Abstract:
An access device places a medical article within a body space of a patient. The device has a needle section that includes an elongated body and a needle hub. The device further includes a dilator portion that has a dilator and a dilator hub. The dilator is coaxially disposed and slideable over the elongated body of the needle section. The device further includes a sheath section that has a sheath and a sheath hub. The sheath is coaxially disposed and slideable over the dilator. The device further includes a first locking mechanism operably disposed between the needle hub and the dilator hub to inhibit at least unintentional axial movement between the needle section and the dilator portion and a second locking mechanism operably disposed between the dilator hub and the sheath hub to inhibit at least unintentional axial movement between the dilator portion and the sheath section.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/019,598, filed on Jan. 24, 2008 and entitled “ACCESS DEVICE,” which claims the benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 60/886,443, filed Jan. 24, 2007, the entire contents of each hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention is generally directed to access devices for introducing and delivering a catheter cannula or sheath into an artery, vein, vessel, body cavity, or drainage site. 
         [0004]    2. Description of the Related Art 
         [0005]    A preferred non-surgical method for inserting a catheter or vascular sheath into a blood vessel involves the use of the Seldinger technique, which includes an access needle that is inserted into a patient&#39;s blood vessel. A guidewire is inserted through the needle and into the vessel. The needle is removed, and a dilator and sheath combination are then inserted over the guidewire. The dilator and sheath combination is then inserted a short distance through the tissue into the vessel, after which the dilator and guidewire are removed and discarded. The catheter may then be inserted through the sheath into the vessel to a desired location. 
         [0006]    A number of vascular access devices are known. U.S. Pat. Nos. 4,241,019, 4,289,450, 4,756,230, 4,978,334, 5,124,544, 5,424,410, 5,312,355, 5,212,052, 5,558,132, 5,885,217, 6,120,460, 6,179,823, and 6,210,332 disclose examples of such devices. None of these devices, however, has the ease and safety of use that physicians and other healthcare providers would prefer and, thus, there is a need for an easier-to-use and safer vascular access device, especially one that would clearly indicate when a blood vessel has been punctured. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention involves several features for an access device useful for the delivery of a catheter or sheath into a space within a patient&#39;s body, such as, for example, a blood vessel or drainage site. Without limiting the scope of this invention, its more prominent features will be discussed briefly. After considering this discussion, and particularly after reading the Detailed Description of the Preferred Embodiments section below in combination with this section, one will understand how the features and aspects of this invention provide several advantages over prior access devices. 
         [0008]    One aspect of the present invention is an access device for placing a medical article within a body space. The device has a needle section that includes an elongated body and a needle hub. The elongated body has distal and proximal ends. The distal end is configured for insertion into a patient&#39;s body. The proximal end is coupled with the needle hub. The device further includes a dilator portion including a dilator and a dilator hub. The dilator is coaxially disposed and slideable over the elongated body of the needle section with the dilator hub being disposed distal of the needle hub. The device further includes a sheath section that has a sheath and a sheath hub. The sheath is coaxially disposed and slideable over the dilator with the sheath hub being disposed distal of the dilator hub. The device further includes a first locking mechanism operably disposed between the needle hub and the dilator hub to inhibit at least unintentional axial movement between the needle section and the dilator portion when the first locking mechanism is engaged and a second locking mechanism operably disposed between the dilator hub and the sheath hub to inhibit at least unintentional axial movement between the dilator portion and the sheath section when the second locking mechanism is engaged. Each of said first and second locking mechanisms is configured to be engaged by moving the respective hubs in a non-axial manner relative to each other. The first locking mechanism is configured to move in a manner different from the manner in which the second locking mechanism is engaged. 
         [0009]    Another aspect of the invention is an access device for placing a medical article within a body space. The device includes a needle section including an elongated needle body with a sharp distal tip and a needle hub from which the needle body extends. The device further includes a dilator portion that includes a dilator and a dilator hub. The dilator is coaxially disposed and slideable over the needle body with the dilator hub being disposed distal of the needle hub. The device further includes a sheath section that includes a sheath and a sheath hub. The sheath is coaxially disposed and slideable over the dilator with the sheath hub being disposed distal of the dilator hub. The device further includes a locking mechanism disposed within the dilator and selectively operating between the needle body and the dilator. The locking mechanism is configured to arrest axial movement of the needle body at least in the distal direction once the distal tip of the needle body is drawn into the dilator portion to sheath the distal tip. 
         [0010]    Yet another aspect of the invention is an access device for placing a medical article within a body space. The device includes a dilator hub that has a passageway configured to receive an elongated needle. The needle has at least one side receptacle. The device further includes one or more fingers or tangs disposed in the dilator hub and configured to engage with the at least one side receptacle at least when the needle is retracted through the passageway. 
         [0011]    Additionally, a releasable interlock can be provided in some embodiments to inhibit relative rotational movement between the needle section and the dilator section, at least when the needle is inserted into a patient. By inhibiting such relative rotational movement, communicating side openings in the needle and the dilator can be held in alignment to provide a simplified passageway through which the blood or fluid may flow. Thus, when the needle enters a blood vessel or drainage site in the patient, blood or other body fluid quickly flows into the passageway. The resulting blood or fluid flash is visible through the sheath section (or catheter) to indicate that the needle tip has entered the vessel or drainage site. 
         [0012]    For example, but without limitation, the dilator portion or section can comprise, in some embodiments, a dilator hub and dilator having one or more side openings. The dilator hub may have a luer connection and a releasable locking mechanism. The releasable locking mechanism can be configured to releasably engage and secure the dilator section to another part, such as the needle hub. When the needle hub and the dilator hub are releasably locked to prevent rotation therebetween, one or more of the side openings in the dilator are aligned with one or more side openings in the needle. The locking mechanism can also be configured to inhibit unintentional relative axial movement between the needle and the dilator. 
         [0013]    The sheath section preferably, but not necessarily, includes a sheath and sheath hub. The sheath may be made partially or completely from a clear, translucent, semi-opaque, or transparent material. Such transparent, translucent, semi-opaque and clear materials allow a clinician the ability to see when blood or other body fluids flows into the needle, through the needle side opening(s), through the side dilator opening(s), and into the viewing space between the dilator and sheath. 
