Abstract:
Methods of manufacturing a catheter introducer or needle assembly and needle shield are disclosed. A needle shield has a blocking object (preferably a ball) which moves from an non-shielding position to a shielding position. The catheter introducer is made by placing the blocking object into the shield and inserting the proximal end of the needle into the shield while the blocking object is in the shielding position. The catheter introducer is made using extruded polymeric tubes which may have coextruded reinforcing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application claims priority from, and expressly incorporates by reference, the following provisional patent applications:
       60/659,226—Shielding Apparatus for Locking onto a Needle—filed on Mar. 7, 2005;   60/659,217—Needle Shielding Apparatus with Tubular Needle Cover—filed on Mar. 7, 2005;   60/659,213—Needle Shielding Apparatus with Tether to Needle Hub—filed on Mar. 7, 2005;   60/714,954—Blood Collection Device with Needle Shield—filed on Sep. 7, 2005.       
 
     
    
     BACKGROUND 
       [0006]    This patent application relates to medical devices using needles such as spinal needles, intravenous catheter introducers, blood collection devices and syringes. It includes methods of manufacturing needle based devices and needle shields for such devices. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention includes a method of making a needle assembly. The needle has a proximal end, a sharp distal end and a longitudinal axis. A needle shield assembly is provided with a blocking object carrier, a blocking object (preferably a ball) and a lumen coaxial with the longitudinal axis of the needle. The lumen has a proximal end and a distal end. The blocking object is moveable from a shielding position in which the blocking object at least partially occludes the lumen and a non-shielding position in which the needle can slide along the lumen. The blocking object is placed in the blocking object carrier in the shielding position. The proximal end of the needle is inserted into the distal end of the lumen and the needle shield assembly is moved such that the needle moves the blocking object from the shielding position to a non-shielding position. 
         [0008]    A spring is attached to the blocking object carrier such that the spring biases the blocking object towards the longitudinal axis of the needle. If the device is a catheter introducer assembly then a catheter tube is threaded over the needle. A catheter adapter is snapped onto the needle shield assembly. At least part of the needle shield assembly is placed inside a catheter adapter. The blocking object is preferably a ball, but may be a non-spherical object such as a roller. 
         [0009]    The blocking object carrier preferably holds the blocking object in a position offset from the longitudinal axis of the needle in the shielding position. At least part of the needle shield assembly is placed inside a catheter adapter. 
         [0010]    A method of manufacturing a catheter introducer assembly is also disclosed. A polymeric tube is extruded and attached to a needle hub such that it slides relative to the needle hub. A catheter assembly is placed on the needle. In a further method of the invention, a second polymeric tube is extruded and secured to the needle hub. The first and second polymeric tubes are concentric. The step of extruding the polymeric tube may include providing reinforcing in the polymeric tube. The polymeric tube and the reinforcing may be coextruded. 
         [0011]    Another method involves extruding a polymeric tube, securing a needle hub and a needle to the distal end of the polymeric tube and placing a catheter assembly on the needle. The polymeric tube may have a second, substantially parallel polymeric tube such that the polymeric tube comprises more than one lumen. 
         [0012]    These and other features of the invention are described in greater detail below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0013]      FIGS. 1A , B and C are cross-sectional views showing an embodiment of the invention as applied to a catheter introducer; 
           [0014]      FIG. 2  is a cross sectional view through the needle shield in a deployed position; 
           [0015]      FIG. 3  is an orthogonal cross-sectional view showing the angles between needle bevel and shield wall; 
           [0016]      FIG. 4  is an orthogonal cross-sectional view through a catheter introducer assembly with the needle shield in a non-deployed position; 
           [0017]      FIG. 5  is an orthogonal cross-sectional view through a catheter introducer assembly with the needle shield in a deployed position; 
           [0018]      FIG. 6  is an isometric cross-sectional view through a catheter introducer assembly with the needle shield in a non-deployed position; 
           [0019]      FIG. 7  is an isometric cross-sectional view through a catheter introducer assembly with  15  the needle shield in a deployed position; 
           [0020]      FIG. 8  is an exploded view of the components of the needle shielding device and the needle hub; 
           [0021]      FIG. 9  is an orthogonal cross-sectional view through a catheter introducer assembly with the needle shield in a non-deployed position; 
           [0022]      FIG. 10  is an orthogonal cross-sectional view through a catheter introducer assembly with the needle shield in a deployed position; 
           [0023]      FIG. 11  is an isometric cross-sectional view through a catheter introducer assembly with the needle shield in a non-deployed position; 
           [0024]      FIG. 12  is an isometric cross-sectional view through a catheter introducer assembly with the needle shield in a deployed position; 
           [0025]      FIG. 13  is an exploded view of the components of the needle shielding device and the needle hub; 
           [0026]      FIG. 14  is an isometric view of an extruded polymeric tube used in one embodiment of the invention; 
           [0027]      FIG. 15  is an orthogonal cross-sectional view through a catheter introducer assembly with the needle shield in a non-deployed position; 
           [0028]      FIG. 16  is an orthogonal cross-sectional view through a catheter introducer assembly with the needle shield in a deployed position; 
           [0029]      FIG. 17  is an isometric cross-sectional view through a catheter introducer assembly with the needle shield in a non-deployed position; 
           [0030]      FIG. 18  is an isometric cross-sectional view through a catheter introducer assembly with the needle shield in a deployed position; 
           [0031]      FIG. 19  is an exploded view of the components of the needle shielding device and the needle hub; 
           [0032]      FIG. 20  is an isometric view of a catheter introducer with a needle shield in which the shield housing is made from an extruded polymeric tube; 
           [0033]      FIG. 21  is a cross-sectional through the housing of the embodiment of  FIG. 20 ; 
           [0034]      FIG. 22  is an orthogonal cross-sectional view of the housing of the embodiment of  FIG. 20 ; 
           [0035]      FIG. 23  is an orthogonal cross-sectional view through a syringe needle shielding apparatus with the needle shield in a non-deployed position; 
           [0036]      FIG. 24  is an orthogonal cross-sectional view through a syringe needle shielding apparatus with the needle shield in a deployed position; 
           [0037]      FIG. 25  is an isometric view of a syringe needle shielding apparatus with the needle shield in a non-deployed position; 
           [0038]      FIG. 26  is an exploded view of the components of the syringe needle shielding apparatus; 
           [0039]      FIGS. 27-30  are isometric views of winged catheter introducers equipped with the needle shield; 
           [0040]      FIGS. 31-32  are isometric views of winged catheter introducers equipped with the needle shield; 
           [0041]      FIGS. 33-34  are isometric views of the needle shield applied to a Huber needle used with an implantable access port; 
           [0042]      FIG. 35  is an isometric view of a blood collection device with the needle shield; 
           [0043]      FIGS. 36-51  are orthogonal views of alternative embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0044]    The following is a description of embodiments of the invention as applied to catheter introducers, a syringes and other needle based devices. It is not intended to limit the scope of the invention. 
