Land vehicles – Wheeled – Attachment
Reexamination Certificate
1999-08-04
2001-03-06
Johnson, Brian L. (Department: 3618)
Land vehicles
Wheeled
Attachment
Reexamination Certificate
active
06196586
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to forklift vehicles, and more particularly to forklift vehicles having frame leveling and stabilizing devices.
Forklift vehicles or “forklifts” are well known. Such vehicles generally include a vehicle frame and two axles with wheels mounted thereon attached to the frame. Further, an operator station and a lifting mechanism (i.e. a “fork-lift”) are each mounted on the frame. Particularly with forklift vehicles used in uneven or rough terrain, such forklift vehicles are often provided with both a frame leveling device and a stabilizing device. A frame leveling device or “frame leveler” typically includes one or more hydraulic cylinders extending between the frame and at least one of the axles. The frame leveler functions by moving the frame relative to the axle(s) such that the frame is generally horizontally positioned on the adjacent ground surface (i.e., “level”). Further, a stabilizing device or “stabilizer” typically includes a pair of support arms mounted to either the frame or one of the axles and which are engageable with the ground surface adjacent to the forklift vehicle. The stabilizer arms support the vehicle to prevent lateral movement and/or toppling of the vehicle during use.
Generally, presently known systems for leveling and stabilizing a forklift vehicle frame have disadvantages. With a vehicle having a stabilizer device mounted to the vehicle frame, the frame cannot be leveled when the stabilizer arms are deployed as the arms act as “bracing” members that resist or prevent the necessary movement of the frame with respect to the axle. Further, systems in which the stabilizers are mounted to the axle require reinforced axles, are difficult to install and service and are generally much more expensive to produce than frame-mounted stabilizer devices. Therefore, it is desirable to provide a system for leveling and stabilizing a forklift vehicle which overcomes the limitations of known systems.
SUMMARY OF THE INVENTION
In one aspect, the present invention is a system for leveling and stabilizing a vehicle upon a ground surface, the vehicle having a frame and at least one axle pivotally connected with the frame. The system comprises a frame leveler device configured to move the frame with respect to the axle. A stabilizer device is mounted to the frame and includes a pair of arms, each arm having a portion contactable with the ground surface, and two stabilizer hydraulic cylinders. Each stabilizer cylinder has a piston with a rod connected with a separate one of the arms and a base chamber on one side of the piston. Further, a fluid exchange line extends between the base chamber of one stabilizer cylinder and the base chamber of the other stabilizer cylinder. Movement of the frame with respect to the axle when the arm portions are in contact with the ground surface causes hydraulic fluid to flow from one stabilizer cylinder and into the other stabilizer cylinder such that the piston rod of the one cylinder to retract and the piston rod of the other cylinder to extend while the stabilizer arms remain substantially stationary.
In another aspect, the present invention is also a system for leveling and stabilizing a vehicle having a frame and an axle pivotally connected with the frame. The system comprises a frame leveler device including a leveler hydraulic cylinder having a first end connected with the frame and a second end connected with the axle and configured to move the frame with respect to the axle. A stabilizer device is mounted to the frame and includes a pair of arms and two stabilizer hydraulic cylinders. Each stabilizer cylinder has a piston with a rod connected with a separate one of the arms and a base chamber on one side of the piston. Further, a fluid exchange line extends between the base chamber of one stabilizer cylinder and the base chamber of the other stabilizer cylinder and an exchange valve controls flow through the fluid exchange line. A controller is connected with the leveler cylinder and with the exchange valve and is configured to open the valve when the leveler cylinder displaces the frame with respect to the axle such that the stabilizer cylinders are each retractable and extendable during movement of the frame.
REFERENCES:
patent: 3709518 (1973-01-01), Gauchet
patent: 3710695 (1973-01-01), Miller et al.
patent: 4120507 (1978-10-01), Miller
patent: 4860539 (1989-08-01), Parrett et al.
patent: 5497692 (1996-03-01), Marcott
Ingersoll-Rand Company
Johnson Brian L.
Klebe G
Michael & Best & Friedrich LLP
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