         [0014]    These and other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments, which refers to the attached figures. The invention is not limited, however, to the particular embodiments that are disclosed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    These and other features, aspects, and advantages of the invention disclosed herein are described below with reference to the drawings of preferred embodiments, which are intended to illustrate and not to limit the invention. 
           [0016]      FIG. 1A  is a perspective view of a preferred embodiment of an access device configured in accordance with the present invention. 
           [0017]      FIG. 1B  is an enlarged plan view of a needle hub, a dilator hub, and a sheath hub of the access device illustrated in  FIG. 1A , shown in an assembled state. 
           [0018]      FIG. 1C  is a perspective view of the assembly of the needle hub, dilator hub and sheath hub illustrated in  FIG. 1B . 
           [0019]      FIG. 2A  is side view of a needle section of the embodiment depicted in  FIG. 1A . 
           [0020]      FIG. 2B  is a cross-sectional view of the needle section of the embodiment depicted in  FIG. 2A  taken along line A-A. 
           [0021]      FIG. 2C  is an enlarged plan view of the needle hub of the needle section of  FIG. 2B . 
           [0022]      FIG. 3A  is a side view of the dilator portion of the embodiment depicted in  FIG. 1A . 
           [0023]      FIG. 3B  is a proximal end view of the dilator portion of  FIG. 3A . 
           [0024]      FIG. 3C  is a cross-sectional view of the dilator portion of the embodiment depicted in  FIG. 3A , taken along line B-B. 
           [0025]      FIG. 3D  is an enlarged perspective view of the dilator hub of the dilator portion of  FIG. 3A . 
           [0026]      FIG. 4A  is a side view of a sheath section of the embodiment from  FIG. 1A . 
           [0027]      FIG. 4B  is a proximal end view of the sheath section of  FIG. 4A . 
           [0028]      FIG. 4C  is an enlarged perspective view of the sheath hub of the sheath section of  FIG. 4A . 
           [0029]      FIG. 5  is a side view of the access device of  FIG. 1A . 
           [0030]      FIG. 6  is an enlarged cross-sectional view of a portion of the embodiment illustrated in  FIG. 5  which is circled by line C-C. 
           [0031]      FIG. 7A  is a schematic, enlarged cross-sectional view of a portion of the needle within the dilator and illustrates an embodiment of a locking mechanism configured in accordance with one aspect of the present invention. 
           [0032]      FIGS. 7B-7D  illustrate the operational steps of the locking mechanism of  FIG. 7A  when arresting relative axial movement between the needle and the dilator. 
           [0033]      FIG. 8A  is a similar cross-sectional view of a portion of a locking mechanism which is configured in accordance with another preferred embodiment of present invention.  FIG. 8A  illustrates the locking mechanism in an unlocked state. 
           [0034]      FIG. 8B  illustrates the locking mechanism of  FIG. 8A  in a locked state. 
           [0035]      FIG. 9A  is a schematic, enlarged cross-sectional view of a locking mechanism configured in accordance with an additional embodiment of the present invention.  FIG. 9A  illustrates the locking mechanism in an unlocked state. 
           [0036]      FIG. 9B  illustrates the locking mechanism of  FIG. 9A  in a locked state. 
           [0037]      FIG. 10A  is a schematic, enlarged cross-sectional view of a locking mechanism configured in accordance with a further embodiment of the present invention.  FIG. 10A  illustrates the locking mechanism in an unlocked state. 
           [0038]      FIG. 10B  is a cross-sectional view of the locking mechanism of  FIG. 10A  taken along lines  10 B- 10 B. 
           [0039]      FIG. 11  is an enlarged exploded view of a dilator hub and locking plate assembly configured in accordance with an additional preferred embodiment of the present invention. 
           [0040]      FIG. 12A  is an enlarged view of an embodiment of the locking plate that can be used with the dilator hub shown in  FIG. 11 . 
           [0041]      FIG. 12B  is an enlarged view of another embodiment of the locking plate that can be used with the dilator hub shown in  FIG. 11 . 
           [0042]      FIG. 12C  is an enlarged view of an additional embodiment of the locking plate that can be used with the dilator hub shown in  FIG. 11 . 
           [0043]      FIGS. 13A-13D  are enlarged views of perimeter shapes that the locking plate can have in accordance with additional embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0044]    The present disclosure provides an access device for the delivery of a catheter or sheath to a blood vessel or drainage site.  FIG. 1  illustrates an access device  102  that is configured to be inserted into a blood vessel in accordance with a preferred embodiment of the present invention. While the access device is described below in this context (i.e., for vascular access), the access device also can be used to access and place a catheter or sheath into other locations within a patient&#39;s body (e.g., for draining an abscess) and for other purposes. 
         [0045]      FIG. 1A  is a perspective view of a preferred embodiment of an access device  102 . The access device  102  comprises a needle section  20 , a dilator portion  28 , a sheath section (e.g., catheter or cannula)  58 , and a guidewire  120 . In preferred embodiments, the dilator portion  28  is coaxially mounted on the needle section  20 , and the sheath section  58  is coaxially mounted on the dilator portion  28 . The needle section  20  comprises a needle  22  and a needle hub  21 . The needle hub  21  is disposed on a proximal end of the needle  22 . The dilator portion  28  comprises a dilator  30  and a dilator hub  32 . The dilator hub  32  is disposed on the proximal end of the dilator  30 . The sheath section  58  comprises a sheath  54  and a sheath hub  53 . The sheath hub  53  is disposed on the proximal end of the sheath  54 . 
         [0046]      FIG. 1B  is an enlarged plan view of the needle hub  21 , the dilator hub  32 , and the sheath hub  53  of the access device illustrated in  FIG. 1A , shown in an assembled state. The needle hub  21 , the dilator hub  32 , and the sheath hub  53  include structures that releasably interlock the hubs so as to provide a structural and fluid connection between the needle section  20 , the dilator portion  28 , and the sheath section  58 . 
         [0047]      FIG. 1C  is a perspective view of the assembly of the needle hub  21 , dilator hub  32  and sheath hub  53  illustrated in  FIG. 1B . With reference to  FIGS. 1A and 1B , the needle section  20 , dilator portion  28 , and sheath section  58  are interlocked at the proximal end  110  of the access device  102 . In some embodiments, the releasable interlock between the needle section  20 , dilator portion  28 , and sheath section  58  is a tandem interlock where the dilator portion  28  is locked to the needle section  20  at interface  101  and the sheath section  58  is locked to the dilator portion  28  at interface  103 . In additional to a structural connection, the interlocks provide a fluidic connection through the access device  102 . 
