Abstract:
A tilt bed for a truck or a trailer, the tilt bed being able of carrying loads and providing its own ramp. The tilt bed comprises a frame, and a deck mounted on and supported by the frame, the deck having a front portion and a rear portion. The deck has rollers connected to the front portion, and the frame has tracks mounted at an angle, the tracks for guiding the deck rollers. The trailer bed further comprises a hydraulic cylinder that has a first end connected to the frame and a second end connected to the trailer bed. The hydraulic cylinder has a piston and a cylinder. As the piston moves from an extended state into a retracted state, it causes the trailer bed to move in a rearward position. At the same time, the tracks force the deck rollers in an upward motion and cause the trailer bed to tilt. Finally, the hydraulic cylinder remains parallel to the trailer deck at all times. This orientation is accomplished because the trailer deck and the hydraulic cylinder tilt around a common axis.

Description:
This is a Continuation of application Ser. No. 08/108,041, filed Aug. 16, 1993. 
    
    
     TECHNICAL FIELD 
     The present invention relates to trailers for carrying vehicles and movable equipment with a low ground clearance, and more particularly to a trailer in which the trailer bed will simultaneously rollback and tilt into a loading position so that a cargo vehicle or movable equipment with low ground clearance may be driven, pushed, or pulled onto the trailer bed. 
     BACKGROUND 
     Apparatuses for towing or transporting vehicles have been around for a long time. One of the more recent devices for transporting automobiles is tilt-bed trucks in which the bed of the truck tilts so that the back edge of the trailer bed is adjacent to the ground. A winch is then used to pull the automobile up onto the trailer bed. After the automobile is loaded on the trailer bed, it is tilted back to a horizontal position for transporting the vehicle to another location. The problem with this current type of tilt-bed trailer is that the load angle is typically about 45°. Because of this high load angle, only vehicles with a large road clearance may be loaded for transportation. Therefore, the current form of tilt bed trucks and trailers does not allow the loading and unloading of cargo vehicles and movable equipment that has a low ground clearance Examples of movable equipment with low ground clearance includes paving equipment, which has a maximum load angle of about 7°. 
     Current apparatuses and methods for loading cargo vehicles and movable equipment with a low clearance include the use of ramps. Oftentimes a low flat trailer will include removable or hydraulic ramps for loading or unloading cargo vehicles or movable equipment. The ramps are either (1) carried with the trailer and are attached to the rear portion of the trailer bed for loading and unloading, or (2) are hydraulically attached to the rear portion of the trailer and are raised or lowered for loading and unloading. The cargo vehicle may then be driven, pushed or pulled onto or off of the trailer bed. 
     The problem with the use of ramps is that the junction between the ramp and the trailer bed forms an angled corner, and the tires of the cargo vehicle rest on a geometric plane. After the front tires move onto the trailer bed, the angled corner will protrude beyond the geometric plane to a point that approached the bottom of the cargo vehicle. If the ramp is too steep, the angled corner will protrude beyond the geometric plane and strike the bottom of the cargo vehicle. Therefore, cargo vehicles that have a very low ground clearance require extra long ramps in order to minimize the angled corner. 
     Different problems are caused if the cargo vehicle has continuous tracks such as the tracks of a bulldozer. The cargo vehicle will continue to move at the same angle of the ramp even as it moves beyond the ramp. The cargo vehicle will then drop down onto the trailer bed after more than 50% of its weight moves beyond the angled corner. The impact caused by the drop may cause damage to the trailer or the cargo vehicle. Again, extra long ramps must be used in order to minimize this problem. 
     The use of extra long hydraulic ramps is impractical. If the ramp forms a portion of the trailer bed, it cannot extend forward of the trailer wheels and suspension. As a result, extra long ramps would have to extend behind the tires a great distance resulting in design problems that would make the trailer unsafe and difficult to pull. If the hydraulic ramp was hinged to the rear end of the trailer, the ramp would extend into the air a great distance when it is moved up into a vertical position for transport. This projection into the air would cause alternative problems including a potential increase in the clearance height of the truck/trailer and a loss of gas mileage because of poor aerodynamics. 
     An additional problem with detachable ramps is that they may be forgotten or lost during transport. If this happens, the cargo vehicle or movable equipment may not be loaded onto or unloaded from the trailer bed. 