         [0045]    The invention may be applied to a wide variety of needle based devices such as catheter introducers, syringes, winged needles and Huber needles. In almost all cases, shielding a needle involves providing a needle shield and ensuring that it does not come off the sharp distal end of the needle or move proximally, thereby re-exposing the sharp distal end. Some sort of locking mechanism or mechanisms must therefore prevent distal and proximal movement of the shield once the needle is shielded. 
         [0046]    In the present invention, proximal movement of the shield is prevented by the assembly shown in  FIGS. 1A , B and C and  FIG. 2 . Assembly  1  comprises needle  10 , having a longitudinal axis  11 , an outer surface  12  and a sharp distal end  15 . Needle shield assembly  90  has an internal lumen  93 , which is coaxial with needle  10 . Needle shield assembly  90  is shown inside a catheter adapter or hub  23  in  FIG. 1A . Shield assembly  90  is made up of a first housing  95  which is covered with a cap  100 . First housing  95  has a stepped area or area of reduced diameter  105  onto which spring  2  is threaded. First housing  95  has an opening  18  which with first housing  95  forms a holder or carrier  16  (as shown in  FIGS. 1A and 4 ) for ball  3 . Opening  18  extends from outer wall  19  through to lumen  93 . Opening  18  is configured such that ball  3  can move in it but the movement of ball  3  is restricted radially, longitudinally and circumferentially relative to axis  11 . 
         [0047]    In the non-shielding position shown in  FIG. 1A , ball  3  protrudes through hole  21  in cap  100 . Spring  2  exerts a force on ball  3  which has an axial component and a component radially towards axis  11 . In the non-shielding position, ball  3  touches outer surface  12  of needle  10 . The biasing force of spring  2  thus makes ball  3  tend towards axis  11 . 
         [0048]    As shield assembly  90  slides along needle  10 , it approaches distal end  15 . The biasing force in spring  2  forces ball  3  at least partially into lumen  93  and it leaves hole  21  and moves radially towards axis  11  in opening  18 , as the bevel of needle  10  passes ball  3 . Due to the geometry of opening  18 , when the bevel has passed by, ball  3  lies at least partially in lumen  93 . 
         [0049]    Axis  24  of ball  3  lies offset from axis  11 . Radial movement of ball  3  is restricted by spring  2  and by top wall  20  of cap  100 . Axial movement of the ball is also restricted by front wall  22  of opening  18 . Distal movement of needle  10  forces ball  3  against wall  22 . If shield  90  now slides proximally (i.e. needle  10  slides distally), needle  10  will be blocked by ball  3 , which lies at least partially in lumen  15  and movement of which is limited by spring  2  and walls  20  and  22 . 
         [0050]    Referring to  FIG. 3 , wall  20  of cap  100  forms an angle α tangential to ball  3  when ball  3  is moving into its position at least partially occluding lumen  93 . This angle α is set at a value less than the smallest bevel angle of needle tip  15 . In the embodiment described here, the angle α between wall  20  and ball  3  is about zero degrees. If that angle is made too large relative to angle, ball  3  will not be trapped. 
         [0051]    The above operation is described in greater detail and with slight variations in the remainder of this specification in the context of catheter introducers, syringes and other needle-based medical devices. Three types of catheter introducer are shown. In the first, distal movement of the needle shield off the sharp end of the needle is restrained by means of an abutment between the needle shield and a discontinuity on the introducer needle. In the second, the needle shield is on the end of a tubular member, distal movement of which is restrained by an abutment with a member attached to the needle hub. In the third, the needle shield is tethered to the needle hub, thereby preventing distal movement of the needle shield off the sharp end of the needle. The same applies to the syringe. In all cases, proximal movement and hence pulling back of the needle to expose the sharp end of the needle, is prevented by the device described above. 
         [0052]    The following is a description of the invention as applied to a first type of catheter introducer assembly in which distal movement of the needle shield assembly is restrained by a discontinuity on the needle such as a bump or crimp. Reference is made to  FIGS. 4-8 . 
         [0053]    The purpose of catheter introducer assembly  5  is to pierce a human or animal body with a needle, make an opening, insert a catheter tube into it and then remove the needle. In order to prevent the spread of infectious disease through needle sticks, the tip of the needle should be shielded once it is removed. 
         [0054]    The body is pierced by needle  10 , which has an outer surface  12 , a proximal end  15 , a distal end  20  and a lumen  22 . Distal end  20  has a sharp tip or point  25 . Distal end is beveled. In the drawings it is shown with two bevels—surfaces  30  and  40  forming a slope extending from the sharp point  25  in a proximal direction. More or less than two bevels may be used. Proximal end  15  is secured to needle hub  45 . Needle  10  has an area of enlarged cross section  14  located close to distal end  20 . This enlarged cross section can be in the form of an annular ring, enlarging the diameter of needle  10 , a segmented ring or a discontinuity, bump or crimp on the needle. The enlarged cross section can be formed on needle  10  by crimping, grinding, deforming or depositing material on the surface of the needle. The difference between the diameter of needle  10  and this enlarged cross section is very small—about 0.004 inches—and its length is only about 0.03 inches. 
         [0055]    Catheter assembly  50  has a catheter hub  52  having proximal end  55 , distal end  60  and lumen  70  extending between the proximal and distal ends. Catheter tube  65  extends distally out of distal end  60 . Needle  10  lies within lumen  70  of catheter assembly  50  prior to insertion into the body. Once needle  10  has been inserted into the patient, together with catheter tube  65 , needle  10  is withdrawn by pulling it in a proximal direction. Catheter hub  52  has an inner surface  80  and an outer surface  82 . Inner surface  80  is provided with a circumferential groove  75 , the purpose of which will be explained in due course. A single depression, indentation, circumferential ridge or raised portion will serve the same purpose as the circumferential groove. 
