Abstract:
A truck bed extension which is concealed beneath a truck when not being used is disclosed. The truck bed extension comprises a frame and two wheel assemblies for permitting the extension to be pulled behind a truck. During non-use, an elongated member of the truck bed extension is received by a guide channel to facilitate positioning the truck bed extension beneath the truck. When the truck bed extension is not being used the wheel assemblies rotate up under the truck wheel wells and attach thereto. A locking mechanism secures the truck bed extension in place during use. Optional removable side walls attach to the truck bed extension and may alternatively be used as ramps for loading wheeled-vehicles. A hoist slidably engaging side walls of the truck bed permits heavy and cumbersome materials to be loaded and unloaded.

Description:
FIELD OF THE INVENTION 
   The embodiments of the present invention relate to a truck bed extension. More particularly, the embodiments relate to a truck bed extension concealed beneath a vehicle during non-use and extendable behind the vehicle during use. 
   BACKGROUND 
   The use of pick-up trucks for moving materials is not a new one. In fact, the first pick-up trucks were built nearly 90 years ago. Although truck beds have been lengthened over the years to accommodate more materials, they still do not accommodate very long materials such as lumber, rebar and similar materials. 
   Consequently, there have been numerous attempts to develop truck bed extensions. U.S. Pat. Nos. 1,366,771, 2,328,138, 3,877,714, 4,475,760, 4,951,991 and 6,050,627 disclose such truck bed extensions. However, each of the disclosed truck bed extensions suffers from one or more drawbacks which are discussed in more detail below. In general, the previous truck bed extensions are complex in design, burdensome to manufacture and/or lack required versatility. 
   Therefore, there continues to be the need for a truck bed extension which overcomes the aforementioned drawbacks. 
   SUMMARY 
   Accordingly, a first embodiment of the present invention comprises a truck bed extension which remains concealed during non-use and which is extendable when needed. In one embodiment, the truck bed extension comprises a frame supported, during use, by two wheels at a rear portion thereof. During non-use, a central frame member inserts into a tubular channel attached to an underside of the vehicle so that the frame is positioned underneath the vehicle. The wheels then rotate and are concealed proximated the vehicie&#39;s wheel wells. Thus, during non-use the entire frame and wheels are concealed beneath the vehicle. 
   Optionally, hydraulic, spring or air shocks may be used to stabilize the wheels of the truck bed extension to provide a smooth ride for the truck bed extension and its load. 
   A rear portion of the frame is suitable for attachment of the vehicle&#39;s original rear bumper to further conceal the truck bed extension during non-use. In addition, the rear bumper permits the original look and feel of the truck to remain unchanged. 
   Other features, variations and embodiments will become evident from the detailed description, drawings and claims set forth below. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a perspective top view of a first truck bed extension; 
       FIG. 2  shows a perspective rear view of the first truck bed extension; 
       FIG. 3  shows a perspective side view of the first truck bed extension including one wheel assembly, support plate, spare tire and rear bumper; 
       FIG. 4  shows a side view of the first truck bed extension including one wheel assembly, support plate and spare tire; 
       FIG. 5  shows a top view of the first truck bed extension including one wheel assembly; 
       FIG. 6  shows a rear portion of a vehicle wherein the truck bed extension slides beneath the truck; 
       FIG. 7  shows a channel for receiving a central frame member during non-use of the truck bed extension; 
       FIG. 8  shows a hooking mechanism for connecting the wheel assemblies to the truck during non-use; 
       FIG. 9  shows a clip portion of the hooking mechanism; 
       FIG. 10  shows the support plate and rear bumper in place on the truck bed extension; 
       FIG. 11  shows the support plate in reference to the vehicle during use; 
       FIG. 12  shows the support plate connection; 
       FIG. 12(   a ) shows a top view of the support plate attached to the vehicle; 
       FIG. 13  shows a truck bed having multiple supports for large loads; 
       FIG. 14  shows a locking member for maintaining the truck bed extension in an extended position; 
       FIG. 15  shows a hoist attached to side walls of a vehicle bed; and 
       FIG. 16  shows an underneath view of the truck bed extension including a male connector. 
   

   DETAILED DESCRIPTION 
   The detailed description below sets forth one or more embodiments of a truck bed extension which is able to be extended from beneath a truck during use and which resides concealed beneath the truck during use. As the device is mechanical in nature it comprises multiple components and connection means. Although certain components and connection means are specifically disclosed, it should be understood that other undisclosed components and/or connection means may be used without departing from the spirit and scope of the embodiments of the present invention. 
   Reference is now made to the figures wherein like parts are referred to by like numerals throughout.  FIGS. 1 and 2  show a top and rear view of one embodiment of the truck bed extension generally referred to by reference numeral  100 . In general, the truck bed extension comprises an A-shaped frame  110  having elongated extension member  120 , two wheel assemblies  125  and horizontal support beam  130 . While an A-shaped frame  110  is shown, the frame may take any number of shapes providing the frame fits conveniently beneath the vehicle. 
