Abstract:
A blood collection set includes a needle having a puncture tip, a hub supporting the needle and including a release member, a safety shield, a drive member, and a packaging shield disposed on the hub. The safety shield is movable from a retracted position within the hub to an extended position shielding the puncture tip of the needle. The packaging shield encloses the puncture tip of the needle in the retracted position of the safety shield. The shielding feature of the blood collection set is activated by applying radial pressure to the release member, causing the release member to release the packaging shield from the hub, and maintain the safety shield in the retracted position. Upon sufficient or partial release of radial pressure, the drive member disengages the release member from the safety shield and moves the safety shield from the retracted position to the extended positions.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to blood collection sets for safe and convenient handling of needles used in blood collection procedures. More particularly, the present invention relates to a blood collection set including a forward-shielding needle safety shield for protecting users from a used needle tip, and further including a packaging shield adapted to prevent premature actuation of the safety features of the blood collection set.  
         [0003]     2. Description of Related Art  
         [0004]     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. Consequently, existing blood collection devices often employ some form of durable, reusable holder on which detachable and 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 disassembled after use. Thus, these blood collection devices allow repeated use of a relatively expensive holder upon replacement of relatively inexpensive medical needles and/or fluid collection tubes. In addition to reducing the cost of collecting blood specimens, these blood collection devices help minimize the production of hazardous waste material.  
         [0005]     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.  
         [0006]     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.  
         [0007]     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.  
         [0008]     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.  
         [0009]     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.  
         [0010]     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.  
         [0011]     In view of the foregoing, a need exists for a blood collection set including a shielding needle assembly that achieves secure and effective shielding of a used needle cannula, and which is simple and inexpensive to manufacture and easy to operate. An additional need exists for a blood collection set that is passively operated and includes structures that prevent premature actuation of the safety features of the blood collection set.  
       SUMMARY OF THE INVENTION  
       [0012]     The foregoing needs are fulfilled with a shielding blood collection set and a shielding needle assembly in accordance with the present invention. The shielding blood collection set generally includes a flexible tube, a needle cannula, a hub, a safety shield, and a drive member. The flexible tube has opposed first and second ends, with the first end of the tube adapted for connection to a fixture such as a receptacle or holder. The needle cannula has a proximal end and a distal end with a puncture tip. The hub has a proximal end and a distal end. An interior portion of the hub proximal end supports the needle cannula proximal end, and the second end of the tube is connected to an exterior portion of the hub proximal end. The hub further includes at least one release member. The safety shield is movably associated with the hub from a retracted position disposed generally coaxially with the hub, to an extended position shielding the puncture tip of the needle cannula. The drive member is associated with the hub and is generally adapted to move the safety shield from the retracted to the extended positions. The hub and at least one release member are generally adapted such that application of radial pressure to the at least one release member causes the at least one release member to engage the safety shield and maintain the safety shield in the retracted position, and at least partial release or lessening of the radial pressure allows the drive member to disengage the at least one release member from the safety shield and move the safety shield from the retracted position to the extended position.  
         [0013]     The drive member may be a coil spring. The at least one release member may be pivotally connected to the hub, for example, substantially at the hub proximal end.  
         [0014]     A finger tab may be provided on the at least one release member for applying the radial pressure to the at least one release member. The at least one release member may include a pair of opposing release members 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 pressure to the release members.  
         [0015]     The at least one release member may include a locking tab adapted to engage a locking recess in the safety shield in the extended position of the safety shield. The locking recess may extend circumferentially about the safety shield.  
         [0016]     A packaging shield may be disposed on the hub distal end and enclose the puncture tip of the needle cannula in the retracted position of the safety shield. The at least one release member may include a locking tab engaging a locking groove in the packaging shield, generally preventing removal of the packaging shield until the application of the radial pressure on the at least one release member causes the at least one release member to pivot radially inward and disengage the locking tab from the locking groove.  
         [0017]     The present invention is further directed to a shielding needle assembly that may be used, for example, in the blood collection set described hereinabove. The shielding needle assembly in one embodiment of the present invention includes a needle cannula, a hub associated with the needle cannula, a safety shield for shielding at least a distal end of the needle cannula, and a drive member for actuating or moving the safety shield. The needle cannula has a proximal end and a distal end with a puncture tip. The hub supports the needle cannula. The hub includes at least one release member. The safety shield is movably associated with the hub from a retracted position disposed generally coaxial with the hub to an extended position shielding the puncture tip of the needle cannula. The drive member is associated with the hub and is generally adapted to move the safety shield from the retracted position to the extended position. The hub and at least one release member may be adapted such that application of radial pressure to the at least one release member causes the at least one release member to engage the safety shield and maintain the safety shield in the retracted position, and at least partial release or lessening of the radial pressure allows the drive member to disengage the at least one release member from the safety shield and move the safety shield from the retracted position to the extended position.  
         [0018]     The drive member may be a coil spring. The at least one release member may be pivotally connected to the hub, for example, substantially at the hub proximal end. A finger tab may be provided on the at least one release member for applying the radial pressure to the at least one release member.  
         [0019]     The at least one release member may include a pair of opposing release members 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 pressure to the release members.  
         [0020]     The at least one release member may include a locking tab adapted to engage a locking recess in the safety shield in the extended position of the safety shield. The locking recess may extend circumferentially about the safety shield.  
         [0021]     In a modification of the foregoing shielding needle assembly, the shielding needle assembly may further include a packaging shield disposed on a distal end of the hub and enclose the puncture tip of the needle cannula in the retracted position of the safety shield. The at least one release member may include a locking tab engaging a locking groove in the packaging shield to prevent inadvertent removal of the packaging shield. The hub and at least one release member may be further adapted such that application of radial pressure to the at least one release member causes the at least one release member to pivot radially inward and disengage the locking tab from the locking groove, thereby generally releasing the packaging shield from the hub, and further causing the at least one release member to engage the safety shield and maintain the safety shield in the retracted position. At least partial release or lessening of the radial pressure preferably allows the drive member to disengage the at least one release member from the safety shield and move the safety shield from the retracted position to the extended position.  
         [0022]     The at least one release member may further include a second locking tab adapted to engage a locking recess in the safety shield in the extended position of the safety shield. The locking recess in the safety shield may extend circumferentially about the safety shield.  
         [0023]     In another embodiment, the present invention is a shielding needle assembly with a passively-removable packaging shield. The needle assembly generally includes a needle cannula, a hub, and the passively-removable packaging shield. The needle cannula includes a proximal end and a distal end with a puncture tip. The hub supports the needle cannula. The packaging shield is disposed about a distal end of the hub and encloses the puncture tip of the needle cannula prior to using the needle assembly. The packaging shield is releasably associated with the distal end of the hub. The hub includes at least one release member disposed at least partially within the packaging shield, which is adapted to flex radially inward toward a central longitudinal axis of the needle assembly upon applying radial pressure thereto, to allow substantial automatic release of the packaging shield from the distal end portion of the hub. Thus, application of radial pressure applied to the at least one release member is required for removal of the packaging shield from the hub, and sequential change, for example lessening, is radial pressure applied to the at least one release member is required for allowing the drive member to disengage the at least one release member from the safety shield and move the safety shield from the retracted position to the extend position.  
         [0024]     The hub is preferably capable of direct or indirect fluid communication with a syringe through, for example, a syringe&#39;s male luer distal taper, or with a blood collection tube receptacle or holder.  
         [0025]     The at least one release member may be pivotally connected to the hub, for example, substantially at a proximal end of the hub. The at least one release member may include a pair of opposing release members pivotally connected to the hub, for example, substantially at the proximal end of the hub. A finger tab may be provided on each of the release members for applying the radial pressure to the release members and pivoting the release members radially inward toward the central longitudinal axis of the needle assembly.  
         [0026]     The present invention is further directed to a method of actuating a shielding needle assembly, for example, one of the shielding needle assemblies discussed previously. The method generally includes providing the shielding needle assembly including a needle cannula having a puncture tip, a hub supporting the needle cannula, a safety shield movably associated with the hub and disposed generally coaxially with the hub, and a drive member associated with the hub for moving the safety shield relative to the hub, the hub including at least one release member. Additionally, the method includes applying radial pressure to the at least one release member, such that the at least one release member engages the safety shield to maintain the safety shield in a retracted position disposed generally coaxially with the hub. The method may include a further step of at least partially releasing the radial pressure, such that the drive member automatically disengages the at least one release member from the safety shield and moves the safety shield from the retracted position to an extended position shielding the puncture tip of the needle cannula. As indicated previously, the shielding needle assembly may further include a packaging shield disposed on a distal end of the hub and enclosing the puncture tip of the needle cannula in the retracted position of the safety shield. The at least one release member may have a locking tab engaging a locking groove in the packaging shield, which prevents removal of the packaging shield until the application of the radial pressure to the at least one release member causes the at least one release member to displace radially inward into the hub and disengages the locking tab from the locking groove.  
         [0027]     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  
       [0028]      FIG. 1  is a perspective view of a shielding blood collection set in accordance with the present invention and having a releasable packaging shield disposed at a distal end of the blood collection set;  
         [0029]      FIG. 2  is a longitudinal cross-sectional view of the blood collection set of  FIG. 1 ;  
         [0030]      FIG. 3  is a longitudinal cross-sectional view of the blood collection set of  FIG. 1 , showing a user manipulating a shielding needle assembly portion of the blood collection set;  
         [0031]      FIG. 4  is a longitudinal cross-sectional view of the blood collection set of  FIG. 1 , showing the user applying radial pressure to the shielding needle assembly portion of the blood collection set and the subsequent removal of the packaging shield;  
         [0032]      FIG. 5  is a cross-sectional view of the blood collection set of  FIG. 1 , showing a needle cannula of the blood collection set inserted into the body of a patient;  
         [0033]      FIG. 6  is a longitudinal cross-sectional view of the blood collection set of  FIG. 1 , showing the blood collection set after the user has substantially released the radial pressure allowing the shielding needle assembly to shield a needle cannula of the assembly;  
         [0034]      FIG. 7  is a longitudinal cross-sectional view of the blood collection set of  FIG. 1 , showing the final disposition of the shielding needle assembly shielding the needle cannula; and  
         [0035]      FIG. 8  is a perspective view showing the direction of forces needed to actuate the shielding needle assembly portion of the blood collection set. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]     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 the present invention and its related features. The present invention is generally described in terms of a blood collection set, and encompasses such a blood collection set, as well as a shielding needle assembly for use in such a blood collection set.  
         [0037]     As shown generally in  FIG. 1 , the blood collection set  10  includes a 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 packaging cover or shield  18  removably mounted to the needle assembly  12  opposite tube  14 , such as through a frictional engagement. The blood collection set  10  and shielding needle assembly  12  of the present invention are shown in greater detail in  FIGS. 2-8 , and generally include a needle cannula  20 , a hub  30 , a needle cannula safety shield  70 , and a drive member  80  for moving the safety shield  50 .  
         [0038]     The needle cannula  20  includes a proximal end  22  and an opposing 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  is 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.  
         [0039]     The needle assembly  12  further includes the hub  30 . The hub  30  may be a unitary structure, desirably molded from a thermoplastic material, or a multi-component structure as described herein. The hub  30  includes a proximal end  32  and a 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.  
         [0040]     As depicted in the Figures, the needle cannula  20  and the hub  30  are preferably separate parts that are preferably fixedly attached and secured through an appropriate medical grade adhesive, for example, epoxy and 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 an 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, 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 .  
         [0041]     The hub  30  is generally tubular or cylindrical in shape, and preferably further includes 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.  
         [0042]     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 . 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 .  
         [0043]     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 shield or cover  18 , as discussed further herein.  
         [0044]     The needle assembly  12  further includes the safety shield  70 , which 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 , as will be described in more detail herein. The safety shield  70  is a unitary structure, desirably molded from a thermoplastic material, and includes a proximal end  72  and a distal end  74 . The distal end  74  defines a central opening  76  through which the needle cannula  20  extends. The central opening  76  permits the safety shield  70  to move along the needle cannula  20  between the retracted and extended positions. The safety shield  70  is further formed to encompass the drive member  80 , as shown in  FIGS. 2-5 , prior to actuating the drive member  80 , which is generally adapted to move the safety shield  70  axially along the needle cannula  20  from the retracted position to the extended position, as will be described in more detail herein.  
         [0045]     The drive member  80  is generally coaxially positioned within the safety shield  70  and the hub  30  in the retracted position of the safety shield  70 . 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  from the retracted position to the extended position. 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 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 .  
         [0046]     The packaging shield  18  is provided on the distal end  34  of the hub  30  and is preferably provided on the hub  30  during the manufacturing process of the blood collection set  10  and needle assembly  12 . The packaging shield  18  is preferably in frictional engagement with the distal end  34  of the hub  30 , but is secured in engagement with the hub  30  by a connecting structure described herein.  
         [0047]     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 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 .  
         [0048]     The packaging shield  18  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 shield  18  is 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 shield  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.  
         [0049]     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 shield  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 shield  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 shield  18  prevents premature removal of the packaging shield  18  from the distal end  34  of the hub  30 , and therefore premature actuation of the needle assembly  12 .  
         [0050]     An optional mechanism for retaining the packaging shield  18  onto hub  30  includes using the locking tabs  60  as external threads to ride within corresponding internal threads (not shown) in the packaging shield  18 . In this embodiment, the internal threads would act more like slots than true threads, and the packaging shield  18  would have to be rotated to a position where the locking tabs  60  (i.e., external threads) would allow for the packaging shield  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 shield  18  which connect to internal axial slots in the packaging shield  18 . In such a variation, rotation of the packaging shield  18  would cause the locking tabs  60  to slide within the circumferential slots until reaching the axial slots, which would allow the packaging shield  18  to be removed from the hub  30 .  
         [0051]     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 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 fixture (not shown), such as a blood collection receptacle.  
         [0052]     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 shield  18 . With the disengagement of the locking tabs  60  from the locking groove  90 , the packaging shield  18  is released of 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 shield  18  from the distal end  34 .  
         [0053]     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 prevents 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 shield  18  for maintaining the safety shield  70  in the retracted position and counteracting the biasing force of the drive member  80 .  
         [0054]     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 causes the needle assembly  12  to actuate the safety shield  70  is not intended to be limited to the complete discontinuing of radial pressure on the finger tabs  52 . 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  will determine the amount of lessening of the radial pressure required to allow the needle assembly  12  to actuate.  
         [0055]     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 .  
         [0056]     The safety shield  70  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  forms 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 shield  18  need not be continuous around the internal circumference of the packaging shield  18 . Moreover, it will further be appreciated that the needle shield  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.  
         [0057]     The shielding feature of the present invention is passively actuated upon normal usage of the device. In particular, upon removal of the packaging shield 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.  
         [0058]     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, according to the present invention, does not involve the inconvenience of having to use a new blood collection set following each unsuccessful venipuncture attempt.  
         [0059]     While the needle assembly of the present invention has been described in terms of one embodiment 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.