Abstract:
An adjustable skid to be attached to the frame of a boat trailer just forward of the trailer wheels. Two skids would commonly be used, one for each side of the trailer. The function of the skids is to prevent the wheels of the trailer from rolling over the end of the launching ramp.

Description:
BACKGROUND 
     1. Field of Invention 
     This invention relates to the field of boat trailers. More specifically, the invention comprises a skid assembly which may be attached to the frame of a boat trailer just forward of the wheels. The purpose of the skid assembly is to prevent the boat trailer wheel from dropping abruptly off the end of a ramp, thereby causing the trailer to become stuck. 
     2. Description of Prior Art 
     Boat trailers are well known in the prior art. They commonly have two dominant principles guiding their design: (1) they must carry the boat securely as it is towed down the highway, and (2) they must facilitate the launching and recovery of the boat, typically using a concrete ramp. It is this second concern which often proves the most daunting challenge. 
     Boat launching ramps must be fairly steep, typically having a grade between 5% and 9%. This results from the fact that the trailer must be sufficiently submerged to float the boat free while the car or truck is still on dry ground. The steep grade causes difficulty when the boat is recovered and the car or truck attempts to pull it up the ramp. 
     FIG. 1 illustrates a typical prior art trailer. Trailer  10  has primary elements trailer frame  12 , hitch  14 , and wheels  16 . FIG. 2 illustrates trailer  10  positioned on ramp  18 . The vehicle towing trailer  10  is not illustrated, although persons skilled in the art will readily comprehend that the towing vehicle is attached to trailer  10  at hitch  14 . As shown, wheel  16  has slipped over ramp end  20 . Ramp end  20  is an abrupt edge commonly found on the end of concrete ramps, especially in coastal regions where the sand bottom is scoured away from the ramp by wave and tidal actions. Ideally, trailer  10  would not be backed far enough to place wheel  16  over the end of ramp  18 . However, when the water is low—such as near the time of low tide—the user must back trailer  10  to this point in order to get enough water over trailer  10  to recover the boat. FIG.2 illustrates a common situation where the sand or mud immediately off the end of ramp  18  has been scoured away by wave and propeller action. This phenomenon obviously worsens the problem described. 
     The reader will easily appreciate that once the boat is loaded on trailer  10  in this position, wheel  16  will be pulled forward against ramp end  20  as the towing vehicle attempts to pull trailer  10  up the ramp. Ramp end  20  acts as a wheel chock, making it very difficult to extract trailer  10 . In addition, trailer  10  may actually be resting on the concrete surface, introducing further resistance to forward motion. 
     Several prior art inventions have attempted to generally remedy this concern. U.S. Pat. No. 5,228,713 to Kovach (1993) discloses a pivoting trailer which allows the boat to remain partially supported by the water as the trailer advances up the ramp. The primary purpose of the Kovach device is to properly position the boat over the trailer frame, with the result that the trailer may be safely placed in deeper water. It does not, however, directly address the objective of the present invention. In addition, the Kovach device is quite complex, requiring a moving assembly capable of guiding and supporting an object as heavy as a boat. This added complexity necessarily entails greater expense in the manufacturing of the trailer. 
     A simpler approach is disclosed in U.S. Pat. No. 4,895,347 to Anderson (1990). The Anderson device uses starting ramps placed on the launching ramp itself. These starting ramps allow the towing vehicle a short starting run in which the rear axle is not moving uphill. The Anderson device also discloses a system of chains and springs which are used to anchor the mobile ramps in position. Of course, the ramps must be carefully placed as the trailer is being backed into the water. This requirement means that either two persons are needed, or the vehicle driver must repeatedly stop and exit the vehicle. In addition, the use of large springs in the device introduces a safety hazard because they will store energy as they are extended. 
     The known devices for aiding the recovery of a boat trailer are therefore limited in that they: 
     1. Require the use of a large moveable assembly on the boat trailer; 
     2. Are expensive to produce; 
     3. Require the vehicle driver to repeatedly stop and exit the vehicle; and 
     4. Introduce a safety hazard. 
     OBJECTS AND ADVANTAGES 
     Accordingly, several objects and advantages of the present invention are: 
     1. To eliminate the use of any moveable assemblies on the trailer; 
     2. To provide a relatively inexpensive device; 
     3. To provide a device which does not require the driver to stop and exit the vehicle; and 
     4. To provide a device which does not use springs or other energy storage devices which could introduce a safety hazard. 
    
