Abstract:
A device for preventing fluid flow out of a patient when a medical component is withdrawn from a catheter connected to the patient. The device includes a tubular hub and a clamp slidably mounted on the hub. A clamp arm is normally biased into a position in which it squeezes the cannula to prevent flow therethrough. The arm is either self biased or urged into closed position by a resilient element. Connecting the upstream end of the hub to the medical component produces relative movement between the hub and the clamp that causes cam surfaces on those members to bias the clamp arms into an open position that permits fluid flow through the cannula.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to medical catheters in general, and specifically to a device and method for sealing a catheter from unwanted fluid flow.  
           [0003]    2. Description of the Related Art  
           [0004]    In the medical field it is often necessary to insert a catheter into a portion of the human body such as the bloodstream. One significant problem with implanting a catheter in the bloodstream of a patient is the tendency of blood to flow through the catheter upon removal of the insertion needle, stylet, trocar, or guidewire used in the procedure of piercing the body and placement of the catheter therein. Once the passageway between the bloodstream and the catheter opening is opened, blood tends to flow out of the body. Additionally, Luer connections such as intravenous feeding mechanisms occasionally become disconnected by the patient (intentionally or accidentally) thus allowing blood to flow from the patient out of the catheter. This unwanted blood flow out of the patient is obviously an undesirable result. It is therefore desirable to have a device which seals a catheter from fluid flow in one or both directions upon removal of the insertion needle, stylet, trocar, or guidewire.  
           [0005]    Many solutions to the above-stated problem have been suggested. For example; U.S. Pat. No. 5,405,323 teaches a catheter check valve assembly which incorporates a duckbill valve and a manually operable separator. U.S. Pat. No. 4,449,693 discloses a valve of resilient tubing into which a stopper having an oval sealing ring is placed. U.S. Pat. No. 5,073,168 teaches a y-adapter with a check valve formed from conformable sheets. U.S. Pat. Nos. 5,112,301; 5,156,600 and 5,167,636 also teach other types of catheter check valves.  
           [0006]    Some existing bi-directional catheter check valves rely on a differential fluid pressure across a membrane in order to seal the catheter from fluid flow. This will unfortunately not solve the problem of accidentally disconnected Luer connections, as blood pressure is typically higher than atmospheric air pressure, thus blood would leak out of such a valve in the absence of a second fluid. Others of the check valves described in the above-mentioned patents generally share the disadvantage that they require a conscious action to fully close the valve and seal the cannula from allowing blood to flow out. This extra step can be forgotten, thus leaving the catheter open to unwanted fluid flow.  
           [0007]    It is desirable to have a check valve which will always be closed when the Luer Lock is disconnected, and which requires no extra movement of parts in order to further seal the catheter. It is also desirable to have a valve which is inexpensive to manufacture and relatively simple to operate.  
         SUMMARY OF THE INVENTION  
         [0008]    It is therefore an object of the present invention to provide a device for preventing fluid flow out of a patient when a medical device is withdrawn from a catheter connected to the patient. In one embodiment, the device preferably comprises a tubular catheter hub having an upstream end configured to receive a medical device, and having a catheter cannula attached to a downstream end. The device of the present embodiment also includes an occluder or clamp mounted on the hub and being configured to prevent fluid passage through the cannula. The occluder is preferably biased into an occluding position and requires a positive act to move it into a position in which fluid can flow through the cannula.  
           [0009]    In another embodiment, the clamp includes a flexible arm supporting a clamping jaw which is biased into a position to squeeze the cannula to prevent fluid flow therethrough. The arm may be self-biased into said closed position, or a resilient element which biases the arm and jaw into the closed position may be included.  
           [0010]    In another embodiment, the device may include a pair of opposing clamping surfaces for pinching the flexible cannula, at least one of the surfaces being a portion of the occluder. The occluder may have a pair of jaws for pinching the flexible cannula, and the jaws may be normally biased into the pinching position. One of the clamping surfaces may be fixed to the hub.  