         [0048]    Preferably, the needle section  20  locks to the dilator portion  28  via a lock mechanism  26 . The lock mechanism  26  may comprise an engaging mechanism such as hinged clips  27  with actuator sides  29 . The hinged clips  27  may releasably engage and secure to corresponding catches  25  on the dilator portion  28 . In some embodiments, the clip sides  29  engage and secure the dilator portion  28  by clipping to the outer lip of a luer connection  33  on the dilator portion  28 . Although hinged clips  27  are shown, the lock member  26  may comprise any suitable engaging mechanism known in the art. In the illustrated embodiment, as best seen in  FIG. 3B , the portions of the outer lip onto which the hinge clips  27  engage are flats to inhibit rotation of the needle hub  21  relative to the dilator hub  32  after a certain degree of relative rotation (e.g., 180 degrees) between the needle hub  21  and the dilator hub  32 . 
         [0049]    Similarly, the sheath section  58  is secured to the dilator portion  28  through a lock member  59 . The sheath section  58  may, preferably, comprise a twist lock member  59  so that the user may releasably engage and secure the dilator portion  28  to the sheath section  58 . In some preferred embodiments, the dilator portion  28  comprises teeth or prongs that are configured to mate or attach to corresponding areas on the sheath section  58 . Preferably, the needle  20 , dilator  28  and sheath  58  are releasably locked so that a physician or user may remove sections or portions of the access device as needed for treatment. 
         [0050]      FIG. 2A  is side view of the needle section  20  of the embodiment depicted in  FIG. 1A .  FIG. 2B  is a cross-sectional view of the needle section  20  depicted in  FIG. 2A  taken along line A-A. As shown in both  FIGS. 2A and 2B , the needle section  20  has a needle  22 , distal portion  106 , and proximal portion  24 . Preferably, the proximal portion  24  has the needle hub  21  and the lock member  26 . In addition, the needle  22  may have a bevel tip  108  disposed on the distal portion  106 . The needle  22  may further comprise one or more side openings  34 . 
         [0051]      FIG. 2C  is an enlarged plan view of the needle hub  21  of the needle section  20  of  FIG. 2B . As most clearly shown in  FIG. 2C , the needle hub  21  may also have a luer connection  35  at the proximal portion  24  of the needle  20 . This allows the physician or healthcare provider, for example, to introduce a guidewire  120  through the hollow portion of the luer connection  35 , through the needle  22 , and into a punctured vessel. Additionally, a physician or healthcare provider may also attach a syringe to the luer connection  35  to perform other procedures as desired. 
         [0052]    As discussed above, in preferred embodiments, the needle hub  21  comprises the lock member  26 . The lock member  26  may be configured to lock or secure another part such as, for example, the dilator portion  28  or the sheath section  58 , to the needle section  20 . As shown most clearly in  FIG. 2C , the lock member  26  can comprise an engaging mechanism such as a pair of hinged clips  27 , although other types of locking mechanisms comprising tabs and/or slots can also be used. Preferably, the clip sides  29  of the hinged clips  27  can engage a lipped surface such as the outer lip of a luer connection  33 , shown in  FIG. 1A . Once engaged, the clip sides  29  prevent the locked part from undesired slipping or releasing. In certain embodiments, the clips  27  are hinged to provide a bias towards the center of the needle hub  21 . Preferably, the bias prevents the secured part from slipping or disengaging from the hinged clips  27 . More preferably, the bias of the hinged clips  27  can be overcome by simultaneously applying pressure on the sides  29  of the clips  27  to release, for example, the luer connection  33  from the needle hub  21 . To apply the appropriate releasing pressure, a physician or healthcare provider may, for example, place an index finger and thumb on the sides  29  of the hinged clips  27  and apply squeezing pressure to overcome the hinge bias. The hinged clips  27  will, preferably, release only when sufficient releasing pressure is applied to both clip sides  29 . 
         [0053]    As shown most clearly in  FIG. 2A , the needle proximal portion  24  may have color coding, words, or other indicia, such as a pivot or notch, to indicate to the operator the position of the bevel tip  108  relative to the dilator  28  or the sheath section  58 . For example, the arrow embedded into the needle hub  21  indicates the bevel up position of the needle  22  and may further indicate to the healthcare provider the proper way to use the device. Also, there may be a mechanical fit between the dilator  28  and the needle  22  so that the physician or healthcare provider would sense by feel or sound (e.g., by a click) when the needle  22  has been rotated to change the position of the bevel tip  108 . 
         [0054]      FIG. 3A  is a side view of the dilator portion  28  of the embodiment depicted in  FIG. 1A .  FIG. 3B  is a proximal end view of the dilator portion  28  of  FIG. 3A .  FIG. 3C  is a cross-sectional view of the dilator portion  28  of the embodiment depicted in  FIG. 3A , taken along line B-B. As shown, the dilator portion  28  may comprise the dilator  30  and the dilator hub  32 . The dilator  30  may further comprise one or more side openings  111 . The dilator hub  32  preferably comprises a luer connection  33  with an outer lip  37 . In some embodiments, the outer lip  37  can be configured to engage to the lock member  26  on the needle section  20  illustrated in  FIG. 2C . 
         [0055]    Additionally, the dilator  30  may be coaxially mounted to the needle  22  by slipping a hollow section  113  of the dilator  30  over the needle  22  and releasably securing the dilator hub  32  to the needle hub  21 . Preferably, the proximal end  45  of the dilator hub  32  is configured to mechanically fit and interlock with the needle lock member  26  to inhibit at least some rotational and axial motion. More preferably, the dilator  30  is releasably mounted to the needle  22  so that the dilator  30  can be mounted and released, or vice versa, from a coaxial position relative to the needle  22 . 
