Abstract:
A needle shield assembly with a needle having a distal tip and a static feature is provided. The needle shield assembly includes an adapter having an open distal terminus and an open proximal terminus to allow passage of the needle and a needle shield slidably associated with the adapter having an open distal end and an open proximal end where the open proximal end is sufficiently narrow to restrict proximal movement of the needle static feature causing the shield to move in a proximal direction when the needle is pulled proximally after the static feature has established contact with the needle shield proximal end. The assembly includes a canting plate having an unactivated first position and an activated second position that restricts needle movement. The canting plate is activated via a canting plate retention system in communication with the canting plate and responsive to proximal movement of the needle.

Description:
RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application Ser. No. 60/390,499 filed Jun. 20, 2002. 
     This application is related to the following previously filed applications, each of which is incorporated by reference: This application is a continuation-in-part of Ser. No. 10/320,960, filed Dec. 17, 2002, now U.S. Pat. No. 6,652,490, which is a continuation of Ser. No. 09/499,331, filed Feb. 4, 2000, now abandoned, which is a continuation-in-part of Ser. No. 09/312,335, filed May 14, 1999, now U.S. Pat. No. 6,379,333, which is a continuation-in-part of application Ser. No. 09/057,718, filed Apr. 9, 1998, now U.S. Pat. No. 6,004,294. 
     This application is also a continuation-in-part of Ser. No. 09/717,148, filed Nov. 21, 2000, which is a continuation-in-part of Ser. No. 09/590,600 filed Jun. 9, 2000, now abandoned which is a continuation-in-part of Ser. No. 09/312,335, filed May 14, 1999, now U.S. Pat. No. 6,379,333, which is a continuation-in-part of application Ser. No. 09/057,718, filed Apr. 9, 1998, now U.S. Pat. No. 6,004,294. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention relates to a needle shield assembly constructed to safely shield the sharp distal tip of a needle, and restrict distal movement of the needle tip via a tilting or “canting” plate after the tip is shielded. 
     2. Background of the Invention 
     Intravenous (IV) catheters are used for infusing fluid, such as normal saline solution, various medicaments and total parenteral nutrition, into a patient or withdrawing blood from a patient. Peripheral IV catheters tend to be relatively short, and are on the order of about one and one-half inches in length. A common type of IV catheter is an over the needle peripheral IV catheter. As its name implies, an over the needle catheter is mounted over an introducer needle having a sharp distal tip. The catheter and the introducer needle are assembled so that the distal tip of the introducer needle extends beyond the distal tip of the catheter with the bevel of the needle facing up away from the patient&#39;s skin. 
     The catheter and introducer needle assembly are inserted at a shallow angle through the patient&#39;s skin into a peripheral blood vessel (i.e., a smaller blood vessel that is not connected directly to the heart but is one of the branches of the central blood vessels that is directly connected to the heart). In order to verify proper placement of the assembly in the blood vessel, the clinician confirms that there is flashback of blood in the needle and in a flashback chamber located at the proximal end of the needle. Typically, the flashback chamber is formed as part of the needle hub. Once proper placement is confirmed, the clinician applies pressure to the blood vessel by pressing down on the patient&#39;s skin near the distal tip of the introducer needle and the catheter. This finger pressure occludes further blood flow through the introducer needle. The clinician withdraws the introducer needle, leaving the catheter in place, and attaches a fluid-handling device to the catheter hub. Once the introducer needle is withdrawn from the catheter, it is deemed a “blood contaminated sharp” and must be properly handled. 
     In recent years, there has been great concern over the contamination of clinicians with a patient&#39;s blood and a recognition that “blood contaminated sharps” must be immediately disposed. This concern has arisen, in part, to reduce the risks associated with spreading diseases that can be transmitted by the exchange of body fluids from an infected person to another person. Thus, it is desirable to avoid contact with the body fluid of an infected person. Various needle shields have been developed. Generally, such needle shields work for their intended purpose but could be improved. For example, some needle shields are bulky, difficult to use or require special features or techniques to be operative. 
     SUMMARY OF THE INVENTION 
     In accord with one aspect of the invention, an over the needle catheter assembly includes a catheter adapter and a needle. The needle has a diameter and a distal tip, slidingly disposed within the catheter adapter. A needle shield assembly is slidably mounted on the needle. The needle shield assembly has an open distal end and an open proximal end though which the needle passes. A rigid plate, referred to as a “canting plate,” is disposed within the needle shield assembly and has an unactivated first position and an activated second position. In the second position, the canting plate restricts needle movement. Means for retaining the canting plate are provided. The canting plate retention means is in communication with the canting plate and responsive to proximal movement of the needle, whereby, when the needle tip is housed within the needle shield assembly, the canting plate retention means is actuated, causing distal movement of the needle to urge the canting plate from the unactivated first position to the activated second position. 
     In accord with certain implementations of this aspect of the invention, the canting plate retention means comprises a spring, a retention arm, and a retention washer. The spring may be selected from the group consisting of a coil spring, a wave washer, and a leaf spring or the like. The needle shield assembly may have a plurality of canting plates responsive to the canting plate retention means. The canting plate retention means may include a canting plate retention arm and a retention washer attached to the canting plate and having a built-in spring. The retention washer may be housed entirely within the shield. The canting plate retention means may include an elastomeric washer and an alignment arm. The elastomeric washer may have a truncated distal end. The catheter adapter and the shield may be held together by an interlock. A static feature may be provided on the needle, wherein said interlock is released prior to or substantially simultaneous with the static feature on the needle contacting the shield proximal end. The length between the needle tip and the static feature is such that when said static feature contacts the shield proximal end, the needle tip is housed within the shield. The canting plate may contain a hole for passage of the needle and be located distally of the proximal end of the shield. The canting plate may be returned to an unactivated position when the needle is no longer urged in a distal direction. 
     In accord with another aspect of the invention, the over the needle catheter, discussed above, may be used in accord with a method including pulling the needle proximally until the static feature contacts the needle shield&#39;s proximal end, confirming that the needle tip is within the shield, and urging the needle distally to cause the canting plate to lock to prevent further distal movement. 
     In accord with one aspect of the invention, an apparatus is provided for shielding a needle including a housing. A needle shield assembly is movable from an unlocked position within the housing and a locked position outside the housing. The needle shield assembly includes a shield body having a sidewall, a proximal end and a distal end. A canting member is disposed within the shield body for movement from an aligned condition to an off-alignment condition. A spring is operably engaged to the shield body and the canting member, urging the canting member to the off-alignment condition. A retention arm is engaged to the shield body and is displaceable from an engaged position to a disengaged position. When the needle shield assembly is within the housing, the housing displaces the retention arm to the engaged position in which the retention arm engages the canting member and maintains the canting member in the aligned condition. When the needle shield is outside the housing, the retention arm moves to the disengaged position in which the retention arm disengages the canting member, and the canting member is displaced to the off-alignment condition by the spring. 
     Certain implementations of this aspect of the invention provide the canting member is a canting plate. The spring may be a leaf spring integrally formed with the canting member. The shield body, canting plate and spring may be integrally formed. The shield body may include a retention washer disposed at the proximal end of the shield body, and the retention washer defines an opening through which the needle passes. 
     The apparatus discussed above may be used with a needle including a feature having a diameter greater than the body of the needle. The opening in the retention washer is sized to permit the needle body to pass but to prevent the feature from passing therethrough. The shield body may include a retention arm that, when the needle shield assembly is within the housing, is biased radially inward to engage the canting member and, when the needle shield assembly is outside the housing, moves radially outward to disengage the canting member. The shield body may include a ledge, disposed opposite the retention arm, and abutting the canting member. The ledge may be integrally formed with the sidewall. 
