Patent Publication Number: US-10772661-B2

Title: Method and structure for selectively locking portions of a seal assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 15/875,480, filed Jan. 19, 2018, which is a continuation of U.S. patent application Ser. No. 15/002,832, filed Jan. 21, 2016, now U.S. Pat. No. 9,895,164, which is a continuation of U.S. patent application Ser. No. 13/933,344, filed Jul. 2, 2013, now U.S. Pat. No. 9,247,956, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/673,390, filed on Jul. 19, 2012, the entire disclosure of each of which is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a surgical device and, more particularly, but not exclusively, relates to a mechanism for selectively locking portions of a seal assembly relative to each other. 
     BACKGROUND 
     Minimally invasive and laparoscopic procedures generally require that any instrumentation inserted into the body is sealed, e.g., provisions must be made to ensure that gases and/or fluids do not enter or exit the body through an endoscopic incision, such as, for example in surgical procedures where the surgical region is insufflated. For such procedures, the introduction of a tube into anatomical cavities, such as the peritoneal cavity, is usually accomplished by use of a system incorporating a trocar and cannula assembly. Since the cannula is in direct communication with the interior of the peritoneal cavity, insertion of the cannula into an opening in the patient&#39;s body to reach the inner abdominal cavity should be adapted to maintain a fluid tight interface between the abdominal cavity and the outside atmosphere. In view of the need to maintain the atmospheric integrity of the inner area of the cavity, a seal assembly for a cannula, which permits introduction of a wide range of surgical instrumentation and maintains the atmospheric integrity of the inner area of the cavity is desirable. 
     SUMMARY 
     The present invention, in accordance with various embodiments thereof, may be directed to a surgical access device comprising: a seal assembly including an upper housing portion having a first seal and a lower housing portion including a second seal, the upper housing portion being rotatably connectable to the lower housing portion; and a rotation prevention mechanism configured to prevent inadvertent relative rotation, and disconnection, the upper housing portion and the lower housing portion, the rotation prevention mechanism further configured to be selectively actuated by a user, such that, when actuated, the upper housing portion is selectively rotatable relative to, and disconnectable from, the lower housing portion. 
     The rotation prevention mechanism may include components that are integrally formed with one or both of the upper housing portion and the lower housing portion. The rotation prevention mechanism may include components that are integrally formed with other components that are fixedly connected to one or both of the upper housing portion and the lower housing portion. The rotation prevention mechanism may include a first component that is integrally formed with the upper housing portion and a second component that is fixedly connected to the lower housing portion. 
     In an example embodiment, the first component may comprise a finger. The finger may be integrally formed with a circumferential edge of a main housing, the main housing being fixedly connected to lower housing portion. The finger may include a ramp located on its upper surface. The second component of the rotation prevention mechanism may include a protrusion, the protrusion being integrally formed with a circumferential edge of upper housing portion and including a distal-extending member. The finger may be configured for resilient movement relative to the main housing about its point of attachment thereto, such that at least a portion of the finger is moveable distally relative to the main housing. 
     In an embodiment, as the upper housing portion of the seal assembly is rotated in a first direction, the distal-extending member of the protrusion travels up the sloping surface of the ramp and exerts a force on the finger sufficient to cause the finger to move distally relative to the main housing until, when the distal-extending member of the protrusion reaches the end of the sloping surface of the ramp, the force exerted on the ramp by the distal-extending member of the protrusion is removed, and the finger, by virtue of its resilience, is allowed to move proximally to a position in which the distal-extending member of the protrusion is distal relative to the uppermost point of the ramp, thereby preventing the upper housing portion from rotating in a second direction opposite to the first direction. 