           [0011]    The occluder may be movably mounted on the hub, and the occluder and the hub may be configured so that the connection of a medical device to the upstream end of the hub will move the occluder into an open position wherein it is not restricting flow through the flexible valve portion. The occluder and hub preferably include engaging surfaces that will move the occluder into an open position when the occluder is moved in a downstream direction. The inter-engaging surfaces may cause the flexible valve arm on the occluder to be biased radially outwardly so as to not pinch the cannula. The hub of the device may include guides which guide movement of the occluder into linear movement and restrict rotational movement. The hub upstream end may be configured so that the connection of a medical device to the hub upstream end will automatically cause the occluder to move in a downstream direction relative to the hub and into an open position.  
           [0012]    The cannula may include a rigid section extending into the hub and a flexible portion extending further into the hub and in position to be engaged by the occluder. The occluder may include a jaw normally biased into a position to press the flexible section of the cannula into engagement with a surface on the hub. The occluder and the hub may include inter-engaging cams configured to move a jaw on the occluder radially outwardly from the cannula when the occluder is moved in a downstream direction. The occluder is preferably movable between a first position in which it pinches the cannula closed and a second position in which the pinching surfaces are separated sufficiently to allow fluid to flow through the cannula.  
           [0013]    Another object of the present invention is to provide a method of controlling fluid flow through a catheter to prevent fluid from flowing out of a patient when a medical device is disconnected from the catheter. In one embodiment, the method comprises the steps of: connecting a medical device to an upstream end of a catheter hub while moving an occluder into an open position in which it does not occlude flow through the catheter, the occluder being normally biased into a closed position wherein it prevents flow through the catheter; and disconnecting the medical device from the catheter allowing the occluder to move into its normally closed position, thereby automatically preventing fluid flow out of a patient when the medical device is withdrawn.  
           [0014]    In another embodiment, a method of preventing fluid flow out of a patient when a medical device is withdrawn from a catheter connected to a patient may comprise the steps of: providing a tubular catheter hub having one end adapted to receive a medical device and having a catheter cannula attached to the second end; and providing an occluder slidably mounted on the hub; and normally biasing the occluder into a position in which it pinches the cannula so as to prevent fluid flow through the cannula. The method of the present embodiment further comprises configuring the occluder in the hub so that when a medical device is connected to the first end of the hub, the occluder is moved into an open position in which fluid flow is allowed through the cannula. According to this embodiment, the occluder will automatically move to a closed position when the medical device is withdrawn from the hub.  
           [0015]    For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.  
           [0016]    All of these embodiments are intended to be within the scope of the present invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    Having thus summarized the general nature of the invention and its essential features and advantages, certain preferred embodiments and modifications thereof will become apparent to those skilled in the art from the detailed description herein having reference to the figures that follow, of which:  
         [0018]    [0018]FIG. 1 is a side view of a catheter shut-off valve having features and advantages of the present invention shown in the closed position;  
         [0019]    [0019]FIG. 2 is a side view of the catheter shut-off valve of FIG. 1 shown in the open position, and having a medical device attached;  
         [0020]    [0020]FIG. 3 is a top view of the catheter shut-off valve of FIG. 1;  
         [0021]    [0021]FIG. 4 is a side section view of the catheter shut-off valve taken along line  4 - 4  of FIG. 3;  
         [0022]    [0022]FIG. 5 is a catheter hub member of the catheter shut-off valve of FIG. 1;  