     An alternative method to solving the problem of loading cargo vehicles and movable equipment is the use of trailers that have a bed that is permanently oriented at an angle. In this situation the ramps are used to extend the length of trailer bed so that it reaches the ground. Cargo vehicles may then be loaded or unloaded. The problem with this design is the cargo vehicle secure a constant force on the straps and chains that exert it to the trailer bed and there is a much greater chance that the cargo vehicle will break loose during transport and roll off the back of the trailer. Additionally, the detachable extension ramps may be forgotten or lost. 
     Yet another solution to the problem is detachable goose neck trailers. These are semi-truck trailers in which the front end of the trailer is attached to a goose neck. The opposite side of the goose neck is attached to the king pin. In operation, a hydraulic system will lower the front end of the trailer bed until it reaches the ground, and the goose neck is then detached. A cargo vehicle or movable equipment may then be loaded onto the trailer bed. The goose neck is then reattached and the front end of the trailer bed is raised for transport. The difficulty with this system is that it is cumbersome to use and is only practical for a semi-truck trailer. Thus, the trailer is more expensive and requires the purchase of an expensive semi-truck. 
     Therefore, there remains need for a trailer that may be towed by different types of trucks and is able to provide a minimal loading angle in order to permit the loading and unloading of load vehicles and movable equipment having a very low clearance. 
     SUMMARY 
     Furthermore, the present invention eliminates the need for any type of a loading ramp, permanently angled trailer bed, or detachable goose neck. 
     The present invention consists of a frame and a deck that is mounted on and supported by the frame. The invention further has a hydraulic cylinder for selectively moving the deck between a substantially horizontal load-carrying position and an inclined loading position. When the deck is in the inclined loading position, the rear portion of the deck is proximate to the ground so that a cargo vehicle or movable equipment may be driven, pushed, or pulled onto the deck. Furthermore, the angle of the deck is less than 10°. 
     A more specific description of a preferred embodiment of the invention is a tilt-bed trailer that has a frame and a deck mounted on and supported by the frame. The deck is movable and tiltable between a horizontal load-carrying position and an inclined loading position. The invention further has an angled track connected to the frame for guiding rollers that are attached to a front portion of the deck. A hydraulic cylinder is connected between the deck and the frame. When the hydraulic cylinder moves into a retracted configuration, the deck is caused to move rearward, and the tracks force the front end of the deck to move in an upward direction, thereby tilting the deck. When the deck is moved to its full rearward position, i.e. when the rollers of the deck are moved to the rear ends of the tracks, the rear portion of the deck is proximate to the ground so that cargo with a low ground clearance may be driven, pushed, or pulled onto the deck. The hydraulic cylinder may then be moved into an extended configuration, which causes the deck to move in a forward direction, and the track forces the front of the trailer to move downward, thereby causing the deck to move into a horizontal load carrying position. The hydraulic cylinder is anchored to the frame in such a manner that the hydraulic cylinder remains parallel to the deck at all times, regardless of whether the trailer bed is in the horizontal load-carrying position or the inclined loading position. 
     These and other advantages of the present invention will become apparent from the more detailed description of the preferred embodiment that follows. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top elevational view of the trailer with a breakout showing the pivot point roller assembly. 
     FIG. 2 is a side elevational view of the trailer, shown in FIG. 1, with the trailer bed in the horizontal load carrying position, with a breakout that shows the track roller assembly, and with hidden lines that represent the track. 
     FIG. 3 is a side elevational view of the trailer, shown in FIG. 1, with the trailer bed in an inclined loading position. 
     FIG. 4 is a partial perspective view of the subframe; hydraulic cylinder; and track roller assembly, which is shown in the breakout of FIG.  2 . 
     FIG. 5 is a fragmentary view of the pivot point roller assembly, shown in the breakout of FIG.  1 . 
     FIG. 6 is a partial sectional view of the trailer shown in FIG. 1 taken along line  6 — 6  with the trailer bed tilted as if the terrain underneath the trailer was even. 
     FIG. 7 is a partial sectional view of the trailer shown in FIG. 1 taken along line  7 — 7  with the trailer bed tilted as if the terrain underneath the trailer was uneven. 
     FIG. 8A is a partial side view of the roller assembly corresponding to the trailer configuration depicted in FIG.  2 . 
