Abstract:
A surgical access device, such as a trocar, is described. The trocar includes a first housing member selectively coupled to a second housing member, such as with a latching assembly, and a seal which can be compressed when the housing members are coupled together, the seal for preventing or reducing transverse escape of insufflation gas or other fluid from between the coupled together first and second members.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 61/316,525 filed 23 Mar. 2010. 
    
    
     CROSS REFERENCE TO RELATED APPLICATION 
     This application cross references and incorporates by reference commonly assigned U.S. patent application Ser. No. 10/943,222 filed Sep. 17, 2004, and published as US2005/0070947. 
     FIELD OF THE INVENTION 
     The invention relates to access devices, such as trocars. More particularly, the invention relates to sealing between separable components of trocars, such as to prevent or reduce fluid leakage and assist in maintaining insufflation. 
     BACKGROUND 
     A trocar assembly is a surgical instrument that is used to gain access to a body cavity. A trocar assembly generally comprises two major components, a trocar sleeve, composed of a trocar housing and a trocar cannula, and a trocar obturator. The trocar cannula, having the obturator inserted therethrough, is directed through the skin to access a body cavity. Once the body cavity is accessed, laparoscopic or arthroscopic surgery and endoscopic procedures may be performed. In order to penetrate the skin, the distal end of the trocar cannula is placed against the skin that has been previously cut with a scalpel. The trocar obturator is then used to penetrate the skin and access the body cavity. By applying pressure against the proximal end of the trocar obturator, the sharp point of the trocar obturator is forced through the skin until it enters the body cavity. The trocar cannula is inserted through the perforation/incision made by the trocar obturator and the trocar obturator is withdrawn, leaving the trocar cannula as an access way to the body cavity. 
     The proximal end portion of the trocar cannula is typically joined to a trocar housing that defines a chamber having an open distal end portion in communication with the interior lumen defined by the trocar cannula. Elongated surgical instruments axially extend into and are withdrawn from the trocar cannula through the proximal end portion of the chamber defined by the trocar housing. 
     As those skilled in the art will certainly appreciate, many trocar housings are formed with first and second housing members. The first housing member may include an instrument seal for providing a seal about an instrument inserted through the trocar housing, and the second housing member may include a zero closure seal assembly, such as a duckbill seal assembly, for preventing escape of insufflations gas when no instrument is inserted through the trocar. It will be understood by those skilled in the art that such instrument seals and duckbill seals are employed to prevent escape of insufflations gas in an axial (longitudinal) direction from the body cavity, through the trocar cannula and housing, to the outside environment (along a direction generally parallel to the long axis of the cannula of the trocar.) 
     The first and second housing members may be selectively coupled together in a way that the first and second members may be separated, one from the other, to facilitate various surgical procedures. For example, it is often desirable to remove the first housing member during the removal of a specimen. The removal of the first housing member allows the specimen to pass through only the duckbill seal assembly, instead of passing through both the duckbill seal assembly and the proximal seal assembly. This provides for easier specimen removal and less trauma to the specimen during the removal process. The above incorporated patent application US 2005/0070947 discloses a trocar housing assembly having a first housing member selectively coupled to a second housing member. 
     During certain surgical procedures, such as bariatric procedures, relatively high bending and/or torsional loads may be placed on the trocar housing, such as when an instrument is inserted through the trocar, and the instrument and/or trocar is manipulated (e.g. by applying a force or torque to the instrument or trocar to rotate or pivot the trocar within the perforation/incision) to access/reach the required tissue in high body mass index (BMI) patients. 
     While having separable first and second seal housing members provides for convenient specimen removal, the interface between the first and second sealing members may provide a potential radial leak path of insufflations gas, especially when bending or torsional loads are applied to the trocar housing. 
     SUMMARY 
     Applicant has recognized the desirability of providing separable first and second housing members in combination with a deformable seal, such as gasket seal operable to reduce leakage of insufflations gas or other fluids from between the first and second housing members when the trocar housing is subjected to torsion and bending loads. 
     Applicant has also recognized the desirability of providing a deformable seal which is compressed when the separable housing members are releasably joined together, such as with a latching assembly, and where the seal is configured so as to not require an excessive compressive force or clamping force for joining the first and second housing members. 
