Torque tube liftgate

Details Torque tube liftgate Torque tube liftgate

2000-08-16

2001-10-09

Strimbu, Gregory J. (Department: 3634)

Movable or removable closures

With operator for movably mounted closure

Operating lever or link and closure swing about parallel axes

C049S346000, C296S076000, C296S106000, C296S146800

Reexamination Certificate

active

06298604

ABSTRACT:

TECHNICAL FIELD
This invention relates to vehicle power liftgates in general, and specifically to a liftgate in which a power mechanism on only one side can apply torque to both sides of the gate.
BACKGROUND OF THE INVENTION
A recent trend in automotive vehicles has been the provision of power devices to open and close doors, liftgates, hoods, trunks and any other swinging, heavy closure panel. Each type of closure panel presents unique challenges. The rear liftgates on mini vans or SUVs are large, heavy, generally rectangular structures, typically latched at the bottom and hinged across the top to swing up and down. Gas springs generally support the liftgate on both sides at its up, open position, and assist in lifting it. The hold open force of the springs has to be manually overcome during closing, of course. Latches are located at the bottom center of the liftgate, so the manual opening and closing force is centered and evenly distributed. Any powered opening and closing device, however, will generally have to be located at the side of the liftgate opening, so as to be concealed or at least out of the way. As gates lift become larger and are made from lighter, thinner and more flexible materials, they become more subject to twisting with unbalanced forces. This means that unless two power devices are provided, one on each side of the liftgate, it could flex unevenly as it was opened or closed. Obviously, a power opener using a single actuator acting on a single side of the liftgate would be far less expensive, but it is not obvious how it could possibly provide a lifting force to both sides of the panel.
SUMMARY OF THE INVENTION
The invention provides a power opening and closing device for a rear liftgate or the like which does use a single actuator actuator on only one side, but which is able to apply lifting force evenly to both sides of the liftgate.
In the embodiment disclosed, a vehicle having a large area liftgate is pivoted to a vehicle body to swing open and closed about a main axis. As is typical, the liftgagte is formed as a double walled, hollow structure of two interconnected metal sheets or walls. A powered actuator moves up and down in a track that runs generally along one side of the rear liftgate opening of the vehicle. The inner end of a lift rod rides up and down in the track, with sufficient force and distance to raise and lower the liftgate, while the outer end comprises a ball joint. Conventionally, the outer end of the lift rod would be directly attached to the liftgate, and would apply opening and closing force or torque to only one side. Therefore, two would be needed for an even lifting action on each side.
In the disclosed invention, the single actuator acts on the near side of the liftgate directly, and on the far side, indirectly, through an interposed toque tube. The torque tube is generally U shaped, with first and second integral arms bent out generally, generally, but not absolutely, perpendicular to a central, generally straight stem. In a non stressed, free state, the two arms are generally co planar, but the stem is capable of resiliently twisting as the two arms are turn relative to one another out of their co planar free state. The torque tube is located inside the hollow structure of the liftgate, with the stem running along the top edge of the liftgate and the two arms running along the sides thereof. The end of the second arm is fixed to the far side of the liftgate, but the stem is free to turn within a pair of journals that orient the stem along a second axis parallel to the main axis. A ball joint attaches the end of the first arm of the torque tube to the outer end of the lift rod. The torque tube first arm is not fixed to the near side of the liftgate, but is free to turn back and forth, out of its free state, relative to the fixed arm. The degree of relative turning between the fixed and free torque tube arms is determined by a slot or other structure on the liftgate that acts as a stop to constrain the end of the non fixed arm in each direction.
In operation, as the actuator begins to move up, the lift rod pushes up on the torque tube free arm, twisting the stem resiliently and transferring torque to the fixed arm. A lifting force or torque is thereby applied indirectly to the far side of the liftgate. The torque tube continues to twist until the end of the free arm hits the outer end of the slot, at which point the first arm begins to directly lift the near side of the liftgate. Lifting force is thereafter applied to both sides of the liftgate until it reaches the fully open position and the actuator stops. At the fully open position, gas springs or some other hold open device provides a counterbalancing, hold open force. When the actuator reverses to close the liftgate, the twisting action of the torque tube reverses, applying a closing force to both sides of the liftgate, overcoming the counterbalancing force and pulling the liftgate closed.


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