   Now referring to  FIGS. 3–5 , the wheel assemblies  125  each comprise a tire  140 , bushing  145 , rod  150 , pair of forks  155 , fork support unit  160  including connection plate  165 , shock collar  170 , cover disk  175  and connection post  180 . More specifically, first ends of each pair of forks  155  attach on opposite sides of a corresponding tire  140  to the rod  150  which extends through a center point of the tire  140 . Each pair of forks  155  is held in place by a pair of cotter pins  156  and a corresponding pair of collars  157 . Second ends of the pair of forks  155  are each rotatably attached to the fork support unit  160 . As disclosed in more detail below, the forks  155  are rotatable in a vertical plane such that the pair of forks  155  and corresponding tire  140  may be positioned beneath the bed of the truck during non-use. 
   The fork support units  160  are joined to the connection post  180  in a swivel arrangement. Consequently, during use, the forks  155  and tires  140  are able to swivel in a horizontal plane for maintaining the tires  140  in an optimum position during transport. In other words, the fork support unit  160  is able to shift in a horizontal plane to accommodate for fluctuations in the position of tire  140  during transport. The ability to swivel can be controlled by tightening means in the form of a bolt or screw  185  which tightens or loosens a connection between the connection plates  165  and the fork support units  160 . The connection plates  165  and the fork support units  160  are connected via a set of nuts and bolts  167 . By tightening or loosening the connection using the screw  185 , the friction between the connection plates  165  and fork support units  160  is increased or decreased, respectively. This overall arrangement of vertical displacement and horizontal swivel or rotation allows for a smooth transport of materials regardless of the terrain. 
   To further increase the stability of the tires  140  during transport, a spring (not shown) housed by shock collar  170  absorbs vertical displacement of the fork support units  160 . Each fork support unit  160  vertically displaces along a corresponding connection post  180 . Accordingly, a first end of each connection post  180  extends through a central opening of a corresponding shock collar  170 , cover disk  175  and connection plate  165 . It is conceivable that conventional hydraulic or air shock absorbers may replace or enhance the spring-biased system. 
   Referring again to  FIGS. 1 and 2 , a method of using the truck bed extension  100  of the present invention can be visualized. The truck bed extension  100  is ideal for transporting long load or materials such as lumber, piping, carpet and re-bar. In each instance, the materials are laid down with one end in the truck bed  190  and a second end on the truck bed extension  100 . Ideally, the materials extend over the horizontal support beam  130  at the rear of the truck bed extension  100 . Depending on their length, the first end of the materials may be positioned near a rear portion of the truck bed  190  to allow the materials to extend over the horizontal support beam  130 . 
   As shown in  FIGS. 2 and 13 , to enhance stability of the materials during transport, brackets  195  are fixed to the truck bed  190 . Each end of the brackets  195  includes a rotatable ring  200  attached thereto for securing a cable, chain  210  or similar item. The chains  210  are tightened over the materials using a conventional tightening tool used for such a purpose. In this manner, the chains  210  secure the materials to the truck bed  190 . Straps  205  are then used to secure the materials to the truck bed extension  100 . The straps  205  are hooked at one end to the brackets  195  and a second end to the truck bed extension  100 . Clasping elements  210  at ends of the straps  205  grip the brackets  195  and a handle  215  connected to the horizontal support beam  130 . In this manner, the chains  210  secure the materials to the truck bed extension  100 . 
   As shown in  FIGS. 3–5  and  10 – 12 , optionally, a flat surface or bed is connected to said frame  110  of the truck bed extension  100 . In one embodiment, the bed comprises a heavy plate  225  able to support large loads. Ideally, the plate  225  is removably attached at a first end  235  to a flange  226  of a rigid rod  227  attached to a rear of the truck bed  190 . The rigid rod  227  extends between truck bed walls  195  near an opening at a rear of the truck bed  190 . The size of the rod  227  should be such that a truck bed gate (not shown) may operate in a conventional fashion. A second end  230  of the plate  225  may be removably attached to a rear portion of the frame  110 , namely the support beam  130 , or may simply rest thereon. During non-use, the plate  225  may be stored horizontally in the truck bed  190 . In this manner, the plate  225  is readily available and also functions like a bed liner. 
   Another optional feature of the truck bed extension  100  is a pair of temporary side walls (not shown). The side walls attach to outer edges of the plate  225  to create a semi-confined area for materials. Optionally, the side walls may function as ramps to facilitate the loading and unloading of wheeled-vehicles or similar items. When not being used, the temporary side walls, like the plate  225 , are stored in the truck bed  190 . To facilitate the storage of the side walls, truck wheel wells  305  are modified to incorporate slots (not shown) which receive the side walls. In this arrangement, each slot accepts a side wall during storage such that the side walls are positioned adjacent to the side walls  195  of the truck bed  190 . 
