Abstract:
An access system comprises an access device. The access device is adapted to be disposed within an opening in a body wall. The access device has an external flange adapted to be disposed external to the body wall and an internal flange adapted to be disposed internal to the body wall. Holes extend through the access device between an external surface and an internal surface of the access device. The holes span the thickness of the body wall between a location external to the body wall and a location internal to the body wall. The access device is formed of an elastomeric material adapted to conform to surfaces of instruments inserted through the holes to form instrument seals along at least a portion of a length spanning the thickness of the body wall. The elastomeric material is compressible and adapted to form a seal with the body wall.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. application Ser. No. 12/960,458, filed Dec. 3, 2010, which is a continuation of U.S. application Ser. No. 12/360,710, filed Jan. 27, 2009, which is a continuation of U.S. application Ser. No. 11/244,647, filed Oct. 5, 2005, now U.S. Pat. No. 7,481,765, which is a continuation of U.S. application Ser. No. 10/381,220, filed Mar. 20, 2003, now U.S. Pat. No. 7,473,221, which is the National Phase application under 35 U.S.C. §371 of International Application No. PCT/US2001/029682, filed Sep. 21, 2001, which published in English as International Publication No. WO 2002/034108 A1 on May 2, 2002, which claims the benefit of U.S. Application No. 60/241,958, filed Oct. 19, 2000, all of the disclosures of which are incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates generally to devices and other apparatus facilitating sealed access with surgical instruments, such as a surgeon&#39;s hand, across a body wall and into a body cavity. 
         [0004]    2. Background of the Invention 
         [0005]    In several areas of surgery there exists a need to have mechanisms or devices that can seal a body cavity or space, and yet permit the introduction of surgical instruments such as guidewires, endoscopes, and even the hand of a surgeon. Typical of these areas of surgery is laparoscopic surgery which relies on surgical instruments inserted through the abdominal wall to reach an operative site within the abdominal cavity. In order to increase space around the operative site within the cavity, insufflation gases are typically introduced to inflate the cavity and elevate the abdominal wall. This pressurizing of the abdominal cavity is referred to as pneumoperitoneum. In this context, the need to seal the body cavity or space arises from the need to maintain the pneumoperitoneum even when instruments are present. 
         [0006]    Trocars have been commonly used to provide instrument access in laparoscopic surgeries. These trocars have included elaborate seal structures having zero seals which prevent escape of the gases in the absence of instruments, and instrument seals which prevent escape of the gases in the presence of instruments. Unfortunately, the instrument seals have been able to accommodate only a narrow range of instrument diameters. Where wider ranges were desired multiple seal pairs had to be provided. 
         [0007]    Some instruments, such as the hand of the surgeon, have been too large for trocar access. Under these circumstances, hand-assisted laparoscopic seals have been provided. Such devices have been large, cumbersome, and largely ineffective in providing the required sealing mechanism. Other access devices, such as Touhy-Borst seals, have been used but only for very small diameter access such as that required by a guidewire. 
         [0008]    Each of the prior devices suffers from drawbacks which make the device difficult or cumbersome to use. For example, a Touhy-Borst seal requires two hands to use and does not form a seal when a guidewire or other device is about to be introduced. Present trocar seals and hand-assisted seals require two valves, one forming an instrument seal in the presence of the instrument, and the other forming a zero seal in the absence of the instrument. For example, in hand-assisted devices, elaborate mechanisms have been required to seal around the surgeon&#39;s arm. When the arm is removed, a separate zero seal has been required to prevent the escape of blood or insufflation gases. 
       SUMMARY OF THE INVENTION 
       [0009]    These deficiencies of the prior art are overcome with the present invention which includes both a seal apparatus and a method for using this apparatus to perform elaborate surgeries. In one embodiment, the device includes a valve structure formed of a gel including, for example, a thermoplastic base such as KRATON (a trademark of Shell Corporation) and an oil. The resulting elastomer has an excellent tear strength, elongation greater than 1,000 percent, a very low durometer or hardness, and biocompatibility. A process for manufacturing this device is greatly simplified using molding techniques. 
         [0010]    Importantly, the access device can function as both a zero seal and an instrument seal. Furthermore, it can accommodate a full range of instrument diameters, such as a range from two French in the case of a guidewire, to three or four inches in the case of a surgeon&#39;s hand. In addition, several instruments can be accommodated at the same time with a single access device. 
         [0011]    Both tear resistance and sealing capability can be enhanced by encapsulating the gel in a sheath or otherwise providing circumferential reinforcement for the valve structure. Additives can be provided either on or in the gel to enhance properties such as lubricity, appearance, wound treatment and/or protection, anti-cancer protection and anti-microbial protection. Additional chemicals, compounds, pharmaceuticals or even mechanical devices can be mixed with or embedded in the gel material to vary chemical, pharmaceutical or physical properties of the access device. 
