Abstract:
A utility trailer convertible between an open bed configuration and a cargo box configuration includes an open-bed trailer and a removable cargo box. The bed of the trailer includes multiple full-length, parallel, longitudinal grooves. Adjacent each groove is a rail that is elevated slightly above the elevation of the bed. The rails function both as deck protectors and friction reducers for the cargo box that is designed for a slide-in, non-interference fit between the walls of the trailer. The cargo box-has a sheathing covered frame with a door at the rear end thereof. Multiple anchors that align with the grooves, are attached to the underside of the cargo box frame. When properly positioned on the trailer, the anchors are removably securable to the bed. Multiple jacks can be used to elevate the cargo box and slide the trailer from beneath the cargo box.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to trailers and, more particularly, to open-bed, walled utility trailers that can be converted to closed utility trailers by the addition of an enclosed cargo box. 
   2. Description of the Prior Art 
   Utility trailers having cargo boxes are used extensively by workers in the construction industry to haul valuable tools and supplies to job sites. Open bed, walled utility trailers, on the other hand, are used extensively to haul motorcycles, all-terrain vehicles, and other motorized equipment to recreational sites. For such an application, a utility trailer having a cargo box is a liability, as it can be damaged by overhanging tree branches and other obstacles often found en route to recreational sites. Consequently, many individuals must own both a cargo box utility trailer and an open bed utility trailer to satisfy their load carrying needs. There are two obvious problems with owning two trailers. The first is the added expense of owning two trailers. A double-axle, open bed utility trailer typically costs from $2,000 to $4,000. A double-axle, cargo box utility trailer, on the other hand, can cost $2,000 more than a comparable open bed trailer. The second is the problem of finding space to park two utility trailers, a towing vehicle and other family transportation vehicles at one&#39;s residence. Many municipalities have regulations which prohibit the parking of vehicles, including trailers, on public streets for extended periods of time. In addition, having one&#39;s driveway cluttered with vehicles and trailers is generally not endearing to neighbors. 
   What is needed is a convertible utility trailer that can be used as both an open-bed trailer and a cargo box trailer. Ideally, the conversion process should be simple, quickly executable, and capable of being performed by a single individual. If these criteria are not met, there is little likelihood that such a trailer could be a commercial success. 
   SUMMARY OF THE INVENTION 
   The present invention solves the heretofore expressed need for a convertible utility trailer that can be used as both an open-bed trailer and a cargo box trailer. The convertible trailer includes a specially-designed, open-bed, walled utility trailer having multiple full-length, parallel, longitudinal grooves in the bed thereof. Adjacent each groove is a rail that is elevated slightly above the elevation of the bed. The rails function as friction reducers for a cargo box that is installable on the bed and within the walls of the utility trailer. Wood or steel decking can be used to fill spaces between the rails on the bed. A cargo box is designed for a slide-in, non-interference fit between the walls of the open bed trailer. Construction of the cargo box is conventional, except for several significant features which will be later explained. For a preferred embodiment of the invention, the cargo box includes a frame constructed of structural metal, such as but not limited to steel and aluminum. The frame is covered with metal, wood or composite sheathing to provide a generally weatherproof enclosure. For a preferred embodiment of the invention, at least one lockable door is incorporated in the rear end of the cargo box. The first significant deviation from conventionality is the inclusion of a plurality of vertically oriented anchors which are welded, bolted, or otherwise attached to the underside of the cargo box frame. These anchors are positioned to align with the longitudinal grooves of the open bed utility trailer. The cargo box is designed to slide onto the bed of the trailer. When properly positioned on the trailer, the anchors are removably secured to the bed of the trailer using bolts or removable locking pins. The second deviation from conventionality is the inclusion of at least four jack attachment points on the cargo box. One jack attachment point on each side of the front of the cargo box permits a jack to be installed on the cargo box such that its jacking stand is spaced wider than the track of the trailer, plus the width of any fenders thereon. An additional jack attachment point is located at the rear of the cargo box on either the side or rear end thereof. When the anchors on the cargo box are not secured to the bed of the trailer and at least four jacks are installed at the attachment points, the cargo box can be elevated over the trailer, and the trailer can be pulled from beneath the cargo box. Replacement of the cargo box on the trailer is the reverse of the removal process. of the cargo box. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side elevational assembled view of a double-axle, first embodiment convertible trailer, showing the cargo box installed on the walled utility trailer; 
