Abstract:
An interlock vessel having an air-tight body with opposing ends. A portion of the body is designed to fit into a decompression (hyperbaric) chamber, wherein a diver or a patient undergoing a decompression treatment is positioned. The opposing ends are closed by pivotally moveable doors and locking assemblies that retain the doors in a closed position until the pressure inside the decompression chamber and the exterior of the chamber can be equalized. The outer door has two locking systems: (a) an interlock system and (b) a safety/delay locking system. Both locking assemblies are manually operated.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of PCT Application Serial No. PCT/US07/85471, filed Nov. 23, 2007, which was a continuation-in-part of U.S. patent application Ser. No. 11/893,174, filed Aug. 15, 2007, which application was a continuation-in-part of U.S. patent application Ser. No. 11/626,648, filed 24 Jan. 2007, and priority of each of the above referenced applications is hereby claimed. 
         [0002]    PCT Application Serial No. PCT/US07/85471, filed Nov. 23, 2007, is incorporated herein by reference. 
         [0003]    U.S. patent application Ser. No. 11/893,174, filed 15 Aug. 2007, is incorporated herein by reference. 
         [0004]    U.S. patent application Ser. No. 11/626,648, filed 24 Jan. 2007, is incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0005]    Not applicable 
       REFERENCE TO A “MICROFICHE APPENDIX” 
       [0006]    Not applicable 
       BACKGROUND 
       [0007]    Hyperbaric and/or decompression chambers are used in many applications, and in many situations require the transfer of items either to and/or from the interior of the chambers. For example, deep sea diving, whether for pleasure or work, is associated with a serious risk of trauma to the divers. Without proper treatment, major problems from diving accidents, most commonly decompression sickness (or the “bends”) and Air Embolism, can lead to permanent disabling injuries and in some instances be fatal. Conventionally, offshore rig divers who work at great depths for considerable amounts of time must undergo decompression for extended periods time (e.g., up to two weeks). Normally the decomposition takes place in a conventional decompression chamber on the offshore rig or on a deck of a dive boat. 
         [0008]    Dive chambers are examples of a category of pressure vessel referred to as a pressure vessel for human occupancy (“PVHO”). Once the divers are inside the vessels of the transfer system their condition must be kept stable. In keeping with this objective the problem arises of keeping the gas mixtures constant within the vessels of the transfer system. This includes both the pressures and concentrations of the compression gas, the breathing gas and the oxygen within the chamber. It is especially true for the oxygen supply within the vessel which must be replenished as it is used. 
         [0009]    While the individual is in the decompression chamber, if medicines, supplies, food, drink, or other items are to be provided to the individual, a method and apparatus for supplying such items without substantially impacting the interior pressure and gas concentration inside the chamber needs to be provided. Additionally, it is desirable that in making this transfer that a minimum amount of interior gas pressure and/or gas concentration is lost. 
         [0010]    One conventional method for providing access to the individual while inside the chamber is through an air lock which is independent of the entrance to the chamber. The air lock on a dive chamber can include a steel tube penetrating the chamber&#39;s wall. The steel tube can have doors called “closures” on each end. 
         [0011]    Certain design conditions need to be addressed for an air lock or transfer portal to a decompression chamber. For example, in a portal with outer and inner doors, the outer door should be able to withstand the internal pressure of the dive chamber when the inner door is open. 
         [0012]    In one embodiment a quick lock/quick unlock can be provided for the outer door. In one embodiment the quick lock/quick unlock for a small diameter portal can include a breech-lock type “two-ring” design familiar to those skilled in the art of quick opening closures. A two-ring style door can use a body ring welded to the body of the portal which rotatably houses a door. In one embodiment the door can have a plurality of radial extending protrusions. In one embodiment the body ring can have a plurality of enlarged openings which correspond to the plurality of radially extending protrusions of the door. In one embodiment the door can be rotated relative to the ring such that the plurality of radially extending protrusions slidable lock with the ring and prevent longitudinal movement of the door relative to the portal thereby keeping the door closed. In one embodiment the outer door can be rotated relative to the ring such that the plurality of radially extending protrusions enter the plurality of enlarged openings so that longitudinal movement of the door relative to the portal is allowable thereby allowing the door to be opened. 
         [0013]    In one embodiment one or more of the plurality of radially extending protrusions can have a sloped section (in a rotational direction), such that when the outer door is rotated in the direction of slope the door tends to move in a longitudinal direction towards the interior of the portal. In this way the seal between the exterior door and the portal (such as an O-ring) can be more tightly sealed or energized. In one embodiment a perimeter groove in the ring can include a plurality of sloped sections such that when the outer door is rotated in a first direction the door tends to move in a longitudinal direction towards the interior of the portal causing a tighter seal to be made between the door and the portal. In one embodiment corresponding sloped areas are provided on both the plurality of radially extending protrusions of the exterior door and the plurality of sloped sections by the corresponding plurality of enlarged openings, such that both sloped portions tend to cause the door to more tightly seal against the portal when the door is rotated. 
         [0014]    In some instances “three-ring” closures can be used on outer doors. In three-ring closures the door and body ring (first and second rings) do not rotate. Instead, a third ring (locking ring) located outside of the door and body rings itself rotates to engage mating lugs on the door and/or body rings and thereby obtain a seal. Two ring closures are preferred over three ring closures for various reasons: two ring closures are less expensive because they do not have a third ring; do not require lubrication of the sliding surfaces of this third ring; and do not have high stress areas hidden under such a third ring (which can inhibit a pre-failure detection analysis). Advantages of two ring versus three ring closures are particularly useful in competitive commercial applications such as dive chambers where they are subjected to harsh outdoor marine environments. 
         [0015]    One hazard for conventional locks for closures is that the operator can attempt to open the air lock while the door is under pressure. As a consequence of this pressure differential, the door can be forced open very fast and the operator can be injured or the person inside the chamber can be injured by the inner door swinging open explosively. 
         [0016]    Conventional locks for preventing two-ring closures from being opened while under pressure rely on indicators. Examples of “indicators” include pressure gages or pressure actuated spring loaded pop-up pistons. However, indicators only “notify/flag” operators, and depend on the operator recognizing and acting on the information provided by the indicators. Additionally, spring-loaded piston indicators retract when a small pressure still remains in the closure so that a false “OK” signal can be communicated. Even relatively small pressure differentials between the interior of the portals and the area where the closure is being opened can cause large forces on the closures and cause them to open fast causing injury. 
         [0017]    Another potential problem with two-ring closures (or doors) relates to the door support allowing the door to both “swing out” (e.g., open and close) but also rotate about its axis (for locking/sealing and unlocking/unsealing). Because two distinct movements are required, a two-ring door hinge typically connects the door using a longitudinal bearing in the hinge blade which longitudinal bearing supports an axle in the center of the door. However, these bearings eventually wear, and such wear allows changes in concentric alignments of the door relative to the locking ring. 
         [0018]    Alignment of the door relative to the locking ring is important because O-rings are preferred for sealing. O-rings (which are self-energizing gaskets) use the pressure of the fluid or gas being sealed to contribute to (or energize) their sealing effect. O-ring seals require containment in a cavity with limited gaps to prevent a form of failure referred to as “extrusion.” Extrusion failure of O-rings and the design gap sizes required to prevent it are described in O-ring design handbooks such as the “Parker O-Ring Handbook” and are familiar to those skilled in the art of O-ring joint design. For a closure where human life depends on its proper operation a concentricity misalignment of the door which leads to a gap and possible extrusion failure is unacceptable. 
         [0019]    Conventionally available locks can be interlocks which are devices constraining the operator from opening the closure (door) until after the air locked has started to vent. Conventional interlocks for two-ring doors include threaded vent plugs in the door which vent plugs are chained to a stationary part of the vessel. These “vent-plug-on-chains interlocks” can restrict opening of the door, but they are slow and awkward. 
         [0020]    Another problem with dive chamber air locks relates to the operation of the inner closure or door. Interior pressures of chambers are typically elevated compared to outside pressures. Because the inner door swings inwards when opening, the higher interior pressure of the dive chamber (or living space), compared to the pressure outside the chamber, causes the inner door to be pushed against the portal and pushed against a sealing O-ring (between the interior door and the portal). The force created by the higher interior pressure energizes the sealing O-ring, and seals the interior from the portal. Because of this higher interior pressure the inner door does not require a lock (or locking ring) to create a seal when in use and pressurized. However, dive chambers are not always in use and pressurized and when on ships, and when not pressurized dive chambers can be subjected to large jerking motions (such as wave action) causing the “unlocked” inner door to swing open and shut causing damage. Also, large motions can be seen during other activities of ships such as during the discharge if cargo which can cause an unlatched inner door to swing open and closed on its own. Additionally, dive chambers can be transported from one ship to another location such as by truck also subjecting the dive chamber to large jerking motions. During periods in which a dive chamber is subjected to large jerking motions, an “unsecured inner door” can bounce open and closed, which can cause damage to the inner door, O-ring, and/or portal. 
         [0021]    Furthermore, if the inner door is somehow opened when the interior of the dive chamber is pressurized but unoccupied, a person standing outside the dive chamber would be unable to reach through the outer door and grab hold and close the inner door. However, even assuming that the interior door can be reached from the exterior, attempting to close the inner door from the exterior is very dangerous because the increased interior pressure can cause the interior door to slam shut very quickly, which slamming shut can harm the person attempting to close. 
         [0022]    A seemingly simple solution for the interior door is to use a swing bolt latch or other clamping latch. However, swing bolts or clamping latches have the disadvantage of continuing to hold shut the inner door even where the portal pressure (or exterior pressure) is substantially greater than the interior dive chamber pressure. For example, locked swing bolts or clamping latches can trap elevated pressures inside the portal as the interior pressure of the dive chamber is reduced during a depressurization cycle. A trapped high differential pressure behind the inner door risks this door being slammed open and harming a person in the interior of the dive chamber—such as where the swing bolt or clamping latch is released (or fails) with a trapped high differential pressure behind the inner door. Such a condition could lead to an explosive release of the inner door. 
         [0023]    Another disadvantage with conventionally available air locks (or access portals) is their lack of dealing with the time delay between: (a) starting the venting process of the interior of the portal and (b) the finishing of the venting process. Even where an interlock is used on the outer door to start venting and also “unlock” the outer door, a time lag exists between the start of the venting process to the time where the pressure differential between the interior of the portal and the exterior is at an acceptable level so that the outer door is not cause to explosively swing open. 
       BRIEF SUMMARY 
       [0024]    In one embodiment is provided an interlock assembly for use with an air lock or portal fluidly connected to decompression or hyperbaric chambers. In one embodiment this air lock converts the decompression or hyperbaric chamber to a hyperbaric transfer system. 
         [0025]    In one embodiment the decompression chamber can be cylindrical in shape with a sidewall forming the cylinder. 
         [0026]    In one embodiment is provided an interlock air lock assembly for use with decompression chambers or hyperbaric chambers. The interlock assembly can be a portal comprising a hollow air tight vessel with open ends which are selectively closed/opened by a respective inner door and an outer door. 
         [0027]    In one embodiment is provided a portal having a body with a sidewall extending between the opposite ends, and the inner door and the outer door having hinged assemblies that are secured to the body for pivotal movement of the doors. 
         [0028]    In one embodiment the air lock or portal can be attached to the sidewall of the decompression or hyperbaric chamber. 