     FIG. 8B is a partial side view of the roller assembly corresponding to the trailer configuration depicted in FIG.  3 . 
    
    
     DETAILED DESCRIPTION 
     Referring now to the figures, there is illustrated preferred embodiments of a tilt bed trailer constructed according to the principles of the present invention. As shown in FIGS. 1,  2 , and  3  the tilt bed trailer includes a frame  1 , a hydraulic cylinder  7 , a pivot-point roller assembly  3 , a trailer bed  5 , and a track roller assembly  10 . As shown in FIGS. 2 and 3, when trailer bed  5  is moved in a rearward direction relative to the frame  1 , it tilts around pivot-point roller assembly  3  into an inclined position for loading. The angle of trailer bed  5 , from the horizontal, is approximately 7° in the full inclined loading position. Conversely, when trailer bed  5  is moved in a forward direction relative to the frame  1 , it tilts around pivot-point roller assembly  3  into a horizontal load-carrying position. 
     Frame  1  has I beams  2   a  and  2   b  which are parallel to one another. Forward beam  4  is attached to the front end of I beams  2   a  and  2   b  and rear beam  6  is attached to the rear end of I beams  2   a  and  2   b . As one skilled in the art will appreciate, there are several cross-members that perpendicular to I beams  2   a  and  2   b  and extend from I beam  2   a  to I beam  2   b . As one skilled in the art will further appreciate, eyelet  8  is attached to forward beam  4  and is adapted for use in a clevis-type trailer hitch, suspension members  87   a ,  87   b ,  87   c  are connected to I-beams  2   a  and  2   b , and wheels  89  are connected to suspension members  87   a ,  87   b ,  87   c . The preferred tires are 215/75R17.5, and the preferred suspension is Spring Part No. 365-00 manufactured by Hutch Industries of Springfield, Mo. 
     As shown in FIG. 4, hydraulic cylinder  7  has a cylinder  9  and a piston  11 . Attachment tube  67  is secured by conventional means to the end of piston  11  and, as described below, is adapted for attachment to trailer bed  5 . As shown in FIG. 5, cylinder  9  has raised portions  15   a ,  15   b , and  15   c , and pins  17   a  and  17   b , which extend from either side of raised portion  15   a . As one skilled in the art will appreciate, a hydraulic system is attached to the hydraulic cylinder  7  in order to cause the piston  11  to retract into and extend from cylinder  9 . 
     Pivot-point roller assembly  3  is shown in FIG.  5 . Pivot-point roller assembly  3  includes a cradle  21  that defines two vertically oriented slots  19   a  and  19   b  in which pins  17   a  and  17   b  are located, respectively. Clamps  23   a  and  23   b  wrap around raised portions  15   a  and  15   c , respectively, and are secured to cradle  21  by bolts. Thus, the pins  17   a  and  17   b  and clamps  23   a  and  23   b  secure cylinder  9  to cradle  21 . The bottom portion of cylinder cradle  21  has a flange  22  that defines a bushing hole  25 . An identical flange and bushing hole, not shown, are located at the opposite side of the cradle  21 . A cradle bushing, not shown, fits in bushing hole  25  and extends to and fits in the identical bushing-hole. The cradle bushing is secured to flange  22  and the identical flange by conventional means. Roller shaft  27  has axis  28  and passes through the cradle bushing. The inside surface of the cradle bushing is lined with grease so that cradle  21  will freely rotate around roller shaft  27  and hence axis  28 . The advantage of this design is that hydraulic cylinder  7  will tilt around axis  28 . 
     Cross-member  31  defines channel  32  and has one end secured to I beam  2   a  and an opposite end secured to I beam  2   b . Bracket  29  is attached to cross-member  31  at a point within channel  32  and has hole  30 . An identical bracket, not shown, is located at the opposite side of cradle  21 . Thus, flange  22  on cradle  21  is sandwiched between brackets (one of which is designated as  29 ) and rotates relative thereto, as shown in FIGS. 8A and 8B. Roller shaft  27  extends from I beam  2   a  to I beam  2   b  and passes through hole  30  in bracket  29  and through a hole in the identical bracket. Roller bushing  33  circumscribes the end portion of roller shaft  27  and is secured to roller shaft  27  with a bolt. Roller  35  circumscribes roller bushing  33 . Bearings, not shown, are located between roller  35  and roller bushing  33  so that roller  35  may rotate freely. Brackets  37   a  and  37   b  support roller bushing  33  and are welded to cross-member  31  at a point within channel  32 . An identical assembly is located at the opposite end of roller shaft  27  and has roller bushing  39 , roller  41 , brackets  43   a  and  43   b , and bearings, not shown. 