         [0023]    [0023]FIG. 6 is a cross-sectional view of the catheter hub member on line  6 - 6  of FIG. 5;  
         [0024]    [0024]FIG. 7 is a cross-sectional view of the catheter hub member on line  7 - 7  of FIG. 5;  
         [0025]    [0025]FIG. 8 is an alternative embodiment of the catheter hub member of the catheter shut-off valve of FIG. 1;  
         [0026]    [0026]FIG. 9 is a cross-sectional view of the catheter hub member on line  9 - 9  of FIG. 8;  
         [0027]    [0027]FIG. 10 is a side view of the occluder of the catheter shut-off valve of FIG. 1;  
         [0028]    [0028]FIG. 11 a  is a front end view of the occluder of FIG. 10;  
         [0029]    [0029]FIG. 11 b  is a front end view of an alternative embodiment of the occluder of FIG. 10;  
         [0030]    [0030]FIG. 12 a  is a is a rear end view of the occluder of FIG. 10;  
         [0031]    [0031]FIG. 12 b  is a is a rear end view of an alternative embodiment of the occluder of FIG. 10;  
         [0032]    [0032]FIG. 13 is a side view of an alternative embodiment of a catheter shut-off valve having features and advantages of the present invention shown in the closed position;  
         [0033]    [0033]FIG. 14 is a top view of the catheter shut-off valve of FIG. 13;  
         [0034]    [0034]FIG. 15 is a side cutaway view of the catheter shut-off valve of FIG. 13, shown in the closed position;  
         [0035]    [0035]FIG. 16 is a side cutaway view of the catheter shut-off valve of FIG. 13, shown in an open position;  
         [0036]    [0036]FIG. 17 is a cross section of another embodiment of the invention employing a threaded coupling for receiving a flange on a catheter connected to a patient; and  
         [0037]    FIGS.  18 - 22  illustrate various alternative forms of resilient elements for urging clamp jaws into a closed position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0038]    [0038]FIGS. 1 and 2 show a catheter shut-off device or valve  20  having features and advantages of the present invention. The valve  20  preferably has two main components; an occluder or clamp  30 , and a tubular catheter hub  50 . The catheter hub  50  preferably has a flexible, resilient cannula  40  disposed on its end  52 , which is downstream with respect to fluid flow into a patient. An interface  56  suitable for receiving a medical device  100  is at the hub rear or upstream end  60 . A pair of circumferentially spaced cams  34  extend outwardly from the downstream end of the hub  50 . The occluder  30  is disposed such that it is co-axial with the catheter hub  50  and is free to move linearly along the shared axis relative to the catheter hub  50 . The occluder  30  preferably has opposing jaws  61   a  and  61   b  through which the cannula  40  extends. The jaw members  61   a  and  61   b  are biased toward a closed or occluded position in which they “pinch” the soft tubing of the cannula  40 , thereby closing the valve.  
         [0039]    The outer member or occluder  30  and catheter hub  50  are preferably made of molded polycarbonate or alternatively from any other material suitable for use in medical applications, and capable of providing the features and advantages of the present invention.  
         [0040]    FIGS.  1 - 4  show the occluder  30  as it is preferably disposed relative to the catheter hub  50 . The cannula  40  attached to the catheter hub  50  extends forward through the space between the jaws  61   a  and  61   b , thus placing the occluder  30  and cannula  40  in an operative relationship. The outer member  30  has a pair of cams  54  which mate with the cams  34 . The catheter hub  50  and the occluder  30  are disposed relative to one another such that when a medical device  100  is attached to the interface  56  of the hub  50 , the occluder  30  is pushed forward relative to the catheter hub  50  such that the cam surfaces  34  and  54  engage, thus causing the jaws  61   a  and  61   b  to separate, releasing the cannula  40  and allowing fluid to flow bi-directionally through the catheter  40 . This position, with the jaw members  61   a  and  61   b  separated (shown in FIG. 2), is referred to herein as the open position. When the medical device  100  is removed from the interface  56  of the hub  50 , the bias of the clamping arms  62   a  and  62   b  causes the jaw members  61   a  and  61   b  to pinch the cannula  40 , thus closing the valve  20 . This position, shown in FIGS. 1 and 3 a , is referred to herein as the closed position.  