         [0056]      FIG. 3D  is an enlarged perspective view of the dilator hub  32  of the dilator portion  28  of  FIG. 3A . As is most clearly illustrated in  FIG. 3D , the dilator hub  32  may further comprise a locking mechanism  39 . The locking mechanism  39  comprises one or more posts, teeth, or prongs projecting from the dilator hub  32 . The locking mechanism  39 , which may be in the form of teeth, can be configured to mate or attach to corresponding receiving areas disposed on another part such as the sheath section  58  or the needle hub  21 . This locking mechanism  39  will be explained in greater detail in the following section. 
         [0057]      FIG. 4A  is a side view of the sheath section  58  of the embodiment from  FIG. 1A .  FIG. 4B  is a proximal end view of the sheath section  58  of  FIG. 4A . In preferred embodiments, the sheath section  58  comprises a sheath  54  and a sheath hub  53 . The sheath  54  may also be made partially or completely from clear, translucent, transparent, or semi-opaque material. The sheath hub  53  may further comprise winged ends  55  and a lock member  59 . 
         [0058]      FIG. 4C  is an enlarged perspective view of the sheath hub  53  of the sheath section  58  of  FIG. 4A . Preferably, the locking member  59  may comprise a locking or attaching structure that mates or engages with a corresponding structure. As most clearly shown in  FIGS. 4B and 4C , the locking member  59  may comprise indentations, bumps, or grooves designed to engage and secure the locking mechanism or teeth  39  on the dilator hub  32  described above with reference to  FIG. 3D . 
         [0059]    The sheath hub  53 , as best seen in  FIGS. 4B and 4C , preferably is designed so that the locking mechanism or teeth  39  of the dilator hub  32  can enter the sheath hub  53  substantially unobstructed. However, in use, once the sheath hub  53  is placed at a desired location over the dilator  30 , the physician or healthcare provider can twist the sheath hub  53  and disengage or engage the locking member  59 . The locking member  59  can be, for example, a protruding bump, dent, etc., that creates a mechanical fit so that the dilator hub  32  and the sheath hub  53  are releasably interlocked. In the illustrated embodiment, the locking member  59  of the sheath hub  53  comprises a pair of axial arranged grooves which extend from a distal side of the sheath hub  53  and terminate at a protruding bump, dent, etc. Preferably, the locked position can be disengaged by twisting the dilator hub  32  relative to the sheath hub  53 . Additionally, the sheath hub may comprise wings  55  or handle structures to allow for easy release and removal of the sheath  54  from other parts of the access device  102 . 
         [0060]    In some applications, the wings  55  are sized to provide the healthcare provider with leverage for breaking apart the sheath hub  53 . For example, the sheath hub  53  may comprise a thin membrane  61  connecting the halves of the sheath hub  53 . The membrane  61  is sized to keep the halves of the sheath hub  53  together until the healthcare provider decides to remove the sheath hub  53  from the access device. The healthcare provider manipulates the wings  55  to break the membrane  61  and separate the sheath hub  53  into removable halves. 
         [0061]      FIG. 5  is a side view of the access device of  FIG. 1A  in which the needle section  20 , dilator portion  28 , and sheath section  58  are interlocked together. In the assembly, as noted above the needle section  20 , dilator portion  28  and sheath section  58  are coaxially disposed about a common longitudinal axis and form a central fluid connection. 
         [0062]      FIG. 6  is an enlarged cross-sectional view of a portion of the embodiment illustrated in  FIG. 5  which is circled by line C-C. As noted above, the needle  22 , preferably, comprises one or more side openings  34  in its side wall. Additionally, the dilator may comprise one or more side openings  111 .  FIG. 6 , however, illustrates the alignment between only one set of corresponding side openings. Other sets of side openings can also be aligned or be misaligned depending upon the relative orientations of the needle and the dilator. 
         [0063]    Preferably the dilator  30  may be coaxially positioned to minimize the annular space  36  between the needle  22  and the dilator  30 . The inner surface  38  of the dilator  30  need not, though it can, lie directly against the outer-surface  40  of the needle  22 . Preferably, the annular interface  36  between the outer-surface  40  of the needle  22  and the inner surface  38  of the dilator  30  is minimized to inhibit the flow of blood or its constituents (or other bodily fluids) into the annular interface  36  between the dilator  30  and needle  22 . Advantageously, this feature minimizes the blood&#39;s exposure to multiple external surfaces and reduces the risk of contamination, infection, and clotting. 
         [0064]    The sheath  54  is made partially or completely from clear, semi-opaque, translucent, or transparent material so that when blood flows into the needle  22 , (1) through the needle side opening  34 , (2) through the dilator side opening  111 , and (3) into an annular space  60  between the dilator  30  and the sheath  54 , the physician or healthcare provider can see the blood. This will indicate to the physician or healthcare provider that the bevel tip  108  of the needle  22  has punctured a blood vessel. 
         [0065]    More preferably, the dilator  30  can be coaxially mounted to the needle  22  such that at least one side opening  34  disposed on the needle  22  is rotationally aligned with at least one side opening  111  on the dilator  30 . In some embodiments, the needle  22  and dilator  30  may (both) have multiple side openings  34 ,  111  where some or all of these side openings  34 ,  111  can be rotationally aligned. Preferably, the needle  22  and dilator  30  maintain rotational alignment so that blood flows substantially unobstructed through the needle side opening  34  and dilator side opening  111 . 
         [0066]    While the side openings  34 ,  111  in the needle  22  and the dilator  30  are aligned in the embodiment illustrated in  FIG. 6 , the side openings alternatively can overlap with each other or can be connected via a conduit. The conduit can be formed between the side openings  111 ,  34  in the dilator and the needle. 
         [0067]    In accordance with another aspect of the present invention, there is provided an interlock or interconnection between the needle  22  and at least one of the dilator  30  or dilator hub  32 . The interlock or interconnection inhibits the bevel tip  108  disposed on the distal portion  106  of the needle  22  from being advanced beyond the distal end of the dilator  30  once the dilator  30  has been advanced over the needle  22  during use. The dilator  30  thus sheaths the sharp bevel tip  108  of the needle  22  to inhibit accidental needle sticks from occurring. 