     In accord with another aspect of the invention, a needle shield assembly includes a shield body having a sidewall, a proximal end and a distal end. A member, such as an elastomeric washer, is disposed within the shield body and has a central cavity. The cavity is sized to frictionally engage the needle. A canting member is disposed within the shield body and movable between an aligned condition and an off-alignment condition. The member is selectively engaged to the canting member such that, as the needle is moved in a proximal direction with respect to the shield body, the needle displaces the member which, in turn, displaces the canting member to the off-alignment condition. 
     Certain implementations of this aspect of the invention provide that the member is an elastomeric member and the canting member is a canting plate. Means may be provided for retaining the canting member in the aligned condition. An alignment arm is mounted to the shield body and abuts the canting member. The member is an elastomeric washer abutting the canting member and the proximal end of the shield body. The member is attached permanently and directly to the canting member. A ledge may be fixedly attached to the shield body, disposed distal to the canting member and abutting the canting member. An interlocking flange may be mounted at the distal end of the shield body and an adapter release may be slidably disposed within the shield body. The adapter release includes a release pin that engages the interlocking flange when the canting plate is in the aligned condition and biases the interlocking flange into engagement with a catheter adapter. 
     In accord with another aspect of the invention, a catheter assembly is provided including a catheter adapter and a needle having a tip. A feature is attached to the needle at a selected distance from the tip. A needle shield assembly is slidably disposed about the needle. The needle shield assembly includes a sidewall, a proximal end and a distal end. An interlocking flange is mounted at the distal end of the shield body and biased radially outward. An adapter release is slidably disposed within the shield body for movement from a distal position to a proximal position. The adapter release includes a release pin that engages the interlocking flange when the adapter release is in the distal position. A canting plate is secured within the housing and includes an opening defined by an edge. The needle is slidably disposed within the opening. The canting plate is movable from an aligned position, in which the needle passes without interference from the edge, to an off alignment position, in which the edge binds the needle. A friction member is moveably disposed within the housing and frictionally engaged to the needle. When the adapter release is in the distal position, it biases the interlocking flange into engagement with the catheter adapter. Conversely, when the adapter release is in the proximal position, the interlocking flange is released from engagement with the catheter adapter. When the needle is displaced proximally with respect to the needle shield assembly, the friction member is displaced, causing the canting plate to move to the off alignment position. 
     In accord with another aspect of the invention, a needle shield assembly is provided for a needle having a tip and a needle axis. Specifically, a housing has a proximal end and a distal end. A friction member is disposed within the housing and is frictionally engaged to the needle. A canting member is disposed within the housing and includes an edge that defines a member opening. The canting member is displaceable from a first position, in which the member opening is aligned with the needle axis, to a second position, in which the edge lockingly engages the needle. The friction member is operably engaged to the canting member such that movement of the friction member displaces the canting member to the second position. 
     Certain implementations of this aspect of the invention provide that a retention washer is positioned at the proximal end of the housing and a hole having a selected hole size is disposed in the retention washer. 
     In accord with another aspect of the invention, a method is provided for shielding a needle. A canting member is in operational engagement with a needle. The canting member is displaceable with respect to the needle, from a first position in which the canting member does not engage the needle, to a second position in which the canting member binds the needle. An actuating member is in frictional engagement with the needle. The needle is displaced with respect to the canting member such that the actuating member is displaced. The canting member is moved to the second position by the actuating member as it is displaced. Certain implementations of this aspect of the invention provide that the friction between the actuating member and the needle causes the actuating member to be displaced with the needle, or that the actuating member acts directly on the canting member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiments are illustrated in the drawings in which like reference numerals refer to like elements and in which: 
         FIG. 1  is a perspective view of an over the needle catheter assembly for use in accord with an aspect of the invention; 
         FIG. 2A  is a cross-sectional view of one embodiment of the invention shown in an unactuated condition, where the needle has been partly withdrawn through the catheter but the sharp distal tip of the introducer needle has yet to be withdrawn into the needle shield; 
         FIG. 2B  is a cross-sectional view of the embodiment of the needle shield in  FIG. 2A  in an actuated condition where the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield assembly; 
         FIG. 3A  is a perspective view of the needle shield as depicted in  FIG. 2A  in partial cross section; 
         FIG. 3B  is a perspective view of the needle shield as depicted in  FIG. 2B  in partial cross section; 
         FIG. 4A  is a cross-sectional view of another embodiment of the invention, with the canting plate and spring integral to the shield, shown in an unactuated condition, where the needle has been partly withdrawn through the catheter but the sharp distal tip of the introducer needle has yet to be withdrawn into the needle shield; 
         FIG. 4B  is a cross-sectional view of the embodiment in  FIG. 4A  in an actuated condition where the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield assembly; 
         FIG. 5A  is a cross-sectional perspective view of the needle shield of  FIG. 4A ; 
         FIG. 5B  is a cross-sectional perspective view of the needle shield assembly depicted in  FIG. 4B ; 
         FIG. 6A  is a cross-sectional view of another embodiment of the invention, with the canting plate, retention washer and spring integrally formed, shown in an unactuated condition, where the needle has been partly withdrawn through the catheter but the sharp distal tip of the introducer needle has yet to be withdrawn into the needle shield; 
         FIG. 6B  is a cross-sectional view of the embodiment in  FIG. 6A  in an actuated condition where the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield assembly; 
         FIG. 7A  is a cross-sectional perspective view of the needle shield of  FIG. 6A ; 
         FIG. 7B  is a perspective view of the needle shield assembly depicted in  FIG. 6B  in partial cross section; 
         FIG. 8A  is a cross-sectional view of another embodiment of the invention in which the canting plate is actuated by friction on the needle, shown in an unactuated condition, where the needle has been partly withdrawn through the catheter but the sharp distal tip of the introducer needle has yet to be withdrawn into the needle shield; 
         FIG. 8B  is a cross-sectional view of the embodiment in  FIG. 8A  where the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield assembly; 
         FIG. 8C  is a cross-sectional view of the embodiment in  FIG. 8A  where the sharp distal tip of the introducer needle is being urged distally and the canting plate is tilted to an actuated condition; 
         FIG. 9A  is a perspective view of the needle shield assembly depicted in  FIG. 8A  in partial cross section; 
         FIG. 9B  is a perspective view of the needle shield assembly depicted in  FIG. 8B  in partial cross section; 
         FIG. 9C  is a perspective view of the needle shield assembly depicted in  FIG. 8C  in partial cross section; 
         FIG. 10A  is a cross-sectional view of another embodiment of the invention in which the canting plate is actuated by friction on the needle and including an interlock, shown in an unactuated condition, where the needle has been partly withdrawn through the catheter but the sharp distal tip of the introducer needle has yet to be withdrawn into the needle shield; 
         FIG. 10B  is a cross-sectional view of the embodiment in  FIG. 10A  where the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield assembly and the catheter adapter has been partially removed; 
         FIG. 10C  is a cross sectional view of the embodiment of  FIG. 10A  where the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield assembly and the catheter adapter has been completely removed; 
         FIG. 11A  is a cross-sectional view of another embodiment of the invention in which the canting plate is actuated by friction on the needle, shown in an unactuated condition, where the needle has been partly withdrawn through the catheter but the sharp distal tip of the introducer needle has yet to be withdrawn into the shield; 
         FIG. 11B  is a cross-sectional view of the embodiment in  FIG. 11A  where the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield; 
         FIG. 11C  is a cross-sectional view of the embodiment of  FIG. 11A  where the sharp distal tip of the introducer needle is being urged distally and the canting plate is tilted to an actuated condition; 
