Abstract:
A vehicle tailgate includes a lower section carrying pivots adapted to be mounted to a vehicle bed; an upper section slidingly mounted to the lower section, so as to be able to move between an extended position and a retracted position relative to the lower section; and a biasing device which urges the upper section towards the extended position. The biasing device is selected so as to permit the upper section to move towards the retracted position when a predetermined force is applied.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to vehicle tailgates and more particularly to a tailgate which can absorb impacts and rebound from them. 
   Trucks and other vehicles, in particular “pickup” trucks are frequently equipped with beds or boxes for carrying loads. The rear end of the bed or box is usually closed off by a tailgate which can pivot between an upright closed position for hauling loads, and a generally horizontal open position which facilitates loading and unloading. 
   Especially when they are used in industry, construction or other commercial work, tailgates are subject to impact hazards in the open position. For example, the vehicle with the tailgate may be backed into posts, buildings, or other objects, or the tailgate may be struck by other vehicles, e.g. forklifts. Over time, the tailgates become too damaged for further use and have to be replaced. 
   BRIEF SUMMARY OF THE INVENTION 
   These and other shortcomings of the prior art are addressed by the present invention, which provides a tailgate capable of retracting when pushed or struck. 
   According to one aspect of the invention a vehicle tailgate includes: a lower section carrying pivots adapted to be mounted to a vehicle bed; an upper section slidingly mounted to the lower section, so as to be able to move between an extended position and a retracted position relative to the lower section; and biasing means for urging the upper section towards the extended position, the biasing means selected so as to permit the upper section to move towards the retracted position when a predetermined force is applied. 
   According to another aspect of the invention, a vehicle bed assembly includes: a pair of spaced-apart sidewalls; a floor extending between the sidewalls; and a tailgate. The tailgate includes: a lower section carried by the sidewalls so as to be pivotable between an upright, closed position, and a generally horizontal open position; an upper section slidingly mounted to the lower section, so as to be able to move between an extended position and a retracted position relative to the lower section; and biasing means for urging the upper section towards the extended position, the biasing means selected so as to permit the upper section to move towards the retracted position when a predetermined force is applied. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which: 
       FIG. 1  is a perspective view of a truck including a tailgate constructed according to an aspect of the present invention; 
       FIG. 2  is a side view of the truck of  FIG. 1 , showing the tailgate in an extended position; 
       FIG. 3  is a side view of the truck of  FIG. 1 , showing the tailgate in a retracted position; 
       FIG. 4  is a partially cut-away rear view of the tailgate of  FIG. 1 ; 
       FIG. 5  is a view taken along lines  5 - 5  of  FIG. 4 ; 
       FIG. 6  is cross-sectional view of a support column of the tailgate; 
       FIG. 7  is a circuit schematic depicting a warning device operated by the tailgate; 
       FIG. 8  is a perspective view of tailgate fixed in a lowered position; 
       FIG. 9  is a side view of an alternative latch for use with the tailgate of  FIG. 1 ; and 
       FIG. 10  is a side view of another alternative latch for use with the tailgate of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,  FIG. 1  depicts a rear portion of a truck  10  having a bed  12  comprising a floor  14  and a pair of spaced-apart sidewalls  16 . An exemplary tailgate  18  constructed according to an aspect of the present invention is mounted between the aft ends of the sidewalls  16  so that it can pivot between an upright, closed position (shown in  FIG. 1 ) and a generally horizontal, open position (shown in  FIGS. 2 and 3 ). While the invention is described in the context of a conventional “pickup” truck, it will be understood that the principle of the invention is equally applicable to other types of vehicles having a gate or door with an exposed edge. 
     FIG. 2  shows the tailgate  18  in the open position. It is supported in this position by one or more folding braces  20  of a known type. Chains, cables, or ropes could also be used for this purpose. In  FIG. 2 , the tailgate is fully extended and its overall length, denoted “L”, is approximately equal to the height “H” of the sidewalls  16  (see  FIG. 1 ), in accordance with conventional practice for pickup trucks.  FIG. 3  shows the action of the tailgate  18  when it is subjected to a force in the direction of arrow “A”. This could result from backing the truck  10  into a fixed obstacle such as a building or post, or from an impact on the tailgate  18  by another vehicle. When the force is applied, the tailgate  18  collapses into a retracted position so that its total length is less than the extended length L. By giving way in response to the force, the tailgate  18  is protected from damage. This may also reduce or prevent damage to the object in contact with the tailgate  18 . When the force or obstacle is removed, biasing means (described below) return the tailgate  18  to the extended position as shown in  FIG. 2 , and it is ready for further use. 
   The force required to cause the tailgate  18  to retract should be low enough such that it will retract before it dents or bends, and high enough that the tailgate  18  remains extended during normal operations and does not “rattle” or retract because of normal vehicle maneuvers, such as braking or acceleration. The force required to start retraction may be varied to suit a particular application, depending, for example, on the size of the tailgate  18  and the weight of its components. For example, in a typical pickup truck application the force to start retraction may be set at about 270 N (60 lbs.) to about 445 N (100 lbs.). 