         [0012]    These and other features and advantageous of the invention will be clarified with a description of preferred embodiments and reference to the associated drawings. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view showing a patient prone on an operating table with his abdomen insufflated, and with instrument access provided by trocars and the access device of the present invention; 
           [0014]      FIG. 2  is an enlarged side elevation view of the access device of  FIG. 1  operatively disposed exteriorly as the abdominal wall; 
           [0015]      FIG. 3  is a side elevation view similar to  FIG. 2  showing the access device operatively disposed interiorly of the abdominal wall; 
           [0016]      FIG. 4  is a side elevation view similar to  FIG. 2  showing the access device operatively disposed within an incision in the abdominal wall; 
           [0017]      FIG. 5  is a plan view taken along lines  5 - 5  of  FIG. 2 ; 
           [0018]      FIG. 6  is a side elevation view similar to  FIG. 2  and illustrating a further embodiment of the access device having an external flange and an internal flange; 
           [0019]      FIG. 7  is a side elevation view similar to  FIG. 6  and illustrating the hand of a surgeon being inserted through the access device; 
           [0020]      FIG. 8  is an axially cross section view of the access device illustrated in  FIG. 6 ; 
           [0021]      FIG. 9  is a cross section view similar to  FIG. 8  and illustrating an embodiment with circumferential reinforcement members; 
           [0022]      FIG. 10  is an axial cross section view similar to  FIG. 9  and illustrating a double-ring retractor with an access device of the present invention; 
           [0023]      FIG. 11  is a radial cross section view similar to  FIG. 8  and illustrating an embodiment having a lead-in cavity or pocket; 
           [0024]      FIG. 12  is a top plan view of the embodiment illustrated in  FIG. 11 ; 
           [0025]      FIG. 13  is an axial cross section view taken along lines  13 - 13  of  FIG. 12 ; 
           [0026]      FIG. 14  is an axial cross section view taken along lines  14 - 14  of  FIG. 12 ; 
           [0027]      FIG. 15  is an axial cross section view similar to  FIG. 13  and illustrating an embodiment with a duct-bill valve; 
           [0028]      FIG. 16  is an axial cross-section view taken along lines  16 - 16  of  FIG. 15 ; 
           [0029]      FIG. 17  is a radial cross section view similar to  FIG. 13  comprising a softer hand seal and a firmer base seal; 
           [0030]      FIG. 18  is an axial cross section view taken along lines  18 - 18  of  FIG. 17 ; 
           [0031]      FIG. 19  is an axial cross section view of an embodiment having a lead-in cavity or pocket with a conical or funnel configuration; 
           [0032]      FIG. 20  is a top plan view of the embodiment illustrated in  FIG. 19 ; 
           [0033]      FIG. 21  is an axial cross section view similar to  FIG. 13  and showing another embodiment with a trapezoidal slit; 
           [0034]      FIG. 22  is an axial cross section view taken along lines  22 - 22  of  FIG. 21 ; 
           [0035]      FIG. 23  is an axial cross section view similar to  FIG. 22  taken along lines  23 - 23  of  FIG. 21  and illustrating a slit having other than a perpendicular relationship to the plane of the pad; 
           [0036]      FIG. 24  is a perspective view of a further embodiment of the access device having an opening formed by multiple slits angularly disposed and axially spaced relative to each other; 
           [0037]      FIG. 25  is a side elevation view of an access device with a slit having a spiral configuration; 
           [0038]      FIG. 26  is a top plan view of an access device having a spiral slit and axial channel; 
           [0039]      FIG. 27  is a side elevation view of an embodiment having a spiral slit and a septum seal; 
           [0040]      FIG. 28  is an axial cross section view of a further embodiment including a superelastic conical seal and a flexible base with annular spoke-like cams; 
           [0041]      FIG. 29  is an axial cross section view taken along lines  29 - 29  of  FIG. 22 ; 
           [0042]      FIG. 30  is an axial cross section view taken along lines  30 - 30  of  FIG. 22 ; 
           [0043]      FIG. 31  is an axial cross section view similar to  FIG. 28  and illustrating an embodiment including flappers; 
           [0044]      FIG. 32  is a perspective exploded view of a further embodiment including a gel cap, a base, and a retraction sheath; 
           [0045]      FIG. 33  is a top plan view of the gel cap of  FIG. 32 ; 
           [0046]      FIG. 34  is an axial cross section view taken along lines  34 - 34  of  FIG. 33 ; 
           [0047]      FIG. 35  is a top plan view of the base illustrated in  FIG. 32 ; 
           [0048]      FIG. 36  is an axial cross section view taken along lines  36 - 36  of  FIG. 35 ; 
           [0049]      FIG. 37  is a side elevation view of the retraction sheath illustrated in  FIG. 32 ; 
           [0050]      FIG. 38  is a side elevation view of a further embodiment of the retraction sheath; 
           [0051]      FIGS. 39-42  illustrate progressive steps in a preferred method of use associated with the embodiment of  FIG. 32 ; 
           [0052]      FIG. 39  is a top plan view showing use of a template; 
           [0053]      FIG. 40  is a top plan view of showing placement of the retraction sheath; 
           [0054]      FIG. 41  is a top plan view showing placement of the base ring and securement of the traction sheath; and 
           [0055]      FIG. 42  is an axial cross section view partially in section showing placement of the gel cap relative to the base. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0056]    A patient is illustrated in  FIG. 1  and designated generally by the reference numeral  10 . The patient  10  is shown in a prone position on an operating table  12 , where abdominal surgery is being performed by a surgeon  14  having an arm  16  and a hand  17 . In the illustrated example, the operative procedure is performed within an abdominal cavity  18  with instrument access provided through an abdominal wall  21 . In this type of operation, commonly referred to as laparoscopic surgery, trocars  23  and  25  are commonly used to provide minimally invasive access through the abdominal wall  21  for instruments such as a grasper  27  and an endoscope  30   
         [0057]    Although the specific focus of this disclosure will be on a preferred laparoscopic procedure, it will be noted that laparoscopic surgery is merely representative of a type of operation wherein a procedure can be performed in a body cavity with minimal access through a body wall. 
         [0058]    Notwithstanding the foregoing generality, it is important to note that with respect to laparoscopic surgery, it is often desirable that the surgeon  14  be able to insert his/her hand  17  through the abdominal wall  21  and into the abdominal cavity  18 . This insertion of the hand  17  provides the surgeon  14  with direct access to various elements of the anatomy 
         [0059]    In order to accommodate the hand  17  and arm  16  of the surgeon  14 , a small incision  32  is typically created in the abdominal wall  21 . An access device  34  of the present invention can be provided to further facilitate this access by the hand of the surgeon  14 . 
         [0060]    Particularly in the case of laparoscopic surgery, it is advantageous to insufflate the abdominal cavity  18  with a gas, such as carbon dioxide, in order to elevate the abdominal wall  21  and thereby increase the volume of the working space within the cavity  18 . Maintenance of this insufflation pressure, commonly referred to as pneumoperitoneum, is particularly difficult where access is desired across the abdominal wall  21 , for example, through the trocars  23 ,  25 , as well as the access device  34 . For this reason, a substantial effort has been directed to providing such access devices with sealing characteristics both in the presence of instruments and in the absence of instruments, such as the grasper  29 , scope  30  and hand  27 . 
         [0061]    Thus, the trocars  23  and  25  have typically been provided with complex valve structures, including, for each narrow range of instrument sizes, an instrument valve which forms an instrument seal in the presence of an instrument, and a zero valve which forms a zero seal in the absence of an instrument. By providing both an instrument seal and a zero seal the valve structures have been able to inhibit the escape of gases through the trocars both in the presence and the absence of an instrument, respectively. 