         [0029]    In one embodiment one or both the inner door and/or the outer door can be equipped with latch assemblies for safely closing the doors to maintain an air tight environment. 
         [0030]    In one embodiment the outer door can be also rotatable in relation to the portal. In one embodiment the outer door can be both rotatable and pivotal in relation to the portal. 
         [0031]    In another embodiment is provided an interlock assembly that has a plurality of locking/latching safety locks which prevent an undesirable rapid venting of the decompression chamber wherein a diver and/or patient is situated. 
         [0032]    In one embodiment the inner door is mounted at an interior end of the vessel in fluid communication with the decompression chamber when the inner door is open. 
         [0033]    In one embodiment one or both the inner door and the outer door can be provided with seals (such as sealing O-ring fitted on the inside surface of the respective door) to facilitate the air tight engagement of the door with the body of the portal. 
         [0034]    In one embodiment is provided a locking ring mounted at the outside edge of the vessel or portal allowing at least one locking bar to selectively extend therethrough (from the rear) to prevent undesirable rotation and opening of the outer door at a time when the vessel or portal is at an elevated pressure. 
         [0035]    In one embodiment is provided a quick lock/quick unlock interlock system which both releases a lock against rotation of the outer door and starts venting the interior of the portal. 
         [0036]    In one embodiment a pressure relief valve can be operatively connected to the locking member for rapidly venting pressure inside the portal when the quick lock/quick unlock is switched to an open state. 
         [0037]    In one embodiment is provided a venting valve which is operably connected to a sliding locking member. 
         [0038]    In one embodiment the venting valve is fluidly connected to the sidewall of the body of the air lock or portal. 
         [0039]    In one embodiment the operative connection between the venting valve and sliding locking bar is made through a four bar linkage system which includes a slider. 
         [0040]    In one embodiment the slider connection passes through a locking ring of the portal from the rear of the locking ring. 
         [0041]    In one embodiment the slider connection has a first end and when it moves from the unlocked state to the locked state the first end moves away from the inner door and towards the outer door. 
         [0042]    In one embodiment the slider connection has a first end and when it moves from the locked state to the unlocked state the first end moves away from the outer door and towards the inner door. In one embodiment the slider connection has a first end and when it moves from the unlocked state to the locked state the first end moves away from the inner door (at a time which the first end is between a plane bisecting a perimeter groove and the inner door) and towards the outer door (the first end passing through the bisecting plane). 
         [0043]    In one embodiment the slider connection has a first end and when it moves from the locked state to the unlocked state the first end moves away from the outer door (at a time which the first end is in front of a plane bisecting a perimeter groove and the inner door) and towards the outer door (the first end passing through the bisecting plane). 
         [0044]    In one embodiment the slider connection has a first end and when it moves to the locked condition the first end passes from behind the middle of the locking ring to in front of the locking ring. 
         [0045]    In one embodiment the slider connection has a first end and when it moves to the unlocked condition the first end passes from in front of the middle of the locking ring to behind the middle of the locking ring. 
         [0046]    In one embodiment the slider connection has a locking bar and the locking bar is located between the exterior of the sidewall of the portal and the outside of the locking ring. 
         [0047]    In one embodiment a quick lock/quick unlock sensitive to the pressure differential between the interior of the portal and the exterior can be used to rotational lock the outer door. 
         [0048]    In one embodiment the pressure sensitive quick lock/quick unlock can be a second lock in addition to an interlock quick lock/quick unlock. 
         [0049]    In one embodiment the second lock can be operatively connected to the first lock, switching from open to closed (or from closed to open) states in a time delayed manner relative to the first lock. 
         [0050]    In one embodiment is provided a safety lock/unlock which will generally take between about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 seconds to unlock from the start of venting of the interior of the portal and the time the quick lock/quick unlock enters an unlocked state. In various embodiments ranges between any of the above referenced time delays are envisioned. 
         [0051]    In one embodiment is provided a safety lock/unlock which will generally enter an unlocked stated when the different between the interior pressure of the portal and the exterior is below a specified safety level. In one embodiment the acceptable differential is less than about 5 psi, 4 psi, 3 psi, 2 psi, 1 psi, and/or V 2  psi (34.5, 27.6, 20.7, 13.8, 6.9, and/or 3.4 kilopascals). In various embodiments ranges between any of the above referenced pressure differentials are envisioned. 
         [0052]    In one embodiment the amount of rotation of the outer door is limited in both first and second directions. In one embodiment this rotational limit is obtained by a slot and pin mechanism. 
         [0053]    In one embodiment rotation of the outer door causes the door to tighten (shut more securely and seal) relative to the interior of the portal. 
         [0054]    In one embodiment a seal is set up between the inner door and the interior of the dive chamber when the pressure of the interior of the dive chamber becomes greater than the pressure of the interior of the portal. 
         [0055]    In one embodiment the interior door includes a latching mechanism which opens partially based on a differential higher pressure between the interior of the portal and the interior of the dive chamber. Such partial opening allows the interior of the portal to vent into the interior of the chamber. 
         [0056]    In one embodiment the latching mechanism includes first, second, and third latching conditions, where the first latching condition is entered when the inner door seals the interior of the chamber from the interior of the portal, the second latching condition includes a partial opening of the inner door so that venting occurs from the interior of the portal to the interior of the chamber, and the third latching condition is an open condition—where the inner door is no longer constrained by the latch. 
         [0057]    In one embodiment, when the interior pressure of the portal exceeds the interior pressure of the dive chamber the latching mechanism moves from the first latching condition to the second latching condition and allows pressure to vent from the interior of the portal to the interior of the dive chamber but restricts the extent to which the interior door can open. In one embodiment the inner door can open less than about 1/200, 1/100, 1/90, 1/80, 1/70, 1/60, 1/50, 1/40, 1/30, 1/20, 1/10, ½, 1, 1½, 2, 2½ 3, 4, 5, 6, 7, 8, 9, and 10 millimeters. In various embodiments ranges between any of the above referenced distances are envisioned. 
         [0058]    In one embodiment the latching mechanism on the inner door includes a spring which is biased to cause the latch to move in a latched condition. 
         [0059]    In one embodiment the latching mechanism includes a handle which has first and second sloped portions, the first sloped portion tending to be sloped towards the longitudinal centerline of the portal, and the second sloped portion tending to be sloped away from the longitudinal centerline of the portal. 
         [0060]    In one embodiment the inner door includes a quick connect/quick disconnect mechanism for attaching to the interior end of the portal. 
         [0061]    In one embodiment the inner door includes a floating connection with its hinge, this floating connection assisting in aligning the door with the interior opening of the portal. In one embodiment the inner door includes a centrally protruding section which can assist in aligning concentrically the inner door with the interior opening of the portal. 
         [0062]    In one embodiment the inner door includes a venting valve for venting between the interior of the chamber and the interior of the portal. In one embodiment the venting valve can be located on the body of the air lock or portal. 
         [0063]    In one embodiment the inner door rotates about an axis which is included in a horizontal plane. 
         [0064]    In one embodiment the inner door rotates about an axis which is included in a vertical plane. 
         [0065]    In one embodiment the outer door rotates about an axis which is included in a horizontal plane. 
         [0066]    In one embodiment the outer door rotates about an axis which is included in a vertical plane. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0067]    Reference will now be made to the drawings, wherein like parts are designated by like numerals, and wherein 
           [0068]      FIG. 1  is a perspective view of a decompression chamber with air lock or portal. 
           [0069]      FIG. 2  is an enlarged perspective view of the interlocking air lock or portal of  FIG. 1  looking at the portal from the front of the chamber, and where a portion of the sidewall of the decompression chamber has been removed to show the inner and outer ends of the portal. 
           [0070]      FIG. 3  is an enlarged perspective view of the interlocking air lock or portal of  FIG. 2 , but now looking at the portal from the rear of the chamber and where a portion of the upper section of the portal has been removed to reveal the interior of the portal. 
           [0071]      FIG. 4  is an enlarged perspective view of the interlocking portal of  FIG. 2 , showing the quick lock/quick unlock system now placed in an unlocked state along with schematically showing the venting of the interior of the portal, and the safety or delayed lock system being pressure sensitive and moving from a locked to an unlocked state. 
           [0072]      FIG. 5  is an enlarged perspective view of the interlocking air lock or portal of  FIG. 2  with the outer door opened and schematically showing an item being placed in the interior of the portal. 
           [0073]      FIG. 6  is an enlarged perspective view of the interlocking air lock or portal of  FIG. 2  showing the item placed in the portal with the outer door closed, and the quick lock/quick unlock system now placed in a locked state, and the venting valve on the inner door opened to vent pressure from the interior of the dive chamber to the interior of the portal, and the safety or delayed locking system being pressure sensitive and moving from an unlocked state to a locked state. 
           [0074]      FIG. 7  is an enlarged perspective view of the interlocking portal of  FIG. 2  showing the inner door being opened and the item being moved from the interior of the portal to the interior of the dive chamber. 
           [0075]      FIG. 8  is a perspective view of the interlocking air lock or portal of  FIG. 2 , where a portion of the outer door and locking ring has been removed to show the body of the portal along with the quick lock/quick unlock and safety or delayed locking systems. 
           [0076]      FIG. 9  is a perspective view of the interlocking air lock or portal of  FIG. 4  with the quick lock/quick unlock locking member placed in an unlocked state and the safety or delayed locking system&#39;s locking member remaining in a locked state. 
           [0077]      FIG. 10  is perspective view of the interlocking portal of  FIG. 2  with a portion of the locking ring removed to show the interaction between the first locking rod and of one of the radial protrusions of the outer door, and also showing the interaction between the second locking rod and another of the radial protrusions. 
           [0078]      FIG. 11  is perspective view of the interlocking portal of  FIG. 2  with the outer door opened and a portion of the locking ring and outer door removed to show the body of the portal along with the quick lock/quick unlock and safety or delayed locking systems. 
           [0079]      FIG. 12  is a sectional diagram showing the quick lock/quick unlock locking system, along with closed and open states of the handle for this locking system. 
           [0080]      FIG. 13  is a sectional view of the locking member for the quick lock/quick unlock locking system, where it is shown in open and closed states for the locking member, but with an alternative embodiment for the outer door which outer door contains an O-ring and recess for such O-ring. 
           [0081]      FIG. 14  is a sectional view of the safety or delayed locking system which is pressure sensitive and which is shown in a locked state. 
           [0082]      FIG. 15  is a sectional view of the safety or delayed locking system which is pressure sensitive and which is shown in an unlocked state. 
           [0083]      FIG. 16  is a perspective view of the interior door shown not connected to the portal with the door in an open state. 
           [0084]      FIG. 17  is a sectional view of the latching system for the inner door shown in a locked state but where there is not a pressure differential between the interior of the dive chamber and the interior of the portal. 
           [0085]      FIG. 18  is a sectional view of the latching system for the inner door shown in a locked state but where the interior pressure of the dive chamber is higher than the interior pressure of the portal, and the inner door is pressed closed based on the force of the larger interior dive chamber pressure. 
           [0086]      FIG. 19  is a sectional view of the latching system for the inner door shown in a locked state, but where there is not a pressure differential between the interior of the dive chamber and the interior of the portal 
           [0087]      FIG. 20  is a sectional view of the latching system for the inner door shown in an unlocked or open state where the interior door is opened. 
       