     Trailer bed  5  has a subframe  44  that is represented in FIG.  4 . Subframe  44  has two parallel subframe I beams  45   a  and  45   b  that have webs  46   a  and  46   b , top flanges  48   a  and  48   b , and bottom flanges  50   a  and  50   b , respectively. Front rail  61  is attached to the front of subframe I-beams  45   a  and  45   b . Piston brackets  63   a  and  63   b  are attached to front rail  61  and extend downward. The distance between piston brackets  63   a  and  63   b  is slightly larger than the length of attachment tube  67 . Both piston brackets  63   a  and  63   b  have holes that are in axial alignment with attachment tube  67 . Pin  69  passes through attachment tube  67  and the holes in piston brackets  63   a  and  63   b . Pin  69  is secured in place by suitable means such as a cotter pins. 
     Brace  91  extends from a position underneath bottom flange  50   a  to a position underneath bottom flange  50   b . Brace flange  93  is attached to brace  91  and extends over the top of bottom flange  50   a , and an identical brace flange, not shown, extends over the top of bottom flange  50   b . Clamp  95  is attached to brace  91  and secures brace  91  to cylinder  9 . Thus, as trailer bed  5  moves in a forward or rearward direction, relative to frame  1  I beams  45   a  and  45   b  slide along brace  91 . Bottom flange  50   a  rests on roller  35 , and bottom flange  50   b  rests on roller  41 . Therefore, trailer bed  5  is movable over rollers  35  and  41  in a forward and rearward direction. Additionally, trailer bed  5  is tiltable over rollers  35  and  41  and hence is tiltable around axis  28 . As one skilled in the art will appreciate, deck  12  is attached to top flanges  48   a  and  48   b  by conventional means, and subframe cross members, not shown, extend from subframe I beam  48   a  to subframe I beam  48   b  to support deck  12 . 
     Track roller assembly  10  has brackets  49   a  and  49   b  which extend downward from bottom flanges  50   a  and  50   b , respectively, and define holes, not shown. Bushing  51  extends from bracket  49   a  to bracket  49   b  and is in axial alignment with the holes. Track roller shaft  53  extends through the holes and bushing  51 . Track roller  55  circumscribes the end portion of roller shaft  53 . Bearings, not shown, are located between track roller  55  and track roller shaft  53  so that track roller  55  may freely rotate around track roller shaft  53 . An identical track roller  57  and bearings, not shown, are mounted at the opposite end of track roller shaft  53 . An additional cross-member  59  extends from bracket  49   a  to bracket  49   b  in order to provide stability and strength to brackets  49   a  and  49   b  and to protect bushing  51  from debris that get kicked up from the road. 
     As shown in FIG. 6, track  71  extends along a portion of the web  13   a  of I-beam  2   a . Track  71  is formed by a top rail  73  and a bottom rail  75  which are parallel to one another for most of their length and are welded to the inside of web  13   a . Furthermore, the distance between the top rail  73  and the bottom rail  75  is slightly larger than the diameter of the track rollers  55  and  57 . Track  71  is angled so that the rear end  79  has an elevation that is higher than the front end  77 . The bottom rail  75  has a horizontal portion  81  located at the rear end  79 . As a result, the distance between the top rail  73  and the bottom rail  75  is consistent except for the portion that extends along horizontal portion  81  at which point the distance between the top rail  73  and the bottom rail  75  increases. As described below, this divergence of the rails accommodates loading the trailer bed  5  when the terrain has an uneven elevation. Roller  57  is located in track  71  between top rail  73  and bottom rail  75 . An identical track  72  is located on the inside of web of I-beam  2   b  and guides the second roller  55 . 
     As one skilled in the art will appreciate, fold down approach ramp  85  is attached to the rear portion of trailer bed  5 . As one skilled in the art will further appreciate, fold down approach ramp  85  is attached to a second hydraulic cylinder, not shown, by conventional means. The hydraulic system is also attached to this second hydraulic cylinder. The second hydraulic cylinder is capable of moving fold down approach ramp  85  between a vertical orientation and a horizontal orientation. 