         [0062]    The instrument seals have been particularly cumbersome, as noted, and have only been effective for a small range of instrument diameters. For example, separate instrument seals have been needed for instruments, such as guidewires, which may have a diameter of only two French to three French. For medium-sized instruments having diameters of three millimeter to five millimeters, a second instrument seal has been required. In some cases, even a third instrument seal has been necessary in order to accommodate instruments having diameters such as nine millimeters to 12 millimeters. 
         [0063]    Typically the varying sizes of instruments have also required individual zero seals for each range. Thus, in a complex trocar, such as the trocar  23 , there might be as many as six separate seals associated with the access device. 
         [0064]    If not for the desire to maintain the pneumoperitoneum, there would be no need for the trocars  23 ,  25  or the access device  34 . One would merely cut an incision in the abdominal wall  21  and insert the instrument directly through the incision. However, without appropriate valves or seals, the insufflation gases would merely escape through the incisions. This would be particularly detrimental in the case of the incision  32  which must be sufficiently large to accept the hand  17  of the surgeon  14 . Thus it is a primary purpose of the access device  34  to form with the incision  32  an access or working channel  34 , and to provide a valve or other sealing structure across the working channel  34  in order to maintain the pneumoperitoneum. 
         [0065]    An enlarged view of one embodiment of the access device  34  is illustrated in  FIG. 2  which also shows the abdominal wall  21  and the incision  32 . In this simple form, the access device  34  has the general configuration of a pad  35 , meaning that it is generally flat and disposed in a plane such as the plane  38 . Typically parallel to this plane  38  are a pair of major surfaces of  41  and  43  which provide the pad  35  with a substantial surface area. An opening or slit  45  can be formed through the pad  35 , generally along an axis  47  perpendicular to the plane  38 . 
         [0066]    When operatively disposed, the opening  45  of the pad  35  is in communication with the incision  32  and, in this case, forms with the incision  32 , the working channel  36 . The alignment of the opening  45  and incision  32  can occur with the pad  35  disposed exteriorly of the abdominal wall as illustrated in  FIG. 2 , interiorly of the abdominal wall is  21  as illustrated in  FIG. 3 , or within the abdominal wall  21  as illustrated in  FIG. 4 . In any of these positions, operative disposition of the pad  35  relative to the abdominal wall  21  requires that the pad  35  be maintained in its operative position and that it form a seal around the incision  32 . Referring to the plan view of  FIG. 5 , these two functions are accomplished with an adhesive  50  disposed around the incision  32  between the pad  35  and the abdominal wall  21 . 
         [0067]    If this adhesive  50  is formed as a continuous ring  52 , as illustrated in  FIG. 5 , the pad  35  can be disposed with the ring  52  positioned circumferentially around the incision  32  to form a seal between the pad  35  and the abdominal wall  21 . In the illustrated example, when the pad  35  is operatively positioned, the escape of insufflation gases is inhibited between the pad  35  and the abdominal wall  21  by the adhesive ring  52 . 
         [0068]    The escape of insufflation gases is inhibited through the opening  45  of the pad  35  by the self-sealing characteristics of the material forming the pad  35 . This material and its highly advantageous properties are discussed in significant detail below. 
         [0069]    It will be appreciated that the functions of the adhesive ring  52  can be accomplished in many different ways using many different materials and shapes. For example, many materials other than adhesives can be used to maintain the pad  35  in position over the incision  32 . The formation of a seal around the incision  32  can also be accomplished with methods other than adhesion. Furthermore, the shape of the continuous seal formed by the adhesive  50  need not be in the shape of a circle. Rather, any continuous pattern sufficiently large to form a perimeter around the incision  32  could facilitate the desired sealing relationship. Finally, it will be noted that the mere placement of the pad  35 , for example, interiorly of the abdominal wall  21  as illustrated in  FIG. 3 , may produce a perimeter seal merely as a result of the insufflation pressure. 
         [0070]    A further embodiment of the access device  34  is illustrated in  FIG. 6  where elements of structure similar to those previously disclosed or designated with the same reference numeral followed by the lower case “a.” In this embodiment, the functions of position-maintenance and sealing are accomplished with an alternative configuration for the access device itself. The pad  35  in this case is disposed within the incision  32  as illustrated in  FIG. 4 . However, an external flange  54  and an internal flange  56  are formed integral with the pad  35 . As shown, for example, in the axial cross section view of  FIG. 8 , the access pad with flanges is formed monolithically. 
         [0071]    When operatively disposed, the external flange  54  is positioned outside of the abdominal wall  21  while the internal flange  56  is disposed interiorly of the abdominal wall  21   a.  In this matter, the pad  35  can be disposed within the incision  32   a  and held in position by the flanges  54 ,  56 . When the hand  17  of the surgeon  14  is inserted through the access device  34 , the exterior flange  54  prevents the pad  35   a  from moving distally. Similarly, when the hand  17  of the surgeon  14  is withdrawn, the interior flange  56  prevents the pad  35   a  from moving proximally 
         [0072]    In this embodiment, the opening  45   a  extends through the pad  35   a  as well as the flanges  54  and  56 , and completely defines the working channel  34  through the incision  32 . 
         [0073]    The primary seal which is required between the access device  34   a  and the abdominal wall  21 , can be formed with the adhesive ring  52   a  as discussed with reference to  FIG. 6 . Alternatively, this embodiment including the interior flange  56  may rely merely upon the surface contact between the flange  56   a  and the abdominal wall  21 . In this case, the primary seal can be formed between these structural elements and enhanced by the pneumoperitoneum pressure which forces the interior flange  56  against the abdominal wall as illustrated by a plurality of arrows  58 . This seal is formed primarily in a radial plan generally perpendicular to the axis  47 . 
         [0074]    The function of the primary seal may be further enhanced by additional sealing which occurs between the pad  35   a  and the portions of the abdominal wall  21  forming the incision  32 . In this location, the abdominal wall  21  is radially compressed by the mere presence of the pad  35  within the incision  32 . The resulting pressure produces an axial seal between the pad  35   a  and the abdominal wall  21 . 
         [0075]    If the adhesive ring  52   a  is desired for this embodiment, it is most advantageously placed around the incision  32 , between the exterior flange  54  and the abdominal wall  21 . 
         [0076]    It will be noted that whenever an instrument, such as the arm  16  or hand  17  of the surgeon  14 , is inserted through the pad  35 , the material of the pad conforms to the surface of the instrument and forms the instrument seal with the instrument. Accordingly, during the entire period beginning with insertion of the instrument and ending with withdrawal of the instrument, there is substantially no loss of insufflation gas through the pad  35   a  nor any loss of pneumoperitoneum within the abdominal cavity  18 . 
