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This application claims the benefit of U.S. provisional patent application Ser. No. 61/027,806, filed Feb. 11, 2008. 
    
    
     FIELD OF INVENTION 
     The present invention generally relates to the field of livestock hauling trailers; and, more particularly, to a stock trailer with reinforced sliding door mechanisms thereby enhancing safety during handling of livestock. 
     BACKGROUND OF THE INVENTION 
     A major hazard encountered during the handling of livestock occurs when animals are loaded onto stock trailers for transport. Prior art livestock trailers incorporate swinging doors on the rear and sides of the trailer. When livestock is loaded on to the trailer, the rear loading door, which swings from hinges at the side of the trailer, is pushed closed by the operator. As the door closes, animals often panic as the light diminishes from the outside and the interior of the trailer darkens. Consequently, the animals tend to kick at the door. An operator, unprepared for a kick and not being able to see into the trailer to observe the kick, is thrust back often resulting in serious injuries. Similar injuries can occur during unloading. 
     Some livestock loading and unloading situations require the livestock trailer to be backed up against a loading ramp or other dock. Prior art trailers incorporating swinging doors require the livestock trailer to be positioned at a distance from the ramp in order to establish clearance from the ramp to open or close the door thereby requiring multiple operators to maneuver the trailer and to monitor livestock in the trailer while the trailer is repositioned. 
     What is needed is an improved livestock trailer and door mechanism to reduce injuries endured during loading and unloading livestock such that the operator can, as a minimum, observe the animals and to provide a means for operating the door mechanism when docked to a loading ramp. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a new livestock trailer, and, more specifically, to a livestock trailer incorporating a reinforced sliding door mechanism, thereby substantially obviating one or more of the problems due to the limitations and disadvantages of the related art. 
     The present invention is a livestock trailer comprising a steel reinforced sliding door mechanism permitting an operator to continuously observe the livestock during loading and to prevent injuries from kicking. 
     A slidable two piece door mechanism is fixed at the top of the rear of a stock trailer by a slidable rail assembly wherein each door section has a width of approximately half the width of the trailer. The door sections are interlocked such that as the doors are opened from left to right the first door section slides to the right until the left half of the trailer is open and then interlocking with the second door section, both continue to slide to the right until the trailer is fully open. The bottom of the door sections are retained by reinforced guides at the bottom of the trailer opening such that when an animal kicks the doors remain in place as the guides prevent the door sections from swinging outwardly and upwardly. To operate the sliding safety door, the operator first slides open the first door section while being protected by the door section, then the second door section again protected by the door; and, in this manner, is protected from injury. As the door is slidable towards the side of the trailer, the door is operable whilst docked to a loading ramp thereby eliminating the step of repositioning the trailer to facilitate opening the door. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate embodiments of the invention and, together with the description, serve to explain the features, advantages, and principles of the invention. 
       In the drawings: 
         FIG. 1  is a rear perspective view of the livestock trailer with sliding safety door according to the present invention wherein the rear sliding door is closed. 
         FIG. 2  is a rear perspective view, similar to  FIG. 1 , wherein the first door section is fully open. 
         FIG. 3  is a rear perspective view, similar to  FIGS. 1 and 2 , wherein the first and second door sections are both fully open. 
         FIG. 4  is a cross section view, taken on Line  4 - 4  of  FIG. 1 , illustrating the sliding safety door according to the present invention fully closed. 
         FIG. 5  is a cross section view, taken on Line  5 - 5  of  FIG. 2 , illustrating the interlocking of the first door section with the second door section. 
         FIG. 6  is a cross section view, taken on Line  6 - 6  of  FIG. 3 , showing both door sections fully open. 
         FIG. 7  is a rear elevation view of the livestock trailer sliding safety door fully closed. 
         FIG. 8  is a top plan view of the sliding safety door portion of the livestock trailer showing the door fully closed as in  FIG. 7 . 
         FIG. 9  is a rear elevation view of the livestock trailer sliding safety door fully open. 
         FIG. 10  is a cross section view, taken on Line  10 - 10  of  FIG. 8 , illustrating the roller mechanisms upon which the doors hang. 
         FIG. 11  is a left side elevation view, taken on Line  11 - 11  of  FIG. 7 , showing details of the slidable rail assembly construction. 
         FIG. 12  is a cross section view, taken on Line  12 - 12  of  FIG. 7 , showing the door rail resting on the truck mounting flange which supports the sliding safety door according to the present invention. 
         FIG. 13  is a cross section view, taken on Line  13 - 13  of  FIG. 7 , showing details of the hanger system for the second door section. 