     FIGS. 4 and 5  illustrate the construction of the tailgate  18  in more detail. it has a box-like lower section  22  which includes pivots  24  (hinge pins which fit mating holes in the bed  12  are illustrated), as well as attachment points  26  for the above-mentioned braces  20 . The lower edge of the lower section  22  defines the bottom edge  28  of the tailgate  18  (see  FIG. 1 ). A box-like upper section  30  fits over the lower section  22 . The upper edge of the upper section  30  defines the top edge  32  of the tailgate  18  (see  FIG. 1 ). In the illustrated example, the cross-sectional dimensions of the upper section  30  are slightly greater than those of the lower section  22  so as to allow sliding motion between the two components. In this configuration, the upper section  30  acts like an “umbrella” which sheds water off the tailgate  18 . However, the opposite configuration (i.e. lower section  22  larger than upper section  30 ) could also be used. Furthermore, alternative physical configurations of the tailgate  18  may be substituted for the two-part telescoping structure described herein, so long as the tailgate  18  is able to move between extended and retracted positions. The upper section  30  also carries a pair of retractable latch bolts  34 , an operating handle  36 , and a latch mechanism of a known type (not shown) that retracts the latch bolts  34  when the operating handle  36  is pulled. 
   Biasing means are provided for urging the tailgate  18  into the extended position. In the illustrated example, a pair of telescoping support columns  38  are installed in the interior of the tailgate  18  between the upper and lower sections  30  and  22 . As shown in  FIG. 6 , the support columns  38  each include inner and outer tubes  40  and  42 , and end plates  44  and  46 . A spring  48  extends between the upper end plate  44  and a shoulder  50  of the outer tube  42 . A pin  52  which is carried by the inner tube  40  rides in a longitudinal slot  54  in the wall of the outer tube  42  and controls the range of motion of the support column  38 , and thus limits the motion of the upper section  30  to a predetermined stroke. In the illustrated example, the upper section  30  has a stroke of about 15.24 cm (6 in.), but this may be varied to suit a particular application. Other means such as shock absorbers, cables and pulleys, hydraulic dampeners, directly mounted springs, etc. may be substituted for the support columns  38 . In the illustrated example, the support columns  38  are mounted between upper and lower reinforcing rails  56  and  58  which are carried in the upper and lower sections  30  and  22 , respectively. 
   When the tailgate  18  is closed, the latch bolts  34  engage openings  60  in conventional latch plates  62  (see  FIG. 2 ) mounted to the sidewalls  16 . This engagement positively holds the tailgate  18  in the extended position so that a load can be placed on the top edge  32  of the tailgate  18 , if desired. 
   Even with the features described above, the tailgate  18  may ultimately be damaged if it is impacted severely, or if the vehicle is moved further after the tailgate  18  has made contact. Therefore, optional means may be provided for warning the vehicle operator, bystanders, or both, than an impact has occurred.  FIG. 7  illustrates schematically a circuit that may be used for this purpose. It includes a power source  64  (which may be the vehicle&#39;s existing battery), a switch  66  operatively connected to the tailgate  18  and arranged to close when relative motion takes place between the upper and lower sections  30  and  22 , and a warning device which is activated when the switch  66  is closed. Non-limiting examples of warning devices include aural devices such as bells, buzzers, alarms, loudspeakers, and voice modules, visual devices such as lights, strobes, and LCD or LED displays, and tactile devices such as vibrators or shakers, and the like. In the illustrated example, the circuit powers the vehicle&#39;s horn  68  and taillights  70 , an in-cab light  72 , and an in-cab buzzer  74 . 
   In some cases, it may be desirable to pull a “gooseneck”-style trailer (not shown) which connects to “fifth wheel” type hitch  76  mounted on the floor  14  of the bed  12  (see  FIG. 8 ). Often, a conventional tailgate would interfere with such a trailer in the open position. Accordingly, the tailgate  18  may optionally be arranged so that it can be latched in partially-retracted position as shown in  FIG. 8 . To accomplish this, a pair of alternative latch plates  62 ′ (shown in  FIG. 9 ), each with an additional opening  60 ′ in a lowered position, are mounted on the sidewalls  16  of the bed  12 . The tailgate  18  may then be pushed into a partially-retracted position as it is closed, and the latch bolts  34  will engage the additional openings  60 ′. This holds the tailgate  18  in the lowered position shown in  FIG. 8 , where its top edge  32  is substantially lower than a top edge  78  of the sidewalls  16 . 
   Optionally, the tailgate  18  may be retractable in the closed or upright position. To accomplish this, a pair of alternative latch plates  62 ″ (shown in  FIG. 10 ) each with a single vertically elongated opening  60 ″, would be mounted on the sidewalls  16  of the bed  12 . If force should be applied to the tailgate  18 , for example by interference with a “gooseneck” of a trailer, the tailgate  18  can collapse into a retracted position so that its total length is less than the extended length, as described above. 
   The foregoing has described an impact absorbing tailgate. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention. Accordingly, the foregoing description of the preferred embodiments of the invention and the best mode for practicing the invention are provided for the purpose of illustration only.