corresponding protuberance or protrusion extending within the opening between the pair of planar leafs for interference engagement with the detent of the spine when external pressure is applied between the pair of planar leafs and the spine. 
     The housing and the shield may be provided with interengaging structure for interfering engagement therebetween when the shield is in the extended position to prevent a return movement of the shield to the retracted position. For example, the housing may further include at least one flexible cutout portion along a wall thereof, with the flexible cut out portion biased inwardly toward the passageway of the housing, such that the flexible cut out portion is adapted for interfering engagement with a portion of the shield when the shield is in the extended position to prevent a return movement of the shield to the retracted position. Moreover, the housing may include a pair of wings extending laterally from opposing sides thereof. Such wings are in fixed relation to the housing, and are of a relative size and shape such that corresponding engagement of the dorsal member of the housing and the grip structure of the shield form a dorsal grasping structure when the shield is in the retracted position, with the dorsal grasping structure having a profile larger than the pair of wings on the housing. 
     A further embodiment involves a method of passively activating a shieldable needle device, such as one of the particular devices noted above. Such a method generally includes providing the shielding needle device including a needle cannula having a puncture tip, a hub supporting the needle cannula, a shield member in telescoping association with the hub and disposed generally coaxially with the hub, and a drive member associated with the hub and the shield member biasing the hub and the shield member axially away from each other. Additionally, the method includes applying radial pressure to one or both of the hub and the shield member, such that they engage each other, thereby preventing the drive member from biasing the hub and the shield member axially away from each other to maintain the needle device in a first position with the puncture tip exposed from the shield. 
     In one particular embodiment, the method involves providing the needle device including a housing having a dorsal member extending from an external surface thereof and a needle cannula having a puncture tip extending from a forward end thereof; a shield axially moveable with respect to the housing between a retracted position in which the puncture tip is exposed and biased toward an extended position covering the puncture tip, the shield including grip structure extending dorsally from an external surface thereof for corresponding engagement with the dorsal member of the housing to form a dorsal grasping element when the shield is in the retracted position; and a protective cap releasably attached to a forward end of the needle device for maintaining the shield in the retracted position against the bias and covering the puncture tip. The method further involves grasping the needle device at the dorsal grasping element applies external pressure between the grip structure of the shield and the dorsal member of the housing and removing the protective cap from the forward end of the housing. Upon release of the external pressure between the grip structure of the shield and the dorsal member of the housing, the biasing force will move the shield axially toward the extended position. The grasping step establishes frictional engagement between the grip structure of the shield and the dorsal member of the housing. The method may further include the step of preventing the shield from returning to the retracted position after moving to the extended position, such as by providing interengaging structure for interfering engagement therebetween when the shield is in the extended position to prevent a return movement of the shield to the retracted position. 
     Further details and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a shielding blood collection set including a needle device in accordance with an embodiment of the present invention, having a releasable packaging cover disposed at a distal end of the needle device. 
         FIG. 2  is a longitudinal cross-sectional view of the needle device shown in  FIG. 1 . 
         FIG. 3  is a longitudinal cross-sectional view of the needle device shown in  FIG. 1 , showing a user manipulating the needle device. 
         FIG. 4  is a longitudinal cross-sectional view of the needle device shown in  FIG. 1 , showing the user applying radial pressure to the needle device and the subsequent removal of the packaging cover. 
         FIG. 5  is a cross-sectional view of the needle device shown in  FIG. 1 , showing a needle cannula inserted into the body of a patient. 
         FIG. 6  is a longitudinal cross-sectional view of the needle device shown in  FIG. 1 , showing the needle device after the user has substantially released the radial pressure allowing shielding of the needle cannula. 
         FIG. 7  is a longitudinal cross-sectional view of the needle device shown in  FIG. 1 , showing the final disposition with shielding of the needle cannula. 
         FIG. 8  is a perspective view showing the direction of forces for actuation of the shielding needle device. 
         FIG. 9  is a perspective view of a shielding blood collection set including a needle device in accordance with another embodiment of the present invention, having a releasable packaging cover disposed at a distal end of the needle device. 
         FIG. 10  is an exploded perspective view of the specific elements of the needle device shown in  FIG. 9 . 
         FIG. 11  is a side view of the hub of the needle device of  FIG. 9 . 
         FIG. 12  is a perspective view showing the direction of forces for actuation of the shielding needle device of  FIG. 9 . 
         FIG. 13  is a perspective view showing of the shielding needle device of  FIG. 9  with the packaging cover removed in the retracted position with the needle cannula exposed for use. 
         FIG. 14  is a perspective view showing of the shielding needle device of  FIG. 9  in the extended position with the shield encompassing the needle cannula. 
         FIG. 15  is a longitudinal cross-sectional view of the needle device taken along lines  15 - 15  of  FIG. 9 . 
         FIG. 16  is a longitudinal cross-sectional view of the needle device taken along lines  16 - 16  of  FIG. 13 . 
         FIG. 17  is a longitudinal cross-sectional view of the needle device taken along lines  17 - 17  of  FIG. 14 . 
         FIG. 18  is a partial cross-sectional view of the needle device in the extended position as shown in the  FIG. 14 , depicting the locking elements for maintaining the shield in the shielding position. 
         FIG. 19  is a perspective view of a packaging cover in accordance with the embodiment of  FIG. 9 . 
         FIG. 20  is a perspective view of a shielding blood collection set including a needle device in accordance with a further embodiment of the present invention, having a releasable packaging cover disposed at a distal end of the needle device. 
         FIG. 21  is a longitudinal cross-sectional view of the needle device of  FIG. 20 . 
         FIG. 22  is an exploded perspective view of a hub of the needle device of  FIG. 20 . 
         FIG. 23A  is a side view of a hub of the needle device of  FIG. 20 . 
         FIG. 23B  is a side view of an alternate hub useful in the needle device of  FIG. 20 . 
         FIG. 24  is a side view of a shield of the needle device of  FIG. 20 . 
         FIG. 25  is a top cross-sectional view of the needle device of  FIG. 20 , shown with the packaging cover removed and in the first position ready for use. 
         FIG. 26  is a perspective view showing the direction of forces for actuation of the shielding needle device of  FIG. 20 . 
         FIG. 27  is a perspective view showing of the shielding needle device of  FIG. 20  with the packaging cover removed and with a user&#39;s fingers maintaining the needle device in the first position with the needle cannula exposed for use. 
         FIG. 28  is a perspective view showing of the shielding needle device of  FIG. 20  in the first position after the user&#39;s fingers are released during activation. 
         FIG. 29  is a perspective view showing of the shielding needle device of  FIG. 20  in the second position with the shield encompassing the needle cannula. 
         FIG. 30  is a side view of the shielding needle device of  FIG. 20  shown in the second position with the shield encompassing the needle cannula. 
         FIG. 31  is a top cross-sectional view of the needle device of  FIG. 20 , shown in the second position with the shield encompassing the needle cannula. 
         FIG. 32  is a longitudinal cross-sectional view of the needle device of  FIG. 20 , shown in the second position with the shield encompassing the needle cannula. 