     In an embodiment, upon a user exerting a force on the finger, the finger is moveable distally relative to the main housing until the uppermost point of the ramp is located distal relative to the distal-extending member of the protrusion such that the upper housing portion of the seal assembly is not prevented from rotating, but rather is free to rotate, in the second direction relative to the lower housing portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features of the present disclosure will become more readily apparent and will be better understood by referring to the following detailed description of various embodiments, which are described hereinbelow with reference to the drawings wherein: 
         FIGS. 1-2  are perspective views of a cannula assembly and a seal assembly in accordance with an example embodiment of the present disclosure; 
         FIG. 3  is a perspective view with parts separated of the cannula and seal assemblies of  FIG. 1 ; 
         FIG. 4  is a side cross-sectional view of the cannula and seal assemblies; 
         FIGS. 5-6  are top and bottom perspective views of a gimbal mount of the seal assembly; 
         FIGS. 7-8  are cross-sectional views of the gimbal mount; 
         FIG. 9  is a perspective view illustrating the components of the gimbal mount; 
         FIGS. 10-12  are perspective views illustrating the range of movement of the gimbal mount within the seal housing; 
         FIG. 13  is a view illustrating the cannula assembly and seal assembly accessing an internal cavity with an instrument introduced therein; and 
         FIG. 14  is a side cross-sectional view of the cannula and seal assemblies illustrating a range of movement of the surgical instrument. 
         FIGS. 15-17  are perspective views of an example embodiment of a mechanism for preventing inadvertent rotation, and potential inadvertent disconnection, of an upper housing portion and a lower housing portion of a seal assembly. 
     
    
    
     The figures depict various embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the present disclosure described herein. 
     DETAILED DESCRIPTION 
     As set forth above, the present invention, in accordance with various embodiments thereof, may be directed to an arrangement for preventing a rotatably connectable upper housing portion of a seal housing from inadvertently rotating relative to a lower housing portion of the seal housing during use and thereby undesirably disconnecting therefrom. In this regard, the present invention, in accordance with various embodiments thereof, may also be directed to an arrangement which provides a selectively actuatable mechanism that enables a user, e.g., a surgeon, upon actuation, to rotate an upper housing portion of a seal housing that is connected to lower housing portion of the seal housing and thereby disconnect the two portions from each other. By providing a selectively actuatable mechanism that i) when in a first position, automatically prevents a rotatably connectable upper housing portion of a seal housing from inadvertently rotating relative to a lower housing portion of the seal housing during use, and that ii) when actuated, enables a user to rotate and thereby disconnect the upper housing portion from lower housing portion of the seal housing, various advantages may be achieved, as will be set for the ion greater detail below. 
     It should be noted that the seal assembly set forth herein, e.g., a gimbal seal, is merely one example of a seal arrangement that may be employed in the present invention. Any type of seal arrangement may be employed and still be within the scope of the present invention. In the example shown herein, the seal assembly, either alone or in combination with a seal system internal to a cannula assembly, provides a substantial seal between a body cavity of a patient and the outside atmosphere before, during and after insertion of an instrument through the cannula assembly. Moreover, the seal assembly of the present invention is advantageously capable of accommodating instruments of varying diameters, e.g., from 5 mm to 15 mm, by providing a gas tight seal with each instrument when inserted. The flexibility of the present seal assembly greatly facilitates endoscopic surgery where a variety of instruments having differing diameters are often needed during a single surgical procedure. 
     The seal assembly contemplates the introduction and manipulation of various types of instrumentation adapted for insertion through a trocar and/or cannula assembly while maintaining a fluid tight interface about the instrumentation to preserve the atmospheric integrity of a surgical procedure from gas and/or fluid leakage. Specifically, the seal assembly accommodates angular manipulation of the surgical instrument relative to the seal axis. This feature of the present disclosure desirably minimizes the entry and exit of gases and/or fluids to/from the body cavity. Examples of instrumentation include clip appliers, graspers, dissectors, retractors, staplers, laser probes, photographic devices, endoscopes and laproscopes, tubes, and the like. Such instruments will be collectively referred to herein as “instruments or instrumentation”. 
     In the following description, as is traditional the term “proximal” refers to the portion of the instrument closest to the operator while the term “distal” refers to the portion of the instrument remote from the operator. 
