Abstract:
A tail gate assist is provided for an open trailer and includes an elastic member mounted so as to provide assistance in raising the tail gate without substantially adding to the force required to open the tail gate.

Description:
BACKGROUND 
   Open trailers with tail gates are often used to transport lawn care equipment and other products. As the tail gate may be long and heavy, it can be difficult to operate by hand. In a typical arrangement, with a tail gate that is five feet long from the hinge to the free end, a force of 80 pounds must be applied at the free end of the tail gate in order to lift the tail gate when it is in the open position. Several types of lift devices have been used in the past, but they all have problems. In many cases, the lift device includes a spring or other elastic member which substantially increases the resistance against which a person must work in order to open the tail gate from its closed position, making it much more difficult to open the tail gate than if there were no assist at all. So, while the elastic member does provide an advantage in that it helps with lifting the tail gate, it also creates a substantial disadvantage by making the tail gate more difficult to open than it would be without the assist. 
   For example, U.S. Pat. No. 6,485,004 “Licata” shows a lift spring for a tail gate in which the lift spring is mounted to the side rail of the trailer and to the tail gate. The spring extends upwardly from the side rail to the tail gate when the tail gate is closed and downwardly from the side rail to the tail gate when the tail gate is fully open. The spring is in tension throughout the entire distance of travel of the tail gate and its length does not increase substantially from the raised position to the lowered position, so the spring force does not change appreciably from the closed position to the open position. In this case, since the spring force is roughly the same throughout the travel of the tail gate and since the angles at which the spring applies its force are not advantageous, the operator must exert a substantial force against the spring in order to open the tail gate, and very little of the spring force actually helps counteract the weight of the tail gate in order to help the operator raise the tail gate. At the beginning of travel from the closed position, the spring is pulling primarily downwardly on the tail gate, but it also exerts a horizontal force against which the operator must pull in order to open the tail gate. As the operator begins to open the tail gate and throughout the rest of the travel of the tail gate, the spring force acts primarily in the horizontal direction, so the operator has to pull the tail gate outwardly against that spring force in order to open the tail gate. Even in the fully open position, the spring angle is such that most of the spring force is acting in the horizontal direction and very little of the spring force is acting in an upward direction to help counteract the weight of the tail gate. 
   U.S. Pat. No. 6,126,223 “Rayburn” mounts an elongated assist system along the top of the side rail of the trailer. This occupies a substantial distance along the side rail, which is undesirable, because it prevents that space from being used for other purposes. In this design, the elastic member includes a spring and a cable mounted onto the spring. The cable passes over rollers and the elastic member does not remain in a straight line but rather bends around the rollers. Again, the elastic member does not elongate appreciably from the fully closed position to the fully open position, so it is exerting a substantial spring force against the tail gate in all positions. In order to begin opening the tail gate, the operator must apply a substantial horizontal force to counteract the horizontal force of the spring, and most of the spring force continues to be applied in a horizontal direction, even at the fully opened position of the tail gate, so only a small portion of the spring force actually helps act against gravity to help lift the tail gate. 