         FIG. 33  is a longitudinal cross-sectional similar to  FIG. 32 , but including the alternate hub of  FIG. 23B . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings in which like reference characters refer to like parts throughout the several views thereof,  FIG. 1  illustrates generally a blood collection set  10  in accordance with an embodiment of the present invention and its related features. The present invention is generally described herein in terms of a safety shielding needle assembly for use in a blood collection set, and encompasses a shielding needle assembly, as well as a blood collection set incorporating shielding needle assemblies. It is contemplated that the shielding needle assembly may be incorporated into other medical devices in alternate embodiments of the invention, such as intravenous assemblies, fluid infusion sets, hypodermic syringes, and the like. 
     As shown generally in  FIG. 1 , the blood collection set  10  includes a safety shielding needle device or assembly  12 , a flexible tube  14  extending from the needle device or assembly  12  and having first and second ends  15 ,  16 , and a protective cap or shield such as packaging cover  18  removably mounted to the needle assembly  12  opposite tube  14 , such as through a frictional engagement. Needle assembly  12  extends from a first end  15  of flexible tube  14 , while the second end  16  of flexible tube  14  is adapted for connection with a receptacle for blood collection. For example, the second end  16  of flexible tube  14  may be provided with a proximal fitting  17  which is adapted for engagement with a conventional needle holder (not shown) as is known in the art. Fitting  17  may further define a hub element including a non-patient needle assembly (not shown) as is commonly known in the art for use in blood collection sets. Alternatively, fitting  17  may define a luer connector that can be mated with an appropriate connector of a separate device as is known in the art, such as for mating with an infusion set for infusing a medication into a patient. 
     With general reference to  FIGS. 2-8 , one embodiment of the invention defines the shielding needle assembly  12  generally including a needle cannula  20 , a hub  30 , a needle cannula safety shield member  70 , and a drive member  80  for moving the safety shield  70 . The needle cannula  20  includes a rearward or proximal end  22  and an opposing forward or distal end  24 , with a lumen  26  extending through needle cannula  20  from the proximal end  22  to the distal end  24 . The distal end  24  of needle cannula  20  may be beveled to define a sharp puncture tip  28 , such as an intravenous puncture tip. The 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. Needle cannula  20  is desirably constructed of a medical grade metallic material, such as surgical steel or the like. 
     The needle assembly  12  further includes a hub  30 . The hub  30  is generally tubular or cylindrical in shape, and may be a unitary structure, desirably molded from a resilient thermoplastic material, or may be a multi-component structure. The hub  30  includes a rearward or proximal end  32  and a forward or distal end  34 . The proximal end  32  of the hub  30  includes an external portion or structure  36  for mating with the first end  15  of the flexible tube  14 , and an internal portion or structure  38  for engaging the drive member  80 , which is preferably in the form of a coil spring or like element for biasing the safety shield  70  in the manner described herein. The external and internal portions or structures  36 ,  38  are generally tubular shaped components adapted to cooperate with the flexible tube  14  and drive member  80 , respectively. The external structure  36  may be adapted to cooperate with the flexible tube  14  in a friction-fit manner, and a suitable medical grade adhesive may be used to secure the connection. 
     As depicted in  FIGS. 2-8 , the needle cannula  20  and the hub  30  may be separate parts that are preferably fixedly attached and secured through an appropriate medical grade adhesive, for example, epoxy or the like. In particular, the proximal end  22  of the needle cannula  20  is supported by the proximal end  32  of the hub  30  and, in particular, the internal structure  38  formed in the proximal end  32  of the hub  30 . For this purpose, the hub  30  defines a passageway or opening  40  extending between the internal structure  38  and the external structure  36  for receiving and securing the proximal end  22  of the needle cannula  20  therein. The opening  40  preferably extends through the proximal end  32  of the hub  30  and is used to place the needle assembly  12  in fluid communication with the flexible tube  14 , or another medical device, such as a tube holder, syringe, and like devices. The proximal end  22  of the needle cannula  20  may extend into the opening  40  and extend into the external structure  36  provided on the proximal end  32  of the hub  30 . The needle cannula  20  is secured within the opening  40  by an appropriate medical grade adhesive, and generally extends toward the distal end of the needle assembly  12  through an internal passageway  42  extending through hub  30 , with the puncture tip  28  at distal end  24  of needle cannula  20  extending through the forward or distal end  34  of hub  30 . 
     The needle assembly  12  further includes a shield member such as safety shield  70 , which extends telescopically about needle cannula  20 , such as in a generally coaxial manner. The safety shield  70  is in telescoping association with the hub  30 , such that at least one of hub  30  and/or shield  70  are adapted for relative movement with respect to the other in a generally axial direction, that is in a general direction with respect to the general longitudinal axis L of needle assembly  12 . More particularly, the shield  70  and/or the hub  30  are telescopically movable with respect to one another between a first position of the needle assembly  12  in which the puncture tip  28  of needle cannula  20  is exposed from a forward end of the shield  70 , and a second position in which the shield  70  generally encompasses the needle cannula  20  and, more particularly, the puncture tip  28 , as will be described in more detail herein. The safety shield  70  is generally tubular or cylindrical in shape, and may be a unitary structure, desirably molded from a thermoplastic material, including a rearward or proximal end  72  and a forward or distal end  74 . The distal end  74  defines a central opening  76  through which the needle cannula  20  extends. The central opening  76  permits relative telescopic movement between the safety shield  70  and the needle cannula  20  between the first and second positions of the needle assembly  12  noted above. 
     The needle assembly  12  further includes drive member  80  extending between the hub  30  and the shield  70 , providing a biasing force to bias the hub  30  and the shield  70  axially or longitudinally away from each other. Drive member  80  is generally coaxially positioned with the shield  70  and/or the hub  30 , with the needle assembly  12  in the first position. The drive member  80  may be in the form of a coil compression spring or like biasing element and is generally adapted to move the safety shield  70  and/or the hub  30  with respect to each other between the first position and the second position of the needle assembly  12 . The drive member  80  has a proximal end  82  and a distal end  84 . The proximal end  82  is generally disposed on the internal structure  38  formed internally at the proximal end  32  of the hub  30 . The distal end  84  is generally in contact with a portion of the shield  70 , such as an interior surface  86  defined within the distal end  74  of the safety shield  70 . The biasing force of the drive member  80  is described herein in terms of biasing the hub  30  and shield  70  with respect to each other, such as a biasing force biasing the hub  30  an the shield  70  axially away from each other. It is noted that activation of the needle assembly  12  is based on this biasing force of drive member  80  causing movement of either the hub  30  or the shield  70 , or movement of both the hub  30  and the shield  70  with respect to each other. For example, it the user is holding the hub  30  during activation, the biasing member  80  will cause the shield  70  to extend or move distally with respect to hub  30  to the second shielding position of needle assembly  12 . On the other hand, if the user is holding the shield  70  during activation, the biasing member  80  will cause the hub  30  to retract or move proximally with respect to shield  70  to the second shielding position of the needle assembly  12 . 
     A packaging cover  18  may also be provided on the needle assembly  12 , such as at the distal end  34  of hub  30 , and is preferably provided on the needle assembly  12  during the manufacturing process. 