         FIG. 12A  is a perspective view of a needle shield assembly depicted in  FIG. 11A  in partial cross-section; 
         FIG. 12B  is a perspective view of the needle shield assembly depicted in  FIG. 11B  in partial cross-section; 
         FIG. 12C  is a perspective view of the needle shield assembly depicted in  FIG. 11C  in partial cross-section; 
         FIG. 13A  is a cross-sectional view of another embodiment of the invention in which the canting plate is actuated by friction on the needle shown in an unactuated condition where the needle has been partly withdrawn through the catheter but the sharp distal tip of the introducer needle has yet to be withdrawn into the needle shield; 
         FIG. 13B  is a cross-sectional view of the embodiment in  FIG. 13A  where the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield assembly; 
         FIG. 13C  is a cross-sectional view of the embodiment in  FIG. 13A  where the sharp distal tip of the introducer needle is being urged distally and the canting plate is tilted in an actuated condition; 
         FIG. 14A  is a cross-sectional view of another embodiment of the invention in which the canting plate is actuated by friction on the needle, shown in an unactuated condition, where the needle has been partly withdrawn through the catheter but the sharp distal tip of the introducer needle has yet to be withdrawn into the shield; 
         FIG. 14B  is a cross-sectional view of the embodiment in  FIG. 14A  where the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield assembly; 
         FIG. 14C  is a cross-sectional view of the embodiment in  FIG. 14A  where the sharp distal tip of the introducer needle is being urged distally and the canting plate is tilted to an actuated condition; 
         FIG. 15A  is a cross-sectional view of another embodiment of the invention in which the canting plate is actuated by friction on the needle, and including a tether to connect a needle hub to the needle shield assembly, shown in an unactuated condition, where the needle has been partly withdrawn through the catheter but the sharp distal tip of the introducer needle has yet to be withdrawn completely into the needle shield; 
         FIG. 15B  is a cross-sectional view of the embodiment of  FIG. 15A  in which the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield assembly; 
         FIG. 15C  is a cross-sectional view of the embodiment of  FIG. 15B  in which the sharp distal tip of the introducer needle is being urged distally and the canting plate is tilted to an actuated condition; 
         FIG. 16A  is a perspective view of another embodiment of the invention in which the canting plate is actuated by friction on the needle, shown in an unactuated condition; 
         FIG. 16B  is a cross-sectional view of the embodiment in  FIG. 17A  where the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield assembly; 
         FIG. 16C  is a cross-sectional view of the embodiment of  FIG. 17A  in which the sharp distal tip of the introducer needle has been withdrawn proximally into the needle shield assembly and the canting plate has been urged to engage the needle to prevent further proximal movement; and 
         FIG. 16D  is a cross-sectional view of the embodiment of  FIG. 17A  in which the sharp distal tip of the introducer needle is being urged distally and the canting plate is tilted to an actuated condition. 
         FIG. 17A  is a perspective view in partial cross-section of another embodiment of the invention in which the canting plate is actuated by an angled guide on a clip, shown in an unactuated position. 
         FIG. 17B  is a rear perspective view of the embodiments depicted in  FIG. 17A ; 
         FIG. 17C  is a front cross-sectional view of the embodiment in  FIG. 17A  shown in an actuated condition; 
         FIG. 17D  is a rear perspective view of the embodiment depicted in  FIG. 17A  in an actuated condition; 
         FIG. 18A  is a front perspective view of another embodiment of the invention in which the canting plate is actuated by an integral spring member shown in an unactuated condition; 
         FIG. 18B  is a side cross-sectional view of the embodiment shown in  FIG. 18A  in an unactuated condition; 
         FIG. 18C  is a front perspective view of the embodiment shown in  FIG. 18A  shown in an actuated condition; 
         FIG. 18D  is a cut-away side view of the embodiment shown in  FIG. 18A  in an actuated condition; 
         FIG. 19A  is a front perspective view of another embodiment of the invention in which the needle shield assembly is engaged with a catheter hub until the needle tip is withdrawn into the needle shield assembly, shown in an unactuated condition; 
         FIG. 19B  is a front perspective view of the embodiment shown in  FIG. 19A  in an actuated condition; 
         FIG. 20A  is a front perspective view in partial cut-away of another embodiment of the invention in which the canting plate is integrally formed with a retention washer and a tip trigger, shown in an unactuated condition; and 
         FIG. 20B  is a front perspective view of the embodiment shown in  FIG. 20A  in an actuated condition. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the term “proximal” refers to a location on the catheter and needle shield assembly of this invention closest to the clinician using the device and farthest from the patient in connection with whom the device is used when the device is used in its normal operation. Conversely, the term “distal” refers to a location on the catheter and needle shield assembly of this invention farthest from the clinician using the device and closest to the patient in connection with whom the device is used when the device is used in its normal operation. 
     A catheter assembly  100  may include a catheter adapter  8  having a catheter  108  attached at its distal end. Wings  130  may be provided on the adapter  8 . Before use and during insertion (as depicted in  FIG. 1 ), a needle  30  is disposed within the catheter such that the tip or distal point  32  that extends out of the distal end of the catheter. The proximal end of the needle is attached to a needle hub  110 . A finger grip  120  may be incorporated into the needle hub  110 . Such a structure, in conjunction with the wings  130 , permits the caregiver to employ various technique for catheter insertion, as discussed in U.S. patent application Ser. No. 09/865,915, filed May 25, 2001, incorporated herein by reference. 
     A needle shield assembly  5  is disposed about the needle, between the needle hub  110  and the catheter adapter  8 , as shown in  FIG. 1 . Alternatively, as shown in, inter alia,  FIGS. 2A and 2B , the needle shield assembly  5  may be disposed completely within the catheter adapter and still practice aspects of the invention. It will be appreciated that embodiments of the invention may be implemented with either a needle shield assembly within the catheter adapter, or with a needle shield assembly disposed between the needle hub and the catheter adapter, or at other locations along the needle. Further, implementations of the invention may be employed with needles and sharps used in other devices, such as syringes and blood collection sets. 
     As discussed more fully below, implementations of the needle shield assembly  5  are designed such that, after insertion of the over the needle catheter  108  into the patient, when the needle  30  is withdrawn, the tip  32  of the needle enters the needle shield assembly. At that point, the needle shield assembly locks onto the needle tip, preventing further displacement of the shield assembly along the needle. As such, the needle shield assembly cannot simply be slipped off the tip of the needle and removed. Additionally, when the needle shield assembly locks onto the needle, it prevents reemergence of the tip from the distal end of the needle shield assembly. 
     To achieve this locking between the needle shield assembly  5  and the needle  30 , the needle shield assembly includes a tilting member or canting plate  40  whose movement is constrained with respect to the needle shield assembly. Preferably, the tilting member is a rigid plate contained within the needle shield assembly. A hole  42  in the canting plate is defined by an edge  43 . The needle passes through the hole  42  in the canting plate. In the unlocked condition (seen, e.g., in  FIG. 2A ), the canting plate is retained in an aligned position with the needle by a retention system or canting plate retention means such that the needle passes through the canting plate without substantial interference. As discussed more fully below, the canting plate retention means may include combinations of fixed structures and movable elements, springs and/or friction members that cooperate to control the position of the canting plate. As the tip  32  of the needle is withdrawn into the needle shield assembly, the canting plate retention means is triggered, causing the canting plate to come “off alignment” or be “actuated.” The canting plate is tilted such that it binds against the exterior of the needle, preventing relative movement of the needle to the canting plate. Since the canting plate is also constrained with respect to the needle shield assembly, the needle and its tip are also constrained with respect to the needle shield assembly—thereby locking the needle tip within the needle shield assembly. A feature  35  may be provided on the needle to further prevent the needle shield assembly from slipping off the needle tip. A tether  400  may also be provided to prevent the needle shield assembly from slipping off the needle tip. As discussed below, the feature and the tether can also serve to withdraw the needle shield assembly from the catheter adapter  8  as the needle hub  110  is moved proximally. Once locked in place, the shielded needle may be disposed of. 