     Referring now to the drawings, in which like reference numerals identify identical or substantially similar parts throughout the several views,  FIGS. 1-2  illustrate the seal assembly  100  of the present disclosure mounted to cannula assembly  200 . Cannula assembly  200  may be any conventional cannula suitable for the intended purpose of accessing a body cavity and permit introduction of instruments therethrough. Cannula assembly  200  is particularly adapted for use in laparoscopic surgery where the peritoneal cavity is insufflated with a suitable gas, e.g., CO 2 , to raise the cavity wall from the internal organs therein. Cannula assembly  200  is typically used with an obturator assembly (not shown) which is an instrument positionable within the passageway of the cannula assembly  200 . The obturator assembly is utilized to penetrate the abdominal wall and then subsequently removed from the cannula assembly to permit introduction of the surgical instrumentation utilized to perform the procedure. 
     Cannula assembly  200  includes cannula sleeve  202  and cannula housing  204  mounted to an end of the sleeve  202 . Cannula sleeve  202  defines a longitudinal axis “a” extending along the length of sleeve  202 . Sleeve  202  further defines an internal longitudinal passage dimensioned to permit passage of surgical instrumentation. Sleeve  202  may be formed of stainless steel or other rigid materials such as a polymeric material or the like. Sleeve  202  may be clear or opaque. The diameter of sleeve  202  may vary, but typically ranges from 10 to 15 mm for use with the seal assembly  100  of the present disclosure. 
     Cannula housing  204  includes two components, specifically, housing flange  206  which is attached to the proximal end of cannula sleeve  202  and main housing  208  as shown in  FIGS. 3-4 . Main housing  208  is connectable to housing flange  206  through a bayonet coupling consisting of radially spaced tongues  210  on the exterior of housing flange  206  and corresponding recesses  212  within the interior of main housing  208 . Tongues  210  are receivable within recesses  212 . Thereafter, housing flange  206  and main housing  208  are rotated to securely lock the tongues  210  within the recesses  212 . Other conventional means, e.g., a snap fit, ultrasonic welding or any other means envisioned by one skilled in the art including, e.g., adhesive means, may be incorporated to connect housing flange  206  and main housing  208 . Main housing  208  further includes diametrically opposed housing grips  214  dimensioned and arranged for gripping engagement by the fingers of the user. Although shown and described as two components, cannula housing  204  may be a single component and attached to cannula sleeve  202  by any of the aforementioned means. 
     With reference to  FIG. 3 , in conjunction with  FIGS. 1-2 , cannula housing  204  further includes duck bill or zero closure valve  216  which tapers distally and inwardly to a sealed configuration as shown in the figure. Valve  216  opens to permit passage of the surgical instrumentation and closes in the absence of the instrumentation. Valve  216  is preferably adapted to close upon exposure to the forces exerted by the insufflation gases in the internal cavity. Other zero closure valves are also contemplated including single or multiple slit valve arrangements, trumpet valves, flapper valves, etc. 
     Referring now to  FIGS. 3-4 , in conjunction with  FIGS. 1-2 , seal assembly  100  will be discussed in detail. Seal assembly  100  includes seal housing, generally identified as reference numeral  102 , and gimbal mount  104  which is disposed within the seal housing  102 . Seal housing  102  houses the sealing components of the assembly and defines the outer valve or seal body of the seal assembly  100 . Seal housing  102  defines central seal housing axis “b” which is preferably parallel to the axis “a” of cannula sleeve  202  and, more specifically, coincident with the axis “a” of the cannula. Seal housing  102  incorporates three housing components, namely, proximal, distal and inner housing components  106 ,  108 ,  110 , respectively, which, when assembled together, form the seal housing  102 . Assembly of housing components  106 ,  108 ,  110  may be affected by any of the aforementioned connection means discussed with respect to cannula housing  204 . Further, seal housing  102  may be considered as having an upper housing portion  109  formed by components  106   108 , as shown separately in  FIGS. 10-12 , and a detachable lower housing portion formed by component  110 . 
