Spring devices – Vehicle – Comprising compressible fluid
Utility Patent
1998-03-25
2001-01-02
Butler, Douglas C. (Department: 3613)
Spring devices
Vehicle
Comprising compressible fluid
C267S226000, C244S1040LS
Utility Patent
active
06168142
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to landing gear for aircraft, and particularly helicopters. More specifically, this invention relates to improvements in the hydraulic damper assembly that provide increased ground clearance of the helicopter under various conditions while maintaining appropriate ground resonance performance.
2. Description of the Related Art
Aircraft landing gears are typically equipped with hydraulic damper systems and struts to absorb forces during aircraft landing and to help support the aircraft while on the ground. Hydraulic damper systems are present in airplanes, helicopters, and other aircraft. Helicopter landing gears absorb the energy from landings through damper motion and elastic deformation of struts.
Helicopter landing gears have unique design requirements. The military helicopter landing gears are required to function in vertical sink speeds ranging from 8 ft/sec limit landing to 42 ft/sec crash landing conditions. In order to provide protection to the airframe, mission equipment package, and occupants in this wide range of sink speeds, multi-stage shock struts with controlled mechanical failures are utilized. Some civil helicopters utilize shock struts in combination with skid gears. Although the sink speed ranges for civil helicopters are less stringent, the kinematic constraints of the skid gears, ground resonance, static ground position, structural and economic considerations are still relevant.
One of the critical design requirements for helicopters is static ground clearance, or the ability of the landing gear to support the helicopter weight without “bottoming out.” This is related to all the other design requirements of helicopter landing gear: energy absorption capability, load factor, and ground resonance. The damper assembly is one of the key gear components most influenced by the design requirements.
Static ground clearance can be increased by reducing damper stroke, which in turn can be done by increasing the pressure of the nitrogen in the damper. However, higher nitrogen pressures result in full extension of the damper under low load conditions, which is not desirable. This can be overcome by going to multistage shock struts with controlled mechanical failures, but at an increased cost.
A complication in changing damper design is that product improvements to both civil and military helicopters need to be accomplished with minimal changes to the existing landing gear configurations. The existing shock strut designs are already at the limits of current technology and, therefore, cannot be scaled to accommodate the derivative helicopters with higher gross weights without an infusion of new and innovative technologies and design approaches.
Therefore, it is desirable to have a single stage damper assembly for an aircraft landing gear that permits high nitrogen pressures to increase ground clearance at high aircraft gross weights and not be fully extended at low aircraft weights to avoid ground resonance problems.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a damper assembly for aircraft landing gears that permit high nitrogen pressures to increase ground resonance clearance at high aircraft gross weight and not be fully extended at low aircraft gross weights to avoid ground resonance problems.
It is another object of the invention to provide a cost effective damper assembly that is easily retrofitted into current designs of helicopter landing gears.
In order to achieve this and other objects of the invention, a hydraulic damper assembly is provided having a barrel-piston assembly and a spring assembly. The barrel-piston assembly has a barrel with a top portion having an open end, and a piston extending through the open end. The piston has a bottom portion that is located inside the barrel. The piston and the barrel also define an annular space in which is a barrel shoulder and a piston shoulder. The barrel shoulder radially extends into the annular space from the barrel top portion. The piston shoulder radially extends into the annular space from the piston bottom portion. The spring assembly is disposed in the annular space between the barrel shoulder and the piston shoulder. When the piston is extended from the barrel, the shoulders compress the spring assembly and, thereby, reduce the amount of force required to compress the piston.
REFERENCES:
patent: 2057893 (1936-10-01), Gross
patent: 3806105 (1974-04-01), Knoishi et al.
patent: 4527674 (1985-07-01), Mourray
patent: 4657228 (1987-04-01), Lautzenhiser
patent: 4838393 (1989-06-01), Mourray et al.
patent: 5158270 (1992-10-01), Lin
patent: 5248131 (1993-09-01), Jobelius
patent: 5330132 (1994-07-01), Lucienne et al.
patent: 5437436 (1995-08-01), Holson et al.
patent: 5465811 (1995-11-01), Katz
patent: 5667041 (1997-09-01), Jensen
patent: 36 13 677 A1 (1987-10-01), None
patent: 0 458 467 A2 (1991-11-01), None
patent: 2 306 141 (1997-05-01), None
Bolukbasi Akif O.
Pester Lowell
Saliba Paul
Butler Douglas C.
McDonnell Douglas Helicopter Company
Rodriguez Pamela J.
Stout Donald E.
Stout, Uxa Buyan & Mullins, LLP
LandOfFree
Hydraulic damper with elastomeric spring assembly does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic damper with elastomeric spring assembly, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic damper with elastomeric spring assembly will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2545317