     Still further the Applicant has also recognized the desirability of providing a seal where at least a portion of the seal is spaced radially from the outer perimeter of at least one of the instrument seal and the duckbill seal. Still further, the Applicant has also recognized the desirability of providing an inter-housing member seal, at least a portion of which is non-circular, and where the inter-housing member seal has a long axis (major axis) which is oriented with respect to a latch feature for joining the housing members, such as where the long axis of the seal extends substantially perpendicular to a latching axis of the first and second housing members, and such that the long axis of the seal is generally perpendicular to an axis about which one housing member may pivot with respect to the other housing member when the housing members are releasably joined together, such as by a latch assembly. 
     In one embodiment, the invention provides a surgical access device, such as a trocar, having first and second housing member, and a deformable, compressible seal disposed for sealing between opposed faces of the members when the members are joined together, such as with a latching assembly. The seal can be configured so that the seal is compressed when the first and second housing members are joined together, such that seal is provided with (or otherwise induced to have) a compressive load for counter-acting in-use torsional and bending forces applied to the trocar, which forces might otherwise result in a leak gap between the first and second housing members. Accordingly, the seal&#39;s compressive load may be employed to help prevent separation of, and fluid leakage from between, the first and second housing members. 
     In one non-limiting embodiment, the seal comprises a relatively compressible, relatively lower hardness gasket seal overmolded with one of the housing members, such that the gasket seal includes a portion extending from a groove or other recess formed in a relatively higher hardness surface of one of the housing members. 
     In one embodiment, the seal may have a perimeter, at least a portion of which is non-circular, and the seal may further comprise a circular portion surrounding and radially offset from a channel through which instruments pass. The seal may have a long axis (major) axis oriented with respect to a latching feature, such that the seal may resist bending/torsion about a latching axis of the first and second housing members. 
     In one non-limiting embodiment, the seal comprises a relatively low durometer (low hardness) gamma sterilizable silicone having a durometer of less than about 15 Shore A, and more particularly less than or equal to about 10 Shore A, and in one embodiment between about 4 and about 6 shore A. The seal may be configured such that a clamping force of no more than about 15 pounds, and more particularly no more than about 10 pounds is required to push together and latch (or otherwise join) the first and second housing members. 
     In one non-limiting embodiment, the gasket seal is overmolded in a groove or other recess formed in a face of one of the housing members, with the groove having a height between about 0.010 and about 0.025 inch, (more particularly between about 0.015 inch and about 0.020 inch inclusive), and a groove width of about 0.050 inch to about 0.075 inch. The gasket seal can have a rounded/hemispherical top, and in an uncompressed state, the gasket seal can extend above the surface in which the groove is formed a height of between about 0.020 inch and about 0.050 inch, and more particularly, between about 0.025 inch and about 0.045 inch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a trocar assembly as shown in US Patent Application publication US2005/0070947. 
         FIG. 2  is an exploded view of the trocar assembly shown in  FIG. 1 . 
         FIG. 3  is a cross sectional view of the trocar assembly shown in  FIG. 1 . 
         FIG. 4  is an exploded cross sectional view of the trocar assembly shown in  FIG. 1 . 
         FIG. 5  is a perspective view of the trocar of  FIGS. 1-4  illustrating portions of the latching assembly. 
         FIG. 6  is a perspective view of trocar according to one embodiment of the present invention, the trocar shown with an upper seal housing member separated from the lower seal housing member, and showing an asymmetric seal gasket overmolded to a bottom facing surface of the upper seal housing member, with the seal gasket comprising a circular portion and a non-circular portion, the seal gasket having a long (major) axis and a short axis. 
         FIG. 7  is an exploded view of an upper housing member of  FIG. 6 . 
         FIG. 8  is an exploded view of a cannula and components of the lower housing member shown in  FIG. 6 . 
         FIG. 9  is a plane view of the bottom (distal) surface of the seal base shown in  FIG. 7 , including a seal according to the present invention disposed in a groove in a surface of seal base. 
         FIG. 10  is a cross sectional illustration of seal base in  FIG. 7  taken along axis B-B. 
         FIG. 11  is a cross sectional illustration of the seal base of  FIG. 7  taken along axis A-A. 
