Abstract:
A personal flotation unit for supporting a person in a generally sitting position in the water, with the person&#39;s head and part of the person&#39;s torso above the water has a rear panel and a front panel each made from a flexible flotation material. A fabric seat is connected between bottom edges of the panels. Left edges of the panels are connected by strapping of some kind, as are the right edges of the panels. The seat and the strapping cooperate to form the panels into a diaper or pair of shorts that provides flotation allowing the user to sit in an upright position in water. Preferably the front panel has a T shape with arms that during use are bent backwards by the strapping to provide lateral flotation support for the wearer.

Description:
BACKGROUND OF THE INVENTION 
   Conventional water supports for people, also known as personal flotation devices (PFDs), usually have the form of a vest or jacket worn on the upper body of the wearer. This locates the buoyancy relatively high on the torso, so that the wearer&#39;s head is above the water, which is desirable for cases where the wearer may be weak or unconscious, or where current or waves are present. 
   In quiet water such as in a pool or in a lake, people may sometimes want simply to lounge or float in the water, say on a hot day. Inflatable mattresses and foam mattresses and sausages have commonly served this purpose, but they do not allow for controlled and consistent immersion of the user in the water, and they lack stability and reliable support for the user. 
   BRIEF DESCRIPTION OF THE INVENTION 
   We have developed a personal flotation unit (PFU) in the general form of a diaper, shorts, or brief. This design is suitable for swimming pools or other quiet water to support the user in a generally sitting position with his or her upper torso above the water, and without the encumbrance of a standard PFD. 
   In one form, such a PFU has a front panel formed of a panel-like block of flotation material such as closed-cell plastic foam. The front panel has upper and lower and left and right edges. The front panel may be in the form of a T having a relatively thick stem forming a front section and left and right sections comprising two thick arms of the T. The arms serve to provide at least a small amount of lateral buoyancy for the user. The flotation material in the left and right sections may be unitary with the front section or may be separate therefrom, and held to the front section by fabric or sheeting. 
   A rear panel of the PFU is formed of a second panel-like block of flotation material. The rear panel has upper and lower and left and right edges as well. A preferred embodiment uses flexible flotation material for both the front and rear panels. 
   A seat is formed of flexible material such as fabric. The seat has a back edge attached to the rear panel&#39;s bottom edge and a front edge attached to the front panel&#39;s bottom edge. 
   A strap is attached to the front and rear panels adjacent to the upper edge of each panel. The strap connects the left edge of the front panel to the left edge of the rear panel and the right edge of the front panel to the right edge of the rear panel. 
   A user wears this PFU as a diaper. When in water, the panels provide buoyancy for the user, who will float with a portion of his or her body above the water. Ideally, sufficient flotation material is present in the panels to support all of the user&#39;s head and at least a portion of the user&#39;s torso or trunk above the water. The flotation material will ideally be distributed between the front and the rear panels to provide support that sustains the user in an upright position and restores the user to an upright position if tilted or heeled in a particular direction from an upright position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the PFU. 
       FIG. 2  is a front elevation view of the PFU&#39;s front panel, flattened. 
       FIG. 3  is a front elevation view of the PFU as approximately shaped when the PFU is worn by a user that has a relatively small amount of mass as compared to the amount of flotation present. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The PFU  10  shown in  FIGS. 1–3  comprises a front flotation panel  11  and a rear flotation panel  15 . Panels  11  and  15  are formed from flotation material typically comprising fabric-covered closed-cell foam blocks that typically provides buoyancy in the range of 55–60 lb./ft. 3 . In most cases the foam flotation material is flexible. Closed cell foam blocks with total thickness of approximately 1–1½ in. are suitable for each of panels  11  and  15 . The foam blocks may be either unitary or formed from a number of thinner sheets of foam held together by the fabric covering. 
   Any fabric forming an outer surface of panels  11  and  15  should be of a type that is comfortable when contacting a wearer&#39;s skin and that has good wet strength. Typically, the fabric is formed into a pocket or bag of appropriate shape and size to neatly and closely hold the foam blocks. 
   The front panel  11  has upper, lower, left and right edges as viewed in  FIGS. 1 and 2 . Preferably, panel  11  is roughly shaped in a T. When so shaped, it is convenient to divide front panel  11  into a front section  19 , a left side section  17 , and a right side section  22 . (All references to “left” and “right” are as viewed by a person wearing PFU  10 .) The left and right side sections  17  and  22  form the arms of the T, and the front section forms the stem of the T. Sections  17  and  22  may be integral with the front section  19  as shown or may comprise separate foam blocks attached to front section  19  by the fabric cover. 
   Right section  22  is shown in  FIG. 2  as comprising the portion of front panel  11  to the right of line  22   a . Left section  17  is shown in  FIG. 2  as comprising the portion of front panel  11  to the left of line  17   a.  Since the preferred structure for panel  11  is as a flexible block or sheet that is not completely stable dimensionally, the positions of lines  17   a  and  22   a  only approximately delimit sections  17  and  22 . 
   Rear panel  15  has similar construction to front panel  11 , but with an approximately squared shape. Panel  15  also has upper, lower, left and right edges. 