     Proximal housing component  106  defines inner guide wall  112  and outer wall  114  disposed radially outwardly of the inner guide wall  112 . Inner guide wall  112  defines central passage  116  which is dimensioned to receive a surgical instrument and laterally confine the instrument within seal housing  102 . Inner guide wall  112  is generally cylindrical in configuration and terminates in a distal arcuate surface  118 . Outer wall  114  defines first and second annular recesses  120 ,  122  adjacent its distal end. Recesses  120 ,  122  receive corresponding structure, e.g., annular lips  124 ,  126  of distal housing component  108  to facilitate connection of the two components. As appreciated, proximal housing component  106  may also incorporate locking tabs which engage corresponding structure of distal housing component  108  upon relative rotation of the components  106 ,  108  to securely connect the components. 
     Inner housing component  110  is disposed within the interior of distal housing component  108  and is connectable to the distal housing component  108  through a bayonet coupling. Such coupling includes radially spaced tongues  128  which depend radially inwardly to be received within correspondingly arranged grooves or recesses  130  on the exterior of inner housing component  110 . Coupling of distal and inner housing components  108 ,  110 , and thus coupling of upper housing portion  109  and lower housing portion  110 , is thereby affected through rotation of the components. In order to prevent inadvertent relative rotation, and thus potential decoupling, of upper housing portion  109  and lower housing portion  110 , the present invention, in accordance with various example embodiments thereof, may include a rotation prevention mechanism  1000 , shown schematically in, e.g.,  FIGS. 1-4 and 13 . Further details of a specific example of such a rotation prevention mechanism  1000  are shown, e.g., in  FIGS. 15-17 . 
     In general, the rotation prevention mechanism  1000  is a mechanism that may prevent inadvertent relative rotation, and thus potential decoupling, of upper housing portion  109  and lower housing portion  110 . In addition, the rotation prevention mechanism  1000  is a mechanism that may enable a user, e.g., a surgeon, upon actuation, to selectively rotate an upper housing portion of a seal housing relative to a lower housing portion of the seal housing and thereby selectively disconnect the two portions from each other. The rotation prevention mechanism  1000  may include components that are separate from the seal assembly  100  and/or the cannula assembly  200 , but preferably include components that are integrally formed with one or more components of either the seal assembly  100  and/or the cannula assembly  200 . In an embodiment, the rotation prevention mechanism  1000  may include components that are integrally formed with one or both of the upper housing portion of a seal housing and the lower housing portion of the seal housing. Additionally or alternatively, the rotation prevention mechanism  1000  may include components that are integrally formed with components that are fixedly connected to one or both of the upper housing portion and the lower housing portion of the seal housing. 
     The embodiment shown and described herein provides an example of this latter arrangement. Specifically, the embodiment shown and described herein in  FIGS. 15-17  provides an example of the rotation prevention mechanism  1000  which includes a first component that is integrally formed with the upper housing portion  109  and a second component that is fixedly connected to the lower housing portion  110  of the seal housing  102 . Alternate embodiments may include different arrangements, e.g., wherein the rotation prevention mechanism  1000  includes components that are integrally formed with different components that are fixedly connected to either the upper housing portion  109  and/or the lower housing portion  110  of the seal housing  102 . It should also be recognized that, while the example embodiment shown and discussed herein provides for an arrangement in which the rotation prevention mechanism  1000  includes, e.g., two, components, other embodiments are envisioned in which the rotation prevention mechanism  1000  includes only one component (e.g., a component that is part of or connected to a single one of the upper housing portion  109  and/or the lower housing portion  110  of the seal housing  102 ), or includes more than two components (e.g., components that are part of or connected to other components in addition to the upper housing portion  109  and the lower housing portion  110  of the seal housing  102 ). 