       FIG. 2  is a rear elevational assembled view of the first embodiment convertible trailer, showing the cargo box installed on the walled utility trailer; 
       FIG. 3  is a side elevational exploded view of the first embodiment convertible trailer, showing the cargo box elevated above the open-bed, walled utility trailer; 
       FIG. 4  is a rear elevational exploded view of the first embodiment convertible trailer, showing the cargo box elevated above the open-bed, walled utility trailer; 
       FIG. 5  is a top plan view of the walled utility trailer frame of the first embodiment convertible trailer; 
       FIG. 6  is a top plan view of the walled utility trailer frame of the first embodiment convertible trailer, after installation of planking thereon; 
       FIG. 7  is a rear elevational view of the cargo box and the fore and aft lifting and support apparatus of the first embodiment convertible trailer; 
       FIG. 8  is a front elevational view of the cargo box and the fore and aft lifting and support apparatus of the first embodiment convertible trailer; 
       FIG. 9  is a top plan view of the cargo box and the fore an aft lifting and support apparatus of the first embodiment convertible trailer; 
       FIG. 10  is a side elevational assembled view of a single-axle, second embodiment convertible trailer, showing the cargo box installed on the walled utility trailer; 
       FIG. 11  is a rear elevational assembled view of the second embodiment convertible trailer, showing the cargo box installed on the walled utility trailer; 
       FIG. 12  is a top plan assembled view of the second embodiment convertible trailer; 
       FIG. 13  is a side elevational view of the second embodiment convertible trailer after the cargo box has been released from the walled utility trailer, and following the elevation of the walled utility trailer and cargo box with the jack; 
       FIG. 14  is a side elevational view of the second embodiment convertible trailer after the cargo box has been allowed to roll down the walled utility trailer by letting out the loading cable with the attached winch; and 
       FIG. 15  is a side elevational view of the second embodiment convertible trailer after the cargo box has been allowed to roll completely free of the walled utility trailer by letting out additional cable with the winch. 
   

   DETAILED DESCRIPTION OF THE INVENTION  
   The invention will now be described with reference to the attached drawing figures.  FIGS. 1 through 9  depict a double-axle first embodiment of the convertible trailer, which employs a jack attached to each of the four corners of the cargo box to elevate the cargo box after detaching it from the walled utility trailer so that the trailer can be pulled from beneath the cargo box.  FIGS. 10 through 15  depict a single-axle second embodiment of the convertible trailer, which employs a single jack to elevate the front portion of the unit so that the cargo box can be rolled down the walled utility trailer with a winch and cable after the former is detached from the latter. 
   Referring now to  FIG. 1 , this assembled view of the double-axle, first embodiment convertible trailer  100 , combines a double-axle utility trailer  101  and a cargo box  102 . The cargo box  102  has a skeleton frame (shown in  FIG. 3 ) to which is riveted metal sheeting  103 . Although the utility trailer  101  is shown as having a perimetric fence  104 , this is not an essential element of the convertible trailer  100 , as the invention can be practiced using a flat-bed utility trailer as well. The cargo box  102  is secured to the utility trailer  101  with fasteners  105 , such as, but not limited to, locking pins and screw-type fasteners (e.g., bolts and nuts). The utility trailer  101  has a tongue  106  and a coupler  107  attached to the tongue  106 . The cargo box  102  is equipped with a jack secured to each of the four corners thereof. In this drawing figure, the left-side front jack  108 L and the left-side rear jack  109 L are visible. The right-side jacks  108 R and  109 R are visible in subsequent drawing figures. The circular aperture near the top of each of the jack is a receptacle  110  for a removeable jack hand crank (not shown). It will be noted that each front jack  108 L and  108 R has a removable strut  111 , which can be inserted into the extendable center post  112  of each front jack. Although for this particular embodiment of the invention, the rear jacks  109 L and  109 R are secured to the rear vertical surface  113  of the cargo box, for an alternative embodiment of the invention, the rear jacks  109 L and  109 R may be incorporated into the rear corner posts  114 L and  114 R (the latter corner post is not visible in this drawing figure). If the rear jacks  109 L and  109 R are incorporated into the rear corner posts  114 L and  114 R, it is necessary either to extend the cargo box  102  over the rear edge of the platform  115  of utility trailer  101  or notch the rear edge of the platform  115  beneath each jack  109 L and  109 R. The ground is represented by item number  116 . The rivets, which secure the metal sheeting  103  to the skeleton frame are represented by item number  117 . 