     In a general sense, the hub  30  and the shield  70  are maintained from movement with respect to each other against the bias of the drive member  80  to maintain needle assembly  12  in the first position with puncture tip  28  extending from the forward end of the shield  70 . The hub  30  and shield  70  may be maintained in this manner through external pressure applied externally to the structure of needle assembly  12  by a user during the normal use of needle assembly  12 . Such external pressure provides an engagement between the hub  30  and the shield  70  to prevent the drive member  80  from biasing the hub  30  and the shield  70  away from each other in a longitudinal direction. Generally speaking, in an initial state such as during shipment and storage, packaging cover or cover  18  may be adapted to apply external pressure to the hub  30  and/or the shield  70  to prevent the drive member  80  from biasing the hub  30  and the shield  70  axially away from each other. Generally during use, a user grasps needle assembly  12  to apply external pressure to the hub  30  and/or the shield  70  and removes the packaging cover  18 , with the user maintaining the external pressure on the hub  30  and/or the shield  70  until activation of the needle assembly  12  is desired. In this manner, needle assembly  12  represents a passively activatable structure in that activation occurs during the normal use of the needle assembly  12 . 
     The hub  30  and safety shield  70  may be provided in various arrangements, as will now be discussed in more detail with reference to specific embodiments of the invention. 
       FIGS. 2-8  depict a specific embodiment of the invention in which the shield  70  is retained within the hub  30  against the bias of drive member  80 . In particular, as shown in  FIGS. 2-8 , the hub  30  may include two opposing release members  44 . The release members  44  generally extend along opposing sides  46 ,  48  of the hub  30  and form part of the body of the hub  30 . The release members  44  are generally adapted to maintain the safety shield  70  and drive member  80  in a pre-actuated state or position within the body of the hub  30 , and also operate to release or actuate the drive member  80 , which is generally operable to move the safety shield  70  to a shielding position relative to the needle cannula  20 , as discussed in detail herein. 
     The release members  44  are desirably pivotally connected to the hub  30 , for example, by respective hinge structures  50  (i.e., hinges). The release members  44  are preferably integrally-molded with the body of the hub  30 , which is preferably formed of molded plastic material. The hinge structures  50  are thus formed integrally (i.e., as a living hinge) with the release members  44  and the body of the hub  30 . The hinge structures  50  permit the release members  44  to pivot relative to the body of the hub  30  and, in particular, to pivot inward toward a central longitudinal axis L of the blood collection set  10  and shielding needle assembly  12 . Alternatively, the release members  44  may be formed separately from the hub  30  and connected thereto by conventional hinges. The release members  44  produce an angle vertex opening towards the distal end  34  of the hub  30 . The release members  44  partially form the sidewall of the hub  30 , but may pivotally extend inward into the hub  30 . 
     The opposing release members  44  further include respective finger tabs  52  which provide locations for a user&#39;s fingers when manipulating the blood collection set  10  and needle assembly  12 . The finger tabs  52  may include raised structures or protrusions  54 , such as bumps, for improving the handling characteristics of the needle assembly  12  when manipulated by the user. The release members  44  each include distal ends  56  formed with opposing locking tabs  58 ,  60 . The locking tabs  58 ,  60  are generally formed as inward-projecting locking tabs  58  and outward-projecting locking tabs  60 , which are also referred to herein as first and second locking tabs  58 ,  60 . The first or inward-projecting locking tabs  58  on the release members  44  are generally adapted to engage the safety shield  70 , and the second or outward-projecting locking tabs  60  are generally adapted to engage the packaging cover  18 , as discussed further herein. 
     In particular, in the embodiment of  FIGS. 2-8 , the safety shield  70  extends generally coaxially about needle cannula  20  and is movable along needle cannula  20  between a first or retracted position coaxially received within the hub  30  (See  FIGS. 2-5 ), and a second or extended position (See  FIGS. 6 and 7 ) generally encompassing the needle cannula  20  and, more particularly, the puncture tip  28 . The drive member  80  is generally adapted to move the safety shield  70  axially along the needle cannula  20  from the retracted position to the extended position. In particular, the distal end  84  of the drive member  80  is generally in contact with the distal end  74  of the safety shield  70  and, in particular, an internal side  86  of the distal end  74  of the safety shield  70 . The engagement of the distal end  84  of the drive member  80  with the distal end  74  of the safety shield  70  forms the physical interface between the drive member  80  and the safety shield  70  for moving the safety shield  70  from the retracted position to the extended position. The distal end  74  of the safety shield  70  further includes an outward-facing or distal end surface  88 , which engages the first or inward-projection locking tabs  58  in the retracted position of the safety shield  70 . 
     Alternatively, the release members  44  may represent the sidewalls of the hub  30 , while they are radially flexible inwardly due to the physical structure of the hub  30 . For example, the release members  44  (i.e., hub sidewalls) may be constructed to flex radially inwardly when external lateral pressure is applied to opposing sides of the hub  30 . To facilitate this flexing, the opposing sidewalls of the hub  30  may be constructed or molded with a thinner thickness than the proximal or distal portions of the hub  30 , allowing for flexing of the opposing sides of the hub  30  at the release members  44 . Such inward radial pressure at the release members  44  creates a compressive force establishing a frictional engagement against the safety shield  70  to hold the safety shield  70  in the retracted position. Such an arrangement may also include the locking tabs  58 ,  60  for further retention of the safety shield  70 . 
     The packaging cover  18  is provided on the distal end  34  of the hub  30  and is preferably secured to the hub  30  during manufacturing and assembly of the needle assembly  12 . The packaging cover  18  is preferably in frictional engagement with the distal end  34  of the hub  30 , and is generally adapted to maintain the needle assembly  12  in the pre-actuated state or condition shown, for example, in  FIGS. 2-4 , with the safety shield  70  in the retracted position. For this purpose, the packaging cover  18  may be formed with an internal locking groove  90 , which is engaged by the second or outward-projecting locking tabs  60  formed at the distal ends  56  of the release members  44 . The engagement of the outward-projecting locking tabs  60  secures the packaging cover  18  on the distal end  34  of the hub  30 , with the aid of the drive member  80 , until the needle assembly  12  is actuated by a user. 
     In the pre-actuated or “pre-packaged” state or condition of the needle assembly  12 , the drive member  80  exerts a distally-directed force on the internal side  86  of the safety shield  70 , which urges the distal end  74  of the safety shield  70  into engagement or contact with the first or inward-projecting locking tabs  58  formed on the distal ends  56  of the release members  44 . In particular, the distal end surface  88  of the safety shield  70  is urged into contact or engagement with the first or inward-projecting locking tabs  58  on the distal ends  56  of the release members  44 . Without the presence of the packaging cover  18 , the distally-directed force acting on the distal ends  56  of the release members  44  would cause the release members  44  to pivot outward about their respective hinge structures  50 . However, this distally-directed force is prevented from prematurely actuating the needle assembly  12  by the presence of the packaging cover  18 , which provides a counter-acting radial force maintaining the compression of the drive member  80  within the safety shield  70  and hub  30 . The engagement of the first or outward-projecting locking tabs  60  with the locking groove  90  in the packaging cover  18  prevents premature removal of the packaging cover  18  from the distal end  34  of the hub  30 , and therefore premature actuation of the needle assembly  12 . 