         [0077]    With further reference to  FIG. 7 , it will be appreciated that the arm  16  and hand  17  of the surgeon  14  are merely examples of instruments which can be inserted through the access device  34   a.  In the absence of the instrument, or hand  17  in the case of  FIG. 7 , the opening or slit  45   a  merely closes against itself to form a zero seal, thus preventing the escape of insufflation gases through the access device  34   a.  When the instrument, such as the hand  17 , is inserted through the opening or slit  45   a,  an instrument seal is formed between the material of the access device  34   a  and the exterior surface of the instrument. This prevents the escape of insufflation gases through the access device  34   a,  even when an instrument is present. Thus, insufflation pressures can be maintained within the abdominal cavity  18  whether or not the instrument is in place. Note that these seals, the zero seal and the abdominal seal, can be formed as a single valve structure having properties for accommodating a full range of instrument sizes. 
         [0078]    Formation of the pad  35   a  will typically be accomplished in a simple molding process described in greater detail below. In such a process, the opening or slit  45   a  may be formed as part of the molding process. 
         [0079]    In most cases, the single access opening  45   a  will be sufficient to accommodate the operative procedure. However, a further advantage of the access device  34   a  will be particularly appreciated by the surgeon  14  who requires even more access through the pad  35   a.  Consider for example, the surgeon  14  having his/her arm  16  inserted through the opening  45   a  when he/she decides that a further instrument is required for the operative procedure. Under these circumstances, a further opening through the pad  35   a  can be established by merely inserting the desired operative instrument through the pad  35   a.  In this manner, the instrument can create its own access hole beside the primary opening  45   a.    
         [0080]    Particularly for those operative instruments having pointed distal ends, the instrument can merely be forced through the pad  35   a  forming its own access hole, such as the opening  45   a,  as it is moved distally. This opening, created by the operative instrument itself, would automatically form an instrument seal as the instrument is inserted, as well as a zero seal as the instrument is withdrawn. 
         [0081]    For operative instruments not having pointed distal ends, it is possible to form a new access hole using a secondary instrument, such as a trocar obturator. After the access hole is formed, the obturator can be removed, vacating the access hole to receive the operative instrument. Throughout this process of initially forming an access hole and ultimately inserting an operative instrument through the hole, both zero seals and instrument seals are formed to maintain the pneumoperitoneum. 
         [0082]    With the advantages associated with 1) the formation of an instrument seal and a zero seal with a single valve accommodating a wide range of diameters, and 2) the formation of an instrument opening using the instrument itself, it will be appreciated that the concept of this invention will typically be embodied with a structure that is particularly dependent upon the material which forms the access device  34 . In a preferred embodiment, the pad  35  is formed of a KRATON/oil mixture including a KRATON Tri-block with a Styrene-Ethylene/Butylene-Styrene (S-E/B-S) structure in combination with a mineral oil. Other tri-block polymers can be used for this application such as Styrene-Isoprene-Styrene, (S-I-S), Styrene-Butadiene-Styrene (S-B-S), Styrene-Ethylene/Propylene-Styrene (S-E/P-S) manufactured under the trademark SEPTON by the Kuraray Co. These general formulas can be further distinguished by the ratio of the styrene to rubber content: for example, Grade 1650 is a S-E/B-S tri-block with a 29/71 styrene to rubber ratio. 
         [0083]    In addition to tri-blocks there are also di-block versions of these materials where styrene is present at only one end of the formula, for example, Styrene-Ethylene/Butylene (S-E/B) di-block. 
         [0084]    The various base formulas may also be alloyed with one another to achieve a variety of intermediate properties. For example KRATON G1701X is a 70% S-E/B 30% S-E/B-S mixture with an overall Styrene to rubber ratio of 28/72. It can be appreciated that an almost infinite number of combinations, alloys, and Styrene to rubber ratios can be formulated, each capable of providing advantages to a particular embodiment of the invention. These advantages will typically include low durometer, high elongation, and good tear strength. 
         [0085]    It is contemplated that the material of the pad  35  may also include silicone, soft urethanes and even harder plastics which might provide the desired sealing qualities with the addition of a foaming agent. The silicone materials can be of the types currently used for electronic encapsulation. The harder plastics may include PVC, Isoprene, KRATON neat, and other KRATON/oil mixtures. In the KRATON/oil mixture, for example, oils such as vegetable oils, petroleum oils and silicone oils might be substituted for the mineral oil. In the broadest sense, all of these mixtures can be described generally as a gel. The gel will typically have properties including an ability to “flow” which approaches that of a fluid. Particularly in the vicinity of any opening or slit  45  extending through the access device  34 , propagation of the opening may be of concern. Stresses resulting from the presence of an instrument will be concentrated at the ends of such an opening or slit. For this reason, a good tear resistance is desired for the gel material. Such a tear resistance is often inherent in the KRATON/oil mixtures and may be enhanced by encapsulating the gel in other materials. For example, a low tear resistant gel could be encapsulated in a urethane sheath to improve the tear resistant qualities of the resulting products. Such a sheath need not be elastic but could be comprised, for example, of overlapping sheets of a non-elastic material. 
         [0086]    Any of the gel materials contemplated could be modified to achieve different properties such as enhanced lubricity, appearance, and wound protection, or to provide anti-cancer or anti-microbial activity. Additives can be incorporated directly into the gel, for example in the case of pharmaceuticals, or applied as a surface treatment to the gel, for example, to improve lubricity or appearance. Other compounds could be added to the gel to modify its physical properties or to assist in subsequent modification of the surface by providing bonding sites or a surface charge. Antioxidants and antirads can be added to the mixture to extend the shelf life of the finished product or increase its ability to withstand radiation sterilization. 
         [0087]    Sealing materials used in medical access devices of the past have been chosen primarily for their durometer and elongation. It is these properties which measure the ability of the material to move into small spaces and crevices as may be required to form an instrument seal across the working channel of a trocar. For example, in the past, a silicone mixture was used in medical valves. This mixture had the following properties: an ultimate elongation less than about 1000 percent and a durometer not less than about 5 Shore A. 