   SUMMARY 
   The present invention provides a tail gate assist for an open trailer in which an elastic member is oriented to provide help in acting against gravity to help the operator raise the tail gate with very little effort while, at the same time, not creating a substantial force against which the operator has to act in order to open the tail gate. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a trailer including a tail gate assist arrangement made in accordance with the present invention; 
       FIG. 2  is a side view of the rear portion of the trailer of  FIG. 1 ; 
       FIG. 3  is the same view as  FIG. 2  but showing the tail gate and the assist arrangement in various positions as the tail gate is moved from the fully closed position to the fully open position; 
       FIG. 4  is a view taken along the line  4 — 4  of  FIG. 2 , showing the upper portion of the upright post; 
       FIG. 5  is a side view of the upper portion of the upright post of  FIG. 4 ; 
       FIG. 6  is a view taken along the line  6 — 6  of  FIG. 2 , showing the bracket and connection between the elastic member and the tail gate; 
       FIG. 7  is a side view of the bracket and connection of  FIG. 6 ; 
       FIG. 8  is a view similar to  FIG. 4  but showing an alternative connection between the elastic member and the upright post; 
       FIG. 9  is a side view of the arrangement of  FIG. 8 ; 
       FIG. 10  is a side view of an alternative connection between the elastic member and the upright post and an alternative upright post, in which the post is made of telescoping members; 
       FIG. 11  is an enlarged side view of the mounting bracket and tail gate portion of  FIG. 7  but with the tail gate in the open position; 
       FIG. 12  is the same view as  FIG. 11  but with the mounting bracket mounted in a first alternative way on the tail gate; 
       FIG. 13  is the same view as  FIG. 11  but with the mounting bracket mounted in a second alternative way on the tail gate; and 
       FIG. 14  is the same view as  FIG. 11 , but with the mounting bracket mounted in a third alternative way on the tail gate. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  is a perspective view of a trailer  10  including a tail gate assist arrangement made in accordance with the present invention. The trailer  10  includes a frame  12 , and a floor  13 , with left and right parallel side rails  14 ,  16  extending at an elevation above the floor  13 . In this case, the side rails  14 ,  16  are parallel to the floor  13 . However, other arrangements are known in which the side rails lie at an angle to the floor. Typically, the floor  13  or bed of the trailer  10  is about sixteen to twenty inches above the ground, and the side rails  14 ,  16  are about one foot above the bed  13  of the trailer or twenty-eight to thirty-two inches above the ground. This trailer  10  also has a front rail  18  and a tongue  20 . This trailer  10  also has two wheels  22 , which support the frame  12 , floor  13 , and rails  14 ,  16 ,  18 . 
   A tail gate  24  is pivotably mounted to the frame  12  by means of a hinge  26 , having a horizontal pivot axis. Typically, the tail gate  24  is about forty-two to sixty inches long from its first end, which is mounted to the hinge  26 , to its free end. The tail gate  24  is shown in the closed position in  FIG. 1 . An upright post  28  is mounted onto the top of the left side rail  14  near the rear of the trailer  10 . This particular post  28  is three feet long, but it could be longer or shorter, depending upon the trailer. In this case, since the post  28  is mounted on top of the side rail  14 , it projects upwardly above the hinge  26  a distance of four feet, putting it a bit lower than the top of the tail gate  24 , or roughly at the same elevation as the tail gate when the tail gate is in the closed position. It is preferred that the top of the upright post  28  be a distance above the hinge  26  that is at least half the length of the tail gate  24 . 
   A helical coil spring  30  is secured at one end  34  of the post  28  near the top of the post  28  and at the other end to the side of the tail gate  24 . A retaining cable  32  extends through the longitudinal opening in the spring  30  and is also secured to the post  28  and to the side of the tail gate  24 . The retaining cable  32  is substantially non-elastic and is intended to retain the spring  30  in the event that the spring  30  breaks. 
     FIGS. 2 and 3  show that the spring  30  (the elastic member) extends in a straight line and at a downward angle from the post  28  to the tail gate  24  at all positions of the tail gate  24 , from the substantially vertical closed position shown in  FIG. 2  (and shown in phantom in  FIG. 3 ) to the substantially horizontal open position shown in  FIG. 3 . The downward angle “a” between the spring  30  and the upright post  28  when the tail gate  24  is closed is an acute angle, and the downward angle “b” between the spring  30  and the upright post  28  when the tail gate is open is also an acute angle. It is preferred that the angles “a” and “b” be less than 60 degrees and more preferred that they be less than 45 degrees so that the vertical component of the spring force is substantial and preferably greater than the horizontal component.  FIG. 3  shows that the spring  30  elongates substantially from the closed position to the open position, so the spring force increases substantially from the closed position to the open position, with the spring  30  applying very little force on the tail gate when the tail gate is closed, and with the spring force increasing as the tail gate opens, until the maximum spring force is applied when the tail gate is in the open position. In this embodiment, the spring is 30 inches long in the retracted position and 50 inches long in the open position. It is preferred that the length of the spring increase at least 20% from the closed position to the open position. 
