US 5,839,719 AGranted

Pneumatic strut for a motor vehicle with an adjustable limit position

AssigneeStabilus GmbH

InventorsHans-Josef Hosan, Castor Fuhrmann, Hans-Klaus Schnitzius

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Abstract

A pneumatic strut for use as an opening power assist mechanism for a motor vehicle tailgate has a piston rod extending from a piston contained within a cylinder. The piston separates the cylinder into two work chambers, each containing a gas charge under pressure. A bypass opening is active to connect the work chambers during the initial opening displacement of the tailgate to automatically open the tailgate through a first opening angle range. A second valve can be externally actuated to connect the two work chambers to further selectively open the tailgate into a second opening angle range. To close the tailgate, a third, directionally dependent valve can automatically connect the two work chambers during the closing displacement of the tailgate.

Claims19

Dependent claims

A gas spring fastened rotationally to a vehicle body and fastened to a vehicle tailgate to be opened, whereby the gas spring acts as a lifting mechanism for an opening range of the tailgate, said gas spring comprising:

a cylinder comprising a gas charge under pressure;
the cylinder comprising a base on one end and a seal-guide unit on another end;
a piston rod being configured to be displaced axially;
the piston rod being positioned by the seal-guide unit concentric to the cylinder;
a piston being disposed on the piston rod to divide the cylinder into two working chambers;
the cylinder comprising a first segment and a second segment;
the opening range of the tailgate having a first opening angle range and a second opening angle range;
the piston rod being configured to be displaced axially in the first segment of the cylinder to move the vehicle tailgate in the first opening angle range;
the gas charge being configured to exert a thrust force on the piston rod cross section to displace the piston rod in the first segment of the cylinder;
the second opening angle range of the vehicle tailgate corresponding to movement of the vehicle tailgate beyond the first opening angle range;
the piston rod being configured to be displaced axially in the second segment of the cylinder to move the vehicle tailgate in the second opening angle range;
the piston comprising an arrangement to stop displacement of the piston rod in the second segment of the cylinder to stop the vehicle tailgate in any position in the second opening angle range;
a valve system to connect the two working chambers;
a bypass opening being configured to be active upon the piston rod being disposed in the first segment of the cylinder;
the valve system comprising a connecting channel with a directionally dependent pilot valve disposed between the two working chambers to permit flow from a first of the two working chambers to a second of the two working chambers and to limit flow from the second working chamber to the first working chamber;
the valve system comprising a piston valve;
the piston valve having an open position and a closed position;
the open position of the piston valve being configured to permit the piston rod to be displaced in the second segment of the cylinder to permit movement of the vehicle tailgate in the second opening angle range;
a valve tappet being disposed to move the piston valve into the open position;
and
an external actuation mechanism to actuate the valve tappet to open the piston valve and to permit closing of the piston valve.

18 more elements

A strut for permitting the moving and positioning and the holding of a tailgate of a motor vehicle with respect to the motor vehicle, said strut comprising:

a cylinder having a longitudinal axis;
said cylinder being configured to be attached to one of the tailgate and the motor vehicle;
a piston rod having a first end portion and a second end portion;
said first end portion of said piston rod being disposed within said cylinder;
said second end portion of said piston rod extending out of said cylinder;
said second end portion of said piston rod being configured to be attached to the other of the tailgate and the motor vehicle;
a piston being disposed within said cylinder;
said piston being connected to said first end portion of said piston rod;
said piston being disposed to divide said cylinder into first and second chamber portions;
working fluid being disposed within said first and second chamber portions;
said working fluid having a first pressure in said first chamber portion and a second pressure in said second chamber portion;
said piston and said piston rod being disposed to be axially movable with respect to said cylinder;
said piston and said piston rod being extendable from a first position corresponding to the tailgate being closed to a second position corresponding to the tailgate being partially opened;
said piston and said piston rod being further extendable from the second position to a third position corresponding to the tailgate being substantially completely opened;
the first pressure of said working fluid in said first chamber portion generating a force on said piston to move said piston and said piston rod from the first position towards the second and third positions;
a first flow channel extending between said first chamber portion and said second chamber portion;
said piston comprising a first valve arrangement to open and close said first flow channel;
said piston comprising a second valve arrangement to permit said piston and said piston rod to selectively maintain a stationary position between the second position and the third position to hold the tailgate stationary with respect to the motor vehicle;
an actuator to operate said first valve arrangement;
said actuator being operatively connected to said first valve arrangement to permit selective opening and closing of said first valve arrangement;
a mechanism extending externally from said strut being configured and disposed to permit actuation of said actuator;
said actuator comprising a tappet;
said tappet being operatively connected to said first valve arrangement;
said tappet being axially movable to open and close said first valve arrangement;
said externally extending mechanism comprising structure being configured and disposed to move said tappet;
said first valve arrangement being configured to permit extension of said piston and said piston rod from the second position toward the third position by the force of the first pressure in the first chamber portion acting on said piston upon said first valve arrangement being opened by said actuator;
at least one of said cylinder and said piston being configured to form a second flow channel upon said piston and said piston rod being disposed between the first and second positions;
said second flow channel being configured to permit said piston and said piston rod to be extended from the first position to the second position by the force of the first pressure in said first chamber portion acting on said piston;
and
said second flow channel extending between said first chamber portion and said second chamber portion.

27 more elements

Dependencies are inferred from the claim text.