Abstract:
A tailgate has an internal control mechanism used to exert a force on a pivot. The control mechanism may be combined with a torque rod. The rotational force is used to aid in the lowering and/or raising of the tailgate. The internal control mechanism is free from corrosion and debris and therefore allows for greater durability.

Description:
RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of U.S. application Ser. No. 11/490,836, filed Jul. 21, 2006 which claims the benefit of U.S. Provisional Application No. 60/701,296, filed on Jul. 21, 2005. The entire teachings of the above application are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     Tailgates for pickup trucks typically range in weight from 40 to 60 pounds and are hinged at the rear of a truck bed such that when the tailgate is unlocked by the pulling of a lever or handle, the tailgate opens to a point level with the truck bed where it is restrained, usually by detachable folding straps. Typically, the tailgates can be removed from the truck body when the tailgate is pivoted to a partially open tailgate removal position.  
         [0003]     The weight of the tailgate precludes one handed operation for any but the strongest individual. People of normal build have to use their second hand, shoulder or knee to raise the tailgate or to support the tailgate in an effort to keep it from dropping too quickly. Often it is the case where an individual opening a tailgate will only have one free hand, thus causing a strain in the wrist of the individual as the wrist must bear the weight of the tailgate.  
         [0004]     Normally a person drops the gate or sometimes raises his or her knee in order to arrest the fall of the tailgate. By so doing, the individual has a chance of being injured if the tailgate falls on the knee by this process. The raising of one&#39;s knee to prevent the tailgate from dropping has reportedly resulted in crushed knee caps or other damage to the knee. It will be appreciated that a free falling tailgate can, in fact, crush anything that is underneath it and can, for instance, hurt children who are standing at the back of the tailgate when it falls.  
         [0005]     One common solution to counterbalancing the weight of the tailgate is by the use of a torque rod that is fixed to the tailgate at one end and coupled to the truck body at the other end (U.S. Pat. No. 5,358,301, US2005/0194808A1 et al).  
         [0006]     Dampers have been employed to achieve a controlled rate of descent. One solution utilizes a spring with viscous damping that is mounted between the tailgate and the truck body and controls the motion of the tailgate with a bell crank and an actuation shaft (U.S. Pat. No. 6,773,047 B2). Another attempted solution has been a power tailgate installation described in U.S. Pat. No. 6,357,813 that consists of a motor mounted on the truck that actuates the tailgate by a crank arm and a sliding component.  
       SUMMARY OF THE INVENTION  
       [0007]     A problem with prior art methods of counterbalancing the weight of the tailgate is that the additional number of parts necessary to control the tailgate are exposed to road grit and corrosion, thus deteriorating the efficiency of the counter balance. In order to minimize the effects of corrosion, other solutions have mounted the spring and damper internal to the tailgate to provide a protected environment as in U.S. Pat. Nos. 6,820,910 B1 and 6,854,781 B2. Both of these solutions rely on cables that unreel from the interior of the tailgate and attach to the truck body to control its motion. Intricate fair lead mechanisms are required to minimize chafing as the cables unreel from the tailgate in a direction that changes progressively as the tailgate pivots. The cables are exposed when the gate is in the open position. This sliding component complicates the easy removal and installation of the tailgate and the whole mechanism is exposed to road grit and corrosion.  
         [0008]     Thus, it would be desirable to control the opening and closure of a tailgate with modules that are internal to the tailgate for protection from corrosion whilst facilitating the easy removal and installation of the tailgate in the conventional way.  
         [0009]     According to an aspect of the present invention, motion control devices are mounted inside a tailgate and coupled to a rotating shaft therein, such as a torque rod. Tailgates are generally formed by an inside and an outside panel and a right and left sidewall that defines a box like structure with an enclosed interior space. The tailgate hinges on bushings. A torque rod is generally installed with one end fixed to the tailgate at one side thereof and the other end fixed to a pivot body which rotates inside one of the bushings at the opposite side of the tailgate. The pivot body engages the truck body via an elongated pin that facilitates easy removal of the tailgate but limits rotation relative to the truck body. While the pivot body does not rotate relative to the truck, it does rotate relative to the tailgate as it opens and closes; that is, the pivot body remains fixed to the truck body as the tailgate rotates. A principal feature of this invention is to make use of this relative rotation of the pivot body to control the motion of the tailgate from within the tailgate.  
         [0010]     A mechanism mounted inside the tailgate for controlling the drop of a tailgate is described. The control mechanism comprises a damper having a proximal end and a distal end, the proximal end of the damper coupled to a pivot body such as through a crank arm, and the distal end of the damper coupled to the tailgate, such as to a first interior side of the tailgate. The pivot body may attach to a torsion rod inside the tailgate and engage a pin fixed to the truck body outside the tailgate. The damper may comprise a viscous damper or a bumper made of a high hysteresis elastometer.  
         [0011]     Another mechanism mounted inside the tailgate for controlling the drop of a tailgate is described. This control mechanism comprises a gas spring having a proximal end and a distal end, the proximal end of the gas spring coupled to a pivot body, such as through a crank arm, and the distal end of the gas spring coupled to the first interior side of the tailgate. The pivot body may rotate inside a bearing inside the tailgate and engage a pin fixed to the truck body outside the tailgate.  
         [0012]     A mechanism mounted inside the tailgate for automatically closing the tailgate is also described. The mechanism comprises an electric motor geared to a pivot body. The pivot body may attach to a torsion rod inside the tailgate and engage a pin fixed to the truck body outside the tailgate as described above.  
         [0013]     A method and mechanism for providing and a tailgate of a vehicle comprising a pivot, the pivot being fixed relative to a truck bed is disclosed. The tailgate further comprises a rod, the rod being internally mounted in the tailgate, such as on a bottom surface, and being in connectivity with the pivot and a control mechanism, the control mechanism being internally mounted in the tailgate and the control mechanism exerting a force on the rod. The rod in return exerts a rotational force on the pivot. The control mechanism may be in connection to the rod via a crank arm. The rod may be a torque rod or a shaft rod. The control mechanism, as an example, may be a damper, a motor, or a gas spring. The control mechanism may be mounted solely on one end of the tailgate. The rotational force may be used to control the lowering of the tailgate and assist in raising it.  
         [0014]     Thus the present invention facilitates ease of closing and safe and controlled opening of the tailgate in various ways, yet permits rapid removal of the tailgate from the truck body in the conventional way, while protecting the mechanism from outside debris. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.  
         [0016]      FIGS. 1A and 1B  show an internal damper and torque rod disposed within a tailgate;  
         [0017]      FIGS. 2A and 2B  show an internal gas spring disposed within a tailgate; and  
         [0018]      FIGS. 3A and 3B  show an internal power mechanism disposed within a tailgate. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]      FIGS. 1A and 1B  depict a tailgate featuring an internal spring and damping mechanism.  FIG. 1B  is an enlarged exploded view of the internal mechanism rotated clockwise. The tailgate  112  comprises side faces  113  and  114 , outside face  115 , and inside face  116  (partially cut away to show the interior of tailgate  112 ). Tailgate  112  is pivotally attached to the truck body (not shown) by bushings  117  and  118 . Bushing  117  houses an insert  119  which mates with a key (hidden in this view) attached to bracket  123 . Bracket  123  bolts to the truck body with two flat head bolts (not shown). Bushing  118  on the opposite side of tailgate  112  houses pivot body  120  which mates with key  122  attached to bracket  124 . Bracket  124  bolts on to the truck body with two flat head bolts (not shown).  
         [0020]     The internal damping mechanism  160  is pivotably attached to the sidewall  114  of tailgate  112  with a stanchion  161 . It should be appreciated that the internal damping mechanism may be attached to either sidewall. A piston rod  162  slides in and out of the damper  160 . The damper  160  is a viscous damper which exerts a retaining force on the piston rod  162  proportional to the speed of its withdrawal, thus controlling the fall of the tailgate, but only a negligible force to its insertion so as not to inhibit raising of the tailgate. The piston rod  162  terminates in a yoke  163 . The yoke  163  is pivotably attached to a crank arm  165  with a pin  164 . The crank arm  165  has a boss  166  with a bore for the torque rod  175 . Boss  166  terminates in two fingers  167  and  168  that engage the two notches  172  and the second notch, being hidden from view, of the boss  169  of pivot body  120 . Thus, through the crank arm, the damper applies a rotating force to the pivot body  120 .  
         [0021]     Fingers  167  and  168  carry a groove  171  and notches  172  and  173  carry a matching groove  170 . Snap ring  174  snaps into the grooves  170  and  171  prevents the fingers from disengaging the notches.  
         [0022]     Torque rod  175  has two flats  177  and  178  at each end. Flat  177  mates with a tight fitting bore (not shown) of the boss  169  of pivot body  120 . Pivot body  120  has a slot shaped cavity  180  which engages the key  122  of the bracket  124 . Flat  178  is retained by pinch block  179  mounted to the far end of the tailgate. In this manner, the pivot body  120  is restrained from rotating as the tailgate is lowered and will impart a proportional twist to the torque rod  175 . This twist adds a counterbalancing torque to the weight of the tailgate. An additional restraining torque is applied to the tailgate by the damper  160  and the stanchion  161  as the rod  162  remains attached to the stationary crank arm  165  while the damper  160  and the stanchion  161  orbit around the crank arm  165 . This forces the piston rod  162  to withdraw from the damper  160 , creating the aforementioned retaining force. This retaining force of the damper  160  can be sized to limit the rate of descent of the tailgate to a controlled rate around 2 to 4 seconds as opposed to a nearly instantaneous drop without a damper. Additional support for the torque rod  175  to resist the thrust loads of the crank arm  165  generated in this process may be provided by a bearing pillow block  176  attached to the tailgate.  