   In this embodiment, the horizontal force required to begin opening the tail gate  24  when it is in the closed position is very little—approximately two pounds. This is about the same as the force that would be required to begin opening the tail gate  24  if the spring  30  were not present. It is preferred that the spring  30  not increase the force needed to open the tail gate by more than five pounds over what would be required without the spring. 
   In this embodiment, if the spring were not present, the user would have to apply about 80 pounds of upward force at the free end of the tail gate  24  in order to begin closing the tail gate  24  when it is in the open position. With the spring present, the force that is required at the free end of the tail gate  24  in order to begin lifting it is less than fifteen pounds, reducing the required force by more than 80%. It is preferred that the external lifting force that needs to be applied by the user in order to begin closing the tail gate  24  be reduced by 75% or more. 
     FIG. 4  shows the top portion of the upright post  28  with a bolt  36  extending through a hole in the upright  28 , through a loop  38  in the cable  32  through a loop  40  on the end of the spring  30 , through a washer  42  and through a nut  44  to secure the spring  30  and cable  32  to the upright  28 .  FIG. 5  is a side view of the same arrangement. In this view it can be seen that there are multiple holes  46  through the upright  28 , which effectively allows adjustment of the height of the upright  28 . 
     FIG. 6  shows the bottom end of the spring  30  and cable  32 , showing how they are secured to the tailgate  24 . A bolt  36  extends through a washer  42 , through a loop  40  in the bottom of the spring  30 , through a loop  38  in the bottom of the cable  32 , through a nut  44 A, through a hole  50 A in a bracket  50  secured to the tail gate  24 , and through another nut  44 B in order to secure the cable and spring to the tail gate  24 . The bracket  50  is a flat piece, having parallel flat faces, with one of the flat faces lying against the tail gate  24 . The bracket  50  has three holes  50 A,  50 B,  50 C, one of which receives the bolt  36  that secures the spring  30  and cable  32 , and the other two of which receive bolts that secure the bracket  50  to the side of the tail gate  24 . The three bolt holes  50 A–C form a triangle, and the hole  50 A is closer to the hole  50 C than to the hole  50 B. This permits the bracket to be used to adjust the point at which the spring  30  and cable  32  are secured without changing the positions of the holes through the tail gate  24  through which the bracket  50  is secured to the tail gate  24 . 
     FIGS. 11–14  show the spring  30  mounted in four different positions using the same bracket  50  mounted through the same two holes in the tail gate  24 .  FIG. 11  has the bracket  50  mounted as shown in  FIG. 7 , with the first flat face of the bracket against the side of the tail gate  24  and the hole  50 A projecting above the tail gate  24 . In  FIG. 12 , the first flat face of the bracket  50  is still against the side of the tail gate  24 , but the bracket  50  has been rotated 180 degrees, so the hole  50 A now projects below the tail gate  24 . The arrangement of  FIG. 13  is produced by taking the bracket as shown in  FIG. 12  and flipping it over, so the second flat face of the bracket lies against the side of the tail gate  24 . In this position, the hole  50 A projects downwardly as in  FIG. 12 , but it is shifted toward the hinge  26 . To go from the arrangement of  FIG. 13  to the arrangement of  FIG. 14  requires rotating the bracket  50  180 degrees, so the hole  50 A projects above the tail gate  24 . This is similar to the arrangement of  FIG. 11 , except the hole  50 A is farther away from the hinge  26 . 
     FIGS. 8–10  show different mounting arrangements for mounting the spring  30  and cable  32  to the upright post  28 . In  FIGS. 8 and 9 , an eye bolt  36 A is used instead of the straight bolt of  FIG. 4 . In  FIG. 10 , a second eye bolt  36 B is mounted through the first eye bolt  36 A. The spring  30  and cable  32  are secured to the second eye bolt  36 A, and the second eye bolt  36 B can be rotated relative to its nut to effectively lengthen or shorten the cable  32  and spring  30 . Also, as shown in  FIG. 10 , the upright post  24  is a telescoping member, which can be lengthened or shortened depending upon which pair of holes is aligned and receives the pin  52 . 