     An optional mechanism for retaining the packaging cover  18  onto hub  30  includes using the locking tabs  60  as external threads to ride within corresponding internal threads (not shown) in the packaging cover  18 . In this embodiment, the internal threads would act more like slots than true threads, and the packaging cover  18  would have to be rotated to a position where the locking tabs  60  (i.e., external threads) would allow for the packaging cover  18  to be removed from the hub  30 . An alternative configuration to the foregoing could include the locking tabs  60  engaging internal circumferential slots in the packaging cover  18  which connect to internal axial slots in the packaging cover  18 . In such a variation, rotation of the packaging cover  18  would cause the locking tabs  60  to slide within the circumferential slots until reaching the axial slots, which would allow the packaging cover  18  to be removed from the hub  30 . 
     The blood collection set  10  may be packaged in a conventional blister package (not shown). Prior to use, the blood collection set  10  is removed from its package and, if necessary, the second end  16  of the flexible tube  14  may be connected to an appropriate receptacle for providing fluid communication with the lumen  28  through the needle cannula  20 . In use, the blood collection set  10  is provided with the needle assembly  12  and flexible tube  14  extending from needle assembly  12  and connected to an appropriate device (not shown), such as a blood collection receptacle. 
     To use the blood collection set  10  and needle assembly  12 , the user generally grasps the opposing finger tabs  52  provided on the needle assembly  12 , as shown in  FIGS. 3-5 . The user then applies radial pressure to the finger tabs  52 .  FIG. 8  illustrates the direction of radially applied pressure that is necessary to begin actuation of the blood collection set  10  and needle assembly  12 . As the user applies radial pressure to the finger tabs  52 , the release members  44  will generally pivot inward toward the central longitudinal axis L of the blood collection set  10  and needle assembly  12 . The release members  44  will generally pivot about their respective hinge structures  50 , and will displace inward toward the central longitudinal axis L of the blood collection set  10  and needle assembly  12 , as shown in  FIG. 4 . As shown in  FIG. 4 , the radial inward displacement of the release members  44  causes the second or outward-projection locking tabs  60  formed at the distal end  56  of the release members  44  to disengage substantially automatically from the locking groove  90  in the packaging cover  18 . With the disengagement of the locking tabs  60  from the locking groove  90 , the packaging cover  18  is releasable from secured engagement with the hub  30 , and may be removed from the distal end  34  of the hub  30  by the user. The inward movement of the release members  44  generally reduces the diameter (i.e., cross-sectional area) of the distal end  34  of the hub  30  and automatically releases the packaging cover  18  from the distal end  34 . 
     The user preferably maintains the radial force applied to the finger tabs  52 , which causes the release members  44  to remain in substantially laterally-extending positions along the lateral sides  46 ,  48  of the hub  30 . In this configuration, the first or inward-projection locking tabs  58  remain engaged with the outward-facing or distal end surface  88  at the distal end  74  of the safety shield  70 , and prevent the drive member  80  from moving the safety shield  70  from the retracted position to the extended position. In particular, the distal end surface  88  of the safety shield  70  engages opposing inward-facing surfaces  92  on the first or inward-projection locking tabs  58  formed on the release members  44 . The radial pressure applied by the user maintains the engagement of the locking tabs  58  with the distal end  74  of the safety shield  70 , thereby maintaining the safety shield  70  in the retracted position and counteracting the distally-directed biasing force of the drive member  80 . The radial pressure applied to the finger tabs  52  generally takes the place of the removed packaging cover  18  for maintaining the safety shield  70  in the retracted position and counteracting the biasing force of the drive member  80 . 
     The user may then urge the puncture tip  28  at distal end  24  of the needle cannula  20  into a targeted blood vessel of a patient in order to conduct a blood collection procedure or other procedure as desired. When the user releases the radial pressure applied to the finger tabs  52 , the drive member  80  is free to exert a distally-directed biasing force on the distal end  74  of the safety shield  70 . In particular, with the release of the radial pressure, the drive member  80  urges the outward-facing or distal end surface  88  of the safety shield  70  to slide along the inward-facing surfaces  92  on the inward-projecting locking tabs  58 , and generally urges the release members  44  to spread radially apart. The inward-facing surfaces  92  of the locking tabs  58  may be tapered to facilitate the sliding movement of the distal end surface  88  of the safety shield  70 , and the concurrent outward-directed movement of the release members  44 . As used in this disclosure, the term “release of radial pressure” and like phrases used to describe how the user actuates the needle assembly  12  is not intended to be limited to the complete discontinuing of radial pressure. This terminology is specifically intended to include such a complete discontinuing of radial pressure, such as the user totally removing his or her fingers from the finger tabs  52 , as well as a partial or sequential lessening or reducing of radial pressure on the finger tabs  52  sufficient to allow the drive member  80  to move the locking tabs  58  out of engagement with the distal end  74  of the safety shield  70  and move the safety shield  70  to the extended or shielding position. The biasing force inherent in the drive member  80  as well as the profile of any interfering surfaces between the hub  30  and the shield  70  will determine the amount of lessening of the radial pressure required to allow the needle assembly  12  to actuate. 
     Once the locking tabs  58  are displaced radially out of engagement with the distal end  74  of the safety shield  70 , the safety shield  70  is completely unrestrained and subject entirely to the distally-directed biasing force of the drive member  80 . The drive member  80  propels the safety shield  70  distally along needle cannula  20  in an axial direction of arrow  100  (see  FIG. 6 ), with the safety shield  70  sliding or gliding along needle cannula  20  toward distal end  24 . During an actual blood collection procedure, the distal movement of the safety shield  70  will terminate when the distal end  74  of the safety shield  70  contacts the skin of the patient, as shown in  FIG. 5 . The drive member  80  still exerts a distally-directed biasing force on the safety shield  70 , but this force is resolved by the frictional force that acts on the needle cannula  20 , as a result of being in the blood vessel of the patient. The user may then proceed to complete the blood collection procedure, for example, using evacuated blood collection tubes or a syringe. The user then proceeds to remove the blood collection set  10  from the blood vessel of the patient using the finger tabs  52 . As the needle cannula  20  is removed from the blood vessel of the patient, the safety shield  70  is urged by the drive member  80  to move closer to the distal end  24  of the needle cannula  20 . As the needle cannula  20  is fully removed from the patient&#39;s blood vessel, the safety shield  70  is urged by the drive member  80  to fully encompass the needle cannula  20 , as generally depicted in  FIGS. 6 and 7 . The drive member  80  now extends internally between the distal end  74  of the safety shield  70  and the internal structure  38  formed within the hub  30  at the proximal end  32  of the hub  30 , and exerts a biasing force that will aid in preventing the re-emergence of the puncture tip  28  from the central opening  76  in the distal end  74  of the safety shield  70 . 
     The safety shield  70  may further includes an external locking structure  102  for securing the safety shield  70  in the extended position, once the needle assembly  12  has been actuated. The external locking structure  102  may incorporate an external locking recess or groove  104 , which is configured to be engaged by the inward-projecting locking tabs  58  when the safety shield  70  is moved to the extended position. In particular, when the safety shield  70  is moved to the extended position by the drive member  80 , the locking tabs  58  preferably snap into engagement with the locking recess  104 . It will be appreciated that the external locking recess  104  need not be continuous about the circumference of the safety shield  70 . Likewise, the internal locking groove  90  in the packaging cover  18  need not be continuous around the internal circumference of the packaging cover  18 . Moreover, it will further be appreciated that the needle assembly  12  may be configured to operate with a single release member  44  rather than the opposing pair of release members  44  discussed previously. However, the use of two opposing release members  44  is believed to be more intuitive for the user of the blood collection set  10  and needle assembly  12 , and is presently preferred. 