     Retention Washer with Integral Spring 
     Referring now to  FIGS. 2A-3B , one implementation of the invention is shown.  FIGS. 2A and 3A  depict the needle  30  partially withdrawn into the needle shield assembly  5 , but before the needle shield assembly is actuated, or locked, onto the needle.  FIGS. 2B and 3B  depict the needle shield assembly after actuation, locked onto the needle. In the unlocked or unactuated condition ( FIGS. 2A and 3A ), the needle shield assembly  5  is positioned within the catheter adapter (or simply “adapter”)  8 . For the sake of clarity, the catheter  108  has been omitted. It will be appreciated that the catheter is secured to the distal end of the catheter adapter and the needle extends coaxially through the catheter before use, as seen in  FIG. 1 . The adapter  8  includes an internal chamber forming a shield housing  6  in which the needle shield assembly  5  sits. The shield housing may also be a structure distinct from the adapter. The needle shield assembly has a shield body  10  that includes a sidewall  9  and a distal end  11  and proximal end  12 . Typically, the sidewall is cylindrical to fit snugly within the shield housing. The sidewall may have other shapes to achieve a fit within the catheter adapter. The shield ends  11 ,  12  include a distal opening  13  at the distal end and a proximal opening  14  at the proximal end. 
     The needle  30  has a distal needle point or tip  32  and an axis  99  and is disposed within the adapter  8 , extending through the shield assembly  5  before use. Specifically, the needle passes through the shield openings  13 ,  14 , and extends out of the distal end  7  of adapter  8 , through an over-the-needle catheter  108  (not shown in  FIGS. 2A-3B  for the sake of clarity). The needle diameter is sized to pass through the distal opening  13  and the proximal opening  14  of the shield body  10  without interference. 
     In accord with certain implementations of the invention, a static feature  35  is also provided on the needle  30  at a selected distance from the tip  32 . The static feature  35  is designed such that it is not capable of passage through the proximal opening  14  of shield body  10 , such as disclosed in U.S. Pat. Nos. 5,558,651 and 5,215,528, both incorporated herein by reference. The static feature could be an increased diameter portion on the needle  30  (that is, an enlarged dimension, such as formed by a crimp, collar, enlarged diameter sleeve or ferrule), or a roughened surface that locks onto proximal end  12  of the needle shield assembly  5 . Other structures can be employed to restrict movement of the needle tip out of the proximal end of the shield (such as a tether, discussed below) and still practice aspects of the invention. 
     The needle shield assembly  5  contains a shielding mechanism including a canting plate  40  to restrict axial movement of the needle  30  within the shield body  10 . The canting plate includes a hole  42  defined by an edge  43  through which the needle passes. The proximal end  12  of the needle shield assembly forms a retention washer  15 . The retention washer is attached at one end (the top as seen in  FIG. 2A ) to the sidewall  9 . A spring  45  is attached at the other end of the retention washer. The spring engages canting plate, urging it to an off alignment position (that is, the actuated or locked position), as shown in  FIGS. 2B and 3B . As shown, the retention washer and spring are integrally formed. It will be appreciated that these pieces could be separately formed and attached such as by welding or the like. 
     The needle shield assembly  5  also includes a retention arm  16 . Preferably, the retention arm is a leaf spring, integrally formed with the sidewall  9  and including a lip  127  at its proximal end. Of course, other structures could be employed and practice aspects of the invention. The retention arm is biased radially outward from the needle shield assembly, as seen in  FIG. 2B . When the needle shield assembly is disposed in the shield housing  6 , the shield housing forces the retention arm radially inward, as seen in  FIG. 2A . As discussed below, the retention arm helps maintain the canting plate  40  in a needle aligned position (that is, the unactuated or unlocked position) while the needle shield assembly is in the shield housing. 
     The needle shield assembly  5  includes a ledge  27  formed in the sidewall  9 , remote from the retention arm  16 . As shown, the ledge is formed by deforming a portion of the sidewall such that it projects radially inwardly. It will be appreciated that the ledge could be formed in other manners (such as by adhering a distinct ledge structure to the inside of the side wall, or by crimping or otherwise creating a bulge in the sidewall). Importantly, the ledge forms a stop that prevents a portion of the canting plate from moving with respect to the needle shield assembly. 
     The operation of the needle shield assembly  5  of  FIGS. 2A-3B  will now be discussed. Referring to  FIG. 2A , in the aligned or unlocked condition, the canting plate  40  is held in place by a retention system, specifically by the cooperation of the spring  45 , the lip  127  of the retention arm  16  and the ledge  27 . The spring urges the top of the canting plate in the distal direction (to the right in  FIG. 2A ). When the needle shield assembly is positioned in the shield housing  6  of the catheter adapter  8 , the canting plate is prevented from rotating or displacing by the lip of the retention arm, which engages the top of the canting plate, and the ledge, which engages the bottom of the canting plate. The canting plate thus is maintained in the aligned condition and the needle may pass freely through the hole  42  in the canting plate without substantially engaging the edge  43 . 
     After insertion into a patient&#39;s vein, the needle  30  is withdrawn through the catheter  108  and the catheter adapter  8 . The feature  35  on the needle engages the proximal end  12  of the needle shield assembly  5 . As shown in  FIGS. 2B and 3B , the feature  35  on the needle does not fit through the hole  14  in the retention washer  15 . Consequently, as the caregiver pulls the needle through the catheter adapter  8 , the entire needle shield assembly  5  is pulled out of the shield housing  6 . Upon removal of the needle shield assembly, the retention arm  16  succumbs to its natural bias, moving radially outward such that the lip  127  disengages the top of the canting plate  40 . Once disengaged, the canting plate is free to rotate under the urging of the spring  45 . As the canting plate rotates, edge  43  of the hole  42  binds onto the exterior surface of the needle  30 . The canting plate is held in this locked condition by the cooperation of the needle, the ledge  127  and the spring  45 . Should the needle be pushed distally in an effort to cause the needle tip to reemerge from the needle shield assembly, the friction on the needle (urging the canting plate distally) and the ledge (preventing movement of the bottom of the canting plate) will cause the canting plate to tilt more severely with respect to the needle, increasing the binding force between the canting plate and the needle, thereby resisting such movement. It will also be appreciated that the feature  35  may be sized so that it does not fit through the hole  42  in the canting plate when the canting plate is off alignment. This will provide further resistance to re-emergence of the needle tip. 
     As readily seen in  FIG. 3A , the canting plate  40  may be a rigid disk with a hole  42  through the middle of it. As shown, the canting plate  40  is substantially circular in shape but could be any of various other shapes including square, rectangular, triangular, oval, symmetrical, asymmetrical, etc. The hole  42  in the center of the canting plate  40  is preferably substantially the same shape as the needle  30  that goes through it. However, other hole shapes could be employed, such as rectangular, triangular or oval shape or any of a variety of other shapes, and still practice aspects of the invention. Further, the canting plate need not be flat. It can be curved or stepped or otherwise shaped for any given application. 
     The hole  42  in the canting plate  40  is sized to achieve adequate binding force on the needle  30  in view of the geometry of the needle and the geometry of the canting plate. Specifically, the hole should be at least larger than the largest diameter of the feature  35  (when the feature is an enlarged portion of the needle) and, in certain implementations, may increase to be around 100% larger than the diameter of the static feature  35  on the needle  30 . In certain other applications, it is preferred that the hole  42  is sized between just larger than the largest diameter of the static feature  35  on the needle  30  to a hole  42  about 10-30% larger than the largest diameter of the static feature  35  on the needle  30 . In yet other implementations, it is desirable that the hole be sized, in view of the geometry of the needle shield assembly, such that it engages the needle when the canting plate is tilted between 0° and 45° from perpendicular to the axis  99 . It will be appreciated that the canting angle may be selected based on the geometry and materials of the canting plate, the needle shield assembly and the needle and the desired binding force. 