         [0023]      FIGS. 2A and 2B  depict a tailgate a mechanism  200  with a gas spring that carries out the functions of the damper and the torque rod described above. Aside from the fact that the torque rod  175  and pinch block  179  are replaced by the shaft  277  and bearing pillow block  276 , the two constructions are identical and the numerals used to designate the like components in  FIGS. 1A and 1B  are carried over in  FIGS. 2A and 2B . Gas spring  260  is of the type known as Tension Gas Spring and exerts a spring force that retracts the piston rod  262 . Additionally, gas spring  260  acts as a viscous damper which exerts a retaining force on the piston rod  262  proportional to the speed of its withdrawal. Thus, the gas spring exerts a force on the shaft  277  via the crank arm. The shaft in turn exerts a rotation force to the pivot body. The gas spring thus damps lowering of the tailgate and assists in raising it.  
         [0024]      FIGS. 3A and 3B  show a tailgate featuring an internal power mechanism  300  which includes a DC motor  360 , a pinion gear  363 , and a sector gear  365 , wherein sector gear  365  is equivalent in terms of operation to crank arm  165 . The pinion is attached to an output shaft  362  of the DC motor  360 . The sector gear  365  mounts in place of the previously described lever  165  and is driven by the pinion gear  363  on the output shaft  362  of the reduction gear DC motor  360 . The sector gear  365  carries a hub  366  with two fingers (hidden in view) that engage the two notches  172  and  173  (hidden in view) of the boss  169  of the pivot body  120 . The DC motor  360  mounts on a bracket  361  that attaches to the bottom side of the tailgate  312 . The bracket  361  also carries a bearing  380  that retains a torque rod  317  from bending due to the thrust loads of the pinion gears  363  and sector gear  365 . The torque rod  317  attaches rigidly to the tailgate  312  inside the pinch block  318 . The other end of the torque rod  317  attaches rigidly to the pivot body  120 . The torque rod  317  is used to assist the motor  360  in raising the tailgate  312  and also counter balance the gravity forces when the tailgate  312  is lowered. Thus, the DC motor exerts a force on the sector gear, which in return exerts a force on the torque rod. The torque rod then exerts a rotational force on the pivot body. Therefore the sector gear operates in a similar fashion as the crank arm  165 . It will be appreciated that the mechanism could also function without the use of a torque rod, alone or in conjunction with a gas spring as described in  FIGS. 2A and 2B . The internal friction of the motor  360  can be utilized to slow the descend of the tailgate  312  or an additional damper may be installed as described in  FIGS. 1A and 1B .  
         [0025]     In operation, the motor  360  causes the pinion gear  363  to rotate, resulting in the rotation of sector gear  365 . The rotation of sector gear  365 , in turn, causes the rotation of the pivot body  320 , thus exerting an opening or closing moment to the tailgate  312  depending on the direction of rotation. The operation of motor  360  may be limited to only raising the tailgate  312  by activating a suitable switch or by remote control. It may also be used to control the descend of the tailgate  312  in conjunction with an apparatus for remote opening of the tailgate as described in U.S. Pat. No. 6,994,390 B2. Motor  360  may also comprise a clutch to disengage it for manual operation.  
         [0026]     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.  
         [0027]     The scope of the invention however is not limited to these devices; other mechanical linkages may be employed, such as a cam, a drum and cable or belts or a sprocket and chain. Other motion controllers, such as a rotary damper or a detent to arrest the movement of the tailgate may be installed inside the tailgate and linked to the pivot body. In addition, any combination of the above mentioned embodiments may be used in combination. For example some of the preferred combinations may be, the damper and the torque rod, the gas spring and damper, and the motor in combination with the gas spring. It should also be appreciated that other forms of springs may be used, for example coil or torsion springs.  
         [0028]     As may be seen from  FIGS. 1A-3B , all of the components of the control motion mechanisms are disposed within the tailgate. Therefore, the control motion mechanisms are protected from cargo and road debris. Furthermore, in order to detach the tailgate from the truck body, it is no longer necessary to detach the individual components of the control motion mechanisms since they are now contained internally in the tailgate.