     An alternate version of the above-described needle assembly is depicted in a further embodiment described with particular reference to  FIGS. 9-19 . The embodiment of  FIGS. 9-19  generally depicts a specific embodiment of the invention in which the shield is retained within the hub against the bias of drive member through a dorsal grasping structure, with a dorsal member and dorsal gripping structure adapted for providing engagement between the hub and the shield upon application of external pressure thereto to retain the shield with respect to the hub against the bias of the drive member. In the embodiment described with reference to  FIGS. 9-19 , similar components performing similar functions will be numbered identically to those components of  FIGS. 1-8 , except that a suffix “a” will be used to identify those similar components in  FIGS. 9-19 . 
     Needle assembly  12   a  as shown in  FIGS. 9-19  includes a housing in the form of hub  30   a  similar to that described above in connection with  FIGS. 1-8 , with a rearward or proximal end  32   a  and a forward or distal end  34   a , and including an external structure  36   a  for mating with the first end  15   a  of the flexible tube  14   a , and an internal structure  38   a  for engaging the drive member  80   a  and for supporting needle cannula  20   a . The second end  16   a  of the flexible tube  15   a  may also include a fixture  17   a  for connection with a separate medical device, for example, to provide a blood collection set  10   a . The proximal end  22   a  of needle cannula  20   a  is supported at internal structure  38   a , and extends through the internal passageway  42   a  of hub  30   a,  with puncture tip  28   a  extending out from the distal end  34   a  thereof. 
     Shield  70   a  extends generally coaxially about needle cannula  20   a  and is movable along needle cannula  20   a  between a first or retracted position coaxially received within the passageway  42   a  of hub  30   a  as shown in  FIGS. 11 and 15 , and a second or extended position generally encompassing the needle cannula  20   a  and, more particularly, the puncture tip  28   a  as shown in  FIGS. 16 and 17 . The drive member  80   a  is generally adapted to move the shield  70   a  axially along the needle cannula  20   a  from the retracted position to the extended position. In particular, the distal end  84   a  of the drive member  80   a  is generally in contact with a portion of the shield  70   a  such as an abutment structure  78   a  provided on an external surface of the shield  70   a . The engagement of the distal end  84   a  of the drive member  80   a  with the abutment structure  78   a  of the shield  70   a  forms the physical interface between the drive member  80   a  and the shield  70   a  for moving the shield  70   a  from the retracted position to the extended position. 
     Needle assembly  12   a  includes structure adapted to maintain the shield  70   a  and drive member  80   a  in a pre-actuated state or position within the body of the hub  30   a  and to release or actuate the drive member  80   a , in a similar manner as with release members  44  described above with reference to  FIGS. 1-8 . In particular, in the present embodiment, engagement between the hub  30   a  and the shield  70   a  is provided through an actuation mechanism in the form of a dorsal grasping structure  108   a  including a dorsal member  30   a  extending from an external surface of the hub  30   a  and a grip structure  112   a  extending from an external surface of the shield  70   a . Dorsal grasping structure  108   a  is generally symmetrically aligned with the bevel-up orientation of the puncture tip  28   a  of the needle cannula  20   a.    
     More particularly, hub  30   a  includes dorsal member  110   a , which extends dorsally from a top surface thereof in the form of a generally planar spine member extending in a plane corresponding to longitudinal axis L defined by the needle cannula  20   a . Shield  70   a  includes a main body portion such as tubular body  71   a , with a grip structure  112   a  extending from the top surface of the body  71   a  of shield  70   a  at the forward or distal end  74   a  thereof. Grip structure  112   a  of shield  70   a  includes a profile generally corresponding to the dorsal member  110   a , and may be in the form of at least one, and preferably a pair of flexibly resilient planar leafs  114   a ,  116   a , uniting at forward ends thereof through a bridge  118   a . In this manner, the grip structure  112   a  extends from the body  71   a  of shield  70   a  through the bridge  118   a , with planar leafs  114   a ,  116   a  extending toward the rearward or proximal end  72   a  of the shield  70   a  along a top end of the body  71   a . The planar leafs  114   a ,  116   a  are spaced from each other to define an opening or gap  120   a  therebetween for accommodating the spine of dorsal member  30   a  therein when the shield  70   a  is in the retracted position within hub  30   a . The planar leafs  114   a ,  116   a  are resilient members which can be bent or flexed toward each other, and are therefore essentially pivotally connected through the bridge  118   a  in a hinged manner. The shield  70   a  is preferably molded as a single structure of molded plastic material including the body  71   a , bridge  118   a  and planar leafs  114   a ,  116   a  integrally formed. Additionally, one or more bumps  122   a  may be provided on an external surface of one or both of planar leafs  114   a ,  116   a , providing a tactile surface for the user to grasp the grip structure  112   a  during use. 
     Shield  70   a  extends coaxially within the internal passageway  42   a  of hub  30   a . To assist in accommodating the grip structure  112   a  of shield  70   a  therein, hub  30   a  may include a cutaway portion  62   a  at a top surface adjacent distal end  34   a  thereof. In this manner, the bridge  118   a  of shield  70   a  can be slidably accommodated within cutaway portion  62   a  of hub  30   a  when the shield  70   a  is maintained in the first position retracted within the hub  30   a.    
     External pressure applied between the grip structure  112   a  of the shield  70   a  and the dorsal member  110   a  of the hub  30   a  maintains the shield  70   a  in the retracted position against the bias of the drive member  80   a . In particular, in the embodiment of  FIGS. 9-19 , external pressure applied between the planar leafs  114   a ,  116   a , establishes frictional engagement between one or both of the planar leafs  114   a ,  116   a  and dorsal member  110   a  of hub  30   a , thereby maintaining the shield  30   a  in fixed relation with respect to the hub  30   a  against the bias of the drive member  80   a , as will be discussed in more detail herein. Such inward pressure at the planar leafs  114   a ,  116   a  creates a compressive force establishing a frictional engagement against the spine of dorsal member  110   a , thereby holding the safety shield  70   a  in the retracted position with respect to the hub  30   a . It is contemplated that the grip structure  112   a  may include only a single planar leaf extending from the shield  70   a , in which case engagement of the single planar leaf with the dorsal member  110   a  of the hub  30   a  is accomplished by gripping directly between the single planar leaf and the dorsal member  110   a  between the user&#39;s fingers. 
     Moreover, the planar leafs  114   a ,  116   a , and the dorsal member  110   a  may include corresponding structure adapted for interference engagement therebetween when external pressure is applied. For example, dorsal member  110   a  may include one or more detents  124   a  on an external surface thereof, and planar leafs  114   a ,  116   a  may include one or more corresponding protrusions or protuberances  126   a  on a corresponding surface within gap  120   a . The opposing planar leafs  114   a ,  116   a  may also include structure on external finger surfaces thereof for providing a tactile feel for a user&#39;s fingers when manipulating the needle assembly  12   a  and during use, such as raised structures or protrusions in the form of bumps  122   a.    