         [0056]    Needle shield assembly  90  is contained in two mating parts—first housing  95  and second housing or cap  100 . Needle assembly housing  90  can fit within catheter hub  50 . First housing  95  has a distal end  97  and a proximal end  99 . Extending between the proximal and distal ends is lumen  93 , which is dimensioned so that first housing  95  can slide axially and rotate on needle  10 . Extending from near distal end  97  towards proximal end  99  is stepped area  105 . This is an area of reduced diameter which allows coil spring  110  to be placed on first housing  95 . Spring  110  is a compression spring, which exerts a force axially in the proximal and distal directions. Other types of springs can be used, for example, a leaf spring (see  FIG. 41 ) or a wave spring washer (see  FIG. 42 ). 
         [0057]    Towards distal end  97  of first housing  95 , but still in the stepped area  105 , first housing  95  is provided with an opening  120 , dimensioned to accommodate ball  122 . Second housing or cap  100  has a proximal end  130  and a distal end  135 . Proximal end  130  is provided with opening  140  which is dimensioned such that it is slightly larger than the diameter of needle  10 , but slightly smaller than the diameter of area of enlarged cross section  14 . Thus, second housing can slide axially along the needle from proximal end  15  towards distal end  20 , until its opening  140  abuts area of enlarged cross section  14 , at which time it cannot slide further in the distal direction. When first and second housings  95  and  100  are assembled, second housing  100  covers most of first housing  95 , except for distal end  97  of the first housing. Second housing  100  thus covers spring  110 . Second housing  100  is provided with opening  150  which is dimensioned such that part of ball  122  can protrude through it and into groove  75 . 
         [0058]    When needle shield assembly  90  is in catheter hub  52 , prior to deployment, part of ball  122  protrudes through opening  150  and lies in groove  75 . This locks needle shield assembly  90  to catheter hub  52 , while allowing catheter hub  52  to rotate relative to needle shield assembly  90 , depending on the extent of groove  75  (i.e. whether it is circumferential or permits only limited movement because it does not extend around the entire inner circumference of the catheter hub). Part of ball  122  also lies in lumen  93  of first housing  95  and abuts outer surface  12  of needle  10  (i.e. ball  122  touches outer wall  12  of needle  10 ). Needle  10  and shield assembly  90  can slide and rotate relative to each other with very low friction. Ball  122  is radially constrained by groove  75  and needle  10 . Needle shield assembly  90  is thus locked into catheter hub  52 . Spring  110  exerts a force on ball  122  axially, in the distal direction. Moreover, the presence of needle  10  abutting ball  122  radially constrains ball  122  and prevents it from moving out of groove  75 . 
         [0059]    Once catheter tube  65  has been placed in the patient, needle  10  is pulled in a proximal direction (that is to say, as needle shield assembly  90  moves towards tip  25  of needle  10 ). If first bevels  30  and  40  are facing ball  122 , then, when first bevel  40  comes into alignment with ball  122 , ball  122  is less radially constrained by needle  10  and, urged by spring  110 , it begins to move in opening  120 , distally and radially. Ball  122  thus moves out of opening  150  and groove  75  and radially inwards further into lumen  93  of shield assembly  90 , pivoting about edge  155 , (a wall of opening  150  in second housing  100 ) and sliding distally along the length of opening  120 . As needle  10  continues its proximal movement, it no longer constrains it radially and ball  122  moves completely out of groove  75 . When ball  122  is positioned such that edge  155  is above it, ball  122  will have traveled radially into lumen  93  as far as it can, constrained by the dimensions of opening  120  and partially occluding lumen  93 . 
         [0060]    If bevels  30  and  40  are not facing ball  122  or are partially facing ball  122 , the device operates in a similar manner. That is to say, when needle tip  25  passes ball  122 , needle  10  no longer constrains ball  122 . Spring  110  urges ball  122  along opening  120  so that ball  122  moves out of groove  75  and pivots about edge  155 . Ball  122  is constrained from entering lumen  93  by the dimensions and geometry of opening  120 . Ball  122  thus partially occludes lumen  93 . 
         [0061]    The position of ball  122  in opening  120  and partially occluding lumen  93  is shown in  FIGS. 5 &amp; 7 . When ball  122  has moved to the point where it partially occludes lumen  93  as described, area of enlarged cross section  14  abuts rear opening  140  of cap  100 , and further pulling of needle  10  causes shield assembly  90  to come out of catheter hub  52  due to the fact that ball  122  is no longer in groove  75 . The force of groove  75  against ball  122  due to the pulling of the needle in a proximal direction may also urge ball  122  radially into lumen  93 . 
         [0062]    Movement of the shield assembly in the distal direction (such that shield assembly  90  slides off distal end  20  of the needle) is prevented by the interaction of area of enlarged cross section  14  on needle  10  and rear opening  140  of second housing  100 . Movement of the shield assembly in the proximal direction (to expose needle tip  25 ) is prevented by distal end  20  of needle  10  abutting ball  122 . 
         [0063]    The distance from enlarged cross section  14  to tip  25  is set so that when tip  25  is aligned with ball  122 , there is sufficient space for the ball to move beneath second housing  100  in opening  120 . The angle formed by upper surface  136  tangential to ball  122  is as described above with reference to  FIG. 3 . Distal end  97  of first housing  95  and cap  100  are dimensioned to overhang so that tip  25  can never emerge from distal end  97  of shield  90 . It is possible to employ multiple balls sitting in multiple openings the same as openings  120  and  150 . If this is done, the overhang on distal end  97  and cap  100  can be reduced, making shield assembly  90  more compact. 
         [0064]    After deployment, but before needle  10  moves distally, part of ball  122  lies in lumen  93  and part of it is urged against distal wall  157  of opening  120  by spring  110 . The top of ball  122  lies beneath distal end  135  of second housing  100 . In an alternative embodiment, spring  110 , having expanded, closes off the top of opening  120 . Ball  122  is thus radially and axially constrained in opening  120 . If needle  10  moves distally, it will abut ball  122 , which will be forced against distal wall  157  of second housing  100  and surface  136 . Further distal movement of needle  10  and hence emergence of needle tip  25  from the shield assembly will be prevented. 
         [0065]    Lumen  93  is sized such that needle  10  fits relatively snugly inside it. Thus, when needle  10  is moved distally (i.e. shield  90  is moved proximally) and ball  122  abuts needle tip  25 , needle  10  will not move away from ball  122 . Lumen  93  thus provides support opposite ball  122  to prevent needle  10  from wiggling, and to prevent tip  25  from moving such that it pierces first housing  95 . The snugness of the fit between lumen  93  and needle  10  also facilitates the threading of shield  90  onto needle  10  (i.e. the distal end of shield  90  is threaded onto the proximal end of the needle). The snug fit means that the shield is guided so that proximal end  15  of needle  10  enters opening  140  in proximal end  130  of cap  100 . This is important because opening  140  is typically only 0.001 inch larger than the diameter of needle  10 . 