     Referring now to  FIGS. 15-17 , there is shown an example embodiment of the present invention. In this embodiment, as mentioned previously, there is provided an example of the rotation prevention mechanism  1000  which includes a first component  1002  and a second component  1008 . As shown, the first component  1002  consists of a finger  1003  that is integrally formed with a circumferential edge of the main housing  208 , the finger having a ramp  1004  located on its upper surface. It is noted that the main housing  208 , in this embodiment, is fixedly connected to lower housing portion  110 . In addition, as shown in this embodiment, the second component  1008  of the rotation prevention mechanism  1000  is a protrusion  1007  that is integrally formed with a circumferential edge of the distal housing component  108  of the upper housing portion  109  of the seal housing  102 . In addition, the protrusion  1007  includes a distal-extending member  1005 . The finger  1003  is configured for resilient movement relative to the main housing  208  about its point of attachment thereto, such that at least a portion of the finger, e.g., the portion including the ramp  1004 , is moveable distally relative to the main housing  208 . In this way, as the upper housing portion  109  of the seal assembly is rotated in a first direction (e.g., clockwise when  FIG. 15  is viewed from above), the distal-extending member  1005  of the protrusion  1007  travels up the sloping surface of the ramp  1004  until it reaches the end of the sloping surface. As the distal-extending member  1005  of the protrusion  1007  travels up the sloping surface of the ramp  1004 , it exerts a force, e.g., a force directed in the distal direction, on the ramp  1004 , and thus also on the finger  1003 , the distally-directed force being sufficient to cause the finger  1003  to move distally relative to the main housing  208  about its point of attachment thereto. Once the distal-extending member  1005  of the protrusion  1007  reaches the end of the sloping surface of the ramp  1004 , the distally-directed force exerted on the ramp  1004  by the distal-extending member  1005  of the protrusion  1007  is removed, and the finger  1003 , by virtue of its resilience, is allowed to move proximally, thereby returning to its original position relative to the main housing  208  (e.g., its position prior to being moved by the force exerted by the distal-extending member  1005  of the protrusion  1007 ). In this original position, the distal-extending member  1005  of the protrusion  1007  extends to a position that is distal relative to the uppermost point of the ramp, and thus the upper housing portion  109  of the seal assembly is prevented from rotating in a second direction (e.g., counter-clockwise when  FIG. 15  is viewed from above) opposite to the first direction. In this manner, the rotation prevention mechanism  1000  automatically prevents the upper housing portion  109  of the seal housing  102  from inadvertently rotating relative to, and thus inadvertently becoming disconnected from, the lower housing portion  110  once the upper housing portion  109  of the seal housing  102  reaches this locked position. 
     Once a user determines that it would be desirable to disconnect and/or remove the upper housing portion  109  of the seal housing  102  from the lower housing portion  110 , the user may then exert a force, e.g., a force directed in the distal direction, on the finger  1003 . This distally-directed force may be sufficient to cause the finger  1003  to move distally relative to the main housing  208  about its point of attachment thereto until the uppermost point of the ramp  1004  is located distal relative to the distal-extending member  1005  of the protrusion  1007  of the upper housing portion  110 . In this position, the upper housing portion  109  of the seal assembly is no longer prevented from rotating, but rather is free to rotate, in the second direction (e.g., counter-clockwise when  FIG. 15  is viewed from above) relative to the lower housing portion  110 . In this manner, the rotation prevention mechanism  1000  provides a selectively actuatable mechanism that, when actuated, enables a user to rotate and thereby disconnect an upper housing portion from a lower housing portion of the seal housing. 
     With continued reference to  FIGS. 3 and 4 , seal assembly  100  further includes skirt seal  132  mounted about the proximal end of inner housing component  110  or on the upper surface of the inner housing component  110  (constituting a lower component) of the seal housing  102 . Skirt seal  132  functions in minimizing the loss of insufflation gases through seal housing  102 . Skirt seal  132  also engages gimbal mount  104  and serves to bias the gimbal mount in a proximal direction against inner guide wall  112  of proximal housing  106  as will be discussed. Skirt seal  132  is preferably fabricated from a suitable elastomeric material or the like to provide a spring-like characteristic sufficient to appropriately bias gimbal mount  104 . 