   Referring now to  FIG. 2 , this rear view of the first embodiment convertible trailer  100  shows the cargo box  102  mounted atop the double-axle utility trailer  101 . Both rear jacks  109 L and  109 R are visible in this view, as is the hand crank receptacle  110  for each rear jack. 
   Referring now to the side view of  FIG. 3 , the cargo box  102  is shown elevated above the double-axle utility trailer  101  following removal of the fasteners  105 . It will be noted that in this view, the cargo box  102  is shown as a skeleton frame  301  with the outer sheeting  103  removed to show the edge of the flooring  302 . which covers a bottom portion of the skeleton frame  301 . It will also be noted that the cargo box  102  is equipped with fastener apertures  303 F and  303 R, and the frame rails  304  of the utility trailer  101  are also equipped with fastener apertures  305 F and  305 R. It should be understood that it is unnecessary, and certainly not adviseable, to raise the cargo box  102  to such a height in order to pull the utility trailer  101  from beneath the cargo box  102 ; it is necessary to elevate the cargo box  102  only enough so that is is not is contact with the upper surface of the platform  115  of the utility trailer  101 . An elevation of 1 to 2 centimeters is generally sufficient if the trailer is parked on level ground. 
   Referring now to the rear view of  FIG. 4 , the cargo box  102  is shown elevated above the double-axle utility trailer  101  following removal of the fasteners  105 . It will be noted that the cargo box  102  is equipped with three downwardly-projecting longitudinal ribs: a left rib  401 L, a center rib  401 C and a right rib  401 R. Each of the downwardly-projecting ribs  401 L,  401 C and  401 R fit into a corresponding longitudinal groove  402 L,  402 C and  402 R, respectively, in the platform  115  of the utility trailer  101 . The ribs  401 L,  401 C and  401 R cooperate with the longitudinal grooves  402 L,  402 C and  402 R to align and center the cargo box  102  as it slides on or off the utility trailer  101 . For a preferred embodiment of the invention, the apertures  303 F and  303 R are located in the left and right ribs fasteners  401 L and  401 R, respectively. 
   Referring now to  FIG. 5 , the utility trailer  101  is shown from above with the planking removed to show the utility trailer framework  501 . It will be noted that each of the longitudinal grooves  402 L,  402 C and  402 R extend the entire length of the platform  109 . The rearmost end of each groove  402 L,  402 C and  402 R has a widened entrance  502 L,  502 C and  502 R, respectively, which facilitates alignment of the ribs  401 L,  401 C and  401 R when installing the cargo box  102  on the utility trailer  101 . 
   Referring now to  FIG. 6 , the utility trailer framework  501  has been covered with planking  601  in order to complete the platform  109 . 
   Referring now to  FIG. 7 , the cargo box  201  is shown from the rear, supported on its four corner jacks  108 L,  108 R,  109 L and  109 R. As will subsequently be appreciated, the left-side front jack  108 L is mounted to a pair of horizontal beams  701 U and  701 L, while the right-side front jack  108 R is mounted to a pair of horizontal beams  702 U and  702 L. Each pair of horizontal beams  701 U/ 701 L and  702 U/ 702 L can be extended from and retracted into the skeleton frame  103  of the cargo box  102 . 
   Referring now to  FIG. 8 , the cargo box  201  is shown from the front, supported on its four corner jacks  108 L,  108 R,  109 L and  109 R. In this view, it can be seen that upper horizontal beams  701 U and  702 U both slide into an upper, transverse, horizontal jack support tube  801 , while lower horizontal beams  701 L and  702 L slide into a lower, transverse, horizontal jack support tube  802 . The front left jack  108 L, when fully retracted and with the strut  111  removed, fits into a left recess  803 L in the left front corner post  804 L of the cargo box  102 . Likewise, the front right jack  105 R, when fully retracted and with the strut  109  removed, fits into a right recess  803 R in the right front corner post  804 R of the cargo box  102 . 