         [0068]      FIG. 7A  is a schematic, enlarged cross-sectional view of a portion of the needle  22  within the dilator  30  and illustrates an embodiment of a locking mechanism  115  configured in accordance with one aspect of the present invention. When engaged, the locking mechanism  115  inhibits movement of the needle  22  with respect to the dilator  30  in at least one direction. For example, the locking mechanism  115  can inhibit movement of the needle  22  at least in the distal direction once the distal tip of the needle body is drawn into the dilator portion to sheath the distal tip. The embodiment of the locking mechanism  115  illustrated in  FIG. 7A  comprises one or more arms or tangs  117 ,  119 , one or more bases  121 ,  123 , and one or more pivot couplings or hinges  127 ,  129 . 
         [0069]    The arm  117  may be axially aligned with the arm  119 . Alternatively, the arms  117 ,  119  may be offset from each other in a radial direction. The arms  117 ,  119  may be slightly rotated relative to each other or disposed at different radial locations on the inside surface of the dilator  30 . The tang or arm  117 ,  119  may move in a direction generally transverse to a longitudinal axis of the needle body when engaging the receptacle or hole  131 . 
         [0070]    The locking mechanism  115  is illustrated on the dilator  30 . However, the needle  22  may instead comprise the locking mechanism  115 . In the illustrated embodiment, the needle  22  comprises a receptacle, recess, opening, or hole  131  which interacts with the locking mechanism  115  of the dilator  30  when the needle  22  is sufficiently retracted into the dilator  30 . The receptacle, recess, opening, or hole  131  may extend entirely around the needle  22  forming an annular groove or around only a portion of the needle  22 . 
         [0071]    For embodiments that have arms  117 ,  119  disposed at different radial locations on the inside surface of the dilator  30 , the needle  22  may comprise more than one recess, opening, or hole  131 . The multiple recesses, openings, or holes  131  are disposed at radial locations around the outer surface of the needle  22  that correspond to the radial spacing of the arms  117 ,  119  around the inside surface of the dilator  30 . 
         [0072]    The arm  117  is coupled to the base  121  via hinge  127  and rotates from an unlocked position to a locked position in a counter-clockwise direction. The arm  119  is coupled to the base  123  via hinge  129  and rotates from an unlocked position to a locked position in a clockwise direction. In the illustrated embodiment, each arm  117 ,  119  rotates approximately 90 degrees between the unlocked position and the locked position. However, the locked position may be more or less than 90 degrees from the unlocked position. The arms  117 ,  119  need only rotate a sufficient amount to allow their distal ends to abut against a portion of the perimeter of the recess, opening, or hole  131 . 
         [0073]    The recess, opening, or hole  131  in the needle  22  locally increases a gap located between an outside surface of the needle  22  and an inside surface of the dilator  30  a sufficient amount to allow the arms  117 ,  119  to rotate about their respective hinges  121 ,  123  and towards the locked position. When the arm  117  is in the locked position, the needle  22  is inhibited from relative axial movement with respect to the dilator  30  in a proximal direction. When the arm  119  is in the locked position, the needle  22  is inhibited from relative axial movement with respect to the dilator  30  in a distal direction. 
         [0074]    The one or more bases  121 ,  123  are attached to or integral with the dilator  30  and extend generally towards the coaxially aligned needle  22 . The bases  121 ,  123  are sized so as to not interfere with movement of the needle  22  through the dilator  30  while providing hinge points for attachment of the arms  117 ,  119 . The arms  117 ,  119  are sized to allow movement of the needle  22  through the dilator  30  when the arms  117 ,  119  are in the unlocked position. The hinges  127 ,  129  permit the arms  117 ,  119  to move from the unlocked position illustrated in  FIG. 7A  to a locked position illustrated in  FIG. 7D . 
         [0075]    Each arm  117 ,  119  can separately move to the locked position when the arm  117 ,  119  is axially aligned with the recess, opening, or hole  131  in the needle  22 . Once in the locked position, the hinge  127 ,  129  does not permit the arm  117 ,  119  to move back to the unlocked position. In some embodiments, the hinges  127 ,  129  slightly bias the arms  117 ,  119  to move towards the locked position. For example, the tang or arm  117 ,  119  can be biased toward the receptacle, recess, opening, or hole  131 . 
         [0076]      FIGS. 7B-7D  illustrate the operational steps of the locking mechanism  115  of  FIG. 7A  when arresting relative axial movement between the needle  22  and the dilator  30 .  FIG. 7B  illustrates the arms  117 ,  119  in the unlocked position. In the unlocked position, the recess, opening, or hole  131  in the needle  22  is not axial aligned with the arms  117 ,  119  of the locking mechanism  115 . A healthcare provider can move the needle  22  with respect to the dilator  30  in both proximal and distal directions as long as the recess, opening, or hole  131  in the needle  22  stays on the proximal side of the locking mechanism  115  as is illustrated in  FIG. 7B . 
         [0077]      FIG. 7C  illustrates the arm  117  in the locked position. In the locked position, the distal end of the arm  117  is disposed within the recess, opening, or hole  131  in the needle  22 . Once in the locked position, the hinge  127  does not permit the arm  117  to rotate back to the unlocked position. When the arm  117  is in the locked position, the needle  22  may still move in a distal direction with respect to the dilator  32  until the recess, opening, or hole  131  is aligned with the arm  119 . 
         [0078]      FIG. 7D  illustrates both arms  117 ,  119  in the locked position. In the dual locked position, the distal ends of the arms  117 ,  119  are disposed within the recess, opening, or hole  131  in the needle  22 . Once in the dual locked position, the hinges  127 ,  129  do not permit the arms  117 ,  119  to rotate back to the unlocked position. When the arm  119  is in the locked position, the needle  22  is inhibited from moving in the distal direction with respect to the dilator  32 . 
         [0079]      FIG. 8A  is a similar cross-sectional view of a portion of a locking mechanism  137  which is configured in accordance with another preferred embodiment of present invention. When engaged, the locking mechanism  137  inhibits movement of the needle  22  with respect to the dilator  30  in both directions. The embodiment of the locking mechanism  137  illustrated in  FIG. 8A  comprises one or more pairs of v-shaped arms  135 ,  137 . The pairs of arms  135 ,  137  are disposed on diametrically opposite sides of the needle  22 . Alternatively, the arms  135 ,  137  may be offset from each other in a radial direction more or less than 180 degrees apart. 