     With particular reference to  FIG. 4 , gimbal mount  104  is accommodated within an annular space  134  defined between inner and outer walls  112 ,  114  of proximal housing component  106 . Gimbal mount  104  is mounted in a manner which permits angulation of the gimbal mount  104  relative to seal axis “b”. Specifically, gimbal mount  104  is free to angulate about an axis or center of rotation “c” through a range of motion defined within the confines of annular space  134 . An annular stop  136  may extend within annular space  134 . Annular stop  136  is positioned to limit the degree of angulation of gimbal mount  104  if desired. The range of movement of gimbal mount  104  will be discussed in greater detail hereinbelow. 
     Referring now to  FIGS. 5-9 , in conjunction with  FIG. 4 , the components of gimbal mount  104  will be discussed in further detail. Gimbal mount  104  includes first and second gimbal housings  138 ,  140  and resilient seal member  142  which is mounted between the housings  138 ,  140 . In a preferred arrangement, first and second gimbal housings  138 ,  140  and seal member  142  each define a general hemispherical configuration as shown. First gimbal housing  138  is preferably seated within second gimbal housing  140  and secured to the second gimbal housing  140  through a snap fit connection or the like. Preferably, first gimbal housing  138  includes a plurality of mounting legs  144  radially spaced about the outer periphery of the housing component  138 . Legs  144  define locking surfaces  146  which extend in general transverse relation to the axis “b” of seal assembly  200 . Similarly, second gimbal housing  140  includes a plurality of corresponding locking detents  148  spaced about the interior of the housing  140 . Upon insertion of first gimbal housing  138  within second gimbal housing  140 , mounting legs  144  slide along locking detents  148  whereby upon clearing the detents  148 , locking surfaces  146  of the mounting legs  146  securely engage the locking detents  148  to fix first gimbal housing  138  within second gimbal housing  140  and securing resilient seal member  142  between the components in sandwiched relation. As appreciated, first gimbal housing  138  may be sufficiently resilient to deflect upon insertion to permit mounting legs  144  to clear locking detents  148  and return to their initial position to engage the detents  148 . 
     As mentioned hereinabove, seal member  142  of gimbal mount  104  is secured in interposed relation between first and second gimbal housings  138 ,  140 . Seal member  142  preferably comprises a resilient center material (e.g., polyisoprene or natural rubber) with first and second layers of fabric  150 , 152  impregnated on the respective proximal and distal surfaces of the resilient center material. Fabric may be of any suitable fabric for example, a SPANDEX material containing about 20% LYCRA and about 80% NYLON available from Milliken. A suitable seal member or seal type is disclosed in commonly assigned U.S. patent application Ser. No. 09/449,368, filed Nov. 24, 1999, the contents of which are incorporated herein by reference. Seal member  142  defines central aperture  154  for sealed reception of a surgical instrument. In a preferred arrangement, first layer  150  is arranged to extend or overlap into aperture  154 . In this manner, the fabric (which is stronger relative to the resilient material) is positioned to engage the surgical instrument upon passage through aperture  154  of seal member  142  thereby protecting the resilient material defining the aperture. This advantageously minimizes the potential of piercing, penetrating or tearing of the resilient material by the instrument. Alternatively, an additional layer of fabric on the proximal surface of seal member  142  may be superposed and arranged to drape within aperture  154  (not shown). Seal member  142  includes an annular depression  156  on its distal surface, i.e., within second layer  152  of fabric. Depression  156  receives ledge  158  of second gimbal housing  140  to facilitate fixation of seal member  142  between first and second gimbal housings  138 ,  140 . 
     Although seal member  142  is disclosed as an impregnated fabric arrangement, it is appreciated that other seal types may be used and still achieve the objectives of the present disclosure. Further,  FIG. 6  illustrates annular depressions  153 ,  155  which have been pressed by a molding tool into layer  152 . One or more similar depressions may be pressed into layer  150  to assist positioning of fabric during manufacture of seal member  142 . 