   During non-use, the truck bed extension  100  described herein resides beneath a subject truck and truck bed extension. When required, the truck bed extension  100  is extended from beneath the truck. 
   A guide channel  240 , shown in  FIGS. 7 and 14 , connected to an underside of the truck retains and accepts elongated extension member  120 . During use, the channel  240  retains and holds the extension member  120  in place. When the truck bed extension  100  is required, the guide channel  240  allows the extension member  120  to slide therealong until it reaches a locking position proximate a rear portion of the truck bed  190 . As shown in  FIGS. 6 and 14 , locking the truck bed extension  100  is facilitated by a sliding member  315 , peg  320  and cotter pin  325 . Once the elongated extension member  120  is pulled from the channel  240 , the member  120  is lifted slightly such that the sliding member  315  may be positioned beneath the member  120  to support the member  120 . The peg  320  is then placed vertically through an opening in the member  120  and corresponding opening in the sliding member  315  such that the cotter pin  325  may be inserted through a second opening in the peg  320  beneath the sliding member  315 . This prevents the extension member  120  from sliding back along or into the guide channel  240  during use. If the extension member  120  were to begin to slide back along the guide channel  240  during use, the truck bed extension  100  would follow thereby potentially causing a load to shift or be lost. 
   The guide channel  240  is attached to the underside of the truck using any conventional means available including U-shaped brackets, nuts and bolts, welds and rivets. Depending on the make of the truck, the guide channel  240  can pass between an underside of the truck bed  190  and the rear differential housing  245  of the truck. Alternative placement of the guide channel  240  may be used should the proper spacing between the underside of the truck bed  190  and differential housing  245  not be available. 
   Accordingly, during non-use of the truck bed extension  100 , the extension member  120  resides within the guide channel  240  and the truck bed extension frame  110  is positioned underneath the truck and truck bed  190 . While the guide channel  240  serves to support a percentage of the weight of the truck bed extension  100 , additional support means are preferable. Accordingly, a pair of elongated connector units  250  (shown in  FIG. 16 ) proximate a rear of the truck bed extension  100  corresponds to a pair of openings  255  (shown in  FIGS. 6 and 7 ) on the truck. Once the male connector units  250  pass through the openings  255 , they rotate 90 degrees to maintain the connection. In this manner, the entire truck chassis and/or truck frame support the truck bed extension  100  during non-use. 
   Once the truck bed extension  100  has been positioned and secured beneath the truck and truck bed  190 , the wheel assemblies  120  are positioned beneath the truck and truck bed  190 . The wheel assemblies  120  are rotated in a forward direction (i.e., toward the front of the truck) about the fork support unit  160 . Ideally, the wheel assemblies  120  are positioned proximate the opposite wheel wells of the truck. Now referring to  FIGS. 8 and 9 , a pair of hook systems  260  maintains the wheel assemblies  120  in their position beneath the truck. Each hook system  260  comprises a first eye screw  265  bolted at a first end to the truck and connected at a second end to a releasable hooking device  270 . The releasable hooking device  270  captures a corresponding loop or ring  275  on the wheel assembly  120  thereby permitting the hooking device  270  and truck frame to support the weight of the wheel assemblies  120 . 
   To maintain the original appearance of the truck, the truck&#39;s original rear bumper  280  is attached to a rear face of the truck bed extension  100 . Consequently, when the truck bed extension  100  is positioned beneath the truck, the truck bumper  280  is located in its conventional position. 
   As shown in  FIG. 15 , an optional hoist  400  incorporated on the truck bed  190  facilitates loading and unloading of the truck bed  190  and truck bed extension  100 . The hoist  400  generally comprises a frame  410  with opposite ends  420  slidably engaged, and extending longitudinally along, the truck bed side walls  195 . More particularly, tracks  430  engage the hoist  400  such that the joist  400  is free to move. Accordingly, the hoist  400  may slide from the truck cab to a rear of the truck bed  100  as identified by arrow A. One or more locking mechanisms permit the hoist  400  to be locked in place along the length of the truck bed  190 . Ideally, the hoist frame  400  extends above the height of the truck cab for sufficient clearance. An extendible arm  440  is slidably connected to the hoist  400  and is free to move in a lateral direction as identified by arrow B. The arm  440  may also rotate as identified by arrow C. A second end of the arm  440  supports a manual or automatic winch  450  for lifting materials to be loaded onto the truck bed  190  and/or truck bed extension  100 . 
   Although the invention has been described in detail with reference to several embodiments, additional variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.