Abstract:
A lightweight seat suitable for applications such as those in which the seat and occupant must withstand extreme amounts of applied force during use, e.g., encountering high waves in boats of seven meters (23 feet) or greater at speeds of at least 20 knots (37 km/h (or 10.3 m/s)).

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 61/490,775 filed May 27, 2011. 
     TECHNICAL FIELD 
     This application concerns lightweight seats for environments where the occupant is subjected to substantial random and/or sudden dynamic forces, e.g. buffeting, pounding, bouncing and the like. 
     BACKGROUND 
     High-performance vehicles subject their occupants to substantial random and/or sudden dynamic forces, and therefore the seats in which such occupants sit during motion must be extremely rugged in design and performance. An example is the seats suitable for high-speed, rugged marine craft such as rotationally molded boats in very large dimensions (e.g., seven meters (23 feet) or greater). The occupants of such seats must withstand extreme amounts of applied force during use, e.g., encountering high waves in boats of seven meters (23 feet) or greater at speeds of at least 20 knots (37 km/h (or 10.3 m/s)). At the same time, weight is always a concern in high-performance vehicles and, of course, the seat must be comfortable. 
     SUMMARY 
     A preferred embodiment of a lightweight seat is illustrated in the accompanying Figures and described below. This is only an example to illustrate the principles of the invention. The seat proper is mounted on a pedestal and base which has a permanently or temporarily inflated air bag to provide cushioning and, in the preferred embodiment, approximately 4 inches of vertical clearance to absorb forces and therefore moderate motion of the seat. A keyway or equivalent feature prevents the seat from pivoting around the vertical axis. Two rings help maintain the performance of the air bag. 
     The lightweight seat is particularly suitable for use with the Widmer Flex-Ride Night Raider, a boat having a plastic hull which flexes and absorbs impacts produced at high speeds in rough water because the impact G-forces are absorbed by the hull instead of directly translated to the occupants. The lightweight seat disclosed here further absorbs such forces instead of translating them to the occupants, and it does so at a substantial reduction in weight, which is a critical parameter in the design of an effective boat of this type and for this application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings show particular embodiments as examples only, and are not intended to limit the scope of the claims. 
         FIGS. 1-5  are perspective, front, back, left side (the right side being a mirror image of the left side), and top views of an assembled chair assembly. 
         FIG. 6  is a perspective view of a portion of the assembly of  FIGS. 1-5 . 
         FIGS. 7 and 8  are cross-sectional views of portions of the assembly of  FIGS. 1-5 . 
         FIG. 9  is a lower perspective view of the seat component of the assembly of  FIGS. 1-5 . 
         FIG. 10  is a partial cut-away side view of the assembly of  FIGS. 1-5 , as indicated in  FIG. 4 . 
         FIGS. 11-13  are perspective views of other components of the assembly of  FIGS. 1-5 . 
     
    
    
     DETAILED DESCRIPTION 
     General 
     While this application describes a seat for the preferred application of a rotationally molded boat other water-borne vehicles, those are only examples. Turning to the figures, in general terms assembly  100  comprises a base  1  mounted to the hull or deck of the boat (perhaps through an intermediate mounting system not shown) using mounting holes  11  or other features supporting the connection. For example, if threaded nuts or similar features are molded into the boat, the seat may be bolted to the boat though the mounting holes  11 . Other means for attachment are equivalent. By way of example only, six mounting holes  11  are provided in base  1 , only three of which are visible in  FIG. 1 . 
     Turning briefly to  FIG. 6 , a pedestal  12  (not visible in  FIGS. 1-5 ) is mounted or molded into the base  1 . The seat  2  is mounted into central opening  13  formed in the pedestal  12  combination. 
     Returning to  FIGS. 1-5 , the seat  2  is preferably a single molded piece (not considering any stiffening members which may be molded into it), generally L-shaped in profile and contoured according to conventional principles. Either or both sides of the seat may have optional armrest(s)  5  that may be formed by a pin-and-socket arrangement (for example) so that they may be folded up or down as desired. It is desirable for purposes of reducing weight and material usage, and to ensure sufficient flow of the material during molding, that one or more openings be molded into the seat. 
     In general, the components of the base  1  and seat  2  are rotationally molded polymers or marine-environment-suitable metals. Materials are selected based on a sufficient balance of cost, strength, weight, ease of handling, and the like. Preferred molding materials for high performance watercraft and similar applications are high density cross-linked polyethylenes (HDXLPE), which are commercially available. Other materials known to be suitable for rotational molding may also be used, including the less costly (but less strong) high density polyethylenes (HDPE) which are also commercially available. The base  1  has a preferred thickness of 0.156 inch and preferably a sandblasted finish, but those are only examples. 
