Abstract:
A passively activated safety needle assembly includes a needle assembly, a shield assembly and a safety cap. The needle assembly includes a hub and a needle cannula that projects from the hub. The shield assembly includes a safety shield that is mounting for sliding movement along the needle cannula. The shield assembly also includes a plurality of arms articulated to one another to permit sliding movement of the safety shield along the needle cannula from a proximal position to a distal position where the tip of the needle cannula is shielded. A spring is mounted to the shield assembly and is operative to drive the safety shield from its proximal position to its distal position. The safety cap is mounted over shield assembly and holds the shield assembly in the proximal position. The arms are held during usage of the safety needle. Upon release of the arms, the spring automatically drives the shield distally without any user activation.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The subject invention relates to a passively activated safety needle assembly to prevent accidental needle sticks.  
           [0003]    2. Description of the Related Art  
           [0004]    Many medical procedures require the use of a sharply pointed metallic needle cannula for obtaining a sample of fluid from a patient or for delivering a fluid to the patient. The sharply pointed metallic needle cannula must be handled carefully to avoid an accidental stick with the point of the needle cannula. An accidental stick with a sterile needle cannula is painful and can leave an open wound that is subject to infection. An accidental needle stick with a used needle cannula can transmit disease.  
           [0005]    Safety shields are employed widely in the health care industry to eliminate or reduce the risk of accidental needle sticks. Safety shields have taken many forms, including shields that telescope along the needle cannula from a proximal position to a distal position. The distal tip of the needle cannula is exposed for use when the shield is in the proximal position. However the pointed tip of the needle cannula is covered when the shield is in the distal position.  
           [0006]    Some shields are large and telescope over a syringe, needle holder or other medical implement. Some such large shields also include coil springs to propel the shield distally. The spring typically is locked in a collapsed condition around proximal portions of the medical implement when the shield is retained in the proximal position. An actuator is triggered after use of the medical implement to release the spring and drive the shield distally into a shielding disposition around the needle cannula.  
           [0007]    Other shields are much smaller and are configured to telescope only along the needle cannula. The shield in these prior art devices may be connected to the syringe or the needle hub by a tether or a linked array of hinged arms to limit the range of movement of the shield relative to the needle cannula. Thus, the shield can be moved distally into surrounding relationship with the tip of the needle cannula. However, the tether or hinged arms prevent the shield from sliding completely off the needle cannula. Some shield assemblies of this general type include a spring mechanism for assisting a portion of the distal movement of the shield along the needle cannula. A shielding assembly of this general type is shown in U.S. Pat. No. 5,348,544 which is assigned to the assignee of the subject invention. The shielding assembly shown in U.S. Pat. No. 5,348,544 requires the user to initiate shielding by exerting digital pressure on one of the hingedly connected arms. This initial digital pressure will be resisted by the spring. However, after a certain range of movement, the hingedly connected arms will be positioned such that the spring assists the distal movement of the shield. The needle shielding device shown in U.S. Pat. No. 5,348,544 is very effective. However, a device with passive or automatic shield actuation could provide certain advantages over the prior art.  
         SUMMARY OF THE INVENTION  
         [0008]    The subject invention is directed to a passively activated safety needle assembly with a shield configured for sliding movement along a needle cannula. The needle cannula comprises a proximal end and a distal end that is sufficiently pointed for penetrating skin and adjacent tissue of a patient. The proximal end of the needle cannula may be mounted in a hub. The hub may be molded from plastic and may be configured for mounting to a syringe, a needle holder or other medical implement.  
           [0009]    The shield of the passively activated safety needle assembly may be slidably movable along the needle cannula from a proximal position substantially adjacent the hub to a distal position for shielding the tip of the needle cannula. The needle shield may include a spring latch formed from a metallic material and biased against a lateral side of the needle cannula as the shield moves from the proximal position toward the distal position. The spring latch may be dimensioned and configured to overlie the distal tip of the needle cannula when the shield reaches its distal position.  
