Note: Descriptions are shown in the official language in which they were submitted.
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TRUCK TAILGATE WITH MOTION CONTROL DEVICES
RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application No.
60/926,098, filed on April 25, 2007. The entire teachings of the above
application
are incorporated herein by reference.
BACKGROUND
Tailgates for pickup trucks typically range in weight from 40 to 60 powids
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.
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.
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'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.
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 (US 5,358,301, US2005/0194808A1 et al).
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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 (US 6,773,047 92). Another attempted solution has been a power
tailgate installation described in US 6,357,813 that consists of a motor
mounted on
the truck that acttiates the tailgate by a crank arm and a sliding component.
SUMMARY
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 US 6,820,910 B1 and 6,854,781132. 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.
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.
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
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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.
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.
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.
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.
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 mechanisin 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
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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.
In other example embodiments a control mechanism that may adapted to
preexisting tailgate systems is also presented. An external control mechanism
may
be externally retrofitted to any tailgate system in order to provide further
support in
the opening and closing of the tailgate.
As an example, embodiments may include a tailgate of a vehicle featuring a
pivoting main body and a pivot about which the main body pivots. The pivot may
be fixed relative to a truck bed. The tailgate may further include a piston
element
including a first end connected to the pivot and a second end connected to the
main
body, where the second end may be positioned above the first end when the main
body is in a closed position, the piston element being configured to provide a
counter force as the main body is lowered.
The piston element may be a damper or gas spring and may be retrofitted
externally to the tailgate. The piston element may also be configured to
rotate with
and in the same direction as the main body.
The pivoting main body may also include a torque rod. The torque rod may
be preexisting and internal to the pivoting main body, and/or the torque rod
may be
retrofitted internally or externally to the pivoting main body.
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
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.
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FIGS. lA and I B show an internal damper and torque rod disposed within a
tailgate;
FIGS. 1 C and 1 D illustrate a prior damper mechanism used in a tailgate in a
fully closed and fully opened configuration, respectively;
FIGS. lE and IF illustrate a damper mechanism used in a tailgat.e in a fully
closed and fully opened configuration, respectively, according to example
embodiments;
FIGS. 2A and 2B show an internal gas spring disposed within a tailgate;
FIGS. 3A and 3B show an internal power mechanism disposed within a
tailgate;
FIGS. 4A-4C show a retrofitted external damper mechanism used in a
tailgate featuring a preexisting torque rod according to example embodiments;
FIG. 5 illustrates a retrofitted external damper mechanism used in a tailgate
featuring a preexisting torque rod according to another example embodiment;
FIG. 6 shows a retrofitted external damper mechanism used in a tailgate
system that does not feature a preexisting torque rod according to example
embodiments; and
FIGS. 7A and 7B illustrate a retrofitted external damper mechanism and a
retrofitted external torque rod used in a tailgate according to example
embodiments.
DETAILED DESCRIPTION
Figs. 1 A and 1 B depict a tailgate featuring an internal spring and damping
mechanism. Fig. I B 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).
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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.
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.
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
darnper. 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.
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It should be appreciated that the mounting position of the internal spring and
damping mechanism of Figs. lA and IB differ from the mounting position of
internal spring and damping mechanisms known in the art. Figs. 1C and 1D
illustrate a prior art mounting configuration of internal spring and damping
mechanism when the tailgate 112 is in a closed and opened position,
respectively.
As shown in Figs. 1 C and 1 D the upper end 188 of the damping mechanism is
fixed
to the truck body 187, while the lower end 189 is attached to the tailgate
112. In the
closed or vertical position, the distance between the upper and lower ends 188
and
189, respectively, equals the length of the damper mechanism in its contracted
position (D). The initial position of the damper mechanism is thus normal with
respect to the ground within a few degrees.
As the tailgate opens to a horizontal position, as illustrated in Fig. ID, the
damper mechanism extends fully. Since the extended length of the damper
mechanism can never be more than twice the contracted length the final
position can
never pivot more than 25 away from the initial vertical position. This may be
mathematically proven by Pythagorean's Theorem for right triangles where the
final
position may be described as (D+L)2 +LZ = (Dx)2. D is the contracted length of
the damper mechanism, L is the distance between the lower end 189 of the
damper
and the tailgate pivot 190, and x is an extension factor associated with the
elongated
tailgate, where the product of Dx equals the extended length of the damper
mechanism. It should be noted that using the configuration illustrated in
Figs. 1C
and 1 D, the maximum angle 0 the damper mechanism may be displaced in the
fully
opened position is no more than 25 . It should also be noted that the upper
end 188
of the damper mechanism 186 remains above the lower end 189 during the
operation
of the tailgate (e.g., in the fully opened and closed positions of the
tailgate as well as
all positions in between).