     With reference now to  FIGS. 10-12 , in conjunction with  FIG. 4 , gimbal mount  104  is free to move within the annular space  134  defined between inner and outer walls  112 , 114  to permit angulation of the instrument relative to the seal axis “b” while still maintaining a seal thereabout. Specifically, gimbal mount  104  is adapted for swiveling movement about a center of rotation “c” which is coincident with the axis of seal assembly  100 . In this regard, the axis of the aperture  154  of seal member  142  intersects the axis “b” of the seal assembly  100  during angulation of the instrument. During angulation, gimbal mount  104  is only in contact with seal housing  102  along distal arcuate surface  118  of proximal housing  106  as well as along skirt seal  132 . Specifically, the arcuate inner surface of first gimbal housing  138  rides along distal arcuate surface  118  of inner wall  112  in contacting relation therewith (under the bearing influence of skirt seal  132 ) to permit gimbal mount  104  to swivel within seal housing  102 . Preferably, there is no other contact of gimbal mount  104  with any of the other components of seal housing, which thereby substantially minimizes resistance to the angulating movement. A lubricant may be provided between distal arcuate surface  118  and the inner surface of first gimbal housing  138  to facilitate angulation. 
     In a preferred arrangement, gimbal mount  104  may angulate or rotate through an angle inclusive of about 25 degrees, more preferably about 22.5 degrees, relative to seal axis “b”. Annular stop  136  may further restrict angulation by a couple of degrees of movement to be inclusive of an angle of about 19 degrees relative to axis “b”. 
     Seal assembly  100  may be associated with, or joined to, cannula assembly  200  in a variety of ways. In a preferred embodiment, seal housing  102  of seal assembly  100  and cannula housing  204  of cannula assembly  200  are adapted to detachably engage each other, e.g., through a bayonet lock or like mechanical means. As previously discussed, proximal and distal housing components  106 ,  108  may define an upper housing component  109  which is mountable directly to cannula assembly  200 . Alternatively, inner housing portion  110  which defines a lower housing component may be directly mounted to cannula assembly  200  independent of the upper housing component  109 . Specifically, the lower housing component  110  which houses gimbal mount  104  may be mounted to cannula assembly independent of the remaining housing components. The upper housing may then be mounted to lower housing or cannula assembly  200  as needed. Even further, upper housing component  109  may be mounted to cannula assembly  200  without lower housing component  110 . Other means of joining seal assembly  100  to cannula assembly  200  will be readily apparent to one of ordinary skill in the art. 
     Referring now to  FIGS. 13-14 , use of the seal assembly  100  and cannula assembly  200  in connection with introduction of a surgical instrument will be discussed. Seal assembly  100  is mounted to cannula assembly  200  which is previously introduced into an insufflated abdominal cavity. An instrument is inserted into seal assembly  100  through passage  116  of inner cylindrical guide wall  112  in seal housing  102 . If the axis of the instrument is not perfectly aligned with the axis “a” of cannula assembly  200  or axis “b” of seal assembly  100 , then the surgical instrument will contact the inner guide wall  112  and/or the inner surface of seal member  142 . Contact with the seal member  142  can cause some deformation of the seal member  142 . The instrument slides along the surface of the gimbal mount  104  and/or the seal member  142 , to the aperture  154 . Aperture  154  stretches to accommodate the instrument diameter, as necessary. The instrument passes further distally into the cannula housing  204  passing through duckbill valve  216  and cannula sleeve  202  into the body cavity. Once the instrument is disposed within the aperture  154 , and the friction at the skirt seal  132 , gimbal mount  104  and arcuate surface  118  is overcome, gimbal mount  104  swivels with respect to seal housing  102  as the instrument is manipulated. The gimbal mount  104  is free to swivel relative to housing  102 , while allowing seal member  142  to maintain sealing engagement with the instrument passed therethrough, as well as maintaining the seal around the gimbal mount  104 . Preferably, the seal member  142  includes resilient material and fabric material which resists deformation of the aperture  154 , as well as tearing of the seal member  142 . 
