Abstract:
An intravenous cannula device ( 10 ) having a cannula body ( 12 ), a needle carrier ( 20 ), and a needle carrier container ( 36 ) nested in series. The needle carrier is spring loaded ( 48 ) toward the container, and the container carries an external lever assembly ( 50 ) that triggers the spring as the cannula is pushed forward of the container toward full insertion in the patient, whereby the released spring drives the needle carrier including needle ( 30 ) into the container.

Description:
BACKGROUND 
       [0001]    The present invention relates to intra venous (IV) cannulas that incorporate a safety feature whereby the needle is retracted after the cannula has been fully inserted into the patient. 
         [0002]    A typical IV cannula features a steel needle with a sharp tip protruding through a slightly larger diameter flexible cannula tube. After the skin has been penetrated and the flexible tube inserted, the needle can be removed and discarded. There are however two major areas of concern. First there is a danger of injury because of the exposed sharp tip and secondly there is also a risk of infection because the outside diameter of the needle which was in contact with patient&#39;s blood might be contaminated. Safety cannulas are known in which if the needle was removed from the patient following proper procedure, the needle tip will remain within a special cavity in the needle carrier, where a protective flap pivots into position. Such safety cannulas are somewhat complex, but more importantly, if the proper procedure is not carefully followed, it is also possible to remove the needle without triggering the automatic cover flap because the separation between the cannula housing and the needle carrier can occur in more than one place. 
         [0003]    Yet another disadvantage with the above described cannula arises from the needle diameter being deformed in one location to prevent the metallic needle tip protection shield from slipping off the needle and exposing the sharp tip. This deformation however obstructs the flow through the needle so blood has to flow through the gap between needle and the flexible tube and because of that it can take longer before the blood flows into the cannula body chamber, thereby confirming that the target was indeed been hit and the needle can now be removed. 
       SUMMARY 
       [0004]    The present invention effectively overcomes these functional disadvantages while substantially reducing the number of components required for assembly. 
         [0005]    In a general aspect, the invention is directed to an intravenous cannula device having a cannula body, a needle carrier, and a needle carrier container nested in series, wherein the needle carrier is spring loaded toward the container, and the container carries an external lever assembly that triggers the spring as the cannula is pushed forward of the container toward full insertion in the patient, whereby the released spring drives the needle carrier including needle into the container 
         [0006]    The disclosed device has a cannula body with a forward projecting tube, a needle carrier that is spring loaded toward a needle container having a receiving compartment that extends behind the needle carrier, and a lever assembly having locking arms that extend longitudinally along the exterior of the needle container. Each arm has a base that is longitudinally fixed with respect to the container, a free end having a hook that passes through openings in the container and engages a shoulder on the needle carrier to hold the needle carrier and thus prevent entry into the compartment of the container, and a trigger for releasing the spring, actuated by longitudinal motion of the cannula body relative to the container. 
         [0007]    Preferably, the container, needle carrier, and lever assembly are longitudinally slidable together relative to the cannula body such that beyond a predetermined position of the container relative to the cannula body the trigger is actuated and thereby releases the hooks from the shoulder, whereby the spring drives the needle carrier including needle into the cavity of the container. 
         [0008]    The implementing embodiments of a safety cannula device as disclosed herein, include a hollow cannula body having an elongated tube extending forward from the body. A tubular needle carrier is axially aligned behind cannula body, and supports a needle that extends through the cannula body and cannula tube to a free end that projects forwardly of the cannula tube. A tubular needle container is fixed to and encapsulates the needle carrier and has a front portion slidingly engaging the cannula body, an intermediate portion defining a cavity, and a back portion having a length at least equal to the extension of the needle through the cannula tube. In the cavity, the needle carrier has a shoulder and a spring acts between the container and a shoulder on the needle carrier, biasing the carrier toward the back portion of the container. The arms of the lever assembly extend longitudinally along the exterior at the intermediate portion of the needle container, each arm having a base that is longitudinally fixed with respect to the container, a free end having a hook that passes through one of said openings and engages the shoulder. 
         [0009]    The cannula device can be held by a nurse between the thumb and middle finger at the locking arms. After blood is drawn through the needle and appears in a view window, the nurse gradually pushes the cannula off the needle. The container, needle carrier, and lever assembly together slide relative to the cannula body such that beyond a predetermined position of the cannula relative to the container the trigger is actuated and thereby releases the hooks from the shoulder, whereby the spring drives the needle carrier including needle into the back portion of the container. 