     A permanently or temporarily inflated air bag  4  surrounds the pedestal  12  to provide cushioning and, in the preferred embodiment, approximately 4 inches of vertical clearance to absorb forces. The air bag  4  is generally similar to that described in U.S. Pat. No. 4,560,145 (Widmer), the entire contents of which is incorporated by reference. In general, the air bag is an inflatable member made of a flexible material, having a uniform thickness and comprising a plurality of annular sections. The sections sequentially taper in diameter to form a generally pyramidal shape. The air bag may be inflated by conventional means, e.g., as described in the Widmer &#39;145 patent incorporated by reference. 
     Two rings  6 ,  7  ( FIGS. 2-4 ) help maintain the performance of the air bag. The upper and lower rings, one between each pair of adjacent sections of the air bag, extend around the outside of the air bag to provide annular support between the sections and to control bulges and stretching. The rings provide support without the danger of the inflatable member “thinning” in the ring area when inflated. “Thinning” of the inflatable member could result in a rupture or bulge. Each ring has a circular cross section. Preferred dimensions for the O-rings are 10.47 inch (26.6 cm) and 11.21 inch (28.5 cm) diameter for the upper and lower rings, respectively, each being 0.5 inch (1.27 cm) in cross-sectional diameter. 
     Turning to  FIG. 7 , viewed from the side in cross-section, the air bag  4  has three generally toroidal sections  21 ,  22 ,  23  stacked above and connected to each other, and a smaller cylindrical section  24  stacked above and connected to the uppermost section  23  of the three toroidal sections. The bottom and top faces  25 ,  26  are generally flat to accommodate the upper flat surface of the pedestal and the lower surface of the annular region of the underside of the chair, respectively. The central portion  27  of the air bag is generally cylindrical and has an inner diameter profile corresponding to the outer diameter profile of the pedestal. That profile can be understood as being a series of four cylindrical portions, the first (lowest) and third portions  27   a ,  27   c  having inwardly (proceeding in the upward direction) sloping sides and the second and fourth (highest) portions  27   b ,  27   d  having vertically straight sides (e.g., right circular cylinders). The transitions between such sections are beveled or rounded as appropriate, as are the lower and upper ends of central portion  27 . Each of the two transitions  28   a ,  28   b  where two immediately adjacent toroidal sections join together defines upper and lower necks around the outer surface of the air bag. These locations are where the upper and lower O-rings  6 ,  7  are located. These locations correspond to the locations of the top of pedestal  12  and shoulder  32   c  discussed further below. 
     In terms of materials, the air bag  4  is constructed from polymer such as a suitable elastomer, e.g., a vinyl plastic of about 70 durometer on the A scale. The O-rings  6 ,  7  are made of elastic or elastomeric material, such as neoprene rubber, for example in the range of 80 durometer. As noted above, in the preferred embodiment illustrated in the Figures, the air bag  4  provides approximately four inches of cushioned vertical travel in the preferred embodiment. 
     Turning to  FIG. 8 , base  1  is a preferably a single piece but can be an assembly of multiple pieces if desired (although strength and performance may suffer). As illustrated, it comprises a plate section  30  defining a pair of straight, downward-opening channels  31  that may be used to adjust its position relative to the boat deck or hull. The pedestal  12  is axially symmetric and generally conical, extending above the flat plate section  30 . The air bag  4  described above is mounted around the pedestal, and the seat  2  described above is mounted (above the uppermost surface of the air bag  4 ) above the pedestal  12 . As the cross sectional view illustrates, the inner and outer faces  32 ,  33  of the pedestal  12  need not be identical, and in the preferred embodiment they have surface profiles which are not similar to each other (i.e., they are not “parallel” to each other) at all. The inner face  32  is generally a pair of axially aligned right circular cylinders  32   a ,  32   b  (although the lower  32   a  is slightly tapered in the preferred embodiment illustrated). The diameter of the upper  32   b  is less than that of the lower  32   a , producing a shoulder  32   c  where they meet. The outer face  33  has three axially concentric sections, a lowermost section  33   a  being more noticeably tapered than its corresponding inner diameter profile, for strength and additional stability. The middle section  33   b  is a right circular cylinder and the uppermost section  33   c  tapers inward. As noted elsewhere, these three outer profiles conform to the three lowermost portions  27   a ,  27   b , and  27   c  of the inner profile of air bag  4 . The inner profile is designed to provide maximum support for the seat as it undergoes vertical motion due to the high-performance environment in which it is placed. 
     Turning to  FIG. 9 , the lower face of the seat  2  includes a shaft  40  or similar extension for insertion into the central opening  13  of the pedestal (see  FIGS. 6 ,  8 , and  10 ). For example, such a feature could be molded directly into the seat  2 . Surrounding shaft  40  is annular ridge  41  which fits around the outer diameter of the uppermost portion  24  of air bag  4  (see  FIG. 7 ). The lower face of seat  2  then fits against upper face  26  of air bag  4 . This arrangement keeps the seat aligned with the vertical axis despite the forces created by downward motion of the seat toward the boat (or upward motion of the boat toward the occupant of the seat) being transferred into compression of the air bag. Considering also  FIG. 8 , the length of the shaft  40  must be sufficient to extend substantially into the upper portion  32   b  of pedestal  12 , or about eight inches beyond the lower edge of annular ridge  41  in the preferred embodiment. Thus, considering also  FIG. 7 , the end of shaft  40  extends into central opening  13 , occupying the space corresponding to portions  27   b ,  27   c  and  27   d  of air bag  4 . 