         FIG. 14  is a right side elevation view, taken on Line  14 - 14  of  FIG. 7 , according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims. Referring now in greater detail to the various figures of the drawings wherein like reference characters refer to like parts, there is shown in a perspective view at  10  in  FIG. 1 , a new type of livestock trailer having a reinforced sliding safety door for enhanced operator safety. 
     As illustrated in  FIG. 1 , the sliding safety door is comprising a first and left door section  12  and a second and right door section  14  wherein each door slides and is hung from the slidable rail assembly  18  and is prevented from being pushed out from the trailer by the lower door guide  16 . When opening the safety door, the first door section  12  is slid to the right behind the second door section until the first door section  12  is fully open as illustrated in  FIG. 2 . The operator stands behind the first door section  12  and pulls the first door section  12  open to begin the disembarkment of the livestock. As the door section  12  is pulled open, the animals tend to kick at the door as light enters the trailer. Because the door sections are retained by the slidable rail assembly  18  at the top and the lower door guide  16  at the bottom of the doors, the operator is safely positioned with the door sections between the operator and the animals. Further, because the doors are secured top and bottom, the operator may confidently anticipate that no injuries will occur if the animals kick the door. Note the handle  68  fixed to the first door section and latch  70  fixed to the trailer. The handle  68  and latch  70  are optionally provided for convenience of handling and security. 
     Referring now to  FIG. 3 , showing the both door sections  12  and  14  fully open, the first door section  12  is slid behind the second door section  14 . Both door sections are supported from the top by portions of the slidable rail assembly  18 . The bottom ends of the door sections are retained by the lower guide  16 . 
     Referring to  FIGS. 4 ,  5 , and  6 , showing cross sections of the door section in the open, partially open and fully open positions, note that the first door section  12  is positioned behind the second door section  14 . As the first door section  12  slides open the first door section  12  interlocks with the second door section  14  at the position where the first door section  12  is open as shown in  FIG. 5 . Any further motion to open the safety door further results in both door sections  12  and  14  to travel together to eventually be located in the fully open position shown in  FIG. 6 . 
     Referring to  FIG. 7 , a rear elevation view of the sliding safety door incorporated into the rear of the livestock trailer, the slidable rail assembly  18 , from which both door sections are hung, is shown mounted at the top of the rear of the trailer. The slidable rail assembly  18  is comprising a square tubular steel door rail  26  resting upon a polymer guide pad  32  secured the trailer mounting flange  28 . The polymer guide pad  32  runs the length of the door rail  26  where feasible so as not to obstruct other features and is fixed to the trailer mounting flange  28 . The polymer guide pad  32  facilitates the sliding of the door rail  26  along the length of the trailer mounting flange  28 . The trailer mounting flange  28  is an L shaped metal bracket with both face widths approximately of the width of the second square tubular steel door rail  26 , a length of the trailer opening and one face is welded upwardly along the length to the top of the trailer opening with the opposing perpendicular face directed outwardly from the rear of the trailer so as to provide a shelf structure being the principle support for the sliding safety door. A typical trailer rear opening usually comprises a trailer upper  60  and lower  62  rear mounts as illustrated in  FIGS. 11 ,  12 ,  13  and  14 . If these mounts are not present, the rear mounts must be added to the trailer in order to incorporate the sliding safety door. 
     The second door rail  26  of the slidable rail assembly  18  is retained in position by three rail guides  34 ,  36  and  38 . The rail guides are constructed from square tubular metal material having internal dimensions to compliment the external dimensions of the door rail  26  thereby each providing a guide through which the door rail  26  may slide. It will be appreciated that the polymer guide pad  32  thickness is slightly thicker than the thickness of the rail guides such that the door rail  26  rests primarily upon the polymer guide pad  32 . The rail guides  34 ,  36  and  38  are welded to the top of the rearward extending face of the trailer mounting flange  28 . Guide  34  is positioned at the left, guide  36  is welded in the center and guide  38  is welded near the right end at a distance to the left from the right end so as to permit clearance for the second door section  14  track T bracket  46  from which the second door section  14  hangs. 
     Still referring to  FIG. 7 , the first door section  12  is suspended by rollers  52  and  54  in a roller track  20  portion of the slidable rail assembly  18  wherein the roller track  20  is formed as a downwardly facing U section with the edges rolled inwardly to conform to and retain the wheels of the rollers leaving a slot along the length of the track for the hanger sections,  56  and  58 , of the rollers from which the first door section  12  is hung. The roller track  20  has the same length as the second door rail  26  and is attached to the rail  26  by roller track L bracket  42  and track T brackets  44  and  46 . 