         [0080]    The locking mechanism  133  is illustrated on the dilator  30 . However, the needle  22  may instead comprise the locking mechanism  133 . In the illustrated embodiment, the needle  22  comprises a recess, opening, or hole  139  which interacts with the locking mechanism  133  of the dilator  30  when the needle  22  is sufficiently retracted into the dilator  30 . The receptacle, recess, opening, or hole  139  may extend entirely around the needle  22  forming an annular groove or around only a portion of the needle  22 . The needle  22  may comprise more than one recess, opening, or hole  139 . The multiple recesses, openings, or holes  139  are disposed at radial locations around the outer surface of the needle  22  that correspond to the radial spacing of the arms  135 ,  137  around the inner surface of the dilator  30 . 
         [0081]    The pairs of arms  135 ,  137  extend from the dilator  30  towards the needle  22 . Each pair of arms  135 ,  137  is biased towards the needle  22  and is illustrated in a compressed or unlocked state in  FIG. 8A . In the unlocked state or position, the recess, opening, or hole  139  in the needle  22  is not axial aligned with the arms  135 ,  137  of the locking mechanism  133 . A healthcare provider can move the needle  22  with respect to the dilator  30  in both proximal and distal directions as long as the recess, opening, or hole  139  in the needle  22  stays on the proximal side of the locking mechanism  133  as is illustrated in  FIG. 8B . Each pair of arms  135 ,  137  gently presses against the outer surface of the needle  22  as the needle  22  slides within the dilator  30  when the arms are in the unlocked state. Each pair of arms  135 ,  137  can rotate or bend to reach a locked state when the arms  135 ,  137  are axially aligned with the recess, opening, or hole  139 . 
         [0082]    In the illustrated embodiment, each arm of each pair of arms  135 ,  137  rotates towards the other arm between the unlocked position and the locked position. The arms  135 ,  137  need only be sufficiently biased so that when the arms  135 ,  137  align with the hole  139  their distal ends abut against a portion of the perimeter of the recess, opening, or hole  139 . In the locked position, the distal ends of the arms  135 ,  137  are disposed within the recess, opening, or hole  139  in the needle  22 . 
         [0083]    The recess, opening, or hole  139  in the needle  22  locally increases a gap located between an outside surface of the needle  22  and an inside surface of the dilator  30  a sufficient amount to allow the arms  135 ,  137  to flex from their biased or unlocked state towards the locked position.  FIG. 8B  illustrates the pair of arms  135  of the locking mechanism  133  of  FIG. 8A  in a locked state. When one or both of the pair of arms  135 ,  137  is in the locked position the needle  22  is inhibited from relative axial movement with respect to the dilator  30  in both proximal and distal directions. 
         [0084]    In the unlocked state Illustrated in  FIG. 8A , the arms  135 ,  137  are biased to contact the needle  22  but not substantially interfere with movement of the needle  22  through the dilator  30 . The arms  135 ,  137  are sized in their unbiased or locked state to inhibit movement of the needle  22  through the dilator  30 . The biasing of the arms  135 ,  137  moves the arms  135 ,  137  from the unlocked position illustrated in  FIG. 8A  to the locked position illustrated in  FIG. 8B . 
         [0085]    Each pair of arms  135 ,  137  can separately move to the locked position when the pair of arms  135 ,  137  is axially aligned with the recess, opening, or hole  139  in the needle  22 . Once in the locked position, the size and shape of the pair of arms  135 ,  137  inhibit movement back to the unlocked position. 
         [0086]      FIG. 9A  is a schematic, enlarged cross-sectional view of a locking mechanism  141  configured in accordance with an additional embodiment of the present invention. When engaged, the locking mechanism  141  inhibits movement of the needle  22  with respect to the dilator  30  in both directions. The embodiment of the locking mechanism  141  illustrated in  FIG. 9A  comprises a protrusion  143 . 
         [0087]    The locking mechanism  141  is illustrated on the dilator  30 . However, the needle  22  may instead comprise the locking mechanism  141 . In the illustrated embodiment, the needle  22  comprises a recess, opening, or hole  145  which interacts with the locking mechanism  141  of the dilator  30  when the needle  22  is sufficiently retracted into the dilator  30 . The receptacle, recess, opening, or hole  145  may extend entirely around the needle  22  forming an annular groove or around only a portion of the needle  22 . The needle  22  may comprise more than one recess, opening, or hole  145 . 
         [0088]    The protrusion  143  extends from the dilator  30  towards the needle  22  and is biased towards the needle  22 .  FIG. 9A  illustrates the protrusion  143  in a compressed or unlocked state. In the unlocked state or position, the recess, opening, or hole  145  in the needle  22  is not axial aligned with the protrusion  143  of the locking mechanism  141 . A healthcare provider can move the needle  22  with respect to the dilator  30  in both proximal and distal directions as long as the recess, opening, or hole  145  in the needle  22  stays on the proximal side of the locking mechanism  141  as is illustrated in  FIG. 9A . The protrusion  143  gently presses against the outer surface of the needle  22  as the needle  22  slides within the dilator  30  when the locking mechanism  141  is in the unlocked state. At least a portion of the protrusion  143  can extend to reach a locked state when the protrusion  143  is axially aligned with the recess, opening, or hole  145 . 
         [0089]    The protrusion  143  need only be sufficiently biased so that when the protrusion  143  aligns with the hole  145  its distal end abuts against a portion of the perimeter of the recess, opening, or hole  145 . In the locked position, the distal end of the protrusion  143  is disposed within the recess, opening, or hole  145  in the needle  22 . 
         [0090]    The recess, opening, or hole  145  in the needle  22  locally increases a gap located between an outside surface of the needle  22  and an inside surface of the dilator  30  a sufficient amount to allow the protrusion  143  to flex or extend from its biased or unlocked state towards the locked position.  FIG. 9B  illustrates the protrusion  143  of the locking mechanism  141  of  FIG. 9A  in a locked state. When the protrusion  143  is in the locked position the needle  22  is inhibited from relative axial movement with respect to the dilator  30  in both proximal and distal directions. 
         [0091]    In the unlocked state Illustrated in  FIG. 9A , the protrusion  143  is biased to contact the needle  22  but not substantially interfere with movement of the needle  22  through the dilator  30 . The protrusion  143  is sized in its unbiased or locked state to inhibit movement of the needle  22  through the dilator  30 . The biasing of the protrusion  143  moves the distal end of the protrusion from the unlocked position illustrated in  FIG. 9A  to the locked position illustrated in  FIG. 9B . 