         [0088]    These properties of the prior art materials are far exceeded by the properties associated with the present invention which in some respects provide a full magnitude of advantage. In fact, the difference between the materials of the prior art and the materials of the present invention are sufficiently substantial, that it is perhaps misleading to refer to the present material as merely a gel. According, the material of the present invention, having properties including an ultimate elongation greater than about 1000 percent and a durometer less than about 5 Shore A, will be referred to herein as an “ultragel.” 
         [0089]    In a preferred embodiment of the present invention, the ultragel includes KRATON and mineral oil and provides a sealing material with the following properties: an ultimate elongation exceeding about 1500 percent, and a durometer of less than about 200 Bloom. The durometer in this case is considerably lower than that of the prior art materials. In fact, the durometer of the present material is so soft it cannot even be measured on the Shore A scale. 
         [0090]    The resulting elongation and durometer of the present material facilitates its use with as an access valve which is capable of forming seals with a full range of instrument sizes, but is also capable of functioning as a zero seal. Whereas access devices of the prior art may have required as many as six separate seals in order to accommodate a full range of instrument sizes, access devices can now be made with only a single valve formed of the ultragel material. 
         [0091]    In a typical manufacturing process, the KRATON G1651 is mixed with the mineral oil in a ratio by weight of 1 to 9. In order to manufacture this material, the combination is heated to a temperature of about 200° centigrade. In a preferred method of manufacturing, the mold is provided with a circumferential ring insert which is molded into the gel, and slit inserts which can be removed from the gel to form the opening or slit  45 . The resulting gel can be coated with cornstarch to reduce tack and cooled at room temperature. 
         [0092]    Many of the properties of the KRATON/oil mixture will vary with adjustments in the weight ratio of the components. In general, the greater the percentage of mineral oil, the more fluid the mixture; the greater the percentage of KRATON, the more rigid the material. Weight ratios of KRATON to oil as low as 1 to 5 have been contemplated for a more rigid structure. As the KRATON/oil weight ratio approaches 1 to 10, the mixture becomes more liquid. Ratios as high as 1 to 15 have been contemplated for this invention. 
         [0093]    The processing temperature can also vary considerably as it is primarily dependent on the type of KRATON used. Temperatures in a range of about 150° centigrade to about 250° centigrade have been contemplated. 
         [0094]    With an appreciation that these ratios and temperatures can develop considerably different properties, it is now apparent that these materials can be layered to provide generally different properties within each layer. For example, an outer layer might be formed of a KRATON/oil mixture having more rigid properties, thereby providing the pad  35  with an outer layer that is more rigid. After that layer is at least partially cured, another layer of the material can be poured inside of the outer layer. This second layer might be softer providing the pad  35  with the significant sealing properties. It has been found that successive layers will tend to fuse slightly at their interface, but will generally maintain their separate identities. Additional layers could be added to provide a progression of properties in a particular device. 
         [0095]    Having discussed the properties desirable for the gel material, and the process of manufacture, one can now address the other embodiments of the concept which may provide additional advantages for particular surgical procedures. An embodiment of the access device  34 , shown in its operative position in  FIG. 6 , is illustrated by itself in the axial cross section view of  FIG. 8 , wherein the access seal with flanges is formed monolithically. 
         [0096]    This same embodiment can be reinforced with o-rings  61  and  63  as illustrated in  FIG. 9  where elements of structure are designated by the same reference number followed by the lower case letter “b.” Providing these o-rings  61  and  63  may facilitate several functions associated with the access device  34   b.  For example, the rings  61 ,  63  will typically aid in maintaining a radial sealing pressure on all sides of the opening  45   b.  The rings  61  and  63  will also tend to maintain the flanges  54   b  and  56   b  respectively, in their generally planar configurations. This further ensures that the flanges  54 ,  56  will not collapse into the incision  32  with the insertion or withdrawal of an instrument, such as the surgeon&#39;s hand  17 . Of course, the o-rings  61  and  63  must be sufficiently large to accommodate the instrument during insertion and removal. 
         [0097]    A further embodiment of the invention is illustrated in  FIG. 10 , where elements of structure are similar to those previously disclosed are designated with the same reference numerals followed by the lower case letter “c.” This embodiment includes the pad  35   c  with the opening or slit  45   c.  The external perimeter o-ring  61   c  is inserted molded into the circumference of the pad  35   c.  The internal o-ring  63   c  is coupled to the pad  35   c,  for example, by way of attachment to the o-ring  61   c  for example, by a membrane  65 . In this case, the membrane  65  has a generally cylindrical configuration and elastomeric properties. In preferred embodiments, the membrane  65  is formed of urethane, neoprene or isoprene. 
         [0098]    When the embodiment of  FIG. 10  is being operatively positioned, the internal o-ring  63   b  is initially gathered and inserted through the incision  32  ( FIG. 2 ). The pad  35   c  and external o-ring  61   c  are left outside the incision  32  so that the only material extending across the incision  32  is the membrane  65 . It will be noted that in this case, the working channel  36   c  is formed by the slit  45   c,  the cylindrical membrane  65 , and the internal o-ring  63   c.    
         [0099]    In this particular embodiment, the pad  35   c  functions generally as described with reference to  FIG. 2 . The primary seal between the pad  35   c  and the abdominal wall  21  can be formed either with a circumferential ring, such as the adhesive ring  52   c,  or by relying on the sealing characteristics of the insufflation gas  58   c  against the internal o-ring  63   c  and membrane  65 . 
         [0100]    This embodiment of  FIG. 10  is of particular advantage as it incorporates the pad  35   c  in perhaps its simplest configuration, while providing a primary seal between the device  34   c  and the abdominal wall  21  which is facilitated by the insufflation pressure. Furthermore, the membrane  65  enhances the sealing characteristics of the device  34   c,  and provides a lining for the incision  32 . With the membrane  65 , the incision  32  need not be stretched to a diameter greater than that required by any instrument inserted through the working channel  36   c.    
         [0101]    A further embodiment of the invention is illustrated in  FIG. 11  where elements of structure similar to those previously disclosed are designated with the same reference numeral followed by the lower case letter “d.” This embodiment is similar to that of  FIG. 8  in that it includes the pad  35   b,  slit  45   d,  exterior flange  54   d,  and internal flange  56   d.  The embodiment of  FIG. 11  differs from that of  FIG. 8  in that it includes a lead-in cavity  70  which is in communication with the slit  45   d.    
