Abstract:
A watercraft allowing relative motion of its deck relative to its hull structure to increase passenger comfort. The deck is mounted to the hull structure in a manner which permits relative motion of the deck structure to the hull in at least two independent axes.

Description:
FIELD OF THE INVENTION 
     This invention relates to a suspension system for a speed boat. More specifically, the invention is a suspension system in which the deck of the boat is allowed to move in a controlled manner in the pitch, yaw and roll axes to absorb shock and increase the comfort of the boat&#39;s passengers. 
     BACKGROUND OF THE INVENTION 
     Conventional boats are subject to wave action and, particularly for smaller boats or rougher water or faster boats, the resulting movements of the boat can be very uncomfortable for the passengers. In order to increase passenger comfort, some boats have incorporated suspension systems into the seating, or in the case of personal watercraft, the seating area. Other boats have used pontoon systems to control the entire boat&#39;s attitude and response to wave conditions. 
     One arrangement of a suspended seating area is shown in U.S. Pat. No. 5,603,281, issued Feb. 18, 1997. In the personal watercraft shown in that patent, various arrangements of suspension which act only in the primarily vertical plane are shown. The embodiments of the suspension shown in the patent are analogous to motorcycle suspensions since they only provide travel in the plane perpendicular to the underside of the watercraft. Thus, only the pitch motion of the watercraft is controlled. When the wave motion is oblique to the boat&#39;s direction of travel, the suspension cannot act to reduce components of acceleration and shock which are not in the plane in which the suspension system acts. 
     Since a boat must be capable of travelling in any direction relative to the waves, there are almost always pitch, roll and yaw components of motion dynamically induced by wave interaction. All of these components of motion cannot be reduced by a single plane suspension system primarily acting in the pitch axis. 
     Another attempt to improve occupant comfort in watercraft has been by using adjustable or dynamic pontoon arrangements on multi-hull watercraft. These arrangements are only applicable to multi-hull boats and require large, complicated hull assemblies which move relative to each other or to a main hull and attenuate the boat&#39;s dynamic response to wave action. Typically, the pontoons move primarily in the roll axis and can produce complex dynamic response to some wave conditions. 
     In view of the above and other limitations of the prior art, there exists a need for a watercraft ride enhancement system which attenuate more than just pitch motion. 
     Accordingly, an object of the present invention is to provide for dynamic control of the deck of a boat about the pitch, yaw and roll axes. 
     Another object of the present invention is to provide a dynamic control system or ride enhancement for the deck of a boat which is readily adaptable to a wide variety of hull designs, including single and multi-hull boat designs. 
     It is also an object of this invention to provide a dynamic control system which may have different spring and damping characteristics in the substantially pitch and substantially yaw axes. 
     An additional object of the present invention is to further enhance dynamic control of the boat&#39;s deck through use of the aerodynamic restorative force created by an airfoil. 
     SUMMARY OF THE INVENTION 
     In achieving the above objects and overcoming the drawbacks and limitations of the prior art, the present invention provides for the dynamic isolation of the deck, relative to the hull, to increase occupant comfort in a watercraft over a wide variety of water conditions, speeds, and directions relative to the waves. The deck is mounted to the hull structure in a manner which permits relative motion of the deck structure to the hull in at least two independent axes. Generally, at the bow end of the boat the deck is mounted to the hull structure through a multiaxes pivot mounting. At the stern end of the boat, the deck and hull structure are mounted together through a series of dampeners which are oriented to alternate pitch, yaw and roll motion. The suspension system provided for this purpose is extremely simple and rugged in structure and uses common, low cost components. 
     Still, further objects and advantages will become readily apparent to one skilled in this technology from a consideration of the ensuing description and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiment of the invention is described in conjunction with the following drawings: 
     FIG. 1 is schematic view from the stern of a mono-hull boat incorporating the principles of the present invention; 
     FIG. 2 is a bottom view of the boat seen in FIG. 1; 
     FIG. 3 is a side schematic view of the pivot joint located at the bow of the boat; 
     FIG. 4 is a schematic perspective view of the present invention as applied to a multi-hulled boat, more specifically a catamaran; 
     FIG. 5 is a rear view of the embodiment shown in FIG. 4; 
     FIG. 6 shows an airfoil added to the embodiment shown in FIG. 5; and 
     FIG. 7 is a side view of the embodiment shown in FIG.  6 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A watercraft or boat  10  according to the principles of the present invention has a hull  20  and a separate deck  22 . The deck  22  contains the normal furnishings of a boat cockpit including steering means, a throttle and at the controls, operator seating and passenger seating. The bow of the hull  20  and the deck  22  are pivotally connected together by a pivot joint  24 . As seen in FIGS. 1 and 2, the stern of the hull  20  and deck  22  are connected to one another by a left vertical shock assembly  28 , a right vertical shock assembly  26 , a right lateral shock assembly  30  and a left lateral shock absorber assembly  32 . Where mounted to the hull  20 , the shock absorber assemblies  26 ,  28 ,  30  and  32  are secured by mounting brackets  27 ,  29 ,  31  and  33 . The mounting brackets  27 ,  29 ,  31  and  33  are of a variety suitable for the particular shock absorber assemblies  26 ,  28 ,  30  and  32  being used. Similarly, where secured to the deck  22 , mounting brackets  35  and  37  of suitable style are used. As seen in FIGS. 1 and 2, in the first embodiment of the present invention the right side shock absorber assemblies  26  and  30  are mounted to the stern wall  21  at a common point, mounting bracket  35 . The left side shock absorbers assemblies  28  and  32  are likewise mounted to the stern wall  21  at a common point, mounting bracket  37 . 