     A packaging cover  18   a  may also be provided on the distal end  34   a  of the hub  30   a  in a similar manner as described above with respect to  FIGS. 1-8 . The packaging cover  18   a  is preferably in frictional engagement with the hub  30   a , and is generally adapted to maintain the needle assembly  12   a  in the pre-actuated state with the safety shield  70   a  in the retracted position. In this manner, the packaging cover  18   a  includes opposing longitudinal arms  128   a  and  130   a,  with an opening  132   a  extending therebetween. With packaging cover  18   a  secured to the distal end  34   a  of hub  30   a , longitudinal arms  128   a  and  130   a  extend rearward along opposing lateral sides of hub  30   a . Longitudinal arms  128   a  and  130   a  are desirably constructed in a manner so as to be naturally biased radially inwardly, so as to exert a radially compressive force against the outer surface of hub  30   a , thereby maintaining packaging cover  18   a  in a frictional fit over hub  30   a . The packaging cover  18   a  may contact the distal end  74   a  of the shield  70   a , with the radial compressive force of the longitudinal arms  128   a  and  130   a  being sufficiently strong so as to maintain shield  70   a  in the retracted position against the bias of drive member  80   a . Moreover, the longitudinal arms  128   a  and  130   a  may be sized and shaped so as to contact at least a portion of the respective external surfaces of planar leafs  114   a ,  116   a . In this manner, the radially compressive force exerted by the longitudinal arms  128   a  and  130   a  will be transferred to the planar leafs  114   a ,  116   a , thereby providing an external compressive force thereagainst as depicted in  FIG. 12  to further maintain shield  70   a  in the retracted position with respect to hub  30   a . In addition or alternatively thereto, the packaging cover  18   a  may include structure for interlocking engagement with a portion of shield  70   a  as described above with reference to  FIGS. 1-8 , such that when planar leafs  114   a ,  116   a  are grasped during use, packaging cover  18   a  is released. 
     The hub  30   a  may further include a pair of wings  134   a ,  136   a , extending laterally from opposing sides of the hub  30   a . The wings  134   a ,  136   a  are fixed in relation to the hub  30   a,  and are desirably integrally molded with the hub  30   a  as a rigid structure. The wings  134   a ,  136   a  provide structure for guiding the needle assembly  12   a  during use thereof, and can be taped to the skin of a patient to maintain the needle assembly  12   a  in a fixed position during use in a medical procedure such as blood collection. Desirably, the dorsal grasping structure  108   a  formed by the engagement between the planar leafs  114   a ,  116   a  and dorsal member  110   a  has a profile larger than the profile of wings  134   a ,  136   a . In this manner, a user is encouraged to grasp the needle assembly  12   a  by the dorsal grasping structure  108   a  for use, as opposed to grasping needle assembly  12   a  by attempting to bend wings  134   a ,  136   a  toward each other, as is common with conventional needle assemblies. 
     To use the needle assembly  12   a  of the embodiment set forth in  FIGS. 9-19 , the user generally grasps the dorsal grasping structure  108   a  to apply external pressure between opposing surfaces of the planar leafs  114   a ,  116   a  and the dorsal member  110   a  in the direction of shown in  FIG. 15 . As the user applies external pressure to the planar leafs  114   a ,  116   a , the packaging cover  18   a  is removed from the distal end  34   a  of the hub  30   a  by the user. The user maintains the external force applied to the planar leafs  114   a ,  116   a , which causes them to engage with the dorsal member  110   a  of the hub  30   a  in a frictional engagement, and in particular causes the protrusions  126   a  on the planar leafs  114   a ,  116   a  to engage the corresponding detents  124   a  on the dorsal member  110   a  in an interference engagement. In this manner, the pressure applied by the user maintains the engagement between the planar leafs  114   a ,  116   a  and the dorsal member  110   a , thereby maintaining the safety shield  70   a  in the retracted position and counteracting the distally-directed biasing force of the drive member  80   a . The radial pressure applied to the planar leafs  114   a ,  116   a  generally takes the place of the removed packaging cover  18   a  for maintaining the safety shield  70   a  in the retracted position and counteracting the biasing force of the drive member  80   a.    
     The user may then urge the puncture tip  28   a  at distal end  24   a  of the needle cannula  20   a  into a targeted blood vessel of a patient in order to conduct a blood collection procedure or other procedure as desired. After proper positioning, when the user releases the applied pressure applied to the planar leafs  114   a ,  116   a , the drive member  80   a  is free to exert a distally-directed biasing force on the distal end  74   a  of the safety shield  70   a . The drive member  80   a  then propels the safety shield  70   a  distally along needle cannula  20   a  in an axial direction of arrow  110   a  in  FIG. 14 , with the safety shield  70   a  sliding or gliding along needle cannula  20   a  toward distal end  24   a . During an actual blood collection procedure, the distal movement of the safety shield  70   a  will terminate when the distal end  74   a  of the safety shield  70   a  contacts the skin of the patient. The drive member  80   a  still exerts a distally-directed biasing force on the safety shield  70   a , but this force is resolved by the frictional force that acts on the needle cannula  20   a , as a result of being in the blood vessel of the patient. The user may then proceed to complete the blood collection procedure, for example, using evacuated blood collection tubes or a syringe. The user then proceeds to remove the needle assembly  12   a  from the blood vessel of the patient by grasping the dorsal member  110   a . As the needle cannula  20   a  is removed from the blood vessel of the patient, the safety shield  70   a  is urged by the drive member  80   a  to move closer to the distal end  24   a  of the needle cannula  20   a . As the needle cannula  20   a  is fully removed from the patient&#39;s blood vessel, the safety shield  70   a  is urged by the drive member  80   a  to fully encompass the needle cannula  20   a , as generally depicted in  FIGS. 14 and 17 . The drive member  80   a  exerts a biasing force that will aid in preventing the re-emergence of the puncture tip  28   a  from the central opening  76   a  in the distal end  74   a  of the safety shield  70   a.    
     The safety shield  70   a  and the hub  30   a  may further include interengaging structure for interfering engagement therebetween for securing the safety shield  70   a  in the extended position to prevent a return movement once the needle assembly  12   a  has been actuated. For example, the safety shield  70   a  may include external locking structure in a similar manner as described above with respect to  FIGS. 1-8 , such as an external locking recess or groove, which is preferably provided through abutment structure  78   a  in the embodiment of  FIGS. 9-19 , and which is configured to be engaged by the inward-projecting locking tabs  58   a  on opposing lateral sides of hub  30   a  when the safety shield  70   a  is moved to the extended position, as shown in  FIG. 18 . Needle assembly  12   a  can thereafter be appropriately discarded. 
     A further variation of the needle assembly is depicted in yet a further embodiment described with particular reference to  FIGS. 20-33 . The embodiment of  FIGS. 20-33  generally depicts a specific embodiment of the invention in which the shield is a barrel-like structure maintained coaxially about the hub against the bias of the drive member, with one or more corresponding release tabs of the shield adapted for providing engagement with a release member of the hub upon application of external pressure thereto to maintain the shield and the hub in fixed relation against the bias of the drive member. In the embodiment described with reference to  FIGS. 20-33 , similar components performing similar functions will be numbered identically to those components of  FIGS. 1-8 , except that a suffix “b” will be used to identify those similar components in  FIGS. 20-33 . 