         [0102]    In a preferred embodiment, this cavity  70  is sized and configured to receive the arm  16  of the surgeon  14  in a manner illustrated in  FIG. 7 . In this case, the slit  45   d  would function primarily to maintain a zero seal, while the portions of the pad  35   d  or flange  54   d  which form the cavity  70  would function primarily to form the instrument seal. 
         [0103]    A further embodiment of the invention is illustrated in the plan view of  FIG. 12  and the cross section views of  FIGS. 13 and 14 . In this embodiment, elements of structure similar to those previously discussed are designated with the same reference numeral followed by the lower case letter “e.” In this case, the lead-in cavity has the general shape of a cylinder  72  with an axis that is collinear with the axis  47   e  of the pad  35   e.    
         [0104]    As perhaps best illustrated in  FIG. 13 , the slit  45   e  has a trapezoidal configuration. Thus, it begins proximally with a narrow length which may generally be equivalent to the diameter of the cylinder  32 . From the cavity  70   e,  the length of the slit  45   e  increases with progressive positions distally through the pad  35   e.  In the illustrated embodiment, the trapezoidal slit  45   e  is formed as the frustum of an isosceles triangle. 
         [0105]    A further embodiment of the invention is illustrated in  FIGS. 15 and 16  wherein elements of structure similar to those previously described are designated with the same reference numeral followed by the lower case letter “f.” As previously discussed with reference to  FIG. 12 , this embodiment of the pad  35   f  is formed with a proximal surface  71  and a distal surface  73 . The pad  35   f  also includes the coaxial lead-in cylinder  72   f  and the trapezoidal slit  45   f.  However, in this case, a duck-bill valve  74  is provided to further enhance the characteristics of the zero zeal. As illustrated, the working channel  36   f  is formed by the lead-in cavity  70   f,  the slit  45   f,  and an extension of the slit  45   f  which is defined by the duck-bill valve  74   f.    
         [0106]    The duck-bill valve  72  can be formed with opposing flanges  76  and  78  which extend distally of the distal surface  73 . When operatively disposed, the pad  35   f  can be positioned with its distal surface  73  against the exterior surface of the abdominal wall  21  ( FIG. 2 ) and with the flanges  76  and  78  extending into the incision  32 . With this configuration and operative disposition, the abdominal wall  21  at the incision  32  will produce opposing forces on the flanges  76  and  78  which tend to close the slit  45   f,  particularly in the absence of an instrument. In this manner, the duck-bill valve  74  can be relied on to enhance the characteristics of the zero seal. 
         [0107]    A further embodiment of the invention is illustrated in  FIGS. 17 and 18  wherein elements of structure similar to those previously discussed are designated by the same reference numeral followed by the lower case letter “g.” In this embodiment of the access device  34   g,  the pad  35   g  can be formed generally as discussed with reference to  FIG. 13 . In this embodiment, however, the pad  35   g  can be enclosed along its sides and the distal surface  73   g,  by a base  81 . In this case, the pad  35   g  might be formed by the highly elastic material previously discussed, while the base  81  might be formed of a more rigid but nevertheless flexible material such as a urethane. With this configuration, the duck-bill valve  74   f  would be structured to extend distally of a distal surface  83  associated with the base  81 . This would enable the duck-bill valve  74   f  to be formed of the base material rather than the superelastic material. This might also improve the zero seal characteristics for particular operative applications. 
         [0108]    Another simplified form of the invention is illustrated in  FIGS. 19 and 20 , where elements of structure similar to those previously discussed or designated with the same reference numeral followed by the lower case letter “h.” The lead-in cavity  78   h,  in this case, is formed as an inverted cone  77  having its base at the proximal surface  71   h  and its apex in proximity to the distal surface  73   h.  Thus, the lead-in cavity  70   h  has an area in radial cross section which decreases with progressive positions distally through the pad  35   h.  In this embodiment, the proximal regions near the base of the cone  87  form the instrument seal, while the distal regions at the apex of the cone form the zero seal. The conical configuration of the lead-in cavity  70   h  also tends to funnel an instrument into the opening  45   h  leading distally to the apex of the cone  87 . 
         [0109]    It will be appreciated generally, that the slit  45  and lead-in cavity  70  can be provided with many different individual and cooperative configurations. By way of example, perhaps the simplest form for the pad  35  is illustrated in the embodiment of  FIGS. 21 and 22  wherein elements of structure similar to those previously described are designated by the same reference numeral followed by the lower case letter “j.” In this embodiment, the pad  35   j  with its proximal surface  71   j  and distal surface  73   j,  is provided with a simple trapezoidal slit  45   j.  In this case, the slit  45   j  extends between the proximal surface  71   j  and the distal surface  73   j.    
         [0110]    The slit  45   j  in this embodiment of  FIG. 21  is typical of many structures which will define the slit  45   j  with a planar configuration. In such a case, the portions of the pad  35   j  which form the slit will comprise opposing planar surfaces such as those designated by the reference numerals  90  and  92  in  FIG. 22 . 
         [0111]    It will be apparent that the slit  45  need not be formed by opposing surfaces having a planar configuration. Nevertheless, these opposing surfaces need to be capable of coming into sealing contact with each other in order to establish the zero seal. Other slit configurations capable of accomplishing this function, may offer further advantages in particular procedures. Other examples of slit configurations are illustrated merely by way of example in  FIGS. 23-26 . 
         [0112]    The embodiment of  FIG. 23  is similar to that of  FIG. 22  in that the opening  45   j  comprises a single slit which extends from the proximal surface  71   j  to the distal surface  73   j.  In the case of the  FIG. 22  embodiment, the axis  47   j  is disposed within the plane of the slit  45   j.  In the case of the  FIG. 23  embodiment, the plane of the slit  45   j  does not include the axis  47   j.  Rather, the slit  45   j  is formed in a plane which has an angular relationship with the axis  47   j,  the proximal surface  71   j,  as well as the distal surface  73   j.  This construction enables the slit  45   j  to have a length greater than the thickness of the pad  35   j.    
         [0113]    In the embodiment of  FIG. 24 , elements of structure similar to those previously discussed are designated with the same reference numeral followed by the lower case letter “k.” In this case, the opening  45   k  is configured as two slits  94  and  96  formed in individual planes that are angularly spaced with respect to each other. Of course, two or more of the planar slits  94  and  96  may be equally angularly spaced around the axis  47   k.  In one embodiment, the individual planar slits  94  and  96  intersect at the axis  47   k.  Alternatively, the slits  94  and  96  may be axially spaced in order to facilitate formation of the instrument seal. 