         FIG. 12  is an enlarged cross sectional view of a portion of the seal in  FIG. 10  shown disposed in a groove in a distally facing surface of the seal base. 
         FIG. 13  is a partial cross-sectional illustration showing the seal base and lower housing cap joined together (such as by the latching assembly), so as to compress the gasket seal between opposing surfaces. 
         FIG. 14  illustrates an alternative seal cross section having a generally Z shaped configuration. 
         FIG. 15  illustrates an alternative seal cross section having a generally V-shaped configuration. 
         FIG. 16  is a partial cross-sectional illustration taken along an axis corresponding to axis B-B in  FIG. 9 , and showing in cross section the upper and lower housing members joined together. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed embodiments of the present invention are disclosed herein. It should be understood, however, that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the details disclosed herein are not to be interpreted as limiting, but merely as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. 
       FIGS. 1-5  illustrate a trocar assembly as disclosed in US Patent Publication US 2005/0070947, incorporated herein by reference in its entirety.  FIGS. 1-5  and the associated description are provided for reference.  FIG. 6-16  illustrate a trocar according to one non-limiting embodiment of the present invention. 
     Trocar of US Publication 2005/0070947 
     Referring to  FIGS. 1 to 5 , the trocar assembly  10  as shown in US 2005/0070947 generally includes a trocar cannula  12 , a trocar obturator  14 , and a trocar housing (or handle)  16 . The trocar cannula  12  defines an interior lumen  18  having an open distal end portion  20  and an open proximal end portion  22 . The proximal end portion  22  extends into and is mounted in the distal end portion  24  of trocar housing  16 . 
     The trocar housing  16  has an open proximal end portion  26  that defines an opening  28 . (See  FIG. 2 ). The opening  28  communicates with a proximal seal assembly  30 , which may include an instrument seal for sealing about an instrument shaft inserted in opening  28 . A zero closure seal assembly, such as a duckbill seal assembly  32  is shown positioned beneath (distal of) the seal assembly  28 . 
     In general, the trocar sleeve  44  is composed of a trocar cannula  12  and a trocar housing  16 . The trocar housing  16  is shown including first housing member  36  and a second housing member  38 . The first and second housing members  36 / 38  may be releasably secured to one another, such that the first housing member  36  may be separated from the second housing member  38 , and then re-secured to one another if desired, as described more fully below. 
     The distal tip of the trocar obturator  14  can be inserted through the opening  28  of the housing  16 , through the proximal seal assembly  30 , through the duckbill seal assembly  32 , and through an axial passageway in the trocar cannula  12 , such that the distal tip of the obturator  14  extends through the open distal end of the cannula  12 . An obturator handle  34  is provided at the proximal end of the trocar obturator  14  and a point or blade (not shown) may be included at the distal end of the obturator. As is well known in the art, the proximal seal assembly  30  cooperates with the exterior of the instruments (for example, trocar obturators and other tools adapted for use in conjunction with trocar based procedures) extending through the trocar to sealingly engage the exterior surface thereof and thereby preclude the passage of fluids (including liquids and insufflations gas) in an axial direction through the trocar housing  16 . 
     Referring to  FIG. 2 , the trocar housing  16  is shown with the first and second housing members  36  and  38  separated, one from the other, and with the obturator removed. The housing member  36  and housing member  38  which are selectively coupled together, so that the members  36  can be removed from the member  38 . The first and second housing members  36 ,  38  include aligned apertures  40 ,  42  shaped and dimensioned for the receipt of instruments that are selectively passed through the trocar housing  16 . 
     First and second housing members  36 ,  38  can be attached together during the insertion of the trocar into the abdominal wall, as well as during the normal course of a procedure. However, it can also desirable to remove the first housing member  36  during the removal of a specimen, for example, from the abdominal cavity. The removal of the first housing member  36  allows the specimen to pass through (such as by being pulled with a grasper) through the cannula  12  and the duckbill seal assembly  32 , but without passing the specimen through proximal instrument seal assembly  30 . This provides for easier specimen removal and less trauma to the specimen during the removal process. 
     The first housing member  36 , which can be in the form of an upper housing cap, is shown supporting the proximal sealing assembly  30  and sits atop the second housing member  38  in which the duckbill seal assembly  32  is mounted. The first housing member  36  includes an aperture  40  extending therethrough. The proximal seal assembly  30  is positioned within the aperture  40  of the first housing member  36 . 