     When the needle shield assembly  5  is in the unlocked condition (and the canting plate is therefore aligned with the needle), the hole  42  in the canting plate  40  is aligned concentrically to the perimeter circular shape  46  of the body of the canting plate  40 . The plate  40  could also be designed to have an eccentric center hole  42  or a hole in any location on the canting plate  40  to achieve desirable binding forces. Further, the hole  42  may be positioned at the exterior or outer edge  46  of the canting plate such that it breaks the outer edge  46 . Such a structure will create a “slotted” style of canting plate  40  in accord with certain implementations of the invention. Such may be particularly desirable to permit side loading of the needle into the plate or for use with a guide-wire. 
     The plate  40  has a thickness suitable for use in providing edges  43  to bind down on the needle surface  31  when the plate  40  is canted or off alignment. This thickness  43 , however, may vary depending on other parameters, such as the materials used, the specific geometry of the other parts of the needle shield assembly and the binding force desired. 
     The canting plate  40  could be entirely housed within the shield body  10  or could be partially within and partially without the shield body  10 . A single canting plate  40  or a plurality of canting plates, could be used. In the case of a plurality of canting plates, they could be disposed immediately adjacent to each other, separated by a gap between them, or a combination of both. 
     Canting Plate and Spring Integral to the Shield 
     Turning to the implementation of the invention shown in  FIGS. 4A-5B , the operation of the structure is similar to that depicted in  FIGS. 2A-3B . In this implementation, however, the canting plate or member  40  and the retention washer  15  are integrally formed from the same piece of material as the shield body  10  of the needle shield assembly  5 . The canting plate is preferably made of stainless steel, or like material. The material that connects the canting plate  40  to the retention washer  15  serves as the spring  45 , urging the canting plate into an off alignment condition. Again, during and after actuation, proximal motion of the needle  30  with respect to the needle shield assembly  5  is halted by the interference between the static feature  35  on the needle  30  and the retention washer  15 . After actuation, distal motion of the needle  30  with respect to the needle shield assembly  5  is halted by the engagement of the canting plate  40  to the needle, as discussed above. It will be appreciated that no ledge  27  is required because the spring  45 , and its connection with the retention washer  15 , restrain the bottom edge of the canting plate from moving with respect to the needle shield assembly. Further, a tether could be employed instead of feature  35  to limit the relative movement of the needle hub and the catheter adapter. 
     Canting Plate, Spring and Retention Washer Integral to Each Other 
     Turning to the implementation of the invention shown in  FIGS. 6A-7B , the canting plate  40 , the spring  45  and the retention washer  15  are integral to each other, but separate from the proximal end  12  of the needle shield assembly  5 . The retention washer is attached to the shield body  10  at the proximal end such as by welding, gluing or the like. As depicted, the retention washer is attached on the inner surface of the proximal end of the shield body, but it will be appreciated that the retention washer may be attached at the exterior surface as well. The operation of this implementation is otherwise similar to the prior implementations. 
     Canting Plate with Friction Member 
     Referring to  FIGS. 8A-C  and  9 A-C, this implementation of the invention employs a member  28 , frictionally engaged to the needle  30 , to retain the canting plate  40  in the aligned condition and to move the canting plate to an off-alignment condition when the needle is moved distally with respect to the needle shield assembly  5 . Specifically, the needle shield assembly  5  includes a canting plate  40  and a friction member  28 , such as an elastomeric washer. Other structures could be employed that frictionally engage the needle and contact the canting plate and still practice aspects of the invention. The elastomeric washer is preferably designed to fit slidably within the shield body  10 . The elastomeric washer  28  has a central cavity  29  extending from the proximal end  36  to the distal end  37 . The needle  30  passes through the cavity  29  with the washer  28  engaged in a frictional fit on the needle  30 . As the needle  30  moves distally and proximally through the elastomeric washer  28 , the friction between them causes the elastomeric washer  28  to want to move in concert with the needle  30 . 
     The shield body  10  of the needle shield assembly  5  includes a proximal portion  12  defining a retention washer  15 . The shield body has a distal opening  13  and the retention washer has a proximal opening  14 . The proximal opening  14  is designed to be just larger than the diameter of the shaft of the needle  30 , but not large enough to permit the static feature  35  on the needle  30  to pass through. The retention washer  15  also serves as a backstop for the elastomeric washer  28 , securing it within the shield body behind the canting plate  40 . As the elastomeric washer  28  is being dragged proximally by the needle  30 , it will eventually bottom out on the retention washer  15  and will not be allowed further movement relative to the needle shield assembly see  FIG. 8B ). 
     The canting plate  40  is positioned distal of the elastomeric washer  28  and is contained axially by the needle  30 . Protruding inwardly from the shield body  10  is an alignment arm  19 . The alignment arm  19  defines a positive stop restricting the canting plate  40  from moving in a distal direction at that point. The opposing internal surface of the sidewall  9  of shield body  10  is smooth and offers no resistance to the potential distal motion of the canting plate  40 . Hence the alignment arm  19  defines a point at which the canting plate  40  will rotate. As with other implementations of the invention, when the canting plate is rotated far enough it will begin to bind on the needle shaft  30  in a manner similar to that previously described. In this instance, the alignment arm  19  and elastomeric washer  28  therefore serve as the canting plate retention means or retention system. 
     The elastomeric washer  28 , in cooperation with the alignment arm  19 , induces the tilt or actuation of the canting plate  40 . Since the elastomeric washer  28  is frictionally fit to the needle shaft  30 , when the needle shaft  30  is driven distally with respect to the needle shield assembly  5 , the elastomeric washer  28  is dragged with it. As shown in  FIG. 8C , the elastomeric washer  28  will bear on the canting plate  40  urging it distally as well. Since the canting plate is restrained only on one side (by retention arm  19 ), it will tilt and bind on the needle  30 . A cavity  128  is formed at the distal end of the washer  128  to deliver force from the washer to the periphery of the canting plate, encouraging the tilting. 
     The elastomeric washer  28  could be a variety of lengths or shapes and still practice aspects of the invention. As shown in  FIGS. 8A-C  through  9 A-C, the washer has an hourglass shape. The washer could also be a simple flat disc, donut-shaped ring or the like. The particular shape of the washer can be selected by one skilled in the art based on the particular application. While the washer depicted in  FIG. 8A  is not attached to the canting plate  40 , it will be appreciated that the washer could be attached to the canting plate and still function. 
     The cavity  48  created between the retention washer  15  and the alignment arm  19  can be any length suitable for permitting the elastomeric washer  28  to reside within the shield body  10 . The inner diameter of the elastomeric washer  28  (that is, the surface which is in contact with the needle shaft  30 ) can be smooth or textured. It can also have an array of fins or ribs or any of an assortment of features designed to regulate the friction created against the needle  30 . The elastomeric washer  28  can be cylindrical in nature and in contact with the entire surface of the canting plate  40 . The washer  28  could be truncated on its distal end  37  and aligned specifically to have its most distal portion in contact against the canting plate  40  in a position directly opposite of the alignment arm  19  to facilitate a more undiluted force against the canting plate  40  during distal motion of the needle  30 . 