         [0114]    In the embodiment of  FIG. 25 , elements of structure similar to those previously discussed are designated with the same reference numeral followed by the lower case letter “m.” In this embodiment, the opening  45   m  is defined as a slit  98  having a curved rather than planar configuration. In the illustrated embodiment, the curved slit  98  is formed as a spiral around the axis  47   m.  Along the axis  47   m,  the opposing surfaces forming the spiral slit  98  can “flow” into sealing proximity in order to produce the zero seal. 
         [0115]      FIG. 26  illustrates a similar embodiment including a spiral slit. In this figure, elements of structure similar to those previously discussed are designated by the same reference numeral followed by the lower case letter “n.” The spiral slit  98   n  in this embodiment is also formed around the axis  47   n  of the pad  35   n,  but in this case the portions forming the slit  98   n  do not extend completely to the axis  47   n.  As a result, an axial channel  100  is formed at least partially along the axis  47   n.  This channel  100  can function in a manner similar to the lead-in cavity  70  discussed with reference to  FIGS. 11-12 . This channel  100  can even be formed with a conical configuration similar to that discussed with reference to  FIG. 19 . 
         [0116]    In an embodiment where the channel  100  is left open, a zero seal might be provided by positioning a septum valve across the channel  100 . Such an embodiment is illustrated in  FIG. 27 , wherein the septum valve is designated with a reference numeral  101  and the other elements of structure similar to those previously discussed are designated with the same reference numerals followed by the lower case letter “p.” Thus the embodiment of  FIG. 27  includes the spiral slit  98   p,  the pad  35   p,  and the axis  47   p.  This embodiment of  FIG. 27  is merely representative of many other embodiments that will combine a slit, such as the slit  98   p,  with other valve structures, such as the septum valve  101 . 
         [0117]    Other curved slit configurations would include embodiments wherein the slit is curved, sinusoidal, or S-shaped in a side elevation view. Such configurations provide a slit part having a length greater than the thickness of the pad. Normally, the more circuitous the slit path, the better the sealing characteristics. 
         [0118]    A further and more complex configuration for the opening  45  is illustrated in the embodiment of  FIG. 28  wherein elements of structure similar to those previously disclosed are designated with the same reference numeral followed by the lower case letter “q.” This embodiment is representative of many other complex embodiments which can be formed with intricate shapes and different materials in order to accomplish the desirable function of forming, with a single valve, a zero seal as well as an instrument capable of accommodating a full range of instrument sizes. In the embodiment of  FIG. 28 , the pad  35   q  is formed with a base  110  which is disposed circumferentially of a core  112 . In this case, the core  112  is formed of the superelastic material or gel and provided with the shape of the cone  87   q  as discussed with reference to  FIGS. 19 and 20 . The base  110  is formed from a material that may not be elastic, but preferably is flexible. In the preferred embodiment, the base  110  is formed of a urethane. 
         [0119]    In this construction, the base  110  is provided with a plurality of spokes  114  each of which extends radially inwardly from a base  116  to a tip  118 . The core  112  extends from the axis  47   q  outwardly to the tips  118  of the spokes  114 . In the illustrated embodiment, the core  112  has fingers  121  which extend beyond the tips  118  and toward the bases  116  between each adjacent pair of the spokes  114 . These fingers  121  extend radially outwardly to an end surface  123  which stops short of the base  116  leaving a void  125  therebetween. 
         [0120]    The voids  125  are of particular interest to this embodiment and can be incorporated into any of the embodiments previously discussed. Such voids  125  provide a space or absence of material into which the highly elastic material, such as that of the fingers  121 , can expand during insertion of an instrument such as the arm  16  ( FIG. 7 ). Since the gel material is almost fluid in its properties, the voids  125  permit expansion of the gel with very little resistance. Voids, such as the voids  125  in the embodiment of  FIG. 28 , can be defined solely in the gel material or between the gel material and any other base material. 
         [0121]    In the case of  FIG. 28 , the spokes  114  and fingers  121  are defined generally in planes which are parallel to the axis  47   q.  Similar fingers, illustrated in the embodiment of  FIG. 31  are defined generally in a plane which is perpendicular to the axis. In this embodiment, elements of structure similar to those previously disclosed are designated by the same reference numeral followed by the lower case letter “r.” As illustrated, the pad  35   r  can be formed with a relatively large opening  45   r  having the configuration of a coaxial cylinder  130 . A plurality of fingers or flaps  132  extend into the opening  45   r  and tend to form a lead-in cavity  70   r  with properties such as those discussed with reference to  FIG. 19 . In this case, the annular flaps  132  have a conical configuration extending from a base  134  to an apex  136 . It will be noted that the areas between the flaps  132 , form voids  125   r  into which the flaps  132  can be displaced upon insertion of an instrument, such as the arm  16 . 
         [0122]    A further embodiment of the invention is illustrated in  FIG. 32  where elements of structure similar to those previously disclosed are designated with the same reference numeral followed by the lower case letter “s.” This exploded view of the access device  34   s  includes not only the pad  35   s  but also a complimentary structure for maintaining the position of the pad  35   s,  for forming a seal between the pad  35   s  and the abdominal wall  21 , and for dilating the incision  32  to a variable extent as required by the surgeon  14 . In this case, the access device  34   s  includes three components, a gel cap  143 , base  145 , and a retraction sheath  147 . 
         [0123]    The gel cap  143  includes not only the gel pad  35   s,  but also a circumferential cap ring  154  which can be inserted and molded to the pad  35   s.  The resulting gel cap  143  forms a seal with the base  145 , thereby defining the working channel  36   s  through the pad  35   s,  the cap ring  154 , the base  145 , and the retraction sheath  147 . In the manner previously discussed, this working channel  36   s  includes the single valve formed by the gel pad  35   s  which provides both a zero seal and an instrument seal for a wide range of instrument diameters. 
         [0124]    The structure associated with the gel cap  143  is described in greater detail with reference to  FIGS. 33 and 34 . In the plan view of  FIG. 33 , it can be seen that this embodiment includes the gel pad  35   s  centrally disposed within the circumferential cap ring  154 . Holding tabs  156  can be provided to extend radially outwardly of the cap ring  154 . These holding tabs  156  can facilitate the sealing engagement of the gel cap  143  with the base  145  in the manner described in greater detail below. 