    
     DRAWING FIGURES 
     FIG. 1 is an isometric view, showing a prior art boat trailer. 
     FIG. 2 is a side elevation view, showing a prior art trailer on a launching ramp. 
     FIG. 3 is an isometric view, showing the same configuration illustrated in FIG.  2 . 
     FIG. 4 is an isometric view, showing the proposed invention. 
     FIG. 5 is an exploded isometric view, showing more detail of the proposes invention. 
     FIG. 6 is an isometric view, showing the proposed invention attached to a prior art boat trailer. 
     FIG. 7 is an isometric view showing more detail of the configuration illustrated in FIG.  6 . 
     FIG. 8 is a side elevation view, showing the operation of the invention. 
     FIG. 9 is an isometric view, showing the same configuration illustrated in FIG.  8 . 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Reference Numerals in Drawings 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 10 
                 trailer 
               
               
                   
                 12 
                 trailer frame 
               
               
                   
                 14 
                 hitch 
               
               
                   
                 16 
                 wheel 
               
               
                   
                 18 
                 ramp 
               
               
                   
                 20 
                 ramp end 
               
               
                   
                 22 
                 skid assembly 
               
               
                   
                 24 
                 skid plate 
               
               
                   
                 26 
                 rear skid mount 
               
               
                   
                 28 
                 front skid mount 
               
               
                   
                 30 
                 front mounting hole 
               
               
                   
                 32 
                 rear adjustment hole 
               
               
                   
                 34 
                 rear link 
               
               
                   
                 36 
                 front link 
               
               
                   
                 38 
                 front mounting bracket 
               
               
                   
                 40 
                 rear mounting bracket 
               
               
                   
                 42 
                 top clamp 
               
               
                   
                 44 
                 clamp bolt 
               
               
                   
                 46 
                 cross bolt 
               
               
                   
                 48 
                 rear link hole 
               
               
                   
                 50 
                 front link hole 
               
               
                   
                 52 
                 front bracket hole 
               
               
                   
                 54 
                 rear bracket hole 
               
               
                   
                   
               
             
          
         
       
     
    