     Returning briefly to  FIG. 9 , shaft  40  is provided with a slot or keyway feature  42 . This is the preferred embodiment of any feature which prevents rotation of the seat around the vertical axis. Because the lower face of the seat (at the top of shaft  40  and within the diameter of annular ridge  41 ) lies against the top surface  26  of air bag  4 , rotation of the seat would introduce undesirable wear and tear on the air bag. In conjunction with slot  42 , to provide a smoother surface fit for the outer surface of shaft  40  as it travels up and down within central opening  13 , a mold-in sleeve  50  as shown in  FIG. 11  is added to the inner diameter of the pedestal. The mold-in sleeve  50  is a hollow cylinder having an inner diameter only slightly greater than the outer diameter of shaft  40 , and an inwardly extending mating ridge  52  formed into its entire height. The cross-sectional shape of the ridge  52  is a matter of preference—provided it is compatible with the slot  42  of shaft  40 , which typically but not necessarily means the profiles are identical—and thus in the preferred embodiment illustrated, it is rectangular. In the preferred embodiment, mold-in sleeve  50  is incorporated into the pedestal during rotational molding but it could be added afterward in other embodiments. Also, as illustrated, in the preferred embodiment the slot  42  faces forward (and thus the ridge  52  faces backward, or aft in the case of a nautical or aeronautical installation), but this is only a matter of choice. In the most preferred embodiment, for a radius of 4.0 inch (10.2 mm) and 0.020 inch (0.51 mm) material thickness, the channel may be 0.31 inch (7.9 mm) wide and 0.19 inch (4.8 mm) deep. (The preferred corresponding dimensions of slot  42  are 0.33 inch (8.4 mm) and 0.19 inch (4.8 mm), respectively, as a tight fit is desired.) A preferred height of the mold-in sleeve is 4.38 inch (11.1 mm). The preferred material is type 316 stainless steel. 
     Turning to  FIG. 12 , to improve the strength and rigidity of seat  2 , a flanged pedestal support plate  54  is molded into the seat. The uppermost plate portion  55 , which aligns with the underside of the seat, is preferably circular in the horizontal plane but could be other shapes. As illustrated, it has several holes  56  (nine are visible of the ten provided in the preferred embodiment) to reduce weight without sacrificing strength and to allow for the polymeric material that forms the seat to flow through the holes and increase the strength of the plate/seat combination. The pedestal support plate further includes a hollow cylindrical extension portion  57 , which extends downward into the shaft  40  described above. 
       FIG. 13  illustrates a plate  60  which may be molded into the lowermost portion of shaft  40  to add strength and rigidity. Like the uppermost plate portion  55  of pedestal support plate  54 , plate  60  is preferably circular in the horizontal plane but could be other shapes. As illustrated, it has several large diameter holes  61  to reduce weight without sacrificing strength and to allow for the polymeric material that forms the seat to flow through the holes and increase the strength of the plate/shaft combination. The central hole may support a bolt lug (connected to a centered hole in the outer surface of the end of the shaft), and the four smaller holes may support studs. Plate  60  is preferably molded into shaft  40  adjacent its lowest end. 
     Applications 
     In addition to the applications noted above, specifically preferred applications are boats which are required to withstand blast, impact, and/or structural loads when they are used to blow up mines, when moving through rough seas at high speed and/or when they are hoisted aboard another structure (e.g. another vessel or a platform). Although the principles above are described and illustrated primarily with respect to boats and other watercraft, such articles are only examples. Other transportation vehicles, and the like, such as airplanes, could be considered. 
     Preferred Dimensions 
     In addition to dimensions noted above, specifically preferred dimensions for the preferred embodiment of a seat suitable for a high performance boat of the type described above include the following. Overall front-back seat length: 22.5 inch (57.2 cm). Seat width: 19 inch (48.3 cm). Seat height above deck: 18.74 inch (47.6 cm). Arm rest height above deck: 27.97 inch (71.0 cm); pivot point of arm rest height above front edge of seat: 7.25 inch (18.4 cm). Base dimensions: 14 inch (35.6 cm) square and 1.5 inch (3.8 cm) thickness; 6.0 inch (15.3 cm) hole separation, 11 inch (27.9 cm) track-to-track pitch, 1.5 inch (3.8 cm) side clearance and 1.0 inch (2.5 cm) front/back clearance measured from the centerline of each hole to the edge of the base plate. Seat shaft diameter: 4 inch (10.2 cm). Seat shaft length: 8 inch (20.3 cm). Annular ridge inner diameter: 8.25 inch (21 cm); annular ridge outer diameter: 9.75 inch (24.8 cm); annular ridge height: 1.5 inch (3.8 cm).