     As previously mentioned, by providing a selectively actuatable mechanism that i) when unactuated, prevents a rotatably connectable upper housing portion of a seal housing from inadvertently rotating relative to a lower housing portion of the seal housing during use, and that ii) when actuated, enables a user to rotate and thereby disconnect the upper housing portion from lower housing portion of the seal housing, various advantages may be achieved. For example, by enabling a user to rotate and thereby disconnect the upper housing portion from lower housing portion of the seal housing, one advantage that may be achieved is that a specimen may be removed from a surgical site through the lower housing portion (typically through a duckbill or other type of zero seal valve located therein) and without the need to pull the specimen through the upper housing portion (which typically would require pulling the specimen through a more restrictive instrument seal located therein). 
     Another advantage that may be achieved by providing a selectively actuatable mechanism of the type described herein is that inadvertent rotation of the upper housing portion relative to the lower housing portion may be prevented. Such inadvertent rotation of the upper housing portion relative to the lower housing portion may be particularly important in embodiments in which the obturator assembly (not shown) is bladeless, since it is often the case that bladeless obturators are “clocked” (inserted using a back-and-forth twisting motion while simultaneously providing a distal force) in order to facilitate entry through tissue layers and into the body. This clocking motion may increase the likelihood for inadvertent rotation, and thus inadvertent disconnection, of the upper housing portion  109  relative to the lower housing portion  110 . Of course, these twisting forces may also occur when a bladed, e.g., sharp, obturator assembly is employed, and thus the present invention, in accordance with various embodiments thereof, is also applicable to embodiments that employ a bladed obturator assembly. 
     Another advantage that may be achieved by providing a selectively actuatable mechanism of the type described herein is that it may reduce the amount of rotation needed in order to connect the upper housing portion relative to the lower housing portion. Various existing rotatable valve housing connection arrangements (e.g., existing valve housing connection arrangements that employ a bayonet type connection between the upper housing portion and the lower housing portion, typically requires that the upper housing portion be rotated a quarter turn, e.g., 90 degrees, relative to the lower housing portion. By providing a rotation prevention mechanism, such as rotation prevention mechanism  1000  shown in the example embodiments of  FIGS. 15-17 , the amount of rotation needed for connecting the upper housing portion and the lower housing portion may be reduced so as to be smaller than a quarter turn. This reduction in the amount of rotation needed in order to connect the upper housing portion and the lower housing portion may make it easier for a user, e.g., a surgeon, to remove the upper housing portion from the lower housing portion during surgery, especially if the surgeon desires to, or is only able to, use a single hand to do so, as is often the case in complicated surgical procedures. 
     Making it easier for a user, e.g., a surgeon, to remove the upper housing portion from the lower housing portion during surgery, particularly if a surgeon uses a single hand to do so, is also an advantage that is provided by various ones of the example embodiments disclosed hereinabove. For example, the distal movement of the finger  1003  that is employed in order to disconnect the upper housing portion  109  from the lower housing portion  110  is relatively easy for a user to perform, especially when the user has only a single hand to do so. The user can exert a distal force on the finger  1003  with the user&#39;s finger of the hand that is already gripping the cannula, thereby potentially obviating the need for the user to use a second hand (which might be engaged in performing other aspects of the surgical procedure). 
     While the invention has been particularly shown, and described with reference to the preferred embodiments, it will be understood by those skilled in the art that various modifications and changes in form and detail may be made therein without departing from the scope and spirit of the invention. Accordingly, modifications such as those suggested above, but not limited thereto, are to be considered within the scope of the invention. 
     While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of presently disclosed embodiments. Thus the scope of the embodiments should be determined by the appended claims and their legal equivalents, rather than by the examples given.