         [0010]    The advantages include:
       Passive safety feature (automatic needle retraction)   Lost motion provides partial needle tip retraction and by that provides support for smaller diameter cannula tubes   Complete encapsulation of potentially contaminated needle after use   Unchanged cannula (catheter) body (identical with current production cannulas)   Identical components can be used with either wingless or wing type cannulas   Modular design option minimizes tooling costs   Aesthetically pleasing, compact design       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0018]    Embodiments will be described with reference to the accompanying drawing, in which: 
           [0019]      FIG. 1  is an oblique view of a first embodiment of a complete cannula device as removed from a sterile pouch, ready for use; 
           [0020]      FIG. 2  is an oblique view similar to  FIG. 1 , in longitudinal section; 
           [0021]      FIG. 3  is a longitudinal section view of the region of the device where the cannula body, needle carrier, carrier container and lever assembly are interconnected in the condition shown in  FIG. 2 ; 
           [0022]      FIG. 4  is an oblique schematic view showing how the locking arms of the lever assembly are prevented from pivoting radially outward so long as the trigger arms are in contact with the canula body in the condition shown in  FIG. 2 ; 
           [0023]      FIG. 5  is an illustration of how the medical technician can hold the device in the condition shown in  FIG. 2 , immediately before insertion of the needle into the patient; 
           [0024]      FIG. 6  is a longitudinal section view showing a condition after the technician has pushed the cannula body forward relative to the container, needle carrier, and lever assembly, immediately before triggering of the spring release of the lever assembly; 
           [0025]      FIG. 7  shows the safe condition following the exit of the cannula body from the container, in which the lever assembly has been triggered and the spring has driven the needle carrier with needle fully into the container; 
           [0026]      FIG. 8  is an oblique view of the preferred needle carrier; 
           [0027]      FIG. 9  shows the details of the type of lever assembly of the first embodiment, with an alternative shape for the hooks; 
           [0028]      FIGS. 10-12  show a second embodiment for the lever assembly; 
           [0029]      FIG. 13  shows a third embodiment of the lever assembly; and 
           [0030]      FIG. 14  shows a variation of the container, having a variable length snap extension to accommodate different length needles. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]      FIGS. 1-8  show a first embodiment of a safety IV cannula according to the present disclosure. The safety cannula device  10  comprises a hollow cannula body  12  having a larger diameter back portion  14 , a smaller diameter front portion  16 , and an elongated tube  18  extending forward from the front portion of the body. A tubular needle carrier  20  having front  22 , intermediate  24 , and back portions  26 , is nested on the body, with the front portion  22  within the back portion  14  of the cannula body and the intermediate portion  24  longitudinally spaced in cavity  28  behind the back portion  14  of the cannula body. The front portion  22  supports a needle  30  that extends through the cannula body  12  and cannula tube  18  to a free end  32  that projects forwardly of the cannula tube  18 . The intermediate portion  24  forms a shoulder  34  in cavity  28 . 
         [0032]    A tubular needle container  36  is nested with the cannula body  12  and the needle carrier  20 , having a front portion  38  captured between the front portion  22  of the needle carrier and the back portion  14  of the cannula body, an intermediate portion  40  having a plurality of elongated external channels  42 , and a back portion  44  defining a compartment having a length at least equal to the extension of the needle  30  through the cannula tube  18 . The channels  42  each have a radial opening  46  into the cavity  28 , adjacent to the shoulder  34  on the needle carrier. A helical or coil spring  48  has one end seated near the front end  38  of the carrier at the forward end of the cavity  28  that extends through the intermediate portion  40  of the container. The other end of the spring  48  acts axially on the needle carrier  20 , biasing the carrier toward the back portion  44  of the container. 
         [0033]    A lever assembly  50  has locking arms  52   a,    52   b  that extend longitudinally in respective channels  42  of the needle container  36 , each arm having a base  54  that is longitudinally fixed with respect to the container  36 , and a free end  56  having a hook  58  that passes through one of the openings  46  and engages the shoulder  34  of the needle carrier. The shoulder  34  imposes a radially outward force component on each hook  58  while a longitudinally directed force component resists the bias of the spring and prevents the needle carrier  20  from entering the back portion  44  of the container  36 , until the locking arms are triggered. The trigger  60  is actuated passively and automatically by longitudinal motion of the cannula body  12  relative to the container  36 , as the medical technician advances the cannula into the patient. This is possible because the container  36 , needle carrier  20 , and lever assembly  50  together are longitudinally slidable relative to the cannula body  12  such that beyond a predetermined position P of the cannula body  12  relative to the container (or trigger) the trigger  60  is actuated and thereby adds another radially outward force component to the hooks  58  such that the hooks move radially outward from the shoulder  34 . This releases the intermediate portion  24  of the needle carrier, whereby the spring  48  drives the needle carrier  20  including needle  30  into the back portion  44  of the container. Preferably, the trigger comprises a plurality of trigger arms  60   a,    60   b  in alignment with the corresponding plurality of locking arms  50   a.    50   b,  with the trigger arms extending forward beyond the front portion  38  of the container. 