         [0041]    One embodiment of a hub  50  having features and advantages of the present invention is shown in FIGS.  4 - 7 . The hub  50  of this embodiment preferably comprises a substantially tubular member having a cam  54  near its front end  52 , a central section  55 , and an interface section  56  near its rear end  60 . Alternatively, the cam section  54  may be advantageously located at other points along the length of the catheter hub  50  such that features and advantages of the present invention are realized.  
         [0042]    As shown in FIG. 4, the hub  50  has an internal passage  82  to provide fluid communication between a medical device ( 100  FIG. 2) attached at the interface  56  and the cannula attached at the downstream end  52  of the hub  52 . The cannula  40  is preferably retained within the hub  50  such that fluid communication is facilitated between the interface section  56  of the hub  50  and the cannula  40 . The cannula  40  may be secured to the catheter hub using any suitable method known to those skilled in the art. For example, the cannula  40  may be glued, sonic welded, or frictionally retained on or within the hub  50 .  
         [0043]    As shown in FIG. 5, the cam section  53  of the catheter hub  50  preferably comprises a cam surface  54  in the form of a section with sides sloping radially and in the downstream direction. The cam surface is preferably annular, as seen in FIG. 6, but need only extend circumferentially sufficiently to engage the mating cam on the occluder  30 . The height ‘h’  92  of the cam section is preferably at least as great as the amount of separation of the jaw members ( 61   a ,  61   b  FIG. 2) required in order to release the cannula  40  (FIG. 2), thereby opening the valve  20 . As shown in FIG. 6, the cam surface may extend about the circumference of the catheter hub  50 .  
         [0044]    Alternatively, as shown in FIGS. 8 &amp; 9, the cam surface  54  may comprise two separate sloped sections  54   a  and  54   b  extending radially outward from the surface of the hub  50 .  
         [0045]    The central section  55  of the catheter hub  50  includes guides  58  which extend outward from the tubular portion of the hub. The guides  58  are disposed such that they interact with the axial guide  82  of the occluder  30  (FIG. 2) in such a way as to restrict rotation of the catheter hub  50  and occluder  30  relative to one another. Additionally, the guides  58  may be used to guide the relative linear motion of the two parts  30  and  50  in order to operate the valve  20  (FIG. 2) in accordance with the present invention.  
         [0046]    In the embodiment shown in FIG. 5, the interface section  56  near the rear  60  of the catheter hub  50  is preferably adapted such that a device  100  (FIG. 2) may threadably engage the catheter hub, thus securing the device  100  to the catheter hub  50  and placing the device in fluid communication with the catheter hub  50 . The interface  56  preferably comprises a pair of lugs  90  which may threadably engage the medical device  100  such as an ISO standard syringe. The interface  56  may be a Luer lock fitting of the type set forth in American National Standard Institute No. ANSI/HIM MD70.1-983 which is incorporated herein by reference.  
         [0047]    FIGS.  10 - 12   b  show the occluder  30  separated from the hub and having features and advantages of the present invention. The occluder  30  has a clamping section  32  near its forwardmost end  31 , a cam section  36  rearward therefrom, and an attachment section  38  at the rearmost end of the occluder  30 . As shown in FIGS. 11 a and 12 a , the occluder  30  preferably comprises a substantially circular cross section with a gap or space  86  formed by edges  84 . Alternatively, the occluder  30  may comprise a substantially rectangular cross section as shown in FIGS. 11 b  and  12   b . As will be recognized by those skilled in the art, other cross-sectional shapes may be used without departing from the spirit of the present invention.  
         [0048]    The cam section  36  of the occluder  30  is preferably characterized by cam surfaces  34  on the inside of the top and bottom clamping arms  62   a  and  62   b  respectively. The cam surfaces  34  are preferably sized and shaped such that they may cause the jaws  61   a  and  61   b  to separate when a medical device is attached to the interface  36  section of the catheter hub  50 , thus opening the valve  20  as described above with reference to FIGS. 1 and 2.  