     The second housing member  38  is shown supporting the duckbill seal assembly  32 , with the second housing member  38  including an aperture  42  extending therethrough. The duckbill seal assembly  32  is positioned within the aperture  42  of the second housing member  38  adjacent the top surface  50  of the second housing member  38 . In the trocar shown in  FIGS. 1-4 , the peripheral rim  52  of the duckbill seal assembly  32  is shown positioned directly adjacent the top surface  50  of the second housing member  38  for engagement with a feature (such as a rim or lip) on the lower surface  54  of the first housing member  36  to provide sealing when the members  36  and  38  are joined. 
     Connection of the first housing member  36  to the second housing member  38  is facilitated by a rotary latch assembly  56 . In particular, the first housing member  36  includes first and second downwardly extending arms  58 . Each of the downwardly extending arms  58  includes a downwardly facing camming surface  60  and an outwardly facing latching surface  62 . 
     The second housing member  38  similarly includes a latching ring  64  (See  FIG. 5 ) with first and second latch members  66  for respectively engaging the respective latching surfaces  62  of the first and second downwardly extending arms  58  of the first housing member  36 . The latching ring  64  is axially aligned with the central axis of the trocar sleeve  44  and lies in an annular groove  68  around the perimeter of the duckbill seal assembly  32 . The latching ring  64  is capable of rotating about the central axis of the trocar sleeve  44 . The spring  70  holds the latching ring  64  in a locked position with a small amount of preloaded bias. However, the spring  70  allows rotation of the latching ring  64  during the attachment of the first housing member  36 . The first and second latch members  66  respectively include upwardly facing camming surfaces  72  that interface with downwardly facing camming surfaces  60  of the first and second downwardly extending arms  58  of the first housing member  36 . 
     The first and second latch members  66  each include an upwardly facing camming surface  72  shaped and dimensioned to respectively engage the camming surfaces  60  of the downwardly extending arms  58 . Similarly, the first and second latch members  66  include inwardly facing latching surfaces  74  shaped and dimensioned for engaging the outwardly facing latching surfaces  62  of the first and second downwardly extending arms  58 . 
     In practice, latching of the first and second housing members  36 ,  38  is achieved by passing the first and second downwardly extending arms  58  through holes  76  formed in the top surface  50  of the second housing member  38 . As the first and second downwardly extending arms  58  extend through the respective holes  76  adjacent the first and second latch members  66  of the latching ring  64 , the camming surfaces  60  of the respective first and second downwardly extending arms  58  engage the camming surfaces  72  of the first and second latch members  66 . The engagement causes the latch ring  64  to rotate in a manner permitting the first and second downwardly extending arms  58  to extend past the first and second latch members  66 . This rotation is against the bias provided by the spring  70 . 
     Once the first and second downwardly extending arms  58  move past the first and second latch members  66 , the spring  70  biasing the latching ring  64  causes the latching ring  64  to return to its original position and the outwardly facing latching surfaces  62  of the first housing member  36  engage the inwardly facing latching surfaces  74  of the second housing member  38  to securely couple the first housing member  36  to the second housing member  38 . The first and second housing members  36 ,  38  are selectively disengaged through the actuation of a lever  78  attached to the latching ring  64 . Rotation of the lever  78  causes the latching ring  64  to rotate, moving the first and second latching members  66  out of engagement with the downwardly extending arms  58 . 
     The top surface  50  of the second housing member  38  includes holes  76  allowing the downwardly extending arms  58  of the first housing member  36  to pass through. The trocar housing  16  is disassembled by pushing the lever  78  in a horizontal rotation, causing rotation of the latching ring  64  about the central axis of the trocar sleeve  44  in a manner overcoming the spring force. The lever  78  is accessible to the surgeon through a slot in the side of the trocar housing  16 . When the lever  78  is pressed/moved circumferentially, the first and second latching members  66  of the latching ring  64  rotate past the first and second downwardly extending arms  58 , and the first housing member  36  is released from the second housing member  38 . 