    
    
     DETAILED DESCRIPTION 
       [0088]    Turning now to the drawings in more detail an airlock assembly or portal is generally designated by numeral  200 . In the following description, the terms “portal,” “airlock assembly,” interlock vessel,” and interlock assembly are used interchangeably. The portal  200  is designed to be used in a hyperbaric chamber (e.g., decompression chamber)  10  transfer system. 
         [0089]      FIG. 1  is a perspective view of a decompression chamber  10  with air lock or portal  200 . In one embodiment a decompression chamber  10  having a fluidly connected portal  200  is included. Decompression chamber  10  can include first end  20 , second end  30 , and side wall  40 . Base  50  can be included to support chamber  10 . For entering chamber  10  a door  60  can be provided. Door  60  can be sealed with conventionally available seal  70 . Chamber  10  can have interior  80 , and sidewall  40  can separate interior  80  from the exterior  85  (or ambient environment). Preferably, door  60  opens to the interior  80  of chamber  10 . 
         [0090]    As will be described below, portal  200  can be used to transmit one or more items from the exterior  85  to the interior  80 , while the interior  80  is at elevated pressures. Additionally, as will be described below, portal  200  can be used to transmit one or more items from the interior  80  to the exterior  85 , while the interior is at elevated pressures. 
         [0091]    While chamber  10  is at elevated pressures with a person in the interior  80  of chamber  10 , there arises the need to quickly and easily transmit one or more items to such person, or receive one or more items from such person while maintaining chamber  10  at elevated pressures. For example, food and/or medicines may need to be provided to the person inside the chamber while the person is going through a decompression cycle while chamber  10  is maintained at elevated pressures. Such quick access is preferably obtained without substantially impacting the elevated internal  80  pressure Pc of chamber  10 . Portal  200  allows such access without substantially impacting the elevated pressure of interior  80  because the volume of interior  204  of portal  200  is typically much less than the volume of interior  80  of chamber  10 . Portal  200  is preferred to an airlock device by door  60  because such air lock device would substantially reduce the available space in interior  80  of chamber  10 , along with slowing down the time necessary to transfer one or more items (and possibly impacting the elevated pressures of interior  80 ). 
         [0092]      FIGS. 2 through 7  show the process of an item  3000  being transmitted through portal  200  to the interior  80  of chamber  10 .  FIG. 2  is an enlarged perspective view of interlocking portal  200  at the portal from the front of the chamber  10 , and where a portion of the sidewall  40  of the decompression chamber has been removed to show the front  210  and rear  220  ends of the portal.  FIG. 3  is an enlarged perspective view of portal  200 , but now looking at the portal from the rear  30  of the chamber  10  and where a portion of the upper section of the portal  200  has been removed to reveal the interior  204  of portal  200 .  FIG. 4  is an enlarged perspective view of portal  200 , but showing the interlocking system (lock  800  and safety lock  1000 ) now placed in an unlocked state along with schematically showing the venting of the interior  204  of the portal  200 , and the second pressure sensitive locking mechanism  1000  moving from a locked to an unlocked state.  FIG. 5  is an enlarged perspective view of the interlocking portal  200  with outer door  400  opened and schematically showing an item  3000  being placed in the interior  204  of the portal  200 .  FIG. 6  is an enlarged perspective view of portal  200  showing the item  3000  placed in the portal  200  with outer door  400  closed and the interlocked system (lock  800  and  1000 ) now placed in locked states, and the venting valve  1600  on the inner door  1400  opened to vent pressure from the interior  80  of the dive chamber  10  to the interior  204  of the portal  200 , and the second pressure sensitive locking mechanism  1000  moving from an unlocked state to a locked state.  FIG. 7  is an enlarged perspective view portal  200  showing the inner door  1400  being opened and the item  3000  being moved from the interior  204  of the portal  200  to the interior  80  of the dive chamber  10 . 
         [0093]      FIGS. 8 through 11  show various views of one embodiment of portal  200 .  FIG. 8  is a perspective view of portal  200 , where a portion of outer door  400  and locking ring  250  has been removed to show first end  210  body  230  along with quick lock/quick unlock  800  and safety lock  1000 .  FIG. 9  is a perspective view of portal  200  with quick lock/quick unlock  800  placed in a unlocked state and safety lock  1000  in a locked state.  FIG. 10  is perspective view of portal  200  with a portion of locking ring  250  removed to show the interaction between the locking bar  810  and of one of the radial protrusions  510  of outer door  400 , and also showing the interaction between locking bar  1010  and another of radial protrusions  540 .  FIG. 11  is perspective view of portal  200  with outer door  400  opened and a portion of locking ring  250  and outer door  400  removed to show the first end  210  of portal  200  body  230  along with quick lock/quick unlock  800  and safety lock  1000  systems. 
         [0094]    Portal  200  can comprise body  230  with first end  210  and second end  220 . Between first and second ends  210 , 220  and body  230  can be interior  214 . Body  230  can have a continuous sidewall  240  which can be configured to form a cylindrical vessel. On first end  210  of body  230  can be an outwardly extending shoulder  211 , on which outer door  400  contacts when closed. In one embodiment portal  200  comprises an airtight body  230  closed on one end by an inner door  1400  and closed on the opposite end by an outer door  400  having two degrees of freedom for pivoting (e.g., it can pivot about two axes which are substantially perpendicular to each other). 
         [0095]    Second end  220  of portal  200  can be in communication with interior  80  of chamber  10 , while first end  210  can extend past sidewall  40  (of chamber  10 ) and be in fluid communication with exterior  85  (or environment). 
         [0096]    A portion of body  230  (e.g., second end  220 ) with the inner door  1400  normally extends into interior  80  of chamber  10  (the interior housing a person at elevated or hyperbaric pressures). A portion of the body  230  (e.g., first end  210 ) that has outer door  400  normally extends outside of chamber  10 . A person inside chamber  10  normally has access to inner door  1400  and can operate door  1400  to open and close the door. However, such person in interior  80  would not have access to handles operating the outer door  400 . 
       Outer Door 
       [0097]    On first end  210  can be outer door  400 . Door  400  can be rotatably mounted in relation to the shoulder  211 . Also on first end  210  can be locking ring  250  which can longitudinally lock in place outer door  400 . Locking ring  250  can be attached to first end  210  and include a perimeter groove  290  along with a plurality of unlocking openings  300 . In one embodiment the plurality of unlocking openings can be symmetrically spaced about the circumference of locking ring  250 . 
         [0098]    On second end  220  can be inner door  1400 . As will be described below outer door  400  can seal interior  214  from exterior  85  using seal  212 . As will be described below inner door  1400  can seal interior  214  from interior  80  of chamber  10  using seal  1422 . 
         [0099]    Outer door  400  can comprise first end  410 , second end  420 , along with a plurality of locking projections  500  which detachably lock with locking ring  250 . In one embodiment door  400  can include radial projections  510 ,  520 ,  530 , and  540 . More or less locking projections than four can be used. 
         [0100]    Outer door  400  can be pivotally connected to portal  200  by support bracket  700 , which support bracket can be connected to portal  200  such as by being welded to sidewall  230 . In one embodiment outer door  400  can pivot around a vertical axis, such as around hinge  710  (where hinge  710  pivotally attaches to support plate  450  to connection points  720 ). Such rotation about a vertical axis allows outer door  400  to be opened and closed and provides access to interior  204  In one embodiment outer door  400  can also rotate about a horizontal axis, such as fastener  440 . In this manner outer door  400  can both rotate about two axes which are perpendicular to each other (e.g., horizontal axis of fastener  440  which is perpendicular to vertical axis of hinge  710 ). As shown in  FIG. 2 , the extent of rotation of outer door  400  about a horizontal axis can be limited. The extent of rotation of outer door  400  about a horizontal axis is limited by the movement of rotation stop  460  within rotation slot  470  (slot  470  being contained in support plate  450  and stop  460  being attached to door  400 ). Slot  470  setting up a pre-determined arc or rotation for door  400  which arc of door rotation has a length equal to that of the length of slot  470 . That is, no further horizontal rotation of outer door  400  can be made once rotation stop  460  hits either end of rotation slot  470 . As will be described above the horizontal rotation of outer door  400  allows door to be locked in locking ring and maintain a tight seal against first end  210  of body  230 . Also as will be described below rotation slot  460  can be used to rotationally position plurality of locking projections  500  in plurality of unlocking openings  300  of locking ring  250  to allow outer door  400  to detachably lock and unlock in locking ring  250 . 
         [0101]    Locking of outer door  400  in locking ring is shown in  FIGS. 5 and 6 . In  FIG. 5  outer door  400  is open and in  FIG. 6  outer door  400  is closed. When outer door  400  closes, a plurality of projections  500  ( 510 ,  520 ,  530 , and  540 ) enter a plurality of their respective unlocking openings  300  ( 310 ,  320 ,  330 , and  340 ) to allow door  400  to rest in locking ring  250 . Stop pin  470  is shown in contact with first end  462  of arcuate slot  460  so that door  400  has been rotated the maximum extent in a counter clockwise direction (schematically shown by arrow  2610  and  2620 ). At this maximum counter clockwise rotation plurality of projections  500  line up with plurality of unlocking openings  300  and outer door  400  can be shut. However, to shut and seal outer door  400  against body  230 , door  400  should be turned in a clockwise direction (in the opposite direction as arrows  2610 ,  2620 ). Plurality of projections  500  will enter perimeter groove  290  of locking ring  250 . 
         [0102]    In a preferred embodiment one or more of plurality of projections  500  can have an upwardly sloping surface so that as outer door  400  is rotated clockwise locking ring  250  pushing on the sloping surfaces will cause door  400  to be pushed tighter against body  230  and energizing the seal between body  230  and door  400 . In  FIG. 5  sloped surface  512  is schematically shown, however, projections  520 ,  530 , and  540  can each have similar sloped surfaces. 
         [0103]    In one embodiment plurality of projections  500  extend diametrically to an extent which is slightly less than the largest diametrical extent of the plurality of unlocking openings  300 . This dimensional constraint can prevent outer door  400  from moving out of concentricity even if the center bearing (rotatively connecting door  400  to support bracket  450 ) wears or if hinge  710  is caused to become misaligned in such a way that a door concentricity error would otherwise be created. 
         [0104]    In one embodiment one or more of plurality of projections  500  can have a beveled surface (beveled inwards from first side  410  (facing exterior  85  to second end  420  facing interior  204 ) so that, as door  400  is pushed closed (i.e., rotated on hinge  710 ) against body  230 , locking ring  250  tends to align door  400  concentrically in relation to interior  204  of body  230 . In  FIG. 5  beveled surface  514  is schematically shown, however, projections  520 ,  530 , and  540  can each have similar beveled surfaces. That is locking ring  250  radially pushing on the beveled surfaces will cause door  400  to be concentrically aligned in relation to interior  204 . 
         [0105]    In a preferred embodiment one or more of plurality of projections  500  can have a second radially sloping surface  514 ′ so that, as door  400  is rotated clockwise, locking ring  250  tends to concentrically align door  400  in relation to interior  204  of body  230 . That is locking ring  250  radially pushing on the sloping surfaces will cause door  400  to be concentrically aligned in relation to interior  204 . In  FIG. 5  sloped surface  514  is schematically shown, however, projections  520 ,  530 , and  540  can each have similar sloped surfaces. 
         [0106]    In certain situations outer door  400  may not be concentric (or may lose concentricity) with respect to locking ring  250  (and body  230 ). As shown in  FIGS. 11 and 13 , in one embodiment outer door  400  can include one or more raised sections  412  (which interact with the edges of the locking tabs, such as edge  323  of tab  322 ) to assist and concentrically aligning inner door  400  with body  230 . In one embodiment a single raised section  412  can be provided. Where outer door  400  is out of concentricity, raised section  412  can contact edge  323  (when rotated clockwise) and cause outer door  400  to move into a concentric position. With such adjustment for concentricity, a good seal can be maintained between outer door  400  and body  230  when outer door  400  is closed or shut. This can prevent extrusion of O-ring  212  from groove  214 . 
         [0107]    In one embodiment a seal can be included between outer door  400  and body  230 . In one embodiment ( FIGS. 12 ,  14 , and  15 ) the seal can be attached to first end  210  of body  230 . In one embodiment the seal can be an O-ring  212 ′ is fitted in a dovetail-shaped groove  214 ′ formed in first end  210  of body  230 . In another embodiment (which is shown in  FIG. 13 ) the O-ring  212  can be placed in a groove  214  on door  400 . To prevent O-ring  212  from falling out of the groove  214  when outer door  400  is open, the upper portion of groove  214  can be smaller than the lower portion of groove  214 . O-ring  212  can be sized to be 1½ percent smaller than the theoretical size of groove  214  so that the O-ring remains in groove  214  when door  400  is opened. 
         [0108]    Outer door  400  can be provided with a pair of handles  600 ,  610  extending from an outside surface thereof. Handles  600 ,  610  allow the user to pivot door  400  about a central axis when quick lock/quick unlock  800  and lock  1000  are in unlocked states. Door  400  can be rotatively attached to support bracket  450 . 
       Quick Lock/Quick Unlock 
       [0109]      FIG. 12  is a sectional diagram showing quick lock/quick unlock  800  system, along with closed  880  and open states  880 ′ of handle  880  for this locking system. 
         [0110]      FIG. 13  is a sectional view of locking member  810  for quick lock/quick unlock  800  showing open (position of first end  820 ) and closed (position of first end  820 ′) states for locking member  810 , showing door  400  where O-ring  212 ′ and O-ring recess  214  are located in outer door  400 . As will be described below for inner door  1400  placing the seal in the door can make it easier to correct/fix problems with the groove  214 ′ for O-ring  212 ′. 
         [0111]    A quick lock/quick unlock  800  can be operatively attached to portal  200  and set up locked and unlocked states for outer door  400 . Generally, quick lock/quick unlock  800  can comprise locking bar  810  operatively connected to valve  900  such that when valve  900  is opened locking bar  810  moves into an unlocked stated, and when valve  900  is closed, locking bar  810  moves into a locked state. Valve  900  can be secured to sidewall  240  and fluidly connect interior  204  of portal  200  with exterior  85 . Vent tube  950  of valve  900  can fluidly connect valve  900  to interior  204 . When opened, valve  900  equalizes pressure between interior  204  of portal  200  and exterior  85  of chamber  10  (which is typically atmospheric or ambient pressure). When closed, valve  900  prevents air flow between interior  204  of portal  200  and exterior thereof. 
         [0112]    Handle  880  can be operatively connected to valve  900 , and can be used to open and close valve  900 , such as by being pivotally attached to valve  900  where rotational movement opens and closes valve  900 , such as in a ball valve. Rotation of handle  880  in a first direction can open valve  900 . Rotation of handle  880  in the opposite direction as the first direction can close valve  900 . 
         [0113]    Handle  880  can also be operatively connected to locking bar  810  through linkage  850 . Rotation of handle  880  in the first direction can cause locking bar  810  to enter an unlocked state. Rotation of handle  880  in the opposite direction can cause locking bar  810  into a locked state. When in a locked state locking shaft can pass through (between its upper and lower diametric dimensions, and at least past the 50 percent point of its rear depth or from its second end  270  to its first end  260 ). When in a locked state, locking bar  810  will restrict rotational movement of at least one of the plurality of locking projections  500  of door  400 . That is, door  400  can be rotated until one of the plurality of locking projections comes in contact with locking bar  810  at which point further rotational movement of door  400  can be prevented. For example, locking bar  810  can enter unlocking opening  310  and resist counterclockwise rotation of door  400 . The extent of clockwise rotation of door  400  is limited by second end  464  of slot  460  coming in contact with rotation stop  470 . In this manner the rotation of door (clockwise and counterclockwise) can be limited so that plurality of locking projections  500  remain at least partially in perimeter groove  290  (and not in plurality of unlocking openings  300 ), and door  400  is kept in a locked state. 
         [0114]    Linkage  850  can comprise handle  880 , first bar  860 , and first bar&#39;s  860  pivoting connections between handle  880  and locking bar  810 . Locking bar  810  can be slidably connected to locking ring  250 . In this manner handle  880 , linkage  850 , and locking bar  810  can be a special type of four bar system, or a crank and slider configuration. In one embodiment linkage  850  can be configured such that there is a type of dwelling between the beginning rotational movement of handle  880  to open and sliding movement of locking bar  810  to cause locking bar  810  to change into an unlocked state. For example, the pivoting connection between first bar  860  and locking bar  810  can be offset from the pivot point of handle  880  on valve  900  (such as by about 10 degrees) such that initial rotational movement of handle  880  in a first direction tends to cause locking shaft to extend out (in a more locked position) until continued movement of handle  880  in the same rotational direction finally starts to cause locking bar  810  to stroke back an enter an unlocked state. As a result, the initial movement of the handle  880  does not produce an immediate retraction of the locking bar  810  from locking ring  250 . When the handle  880  travels to about 90 degree position (shown in  FIG. 4 ) in relation to its original position (shown in  FIG. 2 ) first bar  860  travels about 70-80 degrees. 
         [0115]    Locking bar  810  can be pivotally attached to first bar  860 , such that rotational movement of handle  880  transfers locking bar  810  from locked (extended) to unlocked (retracted) states. In one embodiment, to resist wear between locking bar  810  and locking ring  250  a wear/lubricating/guide sleeve can be placed in locking ring  250 . 
         [0116]    Operatively connecting handle  880  to both venting valve  900  and locking bar  810  is beneficial in that locking shaft can only be in an unlocked stated at a time when interior  204  of portal is venting (or has vented) to exterior  85 . However, the venting of interior  204  of portal  200  will take a finite (i.e., non-zero) time and there still exists the possibility that an operator will not allow interior  204  to adequately vent, but will immediately attempt to open outer door  400  after opening handle  880  (i.e., when there still is increased pressure in interior  204 ). If this were to happen the increased pressure in interior  204  could provide a force (the difference between [interior  204  pressure and pressure of the exterior] times the cross sectional area of interior  204 ) which can cause door  400  to swing out quickly and harm the operator. Because of this risk of operator attempting to open door  400  while interior  204  has not adequately vented, a second pressure actuated lock can be provided. 
       Safety Pressure Lock 
       [0117]      FIG. 14  is a sectional view of the second or safety lock  1000  system which is pressure sensitive and which is shown in a locked state.  FIG. 15  is a sectional view of second or safety lock  1000  system which is pressure sensitive and which is shown in an unlocked state. 
         [0118]    An independent safety lock  1000  can be provided for outer door  400 . Safety lock  1000  can have a locking motion similar to quick lock/quick unlock  800  (in that it uses a sliding locking bar  1010  through locking ring  250  which resists rotation of one or more of the plurality of locking projections  500 ). Safety lock  100  is intended to provide a factor of safety (beyond quick lock/quick unlock  800 ) to avoid outer door  400  being opened where a high pressure is still found in interior  204  of portal  200 . 
         [0119]    Safety lock  1000  can have locked and unlocked states which states are dependent at least in part on the pressure of interior  204  of portal  200 . In one embodiment safety lock  1000  which will generally enter an unlocked state when the difference between interior  204  pressure of portal  200  and exterior  85  is below a specified safety pressure level. In one embodiment the acceptable differential unlocking pressure is less than or equal to about 5 psi, 4 psi, 3 psi, 2 psi, and/or 1 psi. In various embodiments ranges between any of the above referenced pressure differentials are envisioned. 
         [0120]    Safety lock  1000  can also enter an unlocked mode in a time delayed fashion compared to the start of venting of interior  204  of portal  200 . This time delay can provide an additional factor of safety to allow an adequate quantity of excess pressure in interior  204  to be vented before outer door  400  can be opened. In one embodiment safety lock  1000  will generally take between 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 seconds to enter an unlocked stated from the start of venting of interior  200  and the time the safety lock  1000  enters the unlocked state. 
         [0121]    Safety lock  1000  can comprise locking bar  1010  which is operatively connected to piston/cylinder system  1100 . Piston/cylinder system  1100  can be fluidly connected to interior  204  of portal  200  via connecting tube  1160 . Piston/cylinder system  1100  can include cylinder  1110  having first end  1120  and second end  1130 . Cylinder  1100  can include first end  1120  and second end  1130 . On second end  1130  can be a cap  1132  which can be detachably connected to cylinder  1100  (such as by threads). Cap  1132  can be sealed with a seal such as O-ring  1134 . The interior  1140  of cylinder  1100  can be fluidly connected to interior  204  of portal through connecting tube  1160 . A restriction (such as valve  1170 ) can be used to restrict or slow down gas flow between interior  204  and interior  1140 . In one embodiment an adjustable restrictor is used which can change the amount of restriction to gas flow. For example, valve  1170  can be partially closed limiting the quantity per unit time of gas flow. As another example the internal size of tube  1160  can be sized to limit the quantity per unit time of gas flow. As another example, flow weirs/baffles can be used to restrict/slow gas flow. 
         [0122]    Slidably connected to cylinder  1110  can be piston  1200 . Piston  1200  can have first end  1210 , and second end  1220 . First end  1210  can be detachably connected to locking bar  1010  (such as through a fastener which may be threaded). Second end  1220  can include an enlarged base and seal  1230  (which can be an o-ring). 
         [0123]    Between second end  1220  of piston  1200  and first end  1120  of cylinder  1100  can be a biasing member  1150  (such as a helical spring) which tends to push piston towards second end  1130  of cylinder (schematically shown in  FIG. 15  by arrow  2610 ). 
         [0124]    Where interior  204  has a pressure Pc which exceeds a specified amount, such high pressure can be transmitted through tube  1160  to push against enlarged base at second end  1220  of piston  1200 , overcoming the resistance of biasing member  1150 , and pushing piston  1200  up (in the opposition direction of arrow  2610 ). Because piston  1200  is attached to locking rod  1010 , such upward movement of piston  1200  will also move up locking rod  1010 . The amount of excess pressure needed to push up piston  1200  will be a function of the cross sectional areas of enlarged base along with the resistance of biasing member  1150  (which is a function of its spring constant), frictional forces, along with the ambient pressure (which can enter interior  1140  of cylinder  1100  at first end  1120  at opening  1124  as this opening is not sealed). Alternatively, a weep hole can be placed on first end  1120  of piston. 
         [0125]    When interior  204  is pressurized, locking rod  1010  will be in a locked state. This is because the interior  204  pressure Pc overcomes the resisting forces of movement of piston  1200  and pushes up (movement in the opposite direction of arrow  2610 ) locking bar  1010 . 
         [0126]    Movement of locking rod  1010  in the opposite direction of arrow  2610  causes locking bar  1010  to enter a locked state. When in a locked state locking bar  1010  can pass through locking ring  250  (between its upper and lower diametric dimensions, and at least past the 50 percent point of its rear depth or from its second end  270  to its first end  260 ). When in a locked state, locking bar  1010  will restrict rotational movement of at least one of the plurality of locking projections  500  of door  400 . That is, door  400  can be rotated until one of the plurality of locking projections comes in contact with locking bar  1010  at which point further rotational movement of door  400  can be prevented. For example, locking bar  1010  can enter unlocking opening  340  and resist counterclockwise rotation of door  400 . The extent of clockwise rotation of door  400  is limited by second end  464  of slot  460  coming in contact with rotation stop  470 . In this manner the rotation of door (clockwise and counterclockwise) can be limited so that plurality of locking projections  500  remain at least partially in perimeter groove  290  (and not in plurality of unlocking openings  300 ), and door  400  is kept in a locked state at least until locking shaft enters an unlocked state. 
         [0127]    However, when interior  204  is vented to atmosphere (exterior  80 ), such as when valve  900  is opened by handle  880 , the elevated pressure Pc which had previously pushed up piston  1200 , will gradually reduce. When Pc in interior  204  is reduced, pressure Pv in the interior  1140  of cylinder will gradually bleed into interior  204  of portal  200 . As described above this bleeding process can be slowed down by restrictions to slow down the bleeding process. As the pressure Pv decreases biasing member  1150  will push down (in the direction of arrow  2610 ) piston  1200 . Such downward movement of piston  1200  will cause a downward movement (in the direction of arrow  2510 ) of locking bar  1010 . Locking shaft will eventually move down a sufficient extent to enter an unlocked state. Because the timing of locking bar  1010  entering an unlocked state is delayed and/or because locking bar  1010  entering an unlocked state occurs only when the differential pressure between interior  204  of portal  200  and exterior  85 , safety lock provides an additional factor of safety to prevent operators from opening outer door  400  before interior  204  has been adequately depressurized. 
         [0128]    When both quick lock/quick unlock  800  and safety lock  1000  are in unlocked states, outer door  400  can be opened by clockwise rotation (to align plurality of locking projections  500  with plurality of openings  300 ) and then swinging out outer door  400 . 
       Inner Door 
       [0129]    Turning now to  FIGS. 16-20 , inner door  1400  will be described in more detail.  FIG. 16  is a perspective view of interior door  1400  shown not connected to portal  200  with door  1400  and where the door is in an open state.  FIG. 17  is a sectional view of latching system  1900  for inner door  1400  where the latching system is shown in a locked state, but where there is not a pressure differential between interior  80  of dive chamber  10  and interior  204  of portal  200  (or where interior  204  pressure Pc′ is higher than interior  80  pressure Pc).  FIG. 18  is a sectional view of latching system  1900  shown in a locked state, but where interior  80  pressure Pc of dive chamber  10  is higher than interior  204  pressure Pc′ of portal  200  (and inner door  1400  is forced closed against portal  200  body  230  based on the larger interior  80  dive chamber  10  pressure Pc).  FIG. 19  is a sectional view of latching system  1900  shown in a locked state but where there is not a pressure differential between interior  80  of dive chamber  10  and interior  204  of portal  200 .  FIG. 20  is a sectional view of latching system  1900  shown in an unlocked state and where interior door  1400  is opened. 
         [0130]    As can be seen in the drawings, inner door  1400  can be mounted for pivotal movement in relation to the body  230  between (a) an open position, (b) a closed-sealed position, and (c) a plurality of partially open/closed positions. Inner door  1400  can be connected to support bracket  1402 , which bracket is secured to a hinge or pivot axle  1404  of base  1406 . 
         [0131]    Although not shown, hinge  1404  can be attached to a base  1406 , which base can be welded to body  230 . 
         [0132]    Alternatively, hinge  1404  can be secured to an adjustable connecting strap  1700 . Connecting strap  1700  can be adjustable and detachably connectable to second end  220  of portal  200 . Adjustability of connecting strap  1700  can be obtained through use of a connecting band secured to base  1404  through one or two adjustment mechanisms  1720  (such as threaded fasteners). As adjustment mechanisms are tightened band  1710  tightens around body  230  and a frictional connection is obtained. 
         [0133]    Inner door  1400  itself can be adjustable concentrically by using a floating connection  1403  between door  1400  and support bracket  1402 . 
         [0134]    Handle  1408  can be attached to the outside surface of door  1400 . 
         [0135]    Opposite hinge  1404  can be a latch  1900 . Latch  1900  can comprise body  1905 , base  1950 , and body  1905  can be pivotally connected to base  1950 . Body  1905  can include first end  1910 , second end  1920 , base  1950 , locking cavity  2010 , and locking tip  2000 . Body  1905  can be pivotally biased to a closed position by spring  1970  (which can be a torsional spring wrapped around pivot point or pin  1960 ), which biasing is schematically indicated by arrow  1972 . In one embodiment locking cavity  2010  can detachably lock connecting bar  1500  of inner door  1400  where spring  1970  normally urges body  1905  into a closed position. Locking cavity  2010  can engage connecting member  1500 , and can have a generally hook-shaped configuration for engaging connecting member  1500 . 
         [0136]    Outwardly sloped portion preferably forms an approximately 30 degree angle in relation to arrow  1504  when body  1905  is fully rotated in the direction of arrow  1972 . Upwardly sloped or curved section  2011  preferably forms a relatively small angle from the direction of arrow  1972 , approximately 45 degrees when body  1905  is fully latched onto connecting member  1500 . 
         [0137]    The size and shape of locking cavity  2010  can be made to retain inner door  1400  in a normally closed position. An O-ring  1422  can be positioned in a groove  1424  formed on second end  1420  of door  1400 . O-ring  1422  can be fitted in a dovetail-shaped groove  1424  formed on second end (inner surface)  1420  of inner door  1400 . O-ring  1422  seals door  1400  against an edge of body  230  when door  1400  is closed. 
         [0138]    In one embodiment, even when body  1905  of latch  1900  is fully rotated in the direction of arrow  1972 , locking cavity  2010  continues to allow a limited extent of possible vertical movement of connecting member  1500  (i.e., there will be a limited amount of play). This extent of possible vertical movement or play is schematically indicate d by arrows  1502 . Alternatively, an extent of possible vertical movement of connecting bar  1500  can be allowed by base  1905  giving way (e.g., rotating in a direction opposite to arrow  1972 ) a certain extent when a force in the direction of arrow  1504  is applied) on inner door  1400  (such as by a differentially higher pressure in interior  204  compared to interior  80 ), but while base  1905  remains latched and resisting (albeit partially) movement of connecting bar  1500 . The force on inner door  1400  will be transferred to connecting member  1500 , and then transferred to body  1905  causing body  1905  to rotate at least partially in the opposite direction of arrow  1972  (however, spring  1970  will continue to maintain a torsional force on body  1905  tending to make body  1905  want to rotate in the direction of arrow  1972 ). In this manner spring  1970  and latch body  1905  can allow inner door  1400  to slightly open, breaking the seal and venting the differentially higher interior  204  pressure to interior  80  without ever setting up a situation where an explosive differentially higher interior  204  pressure can be seen. After the pressure vents, body  1905  will pull door  1400  closed again. Once the interior  204 ,  80  pressures equalize, inner door  1400  will again be pushed in the opposite direction of arrow  1504  by spring  1970  rotating body  1905  in the direction of arrow  1972  causing locking cavity  2010  to pull down connecting member  1500 . 
         [0139]    This extent of possible vertical movement is envisioned to allow a break in the seal between O-ring  1422  and body  230  so that an increased pressure (relative to interior  80 ) in the interior  204  of portal  200  can vent into interior  80  of chamber  10  and not risk an excessive pushing force in the direction of arrow  1504  on inner door  1400 . In one embodiment, locking cavity  2010  can include an upwardly sloped or curved section  2011  so that an differential increase in the pressure in interior  204  (relative to interior  80 ) tends to push inner door  1400  in the direction of arrow  1504 , which tends to push connecting member  1500  in the same direction. Movement of connecting member  1500  in the direction of arrow  1504 , by contact with section  2011 , will tend to cause body  1905  to rotate in the opposite direction of arrow  1972 , and allow inner door  1400  to move slightly in the direction of arrow  1504 —at least until a seal of O-ring  1422  between inner door  1400  and body  230  is broken and interior  204  starts to vent into interior  80 . In this way only a relatively small incremental increase in pressure of interior  204  of portal  200  relative to interior  80  of vessel  10  is allowed (before venting to interior  80  starts) thereby decreasing the risk that a relatively large incremental increased pressure of interior  204  relative to interior  80  will be set up—which large pressure differential could “swing out hard” inner door  1400  and harm someone. 
         [0140]    In one embodiment the extent of possible differential (e.g., outward or vertical) movement between inner door  1400  and body  230  can be less than about 5, 4, 3, 2, 1, ½, ¼, ⅛, 1/10, 1/20, 1/30, 1/40, 1/50, 1/60, 1/70, 1/80, 1/90, 1/100, and/or 1/200 millimeters. In one embodiment the extent of possible differential movement can be limited to the “flexing” size differential allowed by O-ring  1422 . In one embodiment the extent of possible vertical movement of the door is limited to an extent to where the sealing O-ring is between about 50 percent 1 percent compressed, 40 and 1, 30 and 1, 25 and 1, 20 and 1, 15 and 1, 10 and 1, and 5 and 1. In one embodiment the extent of possible vertical movement of the door is limited to an extent to where the sealing O-ring is between about 50 percent 5 percent compressed, 40 and 5, 30 and 5, 25 and 5, 20 and 5, 15 and 5, 10 and 5, and 5 and 2. In various embodiments ranges between any two of the above specified possible ranges can be limited for O-ring compression. 
         [0141]    A limit on the extent of possible vertical movement will allow inner door  1400  to be transported in a “closed” position, but limit the swinging back and forth of inner door  1400  differential movements (or jerking movements) during transportation. Additionally, a limit on the extent of possible vertical movement can resist banging open and shut inner door  1400  relative to body  230  when in use, such as by jerking caused by wave movement on a ship on which chamber  10  is installed. Preferably, the limit of vertical movement is the “flexing” of O-ring  1422  because then O-ring  1422  can also reduce the amount of banging because the polymer composition of O-ring  1422  softens/dampens the shutting of door  1400  by resisting movement. Even where the limited amount of vertical movement is larger than the flexing extent of O-ring, when inner door  1400  starts to come in contact with body  230 , O-ring can contact first and start to soften (or even prevent) metal to metal contact between inner door  1400  and body  230  (which reduces or prevents banging of inner door). 
         [0142]    In closing inner door  1400 , handle  1408  can be used to move door  1400  in the opposite direction of arrow  1972  until connecting member  1500  contacts outwardly sloped portion  2050  of body  1905 . As door  1400  is continued to be pushed closed the force of spring  1970  is overcome and body  1905  rotates in the opposite direction as arrow  1972 , at least until point  2014  is reached. As door is continued to be pushed closed in the opposite direction as arrow  1504 , spring  1970  causes body to rotate in the direction of arrow  1972  and connecting member  1500  to be “locked” inside of locking cavity  2010 . 
         [0143]    Where interior  80  pressure in chamber  10  is greater than interior  204  pressure, such differential higher pressure relative to interior  204  of portal  200  tends to push against (create a force pushing) inner door  1400  (in the direction opposite to arrow  1504 ) causing inner door  1400  will seal against body  230  with O-ring  1422 . A seal between interior  80  and interior  204  can be maintained by O-ring  1424  because the higher interior  80  pressure pushes door  1400  against body  230  energizing the sealing effect of O-ring  1424  between door  1400  and body  230 . 
         [0144]    To open inner door handle  1408  can be used to swing inner door  1400  in the direction of arrow  1972 . Connecting member  1500  will contact section  2011  and push up/push out section  2011  causing body  1905  to rotate in the opposite direction of arrow  1972 , allowing inner door  1400  to continue to move in the direction of arrow  1504  and pass point  2014  which is maximum extent of upwardly sloped section  2011 . After this point inner door  1400  can be opened completely. Once connecting member  1500  passes point  2014 , spring  1960  will cause body  1905  to rotate in the direction of arrow  1972 . 
         [0145]    Alternatively, outwardly sloped portion  2050  can be used by the person in the interior to manually push body  1905  in the opposite direction of arrow  1972 , such as by using the person&#39;s thumb to push on portion  2050  at the same time as pulling up on handle  1408 . If the user wishes to open the door  1400 , the user will push on outwardly sloped portion  2050 , causing latch body  1905  to pivot away (rotate in a direction opposite of arrow  1972 ) from the connecting member  1500 , thereby allowing door  1400  to be pivoted into an open position. 
         [0146]    In the event that an increased pressure of the interior  204  (relative to the interior  80 ) exists which is not enough to start venting interior  204  by itself, a type of manual venting occurs before latch  1900  is unlocked. That is, as handle  1408  is pulled upwardly in the direction of arrow  1504 , door  1400  will also start to move in this direction and the seal of O-ring  1422  (between door  1400  and body  230 ) will break and venting will start to occur even before connecting member  1500  comes out of locking cavity  2010 . Here, while it continues to remain in locking cavity  2010 , inner door  1400  remains “locked” but allows venting to occur before inner door  1400  is completely released by latch  1900 . 
         [0147]    In one embodiment, handle  1408  can be located above upwardly sloped or curved section  2011  so that section  2011  can be “thumb-pressed” to manually release connecting member  1500  from locking cavity  2010 . Such a positioning also prevents finger pinching by the latch. 
         [0148]    In certain situations inner door  1400  may not be concentric (or may lose concentricity) with respect to body  230 . In one embodiment inner door  1400  can include one or more guides to assist and concentrically aligning inner door  1400  with body  230 . In one embodiment a raised center  1430  with angled portion  1432  can be provided. Where inner door  1400  is out of concentricity, angled portion  1432  can contact body  230  and cause inner door  1400  to move into a concentric position. In one embodiment this process of being aligned concentrically is facilitated by inner door  1400  being connected to support bracket  1402  with a floating connection  1403 . Floating connection, although it maintains a nominal concentric position of inner door  1400  with respect to support bracket  1402 , inner door  1400  can move position relative to support bracket, and such relative movement can adjust the concentricity of inner door  1400  relative to body  230 . With such adjustment for concentricity, a good seal can be maintained between inner door  1400  and body  230  when inner door  1400  is closed or shut. 
         [0149]    In one embodiment latch  1900  holds inner door  1400  “securely closed” during shipment, but yet allows (during use) inner door  1400  to temporarily (and/or partially) lift off of the seal (O-ring  1422 ) and “vent” any differential increase in pressure which may exist in portal  200  (or decrease in pressure in chamber  10 ). In the event of a pressure differential attempting to open inner door  1400 , latch  1900  allows door  1400  to “lift off” of the seal to vent the pressure. However, when the differential pressure has been equalized (by the venting), spring  1970  and sloping contact surface  2011  of locking cavity  2010  pull door  1400  “closed” again. 
         [0150]    In one embodiment latch  1900  also allows door  1400  to be closed without manually depressing latch body  1905  (e.g., pushing on outwardly sloped portion  2050 ) because the angle of sloped portion  2050  combined with the spring action (of spring  1970  on body  1905 ) allow body to first rotate in the opposite direction of arrow  1972  (to open latch  1900 ) and then snap back in the direction of arrow  1972  against connecting member  1500  when door  1400  is pressed closed. 
         [0151]    In one embodiment O-ring  1422  and groove  1424  are placed in inner door  1400 . Conventional methods for sealing provide for the O-ring and groove to be placed in the non-moving portion of a door/closure seal (and not the moving door). The disadvantage of this solution can be seen where the O-ring groove becomes damaged requiring machining to repair. If O-ring groove  1424  was placed in the end of body  230  and became damaged, the entire chamber  10  would need to be taken out of service so that body  230  could be re-machined (possibly requiring the cutting out of body  230  from chamber  10 ); or a very expensive in-place machining operation must be performed if it is available. Placing O-ring  1422  and groove  1424  in inner door  1400  minimizes the possibility that expensive machining on body  230  will have to be done in place. First, the sealing face (location where seal occurs between door  1400  and body  230 ) on the end body  12  is now merely flat. A flat surface is less likely to become damaged, and, if damaged, such flat surface can be repaired using inexpensive manual methods (e.g.,—a hand file). Furthermore, O-ring groove  1424  can now be easily repaired because inner door  1400  can be easily removed from portal  200  (and chamber  10 ) and taken to a machine shop. 
         [0152]    Placing O-ring groove  1422  in inner door  1400  creates a condition that must be addressed. If inner door  1400  moves concentrically out of position relative to portal  230 , an offset can be created between O-ring groove  1424  and the flat end of body  230  which offset could allow O-ring  1422  to fail in extrusion (such as to interior  204  of portal  200 ). In one embodiment this risk is addressed by providing a guide on inner door  1400  to assist in concentrically aligning inner door  1400  with body  230 . As described above one embodiment of this adjustment guides includes an angled portion on inner door  1400  with the possible use of a floating connection  1403  between door  1400  and support bracket  1402 . Another possible solution is to have the end of tube (with the flat sealing surface) widened to compensate for possible eccentric movement of inner door  1400 . 
       Method of Use 
       [0153]      FIGS. 1-6  show various steps where portal  200  is used to transmit an item  3000  to an individual located in the interior  80  of chamber  10  while chamber  10  is pressurized.  FIG. 1  is a perspective view of decompression chamber  10  with interlocking portal  200 . Chamber  10  has first end  20 , second end  30 , and cylindrical wall  40 . Chamber  10  also has an interior  80  which is at an elevated pressure relative to exterior  80 . Item  3000  is to be transferred from exterior, through portal  200 , and into interior  80  where interior  80  is to remain at an elevated pressure. 
         [0154]      FIG. 2  is an enlarged perspective view portal  200  looking at portal  200  from the front  20  of chamber  10 , and where a portion of sidewall  40  of chamber  10  has been removed to show the front  210  and rear  220  ends of portal  200 .  FIG. 3  is an enlarged perspective view of portal  200 , but now looking at portal  230  from the rear  30  of chamber and where a portion of the upper section has been removed to reveal interior  204  of the portal  230 . Here, interior  204  is shown as being at pressure Pc and interior  80  of chamber is at equal pressure Pc. Exterior  85  of chamber  10  is shown as being at pressure Pa, and Pc is elevated compared to Pa—which is the normal situation for decompression (or hyperbaric) chambers during operation. Outer door  400  is sealed relative to interior  204  pressure Pc, however, elevated pressure Pc will push on outer door  400 . Locking ring  250  maintains outer door  400  shut. Outer door  400  can be opened by rotating it in a counterclockwise direction (arrow  2613 ) to align plurality of locking projections  500  with plurality of unlocking openings  300 . However, to prevent an explosive event (i.e., the high pressure Pc causing an explosive opening of door  400 ) a double safety lock system is provided for outer door  400  which includes quick lock/quick unlock  800  along with second safety lock  1000  and are both in locked states. 
         [0155]      FIG. 4  is an enlarged perspective view of portal  230 , but showing both quick lock/quick unlock  800  and second safety lock  1000  having moved into “unlocked” states. Here, quick lock/quick unlock  800  has been placed in an unlocked state by pushing handle  880  in the direction of arrow  2504 . Handle  880  is operatively connected to first locking bar  810  (through linkage mechanism  850 ), and turning handle  880  in the direction of arrow  2504  causes bar  810  to slide backward in locking ring  250  so that shaft  880  no longer restricts rotation of locking projection  510 . Handle  880  is also operatively connected to valve  900 , so that at the same time rotation of handle  880  opens valve  900  which starts the venting process of excess pressure Pc (located inside interior  204  of portal  200 ) to exterior  80 . Inner door  1400  was previously closed (with valve  1600  shut) so that when interior  204  pressure Pc′ vents out and decreases, now pressure Pc′ becomes less than interior  80  pressure Pc inside chamber  10 . Now excess pressure Pc (compared to Pc′) pushes on inner door  1400  which energizes O-ring  1422  seal to maintain a seal between interior  80  of chamber  10  and interior  204  of portal  200 —so that interior  80  of chamber  10  will not lose (e.g., vent) its elevated pressure Pc. As described above, in a preferred embodiment locking bar  810  experiences a dwell period before it starts it sliding back in relation to rotation of handle  880  to allow vent  900  to first open and at least start venting interior  204  of portal before locking bar  810  enters an unlocked state. Additionally, locking bar  810 , when moving from locked to unlocked (and from unlocked to locked) states, respective exits and enters perimeter groove  290  of locking ring  250  (i.e., between the outer edge of locking ring  250  and the outer wall of body  230 ). Additionally, when moving from an unlocked state to a locked stated locking bar  810  moves away from inner door  1400  towards outer door  400  (and when moving from an unlocked state to a locked state, moves away from outer door  400  towards inner door  1400 ). 
         [0156]    However, even though quick lock/quick unlock  800  may move to an unlocked state, outer door  400  still cannot be opened until safety lock  1000  also moves to an unlocked state. Safety lock  1000  is a pressure based safety lock and time delayed compared to the time in which quick lock/quick unlock  800  is placed in an unlocked state. After quick lock/quick unlock is placed in an unlocked state and interior  204  starts to vent, the interior volume  1140  of piston/cylinder  1100  will start to vent into interior  204  dropping pressure Pv (which before the start of venting of interior  2014  was the same as pressure Pc) allowing spring  1150  to push piston  1200  in the direction of arrow  2610  and move delay locking bar  1010  in the direction of arrow  2510  until delay locking bar  1010  moves to an unlocked state, no longer restricting rotational movement of outer door  400 . Additionally, when moving from an unlocked state to a locked stated delay locking bar  1010  moves away from inner door  1400  towards outer door  400  (and when moving from an unlocked state to a locked state, moves away from outer door  400  towards inner door  1400 ). Accordingly, if for some reason placing quick lock/quick unlock  800  in an unlocked state does not vent interior  204  of portal, safety lock  1000  will remain in a locked state also preventing the opening of door  400 . Furthermore, safety lock  1000  is designed such that it can only enter an unlocked state when a certain maximum interior pressure Pc′ is reached in interior  204  to prevent door  400  from being opened at a time when interior pressure Pc′ can still push and swing door  400  open in a manner which can do harm. This minimum pressure for unlocking can be achieved by using a spring  1150  of a certain stiffness compared to the cross sectional area of second end  1220  of piston  1200 . In one embodiment safety lock  1000  which will generally enter an unlocked state when the difference between interior  204  pressure of portal  200  and exterior  85  is below a specified safety pressure level. In one embodiment the acceptable differential unlocking pressure is less than or equal to about 5 psi, 4 psi, 3 psi, 2 psi, and/or 1 psi. In various embodiments ranges between any of the above referenced pressure differentials are envisioned. In one embodiment safety lock  1000  can also enter an unlocked mode in a time delayed fashion compared to the start of venting of interior  204  of portal  200 . This time delay can provide an additional factor of safety to allow an adequate quantity of excess pressure in interior  204  to be vented before outer door  400  can be opened. In one embodiment safety lock  1000  will generally take between about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 seconds to enter an unlocked stated from the start of venting of interior  200  and the time the safety lock  1000  enters the unlocked state. A time delay can be obtained by providing a restriction/limiter to flow out of volume  1140  to interior  204 . 
         [0157]    Once both quick lock/quick unlock  800  and safety lock  1000  have entered unlocked states, outer door  400  can be opened providing access to interior  204 . Because interior  204  has been fully vented to exterior  80  (through valve  900 ), interior  204  pressure Pc′ is now equal to exterior  85  pressure Pa. Door  400  can be opened by rotating it counterclockwise and then pulling it open. The seal between inner door  1400  and body  230  prevents venting from interior  80  of chamber to the outside.  FIG. 5  is an enlarged perspective view of portal  200  with outer door  400  opened and schematically showing an item  3000  being placed (arrow  3010 ) in the interior  204  of the portal  230 . Now that item  3000  has been placed in the interior  204 , outer door  400  can be closed.  FIG. 6  is an enlarged perspective view of portal  200  showing item  3000  placed in portal  200  with outer door  400  closed and both quick lock/quick unlock  800  and safety lock  100  having been moved into locked states. Outer door  400  is shut by swinging it closed and turning it clockwise (in the direction of arrows  2612  and  2622 ) using handles  600 ,  610 . Quick lock/quick unlock  800  is placed in a locked state by pushing handle in the direction of arrow  2506  which both slides locking bar  810  in a locked state (restricting counterclockwise rotation of door  400 ), and closes valve  900  (sealing interior  204  from exterior  85  as outer door  400  is sealed with respect to body  230  by O-ring  212 ). Interior  204  has remained sealed from interior  80  of chamber because inner door  400  has continually been pushed shut because of higher interior  80  pressure Pc compared to interior  204  pressure Pc′ (which is equal to exterior  85  pressure Pa). To allow access from interior  80  to interior  204 , inner door  400  must be opened. This can be done by venting interior  80  pressure Pc into interior  204 —by opening valve  1600 . Arrows  1650  schematically indicate the venting of interior  80  pressure into interior  204  through vent opening. As this venting occurs (between interiors  80  and  204 ) the interior  204  pressure Pc′ will gradually rise to equal interior  80  pressure Pc and no longer will there be a closing force on inner door  1400 . Also as this venting occurs, the rising interior  204  pressure will cause safety lock  1000  to move into a locked state as pressure also vents into the piston/cylinder  1100  causing piston  1200  to extend and locking bar  1010  to move into a locked state. 
         [0158]    When interior  204  pressure Pc′ equalizes with interior  80  pressure Pc, the individual inside chamber  10  can open latch  1900 , open inner door  1400 , and remove item  3000 .  FIG. 7  is an enlarged perspective view of portal  200  showing inner door  1400  being opened (swung in the direction of arrow  1401 ) and item  3000  being moved from interior  204  of portal  200  to interior  80  of chamber  10  (schematically shown by arrow  3012 ). Opening latch  1900  is schematically indicated by arrow  2100 . 
         [0159]    After removal of item  3000 , portal  200  can be readied for the next transfer. To do this valve  1600  should be shut, and inner door  1400  should be swung closed (opposite direction as arrow  1401 ) so that it is latched by latch  1900 . At this point interior  204  of portal  200  will be the same pressure Pc′ as interior  80  of chamber  80 . 
         [0160]    To transfer an item  3000  from interior  80  to exterior  85 , the first step would have been to have the individual inside chamber  10  place item  3000  in interior  204  of portal  200  and close inner door  1400 . Then the steps previously described for opening outer door  400  would be followed for a person outside of chamber  10  to remove item  3000  from inside of portal  200 . 
         [0161]    When venting from interior  80  of chamber  10  to interior  204  of portal  200  it is not expected that interior  80  of chamber will lose much pressure. This is because the volume of interior  80  of chamber is so much larger than the interior  204  of portal. 
         [0162]    The following is a list of reference materials: 
         [0000]    
       
         
               
             
               
               
             
               
               
             
           
               
                   
               
               
                 LIST FOR REFERENCE NUMERALS 
               
             
          
           
               
                 (Part No.) 
                 (Description) 
               
               
                 Reference Numeral 
                 Description 
               
               
                   
               
             
          
           
               
                 10 
                 decompression chamber 
               
               
                 20 
                 first end 
               
               
                 30 
                 second end 
               
               
                 40 
                 wall 
               
               
                 50 
                 base 
               
               
                 60 
                 door 
               
               
                 70 
                 seal 
               
               
                 80 
                 interior 
               
               
                 85 
                 exterior 
               
               
                 200 
                 portal 
               
               
                 204 
                 interior 
               
               
                 210 
                 first end 
               
               
                 211 
                 shoulder 
               
               
                 212 
                 O-ring 
               
               
                 214 
                 O-ring groove 
               
               
                 216 
                 enlarged area 
               
               
                 218 
                 reduced area 
               
               
                 220 
                 second end 
               
               
                 230 
                 body 
               
               
                 240 
                 side wall 
               
               
                 250 
                 locking ring 
               
               
                 254 
                 opening 
               
               
                 260 
                 first end 
               
               
                 270 
                 second end 
               
               
                 280 
                 body 
               
               
                 284 
                 height 
               
               
                 290 
                 perimeter groove 
               
               
                 300 
                 plurality of unlocking openings 
               
               
                 310 
                 first opening 
               
               
                 312 
                 locking tab 
               
               
                 313 
                 edge 
               
               
                 320 
                 second opening 
               
               
                 322 
                 locking tab 
               
               
                 323 
                 edge 
               
               
                 330 
                 third opening 
               
               
                 332 
                 locking tab 
               
               
                 333 
                 edge 
               
               
                 340 
                 fourth opening 
               
               
                 342 
                 locking tab 
               
               
                 343 
                 edge 
               
               
                 400 
                 outer door 
               
               
                 410 
                 first end 
               
               
                 412 
                 extended end 
               
               
                 414 
                 angled beveled end 
               
               
                 416 
                 outer end 
               
               
                 418 
                 inner end 
               
               
                 420 
                 second end 
               
               
                 430 
                 center 
               
               
                 440 
                 fastener 
               
               
                 450 
                 support plate 
               
               
                 460 
                 rotation slot 
               
               
                 462 
                 first end 
               
               
                 464 
                 second end 
               
               
                 470 
                 rotation stop 
               
               
                 500 
                 plurality of locking projections 
               
               
                 510 
                 first projection 
               
               
                 512 
                 sloped surface 
               
               
                 514 
                 beveled surface 
               
               
                 520 
                 second projection 
               
               
                 530 
                 third projection 
               
               
                 540 
                 fourth projection 
               
               
                 600 
                 handle 
               
               
                 610 
                 handle 
               
               
                 700 
                 support bracket 
               
               
                 710 
                 hinge 
               
               
                 720 
                 connection points 
               
               
                 800 
                 first quick lock 
               
               
                 802 
                 arrow 
               
               
                 810 
                 locking bar 
               
               
                 812 
                 wear/lubrication sleeve 
               
               
                 820 
                 first end 
               
               
                 830 
                 second end 
               
               
                 850 
                 linkage mechanism 
               
               
                 852 
                 pivot point 
               
               
                 854 
                 pivot point 
               
               
                 856 
                 pivot point 
               
               
                 860 
                 first bar 
               
               
                 870 
                 second bar 
               
               
                 880 
                 handle 
               
               
                 900 
                 valve 
               
               
                 910 
                 first end 
               
               
                 920 
                 second end 
               
               
                 950 
                 vent tube 
               
               
                 960 
                 first end 
               
               
                 970 
                 second end 
               
               
                 1000 
                 second delay lock 
               
               
                 1010 
                 delay locking bar 
               
               
                 1012 
                 wear/lubrication sleeve 
               
               
                 1020 
                 first end 
               
               
                 1030 
                 second end 
               
               
                 1050 
                 linkage mechanism 
               
               
                 1100 
                 piston/cylinder system 
               
               
                 1110 
                 cylinder 
               
               
                 1120 
                 first end 
               
               
                 1124 
                 opening on first end 
               
               
                 1130 
                 second end 
               
               
                 1132 
                 cap 
               
               
                 1134 
                 O-ring 
               
               
                 1140 
                 interior 
               
               
                 1150 
                 biasing member 
               
               
                 1160 
                 connecting tube 
               
               
                 1170 
                 flow control 
               
               
                 1172 
                 arrow 
               
               
                 1200 
                 piston 
               
               
                 1210 
                 first end 
               
               
                 1220 
                 second end 
               
               
                 1230 
                 seal 
               
               
                 1400 
                 inner door 
               
               
                 1401 
                 arrow 
               
               
                 1402 
                 support bracket 
               
               
                 1403 
                 floating connection 
               
               
                 1404 
                 hinge 
               
               
                 1406 
                 base 
               
               
                 1408 
                 handle 
               
               
                 1410 
                 first end 
               
               
                 1420 
                 second end 
               
               
                 1422 
                 O-ring 
               
               
                 1424 
                 O-ring groove 
               
               
                 1426 
                 enlarged area 
               
               
                 1428 
                 reduced area 
               
               
                 1430 
                 raised center 
               
               
                 1432 
                 angled portion 
               
               
                 1434 
                 base 
               
               
                 1500 
                 connecting bar 
               
               
                 1502 
                 arrows 
               
               
                 1504 
                 arrow 
               
               
                 1600 
                 interior venting valve 
               
               
                 1610 
                 handle 
               
               
                 1620 
                 vent opening 
               
               
                 1630 
                 arrow 
               
               
                 1640 
                 arrow 
               
               
                 1650 
                 arrow 
               
               
                 1700 
                 connecting strap 
               
               
                 1710 
                 band 
               
               
                 1720 
                 adjustment mechanism for band 
               
               
                 1800 
                 hinge 
               
               
                 1810 
                 connection points for door 
               
               
                 1900 
                 latch or quick lock for inner door 
               
               
                 1905 
                 body 
               
               
                 1910 
                 first end 
               
               
                 1920 
                 second end 
               
               
                 1950 
                 base 
               
               
                 1960 
                 pivot point 
               
               
                 1970 
                 spring 
               
               
                 1972 
                 arrow 
               
               
                 2000 
                 locking tip 
               
               
                 2010 
                 locking cavity 
               
               
                 2011 
                 upwardly sloped or curved section 
               
               
                 2014 
                 maximum extend of upwardly sloped portion 
               
               
                 2050 
                 outwardly sloped portion 
               
               
                 2100 
                 arrow 
               
               
                 2500 
                 arrow 
               
               
                 2502 
                 arrow 
               
               
                 2510 
                 arrow 
               
               
                 2512 
                 arrow 
               
               
                 2520 
                 arrow 
               
               
                 2522 
                 arrow 
               
               
                 2530 
                 arrow 
               
               
                 2532 
                 arrow 
               
               
                 2540 
                 arrow 
               
               
                 2542 
                 arrow 
               
               
                 2550 
                 arrow 
               
               
                 2552 
                 arrow 
               
               
                 2560 
                 arrow 
               
               
                 2562 
                 arrow 
               
               
                 2570 
                 arrow 
               
               
                 2572 
                 arrow 
               
               
                 2580 
                 arrow 
               
               
                 2582 
                 arrow 
               
               
                 2590 
                 arrow 
               
               
                 2592 
                 arrow 
               
               
                 2600 
                 arrow 
               
               
                 2602 
                 arrow 
               
               
                 2610 
                 arrow 
               
               
                 2613 
                 arrow 
               
               
                 2620 
                 arrow 
               
               
                 3000 
                 item 
               
               
                 3010 
                 arrow 
               
               
                 3012 
                 arrow 
               
               
                   
               
             
          
         
       
     
         [0163]    All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise. All materials used or intended to be used in a human being are biocompatible, unless indicated otherwise. 
         [0164]    It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention set forth in the appended claims. The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.