         [0049]    The clamping section  32  of the present embodiment, as best seen in FIG. 10 preferably comprises a pair of jaws  61   a  and  61   b  attached to clamping arms  62   a  and  62   b  which are biased towards a closed position. The bias is preferably caused by the resilience of the material. Additionally, an O-ring  70  may be disposed in grooves  72  on the clamping arms  62   a  and  62   b . The O-ring  70  is preferably made of a substantially resilient material such as rubber. The bias created by the clamping arms  62   a  and  62   b , or the combination of the O-ring  70  and clamping arms  62   a  and  62   b , is preferably sufficient to provide a clamping force to pinch closed the soft cannula  40  extending from the front  52  of the catheter hub  50  (FIG. 2).  
         [0050]    The clamping edges  74   a  and  74   b  of the jaw members  61   a  and  61   b  preferably comprise shapes such that they may advantageously close a catheter cannula  40  as described herein. In one preferred embodiment, as best seen in FIG. 4, the clamping edge  74   a  of the jaw  61   a  preferably has a substantially convex arch shape. The clamping edge  74   b  of the jaw  61   b  has a corresponding concave arch shape when seen in end views (FIGS. 11 a  and  11   b ), and a substantially convex shape when seen in side view (FIG. 10). The arch-shaped clamping surfaces  74   a  and  74   b  are believed to provide optimal closure of the cannula  40 . The clamping surfaces may alternatively be substantially flat (as shown in FIG. 2) or otherwise shaped such that they will pinch the cannula  40  closed as shown and described herein.  
         [0051]    As shown in FIG. 10, the occluder  30  preferably comprises an attachment section  38  having the gap  86  sized such that the catheter hub  50  (FIG. 5) may “snap” into the occluder  30  in order to place the two parts  30  and  50  in the position shown in FIG. 1.  
         [0052]    As shown in FIG. 10 the occluder  30  includes a guide  82  which extends axially toward the clamping section  32  of the occluder  30 . If desired, the guide  82  may be sized and disposed such that it may interact with guide  58  on the catheter hub  50  (FIG. 1) in order to restrain the catheter hub  50  and the occluder  30  from rotation relative to one another. As best seen in FIG. 6 b , the end of the attachment section  38  preferably comprises a substantially circular opening into which the catheter hub  50  is positioned after assembly.  
         [0053]    FIGS.  13 - 17  show an alternative embodiment of a catheter shut-off valve  120  having features and advantages of the present invention. This embodiment generally comprises an occluder  130  and a hub  150  preferably disposed such that they may be moved linearly relative to one another in order to allow interactions causing the valve  120  to be opened and closed as described below. The occluder  130 , in the closed position in FIG. 13, includes a jaw  138  and pinches a section of soft tubing  176  disposed therein against an internal surface of the hub  150 . When a medical device  100  (FIG. 16) is attached to the hub member  150 , the occluder  130  is pushed forward relative to the hub  150 , causing the section of tubing  176  to be released, thereby opening the valve  120 .  
         [0054]    Referring to FIGS. 13 and 14, the occluder  130  is preferably characterized by a ring section  132  at its rearmost end  131  and an elongate flexible arm  136  extending forward from the ring section  132 . The ring section  132  preferably comprises a substantially circular cross-sectional shape that is open at its lower portion to enable it to be clipped on the hub  13 . However, it may comprise any cross sectional shape such that it may interact with the hub member  150  as described herein. The arm  136  which extends forward from the ring section  164  has a cam surface  134  near its downstream end  142 . At that end, the arm  136  extends inward towards the hub  150  forming the jaw  138  terminating in a clamping surface  144 . The clamping arm preferably comprises a groove  172  formed in the outside surface  146  of the arm  136  near the cam surface  134 . The groove  172  is adapted to receive and retain a portion of an O-ring  170  which urges the arm towards the hub  150 .  
         [0055]    The clamping surface  144  of the jaw  138  preferably has a substantially convex arch-shape when viewed from the side (as seen best in FIG. 14). Alternatively, the clamping surface  144  may comprise a more “pointed” shape as shown in FIG. 13. The clamping surface  144  may alternatively comprise a substantially flat, concave, or other shape such that functions as described herein.  