     While use of common mounting points is believed to offer ride enhancement benefits, it will be appreciated that individual mounting brackets on the stern for each shock absorber assembly could be employed. Also, while the shock absorber assemblies are illustrated and referred to as either vertical or horizontal, these terms are not intended to be strictly interpreted as the orientation of their respective assemblies. The assemblies  26 ,  28 ,  30  and  32  can be provided in other orientations so long as vertical and horizontal components of movement will be attenuated by the overall system. Depending on the boat  10  design and the water conditions in which the boat  10  is intended to be operated, other orientations may prove to be more desirable. 
     The mounting brackets  35  and  37  themselves may also be positioned other than on the stern wall  21 . For example, the brackets  35  and  37  may be positioned on the corner where the stern wall  21  meets the side walls or gunwalls of the boat  10 . Through use of the pivot joint  24  and the various shock assemblies  26 ,  28 ,  30  and  32 , movement about a roll axis pivot  34 , a pitch axis pivot  36  and a yaw axis pivot  38  (as seen in FIG. 3) can be controlled. 
     In operation the deck  22  of the boat  10  is free to pivot about pivot joint  24  and move within the hull  20  as controlled by shock absorber assemblies  26 ,  28 ,  30  and  32 . Relative motion between the deck  22  and hull  20  is allowed in the pitch, yaw and roll axes to account for all possible wave induced motion. Based on the desired dynamic response characteristics of the boat  10 , the lateral shock absorber assemblies  30  and  32  may have different spring and damping characteristics than the vertical shock absorber assemblies  26  and  28 . 
     In FIGS. 4 and 5, another embodiment of the invention is shown. The deck (not shown) is supported by a deck frame  48  mounted to a catamaran watercraft with left hull  40 , right hull  42 , forward transverse member  44  and rear transverse member  46  forming a rigid multi-hulled structure. The deck frame  48  pivots about pivot joint  24 , which has the same configuration as shown in FIG.  3  and the rear portion of the deck frame  48  is movably connected to the rear transverse member  46  by right lower shock absorber assembly  50 , left lower shock absorber assembly  52 , right upper shock absorber assembly  54 , and left upper shock absorber assembly  56 . In this embodiment, each pair of left and right side shock absorbers,  56 ,  52 , and  54  and  50  are not located on approximately orthogonal axes as in the prior embodiment. Movement of the deck relative to the hull structure is still allowed in the pitch, yaw and roll axes. 
     In FIGS. 6 and 7, an airfoil  58  is rigidly mounted to the top of the deck frame  48  so as to be positioned above and generally aft of the occupant compartment or cockpit of the boat  10 . As seen in FIG. 7, the airfoil  58  is symmetrical about its chordal axis  59 . When the watercraft  10  is moving forward, the aerodynamic effect of the airfoil applies a restorative force to the deck frame  48  to pivot it to a neutral position about the pitch axis. For example, when the fore end of deck frame  48  and deck are caused to be pitched upward relative to the aft end of the boat  10 , the airfoil  58  is provided with an angle of attack relative to the airflow which applies an upward force to the airfoil  58  and to the deck frame  48 . Likewise, when the aft end of the deck frame  48  pivots upward, a downward force is generated on the airfoil  58 . Thus, the effect of the airfoil  10  is to provide additional restorative force to the deck frame  48  when the watercraft  10  travels at higher speeds or is pitched severely. 
     Accordingly, the reader will see that the watercraft of the present invention provides a deck suspension system, controlling acceleration and shock, which enhances the ride comfort of the users. Furthermore, the watercraft with deck suspension system has the additional advantages in that: 
     It is adaptable to many configurations of watercraft; 
     It uses readily available suspension components from other types of vehicles; 
     It is further adaptable to active control systems such as hydraulics or electric cylinders; 
     It is further adaptable to servo control. 
     Although the description above contains many specificities, these should not be construed as limiting the scope of the invention by merely providing illustrations of some of the presently preferred embodiments of this invention. For example, the suspension could use fewer or more shock absorber assembly units. The shock absorber assembly units could be user adjustable to tune the system to the wave conditions, etc. 
     Thus, the scope of the invention should be determined by the appended claims and their legal equivalence, rather than by the examples given.