     In use, the needle tip  32  of the catheter assembly  100  is inserted into the patient&#39;s vein, positioning the catheter in the vein as well. The needle  30  is then withdrawn through the catheter  108 . The needle exerts a friction force on the elastomeric washer  28 , urging it proximally as the needle is drawn through the needle shield assembly  5 . As shown in  FIGS. 8A-C , the elastomeric washer abuts the proximal end  12  of the needle shield assembly, stopping the friction member as the needle slides through the central cavity  29 . When the feature  35  on the needle contacts the proximal end  12  of the needle shield assembly (for example, the retention washer  15 ), the feature engages the proximal end, preventing further proximal movement of the needle with respect to the needle shield assembly. As the needle  30  is withdrawn further through the catheter adapter  8 , the needle shield assembly  5  is pulled out of the shield housing  6 , as shown in  FIG. 8B  (referred to as “bottoming out”). 
     As the needle  30  is displaced distally with respect to the needle shield assembly  5 , the friction member  28  is urged by friction with the needle  30  in the distal direction. As the friction member engages the canting plate  40 , the canting plate is also urged distally. The alignment arm  19 , which abuts a portion of the canting plate, restrains that portion, causing the canting plate to tilt to an off alignment, or actuated, condition, as seen in  FIG. 8C . As depicted in  FIGS. 8C and 9C , the feature  35  engages the friction member, causing it to move distally and engage the canting plate. As seen in  FIGS. 11C and 12C , the friction member can be more tightly fit on the needle such that it moves with the needle whether the feature engages the friction member or not. In either case, when the canting plate  40  is tilted, the edge  43  of the hole  42  in the canting plate then binds on the exterior of the needle, preventing further displacement of the needle  30  with respect to the canting plate  40  (and thus the needle shield assembly  5 ). The shield body  10  of the needle shield assembly is long enough to ensure that the tip  32  of the needle  30  does not reemerge from the distal end  11  of the needle shield assembly when the canting plate is actuated. 
     Canting Plate with Rubber Washer and Interlock 
     A further implementation of an aspect of the instant invention is illustrated in  FIGS. 10A-B . An interlock  50  is included to lock the catheter adapter  8  to the shield body  10  until the needle  30  is in a shielded position. The static feature  35  on the needle is employed to activate an adapter release  55 , thereby disengaging the needle shield assembly  5  from the catheter adapter. The canting plate  40  is maintained in the aligned position by the elastomeric washer  28 , the ledge  27  and an alignment arm  227 . The ledge is fixedly attached to the needle shield assembly  5 . The alignment arm may be in the form of a leaf spring attached to the adapter release  55 . 
     As shown in  FIG. 10B , the static feature  35  on the needle  30 , prior to bottoming out on the proximal end  12  of the shield body or the retention washer  15 , engages the proximal wall  155  of a release pin  56 , dragging it from a distal position  57  to a proximal position  58  (compare  FIGS. 10A and 10B ). The needle shield assembly  5  includes locking flanges  158  in the form of leaf springs attached near the distal end of the needle shield assembly and extending proximally. In their original, undeformed condition, the flanges extend relatively straight (that is, parallel to the axis of the needle shield assembly  5 ) ( FIG. 10C ). When assembled, the locking flanges  158  engage the collar  180  of the adapter  8 , preventing the collar (and thus the adapter) from coming out of the needle shield assembly. See  FIG. 10A . When it is in the distal position  57  shown in  FIG. 10A , the release pin  56  prevents the locking flanges  158  from displacing radially inward. As the release pin is moved to the proximal position  58 , it disengages the flanges  158  such that they are free to flex radially outwardly. Thus, as the catheter adapter  8  is displaced distally with respect to the needle shield assembly, the collar forces the locking flanges radially outwardly, as seen in  FIG. 10B , thereby allowing the collar to slide passed the locking flanges. Consequently, the needle shield assembly  5  may slide off the adapter  8 . As depicted in the drawings, the distal opening  13  of the needle shield assembly  5  is open, even after the needle tip  32  is shielded. It will be appreciated that the length of the needle shield clips or other such mechanisms further may be employed to create a transverse barrier to further prevent reemergence. Further, static feature  35  is employed to resist slipping the needle shield assembly  5  off the tip  32  of the needle  30 . It will be appreciated that other structures, such as a tether, may be employed to prevent such removal. 
     In use, the needle tip  32  of the catheter assembly  100  is inserted into the patient&#39;s vein, positioning the catheter  108  in the vein as well. The needle  30  is withdrawn through the catheter  108  and the catheter adapter  8 . The needle exerts a friction force on the washer  28 . The washer is retained in position by the proximal wall  155  of the adapter release  55 . When the feature  35  on the needle engages the proximal wall, it cannot fit through the opening in the wall, and pulls the adapter release proximally with respect to the shield body  10 . As the adapter release moves proximally, the alignment arm  227  deflects over the canting plate  40 . The alignment arm has an angled shape such that, when it is moved distally, it then tilts the canting plate to an off alignment condition. The adapter release continues to move within the shield body until the proximal wall  155  contacts the proximal end  12  of the shield body. At that point, further distal movement of the needle with respect to the needle shield assembly is prevented (see  FIG. 10B ). 
     As the adapter release  55  is moved from its distal position  57  to its proximal position  58 , the release pin  56  is withdrawn from engagement with the locking flange  158 . The locking flange is then free to displace radially outwardly as the collar  180  forces its way out of the needle shield assembly. As such, the needle shield assembly  5  can be separated from the adapter  8 . 
     As the needle  30  is urged distally with respect to the needle shield assembly  5 , friction between washer  28  and the needle urges the washer distally as well. The washer engages the canting plate  40 , urging it distally. The canting plate is restrained at one edge by the ledge  27 . Consequently, as the needle is moved distally, the canting plate is tilted more, binding more firmly on the needle and preventing further movement of the needle with respect to the needle shield assembly  5 . 
     Canting Plate with Spring Arm Retention 
     Referring to  FIGS. 11A-C  and  12 A-C, this implementation of the invention is similar in operation to that depicted in  FIGS. 8A-C  and  9 A-C. However, in this implementation, a spring arm  427  is compressed radially inward before actuation to assist in maintaining the canting plate  40  in alignment before use. See  FIG. 11A . The canting plate  40  is maintained in alignment before actuation by the cooperation of elastomeric washer  28  with retention arm  16  and ledge  27 . Before the needle shield assembly  5  is actuated, the needle  30  can be moved proximally and distally within the assembly. In use, the needle is withdrawn until the feature  35  contacts the retention washer  15 . Further movement of the needle causes the needle shield assembly  5  to pull out of the shield housing  6  in the adapter  8 . See  FIG. 11C . At that point, the spring arm  427  moves radially outward to an unstressed condition. The ledge  27  therefore disengages the bottom edge of the canting plate  40 , allowing it to rotate. As the needle is urged distally with respect to the needle shield assembly  5 , it acts on the washer  28 , urging it distally as well. The washer engages the canting plate, in turn, urging it distally. The top edge of the canting plate is prevented from moving by retention arm  16 . Consequently, the canting plate is rotated onto and binds onto the needle  30 , preventing further proximal movement. See  FIG. 11C . 
     Single Bi-Directional Canting Plate 
       FIGS. 13A through 13C  depict another implementation of an aspect of the invention including a single canting plate  40  which binds onto the needle  30 , thereby preventing movement of the needle with respect to the needle shield assembly  5  in both the proximal and distal directions. The needle shield assembly includes a proximal retention arm  216  and a distal retention arm  116  integrally formed with the shield body  10 . A proximal ledge  227  and a distal ledge  327  are mounted on spring arm  427 . As depicted in  FIG. 13A , the shield housing  6  of the adapter  8  compresses or flexes the spring arm radially inwardly, and into engagement with the canting plate  40 . An elastomeric washer  228  is attached to the canting plate and is frictionally engaged to the needle. A feature  35  is permanently attached to the needle. The retention washer  15  at the distal end of the needle shield assembly includes an opening  14  that is sized to permit movement of the needle therethrough but to prevent passage of the feature  35 . 