     Needle assembly  12   b  as shown in  FIGS. 20-33  includes a hub  30   b  similar to that described above in connection with  FIGS. 1-8 . In particular, as shown in  FIGS. 22 and 23A , the hub  30   b  includes a proximal end  32   b , a distal end  34   b  and an internal passageway  42   b  extending between the ends. The first end  15   b  of flexible tubing  14   b  connects with the hub  30   b  in a manner as described above. Alternatively, portions of internal passageway  42   b  adjacent proximal end  32   b  may be dimensioned to receive the first end  15   b  of flexible tubing  14   b . More particularly, the first end  15   b  of the tubing  14   b  may be telescoped into passageway  42   b  of the hub  30   b  and bonded in position adjacent the proximal end  32   b  of the hub  30   b . Portions of the passageway  42   b  adjacent the distal end  34   b  of the hub  30   b  may also dimensioned for slidable receipt of the proximal end  22   b  of the needle cannula  20   b.    
     External portions of the hub  30   b  may define a cylindrical portion  140   b  having a reduced diameter for mounting the drive member  80   b  thereover. A flange  142   b  defines a limit for proximal movement of the drive member  80   b  on the hub  30   b  and a limit for distal movement of the hub  30   b  relative to the shield  70   b.    
     A release member in the form of a protrusion or button  144   b  extends distally outwardly from an external surface at the forward or distal end  34   b  of the hub  30   b . The button  144   b  may be symmetrically aligned with the bevel-up orientation of the puncture tip  28   b  of the needle cannula  20   b . The proximal end of the button  144   b  defines a surface at locking edge  146   b  which establishes an interference engagement with corresponding structure on the shield  70   b , as will be described in more detail herein. 
       FIG. 23B  and  FIG. 33  depict an alternate version of the hub  30   b  which is similar to that shown in  FIG. 23A , but with the button  144   b  being radially flexible with respect to the body of the hub  30   b . In particular, in the embodiment of the hub  30   b  shown in  FIG. 23B  and  FIG. 33 , the button is not merely a protrusion extending outwardly from the external surface of the hub  30   b , but instead extends from an actuator arm of the hub  30   b  which is cantilevered to extend outwardly and distally from the proximal end of hub  30   b , in a similar manner as is described with respect to the hub of the retractable needle assembly of U.S. Patent Application Publication No. 2003/0078540 to Saulenas, the disclosure of which is incorporated herein by reference. In this manner, button  144   b  is flexible radially inwardly. Such flexing may assist in movement of the hub  30   b  in the proximal direction during actuation of the assembly, in that the button  144   b  can radially flex inwardly during retraction of the hub  30   b  to prevent any frictional or interference engagement with the shield  70   b.    
     In the embodiment of  FIGS. 20-33 , the shield  70   b  may be provided as a barrel extending between proximal end  72   b  and distal end  74   b , with an internal passageway  75   b  therethrough and a central opening  76   b  extending through the distal end  74   b  thereof. Desirably, the proximal end  72   b  and the distal end  74   b  define separate rearward and forward structures, respectively, which are unitarily formed, interconnected or otherwise attached together. For example, the proximal end of the shield  70   b  may be provided as a rearward shield structure  150   b , in a cylindrical or barrel-like form. Rearward shield structure  150   b  has an internal diameter substantially the same as or slightly larger than the external diameter of the hub  30   b,  including the button  144   b , and is therefore capable of accommodating hub  30   b  including the button  144   b  therethrough in a slidable manner. Rearward shield structure  150   b  is connected with forward shield structure  152   b  at a bridge section  154   b . The bridge section  154   b  establishes the rearward shield structure  150   b  and the forward shield structure  152   b  as separate ends which are joined to each other. 
     The distal end  74   b  of the shield  70   b  defined by forward shield structure  152   b  defines an inwardly extending annular distal flange  156   b  with an inside diameter less than the outside diameter of the drive member  80   b . Thus, distal flange  156   b  defines a distal stop for drive member  80   b  and enables drive member  80   b  to be compressed within the shield  70   b . An internal portion of forward shield structure  152   b  may also define a fixed limit for distal movement of the hub  30   b  therein. 
     Needle assembly  12   b  includes structure adapted to maintain the hub  30   b  and drive member  80   b  in a pre-actuated state or position within the body of the shield  70   b  and to release or actuate the drive member  80   b , in a similar manner as with release members  44  described above with reference to  FIGS. 1-8 . In particular, the forward shield structure  152   b  includes at least one, and preferably a pair of release tabs  158   b ,  160   b  on opposing lateral sides thereof. The release tabs  158   b ,  160   b  extend longitudinally along opposing sides of the forward shield structure  152   b , such as in a proximal manner toward rearward shield structure  150   b . The release tabs  158   b ,  160   b  are desirably integrally formed with the forward shield structure  152   b,  and may form structure similar to the release members  44  described above in connection with  FIGS. 1-8 . The release tabs  158   b ,  160   b  include distal edge surfaces  162   b ,  164   b , respectively, as well as mating edges  166   b ,  168   b , respectively. In a relaxed and unbiased state, the release tabs  158   b ,  160   b  naturally deflect outwardly, such as radially outwardly from the overall barrel structure of the shield  70   b , with mating edges  166   b ,  168   b , deflected away from each other. The release tabs  158   b ,  160   b  are flexible members with respect to forward shield structure  152   b , and can be deflected inwardly to a biased state, such as radially inwardly to a position in which mating edges  166   b  and  168   b  substantially meet. In such a biased state of the release tabs  158   b  and  160   b , the distal edge surfaces  162   b  and  164   b  of the opposing release tabs  158   b  and  160   b  form a perimeter edge of an opening or aperture  170   b  through the forward shield structure  152   b.  The aperture  170   b  thus formed is dimensioned and configured to receive button  144   b , with the perimeter edge defined by the distal edge surfaces  162   b  and  164   b  configured for engaging proximal edge  146   b  of the button  144   b.    
     In this manner, the hub  30   b  and the shield  70   b  can be maintained in a first position against the biasing force of the drive member  80   b  biasing the hub  30   b  and the shield  70   b  away from each other, i.e., biasing the hub  30   b  toward the proximal direction. External pressure applied between the opposing release tabs  158   b  and  160   b  of the shield  70   b  at the forward shield structure  152   b  in a radially inward direction deflects and biases the release tabs  158   b  and  160   b  against their relaxed state, causing mating edges  166   b ,  168   b  to meet, thereby establishing aperture  170   b . The proximal edge  146   b  of button  144   b  is thereby in interference engagement with one or both of the distal edge surfaces  162   b ,  164   b . As such, the drive member  80   b  is prevented from causing axial movement of the hub  30   b  and the shield  70   b  with respect to each other. Such pressure may also create a compressive force establishing a frictional engagement between the inner surfaces of the release tabs  158   b ,  160   b  and the external surface of the hub  30   b , thus further holding the hub  30   b  within the shield  70   b  in the first position. 