         [0056]    Referring to FIGS.  13 - 15 , a hub  150  having features and advantages of the present invention preferably has an interface section  162  at its rear end  160 , a substantially cylindrical rear section  164 , a central section  166  of slightly smaller diameter and having a cam surface  154 , and a front section  168 . A catheter cannula  140  extends downstream from the front  169  of the hub  150 . The catheter cannula  140  may be either a substantially rigid tube, a substantially flexible tube, or any other cannula known to those skilled in the art to be suitable for use in medical transmission of fluids. The catheter cannula  140  is bonded within the internal space  180  of the hub  150 . A section of substantially flexible tubing  176  is disposed within the hub  150  and joins the catheter cannula  140  at a junction  178 .  
         [0057]    At the rear of the hub  160 , the internal space  180  defines an inlet space  184 . The upstream portion of the tubing  176  is bonded to the internal passage of the hub  150 . Alternatively, the catheter cannula  140  may comprise a soft tube which extends through the hub  150 .  
         [0058]    The hub interface section  162  includes lugs  190  which allow a medical device such as a syringe to be spreadably attached thereto. The rear section  164  has an internal lumen  184  open to the passage  160  of the interface section. At the junction between the rear section  164  and the central section  166 , there is a guide  158  on the outer surface of the hub and positioned to restrain relative rotation between the two members  130  and  150  about their shared longitudinal axis.  
         [0059]    The central section  166  of the hub  150  has a portion of a groove  172  in the outer surface  182  that together with the groove  172  in the arm  136  receives the O-ring  170 . The clamp central section  166  has a cam surface  154  which extends out from the outer surface of the hub  150 . The cam surface  154  is preferably sized and adapted such that it may interact with a similar cam surface  134  on the occluder  130 .  
         [0060]    As best seen in FIGS. 14 and 15, the hub has a hole  198  in its top surface near the forward end  169  sized such that the jaw section  138  of the occluder  130  may extend through the hole  198  and compress the exposed portion of tubing  176 . An interior surface  196  is preferably substantially flat, and effectively acts as a clamping surface against which the section of tubing  176  will be pinched by the clamping surface  144  of jaw  138  when the valve  120  is in its closed position. Alternatively, the bottom  196  of the hole  198  may comprise a convex or concave arch-shape to provide a substantial seal when pinching the tubing  176 .  
         [0061]    FIGS.  15 - 17  illustrate the operation of the valve  120  of the present embodiment. With the medical device  100  removed from the interface portion  162  of the hub member  150  (FIG. 15), the valve  120  is in a closed position. While in the closed position, the bias of the clamping arm  136  and O-ring  170  (if present) causes the clamping surface  144  of the jaw section  138  to press against on the exposed soft tubing section  176  such that fluid flow is fully occluded. As a medical device  100  is attached, as shown in FIG. 16, the occluder  130  is forced forwards in the direction of the arrow  210 , and causing the clamping arm jaw  138  to be flexed outwards by the engaging cam surfaces  134  and  154 . As the jaw  138  moves outwards, the pressure of the clamping surface  144  on the soft tubing section  176  is released, allowing fluid communication between the medical device  100  and the cannula  140 . This second position, shown in FIG. 16 is referred to as the open position.  
         [0062]    Upon removal of the medical device  100  from the interface section  162 , the bias of the clamp arm  136  and the O-ring  170  moves the arm once more toward the closed position and causes the cam section  134  to slide inwardly on the cam surface  154 . The horizontal component of this force causes the occluder  130  to be moved rearward in the opposite direction of the arrow  210  relative to the hub member  150 . The guide  158  cooperates with the arm  136  to guide movement of the clamp  130 . As the medical device  100  is removed, the occluder  130  returns to its closed position (FIG. 14) with the clamping surface  144  again pinching the soft tubing section  176 , thus stopping fluid flow through the hub  150 .  