     In use, the user inserts the needle tip  32  of the over-the-needle catheter assembly  10  into the patient&#39;s vein. Upon confirmation flashback, the user grasps the needle hub  110 , pulling the needle hub away from the catheter adapter  8 , thereby causing the needle  30  to be withdrawn through the catheter adapter  8  and the needle shield assembly  5 . See  FIG. 13A . The needle continues to be withdrawn through the needle shield assembly until the feature  35  contacts the retention washer  15 . Further displacement of the needle causes the needle shield assembly  5  to be withdrawn from the shield housing  6  in the adapter  8 . See  FIG. 13B . As the needle shield assembly is fully withdrawn from the shield housing in the catheter adapter, the spring arm  427  is free to rotate radially outward from the needle shield assembly. Consequently, the proximal ledge  227  and the distal ledge  327  disengage the canting plate  40 . See  FIG. 13C . Consequently, the canting plate can be rotated. The upper edge of the canting plate is prevented from moving either distally or proximally by the retention arms  116 ,  216 . 
     Double Canting Plate 
     Another implementation of the invention is disclosed in  FIGS. 14A through 14C . The needle shield assembly  5  includes a distal retention arm  116  and a proximal retention arm  216  which are preferably integrally formed with the shield body  10 . As depicted, the retention arms are deformed radially inward, such as by bending. A distal canting plate  140  and a proximal canting plate  240  are disposed within the shield body. The canting plates are maintained in an aligned condition by the cooperation of the retention arms with distal ledge  327  and proximal ledge  227  and the elastomeric washer  28 , discussed below. The ledges  227 ,  327  are mounted to a spring arm  527 . When the needle shield assembly is disposed within the shield housing  6  of adapter  8 , the spring arm  527  is biased radially inward such that the ledges  227 ,  327  engage the canting plates  140 ,  240 . A friction member, such as hourglass-shaped washer  28 , is disposed between the distal canting plate  40  and the proximal canting plate  240  within the shield body  10 . The elastomeric washer  28  is frictionally engaged to the needle. In certain implementations of this aspect of the invention, the elastomeric washer  28  may be compressed when disposed between the two canting plates as depicted in  FIG. 14A . In such case, the washer is exerting a continuous biasing force on the canting plates which is resisted by the needle shield assembly. 
     In use, needle tip  32  of the over-the-needle catheter assembly  100  is inserted into the patient&#39;s vein. Upon confirmation flashback, the needle  30  is withdrawn through the catheter  108  such that the needle passes through the needle shield assembly  5 . The distal canting plate  140  is maintained in alignment with the needle by the cooperation of the elastomeric washer  28 , the distal retention arm  116  and the distal ledge  327 . The proximal canting plate  240  is maintained in alignment by the cooperation of the elastomeric washer, the proximal retention arms  216  and the proximal ledge  227  despite urging of the washer  28  (which is seeking to follow the needle and, thus, being moved against the canting plates). Since the canting plates are in alignment with the needle, the needle passes freely through the openings in the canting plates. Upon further withdrawal of the needle, the feature  35  engages the retention washer  15 , causing the needle shield assembly  5  to be pulled out of the shield housing  6  in the adapter  8 . See  FIG. 14B . Upon removal of the needle shield assembly from the catheter adapter, the spring arm  527  is free to expand radially outward from the shield body, such that the proximal ledge  227  disengages the proximal canting plate  240  and the distal ledge  327  disengages the distal canting plate  140 . This disengagement permits the canting plate to rotate. If the washer had been compressed, it will be free to expand, thereby causing immediate tilting of the canting plates. As the needle  30  is urged proximally with respect to the needle shield assembly  5 , the needle will urge the washer  28  distally which, in turn, will cause the proximal canting plate  240  to rotate, as seen in  FIG. 14B . As the needle is urged distally with respect to the needle shield assembly, the washer  28  will move distally, urging the distal canting plate  140  to move distally. The distal retention arm  116  will prevent the distal canting plate  140  from translating distally within the needle shield body  10 , resulting in tilting of the distal canting plate and binding on the needle. See  FIG. 14C . 
     Dual Canting Plate with Tether 
     Referring to  FIGS. 15A  through C, an implementation of the invention is depicted which employs a tether  400  to extract the needle shield assembly  5  from the shield housing  6  of the catheter adapter  8 . The tether is attached to the needle hub  110  and to the proximal end  12  of the needle shield assembly. As depicted in  FIGS. 15A  through C, the tether is attached to the retention washer  15 . Because the tether extracts the needle shield assembly from the catheter adapter, no feature  35  on the needle is required. In use, the needle tip  32  is inserted into the patient&#39;s vein, delivering the tip of the catheter  108  to the vein as well. The caregiver then withdraws the needle hub  110  while holding the catheter adapter  8  in place. See  FIG. 15B . As the needle hub is moved proximally, the tether  400  extends until it is at its full length. As the needle hub is moved further proximally, the needle shield assembly  5  is pulled out of the shield housing  6  in the catheter adapter  8 . See  FIG. 15B . The operation of this implementation is otherwise similar to the implementation depicted and described in connection with  FIGS. 14A through 14C . 
     Single Canting Plate and Tether 
     Referring now to  FIGS. 16A through 16D , an implementation of the invention similar to that depicted in  FIGS. 13A through 13C  is depicted. However, a tether  400  is used to extract the needle shield assembly  5  from the shield housing  6  in the catheter adapter  8 . Consequently, no feature  35  is required on the needle. A single canting plate  40  binds onto the needle  30  after actuation, thereby preventing movement of the needle with respect to the needle shield assembly in both the proximal and distal directions. The needle shield assembly  5  includes a proximal retention arm  216  and a distal retention arm  116  integrally formed with the shield body  10 . A proximal ledge  227  and a distal ledge  327  are mounted on spring arm  427 . As depicted in  FIG. 16A , the shield housing  6  of the adapter  8  compresses or flexes the spring arm radially inwardly, and into engagement with the canting plate  40 . An elastomeric washer  228  is attached to the canting plate and is frictionally engaged to the needle. A feature  35  is permanently attached to the needle. 
     In use, the user inserts the needle tip  32  of the over-the-needle catheter  100  into the patient&#39;s vein, thereby positioning the tip of the catheter  108  in the vein as well. Upon confirmation flashback, the user grasps the needle hub  110 , pulling the needle hub away from the catheter adapter  8 , thereby causing the needle  30  to be withdrawn through the catheter adapter  8  and the needle shield assembly  5 . See  FIG. 16B . When the tether  400  is extended to its full length, further proximal movement of the needle hub begins withdrawing the needle shield assembly from the catheter adapter. See  FIG. 16B . As the needle shield assembly is fully withdrawn from the shield housing in the catheter adapter, the spring arm  427  is free to rotate radially outward from the needle shield assembly. Consequently, the proximal ledge  227  and the distal ledge  327  disengage the canting plate  40 . See  FIG. 16C . Consequently, the canting plate can be rotated. The upper edge of the canting plate is prevented from moving either distally or proximally by the retention arms  116 ,  216 . Re-emergence of the needle is prevented by a binding force from the canting plate on the exterior wall of the needle  30 , as discussed in connection with  FIGS. 13A-C . See  FIG. 16D . 