Figs, IE and 1 F illustrate the opening and closing of the damper mechanism
of Figs. 1 A and 1 B. The damper mechanism 160 includes a reverse orientation
as
compared to the damper mechanism 186, where the upper end 161 is attached to
the
tailgate 112 and the lower end 162 is attached to the truck body 187. Similar
to the
damper mechanism 186 illustrated in Figs. IC and ID, when the tailgate 112 is
in a
closed position, the damper mechanism 160 is in a substantially vertical
position.
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However, when the tailgate 112 is in a fully opened position, the damper
mechanism
orbits more than 90 , depending on the distance between the lower end 162 and
the
tailgate pivot 120 (L). It should be noted that while the tailgate is in the
fully closed
position, the upper end 161 of the damper mechanism 160 is positioned above
the
lower end 162. As the tailgate is lowered, the upper end 161 gradually
descends
with the tailgate, resulting in the upper end 161 being in a lower position
with
respect to the lower end 162.
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 in
relation to Figs. 1 A and 1 B. 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 I A and 1 B 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.
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
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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. l A and 1 B.
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 US
6,994,390 B2. Motor 360 may also comprise a clutch to disengage it for manual
operation.
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.
The scope of the invention is not limited to the devices described above;
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.
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As may be seen from Figs. lA-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.
In other example embodiments, motion control, devices suitable for
retrofitting may be employed. The retrofitted motion control devices may be
used in
preexisting tailgates to provide further support in balancing the weight of
the tailgate
during its opening and closing. The retrofitted motion control device may be
used in
tailgates that may or may not include a preexisting torque rod.
Fig. 4A-4C illustrate a retrofitted damper mechanism 430 mounted to a
tailgate 112 featuring a preexisting torque rod 423 according to example
embodiments. An attachment component 400 may include a crank arm 410 that
may be fixed to an existing ferrule 412 by screws 414 or any other suitable
means.
The ferrule 412 includes an internal notch 418 that niay mate with an existing
oblong trunnion. 420 mounted on one side of the truck bed with screws 421 and
422.
The trunnion 420 holds the ferrule fixed as a cup 416 rotates with the
tailgate about
the ferrule. The existing torque rod 423 may be fixed to the ferrule 412 at
one end
and fixed to the tailgate 112 at an opposite end with a pinch block 425 as
shown in
the partially cut away view in Fig. 4B. The crank arm 410 may also include a
pin
426 that may be pivotally attached to one end of the damper mechanism 430 by
end
fitting 432. The other end of the damper mechanism 430 may attach pivotally to
a
mounting bracket 434 by an end fitting 136. The mounting bracket 434 may
attach
to the tailgate 112 with screws 426 and 427. The damper mechanism 430 may be a
viscous damper or a friction damper that exerts a restraining force in
extension but
not in compression.
In operation, as the tailgate 112 is lowered, the ferrule 412 is restrained
from
rotation relative to the truck by the fixed oblong trunnion 420 and must
therefore
rotate relative to the tailgate 112 inside the cup 416. Since the crank arm
410 is
fixed to the ferrule 412, the crank arm 410 must also rotate relative to the
tailgate
112. As the crank arm 410 rotates, it extends the damper mechanism 430. As the
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damper mechanism 430 extends, it exerts a restraining force cushioning the
descent
of the tailgate 112. The two stages from a fully closed to a fully open
tailgate are
illustrated in Fig. 4B and 4C, respectively.
It should be appreciated that the thickness of the attachment component 400
and the crank arm 410 may be as thin as 0.062" and possibly thinner if made
from a
high strength alloy. Such an attachment component and crank arm may easily fit
between the trunnion 420 of the truck, and the ferrule 412 of the tailgate 112
without
adversely affecting the existing play between the two.