   Front section  19  has a minimum width or horizontal dimension near the bottom of the stem of the T, and a maximum width dimension between the left and right edges. Rear panel  15  has a width dimension as well between the left and right edges. The rear panel  15  width dimension is typically less than the front panel  11  maximum width dimension and larger than the minimum width dimension of front panel  11 . 
   A seat  13  formed of a flexible sheet connects the lower edge of front panel  11  to the lower edge of rear panel  15 . Seat  13  should have a width that passes comfortably between the wearer&#39;s thighs. Seat  13  may be formed of flexible and elastic fabric or sheeting with sufficient wet strength to support the user. Preferably, seat  13  is attached by sewing or other secure means to the fabric covering the front and rear panels  11  and  15 . 
   Strapping comprising straps  24  connects the left edge of the left section  17  to the left edge of front panel  15  in a spaced apart relationship. Straps  24  also connect the right edge of the right section  22  to the right edge of front panel  15 , also in a spaced relationship. In the preferred design shown in  FIGS. 1–3 , straps  24  connect sections  17  and  22  to front panel  15  by completely encircling panels  15  and  11 . 
   Straps  24  include length adjustment fittings  33  adjacent to front section  19  to allow the wearer to quickly adjust PFU  10  for the user&#39;s size and comfort. Fittings  33  may also include disconnects to assist putting on and removing PFU  10 , and also to reduce space that PFU  10  occupies during storage or transport. Length adjustment fittings  33  for straps  24  may be designed either to accommodate a wide range of body sizes or to limit comfortable use to wearers that fall within an appropriate range of body mass for the amount of flotation in PFU  10 . 
   While straps  24  are shown as continuous except for the fittings  33 , another design could use only short sections of strapping to connect the left edges and the right edges of panels  11  and  15 . Such an arrangement may have the length adjustment and disconnect fittings between the left edges and the right edges of panels  11  and  15 , with ends of the strapping sewn to front panel  15  and sections  17  and  22 . 
   Although not preferred at this time, it is possible to mold front and rear panels  11  and  15  as a single integral block of foam. One disadvantage of forming both panels  11  and  15  as a single piece of foam is that it becomes difficult to adjust the PFU  10  to the individual sizes of users. Theoretically, adjustment of the size of PFU  10  may be done at one side only, but this may lead to a less comfortable fit to some users. Even though this design appears to be inferior at this time, nevertheless this design variation is essentially the functional and structural equivalent of PFU  10  as shown in  FIGS. 1–3 . 
   In other configurations more similar to that of the PFU  10  shown, cords, strings, small ropes, fabric panels, and other flexible attachment means may perform the function of the straps  24  to attach the left sides of panels  11  and  15  to each other and to attach the right sides of panels  11  and  15  to each other. The terms “strap” and “strapping” in this application are intended to include these various means for attaching panels  11  and  15  to each other. 
   Straps  24  configure PFU  10  as shown in  FIG. 3  as a roughly box-shaped brief or diaper that stably supports the wearer in a sitting position. A suitable volume of buoyancy from the flotation in panels  11  and  15  will place the wearer&#39;s shoulders from 6–12 in. above the water surface. 
   Seat  13  may have elasticity sufficient for both support and comfort. Seat  13  when unstretched may have a side to side length at some point approximately half that of the front to back length. Seat  13  supports only the weight of the user above the water line. Considerations such as ease of putting on PFU  10  and reliably keeping on PFU  10  when the user tilts from an upright position are important, as of course is comfort in selecting the size and shape of seat  13 , and the fabric or other material from which seat  13  is made. 
     FIGS. 2 and 3  show front panel  11  with a representative water line  36  drawn thereon. PFU  10  is preferably designed to support perhaps 5–15% of the wearer&#39;s body weight above water. The average specific gravity of a human body is very close to 1.00, and depends on the amount of air in the person&#39;s lungs. That means that the above-water weight of a user of a PFU  10  of this type will be nearly equal to the buoyancy in the PFU  10  itself. 
     FIG. 3  shows PFU  10  flexed into a typical shape when worn by a user. When PFU  10  is in use, panel  11  when formed of flexibly material is bent under the influence of straps  24  in the neighborhood of lines  17   a  and  22   a  so that left and right sections  17  and  22  are each at an interior included angle with respect to front section  19 . This angle will typically be about 90° to 150° depending on the wearer&#39;s chest size. The bends at lines  17   a  and  22   a  however are not sharp so only parts of side sections  17  and  22  will have the suggested angle with respect to front section  19 . 
   Since the foam from which front panel  11  is preferably made is reasonably flexible, the user can easily tighten straps  24  to bend front panel  11  into a shape that comfortably molds to or accommodates the user&#39;s body. The shape of individual sections  17 ,  19 , and  22  will usually also individually bend into concave shapes that to some extent conform to the user&#39;s body shape. The bend lines and the angles between front section  19  and side sections  17  and  22  will be more accurately defined where front panel  11  comprises three separate blocks of relatively rigid foam forming sections  17 ,  19 , and  22 . 
   The buoyancy of panels  11  and  15  must provide both adequate flotation and stability for the user. Dealing first with the flotation issue, the total buoyancy in front and rear panels  15  and  11  should be approximately 5–15% of the wearer&#39;s mass, with larger percentages for lighter wearers. 
   In one design suitable for a wearer whose mass is in the range of 175–250 lb., the following table sets out approximate design values for PFU  10 . 
   