   A preferred method for mounting the tail gate assist arrangement of this embodiment to the trailer  10  is accomplished with the following procedure. 
   1. Hold the upright post  28  in a desired position on the left or right trailer side rails  14 ,  16  near the rear of the trailer  10  (usually about a foot from the rear). 
   2. With the tailgate  24  closed, mark the desired location for the gate bracket  50  on the same side (left or right) of the tailgate by measuring 30 inches (the retracted length of the spring in this embodiment) from the hole  46  to the tailgate. For most tailgates, this will be approximately 14 inches from the hinge  26 . 
   3. Open the tailgate and measure the distance from the hole  46  in the top of the upright  24  to the location marked in Step 2. The distance should not be more than 53 inches, which, in this embodiment, is the maximum length of the spring. If it is more than 53 inches, then the position of the upright post  28  should be adjusted and Steps 1–3 repeated. Once the proper locations for the upright  28  and bracket  50  are determined, proceed to Step 4. 
   4. Attach the upright post  28  to the left or right trailer side rails  14 ,  16  by drilling four holes through the side rail and attaching it with four ⅜ inch grade “5” bolts and lock nuts. 
   5. Attach the gate bracket  50  to the tailgate  24  at the marked location by using the two small holes  50 B,  50 C in the bracket and two ½ inch by 1½ inch grade “5” bolts and lock nuts (Note: holes will have to be drilled through the tailgate). 
   6. Insert one end of the cable  32  inside the spring  30  and feed it through the spring until it exits the other end of the spring. 
   7. Attach one end of the spring and cable to the upright post  24  with a % inch by 4½ inch grade “5” bolt using the following configuration. (Shown in  FIGS. 4 &amp; 5 )
         a. Slide the bolt  36  through the hole  46  at the top of the upright post  24  such that the head of the bolt is on the inside (toward the trailer) and the threads are on the outside (away from the trailer).   b. Slide the end loop of the cable  32  over the bolt.   c. Slide the end loop of the spring  30  over the bolt.   d. Slide a ⅝ inch washer  42  over the bolt.   e. Thread a lock nut  44  onto the bolt until a minimum of three threads are showing on the bolt.       

   8. Make sure the tailgate is in the closed position and attach the other end of the spring and cable to the gate bracket with a ⅝ inch by 4½ inch grade “5” bolt using the following configuration. (Shown in  FIGS. 6 &amp; 7 )
         a. Slide a ⅝ inch washer  42  over the bolt  36 .   b. Slide the end loop of the spring  30  over the bolt.   c. Slide the end loop of the cable  32  over the bolt.   d. Securely tighten a ⅝ inch standard nut  44 A against the shoulder of the bolt.   e. Insert the bolt  36  through the remaining large hole  50 A in the gate bracket  50  such that the head of the bolt is on the outside (away from the trailer) and the threads are on the inside (toward the trailer).   f. Thread a lock nut  44 B onto the bolt until it tightens against the bracket  50 .       

   9. The tail gate assist arrangement is now ready for use. 
   To change the leverage (or lift) of the tailgate, the bracket  50  can be repositioned using the same two holes  50 B,  50 C in the tailgate (See  FIGS. 11–14 ). To reposition the bracket, first make sure the tailgate is in the closed position. Then, unscrew the two lock nuts and remove the bracket. Depending on the desired position, it may also be necessary to remove the bolt  36  from the bracket by removing the third lock nut  44 B. For instance, changing from the position shown in  FIG. 11  or  12  to the position shown in  FIG. 13  or  14  would require removal of the bolt  36  to “flip” the bracket  50 , but changing from the position shown in  FIG. 11  to the position shown in  FIG. 12  would not require removal of the bolt. Once the desired position is chosen by rotating and/or flipping the bracket, the bracket is simply reattached to the same holes  50 B,  50 C with the bolts and lock nuts. 
   The leverage or tension also may be adjusted by changing the mounting position on the upright post  28  or by telescoping the upright post, or by adjusting the length of the turnbuckle  36 B, or other similar means. 
   It will be obvious to those skilled in the art that modifications may be made to the embodiments described above without departing from the scope of the present invention.