     As previously discussed, trailer bed  5  has two positions. In the first position, shown in FIG. 2, trailer bed  5  is in a forward horizontal position for transporting loads such as cargo vehicles and movable equipment. In this position, fold down approach ramp  85  is vertical, extending downward from trailer bed  5 . In the second position, shown in FIG. 3, fold down approach ramp  85  is inclined so that a cargo vehicle may be driven, pushed, or pulled onto trailer bed  5 . 
     In order to move trailer bed  5  from the horizontal to the inclined position, fold-down approach ramp  85  must be rotated so that it is in the same horizontal plane as trailer bed  5  and extends outward from trailer bed  5  thereby becoming an extension of deck  12 . Hydraulic cylinder  7  is then activated causing piston  11  to retract into cylinder  9 . As piston  11  retracts, it pulls trailer bed  5  in a rearward motion so that subframe I beams  45   a  and  45   b  move along rollers  35  and  41 , respectively. Additionally, track rollers  55  and  57  are caused to move along tracks  71  and  72 , respectively. Tracks  71  and  72  force track rollers  55  and  57  in an upward motion which causes trailer bed  5  to tilt. As a result, trailer bed  5  pivots around axis  28  of roller shaft  27 . Trailer bed  5  is caused to gradually tilt until it reaches its full inclined position because top rails  73  and  74  and bottom rails  75  and  76 , respectively, are parallel for most their length and the distance between top rails  73  and  74  and bottom rails  75  and  76 , respectively, is only slightly larger than the diameter of track rollers  55  and  57 . In other words, trailer bed  5  will not drop into the full inclined position as soon as more than half the combined weight of trailer bed  5  and load is shifted to a position that is behind rollers  35  and  41 . 
     Because hydraulic cylinder  7  has one end anchored to front rail  61  and the other end anchored to cradle  21 , it is also caused to pivot around axis  28  of roller shaft  27 . Therefore, hydraulic cylinder  7  and trailer bed  5  pivot around the same point and always remain parallel to one another. 
     If the elevation of the ground behind the tilt-bed trailer is the same as the ground under the tires, trailing edge  84  of fold-down approach ramp  85  and the tires will be resting on the same plane. As a result, track rollers  55  and  57  will be resting on the horizontal portions  81  and  82  of bottom rails  75  and  76 , respectively. If the elevation of the ground behind the tilt-bed trailer is lower than the elevation of the ground under the tires, trailing edge  84  of fold-down approach ramp  85  will be resting at a point that is lower than that of the tires. As a result, trailer bed  5  will have a slightly larger incline and track rollers  55  and  57  will move upwards and be resting against top rails  73  and  74 , respectively. Thus, the increased gap between top rails  73  and  74  and bottom rails  75  and  76 , respectively, allows the incline of trailer bed  5  to adjust to uneven terrain. 
     In the full inclined position, the height of unloaded deck  12  at a point directly above rollers  35  and  41  is approximately 36.25 inches and the length of that portion of deck  12  that is behind rollers  35  and  41 , i.e., in back of, or on the right side of, the pivot axis  28  when viewing FIG. 3, is approximately 252 inches. Once trailer bed  5  is moved into the inclined position, the load can be driven, pushed, or pulled onto trailer bed  5 . After trailer bed  5  is loaded, it is moved forward from an inclined loading position into the horizontal load-carrying position. This forward movement is caused by activating hydraulic cylinder  7  so that piston  11  is caused to extend from cylinder  9 . As a result, trailer bed  5  is pushed in a forward direction and caused to tilt into a horizontal position. Once trailer bed  5  is moved into the forward horizontal load-carrying position, fold-down approach ramp  85  is caused to rotate so that is moves from the horizontal position to the vertical position. In this vertical position, fold-down approach ramp  85  will prevent an automobile from driving underneath trailer bed  5 . 
     While the invention has been described in conjunction with a specific embodiment thereof, it is evident that different alternatives, modifications, and variations will be apparent to those skilled in the art in view of the foregoing description. Accordingly, the invention is not limited to these embodiments or the use of elements having specific configurations and shapes as presented herein.