   Referring now to  FIG. 9 , the cargo box skeleton frame  103  is shown from the top with the front corner jacks  108 L and  108 R deployed. For this particular embodiment, the rear corner jacks  109 L and  109 R have been incorporated into the rear corner posts  114 L and  114 R of the skeleton frame  103 . 
   Referring now to  FIG. 10 , this assembled view of the single-axle, second embodiment convertible trailer  1000 , combines a single-axle utility trailer  1001  and a cargo box  1002 . Although this particular embodiment of the utility trailer  1001  incorporates a fence  1103  around the permiter of the bed  1012 , a flat-bed trailer having no fence or wall may also be used. The second embodiment convertible trailer  1001  incorporates a winch  1004 , which is coupled to the cargo box  1002  with a cable  1005 . A foldable jack  1006  is pivotably mounted to to tongue  1007  of the utility trailer  1001 . The cargo box  1002  incorporates a recessed, rubber-tired wheel  1008  rotatably mounted at each corner thereof. The wheels  1008  on the left side of the cargo box  1002  ride in a left recessed track  1009 L, while the wheels  1008  (not shown in this view) on the right side of the cargo box  1002  ride in a right recessed track  1009 R. Both recessed tracks  1009 L and  1009 R, which are parallel and run the length of the bed, may also be characterized as longitudinal guides or grooves. It will be noted that the left recessed track  1009 L has a front depression  1010 F and a rear depression  1010 R. The right recessed track  1009 R has similar depressions  1010 F and  1010 R. The depressions  1010 F and  1010 R permit the lower surface of the cargo box  1002  to rest on the bed  1012  of the utility trailer  1001  when the cargo box  1002  it in the installed position on the utility trailer  1001 . It will also be noted that each recessed track  1009 L and  1009 R has a front extension, of which only the left extension  1011 L is visible in this view. 
   Referring now to  FIG. 11 , this rear view of the second embodiment convertible trailer  1000  shows the recessed rear wheels  1008  that are rotatably attached to the cargo box  1002 . The rear left wheel  1008  rides in a left recessed track  1009 L, while the rear right wheel  1008  rides in a right recessed track  1009 R. As with the first embodiment convertible trailer  100 , the cargo box  1002  is secured to the utility trailer  1001  with fasteners  1101 , such as locking pins or threaded fasteners. 
   Referring now to  FIG. 12 , the winch  1004 , the cable  1005  and foldable jack  1006  are visible. It will be noted that the recessed right front rubber-tired wheel  1008  and the recessed left front rubber-tired wheel  1008  extend forward of the cargo box  1002  on track extensions  1011 R and  1011 L, respectively. 
   Referring now to  FIG. 13 , the foldable jack  1006  has been extended and braced to the tongue  1007  with a pair of diagonal braces  1301 L and  1301 R (the latter brace is not visible in this view). After unsecuring the cargo box  1002  from the utility trailer  1001  by removal of the fasteners  1102 , the foldable jack  1006  is used to elevate the front and lower the rear of the utility trailer  1001 . It will be further noted that chocks  1302 A and  1302 B have been placed in front of and behind the left wheel  1304  of the utility trailer  1001 . Additional chocks (not shown) are also placed around the right wheel (also not shown in this view). 
   Referring now to  FIG. 14 , as the cable  1005  is released using the winch  1004 , the cargo box  1002  begins to roll down the recessed tracks  1009 L and  1009 R. In order to reduce friction, the front wheels  1008  rise out of the front depressions  1010 F. The recessed rubber-tired rear wheels  1008  roll off the trailer  1001  and begin to roll on the ground  116 . 
   By further releasing the cable  1005  with the winch  1004 , the cargo box  1002  rolls completely off the trailer  1001 . Replacement of the cargo box  1002  on the trailer  1001  is the exact opposite of the removal process. Once the cable  1005  is disconnected from the cargo box  1002 , the single-axle utility trailer  1001  may be used independently of the cargo box. While it is unattached to the trailer  1001 , the cargo box  1002  may serve as a stationary storage shed. 
   Although only several embodiments of the invention has been shown and described, it will be obvious to those having ordinary skill in the art that changes and modifications may be made thereto without departing from the scope and the spirit of the invention as hereinafter claimed.