         [0034]      FIG. 1  shows that the sharp needle tip  32  initially projects from the cannula tube  18 . The device is, however, initially distributed in sterile packaging with a tubular safety cover  62  as shown in  FIG. 2 . The cover  62  is held by friction between the front portion  16  of the cannula body and the front portion of the trigger arms  60  that overhang the front portion  38  container. This cover must be removed and discarded before the use. 
         [0035]    In use, the device  10  automatically retracts the needle carrier  20  into the container  36 . The locking arms  52  and trigger arms  60  are connected via a circular ring  76 . The inner circumference  76  defines the base  54  of each locking arm, and is captured in a groove  78  on the exterior of the front portion  38  of the container  36 , thus fixing the lever assembly  50  with respect to the container  36 . The central ring  76  of the integral lever pair is snapped into a corresponding circular groove  78 . As a result, after the needle container  36  is removed from the cannula body  12  the lever assembly  50  will remain attached to the container, avoiding loose parts. 
         [0036]    A view window  64  is provided on the container  36 , where the transparent back portion  26  of the needle carrier forms an axially extending bore or chamber  66 . A porous plug  70  is located at the back end of the chamber and protrudes about 1 to 2 mm beyond the back edge of the carrier. This plug  70  has a dual function. The porosity of the plug allows air displaced by the blood flowing into the view chamber  66  after the sharp tip  32  has penetrated a patient&#39;s vein to escape and it also dampens the impact against the back wall  72  of container after the spring  48  has been released. 
         [0037]    The cannula device can be held by a nurse between the thumb and middle finger at the container alongside the locking arms  52 . After blood is drawn through the needle  30  and appears in the view window  64 , the nurse gradually pushes the cannula  12  off the needle carrier  36 , preferably by pushing with the index finger on external tab  74  formed on the cannula body  12 , and accessible between the trigger arms  60  of the lever assembly. The container  36 , needle carrier  20 , and lever assembly  50  together slide relative to the cannula body  12  such that beyond a predetermined position P the trigger  60  is actuated and thereby releases the hooks  58  from the shoulder  34 , whereby the spring  48  drives the needle carrier  20  including needle  30  into the back portion  44  of the container. Preferably, the trigger actuates when the back end of the cannula body passes the front ends of the trigger arms  60 . 
         [0038]    The channel walls  80  are radially outside the neutral position of the locking arms  52 . Because the walls act as barriers, the locking arms are able to open up and pull the hooks  58  off the shoulder  34 , even if the nurse continues to hold the device as shown in  FIG. 5 . If the barriers  80  were the same height or lower than the locking arms  52  then the nurse would squeeze the levers directly which could prevent or delay unhooking at the shoulder  34 . 
         [0039]    As shown in  FIG. 4 , each locking arm  52  and its aligned trigger arm  60  is connected through ring  76  to form one long lever that pivots at the ring. The radial outward acting force generated by the spring tries to spread the locking levers  52 . This is however not possible so long the cannula body  12  (represented here as a cylinder) prevents the trigger arms  60  from moving closer together. Once the cylinder is removed the locking arms open up and release the spring. Until this occurs, the radial force is trying to stretch the connecting ring  76  but because this radial force is very small (about 0.04 N or 1.4 oz) and the rigidity of the connecting ring in this direction is adequate no deformation takes place. The rigidity of the ring in the arm bending direction is however small and the ring will deform easily. 
         [0040]    By characterizing the lever assembly  50  in this embodiment as integral, the inventors mean that the locking arms  52   a,    52   b,  respective trigger arms  60   a,    60   b  and ring  76  are either formed as a unitary part or formed of distinct components that are substantially permanently joined. In this context, permanently joined means the lever assembly  50  is self-contained in normal use, i.e., the components are not expected to come apart. 
         [0041]      FIG. 3  shows the initial relationship of the cannula body  12  to the lever assembly  50 , container  36 , and needle carrier  20  and  FIG. 6  shows this relationship at the moment just before the back portion  14  of the cannula  12  exits the lever assembly  50  to thereby release the spring. The cannula  12  has external ears  82  that ride in internal grooves  84  of the trigger arms. The ears need not bear radially against the grooves. The reason for the ears  82  riding in and being supported by the grooves  84  is to prevent premature spring release. When the needle container  36  is moved back by the thumb and the middle finger as shown in  FIG. 5  the index finger (not shown) is holding the cannula body  12  by the protrusion  74 . Especially with thin needles and in the absence of these grooves  84 , it is possible that the force applied by the index finger inadvertently deflects the needle and by that laterally pushes the cannula body out of engagement with, and thereby prematurely triggering, the trigger arms  60 . 
         [0042]    Because of the inclination of the surfaces on both parts  58 ,  34  the spring force creates a radial force component trying to spread the levers which however is prevented so long the cylindrical portion of cannula body  12  is captured by the trigger arms  60  of the lever assembly  50 . 