         [0092]      FIG. 10A  is a schematic, enlarged cross-sectional view of a locking mechanism  147  configured in accordance with a further embodiment of the present invention. When engaged, the locking mechanism  141  inhibits movement of the needle  22  with respect to the dilator  30  in both directions. The embodiment of the locking mechanism  141  illustrated in  FIG. 10A  comprises a detent  149 . 
         [0093]    The locking mechanism  147  is illustrated on the dilator  30 . However, the needle  22  may instead comprise the locking mechanism  147 . In the illustrated embodiment, the needle  22  comprises a recess, opening, or hole  151  which interacts with the locking mechanism  149  of the dilator  30  when the needle  22  is sufficiently retracted into the dilator  30 . The receptacle, recess, opening, or hole  151  may extend entirely around the needle  22  forming an annular groove or around only a portion of the needle  22 . The needle  22  may comprise more than one recess, opening, or hole  151 . 
         [0094]    The detent  149  extends from the dilator  30  towards the needle  22  and rides in an axial groove in the needle  22 . The proximal end of the groove connects with the hole  151 .  FIG. 10A  illustrates the detent  149  in an unlocked state. In the unlocked state or position, the recess, opening, or hole  151  in the needle  22  is not axial aligned with the detent  149  of the locking mechanism  147 . A healthcare provider can move the needle  22  with respect to the dilator  30  in both proximal and distal directions as long as the recess, opening, or hole  151  in the needle  22  stays on the proximal side of the locking mechanism  147  as is illustrated in  FIG. 10A . The detent  149  rides in the groove in the outer surface of the needle  22  as the needle  22  slides within the dilator  30  when the locking mechanism  147  is in the unlocked state. The detent  149  and groove further inhibit relative rotation of the needle  22  with respect to the dilator  30 . The detent  149  reaches a locked state when the detent  149  is axially aligned with the recess, opening, or hole  151 . 
         [0095]    The recess, opening, or hole  151  in the needle  22  locally increases a gap located between a bottom surface of the groove in the needle  22  and an inside surface of the dilator  30  a sufficient amount to allow the detent  149  to flex or extend from a biased or unlocked state towards the locked position.  FIG. 10B  illustrates the detent  149  of the locking mechanism  147  in the unlocked state. While not illustrated, when the detent  149  is in the locked position the needle  22  is inhibited from relative axial movement with respect to the dilator  30  in both proximal and distal directions. 
         [0096]    In the unlocked state illustrated in  FIGS. 10A and 10B , the detent  149  is slightly biased to contact the bottom of the groove in the needle  22  but not to substantially interfere with movement of the needle  22  through the dilator  30 . The detent  149  is sized in its unbiased or locked state to inhibit movement of the needle  22  through the dilator  30 . 
         [0097]      FIG. 11  is an enlarged exploded view of a dilator hub and locking plate assembly  153  configured in accordance with an additional preferred embodiment of the present invention. The assembly  153  includes a dilator hub  155  and one or more fingers or tangs  162 . The one or more fingers or tangs  162  are spaced and sized such that they enter or snap into the side hole or holes in the needle  22  when the needle  22  is retracted. In some applications, a single finger or tang  162  is employed. 
         [0098]    The one or more fingers or tangs  162  inhibit the bevel tip  108  disposed on the distal portion  106  of the needle  22  from being advanced beyond the distal end of the dilator  30  once the dilator  30  has been advanced over the needle  22  during use. The dilator  30  thus sheaths the sharp bevel tip  108  of the needle  22  to inhibit accidental needle sticks from occurring. 
         [0099]    The one or more fingers or tangs  162  may be integrated into the dilator hub  155  or part of a separate structure that is combined with the dilator hub  155 . In the embodiment illustrated in  FIG. 11 , the one or more fingers or tangs  162  are formed on a separate structure in the form of a locking plate  157 ( a )-( c ). In this way, the locking plate  157 ( a )-( c ) comprises the one or more fingers or tangs  162 . Exemplary locking plates  157 ( a )-( c ) are illustrated in  FIGS. 12A-12C . Of course the structure of the locking plates  157 ( a )- (c ) is not limited to the illustrated embodiments. For example, the locking plate  157  could be configured to include one or more of the locking mechanisms illustrated in  FIGS. 7A ,  8 A,  9 A, and  10 A. For embodiments that have the one or more fingers or tangs  162  integrated into the dilator  155 , the assembly  153  need not include a separate locking plate  157 . 
         [0100]    The dilator hub  155  and locking plate  157 ( a )-( c ) may be separately manufactured and assembled as is illustrated in  FIG. 11  or manufactured as a unitary assembly. The dilator hub  155  and locking plate  157 ( a )-( c ) may be manufactured from the same or different materials, including, for example, plastics, metals, combinations thereof, and other materials. The locking plate  157  can be co-molded within the dilator hub  155  to form a unitary assembly. For example, a metal locking plate  157  can be molded into a plastic dilator hub  155 . As explained above, a separate structure in the form of the locking plate  157  is for the In some applications, the locking plates  157 ( a )-( c ) are movable with respect to the dilator hub  155  between unlocked and locked positions. 
         [0101]    The dilator hub  155  is similar to the dilator hub  32  illustrated in  FIG. 3A  except that the dilator hub  155  is configured to slideingly receive the one or more locking plates  157 ( a )-( c ) through one or more slots  158 ( a )-( c ). While multiple locking plates  157 ( a ) -( c ) and slots  158 ( a )-( c ) are illustrated in  FIG. 11 , only a single locking plate  157 ( a )-( c ) and slot  158 ( a )-( c ) can inhibit movement of the needle  22 . In some applications, multiple locking plates  157 ( a )-( c ) are inserted from different sides of the dilator hub  155  so that the fingers or tangs  162  from the locking plates  157 ( a )-( c ) combine to completely surround the needle  22  even though separately the tangs or fingers  162  of each locking plate  157  would not surround the needle  22 . The slot  158 ( a )-( c ) need not be arranged perpendicular to the axis of the needle  22  or located in a specific side or surface of the dilator hub  155  as is illustrated in  FIG. 11 . Multiple locking plates  157 ( a )-( c ) may be inserted into a single slot  158 . 