     Referring briefly to  FIG. 12 , a side elevation cross section view of the left side of the sliding safety door taken along Line  12 - 12  of  FIG. 7 , the upwardly facing portion of the roller track L bracket  42  is welded to the rearward facing surface of the door rail  26  with the opposing perpendicular L portion positioned inwardly and under the trailer mounting flange  28 . The roller track  20  is positioned toward the trailer to permit clearance for the first door section  12  to pass behind the second door section  14  and is welded to the bottom of the roller track L bracket  42  inwardly facing portion. Similarly, as illustrated in  FIG. 13 , a similar cross section view taken along Line  13 - 13  of  FIG. 7 , the roller track  20  is welded to the bottom of the T section of the track T brackets  44  and  46  wherein the upwardly extending portions of the track T brackets are similarly welded to the rail  26 . The downwardly extending portion of the T brackets form straps from which the second door section  14  is hung and secured by second door section fasteners  22  and  24 . 
     As shown in  FIG. 8 , a top plan view of the sliding safety door, the rail guide  34  is positioned at the far left of the assembly and acts as a stop for the first door section roller track L bracket  42  when the first door section  12  is closed by sliding the door rail  26  to the closed position. Similarly, rail guide  36  also provides a stop for the track T bracket  44 , which supports the roller track  20  and as a hanger strap for the second door section  14  thereby defining the closed position of the second door section  14 . The rail guide  36  also provides a stop for the roller track L bracket  42  when the sliding safety door is fully open as in  FIG. 9  where the roller track L bracket  42  is stopped by rail guide  36 . Also note in  FIG. 9  that the track T bracket  44  is also stopped by rail guide  38  on the left. In this manner the sliding safety door is prevented from sliding off the trailer mounting flange  28 . 
     In  FIG. 10 , a cross section view of the door taken along Line  10 - 10  of  FIG. 8 , more clearly details the various elements of the sliding safety door while in the fully closed position. Note the rollers  52  and  54  resting in the roller track  20  with roller hanger sections  56  and  58  supporting the first door section  12  at the top of the door. In the illustrated embodiment, a roller track end stop  66  is incorporated to prevent the first door section from rolling out of the track  20 ; however, this element is optional. The roller track  20  is welded to the L bracket  42  and T brackets  44  and  46  which, in turn, are welded to the rearward face of the door rail  26 . The rail guides  34 ,  36  and  38  can be seen surrounding the door rail  26  and being welded to the truck mounting flange  28  with polymer guide pad  32  material between the door rail  26  and the truck mounting flange  28 . 
     The bottom ends of the door sections are retained by lower door guide  16  assembly. The function of the lower door guide  16  assembly is to provide a track in which the door sections slide while also preventing the bottom ends of the door sections from being pushed out resulting in the bottoms swinging out from the slidable rail assembly  18 . Referring to  FIGS. 11 ,  12 ,  13  and  14 , the lower door guide  16  assembly is comprising a lower door rail  72  constructed of L shaped angle iron dimensioned in length to match the trailer width and welded to the trailer&#39;s rear lower mount  62  to form an extension of the trailer floor with the opposing perpendicular face directed downward as shown. The rail  72  is additionally supported by cross members  74  welded at angle between the rear lower mount  62  and the interior of the rail  72 . The combination lower door rail  72  and cross member supports  74  form a downward facing element along the rear of the trailer rear bottom forming a track for lower door track receivers  76 ,  78  and  80 . The lower door track receivers are constructed of angle iron and flat strips so as to form a slot to receive the lower door rail wherein receivers  78  and  80  are welded to the outward facing bottom portion of the second door section  14 . Note that the receiver  76  additionally comprises a vertical plate perpendicularly fixed to the receiver and is welded to the left edge of the first door section  12  as the first door section is positioned behind the second door section  14 . 
     The various elements of the present invention may be constructed of any suitable material; however, elements except otherwise specified are preferably manufactured from a high strength steel alloy so as to withstand blows from livestock thereby assuring the safety of the operator.

Summary:
A livestock trailer with sliding safety door having a trailer with a two section sliding door mounted at the rear and hung from a slidable rail assembly at the top and retained by a guide at the bottom wherein the guides are steel reinforced. The sliding safety door, being secured at top and bottom, facilitates the loading and unloading of livestock by minimizing injuries sustained from kicking the door and eliminating injuries sustained when utilizing prior art swinging door type livestock trailers. The sliding door mechanism further eliminates the need to reposition the trailer while docking to a loading ramp so as to provide clearance to operate the door.