     The trocar shown in  FIGS. 1-5  provides a seal between first housing member  36  and the second housing member  38  by using a downwardly extending flange  80  (See  FIG. 3 ) on the lower surface  54  of the first housing member  36  to compress a perimeter portion of the duckbill seal assembly  32  adjacent the top surface  50  of the second housing member  38 . The flange  80  and the duckbill seal assembly  32  include opposed angled surfaces. This provides an angular interface between the flange  80  on the first housing member  36  and the duckbill seal assembly  32  interface of the second housing member  38 . 
     The downwardly extending flange  80  of the first housing member  36  includes an angular interface that exerts a radial force component on the duckbill seal assembly  32 . The angular interface also creates a vertical force component that translates into assembly force. The radial force dilates the interfacing feature, that is, the peripheral rim  52  of the duckbill seal assembly  32 . Since the vertical force is only a portion of the total normal force, the assembly force is reduced as a function of the angle of the interface. 
     Proper alignment between the first and second housing members  36 ,  38  is achieved by the provision of an alignment pin  82  extending downwardly from the lower surface  54  of the first housing member  36  and a mating hole  84  shaped and dimensioned for receiving the alignment pin  82  formed along the top surface  50  of the second housing member  38 . 
     Trocar Having Improved Sealing 
     Referring now to  FIGS. 6 to 16 , a trocar  1000  according to one embodiment of the present invention is illustrated. The trocar  1000  may incorporate one or more of the features disclosed in US 2005/0070947, incorporated herein by reference. 
     As shown in  FIG. 6 , the trocar  1000  comprises a cannula  1012 , first housing member  1036 , and a second housing member  1038 . In  FIG. 6 , the first housing member  1036  is shown separated from and rotated with respect to the second housing member  1038 , so that the distal end (lower end) of the first housing member  1036  is visible, and to reveal a seal  2000  for providing sealing between upper housing member  1036  and lower housing member  1038  when members  1036  and  1038  are coupled together, such as by a latching assembly. The latching assembly may include latch arms  1058  extending from housing member  1036  and into receiving openings  1076  formed in an upper surface of housing member  1038 . Seal  2000  may be formed of a material such that seal  2000  is compressed between opposed surfaces of members  1036 ,  1038  when members  1036 ,  1038  are joined together Seal  2000  is described in more detail below. 
     The first housing member  1036  may support a proximal seal assembly  1030  disposed in an opening  1040 , and the second housing member  1038  may support a more distal (lower) duckbill seal assembly  1032  disposed in an opening  1042 . Proximal seal assembly  1030  can provide sealing about (e.g. around the circumference of) an instrument (or obturator) passing through the trocar housing. Duckbill seal assembly  1032  may be employed to restrict axial flow of insufflation gas upward (along the long axis of cannula  1012 ) when no instrument (or obturator) is disposed in the housing. 
     Seal  2000  can be in the form of a gasket overmolded in a groove or recess in the lower (distally facing) surface  1054  of the upper housing member  1036 . Alternatively, the seal  2000  could be overmolded in a groove or recess in the upwardly facing surface  1050  of lower housing member  1038 . In still another embodiment, the seal  2000  can be separate component captured between opposed surfaces  1050  and  1054 . 
     As explained above with respect to trocar  10  shown in  FIG. 1-5 , the peripheral rim  52  of the duckbill seal assembly  32  is shown positioned for engagement with a feature on the lower surface  54  of the first housing member  36  to provide sealing between the housing member  36  and  38  when the members  36  and  38  are joined. 
     In contrast, the seal  2000  of the present invention does not require engagement of the perimeter of the duckbill seal  1032  with a feature on the lower surface of the housing member  1036 , nor registration with a rim or lip on the lower surface. 
     Referring to  FIGS. 6-12 , seal  2000  is spaced radially outward from the perimeter of the duckbill seal assembly  1032 , radially outward from the perimeter of opening  1042  in the upper surface  1050  of housing member  1038 , and radially outward from the perimeter of opening  1040  in lower surface  1054  of housing member  1036 . Such radially outward spacing of the seal  2000  can be advantageous in resisting torsional and/or bending loads which would tend to “rock” or otherwise displace housing member  1036  with respect to housing member  1038 , and which could provide for leakage of insufflations gas or other fluid from between members  1036  and  1038 . 