           [0010]    The passively activated safety needle assembly of the subject invention further comprises connection means for limiting movement of the shield along the needle cannula. The connection means may comprise a flexible tether or a plurality of hingedly articulating arms that can move from a collapsed condition to an extended condition. The connection means is in the collapsed condition when the shield is in its proximal position relative to the needle cannula. However, the connection means is in a fully extended condition when the shield has advanced into shielding disposition around the tip of the needle cannula.  
           [0011]    The connection means may comprise a distal end that is articulated to the shield and a proximal end that is articulated to or near the needle hub. More particularly, the proximal end of the connection means may be articulated directly to the needle hub. Alternatively, the proximal end of the connection means may be articulated to a base which in turn is connected securely to the needle hub.  
           [0012]    The passively activated safety needle assembly of the subject invention further comprises a biasing means for urging the shield from the proximal position to the distal position. The biasing means may comprise a torsion spring mounted between a plurality of hingedly connected arms of the connection means. Alternatively, the biasing means may comprise a coil spring that surrounds the needle cannula at locations between the shield and the needle hub. The biasing means is disposed and configured for having stored energy when the safety shield is in its proximal position. Additionally, the biasing means is configured relative to the shield and the connection means such that the stored energy will urge the shield distally at all points along the range of movement of the shield. Thus, the biasing means is configured and disposed for urging the shield distally even when the shield is in its extreme proximal position. Accordingly, the biasing means avoids the need to initially exert digital pressure on the shield or on a hinged arm to start the shield moving toward the distal shielding position.  
           [0013]    The passively activated needle assembly of the subject invention further comprises a safety cap that is removably engaged over the needle cannula prior to use. The safety cap may be formed from a rigid plastic material and may be dimensioned to cover the entirety of the needle cannula from the distal end to the proximal end. Proximal portions of the safety cap may be dimensioned for removable frictional engagement over the needle hub and/or over any base that may be provided to mount the connection means on the hub. A notch or slot may extend distally from the proximal end of the safety cap a sufficient distance for receiving the hingedly connected arms or other such connection means. The safety cap performs two functions. First, the safety cap prevents accidental sticks with the needle cannula prior to use. Additionally, the safety cap releasably holds the safety shield in a proximal position.  
           [0014]    The shield of the subject invention initially is in its proximal position on the needle cannula with the connecting means in the collapsed condition and with the stored energy in the biasing means. The safety cap then is mounted over the needle cannula and over the shield sufficiently for removable frictional engagement of the safety cap with either the needle hub or with the base to which the connection means is articulated. This initial positioning of the safety shield and the safety cap is carried out at the place of manufacture and does not require any action by the health care worker.  
           [0015]    A health care worker may mount the passively activated safety needle assembly to a syringe, needle holder or other medical implement in a conventional manner. This mounting may involve the mere axially movement of a Luer tip into a Luer receptacle of the needle hub. Alternatively, the needle hub of the passively activated safety needle can be threaded into engagement with a Luer collar.  
           [0016]    The health care worker then grips the connection means and the syringe or needle holder between a thumb and forefinger. This engagement ensures that the shield will remain in a proximal position. The health care worker then grabs the safety cap with the other hand and pulls sufficiently to disengage the safety cap. The required pulling force is approximately the same as the pulling force to separate any safety cap from a needle assembly in the prior art. The health care worker then continues to exert digital pressure on the connection means and urges the exposed distal tip of the needle cannula into a targeted location on the patient for obtaining a fluid sample or for delivering a fluid drug to the patient. After the needle cannula has been placed in communication with the patient, the health care worker may release the grip on the connection means. This release of the connection means enables the spring to drive the safety shield distally. The distal movement of the safety shield along the needle cannula terminates when the distal end of the safety shield contacts the skin of the patient.  
           [0017]    The needle cannula is removed from the patient after an appropriate volume of liquid has been withdrawn or after an appropriate dosage of a drug has been administered. Proximal movement of the needle cannula associated with the withdrawal of the needle cannula from the patient permits the safety shield to be driven further in a distal direction by the biasing means. Thus, the distal end of the safety shield will remain in contact with the skin of the patient as the needle is moved proximally relative to the patient. Upon complete removal of the needle cannula from the patient, the biasing means will advance the shield into its full shielding condition around the distal tip of the needle cannula. The safely shielded needle then can be separated from the syringe or needle holder and discarded into an appropriate sharps receptacle. Alternatively, the entire needle assembly and needle holder may be discarded.  
           [0018]    The health care facility occasionally is a hectic environment, and fluids near the patient may make medical implements slippery. Thus, the potential exists for the health care worker to drop the needle assembly before use. Inadvertent dropping of the passively activated safety needle will immediately cause the shield to be propelled by the spring into its distal shielding position around the needle cannula. Hence, accidental sticks are avoided even in situations where the unused needle cannula is accidentally dropped. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a side elevational view of a passively activated safety needle assembly in accordance with the subject invention.  
         [0020]    [0020]FIG. 2 is a longitudinal cross-sectional view of the passively activated safety needle assembly mounted to a needle holder.  
         [0021]    [0021]FIG. 3 is a cross-sectional view similar to FIG. 2, but showing the safety cap removed and showing the needle assembly in use.  
         [0022]    [0022]FIG. 4 is a cross-sectional view similar to FIGS. 2 and 3 after removal of the needle cannula from the patient and showing the shield in its fully extended condition.  
         [0023]    [0023]FIG. 5 is a cross-sectional view similar to FIG. 2, but showing the second embodiment.  
         [0024]    [0024]FIG. 6 is a cross-sectional view similar to FIGS. 2 and 5 but showing a third embodiment.  
         [0025]    [0025]FIG. 7 is a cross-sectional view similar to FIGS. 2, 5 and  6  but showing a fourth embodiment.  
     
    
     DETAILED DESCRIPTION  
       [0026]    A passively activated safety needle in accordance with the subject invention is identified generally by the numeral  10  in FIG. 1. Passively activated safety needle assembly  10  comprises a needle assembly  12 , a safety cap  14  and a shield assembly  16 . Safety needle assembly  10  can be mounted to a medical implement, such as a syringe or a needle holder. For example, FIG. 2 shows passively activated safety needle assembly  10  mounted to a needle holder  18  that is intended for use with evacuated blood collection tubes to collect samples of a patient&#39;s blood. Needle holder  18  may be of prior art design and is formed with a Luer tip  20  that has a passage therethrough.  
         [0027]    Needle assembly  12  includes a needle cannula  22  with a proximal end  24 , a distal end  26  that is beveled to a sharp tip and a lumen  28  extending between ends  24  and  26 . Needle assembly  12  further includes a plastic hub  30 . Proximal end  24  of needle cannula  22  is secured in hub  30  by adhesive  32 . Hub  30  includes a proximal end  34  with a recess  36  configured for mounting over Luer tip  20  of needle holder  18  or over a Luer tip on another medical implement with which passively activated safety needle assembly  10  is employed. Thus, hub  30  permits communication between lumen  28  of needle cannula  22  and the passage through Luer tip  20  of needle holder  18 .  
         [0028]    Passively activated safety needle assembly  10  comprises a safety shield  38  slidably mounted over needle cannula  22  for movement from a proximal position adjacent hub  30  to a distal position where safety shield  38  surrounds distal end  26  of needle cannula  22 . Safety shield  38  also is provided with a safety latch  40  formed from a metallic material. Latch  40  is biased against a side of needle cannula  32  when safety shield  38  is in the proximal position shown in FIG. 2. Latch  40  then slides against the side of needle cannula  22  as safety shield  38  is advanced from the proximal position shown in FIG. 2 toward the distal position shown in FIG. 4. When safety shield  38  reaches the distal position shown in FIG. 4, safety latch  40  will pass distal tip  26  of needle cannula  22 . The inherent biasing forces of safety latch  40  will urge safety latch  40  over distal tip  26  of needle cannula  22  to prevent re-exposure of needle cannula  22 .  