     A packaging cover  18   b  is provided about the needle cannula  20   b  in engagement with a portion of the forward shield structure  152   b , similar to that described above with respect to  FIGS. 1-8 . The packaging cover  18   b  is preferably in frictional engagement with the distal end  74   b  of the shield  70   b  at forward shield structure  152   b , and is generally adapted to maintain the needle assembly  12   b  in the pre-actuated state with the hub  30   b  in the first position. Accordingly, the internal diameter of the packaging cover  18   b  is sized so as to exert a radially compressive force against the outer surface of the release tabs  158   b ,  160   b  so as to deflect and bias the release tabs  158   b  and  160   b  radially inwardly against their relaxed state. The outward pressure exerted by the release tabs  158   b  and  160   b  may be sufficient to frictionally maintain the packaging cover  18   b  in a frictional fit over forward shield structure  152   b . Further, the packaging cover  18   b  may include structure for interlocking engagement with a portion of forward shield structure  152   b  in a similar manner as described above with reference the release members  44  of  FIGS. 1-8 , such that when the release tabs  158   b  and  160   b  are grasped during use, any such interlocking engagement with the packaging cover  18   b  is released. 
     To use the needle assembly  12   b  of the embodiment set forth in  FIGS. 20-33 , the user generally grasps the assembly at opposing sides thereof to apply external pressure between opposing surfaces of the release tabs  158   b ,  160   b  in the direction shown in  FIG. 27 . As the user applies external force through inwardly or radially directed pressure to the release tabs  158   b,    160   b , the packaging cover  18   b  is removed from the forward shield structure  152   b  at the distal end  74   b  of the shield  70   b  by the user. The user maintains the external force of the inwardly directed pressure applied to the release tabs  158   b ,  160   b , which maintains the mating edges  166   b,    168   b  in a position substantially meeting each other. As such, button  144   b  is maintained within the aperture  170   b , with the proximal edge  146   b  of button  144   b  in interference engagement with distal edge surfaces  162   b ,  164   b . In this manner, the pressure applied by the user maintains the interference engagement between the release tabs  158   b ,  160   b  and the release member of button  144   b , thereby maintaining the hub  30   b  in the first position and counteracting the proximally-directed biasing force of the drive member  80   b  against the hub  30   b . The radial pressure applied to the release tabs  158   b ,  160   b  generally takes the place of the removed packaging cover  18   b  for maintaining the hub  30   b  in the first position and counteracting the biasing force of the drive member  80   b.    
     The user may then urge the puncture tip  28   b  at distal end  24   b  of the needle cannula  20   b  into a targeted blood vessel of a patient in order to conduct a blood collection procedure or other procedure as desired. After proper positioning, when the user ,releases the applied pressure applied to the release tabs  158   b ,  160   b , the release tabs  158   b ,  160   b  deflect outwardly to their relaxed unbiased state, with mating edges  166   b ,  168   b  moving away from each other. At this point, the interference engagement between the proximal edge  146   b  of the button  144   b  and the distal edge surface  162   b ,  164   b  is released. As such, the drive member  80   b  is free to exert a biasing force between the hub  30   b  and the shield  70   b , with the drive member  80   b  propelling the hub  30   b  proximally through the rearward shield structure  150   b . During an actual blood collection procedure, the compressive force of the drive member  80   b  is insufficient to withdraw the needle cannula  20   b  from the patient, and instead the shield  70   b  will move distally and terminate when the distal end  74   b  of the safety shield  70   b  contacts the skin of the patient. The drive member  80   b  still exerts a biasing force between the shield  70   b  and the hub  30   b , but this force is resolved by the frictional force that acts on the needle cannula  20   b , as a result of being in the blood vessel of the patient. The user may then proceed to complete the blood collection procedure, for example using evacuated blood collection tubes or a syringe. 
     The user then proceeds to remove the needle assembly  12   b  from the blood vessel of the patient. As the needle cannula  20   b  is removed from the blood vessel of the patient, the safety shield  70   b  is urged by the drive member  80   b  to move closer to the distal end  24   b  of the needle cannula  20   b . As the needle cannula  20   b  is fully removed from the patient&#39;s blood vessel, the safety shield  70   b  is urged by the drive member  80   b  to fully encompass the needle cannula  20   b , as generally depicted in  FIGS. 29 and 30 . The drive member  80   b  exerts a biasing force that will aid in preventing the re-emergence of the puncture tip  28   b  from the central opening  76   b  in the distal end  74   b  of the safety shield  70   b.    
     The safety shield  70   b  and the hub  30   b  may further include interengaging structure for interfering engagement therebetween for securing the safety shield  70   b  in the extended position to prevent a return movement once the needle assembly  12   b  has been actuated. For example, the safety shield  70   b  may include external locking structure in a similar manner as described above with respect to  FIGS. 1-8 . For example, the rearward shield structure  150   b  may include resiliently deflectable locking fingers or tabs  58   b  that are cantilevered proximally and inwardly from opposed locations. As shown in  FIG. 31 , each locking finger or tab  58   b  is adapted to engage a portion of the hub  30   b  when the hub  30   b  is in the second position with the needle cannula safely encompassed within shield  70   b . Needle assembly  12   b  can thereafter be appropriately discarded. 
     The particular elements of the needle assembly can be manufactured of any known materials. Desirably, the hub, the shield, and the packaging cover are individually molded from plastic materials such as polycarbonate, polypropylene, polyethylene, acrylic, polystyrene and ABS. Preferably the hub and/or the shield are molded from a transparent or translucent material to enable observation of blood or other fluid flowing through the hub during use of the device. 
     The shielding feature of the present invention is passively actuated upon normal usage of the device. In particular, upon removal of the packaging cover prior to insertion, the safety feature is primed and charged, ready for shielding the needle once the user releases the opposing finger tabs. Moreover, in some instances, the needle assembly may be dropped or knocked from the hand of the user before, during, or after use. The shielding feature described above will commence automatically when the needle assembly is dropped or knocked from the user&#39;s hand. Thus, the automatic shielding may be triggered by the intentional or unintentional release of the finger tabs by the user. 
     Additionally, a user, such as a medical practitioner, does not always enter the targeted blood vessel during the first venipuncture attempt. However, a medical practitioner typically retains a close grip on the needle assembly until the targeted blood vessel has been entered. In this instance, the continued gripping of the finger tabs will prevent the needle assembly from shielding until the targeted blood vessel has been punctured. The second attempt at accessing a targeted blood vessel generally is a very low risk procedure in which the user&#39;s hand is spaced considerably from the puncture tip of the needle cannula. Thus, the blood collection set does not involve the inconvenience of having to use a new blood collection set following each unsuccessful venipuncture attempt. 
     While the needle assembly of the present invention has been described in terms of various embodiments for use in connection with a blood collection system, it is further contemplated that the needle assembly could be used with other medical procedures, such as in conjunction with a conventional intravenous infusion set, which are well-known in the art for use with needle assemblies. While the present invention is satisfied by embodiments in many different forms, there is shown in the drawings and described herein in detail, the preferred embodiments of the invention, with the understanding that the present disclosure is to be considered as exemplary of the principles of the invention and is 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 invention will be measured by the appended claims and their equivalents.