         [0043]    Once the ears  82  completely exit the guide grooves  84 , the radial force component at the shoulder  34  arising from the bias of the spring  48  will spread the locking arms  52  and release the spring. Any potential opposite radial force appearing between the hooks  58  due to deformation of the connecting ring  76  after the spring is released should be minimized to insure full retraction of the needle. The force must not be able to stop the motion by interference with the spring coils. 
         [0044]    As the spring is never in contact with blood a lesser grade of stainless steel can be used instead of otherwise required medical grade stainless steel. 
         [0045]    The lost motion of the cannula  12  until spring release allows for full insertion of the cannula tube  18  in the vein because the tube is partially supported by the more rigid needle  30 . This feature is especially important for the smaller diameter cannula tubes which lack the rigidity to support insertion forces and because of that could collapse before the tube is fully inserted. 
         [0046]      FIG. 7  shows the condition of the container  36 , needle carrier  20 , and lever assembly  50  after the cannula  12  was removed and the spring  48  was released. This shows the ideal natural (neutral) shape of the components of the lever assembly  50 , i.e., the trigger arms  60  are inclined toward the axis while the locking arms  52  are contained substantially entirely within the openings  46  in the carrier  36 . 
         [0047]    As shown in  FIG. 8 , the needle carrier  20  can have two lateral grooves  86  or similar recesses, which are situated in back of the shoulder  34  of the assemble device and accommodate the hooks  58  of both locking levers  52  to keep the spring compressed. A visual or structural marker, such as notch  88 , can also be provided to insure proper orientation of the obliquely cut needle tip  32  during assembly. The locking arm channels  42  of the needle carrier are spaced 180° apart and because of that it would be possible to install the needle carrier  20  with the needle tip  32  wrongly pointing up. In order to prevent this mistake, the notch  88  on the needle carrier is used as a signal indicating the correct position of the sharp point. This reference notch or groove can engage with a corresponding protrusion of the assembly tool to insure the proper orientation. 
         [0048]      FIG. 9  shows the details of the type of lever assembly of the first embodiment, with an alternative shape for the hooks. In this lever assembly  50 ′, there are only two differences relative to  FIG. 4 . The hooks  58  of  FIG. 4  have a parabolic surface, whereas the hooks of  FIG. 9  have a rectangular surface.  FIG. 9  also shows in greater detail how the lever assemblies  50  and  50 ′ are composed of three parts, i.e., one lever consisting of arms  52   a  and  60   a;  another lever consisting of arms  52   b  and  60   b;  and a central ring  76  snap fit into notches or grooves  90  in arms  60  at the transition to arms  52 . 
         [0049]      FIGS. 10-12  show another embodiment  92  of the lever assembly, consisting of one lever having integral locking and trigger arms  94   a,    96   a  and another lever having integral locking and trigger arms  94   b,    96   b.  At the transition between the arms of each lever, a pair of opposed posts  98  project laterally. The posts  98  engage respective pairs holes  100  in cage  102 . The cage  102  has a central ring  104  that is coaxial with the longitudinal axis of the device, and two wings  106  that extend tangentially to the ring and transverse to the axis of the device. Each wing has a hole at opposite ends, whereby four posts  98  engage four holes  100 . In the assembled condition, the wings and posts define a four sided frame that firmly surrounds container  20 . Each pair of posts can pivot at the respective pair of holes. The advantage of this embodiment is the absence of any radial force which could possibly prevent complete retraction of the needle as a consequence of the locking hooks interfering with the coils of the spring. 
         [0050]      FIG. 11  also shows that the front end  96   a ′ of each the trigger arm can have a detent type cooperation with the back end  62 ′ of the safety cover, to substitute for or enhance the previously described friction fit. 
         [0051]      FIG. 13  shows a third embodiment  108  of a lever assembly, wherein the cage of  FIG. 11  has been reduced to the form of a simple elastic ring  110  at the transition (pivot point) of the lever arms. The ring  110  provides a radially inward force at its entire inner surface, thereby securing the lever assembly  108  longitudinally on the container but permitting the necessary pivoting action to release the spring. This embodiment has the advantage of inexpensive tooling, however the components will likely fall apart after the cannula has been removed from the patient. 
         [0052]      FIG. 14  shows an alternative embodiment of the container, in which an extension tube  112  is snap fit on the open back end  36 ′ of the container  36 . Preferably, the back end  36 ′ has a reduced OD that easily fits into the ID of a complementary bore ID at the front of the tube. Cooperating positive  114  (protruding) and negative  116  (receding) structure care engaged as the tube is slid onto the back end  36 ′ of the container  36 . Any form of detent type cooperation is suitable for this purpose. This embodiment provides a very simple variable length snap on extension of the length of the container  36 . As a consequence, the tooling for the fabrication and assembly of the lever assembly and associated triggering components can be identical for cannula devices having different lengths of needles.