         [0029]    Shield assembly  16  further includes a distal arm  42  that is connected unitarily to safety shield  38  by a first living hinge  44  that permits hinged movement between distal arm  42  and safety shield  38 . A proximal arm  46  is hingedly connected to distal arm  42  by a hinge pin  48 . Proximal arm  46  is connected unitarily to a safety shield base  50  by a second living hinge  52 . Base  50  of shield assembly  16  is a generally tubular structure that is locked securely over hub  30  of needle assembly  12  in a manner that prevents removal without destruction of the respective components.  
         [0030]    Shield assembly  16  further includes a torsion spring  54  with a coil  56 , a proximal leg  58  and a distal leg  60 . Coil  56  of torsion spring  54  is mounted over hinge pin  48  such that torsion spring  54  is effectively captured on shield assembly  16 . Proximal leg  58  of torsion spring  54  is engaged with proximal arm  46  of shield assembly  16 . Distal leg  60  of torsion spring  54  is engaged with distal arm  42  of shield assembly  16 .  
         [0031]    Arms  42  and  46  of shield assembly  16  are dimensioned and configured to permit safety shield  38  to be moved into the proximal position shown in FIG. 2, such that safety shield  38  abuts needle hub  30 . Additionally, arms  42  and  46  of shield assembly  16  are dimensioned to permit safety shield  38  to be slid distally along needle cannula  22  and into a position where latch  40  snaps into engagement over distal end  26  of needle cannula  22 . Torsion spring  54  is biased into a collapsed condition when safety shield  38  is in its proximal position along needle cannula  22  and substantially adjacent needle hub  30 . Biasing forces of torsion spring  54  urge spring legs  58  and  60  away from one another, and thereby tend to urge arms  42  and  46  about hinge pin  48  and into an expanded condition. Thus, torsion spring  54  propels safety shield  38  distally along needle cannula  22 . These forces of torsion spring  54  exist when safety shield  52  is in the proximal position shown in FIG. 2. Hence, there is no need to provide digital assistance through the first part of movement of safety shield  38 , as had existed in the prior art.  
         [0032]    Safety cap  14  of passively activated safety needle assembly  10  is molded unitarily from a rigid plastic material and includes an open proximal end  62 , a closed distal end  64  and a rigid closed sidewall  66  extending between ends  62  and  64 . Portions of tubular sidewall  66  adjacent distal end  62  are formed with a notch  68  that is dimensioned to slidably receive arms  42  and  46  when safety shield  38  is in the proximal position of FIG. 2. More particularly, notch  68  includes a distal end edge  70  that will abut against and lie partly over distal arm  42  of shield assembly  16 . Simultaneously, portions of safety cap  14  adjacent proximal end  62  snap into engagement with base  50  of shield assembly  16 . Thus, safety cap  14  is retained releasably over both needle assembly  12  and shield assembly  16  and holds shield assembly  16  in the collapsed condition of FIG. 2.  
         [0033]    Passively activated safety needle assembly  10  is shown in FIG. 1 after removal from its sterile packaging and prior to mounting on a medical implement. Safety needle assembly  10  is mounted to needle holder  18  or other medical implement by urging your receptacle  36  at proximal end  34  of needle holder  30  onto Luer tip  20  as shown in FIG. 2. The health care worker then grips needle holder  18  and distal arm  42  of shield assembly  16  with a thumb and forefinger and pulls distally on safety cap  14  with the other hand. A slight pulling force separates safety cap  14  from the remainder of needle assembly  10  to expose distal end  26  of needle cannula  22 . At this point, the health care worker still retains a finger on distal arm  42  of shield assembly  16  to hold safety shield  38  in the proximal position shown in FIG. 2.  