     Clip with Canting Slot 
     Referring now to  FIGS. 17A through 17D , an implementation of the invention is depicted in which a clip  130  is disposed within the housing of the needle shield assembly  5 . The clip is a substantially v-shaped member with a first leg  131  securely mounted to the housing. The second leg  132  is mounted to the first leg via a flexural hinge  133 . Slide tabs  134  are formed in the second leg to reduce the interference between the needle  30  and the second leg during actuation and slidingly engage the needle  30 . As shown in  FIGS. 17A and 17B , before actuation, the clip  130  is compressed and maintained in the compressed condition by the presence of the needle within the needle shield  5  at a point aligned with the clip. A trap arm  730  is attached to the second leg  132  and engages a catheter adapter (not shown), preventing its removal from the needle shield assembly. As the needle is withdrawn, it ceases to engage the second leg such that the flexural hinge  133  springs open. See  FIGS. 17C and 17D . The trap arm then moves out of engagement with the catheter adapter so that it can be removed from the needle shield assembly. 
     A guide plate  140  is attached to the second leg  132  of the clip  130 . The guide plate includes a guide slot  141 . A canting pin  142  is attached to the canting plate  40 . The canting pin may be integrally formed with the canting plate. The canting pin is disposed within the guide slot  141 . In the unactuated condition, as shown in  FIG. 17A , the position of the canting pin in the canting slot maintains the canting plate in an aligned condition with the needle  30 . Consequently, the needle may be withdrawn through the opening in the canting plate without interference. As the needle is withdrawn beyond the clip, the clip springs open, causing the guide plate to move accordingly. See  FIGS. 17C and 17D . The movement of the guide plate results in the pin  142  being displaced in a distal direction. The bottom edge of the canting plate is prevented from translating proximally or distally because it is retained within a groove  740  in the needle shield assembly housing. As the pin  142  is moved distally, the canting plate is rotated into binding engagement with the needle. As the needle is urged distally with respect to the needle shield assembly, the engagement of the canting plate prevents the needle from re-emerging out of the needle shield assembly. The retention washer  15  prevents movement of the feature  35  (and therefore movement of the needle tip  32 ) out of the proximal end of the needle shield assembly. It will be appreciated that the feature could be removed and a tether provided to prevent the needle shield assembly from sliding off the tip of the needle. 
     Integrated Washer and Floating Plate 
     Referring now to  FIGS. 18A through 18D , an implementation of the invention is depicted including a retention washer  15  integrally formed with an actuator arm  150 . An opening  14  is disposed in the retention washer. A lip may be formed about the opening  14  to ease the passage of the needle and to ensure relatively perpendicular alignment between the retention washer and the needle. The actuator arm includes a front wall  151  and a slide plate  152 . An aperture  153  is disposed in the front wall but may be eliminated in certain implementations. The canting plate  40  is maintained in position about the needle by a pair of u-shaped sleeves  154 . The sleeves are in a relatively close fit with the canting plate  40  but not so close that the canting plate cannot slide within the sleeves. Compare  FIGS. 18B and 18D . The u-shaped sleeves are themselves attached to the arm  150 . An aperture  155  is disposed in the arm directly above the canting plate. 
     In the unactuated condition, as seen in  FIGS. 18A and 18B , the retention plate  15  and the arm  150  are flexed away from each other (that is, biased open) and maintained in this flexed condition by the presence of the needle  30  in the opening  14  of the retention washer, and the engagement of the needle with the plate  152 . After insertion of the catheter  108  into the patient&#39;s vein, the needle shield assembly  5  is moved toward the needle tip  32  (or, alternatively, the needle  30  is withdrawn through the needle shield assembly). As the needle moves proximally with respect to the needle shield assembly  5 , the tip  32  of the needle passes beyond the slide plate  152  such that the arm  150  and retention plate  15  can return to their unbiased condition, rotating toward each other, as seen in  FIGS. 18C and 18D . In this unbiased or actuated condition, the u-shaped members  154  are displaced with respect to the retention washer  15  (specifically, the u-shaped members are rotated with respect to the retention plate). Compare  FIG. 18B  with  FIG. 18D . As such, the canting plate  40  is also displaced with respect to the retention washer (and thus the needle). Effectively, the canting plate is tilted with respect to the needle and thereby engages the exterior of the needle. In the actuated condition, the top of the canting plate protrudes through the aperture  155  in the arm  150 . It will be appreciated that the arm  150  could be designed such that such an aperture  155  would not be required but this would result in a larger needle shield assembly  5 . 
     Integrated Plate and Engagement Hooks 
     Referring now to  FIGS. 19A and 19B , an implementation of the invention is depicted that includes a mechanism for engaging a catheter adapter  8  until the needle tip  32  has been withdrawn into the needle shield assembly  5 , somewhat similar to the implementation depicted in  FIGS. 4A-B . The needle shield assembly includes two engagement arms  190  (preferably in the form of leaf springs integrally formed with the shield body  10 ) that are biased radially outwardly from the body of the needle shield assembly. Hooks  191  are attached to the distal end of the engagement arms  190 . In the unactuated condition, the needle  30  is positioned between the hooks, thereby urging the hooks and the engagement arms radially outward. The hooks therefore are disposed within an annular groove  192  in the catheter adapter  8 . Consequently, the catheter adapter may not be displaced off of the needle shield assembly. As the needle is withdrawn from between the hooks, the engagement arms flex radially inward to their unstressed condition as seen in  FIG. 19B . As such, the hooks  191  disengage the annular groove  192 . Consequently, the needle shield assembly  5  may now be removed from the catheter adapter  8 . 
     The needle shield assembly  5  also includes a retention washer  15  integrally formed with a canting plate  40  and connected by a flexural hinge member  193 . The hinge member is a spring which urges the canting plate  40  into a canted condition. When assembled and before actuation (see  FIG. 19A ), the canting plate is maintained in alignment with the needle by the cooperation of the force exerted by the flexural hinge  193  and interference with the proximal end of the catheter adapter  8 . Consequently, the needle  30  is free to pass through the canting plate without interference. As the needle shield assembly is disengaged from the catheter adapter and moves proximally out of the catheter adapter, the canting plate is free to succumb to the bias of the flexural hinge  193  and thus engage the exterior of the needle  30  (see  FIG. 19B ). 
     Integral Washer, Hinge and Canting Plate with Actuation Arm 
     Referring now to  FIGS. 20A and 20B , an implementation of the invention is depicted including a retention washer  15  integrally formed with a flexural hinge  193  which in turn integrally formed with a canting plate  40  which is in turn integrally formed with an actuation arm  150 . The retention washer is attached to the proximal end  12  of a shield body  10 . In the unactuated condition, the canting plate is maintained in alignment with the needle  30  by the cooperation of the force exerted by the flexural hinge  193  and the restraint exerted by actuation arm  150 . Specifically, the flexural hinge  193  acts as a spring urging the canting plate into a canted or engaging condition. This movement of the canting plate is prevented by the actuation arm which itself is engaged to the needle. See  FIG. 20A . As the needle tip  32  is withdrawn, the actuation arm  150  comes out of engagement with the needle tip and is therefore free to move within the shield body  10 . Consequently, the canting plate  40  succumbs to the bias exerted by the flexural hinge  193 . As the canting plate is tilted out of alignment with the needle, it bindingly engages to the exterior of the needle. A cutout  159  may be provided on the actuation arm to permit movement of the actuation arm after passage of the needle tip without interference from the needle. 
     As disclosed above, certain implementations of the invention employ a feature  35  on the needle  30  to limit motion of the needle shield assembly  5  with respect to the tip  32  of the needle. Other implementations employ a tether  400  to limit motion of the needle tip with respect to the needle shield assembly. It will be appreciated that in the various embodiments, the feature may be replaced with a tether (or the tether replaced with a feature) and still practice the invention. Further, the friction member is referred to, in certain implementations as an elastomeric washer. It will be appreciated that the friction member may be made of elastomers, or other materials having different properties and various shapes and still practice aspects of the invention. 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the purview and spirit of this invention. For example, implementations of the invention may be employed with other needles, such as anesthesia needles or syringes or blood sample collection sets. The scope of legal protection given to this invention can only be determined by studying the following claims.