         [0102]    A healthcare provider slides the locking plate  157 ( a )-( c ) from an unlocked position to a locked position relative to the dilator hub  155 . The locking plate  157 ( a )-( c ) may be completely removed from the slot  158 ( a )-( c ) or partially inserted into the slot  158 ( a )-( c ) when in the unlocked position. When the locking plate  157 ( a )-( c ) is in the locked position, the needle  22  is disposed in a hole or center region  160  of the locking plate  157 ( a )-( c ). The small size of the guide wire  120  inside the needle  22  does not affect the locking feature of the assembly. 
         [0103]      FIG. 12A  is an enlarged view of an embodiment of a locking plate  159  that can be used with the dilator hub  155  shown in  FIG. 11 . The locking plate  159  comprises a hole  160  surrounded by one or more fingers or tangs  162 . An opening  164  extends from an outer perimeter of the locking plate  159  to the hole  160 . The opening  164  permits the locking plate  159  to be inserted into the dilator hub  155  after the needle  22  is inserted through the dilator hub  155 . The needle  22  passes through the opening  164  as the locking plate  159  is slid into the slot  158  and eventually enters the hole  160  when the locking plate  159  is in the locked position or state. Since the one or more fingers or tangs  162  do not extend entirely around the needle  22  when the needle  22  is inserted through the dilator hub  155 , preferably the one or more side holes, receptacles, or annular groove in the needle  22  extend or are spaced radially about the needle  22  so that one of the fingers or tangs  162  will catch the one or more side holes, receptacles, or annular groove when the one or more side holes, receptacles, or annular groove passes through the locking plate  159 . 
         [0104]    When in the locked position, at least one of the distal ends of the fingers or tangs  162  extends a sufficient distance toward the needle  22  to enter a hole or slot in the needle  22  and inhibit further axial movement of the needle  22 . In some applications, the hole or slot in the needle  22  falls onto the finger or tang  162 . The hole may be the one or more side openings  34  in the side wall of the needle  22  or the receptacle, recess, opening, or hole  131 ,  139 ,  145 , and  151  illustrated in, for example,  FIGS. 7A ,  8 A,  9 A, and  10 A, respectively. In some applications, the receptacle, recess, opening, or hole  131 ,  139 ,  145 , and  151  is the same structure as the one or more side openings  34 . 
         [0105]      FIG. 12B  is an enlarged view of another embodiment of a locking plate  161  that can be used with the dilator hub  155  shown in  FIG. 11 . The locking plate  161  comprises a hole  160  surrounded by one or more fingers or tangs  162 . An opening  164  extends from an outer perimeter of the locking plate  161  to the hole  160 . The opening  164  permits the locking plate  161  to be inserted into the dilator hub  155  after the needle  22  is inserted through the dilator hub  155 . The needle  22  passes through the opening  164  as the locking plate  161  is slid into the slot  158  and eventually enters the hole  160  when the locking plate  161  is in the locked position or state. 
         [0106]    Since the one or more fingers or tangs  162  do not extend entirely around the needle  22  when the needle  22  is inserted through the dilator hub  155 , preferably the one or more side holes, receptacles, or annular groove in the needle  22  extend or are spaced radially about the needle  22  so that one of the fingers or tangs  162  will catch the one or more side holes, receptacles, or annular groove when the one or more side holes, receptacles, or annular groove passes through the locking plate  161 . 
         [0107]      FIG. 12C  is an enlarged view of an additional embodiment of a locking plate  163  that can be used with the dilator hub  155  shown in  FIG. 11 . The locking plate  163  comprises a hole  160  surrounded by one or more fingers or tangs  162 . Unlike the embodiments illustrated in  FIGS. 12A and 12B , the locking plate  163  has a closed pedal  166  instead of an opening. Further, the fingers or tangs  162  extend all the way around the needle  22 . When the needle  22  passes through the dilator hub  155 , the side hole in the needle  22  will be caught by the fingers or tangs  162  irrespective of whether the needle  22  is rotated relative to the dilator hub  155 . 
         [0108]    In this embodiment, the locking plate  163  is inserted in the dilator hub  155  before the needle  22  is axially inserted into the dilator hub  155 . Since the fingers or tangs  155  extend entirely around the needle  22 , a sheath or mandrel temporarily covers the side hole in the needle  22  to allow the needle  22  to be assembled through the dilator hub  155 . Once assembled, the sheath or mandrel is removed from the needle  22 . 
         [0109]      FIGS. 13A-13D  are enlarged views of perimeter shapes that the locking plate  157 ( a )-( c ) can have in accordance with additional embodiments of the present invention. Any of the perimeter shapes illustrated in  FIGS. 13A-D  can be added to any of the locking plates  159 ,  161 ,  163 . Of course the perimeter shapes are not limited to the illustrated embodiments. In some applications, the perimeter shape is selected to prevent the locking plate  157  from being removed from the dilator hub  155  or merely inhibit the locking plate  157  from falling out of the dilator hub  155 . 
         [0110]    The slot  158 ( a )-( c ) in the dilator hub  155  would include corresponding shaped surfaces which engage with the perimeter shape  165 ,  167 ,  169  of the locking plate to inhibit the healthcare provider from removing the locking plate from the dilator hub  155  once the locking plate  157  has been slid to the locked position. In this way, the healthcare provider is prevented from accidently removing the locking plate and releasing the needle  22 . 
         [0111]    The embodiments herein described are comprised of conventional, biocompatible materials. For example, the needle preferably consists of a rigid polymer or a metal such as stainless steel, nitinol, or the like. The other elements can be formed of suitable polymeric materials, such as nylon, polyethylene, high-density polyethylene, polypropylene, fluoropolymers and copolymers such as perfluoro (ethylene-propylene) copolymer, polyurethane polymers or co-polymers. 
         [0112]    As noted above, the present access device can be used to place a catheter at other locations within a patient&#39;s body. Thus, for example, but without limitation, the access device can be used with a variety of catheters to drain fluids from abscesses, to drain air from a pneumotorax, and to access the peritoneal cavity. In such applications, body fluids flow into the viewing space to indicate when the needle has been properly placed. 
         [0113]    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. In addition, while a number of variations of the invention have been shown and described in detail, other modifications, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the disclosed invention. 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 disclosure.