     
       
             
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
               Buoyancy/ft. 3  of flotation material 
               55 
               lb. 
             
             
                 
               Rear panel thickness 
               1.25 
               in. 
             
             
                 
               Rear panel 15 height 
               10.5 
               in. 
             
             
                 
               Rear panel 15 width 
               17 
               in. 
             
             
                 
               Front panel thickness 
               1.5 
               in. 
             
             
                 
               Front section 19 height 
               11.5 
               in. 
             
             
                 
               Front panel 11 max. width 
               26 
               in. 
             
             
                 
               Front panel 11 min. width 
               16 
               in. 
             
             
                 
               Side sections 17 and 22 areas 
               60 
               in. 2   
             
             
                 
                 
             
           
        
       
     
   
   These values yield the following approximate buoyancy values: 
   
     
       
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
               Rear panel 15 
                7.0 lb. 
             
             
                 
               Front section 19 
                5.5 lb 
             
             
                 
               Left side section 17 
                3.5 lb. 
             
             
                 
               Right side section 22 
                3.5 lb 
             
             
                 
               Total PFU 10 buoyancy 
               19.5 lb. 
             
             
                 
                 
             
           
        
       
     
   
   Typically, the flotation volume in rear panel  15  will be larger than for the front section  19  alone. The ratio of the total buoyancy in the front panel  11  to the buoyancy in the rear panel  15  may be in the range of approximately 1.5 to 2 to thereby provide front to back stability. 
   The left and right side sections  17  and  22  should each have equal buoyancy and together may approximately equal the buoyancy of rear panel  15 . To put another way, each side section  17  and  22  may have a volume of flotation equal to approximately 40–60% of the rear panel  15  flotation. Left and right side sections  17  and  22  should have sufficient buoyancy to provide appreciable lateral stability for the wearer. Buoyancy for each of sections  17  and  22  in the range of 2–5 lb. seem to be about right. 
   PFU  10  may at some point with or without modifications, carry US Coast Guard certification. Therefore, safety as well as comfort, stability, and ease of use suggests that some buoyancy at the left and right sides of a user is appropriate. 
   Although not yet determined experimentally, it is also likely that left and right side sections  17  and  22  should each have buoyancy in the neighborhood of half the buoyancy of front section  19  for adequate lateral stability. For the example above, the buoyancy of each side section  17  and  22  is about 40% of the buoyancy of front section  19 . 
   The sections  17 ,  19 , and  22  and rear panel  15  should extend upwards toward the wearer&#39;s shoulders sufficiently to assure stability, perhaps to within 6–15 in. from the top of the shoulders but below the user&#39;s armpits. Increasing the front to back length of seat  13  increases overall stability for a user. For further stability, preferred materials for seat  13  have little or no buoyancy. 
   To allow a user to further configure PFU  10  for extreme body weights, front section  19  may have a slot or opening  27  that allows insertion or removal of buoyancy panels. Most desirably, slot  27  is located at the bottom of front section  19 . A zipper may close slot  27  to prevent buoyancy panels from inadvertently escaping from panel  11  during use. Rear panel  15  may have a similar zippered slot to allow buoyancy panels to be inserted or removed. 
   A further modification of the preferred embodiment gives the rear panel  15  a T shape and the front panel  11  a rectangular shape. This design may require different ratios of flotation volume than that specified for the design shown in  FIGS. 1–3 . 
   Where panels  11  and  15  are fabric-covered, drainage of the volume enclosed by the fabric is desirable. This drainage may arise from vents or mesh sections at either or both of the upper and lower edges of panels  11  and  15 . Or the fabric may itself be water-permeable to quickly drain water from the fabric-enclosed volume. A preferred design has mesh sections  25  and  26  at the top and bottom of the fabric forming the exterior of panel  11  as shown and similarly on panel  15  as well. Sections  25  and  26  provide for quick drainage of the fabric-enclosed volume. Sections  25  and  26  may extend along either part or all of the upper and lower edges of panels  11  and  15 . 
   For some applications, PFU  10  may include loops useful for lifting the wearer from the water. Such loops may be formed from straps attached to the tops of panels  11  and  15 . The straps may pass below seat  13  from front to back and between the user&#39;s legs to provide adequate strength and support for all of the weight of a human body. Such a design may retain an unconscious person safely in PFU  10  during such lifting.