Fig. 5 also illustrates an example embodiment of a retrofitted damper
mechanism 530 employed in a tailgate 112 featuring a preexisting torque rod
(not
shown). The attachment component 500 of Fig. 5 differs from the attachment
component 400 of Figs. 4A-4C in that the attachment component 500 is not
attached
to a ferrule but is instead positioned coaxially with a cup 516 by three
flanges 505 or
a collar (not shown) mating with the outside diameter of the cup 516. In this
manner
the attachment component 500 may rotate relative to the tailgate 112. The
attachment component 500 may include a slot 518 that may mate with the
existing
oblong trunnion 520 mounted on one side of the truck bed. The damper mechanism
530 may also include end fittings 528 and 536, a crank arm 510, a pin 526, and
a
mounting bracket 534 that may function in the manner described in relation to
Figs.
4A-4C.
In operation, the damper mechanism of Fig. 5 may operate in a similar
manner to the damper mechanism of Figs. 4A-4C with the exception that the
damper mechanism 530 does not rely on the ferrule to restrain it from rotating
relative to the truck body but relies on the slot 518 that engages the
trunnion (420,
Figs. 4B and 4C) to keep the attachment component 500 aligned with the truck
body. The attachment component 500 is held in place axially by flanges 505 and
transversely by the lateral rigidity of the linkage made up of the crank arm
510, the
pin 526, the damper mechanism 530, and end fittings 518 and 536. To assure
that
the slot 518 is aligned correctly to facilitate the installation of the
tailgate 112, the
damper mechanism 530 may include an internal spring (not shown) that retracts
the
damper and aligns the crank arm 210.
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Fig. 6 illustrates another example embodiment including a retrofitted damper
mechanism 630 employed in a tailgate 112 that does not include a preexisting
torque
rod. Trucks that do not feature torque rods typically include a cylindrical
trunnion
621 that may be configured to mate with a cup 617. ln order to adapt to the
cylindrical trunnion 621, the damper mechanism configuration of Fig. 6
includes a
modification made with respect to the configuration illustrated in Fig. 5. The
modification may include two additional components. The first component may be
a post that is attached to the truck panel that faces the side of the tailgate
112. As an
example, a mounting screw 601 featuring a raised head 602 with respect to the
trunnion may serve as such a pin. The second component may be a notch 603 that
may be formed at the side of the attachment component 600. The notch 603 may
be
formed by two sides 608 and 609 that engage the raised head 602 and prevent
the
rotation of the attachment component 600 relative to the truck as the tailgate
112 is
swung open and closed.
Figs, 7A and 7B illustrate another example embodiment where a retrofitted
damping mechanism 730 and a retrofitted external torque rod 714 are employed
in a
tailgate 112 that does not feature a preexisting torque rod. The attachment
component 700 may be similar to the attachment component 600 described in
relation to Fig. 6. The attachment component 700 may also include a notch 703
and
sides 708 and 709 that may mate with a post mounted on the truck body (not
shown) to prevent the rotation of the attachment component 700. The attachment
component 700 may also include a boss 710 with a bore 712 to accept the
extemal
torque rod 714. The end of the torque rod 714 may include a flat 715 that may
mate
with the flat 717 of the bore 712 to prevent the rotation of the torque rod
714 but
may allow axial sliding. Other means such as a key and a groove may serve the
same purpose. The other end of the torque rod 714 may also include a flat 721
that
may mate with a flat 723 of a pinch block 725. The pinch block 725 may attach
to
the underside 728 of the tailgate 112.
in operation, the end of the torque rod 714 near the attachment component
700 remains stationary while the other end that is attached to the underside
of the
tailgate 112 orbits around the axis of rotation of the tailgate and rotates
with it. As
that end of the torque rod rotates while the other end remains stationary, it
imparts a
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twist to the torque rod 714 which exerts a counter balancing turning moment to
the
tailgate 112. The play between the various components, or the sliding joint
between
the torque rod 714 and the boss 710 can compensate for the small axial
misalignment which results from the fact that the torque rod 714 does not
rotate
exactly along the axis of rotation of the tailgate 112.
It should be appreciated that although the illustrated examples of the
attachment components of Figs. 4A-7B are all positioned on the driver's side
of the
tailgate, the attachment components may also be positioned on the passenger
side of
the tailgate, It should also be appreciated that a locking mechanism may also
be
used in conjunction with the retrofitted motion control devices in order to
lock the
tailgate in its fully opened position.