    
     DESCRIPTION OF THE INVENTION 
     FIG. 1 depicts a conventional, prior art boat trailer. While many different types of boat trailers are in use, the primary features of the trailer type illustrated will suffice to explain how the proposed invention may be applied to virtually any type. 
     FIG. 6 illustrates the proposed invention attached to the prior art trailer depicted in FIG. 1. A pair of skid assemblies  22  are attached to trailer frame  12 , just forward of each wheel  16 . FIG. 7 shows the position of skid assemblies  22  in greater detail. 
     FIG. 4 shows the components comprising skid assembly  22 . Skid plate  24  is a long and relatively narrow piece typically made of metal. Rear skid mount  26  is attached to skid plate  22  near its rear portion as shown, typically by welding. Rear skid mount  26  has several rear adjustments holes  32  passing completely through from side to side. 
     Front skid mount  28  is attached to skid plate  22  near its forward portion. Front skid mount  28  has a single front mounting hole  30  passing completely through from side to side. Rear mounting bracket  40  is positioned roughly above rear skid mount  26 , and is attached to rear skid mount  26  by rear link  34 . Likewise, front mounting bracket  38  is positioned roughly above front skid mount  28  and is attached to front skid mount  28  by front link  36 . Cross bolts  46  are employed to lock the various components together, as will be explained in the following. 
     The upper portions of front mounting bracket  38  and rear mounting bracket  40  are designed to bear against a lower surface of trailer frame  12 . Top clamps  42  are positioned above both front mounting bracket  38  and rear mounting bracket  40 . Top clamps  42  are drawn down against the upper surface of trailer frame  12  by four clamp bolts  44 , as shown. 
     FIG. 7 shows a detailed view of skid assembly  22  clamped to trailer frame  12 . The reader may easily observe in this view how the action of clamp bolts  44  and top clamps  42  secure the device to trailer frame  12 . 
     Turning to FIG. 5, the use of cross bolts  46  to lock the components together will be explained. Rear link  34  is free to slide up and down within a hollow cavity inside rear mounting bracket  40 . Rear link  34  has several transverse rear link holes  48 , which pass completely through it. The lower portion of rear mounting bracket  40  has a single rear bolt hole  54  passing completely through it. The user may extend or retract rear link  34  within rear mounting bracket  40  until the desired rear link hole  48  aligns with rear bolt hole  54 . The user then locks rear link  34  in position by placing a cross bolt  46  through the aligned assembly. Cross bolt  46  may be held in place using a nut, a cotter pin, or other conventional device. The lowest rear link hole  48  is then aligned with one of the rear adjustment holes  32  on rear skid mount  26 . Once alignment is achieved, the user locks rear link  34  to skid plate  24  by placing a second cross bolt  46  through the aligned assembly, again holding cross bolt  46  in place by conventional means. 
     A similar process is followed for front mounting bracket  38 . Front link  36  is extended and retracted to align front link holes  50  with the single front bracket hole  52 . Once alignment is achieve, the user places a third cross bolt  46  through the assembly. The user then locks front link  36  to skid plate  24  by placing a fourth cross bolt  46  through front mounting hole  30  and through the lowest front link hole  50 . 
     Those skilled in the art will appreciate that the previously described adjustment devices allow the user to place skid assembly  22  is virtually any required position. Skid assembly  22  may be moved forward and backward along trailer  10  by loosening clamp bolts  44 . The vertical drop of both the forward and rear portions of skid plate  24 , relative to trailer frame  12 , may be adjusted. Finally, the angle of skid plate  24  relative to trailer  10  may be adjusted by moving rear mounting bracket  40  closer to or further away from front mounting bracket  38 . 
     FIG. 6 shows a pair of skid assemblies  22  attached to a boat trailer. FIG. 7 shows a closer view of the same configuration. Front mounting bracket  38  and rear mounting bracket  40  are positioned against the underside of trailer frame  12 . Top clamps  42  are positioned against the upper side of trailer frame  12 . Four clamp bolts  44  are then passed through the holes provided in top clamps  42 , front mounting bracket  38 , and rear mounting bracket  40 —as shown. Nuts are placed on clamp bolts  44  and these are tightened to draw the assembly together, clamping it against trailer frame  12 . Those skilled int he art will realize that skid assembly  22  may be very tightly locked to trailer frame  12  using the components described. This fact is signficant, as considerable weight must be supported by skid assembly  22 . 
     FIG. 8 shows the device properly positioned and in its intended use. The reader will observe that skid assembly  22  is placed just forward of tire  16 . The user has backed trailer  10  to a position where tire  16  would normally have rolled abruptly off of ramp end  20 , thereby creating the problem described in the “BACKGROUND” section of this disclosure. However, the present invention has prevented this problem. The reader will observe that the weight of the trailer is now supported by skid assembly  22 , which rests on the edge of ramp  18 . The action of skid assembly  22  has in effect extended the useful length of the ramp. 
     FIG. 9 shows the same situation in an isometric view for greater clarity. The pair of properly positioned skid assemblies  22  have prevented wheels  16  from rolling over ramp end  20 . 
     When skid plates  24  come to rest on the surface of ramp  18 , friction is greatly increased. The user will notice that the backing has gone from a smooth rolling action, where wheels  16  were rolling along, to an abrupt grating action as skid plates  24  are forced along the commonly rough surface of ramp  18 . This change alerts the user that he or she should back no further. 
     Material selection is significant for the components of skid assembly  22 . The assembly must be able to support considerable weight. Corrosion is also a primary concern, since the assembly will be periodically immersed in water (often salt water). Likewise, galvanic corrosion between the trailer and skid assembly  22  is a concern. Steel and aluminum have been found to be suitable materials. Both these materials must be coated to resist corrosion. It is also important to match the materials to the trailer; i.e., aluminum skid material on an aluminum trailer. Otherwise, galvanic corrosion is a problem. 
     Summary, Ramifications, and Scope 
     Accordingly, the reader will appreciate that the proposed invention greatly reduces the possibility that the user will back the trailer wheels over the end of a boat ramp. The invention has further advantages in that it: 
     1. eliminates the use of any moveable assemblies on the trailer; 
     2. provides a relatively inexpensive solution; 
     3. does not require the driver to stop and exit the vehicle during operation; 
     4. does not use springs or other energy storage devices which could introduce a safety hazard. 
     Although the preceding description contains significant detail, it should not be construed as limiting the scope of the invention but rather as providing illustrations of the preferred embodiment of the invention. For example, many different approaches could be used to attach skid plate  24  to trailer frame  12 , many different types of adjustment could be provided, many different type of retaining devices could be used to secure cross bolts  46  in place, etc. Thus, the scope of the invention should be fixed by the following claims, rather than by the examples given.