         [0125]    The gel pad  35   s  can be formed of any of the materials previously discussed although the preferred embodiment includes the KRATON/mineral oil gel. The cap ring  154  for such an embodiment can be advantageously formed of KRATON only. This will make the cap ring  154  more rigid than the gel pad  35   s  while maintaining an excellent material interface between the pad  35   s  and the ring  154 . In a typical manufacturing operation, the cap ring will be pre-disposed in the mold for the gel pad  35   s  with the unitary structure of the gel cap  143  resulting. 
         [0126]    The cross section view of  FIG. 34  shows the gel cap  143   s  and illustrates an annular void  158  formed on the inner circumference of the cap ring  154 . This void  158  is of particular advantage in forming a sealing relationship with the base  145  in the manner discussed in greater detail below. 
         [0127]    The base  145  of this embodiment is shown in greater detail in the plan and cross section of views of  FIGS. 34 and 35 , respectively. From these views it will be noted that the base  145  can be provided with a smooth generally cylindrical inner surface  161  which extends proximally to a rounded end surface  163  and outwardly from the end surface  163  along an annular lip  165 . A plurality of tabs  167  can be equally spaced to extend outwardly and distally around the circumference of the lip  165 . 
         [0128]    Distally of the inner surface  163 , an annular flange  170  can be provided with an annular projection  172  sized and configured to form the desired sealing relationship between the gel cap  143  and the base  145 . The process of molding the base  145  can be facilitated by forming the base as two separate components divided, for example, by a dotted line  174  in  FIG. 35 . In a preferred embodiment, the base  145  is molded from a polycarbonate material. 
         [0129]    A preferred embodiment of the retracting sheath  147  is illustrated in  FIG. 37 . In this view it can be seen that the retraction sheath  147  includes a tubular wall  175  which has the configuration of the frustum of a cone  176  at its distal end and the configuration of a cylinder  177  at its proximal end. A flexible retaining ring  152  terminates the distal end while a fold  154  is formed at the proximal end. The tubular wall  175  is illustrated to include an outer surface  180  and an inner surface  181 . In a preferred embodiment, the sheath  147  is formed of an elastomer, such as neoprene, so its frustule conical and cylindrical configurations exist primarily in the natural unstretched state. 
         [0130]    As the sheath  147  is stretched axially, the diameter of the cylindrical proximal end increases thereby placing radial forces on the incision  32 . The more the sheath  147  is stretched axially, the greater becomes the diameter of the sheath and consequently the larger becomes the opening through the incision  32 . This feature is of particular advantage as it permits the surgeon to define the size of the incision  32  with an appropriate degree of axial tension on the sheath  147 . By maintaining this tension, the preferred size of the incision  132  is maintained throughout the operation. In a preferred apparatus and method, the axial tension is maintained by stretching the sheath  147  over the tabs  167  ( FIG. 34 ) of the base  145 . Indicia  182  can be printed on the sheath  147  to provide an indication of the relationship between the axial stretch of the sheath  147  and the size of the incision  32 . 
         [0131]    The fold  153  is provided to facilitate a grip on the proximal end of the sheath  147 . This fold  153  can also function to provide reinforcement where the walls of the sheath  147  engage the tabs  167  of the base  145 . In the embodiment illustrated in  FIG. 38  additional folds  184 ,  186  are provided at spaced axial locations, such as those defined by the indicia  182  in  FIG. 37 . With these folds  184  and  186 , additional points of reinforcement are provided to engage the tabs  167  while providing the sheath  147  with predetermined degrees of axial stretch associated with different sizes of the incision  32 . 
         [0132]    The method of using the embodiment of  FIG. 32  is illustrated the progressive use of  FIGS. 39-42 . In  FIG. 39 , a top plan view of the abdominal wall  21  of the patient  10  is illustrated with a template  195  positioned to facilitate location of the incision  32 . The size of the incision  32  can be determined with the indicia  182  on the template  195  showing, for example, multiple lengths of a line  197 , each length being equated with a glove size for the surgeon&#39;s hand  17  ( FIG. 7 ). Knowing his/her glove size, the surgeon will merely cut the incision in accordance with an appropriate length of the line  197 . The longer lengths of the line  197  are associated with the larger incisions, the larger glove sizes and accordingly the larger hands  17 . After the incision  32  has been cut along the line  197 , the template  195  can be removed. 
         [0133]    As illustrated in  FIG. 40 , the retraction sheath  147  can then be mounted through the incision  32 . Initially the ring  152  is compressed and fed through the incision  32 . On the inner surface of the abdominal wall  21 , the ring  152  is free to expand to its larger diameter, as shown by a dotted line  158  in  FIG. 40 . The portions of the wall  176  which define the cylinder  177  are left to extend proximally through the opening  32  as shown in  FIG. 40 . 
         [0134]    Prior to or after inserting the sheath  147 , the base  145  can be disposed around the incision  32 . Then the exposed portions of the sheath  147  will extend through the incision  32  and within the circumferential base  145 . As illustrated in  FIG. 41 , the wall  176  of the sheath  147  can then be drawn proximally, outwardly of the page in  FIG. 41 , to axially stretch the sheath  147 . As noted, when the sheath  147  is axially stretched, it will create radial forces on the abdominal wall  21  which will tend to enlarge the incision  32 . The greater the axial stretch, the larger the incision  32 . 
         [0135]    When the incision  32  has the desired size, the stretched sheath  147  can be drawn over the tabs  167  to maintain the axial stretch and the desired size for the incision  32 . Either the indicia  182 , as shown in  FIG. 36 , or the additional folds  184  and  186  as shown in  FIG. 37 , can be aligned with the tabs  167  to provide a predetermined size for the incision  32 . At this point, the seal between the abdominal wall  21 , the sheath  147 , and the base  145  is fully established. 
         [0136]    A final step remaining in this process is the attachment of the gel cap  143  to the base  145 . This is accomplished as illustrated in  FIG. 36  by capturing the lip  172  of the base  145  in the annular void  158  of the gel cap  143 . Bending the holding tabs  156  upwardly and outwardly facilitates this engagement which ultimately forms a seal between the base  145  and the gel cap  143 . 
         [0137]    Although this invention has been disclosed with reference to certain structural configurations, it will be appreciated that these products are merely representative of many different embodiments of the invention. Accordingly, one is cautioned not to limit the concept only to the disclosed embodiments, but rather encouraged to determine the scope of the invention only with reference to the following claims.