       FIG. 7  depicts an exploded view of the first (upper) housing member  1036 . Housing member  1036  includes upper cap  1122  having opening  1140  therein, a lower base  1160 , and seal  2000 , which can be disposed on distally facing surface  1054  of seal base  1160 . Cap  1122  and base  1160  can capture components of the proximal instrument seal assembly. The proximal instrument seal assembly is shown to include a crown  1210 , bellows  1220 , seal protector  1230 , upper seal retaining ring  1240 , instrument seal  1250 , and lower seal retaining ring  1260 . 
       FIG. 8  depicts an exploded view of the cannula  1012 , insufflation valve assembly  1300 , and components of the second (lower) housing member  1038 , including lower housing cap  1438 , latch ring  1440 , duckbill valve  1450 , and lower housing portion  1460 . As shown in  FIG. 8 , the housing cap  1438  may include a generally horizontal, generally planar upwardly facing surface  1050  having latch openings  1076  therein. 
       FIG. 9  illustrates the orientation of seal  2000  with respect to various features of the seal base  1160  shown in  FIG. 7 .  FIG. 9  is a bottom view (looking proximally from below seal base  1160 ). Seal  2000  can be disposed in a groove, slot, or other recess formed in the surface  1054  of seal base  1160 . Seal base  1160  can be formed of a relatively harder material, such as being molded of polycarbonate or other suitable medical grade plastic or polymer. In contrast, seal  2000  can be relatively softer, and can be a separate piece, or can be overmolded to seal base  1160  in a “two shot” molding process when base  1160  is molded, such as from polycarbonate. 
     As can be seen in  FIG. 9 , the seal  2000  may have a gasket configuration, and can include a generally circular portion  2100  and a generally non-circular portion  2200 . The circular portion  2100  can provide a first seal opening  2110  having a diameter greater than opening  1040  in seal base  1160 . The generally non-circular portion  2200  can provide second and third seal openings  2120  and  2130 . Accordingly, seal  2000  can have multiple openings to reduce the total seal surface area (as viewed in  FIG. 9 ) and the force required to compress the seal. 
     The seal  2000  can be longer than it is wide, having a major axis A-A and a minor axis B-B, as shown in  FIG. 9 . The circular portion  2100  can be generally concentric with opening  1040 , but can be offset radially outwardly from opening  1040 , such as by a radial offset “D”. Accordingly the diameter of the perimeter of the circular portion  2100  is shown to be larger than the diameter of opening  1040 . 
     The non-circular portion  2200  is shown as comprising two lobe shaped gasket extensions  2210  and  2220 . The lobe shaped extensions can have the same or different shapes. The lobe shaped gasket extensions are shown as each being generally symmetric about major axis A-A of seal  2000 . 
     As shown in  FIG. 9 , the minor axis B-B of seal  2000  can be collinear with a diameter of opening  1040  and can extend through the latch arms  1058 , so that axis B-B corresponds to a latching axis of the trocar. Major axis A-A can extend along a diameter of opening  1040  which is generally perpendicular to axis B-B. Orienting the long dimension (major axis) of the seal  2000  generally perpendicular to an imaginary axis extending though latch arms  1058  provides a larger lever arm to resist forces applied to housing  1036 / 1038  which may, under some loading conditions, cause “rocking” or pivoting of the upper housing member  1036  relative to lower housing member  1038  about axis B-B. 
     Additionally, by spacing the circular portion  2100  of seal  2000  outwardly from opening  1040  and the perimeter of the instrument seal and/or the duckbill seal, the circular portion  2100  has a larger radial distance from the center of opening  1040 , and accordingly more leverage to resist leakage when the trocar is subjected to torsion or bending loads. In one non-limiting embodiment, when seal  2000  is placed in compression (such as by latching housing member  1036  to housing member  1038 ), the resulting compression of seal  2000  can act in the manner of a gasket preload to resist separation of housing member  1036  from housing member  1038 . 