         [0066]    In an alternative embodiment, ball  122  fully enters lumen  93 . Ball  122  has a diameter slightly larger than that of lumen  93 . Ball  122  is then axially constrained by lumen  93  and needle  10 . In this case, lumen  93  is also dimensioned to provide support for needle  10  opposite ball  122 , thus preventing wiggle of the needle and preventing tip  25  from piercing first housing  95 . 
         [0067]    In order to move out of groove  75  ball  122  moves a distance at least equal to the amount by which it protrudes from opening  150  plus the wall thickness of cap  100  (approx. 0.003″ to 0.005″). When the shield is deployed ball  122  extends into lumen  93  by an amount approximately equal to that distance. This leaves part of lumen  93  occluded. If a small gauge needle is used, a larger ball is needed in order to occlude lumen  93  sufficiently to prevent needle tip  25  from poking through the un-occluded part of lumen  93 . If a large gauge needle is used, the ball can be smaller (i.e if the needle has a large diameter, the ball can be smaller). 
         [0068]    The above description includes operation of needle shield  90  with catheter assembly  50 , providing, in addition to a needle shielding function, a mechanism for locking shield  90  to catheter assembly  50  and unlocking it. This provides the added benefit of ensuring that shield  90  can never be removed from catheter hub  52  until needle tip  25  is shielded. In cases where a catheter lock is not needed, cap  100  can be closed (i.e. lack opening  120 ) and slightly enlarged to accommodate the entire diameter of ball  122 . 
         [0069]    The following is a description of a second type of catheter introducer assembly embodying the invention. In this second type of catheter introducer, when the needle is shielded, a tube covers the entire length of the needle and restrains the needle shield from further distal movement. Reference is made to  FIGS. 9-14 . 
         [0070]    The body is pierced by needle  210 , which has an outer surface  212 , a proximal end  215 , a distal end  220  and a lumen  222 . Distal end  220  has a sharp point  225 . Distal end is beveled, with two bevels—surfaces  230  and  240  forming a slope extending from the sharp point  225  in a proximal direction. More or less than two bevels may be used. Proximal end  215  is secured to needle hub  245 . 
         [0071]    Needle hub  245  has a tube  250  extending backwards from where it is secured to proximal end  215  of needle  210 . Needle hub tube  250  has a proximal end  254  and a distal end  252  (to which needle  210  is secured). Needle hub tube  250  has lumen  260  which is coaxial with lumen  220  of needle  210  so that fluid can flow along lumen  222  and into lumen  260 . Needle hub tube  250  is integral and coaxial with another tube  255  which forms a handle and has proximal end  258  and distal end  256 . Tubes  250  and  255  are joined at the back  275  (proximal end) of the assembly. That is to say proximal end  254  of needle tube  250  and proximal end  258  of handle tube  255  are joined at back  275 . Needle hub  250  is open at the back (has hole  270 ), which is fitted with a vent plug to permit air but not liquid to escape as fluid enters lumen  222  and flows into lumen  260 . Both tubes  250  and  255  are transparent (or at least have a transparent part) so that the flow of fluid can be seen by the user. Tube  255  has an exterior circumferential flange  272  located at distal end  256 , approximately in line with the area where proximal end  215  of needle  210  is secured to needle hub  245 . Tube  255  also has an interior circumferential flange  274  substantially in line with exterior flange  272 . The combination of needle hub tube  250  and handle tube  255  can be regarded as two concentric cylinders. Between tubes  250  and  255  is an annular space  276  which extends from distal end  256  to back  275 . 
         [0072]    Catheter assembly  280  has a catheter adapter or hub  282  having proximal end  285 , distal end  288  and lumen  290  extending between the proximal and distal ends. Catheter tube  286  extends distally out of distal end  288 . Needle  210  lies within lumen  290  of catheter assembly  280  prior to insertion into the body. Once needle  210  has been inserted into the patient, together with catheter tube  286  needle  210  is withdrawn by pulling it in a proximal direction. Catheter hub  282  has an inner surface  292  and an outer surface  291 . Inner surface  292  is provided with a circumferential groove  293 , the purpose of which has been explained above and will be explained in due course. A single depression, indentation, circumferential ridge or raised portion will serve the same purpose as the circumferential groove. 
         [0073]    Needle shield assembly  2110  has a proximal end  2120 , a distal end  2115  and a lumen  2112  extending from the proximal to the distal end. Lumen  2112  is dimensioned at distal end  2115  so that shield assembly  2110  can slide axially and rotate on needle  210 . Shield assembly  2110  includes two parts—first housing  295  and cap  2100 . Cap  2100  is at distal end  2115  and fits inside catheter hub  282 . Shield  2110  is concentric with tubes  250  and  255 . First housing  295  of shield  2110  lies at least partially in annular space  276  when the shield is in its non-deployed position. First housing  295  can slide back and forth in an axial direction in annular space  276 . First housing  295  is also at least partially transparent to permit the user to see fluid flow. Proximal end  2120  of shield  2110  is provided with circumferential flange  2117 . When shield  2110  moves in a distal direction axially along annular space  276 , flange  2117  will eventually abut interior flange  274  of handle tube  255  and will be prevented from further distal movement. In the deployed position, proximal end  2121  abuts interior flange  274  at distal end  256  of handle tube  255 . 
         [0074]    First housing  295  has a distal end  297  with stepped area  2105 —an area of reduced diameter which allows coil spring  2111  to be placed on first housing  295  and cap  2100  to be placed over it. Stepped area  2105  can be formed separately from first housing  295  and attached to it. Spring  2111  is a compression spring, which exerts a force axially in the proximal and distal directions. Towards distal end  297  of first housing  295 , but still in the stepped area  2105 , first housing is provided with an opening  2120 , dimensioned to accommodate ball  2122 . 
         [0075]    Cap  2100  is a metal stamping having a proximal end  2130  and a distal end  2135 . When first housing  295  and cap  2100  are assembled, second housing  2100  covers distal end  297  of the first housing and spring  2111 . Cap  2100  is provided with opening  2150  which is dimensioned such that part of ball  2122  can protrude through it and into groove  293 . Cap  2100  is dimensioned to fit in catheter hub  282 . The part of first housing  295  immediately adjacent stepped area  2104  also fits in catheter hub  282 . 
         [0076]    When needle shield assembly  2110  is attached to catheter hub  282  (i.e. cap  2100  and part of first housing  295  are in catheter hub  282 ), prior to deployment, part of ball  2122  protrudes through opening  2150  and lies in groove  293 . This locks needle shield assembly  2110  to catheter hub  282 , while allowing catheter hub  282  to rotate relative to needle shield assembly  2110 , depending on the extent of groove  293  (i.e. whether it is circumferential or permits only limited movement because it does not extend around the entire inner circumference of the catheter hub). Part of ball  2122  also lies in lumen  2112  of first shield assembly  2110  and abuts outer surface  212  of needle  210  (i.e. ball  2122  touches outer wall  212  of needle  210 ). Needle  210  and shield assembly  2110  can slide and rotate relative to each other with very low friction. Ball  2122  is radially constrained by groove  293  and needle  210 . Needle shield assembly  2110  is thus locked into catheter hub  282 . Spring  2111  exerts a force on ball  2122  axially, in the distal direction. Moreover, the presence of needle  10  abutting ball  2122  radially constrains ball  2122  and prevents it from moving out of groove  293 . This is shown in  FIG. 11 . 
         [0077]    Once catheter tube  286  has been placed in the patient, needle  210  is pulled in a proximal direction (that is to say, as needle shield assembly  2110  moves towards tip  225  of needle  210  or needle hub  245  is pulled proximally). If bevels  230  and  240  are facing ball  2122 , then, when first bevel  240  comes into alignment with ball  2122 , ball  2122  is less radially constrained by needle and, urged by spring  2111 , it begins to move in opening  2120 , distally and radially. Ball  2122  thus moves out of opening  2150  in cap  2100  and groove  293  in catheter hub  282  and radially inwards further into lumen  2112  of shield assembly  2110 , pivoting about edge  2155 , (a wall of opening  2150  in cap  2100 ) and sliding distally along the length of opening  2120 . When second bevel  230  is aligned with ball  2122 , needle  210  no longer constrains it radially and it moves completely out of groove  293 . When ball  2122  is positioned such that edge  2155  is above it, ball  2122  will have traveled radially into lumen  1212  as far as it can, constrained by the dimensions of opening  2120  and partially occluding lumen  2112 . 
         [0078]    If bevels  230  and  240  are not facing ball  2122  or are partially facing ball  2122 , the device operates in a similar manner as described above. Spring  2111  urges ball  2122  along opening  2120  so that ball  2122  moves out of groove  293  and pivots about edge  2155 . Ball  2122  is constrained from entering lumen  293  by the dimensions and geometry of opening  2120 . Ball  2122  thus partially occludes lumen  2112 . 
         [0079]    After ball  2122  has moved to the point where it partially occludes lumen  2112  as described, flange  2117  of shield assembly  2110  abuts interior flange  274  of tube  255 , and further pulling of needle  210  causes shield assembly  2110  to come out of catheter hub  282  due to the fact that ball  2122  is no longer in groove  293 . The force of groove  293  against ball  2122  due to the pulling of the needle in a proximal direction may also urge ball  2122  radially into lumen  2112 . 
         [0080]    Movement of the shield assembly in the distal direction (such that shield assembly  2110  eventually slides off distal end  220  of the needle) is prevented by the interaction of flanges  274  and  2117 . Movement of the shield assembly in the proximal direction (to expose needle tip  225 ) is prevented by distal end  220  of needle  210  abutting ball  2122  which abuts wall  2157  of first housing  295  and upper inner wall  2136  of second housing or cap  2100 . 
         [0081]    The distance from flange  2117  to needle tip  225  is set so that when tip  225  is aligned with ball  2122 , there is sufficient space for the ball to move beneath cap  2100  in opening  2120 . The considerations for angles α and β (i.e. the tangent formed between ball  2122  and surface  2136  and the smallest bevel angle) are as set forth above in relation to  FIG. 3 . 
         [0082]    After deployment, but before needle  210  moves distally, part of ball  2122  lies in lumen  2112  and part of it is urged against distal wall  2157  of opening  2120  by spring  2111 . The top of ball  2122  lies beneath upper surface  2136  of distal end  2135  of cap  2100 . Distal end  299  of first housing  295  and cap  2100  are likewise dimensioned to overhang so that tip  225  can never emerge from distal end  2115 . Multiple balls can likewise be used. The foregoing design also provides a catheter locking feature as previously described. 
         [0083]    Once the shield has been deployed, but before needle  210  moves distally, part of ball  2122  lies in lumen  2112  and part of it is urged against wall  2157  of opening  2120  by spring  2111 . The top of ball  2122  lies beneath upper surface  2136  of distal end  2135  of cap  2100 . Opening  2120  maybe closed off by spring  2111 . Ball  2122  is radially and axially constrained in opening  2120 . If needle  210  moves distally, it will abut ball  2122 , which will be forced against distal wall  2157  of first housing  295  and wall  2136  of cap  2100 . Needle  210  thus cannot emerge distally from the shield. 
         [0084]    Lumen  2112  provides anti-wiggle support for needle  210  as described above in relation to an earlier embodiment. Similar considerations as described above apply to movement of the ball and the dimensions of the ball relative to the needle gauge size. That is to say, larger balls are used for smaller gauge sizes and vice versa. 
         [0085]    First housing  295  and the tube part of shield  2110  can be made out of an extruded polymeric tube  950  as shown in  FIG. 14  (see also  FIGS. 20-22 ). Polymeric tube  950  is relatively thin and flexible. This, and the fact that it is extruded, makes it extremely light and simple to manufacture and the amount of materials needed to manufacture it is reduced relative to rigid molded members. In order to provide stiffness and strength, the polymeric tube may be reinforced with coextruded metal wires  956 . Wires  956  are shown as longitudinal wires running along the length of tube  955 . Alternatives to longitudinal wires are a coextruded woven fabric, mesh, lattice or spiral. 
         [0086]    The following is a description of a catheter introducer assembly embodying the invention, in which distal movement of the needle shield is restrained by a tether secured to the needle hub. Reference is made to  FIGS. 15-19 . Needle hub  45  has a tube  50  extending backwards from where it is secured to proximal end  15  of needle  10 . Needle hub tube  50  has a proximal end  54  and a distal end  52  (to which needle  10  is secured). Needle hub tube  50  has lumen  60  which is coaxial with lumen  22  of needle  10  so that fluid can flow along lumen  22  and into lumen  60 . Needle hub tube  50  forms a handle by which the user can grasp catheter assembly  5  in order to insert needle  10  into a patient. 
         [0087]    Needle hub  50  is open at the back (has hole  70 ), which may be fitted with a vent plug to permit air but not liquid to escape as fluid enters lumen  22  and flows into lumen  60 . Tube  50  is transparent (or at least has a transparent part) so that the flow of fluid can be seen by the user. Tube  50  has an exterior circumferential flange  72  located at distal end  52 , approximately in line with the area where proximal end  15  of needle  10  is secured to needle hub  45 . 
         [0088]    Circumferential flange  72  is provided with a small opening  74 , through which is threaded tether  75 . Tether  75  has a proximal end  77  and a distal end  76 . Proximal end is T-shaped. Arm  79  of the T prevents tether  75  from escaping through opening  74  when tether  75  moves distally. Distal end  76  is secured to needle shield assembly  110  (described below). Tether  75  thus prevents needle shield assembly from moving off tip  25  of needle  10  in the distal direction. Tether  75  can be made of nylon and closely resembles a label holder used in the retail industry to secure labels to items of clothing. Tether  75  may be integrally molded with first housing  95  but does not have to be. 
         [0089]    Catheter assembly  80  has a catheter hub  82  having proximal end  85 , distal end  88  and lumen  90  extending between the proximal and distal ends. Catheter tube  86  extends distally out of distal end  88 . Needle  10  lies within lumen  90  of catheter assembly  80  prior to insertion into the body. Once needle  10  has been inserted into the patient, together with catheter tube  86 , needle  10  is withdrawn by pulling it in a proximal direction. Catheter hub  82  has an inner surface  92  and an outer surface  91 . Inner surface  92  is provided with a circumferential groove  93 , the purpose of which will be explained in due course. A single depression, indentation, circumferential ridge or raised portion will serve the same purpose as the circumferential groove. 
         [0090]    Needle shield assembly  110  has a proximal end  118 , a distal end  115  and a lumen  112  extending from the proximal to the distal end. Lumen  112  is dimensioned so that shield assembly  110  can slide axially and rotate on needle  10 . Shield assembly  110  is contained in mating parts—first housing  95  and cap  100 . Cap  100  is at distal end  115  and fits inside catheter assembly  80 . 
         [0091]    First housing  95  has a distal end  97  with stepped area  105 —an area of reduced diameter which allows coil spring  111  to be placed on first housing  95  and cap  100  to be placed over it. Spring  111  is a compression spring, which exerts a force axially in the proximal and distal directions. Towards distal end  97  of first housing  95 , but still in the stepped area  105 , first housing is provided with an opening  120 , dimensioned to accommodate ball  122 . 
         [0092]    Cap  100  is a metal stamping having a proximal end  130  and a distal end  135 . Cap  100  covers distal end  97  of the first housing and spring  111 . Cap  100  is provided with opening  150  which is dimensioned such that part of ball  122  can protrude through it and into groove  93 . Cap  100  is dimensioned to fit in catheter hub  82 . The part of first housing  95  immediately adjacent stepped area  104  also fits in catheter hub  82 . 
         [0093]    When needle shield assembly  110  is attached to catheter hub  82  (i.e. cap  100  and part of first housing  95  are in catheter hub  82 ), prior to deployment, part of ball  122  protrudes through opening  150  and lies in groove  93 . This locks needle shield assembly  110  to catheter hub  82 , while allowing catheter hub  82  to rotate relative to needle shield assembly  110 , depending on the extent of groove  93  (i.e. whether it is circumferential or permits only limited movement because it does not extend around the entire inner circumference of the catheter hub). Part of ball  122  also lies in lumen  112  of first shield assembly  110  and abuts outer surface  12  of needle  10  (i.e. ball  122  touches outer wall  12  of needle  10 ). Needle  10  and shield assembly  110  can slide and rotate relative to each other with very low friction. Ball  122  is radially constrained by groove  93  and needle  10 . Spring  111  exerts a force on ball  122  axially, in the distal direction. Moreover, the presence of needle  10  abutting ball  122  radially constrains ball  122  and prevents it from moving out of groove  93 . 
         [0094]    Once catheter tube  86  has been placed in the patient, needle  10  is pulled in a proximal direction (that is to say, as needle shield assembly  110  moves towards tip  25  of needle  10  or needle hub  45  is pulled proximally). If bevels  30  and  40  are facing ball  122 , then, when first 20 bevel  40  comes into alignment with ball  122 , ball  122  is less radially constrained by needle  10  and, urged by spring  111 , it begins to move in opening  120 , distally and radially. Ball  122  thus moves out of opening  150  in cap  100  and groove  93  in catheter hub  82  and radially inwards further into lumen  112  of shield assembly  110 , pivoting about edge  155 , (distal wall of opening  150  in cap  100 ) and sliding distally along the length of opening  120 . When second bevel  30  is aligned with ball  122 , needle  10  no longer constrains it radially and it moves completely out of groove  93 . When ball  122  is positioned such that edge  155  is above it, ball  122  will have traveled radially into lumen  112  as far as it can, constrained by the dimensions of opening  120  and partially occluding lumen  112 . This is shown in  FIG. 6 . The above operation is similar if bevels  30  and  40  are not facing ball  122 , as described above in the context of another embodiment. 
         [0095]    As needle hub  45  moves proximally, tether  75  plays out through opening  74 , such that arm  79  moves distally. When ball  122  has moved to the point where it partially occludes lumen  112  as described, arm  79  of tether  75  abuts flange  72 , and further pulling of needle  10  causes shield assembly  110  to come out of catheter hub  82  due to the fact that ball  122  is no longer in groove  93 . The force of groove  93  against ball  122  due to the pulling of the needle in a proximal direction may also urge ball  122  radially into lumen  112 . 
         [0096]    Movement of the shield assembly in the distal direction (such that shield assembly  110  eventually slides off the distal end of the needle) is prevented by the interaction of arm  79  and flange  72 . Movement of the shield assembly in the proximal direction (to expose needle tip  25 ) is prevented by distal end  20  of needle  10  abutting ball  122  which abuts wall  157  of opening  120 . 
         [0097]    The distance from tether arm  79  to needle tip  25  is set so that when tip  25  is aligned with ball  122 , there is sufficient space for the ball to move beneath cap  100  in opening  120 . The relationship between α (the tangential angle between ball  122  and upper surface  136  of distal end  135  of cap  100 ) and β (the smallest needle bevel angle) is described above, as are the considerations of the support provided by lumen  112  opposite ball  122  to prevent needle  10  from wiggling, and to prevent tip  25  from moving such that it pierces first housing  95 . The relationship between ball and needle gauge size is also as described above. 
         [0098]    As shown in  FIG. 20 , needle hub  45  in the embodiments shown in  FIGS. 15-19  can be constructed out of a rigid plastic member  940 , having barb  945  at its proximal end  947 . Barb  945  mates with extruded polymeric tube  950  as shown in  FIG. 22 . Polymeric tube  950  is coextruded with lower tube  960 , which forms a conduit along which tether  75  runs. Polymeric tubes  950  and  960  are relatively thin and 5 flexible. This, and the fact that they are extruded, makes the device extremely light and simple to manufacture and the amount of materials needed to manufacture it is reduced relative to rigid molded members. In order to provide stiffness and strength, polymeric tube may be reinforced with coextruded metal wires, woven fabric, wire mesh, wire lattice or spiral wires. This is shown in  FIG. 14 . 
         [0099]    The following is a description of the application of the needle shield to a hypodermic syringe (a needle-based device without a catheter threaded onto it). Reference is made to  FIGS. 23-26 . Syringe and needle assembly  5  is made up of syringe body  502  with male luer adapter  506  with which female needle adapter  508  is mated. Needle adapter  508  has a hub  512  into which proximal end  505  of needle  510  is bonded. Needle  510  has a sharp distal end  525 . 
         [0100]    Needle shield assembly  900  is made up of two mating parts—first housing  905  and second housing or cap  910 . First housing  905  has a proximal end  909  and a distal end  907 . Extending between the proximal and distal ends is lumen  913 , which is dimensioned so that first housing  905  can slide axially on needle  10 . Extending from proximal end  909  towards distal end  907  is stepped area  915 . This is an area of reduced diameter which allows coil spring  911  to be placed on first housing  905 . Spring  911  is a compression spring, which exerts a force axially in the proximal and distal directions. Towards distal end  907  of first housing  905 , but still in the stepped area  915 , first housing is provided with an opening  920 , dimensioned to accommodate ball  922 . 
         [0101]    Second housing or cap  910  has a proximal end  930  and a distal end  935 . Proximal end  930  is provided with opening  937  which is dimensioned such that it is slightly larger than the diameter of needle  510 . Thus, second housing  910  can slide axially along the needle from proximal end  505  towards distal end  525 . When first and second housings  905  and  910  are assembled, second housing  910  covers most of first housing  905 , except for the proximal end. Second housing thus covers spring  911 . Second housing  910  is provided with opening  940  which is dimensioned such that part of ball  922  can protrude through it. This makes needle shield assembly  900  very compact. However, second housing  910  can me made slightly larger or provided with a blister to accommodate ball  922 , so that ball  922  is completely covered. 
         [0102]    When needle shield assembly is at needle hub  512 , prior to deployment, part of ball  922  protrudes through opening  940 . Part of ball  922  also lies in lumen  913  of first housing  905  and abuts outer surface  522  of needle  510  (i.e. ball  922  touches outer wall  522  of needle  510 ). Shield assembly  900  can slide from this position along needle  510  in a distal direction with very low friction. Ball  922  is radially constrained by the diameter of opening  940 , which is sized so that ball  922  cannot escape through opening  940  and out of shield  900 . Ball  922  is also radially constrained by needle  510  in the other direction. Spring  911  exerts a force  5  on ball  922  axially, in the distal direction. 
         [0103]    Tether or strap  800  is attached to proximal end  909  of first housing  905 . It is preferably made in the same molding as first housing  905  but need not be. Tether  800  has distal end  802  (attached to proximal end  909  of first housing  905 ) and proximal end  804  which extends back and outwards from shield  900 . At proximal end  804  is handle  806 , which can be grasped by a user. This is molded with strap  800  but can be a separate piece attached to strap  800 . Tether or strap  800  is made of a flexible, semi-rigid material such as nylon. Any material that bends but provides some longitudinal compressive strength will be suitable as long as it allows force to be imparted to shield  900  via tether  800 . 
         [0104]    Needle hub  512  is provided with integrally molded with restraint  514 . Restraint  514  has a track  516  along which tether  800  can slide in a distal direction as needle shield  900  slides distally along needle  510 . Restraint  514  has stop  518  which prevents further travel of tether  800  when handle  806  reaches stop  518 . Restraint  514  has an open channel  520  which allows tether  800  to be placed in track  516  during manufacture but which prevents tether  800  from being easily removed. 
         [0105]    Once needle  510  has been used and is to be shielded, the user simply grasps handle  806  and pushes it so that needle shield  900  slides distally along needle  510 . When needle shield  900  reaches a point where needle tip  525  passes ball  922 , ball  922  is less radially constrained by needle  510  and, urged by spring  911 , it begins to move in opening  920 , distally and radially. Ball  922  thus moves out of opening  940  and radially inwards further into lumen  913  of shield assembly  900 , pivoting about edge  955 , which is a wall of opening  940  in second housing  910 . When needle tip  525  passes ball  922 , needle  510  no longer constrains ball  922 . Spring  911  urges ball  922  along opening  920  so that ball  922  pivots about edge  955 . Ball  922  is constrained from entering lumen  913  of first housing  905  by the dimensions and geometry of opening  920 . Ball  922  thus partially occludes lumen  913 . 
         [0106]    When ball  922  has moved to a point where it partially occludes lumen  913 , handle  806  has reached stop  518 , preventing further pushing of handle  806  and hence tether  800 . Movement of shield assembly  900  in the distal direction (such that shield assembly  900  slides off distal end  525  of the needle) is prevented by the abutment of stop  518  and handle  806 . Movement of the shield assembly in the proximal direction (to expose needle tip  525 ) is prevented by distal end  525  of needle  510  abutting ball  922 . 
         [0107]    The length of tether  800  (to tip  525 ) relative to the length of first housing  905  is set so that when tip  525  is aligned with ball  922 , there is sufficient space for the ball to move at least partially into lumen  913 . Similar considerations described above in the context of a catheter inserter apply when selecting the angle formed between ball  922  and the part of needle shield  900  that is immediately radially outward of ball  922  and which ball  922  abuts when the shield is deployed. Proximal end  909  of first housing  905  is dimensioned to overhang so that tip  525  can never emerge from distal end  907 . 
         [0108]    When shield  900  is deployed, part of ball  922  lies in lumen  913  and part of it lies beneath distal end  935  of second housing  910 , which radially constrains it. If shield assembly  900  is moved proximally, ball  922  will abut needle tip  525  and be forced against the distal and upper inside walls of second housing  910 . Further proximal movement of the shield assembly and hence emergence of needle tip  25  will be prevented. 
         [0109]    Lumen  913  is sized such that needle  510  fits relatively snugly in lumen  913 . Thus, when needle shield  900  is moved proximally into deployment and ball  922  abuts needle tip  525 , needle  510  will not move away from ball  922 . Lumen  913  thus provides support opposite ball  922  to prevent needle  510  from wiggling, and to prevent tip  525  from moving such that it pierces first housing  905 . 
         [0110]    In an alternative embodiment, ball  922  fully enters lumen  913 . Ball  922  has a diameter slightly larger than that of lumen  913 . In this case, lumen  913  is also dimensioned to provide support for needle  910  opposite ball  922 , thus preventing wiggle of the needle and preventing tip  525  from piercing first housing  905 . 
         [0111]    Application of the invention to a winged needle is shown in  FIGS. 27 and 28 . In that embodiment, shield assembly  6110  (of the type described with reference to  FIGS. 9-13 ) is attached to sheath  600 . Sheath  600  has slits  603 , which make it slidable over wings  602  and tube  606 . Distal movement of shield assembly  6110  is prevented by back  604  of slit  603  abutting wings  602 . 
         [0112]    Another winged needle application is shown in  FIGS. 29 and 30 . In that application, needle assembly  7110  (also of the type described with reference to  FIGS. 9-13 ) is provided with wings  702 . Needle hub  45  is squeezed between the finger tips to release it from body tube  704 . A flange on tube  700  abuts a collar at  706  to prevent further proximal movement of needle hub  45 , at which point needle shield assembly is deployed, preventing distal movement of tip  25 . 
         [0113]    The invention is shown in the context of a another winged needle (with or without catheter) in  FIGS. 31 and 32 . In that embodiment, needle hub  845  is attached to first and second wings  802  and  804 . Wings  802  and  804  are arranged about tube  806 . Wings  802  and  804  respectively have protrusions  812 ,  814  and  808 ,  810  which act as hinges allowing some rotation of wings  802  and  804  about tube  806 . Protrusion  808  is attached to or abuts needle assembly  8110  at proximal end  8120  and is provided with a short lumen so that protrusion  808  and hence wing  804  can slide axially along needle  10 . Protrusion  810  also has a lumen that allows it to slide axially along tube  806 . Movement of wing  804  is constrained between protrusions  812  and  814  of wing  802 . 
         [0114]    When the ball has moved into its shielding position as described above, preventing proximal movement of shield assembly  8110 , protrusion  810  of wing  804  abuts protrusion  812  of wing  802 , preventing distal movement of wing  804  and hence of shield assembly  8110 . 
         [0115]    The invention in the context of a Huber needle is shown in  FIGS. 33 and 34 . In that embodiment, needle hub  1045  is generally L-shaped and tether  1075  is generally parallel to needle  1010 , except that it arcs slightly due to gravity. Wing  1004  has an opening  1002 , in which needle shield assembly  10110  (of the type described with reference to  FIGS. 16-19 ) resides prior to deployment, locked in place by ball  10122 . When needle tip  1025  is shielded, ball  10122  allows shield assembly to be removed from opening  1002 . At this point, tether  1075  is fully played out and distal movement of shield assembly  10110  is prevented. 
         [0116]    A blood collection device incorporating the shield shown in  FIGS. 23-26  is shown in  FIG. 35 . Some alternative embodiments are shown in  FIGS. 36-48 .  FIG. 36  shows spring  111  lying on one side of needle  10 , parallel to the needle axis rather than around needle  10 . In  FIG. 37  spring  111  is a torsion spring which provides a twisting force around the axis of needle  10 . This exerts a circumferential force on ball  122 . Opening  120  is configured to allow ball  122  to move circumferentially and towards lumen  93 .  FIG. 38  shows spring  111  placed outside first housing  95 .  FIG. 39  shows a piston  101  interposed between spring  111  and ball  122 . In  FIG. 40  piston  101  is in the form of a cap interposed between spring  111  and ball  122 . In this embodiment spring  111  is not enclosed by cap  100 . 
         [0117]      FIG. 41  shows spring  111  in the form of a leaf spring, integral with cap  100 . Spring  111  may be a separate member from cap  100  or may be formed with cap  100 .  FIG. 42  shows a spring  111  in the form of a thin wave washer threaded over needle  10 . 
         [0118]    While a sphere is the preferred choice for ball  122 , a perfectly spherical object is not essential. In the embodiment of  FIG. 43 , roller  102  is substituted for ball  122 . 
         [0119]    In  FIG. 44 , groove  75  is lined with metal to provide a high pull out force and to minimize the undercut in catheter  52 , thus making it easier to mold catheter hub  52 . In this embodiment, metal liner  750  is an extension of metal wedge  751  which secures catheter tube  86  the catheter hub. Metal liner  750  may of course be a separate ring or partial ring. 
         [0120]    Ball  122  can be enclosed within cap  100  as shown in  FIGS. 45-47 . In that case, ball  122  does not provide a lock with the catheter hub. In the embodiment shown in  FIG. 47 , cap  100  is enclosed by flexible metal or plastic skin  105  that covers opening  150  and allows movement of ball  122  so that it can unlock from catheter hub  52 . This structure can be replaced by a protrusion formed of rigid metal or circumferential bulge, neck down or channel. 
         [0121]    In the embodiment in  FIG. 48 , ball  122  is seated on piston  800  which abuts needle  10  in the non-deployed position. Piston  800  moves with ball  122  as the shield is deployed. The size of piston  800  changes depending on the gauge of the needle. This embodiment thus allows one size of ball to be used with a variety of needle sizes. 
         [0122]    In the embodiment of  FIGS. 49-51 , the shield assembly described above is applied to a Y shaped catheter introducer assembly in which needle  10  is drawn through a septum  6000 . 
         [0123]    Although limited embodiments of the needle shield assemblies, their components, and their applications on different needle devices have been specifically described and illustrated, the descriptions are not intended to limit the scope of the basic invention. Many modifications and variations will be apparent to those skilled in the art. Accordingly, it is to be understood that the needle shield assemblies and their components constructed according to principles of this invention may be embodied other than as specifically described herein. The invention is also defined in the following claims.