         [0034]    The health care worker next guides the distal end  26  of needle cannula  22  into a targeted location on a patient substantially in the conventional manner. The health care worker may release the grip on distal arm  42  of shield assembly  16  once there is assurance that the targeted location of the patient has been entered. The removal of the digital force enables torsion spring  54  to expand, and immediately urges safety shield  38  distally along needle cannula  22 . Safety shield  38  will terminate its distal movement upon contact with the skin of the patient as shown in FIG. 3.  
         [0035]    Needle assembly  12  is removed from the patient after a sufficient volume of fluid has been collected or delivered. Removal of needle cannula from the patient merely involves a proximal movement of passively activated safety needle assembly  10  and needle holder  18 . This proximal movement permits further distal movement of safety shield  38  along needle cannula  22  in response to continuing forces exerted by torsion spring  54 . Upon complete removal of needle cannula  22  from the patient, safety shield  38  will have been propelled distally a sufficient distance for latch  40  to spring over distal tip  26  of needle cannula  20  and to prevent re-exposure of needle cannula  22 . Sliding movement of safety shield  38  along needle cannula  22  is entirely passive and requires no initial assistance by the health care worker. Needle assembly  12  then can be discarded with or without the holder  18  in an appropriate sharps receptacle.  
         [0036]    A second embodiment of the passively activated safety needle assembly is illustrated in FIG. 5 and is identified generally by the numeral  10   a . Passively activated safety needle assembly  10   a  is identical to safety needle assembly  10  described and illustrated above in most respects. However, a rigid thumb grip  72  projects from a side of base  50  diametrically opposite arms  44  and  46 . Safety cap  14   a  includes a second notch  74  diametrically opposite notch  68  and dimensioned to slidably receive thumb grip  72 . Thumb grip  72  provides a convenient gripping location that is similar to grips provided on many needle sets used for fluid specimen collection purposes.  
         [0037]    The health care technician can use passively activated safety needle assembly  10   a  substantially as described above, but will grip both distal arm  42  and thumb grip  72  during removal of safety cap  14  and during initial insertion of needle cannula  22  into the patient. The health care worker then can release the finger grip on the distal arm  42 , thereby permitting torsion spring  54  to propel safety shield  38  distally along needle cannula  22 , as described above.  
         [0038]    A third embodiment of the passively shieldable safety needle assembly is identified by the numeral  10   b  by FIG. 6. Passively activated safety needle assembly  10   b  is identical to safety needle assembly  10  of FIGS.  1 - 4  in most respects. However, passively activated safety needle assembly  10   b  has a coil spring  76  mounted around needle cannula  22  and disposed between needle hub  30  and safety shield  38 . Coil spring  76  replaces torsion spring  54  of the first embodiment, and works with a similar result. However coil spring  76  exerts biasing forces directly on safety shield  38 . As a result, arm  42  and  46  of shield assembly  16  merely follow safety shield  38  rather than driving safety shield  38 . Arms  42  and  46  continue to perform their function of limiting the amount of distal movement of safety shield  38  along needle cannula  22 .  
         [0039]    A fourth embodiment of the passively activated safety needle assembly of the subject invention is identified by the numeral  10   c  in FIG. 7. Passively activated safety needle assembly  10   c  is substantially identical to passively activated safety needle assembly  10  of FIGS.  1 - 5  in virtually all respects. However, a torsion spring  80  is provided between base  50  of shield assembly  16  and proximal arm  46 . Torsion spring  80  rotatably drives proximal arm  58  about second living hinge  52 . This rotation of proximal arm  46  causes a corresponding rotational movement of distal arm  42  and drives safety shield  38  distally along needle cannula  22  substantially as described above.