       FIG. 10  is a cross-section of the seal base and seal  2000  taken along axis B-B (see arrows associated with axis B-B in  FIG. 10 ), and  FIG. 11  is a cross section taken along axis A-A. In the embodiment shown in  FIGS. 10 and 11 , a portion of the cross-section of the seal is disposed in a slot in the bottom surface (surface  1054 ) of seal base  1160 , and the seal  2000  extends downwardly (distally) from the slot and bottom surface of the seal base  1160 . The cross section in  FIG. 10  is taken through the circular portion  2100  of seal  2000  aligned with axis B-B. In  FIG. 11 , the cross section is taken through both the circular portion  2100  and the non-circular portion  2200  of seal  2000 . 
       FIG. 12  is an enlarged cross-sectional illustration of a the seal  2000  having a base portion  2002  disposed in a groove  1165  formed in surface  1054 , and a seal contact portion  2004  extending downward from surface  1054  for providing sealing engagement with an opposing surface on lower housing member  1038  (for instance, sealing engagement with surface  1050 ). Seal portion  2004  can have a generally semicircular shape in cross section, so as to approximate continuous line contact around the perimeter of the seal against an opposing surface, thereby increasing the contact pressure between the seal  2000  and the surfaced against which it is compressed. 
     Both surface  1050  and  1054  can be formed for relatively harder materials, and seal  2000  can be formed of a relatively softer material. The seal material can have a cured/molded durometer of less than about 50 Shore A, more particularly less than or equal to about 20 Shore A, and still more particularly between about 4 and about 10 Shore A. In one embodiment, the seal  2000  can have a Durometer, Type 00 of about 40. The seal  2000  can be formed of a relatively soft material and dimensioned to avoid requiring a large compressive force/clamping force when seal  2000  is compress upon latching housing members  1036  and  1038  together. In particular, the combined area of the openings  2110 ,  2120 , and  2130  enclosed by the seal  2000  can be larger than the combined area (as viewed in  FIG. 9 ) of the circular and non circular portions of the seal  2000  that are compressed when housing members  1036  and  1038  are joined. 
     In one non-limiting embodiment, the seal  2000  can be comprise a silicone rubber over molded to be supported in a slot in surface  1054 . A suitable liquid silicone rubber is commercially available as MED-4901 from NuSil Technology of Carpinteria, Calif. Another suitable seal material is COHRLASTIC R-10470 Medium General Purpose Silicone Sponge available from Stockwell Elastomerics, an authorized supplier of Saint-Gobain products. Other seal materials include Poron 4790-92 Urethane gasket material and Bisco BF-1000 Silicone gasket material. A lubricant, such as NuSil Med 361 or 400 can be applied to the seal  2000  to assist in sealing. 
     The seal cross section shown in  FIG. 12  is in depicted in an uncompressed state, prior to joining (such as by latching) housing member  1036  to housing member  1038 . While various seal materials and seal dimensions may be employed, in one embodiment the groove  1165  can have a generally uniform groove depth H 1  between about 0.010 and about 0.025 inch, and more particularly between about 0.015 inch and about 0.020 inch. The seal  2000  can have a free, uncompressed height H 2  above the groove and surface  1054  of between about 0.010 inch and about 0.060 inch, more particularly between about 0.025 inch and about 0.045 inch. The seal  2000  can have a cross-sectional width W of between about 0.050 inch and about 0.074 inch. 
       FIG. 13  is a partial cross-sectional illustration showing the seal base  1160  and lower housing cap  1438  joined together (such as by the latching assembly), so as to compress seal  2000  between opposing surfaces of base  1160  and cap  1438 .  FIG. 13  is a cross-sectional illustration taken along an axis corresponding to axis A-A in  FIG. 9 , such that the seal  2000  is visible as four cross-sections in the section view. 
       FIG. 16  is a partial cross-sectional illustration taken along an axis corresponding to axis B-B in  FIG. 9 , and showing in cross section the upper and lower housing members joined together.  FIG. 16  illustrates the position of instrument seal  1250  and the duckbill seal  1450  having inner wall  1453 . As seen in  FIG. 16 , the seal  2000  is radially offset outward of the inner wall  1453  of the duckbill seal  1450 . 
       FIGS. 14 and 15  illustrate alternative seal cross-sectional configurations.  FIG. 14  illustrates a seal cross section  2300  having a generally Z shaped configuration.  FIG. 15  illustrates a seal cross section  2400  having a generally V-shaped configuration with a relatively pointed tip for engaging an opposing surface. 
     While one or more embodiments have been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims.