Patent Publication Number: US-9889911-B1

Title: Back pack cinch

Description:
FIELD OF THE INVENTION 
     This invention generally relates to a back pack for an underwater breathing gas tank. 
     BACKGROUND OF THE INVENTION 
     A back pack for underwater diving generally is worn by a diver to secure the diver to his underwater breathing gas tank (hereinafter, “gas tank”). The diver&#39;s back is on one side of the backpack and a gas tank is on the other side of the back pack. 
     The back pack may have a strap that joins the gas tank to the back pack for a diver&#39;s use during diving. The strap length as it surrounds the gas tank is generally lessened to tighten the gas tank connection to the back pack. Once the desired length around the gas tank is reached to properly keep the gas tank connected to the back pack, the length of the strap is generally fixed by a device such as a cinch that is hereinafter referred to interchangeably as a buckle. 
     The buckle generally permits the length of the strap to be adjusted as desired for a tight fit during the dive and thereafter a loose fit such that the gas tank may be replaced. For example, one such buckle is shown in U.S. Pat. No. 5,567,084 where a buckle is shown located on the side of the gas tank farthest away from a diver&#39;s back. The buckle is left unprotected on the surface of the its gas tank such that any structure that the diver may inadvertently hit or any object, including another diver may hit the buckle on the exposed surface where it is located. Unfortunately, such a buckle may become unlatched when struck such that its strap can loosen such that the gas tank may separate from the back pack. 
     The invention seeks to provide a back pack that offers greater protection than heretofore known for a back pack that includes a buckle that secures the backpack to the gas tank. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect, the invention provides a back pack for an underwater breathing gas tank comprising a tank mounting structure. The tank mounting structure has a front surface facing away from an underwater breathing gas tank when an underwater breathing gas tank is operably mounted to the tank mounting structure. The tank mounting structure defines a recess. The front surface of the tank mounting structure defines an opening of the recess. The tank mounting structure also defines a bottom surface of the recess opposite the opening in the front surface. The back pack further comprises a strap and a buckle. The buckle has a latched state for securing the strap in a fixed position for securing a underwater breathing gas tank to the tank mounting structure. The buckle, when in a latched state, is positioned at least partially within the recess. 
     In another aspect, the invention provides a back pack for an underwater breathing gas tank comprising a tank mounting structure having a front surface facing away from an underwater breathing gas tank when a gas tank is operably mounted to the tank mounting structure. The tank mounting structure defines a recess. The front surface defines an opening of the recess. The tank mounting structure defines a bottom of the recess opposite the opening in the front surface. The back pack further comprises a buckle having a latched state for securing a strap in a fixed position for securing an underwater breathing gas tank to the tank mounting structure. The buckle has a handle portion that passes through the opening of the recess when the buckle transitions from an unlatched state to the latched state. 
     In yet another aspect, the invention provides a back pack for an underwater breathing gas tank comprising a first mounting plate and a second mounting plate releasably coupled to one another. The first and second mounting plates define a tank mounting structure having a front surface facing away from an underwater breathing gas tank when a gas tank is operably mounted to the tank mounting structure. The tank mounting structure defines a recess. The front surface defines an opening of the recess. The tank mounting structure defines a bottom surface of the recess opposite the opening in the front surface. The back pack further comprises a dive bladder releasably coupled between the first and second mounting plates. The back pack may include a buckle and a strap. The buckle may be an over the center buckle. The buckle secures the strap to fix a length of the strap surrounding an underwater breathing gas tank, the dive bladder and the tank mounting structure. The buckle is located at least partially within the recess when the strap is secured. 
     In an embodiment of the back pack, the buckle may be pivotably attached to the tank mounting structure for rotation about a first rotational axis. The buckle may be an over-center mechanism such that in the latched state, the strap generates a torque on the latch in a first direction around the rotational axis biasing the latch toward the latched state and, in the unlatched state, any torque generated by the strap biases the buckle in an opposite second direction around the rotational axis toward the unlatched state. Unlike a traditional over-center mechanism the buckle remains in a latched state without an additional locking mechanism. 
     In another embodiment, the tank mounting structure includes a first mounting plate that defines, at least in part, the recess. The tank mounting structure also may include a second mounting plate that defines at least in part, the bottom of the recess opposite the opening in the front surface. The second mounting plate may be located between the first mounting plate and a gas tank when a gas tank is mounted to the tank mounting structure. A dive bladder may be fixed between the first mounting plate and the second mounting plate. 
     In yet another embodiment, the strap may extend around at least a portion of the gas tank when operably mounted to the tank mounting structure. The strap has a first end and a second end. The first end is attached to the buckle and the second end is adjustable relative to the buckle to fix a length of the buckle when the buckle is in the latched state such that underwater breathing gas tanks of different sizes can be secured to the tank mounting structure. 
     In another embodiment, the buckle, in the latched state, is between the front surface of the tank mounting structure a diver&#39;s back when a gas tank is operably connected to the tank mounting structure and a diver. 
     In an embodiment, in the latched state, the buckle is in the recess and does not extend out of the opening. In transition between the unlatched state and the latched state, a handle portion of the buckle extends out of the opening beyond the front surface. 
     In another embodiment, the opening of the recess in the tank mounting structure includes a portion that extends into a side of the tank mounting structure as well as the front surface. A handle portion of the buckle extends into the portion of the recess that extends into the side of the tank mounting structure when the buckle is in the unlatched state. The tank mounting structure defines an outer periphery and the handle extends out of the outer periphery defined by the tank mounting structure in the unlatched state and is at least partially within the outer periphery in the latched state. 
     In still another embodiment, the buckle in the latched state is positioned within the recess between the bottom surface and the opening in the front surface. 
     In an embodiment, the buckle is an over center buckle. The tank mounting structure defines an outer periphery. The handle portion may be positioned at least partially within the outer periphery defined by the tank mounting structure when the buckle is in the latched state. 
     In an embodiment, the handle may extend out of the recess and the outer periphery when the buckle is in the unlatched state. 
     In yet another embodiment, the handle portion is positioned entirely within the outer periphery defined by the tank mounting structure when the buck is in the latched state. 
     In another embodiment, the tank mounting structure includes a first mounting plate and a second mounting plate. The first mounting plate includes a top portion, a middle portion, and a bottom portion. The top and bottom portions may each have a mounting aperture for mounting a second mounting plate. The top portion of the first mounting plate comprises a top concave portion of the front face of the tank mounting structure. The top portion may comprise a carrying handle. The carrying handle extends away from an underwater breathing gas tank when a gas tank is operably mounted to the tank mounting structure. The middle portion includes the recess and defines a first side wall and a second side wall of the recess. The bottom portion defines a bottom concave portion of the front surface of the tank mounting structure. The bottom portion has opposed wings extending away from a gas tank when operably coupled to the tank mounting structure. 
     In still another embodiment, the first mounting plate includes a handle and the back pack is transportable via the handle. 
     In another embodiment, the second mounting plate includes a top, middle and bottom portion. The middle portion defines channel having a top wall, a bottom wall and a portion of the bottom of the recess. 
     Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a perspective view of a back pack having a buckle in a latched state, the back pack operably connected to an underwater breathing gas tank; 
         FIG. 2  is an exploded view of the back pack of  FIG. 1 ; 
         FIG. 3  is a perspective view of the back face of the first mounting plate of the tank mounting structure of the back pack of  FIG. 1 ; 
         FIG. 4  is a perspective view of the back face of the second mounting plate of the tank mounting structure of the back pack of  FIG. 1 . 
         FIG. 5  is cross section take about line  5 - 5  of  FIG. 1  but with the buckle in an unlatched state. 
         FIG. 6 . is a cross section taken about line  5 - 5  of  FIG. 1  with the buckle in a latched state. 
         FIG. 7 . is an exploded view of a second embodiment of a back pack having a dive bladder. 
     
    
    
     While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a back pack  10  for an underwater breathing gas tank  12 . The back pack  10  includes a tank mounting structure  14  having a front surface  16  that faces away from an underwater breathing gas tank  12  when the underwater breathing gas tank  12  is operably mounted to the tank mounting structure  14 . The front surface  16  faces towards a diver&#39;s back (not illustrated) when the back pack  10  is operably coupled to a diver for diving operations. The tank mounting structure  14  defines a recess  18 . The front surface  16  of the tank mounting structure  14  defines an opening  20  of the recess  18 . The tank mounting structure  14  defines a bottom surface  22  ( FIG. 2 ) of the recess  18 . The bottom surface  22  of the recess  18  is opposite the opening  20  in the front surface  16 . 
     The back pack further includes a strap  24  and a buckle  26 . The strap  24  and buckle  26  cooperate, as will be discussed in greater detail below, to permit the length of the strap  24  to be infinitely adjusted (as opposed to straps that are pre-configured for fixed/discrete lengths) as its surrounds an underwater breathing gas tank  12  to secure the underwater breathing gas tank  12  to the back pack  10 . The infinite adjustability provided by the buckle  26  and strap  24  advantageously allow for varying diameters of underwater breathing gas tanks to be couple to the back pack  10 . As will be discussed in greater detail below, the buckle  26  of the back pack  10  has a latched state ( FIG. 1 ) and an unlatched state ( FIG. 5 ) to permit adjustment of the length of the strap  24 . 
     In the latched state, the buckle  26  fixes the length of the strap  24  surrounding the tank mounting structure  14  and underwater breathing gas tank  10  so as to tightly secure an underwater breathing gas tank  12  to the tank mounting structure  14 . The strap  24  in the latched state cannot move unless the buckle  26  is unlatched to allow the strap  24  to be adjusted. 
     As illustrated in  FIG. 1 , the buckle  26  in the latched state may be positioned within the recess  18  between the bottom surface  22  of the recess  18  and the opening  20  defined by the front surface  16 . The opening  20  of the recess  18  in the tank mounting structure  14  includes a portion that extends into a side  19 ,  21  of the tank mounting structure  14  as well as the front surface  16 . The buckle  26 , in the latched state, is in the recess  18  between an underwater breathing gas tank  12  and a diver&#39;s back when the underwater breathing gas tank  12  is operably connected to the tank mounting structure  14  and a diver. In the latched state, the buckle  26  may be in the recess  18  and does not extend out of the opening  20  either through the sides  19 ,  21  or front surface  16 . However, in other embodiments, the buckle  26  in the latched state is positioned partially within the recess  18  and may extend at least partially beyond any one or more of the opening  20 , front surface  16 , and sides  19 ,  21 . In such embodiments, the buckle  26  is still advantageously positioned between the bottom surface  22  and a diver&#39;s back when the back pack  10  is operably worn on a diver&#39;s back. 
     Further, the tank mounting structure  14  defines an outer periphery  28  of the tank mounting structure  14 . In the latched state, a handle  104  of the buckle  26  does not extend out of, that is beyond, the outer periphery  28  defined by the tank mounting structure  14 . The handle in the latched state is completely positioned within the outer periphery  28  of the tank mounting structure  14  to prevent it from becoming inadvertently unlatched. On the other hand, in the unlatched state of the buckle  26  ( FIG. 5 ), the handle  104  extends out, that is beyond the outer periphery  28  defined by the tank mounting structure  14  and in the unlatched state the handle  104  is partially located outside the recess  18 . 
     The latched buckle  26  located entirely inside the recess  18  provides an advantage for a diver utilizing the back pack  10  for securing an underwater breathing gas tank  12  to the tank mounting structure  14 . During a dive, a diver&#39;s back faces the front surface  16  of the tank mounting structure  14 . As such, the diver&#39;s back advantageously acts as a protective cover over the recess  18  concealing the buckle  26  within it. Further, the bottom surface  22  of the recess  18  protects the opposite side of the buckle  26  within the recess  18  from hitting structure or being hit by objects during a dive. In this way, the buckle  26  is protected within the recess  18  from being inadvertently hit or bumped by an object or structure that would cause the buckle  26  to come unlatched and separate the underwater breathing tank  12  from the back pack  10 . 
     Turning now to the exploded view of the back pack  10  as illustrated in  FIG. 2 , the tank mounting structure  14  of  FIG. 1  will be discussed in greater detail. The tank mounting structure  14  may include a first mounting plate  30  that defines, at least in part, the recess  18  and a second mounting plate  32 . The first mounting plate  30  has a top portion  34 , a middle portion  36 , and a bottom portion  38 . The top portion  34  has a top mounting aperture  40 . The bottom portion  38  has a bottom mounting aperture  42 . The mounting apertures  40 ,  42  are for securing the first mounting plates to the second mounting plate  32 . In alternative embodiments, the tank mounting structure  14  may be made of a single mounting plate. Further, as can be readily appreciated the structures and contours, such as recess  18  and handle  28 , may be made in certain embodiments on either one of the plates or in embodiments that comprise only a single mounting plate for the tank mounting structure. 
     The top portion  34  of the first mounting plate  30  further includes a top concave portion  44  of the front face  16  of the tank mounting structure  14  and a carrying handle  46 . The carrying handle  46  is canted such that it extends away from a gas tank  12  when the underwater breathing gas tank  12  is operably mounted to the tank mounting structure  14 . The handle  46  includes a handle aperture  48  that extends through the front surface  16  and a back surface  50  of the first mounting plate  30 . The back pack  10  can be advantageously transported via the handle  46  built into the first mounting plate  30 . As previously discussed, in yet other embodiments, the handle  46  may be built into or carried by the second mounting plate  32  and in yet other embodiments where the tank mounting structure  14  is a single mounting plate, the handle  46  may be built into or carried by the single mounting plate. One of the advantages of the handle  46  position is that the handle  46  does not interfere with either the underwater breathing gas tank  12  or the diver during a dive because of its advantageous extension away from the underwater breathing gas tank  12  while at the same time allowing tight contact between the back pack  10 , the diver and an underwater breathing gas tank  12 . The top portion  34  of the tank mounting structure  14  extends longitudinally between the outermost periphery  28  at the carrying handle  46  and an upper edge  52  of the opening  20  of the recess  18  in the front surface  16 . 
     The middle portion  36  of the first mounting plate  30  extends longitudinally between the upper edge  52  and a bottom edge  54  of the opening  20  of the recess  18  in the front surface  16 . The middle portion  36  includes the recess  18  and a first side wall  56  and a second sidewall  58  of the recess  18 . The sidewalls  56 ,  58  are in opposed space relation. 
     The bottom portion  38  of the first mounting plate  30  extends longitudinally between the bottom edge  54  of the opening of the recess  18  and a bottom  118  of the first mounting plate  30 . The bottom portion  38  defines a bottom concave portion  62  of the front surface  16  of the tank mounting structure  14 . The bottom portion  38  further includes opposed wings  64  that extend away from an underwater breathing gas tank  12  when operably coupled to the tank mounting structure  14 . The opposed wings  64  advantageously provide for a tight fit between the back pack  10  and a diver. The advantageous contour of the wings  64  together with the bottom concave portion  62  conform to the contour of the diver&#39;s back to provide for the comfortable and tight fit. 
     The tank mounting portion  14  also includes the second mounting plate  32 . The second mounting plate  32  defines, at least in part, the bottom surface  22  of the recess  18  opposite the opening  20  in the front surface  16 . The second mounting plate  32  is located between the first mounting plate  30  and the underwater breathing gas tank  12  when the underwater breathing gas tank  12  is mounted to the tank mounting structure  14 . The second mounting plate  32  includes a top portion  64 , middle portion  66  and bottom portion  68  that are designed to mount to top portion  34 , the middle portion  36 , and the bottom portion  38  of the first mounting plate, respectively. The top portion  64  includes a top apertured mounting boss  70 . The top  64  further includes top male mounting members  72  in spaced relation. The top portion  64  further includes a convex front surface  74 . 
     The middle portion  66  of the second mounting plate  32  defines u shaped channel  76  having an upper wall  78 , a lower wall  80  and a bottom wall  82 . The bottom wall  82  includes the bottom surface  22  of the recess  18  and extends between the upper and lower walls  76 ,  78 . Although a u shaped channel is illustrated, it may be readily appreciated that the channel may take other shapes provided that the buckle  26  is permitted to remain at least partially between bottom surface  22  of the recess and the diver&#39;s back when an underwater breathing gas tank  12  is operably connected to the tank mounting structure  14  and a diver. 
     The bottom portion  68  of the second mounting plate  32  includes a bottom apertured mounting boss aperture  84  and bottom male mounting members  86  in opposed space relation. The bottom portion  68  further includes a bottom convex front surface  88 . 
     Still with respect to  FIG. 2 , buckle  26  of the back pack  10  is illustrated. Buckle  26  includes an upper arm member  90  and a lower arm member  92  that are spaced apart from one another. The arm members  90 ,  92  are generally parallel and mirror symmetric to one another and as such the lower arm  92  will be described as the upper arm  90  mirrors the lower arm  92 . The lower arm member  92  has at a first end  94 , a first aperture  96 , a second aperture  98  and a third aperture  100 . A bottom mounting pin  102  passes through the first aperture  96  and into the lower wall  80  to pivotally connect the buckle  26  to the second mounting plate  32 . A top mounting pin  103  passes through an aperture in the upper arm  90  and into the upper wall  78  to pivotally connect the buckle  26  to the second mounting plate  32 . The bottom mounting pin  102  and the top mounting pin  103  define an axis of rotation  124  (see  FIG. 5 ) about which the buckle  26  may pivot to provide the over the center function to secure the strap  24  in moving from the unlatched state ( FIG. 5 ) to the latched state ( FIG. 6 ). However, unlike a traditional or standard cam over-center buckle, buckle  26  remains closed, that is, remains in a latched state by itself with no additional locking mechanism necessary. Further, although a cinch in the form of buckle  26  is discussed with respect to the illustrated embodiment, it may be readily appreciated the cinch is not limited to embodiments of buckle  26 . Other embodiments with varying structures for the cinch may be utilized to provide the over center function. 
     The buckle  26  is manipulated by a diver between its latched state and unlatched state via the buckle handle  104  located at a second end  106  of the buckle  26  opposite the first end  94 . The buckle handle  104  has a generally rectangular buckle face  108 . Buckle handle  104  connects upper arm member  90  and lower arm member  92 . Further, connection between the upper arm member  90  and lower arm member is provided by a first buckle pin  110  having a first end that is fixed in the second aperture  98  of the lower member  92  and a second end that is fixed in the corresponding aperture of the upper arm member  90 . A second buckle pin  112  has a first end that pass into the third aperture  100  of the lower arm member  92  and a second end that is fixed in the corresponding aperture of the upper arm member  90 . 
     Buckle pins  110 ,  112  may be press fit into the apertures, welded or soldered so as to connect the upper  90  and lower  92  arm members via buckle pins  110 ,  112 . In yet other embodiments, the buckle pins  110 ,  112  may pass through the buckle  26  through either or both of upper  90  and lower  92  members to connect to tank mounting structure  14 . In the embodiment illustrated, buckle pins  110  and  112  permit the strap  24  to change direction as it passes through the buckle  26  so as to create the necessary torque and friction to allow the over the center function of the buckle  26  to fix the length of the strap  24 . 
     In addition to buckle pins  110 , 112  recess pins  114  and  116  assist in the over the center function of the buckle  26 . Recess pins  114 ,  116  do not pass through the buckle  26  but do traverse and thereby connect upper wall  78  of the second mounting plate  32  with lower wall  80  of the recess  18  to create a pathway through which strap  24  may pass. Strap  24  has a first end  120  that wraps around and may pivotally attach to recess pin  116  while a second end  122  of the strap  24  is free to pass around the underwater breathing gas tank  12  and then back into the recess  18  and through buckle  26  to fix the length of the strap  24  so as to tightly hold the back pack  10  to the underwater breathing gas tank  12 . 
     Turning to  FIG. 3 , the back surface  50  of the first mounting plate  30  is illustrated. The top mounting aperture  40  and bottom aperture  42  traverse the front surface  16  and back surface  50  as does the handle aperture  48 . The back surface  50  of the top portion  34  of the first mounting plate  30  also defines a top back concave surface  126 . The back surface  50  of the bottom portion  38  of the first mounting plate  30  also defines a bottom back concave surface  128 . The back concave surfaces  126 ,  128  are, respectively, complimentary to the top convex front surface  74  of the top portion  64  of the second mounting plate  32  and the bottom convex front surface  88 . The back concave surfaces  126 ,  128  are advantageously contoured to compliment and mate with, respectively, the top convex surface  74  and bottom convex surface  88  of the second mounting plate  32  when joined to the first mounting plate  30 . 
     The back surface  50  of the first mounting plate  30  also includes a pair of back top portion receiving apertures  130  and back bottom portion receiving apertures  132 . The receiving apertures  130 ,  132  are complimentary to and receive, respectfully top male mounting members  72  and bottom male mounting members  86  to provide a press fit there between when the first mounting plate  30  and second mounting plate  32  are joined. So too, it can be readily appreciated that the top and bottom apertured mounting bosses  70  and  84  mate with and are received into, respectively, the top and bottom mounting apertures  40 ,  42 . 
     Turning to  FIG. 4 , the back surface  60  of the second mounting plate  32  is illustrated. The back surface  60  includes concave back top surface  134 , the concave back bottom wall surface  136  and concave back bottom surface  138 . The apertures of the top and bottom apertured mounting bosses  70 ,  84  extend, respectively through the concave back top and bottom surfaces  134 ,  138 . The concave back surfaces  134 ,  136 ,  138  advantageously conform with the convex surface of the underwater breathing gas tank  12  to provide a tight fit when joined together during diving operations. Concave back bottom wall surface  136  advantageously protects in part the buckle  26  in its latched state in recess  18  such that buckle  26  cannot be hit by an obstacle or structure during a dive. 
     As illustrated in  FIGS. 2-4  the first mounting plate  30  and second mounting plate  32  may be releasably connected. The convex surfaces  74 ,  88  of the second mounting plate  32  are complimentary to the concave surfaces  126 , 128  of the first mounting plate  30  and cooperate in their contoured fit to assist in joining with strength the first and second mounting plates  30 ,  32 . So too, the male mounting members  72 ,  74  insert, respectively, into receiving apertures  130 ,  132  to provide a press fit between the first and second mounting plates  30 ,  32 . Moreover, the top and bottom apertured mounting bosses  70 ,  84  of the second mounting plate  32  are received into the top and bottom mounting apertures  40  and  42  of first mounting plate  30  when the first and second mounting plates  30 ,  32  are joined. 
     With additional reference to  FIG. 2 , the joining of the first and second mounting plates  30 ,  32  may be completed with fasteners  140  that are inserted through the top and bottom apertured mounting bosses  70 ,  84  as well as the top and bottom mounting apertures  40 ,  42  of first mounting plate  30 . A nut  142  attaches to each fastener  140  within the respective top and bottom mounting aperture  40 ,  42 . As the nut  142  is tightened the first and second mounting plates  30 ,  32  are drawn together for a tight fit and the nuts  142  rest inside their respective top and bottom mounting apertures  40 ,  42  such that they do not extend beyond, protrude past, or interrupt the front surface  16 . 
     When the first and second mounting plates  30 ,  32  are joined the upper wall  78  and lower wall  80  pass into the opening in the recess  18  to define together with sidewalls  56 , 58  the channel  76  of the recess  18  in which the buckle  26  resides in its latched state. 
       FIGS. 5 and 6  illustrate the cross section of the buckle  26  and the strap  24  through recess  18  about line  5 - 5  of  FIG. 1 .  FIG. 5  illustrates the buckle  26  in the latched state and  FIG. 6  illustrates the buckle in the unlatched state. 
     To create the over the center function of the buckle  26 , fixed end  120  of strap  24  is attached to recess pin  116  such that it may pivot about recess pin  116 . The strap  24  extends through a first gap  146  in the recess  18  between side wall  58  of the recess  18  and an edge  83  of bottom wall  82  as it is wrapped counter clockwise in the illustrated figures around an underwater breathing gas  12  for diving operations. Clockwise and counterclockwise are used simply for illustrative purposes with respect to the drawings. Once strap  24  completely surrounds an underwater breathing gas tank  12 , the strap  24  is passed through a second gap  148  in the recess  18  between an edge  85  of the side wall  56  of the recess  18  and the bottom wall  82  of the recess  18 . Thereafter, the strap  24  is wrapped counter clockwise around buckle pin  112  and inserted between buckle pins  112  and  110  such that strap  24  wraps clock wise around buckle pin  110 . Strap  24  then passes clockwise around recess pin  118  and passes between recess pin  118  and recess pin  116 . Free end  122  of strap  24  is then wrapped counterclockwise around buckle pin  116  with the buckle  26 . 
     By unlatched state of the buckle  26  it is meant that the strap  24  is adjustable such that it may be tightened or loosened by decreasing or increasing its length as it surrounds an underwater breathing gas tank  12 . In the unlatched state, buckle handle  104  is located at least partially outside the recess  18  such that the buckle front face  108  is facing toward the underwater breathing gas tank  12  while the buckle back face  107  faces away from the underwater breathing gas tank  12  and towards a diver&#39;s back when the underwater breathing gas tank  12  is placed in a position to be operably coupled to the tank mounting structure  14 . In the unlatched state of the buckle  26 , the outermost periphery of the buckle at the second end  106  is outside of the recess  18  extending laterally beyond side wall  56  such that buckle front and back faces  106 ,  107  are generally parallel to the bottom surface  22  of the recess  18 . A portion of the handle  104  of the buckle  26  extends into a portion of the recess  18  that extends into the side  19 ,  21  of the tank mounting structure  14  when the buckle  26  is in the unlatched state. This provides a visual indication to the diver that the buckle  26  is unlatched. It also allows the diver to easily grip and apply force to the buckle  26  to transition it into the latched state. 
     In the unlatched state of the buckle  26 , the length of the strap  26  is adjusted by pulling on the free end  122  of the strap  24  to move the strap in a generally counterclockwise manner to tighten and thus shorten the length of the strap  24  length as it surrounds an underwater breathing gas tank  12 . On the other hand, the length of the strap  24  as it surrounds the underwater breathing gas tank  12  may be increased, that is loosened in the open state of the buckle  26  by pulling on any part of the strap  24  away from the fixed end  120  to move the strap  24  in a generally clockwise direction. Strap  24  may also have pre-configured visible lines (not illustrated) along its length for alignment with the tank mounting structure  14 , buckle  26  or the strap  24  or all to advantageously provide a visible reference for adjusting the length of the strap  24  to tightly fit around varying predetermined circumferences of underwater breathing gas tank as they are operably coupled to the tank mounting structure  14 . 
     Also illustrated in  FIG. 5  is bottom mounting pin  102  which together with top mounting pin  104  (not illustrated in  FIG. 6 ) defines the rotation axis  124  about which buckle  26  rotates as it passes between the unlatched state of the buckle  26  (which may also be interchangeably referred to as the open state of the buckle  26 ) and the latched state of the buckle  26  (which may also be interchangeably referred to as the closed state of the buckle  26 ). 
     Buckle  26  is manipulated to rotate in a counterclockwise rotation about rotation axis  124  to transition from the unlatched state to the latched state. In transition, at least a portion of the handle  104  extends out of the opening  20  of the recess  18  beyond the front surface  16 . The buckle  26  is an over center mechanism such that in the latched state, the strap  24  creates a force  156  that is directed to generate a latching torque  158  in a first angular direction on the buckle  26  around the rotational axis  124  biasing the buckle  26  toward the latched state and maintaining the buckle in the latched state. In the latched state, the force  156  generated by the strap  24  on the buckle  26  lies on a first side  160  of rotational axis  124 . In the unlatched state, the strap  24  creates a force  162  that generates a torque  164  on the buckle  26 , in a direction opposite torque  158 , around the rotational axis  124  biasing the buckle  26  toward the unlatched state. In the unlatched state the force  162  acts on an opposite second side  166  of rotational axis  124  as force  156 . 
     As illustrated in  FIG. 6 , when the buckle  26  is in the latched state the length of the strap  24  is fixed and the buckle  26  is located entirely within the recess  18  such that it does not extend beyond the front surface  16  or the sides  19 ,  21  of the tank mounting structure  14 . In the latched state, the front face  108  of the buckle  26  is located entirely within recess  18  and opening  20  such that the front face  108  does not extend beyond front face  16  of the tank mounting structure  14 . Advantageously, in the latched state, when in a dive, the buckle  26  is protected from becoming inadvertently unlatched, because it is protected by the bottom wall  82  of the recess  18  as well as a diver&#39;s back over opening  20  such that an object or structure cannot penetrate the recess  18  to generate enough force to overcome the torque keeping the over-the-center buckle  26  closed in the latched state. 
     Further the handle  104  is advantageously dimensioned such that its length prevents rotation from the latched state to the unlatched state when worn by a diver as the handle  104  will hit the diver&#39;s back prior to being able to be rotated to the unlatched state. The particular relevant dimension is the distance from rotation axis  124  relative to spacing between rotation axis  124  and a diver&#39;s back when worn. Accordingly, in other embodiments, tank mounting structure  14  provides for a recess  18  that receives a buckle  26  such that buckle  26  may extend beyond opening  20  and front face  16  towards a divers back. In such embodiments, at least a portion of buckle  26  remains in the recess  18 . In the latched state, when the tank mounting structure  14  is worn on a diver&#39;s back, the diver&#39;s back prevents the buckle  26  from inadvertently transitioning from the latched state to the unlatched state. 
     Turning now to  FIG. 7 , back pack  110  is illustrated. Back pack  210  is identical to back pack  10  except back pack  210  includes dive bladder  344 . 
     The back pack  210  for an underwater breathing gas tank  212  includes a first mounting plate  230  and a second mounting plate  232  releasably coupled to one another. By releasably coupled it is understood that the first and second mounting plates  230  and  232  may be joined together for use and then as desired for any number of reasons such as maintenance or cleaning by way of non-limiting examples the first and second mounting plates  230 ,  232  may be easily disassembled/unjoined as opposed to a forced disassembly, for example, by having to break welds or rivets. 
     The first and second mounting plates  230 ,  232  define a tank mounting structure  214  having a front surface  216  facing away from a gas tank  212  when a gas tank  212  is operably mounted to the tank mounting structure  214 . The tank mounting structure  214  defines a recess  218 . The front surface  216  defines an opening  220  of the recess  218 . The tank mounting structure  214  defines a bottom surface  222  of the recess  218  opposite the opening  220  in the front surface  216 . The back pack  210  includes the dive bladder  344  that is releasably coupled between the first and second mounting plates  230 ,  232 . 
     The dive bladder  344  includes a first  350  and second  352  dive bladder aperture. The first dive bladder aperture  350  aligns with the top apertured mounting boss  270  of the second mounting plate  232  and the top mounting aperture  240  of the first mounting plate  230  such that fastener  340  may be easily inserted therethrough and fastened with nut  342 . The second dive bladder aperture  352  aligns with the bottom apertured mounting boss  284  of the second mounting plate  232  and the bottom mounting aperture  242  of the first mounting plate  230  such that fastener  340  may be easily inserted therethrough and fastened with nut  342 . 
     Dive bladder  344  may further include a third dive bladder aperture  354  located between the first and second dive bladder apertures  350 ,  352 . The third dive bladder aperture  354  is formed such that it permits the upper  278  and lower  280  walls of the middle portion  266  of the second mounting plate  232 , the top  272  and bottom  286  male mounting members and the first  256  and second  258  side walls of the recess  218  to pass therethrough as the first  230  and second  232  mounting plates are joined to form the tank mounting structure  214 . 
     Dive bladder  344  is made of a material that is flexible enough to permit the dive bladder  344  to conform to the convex front surfaces of the second mounting plate  232  and the concave back surfaces of the first mounting plate  230  such that they cooperate with one another to ensure a tight fit between the first  230  and second  232  mounting plates when they are releasably joined together in the manner heretofore discussed. Specifically, the dive bladder  344  may be a single bladder made of high frequency weldable fabric such as polyurethane coated nylon fabric ( 210 ,  420 ,  840  or  1000  denier) or dive bladder  344  may be a double bladder that includes a polyurethane inner air-cell and an outer bladder made of nylon fabric just discussed but without the polyurethane coat. 
     Back pack  210  further includes the over the center buckle  226  and the strap  324 . The first end of the  320  of the strap  324  is pivotally attached the over the center buckle  226 . The over center buckle  226  receives the second end  322  of the strap  324  for securing the strap  324  in a fixed position. The strap  324  in its fixed position surrounds an underwater breathing gas tank  212 , the dive bladder  344 , the tank mounting structure when an underwater breathing gas tank  212  is operably connected to the back pack  210  for a dive. When the strap  324  is in the fixed position, the buckle  226  is located within the recess  218  between the bottom surface  222  and the opening  220  defined by the front surface  216  of the tank mounting structure  214 . 
     With reference to back packs  110 ,  210 , the tank mounting structure  14 ,  214  may be made of fiberglass reinforced nylon. The fastener  140 ,  340  and nut  340 ,  342  may be made of nickel/chrome plated brass or stainless steel. The buckle  26 ,  226  may be made of stainless steel or it may be of injection molded fiberglass reinforced nylon. The strap  24 ,  324  may be made of polyester or nylon based webbing. 
     All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.