         [0063]    Referring to FIG. 17, another form of the shutoff device or valve  220  of the invention is illustrated. It employs the basic components of the previously described arrangements, including an interior tubular hub  250  and an outer clamp or occluder  230 . These components are mounted for slideable relative axial movement to the closed and open positions by a resilient component  270  and interengaging cams. The tubular hub, however, differs from the foregoing arrangements by including an elongated downstream portion on which is rotatably mounted an internally threaded coupling  260 . As may be seen, the downstream portion of the hub  250  has an annular groove  251  in its outer surface spaced rearwardly from the downstream end of the hub. The coupling  260  has on its upstream end an inwardly extending annular rib  261  which fits within the groove  251 . The threaded interior of the coupling  260  is spaced outwardly from the exterior of the hub, thus creating an annular space  280  for receiving the end of a catheter, schematically indicated at  200 . That is, the catheter hub can be inserted into the space  280  and the coupling rotated so as to draw the catheter hub into tight engagement with the hub  270 . The catheter interior is of course in communication with the tubing positioned within the clamping device  220 .  
         [0064]    FIGS.  18 - 22  illustrate arrangements with alternate elements for urging the jaws closed. FIG. 18 illustrates a resilient element  370  that holds clamp arms  362  in the closed position. An outwardly extending projection or button  362   a  is formed on each of the clamp arms  362 . Opposite ends  370   a  of the resilient element  370  are snapped on to the buttons  362   a  while a central section  370   b  extends between the ends  370   a . The resilient element  370  is configured so that the element provides a continual biasing force on the clamp arms  362  into the closed position. Also shown are the interengaging cams  334  and  354  that cause the clamp arm  362  to be forced radially outwardly when a medical device is connected to the upstream end of the hub  350 .  
         [0065]    [0065]FIG. 19 illustrates a different form of resilient element  470  having generally flat end portions  470   a  that snap onto buttons  462   a  formed on the clamp arms  462 . These end portions extend generally in an axial direction and include generally U-shaped forward portions  470   c  that are joined by a central section  470   b  that is curved to conform to and surround a portion of the hub  450 . The U-shaped portions  470   c  in effect form springs that urge the ends  470   a  to bias the clamp arms  462  into the closed position.  
         [0066]    [0066]FIG. 20 illustrates yet another embodiment for urging clamp arms  562  into closed position. As can be seen, the outer surface of the downstream end of each clamp arm  562  is formed with an outwardly opening slot  562   a . A biasing element  570  straddles the hub  550  and the clamp  530 . The element  570  includes generally flat ends  570   a , each of which fits into a respective one of the slots  562   a  in the clamp arms  562 . The ends are joined by a flat central section  570   b . The biasing element  570  is configured so that the clamp arms  562  are held in the closed position, but can flex to permit the clamp arms to be moved to the open position as relative axial movement of the hub and clamp are caused by the interengaging cams, as previously described.  
         [0067]    [0067]FIG. 21 illustrates yet another form of biasing element  670  which has a generally flat partial disk-shape that has ends  670   a , each of which snaps on to a button  662   a  formed on the downstream end of each clamp arm  662 . The element  670  is biased to hold the arms into a closed position but is sufficiently flexible to permit the arms to be moved outwardly.  
         [0068]    [0068]FIG. 22 illustrates yet another arrangement for biasing clamp arms  762  into a closed position. As can be seen, an element  770  has a rod-like cross section formed into a wide U-shape which straddles the hub  750  and the clamp arms  762 . The outer surface of the downstream end of the clamp arm  762  is formed with a socket or hole  762   a , and each end  770   a  of the biasing element  770  is formed with an inwardly extending projection  770   c  which fits within the socket or hole  762   a  so as to retain the biasing element  770  on the clamp arms. The biasing element  770  is configured such that it normally holds the clamp arm in a closed position, but will flex to allow the clamp arms to be moved radially outwardly into open position.  
         [0069]    Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.